Sub-micron elastic property characterization of materials using a near-field scanning optical microscope

NASA Astrophysics Data System (ADS)

Blodgett, David W.; Spicer, James B.

2001-12-01

The ability to characterize the sub-surface mechanical properties of a bulk or thin film material at the sub-micron level has applications in the microelectronics and thin film industries. In the microelectronics industry, with the decrease of line widths and the increase of component densities, sub-surface voids have become increasingly detrimental. Any voids along an integrated circuit (IC) line can lead to improper electrical connections between components and can cause failure of the device. In the thin film industry, the detection of impurities is also important. Any impurities can detract from the film's desired optical, electrical, or mechanical properties. Just as important as the detection of voids and impurities, is the measurement of the elastic properties of a material on the nanometer scale. These elastic measurements provide insight into the microstructural properties of the material. We have been investigating a technique that couples the high-resolution surface imaging capabilities of the apertureless near-field scanning optical microscope (ANSOM) with the sub-surface characterization strengths of high-frequency ultrasound. As an ultrasonic wave propagates, the amplitude decreases due to geometrical spreading, attenuation from absorption, and scattering from discontinuities. Measurement of wave speeds and attenuation provides the information needed to quantify the bulk or surface properties of a material. The arrival of an ultrasonic wave at or along the surface of a material is accompanied with a small surface displacement. Conventional methods for the ultrasound detection rely on either a contact transducer or optical technique (interferometric, beam deflection, etc.). However, each of these methods is limited by the spatial resolution dictated by the detection footprint. As the footprint size increases, variations across the ultrasonic wavefront are effectively averaged, masking the presence of any nanometer-scale sub-surface or surface mechanical property variations. The use of an ANSOM for sensing ultrasonic wave arrivals reduces the detection footprint allowing any nanometer scale variations in the microstructure of a material to be detected. In an ANSOM, the ultrasonic displacement is manifested as perturbations on the near-field signal due to the small variations in the tip-sample caused by the wave arrival. Due to the linear dependence of the near-field signal on tip-sample separation, these perturbations can be interpreted using methods identical to those for conventional ultrasonic techniques. In this paper, we report results using both contact transducer (5 MHz) and laser-generated ultrasound.

Monte Carlo simulation of ion-material interactions in nuclear fusion devices

NASA Astrophysics Data System (ADS)

Nieto Perez, M.; Avalos-Zuñiga, R.; Ramos, G.

2017-06-01

One of the key aspects regarding the technological development of nuclear fusion reactors is the understanding of the interaction between high-energy ions coming from the confined plasma and the materials that the plasma-facing components are made of. Among the multiple issues important to plasma-wall interactions in fusion devices, physical erosion and composition changes induced by energetic particle bombardment are considered critical due to possible material flaking, changes to surface roughness, impurity transport and the alteration of physicochemical properties of the near surface region due to phenomena such as redeposition or implantation. A Monte Carlo code named MATILDA (Modeling of Atomic Transport in Layered Dynamic Arrays) has been developed over the years to study phenomena related to ion beam bombardment such as erosion rate, composition changes, interphase mixing and material redeposition, which are relevant issues to plasma-aided manufacturing of microelectronics, components on object exposed to intense solar wind, fusion reactor technology and other important industrial fields. In the present work, the code is applied to study three cases of plasma material interactions relevant to fusion devices in order to highlight the code's capabilities: (1) the Be redeposition process on the ITER divertor, (2) physical erosion enhancement in castellated surfaces and (3) damage to multilayer mirrors used on EUV diagnostics in fusion devices due to particle bombardment.

The effect of different surface materials on runoff quality in permeable pavement systems.

PubMed

Li, Haiyan; Li, Zhifei; Zhang, Xiaoran; Li, Zhuorong; Liu, Dongqing; Li, Tanghu; Zhang, Ziyang

2017-09-01

To investigate the effect of different permeable pavement surface materials on the removal of pollutants from urban storm-runoff, six commonly surface materials (porous asphalt, porous concrete, cement brick, ceramic brick, sand base brick, and shale brick) were selected in this study and the research was carried out by column experiments. Except the concentrations of total suspended solids (TSS), chemical oxygen demand (COD), ammonia nitrogen (NH 4 -N), nitrate nitrogen (NO 3 -N), total nitrogen (TN), and total phosphorus (TP) in the influent and effluent that were measured, the removal mechanism of pollutants was discussed further. The results indicate that the surface materials influence the removal efficiency of pollutants greatly and have different effects on certain pollutant. Furthermore, the physical interception and adsorption would be the main mechanism for the removal of pollutants from runoff. For example, for all surface materials, the average removal efficiency of TSS is nearly about 90.0% because of physical interception. Due to the amount of iron oxide, the removal efficiency of COD, NO 3 -N, and TN of shale brick was 88.2, 35.1, and 17.5%, respectively. NH 4 -N and TN can be easily removed by porous asphalt due to the high content of organic matter. By lacking of useful adsorption sites, all the surface materials had little effect on the removal of TP from runoff. This research could offer useful guidelines for the better design of permeable pavement system and promote the insight into the removal mechanism of pollutants in permeable pavement system. Graphical abstract Different types of materials for the different types of pollutants in the runoff purification capacity were significantly different, overall, shale brick and porous asphalt Shale bricks and porous asphalt have a better purification effect according to the six kinds of materials.

The use of inverse phase gas chromatography to measure the surface energy of crystalline, amorphous, and recently milled lactose.

PubMed

Newell, H E; Buckton, G; Butler, D A; Thielmann, F; Williams, D R

2001-05-01

To assess differences in surface energy due to processing induced disorder and to understand whether the disorder dominated the surfaces of particles. Inverse gas chromatography was used to compare the surface energies of crystalline, amorphous, and ball milled lactose. The milling process made ca 1% of the lactose amorphous, however the dispersive contribution to surface energy was 31.2, 37.1, and 41.6 mJ m(-2) for crystalline, spray dried and milled lactose, respectively. A physical mixture of crystalline (99%) and amorphous (1%) material had a dispersive surface energy of 31.5 mJ m(-2). Milling had made the surface energy similar to that of the amorphous material in a manner that was very different to a physical mixture of the same amorphous content. The milled material will have similar interfacial interactions to the 100% amorphous material.

Thermal control surfaces on the MSFC LDEF experiments

NASA Technical Reports Server (NTRS)

Wilkes, Donald R.; Whitaker, Ann F.; Zwiener, James M.; Linton, Roger C.; Shular, David; Peters, Palmer N.; Gregory, John C.

1992-01-01

There were five Marshall Space Flight Center (MSFC) experiments on the LDEF. Each of those experiments carried thermal control surfaces either as test samples or as operational surfaces. These materials experienced varying degrees of mechanical and optical damage. Some materials were virtually unchanged by the extended exposure while others suffered extensive degradation. The synergistic effects due to the constituents of the space environment are evident in the diversity of these material changes. The sample complement for the MSFC experiments is described along with results of the continuing analyses efforts.

Friction and Surface Damage of Several Corrosion-resistant Materials

NASA Technical Reports Server (NTRS)

Peterson, Marshall B; Johnson, Robert L

1952-01-01

Friction and surface damage of several materials that are resistant to corrosion due to liquid metals was studied in air. The values of kinetic friction coefficient at low sliding velocities and photomicrographs of surface damage were obtained. Appreciable surface damage was evident for all materials tested. The friction coefficients for the combinations of steel, stainless steel, and monel sliding against steel, stainless steel, nickel, Iconel, and Nichrome ranged from 0.55 for the monel-Inconel combination to 0.97 for the stainless-steel-nickel combination; for steel, stainless steel, monel, and tungsten carbide against zirconium, the friction coefficient was approximately 0.47. Lower coefficients of friction (0.20 to 0.60) and negligible surface failure at light loads were obtained with tungsten carbide when used in combination with various plate materials.

Computational characterization of ordered nanostructured surfaces

NASA Astrophysics Data System (ADS)

Mohieddin Abukhdeir, Nasser

2016-08-01

A vital and challenging task for materials researchers is to determine relationships between material characteristics and desired properties. While the measurement and assessment of material properties can be complex, quantitatively characterizing their structure is frequently a more challenging task. This issue is magnified for materials researchers in the areas of nanoscience and nanotechnology, where material structure is further complicated by phenomena such as self-assembly, collective behavior, and measurement uncertainty. Recent progress has been made in this area for both self-assembled and nanostructured surfaces due to increasing accessibility of imaging techniques at the nanoscale. In this context, recent advances in nanomaterial surface structure characterization are reviewed including the development of new theory and image processing methods.

Transfer of Materials from Water to Solid Surfaces Using Liquid Marbles.

PubMed

Kawashima, Hisato; Paven, Maxime; Mayama, Hiroyuki; Butt, Hans-Jürgen; Nakamura, Yoshinobu; Fujii, Syuji

2017-09-27

Remotely controlling the movement of small objects is desirable, especially for the transportation and selection of materials. Transfer of objects between liquid and solid surfaces and triggering their release would allow for development of novel material transportation technology. Here, we describe the remote transport of a material from a water film surface to a solid surface using quasispherical liquid marbles (LMs). A light-induced Marangoni flow or an air stream is used to propel the LMs on water. As the LMs approach the rim of the water film, gravity forces them to slide down the water rim and roll onto the solid surface. Through this method, LMs can be efficiently moved on water and placed on a solid surface. The materials encapsulated within LMs can be released at a specific time by an external stimulus. We analyzed the velocity, acceleration, and force of the LMs on the liquid and solid surfaces. On water, the sliding friction due to the drag force resists the movement of the LMs. On a solid surface, the rolling distance is affected by the surface roughness of the LMs.

Round-patterned ZnO nanostructure coated with siloxane-based polymer for nerve agent detection

NASA Astrophysics Data System (ADS)

Choi, Hyun Ji; Lee, Ji Won; Jeong, Dong-Cheol; Ha, Seonggyun; Song, Changsik; Boo, Jin-Hyo

2018-01-01

The alignment of zinc oxide (ZnO) nanostructures is expected to improve device sensitivities due to large surface areas which can be utilized to capture significant quantities of gas particles. In this study, we investigated patterned ZnO nanorods modified with polystyrene monolayers synthesized directly onto a quartz crystal microbalance (QCM) cell to increase the coating surface area of the sensing material. Also, we designed and synthesized a siloxane-based polymer (S1 polymer) as a sensing material. The patterned ZnO nanorods coated with S1 polymers were fabricated and used for the detection of dimethyl methylphosphonate (DMMP). The resonance frequency of QCM was shifted due to the adsorption and desorption of a compound at the surface of the modified electrodes. We have synthesized an S1 polymer that exhibited high sensitivity to DMMP. The patterned ZnO nanorods coated with the polymer also exhibited improved sensitivity due to an enhanced surface area capable of adsorbing more DMMP vapor.

The Nature of Residual Stress and Its Measurement.

DTIC Science & Technology

1981-07-16

that stress can relax due to microplasticity in the near- surface region (see the chapter by James). As the surface is ini- tially in compression, the...material by boring or electro- polishing and to determine the stress from measurements of strain on the surface opposite to the one where material is...Naval Research, particularly Dr. B. A. MacDcnald. APPENDIX We consider the determination by diffraction of the three-di- mensional stress tensor for a

Investigations of Effect of Rotary EDM Electrode on Machining Performance of Al6061 Alloy

NASA Astrophysics Data System (ADS)

Robinson Smart, D. S.; Jenish Smart, Joses; Periasamy, C.; Ratna Kumar, P. S. Samuel

2018-04-01

Electric Discharge Machining is an essential process which is being used for machining desired shape using electrical discharges which creates sparks. There will be electrodes subjected to electric voltage and which are separated by a dielectric liquid. Removing of material will be due to the continuous and rapid current discharges between two electrodes.. The spark is very carefully controlled and localized so that it only affects the surface of the material. Usually in order to prevent the defects which are arising due to the conventional machining, the Electric Discharge Machining (EDM) machining is preferred. Also intricate and complicated shapes can be machined effectively by use of Electric Discharge Machining (EDM). The EDM process usually does not affect the heat treat below the surface. This research work focus on the design and fabrication of rotary EDM tool for machining Al6061alloy and investigation of effect of rotary tool on surface finish, material removal rate and tool wear rate. Also the effect of machining parameters of EDM such as pulse on & off time, current on material Removal Rate (MRR), Surface Roughness (SR) and Electrode wear rate (EWR) have studied. Al6061 alloy can be used for marine and offshore applications by reinforcing some other elements. The investigations have revealed that MRR (material removal rate), surface roughness (Ra) have been improved with the reduction in the tool wear rate (TWR) when the tool is rotating instead of stationary. It was clear that as rotary speed of the tool is increasing the material removal rate is increasing with the reduction of surface finish and tool wear rate.

Suppressing surface reconstruction of superhydrophobic PDMS using a superhydrophilic zwitterionic polymer.

PubMed

Keefe, Andrew J; Brault, Norman D; Jiang, Shaoyi

2012-05-14

Poly(dimethyl siloxane) (PDMS) is extensively used for biomedical applications due to its low cost, ease of fabrication, high durability and flexibility, oxygen permeability, and self-healing properties. PDMS, however, has some significant drawbacks. PDMS endures unacceptably high levels of nonspecific protein fouling when used with biological samples due to its superhydrophobic characteristics. Unfortunately, conventional surface modification methods do not work for PDMS due to its low glass transition temperature. This phenomenon has been well-known for years as "hydrophobic regeneration". For the same reason, it is also very difficult to bring functionalities onto PDMS surfaces. Herein, we demonstrate how a superhydrophilic zwitterionic material, poly(carboxybetaine methacrylate) (pCBMA), can provide a highly stable coating with long-term stabilty due to the sharp contrast in hydrophobicity between pCBMA and PDMS. This material is able to suppress nonspecific protein adsorption in complex media and functionalize desired biomolecules needed in applications, such as diagnostics, without sacrificing its nonfouling characteristics.

