Modulation of mesenchymal stem cell behavior by nano- and micro-sized β-tricalcium phosphate particles in suspension and composite structures

NASA Astrophysics Data System (ADS)

Smoak, Mollie; Hogan, Katie; Kriegh, Lisa; Chen, Cong; Terrell, LeKeith B.; Qureshi, Ammar T.; Todd Monroe, W.; Gimble, Jeffrey M.; Hayes, Daniel J.

2015-04-01

Interest has grown in the use of microparticles and nanoparticles for modifying the mechanical and biological properties of synthetic bone composite structures. Micro- and nano-sized calcium phosphates are of interest for their osteoinductive behavior. Engineered composites incorporating polymers and ceramics, such as poly-l-lactic acid (PLLA) and beta-tricalcium phosphate (β-TCP), for bone tissue regeneration have been well investigated for their proliferative and osteoinductive abilities. Only limited research has been done to investigate the effects of different sizes of β-TCP particles on human mesenchymal stromal cell behavior. As such, the aim of this study was to investigate the modulations of human adipose-derived stem cell (hASCs) behavior within cell/particle and cell/composite systems as functions of particle size, concentration, and exposure time. The incorporation of nanoscale calcium phosphate resulted in improved mechanical properties and osteogenic behavior within the scaffold compared to the microscale calcium phosphate additives. Particle exposure results indicate that cytotoxicity on hASCs correlates inversely with particle size and increases with the increasing exposure time and particle concentration. Composites with increasing β-TCP content, whether microparticles or nanoparticles, were less toxic than colloidal micro- and nano-sized β-TCP particles directly supplied to hASCs. The difference in viability observed as a result of varying exposure route is likely related to the increased cell-particle interactions in the direct exposure compared to the particles becoming trapped within the scaffold/polymer matrix.

Spherical composite particles of rice starch and microcrystalline cellulose: a new coprocessed excipient for direct compression.

PubMed

Limwong, Vasinee; Sutanthavibul, Narueporn; Kulvanich, Poj

2004-03-12

Composite particles of rice starch (RS) and microcrystalline cellulose were fabricated by spray-drying technique to be used as a directly compressible excipient. Two size fractions of microcrystalline cellulose, sieved (MCS) and jet milled (MCJ), having volumetric mean diameter (D50) of 13.61 and 40.51 microm, respectively, were used to form composite particles with RS in various mixing ratios. The composite particles produced were evaluated for their powder and compression properties. Although an increase in the microcrystalline cellulose proportion imparted greater compressibility of the composite particles, the shape of the particles was typically less spherical with rougher surface resulting in a decrease in the degree of flowability. Compressibility of composite particles made from different size fractions of microcrystalline cellulose was not different; however, using MCJ, which had a particle size range close to the size of RS (D50 = 13.57 microm), provided more spherical particles than using MCS. Spherical composite particles between RS and MCJ in the ratio of 7:3 (RS-MCJ-73) were then evaluated for powder properties and compressibility in comparison with some marketed directly compressible diluents. Compressibility of RS-MCJ-73 was greater than commercial spray-dried RS (Eratab), coprocessed lactose and microcrystalline cellulose (Cellactose), and agglomerated lactose (Tablettose), but, as expected, lower than microcrystalline cellulose (Vivapur 101). Flowability index of RS-MCJ-73 appeared to be slightly lower than Eratab but higher than Vivapur 101, Cellactose, and Tablettose. Tablets of RS-MCJ-73 exhibited low friability and good self-disintegrating property. It was concluded that these developed composite particles could be introduced as a new coprocessed direct compression excipient.

Control of particle size by feed composition in the nanolatexes produced via monomer-starved semicontinuous emulsion copolymerization.

PubMed

Sajjadi, Shahriar

2015-05-01

Conventional batch and semicontinuous emulsion copolymerizations often produce large particles whose size cannot be easily correlated with the comonomer feed compositions, and are to some degree susceptible to composition drift. In contrast, we found that copolymer nanolatexes made via semicontinuous monomer-starved emulsion copolymerizations are featured with an average nanoparticle size being controlled by the feed composition, a high conversion achieved, and a high degree of particle composition uniformity. This was achieved because the rate of particle growth, during nucleation, was controlled by the rate of comonomer addition, and the copolymer composition, surfactant parking area on the particles, and nucleation efficiency determined by the comonomer feed composition. Two model systems, methyl methacrylate/styrene and vinyl acetate/butyl acrylate, with significant differences in water solubility were studied. Monomers were added to the aqueous solution of sodium dodecylsulfate and potassium persulfate at a low rate to achieve high instantaneous conversions. Copyright © 2015 Elsevier Inc. All rights reserved.

Size-segregated compositional analysis of aerosol particles collected in the European Arctic during the ACCACIA campaign

NASA Astrophysics Data System (ADS)

Young, G.; Jones, H. M.; Darbyshire, E.; Baustian, K. J.; McQuaid, J. B.; Bower, K. N.; Connolly, P. J.; Gallagher, M. W.; Choularton, T. W.

2016-03-01

Single-particle compositional analysis of filter samples collected on board the Facility for Airborne Atmospheric Measurements (FAAM) BAe-146 aircraft is presented for six flights during the springtime Aerosol-Cloud Coupling and Climate Interactions in the Arctic (ACCACIA) campaign (March-April 2013). Scanning electron microscopy was utilised to derive size-segregated particle compositions and size distributions, and these were compared to corresponding data from wing-mounted optical particle counters. Reasonable agreement between the calculated number size distributions was found. Significant variability in composition was observed, with differing external and internal mixing identified, between air mass trajectory cases based on HYbrid Single-Particle Lagrangian Integrated Trajectory (HYSPLIT) analyses. Dominant particle classes were silicate-based dusts and sea salts, with particles notably rich in K and Ca detected in one case. Source regions varied from the Arctic Ocean and Greenland through to northern Russia and the European continent. Good agreement between the back trajectories was mirrored by comparable compositional trends between samples. Silicate dusts were identified in all cases, and the elemental composition of the dust was consistent for all samples except one. It is hypothesised that long-range, high-altitude transport was primarily responsible for this dust, with likely sources including the Asian arid regions.

Airborne single particle mass spectrometers (SPLAT II & miniSPLAT) and new software for data visualization and analysis in a geo-spatial context.

PubMed

Zelenyuk, Alla; Imre, Dan; Wilson, Jacqueline; Zhang, Zhiyuan; Wang, Jun; Mueller, Klaus

2015-02-01

Understanding the effect of aerosols on climate requires knowledge of the size and chemical composition of individual aerosol particles-two fundamental properties that determine an aerosol's optical properties and ability to serve as cloud condensation or ice nuclei. Here we present our aircraft-compatible single particle mass spectrometers, SPLAT II and its new, miniaturized version, miniSPLAT that measure in-situ and in real-time the size and chemical composition of individual aerosol particles with extremely high sensitivity, temporal resolution, and sizing precision on the order of a monolayer. Although miniSPLAT's size, weight, and power consumption are significantly smaller, its performance is on par with SPLAT II. Both instruments operate in dual data acquisition mode to measure, in addition to single particle size and composition, particle number concentrations, size distributions, density, and asphericity with high temporal resolution. We also present ND-Scope, our newly developed interactive visual analytics software package. ND-Scope is designed to explore and visualize the vast amount of complex, multidimensional data acquired by our single particle mass spectrometers, along with other aerosol and cloud characterization instruments on-board aircraft. We demonstrate that ND-Scope makes it possible to visualize the relationships between different observables and to view the data in a geo-spatial context, using the interactive and fully coupled Google Earth and Parallel Coordinates displays. Here we illustrate the utility of ND-Scope to visualize the spatial distribution of atmospheric particles of different compositions, and explore the relationship between individual particle compositions and their activity as cloud condensation nuclei.

Improving Dielectric Properties of PVDF Composites by Employing Surface Modified Strong Polarized BaTiO₃ Particles Derived by Molten Salt Method.

PubMed

Fu, Jing; Hou, Yudong; Zheng, Mupeng; Wei, Qiaoyi; Zhu, Mankang; Yan, Hui

2015-11-11

BaTiO3/polyvinylidene fluoride (BT/PVDF) is the extensive reported composite material for application in modern electric devices. However, there still exists some obstacles prohibiting the further improvement of dielectric performance, such as poor interfacial compatibility and low dielectric constant. Therefore, in depth study of the size dependent polarization and surface modification of BT particle is of technological importance in developing high performance BT/PVDF composites. Here, a facile molten-salt synthetic method has been applied to prepare different grain sized BT particles through tailoring the calcination temperature. The size dependent spontaneous polarizationof BT particle was thoroughly investigated by theoretical calculation based on powder X-ray diffraction Rietveld refinement data. The results revealed that 600 nm sized BT particles possess the strong polarization, ascribing to the ferroelectric size effect. Furthermore, the surface of optimal BT particles has been modified by water-soluble polyvinylprrolidone (PVP) agent, and the coated particles exhibited fine core-shell structure and homogeneous dispersion in the PVDF matrix. The dielectric constant of the resulted composites increased significantly, especially, the prepared composite with 40 vol % BT loading exhibited the largest dielectric constant (65, 25 °C, 1 kHz) compared with the literature values of BT/PVDF at the same concentration of filler. Moreover, the energy storage density of the composites with tailored structure was largely enhanced at the low electric field, showing promising application as dielectric material in energy storage device. Our work suggested that introduction of strong polarized ferroelectric particles with optimal size and construction of core-shell structured coated fillers by PVP in the PVDF matrix are efficacious in improving dielectric performance of composites. The demonstrated approach can also be applied to the design and preparation of other polymers-based nanocomposites filled with ferroelectric particles to achieve desirable dielectric properties.

Effect of particle size and percentages of Boron carbide on the thermal neutron radiation shielding properties of HDPE/B4C composite: Experimental and simulation studies

NASA Astrophysics Data System (ADS)

Soltani, Zahra; Beigzadeh, Amirmohammad; Ziaie, Farhood; Asadi, Eskandar

2016-10-01

In this paper the effects of particle size and weight percentage of the reinforcement phase on the absorption ability of thermal neutron by HDPE/B4C composites were investigated by means of Monte-Carlo simulation method using MCNP code and experimental studies. The composite samples were prepared using the HDPE filled with different weight percentages of Boron carbide powder in the form of micro and nano particles. Micro and nano composite were prepared under the similar mixing and moulding processes. The samples were subjected to thermal neutron radiation. Neutron shielding efficiency in terms of the neutron transmission fractions of the composite samples were investigated and compared with simulation results. According to the simulation results, the particle size of the radiation shielding material has an important role on the shielding efficiency. By decreasing the particle size of shielding material in each weight percentages of the reinforcement phase, better radiation shielding properties were obtained. It seems that, decreasing the particle size and homogeneous distribution of nano forms of B4C particles, cause to increase the collision probability between the incident thermal neutron and the shielding material which consequently improve the radiation shielding properties. So, this result, propose the feasibility of nano composite as shielding material to have a high performance shielding characteristic, low weight and low thick shielding along with economical benefit.

REAL-TIME MEASUREMENTS OF THE CHEMICAL COMPOSITION OF SIZE-RESOLVED PARTICLES DURING A SANTA ANA WIND EPISODE, CALIFORNIA USA. (R826240)

EPA Science Inventory

Size-resolved particle composition, mass and number concentrations, aerosol scattering coefficients, and prevailing meteorological conditions were measured at the Ellen Browning Scripps Memorial Pier located in La Jolla, California on 15 December 1998. Aerosol particles were s...

Facile and rapid one-pot microwave-assisted synthesis of Pd-Ni magnetic nanoalloys confined in mesoporous carbons

NASA Astrophysics Data System (ADS)

Martínez de Yuso, Alicia; Le Meins, Jean-Marc; Oumellal, Yassine; Paul-Boncour, Valérie; Zlotea, Claudia; Matei Ghimbeu, Camelia

2016-12-01

An easy and rapid one-pot microwave-assisted soft-template synthesis method for the preparation of Pd-Ni nanoalloys confined in mesoporous carbon is reported. This approach allows the formation of mesoporous carbon and the growth of the particles at the same time, under short microwave irradiation (4 h) compared to the several days spent for the classical approach. In addition, the synthesis steps are diminished and no thermopolymerization step or reduction treatment being required. The influence of the Pd-Ni composition on the particle size and on the carbon characteristics was investigated. Pd-Ni solid solutions in the whole composition range could be obtained, and the metallic composition proved to have an important effect on the nanoparticle size but low influence on carbon textural properties. Small and uniformly distributed nanoparticles were confined in mesoporous carbon with uniform pore size distribution, and dependence between the nanoparticle size and the nanoalloy composition was observed, i.e., increase of the particle size with increasing the Ni content (from 5 to 14 nm). The magnetic properties of the materials showed a strong nanoparticle size and/or composition effect. The blocking temperature of Pd-Ni nanoalloys increases with the increase of Ni amount and therefore of particle size. The magnetization values are smaller than the bulk counterpart particularly for the Ni-rich compositions due to the formed graphitic shells surrounding the particles inducing a dead magnetic layer.

Airborne Single Particle Mass Spectrometers (SPLAT II & miniSPLAT) and New Software for Data Visualization and Analysis in a Geo-Spatial Context

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zelenyuk, Alla; Imre, D.; Wilson, Jacqueline M.

2015-02-01

Understanding the effect of aerosols on climate requires knowledge of the size and chemical composition of individual aerosol particles - two fundamental properties that determine an aerosol’s optical properties and ability to serve as cloud condensation or ice nuclei. Here we present miniSPLAT, our new aircraft compatible single particle mass spectrometer, that measures in-situ and in real-time size and chemical composition of individual aerosol particles with extremely high sensitivity, temporal resolution, and sizing precision on the order of a monolayer. miniSPLAT operates in dual data acquisition mode to measure, in addition to single particle size and composition, particle number concentrations,more » size distributions, density, and asphericity with high temporal resolution. When compared to our previous instrument, SPLAT II, miniSPLAT has been significantly reduced in size, weight, and power consumption without loss in performance. We also present ND-Scope, our newly developed interactive visual analytics software package. ND-Scope is designed to explore and visualize the vast amount of complex, multidimensional data acquired by our single particle mass spectrometers, along with other aerosol and cloud characterization instruments on-board aircraft. We demonstrate that ND-Scope makes it possible to visualize the relationships between different observables and to view the data in a geo-spatial context, using the interactive and fully coupled Google Earth and Parallel Coordinates displays. Here we illustrate the utility of ND-Scope to visualize the spatial distribution of atmospheric particles of different compositions, and explore the relationship between individual particle composition and their activity as cloud condensation nuclei.« less

Effect of crumb-rubber particle size on mechanical response of polyurethane foam composites

NASA Astrophysics Data System (ADS)

Sanjay, Omer Sheik

The compression properties of foam are governed by by three factors: i) cell edge bending ii) compression of cell fluid iii) membrane stresses in the cell faces. The effect of reinforcement, granular form of scrap tire rubber on contribution of each of these effects along with the physical properties of polyurethane foam is investigated. It is seen that the addition of crumb-rubber hinders the formation of cell membranes during the foaming process. Four different sizes of particles were chosen to closely study the effect of particle size on the physical properties of the foam composite. There is a definite pattern seen in each of the physical property of the composite with change in the particle size. Addition of crumb-rubber decreases the compressive strength but in turn increases the elastic modulus of the composite. The rubber particles act as the sites for stress concentration and hence the inclusion of rubber particles induces the capability to transfer the axial load laterally along the surface of the foam. Also, the filler material induces porosity into the foam, which is seen in the SEM images, and hence the addition of rubber particles induces brittleness, which makes the foam composites extensively applicable for structural application in sandwich components. The lightweight composite therefore is a potential substitute to the heavier metal foams and honeycombs as a protective layer.

Effects of ultrasonic vibration on microstructure and mechanical properties of nano-sized SiC particles reinforced Al-5Cu composites.

PubMed

Li, Jianyu; Lü, Shulin; Wu, Shusen; Gao, Qi

2018-04-01

Ultrasonic vibration (UV) treatment has been successfully applied to improve the particles distribution of nano-sized SiC particles (SiC p ) reinforced Al-5Cu alloy matrix composites which were prepared by combined processes of dry high energy ball milling and squeeze casting. When UV treatment is applied, the distribution of nano-sized SiC p has been greatly improved. After UV for 1 min, large particles aggregates are broken up into small aggregates due to effects of cavitation and the acoustic streaming. After UV for 5 min, all the particles aggregates are dispersed and the particles are uniformly distributed in the composites. Compared with the Al-5Cu matrix alloy, the ultimate tensile strength, yield strength and elongation of the 1 wt% nano-sized SiC p /Al-5Cu composites treated by UV for 5 min are 270 MPa, 173 MPa and 13.3%, which are increased by 7.6%, 6.8% and 29%, respectively. The improvements of mechanical properties after UV are attributed to the uniform distribution of nano particles, grain refinement of aluminum matrix alloy and reduction of porosity in the composites. Copyright © 2017 Elsevier B.V. All rights reserved.

Ion transport studies on Pb(NO3)2:Al2O3 composite solid electrolytes: Effect of dispersoid particle size

NASA Astrophysics Data System (ADS)

Reddy, Y. Govinda; Sekhar, M. Chandra; Sadananda Chary, A.; Narender Reddy, S.

2018-02-01

Composites of Alumina dispersed Lead Nitrate of different particles sizes (0.3µm, 36.9µm) were prepared through mechanical mixing process. These composites have been characterized by using XRD and SEM. Transport properties of these systems have been studied by means of impedance spectroscopy in the frequency range 100Hz to 4MHz in the temperature range from room temperature to 300°C. Temperature dependent conductivity spectra for composites with different mole percentages of alumina and with different particle sizes (0.3µm, 36.9µm) studied. The contact surface area between host and dispersoid increases with the decrease in particle size. These studies indicate that the conductivity in these systems is mainly due to the contribution enhanced concentration of mobile ions at the interfacial regions of host and dispersoid materials and increased mobility of charge carriers along the grain boundaries. It is believed that mechanism of conductivity through anti-Frenkel disorder (NO3 - ions) in these composites.

Size-resolved ultrafine particle composition analysis 1. Atlanta

NASA Astrophysics Data System (ADS)

Rhoads, K. P.; Phares, D. J.; Wexler, A. S.; Johnston, M. V.

2003-04-01

During August 1999 as part of the Southern Oxidants Study Supersite Experiment, our group collected size-resolved measurements of the chemical composition of single ambient aerosol particles with a unique real-time laser desorption/ionization mass spectrometry technique. The rapid single-particle mass spectrometry instrument is capable of analyzing "ultrafine" particles with aerodynamic diameters ranging from 0.01 to 1.5 μm. Under the heaviest loading observed in Atlanta, particles were analyzed at a rate of roughly one per second in sizes ranging from 0.1 to 0.2 μm. Nearly 16,000 individual spectra were recorded over the course of the month during both daytime and nighttime sampling periods. Evaluation of the data indicates that the composition of the ultrafine (less than 100 nm) particles is dominated by carbon-containing compounds. Larger particles show varied compositions but typically appeared to have organic carbon characteristics mixed with an inorganic component (e.g., crustal materials, metals, etc.). During the experiment, 70 composition classes were identified. In this paper we report the average spectra and correlations with various meteorological parameters for all major compound classes and a number of minor ones. The major composition classes are identified from the primary peaks in their spectra as organic carbon (about 74% of the particles), potassium (8%), iron (3%), calcium (2%), nitrate (2%), elemental carbon (1.5%), and sodium (1%). Many of these compound classes appeared in repeatable size ranges and quadrants of the wind rose, indicating emission from specific sources.

Study on effective thermal conductivity of silicone/phosphor composite and its size effect by Lattice Boltzmann method

NASA Astrophysics Data System (ADS)

Li, Lan; Zheng, Huai; Yuan, Chao; Hu, Run; Luo, Xiaobing

2016-12-01

The silicone/phosphor composite is widely used in light emitting diode (LED) packaging. The composite thermal properties, especially the effective thermal conductivity, strongly influence the LED performance. In this paper, a lattice Boltzmann model was presented to predict the silicone/phosphor composite effective thermal conductivity. Based on the present lattice Boltzmann model, a random generation method was established to describe the phosphor particle distribution in composite. Benchmarks were conducted by comparing the simulation results with theoretical solutions for simple cases. Then the model was applied to analyze the effective thermal conductivity of the silicone/phosphor composite and its size effect. The deviations between simulation and experimental results are <7 %, when the phosphor volume fraction varies from 0.038 to 0.45. The simulation results also indicate that effective thermal conductivity of the composite with larger particles is higher than that with small particles at the same volume fraction. While mixing these two sizes of phosphor particles provides an extra enhancement for the effective thermal conductivity.

Evaluation of particles released from single-wall carbon nanotube/polymer composites with or without thermal aging by an accelerated abrasion test.

PubMed

Jiang, Lin; Kondo, Akira; Shigeta, Masahiro; Endoh, Shigehisa; Uejima, Mitsugu; Ogura, Isamu; Naito, Makio

2014-01-01

To provide data required for assessing the environmental health and safety risks of nanocomposites, abrasion-induced particle release from single-wall carbon nanotube (SWCNT)/polymer composites with or without thermal aging were evaluated by a shot blast system. First, overall composite weight loss (i.e., overall particle release) as a result of shot blasting was measured. Incorporating 5 wt% SWCNTs in polystyrene (PS) matrix was observed to reduce overall particle release by approximately 30% compared with pure PS. Heat treatment of the 5 wt% SWCNT/PS composites at 100°C for 10 days induced very slight change in overall particle release due to shot blasting. However, heat treatment at 350°C for 1 hr greatly deteriorated the abrasion resistance of the composites, enhancing overall particle release. Second, to verify the existence and form of SWCNTs released from the composites, released particles were observed by electron microscopy. Micron-sized particles with protruding SWCNTs and submicron-sized SWCNT clusters were observed in the particles released from the composites. Heat treatment of the composites at 350°C for 1 hr enhanced SWCNT release, which mainly formed clusters or rope-like bundles.

Size and composition distribution of fine particulate matter emitted from wood burning, meat charbroiling, and cigarettes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kleeman, M.J.; Schauer, J.J.; Cass, G.R.

A dilution source sampling system is augmented to measure the size-distributed chemical composition of fine particle emissions from air pollution sources. Measurements are made using a laser optical particle counter (OPC), a differential mobility analyzer/condensation nucleus counter (DMA/CNC) combination, and a pair of microorifice uniform deposit impactors (MOUDIs). The sources tested with this system include wood smoke (pine, oak, eucalyptus), meat charbroiling, and cigarettes. The particle mass distributions from all wood smoke sources have a single mode that peaks at approximately 0.1--0.2 {micro}m particle diameter. The smoke from meat charbroiling shows a major peak in the particle mass distribution atmore » 0.1--0.2 {micro}m particle diameter, with some material present at larger particle sizes. Particle mass distributions from cigarettes peak between 0.3 and 0.4 {micro}m particle diameter. Chemical composition analysis reveals that particles emitted from the sources tested here are largely composed of organic compounds. Noticeable concentrations of elemental carbon are found in the particles emitted from wood burning. The size distributions of the trace species emissions from these sources also are presented, including data for Na, K, Ti, Fe, Br, Ru, Cl, Al, Zn, Ba, Sr, V, Mn, Sb, La, Ce, as well as sulfate, nitrate, and ammonium ion when present in statistically significant amounts. These data are intended for use with air quality models that seek to predict the size distribution of the chemical composition of atmospheric fine particles.« less

WOOD STOVE EMISSIONS: PARTICLE SIZE AND CHEMICAL COMPOSITION

EPA Science Inventory

The report summarizes wood stove particle size and chemical composition data gathered to date. [NOTE: In 1995, EPA estimated that residential wood combustion (RWC), including fireplaces, accounted for a significant fraction of national particulate matter with aerodynamic diameter...

Effects of Particle Size and Porosity on In Vivo Remodeling of Settable Allograft Bone/Polymer Composites

PubMed Central

Prieto, Edna M.; Talley, Anne D.; Gould, Nicholas R.; Zienkiewicz, Katarzyna J.; Drapeau, Susan J.; Kalpakci, Kerem N.

2014-01-01

Established clinical approaches to treat bone voids include the implantation of autograft or allograft bone, ceramics, and other bone void fillers (BVFs). Composites prepared from lysine-derived polyurethanes and allograft bone can be injected as a reactive liquid and set to yield BVFs with mechanical strength comparable to trabecular bone. In this study, we investigated the effects of porosity, allograft particle size, and matrix mineralization on remodeling of injectable and settable allograft/polymer composites in a rabbit femoral condyle plug defect model. Both low viscosity (LV) and high viscosity (HV) grafts incorporating small (<105 μm) particles only partially healed at 12 weeks, and the addition of 10% demineralized bone matrix did not enhance healing. In contrast, composite grafts with large (105 – 500 μm) allograft particles healed at 12 weeks post-implantation, as evidenced by radial μCT and histomorphometric analysis. This study highlights particle size and surface connectivity as influential parameters regulating the remodeling of composite bone scaffolds. PMID:25581686

Evaluation of the Community Multiscale Air Quality (CMAQ) modeling system against size-resolved measurements of inorganic particle composition across sites in North America

EPA Science Inventory

This work evaluates particle size-composition distributions simulated by the Community Multiscale Air Quality (CMAQ) model using Micro-Orifice Uniform Deposit Impactor (MOUDI) measurements at 18 sites across North America. Size-resolved measurements of particulate SO₄<...

In-situ heating TEM observation of microscopic structural changes of size-controlled metallic copper/gelatin composite.

PubMed

Narushima, Takashi; Hyono, Atsushi; Nishida, Naoki; Yonezawa, Tetsu

2012-10-01

Copper/gelatin composite particles with controlled sizes were prepared at room temperature from cupric sulfate pentahydrate in the presence of gelatin as a protective reagent by using hydrazine monohydrate as a reducing agent. The formed particles with the size between 190-940 nm were secondary aggregated particles which were composed of smaller nanosized particles ("particle-in-particle"), the presence of which was established by XRD patterns and a cross-sectional TEM image. The sintering behavior of these copper/gelatin composite particles was demonstrated by in-situ heating TEM under a high vacuum (approximately 10(-5) Pa) and separately with the oxygen partial pressure controlled at the 10(-4) Pa level. It was established that the particles began to sinter at about 330 degrees C with the oxygen and that they sublimate above 450 degrees C both in the vacuum and oxygen conditions. This result shows that the introduction of an adequate amount of oxygen was effective to remove the gelatin surrounding the particles. It can also be concluded that the sintering of the copper/gelatin composite particles occurred even in the absence of a reducing agent such as hydrogen gas.

Composition for forming an optically transparent, superhydrophobic coating

DOEpatents

Simpson, John T.; Lewis, Linda A.

2015-12-29

A composition for producing an optically clear, well bonded superhydrophobic coating includes a plurality of hydrophobic particles comprising an average particle size of about 200 nm or less, a binder at a binder concentration of from about 0.1 wt. % to about 0.5 wt. %, and a solvent. The hydrophobic particles may be present in the composition at a particle concentration of from about 0.1 wt. % to about 1 wt. %. An optically transparent, superhydrophobic surface includes a substrate, a plurality of hydrophobic particles having an average particle size of about 200 nm or less dispersed over the substrate, and a discontinuous binder layer bonding the hydrophobic particles to the substrate, where the hydrophobic particles and the binder layer form an optically transparent, superhydrophobic coating.

Exploring the variability of aerosol particle composition in the Arctic: a study from the springtime ACCACIA campaign

NASA Astrophysics Data System (ADS)

Young, G.; Jones, H. M.; Darbyshire, E.; Baustian, K. J.; McQuaid, J. B.; Bower, K. N.; Connolly, P. J.; Gallagher, M. W.; Choularton, T. W.

2015-10-01

Single-particle compositional analysis of filter samples collected on-board the FAAM BAe-146 aircraft is presented for six flights during the springtime Aerosol-Cloud Coupling and Climate Interactions in the Arctic (ACCACIA) campaign (March-April 2013). Scanning electron microscopy was utilised to derive size distributions and size-segregated particle compositions. These data were compared to corresponding data from wing-mounted optical particle counters and reasonable agreement between the calculated number size distributions was found. Significant variability in composition was observed, with differing external and internal mixing identified, between air mass trajectory cases based on HYSPLIT analyses. Dominant particle classes were silicate-based dusts and sea salts, with particles notably rich in K and Ca detected in one case. Source regions varied from the Arctic Ocean and Greenland through to northern Russia and the European continent. Good agreement between the back trajectories was mirrored by comparable compositional trends between samples. Silicate dusts were identified in all cases, and the elemental composition of the dust was consistent for all samples except one. It is hypothesised that long-range, high-altitude transport was primarily responsible for this dust, with likely sources including the Asian arid regions.

Mechanical Properties of Mg2Si/Mg Composites via Powder Metallurgy Process

NASA Astrophysics Data System (ADS)

Muramatsu, Hiroshi; Kondoh, Katsuyoshi; Yuasa, Eiji; Aizawa, Tatsuhiko

The mechanical properties of the Mg2Si/Mg composites solid-state synthesized from the mixed Mg-Si powders have been investigated. The macro-hardness (HRE) and the tensile strength of the composites increase with increasing the Si content and decreasing the Si size. The particle size of the synthesized Mg2Si depends on the initial Si size; the mechanical properties of the Mg2Si/Mg composite are remarkably improved by using fine Si particles or by decreasing the grain size of Mg matrix grains when the powder mixture was prepared via bulk mechanical alloying process.

Structural composition of organic matter in particle-size fractions of soils along a climo-biosequence in the main range of Peninsular Malaysia

NASA Astrophysics Data System (ADS)

Jafarzadeh-Haghighi, Amir Hossein; Shamshuddin, Jusop; Hamdan, Jol; Zainuddin, Norhazlin

2016-09-01

Information on structural composition of organic matter (OM) in particle-size fractions of soils along a climo-biosequence is sparse. The objective of this study was to examine structural composition and morphological characteristics of OM in particle-size fractions of soils along a climo-biosequence in order to better understand the factors and processes affecting structural composition of soil organic matter. To explore changes in structural composition of OM in soils with different pedogenesis, the A-horizon was considered for further analyses including particle-size fractionation, solid-state 13C nuclear magnetic resonance (NMR) spectroscopy and scanning electron microscopy (SEM). Due to the increase in the thickness of organic layer with increasing elevation, the A-horizon was situated at greater depth in soils of higher elevation. The relationship between relative abundances of carbon (C) structures and particle-size fractions was examined using principal component analysis (PCA). It was found that alkyl C (20.1-73.4%) and O-alkyl C (16.8-67.7%) dominated particle-size fractions. The proportion of alkyl C increased with increasing elevation, while O-alkyl C showed an opposite trend. Results of PCA confirmed this finding and showed the relative enrichment of alkyl C in soils of higher elevation. Increase in the proportion of alkyl C in 250-2000 μm fraction is linked to selective preservation of aliphatic compounds derived from root litter. SEM results showed an increase in root contribution to the 250-2000 μm fraction with increasing elevation. For the <53 μm fraction, pedogenic process of podzolization is responsible for the relative enrichment of alkyl C. This study demonstrates that changes in structural composition of OM in particle-size fractions of soils along the studied climo-biosequence are attributed to site-specific differences in pedogenesis as a function of climate and vegetation.

Evaluation of micron-sized wood and bark particles as filler in thermoplastic composites

Treesearch

David P. Harper; Thomas L. Eberhardt

2010-01-01

Micron-sized particles, prepared from loblolly pine (Pinus taeda L.) wood and bark, were evaluated for use in wood-plastic composites (WPCs). Particles were also prepared from hard (periderm) and soft (obliterated phloem) components in the bark and compared to whole wood (without bark) filler commonly used by the WPC industry. All bark fillers had...

Solid oxide fuel cell cathode infiltrate particle size control and oxygen surface exchange resistance determination

NASA Astrophysics Data System (ADS)

Burye, Theodore E.

Over the past decade, nano-sized Mixed Ionic Electronic Conducting (MIEC) -- micro-sized Ionic Conducting (IC) composite cathodes produced by the infiltration method have received much attention in the literature due to their low polarization resistance (RP) at intermediate (500-700°C) operating temperatures. Small infiltrated MIEC oxide nano-particle size and low intrinsic MIEC oxygen surface exchange resistance (Rs) have been two critical factors allowing these Nano-Micro-Composite Cathodes (NMCCs) to achieve high performance and/or low temperature operation. Unfortunately, previous studies have not found a reliable method to control or reduce infiltrated nano-particle size. In addition, controversy exists on the best MIEC infiltrate composition because: 1) Rs measurements on infiltrated MIEC particles are presently unavailable in the literature, and 2) bulk and thin film Rs measurements on nominally identical MIEC compositions often vary by up to 3 orders of magnitude. Here, two processing techniques, precursor nitrate solution desiccation and ceria oxide pre-infiltration, were developed to systematically produce a reduction in the average La0.6Sr0.4Co0.8Fe 0.2O3-delta (LSCF) infiltrated nano-particle size from 50 nm to 22 nm. This particle size reduction reduced the SOFC operating temperature, (defined as the temperature where RP=0.1 Ocm 2) from 650°C to 540°C. In addition, Rs values for infiltrated MIEC particles were determined for the first time through finite element modeling calculations on 3D Focused Ion Beam-Scanning Electron Microscope (FIB-SEM) reconstructions of electrochemically characterized infiltrated electrodes.

Aerobiological Stabilities of Different Species of Gram-Negative Bacteria, Including Well-Known Biothreat Simulants, in Single-Cell Particles and Cell Clusters of Different Compositions

PubMed Central

Skogan, Gunnar

2017-01-01

ABSTRACT The ability to perform controlled experiments with bioaerosols is a fundamental enabler of many bioaerosol research disciplines. A practical alternative to using hazardous biothreat agents, e.g., for detection equipment development and testing, involves using appropriate model organisms (simulants). Several species of Gram-negative bacteria have been used or proposed as biothreat simulants. However, the appropriateness of different bacterial genera, species, and strains as simulants is still debated. Here, we report aerobiological stability characteristics of four species of Gram-negative bacteria (Pantoea agglomerans, Serratia marcescens, Escherichia coli, and Xanthomonas arboricola) in single-cell particles and cell clusters produced using four spray liquids (H2O, phosphate-buffered saline[PBS], spent culture medium[SCM], and a SCM-PBS mixture). E. coli showed higher stability in cell clusters from all spray liquids than the other species, but it showed similar or lower stability in single-cell particles. The overall stability was higher in cell clusters than in single-cell particles. The highest overall stability was observed for bioaerosols produced using SCM-containing spray liquids. A key finding was the observation that stability differences caused by particle size or compositional changes frequently followed species-specific patterns. The results highlight how even moderate changes to one experimental parameter, e.g., bacterial species, spray liquid, or particle size, can strongly affect the aerobiological stability of Gram-negative bacteria. Taken together, the results highlight the importance of careful and informed selection of Gram-negative bacterial biothreat simulants and also the accompanying particle size and composition. The outcome of this work contributes to improved selection of simulants, spray liquids, and particle size for use in bioaerosol research. IMPORTANCE The outcome of this work contributes to improved selection of simulants, spray liquids, and particle size for use in bioaerosol research. Taken together, the results highlight the importance of careful and informed selection of Gram-negative bacterial biothreat simulants and also the accompanying particle size and composition. The results highlight how even moderate changes to one experimental parameter, e.g., bacterial species, spray liquid, or particle size, can strongly affect the aerobiological stability of Gram-negative bacteria. A key finding was the observation that stability differences caused by particle size or compositional changes frequently followed species-specific patterns. PMID:28687646

Effect of iron particle size and volume fraction on the magnetic properties of Fe/silicate glass soft magnetic composites

NASA Astrophysics Data System (ADS)

Ding, Wei; Jiang, Longtao; Liao, Yaqin; Song, Jiabin; Li, Bingqing; Wu, Gaohui

2015-03-01

Fe/silicate glass soft magnetic composites (SMC) were fabricated by powder metallurgy with 1000 MPa pressure at room temperature, and then annealed at 700 °C for 90 min. The iron particles distributed uniformly in the composites, and have been separated from each other by a continuous silicate glass insulating layer. Fe/glass interface was well bonded and a quasi-continuous layer Fe3O4 and FeO exited. Very fine crystalline phases Na12Ca3Fe2(Si6O18)2 were formed in silicate glass. Composite containing 57 vol% 75 μm iron particles demonstrated highest resistivity of 7.8×10-3 Ω m. The μm, Bs and Bt increased while Hc of Fe/silicate glass composites decreased with the increase of average size of iron particles. The composite with highest amount (82 vol%) and largest average size (140 μm) of iron particles demonstrated best μm, Bs and Bt and Hc, which were 622, 1.57 T, 1.43 T, 278 A/m, respectively. The composite containing 57 vol% 75 μm iron particles demonstrated minimum core loss of 3.5 W/kg at 50 Hz and 28.1 W/kg at 400 Hz, while the composite containing 82 vol% 140 μm iron particles exhibited maximum core loss of 5.2 W/kg at 50 Hz and 67.7 W/kg at 400 Hz.

Small Particle Driven Chain Disentanglements in Polymer Nanocomposites

DOE Office of Scientific and Technical Information (OSTI.GOV)

Senses, Erkan; Ansar, Siyam M.; Kitchens, Christopher L.

2017-04-01

Using neutron spin-echo spectroscopy, X-ray photon correlation spectroscopy and bulk rheology, we studied the effect of particle size on the single chain dynamics, particle mobility, and bulk viscosity in athermal polyethylene oxide-gold nanoparticle composites. The results reveal an ≈ 25 % increase in the reptation tube diameter with addition of nanoparticles smaller than the entanglement mesh size (≈ 5 nm), at a volume fraction of 20 %. The tube diameter remains unchanged in the composite with larger (20 nm) nanoparticles at the same loading. In both cases, the Rouse dynamics is insensitive to particle size. These results provide a directmore » experimental observation of particle size driven disentanglements that can cause non-Einstein-like viscosity trends often observed in polymer nanocomposites.« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tuhkala, M., E-mail: mtuhkala@ee.oulu.fi; Maček, M.; Siponkoski, T.

Highlights: • Elongated micrometre sized BaTiO{sub 3} particles had strong effect on permittivity. • Effect was significantly stronger compared to μm and nm sized spherical particles. • Properties could be tailored by varying the particle shapes of dielectric powders. • Could be utilized, e.g., in a production of electrical composites for RF applications. - Abstract: The effect of BaTiO{sub 3} particle shape on the properties of 0.98MgTiO{sub 3}–0.02BaTiO{sub 3} composite powders was characterized and analyzed using an indirectly coupled open-ended coaxial cavity resonator at gigahertz frequencies. Elongated micrometre sized BaTiO{sub 3} particles were found to have a significantly stronger effectmore » on permittivity when compared to composite powders having micro and nano sized spherical BaTiO{sub 3} particles. Inclusion permittivities and dielectric loss tangents of composite powders increased from that of pure MgTiO{sub 3} powder, 13.3 and 4.6 × 10{sup −3}, up to 15.7 and 1.7 × 10{sup −2} with needle shaped BaTiO{sub 3} particles, respectively. The presented results give valuable information for tailoring the properties of dielectrics which can be utilized in the vast field of electronic component manufacturing.« less

Comprehensive Characterization Of Ultrafine Particulate Emission From 2007 Diesel Engines: PM Size Distribution, Loading And Indidividual Particle Size And Composition.

NASA Astrophysics Data System (ADS)

Zelenyuk, A.; Cuadra-Rodriguez, L. A.; Imre, D.; Shimpi, S.; Warey, A.

2006-12-01

The strong absorption of solar radiation by black carbon (BC) impacts the atmospheric radiative balance in a complex and significant manner. One of the most important sources of BC is vehicular emissions, of which diesel represents a significant fraction. To address this issue the EPA has issues new stringent regulations that will be in effect in 2007, limiting the amount of particulate mass that can be emitted by diesel engines. The new engines are equipped with aftertreatments that reduce PM emissions to the point, where filter measurements are subject to significant artifacts and characterization by other techniques presents new challenges. We will present the results of the multidisciplinary study conducted at the Cummins Technical Center in which a suite of instruments was deployed to yield comprehensive, temporally resolved information on the diesel exhaust particle loadings and properties in real-time: Particle size distributions were measured by Engine Exhaust Particle Sizer (EEPS) and Scanning Mobility Particle Sizer (SMPS). Total particle diameter concentration was obtained using Electrical Aerosol Detector (EAD). Laser Induced Incandescence and photoacoustic techniques were used to monitor the PM soot content. Single Particle Laser Ablation Time-of- flight Mass Spectrometer (SPLAT) provided the aerodynamic diameter and chemical composition of individual diesel exhaust particles. Measurements were conducted on a number of heavy duty diesel engines operated under variety of operating conditions, including FTP transient cycles, ramped-modal cycles and steady states runs. We have also characterized PM emissions during diesel particulate filter regeneration cycles. We will present a comparison of PM characteristics observed during identical cycles, but with and without the use of aftertreatment. A total of approximately 100,000 individual particles were sized and their composition characterized by SPLAT. The aerodynamic size distributions of the characterized particles were between 50 and 300 nm, depending on engine operating conditions and particle composition. We will show that while the drastically reduced diesel PM emissions often render the PM filter measurements inadequate due to organic vapor artifacts SPLAT demonstrated its capability to provide real-time information on size and composition of individual diesel exhaust particles as function of engine operating conditions with better than 1 minute resolution.

Composition of Metallic Elements and Size Distribution of Fine and Ultrafine Particles in a Steelmaking Factory.

PubMed

Marcias, Gabriele; Fostinelli, Jacopo; Catalani, Simona; Uras, Michele; Sanna, Andrea Maurizio; Avataneo, Giuseppe; De Palma, Giuseppe; Fabbri, Daniele; Paganelli, Matteo; Lecca, Luigi Isaia; Buonanno, Giorgio; Campagna, Marcello

2018-06-07

The characteristics of aerosol, in particular particle size and chemical composition, can have an impact on human health. Particle size distribution and chemical composition is a necessary parameter in occupational exposure assessment conducted in order to understand possible health effects. The aim of this study was to characterize workplace airborne particulate matter in a metallurgical setting by synergistically using two different approaches; Methodology: Analysis of inhalable fraction concentrations through traditional sampling equipment and ultrafine particles (UFP) concentrations and size distribution was conducted by an Electric Low-Pressure Impactor (ELPI+™). The determination of metallic elements (ME) in particles was carried out by inductively coupled plasma mass spectrometry; Results: Inhalable fraction and ME concentrations were below the limits set by Italian legislation and the American Conference of Governmental Industrial Hygienists (ACGIH, 2017). The median of UFP was between 4.00 × 10⁴ and 2.92 × 10⁵ particles/cm³. ME concentrations determined in the particles collected by ELPI show differences in size range distribution; Conclusions: The adopted synergistic approach enabled a qualitative and quantitative assessment of the particles in steelmaking factories. The results could lead to a better knowledge of occupational exposure characterization, in turn affording a better understanding of occupational health issues due to metal fumes exposure.

Experimental investigation of aerosol composition and growth rates

NASA Astrophysics Data System (ADS)

Wimmer, Daniela; Winkler, Paul; Kulmala, Markku; Petäjä, Tuukka

2017-04-01

Atmospheric aerosol particles have relevant influence on human lives. Human health is affected, as by breathing in the aerosol particles, they deposit in the lungs causing various health problems. Also they interfere indirectly and directly with sunlight, which affects the climate on Earth. Primary aerosol particles originate for example from anthropogenic sources, such as Diesel cars or natural sources such as dessert dust. Secondary aerosol particles are formed via condensation of low volatile gas phase compounds. First, small clusters consisting of a few gas molecules only are formed, which can then grow to bigger aerosol particles. These then form seeds for cloud droplets. The chemical composition of the cloud particles determines whether the cloud absorbs or scatters sunlight more. Intensive experimental and theoretical work has been put into understanding the details of the initial processes leading to the natural formation of these secondary aerosol particles. According to modelling studies, aerosol particles formed via the nucleation process are responsible for about 50% of the global cloud condensation nuclei concentration. With currently used methods, the chemical composition of small molecular clusters (up to 2nm in diameter) can be resolved. Also standard methods to determine aerosol particle composition at sizes >10 nm are available. Within this project, the aerosol particle composition in the 2-4 nm size range will be investigated experimentally. The setup will consist of a combination of an electrical method that allows determine the electrical mobility of the particles which then can be converted to a diameter. By letting the charged particles travel through a changing electrical field, they travel at different speeds according to their mobility. That allows to particles with certain mobilities, which then can be converted to a diameter. After the size selection, the particles are counted by means of optical detection. Condensation particle counters (CPCs) grow the particles internally, after which they are detected optically. By changing the condensing liquid, depending on the aerosol particle composition, they are activated differently. By combining the electrical size selection with CPCs with different liquids, information about particle composition can be determined. The project includes laboratory studies and field measurements in different locations (one rural site and two urban sites). I wish to acknowledge the Austrian Science Fund (FWF; Grant No J3951 - N36).

Structure analysis and size distribution of particulate matter from candles and kerosene combustion in burning chamber

NASA Astrophysics Data System (ADS)

Baitimirova, M.; Osite, A.; Katkevics, J.; Viksna, A.

2012-08-01

Burning of candles generates particulate matter of fine dimensions that produces poor indoor air quality, so it may cause harmful impact on human health. In this study solid aerosol particles of burning of candles of different composition and kerosene combustion were collected in a closed laboratory system. Present work describes particulate matter collection for structure analysis and the relationship between source and size distribution of particulate matter. The formation mechanism of particulate matter and their tendency to agglomerate also are described. Particles obtained from kerosene combustion have normal size distribution. Whereas, particles generated from the burning of stearin candles have distribution shifted towards finer particle size range. If an additive of stearin to paraffin candle is used, particle size distribution is also observed in range of towards finer particles. A tendency to form agglomerates in a short time is observed in case of particles obtained from kerosene combustion, while in case of particles obtained from burning of candles of different composition such a tendency is not observed. Particles from candles and kerosene combustion are Aitken and accumulation mode particles

[Preparation of ibuprofen/EC-PVP sustained-release composite particles by supercritical CO2 anti-solvent technology].

PubMed

Cai, Jin-Yuan; Huang, De-Chun; Wang, Zhi-Xiang; Dang, Bei-Lei; Wang, Qiu-Ling; Su, Xin-Guang

2012-06-01

Ibuprofen/ethyl-cellulose (EC)-polyvinylpyrrolidone (PVP) sustained-release composite particles were prepared by using supercritical CO2 anti-solvent technology. With drug loading as the main evaluation index, orthogonal experimental design was used to optimize the preparation process of EC-PVP/ibuprofen composite particles. The experiments such as encapsulation efficiency, particle size distribution, electron microscope analysis, infrared spectrum (IR), differential scanning calorimetry (DSC) and in vitro dissolution were used to analyze the optimal process combination. The orthogonal experimental optimization process conditions were set as follows: crystallization temperature 40 degrees C, crystallization pressure 12 MPa, PVP concentration 4 mgmL(-1), and CO2 velocity 3.5 Lmin(-1). Under the optimal conditions, the drug loading and encapsulation efficiency of ibuprofen/EC-PVP composite particles were 12.14% and 52.21%, and the average particle size of the particles was 27.621 microm. IR and DSC analysis showed that PVP might complex with EC. The experiments of in vitro dissolution showed that ibuprofen/EC-PVP composite particles had good sustained-release effect. Experiment results showed that, ibuprofen/EC-PVP sustained-release composite particles can be prepared by supercritical CO2 anti-solvent technology.

Particle size effect on strength, failure, and shock behavior in polytetrafluoroethylene-Al-W granular composite materials

NASA Astrophysics Data System (ADS)

Herbold, E. B.; Nesterenko, V. F.; Benson, D. J.; Cai, J.; Vecchio, K. S.; Jiang, F.; Addiss, J. W.; Walley, S. M.; Proud, W. G.

2008-11-01

The variation of metallic particle size and sample porosity significantly alters the dynamic mechanical properties of high density granular composite materials processed using a cold isostatically pressed mixture of polytetrafluoroethylene (PTFE), aluminum (Al), and tungsten (W) powders. Quasistatic and dynamic experiments are performed with identical constituent mass fractions with variations in the size of the W particles and pressing conditions. The relatively weak polymer matrix allows the strength and fracture modes of this material to be governed by the granular type behavior of agglomerated metal particles. A higher ultimate compressive strength was observed in relatively high porosity samples with small W particles compared to those with coarse W particles in all experiments. Mesoscale granular force chains of the metallic particles explain this unusual phenomenon as observed in hydrocode simulations of a drop-weight test. Macrocracks forming below the critical failure strain for the matrix and unusual behavior due to a competition between densification and fracture in dynamic tests of porous samples were also observed. Numerical modeling of shock loading of this granular composite material demonstrated that the internal energy, specifically thermal energy, of the soft PTFE matrix can be tailored by the W particle size distribution.

Facile Fabrication of 100% Bio-Based and Degradable Ternary Cellulose/PHBV/PLA Composites

PubMed Central

Wang, Jinwu

2018-01-01

Modifying bio-based degradable polymers such as polylactide (PLA) and poly(hydroxybutyrate-co-hydroxyvalerate) (PHBV) with non-degradable agents will compromise the 100% degradability of their resultant composites. This work developed a facile and solvent-free route in order to fabricate 100% bio-based and degradable ternary cellulose/PHBV/PLA composite materials. The effects of ball milling on the physicochemical properties of pulp cellulose fibers, and the ball-milled cellulose particles on the morphology and mechanical properties of PHBV/PLA blends, were investigated experimentally and statistically. The results showed that more ball-milling time resulted in a smaller particle size and lower crystallinity by way of mechanical disintegration. Filling PHBV/PLA blends with the ball-milled celluloses dramatically increased the stiffness at all of the levels of particle size and filling content, and improved their elongation at the break and fracture work at certain levels of particle size and filling content. It was also found that the high filling content of the ball-milled cellulose particles was detrimental to the mechanical properties for the resultant composite materials. The ternary cellulose/PHBV/PLA composite materials have some potential applications, such as in packaging materials and automobile inner decoration parts. Furthermore, filling content contributes more to the variations of their mechanical properties than particle size does. Statistical analysis combined with experimental tests provide a new pathway to quantitatively evaluate the effects of multiple variables on a specific property, and figure out the dominant one for the resultant composite materials. PMID:29495315

Application of close-packed structures in dental resin composites.

PubMed

Wang, Ruili; Habib, Eric; Zhu, X X

2017-03-01

The inorganic filler particles in dental resin composites serve to improve their mechanical properties and reduce polymerization shrinkage during their use. Efforts have been made in academia and industry to increase the filler particle content, but, few studies examine the theoretical basis for the maximum particle loading. This work evaluates the packing of spherical particles in a close-packed state for highly loaded composites. Calculations show that for low dispersity particles, the maximum amount of particles is 74.05vol%, regardless of the particle size. This can be further improved by using a mix of large and small particles or by the use of non-spherical particles. For representative spherical particles with a diameter of 1000nm, two types of secondary particles with respective sizes of 414nm (d I ) and 225nm (d II ) are selected. The results show that after embedding secondary particles I & II into primary spherical particles, the packing factor is increased to 81.19% for the close-packed structures, which shows an improvement of 9.64%, compared to the 74.05% obtained only with primary spherical particles. This packing factor is also higher than either structure with the embedded secondary particles I or II. Examples of these mixtures with different spherical particle sizes are shown as a theoretical estimation, serving as a guideline for the design and formulation of new dental resin composites with better properties and improved performance. Copyright © 2017 The Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

Tunable diode laser IR spectrometer for in situ measurements of the gas phase composition and particle size distribution of Titan's atmosphere

NASA Technical Reports Server (NTRS)

Webster, Christopher R.; Sander, Stanley P.; Beer, Reinhard; May, Randy D.; Knollenberg, Robert G.

1990-01-01

A new instrument, the Probe Infrared Laser Spectrometer (PIRLS), is described for in situ sensing of the gas composition and particle size distribution of Titan's atmosphere on the NASA/ESA Cassini mission. For gas composition measurements, several narrow-band (0.0001/cm) tunable lead-salt diode lasers operating near 80 K at selected mid-IR wavelengths are directed over a path length defined by a small reflector extending over the edge of the probe spacecraft platform; volume mixing ratios of 10 to the -9th should be measurable for several species of interest. A cloud-particle-size spectrometer using a diode laser source at 780 nm shares the optical path and deployed reflector; a combination of imaging and light scattering techniques is used to determine sizes of haze and cloud particles and their number density as a function of altitude.

Effect of milling methods on performance of Ni-Y 2O 3-stabilized ZrO 2 anode for solid oxide fuel cell

NASA Astrophysics Data System (ADS)

Cho, Hyoup Je; Choi, Gyeong Man

A Ni-YSZ (Y 2O 3-stabilized ZrO 2) composite is commonly used as a solid oxide fuel cell anode. The composite powders are usually synthesized by mixing NiO and YSZ powders. The particle size and distribution of the two phases generally determine the performance of the anode. Two different milling methods are used to prepare the composite anode powders, namely, high-energy milling and ball-milling that reduce the particle size. The particle size and the Ni distribution of the two composite powders are examined. The effects of milling on the performance are evaluated by using both an electrolyte-supported, symmetric Ni-YSZ/YSZ/Ni-YSZ cell and an anode-supported, asymmetric cell. The performance is examined at 800 °C by impedance analysis and current-voltage measurements. Pellets made by using high-energy milled NiO-YSZ powders have much smaller particle sizes and a more uniform distribution of Ni particles than pellets made from ball-milled powder, and thus the polarization resistance of the electrode is also smaller. The maximum power density of the anode-supported cell prepared by using the high-energy milled powder is ∼850 mW cm -2 at 800 °C compared with ∼500 mW cm -2 for the cell with ball-milled powder. Thus, high-energy milling is found to be more effective in reducing particle size and obtaining a uniform distribution of Ni particles.

Effect of process variables on the calorific value and compressive strength of the briquettes made from high moisture Empty Fruit Bunches (EFB)

NASA Astrophysics Data System (ADS)

Helwani, Z.; Fatra, W.; Arifin, L.; Othman, M. R.; Syapsan

2018-04-01

In this study, the manual hydraulic press was designed to prepare the briquettes from selected biomass waste. Each biomass was sun-dried and milled into small particle sizes before mixing with crude glycerol that used as a biomass binder. The effects of applied pressure levels of 100, 110, 120 bars, the particle size of 60, 80 and 100 mesh and the binder composition on the density, compressive strength and calorific heating value of the prepared briquettes were investigated using response surface methodology (RSM). Results showed that the briquettes have an average inside diameter, average outside diameter, and height of 12, 38, and 25-30 mm, respectively. The density of the briquettes increased with increasing the applied pressure, was in the range of 623-923 kg/m3. The densest briquettes were obtained at 80 mesh of particle size, 53:47 binder composition ratio and 110 bars of pressurizing. The heating value of the briquette reached up to 28.99 MJ/kg obtained on the particle size of 80 mesh, 53:47 binder composition, and 110 bars and the best compressive strength of 6.991 kg/cm2 obtained at a particle size of 100 mesh, 60:40 binder composition, and 120 bars. Process conditions influence the calorific value significantly.

The influences of ambient particle composition and size on particle infiltration in Los Angeles, CA, residences.

PubMed

Sarnat, Stefanie Ebelt; Coull, Brent A; Ruiz, Pablo A; Koutrakis, Petros; Suh, Helen H

2006-02-01

Particle infiltration is a key determinant of the indoor concentrations of ambient particles. Few studies have examined the influence of particle composition on infiltration, particularly in areas with high concentrations of volatile particles, such as ammonium nitrate (NH4NO3). A comprehensive indoor monitoring study was conducted in 17 Los Angeles-area homes. As part of this study, indoor/outdoor concentration ratios during overnight (nonindoor source) periods were used to estimate the fraction of ambient particles remaining airborne indoors, or the particle infiltration factor (FINF), for fine particles (PM2.5), its nonvolatile (i.e., black carbon [BC]) and volatile (i.e., nitrate [NO3-]) components, and particle sizes ranging between 0.02 and 10 microm. FINF was highest for BC (median = 0.84) and lowest for NO3- (median = 0.18). The low FINF for NO3- was likely because of volatilization of NO3- particles once indoors, in addition to depositional losses upon building entry. The FINF for PM2.5 (median = 0.48) fell between those for BC and NO3-, reflecting the contributions of both particle components to PM25. FINF varied with particle size, air-exchange rate, and outdoor NO3- concentrations. The FINF for particles between 0.7 and 2 microm in size was considerably lower during periods of high as compared with low outdoor NO3- concentrations, suggesting that outdoor NO3- particles were of this size. This study demonstrates that infiltration of PM2.5 varies by particle component and is lowest for volatile species, such as NH4NO3. Our results suggest that volatile particle components may influence the ability for outdoor PM concentrations to represent indoor and, thus, personal exposures to particles of ambient origin, because volatilization of these particles causes the composition of PM2.5 to differ indoors and outdoors. Consequently, particle composition likely influences observed epidemiologic relationships based on outdoor PM concentrations, especially in areas with high concentrations of NH4NO3 and other volatile particles.

Sensing/actuating materials made from carbon nanotube polymer composites and methods for making same

NASA Technical Reports Server (NTRS)

Ounaies, Zoubeida (Inventor); Park, Cheol (Inventor); Harrison, Joycelyn S. (Inventor); Holloway, Nancy M. (Inventor); Draughon, Gregory K. (Inventor)

2008-01-01

An electroactive sensing or actuating material comprises a composite made from a polymer with polarizable moieties and an effective amount of carbon nanotubes incorporated in the polymer for a predetermined electromechanical operation of the composite when such composite is affected by an external stimulus. In another embodiment, the composite comprises a third component of micro-sized to nano-sized particles of an electroactive ceramic that is also incorporated in the polymer matrix. The method for making the three-phase composite comprises either incorporating the carbon nanotubes in the polymer matrix before incorporation of the particles of ceramic or mixing the carbon nanotubes and particles of ceramic together in a solution before incorporation in the polymer matrix.

Method of Making an Electroactive Sensing/Actuating Material for Carbon Nanotube Polymer Composite

NASA Technical Reports Server (NTRS)

Ounaies, Zoubeida (Inventor); Park, Cheol (Inventor); Harrison, Joycelyn S. (Inventor); Holloway, Nancy M. (Inventor); Draughon, Gregory K. (Inventor)

2009-01-01

An electroactive sensing or actuating material comprises a composite made from a polymer with polarizable moieties and an effective amount of carbon nanotubes incorporated in the polymer for a predetermined electromechanical operation of the composite when such composite is affected by an external stimulus. In another embodiment, the composite comprises a, third component of micro -sized to nano-sized particles of an electroactive ceramic that is also incorporated in the polymer matrix. The method for making the three-phase composite comprises either incorporating the carbon nanotubes in the polymer matrix before incorporation of the particles of ceramic or mixing the carbon nanotubes and particles of ceramic together in a solution before incorporation in the polymer matrix.

Phospholipid lung surfactant and nanoparticle surface toxicity: Lessons from diesel soots and silicate dusts

NASA Astrophysics Data System (ADS)

Wallace, William E.; Keane, Michael J.; Murray, David K.; Chisholm, William P.; Maynard, Andrew D.; Ong, Tong-man

2007-01-01

Because of their small size, the specific surface areas of nanoparticulate materials (NP), described as particles having at least one dimension smaller than 100 nm, can be large compared with micrometer-sized respirable particles. This high specific surface area or nanostructural surface properties may affect NP toxicity in comparison with micrometer-sized respirable particles of the same overall composition. Respirable particles depositing on the deep lung surfaces of the respiratory bronchioles or alveoli will contact pulmonary surfactants in the surface hypophase. Diesel exhaust ultrafine particles and respirable silicate micrometer-sized insoluble particles can adsorb components of that surfactant onto the particle surfaces, conditioning the particles surfaces and affecting their in vitro expression of cytotoxicity or genotoxicity. Those effects can be particle surface composition-specific. Effects of particle surface conditioning by a primary component of phospholipid pulmonary surfactant, diacyl phosphatidyl choline, are reviewed for in vitro expression of genotoxicity by diesel exhaust particles and of cytotoxicity by respirable quartz and aluminosilicate kaolin clay particles. Those effects suggest methods and cautions for assaying and interpreting NP properties and biological activities.

Particle Size Influence on the Effective Permeability of Composite Materials

NASA Astrophysics Data System (ADS)

Xiang, Tai; Zhong, Ru-Neng; Yao, Bin; Qin, Shao-Jing; Zheng, Qin-Hong

2018-05-01

The energy method, which estimates the effective permeability of composite material is proposed. We approximate the effective static magnetic permeability by energy method and Maxwell-Garnett method for spherical particles dispersing system. Considering the effect of the interface layer between the medium and the particle, we study the nanoparticles embedded in a medium exactly. The interface layer property plays a significant factor for the effective permeability of the composite material in which nano-sized particles embedded. Supported by National Natural Science Foundation of Yunnan province under Grant No. 2014FB141 and National Natural Science Foundation under Grant No. 1121403 of China

Determination of the size and phase composition of silver nanoparticles in a gel film of bacterial cellulose by small-angle X-ray scattering, electron diffraction, and electron microscopy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Volkov, V. V.; Klechkovskaya, V. V., E-mail: klechvv@ns.crys.ras.ru; Shtykova, E. V.

2009-03-15

The nanoscale structural features in a composite (gel film of Acetobacter Xylinum cellulose with adsorbed silver nanoparticles, stabilized by N-polyvinylpyrrolidone) have been investigated by small-angle X-ray scattering. The size distributions of inhomogeneities in the porous structure of the cellulose matrix and the size distributions of silver nanoparticles in the composite have been determined. It is shown that the sizes of synthesized nanoparticles correlate with the sizes of inhomogeneities in the gel film. Particles of larger size (with radii up to 100 nm) have also been found. Electron microscopy of thin cross sections of a dried composite layer showed that largemore » particles are located on the cellulose layer surface. Electron diffraction revealed a crystal structure of silver nanoparticles in the composite.« less

Quantifying Grain-Size Variability of Metal Pollutants in Road-Deposited Sediments Using the Coefficient of Variation

PubMed Central

Wang, Xiaoxue; Li, Xuyong

2017-01-01

Particle grain size is an important indicator for the variability in physical characteristics and pollutants composition of road-deposited sediments (RDS). Quantitative assessment of the grain-size variability in RDS amount, metal concentration, metal load and GSFLoad is essential to elimination of the uncertainty it causes in estimation of RDS emission load and formulation of control strategies. In this study, grain-size variability was explored and quantified using the coefficient of variation (Cv) of the particle size compositions, metal concentrations, metal loads, and GSFLoad values in RDS. Several trends in grain-size variability of RDS were identified: (i) the medium class (105–450 µm) variability in terms of particle size composition, metal loads, and GSFLoad values in RDS was smaller than the fine (<105 µm) and coarse (450–2000 µm) class; (ii) The grain-size variability in terms of metal concentrations increased as the particle size increased, while the metal concentrations decreased; (iii) When compared to the Lorenz coefficient (Lc), the Cv was similarly effective at describing the grain-size variability, whereas it is simpler to calculate because it did not require the data to be pre-processed. The results of this study will facilitate identification of the uncertainty in modelling RDS caused by grain-size class variability. PMID:28788078

Fracture Toughness of Polypropylene-Based Particulate Composites

PubMed Central

Arencón, David; Velasco, José Ignacio

2009-01-01

The fracture behaviour of polymers is strongly affected by the addition of rigid particles. Several features of the particles have a decisive influence on the values of the fracture toughness: shape and size, chemical nature, surface nature, concentration by volume, and orientation. Among those of thermoplastic matrix, polypropylene (PP) composites are the most industrially employed for many different application fields. Here, a review on the fracture behaviour of PP-based particulate composites is carried out, considering the basic topics and experimental techniques of Fracture Mechanics, the mechanisms of deformation and fracture, and values of fracture toughness for different PP composites prepared with different particle scale size, either micrometric or nanometric.

Physical characteristics and magnetic properties of BaFe{sub 12}O{sub 19}/SrTiO{sub 3} based composites derived from mechanical alloying

DOE Office of Scientific and Technical Information (OSTI.GOV)

Widodo, Rahmat Doni, E-mail: rahmat-doni@yahoo.com; Manaf, Azwar

2016-04-19

A composite system BaFe{sub 12}O{sub 19}/SrTiO{sub 3} with ferrimagnetic BaFe{sub 12}O{sub 19} phase (BHF) and ferroelectric SrTiO{sub 3} phase (STO) have been prepared by mechanical alloying and subsequent heat treatment. The composite powders were studied by Particle Size Analyze, X-ray diffraction and magnetic measurement. It was found that the particle size of composite powders initially increased due to laminated layers formation of a composite and then decreased to an asymptotic value of ∼8 µm as the milling time extended even to a relatively longer time. However, based on results of line broadening analysis the mean grain size of the particles wasmore » found in the nanometer scale. We thus believed that mechanical blending and milling of mixture components for the composite materials has promoted heterogeneous nucleation and only after successive sintering at 1100°C the milled powder transformed into particles of nanograin. In this report, microstructure as well as magnetic properties for the composite is also briefly discussed.« less

Synthesis and characterization of nanocrystalline Al 2024-B4C composite powders by mechanical alloying

NASA Astrophysics Data System (ADS)

Varol, T.; Canakci, A.

2013-06-01

In the present work, the effect of milling parameters on the morphology and microstructure of nanostructure Al2024-B4C composite powders obtained by mechanical alloying (MA) was studied. The effects of milling time and B4C content on the morphology, microstructure and particle size of nanostructure Al2024-B4C composite powders have been investigated. Different amounts of B4C particles (0, 5, 10 and 20 wt.%) were mixed with Al2024 powders and milled in a planetary ball mill for 30, 60, 120, 300, 420 and 600 min. Al 2024-B4C composite powders were characterized using a scanning electron microscope (SEM), laser particle-size analyzer, X-ray diffraction analysis (XRD) and the Vickers microhardness test. The results showed that the nanostructure Al2024-B4C composite powders were produced when they were milled for 600 min. The size of composite powder in the milled powder mixture was affected by the milling time and content of B4C particles. Moreover, it was observed that when MA reached a steady state, the properties of composite powders were stabilized.

Role of particle size and composition in metal adsorption by solids deposited on urban road surfaces.

PubMed

Gunawardana, Chandima; Egodawatta, Prasanna; Goonetilleke, Ashantha

2014-01-01

Despite common knowledge that the metal content adsorbed by fine particles is relatively higher compared to coarser particles, the reasons for this phenomenon have gained little research attention. The research study discussed in the paper investigated the variations in metal content for different particle sizes of solids associated with pollutant build-up on urban road surfaces. Data analysis confirmed that parameters favourable for metal adsorption to solids such as specific surface area, organic carbon content, effective cation exchange capacity and clay forming minerals content decrease with the increase in particle size. Furthermore, the mineralogical composition of solids was found to be the governing factor influencing the specific surface area and effective cation exchange capacity. There is high quartz content in particles >150 μm compared to particles <150 μm. As particle size reduces below 150 μm, the clay forming minerals content increases, providing favourable physical and chemical properties that influence adsorption. Copyright © 2013 Elsevier Ltd. All rights reserved.

Evaluation of titanium carbide metal matrix composites deposited via laser cladding

NASA Astrophysics Data System (ADS)

Cavanaugh, Daniel Thomas

Metal matrix composites have been widely studied in terms of abrasion resistance, but a particular material system may behave differently as particle size, morphology, composition, and distribution of the hardening phase varies. The purpose of this thesis was to understand the mechanical and microstructural effects of combining titanium carbide with 431 series stainless steel to create a unique composite via laser cladding, particularly regarding wear properties. The most predominant effect in increasing abrasion resistance, measured via ASTM G65, was confirmed to be volume fraction of titanium carbide addition. Macrohardness was directly proportional to the amount of carbide, though there was an overall reduction in individual particle microhardness after cladding. The reduction in particle hardness was obscured by the effect of volume fraction carbide and did not substantially contribute to the wear resistance changes. A model evaluating effective mean free path of the titanium carbide particles was created and correlated to the measured data. The model proved successful in linking theoretical mean free path to overall abrasion resistance. The effects of the titanium carbide particle distributions were limited, while differences in particle size were noticeable. The mean free path model did not correlate well with the particle size, but it was shown that the fine carbides were completely removed by the coarse abrasive particles in the ASTM G65 test. The particle morphology showed indications of influencing the wear mode, but no statistical reduction was observed in the volume loss figures. Future studies may more specifically focus on particle morphology or compositional effects of the carbide particles.

[Preparation of curcumin-EC sustained-release composite particles by supercritical CO2 anti-solvent technology].

PubMed

Bai, Wei-li; Yan, Ting-yuan; Wang, Zhi-xiang; Huang, De-chun; Yan, Ting-xuan; Li, Ping

2015-01-01

Curcumin-ethyl-cellulose (EC) sustained-release composite particles were prepared by using supercritical CO2 anti-solvent technology. With drug loading and yield of inclusion complex as evaluation indexes, on the basis of single factor tests, orthogonal experimental design was used to optimize the preparation process of curcumin-EC sustained-release composite particles. The experiments such as drug loading, yield, particle size distribution, electron microscope analysis (SEM) , infrared spectrum (IR), differential scanning calorimetry (DSC) and in vitro dissolution were used to analyze the optimal process combination. The orthogonal experimental optimization process conditions were set as follows: crystallization temperature 45 degrees C, crystallization pressure 10 MPa, curcumin concentration 8 g x L(-1), solvent flow rate 0.9 mL x min(-1), and CO2 velocity 4 L x min(-1). Under the optimal conditions, the average drug loading and yield of curcumin-EC sustained-release composite particles were 33.01% and 83.97%, and the average particle size of the particles was 20.632 μm. IR and DSC analysis showed that curcumin might complex with EC. The experiments of in vitro dissolution showed that curcumin-EC composite particles had good sustained-release effect. Curcumin-EC sustained-release composite particles can be prepared by supercritical CO2 anti-solvent technology.

Identifying airborne metal particles sources near an optoelectronic and semiconductor industrial park

NASA Astrophysics Data System (ADS)

Chen, Ho-Wen; Chen, Wei-Yea; Chang, Cheng-Nan; Chuang, Yen-Hsun; Lin, Yu-Hao

2016-06-01

The recently developed Central Taiwan Science Park (CTSP) in central Taiwan is home to an optoelectronic and semiconductor industrial cluster. Therefore, exploring the elemental compositions and size distributions of airborne particles emitted from the CTSP would help to prevent pollution. This study analyzed size-fractionated metal-rich particle samples collected in upwind and downwind areas of CTSP during Jan. and Oct. 2013 by using micro-orifice uniform deposited impactor (MOUDI). Correlation analysis, hierarchical cluster analysis and particle mass-size distribution analysis are performed to identify the source of metal-rich particle near the CTSP. Analyses of elemental compositions and particle size distributions emitted from the CTSP revealed that the CTSP emits some metals (V, As, In Ga, Cd and Cu) in the ultrafine particles (< 1 μm). The statistical analysis combines with the particle mass-size distribution analysis could provide useful source identification information. In airborne particles with the size of 0.32 μm, Ga could be a useful pollution index for optoelectronic and semiconductor emission in the CTSP. Meanwhile, the ratios of As/Ga concentration at the particle size of 0.32 μm demonstrates that humans near the CTSP would be potentially exposed to GaAs ultrafine particles. That is, metals such as Ga and As and other metals that are not regulated in Taiwan are potentially harmful to human health.

A size-composition resolved aerosol model for simulating the dynamics of externally mixed particles: SCRAM (v 1.0)

NASA Astrophysics Data System (ADS)

Zhu, S.; Sartelet, K. N.; Seigneur, C.

2015-06-01

The Size-Composition Resolved Aerosol Model (SCRAM) for simulating the dynamics of externally mixed atmospheric particles is presented. This new model classifies aerosols by both composition and size, based on a comprehensive combination of all chemical species and their mass-fraction sections. All three main processes involved in aerosol dynamics (coagulation, condensation/evaporation and nucleation) are included. The model is first validated by comparison with a reference solution and with results of simulations using internally mixed particles. The degree of mixing of particles is investigated in a box model simulation using data representative of air pollution in Greater Paris. The relative influence on the mixing state of the different aerosol processes (condensation/evaporation, coagulation) and of the algorithm used to model condensation/evaporation (bulk equilibrium, dynamic) is studied.

Simulation of Particle Size Effect on Dynamic Properties and Fracture of PTFE-W-Al Composites

NASA Astrophysics Data System (ADS)

Herbold, E. B.; Cai, J.; Benson, D. J.; Nesterenko, V. F.

2007-12-01

Recent investigations of the dynamic compressive strength of cold isostatically pressed composites of polytetrafluoroethylene (PTFE), tungsten (W) and aluminum (Al) powders show significant differences depending on the size of metallic particles. The addition of W increases the density and changes the overall strength of the sample depending on the size of W particles. To investigate relatively large deformations, multi-material Eulerian and arbitrary Lagrangian-Eulerian methods, which have the ability to efficiently handle the formation of free surfaces, were used. The calculations indicate that the increased sample strength with fine metallic particles is due to the dynamic formation of force chains. This phenomenon occurs for samples with a higher porosity of the PTFE matrix compared to samples with larger particle size of W and a higher density PTFE matrix.

Ablation and Chemical Alteration of Cosmic Dust Particles during Entry into the Earth’s Atmosphere

NASA Astrophysics Data System (ADS)

Rudraswami, N. G.; Shyam Prasad, M.; Dey, S.; Plane, J. M. C.; Feng, W.; Carrillo-Sánchez, J. D.; Fernandes, D.

2016-12-01

Most dust-sized cosmic particles undergo ablation and chemical alteration during atmospheric entry, which alters their original properties. A comprehensive understanding of this process is essential in order to decipher their pre-entry characteristics. The purpose of the study is to illustrate the process of vaporization of different elements for various entry parameters. The numerical results for particles of various sizes and various zenith angles are treated in order to understand the changes in chemical composition that the particles undergo as they enter the atmosphere. Particles with large sizes (> few hundred μm) and high entry velocities (>16 km s‑1) experience less time at peak temperatures compared to those that have lower velocities. Model calculations suggest that particles can survive with an entry velocity of 11 km s‑1 and zenith angles (ZA) of 30°–90°, which accounts for ∼66% of the region where particles retain their identities. Our results suggest that the changes in chemical composition of MgO, SiO2, and FeO are not significant for an entry velocity of 11 km s‑1 and sizes <300 μm, but the changes in these compositions become significant beyond this size, where FeO is lost to a major extent. However, at 16 km s‑1 the changes in MgO, SiO2, and FeO are very intense, which is also reflected in Mg/Si, Fe/Si, Ca/Si, and Al/Si ratios, even for particles with a size of 100 μm. Beyond 400 μm particle sizes at 16 km s‑1, most of the major elements are vaporized, leaving the refractory elements, Al and Ca, suspended in the troposphere.

Laboratory evaluation of airborne particulate control treatments for simulated aircraft crash recovery operations involving carbon fiber composite materials.

PubMed

Ferreri, Matthew; Slagley, Jeremy; Felker, Daniel

2015-01-01

This study compared four treatment protocols to reduce airborne composite fiber particulates during simulated aircraft crash recovery operations. Four different treatments were applied to determine effectiveness in reducing airborne composite fiber particulates as compared to a "no treatment" protocol. Both "gold standard" gravimetric methods and real-time instruments were used to describe mass per volume concentration, particle size distribution, and surface area. The treatment protocols were applying water, wetted water, wax, or aqueous film-forming foam (AFFF) to both burnt and intact tickets of aircraft composite skin panels. The tickets were then cut using a small high-speed rotary tool to simulate crash recovery operations. Aerosol test chamber. None. Airborne particulate control treatments. Measures included concentration units of milligrams per cubic meter of air, particle size distribution as described by both count median diameter and mass median diameter and geometric standard deviation of particles in micrometers, and surface area concentration in units of square micrometers per cubic centimeter. Finally, a Monte Carlo simulation was run on the particle size distribution results. Comparison was made via one-way analysis of variance. A significant difference (p < 0.0001) in idealized particle size distribution was found between the water and wetted water treatments as compared to the other treatments for burnt tickets. Emergency crash recovery operations should include a treatment of the debris with water or wetted water. The resulting increase in particle size will make respiratory protection more effective in protecting the response crews.

Laboratory evaluation of airborne particulate control treatments for simulated aircraft crash recovery operations involving carbon fiber composite materials.

PubMed

Ferreri, Matthew; Slagley, Jeremy; Felker, Daniel

2015-01-01

This study compared four treatment protocols to reduce airborne composite fiber particulates during simulated aircraft crash recovery operations. Four different treatments were applied to determine effectiveness in reducing airborne composite fiber particulates as compared to a "no treatment" protocol. Both "gold standard" gravimetric methods and real-time instruments were used to describe mass per volume concentration, particle size distribution, and surface area. The treatment protocols were applying water, wetted water, wax, or aqueous film-forming foam (AFFF) to both burnt and intact tickets of aircraft composite skin panels. The tickets were then cut using a small high-speed rotary tool to simulate crash recovery operations. Aerosol test chamber. None. Airborne particulate control treatments. Measures included concentration units of milligrams per cubic meter of air, particle size distribution as described by both count median diameter and mass median diameter and geometric standard deviation of particles in micrometers, and surface area concentration in units of square micrometers per cubic centimeter. Finally, a Monte Carlo simulation was run on the particle size distribution results. Comparison was made via one-way analysis of variance. A significant difference (p<0.0001) in idealized particle size distribution was found between the water and wetted water treatments as compared to the other treatments for burnt tickets. Emergency crash recovery operations should include a treatment of the debris with water or wetted water. The resulting increase in particle size will make respiratory protection more effective in protecting the response crews.

Influences of aerosol physiochemical properties and new particle formation on CCN activity from observation at a suburban site of China

NASA Astrophysics Data System (ADS)

Li, Yanan; Zhang, Fang; Li, Zhanqing; Sun, Li; Wang, Zhenzhu; Li, Ping; Sun, Yele; Ren, Jingye; Wang, Yuying; Cribb, Maureen; Yuan, Cheng

2017-05-01

With the aim of understanding the impact of aerosol particle size and chemical composition on CCN activity, the size-resolved cloud condensation nuclei (CCN) number concentration (NCCN), particle number size distribution (PSD) (10-600 nm), and bulk chemical composition of particles with a diameter < 1.0 μm (PM1) were measured simultaneously at Xinzhou, a suburban site in northern China, from 22 July to 26 August 2014. The NCCN was measured at five different supersaturations (SS) ranging from 0.075%-0.76%. Diurnal variations in the aerosol number concentration (NCN), NCCN, the bulk aerosol activation ratio (AR), the hygroscopicity parameter (κchem), and the ratio of 44 mass to charge ration (m/z 44) to total organic signal in the component spectrum (f44), and the PSD were examined integrally to study the influence of particle size and chemical composition on CCN activation. We found that particle size was more related to the CCN activation ratios in the morning, whereas in the afternoon ( 1400 LST), κchem and f44 were more closely associated with the bulk AR. Assuming the internal mixing of aerosol particles, NCCN was estimated using the bulk chemical composition and real-time PSD. We found that the predicted CCN number concentrations were underestimated by 20-30% at SS < 0.2% probably due to the measurement uncertainties. Estimates were more accurate at higher SS levels, suggesting that the hygroscopicity parameter based on bulk chemical composition information can provide a good estimate of CCN number concentrations. We studied the impacts of new particle formation (NPF) events on size-resolved CCN activity at the ;growth; stage and ;leveling-off; stage during a typical NPF event by comparing with the case during non-NPF event. It has been found that CCN activation was restrained at the ;growth; stage during which larger particle diameters were needed to reach an activation diameter(Da), and the bulk AR decreased as well. However, during the ;leveling-off; stage, a lower Da was observed and CCN activation was greatly enhanced.

Fracture behavior of 20% Nb particulate reinforced alumina composite

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lane, S.; Biner, S.B.; Buck, O.

