On Maximal Hard-Core Thinnings of Stationary Particle Processes

NASA Astrophysics Data System (ADS)

Hirsch, Christian; Last, Günter

2018-02-01

The present paper studies existence and distributional uniqueness of subclasses of stationary hard-core particle systems arising as thinnings of stationary particle processes. These subclasses are defined by natural maximality criteria. We investigate two specific criteria, one related to the intensity of the hard-core particle process, the other one being a local optimality criterion on the level of realizations. In fact, the criteria are equivalent under suitable moment conditions. We show that stationary hard-core thinnings satisfying such criteria exist and are frequently distributionally unique. More precisely, distributional uniqueness holds in subcritical and barely supercritical regimes of continuum percolation. Additionally, based on the analysis of a specific example, we argue that fluctuations in grain sizes can play an important role for establishing distributional uniqueness at high intensities. Finally, we provide a family of algorithmically constructible approximations whose volume fractions are arbitrarily close to the maximum.

A deformation mechanism of hard metal surrounded by soft metal during roll forming

PubMed Central

YU, Hailiang; TIEU, A. Kiet; LU, Cheng; LIU, Xiong; GODBOLE, Ajit; LI, Huijun; KONG, Charlie; QIN, Qinghua

2014-01-01

It is interesting to imagine what would happen when a mixture of soft-boiled eggs and stones is deformed together. A foil made of pure Ti is stronger than that made of Cu. When a composite Cu/Ti foil deforms, the harder Ti will penetrate into the softer Cu in the convex shapes according to previously reported results. In this paper, we describe the fabrication of multilayer Cu/Ti foils by the roll bonding technique and report our observations. The experimental results lead us to propose a new deformation mechanism for a hard metal surrounded by a soft metal during rolling of a laminated foil, particularly when the thickness of hard metal foil (Ti, 25 μm) is much less than that of the soft metal foil (Cu, 300 μm). Transmission Electron Microscope (TEM) imaging results show that the hard metal penetrates into the soft metal in the form of concave protrusions. Finite element simulations of the rolling process of a Cu/Ti/Cu composite foil are described. Finally, we focus on an analysis of the deformation mechanism of Ti foils and its effects on grain refinement, and propose a grain refinement mechanism from the inside to the outside of the laminates during rolling. PMID:24853192

Process for casting hard-faced, lightweight camshafts and other cylindrical products

DOEpatents

Hansen, Jeffrey S.; Turner, Paul C.; Argetsinger, Edward R.; Wilson, Rick D.

1996-01-01

A process for casting a hard-faced cylindrical product such as an automobile camshaft includes the steps of: (a) preparing a composition formed from a molten base metal and an additive in particle form and having a hardness value greater than the hardness value of the base metal; (b) introducing the composition into a flask containing a meltable pattern of a cylindrical product such as an automobile camshaft to be manufactured and encased in sand to allow the composition to melt the pattern and assume the shape of the pattern within the sand; and (c) rotating the flask containing the pattern about the longitudinal axes of both the flask and the pattern as the molten base metal containing the additive in particle form is introduced into the flask to cause particles of the additive entrained in the molten base metal to migrate by centrifugal action to the radial extremities of the pattern and thereby provide a cylindrical product having a hardness value greater at it's radial extremities than at its center when the molten base metal solidifies.

Statistical theory of correlations in random packings of hard particles.

PubMed

Jin, Yuliang; Puckett, James G; Makse, Hernán A

2014-05-01

A random packing of hard particles represents a fundamental model for granular matter. Despite its importance, analytical modeling of random packings remains difficult due to the existence of strong correlations which preclude the development of a simple theory. Here, we take inspiration from liquid theories for the n-particle angular correlation function to develop a formalism of random packings of hard particles from the bottom up. A progressive expansion into a shell of particles converges in the large layer limit under a Kirkwood-like approximation of higher-order correlations. We apply the formalism to hard disks and predict the density of two-dimensional random close packing (RCP), ϕ(rcp) = 0.85 ± 0.01, and random loose packing (RLP), ϕ(rlp) = 0.67 ± 0.01. Our theory also predicts a phase diagram and angular correlation functions that are in good agreement with experimental and numerical data.

Interaction of Burning Metal Particles

NASA Technical Reports Server (NTRS)

Dreizin, Edward L.; Berman, Charles H.; Hoffmann, Vern K.

1999-01-01

Physical characteristics of the combustion of metal particle groups have been addressed in this research. The combustion behavior and interaction effects of multiple metal particles has been studied using a microgravity environment, which presents a unique opportunity to create an "aerosol" consisting of relatively large particles, i.e., 50-300 micrometer diameter. Combustion behavior of such an aerosol could be examined using methods adopted from well-developed single particle combustion research. The experiment included fluidizing relatively large (order of 100 micrometer diameter) uniform metal particles under microgravity and igniting such an "aerosol" using a hot wire igniter. The flame propagation and details of individual particle combustion and particle interaction have been studied using a high speed movie and video-imaging with cameras coupled with microscope lenses to resolve individual particles. Interference filters were used to separate characteristic metal and metal oxide radiation bands form the thermal black body radiation. Recorded flame images were digitized and employed to understand the processes occurring in the burning aerosol. The development of individual particle flames, merging or separation, and extinguishing as well as induced particle motion have been analyzed to identify the mechanisms governing these processes. Size distribution, morphology, and elemental compositions of combustion products were characterized and used to link the observed in this project aerosol combustion phenomena with the recently expanded mechanism of single metal particle combustion.

Interaction of Burning Metal Particles

NASA Technical Reports Server (NTRS)

Dreizin, Edward L.; Berman, Charles H.; Hoffmann, Vern K.

1999-01-01

Physical characteristics of the combustion of metal particle groups have been addressed in this research. The combustion behavior and interaction effects of multiple metal particles has been studied using a microgravity environment, which presents a unique opportunity to create an "aerosol" consisting of relatively large particles, i.e., 50-300 m diameter. Combustion behavior of such an aerosol could be examined using methods adopted from well-developed single particle combustion research. The experiment included fluidizing relatively large (order of 100 m diameter) uniform metal particles under microgravity and igniting such an "aerosol" using a hot wire igniter. The flame propagation and details of individual particle combustion and particle interaction have been studied using a high speed movie and video-imaging with cameras coupled with microscope lenses to resolve individual particles. Interference filters were used to separate characteristic metal and metal oxide radiation bands from the thermal black body radiation. Recorded flame images were digitized and various image processing techniques including flame position tracking, color separation, and pixel by pixel image comparison were employed to understand the processes occurring in the burning aerosol. The development of individual particle flames, merging or separation, and extinguishment as well as induced particle motion have been analyzed to identify the mechanisms governing these processes. Size distribution, morphology, and elemental compositions of combustion products were characterized and used to link the observed in this project aerosol combustion phenomena with the recently expanded mechanism of single metal particle combustion.

Density functional theory for hard uniaxial particles: Complex ordering of pear-shaped and spheroidal particles near a substrate

NASA Astrophysics Data System (ADS)

Schönhöfer, Philipp W. A.; Schröder-Turk, Gerd E.; Marechal, Matthieu

2018-03-01

We develop a density functional for hard particles with a smooth uniaxial shape (including non-inversion-symmetric particles) within the framework of fundamental measure theory. By applying it to a system of tapered, aspherical liquid-crystal formers, reminiscent of pears, we analyse their behaviour near a hard substrate. The theory predicts a complex orientational ordering close to the substrate, which can be directly related to the particle shape, in good agreement with our simulation results. Furthermore, the lack of particle inversion-symmetry implies the possibility of alternating orientations in subsequent layers as found in a smectic/lamellar phase of such particles. Both theory and Monte Carlo simulations confirm that such ordering occurs in our system. Our results are relevant for adsorption processes of asymmetric colloidal particles and molecules at hard interfaces and show once again that tapering strongly affects the properties of orientationally ordered phases.

Porous Biodegradable Metals for Hard Tissue Scaffolds: A Review

PubMed Central

Yusop, A. H.; Bakir, A. A.; Shaharom, N. A.; Abdul Kadir, M. R.; Hermawan, H.

2012-01-01

Scaffolds have been utilized in tissue regeneration to facilitate the formation and maturation of new tissues or organs where a balance between temporary mechanical support and mass transport (degradation and cell growth) is ideally achieved. Polymers have been widely chosen as tissue scaffolding material having a good combination of biodegradability, biocompatibility, and porous structure. Metals that can degrade in physiological environment, namely, biodegradable metals, are proposed as potential materials for hard tissue scaffolding where biodegradable polymers are often considered as having poor mechanical properties. Biodegradable metal scaffolds have showed interesting mechanical property that was close to that of human bone with tailored degradation behaviour. The current promising fabrication technique for making scaffolds, such as computation-aided solid free-form method, can be easily applied to metals. With further optimization in topologically ordered porosity design exploiting material property and fabrication technique, porous biodegradable metals could be the potential materials for making hard tissue scaffolds. PMID:22919393

SQUID sensor application for small metallic particle detection

NASA Astrophysics Data System (ADS)

Tanaka, Saburo; Hatsukade, Yoshimi; Ohtani, Takeyoshi; Suzuki, Shuichi

2009-04-01

High-Tc superconducting quantum interference device (SQUID) is an ultra-sensitive magnetic sensor. Since the performance of the SQUID is improved and stabilized, now it is ready for application. One strong candidate for application is a detection system of magnetic foreign matters in industrial products or beverages. There is a possibility that ultra-small metallic foreign matter has been accidentally mixed with industrial products such as lithium ion batteries. If this happens, the manufacturer of the product suffers a great loss recalling products. The outer dimension of metallic particles less than 100 μm cannot be detected by an X-ray imaging, which is commonly used for the inspection. Ionization of the material is also a big issue for beverages in the case of the X-ray imaging. Therefore a highly sensitive and safety detection system for small foreign matters is required. We developed detection systems based on high-Tc SQUID with a high-performance magnetic shield. We could successfully measure small iron particles of 100 μm on a belt conveyer and stainless steel balls of 300 μm in water. These detection levels were hard to be achieved by a conventional X-ray detection or other methods.

Hard convex lens-shaped particles: Densest-known packings and phase behavior

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

Cinacchi, Giorgio, E-mail: giorgio.cinacchi@uam.es; Torquato, Salvatore, E-mail: torquato@princeton.edu

2015-12-14

By using theoretical methods and Monte Carlo simulations, this work investigates dense ordered packings and equilibrium phase behavior (from the low-density isotropic fluid regime to the high-density crystalline solid regime) of monodisperse systems of hard convex lens-shaped particles as defined by the volume common to two intersecting congruent spheres. We show that, while the overall similarity of their shape to that of hard oblate ellipsoids is reflected in a qualitatively similar phase diagram, differences are more pronounced in the high-density crystal phase up to the densest-known packings determined here. In contrast to those non-(Bravais)-lattice two-particle basis crystals that are themore » densest-known packings of hard (oblate) ellipsoids, hard convex lens-shaped particles pack more densely in two types of degenerate crystalline structures: (i) non-(Bravais)-lattice two-particle basis body-centered-orthorhombic-like crystals and (ii) (Bravais) lattice monoclinic crystals. By stacking at will, regularly or irregularly, laminae of these two crystals, infinitely degenerate, generally non-periodic in the stacking direction, dense packings can be constructed that are consistent with recent organizing principles. While deferring the assessment of which of these dense ordered structures is thermodynamically stable in the high-density crystalline solid regime, the degeneracy of their densest-known packings strongly suggests that colloidal convex lens-shaped particles could be better glass formers than colloidal spheres because of the additional rotational degrees of freedom.« less

Hard metal lung disease: a case series.

PubMed

Mizutani, Rafael Futoshi; Terra-Filho, Mário; Lima, Evelise; Freitas, Carolina Salim Gonçalves; Chate, Rodrigo Caruso; Kairalla, Ronaldo Adib; Carvalho-Oliveira, Regiani; Santos, Ubiratan Paula

2016-01-01

To describe diagnostic and treatment aspects of hard metal lung disease (HMLD) and to review the current literature on the topic. This was a retrospective study based on the medical records of patients treated at the Occupational Respiratory Diseases Clinic of the Instituto do Coração, in the city of São Paulo, Brazil, between 2010 and 2013. Of 320 patients treated during the study period, 5 (1.56%) were diagnosed with HMLD. All of those 5 patients were male (mean age, 42.0 ± 13.6 years; mean duration of exposure to hard metals, 11.4 ± 8.0 years). Occupational histories were taken, after which the patients underwent clinical evaluation, chest HRCT, pulmonary function tests, bronchoscopy, BAL, and lung biopsy. Restrictive lung disease was found in all subjects. The most common chest HRCT finding was ground glass opacities (in 80%). In 4 patients, BALF revealed multinucleated giant cells. In 3 patients, lung biopsy revealed giant cell interstitial pneumonia. One patient was diagnosed with desquamative interstitial pneumonia associated with cellular bronchiolitis, and another was diagnosed with a hypersensitivity pneumonitis pattern. All patients were withdrawn from exposure and treated with corticosteroid. Clinical improvement occurred in 2 patients, whereas the disease progressed in 3. Although HMLD is a rare entity, it should always be included in the differential diagnosis of respiratory dysfunction in workers with a high occupational risk of exposure to hard metal particles. A relevant history (clinical and occupational) accompanied by chest HRCT and BAL findings suggestive of the disease might be sufficient for the diagnosis. Descrever aspectos relacionados ao diagnóstico e tratamento de pacientes com doença pulmonar por metal duro (DPMD) e realizar uma revisão da literatura. Estudo retrospectivo dos prontuários médicos de pacientes atendidos no Serviço de Doenças Respiratórias Ocupacionais do Instituto do Coração, localizado na cidade de S�

Metal release from stainless steel particles in vitro-influence of particle size.

PubMed

Midander, K; Pan, J; Wallinder, I Odnevall; Leygraf, C

2007-01-01

Human inhalation of airborne metallic particles is important for health risk assessment. To study interactions between metallic particles and the human body, metal release measurements of stainless steel powder particles were performed in two synthetic biological media simulating lung-like environments. Particle size and media strongly influence the metal release process. The release rate of Fe is enhanced compared with Cr and Ni. In artificial lysosomal fluid (ALF, pH 4.5), the accumulated amounts of released metal per particle loading increase drastically with decreasing particle size. The release rate of Fe per unit surface area increases with decreasing particle size. Compared with massive sheet metal, fine powder particles (<4 microm) show similar release rates of Cr and Ni, but a higher release rate of Fe. Release rates in Gamble's solution (pH 7.4), for all powders investigated, are significantly lower compared to ALF. No clear trend is seen related to particle size in Gamble's solution.

Steady flow of smooth, inelastic particles on a bumpy inclined plane: Hard and soft particle simulations

NASA Astrophysics Data System (ADS)

Tripathi, Anurag; Khakhar, D. V.

2010-04-01

We study smooth, slightly inelastic particles flowing under gravity on a bumpy inclined plane using event-driven and discrete-element simulations. Shallow layers (ten particle diameters) are used to enable simulation using the event-driven method within reasonable computational times. Steady flows are obtained in a narrow range of angles (13°-14.5°) ; lower angles result in stopping of the flow and higher angles in continuous acceleration. The flow is relatively dense with the solid volume fraction, ν≈0.5 , and significant layering of particles is observed. We derive expressions for the stress, heat flux, and dissipation for the hard and soft particle models from first principles. The computed mean velocity, temperature, stress, dissipation, and heat flux profiles of hard particles are compared to soft particle results for different values of stiffness constant (k) . The value of stiffness constant for which results for hard and soft particles are identical is found to be k≥2×106mg/d , where m is the mass of a particle, g is the acceleration due to gravity, and d is the particle diameter. We compare the simulation results to constitutive relations obtained from the kinetic theory of Jenkins and Richman [J. T. Jenkins and M. W. Richman, Arch. Ration. Mech. Anal. 87, 355 (1985)] for pressure, dissipation, viscosity, and thermal conductivity. We find that all the quantities are very well predicted by kinetic theory for volume fractions ν<0.5 . At higher densities, obtained for thicker layers ( H=15d and H=20d ), the kinetic theory does not give accurate prediction. Deviations of the kinetic theory predictions from simulation results are relatively small for dissipation and heat flux and most significant deviations are observed for shear viscosity and pressure. The results indicate the range of applicability of soft particle simulations and kinetic theory for dense flows.

Stability of metal particle and metal particulate media

NASA Technical Reports Server (NTRS)

Okamoto, Kazuhiro

1992-01-01

Metal particulate (MP) video tape was launched for 8 mm video tape in 1985. Since then MP tapes have been applied to several consumer formats and instrumental formats because of its superior electrical performance. Recently data storage media, such as DDS and D-8, have started employing MP tape. However, there are serious concerns with archival stability of MP tape particularly in the case of data storage use, as metal particles essentially have problems with chemical instability and are susceptible to oxidation and corrosion. Although there were some studies about the archival stability of metal particles or MP tapes, a clear understanding has yet to be reached. In this paper, we report the stability of magnetic properties of current metal particles, and then discuss the new technologies to improve the stability further.

Nanoindentation hardness of particles used in magnetorheological finishing (MRF).

PubMed

Shorey, A B; Kwong, K M; Johnson, K M; Jacobs, S D

2000-10-01

Knowledge of the hardness of abrasive particles that are used in polishing is a key to the fundamental understanding of the mechanisms of material removal. The magnetorheological-finishing process uses both magnetic and nonmagnetic abrasive particles during polishing. The nanohardnesses of the micrometer-sized magnetic carbonyl iron and nonmagnetic abrasive particles have been measured successfully by use of novel, to our knowledge, sample-preparation and nanoindentation techniques. Some of the results reported compare favorably with existing microhardness data found in the literature, whereas other results are new.

Decomposition Mechanism and Decomposition Promoting Factors of Waste Hard Metal for Zinc Decomposition Process (ZDP)

NASA Astrophysics Data System (ADS)

Pee, J. H.; Kim, Y. J.; Kim, J. Y.; Seong, N. E.; Cho, W. S.; Kim, K. J.

2011-10-01

Decomposition promoting factors and decomposition mechanism in the zinc decomposition process of waste hard metals which are composed mostly of tungsten carbide and cobalt were evaluated. Zinc volatility amount was suppressed and zinc steam pressure was produced in the reaction graphite crucible inside an electric furnace for ZDP. Reaction was done for 2 hrs at 650 °C, which 100 % decomposed the waste hard metals that were over 30 mm thick. As for the separation-decomposition of waste hard metals, zinc melted alloy formed a liquid composed of a mixture of γ-β1 phase from the cobalt binder layer (reaction interface). The volume of reacted zone was expanded and the waste hard metal layer was decomposed-separated horizontally from the hard metal. Zinc used in the ZDP process was almost completely removed-collected by decantation and volatilization-collection process at 1000 °C. The small amount of zinc remaining in the tungsten carbide-cobalt powder which was completely decomposed was fully removed by using phosphate solution which had a slow cobalt dissolution speed.

Laboratory studies on the tribology of hard bearing hip prostheses: ceramic on ceramic and metal on metal.

PubMed

Vassiliou, K; Scholes, S C; Unsworth, A

2007-01-01

Total hip replacements offer relief to a great many patients every year around the world. With an expected service life of around 25 years on most devices, and with younger and younger patients undergoing this surgery, it is of great importance to understand the mechanisms of their function. Tribological testing of both conventional and hard bearing joint combinations have been conducted in many centres throughout the world, and, after being initially abandoned owing to premature failures, hard bearing combinations have been revisited as viable options for joint replacements. Improved design, manufacturing procedures, and material compositions have led to improved performance over first-generation designs in both metal-on-metal and ceramic-on-ceramic hip prostheses. This paper offers a review of the work conducted in an attempt to highlight the most important factors affecting joint performance and tribology of hard bearing combinations. The tribological performance of these joints is superior to that of conventional metal- or ceramic-on-polymer designs.

Soft metal plating enables hard metal seal to operate successfully in low temperature, high pressure environment

NASA Technical Reports Server (NTRS)

Lamvermeyer, D. J.

1967-01-01

Soft metal plating of hard metal lip seal enables successful operation of seal in a cryogenic fluid line under high pressure. The seal is coated with a thin film of 24 carat gold on the lip area to provide antigall and seal properties.

Development of in-Situ Al-Si/CuAl₂ Metal Matrix Composites: Microstructure, Hardness, and Wear Behavior.

PubMed

Tash, Mahmoud M; Mahmoud, Essam R I

2016-06-02

In the present work, in-situ metal matrix composites were fabricated through squeeze casting. The copper particles were dispersed with different weight percentages (3%, 6%, 10%, and 15%) into Al-12% Si piston alloy. Also, heat treatments were performed at 380 °C and 450 °C for holding times of 6 and 18 h. The microstructures, X-ray diffractometer (XRD) pattern, hardness, and wear characteristics were evaluated. The results showed that these copper particles have reacted with the aluminum under all of the aforementioned processing conditions resulting in the formation of fine copper aluminide intermetallics. Most of the intermetallics were CuAl₂, while AlCu appeared in a small ratio. Additionally, these intermetallics were homogenously distributed within the alloy matrix with up to 6% Cu addition. The amounts of those intermetallics increased after performing heat treatment. Most of these intermetallics were CuAl₂ at 380 °C, while the Cu-rich intermetallics appeared at 450 °C. Increasing the holding time to 18 h, however, led to grain coarsening and resulted in the formation of some cracks. The hardness of the resulting composite materials was improved. The hardness value reached to about 170 HV after heat treating at 380 °C for 8 h. The wear resistance of the resulting composite materials was remarkably improved, especially at lower additions of Cu and at the lower heat treatment temperature.

Smectic phases in hard particle mixtures: Koda's theory

NASA Astrophysics Data System (ADS)

Vesely, Franz J.

Mixtures of parallel linear particles and spheres tend to demix upon compression. The linear species usually concentrates in regular layers, thus forming a smectic phase. With increasing concentration of spheres this 'smectic demixing' transition occurs at ever lower packing densities. For the specific case of hard spherocylinders and spheres Koda et al. [T. Koda, M. Numajiri, S. Ikeda, J. Phys. Jap., 65, 3551 (1996)] have explained the layering effect in terms of a second virial approximation to the free energy. We extend this approach from spherocylinders to other linear particles, namely fused spheres, ellipsoids and sphero-ellipsoids.

Lower Bound on the Mean Square Displacement of Particles in the Hard Disk Model

NASA Astrophysics Data System (ADS)

Richthammer, Thomas

2016-08-01

The hard disk model is a 2D Gibbsian process of particles interacting via pure hard core repulsion. At high particle density the model is believed to show orientational order, however, it is known not to exhibit positional order. Here we investigate to what extent particle positions may fluctuate. We consider a finite volume version of the model in a box of dimensions 2 n × 2 n with arbitrary boundary configuration, and we show that the mean square displacement of particles near the center of the box is bounded from below by c log n. The result generalizes to a large class of models with fairly arbitrary interaction.

Jumping liquid metal droplet in electrolyte triggered by solid metal particles

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

Tang, Jianbo; University of Chinese Academy of Sciences, Beijing 100049; Wang, Junjie

2016-05-30

We report the electron discharge effect due to point contact between liquid metal and solid metal particles in electrolyte. Adding nickel particles induces drastic hydrogen generating and intermittent jumping of a sub-millimeter EGaIn droplet in NaOH solution. Observations from different orientations disclose that such jumping behavior is triggered by pressurized bubbles under the assistance of interfacial interactions. Hydrogen evolution around particles provides clear evidence that such electric instability originates from the varied electric potential and morphology between the two metallic materials. The point-contact-induced charge concentration significantly enhances the near-surface electric field intensity at the particle tips and thus causes electricmore » breakdown of the electrolyte.« less

Diffusion rate limitations in actin-based propulsion of hard and deformable particles.

PubMed

Dickinson, Richard B; Purich, Daniel L

2006-08-15

The mechanism by which actin polymerization propels intracellular vesicles and invasive microorganisms remains an open question. Several recent quantitative studies have examined propulsion of biomimetic particles such as polystyrene microspheres, phospholipid vesicles, and oil droplets. In addition to allowing quantitative measurement of parameters such as the dependence of particle speed on its size, these systems have also revealed characteristic behaviors such a saltatory motion of hard particles and oscillatory deformation of soft particles. Such measurements and observations provide tests for proposed mechanisms of actin-based motility. In the actoclampin filament end-tracking motor model, particle-surface-bound filament end-tracking proteins are involved in load-insensitive processive insertion of actin subunits onto elongating filament plus-ends that are persistently tethered to the surface. In contrast, the tethered-ratchet model assumes working filaments are untethered and the free-ended filaments grow as thermal ratchets in a load-sensitive manner. This article presents a model for the diffusion and consumption of actin monomers during actin-based particle propulsion to predict the monomer concentration field around motile particles. The results suggest that the various behaviors of biomimetic particles, including dynamic saltatory motion of hard particles and oscillatory vesicle deformations, can be quantitatively and self-consistently explained by load-insensitive, diffusion-limited elongation of (+)-end-tethered actin filaments, consistent with predictions of the actoclampin filament-end tracking mechanism.

In vitro expression of hard metal dust (WC-Co) - responsive genes in human peripheral blood mononucleated cells

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

Lombaert, Nooemi; Lison, Dominique; Van Hummelen, Paul

Hard metals consist of tungsten carbide (WC) and metallic cobalt (Co) particles and are important industrial materials produced for their extreme hardness and high wear resistance properties. While occupational exposure to metallic Co alone is apparently not associated with an increased risk of cancer, the WC-Co particle mixture was shown to be carcinogenic in exposed workers. The in vitro mutagenic/apoptogenic potential of WC-Co in human peripheral blood mononucleated cells was previously demonstrated by us. This study aimed at obtaining a broader view of the pathways responsible for WC-Co induced carcinogenicity, and in particular genotoxicity and apoptosis. We analyzed the profilemore » of gene expression induced in vitro by WC-Co versus control (24 h treatment) in human PBMC and monocytes using microarrays. The most significantly up-regulated pathways for WC-Co treated PBMC were apoptosis and stress/defense response; the most down-regulated was immune response. For WC-Co treated monocytes the most significantly up- and down-regulated pathways were nucleosome/chromatin assembly and immune response respectively. Quantitative RT-PCR data for a selection of the most strongly modulated genes (HMOX1, HSPA1A, HSPA1L, BNIP3, BNIP3L, ADORA2B, MT3, PLA2G7, TNFAIP6), and some additionally chosen apoptosis related genes (BCL2, BAX, FAS, FASL, TNF{alpha}), confirmed the microarray data after WC-Co exposure and demonstrated limited differences between the Co-containing compounds. Overall, this study provides the first analysis of gene expression induced by the WC-Co mixture showing a large profile of gene modulation and giving a preliminary indication for a hypoxia mimicking environment induced by WC-Co exposure.« less

Controllable reductive method for synthesizing metal-containing particles

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

Moon, Ji-Won; Jung, Hyunsung; Phelps, Tommy Joe

The invention is directed to a method for producing metal-containing particles, the method comprising subjecting an aqueous solution comprising a metal salt, E.sub.h, lowering reducing agent, pH adjusting agent, and water to conditions that maintain the E.sub.h value of the solution within the bounds of an E.sub.h-pH stability field corresponding to the composition of the metal-containing particles to be produced, and producing said metal-containing particles in said aqueous solution at a selected E.sub.h value within the bounds of said E.sub.h-pH stability field. The invention is also directed to the resulting metal-containing particles as well as devices in which they aremore » incorporated.« less

The rhizotoxicity of metal cations is related to their strength of binding to hard ligands.

PubMed

Kopittke, Peter M; Menzies, Neal W; Wang, Peng; McKenna, Brigid A; Wehr, J Bernhard; Lombi, Enzo; Kinraide, Thomas B; Blamey, F Pax C

2014-02-01

Mechanisms whereby metal cations are toxic to plant roots remain largely unknown. Aluminum, for example, has been recognized as rhizotoxic for approximately 100 yr, but there is no consensus on its mode of action. The authors contend that the primary mechanism of rhizotoxicity of many metal cations is nonspecific and that the magnitude of toxic effects is positively related to the strength with which they bind to hard ligands, especially carboxylate ligands of the cell-wall pectic matrix. Specifically, the authors propose that metal cations have a common toxic mechanism through inhibiting the controlled relaxation of the cell wall as required for elongation. Metal cations such as Al(3+) and Hg(2+), which bind strongly to hard ligands, are toxic at relatively low concentrations because they bind strongly to the walls of cells in the rhizodermis and outer cortex of the root elongation zone with little movement into the inner tissues. In contrast, metal cations such as Ca(2+), Na(+), Mn(2+), and Zn(2+) , which bind weakly to hard ligands, bind only weakly to the cell wall and move farther into the root cylinder. Only at high concentrations is their weak binding sufficient to inhibit the relaxation of the cell wall. Finally, different mechanisms would explain why certain metal cations (for example, Tl(+), Ag(+), Cs(+), and Cu(2+)) are sometimes more toxic than expected through binding to hard ligands. The data presented in the present study demonstrate the importance of strength of binding to hard ligands in influencing a range of important physiological processes within roots through nonspecific mechanisms. © 2013 SETAC.

Molecular Level Coating of Metal Oxide Particles

NASA Technical Reports Server (NTRS)

McDaniel, Patricia R. (Inventor); St.Clair, Terry L. (Inventor)

2002-01-01

Polymer encapsulated metal oxide particles are prepared by combining a polyamide acid in a polar osmotic solvent with a metal alkoxide solution. The polymer was imidized and the metal oxide formed simultaneously in a refluxing organic solvent. The resulting polymer-metal oxide is an intimately mixed commingled blend, possessing, synergistic properties of both the polymer and preceramic metal oxide. The encapsulated metal oxide particles have multiple uses including, being useful in the production of skin lubricating creams, weather resistant paints, as a filler for paper. making ultraviolet light stable filled printing ink, being extruded into fibers or ribbons, and coatings for fibers used in the production of composite structural panels.

Molecular Level Coating for Metal Oxide Particles

NASA Technical Reports Server (NTRS)

McDaniel, Patricia R. (Inventor); Saint Clair, Terry L. (Inventor)

2000-01-01

Polymer encapsulated metal oxide particles are prepared by combining a polyamide acid in a polar aprotic solvent with a metal alkoxide solution. The polymer was imidized and the metal oxide formed simultaneously in a refluxing organic solvent. The resulting polymer-metal oxide is an intimately mixed commingled blend, possessing synergistic properties of both the polymer and preceramic metal oxide. The encapsulated metal oxide particles have multiple uses including, being useful in the production of skin lubricating creams, weather resistant paints, as a filler for paper, making ultraviolet light stable filled printing ink, being extruded into fibers or ribbons, and coatings for fibers used in the production of composite structural panels.

Application of hard sphere perturbation theory for thermodynamics of model liquid metals

NASA Astrophysics Data System (ADS)

Mon, K. K.

2001-06-01

Hard sphere perturbation theory (HSPT) has contributed toward the fundamental understanding of dense fluids for over 30 years. In recent decades, other techniques have been more popular. In this paper, we argue for the revival of hard sphere perturbation theory for the study of thermodynamics of dense liquid in general, and in liquid metal in particular. The weakness of HSPT is now well understood, and can be easily overcome by using a simple convenient Monte Carlo method to calculate the intrinsic error of HSPT free energy density. To demonstrate this approach, we consider models of liquid aluminum and sodium. We obtain the intrinsic error of HSPT with the Monte Carlo method. HSPT is shown to provide a lower free energy upper bound than one-component plasma (OCP) for alkali metals and polyvalent metals. We are thus able to provide insight into the long standing observation that a OCP is a better reference system than a HS for alkali metals.

Development of in-Situ Al-Si/CuAl2 Metal Matrix Composites: Microstructure, Hardness, and Wear Behavior

PubMed Central

Tash, Mahmoud M.; Mahmoud, Essam R. I.

2016-01-01

In the present work, in-situ metal matrix composites were fabricated through squeeze casting. The copper particles were dispersed with different weight percentages (3%, 6%, 10%, and 15%) into Al-12% Si piston alloy. Also, heat treatments were performed at 380 °C and 450 °C for holding times of 6 and 18 h. The microstructures, X-ray diffractometer (XRD) pattern, hardness, and wear characteristics were evaluated. The results showed that these copper particles have reacted with the aluminum under all of the aforementioned processing conditions resulting in the formation of fine copper aluminide intermetallics. Most of the intermetallics were CuAl2, while AlCu appeared in a small ratio. Additionally, these intermetallics were homogenously distributed within the alloy matrix with up to 6% Cu addition. The amounts of those intermetallics increased after performing heat treatment. Most of these intermetallics were CuAl2 at 380 °C, while the Cu-rich intermetallics appeared at 450 °C. Increasing the holding time to 18 h, however, led to grain coarsening and resulted in the formation of some cracks. The hardness of the resulting composite materials was improved. The hardness value reached to about 170 HV after heat treating at 380 °C for 8 h. The wear resistance of the resulting composite materials was remarkably improved, especially at lower additions of Cu and at the lower heat treatment temperature. PMID:28773564

Characterization of solid particle erosion resistance of ductile metals based on their properties

NASA Technical Reports Server (NTRS)

Rao, P. V.; Buckley, D. H.

1985-01-01

This paper presents experimental results pertaining to spherical glass bead and angular crushed glass particle impingement. A concept of energy absorption to explain the failure of material is proposed and is correlated with the erosion characteristics of several pure metals. Analyses of extensive erosion data indicate that the properties - surface energy, specific melting energy, strain energy, melting point, bulk modulus, hardness, atomic volume - and the product of the parameters - linear coefficient of thermal expansion x bulk modulus x temperature rise required for melting, and ultimate resilience x hardness - exhibit the best correlations. The properties of surface energy and atomic volume are suggested for the first time for correlation purposes and are found to correlate well with erosion rates at different angles of impingement. It further appears that both energy and thermal properties contribute to the total erosion.

Lock-and-key dimerization in dense Brownian systems of hard annular sector particles

NASA Astrophysics Data System (ADS)

Hodson, Wade D.; Mason, Thomas G.

2016-08-01

We develop a translational-rotational cage model that describes the behavior of dense two-dimensional (2D) Brownian systems of hard annular sector particles (ASPs), resembling C shapes. At high particle densities, pairs of ASPs can form mutually interdigitating lock-and-key dimers. This cage model considers either one or two mobile central ASPs which can translate and rotate within a static cage of surrounding ASPs that mimics the system's average local structure and density. By comparing with recent measurements made on dispersions of microscale lithographic ASPs [P. Y. Wang and T. G. Mason, J. Am. Chem. Soc. 137, 15308 (2015), 10.1021/jacs.5b10549], we show that mobile two-particle predictions of the probability of dimerization Pdimer, equilibrium constant K , and 2D osmotic pressure Π2 D as a function of the particle area fraction ϕA correspond closely to these experiments. By contrast, predictions based on only a single mobile particle do not agree well with either the two-particle predictions or the experimental data. Thus, we show that collective entropy can play an essential role in the behavior of dense Brownian systems composed of nontrivial hard shapes, such as ASPs.

Magnetic properties of hybrid elastomers with magnetically hard fillers: rotation of particles

NASA Astrophysics Data System (ADS)

Stepanov, G. V.; Borin, D. Yu; Bakhtiiarov, A. V.; Storozhenko, P. A.

2017-03-01

Hybrid magnetic elastomers belonging to the family of magnetorheological elastomers contain magnetically hard components and are of the utmost interest for the development of semiactive and active damping devices as well as actuators and sensors. The processes of magnetizing of such elastomers are accompanied by structural rearrangements inside the material. When magnetized, the elastomer gains its own magnetic moment resulting in changes of its magneto-mechanical properties, which remain permanent, even in the absence of external magnetic fields. Influenced by the magnetic field, magnetized particles move inside the matrix forming chain-like structures. In addition, the magnetically hard particles can rotate to align their magnetic moments with the new direction of the external field. Such an elastomer cannot be demagnetized by the application of a reverse field.

Tuning the bridging attraction between large hard particles by the softness of small microgels.

PubMed

Luo, Junhua; Yuan, Guangcui; Han, Charles C

2016-09-20

In this study, the attraction between large hard polystyrene (PS) spheres is studied by using three types of small microgels as bridging agents. One is a purely soft poly(N-isopropylacrylamide) (PNIPAM) microgel, the other two have a non-deformable PS hard core surrounded by a soft PNIPAM shell but are different in the core-shell ratio. The affinity for bridging the large PS spheres is provided and thus affected by the PNIPAM constituent in the microgels. The bridging effects caused by the microgels can be indirectly incorporated into their influence on the effective attraction interaction between the large hard spheres, since the size of the microgels is very small in comparison to the size of the PS hard spheres. At a given volume fraction of large PS spheres, they behave essentially as hard spheres in the absence of small microgels. By gradually adding the microgels, the large spheres are connected to each other through the bridging of small particles until the attraction strength reaches a maximum value, after which adding more small particles slowly decreases the effective attraction strength and eventually the large particles disperse individually when saturated adsorption is achieved. The aggregation and gelation behaviors triggered by these three types of small microgels are compared and discussed. A way to tune the strength and range of the short-range attractive potential via changing the softness of bridging microgels (which can be achieved either by using core-shell microgels or by changing the temperature) is proposed.

Combined effect of smoking habits and occupational exposure to hard metal on total IgE antibodies.

PubMed

Shirakawa, T; Kusaka, Y; Morimoto, K

1992-06-01

A survey was made within a population of workers (n = 706) exposed to hard metal dust (an alloy including cobalt), an agent known to cause occupational allergy. Twenty-seven (4 percent) of 733 workers were eliminated from consideration in this study because of atopic status identified prior to starting work in the plant. Using a Phadebas PRIST, the subjects' total IgE levels were determined and related to their smoking and exposure status. Nonexposed male smokers (n = 135) had a higher geometric mean IgE level (39.7 IU/ml) than did nonexposed subjects who had never smoked (33.1 IU/ml; n = 99); those with a higher Brinkman index (greater than 300), a smoking index obtained by multiplying the number of cigarettes per day by the duration of smoking in years, had significantly (p less than 0.05) decreased IgE levels. Although ex-smokers (n = 72) had a higher geometric mean IgE level (73.3 IU/ml) than did those who had never smoked, their serum IgE level declined with age since the time they quit smoking, regardless of their hard metal exposure status. Hard metal (cobalt) exposure may play a significant role as an adjuvant in the production of total IgE. A multivariate analysis demonstrated that hard metal exposure and a smoking habit together arithmetically (p less than 0.05) increased total IgE levels. These two factors may be preventable risk factors for occupational allergy in hard metal workers.

Natural Indices for the Chemical Hardness/Softness of Metal Cations and Ligands

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

Xu, Huifang; Xu, David C.; Wang, Yifeng

Quantitative understanding of reactivity and stability for a chemical species is fundamental to chemistry. The concept has undergone many changes and additions throughout the history of chemistry, stemming from the ideas such as Lewis acids and bases. For a given complexing ligand (Lewis base) and a group of isovalent metal cations (Lewis acids), the stability constants of metal–ligand (ML) complexes can simply correlate to the known properties of metal ions [ionic radii (r Mn+), Gibbs free energy of formation (ΔG° f,Mn+), and solvation energy (ΔG° s,Mn+)] by 2.303RT log K ML = (α* MLΔG° f,Mn+ – β* MLr Mn+ +more » γ* MLΔG° s,Mn+ – δ* ML), where the coefficients (α* ML, β* ML, γ* ML, and intercept δ* ML) are determined by fitting the equation to the existing experimental data. Coefficients β* ML and γ* ML have the same sign and are in a linear relationship through the origin. Gibbs free energies of formation of cations (ΔG° f,Mn+) are found to be natural indices for the softness or hardness of metal cations, with positive values corresponding to soft acids and negative values to hard acids. The coefficient α* ML is an index for the softness or hardness of a complexing ligand. Proton (H +) with the softness index of zero is a unique acid that has strong interactions with both soft and hard bases. The stability energy resulting from the acid–base interactions is determined by the term α* MLΔG° f,Mn+; a positive product of α* ML and ΔG° f,Mn+ indicates that the acid–base interaction between the metal cation and the complexing ligand stabilizes the complex. The terms β* MLr Mn+ and γ* MLΔG° s,Mn+, which are related to ionic radii of metal cations, represent the steric and solvation effects of the cations. The new softness indices proposed here will help to understand the interactions of ligands (Lewis bases) with metal cations (Lewis acids) and provide guidelines for engineering materials with desired chemical reactivity and

Natural Indices for the Chemical Hardness/Softness of Metal Cations and Ligands

DOE PAGES

Xu, Huifang; Xu, David C.; Wang, Yifeng

2017-10-26

Quantitative understanding of reactivity and stability for a chemical species is fundamental to chemistry. The concept has undergone many changes and additions throughout the history of chemistry, stemming from the ideas such as Lewis acids and bases. For a given complexing ligand (Lewis base) and a group of isovalent metal cations (Lewis acids), the stability constants of metal–ligand (ML) complexes can simply correlate to the known properties of metal ions [ionic radii (r Mn+), Gibbs free energy of formation (ΔG° f,Mn+), and solvation energy (ΔG° s,Mn+)] by 2.303RT log K ML = (α* MLΔG° f,Mn+ – β* MLr Mn+ +more » γ* MLΔG° s,Mn+ – δ* ML), where the coefficients (α* ML, β* ML, γ* ML, and intercept δ* ML) are determined by fitting the equation to the existing experimental data. Coefficients β* ML and γ* ML have the same sign and are in a linear relationship through the origin. Gibbs free energies of formation of cations (ΔG° f,Mn+) are found to be natural indices for the softness or hardness of metal cations, with positive values corresponding to soft acids and negative values to hard acids. The coefficient α* ML is an index for the softness or hardness of a complexing ligand. Proton (H +) with the softness index of zero is a unique acid that has strong interactions with both soft and hard bases. The stability energy resulting from the acid–base interactions is determined by the term α* MLΔG° f,Mn+; a positive product of α* ML and ΔG° f,Mn+ indicates that the acid–base interaction between the metal cation and the complexing ligand stabilizes the complex. The terms β* MLr Mn+ and γ* MLΔG° s,Mn+, which are related to ionic radii of metal cations, represent the steric and solvation effects of the cations. The new softness indices proposed here will help to understand the interactions of ligands (Lewis bases) with metal cations (Lewis acids) and provide guidelines for engineering materials with desired chemical reactivity and

Fabrication of Janus particles composed of poly (lactic-co-glycolic) acid and hard fat using a solvent evaporation method.

PubMed

Matsumoto, Akihiro; Murao, Satoshi; Matsumoto, Michiko; Watanabe, Chie; Murakami, Masahiro

The feasibility of fabricating Janus particles based on phase separation between a hard fat and a biocompatible polymer was investigated. The solvent evaporation method used involved preparing an oil-in-water (o/w) emulsion with a mixture of poly (lactic-co-glycolic) acid (PLGA), hard fat, and an organic solvent as the oil phase and a polyvinyl alcohol aqueous solution as the water phase. The Janus particles were formed when the solvent was evaporated to obtain certain concentrations of PLGA and hard fat in the oil phase, at which phase separation was estimated to occur based on the phase diagram analysis. The hard fat hemisphere was proven to be the oil phase using a lipophilic dye Oil Red O. When the solvent evaporation process was performed maintaining a specific volume during the emulsification process; Janus particles were formed within 1.5 h. However, the formed Janus particles were destroyed by stirring for over 6 h. In contrast, a few Janus particles were formed when enough water to dissolve the oil phase solvent was added to the emulsion immediately after the emulsification process. The optimized volume of the solvent evaporation medium dominantly formed Janus particles and maintained the conformation for over 6 h with stirring. These results indicate that the formation and stability of Janus particles depend on the rate of solvent evaporation. Therefore, optimization of the solvent evaporation rate is critical to obtaining stable PLGA and hard fat Janus particles.

Separating and recycling metals from mixed metallic particles of crushed electronic wastes by vacuum metallurgy.

PubMed

Zhan, Lu; Xu, Zhenming

2009-09-15

During the treatment of electronic wastes, a crushing process is usually used to strip metals from various base plates. Several methods have been applied to separate metals from nonmetals. However, mixed metallic particles obtained from these processes are still a mixture of various metals, including some toxic heavy metals such as lead and cadmium. With emphasis on recovering copper and other precious metals, there have hitherto been no satisfactory methods to recover these toxic metals. In this paper, the criterion of separating metals from mixed metallic particles by vacuum metallurgy is built. The results show that the metals with high vapor pressure have been almost recovered completely, leading to a considerable reduction of environmental pollution. In addition, the purity of copper in mixed particles has been improved from about 80 wt % to over 98 wt %.

Microstructure and thermal history of metal particles in CH chondrites

NASA Astrophysics Data System (ADS)

Goldstein, J. I.; Jones, R. H.; Kotula, P. G.; Michael, J. R.

2007-06-01

We have studied metal microstructures in four CH chondrites, Patuxent Range (PAT) 91546, Allan Hills (ALH) 85085, Acfer 214, and Northwest Africa (NWA) 739, to examine details of the thermal histories of individual particles. Four types of metal particles are common in all of these chondrites. Zoned and unzoned particles probably formed as condensates from a gas of chondritic composition in a monotonic cooling regime, as has been shown previously. We have demonstrated that these particles were cooled rapidly to temperatures below 500 K after they formed, and that condensation effectively closed around 700 K. Zoned and unzoned particles with exsolution precipitates, predominantly high-Ni taenite, have considerably more complex thermal histories. Precipitates grew in reheating episodes, but the details of the heating events vary among individual grains. Reheating temperatures are typically in the range 800-1000 K. Reheating could have been the result of impact events on the CH parent body. Some particles with precipitates may have been incorporated into chondrules, with further brief heating episodes taking place during chondrule formation. In addition to the four dominant types of metal particles, rare Ni-rich metal particles and Si-rich metal particles indicate that the metal assemblage in CH chondrites was a mixture of material that formed at different redox conditions. Metal in CH chondrites consists of a mechanical mixture of particles that underwent a variety of thermal histories prior to being assembled into the existing brecciated meteorites.

Optical trapping performance of dielectric-metallic patchy particles

PubMed Central

Lawson, Joseph L.; Jenness, Nathan J.; Clark, Robert L.

2015-01-01

We demonstrate a series of simulation experiments examining the optical trapping behavior of composite micro-particles consisting of a small metallic patch on a spherical dielectric bead. A full parameter space of patch shapes, based on current state of the art manufacturing techniques, and optical properties of the metallic film stack is examined. Stable trapping locations and optical trap stiffness of these particles are determined based on the particle design and potential particle design optimizations are discussed. A final test is performed examining the ability to incorporate these composite particles with standard optical trap metrology technologies. PMID:26832054

Variation of Hardness and Modulus across thickness of Zr-Cu-Al Metallic Glass Ribbons

Treesearch

Z. Humberto Melgarejo; J.E. Jakes; J. Hwang; Y.E. Kalay; M.J. Kramer; P.M. Voyles; D.S. Stone

2012-01-01

We investigate through-thickness hardness and modulus of Zr50Cu45Al5 metallic glass melt-spun ribbon. Because of their thinness, the ribbons are challenging to measure, so we employ a novel nanoindentation based-method to remove artifacts caused by ribbon flexing and edge effects. Hardness and modulus...

Effect of hardness on acute toxicity of metal mixtures using Daphnia magna: prediction of acid mine drainage toxicity.

PubMed

Yim, Jin Hee; Kim, Kyoung W; Kim, Sang D

2006-11-02

In this study, the effect of hardness on the combined outcome of metal mixtures was investigated using Daphnia magna. The toxic unit (TU) was calculated using modified LC(50) values based on the hardness (i.e., LC(50-soft) and LC(50-hard)). From a bioassay test, the degree of sensitivity to hardness on the toxicity changes was in the order: Cdhard test solution was replaced with a soft test solution. In mixture toxicity tests, the difference in the test solution hardness was found to clearly cause different toxicities, as determined by the TU calculated by the LC(50-hard), using the toxicity of a standard culture medium as the reference. That is, approximately four to five times higher toxicity was observed in soft (i.e., 44+/-4 mg/L as CaCO(3)) rather than hard water (i.e., 150+/-10mg/L as CaCO(3)) test solutions. In the tests where the modified reference toxicity values (i.e., LC(50-soft) and LC(50-hard) for soft and hard test solution, respectively) obtained from the individual metal toxicity tests with different hardness were used to calculate the TU, the results showed very similar D. magna toxicities to those of the TU from the mixture of soft and hard test solutions, regardless of the hardness. According to the toxicity results of the mixture, the aquatic toxic effects of the acid mine drainage (AMD) collected from mine areas that contained metal mixtures were investigated using Daphnia magna and the modified LC(50) value of the TU hardness function calculated for varying solution hardness. The results of the biological WET test closely matched our overall prediction, with significant correlation, having a p-value of 0.513 in one way ANOVA test (n=19). Therefore, this study revealed that the predicted toxicity of the metal mixture agreed well with the biological toxicity test when the modified LC(50) value was employed as the basis of hardness in the TU calculation.

Hydrogen absorption induced metal deposition on palladium and palladium-alloy particles

DOEpatents

Wang, Jia X [East Setauket, NY; Adzic, Radoslav R [East Setauket, NY

2009-03-24

The present invention relates to methods for producing metal-coated palladium or palladium-alloy particles. The method includes contacting hydrogen-absorbed palladium or palladium-alloy particles with one or more metal salts to produce a sub-monoatomic or monoatomic metal- or metal-alloy coating on the surface of the hydrogen-absorbed palladium or palladium-alloy particles. The invention also relates to methods for producing catalysts and methods for producing electrical energy using the metal-coated palladium or palladium-alloy particles of the present invention.

Structural and electronic properties of OsB2 : A hard metallic material

NASA Astrophysics Data System (ADS)

Chen, Z. Y.; Xiang, H. J.; Yang, Jinlong; Hou, J. G.; Zhu, Qingshi

2006-07-01

We calculate the structural and electronic properties of OsB2 using density functional theory with or without taking into account the spin-orbit (SO) interaction. Our results show that the bulk modulus with and without SO interactions are 364 and 365GPa , respectively, both are in good agreement with experiment (365-395GPa) . The evidence of covalent bonding of Os-B, which plays an important role to form a hard material, is indicated both in charge density, atoms in molecules analysis, and density of states analysis. The good metallicity and hardness of OsB2 might suggest its potential application as hard conductors.

Characterization of typical metal particles during haze episodes in Shanghai, China.

PubMed

Li, Rui; Yang, Xin; Fu, Hongbo; Hu, Qingqing; Zhang, Liwu; Chen, Jianmin

2017-08-01

Aerosol particles were collected during three heavy haze episodes at Shanghai in the winter of 2013. Transmission electron microscopy (TEM) coupled with energy dispersive X-ray spectroscopy was used to study the morphology and speciation of typical metal particles at a single-particle level. In addition, time-of-flight aerosol mass spectrometry (ATOFMS) was applied to identify the speciation of the Fe-containing particles. TEM analysis indicated that various metal-containing particles were hosted by sulfates, nitrates, and oxides. Fe-bearing particles mainly originated from vehicle emissions and/or steel production. Pb-, Zn-, and Sb-bearing particles were mainly contributed by anthropogenic sources. Fe-bearing particles were clustered into six groups by ATOFMS: Fe-Carbon, Fe-Inorganic, Fe-Trace metal, Fe-CN, Fe-PO 3, and Fe-NO 3 . ATOFMS data suggested that Fe-containing particles corresponded to different origins, including industrial activities, resuspension of dusts, and vehicle emissions. Fe-Carbon and Fe-CN particles displayed significant diurnal variation, and high levels were observed during the morning rush hours. Fe-Inorganic and Fe-Trace metal particle levels peaked at night. Furthermore, Fe-Carbon and Fe-PO 3 were mainly concentrated in the fine particles. Fe-CN, Fe-Inorganic, and Fe-Trace metal exhibited bimodal distribution. The mixing state of the particles revealed that all Fe-bearing particles tended to be mixed with sulfate and nitrate. The data presented herein is essential for elucidating the origin, evolution processes, and health effects of metal-bearing particles. Copyright © 2017 Elsevier Ltd. All rights reserved.