Suppressing Surface Reconstruction of Superhydrophobic PDMS using a Superhydrophilic Zwitterionic Polymer

PubMed Central

Keefe, Andrew J.; Brault, Norman D.; Jiang, Shaoyi

2014-01-01

Poly(dimethyl siloxane) (PDMS) is extensively used for biomedical applications due to its low cost, ease of fabrication, high durability and flexibility, oxygen permeability, and self-healing properties. PDMS, however, has some significant drawbacks. PDMS endures unacceptably high levels of non-specific protein fouling when used with biological samples due to its superhydrophobic characteristics. Unfortunately, conventional surface modification methods do not work for PDMS due to its low glass transition temperature. This phenomenon has been well-known for years as “hydrophobic regeneration”. For the same reason, it is also very difficult to bring functionalities onto PDMS surfaces. Herein, we demonstrate how a superhydrophilic zwitterionic material, poly(carboxybetaine methacrylate) (pCBMA), can provide a highly stable coating with long term stabilty due to the sharp contrast in hydrophobicity between pCBMA and PDMS. This material is able to suppress nonspecific protein adsorption in complex media and functionalize desired biomolecules needed in applications, such as diagnostics, without sacrificing its nonfouling characteristics. PMID:22512660

Different effects of surface heterogeneous atoms of porous and non-porous carbonaceous materials on adsorption of 1,1,2,2-tetrachloroethane in aqueous environment.

PubMed

Chen, Weifeng; Ni, Jinzhi

2017-05-01

The surface heterogeneous atoms of carbonaceous materials (CMs) play an important role in adsorption of organic pollutants. However, little is known about the surface heterogeneous atoms of CMs might generate different effect on adsorption of hydrophobic organic compounds by porous carbonaceous materials - activated carbons (ACs) and non-porous carbonaceous materials (NPCMs). In this study, we observed that the surface oxygen and nitrogen atoms could decrease the adsorption affinity of both ACs and NPCMs for 1,1,2,2-tetrachloroethane (TeCA), but the degree of decreasing effects were very different. The increasing content of surface oxygen and nitrogen ([O + N]) caused a sharper decrease in adsorption affinity of ACs (slope of lg (k d /SA) vs [O + N]: -0.098∼-0.16) than that of NPCMs (slope of lg (k d /SA) vs [O + N]: -0.025∼-0.059) for TeCA. It was due to the water cluster formed by the surface hydrophilic atoms that could block the micropores and generate massive invalid adsorption sites in the micropores of ACs, while the water cluster only occupied the surface adsorption sites of NPCMs. Furthermore, with the increasing concentration of dissolved TeCA, the effect of surface area on adsorption affinity of NPCMs for TeCA kept constant while the effect of [O + N] decreased due to the competitive adsorption between water molecule and TeCA on the surface of NPCMs, meanwhile, both the effects of micropore volume and [O + N] on adsorption affinity of ACs for TeCA were decreased due to the mechanism of micropore volume filling. These findings are valuable for providing a deep insight into the adsorption mechanisms of CMs for TeCA. Copyright © 2017 Elsevier Ltd. All rights reserved.

Issues Related to Cleaning Complex Geometry Surfaces with ODC-Free Solvents

NASA Technical Reports Server (NTRS)

Bradford, Blake F.; Wurth, Laura A.; Nayate, Pramod D.; McCool, Alex (Technical Monitor)

2001-01-01

Implementing ozone depleting chemicals (ODC)-free solvents into full-scale reusable solid rocket motor cleaning operations has presented problems due to the low vapor pressures of the solvents. Because of slow evaporation, solvent retention is a problem on porous substrates or on surfaces with irregular geometry, such as threaded boltholes, leak check ports, and nozzle backfill joints. The new solvents are being evaluated to replace 1,1,1-trichloroethane, which readily evaporates from these surfaces. Selection of the solvents to be evaluated on full-scale hardware was made based on results of subscale tests performed with flat surface coupons, which did not manifest the problem. Test efforts have been undertaken to address concerns with the slow-evaporating solvents. These concerns include effects on materials due to long-term exposure to solvent, potential migration from bolthole threads to seal surfaces, and effects on bolt loading due to solvent retention in threads. Tests performed to date have verified that retained solvent does not affect materials or hardware performance. Process modifications have also been developed to assist drying, and these can be implemented if additional drying becomes necessary.

Machining approach of freeform optics on infrared materials via ultra-precision turning.

PubMed

Li, Zexiao; Fang, Fengzhou; Chen, Jinjin; Zhang, Xiaodong

2017-02-06

Optical freeform surfaces are of great advantage in excellent optical performance and integrated alignment features. It has wide applications in illumination, imaging and non-imaging, etc. Machining freeform surfaces on infrared (IR) materials with ultra-precision finish is difficult due to its brittle nature. Fast tool servo (FTS) assisted diamond turning is a powerful technique for the realization of freeform optics on brittle materials due to its features of high spindle speed and high cutting speed. However it has difficulties with large slope angles and large rise-and-falls in the sagittal direction. In order to overcome this defect, the balance of the machining quality on the freeform surface and the brittle nature in IR materials should be realized. This paper presents the design of a near-rotational freeform surface (NRFS) with a low non-rotational degree (NRD) to constraint the variation of traditional freeform optics to solve this issue. In NRFS, the separation of the surface results in a rotational part and a residual part denoted as a non-rotational surface (NRS). Machining NRFS on germanium is operated by FTS diamond turning. Characteristics of the surface indicate that the optical finish of the freeform surface has been achieved. The modulation transfer function (MTF) of the freeform optics shows a good agreement to the design expectation. Images of the final optical system confirm that the fabricating strategy is of high efficiency and high quality. Challenges and prospects are discussed to provide guidance of future work.

Review of literature surface tension data for molten silicon

NASA Technical Reports Server (NTRS)

Hardy, S.

1981-01-01

Measurements of the surface tension of molten silicon are reported. For marangoni flow, the important parameter is the variation of surface tension with temperature, not the absolute value of the surface tension. It is not possible to calculate temperature coefficients using surface tension measurements from different experiments because the systematic errors are usually larger than the changes in surface tension because of temperature variations. The lack of good surface tension data for liquid silicon is probably due to its extreme chemical reactivity. A material which resists attack by molten silicon is not found. It is suggested that all of the sessile drip surface tension measurements are probably for silicon which is contaminated by the substrate materials.

Overview on the Surface Functionalization Mechanism and Determination of Surface Functional Groups of Plasma Treated Carbon Nanotubes.

PubMed

Saka, Cafer

2018-01-02

The use of carbon materials for many applications is due to the unique diversity of structures and properties ranging from chemical bonds between the carbon atoms of the materials to nanostructures, crystallite alignment, and microstructures. Carbon nanotubes and other nanoscale carbonaceous materials draw much attention due to their physical and chemical properties, such as high strength, high resistance to corrosion, electrical and thermal conductivity, stability and a qualified adsorbent. Carbon-based nanomaterials, which have a relatively large specific area and layered structure, can be used as an adsorbent for efficient removal of organic and inorganic contaminants. However, one of the biggest obstacles to the development of carbon-based nanomaterials adsorbents is insolubility and the lack of functional groups on the surface. There are several approaches to introduce functional groups on carbon nanotubes. One of these approaches, plasma applications, now has an important place in the creation of surface functional groups as a flexible, fast, and environmentally friendly method. This review focuses on recent information concerning the surface functionalization and modification of plasma treated carbon nanotube. This review considers the surface properties, advantages, and disadvantages of plasma-applied carbon nanotubes. It also examines the reaction mechanisms involved in the functional groups on the surface.

(Bio)hybrid materials based on optically active particles

NASA Astrophysics Data System (ADS)

Reitzig, Manuela; Härtling, Thomas; Opitz, Jörg

2014-03-01

In this contribution we provide an overview of current investigations on optically active particles (nanodiamonds, upconversion phospors) for biohybrid and sensing applications. Due to their outstanding properties nanodiamonds gain attention in various application elds such as microelectronics, optical monitoring, medicine, and biotechnology. Beyond the typical diamond properties such as high thermal conductivity and extreme hardness, the carbon surface and its various functional groups enable diverse chemical and biological surface functionalization. At Fraunhofer IKTS-MD we develop a customization of material surfaces via integration of chemically modi ed nanodiamonds at variable surfaces, e.g bone implants and pipelines. For the rst purpose, nanodiamonds are covalently modi ed at their surface with amino or phosphate functionalities that are known to increase adhesion to bone or titanium alloys. The second type of surface is approached via mechanical implementation into coatings. Besides nanodiamonds, we also investigate the properties of upconversion phosphors. In our contribution we show how upconversion phosphors are used to verify sterilization processes via a change of optical properties due to sterilizing electron beam exposure.

Development of Si3N4 and SiC of improved toughness. [for gas turbine engines

NASA Technical Reports Server (NTRS)

Brennan, J. J.; Hulse, C. O.

1977-01-01

The application of energy absorbing surface layers to Si3N4 and SiC was investigated. Among the layers studied were microcracked materials such as iron titanate and a silica-zircon mixture and porous materials such as reaction sintered Si3N4. Energy absorption due to microcrack extension upon impact was found not to be an important mechanism. Instead, the fivefold improvement in Charpy and ballistic impact at elevated temperature (1250 C and 1370 C) found for Fe2TiO5 was due to plastic deformation while similar improvement found for silica-zircon mixtures at RT was due to crushing of the porous material. Due to thermal expansion mismatch, these two materials could not withstand thermal cycling when used as energy absorbing surface layers on Si3N4. Reaction sintered Si3N4 layers on dense Si3N4 were found to give up to a sevenfold increase in ballistic impact resistance due to crushing of the layer upon impact. High porosity (45%), large particle size R.S. Si3N4 layers fabricated from -100, +200 mesh Si powder gave better impact improvement than less porous (30%), small particle size layers fabricated from -325 mesh Si powder.

Consideration of Materials for Aircraft Brakes

NASA Technical Reports Server (NTRS)

Peterson, M. B.; Ho, T.

1972-01-01

An exploratory investigation was conducted concerning materials and their properties for use in aircraft brakes. Primary consideration was given to the heat dissipation and the frictional behavior of materials. Used brake pads and rotors were analyzed as part of the investigation. A simple analysis was conducted in order to determine the most significant factors which affect surface temperatures. It was found that where size and weight restrictions are necessary, the specific heat of the material, and maintaining uniform contact area are the most important factors. A criterion was suggested for optimum sizing of the brake disks. Bench friction tests were run with brake materials. It was found that there is considerable friction variation due to the formation and removal of surface oxide films. Other causes of friction variations are surface softening and melting. The friction behavior at high temperature was found to be more characteristic of the steel surface rather than the copper brake material. It is concluded that improved brake materials are feasible.

Enhancing wear resistance of working bodies of grinder through lining crushed material

NASA Astrophysics Data System (ADS)

Romanovich, A. A.; Annenko, D. M.; Romanovich, M. A.; Apukhtina, I. V.

2018-03-01

The article presents the analysis of directions of increasing wear resistance of working surfaces of rolls. A technical solution developed at the level of the invention is proposed, which is simple to implement in production conditions and which makes it possible to protect the roll surface from heavy wear due to surfacing of wear-resistant mesh material, cells of which are filling with grinding material in the process of work. Retaining them enables one to protect the roll surface from wear. The paper dwells on conditions of pressing materials in cells of eccentric rolls on the working surface with a grid of rectangular shape. The paper presents an equation for calculation of the cell dimension that provides the lining of the working surface by a mill material with respect to its properties. The article presents results of comparative studies on the grinding process of a press roller grinder (PRG) between rolls with and without a fusion-bonded mesh. It is clarified that the lining of rolls working surface slightly reduces the quality of the grinding, since the material thickness in the cell is small and has a finely divided and compacted structure with high strength.

Density functional theory study of phase stability and defect thermodynamics in iron-oxyhydroxide mineral materials

NASA Astrophysics Data System (ADS)

Pinney, Nathan Douglas

Due to their high surface area and reactivity toward a variety of heavy metal and oxyanion species of environmental concern, Fe-(oxyhydr)oxide materials play an important role in the geochemical fate of natural and anthropogenic contaminants in soils, aquifers and surface water environments worldwide. In this research, ab initio simulations describe the bulk structure, magnetic properties, and relative phase stability of major Fe-(oxyhydr)oxide materials, including hematite, goethite, lepidocrocite, and ferrihydrite.These bulk models are employed in further studies of point defect and alloy/dopant thermodynamics in these materials, allowing construction of a phase stability model that better replicates the structure and composition of real materials. Li + adsorption at the predominant goethite (101) surface is simulated using ab initio methods, offering energetic and structural insight into the binding mechanisms of metal cations over a range of surface protonation conditions.

Metal segregation in hierarchically structured cathode materials for high-energy lithium batteries

DOE PAGES

Lin, Feng; Xin, Huolin L.; Nordlund, Dennis; ...

2016-01-11

Controlling surface and interfacial properties of battery materials is key to improving performance in rechargeable Li-ion devices. Surface reconstruction from a layered to a rock salt structure in metal oxide cathode materials is commonly observed and results in poor high-voltage cycling performance, impeding attempts to improve energy density. Hierarchically structured LiNi 0.4Mn 0.4Co 0.2O 2 (NMC-442) spherical powders, made by spray pyrolysis, exhibit local elemental distribution gradients that deviate from the global NMC-442 composition; specifically, they are Ni-rich and Mn-poor at particle surfaces. These materials demonstrate improved Coulombic efficiencies, discharge capacities, and high-voltage capacity retention in lithium half-cell configurations. Themore » subject powders show superior resistance against surface reconstruction due to the tailored surface chemistry, compared to conventional NMC-442 materials. This paves the way towards the development of a new generation of robust and stable high-energy NMC cathodes for Li-ion batteries.« less

The structural coloration of textile materials using self-assembled silica nanoparticles

NASA Astrophysics Data System (ADS)

Gao, Weihong; Rigout, Muriel; Owens, Huw

2017-09-01

The work presented investigates how to produce structural colours on textile materials by applying a surface coating of silica nanoparticles (SNPs). Uniform SNPs with particle diameters in a controlled micron size range (207-350 nm) were synthesized using a Stöber-based solvent varying (SV) method which has been reported previously. Photonic crystals (PCs) were formed on the surface of a piece of textile fabric through a process of natural sedimentation self-assembly of the colloidal suspension containing uniform SNPs. Due to the uniformity and a particular diameter range of the prepared SNPs, structural colours were observed from the fabric surface due to the Bragg diffraction of white light with the ordered structure of the silica PCs. By varying the mean particle diameter, a wide range of spectral colours from red to blue were obtained. The comparison of structural colours on fabrics and on glasses suggests that a smooth substrate is critical when producing materials with high colour intensity and spatial uniformity. This work suggested a promising approach to colour textile materials without the need for traditional dyes and/or pigments. [Figure not available: see fulltext.

The structural coloration of textile materials using self-assembled silica nanoparticles.