1993-11-01

The composites consist of alumina matrix with 0.05 wt % MgO and 20 Vol % Nb with an average particle size of 30 to 100 microns produced by dry mixing and sintering to near their theoretical densities. Fracture toughness tests were carried out in three point bending on chevron notched samples. Results indicate that R-curve of the composites exhibited more than 300% increase in crack growth resistance compared to crack growth resistance of alumina produced with the identical procedures. Crack growth resistance curve of the composites increased with increasing Nb particle size. Metallorgraph indicated that failure of Nb particles inmore » crack path ranges from full interface separation without any significant deformation of Nb particles to cleavage failure without any evidence of interface separation.« less

Transformations of inorganic coal constituents in combustion systems

DOE Office of Scientific and Technical Information (OSTI.GOV)

Helble, J.J.; Srinivasachar, S.; Wilemski, G.

1992-11-01

The inorganic constituents or ash contained in pulverized coal significantly increase the environmental and economic costs of coal utilization. For example, ash particles produced during combustion may deposit on heat transfer surfaces, decreasing heat transfer rates and increasing maintenance costs. The minimization of particulate emissions often requires the installation of cleanup devices such as electrostatic precipitators, also adding to the expense of coal utilization. Despite these costly problems, a comprehensive assessment of the ash formation and had never been attempted. At the start of this program, it was hypothesized that ash deposition and ash particle emissions both depended upon themore » size and chemical composition of individual ash particles. Questions such as: What determines the size of individual ash particles What determines their composition Whether or not particles deposit How combustion conditions, including reactor size, affect these processes remained to be answered. In this 6-year multidisciplinary study, these issues were addressed in detail. The ambitious overall goal was the development of a comprehensive model to predict the size and chemical composition distributions of ash produced during pulverized coal combustion. Results are described.« less

Alterations in welding process voltage affect the generation of ultrafine particles, fume composition, and pulmonary toxicity.

PubMed

Antonini, James M; Keane, Michael; Chen, Bean T; Stone, Samuel; Roberts, Jenny R; Schwegler-Berry, Diane; Andrews, Ronnee N; Frazer, David G; Sriram, Krishnan

2011-12-01

The goal was to determine if increasing welding voltage changes the physico-chemical properties of the fume and influences lung responses. Rats inhaled 40 mg/m³ (3 h/day × 3 days) of stainless steel (SS) welding fume generated at a standard voltage setting of 25 V (regular SS) or at a higher voltage (high voltage SS) of 30 V. Particle morphology, size and composition were characterized. Bronchoalveolar lavage was performed at different times after exposures to assess lung injury. Fumes collected from either of the welding conditions appeared as chain-like agglomerates of nanometer-sized primary particles. High voltage SS welding produced a greater number of ultrafine-sized particles. Fume generated by high voltage SS welding was higher in manganese. Pulmonary toxicity was more substantial and persisted longer after exposure to the regular SS fume. In summary, a modest raise in welding voltage affected fume size and elemental composition and altered the temporal lung toxicity profile.

Metal Matrix Composites Directionally Solidified

NASA Astrophysics Data System (ADS)

Ares, Alicia Esther; Schvezov, Carlos Enrique

The present work is focus on studying the dendritic solidification of metal matrix composites, MMCs, (using zinc-aluminum, ZA, alloys as matrix and the addition of SiC and Al2O3 particles). The compounds were obtained by as-cast solidification, under continuous stirring and in a second stage were directionally solidified in order to obtain different dendritic growth (columnar, equiaxed and columnar-to-equiaxed transition (CET)). The results in MMCs were compared with those obtained in directional solidification of ZA alloys, primarily with regard to structural parameters. The size and evolution of microstructure, according to the size of the MMCs particles and the variation of the thermal parameters was analyzing. In general it was found that the size of the microstructure (secondary dendritic spacing) decreases with the increase of particles in the matrix. When cooling rate increases, particle size decreases, and a higher cooling rate causes finer and more homogeneous dendrites Also, the segregation which was found in the matrix of the composites was significantly less than in the case of ZA alloys.

In-Situ Characterization of Cloud Condensation Nuclei, Interstitial, and background Particles using Single Particle Mass Spectrometer, SPLAT II

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zelenyuk, Alla; Imre, D.; Earle, Michael

2010-10-01

Aerosol indirect effect remains the most uncertain aspect of climate change modeling because proper test requires knowledge of individual particles sizes and compositions with high spatial and temporal resolution. We present the first deployment of a single particle mass spectrometer (SPLAT II) that is operated in a dual data acquisition mode to measure all the required individual particle properties with sufficient temporal resolution to definitively resolve the aerosol-cloud interaction in this exemplary case. We measured particle number concentrations, asphericity, and individual particle size, composition, and density with better than 60 seconds resolution. SPLAT II measured particle number concentrations between 70more » particles cm-3and 300 particles cm-3, an average particle density of 1.4 g cm-3. Found that most particles are composed of oxygenated organics, many of which are mixed with sulfates. Biomass burn particles some with sulfates were prevalent, particularly at higher altitudes, and processed sea-salt was observed over the ocean. Analysis of cloud residuals shows that with time cloud droplets acquire sulfate by the reaction of peroxide with SO2. Based on the particle mass spectra and densities we find that the compositions of cloud condensation nuclei are similar to those of background aerosol but, contain on average ~7% more sulfate, and do not include dust and metallic particles. A comparison between the size distributions of background, activated, and interstitial particles shows that while nearly none of the activated particles is smaller than 115 nm, more than 80% of interstitial particles are smaller than 115 nm. We conclude that for this cloud the most important difference between CCN and background aerosol is particle size although having more sulfate also helps.« less

Composition distributions in FePt(Au) nanoparticles

NASA Astrophysics Data System (ADS)

Srivastava, C.; Nikles, D. E.; Harrell, J. W.; Thompson, G. B.

2010-08-01

Ternary alloy FePt(Au) nanoparticles were prepared by the co-reduction of platinum(II) acetylacetonate and gold(III) acetate and the thermal decomposition of iron pentacarbonyl in hot phenyl ether in the presence of oleic acid and oleylamine ligands. This gave spherical particles with an average diameter of 4.4 nm with a range of diameters from approximately 1.6-9 nm. The as-synthesized particles had a solid solution, face-centered-cubic structure. Though the average composition of the particles was Fe44Pt45Au11, individual particle analysis by Scanning Transmission Electron Microscopy-X-ray Energy Dispersive Spectroscopy showed a broad distribution in composition. In general, smaller-sized particles tended to have a lower amount of Au as compared to larger-sized particles. As the Au content increased, the ratio of Fe/Pt widened.

Thermo-mechanical characterization of siliconized E-glass fiber/hematite particles reinforced epoxy resin hybrid composite

NASA Astrophysics Data System (ADS)

V. R., Arun prakash; Rajadurai, A.

2016-10-01

In this present work hybrid polymer (epoxy) matrix composite has been strengthened with surface modified E-glass fiber and iron(III) oxide particles with varying size. The particle sizes of 200 nm and <100 nm has been prepared by high energy ball milling and sol-gel methods respectively. To enhance better dispersion of particles and improve adhesion of fibers and fillers with epoxy matrix surface modification process has been done on both fiber and filler by an amino functional silane 3-Aminopropyltrimethoxysilane (APTMS). Crystalline and functional groups of siliconized iron(III) oxide particles were characterized by XRD and FTIR spectroscopy analysis. Fixed quantity of surface treated 15 vol% E-glass fiber was laid along with 0.5 and 1.0 vol% of iron(III) oxide particles into the matrix to fabricate hybrid composites. The composites were cured by an aliphatic hardener Triethylenetetramine (TETA). Effectiveness of surface modified particles and fibers addition into the resin matrix were revealed by mechanical testing like tensile testing, flexural testing, impact testing, inter laminar shear strength and hardness. Thermal behavior of composites was evaluated by TGA, DSC and thermal conductivity (Lee's disc). The scanning electron microscopy was employed to found shape and size of iron(III) oxide particles adhesion quality of fiber with epoxy matrix. Good dispersion of fillers in matrix was achieved with surface modifier APTMS. Tensile, flexural, impact and inter laminar shear strength of composites was improved by reinforcing surface modified fiber and filler. Thermal stability of epoxy resin was improved when surface modified fiber was reinforced along with hard hematite particles. Thermal conductivity of epoxy increased with increase of hematite content in epoxy matrix.

Exposure to nanoscale particles and fibers during machining of hybrid advanced composites containing carbon nanotubes

NASA Astrophysics Data System (ADS)

Bello, Dhimiter; Wardle, Brian L.; Yamamoto, Namiko; Guzman deVilloria, Roberto; Garcia, Enrique J.; Hart, Anastasios J.; Ahn, Kwangseog; Ellenbecker, Michael J.; Hallock, Marilyn

2009-01-01

This study investigated airborne exposures to nanoscale particles and fibers generated during dry and wet abrasive machining of two three-phase advanced composite systems containing carbon nanotubes (CNTs), micron-diameter continuous fibers (carbon or alumina), and thermoset polymer matrices. Exposures were evaluated with a suite of complementary instruments, including real-time particle number concentration and size distribution (0.005-20 μm), electron microscopy, and integrated sampling for fibers and respirable particulate at the source and breathing zone of the operator. Wet cutting, the usual procedure for such composites, did not produce exposures significantly different than background whereas dry cutting, without any emissions controls, provided a worst-case exposure and this article focuses here. Overall particle release levels, peaks in the size distribution of the particles, and surface area of released particles (including size distribution) were not significantly different for composites with and without CNTs. The majority of released particle surface area originated from the respirable (1-10 μm) fraction, whereas the nano fraction contributed 10% of the surface area. CNTs, either individual or in bundles, were not observed in extensive electron microscopy of collected samples. The mean number concentration of peaks for dry cutting was composite dependent and varied over an order of magnitude with highest values for thicker laminates at the source being >1 × 106 particles cm-3. Concentration of respirable fibers for dry cutting at the source ranged from 2 to 4 fibers cm-3 depending on the composite type. Further investigation is required and underway to determine the effects of various exposure determinants, such as specimen and tool geometry, on particle release and effectiveness of controls.

Characterization of third-body media particles and their effect on in vitro composite wear

PubMed Central

Lawson, Nathaniel C.; Cakir, Deniz; Beck, Preston; Litaker, Mark S.; Burgess, John O.

2012-01-01

Objectives The purpose of this study was to compare four medium particles currently used for in vitro composite wear testing (glass and PMMA beads and millet and poppy seeds). Methods Particles were prepared as described in previous wear studies. Hardness of medium particles was measured with a nano-indentor, particle size was measured with a particle size analyzer, and the particle form was determined with light microscopy and image analysis software. Composite wear was measured using each type of medium and water in the Alabama wear testing device. Four dental composites were compared: a hybrid (Z100), flowable microhybrid (Estelite Flow Quick), micromatrix (Esthet-X), and nano-filled (Filtek Supreme Plus). The test ran for 100,000 cycles at 1.2Hz with 70N force by a steel antagonist. Volumetric wear was measured by non-contact profilometry. A two-way analysis of variance (ANOVA) and Tukey's test was used to compare both materials and media. Results Hardness values (GPa) of the particles are (glass, millet, PMMA, poppy respectively): 1.310(0.150), 0.279(.170), 0.279(0.095), and 0.226(0.146). Average particle sizes (μm) are (glass, millet, PMMA, poppy respectively): 88.35(8.24), 8.07(4.05), 28.95(8.74), and 14.08(7.20). Glass and PMMA beads were considerably more round than the seeds. During composite wear testing, glass was the only medium that produced more wear than the use of water alone. The rank ordering of the materials varied with each medium, however, the glass and PMMA bead medium allowed better discrimination between materials. Significance PMMA beads are a practical and relevant choice for composite wear testing because they demonstrate similar physical properties as seeds but reduce the variability of wear measurements. PMID:22578990

Particle Shape and Composition of NU-LHT-2M

NASA Technical Reports Server (NTRS)

Rickman, D. L.; Lowers, H.

2012-01-01

Particle shapes of the lunar regolith simulant NU-LHT-2M were analyzed by scanning electron microscope of polished sections. These data provide shape, size, and composition information on a particle by particle basis. 5,193 particles were measured, divided into four sized fractions: less than 200 mesh, 200-100 mesh, 100-35 mesh, and greater than 35 mesh. 99.2% of all particles were monominerallic. Minor size versus composition effects were noted in minor and trace mineralogy. The two metrics used are aspect ratio and Heywood factor, plotted as normalized frequency distributions. Shape versus composition effects were noted for glass and possibly chlorite. To aid in analysis, the measured shape distributions are compared to data for ellipses and rectangles. Several other simple geometric shapes are also investigated as to how they plot in aspect ratio versus Heywood factor space. The bulk of the data previously reported, which were acquired in a plane of projection, are between the ellipse and rectangle lines. In contrast, these data, which were acquired in a plane of section, clearly show that a significant number of particles have concave hulls in this view. Appendices cover details of measurement error, use of geometric shapes for comparative analysis, and a logic for comparing data from plane of projection and plane of section measurements.

Three-phase boundary length in solid-oxide fuel cells: A mathematical model

NASA Astrophysics Data System (ADS)

Janardhanan, Vinod M.; Heuveline, Vincent; Deutschmann, Olaf

A mathematical model to calculate the volume specific three-phase boundary length in the porous composite electrodes of solid-oxide fuel cell is presented. The model is exclusively based on geometrical considerations accounting for porosity, particle diameter, particle size distribution, and solids phase distribution. Results are presented for uniform particle size distribution as well as for non-uniform particle size distribution.

The kinetics of composite particle formation during mechanical alloying

NASA Technical Reports Server (NTRS)

Aikin, B. J. M.; Courtney, T. H.

1993-01-01

The kinetics of composite particle formation during attritor milling of insoluble binary elemental powders have been examined. The effects of processing conditions (i.e., mill power, temperature, and charge ratio) on these kinetics were studied. Particle size distributions and fractions of elemental and composite particles were determined as functions of milling time and processing conditions. This allowed the deduction of phenomenological rate constants describing the propensity for fracture and welding during processing. For the mill-operating conditions investigated, the number of particles in the mill generally decreased with milling time, indicating a greater tendency for particle welding than fracture. Moreover, a bimodal size distribution is often obtained as a result of preferential welding. Copper and chromium 'alloy' primarily by encapsulation of Cr particles within Cu. This form of alloying also occurs in Cu-Nb alloys processed at low mill power and/or for short milling times. For other conditions, however, Cu-Nb alloys develop a lamellar morphology characteristic of mechanically alloyed two-phase ductile metals. Increasing mill power or charge (ball-to-powder weight) ratio (CR) increases the rate of composite particle formation.

Performance and Aging of Mn/MnO2 as an Environmentally Friendly Energetic Time Delay Composition

DTIC Science & Technology

2014-04-16

for the powders used in these experiments are summarized in Table 1. Particle size distributions for Mn and MnO2 were obtained using a Malvern... particle size data. Mn/MnO2 compositions were dry mixed in 30 mL HDPE bottles using a Resodyn LabRAM mixer at 80% intensity in 2 min intervals for a...predicted. Due to the high heat losses of the small Table 1. Vendor Information of Reactant Powders powder nominal particle size vendor Bi2O3 15.4 μm Alfa

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rudraswami, N. G.; Prasad, M. Shyam; Dey, S.

Most dust-sized cosmic particles undergo ablation and chemical alteration during atmospheric entry, which alters their original properties. A comprehensive understanding of this process is essential in order to decipher their pre-entry characteristics. The purpose of the study is to illustrate the process of vaporization of different elements for various entry parameters. The numerical results for particles of various sizes and various zenith angles are treated in order to understand the changes in chemical composition that the particles undergo as they enter the atmosphere. Particles with large sizes (> few hundred μ m) and high entry velocities (>16 km s{sup −1})more » experience less time at peak temperatures compared to those that have lower velocities. Model calculations suggest that particles can survive with an entry velocity of 11 km s{sup −1} and zenith angles (ZA) of 30°–90°, which accounts for ∼66% of the region where particles retain their identities. Our results suggest that the changes in chemical composition of MgO, SiO{sub 2}, and FeO are not significant for an entry velocity of 11 km s{sup −1} and sizes <300 μ m, but the changes in these compositions become significant beyond this size, where FeO is lost to a major extent. However, at 16 km s{sup −1} the changes in MgO, SiO{sub 2}, and FeO are very intense, which is also reflected in Mg/Si, Fe/Si, Ca/Si, and Al/Si ratios, even for particles with a size of 100 μ m. Beyond 400 μ m particle sizes at 16 km s{sup −1}, most of the major elements are vaporized, leaving the refractory elements, Al and Ca, suspended in the troposphere.« less

Size-segregated urban aerosol characterization by electron microscopy and dynamic light scattering and influence of sample preparation

NASA Astrophysics Data System (ADS)

Marvanová, Soňa; Kulich, Pavel; Skoupý, Radim; Hubatka, František; Ciganek, Miroslav; Bendl, Jan; Hovorka, Jan; Machala, Miroslav

2018-04-01

Size-segregated particulate matter (PM) is frequently used in chemical and toxicological studies. Nevertheless, toxicological in vitro studies working with the whole particles often lack a proper evaluation of PM real size distribution and characterization of agglomeration under the experimental conditions. In this study, changes in particle size distributions during the PM sample manipulation and also semiquantitative elemental composition of single particles were evaluated. Coarse (1-10 μm), upper accumulation (0.5-1 μm), lower accumulation (0.17-0.5 μm), and ultrafine (<0.17 μm) PM fractions were collected by high volume cascade impactor in Prague city center. Particles were examined using electron microscopy and their elemental composition was determined by energy dispersive X-ray spectroscopy. Larger or smaller particles, not corresponding to the impaction cut points, were found in all fractions, as they occur in agglomerates and are impacted according to their aerodynamic diameter. Elemental composition of particles in size-segregated fractions varied significantly. Ns-soot occurred in all size fractions. Metallic nanospheres were found in accumulation fractions, but not in ultrafine fraction where ns-soot, carbonaceous particles, and inorganic salts were identified. Dynamic light scattering was used to measure particle size distribution in water and in cell culture media. PM suspension of lower accumulation fraction in water agglomerated after freezing/thawing the sample, and the agglomerates were disrupted by subsequent sonication. Ultrafine fraction did not agglomerate after freezing/thawing the sample. Both lower accumulation and ultrafine fractions were stable in cell culture media with fetal bovine serum, while high agglomeration occurred in media without fetal bovine serum as measured during 24 h.

Collocated observations of cloud condensation nuclei, particle size distributions, and chemical composition

PubMed Central

Schmale, Julia; Henning, Silvia; Henzing, Bas; Keskinen, Helmi; Sellegri, Karine; Ovadnevaite, Jurgita; Bougiatioti, Aikaterini; Kalivitis, Nikos; Stavroulas, Iasonas; Jefferson, Anne; Park, Minsu; Schlag, Patrick; Kristensson, Adam; Iwamoto, Yoko; Pringle, Kirsty; Reddington, Carly; Aalto, Pasi; Äijälä, Mikko; Baltensperger, Urs; Bialek, Jakub; Birmili, Wolfram; Bukowiecki, Nicolas; Ehn, Mikael; Fjæraa, Ann Mari; Fiebig, Markus; Frank, Göran; Fröhlich, Roman; Frumau, Arnoud; Furuya, Masaki; Hammer, Emanuel; Heikkinen, Liine; Herrmann, Erik; Holzinger, Rupert; Hyono, Hiroyuki; Kanakidou, Maria; Kiendler-Scharr, Astrid; Kinouchi, Kento; Kos, Gerard; Kulmala, Markku; Mihalopoulos, Nikolaos; Motos, Ghislain; Nenes, Athanasios; O’Dowd, Colin; Paramonov, Mikhail; Petäjä, Tuukka; Picard, David; Poulain, Laurent; Prévôt, André Stephan Henry; Slowik, Jay; Sonntag, Andre; Swietlicki, Erik; Svenningsson, Birgitta; Tsurumaru, Hiroshi; Wiedensohler, Alfred; Wittbom, Cerina; Ogren, John A.; Matsuki, Atsushi; Yum, Seong Soo; Myhre, Cathrine Lund; Carslaw, Ken; Stratmann, Frank; Gysel, Martin

2017-01-01

Cloud condensation nuclei (CCN) number concentrations alongside with submicrometer particle number size distributions and particle chemical composition have been measured at atmospheric observatories of the Aerosols, Clouds, and Trace gases Research InfraStructure (ACTRIS) as well as other international sites over multiple years. Here, harmonized data records from 11 observatories are summarized, spanning 98,677 instrument hours for CCN data, 157,880 for particle number size distributions, and 70,817 for chemical composition data. The observatories represent nine different environments, e.g., Arctic, Atlantic, Pacific and Mediterranean maritime, boreal forest, or high alpine atmospheric conditions. This is a unique collection of aerosol particle properties most relevant for studying aerosol-cloud interactions which constitute the largest uncertainty in anthropogenic radiative forcing of the climate. The dataset is appropriate for comprehensive aerosol characterization (e.g., closure studies of CCN), model-measurement intercomparison and satellite retrieval method evaluation, among others. Data have been acquired and processed following international recommendations for quality assurance and have undergone multiple stages of quality assessment. PMID:28291234

Collocated observations of cloud condensation nuclei, particle size distributions, and chemical composition

NASA Astrophysics Data System (ADS)

Schmale, Julia; Henning, Silvia; Henzing, Bas; Keskinen, Helmi; Sellegri, Karine; Ovadnevaite, Jurgita; Bougiatioti, Aikaterini; Kalivitis, Nikos; Stavroulas, Iasonas; Jefferson, Anne; Park, Minsu; Schlag, Patrick; Kristensson, Adam; Iwamoto, Yoko; Pringle, Kirsty; Reddington, Carly; Aalto, Pasi; Äijälä, Mikko; Baltensperger, Urs; Bialek, Jakub; Birmili, Wolfram; Bukowiecki, Nicolas; Ehn, Mikael; Fjæraa, Ann Mari; Fiebig, Markus; Frank, Göran; Fröhlich, Roman; Frumau, Arnoud; Furuya, Masaki; Hammer, Emanuel; Heikkinen, Liine; Herrmann, Erik; Holzinger, Rupert; Hyono, Hiroyuki; Kanakidou, Maria; Kiendler-Scharr, Astrid; Kinouchi, Kento; Kos, Gerard; Kulmala, Markku; Mihalopoulos, Nikolaos; Motos, Ghislain; Nenes, Athanasios; O'Dowd, Colin; Paramonov, Mikhail; Petäjä, Tuukka; Picard, David; Poulain, Laurent; Prévôt, André Stephan Henry; Slowik, Jay; Sonntag, Andre; Swietlicki, Erik; Svenningsson, Birgitta; Tsurumaru, Hiroshi; Wiedensohler, Alfred; Wittbom, Cerina; Ogren, John A.; Matsuki, Atsushi; Yum, Seong Soo; Myhre, Cathrine Lund; Carslaw, Ken; Stratmann, Frank; Gysel, Martin

2017-03-01

Cloud condensation nuclei (CCN) number concentrations alongside with submicrometer particle number size distributions and particle chemical composition have been measured at atmospheric observatories of the Aerosols, Clouds, and Trace gases Research InfraStructure (ACTRIS) as well as other international sites over multiple years. Here, harmonized data records from 11 observatories are summarized, spanning 98,677 instrument hours for CCN data, 157,880 for particle number size distributions, and 70,817 for chemical composition data. The observatories represent nine different environments, e.g., Arctic, Atlantic, Pacific and Mediterranean maritime, boreal forest, or high alpine atmospheric conditions. This is a unique collection of aerosol particle properties most relevant for studying aerosol-cloud interactions which constitute the largest uncertainty in anthropogenic radiative forcing of the climate. The dataset is appropriate for comprehensive aerosol characterization (e.g., closure studies of CCN), model-measurement intercomparison and satellite retrieval method evaluation, among others. Data have been acquired and processed following international recommendations for quality assurance and have undergone multiple stages of quality assessment.

Lead-free precussion primer mixes based on metastable interstitial composite (MIC) technology

DOEpatents

Dixon, George P.; Martin, Joe A.; Thompson, Don

1998-01-01

A lead-free percussion primer composition and a percussion cup containing e composition. The lead-free percussion primer composition is comprised of a mixture of about 45 wt % aluminum powder having an outer coating of aluminum oxide and molybdenum trioxide powder or a mixture of about 50 wt % aluminum powder having an outer coating of aluminum oxide and polytetrafluoroethylene powder. The aluminum powder, molybdenum trioxide powder and polytetrafluoroethylene powder has a particle size of 0.1 .mu.m or less, more preferably a particle size of from about 200-500 angstroms.

Lunar Dust Characterization Activity at GRC

NASA Technical Reports Server (NTRS)

Street, Kenneth W.

2008-01-01

The fidelity of lunar simulants as compared to actual regolith is evaluated using Figures of Merit (FOM) which are based on four criteria: Particle Size, Particle Shape, Composition, and Density of the bulk material. In practice, equipment testing will require other information about both the physical properties (mainly of the dust fraction) and composition as a function of particle size. At Glenn Research Center (GRC) we are involved in evaluating a number of simulant properties of consequence to testing of lunar equipment in a relevant environment, in order to meet Technology Readiness Level (TRL) 6 criteria. Bulk regolith has been characterized for many decades, but surprisingly little work has been done on the dust fraction (particles less than 20 micrometers in diameter). GRC is currently addressing the information shortfall by characterizing the following physical properties: Particle Size Distribution, Adhesion, Abrasivity, Surface Energy, Magnetic Susceptibility, Tribocharging and Surface Chemistry/Reactivity. Since some of these properties are also dependent on the size of the particles we have undertaken the construction of a six stage axial cyclone particle separator to fractionate dust into discrete particle size distributions for subsequent evaluation of these properties. An introduction to this work and progress to date will be presented.

Particle size distribution of distillers dried grains with solubles (DDGS) and relationships to compositional and color properties.

PubMed

Liu, Keshun

2008-11-01

Eleven distillers dried grains with solubles (DDGS), processed from yellow corn, were collected from different ethanol processing plants in the US Midwest area. Particle size distribution (PSD) by mass of each sample was determined using a series of six selected US standard sieves: Nos. 8, 12, 18, 35, 60, and 100, and a pan. The original sample and sieve sized fractions were measured for surface color and contents of moisture, protein, oil, ash, and starch. Total carbohydrate (CHO) and total non-starch CHO were also calculated. Results show that there was a great variation in composition and color among DDGS from different plants. Surprisingly, a few DDGS samples contained unusually high amounts of residual starch (11.1-17.6%, dry matter basis, vs. about 5% of the rest), presumably resulting from modified processing methods. Particle size of DDGS varied greatly within a sample and PSD varied greatly among samples. The 11 samples had a mean value of 0.660mm for the geometric mean diameter (dgw) of particles and a mean value of 0.440mm for the geometric standard deviation (Sgw) of particle diameters by mass. The majority had a unimodal PSD, with a mode in the size class between 0.5 and 1.0mm. Although PSD and color parameters had little correlation with composition of whole DDGS samples, distribution of nutrients as well as color attributes correlated well with PSD. In sieved fractions, protein content, L and a color values negatively while contents of oil and total CHO positively correlated with particle size. It is highly feasible to fractionate DDGS for compositional enrichment based on particle size, while the extent of PSD can serve as an index for potential of DDGS fractionation. The above information should be a vital addition to quality and baseline data of DDGS.

Effect of particle size and particle size distribution on physical characteristics, morphology and crystal structure of explosively compacted high-T(sub c) superconductors

NASA Technical Reports Server (NTRS)

Kotsis, I.; Enisz, M.; Oravetz, D.; Szalay, A.

1995-01-01

A superconductor, of composition Y(Ba,K,Na)2Cu3O(x)/F(y) and a composite of composition Y(Ba,K,Na)2Cu3O(x)/F(y) + Ag, with changing K, Na and F content but a constant silver content (Ag = 10 mass%) was prepared using a single heat treatment. the resulting material was ground in a corundum lined mill, separated to particle size fractions of 0-40 micron, 0-63 micron and 63-900 micron and explosively compacted, using an explosive pressure of 10(exp 4) MPa and a subsequent heat treatment. Best results were obtained with the 63-900 micron fraction of composition Y(Ba(1.95) K(0.01)Cu3O(x)F(0),(05)/Ag: porosity less than 0.01 cu cm/g and current density 2800 A/sq cm at 77K.

Wear model simulating clinical abrasion on composite filling materials.

PubMed

Johnsen, Gaute Floer; Taxt-Lamolle, Sébastien F; Haugen, Håvard J

2011-01-01

The aim of this study was to establish a wear model for testing composite filling materials with abrasion properties closer to a clinical situation. In addition, the model was used to evaluate the effect of filler volume and particle size on surface roughness and wear resistance. Each incisor tooth was prepared with nine identical standardized cavities with respect to depth, diameter, and angle. Generic composite of 3 different filler volumes and 3 different particle sizes held together with the same resin were randomly filled in respective cavities. A multidirectional wet-grinder with molar cusps as antagonist wore the surface of the incisors containing the composite fillings in a bath of human saliva at a constant temperature of 37°C. The present study suggests that the most wear resistant filling materials should consist of medium filling content (75%) and that particles size is not as critical as earlier reported.

Characterization of exposures to nanoscale particles and fibers during solid core drilling of hybrid carbon nanotube advanced composites.

PubMed

Bello, Dhimiter; Wardle, Brian L; Zhang, Jie; Yamamoto, Namiko; Santeufemio, Christopher; Hallock, Marilyn; Virji, M Abbas

2010-01-01

This work investigated exposures to nanoparticles and nanofibers during solid core drilling of two types of advanced carbon nanotube (CNT)-hybrid composites: (1) reinforced plastic hybrid laminates (alumina fibers and CNT); and (2) graphite-epoxy composites (carbon fibers and CNT). Multiple real-time instruments were used to characterize the size distribution (5.6 nm to 20 microm), number and mass concentration, particle-bound polyaromatic hydrocarbons (b-PAHs), and surface area of airborne particles at the source and breathing zone. Time-integrated samples included grids for electron microscopy characterization of particle morphology and size resolved (2 nm to 20 microm) samples for the quantification of metals. Several new important findings herein include generation of airborne clusters of CNTs not seen during saw-cutting of similar composites, fewer nanofibers and respirable fibers released, similarly high exposures to nanoparticles with less dependence on the composite thickness, and ultrafine (< 5 nm) aerosol originating from thermal degradation of the composite material.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Reents, W.D. Jr.

Particles present in the environment have significant affects in many areas from personal health due to atmospheric particles to various industrial processes that can be ruined due to particulate contamination such as semiconductor device manufacture and manufacture of sterile health products. The ability to detect deleterious contamination requires appropriate instrumentation to detect these particles. To prevent such contamination, the particle source must be identified by determining the composition of the offending particles. In a controlled environment, particle contamination often occurs in transients. In order to identify unknown particles, a technique must obtain compositional and size information regardless of particle identity,more » and perform this analysis in real-time so as to separate {open_quotes}background{close_quotes} particles from those produced in the transient event. Since processes are sensitive to certain particle size regimes and possibly, compositions, the instrumentation must be designed with these needs in mind. The authors have developed an instrument, the Ultra-Sensitive Particle Analysis System (USPAS) for situations where ultrafine particles, down to 0.002 micron, are of concern, such as the semiconductor manufacturing industry and the ambient environment.« less

Simulation of Particle Size Effect on Dynamic Properties and Fracture of PTFE-W-Al Composites

NASA Astrophysics Data System (ADS)

Herbold, Eric; Cai, Jing; Benson, David; Nesterenko, Vitali

2007-06-01

Recent investigations of the dynamic compressive strength of cold isostatically pressed (CIP) composites of polytetrafluoroethylene (PTFE), tungsten and aluminum powders show significant differences depending on the size of metallic particles. PTFE and aluminum mixtures are known to be energetic under dynamic and thermal loading. The addition of tungsten increases density and overall strength of the sample. Multi-material Eulerian and arbitrary Lagrangian-Eulerian methods were used for the investigation due to the complexity of the microstructure, relatively large deformations and the ability to handle the formation of free surfaces in a natural manner. The calculations indicate that the observed dependence of sample strength on particle size is due to the formation of force chains under dynamic loading in samples with small particle sizes even at larger porosity in comparison with samples with large grain size and larger density.

Airborne particulate matter and spacecraft internal environments

NASA Technical Reports Server (NTRS)

Liu, Benjamin Y. H.; Rubow, Kenneth L.; Mcmurry, Peter H.; Kotz, Thomas J.; Russo, Dane

1991-01-01

Instrumentation, consisting of a Shuttle Particle Sampler (SPS) and a Shuttle Particle Monitor (SPM), has been developed to characterize the airborne particulate matter in the Space Shuttle cabin during orbital flight. The SPS size selectively collects particles in four size fractions (0-2.5, 2.5-10, 10-100, and greater than 100 microns) which are analyzed postflight for mass concentration and size distribution, elemental composition, and morphology. The SPM provides a continuous record of particle concentration through photometric light scattering. Measurements were performed onboard Columbia, OV-102, during the flight of STS-32 in January 1990. No significant changes were observed in the particle mass concentration, size distribution, or chemical composition in samples collected during flight-day 2 and flight-day 7. The total mass concentration was 56 microg/cu cm with approximately half of the particles larger than 100 microns. Elemental analysis showed that roughly 70 percent of the particles larger than 2.5 microns were carbonaceous with small amounts of other elements present. The SPM showed no temporal or spatial variation in particle mass concentration during the mission.

Material comprising two different non-metallic parrticles having different particle sizes for use in solar reactor

DOE Office of Scientific and Technical Information (OSTI.GOV)

Klausner, James F.; Momen, Ayyoub Mehdizadeh; Al-Raqom, Fotouh A.

Disclosed herein is a composite particle comprising a first non-metallic particle in which is dispersed a second non-metallic particle, where the first non-metallic particle and the second non-metallic particle are inorganic; and where a chemical composition of the first non-metallic particle is different from a chemical composition of the second non-metallic particle; and where the first non-metallic particle and the second non-metallic particle are metal oxides, metal carbides, metal nitrides, metal borides, metal silicides, metal oxycarbides, metal oxynitrides, metal boronitrides, metal carbonitrides, metal borocarbides, or a combination thereof.

Decending motion of particle and its effect on ozone hole chemistry

NASA Technical Reports Server (NTRS)

Iwasaka, Y.

1988-01-01

Particle descending motion is one possible process which causes ozone loss near the tropopause in the Antarctic spring. However, this particle size distribution has not yet been measured. Particle settling is an important redistribution process of the chemical constituents contained in the particles. To understand particle settling effects on the Ozone Hole, information on the size distribution and the chemical composition of the particles is necessary.

Atomic-level study on mechanical properties and strengthening mechanisms of Al/SiC nano-composites

NASA Astrophysics Data System (ADS)

Huo, Shiyan; Xie, Lijing; Xiang, Junfeng; Pang, Siqin; Hu, Fang; Umer, Usama

2018-02-01

Molecular dynamics (MD) models for the study on the mechanical properties of β-SiC particles-reinforced aluminum matrix nano-composites (Al/SiC nano-composites) are established. The nano-composites in the model are fabricated by a powder metallurgy (P/M) process, followed by a hot isostatic pressing and then annealing to room temperature. The fabricated nano-composites have dense and even distributions of reinforced particles. Then representative volume elements (RVEs) of the fabricated nano-composites are built by adding periodic boundary conditions (PBCs). In this way, RVEs with different volume fractions and particle sizes of SiC are produced and put into the simulation of tension tests. The elasticity and strength in single axial tension obtained from MD analysis are in good agreement with those calculated according to the rule of mixture. It is found that the dispersion of SiC particles into the Al matrix leads to a significant enhancement in the strength of nano-composites compared to pure Al, which is also dramatically affected by both the volume fraction and particle size. Additionally, the Al/SiC nano-composites with finer SiC particles get greater enhancement in the mechanical behavior than those with coarser ones. MD analysis clearly shows the contributions of load-transfer effect, thermal mismatch strengthening and Orowan strengthening to the strengthening of Al/SiC nano-composites.

Electroactive compositions with poly(arylene oxide) and stabilized lithium metal particles

DOEpatents

Zhang, Zhengcheng; Yuan, Shengwen; Amine, Khalil

2015-05-12

An electroactive composition includes an anodic material; a poly(arylene oxide); and stabilized lithium metal particles; where the stabilized lithium metal particles have a size less than about 200 .mu.m in diameter, are coated with a lithium salt, are present in an amount of about 0.1 wt % to about 5 wt %, and are dispersed throughout the composition. Lithium secondary batteries including the electroactive composition along with methods of making the electroactive composition are also discussed.

Elastohydrodynamic lubrication in point contact on the surfaces of particle-reinforced composite

NASA Astrophysics Data System (ADS)

Chen, Keying; Zeng, Liangcai; Wu, Zhenpeng; Zheng, Feilong

2018-04-01

Appreciable friction and serious wear are common challenges in the operation of advanced manufacturing equipment, and friction pairs may be susceptible to damage even with oil lubrication when point contact exists. In this study, a type of particle-reinforced composite material is introduced for one of the components of a heavy-load contact pair, and the performance improvement of elastohydrodynamic lubrication (EHL) is analyzed considering the rheological properties of non-Newtonian fluids. The Ree-Eyring EHL model is used considering the surface of the particle-reinforced composite, in which the film thickness includes the particle-induced elastic deformation. The problem of inclusions with different eigenstrains is solved by using Galerkin vectors. The influences of particle properties, size, burial depth, and interparticle distance on point-contact EHL are investigated. Furthermore, using several cases, the structural parameters of the particles in the composites are optimized, and an appropriate parameter range is obtained with the goal of reducing friction. Finally, the results for the EHL traction coefficient demonstrate that appropriate particle properties, size, burial depth, and interparticle distance can effectively reduce the traction coefficient in heavy-load contact.

[Preparation of panax notoginseng saponins-tanshinone H(A) composite method for pulmonary delivery with spray-drying method and its characterization].

PubMed

Wang, Hua-Mei; Fu, Ting-Ming; Guo, Li-Wei

2013-02-01

To prepare panax notoginseng saponins-tanshinone II(A) composite particles for pulmonary delivery, in order to explore a dry powder particle preparation method ensuring synchronized arrival of multiple components of traditional Chinese medicine compounds at absorption sites. Panax notoginseng saponins-tanshinone II(A) composite particles were prepared with spray-drying method, and characterized by scanning electron microscopy (SEM), confocal laser scanning microscope (CLSM), X-ray diffraction (XRD), infrared analysis (IR), dry laser particle size analysis, high performance liquid chromatography (HPLC) and the aerodynamic behavior was evaluated by a Next Generation Impactor (NGI). The dry powder particles produced had narrow particle size distribution range and good aerodynamic behavior, and could realize synchronized administration of multiple components. The spray-drying method is used to combine traditional Chinese medicine components with different physical and chemical properties in the same particle, and product into traditional Chinese medicine compound particles in line with the requirements for pulmonary delivery.

Molecular Diversity of Sea Spray Aerosol Particles: Impact of Ocean Biology on Particle Composition and Hygroscopicity

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cochran, Richard E.; Laskina, Olga; Trueblood, Jonathan V.

The impact of sea spray aerosol (SSA) on climate depends on the size and chemical composition of individual particles that make-up the total SSA ensemble. While the organic fraction of SSA has been characterized from a bulk perspective, there remains a lack of understanding as to the composition of individual particles within the SSA ensemble. To better understand the molecular components within SSA particles and how SSA composition changes with ocean biology, simultaneous measurements of seawater and SSA were made during a month-long mesocosm experiment performed in an ocean-atmosphere facility. Herein, we deconvolute the composition of freshly emitted SSA devoidmore » of anthropogenic and terrestrial influences by characterizing classes of organic compounds as well as specific molecules within individual SSA particles. Analysis of SSA particles show that the diversity of molecules within the organic fraction varies between two size fractions (submicron and supermicron) with contributions from fatty acids, monosaccharides, polysaccharides and siliceous material. Significant changes in the distribution of these compounds within individual particles are observed to coincide with the rise and fall of phytoplankton and bacterial populations within the seawater. Furthermore, water uptake is impacted as shown by hygroscopicity measurements of model systems composed of representative organic compounds. Thus, the how changes in the hygroscopic growth of SSA evolves with composition can be elucidated. Overall, this study provides an important connection between biological processes that control the composition of seawater and changes in single particle composition which will enhances our ability to predict the impact of SSA on climate.« less

Size-Resolved Composition of Organic Aerosol on the California Central Coast

NASA Astrophysics Data System (ADS)

Babila, J. E.; Depew, C. J.; Heinrich, S. E.; Zoerb, M.

2016-12-01

Organic compounds represent a significant mass fraction of submicrometer aerosol and can influence properties such as radiative forcing and cloud formation. Despite their broad importance, a complete description of particle sources and composition is lacking. Here we present measurements of solvent-extracted organic compounds in ambient aerosol in San Luis Obispo, CA. Ambient particles were sampled and size segregated with a micro-orifice uniform deposit impactor (MOUDI). Water and methanol soluble organic carbon was characterized with electrospray ionization mass spectrometry (ESI-MS) and UV/Vis spectroscopy. Particle composition and influences from local and regional sources on the organic fraction will be discussed.

Radio frequency shielding behaviour of silane treated Fe2O3/E-glass fibre reinforced epoxy hybrid composite

NASA Astrophysics Data System (ADS)

Arun prakash, V. R.; Rajadurai, A.

2016-10-01

In this work, radio frequency shielding behaviour of polymer (epoxy) matrixes composed of E-glass fibres and Fe2O3 fillers have been studied. The principal aim of this project is to prepare suitable shielding material for RFID application. When RFID unit is pasted on a metal plate without shielding material, the sensing distance is reduced, resulting in a less than useful RFID system. To improve RF shielding of epoxy, fibres and fillers were utilized. Magnetic behaviour of epoxy polymer composites was measured by hysteresis graphs (B-H) followed by radio frequency identifier setup. Fe2O3 particles of sizes 800, 200 and 100 nm and E-glass fibre woven mat of 600 g/m2 were used to make composites. Particle sizes of 800 nm and 200 nm were prepared by high-energy ball milling, whereas particles of 100 nm were prepared by sol-gel method. To enhance better dispersion of particles within the epoxy matrix, a surface modification process was carried out on fillers by an amino functional coupling agent called 3-Aminopropyltrimethoxysilane (APTMS). Crystalline and functional groups of siliconized Fe2O3 particles were characterized by XRD and FTIR spectroscopy analysis. Variable quantity of E-glass fibre (25, 35, and 45 vol%) was laid down along with 0.5 and 1.0 vol% of 800, 200, and 100 nm size Fe2O3 particles into the matrix, to fabricate the hybrid composites. Scanning electron microscopy and transmission electron microscopy images reveal the shape and size of Fe2O3 particles for different milling times and particle dispersion in the epoxy matrix. The maximum improved sensing distance of 45.2, 39.4 and 43.5 % was observed for low-, high-, and ultra-high radio frequency identifier setup along with shielding composite consist of epoxy, 1 vol% 200 nm Fe2O3 particles and 45 vol% of E-glass fibre.

The influence of magnetic and dielectric loss on the noise absorption of iron particles-rubber composites attached to a microstrip line

NASA Astrophysics Data System (ADS)

Kim, Sun-Tae; Park, Yong-Gwon; Kim, Sung-Soo

2008-04-01

Magnetic and dielectric loss are systematically controlled by using iron flake powders with various initial sizes (7 μm and 70 μm) as the absorbent fillers in the rubber matrix, and their noise absorbing characteristics have been investigated as a function of frequency and sheet thickness. Flake iron particles were prepared by the mechanical forging of spherical powders using an attrition mill. Composite sheets (thickness=0.2 mm-1.0 mm) were prepared with a mixture of iron particles and silicone rubber. Attaching the composite sheets to a microstrip line of 50 Ω, a network analyzer was used to measure the reflection and transmission parameters (S11 and S21, respectively). A nearly constant value of S11 (about -10 dB) was observed, irrespective of particle size. However, S21 is strongly dependent upon initial particle size. For the composites of 7 μm particles (with high magnetic loss), S21 is reduced below -20 dB in the frequency range of 1 GHz to 10 GHz, and the corresponding bandwidth of noise absorption is not so greatly diminished by reducing the sheet thickness as low as 0.2 mm. For the composites of 70 μm particles (with high dielectric loss), however, the bandwidth is greatly reduced with a decrease in sheet thickness. It is concluded that the attenuation of conduction noise through the microstrip line is primarily controlled by the magnetic loss of the iron particles due to strong magnetic field around the microstrip line.

Transformations of inorganic coal constituents in combustion systems. Volume 1, sections 1--5: Final report

DOE Office of Scientific and Technical Information (OSTI.GOV)

Helble, J.J.; Srinivasachar, S.; Wilemski, G.

1992-11-01

The inorganic constituents or ash contained in pulverized coal significantly increase the environmental and economic costs of coal utilization. For example, ash particles produced during combustion may deposit on heat transfer surfaces, decreasing heat transfer rates and increasing maintenance costs. The minimization of particulate emissions often requires the installation of cleanup devices such as electrostatic precipitators, also adding to the expense of coal utilization. Despite these costly problems, a comprehensive assessment of the ash formation and had never been attempted. At the start of this program, it was hypothesized that ash deposition and ash particle emissions both depended upon themore » size and chemical composition of individual ash particles. Questions such as: What determines the size of individual ash particles? What determines their composition? Whether or not particles deposit? How combustion conditions, including reactor size, affect these processes? remained to be answered. In this 6-year multidisciplinary study, these issues were addressed in detail. The ambitious overall goal was the development of a comprehensive model to predict the size and chemical composition distributions of ash produced during pulverized coal combustion. Results are described.« less

Inhable particulate matter from lime industries: Chemical composition and deposition in human respiratory tract

NASA Astrophysics Data System (ADS)

Godoi, Ricardo H. M.; Braga, Darci M.; Makarovska, Yaroslava; Alfoldy, Balint; Carvalho Filho, Marco A. S.; Van Grieken, Réne; Godoi, Ana Flavia L.

Air pollution caused by the lime production industry has become a serious problem with potential effects to human health, especially in developing countries. Colombo is a city included in the Metropolitan Region of Curitiba (capital of Paraná State) in South Brazil. In Colombo city, a correlation has been shown between the lime production and the number of persons who need respiratory treatment in a local hospital, indicating that the lime industry can cause deleterious health effects in the exposed workers and population. This research was conducted to deal firstly with the characterization of the size distribution and chemical compositions of particles emitted from lime manufacturing and subsequently to assess the deposition rate of inhaled dolomitic lime aerosol particles in the human respiratory tract. The elemental chemical composition and particle size of individual atmospheric particles was quantitatively elucidated, including low-Z components like C, N and O, as well as higher-Z elements, using automated electron probe microanalysis. Information concerning the bulk composition is provided by energy-dispersive X-ray detection. The majority of the respirable particulate matter identified was composed of aluminosilicates, Ca-Mg oxides, carbon-rich particles, mixtures of organic particles and Ca-Mg carbonates, soot and biogenic particles. In view of the chemical composition and size distribution of the aerosol particles, local deposition efficiencies in the human respiratory system were calculated, revealing the deposition of CaO·MgO at extrathoracic, tracheobronchial and pulmonary levels. The results of this study offer evidence to the threat of the fine and coarse particles emitted from dolomite lime manufacturing, allowing policy-makers to better focus their mitigation strategies in an effective way, as well as to the dolomite producers for the purpose of designing and/or implementing improved emission controls.

Impacts of the mixing state and chemical composition on the cloud condensation nuclei (CCN) activity in Beijing during winter, 2016

NASA Astrophysics Data System (ADS)

Ren, J.; Zhang, F.

2017-12-01

Abstract.Understanding aerosol chemical composition and mixing state on CCN activity in polluted urban area is crucial to determine NCCN accurately and thus to quantify aerosol indirect effects. Aerosol hrgroscopicity, size-resolved cloud condensation nuclei (CCN) concentration and chemical composition are measured under polluted and background conditions in Beijing based on the Air Pollution and Human Health (APHH) field campaign in winter 2016. The CCN number concentration (NCCN) is predicted by using κ-Köhler theory from the PNSD and five simplified of the mixing state and chemical composition. The assumption of EIS (sulfate, nitrate and SOA internally mixed, and POA and BC externally mixed with size-resolved chemical composition) shows the best closure to predict NCCN with the ratio of predicted to measured NCCN of 0.96-1.12 both in POL and BG conditions. Under BG conditions, IB (internal mixture with bulk chemical composition) scheme achieves the best CCN closure during any periods of a day. In polluted days, EIS and IS (internal mixture with size-resolved chemical composition) scheme may achieve better closure than IB scheme due to the heterogeneity in particles composition across different size. ES (external mixture with size-resolved chemical composition) and EB (external mixture with bulk chemical composition) scheme markedly underestimate the NCCN with the ratio of predicted to measured NCCN of 0.6-0.8. In addition, we note that assumptions of size-resolved composition (IS or ES) show very limited promotes by comparing with the assumptions of bulk composition (IB or EB), furthermore, the prediction becomes worse by using size-resolved assumption in clean days. The predicted NCCN during eve-rush periods shows the most sensitivity to the five different assumptions, with ratios of the predicted and measured NCCN ranging from 0.5 to 1.4, reflecting great impacts from evening traffic and cooking sources. The result from the sensitivity examination of predict NCCN to particles mixing state and organic volume fractions with the aging of organic particles suggests that the mixing state of particles plays a minor role when the κorg exceeds 0.1. Our study could provide new dataset to evaluate the CCN parameterization in models in those heavily polluted regions with large fraction of POA and BC.

Influence of particle size on Cutting Forces and Surface Roughness in Machining of B4Cp - 6061 Aluminium Matrix Composites

NASA Astrophysics Data System (ADS)

Hiremath, Vijaykumar; Badiger, Pradeep; Auradi, V.; Dundur, S. T.; Kori, S. A.

2016-02-01

Amongst advanced materials, metal matrix composites (MMC) are gaining importance as materials for structural applications in particular, particulate reinforced aluminium MMCs have received considerable attention due to their superior properties such as high strength to weight ratio, excellent low-temperature performance, high wear resistance, high thermal conductivity. The present study aims at studying and comparing the machinability aspects of B4Cp reinforced 6061Al alloy metal matrix composites reinforced with 37μm and 88μm particulates produced by stir casting method. The micro structural characterization of the prepared composites is done using Scanning Electron Microscopy equipped with EDX analysis (Hitachi Su-1500 model) to identify morphology and distribution of B4C particles in the 6061Al matrix. The specimens are turned on a conventional lathe machine using a Polly crystalline Diamond (PCD) tool to study the effect of particle size on the cutting forces and the surface roughness under varying machinability parameters viz., Cutting speed (29-45 m/min.), Feed rate (0.11-0.33 mm/rev.) and depth of cut (0.5-1mm). Results of micro structural characterization revealed fairly uniform distribution of B4C particles (in both cases i.e., 37μm and 88μm) in 6061Al matrix. The surface roughness of the composite is influenced by cutting speed. The feed rate and depth of cut have a negative influence on surface roughness. The cutting forces decreased with increase in cutting speed whereas cutting forces increased with increase in feed and depth of cut. Higher cutting forces are noticed while machining Al6061 base alloy compared to reinforced composites. Surface finish is high during turning of the 6061Al base alloy and surface roughness is high with 88μm size particle reinforced composites. As the particle size increases Surface roughness also increases.

Mechanical, Dielectric, and Spectroscopic Characteristics of "Micro/Nanocellulose + Oxide" Composites.

PubMed

Nedielko, Maksym; Hamamda, Smail; Alekseev, Olexander; Chornii, Vitalii; Dashevskii, Mykola; Lazarenko, Maksym; Kovalov, Kostiantyn; Nedilko, Sergii G; Tkachov, Sergii; Revo, Sergiy; Scherbatskyi, Vasyl

2017-12-01

The set of composite materials that consist of micro/nanocellulose and complex K 2 Eu(MoO 4 )(PO 4 ) luminescent oxide particles was prepared. The composites were studied by means of scanning electron microscopy, XRD analysis, dilatometry, differential scanning calorimetry and thermogravimetric analysis, and dielectric and luminescence spectroscopy.Dependencies of density, crystallinity, relative extension, thermal extension coefficient, dielectric relaxation parameters, intensity and shape of photoluminescence bands on temperature, and content of oxide component were studied. The structure of the composite without oxide is formed by grains of nearly 5-50 μm in size (crystallinity is about ~56%). Structure of the micro/nanocellulose samples which contain oxide particles is similar, but the cellulose grains are deformed by oxide particles. Dependencies of the abovementioned properties on temperature and oxide content were analyzed together with data on the size distribution of oxide particles for the samples for various oxide and molecules of water concentrations.

Variation in the Composition and In Vitro Proinflammatory Effect of Urban Particulate Matter from Different Sites

PubMed Central

Manzano-León, Natalia; Quintana, Raúl; Sánchez, Brisa; Serrano, Jesús; Vega, Elizabeth; Vázquez-López, Inés; Rojas-Bracho, Leonora; López-Villegas, Tania; O’Neill, Marie S.; Vadillo-Ortega, Felipe; De Vizcaya-Ruiz, Andrea; Rosas, Irma

2015-01-01

Spatial variation in particulate matter–related health and toxicological outcomes is partly due to its composition. We studied spatial variability in particle composition and induced cellular responses in Mexico City to complement an ongoing epidemiologic study. We measured elements, endotoxins, and polycyclic aromatic hydrocarbons in two particle size fractions collected in five sites. We compared the in vitro proinflammatory response of J774A.1 and THP-1 cells after exposure to particles, measuring subsequent TNFα and IL-6 secretion. Particle composition varied by site and size. Particle constituents were subjected to principal component analysis, identifying three components: C1 (Si, Sr, Mg, Ca, Al, Fe, Mn, endotoxin), C2 (polycyclic aromatic hydrocarbons), and C3 (Zn, S, Sb, Ni, Cu, Pb). Induced TNFα levels were higher and more heterogeneous than IL-6 levels. Cytokines produced by both cell lines only correlated with C1, suggesting that constituents associated with soil induced the inflammatory response and explain observed spatial differences. PMID:23335408

Preparation of biocompatible magnetite-carboxymethyl cellulose nanocomposite: characterization of nanocomposite by FTIR, XRD, FESEM and TEM.

PubMed

Habibi, Neda

2014-10-15

The preparation and characterization of magnetite-carboxymethyl cellulose nano-composite (M-CMC) material is described. Magnetite nano-particles were synthesized by a modified co-precipitation method using ferrous chloride tetrahydrate and ferric chloride hexahydrate in ammonium hydroxide solution. The M-CMC nano-composite particles were synthesized by embedding the magnetite nanoparticles inside carboxymethyl cellulose (CMC) using a freshly prepared mixture of Fe3O4 with CMC precursor. Morphology, particle size, and structural properties of magnetite-carboxymethyl cellulose nano-composite was accomplished using X-ray powder diffraction (XRD), transmission electron microscopy (TEM), Fourier transformed infrared (FTIR) and field emission scanning electron microscopy (FESEM) analysis. As a result, magnetite nano-particles with an average size of 35nm were obtained. The biocompatible Fe3O4-carboxymethyl cellulose nano-composite particles obtained from the natural CMC polymers have a potential range of application in biomedical field. Copyright © 2014 Elsevier B.V. All rights reserved.

In Situ Identification of Pigment Composition and Particle Size on Wall Paintings Using Visible Spectroscopy as a Noninvasive Measurement Method.

PubMed

Li, Junfeng; Wan, Xiaoxia; Bu, Yajing; Li, Chan; Liang, Jinxing; Liu, Qiang

2016-11-01

Noninvasive examination methods of chemical composition and particle size are presented here based on visible spectroscopy to achieve the identification and recording of mineral pigments used on ancient wall paintings. The normalized spectral curve, slope and curvature extracted from visible spectral reflectance are combined with adjustable weighting coefficients to construct the identification feature space, and Euclid distances between spectral reflectance from wall paintings and a reference database are calculated in the feature space as the discriminant criterion to identify the chemical composition of mineral pigments. A parametric relationship between the integral quantity of spectral reflectance and logarithm of mean particle size is established using a quadratic polynomial to accomplish the noninvasive prediction of mineral pigment particle size used on ancient wall paintings. The feasibility of the proposed methods is validated by the in situ nondestructive identification of the wall paintings in the Mogao Grottoes at Dunhuang. Chinese painting styles and historical evolution are then analyzed according to the identification results of 16 different grottoes constructed from the Sixteen Kingdoms to the Yuan Dynasty. © The Author(s) 2016.

Post-processing of metal matrix composites by friction stir processing

NASA Astrophysics Data System (ADS)

Sharma, Vipin; Singla, Yogesh; Gupta, Yashpal; Raghuwanshi, Jitendra

2018-05-01

In metal matrix composites non-uniform distribution of reinforcement particles resulted in adverse affect on the mechanical properties. It is of great interest to explore post-processing techniques that can eliminate particle distribution heterogeneity. Friction stir processing is a relatively newer technique used for post-processing of metal matrix composites to improve homogeneity in particles distribution. In friction stir processing, synergistic effect of stirring, extrusion and forging resulted in refinement of grains, reduction of reinforcement particles size, uniformity in particles distribution, reduction in microstructural heterogeneity and elimination of defects.

Size-specific composition of aerosols in the El Chichon volcanic cloud

NASA Technical Reports Server (NTRS)

Woods, D. C.; Chuan, R. L.

1983-01-01

A NASA U-2 research aircraft flew sampling missions in April, May, July, November, and December 1982 aimed at obtaining in situ data in the stratospheric cloud produced from the March-April 1982 El Chichon eruptions. Post flight analyses provided information on the aerosol composition and morphology. The particles ranged in size from smaller than 0.05 m to larger than 20 m diameter and were quite complex in composition. In the April, May, and July samples the aerosol mass was dominated by magmatic and lithic particles larger than about 3 m. The submicron particles consisted largely of sulfuric acid. Halite particles, believed to be related to a salt dome beneath El Chichon, were collected in the stratosphere in April and May. On the July 23 flight, copper-zinc oxide particles were collected. In July, November, and December, in addition to the volcanic ash and acid particles, carbon-rich particles smaller than about 0.1 m aerodynamic diameter were abundant.

Linking Different Exposure Patterns to Internal Lung Dose for Heterogeneous Ambient Aerosols

EPA Science Inventory

Particulate matter (PM) in the ambient air is a complex mixture of particles with different sizes and chemical compositions. Because potential health effects are known to be different for different size particles, specific dose of size-fractionated PM under realistic exposure con...

Multifunctional shape and size specific magneto-polymer composite particles.

PubMed

Nunes, Janine; Herlihy, Kevin P; Mair, Lamar; Superfine, Richard; DeSimone, Joseph M

2010-04-14

Interest in uniform multifunctional magnetic particles is driven by potential applications in biomedical and materials science. Here we demonstrate the fabrication of highly tailored nanoscale and microscale magneto-polymer composite particles using a template based approach. Regiospecific surface functionalization of the particles was performed by chemical grafting and evaporative Pt deposition. Manipulation of the particles by an applied magnetic field was demonstrated in water and hydrogen peroxide.

Optimizing manufacturing and composition of a TLR4 nanosuspension: physicochemical stability and vaccine adjuvant activity

PubMed Central

2013-01-01

Background Nanosuspensions are an important class of delivery system for vaccine adjuvants and drugs. Previously, we developed a nanosuspension consisting of the synthetic TLR4 ligand glucopyranosyl lipid adjuvant (GLA) and dipalmitoyl phosphatidylcholine (DPPC). This nanosuspension is a clinical vaccine adjuvant known as GLA-AF. We examined the effects of DPPC supplier, buffer composition, and manufacturing process on GLA-AF physicochemical and biological activity characteristics. Results DPPC from different suppliers had minimal influence on physicochemical and biological effects. In general, buffered compositions resulted in less particle size stability compared to unbuffered GLA-AF. Microfluidization resulted in rapid particle size reduction after only a few passes, and 20,000 or 30,000 psi processing pressures were more effective at reducing particle size and recovering the active component than 10,000 psi. Sonicated and microfluidized batches maintained good particle size and chemical stability over 6 months, without significantly altering in vitro or in vivo bioactivity of GLA-AF when combined with a recombinant malaria vaccine antigen. Conclusions Microfluidization, compared to water bath sonication, may be an effective manufacturing process to improve the scalability and reproducibility of GLA-AF as it advances further in the clinical development pathway. Various sources of DPPC are suitable to manufacture GLA-AF, but buffered compositions of GLA-AF do not appear to offer stability advantages over the unbuffered composition. PMID:24359024

Ferroelectric properties of composites containing BaTiO 3 nanoparticles of various sizes

NASA Astrophysics Data System (ADS)

Adam, Jens; Lehnert, Tobias; Klein, Gabi; McMeeking, Robert M.

2014-01-01

Size effects, including the occurrence of superparaelectric phases associated with small scale, are a significant research topic for ferroelectrics. Relevant phenomena have been explored in detail, e.g. for homogeneous, thin ferroelectric films, but the related effects associated with nanoparticles are usually only inferred from their structural properties. In contrast, this paper describes all the steps and concepts necessary for the direct characterization and quantitative assessment of the ferroelectric properties of as-synthesized and as-received nanoparticles. The method adopted uses electrical polarization measurements on polymer matrix composites containing ferroelectric nanoparticles. It is applied to ten different BaTiO3 particle types covering a size range from 10 nm to 0.8 μm. The influence of variations of particle characteristics such as tetragonality and dielectric constant is considered based on measurements of these properties. For composites containing different particle types a clearly differing polarization behaviour is found. For decreasing particle size, increasing electric field is required to achieve a given level of polarization. The size dependence of a measure related to the coercive field revealed by this work is qualitatively in line with the state of the knowledge for ferroelectrics having small dimensions. For the first time, such results and size effects are described based on data from experiments on collections of actual nanoparticles.

Investigations of the effects of particle properties on the wear resistance of the particle reinforced composites using a novel wear model

NASA Astrophysics Data System (ADS)

Prabhu, T. Ram

2016-08-01

A wear model is developed based on the discrete lattice spring-mass approach to study the effects of particle volume fraction, size, and stiffness on the wear resistance of particle reinforced composites. To study these effects, we have considered three volume fractions (10%, 20% and 30%), two sizes (10 × 10 and 4 × 4 sites), and two different stiffness of particles embedded in the matrix in a regular pattern. In this model, we have discretized the composite system (400 × 100 sites) into the lumped masses connected with interaction spring elements in two dimensions. The interaction elements are assumed as linear elastic and ideal plastic under applied forces. Each mass is connected to its first and second nearest neighbors by springs. The matrix and particles sites are differentiated by choosing the different stiffness values. The counter surface is simulated as a rigid body that moves on the composite material at a constant sliding speed along the horizontal direction. The governing equations are formed by equating the spring force between the pair of sites given by Hooke’s law plus external contact forces and the force due to the motion of the site given by the equation of motion. The equations are solved for the plastic strain accumulated in the springs using an explicit time stepping procedure based on a finite difference form of the above equations. If the total strain accumulated in the spring elements connected to a lump mass site exceeds the failure strain, the springs are considered to be broken, and the mass site is removed or worn away from the lattice and accounts as a wear loss. The model predicts that (i) increasing volume fraction, reducing particle size and increasing particle stiffness enhance the wear resistance of the particle reinforced composites, (ii) the particle stiffness is the most significant factor affecting the wear resistance of the composites, and (iii) the wear resistance reduced above the critical volume fraction (Vc), and Vc increases with increasing particle size. Finally, we have qualitatively compared the model results with our previously published experimental results to prove the effectiveness of the model to analysis the complex wear systems.

Preparation and encapsulation of white/yellow dual colored suspensions for electrophoretic displays

NASA Astrophysics Data System (ADS)

Han, Jingjing; Li, Xiaoxu; Feng, Yaqing; Zhang, Bao

2014-11-01

C.I. Pigment Yellow 181 (PY181) composite particles encapsulated by polyethylene (PE) were prepared by dispersion polymerization method, and C.I. Pigment Yellow 110 (PY110) composite particles encapsulated by polystyrene (PS) with mini-emulsion polymerization method were achieved, respectively. The modified pigments were characterized by fourier transform infrared spectroscopy, scanning electron microscope and transmission electron microscope. Compared with the PE-coated PY 181 pigments, the PS-coated PY-110 particles had a narrow particle size distribution, regular spherical and average particle size of 450 nm. Suspension 1 and suspension 3 were prepared by the two composite particles dispersed in isopar M. A chromatic electrophoretic display cell consisting of yellow particles was successfully fabricated using dispersions of yellow ink particles in a mixed dielectric solvent with white particles as contrast. The response behavior and the contrast ratio to the electric voltage were also examined. The contrast ratio of pigments modified by polystyrene was 1.48, as well as the response time was 2 s, which were better than those of pigments modified by polyethylene.

Stable Carbon Fractionation In Size Segregated Aerosol Particles Produced By Controlled Biomass Burning

NASA Astrophysics Data System (ADS)

Masalaite, Agne; Garbaras, Andrius; Garbariene, Inga; Ceburnis, Darius; Martuzevicius, Dainius; Puida, Egidijus; Kvietkus, Kestutis; Remeikis, Vidmantas

2014-05-01

Biomass burning is the largest source of primary fine fraction carbonaceous particles and the second largest source of trace gases in the global atmosphere with a strong effect not only on the regional scale but also in areas distant from the source . Many studies have often assumed no significant carbon isotope fractionation occurring between black carbon and the original vegetation during combustion. However, other studies suggested that stable carbon isotope ratios of char or BC may not reliably reflect carbon isotopic signatures of the source vegetation. Overall, the apparently conflicting results throughout the literature regarding the observed fractionation suggest that combustion conditions may be responsible for the observed effects. The purpose of the present study was to gather more quantitative information on carbonaceous aerosols produced in controlled biomass burning, thereby having a potential impact on interpreting ambient atmospheric observations. Seven different biomass fuel types were burned under controlled conditions to determine the effect of the biomass type on the emitted particulate matter mass and stable carbon isotope composition of bulk and size segregated particles. Size segregated aerosol particles were collected using the total suspended particle (TSP) sampler and a micro-orifice uniform deposit impactor (MOUDI). The results demonstrated that particle emissions were dominated by the submicron particles in all biomass types. However, significant differences in emissions of submicron particles and their dominant sizes were found between different biomass fuels. The largest negative fractionation was obtained for the wood pellet fuel type while the largest positive isotopic fractionation was observed during the buckwheat shells combustion. The carbon isotope composition of MOUDI samples compared very well with isotope composition of TSP samples indicating consistency of the results. The measurements of the stable carbon isotope ratio in size segregated aerosol particles suggested that combustion processes could strongly affect isotopic fractionation in aerosol particles of different sizes thereby potentially affecting an interpretation of ambient atmospheric observations.

Effects of nano-SiO{sub 2} particles on surface tracking characteristics of silicone rubber composites

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liu, Yong, E-mail: tjuliuyong@tju.edu.cn; Li, Zhonglei; Du, Boxue

Compared with neat silicone rubber composites (SiRCs), SiRCs filled with nano-sized SiO{sub 2} particles at weight ratios from 0.1 to 1.0 wt. % exhibit a higher surface flashover voltage and a greater resistance to surface tracking. Scanning electron microscopy images of tracking morphologies indicate that the SiO{sub 2} particles are situated in close proximity to the polymeric chains and act as bridges to stabilize the chains and maintain the structure of the composite. Higher concentrations of nano-sized SiO{sub 2} particles, however, (above 0.3 wt. %) produce defects in the molecular network which lead to reductions in both the surface flashover voltage and the resistancemore » to surface tracking, although these reduced values are still superior to those of neat SiRCs. Therefore, SiRCs filled with nano-sized SiO{sub 2} particles, especially at an optimal weight ratio (0.1 to 0.3 wt. %), may have significant potential applications as outdoor insulators for power systems.« less

Depositing nanometer-sized particles of metals onto carbon allotropes

NASA Technical Reports Server (NTRS)

Delozier, Donavon M. (Inventor); Fallbach, Michael J. (Inventor); Smith, Joseph G. (Inventor); Watson, Kent A. (Inventor); Ghose, Sayata (Inventor); Connell, John W. (Inventor)

2010-01-01

A process for depositing nanometer-sized metal particles onto a substrate in the absence of aqueous solvents, organic solvents, and reducing agents, and without any required pre-treatment of the substrate, includes preparing an admixture of a metal compound and a substrate by dry mixing a chosen amount of the metal compound with a chosen amount of the substrate; and supplying energy to the admixture in an amount sufficient to deposit zero valance metal particles onto the substrate. This process gives rise to a number of deposited metallic particle sizes which may be controlled. The compositions prepared by this process are used to produce polymer composites by combining them with readily available commodity and engineering plastics. The polymer composites are used as coatings, or they are used to fabricate articles, such as free-standing films, fibers, fabrics, foams, molded and laminated articles, tubes, adhesives, and fiber reinforced articles. These articles are well-suited for many applications requiring thermal conductivity, electrical conductivity, antibacterial activity, catalytic activity, and combinations thereof.

Use of natural particles for the removal of paint from aeronautical composite materials

NASA Astrophysics Data System (ADS)

Guy, Thu-Ha; Lankarani, Hamid M.; Talia, Jorge E.

Paint removal by blasting and its effects on the surface morphology of aeronautical composite materials are investigated. An ideal combination of the parameters for mechanical paint removal by blasting such as particle type, size, velocity and angle of incidence yields a stripped aircraft skin substrate with minimal or no damage. Natural particles, specifically white corn flour, seem to be a good choice for paint removal by blasting. Since they are softer as well as smaller in size than other particles used for paint removal, they minimize the amount of damage to the surface of the composite. They are also cheaper and produce no harm to environment. The variation of the degree of surface roughness and the amount of broken fibers were correlated with some stripping parameters, such as particle impact angle and velocity. This defined an optimum environment for paint removal by blasting.

Effect of annealing on magnetic properties of Ni80Fe20 permalloy nanoparticles prepared by polyol method.

PubMed

Qin, G W; Pei, W L; Ren, Y P; Shimada, Y; Endo, Y; Yamaguchi, M; Okamoto, S; Kitakami, O

2011-12-01

Ni80Fe20 permalloy nanoparticles with narrow size distribution and homogeneous composition have been prepared by the polyol processing at 180 degrees C for 2 h and their particle sizes can be tunable in the size range of 20-440 nm by proper addition of K2PtCI4 agent. X-ray diffraction results show that the NiFe nanoparticles are of face centered cubic structure. The addition of K2PtCl4 does not affect the composition of NiFe NPs but decreases the particle size remarkably. Both saturation magnetization and coercivity of the as-prepared NiFe nanoparticles decrease with decreasing particle size. Annealed at 280 degrees C, however, the saturation magnetization of various sized NiFe nanoparticles increases drastically and approaches to the bulk for the -440 nm NiFe particles, and a maximum coercivity (-270 Oe) happens at a critical size of -50 nm. The magnetic property dependency of these NiFe nanoparticles on annealing has been discussed by considering the surface chemistry.

Study of the chemical composition of atmospheric aerosol particles in Hungary: a review

NASA Astrophysics Data System (ADS)

Mészáros, E.

The methods used in Hungarian laboratories to study the chemical composition of atmospheric aerosol particles over the last 30 years are reviewed. Individual particles were identified by topochemical techniques and morphological identification with an electron microscope. Bulk analyses were also carried out by applying wet chemical methods, and more recently by the PIXE procedure. The results gained are summarized in connection with the general development of atmospheric aerosol science during the last decades. These studies demonstrated that cloud condensation nuclei are water soluble Aitken sized particles which are composed of sulfates. Neutralized and acidic sulfate particles constitute the main class of fine aerosol particles under continental and oceanic background conditions. Coarse particles contain mostly sodium, silicon and aluminium. The formation and origin of particles in different size ranges are also discussed.

Passive Sampling to Capture the Spatial Variability of Coarse Particles by Composition in Cleveland, OH

EPA Science Inventory

Passive samplers deployed at 25 sites for three week-long intervals were used to characterize spatial variability in the mass and composition of coarse particulate matter (PM_10-2.5) in Cleveland, OH in summer 2008. The size and composition of individual particles deter...

Volatiles in interplanetary dust particles: A comparison with CI and CM chondrites

NASA Technical Reports Server (NTRS)

Bustin, Roberta

1992-01-01

In an effort to classify and determine the origin of interplanetary dust particles (IDPs), 14 of these particles were studied using a laser microprobe/mass spectrometer. The mass spectra for these particles varied dramatically. Some particles released hydroxide or water which probably originated in hydroxide-bearing minerals or hydrates. Others produced spectra which included a number of hydrocarbons and resembled meteorite spectra. However, none of the individual IDPs gave spectra which could be matched identically with a particular meteorite type such as a CI or CM carbonaceous chondrite. We believe this was due to the fact that 10-20 micron size IDPs are too small to be representative of the parent body. To verify that the diversity was due primarily to the small particle sizes, small grains of approximately the same size range as the IDPs were obtained from two primitive meteorites, Murchison and Orgueil, and these small meteorite particles were treated exactly like the IDPs. Considerable diversity was observed among individual grains, but a composite spectrum of all the grains from one meteorite closely resembled the spectrum obtained from a much larger sample of that meteorite. A composite spectrum of the 14 IDPs also resembled the spectra of the CM and CI meteorites, pointing to a possible link between IDPs and carbonaceous chondrites. This also illustrates that despite the inherent diversity in particles as small as 10-20 micron, conclusions can be drawn about the possible origin and overall composition of such particles by looking not only at results from individual particles but also by including many particles in a study and basing conclusions on some kind of composite data.

Early Size Distributions of Chondrule Subgroups Overprinted by the Final Accumulation Process of Particle Components in Allende

NASA Technical Reports Server (NTRS)

McCain, K. A.; Simon, J. I.; Cuzzi, J. N

2015-01-01

Populations of compositionally distinct particles are fundamental components of undifferentiated chondritic meteorites. Many theories explain the formation of chondrites, one class of which includes mechanisms for sorting the component particles in the solar nebula prior to their accretion. Mechanisms include sorting by mass, turbulent concentration, X-winds, and photophoresis, which will produce characteristic distributions of observable properties such as particle size. Distinguishing processes that occur in specific astrophysical environments requires characterization of particle types, which include refractory Ca-Al-rich Inclusions (CAIs) and less-refractory chondrules. Previous investigations of modal abundances of CAIs and chondrules exist, but differences within and between these two groups, both of which are made up of diverse subgroups with different thermal histories and chemical compositions, remain mostly unstudied. The presence of rims, a significant event occurring after the formation of at least some chondrules, have also yet to be considered with respect to sorting. Here we present the sizes of CAIs and chondrules in Allende with attention to the smallest sizes, subgroups, and particle rims.

The effects of CuO particle size on microstructure evolution of AgCuO compo-sites in plastic deformation process: finite element simulation and experimental study

NASA Astrophysics Data System (ADS)

Li, Zhiguo; Cao, Hanxing; Zhou, Xiaolong; Zhou, Zhaobo; Cao, Jianchun

2018-04-01

The effects of CuO with different particle sizes on the microstructure evolution of AgCuO composite material during plastic deformation process were investigated by finite element (FE) analysis and experiment. The results are as follows: with the decrease of CuO particle size, the degree of radial compression and axial elongation of CuO particle cluster increase gradually, as well as the dispersion of CuO also increase. Meanwhile, the shape of CuO particles is constantly transformed from polygonal to fibrous, which makes the number of linear fibrous CuO increase continuously while bent fibrous CuO reduce gradually. By comparing the simulation and experiment results we find that there are four different typical microstructure regions, which caused by the interaction between monoclinic and cubic CuO during the extrusion process.

Characterization of airborne particles at a high-btu coal-gasification pilot plant.

PubMed

Davidson, C I; Santhanam, S; Stetter, J R; Flotard, R D; Gebert, E

1982-12-01

Airborne particles in fugitive emissions have been measured at a slagging fixed-bed coal-gasification pilot plant using lignite. Sampling was conducted during shutdown operations and opening of the gasifier following an aborted startup. Aerosol collected with a Sierra high-volume impactor was subjected to analysis by gas chromatography, mass spectrometry, and scanning electron microscopy; aerosol collected with an Andersen low-volume impactor was subjected to flameless atomic absorption analysis. The data show that the bulk of the trace organic material is associated with small particles: these data are similar to data on ambient air reported in the literature. Particle morphologies resemble those of fly ash from coal combustion, including smooth spheres, vesicular spheres, and crystalline material. Trace element size distributions are bimodal and resemble data for ambient air. Pb-containing particles are generally submicron, while particles containing Al, Fe, and other crustal species are mostly of supermicron size. Aluminum-based aerosol enrichment factors calculated from the lignite composition show that the composition of the aerosol resembles that of the coal, with the exception of modest enrichments of Mg, Na, As, and Pb in the submicron size range. Aerosol enrichment factors based on the earth's crustal composition are somewhat greater than those based on coal composition for several elements, suggesting potential errors in using crustal enrichment data to investigate chemical fractionation during aerosol formation.

Experimental study of the effect of grain sizes in a bimodal mixture on bed slope, bed texture, and the transition to washload

NASA Astrophysics Data System (ADS)

Hill, Kimberly M.; Gaffney, John; Baumgardner, Sarah; Wilcock, Peter; Paola, Chris

2017-01-01

When fine sediment is added to a coarse-grained system, the mobility and composition of the bed can change dramatically. We conducted a series of flume experiments to determine how the size of fine particles introduced to an active gravel bed influences the mobility and composition of the bed. We initiated our experiments using a constant water discharge and feed rate of gravel. After the system reached steady state, we doubled the feed rate by supplying a second sediment of equal or lesser size, creating size ratios from 1:1 to 1:150. As we decreased the relative size of the fine particles, the system transitioned among three regimes: (1) For particle size ratios close to one, the bed slope increased to transport the additional load of similar-sized particles. The bed surface remained planar and unchanged. (2) For intermediate particle size ratios, the bed slope decreased with the additional fines. The bed surface became patchy with regions of fine and coarse grains. (3) For the largest particle size ratios (the smallest fines), the bed slope remained relatively unchanged. The subsurface became clogged with fine sediment, but fine particles were not present in the surface layer. This third regime constitutes washload, defined by those fractions that do not affect bed-material transport conditions. Our results indicate washload should be defined in terms of three conditions: small grain size relative to that of the bed material, full suspension based on the Rouse number, and a small rate of fine sediment supply relative to transport capacity.

Synthesis and characterization of grinding aid fly ash blended mortar effect on bond strength of masonry prisms

NASA Astrophysics Data System (ADS)

Krishnaraj, L.; Ravichandran, P. T.; Sagadevan, Suresh

2018-04-01

The aim of the present work is to study the effect of particle size reduction by applying top-down nanotechnology such as ball mill grinding process with the addition of amine-based grinding aids. The particle size reduction in synthesis process and its characterization were investigated for fly ash particles. The Rosin-Rammler-Bennet (RRB) distribution model using mathematical formulations were studied for fly ash ground particles. The hardened properties of grinding aid fly ash composite mortar were studied using compressive strength test. The optimum grinding time was 120 min identified through the particle size distribution analysis. The mean particle size decreased from 92.09 μm to 10.5 μm in which there is 89% reduction in particle size due to the grinding of fly ash particle with grinding aids. The compressive strength results show that substitutions of Ordinary Portland Cement (OPC) mortar by Amine-based Grinding aid Fly Ash (AGFA) 15% gives 12, 23% and at 30% gives 6, 8% of higher strength compare to the substitutions of raw fly ash. The addition of grinding aids in grinding process gives more advantages to reduce the particle size without changing chemical composition. The AGFA sample shows better performance in compressive strength and bond strength behavior of masonry prism. It may suggest that amine based grinding aids play a vital role and feasible to use in fly ash grinding process.

Source apportionment of aerosol particles at a European air pollution hot spot using particle number size distributions and chemical composition.