Virial coefficients of anisotropic hard solids of revolution: The detailed influence of the particle geometry

NASA Astrophysics Data System (ADS)

Herold, Elisabeth; Hellmann, Robert; Wagner, Joachim

2017-11-01

We provide analytical expressions for the second virial coefficients of differently shaped hard solids of revolution in dependence on their aspect ratio. The second virial coefficients of convex hard solids, which are the orientational averages of the mutual excluded volume, are derived from volume, surface, and mean radii of curvature employing the Isihara-Hadwiger theorem. Virial coefficients of both prolate and oblate hard solids of revolution are investigated in dependence on their aspect ratio. The influence of one- and two-dimensional removable singularities of the surface curvature to the mutual excluded volume is analyzed. The virial coefficients of infinitely thin oblate and infinitely long prolate particles are compared, and analytical expressions for their ratios are derived. Beyond their dependence on the aspect ratio, the second virial coefficients are influenced by the detailed geometry of the particles.

Virial coefficients of anisotropic hard solids of revolution: The detailed influence of the particle geometry.

PubMed

Herold, Elisabeth; Hellmann, Robert; Wagner, Joachim

2017-11-28

We provide analytical expressions for the second virial coefficients of differently shaped hard solids of revolution in dependence on their aspect ratio. The second virial coefficients of convex hard solids, which are the orientational averages of the mutual excluded volume, are derived from volume, surface, and mean radii of curvature employing the Isihara-Hadwiger theorem. Virial coefficients of both prolate and oblate hard solids of revolution are investigated in dependence on their aspect ratio. The influence of one- and two-dimensional removable singularities of the surface curvature to the mutual excluded volume is analyzed. The virial coefficients of infinitely thin oblate and infinitely long prolate particles are compared, and analytical expressions for their ratios are derived. Beyond their dependence on the aspect ratio, the second virial coefficients are influenced by the detailed geometry of the particles.

Determination of silica coating efficiency on metal particles using multiple digestion methods.

PubMed

Wang, Jun; Topham, Nathan; Wu, Chang-Yu

2011-10-15

Nano-sized metal particles, including both elemental and oxidized metals, have received significant interest due to their biotoxicity and presence in a wide range of industrial systems. A novel silica technology has been recently explored to minimize the biotoxicity of metal particles by encapsulating them with an amorphous silica shell. In this study, a method to determine silica coating efficiency on metal particles was developed. Metal particles with silica coating were generated using gas metal arc welding (GMAW) process with a silica precursor tetramethylsilane (TMS) added to the shielding gas. Microwave digestion and Inductively Coupled Plasma-Atomic Emission Spectroscopy (ICP-AES) were employed to solubilize the metal content in the particles and analyze the concentration, respectively. Three acid mixtures were tested to acquire the appropriate digestion method targeting at metals and silica coating. Metal recovery efficiencies of different digestion methods were compared through analysis of spiked samples. HNO(3)/HF mixture was found to be a more aggressive digestion method for metal particles with silica coating. Aqua regia was able to effectively dissolve metal particles not trapped in the silica shell. Silica coating efficiencies were thus calculated based on the measured concentrations following digestion by HNO(3)/HF mixture and aqua regia. The results showed 14-39% of welding fume particles were encapsulated in silica coating under various conditions. This newly developed method could also be used to examine the silica coverage on particles of silica shell/metal core structure in other nanotechnology areas. Copyright © 2011 Elsevier B.V. All rights reserved.

Plasma polymer-functionalized silica particles for heavy metals removal.

PubMed

Akhavan, Behnam; Jarvis, Karyn; Majewski, Peter

2015-02-25

Highly negatively charged particles were fabricated via an innovative plasma-assisted approach for the removal of heavy metal ions. Thiophene plasma polymerization was used to deposit sulfur-rich films onto silica particles followed by the introduction of oxidized sulfur functionalities, such as sulfonate and sulfonic acid, via water-plasma treatments. Surface chemistry analyses were conducted by X-ray photoelectron spectroscopy and time-of-flight secondary ion mass spectroscopy. Electrokinetic measurements quantified the zeta potentials and isoelectric points (IEPs) of modified particles and indicated significant decreases of zeta potentials and IEPs upon plasma modification of particles. Plasma polymerized thiophene-coated particles treated with water plasma for 10 min exhibited an IEP of less than 3.5. The effectiveness of developed surfaces in the adsorption of heavy metal ions was demonstrated through copper (Cu) and zinc (Zn) removal experiments. The removal of metal ions was examined through changing initial pH of solution, removal time, and mass of particles. Increasing the water plasma treatment time to 20 min significantly increased the metal removal efficiency (MRE) of modified particles, whereas further increasing the plasma treatment time reduced the MRE due to the influence of an ablation mechanism. The developed particulate surfaces were capable of removing more than 96.7% of both Cu and Zn ions in 1 h. The combination of plasma polymerization and oxidative plasma treatment is an effective method for the fabrication of new adsorbents for the removal of heavy metals.

Method of forming a relatively stable slip of silicon metal particles and yttrium containing particles

DOEpatents

Dickie, Ray A.; Mangels, John A.

1984-01-01

The method concerns forming a relatively stable slip of silicon metal particles and yttrium containing particles. In one embodiment, a casting slip of silicon metal particles is formed in water. Particles of a yttrium containing sintering aid are added to the casting slip. The yttrium containing sintering aid is a compound which has at least some solubility in water to form Y.sup.+3 ions which have a high potential for totally flocculating the silicon metal particles into a semiporous solid. A small amount of a fluoride salt is added to the casting slip which contains the yttrium containing sintering aid. The fluoride salt is one which will produce fluoride anions when dissolved in water. The small amount of the fluoride anions produced are effective to suppress the flocculation of the silicon metal particles by the Y.sup.+3 ions so that all particles remain in suspension in the casting slip and the casting slip has both an increased shelf life and can be used to cast articles having a relatively thick cross-section. The pH of the casting slip is maintained in a range from 7.5 to 9. Preferably, the fluoride salt used is one which is based on a monovalent cation such as sodium or ammonia. The steps of adding the yttrium containing sintering aid and the fluoride salt may be interchanged if desired, and the salt may be added to a solution containing the sintering aid prior to addition of the silicon metal particles.

Electrochemical removal of metallic implants from Technovit 9100 New embedded hard and soft tissues prior to histological sectioning.

PubMed

Willbold, Elmar; Reebmann, Mattias; Jeffries, Richard; Witte, Frank

2013-11-01

Solid metallic implants in soft or hard tissues are serious challenges for histological processing. However, metallic implants are more frequently used in e.g. cardiovascular or orthopaedic therapies. Before clinical use, these devices need to be tested thoroughly in a biological environment and histological analysis of their biocompatibility is a major requirement. To allow the histological analysis of metallic implants in tissues especially in calcified hard tissues, we describe a method for embedding these tissues in the resin Technovit 9100 New and removing the metallic implants by electrochemical dissolution. With the combination of these two processes, we are able to achieve 5 μm thick sections from soft or hard tissues with a superior preservation of tissue architecture and especially the implant-tissue interface. These sections can be stained by classical stainings, immunohistochemical and enzymehistochemical as well as DNA-based staining methods.

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.

Numerical modelling of electrochemical polarization around charged metallic particles

NASA Astrophysics Data System (ADS)

Bücker, Matthias; Undorf, Sabine; Flores Orozco, Adrián; Kemna, Andreas

2017-04-01

We extend an existing analytical model and carry out numerical simulations to study the polarization process around charged metallic particles immersed in an electrolyte solution. Electro-migration and diffusion processes in the electrolyte are described by the Poisson-Nernst-Planck system of partial differential equations. To model the surface charge density, we consider a time- and frequency-invariant electric potential at the particle surface, which leads to the build-up of a static electrical double layer (EDL). Upon excitation by an external electric field at low frequencies, we observe the superposition of two polarization processes. On the one hand, the induced dipole moment on the metallic particle leads to the accumulation of opposite charges in the electrolyte. This charge polarization corresponds to the long-known response of uncharged metallic particles. On the other hand, the unequal cation and anion concentrations in the EDL give rise to a salinity gradient between the two opposite sides of the metallic particle. The resulting concentration polarization enhances the magnitude of the overall polarization response. Furthermore, we use our numerical model to study the effect of relevant model parameters such as surface charge density and ionic strength of the electrolyte on the resulting spectra of the effective conductivity of the composite model system. Our results do not only give interesting new insight into the time-harmonic variation of electric potential and ion concentrations around charged metallic particle. They are also able to reduce incongruities between earlier model predictions and geophysical field and laboratory measurements. Our model thereby improves the general understanding of IP signatures of metallic particles and represents the next step towards a quantitative interpretation of IP imaging results. Part of this research is funded by the Austrian Federal Ministry of Science, Research and Economy under the Raw Materials Initiative.

Study on the Effect of Heavy metals toxicity according to changing Hardness concentration using D.magna

NASA Astrophysics Data System (ADS)

Chun Sang, H.

2016-12-01

n order to determine and prevent the number of ecological effects of heavy metals in the materials, we have to accurately measure the heavy metals present in the water-based protection ecosystems and may determine the effects to humans. Heavy metals occurred in the industrial effluent which is a state in which the monitor, based on the emission standards are made by the Ministry of Environment and managed and waste water contained Copper, Zinc, lead, etc. These heavy metals are able to express the toxic effects only when present in the free-ions in the aqueous condition, which appears differently affected by the degree to hardness change in accordance with the season, precipitation. Generally changing hardness concentration can not precisely evaluate toxic effects of heavy metals in the water system. Anderson announced a study on bioassay for heavy metals from industrial waste water using Daphnia magna(Anderson, 1944, 1948). Breukelman published study the resitivity difference for the mercury Chloride(HgCl2). Braudouin(1974) compared the zooplankton(Daphnia sp.) acute toxicity of the different heavy metals and confirmed the sensitivity. Shcherban(1979) presented for toxicity evaluation results for the heavy metal of the Daphnia magna according to different temperature conditions. In the United States Environmental Protection Agency(EPA) established a standard test method for water fleas, managed and supervised water ecosystems, and announced the adoption of a bioassay standard method. This study was performed to evaluate acute inhibition using the Daphnia magna for the biological effect of heavy metal ions in water-based toxicity in the hardness change. Evaluation methods were conducted in EPA Water Quality process test criteria. TU(Toxic Unit), NOEC (No Observable Effect Concentration), LOEC (Lowest Observable Effect Concentration), EC50 (Median Effective Concentration) was calculated by Toxcalc 5.0 Program. Keywords : D. magna, Hardness, Toxic Unit, Heavy metal

Fluidized Bed Sputtering for Particle and Powder Metallization

DTIC Science & Technology

2013-04-01

Introduction Small particles are often added to material systems to modify mechanical, dielectric, optical, or other properties . However, the particle...the poor mechanical properties of the wax degrade the bulk mechanical properties of the composite material . Thin metal coatings on the catalyst...to create precisely tailored optical properties . Alternating layers of ceramic and metal thin films can be designed to create optical filters that

Porous metal oxide particles and their methods of synthesis

DOEpatents

Chen, Fanglin; Liu, Qiang

2013-03-12

Methods are generally disclosed for synthesis of porous particles from a solution formed from a leaving agent, a surfactant, and a soluble metal salt in a solvent. The surfactant congregates to form a nanoparticle core such that the metal salt forms about the nanoparticle core to form a plurality of nanoparticles. The solution is heated such that the leaving agent forms gas bubbles in the solution, and the plurality of nanoparticles congregate about the gas bubbles to form a porous particle. The porous particles are also generally disclosed and can include a particle shell formed about a core to define an average diameter from about 0.5 .mu.m to about 50 .mu.m. The particle shell can be formed from a plurality of nanoparticles having an average diameter of from about 1 nm to about 50 nm and defined by a metal salt formed about a surfactant core.

Trapping and rotating of a metallic particle trimer with optical vortex

NASA Astrophysics Data System (ADS)

Shen, Z.; Su, L.; Yuan, X.-C.; Shen, Y.-C.

2016-12-01

We have experimentally observed the steady rotation of a mesoscopic size metallic particle trimer that is optically trapped by tightly focused circularly polarized optical vortex. Our theoretical analysis suggests that a large proportion of the radial scattering force pushes the metallic particles together, whilst the remaining portion provides the centripetal force necessary for the rotation. Furthermore, we have achieved the optical trapping and rotation of four dielectric particles with optical vortex. We found that, different from the metallic particles, instead of being pushed together by the radial scattering force, the dielectric particles are trapped just outside the maximum intensity ring of the focused field. The radial gradient force attracting the dielectric particles towards the maximum intensity ring provides the centripetal force for the rotation. The achieved steady rotation of the metallic particle trimer reported here may open up applications such as the micro-rotor.

Cryochemical method for forming spherical metal oxide particles from metal salt solutions

DOEpatents

Tinkle, M.C.

1973-12-01

A method is described of preparing small metal oxide spheres cryochemically utilizing metal salts (e.g., nitrates) that cannot readily be dried and calcined without loss of sphericity of the particles. Such metal salts are cryochemically formed into small spheres, partially or completely converted to an insoluble salt, and dried and calcined. (Official Gazette)

Microstructure and Thermal History of Metal Particles in CH Chondrites

NASA Technical Reports Server (NTRS)

Goldstein, J. I.; Jones, R. H.; Kotula, P. G.; Michael, J. R.

2005-01-01

Fe-Ni metal particles with smooth Ni, Co, and Cr zoning patterns, 8-13 wt.% Ni in the center of the particle to 3-5 wt% Ni at the rim, have been identified in several CR-clan (CH, Bencubbinlike, and CR) chondrites. These zoning patterns are broadly consistent with an origin by gas-solid condensation in the solar nebula at temperatures between approximately 1500 to 1300 K and fast cooling rates, 2 to 25 K/day. Apparently, this condensate metal was not melted during chondrule formation or affected significantly in the solid-state by alteration during parent body processing. Consideration of diffusional redistribution of Ni, Co, Cr and siderophile elements have further constrained the calculated condensation temperatures and cooling rates of the zoned condensates. These condensate metals have irregular shapes and vary in size from 50 to 350 m as revealed in some detail by optical and SEM techniques. In addition to zoned condensate particles, other types of metal particles have been observed. These include zoned condensates with exsolution-precipitates, unzoned homogeneous metal with no exsolution precipitates, unzoned metal exhibiting exsolution precipitates and high Ni metal grains.

Hard X-ray Emission and Efficient Particle Acceleration by Supernova Remnants

NASA Astrophysics Data System (ADS)

Vink, Jacco

2009-05-01

I discuss the non-thermal X-ray emission from young supernova remnants. Over the last decade it has become clear from both X-ray and γ-ray observations that young supernovae accelerate particles up to 100 TeV. In soft X-rays the accelerated >10 TeV electrons produce synchrotron radiation, coming from narrow filaments located at the shock fronts. The width of these filaments shows that the magnetic fields are relatively high, thus providing evidence for magnetic field amplification. The synchrotron radiation of several remnants is known to extend into the hard X-ray regime. In particular Cas A, has a spectrum that appears as a power law up to almost 100 TeV. This is very surprising, as a steepening is expected going from the soft to the hard X-ray band. The spectrum is likely a result of many superimposed individual spectra, each steepening at different energies. This implies considerable spatial variation in hard X-rays, an obvious target for Simbol-X. The variations will be important to infer local shock acceleration properties, but also magnetic field fluctuations may cause spatial and temporal variations. Finally, I draw the attention to super bubbles and supernovae as sources of cosmic rays. As such they may be sources of hard X-ray emission. In particular, supernovae exploding inside the dense red supergiants winds of their progenitors ares promising candidates for hard X-ray emission.

Hard X-ray Emission and Efficient Particle Acceleration by Supernova Remnants

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

Vink, Jacco

I discuss the non-thermal X-ray emission from young supernova remnants. Over the last decade it has become clear from both X-ray and {gamma}-ray observations that young supernovae accelerate particles up to 100 TeV. In soft X-rays the accelerated >10 TeV electrons produce synchrotron radiation, coming from narrow filaments located at the shock fronts. The width of these filaments shows that the magnetic fields are relatively high, thus providing evidence for magnetic field amplification.The synchrotron radiation of several remnants is known to extend into the hard X-ray regime. In particular Cas A, has a spectrum that appears as a power lawmore » up to almost 100 TeV. This is very surprising, as a steepening is expected going from the soft to the hard X-ray band. The spectrum is likely a result of many superimposed individual spectra, each steepening at different energies. This implies considerable spatial variation in hard X-rays, an obvious target for Simbol-X. The variations will be important to infer local shock acceleration properties, but also magnetic field fluctuations may cause spatial and temporal variations.Finally, I draw the attention to super bubbles and supernovae as sources of cosmic rays. As such they may be sources of hard X-ray emission. In particular, supernovae exploding inside the dense red supergiants winds of their progenitors ares promising candidates for hard X-ray emission.« less

Scaled Particle Theory for Multicomponent Hard Sphere Fluids Confined in Random Porous Media.

PubMed

Chen, W; Zhao, S L; Holovko, M; Chen, X S; Dong, W

2016-06-23

The formulation of scaled particle theory (SPT) is presented for a quite general model of fluids confined in a random porous media, i.e., a multicomponent hard sphere (HS) fluid in a multicomponent hard sphere or a multicomponent overlapping hard sphere (OHS) matrix. The analytical expressions for pressure, Helmholtz free energy, and chemical potential are derived. The thermodynamic consistency of the proposed theory is established. Moreover, we show that there is an isomorphism between the SPT for a multicomponent system and that for a one-component system. Results from grand canonical ensemble Monte Carlo simulations are also presented for a binary HS mixture in a one-component HS or a one-component OHS matrix. The accuracy of various variants derived from the basic SPT formulation is appraised against the simulation results. Scaled particle theory, initially formulated for a bulk HS fluid, has not only provided an analytical tool for calculating thermodynamic properties of HS fluid but also helped to gain very useful insight for elaborating other theoretical approaches such as the fundamental measure theory (FMT). We expect that the general SPT for multicomponent systems developed in this work can contribute to the study of confined fluids in a similar way.

Microfluidic Examination of the "Hard" Biomolecular Corona Formed on Engineered Particles in Different Biological Milieu.

PubMed

Weiss, Alessia C G; Kempe, Kristian; Förster, Stephan; Caruso, Frank

2018-04-18

The formation of a biomolecular corona around engineered particles determines, in large part, their biological behavior in vitro and in vivo. To gain a fundamental understanding of how particle design and the biological milieu influence the formation of the "hard" biomolecular corona, we conduct a series of in vitro studies using microfluidics. This setup allows the generation of a dynamic incubation environment with precise control over the applied flow rate, stream orientation, and channel dimensions, thus allowing accurate control of the fluid flow and the shear applied to the proteins and particles. We used mesoporous silica particles, poly(2-methacryloyloxyethylphosphorylcholine) (PMPC)-coated silica hybrid particles, and PMPC replica particles (obtained by removal of the silica particle templates), representing high-, intermediate-, and low-fouling particle systems, respectively. The protein source used in the experiments was either human serum or human full blood. The effects of flow, particle surface properties, incubation medium, and incubation time on the formation of the biomolecular corona formation are examined. Our data show that protein adhesion on particles is enhanced after incubation in human blood compared to human serum and that dynamic incubation leads to a more complex corona. By varying the incubation time from 2 s to 15 min, we demonstrate that the "hard" biomolecular corona is kinetically subdivided into two phases comprising a tightly bound layer of proteins interacting directly with the particle surface and a loosely associated protein layer. Understanding the influence of particle design parameters and biological factors on the corona composition, as well as its dynamic assembly, may facilitate more accurate prediction of corona formation and therefore assist in the design of advanced drug delivery vehicles.

Fabrication of cast particle-reinforced metals via pressure infiltration

NASA Technical Reports Server (NTRS)

Klier, E. M.; Mortensen, A.; Cornie, J. A.; Flemings, M. C.

1991-01-01

A new casting process for fabrication of particle-reinforced metals is presented whereby a composite of particulate reinforcing phase in metal is first produced by pressure infiltration. This composite is then diluted in additional molten metal to obtain the desired reinforcement volume fraction and metal composition. This process produces a pore-free as-cast particulate metal-matrix composite. This process is demonstrated for fabrication of magnesium-matrix composites containing SiC reinforcements of average diameter 30, 10 and 3 microns. It is compared with the compocasting process, which was investigated as well for similar SiC particles in Mg-10 wt pct Al, and resulted in unacceptable levels of porosity in the as-cast composite.

On the nature of the Fe-bearing particles influencing hard anodizing behavior of AA 7075 extrusion products

NASA Astrophysics Data System (ADS)

Mukhopadhyay, A. K.

1998-03-01

The deleterious effects of Fe-bearing constituent particles on the fracture toughness of wrought A1 alloys have been known. Recent studies have shown that the presence of Fe-bearing, constituent particles is also determental to the nature and growth of the hard anodic oxide coating formed on such materials. The present study, using a combination of scanning electron microscopy (SEM), transmission electron microscopy (TEM), and electron probe microanalysis (EPMA), was made to examine the influence of the nature of the Fe-bearing particles on the hard anodizing behavior of AA 7075 extrusion products containing varying amounts of Si, Mn, and Fe impurities. It was found that, in the alloy containing 0.25 wt pct Si, 0.27 wt pct Mn, and 0.25 wt pct Fe, the Fe-bearing constituent particles are based on the Al12(FeMn)3Si phase (bcc with α=1.260 nm). These particles survive the hard anodizing treatment, add resistance to the electrical path, causing a rapid rise in the bath voltage with time, and cause a nonuniform growth of the anodic oxide film. In the materials containing 0.05 wt pct Si, 0.04 wt pct Mn, and 0.18 wt pct Fe, on the other hand, the formation of the Al12(FeMn)3Si-based phase is suppressed, and two different Fe-bearing phases, based on Al-Fe-Cu-Mn-based (simple cubic with a=1.265 nm) and Al7Cu2Fe, respectively form. Neither the Al-Fe-Cu-Mn-based phase nor the Al7Cu2Fe-based phase survive the hard anodizing treatment, and this results in a steady rise in the bath voltage with time and a relatively uniform growth of the anodic oxide film. Consideration of the size of the Fe-bearing, particles reveals that the smaller the particle, the more uniform the growth of the anodic oxide film.

Aerosol reduction/expansion synthesis (A-RES) for zero valent metal particles

DOEpatents

Leseman, Zayd; Luhrs, Claudia; Phillips, Jonathan; Soliman, Haytham

2016-04-12

Various embodiments provide methods of forming zero valent metal particles using an aerosol-reductive/expansion synthesis (A-RES) process. In one embodiment, an aerosol stream including metal precursor compound(s) and chemical agent(s) that produces reducing gases upon thermal decomposition can be introduced into a heated inert atmosphere of a RES reactor to form zero valent metal particles corresponding to metals used for the metal precursor compound(s).

Eddy Current, Magnetic Particle and Hardness Testing, Aviation Quality Control (Advanced): 9227.04.

ERIC Educational Resources Information Center

Dade County Public Schools, Miami, FL.

This unit of instruction includes the principles of eddy current, magnetic particle and hardness testing; standards used for analyzing test results; techniques of operating equipment; interpretation of indications; advantages and limitations of these methods of testing; care and calibration of equipment; and safety and work precautions. Motion…

Arthroscopic surgical tools: A source of metal particles and possible joint damage

PubMed Central

Pedowitz, Robert A.; Billi, Fabrizio; Kavanaugh, Aaron; Colbert, Andrew; Liu, Sen; Savoie, Felix H.; You, Zongbing

2013-01-01

Purpose Our goals were (1) to characterize metal micro-particles created by standard arthroscopic instruments, and (2) to examine the in-vitro cellular responses induced by those particles, including possible synergistic effects with local anesthetic. Methods We applied standard surgical tools to 16 foam bone blocks immersed in saline (plus 3 non-instrumented controls). Eight specimens had four minutes of exposure to a 4.0 mm full radius shaver rotating forward at 6,000 RPM. In the other blocks, four holes were created with a 3.0 mm drill via a sleeve. Particles were isolated onto silicon wafers by density gradient ultra-centrifugation, and SEM analyzed a minimum of 1000 particles per wafer. Metal particles were then isolated and purified. Aliquots of sterilized micro-particles were applied to cultured bovine chondrocytes (+/- local anesthetic) and to cultured human or bovine synoviocytes. Chondrocyte viability was assessed with live/dead cell assay by flow cytometry. Synoviocyte responses were assessed with qPCR. Results Stainless steel or aluminum particles were found in each sample (same composition as surgical instruments). Average particle size was 1 to 2 μm (range 50 nm to 20 μm). Chondrocyte exposure (1 hour) to metal debris induced a small but statistically significant increase in cell death, without any synergistic effect of local anesthetic. Proinflammatory chemokines were consistently upregulated in both human and bovine synoviocytes exposed to metallic micro-particles for 3, 24, and 48 hours. Conclusions The current study demonstrates that metallic microdebris is liberated by common arthroscopic instruments, at scales much smaller than previously recognized. These particles are bioactive as demonstrated by the in-vitro synoviocyte responses initiated by metallic micro-particles. Clinical Relevance Our findings suggest that metallic micro-particles could induce intra-articular damage via a synoviocyte-mediated cytokine response if their concentrations

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.

Electromechanical characterization of individual micron-sized metal coated polymer particles

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

Bazilchuk, Molly; Kristiansen, Helge; Conpart AS, Skjetten 2013

Micron-sized polymer particles with nanoscale metal coatings are essential in conductive adhesives for electronics assembly. The particles function in a compressed state in the adhesives. The link between mechanical properties and electrical conductivity is thus of the utmost importance in the formation of good electrical contact. A custom flat punch set-up based on nanoindentation has been developed to simultaneously deform and electrically probe individual particles. The set-up has a sufficiently low internal resistance to allow the measurement of sub-Ohm contact resistances. Additionally, the set-up can capture mechanical failure of the particles. Combining this data yields a fundamental understanding of contactmore » behavior. We demonstrate that this method can clearly distinguish between particles of different sizes, with different thicknesses of metal coating, and different metallization schemes. The technique provides good repeatability and physical insight into the behavior of these particles that can guide adhesive design and the optimization of bonding processes.« less

Unmelted cosmic metal particles in the Indian Ocean

NASA Astrophysics Data System (ADS)

Shyam Prasad, Mokkapati; Rudraswami, N. G.; De Araujo, Agnelo A.; Khedekar, Vijay D.

2017-06-01

Fe-Ni metal is a common constituent of most meteorites and is an indicator of the thermal history of the respective meteorites, it is a diagnostic tool to distinguish between groups/subgroups of meteorites. In spite of over a million micrometeorites collected from various domains, reports of pure metallic particles among micrometeorites have been extremely rare. We report here the finding of a variety of cosmic metal particles such as kamacite, plessite, taenite, and Fe-Ni beads from deep-sea sediments of the Indian Ocean, a majority of which have entered the Earth unaffected by frictional heating during atmospheric entry. Such particles are known as components of meteorites but have never been found as individual entities. Their compositions suggest precursors from a variety of meteorite groups, thus providing an insight into the metal fluxes on the Earth. Some particles have undergone heating and oxidation to different levels during entry developing features similar to I-type cosmic spherules, suggesting atmospheric processing of individual kamacites/taenite grains as another hitherto unknown source for the I-type spherules. The particles have undergone postdepositional aqueous alteration transforming finally into the serpentine mineral cronstedtite. Aqueous alteration products of kamacite reflect the local microenvironment, therefore they have the potential to provide information on the composition of water in the solar nebula, on the parent bodies or on surfaces of planetary bodies. Our observations suggest it would take sustained burial in water for tens of thousands of years under cold conditions for kamacites to alter to cronstedtite.

Scaling of the space-time correlation function of particle currents in a suspension of hard-sphere-like particles: exposing when the motion of particles is Brownian.

PubMed

van Megen, W; Martinez, V A; Bryant, G

2009-12-18

The current correlation function is determined from dynamic light scattering measurements of a suspension of particles with hard spherelike interactions. For suspensions in thermodynamic equilibrium we find scaling of the space and time variables of the current correlation function. This finding supports the notion that the movement of suspended particles can be described in terms of uncorrelated Brownian encounters. However, in the metastable fluid, at volume fractions above freezing, this scaling fails.

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.

Photobiomolecular metallic particles and films

DOEpatents

Hu, Zhong-Cheng

2003-05-06

The method of the invention is based on the unique electron-carrying function of a photocatalytic unit such as the photosynthesis system I (PSI) reaction center of the protein-chlorophyll complex isolated from chloroplasts. The method employs a photo-biomolecular metal deposition technique for precisely controlled nucleation and growth of metallic clusters/particles, e.g., platinum, palladium, and their alloys, etc., as well as for thin-film formation above the surface of a solid substrate. The photochemically mediated technique offers numerous advantages over traditional deposition methods including quantitative atom deposition control, high energy efficiency, and mild operating condition requirements.

[Particle disease. Is tribology a topic in revision surgery?].

PubMed

Elke, R

2001-05-01

To improve the longevity of endoprostheses, the main goal is to reduce wear. Polyethylene together with metal or ceramic is currently the most frequently used combination. Their clinical success is well documented in the literature. Many attempts to improve polyethylene in the past have failed. Materials successful in the laboratory have failed in clinical use. The most recent competitors of ultra-high molecular weight polyethylene (UHMWPE) are the highly cross-linked polyethylenes (HCLPE) and the hard-on-hard couplings such as metal-on-metal or ceramic-on-ceramic. Advantages and downsides regarding particle generation and higher standards of precision in positioning the components are discussed.

The grape cluster, metal particle 63344,1. [in lunar coarse fines

NASA Technical Reports Server (NTRS)

Goldstein, J. I.; Axon, H. J.; Agrell, S. O.

1975-01-01

The grape cluster metal particle 63344,1 found in lunar coarse fines is examined using the scanning electron microscope (SEM), electron microprobe, and an optical microscope. This metal particle is approximately 0.5 cm in its largest dimension and consists of hundreds of metallic globules welded together to form a structure somewhat like a bunch of grapes. Electron microprobe analysis for Fe, Ni, Co, P, and S in the metal was carried out using wavelength dispersive detectors. No primary solidification structure is observed in the globules, and the particle is slow cooled from the solidification temperature (nearly 1300 C) taking days to probably months to reach 600 C. Two mechanisms for the formation of globules are proposed. One mechanism involves the primary impact of an iron meteorite which produces a metallic liquid and vapor phase. The second mechanism involves the formation of a liquid pool of metal after impact of an iron meteorite projectile followed by a secondary impact in the liquid metal pool.

Effect of Ceramic Particle Velocity on Cold Spray Deposition of Metal-Ceramic Coatings

NASA Astrophysics Data System (ADS)

Sova, A.; Kosarev, V. F.; Papyrin, A.; Smurov, I.

2011-01-01

In this paper, metal-ceramic coatings are cold sprayed taking into account the spray parameters of both metal and ceramic particles. The effect of the ceramic particle velocity on the process of metal-ceramic coating formation and the coating properties is analyzed. Copper and aluminum powders are used as metal components. Two fractions of aluminum oxide and silicon carbide are sprayed in the tests. The ceramic particle velocity is varied by the particle injection into different zones of the gas flow: the subsonic and supersonic parts of the nozzle and the free jet after the nozzle exit. The experiments demonstrated the importance of the ceramic particle velocity for the stability of the process: Ceramic particles accelerated to a high enough velocity penetrate into the coating, while low-velocity ceramic particles rebound from its surface.

Shock Interaction of Metal Particles in Condensed Explosive Detonation

NASA Astrophysics Data System (ADS)

Ripley, Robert; Zhang, Fan; Lien, Fue-Sang

2005-07-01

For detonation propagation in a condensed explosive with metal particles, a macro-scale physical model describing the momentum transfer between the explosive and particles has yet to be completely established. Previous 1D and 2D meso-scale modeling studies indicated that significant momentum transfer from the explosive to the particles occurs as the leading shock front crosses the particles, thus influencing the initiation and detonation structure. In this work, 3D meso-scale modeling is conducted to further study the two-phase momentum transfer during the shock diffraction and subsequent detonation in liquid nitromethane containing packed metal particles. Detonation of the condensed explosive is computed using an Arrhenius reaction model and a hybrid EOS model that combines the Mie-Gruneisen equation for reactants and the JWL equation for products. The compressible particles are modeled using the Tait EOS, where the material strength is negligible. The effect of particle packing configuration and inter-particle spacing is shown by parametric studies. Finally, a physical description of the momentum transfer is discussed.

The Particle Distribution in Liquid Metal with Ceramic Particles Mould Filling Process

NASA Astrophysics Data System (ADS)

Dong, Qi; Xing, Shu-ming

2017-09-01

Adding ceramic particles in the plate hammer is an effective method to increase the wear resistance of the hammer. The liquid phase method is based on the “with the flow of mixed liquid forging composite preparation of ZTA ceramic particle reinforced high chromium cast iron hammer. Preparation method for this system is using CFD simulation analysis the particles distribution of flow mixing and filling process. Taking the 30% volume fraction of ZTA ceramic composite of high chromium cast iron hammer as example, by changing the speed of liquid metal viscosity to control and make reasonable predictions of particles distribution before solidification.

Controlled modulation of hard and soft X-ray induced tunneling currents utilizing coaxial metal-insulator-metal probe tips

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

Cummings, Marvin; Shirato, Nozomi; Kersell, Heath

Here, the effect of a local external electric field on the barrier potential of a tunneling gap is studied utilizing an emerging technique, synchrotron x-ray scanning tunneling microscopy. Here, we demonstrate that the shape of the potential barrier in the tunneling gap can be altered by a localized external electric field, generated by voltages placed on the metallic outer shield of a nanofabricated coaxial metal-insulator-metal tip, resulting in a controlled linear modulation of the tunneling current. Experiments at hard and soft x-ray synchrotron beamlines reveal that both the chemical contrast and magnetic contrast signals measured by the tip can bemore » drastically enhanced, resulting in improved local detection of chemistry and magnetization at the surface.« less

Controlled modulation of hard and soft X-ray induced tunneling currents utilizing coaxial metal-insulator-metal probe tips

DOE PAGES

Cummings, Marvin; Shirato, Nozomi; Kersell, Heath; ...

2017-01-05

Here, the effect of a local external electric field on the barrier potential of a tunneling gap is studied utilizing an emerging technique, synchrotron x-ray scanning tunneling microscopy. Here, we demonstrate that the shape of the potential barrier in the tunneling gap can be altered by a localized external electric field, generated by voltages placed on the metallic outer shield of a nanofabricated coaxial metal-insulator-metal tip, resulting in a controlled linear modulation of the tunneling current. Experiments at hard and soft x-ray synchrotron beamlines reveal that both the chemical contrast and magnetic contrast signals measured by the tip can bemore » drastically enhanced, resulting in improved local detection of chemistry and magnetization at the surface.« less

The erosion performance of particle reinforced metal matrix composite coatings produced by co-deposition cold gas dynamic spraying

NASA Astrophysics Data System (ADS)

Peat, Tom; Galloway, Alexander; Toumpis, Athanasios; McNutt, Philip; Iqbal, Naveed

2017-02-01

This work reports on the erosion performance of three particle reinforced metal matrix composite coatings, co-deposited with an aluminium binder via cold-gas dynamic spraying. The deposition of ceramic particles is difficult to achieve with typical cold spray techniques due to the absence of particle deformation. This issue has been overcome in the present study by simultaneously spraying the reinforcing particles with a ductile metallic binder which has led to an increased level of ceramic/cermet particles deposited on the substrate with thick (>400 μm) coatings produced. The aim of this investigation was to evaluate the erosion performance of the co-deposited coatings within a slurry environment. The study also incorporated standard metallographic characterisation techniques to evaluate the distribution of reinforcing particles within the aluminium matrix. All coatings exhibited poorer erosion performance than the uncoated material, both in terms of volume loss and mass loss. The Al2O3 reinforced coating sustained the greatest amount of damage following exposure to the slurry and recorded the greatest volume loss (approx. 2.8 mm3) out of all of the examined coatings. Despite the poor erosion performance, the WC-CoCr reinforced coating demonstrated a considerable hardness increase over the as-received AA5083 (approx. 400%) and also exhibited the smallest free space length between adjacent particles. The findings of this study reveal that the removal of the AA5083 matrix by the impinging silicon carbide particles acts as the primary wear mechanism leading to the degradation of the coating. Analysis of the wear scar has demonstrated that the damage to the soft matrix alloy takes the form of ploughing and scoring which subsequently exposes carbide/oxide particles to the impinging slurry.

Influence of emissivity on behavior of metallic dust particles in plasmas

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

Tanaka, Y.; Smirnov, R. D.; Pigarov, A. Yu.

Influence of thermal radiation emissivity on the lifetime of a dust particle in plasmas is investigated for different fusion relevant metals (Li, Be, Mo, and W). The thermal radiation is one of main cooling mechanisms of the dust in plasmas especially for dust with evaporation temperature higher than 2500 K. In this paper, the temperature- and radius-dependent emissivity of dust particles is calculated using Mie theory and temperature-dependent optical constants for the above metallic materials. The lifetime of a dust particle in uniform plasmas is estimated with the calculated emissivity using the dust transport code DUSTT[A. Pigarov et al., Physicsmore » of Plasmas 12, 122508 (2005)], considering other dust cooling and destruction processes such as physical and chemical sputtering, melting and evaporation, electron emission etc. The use of temperature-dependent emissivity calculated with Mie theory provides a longer lifetime of the refractory metal dust particle compared with that obtained using conventional emissivity constants in the literature. The dynamics of heavy metal dust particles are also presented using the calculated emissivity in a tokamak plasma.« less

Processes of conversion of a hot metal particle into aerogel through clusters

NASA Astrophysics Data System (ADS)

Smirnov, B. M.

2015-10-01

Processes are considered for conversion into a fractal structure of a hot metal micron-size particle that is located in a buffer gas or a gas flow and is heated by an external electric or electromagnetic source or by a plasma. The parameter of this heating is the particle temperature, which is the same in the entire particle volume because of its small size and high conductivity. Three processes determine the particle heat balance: particle radiation, evaporation of metal atoms from the particle surface, and heat transport to the surrounding gas due to its thermal conductivity. The particle heat balance is analyzed based on these processes, which are analogous to those for bulk metals with the small particle size, and its high temperature taken into account. Outside the particle, where the gas temperature is lower than on its surface, the formed metal vapor in a buffer gas flow is converted into clusters. Clusters grow as a result of coagulation until they become liquid, and then clusters form fractal aggregates if they are removed form the gas flow. Subsequently, associations of fractal aggregates join into a fractal structure. The rate of this process increases in medium electric fields, and the formed fractal structure has features of aerogels and fractal fibers. As a result of a chain of the above processes, a porous metal film may be manufactured for use as a filter or catalyst for gas flows.

Coalescence growth mechanism of ultrafine metal particles

NASA Astrophysics Data System (ADS)

Kasukabe, S.

1990-01-01

Ultrafine particles produced by a gas-evaporation technique show clear-cut crystal habits. The convection of an inert gas makes distinct growth zones in a metal smoke. The coalescence stages of hexagonal plates and multiply twinned particles are observed in the outer zone of a smoke. A model of the coalescence growth of particles with different crystal habits is proposed. Size distributions can be calculated by counting the ratio of the number of collisions by using the effective cross section of collisions and the existence probability of the volume of a particle. This simulation model makes clear the effect on the growth rate of coalescence growth derived from crystal habit.

In Situ Production of Hard Metal Matrix Composite Coating on Engineered Surfaces Using Laser Cladding Technique

NASA Astrophysics Data System (ADS)

Raza, Mohammad Shahid; Hussain, Manowar; Kumar, Vikash; Das, Alok Kumar

2017-01-01

The growing need for high wear-resistant surface with enhanced physical properties has led to extensive researches in the field of surface engineering. Laser cladding emerged to be a promising method to achieve these objectives in a cost-effective way. The present paper studies the viability of cladding of tungsten disulfide (WS2) powder by using 400 W continuous-wave fiber laser. WS2 was used as a coating material, which was decomposed at higher temperature and underwent several chemical reactions. By this process, in situ formation of metal matrix composites and hard face coating on the substrate surface were attained. The characterization of laser cladded surface was done to study its morphological, microstructural, mechanical and tribological properties. It was observed that cladding of WS2 powder on 304 SS resulted in the formation of Cr-W-C-Fe metal matrix composite having improved mechanical and tribological properties. The value of microhardness of the coated surface was found to increase three to four times in comparison with the parent material surface. Wear test results indicated a decrease in wear by 1/9th (maximum) as compared to the parent 304 SS surface. The volume fractions of tungsten particles on the cladded surface were also investigated through EDS analysis.

Investigations on the osmoregulation of freshwater fish (Oreochromis niloticus) following exposures to metals (Cd, Cu) in differing hardness.

PubMed

Saglam, Dilek; Atli, Gülüzar; Canli, Mustafa

2013-06-01

Hardness is one of the most important factors in water chemistry as it affects fish physiology and metal toxicity. The aim of this study was to investigate osmoregulatory responses in the Nile tilapia Oreochromis niloticus exposed to copper and cadmium (1.0μg/mL) in soft water (SW) (hardness 80mg CaCO3/L and conductivity 1.77mS/cm) and hard water (HW) (hardness 320mg CaCO3/L and conductivity 5.80mS/cm) for 0, 1, 7 and 14 days. Following the exposures, Na(+)/K(+)-ATPase activity, ion and Cu levels in the gill, kidney and intestine were measured. There was no fish mortality within 14 days, except Cu exposure in SW which killed all fish between 8 and 12 days. Generally, Na(+)/K(+)-ATPase activity was altered by both metal exposures in the gill and kidney as it increased in HW condition, but decreased in SW condition. There were also alterations in Na(+)/K(+)-ATPase activity in the intestine as its activity generally decreased. Data, in general, showed that Cd was more effective on Na(+)/K(+)-ATPase activity comparing to Cu. However, ion levels altered mainly in the kidney and intestine. Tissue metal accumulation was higher in fish tissues from SW condition comparing to HW condition. Data represented here showed that the effects of metals differed in differing water hardness. This suggests that special attention should be paid to the water chemistry when natural monitoring studies are carried out. This study also suggests that the response of osmoregulation system of fish may be a sensitive indicator under stressful conditions in different natural waters. Copyright © 2013 Elsevier Inc. All rights reserved.

Electrochemical synthesis of hard-alloy compositions based on tungsten carbide and an iron triad metal

NASA Astrophysics Data System (ADS)

Kushkhov, Kh. B.; Adamokova, M. N.; Kvashin, V. A.; Kardanov, A. L.

2010-08-01

Single and cyclic voltammetry is used to study the electrode processes that occur during electrochemical synthesis of hard-alloy compositions based on tungsten carbide and an iron triad metal in tungstate and tungstate-carbonate Na2WO4-Li2WO4-Li2CO3 (5.0-22.0 wt %) melts. The conditions of bringing the electroprecipitation potentials of tungsten, carbon, and an iron triad metal into coincidence are determined.

Effect of sonication on particle dispersion, administered dose and metal release of non-functionalized, non-inert metal nanoparticles.

PubMed

Pradhan, Sulena; Hedberg, Jonas; Blomberg, Eva; Wold, Susanna; Odnevall Wallinder, Inger

2016-01-01

In this study, we elucidate the effect of different sonication techniques to efficiently prepare particle dispersions from selected non-functionalized NPs (Cu, Al, Mn, ZnO), and corresponding consequences on the particle dose, surface charge and release of metals. Probe sonication was shown to be the preferred method for dispersing non-inert, non-functionalized metal NPs (Cu, Mn, Al). However, rapid sedimentation during sonication resulted in differences between the real and the administered doses in the order of 30-80 % when sonicating in 1 and 2.56 g/L NP stock solutions. After sonication, extensive agglomeration of the metal NPs resulted in rapid sedimentation of all particles. DLVO calculations supported these findings, showing the strong van der Waals forces of the metal NPs to result in significant NP agglomeration. Metal release from the metal NPs was slightly increased by increased sonication. The addition of a stabilizing agent (bovine serum albumin) had an accelerating effect on the release of metals in sonicated solutions. For Cu and Mn NPs, the extent of particle dissolution increased from <1.6 to ~5 % after sonication for 15 min. A prolonged sonication time (3-15 min) had negligible effects on the zeta potential of the studied NPs. In all, it is shown that it is of utmost importance to carefully investigate how sonication influences the physico-chemical properties of dispersed metal NPs. This should be considered in nanotoxicology investigations of metal NPs.

Diffusion of finite-sized hard-core interacting particles in a one-dimensional box: Tagged particle dynamics.

PubMed

Lizana, L; Ambjörnsson, T

2009-11-01

We solve a nonequilibrium statistical-mechanics problem exactly, namely, the single-file dynamics of N hard-core interacting particles (the particles cannot pass each other) of size Delta diffusing in a one-dimensional system of finite length L with reflecting boundaries at the ends. We obtain an exact expression for the conditional probability density function rhoT(yT,t|yT,0) that a tagged particle T (T=1,...,N) is at position yT at time t given that it at time t=0 was at position yT,0. Using a Bethe ansatz we obtain the N -particle probability density function and, by integrating out the coordinates (and averaging over initial positions) of all particles but particle T , we arrive at an exact expression for rhoT(yT,t|yT,0) in terms of Jacobi polynomials or hypergeometric functions. Going beyond previous studies, we consider the asymptotic limit of large N , maintaining L finite, using a nonstandard asymptotic technique. We derive an exact expression for rhoT(yT,t|yT,0) for a tagged particle located roughly in the middle of the system, from which we find that there are three time regimes of interest for finite-sized systems: (A) for times much smaller than the collision time tparticle concentration and D is the diffusion constant for each particle, the tagged particle undergoes a normal diffusion; (B) for times much larger than the collision time t >taucoll but times smaller than the equilibrium time ttaue , rhoT(yT,t|yT,0) approaches a polynomial-type equilibrium probability density function. Notably, only regimes (A) and (B) are found in the previously considered infinite systems.

A bis(3-hydroxy-4-pyridinone)-EDTA derivative as a strong chelator for M3+ hard metal ions: complexation ability and selectivity.

PubMed

Gama, Sofia; Dron, Paul; Chaves, Silvia; Farkas, Etelka; Santos, M Amélia

2009-08-21

The study of chelating compounds is very important to solve problems related to human metal overload. 3-Hydroxy-3-pyridinones (HP), namely deferiprone, have been clinically used for chelating therapy of Fe and Al over the last decade. A multi-disciplinary search for alternative molecules led us to develop poly-(3-hydroxy-4-pyridinones) to increase metal chelation efficacy. We present herein a complexation study of a new bis-(3-hydroxy-4-pyridinone)-EDTA derivative with a set of M(3+) hard metal ions (M = Fe, Al, Ga), as well as Zn(2+), a biologically relevant metal ion. Thus a systematic aqueous solution equilibrium study was performed using potentiometric and spectroscopic techniques (UV-Vis, NMR methods). These set of results enables the establishment of specific models as well as the determination of thermodynamic stability constants and coordination modes of the metal complexes. The results indicate that this ligand has a higher affinity for chelating to these hard metal ions than deferiprone, and that the coordination occurs mostly through the HP moieties. Furthermore, it was also found that this ligand has a higher selectivity for chelating to M(3+) hard metal ions (M = Fe, Al, Ga) than Zn(2+).

Identification of the typical metal particles among haze, fog, and clear episodes in the Beijing atmosphere.

PubMed

Hu, Yunjie; Lin, Jun; Zhang, Suanqin; Kong, Lingdong; Fu, Hongbo; Chen, Jianmin

2015-04-01

For a better understanding of metal particle morphology and behaviors in China, atmospheric aerosols were sampled in the summer of 2012 in Beijing. The single-particle analysis shows various metal-bearing speciations, dominated by oxides, sulfates and nitrates. A large fraction of particles is soluble. Sources of Fe-bearing particles are mainly steel industries and oil fuel combustion, whereas Zn- and Pb-bearing particles are primarily contributed by waste incineration, besides industrial combustion. Other trace metal particles play a minor rule, and may come from diverse origins. Mineral dust and anthropogenic source like vehicles and construction activities are of less importance to metal-rich particles. Statistics of 1173 analyzed particles show that Fe-rich particles (48.5%) dominate the metal particles, followed by Zn-rich particles (34.9%) and Pb-rich particles (15.6%). Compared with the abundances among clear, haze and fog conditions, a severe metal pollution is identified in haze and fog episodes. Particle composition and elemental correlation suggest that the haze episodes are affected by the biomass burning in the southern regions, and the fog episodes by the local emission with manifold particle speciation. Our results show the heterogeneous reaction accelerated in the fog and haze episodes indicated by more zinc nitrate or zinc sulfate instead of zinc oxide or carbonate. Such information is useful in improving our knowledge of fine airborne metal particles on their morphology, speciation, and solubility, all of which will help the government introduce certain control to alleviate metal pollution. Copyright © 2014 Elsevier B.V. All rights reserved.

Hard-on-hard lubrication in the artificial hip under dynamic loading conditions.

PubMed

Sonntag, Robert; Reinders, Jörn; Rieger, Johannes S; Heitzmann, Daniel W W; Kretzer, J Philippe

2013-01-01

The tribological performance of an artificial hip joint has a particularly strong influence on its success. The principle causes for failure are adverse short- and long-term reactions to wear debris and high frictional torque in the case of poor lubrication that may cause loosening of the implant. Therefore, using experimental and theoretical approaches models have been developed to evaluate lubrication under standardized conditions. A steady-state numerical model has been extended with dynamic experimental data for hard-on-hard bearings used in total hip replacements to verify the tribological relevance of the ISO 14242-1 gait cycle in comparison to experimental data from the Orthoload database and instrumented gait analysis for three additional loading conditions: normal walking, climbing stairs and descending stairs. Ceramic-on-ceramic bearing partners show superior lubrication potential compared to hard-on-hard bearings that work with at least one articulating metal component. Lubrication regimes during the investigated activities are shown to strongly depend on the kinematics and loading conditions. The outcome from the ISO gait is not fully confirmed by the normal walking data and more challenging conditions show evidence of inferior lubrication. These findings may help to explain the differences between the in vitro predictions using the ISO gait cycle and the clinical outcome of some hard-on-hard bearings, e.g., using metal-on-metal.