PubMed

Gao, Weihong; Rigout, Muriel; Owens, Huw

2017-01-01

The work presented investigates how to produce structural colours on textile materials by applying a surface coating of silica nanoparticles (SNPs). Uniform SNPs with particle diameters in a controlled micron size range (207-350 nm) were synthesized using a Stöber-based solvent varying (SV) method which has been reported previously. Photonic crystals (PCs) were formed on the surface of a piece of textile fabric through a process of natural sedimentation self-assembly of the colloidal suspension containing uniform SNPs. Due to the uniformity and a particular diameter range of the prepared SNPs, structural colours were observed from the fabric surface due to the Bragg diffraction of white light with the ordered structure of the silica PCs. By varying the mean particle diameter, a wide range of spectral colours from red to blue were obtained. The comparison of structural colours on fabrics and on glasses suggests that a smooth substrate is critical when producing materials with high colour intensity and spatial uniformity. This work suggested a promising approach to colour textile materials without the need for traditional dyes and/or pigments. Graphical abstract.

Impact of initial surface parameters on the final quality of laser micro-polished surfaces

NASA Astrophysics Data System (ADS)

Chow, Michael; Bordatchev, Evgueni V.; Knopf, George K.

2012-03-01

Laser micro-polishing (LμP) is a new laser-based microfabrication technology for improving surface quality during a finishing operation and for producing parts and surfaces with near-optical surface quality. The LμP process uses low power laser energy to melt a thin layer of material on the previously machined surface. The polishing effect is achieved as the molten material in the laser-material interaction zone flows from the elevated regions to the local minimum due to surface tension. This flow of molten material then forms a thin ultra-smooth layer on the top surface. The LμP is a complex thermo-dynamic process where the melting, flow and redistribution of molten material is significantly influenced by a variety of process parameters related to the laser, the travel motions and the material. The goal of this study is to analyze the impact of initial surface parameters on the final surface quality. Ball-end micromilling was used for preparing initial surface of samples from H13 tool steel that were polished using a Q-switched Nd:YAG laser. The height and width of micromilled scallops (waviness) were identified as dominant parameter affecting the quality of the LμPed surface. By adjusting process parameters, the Ra value of a surface, having a waviness period of 33 μm and a peak-to-valley value of 5.9 μm, was reduced from 499 nm to 301 nm, improving the final surface quality by 39.7%.

Crack propagation and coalescence due to dual non-penetrating surface flaws and their effect on the strength of rock-like material

NASA Astrophysics Data System (ADS)

Xu, Jun; Zheng, Zheyuan; Xiao, Xiaochun; Li, Zhaoxia

2018-06-01

Non-penetrating surface flaws play a key role in the fracture process of rock-like material, and could cause localized collapse and even failure of the materials. Until now, the mechanism and the effect of surface crack propagation have remained unclear. In this paper, compression tests on gypsum (a soft rock material) are conducted to investigate crack propagation and coalescence due to non-penetrating surface flaws and their effect on the material strength. Specimens are tested under dual pre-existing surface flaws with various combinations of depth and spacing. The results show that when the pre-existing flaws are non-penetrating, the d/t ratio (flaw depth ratio, d is the pre-existing flaw cutting depth and t is the specimen thickness) and the spacing (the distance between the two flaw internal tips) have a strong influence on surface crack patterns and specimen strength. Few cracks emanate from the pre-existing flaws when the flaw depth ratio is equal to 1/3, and more cracks occur with the increase of the flaw depth ratio. When the pre-existing flaw penetrates completely through the specimen, the spacing has a small effect on the specimen strength. A larger flaw depth ratio could advance the occurrence of the peak load (PL) and result in a smaller specimen residual strength. The failure process of the specimen is divided into several stages featured by a stepped decline of the load value after PL, which is closely related to the initiation and propagation of secondary cracks. In addition, the spalling (failure of a portion of the surface caused by coalescence of cracks) can be regarded as indicating the failure of the specimen, and two possible types of spalling formation are briefly discussed.

Investigation of the crater-like microdefects induced by laser shock processing with aluminum foil as absorbent layer

NASA Astrophysics Data System (ADS)

Ye, Y. X.; Xuan, T.; Lian, Z. C.; Feng, Y. Y.; Hua, X. J.

2015-06-01

This paper reports that 3D crater-like microdefects form on the metal surface when laser shock processing (LSP) is applied. LSP was conducted on pure copper block using the aluminum foil as the absorbent material and water as the confining layer. There existed the bonding material to attach the aluminum foil on the metal target closely. The surface morphologies and metallographs of copper surfaces were characterized with 3D profiler, the optical microscopy (OM) or the scanning electron microscopy (SEM). Temperature increases of metal surface due to LSP were evaluated theoretically. It was found that, when aluminum foil was used as the absorbent material, and if there existed air bubbles in the bonding material, the air temperatures within the bubbles rose rapidly because of the adiabatic compression. So at the locations of the air bubbles, the metal materials melted and micromelting pool formed. Then under the subsequent expanding of the air bubbles, a secondary shock wave was launched against the micromelting pool and produced the crater-like microdefects on the metal surface. The temperature increases due to shock heat and high-speed deformation were not enough to melt the metal target. The temperature increase induced by the adiabatic compression of the air bubbles may also cause the gasification of the metal target. This will also help form the crater-like microdefects. The results of this paper can help to improve the surface quality of a metal target during the application of LSP. In addition, the results provide another method to fabricate 3D crater-like dents on metal surface. This has a potential application in mechanical engineering.

Space environmental effects on spacecraft: LEO materials selection guide, part 1

NASA Astrophysics Data System (ADS)

Silverman, Edward M.

1995-08-01

This document provides performance properties on major spacecraft materials and subsystems that have been exposed to the low-Earth orbit (LEO) space environment. Spacecraft materials include metals, polymers, composites, white and black paints, thermal-control blankets, adhesives, and lubricants. Spacecraft subsystems include optical components, solar cells, and electronics. Information has been compiled from LEO short-term spaceflight experiments (e.g., space shuttle) and from retrieved satellites of longer mission durations (e.g., Long Duration Exposure Facility). Major space environment effects include atomic oxygen (AO), ultraviolet radiation, micrometeoroids and debris, contamination, and particle radiation. The main objective of this document is to provide a decision tool to designers for designing spacecraft and structures. This document identifies the space environments that will affect the performance of materials and components, e.g., thermal-optical property changes of paints due to UV exposures, AO-induced surface erosion of composites, dimensional changes due to thermal cycling, vacuum-induced moisture outgassing, and surface optical changes due to AO/UV exposures. Where appropriate, relationships between the space environment and the attendant material/system effects are identified. Part 1 covers spacecraft design considerations for the space environment; advanced composites; polymers; adhesives; metals; ceramics; protective coatings; and lubricants, greases, and seals.

Space environmental effects on spacecraft: LEO materials selection guide, part 2

NASA Astrophysics Data System (ADS)

Silverman, Edward M.

1995-08-01

This document provides performance properties on major spacecraft materials and subsystems that have been exposed to the low-Earth orbit (LEO) space environment. Spacecraft materials include metals, polymers, composites, white and black paints, thermal-control blankets, adhesives, and lubricants. Spacecraft subsystems include optical components, solar cells, and electronics. Information has been compiled from LEO short-term spaceflight experiments (e.g., space shuttle) and from retrieved satellites of longer mission durations (e.g., Long Duration Exposure Facility). Major space environment effects include atomic oxygen (AO), ultraviolet radiation, micrometeoroids and debris, contamination, and particle radiation. The main objective of this document is to provide a decision tool to designers for designing spacecraft and structures. This document identifies the space environments that will affect the performance of materials and components, e.g., thermal-optical property changes of paints due to UV exposures, AO-induced surface erosion of composites, dimensional changes due to thermal cycling, vacuum-induced moisture outgassing, and surface optical changes due to AO/UV exposures. Where appropriate, relationships between the space environment and the attendant material/system effects are identified. Part 2 covers thermal control systems, power systems, optical components, electronic systems, and applications.

Space environmental effects on spacecraft: LEO materials selection guide, part 2

NASA Technical Reports Server (NTRS)

Silverman, Edward M.

1995-01-01

This document provides performance properties on major spacecraft materials and subsystems that have been exposed to the low-Earth orbit (LEO) space environment. Spacecraft materials include metals, polymers, composites, white and black paints, thermal-control blankets, adhesives, and lubricants. Spacecraft subsystems include optical components, solar cells, and electronics. Information has been compiled from LEO short-term spaceflight experiments (e.g., space shuttle) and from retrieved satellites of longer mission durations (e.g., Long Duration Exposure Facility). Major space environment effects include atomic oxygen (AO), ultraviolet radiation, micrometeoroids and debris, contamination, and particle radiation. The main objective of this document is to provide a decision tool to designers for designing spacecraft and structures. This document identifies the space environments that will affect the performance of materials and components, e.g., thermal-optical property changes of paints due to UV exposures, AO-induced surface erosion of composites, dimensional changes due to thermal cycling, vacuum-induced moisture outgassing, and surface optical changes due to AO/UV exposures. Where appropriate, relationships between the space environment and the attendant material/system effects are identified. Part 2 covers thermal control systems, power systems, optical components, electronic systems, and applications.

Space environmental effects on spacecraft: LEO materials selection guide, part 1

NASA Technical Reports Server (NTRS)

Silverman, Edward M.

1995-01-01

This document provides performance properties on major spacecraft materials and subsystems that have been exposed to the low-Earth orbit (LEO) space environment. Spacecraft materials include metals, polymers, composites, white and black paints, thermal-control blankets, adhesives, and lubricants. Spacecraft subsystems include optical components, solar cells, and electronics. Information has been compiled from LEO short-term spaceflight experiments (e.g., space shuttle) and from retrieved satellites of longer mission durations (e.g., Long Duration Exposure Facility). Major space environment effects include atomic oxygen (AO), ultraviolet radiation, micrometeoroids and debris, contamination, and particle radiation. The main objective of this document is to provide a decision tool to designers for designing spacecraft and structures. This document identifies the space environments that will affect the performance of materials and components, e.g., thermal-optical property changes of paints due to UV exposures, AO-induced surface erosion of composites, dimensional changes due to thermal cycling, vacuum-induced moisture outgassing, and surface optical changes due to AO/UV exposures. Where appropriate, relationships between the space environment and the attendant material/system effects are identified. Part 1 covers spacecraft design considerations for the space environment; advanced composites; polymers; adhesives; metals; ceramics; protective coatings; and lubricants, greases, and seals.

In situ evaluation of surface roughness and micromorphology of temporary soft denture liner materials at different time intervals.

PubMed

Araújo, Célio U; Basting, Roberta T

2018-03-01

To perform an in situ evaluation of surface roughness and micromorphology of two soft liner materials for dentures at different time intervals. The surface roughness of materials may influence the adhesion of micro-organisms and inflammation of the mucosal tissues. The in situ evaluation of surface roughness and the micromorphology of soft liner materials over the course of time may present results different from those of in vitro studies, considering the constant presence of saliva and food, the changes in temperature and the pH level in the oral cavity. Forty-eight rectangular specimens of each of the two soft liner materials were fabricated: a silicone-based material (Mucopren Soft) and an acrylic resin-based material (Trusoft). The specimens were placed in the dentures of 12 participants (n = 12), and the materials were evaluated for surface roughness and micromorphology at different time intervals: 0, 7, 30 and 60 days. Roughness (Ra) was evaluated by means of a roughness tester. Surface micromorphology was evaluated by scanning electron microscopy. Analysis of variance for randomised block design and Tukey's test showed that surface roughness values were lower in the groups using the silicone-based material at all the time intervals (P < .0001). The average surface roughness was higher at time interval 0 than at the other intervals, for both materials (P < .0001). The surface micromorphology showed that the silicone material presented a more regular and smoother surface than the acrylic resin-based material. The surface roughness of acrylic resin-based and silicone-based denture soft liner materials decreased after 7 days of evaluation, leading to a smoother surface over time. The silicone-based material showed lower roughness values and a smoother surface than the acrylic resin-based material, thereby making it preferred when selecting more appropriate material, due its tendency to promote less biofilm build-up. © 2017 John Wiley & Sons A/S and The Gerodontology Association. Published by John Wiley & Sons Ltd.

Smart wing wind tunnel test results

NASA Astrophysics Data System (ADS)

Scherer, Lewis B.; Martin, Christopher A.; Appa, Kari; Kudva, Jayanth N.; West, Mark N.

1997-05-01

The use of smart materials technologies can provide unique capabilities in improving aircraft aerodynamic performance. Northrop Grumman built and tested a 16% scale semi-span wind tunnel model of the F/A-18 E/F for the on-going DARPA/WL Smart Materials and Structures-Smart Wing Program. Aerodynamic performance gains to be validated included increase in the lift to drag ratio, increased pitching moment (Cm), increased rolling moment (Cl) and improved pressure distribution. These performance gains were obtained using hingeless, contoured trailing edge control surfaces with embedded shape memory alloy (SMA) wires and spanwise wing twist via a SMA torque tube and are compared to a conventional wind tunnel model with hinged control surfaces. This paper presents an overview of the results from the first wind tunnel test performed at the NASA Langley's 16 ft Transonic Dynamic Tunnel. Among the benefits demonstrated are 8 - 12% increase in rolling moment due to wing twist, a 10 - 15% increase in rolling moment due to contoured aileron, and approximately 8% increase in lift due to contoured flap, and improved pressure distribution due to trailing edge control surface contouring.

Silver coated aluminium microrods as highly colloidal stable SERS platforms.

PubMed

Pazos-Perez, Nicolas; Borke, Tina; Andreeva, Daria V; Alvarez-Puebla, Ramon A

2011-08-01

We report on the fabrication of a novel material with the ability to remain in solution even under the very demanding conditions required for structural and dynamic characterization of biomacromolecule assays. This stability is provided by the increase in surface area of a low density material (aluminium) natively coated with a very hydrophilic surface composed of aluminium oxide (Al(2)O(3)) and metallic silver nanoparticles. Additionally, due to the dense collection of active hot spots on their surface, this material offers higher levels of SERS intensity as compared with the same free and aggregated silver nanoparticles. This journal is © The Royal Society of Chemistry 2011

Surface treatment of alumina-based ceramics using combined laser sources

NASA Astrophysics Data System (ADS)

Triantafyllidis, D.; Li, L.; Stott, F. H.