PubMed

Leoni, Cecilia; Pokorná, Petra; Hovorka, Jan; Masiol, Mauro; Topinka, Jan; Zhao, Yongjing; Křůmal, Kamil; Cliff, Steven; Mikuška, Pavel; Hopke, Philip K

2018-03-01

Ostrava in the Moravian-Silesian region (Czech Republic) is a European air pollution hot spot for airborne particulate matter (PM), polycyclic aromatic hydrocarbons (PAHs), and ultrafine particles (UFPs). Air pollution source apportionment is essential for implementation of successful abatement strategies. UFPs or nanoparticles of diameter <100 nm exhibit the highest deposition efficiency in human lungs. To permit apportionment of PM sources at the hot-spot including nanoparticles, Positive Matrix Factorization (PMF) was applied to highly time resolved particle number size distributions (NSD, 14 nm-10 μm) and PM 0.09-1.15 chemical composition. Diurnal patterns, meteorological variables, gaseous pollutants, organic markers, and associations between the NSD factors and chemical composition factors were used to identify the pollution sources. The PMF on the NSD reveals two factors in the ultrafine size range: industrial UFPs (28%, number mode diameter - NMD 45 nm), industrial/fresh road traffic nanoparticles (26%, NMD 26 nm); three factors in the accumulation size range: urban background (24%, NMD 93 nm), coal burning (14%, volume mode diameter - VMD 0.5 μm), regional pollution (3%, VMD 0.8 μm) and one factor in the coarse size range: industrial coarse particles/road dust (2%, VMD 5 μm). The PMF analysis of PM 0.09-1.15 revealed four factors: SIA/CC/BB (52%), road dust (18%), sinter/steel (16%), iron production (16%). The factors in the ultrafine size range resolved with NSD have a positive correlation with sinter/steel production and iron production factors resolved with chemical composition. Coal combustion factor resolved with NSD has moderate correlation with SIA/CC/BB factor. The organic markers homohopanes correlate with coal combustion and the levoglucosan correlates with urban background. The PMF applications to NSD and chemical composition datasets are complementary. PAHs in PM 1 were found to be associated with coal combustion factor. Copyright © 2017 Elsevier Ltd. All rights reserved.

Morphological and chemical analysis of bone substitutes by scanning electron microscopy and microanalysis by spectroscopy of dispersion energy.

PubMed

da Cruz, Gabriela Alessandra; de Toledo, Sérgio; Sallum, Enilson Antonio; de Lima, Antonio Fernando Martorelli

2007-01-01

This study evaluated the morphological and chemical composition of the following bone substitutes: cancellous and cortical organic bovine bone with macro and microparticle size ranging from 1.0 to 2.0 mm and 0.25 to 1.0 mm, respectively; inorganic bovine bone with particle size ranging from 0.25 to 1.0 mm; hydroxyapatite with particle size ranging from 0.75 to 1.0 mm; and demineralized freeze-dried bone allograft with particle size ranging from 0.25 to 0.5 mm. The samples were sputter-coated with gold in an ion coater, the morphology was observed and particle size was measured under vacuum by scanning electron microscopy (SEM). The chemical composition was evaluated by spectroscopy of dispersion energy (EDS) microanalysis using samples without coating. SEM analysis provided visual evidence that all examined materials have irregular shape and particle sizes larger than those informed by the manufacturer. EDS microanalysis detected the presence of sodium, calcium and phosphorus that are usual elements of the bone tissue. However, mineral elements were detected in all analyzed particles of organic bovine bone except for macro cancellous organic bovine bone. These results suggest that the examined organic bovine bone cannot be considered as a pure organic material.

Properties of CuInS₂ Nano-Particles on TiO₂ by Spray Pyrolysis for CuInS₂/TiO₂ Composite Solar Cell.

PubMed

Park, Gye-Choon; Li, Zhen-Yu; Yang, O-Bong

2017-04-01

In this letter, for the absorption layer of a CuInS₂/TiO₂ composite solar cell, I–III–VI2 chalcopyrite semiconductor CuInS₂ nano-particles were deposited by using spray pyrolysis method on TiO2 porous film. Their material characteristics including structural and optical properties of CuInS₂ nano-particles on TiO₂ nanorods were analyzed as a function of its composition ratios of Cu:In:S. Crystalline structure, surface morphology and crystalline size were also investigated by X-ray Diffraction (XRD), Field Emission Scanning Electron Microscope (FESEM), and High-Resolution TEM (HRTEM), respectively. On the other hand, optical property was characterized by an UV-Visible Spectrophotometer. As a result, it was found that the size of CuInS₂ nano-particles, which was formed at 300±5 °C, was smaller than 16 nm from HRTEM analyses, and it was identified that the CuInS₂ particle size was increased as increasing the heat-treatment temperature and time. However, as the size of CuInS₂ nano-particle becomes smaller, optical absorption edge of ternary compound film tends to move to the blue wavelength band. It turns out that the optical energy-band gap of the compound films was ranging from 1.48 eV to 1.53 eV.

Microexplosions and ignition dynamics in engineered aluminum/polymer fuel particles

DOE PAGES

Rubio, Mario A.; Gunduz, I. Emre; Groven, Lori J.; ...

2016-11-11

Aluminum particles are widely used as a metal fuel in solid propellants. However, poor combustion efficiencies and two-phase flow losses result due in part to particle agglomeration. Engineered composite particles of aluminum (Al) with inclusions of polytetrafluoroethylene (PTFE) or low-density polyethylene (LDPE) have been shown to improve ignition and yield smaller agglomerates in solid propellants, recently. Reductions in agglomeration were attributed to internal pressurization and fragmentation (microexplosions) of the composite particles at the propellant surface. We explore the mechanisms responsible for microexplosions in order to better understand the combustion characteristics of composite fuel particles. Single composite particles of Al/PTFE andmore » Al/LDPE with diameters between 100 and 1200 µm are ignited on a substrate to mimic a burning propellant surface in a controlled environment using a CO 2 laser in the irradiance range of 78–7700 W/cm 2. Furthermore, the effects of particle size, milling time, and inclusion content on the resulting ignition delay, product particle size distributions, and microexplosion tendencies are reported. For example particles with higher PTFE content (30 wt%) had laser flux ignition thresholds as low as 77 W/cm 2, exhibiting more burning particle dispersion due to microexplosions compared to the other materials considered. Composite Al/LDPE particles exhibit relatively high ignition thresholds compared to Al/PTFE particles, and microexplosions were observed only with laser fluxes above 5500 W/cm 2 due to low LDPE reactivity with Al resulting in negligible particle self-heating. However, results show that microexplosions can occur for Al containing both low and high reactivity inclusions (LDPE and PTFE, respectively) and that polymer inclusions can be used to tailor the ignition threshold. Furthermore, this class of modified metal particles shows significant promise for application in many different energetic materials that use metal fuels.« less

Effects of age condition on the distribution and integrity of inorganic fillers in dental resin composites.

PubMed

D'Alpino, Paulo Henrique Perlatti; Svizero, Nádia da Rocha; Bim Júnior, Odair; Valduga, Claudete Justina; Graeff, Carlos Frederico de Oliveira; Sauro, Salvatore

2016-06-01

The aim of this study is to evaluate the distribution of the filler size along with the zeta potential, and the integrity of silane-bonded filler surface in different types of restorative dental composites as a function of the material age condition. Filtek P60 (hybrid composite), Filtek Z250 (small-particle filled composite), Filtek Z350XT (nanofilled composite), and Filtek Silorane (silorane composite) (3M ESPE) were tested at different stage condition (i.e., fresh/new, aged, and expired). Composites were submitted to an accelerated aging protocol (Arrhenius model). Specimens were obtained by first diluting each composite specimen in ethanol and then dispersed in potassium chloride solution (0.001 mol%). Composite fillers were characterized for their zeta potential, mean particle size, size distribution, via poly-dispersion dynamic light scattering. The integrity of the silane-bonded surface of the fillers was characterized by FTIR. The material age influenced significantly the outcomes; Zeta potential, filler characteristics, and silane integrity varied both after aging and expiration. Silorane presented the broadest filler distribution and lowest zeta potential. Nanofilled and silorane composites exhibited decreased peak intensities in the FTIR analysis, indicating a deficiency of the silane integrity after aging or expiry time. Regardless to the material condition, the hybrid and the small-particle-filled composites were more stable overtime as no significant alteration in filler size distribution, diameter, and zeta potential occurred. A deficiency in the silane integrity in the nanofilled and silorane composites seems to be affected by the material stage condition. The materials conditions tested in this study influenced the filler size distribution, the zeta potential, and integrity of the silane adsorbed on fillers in the nanofilled and silorane composites. Thus, this may result in a decrease of the clinical performance of aforementioned composites, in particular, if these are used after inappropriate storage conditions.

Influence of coal slurry particle composition on pipeline hydraulic transportation behavior

NASA Astrophysics Data System (ADS)

Li-an, Zhao; Ronghuan, Cai; Tieli, Wang

2018-02-01

Acting as a new type of energy transportation mode, the coal pipeline hydraulic transmission can reduce the energy transportation cost and the fly ash pollution of the conventional coal transportation. In this study, the effect of average velocity, particle size and pumping time on particle composition of coal particles during hydraulic conveying was investigated by ring tube test. Meanwhile, the effects of particle composition change on slurry viscosity, transmission resistance and critical sedimentation velocity were studied based on the experimental data. The experimental and theoretical analysis indicate that the alter of slurry particle composition can lead to the change of viscosity, resistance and critical velocity of slurry. Moreover, based on the previous studies, the critical velocity calculation model of coal slurry is proposed.

Effects of cirrus composition on atmospheric radiation budgets

NASA Technical Reports Server (NTRS)

Kinne, Stefan; Liou, Kuo-Nan

1988-01-01

A radiative transfer model that can be used to determine the change in solar and infrared fluxes caused by variations in the composition of cirrus clouds was used to investigate the importance of particle size and shape on the radiation budget of the Earth-atmosphere system. Even though the cloud optical thickness dominates the radiative properties of ice clouds, the particle size and nonsphericity of ice crystals are also important in calculations of the transfer of near-IR solar wavelengths. Results show that, for a given optical thickness, ice clouds composed of larger particles would produce larger greenhouse effects than those composed of smaller particles. Moreover, spherical particles with equivalent surface areas, frequently used for ice crystal clouds, would lead to an overestimation of the greenhouse effect.

The role of jet and film drops in controlling the mixing state of submicron sea spray aerosol particles

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Xiaofei; Deane, Grant B.; Moore, Kathryn A.

Covering 71% of the Earth’s surface, oceans represent a significant global source of atmospheric aerosols. The size and composition of sea spray aerosols (SSA) affect their ability to serve as cloud seeds and thus understanding the factors controlling their composition is critical to predicting their impact on clouds and climate. SSA particles have been shown to be an external mixture of particles with different compositions. Film and jet drop production mechanisms ultimately determine the individual particle compositions which are comprised of an array of salt/organic mixtures ranging from pure sea salt to nearly pure organic particles. It is often assumedmore » that the majority of submicron SSA are formed by film drops produced from bursting hydrophobic organic-rich bubble film caps at the sea surface, and in contrast, jet drops are postulated to produce larger supermicron particles from underlying seawater comprised largely of salts and water soluble organic species. However, here we show that jet drops produced by bursting sub-100 m bubbles account for up to 40 % of all submicron particles. They have distinct chemical compositions, organic volume fractions and ice nucleating activities from submicron film drops. Thus a substantial fraction of submicron particles will not necessarily be controlled by the composition of the sea surface microlayer as has been assumed in many studies. This finding has significant ramifications for the size-resolved mixing states of SSA particles which must be taken into consideration when accessing SSA impacts on clouds.« less

The role of jet and film drops in controlling the mixing state of submicron sea spray aerosol particles

DOE PAGES

Wang, Xiaofei; Deane, Grant B.; Moore, Kathryn A.; ...

2017-06-19

Covering 71% of the Earth’s surface, oceans represent a significant global source of atmospheric aerosols. The size and composition of sea spray aerosols (SSA) affect their ability to serve as cloud seeds and thus understanding the factors controlling their composition is critical to predicting their impact on clouds and climate. SSA particles have been shown to be an external mixture of particles with different compositions. Film and jet drop production mechanisms ultimately determine the individual particle compositions which are comprised of an array of salt/organic mixtures ranging from pure sea salt to nearly pure organic particles. It is often assumedmore » that the majority of submicron SSA are formed by film drops produced from bursting hydrophobic organic-rich bubble film caps at the sea surface, and in contrast, jet drops are postulated to produce larger supermicron particles from underlying seawater comprised largely of salts and water soluble organic species. However, here we show that jet drops produced by bursting sub-100 m bubbles account for up to 40 % of all submicron particles. They have distinct chemical compositions, organic volume fractions and ice nucleating activities from submicron film drops. Thus a substantial fraction of submicron particles will not necessarily be controlled by the composition of the sea surface microlayer as has been assumed in many studies. This finding has significant ramifications for the size-resolved mixing states of SSA particles which must be taken into consideration when accessing SSA impacts on clouds.« less

The Diurnal Cycle of Particle Sizes, Compositions, and Densities observed in Sacramento, CA during CARES Field Campaign

NASA Astrophysics Data System (ADS)

Beránek, J.; Vaden, T.; Imre, D. G.; Zelenyuk, A.

2010-12-01

A central objective of the Carbonaceous Aerosol and Radiative Effects Study (CARES) was to characterize unequivocally all aspects related to organics in aerosols. To this end, a range of instruments measured loadings, size distributions, compositions, densities, CCN activities, and optical properties of aerosol sampled in Sacramento, CA over the month of June 2010. We present the results of measurements conducted by our single particle mass spectrometer, SPLAT. SPLAT was used to measure the size, composition, and density of individual particles with diameters between 50 to 2000 nm. SPLAT measured the vacuum aerodynamic diameters (dva) of more than 2 million particles and the compositions of ~350,000 particles, each day. In addition, SPLAT was used in combination with a differential mobility analyzer to measure the density, or effective density of individual particles. These measurements were typically conducted twice per day: in the morning, and mid-afternoon. Preliminary analysis of the data shows that under most conditions, the particles were relatively small (below 200 nm), and the vast majority of them were composed of oxygenated organics mixed with various amounts of sulfates. Analysis of the mass spectra shows that the oxygenated organics in these particles are the oxidized products of biogenic volatile organic precursors. In addition to particles composed of SOA mixed with sulfates, we detected and characterized fresh and processed soot particles, biomass burning aerosol, organic amines, sea salt - fresh and processed - and a small number of dust and other inorganic particles, commonly found in urban environment. SOA mixed with sulfates were the vast majority of particles at all times, while the other particle types exhibited episodic behavior. The data shows a reproducible diurnal pattern in SOA size distributions, number concentrations, and compositions. Early in the morning the particle number concentrations are relatively low, and the particle size distributions peak at ~70 nm. Smaller particles (80 nm) have a density of 1.3 g cm<-3/sup>, while the density of larger particles (200 nm) is 1.6 g cm<-3/sup>. The mass spectra show that the smaller particles are composed of organics mixed with ~10% of sulfates and larger ones contain mostly sulfate with a small amount of organics. As biogenic emissions are processed, nucleation events lead to a large increase in the concentrations of very small particles. As the day progresses particle number concentrations increase and particles grow. By mid-afternoon, these particles are sufficiently large to be characterized by SPLAT. At this point, the density of 80 to 200 nm particles is ~1.3 g cm<-3/sup>. These particles are composed of oxygenated organics mixed with a ~10% sulfate. A detailed analysis of the mass spectra shows that there are two types of SOA particles, which we labeled Type 43 and Type 44, to indicate which of the two peaks caries more intensity in the individual particle mass spectra. Interestingly, we find evidence to suggest that in both particle types a large fraction of the intensity in peaks 44 and 73 is related to surface compound.

Predicting the mineral composition of dust aerosols: Insights from elemental composition measured at the Izaña Observatory

NASA Astrophysics Data System (ADS)

Pérez García-Pando, Carlos; Miller, Ron L.; Perlwitz, Jan P.; Rodríguez, Sergio; Prospero, Joseph M.

2016-10-01

Regional variations of dust mineral composition are fundamental to climate impacts but generally neglected in climate models. A challenge for models is that atlases of soil composition are derived from measurements following wet sieving, which destroys the aggregates potentially emitted from the soil. Aggregates are crucial to simulating the observed size distribution of emitted soil particles. We use an extension of brittle fragmentation theory in a global dust model to account for these aggregates. Our method reproduces the size-resolved dust concentration along with the approximately size-invariant fractional abundance of elements like Fe and Al in the decade-long aerosol record from the Izaña Observatory, off the coast of West Africa. By distinguishing between Fe in structural and free forms, we can attribute improved model behavior to aggregation of Fe and Al-rich clay particles. We also demonstrate the importance of size-resolved measurements along with elemental composition analysis to constrain models.

Analysis of Particle Distribution in Milled Al-Based Composites Reinforced by B4C Nanoparticles

NASA Astrophysics Data System (ADS)

Alihosseini, Hamid; Dehghani, Kamran

2017-04-01

In the present work, high-energy ball milling was employed to synthesize Al-(5-10 wt.%)B4C nanocomposite. To do this, two sizes of particles of 50 nm as nanoparticles (NPs) and 50 μm as coarse particles (CPs) were used. The morphology and microstructure of the milled powders were characterized using particle size analyzer, SEM, TEM and EDX techniques. It was found that milling time, B4C particles size and their content strongly affect the characteristics of powders during milling process. The breaking and cold welding of powders was recognized as two main competitive actions during the milling process that influence the microstructural evolutions. It was found that the presence of CPs led to the formation of microcracks which promote the fracture process of Al powders. The dominated mechanisms during the fabrication of composites and nanocomposites were discussed. Also, the theoretical issues regarding the changes in morphology and distribution of B4C particles in CPs and NPs are clarified.

Hysteresis heating based induction bonding of composite materials

NASA Astrophysics Data System (ADS)

Suwanwatana, Witchuda

The viability of using magnetic particulate susceptor materials for induction heating during bonding of polymer matrix composites is well established in this work. The unique ability to offer localized heating, geometric flexibility, and self-controlled temperature is the major advantage of this technique. Hysteresis heating is tailored through careful design of the microstructure of nickel particulate polymer films (Ni/PSU). An excellent heating rate can be attained in the frequency range of 1 to 10 MHz for particle volume fraction below percolation of 0.26. The diameter of nickel particle should be kept between 65 nm to 10 mum to ensure multi-domain heating, Curie temperature control, negligible shielding effect, minimum eddy current, and slight particle oxidation. The hysteresis heating behavior of the Ni/PSU films is found to be volumetric in nature and proportional to the cube of applied magnetic field. On the other hand, heat generation is inversely proportional to the size of the multi-domain particles. The frequency effect; however, provide maximum heat generation at the domain wall resonance frequency. Curie temperature control is observed when sufficiently high magnetic fields (˜138 Oe) are applied. The master curves of AC heat generation in Ni/PSU films are established and show a strong particle size effect. Hysteresis fusion bonding of glass/polyphenylene sulfide thermoplastic composites using a magnetic film as the thermoplastic adhesive shows that the bond strength of hysteresis-welded materials is comparable to that of autoclave-welded materials while offering an order of magnitude reduction in cycle time. The relative contribution of the intimate contact and healing mechanisms to the fusion bonding process indicates that hysteresis bonding is controlled by intimate contact. The macroscopic failure modes vary from mostly adhesive composite/film (low bond strength) to a combination of adhesive composite/film, cohesive film, cohesive composite and mostly cohesive composite (high bond strength). Inspection of the microscopic failure at the nickel particle/polymer interface in the film indicates quasi-brittle failure mode. The amount of adhesive failure increases with decreasing particle size and increasing particle volume fraction. The XPS peaks confirm nickel oxide in the form of NiO on the failure surface of particle/polymer debonding of hysteresis susceptor film.

Effect of Fe-Mn addition on microstructure and magnetic properties of NdFeB magnetic powders

NASA Astrophysics Data System (ADS)

Kurniawan, C.; Purba, A. S.; Setiadi, E. A.; Simbolon, S.; Warman, A.; Sebayang, P.

2018-03-01

In this paper, the effect of Fe-Mn alloy addition on microstructures and magnetic properties of NdFeB magnetic powders was investigated. Varied Fe-Mn compositions of 1, 5, and 10 wt% were mixed with commercial NdFeB type MQA powders for 15 minutes using shaker mill. The characterizations were performed by powder density, PSA, XRD, SEM, and VSM. The Fe-Mn addition increased the powder density of NdFeB/Fe-Mn powders. On the other side, particle size distribution slightly decreased as the Fe-Mn composition increases. Magnetic properties of NdFeB/Fe-Mn powders changed with the increasing of Fe-Mn content. SEM analysis showed the particle size of NdFeB/Fe-Mn powder was smaller as the Fe-Mn composition increases. It showed that NdFeB/Fe-Mn particles have different size and shape for NdFeB and Fe-Mn particles separately. The optimum magnetic properties of NdFeB/Fe-Mn powder was achieved on the 5 wt% Fe-Mn composition with remanence M r = 49.45 emu/g, coercivity H c = 2.201 kOe, and energy product, BH max = 2.15 MGOe.

A numerical determination of the evolution of cloud drop spectra due to condensation on natural aerosol particles

NASA Technical Reports Server (NTRS)

Lee, I. Y.; Haenel, G.; Pruppacher, H. R.

1980-01-01

The time variation in size of aerosol particles growing by condensation is studied numerically by means of an air parcel model which allows entrainment of air and aerosol particles. Particles of four types of aerosols typically occurring in atmospheric air masses were considered. The present model circumvents any assumption about the size distribution and chemical composition of the aerosol particles by basing the aerosol particle growth on actually observed size distributions and on observed amounts of water taken up under equilibrium by a deposit of the aerosol particles. Characteristic differences in the drop size distribution, liquid water content and supersaturation were found for the clouds which evolved from the four aerosol types considered.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rubio, Mario A.; Gunduz, I. Emre; Groven, Lori J.

Aluminum particles are widely used as a metal fuel in solid propellants. However, poor combustion efficiencies and two-phase flow losses result due in part to particle agglomeration. Engineered composite particles of aluminum (Al) with inclusions of polytetrafluoroethylene (PTFE) or low-density polyethylene (LDPE) have been shown to improve ignition and yield smaller agglomerates in solid propellants, recently. Reductions in agglomeration were attributed to internal pressurization and fragmentation (microexplosions) of the composite particles at the propellant surface. We explore the mechanisms responsible for microexplosions in order to better understand the combustion characteristics of composite fuel particles. Single composite particles of Al/PTFE andmore » Al/LDPE with diameters between 100 and 1200 µm are ignited on a substrate to mimic a burning propellant surface in a controlled environment using a CO 2 laser in the irradiance range of 78–7700 W/cm 2. Furthermore, the effects of particle size, milling time, and inclusion content on the resulting ignition delay, product particle size distributions, and microexplosion tendencies are reported. For example particles with higher PTFE content (30 wt%) had laser flux ignition thresholds as low as 77 W/cm 2, exhibiting more burning particle dispersion due to microexplosions compared to the other materials considered. Composite Al/LDPE particles exhibit relatively high ignition thresholds compared to Al/PTFE particles, and microexplosions were observed only with laser fluxes above 5500 W/cm 2 due to low LDPE reactivity with Al resulting in negligible particle self-heating. However, results show that microexplosions can occur for Al containing both low and high reactivity inclusions (LDPE and PTFE, respectively) and that polymer inclusions can be used to tailor the ignition threshold. Furthermore, this class of modified metal particles shows significant promise for application in many different energetic materials that use metal fuels.« less

A regression analysis of filler particle content to predict composite wear.

PubMed

Jaarda, M J; Wang, R F; Lang, B R

1997-01-01

It has been hypothesized that composite wear is correlated to filler particle content. There is a paucity of research to substantiate this theory despite numerous projects evaluating the correlation. The purpose of this study was to determine whether a linear relationship existed between composite wear and filler particle content of 12 composites. In vivo wear data had been previously collected for the 12 composites and served as basis for this study. Scanning electron microscopy and backscatter electron imaging were combined with digital imaging analysis to develop "profile maps" of the filler particle composition of the composites. These profile maps included eight parameters: (1) total number of filler particles/28742.6 microns2, (2) percent of area occupied by all of the filler particles, (3) mean filler particle size, (4) percent of area occupied by the matrix, (5) percent of area occupied by filler particles, r (radius) 1.0 < or = micron, (6) percent of area occupied by filler particles, r = 1.0 < or = 4.5 microns, (7) percent of area occupied by filler particles, r = 4.5 < or = 10 microns, and (8) percent of area occupied by filler particles, r > 10 microns. Forward stepwise regression analyses were used with composite wear as the dependent variable and the eight parameters as independent variables. The results revealed a linear relationship between composite wear and the filler particle content. A mathematical formula was developed to predict composite wear.

Electro-codeposition of Ni-SiO2 nanocomposite coatings from deep eutectic solvent with improved corrosion resistance

NASA Astrophysics Data System (ADS)

Li, Ruiqian; Hou, Yuanyuan; Liang, Jun

2016-03-01

Electro-codeposition of nano-sized SiO2 particles into the metal matrix in aqueous solution is generally difficult. In this paper, the nano-sized SiO2 particles were successfully codeposited in the Ni matrix from a choline chloride (ChCl)/ethylene glycol (EG) based deep eutectic solvent (DES) by pulse electro-codeposition. The effects of nano-sized SiO2 particles on electrochemical behaviour of Ni(II) were investigated. The microstructure, composition and corrosion resistance of pure Ni and Ni-SiO2 nanocomposite coatings were explored. Results showed that the SiO2 nanoparticles exhibited excellent dispersion stability in ChCl:2EG DES without any stabilizing additives and the presence of SiO2 nanoparticles have significant effects on the nucleation mechanism of Ni. The maximum content of SiO2 nanoparticles in composite coatings can achieve 4.69 wt.%, which closes to the level of co-deposition micro-sized SiO2 particles from aqueous solution. The Ni-SiO2 nanocomposite coatings exhibit much better corrosion resistance than pure Ni coating, and the corrosion resistance performance increases with increasing SiO2 content in the composite coatings.

The mineral composition and the effect of particle size of carbonized rice straw as colorant of a traditional cake kue jongkong Surabaya

NASA Astrophysics Data System (ADS)

Murtini, E. S.; Yuwono, S. S.; Setyawan, H. Y.

2018-03-01

Carbonized rice straw (CRS) is a term defined for the residue of incomplete combustion of rice straw. Utilization of CRS as a natural food coloring agent has been the local Indonesian wisdom. However, study of this local food coloring agent is rare in the literature. This study was aimed to determine the mineral composition of the CRS, and to investigate the effect of particle size of the CRS to the black color intensity of a traditional Indonesian cake called kue jongkong Surabaya. The mineral content of the CRS was analyzed using X-ray fluorescence (XRF). The CRS was grounded and sieved passing through different screen sizes (40, 80, 100, 120 and 200 mesh).The particle size distribution was measured using particle size analyzer. The CRS with different particle sizes were then applied as a natural coloring agent of the kue jongkong, from which the intensity of black color was determined using a color reader. It was found that the dominant minerals of the CRS were SiO2, carbon, and K2O. Other trace elements found were Cl, CaO, Na2O, MgO, P, S, Fe, Al2O3 and Mn. The CRS which passed to the sieve of 40 mesh has particle size distribution of 28μm, 115μm, and 348μm for a standard of D10, D50, and D90, respectively. However, CRS that passing through the sieve of 60-200 mesh have similar particle sizes (D10: 12-14μm, D50: 49-60μm, and D90: 114-145 μm). The smaller of CRS particle size produced a darker color of the kue jongkong due to better molecule dispersion and wider surface area.

X-ray tomography investigation of intensive sheared Al–SiC metal matrix composites

DOE Office of Scientific and Technical Information (OSTI.GOV)

De Giovanni, Mario; Warnett, Jason M.; Williams, Mark A.

2015-12-15

X-ray computed tomography (XCT) was used to characterise three dimensional internal structure of Al–SiC metal matrix composites. The alloy composite was prepared by casting method with the application of intensive shearing to uniformly disperse SiC particles in the matrix. Visualisation of SiC clusters as well as porosity distribution were evaluated and compared with non-shearing samples. Results showed that the average particle size as well as agglomerate size is smaller in sheared sample compared to conventional cast samples. Further, it was observed that the volume fraction of porosity was reduced by 50% compared to conventional casting, confirming that the intensive shearingmore » helps in deagglomeration of particle clusters and decrease in porosity of Al–SiC metal matrix composites. - Highlights: • XCT was used to visualise 3D internal structure of Al-SiC MMC. • Al-SiC MMC was prepared by casting with the application of intensive shearing. • SiC particles and porosity distribution were evaluated. • Results show shearing deagglomerates particle clusters and reduces porosity in MMC.« less

Poly(vinylidene fluoride)-La(0.5)Sr(0.5)CoO(3-δ) composites: the influence of LSCO particle size on the structure and dielectric properties.

PubMed

Deepa, K S; Shaiju, P; Sebastian, M T; Gowd, E Bhoje; James, J

2014-08-28

Dielectric composites composed of poly(vinylidene fluoride) (PVDF) and La0.5Sr0.5CoO3-δ (LSCO) with high permittivity, low loss and high breakdown strength have been developed. The effects of particle size of LSCO (fine (∼250 nm) and coarse (∼3 μm)) on the phase crystallization of PVDF and dielectric properties of polymer-LSCO composites are studied. The inclusion of fine LSCO into PVDF readily favours the formation of polar crystals (β and γ-phases), which makes the composite suitable for both electromechanical and high charge storage embedded capacitor applications. Moreover, the addition of fine LSCO particles also increases the overall crystallization rate as well as the melting point of PVDF. The composite containing fine LSCO particles gave a percolation threshold at about 25 volume percentage, while that with coarse particles did not show any percolation even at very high volume percentage. As a result of fine LSCO particle loading, the composite exhibited a relative permittivity (εr) of ∼600, a conductivity of 2.7 × 10(-7) S cm(-1), a dielectric loss (tan δ) of 0.7 at 1 kHz and a breakdown voltage of 100 V even at 20 volume percentage of a filler, demonstrating promising applications in the embedded capacitors.

Nano polypeptide particles reinforced polymer composite fibers.

PubMed

Li, Jiashen; Li, Yi; Zhang, Jing; Li, Gang; Liu, Xuan; Li, Zhi; Liu, Xuqing; Han, Yanxia; Zhao, Zheng

2015-02-25

Because of the intensified competition of land resources for growing food and natural textile fibers, there is an urgent need to reuse and recycle the consumed/wasted natural fibers as regenerated green materials. Although polypeptide was extracted from wool by alkaline hydrolysis, the size of the polypeptide fragments could be reduced to nanoscale. The wool polypeptide particles were fragile and could be crushed down to nano size again and dispersed evenly among polymer matrix under melt extrusion condition. The nano polypeptide particles could reinforce antiultraviolet capability, moisture regain, and mechanical properties of the polymer-polypeptide composite fibers.

Internal zone growth method for producing metal oxide metal eutectic composites

DOEpatents

Clark, Grady W.; Holder, John D.; Pasto, Arvid E.

1980-01-01

An improved method for preparing a cermet comprises preparing a compact having about 85 to 95 percent theoretical density from a mixture of metal and metal oxide powders from a system containing a eutectic composition, and inductively heating the compact in a radiofrequency field to cause the formation of an internal molten zone. The metal oxide particles in the powder mixture are effectively sized relative to the metal particles to permit direct inductive heating of the compact by radiofrequency from room temperature. Surface melting is prevented by external cooling or by effectively sizing the particles in the powder mixture.

Acid Hydrolysis and Molecular Density of Phytoglycogen and Liver Glycogen Helps Understand the Bonding in Glycogen α (Composite) Particles

PubMed Central

Powell, Prudence O.; Sullivan, Mitchell A.; Sheehy, Joshua J.; Schulz, Benjamin L.; Warren, Frederick J.; Gilbert, Robert G.

2015-01-01

Phytoglycogen (from certain mutant plants) and animal glycogen are highly branched glucose polymers with similarities in structural features and molecular size range. Both appear to form composite α particles from smaller β particles. The molecular size distribution of liver glycogen is bimodal, with distinct α and β components, while that of phytoglycogen is monomodal. This study aims to enhance our understanding of the nature of the link between liver-glycogen β particles resulting in the formation of large α particles. It examines the time evolution of the size distribution of these molecules during acid hydrolysis, and the size dependence of the molecular density of both glucans. The monomodal distribution of phytoglycogen decreases uniformly in time with hydrolysis, while with glycogen, the large particles degrade significantly more quickly. The size dependence of the molecular density shows qualitatively different shapes for these two types of molecules. The data, combined with a quantitative model for the evolution of the distribution during degradation, suggest that the bonding between β into α particles is different between phytoglycogen and liver glycogen, with the formation of a glycosidic linkage for phytoglycogen and a covalent or strong non-covalent linkage, most probably involving a protein, for glycogen as most likely. This finding is of importance for diabetes, where α-particle structure is impaired. PMID:25799321

Plackett-Burman experimental design for bacterial cellulose-silica composites synthesis.

PubMed

Guzun, Anicuta Stoica; Stroescu, Marta; Jinga, Sorin Ion; Voicu, Georgeta; Grumezescu, Alexandru Mihai; Holban, Alina Maria

2014-09-01

Bacterial cellulose-silica hybrid composites were prepared starting from wet bacterial cellulose (BC) membranes using Stöber reaction. The structure and surface morphology of hybrid composites were examined by FTIR and SEM. The SEM pictures revealed that the silica particles are attached to BC fibrils and are well dispersed in the BC matrix. The influence of silica particles upon BC crystallinity was studied using XRD analysis. Thermogravimetric (TG) analysis showed that the composites are stable up to 300°C. A Plackett-Burman design was applied in order to investigate the influence of process parameters upon silica particle sizes and silica content of BC-silica composites. The statistical model predicted that it is possible for silica particles size to vary the synthesis parameters in order to obtain silica particles deposed on BC membranes in the range from 34.5 to 500 nm, the significant parameters being ammonia concentration, reaction time and temperature. The silica content also varies depending on process parameters, the statistical model predicting that the most influential parameters are water-tetraethoxysilane (TEOS) ratio and reaction temperature. The antimicrobial behavior on Staphylococcus aureus of BC-silica composites functionalized with usnic acid (UA) was also studied, in order to create improved surfaces with antiadherence and anti-biofilm properties. Copyright © 2014 Elsevier B.V. All rights reserved.

Formation mechanisms of metal colloids

NASA Astrophysics Data System (ADS)

Halaciuga, Ionel

Highly dispersed uniform metallic particles are widely used in various areas of technology and medicine and are likely to be incorporated into many other applications in the future. It is commonly accepted that size, shape and composition of the particles represent critical factors in most applications. Thus, understanding the mechanisms of formation of metal particles and the ways to control the physical (e.g. shape, size) and chemical (e.g. composition) properties is of great importance. In the current research, the formation of uniform silver spheres is investigated experimentally. The parameters that influence the formation of silver particles when concentrated iso-ascorbic acid and silver-polyamine complex solutions are rapidly mixed were studied in the absence of dispersants. We found that by varying the nature of the amine, temperature, concentration of reactants, silver/amine molar ratio, and the nature of the silver salt, the size of the resulting silver particles can be varied in a wide range (0.08--1.5 microm). The silver particles were formed by aggregation of nanosize subunits as substantiated by both electron microscopy and X-ray diffraction techniques and by the vivid rapid color changes during the chemical precipitation process. From the practical standpoint, the goal of this research was to prepare well dispersed spherical silver particles having a relatively smooth surface and a diameter of about 1 microm to satisfy the demands of the current electronic materials market. A two stage particle growth model previously developed to explain the narrow size distribution occurring in synthesis of gold spheres was applied to the present experimental system, and the parameters that control the size distribution characteristics were identified. The kinetic parameter required to match the final particle size was found to be in agreement with the one used previously in modeling formation of gold spheres, suggesting that similar kinetics governs the aggregation process. Furthermore, the two-stage particle growth model was used to account for the effects of solvent viscosity and temperature on the particle properties, particularly their size. As an application of the above mentioned study, the aggregation process that led to the formation of large silver spheres was used to deposit in a controlled manner layers of silver and other metals (Ni, Au) onto various metallic and non-metallic substrates. In the final section of this thesis methods to form nanosized primary particle strictly through diffusional growth are described. The highly crystalline metallic particles of various sizes and composition prepared provide performance characteristics that are complementary to the polycrystalline metallic particles described in the preceding sections.

Study of erosion characterization of carbon fiber reinforced composite material

NASA Astrophysics Data System (ADS)

Debnath, Uttam Kumar; Chowdhury, Mohammad Asaduzzaman; Kowser, Md. Arefin; Mia, Md. Shahin

2017-06-01

Carbon fiber composite materials are widely used at different engineering and industrial applications there are good physical, mechanical, chemical properties and light weight. Erosion behavior of materials depends on various factors such as impact angle, particle velocity, particle size, particle shape, particle type, particle flux, temperature of the tested materials. Among these factors impact angle and particle velocity have been recognized as two parameters that noticeably influence the erosion rates of all tested materials. Irregular shaped sand (SiO2) particles of various sizes (200-300 µm, 400-500 µm, and 500-600 µm) were selected erosive element. Tested conditions such as impingement angles between 15 degree to 90 degree, impact velocities between 30-50 m/sec, and stand-off distances 15-25 mm at surrounding room temperature were maintained. The highest level of erosion of the tested composite is obtained at 60° impact angle, which signifies the semi-ductile behavior of this material. Erosion showed increasing trend with impact velocity and decreasing nature in relation to stand-off distance. Surface damage was analyzed using SEM to examine the nature of the erosive wear mechanism.

Particles and Zinc on the Absorbed Impact Energy of Gravity Cast Aluminum Matrix Composites

NASA Astrophysics Data System (ADS)

Corchado, Marcos; Reyes, Fernando; Suárez, Oscar Marcelo

2014-06-01

The effect of different amounts of boron, in the form of AlB2 particles, as well as zinc concentration in a gravity cast Al-B-Zn composite, was studied and related to the absorbed energy upon fracture during Charpy impact experiments. In addition, the authors correlated the composite Brinell hardness with the quantitative assessment of brittle and ductile fracture areas of the Charpy fractured specimens and found that increasing AlB2 particle concentration resulted in a reduction of absorbed impact energy. Although larger zinc levels produced somewhat similar results, the AlB2 effect was prevalent. The energy absorption upon impact reached a maximum when no particles were present; conversely, the lowest amount of absorbed energy corresponded to a composite with a composition of 15 wt.% Zn and 8% in volume of AlB2, i.e., the highest concentration of AlB2 and zinc studied. Raising the amount of AlB2 as well as zinc, as expected, resulted in higher Brinell hardness. A statistical analysis allowed studying of the particle size distribution, whereas values for crack tip opening displacement were subsequently calculated for the range of particle sizes found and the corresponding AlB2 particle volume percent. Higher porosity values were measured for larger AlB2 volume percent. Finally, analyses of fracture surfaces corroborated that brittle fracture was favored in composites with higher amounts of AlB2 and zinc.

Structural and magnetic characteristics of PVA/CoFe{sub 2}O{sub 4} nano-composites prepared via mechanical alloying method

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rashidi, S.; Ataie, A., E-mail: aataie@ut.ac.ir

Highlights: • Single phase CoFe{sub 2}O{sub 4} nano-particles synthesized in one step by mechanical alloying. • PVA/CoFe{sub 2}O{sub 4} magnetic nano-composites were fabricated via mechanical milling. • FTIR confirmed the interaction between PVA and magnetic CoFe{sub 2}O{sub 4} particles. • Increasing in milling time and PVA amount led to well dispersion of CoFe{sub 2}O{sub 4}. - Abstract: In this research, polyvinyl alcohol/cobalt ferrite nano-composites were successfully synthesized employing a two-step procedure: the spherical single-phase cobalt ferrite of 20 ± 4 nm mean particle size was synthesized via mechanical alloying method and then embedded into polymer matrix by intensive milling. Themore » results revealed that increase in polyvinyl alcohol content and milling time causes cobalt ferrite particles disperse more homogeneously in polymer matrix, while the mean particle size and shape of cobalt ferrite have not been significantly affected. Transmission electron microscope images indicated that polyvinyl alcohol chains have surrounded the cobalt ferrite nano-particles; also, the interaction between polymer and cobalt ferrite particles in nano-composite samples was confirmed. Magnetic properties evaluation showed that saturation magnetization, coercivity and anisotropy constant values decreased in nano-composite samples compared to pure cobalt ferrite. However, the coercivity values of related nano-composite samples enhanced by increasing PVA amount due to domain wall mechanism.« less

Effects of Hyperfine Particles on Reflectance Spectra from 0.3 to 25 μm

NASA Astrophysics Data System (ADS)

Mustard, John F.; Hays, John E.

1997-01-01

Fine grained particles <50 μm in size dominate particle size distributions of many planetary surfaces. Despite the predominance of fine particles in planetary regoliths, there have been few investigations of the systematic effects of the finest particles on reflectance spectra, and on the ability of quantitative models to extract compositional and/or textural information from remote observations. The effects of fine particles that are approximately the same size as the wavelength of light on reflectance spectra were investigated using narrow particle size separates of the minerals olivine and quartz across the wavelength range 0.3 to 25 μm. The minerals were ground with a mortar and pestle and sieved into five particle size separates of 5-μm intervals from <5 μm to 20-25 μm. The exact particle size distributions were determined with a particle size analyzer and are shown to be Gaussian about a mean within the range of each sieve separate. The reflectance spectra, obtained using a combination of a bidirectional reflectance spectrometer and an FTIR, exhibited a number of systematic changes as the particle size decreased to become approximately the same size and smaller than the wavelength. In the region of volume scattering, the spectra exhibited a sharp drop in reflectance with the finest particle size separates. Christiansen features became saturated when the imaginary part of the index of refraction was non-negligible, while the restrahlen bands showed continuous decrease in spectral contrast and some change in the shape of the bands with decreasing particle size, though the principal features diagnostic of composition were relatively unaffected. The transparency features showed several important changes with decreasing particle size: the spectral contrast increased then decreased, the position of the maximum reflectance of the transparency features shifted systematically to shorter wavelengths, and the symmetry of the features changed. Mie theory predicts that the extinction and scattering efficiencies should decline rapidly when particle size and wavelength are approximately equal. Using these relationships, a critical diameter where this change is predicted to occur was calculated as a function of wavelength and shown to be effective for explaining qualitatively the observed changes. Each of the mineral particle size series were then modeled quantitatively using Mie calculations to determine single-scattering albedo and a Hapke model to calculate reflectance. The models include the complex indices of refraction for olivine and quartz and the exact particle size distributions. The olivine particle size series was well modeled by these calculations, and correctly reproduced the systematic changes in the volume scattering region, the Christiansen feature, restrahlen bands, and transparency features. The quartz particle size series were less well modeled, with the greatest discrepancies in the restrahlen bands and the overall spectral contrast.

Organic component vapor pressures and hygroscopicities of aqueous aerosol measured by optical tweezers.

PubMed

Cai, Chen; Stewart, David J; Reid, Jonathan P; Zhang, Yun-hong; Ohm, Peter; Dutcher, Cari S; Clegg, Simon L

2015-01-29

Measurements of the hygroscopic response of aerosol and the particle-to-gas partitioning of semivolatile organic compounds are crucial for providing more accurate descriptions of the compositional and size distributions of atmospheric aerosol. Concurrent measurements of particle size and composition (inferred from refractive index) are reported here using optical tweezers to isolate and probe individual aerosol droplets over extended timeframes. The measurements are shown to allow accurate retrievals of component vapor pressures and hygroscopic response through examining correlated variations in size and composition for binary droplets containing water and a single organic component. Measurements are reported for a homologous series of dicarboxylic acids, maleic acid, citric acid, glycerol, or 1,2,6-hexanetriol. An assessment of the inherent uncertainties in such measurements when measuring only particle size is provided to confirm the value of such a correlational approach. We also show that the method of molar refraction provides an accurate characterization of the compositional dependence of the refractive index of the solutions. In this method, the density of the pure liquid solute is the largest uncertainty and must be either known or inferred from subsaturated measurements with an error of <±2.5% to discriminate between different thermodynamic treatments.

Single particle aerosol mass spectrometry of coal combustion particles associated with high lung cancer rates in Xuanwei and Fuyuan, China.

PubMed

Lu, Senlin; Tan, Zhengying; Liu, Pinwei; Zhao, Hui; Liu, Dingyu; Yu, Shang; Cheng, Ping; Win, Myat Sandar; Hu, Jiwen; Tian, Linwei; Wu, Minghong; Yonemochi, Shinich; Wang, Qingyue

2017-11-01

Coal combustion particles (CCPs) are linked to the high incidence of lung cancer in Xuanwei and in Fuyuan, China, but studies on the chemical composition of the CCPs are still limited. Single particle aerosol mass spectrometry (SPAMS) was recently developed to measure the chemical composition and size of single particles in real-time. In this study, SPAMS was used to measure individual combustion particles emitted from Xuanwei and Fuyuan coal samples and the results were compared with those by ICP-MS and transmission electron microscopy (TEM). The total of 38,372 particles mass-analyzed by SPAMS can be divided into 9 groups based on their chemical composition and their number percentages: carbonaceous, Na-rich, K-rich, Al-rich, Fe-rich, Si-rich, Ca-rich, heavy metal-bearing, and PAH-bearing particles. The carbonaceous and PAH-bearing particles are enriched in the size range below 0.56 μm, Fe-bearing particles range from 0.56 to 1.0 μm in size, and heavy metals such as Ti, V, Cr, Cu, Zn, and Pb have diameters below 1 μm. The TEM results show that the particles from Xuanwei and Fuyuan coal combustion can be classified into soot aggregates, Fe-rich particles, heavy metal containing particles, and mineral particles. Non-volatile particles detected by SPAMS could also be observed with TEM. The number percentages by SPAMS also correlate with the mass concentrations measured by ICP-MS. Our results could provide valuable insight for understanding high lung cancer incidence in the area. Copyright © 2017 Elsevier Ltd. All rights reserved.

Evaluation of the method of collecting suspended sediment from large rivers by discharge-weighted pumping and separation by continuous- flow centrifugation

USGS Publications Warehouse

Moody, J.A.; Meade, R.H.

1994-01-01

The efficacy of the method is evaluated by comparing the particle size distributions of sediment collected by the discharge-weighted pumping method with the particle size distributions of sediment collected by depth integration and separated by gravitational settling. The pumping method was found to undersample the suspended sand sized particles (>63 ??m) but to collect a representative sample of the suspended silt and clay sized particles (<63??m). The success of the discharge-weighted pumping method depends on how homogeneously the silt and clay sized particles (<63 ??m) are distributed in the vertical direction in the river. The degree of homogeneity depends on the composition and degree of aggregation of the suspended sediment particles. -from Authors

Core lipid, surface lipid and apolipoprotein composition analysis of lipoprotein particles as a function of particle size in one workflow integrating asymmetric flow field-flow fractionation and liquid chromatography-tandem mass spectrometry

PubMed Central

Jones, Jeffery I.; Gardner, Michael S.; Schieltz, David M.; Parks, Bryan A.; Toth, Christopher A.; Rees, Jon C.; Andrews, Michael L.; Carter, Kayla; Lehtikoski, Antony K.; McWilliams, Lisa G.; Williamson, Yulanda M.; Bierbaum, Kevin P.; Pirkle, James L.; Barr, John R.

2018-01-01

Lipoproteins are complex molecular assemblies that are key participants in the intricate cascade of extracellular lipid metabolism with important consequences in the formation of atherosclerotic lesions and the development of cardiovascular disease. Multiplexed mass spectrometry (MS) techniques have substantially improved the ability to characterize the composition of lipoproteins. However, these advanced MS techniques are limited by traditional pre-analytical fractionation techniques that compromise the structural integrity of lipoprotein particles during separation from serum or plasma. In this work, we applied a highly effective and gentle hydrodynamic size based fractionation technique, asymmetric flow field-flow fractionation (AF4), and integrated it into a comprehensive tandem mass spectrometry based workflow that was used for the measurement of apolipoproteins (apos A-I, A-II, A-IV, B, C-I, C-II, C-III and E), free cholesterol (FC), cholesterol esters (CE), triglycerides (TG), and phospholipids (PL) (phosphatidylcholine (PC), sphingomyelin (SM), phosphatidylethanolamine (PE), phosphatidylinositol (PI) and lysophosphatidylcholine (LPC)). Hydrodynamic size in each of 40 size fractions separated by AF4 was measured by dynamic light scattering. Measuring all major lipids and apolipoproteins in each size fraction and in the whole serum, using total of 0.1 ml, allowed the volumetric calculation of lipoprotein particle numbers and expression of composition in molar analyte per particle number ratios. Measurements in 110 serum samples showed substantive differences between size fractions of HDL and LDL. Lipoprotein composition within size fractions was expressed in molar ratios of analytes (A-I/A-II, C-II/C-I, C-II/C-III. E/C-III, FC/PL, SM/PL, PE/PL, and PI/PL), showing differences in sample categories with combinations of normal and high levels of Total-C and/or Total-TG. The agreement with previous studies indirectly validates the AF4-LC-MS/MS approach and demonstrates the potential of this workflow for characterization of lipoprotein composition in clinical studies using small volumes of archived frozen samples. PMID:29634782

Chemical and Physical Properties of Individual Aerosol Particles Characterized in Sacramento, CA during CARES Field Campaign

NASA Astrophysics Data System (ADS)

Zelenyuk, A.; Beranek, J.; Vaden, T.; Imre, D. G.; Zaveri, R. A.

2011-12-01

We present results of measurements conducted by our Single Particle Mass Spectrometer, SPLAT II, in Sacramento, CA over the month of June 2010. SPLAT II measured the size of 195 million particles, and compositions of 10 million particles. In addition to size and composition, SPLAT II simultaneously measured size, density and composition of 121,000 individual particles. These measurements were conducted 2 - 3 times per day, depending on conditions. The data show that throughout the day particles were relatively small (<200 nm), and the vast majority were composed of oxygenated organics mixed with various amounts of sulfate. In addition, we characterized fresh and processed soot, biomass burning aerosol, organic amines, fresh and processed sea salt, and few dust particles. The data show a reproducible diurnal pattern in aerosol size distributions, number concentrations, and compositions. Early in the day, number concentrations were low, particles were very small, and the size distributions peaked at ~70 nm. At this time of the day, 80 nm particles had a density of 1.3 g cm-3; while the density of 200 nm particles was 1.6 g cm-3, consistent with our mass spectra showing that smaller particles were composed of organics mixed with ~10% sulfates, while larger particles were composed mostly of sulfate mixed with a small amount of organics. Later in the day, secondary organic aerosols (SOA) formation led to a number of nucleation events that significantly increased the number concentrations of very small particles. By mid-afternoon, as more SOA formed and condensed, particles increased in size the number concentrations of particles larger than 70 nm increased and the densities of particles 80 to 200 nm particles was ~1.3 g cm-3. The vast majority of these particles were composed of oxygenated organics mixed with a ~10% sulfate. In other words they were SOA particles mixed with a small amount of sulfate. The mass spectra of these particles shows that there were two types of SOA particles, which we labeled Type 43 and Type 44, to indicate which of the two mass-spectral peaks caries higher intensity. We were also able to conduct room temperature evaporation studies of these particles on four separate occasions and found the evaporation kinetics to be reproducible. The data show that after 4 hours of evaporation, in an organic vapor free environment, particles lose only ~20% of their volume. Moreover, evaporation starts with a relatively fast phase and proceeds with a much slower stage about 2 hours after evaporation starts. It is important to keep in mind that these slow evaporating SOA particles were relatively fresh. Based on these studies and similar studies conducted in our laboratory we conclude that these atmospheric SOA particles are quasi-solids. Moreover the data indicate that to first order it is reasonable to approximate SOA particles as being non-volatile. Interestingly, we find that in both SOA particle types a large fraction of the intensity in peaks 44 and 73 was related to a small amount of surface compounds that evaporated within a few minutes.

Effects of TiB2 Particle and Short Fiber Sizes on the Microstructure and Properties of TiB2-Reinforced Composite Coatings

NASA Astrophysics Data System (ADS)

Lin, Yinghua; Yao, Jianhua; Wang, Liang; Zhang, Qunli; Li, Xueqiao; Lei, Yongping; Fu, Hanguang

2018-03-01

In this study, particle and short fiber-reinforced titanium matrix composite coatings are prepared via laser in situ technique using (0.5 and 50 μm) TiB2 and Ti powder as cladding materials. The microstructure and properties of the composite coatings are studied, and the changing mechanism of the microstructure is discussed. The results reveal that particle agglomeration is prone to appear with using fine TiB2 particles. Decomposition of the particles preferentially occurs with using coarse TiB2 particles. The cracks and pores on the surface of the coating are formed at a lower laser energy density. With the increase in the laser energy density, cracking on the surface of the coating diminishes, but the coating exhibits depression behavior. The depression extent of the coating using fine TiB2 particle as the reinforcement is much less than that of the coating using coarse TiB2 particle. Moreover, the size of the aggregate and the tendency of cracking can be reduced with the increase in Ti addition. Meanwhile, short TiB fiber bundles are formed by the diffusion mechanism of rod aggregate, and randomly oriented TiB short fibers are formed mainly by the dissolution-precipitation mechanism of fine TiB2 particles. Moreover, the growth of short TiB fibers can be in an alternating manner between B27 and Bf structures. The micro-hardness and wear resistance of the coatings are evidently higher than that of the titanium alloy substrate. The wear resistance of the large size TiB2 coating is higher than that of the small size TiB2 coating under the condition of low load.

Effect of cuprous oxide with different sizes on thermal and combustion behaviors of unsaturated polyester resin.

PubMed

Hou, Yanbei; Hu, Weizhao; Gui, Zhou; Hu, Yuan

2017-07-15

Cuprous oxide (Cu 2 O) as an effective catalyst has been applied to enhance the fire safety of unsaturated polyester resin (UPR), but the particle size influence on combustion behaviors has not been previously reported. Herein, the UPR/Cu 2 O composites (metal oxide particles with average particle-size of 10, 100, and 200nm) were successfully synthesized by thermosetting process. The effects of Cu 2 O with different sizes on thermostability and combustion behaviors of UPR were characterized by TGA, MCC, TG-IR, FTIR, and SSTF. The results revel that the addition of Cu 2 O contributes to sufficient decomposition of oxygen-containing compounds, which is beneficial to the release of nontoxic compounds. The smallest-sized Cu 2 O performs the excellent catalytic decomposition effect and promotes the complete combustion of UPR, which benefits the enhancement of fire safety. While the other additives retard pyrolysis process and yield more char residue, and thus the flame retardancy of UPR composites was improved. Therefore, catalysis plays a major role for smaller-sized particles during thermal decomposition of matrix, while flame retarded effect became gradual distinctly for the larger-sized additives. Copyright © 2017 Elsevier B.V. All rights reserved.

Effects of in situ synthesized mullite whisker on mechanical properties of Al2O3-SiC composite by microwave sintering

NASA Astrophysics Data System (ADS)

Dang, Xudan; Wei, Meng; Fan, Bingbing; Guan, Keke; Zhang, Rui; Long, Weimin; Zhang, Hongsong

2017-06-01

In situ synthesis of mullite whisker was introduced to Al2O3-SiC composite by microwave sintering. The effects of sintering parameters (sintering temperature, holding time and SiC particle size) on thermal shock resistance of Al2O3-SiC composite were also studied in this paper. Original SiC particles coated with SiO2 by a sol-gel method were reacted with Al2O3 particles, resulting in the in situ growth of mullite. The phase composition was identified by x-ray diffraction (XRD). The bridging of mullite whisker between Al2O3 and SiC particles was observed by scanning electron microscopy (SEM) analysis. The thermal shock resistance of samples was investigated through the combination of water quenching and three-point bending methods. The results show that the thermal shock resistance of Al2O3-SiC composite with mullite whisker reinforced remarkably, indicating better mechanical properties than the Al2O3-SiC composite without mullite whisker. Finally, the optimum process parameters (the sintering temperature of 1500 °C, the holding time of 30 min, and the SiC particle size of 5 µm) for toughening Al2O3-SiC composite by in situ synthesized mullite whisker were obtained.

Study of the thermal degradation mechanism of a composite propellant. [using electron microscopes

NASA Technical Reports Server (NTRS)

Schmidt, W. G.

1975-01-01

The current experimental program was designed to systematically investigate the role of the oxidizer in the thermal degradation process of composite propellants. The scanning electron microscope (SEM) was used to examine the failure sites in thermally degraded propellant samples. The formulation variables tested were oxidizer purity, oxidizer particle size, and oxidizer to binder bonding agent. The binder, a saturated hydrocarbon, was kept constant throughout the experiments. The oxidizers were: AP, chlorate-doped AP, arsenate-doped AP, and phosphate-doped AP. The oxidizer particle size distribution was 60% of the large fraction and 40% of the small fraction. The bonding agent, when present, was used at the 0.15% level. The data showed that both the oxidizer purity and particle size had an important affect on the thermal degradation process. The affect of the oxidizer particle size was more noticeable at the higher temperature and stress levels. An examination of the failure site, by SEM, of propellants subject to these latter conditions indicated that the fracturing of the large oxidizer particles led to the propellant cracking.

Analysis of the Murine Immune Response to Pulmonary Delivery of Precisely Fabricated Nano- and Microscale Particles

PubMed Central

Roberts, Reid A.; Shen, Tammy; Allen, Irving C.; Hasan, Warefta; DeSimone, Joseph M.; Ting, Jenny P. Y.

2013-01-01

Nanomedicine has the potential to transform clinical care in the 21st century. However, a precise understanding of how nanomaterial design parameters such as size, shape and composition affect the mammalian immune system is a prerequisite for the realization of nanomedicine's translational promise. Herein, we make use of the recently developed Particle Replication in Non-wetting Template (PRINT) fabrication process to precisely fabricate particles across and the nano- and micro-scale with defined shapes and compositions to address the role of particle design parameters on the murine innate immune response in both in vitro and in vivo settings. We find that particles composed of either the biodegradable polymer poly(lactic-co-glycolic acid) (PLGA) or the biocompatible polymer polyethylene glycol (PEG) do not cause release of pro-inflammatory cytokines nor inflammasome activation in bone marrow-derived macrophages. When instilled into the lungs of mice, particle composition and size can augment the number and type of innate immune cells recruited to the lungs without triggering inflammatory responses as assayed by cytokine release and histopathology. Smaller particles (80×320 nm) are more readily taken up in vivo by monocytes and macrophages than larger particles (6 µm diameter), yet particles of all tested sizes remained in the lungs for up to 7 days without clearance or triggering of host immunity. These results suggest rational design of nanoparticle physical parameters can be used for sustained and localized delivery of therapeutics to the lungs. PMID:23593509

Properties of Arctic Aerosol Particles and Residuals of Warm Clouds: Cloud Activation Efficiency and the Aerosol Indirect Effect

NASA Astrophysics Data System (ADS)

Zelenyuk, A.; Imre, D. G.; Leaitch, R.; Ovchinnikov, M.; Liu, P.; Macdonald, A.; Strapp, W.; Ghan, S. J.; Earle, M. E.

2012-12-01

Single particle mass spectrometer, SPLAT II, was used to characterize the size, composition, number concentration, density, and shape of individual Arctic spring aerosol. Background particles, particles above and below the cloud, cloud droplet residuals, and interstitial particles were characterized with goal to identify the properties that separate cloud condensation nuclei (CCN) from background aerosol particles. The analysis offers a comparison between warm clouds formed on clean and polluted days, with clean days having maximum particle concentrations (Na) lower than ~250 cm-3, as compared with polluted days, in which maximum concentration was tenfold higher. On clean days, particles were composed of organics, organics mixed with sulfates, biomass burning (BB), sea salt (SS), and few soot and dust particles. On polluted days, BB, organics associated with BB, and their mixtures with sulfate dominated particle compositions. Based on the measured compositions and size distributions of cloud droplet residuals, background aerosols, and interstitial particles, we conclude that these three particle types had virtually the same compositions, which means that cloud activation probabilities were surprisingly nearly composition independent. Moreover, these conclusions hold in cases in which less than 20% or more than 90% of background particles got activated. We concluded that for the warm clouds interrogated in this study particle size played a more important factor on aerosol CCN activity. Comparative analysis of all studied clouds reveals that aerosol activation efficiency strongly depends on the aerosol concentrations, such that at Na <200 cm-3, nearly all particles activate, and at higher concentrations the activation efficiency is lower. For example, when Na was greater than 1500 cm-3, less than ~30% of particles activated. The data suggest that as the number of nucleated droplets increases, condensation on existing droplets effectively competes with particle activation, limiting maximum droplet concentrations Nd = 525 ± 50 cm-3, which is lower than the 750 cm-3 limit found by Leaitch et al. (1986) for mid-latitude continental cloud that had generally larger updraft speeds than the clouds interrogated in Arctic. These findings are important for the aerosol indirect effect, in which increase in aerosol particle number concentrations is expected to result in increase in Nd and decrease in droplet size, leading to increased cloud albedo and potentially lifetimes. Our conclusions point to limited susceptibility to changes in ambient aerosol concentrations, providing simple explanation for the finding of weaker than expected indirect effect. In summary, the data presented here show that Nd increases as the cloud base particle number concentration increases; however, they also show a limit on Nd that is in the range of 500-600 cm-3.

Workplace exposure to nanoparticles from gas metal arc welding process

NASA Astrophysics Data System (ADS)

Zhang, Meibian; Jian, Le; Bin, Pingfan; Xing, Mingluan; Lou, Jianlin; Cong, Liming; Zou, Hua

2013-11-01

Workplace exposure to nanoparticles from gas metal arc welding (GMAW) process in an automobile manufacturing factory was investigated using a combination of multiple metrics and a comparison with background particles. The number concentration (NC), lung-deposited surface area concentration (SAC), estimated SAC and mass concentration (MC) of nanoparticles produced from the GMAW process were significantly higher than those of background particles before welding ( P < 0.01). A bimodal size distribution by mass for welding particles with two peak values (i.e., 10,000-18,000 and 560-320 nm) and a unimodal size distribution by number with 190.7-nm mode size or 154.9-nm geometric size were observed. Nanoparticles by number comprised 60.7 % of particles, whereas nanoparticles by mass only accounted for 18.2 % of the total particles. The morphology of welding particles was dominated by the formation of chain-like agglomerates of primary particles. The metal composition of these welding particles consisted primarily of Fe, Mn, and Zn. The size distribution, morphology, and elemental compositions of welding particles were significantly different from background particles. Working activities, sampling distances from the source, air velocity, engineering control measures, and background particles in working places had significant influences on concentrations of airborne nanoparticle. In addition, SAC showed a high correlation with NC and a relatively low correlation with MC. These findings indicate that the GMAW process is able to generate significant levels of nanoparticles. It is recommended that a combination of multiple metrics is measured as part of a well-designed sampling strategy for airborne nanoparticles. Key exposure factors, such as particle agglomeration/aggregation, background particles, working activities, temporal and spatial distributions of the particles, air velocity, engineering control measures, should be investigated when measuring workplace exposure to nanoparticles.

Electrical percolation threshold of magnetostrictive inclusions in a piezoelectric matrix under simulated sintering conditions

NASA Astrophysics Data System (ADS)

Bedard, Antoine Joseph; Barbero, Ever J.

2018-03-01

Magnetoelectric (ME) composites can be produced by embedding magnetostrictive H particles in a piezoelectric E matrix derived from a piezoelectric powder precursor. Previously, using a bi-disperse hard-shell model (Barbero and Bedard in Comput Part Mech, 2018. https://doi.org/10.1007/s40571-017-0165-4), it has been shown that the electrical percolation threshold of the conductive H phase can be increased by decreasing the piezoelectric E particle size, relative to the H phase particle size, and by increasing short-range affinity between the E and H particles. This study builds on our previous study by exploring what happens during sintering of the ME composite when either the H or E particles undergo deformation. It was found that deformation of the H particles reduces the percolation threshold, and that deformation of E particles increases inter-phase H-E mechanical coupling, thus contributing to enhancing of ME coupling.

Estimation of the superhigh-frequency magnetic permeability of alsifer from the measured permeability of composites

NASA Astrophysics Data System (ADS)

Starostenko, S. N.; Rozanov, K. N.; Shiryaev, A. O.; Lagar'kov, A. N.; Shalygin, A. N.

2017-11-01

The magnetic permeability of alsifer was restored from the frequency dependences of the dielectric and magnetic permeabilities of powder alsifer (AlSiFe alloy)-wax matrix composites. The permeabilities were measured using the coaxial line technique within a frequency range of 0.05-20 GHz. The effect of the concentration, shape, and size of powder particles on the microwave magnetic properties of composites was considered. A good agreement between the measurement results and the Maxwell-Garnett formula generalized with consideration for the particle shape, the percolation threshold, and the skin-effect was obtained. The found sizes of particles agreed with electron microscopy and granulometry data. Both the frequency and the ferromagnetic resonance line figure of merit (FOM) for lamellar particles proved to be higher than for spherical ones. Alsifer powders were shown to be promising fillers for radioabsorbing materials.

SIZE-SELECTING AEROSOL CHARACTERIZATION INSTRUMENT - PHASE II

EPA Science Inventory

Aerodyne Research, Inc., proposes to develop a new monitor that provides composition information of particles in the ultrafine (10-100 nm), fine (100 nm-2.5 µm) and coarse (2.5-10 µm) size modes in near real time. Particle monitoring technologies are important f...

Iron isotope composition of particles produced by UV-femtosecond laser ablation of natural oxides, sulfides, and carbonates.

PubMed

d'Abzac, Francois-Xavier; Beard, Brian L; Czaja, Andrew D; Konishi, Hiromi; Schauer, James J; Johnson, Clark M

2013-12-17

The need for femtosecond laser ablation (fs-LA) systems coupled to MC-ICP-MS to accurately perform in situ stable isotope analyses remains an open question, because of the lack of knowledge concerning ablation-related isotopic fractionation in this regime. We report the first iron isotope analysis of size-resolved, laser-induced particles of natural magnetite, siderite, pyrrhotite, and pyrite, collected through cascade impaction, followed by analysis by solution nebulization MC-ICP-MS, as well as imaging using electron microscopy. Iron mass distributions are independent of mineralogy, and particle morphology includes both spheres and agglomerates for all ablated phases. X-ray spectroscopy shows elemental fractionation in siderite (C-rich agglomerates) and pyrrhotite/pyrite (S-rich spheres). We find an increase in (56)Fe/(54)Fe ratios of +2‰, +1.2‰, and +0.8‰ with increasing particle size for magnetite, siderite, and pyrrhotite, respectively. Fe isotope differences in size-sorted aerosols from pyrite ablation are not analytically resolvable. Experimental data are discussed using models of particles generation by Hergenröder and elemental/isotopic fractionation by Richter. We interpret the isotopic fractionation to be related to the iron condensation time scale, dependent on its saturation in the gas phase, as a function of mineral composition. Despite the isotopic variations across aerosol size fractions, total aerosol composition, as calculated from mass balance, confirms that fs-LA produces a stoichiometric sampling in terms of isotopic composition. Specifically, both elemental and isotopic fractionation are produced by particle generation processes and not by femtosecond laser-matter interactions. These results provide critical insights into the analytical requirements for laser-ablation-based stable isotope measurements of high-precision and accuracy in geological samples, including the importance of quantitative aerosol transport to the ICP.

Study on the mechanical properties of Cu/LDPE composite IUDs.

PubMed

Tang, Ying; Xia, Xianping; Wang, Yun; Xie, Changsheng

2011-03-01

The copper/low-density polyethylene composite (Cu/LDPE composite) intrauterine devices (IUDs), which can eliminate or lessen the side effects of existing IUDs, have been developed in our laboratory. As a novel type of copper-containing IUDs, it is not clear whether the mechanical properties of the Cu/LDPE composite IUDs can meet the need of clinical use or not. Therefore, the mechanical properties of the Cu/LDPE composite IUDs have been studied in the present article. The influence of copper particle content and size on the mechanical properties of the Cu/LDPE composite IUDs was analyzed firstly to provide guidance for the material composition design of the Cu/LDPE composite IUDs, and then the BaSO(4)/LDPE composite, which has been applied as a framework of the existing copper-containing IUDs in clinical use for decades, has been used as reference to judge whether the mechanical properties of the Cu/LDPE composite IUDs can meet the need of clinical use or not. However, the mechanical properties of IUDs cannot be characterized directly. Therefore, the mechanical properties of both the Cu/LDPE composite IUDs and the framework of the existing copper-containing IUDs were investigated by means of tensile test using standard tensile samples, and the fracture surface morphology of the tensile samples was characterized by scanning electron microscopy (SEM). Both the elongation at break and the tensile strength decrease with increasing of copper particle content and increase with increasing of the copper particle size, while the elastic modulus shows an opposite tendency. The tensile strength and elastic modulus of both the Cu/LDPE microcomposite IUDs and the Cu/LDPE nanocomposite IUDs with 25 wt.% of copper particles are higher than those of existing copper-containing IUDs (TCu220C; its framework is made of the BaSO(4)/LDPE composite with 20 wt.% of BaSO(4)). The content and size of the copper particles have significant effect on the mechanical properties of Cu/LDPE composite IUDs. The mechanical properties of both the Cu/LDPE microcomposite IUDs and the Cu/LDPE nanocomposite IUDs with 25 wt.% of copper particles were superior to that of existing copper-containing IUDs, indicating that the novel Cu/LDPE composite IUDs can satisfy the requirement of mechanical properties in clinical application. Copyright © 2011 Elsevier Inc. All rights reserved.

Application of Aerosol Hygroscopicity Measured at the Atmospheric Radiation Measurement Program's Southern Great Plains Site to Examine Composition and Evolution

NASA Technical Reports Server (NTRS)

Gasparini, Roberto; Runjun, Li; Collins, Don R.; Ferrare, Richard A.; Brackett, Vincent G.

2006-01-01

A Differential Mobility Analyzer/Tandem Differential Mobility Analyzer (DMA/TDMA) was used to measure submicron aerosol size distributions, hygroscopicity, and occasionally volatility during the May 2003 Aerosol Intensive Operational Period (IOP) at the Central Facility of the Atmospheric Radiation Measurement Program's Southern Great Plains (ARM SGP) site. Hygroscopic growth factor distributions for particles at eight dry diameters ranging from 0.012 micrometers to 0.600 micrometers were measured throughout the study. For a subset of particle sizes, more detailed measurements were occasionally made in which the relative humidity or temperature to which the aerosol was exposed was varied over a wide range. These measurements, in conjunction with backtrajectory clustering, were used to infer aerosol composition and to gain insight into the processes responsible for evolution. The hygroscopic growth of both the smallest and largest particles analyzed was typically less than that of particles with dry diameters of about 0.100 micrometers. It is speculated that condensation of secondary organic aerosol on nucleation mode particles is largely responsible for the minimal hygroscopic growth observed at the smallest sizes considered. Growth factor distributions of the largest particles characterized typically contained a nonhygroscopic mode believed to be composed primarily of dust. A model was developed to characterize the hygroscopic properties of particles within a size distribution mode through analysis of the fixed size hygroscopic growth measurements. The performance of this model was quantified through comparison of the measured fixed size hygroscopic growth factor distributions with those simulated through convolution of the size-resolved concentration contributed by each of the size modes and the mode-resolved hygroscopicity. This transformation from sizeresolved hygroscopicity to mode-resolved hygroscopicity facilitated examination of changes in the hygroscopic properties of particles within a size distribution mode that accompanied changes in the sizes of those particles. This model was used to examine three specific cases in which the sampled aerosol evolved slowly over a period of hours or days.

Size and chemical characterization of individual particles resulting from biomass burning of local southern California species

Treesearch

Philip J. Silva; Don-Yuan Liu; Christopher A. Noble; Kimberly A. Prather

1999-01-01

The chemical composition and size of individual particles derived from combustion products of several species found in Southern California were obtained using aerosol time-of-flight mass spectrometry. The major inorganic species observed in >90% of all biomass burning particles is potassium, indicated by the atomic ion, as well as clusters containing chloride,...

Thermal and mechanical behaviour of sub micron sized fly ash reinforced polyester resin composite

NASA Astrophysics Data System (ADS)

Nantha Kumar, P.; Rajadurai, A.; Muthuramalingam, T.

2018-04-01

The utilization of particles reinforced resin matrix composites is being increased owing to its lower density and high strength to weight ratio. In the present study, an attempt has been made to synthesize fly ash particles reinforced polyester resin composite for engine cowling application. The thermal stability and mechanical behaviours such as hardness and flexural strength of the composite with 2, 3 and 4 weight % of reinforcement is studied and analyzed. The thermo gravimetric analysis indicates that the higher addition of reinforcement increases the decomposition temperature due to its refractory nature. It is also observed that the hardness increases with higher filler addition owing to the resistance of FA particles towards penetration. The flexural strength is found to increase up to the addition of 3% of FA particles, whereas the polyester resin composite prepared with 4% FA particles addition is observed to have low flexural strength owing to agglomeration of particles.

Infrared Spectroscopic Study on Structural Change and Interfacial Interaction in Rubber Composites Filled with Silica-Kaolin Hybrid Fillers

NASA Astrophysics Data System (ADS)

Chen, Y.; Guan, J.; Hu, H.; Gao, H.; Zhang, L.

2016-07-01

A series of natural rubber/styrene butadiene rubber/polybutadiene rubber composites was prepared with nanometer silica and micron kaolin by a dry modification process, mechanical compounding, and mold vulcanization. Fourier transform infrared spectroscopy and a scanning electron microscope were used to investigate the structural changes and interfacial interactions in composites. The results showed that the "seesaw" structure was formed particularly with the incorporation of silica particles in the preparation process, which would be beneficial to the dispersibility of fillers in the rubber matrix. The kaolinite platelets were generally arranged in directional alignment. Kaolinite with smaller particle size and low-defect structure was more stable in preparation, but kaolinite with larger particle size and high defect structure tended to change the crystal structure. The composite prepared in this research exhibited excellent mechanical and thermal properties.

Predicting the Effective Elastic Properties of Polymer Bonded Explosives based on Micromechanical Methods

NASA Astrophysics Data System (ADS)

Wang, Jingcheng; Luo, Jingrun

2018-04-01

Due to the extremely high particle volume fraction (greater than 85%) and damage feature of polymer bonded explosives (PBXs), conventional micromechanical methods lead to inaccurate estimates on their effective elastic properties. According to their manufacture characteristics, a multistep approach based on micromechanical methods is proposed. PBXs are treated as pseudo poly-crystal materials consisting of equivalent composite particles (explosive crystals with binder coating), rather than two-phase composites composed of explosive particles and binder matrix. Moduli of composite spheres are obtained by generalized self-consistent method first, and the self-consistent method is modified to calculate the effective moduli of PBX. Defects and particle size distribution are considered by Mori-Tanaka method. Results show that when the multistep approach is applied to PBX 9501, estimates are far more accurate than the conventional micromechanical results. The bulk modulus is 5.75% higher, and shear modulus is 5.78% lower than the experimental values. Further analyses discover that while particle volume fraction and the binder's property have significant influences on the effective moduli of PBX, the moduli of particles present minor influences. Investigation of another particle size distribution indicates that the use of more fine particles will enhance the effective moduli of PBX.

Aerosol detection efficiency in inductively coupled plasma mass spectrometry

NASA Astrophysics Data System (ADS)

Hubbard, Joshua A.; Zigmond, Joseph A.

2016-05-01

An electrostatic size classification technique was used to segregate particles of known composition prior to being injected into an inductively coupled plasma mass spectrometer (ICP-MS). Size-segregated particles were counted with a condensation nuclei counter as well as sampled with an ICP-MS. By injecting particles of known size, composition, and aerosol concentration into the ICP-MS, efficiencies of the order of magnitude aerosol detection were calculated, and the particle size dependencies for volatile and refractory species were quantified. Similar to laser ablation ICP-MS, aerosol detection efficiency was defined as the rate at which atoms were detected in the ICP-MS normalized by the rate at which atoms were injected in the form of particles. This method adds valuable insight into the development of technologies like laser ablation ICP-MS where aerosol particles (of relatively unknown size and gas concentration) are generated during ablation and then transported into the plasma of an ICP-MS. In this study, we characterized aerosol detection efficiencies of volatile species gold and silver along with refractory species aluminum oxide, cerium oxide, and yttrium oxide. Aerosols were generated with electrical mobility diameters ranging from 100 to 1000 nm. In general, it was observed that refractory species had lower aerosol detection efficiencies than volatile species, and there were strong dependencies on particle size and plasma torch residence time. Volatile species showed a distinct transition point at which aerosol detection efficiency began decreasing with increasing particle size. This critical diameter indicated the largest particle size for which complete particle detection should be expected and agreed with theories published in other works. Aerosol detection efficiencies also displayed power law dependencies on particle size. Aerosol detection efficiencies ranged from 10- 5 to 10- 11. Free molecular heat and mass transfer theory was applied, but evaporative phenomena were not sufficient to explain the dependence of aerosol detection on particle diameter. Additional work is needed to correlate experimental data with theory for metal-oxides where thermodynamic property data are sparse relative to pure elements. Lastly, when matrix effects and the diffusion of ions inside the plasma were considered, mass loading was concluded to have had an effect on the dependence of detection efficiency on particle diameter.

Effect of particle size and particle size distribution on physical characteristics, morphology and crystal strucutre of explosively compacted high-Tc superconductors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kotsis, I.; Enisz, M.; Oravetz, D.

1994-12-31

A superconductor, of composition Y(Ba,K,Na){sub 2}Cu{sub 3}O{sub x}/F{sub y} and a composite, of composition Y(Ba,K,Na){sub 2}Cu{sub 3}O{sub x}/F{sub y}+Ag, with changing K, Na and F content, but a constant silver content (Ag=10 mass per cent) was prepared using a single heat treatment. The resulting material was ground in a corundum lined mill, separated to particle size fractions of 0-40 {mu}m, 0-63 {mu}m and 63-900 {mu}m and explosively compacted, using an explosive pressure of 10{sup 4} MPa and a subsequent heat treatment. Best results were obtained with the 63-900 {mu}m fraction of composition Y(Ba{sub 1,95}K{sub 0,01})Cu{sub 3}O{sub x}F{sub 0,05}/Ag: porosity <0.01more » cm{sup 3}/g and current density 2800 A/cm{sup 2} at 77 K.« less

Cryptoachneliths: Hidden glassy ash in composite spheroidal lapilli

NASA Astrophysics Data System (ADS)

Carracedo Sánchez, M.; Arostegui, J.; Sarrionandia, F.; Larrondo, E.; Gil Ibarguchi, J. I.

2010-09-01

Cryptoachneliths, perceptible by means of electron microscopy but unresolved under the optical microscope, occur unnoticed inside spheroidal lapilli of ultrabasic composition of the Cabezo Segura volcano (Calatrava volcanic province, Spain). The cryptoachneliths are glassy spherical particles that have compositions of Al-rich silicate with minor amounts of Fe, Ca and other elements. The smallest cryptoachneliths of < 1 μm in diameter (nanoachneliths) joined by coalescence to form microspheres > 1 μm (microachneliths) and homogeneous less regular masses of similar composition. Nano and microachneliths welded each other or to other types of volcanic particles (crystals, crystal fragments, spinning droplets, cognate lithic clasts, etc.) to form spheroidal lapilli and even bomb size clasts within proximal fall deposits of the Cabezo Segura volcano. The welding processes took place inside the eruptive column, previous to the fall of the spheroidal lapilli on top of the volcanic cone. The presence of the cryptoachneliths implies that lapilli and even bomb size tephra within deposits formed during explosive eruptions of low-viscosity basic to ultrabasic magmas should be carefully examined in order to establish key parameters of eruption dynamics, like size, amount and distribution of juvenile fine particles.

Effect of Nanofiller Shape on Effective Thermal Conductivity of Fluoropolymer Composites

DTIC Science & Technology

2015-08-24

SECURITY CLASSIFICATION OF: Filler particle size and shape influence interconnectivity within a polymer matrix and play a significant role in controlling...the effective thermal conductivity of a composite. This study examines the effect of nanofiller particle shape in a polytetrafluorethylene (PTFE...carbon fillers: nano-diamond spheres, carbon nanotubes (CNT) and graphene flakes. The experimental results are coupled with a particle connectivity model

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ivashchenko, R.K.; Fedorenko, V.K.; Kadryov, V.K.