Hard-on-Hard Lubrication in the Artificial Hip under Dynamic Loading Conditions

PubMed Central

Sonntag, Robert; Reinders, Jörn; Rieger, Johannes S.; Heitzmann, Daniel W. W.; Kretzer, J. Philippe

2013-01-01

The tribological performance of an artificial hip joint has a particularly strong influence on its success. The principle causes for failure are adverse short- and long-term reactions to wear debris and high frictional torque in the case of poor lubrication that may cause loosening of the implant. Therefore, using experimental and theoretical approaches models have been developed to evaluate lubrication under standardized conditions. A steady-state numerical model has been extended with dynamic experimental data for hard-on-hard bearings used in total hip replacements to verify the tribological relevance of the ISO 14242-1 gait cycle in comparison to experimental data from the Orthoload database and instrumented gait analysis for three additional loading conditions: normal walking, climbing stairs and descending stairs. Ceramic-on-ceramic bearing partners show superior lubrication potential compared to hard-on-hard bearings that work with at least one articulating metal component. Lubrication regimes during the investigated activities are shown to strongly depend on the kinematics and loading conditions. The outcome from the ISO gait is not fully confirmed by the normal walking data and more challenging conditions show evidence of inferior lubrication. These findings may help to explain the differences between the in vitro predictions using the ISO gait cycle and the clinical outcome of some hard-on-hard bearings, e.g., using metal-on-metal. PMID:23940772

Metals in airpollution particles decrease whole blood coagulation time

EPA Science Inventory

The mechanism underlying the pro-coagulative effect of air pollution particle exposure is not known. We tested the postulate that 1) the soluble fraction ofan air pollution particle can affect whole blood coagulation time and 2) metals included in the soluble fraction are respons...

Manipulation of metal-dielectric core-shell particles in optical fields

NASA Astrophysics Data System (ADS)

Chvátal, Lukáš; Šiler, Martin; Zemánek, Pavel

2014-12-01

Metal-dielectric core-shell particles represent promising tools in nanoplasmonics. In combination with optical tweezers they can be manipulated in a contactless way through fluid and their plasmonic properties can be used to probe or modify the local environment. We perform a numerical parametric study to find the particle geometry and material parameters under which such particle can be stably confined in optical tweezers. We use the theory based on Mie scattering in the focal field of an ideal water immersion objective of numerical aperture NA=1.2. For very thin metal layers we find that strong trapping on the optical axis can be achieved.

Ultrafine Ceramic Grains Embedded in Metallic Glass Matrix: Achieving Superior Wear Resistance via Increase in Both Hardness and Toughness.

PubMed

Yang, Lina; Wen, Mao; Dai, Xuan; Cheng, Gang; Zhang, Kan

2018-05-09

As structural materials, crystalline or metallic glass materials have attracted scientific and practical interests. However, some mechanisms involving critical size and shear bands have adverse effects on their mechanical properties. Here, we counter these two effects by introducing a special structure with ultrafine ceramic grains (with a diameter of ∼2.0 nm) embedded into a metallic glass matrix, wherein the grains are mainly composed of a Ta-W-N solid solution structure in nature, surrounded by a W-based amorphous matrix that contains Ta and N atoms. Such a structure is in situ formed during preparation, which combines the merits of both phases to achieve simultaneous increase in hardness and toughness relative to references (pure TaN and W) and thus superior wear resistance. Even more remarkable, a favorable variation of increased hardness but reduced elasticity modulus can be induced by this structure. Intrinsically, ultrafine ceramic grains (free of dislocations), embedded in the metallic glass matrix, could prevent shear band propagation within the glass matrix and further improve the hardness of the matrix material. In return, such glass matrix allows for stiffness neutralization and structural relaxation to reduce the elasticity modulus of ceramic grains. This study will offer a new guidance to fabricate ultrahigh-performance metal-based composites.

Application of vacuum metallurgy to separate pure metal from mixed metallic particles of crushed waste printed circuit board scraps.

PubMed

Zhan, Lu; Xu, Zhenming

2008-10-15

The principle of separating pure metal from mixed metallic particles (MMPs) byvacuum metallurgy is that the vapor pressures of various metals at the same temperature are different As a result, the metal with high vapor pressure and low boiling point can be separated from the mixed metals through distillation or sublimation, and then it can be recycled through condensation under a certain condition. The vacuum metallurgy separation (VMS) of MMPs of crushed waste printed circuit boards (WPCBs) has been studied in this paper. Theoretical analyses show that the MMPs (copper, zinc, bismuth, lead, and indium, for example) can be separated by vacuum metallurgy. The copper particles (0.15-0.20 mm) and zinc particles (<0.30 mm) were chosen to simulate the MMPs of crushed WPCBs. Experimental results show that the separated efficiency of zinc in the copper-rich particles achieves 96.19 wt % when the vacuum pressure is 0.01-0.10 Pa, the heating temperature is 1123 K, and the heating time is 105 min. Under this operation condition, the separated efficiency of zinc in the copper-rich particles from crushed WPCBs achieves 97.00 wt % and the copper purity increases from 90.68 to 99.84 wt %.

WHO water quality standards Vs Synergic effect(s) of fluoride, heavy metals and hardness in drinking water on kidney tissues.

PubMed

Wasana, Hewa M S; Perera, Gamage D R K; Gunawardena, Panduka De S; Fernando, Palika S; Bandara, Jayasundera

2017-02-14

Despite WHO standards, waterborne diseases among the human being are rising alarmingly. It is known that the prolong exposure to contaminated water has major impact on public health. The effect of chemical contaminations in drinking water on human being is found to be chronic rather than acute and hence can be defined "consumption of contaminated drinking water could be a silent killer". As the WHO recommended water quality standards are only for individual element and synergic effects of trace metals and anions have not been considered, investigation of synergic effects of trace metals and anions and their effect on human being is of prime important research. By an animal trial, we investigated the synergic effect(s) of heavy metals, aluminium, arsenic, fluoride and hardness in drinking water on kidney tissues of mice. Our investigation strongly suggests existing of a synergic effect especially among Cd, F and hardness of water which could lead to severe kidney damage in mice, even at WHO maximum recommended levels. Hence, the synergic effect(s) of trace metals, fluoride and hardness present in drinking water should be investigated meticulously when stipulating the water quality at WHO maximum recommended levels.

WHO water quality standards Vs Synergic effect(s) of fluoride, heavy metals and hardness in drinking water on kidney tissues

NASA Astrophysics Data System (ADS)

Wasana, Hewa M. S.; Perera, Gamage D. R. K.; Gunawardena, Panduka De S.; Fernando, Palika S.; Bandara, Jayasundera

2017-02-01

Despite WHO standards, waterborne diseases among the human being are rising alarmingly. It is known that the prolong exposure to contaminated water has major impact on public health. The effect of chemical contaminations in drinking water on human being is found to be chronic rather than acute and hence can be defined “consumption of contaminated drinking water could be a silent killer”. As the WHO recommended water quality standards are only for individual element and synergic effects of trace metals and anions have not been considered, investigation of synergic effects of trace metals and anions and their effect on human being is of prime important research. By an animal trial, we investigated the synergic effect(s) of heavy metals, aluminium, arsenic, fluoride and hardness in drinking water on kidney tissues of mice. Our investigation strongly suggests existing of a synergic effect especially among Cd, F and hardness of water which could lead to severe kidney damage in mice, even at WHO maximum recommended levels. Hence, the synergic effect(s) of trace metals, fluoride and hardness present in drinking water should be investigated meticulously when stipulating the water quality at WHO maximum recommended levels.

FDTD approach to optical forces of tightly focused vector beams on metal particles.

PubMed

Qin, Jian-Qi; Wang, Xi-Lin; Jia, Ding; Chen, Jing; Fan, Ya-Xian; Ding, Jianping; Wang, Hui-Tian

2009-05-11

We propose an improved FDTD method to calculate the optical forces of tightly focused beams on microscopic metal particles. Comparison study on different kinds of tightly focused beams indicates that trapping efficiency can be altered by adjusting the polarization of the incident field. The results also show the size-dependence of trapping forces exerted on metal particles. Transverse tapping forces produced by different illumination wavelengths are also evaluated. The numeric simulation demonstrates the possibility of trapping moderate-sized metal particles whose radii are comparable to wavelength.

The fate of meteoric metals in ice particles: Effects of sublimation and energetic particle bombardment

NASA Astrophysics Data System (ADS)

Mangan, T. P.; Frankland, V. L.; Murray, B. J.; Plane, J. M. C.

2017-08-01

The uptake and potential reactivity of metal atoms on water ice can be an important process in planetary atmospheres and on icy bodies in the interplanetary and interstellar medium. For instance, metal atom uptake affects the gas-phase chemistry of the Earth's mesosphere, and has been proposed to influence the agglomeration of matter into planets in protoplanetary disks. In this study the fate of Mg and K atoms incorporated into water-ice films, prepared under ultra-high vacuum conditions at temperatures of 110-140 K, was investigated. Temperature-programmed desorption experiments reveal that Mg- and K-containing species do not co-desorb when the ice sublimates, demonstrating that uptake on ice particles causes irreversible removal of the metals from the gas phase. This implies that uptake on ice particles in terrestrial polar mesospheric clouds accelerates the formation of large meteoric smoke particles (≥1 nm radius above 80 km) following sublimation of the ice. Energetic sputtering of metal-dosed ice layers by 500 eV Ar+ and Kr+ ions shows that whereas K reacts on (or within) the ice surface to form KOH, adsorbed Mg atoms are chemically inert. These experimental results are consistent with electronic structure calculations of the metals bound to an ice surface, where theoretical adsorption energies on ice are calculated to be -68 kJ mol-1 for K, -91 kJ mol-1 for Mg, and -306 kJ mol-1 for Fe. K can also insert into a surface H2O to produce KOH and a dangling H atom, in a reaction that is slightly exothermic.

Differentiation of nonferrous metal particles in lubrication oil using an electrical conductivity measurement-based inductive sensor

NASA Astrophysics Data System (ADS)

Wu, Yu; Zhang, Hongpeng; Wang, Man; Chen, Haiquan

2018-02-01

A method that measures the electrical conductivity of metal based on monitoring the inductance changes of coils via an inductive sensor is introduced in this work to differentiate metal particles in lubrication oil. Theoretical analysis coupled with experimentation is employed to differentiate varieties of nonferrous metal particles, including copper and aluminum particles, ranging from 860 μm to 880 μm in diameter. The results show that the inductive sensor is capable of the identification and differentiation of nonferrous metal particles in lubrication oil based on the electrical conductivity measurement. The concept demonstrated in this paper can be extended to inductive sensors in metal particle detection and other scientific and industrial applications.

Enhanced sun protection of nano-sized metal oxide particles over conventional metal oxide particles: an in vitro comparative study.

PubMed

Singh, P; Nanda, A

2014-06-01

A systematic and detailed study has been designed and conducted, taking into account some of the proposed benefits such as increased efficiency, transparency, unique texture, protection of active ingredient and higher consumer compliance of cosmetics containing nano-sized metal oxides. This study also presents an in vitro method to determine sun protection factor of the investigational sunscreen cream samples containing zinc oxide and titanium dioxide with a varied range of particle size. Finally, a comparative study has been conducted between metal oxide particles, conventional as well as nanoparticles. All the skin cosmetics formulated were thermally stable with a pH ranging from 7.9 to 8.2. Moreover, the fatty acid substance content and residue were found to be analogous to the standard values in each skin cosmetic. The skin cosmetics containing the titanium or zinc oxide nanoparticles were found to have improved spreadability as compared to skin cosmetics containing conventional titanium or zinc oxide particles, respectively. All skin cosmetics were found to have uniform distribution of the particles. The sunscreen creams containing zinc oxide nanoparticles and titanium dioxide nanoparticles were found to have higher in vitro sun protection factor (SPF of 3.65 for ZnO nanoparticles and 4.93 for TiO2 nanoparticles) as compared to that of sunscreen creams containing conventional zinc oxide particles (SPF = 2.90) and conventional titanium dioxide (SPF = 1.29), clearly indicating the effect of reduction in particles size, from micro to nano, on the sun protection factor. Good texture, better spreadability and enhanced in vitro SPF proved the advantageous role of nanoparticles in cosmetics. © 2014 Society of Cosmetic Scientists and the Société Française de Cosmétologie.

Preparation of magnesium metal matrix composites by powder metallurgy process

NASA Astrophysics Data System (ADS)

Satish, J.; Satish, K. G., Dr.

2018-02-01

Magnesium is the lightest metal used as the source for constructional alloys. Today Magnesium based metal matrix composites are widely used in aerospace, structural, oceanic and automobile applications for its light weight, low density(two thirds that of aluminium), good high temperature mechanical properties and good to excellent corrosion resistance. The reason of designing metal matrix composite is to put in the attractive attributes of metals and ceramics to the base metal. In this study magnesium metal matrix hybrid composite are developed by reinforcing pure magnesium with silicon carbide (SiC) and aluminium oxide by method of powder metallurgy. This method is less expensive and very efficient. The Hardness test was performed on the specimens prepared by powder metallurgy method. The results revealed that the micro hardness of composites was increased with the addition of silicon carbide and alumina particles in magnesium metal matrix composites.

Microstructural and hardness investigations on a dissimilar metal weld between low alloy steel and Alloy 82 weld metal

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

Chen, Z.R., E-mail: raymix@aliyun.com

The investigation on microstructure and hardness at the fusion boundary (FB) region of a dissimilar metal weld (DMW) between low alloy steel (LAS) A508-III and Alloy 82 weld metal (WM) was carried out. The results indicated that there were two kinds of FBs, martensite FB and sharp FB, with obvious different microstructures, alternately distributed in the same FB. The martensite FB region had a gradual change of elemental concentration across FB, columnar WM grains with high length/width ratios, a thick martensite layer and a wide heat affected zone (HAZ) with large prior austenite grains. By comparison, the sharp FB regionmore » had a relatively sharp change of elemental concentration across the FB, WM grains with low length/width ratios and a narrow HAZ with smaller prior austenite grains. The martensite possessed a K-S orientation relationship with WM grains, while no orientation relationship was found between the HAZ grains and WM grains at the sharp FB. Compared with sharp FB there were much more Σ3 boundaries in the HAZ beside martensite FB. The hardness maximum of the martensite FB was much higher than that of the sharp FB, which was attributed to the martensite layer at the martensite FB. - Highlights: •Martensite and sharp FBs with different microstructures were found in the same FB. •There were high length/width-ratio WM grains and a wide HAZ beside martensite FB. •There were low length/width-ratio WM grains and a narrow HAZ beside sharp FB. •Compared with sharp FB, there were much more Σ3 boundaries in HAZ of martensite FB. •Hardness maximium of martensite FB was much higher than that of sharp FB.« less

Ti1-xAux Alloys: Hard Biocompatible Metals and Their Possible Applications

NASA Astrophysics Data System (ADS)

Svanidze, Eteri; Besara, Tiglet; Ozaydin, M. Fevzi; Xin, Yan; Han, Ke; Liang, Hong; Siegrist, Theo; Morosan, Emilia

2015-03-01

The search for new hard materials is often challenging from both theoretical and experimental points of view. Furthermore, using materials for biomedical applications calls for alloys with high biocompatibility which are even more sparse. The Ti1-xAux (0 . 22 <= x <= 0 . 8) exhibit extreme hardness and strength values, elevated melting temperatures (compared to those of constituent elements), reduced density compared to Au, high malleability, bulk metallicity, high biocompatibility, low wear, reduced friction, potentially high radio opacity, as well as osseointegration. All these properties render the Ti1-xAux alloys particularly useful for orthopedic, dental, and prosthetic applications, where they could be used as both permanent and temporary components. Additionally, the ability of Ti1-xAux alloys to adhere to ceramic parts could reduce the weight and cost of these components. The work at Rice was supported by NSF DMR 0847681 (E.M. and E.S.).

Adsorption of Heavy Metals in Industrial Wastewater by Magnetic Nano-particles

NASA Astrophysics Data System (ADS)

Tu, Y.; You, C.

2010-12-01

Industrial wastewater containing heavy metals is of great concern because of their toxic impact to living species and environments. Removal of metal ions from industrial effluent using nano-particles is an area of extensive research. This study collected wastewaters and effluents from 11 industrial companies in tanning, electronic plating, printed circuit board manufacturing, semi-conductor, and metal surface treatment industry and studied in detailed the major and trace element compositions to develop potential fingerprinting technique for pollutant source identification. The results showed that electronic plating and metal surface treatment industry produce high Fe, Mn, Cr, Zn, Ni and Mo wastewater. The tanning industry and the printed circuit board manufacturing industry released wastewater with high Fe and Cr, Cu and Ni, respectively. For semi-conductor industry, significant dissolved In was detected in wastewater. The absorption experiments to remove heavy metals in waters were conducted using Fe3O4 nano-particles. Under optimal conditions, more than 99 % dissolved metals were removed in a few minutes.

Aerosol synthesis of nano and micro-scale zero valent metal particles from oxide precursors

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

Phillips, Jonathan; Luhrs, Claudia; Lesman, Zayd

2010-01-01

In this work a novel aerosol method, derived form the batch Reduction/Expansion Synthesis (RES) method, for production of nano / micro-scale metal particles from oxides and hydroxides is presented. In the Aerosol-RES (A-RES) method, an aerosol, consisting of a physical mixture of urea and metal oxide or hydroxides, is passed through a heated oven (1000 C) with a residence time of the order of 1 second, producing pure (zero valent) metal particles. It appears that the process is flexible regarding metal or alloy identity, allows control of particle size and can be readily scaled to very large throughput. Current workmore » is focused on creating nanoparticles of metal and metal alloy using this method. Although this is primarily a report on observations, some key elements of the chemistry are clear. In particular, the reducing species produced by urea decomposition are the primary agents responsible for reduction of oxides and hydroxides to metal. It is also likely that the rapid expansion that takes place when solid/liquid urea decomposes to form gas species influences the final morphology of the particles.« less

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.

Size of metallic and polyethylene debris particles in failed cemented total hip replacements

NASA Technical Reports Server (NTRS)

Lee, J. M.; Salvati, E. A.; Betts, F.; DiCarlo, E. F.; Doty, S. B.; Bullough, P. G.

1992-01-01

Reports of differing failure rates of total hip prostheses made of various metals prompted us to measure the size of metallic and polyethylene particulate debris around failed cemented arthroplasties. We used an isolation method, in which metallic debris was extracted from the tissues, and a non-isolation method of routine preparation for light and electron microscopy. Specimens were taken from 30 cases in which the femoral component was of titanium alloy (10), cobalt-chrome alloy (10), or stainless steel (10). The mean size of metallic particles with the isolation method was 0.8 to 1.0 microns by 1.5 to 1.8 microns. The non-isolation method gave a significantly smaller mean size of 0.3 to 0.4 microns by 0.6 to 0.7 microns. For each technique the particle sizes of the three metals were similar. The mean size of polyethylene particles was 2 to 4 microns by 8 to 13 microns. They were larger in tissue retrieved from failed titanium-alloy implants than from cobalt-chrome and stainless-steel implants. Our results suggest that factors other than the size of the metal particles, such as the constituents of the alloy, and the amount and speed of generation of debris, may be more important in the failure of hip replacements.

Particle size and metals concentrations of dust from a paint manufacturing plant.

PubMed

Huang, Siew Lai; Yin, Chun-Yang; Yap, Siaw Yang

2010-02-15

In this study, the particle size distribution and concentration of metallic elements of solvent- and water-based paint dust from bulk dust collected from dust-collecting hoppers were determined. The mean particle size diameter over a 12-week sampling period was determined using a particle size analyzer. The metals composition and concentration of the dust were determined via acid digestion technique followed by concentration analysis using inductively coupled plasma. The volume weighted mean particle diameters were found to be 0.941+/-0.016 and 8.185+/-0.201 microm for solvent- and water-based paint dust, respectively. The mean concentrations of metals in solvent-based paint dust were found to be 100+/-20.00 microg/g (arsenic), 1550+/-550.00 microg/g (copper), 15,680+/-11,780.00 microg/g (lead) and 30,460+/-10,580.00 microg/g (zinc) while the mean concentrations of metals in water-based paint dust were found to be 20.65+/-6.11 microg/g (arsenic), 9.14+/-14.65 microg/g (copper), 57.46+/-22.42 microg/g (lead) and 1660+/-1260 microg/g (zinc). Both paint dust types could be considered as hazardous since almost all of the dust particles were smaller than 10 microm. Particular emphasis on containment of solvent-based paint dust particles should be given since it was shown that they were very fine in size (<1 microm) and had high lead and zinc concentrations.

Numerical Simulations of Particle Deposition in Metal Foam Heat Exchangers

NASA Astrophysics Data System (ADS)

Sauret, Emilie; Saha, Suvash C.; Gu, Yuantong

2013-01-01

Australia is a high-potential country for geothermal power with reserves currently estimated in the tens of millions of petajoules, enough to power the nation for at least 1000 years at current usage. However, these resources are mainly located in isolated arid regions where water is scarce. Therefore, wet cooling systems for geothermal plants in Australia are the least attractive solution and thus air-cooled heat exchangers are preferred. In order to increase the efficiency of such heat exchangers, metal foams have been used. One issue raised by this solution is the fouling caused by dust deposition. In this case, the heat transfer characteristics of the metal foam heat exchanger can dramatically deteriorate. Exploring the particle deposition property in the metal foam exchanger becomes crucial. This paper is a numerical investigation aimed to address this issue. Two-dimensional (2D) numerical simulations of a standard one-row tube bundle wrapped with metal foam in cross-flow are performed and highlight preferential particle deposition areas.

Photobiomolecular deposition of metallic particles and films

DOEpatents

Hu, Zhong-Cheng

2005-02-08

The method of the invention is based on the unique electron-carrying function of a photocatalytic unit such as the photosynthesis system I (PSI) reaction center of the protein-chlorophyll complex isolated from chloroplasts. The method employs a photo-biomolecular metal deposition technique for precisely controlled nucleation and growth of metallic clusters/particles, e.g., platinum, palladium, and their alloys, etc., as well as for thin-film formation above the surface of a solid substrate. The photochemically mediated technique offers numerous advantages over traditional deposition methods including quantitative atom deposition control, high energy efficiency, and mild operating condition requirements.

Identifying Metals as Marker for Waste Burning Aerosol Particles in New Delhi

NASA Astrophysics Data System (ADS)

Kumar, Sudhanshu

2012-07-01

{Identifying Metals as Marker for Waste Burning Aerosol Particles in New Delhi } Tracing of aerosol sources is an important task helpful for making control strategy, and for climate change study. However, it is a difficult job as aerosols have several sources, involve in complex atmospheric processing, degradation and removal processes. Several approaches have been used for this task, e.g., models, which are based on the input of chemical species; stable- and radio-isotope compositions of certain species; chemical markers in which trace metals are the better options because they persist in atmosphere until the life of a particle. For example, K and Hg are used for biomass and coal burning tracings, respectively. Open waste burning has recently been believed to be a considerable source of aerosols in several mega cities in India and China. To better understand this source contribution in New Delhi aerosols, we have conducted aerosol sampling at a landfill site (Okhla), and in proximity (within 1 km distance) of this site. Aerosol filter samples were acid digested in microwave digestion system and analyzed using inductively coupled plasma -- high resolution mass spectrometry (ICP-HRMS) for getting metal signatures in particles. The metals, e.g., Sn, Sb and As those are found almost negligible in remote aerosols, are maximized in these waste burning aerosols. Sample collected in other location of New Delhi also shows the considerable presence of these metals in particles. Preliminary studies of isotopic ratios of these metals suggested that these metals, especially Sn can be used as marker for tracing the open waste burning sources of aerosols in New Delhi.

Detection of small metal particles by a quasi-optical system at sub-millimeter wavelength

NASA Astrophysics Data System (ADS)

Kitahara, Yasuyuki; Domier, C. W.; Ikeda, Makoto; Pham, Anh-Vu; Luhmann, Neville C.

2016-04-01

Inspection of alien metal particles in electronic materials such as glass fibers and resins is a critical issue to control the quality and guarantee the safety of products. In this paper, we present a new detection technique using sub-millimeter wave for films as electric materials in product lines. The advantage of using sub-millimeter wave frequency is that it is easy to distinguish conductive particles from a nonconductive material such as plastic films. Scattering of a submillimeter wave by a metal particle is used as the detection principle. By simulation, it is observed that the scattering pattern varies intricately as the diameter varies from 10 to 700 μm at 300 GHz. The demonstration system is composed of a Keysight performance network analyzer (N5247A PNA-X) with 150-330 GHz VDI extension modules, transmitting and receiving antennas, and focusing dielectric lens. An output signal is radiated via an antenna and focused onto a metal particle on a film. The wave scattered by the metal particle is detected by an identical antenna through a lens. The signal scattered from a metal particle is evaluated from the insertion loss between antennas (S21). The result shows that a particle of diameter 300 μm is detectable at 150-330 GHz through S21 in the experimental system that we prepared. Peaks calculated in simulation were detected in experimental data as well as in the curves of the particle diameter versus S21. It was shown that using this peak frequency could improve S21 level without higher frequency.

Organizing principles for dense packings of nonspherical hard particles: Not all shapes are created equal

NASA Astrophysics Data System (ADS)

Torquato, Salvatore; Jiao, Yang

2012-07-01

We have recently devised organizing principles to obtain maximally dense packings of the Platonic and Archimedean solids and certain smoothly shaped convex nonspherical particles [Torquato and Jiao, Phys. Rev. EPLEEE81539-375510.1103/PhysRevE.81.041310 81, 041310 (2010)]. Here we generalize them in order to guide one to ascertain the densest packings of other convex nonspherical particles as well as concave shapes. Our generalized organizing principles are explicitly stated as four distinct propositions. All of our organizing principles are applied to and tested against the most comprehensive set of both convex and concave particle shapes examined to date, including Catalan solids, prisms, antiprisms, cylinders, dimers of spheres, and various concave polyhedra. We demonstrate that all of the densest known packings associated with this wide spectrum of nonspherical particles are consistent with our propositions. Among other applications, our general organizing principles enable us to construct analytically the densest known packings of certain convex nonspherical particles, including spherocylinders, “lens-shaped” particles, square pyramids, and rhombic pyramids. Moreover, we show how to apply these principles to infer the high-density equilibrium crystalline phases of hard convex and concave particles. We also discuss the unique packing attributes of maximally random jammed packings of nonspherical particles.

Direct identification of trace metals in fine and ultrafine particles in the Detroit urban atmosphere.

PubMed

Utsunomiya, Satoshi; Jensen, Keld A; Keeler, Gerald J; Ewing, Rodney C

2004-04-15

Exposure to airborne particulates containing low concentrations of heavy metals, such as Pb, As, and Se, may have serious health effects. However, little is known about the speciation and particle size of these airborne metals. Fine- and ultrafine particles with heavy metals in aerosol samples from the Detroit urban area, Michigan, were examined in detail to investigate metal concentrations and speciation. The characterization of individual particles was completed using high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) combined with conventional high-resolution TEM techniques. The trace elements, Pb, As, La, Ce, Sr, Zn, Cr, Se, Sn, Y, Zr, Au, and Ag, were detected, and the elemental distributions were mapped in situ atthe nanoscale. The crystal structures of the particles containing Pb, Sr, Zn, and Au were determined from their electron diffraction patterns. Based on the characterization of the representative trace element particles, the potential health effects are discussed. Most of the trace element particles detected in this study were within a range of 0.01-1.0 microm in size, which has the longest atmospheric residence time (approximately 100 days). Increased chemical reactivity owing to the size of nanoparticles may be expected for most of the trace metal particles observed.

Fine metal dust particles on the wall probes from JET-ILW

NASA Astrophysics Data System (ADS)

Fortuna-Zaleśna, E.; Grzonka, J.; Moon, Sunwoo; Rubel, M.; Petersson, P.; Widdowson, A.; Contributors, JET

2017-12-01

Collection and ex situ studies of dust generated in controlled fusion devices during plasma operation are regularly carried out after experimental campaigns. Herewith results of the dust survey performed in JET after the second phase of operation with the metal ITER-like wall (2013-2014) are presented. For the first-time-ever particles deposited on silicon plates acting as dust collectors installed in the inner and outer divertor have been examined. The emphasis is on analysing metal particles (Be and W) with the aim to determine their composition, size and surface topography. The most important is the identification of beryllium dust in the form of droplets (both splashes and spherical particles), flakes of co-deposits and small fragments of Be tiles. Tungsten and nickel rich (from Inconel) particles are also identified. Nitrogen from plasma edge cooling has been detected in all types of particles. They are categorized and the origin of various constituents is discussed.

Electrochemical method for synthesizing metal-containing particles and other objects

DOEpatents

Rondinone, Adam Justin; Ivanov, Ilia N.; Smith, Sean Campbell; Liang, Chengdu; Hensley, Dale K.; Moon, Ji-Won; Phelps, Tommy Joe

2017-05-02

The invention is directed to a method for producing metal-containing (e.g., non-oxide, oxide, or elemental) nano-objects, which may be nanoparticles or nanowires, the method comprising contacting an aqueous solution comprising a metal salt and water with an electrically powered electrode to form said metal-containing nano-objects dislodged from the electrode, wherein said electrode possesses a nanotextured surface that functions to confine the particle growth process to form said metal-containing nano-objects. The invention is also directed to the resulting metal-containing compositions as well as devices in which they are incorporated.

Demixing, surface nematization, and competing adsorption in binary mixtures of hard rods and hard spheres under confinement

NASA Astrophysics Data System (ADS)

Wu, Liang; Malijevský, Alexandr; Avendaño, Carlos; Müller, Erich A.; Jackson, George

2018-04-01

A molecular simulation study of binary mixtures of hard spherocylinders (HSCs) and hard spheres (HSs) confined between two structureless hard walls is presented. The principal aim of the work is to understand the effect of the presence of hard spheres on the entropically driven surface nematization of hard rod-like particles at surfaces. The mixtures are studied using a constant normal-pressure Monte Carlo algorithm. The surface adsorption at different compositions is examined in detail. At moderate hard-sphere concentrations, preferential adsorption of the spheres at the wall is found. However, at moderate to high pressure (density), we observe a crossover in the adsorption behavior with nematic layers of the rods forming at the walls leading to local demixing of the system. The presence of the spherical particles is seen to destabilize the surface nematization of the rods, and the degree of demixing increases on increasing the hard-sphere concentration.

Demixing, surface nematization, and competing adsorption in binary mixtures of hard rods and hard spheres under confinement.

PubMed

Wu, Liang; Malijevský, Alexandr; Avendaño, Carlos; Müller, Erich A; Jackson, George

2018-04-28

A molecular simulation study of binary mixtures of hard spherocylinders (HSCs) and hard spheres (HSs) confined between two structureless hard walls is presented. The principal aim of the work is to understand the effect of the presence of hard spheres on the entropically driven surface nematization of hard rod-like particles at surfaces. The mixtures are studied using a constant normal-pressure Monte Carlo algorithm. The surface adsorption at different compositions is examined in detail. At moderate hard-sphere concentrations, preferential adsorption of the spheres at the wall is found. However, at moderate to high pressure (density), we observe a crossover in the adsorption behavior with nematic layers of the rods forming at the walls leading to local demixing of the system. The presence of the spherical particles is seen to destabilize the surface nematization of the rods, and the degree of demixing increases on increasing the hard-sphere concentration.

Structure changes in steels and hard metal induced by nanosecond and femtosecond laser processing

NASA Astrophysics Data System (ADS)

Dumitru, Gabriel; Romano, Valerio; Weber, Heinz P.; Haefke, Henry; Gerbig, Yvonne; Sentis, Marc L.; Hermann, Joerg; Bruneau, Sebastien

2003-11-01

Investigations on the occurrence of structure and hardness changes (for two sorts of steel and for a hard metal substrate) in the immediate vicinity of laser induced craters are presented in this work. Experiments with femtosecond pulses were performed in air with a Ti:sapphire laser (800 nm, 100 fs) at mean fluences of 2, 5 and 10 J/cm2. Series of microcraters were induced with 100 to 5,000 laser pulses per hole. Experiments with similar fluences, but 10 to 40 pules per hole, were performed on the same materials using a Nd:YAG delivering 100 ns pulese. After laser irradiation, cuts were made through the processed samples and the changes occurred in the crystalline structure of the target materials were evidenced by metallographical analysis of the resulting cross-sections. Hardness measurements were performed in points situated in the immediate vicinity of the laser-induced pores. Affected zones in the material surrounding laser induced pores were always found in the ns-regime, however with different properties for various laser parameters. In the fs-regime, zones of modified materials were also found and in such zones a significant hardness increasing was evidenced; the limit of the low fluences regime, where no structure changes occurred, was found to be slightly above 2 J/cm2.

Electrically recharged battery employing a packed/spouted bed metal particle electrode

DOEpatents

Siu, Stanley C.; Evans, James W.; Salas-Morales, Juan

1995-01-01

A secondary metal air cell, employing a spouted/packed metal particle bed and an air electrode. More specifically a zinc air cell well suited for use in electric vehicles which is capable of being either electrically or hydraulically recharged.

The origins of particle size effects in heterogeneous catalysis

NASA Astrophysics Data System (ADS)

Bond, Geoffrey C.

1985-06-01

Model calculations are presented to show how the fraction of atoms at the surface of small metal particles increases as their size diminishes in the range 10 to 2 nm. Such particles are prepared either by condensing atoms or aggregates from the vapour phase onto a support, or by chemical methods in the liquid phase, i.e. the traditional routes for preparing supported metal catalysts. The first group of methods leads to artificially pure materials in which the contact between metal and support is poor. The second group of methods leads to the introduction of impurities, to a greater variety of forms of particle, but to a generally firmer binding of metal to support: this permits electronic interactions between the components to occur. Recent literature on the chemisorptive and catalytic properties of metal particles, usually less than 10 nm in size, suggests that certain classes of reaction may be designated as "structure-insensitive" in that their rates depend only minimally on particle size, whereas others, denoted as "structure-sensitive", have rates which either increase or decrease with size. After discounting trivial effects, a hard core of results remains, demanding explanation. Although certain hydrocarbon transformations appear to need sites comprising more than a certain minimum number of atoms, it is thought that the electronic character of surface atoms plays a greater role than their geometric disposition.

Method of making metal matrix composites reinforced with ceramic particulates

DOEpatents

Cornie, James A.; Kattamis, Theodoulos; Chambers, Brent V.; Bond, Bruce E.; Varela, Raul H.

1989-01-01

Composite materials and methods for making such materials are disclosed in which dispersed ceramic particles are at chemical equilibrium with a base metal matrix, thereby permitting such materials to be remelted and subsequently cast or otherwise processed to form net weight parts and other finished (or semi-finished) articles while maintaining the microstructure and mechanical properties (e.g. wear resistance or hardness) of the original composite. The composite materials of the present invention are composed of ceramic particles in a base metal matrix. The ceramics are preferably carbides of titanium, zirconium, tungsten, molybdenum or other refractory metals. The base metal can be iron, nickel, cobalt, chromium or other high temperature metal and alloys thereof. For ferrous matrices, alloys suitable for use as the base metal include cast iron, carbon steels, stainless steels and iron-based superalloys.

Method of making metal matrix composites reinforced with ceramic particulates

DOEpatents

Cornie, J.A.; Kattamis, T.; Chambers, B.V.; Bond, B.E.; Varela, R.H.

1989-08-01

Composite materials and methods for making such materials are disclosed in which dispersed ceramic particles are at chemical equilibrium with a base metal matrix, thereby permitting such materials to be remelted and subsequently cast or otherwise processed to form net weight parts and other finished (or semi-finished) articles while maintaining the microstructure and mechanical properties (e.g. wear resistance or hardness) of the original composite. The composite materials of the present invention are composed of ceramic particles in a base metal matrix. The ceramics are preferably carbides of titanium, zirconium, tungsten, molybdenum or other refractory metals. The base metal can be iron, nickel, cobalt, chromium or other high temperature metal and alloys thereof. For ferrous matrices, alloys suitable for use as the base metal include cast iron, carbon steels, stainless steels and iron-based superalloys. 2 figs.

Refractory metal particles in refractory inclusions in the Allende meteorite

NASA Technical Reports Server (NTRS)

Fuchs, L. H.; Blander, M.

1980-01-01

SEM and X-ray analysis were used to study refractory metal particles in five calcium-aluminum-rich inclusions in the Allende meteorite, and a complex variety of compositions and large departures from equilibrium were found. It is suggested that these particles could have been primordial condensates which were isolated from the nebula and from each other at different times by cocondensing oxides. Selective diffusion and/or oxidation of the more oxidizable metals (Mo, W, Fe, and Ni), phase segregations into different alloy phases (fcc, bcc, hcp, and, possibly, ordered phases), and the formation of metastable condensates could have been involved in the genesis of these materials

Particles, sweat, and tears: a comparative study on bioaccessibility of ferrochromium alloy and stainless steel particles, the pure metals and their metal oxides, in simulated skin and eye contact.

PubMed

Hedberg, Yolanda; Midander, Klara; Wallinder, Inger Odnevall

2010-07-01

Ferrochromium alloys are manufactured in large quantities and placed on the global market for use as master alloys (secondary raw materials), primarily for stainless steel production. Any potential human exposure to ferrochromium alloy particles is related to occupational activities during production and use, with 2 main exposure routes, dermal contact and inhalation and subsequent digestion. Alloy and reference particles exposed in vitro in synthetic biological fluids relevant for these main exposure routes have been investigated in a large research effort combining bioaccessibility; chemical speciation; and material, surface, and particle characteristics. In this paper, data for the dermal exposure route, including skin and eye contact, will be presented and discussed. Bioaccessibility data have been generated for particles of a ferrochromium alloy, stainless steel grade AISI 316L, pure Fe, pure Cr, iron(II,III)oxide, and chromium(III)oxide, upon immersion in artificial sweat (pH 6.5) and artificial tear (pH 8.0) fluids for various time periods. Measured released amounts of Fe, Cr, and Ni are presented in terms of average Fe and Cr release rates and amounts released per amount of particles loaded. The results are discussed in relation to bulk and surface composition of the particles. Additional information, essential to assess the bioavailability of Cr released, was generated by determining its chemical speciation and by providing information on its complexation and oxidation states in both media investigated. The effect of differences in experimental temperature, 30 degrees C and 37 degrees C, on the extent of metal release in artificial sweat is demonstrated. Iron was the preferentially released element in all test media and for all time periods and iron-containing particles investigated. The extent of metal release was highly pH dependent and was also dependent on the medium composition. Released amounts of Cr and Fe were very low (close to the limit of

In situ growth of metal particles on 3D urchin-like WO3 nanostructures.

PubMed

Xi, Guangcheng; Ye, Jinhua; Ma, Qiang; Su, Ning; Bai, Hua; Wang, Chao

2012-04-18

Metal/semiconductor hybrid materials of various sizes and morphologies have many applications in areas such as catalysis and sensing. Various organic agents are necessary to stabilize metal nanoparticles during synthesis, which leads to a layer of organic compounds present at the interfaces between the metal particles and the semiconductor supports. Generally, high-temperature oxidative treatment is used to remove the organics, which can extensively change the size and morphology of the particles, in turn altering their activity. Here we report a facile method for direct growth of noble-metal particles on WO(3) through an in situ redox reaction between weakly reductive WO(2.72) and oxidative metal salts in aqueous solution. This synthetic strategy has the advantages that it takes place in one step and requires no foreign reducing agents, stabilizing agents, or pretreatment of the precursors, making it a practical method for the controlled synthesis of metal/semiconductor hybrid nanomaterials. This synthetic method may open up a new way to develop metal-nanoparticle-loaded semiconductor composites. © 2012 American Chemical Society

Electrically recharged battery employing a packed/spouted bed metal particle electrode

DOEpatents

Siu, S.C.; Evans, J.W.; Salas-Morales, J.

1995-08-15

A secondary metal air cell, employing a spouted/packed metal particle bed and an air electrode, is described. More specifically a zinc air cell well suited for use in electric vehicles which is capable of being either electrically or hydraulically recharged. 5 figs.

Tailoring the synthesis of supported Pd catalysts towards desired structure and size of metal particles.

PubMed

Suresh, Gatla; Radnik, Jörg; Kalevaru, Venkata Narayana; Pohl, Marga-Martina; Schneider, Matthias; Lücke, Bernhard; Martin, Andreas; Madaan, Neetika; Brückner, Angelika

2010-05-14

In a systematic study, the influence of different preparation parameters on phase composition and size of metal crystallites and particles in Pd-Cu/TiO(2) and Pd-Sb/TiO(2) catalyst materials has been explored. Temperature and atmosphere of thermal pretreatment (pure He or 10% H(2)/He), nature of metal precursors (chlorides, nitrates or acetates) as well as of ammonium additives (ammonium sulfate, nitrate, carbonate) and urea were varied with the aim of tailoring the synthesis procedure for the preferential formation of metal particles with similar size and structure as observed recently in active catalysts after long-term equilibration under catalytic reaction conditions in acetoxylation of toluene to benzylacetate. Among the metal precursors and additives, the chloride metal precursors and (NH(4))(2)SO(4) were most suitable. Upon thermal pretreatment of Pd-Sb or Pd-Cu precursors, chloroamine complexes of Pd and Cu are formed, which decompose above 220 degrees C to metallic phases independent of the atmosphere. In He, metallic Pd particles were formed with both the co-components. In H(2)/He flow, Pd-Cu precursors were converted to core-shell particles with a Cu shell and a Pd core, while Sb(1)Pd(1) and Sb(7)Pd(20) alloy phases were formed in the presence of Sb. Metal crystallites of about 40 nm agglomerate to particles of up to 150 nm in He and to even larger size in H(2)/He.

Distribution, bioavailability, and leachability of heavy metals in soil particle size fractions of urban soils (northeastern China).

PubMed

Yutong, Zong; Qing, Xiao; Shenggao, Lu

2016-07-01

This study examines the distribution, mobility, and potential environmental risks of heavy metals in various particle size fractions of urban soils. Representative urban topsoils (ten) collected from Anshan, Liaoning (northeastern China), were separated into six particle size fractions and their heavy metal contents (Cr, Cu, Cd, Pb, and Zn) were determined. The bioaccessibility and leachability of heavy metals in particle size fractions were evaluated using the toxicity characteristic leaching procedure (TCLP) and ethylenediaminetetraacetic acid (EDTA) extraction, respectively. The results indicated that the contents of five heavy metals (Cd, Cr, Cu, Pb and Zn) in the size fractions increased with the decrease of particle size. The clay fraction of <2 μm had the highest content of heavy metals, indicating that the clay fraction was polluted by heavy metals more seriously than the other size fractions in urban topsoils. Cr also concentrated in the coarse fraction of 2000-1000 μm, indicating a lithogenic contribution. However, the dominant size fraction responsible for heavy metal accumulation appeared to belong to particle fraction of 50-2 μm. The lowest distribution factors (DFs) of heavy metals were recorded in the 2000- to 1000-μm size fraction, while the highest in the clay fraction. The DFs of heavy metals in the clay fraction followed Zn (3.22) > Cu (2.84) > Pb (2.61) > Cr (2.19) > Cd (2.05). The enrichment factor suggested that the enrichment degree of heavy metal increased with the decrease of the particle size, especially for Cd and Zn. The TCLP- and EDTA-extractable concentrations of heavy metals in the clay fraction were relatively higher than those in coarse particles. Cd bioavailability was higher in the clay fraction than in other fractions or whole soils. In contrast, Cr exhibits similar bioaccessibilities in the six size fractions of soils. The results suggested that fine particles were the main sources of potentially toxic

Control of Partial Coalescence of Self-Assembled Metal Nano-Particles across Lyotropic Liquid Crystals Templates towards Long Range Meso-Porous Metal Frameworks Design

PubMed Central

Dumée, Ludovic F.; Lemoine, Jean-Baptiste; Ancel, Alice; Hameed, Nishar; He, Li; Kong, Lingxue

2015-01-01

The formation of purely metallic meso-porous metal thin films by partial interface coalescence of self-assembled metal nano-particles across aqueous solutions of Pluronics triblock lyotropic liquid crystals is demonstrated for the first time. Small angle X-ray scattering was used to study the influence of the thin film composition and processing conditions on the ordered structures. The structural characteristics of the meso-structures formed demonstrated to primarily rely on the lyotropic liquid crystal properties while the nature of the metal nano-particles used as well as the their diameters were found to affect the ordered structure formation. The impact of the annealing temperature on the nano-particle coalescence and efficiency at removing the templating lyotropic liquid crystals was also analysed. It is demonstrated that the lyotropic liquid crystal is rendered slightly less thermally stable, upon mixing with metal nano-particles and that low annealing temperatures are sufficient to form purely metallic frameworks with average pore size distributions smaller than 500 nm and porosity around 45% with potential application in sensing, catalysis, nanoscale heat exchange, and molecular separation. PMID:28347094

Individual metal-bearing particles in a regional haze caused by firecracker and firework emissions.

PubMed

Li, Weijun; Shi, Zongbo; Yan, Chao; Yang, Lingxiao; Dong, Can; Wang, Wenxing

2013-01-15

Intensive firecracker/firework displays during Chinese New Year (CNY) release fine particles and gaseous pollutants into the atmosphere, which may lead to serious air pollution. We monitored ambient PM(2.5) and black carbon (BC) concentrations at a regional background site in the Yellow River Delta region during the CNY in 2011. Our monitoring data and MOUDI images showed that there was a haze event during the CNY. Daily average PM(2.5) concentration reached 183 μg m(-3) during the CNY, which was six times higher than that before and after the CNY. Similarly, the black carbon (BC) concentrations were elevated during the CNY. In order to confirm whether the firecracker/firework related emission is the main source of the haze particles, we further analyzed the morphology and chemical composition of individual airborne particles collected before, during and after the CNY by using transmission electron microscopy coupled with energy-dispersive X-ray spectroscopy (TEM/EDS). We found that sulfate and organic-rich particles were dominant in the atmosphere before and after the CNY. In contrast, K-rich sulfates and other metal (e.g., Ba-rich, Al-rich, Mg-rich, and Fe-rich) particles were much more abundant than ammoniated sulfate particles during the CNY. These data suggest that it was the aerosol particles from the firecracker/firework emissions that induced the regional haze episode during the CNY. In individual organic and K-rich particles, we often found more than two types of nano-metal particles. These metal-bearing particles also contained abundant S but not Cl. In contrast, fresh metal-bearing particles from firecrackers generated in the laboratory contained abundant Cl with minor amounts of S. This indicates that the firecracker/firework emissions during the CNY significantly changed the atmospheric transformation pathway of SO(2) to sulfate. Copyright © 2012 Elsevier B.V. All rights reserved.

Corrosion of metal particle and metal evaporated tapes

NASA Technical Reports Server (NTRS)

Speliotis, Dennis E.

1991-01-01

Very high coercivity metal particle (MP) and metal evaporated (ME) tapes are being used in 8mm video and digital audio tape applications, and more recently in digital data recording applications. In view of the inherent susceptibility of such media to environmental corrosion, a number of recent studies have addressed their long term stability and archivability. These studies have used an accelerated corrosion test based either on elevated temperature-humidity or polluting gas atmospheres known as Battelle tests. A comparison of the Battelle test results performed at different laboratories reveals a large variation from one location to another, presumably due to incorrect replication of the Battelle condition. Furthermore, when the Battelle tests are performed on enclosed cartridges, it is quite possible that diffusion limits the penetration of the extremely low concentration polluting gaseous species to the inner layers of the tapes during the short time of the accelerated test, whereas in real life these diffusion limitations may not apply. To avoid this uncertainty, the corrosion behavior of commercial 8mm MP and ME tapes when cassettes without their external plastic cases were exposed to 50 deg C and 80 percent RH for 7.5 weeks is investigated.

Mechanical Fracturing of Core-Shell Undercooled Metal Particles for Heat-Free Soldering.

PubMed

Çınar, Simge; Tevis, Ian D; Chen, Jiahao; Thuo, Martin

2016-02-23

Phase-change materials, such as meta-stable undercooled (supercooled) liquids, have been widely recognized as a suitable route for complex fabrication and engineering. Despite comprehensive studies on the undercooling phenomenon, little progress has been made in the use of undercooled metals, primarily due to low yields and poor stability. This paper reports the use of an extension of droplet emulsion technique (SLICE) to produce undercooled core-shell particles of structure; metal/oxide shell-acetate ('/' = physisorbed, '-' = chemisorbed), from molten Field's metal (Bi-In-Sn) and Bi-Sn alloys. These particles exhibit stability against solidification at ambient conditions. Besides synthesis, we report the use of these undercooled metal, liquid core-shell, particles for heat free joining and manufacturing at ambient conditions. Our approach incorporates gentle etching and/or fracturing of outer oxide-acetate layers through mechanical stressing or shearing, thus initiating a cascade entailing fluid flow with concomitant deformation, combination/alloying, shaping, and solidification. This simple and low cost technique for soldering and fabrication enables formation of complex shapes and joining at the meso- and micro-scale at ambient conditions without heat or electricity.

Mechanical Fracturing of Core-Shell Undercooled Metal Particles for Heat-Free Soldering

PubMed Central

Çınar, Simge; Tevis, Ian D.; Chen, Jiahao; Thuo, Martin

2016-01-01

Phase-change materials, such as meta-stable undercooled (supercooled) liquids, have been widely recognized as a suitable route for complex fabrication and engineering. Despite comprehensive studies on the undercooling phenomenon, little progress has been made in the use of undercooled metals, primarily due to low yields and poor stability. This paper reports the use of an extension of droplet emulsion technique (SLICE) to produce undercooled core-shell particles of structure; metal/oxide shell-acetate (‘/’ = physisorbed, ‘-’ = chemisorbed), from molten Field’s metal (Bi-In-Sn) and Bi-Sn alloys. These particles exhibit stability against solidification at ambient conditions. Besides synthesis, we report the use of these undercooled metal, liquid core-shell, particles for heat free joining and manufacturing at ambient conditions. Our approach incorporates gentle etching and/or fracturing of outer oxide-acetate layers through mechanical stressing or shearing, thus initiating a cascade entailing fluid flow with concomitant deformation, combination/alloying, shaping, and solidification. This simple and low cost technique for soldering and fabrication enables formation of complex shapes and joining at the meso- and micro-scale at ambient conditions without heat or electricity. PMID:26902483

Synthesis of poly(N-isopropylacrylamide) particles for metal affinity binding of peptides

PubMed Central

Tsai, Hsin-Yi; Lee, Alexander; Peng, Wei; Yates, Matthew Z.

2013-01-01

Temperature-sensitive poly(N-isopropylacrylamide) (PNIPAM) microgel particles with metal affinity ligands were prepared for selective binding of peptides containing the His6-tag (six consecutive histidine residues). The PNIPAM particles were copolymerized with the functional ligand vinylbenzyl iminodiacetic acid (VBIDA) through a two-stage dispersion polymerization using poly(N-vinyl pyrrolidone) (PVP) as a steric stabilizer. The resulting particles were monodisperse in size and colloidally stable over a wide range of temperature and ionic strength due to chemically grafted PVP chains. The particle size was also found to be sensitive to ionic strength and pH of the aqueous environment, likely due to the electrostatic repulsion between ionized VBIDA groups. Divalent nickel ions were chelated to the VBIDA groups, allowing selective metal affinity attachment of a His6-Cys peptide. The peptide was released upon the addition of the competitive ligand imidazole, demonstrating that the peptide attachment to the particles is reversible and selective. PMID:24176889

Nuclear Reactions in Micro/Nano-Scale Metal Particles

NASA Astrophysics Data System (ADS)

Kim, Y. E.

2013-03-01

Low-energy nuclear reactions in micro/nano-scale metal particles are described based on the theory of Bose-Einstein condensation nuclear fusion (BECNF). The BECNF theory is based on a single basic assumption capable of explaining the observed LENR phenomena; deuterons in metals undergo Bose-Einstein condensation. The BECNF theory is also a quantitative predictive physical theory. Experimental tests of the basic assumption and theoretical predictions are proposed. Potential application to energy generation by ignition at low temperatures is described. Generalized theory of BECNF is used to carry out theoretical analyses of recently reported experimental results for hydrogen-nickel system.