2002-01-01

Alumina-based refractory materials are extensively used as linings in incinerators and furnaces. These materials are subject to molten salt corrosion and chemical degradation because of the existence of porosity and material inhomogeneity. Efforts to improve the performance of these materials have so far concentrated mainly on the optimisation of the manufacturing processes (e.g. producing denser refractory bricks) and in-service monitoring. Laser surface treatment has also been used to improve performance. The main problem identified with laser surface treatment is solidification cracking due to the generation of very large temperature gradients. The aim of this paper is to investigate the surface modification of alumina-based ceramics by using two combined laser sources in order to control the thermal gradients and cooling rates during processing so that crack formation can be eliminated. The material under investigation is 85% alumina refractory ceramic, used as lining material in incineration plants. The surface morphology and cross-section of the treated samples are analysed using optical and scanning electron microscopy (SEM) and compared with single laser beam treated samples.

Surface roughness analysis after laser assisted machining of hard to cut materials

NASA Astrophysics Data System (ADS)

Przestacki, D.; Jankowiak, M.

2014-03-01

Metal matrix composites and Si3N4 ceramics are very attractive materials for various industry applications due to extremely high hardness and abrasive wear resistance. However because of these features they are problematic for the conventional turning process. The machining on a classic lathe still requires special polycrystalline diamond (PCD) or cubic boron nitride (CBN) cutting inserts which are very expensive. In the paper an experimental surface roughness analysis of laser assisted machining (LAM) for two tapes of hard-to-cut materials was presented. In LAM, the surface of work piece is heated directly by a laser beam in order to facilitate, the decohesion of material. Surface analysis concentrates on the influence of laser assisted machining on the surface quality of the silicon nitride ceramic Si3N4 and metal matrix composite (MMC). The effect of the laser assisted machining was compared to the conventional machining. The machining parameters influence on surface roughness parameters was also investigated. The 3D surface topographies were measured using optical surface profiler. The analysis of power spectrum density (PSD) roughness profile were analyzed.

Studies of Itokawa's Surface Exposure by Measurements of Cosmic-ray Produced Nuclides

NASA Technical Reports Server (NTRS)

Caffee, M. W.; Nishiizumi, K.; Tsuchiyama, A.; Uesugi, M.; Zolensky, M. E.

2014-01-01

We plan to investigate the evolutionary history of surface materials from 25143 Itokawa, the Hayabusa samples. Our studies are based on the measurement of nuclides produced in asteroidal surface materials by cosmic rays. Cosmogenic radionuclides are used to determine the duration and nature of the exposure of materials to energetic particles. Our goals are to understand both the fundamental processes on the asteroidal surface and the evolutionary history of its surface materials. They are also key to understanding the history of Itokawa's surface and asteroid-meteoroid evolutionary dynamics. To achieve our key goals, in particular reconstructing the evolutionary histories of the asteroidal surface, we proposed: (1) characterizing Itokawa particles using SXCT, SXRD, and FE-SEM without modification of the sample; (2) embedding each particle in acrylic resin, then slicing a small corner with an ultra-microtome and examining it using super-STEM and SIMS for characterizing surface morphology, space weathering, and oxygen three-isotope analysis; and finally (3) measuring small amounts of cosmogenic radionuclides (104-105 atoms) in Hayabusa samples by AMS. However, we have to modify our plan due to unexpected situation.

Microcolumn Formation due to Induced-Charge Electroosmosis in a Floating Mode

NASA Astrophysics Data System (ADS)

Sugioka, Hideyuki; Dan, Hironobu; Hanazawa, Yuya

2017-10-01

Self-organization of particles is important since it may provide new functional materials. Previously, by using two-dimensional multiphysics simulations, we theoretically showed microcolumn formation due to induced-charge electroosmosis (ICEO). In this study, we experimentally demonstrate that gold leaves on a water surface move slowly and dynamically form a microcolumn due to a hydrodynamic interaction under an ac electric field. Further, by numerically analyzing video data, we show the time evolutions of the maximum cluster length and the maximum cluster area. In addition, by cluster analysis, we show the dependences of the average velocity on the applied voltage and frequency to clarify the phenomena. We believe that our findings make a new stage in the development of new functional materials on a water surface.

Direct exfoliation and dispersion of two-dimensional materials in pure water via temperature control.

PubMed

Kim, Jinseon; Kwon, Sanghyuk; Cho, Dae-Hyun; Kang, Byunggil; Kwon, Hyukjoon; Kim, Youngchan; Park, Sung O; Jung, Gwan Yeong; Shin, Eunhye; Kim, Wan-Gu; Lee, Hyungdong; Ryu, Gyeong Hee; Choi, Minseok; Kim, Tae Hyeong; Oh, Junghoon; Park, Sungjin; Kwak, Sang Kyu; Yoon, Suk Wang; Byun, Doyoung; Lee, Zonghoon; Lee, Changgu

2015-09-15

The high-volume synthesis of two-dimensional (2D) materials in the form of platelets is desirable for various applications. While water is considered an ideal dispersion medium, due to its abundance and low cost, the hydrophobicity of platelet surfaces has prohibited its widespread use. Here we exfoliate 2D materials directly in pure water without using any chemicals or surfactants. In order to exfoliate and disperse the materials in water, we elevate the temperature of the sonication bath, and introduce energy via the dissipation of sonic waves. Storage stability greater than one month is achieved through the maintenance of high temperatures, and through atomic and molecular level simulations, we further discover that good solubility in water is maintained due to the presence of platelet surface charges as a result of edge functionalization or intrinsic polarity. Finally, we demonstrate inkjet printing on hard and flexible substrates as a potential application of water-dispersed 2D materials.

A robust, melting class bulk superhydrophobic material with heat-healing and self-cleaning properties

PubMed Central

Ramakrishna, S.; Santhosh Kumar, K. S.; Mathew, Dona; Reghunadhan Nair, C. P.

2015-01-01

Superhydrophobic (SH) materials are essential for a myriad of applications such as anti-icing and self-cleaning due to their extreme water repellency. A single, robust material simultaneously possessing melt-coatability, bulk water repellency, self-cleanability, self-healability, self-refreshability, and adhesiveness has been remaining an elusive goal. We demonstrate a unique class of melt-processable, bulk SH coating by grafting long alkyl chains on silica nanoparticle surface by a facile one-step method. The well-defined nanomaterial shows SH property in the bulk and is found to heal macro-cracks on gentle heating. It retains wettability characteristics even after abrading with a sand paper. The surface regenerates SH features (due to reversible self-assembly of nano structures) quickly at ambient temperature even after cyclic water impalement, boiling water treatment and multiple finger rubbing tests. It exhibits self-cleaning properties on both fresh and cut surfaces. This kind of coating, hitherto undisclosed, is expected to be a breakthrough in the field of melt-processable SH coatings. PMID:26679096

First Photograph Taken On Mars Surface

NASA Image and Video Library

1996-12-12

This is the first photograph ever taken on the surface of the planet Mars. It was obtained by Viking 1 just minutes after the spacecraft landed successfully early today [July 20, 1976]. The center of the image is about 1.4 meters (five feet) from Viking Lander camera #2. We see both rocks and finely granulated material--sand or dust. Many of the small foreground rocks are flat with angular facets. Several larger rocks exhibit irregular surfaces with pits and the large rock at top left shows intersecting linear cracks. Extending from that rock toward the camera is a vertical linear dark band which may be due to a one-minute partial obscuration of the landscape due to clouds or dust intervening between the sun and the surface. Associated with several of the rocks are apparent signs of wind transport of granular material. The large rock in the center is about 10 centimeters (4 inches) across and shows three rough facets. To its lower right is a rock near a smooth portion of the Martian surface probably composed of very fine-grained material. It is possible that the rock was moved during Viking 1 descent maneuvers, revealing the finer-grained basement substratum; or that the fine-grained material has accumulated adjacent to the rock. There are a number of other furrows and depressions and places with fine-grained material elsewhere in the picture. At right is a portion of footpad #2. Small quantities of fine grained sand and dust are seen at the center of the footpad near the strut and were deposited at landing. The shadow to the left of the footpad clearly exhibits detail, due to scattering of light either from the Martian atmosphere or from the spacecraft, observable because the Martian sky scatters light into shadowed areas. http://photojournal.jpl.nasa.gov/catalog/PIA00381

An Investigation of Low Earth Orbit Internal Charging

NASA Technical Reports Server (NTRS)

NeergaardParker, Linda; Minow, Joseph I.; Willis, Emily M.

2014-01-01

Low Earth orbit is usually considered a relatively benign environment for internal charging threats due to the low flux of penetrating electrons with energies of a few MeV that are encountered over an orbit. There are configurations, however, where insulators and ungrounded conductors used on the outside of a spacecraft hull may charge when exposed to much lower energy electrons of some 100's keV in a process that is better characterized as internal charging than surface charging. For example, the minimal radiation shielding afforded by thin thermal control materials such as metalized polymer sheets (e.g., aluminized Kapton or Mylar) and multilayer insulation may allow electrons of 100's of keV to charge underlying materials. Yet these same thermal control materials protect the underlying insulators and ungrounded conductors from surface charging currents due to electrons and ions at energies less than a few keV as well as suppress the photoemission, secondary electron, and backscattered electron processes associated with surface charging. We investigate the conditions required for this low Earth orbit "internal charging" to occur and evaluate the environments for which the process may be a threat to spacecraft. First, we describe a simple one-dimensional internal charging model that is used to compute the charge accumulation on materials under thin shielding. Only the electron flux that penetrates exposed surface shielding material is considered and we treat the charge balance in underlying insulation as a parallel plate capacitor accumulating charge from the penetrating electron flux and losing charge due to conduction to a ground plane. Charge dissipation due to conduction can be neglected to consider the effects of charging an ungrounded conductor. In both cases, the potential and electric field is computed as a function of time. An additional charge loss process is introduced due to an electrostatic discharge current when the electric field reaches a prescribed breakdown strength. For simplicity, the amount of charge lost in the discharge is treated as a random percentage of the total charge between a set maximum and minimum amount so a user can consider partial discharges of insulating materials (small loss of charge) or arcing from a conductor (large loss of charge). We apply the model to electron flux measurements from the NOAA-19 spacecraft to demonstrate that charging can reach levels where electrostatic discharges occur and estimate the magnitude of the discharge.

Etching Behavior of Aluminum Alloy Extrusions

NASA Astrophysics Data System (ADS)

Zhu, Hanliang

2014-11-01

The etching treatment is an important process step in influencing the surface quality of anodized aluminum alloy extrusions. The aim of etching is to produce a homogeneously matte surface. However, in the etching process, further surface imperfections can be generated on the extrusion surface due to uneven materials loss from different microstructural components. These surface imperfections formed prior to anodizing can significantly influence the surface quality of the final anodized extrusion products. In this article, various factors that influence the materials loss during alkaline etching of aluminum alloy extrusions are investigated. The influencing variables considered include etching process parameters, Fe-rich particles, Mg-Si precipitates, and extrusion profiles. This study provides a basis for improving the surface quality in industrial extrusion products by optimizing various process parameters.

Plasma power recycling at the divertor surface

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

Tang, Xian -Zhu; Guo, Zehua

With a divertor made of solid materials like carbon and tungsten, plasma ions are expected to be recycled at the divertor surface with a time-averaged particle recycling coefficient very close to unity in steady-state operation. This means that almost every plasma ion (hydrogen and helium) will be returned to the plasma, mostly as neutrals. The power flux deposited by the plasma on the divertor surface, on the other hand, can have varying recycling characteristics depending on the material choice of the divertor; the run-time atomic composition of the surface, which can be modified by material mix due to impurity migrationmore » in the chamber; and the surface morphology change over time. In general, a high-Z–material (such as tungsten) surface tends to reflect light ions and produce stronger power recycling, while a low-Z–material (such as carbon) surface tends to have a larger sticking coefficient for light ions and hence lower power recycling. Here, an explicit constraint on target plasma density and temperature is derived from the truncated bi-Maxwellian sheath model, in relation to the absorbed power load and power recycling coefficient at the divertor surface. Lastly, it is shown that because of the surface recombination energy flux, the attached plasma has a sharper response to power recycling in comparison to a detached plasma.« less

Plasma power recycling at the divertor surface

DOE PAGES

Tang, Xian -Zhu; Guo, Zehua

2016-12-03

With a divertor made of solid materials like carbon and tungsten, plasma ions are expected to be recycled at the divertor surface with a time-averaged particle recycling coefficient very close to unity in steady-state operation. This means that almost every plasma ion (hydrogen and helium) will be returned to the plasma, mostly as neutrals. The power flux deposited by the plasma on the divertor surface, on the other hand, can have varying recycling characteristics depending on the material choice of the divertor; the run-time atomic composition of the surface, which can be modified by material mix due to impurity migrationmore » in the chamber; and the surface morphology change over time. In general, a high-Z–material (such as tungsten) surface tends to reflect light ions and produce stronger power recycling, while a low-Z–material (such as carbon) surface tends to have a larger sticking coefficient for light ions and hence lower power recycling. Here, an explicit constraint on target plasma density and temperature is derived from the truncated bi-Maxwellian sheath model, in relation to the absorbed power load and power recycling coefficient at the divertor surface. Lastly, it is shown that because of the surface recombination energy flux, the attached plasma has a sharper response to power recycling in comparison to a detached plasma.« less

Chemical and physical effects on the adhesion, maturation, and survival of monocytes, macrophages, and foreign body giant cells

NASA Astrophysics Data System (ADS)

Collier, Terry Odell, III

Injury caused by biomedical device implantation initiates inflammatory and wound healing responses. Cells migrate to the site of injury to degrade bacteria and toxins, create new vasculature, and form new and repair injured tissue. Blood-proteins rapidly adsorb onto the implanted material surface and express adhesive ligands which mediate cell adhesion on the material surface. Monocyte-derived macrophages and multi-nucleated foreign body giant cells adhere to the surface and degrade the surface of the material. Due to the role of macrophage and foreign body giant cell on material biocompatibility and biostability, the effects of surface chemistry, surface topography and specific proteins on the maturation and survival of monocytes, macrophages and foreign body giant cells has been investigated. Novel molecularly designed materials were used to elucidate the dynamic interactions which occur between inflammatory cells, proteins and surfaces. The effect of protein and protein adhesion was investigated using adhesive protein depleted serum conditions on RGD-modified and silane modified surfaces. The effects of surface chemistry were investigated using temperature responsive surfaces of poly (N-isopropylacrylamide) and micropatterned surfaces of N-(2 aminoethyl)-3-aminopropyltrimethoxysilane regions on an interpenetrating polymer network of polyacrylamide and poly(ethylene glycol). The physical effects were investigated using polyimide scaffold materials and polyurethane materials with surface modifying end groups. The depletion of immunoglobulin G caused decreased levels of macrophage adhesion, foreign body giant cell formation and increased levels of apoptosis. The temporal nature of macrophage adhesion was observed with changing effectiveness of adherent cell detachment with time, which correlated to increased expression of beta1 integrin receptors on detached macrophages with time. The limited ability of the micropatterned surface, polyimide scaffold and surface modified polyurethane materials to control macrophage adhesion indicates the complexity of macrophage adhesion and protein adsorption onto a surface. These studies have indicated components and adhesive mechanisms which can be utilized to create materials with enhanced resistance to macrophage adhesion and/or degradative abilities.