In this work an attempt was made, by lowering the temperature in the detonation zone, decreasing the particle flight velocity, and employing starting powders in which the WC particle size 20-40 mum predominated, to obtain detonation-deposited VK20 alloy coatings approaching closely in structure and phase composition hard-metal composites produced by the powder metallurgy method.

Modelling component evaporation and composition change of traffic-induced ultrafine particles during travel from street canyon to urban background.

PubMed

Nikolova, Irina; MacKenzie, A Rob; Cai, Xiaoming; Alam, Mohammed S; Harrison, Roy M

2016-07-18

We developed a model (CiTTy-Street-UFP) of traffic-related particle behaviour in a street canyon and in the nearby downwind urban background that accounts for aerosol dynamics and the variable vapour pressure of component organics. The model simulates the evolution and fate of traffic generated multicomponent ultrafine particles (UFP) composed of a non-volatile core and 17 Semi-Volatile Organic Compounds (SVOC, modelled as n-alkane proxies). A two-stage modelling approach is adopted: (1) a steady state simulation inside the street canyon is achieved, in which there exists a balance between traffic emissions, condensation/evaporation, deposition, coagulation and exchange with the air above roof-level; and (2) a continuing simulation of the above-roof air parcel advected to the nearby urban park during which evaporation is dominant. We evaluate the component evaporation and associated composition changes of multicomponent organic particles in realistic atmospheric conditions and compare our results with observations from London (UK) in a street canyon and an urban park. With plausible input conditions and parameter settings, the model can reproduce, with reasonable fidelity, size distributions in central London in 2007. The modelled nucleation-mode peak diameter, which is 23 nm in the steady-state street canyon, decreases to 9 nm in a travel time of just 120 s. All modelled SVOC in the sub-10 nm particle size range have evaporated leaving behind only non-volatile material, whereas modelled particle composition in the Aitken mode contains SVOC between C26H54 and C32H66. No data on particle composition are available in the study used for validation, or elsewhere. Measurements addressing in detail the size resolved composition of the traffic emitted UFP in the atmosphere are a high priority for future research. Such data would improve the representation of these particles in dispersion models and provide the data essential for model validation. Enhanced knowledge of the chemical composition of nucleation-mode particles from diesel engine exhaust is needed to predict both their atmospheric behaviour and their implications for human health.

Light scattering by lunar-like particle size distributions

NASA Technical Reports Server (NTRS)

Goguen, Jay D.

1991-01-01

A fundamental input to models of light scattering from planetary regoliths is the mean phase function of the regolith particles. Using the known size distribution for typical lunar soils, the mean phase function and mean linear polarization for a regolith volume element of spherical particles of any composition were calculated from Mie theory. The two contour plots given here summarize the changes in the mean phase function and linear polarization with changes in the real part of the complex index of refraction, n - ik, for k equals 0.01, the visible wavelength 0.55 micrometers, and the particle size distribution of the typical mature lunar soil 72141. A second figure is a similar index-phase surface, except with k equals 0.1. The index-phase surfaces from this survey are a first order description of scattering by lunar-like regoliths of spherical particles of arbitrary composition. They form the basis of functions that span a large range of parameter-space.

Composition and particle size of electrolytic copper powders prepared in water-containing dimethyl sulfoxide electrolytes

NASA Astrophysics Data System (ADS)

Mamyrbekova, Aigul'; Abzhalov, B. S.; Mamyrbekova, Aizhan

2017-07-01

The possibility of the electroprecipitation of copper powder via the cathodic reduction of an electrolyte solution containing copper(II) nitrate trihydrate and dimethyl sulfoxide (DMSO) is shown. The effect electrolysis conditions (current density, concentration and temperature of electrolyte) have on the dimensional characteristics of copper powder is studied. The size and shape of the particles of the powders were determined by means of electron microscopy; the qualitative composition of the powders, with X-ray diffraction.

Synthesis and characterization of magnetic and non-magnetic core-shell polyepoxide micrometer-sized particles of narrow size distribution.

PubMed

Omer-Mizrahi, Melany; Margel, Shlomo

2009-01-15

Core polystyrene microspheres of narrow size distribution were prepared by dispersion polymerization of styrene in a mixture of ethanol and 2-methoxy ethanol. Uniform polyglycidyl methacrylate/polystyrene core-shell micrometer-sized particles were prepared by emulsion polymerization at 73 degrees C of glycidyl methacrylate in the presence of the core polystyrene microspheres. Core-shell particles with different properties (size, surface morphology and composition) have been prepared by changing various parameters belonging to the above seeded emulsion polymerization process, e.g., volumes of the monomer glycidyl methacrylate and the crosslinker monomer ethylene glycol dimethacrylate. Magnetic Fe(3)O(4)/polyglycidyl methacrylate/polystyrene micrometer-sized particles were prepared by coating the former core-shell particles with magnetite nanoparticles via a nucleation and growth mechanism. Characterization of the various particles has been accomplished by routine methods such as light microscopy, SEM, FTIR, BET and magnetic measurements.

The Hardness and Strength Properties of WC-Co Composites

PubMed Central

Armstrong, Ronald W.

2011-01-01

The industrially-important WC-Co composite materials provide a useful, albeit complicated materials system for understanding the combined influences on hardness and strength properties of the constituent WC particle strengths, the particle sizes, their contiguities, and of Co binder hardness and mean free paths, and in total, the volume fraction of constituents. A connection is made here between the composite material properties, especially including the material fracture toughness, and the several materials-type considerations of: (1) related hardness stress-strain behaviors; (2) dislocation (viscoplastic) thermal activation characterizations; (3) Hall-Petch type reciprocal square root of particle or grain size dependencies; and (4) indentation and conventional fracture mechanics results. Related behaviors of MgO and Al2O3 crystal and polycrystal materials are also described for the purpose of making comparisons. PMID:28824143

Particle size dependence on magnetic and electrical properties of (Ni0.8Fe0.2)10C90 granular composites.

PubMed

Mandal, Guruprasad; Srinivas, V; Rao, V V

2011-03-01

The granular structure and electrical transport behavior of ball milled magnetic permalloy particles and graphite forming (Ni0.8Fe0.2)10C90 granular composites have been reported. Retaining the composite composition to be 90:10 and varying the particle size of permalloy, the electronic transport properties have been carried out down to 4 K under the external applied magnetic field of 50 kOe. All the samples show semiconducting like behavior and positive magnetoresistance (MR) in the temperature range 4-300 K. A strong anisotropic magnetoresistance in these samples has also been observed. The highest 31% longitudinal and 6.8% transverse magnetoresistance values have been observed in 40 hrs ball milled (Ni0.8Fe0.2)10C90 composite. From these studies, we suggest that the magnetic component present in the sample may not be playing a major role in obtaining large positive MR values, which is in deviation with the earlier reports.

Droplet activation, separation, and compositional analysis: laboratory studies and atmospheric measurements

NASA Astrophysics Data System (ADS)

Hiranuma, N.; Kohn, M.; Pekour, M. S.; Nelson, D. A.; Shilling, J. E.; Cziczo, D. J.

2011-10-01

Droplets produced in a cloud condensation nuclei chamber (CCNC) as a function of supersaturation have been separated from unactivated aerosol particles using counterflow virtual impaction. Residual material after droplets were evaporated was chemically analyzed with an Aerodyne Aerosol Mass Spectrometer (AMS) and the Particle Analysis by Laser Mass Spectrometry (PALMS) instrument. Experiments were initially conducted to verify activation conditions for monodisperse ammonium sulfate particles and to determine the resulting droplet size distribution as a function of supersaturation. Based on the observed droplet size, the counterflow virtual impactor cut-size was set to differentiate droplets from unactivated interstitial particles. Validation experiments were then performed to verify that only droplets with sufficient size passed through the counterflow virtual impactor for subsequent analysis. A two-component external mixture of monodisperse particles was also exposed to a supersaturation which would activate one of the types (hygroscopic salts) but not the other (polystyrene latex spheres or adipic acid). The mass spectrum observed after separation indicated only the former, validating separation of droplets from unactivated particles. Results from ambient measurements using this technique and AMS analysis were inconclusive, showing little chemical differentiation between ambient aerosol and activated droplet residuals, largely due to low signal levels. When employing as single particle mass spectrometer for compositional analysis, however, we observed enhancement of sulfate in droplet residuals.

Size and elemental composition of dry-deposited particles during a severe dust storm at a coastal site of Eastern China.

PubMed

Niu, Hongya; Zhang, Daizhou; Hu, Wei; Shi, Jinhui; Li, Ruipeng; Gao, Huiwang; Pian, Wei; Hu, Min

2016-02-01

Dry-deposited particles were collected during the passage of an extremely strong dust storm in March, 2010 at a coastal site in Qingdao (36.15 °N, 120.49 °E), a city located in Eastern China. The size, morphology, and elemental composition of the particles were quantified with a scanning electron microscope equipped with an energy dispersive X-ray instrument (SEM-EDX). The particles appeared in various shapes, and their size mainly varied from 0.4 to 10 μm, with the mean diameters of 0.5, 1.5, and 1.0 μm before, during, and after the dust storm, respectively. The critical size of the mineral particles settling on the surface in the current case was about 0.3-0.4 μm before the dust storm and about 0.5-0.7 μm during the dust storm. Particles that appeared in high concentration but were smaller than the critical size deposited onto the surface at a small number flux. The elements Al, Si and Mg were frequently detected in all samples, indicating the dominance of mineral particles. The frequency of Al in particles collected before the dust storm was significantly lower than for those collected during and after the dust storm. The frequencies of Cl and Fe did not show obvious changes, while those of S, K and Ca decreased after the dust arrival. These results indicate that the dust particles deposited onto the surface were less influenced by anthropogenic pollutants in terms of particle number. Copyright © 2015. Published by Elsevier B.V.

Apparatus for rapid measurement of aerosol bulk chemical composition

DOEpatents

Lee, Yin-Nan E.; Weber, Rodney J.

2003-01-01

An apparatus and method for continuous on-line measurement of chemical composition of aerosol particles with a fast time resolution are provided. The apparatus includes a modified particle size magnifier for producing activated aerosol particles and a collection device which collects the activated aerosol particles into a liquid stream for quantitative analysis by analytical methods. The method provided for on-line measurement of chemical composition of aerosol particles includes exposing aerosol carrying sample air to hot saturated steam thereby forming activated aerosol particles; collecting the activated aerosol particles by a collection device for delivery as a jet stream onto an impaction surface; flushing off the activated aerosol particles from the impaction surface into a liquid stream for delivery of the collected liquid stream to an analytical instrument for quantitative measurement.

Apparatus for rapid measurement of aerosol bulk chemical composition

DOEpatents

Lee, Yin-Nan E.; Weber, Rodney J.; Orsini, Douglas

2006-04-18

An apparatus for continuous on-line measurement of chemical composition of aerosol particles with a fast time resolution is provided. The apparatus includes an enhanced particle size magnifier for producing activated aerosol particles and an enhanced collection device which collects the activated aerosol particles into a liquid stream for quantitative analysis by analytical means. Methods for on-line measurement of chemical composition of aerosol particles are also provided, the method including exposing aerosol carrying sample air to hot saturated steam thereby forming activated aerosol particles; collecting the activated aerosol particles by a collection device for delivery as a jet stream onto an impaction surface; and flushing off the activated aerosol particles from the impaction surface into a liquid stream for delivery of the collected liquid stream to an analytical instrument for quantitative measurement.

Rapid Solidification of Sn-Cu-Al Alloys for High-Reliability, Lead-Free Solder: Part I. Microstructural Characterization of Rapidly Solidified Solders

NASA Astrophysics Data System (ADS)

Reeve, Kathlene N.; Choquette, Stephanie M.; Anderson, Iver E.; Handwerker, Carol A.

2016-12-01

Particles of Cu x Al y in Sn-Cu-Al solders have previously been shown to nucleate the Cu6Sn5 phase during solidification. In this study, the number and size of Cu6Sn5 nucleation sites were controlled through the particle size refinement of Cu x Al y via rapid solidification processing and controlled cooling in a differential scanning calorimeter. Cooling rates spanning eight orders of magnitude were used to refine the average Cu x Al y and Cu6Sn5 particle sizes down to submicron ranges. The average particle sizes, particle size distributions, and morphologies in the microstructures were analyzed as a function of alloy composition and cooling rate. Deep etching of the samples revealed the three-dimensional microstructures and illuminated the epitaxial and morphological relationships between the Cu x Al y and Cu6Sn5 phases. Transitions in the Cu6Sn5 particle morphologies from faceted rods to nonfaceted, equiaxed particles were observed as a function of both cooling rate and composition. Initial solidification cooling rates within the range of 103 to 104 °C/s were found to be optimal for realizing particle size refinement and maintaining the Cu x Al y /Cu6Sn5 nucleant relationship. In addition, little evidence of the formation or decomposition of the ternary- β phase in the solidified alloys was noted. Solidification pathways omitting the formation of the ternary- β phase agreed well with observed room temperature microstructures.

Rapid Solidification of Sn-Cu-Al Alloys for High-Reliability, Lead-Free Solder: Part I. Microstructural Characterization of Rapidly Solidified Solders

DOE Office of Scientific and Technical Information (OSTI.GOV)

Reeve, Kathlene N.; Choquette, Stephanie M.; Anderson, Iver E.

Particles of Cu x Al y in Sn-Cu-Al solders have previously been shown to nucleate the Cu 6Sn 5 phase during solidification. In this study, the number and size of Cu 6Sn 5 nucleation sites were controlled through the particle size refinement of Cu x Al y via rapid solidification processing and controlled cooling in a differential scanning calorimeter. Cooling rates spanning eight orders of magnitude were used to refine the average Cu x Al y and Cu 6Sn 5 particle sizes down to submicron ranges. The average particle sizes, particle size distributions, and morphologies in the microstructures were analyzedmore » as a function of alloy composition and cooling rate. Deep etching of the samples revealed the three-dimensional microstructures and illuminated the epitaxial and morphological relationships between the Cu x Al y and Cu 6Sn 5 phases. Transitions in the Cu 6Sn 5 particle morphologies from faceted rods to nonfaceted, equiaxed particles were observed as a function of both cooling rate and composition. Initial solidification cooling rates within the range of 10 3 to 10 4 °C/s were found to be optimal for realizing particle size refinement and maintaining the Cu x Al y /Cu 6Sn 5 nucleant relationship. In addition, little evidence of the formation or decomposition of the ternary-β phase in the solidified alloys was noted. As a result, solidification pathways omitting the formation of the ternary-β phase agreed well with observed room temperature microstructures.« less

Rapid Solidification of Sn-Cu-Al Alloys for High-Reliability, Lead-Free Solder: Part I. Microstructural Characterization of Rapidly Solidified Solders

DOE PAGES

Reeve, Kathlene N.; Choquette, Stephanie M.; Anderson, Iver E.; ...

2016-10-06

Particles of Cu x Al y in Sn-Cu-Al solders have previously been shown to nucleate the Cu 6Sn 5 phase during solidification. In this study, the number and size of Cu 6Sn 5 nucleation sites were controlled through the particle size refinement of Cu x Al y via rapid solidification processing and controlled cooling in a differential scanning calorimeter. Cooling rates spanning eight orders of magnitude were used to refine the average Cu x Al y and Cu 6Sn 5 particle sizes down to submicron ranges. The average particle sizes, particle size distributions, and morphologies in the microstructures were analyzedmore » as a function of alloy composition and cooling rate. Deep etching of the samples revealed the three-dimensional microstructures and illuminated the epitaxial and morphological relationships between the Cu x Al y and Cu 6Sn 5 phases. Transitions in the Cu 6Sn 5 particle morphologies from faceted rods to nonfaceted, equiaxed particles were observed as a function of both cooling rate and composition. Initial solidification cooling rates within the range of 10 3 to 10 4 °C/s were found to be optimal for realizing particle size refinement and maintaining the Cu x Al y /Cu 6Sn 5 nucleant relationship. In addition, little evidence of the formation or decomposition of the ternary-β phase in the solidified alloys was noted. As a result, solidification pathways omitting the formation of the ternary-β phase agreed well with observed room temperature microstructures.« less

Chemical Characterization of Individual Particles and Residuals of Cloud Droplets and Ice Crystals Collected On Board Research Aircraft in the ISDAC 2008 Study

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hiranuma, Naruki; Brooks, Sarah D.; Moffet, Ryan C.

2013-06-24

Although it has been shown that size of atmospheric particles has a direct correlation with their ability to act as cloud droplet and ice nuclei, the influence of composition of freshly emitted and aged particles in nucleation processes is poorly understood. In this work we combine data from field measurements of ice nucleation with chemical imaging of the sampled particles to link aerosol composition with ice nucleation ability. Field measurements and sampling were conducted during the Indirect and Semidirect Aerosols Campaign (ISDAC) over Barrow, Alaska, in the springtime of 2008. In-situ ice nucleation measurements were conducted using a Continuous Flowmore » Diffusion Chamber (CFDC). Measured number concentrations of ice nuclei (IN) varied from frequent values of 0.01 per liter to more than 10 per liter. Residuals of airborne droplets and ice crystals were collected through a counterflow virtual impactor (CVI). The compositions of individual atmospheric particles and the residuals were studied using Computer Controlled Scanning Electron Microscopy with Energy Dispersive X-ray analysis (CCSEM/EDX) and Scanning Transmission X-ray Microscopy coupled with Near Edge X-ray Absorption Fine Structure spectroscopy (STXM/NEXAFS). Chemical analysis of cloud particle residuals collected during an episode of high ice nucleation suggests that both size and composition may influence aerosol's ability to act as IN. The STXM/NEXAFS chemical composition maps of individual residuals have characteristic structures of either inorganic or black carbon cores coated by organic materials. In a separate flight, particle samples from a biomass burning plume were collected. Although it has previously been suggested that episodes of biomass burning contribute to increased numbers of highly effective ice nuclei, in this episode we observed that only a small fraction were effective ice nuclei. Most of the particles from the biomass plume episode were smaller in size and were composed of homogeneous organic material without identifiable cores.« less

Characterization of wood dust from furniture by scanning electron microscopy and energy-dispersive x-ray analysis.

PubMed

Gómez Yepes, Milena Elizabeth; Cremades, Lázaro V

2011-01-01

Study characterized and analyzed form factor, elementary composition and particle size of wood dust, in order to understand its harmful health effects on carpenters in Quindío (Colombia). Once particle characteristics (size distributions, aerodynamic equivalent diameter (D(α)), elemental composition and shape factors) were analyzed, particles were then characterized via scanning electron microscopy (SEM) in conjunction with energy dispersive X-ray analysis (EDXRA). SEM analysis of particulate matter showed: 1) cone-shaped particle ranged from 2.09 to 48.79 µm D(α); 2) rectangular prism-shaped particle from 2.47 to 72.9 µm D(α); 3) cylindrically-shaped particle from 2.5 to 48.79 µm D(α); and 4) spherically-shaped particle from 2.61 to 51.93 µm D(α). EDXRA reveals presence of chemical elements from paints and varnishes such as Ca, K, Na and Cr. SEM/EDXRA contributes in a significant manner to the morphological characterization of wood dust. It is obvious that the type of particles sampled is a complex function of shapes and sizes of particles. Thus, it is important to investigate the influence of particles characteristics, morphology, shapes and D(α) that may affect the health of carpenters in Quindío.

MATRIX-ASSISTED LASER DESORPTION IONIZATION OF SIZE AND COMPOSITION SELECTED AEROSOL PARTICLES. (R823980)

EPA Science Inventory

Matrix-assisted laser desorption/ionization (MALDI) was performed on individual,
size-selected aerosol particles in the 2-8 mu m diameter range, Monodisperse aerosol droplets
containing matrix, analyte, and solvent were generated and entrained in a dry stream of air, The dr...

Continuous flow hygroscopicity-resolved relaxed eddy accumulation (Hy-Res REA) method of measuring size-resolved sodium chloride particle fluxes

EPA Science Inventory

The accurate representation of aerosols in climate models requires direct ambient measurement of the size- and composition-dependent particle production fluxes. Here, we present the design, testing, and analysis of data collected through the first instrument capable of measuring ...

Effect of filler loading and silane modification on the biodegradability of SBR composites reinforced with peanut shell powder

NASA Astrophysics Data System (ADS)

Shaniba, V.; Balan, Aparna K.; Sreejith, M. P.; Jinitha, T. V.; Subair, N.; Purushothaman, E.

2017-06-01

The development of biocomposites and their applications are important in material science due to environmental and sustainability issues. The extent of degradation depends on the nature of reinforcing filler, particle size and their modification. In this article, we tried to focus on the biodegradation of composites of Styrene Butadiene Rubber (SBR) reinforced with Peanut Shell Powder (PSP) by soil burial test. The composites of SBR with untreated PSP (UPSP) and silane modified PSP (SPSP) of 10 parts per hundred rubber (phr) and 20 phr filler loading in two particle size were buried in the garden soil for six months. The microbial degradation were assessed through the measurement of weight loss, tensile strength and hardness at definite period. The study shows that degradation increases with increase in filler loading and particle size. The chemical treatment of filler has been found to resist the degradation. The analysis of morphological properties by the SEM also confirmed biodegradation process by the microorganism in the soil.

The biological response to nanometre-sized polymer particles.

PubMed

Liu, Aiqin; Richards, Laura; Bladen, Catherine L; Ingham, Eileen; Fisher, John; Tipper, Joanne L

2015-09-01

Recently, nanometre-sized UHMWPE particles generated from hip and knee replacements have been identified in vitro and in vivo. UHMWPE particles in the 0.1-1.0μm size range have been shown to be more biologically active than larger particles, provoking an inflammatory response implicated in late aseptic loosening of total joint replacements. The biological activity of nanometre-sized particles has not previously been studied. The biological response to clinically-relevant UHMWPE wear particles including nanometre-sized and micrometre-sized, along with polystyrene particles (FluoSpheres 20nm, 60nm, 200nm and 1.0μm), and nanometre-sized model polyethylene particles (Ceridust 3615®), was determined in terms of osteolytic cytokine release from primary human peripheral blood mononuclear cells (PBMNCs). Nanometre-sized UHMWPE wear particles, nanometre-sized Ceridust 3615® and 20nm FluoSpheres had no significant effect on TNF-α, IL-1β, IL-6 and IL-8 release from PBMNCs at a concentration of 100μm(3) particles per cell after 12 and 24h. The micrometre-size UHMWPE wear particles (0.1-1.0μm) and 60nm, 200nm and 1.0μm FluoSpheres caused significantly elevated osteolytic cytokine release from PBMNCs. These results indicated that particles below circa 50nm fail to activate PBMNCs and that particle size, composition and morphology played a crucial role in cytokine release by particle stimulated macrophages. Copyright © 2015 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

The biological response to nanometre-sized polymer particles

PubMed Central

Liu, Aiqin; Richards, Laura; Bladen, Catherine L.; Ingham, Eileen; Fisher, John; Tipper, Joanne L.

2015-01-01

Recently, nanometre-sized UHMWPE particles generated from hip and knee replacements have been identified in vitro and in vivo. UHMWPE particles in the 0.1–1.0 μm size range have been shown to be more biologically active than larger particles, provoking an inflammatory response implicated in late aseptic loosening of total joint replacements. The biological activity of nanometre-sized particles has not previously been studied. The biological response to clinically-relevant UHMWPE wear particles including nanometre-sized and micrometre-sized, along with polystyrene particles (FluoSpheres 20 nm, 60 nm, 200 nm and 1.0 μm), and nanometre-sized model polyethylene particles (Ceridust 3615®), was determined in terms of osteolytic cytokine release from primary human peripheral blood mononuclear cells (PBMNCs). Nanometre-sized UHMWPE wear particles, nanometre-sized Ceridust 3615® and 20 nm FluoSpheres had no significant effect on TNF-α, IL-1β, IL-6 and IL-8 release from PBMNCs at a concentration of 100 μm3 particles per cell after 12 and 24 h. The micrometre-size UHMWPE wear particles (0.1–1.0 μm) and 60 nm, 200 nm and 1.0 μm FluoSpheres caused significantly elevated osteolytic cytokine release from PBMNCs. These results indicated that particles below circa 50 nm fail to activate PBMNCs and that particle size, composition and morphology played a crucial role in cytokine release by particle stimulated macrophages. PMID:26004221

Aerosolization properties, surface composition and physical state of spray-dried protein powders.

PubMed

Bosquillon, Cynthia; Rouxhet, Paul G; Ahimou, François; Simon, Denis; Culot, Christine; Préat, Véronique; Vanbever, Rita

2004-10-19

Powder aerosols made of albumin, dipalmitoylphosphatidylcholine (DPPC) and a protein stabilizer (lactose, trehalose or mannitol) were prepared by spray-drying and analyzed for aerodynamic behavior, surface composition and physical state. The powders exited a Spinhaler inhaler as particle aggregates, the size of which depending on composition, spray-drying parameters and airflow rate. However, due to low bulk powder tap density (<0.15 g/cm3), the aerodynamic size of a large fraction of aggregates remained respirable (<5 microm). Fine particle fractions ranged between 21% and 41% in an Andersen cascade impactor operated at 28.3 l/min, with mannitol and lactose providing the most cohesive and free-flowing powders, respectively. Particle surface analysis by X-ray photoelectron spectroscopy (XPS) revealed a surface enrichment with DPPC relative to albumin for powders prepared under certain spray-drying conditions. DPPC self-organized in a gel phase in the particle and no sugar or mannitol crystals were detected by X-ray diffraction. Water sorption isotherms showed that albumin protected lactose from moisture-induced crystallization. In conclusion, a proper combination of composition and spray-drying parameters allowed to obtain dry powders with elevated fine particle fractions (FPFs) and a physical environment favorable to protein stability.

The use of BMP-2 coupled – Nanosilver-PLGA composite grafts to induce bone repair in grossly infected segmental defects

PubMed Central

Zheng, Zhong; Yin, Wei; Zara, Janette N.; Li, Weiming; Kwak, Jinny; Mamidi, Rachna; Lee, Min; Siu, Ronald K.; Ngo, Richard; Wang, Joyce; Carpenter, Doug; Zhang, Xinli; Wu, Benjamin; Ting, Kang; Soo, Chia

2010-01-01

Healing of contaminated/infected bone defects is a significant clinical challenge. Prevalence of multi-antibiotic resistant organisms has renewed interest in the use of antiseptic silver as an effective, but less toxic antimicrobial with decreased potential for bacterial resistance. In this study, we demonstrated that metallic nanosilver particles (with a size of 20–40 nm)-poly(lactic-co-glycolic acid) (PLGA) composite grafts have strong antibacterial properties. In addition, nanosilver particles-PLGA composite grafts did not inhibit adherence, proliferation, alkaline phosphatase activity, or mineralization of ongrowth MC3T3-E1 pre-osteoblasts compared to PLGA controls. Furthermore, nanosilver particles did not affect the osteoinductivity of bone morphogenetic protein 2 (BMP-2). Infected femoral defects implanted with BMP-2 coupled 2.0% nanosilver particles-PLGA composite grafts healed in 12 weeks without evidence of residual bacteria. In contrast, BMP-2 coupled PLGA control grafts failed to heal in the presence of continued bacterial colonies. Our results indicate that nanosilver of defined particle size is bactericidal without discernable in vitro and in vivo cytotoxicity or negative effects on BMP-2 osteoinductivity, making it an ideal antimicrobial for bone regeneration in infected wounds. PMID:20864167

Mg-Doped Hydroxyapatite/Chitosan Composite Coated 316L Stainless Steel Implants for Biomedical Applications.

PubMed

Sutha, S; Dhineshbabu, N R; Prabhu, M; Rajendran, V

2015-06-01

In this investigation, ultrasonication process was used for the synthesis of magnesium doped nano-hydroxyapatite (MH) (0, 1, 2, and 3 mol% of Mg concentration) particles with controlled size and surface morphology. The size of the prepared MH particles was in the range of 20-100 nm with narrow distribution. Increase in the concentration of Mg reduced the particle size distribution from 60 to 40 nm. On incorporation of Mg in HAp lattice, an increase of 20-66 nm in specific surface area was observed in microporous HAp particles. XRF and XRD patterns reveal that the particles possess stoichiometric composition with reduced crystallinity with respect to the Mg concentration. Surface morphology of MH/chitosan (CTS) coated implant was found to be uniform without any defects. The corrosion rate of the implant decreased with increase in Mg concentration. The in vitro formation of bonelike apatite layer on the surface of the MH/CTS coated implant was observed from simulated body fluid studies. The antimicrobial activity of the MH/CTS composites against gram-positive and gram-negative bacterial strains indicated that increasing Mg concentration enhanced antimicrobial properties. Nanoindentation analysis of apatite coated implant surface reveals that the mechanical property depends on the concentration of magnesium in HAp. From the cytotoxicity analysis against NIH 3T3 fibroblast, it was observed that the Mg incorporated HAp/CTS composite was less toxic than the MHO/CTS composite. From this result, it was concluded that the MH/CTS nanocomposites coated implant is the excellent material for implants.

Understanding the uncertainty associated with particle-bound pollutant build-up and wash-off: A critical review.

PubMed

Wijesiri, Buddhi; Egodawatta, Prasanna; McGree, James; Goonetilleke, Ashantha

2016-09-15

Accurate prediction of stormwater quality is essential for developing effective pollution mitigation strategies. The use of models incorporating simplified mathematical replications of pollutant processes is the common practice for determining stormwater quality. However, an inherent process uncertainty arises due to the intrinsic variability associated with pollutant processes, which has neither been comprehensively understood, nor well accounted for in uncertainty assessment of stormwater quality modelling. This review provides the context for defining and quantifying the uncertainty associated with pollutant build-up and wash-off on urban impervious surfaces based on the hypothesis that particle size is predominant in influencing process variability. Critical analysis of published research literature brings scientific evidence together in order to establish the fact that particle size changes with time, and different sized particles exhibit distinct behaviour during build-up and wash-off, resulting in process variability. Analysis of the different adsorption behaviour of particles confirmed that the variations in pollutant load and composition are influenced by particle size. Particle behaviour and variations in pollutant load and composition are related due to the strong affinity of pollutants such as heavy metals and hydrocarbons for specific particle size ranges. As such, the temporal variation in particle size is identified as the key to establishing a basis for assessing build-up and wash-off process uncertainty. Therefore, accounting for pollutant build-up and wash-off process variability, which is influenced by particle size, would facilitate the assessment of the uncertainty associated with modelling outcomes. Furthermore, the review identified fundamental knowledge gaps where further research is needed in relation to: (1) the aggregation of particles suspended in the atmosphere during build-up; (2) particle re-suspension during wash-off; (3) pollutant re-adsorption by different particle size fractions; and (4) development of evidence-based techniques for assessing uncertainty; and (5) methods for translating the knowledge acquired from the investigation of process mechanisms at small scale into catchment scale for stormwater quality modelling. Copyright © 2016 Elsevier Ltd. All rights reserved.

Effect of in-situ formed Al3Ti particles on the microstructure and mechanical properties of 6061 Al alloy

NASA Astrophysics Data System (ADS)

Gupta, Rahul; Chaudhari, G. P.; Daniel, B. S. S.

2018-03-01

In this study, in situ Titanium-tri-aluminide (Al3Ti) particles reinforced Al 6061 alloy matrix composites were fabricated by the reaction of potassium hexafluorotitanate (K2TiF6) inorganic salt with molten Al 6061 alloy via liquid metallurgy route. The development of in-situ Al3Ti particles and their effects on the mechanical properties such as yield strength (YS), ductility, ultimate tensile strength (UTS) and hardness, and microstructure of Al 6061 alloy were studied. It was observed from the results that in-situ formed Al3Ti particles were blocky in morphology whose average size was around 2.6 ± 1.1 μm. Microstructure studies showed that grain size of Al matrix was reduced due to the nucleating effect of Al3Ti particles. It was observed from the mechanical properties analysis that when the volume fraction of Al3Ti particles was increased, the hardness, UTS and YS of the composites were also increased as compared to that of Al 6061 alloy. An improvement in ductility was observed with the dispersion of Al3Ti particles in base alloy which is contrary to many other composites.

Cold Spray Deposition of Ni and WC-Reinforced Ni Matrix Composite Coatings

NASA Astrophysics Data System (ADS)

Alidokht, S. A.; Vo, P.; Yue, S.; Chromik, R. R.

2017-12-01

Ni-WC composites are ideal protective coatings against wear and are often fabricated using laser cladding and thermal spray processes, but the high temperatures of these processes result in decarburization, which deteriorates the performance of the coating. Cold spray has the potential to deposit Ni-WC composite coatings and retain the composition of the initial WC feedstock. However, the insignificant plastic deformation of hard WC particles makes it difficult to build up a high WC content coating by cold spray. By using three different WC powder sizes, the effect of feedstock powder size on WC retention was tested. To improve WC retention, a WC/Ni composite powder in mixture with Ni was also sprayed. Microstructural characterization, including the deformed structure of Ni splats, retention, distribution, and fragmentation of WC, was performed by scanning electron microscopy. An improvement in WC retention was achieved using finer WC particles. Significant improvement in WC particles retention was achieved using WC/Ni composite powder, with the WC content in the coating being close to that of the feedstock.

Synthesis And Characterization Of Reduced Size Ferrite Reinforced Polymer Composites

DOE Office of Scientific and Technical Information (OSTI.GOV)

Borah, Subasit; Bhattacharyya, Nidhi S.

2008-04-24

Small sized Co{sub 1-x}Ni{sub x}Fe{sub 2}O{sub 4} ferrite particles are synthesized by chemical route. The precursor materials are annealed at 400, 600 and 800 C. The crystallographic structure and phases of the samples are characterized by X-ray diffraction (XRD). The annealed ferrite samples crystallized into cubic spinel structure. Transmission Electron Microscopy (TEM) micrographs show that the average particle size of the samples are <20 nm. Particulate magneto-polymer composite materials are fabricated by reinforcing low density polyethylene (LDPE) matrix with the ferrite samples. The B-H loop study conducted at 10 kHz on the toroid shaped composite samples shows reduction in magneticmore » losses with decrease in size of the filler sample. Magnetic losses are detrimental for applications of ferrite at high powers. The reduction in magnetic loss shows a possible application of Co-Ni ferrites at high microwave power levels.« less

The reaction probability of N2O5 with sulfuric acid aerosols at stratospheric temperatures and compositions

NASA Technical Reports Server (NTRS)

Fried, Alan; Henry, Bruce E.; Calvert, Jack G.; Mozurkewich, Michael

1994-01-01

We have measured the rate of reaction of N2O5 with H2O on monodisperse, submicrometer H2SO4 particles in a low-temperature flow reactor. Measurements were carried out at temperatures between 225 K and 293 K on aerosol particles with sizes and compositions comparable to those found in the stratosphere. At 273 K, the reaction probability was found to be 0.103 +/- 0.0006, independent of H2SO4 composition from 64 to 81 wt%. At 230 K, the reaction probability increased from 0.077 for compositions near 60% H2SO4 to 0.146 for compositions near 70% H2SO4. Intermediate conditions gave intermediate results except for low reaction probabilities of about 0.045 at 260 K on aerosols with about 78% H2SO4. The reaction probability did not depend on particle size. These results imply that the reaction occurs essentially at the surface of the particle. A simple model for this type of reaction that reproduces the general trends observed is presented. the presence of formaldehyde did not affect the reaction rate.

Impact resistant electrolytes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Veith, Gabriel M.; Armstrong, Beth L.; Tenhaeff, Wyatt E.

A passively impact resistant composite electrolyte composition includes an electrolyte solvent, up to 2M of an electrolyte salt, and shear thickening ceramic particles having a polydispersity index of no greater than 0.1, an average particle size of in a range of 50 nm to 1 .mu.m, and an absolute zeta potential of greater than .+-.40 mV.

Relaxation dynamics in a binary hard-ellipse liquid.

PubMed

Xu, Wen-Sheng; Sun, Zhao-Yan; An, Li-Jia

2015-01-21

Structural relaxation in binary hard spherical particles has been shown recently to exhibit a wealth of remarkable features when size disparity or mixture composition is varied. In this paper, we test whether or not similar dynamical phenomena occur in glassy systems composed of binary hard ellipses. We demonstrate via event-driven molecular dynamics simulation that a binary hard-ellipse mixture with an aspect ratio of two and moderate size disparity displays characteristic glassy dynamics upon increasing density in both the translational and the rotational degrees of freedom. The rotational glass transition density is found to be close to the translational one for the binary mixtures investigated. More importantly, we assess the influence of size disparity and mixture composition on the relaxation dynamics. We find that an increase of size disparity leads, both translationally and rotationally, to a speed up of the long-time dynamics in the supercooled regime so that both the translational and the rotational glass transition shift to higher densities. By increasing the number concentration of the small particles, the time evolution of both translational and rotational relaxation dynamics at high densities displays two qualitatively different scenarios, i.e., both the initial and the final part of the structural relaxation slow down for small size disparity, while the short-time dynamics still slows down but the final decay speeds up in the binary mixture with large size disparity. These findings are reminiscent of those observed in binary hard spherical particles. Therefore, our results suggest a universal mechanism for the influence of size disparity and mixture composition on the structural relaxation in both isotropic and anisotropic particle systems.

X-ray tomography studies on porosity and particle size distribution in cast in-situ Al-Cu-TiB{sub 2} semi-solid forged composites

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mathew, James; Mandal, Animesh

X-ray computed tomography (XCT) was used to characterise the internal microstructure and clustering behaviour of TiB{sub 2} particles in in-situ processed Al-Cu metal matrix composites prepared by casting method. Forging was used in semi-solid state to reduce the porosity and to uniformly disperse TiB{sub 2} particles in the composite. Quantification of porosity and clustering of TiB{sub 2} particles was evaluated for different forging reductions (30% and 50% reductions) and compared with an as-cast sample using XCT. Results show that the porosity content was decreased by about 40% due to semi-solid forging as compared to the as-cast condition. Further, XCT resultsmore » show that the 30% forging reduction resulted in greater uniformity in distribution of TiB{sub 2} particles within the composite compared to as-cast and the 50% forge reduction in semi-solid state. These results show that the application of forging in semi-solid state enhances particle distribution and reduces porosity formation in cast in-situ Al-Cu-TiB{sub 2} metal matrix composites. - Highlights: •XCT was used to visualise 3D internal structure of Al-Cu-TiB{sub 2} MMCs. •Al-Cu-TiB{sub 2} MMC was prepared by casting using flux assisted synthesis method. •TiB{sub 2} particles and porosity size distribution were evaluated. •Results show that forging in semi-solid condition decreases the porosity content and improve the particle dispersion in MMCs.« less

Frequency-scanning particle size spectrometer

NASA Technical Reports Server (NTRS)

Fymat, A. L. (Inventor)

1979-01-01

A particle size spectrometer having a fixed field of view within the forward light scattering cone at an angle theta sub s between approximately 100 and 200 minutes of arc (preferably at 150 minutes), a spectral range extending approximately from 0.2 to 4.0 inverse micrometers, and a spectral resolution between about 0.1 and 0.2 inverse micrometers (preferably toward the lower end of this range of spectral resolution), is employed to determine the distribution of particle sizes, independently of the chemical composition of the particles, from measurements of incident light, at each frequency, sigma (=1/lambda), and scattered light, I(sigma).

Structural Characterization of IgG1 mAb Aggregates and Particles Generated under Various Stress Conditions

PubMed Central

Telikepalli, Srivalli N.; Kumru, Ozan S.; Kalonia, Cavan; Esfandiary, Reza; Joshi, Sangeeta B.; Middaugh, C. Russell; Volkin, David B.

2014-01-01

IgG1 mAb solutions were prepared with and without sodium chloride and subjected to different environmental stresses. Formation of aggregates and particles of varying size was monitored by a combination of size exclusion chromatography (SEC), Nanosight Tracking Analysis (NTA), Micro-flow Imaging (MFI), turbidity, and visual assessments. Stirring and heating induced the highest concentration of particles. In general, the presence of NaCl enhanced this effect. The morphology of the particles formed from mAb samples exposed to different stresses was analyzed from TEM and MFI images. Shaking samples without NaCl generated the most fibrillar particles, while stirring created largely spherical particles. The composition of the particles was evaluated for covalent cross-linking by SDS-PAGE, overall secondary structure by FTIR microscopy, and surface apolarity by extrinsic fluorescence spectroscopy. Freeze-thaw and shaking led to particles containing protein with native-like secondary structure. Heating and stirring produced IgG1 containing aggregates and particles with some non-native disulfide crosslinks, varying levels of intermolecular beta sheet content, and increased surface hydrophobicity. These results highlight the importance of evaluating protein particle morphology and composition, in addition to particle number and size distributions, to better understand the effect of solution conditions and environmental stresses on the formation of protein particles in mAb solutions. PMID:24452866

Structural characterization of IgG1 mAb aggregates and particles generated under various stress conditions.

PubMed

Telikepalli, Srivalli N; Kumru, Ozan S; Kalonia, Cavan; Esfandiary, Reza; Joshi, Sangeeta B; Middaugh, C Russell; Volkin, David B

2014-03-01

IgG1 mAb solutions were prepared with and without sodium chloride and subjected to different environmental stresses. Formation of aggregates and particles of varying size was monitored by a combination of size-exclusion chromatography, Nanoparticle Tracking Analysis, Micro-flow Imaging (MFI), turbidity, and visual assessments. Stirring and heating induced the highest concentration of particles. In general, the presence of NaCl enhanced this effect. The morphology of the particles formed from mAb samples exposed to different stresses was analyzed from transmission electron microscopy and MFI images. Shaking samples without NaCl generated the most fibrillar particles, whereas stirring created largely spherical particles. The composition of the particles was evaluated for covalent cross-linking by SDS-PAGE, overall secondary structure by FTIR microscopy, and surface apolarity by extrinsic fluorescence spectroscopy. Freeze-thaw and shaking led to particles containing protein with native-like secondary structure. Heating and stirring produced IgG1-containing aggregates and particles with some non-native disulfide cross-links, varying levels of intermolecular beta sheet content, and increased surface hydrophobicity. These results highlight the importance of evaluating protein particle morphology and composition, in addition to particle number and size distributions, to better understand the effect of solution conditions and environmental stresses on the formation of protein particles in mAb solutions. © 2014 Wiley Periodicals, Inc. and the American Pharmacists Association.

Size-resolved chemical composition of aerosol emitted by Erebus volcano, Antarctica

NASA Astrophysics Data System (ADS)

Ilyinskaya, E.; Oppenheimer, C.; Mather, T. A.; Martin, R. S.; Kyle, P. R.

2010-03-01

Persistent, open-vent degassing of Erebus volcano, Antarctica, is a significant point source of gases and aerosol to the austral polar troposphere. We report here on the chemical composition and size distribution of the Erebus aerosol, focusing on the water-soluble fraction. The aerosol was sampled at the rim of the active crater using a cascade impactor, which collected and sized particles in 14 size bins from >10 to 0.01 μm. The soluble fraction of the Erebus aerosol is distinct from other volcanic sources in several respects. It is dominated by chloride-bearing particles (over 30% of total mass) and has an unusually high Cl-/SO42- molar ratio of 3.5. Coarse particles contribute little to the total mass of the soluble fraction. Elevated concentrations of F-, Cl-, Br-, and SO42- are found in a narrow particle size fraction of 0.1-0.25 μm. The detection of particulate Br- reinforces our understanding of the potential for quiescent volcanic emissions to deplete tropospheric ozone. The small aerosol size reflects the low atmospheric temperature and humidity, which inhibit particle growth. Halide-alkali metal salts (Na, K)(Cl, F) appear to be the most abundant species in the aerosol. The concentration of Pb is high compared to other volcanoes; its exsolution may be promoted by the high abundance of halogens in Erebus magma. Despite the previously reported high NOx content in the plume, we did not detect significant quantities of nitrate in the near-vent aerosol. Our findings emphasize the potential regional significance of emissions from Erebus for understanding the Antarctic atmospheric composition and glaciochemical records.

Solution-processed photodetectors from colloidal silicon nano/micro particle composite.

PubMed

Tu, Chang-Ching; Tang, Liang; Huang, Jiangdong; Voutsas, Apostolos; Lin, Lih Y

2010-10-11

We demonstrate solution-processed photodetectors composed of heavy-metal-free Si nano/micro particle composite. The colloidal Si particles are synthesized by electrochemical etching of Si wafers, followed by ultra-sonication to pulverize the porous surface. With alkyl ligand surface passivation through hydrosilylation reaction, the particles can form a stable colloidal suspension which exhibits bright photoluminescence under ultraviolet excitation and a broadband extinction spectrum due to enhanced scattering from the micro-size particles. The efficiency of the thin film photodetectors has been substantially improved by preventing oxidation of the particles during the etching process.

Characterizing and Understanding Aerosol Optical Properties: CARES - Final Report

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cappa, Christopher D; Atkinson, Dean B

The scientific focus of this study was to use ambient measurements to develop new insights into the understanding of the direct radiative forcing by atmospheric aerosol particles. The study used data collected by the PI’s and others as part of both the 2010 U.S. Department of Energy (DOE) sponsored Carbonaceous Aerosols and Radiative Effects Study (CARES), which took place in and around Sacramento, CA, and the 2012 Clean Air for London (ClearfLo) study. We focus on measurements that were made of aerosol particle optical properties, namely the wavelength-dependent light absorption, scattering and extinction. Interpretation of these optical property measurements ismore » facilitated through consideration of complementary measurements of the aerosol particle chemical composition and size distributions. With these measurements, we addressed the following general scientific questions: 1. How does light scattering and extinction by atmospheric aerosol particles depend on particle composition, water uptake, and size? 2. To what extent is light absorption by aerosol particles enhanced through the mixing of black carbon with other particulate components? 3. What relationships exist between intensive aerosol particle optical properties, and how do these depend on particle source and photochemical aging? 4. How well do spectral deconvolution methods, which are commonly used in remote sensing, retrieve information about particle size distributions?« less

Effect of Organic Coatings, Humidity and Aerosol Acidity on Multiphase Chemistry of Isoprene Epoxydiols

DOE Office of Scientific and Technical Information (OSTI.GOV)

Riva, Matthieu; Bell, David M.; Hansen, Anne-Maria Kaldal

2016-06-07

Multiphase chemistry of isomeric isoprene epoxydiols (IEPOX) has been shown to be the dominant source of isoprene-derived secondary organic aerosol (SOA). Recent studies have reported particles composed of ammonium bisulfate (ABS) mixed with model organics exhibit slower rates of IEPOX uptake. In the present study, we investigate the effect of atmospherically-relevant organic coatings of α-pinene (AP) SOA on the reactive uptake of trans-β-IEPOX onto ABS particles under different conditions and coating thicknesses. Single particle mass spectrometry was used to characterize in real-time particle size, shape, density, and quantitative composition before and after reaction with IEPOX. We find that IEPOX uptakemore » by pure sulfate particles is a volume-controlled process, which results in particles with uniform concentration of IEPOX-derived SOA across a wide range of sizes. Aerosol acidity was shown to enhance IEPOX-derived SOA formation, consistent with recent studies. The presence of water has a weaker impact on IEPOX-derived SOA yield, but significantly enhanced formation of 2-methyltetrols, consistent with offline filter analysis. In contrast, IEPOX uptake by ABS particles coated by AP-derived SOA is strongly dependent on particle size and composition. IEPOX uptake occurred only when weight fraction of AP-derived SOA dropped below 50 %, effectively limiting IEPOX uptake to larger particles.« less

Refining Mechanism of 7075 Al Alloy by In-Situ TiB₂ Particles.

PubMed

Gan, Guisheng; Yang, Bin; Zhang, Bo; Jiang, Xin; Shi, Yunlong; Wu, Yiping

2017-02-04

The nucleation undercooling of TiB₂/7075 Al matrix composites, the microstructure observed after solidification at different cooling rate, and the size and distribution of TiB₂ particles were investigated. The experimental results have shown that the grain sizes of TiB₂/7075 Al matrix composites firstly decreased, then increased, and finally decreased again with the increase of TiB₂ content. The nucleation undercooling of TiB₂/7075 Al matrix composites first increased, then decreased, and finally increased again with the increase of TiB₂ content when the cooling rates was 5 and 10 °C/min respectively, but kept decreasing with the increase of TiB₂ content at a cooling rate of 20 °C/min. The melting and solidification process showed no significant change with the decrease of cooling rate in 9.0% TiB₂/7075 Al matrix composites. Most small particles can act as heterogeneous nucleus, which induced grain growth and were captured into the grain by the solid/liquid interface. At the same time, most of the larger particles and a minority of the small TiB₂ particles are pushed into the grain boundary; locating in the grain boundary can hinder the Al atoms from diffusing during the solidification process and restrain α-Al phase growth. The influence of particles shifted from dominating by locating to dominating by nucleation as the quantity of TiB₂ particles increased.

Particulate matter analysis at elementary schools in Curitiba, Brazil.

PubMed

Avigo, Devanir; Godoi, Ana F L; Janissek, Paulo R; Makarovska, Yaroslava; Krata, Agnieszka; Potgieter-Vermaak, Sanja; Alfoldy, Balint; Van Grieken, René; Godoi, Ricardo H M

2008-06-01

The particulate matter indoors and outdoors of the classrooms at two schools in Curitiba, Brazil, was characterised in order to assess the indoor air quality. Information concerning the bulk composition was provided by energy-dispersive x-ray fluorescence (EDXRF). From the calculated indoor/outdoor ratios and the enrichment factors it was observed that S-, Cl- and Zn-rich particles are of concern in the indoor environment. In the present research, the chemical compositions of individual particles were quantitatively elucidated, including low-Z components like C, N and O, as well as higher-Z elements, using automated electron probe microanalysis low Z EPMA. Samples were further analysed for chemical and morphological aspects, determining the particle size distribution and classifying them according to elemental composition associations. Five classes were identified based on major elemental concentrations: aluminosilicate, soot, organic, calcium carbonate and iron-rich particles. The majority of the respirable particulate matter found inside of the classroom was composed of soot, biogenic and aluminosilicate particles. In view of the chemical composition and size distribution of the aerosol particles, local deposition efficiencies in the human respiratory system were calculated revealing the deposition of soot at alveolar level. The results showed that on average 42% of coarse particles are deposited at the extrathoracic level, whereas 24% are deposited at the pulmonary region. The fine fraction showed a deposition rate of approximately 18% for both deposition levels.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Apaydin, Ramazan Oguzhan; Ebin, Burcak; Gurmen, Sebahattin

Copper-Nickel (CuNi) nanostructured alloy particles were produced by Ultrasonic Spray Pyrolysis and Hydrogen Reduction Method (USP-HR) from high purity copper and nickel nitrate aqueous solutions. The effect of the precursor solution in the range of 0.1 and 0.5 mol/L on the morphology and crystallite size of CuNi nanoparticles were investigated under 2 h running time, 700 °C operating temperature and 0.5 L/min H{sub 2} flow rate. Particle size, morphology, composition and crystallite structure were characterized by Scanning Electron Microscopy (SEM), Energy Dispersive Spectroscopy (EDS) and X-Ray Diffraction (XRD). Particle characterization studies show that nanostructured alloy particles have cubic crystal structuremore » and they are in submicron size range with spherical morphology. The crystallite sizes of the particles calculated with Scherrer formula are 40 and 34 nm and average particles sizes observed from the SEM images are 300 and 510 nm for each experiment respectively.« less

Epoxy/Fluoroether Composites

NASA Technical Reports Server (NTRS)

Rosser, R. W.; Taylor, M. S.

1986-01-01

Composite materials made from unfilled and glass-fiber-reinforced epoxy toughened by copolymerization with elastomeric prepolymers of perfluoroalkyl ether diacyl fluoride (EDAF). Improved properties due to hydrogen bonding between rubber phase and epoxy matrix, plus formation of rubberlike phase domains that molecularly interpenetrate with epoxy matrix. With optimum rubber content, particle size, and particle shape, entire molecular structure reinforced and toughened. Improved composites also show increased failure strength, stiffness, glass-transition temperature, and resistance to water.

Multi-Ferroic Polymer Nanoparticle Composites for Next Generation Metamaterials

DTIC Science & Technology

2014-07-28

particle size of magnetite nanoparticles. The PI will continue to develop composites that could be utilized for developing high- bandwidth radio frequency...to improve the efficiency and decrease the size of the device. High performance stretchable magneto-dielectric materials can be accomplished using...nanoparticles oxidize at dimensions smaller than the critical size for superparamagnetic to ferromagnetic transition, which is essential for minimal

Preparation and characterization of aluminium-silica metal matrix composite

NASA Astrophysics Data System (ADS)

Mallikarjuna, G. B.; Basavaraj, E.

2018-04-01

Aluminum alloys are widely used in aerospace and automobile industries due to their low density and good mechanical properties, better corrosion resistance and wear, low thermal coefficient of expansion as compared to conventional metals and alloys. The excellent properties of these materials and relatively low production cost make them a very attractive for a variety of applications. In this present work, Al alloy LM13-SiO2 composites were produced by stir casting method. The reinforcement SiO2 particle size used for preparation of composites are 106 µm, 150 µm, 250 µm and 355 µm with varying amount of 3 to 12 wt% in steps of 3. The prepared composite specimens were machined as per test standards. Effects of weight percentage of SiO2 particles on wear, tensile strength of Al alloy LM13-SiO2 composites have been investigated. The microstructures of the composites were studied to know the dispersion of the SiO2 particles in matrix. Experimental results shows that there is enhanced mechanical properties, when silica weighing 9% was added to the base aluminium alloy and also similar trend exists in all four different micron size of silica and also it has been observed that addition of SiO2 particles significantly improves wear resistance properties as compared with that of unreinforced matrix.

In Situ Sampling of Relative Dust Devil Particle Loads and Their Vertical Grain Size Distributions.

PubMed

Raack, Jan; Reiss, Dennis; Balme, Matthew R; Taj-Eddine, Kamal; Ori, Gian Gabriele

2017-04-19

During a field campaign in the Sahara Desert in southern Morocco, spring 2012, we sampled the vertical grain size distribution of two active dust devils that exhibited different dimensions and intensities. With these in situ samples of grains in the vortices, it was possible to derive detailed vertical grain size distributions and measurements of the lifted relative particle load. Measurements of the two dust devils show that the majority of all lifted particles were only lifted within the first meter (∼46.5% and ∼61% of all particles; ∼76.5 wt % and ∼89 wt % of the relative particle load). Furthermore, ∼69% and ∼82% of all lifted sand grains occurred in the first meter of the dust devils, indicating the occurrence of "sand skirts." Both sampled dust devils were relatively small (∼15 m and ∼4-5 m in diameter) compared to dust devils in surrounding regions; nevertheless, measurements show that ∼58.5% to 73.5% of all lifted particles were small enough to go into suspension (<31 μm, depending on the used grain size classification). This relatively high amount represents only ∼0.05 to 0.15 wt % of the lifted particle load. Larger dust devils probably entrain larger amounts of fine-grained material into the atmosphere, which can have an influence on the climate. Furthermore, our results indicate that the composition of the surface, on which the dust devils evolved, also had an influence on the particle load composition of the dust devil vortices. The internal particle load structure of both sampled dust devils was comparable related to their vertical grain size distribution and relative particle load, although both dust devils differed in their dimensions and intensities. A general trend of decreasing grain sizes with height was also detected. Key Words: Mars-Dust devils-Planetary science-Desert soils-Atmosphere-Grain sizes. Astrobiology 17, xxx-xxx.

Laboratory Simulations of Haze Formation in the Atmospheres of Super-Earths and Mini-Neptunes: Particle Color and Size Distribution

NASA Astrophysics Data System (ADS)

He, Chao; Hörst, Sarah M.; Lewis, Nikole K.; Yu, Xinting; Moses, Julianne I.; Kempton, Eliza M.-R.; McGuiggan, Patricia; Morley, Caroline V.; Valenti, Jeff A.; Vuitton, Véronique

2018-03-01

Super-Earths and mini-Neptunes are the most abundant types of planets among the ∼3500 confirmed exoplanets, and are expected to exhibit a wide variety of atmospheric compositions. Recent transmission spectra of super-Earths and mini-Neptunes have demonstrated the possibility that exoplanets have haze/cloud layers at high altitudes in their atmospheres. However, the compositions, size distributions, and optical properties of these particles in exoplanet atmospheres are poorly understood. Here, we present the results of experimental laboratory investigations of photochemical haze formation within a range of planetary atmospheric conditions, as well as observations of the color and size of produced haze particles. We find that atmospheric temperature and metallicity strongly affect particle color and size, thus altering the particles’ optical properties (e.g., absorptivity, scattering, etc.); on a larger scale, this affects the atmospheric and surface temperature of the exoplanets, and their potential habitability. Our results provide constraints on haze formation and particle properties that can serve as critical inputs for exoplanet atmosphere modeling, and guide future observations of super-Earths and mini-Neptunes with the Transiting Exoplanet Survey Satellite, the James Webb Space Telescope, and the Wide-Field Infrared Survey Telescope.

A novel crystallization technique of hydroxyapatite utilizing contact reaction of minute droplet with atmospheric plasmas: Effects of the liquid source composition on the produced crystal properties

NASA Astrophysics Data System (ADS)

Wada, Y.; Kobayashi, T.; Matsumoto, M.; Onoe, K.

2017-10-01

To develop the technique for the control of the crystal composition and properties such as size distribution and morphology utilizing the contact reaction field around the minute droplets in atmospheric pressure plasma, fine spherical particles of hydroxyapatite ((Ca10(PO4)6(OH)2); HAp) were synthesized by a new plasma crystallization method. In this work, to elucidate the effects of the production region and crystal properties of hydroxyapatite for the liquid source composition, Ca2+ concentration and the Ca/P molar ratio in minute droplets were varied. The following results were obtained: (1) fine spherical HAp particles can be produced by the introduction of minute droplets with the initial Ca2+ concentration ((CCa)0) of 0.50 mol/l and the Ca/P molar ratio of 1.67. (2) When the (CCa)0 is set in the range higher than 1.00 mol/l at the constant Ca/P molar ratio of 1.67, fine spherical particles of β-TCP and HAp mixture are crystallized. (3) For the Ca/P molar ratio below 1.67, α-TCP and HAp co-precipitated. (4) The composition of the produced particles depends on both the reactant concentration and Ca/P molar ratio in the HAp source solution. (5) The dependence of the reactant concentration on the average size of the produced HAp particles is large compared with droplet size.

Cytotoxic effects of composite dust on human bronchial epithelial cells.

PubMed

Cokic, Stevan M; Hoet, Peter; Godderis, Lode; Wiemann, Martin; Asbach, Christof; Reichl, Franz X; De Munck, Jan; Van Meerbeek, Bart; Van Landuyt, Kirsten L

2016-12-01

Previous research revealed that during routine abrasive procedures like polishing, shaping or removing of composites, high amounts of respirable dust particles (<5μm) including nano-sized particles (<100nm) may be released. To determine the cytotoxic potential of composite dust particles on bronchial epithelium cells. Composite dust of five commercial composites (one nano-composite, two nano-hybrid and two hybrid composites) was generated following a clinically relevant protocol. Polymerized composite samples were cut with a rough diamond bur (grain size 100μm, speed 200,000rpm) and all composite dust was collected in a sterile chamber. Human bronchial epithelial cells (16HBE14o-) were exposed to serially diluted suspensions of composite dust in cell culture medium at concentrations between 1.1 and 3.3mg/ml. After 24h-exposure, cell viability and membrane integrity were assessed by the WST-1 and the LDH leakage assay, respectively. The release of IL-1β and IL-6 was evaluated. The composite dust particles were characterized by transmission electron microscopy and by dynamic and electrophoretic light scattering. Neither membrane damage nor release of IL-1β was detected over the complete concentration range. However, metabolic activity gradually declined for concentrations higher than 660μg/ml and the release of IL-6 was reduced when cells were exposed to the highest concentrations of dust. Composite dust prepared by conventional dental abrasion methods only affected human bronchial epithelial cells in very high concentrations. Copyright © 2016 The Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

Performance evaluation of bimodal thermite composites : nano- vs miron-scale particles

DOE Office of Scientific and Technical Information (OSTI.GOV)

Moore, K. M.; Pantoya, M.; Son, S. F.

2004-01-01

In recent years many studies of metastable interstitial composites (MIC) have shown vast combustion improvements over traditional thermite materials. The main difference between these two materials is the size of the fuel particles in the mixture. Decreasing the fuel size from the micron to nanometer range significantly increases the combustion wave speed and ignition sensitivity. Little is known, however, about the critical level of nano-sized fuel particles needed to enhance the performance of the traditional thermite. Ignition sensitivity experiments were performed using Al/MoO{sub 3} pellets at a theoretical maximum density of 50% (2 g/cm{sup 3}). The Al fuel particles weremore » prepared as bi-modal size distributions with micron (i.e., 4 and 20 {micro}m diameter) and nano-scale Al particles. The micron-scale Al was replaced in 10% increments by 80 nm Al particles until the fuel was 100% 80 nm Al. These bi-modal distributions allow the unique characteristics of nano-scale materials to be better understood. The pellets were ignited using a 50-W CO{sub 2} laser. High speed imaging diagnostics were used to measure ignition delay times, and micro-thermocouples were used to measure ignition temperatures. Combustion wave speeds were also examined.« less

Numerical Modeling of Electromagnetic Radiation Within a Particulate Medium.

NASA Astrophysics Data System (ADS)

Noe Dobrea, E. Z.

2017-12-01

Numerical modeling of electromagnetic radiation with a particulate medium. Understanding the effect of particulate media and coatings on electromagnetic radiation is key to understanding the effects of multiple scattering on the spectra of geologic materials. Multiple radiative transfer theories have been developed that provide a good approximation to these effects [1,2]. However, approximations regarding particle size, distribution, shape, and other parameters need to be made and in some cases, the theory is limited to specific geometries [2]. In this work, we seek to develop an numerical radiative transfer algorithm to simulate the passage of light through a particulate medium. The code allows arbitrary particle size distributions (uniform, bimodal, trimodal, composition dependent), compositions, and viewing geometries, as well as arbitrary coating thicknesses and compositions. Here, we report on the the status of our model and present comparisons of model predictions with the spectra of well-characterize minerals and mixtures. Future work will include particle size-dependent effects of diffraction as well as particle emittance due to fluorescence and Raman excitation. [1] Hapke, B. (2012). Theory of reflectance and emittance spectroscopy. Cambridge University Press, 2nd edition, 528 p. [2] Shkuratov et al. (1999) Icarus 137

A method for detecting the presence of organic fraction in nucleation mode sized particles

NASA Astrophysics Data System (ADS)

Vaattovaara, P.; Räsänen, M.; Kühn, T.; Joutsensaari, J.; Laaksonen, A.

2005-12-01

New particle formation and growth has a very important role in many climate processes. However, the overall knowlegde of the chemical composition of atmospheric nucleation mode (particle diameter, d<20 nm) and the lower end of Aitken mode particles (d≤50 nm) is still insufficient. In this work, we have applied the UFO-TDMA (ultrafine organic tandem differential mobility analyzer) method to shed light on the presence of an organic fraction in the nucleation mode size class in different atmospheric environments. The basic principle of the organic fraction detection is based on our laboratory UFO-TDMA measurements with organic and inorganic compounds. Our laboratory measurements indicate that the usefulness of the UFO-TDMA in the field experiments would arise especially from the fact that atmospherically the most relevant inorganic compounds do not grow in subsaturated ethanol vapor, when particle size is 10 nm in diameter and saturation ratio is about 86% or below it. Furthermore, internally mixed particles composed of ammonium bisulfate and sulfuric acid with sulfuric acid mass fraction ≤33% show no growth at 85% saturation ratio. In contrast, 10 nm particles composed of various oxidized organic compounds of atmospheric relevance are able to grow in those conditions. These discoveries indicate that it is possible to detect the presence of organics in atmospheric nucleation mode sized particles using the UFO-TDMA method. In the future, the UFO-TDMA is expected to be an important aid to describe the composition of atmospheric newly-formed particles.

A method for detecting the presence of organic fraction in nucleation mode sized particles

NASA Astrophysics Data System (ADS)

Vaattovaara, P.; Räsänen, M.; Kühn, T.; Joutsensaari, J.; Laaksonen, A.

2005-06-01

New particle formation and growth has a very important role in many climate processes. However, the overall knowlegde of the chemical composition of atmospheric nucleation mode (particle diameter, d<20 nm) and the lower end of Aitken mode particles (d≤50 nm) is still insufficient. In this work, we have applied the UFO-TDMA (ultrafine organic tandem differential mobility analyzer) method to shed light on the presence of organic fraction in the nucleation mode size class in different atmospheric environments. The basic principle of the organic fraction detection is based on our laboratory UFO-TDMA measurements with organic and inorganic compounds. Our laboratory measurements indicate that the usefulness of the UFO-TDMA in the field experiments would arise especially from the fact that atmospherically the most relevant inorganic compounds do not grow in subsaturated ethanol vapor, when particle size is 10nm in diameter and saturation ratio is about 86% or below it. Furthermore, internally mixed particles composed of ammonium bisulfate and sulfuric acid with sulfuric acid mass fraction ≤33% show no growth at 85% saturation ratio. In contrast, 10 nm particles composed of various organic compounds of atmospheric relevance are able to grow in those conditions. These discoveries indicate that it is possible to detect the presence of organics in atmospheric nucleation mode sized particles using the UFO-TDMA method. In the future, the UFO-TDMA is expected to be an important aid to describe the composition of atmospheric newly-formed particles.

Composition and Morphology of Major Particle Types from Airborne Measurements during ICE-T and PRADACS Field Studies

NASA Astrophysics Data System (ADS)

Venero, I. M.; Mayol-Bracero, O. L.; Anderson, J. R.

2012-12-01

As part of the Puerto Rican African Dust and Cloud Study (PRADACS) and the Ice in Clouds Experiment - Tropical (ICE-T), we sampled giant airborne particles to study their elemental composition, morphology, and size distributions. Samples were collected in July 2011 during field measurements performed by NCAR's C-130 aircraft based on St Croix, U.S Virgin Island. The results presented here correspond to the measurements done during research flight #8 (RF8). Aerosol particles with Dp > 1 um were sampled with the Giant Nuclei Impactor and particles with Dp < 1 um were collected with the Wyoming Inlet. Collected particles were later analyzed using an automated scanning electron microscope (SEM) and manual observation by field emission SEM. We identified the chemical composition and morphology of major particle types in filter samples collected at different altitudes (e.g., 300 ft, 1000 ft, and 4500ft). Results from the flight upwind of Puerto Rico show that particles in the giant nuclei size range are dominated by sea salt. Samples collected at altitudes 300 ft and 1000 ft showed the highest number of sea salt particles and the samples collected at higher altitudes (> 4000 ft) showed the highest concentrations of clay material. HYSPLIT back trajectories for all samples showed that the low altitude samples initiated in the free troposphere in the Atlantic Ocean, which may account for the high sea salt content and that the source of the high altitude samples was closer to the Saharan - Sahel desert region and, therefore, these samples possibly had the influence of African dust. Size distribution results for quartz and unreacted sea-salt aerosols collected on the Giant Nuclei Impactor showed that sample RF08 - 12:05 UTM (300 ft) had the largest size value (mean = 2.936 μm) than all the other samples. Additional information was also obtained from the Wyoming Inlet present at the C - 130 aircraft which showed that size distribution results for all particles were smaller in size. The different mineral components of the dust have different size distributions so that a fractionation process could occur during transport. Also, the presence of supermicron sea salt at altitude is important for cloud processes.

Neutron detector using lithiated glass-scintillating particle composite

DOEpatents

Wallace, Steven [Knoxville, TN; Stephan, Andrew C [Knoxville, TX; Dai, Sheng [Knoxville, TN; Im, Hee-Jung [Knoxville, TN

2009-09-01

A neutron detector composed of a matrix of scintillating particles imbedded in a lithiated glass is disclosed. The neutron detector detects the neutrons by absorbing the neutron in the lithium-6 isotope which has been enriched from the natural isotopic ratio to a commercial ninety five percent. The utility of the detector is optimized by suitably selecting scintillating particle sizes in the range of the alpha and the triton. Nominal particle sizes are in the range of five to twenty five microns depending upon the specific scintillating particle selected.

Effect of tungsten metal particle sizes on the solubility of molten alloy melt: Experimental observation of Gibbs-Thomson effect in nanocomposites

NASA Astrophysics Data System (ADS)

Lee, M. H.; Das, J.; Sordelet, D. J.; Eckert, J.; Hurd, A. J.

2012-09-01

We investigated the effect of tungsten particle sizes on the thermal stability and reactivity of uniformly dispersed W particles in molten Hf-based alloy melt at elevated temperature (1673 K). The solubility of particles less than 100 nm in radius is significantly enhanced. In case of fine W particles with 20 nm diameter, their solubility increases remarkably around 700% compared to that of coarse micrometer-scale particles. The mechanisms and kinetics of this dynamic growth of particle are discussed as well as techniques developed to obtain frozen microstructure of particle-reinforced composites by rapid solidification.

Fractography, fluidity, and tensile properties of aluminum/hematite particulate composites

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sharma, S.C.; Girish, B.M.; Kamath, R.

1999-06-01

This paper examines the effect of hematite (iron oxide) particles on the fluidity of the molten composite as well as the tensile properties and fracture behavior of the solidified as-cast aluminum composites. The percentage of hematite in the composite was varied from 1 to 7% in steps of 2% by weight. The vortex method was employed to prepare the composites. It followed from the results obtained that the ultimate tensile strength and Young`s modulus of the composite increased while the liquid fluidity and solid ductility decreased with the increase in hematite content in the composite specimens. The fluidity of themore » liquid was greater in a metal mold than in a sand mold, and it decreased with an increase in reinforcing particle size and increased with pouring temperature. The presence of the reinforcing particles altered the fracture behavior of the solid composites considerably. Final fracture of the composite occurred due to the propagation of cracks through the matrix between the reinforcing particles.« less

Influence of clay particles on microfluidic-based preparation of hydrogel composite microsphere

NASA Astrophysics Data System (ADS)

Hong, Joung Sook

2016-05-01

For the successful fabrication of a hydrogel composite microsphere, this study aimed to investigate the influence of clay particles on microsphere formation in a microfluidic device which has flow focusing and a 4.5:1 contraction channel. A poly alginic acid solution (2.0 wt.%) with clay particles was used as the dispersed phase to generate drops in an oil medium, which then merged with drops of a CaCl2 solution for gelation. Drop generations were observed with different flow rates and particles types. When the flow rate increased, drop generation was enhanced and drop size decreased by the build-up of more favorable hydrodynamic flow conditions to detach the droplets. The addition of a small amount of particles insignificantly changed the drop generation behavior even though it reduced interfacial tension and increased the viscosity of the solution. Instead, clays particles significantly affected hydro-gelation depending on the hydrophobicity of particles, which produced further heterogeneity in the shape and size of microsphere.

A Fatigue Model for Discontinuous Particulate-Reinforced Aluminum Alloy Composite: Influence of Microstructure

NASA Astrophysics Data System (ADS)

McCullough, R. R.; Jordon, J. B.; Brammer, A. T.; Manigandan, K.; Srivatsan, T. S.; Allison, P. G.; Rushing, T. W.

2014-01-01

In this paper, the use of a microstructure-sensitive fatigue model is put forth for the analysis of discontinuously reinforced aluminum alloy metal matrix composite. The fatigue model was used for a ceramic particle-reinforced aluminum alloy deformed under conditions of fully reversed strain control. Experimental results revealed the aluminum alloy to be strongly influenced by volume fraction of the particulate reinforcement phase under conditions of strain-controlled fatigue. The model safely characterizes the evolution of fatigue damage in this aluminum alloy composite into the distinct stages of crack initiation and crack growth culminating in failure. The model is able to capture the specific influence of particle volume fraction, particle size, and nearest neighbor distance in quantifying fatigue life. The model yields good results for correlation of the predicted results with the experimental test results on the fatigue behavior of the chosen aluminum alloy for two different percentages of the ceramic particle reinforcement. Further, the model illustrates that both particle size and volume fraction are key factors that govern fatigue lifetime. This conclusion is well supported by fractographic observations of the cyclically deformed and failed specimens.

Synthesis and characterization of metal-dielectric composites with copper nanoparticles embedded in a glass matrix: A multitechnique approach

NASA Astrophysics Data System (ADS)

Lipinska-Kalita, Kristina E.; Krol, Denise M.; Hemley, Russell J.; Mariotto, Gino; Kalita, Patricia E.; Ohki, Yoshimichi

2005-09-01

The precipitation and growth of copper nanoparticles in an optically transparent aluminosilicate glass matrix was investigated. The size of particles in this heterophase glass-based composite was modified in a controlled manner by isothermal heat treatments. A multitechnique approach, consisting of Raman scattering spectroscopy, high-resolution transmission electron microscopy, x-ray diffraction technique, and optical absorption spectroscopy, has been used to study the nucleation and crystallization processes. Optical absorption spectroscopy revealed the presence of intense absorption bands attributed to oscillations of free electrons, known as the surface-plasmon resonance band of copper particles, and confirmed a gradual increase of the particles' mean size and density with annealing time. The Raman scattering on acoustical phonons from Cu quantum dots in the glass matrix measured for off-resonance conditions demonstrated the presence of intense, inhomogeneously broadened peaks that have been assigned to the confined acoustic eigenmodes of copper nanoparticles. The particle-size dependence of the acoustic peak energies and the relation between the size distribution and bandwidths of these peaks were derived. High-resolution transmission electron microscopy was used to monitor the nucleation of the nanoparticles and to estimate their mean size.

Recycled wind turbine blades as a feedstock for second generation composites.

PubMed

Mamanpush, Seyed Hossein; Li, Hui; Englund, Karl; Tabatabaei, Azadeh Tavousi

2018-06-01

With an increase in renewable wind energy via turbines, an underlying problem of the turbine blade disposal is looming in many areas of the world. These wind turbine blades are predominately a mixture of glass fiber composites (GFCs) and wood and currently have not found an economically viable recycling pathway. This work investigates a series of second generation composites fabricated using recycled wind turbine material and a polyurethane adhesive. The recycled material was first comminuted via a hammer-mill through a range of varying screen sizes, resinated and compressed to a final thickness. The refined particle size, moisture content and resin content were assessed for their influence on the properties of recycled composites. Static bending, internal bond and water sorption properties were obtained for all composites panels. Overall improvement of mechanical properties correlated with increase in resin content, moisture content, and particle size. The current investigation demonstrates that it is feasible and promising to recycle the wind turbine blade to fabricate value-added high-performance composite. Copyright © 2018 Elsevier Ltd. All rights reserved.

Filler features and their effects on wear and degree of conversion of particulate dental resin composites.

PubMed

Turssi, C P; Ferracane, J L; Vogel, K

2005-08-01

Based on the incomplete understanding on how filler features influence the wear resistance and monomer conversion of resin composites, this study sought to evaluate whether materials containing different shapes and combinations of size of filler particles would perform similarly in terms of three-body abrasion and degree of conversion. Twelve experimental monomodal, bimodal or trimodal composites containing either spherical or irregular shaped fillers ranging from 100 to 1500 nm were examined. Wear testings were conducted in the OHSU wear machine (n = 6) and quantified after 10(5) cycles using a profilometer. Degree of conversion (DC) was measured by FTIR spectrometry at the surface of the composites (n = 6). Data sets were analyzed using one-way Anova and Tukey's test at a significance level of 0.05. Filler size and geometry was found to have a significant effect on wear resistance and DC of composites. At specific sizes and combinations, the presence of small filler particles, either spherical or irregular, may aid in enhancing the wear resistance of composites, without compromising the percentage of reacted carbon double bonds.

Measurement of Size-dependent Dynamic Shape Factors of Quartz Particles in Two Flow Regimes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Alexander, Jennifer M.; Bell, David M.; Imre, D.

2016-08-02

Understanding and modeling the behavior of quartz dust particles, commonly found in the atmosphere, requires knowledge of many relevant particles properties, including particle shape. This study uses a single particle mass spectrometer, a differential mobility analyzer, and an aerosol particle mass analyzer to measure quartz aerosol particles mobility, aerodynamic, and volume equivalent diameters, mass, composition, effective density, and dynamic shape factor as a function of particle size, in both the free molecular and transition flow regimes. The results clearly demonstrate that dynamic shape factors can vary significantly as a function of particle size. For the quartz samples studied here, themore » dynamic shape factors increase with size, indicating that larger particles are significantly more aspherical than smaller particles. In addition, dynamic shape factors measured in the free-molecular (χv) and transition (χt) flow regimes can be significantly different, and these differences vary with the size of the quartz particles. For quartz, χv of small (d < 200 nm) particles is 1.25, while χv of larger particles (d ~ 440 nm) is 1.6, with a continuously increasing trend with particle size. In contrast χt, of small particles starts at 1.1 increasing slowly to 1.34 for 550 nm diameter particles. The multidimensional particle characterization approach used here goes beyond determination of average properties for each size, to provide additional information about how the particle dynamic shape factor may vary even for particles with the same mass and volume equivalent diameter.« less

Physical characterization and in vitro biological impact of highly aggregated antibodies separated into size-enriched populations by fluorescence-activated cell sorting

PubMed Central

Telikepalli, Srivalli; Shinogle, Heather E.; Thapa, Prem S.; Kim, Jae Hyun; Deshpande, Meghana; Jawa, Vibha; Middaugh, C. Russell; Narhi, Linda O.; Joubert, Marisa K.; Volkin, David B.

2015-01-01

An IgG2 monoclonal antibody (mAb) solution was subjected to stirring, generating high concentrations of nanometer and subvisible particles, which were then successfully size enriched into different size bins by low speed centrifugation or a combination of gravitational sedimentation and Fluorescence-Activated Cell Sorting (FACS). The size-fractionated mAb particles were assessed for their ability to elicit the release of cytokines from a population of donor-derived human peripheral blood mononuclear cells (PBMC) at two phases of the immune response. Fractions enriched in nanometer-sized particles showed a lower response than those enriched in micron-sized particles in this assay. Particles of 5–10 μm in size displayed elevated cytokine release profiles compared to other size ranges. Stir-stressed mAb particles had amorphous morphology, contained protein with partially altered secondary structure, elevated surface hydrophobicity (compared to controls), and trace levels of elemental fluorine. FACS size-enriched the mAb particle samples, yet did not notably alter the overall morphology or composition of particles as measured by Microflow imaging, Transmission Electron Microscopy, and Scanning Electron Microscopy-Energy Dispersive X-ray Spectroscopy. The utility and limitations of FACS for size separation of mAb particles and potential of in-vitro PBMC studies to rank order the immunogenic potential of various types of mAb particles is discussed. PMID:25753756

Development of a size reduction equation for woody biomass: The influence of branch wood properties on Rittinger's constant

DOE PAGES

Naimi, Ladan J.; Sokhansanj, Shahabaddine; Bi, Xiaotao; ...

2015-11-25

Size reduction is an essential but energy-intensive process for preparing biomass for conversion processes. Three well-known scaling equations (Bond, Kick, and Rittinger) are used to estimate energy input for grinding minerals and food particles. Previous studies have shown that the Rittinger equation has the best fit to predict energy input for grinding cellulosic biomass. In the Rittinger equation, Rittinger's constant (k R) is independent of the size of ground particles, yet we noted large variations in k R among similar particle size ranges. In this research, the dependence of k R on the physical structure and chemical composition of amore » number of woody materials was explored. Branches from two softwood species (Douglas fir and pine) and two hardwood species (aspen and poplar) were ground in a laboratory knife mill. The recorded data included power input, mass flow rate, and particle size before and after grinding. Nine material properties were determined: particle density, solid density (pycnometer and x-ray diffraction methods), microfibril angle, fiber coarseness, fiber length, and composition (lignin and cellulose glucan contents). The correlation matrix among the nine properties revealed high degrees of interdependence between properties. The k R value had the largest positive correlation (+0.60) with particle porosity across the species tested. As a result, particle density was strongly correlated with lignin content (0.85), microfibril angle (0.71), fiber length (0.87), and fiber coarseness (0.78). An empirical model relating k R to particle density was developed.« less

Development of a size reduction equation for woody biomass: The influence of branch wood properties on Rittinger's constant

DOE Office of Scientific and Technical Information (OSTI.GOV)

Naimi, Ladan J.; Sokhansanj, Shahabaddine; Bi, Xiaotao

Size reduction is an essential but energy-intensive process for preparing biomass for conversion processes. Three well-known scaling equations (Bond, Kick, and Rittinger) are used to estimate energy input for grinding minerals and food particles. Previous studies have shown that the Rittinger equation has the best fit to predict energy input for grinding cellulosic biomass. In the Rittinger equation, Rittinger's constant (k R) is independent of the size of ground particles, yet we noted large variations in k R among similar particle size ranges. In this research, the dependence of k R on the physical structure and chemical composition of amore » number of woody materials was explored. Branches from two softwood species (Douglas fir and pine) and two hardwood species (aspen and poplar) were ground in a laboratory knife mill. The recorded data included power input, mass flow rate, and particle size before and after grinding. Nine material properties were determined: particle density, solid density (pycnometer and x-ray diffraction methods), microfibril angle, fiber coarseness, fiber length, and composition (lignin and cellulose glucan contents). The correlation matrix among the nine properties revealed high degrees of interdependence between properties. The k R value had the largest positive correlation (+0.60) with particle porosity across the species tested. As a result, particle density was strongly correlated with lignin content (0.85), microfibril angle (0.71), fiber length (0.87), and fiber coarseness (0.78). An empirical model relating k R to particle density was developed.« less

Effects of varying particle size of forage on digestion and chewing behavior of dairy heifers.