30 CFR 56.15002 - Hard hats.

Code of Federal Regulations, 2013 CFR

2013-07-01

... 30 Mineral Resources 1 2013-07-01 2013-07-01 false Hard hats. 56.15002 Section 56.15002 Mineral... HEALTH SAFETY AND HEALTH STANDARDS-SURFACE METAL AND NONMETAL MINES Personal Protection § 56.15002 Hard hats. All persons shall wear suitable hard hats when in or around a mine or plant where falling objects...

30 CFR 56.15002 - Hard hats.

Code of Federal Regulations, 2011 CFR

2011-07-01

... 30 Mineral Resources 1 2011-07-01 2011-07-01 false Hard hats. 56.15002 Section 56.15002 Mineral... HEALTH SAFETY AND HEALTH STANDARDS-SURFACE METAL AND NONMETAL MINES Personal Protection § 56.15002 Hard hats. All persons shall wear suitable hard hats when in or around a mine or plant where falling objects...

30 CFR 57.15002 - Hard hats.

Code of Federal Regulations, 2010 CFR

2010-07-01

... 30 Mineral Resources 1 2010-07-01 2010-07-01 false Hard hats. 57.15002 Section 57.15002 Mineral Resources MINE SAFETY AND HEALTH ADMINISTRATION, DEPARTMENT OF LABOR METAL AND NONMETAL MINE SAFETY AND... Underground § 57.15002 Hard hats. All persons shall wear suitable hard hats when in or around a mine or plant...

30 CFR 57.15002 - Hard hats.

Code of Federal Regulations, 2011 CFR

2011-07-01

... 30 Mineral Resources 1 2011-07-01 2011-07-01 false Hard hats. 57.15002 Section 57.15002 Mineral Resources MINE SAFETY AND HEALTH ADMINISTRATION, DEPARTMENT OF LABOR METAL AND NONMETAL MINE SAFETY AND... Underground § 57.15002 Hard hats. All persons shall wear suitable hard hats when in or around a mine or plant...

30 CFR 56.15002 - Hard hats.

Code of Federal Regulations, 2010 CFR

2010-07-01

... 30 Mineral Resources 1 2010-07-01 2010-07-01 false Hard hats. 56.15002 Section 56.15002 Mineral... HEALTH SAFETY AND HEALTH STANDARDS-SURFACE METAL AND NONMETAL MINES Personal Protection § 56.15002 Hard hats. All persons shall wear suitable hard hats when in or around a mine or plant where falling objects...

30 CFR 56.15002 - Hard hats.

Code of Federal Regulations, 2014 CFR

2014-07-01

... 30 Mineral Resources 1 2014-07-01 2014-07-01 false Hard hats. 56.15002 Section 56.15002 Mineral... HEALTH SAFETY AND HEALTH STANDARDS-SURFACE METAL AND NONMETAL MINES Personal Protection § 56.15002 Hard hats. All persons shall wear suitable hard hats when in or around a mine or plant where falling objects...

30 CFR 56.15002 - Hard hats.

Code of Federal Regulations, 2012 CFR

2012-07-01

... 30 Mineral Resources 1 2012-07-01 2012-07-01 false Hard hats. 56.15002 Section 56.15002 Mineral... HEALTH SAFETY AND HEALTH STANDARDS-SURFACE METAL AND NONMETAL MINES Personal Protection § 56.15002 Hard hats. All persons shall wear suitable hard hats when in or around a mine or plant where falling objects...

30 CFR 57.15002 - Hard hats.

Code of Federal Regulations, 2013 CFR

2013-07-01

... 30 Mineral Resources 1 2013-07-01 2013-07-01 false Hard hats. 57.15002 Section 57.15002 Mineral Resources MINE SAFETY AND HEALTH ADMINISTRATION, DEPARTMENT OF LABOR METAL AND NONMETAL MINE SAFETY AND... Underground § 57.15002 Hard hats. All persons shall wear suitable hard hats when in or around a mine or plant...

30 CFR 57.15002 - Hard hats.

Code of Federal Regulations, 2012 CFR

2012-07-01

... 30 Mineral Resources 1 2012-07-01 2012-07-01 false Hard hats. 57.15002 Section 57.15002 Mineral Resources MINE SAFETY AND HEALTH ADMINISTRATION, DEPARTMENT OF LABOR METAL AND NONMETAL MINE SAFETY AND... Underground § 57.15002 Hard hats. All persons shall wear suitable hard hats when in or around a mine or plant...

30 CFR 57.15002 - Hard hats.

Code of Federal Regulations, 2014 CFR

2014-07-01

... 30 Mineral Resources 1 2014-07-01 2014-07-01 false Hard hats. 57.15002 Section 57.15002 Mineral Resources MINE SAFETY AND HEALTH ADMINISTRATION, DEPARTMENT OF LABOR METAL AND NONMETAL MINE SAFETY AND... Underground § 57.15002 Hard hats. All persons shall wear suitable hard hats when in or around a mine or plant...

Erosion of iron-chromium alloys by glass particles

NASA Technical Reports Server (NTRS)

Salik, J.; Buckley, D. H.

1984-01-01

The material loss upon erosion was measured for several iron-chromium alloys. Two types of erodent material were used: spherical glass beads and sharp particles of crushed glass. For erosion with glass beads the erosion resistance (defined as the reciprocal of material loss rate) was linearly dependent on hardness. This is in accordance with the erosion behavior of pure metals, but contrary to the erosion behavior of alloys of constant composition that were subjected to different heat treatments. For erosion with crushed glass, however, no correlation existed between hardness and erosion resistance. Instead, the erosion resistance depended on alloy composition rather than on hardness and increased with the chromium content of the alloy. The difference in erosion behavior for the two types of erodent particles suggested that two different material removal mechanisms were involved. This was confirmed by SEM micrographs of the eroded surfaces, which showed that for erosion with glass beads the mechanism of material removal was deformation-induced flaking of surface layers, or peening, whereas for erosion with crushed glass it was cutting or chopping.

Particle size effects on uptake of heavy metals from sewage sludge compost using natural zeolite clinoptilolite.

PubMed

Zorpas, Antonis A; Vassilis, Inglezakis; Loizidou, Maria; Grigoropoulou, Helen

2002-06-01

Land application of sewage sludge may be the least energy consuming and the most cost-effective means of sludge disposal or utilization. However, the major technical problem with land application of sludge concerns the high concentrations of heavy metals. These metals may be leached and enter the ecosystem, the food chain, and eventually the human population. This paper deals with the removal of heavy metals from sewage sludge compost using natural zeolite clinoptilolite, in respect to the particle size. The final results indicate that heavy metals can be sufficiently removed by using 25% w/w of zeolite with particle size of 3.3-4.0 mm. Pore clogging and structural damage in smaller particle sizes is probably the reason for lower uptake of metals by the latter.

Formation of Ultrafine Metal Particles by Gas-Evaporation VI. Bcc Metals, Fe, V, Nb, Ta, Cr, Mo and W

NASA Astrophysics Data System (ADS)

Saito, Yahachi; Mihama, Kazuhiro; Uyeda, Ryozi

1980-09-01

The crystal structures and habits of bcc metal particles have been investigated systematically by electron microscopy. The habits for the bcc structure are rhombic dodecahedra truncated by six {100} faces with various degrees of truncation from 0 to 100%. The truncation degree for Fe and V particles grown in the intermediate zone of a metal smoke is in good agreement with that for the Wulff polyhedron expected from the surface energies calculated for {110} and {100} faces. Particles of Cr, Mo and W have the A-15 type structure besides the ordinary bcc structure. The present results support the hypothesis that the A-15 type structure is stable when the particle size is small. The habits for the A-15 type structure are rhombic dodecahedra (Cr), {211} icositetrahedra (Cr and Mo) and rounded cubes (Mo and W).

Mutagenicity of fume particles from metal arc welding on stainless steel in the Salmonella/microsome test.

PubMed

Maxild, J; Andersen, M; Kiel, P

1978-01-01

Mutagenic activity of fume particles produced by metal arc welding on stainless steel (ss) is demonstrated by using the Salmonella/microsome mutagenicity test described by Ames et al., with strain TA100 (base-pair substitution) and TA98 (frame-shift reversion). Results of a representative but limited selection of processes and materials show that mutagenic activity is a function of process and process parameters. Welding on stainless steel produces particles that are mutagenic, whereas welding on mild steel (ms) produces particles that are not. Manual metal arc (MMA) welding on stainless steel produces particles of higher mutagenic activity than does metal inert gas (MIG) welding, and fume particles produced by MIG welding under short-arc transfer. Further studies of welding fumes (both particles and gases) must be performed to determine process parameters of significance for the mutagenic activity.

A novel method for isolation and recovery of ceramic nanoparticles and metal wear debris from serum lubricants at ultra-low wear rates.

PubMed

Lal, S; Hall, R M; Tipper, J L

2016-09-15

Ceramics have been used to deliver significant improvements in the wear properties of orthopaedic bearing materials, which has made it challenging to isolate wear debris from simulator lubricants. Ceramics such as silicon nitride, as well as ceramic-like surface coatings on metal substrates have been explored as potential alternatives to conventional implant materials. Current isolation methods were designed for isolating conventional metal, UHMWPE and ceramic wear debris. In this paper, we describe a methodology for isolation and recovery of ceramic or ceramic-like coating particles and metal wear particles from serum lubricants under ultra-low and low wear performance. Enzymatic digestion was used to digest the serum proteins and sodium polytungstate was used as a novel density gradient medium to isolate particles from proteins and other contaminants by ultracentrifugation. This method demonstrated over 80% recovery of particles and did not alter the size or morphology of ceramic and metal particles during the isolation process. Improvements in resistance to wear and mechanical damage of the articulating surfaces have a large influence on longevity and reliability of joint replacement devices. Modern ceramics have demonstrated ultra-low wear rates for hard-on-hard total hip replacements. Generation of very low concentrations of wear debris in simulator lubricants has made it challenging to isolate the particles for characterisation and further analysis. We have introduced a novel method to isolate ceramic and metal particles from serum-based lubricants using enzymatic digestion and novel sodium polytungstate gradients. This is the first study to demonstrate the recovery of ceramic and metal particles from serum lubricants at lowest detectable in vitro wear rates reported in literature. Copyright © 2016. Published by Elsevier Ltd.

Solution and particle effects on the biosorption of heavy metals by seaweed biomass

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

Leusch, A.; Holan, Z.R.; Volesky, B.

Biosorption of cadmium (Cd), cobalt (Co), copper (Cu), nickel (Ni), lead (Pb), and zinc (Zn) by six fractions of particle sizes, ranging from 0.063 to 1.4 mm of dry marine algal biomass of Sargassum fluitans and Ascophyllum nodosum, is examined. Equilibrium metal uptake by larger particles was higher than that by smaller particles in the order of Pb > Cd > Cu > Co > Zn > Ni for both biomass types, with S. fluitans sorbing slightly more than A. nodosum. Uptakes of metals ranged from the highest, q{sub max} = 369 mg Pb/g (particle size 0.84-1.00 mm), to themore » low Zn and Ni uptakes, q{sub max} = 77 mg/g (size 0.84-1.00 mm) for S. fluitans. A. nodosum adsorbed metals in the range from q{sub max} = 287 mg Pg/g (particle size 0.84-1.00 mm) to q{sub max} = 73 mg Zn/g (particle size 0.84-1.00mm). Harder stipe fractions of S. fluitans demonstrated generally higher metal uptakes than the softer fractions derived from its blades (leaves). The pH dependence of the Zn uptake by S. fluitans exhibited an S-shaped curve between pH 1.5 and pH 7, with 50% of the maximum (pH 7.0) uptake at pH 3.5. Monovalent Na and K ions at higher concentrations inhibited the biosorption of Zn by S. fluitans. A significant inhibition started at 50 mM potassium chloride or sodium acetate, and at 1M the biosorption was completely blocked. 40 refs., 8 figs., 3 tabs.« less

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.

Nanoindentation hardness and atomic force microscope imaging studies of pressure-quenched zirconium metal

NASA Astrophysics Data System (ADS)

Catledge, Shane A.; Spencer, Philemon T.; Vohra, Yogesh K.

2000-11-01

We have carried out mechanical property measurements on zirconium metal compressed in a diamond anvil cell to 19 GPa at room temperature with subsequent quenching to room pressure. The irreversible transformation from the ambient hexagonal-close-packed phase to the simple hexagonal ω phase (AlB2 structure) is confirmed by synchrotron energy dispersive x-ray diffraction followed by nanoindentation of the pressure-quenched sample. We document an 80% increase in hardness as a consequence of the pressure-induced transformation to the ω phase at room temperature. This is a large increase for a metallic phase transformation and can be attributed to the presence of sp2-hybrid bonds forming graphite-like nets in the (0001) plane of the AlB2 structure. Atomic force microscopy of the indents shows that a plastic deformation of 2 μm in depth was achieved with a force of 200 mN.

Analysis of the co-deposition of Al2O3 particles with nickel by an electrolytic route: The influence of organic additives presence and Al2O3 concentration

NASA Astrophysics Data System (ADS)

Temam, H. B.; Temam, E. G.

2016-04-01

Alloy coatings were prepared by co-deposition of Al2O3 particles in Ni matrix on carbon steel substrate from nickel chloride bath in which metallic powders were held in suspension. The influence of metal powder amount in the bath on chemical composition, morphology, thickness, microhardness and corrosion behavior of obtained coatings, has been investigated. It was shown that the presence of Al2O3 particles in deposit greatly improves the hardness and the wear resistance of alloy coatings. Characterization by microanalysis (EDX) of the various deposits elaborated confirms that the rate of particles incorporated increases as the concentration of solid particles increasing. The results showed that the presence of organic additives in Ni-Al2O3 electrolyte deposition led to an increase in the hardness and corrosion resistance of the deposits.

Study on micro-hardness of electroless composite plating of Ni-P with SiC Nano-particles

NASA Astrophysics Data System (ADS)

Sun, Yong; Zhang, Zhaoguo; Li, Jiamin; Xu, Donghui

2007-07-01

In this paper, a Ni-P electroless composite coating containing nano SiC particles was produced. The wearability of the composite coating was studied. Temperature, PH of the plating liquid and the concentration of SiC nanoparticles in the plating liquid were taken as parameters and the experiment with three factors and five levels was designed through the method of quadratic orthogonal rotation combination. SiC nanoparticles were dispersed by ultrasonic. The influence of the testing parameters on the hardness of the coating was studied intensively. The optimal parameters were obtained when the temperature is 86+/-1°C, PH is 6+/-0.5 and the concentration of SiC nanoparticles is 6g/L. The maximal hardness of the coating is over 1700HV after heat treatment.

Anomalous metallic state with strong charge fluctuations in BaxTi8O16 +δ revealed by hard x-ray photoemission spectroscopy

NASA Astrophysics Data System (ADS)

Dash, S.; Kajita, T.; Okawa, M.; Saitoh, T.; Ikenaga, E.; Saini, N. L.; Katsufuji, T.; Mizokawa, T.

2018-04-01

We have studied a charge-orbital driven metal-insulator transition (MIT) in hollandite-type BaxTi8O16 +δ by means of hard x-ray photoemission spectroscopy (HAXPES). The Ti 2 p HAXPES indicates strong Ti3 +/Ti4 + charge fluctuation in the metallic phase above the MIT temperature. The metallic phase is characterized by a power-law spectral function near the Fermi level which would be a signature of bad metal with non-Drude polaronic behavior. The power-law spectral shape is associated with the large Seebeck coefficient of the metallic phase in BaxTi8O16 +δ .

An approach to calculating metal particle detection in lubrication oil based on a micro inductive sensor

NASA Astrophysics Data System (ADS)

Wu, Yu; Zhang, Hongpeng

2017-12-01

A new microfluidic chip is presented to enhance the sensitivity of a micro inductive sensor, and an approach to coil inductance change calculation is introduced for metal particle detection in lubrication oil. Electromagnetic knowledge is used to establish a mathematical model of an inductive sensor for metal particle detection, and the analytic expression of coil inductance change is obtained by a magnetic vector potential. Experimental verification is carried out. The results show that copper particles 50-52 µm in diameter have been detected; the relative errors between the theoretical and experimental values are 7.68% and 10.02% at particle diameters of 108-110 µm and 50-52 µm, respectively. The approach presented here can provide a theoretical basis for an inductive sensor in metal particle detection in oil and other areas of application.

NOTE: Ranges of ions in metals for use in particle treatment planning

NASA Astrophysics Data System (ADS)

Jäkel, Oliver

2006-05-01

In proton and ion radiotherapy, the range of particles is calculated from x-ray computed tomography (CT) numbers. Due to the strong absorption of x-rays in a metal and a cut-off for large Hounsfield units (HU) in the software of most CT-scanners, a range calculation in metals cannot be based on the measured HU. This is of special importance when metal implants such as gold fillings or hip prostheses are close to the treatment volume. In order to overcome this problem in treatment planning for heavy charged particles, the correct ranges of ions in the metal relative to water have to be assigned in the CT data. Measurements and calculations of carbon ion ranges in various metals are presented that can be used in treatment planning to allow for a more accurate range calculation of carbon ion beams in titanium, steel, tungsten and gold. The suggested values for the relative water-equivalent range and their uncertainties are 3.13 (±3%) for titanium, 5.59 (±3%) for stainless steel and 10.25 (±4%) for gold.

Oxalate metal complexes in aerosol particles: implications for the hygroscopicity of oxalate-containing particles

NASA Astrophysics Data System (ADS)

Furukawa, T.; Takahashi, Y.

2011-05-01

Atmospheric aerosols have both a direct and an indirect cooling effect that influences the radiative balance at the Earth's surface. It has been estimated that the degree of cooling is large enough to weaken the warming effect of carbon dioxide. Among the cooling factors, secondary organic aerosols (SOA) play an important role in the solar radiation balance in the troposphere as SOA can act as cloud condensation nuclei (CCN) and extend the lifespan of clouds because of their high hygroscopic and water soluble nature. Oxalic acid is an important component of SOA, and is produced via several formation pathways in the atmosphere. However, it is not certain whether oxalic acid exists as free oxalic acid or as metal oxalate complexes in aerosols, although there is a marked difference in their solubility in water and their hygroscopicity. We employed X-ray absorption fine structure spectroscopy to characterize the calcium (Ca) and zinc (Zn) in aerosols collected at Tsukuba in Japan. Size-fractionated aerosol samples were collected for this purpose using an impactor aerosol sampler. It was shown that 10-60% and 20-100% of the total Ca and Zn in the finer particles (<2.1 μm) were present as Ca and Zn oxalate complexes, respectively. Oxalic acid is hygroscopic and can thus increase the CCN activity of aerosol particles, while complexes with various polyvalent metal ions such as Ca and Zn are not hygroscopic, which cannot contribute to the increase of the CCN activity of aerosols. Based on the concentrations of noncomplexed and metal-complexed oxalate species, we found that most of the oxalic acid is present as metal oxalate complexes in the aerosols, suggesting that oxalic acid does not always increase the hygroscopicity of aerosols in the atmosphere. Similar results are expected for other dicarboxylic acids, such as malonic and succinic acids. Thus, it is advisable that the cooling effect of organic aerosols should be estimated by including the information on metal

Rapid laser sintering of metal nano-particles inks.

PubMed

Ermak, Oleg; Zenou, Michael; Toker, Gil Bernstein; Ankri, Jonathan; Shacham-Diamand, Yosi; Kotler, Zvi

2016-09-23

Fast sintering is of importance in additive metallization processes and especially on sensitive substrates. This work explores the mechanisms which set limits to the laser sintering rate of metal nano-particle inks. A comparison of sintering behavior of three different ink compositions with laser exposure times from micro-seconds to seconds reveals the dominant factor to be the organic content (OC) in the ink. With a low OC silver ink, of 2% only, sintering time falls below 100 μs with resistivity <×4 bulk silver. Still shorter exposure times result in line delamination and deformation with a similar outcome when the OC is increased.

Cytokine secretion from human peripheral blood mononuclear cells cultured in vitro with metal particles.

PubMed

Cachinho, Sandra C P; Pu, Fanrong; Hunt, John A

2013-04-01

The failure of implanted medical devices can be associated with changes in the production of cytokines by cells of the immune system. Cytokines released by peripheral blood mononuclear cells upon contact with metal particles were quantified to understand their role in implantation intergration and their importance as messengers in the recruitment of T-lymphocytes at the implantation site. Opsonization was utilised to understand the influence of serum proteins on particle-induced cytokine production and release. Different metal compositions were used in the particulate format, Titanium (Ti), Titanium alloy (Ti6Al4V), and Stainless Steel 316L (SS), and were cultured in vitro with a mixed population of monocytes/macrophages and lymphocytes. The cells were also exposed to an exogenous stimulant mixture of phytohemagglutinin-P and interferon-gamma (IFN-γ) and opsonized particles with human serum. Interleukins, IL-1α, IL-1β, IL-2, IL-4, IL-6, IL-8, IFN-γ, and tumor necrosis factor-alpha (TNF-α) were investigated using enzyme-linked immunosorbent assay as they are an indicator of the inflammation evoked by particulate metals. It has been experimentally evidenced that metal particles induced higher amounts of IL-6 and IL-1 but very low amounts of TNF-α. T-lymphocyte activation was evaluated by the quantification of IL-2 and IFN-γ levels. The results showed that nonopsonized and opsonized metal particles did not induce the release of increased levels of IL-2 and IFN-γ. Copyright © 2013 Wiley Periodicals, Inc.

Momentum and Heat Transfer Models for Detonation in Nitromethane with Metal Particles

NASA Astrophysics Data System (ADS)

Ripley, Robert; Zhang, Fan; Lien, Fue-Sang

2009-06-01

Models for momentum and heat exchange have been derived from the results of previous 3D mesoscale simulations of detonation in packed aluminum particles saturated with nitromethane, where the shock interaction timescale was resolved. In these models, particle acceleration and heating within the shock and detonation zone have been expressed in terms of velocity and temperature transmission factors, which are a function of metal to explosive density ratio, metal volume fraction and ratio of particle size to detonation zone thickness. These models are incorporated as source terms in the governing equations for continuum dense two-phase flow and macroscopic simulation is then applied to detonation of nitromethane/aluminum in lightly-cased cylinders. Heterogeneous detonation features such as velocity deficit, enhanced pressure, and critical diameter effects are reproduced. Various spherical particle diameters from 3 -- 30 μm are utilized where most of the particles react in the expanding detonation products. Results for detonation velocity, pressure history, failure and U-shaped critical diameter behavior are compared to the existing experiments.

The critical particle size for enhancing thermal conductivity in metal nanoparticle-polymer composites

NASA Astrophysics Data System (ADS)

Lu, Zexi; Wang, Yan; Ruan, Xiulin

2018-02-01

Polymers used as thermal interface materials are often filled with high-thermal conductivity particles to enhance the thermal performance. Here, we have combined molecular dynamics and the two-temperature model in 1D to investigate the impact of the metal filler size on the overall thermal conductivity. A critical particle size has been identified above which thermal conductivity enhancement can be achieved, caused by the interplay between high particle thermal conductivity and the added electron-phonon and phonon-phonon thermal boundary resistance brought by the particle fillers. Calculations on the SAM/Au/SAM (self-assembly-monolayer) system show a critical thickness Lc of around 10.8 nm. Based on the results, we define an effective thermal conductivity and propose a new thermal circuit analysis approach for the sandwiched metal layer that can intuitively explain simulation and experimental data. The results show that when the metal layer thickness decreases to be much smaller than the electron-phonon cooling length (or as the "thin limit"), the effective thermal conductivity is just the phonon portion, and electrons do not participate in thermal transport. As the thickness increases to the "thick limit," the effective thermal conductivity recovers the metal bulk value. Several factors that could affect Lc are discussed, and it is discovered that the thermal conductivity, thermal boundary resistance, and the electron-phonon coupling factor are all important in controlling Lc.

Compaction of granular materials composed of deformable particles

NASA Astrophysics Data System (ADS)

Nguyen, Thanh Hai; Nezamabadi, Saeid; Delenne, Jean-Yves; Radjai, Farhang

2017-06-01

In soft particle materials such as metallic powders the particles can undergo large deformations without rupture. The large elastic or plastic deformations of the particles are expected to strongly affect the mechanical properties of these materials compared to hard particle materials more often considered in research on granular materials. Herein, two numerical approaches are proposed for the simulation of soft granular systems: (i) an implicit formulation of the Material Point Method (MPM) combined with the Contact Dynamics (CD) method to deal with contact interactions, and (i) Bonded Particle Model (BPM), in which each deformable particle is modeled as an aggregate of rigid primary particles using the CD method. These two approaches allow us to simulate the compaction of an assembly of elastic or plastic particles. By analyzing the uniaxial compaction of 2D soft particle packings, we investigate the effects of particle shape change on the stress-strain relationship and volume change behavior as well as the evolution of the microstructure.

Microstructure and Thermal History of Metal Particles in CH Chondrites

NASA Astrophysics Data System (ADS)

Goldstein, J. I.; Jones, R. H.; Kotula, P. G.; Michael, J. R.

2005-03-01

This paper provides detailed microstructural and microchemical information at the nm to µm scale (SEM, EPMA, TEM, EBSD) for a select suite of metal particles in four CH chondrites, ALH 85085, PAT 91546, Acfer 214, NWA 739.

Co-electrodeposition of hard Ni-W/diamond nanocomposite coatings

PubMed Central

Zhang, Xinyu; Qin, Jiaqian; Das, Malay Kumar; Hao, Ruru; Zhong, Hua; Thueploy, Adisak; Limpanart, Sarintorn; Boonyongmaneerat, Yuttanant; Ma, Mingzhen; Liu, Riping

2016-01-01

Electroplated hard chrome coating is widely used as a wear resistant coating to prolong the life of mechanical components. However, the electroplating process generates hexavalent chromium ion which is known carcinogen. Hence, there is a major effort throughout the electroplating industry to replace hard chrome coating. Composite coating has been identified as suitable materials for replacement of hard chrome coating, while deposition coating prepared using traditional co-deposition techniques have relatively low particles content, but the content of particles incorporated into a coating may fundamentally affect its properties. In the present work, Ni-W/diamond composite coatings were prepared by sediment co-electrodeposition from Ni-W plating bath, containing suspended diamond particles. This study indicates that higher diamond contents could be successfully co-deposited and uniformly distributed in the Ni-W alloy matrix. The maximum hardness of Ni-W/diamond composite coatings is found to be 2249 ± 23 Hv due to the highest diamond content of 64 wt.%. The hardness could be further enhanced up to 2647 ± 25 Hv with heat treatment at 873 K for 1 h in Ar gas, which is comparable to hard chrome coatings. Moreover, the addition of diamond particles could significantly enhance the wear resistance of the coatings. PMID:26924136

Co-electrodeposition of hard Ni-W/diamond nanocomposite coatings.

PubMed

Zhang, Xinyu; Qin, Jiaqian; Das, Malay Kumar; Hao, Ruru; Zhong, Hua; Thueploy, Adisak; Limpanart, Sarintorn; Boonyongmaneerat, Yuttanant; Ma, Mingzhen; Liu, Riping

2016-02-29

Electroplated hard chrome coating is widely used as a wear resistant coating to prolong the life of mechanical components. However, the electroplating process generates hexavalent chromium ion which is known carcinogen. Hence, there is a major effort throughout the electroplating industry to replace hard chrome coating. Composite coating has been identified as suitable materials for replacement of hard chrome coating, while deposition coating prepared using traditional co-deposition techniques have relatively low particles content, but the content of particles incorporated into a coating may fundamentally affect its properties. In the present work, Ni-W/diamond composite coatings were prepared by sediment co-electrodeposition from Ni-W plating bath, containing suspended diamond particles. This study indicates that higher diamond contents could be successfully co-deposited and uniformly distributed in the Ni-W alloy matrix. The maximum hardness of Ni-W/diamond composite coatings is found to be 2249 ± 23 Hv due to the highest diamond content of 64 wt.%. The hardness could be further enhanced up to 2647 ± 25 Hv with heat treatment at 873 K for 1 h in Ar gas, which is comparable to hard chrome coatings. Moreover, the addition of diamond particles could significantly enhance the wear resistance of the coatings.

Co-electrodeposition of hard Ni-W/diamond nanocomposite coatings

NASA Astrophysics Data System (ADS)

Zhang, Xinyu; Qin, Jiaqian; Das, Malay Kumar; Hao, Ruru; Zhong, Hua; Thueploy, Adisak; Limpanart, Sarintorn; Boonyongmaneerat, Yuttanant; Ma, Mingzhen; Liu, Riping

2016-02-01

Electroplated hard chrome coating is widely used as a wear resistant coating to prolong the life of mechanical components. However, the electroplating process generates hexavalent chromium ion which is known carcinogen. Hence, there is a major effort throughout the electroplating industry to replace hard chrome coating. Composite coating has been identified as suitable materials for replacement of hard chrome coating, while deposition coating prepared using traditional co-deposition techniques have relatively low particles content, but the content of particles incorporated into a coating may fundamentally affect its properties. In the present work, Ni-W/diamond composite coatings were prepared by sediment co-electrodeposition from Ni-W plating bath, containing suspended diamond particles. This study indicates that higher diamond contents could be successfully co-deposited and uniformly distributed in the Ni-W alloy matrix. The maximum hardness of Ni-W/diamond composite coatings is found to be 2249 ± 23 Hv due to the highest diamond content of 64 wt.%. The hardness could be further enhanced up to 2647 ± 25 Hv with heat treatment at 873 K for 1 h in Ar gas, which is comparable to hard chrome coatings. Moreover, the addition of diamond particles could significantly enhance the wear resistance of the coatings.

Metal wastage design guidelines for bubbling fluidized-bed combustors. Final report

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

Lyczkowski, R.W.; Podolski, W.F.; Bouillard, J.X.

These metal wastage design guidelines identify relationships between metal wastage and (1) design parameters (such as tube size, tube spacing and pitch, tube bundle and fluidized-bed height to distributor, and heat exchanger tube material properties) and (2) operating parameters (such as fluidizing velocity, particle size, particle hardness, and angularity). The guidelines are of both a quantitative and qualitative nature. Simplified mechanistic models are described, which account for the essential hydrodynamics and metal wastage processes occurring in bubbling fluidized beds. The empirical correlational approach complements the use of these models in the development of these design guidelines. Data used for modelmore » and guideline validation are summarized and referenced. Sample calculations and recommended design procedures are included. The influences of dependent variables on metal wastage, such as solids velocity, bubble size, and in-bed pressure fluctuations, are discussed.« less

Particle/fluid simulations of an eruptive flare: Identifying the field-aligned currents responsible for the hard x-rays

NASA Astrophysics Data System (ADS)

Winglee, R. M.

1994-09-01

While magnetohydrodynamics (MHD) can provide a reasonable description of the overall magnetic reconnection that is believed to drive flares, additional, and often separate processes have to be envoked to in order to explain the electron acceleration that is responsible for many of the observed flare emissions. A new model that incorporates the dynamic coronal current sheets, the reconnection site, and possible electron acceleration processes is developed through the use of two-dimensional particle and modified two-fluid simulations. The specific example of an eruptive flare driven by the coalescence of flux tubes supported by prescribed photospheric current elements is evaluated. It is shown that the electrons and ions have differential trajectories through the coronal current sheet which leads to the development of additonal plasma currents that flow around the surface of the current sheet. These surface currents are explicitly neglected in MHD but they are vital to the flare dynamics because they divert current from the coronal current sheet into the chromosphere, producing an effective resistivity that aids the development of fast reconnection. Because the surface currents are in the plane of the magnetic field, electrons in them experience strong acceleration and can account for the observed hard X-ray emissions. Model predictions are compared with observed time profiles of hard X-ray emissions and Doppler shifts seen in soft X-ray line emissions and are able to account for such features as (1) the asymmetry in the rise and decay time of the hard X-rays, (2) the apparent delay between the largest Doppler shifts and the hard X-ray peak, and (3) the relatively low intensity of the blue-shifted component. The use of particle and fluid simulations is important because it provides different, but complementary treatments of the electron acceleration, the global magnetic morphology, and the flare current system.

Insights into metals in individual fine particles from municipal solid waste using synchrotron radiation-based micro-analytical techniques.

PubMed

Zhu, Yumin; Zhang, Hua; Shao, Liming; He, Pinjing

2015-01-01

Excessive inter-contamination with heavy metals hampers the application of biological treatment products derived from mixed or mechanically-sorted municipal solid waste (MSW). In this study, we investigated fine particles of <2mm, which are small fractions in MSW but constitute a significant component of the total heavy metal content, using bulk detection techniques. A total of 17 individual fine particles were evaluated using synchrotron radiation-based micro-X-ray fluorescence and micro-X-ray diffraction. We also discussed the association, speciation and source apportionment of heavy metals. Metals were found to exist in a diffuse distribution with heterogeneous intensities and intense hot-spots of <10 μm within the fine particles. Zn-Cu, Pb-Fe and Fe-Mn-Cr had significant correlations in terms of spatial distribution. The overlapped enrichment, spatial association, and the mineral phases of metals revealed the potential sources of fine particles from size-reduced waste fractions (such as scraps of organic wastes or ceramics) or from the importation of other particles. The diverse sources of heavy metal pollutants within the fine particles suggested that separate collection and treatment of the biodegradable waste fraction (such as food waste) is a preferable means of facilitating the beneficial utilization of the stabilized products. Copyright © 2014. Published by Elsevier B.V.

Femtosecond ablation applied to deep-drilling of hard metals

NASA Astrophysics Data System (ADS)

Bruneau, Sebastien; Hermann, Joerg; Dumitru, Gabriel; Sentis, Marc L.

2004-09-01

Mechanisms responsible for the limitation of the aspect ratio obtained by deep drilling of hard metals are investigated in the present work. Cemented carbide targets have been irradiated with laser pulses of 100 fs duration and 100 μJ maximum energy delivered by a Ti:sapphire laser system. The experiments are carried out in different gas environments (vacuum, air, helium up to atmospheric pressure) with incident laser fluences ranging from 1 to 20 Jcm-2. During deep drilling, the laser-induced ablation plume is characterized by means of in-situ plasma diagnostics. Fast imaging is used to observe the expansion behavior of the plasma plume whereas time- and space-resolved emission spectroscopy is employed to analyze the plasma composition. After irradiation, the laser-produced craters were examined by optical microscopy. A correlation between the ablation plume characteristics and the morphological changes of the mciro-holes is established. The results indicate that nanoclusters, that present a significant part of the ablated material, are responsbile for the alteration of the crater shape in the high laser fluence regime.

Influence of natural organic matter on the adsorption of metal ion onto clay particles

USGS Publications Warehouse

Schmitt, D.; Taylor, Howard E.; Aiken, G.R.; Roth, D.A.; Frimmel, F.H.

2002-01-01

The influence of natural organic matter (NOM) on the adsorption of Al, Fe, Zn, and Pb onto clay minerals was investigated. Adsorption experiments were carried out at pH = 5 and pH = 7 in the presence and absence of NOM. In general, the presence of NOM decreased the adsorption of metal ions onto the clay particles. Al and Fe were strongly influenced by NOM, whereas Zn and Pb adsorption was only slightly altered. The interaction of the metal ions with the minerals and the influence of NOM on this interaction was investigated by coupling SdFFF with an inductively coupled plasma mass spectrometer (ICPMS) or an inductively coupled plasma atomic emission spectrometer (ICPAES). Quantitative atomization of the clay particles in the ICP was confirmed by comparing elemental content determined by direct injection of the clay into the ICPMS with values from acid digestion. Particle sizes of the clays were found to be between 0.1 and 1 μm by sedimentation field-flow fractionation (SdFFF) with UV detection. Aggregation of particles due to metal adsorption was observed using SdFFF-ICPMS measurements. This aggregation was dependent on the specific metal ion and decreased in the presence of NOM and at higher pH value.

Self assembly of nano metric metallic particles for realization of photonic and electronic nano transistors.

PubMed

Shahmoon, Asaf; Limon, Ofer; Girshevitz, Olga; Zalevsky, Zeev

2010-05-25

In this paper, we present the self assembly procedure as well as experimental results of a novel method for constructing well defined arrangements of self assembly metallic nano particles into sophisticated nano structures. The self assembly concept is based on focused ion beam (FIB) technology, where metallic nano particles are self assembled due to implantation of positive gallium ions into the insulating material (e.g., silica as in silicon on insulator wafers) that acts as intermediary layer between the substrate and the negatively charge metallic nanoparticles.

Constraining the particle spectrum in blazar jets: importance of the hard X-ray spectrum

NASA Astrophysics Data System (ADS)

Sinha, Atreyee; Sahayanathan, Sunder; Chitnis, Varsha

2016-07-01

Measurement of the spectral curvature in blazar jets can throw light on the underlying particle spectral distribution, and hence, the acceleration and diffusion processes at play. With the advent of NuSTAR and ASTROSAT, and the upcoming ASTRO-H, this curvature can now be measured accurately across the broadband X-ray energies. We will discuss results from our recent works on two HBLs, Mkn421 (Sinha et al, A&A 2015) and 1ES1011+496 (Sinha et al, ApJ submitted), and show how simultaneous measurement at hard and soft X-ray energies can be crucial in understanding the underlying particle spectrum. Detection of lognormality in blazars is beginning to hint at strong disk-jet connections. India's recently launched multiwavelength satellite, the ASTROSAT will provide simultaneous time resolved data between 0.2-80keV, along with measurements at Optical-UV energies. We will discuss prospects from ASTROSAT for studying jet triggering mechanisms in blazars.

Effective hard x-ray spectrum of a tabletop Mather-type plasma focus optimized for flash radiography of metallic objects

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

Raspa, V.; Moreno, C.; Sigaut, L.

The effective spectrum of the hard x-ray output of a Mather-type tabletop plasma focus device was determined from attenuation data on metallic samples using commercial radiographic film coupled to a Gd{sub 2}O{sub 2}S:Tb phosphor intensifier screen. It was found that the radiation has relevant spectral components in the 40-150 keV range, with a single maximum around 60-80 keV. The radiation output allows for 50 ns resolution, good contrast, and introspective imaging of metallic objects even through metallic walls. A numerical estimation of the induced voltage on the focus during the compressional stage is briefly discussed.

Bioaccessibility of micron-sized powder particles of molybdenum metal, iron metal, molybdenum oxides and ferromolybdenum--Importance of surface oxides.

PubMed

Mörsdorf, Alexander; Odnevall Wallinder, Inger; Hedberg, Yolanda

2015-08-01

The European chemical framework REACH requires that hazards and risks posed by chemicals, including alloys and metals, that are manufactured, imported or used in different products (substances or articles) are identified and proven safe for humans and the environment. Metals and alloys need hence to be investigated on their extent of released metals (bioaccessibility) in biologically relevant environments. Read-across from available studies may be used for similar materials. This study investigates the release of molybdenum and iron from powder particles of molybdenum metal (Mo), a ferromolybdenum alloy (FeMo), an iron metal powder (Fe), MoO2, and MoO3 in different synthetic body fluids of pH ranging from 1.5 to 7.4 and of different composition. Spectroscopic tools and cyclic voltammetry have been employed to characterize surface oxides, microscopy, light scattering and nitrogen absorption for particle characterization, and atomic absorption spectroscopy to quantify released amounts of metals. The release of molybdenum from the Mo powder generally increased with pH and was influenced by the fluid composition. The mixed iron and molybdenum surface oxide of the FeMo powder acted as a barrier both at acidic and weakly alkaline conditions. These findings underline the importance of the surface oxide characteristics for the bioaccessibility of metal alloys. Copyright © 2015 The Authors. Published by Elsevier Inc. All rights reserved.

Self Assembly of Nano Metric Metallic Particles for Realization of Photonic and Electronic Nano Transistors

PubMed Central

Shahmoon, Asaf; Limon, Ofer; Girshevitz, Olga; Zalevsky, Zeev

2010-01-01

In this paper, we present the self assembly procedure as well as experimental results of a novel method for constructing well defined arrangements of self assembly metallic nano particles into sophisticated nano structures. The self assembly concept is based on focused ion beam (FIB) technology, where metallic nano particles are self assembled due to implantation of positive gallium ions into the insulating material (e.g., silica as in silicon on insulator wafers) that acts as intermediary layer between the substrate and the negatively charge metallic nanoparticles. PMID:20559513

Sound controlled rotation of a cluster of small particles on an ultrasonically vibrating metal strip

NASA Astrophysics Data System (ADS)

Zhang, Xueyi; Zheng, Yun; Hu, Junhui

2008-01-01

We show that a vibrating metal strip, mechanically driven by an ultrasonic transducer, can rotate a cluster of small particles around a fixed point, and the diameter of the cluster of small particles can reach a stable value (steady diameter) for a given driving condition. The rotation is very stable when the vibration of the metal strip is appropriate. The revolution speed, its direction, and steady diameter of the particle cluster can be controlled by the operating frequency of the ultrasonic transducer. For shrimp eggs, a revolution speed up to 360rpm can be obtained.

METAL DIFFUSION IN SMOOTHED PARTICLE HYDRODYNAMICS SIMULATIONS OF DWARF GALAXIES

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

Williamson, David; Martel, Hugo; Kawata, Daisuke, E-mail: david-john.williamson.1@ulaval.ca

2016-05-10

We perform a series of smoothed particle hydrodynamics simulations of isolated dwarf galaxies to compare different metal mixing models. In particular, we examine the role of diffusion in the production of enriched outflows and in determining the metallicity distributions of gas and stars. We investigate different diffusion strengths by changing the pre-factor of the diffusion coefficient, by varying how the diffusion coefficient is calculated from the local velocity distribution, and by varying whether the speed of sound is included as a velocity term. Stronger diffusion produces a tighter [O/Fe]–[Fe/H] distribution in the gas and cuts off the gas metallicity distributionmore » function at lower metallicities. Diffusion suppresses the formation of low-metallicity stars, even with weak diffusion, and also strips metals from enriched outflows. This produces a remarkably tight correlation between “metal mass-loading” (mean metal outflow rate divided by mean metal production rate) and the strength of diffusion, even when the diffusion coefficient is calculated in different ways. The effectiveness of outflows at removing metals from dwarf galaxies and the metal distribution of the gas is thus dependent on the strength of diffusion. By contrast, we show that the metallicities of stars are not strongly dependent on the strength of diffusion, provided that some diffusion is present.« less

A preliminary evaluation of immune stimulation following exposure to metal particles and ions using the mouse popliteal lymph node assay

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

Tvermoes, Brooke E., E-mail: brooke.tvermoes@cardn

The objective of this preliminary study was to evaluate the threshold for immune stimulation in mice following local exposure to metal particles and ions representative of normal-functioning cobalt-chromium (CoCr) metal-on-metal (MoM) hip implants. The popliteal lymph node assay (PLNA) was used in this study to assess immune responses in BALB/c mice following treatment with chromium-oxide (Cr{sub 2}O{sub 3}) particles, metal salts (CoCl{sub 2}, CrCl{sub 3} and NiCl{sub 2}), or Cr{sub 2}O{sub 3} particles together with metal salts using single-dose exposures representing approximately 10 days (0.000114 mg), 19 years (0.0800 mg), and 40 years (0.171 mg) of normal implant wear. Themore » immune response elicited following treatment with Cr{sub 2}O{sub 3} particles together with metal salts was also assessed at four additional doses equivalent to approximately 1.5 months (0.0005 mg), 0.6 years (0.0025 mg), 2.3 years (0.01 mg), and 9.3 years (0.04 mg) of normal implant wear. Mice were injected subcutaneously (50 μL) into the right hind foot with the test article, or with the relevant vehicle control. The proliferative response of the draining lymph node cells (LNC) was measured four days after treatment, and stimulation indices (SI) were derived relative to vehicle controls. The PLNA was negative (SI < 3) for all Cr{sub 2}O{sub 3} particle doses, and was also negative at the lowest dose of the metal salt mixture, and the lowest four doses of the Cr{sub 2}O{sub 3} particles with metal salt mixture. The PLNA was positive (SI > 3) at the highest two doses of the metal salt mixture and the highest three doses of the Cr{sub 2}O{sub 3} particles with the metal salt mixture. The provisional NOAEL and LOAEL values identified in this study for immune activation corresponds to Co and Cr concentrations in the synovial fluid approximately 500 and 2000 times higher than that reported for normal-functioning MoM hip implants, respectively. Overall, these results indicate that

Interference effects in laser-induced plasma emission from surface-bound metal micro-particles.

PubMed

Feigenbaum, Eyal; Malik, Omer; Rubenchik, Alexander M; Matthews, Manyalibo J

2017-05-01

The light-matter interaction of an optical beam and metal micro-particulates at the vicinity of an optical substrate surface is critical to the many fields of applied optics. Examples of impacted fields are laser-induced damage in high power laser systems, sub-wavelength laser machining of transmissive materials, and laser-target interaction in directed energy applications. We present a full-wave-based model that predicts the laser-induced plasma pressure exerted on a substrate surface as a result of light absorption in surface-bound micron-scale metal particles. The model predictions agree with experimental observation of laser-induced shallow pits, formed by plasma emission and etching from surface-bound metal micro-particulates. It provides an explanation for the prototypical side lobes observed along the pit profile, as well as for the dependence of the pit shape on the incident laser and particle parameters. Furthermore, the model highlights the significance of the interference of the incident light in the open cavity geometry formed between the micro-particle and the substrate in the resulting pit shape.

Electroerosion micro- and nanopowders for the production of hard alloys

NASA Astrophysics Data System (ADS)

Latypov, R. A.; Ageeva, E. V.; Kruglyakov, O. V.; Latypova, G. R.

2016-06-01

The shape and the surface morphology of the powder particles fabricated by the electroerosion dispersion of tungsten-containing wastes in illuminating oil are studied. The hard alloy fabricated from these powder particles is analyzed by electron-probe microanalysis. The powder synthesized by the electroerosion dispersion of the wastes of sintered hard alloys is found to consist of particles of a spherical or elliptical shape, an irregular shape (conglomerates), and a fragment shape. It is shown that W, Ti, and Co are the main elements in the hard alloy fabricated from the powder synthesized by electroerosion dispersion in illuminating oil.

Bioleaching of metals from spent refinery petroleum catalyst using moderately thermophilic bacteria: effect of particle size.

PubMed

Srichandan, Haragobinda; Singh, Sradhanjali; Pathak, Ashish; Kim, Dong-Jin; Lee, Seoung-Won; Heyes, Graeme

2014-01-01

The present work investigated the leaching potential of moderately thermophilic bacteria in the recovery of metals from spent petroleum catalyst of varying particle sizes. The batch bioleaching experiments were conducted by employing a mixed consortium of moderate thermophilic bacteria at 45°C and by using five different particle sizes (from 45 to >2000 μm) of acetone-washed spent catalyst. The elemental mapping by FESEM confirmed the presence of Al, Ni, V and Mo along with sulfur in the spent catalyst. During bioleaching, Ni (92-97%) and V (81-91%) were leached in higher concentrations, whereas leaching yields of Al (23-38%) were found to be lowest in all particle sizes investigated. Decreasing the particle size from >2000 μm to 45-106 μm caused an increase in leaching yields of metals during initial hours. However, the final metals leaching yields were almost independent of particle sizes of catalyst. Leaching kinetics was observed to follow the diffusion-controlled model showing the linearity more close than the chemical control. The results of the present study suggested that bioleaching using moderate thermophilic bacteria was highly effective in removing the metals from spent catalyst. Moreover, bioleaching can be conducted using spent catalyst of higher particle size (>2000 μm), thus saving the grinding cost and making process attractive for larger scale application.

The successful of finite element to invent particle cleaning system by air jet in hard disk drive

NASA Astrophysics Data System (ADS)

Jai-Ngam, Nualpun; Tangchaichit, Kaitfa

2018-02-01

Hard Disk Drive manufacturing has faced very challenging with the increasing demand of high capacity drives for Cloud-based storage. Particle adhesion has also become increasingly important in HDD to gain more reliability of storage capacity. The ability to clean on surfaces is more complicated in removing such particles without damaging the surface. This research is aim to improve the particle cleaning in HSA by using finite element to develop the air flow model then invent the prototype of air cleaning system to remove particle from surface. Surface cleaning by air pressure can be applied as alternative for the removal of solid particulate contaminants that is adhering on a solid surface. These technical and economic challenges have driven the process development from traditional way that chemical solvent cleaning. The focus of this study is to develop alternative way from scrub, ultrasonic, mega sonic on surface cleaning principles to serve as a foundation for the development of new processes to meet current state-of-the-art process requirements and minimize the waste from chemical cleaning for environment safety.

Metallic particles from the Macha meteorite crater and several placer deposits in Iakutiia

NASA Astrophysics Data System (ADS)

Gurov, E. P.; Kolesov, G. M.; Kudinova, L. A.; Rakitskaia, R. B.; Samoilovich, L. G.

The composition of metallic particles from the Macha crater in Iakutiia is shown to be close to the composition of cosmogenic particles from the region of the Tungusk meteorite as well as Ukrainian placer deposits. A description is given of cosmogenic particles from placer deposits of northern Iakutiia, whose formation may be connected with a large impact event in the northeastern part of the USSR.

Traceability in hardness measurements: from the definition to industry

NASA Astrophysics Data System (ADS)

Germak, Alessandro; Herrmann, Konrad; Low, Samuel

2010-04-01

The measurement of hardness has been and continues to be of significant importance to many of the world's manufacturing industries. Conventional hardness testing is the most commonly used method for acceptance testing and production quality control of metals and metallic products. Instrumented indentation is one of the few techniques available for obtaining various property values for coatings and electronic products in the micrometre and nanometre dimensional scales. For these industries to be successful, it is critical that measurements made by suppliers and customers agree within some practical limits. To help assure this measurement agreement, a traceability chain for hardness measurement traceability from the hardness definition to industry has developed and evolved over the past 100 years, but its development has been complicated. A hardness measurement value not only requires traceability of force, length and time measurements but also requires traceability of the hardness values measured by the hardness machine. These multiple traceability paths are needed because a hardness measurement is affected by other influence parameters that are often difficult to identify, quantify and correct. This paper describes the current situation of hardness measurement traceability that exists for the conventional hardness methods (i.e. Rockwell, Brinell, Vickers and Knoop hardness) and for special-application hardness and indentation methods (i.e. elastomer, dynamic, portables and instrumented indentation).

Theoretic model and computer simulation of separating mixture metal particles from waste printed circuit board by electrostatic separator.

PubMed

Li, Jia; Xu, Zhenming; Zhou, Yaohe

2008-05-30

Traditionally, the mixture metals from waste printed circuit board (PCB) were sent to the smelt factory to refine pure copper. Some valuable metals (aluminum, zinc and tin) with low content in PCB were lost during smelt. A new method which used roll-type electrostatic separator (RES) to recovery low content metals in waste PCB was presented in this study. The theoretic model which was established from computing electric field and the analysis of forces on the particles was used to write a program by MATLAB language. The program was design to simulate the process of separating mixture metal particles. Electrical, material and mechanical factors were analyzed to optimize the operating parameters of separator. The experiment results of separating copper and aluminum particles by RES had a good agreement with computer simulation results. The model could be used to simulate separating other metal (tin, zinc, etc.) particles during the process of recycling waste PCBs by RES.

Method of producing homogeneous mixed metal oxides and metal-metal oxide mixtures

DOEpatents

Quinby, Thomas C.

1978-01-01

Metal powders, metal oxide powders, and mixtures thereof of controlled particle size are provided by reacting an aqueous solution containing dissolved metal values with excess urea. Upon heating, urea reacts with water from the solution leaving a molten urea solution containing the metal values. The molten urea solution is heated to above about 180.degree. C. whereupon metal values precipitate homogeneously as a powder. The powder is reduced to metal or calcined to form oxide particles. One or more metal oxides in a mixture can be selectively reduced to produce metal particles or a mixture of metal and metal oxide particles.