Discovery and Development of Synthetic and Natural Biomaterials for Protein Therapeutics and Medical Device Applications

NASA Astrophysics Data System (ADS)

Keefe, Andrew J.

Controlling nonspecific protein interactions is important for applications from medical devices to protein therapeutics. The presented work is a compilation of efforts aimed at using zwitterionic (ionic yet charge neutral) polymers to modify and stabilize the surface of sensitive biomedical and biological materials. Traditionally, when modifying the surface of a material, the stability of the underlying substrate. The materials modified in this dissertation are unique due to their unconventional amorphous characteristics which provide additional challenges. These are poly(dimethyl siloxane) (PDMS) rubber, and proteins. These materials may seem dissimilar, but both have amorphous surfaces, that do not respond well to chemical modification. PDMS is a biomaterial extensively used in medical device manufacturing, but experiences unacceptably high levels of non-specific protein fouling when used with biological samples. To reduce protein fouling, surface modification is often needed. Unfortunately conventional surface modification methods, such as Poly(ethylene glycol) (PEG) coatings, do not work for PDMS due to its amorphous state. Herein, we demonstrate how a superhydrophilic zwitterionic material, poly(carboxybetaine methacrylate) (pCBMA), can provide a highly stable nonfouling coating with long term stability due to the sharp the contrast in hydrophobicity between pCBMA and PDMS. Biological materials, such as proteins, also require stabilization to improve shelf life, circulation time, and bioactivity. Conjugation of proteins with PEG is often used to increase protein stability, but has a detrimental effect on bioactivity. Here we have shown that pCBMA conjugation improves stability in a similar fashion to PEG, but also retains, or even improves, binding affinity due to enhanced protein-substrate hydrophobic interactions. Recognizing that pCBMA chemically resembles the combination of lysine (K) and glutamic acid (E) amino acids, we have shown how zwitterionic nonfouling peptides can be genetically engineered onto a protein to form recombinant protein-polymer conjugates. This technique avoids the need to post-modify proteins, that is often expensive and time consuming in protein manufacturing. Finally, we have developed two new peptide screening methods that were able to select for nonfouling peptide sequences. The selection for nonfouling sequences is not possible using traditional methods (phage display, yeast display, bacterial display and resin display) due to the presence of background interference. In our first nonfouling peptide screening method, we measured the fouling properties of peptides that were immobilized on the surface of solid glass beads. Peptides first needed to be rationally designed, and then subsequently evaluated for protein binding. Using this method, we were able to screen of 10's of sequences. Our second nonfouling peptide screening method is able to screen thousands of peptide sequences using a combinatorially generated peptide library. This was accomplished using controlled pore glass (CPG) beads as substrates to develop one-bead-one-compound (OBOC) peptide libraries. The choice of a porous substrate made it possible to synthesize enough peptide material to allow for peptide sequencing from a single bead using mass spectrometry techniques.

Hydrogen generation from water/methanol under visible light using aerogel prepared strontium titanate (SrTiO3) nanomaterials doped with ruthenium and rhodium metals

NASA Astrophysics Data System (ADS)

Kuo, Yenting; Klabunde, Kenneth J.

2012-07-01

Nanostructured strontium titanate visible-light-driven photocatalysts containing rhodium and ruthenium were synthesized by a modified aerogel synthesis using ruthenium chloride and rhodium nitrate as dopant precursors, and titanium isopropoxide and strontium metal as the metal sources. The well-defined crystalline SrTiO3 structure was confirmed by means of x-ray diffraction. After calcination at 500 °C, diffuse reflectance spectroscopy shows an increase in light absorption at 370 nm due to the presence of Rh3 + ; however an increase of the calcination temperature to 600 °C led to a decrease in intensity, probably due to a loss of surface area. An increase in the rhodium doping level also led to an increase in absorption at 370 nm however, the higher amounts of dopant lowered the photocatalytic activity. The modified aerogel synthesis allows greatly enhanced H2 production performance from an aqueous methanol solution under visible light irradiation compared with lower surface area conventional materials. We believe that this enhanced activity is due to the higher surface areas while high quality nanocrystalline materials are still obtained. Furthermore, the surface properties of these nanocrystalline aerogel materials are different, as exhibited by the higher activities in alkaline solutions, while conventional materials (obtained via high temperature solid-state synthesis methods) only exhibit reasonable hydrogen production in acidic solutions. Moreover, an aerogel synthesis approach gives the possibility of thin-film formation and ease of incorporation into practical solar devices.

Electronegativity-dependent tin etching from thin films

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

Pachecka, M., E-mail: m.pachecka@utwente.nl; Sturm, J. M.; Kruijs, R. W. E. van de

2016-07-15

The influence of a thin film substrate material on the etching of a thin layer of deposited tin (Sn) by hydrogen radicals was studied. The amount of remaining Sn was quantified for materials that cover a range of electronegativities. We show that, for metals, etching depends on the relative electronegativity of the surface material and Sn. Tin is chemically etched from surfaces with an electronegativity smaller than Sn, while incomplete Sn etching is observed for materials with an electronegativity larger than Sn. Furthermore, the amount of remaining Sn increases as the electronegativity of the surface material increases. We speculate, that,more » due to Fermi level differences in the material’s electronic structure, the energy of the two conduction bands shift such that the availability of electrons for binding with hydrogen is significantly reduced.« less

Submicron Surface-Patterned Fibers and Textiles

DTIC Science & Technology

2016-11-04

These authors contributed equally Keywords: grating, fiber, polymer , patterning, textile Distribution A: approved for public release...requirements. Second, textile materials are primarily polymer -based, while most surface-patterning techniques have been developed for silicon...Alternative substrates, especially flexible polymers , remain challenging to pattern [25,26] due to the highly specific surface chemistry of different

Mucoadhesive microparticles with a nanostructured surface for enhanced bioavailability of glaucoma drug.

PubMed

Park, Chun Gwon; Kim, Young Kook; Kim, Mi Jeung; Park, Min; Kim, Myung Hun; Lee, Seung Ho; Choi, Sung Yoon; Lee, Won Seok; Chung, You Jung; Jung, Young Eun; Park, Ki Ho; Choy, Young Bin

2015-12-28

Topical drug administration to the eye is limited by low drug bioavailability due to its rapid clearance from the preocular surface. Thus, multiple daily administrations are often needed, but patient compliance is low, hence a high chance of unsatisfactory treatment of ocular diseases. To resolve this, we propose mucoadhesive microparticles with a nanostructured surface as potential carriers for delivery of brimonidine, an ocular drug for glaucoma treatment. For sustained drug delivery, the microparticles were composed mainly of a diffusion-wall material, poly(lactic-co-glycolic acid) and a mucoadhesive polymer, polyethylene glycol, was used as an additive. Due to their nanostructured surface, the microparticles with a mucoadhesive material exhibited a 13-fold increase in specific surface area and could thus adhere better to the mucous layer on the eye, as compared with the conventional spherical microparticles. When loaded with brimonidine, the mucoadhesive microparticles with a nanostructured surface increased both drug bioavailability and its activity period by a factor of more than 2 over Alphagan P, a marketed eye drop of brimonidine. Copyright © 2015 Elsevier B.V. All rights reserved.

Designing Microstructures/Structures for Desired Functional Material and Local Fields

DTIC Science & Technology

2015-12-02

utilized to engineer multifunctional soft materials for multi-sensing, multi- actuating , human-machine interfaces. [3] Establish a theoretical framework...model for surface elasticity, (ii) derived a new type of Maxwell stress in soft materials due to quantum mechanical-elasticity coupling and...elucidated its ramification in engineering multifunctional soft materials, and (iii) demonstrated the possibility of concurrent magnetoelectricity and

Erosive Potential of Cola and Orange Fruit Juice on Tooth Colored Restorative Materials

PubMed Central

Rajavardhan, K; Sankar, AJS; Kumar, MGM; Kumar, KR; Pranitha, K; Kishore, KK

2014-01-01

Background: Erosion is a common condition which manifests due to consumption of high caloric and low pH acidic food stuffs such as carbonated drinks and fruit juices which cause irreversible damage to dental hard tissues and early deterioration of the dental restorations. Aim: The main aim of this study is to evaluate and to compare the erosive potential of carbonated drink (cola) and fruit juice (orange fruit juice) by measuring the surface roughness (Ra) values on two commonly used dental restorative materials. Materials and Methods: A total of 36 specimens each were prepared using both testing materials, compomer (Group I) and giomer (Group II). Six specimens in each group were discarded due to wide variation in pre exposed Ra values and the remaining 30 specimens in each group were further sub divided into 10 samples each according to the testing media used. Immersion regime was followed according to Von Fraunhofer and Rogers. The pre and post immersion surface roughness values were recorded using a profilometer. Results: Both tested materials showed statistically-significant surface erosion (P < 0.01) when exposed to cola and orange fruit juice than the control group (water). Discussion: Compomer showed more surface roughness when compared to giomer when exposed to the three tested media which can be attributed to the variation in filler content, decomposition of resin matrix and fallout of the fillers in composites when exposed to acidic drinks. Other factors responsible for this significant erosion were also discussed. Conclusions: Significant surface changes of the dental restorative materials can take place when exposed to low pH drinks for a prolonged period. PMID:25364590

Understanding Environmental Stability of Two-Dimensional Materials and Extending Their Shelf Life by Surface Functionalization

NASA Astrophysics Data System (ADS)

Yang, Sijie

Since the discovery of graphene, two dimensional materials (2D materials) have become a focus of interest for material research due to their many unique physical properties embedded in their 2D structure. While they host many exciting potential applications, some of these 2D materials are subject to environmental instability issues induced by interaction between material and gas molecules in air, which poses a barrier to further application and manufacture. To overcome this, it is necessary to understand the origin of material instability and interaction with molecules commonly found in air, as well as developing a reproducible and manufacturing compatible method to post-process these materials to extend their lifetime. In this work, the very first investigation on environmental stability on Te containing anisotropic 2D materials such as GaTe and ZrTe 3 is reported. Experimental results have demonstrated that freshly exfoliated GaTe quickly deteriorate in air, during which the Raman spectrum, surface morphology, and surface chemistry undergo drastic changes. Environmental Raman spectroscopy and XPS measurements demonstrate that H2O molecules in air interact strongly on the surface while O2, N 2, and inert gases don't show any detrimental effects on GaTe surface. Moreover, the anisotropic properties of GaTe slowly disappear during the aging process. To prevent this gas/material interaction based surface transformation, diazonium based surface functionalization is adopted on these Te based 2D materials. Environmental Raman spectroscopy results demonstrate that the stability of functionalized Te based 2D materials exhibit much higher stability both in ambient and extreme conditions. Meanwhile, PL spectroscopy, angle resolved Raman spectroscopy, atomic force microscopy measurements confirm that many attractive physical properties of the material are not affected by surface functionalization. Overall, these findings unveil the degradation mechanism of Te based 2D materials as well as provide a way to significantly enhance their environmental stability through an inexpensive and reproducible surface chemical functionalization route.

Effect of counterface material type and its topography on the tribological properties of polyimide composites

NASA Technical Reports Server (NTRS)

Fusaro, R. L.

1985-01-01

Graphite fiber reinforced polyimide composite pins were slid against seven different counterfaces to determine the effect of material type on the tribological properties of polymer composites. In addition, the effect of sliding a new pin on a pre-established transfer film was investigated. The results indicated that almost a five order of magnitude difference in composite wear rate can occur just by varying the counterface material. An attempt to make all surfaces as smooth as possible was made, but due to differences in material composition this was not possible and a range of surface roughnesses were obtained. The results indicate that the smoother the surface, the lower the composite wear rate; but that small protrusions (not discernible with arithmetic surface roughness measurements) can markedly increase wear rates. A pre-established transfer film improved both run in and steady state wear rates.

Ion implantation modified stainless steel as a substrate for hydroxyapatite deposition. Part I. Surface modification and characterization.

PubMed

Pramatarova, L; Pecheva, E; Krastev, V; Riesz, F

2007-03-01

Material surfaces play critical role in biology and medicine since most biological reactions occur on surfaces and interfaces. There are many examples showing that the surface properties of the materials control and are directly involved in biological reactions and processes in-vitro like blood compatibility, protein absorption, cell development, etc. The rules that govern the diversity of biological surface phenomenon are fundamental physical laws. Stainless steel doped with Cr, Ni and Mo is widely used material in medicine and dentistry due to its excellent corrosion resistance and mechanical properties. The interest in this material has stimulated extensive studies on improving its bone-bonding properties. This paper describes the surface modification of Cr-Ni stainless steel (AISI 316) by a whole surface sequential implantation of Ca and P ions (the basic ions of hydroxyapatite). Three groups of stainless steel samples are prepared: (i) ion-implanted, (ii) ion-implanted and thermally treated at 600( composite function)C in air for 1 h and (iii) initials. The surface chemistry and topography before and after the surface modification are characterized by X-ray photoelectron spectroscopy, Auger electron spectroscopy, magic mirror method, atomic force microscopy and contact angle measurements.