PubMed

Jaster, E H; Murphy, M R

1983-04-01

Eighteen Holstein heifers were fed long and chopped coarse and fine alfalfa hay ad libitum to evaluate effects of physical form on digestion and chemical composition of feed and fecal particles and to examine the applicability of a sinusoidal model to chewing behavior. Recordings of jaw movement were divided into 1-h segments for analysis. Least square mean size of fecal particles from coarse and finely chopped diets were 290 and 297 micrometers as compared to 227 micrometers on long hay. Intakes of dry matter were greater an digestibilities lower for chopped as compared to long hay. Crude protein content of separated feed and fecal particles increased as particle size decreased. Neural and acid detergent fiber concentrations decreased in feed and feces with decreasing particle size. Lignin content of feed particles decreased as particle size decreased, whereas for fecal particles lignin as a percent of cell wall followed a "U" shaped pattern of declining then increasing as size decreased. Patterns were sinusoidal for eating and ruminating long and chopped hays and total chewing (eating and ruminating) of long hay. Our results suggest a gradual effect on chemical degradation and physical detrition of digesta particles and chewing behavior as forage particle size decreased.

Aerosol detection efficiency in inductively coupled plasma mass spectrometry

DOE PAGES

Hubbard, Joshua A.; Zigmond, Joseph A.

2016-03-02

We used an electrostatic size classification technique to segregate particles of known composition prior to being injected into an inductively coupled plasma mass spectrometer (ICP-MS). Moreover, we counted size-segregated particles with a condensation nuclei counter as well as sampled with an ICP-MS. By injecting particles of known size, composition, and aerosol concentration into the ICP-MS, efficiencies of the order of magnitude aerosol detection were calculated, and the particle size dependencies for volatile and refractory species were quantified. Similar to laser ablation ICP-MS, aerosol detection efficiency was defined as the rate at which atoms were detected in the ICP-MS normalized bymore » the rate at which atoms were injected in the form of particles. This method adds valuable insight into the development of technologies like laser ablation ICP-MS where aerosol particles (of relatively unknown size and gas concentration) are generated during ablation and then transported into the plasma of an ICP-MS. In this study, we characterized aerosol detection efficiencies of volatile species gold and silver along with refractory species aluminum oxide, cerium oxide, and yttrium oxide. Aerosols were generated with electrical mobility diameters ranging from 100 to 1000 nm. In general, it was observed that refractory species had lower aerosol detection efficiencies than volatile species, and there were strong dependencies on particle size and plasma torch residence time. Volatile species showed a distinct transition point at which aerosol detection efficiency began decreasing with increasing particle size. This critical diameter indicated the largest particle size for which complete particle detection should be expected and agreed with theories published in other works. Aerosol detection efficiencies also displayed power law dependencies on particle size. Aerosol detection efficiencies ranged from 10 -5 to 10 -11. Free molecular heat and mass transfer theory was applied, but evaporative phenomena were not sufficient to explain the dependence of aerosol detection on particle diameter. Additional work is needed to correlate experimental data with theory for metal-oxides where thermodynamic property data are sparse relative to pure elements. Finally, when matrix effects and the diffusion of ions inside the plasma were considered, mass loading was concluded to have had an effect on the dependence of detection efficiency on particle diameter.« less

Aerosol size and chemical composition measurements at the Polar Environment Atmospheric Research Lab (PEARL) in Eureka, Nunavut

NASA Astrophysics Data System (ADS)

Hayes, P. L.; Tremblay, S.; Chang, R. Y. W.; Leaitch, R.; Kolonjari, F.; O'Neill, N. T.; Chaubey, J. P.; AboEl Fetouh, Y.; Fogal, P.; Drummond, J. R.

2016-12-01

This study presents observations of aerosol chemical composition and particle number size distribution at the Polar Environment Atmospheric Research Laboratory (PEARL) in the Canadian High Arctic (80N, 86W). The current aerosol measurement program at PEARL has been ongoing for more than a year providing long-term observations of Arctic aerosol size distributions for both coarse and fine modes. Particle nucleation events were frequently observed during the summers of 2015 and 2016. The size distribution data are also compared against similar measurements taken at the Alert Global Atmospheric Watch Observatory (82N, 62W) for July and August 2015. The nucleation events are correlated at the two sites, despite a distance of approximately 500 km, suggesting regional conditions favorable for particle nucleation and growth during this period. Size resolved chemical composition measurements were also carried out using an aerosol mass spectrometer. The smallest measured particles between 40 and 60 nm are almost entirely organic aerosol (OA) indicating that the condensation of organic vapors is responsible for particle growth events and possibly particle nucleation. This conclusion is further supported by the relatively high oxygen content of the OA, which is consistent with secondary formation of OA via atmospheric oxidation.Lastly, surface measurements of the aerosol scattering coefficient are compared against the coefficient values calculated using Mie theory and the measured aerosol size distribution. Both the actual and the calculated scattering coefficients are then compared to sun photometer measurements to understand the relationship between surface and columnar aerosol optical properties. The measurements at PEARL provide a unique combination of surface and columnar data sets on aerosols in the High Arctic, a region where such measurements are scarce despite the important impact of aerosols on Arctic climate.PEARL research is supported by the Natural Sciences and Engineering Research Council (NSERC) of Canada, the Canadian Space Agency (CSA), and Environment and Climate Change Canada (ECCC). In addition, the Alert GAW Observatory is supported by ECCC.

Structure, phases, and mechanical response of Ti-alloy bioactive glass composite coatings.

PubMed

Nelson, G M; Nychka, J A; McDonald, A G

2014-03-01

Porous titanium alloy-bioactive glass composite coatings were manufactured via the flame spray deposition process. The porous coatings, targeted for orthodontic and bone-fixation applications, were made from bioactive glass (45S5) powder blended with either commercially pure titanium (Cp-Ti) or Ti-6Al-4V alloy powder. Two sets of spray conditions, two metallic particle size distributions, and two glass particle size distributions were used for this study. Negative control coatings consisting of pure Ti-6Al-4V alloy or Cp-Ti were sprayed under both conditions. The as-sprayed coatings were characterized through quantitative optical cross-sectional metallography, X-ray diffraction (XRD), and ASTM Standard C633 tensile adhesion testing. Determination of the porosity and glassy phase distribution was achieved by using image analysis in accordance with ASTM Standard E2109. Theoretical thermodynamic and heat transfer modeling was conducted to explain experimental observations. Thermodynamic modeling was performed to estimate the flame temperature and chemical environment for each spray condition and a lumped capacitance heat transfer model was developed to estimate the temperatures attained by each particle. These models were used to establish trends among the choice of alloy, spray condition, and particle size distribution. The deposition parameters, alloy composition, and alteration of the feedstock powder size distribution had a significant effect on the coating microstructure, porosity, phases present, mechanical response, and theoretical particle temperatures that were attained. The most promising coatings were the Ti-6Al-4V-based composite coatings, which had bond strength of 20±2MPa (n=5) and received reinforcement and strengthening from the inclusion of a glassy phase. It was shown that the use of the Ti-6Al-4V-bioactive glass composite coatings may be a superior choice due to the possible osteoproductivity from the bioactive glass, the potential ability to support tissue ingrowth and vascular tissue, and the comparable strength to similar coatings. Copyright © 2013 Elsevier B.V. All rights reserved.

Geostatistical Interpolation of Particle-Size Curves in Heterogeneous Aquifers

NASA Astrophysics Data System (ADS)

Guadagnini, A.; Menafoglio, A.; Secchi, P.

2013-12-01

We address the problem of predicting the spatial field of particle-size curves (PSCs) from measurements associated with soil samples collected at a discrete set of locations within an aquifer system. Proper estimates of the full PSC are relevant to applications related to groundwater hydrology, soil science and geochemistry and aimed at modeling physical and chemical processes occurring in heterogeneous earth systems. Hence, we focus on providing kriging estimates of the entire PSC at unsampled locations. To this end, we treat particle-size curves as cumulative distribution functions, model their densities as functional compositional data and analyze them by embedding these into the Hilbert space of compositional functions endowed with the Aitchison geometry. On this basis, we develop a new geostatistical methodology for the analysis of spatially dependent functional compositional data. Our functional compositional kriging (FCK) approach allows providing predictions at unsampled location of the entire particle-size curve, together with a quantification of the associated uncertainty, by fully exploiting both the functional form of the data and their compositional nature. This is a key advantage of our approach with respect to traditional methodologies, which treat only a set of selected features (e.g., quantiles) of PSCs. Embedding the full PSC into a geostatistical analysis enables one to provide a complete characterization of the spatial distribution of lithotypes in a reservoir, eventually leading to improved predictions of soil hydraulic attributes through pedotransfer functions as well as of soil geochemical parameters which are relevant in sorption/desorption and cation exchange processes. We test our new method on PSCs sampled along a borehole located within an alluvial aquifer near the city of Tuebingen, Germany. The quality of FCK predictions is assessed through leave-one-out cross-validation. A comparison between hydraulic conductivity estimates obtained via FCK approach and those predicted by classical kriging of effective particle diameters (i.e., quantiles of the PSCs) is finally performed.

One-step preparing magnesium hydroxide particles from mother liquor of salt production

NASA Astrophysics Data System (ADS)

Guo, H.; Peng, C. S.; Ding, Z. W.; Yuan, H. T.; Yang, K.

2018-01-01

In this study, MH particles were prepared from mother liquor of salt production in one-step through employing ammonia gas as precipitant and stearic acid as dispersant respectively. Since adopting microporous plate to bubble ammonia gas, the percent conversion of magnesium was boosted obviously. The influence of operating condition of reacting temperature, stirring rate, ammonia flowrate and pore size of plate to magnesium percent conversion were investigated, the maximum is 88.1 % at optimum condition according to experimental results. The MH particle preparing from mother liquor in optimum condition was characterized by XRD, the result indicated the volume of brucite was reach to 99.7% within the composition of the product. In addition, the size distribution and crystal morphology was also detected, the median particle diameter d50 is 883 nm and possessing good dispersibility. From the thermogravimetric analysis of MH particles, the thermostability of product is suitable as flame-retardant composite materials.

Particle size, size distribution and morphological evaluation of glass fiber reinforced plastic (GRP) industrial by-product.

PubMed

Mazzoli, Alida; Moriconi, Giacomo

2014-12-01

The waste management of glass fiber reinforced polymer (GRP) materials, in particular those made with thermosetting resins, is a critical issue for the composites industry because these materials cannot be reprocessed. Therefore, most thermosetting GRP waste is presently sent to landfill, in spite of the significant environmental impact caused by their disposal in this way. The limited GRP waste recycling worldwide is mostly due to its intrinsic thermosetting properties, lack of characterization data and unavailability of viable recycling and recovery routes. One of the possibility for re-using GRP industrial by-product is in form of powder as a partial aggregate replacement or filler addition in cement based composites for applications in sustainable construction materials and technologies. However, the feasibility of this kind of reutilization strongly depends on the morphology and particle size distribution of a powder made up of polymer granules and glass fibers. In the present study, the use of image analysis method, based on scanning electron microscopy (SEM) and ImageJ processing program, is proposed in order to evaluate the morphology of the particles and measure the particle size and size distribution of fine GRP waste powder. The obtained results show a great potential of such a method in order to be considered as a standardized method of measurement and analysis in order to characterize the grain size and size distribution of GRP particles before exploiting any compatibility issue for its recycling management. Copyright © 2014 Elsevier Ltd. All rights reserved.

Magnetostrictive and mechanical properties of Terfenol-D composites based on polymer

NASA Astrophysics Data System (ADS)

Rodríguez, C.; Cuevas, J. M.; Orue, I.; Vilas, J. L.; Barandiarán, J. M.; Fernandez-Gubieda, M. L.; Leon, L. M.

2007-07-01

Several composites, with outstanding magnetostrictive properties, have been synthesized combining a polyurethane base elastomer, with polycrystalline powders of Terfenol-D with a preferential orientation obtained by curing the material in a magnetic field. The morphology of the polymer matrix can be modified by changing the ratio of the hard /soft segment (F) of the polyurethane from 0.6 to 1.5. The influence of the morphology in the magnetostrictive response, for different composites, has been studied by following the storage modulus, E', in DMTA analysis. The magnetostrictive response has been studied as a function of Terfenol-D particle size and distribution (0-300, 212-300, 106-212, 0-38 μm), as well as a function of the content of the magnetostrictive particles in the composite. The highest response (about 1390 ppm) was obtained for a F=1.5 polyurethane and 50% wt of Terfenol-D of 212-300 μm particle size, oriented with a magnetic field of 0.5 T.

Negative Thermal Expansion and Ferroelectric Oxides in Electronic Device Composites

NASA Astrophysics Data System (ADS)

Trujillo, Joy Elizabeth

Electronic devices increasingly pervade our daily lives, driving the need to develop components which have material properties that can be designed to target a specific need. The principle motive of this thesis is to investigate the effects of particle size and composition on three oxides which possess electronic and thermal properties essential to designing improved ceramic composites for more efficient, high energy storage devices. A metal matrix composite project used the negative thermal expansion oxide, ZrW2O 8, to offset the high thermal expansion of the metal matrix without sacrificing high thermal conductivity. Composite preparation employed a powder mixing technique to achieve easy composition control and homogenous phase distribution in order to build composites which target a specific coefficient of thermal expansion (CTE). A tailorable CTE material is desirable for overcoming thermomechanical failure in heat sinks or device casings. This thesis also considers the particle size effect on dielectric properties in a common ferroelectric perovskite, Ba1-xSrxTiO 3. By varying the Ba:Sr ratio, the Curie temperature can be adjusted and by reducing the particle size, the dielectric constant can be increased and hysteresis decreased. These conditions could yield anonymously large dielectric constants near room temperature. However, the ferroelectric behavior has been observed to cease below a minimum size of a few tens of nanometers in bulk or thin film materials. Using a new particle slurry approach, electrochemical impedance spectroscopy allows dielectric properties to be determined for nanoparticles, as opposed to conventional methods which measure only bulk or thin film dielectric properties. In this manner, Ba1-xSrxTiO3 was investigated in a new size regime, extending the theory on the ferroelectric behavior to < 10 nm diameter. This knowledge will improve the potential to incorporate high dielectric constant, low loss ferroelectric nanoparticles in many complex composites. Finally, powder composite processing and impedance spectroscopy techniques were combined to investigate the SrTiO3/(Y2O3) x(ZrO2)1-x (STO/YSZ) oxide system. Thin film heterostructures of STO/YSZ are used in electrochemical energy devices due to their enhanced interfacial ionic conductivity. This work investigated whether this ionic conductivity enhancement could be observed in bulk sintered architectures, which may lead to new device designs for energy storage needs.

The structure and mechanical properties of parts elaborated by direct laser deposition 316L stainless steel powder obtained in various ways

NASA Astrophysics Data System (ADS)

Loginova, I. S.; Solonin, A. N.; Prosviryakov, A. S.; Adisa, S. B.; Khalil, A. M.; Bykovskiy, D. P.; Petrovskiy, V. N.

2017-12-01

In this work the morphology, the size and the chemical composition of the powders of steel 316L received by the two methods was studied: fusion dispersion by a gas stream and reduction of metal chlorides with the subsequent plasma atomization of the received powder particles. The powder particles received by the first method have a spherical shape (aspect ratio 1,0-1,2) with an average size of 77 μm and are characterized by the absence of internal porosity. Particles of the powder received by the second method also have a spherical shape and faultless structure, however, their chemical composition may vary in different particles. The average size of particles is 32 μm. Though the obtained powders had different properties, the experimental samples received by DLD technology demonstrated by equally high durability (Ultimate strength is 623±5 and of 623±18 MPa respectively) and plasticity (38 and 41% respectively). It is established that mechanical properties of DLD samples increase for 7-10% after treatment of the surface.

Interplanetary dust. [survey of last four years' research

NASA Technical Reports Server (NTRS)

Brownlee, D. E.

1979-01-01

Progress in the study of interplanetary dust during the past four years is reviewed. Attention is given to determinations of the relative contributions of interstellar dust grains, collisional debris from the asteroid belt and short-period comets to the interplanetary dust cloud. Effects of radiation pressure and collisions on particle dynamics are discussed, noting the discovery of the variation of the orbital parameters of dust particles at 1 AU with size and in situ measurements of dust density between 0.3 and 5 AU by the Helios and Pioneer spacecraft. The interpretation of the zodiacal light as produced by porous absorbing particles 10 to 100 microns in size is noted, and measurements of the Doppler shift, light-producing-particle density, UV spectrum, photometric axis and angular scattering function of the zodiacal light are reported. Results of analyses of lunar rock microcraters as to micrometeoroid density, flux rate, size distribution and composition are indicated and interplanetary dust particles collected from the stratosphere are discussed. Findings concerning the composition of fragile meteoroid types found as cosmic spherules in deep sea sediments are also presented.

Experimental investigation of amount of nano-Al2O3 on mechanical properties of Al-based nano-composites fabricated by powder metallurgy (PM)

NASA Astrophysics Data System (ADS)

Razzaqi, A.; Liaghat, Gh.; Razmkhah, O.

2017-10-01

In this paper, mechanical properties of Aluminum (Al) matrix nano-composites, fabricated by Powder Metallurgy (PM) method, has been investigated. Alumina (Al2O3) nano particles were added in amounts of 0, 2.5, 5, 7.5 and 10 weight percentages (wt%). For this purpose, Al powder (particle size: 20 µm) and nano-Al2O3 (particle size: 20 nm) in various weight percentages were mixed and milled in a blade mixer for 15 minutes in 1500 rpm. Then, the obtained mixture, compacted by means of a two piece die and uniaxial cold press of about 600 MPa and cold iso-static press (CIP), required for different tests. After that, the samples sintered in 600°C for 90 minutes. Compression and three-point bending tests performed on samples and the results, led us to obtain the optimized particle size for achieving best mechanical properties.

Chapter One: Exposure Measurements.

EPA Science Inventory

Determining human exposure to suspended particualte concentrations requires measurements that quantify different particle properties in microenvironments where people live, work, and play. Particle mass, size, and chemical composition are important exposure variables, and these ...

CHAPTER ONE: EXPOSURE MEASUREMENTS.

EPA Science Inventory

Determining human exposure to suspended particualte concentrations requires measurements that quantify different particle properties in microenvironments where people live, work, and play. Particle mass, size, and chemical composition are important exposure variables, and these ...

Effect of SiC particle size on the microstructure and properties of cold-sprayed Al/SiCp composite coating

NASA Astrophysics Data System (ADS)

Yu, Min; Hua, Junwei

2017-07-01

The Al5056/SiC composite coatings were prepared by cold spraying. Experimental results show that the SiC content in the composite coating deposited with the SiC powder having an average size of 67 μm (Al5056/SiC-67) is similar to that deposited with the SiC powder having an average size of 27 μm (Al5056/SiC-27). The microhardness and cohesion strength of Al5056/SiC-67 coating are higher than those of the Al5056/SiC-27 coating. In addition, the Al5056/SiC-67 coating having a superior wear resistance because of the coarse SiC powder with a superior kinetic energy contributes to the deformation resistance of the matrix Al5056 particles.

Magnetic quenching of photonic activity in Fe3O4-elastomer composite

NASA Astrophysics Data System (ADS)

Ma, Danhao; Hess, Dustin T.; Shetty, Pralav P.; Adu, Kofi W.; Bell, Richard C.; Terrones, Mauricio

2016-01-01

We report a quenching phenomenon within the visible region of the electromagnetic spectrum in the photonic response of a passive Fe3O4-silicone elastomer composite film due to magnetically aligned Fe3O4 nanoparticles. We performed systematic studies of the polarization dependence, the effect of particle size, and an in- and out-of-plane particle alignment on the optical response of the Fe3O4-silicone elastomer composites using a UV/vis/NIR spectrometer. We observed systematic redshifts in the response of the out-of-plane composite films with increasing particle alignment and weight that are attributed to dipole-induced effects. There were no observable shifts in the spectra of the in-plane films, suggesting the orientation of the magnetic dipole and the induced electric dipole play a crucial role in the optical response. A dramatic suppression to near quenching of the photonic response occurred in films containing moderate concentrations of the aligned nanoparticles. This is attributed to the interplay between the intra- and the interparticle dipoles. This occurred even when low magnetic fields were used during the curing process, suggesting that particle alignment and particle size limitation are critical in the manipulation of the photonic properties. A dipole approximation model is used to explain the quenching phenomenon. An active system of such a composite has a potential application in magneto-optic switches.

Magnetic self-assembly for the synthesis of magnetically exchange coupled MnBi/Fe–Co composites

DOE Office of Scientific and Technical Information (OSTI.GOV)

Xu, Xia; Hong, Yang-Ki, E-mail: ykhong@eng.ua.edu; Park, Jihoon

2015-11-15

Exchange coupled hard/soft MnBi/Fe–Co core/shell structured composites were synthesized using a magnetic self-assembly process. MnBi particles were prepared by arc-melting, and Fe–Co nanoparticles were synthesized by an oleic acid assisted chemical reduction method. Grinding a mixture of micron-sized MnBi and Fe–Co nanoparticles in hexane resulted in MnBi/Fe–Co core/shell structured composites. The MnBi/Fe–Co (95/5 wt%) composites showed smooth magnetic hysteresis loops, enhanced remanent magnetization, and positive values in the ΔM curve, indicating exchange coupling between MnBi and Fe–Co particles. - Graphical abstract: Both MnBi and Fe–Co particles were dispersed in hexane for grinding. Because of the oleic acid used during themore » Fe–Co nanoparticle synthesis, they could be well dispersed in hexane. During the grinding, the size of MnBi particles was decreased, hexane was evaporated, and the Fe–Co nanoparticles were concentrated in the solvent and magnetically attracted by MnBi particles, forming a core/shell structure. - Highlights: • Exchange coupled MnBi/Fe–Co composites are synthesized through magnetic selfassembly. • Magnetic exchange coupling is demonstrated by smooth magnetic hysteresis loops, enhanced remanent magnetization, and dominant positive peak in the ΔM curve. • The experimental results in magnetic properties are close to the theoretical calculation results.« less

Fog scavenging of organic and inorganic aerosol in the Po Valley

NASA Astrophysics Data System (ADS)

Gilardoni, S.; Massoli, P.; Giulianelli, L.; Rinaldi, M.; Paglione, M.; Pollini, F.; Lanconelli, C.; Poluzzi, V.; Carbone, S.; Hillamo, R.; Russell, L. M.; Facchini, M. C.; Fuzzi, S.

2014-07-01

The interaction of aerosol with atmospheric water affects the processing and wet removal of atmospheric particles. Understanding such interaction is mandatory to improve model description of aerosol lifetime and ageing. We analyzed the aerosol-water interaction at high relative humidity during fog events in the Po Valley within the framework of the Agenzia Regionale per la Prevenzione e l'Ambiente (ARPA) - Emilia Romagna supersite project. For the first time in this area, the changes in particle chemical composition caused by fog are discussed along with changes in particle microphysics. During the experiment, 14 fog events were observed. The average mass scavenging efficiency was 70% for nitrate, 68% for ammonium, 61% for sulfate, 50% for organics, and 39% for black carbon. After fog formation, the interstitial aerosol was dominated by particles smaller than 200 nm Dva (vacuum aerodynamic diameter) and enriched in carbonaceous aerosol, mainly black carbon and water-insoluble organic aerosol. For each fog event, the size-segregated scavenging efficiency of nitrate and organic aerosol (OA) was calculated by comparing chemical species size distribution before and after fog formation. For both nitrate and OA, the size-segregated scavenging efficiency followed a sigmoidal curve, with values close to zero below 100 nm Dva and close to 1 above 700 nm Dva. OA was able to affect scavenging efficiency of nitrate in particles smaller than 300 nm Dva. A linear correlation between nitrate scavenging and particle hygroscopicity (κ) was observed, indicating that 44-51% of the variability of nitrate scavenging in smaller particles (below 300 nm Dva) was explained by changes in particle chemical composition. The size-segregated scavenging curves of OA followed those of nitrate, suggesting that organic scavenging was controlled by mixing with water-soluble species. In particular, functional group composition and OA elemental analysis indicated that more oxidized OA was scavenged more efficiently than less oxidized OA. Nevertheless, the small variability of organic functional group composition during the experiment did not allow us to discriminate the effect of different organic functionalities on OA scavenging.

Effect of binary organic solvents together with emulsifier on particle size and in vitro behavior of paclitaxel-encapsulated polymeric lipid nanoparticles.

PubMed

Qin, Shuzhi; Sun, Xiangshi; Li, Feng; Yu, Kongtong; Zhou, Yulin; Liu, Na; Zhao, Chengguo; Teng, Lesheng; Li, Youxin

2017-12-21

Biodegradable nanoparticles with diameters between 100 nm and 500 nm are of great interest in the contexts of targeted delivery. The present work provides a review concerning the effect of binary organic solvents together with emulsifier on particle size as well as the influence of particle size on the in vitro drug release and uptake behavior. The polymeric lipid nanoparticles (PLNs) with different particle sizes were prepared by using binary solvent dispersion method. Various formulation parameters such as binary organic solvent composition and emulsifier types were evaluated on the basis of their effects on particle size and size distribution. PLNs had a strong dependency on the surface tension, intrinsic viscosity and volatilization rate of binary organic solvents and the hydrophilicity/hydrophobicity of emulsifiers. Acetone-methanol system together with pluronic F68 as emulsifier was proved to obtain the smallest particle size. Then the PLNs with different particle sizes were used to investigate how particle size at nanoscale affects interacted with tumor cells. As particle size got smaller, cellular uptake increased in tumor cells and PLNs with particle size of ~120 nm had the highest cellular uptake and fastest release rate. The paclitaxel (PTX)-loaded PLNs showed a size-dependent inhibition of tumor cell growth, which was commonly influenced by cellular uptake and PTX release. The PLNs would provide a useful means to further elucidate roles of particle size on delivery system of hydrophobic drugs. Copyright© Bentham Science Publishers; For any queries, please email at epub@benthamscience.org.

Morphologic and chemical composition of particulate matter in motorcycle engine exhaust.

PubMed

Chernyshev, V V; Zakharenko, A M; Ugay, S M; Hien, T T; Hai, L H; Kholodov, A S; Burykina, T I; Stratidakis, A K; Mezhuev, Ya O; Tsatsakis, A M; Golokhvast, K S

2018-01-01

Despite the fact that environmental pollution due to motorcycle exhaust gases reports a great increase, motorcycle production exhibits a great increase through the last years. Countries of Asia and Africa are reported to be the major regions where two-wheeled vehicles are a major transportation mode, with tens of millions of units sold per year. Motorcycle exhaust particles are considered to be the major contributor to environmental pollution due to their airborne dispersion, containing great amount of polycyclic aromatic hydrocarbons (PAHs). This study aims at reporting an objective analysis of the main sources of the ambient air pollution as also particle size distribution and chemical composition analysis of particulate matter originated from the exhausts of two-wheeled vehicles used in the territory of Vladivostok, Russia. Various types of two-wheeled vehicles were examined (motorcycles, ATVs, scooters and wet bikes) using different types of engine and fuel system. Experimental results showed that there was no clear relation to the particle size distribution with the engine displacement of motorcycle and the number of strokes and the fuel system. Instead, there were reported two clear assumptions. The first one is that regarding to the motorcycle brand, a few samples did not exhibit a great percentage of PM 10 fraction. The second one is that more modern vehicles, that have a harmful gas afterburning system, are usually the source of an increased percentage of PM 10 emitted particles. At last, it should be mentioned that the laser particle size analysis method is capable of determining the particle sizes after their agglomeration whereas the optical morphometry method allows to determine the real particle size of emissions. In conclusion, it can be pointed out that the agglomeration of particles can lead to the reduction in the toxicity of particles emissions originated from two wheeled-vehicles.

Particle size studies to reveal crystallization mechanisms of the metal organic framework HKUST-1 during sonochemical synthesis.

PubMed

Armstrong, Mitchell R; Senthilnathan, Sethuraman; Balzer, Christopher J; Shan, Bohan; Chen, Liang; Mu, Bin

2017-01-01

Systematic studies of key operating parameters for the sonochemical synthesis of the metal organic framework (MOF) HKUST-1(also called CuBTC) were performed including reaction time, reactor volume, sonication amplitude, sonication tip size, solvent composition, and reactant concentrations analyzed through SEM particle size analysis. Trends in the particle size and size distributions show reproducible control of average particle sizes between 1 and 4μm. These results along with complementary studies in sonofragmentation and temperature control were conducted to compare these results to kinetic crystal growth models found in literature to develop a plausible hypothetical mechanism for ultrasound-assisted growth of metal-organic-frameworks composed of a competitive mechanism including constructive solid-on-solid (SOS) crystal growth and a deconstructive sonofragmentation. Copyright © 2016 Elsevier B.V. All rights reserved.

Size-resolved chemical composition, effective density, and optical properties of biomass burning particles

NASA Astrophysics Data System (ADS)

Zhai, Jinghao; Lu, Xiaohui; Li, Ling; Zhang, Qi; Zhang, Ci; Chen, Hong; Yang, Xin; Chen, Jianmin

2017-06-01

Biomass burning aerosol has an important impact on the global radiative budget. A better understanding of the correlations between the mixing states of biomass burning particles and their optical properties is the goal of a number of current studies. In this work, the effective density, chemical composition, and optical properties of rice straw burning particles in the size range of 50-400 nm were measured using a suite of online methods. We found that the major components of particles produced by burning rice straw included black carbon (BC), organic carbon (OC), and potassium salts, but the mixing states of particles were strongly size dependent. Particles of 50 nm had the smallest effective density (1.16 g cm-3) due to a relatively large proportion of aggregate BC. The average effective densities of 100-400 nm particles ranged from 1.35 to 1.51 g cm-3 with OC and inorganic salts as dominant components. Both density distribution and single-particle mass spectrometry showed more complex mixing states in larger particles. Upon heating, the separation of the effective density distribution modes confirmed the external mixing state of less-volatile BC or soot and potassium salts. The size-resolved optical properties of biomass burning particles were investigated at two wavelengths (λ = 450 and 530 nm). The single-scattering albedo (SSA) showed the lowest value for 50 nm particles (0.741 ± 0.007 and 0.889 ± 0.006) because of the larger proportion of BC content. Brown carbon played an important role for the SSA of 100-400 nm particles. The Ångström absorption exponent (AAE) values for all particles were above 1.6, indicating the significant presence of brown carbon in all sizes. Concurrent measurements in our work provide a basis for discussing the physicochemical properties of biomass burning aerosol and its effects on the global climate and atmospheric environment.

Thermite combustion enhancement resulting from biomodal luminum distribution

DOE Office of Scientific and Technical Information (OSTI.GOV)

Moore, K. M.; Pantoya, M.; Son, S. F.

2004-01-01

In recent years many studies that incorporated nano-scale or ultrafine aluminum (Al) as part of an energetic formulation and demonstrated significant performance enhancement. Decreasing the fuel particle size from the micron to nanometer range alters the material's chemical and thermal-physical properties. The result is increased particle reactivity that translates to an increase in the combustion wave speed and ignition sensitivity. Little is known, however, about the critical level of nano-sized fuel particles needed to enhance the performance of the energetic composite. Ignition sensitivity and combustion wave speed experiments were performed using a thermite composite of Al and MoO{sub 3} pressedmore » to a theoretical maximum density of 50% (2 g/cm{sup 3}). A bimodal Al particle size distribution was prepared using 4 or 20 {mu}m Al fuel particles that were replaced in 10% increments by 80 nm Al particles until the fuel was 100% 80 nm Al. These bimodal distributions allow the unique characteristics of nano-scale materials to be better understood. The pellets were ignited using a 50W CO{sub 2} laser. High speed imaging diagnostics were used to measure the ignition delay time and combustion wave speed.« less

Compositions produced using an in situ heat treatment process

DOEpatents

Roes, Augustinus Wilhelmus Maria; Nair, Vijay; Munsterman, Erwin Hunh; Van Bergen, Petrus Franciscus; Van Den Berg, Franciscus Gondulfus Antonius

2013-05-28

Methods for treating a subsurface formation and compositions produced therefrom are described herein. At least one method for producing hydrocarbons from a subsurface formation includes providing heat to the subsurface formation using an in situ heat treatment process. One or more formation particles may be formed during heating of the subsurface formation. Fluid that includes hydrocarbons and the formation particles may be produced from the subsurface formation. The formation particles in the produced fluid may include cenospheres and have an average particle size of at least 0.5 micrometers.

Low energy milling method, low crystallinity alloy, and negative electrode composition

DOEpatents

Le, Dihn B; Obrovac, Mark N; Kube, Robert Y; Landucci, James R

2012-10-16

A method of making nanostructured alloy particles includes milling a millbase in a pebble mill containing milling media. The millbase comprises: (i) silicon, and (ii) at least one of carbon or a transition metal, and wherein the nanostructured alloy particles are substantially free of crystalline domains greater than 50 nanometers in size. A method of making a negative electrode composition for a lithium ion battery including the nanostructured alloy particles is also disclosed.

SIZE DISTRIBUTION OF AMBIENT AND INDOOR PARTICLES: DOES THE OVERLAP OF FINE AND COARSE PARTICLES CAUSE PROBLEMS IN THE INTERPRETATION OF RESEARCH RESULTS?

EPA Science Inventory

Measurement of the mass and composition of particulate matter (PM) as a function of size is important for research studies for chemical mass balance, factor analysis, air quality model evaluation, epidemiology, and risk assessment. Such measurements are also important in underst...

Effect of dietary fiber and diet particle size on nutrient digestibility and gastrointestinal secretory function in growing pigs

USDA-ARS?s Scientific Manuscript database

Effect of diet composition (DC) and particle size (PS) on nutrient digestibility, gastrointestinal hormones, total bile acids (TBA), total cholesterol and glucose concentrations in plasma were evaluated in finishing pigs (n=8/diet) fed finely (374±29 µm) or coarsely (631±35 µm) ground corn-soybean m...

The Messy Aerosol Submodel MADE3 (v2.0b): Description and a Box Model Test

NASA Technical Reports Server (NTRS)

Kaiser, J. C.; Hendricks, J.; Righi, M.; Riemer, N.; Zaveri, R. A.; Metzger, S.; Aquila, Valentina

2014-01-01

We introduce MADE3 (Modal Aerosol Dynamics model for Europe, adapted for global applications, 3rd generation), an aerosol dynamics submodel for application within the MESSy framework (Modular Earth Submodel System). MADE3 builds on the predecessor aerosol submodels MADE and MADE-in. Its main new features are the explicit representation of coarse particle interactions both with other particles and with condensable gases, and the inclusion of hydrochloric acid (HCl)chloride (Cl) partitioning between the gas and condensed phases. The aerosol size distribution is represented in the new submodel as a superposition of nine lognormal modes: one for fully soluble particles, one for insoluble particles, and one for mixed particles in each of three size ranges (Aitken, accumulation, and coarse mode size ranges). In order to assess the performance of MADE3 we compare it to its predecessor MADE and to the much more detailed particle-resolved aerosol model PartMC-MOSAIC in a box model simulation of an idealized marine boundary layer test case. MADE3 and MADE results are very similar, except in the coarse mode, where the aerosol is dominated by sea spray particles. Cl is reduced in MADE3 with respect to MADE due to the HClCl partitioning that leads to Cl removal from the sea spray aerosol in our test case. Additionally, aerosol nitrate concentration is higher in MADE3 due to the condensation of nitric acid on coarse particles. MADE3 and PartMC- MOSAIC show substantial differences in the fine particle size distributions (sizes about 2 micrometers) that could be relevant when simulating climate effects on a global scale. Nevertheless, the agreement between MADE3 and PartMC-MOSAIC is very good when it comes to coarse particle size distribution, and also in terms of aerosol composition. Considering these results and the well-established ability of MADE in reproducing observed aerosol loadings and composition, MADE3 seems suitable for application within a global model.

Spatial distribution of mineral dust single scattering albedo based on DREAM model

NASA Astrophysics Data System (ADS)

Kuzmanoski, Maja; Ničković, Slobodan; Ilić, Luka

2016-04-01

Mineral dust comprises a significant part of global aerosol burden. There is a large uncertainty in estimating role of dust in Earth's climate system, partly due to poor characterization of its optical properties. Single scattering albedo is one of key optical properties determining radiative effects of dust particles. While it depends on dust particle sizes, it is also strongly influenced by dust mineral composition, particularly the content of light-absorbing iron oxides and the mixing state (external or internal). However, an assumption of uniform dust composition is typically used in models. To better represent single scattering albedo in dust atmospheric models, required to increase accuracy of dust radiative effect estimates, it is necessary to include information on particle mineral content. In this study, we present the spatial distribution of dust single scattering albedo based on the Dust Regional Atmospheric Model (DREAM) with incorporated particle mineral composition. The domain of the model covers Northern Africa, Middle East and the European continent, with horizontal resolution set to 1/5°. It uses eight particle size bins within the 0.1-10 μm radius range. Focusing on dust episode of June 2010, we analyze dust single scattering albedo spatial distribution over the model domain, based on particle sizes and mineral composition from model output; we discuss changes in this optical property after long-range transport. Furthermore, we examine how the AERONET-derived aerosol properties respond to dust mineralogy. Finally we use AERONET data to evaluate model-based single scattering albedo. Acknowledgement We would like to thank the AERONET network and the principal investigators, as well as their staff, for establishing and maintaining the AERONET sites used in this work.

High magnetization Fe-Co and Fe-Ni submicron and nanosize particles by thermal decomposition and hydrogen reduction

NASA Astrophysics Data System (ADS)

Cui, B. Z.; Marinescu, M.; Liu, J. F.

2014-05-01

This paper reports morphology, structure, and magnetic properties of air-stable soft magnetic FexCo100-x (x = 65, 50, and 34) and Fe50Ni50 (at. %) submicron and nanosize particles fabricated by template-free thermal decomposition of nitrates of Fe, Co, and Ni and subsequent hydrogen reduction. The particle compositions were tuned by modification of the precursor solution concentrations. The as-synthesized Fe-Co and Fe50Ni50 particles have body centered cubic and face centered cubic poly-nanocrystalline structures, respectively. The Fe-Co and Fe50Ni50 particles have particle sizes in the range of 28-200 nm and 70-480 nm, and average grain sizes of 16-29 nm and 20-24 nm, respectively. The particle and grain sizes were controlled by tuning particle composition, and the temperature and time of hydrogen reduction. Saturation magnetization Ms as high as 207-224 emu/g and intrinsic coercivity Hci of 59-228 Oe were obtained in the Fe-Co particles reduced at 550 °C for 90 min. Of special note, the Ms of 224 emu/g (˜2.3 T) obtained in the Fe65Co35 particles is among the highest values for Fe-Co particles reported so far. Ms of 135-137 emu/g and Hci of 59-111 Oe were obtained in the Fe50Ni50 particles reduced at 500 or 550 °C for 20 min.

Influence of jet milling and particle size on the composition, physicochemical and mechanical properties of barley and rye flours.

PubMed

Drakos, Antonios; Kyriakakis, Georgios; Evageliou, Vasiliki; Protonotariou, Styliani; Mandala, Ioanna; Ritzoulis, Christos

2017-01-15

Finer barley and rye flours were produced by jet milling at two feed rates. The effect of reduced particle size on composition and several physicochemical and mechanical properties of all flours were evaluated. Moisture content decreased as the size of the granules decreased. Differences on ash and protein contents were observed. Jet milling increased the amount of damaged starch in both rye and barley flours. True density increased with decreased particle size whereas porosity and bulk density increased. The solvent retention capacity profile was also affected by jet milling. Barley was richer in phenolics and had greater antioxidant activity than rye. Regarding colour, both rye and barley flours when subjected to jet milling became brighter, whereas their yellowness was not altered significantly. The minimum gelation concentration for all flours was 16%w/v. Barley flour gels were stronger, firmer and more elastic than the rye ones. Copyright © 2016 Elsevier Ltd. All rights reserved.

Particle dispersing system and method for testing semiconductor manufacturing equipment

DOEpatents

Chandrachood, Madhavi; Ghanayem, Steve G.; Cantwell, Nancy; Rader, Daniel J.; Geller, Anthony S.

1998-01-01

The system and method prepare a gas stream comprising particles at a known concentration using a particle disperser for moving particles from a reservoir of particles into a stream of flowing carrier gas. The electrostatic charges on the particles entrained in the carrier gas are then neutralized or otherwise altered, and the resulting particle-laden gas stream is then diluted to provide an acceptable particle concentration. The diluted gas stream is then split into a calibration stream and the desired output stream. The particles in the calibration stream are detected to provide an indication of the actual size distribution and concentration of particles in the output stream that is supplied to a process chamber being analyzed. Particles flowing out of the process chamber within a vacuum pumping system are detected, and the output particle size distribution and concentration are compared with the particle size distribution and concentration of the calibration stream in order to determine the particle transport characteristics of a process chamber, or to determine the number of particles lodged in the process chamber as a function of manufacturing process parameters such as pressure, flowrate, temperature, process chamber geometry, particle size, particle charge, and gas composition.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tian, Liang; Ames Lab. and Iowa State Univ., Ames, IA; Anderson, Iver

Recently, a novel Al/Ca composite was produced by severe plastic deformation of Al powders and Ca granules for possible use as a high-voltage power transmission conductor. Since the strength of such composites is inversely proportional to the Ca filament size, fine Ca powders (less than ~250 μm) are needed to achieve the desired high strength for the powder metallurgy production of an Al-matrix composite reinforced by nano-scale Ca filaments. However, fine Ca powders are not commercially available. Therefore, we have developed a method to produce fine Ca powders via centrifugal atomization to supply Ca powder for prototype development of Al/Camore » composite conductor. A secondary goal of the project was to demonstrate that Ca powder can be safely prepared, stored, and handled and could potentially be scaled for commercial production. Our results showed that centrifugal atomization can yield as much as 83 vol. % Ca powder particles smaller than 250 μm. The mean particle size sometimes matches, sometimes deviates substantially from the predictions of the Champagne & Anger equation likely due to unexpected secondary atomization. The particle size distribution is typical for a ligament-disintegration atomization mode. Scanning electron micrographs showed that the morphology of these Ca powders varied with powder size. Spark testing and auto-ignition tests indicated that the atomized powders were difficult to ignite, providing confidence that this material can be handled safely in air.« less

Nanosized-Particle Dispersion-Strengthened Al Matrix Composites Fabricated by the Double Mechanical Alloying Process.

PubMed

Kim, Chungseok

2018-03-01

The objective of this study was to fabricate an Al metal matrix composite strengthened by nanosized Al3Ti particles via double mechanical alloying process. Several Al-xTi alloys were fabricated, including Al-12%Ti, Al-15%Ti, and Al-12%Ti-1%Y2O3. The lattice parameter of as-milled state was calculated to be 4.0485 Å; after a milling time of 540 min, it was 4.0401 Å. This decrease was induced by Ti solutionizing into the Al matrix. The equivalent size of a coarse Al3Ti particle was 200-500 nm after the heat treatment; however, the particles were uniformly distributed and were refined through the MA2 process. The particle size of a Al3Ti phase was 30 nm or less, and the particles were uniformly distributed. These particles remained in a fine state in the matrix without growth and coarsening, even after the hot extrusion process. The microstructure of hot extruded alloys consisted of a uniform distribution of Al3Ti particles and other dispersoids in the Al matrix.

Parking simulation of three-dimensional multi-sized star-shaped particles

NASA Astrophysics Data System (ADS)

Zhu, Zhigang; Chen, Huisu; Xu, Wenxiang; Liu, Lin

2014-04-01

The shape and size of particles may have a great impact on the microstructure as well as the physico-properties of particulate composites. However, it is challenging to configure a parking system of particles to a geometrical shape that is close to realistic grains in particulate composites. In this work, with the assistance of x-ray tomography and a spherical harmonic series, we present a star-shaped particle that is close to realistic arbitrary-shaped grains. To realize such a hard particle parking structure, an inter-particle overlapping detection algorithm is introduced. A serial sectioning approach is employed to visualize the particle parking structure for the purpose of justifying the reliability of the overlapping detection algorithm. Furthermore, the validity of the area and perimeter of solids in any arbitrary section of a plane calculated using a numerical method is verified by comparison with those obtained using an image analysis approach. This contribution is helpful to further understand the dependence of the micro-structure and physico-properties of star-shaped particles on the realistic geometrical shape.

Refining Mechanism of 7075 Al Alloy by In-Situ TiB2 Particles

PubMed Central

Gan, Guisheng; Yang, Bin; Zhang, Bo; Jiang, Xin; Shi, Yunlong; Wu, Yiping

2017-01-01

The nucleation undercooling of TiB2/7075 Al matrix composites, the microstructure observed after solidification at different cooling rate, and the size and distribution of TiB2 particles were investigated. The experimental results have shown that the grain sizes of TiB2/7075 Al matrix composites firstly decreased, then increased, and finally decreased again with the increase of TiB2 content. The nucleation undercooling of TiB2/7075 Al matrix composites first increased, then decreased, and finally increased again with the increase of TiB2 content when the cooling rates was 5 and 10 °C/min respectively, but kept decreasing with the increase of TiB2 content at a cooling rate of 20 °C/min. The melting and solidification process showed no significant change with the decrease of cooling rate in 9.0% TiB2/7075 Al matrix composites. Most small particles can act as heterogeneous nucleus, which induced grain growth and were captured into the grain by the solid/liquid interface. At the same time, most of the larger particles and a minority of the small TiB2 particles are pushed into the grain boundary; locating in the grain boundary can hinder the Al atoms from diffusing during the solidification process and restrain α-Al phase growth. The influence of particles shifted from dominating by locating to dominating by nucleation as the quantity of TiB2 particles increased. PMID:28772492

Single particle measurements of the chemical composition of cirrus ice residue during CRYSTAL-FACE

NASA Astrophysics Data System (ADS)

Cziczo, D. J.; Murphy, D. M.; Hudson, P. K.; Thomson, D. S.

2004-02-01

The first real-time, in situ, investigation of the chemical composition of the residue of cirrus ice crystals was performed during July 2002. This study was undertaken on a NASA WB-57F high-altitude research aircraft as part of CRYSTAL-FACE, a field campaign which sought to further our understanding of the relation of clouds, water vapor, and climate by characterizing, among other parameters, anvil cirrus formed about the Florida peninsula. A counter flow virtual impactor (CVI) was used to separate cirrus ice from the unactivated interstitial aerosol particles and evaporate condensed-phase water. Residual material, on a crystal-by-crystal basis, was subsequently analyzed using the NOAA Aeronomy Laboratory's Particle Analysis by Laser Mass Spectrometry (PALMS) instrument. Sampling was performed from 5 to 15 km altitude and from 12° to 28° north latitude within cirrus originating over land and ocean. Chemical composition measurements provided several important results. Sea salt was often incorporated into cirrus, consistent with homogeneous ice formation by aerosol particles from the marine boundary layer. Size measurements showed that large particles preferentially froze over smaller ones. Meteoritic material was found within ice crystals, indicative of a relation between stratospheric aerosol particles and tropospheric clouds. Mineral dust was the dominant residue observed in clouds formed during a dust transport event from the Sahara, consistent with a heterogeneous freezing mechanism. These results show that chemical composition and size are important determinants of which aerosol particles form cirrus ice crystals.

Tight coupling of particle size and composition in atmospheric cloud droplet activation

NASA Astrophysics Data System (ADS)

Topping, D.; McFiggans, G.

2011-09-01

The substantial uncertainty in the indirect effect on radiative forcing in large part arises from the influences of atmospheric aerosol particles on (i) the brightness of clouds, exerting significant shortwave cooling with no appreciable compensation in the longwave, and on (ii) their ability to precipitate, with implications for cloud cover and lifetime. Predicting the ambient conditions at which aerosol particles may become cloud droplets is largely reliant on an equilibrium relationship derived in 1936. However, the theoretical basis of the relationship restricts its application to particles solely comprising involatile compounds and water, whereas a substantial fraction of particles in the real atmosphere will contain potentially thousands of semi-volatile organic compounds in addition to containing semi-volatile inorganic components such as ammonium nitrate. We show that equilibration of atmospherically reasonable concentrations of organic compounds with a growing particle as the ambient humidity increases has larger implications on cloud droplet formation than any other equilibrium compositional dependence, owing to inextricable linkage between the aerosol composition and a particles size under ambient conditions. Whilst previous attempts to account for co-condensation of gases other than water vapour have been restricted to one inorganic condensate, our method demonstrates that accounting for the co-condensation of any number of organic compounds substantially decreases the saturation ratio of water vapour required for droplet activation. This effect is far greater than any other compositional dependence; moreso even than the unphysical effect of surface tension reduction in aqueous organic mixtures, ignoring differences in bulk and surface surfactant concentrations.

Influence of particle arrangement on the permittivity of an elastomeric composite

NASA Astrophysics Data System (ADS)

Tsai, Peiying J.; Nayak, Suchitra; Ghosh, Suvojit; Puri, Ishwar K.

2017-01-01

Elastomers are used as dielectric layers contained between the parallel conductive plates of capacitors. The introduction of filler particles into an elastomer changes its permittivity ɛ. When particle organization in a composite is intentionally varied, this alters its capacitance. Using numerical simulations, we examine how conductive particle chains introduced into polydimethylsiloxane (PDMS) alter ɛ. The effects of filler volume fraction ψ, interparticle d and interchain spacing a, zigzag angle θ between adjacent particles and overall chain orientation, particle size r, and clearance h between particles and the conductive plates are characterized. When filler particles are organized into chainlike structures rather than being just randomly distributed in the elastomer matrix, ɛ increases by as much as 85%. When particles are organized into chainlike forms, ɛ increases with increasing ψ and a, but decreases with increasing d and θ. A composite containing smaller particles has a higher ɛ when ψ <9 % while larger particles provide greater enhancement when ψ is larger than that value. To enhance ɛ, adjacent particles must be interconnected and the overall chain direction should be oriented perpendicular to the conductive plates. These results are useful for additive manufacturing on electrical applications of elastomeric composites.

Nano-sized particles, processes of making, compositions and uses thereof

DOEpatents

O'Brien, Stephen [New York, NY; Yin, Ming [Los Alamos, NM

2012-05-22

The present invention describes methods for preparing high quality nanoparticles, i.e., metal oxide based nanoparticles of uniform size and monodispersity. The nanoparticles advantageously comprise organic alkyl chain capping groups and are stable in air and in nonpolar solvents. The methods of the invention provide a simple and reproducible procedure for forming transition metal oxide nanocrystals, with yields over 80%. The highly crystalline and monodisperse nanocrystals are obtained directly without further size selection; particle size can be easily and fractionally increased by the methods. The resulting nanoparticles can exhibit magnetic and/or optical properties. These properties result from the methods used to prepare them. Also advantageously, the nanoparticles of this invention are well suited for use in a variety of industrial applications, including cosmetic and pharmaceutical formulations and compositions.

Effect of particle size in preparative reversed-phase high-performance liquid chromatography on the isolation of epigallocatechin gallate from Korean green tea.

PubMed

Kim, Jung Il; Hong, Seung Bum; Row, Kyung Ho

2002-03-08

To isolate epigallocatechin gallate (EGCG) of catechin compounds from Korean green tea (Bosung, Chonnam), a C18 reversed-phase preparative column (250x22 mm) packed with packings of three different sizes (15, 40-63, and 150 microm) was used. The sample extracted with water was partitioned with chloroform and ethyl acetate to remove the impurities including caffeine. The mobile phases in this experiment were composed of 0.1% acetic acid in water, acetonitrile, methanol and ethyl acetate. The injection volume was fixed at 400 microl and the flow rate was increased as the particle size becomes larger. The isolation of EGCG with particle size was compared at a preparative scale and the feasibility of separation of EGCG at larger particle sizes was confirmed. The optimum mobile phase composition for separating EGCG was experimentally obtained at the particle sizes of 15 and 40-63 microm in the isocratic mode, but EGCG was not purely separated at the particle size of 150 microm.

Biomimetic, Strong, Tough, and Self-Healing Composites Using Universal Sealant-Loaded, Porous Building Blocks.

PubMed

Hwang, Sung Hoon; Miller, Joseph B; Shahsavari, Rouzbeh

2017-10-25

Many natural materials, such as nacre and dentin, exhibit multifunctional mechanical properties via structural interplay between compliant and stiff constituents arranged in a particular architecture. Herein, we present, for the first time, the bottom-up synthesis and design of strong, tough, and self-healing composite using simple but universal spherical building blocks. Our composite system is composed of calcium silicate porous nanoparticles with unprecedented monodispersity over particle size, particle shape, and pore size, which facilitate effective loading and unloading with organic sealants, resulting in 258% and 307% increases in the indentation hardness and elastic modulus of the compacted composite. Furthermore, heating the damaged composite triggers the controlled release of the nanoconfined sealant into the surrounding area, enabling moderate recovery in strength and toughness. This work paves the path towards fabricating a novel class of biomimetic composites using low-cost spherical building blocks, potentially impacting bone-tissue engineering, insulation, refractory and constructions materials, and ceramic matrix composites.

Study on titanium-magnesium composites with bicontinuous structure fabricated by powder metallurgy and ultrasonic infiltration.

PubMed

Jiang, S; Huang, L J; An, Q; Geng, L; Wang, X J; Wang, S

2018-05-01

Titanium-magnesium (Ti-Mg) composites with bicontinuous structure have been successfully fabricated by powder metallurgy and ultrasonic infiltration for biomaterial potential. In the composites, Ti phase is distributed continuously by sintering necks, while Mg phase is also continuous, distributing at the interconnected pores surrounding the Ti phase. The results showed that the fabricated Ti-Mg composites exhibited low modulus and high strength, which are very suitable for load bearing biomedical materials. The composites with 100 µm and 230 µm particle sizes exhibited Young's modulus of 37.6 GPa and 23.4 GPa, 500.7 MPa and 340 MPa of compressive strength and 631.5 MPa and 375.2 MPa of bending strength, respectively. Moreover, both of the modulus and strength of the composites increase with decreasing of Ti particle sizes. In vitro study has been done for the preliminary evaluation of the Ti-Mg composites. Copyright © 2018 Elsevier Ltd. All rights reserved.

Mineralogical, chemical and toxicological characterization of urban air particles.

PubMed

Čupr, Pavel; Flegrová, Zuzana; Franců, Juraj; Landlová, Linda; Klánová, Jana

2013-04-01

Systematic characterization of morphological, mineralogical, chemical and toxicological properties of various size fractions of the atmospheric particulate matter was a main focus of this study together with an assessment of the human health risks they pose. Even though near-ground atmospheric aerosols have been a subject of intensive research in recent years, data integrating chemical composition of particles and health risks are still scarce and the particle size aspect has not been properly addressed yet. Filling this gap, however, is necessary for reliable risk assessment. A high volume ambient air sampler equipped with a multi-stage cascade impactor was used for size specific particle collection, and all 6 fractions were a subject of detailed characterization of chemical (PAHs) and mineralogical composition of the particles, their mass size distribution and genotoxic potential of organic extracts. Finally, the risk level for inhalation exposure associated to the carcinogenic character of the studied PAHs has been assessed. The finest fraction (<0.45 μm) exhibited the highest mass, highest active surface, highest amount of associated PAHs and also highest direct and indirect genotoxic potentials in our model air sample. Risk assessment of inhalation scenario indicates the significant cancer risk values in PM 1.5 size fraction. This presented new approach proved to be a useful tool for human health risk assessment in the areas with significant levels of air dust concentration. Copyright © 2013 Elsevier Ltd. All rights reserved.

Controlled and tunable polymer particles' production using a single microfluidic device

NASA Astrophysics Data System (ADS)

Amoyav, Benzion; Benny, Ofra

2018-04-01

Microfluidics technology offers a new platform to control liquids under flow in small volumes. The advantage of using small-scale reactions for droplet generation along with the capacity to control the preparation parameters, making microfluidic chips an attractive technology for optimizing encapsulation formulations. However, one of the drawback in this methodology is the ability to obtain a wide range of droplet sizes, from sub-micron to microns using a single chip design. In fact, typically, droplet chips are used for micron-dimension particles, while nanoparticles' synthesis requires complex chips design (i.e., microreactors and staggered herringbone micromixer). Here, we introduce the development of a highly tunable and controlled encapsulation technique, using two polymer compositions, for generating particles ranging from microns to nano-size using the same simple single microfluidic chip design. Poly(lactic-co-glycolic acid) (PLGA 50:50) or PLGA/polyethylene glycol polymeric particles were prepared with focused-flow chip, yielding monodisperse particle batches. We show that by varying flow rate, solvent, surfactant and polymer composition, we were able to optimize particles' size and decrease polydispersity index, using simple chip designs with no further related adjustments or costs. Utilizing this platform, which offers tight tuning of particle properties, could offer an important tool for formulation development and can potentially pave the way towards a better precision nanomedicine.

In-situ single submicron particle composition analysis of ice residuals from mountain-top mixed-phase clouds in Central Europe

NASA Astrophysics Data System (ADS)

Schmidt, S.; Schneider, J.; Klimach, T.; Mertes, S.; Schenk, L. P.; Curtius, J.; Kupiszewski, P.; Hammer, E.; Vochezer, P.; Lloyd, G.; Ebert, M.; Kandler, K.; Weinbruch, S.; Borrmann, S.

2015-02-01

This paper presents results from the "INUIT-JFJ/CLACE 2013" field campaign at the high alpine research station Jungfraujoch in January/February 2013. The chemical composition of ice particle residuals (IPR) in a size diameter range of 200-900 nm was measured in orographic, convective and non-convective clouds with a single particle mass spectrometer (ALABAMA) under ambient conditions characterized by temperatures between -28 and -4 °C and wind speed from 0.1 to 21 km h-1. Additionally, background aerosol particles in cloud free air were investigated. The IPR were sampled from mixed-phase clouds with two inlets which selectively extract small ice crystals in-cloud, namely the Counterflow Virtual Impactor (Ice-CVI) and the Ice Selective Inlet (ISI). The IPR as well as the aerosol particles were classified into seven different particle types: (1) black carbon, (2) organic carbon, (3) black carbon internally mixed with organic carbon, (4) minerals, (5) one particle group (termed "BioMinSal") that may contain biological particles, minerals, or salts, (6) industrial metals, and (7) lead containing particles. For any sampled particle population it was determined by means of single particle mass spectrometer how many of the analyzed particles belonged to each of these categories. Accordingly, between 20 and 30% of the IPR and roughly 42% of the background particles contained organic carbon. The measured fractions of minerals in the IPR composition varied from 6 to 33%, while the values for the "BioMinSal" group were between 15 and 29%. Four percent to 31% of the IPR contained organic carbon mixed with black carbon. Both inlets delivered similar results of the chemical composition and of the particle size distribution, although lead was found only in the IPR sampled by the Ice-CVI. The results show that the ice particle residual composition varies substantially between different cloud events, which indicates the influence of different meteorological conditions, such as origin of the air masses, temperature and wind speed.

Middle East Health and Air Quality Utilizing NASA EOS in the Saharan and Arabian Deserts to Examine Dust Particle Size and Mineralogy of Aerosols

NASA Technical Reports Server (NTRS)

Keeton, Tiffany; Barrick, Bradley; Cooksey, Kirstin; Cowart, Kevin; Florence, Victoria; Herdy, Claire; Padgett-Vasquez, Steve; Luvall, Jeffrey; Molthan, Andrew

2012-01-01

Ground-based studies conducted in Iraq have revealed the presence of potential human pathogens in airborne dust. According to the Environmental Protection Agency (EPA), airborne particulate matter below 2.5micron (PM2.5) can cause long-term damage to the human respiratory system. NASA fs Earth Observing System (EOS) can be used to determine spectral characteristics of dust particles and dust particle sizes. Comparing dust particle size from the Sahara and Arabian Deserts gives insight into the composition and atmospheric transport characteristics of dust from each desert. With the use of NASA SeaWiFS DeepBlue Aerosol, dust particle sizes were estimated using Angstrom Exponent. Brightness Temperature Difference (BTD) equation was used to determine the area of the dust storm. The Moderate-resolution Imaging Spectroradiometer (MODIS) on Terra satellite was utilized in calculating BTD. Mineral composition of a dust storm that occurred 17 April 2008 near Baghdad was determined using imaging spectrometer data from the JPL Spectral Library and EO-1 Hyperion data. Mineralogy of this dust storm was subsequently compared to that of a dust storm that occurred over the Bodele Depression in the Sahara Desert on 7 June 2003.

Spheroidization by Plasma Processing and Characterization of Stainless Steel Powder for 3D Printing

NASA Astrophysics Data System (ADS)

Ji, Lina; Wang, Changzhen; Wu, Wenjie; Tan, Chao; Wang, Guoyu; Duan, Xuan-Ming

2017-10-01

Stainless steel 316L (SS 316L) powder was spheroidized by plasma processing to improve its suitability for powder 3D printing. The obtained spheroidized (sphero) powder was characterized in terms of its crystalline phases, elemental composition, morphology, particle size and distribution, light absorption, and flow properties. The elemental composition of the sphero powder met the Chinese standard for SS 316L except for its Si content. The volume fraction of ferrite increased after plasma processing. Furthermore, plasma processing was shown to not only reduce the mean size of the particles in the size range of 10 to 100 μm but also generate particles in the size range of 0.1 to 10 μm. The smaller particles filled the voids among larger particles, increasing the powder density. The light absorption was also increased owing to enhanced internal reflection. Although the basic flow energy decreased after plasma processing, the flow function (FF) value was smaller for the sphero powder, indicating a lower flowability of the sphero powder. However, the density of SS 316L pieces printed with commercial and sphero powders was 98.76 pct and 98.16 pct of the SS 316L bulk density, respectively, indicating the suitability of the sphero powder for 3D printing despite an FF below 10.

Effect of microstructure of nano- and micro-particle filled polymer composites on their tribo-mechanical performance

NASA Astrophysics Data System (ADS)

Devaprakasam, D.; Hatton, P. V.; Möbus, G.; Inkson, B. J.

2008-08-01

In this work we have investigated the influence of nanoscale and microscale structure on the tribo-mechanical performance and failure mechanisms of two biocompatible dental polymer composites, with different reinforcing particulates, using advanced microscopy techniques. Nano- and micro structural analysis reveals the shape, size and distribution of the particles in the composites. In the microparticle filled polymer composite (microcomposite), the particles are of irregular shape with sharp edges with non-uniform distribution in the matrix. However, in the nanoparticle filled composites (nanocomposite), filler particles are spherical in shape with uniform distribution in the matrix. From nanoindentation measurements, hardness and reduced modulus of the microcomposite were found to be heterogeneous. However, the hardness and reduced modulus of the nanocomposite were found to be homogeneous. The nanocomposite shows better tribo-mechanical performance compared to that of the microcomposite.

Assessment of Dry Powder Inhaler Carrier Targeted Design: A Comparative Case Study of Diverse Anomeric Compositions and Physical Properties of Lactose.

PubMed

Pinto, Joana T; Zellnitz, Sarah; Guidi, Tomaso; Roblegg, Eva; Paudel, Amrit

2018-06-19

The pulmonary administration landscape has rapidly advanced in recent years. Targeted design of particles by spray-drying for dry powder inhaler development offers an invaluable tool for engineering of new carriers. In this work, different formulation and process aspects of spray-drying were exploited to produce new lactose carriers. Using an integrated approach, lactose was spray-dried in the presence of polyethylene glycol 200 (PEG 200), and the in vitro performance of the resulting particles was compared with other grades of lactose with varying anomeric compositions and/or physical properties. The anomeric composition of lactose in lactose-PEG 200 feed solutions of variable compositions was analyzed via polarimetry at different temperatures. These results were correlated with the solid-state and anomeric composition of the resulting spray-dried particles using modulated differential scanning calorimetry and wide-angle X-ray scattering. The distinct selected grades of lactose were characterized in terms of their micromeritic properties using laser diffraction, helium pycnometry, and gas adsorption, and their particle surface morphologies were evaluated via scanning electron microscopy. Adhesive mixtures of the different lactose carriers with inhalable-sized salbutamol sulfate, as a model drug, were prepared in low doses and evaluated for their blend homogeneity and aerodynamic performance using a Next Generation Impactor. Characterization of the spray-dried particles revealed that predominantly crystalline (in an anomeric ratio 0.8:1 of α to β) spherical particles with a mean size of 50.9 ± 0.4 μm could be produced. Finally, it was apparent that micromeritic, in particular, the shape, and surface properties (inherent to solid-state and anomeric composition) of carrier particles dominantly control DPI delivery. This provided an insight into the relatively inferior performance of the adhesive blends containing the spherical spray-dried lactose-PEG 200 composites.

Mechanical properties and radiopacity of experimental glass-silica-metal hybrid composites.

PubMed

Jandt, Klaus D; Al-Jasser, Abdullah M O; Al-Ateeq, Khalid; Vowles, Richard W; Allen, Geoff C

2002-09-01

Experimental glass-silica-metal hybrid composites (polycomposites) were developed and tested mechanically and radiographically in this fundamental pilot study. To determine whether mechanical properties of a glass-silica filled two-paste dental composite based on a Bis-GMA/polyglycol dimethacrylate blend could be improved through the incorporation of titanium (Ti) particles (particle size ranging from 1 to 3 microm) or silver-tin-copper (Ag-Sn-Cu) particles (particle size ranging from 1 to 50 microm) we measured the diametral tensile strength, fracture toughness and radiopacity of five composites. The five materials were: I, the original unmodified composite (control group); II, as group I but containing 5% (wt/wt) of Ti particles; III, as group II but with Ti particles treated with 4-methacryloyloxyethyl trimellitate anhydride (4-META) to promote Ti-resin bonding; IV, as group I but containing 5% (wt/wt) of Ag-Sn-Cu particles; and V, as group IV but with the metal particles treated with 4-META. Ten specimens of each group were tested in a standard diametral tensile strength test and a fracture toughness test using a single-edge notched sample design and five specimens of each group were tested using a radiopacity test. The diametral tensile strength increased statistically significantly after incorporation of Ti treated with 4-META, as tested by ANOVA (P=0.004) and Fisher's LSD test. A statistically significant increase of fracture toughness was observed between the control group and groups II, III and V as tested by ANOVA (P=0.003) and Fisher's LSD test. All other groups showed no statistically significant increase in diametral tensile strength and fracture toughness respectively when compared to their control groups. No statistically significant increase in radiopacity was found between the control group and the Ti filled composite, whereas a statistically significant increase in radiopacity was found between the control group and the Ag-Sn-Cu filled composite as tested by ANOVA (P=0.000) and Fisher's LSD procedure. The introduction of titanium and silver-tin-copper fillers has potential as added components in composites to provide increased mechanical strength and radiopacity, for example for use in core materials.

Study on selective laser sintering of glass fiber reinforced polystyrene

NASA Astrophysics Data System (ADS)

Yang, Laixia; Wang, Bo; Zhou, Wenming

2017-12-01

In order to improve the bending strength of Polystyrene (PS) sintered parts by selective laser sintering, Polystyrene/glass fiber (PS/GF) composite powders were prepared by mechanical mixing method. The size distribution of PS/GF composite powders was characterized by laser particle size analyzer. The optimum ratio of GF was determined by proportioning sintering experiments. The influence of process parameters on the bending strength of PS and PS/GF sintered parts was studied by orthogonal test. The result indicates that the particle size of PS/GF composite powder is mainly distributed in 24.88 μm~139.8 μm. When the content of GF is 10%, it has better strengthen effect. Finally, the article used the optimum parameter of the two materials to sinter prototype, it is found that the PS/GF prototype has the advantages of good accuracy and high strength.

Effect of filler properties in composite resins on light transmittance characteristics and color.

PubMed

Arikawa, Hiroyuki; Kanie, Takahito; Fujii, Koichi; Takahashi, Hideo; Ban, Seiji

2007-01-01

The purpose of this investigation was to examine the effect of filler particle size and shape as well as filler content on light transmittance characteristics and color of experimental composite resins. A mixture of 30 mol% Bis-GMA and 70 mol% TEGDMA was prepared as a base monomer and to which a photoinitiator (camphorquinone) and a co-initiator (N,N-dimethylaminoethyl methacrylate) were added. Four different irregular- and spherical-shaped filler types with an average particle size of 1.9-11.1 microm were added to the mixture in three different filler contents of 20, 30, and 40 vol%. Light transmittance characteristics including light diffusion characteristics of the materials were evaluated. Color values and color differences among filler contents of the materials were also determined. Materials containing smaller and irregular-shaped fillers showed higher light transmittance and diffusion angle distribution with a sharper peak, as compared with those containing larger and spherical-shape fillers. It was also found that there was a significant correlation between the specific surface area of fillers and the color difference of the materials containing the fillers. Our results indicated that the shape of filler particles, as well as particle size and filler content, significantly affected the light transmittance characteristics--including light diffusion characteristics--and color of composite resins.

Real-time measurement of size-resolved elemental composition ratio for flame synthesized composite nanoparticle aggregates using a tandem SMPS-ICP-OES

PubMed Central

Reed, Nathan; Fang, Jiaxi; Chavalmane, Sanmathi; Biswas, Pratim

2017-01-01

Composite nanoparticles find application in catalysis, drug delivery, and energy storage and require increasingly fine control of their physical properties and composition. While composite nanoparticles have been widely synthesized and characterized, little work has systematically correlated the initial concentration of precursors and the final composition of flame synthesized composite nanoparticles. This relationship is explored in a diffusion flame aerosol reactor by coupling a scanning mobility particle sizer (SMPS) with an inductively coupled plasma optical emission spectrometer (ICP-OES). A framework for studying the relationship between the initial precursor concentrations of different elements and the final nanoparticle composition is explored. The size-resolved elemental composition was measured by directly injecting size-selected fractions of aggregated magnetite and silicon dioxide composite nanoparticles into the ICP-OES plasma. This work showed a correlation between precursor molar ratio and the measured elemental ratio in the mobility size range of 50 to 140 nm. Building on previous work studying size resolved elemental composition of engineered nanoparticles, the analysis is extended to flame synthesized composite nanoparticle aggregates in this work. PMID:28435179

Real-time measurement of size-resolved elemental composition ratio for flame synthesized composite nanoparticle aggregates using a tandem SMPS-ICP-OES.

PubMed

Reed, Nathan; Fang, Jiaxi; Chavalmane, Sanmathi; Biswas, Pratim

2017-01-01

Composite nanoparticles find application in catalysis, drug delivery, and energy storage and require increasingly fine control of their physical properties and composition. While composite nanoparticles have been widely synthesized and characterized, little work has systematically correlated the initial concentration of precursors and the final composition of flame synthesized composite nanoparticles. This relationship is explored in a diffusion flame aerosol reactor by coupling a scanning mobility particle sizer (SMPS) with an inductively coupled plasma optical emission spectrometer (ICP-OES). A framework for studying the relationship between the initial precursor concentrations of different elements and the final nanoparticle composition is explored. The size-resolved elemental composition was measured by directly injecting size-selected fractions of aggregated magnetite and silicon dioxide composite nanoparticles into the ICP-OES plasma. This work showed a correlation between precursor molar ratio and the measured elemental ratio in the mobility size range of 50 to 140 nm. Building on previous work studying size resolved elemental composition of engineered nanoparticles, the analysis is extended to flame synthesized composite nanoparticle aggregates in this work.

Regional haze case studies in the southwestern U.S—I. Aerosol chemical composition

NASA Astrophysics Data System (ADS)

Macias, Edward S.; Zwicker, Judith O.; Ouimette, James R.; Hering, Susanne V.; Friedlander, Sheldon K.; Cahill, Thomas A.; Kuhlmey, Gregory A.; Richards, L. Willard

Aerosol chemical composition as a function of particle size was determined in the southwestern U.S.A. during four weeks of sampling in June, July and December, 1979 as a part of project VISITA. Samples were collected at two ground stations about 80 km apart near Page (AZ) and in two aircraft flying throughout the region. Several different size separating aerosol samplers and chemical analysis procedures were intercompared and were used in determining the size distribution and elemental composition of the aerosol. Sulfur was shown to be in the form of water soluable sulfate, highly correlated with ammonium ion, and with an average [NH +4]/[SO 2-4] molar ratio of 1.65. During the summer sampling period, three distinct regimes were observed, each with a different aerosol composition. The first, 24 h sampling ending 30 June, was characterized by a higher than average value of light scattering due to particles (b sp) of 24 × 10 -6m-1 and a fine particulate mass ( Mf) of 8.5 μg m -1. The fine particle aerosol was dominated by sulfate and carbon. Aircraft measurements showed the aerosol was homogeneous throughout the region at that time. The second regime, 5 July, had the highest average bsp of 51 × 10 -6m -1 during the sampling period with Mf of 3.2 μgm -3. The fine particle aerosol had nearly equal concentrations of carbon and ammonium sulfate. For all three regimes, enrichment factor analysis indicated fine and coarse particle Cu, Zn, Cl, Br, and Pb and fine particle K were enriched above crustal concentrations relative to Fe, indicating that these elements were present in the aerosol from sources other than wind blown dust. Particle extinction budgets calculated for the three regimes indicated that fine particles contributed most significantly, with carbon and (NH 4) 2SO 4 making the largest contributions. Fine particle crustal elements including Si did not contribute significantly to the extinction budget during this study. The December sampling was characterized by very light fine particle loading with two regimes identified. One regime had higher fine mass and sulfate concentrations while the other had low values for all species measured.

Effect of composition on physical properties of food powders

NASA Astrophysics Data System (ADS)

Szulc, Karolina; Lenart, Andrzej

2016-04-01

The paper presents an influence of raw material composition and technological process applied on selected physical properties of food powders. Powdered multi-component nutrients were subjected to the process of mixing, agglomeration, coating, and drying. Wetting liquids ie water and a 15% water lactose solution, were used in agglomeration and coating. The analyzed food powders were characterized by differentiated physical properties, including especially: particle size, bulk density, wettability, and dispersibility. The raw material composition of the studied nutrients exerted a statistically significant influence on their physical properties. Agglomeration as well as coating of food powders caused a significant increase in particle size, decreased bulk density, increased apparent density and porosity, and deterioration in flowability in comparison with non-agglomerated nutrients.

Preparation and Characterization of Extruded Composites Based on Polypropylene and Chitosan Compatibilized with Polypropylene-Graft-Maleic Anhydride.

PubMed

Carrasco-Guigón, Fernando Javier; Rodríguez-Félix, Dora Evelia; Castillo-Ortega, María Mónica; Santacruz-Ortega, Hisila C; Burruel-Ibarra, Silvia E; Encinas-Encinas, Jose Carmelo; Plascencia-Jatomea, Maribel; Herrera-Franco, Pedro Jesus; Madera-Santana, Tomas Jesus

2017-01-25

The preparation of composites of synthetic and natural polymers represent an interesting option to combine properties; in this manner, polypropylene and chitosan extruded films using a different proportion of components and polypropylene-graft-maleic anhydride (PPgMA) as compatibilizer were prepared. The effect of the content of the biopolymer in the polypropylene (PP) matrix, the addition of compatibilizer, and the particle size on the properties of the composites was analyzed using characterization by fourier transform-infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), differential scanning calorimetry (DSC), tensile strength, and contact angle, finding that in general, the addition of the compatibilizer and reducing the particle size of the chitosan, favored the physicochemical and morphological properties of the films.

Overview of TANGENT (Tandem Aerosol Nucleation and Growth ENvironment Tube) 2017 IOP Study

NASA Astrophysics Data System (ADS)

Tiszenkel, L.

2017-12-01

New particle formation consists of two steps: nucleation and growth of nucleated particles. However, most laboratory studies have been conducted under conditions where these two processes are convoluted together, thereby hampering the detailed understanding of the effect of chemical species and atmospheric conditions on two processes. The objective of the Tandem Aerosol Nucleation and Growth ENvironment Tube (TANGENT) laboratory study is to investigate aerosol nucleation and growth properties independently by separating these two processes in two different flow tubes. This research is a collaboration between the University of Alabama in Huntsville and the University of Delaware. In this poster we will present the experimental setup of TANGENT and summarize the key results from the first IOP (intense observation period) experiments undertaken during Summer 2017. Nucleation takes place in a temperature- and RH-controlled fast flow reactor (FT-1) where sulfuric acid forms from OH radicals and sulfur dioxide. Sulfuric acid and impurity base compounds are detected with chemical ionization mass spectrometers (CIMS). Particle sizes and number concentrations of newly nucleated particles are measured with a scanning mobility particle sizer (SMPS) and particle size magnifier (PSM), providing concentrations of particles between 1-100 nm. The nucleation particles are transferred directly to the growth tube (FT-2) where oxidants and biogenic organic precursors are added to grow nucleated nanoparticles. Sizes of particles after growth are analyzed with an additional SMPS and elemental chemical composition of 50 nm and above particles detected with a nano-aerosol mass spectrometer (NAMS). TANGENT provides the unique ability to conduct experiments that can monitor and control reactant concentrations, aerosol size and aerosol chemical composition during nucleation and growth. Experiments during this first IOP study have elucidated the effects of sulfur dioxide, particle size, relative humidity, temperature, oxidants and biogenic organics on nanoparticle formation and growth. In another 3 companion posters, we will discuss findings of these results in detail.

Life cycle impact assessment modeling for particulate matter: A new approach based on physico-chemical particle properties.

PubMed

Notter, Dominic A

2015-09-01

Particulate matter (PM) causes severe damage to human health globally. Airborne PM is a mixture of solid and liquid droplets suspended in air. It consists of organic and inorganic components, and the particles of concern range in size from a few nanometers to approximately 10μm. The complexity of PM is considered to be the reason for the poor understanding of PM and may also be the reason why PM in environmental impact assessment is poorly defined. Currently, life cycle impact assessment is unable to differentiate highly toxic soot particles from relatively harmless sea salt. The aim of this article is to present a new impact assessment for PM where the impact of PM is modeled based on particle physico-chemical properties. With the new method, 2781 characterization factors that account for particle mass, particle number concentration, particle size, chemical composition and solubility were calculated. Because particle sizes vary over four orders of magnitudes, a sound assessment of PM requires that the exposure model includes deposition of particles in the lungs and that the fate model includes coagulation as a removal mechanism for ultrafine particles. The effects model combines effects from particle size, solubility and chemical composition. The first results from case studies suggest that PM that stems from emissions generally assumed to be highly toxic (e.g. biomass combustion and fossil fuel combustion) might lead to results that are similar compared with an assessment of PM using established methods. However, if harmless PM emissions are emitted, established methods enormously overestimate the damage. The new impact assessment allows a high resolution of the damage allocatable to different size fractions or chemical components. This feature supports a more efficient optimization of processes and products when combating air pollution. Copyright © 2015 Elsevier Ltd. All rights reserved.

Elongated dust particles growth in a spherical glow discharge in ethanol

NASA Astrophysics Data System (ADS)

Fedoseev, A. V.; Sukhinin, G. I.; Sakhapov, S. Z.; Zaikovskii, A. V.; Novopashin, S. A.