How to estimate hardness of crystals on a pocket calculator

NASA Astrophysics Data System (ADS)

Šimůnek, Antonín

2007-05-01

A generalization of the semiempirical microscopic model of hardness is presented and applied to currently studied borides, carbides, and nitrides of heavy transition metals. The hardness of OsB, OsC, OsN, PtN, RuC, RuB2 , ReB2 , OsB2 , IrN2 , PtN2 , and OsN2 crystals in various structural phases is predicted. It is found that none of the transition metal crystals is superhard, i.e., with hardness greater than 40GPa . The presented method provides materials researchers with a practical tool in the search for new hard materials.

Dry sliding wear of heat treated hybrid metal matrix composites

NASA Astrophysics Data System (ADS)

Naveed, Mohammed; Khan, A. R. Anwar

2016-09-01

In recent years, there has been an ever-increasing demand for enhancing mechanical properties of Aluminum Matrix Composites (AMCs), which are finding wide applications in the field of aerospace, automobile, defence etc,. Among all available aluminium alloys, Al6061 is extensively used owing to its excellent wear resistance and ease of processing. Newer techniques of improving the hardness and wear resistance of Al6061 by dispersing an appropriate mixture of hard ceramic powder and whiskers in the aluminium alloy are gaining popularity. The conventional aluminium based composites possess only one type of reinforcements. Addition of hard reinforcements such as silicon carbide, alumina, titanium carbide, improves hardness, strength and wear resistance of the composites. However, these composites possessing hard reinforcement do posses several problems during their machining operation. AMCs reinforced with particles of Gr have been reported to be possessing better wear characteristics owing to the reduced wear because of formation of a thin layer of Gr particles, which prevents metal to metal contact of the sliding surfaces. Further, heat treatment has a profound influence on mechanical properties of heat treatable aluminium alloys and its composites. For a solutionising temperature of 5500C, solutionising duration of 1hr, ageing temperature of 1750C, quenching media and ageing duration significantly alters mechanical properties of both aluminium alloy and its composites. In the light of the above, the present paper aims at developing aluminium based hybrid metal matrix composites containing both silicon carbide and graphite and characterize their mechanical properties by subjecting it to heat treatment. Results indicate that increase of graphite content increases wear resistance of hybrid composites reinforced with constant SiC reinforcement. Further heat treatment has a profound influence on the wear resistance of the matrix alloy as well as its hybrid composites

Hard and low friction nitride coatings and methods for forming the same

DOEpatents

Erdemir, Ali; Urgen, Mustafa; Cakir, Ali Fuat; Eryilmaz, Osman Levent; Kazmanli, Kursat; Keles, Ozgul

2007-05-01

An improved coating material possessing super-hard and low friction properties and a method for forming the same. The improved coating material includes the use of a noble metal or soft metal homogeneously distributed within a hard nitride material. The addition of small amounts of such metals into nitrides such as molybdenum nitride, titanium nitride, and chromium nitride results in as much as increasing of the hardness of the material as well as decreasing the friction coefficient and increasing the oxidation resistance.

Endotoxin in Size-Separated Metal Working Fluid Aerosol Particles.

PubMed

Dahlman-Höglund, Anna; Lindgren, Åsa; Mattsby-Baltzer, Inger

2016-08-01

Patients with airway symptoms working in metal working industries are increasing, despite efforts to improve the environmental air surrounding the machines. Our aim was to analyse the amount of endotoxin in size-separated airborne particles of metal working fluid (MWF) aerosol, by using the personal sampler Sioutas cascade impactor, to compare filter types, and to compare the concentration of airborne endotoxin to that of the corresponding MWFs. In a pilot field study, aerosols were collected in two separate machine halls on totally 10 occasions, using glass fibre and polytetrafluoroethylene (PTFE) filters in parallel at each station. Airborne endotoxin was distributed over all size fractions. While a major part was found in the largest size fraction (72%, 2.5-10 µm), up to 8% of the airborne endotoxin was detected in the smallest size fraction (<0.25 µm). Comparing the efficiency of the filter types, a significantly higher median endotoxin level was found with glass fibres filters collecting the largest particle-size fraction (1.2-fold) and with PTFE filters collecting the smallest ones (5-fold). The levels of endotoxin in the size-separated airborne particle fractions correlated to those of the MWFs supporting the aerosol-generating machines. Our study indicates that a significant part of inhalable aerosols of MWFs consists of endotoxin-containing particles below the size of intact bacteria, and thus small enough to readily reach the deepest part of the lung. Combined with other chemical irritants of the MWF, exposure to MWF aerosols containing endotoxin pose a risk to respiratory health problems. © The Author 2016. Published by Oxford University Press on behalf of the British Occupational Hygiene Society.

Economic Assessment for Recycling Critical Metals From Hard Disk Drives Using a Comprehensive Recovery Process

NASA Astrophysics Data System (ADS)

Nguyen, Ruby Thuy; Diaz, Luis A.; Imholte, D. Devin; Lister, Tedd E.

2017-09-01

Since the 2011 price spike of rare earth elements (REEs), research on permanent magnet recycling has blossomed globally in an attempt to reduce future REE criticality. Hard disk drives (HDDs) have emerged as one feasible feedstock for recovering valuable REEs such as praseodymium, neodymium, and dysprosium. Nevertheless, current processes for recycling electronic waste only focus on certain metals as a result of feedstock and metal price uncertainties. In addition, there is a perception that recycling REEs is unprofitable. To shed some light on the economic viability of REE recycling from U.S. HDDs, this article combines techno-economic information of an electro-hydrometallurgical process with end-of-life HDD availability in a simulation model. The results showed that adding REE recovery to an HDD base and precious metal recovery process was profitable given current prices. Recovered REEs from U.S. HDDs could meet up to 5.2% rest-of-world (excluding China) neodymium magnet demand. Feedstock, aluminum, and gold prices are key factors to recycling profitability. REEs contributed 13% to the co-recycling profit.

Adsorption of Cashew Allergens to Acid-Etched Zinc Metal Particles

USDA-ARS?s Scientific Manuscript database

Galvanized metal surfaces are approved by the FDA for use in many food processing steps. Food allergens can cause severe reactions even in very small amounts, and surfaces contaminated with allergens could pose a serious threat. The binding of cashew allergens to zinc particles was evaluated. Whi...

Radiation hardness of β-Ga2O3 metal-oxide-semiconductor field-effect transistors against gamma-ray irradiation

NASA Astrophysics Data System (ADS)

Wong, Man Hoi; Takeyama, Akinori; Makino, Takahiro; Ohshima, Takeshi; Sasaki, Kohei; Kuramata, Akito; Yamakoshi, Shigenobu; Higashiwaki, Masataka

2018-01-01

The effects of ionizing radiation on β-Ga2O3 metal-oxide-semiconductor field-effect transistors (MOSFETs) were investigated. A gamma-ray tolerance as high as 1.6 MGy(SiO2) was demonstrated for the bulk Ga2O3 channel by virtue of weak radiation effects on the MOSFETs' output current and threshold voltage. The MOSFETs remained functional with insignificant hysteresis in their transfer characteristics after exposure to the maximum cumulative dose. Despite the intrinsic radiation hardness of Ga2O3, radiation-induced gate leakage and drain current dispersion ascribed respectively to dielectric damage and interface charge trapping were found to limit the overall radiation hardness of these devices.

New Insights into Hard Phases of CoCrMo Metal-on-Metal Hip Replacements

PubMed Central

Liao, Y.; Pourzal, R.; Stemmer, P.; Wimmer, M.A.; Jacobs, J.J.; Fischer, A.; Marks, L. D.

2012-01-01

The microstructural and mechanical properties of the hard phases in CoCrMo prosthetic alloys in both cast and wrought conditions were examined using transmission electron microscopy and nanoindentation. Besides the known carbides of M23C6-type (M=Cr, Mo, Co) and M6C-type which are formed by either eutectic solidification or precipitation, a new mixed-phase hard constituent has been found in the cast alloys, which is composed of ~100 nm fine grains. The nanosized grains were identified to be mostly of M23C6 type using nano-beam precession electron diffraction, and the chemical composition varied from grain to grain being either Cr- or Co-rich. In contrast, the carbides within the wrought alloy having the same M23C6 structure were homogeneous, which can be attributed to the repeated heating and deformation steps. Nanoindentation measurements showed that the hardness of the hard phase mixture in the cast specimen was ~15.7 GPa, while the M23C6 carbides in the wrought alloy were twice as hard (~30.7 GPa). The origin of the nanostructured hard phase mixture was found to be related to slow cooling during casting. Mixed hard phases were produced at a cooling rate of 0.2 °C/s, whereas single phase carbides were formed at a cooling rate of 50 °C/s. This is consistent with sluggish kinetics and rationalizes different and partly conflicting microstructural results in the literature, and could be a source of variations in the performance of prosthetic devices in-vivo. PMID:22659365

Particle size distribution and characteristics of heavy metals in road-deposited sediments from Beijing Olympic Park.

PubMed

Li, Haiyan; Shi, Anbang; Zhang, Xiaoran

2015-06-01

Due to rapid urbanization and industrialization, heavy metals in road-deposited sediments (RDSs) of parks are emitted into the terrestrial, atmospheric, and water environment, and have a severe impact on residents' and tourists' health. To identify the distribution and characteristic of heavy metals in RDS and to assess the road environmental quality in Chinese parks, samples were collected from Beijing Olympic Park in the present study. The results indicated that particles with small grain size (<150 μm) were the dominant fraction. The length of dry period was one of the main factors affecting the particle size distribution, as indicated by the variation of size fraction with the increase of dry days. The amount of heavy metal (i.e., Cu, Zn, Pb and Cd) content was the largest in particles with small size (<150 μm) among all samples. Specifically, the percentage of Cu, Zn, Pb and Cd in these particles was 74.7%, 55.5%, 56.6% and 71.3%, respectively. Heavy metals adsorbed in sediments may mainly be contributed by road traffic emissions. The contamination levels of Pb and Cd were higher than Cu and Zn on the basis of the mean heavy metal contents. Specifically, the geoaccumulation index (Igeo) decreased in the order: Cd>Pb>Cu>Zn. This study analyzed the mobility of heavy metals in sediments using partial sequential extraction with the Tessier procedure. The results revealed that the apparent mobility and potential metal bioavailability of heavy metals in the sediments, based on the exchangeable and carbonate fractions, decreased in the order: Cd>Zn≈Pb>Cu. Copyright © 2015. Published by Elsevier B.V.

Heavy metal concentrations in particle size fractions from street dust of Murcia (Spain) as the basis for risk assessment.

PubMed

Acosta, Jose A; Faz, Ángel; Kalbitz, Karsten; Jansen, Boris; Martínez-Martínez, Silvia

2011-11-01

Street dust has been sampled from six different types of land use of the city of Murcia (Spain). The samples were fractionated into eleven particle size fractions (<2, 2-10, 10-20, 20-50, 50-75, 75-106, 106-150, 150-180, 180-425, 425-850 μm and 850-2000 μm) and analyzed for Pb, Cu, Zn and Cd. The concentrations of these four potentially toxic metals were assessed, as well as the effect of particle size on their distribution. A severe enrichment of all metals was observed for all land-uses (industrial, suburban, urban and highways), with the concentration of all metals affected by the type of land-use. Coarse and fine particles in all cases showed concentrations of metals higher than those found in undisturbed areas. However, the results indicated a preferential partitioning of metals in fine particle size fractions in all cases, following a logarithmic distribution. The accumulation in the fine fractions was higher when the metals had an anthropogenic origin. The strong overrepresentation of metals in particles <10 μm indicates that if the finest fractions are removed by a vacuum-assisted dry sweeper or a regenerative-air sweeper the risk of metal dispersion and its consequent risk for humans will be highly reduced. Therefore, we recommend that risk assessment programs include monitoring of metal concentrations in dust where each land-use is separately evaluated. The finest particle fractions should be examined explicitly in order to apply the most efficient measures for reducing the risk of inhalation and ingestion of dust for humans and risk for the environment.

Nonlocality and particle-clustering effects on the optical response of composite materials with metallic nanoparticles

NASA Astrophysics Data System (ADS)

Chen, C. W.; Chung, H. Y.; Chiang, H.-P.; Lu, J. Y.; Chang, R.; Tsai, D. P.; Leung, P. T.

2010-10-01

The optical properties of composites with metallic nanoparticles are studied, taking into account the effects due to the nonlocal dielectric response of the metal and the coalescing of the particles to form clusters. An approach based on various effective medium theories is followed, and the modeling results are compared with those from the cases with local response and particles randomly distributed through the host medium. Possible observations of our modeling results are illustrated via a calculation of the transmission of light through a thin film made of these materials. It is found that the nonlocal effects are particularly significant when the particles coalesce, leading to blue-shifted resonances and slightly lower values in the dielectric functions. The dependence of these effects on the volume fraction and fractal dimension of the metal clusters is studied in detail.

Feasibility study on development of metal matrix composite by microwave stir casting

NASA Astrophysics Data System (ADS)

Lingappa, S. M.; Srinath, M. S.; Amarendra, H. J.

2018-04-01

Need for better service oriented materials has boosted the demand for metal matrix composite materials, which can be developed to have necessary properties. One of the most widely utilized metal matrix composite is Al-SiC, which is having a matrix made of aluminium metal and SiC as reinforcement. Lightweight and conductivity of aluminium, when combined with hardness and wear resistance of SiC provides an excellent platform for various applications in the field of electronics, automotives, and aerospace and so on. However, uniform distribution of reinforcement particles is an issue and has to be addressed. The present study is an attempt made to develop Al-SiC metal matrix composite by melting base metal using microwave hybrid heating technique, followed by addition of reinforcement and stirring the mixture for obtaining homogenous mixture. X-Ray Diffraction analysis shows the presence of aluminium and SiC in the cast material. Further, microstructural study shows the distribution of SiC particles in the grain boundaries.

Simultaneous wood and metal particle detection on dark-field radiography.

PubMed

Braig, Eva-Maria; Birnbacher, Lorenz; Schaff, Florian; Gromann, Lukas; Fingerle, Alexander; Herzen, Julia; Rummeny, Ernst; Noël, Peter; Pfeiffer, Franz; Muenzel, Daniela

2018-01-01

Currently, the detection of retained wood is a frequent but challenging task in emergency care. The purpose of this study is to demonstrate improved foreign-body detection with the novel approach of preclinical X-ray dark-field radiography. At a preclinical dark-field x-ray radiography, setup resolution and sensitivity for simultaneous detection of wooden and metallic particles have been evaluated in a phantom study. A clinical setting has been simulated with a formalin fixated human hand where different typical foreign-body materials have been inserted. Signal-to-noise ratios (SNR) have been determined for all test objects. On the phantom, the SNR value for wood in the dark-field channel was strongly improved by a factor 6 compared to conventional radiography and even compared to the SNR of an aluminium structure of the same size in conventional radiography. Splinters of wood < 300 μm in diameter were clearly detected on the dark-field radiography. Dark-field radiography of the formalin-fixated human hand showed a clear signal for wooden particles that could not be identified on conventional radiography. x-ray dark-field radiography enables the simultaneous detection of wooden and metallic particles in the extremities. It has the potential to improve and simplify the current state-of-the-art foreign-body detection.

Distribution of the concentration of heavy metals associated with the sediment particles accumulated on road surfaces.

PubMed

Zafra, C A; Temprano, J; Tejero, I

2011-07-01

The heavy metal pollution caused by road run-off water constitutes a problem in urban areas. The metallic load associated with road sediment must be determined in order to study its impact in drainage systems and receiving waters, and to perfect the design of prevention systems. This paper presents data regarding the sediment collected on road surfaces in the city of Torrelavega (northern Spain) during a period of 65 days (132 samples). Two sample types were collected: vacuum-dried samples and those swept up following vacuuming. The sediment loading (g m(-2)), particle size distribution (63-2800 microm) and heavy metal concentrations were determined. The data showed that the concentration of heavy metals tends to increase with the reduction in the particle diameter (exponential tendency). The concentrations ofPb, Zn, Cu, Cr, Ni, Cd, Fe, Mn and Co in the size fraction <63 microm were 350, 630, 124, 57, 56, 38, 3231, 374 and 51 mg kg(-1), respectively (average traffic density: 3800 vehicles day(-1)). By increasing the residence time of the sediment, the concentration increases, whereas the ratio of the concentration between the different size fractions decreases. The concentration across the road diminishes when the distance between the roadway and the sampling siteincreases; when the distance increases, the ratio between size fractions for heavy metal concentrations increases. Finally, the main sources of heavy metals are the particles detached by braking (brake pads) and tyre wear (rubber), and are associated with particle sizes <125 microm.

Enhancement of bronze alloy surface properties by FSP second-phase particle incorporation

DOE PAGES

Ajayi, O. O.; Lorenzo-Martin, Cinta

2017-06-15

This study presents results of an experimental study to evaluate friction stir processing (FSP) with and without hard second-phase particle incorporation as a means to enhance surface properties and wear performance of C86300 manganese bronze alloy. FSP of flat bronze alloy specimens was conducted with hardened H-13 tool steel to create a 3-mm-thick processed surface layer. The process was also used to incorporate B 4C particles, thereby creating a metal-matrix composite layer on the alloy surface. FSP alone was observed to produce substantial reduction in grain size (from an initial value of 350 mu m to 1-5 μm). FSP withoutmore » particle incorporation resulted in modest surface hardening due to grain refinement and dispersion hardening. Under lubricated contact in block-on-ring testing with a hardened steel counter face, FSP produced substantial reduction (about 3X) in bronze wear after polishing of processing surface roughening. FSP with hard B 4C second-phase particle incorporation further reduced wear by up to 20X. The improvement in wear behavior is attributed to grain refinement and load shielding by second-phase particles, as determined by wear mechanism analysis.« less

Adhesive and abrasive wear mechanisms in ion implanted metals

NASA Astrophysics Data System (ADS)

Dearnaley, G.

1985-03-01

The distinction between adhesive and abrasive wear processes was introduced originally by Burwell during the nineteen-fifties, though some authors prefer to classify wear according to whether it is mild or severe. It is argued here that, on the basis of the performance of a variety of ion implanted metal surfaces, exposed to different modes of wear, the Burwell distinction is a valid one which, moreover, enables us to predict under which circumstances a given treatment will perform well. It is shown that, because wear rates under abrasive conditions are very sensitive to the ratio of the hardness of the surface to that of the abrasive particles, large increases in working life are attainable as a result of ion implantation. Under adhesive wear conditions, the wear rate appears to fall inversely as the hardness increases, and it is advantageous to implant species which will create and retain a hard surface oxide or other continuous film in order to reduce metal-metal contact. By the appropriate combination of physico-chemical changes in an implanted layer it has been possible to reduce wear rates by up to three orders of magnitude. Such rates compensate for the shallow depths achievable by ion implantation.

Microstructure and hardness performance of AA6061 aluminium composite using friction stir processing

NASA Astrophysics Data System (ADS)

Marini, C. D.; Fatchurrohman, N.

2018-04-01

Rice husk ash (RHA) is an industrial waste that has become a potential reinforced material for aluminium matrix composite (AMCs) due to low cost and abundantly available resources. Friction stir processing (FSP) has been introduced as a method to modify surface properties of the metal and alloy including theirs composite as well. The present work reports the production and characterization of AA6061 and AA6061/5 vol% RHA using FSP using parameters rotation speed 1000 rpm and traversed speed 25 mm/min. The microstructure was studied using optical microscopy (OM). A homogenous dispersion of RHA particles was obtained in the composite. No agglomeration or segregation was observed. The produced composite exhibited a fine grain structure. An improvement in hardness profile was observed as AA6061/5 vol% RHA improves in hardness compared to FSPed of AA6061 without reinforcement.

Interfacial effect on physical properties of composite media: Interfacial volume fraction with non-spherical hard-core-soft-shell-structured particles.

PubMed

Xu, Wenxiang; Duan, Qinglin; Ma, Huaifa; Chen, Wen; Chen, Huisu

2015-11-02

Interfaces are known to be crucial in a variety of fields and the interfacial volume fraction dramatically affects physical properties of composite media. However, it is an open problem with great significance how to determine the interfacial property in composite media with inclusions of complex geometry. By the stereological theory and the nearest-surface distribution functions, we first propose a theoretical framework to symmetrically present the interfacial volume fraction. In order to verify the interesting generalization, we simulate three-phase composite media by employing hard-core-soft-shell structures composed of hard mono-/polydisperse non-spherical particles, soft interfaces, and matrix. We numerically derive the interfacial volume fraction by a Monte Carlo integration scheme. With the theoretical and numerical results, we find that the interfacial volume fraction is strongly dependent on the so-called geometric size factor and sphericity characterizing the geometric shape in spite of anisotropic particle types. As a significant interfacial property, the present theoretical contribution can be further drawn into predicting the effective transport properties of composite materials.

Interfacial effect on physical properties of composite media: Interfacial volume fraction with non-spherical hard-core-soft-shell-structured particles

PubMed Central

Xu, Wenxiang; Duan, Qinglin; Ma, Huaifa; Chen, Wen; Chen, Huisu

2015-01-01

Interfaces are known to be crucial in a variety of fields and the interfacial volume fraction dramatically affects physical properties of composite media. However, it is an open problem with great significance how to determine the interfacial property in composite media with inclusions of complex geometry. By the stereological theory and the nearest-surface distribution functions, we first propose a theoretical framework to symmetrically present the interfacial volume fraction. In order to verify the interesting generalization, we simulate three-phase composite media by employing hard-core-soft-shell structures composed of hard mono-/polydisperse non-spherical particles, soft interfaces, and matrix. We numerically derive the interfacial volume fraction by a Monte Carlo integration scheme. With the theoretical and numerical results, we find that the interfacial volume fraction is strongly dependent on the so-called geometric size factor and sphericity characterizing the geometric shape in spite of anisotropic particle types. As a significant interfacial property, the present theoretical contribution can be further drawn into predicting the effective transport properties of composite materials. PMID:26522701

Characterizing Metal-Based Nanoparticles in Surface Water by Single-Particle ICPMS

EPA Science Inventory

Engineered metal-based nanomaterials are being used in increasing quantities in consumer and industrial products. These materials may be introduced into surface waters by a variety of paths depending on usage, and will be superimposed on concentrations of other particles containi...

Metallic impurities-silicon carbide interaction in HTGR fuel particles

NASA Astrophysics Data System (ADS)

Minato, Kazuo; Ogawa, Toru; Kashimura, Satoru; Fukuda, Kousaku; Shimizu, Michio; Tayama, Yoshinobu; Takahashi, Ishio

1990-12-01

Corrosion of the coating layers of silicon carbide (SiC) by metallic impurities was observed in irradiated Triso-coated uranium dioxide particles for high temperature gas-cooled reactors with an optical microscope and an electron probe micro-analyzer. The SiC layers were attacked from the outside of the particles. The main element observed in the corroded areas was iron, but sometimes iron and nickel were found. These elements must have been contained as impurities in the graphite matrix in which the coated particles were dispersed. Since these elements are more stable thermodynamically in the presence of SiC than in the presence of graphite at irradiation temperatures, they were transferred to the SiC layer to form more stable silicides. During fuel manufacturing processes, intensive care should be taken to prevent the fuel from being contaminated with those elements which react with SiC.

Solar Hard X-ray Observations with NuSTAR

NASA Astrophysics Data System (ADS)

Smith, David M.; Krucker, S.; Hudson, H. S.; Hurford, G. J.; White, S. M.; Mewaldt, R. A.; Stern, D.; Grefenstette, B. W.; Harrison, F. A.

2011-05-01

High-sensitivity imaging of coronal hard X-rays allows detection of freshly accelerated nonthermal electrons at the acceleration site. A few such observations have been made with Yohkoh and RHESSI, but a leap in sensitivity could help pin down the time, place, and manner of reconnection. In 2012, the Nuclear Spectroscopic Telescope Array (NuSTAR), a NASA Small Explorer for high energy astrophysics that uses grazing-incidence optics to focus X-rays up to 80 keV, will be launched. NuSTAR is capable of solar pointing, and three weeks will be dedicated to solar observing during the baseline two-year mission. NuSTAR will be 200 times more sensitive than RHESSI in the hard X-ray band. This will allow the following new observations, among others: 1) Extrapolation of the micro/nanoflare distribution by two orders of magnitude down in flux 2) Search for hard X-rays from network nanoflares (soft X-ray bright points) and evaluation of their role in coronal heating 3) Discovery of hard X-ray bremsstrahlung from the electron beams driving type III radio bursts, and measurement of their electron spectrum 4) Hard X-ray studies of polar soft X-ray jets and impulsive solar energetic particle events at the edge of coronal holes, and comparison of these events with observations of 3He and other particles in interplanetary space 5) Study of coronal bremsstrahlung from particles accelerated by coronal mass ejections as they are first launched 6) Study of particles at the coronal reconnection site when flare footpoints are occulted; and 7) Search for hypothetical axion particles created in the solar core via the hard X-ray signal from their conversion to X-rays in the coronal magnetic field. NuSTAR will also serve as a pathfinder for a future dedicated space mission with enhanced capabilities, such as a satellite version of the FOXSI sounding rocket.

Numerical and experimental validation of a particle Galerkin method for metal grinding simulation

NASA Astrophysics Data System (ADS)

Wu, C. T.; Bui, Tinh Quoc; Wu, Youcai; Luo, Tzui-Liang; Wang, Morris; Liao, Chien-Chih; Chen, Pei-Yin; Lai, Yu-Sheng

2018-03-01

In this paper, a numerical approach with an experimental validation is introduced for modelling high-speed metal grinding processes in 6061-T6 aluminum alloys. The derivation of the present numerical method starts with an establishment of a stabilized particle Galerkin approximation. A non-residual penalty term from strain smoothing is introduced as a means of stabilizing the particle Galerkin method. Additionally, second-order strain gradients are introduced to the penalized functional for the regularization of damage-induced strain localization problem. To handle the severe deformation in metal grinding simulation, an adaptive anisotropic Lagrangian kernel is employed. Finally, the formulation incorporates a bond-based failure criterion to bypass the prospective spurious damage growth issues in material failure and cutting debris simulation. A three-dimensional metal grinding problem is analyzed and compared with the experimental results to demonstrate the effectiveness and accuracy of the proposed numerical approach.

Characterization of airborne particles generated from metal active gas welding process.

PubMed

Guerreiro, C; Gomes, J F; Carvalho, P; Santos, T J G; Miranda, R M; Albuquerque, P

2014-05-01

This study is focused on the characterization of particles emitted in the metal active gas welding of carbon steel using mixture of Ar + CO2, and intends to analyze which are the main process parameters that influence the emission itself. It was found that the amount of emitted particles (measured by particle number and alveolar deposited surface area) are clearly dependent on the distance to the welding front and also on the main welding parameters, namely the current intensity and heat input in the welding process. The emission of airborne fine particles seems to increase with the current intensity as fume-formation rate does. When comparing the tested gas mixtures, higher emissions are observed for more oxidant mixtures, that is, mixtures with higher CO2 content, which result in higher arc stability. These mixtures originate higher concentrations of fine particles (as measured by number of particles by cm(3) of air) and higher values of alveolar deposited surface area of particles, thus resulting in a more severe worker's exposure.

A Crossover from High Stiffness to High Hardness: The Case of Osmium and Its Borides

NASA Astrophysics Data System (ADS)

Bian, Yongming; Liu, Xiaomei; Li, Anhu; Liang, Yongcheng

2016-09-01

Transition-metal light-element compounds are currently raising great expectations for hard and superhard materials. Using the widely attracting osmium (Os) and its borides (OsB, Os2B3 and OsB2) as prototypes, we demonstrate by first-principles calculations that heavy transition metals, which possess high stiffness but low hardness, can be converted into highly hard materials by incorporating of light elements to form compounds. Such a crossover is a manifestation that the underlying sources of high stiffness and high hardness are fundamentally different. The stiffness is related to elastic deformation that is closely associated with valence electron density, whereas the hardness depends strongly on plastic deformation that is determined by bonding nature. Therefore, the incorporation of light atoms into transition metal should be a valid pathway of designing hard and superhard materials. This strategy is in principle also applicable to other transition-metal borides, carbides, and nitrides.

Digital image processing of nanometer-size metal particles on amorphous substrates

NASA Technical Reports Server (NTRS)

Soria, F.; Artal, P.; Bescos, J.; Heinemann, K.

1989-01-01

The task of differentiating very small metal aggregates supported on amorphous films from the phase contrast image features inherently stemming from the support is extremely difficult in the nanometer particle size range. Digital image processing was employed to overcome some of the ambiguities in evaluating such micrographs. It was demonstrated that such processing allowed positive particle detection and a limited degree of statistical size analysis even for micrographs where by bare eye examination the distribution between particles and erroneous substrate features would seem highly ambiguous. The smallest size class detected for Pd/C samples peaks at 0.8 nm. This size class was found in various samples prepared under different evaporation conditions and it is concluded that these particles consist of 'a magic number' of 13 atoms and have cubooctahedral or icosahedral crystal structure.

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

Contribution of coarse particles from road surfaces to dissolved and particle-bound heavy metal loads in runoff: A laboratory leaching study with synthetic stormwater.

PubMed

Borris, Matthias; Österlund, Heléne; Marsalek, Jiri; Viklander, Maria

2016-12-15

Laboratory leaching experiments were performed to study the potential of coarse street sediments (i.e. >250μm) to release dissolved and particulate-bound heavy metals (i.e. Cd, Cr, Cu, Ni, Pb and Zn) during rainfall/runoff. Towards this end, street sediments were sampled by vacuuming at seven sites in five Swedish cities and the collected sediments were characterized with respect to their physical and chemical properties. In the laboratory, the sediments were combined with synthetic rainwater and subject to agitation by a shaker mimicking particle motion during transport by runoff from street surfaces. As a result of such action, coarse street sediments were found to release significant amounts of heavy metals, which were predominantly (up to 99%) in the particulate bound phase. Thus, in dry weather, coarse street sediments functioned as collectors of fine particles with attached heavy metals, but in wet weather, metal burdens were released by rainfall/runoff processes. The magnitude of such releases depended on the site characteristics (i.e. street cleaning and traffic intensity), particle properties (i.e. organic matter content), and runoff characteristics (pH, and the duration of, and energy input into, sediment/water agitation). The study findings suggest that street cleaning, which preferentially removes coarser sediments, may produce additional environmental benefits by also removing fine contaminated particles attached to coarser materials. Copyright © 2016 Elsevier B.V. All rights reserved.

Cardiopulmonary responses of intratracheally instilled tire particles and constituent metal components

USGS Publications Warehouse

Gottipolu, R.R.; Landa, E.R.; Schladweiler, M.C.; McGee, J.K.; Ledbetter, A.D.; Richards, J.H.; Wallenborn, G.J.; Kodavanti, U.P.

2008-01-01

Tire and brake wear particles contain transition metals, and contribute to near-road PM. We hypothesized that acute cardiopulmonary injury from respirable tire particles (TP) will depend on the amount of soluble metals. Respirable fractions of two types of TP (TP1 and TP2) were analyzed for water and acid-leachable metals using ICP-AES. Both TP types contained a variety of transition metals, including zinc (Zn), copper (Cu), aluminum, and iron. Zn and Cu were detected at high levels in water-soluble fractions (TP2 > TP1). Male Wistar Kyoto rats (12-14 wk) were intratracheally instilled, in the first study, with saline, TP1 or TP2 (5 mg/kg), and in the second study, with soluble Zn, Cu (0.5 ??mol/kg), or both. Pulmonary toxicity and cardiac mitochondrial enzymes were analyzed 1 d, 1 wk, or 4 wk later for TP and 4 or 24 h later for metals. Increases in lavage fluid markers of inflammation and injury were observed at d 1 (TP2 > TP1), but these changes reversed by wk 1. No effects on cardiac enzymes were noted with either TP. Exposure of rats to soluble Zn and Cu caused marked pulmonary inflammation and injury but temporal differences were apparent (Cu effects peaked at 4 h and Zn at 24 h). Instillation of Zn, Cu, and Zn+ Cu decreased the activity of cardiac aconitase, isocitrate dehydrogenase, succinate dehydrogenase, cytochrome-c-oxidase and superoxide dismutase suggesting mitochondrial oxidative stress. The observed acute pulmonary toxicity of TP could be due to the presence of water soluble Zn and Cu. At high concentrations these metals may induce cardiac oxidative stress. Copyright ?? Informa Healthcare USA, Inc.

Dynamics of spherical metallic particles in cylinder electrostatic separators/purifiers.

PubMed

Lu, Hong-Zhou; Li, Jia; Guo, Jie; Xu, Zhen-Ming

2008-08-15

This paper presents a theoretical analysis of the dynamics of spherical metallic particles in electrostatic separators/purifiers (ESPs). The particle equations of motion are numerically solved in two dimensions using a computational algorithm. The ESPs consist of a pair of conductor cylinder electrodes. The upper cylinder is energized by HVdc, while the lower one is grounded and fixed horizontally on a revolvable axis. Some phenomena and aspects of separation process are explained and depicted including lifting off, impact, "motion collapse" and "sudden bouncing". The results reveal that the several phenomena depend on initial position, radius and density of the particle, curvature of the cylinder electrodes, distance between the electrodes and amplitude of the applied voltage. Optimization of the parameters is presented in order to get better separation/purification processes.

Improved Wear Resistance of Low Carbon Steel with Plasma Melt Injection of WC Particles

NASA Astrophysics Data System (ADS)

Liu, Aiguo; Guo, Mianhuan; Hu, Hailong

2010-08-01

Surface of a low carbon steel Q235 substrate was melted by a plasma torch, and tungsten carbide (WC) particles were injected into the melt pool. WC reinforced surface metal matrix composite (MMC) was synthesized. Dry sliding wear behavior of the surface MMC was studied and compared with the substrate. The results show that dry sliding wear resistance of low carbon steel can be greatly improved by plasma melt injection of WC particles. Hardness of the surface MMC is much higher than that of the substrate. The high hardness lowers the adhesion and abrasion of the surface MMC, and also the friction coefficient of it. The oxides formed in the sliding process also help to lower the friction coefficient. In this way, the dry sliding wear resistance of the surface MMC is greatly improved.

Behavior of suspended particles in the Changjiang Estuary: Size distribution and trace metal contamination.

PubMed

Yao, Qingzhen; Wang, Xiaojing; Jian, Huimin; Chen, Hongtao; Yu, Zhigang

2016-02-15

Suspended particulate matter (SPM) samples were collected along a salinity gradient in the Changjiang Estuary in June 2011. A custom-built water elutriation apparatus was used to separate the suspended sediments into five size fractions. The results indicated that Cr and Pb originated from natural weathering processes, whereas Cu, Zn, and Cd originated from other sources. The distribution of most trace metals in different particle sizes increased with decreasing particle size. The contents of Fe/Mn and organic matter were confirmed to play an important role in increasing the level of heavy metal contents. The Cu, Pb, Zn, and Cd contents varied significantly with increasing salinity in the medium-low salinity region, thus indicating the release of Cu, Pb, Zn, and Cd particles. Thus, the transfer of polluted fine particles into the open sea is probably accompanied by release of pollutants into the dissolved compartment, thereby amplifying the potential harmful effects to marine organisms. Copyright © 2015 Elsevier Ltd. All rights reserved.

Solar Hard X-ray Observations with NuSTAR

NASA Astrophysics Data System (ADS)

Marsh, Andrew; Smith, D. M.; Krucker, S.; Hudson, H. S.; Hurford, G. J.; White, S. M.; Mewaldt, R. A.; Harrison, F. A.; Grefenstette, B. W.; Stern, D.

2012-05-01

High-sensitivity imaging of coronal hard X-rays allows detection of freshly accelerated nonthermal electrons at the acceleration site. A few such observations have been made with Yohkoh and RHESSI, but a leap in sensitivity could help pin down the time, place, and manner of reconnection. Around the time of this meeting, the Nuclear Spectroscopic Telescope ARray (NuSTAR), a NASA Small Explorer for high energy astrophysics that uses grazing-incidence optics to focus X-rays up to 80 keV, will be launched. Three weeks will be dedicated to solar observing during the baseline two-year mission. NuSTAR will be 200 times more sensitive than RHESSI in the hard X-ray band. This will allow the following new observations, among others: 1) Extrapolation of the micro/nanoflare distribution by two orders of magnitude down in flux; 2) Search for hard X-rays from network nanoflares (soft X-ray bright points) and evaluation of their role in coronal heating; 3) Discovery of hard X-ray bremsstrahlung from the electron beams driving type III radio bursts, and measurement of their electron spectrum; 4) Hard X-ray studies of polar soft X-ray jets and impulsive solar energetic particle events at the edge of coronal holes; 5) Study of coronal bremsstrahlung from particles accelerated by coronal mass ejections as they are first launched; 6) Study of particles at the coronal reconnection site when flare footpoints and loops are occulted; 7) Search for weak high-temperature coronal plasmas in active regions that are not flaring; and 8) Search for hypothetical axion particles created in the solar core via the hard X-ray signal from their conversion to X-rays in the coronal magnetic field. NuSTAR will also serve as a pathfinder for a future dedicated space mission with enhanced capabilities, such as a satellite version of the FOXSI sounding rocket.

A concentrated solar cavity absorber with direct heat transfer through recirculating metallic particles

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

Sarker, M. R. I., E-mail: islamrabiul@yahoo.com; Saha, Manabendra, E-mail: manabendra.saha@adelaide.edu.au, E-mail: manab04me@gmail.com; Beg, R. A.

A recirculating flow solar particle cavity absorber (receiver) is modeled to investigate the flow behavior and heat transfer characteristics of a novel developing concept. It features a continuous recirculating flow of non-reacting metallic particles (black silicon carbide) with air which are used as a thermal enhancement medium. The aim of the present study is to numerically investigate the thermal behavior and flow characteristics of the proposed concept. The proposed solar particle receiver is modeled using two phase discrete particle model (DPM), RNG k-flow model and discrete ordinate (DO) radiation model. Numerical analysis is carried out considering a solar receiver withmore » only air and the mixture of non-reacting particles and air as a heat transfer as well as heat carrying medium. The parametric investigation is conducted considering the incident solar flux on the receiver aperture and changing air flow rate and recirculation rate inside the receiver. A stand-alone feature of the recirculating flow solar particle receiver concept is that the particles are directly exposed to concentrated solar radiation monotonously through recirculating flow inside the receiver and results in efficient irradiation absorption and convective heat transfer to air that help to achieve high temperature air and consequently increase in thermal efficiency. This paper presents, results from the developed concept and highlights its flow behavior and potential to enhance the heat transfer from metallic particles to air by maximizing heat carrying capacity of the heat transfer medium. The imposed milestones for the present system will be helpful to understand the radiation absorption mechanism of the particles in a recirculating flow based receiver, the thermal transport between the particles, the air and the cavity, and the fluid dynamics of the air and particle in the cavity.« less

Detection of isolated protein-bound metal ions by single-particle cryo-STEM.

PubMed

Elad, Nadav; Bellapadrona, Giuliano; Houben, Lothar; Sagi, Irit; Elbaum, Michael

2017-10-17

Metal ions play essential roles in many aspects of biological chemistry. Detecting their presence and location in proteins and cells is important for understanding biological function. Conventional structural methods such as X-ray crystallography and cryo-transmission electron microscopy can identify metal atoms on protein only if the protein structure is solved to atomic resolution. We demonstrate here the detection of isolated atoms of Zn and Fe on ferritin, using cryogenic annular dark-field scanning transmission electron microscopy (cryo-STEM) coupled with single-particle 3D reconstructions. Zn atoms are found in a pattern that matches precisely their location at the ferroxidase sites determined earlier by X-ray crystallography. By contrast, the Fe distribution is smeared along an arc corresponding to the proposed path from the ferroxidase sites to the mineral nucleation sites along the twofold axes. In this case the single-particle reconstruction is interpreted as a probability distribution function based on the average of individual locations. These results establish conditions for detection of isolated metal atoms in the broader context of electron cryo-microscopy and tomography.

Detection of isolated protein-bound metal ions by single-particle cryo-STEM

PubMed Central

Elad, Nadav; Bellapadrona, Giuliano; Houben, Lothar; Sagi, Irit; Elbaum, Michael

2017-01-01

Metal ions play essential roles in many aspects of biological chemistry. Detecting their presence and location in proteins and cells is important for understanding biological function. Conventional structural methods such as X-ray crystallography and cryo-transmission electron microscopy can identify metal atoms on protein only if the protein structure is solved to atomic resolution. We demonstrate here the detection of isolated atoms of Zn and Fe on ferritin, using cryogenic annular dark-field scanning transmission electron microscopy (cryo-STEM) coupled with single-particle 3D reconstructions. Zn atoms are found in a pattern that matches precisely their location at the ferroxidase sites determined earlier by X-ray crystallography. By contrast, the Fe distribution is smeared along an arc corresponding to the proposed path from the ferroxidase sites to the mineral nucleation sites along the twofold axes. In this case the single-particle reconstruction is interpreted as a probability distribution function based on the average of individual locations. These results establish conditions for detection of isolated metal atoms in the broader context of electron cryo-microscopy and tomography. PMID:28973937

Evolution of residual stress, free volume, and hardness in the laser shock peened Ti-based metallic glass

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

Wang, Liang; Wang, Lu; Nie, Zhihua

Laser shock peening (LSP) with different cycles was performed on the Ti-based bulk metallic glasses (BMGs). The sub-surface residual stress of the LSPed specimens was measured by high-energy X-ray diffraction (HEXRD) and the near-surface residual stress was measured by scanning electron microscope/focused ion beam (SEM/FIB) instrument. The sub-surface residual stress in the LSP impact direction (about-170MPa) is much lower than that perpendicular to the impact direction (about -350 MPa), exhibiting anisotropy. The depth of the compressive stress zone increases from 400 mu m to 500 mu m with increasing LSP cycles. The highest near-surface residual stress is about -750 MPa.more » LSP caused the free volume to increase and the maximum increase appeared after the first LSP process. Compared with the hardness (567 +/- 7 HV) of the as-cast BMG, the hardness (590 +/- 9 HV) on the shocked surface shows a hardening effect due to the hardening mechanism of compressive residual stress; and the hardness (420 +/- 9 HV) on the longitudinal section shows a softening effect due to the softening mechanism of free volume.« less

Method of preparing silicon carbide particles dispersed in an electrolytic bath for composite electroplating of metals

DOEpatents

Peng, Yu-Min; Wang, Jih-Wen; Liue, Chun-Ying; Yeh, Shinn-Horng

1994-01-01

A method for preparing silicon carbide particles dispersed in an electrolytic bath for composite electroplating of metals includes the steps of washing the silicon carbide particles with an organic solvent; washing the silicon carbide particles with an inorganic acid; grinding the silicon carbide particles; and heating the silicon carbide particles in a nickel-containing solution at a boiling temperature for a predetermined period of time.

Quantitative Analysis of Electroplated Nickel Coating on Hard Metal

PubMed Central

Wahab, Hassan A.; Noordin, M. Y.; Izman, S.

2013-01-01

Electroplated nickel coating on cemented carbide is a potential pretreatment technique for providing an interlayer prior to diamond deposition on the hard metal substrate. The electroplated nickel coating is expected to be of high quality, for example, indicated by having adequate thickness and uniformity. Electroplating parameters should be set accordingly for this purpose. In this study, the gap distances between the electrodes and duration of electroplating process are the investigated variables. Their effect on the coating thickness and uniformity was analyzed and quantified using design of experiment. The nickel deposition was carried out by electroplating in a standard Watt's solution keeping other plating parameters (current: 0.1 Amp, electric potential: 1.0 V, and pH: 3.5) constant. The gap distance between anode and cathode varied at 5, 10, and 15 mm, while the plating time was 10, 20, and 30 minutes. Coating thickness was found to be proportional to the plating time and inversely proportional to the electrode gap distance, while the uniformity tends to improve at a large electrode gap. Empirical models of both coating thickness and uniformity were developed within the ranges of the gap distance and plating time settings, and an optimized solution was determined using these models. PMID:23997678

Speciation dynamics of metals in dispersion of nanoparticles with discrete distribution of charged binding sites.

PubMed

Polyakov, Pavel D; Duval, Jérôme F L

2014-02-07

We report a comprehensive theory to evaluate the kinetics of complex formation between metal ions and charged spherical nanoparticles. The latter consist of an ion-impermeable core surrounded by a soft shell layer characterized by a discrete axisymmetric 2D distribution of charged sites that bind metal ions. The theory explicitly integrates the conductive diffusion of metal ions from bulk solution toward the respective locations of the reactive sites within the particle shell volume. The kinetic constant k for outer-sphere nanoparticle-metal association is obtained from the sum of the contributions stemming from all reactive sites, each evaluated from the corresponding incoming flux of metal ions derived from steady-state Poisson-Nernst-Planck equations. Illustrations are provided to capture the basic intertwined impacts of particle size, overall particle charge, spatial heterogeneity in site distribution, type of particle (hard, core-shell or porous) and concentration of the background electrolyte on k. As a limit, k converges with predictions from previously reported analytical expressions derived for porous particles with low and high charge density, cases that correspond to coulombic and mean-field (smeared-out) electrostatic treatments, respectively. The conditions underlying the applicability of these latter approaches are rigorously identified in terms of (i) the extent of overlap between electric double layers around charged neighbouring sites, and (ii) the magnitude of the intraparticulate metal concentration gradient. For the first time, the proposed theory integrates the differentiated impact of the local potential around the charged binding sites amidst the overall particle field, together with that of the so-far discarded intraparticulate flux of metal ions.

Influence of the Substrate on the Formation of Metallic Glass Coatings by Cold Gas Spraying

NASA Astrophysics Data System (ADS)

Henao, John; Concustell, Amadeu; Dosta, Sergi; Cinca, Núria; Cano, Irene G.; Guilemany, Josep M.

2016-06-01

Cold gas spray technology has been used to build up coatings of Fe-base metallic glass onto different metallic substrates. In this work, the effect of the substrate properties on the viscoplastic response of metallic glass particles during their impact has been studied. Thick coatings with high deposition efficiencies have been built-up in conditions of homogeneous flow on substrates such as Mild Steel AISI 1040, Stainless Steel 316L, Inconel 625, Aluminum 7075-T6, and Copper (99.9%). Properties of the substrate have been identified to play an important role in the viscoplastic response of the metallic glass particles at impact. Depending on the process gas conditions, the impact morphologies show not only inhomogeneous deformation but also homogeneous plastic flow despite the high strain rates, 108 to 109 s-1, involved in the technique. Interestingly, homogenous deformation of metallic glass particles is promoted depending on the hardness and the thermal diffusivity of the substrate and it is not exclusively a function of the kinetic energy and the temperature of the particle at impact. Coating formation is discussed in terms of fundamentals of dynamics of undercooled liquids, viscoplastic flow mechanisms of metallic glasses, and substrate properties. The findings presented in this work have been used to build up a detailed scheme of the deposition mechanism of metallic glass coatings by the cold gas spraying technology.

A Novel Approach to Hardness Testing

NASA Technical Reports Server (NTRS)

Spiegel, F. Xavier; West, Harvey A.

1996-01-01

This paper gives a description of the application of a simple rebound time measuring device and relates the determination of relative hardness of a variety of common engineering metals. A relation between rebound time and hardness will be sought. The effect of geometry and surface condition will also be discussed in order to acquaint the student with the problems associated with this type of method.

Economic assessment for recycling critical metals from hard disk drives using a comprehensive recovery process

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

Nguyen, Ruby Thuy; Diaz, Luis A.; Imholte, D. Devin

Since the 2011 price spike of rare earth elements (REEs), research on permanent magnet recycling has blossomed globally to reduce future REE criticality. Hard disk drives (HDDs) have emerged as one feasible feedstock for recovering valuable REEs such as praseodymium, neodymium, and dysprosium. However, current processes for recycling e-waste only focus on certain metals due to feedstock and metal price uncertainties. In addition, some believe that recycling REEs is unprofitable. To shed some light on the economic viability of REE recycling from HDDs, this paper combines techno-economic information of a hydrometallurgical process with end-of-life HDD availability in a simulation model.more » Results showed that adding REEs to HDD recycling was profitable given current prices. As a result, recovered REEs could meet up to 5.1% rest of world (excluding China) magnet demand. Aluminum, gold, copper scrap and REEs were the primary main revenue streams from HDD recycling.« less

Economic assessment for recycling critical metals from hard disk drives using a comprehensive recovery process

DOE PAGES

Nguyen, Ruby Thuy; Diaz, Luis A.; Imholte, D. Devin; ...

2017-06-05

Since the 2011 price spike of rare earth elements (REEs), research on permanent magnet recycling has blossomed globally to reduce future REE criticality. Hard disk drives (HDDs) have emerged as one feasible feedstock for recovering valuable REEs such as praseodymium, neodymium, and dysprosium. However, current processes for recycling e-waste only focus on certain metals due to feedstock and metal price uncertainties. In addition, some believe that recycling REEs is unprofitable. To shed some light on the economic viability of REE recycling from HDDs, this paper combines techno-economic information of a hydrometallurgical process with end-of-life HDD availability in a simulation model.more » Results showed that adding REEs to HDD recycling was profitable given current prices. As a result, recovered REEs could meet up to 5.1% rest of world (excluding China) magnet demand. Aluminum, gold, copper scrap and REEs were the primary main revenue streams from HDD recycling.« less

Ultrasonic material hardness depth measurement

DOEpatents

Good, M.S.; Schuster, G.J.; Skorpik, J.R.

1997-07-08

The invention is an ultrasonic surface hardness depth measurement apparatus and method permitting rapid determination of hardness depth of shafts, rods, tubes and other cylindrical parts. The apparatus of the invention has a part handler, sensor, ultrasonic electronics component, computer, computer instruction sets, and may include a display screen. The part handler has a vessel filled with a couplant, and a part rotator for rotating a cylindrical metal part with respect to the sensor. The part handler further has a surface follower upon which the sensor is mounted, thereby maintaining a constant distance between the sensor and the exterior surface of the cylindrical metal part. The sensor is mounted so that a front surface of the sensor is within the vessel with couplant between the front surface of the sensor and the part. 12 figs.

Mean-force-field and mean-spherical approximations for the electric microfield distribution at a charged point in the charged-hard-particles fluid

NASA Astrophysics Data System (ADS)

Rosenfeld, Yaakov

1989-01-01

The linearized mean-force-field approximation, leading to a Gaussian distribution, provides an exact formal solution to the mean-spherical integral equation model for the electric microfield distribution at a charged point in the general charged-hard-particles fluid. Lado's explicit solution for plasmas immediately follows this general observation.

Slow waves in microchannel metal waveguides and application to particle acceleration

NASA Astrophysics Data System (ADS)

Steinhauer, L. C.; Kimura, W. D.

2003-06-01

Conventional metal-wall waveguides support waveguide modes with phase velocities exceeding the speed of light. However, for infrared frequencies and guide dimensions of a fraction of a millimeter, one of the waveguide modes can have a phase velocity equal to or less than the speed of light. Such a metal microchannel then acts as a slow-wave structure. Furthermore, if it is a transverse magnetic mode, the electric field has a component along the direction of propagation. Therefore, a strong exchange of energy can occur between a beam of charged particles and this slow-waveguide mode. Moreover, the energy exchange can be sustained over a distance limited only by the natural damping of the wave. This makes the microchannel metal waveguide an attractive possibility for high-gradient electron laser acceleration because the wave can be directly energized by a long-wavelength laser. Indeed the frequency of CO2 lasers lies at a fortuitous wavelength that produces a strong laser-particle interaction in a channel of reasonable macroscopic size (e.g., ˜0.6 mm). The dispersion properties including phase velocity and damping for the slow wave are developed. The performance and other issues related to laser accelerator applications are discussed.