Investigations of the structure and "interfacial" surface chemistry of Bioglass (RTM) materials by solid-state multinuclear NMR spectroscopy

NASA Astrophysics Data System (ADS)

Sarkar, Gautam

Bioactive materials such as BioglassRTM 45S5 (45% SiO 2, 24.5% CaO, 24.5% Na2O, and 6% P2O5 by weight) are sodium-phosphosilicate glasses containing independent three-dimensional silicate and phosphate networks and Na+ and Ca2+ ions as modifying cations. Due to their bioactivity, these materials are currently used as implants and for other surgical and clinical applications. The bioactivity of BioglassesRTM is due to their unique capability to form chemical bonds to tissues through an octacalciumphosphate (OCP)- and/or hydroxyapatite-like (HA) "interfacial" matrix. The formation of OCP and/or HA is preceded by the formation of a silica-rich surface layer and the subsequent growth of an amorphous calcium phosphate (a-CP) layer. Structural characterization of a series of commercial and synthesized Bioglass materials 45S5 52S, 55S, 60S, and synthesized 17O-labelled "Bioglass materials 45S, 52S, 55S and 60S" have been obtained using solid-state single-pulse magic-angle spinning (SP/MAS) 17O, 23Na, 29Si and 31P NMR. The 17O NMR isotropic chemical shifts and estimates of the quadrupole coupling constants (Cq) [at fixed asymmetry parameter ( hQ ) values of zero] have been obtained from solid-state spin-echo 17O SP/MAS NMR spectra of 17O-labelled "Bioglasses". The simulation results of these spectra reveal the presence of both bridging-oxygens (BO, i.e. ≡ Si-17OSi ≡ ) and non-bridging oxygens (NBO, i.e. ≡ Si-17O-Na+/Ca2+ ) in the silicate networks in these materials. 17O NMR spectra of these Bioglass materials do not show any direct evidence for the presence of BO and NBO atoms in the phosphate units; however, they are expected to be present in small amounts. In vitro reactions of BioglassRTM 45S5, 60S and 77S powders have been used to study the "interfacial" surface chemistry of these materials in simulated body-fluid (SBF, Kyoto or K9 solution) and/or 17O-enriched tris-buffer solution. 29Si and 31P SP/MAS NMR have been used to identify and quantify the extent of formation of surface silica species and follow the formation of phosphate species, respectively, while cross-polarization magic-angle spinning (CP/MAS) 29Si and 31P NMR have provided information about low intensity NMR peaks due to various silicon- and phosphorus-species present in the vicinity of associated protons on the surface of in vitro reacted BioglassRTM materials. The solid-state NMR investigations of the "interfacial" surface reactions of BioglassRTM materials are discussed in the context of the structure of these materials and the influence of this structure on the kinetics and the mechanism of their "interfacial" surface chemistry. (Abstract shortened by UMI.) BioglassRTM, trademark, University of Florida, Gainesville, FL, 32611.

Biomimetic polymeric superhydrophobic surfaces and nanostructures: from fabrication to applications.

PubMed

Wen, Gang; Guo, ZhiGuang; Liu, Weimin

2017-03-09

Numerous research studies have contributed to the development of mature superhydrophobic systems. The fabrication and applications of polymeric superhydrophobic surfaces have been discussed and these have attracted tremendous attention over the past few years due to their excellent properties. In general, roughness and chemical composition, the two most crucial factors with respect to surface wetting, provide the basic criteria for yielding polymeric superhydrophobic materials. Furthermore, with their unique properties and flexible configurations, polymers have been one of the most efficient materials for fabricating superhydrophobic materials. This review aims to summarize the most recent progress in polymeric superhydrophobic surfaces. Significantly, the fundamental theories for designing these materials will be presented, and the original methods will be introduced, followed by a summary of multifunctional superhydrophobic polymers and their applications. The principles of these methods can be divided into two categories: the first involves adding nanoparticles to a low surface energy polymer, and the other involves combining a low surface energy material with a textured surface, followed by chemical modification. Notably, surface-initiated radical polymerization is a versatile method for a variety of vinyl monomers, resulting in controlled molecular weights and low polydispersities. The surfaces produced by these methods not only possess superhydrophobicity but also have many applications, such as self-cleaning, self-healing, anti-icing, anti-bioadhesion, oil-water separation, and even superamphiphobic surfaces. Interestingly, the combination of responsive materials and roughness enhances the responsiveness, which allows the achievement of intelligent transformation between superhydrophobicity and superhydrophilicity. Nevertheless, surfaces with poor physical and chemical properties are generally unable to withstand the severe conditions of the outside world; thus, it is necessary to optimize the performances of such materials to yield durable superhydrophobic surfaces. To sum up, some challenges and perspectives regarding the future research and development of polymeric superhydrophobic surfaces are presented.

Dynamic response of RC beams strengthened with near surface mounted Carbon-FRP rods subjected to damage

NASA Astrophysics Data System (ADS)

Capozucca, R.; Blasi, M. G.; Corina, V.

2015-07-01

Near surface mounted (NSM) technique with fiber reinforced polymer (FRP) is becoming a common method in the strengthening of concrete beams. The availability of NSM FRP technique depends on many factors linked to materials and geometry - dimensions of the rods used, type of FRP material employed, rods’ surface configuration, groove size - and to adhesion between concrete and FRP rods. In this paper detection of damage is investigated measuring the natural frequency values of beam in the case of free-free ends. Damage was due both to reduction of adhesion between concrete and carbon-FRP rectangular and circular rods and cracking of concrete under static bending tests on beams. Comparison between experimental and theoretical frequency values evaluating frequency changes due to damage permits to monitor actual behaviour of RC beams strengthened by NSM CFRP rods.

Salt efflorescence due to water-rock interaction on the surface of tuff cave in the Yoshimi-Hyakuana Historic Site, central Japan

NASA Astrophysics Data System (ADS)

Oguchi, Chiaki T.; Kodama, Shogo; Mohammad, Rajib; Tharanga Udagedara, Dashan

2016-04-01

Artificial cave walls in Yoshimi Hyakuana Historic Site have been suffering from salt weathering since 1945 when the caves were made. To consider the processes of weathering and subsequent crystallization of secondary minerals, water-rock experiment using tuff from this area was performed. Rocks, surface altered materials, groundwater and rainwater were collected, and chemical and mineralogical characteristics of those samples were investigated. The XRD and SEM-EDS analyses were carried out for the solid samples and ICP-OES analysis was performed for the solution generated from the experiment, groundwater and rainwater. Gypsum is detected in original tuff, and on grey and whiter coloured altered materials. General chemical changes were observed on this rock. However, it is found that purple and black altered materials were mainly made due to microbiological processes.

The Uppermost Surface of the Moon

NASA Technical Reports Server (NTRS)

Noble, Sarah K.

2009-01-01

The Ap16 Clam shell Sampling Devices (CSSDs) were designed to sample the uppermost surface of lunar soil. The two devices used beta cloth (69003) and velvet (69004) to collect soil from the top 100 and 500 micrometers of the soil, respectively. Due to the difficulty of the sampling method, little material was collected and as a result little research has been done on these samples. Initial studies attempted to look at the material which had fallen off of the fabrics and was subsequently collected from inside the sample containers. However, this material was highly fractionated and did not provide an adequate picture of the uppermost surface. Recently, samples were obtained directly from the beta cloth using carbon tape. While still fractionated, these samples provide a unique glimpse into the undisturbed soil exposed at the lunar surface.

Decay assessment through thermographic analysis in architectural and archaeological heritage

NASA Astrophysics Data System (ADS)

Gomez-Heras, Miguel; Martinez-Perez, Laura; Fort, Rafael; Alvarez de Buergo, Monica

2010-05-01

Any exposed stone-built structure is subject to thermal variations due to daily, seasonal and secular environmental temperature changes. Surface temperature is a function of air temperature (due to convective heat transfer) and of infrared radiation received through insolation. While convective heat transfer homogenizes surface temperature, stone response to insolation is much more complex and the temporal and spatial temperature differences across structures are enhanced. Surface temperature in stone-built structures will be affected by orientation, sunlight inclination and the complex patterns of light and shadows generated by the often intricate morphology of historical artefacts and structures. Surface temperature will also be affected by different material properties, such as albedo, thermal conductivity, transparency and absorbance to infrared radiation of minerals and rocks. Moisture and the occurrence of salts will also be a factor affecting surface temperatures. Surface temperatures may as well be affected by physical disruptions of rocks due to differences in thermal inertia generated by cracks and other discontinuities. Thermography is a non-invasive, non-destructive technique that measures temperature variations on the surface of a material. With this technique, surface temperature rates of change and their spatial variations can be analysed. This analysis may be used not only to evaluate the incidence of thermal decay as a factor that generates or enhances stone decay, but also to detect and evaluate other factors that affect the state of conservation of architectural and archaeological heritage, as for example moisture, salts or mechanical disruptions.

Multifunctional transparent ZnO nanorod films.

PubMed

Kwak, Geunjae; Jung, Sungmook; Yong, Kijung

2011-03-18

Transparent ZnO nanorod (NR) films that exhibit extreme wetting states (either superhydrophilicity or superhydrophobicity through surface chemical modification), high transmittance, UV protection and antireflection have been prepared via the facile ammonia hydrothermal method. The periodic 1D ZnO NR arrays showed extreme wetting states as well as antireflection properties due to their unique surface structure and prevented the UVA region from penetrating the substrate due to the unique material property of ZnO. Because of the simple, time-efficient and low temperature preparation process, ZnO NR films with useful functionalities are promising for fabrication of highly light transmissive, antireflective, UV protective, antifogging and self-cleaning optical materials to be used for optical devices and photovoltaic energy devices.

The influence of Lifshitz forces and gas on premelting of ice within porous materials

NASA Astrophysics Data System (ADS)

Boström, M.; Malyi, O. I.; Thiyam, P.; Berland, K.; Brevik, I.; Persson, C.; Parsons, D. F.

2016-07-01

Premelting of ice within pores in earth materials is shown to depend on the presence of vapor layers. For thick vapor layers between ice and pore surfaces, a nanosized water sheet can be formed due to repulsive Lifshitz forces. In the absence of vapor layers, ice is inhibited from melting near pore surfaces. In between these limits, we find an enhancement of the water film thickness in silica and alumina pores. In the presence of metallic surface patches in the pore, the Lifshitz forces can dramatically widen the water film thickness, with potential complete melting of the ice surface.

Material parameters that determine the surface accuracy of large astronomical mirrors

NASA Astrophysics Data System (ADS)

Amur, G. I.

1983-03-01

The design and manufacture of large astronomical mirrors are examined from both theoretical and practical perspectives. The effects of birefringence, tool-load relief, cord position, and temperature gradient on the surface quality are assessed quantitatively and discussed in terms of material choice and fabrication technique. It is shown that a single cord positioned horizontally produces only minimum image distortion. Formulas for calculating the deformation of the wave front by the mirror surface due to birefringence difference, the optimum load relief, and the deformation temperature, are presented. Graphs of important relationships and a table listing the diameters and surface parameters of recently built large telescopes are provided.

The Anti-Biofouling Properties of Superhydrophobic Surfaces are Short-Lived.

PubMed

Hwang, Gi Byoung; Page, Kristopher; Patir, Adnan; Nair, Sean P; Allan, Elaine; Parkin, Ivan P

2018-06-12

Superhydrophobic surfaces are present in nature on the leaves of many plant species. Water rolls on these surfaces, and the rolling motion picks up particles including bacteria and viruses. Man-made superhydrophobic surfaces have been made in an effort to reduce biofouling. We show here that the anti-biofouling property of a superhydrophobic surface is due to an entrapped air-bubble layer that reduces contact between the bacteria and the surface. Further, we showed that prolonged immersion of superhydrophobic surfaces in water led to loss of the bubble-layer and subsequent bacterial adhesion that unexpectedly exceeded that of the control materials. This behavior was not restricted to one particular type of material but was evident on different types of superhydrophobic surfaces. This work is important in that it suggests that superhydrophobic surfaces may actually encourage bacterial adhesion during longer term exposure.

Friction behavior and other material properties of nickel-titanium and titanium-molybdenum archwires following electrochemical surface refinement.

PubMed

Meier, Miriam Julia; Bourauel, Christoph; Roehlike, Jan; Reimann, Susanne; Keilig, Ludger; Braumann, Bert

2014-07-01

The aim of this work was to investigate whether electrochemical surface treatment of nickel-titanium (NiTi) and titanium-molybdenum (TiMo) archwires (OptoTherm and BetaTitan; Ortho-Dent Specials, Kisdorf, Germany) reduces friction inside the bracket-archwire complex. We also evaluated further material properties and compared these to untreated wires. The material properties of the surface-treated wires (Optotherm/LoFrix and BetaTitan/LoFrix) were compared to untreated wires made by the same manufacturer (see above) and by another manufacturer (Neo Sentalloy; GAC, Bohemia, NY, USA). We carried out a three-point bending test, leveling test, and friction test using an orthodontic measurement and simulation system (OMSS). In addition, a pure bending test was conducted at a special test station, and scanning electron micrographs were obtained to analyze the various wire types for surface characteristics. Finally, edge beveling and cross-sectional dimensions were assessed. Force losses due to friction were reduced by 10 percentage points (from 36 to 26%) in the NiTi and by 12 percentage points (from 59 to 47%) in the TiMo wire specimens. Most of the other material properties exhibited no significant changes after surface treatment. While the three-point bending tests revealed mildly reduced force levels in the TiMo specimens due to diameter losses of roughly 2%, these force levels remained almost unchanged in the NiTi specimens. Compared to untreated NiTi and TiMo archwire specimens, the surface-treated specimens demonstrated reductions in friction loss by 10 and 12 percentage points, respectively.

Synchroton and Simulations Techniques Applied to Problems in Materials Science: Catalysts and Azul Maya Pigments

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

Chianelli, R.