2018-01-01

The formation of elongated dust particles in a spherical dc glow discharge in ethanol was observed for the first time. Dust particles were formed in the process of coagulation of ethanol dissociation products in the plasma of gas discharge. During the process the particles were captured into clouds in the electric potential wells of strong striations of spherical discharge. The size and the shape of dust particles are easily detected by naked eye after the illumination of the laser sheet. The description of the experimental setup and conditions, the analysis of size, shape and composition of the particles, the explanation of spatial ordering and orientation of these particles are presented.

Cloud condensation nuclei droplet growth kinetics of ultrafine particles during anthropogenic nucleation events

NASA Astrophysics Data System (ADS)

Shantz, N. C.; Pierce, J. R.; Chang, R. Y.-W.; Vlasenko, A.; Riipinen, I.; Sjostedt, S.; Slowik, J. G.; Wiebe, A.; Liggio, J.; Abbatt, J. P. D.; Leaitch, W. R.

2012-02-01

Evolution of the cloud condensation nucleus (CCN) activity of 36 ± 4 nm diameter anthropogenic aerosol particles at a water supersaturation of 1.0 ± 0.1% is examined for particle nucleation and growth. During the early stages of one event, relatively few of the anthropogenic particles at 36 nm were CCN active and their growth rates by water condensation were delayed relative to ammonium sulphate particles. As the event progressed, the particle size distribution evolved to larger sizes and the relative numbers of particles at 36 nm that were CCN active increased until all the 36 nm particles were activating at the end of the event. Based on the chemistry of larger particles and the results from an aerosol chemical microphysics box model, the increase in CCN activity of the particles was most likely the result of the condensation of sulphate in this case. Despite the increased CCN activity, a delay was observed in the initial growth of these particles into cloud droplets, which persisted even when the aerosol was most CCN active later in the afternoon. Simulations show that the delay in water uptake is explained by a reduction of the mass accommodation coefficient assuming that the composition of the 36 nm particles is the same as the measured composition of the 60-100 nm particles.

Impact of organic coating on growth of ammonium sulfate particles: light extinction measurements relevant for the direct effect

NASA Astrophysics Data System (ADS)

Robinson, C. B.; Zarzana, K. J.; Hasenkopf, C. A.; Tolbert, M. A.

2012-12-01

Light extinction by particles is strongly dependent on chemical composition, particle size, and water uptake. Relative humidity affects extinction by causing changes in refractive index and particle size due to hygroscopic growth. The ability of particles to take up water depends on their composition and structure. In both laboratory and field studies, inorganic salts completely covered by an organic coating have been observed. The impact of this coating on water uptake is uncertain, and a systematic study that examines water uptake as a function of relative humidity is highly desirable. These data are critical to evaluate the aerosol direct effect on climate, which is one of the most uncertain aspects of future climate change. In this study, we probe the connection between aerosol composition, size and light extinction directly by measuring fRHext, the ratio of the extinction coefficient for humidified particles to the extinction coefficient for dry particles. Particles were composed of 1,2,6-hexanetriol and ammonium sulfate, a system that forms organic coatings around the inorganic core. A cavity ring-down aerosol extinction spectrometer at 532 nm is used to measure the optical growth factor as a function of relative humidity. The fRHext values for a range of %RH for pure ammonium sulfate, pure 1,2,6-hexanetriol, and ammonium sulfate particles with 1,2,6-hexanetriol coatings were measured. The coated particles are created using a method of liquid-liquid separation, where the particles are exposed to water vapor creating a RH% above their deliquescence RH%. The particles are then dried with a Nafion dryer to a RH% that is below the point where liquid-liquid phase separation is observed, but above the efflorescence RH%. Pure 1,2,6-hexanetriol takes up little water over the observed RH range of 45-65%, and therefore fRHext ~ 1. With pure ammonium sulfate for the same RH% range, the fRHext varied from 1.5 - 2, depending on the RH% and the particle size. For the coated particles, at each RH%, the fRHext values fall between those for pure ammonium sulfate and pure 1,2,6-hexanetriol values. This suggests that the organic coating does not prevent water uptake by the ammonium sulfate cores.

Microstructure, mixing rules and interfacial behavior in high k barium titanate epoxy composite

NASA Astrophysics Data System (ADS)

Shi, Yitong (Thomas)

2001-07-01

In this thesis, we have demonstrated the importance of two issues in BaTiO3/epoxy composites. They are (1) the miscibility of a particle blend in organic vehicle, i.e. the capability of particles with different particle sizes to mix at the particle level, and (2) the ceramic/polymer interface as a role in determining the effective dielectric constant. The epoxy matrix between the BaTiO3 particles is not homogeneous and has to be modeled as a two-layer structure. The inhomogeneity causes not only failure of the existing mixing rules but also the particle size dependence of the effective dielectric constant. Since the interfacial behavior is determined by the materials chemistry, the effective dielectric properties experimentally demonstrate strong dependence on the materials selection and processing. If BaTiO3 particles in liquid epoxy resin has a bimodal particle size distribution, the smaller particles do not experimentally fit into the interstitial spaces between the larger spheres in an organic vehicle. ESEM observations indicated that the large particles separated from the small ones. Depending on the paste formula, the particle separation led to either a layer-like or cluster-like microstructure. The mixing free energy of blending smaller particles with larger particles explains the observed phenomena and suggests general criteria for particle miscibility. Whenever the mixing free energy is negative and the mixing free energy curve is convex, the particle blend remains in a random particle distribution. Otherwise, the particles separate into a larger-particle rich "phase" and a smaller-particle rich "phase". A random particle distribution may be the largest degree of mixing we can achieve in an organic vehicle. If there is no specific interaction between the small particles and the large particles, there is no thermodynamic driving force for small particles to fill preferentially into the interstitial spaces between the large spheres. The Hamaker constant H significantly influences the miscibility of a particle blend. An increase in Hamaker constant H causes not only greater driving force for a particle blend to separate but also a more narrowed convex shape---the mixing window. At a specific composition, a particle blend separates in one vehicle but may remain in a random distribution in another vehicle if the later vehicle has significantly reduced the Hamaker constant H.

Composition and digestive tract retention time of ruminal particles with functional specific gravity greater or less than 1.02.

PubMed

Hristov, A N; Ahvenjarvi, S; McAllister, T A; Huhtanen, P

2003-10-01

The objective of this study was to determine composition, particle size distribution, and in vivo kinetics of ruminal particles having functional specific gravity (FSG) greater or less than FSG of particles found in the omasum and reticulum of lactating dairy cows. Particles from the reticulum and the omasal had FSG of 1.03 and 1.02, respectively. Particles from ruminal contents with FSG higher (HP) or lower (LP) than 1.02 were isolated and labeled with Er or Dy, respectively. Four ruminally cannulated, lactating Ayrshire dairy cows were fed all-grass silage (AS) or 54% grass silage:46% concentrate (SC) diets in a cross-over design trial and used to study chemical composition and ruminal and total tract kinetics of HP and LP. Labeled particles were pulse dosed into the rumen of the cows and disappearance of the markers from ruminal HP and LP pools and excretion in feces was monitored for 72 and 120 h, respectively. Fecal marker excretion data were fitted using two-compartment mathematical age-dependent/age-independent (Gn-->G1) models. Inclusion of concentrate in the diet (SC) increased (P < 0.05) apparent total tract digestibility of dietary DM, OM and N. Digestibility of fiber fractions, NDF and ADF, was lower (P < 0.01 and P < 0.05, respectively) for SC compared with AS. The heavy particles had higher (P < 0.01) indigestible NDF and lower (P < 0.01) N concentration than LP. Particles from the HP pool passed from the rumen more rapidly (P < 0.01) than particles from LP (0.044 and 0.019 h(-1), respectively). Diet had no effect on particle rate of disappearance or pool size in the rumen. Across diets, pool size of LP was consistently larger (P < 0.05) than that of HP. Diet had no effect on total tract mean retention time (MRT) of LP or HP. Total tract MRT of LP was greater (P < 0.05) than MRT of HP (59.6 vs. 49.0 h, respectively). Results from this study support the hypothesis that functional specific gravity is an important factor determining the rate of outflow and residence time of feed particles within the reticulo-rumen and total digestive tract. Our data indicate that digesta particles with functional specific gravity greater or less than 1.02 have different composition and flow characteristics. Heavier particles contain more indigestible fiber and less N and are likely depleted of substrate available for microbial fermentation, are smaller in size, and have a higher passage rate/shorter retention time in the digestive tract than lighter particles.

Day and night variation in chemical composition and toxicological responses of size segregated urban air PM samples in a high air pollution situation

NASA Astrophysics Data System (ADS)

Jalava, P. I.; Wang, Q.; Kuuspalo, K.; Ruusunen, J.; Hao, L.; Fang, D.; Väisänen, O.; Ruuskanen, A.; Sippula, O.; Happo, M. S.; Uski, O.; Kasurinen, S.; Torvela, T.; Koponen, H.; Lehtinen, K. E. J.; Komppula, M.; Gu, C.; Jokiniemi, J.; Hirvonen, M.-R.

2015-11-01

Urban air particulate pollution is a known cause for adverse human health effects worldwide. China has encountered air quality problems in recent years due to rapid industrialization. Toxicological effects induced by particulate air pollution vary with particle sizes and season. However, it is not known how distinctively different photochemical activity and different emission sources during the day and the night affect the chemical composition of the PM size ranges and subsequently how it is reflected to the toxicological properties of the PM exposures. The particulate matter (PM) samples were collected in four different size ranges (PM10-2.5; PM2.5-1; PM1-0.2 and PM0.2) with a high volume cascade impactor. The PM samples were extracted with methanol, dried and thereafter used in the chemical and toxicological analyses. RAW264.7 macrophages were exposed to the particulate samples in four different doses for 24 h. Cytotoxicity, inflammatory parameters, cell cycle and genotoxicity were measured after exposure of the cells to particulate samples. Particles were characterized for their chemical composition, including ions, element and PAH compounds, and transmission electron microscopy (TEM) was used to take images of the PM samples. Chemical composition and the induced toxicological responses of the size segregated PM samples showed considerable size dependent differences as well as day to night variation. The PM10-2.5 and the PM0.2 samples had the highest inflammatory potency among the size ranges. Instead, almost all the PM samples were equally cytotoxic and only minor differences were seen in genotoxicity and cell cycle effects. Overall, the PM0.2 samples had the highest toxic potential among the different size ranges in many parameters. PAH compounds in the samples and were generally more abundant during the night than the day, indicating possible photo-oxidation of the PAH compounds due to solar radiation. This was reflected to different toxicity in the PM samples. Some of the day to night difference may have been caused also by differing wind directions transporting air masses from different emission sources during the day and the night. The present findings indicate the important role of the local particle sources and atmospheric processes on the health related toxicological properties of the PM. The varying toxicological responses evoked by the PM samples showed the importance of examining various particle sizes. Especially the detected considerable toxicological activity by PM0.2 size range suggests they're attributable to combustion sources, new particle formation and atmospheric processes.

Modeling the Capillary Pressure for the Migration of the Liquid Phase in Granular Solid-Liquid-Vapor Systems: Application to the Control of the Composition Profile in W-Cu FGM Materials

NASA Astrophysics Data System (ADS)

Missiaen, Jean-Michel; Raharijaona, Jean-Joël; Delannay, Francis

2016-11-01

A model is developed to compute the capillary pressure for the migration of the liquid phase out or into a uniform solid-liquid-vapor system. The capillary pressure is defined as the reduction of the overall interface energy per volume increment of the transferred fluid phase. The model takes into account the particle size of the solid particle aggregate, the packing configuration (coordination number, porosity), the volume fractions of the different phases, and the values of the interface energies in the system. The model is used for analyzing the stability of the composition profile during processing of W-Cu functionally graded materials combining a composition gradient with a particle size gradient. The migration pressure is computed with the model in two stages: (1) just after the melting of copper, i.e., when sintering and shape accommodation of the W particle aggregate can still be neglected and (2) at high temperature, when the system is close to full density with equilibrium particle shape. The model predicts well the different stages of liquid-phase migration observed experimentally.

Effect of nano/micro B4C and SiC particles on fracture properties of aluminum 7075 particulate composites under chevron-notch plane strain fracture toughness test

NASA Astrophysics Data System (ADS)

Morovvati, M. R.; Lalehpour, A.; Esmaeilzare, A.

2016-12-01

Reinforcing aluminum with SiC and B4C nano/micro particles can lead to a more efficient material in terms of strength and light weight. The influence of adding these particles to an aluminum 7075 matrix is investigated using chevron-notch fracture toughness test method. The reinforcing factors are type, size (micro/nano), and weight percent of the particles. The fracture parameters are maximum load, notch opening displacement, the work up to fracture and chevron notch plane strain fracture toughness. The findings demonstrate that addition of micro and nano size particles improves the fracture properties; however, increasing the weight percent of the particles leads to increase of fracture properties up to a certain level and after that due to agglomeration of the particles, the improvement does not happen for both particle types and size categories. Agglomeration of particles at higher amounts of reinforcing particles results in improper distribution of particles and reduction in mechanical properties.

Nanoscale morphogenesis of nylon-sputtered plasma polymer particles

NASA Astrophysics Data System (ADS)

Choukourov, Andrei; Shelemin, Artem; Pleskunov, Pavel; Nikitin, Daniil; Khalakhan, Ivan; Hanuš, Jan

2018-05-01

Sub-micron polymer particles are highly important in various fields including astrophysics, thermonuclear fusion and nanomedicine. Plasma polymerization offers the possibility to produce particles with tailor-made size, crosslink density and chemical composition to meet the requirements of a particular application. However, the mechanism of nucleation and growth of plasma polymer particles as well as diversity of their morphology remain far from being clear. Here, we prepared nitrogen-containing plasma polymer particles by rf magnetron sputtering of nylon in a gas aggregation cluster source with variable length. The method allowed the production of particles with roughly constant chemical composition and number density but with the mean size changing from 80 to 320 nm. Atomic Force Microscopy with super-sharp probes was applied to study the evolution of the particle surface topography as they grow in size. Height–height correlation and power spectral density functions were obtained to quantify the roughness exponent α  =  0.78, the growth exponent β  =  0.35, and the dynamic exponent 1/z  =  0.50. The set of critical exponents indicates that the particle surface evolves in a self-affine mode and the overall particle growth is caused by the accretion of polymer-forming species from the gas phase and not by coagulation. Redistribution of the incoming material over the surface coupled with the inhomogeneous distribution of inner stress is suggested as the main factor that determines the morphogenesis of the plasma polymer particles.

Sampling the structure and chemical order in assemblies of ferromagnetic nanoparticles by nuclear magnetic resonance

PubMed Central

Liu, Yuefeng; Luo, Jingjie; Shin, Yooleemi; Moldovan, Simona; Ersen, Ovidiu; Hébraud, Anne; Schlatter, Guy; Pham-Huu, Cuong; Meny, Christian

2016-01-01

Assemblies of nanoparticles are studied in many research fields from physics to medicine. However, as it is often difficult to produce mono-dispersed particles, investigating the key parameters enhancing their efficiency is blurred by wide size distributions. Indeed, near-field methods analyse a part of the sample that might not be representative of the full size distribution and macroscopic methods give average information including all particle sizes. Here, we introduce temperature differential ferromagnetic nuclear resonance spectra that allow sampling the crystallographic structure, the chemical composition and the chemical order of non-interacting ferromagnetic nanoparticles for specific size ranges within their size distribution. The method is applied to cobalt nanoparticles for catalysis and allows extracting the size effect from the crystallographic structure effect on their catalytic activity. It also allows sampling of the chemical composition and chemical order within the size distribution of alloyed nanoparticles and can thus be useful in many research fields. PMID:27156575

The photoelectronic behaviors of MoO3-loaded ZrO2/carbon cluster nanocomposite materials

NASA Astrophysics Data System (ADS)

Matsui, H.; Ishiko, A.; Karuppuchamy, S.; Hassan, M. A.; Yoshihara, M.

2012-03-01

A novel nano-sized ZrO2/carbon cluster composite materials (Ic's) were successfully obtained by the calcination of ZrCl4/starch complexes I's under an argon atmosphere. Pt- and/or MoO3-loaded ZrO2/carbon clusters composite materials were also prepared by doping Pt and/or MoO3 particles on the surface of Ic's. The surface characterization of the composite materials was carried out using transmission electron microscopy (TEM). The TEM observation of the materials showed the presence of particles with the diameters of a few nanometers, possibly Pt particles, and of 50-100 nm, possibly MoO3 particles, in the matrix. Pt- and/or MoO3-loaded ZrO2/carbon cluster composite materials show the efficient photocatalytic activity under visible light irradiation.

Evaluation of the Community Multiscale Air Quality (CMAQ) ...

EPA Pesticide Factsheets

This work evaluates particle size-composition distributions simulated by the Community Multiscale Air Quality (CMAQ) model using Micro-Orifice Uniform Deposit Impactor (MOUDI) measurements at 18 sites across North America. Size-resolved measurements of particulate SO4+, with the model ranging from an underestimation to overestimation of both the peak diameter and peak particle concentration across the sites. Computing PM2.5 from the modeled size distribution parameters rather than by summing the masses in the Aitken and a

Strain-Detecting Composite Materials

NASA Technical Reports Server (NTRS)

Wallace, Terryl A. (Inventor); Smith, Stephen W. (Inventor); Piascik, Robert S. (Inventor); Horne, Michael R. (Inventor); Messick, Peter L. (Inventor); Alexa, Joel A. (Inventor); Glaessgen, Edward H. (Inventor); Hailer, Benjamin T. (Inventor)

2016-01-01

A composite material includes a structural material and a shape-memory alloy embedded in the structural material. The shape-memory alloy changes crystallographic phase from austenite to martensite in response to a predefined critical macroscopic average strain of the composite material. In a second embodiment, the composite material includes a plurality of particles of a ferromagnetic shape-memory alloy embedded in the structural material. The ferromagnetic shape-memory alloy changes crystallographic phase from austenite to martensite and changes magnetic phase in response to the predefined critical macroscopic average strain of the composite material. A method of forming a composite material for sensing the predefined critical macroscopic average strain includes providing the shape-memory alloy having an austenite crystallographic phase, changing a size and shape of the shape-memory alloy to thereby form a plurality of particles, and combining the structural material and the particles at a temperature of from about 100-700.degree. C. to form the composite material.

A collection of diverse micrometeorites recovered from 100 tonnes of Antarctic blue ice

NASA Technical Reports Server (NTRS)

Maurette, M.; Olinger, C.; Michel-Levy, M. C.; Kurat, G.; Pourchet, M.

1991-01-01

A new type of meteoritic material, intermediate in size between meteorites and interplanetary dust particles (IDPs), is described. Melting and filtering of about 100 tons of blue ice near Cap Prudhomme, Antarctica, yielded 7500 or more irregular, friable particles and about 1500 melted spherules, about 100 microns in size, both showing a 'chondritic' composition suggestive of an extraterrestrial origin. Analyzed irregular particles appear to be unmelted and have similarities with the fine-grained matrix of primitive carbonaceous chondrites, but are extremely diverse in composition. Isotopic analysis of trapped neon confirms an extraterrestrial origin for 16 of 47 irregular particles and 2 of 19 spherules studied and strongly suggests that they were exposed in space as micrometeoroids. These large Antarctic micrometeorites constitute a new family, or at least a new population, of solar system objects, in a mass range corresponding to the bulk of extraterrestrial material accreted by the earth today.

Size-resolved ultrafine particle composition analysis 2. Houston

NASA Astrophysics Data System (ADS)

Phares, Denis J.; Rhoads, Kevin P.; Johnston, Murray V.; Wexler, Anthony S.

2003-04-01

Between 23 August and 18 September 2000, a single-ultrafine-particle mass spectrometer (RSMS-II) was deployed just east of Houston as part of a sampling intensive during the Houston Supersite Experiment. The sampling site was located just north of the major industrial emission sources. RSMS-II, which simultaneously measures the aerodynamic size and composition of individual ultrafine aerosols, is well suited to resolving some of the chemistry associated with secondary particle formation. Roughly 27,000 aerosol mass spectra were acquired during the intensive period. These were classified and labeled based on the spectral peak patterns using the neural networks algorithm, ART-2a. The frequency of occurrence of each particle class was correlated with time and wind direction. Some classes were present continuously, while others appeared intermittently or for very short time durations. The most frequently detected species at the site were potassium and silicon, with lesser amounts of organics and heavier metals.

Fabrication of bifunctional core-shell Fe3O4 particles coated with ultrathin phosphor layer

PubMed Central

2013-01-01

Bifunctional monodispersed Fe3O4 particles coated with an ultrathin Y2O3:Tb3+ shell layer were fabricated using a facile urea-based homogeneous precipitation method. The obtained composite particles were characterized by powder X-ray diffraction, transmission electron microscopy (TEM), quantum design vibrating sample magnetometry, and photoluminescence (PL) spectroscopy. TEM revealed uniform spherical core-shell-structured composites ranging in size from 306 to 330 nm with a shell thickness of approximately 25 nm. PL spectroscopy confirmed that the synthesized composites displayed a strong eye-visible green light emission. Magnetic measurements indicated that the composite particles obtained also exhibited strong superparamagnetic behavior at room temperature. Therefore, the inner Fe3O4 core and outer Y2O3:Tb3+ shell layer endow the composites with both robust magnetic properties and strong eye-visible luminescent properties. These composite materials have potential use in magnetic targeting and bioseparation, simultaneously coupled with luminescent imaging. PMID:23962025

Fabrication of bifunctional core-shell Fe3O4 particles coated with ultrathin phosphor layer

NASA Astrophysics Data System (ADS)

Atabaev, Timur Sh; Kim, Hyung-Kook; Hwang, Yoon-Hwae

2013-08-01

Bifunctional monodispersed Fe3O4 particles coated with an ultrathin Y2O3:Tb3+ shell layer were fabricated using a facile urea-based homogeneous precipitation method. The obtained composite particles were characterized by powder X-ray diffraction, transmission electron microscopy (TEM), quantum design vibrating sample magnetometry, and photoluminescence (PL) spectroscopy. TEM revealed uniform spherical core-shell-structured composites ranging in size from 306 to 330 nm with a shell thickness of approximately 25 nm. PL spectroscopy confirmed that the synthesized composites displayed a strong eye-visible green light emission. Magnetic measurements indicated that the composite particles obtained also exhibited strong superparamagnetic behavior at room temperature. Therefore, the inner Fe3O4 core and outer Y2O3:Tb3+ shell layer endow the composites with both robust magnetic properties and strong eye-visible luminescent properties. These composite materials have potential use in magnetic targeting and bioseparation, simultaneously coupled with luminescent imaging.

Exploring the applicability and limitations of selected optical scattering instruments for PM mass measurement

NASA Astrophysics Data System (ADS)

Zhang, Jie; Marto, Joseph P.; Schwab, James J.

2018-05-01

Two optical scattering instruments for particle mass measurement, the Thermo Personal Data RAM (PDR-1500) and the TSI Environmental DustTrak DRX (Model 8543) were evaluated by (1) using poly- and mono-disperse test aerosol in the laboratory, and (2) sampling ambient aerosol. The responses of these optical scattering instruments to different particle characteristics (size, composition, concentration) were compared with responses from reference instruments. A Mie scattering calculation was used to explain the dependence of the optical instruments' response to aerosol size and composition. Concurrently, the detection efficiency of one Alphasense Optical Particle Counter (OPC-N2) was evaluated in the laboratory as well. The relationship between aerosol mass concentration and optical scattering was determined to be strongly dependent on aerosol size and to a lesser extent on aerosol composition (as reflected in the refractive indices of the materials tested) based on ambient measurements. This confirms that there is no simple way to use optical scattering instruments over a wide range of conditions without adjustments based on knowledge of aerosol size and composition. In particular, a test period measuring ambient aerosol with optical scattering instruments and a mass based method (an Aerodyne Aerosol Mass Spectrometer) determined that roughly two thirds of the variance (R2 = 0.64) of the optical to mass signal ratio is explained by the aerosol mass median diameter alone. These observations and calculations help evaluate the applicability and limitations of these optical scattering instruments, and provide guidance to designing suitable applications for each instrument by considering aerosol sources and aerosol size.

Combustion aerosols: factors governing their size and composition and implications to human health.

PubMed

Lighty, J S; Veranth, J M; Sarofim, A F

2000-09-01

Particulate matter (PM) emissions from stationary combustion sources burning coal, fuel oil, biomass, and waste, and PM from internal combustion (IC) engines burning gasoline and diesel, are a significant source of primary particles smaller than 2.5 microns (PM2.5) in urban areas. Combustion-generated particles are generally smaller than geologically produced dust and have unique chemical composition and morphology. The fundamental processes affecting formation of combustion PM and the emission characteristics of important applications are reviewed. Particles containing transition metals, ultrafine particles, and soot are emphasized because these types of particles have been studied extensively, and their emissions are controlled by the fuel composition and the oxidant-temperature-mixing history from the flame to the stack. There is a need for better integration of the combustion, air pollution control, atmospheric chemistry, and inhalation health research communities. Epidemiology has demonstrated that susceptible individuals are being harmed by ambient PM. Particle surface area, number of ultrafine particles, bioavailable transition metals, polycyclic aromatic hydrocarbons (PAH), and other particle-bound organic compounds are suspected to be more important than particle mass in determining the effects of air pollution. Time- and size-resolved PM measurements are needed for testing mechanistic toxicological hypotheses, for characterizing the relationship between combustion operating conditions and transient emissions, and for source apportionment studies to develop air quality plans. Citations are provided to more specialized reviews, and the concluding comments make suggestions for further research.

Colloids in the River Inn

NASA Astrophysics Data System (ADS)

Ueckert, Martina; Baumann, Thomas

2014-05-01

In the light of an increasing number of technical applications using nanoparticles and reports of adverse effects of engineered nanoparticles, research on the occurrence and stability of particles in all compartments has to be intensified. Colloids in river water represent the geologic setting, environmental conditions, and the anthropogenic use in its catchment. The river not only acts as a sink for nanoparticles but also as the source term due to exchange in the hyporheic zone and in bank filtration setups. The concentration, size distribution and elemental composition of particles in the River Inn were studied from the source in the Swiss Alps to the river mouth at Passau. Samples were collected after each tributary from a sub-catchment and filtered on-site. The elemental composition was determined after acid digestion with ICP/MS. SEM/EDX analyses provided morphological and elemental information for single particles. A complementary chemical analysis of the river water was performed to assess the geochemical stability of indvidual particles. Particles in the upper, rural parts mainly reveal changes in the geological setting of the tributary catchments. Not unexpectedly, particles originating from crystalline rocks, were more stable than particles originating from calcareous rocks. Anthropogenic and industrial influences increase in the lower parts. This went together with a change of the size distribution, an increase of the number of organic particles, and a decrease of the microfauna. Interestingly, specific leisure activities in a sub-catchment, like extensive downhill skiing, manifest itself in the particle composition.

Dragon kings of the deep sea: marine particles deviate markedly from the common number-size spectrum.

PubMed

Bochdansky, Alexander B; Clouse, Melissa A; Herndl, Gerhard J

2016-03-04

Particles are the major vector for the transfer of carbon from the upper ocean to the deep sea. However, little is known about their abundance, composition and role at depths greater than 2000 m. We present the first number-size spectrum of bathy- and abyssopelagic particles to a depth of 5500 m based on surveys performed with a custom-made holographic microscope. The particle spectrum was unusual in that particles of several millimetres in length were almost 100 times more abundant than expected from the number spectrum of smaller particles, thereby meeting the definition of "dragon kings." Marine snow particles overwhelmingly contributed to the total particle volume (95-98%). Approximately 1/3 of the particles in the dragon-king size domain contained large amounts of transparent exopolymers with little ballast, which likely either make them neutrally buoyant or cause them to sink slowly. Dragon-king particles thus provide large volumes of unique microenvironments that may help to explain discrepancies in deep-sea biogeochemical budgets.

Particle Size, Composition, and Ocean Temperature Govern the Global Distribution of Particle Transfer Efficiency to the Mesopelagic

NASA Astrophysics Data System (ADS)

Cram, J. A.; Weber, T. S.; Leung, S.; Deutsch, C. A.

2016-02-01

New analyses of geochemical tracer data detect significant differences between ocean basins in the depth scale of particle remineralization, with deepest in high latitudes, shallowest in the subtropical gyres, and intermediate in the tropics. We evaluate the possible causes of this pattern using a mechanistic model of particle dynamics that includes microbial colonization, detachment, and degradation of sinking particles. The model represents the size structure of particles, the effects of mineral ballast (diagnosed from alkalinity and silicate distributions) and seawater temperature (which influences particle velocity and microbial metabolic rates). We find that diagnosed spatial patterns in particle flux profiles can be best reproduced through a combination of surface particle size distribution and temperature, which both favor low transfer efficiency in subtropical gyres, and high transfer efficiency in higher latitudes and intermediate tropical values. Particle mineral content is shown to significantly modulate these patterns, albeit with a high remaining uncertainty. Implications of these mechanisms for changes in biological carbon storage in a warmer ocean are examined.

Collection of microparticles at high balloon altitudes in the stratosphere

NASA Technical Reports Server (NTRS)

Testa, John P., Jr.; Stephens, John R.; Berg, Walter W.; Cahill, Thomas A.; Onaka, Takashi

1990-01-01

Stratospheric particles were collected between 34 and 36 km, using a combination of cascade impactors and filters lofted by a large helium balloon, and the particle concentration, size distribution, and bulk elemental composition were determined using SEM and proton-induced X-ray emission (PEXE) instrument. In addition, datailed particle morphology, elemental analysis, and electron diffraction data were obtained on 23 particles using a TEM. The concentration of particles between 0.045 and 1.0 micron in radius was found to be orders of magnitude above the concentrations predicted by the model of Hunten et al. (1980), but was consistent with balloon and satellite observations. Elemental composition analysis showed the presence of Cl, S, Ti, Fe, Br, Ni, Zr, Zn, Sr, and Cu in decreasing order of concentration. The 23 particles analyzed by TEM ranged from Al-rich silicates to almost pure Fe to one containing almost exclusively Ba and S. None were definitely chondritic in composition.

Production of morphology-controllable porous hyaluronic acid particles using a spray-drying method.

PubMed

Iskandar, Ferry; Nandiyanto, Asep Bayu Dani; Widiyastuti, W; Young, Lee Sin; Okuyama, Kikuo; Gradon, Leon

2009-05-01

Hyaluronic acid (HA) porous particles with controllable porosity and pore size, ranging from 100 to 300 nm, were successfully prepared using a colloidal templating and spray-drying method. HA powder and polystyrene latex (PSL) particles, which were used as the precursor and templating agent, respectively, were mixed in aqueous solution and spray-dried using a two-fluid nozzle system to produce HA and PSL composite particles. Water was evaporated during spray-drying using heated air with a temperature of 120 degrees C. This simple process was completed within several seconds. The prepared particles were collected and washed with an organic solvent to dissolve the PSL templating agent. The porosity and pore size of the resulting particles were easily controlled by changing the initial mass ratio of precursor to templating agent, i.e., HA to PSL, and by altering the size of the PSL template particles.

Surface-coated fly ash used as filler in biodegradable poly(vinyl alcohol) composite films: Part 1—The modification process

NASA Astrophysics Data System (ADS)

Nath, D. C. D.; Bandyopadhyay, S.; Gupta, S.; Yu, A.; Blackburn, D.; White, C.

2010-02-01

The surfaces of fly ash (FA) particles were modified by surfactant, sodium lauryl sulphate (SLS) and used in fabrication of composite films with polyvinyl alcohol (PVA). Both unmodified fly ash (FA) and modified fly ash (SLS-FA) samples were examined using a range of analytical tools including X-ray fluorescence spectroscopy (XRF), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared (FTIR) and X-ray photoelectron spectroscopy (XPS). The distribution patterns of SLS-FA particles were shifted to the higher regions compared to FA by adding 1.2-4.2 μm in the ranges between 2 and 25 μm, whereas the modification process reduced the size of the particles over 25 μm due to grinding during the activation process. The increased 1.2-4.2 μm in average can be considered the thickness of the surfactant on the SLS-FA surface. On the oxides based chemical analysis by XRF, the compositions were almost unchanged. SEM and TEM were visualised the irregular sizes morphology mostly spherical of the particles, although it is impossible to capture the images of exactly same particles in modified and unmodified forms. The composite films reinforced with SLS-FA showed 33% higher strength than those of FA filled films. The enhancement of tensile strength attributed from the level of physical bonding between SLS-FA and PVA surfaces.

Application of rotatable central composite design in the preparation and optimization of poly(lactic-co-glycolic acid) nanoparticles for controlled delivery of paclitaxel.

PubMed

Kollipara, Sivacharan; Bende, Girish; Movva, Snehalatha; Saha, Ranendra

2010-11-01

Polymeric carrier systems of paclitaxel (PCT) offer advantages over only available formulation Taxol® in terms of enhancing therapeutic efficacy and eliminating adverse effects. The objective of the present study was to prepare poly (lactic-co-glycolic acid) nanoparticles containing PCT using emulsion solvent evaporation technique. Critical factors involved in the processing method were identified and optimized by scientific, efficient rotatable central composite design aiming at low mean particle size and high entrapment efficiency. Twenty different experiments were designed and each formulation was evaluated for mean particle size and entrapment efficiency. The optimized formulation was evaluated for in vitro drug release, and absorption characteristics were studied using in situ rat intestinal permeability study. Amount of polymer and duration of ultrasonication were found to have significant effect on mean particle size and entrapment efficiency. First-order interactions of amount of miglyol with amount of polymer were significant in case of mean particle size, whereas second-order interactions of polymer were significant in mean particle size and entrapment efficiency. The developed quadratic model showed high correlation (R(2) > 0.85) between predicted response and studied factors. The optimized formulation had low mean particle size (231.68 nm) and high entrapment efficiency (95.18%) with 4.88% drug content. The optimized formulation showed controlled release of PCT for more than 72 hours. In situ absorption study showed faster and enhanced extent of absorption of PCT from nanoparticles compared to pure drug. The poly (lactic-co-glycolic acid) nanoparticles containing PCT may be of clinical importance in enhancing its oral bioavailability.

Evaluation of Particle Size Influence on Proximate Composition, Physicochemical, Techno-Functional and Physio-Functional Properties of Flours Obtained from Persimmon (Diospyros kaki Trumb.) Coproducts.

PubMed

Lucas-González, Raquel; Viuda-Martos, Manuel; Pérez-Álvarez, José Ángel; Fernández-López, Juana

2017-03-01

The aim of the work was to study the influence of particle size in the composition, physicochemical, techno-functional and physio-functional properties of two flours obtained from persimmon (Diospyros kaki Trumb. cvs. 'Rojo Brillante' (RBF) and 'Triump' (THF) coproducts. The cultivar (RBF and THF) and particle size significantly affected all parameters under study, although depending on the evaluated property, only one of these effects predominated. Carbohydrates (38.07-46.98 g/100 g) and total dietary fiber (32.07-43.57 g/100 g) were the main components in both flours (RBF and THF). Furthermore, insoluble dietary fiber represented more than 68% of total dietary fiber content. All color properties studied were influenced by cultivar and particle size. For both cultivars, the lower particle size, the higher lightness and hue values. RBF flours showed high values for emulsifying activity (69.33-74.00 mL/mL), while THF presented high values for water holding capacity (WHC: 9.47-12.19 g water/g sample). The bile holding capacity (BHC) and fat/oil binding values were, in general, higher in RBF (19.61-12.19 g bile/g sample and 11.98-9.07, respectively) than THF (16.12-12.40 g bile/g sample and 9.78-7.96, respectively). The effect of particle size was really evident in both WHC and BHC. Due to their dietary fiber content, techno-functional and physio-functional properties, persimmon flours seem to have a good profile to be used as potential functional ingredient.

The characterisation of diesel exhaust particles - composition, size distribution and partitioning.

PubMed

Alam, Mohammed S; Zeraati-Rezaei, Soheil; Stark, Christopher P; Liang, Zhirong; Xu, Hongming; Harrison, Roy M

2016-07-18

A number of major research questions remain concerning the sources and properties of road traffic generated particulate matter. A full understanding of the composition of primary vehicle exhaust aerosol and its contribution to secondary organic aerosol (SOA) formation still remains elusive, and many uncertainties exist relating to the semi-volatile component of the particles. Semi-Volatile Organic Compounds (SVOCs) are compounds which partition directly between the gas and aerosol phases under ambient conditions. The SVOCs in engine exhaust are typically hydrocarbons in the C15-C35 range, and are largely uncharacterised because they are unresolved by traditional gas chromatography, forming a large hump in the chromatogram referred to as Unresolved Complex Mixture (UCM). In this study, thermal desorption coupled to comprehensive Two Dimensional Gas-Chromatography Time-of-Flight Mass-Spectrometry (TD-GC × GC-ToF-MS) was exploited to characterise and quantify the composition of SVOCs from the exhaust emission. Samples were collected from the exhaust of a diesel engine, sampling before and after a diesel oxidation catalyst (DOC), while testing at steady state conditions. Engine exhaust was diluted with air and collected using both filter and impaction (nano-MOUDI), to resolve total mass and size resolved mass respectively. Adsorption tubes were utilised to collect SVOCs in the gas phase and they were then analysed using thermal desorption, while particle size distribution was evaluated by sampling with a DMS500. The SVOCs were observed to contain predominantly n-alkanes, branched alkanes, alkyl-cycloalkanes, alkyl-benzenes, PAHs and various cyclic aromatics. Particle phase compounds identified were similar to those observed in engine lubricants, while vapour phase constituents were similar to those measured in fuels. Preliminary results are presented illustrating differences in the particle size distribution and SVOCs composition when collecting samples with and without a DOC. The results indicate that the DOC tested is of very limited efficiency, under the studied engine operating conditions, for removal of SVOCs, especially at the upper end of the molecular weight range.

Bacteria and Composite Particles in the Glacier-Fed Systems of British Columbia and Alberta, Canada

NASA Astrophysics Data System (ADS)

Barrett, D. C.; Hodder, K. R.

2014-12-01

In controlled environments, bacteria and suspended sediment particles are linked via the creation of a composite structure ("bacteria-sediment associations"; BSA), with associated effects on size, density and hydrodynamics. However, the presence of these particles, and their corresponding effect on sedimentary processes is not well documented in many environments. Here, we compile field data from 20 glacier-fed systems in British Columbia and Alberta, Canada, to illustrate: 1) the presence, and (quantity) of bacteria-sediment associations; 2) the presence of in-situ composite particles and their associated settling velocities; 3) the simulated impact of bacteria-sediment associations on settling velocity via controlled manipulation in the laboratory. In general, a significant portion of the fine suspended sediment typical of these systems was associated with bacteria and/or present in a composite-form -- not as primary, individual particles. Four key findings include: 1) Along a 80 kilometre river transect, up to 40% of bacteria were associated with sediment particles; 2) Manipulation of bacteria concentration in the laboratory has revealed a positive relationship between sediment settling velocity, creation of composite particles and bacteria concentration; 3) Composite particles dominated the suspended sediment load among all 20 systems, especially for larger particles; and 4) Measurements reveal these composite particles are settling at rates significantly below that predicted by Stokes Law. The formation of composite particles is especially important in lakes where laminated sediments are used for paleoenvironmental reconstruction (varved), as bacteria can modulate the rate at which some of this sediment reaches the lake floor. These results highlight the importance of bacteria in Earth surface processes and, more specifically, the sediment dynamics within glacier-fed systems.

Mesoporous Silica Matrix as a Tool for Minimizing Dipolar Interactions in NiFe2O4 and ZnFe2O4 Nanoparticles

PubMed Central

Virumbrales, Maider; Saez-Puche, Regino; Torralvo, María José; Blanco-Gutierrez, Veronica

2017-01-01

NiFe2O4 and ZnFe2O4 nanoparticles have been prepared encased in the MCM (Mobile Composition of Matter) type matrix. Their magnetic behavior has been studied and compared with that corresponding to particles of the same composition and of a similar size (prepared and embedded in amorphous silica or as bare particles). This study has allowed elucidation of the role exerted by the matrix and interparticle interactions in the magnetic behavior of each ferrite system. Thus, very different superparamagnetic behavior has been found in ferrite particles of similar size depending on the surrounding media. Also, the obtained results clearly provide evidence of the vastly different magnetic behavior for each ferrite system. PMID:28640197

Marine Emissions and Atmospheric Processing Influence Aerosol Mixing States in the Bering Strait and Chukchi Sea

NASA Astrophysics Data System (ADS)

Kirpes, R.; Rodriguez, B.; Kim, S.; Park, K.; China, S.; Laskin, A.; Pratt, K.

2017-12-01

The Arctic region is rapidly changing due to sea ice loss and increasing oil/gas development and shipping activity. These changes influence aerosol sources and composition, resulting in complex aerosol-cloud-climate feedbacks. Atmospheric particles were collected aboard the R/V Araon in July-August 2016 in the Alaskan Arctic along the Bering Strait and Chukchi Sea. Offline analysis of individual particles by microscopic and spectroscopic techniques provided information on particle size, morphology, and chemical composition. Sea spray aerosol (SSA) and organic aerosol (OA) particles were the most commonly observed particle types, and sulfate was internally mixed with both SSA and OA. Evidence of multiphase sea spray aerosol reactions was observed, with varying degrees of chlorine depletion observed along the cruise. Notably, atmospherically processed SSA, completely depleted in chlorine, and internally mixed organic and sulfate particles, were observed in samples influenced by the central Arctic Ocean. Changes in particle composition due to fog processing were also investigated. Due to the changing aerosol sources and atmospheric processes in the Arctic region, it is crucial to understand aerosol composition in order to predict climate impacts.

Proposal for a Universal Particle Detector Experiment

NASA Technical Reports Server (NTRS)

Lesho, J. C.; Cain, R. P; Uy, O. M.

1993-01-01

The Universal Particle Detector Experiment (UPDE), which consists of parallel planes of two diode laser beams of different wavelengths and a large surface metal oxide semiconductor (MOS) impact detector, is proposed. It will be used to perform real-time monitoring of contamination particles and meteoroids impacting the spacecraft surface with high resolution of time, position, direction, and velocity. The UPDE will discriminate between contaminants and meteoroids, and will determine their velocity and size distribution around the spacecraft environment. With two different color diode lasers, the contaminant and meteroid composition will also be determined based on laboratory calibration with different materials. Secondary particles dislodged from the top aluminum surface of the MOS detector will also be measured to determine the kinetic energy losses during energetic meteoroid impacts. The velocity range of this instrument is 0.1 m/s to more than 14 km/s, while its size sensitivity is from 0.2 microns to millimeter-sized particles. The particulate measurements in space of the kind proposed will be the first simultaneous multipurpose particulate experiment that includes velocities from very slow to hypervelocities, sizes from submicrometer- to pellet-sized diameters, chemical analysis of the particulate composition, and measurements of the kinetic energy losses after energetic impacts of meteroids. The experiment will provide contamination particles and orbital debris data that are critically needed for our present understanding of the space environment. The data will also be used to validate contamination and orbital debris models for predicting optimal configuration of future space sensors and for understanding their effects on sensitive surfaces such as mirrors, lenses, paints, and thermal blankets.

Proposal for a universal particle detector experiment

NASA Astrophysics Data System (ADS)

Lesho, J. C.; Cain, R. P.; Uy, O. M.

The Universal Particle Detector Experiment (UPDE), which consists of parallel planes of two diode laser beams of different wavelengths and a large surface metal oxide semiconductor (MOS) impact detector, is proposed. It will be used to perform real-time monitoring of contamination particles and meteoroids impacting the spacecraft surface with high resolution of time, position, direction, and velocity. The UPDE will discriminate between contaminants and meteoroids, and will determine their velocity and size distribution around the spacecraft environment. With two different color diode lasers, the contaminant and meteroid composition will also be determined based on laboratory calibration with different materials. Secondary particles dislodged from the top aluminum surface of the MOS detector will also be measured to determine the kinetic energy losses during energetic meteoroid impacts. The velocity range of this instrument is 0.1 m/s to more than 14 km/s, while its size sensitivity is from 0.2 microns to millimeter-sized particles. The particulate measurements in space of the kind proposed will be the first simultaneous multipurpose particulate experiment that includes velocities from very slow to hypervelocities, sizes from submicrometer- to pellet-sized diameters, chemical analysis of the particulate composition, and measurements of the kinetic energy losses after energetic impacts of meteroids. The experiment will provide contamination particles and orbital debris data that are critically needed for our present understanding of the space environment. The data will also be used to validate contamination and orbital debris models for predicting optimal configuration of future space sensors and for understanding their effects on sensitive surfaces such as mirrors, lenses, paints, and thermal blankets.

Combined use of optical and electron microscopic techniques for the measurement of hygroscopic property, chemical composition, and morphology of individual aerosol particles.

PubMed

Ahn, Kang-Ho; Kim, Sun-Man; Jung, Hae-Jin; Lee, Mi-Jung; Eom, Hyo-Jin; Maskey, Shila; Ro, Chul-Un

2010-10-01

In this work, an analytical method for the characterization of the hygroscopic property, chemical composition, and morphology of individual aerosol particles is introduced. The method, which is based on the combined use of optical and electron microscopic techniques, is simple and easy to apply. An optical microscopic technique was used to perform the visual observation of the phase transformation and hygroscopic growth of aerosol particles on a single particle level. A quantitative energy-dispersive electron probe X-ray microanalysis, named low-Z particle EPMA, was used to perform a quantitative chemical speciation of the same individual particles after the measurement of the hygroscopic property. To validate the analytical methodology, the hygroscopic properties of artificially generated NaCl, KCl, (NH(4))(2)SO(4), and Na(2)SO(4) aerosol particles of micrometer size were investigated. The practical applicability of the analytical method for studying the hygroscopic property, chemical composition, and morphology of ambient aerosol particles is demonstrated.

Effects of wood fiber characteristics on mechanical properties of wood/polypropylene composites

Treesearch

Nicole M. Stark; Robert E. Rowlands

2003-01-01

Commercial wood flour, the most common wood-derived filler for thermoplastics, is produced in a mixture of particle sizes and generally has a lower aspect ratio than wood and other natural fibers. To understand how wood flour and fiber characteristics influence the mechanical properties of polypropylene composites, we first investigated the effect of different sizes of...

Production of fine calcium powders by centrifugal atomization with rotating quench bath

DOE PAGES

Tian, Liang; Ames Lab. and Iowa State Univ., Ames, IA; Anderson, Iver; ...

2016-02-08

Recently, a novel Al/Ca composite was produced by severe plastic deformation of Al powders and Ca granules for possible use as a high-voltage power transmission conductor. Since the strength of such composites is inversely proportional to the Ca filament size, fine Ca powders (less than ~250 μm) are needed to achieve the desired high strength for the powder metallurgy production of an Al-matrix composite reinforced by nano-scale Ca filaments. However, fine Ca powders are not commercially available. Therefore, we have developed a method to produce fine Ca powders via centrifugal atomization to supply Ca powder for prototype development of Al/Camore » composite conductor. A secondary goal of the project was to demonstrate that Ca powder can be safely prepared, stored, and handled and could potentially be scaled for commercial production. Our results showed that centrifugal atomization can yield as much as 83 vol. % Ca powder particles smaller than 250 μm. The mean particle size sometimes matches, sometimes deviates substantially from the predictions of the Champagne & Anger equation likely due to unexpected secondary atomization. The particle size distribution is typical for a ligament-disintegration atomization mode. Scanning electron micrographs showed that the morphology of these Ca powders varied with powder size. Spark testing and auto-ignition tests indicated that the atomized powders were difficult to ignite, providing confidence that this material can be handled safely in air.« less

Ultrasonic agitation-floating classification of nano-sized Ba-Mg ferrites particles formed by using self-propagating high temperature synthesis and fabrication of nickel-ferrites thin sheet by pulse-electroforming.

PubMed

Choi, Yong

2013-01-01

Nickel-nano-sized ferrites composites sheet for electromagnetic shielding was produced by pulse-electroforming in a modified nickel sulfamate solution. The ferrite particles were prepared by self-propagating high temperature synthesis (SHS) followed by mechanical milling, and classified with an ultrasonic agitation-floating unit to obtain about 100 nm in size. Average combustion temperature and combustion propagating rate during SHS reaction were 1190 K and 5.8 mm/sec at the oxygen pressure of 1.0 MPa, respectively. The nickel-ferrite composite sheet had preferred orientation which (100) pole clearly concentrated to normal direction, whereas, (110) and (111) poles tended to split to the longitudinal direction, respectively. Maximum magnetization, residual magnetization and coercive force of the nano-sized ferrites were 27.13 A x m2/kg, 6.4 A x m2/kg and 14.58 kA/m, respectively. Complex permeability of the composites decreased with an increase in frequency, and its real value (mu'r) had the maximum at about 0.3 GHz. The dielectric constants of the composites were epsilon'r = 6.7 and epsilon"r = 0.

Effect of secondary organic aerosol coating thickness on the real-time detection and characterization of biomass-burning soot by two particle mass spectrometers

DOE PAGES

Ahern, Adam T.; Subramanian, Ramachandran; Saliba, Georges; ...

2016-12-22

Biomass burning is a large source of light-absorbing refractory black carbon (rBC) particles with a wide range of morphologies and sizes. The net radiative forcing from these particles is strongly dependent on the amount and composition of non-light-absorbing material internally mixed with the rBC and on the morphology of the mixed particles. Understanding how the mixing state and morphology of biomass-burning aerosol evolves in the atmosphere is critical for constraining the influence of these particles on radiative forcing and climate. We investigated the response of two commercial laser-based particle mass spectrometers, the vacuum ultraviolet (VUV) ablation LAAPTOF and the IRmore » vaporization SP-AMS, to monodisperse biomass-burning particles as we sequentially coated the particles with secondary organic aerosol (SOA) from α-pinene ozonolysis. We studied three mobility-selected soot core sizes, each with a number of successively thicker coatings of SOA applied. Using IR laser vaporization, the SP-AMS had different changes in sensitivity to rBC compared to potassium as a function of applied SOA coatings. We show that this is due to different effective beam widths for the IR laser vaporization region of potassium versus black carbon. The SP-AMS's sensitivity to black carbon (BC) mass was not observed to plateau following successive SOA coatings, despite achieving high OA : BC mass ratios greater than 9. We also measured the ion fragmentation pattern of biomass-burning rBC and found it changed only slightly with increasing SOA mass. The average organic matter ion signal measured by the LAAPTOF demonstrated a positive correlation with the condensed SOA mass on individual particles, despite the inhomogeneity of the particle core compositions. This demonstrates that the LAAPTOF can obtain quantitative mass measurements of aged soot-particle composition from realistic biomass-burning particles with complex morphologies and composition.« less

Effect of secondary organic aerosol coating thickness on the real-time detection and characterization of biomass-burning soot by two particle mass spectrometers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ahern, Adam T.; Subramanian, Ramachandran; Saliba, Georges

Biomass burning is a large source of light-absorbing refractory black carbon (rBC) particles with a wide range of morphologies and sizes. The net radiative forcing from these particles is strongly dependent on the amount and composition of non-light-absorbing material internally mixed with the rBC and on the morphology of the mixed particles. Understanding how the mixing state and morphology of biomass-burning aerosol evolves in the atmosphere is critical for constraining the influence of these particles on radiative forcing and climate. We investigated the response of two commercial laser-based particle mass spectrometers, the vacuum ultraviolet (VUV) ablation LAAPTOF and the IRmore » vaporization SP-AMS, to monodisperse biomass-burning particles as we sequentially coated the particles with secondary organic aerosol (SOA) from α-pinene ozonolysis. We studied three mobility-selected soot core sizes, each with a number of successively thicker coatings of SOA applied. Using IR laser vaporization, the SP-AMS had different changes in sensitivity to rBC compared to potassium as a function of applied SOA coatings. We show that this is due to different effective beam widths for the IR laser vaporization region of potassium versus black carbon. The SP-AMS's sensitivity to black carbon (BC) mass was not observed to plateau following successive SOA coatings, despite achieving high OA : BC mass ratios greater than 9. We also measured the ion fragmentation pattern of biomass-burning rBC and found it changed only slightly with increasing SOA mass. The average organic matter ion signal measured by the LAAPTOF demonstrated a positive correlation with the condensed SOA mass on individual particles, despite the inhomogeneity of the particle core compositions. This demonstrates that the LAAPTOF can obtain quantitative mass measurements of aged soot-particle composition from realistic biomass-burning particles with complex morphologies and composition.« less

Toward Quantifying the Mass-Based Hygroscopicity of Individual Submicron Atmospheric Aerosol Particles with STXM/NEXAFS and SEM/EDX

NASA Astrophysics Data System (ADS)

Yancey Piens, D.; Kelly, S. T.; OBrien, R. E.; Wang, B.; Petters, M. D.; Laskin, A.; Gilles, M. K.

2014-12-01

The hygroscopic behavior of atmospheric aerosols influences their optical and cloud-nucleation properties, and therefore affects climate. Although changes in particle size as a function of relative humidity have often been used to quantify the hygroscopic behavior of submicron aerosol particles, it has been noted that calculations of hygroscopicity based on size contain error due to particle porosity, non-ideal volume additivity and changes in surface tension. We will present a method to quantify the hygroscopic behavior of submicron aerosol particles based on changes in mass, rather than size, as a function of relative humidity. This method results from a novel experimental approach combining scanning transmission x-ray microscopy with near-edge x-ray absorption fine spectroscopy (STXM/NEXAFS), as well as scanning electron microscopy with energy dispersive x-ray spectroscopy (SEM/EDX) on the same individual particles. First, using STXM/NEXAFS, our methods are applied to aerosol particles of known composition ‒ for instance ammonium sulfate, sodium bromide and levoglucosan ‒ and validated by theory. Then, using STXM/NEXAFS and SEM/EDX, these methods are extended to mixed atmospheric aerosol particles collected in the field at the DOE Atmospheric Radiation Measurement (ARM) Climate Research Facility at the Southern Great Planes sampling site in Oklahoma, USA. We have observed and quantified a range of hygroscopic behaviors which are correlated to the composition and morphology of individual aerosol particles. These methods will have implications for parameterizing aerosol mixing state and cloud-nucleation activity in atmospheric models.

Thermal Energy Transfer Through All Ceramic Restorations

DTIC Science & Technology

2016-06-01

particles, but newer generations have reduced the size and narrowed the range of particles in the matrix . This evolution in ceramics improved the...crystalline second phase. These ceramics have a lithium silicate glass matrix with approximately 70% lithium-disilicate crystal fill. The micron size and... composition category described by Giordano and McLaren are the Interpenetrating Phase Ceramics . These ceramics were developed as an alternative to the

Uncertainty in Predicting CCN Activity of Aged and Primary Aerosols

NASA Astrophysics Data System (ADS)

Zhang, Fang; Wang, Yuying; Peng, Jianfei; Ren, Jingye; Collins, Don; Zhang, Renyi; Sun, Yele; Yang, Xin; Li, Zhanqing

2017-11-01

Understanding particle CCN activity in diverse atmospheres is crucial when evaluating aerosol indirect effects. Here aerosols measured at three sites in China were categorized as different types for attributing uncertainties in CCN prediction in terms of a comprehensive data set including size-resolved CCN activity, size-resolved hygroscopic growth factor, and chemical composition. We show that CCN activity for aged aerosols is unexpectedly underestimated 22% at a supersaturation (S) of 0.2% when using κ-Kohler theory with an assumption of an internal mixture with measured bulk composition that has typically resulted in an overestimate of the CCN activity in previous studies. We conclude that the underestimation stems from neglect of the effect of aging/coating on particle hygroscopicity, which is not considered properly in most current models. This effect enhanced the hygroscopicity parameter (κ) by between 11% (polluted conditions) and 30% (clean days), as indicated in diurnal cycles of κ based on measurements by different instruments. In the urban Beijing atmosphere heavily influenced by fresh emissions, the CCN activity was overestimated by 45% at S = 0.2%, likely because of inaccurate assumptions of particle mixing state and because of variability of chemical composition over the particle size range. For both fresh and aged aerosols, CCN prediction exhibits very limited sensitivity to κSOA, implying a critical role of other factors like mixing of aerosol components within and between particles in regulating CCN activity. Our findings could help improving CCN parameterization in climate models.

[Influence of wall polymer and preparation process on the particle size and encapsulation of hemoglobin microcapsules].

PubMed

Qiu, Wei; Ma, Guang-Hui; Meng, Fan-Tao; Su, Zhi-Guo

2004-03-01

Methoxypoly (ethylene glycol)- block-poly (DL-lactide) (PELA) microcapsules containing bovine hemoglobin (BHb) were prepared by a W/O/W double emulsion-solvent diffusion process. The P50 and Hill coeffcient were 3466 Pa and 2.4 respectively, which were near to the natural bioactivity of bovine hemoglobin. The results suggested that polymer composition had significant influence on encapsulation efficiency and particle size of microcapsules. The encapsulation efficiency could reach 90% and the particle size 3 - 5 microm when the PELA copolymer containing MPEG 2000 block was used. The encapsulation efficiency and particle size increased with the concentration of PELA. Increasing the concentrations of NaCl in outer aqueous solution resulted in the increase of encapsulation efficiency and the decrease of particle size. As the concentration of stabilizer in outer aqueous solution increased in the range of 10 g/L to 20 g/L, the particle size reduced while encapsulation efficiency was increased, further increase of the stabilizer concentration would decrease encapsulation efficiency. Increasing of primary emulsion stirring rate was advantageous to the improvement of encapsulation efficiency though it had little influence on the particle size. The influence of re-emulsion stirring rate was complicated, which was not apparent in the case of large volume of re-emulsion solution. When the wall polymer and primary emulsion stirring rate were fixed, the encapsulation efficiency decreased as the particle size reduced.

A case study of highly time-resolved evolution of aerosol chemical composition and optical properties during severe haze pollution in Shanghai, China

NASA Astrophysics Data System (ADS)

Zhu, W.; Cheng, Z.; Lou, S.

2017-12-01

Despite of extensive efforts into characterization of the sources in severe haze pollution periods in the megacity of Shanghai, the study of aerosol composition, mass-size distribution and optical properties to PM1 in the pollution periods remain poorly understood. Here we conducted a 47days real-time measurement of submicron aerosol (PM1) composition and size distribution by a High-Resolution Time-of-Flight Aerosol Mass spectrometer (HR-TOF-AMS), particle light scattering by a Cavity Attenuated Phase Shift ALBedo monitor (CAPS-ALB) and Photoacoustic Extinctionmeter (PAX) in Shanghai, China, from November 28, 2016 to January 12, 2017. The average PM1 concentration was 85.9(±14.7) μg/m3 during the pollution period, which was nearly 4 times higher than that of clean period. Increased scattering coefficient during EP was associated with higher secondary inorganic aerosols and organics. We also observed organics mass size distribution for different pollution extents showing different distribution characteristics. There were no obvious differences for ammonium nitrate and ammonium sulfate among the pollution periods, which represented single peak distributions, and peaks ranged at 650-700nm and 700nm, respectively. A strong relationship can be expected between PM1 compounds mass concentration size distribution and scattering coefficient, suggesting that chemical composition, size distribution of the particles and their variations could also contribute to the extinction coefficients. Organics and secondary inorganic species to particle light scattering were quantified. The results showed that organics and ammonium nitrate were the largest contribution to scattering coefficients of PM1. The contribution of (NH4)2SO4 to the light scattering exceeded that of NH4NO3 during clean period due to the enhanced sulfate concentrations. Our results elucidate substantial changes of aerosol composition, formation mechanisms, size distribution and optical properties due to local emissions, region transports and meteorological changes in the pollution period.

Micromechanics-based magneto-elastic constitutive modeling of particulate composites

NASA Astrophysics Data System (ADS)

Yin, Huiming

Modified Green's functions are derived for three situations: a magnetic field caused by a local magnetization, a displacement field caused by a local body force and a displacement field caused by a local prescribed eigenstrain. Based on these functions, an explicit solution is derived for two magnetic particles embedded in the infinite medium under external magnetic and mechanical loading. A general solution for numerable magnetic particles embedded in an infinite domain is then provided in integral form. Two-phase composites containing spherical magnetic particles of the same size are considered for three kinds of microstructures. With chain-structured composites, particle interactions in the same chain are considered and a transversely isotropic effective elasticity is obtained. For periodic composites, an eight-particle interaction model is developed and provides a cubic symmetric effective elasticity. In the random composite, pair-wise particle interactions are integrated from all possible positions and an isotropic effective property is reached. This method is further extended to functionally graded composites. Magneto-mechanical behavior is studied for the chain-structured composite and the random composite. Effective magnetic permeability, effective magnetostriction and field-dependent effective elasticity are investigated. It is seen that the chain-structured composite is more sensitive to the magnetic field than the random composite; a composite consisting of only 5% of chain-structured particles can provide a larger magnetostriction and a larger change of effective elasticity than an equivalent composite consisting of 30% of random dispersed particles. Moreover, the effective shear modulus of the chain-structured composite rapidly increases with the magnetic field, while that for the random composite decreases. An effective hyperelastic constitutive model is further developed for a magnetostrictive particle-filled elastomer, which is sampled by using a network of body-centered cubic lattices of particles connected by macromolecular chains. The proposed hyperelastic model is able to characterize overall nonlinear elastic stress-stretch relations of the composites under general three-dimensional loading. It is seen that the effective strain energy density is proportional to the length of stretched chains in unit volume and volume fraction of particles.

Nitrogen-doped graphene catalysts: High energy wet ball milling synthesis and characterizations of functional groups and particle size variation with time and speed

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhuang, Shiqiang; Nunna, Bharath Babu; Boscoboinik, Jorge Anibal

Nitrogen-doped graphene (N-G) catalyst emerges as one of the promising non-platinum group metal (non-PGM) catalysts with the advantages of low cost, high oxygen reduction reaction (ORR) activity, stability, and selectivity to replace expensive PGM catalysts in electrochemical systems. This research investigated nanoscale high energy wet (NHEW) ball milling for the synthesis of N-G catalysts to make conventional problems such as sintering or localized overheating issues negligible. The successful synthesis of N-G catalysts with comparable catalytic performance to 10 wt% Pt/C by using this method has been published. This paper focuses on understanding the effect of grinding speed and grinding timemore » on the particle size and chemical state of N-G catalysts through the physical and chemical characterization. The research result shows that (1) the final particle size, nitrogen doping percentage, and nitrogen bonding composition of synthesized N-G catalysts are predictable and controllable by adjusting the grinding time, the grinding speed, and other relative experimental parameters; (2) the final particle size of N-G catalysts could be estimated from the derived relation between the cracking energy density and the particle size of ground material in the NHEW ball milling process with specified experimental parameters; and (3) the chemical composition of N-G catalysts synthesized by NHEW ball milling is controllable by adjusting the grinding time and grinding speed.« less

Nitrogen-doped graphene catalysts: High energy wet ball milling synthesis and characterizations of functional groups and particle size variation with time and speed

DOE PAGES

Zhuang, Shiqiang; Nunna, Bharath Babu; Boscoboinik, Jorge Anibal; ...

2017-07-26

Nitrogen-doped graphene (N-G) catalyst emerges as one of the promising non-platinum group metal (non-PGM) catalysts with the advantages of low cost, high oxygen reduction reaction (ORR) activity, stability, and selectivity to replace expensive PGM catalysts in electrochemical systems. This research investigated nanoscale high energy wet (NHEW) ball milling for the synthesis of N-G catalysts to make conventional problems such as sintering or localized overheating issues negligible. The successful synthesis of N-G catalysts with comparable catalytic performance to 10 wt% Pt/C by using this method has been published. This paper focuses on understanding the effect of grinding speed and grinding timemore » on the particle size and chemical state of N-G catalysts through the physical and chemical characterization. The research result shows that (1) the final particle size, nitrogen doping percentage, and nitrogen bonding composition of synthesized N-G catalysts are predictable and controllable by adjusting the grinding time, the grinding speed, and other relative experimental parameters; (2) the final particle size of N-G catalysts could be estimated from the derived relation between the cracking energy density and the particle size of ground material in the NHEW ball milling process with specified experimental parameters; and (3) the chemical composition of N-G catalysts synthesized by NHEW ball milling is controllable by adjusting the grinding time and grinding speed.« less

Spatio-temporal aerosol particle distributions in the UT/LMS measured by the IAGOS-CARIBIC Observatory

NASA Astrophysics Data System (ADS)

Assmann, D. N.; Hermann, M.; Weigelt, A.; Martinsson, B. G.; Brenninkmeijer, C. A. M.; Rauthe-Schoech, A.; van Velthoven, P. J. F.; Boenisch, H.; Zahn, A.

2016-12-01

Submicrometer aerosol particles in the upper troposphere and lowermost stratosphere (UT/LMS) influence the Earth`s radiation budget directly and, more important, indirectly, by acting as cloud condensation nuclei and by changing trace gas concentrations through heterogeneous chemical processes. Since 1997, regular in situ UT/LMS aerosol particle measurements have been conducted by the Leibniz Institute for Tropospheric Research, Leipzig, Germany and the University of Lund, Sweden, using the the CARIBIC (now IAGOS-CARIBIC) observatory (www.caribic-atmospheric.com) onboard a passenger aircraft. Submicrometer aerosol particle number concentrations and the aerosol particle size distribution are measured using three condensation particle counters and one optical particle size spectrometer. Moreover, particle elemental composition is determined using an aerosol impactor sampler and post-flight ion beam analysis (PIXE, PESA) of the samples in the laboratory. Based on this unique data set, including meteorological analysis, we present representative spatio-temporal distributions of particle number, surface, volume, and elemental concentrations in an altitude of 8-12 km covering a large fraction of the northern hemisphere. We discuss the measured values in the different size regimes with respect to sources and sinks in different regions. Additionally, we calculated highly resolved latitudinal and longitudinal cross sections of the particle number size distribution, probability density functions and trends in particle number concentrations, but also in elemental composition, determined from our regular measurements over more than a decade. Moreover, we present the seasonality of particle number concentration in an equivelent latitude - potential temperature coordinate framework (see figure). The results are interpreted with respect to aerosol microphysics and transport using CARIBIC trace gas data like ozone and water vapour. The influence of clouds in the troposphere and the different stratosphere-troposphere-exchange processes are clearly visible. Besides providing information about UT/LMS aerosol particle sources, transport, and sinks, these distributions can be used to validate remote sensing instruments or global atmospheric aerosol models.

Spatio-temporal aerosol particle distributions in the UT/LMS measured by the IAGOS-CARIBIC Observatory

NASA Astrophysics Data System (ADS)

Assmann, Denise; Hermann, Markus; Weigelt, Andreas; Martinsson, Bengt; Brenninkmeijer, Carl; Rauthe-Schöch, Armin; van Velthoven, Peter; Bönisch, Harald; Zahn, Andreas

2017-04-01

Submicrometer aerosol particles in the upper troposphere and lowermost stratosphere (UT/LMS) influence the Earth`s radiation budget directly and, more important, indirectly, by acting as cloud condensation nuclei and by changing trace gas concentrations through heterogeneous chemical processes. Since 1997, regular in situ UT/LMS aerosol particle measurements have been conducted by the Leibniz Institute for Tropospheric Research, Leipzig, Germany and the University of Lund, Sweden, using the the CARIBIC (now IAGOS-CARIBIC) observatory (www.caribic-atmospheric.com) onboard a passenger aircraft. Submicrometer aerosol particle number concentrations and the aerosol particle size distribution are measured using three condensation particle counters and one optical particle size spectrometer. Moreover, particle elemental composition is determined using an aerosol impactor sampler and post-flight ion beam analysis (PIXE, PESA) of the samples in the laboratory. Based on this unique data set, including meteorological analysis, we present representative spatio-temporal distributions of particle number, surface, volume and elemental concentrations in an altitude of 8-12 km covering a large fraction of the northern hemisphere. We discuss the measured values in the different size regimes with respect to sources and sinks in different regions. Additionally, we calculated highly resolved latitudinal and longitudinal cross sections of the particle number size distribution, probability density functions and trends in particle number concentrations, but also in elemental composition, determined from our regular measurements over more than a decade. Moreover, we generated seasonal contour plots for particle number concentrations, the potential temperature, and the equivalent latitude. The results are interpreted with respect to aerosol microphysics and transport using CARIBIC trace gas data like ozone and water vapour. The influence of clouds in the troposphere and the different stratosphere-troposphere-exchange processes is clearly visible. Besides providing information about UT/LMS aerosol particle sources, transport, and sinks, these distributions can be used to validate remote sensing instruments or global atmospheric aerosol models.

Exploring the Atmosphere of Neoproterozoic Earth: The Effect of O2 on Haze Formation and Composition

NASA Astrophysics Data System (ADS)

Hörst, Sarah M.; He, Chao; Ugelow, Melissa S.; Jellinek, A. Mark; Pierrehumbert, Raymond T.; Tolbert, Margaret A.

2018-05-01

Previous studies of haze formation in the atmosphere of the early Earth have focused on N2/CO2/CH4 atmospheres. Here, we experimentally investigate the effect of O2 on the formation and composition of aerosols to improve our understanding of haze formation on the Neoproterozoic Earth. We obtained in situ size, particle density, and composition measurements of aerosol particles produced from N2/CO2/CH4/O2 gas mixtures subjected to FUV radiation (115–400 nm) for a range of initial CO2/CH4/O2 mixing ratios (O2 ranging from 2 ppm to 0.2%). At the lowest O2 concentration (2 ppm), the addition increased particle production for all but one gas mixture. At higher oxygen concentrations (20 ppm and greater), particles are still produced, but the addition of O2 decreases the production rate. Both the particle size and number density decrease with increasing O2, indicating that O2 affects particle nucleation and growth. The particle density increases with increasing O2. The addition of CO2 and O2 not only increases the amount of oxygen in the aerosol, but it also increases the degree of nitrogen incorporation. In particular, the addition of O2 results in the formation of nitrate-bearing molecules. The fact that the presence of oxygen-bearing molecules increases the efficiency of nitrogen fixation has implications for the role of haze as a source of molecules required for the origin and evolution of life. The composition changes also likely affect the absorption and scattering behavior of these particles but optical property measurements are required to fully understand the implications for the effect on the planetary radiative energy balance and climate.

Reinforcement of natural rubber latex by nanosize montmorillonite clay

NASA Astrophysics Data System (ADS)

Tantatherdtam, Rattana

Based on the unique character of montmorillonite namely its layer structure and the ability of silicate particles to separate into nanometer-size platelets, natural rubber (polyisoprene)/clay composites were obtained by mixing rubber latex with clay-water dispersion and coagulating the mixture. The resulting film had greatly improved mechanical properties compared with films using micron-sized fillers. Further, both modulus and toughness were improved; in many composite system an improvement in modulus leads to a loss of toughness. X-ray diffraction results indicated that clay platelets dispersed in the rubber matrix on the nanoscale level with some macromolecules intercalated into the clay gallery. The observed considerable improvement in mechanical properties, coupled with a theoretical model of composite modulus suggests a dispersed structure of clay in the composite. While not all clay particles are exfoliated, data suggest that a reasonable fraction of exfoliated materials is required to explain the experimental results.

The effects of solid rocket motor effluents on selected surfaces and solid particle size, distribution, and composition for simulated shuttle booster separation motors

NASA Technical Reports Server (NTRS)

Jex, D. W.; Linton, R. C.; Russell, W. M.; Trenkle, J. J.; Wilkes, D. R.

1976-01-01

A series of three tests was conducted using solid rocket propellants to determine the effects a solid rocket plume would have on thermal protective surfaces (TPS). The surfaces tested were those which are baselined for the shuttle vehicle. The propellants used were to simulate the separation solid rocket motors (SSRM) that separate the solid rocket boosters (SRB) from the shuttle launch vehicle. Data cover: (1) the optical effects of the plume environment on spacecraft related surfaces, and (2) the solid particle size, distribution, and composition at TPS sample locations.

Comparison of dry sliding wear and friction behavior of Al6061/SiC PMMC with Al6061 alloy

NASA Astrophysics Data System (ADS)

Murthy, A. G. Shankara; Mehta, N. K.; Kumar, Pradeep

2018-04-01

Dry sliding wear and friction behavior tests were conducted on Al6061 alloy and Al6061/SiC particle reinforced metal matrix composites (PMMCs) reinforced with fine particles of 5, 10 and 15 µm size having 5,7.5 and 10% weight content fabricated by stir-casting route. Cylindrical sample pins produced as per ASTM standard were tested for various parameters like SiC size, weight content, load and sliding distance affecting the wear rate or resistance and friction. Results indicated that Al6061/SiCp composites exhibited good wear resistance compared to Al6061 alloy for the tested parameters.

Surface treated carbon catalysts produced from waste tires for fatty acids to biofuel conversion

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hood, Zachary D.; Adhikari, Shiba P.; Wright, Marcus W.

A method of making solid acid catalysts includes the step of sulfonating waste tire pieces in a first sulfonation step. The sulfonated waste tire pieces are pyrolyzed to produce carbon composite pieces having a pore size less than 10 nm. The carbon composite pieces are then ground to produce carbon composite powders having a size less than 50 .mu.m. The carbon composite particles are sulfonated in a second sulfonation step to produce sulfonated solid acid catalysts. A method of making biofuels and solid acid catalysts are also disclosed.

Multilayer Electroactive Polymer Composite Material

NASA Technical Reports Server (NTRS)

Harrison, Joycelyn S. (Inventor); Holloway, Nancy M. (Inventor); Park, Cheol (Inventor); Draughon, Gregory K. (Inventor); Ounaies, Zoubeida (Inventor)

2011-01-01

An electroactive material comprises multiple layers of electroactive composite with each layer having unique dielectric, electrical and mechanical properties that define an electromechanical operation thereof when affected by an external stimulus. For example, each layer can be (i) a 2-phase composite made from a polymer with polarizable moieties and an effective amount of carbon nanotubes incorporated in the polymer for a predetermined electromechanical operation, or (ii) a 3-phase composite having the elements of the 2-phase composite and further including a third component of micro-sized to nano-sized particles of an electroactive ceramic incorporated in the polymer matrix.

Multilayer Electroactive Polymer Composite Material Comprising Carbon Nanotubes

NASA Technical Reports Server (NTRS)

Ounaies, Zoubeida (Inventor); Park, Cheol (Inventor); Harrison, Joycelyn S. (Inventor); Holloway, Nancy M. (Inventor); Draughon, Gregory K. (Inventor)

2009-01-01

An electroactive material comprises multiple layers of electroactive composite with each layer having unique dielectric, electrical and mechanical properties that define an electromechanical operation thereof when affected by an external stimulus. For example, each layer can be (i) a 2-phase composite made from a polymer with polarizable moieties and an effective amount of carbon nanotubes incorporated in the polymer for a predetermined electromechanical operation, or (ii) a 3-phase composite having the elements of the 2-phase composite and further including a third component of micro-sized to nano-sized particles of an electroactive ceramic incorporated in the polymer matrix.

Preparation and Characterization of Extruded Composites Based on Polypropylene and Chitosan Compatibilized with Polypropylene-Graft-Maleic Anhydride

PubMed Central

Carrasco-Guigón, Fernando Javier; Rodríguez-Félix, Dora Evelia; Castillo-Ortega, María Mónica; Santacruz-Ortega, Hisila C.; Burruel-Ibarra, Silvia E.; Encinas-Encinas, Jose Carmelo; Plascencia-Jatomea, Maribel; Herrera-Franco, Pedro Jesus; Madera-Santana, Tomas Jesus

2017-01-01

The preparation of composites of synthetic and natural polymers represent an interesting option to combine properties; in this manner, polypropylene and chitosan extruded films using a different proportion of components and polypropylene-graft-maleic anhydride (PPgMA) as compatibilizer were prepared. The effect of the content of the biopolymer in the polypropylene (PP) matrix, the addition of compatibilizer, and the particle size on the properties of the composites was analyzed using characterization by fourier transform-infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), differential scanning calorimetry (DSC), tensile strength, and contact angle, finding that in general, the addition of the compatibilizer and reducing the particle size of the chitosan, favored the physicochemical and morphological properties of the films. PMID:28772464

Dimensionally stable metallic hydride composition

DOEpatents

Heung, Leung K.

1994-01-01

A stable, metallic hydride composition and a process for making such a composition. The composition comprises a uniformly blended mixture of a metal hydride, kieselguhr, and a ballast metal, all in the form of particles. The composition is made by subjecting a metal hydride to one or more hydrogen absorption/desorption cycles to disintegrate the hydride particles to less than approximately 100 microns in size. The particles are partly oxidized, then blended with the ballast metal and the kieselguhr to form a uniform mixture. The mixture is compressed into pellets and calcined. Preferably, the mixture includes approximately 10 vol. % or more kieselguhr and approximately 50 vol. % or more ballast. Metal hydrides that can be used in the composition include Zr, Ti, V, Nb, Pd, as well as binary, tertiary, and more complex alloys of La, Al, Cu, Ti, Co, Ni, Fe, Zr, Mg, Ca, Mn, and mixtures and other combinations thereof. Ballast metals include Al, Cu and Ni.

Characterizing the Hygroscopicity of Nascent Sea Spray Aerosol from Synthetic Blooms

NASA Astrophysics Data System (ADS)

Forestieri, S.; Cappa, C. D.; Sultana, C. M.; Lee, C.; Wang, X.; Helgestad, T.; Moore, K.; Prather, K. A.; Cornwell, G.; Novak, G.; Bertram, T. H.

2015-12-01

Marine sea spray aerosol (SSA) particles make up a significant portion of natural aerosols and are therefore important in establishing the baseline for anthropogenic aerosol climate impacts. Scattering of solar radiation by aerosols affects Earth's radiative budget and the degree of scattering is size-dependent. Thus, aerosols scatter more light at elevated relative humidities when they grow larger via water uptake. This growth depends critically on chemical composition. SSA can become enriched in organics during phytoplankton blooms, becoming less salty and therefore less hygroscopic. Subsaturated hygroscopic growth factors at 85% relative humidity (GF(85%)) of SSA particles were quantified during two mesocosm experiments in enclosed marine aerosol reference tanks (MARTs). The two experiments were conducted with filtered seawater collected at separate times from the Scripps Institute of Oceanography Pier in La Jolla, CA. Phytoplankton blooms in each tank were induced via the addition of nutrients and photosynthetically active radiation. The "indoor" MART was illuminated with fluorescent light and the other "outdoor" MART was illuminated with sunlight. The peak chlorophyll-a concentrations were 59 micrograms/L and 341 micrograms /L for the indoor and outdoor MARTs, respectively. GF(85%) values for SSA particles were quantified using a humidified cavity ringdown spectrometer and particle size distributions. Particle composition was monitored with a single particle aerosol mass spectrometer (ATOFMS) and an Aerodyne aerosol mass spectrometer (AMS). Relationships between the observed particle GFs and the particle composition markers will be discussed.

Multicomponent inorganic Janus particles with controlled compositions, morphologies, and dimensions.

PubMed

Lyubarskaya, Yekaterina L; Shestopalov, Alexander A

2013-08-14

We report a new protocol for the preparation of shape-controlled multicomponent particles comprising metallic (Au and Ti), magnetic (Ni), and oxide (SiO2, TiO2) layers. Our method allows for a precise control over the composition, shape, and size and permits fabrication of nonsymmetrical particles, whose opposite sides can be orthogonally functionalized using well-established organosilanes and thiol chemistries. Because of their unique geometries and surface chemistries, these colloids represent ideal materials with which to study nonsymmetrical self-assembly at the meso- and microscales.

Calculation of the Rate of Combustion of a Metallized Composite Solid Propellant with Allowance for the Size Distribution of Agglomerates

NASA Astrophysics Data System (ADS)

Poryazov, V. A.; Krainov, A. Yu.

2016-05-01

A physicomathematical model of combustion of a metallized composite solid propellant based on ammonium perchlorate has been presented. The model takes account of the thermal effect of decomposition of a condensed phase (c phase), convection, diffusion, the exothermal chemical reaction in a gas phase, the heating and combustion of aluminum particles in the gas flow, and the velocity lag of the particles behind the gas. The influence of the granulometric composition of aluminum particles escaping from the combustion surface on the linear rate of combustion has been investigated. It has been shown that information not only on the kinetics of chemical reactions in the gas phase, but also on the granulometric composition of aluminum particles escaping from the surface of the c phase into the gas, is of importance for determination of the linear rate of combustion.