Thin Metallic Films From Solvated Metal Atoms

NASA Astrophysics Data System (ADS)

Trivino, Galo C.; Klabunde, Kenneth J.; Dale, Brock

1988-02-01

Metals were evaporated under vacuum and the metal atoms solvated by excess organic solvents at low temperature. Upon warming stable colloidal metal particles were formed by controlled metal atom clustering. The particles were stabilized toward flocculation by solvation and electrostatic effects. Upon solvent removal the colloidal particles grew to form thin films that were metallic in appearance, but showed higher resistivities than pure metallic films. Gold, palladium, platinium, and especially indium are discussed.

Growth dynamics of carbon-metal particles and nanotubes synthesized by CO2 laser vaporization

NASA Astrophysics Data System (ADS)

Kokai, F.; Takahashi, K.; Yudasaka, M.; Iijima, S.

To study the growth of carbon-Co/Ni particles and single-wall carbon nanotubes (SWNTs) by 20 ms CO2 laser-pulse irradiation of a graphite-Co/Ni (1.2 at.%) target in an Ar gas atmosphere (600 Torr), we used emission imaging spectroscopy and shadowgraphy with a temporal resolution of 1.67 ms. Wavelength-selected emission images showed that C2 emission was strong in the region close to the target (within 2 cm), while for the same region the blackbody radiation from the large clusters or particles increased with increasing distance from the target. Shadowgraph images showed that the viscous flow of carbon and metal species formed a mushroom or a turbulent cloud spreading slowly into the Ar atmosphere, indicating that particles and SWNTs continued to grow as the ejected material cooled. In addition, emission imaging spectroscopy at 1200 °C showed that C2 and hot clusters and particles with higher emission intensities were distributed over much wider areas. We discuss the growth dynamics of the particles and SWNTs through the interaction of the ambient Ar with the carbon and metal species released from the target by the laser pulse.

Computer Algebra Reexamination of the Scaled Particle Theory for Hard-Sphere and Lennard-Jones Fluids

NASA Astrophysics Data System (ADS)

Khasare, S. B.

In the present work, an extension of the scaled particle theory (ESPT) for fluid using computer algebra is developed to obtain an equation of state (EOS), for Lennard-Jones fluid. A suitable functional form for surface tension S(r,d,ɛ) is assumed with intermolecular separation r as a variable, given below: $$S(r,d,\\epsilon)=S_{0}[1+2\\delta(d/r)^{m}],\\qquad r\\geq d/2\\,,$$ where m is arbitrary real number, and d and ɛ are related to physical property such as average or suitable molecular diameter and the binding energy of the molecule respectively. It is found that, for hard sphere fluid ɛ = 0, the above assumption when introduced in scaled particle theory (SPT) frame and choosing arbitrary real number, m = 1/3, the corresponding EOS is in good agreement with the computer simulation of molecular dynamics (MD) result. Furthermore, for the value of m = -1 it gives a Percus-Yevick (pressure), and for the value of m = 1, it corresponds Percus-Yevick (compressibility) EOS.

Bond-orientational analysis of hard-disk and hard-sphere structures.

PubMed

Senthil Kumar, V; Kumaran, V

2006-05-28

We report the bond-orientational analysis results for the thermodynamic, random, and homogeneously sheared inelastic structures of hard-disks and hard-spheres. The thermodynamic structures show a sharp rise in the order across the freezing transition. The random structures show the absence of crystallization. The homogeneously sheared structures get ordered at a packing fraction higher than the thermodynamic freezing packing fraction, due to the suppression of crystal nucleation. On shear ordering, strings of close-packed hard-disks in two dimensions and close-packed layers of hard-spheres in three dimensions, oriented along the velocity direction, slide past each other. Such a flow creates a considerable amount of fourfold order in two dimensions and body-centered-tetragonal (bct) structure in three dimensions. These transitions are the flow analogs of the martensitic transformations occurring in metals due to the stresses induced by a rapid quench. In hard-disk structures, using the bond-orientational analysis we show the presence of fourfold order. In sheared inelastic hard-sphere structures, even though the global bond-orientational analysis shows that the system is highly ordered, a third-order rotational invariant analysis shows that only about 40% of the spheres have face-centered-cubic (fcc) order, even in the dense and near-elastic limits, clearly indicating the coexistence of multiple crystalline orders. When layers of close-packed spheres slide past each other, in addition to the bct structure, the hexagonal-close-packed (hcp) structure is formed due to the random stacking faults. Using the Honeycutt-Andersen pair analysis and an analysis based on the 14-faceted polyhedra having six quadrilateral and eight hexagonal faces, we show the presence of bct and hcp signatures in shear ordered inelastic hard-spheres. Thus, our analysis shows that the dense sheared inelastic hard-spheres have a mixture of fcc, bct, and hcp structures.

Interaction of Heavy Metal Ions with Carbon and Iron Based Particles

PubMed Central

Fialova, Dana; Kremplova, Monika; Melichar, Lukas; Kopel, Pavel; Hynek, David; Adam, Vojtech; Kizek, Rene

2014-01-01

Due to the rapid development of industry and associated production of toxic waste, especially heavy metals, there is a great interest in creating and upgrading new sorption materials to remove these pollutants from the environment. This study aims to determine the effectiveness of different carbon forms (graphene, expanded carbon, multi-wall nanotubes) and paramagnetic particles (Fe2O3) for adsorption of cadmium(II), lead(II), and copper(II) on its surface, with different interaction time from 1 min to 24 h. The main attention is paid to the detection of these metals using differential pulse voltammetry. Based on the obtained results, graphene and Fe2O3 are found to be good candidates for removal of heavy metals from the environment. PMID:28788566

Novel and non-traditional use of stable isotope tracers to study metal bioavailability from natural particles

USGS Publications Warehouse

Croteau, Marie-Noële; Cain, Daniel J.; Fuller, Christopher C.

2013-01-01

We devised a novel tracing approach that involves enriching test organisms with a stable metal isotope of low natural abundance prior to characterizing metal bioavailability from natural inorganic particles. In addition to circumventing uncertainties associated with labeling natural particles and distinguishing background metals, the proposed "reverse labeling" technique overcomes many drawbacks inherent to using radioisotope tracers. Specifically, we chronically exposed freshwater snails (Lymnaea stagnalis) to synthetic water spiked with Cu that was 99.4% 65Cu to increase the relative abundance of 65Cu in the snail’s tissues from 32% to >80%. The isotopically enriched snails were then exposed to benthic algae mixed with Cu-bearing Fe–Al particles collected from the Animas River (Colorado), an acid mine drainage impacted river. We used 63Cu to trace Cu uptake from the natural particles and inferred their bioavailability from calculation of Cu assimilation into tissues. Cu assimilation from these particles was 44%, indicating that 44% of the particulate Cu was absorbed by the invertebrate. This demonstrates that inorganic particulate Cu can be bioavailable. The reverse labeling approach shows great potential in various scientific areas such as environmental contamination and nutrition for addressing questions involving uptake of an element that naturally has multiple isotopes.

The magnetohydrodynamic force experienced by spherical iron particles in liquid metal

NASA Astrophysics Data System (ADS)

Ščepanskis, Mihails; Jakovičs, Andris

2016-04-01

The paper contains a theoretical investigation of magnetohydrodynamic force experienced by iron particles (well-conducting and ferromagnetic) in well-conducting liquid. The investigation is performed by extending the Leenov and Kolin's theory to take into account the second-order effect. Therefore, the limits of the parent model are taken over to the present results. It is found that the effective conductivity of iron particles in liquid metal, which is important for practical application of the theoretically obtained force, is approximately equal to 1.5·106 S/m. The last result is obtained using a quasi-empirical approach - a comparison of experimental results with the results of the numerical simulation that was performed for various conductivities of the iron particles.

Cavity method for force transmission in jammed disordered packings of hard particles.

PubMed

Bo, Lin; Mari, Romain; Song, Chaoming; Makse, Hernán A

2014-10-07

The force distribution of jammed disordered packings has always been considered a central object in the physics of granular materials. However, many of its features are poorly understood. In particular, analytic relations to other key macroscopic properties of jammed matter, such as the contact network and its coordination number, are still lacking. Here we develop a mean-field theory for this problem, based on the consideration of the contact network as a random graph where the force transmission becomes a constraint satisfaction problem. We can thus use the cavity method developed in the past few decades within the statistical physics of spin glasses and hard computer science problems. This method allows us to compute the force distribution P(f) for random packings of hard particles of any shape, with or without friction. We find a new signature of jamming in the small force behavior P(f) ∼ f(θ), whose exponent has attracted recent active interest: we find a finite value for P(f = 0), along with θ = 0. Furthermore, we relate the force distribution to a lower bound of the average coordination number z[combining macron](μ) of jammed packings of frictional spheres with coefficient μ. This bridges the gap between the two known isostatic limits z[combining macron]c (μ = 0) = 2D (in dimension D) and z[combining macron]c(μ → ∞) = D + 1 by extending the naive Maxwell's counting argument to frictional spheres. The theoretical framework describes different types of systems, such as non-spherical objects in arbitrary dimensions, providing a common mean-field scenario to investigate force transmission, contact networks and coordination numbers of jammed disordered packings.

Ejection of Metal Particles into Superfluid 4He by Laser Ablation.

PubMed

Buelna, Xavier; Freund, Adam; Gonzalez, Daniel; Popov, Evgeny; Eloranta, Jussi

2016-10-05

The dynamics following laser ablation of a metal target immersed in superfluid $^4$He is studied by time-resolved shadowgraph photography. The delayed ejection of hot micrometer-sized particles from the target surface into the liquid was indirectly observed by monitoring the formation and growth of gaseous bubbles around the particles. The experimentally determined particle average velocity distribution appears similar as previously measured in vacuum but exhibits a sharp cutoff at the speed of sound of the liquid. The propagation of the subsonic particles terminates in slightly elongated non-spherical gas bubbles residing near the target whereas faster particles reveal an unusual hydrodynamic response of the liquid. Based on the previously established semi-empirical model developed for macroscopic objects, the ejected transonic particles exhibit supercavitating flow to reduce their hydrodynamic drag. Supersonic particles appear to follow a completely different propagation mechanism as they leave discrete and semi-continuous bubble trails in the liquid. The relatively low number density of the observed non-spherical gas bubbles indicates that only large micron-sized particles are visualized in the experiments. Although the unique properties of superfluid helium allow a detailed characterization of these processes, the developed technique can be used to study the hydrodynamic response of any liquid to fast propagating objects on the micrometer-scale.

Influence of Ni-P Coated SiC and Laser Scan Speed on the Microstructure and Mechanical Properties of IN625 Metal Matrix Composites

NASA Astrophysics Data System (ADS)

Sateesh, N. H.; Kumar, G. C. Mohan; Krishna, Prasad

2015-12-01

Nickel based Inconel-625 (IN625) metal matrix composites (MMCs) were prepared using pre-heated nickel phosphide (Ni-P) coated silicon carbide (SiC) reinforcement particles by Direct Metal Laser Sintering (DMLS) additive manufacturing process under inert nitrogen atmosphere to obtain interface influences on MMCs. The distribution of SiC particles and microstructures were characterized using optical and scanning electron micrographs, and the mechanical behaviours were thoroughly examined. The results clearly reveal that the interface integrity between the SiC particles and the IN625 matrix, the mixed powders flowability, the SiC ceramic particles and laser beam interaction, and the hardness, and tensile characteristics of the DMLS processed MMCs were improved effectively by the use of Ni-P coated SiC particles.

Wire Composition: Its Effect on Metal Disintegration and Particle Formation in Twin-Wire Arc-Spraying Process

NASA Astrophysics Data System (ADS)

Tillmann, W.; Abdulgader, M.

2013-03-01

The wire tips in twin-wire arc-spraying (TWAS) are heated in three different zones. A high-speed camera was used to observe the melting behavior, metal breakup, and particle formation under different operating conditions. In zone (I), the wire tips are melted (liquidus metal) and directly atomized in the form of smaller droplets. Their size is a function of the specific properties of the molten metal and the exerting aerodynamic forces. Zone (II) is directly beneath zone (I) and the origin of the extruded metal sheets at the wire tips. The extruded metal sheets in the case of cored wires are shorter than those observed while using solid wires. In this study, the effects of adjustable parameters and powder filling on melting behavior, particle formation, and process instability were revealed, and a comparison between solid and cored wires was made. The findings can improve the accuracy of the TWAS process modeling.

Assessment of the hardness of different orthodontic wires and brackets produced by metal injection molding and conventional methods

PubMed Central

Alavi, Shiva; Kachuie, Marzie

2017-01-01

Background: This study was conducted to assess the hardness of orthodontic brackets produced by metal injection molding (MIM) and conventional methods and different orthodontic wires (stainless steel, nickel-titanium [Ni-Ti], and beta-titanium alloys) for better clinical results. Materials and Methods: A total of 15 specimens from each brand of orthodontic brackets and wires were examined. The brackets (Elite Opti-Mim which is produced by MIM process and Ultratrimm which is produced by conventional brazing method) and the wires (stainless steel, Ni-Ti, and beta-titanium) were embedded in epoxy resin, followed by grinding, polishing, and coating. Then, X-ray energy dispersive spectroscopy (EDS) microanalysis was applied to assess their elemental composition. The same specimen surfaces were repolished and used for Vickers microhardness assessment. Hardness was statistically analyzed with Kruskal–Wallis test, followed by Mann–Whitney test at the 0.05 level of significance. Results: The X-ray EDS analysis revealed different ferrous or co-based alloys in each bracket. The maximum mean hardness values of the wires were achieved for stainless steel (SS) (529.85 Vickers hardness [VHN]) versus the minimum values for beta-titanium (334.65 VHN). Among the brackets, Elite Opti-Mim exhibited significantly higher VHN values (262.66 VHN) compared to Ultratrimm (206.59 VHN). VHN values of wire alloys were significantly higher than those of the brackets. Conclusion: MIM orthodontic brackets exhibited hardness values much lower than those of SS orthodontic archwires and were more compatible with NiTi and beta-titanium archwires. A wide range of microhardness values has been reported for conventional orthodontic brackets and it should be considered that the manufacturing method might be only one of the factors affecting the mechanical properties of orthodontic brackets including hardness. PMID:28928783

Assessment of the hardness of different orthodontic wires and brackets produced by metal injection molding and conventional methods.

PubMed

Alavi, Shiva; Kachuie, Marzie

2017-01-01

This study was conducted to assess the hardness of orthodontic brackets produced by metal injection molding (MIM) and conventional methods and different orthodontic wires (stainless steel, nickel-titanium [Ni-Ti], and beta-titanium alloys) for better clinical results. A total of 15 specimens from each brand of orthodontic brackets and wires were examined. The brackets (Elite Opti-Mim which is produced by MIM process and Ultratrimm which is produced by conventional brazing method) and the wires (stainless steel, Ni-Ti, and beta-titanium) were embedded in epoxy resin, followed by grinding, polishing, and coating. Then, X-ray energy dispersive spectroscopy (EDS) microanalysis was applied to assess their elemental composition. The same specimen surfaces were repolished and used for Vickers microhardness assessment. Hardness was statistically analyzed with Kruskal-Wallis test, followed by Mann-Whitney test at the 0.05 level of significance. The X-ray EDS analysis revealed different ferrous or co-based alloys in each bracket. The maximum mean hardness values of the wires were achieved for stainless steel (SS) (529.85 Vickers hardness [VHN]) versus the minimum values for beta-titanium (334.65 VHN). Among the brackets, Elite Opti-Mim exhibited significantly higher VHN values (262.66 VHN) compared to Ultratrimm (206.59 VHN). VHN values of wire alloys were significantly higher than those of the brackets. MIM orthodontic brackets exhibited hardness values much lower than those of SS orthodontic archwires and were more compatible with NiTi and beta-titanium archwires. A wide range of microhardness values has been reported for conventional orthodontic brackets and it should be considered that the manufacturing method might be only one of the factors affecting the mechanical properties of orthodontic brackets including hardness.

Characteristics of trace metals in traffic-derived particles in Hsuehshan Tunnel, Taiwan: size distribution, fingerprinting metal ratio, and emission factor

NASA Astrophysics Data System (ADS)

Lin, Y.-C.; Tsai, C.-J.; Wu, Y.-C.; Zhang, R.; Chi, K.-H.; Huang, Y.-T.; Lin, S.-H.; Hsu, S.-C.

2014-05-01

Traffic emissions are a significant source of airborne particulate matter (PM) in ambient environments. These emissions contain high abundance of toxic metals and thus pose adverse effects on human health. Size-fractionated aerosol samples were collected from May to September 2013 by using micro-orifice uniform deposited impactor (MOUDI). Sample collection was conducted simultaneously at the inlet and outlet sites of Hsuehshan Tunnel in northern Taiwan, which is the second longest freeway tunnel (12.9 km) in Asia. Such endeavor aims to characterize the chemical constituents, size distributions, and fingerprinting ratios, as well as the emission factors of particulate metals emitted by vehicle fleets. A total of 36 metals in size-resolved aerosols were determined through inductively coupled plasma mass spectrometry. Three major groups, namely, tailpipe emissions (Zn, Pb, and V), wear debris (Cu, Cd, Fe, Ga, Mn, Mo, Sb, and Sn), and resuspended dust (Ca, Mg, K, and Rb), of airborne PM metals were categorized on the basis of the results of enrichment factor, correlation matrix, and principal component analysis. Size distributions of wear-originated metals resembled the pattern of crustal elements, which were predominated by super-micron particulates (PM1-10). By contrast, tailpipe exhaust elements such as Zn, Pb, and V were distributed mainly in submicron particles. By employing Cu as a tracer of wear abrasion, several inter-metal ratios, including Fe/Cu (14), Ba/Cu (1.05), Sb/Cu (0.16), Sn/Cu (0.10), and Ga/Cu (0.03), served as fingerprints for wear debris. Emission factor of PM10 mass was estimated to be 7.7 mg vkm-1. The metal emissions were mostly predominated in super-micron particles (PM1-10). Finally, factors that possibly affect particulate metal emissions inside Hsuehshan Tunnel are discussed.

Size-segregated emissions and metal content of vehicle-emitted particles as a function of mileage: Implications to population exposure

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

Golokhvast, Kirill S.; Chernyshev, Valery V.; Chaika, Vladimir V.

2015-10-15

The study aims at investigating the characteristics (size distribution, active surface and metal content) of particles emitted by cars as a function of mileage using a novel methodology for characterizing particulate emissions captured by Exhaust Gas Suspension (EGS). EGS was obtained by passing the exhaust gases through a container of deionized water. EGS analysis was performed using laser granulometry, electron scanning microscopy, and high resolution mass spectrometry. Implications of the differences in key features of the emitted particles on population exposure were investigated using numerical simulation for estimating size-segregated PM deposition across human respiratory tract (HRT). It was found thatmore » vehicle mileage, age and the respective emissions class have almost no effect on the size distribution of the exhaust gas particulate released into the environment; about half of the examined vehicles with low mileage were found to release particles of aerodynamic diameter above 10 μm. The exhaust gas particulate detected in the EGS of all cars can be classified into three major size classes: (1) 0.1–5 µm – soot and ash particles, metals (Au, Pt, Pd, Ir); (2) 10–30 µm – metal (Cr, Fe, Cu, Zr, Ni) and ash particles; (3) 400–1,000 µm – metal (Fe, Cr, Pb) and ash particles. Newer vehicles with low mileage are substantial sources of soot and metal particles with median diameter of 200 nm with a higher surface area (up to 89,871.16 cm{sup 2}/cm{sup 3}). These tend to deposit in the lower part of the human respiratory tract. - Highlights: • Car mileage has virtually no effect on the size of the solid particles released. • Newer diesel vehicles emit particles of lower aerodynamic diameter. • Particle active surface emitted by newer vehicles is on average 3 times higher. • Real-life emissions were translated into actual internal PM exposure.« less

EFFECTS OF METAL COMPONENTS IN CONCENTRATED AMBIENT AIR PARTICLES ON PULMONARY INJURY

EPA Science Inventory

EFFECTS OF METAL COMPONENTS IN CONCENTRATED AMBIENT AIR PARTICLES ON PULMONARY INJURY. Yuh-Chin Huang, Jackie Stonehuerner, Jackie Carter, Andrew J. Ghio, Robert B. Devlin. NHEERL, US EPA, RTP, NC.
The mechanisms for cardiopulmonary morbidity associated with exposure to air po...

Environmental and health impacts of fine and ultrafine metallic particles: assessment of threat scores.

PubMed

Goix, Sylvaine; Lévêque, Thibaut; Xiong, Tian-Tian; Schreck, Eva; Baeza-Squiban, Armelle; Geret, Florence; Uzu, Gaëlle; Austruy, Annabelle; Dumat, Camille

2014-08-01

This study proposes global threat scores to prioritize the harmfulness of anthropogenic fine and ultrafine metallic particles (FMP) emitted into the atmosphere at the global scale. (Eco)toxicity of physicochemically characterized FMP oxides for metals currently observed in the atmosphere (CdO, CuO, PbO, PbSO(4), Sb(2)O(3), and ZnO) was assessed by performing complementary in vitro tests: ecotoxicity, human bioaccessibility, cytotoxicity, and oxidative potential. Using an innovative methodology based on the combination of (eco)toxicity and physicochemical results, the following hazard classification of the particles is proposed: CdCl2~CdO>CuO>PbO>ZnO>PbSO(4)>Sb(2)O(3). Both cadmium compounds exhibited the highest threat score due to their high cytotoxicity and bioaccessible dose, whatever their solubility and speciation, suggesting that cadmium toxicity is due to its chemical form rather than its physical form. In contrast, the Sb(2)O(3) threat score was the lowest due to particles with low specific area and solubility, with no effects except a slight oxidative stress. As FMP physicochemical properties reveal differences in specific area, crystallization systems, dissolution process, and speciation, various mechanisms may influence their biological impact. Finally, this newly developed and global approach could be widely used in various contexts of pollution by complex metal particles and may improve risk management. Copyright © 2014 Elsevier Inc. All rights reserved.

The Role of Second Phase Hard Particles on Hole Stretchability of two AA6xxx Alloys

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

Hu, Xiaohua; Sun, Xin; Golovashchenko, Sergey F.

The hole stretchability of two Aluminum Alloys (AA6111 and AA6022) are studied by using a two stages integrated finite element framework where the edge geometry and edge damages from the hole piercing processes were considered in the subsequent hole expansion processes. Experimentally it has been found that AA6022 has higher hole expansion ratios than those of AA6111. This observation has been nicely captured by finite element simulations. The main cause of differences have been identified to the volume fractions of the random distributed second phase hard particles which play a critical role in determining the fracture strains of the materials.

Interference effects in laser-induced plasma emission from surface-bound metal micro-particles

DOE PAGES

Feigenbaum, Eyal; Malik, Omer; Rubenchik, Alexander M.; ...

2017-04-19

Here, the light-matter interaction of an optical beam and metal micro-particulates at the vicinity of an optical substrate surface is critical to the many fields of applied optics. Examples of impacted fields are laser-induced damage in high power laser systems, sub-wavelength laser machining of transmissive materials, and laser-target interaction in directed energy applications. We present a full-wave-based model that predicts the laser-induced plasma pressure exerted on a substrate surface as a result of light absorption in surface-bound micron-scale metal particles. The model predictions agree with experimental observation of laser-induced shallow pits, formed by plasma emission and etching from surface-bound metalmore » micro-particulates. It provides an explanation for the prototypical side lobes observed along the pit profile, as well as for the dependence of the pit shape on the incident laser and particle parameters. Furthermore, the model highlights the significance of the interference of the incident light in the open cavity geometry formed between the micro-particle and the substrate in the resulting pit shape.« less

Highly Acidic Ambient Particles, Soluble Metals, and Oxidative Potential: A Link between Sulfate and Aerosol Toxicity.

PubMed

Fang, Ting; Guo, Hongyu; Zeng, Linghan; Verma, Vishal; Nenes, Athanasios; Weber, Rodney J

2017-03-07

Soluble transition metals in particulate matter (PM) can generate reactive oxygen species in vivo by redox cycling, leading to oxidative stress and adverse health effects. Most metals, such as those from roadway traffic, are emitted in an insoluble form, but must be soluble for redox cycling. Here we present the mechanism of metals dissolution by highly acidic sulfate aerosol and the effect on particle oxidative potential (OP) through analysis of size distributions. Size-segregated ambient PM were collected from a road-side and representative urban site in Atlanta, GA. Elemental and organic carbon, ions, total and water-soluble metals, and water-soluble OP were measured. Particle pH was determined with a thermodynamic model using measured ionic species. Sulfate was spatially uniform and found mainly in the fine mode, whereas total metals and mineral dust cations were highest at the road-side site and in the coarse mode, resulting in a fine mode pH < 2 and near neutral coarse mode. Soluble metals and OP peaked at the intersection of these modes demonstrating that sulfate plays a key role in producing highly acidic fine aerosols capable of dissolving primary transition metals that contribute to aerosol OP. Sulfate-driven metals dissolution may account for sulfate-health associations reported in past studies.

PULMONARY TOXICOLOGY OF SYNTHETIC AIR POLLUTION PARTICLES CONTAINING METAL SULFATES COMPARED TO CARBON BLACK AND DIESEL

EPA Science Inventory

PULMONARY TOXICITY OF SYNTHETIC AIR POLLUTION PARTICLES CONTAINING METAL SULFATES COMPARED TO CARBON BLACK AND DIESEL.

M Daniels, A Ranade* & MJ Selgrade & MI Gilmour.
Experimental Toxicology Division, ORD/NHEERL, U.S. EPA, RTP, NC. * Particle Technology, College Par...

Metal-enhanced fluorescence of dye-doped silica nano particles.

PubMed

Gunawardana, Kalani B; Green, Nathaniel S; Bumm, Lloyd A; Halterman, Ronald L

2015-03-01

Recent advancements in metal-enhanced fluorescence (MEF) suggest that it can be a promising tool for detecting molecules at very low concentrations when a fluorophore is fixed near the surface of metal nanoparticles. We report a simple method for aggregating multiple gold nanoparticles (GNPs) on Rhodamine B (RhB)-doped silica nanoparticles (SiNPs) utilizing dithiocarbamate (DTC) chemistry to produce MEF in solution. Dye was covalently incorporated into the growing silica framework via co-condensation of a 3-aminopropyltriethoxysilane (APTES) coupled RhB precursor using the Stöber method. Electron microscopy imaging revealed that these mainly non-spherical particles were relatively large (80 nm on average) and not well defined. Spherical core-shell particles were prepared by physisorbing a layer of RhB around a small spherical silica particle (13 nm) before condensing an outer layer of silica onto the surface. The core-shell method produced nanospheres (~30 nm) that were well defined and monodispersed. Both dye-doped SiNPs were functionalized with pendant amines that readily reacted with carbon disulfide (CS2) under basic conditions to produce DTC ligands that have exhibited a high affinity for gold surfaces. GNPs were produced via citrate reduction method and the resulting 13 nm gold nanospheres were then recoated with an ether-terminated alkanethiol to provide stability in ethanol. Fluorescent enhancement was observed when excess GNPs were added to DTC coated dye-doped SiNPs to form nanoparticle aggregates. Optimization of this system gave a fluorescence brightness enhancement of over 200 fold. Samples that gave fluorescence enhancement were characterized through Transmission Emission Micrograph (TEM) to reveal a pattern of multiple aggregation of GNPs on the dye-doped SiNPs.

Evaluating the capabilities of aerosol-to-liquid particle extraction system (ALPXS)/ICP-MS for monitoring trace metals in indoor air.

PubMed

Jayawardene, Innocent; Rasmussen, Pat E; Chenier, Marc; Gardner, H David

2014-09-01

This study investigates the application of the Aerosol-to-Liquid Particle Extraction System (ALPXS), which uses wet electrostatic precipitation to collect airborne particles, for multi-element indoor stationary monitoring. Optimum conditions are determined for capturing airborne particles for metal determination by inductively coupled plasma-mass spectrometry (ICP-MS), for measuring field blanks, and for calculating limits of detection (LOD) and quantification (LOQ). Due to the relatively high flow rate (300 L min(-1)), a sampling duration of 1 hr to 2 hr was adequate to capture airborne particle-bound metals under the investigated experimental conditions. The performance of the ALPXS during a building renovation demonstrated signal-to-noise ratios appropriate for sampling airborne particles in environments with elevated metal concentrations, such as workplace settings. The ALPXS shows promise as a research tool for providing useful information on short-term variations (transient signals) and for trapping particles into aqueous solutions where needed for subsequent characterization. As the ALPXS does not provide size-specific samples, and its efficiency at different flow rates has yet to be quantified, the ALPXS would not replace standard filter-based protocols accepted for regulatory applications (e.g., exposure measurements), but rather would provide additional information if used in conjunction with filter based methods. Implications: This study investigates the capability of the Aerosol-to-Liquid Particle Extraction System (ALPXS) for stationary sampling of airborne metals in indoor workplace environments, with subsequent analysis by ICP-MS. The high flow rate (300 L/min) permits a short sampling duration (< 2 hr). Results indicated that the ALPXS was capable of monitoring short-term changes in metal emissions during a renovation activity. This portable instrument may prove to be advantageous in occupational settings as a qualitative indicator of elevated

Investigation on the effect of Friction Stir Processing Parameters on Micro-structure and Micro-hardness of Rice Husk Ash reinforced Al6061 Metal Matrix Composites

NASA Astrophysics Data System (ADS)

Fatchurrohman, N.; Farhana, N.; Marini, C. D.

2018-03-01

Friction stir processing (FSP) is an alternative way to produce the surface composites of aluminium alloy in order to modify the microstructure and improve the mechanical properties. In this experiment, Al6061 aluminium alloy has been chosen to be used as the matrix base plate for the FSP. Al606 has potential for the use in advanced application but it has low wear resistance. While, the reinforced used was rice husk ash (RHA) in order to produce surface composites which increased the micro hardness of the plate composites. The Al6061 was stirred individually and with 5 weight % of RHA at three different tool rotational speeds of 800 rpm, 1000 rpm and 1200 rpm. After running the FSP, the result in the distribution of particles and the micro hardness of the specimens were identified. The result showed that Al6061 plate with the existing 5 weight % of RHA reinforced at the highest of tool rotational speeds of 1200rpm has the best distribution of particles and the highest result in average of micro hardness with 80Hv.

Multiscale correlations of iron phases and heavy metals in technogenic magnetic particles from contaminated soils.

PubMed

Yu, Xiuling; Lu, Shenggao

2016-12-01

Technogenic magnetic particles (TMPs) are carriers of heavy metals and organic contaminants, which derived from anthropogenic activities. However, little information on the relationship between heavy metals and TMP carrier phases at the micrometer scale is available. This study determined the distribution and association of heavy metals and magnetic phases in TMPs in three contaminated soils at the micrometer scale using micro-X-ray fluorescence (μ-XRF) and micro-X-ray absorption near-edge structure (μ-XANES) spectroscopy. Multiscale correlations of heavy metals in TMPs were elucidated using wavelet transform analysis. μ-XRF mapping showed that Fe was enriched and closely correlated with Co, Cr, and Pb in TMPs from steel industrial areas. Fluorescence mapping and wavelet analysis showed that ferroalloy was a major magnetic signature and heavy metal carrier in TMPs, because most heavy metals were highly associated with ferroalloy at all size scales. Multiscale analysis revealed that heavy metals in the TMPs were from multiple sources. Iron K-edge μ-XANES spectra revealed that metallic iron, ferroalloy, and magnetite were the main iron magnetic phases in the TMPs. The relative percentage of these magnetic phases depended on their emission sources. Heatmap analysis revealed that Co, Pb, Cu, Cr, and Ni were mainly derived from ferroalloy particles, while As was derived from both ferroalloy and metallic iron phases. Our results indicated the scale-dependent correlations of magnetic phases and heavy metals in TMPs. The combination of synchrotron based X-ray microprobe techniques and multiscale analysis provides a powerful tool for identifying the magnetic phases from different sources and quantifying the association of iron phases and heavy metals at micrometer scale. Copyright © 2016 Elsevier Ltd. All rights reserved.

Metallic Nickel Nanoparticles May Exhibit Higher Carcinogenic Potential than Fine Particles in JB6 Cells

PubMed Central

Bowman, Linda; Zou, Baobo; Mao, Guochuan; Xu, Jin; Castranova, Vincent; Zhao, Jinshun; Ding, Min

2014-01-01

While numerous studies have described the pathogenic and carcinogenic effects of nickel compounds, little has been done on the biological effects of metallic nickel. Moreover, the carcinogenetic potential of metallic nickel nanoparticles is unknown. Activator protein-1 (AP-1) and nuclear factor-κB (NF-κB) have been shown to play pivotal roles in tumor initiation, promotion, and progression. Mutation of the p53 tumor suppressor gene is considered to be one of the steps leading to the neoplastic state. The present study examines effects of metallic nickel fine and nanoparticles on tumor promoter or suppressor gene expressions as well as on cell transformation in JB6 cells. Our results demonstrate that metallic nickel nanoparticles caused higher activation of AP-1 and NF-κB, and a greater decrease of p53 transcription activity than fine particles. Western blot indicates that metallic nickel nanoparticles induced a higher level of protein expressions for R-Ras, c-myc, C-Jun, p65, and p50 in a time-dependent manner. In addition, both metallic nickel nano- and fine particles increased anchorage-independent colony formation in JB6 P+ cells in the soft agar assay. These results imply that metallic nickel fine and nanoparticles are both carcinogenetic in vitro in JB6 cells. Moreover, metallic nickel nanoparticles may exhibit higher carcinogenic potential, which suggests that precautionary measures should be taken in the use of nickel nanoparticles or its compounds in nanomedicine. PMID:24691273

Laser-induced Hertzian fractures in silica initiated by metal micro-particles on the exit surface

DOE PAGES

Feigenbaum, Eyal; Raman, Rajesh N.; Cross, David; ...

2016-05-16

Laser-induced Hertzian fractures on the exit surface of silica glass are found to result from metal surface-bound micro particles. Two types of metal micro-spheres are studied (stainless-steel and Al) using ultraviolet laser light. The fracture initiation probability curve as a function of fluence is obtained, resulting in an initiation threshold fluence of 11.1 ± 4.7 J/cm 2 and 16.5 ± 4.5 J/cm 2 for the SS and Al particles, accordingly. The modified damage density curve is calculated based on the fracture probability. Here, the calculated momentum coupling coefficient linking incident laser fluence to the resulting plasma pressure is found tomore » be similar for both particles: 32.6 ± 15.4 KN/J and 28.1 ± 10.4 KN/J for the SS and Al cases accordingly.« less

Momentum and Heat Transfer Models for Detonation in Nitromethane with Metal Particles

NASA Astrophysics Data System (ADS)

Ripley, R. C.; Zhang, F.; Lien, F.-S.

2009-12-01

Models for momentum and heat exchange have been derived from the results of previous 3D mesoscale simulations of detonation in packed aluminum particles saturated with nitromethane, where the shock interaction timescale was resolved. In these models, particle acceleration and heating within the shock and detonation zone are expressed in terms of velocity and temperature transmission factors, which are a function of the metal to explosive density ratio, solid volume fraction and ratio of particle size to detonation zone thickness. These models are incorporated as source terms in the governing equations for continuum dense two-phase flow, and then applied to macroscopic simulation of detonation of nitromethane/aluminum in lightly-cased cylinders. Heterogeneous detonation features such as velocity deficit, enhanced pressure, and critical diameter effects are demonstrated. Various spherical particle diameters from 3-350 μm are utilized where most of the particles react in the expanding detonation products. Results for detonation velocity, pressure history, failure and U-shaped critical diameter behavior are compared to existing experiments.

Short-term acute hypercapnia affects cellular responses to trace metals in the hard clams Mercenaria mercenaria.

PubMed

Ivanina, Anna V; Beniash, Elia; Etzkorn, Markus; Meyers, Tiffany B; Ringwood, Amy H; Sokolova, Inna M

2013-09-15

Estuarine and coastal habitats experience large fluctuations of environmental factors such as temperature, salinity, partial pressure of CO2 ( [Formula: see text] ) and pH; they also serve as the natural sinks for trace metals. Benthic filter-feeding organisms such as bivalves are exposed to the elevated concentrations of metals in estuarine water and sediments that can strongly affect their physiology. The effects of metals on estuarine organisms may be exacerbated by other environmental factors. Thus, a decrease in pH caused by high [Formula: see text] (hypercapnia) can modulate the effects of trace metals by affecting metal bioavailability, accumulation or binding. To better understand the cellular mechanisms of interactions between [Formula: see text] and trace metals in marine bivalves, we exposed isolated mantle cells of the hard clams (Mercenaria mercenaria) to different levels of [Formula: see text] (0.05, 1.52 and 3.01 kPa) and two major trace metal pollutants - cadmium (Cd) and copper (Cu). Elevated [Formula: see text] resulted in a decrease in intracellular pH (pHi) of the isolated mantle cells from 7.8 to 7.4. Elevated [Formula: see text] significantly but differently affected the trace metal accumulation by the cells. Cd uptake was suppressed at elevated [Formula: see text] levels while Cu accumulation has greatly accelerated under hypercapnic conditions. Interestingly, at higher extracellular Cd levels, labile intracellular Cd(2+) concentration remained the same, while intracellular levels of free Zn(2+) increased suggesting that Cd(2+) substitutes bound Zn(2+) in these cells. In contrast, Cu exposure did not affect intracellular Zn(2+) but led to a profound increase in the intracellular levels of labile Cu(2+) and Fe(2+). An increase in the extracellular concentrations of Cd and Cu led to the elevated production of reactive oxygen species under the normocapnic conditions (0.05 kPa [Formula: see text] ); surprisingly, this effect was mitigated in

Improvement of hot-carrier and radiation hardnesses in metal-oxide-nitride-oxide semiconductor devices by irradiation-then-anneal treatments

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

Chang-Liao, K.S.; Hwu, J.G.

The hardnesses of hot-carrier and radiation of metal-oxide nitride-oxide semiconductor (MONOS) devices can be improved by the irradiation-then-anneal (ITA) treatments. Each treatment includes an irradiation of Co-60 with a total dose of 1M rads(SiO[sub 2]) and an anneal in N[sub 2] at 400 C for 10 min successively. This improvement can be explained by the release of SiO[sub 2]/Si interfacial strain.

Environmental and health impacts of fine and ultrafine metallic particles: Assessment of threat scores

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

Goix, Sylvaine; UMR 5245 CNRS-INP-UPS, EcoLab; Lévêque, Thibaut

2014-08-15

This study proposes global threat scores to prioritize the harmfulness of anthropogenic fine and ultrafine metallic particles (FMP) emitted into the atmosphere at the global scale. (Eco)toxicity of physicochemically characterized FMP oxides for metals currently observed in the atmosphere (CdO, CuO, PbO, PbSO{sub 4}, Sb{sub 2}O{sub 3}, and ZnO) was assessed by performing complementary in vitro tests: ecotoxicity, human bioaccessibility, cytotoxicity, and oxidative potential. Using an innovative methodology based on the combination of (eco)toxicity and physicochemical results, the following hazard classification of the particles is proposed: CdCl{sub 2}∼CdO>CuO>PbO>ZnO>PbSO{sub 4}>Sb{sub 2}O{sub 3}. Both cadmium compounds exhibited the highest threat score duemore » to their high cytotoxicity and bioaccessible dose, whatever their solubility and speciation, suggesting that cadmium toxicity is due to its chemical form rather than its physical form. In contrast, the Sb{sub 2}O{sub 3} threat score was the lowest due to particles with low specific area and solubility, with no effects except a slight oxidative stress. As FMP physicochemical properties reveal differences in specific area, crystallization systems, dissolution process, and speciation, various mechanisms may influence their biological impact. Finally, this newly developed and global approach could be widely used in various contexts of pollution by complex metal particles and may improve risk management. - Highlights: • Seven micro- and nano- monometallic characterized particles were studied as references. • Bioaccessibility, eco and cytotoxicity, and oxidative potential assays were performed. • According to calculated threat scores: CdCl{sub 2}∼CdO>CuO>PbO>ZnO>PbSO{sub 4}>Sb{sub 2}O{sub 3}.« less

Interaction mechanisms between ceramic particles and atomized metallic droplets

NASA Astrophysics Data System (ADS)

Wu, Yue; Lavernia, Enrique J.

1992-10-01

The present study was undertaken to provide insight into the dynamic interactions that occur when ceramic particles are placed in intimate contact with a metallic matrix undergoing a phase change. To that effect, Al-4 wt pct Si/SiCp composite droplets were synthesized using a spray atomization and coinjection approach, and their solidification microstructures were studied both qualitatively and quantitatively. The present results show that SiC particles (SiCp) were incor- porated into the matrix and that the extent of incorporation depends on the solidification con- dition of the droplets at the moment of SiC particle injection. Two factors were found to affect the distribution and volume fraction of SiC particles in droplets: the penetration of particles into droplets and the entrapment and/or rejection of particles by the solidification front. First, during coinjection, particles collide with the atomized droplets with three possible results: they may penetrate the droplets, adhere to the droplet surface, or bounce back after impact. The extent of penetration of SiC particles into droplets was noted to depend on the kinetic energy of the particles and the magnitude of the surface energy change in the droplets that occurs upon impact. In liquid droplets, the extent of penetration of SiC particles was shown to depend on the changes in surface energy, ΔEs, experienced by the droplets. Accordingly, large SiC particles encoun- tered more resistance to penetration relative to small ones. In solid droplets, the penetration of SiC particles was correlated with the dynamic pressure exerted by the SiC particles on the droplets during impact and the depth of the ensuing crater. The results showed that no pene- tration was possible in such droplets. Second, once SiC particles have penetrated droplets, their final location in the microstructure is governed by their interactions with the solidification front. As a result of these interactions, both entrapment and rejection of

Hard Competition: Stabilizing the Elusive Biaxial Nematic Phase in Suspensions of Colloidal Particles with Extreme Lengths

NASA Astrophysics Data System (ADS)

Dussi, Simone; Tasios, Nikos; Drwenski, Tara; van Roij, René; Dijkstra, Marjolein

2018-04-01

We use computer simulations to study the existence and stability of a biaxial nematic Nb phase in systems of hard polyhedral cuboids, triangular prisms, and rhombic platelets, characterized by a long (L ), medium (M ), and short (S ) particle axis. For all three shape families, we find stable Nb states provided the shape is not only close to the so-called dual shape with M =√{L S } but also sufficiently anisotropic with L /S >9 ,11 ,14 ,23 for rhombi, (two types of) triangular prisms, and cuboids, respectively, corresponding to anisotropies not considered before. Surprisingly, a direct isotropic-Nb transition does not occur in these systems due to a destabilization of Nb by a smectic (for cuboids and prisms) or a columnar (for platelets) phase at small L /S or by an intervening uniaxial nematic phase at large L /S . Our results are confirmed by a density functional theory provided the third virial coefficient is included and a continuous rather than a discrete (Zwanzig) set of particle orientations is taken into account.

Effect of magneto rheological damper on tool vibration during hard turning

NASA Astrophysics Data System (ADS)

Paul, P. Sam; Varadarajan, A. S.

2012-12-01

Recently, the concept of hard turning has gained considerable attention in metal cutting as it can apparently replace the traditional process cycle of turning, heat treating, and finish grinding for assembly of hard wear resistant steel parts. The present investigation aims at developing a magneto rheological (MR) fluid damper for suppressing tool vibration and promoting better cutting performance during hard turning. The magneto rheological Fluid acts as a viscoelastic spring with non-linear vibration characteristics that are controlled by the composition of the magneto rheological fluid, the shape of the plunger and the electric parameters of the magnetizing field. Cutting experiments were conducted to arrive at a set of electrical, compositional and shape parameters that can suppress tool vibration and promote better cutting performance during turning of AISI 4340 steel of 46 HRC with minimal fluid application using hard metal insert with sculptured rake face. It was observed that the use of MR fluid damper reduces tool vibration and improves the cutting performance effectively. Also commercialization of this idea holds promise to the metal cutting industry.

Microviscoelasticity of adhesive hard sphere dispersions: Tracer particle microrheology of aqueous Pluronic L64 solutions

NASA Astrophysics Data System (ADS)

Kloxin, Christopher J.; van Zanten, John H.

2009-10-01

DWS-based tracer particle microrheology is demonstrated to be a useful way to study the dynamics of aqueous Pluronic L64 solutions, which is viewed as a model adhesive hard sphere (AHS) system. The short-time dynamics of aqueous Pluronic L64 solutions indicate a purely hydrodynamic high frequency microviscosity as predicted by Batchelor for colloidal dispersions. The evolution of the micellar dynamics reveals a zero shear microviscosity in good agreement with steady shear viscosity measurements. As the temperature is increased, the dynamics become dominated by an apparent attractive intermicellar potential observed in microscopic creep measurements. While Pluronic L64 solutions have been reported to form a percolated micellar network, DWS-based microviscoelasticity measurements do not detect the previously observed G'˜G″˜ωΔ scaling expected for a static percolated network at low frequencies. This most likely owes to the fact that tracer particle microrheology is dominated by local Pluronic L64 micelle dynamics in the near sphere region and not the bulk mechanical properties as measured by traditional rheometry. The sensitivity of tracer particle microrheological measurements to the true dynamic nature of the percolated network in weak physical gels highlights the distinct differences between these micro- and macrorheology measurement techniques. Such discrepancies should be most evident in systems that are dominated by association processes such as those occurring in AHS solutions or polymer solutions approaching a phase boundary. Despite this, the AHS potential is qualitatively consistent with the results found here.

Microviscoelasticity of adhesive hard sphere dispersions: tracer particle microrheology of aqueous Pluronic L64 solutions.

PubMed

Kloxin, Christopher J; van Zanten, John H

2009-10-07

DWS-based tracer particle microrheology is demonstrated to be a useful way to study the dynamics of aqueous Pluronic L64 solutions, which is viewed as a model adhesive hard sphere (AHS) system. The short-time dynamics of aqueous Pluronic L64 solutions indicate a purely hydrodynamic high frequency microviscosity as predicted by Batchelor for colloidal dispersions. The evolution of the micellar dynamics reveals a zero shear microviscosity in good agreement with steady shear viscosity measurements. As the temperature is increased, the dynamics become dominated by an apparent attractive intermicellar potential observed in microscopic creep measurements. While Pluronic L64 solutions have been reported to form a percolated micellar network, DWS-based microviscoelasticity measurements do not detect the previously observed G(') approximately G(") approximately omega(Delta) scaling expected for a static percolated network at low frequencies. This most likely owes to the fact that tracer particle microrheology is dominated by local Pluronic L64 micelle dynamics in the near sphere region and not the bulk mechanical properties as measured by traditional rheometry. The sensitivity of tracer particle microrheological measurements to the true dynamic nature of the percolated network in weak physical gels highlights the distinct differences between these micro- and macrorheology measurement techniques. Such discrepancies should be most evident in systems that are dominated by association processes such as those occurring in AHS solutions or polymer solutions approaching a phase boundary. Despite this, the AHS potential is qualitatively consistent with the results found here.

The experimental investigation of the ignition petrol mechanism at high temperature metal single particles

NASA Astrophysics Data System (ADS)

Zakharevich, Arkadiy V.; Osotova, Diana S.

2015-01-01

The flammable substance by single "hot" metallic particle ignition mechanism are experimentally investigated. On the basis experimental data it is established that the gasoline ignition occurs only with interaction of the mixture of its vapors with air and "hot" particle with the vapors concentrations, which correspond to the evaporating the gasoline conditions at room temperatures. The probability of gasoline vapors mixture with air igniting rapidly is reduced in proportion to their withdrawal from the evaporation surface. Ignition occurs neither in the vapor phase nor on the gasoline surface, even if particle is immersed in it in full or in partly, if the particle temperature is lower than the critical.

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.

Water and acid soluble trace metals in atmospheric particles

NASA Technical Reports Server (NTRS)

Lindberg, S. E.; Harriss, R. C.

1983-01-01

Continental aerosols are collected above a deciduous forest in eastern Tennessee and subjected to selective extractions to determine the water-soluble and acid-leachable concentrations of Cd, Mn, Pb, and Zn. The combined contributions of these metals to the total aerosol mass is 0.5 percent, with approximately 70 percent of this attributable to Pb alone. A substantial fraction (approximately 50 percent or more) of the acid-leachable metals is soluble in distilled water. In general, this water-soluble fraction increases with decreasing particle size and with increasing frequency of atmospheric water vapor saturation during the sampling period. The pattern of relative solubilities (Zn being greater than Mn, which is approximately equal to Cd, which is greater than Pb) is found to be similar to the general order of the thermodynamic solubilities of the most probable salts of these elements in continental aerosols with mixed fossil fuel and soil sources.

Mobilization and transport of metal-rich colloidal particles from mine tailings into soil under transient chemical and physical conditions.

PubMed

Lu, Cong; Wu, Yaoguo; Hu, Sihai; Raza, Muhammad Ali; Fu, Yilin

2016-04-01

Exposed mine tailing wastes with considerable heavy metals can release hazardous colloidal particles into soil under transient chemical and physical conditions. Two-layered packed columns with tailings above and soils below were established to investigate mobilization and transport of colloidal particles from metal-rich mine tailings into soil under transient infiltration ionic strength (IS: 100, 20, 2 mM) and flow rate (FR: 20.7, 41, and 62.3 mm h(-1)), with Cu and Pb as representatives of the heavy metals. Results show that the tailing particles within the colloidal size (below 2 μm) were released from the columns. A step-decrease in infiltration IS and FR enhanced, whereas a step-increase in the IS and FR restrained the release of tailing particles from the column. The effects of step-changing FR were unexpected due to the small size of the released tailing particles (220-342 nm, being not sensitive to hydrodynamic shear force), the diffusion-controlled particle release process and the relatively compact pore structure. The tailing particles present in the solution with tested IS were found negatively charged and more stable than soil particles, which provides favorable conditions for tailing particles to be transported over a long distance in the soil. The mobilization and transport of Cu and Pb from the tailings into soil were mediated by the tailing particles. Therefore, the inherent toxic tailing particles could be considerably introduced into soil under certain conditions (IS reduction or FR decrease), which may result in serious environmental pollution.

Particle-size dependence on metal(loid) distributions in mine wastes: Implications for water contamination and human exposure

USGS Publications Warehouse

Kim, C.S.; Wilson, K.M.; Rytuba, J.J.

2011-01-01

The mining and processing of metal-bearing ores has resulted in contamination issues where waste materials from abandoned mines remain in piles of untreated and unconsolidated material, posing the potential for waterborne and airborne transport of toxic elements. This study presents a systematic method of particle size separation, mass distribution, and bulk chemical analysis for mine tailings and adjacent background soil samples from the Rand historic mining district, California, in order to assess particle size distribution and related trends in metal(loid) concentration as a function of particle size. Mine tailings produced through stamp milling and leaching processes were found to have both a narrower and finer particle size distribution than background samples, with significant fractions of particles available in a size range (???250 ??m) that could be incidentally ingested. In both tailings and background samples, the majority of trace metal(loid)s display an inverse relationship between concentration and particle size, resulting in higher proportions of As, Cr, Cu, Pb and Zn in finer-sized fractions which are more susceptible to both water- and wind-borne transport as well as ingestion and/or inhalation. Established regulatory screening levels for such elements may, therefore, significantly underestimate potential exposure risk if relying solely on bulk sample concentrations to guide remediation decisions. Correlations in elemental concentration trends (such as between As and Fe) indicate relationships between elements that may be relevant to their chemical speciation. ?? 2011 Elsevier Ltd.