2005-01-12

Development of synchrotron techniques for the determination of the structure of disordered, amorphous and surface materials has exploded over the past twenty years due to the increasing availability of high flux synchrotron radiation and the continuing development of increasingly powerful synchrotron techniques. These techniques are available to materials scientists who are not necessarily synchrotron scientists through interaction with effective user communities that exist at synchrotrons such as the Stanford Synchrotron Radiation Laboratory (SSRL). In this article we review the application of multiple synchrotron characterization techniques to two classes of materials defined as ''surface compounds.'' One class of surface compounds aremore » materials like MoS{sub 2-x}C{sub x} that are widely used petroleum catalysts used to improve the environmental properties of transportation fuels. These compounds may be viewed as ''sulfide supported carbides'' in their catalytically active states. The second class of ''surface compounds'' is the ''Maya Blue'' pigments that are based on technology created by the ancient Maya. These compounds are organic/inorganic ''surface complexes'' consisting of the dye indigo and palygorskite, a common clay. The identification of both surface compounds relies on the application of synchrotron techniques as described in this report.« less

Investigation Of A Tin-Lithium Alloy As A Liquid Plasma-Facing Material

NASA Astrophysics Data System (ADS)

Sandefur, Heather; Ruzic, David; Kolasinski, Robert; Buchenauer, Dean; Sandia National Laboratories Collaboration; University of Illinois Collaboration

2017-10-01

Sn-Li is a low melting-point alloy that has been identified as a material with favorable performance in plasma material interaction studies. While lithium is a low Z material with a demonstrated ability to absorb impinging ions, pure lithium is plagued by high evaporation rates in the liquid phase. The Sn-Li alloy is a more stable alternative that provides a lower rate of evaporative flux due to the high vapor pressure of tin. In the liquid phase, the bulk segregation of lithium to the surface of the material has also been observed. While the alloy is of considerable interest, little data has been collected on its surface chemistry in a plasma environment. In order to expand the existing body of knowledge in this area, samples of an 80 percent Sn-20 percent Li alloy were prepared and analyzed in order to assess the surface composition and degree of lithium segregation in the liquid phase. The Angle-Resolved Ion Energy Spectrometer (ARIES) at Sandia National Laboratories was used to probe the surfaces of the alloy using the low energy ion scattering method. The lithium coverage at the surface was measured, and the material's affinity for hydrogen chemisorption was investigated.

Techniques for improving material fidelity and contrast consistency in secondary electron mode helium ion microscope (HIM) imaging

NASA Astrophysics Data System (ADS)

Thompson, William; Stern, Lewis; Ferranti, Dave; Huynh, Chuong; Scipioni, Larry; Notte, John; Sanford, Colin

2010-06-01

Recent helium ion microscope (HIM) imaging studies have shown the strong sensitivity of HIM induced secondary electron (SE) yields [1] to the sample physical and chemical properties and to its surface topography. This SE yield sensitivity is due to the low recoil energy of the HIM initiated electrons and their resulting short mean free path. Additionally, a material's SE escape probability is modulated by changes in the material's work function and surface potential. Due to the escape electrons' roughly 2eV mean energy and their nanometer range mean free path, HIM SE mode image contrast has significant material and surface sensitivity. The latest generation of HIM has a 0.35 nanometer resolution specification and is equipped with a plasma cleaning process to mitigate the effects of hydrocarbon contamination. However, for surfaces that may have native oxide chemistries influencing the secondary electron yield, a new process of low energy, shallow angle argon sputtering, was evaluated. The intent of this work was to study the effect of removing pre-existing native oxides and any in-situ deposited surface contaminants. We will introduce the sputter yield predictions of two established computer models and the sputter yield and sample modification forecasts of the molecular dynamics program, Kalypso. We will review the experimental technique applied to copper samples and show the copper grain contrast improvement that resulted when argon cleaned samples were imaged in HIM SE mode.

Electrochemical and kinetic studies of ultrafast laser structured LiFePO4 electrodes

NASA Astrophysics Data System (ADS)

Mangang, M.; Gotcu-Freis, P.; Seifert, H. J.; Pfleging, W.

2015-03-01

Due to a growing demand of cost-efficient lithium-ion batteries with an increased energy and power density as well as an increased life-time, the focus is set on intercalation cathode materials like LiFePO4. It has a high practical capacity, is environmentally friendly and has low material costs. However, its low electrical conductivity and low ionic diffusivity are major drawbacks for its use in electrochemical storage devices or electric vehicles. By adding conductive agents, the electrical conductivity can be enhanced. By increasing the surface of the cathode material which is in direct contact with the liquid electrolyte the lithium-ion diffusion kinetics can be improved. A new approach to increase the surface of the active material without changing the active particle packing density or the weight proportion of carbon black is the laser-assisted generation of 3D surface structures in electrode materials. In this work, ultrafast laser radiation was used to create a defined surface structure in LiFePO4 electrodes. It was shown that by using ultrashort laser pulses instead of nanosecond laser pulses, the ablation efficiency could be significantly increased. Furthermore, melting and debris formation were reduced. To investigate the diffusion kinetics, electrochemical methods such as cyclic voltammetry and galvanostatic intermittent titration technique were applied. It could be shown that due to a laser generated 3D structure, the lithium-ion diffusion kinetic, the capacity retention and cell life-time can be significantly improved.

Analysis of the application of poly-nanocrystalline diamond tools for ultra precision machining of steel with ultrasonic assistance

NASA Astrophysics Data System (ADS)

Doetz, M.; Dambon, O.; Klocke, F.; Bulla, B.; Schottka, K.; Robertson, D. J.

2017-10-01

Ultra-precision diamond turning enables the manufacturing of parts with mirror-like surfaces and highest form accuracies out of non-ferrous, a few crystalline and plastic materials. Furthermore, an ultrasonic assistance has the ability to push these boundaries and enables the machining of materials like steel, which is not possible in a conventional way due to the excessive tool wear caused by the affinity of carbon to iron. Usually monocrystalline diamonds tools are applied due to their unsurpassed cutting edge properties. New cutting tool material developments have shown that it is possible to produce tools made of nano-polycrystalline diamonds with cutting edges equivalent to monocrystalline diamonds. In nano-polycrystalline diamonds ultra-fine grains of a few tens of nanometers are firmly and directly bonded together creating an unisotropic structure. The properties of this material are described to be isotropic, harder and tougher than those of the monocrystalline diamonds, which are unisotropic. This publication will present machining results from the newest investigations of the process potential of this new polycrystalline cutting material. In order to provide a baseline with which to characterize the cutting material cutting experiments on different conventional machinable materials like Cooper or Aluminum are performed. The results provide information on the roughness and the topography of the surface focusing on the comparison to the results while machining with monocrystalline diamond. Furthermore, the cutting material is tested in machining steel with ultrasonic assistance with a focus on tool life time and surface roughness. An outlook on the machinability of other materials will be given.

Assessment of exposures and potential risks to the US adult population from the leaching of elements from gold and ceramic dental restorations.

PubMed

Richardson, G Mark; James, Kyle Jordan; Peters, Rachel Elizabeth; Clemow, Scott Richard; Siciliano, Steven Douglas

2016-01-01

Using data from the 2001 to 2004 US National Health and Nutrition Examination Survey (NHANES) on the number and placement of tooth restorations in adults, we quantified daily doses due to leaching of elements from gold (Au) alloy and ceramic restorative materials. The elements with the greatest leaching rates from these materials are often the elements of lowest proportional composition. As a result, exposure due to wear will predominate for those elements of relatively high proportional composition, while exposure due leaching may predominate for elements of relatively low proportional composition. The exposure due to leaching of silver (Ag) and palladium (Pd) from Au alloys exceeded published reference exposure levels (RELs) for these elements when multiple full surface crowns were present. Six or more molar crowns would result in exceeding the REL for Ag, whereas three or more crowns would be necessary to exceed the REL for Pd. For platinum (Pt), the majority of tooth surfaces, beyond just molar crowns, would be necessary to exceed the REL for Pd. Exposures due to leaching of elements from ceramic dental materials were less than published RELs for all components examined here, including having all restorations composed of ceramic.

Numerical modelling of tool wear in turning with cemented carbide cutting tools

NASA Astrophysics Data System (ADS)

Franco, P.; Estrems, M.; Faura, F.

2007-04-01

A numerical model is proposed for analysing the flank and crater wear resulting from the loss of material on cutting tool surface in turning processes due to wear mechanisms of adhesion, abrasion and fracture. By means of this model, the material loss along cutting tool surface can be analysed, and the worn surface shape during the workpiece machining can be determined. The proposed model analyses the gradual degradation of cutting tool during turning operation, and tool wear can be estimated as a function of cutting time. Wear-land width (VB) and crater depth (KT) can be obtained for description of material loss on cutting tool surface, and the effects of the distinct wear mechanisms on surface shape can be studied. The parameters required for the tool wear model are obtained from bibliography and experimental observation for AISI 4340 steel turning with WC-Co cutting tools.

Samarium Hexaboride: The First True 3D Topological Insulator?

NASA Astrophysics Data System (ADS)

Wolgast, Steven G.

The recent theoretical prediction of a topologically protected surface state in the mixed-valent insulator SmB6 has motivated a series of charge transport studies, which are presented here. It is first studied using a specialized configuration designed to distinguish bulk-dominated conduction from surface-dominated conduction. As the material is cooled below 4 K, it exhibits a crossover from thermally activated bulk transport to metallic surface conduction with a fully insulating bulk. The robustness and magnitude of the surface conductivity, as is manifest in the literature of SmB6, is strong evidence for the topological insulator (TI) metallic surface states predicted for this material. This resolves a decades-old puzzle surrounding the low-temperature behavior of SmB6. Next, the magnetotransport properties of the surface are investigated using a Corbino disk geometry, which can directly measure the conductivity of individual surfaces. Both (011) and (001) crystal surfaces show a strong negative magnetoresistance at all magnetic field angles, due primarily to changes in the carrier density. The low mobility value accounts for the failure so far to observe Shubnikov-de Haas oscillations below 95 T. Small variations in the mobility and temperature dependence suggest a suppression of Kondo scattering from native oxide-layer magnetic moments. At low fields, a dynamical field-sweep-rate-dependent hysteretic behavior is observed. It persists at the slowest sweep rates, and cannot be explained by quantum interference corrections; it is likely due to extrinsic effects such as the magnetocaloric effect or glassy ordering of the native oxide moments. Pulsed magnetic field measurements up to 60 T at temperatures throughout the crossover regime clearly distinguish the surface magnetoresistance from the bulk magnetoresistance. The bulk magnetoresistance is due to a reduction in the bulk gap with increasing magnetic field. Finally, small subsurface cracks formed in SmB6 via systematic scratching or sanding results in a counter-intuitive increase in the electrical conduction due to the unique surface-conducting property of TIs, strengthening the building case for SmB 6's topological nature. This material is attractive as a TI because its bulk is fully insulating at a readily achieved 2 K, but it presents a large number of scientific mysteries and experimental challenges for future research.

Surface energy modification for biomedical material by corona streamer plasma processing to mitigate bacterial adhesion

NASA Astrophysics Data System (ADS)

Alhamarneh, Ibrahim; Pedrow, Patrick

2011-10-01

Bacterial adhesion initiates biofouling of biomedical material but the processes can be reduced by adjusting the material's surface energy. The surface of surgical-grade 316L stainless steel (316L SS) had its hydrophilic property enhanced by processing in a corona streamer plasma reactor using atmospheric pressure Ar mixed with O2. Reactor excitation was 60 Hz ac high-voltage (<= 10 kV RMS) applied to a multi-needle-to-grounded-torus electrode configuration. Applied voltage and streamer current pulses were monitored with a broadband sensor system. When Ar/O2 plasma was used, the surface energy was enhanced more than with Ar plasma alone. Composition of the surface before and after plasma treatment was characterized by XPS. As the hydrophilicity of the treated surface increased so did percent of oxygen on the surface thus we concluded that reduction in contact angle was mainly due to new oxygen-containing functionalities. FTIR was used to identify oxygen containing groups on the surface. The aging effect that accompanies surface free energy adjustments was also observed.

Application of Glow Discharge Plasma to Alter Surface Properties of Materials

NASA Technical Reports Server (NTRS)

Trigwell, Steve; Buhler, Charles R.; Calle, Carlos I.

2005-01-01

Some polymer materials that are considered important for spaceport operations are rendered noncompliant when subjected to the Kennedy Space Center (KSC) Standard electrostatic testing. These materials operate in stringent environmental conditions, such as high humidity. Treating materials that fail electrostatic testing and altering their surface properties so that they become compliant would result in considerable cost savings. Significant improvement in electrostatic dissipation of Saf-T-Vu PVC after treatment with air Atmospheric Plasma Glow Discharge (APGD) was observed and the material now passed the KSC electrostatic test. The O:C ratio on the surface, as monitored by X-ray Photoelectron Spectroscopy, increased from 0.165 tO 0.275 indicating enhanced oxidation, and surface contact angle measurements decreased from 107.5 to 72.6 showing increased hydrophilicity that accounted for the increased conductivity. Monitoring of the aging showed that the materials hydrophobic recovery resulted in it failing the electrostatic test 30 hours after treatment. This was probably due to the out-diffusion of the added Zn, Ba, and Cd salt stabilizers detected on the surface and/or diffusion of low molecular weight oligomers. On going work includes improving the long term hydrophilicity by optimizing the APGD process with different gas mixtures. Treatment of other spaceport materials is also presented.

Experimental exploration of the hydrodynamic effect polishing machinability for different types of material

NASA Astrophysics Data System (ADS)

Peng, W. Q.; Li, Y.; Wang, Z.; Li, S. Y.

2018-01-01

Hydrodynamic effect polishing (HEP), in which the material removal relies on the chemisorption between nanoparticles and the workpiece surface in elastic mode, can realize automatic level smooth surface without surface/subsurface damage. The machinability of different types of optical material (such as monocrystalline silicon and crystalline quartz, amorphous silicate glass, Zerodur and so on) were investigated experimentally. The workpiece surfaces before and after being polished by HEP was observed by atomic force microscopy. The experimental results show the surface roughness of monocrystalline silicon and quartz, amorphous silicate glass have decreased from Rms 0.737nm to Rms 0.175nm, Rms 0.490nm to Rms 0.187nm, Rms 0.469nm to Rms 0.157nm respectively, and meanwhile all the defects and bumpy structures have been removed clearly. However the surface roughness has increased from Rms 0.213nm to Rms 0.321nm with the obvious increment of micro unevenness. By comparison, we can conclude that excellent performance is shown when HEP is applied on the optical material structure with a single monocrystalline or amorphous component. However the ultrasmooth surface cannot be obtained when HEP was applied on the combinational materials such as Zerodur glass. The micro unevenness increases gradually along with polishing process due to the different material removal of the monocrystalline and amorphous component.

The color metamerism evaluation of paint based on ocean spectrum

NASA Astrophysics Data System (ADS)

Chen, Zhongwei; Huang, Hao; Liao, Ningfang

2018-03-01

The surface color of the sea is affected by many factors and will be different the due to the material difference in the sea. And the difference will be reflected in the ocean spectrum. If the paint materials of a ship can simulate the ocean surface color and the ocean spectrum at the same time. This will minimize the metamerism. In this paper, the method of metamerism is used to evaluate paint based on ocean spectrum, so that the color of the material affected by the light source will be reflected in the metamerism index.

Characterization and analysis of surface notches on Ti-alloy plates fabricated by additive manufacturing techniques

NASA Astrophysics Data System (ADS)

Chan, Kwai S.