Controlling chitosan-based encapsulation for protein and vaccine delivery

PubMed Central

Koppolu, Bhanu prasanth; Smith, Sean G.; Ravindranathan, Sruthi; Jayanthi, Srinivas; Kumar, Thallapuranam K.S.; Zaharoff, David A.

2014-01-01

Chitosan-based nano/microencapsulation is under increasing investigation for the delivery of drugs, biologics and vaccines. Despite widespread interest, the literature lacks a defined methodology to control chitosan particle size and drug/protein release kinetics. In this study, the effects of precipitation-coacervation formulation parameters on chitosan particle size, protein encapsulation efficiency and protein release were investigated. Chitosan particle sizes, which ranged from 300 nm to 3 μm, were influenced by chitosan concentration, chitosan molecular weight and addition rate of precipitant salt. The composition of precipitant salt played a significant role in particle formation with upper Hofmeister series salts containing strongly hydrated anions yielding particles with a low polydispersity index (PDI) while weaker anions resulted in aggregated particles with high PDIs. Sonication power had minimal effect on mean particle size, however, it significantly reduced polydispersity. Protein loading efficiencies in chitosan nano/microparticles, which ranged from 14.3% to 99.2%, was inversely related to the hydration strength of precipitant salts, protein molecular weight and directly related to the concentration and molecular weight of chitosan. Protein release rates increased with particle size and were generally inversely related to protein molecular weight. This study demonstrates that chitosan nano/microparticles with high protein loading efficiencies can be engineered with well-defined sizes and controllable release kinetics through manipulation of specific formulation parameters. PMID:24560459

Deciphering the Complex Chemistry of Deep-Ocean Particles Using Complementary Synchrotron X-ray Microscope and Microprobe Instruments.

PubMed

Toner, Brandy M; German, Christopher R; Dick, Gregory J; Breier, John A

2016-01-19

The reactivity and mobility of natural particles in aquatic systems have wide ranging implications for the functioning of Earth surface systems. Particles in the ocean are biologically and chemically reactive, mobile, and complex in composition. The chemical composition of marine particles is thought to be central to understanding processes that convert globally relevant elements, such as C and Fe, among forms with varying bioavailability and mobility in the ocean. The analytical tools needed to measure the complex chemistry of natural particles are the subject of this Account. We describe how a suite of complementary synchrotron radiation instruments with nano- and micrometer focusing, and X-ray absorption spectroscopy (XAS) and X-ray diffraction (XRD) capabilities are changing our understanding of deep-ocean chemistry and life. Submarine venting along mid-ocean ridges creates hydrothermal plumes where dynamic particle-forming reactions occur as vent fluids mix with deep-ocean waters. Whether plumes are net sources or sinks of elements in ocean budgets depends in large part on particle formation, reactivity, and transport properties. Hydrothermal plume particles have been shown to host microbial communities and exhibit complex size distributions, aggregation behavior, and composition. X-ray microscope and microprobe instruments can address particle size and aggregation, but their true strength is in measuring chemical composition. Plume particles comprise a stunning array of inorganic and organic phases, from single-crystal sulfides to poorly ordered nanophases and polymeric organic matrices to microbial cells. X-ray microscopes and X-ray microprobes with elemental imaging, XAS, and XRD capabilities are ideal for investigating these complex materials because they can (1) measure the chemistry of organic and inorganic constituents in complex matrices, usually within the same particle or aggregate, (2) provide strong signal-to-noise data with exceedingly small amounts of material, (3) simplify the chemical complexity of particles or sets of particles with a focused-beam, providing spatial resolution over 6 orders of magnitude (nanometer to millimeter), (4) provide elemental specificity for elements in the soft-, tender-, and hard-X-ray energies, (5) switch rapidly among elements of interest, and (6) function in the presence of water and gases. Synchrotron derived data sets are discussed in the context of important advances in deep-ocean technology, sample handling and preservation, molecular microbiology, and coupled physical-chemical-biological modeling. Particle chemistry, size, and morphology are all important in determining whether particles are reactive with dissolved constituents, provide substrates for microbial respiration and growth, and are delivered to marine sediments or dispersed by deep-ocean currents.

The influence of particle concentration and composition on the fractionation of 210Po and 210Pb along the North Atlantic GEOTRACES transect GA03

NASA Astrophysics Data System (ADS)

Tang, Yi; Stewart, Gillian; Lam, Phoebe J.; Rigaud, Sylvain; Church, Thomas

2017-10-01

The disequilibrium between 210Po and 210Pb has been used as a proxy for the particle flux from the upper ocean. The particle concentration and composition effect on the partitioning behavior of 210Po and 210Pb is, however, still unclear. Here, we investigate this association by comparing dissolved (< 0.45 μm) and particulate (small: 1-51 μm; large: > 51 μm) 210Po and 210Pb activity with size-fractionated major particle concentration and composition data from the US GEOTRACES GA03 zonal transect cruises. We observed inverse relationships between partition coefficients (Kd) for the radionuclides and the concentration of suspended particulate matter (SPM) in the water column, known as the ;particle concentration effect.; We examined the relationships between 210Po, 210Pb, and particle composition in the top 500 m by using Pearson pairwise correlations for individual phases and principal components analysis (PCA) for variations among multiple phases. In addition to these analyses, an end-member mixing model was developed to estimate Kd for 210Po and 210Pb in the small particulate size fraction from the compositional phases. The model predicted the range of observed Kd(Pb) well, but was unable to predict the observed Kd(Po) as consistently, possibly because of the bio-reactive nature of 210Po. Despite this, we found a strong relationship between 210Po and both CaCO3 and POM, as well as between 210Pb and both opal and lithogenic phases. All of our analyses demonstrated that the fractionation of 210Po and 210Pb differed between the margins and open ocean along the GA03 transect.

Organic Functional Group Composition of Submicron Aerosol Particles at Alert, Nunavut, during 2012-2014

NASA Astrophysics Data System (ADS)

Russell, L. M.; Leaitch, W. R.; Liu, J.; Desiree, T. S.; Huang, L.; Sharma, S.; Chivulescu, A.; Veber, D.; Zhang, W.

2016-12-01

Long-term measurements of submicron aerosol particle chemical composition and size distributions are essential for evaluating whether global climate models correctly transport particles from lower latitudes to polar regions, especially in the winter months when satellite retrieval of aerosol properties is limited. In collaboration with ongoing measurements by the Dr. Neil Trivett Global Atmospheric Watch observatory at Alert, Nunavut (82.5°N; elevation 185 m-ASL), we measured the organic functional group composition of submicron aerosol particles sampled from the 10-m inlet from April 2012 to October 2014. The sampling site is approximately 10 km from the Alert station, and vehicle traffic is restricted except when filter sampling is stopped, making the impact of local emissions on submicron particle mass concentrations small. The organic functional group (OFG) composition is measured by Fourier Transform Infrared spectroscopy of samples collected on pre-loaded Teflon filters and stored and shipped frozen to La Jolla, California, for analysis. Samples were collected weekly to complement the twice hourly online measurements of non-refractory organic and inorganic composition by an Aerodyne ACSM. Organic components are shown to contribute a substantial fraction of the measured aerosol submicron mass year round. These measurements illustrate the seasonal contributions to the aerosol size distribution from OFG and illustrate the potential sources of the OFG at this remote site. The three largest OFG sources are transported fossil fuel combustion emissions from lower latitudes, sea spray and other marine particles, and episodic contributions from wildfires, volcanoes, and other high-latitude events. These sources are similar to those identified from earlier OFG measurements at Barrow, Alaska, and during the ICEALOT cruise in the Arctic Ocean.

Direct Synthetic Control over the Size, Composition, and Photocatalytic Activity of Octahedral Copper Oxide Materials: Correlation Between Surface Structure and Catalytic Functionality.

PubMed

Nguyen, Michelle A; Bedford, Nicholas M; Ren, Yang; Zahran, Elsayed M; Goodin, Robert C; Chagani, Fatima F; Bachas, Leonidas G; Knecht, Marc R

2015-06-24

We report a synthetic approach to form octahedral Cu2O microcrystals with a tunable edge length and demonstrate their use as catalysts for the photodegradation of aromatic organic compounds. In this particular study, the effects of the Cu(2+) and reductant concentrations and stoichiometric ratios were carefully examined to identify their roles in controlling the final material composition and size under sustainable reaction conditions. Varying the ratio and concentrations of Cu(2+) and reductant added during the synthesis determined the final morphology and composition of the structures. Octahedral particles were prepared at selected Cu(2+):glucose ratios that demonstrated a range of photocatalytic reactivity. The results indicate that material composition, surface area, and substrate charge effects play important roles in controlling the overall reaction rate. In addition, analysis of the post-reacted materials revealed photocorrosion was inhibited and that surface etching had preferentially occurred at the particle edges during the reaction, suggesting that the reaction predominately occurred at these interfaces. Such results advance the understanding of how size and composition affect the surface interface and catalytic functionality of materials.

Characterization of aerosols and fibers emitted from composite materials combustion.

PubMed

Chivas-Joly, C; Gaie-Levrel, F; Motzkus, C; Ducourtieux, S; Delvallée, A; De Lagos, F; Nevé, S Le; Gutierrez, J; Lopez-Cuesta, J-M

2016-01-15

This work investigates the aerosols emitted during combustion of aircraft and naval structural composite materials (epoxy resin/carbon fibers and vinyl ester/glass fibers and carbon nanotubes). Combustion tests were performed at lab-scale using a modified cone calorimeter. The aerosols emitted have been characterized using various metrological devices devoted to the analysis of aerosols. The influence of the nature of polymer matrices, the incorporation of fibers and carbon nanotubes as well as glass reinforcements on the number concentration and the size distribution of airborne particles produced, was studied in the 5 nm-10 μm range. Incorporation of carbon fibers into epoxy resin significantly reduced the total particle number concentration. In addition, the interlaced orientation of carbon fibers limited the particles production compared to the composites with unidirectional one. The carbon nanotubes loading in vinyl ester resin composites influenced the total particles production during the flaming combustion with changes during kinetics emission. Predominant populations of airborne particles generated during combustion of all tested composites were characterized by a PN50 following by PN(100-500). Copyright © 2015 Elsevier B.V. All rights reserved.

The size, mass, and composition of plastic debris in the western North Atlantic Ocean.

PubMed

Morét-Ferguson, Skye; Law, Kara Lavender; Proskurowski, Giora; Murphy, Ellen K; Peacock, Emily E; Reddy, Christopher M

2010-10-01

This study reports the first inventory of physical properties of individual plastic debris in the North Atlantic. We analyzed 748 samples for size, mass, and material composition collected from surface net tows on 11 expeditions from Cape Cod, Massachusetts to the Caribbean Sea between 1991 and 2007. Particles were mostly fragments less than 10mm in size with nearly all lighter than 0.05 g. Material densities ranged from 0.808 to 1.24 g ml(-1), with about half between 0.97 and 1.04 g ml(-1), a range not typically found in virgin plastics. Elemental analysis suggests that samples in this density range are consistent with polypropylene and polyethylene whose densities have increased, likely due to biofouling. Pelagic densities varied considerably from that of beach plastic debris, suggesting that plastic particles are modified during their residence at sea. These analyses provide clues in understanding particle fate and potential debris sources, and address ecological implications of pelagic plastic debris. Copyright © 2010 Elsevier Ltd. All rights reserved.

Possibility of using waste tire rubber and fly ash with Portland cement as construction materials.

PubMed

Yilmaz, Arin; Degirmenci, Nurhayat

2009-05-01

The growing amount of waste rubber produced from used tires has resulted in an environmental problem. Recycling waste tires has been widely studied for the last 20 years in applications such as asphalt pavement, waterproofing systems and membrane liners. The aim of this study is to evaluate the feasibility of utilizing fly ash and rubber waste with Portland cement as a composite material for masonry applications. Class C fly ash and waste automobile tires in three different sizes were used with Portland cement. Compressive and flexural strength, dry unit weight and water absorption tests were performed on the composite specimens containing waste tire rubber. The compressive strength decreased by increasing the rubber content while increased by increasing the fly ash content for all curing periods. This trend is slightly influenced by particle size. For flexural strength, the specimens with waste tire rubber showed higher values than the control mix probably due to the effect of rubber fibers. The dry unit weight of all specimens decreased with increasing rubber content, which can be explained by the low specific gravity of rubber particles. Water absorption decreased slightly with the increase in rubber particles size. These composite materials containing 10% Portland cement, 70% and 60% fly ash and 20% and 30% tire rubber particles have sufficient strength for masonry applications.

Sol-gel processed thin-layer ruthenium oxide/carbon black supercapacitors: A revelation of the energy storage issues

NASA Astrophysics Data System (ADS)

Panić, V. V.; Dekanski, A. B.; Stevanović, R. M.

Hydrous ruthenium oxide/carbon black nanocomposites were prepared by impregnation of the carbon blacks by differently aged inorganic RuO 2 sols, i.e. of different particle size. Commercial Black Pearls 2000 ® (BP) and Vulcan ® XC-72 R (XC) carbon blacks were used. Capacitive properties of BP/RuO 2 and XC/RuO 2 composites were investigated by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) in H 2SO 4 solution. Capacitance values and capacitance distribution through the composite porous layer were found different if high- (BP) and low- (XC) surface-area carbons are used as supports. The aging time (particle size) of Ru oxide sol as well as the concentration of the oxide solid phase in the impregnating medium influenced the capacitive performance of prepared composites. While the capacitance of BP-supported oxide decreases with the aging time, the capacitive ability of XC-supported oxide is promoted with increasing oxide particle size. The increase in concentration of the oxide solid phase in the impregnating medium caused an improvement of charging/discharging characteristics due to pronounced pseudocapacitance contribution of the increasing amount of inserted oxide. The effects of these variables in the impregnation process on the energy storage capabilities of prepared nanocomposites are envisaged as a result of intrinsic way of population of the pores of carbon material by hydrous Ru oxide particle.

Using different assumptions of aerosol mixing state and chemical composition to predict CCN concentrations based on field measurements in urban Beijing

NASA Astrophysics Data System (ADS)

Ren, Jingye; Zhang, Fang; Wang, Yuying; Collins, Don; Fan, Xinxin; Jin, Xiaoai; Xu, Weiqi; Sun, Yele; Cribb, Maureen; Li, Zhanqing

2018-05-01

Understanding the impacts of aerosol chemical composition and mixing state on cloud condensation nuclei (CCN) activity in polluted areas is crucial for accurately predicting CCN number concentrations (NCCN). In this study, we predict NCCN under five assumed schemes of aerosol chemical composition and mixing state based on field measurements in Beijing during the winter of 2016. Our results show that the best closure is achieved with the assumption of size dependent chemical composition for which sulfate, nitrate, secondary organic aerosols, and aged black carbon are internally mixed with each other but externally mixed with primary organic aerosol and fresh black carbon (external-internal size-resolved, abbreviated as EI-SR scheme). The resulting ratios of predicted-to-measured NCCN (RCCN_p/m) were 0.90 - 0.98 under both clean and polluted conditions. Assumption of an internal mixture and bulk chemical composition (INT-BK scheme) shows good closure with RCCN_p/m of 1.0 -1.16 under clean conditions, implying that it is adequate for CCN prediction in continental clean regions. On polluted days, assuming the aerosol is internally mixed and has a chemical composition that is size dependent (INT-SR scheme) achieves better closure than the INT-BK scheme due to the heterogeneity and variation in particle composition at different sizes. The improved closure achieved using the EI-SR and INT-SR assumptions highlight the importance of measuring size-resolved chemical composition for CCN predictions in polluted regions. NCCN is significantly underestimated (with RCCN_p/m of 0.66 - 0.75) when using the schemes of external mixtures with bulk (EXT-BK scheme) or size-resolved composition (EXT-SR scheme), implying that primary particles experience rapid aging and physical mixing processes in urban Beijing. However, our results show that the aerosol mixing state plays a minor role in CCN prediction when the κorg exceeds 0.1.

Electrical and Electrorheological Properties of Alumina/Natural Rubber (STR XL) Composites

PubMed Central

Tangboriboon, Nuchnapa; Uttanawanit, Nuttapot; Longtong, Mean; Wongpinthong, Piraya; Sirivat, Anuvat; Kunanuruksapong, Ruksapong

2010-01-01

The electrorheological properties (ER) of natural rubber (XL)/alumina (Al2O3) composites were investigated in oscillatory shear mode under DC electrical field strengths between 0 to 2 kV/mm. SEM micrographs indicate a mean particle size of 9.873 ± 0.034 µm and particles that are moderately dispersed in the matrix. The XRD patterns indicate Al2O3 is of the β-phase polytype which possesses high ionic conductivity. The storage modulus (G′) of the composites, or the rigidity, increases by nearly two orders of magnitude, with variations in particle volume fraction and electrical field strength. The increase in the storage modulus is caused the ionic polarization of the alumina particles and the induced dipole moments set up in the natural rubber matrix.

Airborne ultrafine particles in a naturally ventilated metro station: Dominant sources and mixing state determined by particle size distribution and volatility measurements.

PubMed

Mendes, Luís; Gini, Maria I; Biskos, George; Colbeck, Ian; Eleftheriadis, Konstantinos

2018-08-01

Ultrafine particle number concentrations and size distributions were measured on the platform of a metro station in Athens, Greece, and compared with those recorded at an urban background station. The volatility of the sampled particles was measured in parallel, providing further insights on the mixing state and composition of the sampled particles. Particle concentration exhibited a mean value of 1.2 × 10 4 # cm -3 and showed a weak correlation with train passage frequency, but exhibited a strong correlation with urban background particle concentrations. The size distribution appears to be strongly influenced by outdoor conditions, such as the morning traffic rush hour and new particle formation events observed at noon. The aerosol in the metro was externally mixed throughout the day, with particle populations being identified (1) as fully refractory particles being more dominant during the morning traffic rush hours, (2) as core-shell structure particles having a non-volatile core coated with volatile material, and (3) fully volatile particles. The evolution of particle volatility and size throughout the day provide additional support that most nanoparticles in the metro station originate from outdoor urban air. Copyright © 2018 Elsevier Ltd. All rights reserved.

Densification behavior and mechanical properties of nanocrystalline TiC reinforced 316L stainless steel composite parts fabricated by selective laser melting

NASA Astrophysics Data System (ADS)

Zhao, Shuming; Shen, Xianfeng; Yang, Jialin; Teng, Wenhua; Wang, Yingying

2018-07-01

Metal matrix composite parts produced using selective laser melting have superior mechanical properties to those produced using traditional powder metallurgy. In this study, nanocrystalline TiC reinforced 316L stainless steel composite parts were fabricated using selective laser melting, and the effects of the TiC mass fraction, particle size, and processing parameters on the relative density, microhardness, and mechanical properties of the TiC/316L composites were investigated. The results show that the relative density of the fabricated parts is related to the laser power and exposure time, and increases when these parameters are increased. The greater the mass fraction of nano-TiC added, the more severe the degree of spheroidization and the lower the density of the resulting material. The microhardness of the 316L stainless steel parts is enhanced by the nano-TiC particles, and increases with increasing nano-TiC mass fraction. The tensile strength is improved with longer exposure time and with the addition of 2 wt% nano-TiC particles. Compared with pure 316L, the microhardness of the TiC/316L composite parts fabricated with 2 wt% 40 nm TiC enhanced from HV0.3 = 219.1 to 277.6, and the ultimate tensile strength significantly increased from 627.5 to 748.6 MPa. The strengthening mechanism of TiC particles is the refinement of the grain size of the 316L matrix, and the greater amount of TiC particles added, the better the grain refinement of 316L.

Changes in the mechanism of heat transfer in passing from microparticles to nanoparticles

NASA Astrophysics Data System (ADS)

Shakhov, F. M.; Meilakhs, A. P.; Eidelman, E. D.

2016-03-01

On the basis of experimental data on thermal conduction and sound velocity in composites obtained by sintering detonation nanodiamonds with the crystallite size of 4-5 nm and diamond micropowders with a grain size of about 10 μm at a high pressure (5-7 GPa) and high temperature (1200-1800°C), mechanisms of heat transfer in such structures are suggested. These mechanisms are shown to be different in composites of micro- and nanoparticles. In composites of micrometer particles, the conventional macroscopic mechanism of phonon propagation is active. In composites with a grain size of a few nanometers, the main contribution comes from thermal resistance on grain boundaries.

Size-dependent phase diagrams of metallic alloys: A Monte Carlo simulation study on order–disorder transitions in Pt–Rh nanoparticles

PubMed Central

Stahl, Christian; Albe, Karsten

2012-01-01

Summary Nanoparticles of Pt–Rh were studied by means of lattice-based Monte Carlo simulations with respect to the stability of ordered D022- and 40-phases as a function of particle size and composition. By thermodynamic integration in the semi-grand canonical ensemble, phase diagrams for particles with a diameter of 7.8 nm, 4.3 nm and 3.1 nm were obtained. Size-dependent trends such as the lowering of the critical ordering temperature, the broadening of the compositional stability range of the ordered phases, and the narrowing of the two-phase regions were observed and discussed in the context of complete size-dependent nanoparticle phase diagrams. In addition, an ordered surface phase emerges at low temperatures and low platinum concentration. A decrease of platinum surface segregation with increasing global platinum concentration was observed, when a second, ordered phase is formed inside the core of the particle. The order–disorder transitions were analyzed in terms of the Warren–Cowley short-range order parameters. Concentration-averaged short-range order parameters were used to remove the surface segregation bias of the conventional short-range order parameters. Using this procedure, it was shown that the short-range order in the particles at high temperatures is bulk-like. PMID:22428091

Effects of Ni content on nanocrystalline Fe-Co-Ni ternary alloys synthesized by a chemical reduction method

NASA Astrophysics Data System (ADS)

Chokprasombat, Komkrich; Pinitsoontorn, Supree; Maensiri, Santi

2016-05-01

Magnetic properties of Fe-Co-Ni ternary alloys could be altered by changing of the particle size, elemental compositions, and crystalline structures. In this work, Fe50Co50-xNix nanoparticles (x=10, 20, 40, and 50) were prepared by the novel chemical reduction process. Hydrazine monohydrate was used as a reducing agent under the concentrated basic condition with the presence of poly(vinylpyrrolidone). We found that the nanoparticles were composed of Fe, Co and Ni with compositions according to the molar ratio of the metal sources. Interestingly, the particles were well-crystalline at the as-prepared state without post-annealing at high temperature. Increasing Ni content resulted in phase transformation from body centered cubic (bcc) to face centered cubic (fcc). For the fcc phase, the average particle size decreased when increased the Ni content; the Fe50Ni50 nanoparticles had the smallest average size with the narrowest size distribution. In additions, the particles exhibited ferromagnetic properties at room temperature with the coercivities higher than 300 Oe, and the saturation magnetiation decreased with increasing Ni content. These results suggest that the structural and magnetic properties of Fe-Co-Ni alloys could be adjusted by varying the Ni content.

Structural phase composition and effectiveness of gas-dynamic spraying of hybrid coatings based on AlMg2 nanocrystalline matrix reinforced with graphene-like structures and micro-size corundum

NASA Astrophysics Data System (ADS)

Aborkin, A. V.; Sobol'kov, A. V.; Elkin, A. I.; Arkhipov, V. E.

2018-01-01

The method of cold gas-dynamic spraying of mechanically synthesized powders based on a nanocrystalline AlMg2 matrix reinforced with graphene-like structures and micro-sized corundum particles was used for obtaining hybrid coatings. A feature of the formed coatings is the presence of a two-level micro- and nanocomposite structure. It was found that an increase in the content of corundum microdimensional particles in the mixture from 10 to 30% by weight contributes to an increase in the thickness of the coating obtained at the same time by a factor of 2 from 140 to 310 μm. Further increase in the content of a mixture of micron-sized corundum particles to 50% by weight leads to a decrease in the thickness of the coating formed to 40 μm. The resulting coatings correspond to a high microhardness, varying depending on the composition in the range from 1.7 GPa to 3.2 GPa. The high hardness of the coatings is due to the increase in the hardness of the matrix material due to the creation of a nanocomposite structure, which increases the strength of fixing micro-sized corundum particles therein, improving the characteristics of the heterogeneous coating as a whole.

Preparation of chitosan/tripolyphosphate nanoparticles with highly tunable size and low polydispersity.

PubMed

Sawtarie, Nader; Cai, Yuhang; Lapitsky, Yakov

2017-09-01

Nanoparticles prepared through the ionotropic gelation of chitosan with tripolyphosphate (TPP) have been extensively studied as vehicles for drug and gene delivery. Though a number of these works have focused on preparing particles with narrow size distributions, the monodisperse particles produced by these methods have been limited to narrow size ranges (where the average particle size was not varied by more than twofold). Here we show how, by tuning the NaCl concentration in the parent chitosan and TPP solutions, low-polydispersity particles with z-average diameters ranging between roughly 100 and 900nm can be prepared. Further, we explore how the size of these particles depends on the method by which the TPP is mixed into the chitosan solution, specifically comparing: (1) single-shot mixing; (2) dropwise addition; and (3) a dilution technique, where chitosan and TPP are codissolved at a high (gelation-inhibiting) ionic strength and then diluted to lower ionic strengths to trigger gelation. Though the particle size increases sigmoidally with the NaCl concentration for all three mixing methods, the dilution method delivers the most uniform/gradual size increase - i.e., it provides the most precise control. Also investigated are the effects of mixture composition and mixing procedure on the particle yield. These reveal the particle yield to increase with the chitosan/TPP concentration, decrease with the NaCl concentration, and vary only weakly with the mixing protocol; thus, at elevated NaCl concentrations, it may be beneficial to increase chitosan and TPP concentrations to ensure high particle yields. Finally, possible pitfalls of the salt-assisted size control strategy (and their solutions) are discussed. Taken together, these findings provide a simple and reliable method for extensively tuning chitosan/TPP particle size while maintaining narrow size distributions. Copyright © 2017 Elsevier B.V. All rights reserved.

Modeling the evolution of lithium-ion particle contact distributions using a fabric tensor approach

DOE Office of Scientific and Technical Information (OSTI.GOV)

Stershic, A. J.; Simunovic, S.; Nanda, J.

2015-08-25

Electrode microstructure and processing can strongly influence lithium-ion battery performance such as capacity retention, power, and rate. Battery electrodes are multi-phase composite structures wherein conductive diluents and binder bond active material to a current collector. The structure and response of this composite network during repeated electrochemical cycling directly affects battery performance characteristics. We propose the fabric tensor formalism for describing the structure and evolution of the electrode microstructure. Fabric tensors are directional measures of particulate assemblies based on inter-particle connectivity, relating to the structural and transport properties of the electrode. Fabric tensor analysis is applied to experimental data-sets for positivemore » electrode made of lithium nickel manganese cobalt oxide, captured by X-ray tomography for several compositions and consolidation pressures. We show that fabric tensors capture the evolution of inter-particle contact distribution and are therefore good measures for the internal state of and electronic transport within the electrode. The fabric tensor analysis is also applied to Discrete Element Method (DEM) simulations of electrode microstructures using spherical particles with size distributions from the tomography. Furthermore, these results do not follow the experimental trends, which indicates that the particle size distribution alone is not a sufficient measure for the electrode microstructures in DEM simulations.« less

Identification, size classification and evolution of Laves phase precipitates in high chromium, fully ferritic steels.

PubMed

Lopez Barrilao, Jennifer; Kuhn, Bernd; Wessel, Egbert

2017-10-01

To fulfil the new challenges of the German "Energiewende" more efficient, sustainable, flexible and cost-effective energy technologies are strongly needed. For a reduction of consumed primary resources higher efficiency steam cycles with increased operating parameters, pressure and temperature, are mandatory. Therefore advanced materials are needed. The present study focuses on a new concept of high chromium, fully ferritic steels. These steels, originally designed for solid oxide fuel cell applications, provide favourable steam oxidation resistance, creep and thermomechanical fatigue behaviour in comparison to conventional ferritic-martensitic steels. The strength of this type of steel is achieved by a combination of solid-solution hardening and precipitation strengthening by intermetallic Laves phase particles. The effect of alloy composition on particle composition was measured by energy dispersive X-ray spectroscopy and partly verified by thermodynamic modelling results. Generally the Laves phase particles demonstrated high thermodynamic stability during long-term annealing up to 40,000h at 600°C. Variations in chemical alloy composition influence Laves phase particle formation and consequently lead to significant changes in creep behaviour. For this reason particle size distribution evolution was analysed in detail and associated with the creep performance of several trial alloys. Copyright © 2017 Elsevier Ltd. All rights reserved.

Influence of surface and finite size effects on the structural and magnetic properties of nanocrystalline lanthanum strontium perovskite manganites

DOE Office of Scientific and Technical Information (OSTI.GOV)

Žvátora, Pavel; Veverka, Miroslav; Veverka, Pavel

2013-08-15

Syntheses of nanocrystalline perovskite phases of the general formula La{sub 1−x}Sr{sub x}MnO{sub 3+δ} were carried out employing sol–gel technique followed by thermal treatment at 700–900 °C under oxygen flow. The prepared samples exhibit a rhombohedral structure with space group R3{sup ¯}c in the whole investigated range of composition 0.20≤x≤0.45. The studies were aimed at the chemical composition including oxygen stoichiometry and extrinsic properties, i.e. size of the particles, both influencing the resulting structural and magnetic properties. The oxygen stoichiometry was determined by chemical analysis revealing oxygen excess in most of the studied phases. The excess was particularly high for themore » samples with the smallest crystallites (12–28 nm) while comparative bulk materials showed moderate non-stoichiometry. These differences are tentatively attributed to the surface effects in view of the volume fraction occupied by the upper layer whose atomic composition does not comply with the ideal bulk stoichiometry. - Graphical abstract: Evolution of the particle size with annealing temperature in the nanocrystalline La{sub 0.70}Sr{sub 0.30}MnO{sub 3+δ} phase. Display Omitted - Highlights: • The magnetic behaviour of nanocrystalline La{sub 1−x}Sr{sub x}MnO{sub 3+δ} phases was analyzed on the basis of their crystal structure, chemical composition and size of the particles. • Their Curie temperature and magnetization are markedly affected by finite size and surface effects. • The oxygen excess observed in the La{sub 1−x}Sr{sub x}MnO{sub 3+δ} nanoparticles might be generated by the surface layer with deviated oxygen stoichiometry.« less

Controlled Endolysosomal Release of Agents by pH-responsive Polymer Blend Particles.

PubMed

Zhan, Xi; Tran, Kenny K; Wang, Liguo; Shen, Hong

2015-07-01

A key step of delivering extracellular agents to its intracellular target is to escape from endosomal/lysosomal compartments, while minimizing the release of digestive enzymes that may compromise cellular functions. In this study, we examined the intracellular distribution of both fluorecent cargoes and enzymes by a particle delivery platform made from the controlled blending of poly(lactic-co-glycolic acid) (PLGA) and a random pH-sensitive copolymer. We utilized both microscopic and biochemical methods to semi-quantitatively assess how the composition of blend particles affects the level of endosomal escape of cargos of various sizes and enzymes into the cytosolic space. We demonstrated that these polymeric particles enabled the controlled delivery of cargos into the cytosolic space that was more dependent on the cargo size and less on the composition of blend particles. Blend particles did not induce the rupture of endosomal/lysosomal compartments and released less than 20% of endosomal/lysosomal enzymes. This study provides insight into understanding the efficacy and safety of a delivery system for intracellular delivery of biologics and drugs. Blend particles offer a potential platform to target intracellular compartments while potentially minimizing cellular toxicity.

Controlled endolysosomal release of agents by pH-responsive polymer blend particles

PubMed Central

Zhan, Xi; Tran, Kenny K.; Wang, Liguo; Shen, Hong

2015-01-01

Purpose A key step of delivering extracellular agents to its intracellular target is to escape from endosomal/lysosomal compartments, while minimizing the release of digestive enzymes that may compromise cellular functions. In this study, we examined the intracellular distribution of both fluorecent cargoes and enzymes by a particle delivery platform made from the controlled blending of poly (lactic-co-glycolic acid) (PLGA) and a random pH-sensitive copolymer. Methods We utilized both microscopic and biochemical methods to semi-quantitatively assess how the composition of blend particles affects the level of endosomal escape of cargos of various sizes and enzymes into the cytosolic space. Results We demonstrated that these polymeric particles enabled the controlled delivery of cargos into the cytosolic space that was more dependent on the cargo size and less on the composition of blend particles. Blend particles did not induce the rupture of endosomal/lysosomal compartments and released less than 20% of endosomal/lysosomal enzymes. Conclusions This study provides insight into understanding the efficacy and safety of a delivery system for intracellular delivery of biologics and drugs. Blend particles offer a potential platform to target intracellular compartments while potentially minimizing cellular toxicity. PMID:25592550

Silo discharge of binary granular mixtures.

PubMed

Madrid, M; Asencio, K; Maza, D

2017-08-01

We present numerical and experimental results on the mass flow rate during the discharge of three-dimensional silos filled with a bidisperse mixture of grains of different sizes. We analyzed the influence of the ratio between coarse and fine particles on the profile of volume fraction and velocity across the orifice. By using numerical simulations, we have shown that the velocity profile has the same shape as that in the monodisperse case and is insensitive to the composition of the mixture. On the contrary, the volume fraction profile is strongly affected by the composition of the mixture. Assuming that an effective particle size can be introduced to characterize the mixture, we have shown that previous expression for the mass flow rate of monodisperse particles can be used for binary mixtures. A comparison with Beverloo's correlation is also presented.

Effect of indirect non-thermal plasma on particle size distribution and composition of diesel engine particles

NASA Astrophysics Data System (ADS)

Linbo, GU; Yixi, CAI; Yunxi, SHI; Jing, WANG; Xiaoyu, PU; Jing, TIAN; Runlin, FAN

2017-11-01

To explore the effect of the gas source flow rate on the actual diesel exhaust particulate matter (PM), a test bench for diesel engine exhaust purification was constructed, using indirect non-thermal plasma technology. The effects of different gas source flow rates on the quantity concentration, composition, and apparent activation energy of PM were investigated, using an engine exhaust particle sizer and a thermo-gravimetric analyzer. The results show that when the gas source flow rate was large, not only the maximum peak quantity concentrations of particles had a large drop, but also the peak quantity concentrations shifted to smaller particle sizes from 100 nm to 80 nm. When the gas source flow rate was 10 L min-1, the total quantity concentration greatly decreased where the removal rate of particles was 79.2%, and the variation of the different mode particle proportion was obvious. Non-thermal plasma (NTP) improved the oxidation ability of volatile matter as well as that of solid carbon. However, the NTP gas source rate had little effects on oxidation activity of volatile matter, while it strongly influenced the oxidation activity of solid carbon. Considering the quantity concentration and oxidation activity of particles, a gas source flow rate of 10 L min-1 was more appropriate for the purification of particles.

Annual variation in neustonic micro- and meso-plastic particles and zooplankton in the Bay of Calvi (Mediterranean-Corsica).

PubMed

Collignon, Amandine; Hecq, Jean-Henri; Galgani, François; Collard, France; Goffart, Anne

2014-02-15

The annual variation in neustonic plastic particles and zooplankton was studied in the Bay of Calvi (Corsica) between 30 August 2011 and 7 August 2012. Plastic particles were classified into three size classes, small microplastics (0.2-2mm), large microplastics (2-5mm) and mesoplastics (5-10mm). 74% of the 38 samples contained plastic particles of varying composition: e.g. filaments, polystyrene, thin plastic films. An average concentration of 6.2 particles/100 m(2) was observed. The highest abundance values (69 particles/100 m(2)) observed occurred during periods of low offshore wind conditions. These values rose in the same order of magnitude as in previous studies in the North Western Mediterranean. The relationships between the abundance values of the size classes between zooplankton and plastic particles were then examined. The ratio for the intermediate size class (2-5mm) reached 2.73. This would suggest a potential confusion for predators regarding planktonic prey of this size class. Copyright © 2013 Elsevier Ltd. All rights reserved.

Limitations on analysis of small particles with an electron probe: pollution studies

USGS Publications Warehouse

Heidel, R.H.; Desborough, G.A.

1975-01-01

Recent literature concerning the size and composition of airborne lead particles in automobile exhaust emissions determined by electron microprobe analysis reports 14 distinct lead compounds. Particle sizes reported were from 0.2 ??m to 2 ??m in the diameter. The determination of chemical formulae for compounds requires quantitative elemental data for individual particles. It was also assumed that the lead bearing particles analysed were solid (specifically non porous or non fluffy) compounds which occurred as discrete (non aggregate) particles. Intensity data obtained in the laboratory from the excited volume in a 1 ??m diameter sphere of solid lead chloride indicate insufficient precision and sensitivity to obtain chemical formulae as reported in the literature for exhaust emission products.

High Time- and Size-Resolved Measurements of PM and Chemical Composition from Coal Combustion: Implications for the EC Formation Process.

PubMed

Han, Yong; Chen, Yingjun; Ahmad, Saud; Feng, Yanli; Zhang, Fan; Song, Wenhuai; Cao, Fang; Zhang, Yanlin; Yang, Xin; Li, Jun; Zhang, Gan

2018-06-05

Inefficient coal combustion is a significant source of elemental carbon (EC) air pollution in China, but there is a limited understanding of EC's formation processes. In this study, high time-resolved particle number size distributions (PNSDs) and size-resolved chemical compositions were obtained from the combustion of four bituminous coals burned in a quartz tube furnace at 500 and 800 °C. Based on the distinct characteristics of PNSD, the flaming stage was divided into the first-flaming stage (with a PNSD peak at 0.3-0.4 μm) and the second-flaming stage (with a PNSD peak at 0.1-0.15 μm). For the size-segregated EC and OC measurements, more soot-EC was observed in particles larger than 0.3 μm, whereas the smaller ones possessed more char-EC. The results indicated that gas-phase and direct-conversion EC generation mechanisms dominate different burning stages. The analysis of 16 parent PAHs showed more high-molecular-weight PAHs in the second-flaming stage particles, which supports the idea of different formation processes for char-EC and soot-EC. For all four coals, the PNSD and chemical compositions shared a similar trend, confirming that the different formation processes of EC in different flaming stages were common. This study provides novel information concerning EC formation.

Plasmonic Resonances for Spectroscopy Applications using 3D Finite-Difference Time-Domain Models

NASA Astrophysics Data System (ADS)

Ravi, Aruna

Tuning plasmonic extinction resonances of sub-wavelength scale structures is essential to achieve maximum sensitivity and accuracy. These resonances can be controlled with careful design of nanoparticle geometries and incident wave attributes. In the first part of this dissertation, plasmonically enhanced effects on hexagonal-arrays of metal nanoparticles, metal-hole arrays (micro-mesh), and linear-arrays of metal nanorings are analyzed using three-dimensional Finite-Difference Time-Domain (3D-FDTD) simulations. The effect of particle size, lattice spacing, and lack of monodispersity of a self-assembled, hexagonal array layer of silver (Ag) nanoparticles on the extinction resonance is investigated to help determine optimal design specifications for efficient organic solar power harvesting. The enhancement of transmission resonances using plasmonic thin metal films with arrays of holes which enable recording of scatter-free infrared (IR) transmission spectra of individual particles is also explored. This method is quantitative, non-destructive and helps in better understanding the interaction of light with sub-wavelength particles. Next, plasmonically enhanced effects on linear arrays of gold (Au) rings are studied. Simulations employing 3D-FDTD can be used to determine the set of geometrical parameters to attain localized surface plasmon resonance (LSPR). The shifts in resonances due to changes in the effective dielectric of the structure are investigated, which is useful in sensing applications. Computational models enrich experimental studies. In the second part of this dissertation, the effect of particle size, shape and orientation on the IR spectra is investigated using 3D-FDTD and Mie-Bruggeman models. This computational analysis is extended to include clusters of particles of mixed composition. The prediction of extinction and absorption spectra of single particles of mixed composition helps in interpreting their physical properties and predict chemical composition. The chemical composition of respirable particles is of great interest from health, atmospheric, and environmental perspectives. Different environments may pose different hazards and spectroscopic challenges. Common mineral components of airborne and atmospheric dust samples have strong IR transitions with wavelengths that match particle size, giving rise to interesting lineshape distortions. These models enable the determination of volume fractions of components in individual particles that are mixtures of many materials, as are the dust particles inhaled into people's lungs.

Observed aerosol effects on marine cloud nucleation and supersaturation

NASA Astrophysics Data System (ADS)

Russell, Lynn M.; Sorooshian, Armin; Seinfeld, John H.; Albrecht, Bruce A.; Nenes, Athanasios; Leaitch, W. Richard; Macdonald, Anne Marie; Ahlm, Lars; Chen, Yi-Chun; Coggon, Matthew; Corrigan, Ashley; Craven, Jill S.; Flagan, Richard C.; Frossard, Amanda A.; Hawkins, Lelia N.; Jonsson, Haflidi; Jung, Eunsil; Lin, Jack J.; Metcalf, Andrew R.; Modini, Robin; Mülmenstädt, Johannes; Roberts, Greg C.; Shingler, Taylor; Song, Siwon; Wang, Zhen; Wonaschütz, Anna

2013-05-01

Aerosol particles in the marine boundary layer include primary organic and salt particles from sea spray and combustion-derived particles from ships and coastal cities. These particle types serve as nuclei for marine cloud droplet activation, although the particles that activate depend on the particle size and composition as well as the supersaturation that results from cloud updraft velocities. The Eastern Pacific Emitted Aerosol Cloud Experiment (EPEACE) 2011 was a targeted aircraft campaign to assess how different particle types nucleate cloud droplets. As part of E-PEACE 2011, we studied the role of marine particles as cloud droplet nuclei and used emitted particle sources to separate particle-induced feedbacks from dynamical variability. The emitted particle sources included shipboard smoke-generated particles with 0.05-1 μm diameters (which produced tracks measured by satellite and had drop composition characteristic of organic smoke) and combustion particles from container ships with 0.05-0.2 μm diameters (which were measured in a variety of conditions with droplets containing both organic and sulfate components) [1]. Three central aspects of the collaborative E-PEACE results are: (1) the size and chemical composition of the emitted smoke particles compared to ship-track-forming cargo ship emissions as well as background marine particles, with particular attention to the role of organic particles, (2) the characteristics of cloud track formation for smoke and cargo ships, as well as the role of multi-layered low clouds, and (3) the implications of these findings for quantifying aerosol indirect effects. For comparison with the E-PEACE results, the preliminary results of the Stratocumulus Observations of Los-Angeles Emissions Derived Aerosol-Droplets (SOLEDAD) 2012 provided evidence of the cloud-nucleating roles of both marine organic particles and coastal urban pollution, with simultaneous measurements of the effective supersaturations of the clouds in the California coastal region.

Effect of ball milling and dynamic compaction on magnetic properties of Al2O3/Co(P) composite particles

NASA Astrophysics Data System (ADS)

Denisova, E. A.; Kuzovnikova, L. A.; Iskhakov, R. S.; Bukaemskiy, A. A.; Eremin, E. V.; Nemtsev, I. V.

2014-05-01

The evolution of the magnetic properties of composite Al2O3/Co(P) particles during ball milling and dynamic compaction is investigated. To prepare starting composite particles, the Al2O3 granules were coated with a Co95P5 shell by electroless plating. The magnetic and structural properties of the composite particles are characterized by scanning electron microscopy, X-ray diffraction, and the use of the Physical Property Measurement System. The use of composite core-shell particles as starting powder for mechanoactivation allows to decrease treatment duration to 1 h and to produce a more homogeneous bulk sample than in the case of the mixture of Co and Al2O3 powders. The magnetic properties of the milled composite particles are correlated with changes in the microstructure. Reduction in grain size of Co during milling leads to an increase of the volume fraction of superparamagnetic particles and to a decrease of the saturation magnetization. The local magnetic anisotropy field depends on the amount of hcp-Co phase in sample. The anisotropy field value decreases from 8.4 kOe to 3.8 kOe with an increase in milling duration up to 75 min. The regimes of dynamic compaction were selected so that the magnetic characteristics—saturation magnetization and coercive field—remained unchanged.

Photochemical aging of aerosol particles in different air masses arriving at Baengnyeong Island, Korea

NASA Astrophysics Data System (ADS)

Kang, Eunha; Lee, Meehye; Brune, William H.; Lee, Taehyoung; Park, Taehyun; Ahn, Joonyoung; Shang, Xiaona

2018-05-01

Atmospheric aerosol particles are a serious health risk, especially in regions like East Asia. We investigated the photochemical aging of ambient aerosols using a potential aerosol mass (PAM) reactor at Baengnyeong Island in the Yellow Sea during 4-12 August 2011. The size distributions and chemical compositions of aerosol particles were measured alternately every 6 min from the ambient air or through the highly oxidizing environment of a potential aerosol mass (PAM) reactor. Particle size and chemical composition were measured by using the combination of a scanning mobility particle sizer (SMPS) and a high-resolution time-of-flight aerosol mass spectrometer (HR-ToF-AMS). Inside the PAM reactor, O3 and OH levels were equivalent to 4.6 days of integrated OH exposure at typical atmospheric conditions. Two types of air masses were distinguished on the basis of the chemical composition and the degree of aging: air transported from China, which was more aged with a higher sulfate concentration and O : C ratio, and the air transported across the Korean Peninsula, which was less aged with more organics than sulfate and a lower O : C ratio. For both episodes, the particulate sulfate mass concentration increased in the 200-400 nm size range when sampled through the PAM reactor. A decrease in organics was responsible for the loss of mass concentration in 100-200 nm particles when sampled through the PAM reactor for the organics-dominated episode. This loss was especially evident for the m/z 43 component, which represents less oxidized organics. The m/z 44 component, which represents further oxidized organics, increased with a shift toward larger sizes for both episodes. It is not possible to quantify the maximum possible organic mass concentration for either episode because only one OH exposure of 4.6 days was used, but it is clear that SO2 was a primary precursor of secondary aerosol in northeast Asia, especially during long-range transport from China. In addition, inorganic nitrate evaporated in the PAM reactor as sulfate was added to the particles. These results suggest that the chemical composition of aerosols and their degree of photochemical aging, particularly for organics, are also crucial in determining aerosol mass concentrations.

Simulation of mixture microstructures via particle packing models and their direct comparison with real mixtures

NASA Astrophysics Data System (ADS)

Gulliver, Eric A.

The objective of this thesis to identify and develop techniques providing direct comparison between simulated and real packed particle mixture microstructures containing submicron-sized particles. This entailed devising techniques for simulating powder mixtures, producing real mixtures with known powder characteristics, sectioning real mixtures, interrogating mixture cross-sections, evaluating and quantifying the mixture interrogation process and for comparing interrogation results between mixtures. A drop and roll-type particle-packing model was used to generate simulations of random mixtures. The simulated mixtures were then evaluated to establish that they were not segregated and free from gross defects. A powder processing protocol was established to provide real mixtures for direct comparison and for use in evaluating the simulation. The powder processing protocol was designed to minimize differences between measured particle size distributions and the particle size distributions in the mixture. A sectioning technique was developed that was capable of producing distortion free cross-sections of fine scale particulate mixtures. Tessellation analysis was used to interrogate mixture cross sections and statistical quality control charts were used to evaluate different types of tessellation analysis and to establish the importance of differences between simulated and real mixtures. The particle-packing program generated crescent shaped pores below large particles but realistic looking mixture microstructures otherwise. Focused ion beam milling was the only technique capable of sectioning particle compacts in a manner suitable for stereological analysis. Johnson-Mehl and Voronoi tessellation of the same cross-sections produced tessellation tiles with different the-area populations. Control charts analysis showed Johnson-Mehl tessellation measurements are superior to Voronoi tessellation measurements for detecting variations in mixture microstructure, such as altered particle-size distributions or mixture composition. Control charts based on tessellation measurements were used for direct, quantitative comparisons between real and simulated mixtures. Four sets of simulated and real mixtures were examined. Data from real mixture was matched with simulated data when the samples were well mixed and the particle size distributions and volume fractions of the components were identical. Analysis of mixture components that occupied less than approximately 10 vol% of the mixture was not practical unless the particle size of the component was extremely small and excellent quality high-resolution compositional micrographs of the real sample are available. These methods of analysis should allow future researchers to systematically evaluate and predict the impact and importance of variables such as component volume fraction and component particle size distribution as they pertain to the uniformity of powder mixture microstructures.

Far Field Modeling Methods For Characterizing Surface Detonations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Garrett, A.

2015-10-08

Savannah River National Laboratory (SRNL) analyzed particle samples collected during experiments that were designed to replicate tests of nuclear weapons components that involve detonation of high explosives (HE). SRNL collected the particle samples in the HE debris cloud using innovative rocket propelled samplers. SRNL used scanning electronic microscopy to determine the elemental constituents of the particles and their size distributions. Depleted uranium composed about 7% of the particle contents. SRNL used the particle size distributions and elemental composition to perform transport calculations that indicate in many terrains and atmospheric conditions the uranium bearing particles will be transported long distances downwind.more » This research established that HE tests specific to nuclear proliferation should be detectable at long downwind distances by sampling airborne particles created by the test detonations.« less

In-situ synthesis of SiO2@MOF composites for high-efficiency removal of aniline from aqueous solution

NASA Astrophysics Data System (ADS)

Han, Tongtong; Li, Caifeng; Guo, Xiangyu; Huang, Hongliang; Liu, Dahuan; Zhong, Chongli

2016-12-01

A series of SiO2@aluminum-MOF(MIL-68) composites with different SiO2 loadings have been synthesized by a simple and mild compositing strategy for high-efficiency removal of aniline. As evidenced from SEM and TEM images as well as the particle size distribution, the incorporation of SiO2 can improve the dispersity of MIL-68(Al) in composites, and result in the smaller particle size than that of pristine MIL-68(Al). Besides, the adsorption of aniline over SiO2, MIL-68(Al), the physical mixture of these two materials, and SiO2@MIL-68(Al) composites was investigated comparatively, demonstrating a relatively high adsorption capacity (531.9 mg g-1) of 7% SiO2@MIL-68(Al) towards aniline. Combining the ultrafast adsorption dynamics (reaching equilibrium within 40 s) and great reusability, 7% SiO2@MIL-68(Al) shows excellent adsorption performance. This indicates that the SiO2@MIL-68(Al) composites possess great potential applications as a kind of fascinating adsorbent in water pollution protection.

Study on the fabrication of composite photonic crystals with high structural stability by co-sedimentation self-assembly on fabric substrates

NASA Astrophysics Data System (ADS)

Li, Yichen; Zhou, Lan; Liu, Guojin; Chai, Liqin; Fan, Qinguo; Shao, Jianzhong

2018-06-01

The Silica/Poly(methylmethacrylate-butylacrylate)[SiO2/P(MMA-BA)] photonic crystals(PCs) with brilliant structural colors were fabricated on fabric substrates by co-sedimentation self-assembly, in which the relatively smaller P(MMA-BA) copolymer particles filled in the interstices among the larger SiO2 microspheres. The fabricated composite PCs were mechanically robust and strongly bonded to the substrate because of the cementing effect caused by the soft P(MMA-BA) copolymer particles filling in the interstices of the SiO2 microspheres like cement filling in the gap and tightly holding stones in a sturdy cement wall. The volume fraction and the size ratios of the two components significantly influenced the structural colors of the composite PCs, and the larger volume fraction could improve the structural stability of the composite PCs, while the smaller size ratios could enhance the brightness of the structural colors of the composite PCs. The composite PCs with both high structural stability and brilliant structural colors have great application prospect for structural coloration of textiles.

XRF-analysis of fine and ultrafine particles emitted from laser printing devices.

PubMed

Barthel, Mathias; Pedan, Vasilisa; Hahn, Oliver; Rothhardt, Monika; Bresch, Harald; Jann, Oliver; Seeger, Stefan

2011-09-15

In this work, the elemental composition of fine and ultrafine particles emitted by ten different laser printing devices (LPD) is examined. The particle number concentration time series was measured as well as the particle size distributions. In parallel, emitted particles were size-selectively sampled with a cascade impactor and subsequently analyzed by the means of XRF. In order to identify potential sources for the aerosol's elemental composition, materials involved in the printing process such as toner, paper, and structural components of the printer were also analyzed. While the majority of particle emissions from laser printers are known to consist of recondensated semi volatile organic compounds, elemental analysis identifies Si, S, Cl, Ca, Ti, Cr, and Fe as well as traces of Ni and Zn in different size fractions of the aerosols. These elements can mainly be assigned to contributions from toner and paper. The detection of elements that are likely to be present in inorganic compounds is in good agreement with the measurement of nonvolatile particles. Quantitative measurements of solid particles at 400 °C resulted in residues of 1.6 × 10(9) and 1.5 × 10(10) particles per print job, representing fractions of 0.2% and 1.9% of the total number of emitted particles at room temperature. In combination with the XRF results it is concluded that solid inorganic particles contribute to LPD emissions in measurable quantities. Furthermore, for the first time Br was detected in significant concentrations in the aerosol emitted from two LPD. The analysis of several possible sources identified the plastic housings of the fuser units as main sources due to substantial Br concentrations related to brominated flame retardants.

Optical properties of mineral dust aerosol including analysis of particle size, composition, and shape effects, and the impact of physical and chemical processing

NASA Astrophysics Data System (ADS)

Alexander, Jennifer Mary

Atmospheric mineral dust has a large impact on the earth's radiation balance and climate. The radiative effects of mineral dust depend on factors including, particle size, shape, and composition which can all be extremely complex. Mineral dust particles are typically irregular in shape and can include sharp edges, voids, and fine scale surface roughness. Particle shape can also depend on the type of mineral and can vary as a function of particle size. In addition, atmospheric mineral dust is a complex mixture of different minerals as well as other, possibly organic, components that have been mixed in while these particles are suspended in the atmosphere. Aerosol optical properties are investigated in this work, including studies of the effect of particle size, shape, and composition on the infrared (IR) extinction and visible scattering properties in order to achieve more accurate modeling methods. Studies of particle shape effects on dust optical properties for single component mineral samples of silicate clay and diatomaceous earth are carried out here first. Experimental measurements are modeled using T-matrix theory in a uniform spheroid approximation. Previous efforts to simulate the measured optical properties of silicate clay, using models that assumed particle shape was independent of particle size, have achieved only limited success. However, a model which accounts for a correlation between particle size and shape for the silicate clays offers a large improvement over earlier modeling approaches. Diatomaceous earth is also studied as an example of a single component mineral dust aerosol with extreme particle shapes. A particle shape distribution, determined by fitting the experimental IR extinction data, used as a basis for modeling the visible light scattering properties. While the visible simulations show only modestly good agreement with the scattering data, the fits are generally better than those obtained using more commonly invoked particle shape distributions. The next goal of this work is to investigate if modeling methods developed in the studies of single mineral components can be generalized to predict the optical properties of more authentic aerosol samples which are complex mixtures of different minerals. Samples of Saharan sand, Iowa loess, and Arizona road dust are used here as test cases. T-matrix based simulations of the authentic samples, using measured particle size distributions, empirical mineralogies, and a priori particle shape models for each mineral component are directly compared with the measured IR extinction spectra and visible scattering profiles. This modeling approach offers a significant improvement over more commonly applied models that ignore variations in particle shape with size or mineralogy and include only a moderate range of shape parameters. Mineral dust samples processed with organic acids and humic material are also studied in order to explore how the optical properties of dust can change after being aged in the atmosphere. Processed samples include quartz mixed with humic material, and calcite reacted with acetic and oxalic acid. Clear differences in the light scattering properties are observed for all three processed mineral dust samples when compared to the unprocessed mineral dust or organic salt products. These interactions result in both internal and external mixtures depending on the sample. In addition, the presence of these organic materials can alter the mineral dust particle shape. Overall, however, these results demonstrate the need to account for the effects of atmospheric aging of mineral dust on aerosol optical properties. Particle shape can also affect the aerodynamic properties of mineral dust aerosol. In order to account for these effects, the dynamic shape factor is used to give a measure of particle asphericity. Dynamic shape factors of quartz are measured by mass and mobility selecting particles and measuring their vacuum aerodynamic diameter. From this, dynamic shape factors in both the transition and vacuum regime can be derived. The measured dynamic shape factors of quartz agree quite well with the spheroidal shape distributions derived through studies of the optical properties.

Microemulsion impregnated catalyst composite and use thereof in a synthesis gas conversion process

DOEpatents

Abrevaya, Hayim; Targos, William M.

1987-01-01

A catalyst composition for synthesis gas conversion comprising a ruthenium metal component deposited on a support carrier wherein the average metal particle size is less than about 100 A. The method of manufacture of the composition via a reverse micelle impregnation technique and the use of the composition in a Fischer-Tropsch conversion process is also disclosed.

Effect of Morphology and Composition on the Hygroscopicity of Soot Aerosols

NASA Astrophysics Data System (ADS)

Williams, L.; Slowik, J.; Davidovits, P.; Jayne, J.; Kolb, C.; Worsnop, D.; Rudich, Y.

2003-12-01

Freshly generated soot aerosols are initially hydrophobic and unlikely to act as cloud condensation nuclei (CCN). However, during combustion many low vapor pressure gas products are formed that may then condense on existing soot aerosols. Additionally, soot particles may acquire coatings as they age, such as acids, salts, and oxygenated organics. An understanding of this aging process and its effect on soot hygroscopicity is necessary to address the potential of soot to act as a CCN. The transformation of soot from hydrophobic to hydrophilic is the focus of this work. An aim here is to determine the minimum coating required for hygroscopic growth. Soot particles produced by combustion of mixtures of fuel and air are size selected by a Differential Mobility Analyzer (DMA) and entrained in a laminar flow passing through a flow tube. The size selected soot particles are mixed with a controlled amount of the gas phase precursors to produce the coatings to be studied. Initial studies are focused on coatings of H2SO4, NH4NO3, and selected organics. The number of particles per unit volume of air is counted by a Condensation Particle Counter (CPC) and the particles are isokinetically sampled into an Aerosol Mass Spectrometer (AMS). Two distinct types of soot aerosols have been observed depending on the type of fuel and air mixture. With soot produced by the combustion of propane and air, the AMS shows a polydisperse particle size distribution with aerodynamic diameters ranging from 100 nm to 400 nm. The aerodynamic diameter is linearly related to the DMA-determined mobility diameter with the product density x shape factor = 1.2. The organic molecules in this soot are mostly PAH compounds. However, when kerosene is added to the propane flame, the soot particle morphology and composition is strikingly altered. While the DMA shows an essentially unchanged mobility diameter distribution, in the range 100 nm to 400, aerodynamic particle diameter is constant at about 100 nm, independent of the mobility diameter. This type of constancy of the aerodynamic diameter has been observed for soot particles in diesel engine exhaust and has been interpreted in terms of a size-dependent effective density. The soot chemical composition is also altered. In this soot the organics are mainly linear hydrocarbons. The differences between these two types of soot with respect to hygroscopicity and effective area are being investigated.

Simulation of the influence of aerosol particles on Stokes parameters of polarized skylight

NASA Astrophysics Data System (ADS)

Li, L.; Li, Z. Q.; Wendisch, M.

2014-03-01

Microphysical properties and chemical compositions of aerosol particles determine polarized radiance distribution in the atmosphere. In this paper, the influences of different aerosol properties (particle size, shape, real and imaginary parts of refractive index) on Stokes parameters of polarized skylight in the solar principal and almucantar planes are studied by using vector radiative transfer simulations. The results show high sensitivity of the normalized Stokes parameters due to fine particle size, shape and real part of refractive index of aerosols. It is possible to utilize the strength variations at the peak positions of the normalized Stokes parameters in the principal and almucantar planes to identify aerosol types.

Contributions of Organic Sources to Atmospheric Aerosol Particle Concentrations and Growth

NASA Astrophysics Data System (ADS)

Russell, L. M.

2017-12-01

Organic molecules are important contributors to aerosol particle mass and number concentrations through primary emissions as well as secondary growth in the atmosphere. New techniques for measuring organic aerosol components in atmospheric particles have improved measurements of this contribution in the last 20 years, including Scanning Transmission X-ray Microscopy Near Edge X-ray Absorption Fine Structure (STXM-NEXAFS), Fourier Transform Infrared spectroscopy (FTIR), and High-Resolution Aerosol Mass Spectrometry (AMS). STXM-NEXAFS individual aerosol particle composition illustrated the variety of morphology of organic components in marine aerosols, the inherent relationships between organic composition and shape, and the links between atmospheric aerosol composition and particles produced in smog chambers. This type of single particle microscopy has also added to size distribution measurements by providing evidence of how surface-controlled and bulk-controlled processes contribute to the growth of particles in the atmosphere. FTIR analysis of organic functional groups are sufficient to distinguish combustion, marine, and terrestrial organic particle sources and to show that each of those types of sources has a surprisingly similar organic functional group composition over four different oceans and four different continents. Augmenting the limited sampling of these off-line techniques with side-by-side inter-comparisons to online AMS provides complementary composition information and consistent quantitative attribution to sources (despite some clear method differences). Single-particle AMS techniques using light scattering and event trigger modes have now also characterized the types of particles found in urban, marine, and ship emission aerosols. Most recently, by combining with off-line techniques, single particle composition measurements have separated and quantified the contributions of organic, sulfate and salt components from ocean biogenic and sea spray emissions to particles, addressing the persistent question of the sources of cloud condensation nuclei in clean marine conditions.

Bubbles and Dust: Dissolution Rates of Unhydrated Volcanic Ash as a Function of Morphology, Composition, and Particle Size

NASA Astrophysics Data System (ADS)

Wygel, C. M.; Sahagian, D. L.

2017-12-01

Volcanic eruptions are natural hazards due to their explosive nature and widespread transportation and deposition of ash particles. After deposition and subsequent leaching in soils or water bodies, ash deposition positively (nutrients) and negatively (contaminants) impacts the health of flora and fauna, including humans. The effects of ash leachates have been difficult to replicate in field and laboratory studies due to the many complexities and differences between ash particles. Ash morphology is characteristic for each eruption, dependent upon eruption energy, and should play a critical role in determining leaching rates. Morphology reflects overall particle surface area, which is strongly influenced by the presence of surface dust. In addition, ash composition, which in part controls morphology and particle size, may also affect leaching rates. This study determines the extent to which ash morphology, surface area, composition, and particle size control ash dissolution rates. Further, it is necessary to determine whether compound vesicular ash particles permit water into their interior structures to understand if both the internal and external surface areas are available for leaching. To address this, six fresh, unhydrated ash samples from diverse volcanic environments and a large range in morphology, from Pele's spheres to vesicular compound ash, are tested in the laboratory. Ash morphology was characterized on the Scanning Electron Microscope (SEM) before and after leaching and surface area was quantified by Brunauer Emmett Teller (BET) analysis and with geometric calculations. Column Leachate Tests (CLT) were conducted to compare leaching rates over a range of basaltic to silicic ashes as a function of time and surface area, to recreate the effects of ash deposition in diverse volcanic environments. After the CLT, post-leaching water analyses were conducted by Ion Coupled Plasma-Mass Spectrometry (ICP-MS) and Ion Chromatography (IC). We find that leaching rates are correlated to characteristic surface area of ash particles.

Elemental Compositions of Comet 81P/Wild 2 Samples Collected by Stardust

NASA Technical Reports Server (NTRS)

Flynn, G. J.; Bleuet, P.; Borg, J.; Bradley, J.; Brenker, F.; Brennan, S.; Bridges, J.; Brownlee, D. E.; Bullock, E.; Clark, B. C.;

Airborne particles released by crushing CNT composites

NASA Astrophysics Data System (ADS)

Ogura, I.; Okayama, C.; Kotake, M.; Ata, S.; Matsui, Y.; Gotoh, K.

2017-06-01

We investigated airborne particles released as a result of crushing carbon nanotube (CNT) composites using a laboratory scale crusher with rotor blades. For each crushing test, five pellets (approximately 0.1 g) of a polymer (polystyrene, polyamide, or polycarbonate) containing multiwall CNTs (Nanocyl NC7000 or CNano Flotube9000) or no CNTs were placed in the container of the crusher. The airborne particles released by the crushing of the samples were measured. The real-time aerosol measurements showed increases in the concentration of nanometer- and micrometer-sized particles, regardless of the sample type, even when CNT-free polymers were crushed. The masses of the airborne particles collected on filters were below the detection limit, which indicated that the mass ratios of the airborne particles to the crushed pellets were lower than 0.02%. In the electron microscopic analysis, particles with protruding CNTs were observed. However, free-standing CNTs were not found, except for a poorly dispersed CNT-polystyrene composite. This study demonstrated that the crushing test using a laboratory scale crusher is capable of evaluating the potential release of CNTs as a result of crushing CNT composites. The advantage of this method is that only a small amount of sample (several pieces of pellets) is required.

New approaches for the chemical and physical characterization of aerosols using a single particle mass spectrometry based technique

NASA Astrophysics Data System (ADS)

Spencer, Matthew Todd

Aerosols affect the lives of people every day. They can decrease visibility, alter cloud formation and cloud lifetimes, change the energy balance of the earth and are implicated in causing numerous health problems. Measuring the physical and chemical properties of aerosols is essential to understand and mitigate any negative impacts that aerosols might have on climate and human health. Aerosol time-of-flight mass spectrometry (ATOFMS) is a technique that measures the size and chemical composition of individual particles in real time. The goal of this dissertation is to develop new and useful approaches for measuring the physical and/or chemical properties of particles using ATOFMS. This has been accomplished using laboratory experiments, ambient field measurements and sometimes comparisons between them. A comparison of mass spectra generated from petrochemical particles was made to light duty vehicle (LDV) and heavy duty diesel vehicle (HDDV) particle mass spectra. This comparison has given us new insight into how to differentiate between particles from these two sources. A method for coating elemental carbon (EC) particles with organic carbon (OC) was used to generate a calibration curve for quantifying the fraction of organic carbon and elemental carbon on particles using ATOFMS. This work demonstrates that it is possible to obtain quantitative chemical information with regards to EC and OC using ATOFMS. The relationship between electrical mobility diameter and aerodynamic diameter is used to develop a tandem differential mobility analyzer-ATOFMS technique to measure the effective density, size and chemical composition of particles. The method is applied in the field and gives new insight into the physical/chemical properties of particles. The size resolved chemical composition of aerosols was measured in the Indian Ocean during the monsoonal transition period. This field work shows that a significant fraction of aerosol transported from India was from biomass burning and appeared to be internally mixed with sulfate which suggests it was cloud processed during transport. Lastly, noble metal nanoparticles are explored as potential matrices for visible wavelength single particle matrix assisted laser desorption/ionization mass spectrometry (VIS-MALDI). This work demonstrates that noble metal nanoparticle matrices can be used for VIS-MALDI analysis.

[Study of relationship between powder-size gradation and mechanical properties of Zirconia toughened glass infiltrated nanometer-ceramic composite powder].

PubMed

Chai, Feng; Xu, Ling; Liao, Yun-mao; Chao, Yong-lie

2003-07-01

The fabrication of all-ceramic dental restorations is challenged by ceramics' relatively low flexural strength and intrinsic poor resistance to fracture. This paper aimed at investigating the relationships between powder-size gradation and mechanical properties of Zirconia toughened glass infiltrated nanometer-ceramic composite (Al(2)O(3)-nZrO(2)). Al(2)O(3)-nZrO(2) ceramics powder (W) was processed by combination methods of chemical co-precipitation and ball milling with addition of different powder-sized ZrO(2). Field-emission scanning electron microscopy was used to determine the particle size distribution and characterize the particle morphology of powders. The matrix compacts were made by slip-casting technique and sintered to 1,450 degrees C and flexural strength and the fracture toughness of them were measured. 1. The particle distribution of Al(2)O(3)-nZrO(2) ceramics powder ranges from 0.02 - 3.5 micro m and among them the superfine particles almost accounted for 20%. 2. The ceramic matrix samples with addition of nZrO(2) (W) showed much higher flexural strength (115.434 +/- 5.319) MPa and fracture toughness (2.04 +/- 0.10) MPa m(1/2) than those of pure Al(2)O(3) ceramics (62.763 +/- 7.220 MPa; 1.16 +/- 0.02 MPa m(1/2)). The particle size of additive ZrO(2) may impose influences on mechanical properties of Al(2)O(3)-nZrO(2) ceramics matrix. Good homogeneity and reasonable powder-size gradation of ceramic powder can improve the mechanical properties of material.

Interrelating the breakage and composition of mined and drill core coal

NASA Astrophysics Data System (ADS)

Wilson, Terril Edward

Particle size distribution of coal is important if the coal is to be beneficiated, or if a coal sales contract includes particle size specifications. An exploration bore core sample of coal ought to be reduced from its original cylindrical form to a particle size distribution and particle composition that reflects, insofar as possible, a process stream of raw coal it represents. Often, coal cores are reduced with a laboratory crushing machine, the product of which does not match the raw coal size distribution. This study proceeds from work in coal bore core reduction by Australian investigators. In this study, as differentiated from the Australian work, drop-shatter impact breakage followed by dry batch tumbling in steel cylinder rotated about its transverse axis are employed to characterize the core material in terms of first-order and zeroth-order breakage rate constants, which are indices of the propensity of the coal to degrade during excavation and handling. Initial drop-shatter and dry tumbling calibrations were done with synthetic cores composed of controlled low-strength concrete incorporating fly ash (as a partial substitute for Portland cement) in order to reduce material variables and conserve difficult-to-obtain coal cores. Cores of three different coalbeds--Illinois No. 6, Upper Freeport, and Pocahontas No. 5 were subjected to drop-shatter and dry batch tumbling tests to determine breakage response. First-order breakage, characterized by a first-order breakage index for each coal, occurred in the drop-shatter tests. First- and zeroth-order breakage occurred in dry batch tumbling; disappearance of coarse particles and creation of fine particles occurred in a systematic way that could be represented mathematically. Certain of the coal cores available for testing were dry and friable. Comparison of coal preparation plant feed with a crushed bore core and a bore core prepared by drop-shatter and tumbling (all from the same Illinois No.6 coal mining property) indicated that the size distribution and size fraction composition of the drop-shattered/tumbled core more closely resembled the plant feed than the crushed core. An attempt to determine breakage parameters (to allow use of selection and breakage functions and population balance models in the description of bore core size reduction) was initiated. Rank determination of the three coal types was done, indicating that higher rank associates with higher breakage propensity. The two step procedure of drop-shatter and dry batch tumbling simulates the first-order (volume breakage) and zeroth-order (abrasion of particle surfaces) that occur in excavation and handling operations, and is appropriate for drill core reduction prior to laboratory analysis.

Effect of Biophysical Properties of Phosphatidylserine Particle on Immune Tolerance Induction Toward Factor VIII in a Hemophilia A Mouse Model.

PubMed

Ramakrishnan, Radha; Balu-Iyer, Sathy V

2016-10-01

A major complication in the replacement therapy of Factor VIII (FVIII) for Hemophilia A is the development of unwanted immune responses. Previous studies from our laboratory have shown that pretreatment of FVIII in the presence of phosphatidylserine (PS) resulted in hyporesponsiveness to subsequent administration of FVIII alone, due to the ability of PS to convert an immunogen to a tolerogen. We investigated the importance of biophysical properties of PS liposomes on its ability to convert an immunogen to a tolerogen. PS particles were prepared differing in size, protein-lipid topology, lamellarity, and % association to FVIII keeping the composition of the particle same. PS particles were prepared in 2 different sizes with differing biophysical properties: smaller particles in the nanometer range (200 nm) and larger size particles in the micron range (2 μm). Hemophilia A animals treated with both the nanometer and micron size PS particles showed a significant reduction in anti-FVIII antibody titers when compared to animals receiving free FVIII alone. Upon rechallenge with free FVIII animals that received FVIII along with the nanometer size particle continued to show reduced antibody responses. Animals receiving the micron size particle showed a slight increase in titers although they remained significantly lower than the free FVIII treated group. Upon culture with bone marrow derived dendritic cells, the nanometer size particle showed a reduction in CD40 expression and an increase in transforming growth factor-β cytokine production, which was not observed with the micron size particle. These results show that biophysical properties of PS play an important role in tolerance. Copyright © 2016 American Pharmacists Association®. Published by Elsevier Inc. All rights reserved.

Preparation of fluorescent mesoporous hollow silica-fullerene nanoparticles via selective etching for combined chemotherapy and photodynamic therapy

NASA Astrophysics Data System (ADS)

Yang, Yannan; Yu, Meihua; Song, Hao; Wang, Yue; Yu, Chengzhong

2015-07-01

Well-dispersed mesoporous hollow silica-fullerene nanoparticles with particle sizes of ~50 nm have been successfully prepared by incorporating fullerene molecules into the silica framework followed by a selective etching method. The fabricated fluorescent silica-fullerene composite with high porosity demonstrates excellent performance in combined chemo/photodynamic therapy.Well-dispersed mesoporous hollow silica-fullerene nanoparticles with particle sizes of ~50 nm have been successfully prepared by incorporating fullerene molecules into the silica framework followed by a selective etching method. The fabricated fluorescent silica-fullerene composite with high porosity demonstrates excellent performance in combined chemo/photodynamic therapy. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr02769a

Inhalation Exposure and Lung Dose Analysis of Multi-mode Complex Ambient Aerosols

EPA Science Inventory

Rationale: Ambient aerosols are complex mixture of particles with different size, shape and chemical composition. Although they are known to cause health hazard, it is not fully understood about causal mechanisms and specific attributes of particles causing the effects. Internal ...

AEROSOL CHEMICAL CHARACTERISTION ON BOARD THE DOE G1 AIRCRAFT USING A PARTICLE INTO LIQUID SAMPLER DURING THE TEXAQS 2000 EXPERIMENT.

DOE Office of Scientific and Technical Information (OSTI.GOV)

LEE,Y.N.; SONG,Z.; LIU,Y.

2001-01-13

Knowledge of aerosol chemical composition is key to understanding a number of properties of ambient aerosol particles including sources, size/number distribution, chemical evolution, optical properties and human health effects. Although filter based techniques have been widely used to determine aerosol chemical constituents, they generally cannot provide sufficiently fast time resolution needed to investigate sources and chemical evolution that effect aerosol chemical, size and number changes. In order to gain an ability to describe and predict the life cycles of ambient aerosols as a basis for ambient air quality control, fast and sensitive determination of the aerosol chemical composition must bemore » made available. To help to achieve this goal, we deployed a newly developed technique, referred to as PILS (particle-into-liquid-sampler), on the DOE G1 aircraft during the 2000 Texas Air Quality Study (TexAQS 2000) to characterize the major ionic species of aerosol particles with aerodynamic size smaller than 2.5 {micro}m (PM 2.5). The results obtained are examined in the context of other simultaneously collected data for insights into the measurement capability of the PILS system.« less

Preparation of SiO2/(PMMA/Fe3O4) from monolayer linolenic acid modified Fe3O4 nanoparticles via miniemulsion polymerization.

PubMed

He, Lei; Li, Zhiyang; Fu, Jing; Deng, Yan; He, Nongyue; Wang, Zhifei; Wang, Hua; Shi, Zhiyang; Wang, Zunliang

2009-10-01

SiO2/(PMMA/Fe3O4) composite particles were prepared from linolenic acid (LA) instead of oleic acid (OA) modified Fe3O4 nanoparticles by miniemulsion polymerization. LA has three unsaturated double bonds with which it can polymerizate more easily than OA. And coating Fe3O4 with polymethyl methacrylate (PMMA) polymer beforehand can prevent magnetic nanoparticles from the aggregation that usually comes from the increasing of ionic strength during the hydrolyzation of tetraethoxysilane (TEOS) by the steric hindrance. Finally, the resulting PMMA/Fe3O4 nanoparticles were coated with silica, forming SiO2/(PMMA/Fe3O4) core-shell structure particles. The sizes of nanoparticles with core-shell structure were in the range from 300 to 600 nm. The nanoparticles were spherical particles and had consistent size. The result of magnetic measurement showed that the composite particles had superparamagnetic property.

Carbon-coated CoFe–CoFe2O4 composite particles with high and dual-band electromagnetic wave absorbing properties

NASA Astrophysics Data System (ADS)

Guan, Zhen-Jie; Jiang, Jian-Tang; Chen, Na; Gong, Yuan-Xun; Zhen, Liang

2018-07-01

SiO2 and TiO2, as conventional dielectric shells of ferromagnetic/dielectric composite particles, can protect ferromagnetic particles from aggregation and oxidation, but contribute little to electromagnetic loss. In this work, we designed nano-assembled CoFe–CoFe2O4@C composite particles, in which ferrites with high permeability were dielectric elements and carbon was introduced as protective layers, aiming for high-efficiency microwave absorption. These assembled particles with different CoFe contents were prepared through solvothermal methods and subsequent hydrogen-thermal reduction. CoFe nanoparticles were dispersed on a CoFe2O4 matrix via an in situ reduction transformation from CoFe2O4 to CoFe. The microstructure evolution of composite particles and corresponding electromagnetic properties tailoring were investigated. The content and size of CoFe as well as the porosity of composite particles increase gradually as the annealing temperature increases. A maximum reflection loss (RL max) of –71.73 dB is observed at 4.78 GHz in 3.4 mm thick coating using particles annealed at 500 °C as fillers. The coating presents double-band absorbing characteristics, as broad effective absorption bandwidth with RL > 5 (ERL 5) and high RL max are observed in both S-C and X-Ku bands. The tunability as well as the assembled characteristic of the electromagnetic property that endued from the composite structure contributes to the excellent electromagnetic wave absorbing performances.

Carbon-coated CoFe-CoFe2O4 composite particles with high and dual-band electromagnetic wave absorbing properties.

PubMed

Guan, Zhen-Jie; Jiang, Jian-Tang; Chen, Na; Gong, Yuan-Xun; Zhen, Liang

2018-07-27

SiO 2 and TiO 2 , as conventional dielectric shells of ferromagnetic/dielectric composite particles, can protect ferromagnetic particles from aggregation and oxidation, but contribute little to electromagnetic loss. In this work, we designed nano-assembled CoFe-CoFe 2 O 4 @C composite particles, in which ferrites with high permeability were dielectric elements and carbon was introduced as protective layers, aiming for high-efficiency microwave absorption. These assembled particles with different CoFe contents were prepared through solvothermal methods and subsequent hydrogen-thermal reduction. CoFe nanoparticles were dispersed on a CoFe 2 O 4 matrix via an in situ reduction transformation from CoFe 2 O 4 to CoFe. The microstructure evolution of composite particles and corresponding electromagnetic properties tailoring were investigated. The content and size of CoFe as well as the porosity of composite particles increase gradually as the annealing temperature increases. A maximum reflection loss (RL max ) of -71.73 dB is observed at 4.78 GHz in 3.4 mm thick coating using particles annealed at 500 °C as fillers. The coating presents double-band absorbing characteristics, as broad effective absorption bandwidth with RL > 5 (ERL 5 ) and high RL max are observed in both S-C and X-K u bands. The tunability as well as the assembled characteristic of the electromagnetic property that endued from the composite structure contributes to the excellent electromagnetic wave absorbing performances.

Synthesis of silver nanoparticles by silver salt reduction and its characterization

NASA Astrophysics Data System (ADS)

Muzamil, Muhammad; Khalid, Naveed; Danish Aziz, M.; Aun Abbas, S.

2014-06-01

The wet chemical method route by metal salt reduction has been used to synthesize nanoparticles, using silver nitrate as an inorganic salt, aldehyde as a reducing agent and amino acid as a catalyst. During the reaction aldehyde oxidizes to carboxylic acid and encapsulates the silver nanoparticles to prevent agglomeration and provide barrier in the growth of particle. The existing work produces particles using lab grade chemical, here the presented work is by using industrial grade chemicals to make the process more cost & time effective. The nano silver powder has been studied for their formation, particle size, shape & compositional analysis using Scanning Electron Microscope (SEM) equipped with EDS. The particles size distributions were analyzed by Laser Particle Analyzer (LPA), structure & morphological analysis using x-ray diffraction (XRD) and Fourier-transform-infrared Spectroscopy (FTIR) confirmed the stabilization of particles by coating of carboxylic group. These studies infer that the particles are mostly spherical in shape and have an average size between 70 to 350 nm.