Self-assembly of polyhedral metal-organic framework particles into three-dimensional ordered superstructures

NASA Astrophysics Data System (ADS)

Avci, Civan; Imaz, Inhar; Carné-Sánchez, Arnau; Pariente, Jose Angel; Tasios, Nikos; Pérez-Carvajal, Javier; Alonso, Maria Isabel; Blanco, Alvaro; Dijkstra, Marjolein; López, Cefe; Maspoch, Daniel

2018-01-01

Self-assembly of particles into long-range, three-dimensional, ordered superstructures is crucial for the design of a variety of materials, including plasmonic sensing materials, energy or gas storage systems, catalysts and photonic crystals. Here, we have combined experimental and simulation data to show that truncated rhombic dodecahedral particles of the metal-organic framework (MOF) ZIF-8 can self-assemble into millimetre-sized superstructures with an underlying three-dimensional rhombohedral lattice that behave as photonic crystals. Those superstructures feature a photonic bandgap that can be tuned by controlling the size of the ZIF-8 particles and is also responsive to the adsorption of guest substances in the micropores of the ZIF-8 particles. In addition, superstructures with different lattices can also be assembled by tuning the truncation of ZIF-8 particles, or by using octahedral UiO-66 MOF particles instead. These well-ordered, sub-micrometre-sized superstructures might ultimately facilitate the design of three-dimensional photonic materials for applications in sensing.

The role of particle-size soil fractions in the adsorption of heavy metals

NASA Astrophysics Data System (ADS)

Mandzhieva, Saglara; Minkina, Tatiana; Pinsky, David; Batukaev, Abdulmalik; Kalinitchenko, Valeriy; Sushkova, Svetlana; Chaplygin, Viktor; Dikaev, Zaurbek; Startsev, Viktor; Bakoev, Serojdin

2014-05-01

Ion-exchange adsorption phenomena are important in the immobilization of heavy metals (HMs) by soils. Numerous works are devoted to the study of this problem. However, the interaction features of different particle-size soil fractions and their role in the immobilization of HMs studied insufficiently. Therefore, the assessment of the effect of the particle-size distribution on the adsorption properties of soils is a vital task. The parameters of Cu2+, Pb2+ and Zn2+ adsorption by chernozems of the south of Russia and their particle-size fractions were studied. In the particle-size fractions separated from the soils, the concentrations of Cu2+, Pb2+, and Zn2 decreased with the decreasing particle size. The parameters of the adsorption values of k (the constant of the affinity)and Cmax.(the maximum adsorption of the HMs) characterizing the adsorption of HMs by the southern chernozem and its particle-size fractions formed the following sequence: silt > clay > entire soil. The adsorption capacity of chernozems for Cu2+, Pb2+, and Zn2+ depending on the particle-size distribution decreased in the following sequence: clay loamy ordinary chernozem clay loamy southern chernozem> loamy southern chernozem> loamy sandy southern chernozem. According to the parameters of the adsorption by the different particle-size fractions, the heavy metal cations form a sequence analogous to that obtained for the entire soils: Cu2+ ≥ Pb2+ > Zn2+. The parameters of the heavy metal adsorption by similar particle-size fractions separated from different soils decreased in the following order: clay loamy chernozem> loamy chernozem> loamy sandy chernozem. The analysis of the changes in the parameters of the Cu2+, Pb2+, and Zn2+ adsorption by the studied soils and their particle-size fractions showed that the extensive adsorption characteristic - the maximum adsorption (Cmax.) - is a less sensitive parameter characterizing the adsorption capacity of the soils than the intensive characteristic of

Constraining axion-like-particles with hard X-ray emission from magnetars

NASA Astrophysics Data System (ADS)

Fortin, Jean-François; Sinha, Kuver

2018-06-01

Axion-like particles (ALPs) produced in the core of a magnetar will convert to photons in the magnetosphere, leading to possible signatures in the hard X-ray band. We perform a detailed calculation of the ALP-to-photon conversion probability in the magnetosphere, recasting the coupled differential equations that describe ALP-photon propagation into a form that is efficient for large scale numerical scans. We show the dependence of the conversion probability on the ALP energy, mass, ALP-photon coupling, magnetar radius, surface magnetic field, and the angle between the magnetic field and direction of propagation. Along the way, we develop an analytic formalism to perform similar calculations in more general n-state oscillation systems. Assuming ALP emission rates from the core that are just subdominant to neutrino emission, we calculate the resulting constraints on the ALP mass versus ALP-photon coupling space, taking SGR 1806-20 as an example. In particular, we take benchmark values for the magnetar radius and core temperature, and constrain the ALP parameter space by the requirement that the luminosity from ALP-to-photon conversion should not exceed the total observed luminosity from the magnetar. The resulting constraints are competitive with constraints from helioscope experiments in the relevant part of ALP parameter space.

Electronic transport properties of 4f shell elements of liquid metal using hard sphere Yukawa system

NASA Astrophysics Data System (ADS)

Patel, H. P.; Sonvane, Y. A.; Thakor, P. B.

2018-04-01

The electronic transport properties are analyzed for 4f shell elements of liquid metals. To examine the electronic transport properties like electrical resistivity (ρ), thermal conductivity (σ) and thermo electrical power (Q), we used our own parameter free model potential with the Hard Sphere Yukawa (HSY) reference system. The screening effect on aforesaid properties has been examined by using different screening functions like Hartree (H), Taylor (T) and Sarkar (S). The correlations of our resultsand other data with available experimental values are intensely promising. Also, we conclude that our newly constructed parameter free model potential is capable of explaining the above mentioned electronic transport properties.

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.

Trace metal characterization of aerosol particles and cloud water during HCCT 2010

NASA Astrophysics Data System (ADS)

Fomba, K. W.; van Pinxteren, D.; Müller, K.; Iinuma, Y.; Lee, T.; Collett, J. L., Jr.; Herrmann, H.

2015-08-01

Trace metal characterization of bulk and size-resolved aerosol and cloud water samples were performed during the Hill Cap Cloud Thuringia (HCCT) campaign. Cloud water was collected at the top of Mt. Schmücke while aerosol samples were collected at two stations upwind and downwind of Mt. Schmücke. Fourteen trace metals including Ti, V, Fe, Mn, Co, Zn, Ni, Cu, As, Sr, Rb, Pb, Cr, and Se were investigated during four full cloud events (FCEs) that fulfilled the conditions of a continuous air mass flow through the three stations. Aerosol particle trace metal concentrations were found to be lower than those observed in the same region during previous field experiments but were within a similar range to those observed in other rural regions in Europe. Fe and Zn were the most abundant elements with concentration ranges of 0.2-111.6 and 1.1-32.1 ng m-3, respectively. Fe, Mn, and Ti were mainly found in coarse mode aerosols while Zn, Pb, and As were mostly found in the fine mode. Correlation and enrichment factor analysis of trace metals revealed that trace metals such as Ti and Rb were mostly of crustal origin while trace metals such as Zn, Pb, As, Cr, Ni, V, and Cu were of anthropogenic origin. Trace metals such as Fe and Mn were of mixed origins including crustal and combustion sources. Trace metal cloud water concentration decreased from Ti, Mn, Cr, to Co with average concentrations of 9.18, 5.59, 5.54, and 0.46 μg L-1, respectively. A non-uniform distribution of soluble Fe, Cu, and Mn was observed across the cloud drop sizes. Soluble Fe and Cu were found mainly in cloud droplets with diameters between 16 and 22 μm, while Mn was found mostly in larger drops greater than 22 μm. Fe(III) was the main form of soluble Fe especially in the small and larger drops with concentrations ranging from 2.2 to 37.1 μg L-1. In contrast to other studies, Fe(II) was observed mainly in the evening hours, implying its presence was not directly related to photochemical processes

Trace metal characterization of aerosol particles and cloud water during HCCT 2010

NASA Astrophysics Data System (ADS)

Fomba, K. W.; van Pinxteren, D.; Müller, K.; Iinuma, Y.; Lee, T.; Collet, J., Jr.; Herrmann, H.

2015-04-01

Trace metal characterization of bulk and size resolved aerosol and cloud water samples were performed during the Hill Cap Cloud Thuringia (HCCT) campaign. Cloud water was collected at the top of Mt. Schmücke while aerosol samples were collected at two stations upwind and downwind of Mt. Schmücke. Fourteen trace metals including Ti, V, Fe, Mn, Co, Zn, Ni, Cu, As, Sr, Rb, Pb, Cr, and Se were investigated during four full cloud events (FCE) that fulfilled the conditions of a continuous air mass flow through the three stations. Aerosol particle trace metal concentrations were found to be lower than those observed in the same region during previous field experiments but were within a similar range to those observed in other rural regions in Europe. Fe and Zn were the most abundant elements with concentration ranges of 0.2-111.6 and 1.1-32.1 ng m-3, respectively. Fe, Mn and Ti were mainly found in coarse mode aerosols while Zn, Pb and As were mostly found in the fine mode. Correlation and enrichment factor analysis of trace metals revealed that trace metals such as Ti and Rb were mostly of crustal origin while trace metals such as Zn, Pb, As, Cr, Ni, V, and Cu were of anthropogenic origin. Trace metals such as Fe, Mn, were of mixed origins including crustal and combustion sources. Trace metal cloud water concentration decreased from Ti, Mn, Cr, to Co with average concentrations of 9.18, 5.59, 5.54, and 0.46 μg L-1, respectively. A non-uniform distribution of soluble Fe, Cu and Mn was observed across the cloud drop sizes. Soluble Fe and Cu were found mainly in cloud droplets with diameters between 16 and 22 μm while Mn was found mostly in larger drops greater than 22 μm. Fe (III) was the main form of soluble Fe especially in the small and larger drops with concentrations ranging from 2.2 to 37.1 μg L-1. In contrast to other studies, Fe (II) was observed mainly in the evening hours, implying its presence was not directly related to photochemical processes. Aerosol

Heat Transfer Enhancement of Metal Hydride Particle Bed for Heat Driven Type Refrigerator by Carbon Fiber

NASA Astrophysics Data System (ADS)

Bae, Sang-Chul; Tanae, Takayuki; Monde, Masanori; Katsuta, Masafumi

A series of study has been performed on the metal hydride particle beds of Ti0.15Zr0.85Cr0.9Fe0.6Ni0.2Mn0.3Cu0.05 (MH-1, using for heat source), Ti0.73Zr0.27Cr1.2Fe0.3Ni0.1Mn0.4Cu0.05 (MH-2, using for cooling load) to measure the effective thermal conductivities. The effective thermal conductivities of activated and oxidized MH particle bed in helium have been examined. Experiment results show that pressure has great influence on effective thermal conductivity in low pressure range (<0.5 MPa). And that influence decreases rapidly with increase of gas pressure. The reason of pressure dependence at low pressure range is that the mean free path of gas becomes greater than effective thickness of gas film which is important to the heat transfer mechanism of particle bed. In order to enhance the poor thermal conductivity of metal hydride particle bed, carbon fiber mixing method has been used in this study. Three types, two insert methods and five mass percentages of carbon fiber have been examined and compared. The highest effective thermal conductivity of MH particle bed has been reached with Type B carbon fiber which has second higher thermal conductivity, and 2 weight percentage. This method has acquired 5-6 times higher thermal conductivity than pure metal hydride particle beds with quite low quantity of additives, only 2 mass% of carbon fiber. This is a good result comparing to other method which can reach higher effective thermal conductivity but needs much higher percentage of additives too.

Transformation of metal-organic frameworks for molecular sieving membranes

PubMed Central

Li, Wanbin; Zhang, Yufan; Zhang, Congyang; Meng, Qin; Xu, Zehai; Su, Pengcheng; Li, Qingbiao; Shen, Chong; Fan, Zheng; Qin, Lei; Zhang, Guoliang

2016-01-01

The development of simple, versatile strategies for the synthesis of metal-organic framework (MOF)-derived membranes are of increasing scientific interest, but challenges exist in understanding suitable fabrication mechanisms. Here we report a route for the complete transformation of a series of MOF membranes and particles, based on multivalent cation substitution. Through our approach, the effective pore size can be reduced through the immobilization of metal salt residues in the cavities, and appropriate MOF crystal facets can be exposed, to achieve competitive molecular sieving capabilities. The method can also be used more generally for the synthesis of a variety of MOF membranes and particles. Importantly, we design and synthesize promising MOF membranes candidates that are hard to achieve through conventional methods. For example, our CuBTC/MIL-100 membrane exhibits 89, 171, 241 and 336 times higher H2 permeance than that of CO2, O2, N2 and CH4, respectively. PMID:27090597

Effect of Spray Particle Velocity on Cavitation Erosion Resistance Characteristics of HVOF and HVAF Processed 86WC-10Co4Cr Hydro Turbine Coatings

NASA Astrophysics Data System (ADS)

Kumar, R. K.; Kamaraj, M.; Seetharamu, S.; Pramod, T.; Sampathkumaran, P.

2016-08-01

The hydro plants utilizing silt-laden water for power generation suffer from severe metal wastage due to particle-induced erosion and cavitation. High-velocity oxy-fuel process (HVOF)-based coatings is widely applied to improve the erosion life. The process parameters such as particle velocity, size, powder feed rate, temperature, affect their mechanical properties. The high-velocity air fuel (HVAF) technology, with higher particle velocities and lower spray temperatures, gives dense and substantially nonoxidized coating. In the present study, the cavitation resistance of 86WC-10Co4Cr-type HVOF coating processed at 680 m/s spray particle velocity was compared with HVAF coatings made at 895, 960, and 1010 m/s. The properties such as porosity, hardness, indentation toughness, and cavitation resistance were investigated. The surface damage morphology has been analyzed in SEM. The cohesion between different layers has been examined qualitatively through scratch depth measurements across the cross section. The HVAF coatings have shown a lower porosity, higher hardness, and superior cavitation resistance. Delamination, extensive cracking of the matrix interface, and detachment of the WC grains were observed in HVOF coating. The rate of metal loss is low in HVAF coatings implying that process parameters play a vital role in achieving improved cavitation resistance.

Biokinetics and internal dosimetry of inhaled metal tritide particles

NASA Astrophysics Data System (ADS)

Wang, Yansheng

1998-12-01

Metal tritides (MT), stable chemical compounds of tritium, are widely used in nuclear engineering facilities. MT particles can be released as aerosols. Inhaling MT particles is a potential occupational radiation hazard. Little information is available on their dissolution behavior, biokinetics, and dosimetry. The objectives of present dissertation are to estimate dissolution rates, to develop biokinetic models, to improve internal dosimetric considerations, and to classify MT materials. This study consisted of three phases: In vitro dissolution in a simulated lung fluid, In vivo rat experiments on retention and clearance, and biokinetic modeling and dosimetric evaluation. There was a supporting study on self- absorption of tritium beta in MT particles. MT materials used in this study were titanium (Ti) and zirconium (Zr) tritides. Results shows considerable self-absorption of beta particles and their energy, even for respirable MT particles smaller than 5 μm. The self-absorption factors should be required for counting MT particle samples and for estimating absorbed dose to tissues. In vitro and in vivo dissolution data indicate that Ti and Zr tritides are poorly soluble materials. Ti tritide belongs to the W class or M type while Zr tritide can be classified as Y class or S type. Due to long retention time of the MT particles, tritium betas directly from the particles contribute over 90% of the absorbed dose to lung. The lung dose contributes most of the effective dose to the whole body. Dissolved tritium including tritiated water (HTO) and organically bound tritium (OBT) has less effect on the lung dose and effective dose. Results on the annual limit on intake (ALI) indicate that the current radiation protection guideline based on HTO is not adequate for inhalation exposure to MT particles and needs to be modified. The biokinetic models developed in this study have predictive powers to estimate the consequences of a human inhalation exposure to MT aerosols. The

Image processing enhancement of high-resolution TEM micrographs of nanometer-size metal particles

NASA Technical Reports Server (NTRS)

Artal, P.; Avalos-Borja, M.; Soria, F.; Poppa, H.; Heinemann, K.

1989-01-01

The high-resolution TEM detectability of lattice fringes from metal particles supported on substrates is impeded by the substrate itself. Single value decomposition (SVD) and Fourier filtering (FFT) methods were applied to standard high resolution micrographs to enhance lattice resolution from particles as well as from crystalline substrates. SVD produced good results for one direction of fringes, and it can be implemented as a real-time process. Fourier methods are independent of azimuthal directions and allow separation of particle lattice planes from those pertaining to the substrate, which makes it feasible to detect possible substrate distortions produced by the supported particle. This method, on the other hand, is more elaborate, requires more computer time than SVD and is, therefore, less likely to be used in real-time image processing applications.

Development of High Strength Ni-Cu-Zr-Ti-Si-Sn In-Situ Bulk Metallic Glass Composites Reinforced by Hard B2 Phase

NASA Astrophysics Data System (ADS)

Park, Hyo Jin; Hong, Sung Hwan; Park, Hae Jin; Kim, Young Seok; Kim, Jeong Tae; Na, Young Sang; Lim, Ka Ram; Wang, Wei-Min; Kim, Ki Buem

2018-03-01

In the present study, the influence of atomic ratio of Zr to Ti on the microstructure and mechanical properties of Ni-Cu-Zr-Ti-Si-Sn alloys is investigated. The alloys were designed by fine replacement of Ti for Zr from Ni39Cu20Zr36-xTixSi2Sn3. The increase of Ti content enhances glass forming ability of the alloy by suppression of formation of (Ni, Cu)10(Zr, Ti)7 phase during solidification. With further increasing Ti content up to 24 at.%, the B2 phase is introduced in the amorphous matrix with a small amount of B19' phase from alloy melt. The bulk metallic glass composite containing B2 phase with a volume fraction of 10 vol% exhibits higher fracture strength ( 2.5 GPa) than that of monolithic bulk metallic glass ( 2.3 GPa). This improvement is associated to the individual mechanical characteristics of the B2 phase and amorphous matrix. The B2 phase exhibits higher hardness and modulus than those of amorphous matrix as well as effective stress accommodation up to the higher stress level than the yield strength of amorphous matrix. The large stress accommodation capacity of the hard B2 phase plays an important factor to improve the mechanical properties of in situ Ni-based bulk metallic glass composites.

Catalytic Metal Free Production of Large Cage Structure Carbon Particles: A Candidate for Hydrogen Storage

NASA Technical Reports Server (NTRS)

Kimura, Yuki; Nuth, Joseph A., III; Ferguson, Frank T.

2005-01-01

We will demonstrate that carbon particles consisting of large cages can be produced without catalytic metal. The carbon particles were produced in CO gas as well as by introduction of 5% methane gas into the CO gas. The gas-produced carbon particles were able to absorb approximately 16.2 wt% of hydrogen. This value is 2.5 times higher than the 6.5 wt% goal for the vehicular hydrogen storage proposed by the Department of Energy in the USA. Therefore, we believe that this carbon particle is an excellent candidate for hydrogen storage for fuel cells.

Particle-bound metal transport after removal of a small dam in ...

EPA Pesticide Factsheets

The Pawtuxet River in Rhode Island, USA, has a long history of industrial activity and pollutant discharges. Metal contamination of the river sediments is well documented and historically exceeded toxicity thresholds for a variety of organisms. The Pawtuxet River dam, a low-head dam at the mouth of the river, was removed in August 2011. The removal of the dam was part of an effort to restore the riverine ecosystem after centuries of anthropogenic impact. Sediment traps were deployed below the dam to assess changes in metal concentrations and fluxes (Ag, Cd, Cr, Cu, Ni, Pb, and Zn) from the river system into Pawtuxet Cove. Sediment traps were deployed for an average duration of 24 days each, and deployments continued for 15 months after the dam was removed. Metal concentrations in the trapped suspended particulate matter dropped after dam removal (e.g., 460 to 276 mg/kg for Zn) and remained below preremoval levels for most of the study. However, particle-bound metal fluxes increased immediately after dam removal (e.g., 1206 to 4248 g/day for Zn). Changes in flux rates during the study period indicated that river volumetric flow rates acted as the primary mechanism controlling the flux of metals into Pawtuxet Cove and ultimately upper Narragansett Bay. Even though suspended particulate matter metal concentrations initially dropped after removal of the dam, no discernable effect on the concentration or flux of the study metals exiting the river could be associa

Therapeutic effects of OP-1 on metal wear particle induced osteoblasts injury in vitro

PubMed Central

Sun, Guojing; Chen, Jianmin; Yang, Shufeng; Parker, Thomas MN; Goodman, Gary MP; Hasama, Jack M; Zhao, Jianning

2015-01-01

Aseptic lossening is a main reason for the revision of total joint arthroplasty. Metal-wear particles induced deregulation of bone resorption or formation has been considered as the major process of aseptic lossening. Osteogenic protein-1 (OP-1) can be used to improve bone formation. However, such effect is not clearly understood after the metal-wear particles injury. Here, we investigated the molecular mechanisms by which OP-1 regulates the activity of bone formation and anti-inflammatory after injury. Results showed that OP-1 increased cell viability and bone formation ability of impaired osteoblast cells at 72 hours after being injured by cobalt particles. Pathway analyses revealed that both mRNA and protein levels of Smad1 and Smad5 were significantly increased upon the treatment of OP-1 in the cell injury model. Similarly, runt-related transcription factor 2 (Runx2) was also significantly upregulated in the OP-1 treated cells. Moreover, treatment with OP-1 inhibited the secretion of interleukin 6 (IL-6), tumor necrosis factor alpha (TNF-α), and IL-18 in cobalt impaired cells. Collectively, these results suggest that OP-1 could inhibit cobalt particles induced cell injury by activating Smad1, Smad5, and Runx2, and such procedure is accompanied by anti-inflammatory reaction. PMID:26885192

Removal of heavy metals using bentonite supported nano-zero valent iron particles

NASA Astrophysics Data System (ADS)

Zarime, Nur Aishah; Yaacob, Wan Zuhari Wan; Jamil, Habibah

2018-04-01

This study reports the composite nanoscale zero-valent iron (nZVI) which was successfully synthesized using low cost natural clay (bentonite). Bentonite composite nZVI (B-nZVI) was introduced to reduce the agglomeration of nZVI particles, thus will used for heavy metals treatment. The synthesized material was analyzed using physical, mineralogy and morphology analysis such as Brunnaer-Emmett-Teller (BET) surface area, Field Emission Scanning Electron Microscopy (FESEM), X-Ray Diffraction (XRD), Fourier Transform Infrared (FTIR) and X-ray Photoelectron Spectroscopy (XPS). The batch adsorption test of Bentonite and B-nZVI with heavy metals solutions (Pb, Cu, Cd, Co, Ni and Zn) was also conducted to determine their effectiveness in removing heavy metals. Through Batch test, B-nZVI shows the highest adsorption capacity (qe= 50.25 mg/g) compared to bentonite (qe= 27.75 mg/g). This occurred because B-nZVI can reduce aggregation of nZVI, dispersed well in bentonite layers thus it can provide more sites for adsorbing heavy metals.

The van Hove distribution function for Brownian hard spheres: Dynamical test particle theory and computer simulations for bulk dynamics

NASA Astrophysics Data System (ADS)

Hopkins, Paul; Fortini, Andrea; Archer, Andrew J.; Schmidt, Matthias

2010-12-01

We describe a test particle approach based on dynamical density functional theory (DDFT) for studying the correlated time evolution of the particles that constitute a fluid. Our theory provides a means of calculating the van Hove distribution function by treating its self and distinct parts as the two components of a binary fluid mixture, with the "self " component having only one particle, the "distinct" component consisting of all the other particles, and using DDFT to calculate the time evolution of the density profiles for the two components. We apply this approach to a bulk fluid of Brownian hard spheres and compare to results for the van Hove function and the intermediate scattering function from Brownian dynamics computer simulations. We find good agreement at low and intermediate densities using the very simple Ramakrishnan-Yussouff [Phys. Rev. B 19, 2775 (1979)] approximation for the excess free energy functional. Since the DDFT is based on the equilibrium Helmholtz free energy functional, we can probe a free energy landscape that underlies the dynamics. Within the mean-field approximation we find that as the particle density increases, this landscape develops a minimum, while an exact treatment of a model confined situation shows that for an ergodic fluid this landscape should be monotonic. We discuss possible implications for slow, glassy, and arrested dynamics at high densities.

Metal elements in tissue with dental peri-implantitis: a pilot study.

PubMed

Fretwurst, Tobias; Buzanich, Guenter; Nahles, Susanne; Woelber, Johan Peter; Riesemeier, Heinrich; Nelson, Katja

2016-09-01

Dental peri-implantitis is characterized by a multifactorial etiology. The role of metal elements as an etiological factor for peri-implantitis is still unclear. The aim of this study was to investigate the incidence of metal elements in bone and mucosal tissues around dental Grade 4 CP titanium implants with signs of peri-implantitis in human patients. In this prospective pilot study, all patients were enrolled consecutively in two study centers. Bone and soft tissue samples of patients with peri-implantitis with indication for explantation were analyzed for the incidence of different elements (Ca, P, Ti, Fe) by means of synchrotron radiation X-ray fluorescence spectroscopy (SRXRF) and polarized light microscopy (PLM). The existence of macrophages and lymphocytes in the histologic specimens was analyzed. Biopsies of 12 patients (seven bone samples, five mucosal samples) were included and analyzed. In nine of the 12 samples (75%), the SRXRF examination revealed the existence of titanium (Ti) and an associated occurrence with Iron (Fe). Metal particles were detected in peri-implant soft tissue using PLM. In samples with increased titanium concentration, lymphocytes were detected, whereas M1 macrophages were predominantly seen in samples with metal particles. Titanium and Iron elements were found in soft and hard tissue biopsies retrieved from peri-implantitis sites. Further histologic and immunohistochemical studies need to clarify which specific immune reaction metal elements/particles induce in dental peri-implant tissue. © 2015 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

Photocatalytic reduction of heavy metal ions on derivatized titanium dioxide nano-particle surface studied by XAFS

NASA Astrophysics Data System (ADS)

Chen, Lin X.; Rajh, Tijana; Mićić, Olga Wang, Zhiyu; Tiede, David M.; Thurnauer, Marion

1997-12-01

Photoreduction of heavy metal ions, Cu 2- and Hg 2+, on TiO 2 nano-particle surfaces, has been investigated by XAFS measurements. The effects of TiO 2 surface modification reagents on the reaction efficiency have been studied. We observed a significant reaction efficiency enhancement when amino acid alanine was added to a mixture of 0.01 M Cu 2+ and TiO 2 nano-particles. Fifty percent of the adsorbed Cu 2+ has been reduced to Cu 0 after 1-h illumination with a UV-enhanced xenon lamp. Photoreduction of Hg 2+ on TiO 2 colloid surfaces was also investigated without and with thiolactic acid (TLA). In this case, the photoreduction efficiency for Hg 2+ was lowered. Structures of metal ion surroundings in various complexes as well as their role in photoreduction of metal ions are discussed.

Ceramic-metal composites prepared via tape casting and melt infiltration methods

NASA Astrophysics Data System (ADS)

Kim, Hyun Jun

Melt infiltration of preforms prepared by tape casting and lamination has been accomplished using a short-time infiltration process that significantly suppresses reaction product formation. For layered materials produced via infiltration of laminated ceramic tapes, of particular interest is the effect that a large change in microstructure has on infiltration, phase formation, and mechanical properties. Hardness of the fine scale composite layers is approximately three times higher than coarse scale layers, due to greater strength of the fine B4C network. Fractography showed that crack propagation occurred by brittle fracture of the carbide and ductile extension of the metal. Despite large differences in hardness, the fracture mode of the fine and coarse scale microstructures appears identical. Fluid flow modeling for tape casting was conducted with a Newtonian slurry under a parallel blade, and the effect of beveling the blade based on a one dimensional flow model is shown. The discussion on slurry deformation after the blade exit suggests that the mode of slurry deformation depends on the relative importance of the pressure gradient and wall shear and that the existence of zero shear plane might have a negative effect on particle alignment in the tape. The analysis of the flow under a beveled blade predicts that this configuration is more advantageous than the parallel blade for productivity and parallel blade is better for producing uniform particle alignment and thinner tape. Also, the one dimensional flow model for the beveled blade is shown to be a valid approximation of the fluid behavior below a blade angle of 45 degrees. The flow visualization study on tape casting was conducted with a transparent apparatus and model slurry. Most investigators have concluded that the shear stress between the doctor blade and moving carrier causes the particle alignment, but, according to the result of visualization experiment, some degree of particle alignment is already

Numerical investigation of field enhancement by metal nano-particles using a hybrid FDTD-PSTD algorithm.

PubMed

Pernice, W H; Payne, F P; Gallagher, D F

2007-09-03

We present a novel numerical scheme for the simulation of the field enhancement by metal nano-particles in the time domain. The algorithm is based on a combination of the finite-difference time-domain method and the pseudo-spectral time-domain method for dispersive materials. The hybrid solver leads to an efficient subgridding algorithm that does not suffer from spurious field spikes as do FDTD schemes. Simulation of the field enhancement by gold particles shows the expected exponential field profile. The enhancement factors are computed for single particles and particle arrays. Due to the geometry conforming mesh the algorithm is stable for long integration times and thus suitable for the simulation of resonance phenomena in coupled nano-particle structures.

Effect of particle morphology of Ni on the mechanical behavior of AZ91E-Ni coated nano Al2O3 composites

NASA Astrophysics Data System (ADS)

Sameer Kumar, D.; Suman, K. N. S.; Poddar, Palash

2017-06-01

The properties of any composite always depend on the bonding between the matrix and reinforcement phases. One way of improving the wettability of reinforcement in a matrix is to apply a layer of coating on reinforcing particles. The present study aims at developing Ni coating on nano Al2O3 ceramic particles and dispersing them in AZ91E magnesium matrix material. The electroless plating method has been employed to coat the particles and semi solid stir casting technique was adopted to prepare the composites. Several weight fractions of dispersed phase are considered to analyze the behavior of the fabricated composites. Field emission scanning electron microscopy (FESEM) and x-ray diffraction analysis has been carried out to investigate the distribution of particles and phase characteristics of the proposed material. The physical and mechanical behavior of the material was examined through density measurements, hardness, elastic modulus, ductility and tensile strength calculations. The metal coating on reinforcement aids to promote metal-metal bonding interface reactions which result in improved properties of the composite. Tensile fractography was carried out under FESEM and presented.

Crystal-structure prediction via the Floppy-Box Monte Carlo algorithm: Method and application to hard (non)convex particles

NASA Astrophysics Data System (ADS)

de Graaf, Joost; Filion, Laura; Marechal, Matthieu; van Roij, René; Dijkstra, Marjolein

2012-12-01

In this paper, we describe the way to set up the floppy-box Monte Carlo (FBMC) method [L. Filion, M. Marechal, B. van Oorschot, D. Pelt, F. Smallenburg, and M. Dijkstra, Phys. Rev. Lett. 103, 188302 (2009), 10.1103/PhysRevLett.103.188302] to predict crystal-structure candidates for colloidal particles. The algorithm is explained in detail to ensure that it can be straightforwardly implemented on the basis of this text. The handling of hard-particle interactions in the FBMC algorithm is given special attention, as (soft) short-range and semi-long-range interactions can be treated in an analogous way. We also discuss two types of algorithms for checking for overlaps between polyhedra, the method of separating axes and a triangular-tessellation based technique. These can be combined with the FBMC method to enable crystal-structure prediction for systems composed of highly shape-anisotropic particles. Moreover, we present the results for the dense crystal structures predicted using the FBMC method for 159 (non)convex faceted particles, on which the findings in [J. de Graaf, R. van Roij, and M. Dijkstra, Phys. Rev. Lett. 107, 155501 (2011), 10.1103/PhysRevLett.107.155501] were based. Finally, we comment on the process of crystal-structure prediction itself and the choices that can be made in these simulations.

Monte Carlo computer simulation of sedimentation of charged hard spherocylinders.

PubMed

Viveros-Méndez, P X; Gil-Villegas, Alejandro; Aranda-Espinoza, S

2014-07-28

In this article we present a NVT Monte Carlo computer simulation study of sedimentation of an electroneutral mixture of oppositely charged hard spherocylinders (CHSC) with aspect ratio L/σ = 5, where L and σ are the length and diameter of the cylinder and hemispherical caps, respectively, for each particle. This system is an extension of the restricted primitive model for spherical particles, where L/σ = 0, and it is assumed that the ions are immersed in an structureless solvent, i.e., a continuum with dielectric constant D. The system consisted of N = 2000 particles and the Wolf method was implemented to handle the coulombic interactions of the inhomogeneous system. Results are presented for different values of the strength ratio between the gravitational and electrostatic interactions, Γ = (mgσ)/(e(2)/Dσ), where m is the mass per particle, e is the electron's charge and g is the gravitational acceleration value. A semi-infinite simulation cell was used with dimensions Lx ≈ Ly and Lz = 5Lx, where Lx, Ly, and Lz are the box dimensions in Cartesian coordinates, and the gravitational force acts along the z-direction. Sedimentation effects were studied by looking at every layer formed by the CHSC along the gravitational field. By increasing Γ, particles tend to get more packed at each layer and to arrange in local domains with an orientational ordering along two perpendicular axis, a feature not observed in the uncharged system with the same hard-body geometry. This type of arrangement, known as tetratic phase, has been observed in two-dimensional systems of hard-rectangles and rounded hard-squares. In this way, the coupling of gravitational and electric interactions in the CHSC system induces the arrangement of particles in layers, with the formation of quasi-two dimensional tetratic phases near the surface.

Magnetic particles

NASA Technical Reports Server (NTRS)

Chang, Manchium (Inventor); Colvin, Michael S. (Inventor); Rembaum, Alan (Inventor); Richards, Gil F. (Inventor)

1987-01-01

Metal oxide containing polymers and particularly styrene, acrylic or protein polymers containing fine, magnetic iron oxide particles are formed by combining a NO.sub.2 -substituted polymer with an acid such as hydrochloric acid in the presence of metal, particularly iron particles. The iron is oxidized to fine, black Fe.sub.3 O.sub.4 particles which deposit selectively on the polymer particles. Nitrated polymers are formed by reacting functionally substituted, nitrated organic compounds such as trinitrobenzene sulfonate or dinitrofluoro benzene with a functionally coreactive polymer such as an amine modified acrylic polymer or a protein. Other transition metals such as cobalt can also be incorporated into polymers using this method.

Size distributions of ambient air particles and enrichment factor analyses of metallic elements at Taichung Harbor near the Taiwan Strait

NASA Astrophysics Data System (ADS)

Fang, Guor-Cheng; Wu, Yuh-Shen; Chang, Shih-Yu; Huang, Shih-Han; Rau, Jui-Yeh

2006-10-01

This work attempts to characterize metallic elements associated with atmospheric particulate matter on a dry deposition plate, a TE-PUF high-volume air sampler and a universal air sampler. Dry deposition fluxes of particulates and concentrations of total suspended particulate, fine (PM 2.5) and coarse (PM 2.5-10) particulate matters were collected at Taichung harbor sampling sites from August 2004 to January 2005. Chemical analyses of metallic elements were made using a flame atomic absorption spectrophotometer coupled with hollow cathode lamps. Concentrations of metal elements in the forms of coarse particles and fine particles as well as the coarse/fine particulate ratios were presented. Statistical methods such as correlation analysis, principal component analysis and enrichment factor analysis were performed to compare the chemical components and identify possible emission sources at the sampling sites. Metallic elements of Cu, Zn, Pb, Cr, Ni and Mg had higher EF crust ratios in winter and spring than in summer and autumn. Diurnal and nocturnal variations of metallic element concentrations in fine and coarse particles were also discussed.

A study of the effect of solid particle impact and particle shape on the erosion morphology of ductile metals

NASA Technical Reports Server (NTRS)

Rao, P. V.; Young, S. G.; Buckley, D. H.

1984-01-01

Impulsive versus steady jet impingement of spherical glass bead particles on metal surfaces was studied using a gas gun facility and a commercial sand blasting apparatus. Crushed glass particles were also used in the sand blasting apparatus as well as glass beads. Comparisons of the different types of erosion patterns were made. Scanning electron microscopy, surface profilometry and energy dispersive X-ray spectroscopy analysis were used to characterize erosion patterns. The nature of the wear can be divided into cutting and deformation, each with its own characteristic features. Surface chemistry analysis indicates the possiblity of complex chemical and/or mechanical interactions between erodants and target materials.

Metal copper films deposited on cenosphere particles by magnetron sputtering method

NASA Astrophysics Data System (ADS)

Yu, Xiaozheng; Xu, Zheng; Shen, Zhigang

2007-05-01

Metal copper films with thicknesses from several nanometres to several micrometres were deposited on the surface of cenosphere particles by the magnetron sputtering method under different working conditions. An ultrasonic vibrating generator equipped with a conventional magnetron sputtering apparatus was used to prevent the cenosphere substrates from accumulating during film growth. The surface morphology, the chemical composition, the average grain size and the crystallization of cenosphere particles were characterized by field emission scanning electron microscopy (FE-SEM), inductively coupled plasma-atom emission spectrometer, x-ray photoelectron spectroscopy and x-ray diffraction (XRD) analysis, respectively, before and after the plating process. The results indicate that the copper films were successfully deposited on cenosphere particles. It was found from the FE-SEM results that the films were well compacted and highly uniform in thickness. The XRD results show that the copper film coated on cenospheres has a face centred cubic structure and the crystallization of the film sample increases with increasing sputtering power.

Feasibility of granular bed filtration of an aerosol of ultrafine metallic particles including a pressure drop regeneration system.

PubMed

Bémer, D; Wingert, L; Morele, Y; Subra, I

2015-09-01

A process for filtering an aerosol of ultrafine metallic particles (UFP) has been designed and tested, based on the principle of a multistage granular bed. The filtration system comprised a succession of granular beds of varying thickness composed of glass beads of different diameters. This system allows the pressure drop to be regenerated during filtration ("on-line" mode) using a vibrating probe. Tests monitoring the pressure drop were conducted on a "10-L/min" low airflow rate device and on a "100-m(3)/hr" prototype. Granular bed unclogging is automated on the latter. The cyclic operation and filtration performances are similar to that of filter medium-based industrial dust collectors. Filtration of ultrafine metallic particles generated by different industrial processes such as arc welding, metal cutting, or spraying constitutes a difficult problem due to the high filter clogging properties of these particles and to the high temperatures generally encountered. Granular beds represent an advantageous means of filtering these aerosols with difficult properties.

Hard X-ray and Particle Beams Research on 1.7 MA Z-pinch and Laser Plasma Experiments

NASA Astrophysics Data System (ADS)

Shrestha, Ishor; Kantsyrev, Victor; Safronova, Alla; Esaulov, Andrey; Nishio, Mineyuki; Shlyaptseva, Veronica; Keim, Steven; Weller, Michael; Stafford, Austin; Petkov, Emil; Schultz, Kimberly; Cooper, Matthew; PPDL Team

2013-10-01

Studies of hard x-ray (HXR) emission, electron and ion beam generation in z-pinch and laser plasmas are important for Inertial Confinement Fusion (ICF) and development of HXR sources from K-shell and L-shell radiation. The characteristics of HXR and particle beams produced by implosions of planar wire arrays, nested and single cylindrical wire arrays, and X-pinches were analyzed on 100 ns UNR Zebra generator with current up to 1.7 MA. In addition, the comparison of characteristics of HXR and electron beams on Zebra and 350 fs UNR Leopard laser experiments with foils has been performed. The diagnostics include Faraday cups, HXR diodes, different x-ray spectrometers and imaging systems, and ion mass spectrometer using the technique of Thomson parabola. Future work on HXRs and particle beams in HED plasmas is discussed. This work was supported by the DOE/NNSA Cooperative agreement DE-NA0001984 and in part by DE-FC52-06NA27616. This work was also supported by the Defense Threat Reduction Agency, Basic Research Award # HDTRA1-13-1-0033, to University of Nevada, Reno.

Nano- and microsized cubic gel particles from cyclodextrin metal-organic frameworks.

PubMed

Furukawa, Yuki; Ishiwata, Takumi; Sugikawa, Kouta; Kokado, Kenta; Sada, Kazuki

2012-10-15

Sweet cube o' mine: Bottom-up control of gel particles has been regarded as a great challenge. By employing internal cross-linking of cyclodextrin metal-organic frameworks, cubic sugar gels were formed with sharp edges that reflect the shape of the crystals. This enabled the fabrication of shape- and size-controlled polymer gels from porous crystals (see picture). Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

On the hardness of high carbon ferrous martensite

NASA Astrophysics Data System (ADS)

Mola, J.; Ren, M.

2018-06-01

Due to the presence of retained austenite in martensitic steels, especially steels with high carbon concentrations, it is difficult to estimate the hardness of martensite independent of the hardness of the coexisting austenite. In the present work, the hardness of ferrous martensite with carbon concentrations in the range 0.23-1.46 mass-% was estimated by the regression analysis of hardnesses for hardened martensitic-austenitic steels containing various martensite fractions. For a given carbon concentration, the hardness of martensitic-austenitic steels was found to increase exponentially with an increase in the fraction of the martensitic constituent. The hardness of the martensitic constituent was subsequently estimated by the exponential extrapolation of the hardness of phase mixtures to 100 vol.% martensite. For martensite containing 1.46 mass-% carbon, the hardness was estimated to be 1791 HV. This estimate of martensite hardness is significantly higher than the experimental hardness of 822 HV for a phase mixture of 68 vol.% martensite and 32 vol.% austenite. The hardness obtained by exponential extrapolation is also much higher than the hardness of 1104 HV based on the rule of mixtures. The underestimated hardness of high carbon martensite in the presence of austenite is due to the non-linear dependence of hardness on the martensite fraction. The latter is also a common observation in composite materials with a soft matrix and hard reinforcing particles.

Ultrastructural analysis of metal particles released from stainless steel and titanium miniplate components in an animal model.

PubMed

Matthew, I R; Frame, J W

1998-01-01

Low-vacuum scanning electron microscopy (Ivac SEM) was used to characterize the appearance of metal particles released from stressed and unstressed Champy miniplates placed in dogs and to study the relationship of the debris to the surrounding tissues. Under general endotracheal anesthesia, two Champy miniplates (titanium or stainless steel) were placed on the frontal bone in an animal model. One miniplate was bent to fit the curvature of the frontal bone (unstressed) and another miniplate of the same material was bent in a curve until the midpoint was raised 3 mm above the ends. The latter miniplate adapted to the skull curvature under tension during screw insertion (stressed). The miniplates and surrounding tissues were retrieved after intervals of 4, 12, and 24 weeks. Decalcified sections were prepared and examined by light microscopy and Ivac SEM. Under Ivac SEM examination, the titanium particles had a smooth, polygonal outline. Stainless steel particles were typically spherical, with numerous small projections on the surface. Most particles were 1 to 10 microns in diameter. The tissue response to the particles was variable; some particles were covered by fibrous connective tissue or enclosed by bone, and others were intracellular. The metal particles released from stressed or unstressed Champy miniplates were similar, and this was related to their source of origin and duration within the tissues. The tissue response to the particles appeared to depend on their location.

A magnetic braking and sensing technique for deceleration and recovery of moving non-magnetic metallic particles

NASA Astrophysics Data System (ADS)

Cheng, David; Yoshinaka, Akio; Wu, Lawrence

2018-05-01

A magnetic braking and sensing technique developed as a potential alternative to assist with the non-contact deceleration and detection of explosively dispersed non-magnetic metallic particles is discussed. In order to verify the feasibility of such a technique and gain an understanding of how the underlying forces scale with particle size and velocity, a study was conducted whereby an aluminum particle moving along a spatially varying but time-invariant magnetic field was modeled and the corresponding experiment performed.

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.

Analytical model for force prediction when machining metal matrix composites

NASA Astrophysics Data System (ADS)

Sikder, Snahungshu

Metal Matrix Composites (MMC) offer several thermo-mechanical advantages over standard materials and alloys which make them better candidates in different applications. Their light weight, high stiffness, and strength have attracted several industries such as automotive, aerospace, and defence for their wide range of products. However, the wide spread application of Meal Matrix Composites is still a challenge for industry. The hard and abrasive nature of the reinforcement particles is responsible for rapid tool wear and high machining costs. Fracture and debonding of the abrasive reinforcement particles are the considerable damage modes that directly influence the tool performance. It is very important to find highly effective way to machine MMCs. So, it is important to predict forces when machining Metal Matrix Composites because this will help to choose perfect tools for machining and ultimately save both money and time. This research presents an analytical force model for predicting the forces generated during machining of Metal Matrix Composites. In estimating the generated forces, several aspects of cutting mechanics were considered including: shearing force, ploughing force, and particle fracture force. Chip formation force was obtained by classical orthogonal metal cutting mechanics and the Johnson-Cook Equation. The ploughing force was formulated while the fracture force was calculated from the slip line field theory and the Griffith theory of failure. The predicted results were compared with previously measured data. The results showed very good agreement between the theoretically predicted and experimentally measured cutting forces.

Surface texture and hardness of dental alloys processed by alternative technologies

NASA Astrophysics Data System (ADS)

Porojan, Liliana; Savencu, Cristina E.; Topală, Florin I.; Porojan, Sorin D.

2017-08-01

Technological developments have led to the implementation of novel digitalized manufacturing methods for the production of metallic structures in prosthetic dentistry. These technologies can be classified as based on subtractive manufacturing, assisted by computer-aided design/computer-aided manufacturing (CAD/CAM) systems, or on additive manufacturing (AM), such as the recently developed laser-based methods. The aim of the study was to assess the surface texture and hardness of metallic structures for dental restorations obtained by alternative technologies: conventional casting (CST), computerized milling (MIL), AM power bed fusion methods, respective selective laser melting (SLM) and selective laser sintering (SLS). For the experimental analyses metallic specimens made of Co-Cr dental alloys were prepared as indicated by the manufacturers. The specimen structure at the macro level was observed by an optical microscope and micro-hardness was measured in all substrates. Metallic frameworks obtained by AM are characterized by increased hardness, depending also on the surface processing. The formation of microstructural defects can be better controlled and avoided during SLM and MIL process. Application of power bed fusion techniques, like SLS and SLM, is currently a challenge in dental alloys processing.

Glyphosate, Hard Water and Nephrotoxic Metals: Are They the Culprits Behind the Epidemic of Chronic Kidney Disease of Unknown Etiology in Sri Lanka?

PubMed Central

Jayasumana, Channa; Gunatilake, Sarath; Senanayake, Priyantha

2014-01-01

The current chronic kidney disease epidemic, the major health issue in the rice paddy farming areas in Sri Lanka has been the subject of many scientific and political debates over the last decade. Although there is no agreement among scientists about the etiology of the disease, a majority of them has concluded that this is a toxic nephropathy. None of the hypotheses put forward so far could explain coherently the totality of clinical, biochemical, histopathological findings, and the unique geographical distribution of the disease and its appearance in the mid-1990s. A strong association between the consumption of hard water and the occurrence of this special kidney disease has been observed, but the relationship has not been explained consistently. Here, we have hypothesized the association of using glyphosate, the most widely used herbicide in the disease endemic area and its unique metal chelating properties. The possible role played by glyphosate-metal complexes in this epidemic has not been given any serious consideration by investigators for the last two decades. Furthermore, it may explain similar kidney disease epidemics observed in Andra Pradesh (India) and Central America. Although glyphosate alone does not cause an epidemic of chronic kidney disease, it seems to have acquired the ability to destroy the renal tissues of thousands of farmers when it forms complexes with a localized geo environmental factor (hardness) and nephrotoxic metals. PMID:24562182

Anisotropic Metal Deposition on TiO2 Particles by Electric-Field-Induced Charge Separation.

PubMed

Tiewcharoen, Supakit; Warakulwit, Chompunuch; Lapeyre, Veronique; Garrigue, Patrick; Fourier, Lucas; Elissalde, Catherine; Buffière, Sonia; Legros, Philippe; Gayot, Marion; Limtrakul, Jumras; Kuhn, Alexander

2017-09-11

Deposition of metals on TiO 2 semiconductor particles (M-TiO 2 ) results in hybrid Janus objects combining the properties of both materials. One of the techniques proposed to generate Janus particles is bipolar electrochemistry (BPE). The concept can be applied in a straightforward way for the site-selective modification of conducting particles, but is much less obvious to use for semiconductors. Herein we report the bulk synthesis of anisotropic M-TiO 2 particles based on the synergy of BPE and photochemistry, allowing the intrinsic limitations, when they are used separately, to be overcome. When applying electric fields during irradiation, electrons and holes can be efficiently separated, thus breaking the symmetry of particles by modifying them selectively and in a wireless way on one side with either gold or platinum. Such hybrid materials are an important first step towards high-performance designer catalyst particles, for example for photosplitting of water. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Complexation- and ligand-induced metal release from 316L particles: importance of particle size and crystallographic structure.

PubMed

Hedberg, Yolanda; Hedberg, Jonas; Liu, Yi; Wallinder, Inger Odnevall

2011-12-01

Iron, chromium, nickel, and manganese released from gas-atomized AISI 316L stainless steel powders (sized <45 and <4 μm) were investigated in artificial lysosomal fluid (ALF, pH 4.5) and in solutions of its individual inorganic and organic components to determine its most aggressive component, elucidate synergistic effects, and assess release mechanisms, in dependence of surface changes using atomic absorption spectroscopy, Raman, XPS, and voltammetry. Complexation is the main reason for metal release from 316L particles immersed in ALF. Iron was mainly released, while manganese was preferentially released as a consequence of the reduction of manganese oxide on the surface. These processes resulted in highly complexing media in a partial oxidation of trivalent chromium to hexavalent chromium on the surface. The extent of metal release was partially controlled by surface properties (e.g., availability of elements on the surface and structure of the outermost surface) and partially by the complexation capacity of the different metals with the complexing agents of the different media. In general, compared to the coarse powder (<45 μm), the fine (<4 μm) powder displayed significantly higher released amounts of metals per surface area, increased with increased solution complexation capacity, while less amounts of metals were released into non-complexing solutions. Due to the ferritic structure of lower solubility for nickel of the fine powder, more nickel was released into all solutions compared with the coarser powder.

Rapid Mapping of Lithiation Dynamics in Transition Metal Oxide Particles with Operando X-ray Absorption Spectroscopy.

PubMed

Nowack, Lea; Grolimund, Daniel; Samson, Vallerie; Marone, Federica; Wood, Vanessa

2016-02-24

Since the commercialization of lithium ion batteries (LIBs), layered transition metal oxides (LiMO2, where M = Co, Mn, Ni, or mixtures thereof) have been materials of choice for LIB cathodes. During cycling, the transition metals change their oxidation states, an effect that can be tracked by detecting energy shifts in the X-ray absorption near edge structure (XANES) spectrum. X-ray absorption spectroscopy (XAS) can therefore be used to visualize and quantify lithiation kinetics in transition metal oxide cathodes; however, in-situ measurements are often constrained by temporal resolution and X-ray dose, necessitating compromises in the electrochemistry cycling conditions used or the materials examined. We report a combined approach to reduce measurement time and X-ray exposure for operando XAS studies of lithium ion batteries. A highly discretized energy resolution coupled with advanced post-processing enables rapid yet reliable identification of the oxidation state. A full-field microscopy setup provides sub-particle resolution over a large area of battery electrode, enabling the oxidation state within many transition metal oxide particles to be tracked simultaneously. Here, we apply this approach to gain insights into the lithiation kinetics of a commercial, mixed-metal oxide cathode material, nickel cobalt aluminium oxide (NCA), during (dis)charge and its degradation during overcharge.