Synthesis of macroporous structures

DOEpatents

Stein, Andreas; Holland, Brian T.; Blanford, Christopher F.; Yan, Hongwei

2004-01-20

The present application discloses a method of forming an inorganic macroporous material. In some embodiments, the method includes: providing a sample of organic polymer particles having a particle size distribution of no greater than about 10%; forming a colloidal crystal template of the sample of organic polymer particles, the colloidal crystal template including a plurality of organic polymer particles and interstitial spaces therebetween; adding an inorganic precursor composition including a noncolloidal inorganic precursor to the colloidal crystal template such that the precursor composition permeates the interstitial spaces between the organic polymer particles; converting the noncolloidal inorganic precursor to a hardened inorganic framework; and removing the colloidal crystal template from the hardened inorganic framework to form a macroporous material. Inorganic macroporous materials are also disclosed.

Dust in Cometary Comae: Present Understanding of the Structure and Composition of Dust Particles

NASA Technical Reports Server (NTRS)

Levasseur-Regourd, A. C.; Zolensky, M.; Lasue, J.

2007-01-01

In situ probing of a very few cometary comae has shown that dust particles present a low albedo and a low density, and that they consist of both rocky material and refractory organics. Remote observations of solar light scattered by cometary dust provide information on the properties of dust particles in the coma of a larger set of comets. The observations of the linear polarization in the coma indicate that the dust particles are irregular, with a size greater (on the average) than about one micron. Besides, they suggest, through numerical and experimental simulations, that both compact grains and fluffy aggregates (with a power law of the size distribution in the -2.6 to -3 range), and both rather transparent silicates and absorbing organics are present in the coma. Recent analysis of the cometary dust samples collected by the Stardust mission provide a unique ground truth and confirm, for comet 81P/Wild 2, the results from remote sensing observations. Future space missions to comets should, in the next decade, lead to a more precise characterization of the structure and composition of cometary dust particles.

In-situ ductile metal/bulk metallic glass matrix composites formed by chemical partitioning

DOEpatents

Kim, Choong Paul; Hays, Charles C.; Johnson, William L.

2004-03-23

A composite metal object comprises ductile crystalline metal particles in an amorphous metal matrix. An alloy is heated above its liquidus temperature. Upon cooling from the high temperature melt, the alloy chemically partitions, forming dendrites in the melt. Upon cooling the remaining liquid below the glass transition temperature it freezes to the amorphous state, producing a two-phase microstructure containing crystalline particles in an amorphous metal matrix. The ductile metal particles have a size in the range of from 0.1 to 15 micrometers and spacing in the range of from 0.1 to 20 micrometers. Preferably, the particle size is in the range of from 0.5 to 8 micrometers and spacing is in the range of from 1 to 10 micrometers. The volume proportion of particles is in the range of from 5 to 50% and preferably 15 to 35%. Differential cooling can produce oriented dendrites of ductile metal phase in an amorphous matrix. Examples are given in the Zr--Ti--Cu--Ni--Be alloy bulk glass forming system with added niobium.

In-situ ductile metal/bulk metallic glass matrix composites formed by chemical partitioning

DOEpatents

Kim, Choong Paul [Northridge, CA; Hays, Charles C [Pasadena, CA; Johnson, William L [Pasadena, CA

2007-07-17

A composite metal object comprises ductile crystalline metal particles in an amorphous metal matrix. An alloy is heated above its liquidus temperature. Upon cooling from the high temperature melt, the alloy chemically partitions, forming dendrites in the melt. Upon cooling the remaining liquid below the glass transition temperature it freezes to the amorphous state, producing a two-phase microstructure containing crystalline particles in an amorphous metal matrix. The ductile metal particles have a size in the range of from 0.1 to 15 micrometers and spacing in the range of from 0.1 to 20 micrometers. Preferably, the particle size is in the range of from 0.5 to 8 micrometers and spacing is in the range of from 1 to 10 micrometers. The volume proportion of particles is in the range of from 5 to 50% and preferably 15 to 35%. Differential cooling can produce oriented dendrites of ductile metal phase in an amorphous matrix. Examples are given in the Zr--Ti--Cu--Ni--Be alloy bulk glass forming system with added niobium.

Effect of Feedstock Size and its Distribution on the Properties of Detonation Sprayed Coatings

NASA Astrophysics Data System (ADS)

Suresh Babu, P.; Rao, D. S.; Rao, G. V. N.; Sundararajan, G.

2007-06-01

The detonation spraying is one of the most promising thermal spray variants for depositing wear and corrosion resistant coatings. The ceramic (Al2O3), metallic (Ni-20 wt%Cr) , and cermets (WC-12 wt%Co) powders that are commercially available were separated into coarser and finer size ranges with relatively narrow size distribution by employing centrifugal air classifier. The coatings were deposited using detonation spray technique. The effect of particle size and its distribution on the coating properties were examined. The surface roughness and porosity increased with increasing powder particle size for all the coatings consistently. The feedstock size was also found to influence the phase composition of Al2O3 and WC-Co coatings; however does not influence the phase composition of Ni-Cr coatings. The associated phase change and %porosity of the coatings imparted considerable variation in the coating hardness, fracture toughness, and wear properties. The fine and narrow size range WC-Co coating exhibited superior wear resistance. The coarse and narrow size distribution Al2O3 coating exhibited better performance under abrasion and sliding wear modes however under erosion wear mode the as-received Al2O3 coating exhibited better performance. In the case of metallic (Ni-Cr) coatings, the coatings deposited using coarser powder exhibited marginally lower-wear rate under abrasion and sliding wear modes. However, under erosion wear mode, the coating deposited using finer particle size exhibited considerably lower-wear rate.

Effects of Al(OH)O nanoparticle agglomerate size in epoxy resin on tension, bending, and fracture properties

NASA Astrophysics Data System (ADS)

Jux, Maximilian; Finke, Benedikt; Mahrholz, Thorsten; Sinapius, Michael; Kwade, Arno; Schilde, Carsten

2017-04-01

Several epoxy Al(OH)O (boehmite) dispersions in an epoxy resin are produced in a kneader to study the mechanistic correlation between the nanoparticle size and mechanical properties of the prepared nanocomposites. The agglomerate size is set by a targeted variation in solid content and temperature during dispersion, resulting in a different level of stress intensity and thus a different final agglomerate size during the process. The suspension viscosity was used for the estimation of stress energy in laminar shear flow. Agglomerate size measurements are executed via dynamic light scattering to ensure the quality of the produced dispersions. Furthermore, various nanocomposite samples are prepared for three-point bending, tension, and fracture toughness tests. The screening of the size effect is executed with at least seven samples per agglomerate size and test method. The variation of solid content is found to be a reliable method to adjust the agglomerate size between 138-354 nm during dispersion. The size effect on the Young's modulus and the critical stress intensity is only marginal. Nevertheless, there is a statistically relevant trend showing a linear increase with a decrease in agglomerate size. In contrast, the size effect is more dominant to the sample's strain and stress at failure. Unlike microscaled agglomerates or particles, which lead to embrittlement of the composite material, nanoscaled agglomerates or particles cause the composite elongation to be nearly of the same level as the base material. The observed effect is valid for agglomerate sizes between 138-354 nm and a particle mass fraction of 10 wt%.

Pulsed plasma chemical synthesis of carbon-containing titanium and silicon oxide based nanocomposite

NASA Astrophysics Data System (ADS)

Kholodnaya, Galina; Sazonov, Roman; Ponomarev, Denis; Zhirkov, Igor

2018-03-01

The paper presents the results of the experimental investigation of the physical and chemical properties of the TixSiyCzOw composite nanopowders, which were first obtained using a pulsed plasma chemical method. The pulsed plasma chemical synthesis was achieved using a technological electron accelerator (TEA-500). The parameters of the electron beam are as follows: 400-450 keV electron energy, 60 ns half-amplitude pulse duration, up to 200 J pulse energy, and 5 cm beam diameter. The main physical and chemical properties of the obtained composites were studied (morphology, chemical, elemental and phase composition). The morphology of the TixSiyCzOw composites is multiform. There are large round particles, with an average size of above 150 nm. Besides, there are small particles (an average size is in the range of 15-40 nm). The morphology of small particles is in the form of crystallites. In the TixSiyCzOw synthesised composite, the peak with a maximum of 946 cm-1 was registered. The presence of IR radiation in this region of the spectrum is typical for the deformation of atomic oscillations in the Si‒О‒Ti bond, which indicates the formation of the solid solution. The composites consist of two crystal phases - anatase and rutile. The prevailing phase of the crystal structure is rutile.

Individual aerosol particles in and below clouds along a Mt. Fuji slope: Modification of sea-salt-containing particles by in-cloud processing

NASA Astrophysics Data System (ADS)

Ueda, S.; Hirose, Y.; Miura, K.; Okochi, H.

2014-02-01

Sizes and compositions of atmospheric aerosol particles can be altered by in-cloud processing by absorption/adsorption of gaseous and particulate materials and drying of aerosol particles that were formerly activated as cloud condensation nuclei. To elucidate differences of aerosol particles before and after in-cloud processing, aerosols were observed along a slope of Mt. Fuji, Japan (3776 m a.s.l.) during the summer in 2011 and 2012 using a portable laser particle counter (LPC) and an aerosol sampler. Aerosol samples for analyses of elemental compositions were obtained using a cascade impactor at top-of-cloud, in-cloud, and below-cloud altitudes. To investigate composition changes via in-cloud processing, individual particles (0.5-2 μm diameter) of samples from five cases (days) collected at different altitudes under similar backward air mass trajectory conditions were analyzed using a transmission electron microscope (TEM) equipped with an energy dispersive X-ray analyzer. For most cases (four cases), most particles at all altitudes mainly comprised sea salts: mainly Na with some S and/or Cl. Of those, in two cases, sea-salt-containing particles with Cl were found in below-cloud samples, although sea-salt-containing particles in top-of-cloud samples did not contain Cl. This result suggests that Cl in the sea salt was displaced by other cloud components. In the other two cases, sea-salt-containing particles on samples at all altitudes were without Cl. However, molar ratios of S to Na (S/Na) of the sea-salt-containing particles of top-of-cloud samples were higher than those of below-cloud samples, suggesting that sulfuric acid or sulfate was added to sea-salt-containing particles after complete displacement of Cl by absorption of SO2 or coagulation with sulfate. The additional volume of sulfuric acid in clouds for the two cases was estimated using the observed S/Na values of sea-salt-containing particles. The estimation revealed that size changes by in-cloud processing from below-cloud to top-of-cloud altitudes were less than 6% for sizes of 0.5-2 μm diameter. The obtained results will be useful to evaluate the aging effect and transition of aerosol particles through in-cloud processing.

Particle size distribution and perchlorate levels in settled dust from urban roads, parks, and roofs in Chengdu, China.

PubMed

Li, Yiwen; Shen, Yang; Pi, Lu; Hu, Wenli; Chen, Mengqin; Luo, Yan; Li, Zhi; Su, Shijun; Ding, Sanglan; Gan, Zhiwei

2016-01-01

A total of 27 settled dust samples were collected from urban roads, parks, and roofs in Chengdu, China to investigate particle size distribution and perchlorate levels in different size fractions. Briefly, fine particle size fractions (<250 μm) were the dominant composition in the settled dust samples, with mean percentages of 80.2%, 69.5%, and 77.2% for the urban roads, roofs, and the parks, respectively. Perchlorate was detected in all of the size-fractionated dust samples, with concentrations ranging from 73.0 to 6160 ng g(-1), and the median perchlorate levels increased with decreasing particle size. The perchlorate level in the finest fraction (<63 μm) was significantly higher than those in the coarser fractions. To our knowledge, this is the first report on perchlorate concentrations in different particle size fractions. The calculated perchlorate loadings revealed that perchlorate was mainly associated with finer particles (<125 μm). An exposure assessment indicated that exposure to perchlorate via settled road dust intake is safe to both children and adults in Chengdu, China. However, due to perchlorate mainly existing in fine particles, there is a potential for perchlorate to transfer into surface water and the atmosphere by runoff and wind erosion or traffic emission, and this could act as an important perchlorate pollution source for the indoor environment, and merits further study.

Codeformation processing of mechanically-dissimilar metal/intermetallic composites

NASA Astrophysics Data System (ADS)

Marte, Judson Sloan

A systematic and scientific approach has been applied to the study of codeformation processing. A series of composites having mechanically-dissimilar phases were developed in which the high temperature flow behavior of the reinforcement material could be varied independent of the matrix. This was accomplished through the use of a series of intermetallic matrix composites (IMCs) as discontinuous reinforcements in an otherwise conventional metal matrix composite. The IMCs are produced using an in-situ reaction synthesis technique, called the XD(TM) process. The temperature of the exothermic synthesis reaction, called the adiabatic temperature, has been calculated and shown to increase with increasing volume percentage of TiB2 reinforcement. Further, this temperature has been shown to effect the size and spacing of the TiB2, microstructural features which are often used in discontinuous composite strength models. Study of the high temperature flow behavior of the components of the metal/IMC composite is critical to the development of an understanding of codeformation. A series of compression tests performed at 1000° to 1200°C and strain-rates of 10-3 and 10-4 sec-1. Peak flow stresses were used to evaluate the influence of material properties and process conditions. These data were incorporated into phenomenologically-based constitutive equations that have been used to predict the flow behavior. It has been determined that plastic deformation of the IMCs occurs readily, and is largely TiB2 independent, at temperatures approaching the melting point of the intermetallic matrices. Ti-6Al-4V/IMC powder blends were extruded at high temperatures to achieve commensurately deformed microstructures. The results of codeformation processing were analyzed in terms of the plastic strain of the IMC particulates. IMC particle deformation was shown to increase with increasing IMC particle size, volume percentage of IMC, extrusion temperature, homologous temperature, extrusion strain-rate, and decreasing TiB2 reinforcement within the IMCs. A series of finite element models were developed to simulate codeformation processing via the extrusion of a discontinuously-reinforced composite. The results were evaluated through comparison between average equivalent strain in matrix and reinforcement elements. These results show that codeformation should increase with increasing volume percentage of IMC, homologous temperature, volume percentage of IMC, and decreasing IMC particle size. With the exception of the particle size, these results correlate to those of the experimental extrusion analysis.

Strategies for the synthesis of supported gold palladium nanoparticles with controlled morphology and composition.

PubMed

Hutchings, Graham J; Kiely, Christopher J

2013-08-20

The discovery that supported gold nanoparticles are exceptionally effective catalysts for redox reactions has led to an explosion of interest in gold nanoparticles. In addition, incorporating a second metal as an alloy with gold can enhance the catalyst performance even more. The addition of small amounts of gold to palladium, in particular, and vice versa significantly enhances the activity of supported gold-palladium nanoparticles as redox catalysts through what researchers believe is an electronic effect. In this Account, we describe and discuss methodologies for the synthesis of supported gold-palladium nanoparticles and their use as heterogeneous catalysts. In general, three key challenges need to be addressed in the synthesis of bimetallic nanoparticles: (i) control of the particle morphology, (ii) control of the particle size distribution, and (iii) control of the nanoparticle composition. We describe three methodologies to address these challenges. First, we discuss the relatively simple method of coimpregnation. Impregnation allows control of particle morphology during alloy formation but does not control the particle compositions or the particle size distribution. Even so, we contend that this method is the best preparation method in the catalyst discovery phase of any project, since it permits the investigation of many different catalyst structures in one experiment, which may aid the identification of new catalysts. A second approach, sol-immobilization, allows enhanced control of the particle size distribution and the particle morphology, but control of the composition of individual nanoparticles is not possible. Finally, a modified impregnation method can allow the control of all three of these crucial parameters. We discuss the effect of the different methodologies on three redox reactions: benzyl alcohol oxidation, toluene oxidation, and the direct synthesis of hydrogen peroxide. We show that the coimpregnation method provides the best reaction selectivity for benzyl alcohol oxidation and the direct synthesis of hydrogen peroxide. However, because of the reaction mechanism, the sol-immobilzation method gives very active and selective catalysts for toluene oxidation. We discuss the possible nature of the preferred active structures of the supported nanoparticles for these reactions. This paper is based on the IACS Heinz Heinemann Award Lecture entitled "Catalysis using gold nanoparticles" which was given in Munich in July 2012.

Bifunctional air electrodes containing elemental iron powder charging additive

DOEpatents

Liu, Chia-tsun; Demczyk, Brian G.; Gongaware, Paul R.

1982-01-01

A bifunctional air electrode for use in electrochemical energy cells is made, comprising a hydrophilic layer and a hydrophobic layer, where the hydrophilic layer essentially comprises a hydrophilic composite which includes: (i) carbon; (ii) elemental iron particles having a particle size of between about 25 microns and about 700 microns diameter; (iii) an oxygen evolution material; (iv) a nonwetting agent; and (v) a catalyst, where at least one current collector is formed into said composite.

Physicochemical and toxicological characteristics of welding fume derived particles generated from real time welding processes.

PubMed

Chang, Cali; Demokritou, Philip; Shafer, Martin; Christiani, David

2013-01-01

Welding fume particles have been well studied in the past; however, most studies have examined welding fumes generated from machine models rather than actual exposures. Furthermore, the link between physicochemical and toxicological properties of welding fume particles has not been well understood. This study aims to investigate the physicochemical properties of particles derived during real time welding processes generated during actual welding processes and to assess the particle size specific toxicological properties. A compact cascade impactor (Harvard CCI) was stationed within the welding booth to sample particles by size. Size fractionated particles were extracted and used for both off-line physicochemical analysis and in vitro cellular toxicological characterization. Each size fraction was analyzed for ions, elemental compositions, and mass concentration. Furthermore, real time optical particle monitors (DustTrak™, TSI Inc., Shoreview, Minn.) were used in the same welding booth to collect real time PM2.5 particle number concentration data. The sampled particles were extracted from the polyurethane foam (PUF) impaction substrates using a previously developed and validated protocol, and used in a cellular assay to assess oxidative stress. By mass, welding aerosols were found to be in coarse (PM 2.5–10), and fine (PM 0.1–2.5) size ranges. Most of the water soluble (WS) metals presented higher concentrations in the coarse size range with some exceptions such as sodium, which presented elevated concentration in the PM 0.1 size range. In vitro data showed size specific dependency, with the fine and ultrafine size ranges having the highest reactive oxygen species (ROS) activity. Additionally, this study suggests a possible correlation between welders' experience, the welding procedure and equipment used and particles generated from welding fumes. Mass concentrations and total metal and water soluble metal concentrations of welding fume particles may be greatly influenced by these factors. Furthermore, the results also confirmed the hypothesis that smaller particles generate more ROS activity and should be evaluated carefully for risk assessment.

Long-range-transported Saharan dust in the Caribbean - an electron microscopy perspective of aerosol composition and modification

NASA Astrophysics Data System (ADS)

Kandler, Konrad; Hartmann, Markus; Ebert, Martin; Weinbruch, Stephan; Weinzierl, Bernadett; Walser, Adrian; Sauer, Daniel; Wadinga Fomba, Khanneh

2015-04-01

From June to July in 2013, the Saharan Aerosol Long-range Transport and Aerosol-Cloud-Interaction Experiment (SALTRACE) was performed in the Caribbean. Airborne aerosol sampling was performed onboard the DLR Falcon aircraft in altitudes between 300 m and 5500 m. Ground-based samples were collected at Ragged Point (Barbados, 13.165 °N, 59.432 °W) and at the Cape Verde Atmospheric Observatory (Sao Vicente, 16.864 °N, 24.868 °W). Different types of impactors and sedimentation samplers were used to collect particles between 0.1 µm and 4 µm (airborne) and between 0.1 µm and 100 µm (ground-based). Particles were analyzed by scanning electron microscopy with attached energy-dispersive X-ray analysis, yielding information on particle size, particle shape and chemical composition for elements heavier than nitrogen. A particle size correction was applied to the chemical data to yield better quantification. A total of approximately 100,000 particles were analyzed. For particles larger than 0.7 µm, the aerosol in the Caribbean during the campaign was a mixture of mineral dust, sea-salt at different aging states, and sulfate. Inside the Saharan dust plume - outside the marine boundary layer (MBL) - the aerosol is absolutely dominated by mineral dust. Inside the upper MBL, sea-salt exists as minor component in the aerosol for particles smaller than 2 µm in diameter, larger ones are practically dust only. When crossing the Soufriere Hills volcano plume with the aircraft, an extremely high abundance of small sulfate particles could be observed. At Ragged Point, in contrast to the airborne measurements, aerosol is frequently dominated by sea-salt particles. Dust relative abundance at Ragged Point has a maximum between 5 µm and 10 µm particles diameter; at larger sizes, sea-salt again prevails due to the sea-spray influence. A significant number of dust particles larger than 20 µm was encountered. The dust component in the Caribbean - airborne as well as ground-based - is composed of mainly silicates and minor amounts of Ca-rich and Fe-/Fe-Ti-rich particles (less than 10 % of dust fraction). The composition of the silicates indicates a major contribution of kaolinite (Al/Si atomic ratio between 0.6 and 1) and a minor contribution of quartz and feldspar particles. The inter-sample variation of the dust composition is generally low, pointing to a very thorough mixing from differently-composed Saharan sources. The temporal evolution of aerosol composition at Ragged Point shows a variation in dust abundance, but strong isolated events could not be identified. An airmass change induced by the passing by of a hurricane, however, is visible in sulfate abundance and their composition. Strong internally mixed particles of dust and sulfate or dust and sea-salt are very rare (up to 1 % of particles in the airborne samples), but a slight increasing tendency with decreasing altitude was found. In the lower MBL at Ragged point, dust/sea-salt mixtures are more frequent (in the same abundance range as pure dust particles). A first conclusion from the data set is that dust aging with respect to internal mixtures does not happen during the long-range transport across the Atlantic Ocean, but rather at the end during the down-mixing of mineral dust into the Caribbean MBL.

In situ camera observations reveal major role of zooplankton in modulating marine snow formation during an upwelling-induced plankton bloom

NASA Astrophysics Data System (ADS)

Taucher, Jan; Stange, Paul; Algueró-Muñiz, María; Bach, Lennart T.; Nauendorf, Alice; Kolzenburg, Regina; Büdenbender, Jan; Riebesell, Ulf

2018-05-01

Particle aggregation and the consequent formation of marine snow alter important properties of biogenic particles (size, sinking rate, degradability), thus playing a key role in controlling the vertical flux of organic matter to the deep ocean. However, there are still large uncertainties about rates and mechanisms of particle aggregation, as well as the role of plankton community structure in modifying biomass transfer from small particles to large fast-sinking aggregates. Here we present data from a high-resolution underwater camera system that we used to observe particle size distributions and formation of marine snow (aggregates >0.5 mm) over the course of a 9-week in situ mesocosm experiment in the Eastern Subtropical North Atlantic. After an oligotrophic phase of almost 4 weeks, addition of nutrient-rich deep water (650 m) initiated the development of a pronounced diatom bloom and the subsequent formation of large marine snow aggregates in all 8 mesocosms. We observed a substantial time lag between the peaks of chlorophyll a and marine snow biovolume of 9-12 days, which is much longer than previously reported and indicates a marked temporal decoupling of phytoplankton growth and marine snow formation during our study. Despite this time lag, our observations revealed substantial transfer of biomass from small particle sizes (single phytoplankton cells and chains) to marine snow aggregates of up to 2.5 mm diameter (ESD), with most of the biovolume being contained in the 0.5-1 mm size range. Notably, the abundance and community composition of mesozooplankton had a substantial influence on the temporal development of particle size spectra and formation of marine snow aggregates: While higher copepod abundances were related to reduced aggregate formation and biomass transfer towards larger particle sizes, the presence of appendicularia and doliolids enhanced formation of large marine snow. Furthermore, we combined in situ particle size distributions with measurements of particle sinking velocity to compute instantaneous (potential) vertical mass flux. However, somewhat surprisingly, we did not find a coherent relationship between our computed flux and measured vertical mass flux (collected by sediment traps in 15 m depth). Although the onset of measured vertical flux roughly coincided with the emergence of marine snow, we found substantial variability in mass flux among mesocosms that was not related to marine snow numbers, and was instead presumably driven by zooplankton-mediated alteration of sinking biomass and export of small particles (fecal pellets). Altogether, our findings highlight the role of zooplankton community composition and feeding interactions on particle size spectra and formation of marine snow aggregates, with important implications for our understanding of particle aggregation and vertical flux of organic matter in the ocean.

Size-resolved measurements of mixing state and cloud-nucleating ability of aerosols in Nanjing, China

NASA Astrophysics Data System (ADS)

Ma, Yan; Li, Shizheng; Zheng, Jun; Khalizov, Alexei; Wang, Xing; Wang, Zhen; Zhou, Yaoyao

2017-09-01

An integrated aerosol analytical system was deployed in Nanjing, a megacity in the Yangtze River Delta, to measure size-resolved aerosol mixing states, effective densities, cloud condensation nucleus (CCN) activities, and chemical composition in August 2013. It was found that aerosols were predominantly internally mixed. The average effective densities were 1.38 ± 0.09, 1.48 ± 0.08, and 1.53 ± 0.07 g cm-3 for 50, 80, and 120 nm particles, respectively. Although black carbon (BC) represented only 0.3%, 1.6%, and 3.3% of the particle mass, on average, it was present in 7%, 38%, and 47% of the total particle number concentration at 50, 80, and 120 nm, respectively, indicating that BC particles may contribute significantly to the total atmospheric aerosol population. Externally mixed BC was only occasionally observed with an effective density of 0.67-0.97 g cm-3. Aerosols sampled generally exhibited a relatively high CCN activity and hygroscopicity (κ = 0.35 ± 0.13). Both newly formed particles and freshly emitted BC particles were observed to age rapidly from photochemical processes, with a significant enhancement in the particle CCN activity and an increase in the effective density. Aerosols influenced by four different air masses presented similar CCN activation, indicating that CCN activation would be primarily dependent on the particle size rather than the particle origin (and hence original composition). Our results suggest that under highly active photochemical conditions as encountered in this study, particles from both local sources and regional transport can be rapidly converted into efficient CCN by photochemical aging, thereby making important contributions to the atmospheric CCN budget and exerting profound implications on aerosol indirect climate forcing.

Evaluation of the filler packing structures in dental resin composites: From theory to practice.

PubMed

Wang, Ruili; Habib, Eric; Zhu, X X

2018-07-01

The aim of this study is to evaluate the packing properties of uniform silica particles and their mixture with secondary particles yielding maximally loaded dental composites. We intend to verify the difference between the idealized models (the close-packed structures and the random-packed structures) and the actual experimental results, in order to provide guidance for the preparation of dental composites. The influence of secondary particle size and the resin composition on the physical-mechanical properties and the rheological properties of the experimental dental composites was also investigated. Silica particles (S-920, S-360, and S-195) with average diameters of 920, 360, and 195nm were synthesized via the Stöber process. Their morphology and size distribution were determined by field-emission scanning electron microscopy and laser particle sizer. A series of silica fillers, S-920, S-920+195, S-920+360, and S-920+360+195, were then formulated with two Bis-GMA/TEGDMA resins (weight ratios of 70:30 and 50:50). For these experimental dental composites, their maximum filler loadings were assessed and compared to the theory. The mechanical properties, degree of conversion, depth of cure, and polymerization shrinkage of these composites were then evaluated. Their rheological behaviors were measured with a rheometer. Unimodal S-920 had the maximally filler loading of 70.80wt% with the 5B5T resin, close to the theoretical estimation of the random loose packing (71.92wt%). The maximum loading of the S-920+360+195 filled composite was 72.92wt% for the same resin, compared to the theoretical estimation of 89.29wt% obtained for the close-packed structures. These findings indicate that random loose packing matches more closely to the real packing state for the filler formulations used. When maximally loaded, the composite with S-920+360+195 produced the best mechanical properties and the lowest polymerization shrinkage. The degree of conversion and depth of cure were higher with secondary particles added, and the viscosity of all unpolymerized pastes exhibited shear thinning behavior. Theoretical estimations of filler packing structures provide a useful guidance in the design of multimodal filler formulations and the preparation of dental composites with higher filler loading, improved physical-mechanical properties. Copyright © 2018 The Academy of Dental Materials. Published by Elsevier Inc. All rights reserved.

Synthetic control of the size, shape, and polydispersity of anisotropic silica colloids

DOE Office of Scientific and Technical Information (OSTI.GOV)

Murphy, Ryan P.; Hong, Kunlun; Wagner, Norman J.

The particle size and shape determine the microstructure and rheological properties of colloidal suspensions. This work aims to further control the size, shape, and polydispersity of anisotropic silica colloids, to reduce particle size, and to provide additional mechanistic insights on a prevalent, water-in-oil emulsion synthesis method. Key findings show that the dimensions of anisotropic silica particles can be systematically varied by approximately fivefold, with a limiting minimum particle size (D ≈ 60 nm, L ≈ 300 nm) obtained from emulsions with excess polyvinylpyrrolidone (PVP) and sodium citrate. The synthesis conditions are identified and discussed for which the emulsion composition, temperature,more » sonication, polymer entanglements, mixing, and other perturbations may induce or mitigate emulsion instabilities, citrate precipitation, a competing mechanism of templated growth, termination of anisotropic growth, irregular silica structures, and fiber formation. An improved mechanistic understanding will expand the roadmap for rational design and synthetic control of anisotropic colloids using sol-gel silica chemistry confined within water-in-oil emulsions.« less

Synthetic control of the size, shape, and polydispersity of anisotropic silica colloids

DOE PAGES

Murphy, Ryan P.; Hong, Kunlun; Wagner, Norman J.

2017-09-01

The particle size and shape determine the microstructure and rheological properties of colloidal suspensions. This work aims to further control the size, shape, and polydispersity of anisotropic silica colloids, to reduce particle size, and to provide additional mechanistic insights on a prevalent, water-in-oil emulsion synthesis method. Key findings show that the dimensions of anisotropic silica particles can be systematically varied by approximately fivefold, with a limiting minimum particle size (D ≈ 60 nm, L ≈ 300 nm) obtained from emulsions with excess polyvinylpyrrolidone (PVP) and sodium citrate. The synthesis conditions are identified and discussed for which the emulsion composition, temperature,more » sonication, polymer entanglements, mixing, and other perturbations may induce or mitigate emulsion instabilities, citrate precipitation, a competing mechanism of templated growth, termination of anisotropic growth, irregular silica structures, and fiber formation. An improved mechanistic understanding will expand the roadmap for rational design and synthetic control of anisotropic colloids using sol-gel silica chemistry confined within water-in-oil emulsions.« less

Thermodynamics Of Common Atmospheric Particles On The Nanoscale

NASA Astrophysics Data System (ADS)

Onasch, T.; Han, J.; Oatis, S.; Brechtel, F.; Imre, D. G.

2002-12-01

A significant fraction of atmospheric particles are hygroscopic by nature and exhibit the properties of deliquescence and efflorescence. Recent field studies have observed large nucleation events of hygroscopic particles and note discrepancies between predicted and observed particle growth rates after nucleation. These growth rates are governed, in part, by the thermodynamic properties of particles only a few nanometers in diameter. However, little thermodynamic information is currently available for nanometer?sized particles. The Kelvin relation indicates that the surface tension of a particle less than 100nm in diameter can dramatically affect the thermodynamics, and surface states may begin to influence the bulk physical properties in these small particles with high surface to volume ratios. In this context, we are investigating the thermodynamic properties, including pre-deliquescence water adsorption, deliquescence, efflorescence, and supersaturated particle compositions of nanoparticles with mobility diameters in the range of 5 to 50 nm. We have developed a temperature and humidity-controlled laboratory-based Nano Differential Mobility Analyzer (NDMA) system to characterize the hygroscopic properties of the common atmospheric salt particles as a function of size. Two different aerosol generation systems have been used to cover the full size range. The first system (less than 20nm diameter) relies on an Atomizer (TSI 3076) to produce particles which are size?selected using an initial DMA. For particle sizes smaller than 20 nm, the Electrospray Aerosol Generator (EAG, TSI 3480) has been employed as a particle source. The EAG characteristically provides narrow size distributions, comparable to the monodisperse size distribution from a DMA, but with higher number concentrations. Once generated, the monodisperse aerosol flow is then conditioned with respect to humidity at a constant temperature and subsequently analyzed using a TSI Ultrafine CPC (Model 3010) modified for Pulse-Height Analysis. The dry particle sizes are also continually monitored by an external SMPS system (TSI 3936) to rectify errors in the calculated growth factor resulting from any drift in the dry particle size. The size changes of the humidified particles are directly correlated with the relative humidity and temperature. Our results of ammonium sulfate particles from 5 - 50 nm in diameter are consistent with those predicted from the Kelvin relation. The particle size affects both deliquescence and efflorescence of the homogeneous salt particles: the deliquescence relative humidity increases and the efflorescence decreases as particles become smaller. In addition, although the smaller the particle size the more significant water adsorption, the sharp deliquescence phase transition was obvious regardless of the particle sizes. The implications with respect to these observations will be further discussed at the presentation.

Effective and Accurate Morphology Models for Asian and Saharan Mineral Dust Scattering Properties

NASA Astrophysics Data System (ADS)

Stegmann, P.; Yang, P.

2017-12-01

It is well known that mineral dust particles from desert sources can have a significant influence on the planetary radiation balance. In order to determine the sign and magnitude of the dust radiative forcing effect, complex models have been and continue to be developed. Key factors which influence the single-scattering properties of mineral dust are dust source regions and thus mineralogical composition, and its mixture with water, sea salt, and products of human activity, such as soot. The ensemble of mineral dust scattering particles may then be modeled either as a simple placeholder shape, often ellipsoidal, through the utilization of an appropriate effective medium refractive index scheme. On the other hand, the scattering particles may be represented in a more rigorous manner, such as Voronoi-tessellated aggregates including fractal soot chains. The consequences and differences of either choice are investigated in the project at hand. It will be shown that the effective medium model indicates a drastic dependence of the mineral dust particle composition on the particle size. Thus the refractive index of a dust particle is in fact a function of its size, amongst other factors. Regional differences between African and Asian mineral dust are also of significance.

Fast changes in chemical composition and size distribution of fine particles during the near-field transport of industrial plumes.

PubMed

Marris, Hélène; Deboudt, Karine; Augustin, Patrick; Flament, Pascal; Blond, François; Fiani, Emmanuel; Fourmentin, Marc; Delbarre, Hervé

2012-06-15

Aerosol sampling was performed inside the chimneys and in the close environment of a FeMn alloys manufacturing plant. The number size distributions show a higher abundance of ultrafine aerosols (10-100 nm) inside the plume than upwind of the plant, indicating the emissions of nanoparticles by the industrial process. Individual analysis of particles collected inside the plume shows a high proportion of metal bearing particles (Mn-/Fe-) consisting essentially of internally mixed aluminosilicate and metallic compounds. These particles evolve rapidly (in a few minutes) after emission by adsorption of VOC gas and sulfuric acid emitted by the plant but also by agglomeration with pre-existing particles. At the moment, municipalities require a monitoring of industrial emissions inside the chimneys from manufacturers. However those measures are insufficient to report such rapid changes in chemical composition and thus to evaluate the real impact of industrial plumes in the close environment of plants (when those particles leave the industrial site). Consequently, environmental authorities will have to consider such fast evolutions and then to adapt future regulations on air pollution sources. Copyright © 2012 Elsevier B.V. All rights reserved.

Wastewater characterisation by combining size fractionation, chemical composition and biodegradability.

PubMed

Ravndal, Kristin T; Opsahl, Eystein; Bagi, Andrea; Kommedal, Roald

2017-12-18

The potential for resource recovery from wastewater can be evaluated based on a detailed characterisation of wastewater. In this paper, results from fractionation and characterisation of two distinct wastewaters are reported. Using tangential flow filtration, the wastewater was fractionated into 10 size fractions ranging from 1 kDa to 1 mm, wherein the chemical composition and biodegradability were determined. Carbohydrates were dominant in particulate size fractions larger than 100 μm, indicating a potential of cellulose recovery from these fractions. While the particulate size fractions between 0.65 and 100 μm show a potential as a source for biofuel production due to an abundance of saturated C16 and C18 lipids. Both wastewaters were dominated by particulate (>0.65 μm), and oligo- and monomeric (<1 kDa) COD. Polymeric (1-1000 kDa) and colloidal (1000 kDa-0.65 μm) fractions had a low COD content, expected due to degradation in the sewer system upstream of the wastewater treatment plant. Biodegradation rates of particulate fractions increase with decreasing size. However, this was not seen in polymeric fractions where degradation rate was governed by chemical composition. Analytical validation of molecular weight and particle size distribution showed below filter cut-off retention of particles and polymers close to nominal cut-off, shifting the actual size distribution. Copyright © 2017. Published by Elsevier Ltd.

ELEMENTAL COMPOSITION OF FRESHLY NUCLEATED PARTICLES

EPA Science Inventory

The main objective of this work is to develop a method for real-time sampling and analysis of individual airborne nanoparticles in the 5 - 20 nm diameter range. The size range covered by this method is much smaller than existing single particle methods for chemical analysis. S...

Accelerated simulation of stochastic particle removal processes in particle-resolved aerosol models

DOE Office of Scientific and Technical Information (OSTI.GOV)

Curtis, J.H.; Michelotti, M.D.; Riemer, N.

2016-10-01

Stochastic particle-resolved methods have proven useful for simulating multi-dimensional systems such as composition-resolved aerosol size distributions. While particle-resolved methods have substantial benefits for highly detailed simulations, these techniques suffer from high computational cost, motivating efforts to improve their algorithmic efficiency. Here we formulate an algorithm for accelerating particle removal processes by aggregating particles of similar size into bins. We present the Binned Algorithm for particle removal processes and analyze its performance with application to the atmospherically relevant process of aerosol dry deposition. We show that the Binned Algorithm can dramatically improve the efficiency of particle removals, particularly for low removalmore » rates, and that computational cost is reduced without introducing additional error. In simulations of aerosol particle removal by dry deposition in atmospherically relevant conditions, we demonstrate about 50-times increase in algorithm efficiency.« less

The Microstructural Design of Trimodal Aluminum Composites

NASA Astrophysics Data System (ADS)

Jiang, Lin; Ma, Kaka; Yang, Hanry; Li, Meijuan; Lavernia, Enrique J.; Schoenung, Julie M.

2014-06-01

Trimodal composites, consisting of nanocrystalline or ultrafine grains (UFGs), coarse grains (CGs), and ceramic particles, were originally formulated to achieve combinations of physical and mechanical properties that are unattainable with the individual phases, such as strength, ductility, and high-strain-rate deformation. The concept of a trimodal structure is both scientifically novel as well as technologically promising because it provides multiple controllable degrees of freedom that allow for extensive microstructure design. The UFGs provide efficient obstacles for dislocation movement, such as grain boundaries and other crystalline defects. The size, distribution, and spatial arrangement of the CGs can be controlled to provide plasticity during deformation. The size, morphology, and distribution of the reinforcement particles can be tailored to attain various engineering and physical properties. Moreover, the interfaces that form among the various phases also help determine the overall behavior of the trimodal composites. In this article, a review is provided to discuss the selection and design of each component in trimodal Al composites. The toughening and strengthening mechanisms in the trimodal composite structure are discussed, paying particular attention to strategies that can be implemented to tailor microstructures for optimal mechanical behavior. Recent results obtained with high-performance trimodal Al composites that contain nanometric reinforcements are also discussed to highlight the ability to control particle-matrix interface characteristics. Finally, a perspective is provided on potential approaches that can be explored to develop the next generation of trimodal composites, and interesting scientific paradigms that evolve from the proposed design strategies are discussed.

Mixed nano/micro-sized calcium phosphate composite and EDTA root surface etching improve availability of graft material in intrabony defects: an in vivo scanning electron microscopy evaluation.

PubMed

Gamal, Ahmed Y; Iacono, Vincent J

2013-12-01

The use of nanoparticles of graft materials may lead to breakthrough applications for periodontal regeneration. However, due to their small particle size, nanoparticles may be eliminated from periodontal defects by phagocytosis. In an attempt to improve nanoparticle retention in periodontal defects, the present in vivo study uses scanning electron microscopy (SEM) to evaluate the potential of micrograft particles of β-tricalcium phosphate (β-TCP) to enhance the binding and retention of nanoparticles of hydroxyapatite (nHA) on EDTA-treated and non-treated root surfaces in periodontal defects after 14 days of healing. Sixty patients having at least two hopeless periodontally affected teeth designated for extraction were randomly divided into four treatment groups (15 patients per group). Patients in group 1 had selected periodontal intrabony defects grafted with nHA of particle size 10 to 100 nm. Patients in group 2 were treated in a similar manner but had the affected roots etched for 2 minutes with a neutral 24% EDTA gel before grafting of the associated vertical defects with nHA. Patients in group 3 had the selected intrabony defects grafted with a composite graft consisting of equal volumes of nHA and β-TCP (particle size 63 to 150 nm). Patients in group 4 were treated as in group 3 but the affected roots were etched with neutral 24% EDTA as in group 2. For each of the four groups, one tooth was extracted immediately, and the second tooth was extracted after 14 days of healing for SEM evaluation. Fourteen days after surgery, all group 1 samples were devoid of any nanoparticles adherent to the root surfaces. Group 2 showed root surface areas 44.7% covered by a single layer of clot-blended grafted particles 14 days following graft application. After 14 days, group 3 samples appeared to retain fibrin strands devoid of grafted particles. Immediately extracted root samples of group 4 had adherent graft particles that covered a considerable area of the root surfaces (88.6%). Grafted particles appeared to cover all samples in a multilayered pattern. After 14 days, the group 4 extracted samples showed multilayered fibrin-covered nano/micro-sized graft particles adherent to the root surfaces (78.5%). The use of a composite graft consisting of nHA and microsized β-TCP after root surface treatment with 24% EDTA may be a suitable method to improve nHA retention in periodontal defects with subsequent graft bioreactivity.

Temperature evolution in silver nanoparticle doped PETN composite

NASA Astrophysics Data System (ADS)

Kameswari, D. P. S. L.; Kiran, P. Prem

2018-04-01

Optical absorption and the associated spatio-temporal evolution of temperature silver nanoparticles doped energetic material composite is presented. Silver nanoparticles of radii 10 - 150 nm are doped in Penta Erythrtol Tetra Nitrate (PETN), a secondary energetic material to form the composite materials. Of all the composites the ones doped with 35 nm sized nanoparticles have shown maximum absorption at excitation wavelength of 532 nm. The spatio-temporal evolution of temperature within these composites up on excitation with ns laser pulses of energy density 0.5 J/cm2 is studied. The role of particle sizes on the temperature of composites is studied and a maximum temperature of 2200 K at the nanoparticle interface is observed for 35 nm doped PETN composite.

Individual Aerosol Particles from Biomass Burning in Southern Africa. 1; Compositions and Size Distributions of Carbonaceous Particles

NASA Technical Reports Server (NTRS)

Posfai, Mihaly; Simonics, Renata; Li, Jia; Hobbs, Peter V.; Buseck, Peter R.

2003-01-01

Individual aerosol particles in smoke plumes from biomass fires and in regional hazes in southern Africa were studied using analytical transmission electron microscopy (TEM), which allowed detailed characterization of carbonaceous particle types in smoke and determination of changes in particle properties and concentrations during smoke aging. Based on composition, morphology, and microstructure, three distinct types of carbonaceous particles were present in the smoke: organic particles with inorganic (K-salt) inclusions, tar ball particles, and soot. The relative number concentrations of organic particles were largest in young smoke, whereas tar balls were dominant in a slightly aged (1 hour) smoke from a smoldering fire. Flaming fires emitted relatively more soot particles than smoldering fires, but soot was a minor constituent of all studied plumes. Further aging caused the accumulation of sulfate on organic and soot particles, as indicated by the large number of internally mixed organic/sulfate and soot/sulfate particles in the regional haze. Externally mixed ammonium sulfate particles dominated in the boundary layer hazes, whereas organic/sulfate particles were the most abundant type in the upper hazes. Apparently, elevated haze layers were more strongly affected by biomass smoke than those within the boundary layer. Based on size distributions and the observed patterns of internal mixing, we hypothesize that organic and soot particles are the cloud-nucleating constituents of biomass smoke aerosols. Sea-salt particles dominated in the samples taken in stratus clouds over the Atlantic Ocean, off the coast of Namibia, whereas a distinct haze layer above the clouds consisted of aged biomass smoke particles.

Magnetic CuHCNPAN nano composite as an efficient adsorbent for strontium uptake

NASA Astrophysics Data System (ADS)

Mobtaker, Hossein Ghasemi; Pakzad, Seyed Mohammadreza; Yousefi, Taher

2018-06-01

An excellent composite was synthesized for sorption of strontium from solution. The composite (CuHCNPAN) components were copper hexacyanoferrate, magnetite and PAN. The XRD method confirmed the formation and presence of two crystalline phases of magnetite and copper hexacyanoferrate in composite. Particle sizes were determined by XRD and SEM methods. It was found that the particles were nano size. Some other methods such as FT IR, BET and TG methods were also used to determine the properties of the composite. The composite was used for sorption of strontium from solution. It was found that the kinetic of strontium sorption by the composite could be modeled by pseudo-second order. Among the isotherms applied to modeling the sorption in various concentrations, the Langmuir isotherm was founded to be more appropriate to fitting the experimental data. An excellent correlation coefficient was obtained (R2 > 0.98). The qmax for sorption of strontium ions which was calculated by Langmuir model was 80 mg/g. The thermodynamic parameters were calculated by determination of sorption in various temperatures and using the Vant Hoff plot. ΔG°, ΔH°, and ΔS° were calculated as -19.15, 2.28 and 0.071 kJ/mol respectively.

Lunar Dust 101

NASA Technical Reports Server (NTRS)

Gaier, James R.

2008-01-01

Largely due to rock and soil samples returned during the Apollo program, much has been learned about the composition and properties of lunar regolith. Although, for the most part, the mineral composition resembles terrestrial minerals, the characteristics of the lunar environment have led to very different weathering processes. These result in substantial differences in the particle shapes, particle size distributions, and surface chemistry. These differences lead to non-intuitive adhesion, abrasion, and possible health properties that will pose challenges to future lunar missions. An overview of lunar dust composition and properties will be given with a particular emphasis on possible health effects.

Evolution of aerosol downwind of a major highway

NASA Astrophysics Data System (ADS)

Liggio, J.; Staebler, R. M.; Brook, J.; Li, S.; Vlasenko, A. L.; Sjostedt, S. J.; Gordon, M.; Makar, P.; Mihele, C.; Evans, G. J.; Jeong, C.; Wentzell, J. J.; Lu, G.; Lee, P.

2010-12-01

Primary aerosol from traffic emissions can have a considerable impact local and regional scale air quality. In order to assess the effect of these emissions and of future emissions scenarios, air quality models are required which utilize emissions representative of real world conditions. Often, the emissions processing systems which provide emissions input for the air quality models rely on laboratory testing of individual vehicles under non-ambient conditions. However, on the sub-grid scale particle evolution may lead to changes in the primary emitted size distribution and gas-particle partitioning that are not properly considered when the emissions are ‘instantly mixed’ within the grid volume. The affect of this modeling convention on model results is not well understood. In particular, changes in organic gas/particle partitioning may result in particle evaporation or condensation onto pre-existing aerosol. The result is a change in the particle distribution and/or an increase in the organic mass available for subsequent gas-phase oxidation. These effects may be missing from air-quality models, and a careful analysis of field data is necessary to quantify their impact. A study of the sub-grid evolution of aerosols (FEVER; Fast Evolution of Vehicle Emissions from Roadways) was conducted in the Toronto area in the summer of 2010. The study included mobile measurements of particle size distributions with a Fast mobility particle sizer (FMPS), aerosol composition with an Aerodyne aerosol mass spectrometer (AMS), black carbon (SP2, PA, LII), VOCs (PTR-MS) and other trace gases. The mobile laboratory was used to measure the concentration gradient of the emissions at perpendicular distances from the highway as well as the physical and chemical evolution of the aerosol. Stationary sites at perpendicular distances and upwind from the highway also monitored the particle size distribution. In addition, sonic anemometers mounted on the mobile lab provided measurements of turbulent dispersion as a function of distance from the highway, and a traffic camera was used to determine traffic density, composition and speed. These measurements differ from previous studies in that turbulence is measured under realistic conditions and hence the relationship of the aerosol evolution to atmospheric stability and mixing will also be quantified. Preliminary results suggest that aerosol size and composition does change on the sub-grid scale, and sub-grid scale parameterizations of turbulence and particle chemistry should be included in models to accurately represent these effects.

High-yield synthesis of vaterite microparticles in gypsum suspension system via ultrasonic probe vibration/magnetic stirring

NASA Astrophysics Data System (ADS)

Wang, Bo; Pan, Zihe; Cheng, Huaigang; Chen, Zuliang; Cheng, Fangqin

2018-06-01

Vaterite-type calcium carbonate particles have some unique properties such as high hydrophilicity, large surface areas, and hierarchical structures consisting of primary vaterite particles in comparison with calcite or aragonite-type polymorphs. In this paper, gypsum (CaSO4·2H2O) suspension is used to synthesize micro-sized vaterite CaCO3 through magnetic stirring (MS) and ultrasonic probe vibration (UPV) methods. The effects of ammonia concentration, CO2 flow rate, solid-liquid ratio on the gypsum carbonation process, mineral phase composition, morphology and particle size distribution of CaCO3 are investigated. The results show that the carbonation process is significantly influenced by ammonia concentration, CO2 flow rate and ultrasound. Comparing with magnetic stirring, ultrasonic probe vibration take less time to reach the complete carbonate reaction. Gypsum is transformed to vaterite with the conversion rate about ∼95% when the mole ratio of NH4+/Ca2+ is 2.4 otherwise the carbonation reaction was uncompleted with gypsum residues left. Comparing with MS method, the UPV method resulted in smaller size and narrower size distribution of as-prepared microparticles and approximately 80% reduction of the particle size was achieved. It is established that increasing the solid-liquid ratio resulted in larger particle size in MS system and smaller particle size in UPV system. Increasing CO2 flow rate caused the particle size decreased in MS system and increased in UPV system.

Microemulsion impregnated catalyst composite and use thereof in a synthesis gas conversion process

DOEpatents

Abrevaya, H.; Targos, W.M.

1987-12-22

A catalyst composition is described for synthesis gas conversion comprising a ruthenium metal component deposited on a support carrier wherein the average metal particle size is less than about 100 A. The method of manufacture of the composition via a reverse micelle impregnation technique and the use of the composition in a Fischer-Tropsch conversion process is also disclosed.

Fabrication of sub-micrometer-sized jingle bell-shaped hollow spheres from multilayered core-shell particles.

PubMed

Gu, Shunchao; Kondo, Tomohiro; Mine, Eiichi; Nagao, Daisuke; Kobayashi, Yoshio; Konno, Mikio

2004-11-01

Jingle bell-shaped hollow spheres were fabricated starting from multilayered particles composed of a silica core, a polystyrene inner shell, and a titania outer shell. Composite particles of silica core-polystyrene shell, synthesized by coating a 339-nm-sized silica core with a polystyrene shell of thickness 238 nm in emulsion polymerization, were used as core particles for a succeeding titania-coating. A sol-gel method was employed to form the titania outer shell with a thickness of 37 nm. The inner polystyrene shell in the multilayered particles was removed by immersing them in tetrahydrofuran. These successive procedures could produce jingle bell-shaped hollow spheres that contained a silica core in the titania shell.

Effect of surfactant concentration in the electrolyte on the tribological properties of nickel-tungsten carbide composite coatings produced by pulse electro co-deposition

NASA Astrophysics Data System (ADS)

Kartal, Muhammet; Uysal, Mehmet; Gul, Harun; Alp, Ahmet; Akbulut, Hatem

2015-11-01

A nickel plating bath containing WC particles was used to obtain hard and wear-resistant particle reinforced Ni/WC MMCs on steel surfaces for anti-wear applications. Copper substrates were used for electro co-deposition of Ni matrix/WC with the particle size of <1 μm tungsten carbide reinforcements. The influence of surfactant (sodium dodecyl sulfate, SDS) concentration on particle distribution, microhardness and wear resistance of composite coatings has been studied. The nickel films were characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD). The effects of the surfactant on the zeta potential, co-deposition and distribution of WC particles in the nickel matrix, as well as the tribological properties of composite coatings were also investigated. The tribological behaviors of the electrodeposited WC composite coatings sliding against M50 steel ball (Ø 10 mm) were examined on a CSM Instrument. All friction and wear tests were performed without lubrication at room temperature and in the ambient air (relative humidity 55-65%).

Surface Properties and Permeability of Poly(Vinylidene Fluoride)-Clays (PVDF/Clays) Composite Membranes

NASA Astrophysics Data System (ADS)

Pramono, E.; Ahdiat, M.; Simamora, A.; Pratiwi, W.; Radiman, C. L.; Wahyuningrum, D.

2017-07-01

Surface properties are important factors that determine the performance of ultrafiltration membranes. This study aimed to investigate the effects of clay addition on the surface properties and membrane permeability of PVDF (poly-vinylidene fluoride) membranes. Three types of clay with different particle size were used in this study, namely montmorillonite-MMT, bentonite-BNT and cloisite 15A-CLS. The PVDF-clay composite membranes were prepared by phase inversion method using PEG as additive. The hydrophobicity of membrane surface was characterized by contact angle. The membrane permeability was determined by dead- end ultrafiltration with a trans-membrane pressure of 2 bars. In contact angle measurement, water contact angle of composite membranes is higher than PVDF membrane. The addition of clays decreased water flux but increased of Dextran rejection. The PVDF-BNT composite membranes reach highest Dextran rejection value of about 93%. The type and particle size of clay affected the hydrophobicity of membrane surface and determined the resulting membrane structure as well as the membrane performance.

Grain Refinement and Mechanical Properties of Cu–Cr–Zr Alloys with Different Nano-Sized TiCp Addition

PubMed Central

Zhang, Dongdong; Bai, Fang; Wang, Yong; Wang, Jinguo; Wang, Wenquan

2017-01-01

The TiCp/Cu master alloy was prepared via thermal explosion reaction. Afterwards, the nano-sized TiCp/Cu master alloy was dispersed by electromagnetic stirring casting into the melting Cu–Cr–Zr alloys to fabricate the nano-sized TiCp-reinforced Cu–Cr–Zr composites. Results show that nano-sized TiCp can effectively refine the grain size of Cu–Cr–Zr alloys. The morphologies of grain in Cu–Cr–Zr composites changed from dendritic grain to equiaxed crystal because of the addition and dispersion of nano-sized TiCp. The grain size decreased from 82 to 28 μm with the nano-sized TiCp content. Compared with Cu–Cr–Zr alloys, the ultimate compressive strength (σUCS) and yield strength (σ0.2) of 4 wt% TiCp-reinforced Cu–Cr–Zr composites increased by 6.7% and 9.4%, respectively. The wear resistance of the nano-sized TiCp-reinforced Cu–Cr–Zr composites increased with the increasing nano-sized TiCp content. The wear loss of the nano-sized TiCp-reinforced Cu–Cr–Zr composites decreased with the increasing TiCp content under abrasive particles. The eletrical conductivity of Cu–Cr–Zr alloys, 2% and 4% nano-sized TiCp-reinforced Cu–Cr–Zr composites are 64.71% IACS, 56.77% IACS and 52.93% IACS, respectively. PMID:28786937

Improved synthesis of fine zinc borate particles using seed crystals

NASA Astrophysics Data System (ADS)

Gürhan, Deniz; Çakal, Gaye Ö.; Eroğlu, İnci; Özkar, Saim

2009-03-01

Zinc borate is a flame retardant additive used in polymers, wood applications and textile products. There are different types of zinc borate having different chemical compositions and structures. In this study, the production of zinc borate having the molecular formula of 2ZnO·3B 2O 3·3.5H 2O was reexamined by studying the effects of reaction parameters on the properties of product as well as the reaction kinetics. Production of zinc borate from the reaction of boric acid and zinc oxide in the presence of seed crystals was performed in a continuously stirred, temperature-controlled batch reactor having a volume of 1.5 L. Samples taken in regular time intervals during the experiments were analyzed for the concentration of zinc oxide and boron oxide in the solid as well as for the conversion of zinc oxide to zinc borate versus time. The zinc borate production reaction was fit to the logistic model. The reaction rate, reaction completion time, composition and particle size distribution of zinc borate product were determined by varying the following parameters: the boric acid to zinc oxide ratio (H 3BO 3:ZnO=3:1, 3.5:1, 5:1 and 7:1), the particle size of zinc oxide (10 and 25 μm), stirring rate (275, 400, 800 and 1600 rpm), temperature (75, 85 and 95 °C) and the size of seed crystals (10 and 2 μm). The products were also analyzed for particle size distribution. The experimental results showed that the reaction rate increases with the increase in H 3BO 3:ZnO ratio, particle size of zinc oxide, stirring rate and temperature. Concomitantly, the reaction completion time is decreased by increasing the H 3BO 3:ZnO ratio, stirring rate and temperature. The average particle sizes of the zinc borate products are in the range 4.3-16.6 μm (wet dispersion analysis).

Spatially resolved chemical imaging of individual atmospheric particles using nanoscale imaging mass spectrometry: insight into particle origin and chemistry

DOE PAGES

Ghosal, Sutapa; Weber, Peter K.; Laskin, Alexander

2014-01-14

Knowledge of the spatially resolved composition of atmospheric particles is essential for differentiating between their surface versus bulk chemistry and understanding particle reactivity and the potential environmental impact. Here, we demonstrate the application of nanometer-scale secondary ion mass spectrometry (CAMECA NanoSIMS 50 ion probe) for 3D chemical imaging of individual atmospheric particles without any sample pre-treatment, such as sectioning of particles. Use of NanoSIMS depth profile analysis enables elemental mapping of particles with nanometer spatial resolution over a broad range of particle sizes. We have used this technique to probe the spatially resolved composition of ambient particles collected during amore » field campaign in Mexico City. Particles collected during this campaign have been extensively characterized in the past using other particle analysis techniques and hence offer a unique opportunity for exploring the utility of depth-resolved chemical imaging in ambient particle research. The particles that we examined in our study include those collected during a pollution episode related to urban waste incineration as well as background particles from the same location before the episode. Particles from the pollution episode show substantial intra-particle compositional variability typical of particles resulting from multiple emission sources. In contrast, the background particles have relatively homogeneous compositions with enhanced presence of nitrogen, oxygen, and chlorine at the particle surface. We also observed the surface enhancement of nitrogen and oxygen species is consistent with the presence of surface nitrates resulting from gas–particle heterogeneous interactions and is indicative of atmospheric ageing of the particles. The results presented here illustrate 3D characterization of ambient particles for insight into their chemical history.« less

Spatially resolved chemical imaging of individual atmospheric particles using nanoscale imaging mass spectrometry: Insighs into particle origin and chemistry

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ghosal, Sutapa; Weber, Peter K.; Laskin, Alexander

2014-04-21

Knowledge of the spatially-resolved composition of atmospheric particles is essential for differentiating between their surface versus bulk chemistry, understanding particle reactivity and the potential environmental impact. We demonstrate the application of nanometer-scale secondary ion mass spectrometry (Cameca NanoSIMS 50 ion probe) for 3D chemical imaging of individual atmospheric particles without any sample pre-treatment, such as the sectioning of particles. Use of NanoSIMS depth profile analysis enables elemental mapping of particles with nanometer spatial resolution over a broad of range of particle sizes. We have used this technique to probe spatially resolved composition of ambient particles collected during a field campaignmore » in Mexico City. Particles collected during this campaign have been extensively characterized in the past using other particle analysis techniques and hence offer a unique opportunity for exploring the utility of depth resolved chemical imaging in ambient particle research. 1 Particles examined in this study include those collected during a pollution episode related to urban waste incineration as well as background particles from the same location prior to the episode. Particles from the pollution episode show substantial intra-particle compositional variability typical of particles resulting from multiple emission sources. In contrast, the background particles have relatively homogeneous compositions with enhanced presence of nitrogen, oxygen and chlorine at the particle surface. The observed surface enhancement of nitrogen and oxygen species is consistent with the presence of surface nitrates resulting from gas-particle heterogeneous interactions and is indicative of atmospheric ageing of the particles. The results presented here illustrate 3D characterization of ambient particles for insights into their chemical history.« less

Effect of particle size on the photochromic response of PWA/SiO2 nanocomposite

NASA Astrophysics Data System (ADS)

Huang, Feng-Hsi; Chen, Ching-Chung; Lin, Dar-Jong; Don, Trong-Ming; Cheng, Liao-Ping

2010-10-01

A series of photochromic phosphotungstic acid (PWA)/SiO2 composites were synthesized using the sol-gel method. Depending on the feeding schedule of PWA during synthesis, the size of the formed PWA/SiO2 particles varied considerably from as small as 1.2 nm to ca. 10 nm. With decreasing silica particle size, the total contact area/interaction between SiO2 and PWA increases, as revealed by FT-IR and solid-state 29Si-NMR analyses. Particularly, when the size of PWA/SiO2 is 1 nm, crystallization of PWA is inhibited, and PWA presents as amorphous molecular entities distributing uniformly in the SiO2 host, which is in evidence in the XRD spectroscopy and HR-TEM imaging. In contrast, substantial crystallization of PWA takes place when PWA/SiO2 particles are as large as 10 nm, in which case less amount of surface free Si-OH is available for PWA to make bonds with. Photochromism occurs activated by ultraviolet light irradiation. The rate of coloration/bleaching is found to depend strongly on the particle size of PWA/SiO2; specifically, the rate increases twice when the particle size is reduced from 10 nm to 1.2 nm.

Study of various synthesis techniques of nanomaterials

NASA Astrophysics Data System (ADS)

Patil, Madhuri; Sharma, Deepika; Dive, Avinash; Mahajan, Sandeep; Sharma, Ramphal

2018-05-01

Development of synthesis techniques of realizing nano-materials over a range of sizes, shapes, and chemical compositions is an important aspect of nanotechnology. The remarkable size dependent physical & chemical properties of particles have fascinated and inspired research activity in this direction. This paper describes some aspects on synthesis and characterization of particles of metals, metal alloys, and oxides, either in the form of thin films or bulk shapes. A brief discussion on processing of thin-films is also described.

Nanograin Ceramic Optical Composite Window

DTIC Science & Technology

2005-07-15

parts are sintered in air at 1100 C̊. Table 1: Carbon content of the calcined Alumina- Zirconia powders analyzed by LECO Calcination Temperature Carbon...estimated particle size of the Alumina and Zirconia powders Material name Surface area (m2/g) Estimated particle size (nm) Alumina 315.7 4.7 Zirconia...200 300 400 500 600 700 800 900 1000 2-Theta - Scale 20 30 40 50 60 70 80 Figure 3: XRD patterns of zirconia powder prepared by sonochemical method

Chemical composition and mixing-state of ice residuals sampled within mixed phase clouds

NASA Astrophysics Data System (ADS)

Ebert, M.; Worringen, A.; Benker, N.; Mertes, S.; Weingartner, E.; Weinbruch, S.

2010-10-01

During an intensive campaign at the high alpine research station Jungfraujoch, Switzerland, in February/March 2006 ice particle residuals within mixed-phase clouds were sampled using the Ice-counterflow virtual impactor (Ice-CVI). Size, morphology, chemical composition, mineralogy and mixing state of the ice residual and the interstitial (i.e., non-activated) aerosol particles were analyzed by scanning and transmission electron microscopy. Ice nuclei (IN) were identified from the significant enrichment of particle groups in the ice residual (IR) samples relative to the interstitial aerosol. In terms of number lead-bearing particles are enriched by a factor of approximately 25, complex internal mixtures with silicates or metal oxides as major components by a factor of 11, and mixtures of secondary aerosol and soot (C-O-S particles) by a factor of 2. Other particle groups (sulfates, sea salt, Ca-rich particles, external silicates) observed in the ice-residual samples cannot be assigned unambiguously as IN. Between 9 and 24% of all IR are Pb-bearing particles. Pb was found as major component in around 10% of these particles (PbO, PbCl2). In the other particles, Pb was found as some 100 nm sized agglomerates consisting of 3-8 nm sized primary particles (PbS, elemental Pb). C-O-S particles are present in the IR at an abundance of 17-27%. The soot component within these particles is strongly aged. Complex internal mixtures occur in the IR at an abundance of 9-15%. Most IN identified at the Jungfraujoch station are internal mixtures containing anthropogenic components (either as main or minor constituent), and it is concluded that admixture of the anthropogenic component is responsible for the increased IN efficiency within mixed phase clouds. The mixing state appears to be a key parameter for the ice nucleation behaviour that cannot be predicted from the separate components contained within the individual particles.

Calibrations and Comparisons of Aerosol Spectrometers linking Ground and Airborne Measurements

NASA Astrophysics Data System (ADS)

Williamson, C.; Brock, C. A.; Erdesz, F.

2015-12-01

The nucleation-mode aerosol size spectrometer (NMASS), a fast-time response instrument measuring aerosol size distributions between 5 and 60nm, is to sample in the boundary layer and free troposphere on NASA's Atmospheric Tomography mission (ATom), providing contiguous data with global coverage in all four seasons. In preparation for this the NMASS is calibrated for the expected flight conditions and compatibility studies are made with ground-based instrumentation. The NMASS is comprised of 5 parallel condensation particle counters (CPCs) using perfluoro-tributylamine as a working fluid. Understanding the variation of CPC counting efficiencies with respect to the chemical composition of the sample is important for accurate data analysis and can be used to give indirect information about sample chemical composition. This variation is strongly dependent on the working fluid. The absolute responses and associated variations of the NMASS to ammonium sulfate and limonene ozonolysis products, compounds pertinent to the composition of particles nucleated in the free troposphere and boundary later, are compared to those of butanol, diethylene-glycol and water based CPCs, which are more commonly used in ground-based measurements. While fast time-response is key to measuring aerosol size distributions on flights, high size-resolution is often prioritized for ground-based measurements, and so a scanning mobility particle sizer (SMPS) is commonly used. Inter-comparison between NMASS and SMPS data is non-trivial because of the different working principles and resolutions of the instruments and yet it is vital, for example, for understanding the sources of particles observed during flights and the global relevance of phenomena observed from field stations and in chambers. We report compatibility studies on inversions of data from the SMPS and NMASS, evaluating temporal and spatial resolution and sources of uncertainty.

Weight Loss and Exercise Alter the High-Density Lipoprotein Lipidome and Improve High-Density Lipoprotein Functionality in Metabolic Syndrome.

PubMed

Khan, Anmar A; Mundra, Piyushkumar A; Straznicky, Nora E; Nestel, Paul J; Wong, Gerard; Tan, Ricardo; Huynh, Kevin; Ng, Theodore W; Mellett, Natalie A; Weir, Jacquelyn M; Barlow, Christopher K; Alshehry, Zahir H; Lambert, Gavin W; Kingwell, Bronwyn A; Meikle, Peter J

2018-02-01

High-density lipoprotein (HDL) lipid composition and function may better reflect cardiovascular risk than HDL cholesterol concentration. This study characterized the relationships between HDL composition, metabolism, and function in metabolic syndrome (MetS) patients and how changes in composition after weight loss (WL) and exercise treatments are related to function. Plasma samples from MetS patients (n=95) and healthy individuals (n=40) were used in this study. Subsets of the MetS group underwent 12 weeks of no treatment (n=17), WL (n=19), or WL plus exercise (WLEX; n=17). HDL was isolated using density-gradient ultracentrifugation. The HDL lipidome was analyzed by mass spectrometry, and particle size determined by nuclear magnetic resonance. Cholesteryl ester transfer protein activity and ex vivo HDL cholesterol efflux capacity (CEC) were assessed. The HDL lipidome in the MetS patients was substantially different from that in healthy individuals, mean particle size was smaller, and CEC was lower. Several HDL phospholipid and sphingolipid species were associated with HDL diameter and CEC. The HDL lipidome and particle size were modified toward the healthy individuals after WL and WLEX treatments, with greater effects observed in the latter group. Cholesteryl ester transfer protein activity was reduced after WL and WLEX, and CEC was improved after WLEX. WLEX treatment in MetS patients normalizes the HDL lipidome and particle size profile and enhances CEC. HDL lipids associated with diminished CEC may represent novel biomarkers for early prediction of HDL dysfunction and disease risk and may represent potential therapeutic targets for future HDL therapies. URL: http://www.clinicaltrials.gov. Unique identifier: NCT00163943. © 2017 American Heart Association, Inc.

Concentration, Size Distribution, and Infectivity of Airborne Particles Carrying Swine Viruses.

PubMed

Alonso, Carmen; Raynor, Peter C; Davies, Peter R; Torremorell, Montserrat

2015-01-01

When pathogens become airborne, they travel associated with particles of different size and composition. Particle size determines the distance across which pathogens can be transported, as well as the site of deposition and the survivability of the pathogen. Despite the importance of this information, the size distribution of particles bearing viruses emitted by infectious animals remains unknown. In this study we characterized the concentration and size distribution of inhalable particles that transport influenza A virus (IAV), porcine reproductive and respiratory syndrome virus (PRRSV), and porcine epidemic diarrhea virus (PEDV) generated by acutely infected pigs and assessed virus viability for each particle size range. Aerosols from experimentally infected pigs were sampled for 24 days using an Andersen cascade impactor able to separate particles by size (ranging from 0.4 to 10 micrometer (μm) in diameter). Air samples collected for the first 9, 20 and the last 3 days of the study were analyzed for IAV, PRRSV and PEDV, respectively, using quantitative reverse transcription polymerase chain reaction (RT-PCR) and quantified as geometric mean copies/m(3) within each size range. IAV was detected in all particle size ranges in quantities ranging from 5.5x10(2) (in particles ranging from 1.1 to 2.1 μm) to 4.3x10(5) RNA copies/m(3) in the largest particles (9.0-10.0 μm). PRRSV was detected in all size ranges except particles between 0.7 and 2.1 μm in quantities ranging from 6x10(2) (0.4-0.7 μm) to 5.1x10(4) RNA copies/m(3) (9.0-10.0 μm). PEDV, an enteric virus, was detected in all particle sizes and in higher quantities than IAV and PRRSV (p < 0.0001) ranging from 1.3x10(6) (0.4-0.7 μm) to 3.5x10(8) RNA copies/m(3) (9.0-10.0 μm). Infectious status was demonstrated for the 3 viruses, and in the case of IAV and PRRSV, viruses were isolated from particles larger than 2.1 μm. In summary, our results indicated that airborne PEDV, IAV and PRRSV can be found in a wide range of particle sizes. However, virus viability is particle size dependent.

Optimization of extraction parameters of pentacyclic triterpenoids from Swertia chirata stem using response surface methodology.

PubMed

Pandey, Devendra Kumar; Kaur, Prabhjot

2018-03-01

In the present investigation, pentacyclic triterpenoids were extracted from different parts of Swertia chirata by solid-liquid reflux extraction methods. The total pentacyclic triterpenoids (UA, OA, and BA) in extracted samples were determined by HPTLC method. Preliminary studies showed that stem part contains the maximum pentacyclic triterpenoid and was chosen for further studies. Response surface methodology (RSM) has been employed successfully by solid-liquid reflux extraction methods for the optimization of different extraction variables viz., temperature ( X 1 35-70 °C), extraction time ( X 2 30-60 min), solvent composition ( X 3 20-80%), solvent-to-solid ratio ( X 4 30-60 mlg -1 ), and particle size ( X 5 3-6 mm) on maximum recovery of triterpenoid from stem parts of Swertia chirata . A Plackett-Burman design has been used initially to screen out the three extraction factors viz., particle size, temperature, and solvent composition on yield of triterpenoid. Moreover, central composite design (CCD) was implemented to optimize the significant extraction parameters for maximum triterpenoid yield. Three extraction parameters viz., mean particle size (3 mm), temperature (65 °C), and methanol-ethyl acetate solvent composition (45%) can be considered as significant for the better yield of triterpenoid A second-order polynomial model satisfactorily fitted the experimental data with the R 2 values of 0.98 for the triterpenoid yield ( p  < 0.001), implying good agreement between the experimental triterpenoid yield (3.71%) to the predicted value (3.79%).

Sediment composition for the assessment of water erosion and nonpoint source pollution in natural and fire-affected landscapes.

PubMed

Carkovic, Athena B; Pastén, Pablo A; Bonilla, Carlos A

2015-04-15

Water erosion is a leading cause of soil degradation and a major nonpoint source pollution problem. Many efforts have been undertaken to estimate the amount and size distribution of the sediment leaving the field. Multi-size class water erosion models subdivide eroded soil into different sizes and estimate the aggregate's composition based on empirical equations derived from agricultural soils. The objective of this study was to evaluate these equations on soil samples collected from natural landscapes (uncultivated) and fire-affected soils. Chemical, physical, and soil fractions and aggregate composition analyses were performed on samples collected in the Chilean Patagonia and later compared with the equations' estimates. The results showed that the empirical equations were not suitable for predicting the sediment fractions. Fine particles, including primary clay, primary silt, and small aggregates (<53 μm) were over-estimated, and large aggregates (>53 μm) and primary sand were under-estimated. The uncultivated and fire-affected soils showed a reduced fraction of fine particles in the sediment, as clay and silt were mostly in the form of large aggregates. Thus, a new set of equations was developed for these soils, where small aggregates were defined as particles with sizes between 53 μm and 250 μm and large aggregates as particles>250 μm. With r(2) values between 0.47 and 0.98, the new equations provided better estimates for primary sand and large aggregates. The aggregate's composition was also well predicted, especially the silt and clay fractions in the large aggregates from uncultivated soils (r(2)=0.63 and 0.83, respectively) and the fractions of silt in the small aggregates (r(2)=0.84) and clay in the large aggregates (r(2)=0.78) from fire-affected soils. Overall, these new equations proved to be better predictors for the sediment and aggregate's composition in uncultivated and fire-affected soils, and they reduce the error when estimating soil loss in natural landscapes. Copyright © 2015 Elsevier B.V. All rights reserved.

Characterization and variability of particle size distributions in Hudson Bay, Canada

NASA Astrophysics Data System (ADS)

Xi, Hongyan; Larouche, Pierre; Tang, Shilin; Michel, Christine

2014-06-01

Particle size distribution (PSD) plays a significant role in many aspects of aquatic ecosystems, including phytoplankton dynamics, sediment fluxes, and optical scattering from particulates. As of yet, little is known on the variability of particle size distribution in marine ecosystems. In this study, we investigated the PSD properties and variability in Hudson Bay based on measurements from a laser diffractometer (LISST-100X Type-B) in concert with biogeochemical parameters collected during summer 2010. Results show that most power-law fitted PSD slopes ranged from 2.5 to 4.5, covering nearly the entire range observed for natural waters. Offshore waters showed a predominance of smaller particles while near the coast, the effect of riverine inputs on PSD were apparent. Particulate inorganic matter contributed more to total suspended matter in coastal waters leading to lower PSD slopes than offshore. The depth distribution of PSD slopes shows that larger particles were associated with the pycnocline. Below the pycnocline, smaller particles dominated the spectra. A comparison between a PSD slope-based method to derive phytoplankton size class (PSC) and pigment-based derived PSC showed the two methods agreed relatively well. This study provides valuable baseline information on particle size properties and phytoplankton composition estimates in a sub-arctic environment subject to rapid environmental change.

Single particle chemical composition and shape of fresh and aged Saharan dust in Morocco and at Cape Verde Islands during SAMUM I and II

NASA Astrophysics Data System (ADS)

Kandler, K.; Lieke, K.; Schütz, L.; Deutscher, C.; Ebert, M.; Jaenicke, R.; Müller-Ebert, D.; Weinbruch, S.

2009-04-01

The Saharan Mineral Dust Experiment (SAMUM) is focussed to the understanding of the radiative effects of mineral dust. During the SAMUM 2006 field campaign at Tinfou, southern Morocco, chemical and mineralogical properties of fresh desert aerosols were measured. The winter campaign of Saharan Mineral Dust Experiment II was based in Praia, Island of Santiago, Cape Verde. This second field campaign was dedicated to the investigation of transported Saharan Mineral Dust. Aerosol particles between 100 nm and 500 μm (Morocco) respectively 50 μm (Cape Verde) in diameter were collected by nozzle and body impactors and in a sedimentation trap. The particles were investigated by electron microscopic single particle analysis and attached energy-dispersive X-ray analysis. Chemical properties as well as size and shape for each particle were recorded. Three size regimes are identified in the aerosol at Tinfou: Smaller than 500 nm in diameter, the aerosol consists of sulfates and mineral dust. Larger than 500 nm up to 50 μm, mineral dust dominates, consisting mainly of silicates, and - to a lesser extent - carbonates and quartz. Larger than 50 μm, approximately half of the particles consist of quartz. Time series of the elemental composition show a moderate temporal variability of the major compounds. Calcium-dominated particles are enhanced during advection from a prominent dust source in Northern Africa (Chott El Djerid and surroundings). At Praia, the boundary layer aerosol consists of a superposition of mineral dust, marine aerosol and ammonium sulfate, soot, and other sulfates as well as mixtures thereof. During low-dust periods, the aerosol is dominated by sea salt. During dust events, mineral dust takes over the majority of the particle mass up to 90 %. Particles smaller 500 nm in diameter always show a significant abundance of ammonium sulfate. The particle aspect ratio was measured for all analyzed particles. Its size dependence reflects that of the chemical composition. At Tinfou, larger than 500 nm particle diameter, a median aspect ratio of 1.6 is measured. Towards smaller particles, it decreases to about 1.3. Evaluation of the Cape Verde data will show whether a significant difference exists between fresh and aged Saharan dust in aspect ratio.

Evaluating Changes In the Elemental Composition of Micrometeorites During Entry into the Earth’s Atmosphere

NASA Astrophysics Data System (ADS)

Rudraswami, N. G.; Shyam Prasad, M.; Dey, S.; Plane, J. M. C.; Feng, W.; Taylor, S.

2015-11-01

We evaluate the heating of extraterrestrial particles entering the atmosphere using the comprehensive chemical ablation model (CABMOD). This model predicts the ablation rates of individual elements in a particle with a defined size, composition, entry velocity, and entry angle with respect to the zenith (ZA). In the present study, bulk chemical analyses of 1133 Antarctica micrometeorites (collected from the south pole water well) are interpreted using CABMOD. The marked spread in Fe/Si values in unmelted, partially melted, and melted micrometeorites is explained by the loss of relatively volatile Fe during atmospheric entry. The combined theoretical modeling and elemental composition of the micrometeorites (Mg/Si ratios) suggest that ˜85% of particles have a provenance of carbonaceous chondrites, the remaining ˜15% are either ordinary or enstatite chondrites. About 65% of the micrometeorites have undergone <20% ablation, while a further 20% have lost between 20% and 60% of their original mass. This has implications for understanding the micrometeorite flux that reaches the Earth's surface, as well as estimating the pre-atmospheric size of the particles. Our work shows that the unmelted particles that contribute ˜50% to the total micrometeorite collection on Earth's surface have a small entry zone: ZA = 60°-90° if the entry velocity is ˜11 km s-1, and ZA = 80°-90° for >11-21 km s-1.

Extremely fine structured cathode for solid oxide fuel cells using Sr-doped LaMnO3 and Y2O3-stabilized ZrO2 nano-composite powder synthesized by spray pyrolysis

NASA Astrophysics Data System (ADS)

Shimada, Hiroyuki; Yamaguchi, Toshiaki; Sumi, Hirofumi; Nomura, Katsuhiro; Yamaguchi, Yuki; Fujishiro, Yoshinobu

2017-02-01

A solid oxide fuel cell (SOFC) for high power density operation was developed with a microstructure-controlled cathode using a nano-composite powder of Sr-doped LaMnO3 (LSM) and Y2O3-stabilized ZrO2 (YSZ) synthesized by spray pyrolysis. The individual LSM-YSZ nano-composite particles, formed by crystalline and amorphous nano-size LSM and YSZ particles, showed spherical morphology with uniform particle size. The use of this powder for cathode material led to an extremely fine microstructure, in which all the LSM and YSZ grains (approximately 100-200 nm) were highly dispersed and formed their own network structures. This microstructure was due to the two phase electrode structure control using the powder, namely, nano-order level in each particle and micro-order level between particles. An anode-supported SOFC with the LSM-YSZ cathode using humidified H2 as fuel and ambient air as oxidant exhibited high power densities, such as 1.29 W cm-2 under a voltage of 0.75 V and a maximum power density of 2.65 W cm-2 at 800 °C. Also, the SOFC could be stably operated for 250 h with no degradation, even at a high temperature of 800 °C.