Rapid Mapping of Lithiation Dynamics in Transition Metal Oxide Particles with Operando X-ray Absorption Spectroscopy

PubMed Central

Nowack, Lea; Grolimund, Daniel; Samson, Vallerie; Marone, Federica; Wood, Vanessa

2016-01-01

Since the commercialization of lithium ion batteries (LIBs), layered transition metal oxides (LiMO2, where M = Co, Mn, Ni, or mixtures thereof) have been materials of choice for LIB cathodes. During cycling, the transition metals change their oxidation states, an effect that can be tracked by detecting energy shifts in the X-ray absorption near edge structure (XANES) spectrum. X-ray absorption spectroscopy (XAS) can therefore be used to visualize and quantify lithiation kinetics in transition metal oxide cathodes; however, in-situ measurements are often constrained by temporal resolution and X-ray dose, necessitating compromises in the electrochemistry cycling conditions used or the materials examined. We report a combined approach to reduce measurement time and X-ray exposure for operando XAS studies of lithium ion batteries. A highly discretized energy resolution coupled with advanced post-processing enables rapid yet reliable identification of the oxidation state. A full-field microscopy setup provides sub-particle resolution over a large area of battery electrode, enabling the oxidation state within many transition metal oxide particles to be tracked simultaneously. Here, we apply this approach to gain insights into the lithiation kinetics of a commercial, mixed-metal oxide cathode material, nickel cobalt aluminium oxide (NCA), during (dis)charge and its degradation during overcharge. PMID:26908198

Rapid Mapping of Lithiation Dynamics in Transition Metal Oxide Particles with Operando X-ray Absorption Spectroscopy

NASA Astrophysics Data System (ADS)

Nowack, Lea; Grolimund, Daniel; Samson, Vallerie; Marone, Federica; Wood, Vanessa

2016-02-01

Since the commercialization of lithium ion batteries (LIBs), layered transition metal oxides (LiMO2, where M = Co, Mn, Ni, or mixtures thereof) have been materials of choice for LIB cathodes. During cycling, the transition metals change their oxidation states, an effect that can be tracked by detecting energy shifts in the X-ray absorption near edge structure (XANES) spectrum. X-ray absorption spectroscopy (XAS) can therefore be used to visualize and quantify lithiation kinetics in transition metal oxide cathodes; however, in-situ measurements are often constrained by temporal resolution and X-ray dose, necessitating compromises in the electrochemistry cycling conditions used or the materials examined. We report a combined approach to reduce measurement time and X-ray exposure for operando XAS studies of lithium ion batteries. A highly discretized energy resolution coupled with advanced post-processing enables rapid yet reliable identification of the oxidation state. A full-field microscopy setup provides sub-particle resolution over a large area of battery electrode, enabling the oxidation state within many transition metal oxide particles to be tracked simultaneously. Here, we apply this approach to gain insights into the lithiation kinetics of a commercial, mixed-metal oxide cathode material, nickel cobalt aluminium oxide (NCA), during (dis)charge and its degradation during overcharge.

Identification of metal s states in Sn-doped anatase by polarisation dependent hard X-ray photoelectron spectroscopy

NASA Astrophysics Data System (ADS)

Regoutz, A.; Oropeza, F. E.; Poll, C. G.; Payne, D. J.; Palgrave, R. G.; Panaccione, G.; Borgatti, F.; Agrestini, S.; Utsumi, Y.; Tsuei, K. D.; Liao, Y. F.; Watson, G. W.; Egdell, R. G.

2016-03-01

The contributions of Sn 5s and Ti 4s states to the valence band electronic structure of Sn-doped anatase have been identified by hard X-ray photoelectron spectroscopy. The metal s state intensity is strongly enhanced relative to that of O 2p states at high photon energies due to matrix element effects when electrons are detected parallel to the direction of the polarisation vector of the synchrotron beam, but becomes negligible in the perpendicular direction. The experimental spectra in both polarisations are in good agreement with cross section and asymmetry parameter weighted partial densities of states derived from density functional theory calculations.

Interrelation of soft and hard X-ray emissions during solar flares. II - Simulation model

NASA Technical Reports Server (NTRS)

Winglee, R. M.; Dulk, G. A.; Bornmann, P. L.; Brown, J. C.

1991-01-01

Two-dimensional electrostatic particle simulations are presented which incorporate the effect of quasi-static electric fields on particle dynamics as well as effects associated with wave-particle interactions induced by the accelerated particles. The properties of the soft and hard X-ray and microwave emissions from such systems are examined. In particular, it is shown that acceleration by quasi-static electric fields and heating via wave-particle interactions produces electron distributions with a broken-power law, similar to those inferred from hard X-ray spectra. Also, heating of the ambient plasma gives rise to a region of hot plasma propagating down to the chromosphere at about the ion sound speed.

Usefulness of laser ablation ICP-MS for analysis of metallic particles released to oral mucosa after insertion of dental implants.

PubMed

Sajnóg, Adam; Hanć, Anetta; Koczorowski, Ryszard; Makuch, Krzysztof; Barałkiewicz, Danuta

2018-03-01

Despite the fact that titanium is considered highly biocompatible, its presence in the oral cavity (an environment of frequently changing pH and temperature) may result in the release of titanium from intraosseous implants into the oral mucosa, causing a range of reactions from the human body. Fragments of oral mucosa collected from patients after dental implant insertion were analyzed by laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS). The study revealed an elevated content of elements (Ti, Al, V) which are components of the metal implants and temporary cover screws. Dynamic ablation of the tissue surface was used in order to obtain maps of the content and distribution of analyzed elements. The material consisted of 30 oral mucosa tissue fragments collected 3-5 months after implantation and 10 samples collected before implantation (control group). The application of optical microscope allowed for indication and confirmation of the location of metal particles prior to LA-ICP-MS analysis. The so-obtained map permitted location of regions containing metal particles. LA-ICP-MS analysis revealed groups of samples with similar properties of metal particles, thus confirming that those metal particles were the main source of the elevated content of metals (Ti, Al, V) in the tissue after implantation. A calibration strategy based on matrix matched solid standards with powdered egg white proteins as matrix material was applied with 34 S as an internal standard. The accuracy of the analytical method was verified by ablating pellets of certified reference material ERM-BB422 Fish muscle. Copyright © 2017 Elsevier GmbH. All rights reserved.

Grain characterization and milling behaviour of near-isogenic lines differing by hardness.

PubMed

Greffeuille, V; Abecassis, J; Rousset, M; Oury, F-X; Faye, A; L'Helgouac'h, C Bar; Lullien-Pellerin, V

2006-12-01

Wheat grain hardness is a major factor affecting the milling behaviour and end-product quality although its exact structural and biochemical basis is still not understood. This study describes the development of new near-isogenic lines selected on hardness. Hard and soft sister lines were characterised by near infrared reflectance (NIR) and particle size index (PSI) hardness index, grain protein content, thousand kernel weight and vitreousness. The milling behaviour of these wheat lines was evaluated on an instrumented micromill which also measures the grinding energy and flour particle size distribution was investigated by laser diffraction. Endosperm mechanical properties were measured using compression tests. Results pointed out the respective effect of hardness and vitreousness on those characteristics. Hardness was shown to influence both the mode of fracture and the mechanical properties of the whole grain and endosperm. Thus, this parameter also acts on milling behaviour. On the other hand, vitreousness was found to mainly play a role on the energy required to break the grain. This study allows us to distinguish between consequences of hardness and vitreousness. Hardness is suggested to influence the adhesion forces between starch granules and protein matrix whereas vitreousness would rather be related to the endosperm microstructure.

The heavy metal partition in size-fractions of the fine particles in agricultural soils contaminated by waste water and smelter dust.

PubMed

Zhang, Haibo; Luo, Yongming; Makino, Tomoyuki; Wu, Longhua; Nanzyo, Masami

2013-03-15

The partitioning of pollutant in the size-fractions of fine particles is particularly important to its migration and bioavailability in soil environment. However, the impact of pollution sources on the partitioning was seldom addressed in the previous studies. In this study, the method of continuous flow ultra-centrifugation was developed to separate three size fractions (<1 μm, <0.6 μm and <0.2 μm) of the submicron particles from the soil polluted by wastewater and smelter dust respectively. The mineralogy and physicochemical properties of each size-fraction were characterized by X-ray diffraction, transmission electron microscope etc. Total content of the polluted metals and their chemical speciation were measured. A higher enrichment factor of the metals in the fractions of <1 μm or less were observed in the soil contaminated by wastewater than by smelter dust. The organic substance in the wastewater and calcite from lime application were assumed to play an important role in the metal accumulation in the fine particles of the wastewater polluted soil. While the metal accumulation in the fine particles of the smelter dust polluted soil is mainly associated with Mn oxides. Cadmium speciation in both soils is dominated by dilute acid soluble form and lead speciation in the smelter dust polluted soil is dominated by reducible form in all particles. This implied that the polluted soils might be a high risk to human health and ecosystem due to the high bioaccessibility of the metals as well as the mobility of the fine particles in soil. Copyright © 2013 Elsevier B.V. All rights reserved.

Photocatalytic reduction of heavy metal ions on derivatized titanium dioxide nano-particle surface studied by XAFS.

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

Chen, L. X.; Rajh, T.; Micic, O.

1997-01-01

Photoreduction of heavy metal ions, Cu{sup 2-} and Hg{sup 2+}, on TiO{sup 2} nano-particle surfaces, has been investigated by XAFS measurements. The effects of TiO{sup 2} surface modification reagents on the reaction efficiency have been studied. We observed a significant reaction efficiency enhancement when amino acid alanine was added to a mixture of 0.01 M Cu{sup 2+} and TiO{sup 2} nano-particles. Fifty percent of the adsorbed Cu{sup 2+} has been reduced to Cu{sup 0} after 1-h illumination with a UV-enhanced xenon lamp. Photoreduction of Hg{sup 2+} on TiO{sup 2} colloid surfaces was also investigated without and with thiolactic acid (TLA).more » In this case, the photoreduction efficiency for Hg{sup 2+} was lowered. Structures of metal ion surroundings in various complexes as well as their role in photoreduction of metal ions are discussed.« less

Magnetic hyperthermia with hard-magnetic nanoparticles

NASA Astrophysics Data System (ADS)

Kashevsky, Bronislav E.; Kashevsky, Sergey B.; Korenkov, Victor S.; Istomin, Yuri P.; Terpinskaya, Tatyana I.; Ulashchik, Vladimir S.

2015-04-01

Recent clinical trials of magnetic hyperthermia have proved, and even hardened, the Ankinson-Brezovich restriction as upon magnetic field conditions applicable to any site of human body. Subject to this restriction, which is harshly violated in numerous laboratory and small animal studies, magnetic hyperthermia can relay on rather moderate heat source, so that optimization of the whole hyperthermia system remains, after all, the basic problem predetermining its clinical perspectives. We present short account of our complex (theoretical, laboratory and small animal) studies to demonstrate that such perspectives should be related with the hyperthermia system based on hard-magnetic (Stoner-Wohlfarth type) nanoparticles and strong low-frequency fields rather than with superparamagnetic (Brownian or Neél) nanoparticles and weak high-frequency fields. This conclusion is backed by an analytical evaluation of the maximum absorption rates possible under the field restriction in the ideal hard-magnetic (Stoner-Wohlarth) and the ideal superparamagnetic (single relaxation time) systems, by theoretical and experimental studies of the dynamic magnetic hysteresis in suspensions of movable hard-magnetic particles, by producing nanoparticles with adjusted coercivity and suspensions of such particles capable of effective energy absorption and intratumoral penetration, and finally, by successful treatment of a mice model tumor under field conditions acceptable for whole human body.

Cold Sprayability of Mixed Commercial Purity Ti Plus Ti6Al4V Metal Powders

NASA Astrophysics Data System (ADS)

Aydin, Huseyin; Alomair, Mashael; Wong, Wilson; Vo, Phuong; Yue, Stephen

2017-02-01

In the present work, metallic composite coatings of commercial purity Ti plus Ti6Al4V were produced by cold spraying to explore the effect of mixing on porosity and mechanical properties of the coatings. The coatings were deposited using N2 gas at 800 °C and 4 MPa pressure on 1020 steel substrate. Coating characteristics were studied by examining porosity percentages and Vickers's hardness. The microstructure was examined using optical and electron microscopy techniques. It was observed that mixing metal powders can lead to improvements in cold sprayability, specifically decreases in the porosity of the `matrix' powder. It is shown that a critical addition can significantly influence porosity, but above this critical level, there is a little change in porosity. Hardness differences between the two powders are considered to be the first-order influence, but differences in particle sizes and morphology may also be contributing factors.

Production of metal particles and clusters

NASA Technical Reports Server (NTRS)

Mcmanus, S. P.

1982-01-01

The feasibility of producing novel metals or metal clusters in a low gravity environment was studied. The production of coordinately unsaturated metal carbonyls by thermolysis or photolysis of stable metal carbonyls has the potential to generate novel catalysts by this technique. Laser irradiation of available metal carbonyls was investigated. It is found that laser induced decomposition of metal carbonyls is feasible for producing a variety of coordinately unsaturated species. Formation of clustered species does occur but is hampered by weak metal-metal bonds.

Use of a hard mask for formation of gate and dielectric via nanofilament field emission devices

DOEpatents

Morse, Jeffrey D.; Contolini, Robert J.

2001-01-01

A process for fabricating a nanofilament field emission device in which a via in a dielectric layer is self-aligned to gate metal via structure located on top of the dielectric layer. By the use of a hard mask layer located on top of the gate metal layer, inert to the etch chemistry for the gate metal layer, and in which a via is formed by the pattern from etched nuclear tracks in a trackable material, a via is formed by the hard mask will eliminate any erosion of the gate metal layer during the dielectric via etch. Also, the hard mask layer will protect the gate metal layer while the gate structure is etched back from the edge of the dielectric via, if such is desired. This method provides more tolerance for the electroplating of a nanofilament in the dielectric via and sharpening of the nanofilament.

Particle Size Distribution of Heavy Metals and Magnetic Susceptibility in an Industrial Site.

PubMed

Ayoubi, Shamsollah; Soltani, Zeynab; Khademi, Hossein

2018-05-01

This study was conducted to explore the relationships between magnetic susceptibility and some soil heavy metals concentrations in various particle sizes in an industrial site, central Iran. Soils were partitioned into five fractions (< 28, 28-75, 75-150, 150-300, and 300-2000 µm). Heavy metals concentrations including Zn, Pb, Fe, Cu, Ni and Mn and magnetic susceptibility were determined in bulk soil samples and all fractions in 60 soil samples collected from the depth of 0-5 cm. The studied heavy metals except for Pb and Fe displayed a substantial enrichment in the < 28 µm. These two elements seemed to be independent of the selected size fractions. Magnetic minerals are specially linked with medium size fractions including 28-75, 75-150 and 150-300 µm. The highest correlations were found for < 28 µm and heavy metals followed by 150-300 µm fraction which are susceptible to wind erosion risk in an arid environment.

LC and ferromagnetic resonance in soft/hard magnetic microwires

NASA Astrophysics Data System (ADS)

Tian, Bin; Vazquez, Manuel

2015-12-01

The magnetic behavior of soft/hard biphase microwires is introduced here. The microwires consist of a Co59.1Fe14.8Si10.2B15.9 soft magnetic nucleus and a Co90Ni10 hard outer shell separated by an intermediate insulating Pyrex glass microtube. By comparing the resistance spectrums of welding the ends of metallic core (CC) or welding the metallic core and outer shell (CS) to the connector, it is found that one of the two peaks in the resistance spectrum is because the LC resonance depends on the inductor and capacitors in which one is the capacitor between the metallic core and outer shell, and the other is between the outer shell and connector. Correspondingly, another peak is for the ferromagnetic resonance of metallic core. After changing the capacitance of the capacitors, the frequency of LC resonance moves to high frequency band, and furthermore, the peak of LC resonance in the resistance spectrum disappeared. These magnetostatically coupled biphase systems are thought to be of large potential interest as sensing elements in sensor devices.

Adsorption-desorption kinetics of soft particles onto surfaces

NASA Astrophysics Data System (ADS)

Osberg, Brendan; Gerland, Ulrich

A broad range of physical, chemical, and biological systems feature processes in which particles randomly adsorb on a substrate. Theoretical models usually assume ``hard'' (mutually impenetrable) particles, but in soft matter physics the adsorbing particles can be effectively compressible, implying ``soft'' interaction potentials. We recently studied the kinetics of such soft particles adsorbing onto one-dimensional substrates, identifying three novel phenomena: (i) a gradual density increase, or ''cramming'', replaces the usual jamming behavior of hard particles, (ii) a density overshoot, can occur (only for soft particles) on a time scale set by the desorption rate, and (iii) relaxation rates of soft particles increase with particle size (on a lattice), while hard particles show the opposite trend. The latter occurs since unjamming requires desorption and many-bodied reorganization to equilibrate -a process that is generally very slow. Here we extend this analysis to a two-dimensional substrate, focusing on the question of whether the adsorption-desorption kinetics of particles in two dimensions is similarly enriched by the introduction of soft interactions. Application to experiments, for example the adsorption of fibrinogen on two-dimensional surfaces, will be discussed.

The role of nano-particles in the field of thermal spray coating technology

NASA Astrophysics Data System (ADS)

Siegmann, Stephan; Leparoux, Marc; Rohr, Lukas

2005-06-01

Nano-particles play not only a key role in recent research fields, but also in the public discussions about health and safety in nanotechnology. Nevertheless, the worldwide activities in nano-particles research increased dramatically during the last 5 to 10 years. There are different potential routes for the future production of nano-particles at large scale. The main directions envisaged are mechanical milling, wet chemical reactions or gas phase processes. Each of the processes has its specific advantages and limitations. Mechanical milling and wet chemical reactions are typically time intensive and batch processes, whereas gas phase productions by flames or plasma can be carried out continuously. Materials of interest are mainly oxide ceramics, carbides, nitrides, and pure metals. Nano-ceramics are interesting candidates for coating technologies due to expected higher coating toughness, better thermal shock and wear resistance. Especially embedded nano-carbides and-nitrides offer homogenously distributed hard phases, which enhance coatings hardness. Thermal spraying, a nearly 100 years old and world wide established coating technology, gets new possibilities thanks to optimized, nano-sized and/or nano-structured powders. Latest coating system developments like high velocity flame spraying (HVOF), cold gas deposition or liquid suspension spraying in combination with new powder qualities may open new applications and markets. This article gives an overview on the latest activities in nano-particle research and production in special relation to thermal spray coating technology.

Functional Role of Infective Viral Particles on Metal Reduction

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

Coates, John D.

2014-04-01

A proposed strategy for the remediation of uranium (U) contaminated sites was based on the immobilization of U by reducing the oxidized soluble U, U(VI), to form a reduced insoluble end product, U(IV). Previous studies identified Geobacter sp., including G. sulfurreducens and G. metallireducens, as predominant U(VI)-reducing bacteria under acetate-oxidizing and U(VI)-reducing conditions. Examination of the finished genome sequence annotation of the canonical metal reducing species Geobacter sulfurreducens strain PCA and G. metallireduceans strain GS-15 as well as the draft genome sequence of G. uraniumreducens strain Rf4 identified phage related proteins. In addition, the completed genome for Anaeromyxobacter dehalogenans andmore » the draft genome sequence of Desulfovibrio desulfuricans strain G20, two more model metal-reducing bacteria, also revealed phage related sequences. The presence of these gene sequences indicated that Geobacter spp., Anaeromyxobacter spp., and Desulfovibrio spp. are susceptible to viral infection. Furthermore, viral populations in soils and sedimentary environments in the order of 6.4×10{sup 6}–2.7×10{sup 10} VLP’s cm{sup -3} have been observed. In some cases, viral populations exceed bacterial populations in these environments suggesting that a relationship may exist between viruses and bacteria. Our preliminary screens of samples collected from the ESR FRC indicated that viral like particles were observed in significant numbers. The objective of this study was to investigate the potential functional role viruses play in metal reduction specifically Fe(III) and U(VI) reduction, the environmental parameters affecting viral infection of metal reducing bacteria, and the subsequent effects on U transport.« less

Synthesis of mesoporous poly(melamine-formaldehyde) particles by inverse emulsion polymerization.

PubMed

Schwarz, Dana; Weber, Jens

2017-07-15

Mesoporous poly(melamine-formaldehyde) (MF) particles with surface areas of up to 200m 2 g -1 were synthesized by an inverse emulsion polymerization using dodecane and Span80® as continuous phase. The finer details of the shape control (using emulsion techniques) and the porosity control (using silica nanoparticles as hard-template) are discussed. The impact of phase-separation processes on the observable porosity of the 20-200µm sized spherical particles is analysed by gas sorption methods and electron microscopy. The high density of amine and triazine functional groups in the porous MF particles make the material a promising adsorber for heavy metal ions and methylene blue. In a preliminary column experiment, the synthesized material exhibited a total capacity of 2.54mmol/g (≙ 812.4mg/g) for the adsorption of methylene blue. Copyright © 2017 Elsevier Inc. All rights reserved.

The use of poly(vinyl phosphonic acid) microgels for the preparation of inherently magnetic Co metal catalyst particles in hydrogen production

NASA Astrophysics Data System (ADS)

Sahiner, Nurettin; Sagbas, Selin

2014-01-01

Novel poly(vinyl phosphonic acid) (p(VPA)) micro particle and composite p(VPA)-silica micro particle hydrogels are synthesized using a micro-emulsion polymerization technique. Porous p(VPA) particles are generated after removal of silica particles upon treatment of composite p(VPA) with 0.5 M NaOH solution. Bare, composite with silica, and porous p(VPA) micro particle hydrogels are used as templates and as reactors. Metal nanoparticles, Co, Ni, and Cu are generated in situ inside these hydrogels by chemical reduction of the absorbed metal ions with a reducing agent such as sodium boron hydride (NaBH4), and are used as catalyst in hydrogen production by hydrolysis of NaBH4 in a basic medium and ammonia borane (AB). The effects of reloaded metal ions, the reaction temperature, the porosity, the reusability, and the type of metal (Co, Ni, Cu) are investigated. The activation energy for hydrolysis of NaBH4, and AB by p(VPA)-Co is 28.02 and 25.51 kJ mol-1, respectively. The mass susceptibility measurements of composite p(VPA)-Co microgel is found as ferromagnetic. It is found that p(VPA) microgels provided better catalytic performance in comparison to macro p(VPA) hydrogels due to improved properties such as higher surface area, pore structure, and inherently magnetic behavior after multiple loadings-reduction of Co(II) from aqueous medium.

Steady Shear Viscosities of Two Hard Sphere Colloidal Dispersions

NASA Astrophysics Data System (ADS)

Cheng, Zhengdong; Chaikin, Paul M.; Phan, See-Eng; Russel, William B.; Zhu, Jixiang

1996-03-01

Though hard spheres have the simplest inter-particle potential, the many body hydrodynamic interactions are complex and the rheological properties of dispersions are not fully understood in the concentrated regime. We studied two model systems: colloidal poly-(Methyl Methacrylate) spheres with a grafted layer of poly-(12-hydroxy stearic acid) (PMMA/PHSA) and spherical Silica particles (PST-5, Nissan Chemical Industries, Ltd, Tokyo, Japan). Steady shear viscosities were measured by a Zimm viscometer. The high shear relative viscosity of the dispersions compares well with other hard sphere systems, but the low shear relative viscosity of PMMA/PHSA dispersions is η / η 0 = 50 at φ = 0.5 , higher than η / η 0 = 22 for other hard sphere systems, consistent with recently published data (Phys. Rev. Lett. 75(1995)958). Bare Silica spheres are used to clarify the effect of the grafted layer. With the silica spheres, volume fraction can be determined independent of intrinsic viscosity measurements; also, higher concentrated dispersions can be made.

Surface modification of Cu metal particles by the chemical reaction between the surface oxide layer and a halogen surfactant

NASA Astrophysics Data System (ADS)

Yokoyama, Shun; Takahashi, Hideyuki; Itoh, Takashi; Motomiya, Kenichi; Tohji, Kazuyuki

2014-01-01

Surface oxides on small (2-5 μm) copper metal particles can be removed by chemical reaction with tris(2,3-dibromopropyl) isocyanurate (TIC) in diethylene glycol mono-n-hexyl ether (DGHE) solution under mild conditions where metal particles are not damaged. Surface oxides convert to copper bromide species and subsequently dissolve into the solvent. It was found that resultant surface species are resistant to re-oxidation due to remaining surface bromides. This finding opens up a possibility to create microclines based on cheap copper nanoparticles.

Influence of photoactivation method and mold for restoration on the Knoop hardness of resin composite restorations.

PubMed

Brandt, William Cunha; Silva-Concilio, Lais Regiane; Neves, Ana Christina Claro; de Souza-Junior, Eduardo Jose Carvalho; Sinhoreti, Mario Alexandre Coelho

2013-09-01

The aim of this study was to evaluate in vitro the Knoop hardness in the top and bottom of composite photo activated by different methods when different mold materials were used. Z250 (3M ESPE) and XL2500 halogen unit (3M ESPE) were used. For hardness test, conical restorations were made in extracted bovine incisors (tooth mold) and also metal mold (approximately 2 mm top diameter × 1.5 mm bottom diameter × 2 mm in height). Different photoactivation methods were tested: high-intensity continuous (HIC), low-intensity continuous (LIC), soft-start, or pulse-delay (PD), with constant radiant exposure. Knoop readings were performed on top and bottom restoration surfaces. Data were submitted to two-way ANOVA and Tukey's test (p = 0.05). On the top, regardless of the mold used, no significant difference in the Knoop hardness (Knoop hardness number, in kilograms-force per square millimeter) was observed between the photoactivation methods. On the bottom surface, the photoactivation method HIC shows higher means of hardness than LIC when tooth and metal were used. Significant differences of hardness on the top and in the bottom were detected between tooth and metal. The photoactivation method LIC and the material mold can interfere in the hardness values of composite restorations.

Magnetic particles

NASA Technical Reports Server (NTRS)

Chang, Manchium (Inventor); Colvin, Michael S. (Inventor)

1989-01-01

Magnetic polymer particles are formed by swelling porous, polymer particles and impregnating the particles with an aqueous solution of precursor magnetic metal salt such as an equimolar mixture of ferrous chloride and ferric chloride. On addition of a basic reagent such as dilute sodium hydroxide, the metal salts are converted to crystals of magnetite which are uniformly contained througout the pores of the polymer particle. The magnetite content can be increased and neutral buoyancy achieved by repetition of the impregnaton and neutralization steps to adjust the magnetite content to a desired level.

Producing Magnesium Metallic Glass By Disintegrated Melt Deposition

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

Shanthi, M.; Dept. of Mechanical Engineering, National University of Singapore, Singapore 117576; Gupta, M.

Bulk metallic glasses are new class of engineering materials that exhibit high resistance to crystallization in the under cooled liquid state. The development of bulk metallic glasses of thickness 1cm or less has opened new doors for fundamental studies of both liquid state and glass transition previously not feasible in metallic materials. Moreover, bulk metallic glasses exhibit superior hardness, strength, specific strength, and elastic strain limit, along with good corrosion and wear resistance. Thus they are potential candidates in various sports, structural, engineering and medical applications. Among several BMGs investigated, magnesium-based BMGs have attracted considerable attention because of their lowmore » density and superior mechanical properties. The major drawback of this magnesium based BMGs is poor ductility. This can be overcome by the addition of ductile particles/reinforcement to the matrix. In this study, a new technique named disintegrated melt deposition technique was used to synthesize magnesium based BMGs. Rods of different sizes are cast using the current method. Mechanical characterization studies revealed that the amorphous rods produced by the current technique showed superior mechanical properties.« less

Producing Magnesium Metallic Glass By Disintegrated Melt Deposition

NASA Astrophysics Data System (ADS)

Shanthi, M.; Gupta, M.; Jarfors, A. E. W.; Tan, M. J.

2011-01-01

Bulk metallic glasses are new class of engineering materials that exhibit high resistance to crystallization in the under cooled liquid state. The development of bulk metallic glasses of thickness 1cm or less has opened new doors for fundamental studies of both liquid state and glass transition previously not feasible in metallic materials. Moreover, bulk metallic glasses exhibit superior hardness, strength, specific strength, and elastic strain limit, along with good corrosion and wear resistance. Thus they are potential candidates in various sports, structural, engineering and medical applications. Among several BMGs investigated, magnesium-based BMGs have attracted considerable attention because of their low density and superior mechanical properties. The major drawback of this magnesium based BMGs is poor ductility. This can be overcome by the addition of ductile particles/reinforcement to the matrix. In this study, a new technique named disintegrated melt deposition technique was used to synthesize magnesium based BMGs. Rods of different sizes are cast using the current method. Mechanical characterization studies revealed that the amorphous rods produced by the current technique showed superior mechanical properties.

Communication: From close-packed to topologically close-packed: Formation of Laves phases in moderately polydisperse hard-sphere mixtures

NASA Astrophysics Data System (ADS)

Lindquist, Beth A.; Jadrich, Ryan B.; Truskett, Thomas M.

2018-05-01

Particle size polydispersity can help to inhibit crystallization of the hard-sphere fluid into close-packed structures at high packing fractions and thus is often employed to create model glass-forming systems. Nonetheless, it is known that hard-sphere mixtures with modest polydispersity still have ordered ground states. Here, we demonstrate by computer simulation that hard-sphere mixtures with increased polydispersity fractionate on the basis of particle size and a bimodal subpopulation favors the formation of topologically close-packed C14 and C15 Laves phases in coexistence with a disordered phase. The generality of this result is supported by simulations of hard-sphere mixtures with particle-size distributions of four different forms.

Method of producing non-agglomerating submicron size particles

DOEpatents

Bourne, Roy S.; Eichman, Clarence C.; Welbon, William W.

1989-01-01

Submicron size particles are produced by using a sputtering process to deposit particles into a liquid. The liquid is processed to recover the particles therefrom, and the particles have sizes in the range of twenty to two hundred Angstroms. Either metallic or non-metallic particles can be produced, and the metallic particles can be used in "metallic inks".

Solid impingement erosion mechanisms and characterization of erosion resistance of ductile metals

NASA Technical Reports Server (NTRS)

Rao, V. P.; Buckley, D. H.

1982-01-01

Experimental results pertaining to spherical glass bead and angular crushed glass particle impingement are presented. A concept of energy adsorption to explain the failure of material is proposed. The erosion characteristics of several pure metals were correlated with the proposed energy parameters and with other properties. Correlations of erosion and material properties were also carried out with these materials to study the effect of the angle of impingement. Analyses of extensive erosion data indicate that surface energy, strain energy, melting point, bulk modulus, hardness, ultimate resilience, atomic volume and product of linear coefficient of thermal expansion, bulk modulus, and temperature rise required for melting, and ultimate resilience, and hardness exhibit the best correlations. It appears that both energy and thermal properties contribute to the total erosion.

Strain gradient drives shear banding in metallic glasses

NASA Astrophysics Data System (ADS)

Tian, Zhi-Li; Wang, Yun-Jiang; Chen, Yan; Dai, Lan-Hong

2017-09-01

Shear banding is a nucleation-controlled process in metallic glasses (MGs) involving multiple temporal-spatial scales, which hinders a concrete understanding of its structural origin down to the atomic scale. Here, inspired by the morphology of composite materials, we propose a different perspective of MGs as a hard particle-reinforced material based on atomic-scale structural heterogeneity. The local stable structures indicated by a high level of local fivefold symmetry (L5FS) act as hard "particles" which are embedded in the relatively soft matrix. We demonstrate this concept by performing atomistic simulations of shear banding in CuZr MG. A shear band is prone to form in a sample with a high degree of L5FS which is slowly quenched from the liquid. An atomic-scale analysis on strain and the structural evolution reveals that it is the strain gradient effect that has originated from structural heterogeneity that facilitates shear transformation zones (STZs) to mature shear bands. An artificial composite model with a high degree of strain gradient, generated by inserting hard MG strips into a soft MG matrix, demonstrates a great propensity for shear banding. It therefore confirms the critical role strain gradient plays in shear banding. The strain gradient effect on shear banding is further quantified with a continuum model and a mechanical instability analysis. These physical insights might highlight the strain gradient as the hidden driving force in transforming STZs into shear bands in MGs.

Metals and bacteria partitioning to various size particles in Ballona Creek storm water runoff.

PubMed

Brown, Jeffrey S; Stein, Eric D; Ackerman, Drew; Dorsey, John H; Lyon, Jessica; Carter, Patrick M

2013-02-01

Many storm water best management practice (BMP) devices function primarily by capturing particulate matter to take advantage of the well-documented association between storm water particles and pollutants. The hydrodynamic separation or settling methods used by most BMP devices are most effective at capturing medium to large particles; however, these may not be the most predominant particles associated with urban runoff. The present study examined particle size distribution in storm water runoff from an urban watershed in southern California and investigated the pollutant-particle associations of metals (Cu, Pb, Ni, and Zn) and bacteria (enterococci and Escherichia coli). During small storm events (≤0.7 cm rain), the highest concentration of pollutants were associated with a <6-µm filter fraction, which accounted for 70% of the per storm contaminant mass but made up more than 20% of the total particle mass. The pollutant-particle association changed with storm size. Most pollutant mass was associated with >35 µm size particles during a 5-cm rain event. These results suggest that much of the contaminant load in storm water runoff will not be captured by the most commonly used BMP devices, because most of these devices (e.g., hydrodynamic separators) are unable to capture particles smaller than 75 µm. Copyright © 2012 SETAC.

On the role of particle cracking in flow and fracture of metal matrix composites

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

Brockenbrough, J.R.; Zok, F.W.

1995-01-01

The flow response of particle-reinforced metal matrix composites is studied using finite element methods. Unit cells containing either intact or cracked particles in a power law hardening matrix are used to determine the corresponding asymptotic flow strengths. The effects of the hardening exponent and the elastic mismatch between the particles and the matrix on the flow response are examined. For comparison, the flow response of power law hardening solids containing penny-shaped cracks is also evaluated. The latter results are found to be in reasonable agreement with those corresponding to composites that contain low volume fractions of cracked particles. The asymptoticmore » results are used to develop a one-dimensional constitutive law for composites which undergo progressive damage during tensile straining. This law is used to evaluate the strain at the onset of plastic instability. It is proposed that the instability strain be used as a measure of tensile ductility when the particle content is low and the particles are uniformly distributed through the matrix.« less

Mapping Metals Incorporation of a Whole Single Catalyst Particle Using Element Specific X-ray Nanotomography

DOE PAGES

Meirer, Florian; Morris, Darius T.; Kalirai, Sam; ...

2015-01-02

Full-field transmission X-ray microscopy has been used to determine the 3D structure of a whole individual fluid catalytic cracking (FCC) particle at high spatial resolution and in a fast, noninvasive manner, maintaining the full integrity of the particle. Using X-ray absorption mosaic imaging to combine multiple fields of view, computed tomography was performed to visualize the macropore structure of the catalyst and its availability for mass transport. We mapped the relative spatial distributions of Ni and Fe using multiple-energy tomography at the respective X-ray absorption K-edges and correlated these distributions with porosity and permeability of an equilibrated catalyst (E-cat) particle.more » Both metals were found to accumulate in outer layers of the particle, effectively decreasing porosity by clogging of pores and eventually restricting access into the FCC particle.« less

On the features of bursts of neutrons, hard x-rays and alpha-particles in the pulse vacuum discharge with a virtual cathode and self-organization

NASA Astrophysics Data System (ADS)

Kurilenkov, Yu K.; Tarakanov, V. P.; Gus'kov, S. Yu; Samoylov, I. S.; Ostashev, V. E.

2015-11-01

In this paper, we continue the discussion of the experimental results on the yield of DD neutrons and hard x-rays in the nanosecond vacuum discharge (NVD) with a virtual cathode, which was started in the previous article of this issue, and previously (Kurilenkov Y K et al 2006 J. Phys. A: Math. Gen. 39 4375). We have considered here the regimes of very dense interelectrode aerosol ensembles, in which diffusion of even hard x-rays is found. The yield of DD neutrons in these regimes is conditioned not only by the head-on deuteron-deuteron collisions in the potential well of virtual cathode, but also by the channel of “deuteron-deuterium cluster” reaction, which exceeds overall yield of neutrons per a shot by more than an order of magnitude, bringing it up to ∼ 107/(4π). Very bright bursts of hard x-rays are also represented and discussed here. Presumably, their nature may be associated with the appearance in the NVD of some properties of random laser in the x-ray spectrum. Good preceding agreeing of the experiment on the DD fusion in the NVD with its particle-in-cell (PIC) simulations provides a basis to begin consideration of nuclear burning “proton-boron” in the NVD, which will be accompanied by the release of alpha particles only. With this objective in view, there has been started the PIC-simulation of aneutronic burning of p-B11, and its preliminary results are presented.

Potential health risk for residents around a typical e-waste recycling zone via inhalation of size-fractionated particle-bound heavy metals.

PubMed

Huang, Chun-Li; Bao, Lian-Jun; Luo, Pei; Wang, Zhao-Yi; Li, Shao-Meng; Zeng, Eddy Y

2016-11-05

Health risk of residents dwelling around e-waste recycling zones has been a global concern, but has not been adequately examined. The present study was intended to evaluate the potential health risk of residents through inhalation exposure to size-fractionated particle-bound heavy metals in a typical e-waste recycling zone, South China. Anthropogenic metals (Zn, Se, Pb, Sb, As, and Cd) were predominantly enriched in fine particles (Dp<1.8μm), whereas the crustal elements (Ti, Fe, and Co) tended to accumulate in coarse particles (Dp>1.8μm). Although the daily inhalation intakes of the target metals were significantly lower than those through food consumption and ingestion of house dust, the hazard quotients of total metals for adults (95% CI: 1.0-5.5) and children (95% CI: 3.0-17) were greater than 1. Moreover, the incremental lifetime cancer risks of five carcinogenic metals (Cr, Co, Ni, As, and Cd) for adults and children were 1.3×10(-3) (95% CI: 4.1×10(-4)-3.0×10(-3)) and 3.9×10(-3) (95% CI: 1.3×10(-3)-8.6×10(-3)), respectively, substantially higher than the acceptable cancer risk range of 10(-6)-10(-4). All these findings suggested that health risks were high for local residents dwelling around the e-waste recycling zone through inhalation exposure to particle-bound heavy metals, for both adults and children. Copyright © 2016 Elsevier B.V. All rights reserved.

OsB 2 and RuB 2, ultra-incompressible, hard materials: First-principles electronic structure calculations

NASA Astrophysics Data System (ADS)

Chiodo, S.; Gotsis, H. J.; Russo, N.; Sicilia, E.

2006-07-01

Recently it has been reported that osmium diboride has an unusually large bulk modulus combined with high hardness, and consequently is a most interesting candidate as an ultra-incompressible and hard material. The electronic and structural properties of the transition metal diborides OsB 2 and RuB 2 have been calculated within the local density approximation (LDA). It is shown that the high hardness is the result of covalent bonding between transition metal d states and boron p states in the orthorhombic structure.

Single Particle ICPMS for Characterizing Metal-based Nanoparticles and Monitoring Transformation Processes in Surface Water

EPA Science Inventory

Engineered metal-based nanomaterials will likely be used in increasing quantities in consumer and industrial products. These may be introduced into surface waters by a variety of paths depending on usage. Other naturally occurring and anthropogenic particles containing these met...

Optimum Distribution of Metal Particles in the Solid-Propellant Charge in the Approximation of a One-Dimensional Flow Field in a Cylindrical Channel

NASA Astrophysics Data System (ADS)

Min'kov, L. L.; Shrager, É. R.

2015-03-01

A study has been made of ways of optimum distribution of particles of dispersed metal in the solid-propellant charge with a cylindrical central channel, which is firmly fastened to the case. The efficiency of combustion of this metal has been analyzed. Consideration has been given to the influence of the dynamic nonequilibrium of two-phase flow on the optimum distribution of metal particles in the indicated charge in the approximation of one-dimensionality of the flow field.

Separation of Non-metallic Inclusions from a Fe-Al-O Melt Using a Super-Gravity Field

NASA Astrophysics Data System (ADS)

Song, Gaoyang; Song, Bo; Guo, Zhancheng; Yang, Yuhou; Song, Mingming

2018-02-01

An innovative method for separating non-metallic inclusions from a high temperature melt using super gravity was systematically investigated. To explore the separation behavior of inclusion particles with densities less than that of metal liquid under a super-gravity field, a Fe-Al-O melt containing Al2O3 particles was treated with different gravity coefficients. Al2O3 particles migrated rapidly towards the reverse direction of the super gravity and gathered in the upper region of the sample. It was hard to find any inclusion particles with sizes greater than 2 μm in the middle and bottom areas. Additionally, the oxygen content in the middle region of the sample could be reduced to 0.0022 mass pct and the maximum removal rate of the oxygen content reached 61.4 pct. The convection in the melt along the direction of the super gravity was not generated by the super-gravity field, and the fluid velocity in the molten melt consisted only of the rotating tangential velocity. Moreover, the motion behavior of the Al2O3 particles was approximatively determined by Stokes' law along the direction of super gravity.

Superhard composite materials including compounds of carbon and nitrogen deposited on metal and metal nitride carbide and carbonitride

DOEpatents

Wong, M.S.; Li, D.; Chung, Y.W.; Sproul, W.D.; Xi Chu; Barnett, S.A.

1998-03-10

A composite material having high hardness comprises a carbon nitrogen compound, such as CN{sub x} where x is greater than 0.1 and up to 1.33, deposited on a metal or metal compound selected to promote deposition of substantially crystalline CN{sub x}. The carbon nitrogen compound is deposited on a crystal plane of the metal or metal compound sufficiently lattice-matched with a crystal plane of the carbon nitrogen compound that the carbon nitrogen compound is substantially crystalline. A plurality of layers of the compounds can be formed in alternating sequence to provide a multi-layered, superlattice coating having a coating hardness in the range of 45--55 GPa, which corresponds to the hardness of a BN coating and approaches that of a diamond coating. 10 figs.

Superhard composite materials including compounds of carbon and nitrogen deposited on metal and metal nitride, carbide and carbonitride

DOEpatents

Wong, M.S.; Li, D.; Chung, Y.W.; Sproul, W.D.; Chu, X.; Barnett, S.A.

1998-07-07

A composite material having high hardness comprises a carbon nitrogen compound, such as CN{sub x} where x is greater than 0.1 and up to 1.33, deposited on a metal or metal compound selected to promote deposition of substantially crystalline CN{sub x}. The carbon nitrogen compound is deposited on a crystal plane of the metal or metal compound sufficiently lattice-matched with a crystal plane of the carbon nitrogen compound that the carbon nitrogen compound is substantially crystalline. A plurality of layers of the compounds can be formed in alternating sequence to provide a multi-layered, superlattice coating having a coating hardness in the range of 45--55 GPa, which corresponds to the hardness of a BN coating and approaches that of a diamond coating. 10 figs.

Superhard composite materials including compounds of carbon and nitrogen deposited on metal and metal nitride, carbide and carbonitride

DOEpatents

Wong, Ming-Show; Li, Dong; Chung, Yip-Wah; Sproul, William D.; Chu, Xi; Barnett, Scott A.

1998-01-01

A composite material having high hardness comprises a carbon nitrogen compound, such as CN.sub.x where x is greater than 0.1 and up to 1.33, deposited on a metal or metal compound selected to promote deposition of substantially crystalline CN.sub.x. The carbon nitrogen compound is deposited on a crystal plane of the metal or metal compound sufficiently lattice-matched with a crystal plane of the carbon nitrogen compound that the carbon nitrogen compound is substantially crystalline. A plurality of layers of the compounds can be formed in alternating sequence to provide a multi-layered, superlattice coating having a coating hardness in the range of 45-55 GPa, which corresponds to the hardness of a BN coating and approaches that of a diamond coating.

Superhard composite materials including compounds of carbon and nitrogen deposited on metal and metal nitride carbide and carbonitride

DOEpatents

Wong, Ming-Show; Li, Dong; Chung, Yin-Wah; Sproul, William D.; Chu, Xi; Barnett, Scott A.

1998-01-01

A composite material having high hardness comprises a carbon nitrogen compound, such as CN.sub.x where x is greater than 0.1 and up to 1.33, deposited on a metal or metal compound selected to promote deposition of substantially crystalline CN.sub.x. The carbon nitrogen compound is deposited on a crystal plane of the metal or metal compound sufficiently lattice-matched with a crystal plane of the carbon nitrogen compound that the carbon nitrogen compound is substantially crystalline. A plurality of layers of the compounds can be formed in alternating sequence to provide a multi-layered, superlattice coating having a coating hardness in the range of 45-55 GPa, which corresponds to the hardness of a BN coating and approaches that of a diamond coating.

Metallic-nanoparticles-enhanced fluorescence from individual micron-sized aerosol particles on-the-fly.

PubMed

Sivaprakasam, Vasanthi; Hart, Matthew B; Jain, Vaibhav; Eversole, Jay D

2014-08-11

Fluorescence spectra from individual aerosol particles that were either coated or embedded with metallic nanoparticles (MNPs) was acquired on-the-fly using 266 nm and 355 nm excitation. Using aqueous suspensions of MNPs with either polystyrene latex (PSL) spheres or dissolved proteins (tryptophan or ovalbumin), we generated PSL spheres coated with MNPs, or protein clusters embedded with MNPs as aerosols. Both enhanced and quenched fluorescence intensities were observed as a function of MNP concentration. Optimizing MNP material, size and spacing should yield enhanced sensitivity for specific aerosol materials that could be exploited to improve detection limits of single-particle, on-the-fly fluorescence or Raman based spectroscopic sensors.

Geochemical phase and particle size relationships of metals in urban road dust.

PubMed

Jayarathne, Ayomi; Egodawatta, Prasanna; Ayoko, Godwin A; Goonetilleke, Ashantha

2017-11-01

Detailed knowledge of the processes that metals undergo during dry weather periods whilst deposited on urban surfaces and their environmental significance is essential to predict the potential influence of metals on stormwater quality in order to develop appropriate stormwater pollution mitigation measures. However, very limited research has been undertaken in this area. Accordingly, this study investigated the geochemical phase and particle size relationships of seven metals which are commonly associated with urban road dust, using sequential extraction in order to assess their mobility characteristics. Metals in the sequentially extracted fractions of exchangeable, reducible, oxidisable and residual were found to follow a similar trend for different land uses even though they had variable accumulation loads. The high affinity of Cd and Zn for exchangeable reactions in both, bulk and size-fractionated solid samples confirmed their high mobility, while the significant enrichment of Ni and Cr in the stable residual fraction indicated a low risk of mobility. The study results also confirmed the availability of Cu, Pb and Mn in both, stable and mobile fractions. The fine fraction of solids (<150 μm) and antecedent dry days can be highlighted as important parameters when determining the fate of metals associated with urban road dust. The outcomes from this study are expected to contribute to the development of effective stormwater pollution mitigation strategies by taking into consideration the metal-particulate relationships. Copyright © 2017 Elsevier Ltd. All rights reserved.

Bioaccessibility studies of ferro-chromium alloy particles for a simulated inhalation scenario: a comparative study with the pure metals and stainless steel.

PubMed

Midander, Klara; de Frutos, Alfredo; Hedberg, Yolanda; Darrie, Grant; Wallinder, Inger Odnevall

2010-07-01

The European product safety legislation, REACH, requires that companies that manufacture, import, or use chemicals demonstrate safe use and high level of protection of their products placed on the market from a human health and environmental perspective. This process involves detailed assessment of potential hazards for various toxicity endpoints induced by the use of chemicals with a minimum use of animal testing. Such an assessment requires thorough understanding of relevant exposure scenarios including material characteristics and intrinsic properties and how, for instance, physical and chemical properties change from the manufacturing phase, throughout use, to final disposal. Temporary or permanent adverse health effects induced by particles depend either on their shape or physical characteristics, and/or on chemical interactions with the particle surface upon human exposure. Potential adverse effects caused by the exposure of metal particles through the gastrointestinal system, the pulmonary system, or the skin, and their subsequent potential for particle dissolution and metal release in contact with biological media, show significant gaps of knowledge. In vitro bioaccessibility testing at conditions of relevance for different exposure scenarios, combined with the generation of a detailed understanding of intrinsic material properties and surface characteristics, are in this context a useful approach to address aspects of relevance for accurate risk and hazard assessment of chemicals, including metals and alloys and to avoid the use of in vivo testing. Alloys are essential engineering materials in all kinds of applications in society, but their potential adverse effects on human health and the environment are very seldom assessed. Alloys are treated in REACH as mixtures of their constituent elements, an approach highly inappropriate because intrinsic properties of alloys generally are totally different compared with their pure metal components. A large

TRACE METAL LOADING ON WATERBORNE SOIL AND DUST PARTICLES CHARACTERIZED THROUGH THE USE OF SPLIT-FLOW THIN CELL FRACTIONATION

EPA Science Inventory

The fate and transport of metallic pollutants through a watershed are related to the characteristics of undissolved solid particles to which they are bound. Removal of these particles and their associated pollutants via engineered structures such as settling ponds i one goal of s...

In situ ceramic layer growth on coated fuel particles dispersed in a zirconium metal matrix

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

Terrani, Kurt A; Silva, G W Chinthaka M; Kiggans, Jim

2013-01-01

The extent and nature of the chemical interaction between the outermost coating layer of coated fuel particles embedded in zirconium metal during fabrication of metal matrix microencapsulated fuels was examined. Various particles with outermost coating layers of pyrocarbon, SiC, and ZrC have been investigated in this study. ZrC-Zr interaction was least substantial while PyC-Zr reaction can be exploited to produce a ZrC layer at the interface in an in situ manner. The thickness of the ZrC layer in the latter case can be controlled by adjusting the time and temperature during processing. The kinetics of ZrC layer growth is significantlymore » faster from what is predicted using literature carbon diffusivity data in ZrC. SiC-Zr interaction is more complex and results in formation of various chemical phases in a layered aggregate morphology at the interface.« less

Synthesis of nanostructured/macroscopic low-density copper foams based on metal-coated polymer core–shell particles [Templated synthesis of nanowalled low-density copper foams

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

Kim, Sung Ho; Bazin, Nick; Shaw, Jessica I.

A robust, millimeter-sized low-density Cu foam with ~90% (v/v) porosity, ~30 nm thick walls, and ~1 μm diameter spherical pores is prepared by the slip-casting of metal-coated polymer core–shell particles followed by a thermal removal of the polymer. In this paper, we report our key findings that enable the development of the low-density Cu foams. First, we need to synthesize polystyrene (PS) particles coated with a very thin Cu layer (in the range of tens of nanometers). A simple reduction in the amount of Cu deposited onto the PS was not sufficient to form such a low-density Cu foams duemore » to issues related to foam collapse and densification upon the subsequent polymer removal step. Precise control over the morphology of the Cu coating on the particles is essential for the synthesis of a lower density of foams. Second, improving the dispersion of PS–Cu particles in a suspension used for the casting as well as careful optimization of a baking condition minimize the formation of irregular large voids, leading to Cu foams with a more uniform packing and a better connectivity of neighboring Cu hollow shells. Finally, we analyzed mechanical properties of the Cu foams with a depth-sensing indentation test. The uniform Cu foams show a significant improvement in mechanical properties (~1.5× modulus and ~3× hardness) compared to those of uncontrolled foam samples with a similar foam density but irregular large voids. As a result, higher surface areas and a good electric conductivity of the Cu foams present a great potential to future applications.« less