2015-12-01

Rectangular plates of Ti-6Al-4V with extra low interstitial (ELI) were fabricated by layer-by-layer deposition techniques that included electron beam melting (EBM) and laser beam melting (LBM). The surface conditions of these plates were characterized using x-ray micro-computed tomography. The depth and radius of surface notch-like features on the LBM and EBM plates were measured from sectional images of individual virtual slices of the rectangular plates. The stress concentration factors of individual surface notches were computed and analyzed statistically to determine the appropriate distributions for the notch depth, notch radius, and stress concentration factor. These results were correlated with the fatigue life of the Ti-6Al-4V ELI alloys from an earlier investigation. A surface notch analysis was performed to assess the debit in the fatigue strength due to the surface notches. The assessment revealed that the fatigue lives of the additively manufactured plates with rough surface topographies and notch-like features are dominated by the fatigue crack growth of large cracks for both the LBM and EBM materials. The fatigue strength reduction due to the surface notches can be as large as 60%-75%. It is concluded that for better fatigue performance, the surface notches on EBM and LBM materials need to be removed by machining and the surface roughness be improved to a surface finish of about 1 μm.

Biocompatibility and characterization of a Kolsterised® medical grade cobalt-chromium-molybdenum alloy

PubMed Central

Conti, Malcolm Caligari; Karl, Andreas; Wismayer, Pierre Schembri; Buhagiar, Joseph

2014-01-01

High failure rates of cobalt-chromium-molybdenum (Co-Cr-Mo) metal-on-metal hip prosthesis were reported by various authors, probably due to the alloy's limited hardness and tribological properties. This thus caused the popularity of the alloy in metal-on-metal hip replacements to decrease due to its poor wear properties when compared with other systems such as ceramic-on-ceramic. S-phase surface engineering has become an industry standard when citing surface hardening of austenitic stainless steels. This hardening process allows the austenitic stainless steel to retain its corrosion resistance, while at the same time also improving its hardness and wear resistance. By coupling S-phase surface engineering, using the proprietary Kolsterising® treatment from Bodycote Hardiff GmbH, that is currently being used mainly on stainless steel, with Co-Cr-Mo alloys, an improvement in hardness and tribological characteristics is predicted. The objective of this paper is to analyze the biocompatibility of a Kolsterised® Co-Cr-Mo alloy, and to characterize the material surface in order to show the advantages gained by using the Kolsterised® material relative to the original untreated alloy, and other materials. This work has been performed on 3 fronts including; Material characterization, “In-vitro” corrosion testing, and Biological testing conforming to BS EN ISO 10993–18:2009 - Biological evaluation of medical devices. Using these techniques, the Kolsterised® cobalt-chromium-molybdenum alloys were found to have good biocompatibility and an augmented corrosion resistance when compared with the untreated alloy. The Kolsterised® samples also showed a 150% increase in surface hardness over the untreated material thus predicting better wear properties. PMID:24451266

Biocompatibility and characterization of a Kolsterised(®) medical grade cobalt-chromium-molybdenum alloy.

PubMed

Conti, Malcolm Caligari; Karl, Andreas; Wismayer, Pierre Schembri; Buhagiar, Joseph

2014-01-01

High failure rates of cobalt-chromium-molybdenum (Co-Cr-Mo) metal-on-metal hip prosthesis were reported by various authors, probably due to the alloy's limited hardness and tribological properties. This thus caused the popularity of the alloy in metal-on-metal hip replacements to decrease due to its poor wear properties when compared with other systems such as ceramic-on-ceramic. S-phase surface engineering has become an industry standard when citing surface hardening of austenitic stainless steels. This hardening process allows the austenitic stainless steel to retain its corrosion resistance, while at the same time also improving its hardness and wear resistance. By coupling S-phase surface engineering, using the proprietary Kolsterising(®) treatment from Bodycote Hardiff GmbH, that is currently being used mainly on stainless steel, with Co-Cr-Mo alloys, an improvement in hardness and tribological characteristics is predicted. The objective of this paper is to analyze the biocompatibility of a Kolsterised(®) Co-Cr-Mo alloy, and to characterize the material surface in order to show the advantages gained by using the Kolsterised(®) material relative to the original untreated alloy, and other materials. This work has been performed on 3 fronts including; Material characterization, "In-vitro" corrosion testing, and Biological testing conforming to BS EN ISO 10993-18:2009 - Biological evaluation of medical devices. Using these techniques, the Kolsterised(®) cobalt-chromium-molybdenum alloys were found to have good biocompatibility and an augmented corrosion resistance when compared with the untreated alloy. The Kolsterised(®) samples also showed a 150% increase in surface hardness over the untreated material thus predicting better wear properties.

Relative sliding durability of two candidate high temperature oxide fiber seal materials

NASA Technical Reports Server (NTRS)

Dellacorte, Christopher; Steinetz, Bruce M.

1991-01-01

A test program to determine the relative sliding durability of two candidate ceramic fibers for high temperature sliding seal applications is described. Pin on disk tests were used to evaluate potential seal materials. Friction during the tests and fiber wear, indicated by the extent of fibers broken in a test bundle or yarn, was measured at the end of a test. In general, friction and wear increase with test temperature. This may be due to a reduction in fiber strength, a change in the surface chemistry at the fiber/counterface interface due to oxidation, adsorption and/or desorption of surface species and, to a lesser extent, an increase in counterface surface roughness due to oxidation at elevated temperatures. The relative fiber durability correlates with tensile strength indicating that tensile data, which is more readily available than sliding durability data, may be useful in predicting fiber wear behavior under various conditions. A simple model developed using dimensional analysis shows that the fiber durability is related to a dimensionless parameter which represents the ratio of the fiber strength to the fiber stresses imposed by sliding.

Geomorphic Terrains and Evidence for Ancient Volcanism within Northeastern South Pole-Aitken Basin

NASA Technical Reports Server (NTRS)

Petro, Noah; Mest, Scott C.; Teich, Yaron

2010-01-01

The interior of the enigmatic South Pole-Aitken Basin has long been recognized as being compositionally distinct from its exterior. However, the source of the compositional anomaly has been subject to some debate. Is the source of the iron-enhancement due to lower-crustal/upper-mantle material being exposed at the surface, or was there some volume of ancient volcanism that covered portions of the basin interior? While several obvious mare basalt units are found within the basin and regions that appear to represent the original basin interior, there are several regions that appear to have an uncertain origin. Using a combination of Clementine and Lunar Orbiter images, several morphologic units are defined based on albedo, crater density, and surface roughness. An extensive unit of ancient mare basalt (cryptomare) is defined and, based on the number of superimposed craters, potentially represents the oldest volcanic materials within the basin. Thus, the overall iron-rich interior of the basin is not solely due to deeply derived crustal material, but is, in part due to the presence of ancient volcanic units.

Copoly(imide siloxane) Abhesive Materials with Varied Siloxane Oligomer Length

NASA Technical Reports Server (NTRS)

Wohl, Christoper J.; Atkins, Brad M.; Lin, Yi; Belcher, Marcus A.; Connell, John W.

2010-01-01

In this work, low surface energy copoly(imide siloxane)s were synthesized with various siloxane segment lengths. Characterization of these materials revealed that domain formation of the low surface energy component within the matrix was more prevalent for longer siloxane segments as indicated by increased opacity, decreased mechanical properties, and variation of the Tg. Incorporation of siloxanes lowered the polymer s surface energy as indicated by water contact angle values. Topographical modification of these materials by laser ablation patterning further reduced the surface energy, even generating superhydrophobic surfaces. Combined, the contact angle data and particle adhesion testing indicated that copoly(imide siloxane) materials may provide greater mitigation to particulate adhesion than polyimide materials alone. These enhanced surface properties for abhesive applications did result in a reduction of the tensile moduli of the copolymers. It is possible that lower siloxane loading levels would result in retention of the mechanical properties of the polyimide while still affording abhesive surface properties. This hypothesis is currently being investigated. Laser ablation patterning offers further reduction in particle retention as the available surface area for particle adhesion is reduced. Pattern variation and size dependencies are currently being evaluated. For the purposes of lunar dust adhesion mitigation, it is likely that this approach, termed passive due to the lack of input from an external energy source, would not be sufficient to mitigate surface contamination or clean contaminated surfaces for some lunar applications. It is feasible to combine these materials with active mitigation strategies - methods that utilize input from external energy sources - would broaden the applicability of such materials for abhesive purposes. Collaborative efforts along these lines have been initiated with researchers at NASA Kennedy Space Center where experiments are being conducted involving a series of embedded electrodes within polymeric matrices.

Printing polymer optical waveguides on conditioned transparent flexible foils by using the aerosol jet technology

NASA Astrophysics Data System (ADS)

Reitberger, Thomas; Hoffmann, Gerd-Albert; Wolfer, Tim; Overmeyer, Ludger; Franke, Joerg

2016-09-01

The optical data transfer is considered as the future of signal transfer due to its various advantages compared to conventional copper-based technologies. The Aerosol Jet Printing (AJP) technology offers the opportunity to print materials with high viscosities, such as liquid transparent polymer adhesives (epoxy resins), on almost any possible substrate material and even in third dimension. This paper introduces a new flexible and comparatively cost-effective way of generating polymer optical waveguides through AJP. Furthermore, the conditioning of the substrate material and the printing process of planar waveguides are presented. In the first step, two lines with hydrophobic behavior are applied on foil material (PMMA, PVC, PI) by using a flexographic printing machine. These silicone based patterns containing functional polymer form barriers for the core material due to their low surface energy after curing. In the second step, the core material (liquid polymer, varnish) is printed between the barrier lines. Because of the hydrophobic behavior of the lines, the contact angle between the substrate surface and the liquid core material is increased which yields to higher aspect ratio. The distance between the barrier lines is at least 100 μm, which defines the width of the waveguide. The minimum height of the core shall be 50 μm. After UV-curing of the core polymer, the cladding material is printed on the top. This is also applied by using the AJP technology. Various tests were performed to achieve the optimal surface properties for adequate adhesion and machine process parameters.

Multifunctional Textured Surfaces with Enhanced Friction and Hydrophobic Behaviors Produced by Fiber Debonding and Pullout.

PubMed

Rizvi, Reza; Anwer, Ali; Fernie, Geoff; Dutta, Tilak; Naguib, Hani

2016-11-02

Fiber debonding and pullout are well-understood processes that occur during damage and failure events in composite materials. In this study, we show how these mechanisms, under controlled conditions, can be used to produce multifunctional textured surfaces. A two-step process consisting of (1) achieving longitudinal fiber alignment followed by (2) cutting, rearranging, and joining is used to produce the textured surfaces. This process employs common composite manufacturing techniques and uses no reactive chemicals or wet handling, making it suitable for scalability. This uniform textured surface is due to the fiber debonding and pullout occurring during the cutting process. Using well-established fracture mechanics principles for composite materials, we demonstrate how different material parameters such as fiber geometry, fiber and matrix stiffness and strength, and interface behavior can be used to achieve multifunctional textured surfaces. The resulting textured surfaces show very high friction coefficients on wet ice (9× improvement), indicating their promising potential as materials for ice traction/tribology. Furthermore, the texturing enhances the surface's hydrophobicity as indicated by an increase in the contact angle of water by 30%. The substantial improvements to surface tribology and hydrophobicity make fiber debonding and pullout an effective, simple, and scalable method of producing multifunctional textured surfaces.

Development of Functional Surfaces on High-Density Polyethylene (HDPE) via Gas-Assisted Etching (GAE) Using Focused Ion Beams.

PubMed

Sezen, Meltem; Bakan, Feray

2015-12-01

Irradiation damage, caused by the use of beams in electron and ion microscopes, leads to undesired physical/chemical material property changes or uncontrollable modification of structures. Particularly, soft matter such as polymers or biological materials is highly susceptible and very much prone to react on electron/ion beam irradiation. Nevertheless, it is possible to turn degradation-dependent physical/chemical changes from negative to positive use when materials are intentionally exposed to beams. Especially, controllable surface modification allows tuning of surface properties for targeted purposes and thus provides the use of ultimate materials and their systems at the micro/nanoscale for creating functional surfaces. In this work, XeF2 and I2 gases were used in the focused ion beam scanning electron microscope instrument in combination with gallium ion etching of high-density polyethylene surfaces with different beam currents and accordingly different gas exposure times resulting at the same ion dose to optimize and develop new polymer surface properties and to create functional polymer surfaces. Alterations in the surface morphologies and surface chemistry due to gas-assisted etching-based nanostructuring with various processing parameters were tracked using high-resolution SEM imaging, complementary energy-dispersive spectroscopic analyses, and atomic force microscopic investigations.

Surface science and model catalysis with ionic liquid-modified materials.

PubMed

Steinrück, H-P; Libuda, J; Wasserscheid, P; Cremer, T; Kolbeck, C; Laurin, M; Maier, F; Sobota, M; Schulz, P S; Stark, M

2011-06-17

Materials making use of thin ionic liquid (IL) films as support-modifying functional layer open up a variety of new possibilities in heterogeneous catalysis, which range from the tailoring of gas-surface interactions to the immobilization of molecularly defined reactive sites. The present report reviews recent progress towards an understanding of "supported ionic liquid phase (SILP)" and "solid catalysts with ionic liquid layer (SCILL)" materials at the microscopic level, using a surface science and model catalysis type of approach. Thin film IL systems can be prepared not only ex-situ, but also in-situ under ultrahigh vacuum (UHV) conditions using atomically well-defined surfaces as substrates, for example by physical vapor deposition (PVD). Due to their low vapor pressure, these systems can be studied in UHV using the full spectrum of surface science techniques. We discuss general strategies and considerations of this approach and exemplify the information available from complementary methods, specifically photoelectron spectroscopy and surface vibrational spectroscopy. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

In situ plasma fabrication of ceramic-like structure on polymeric implant with enhanced surface hardness, cytocompatibility and antibacterial capability.

PubMed

Liu, Jun; Zhang, Wei; Shi, Haigang; Yang, Kun; Wang, Gexia; Wang, Pingli; Ji, Junhui; Chu, Paul K

2016-05-01

Polymeric materials are commonly found in orthopedic implants due to their unique mechanical properties and biocompatibility but the poor surface hardness and bacterial infection hamper many biomedical applications. In this study, a ceramic-like surface structure doped with silver is produced by successive plasma implantation of silicon (Si) and silver (Ag) into the polyamine 66 (PA66) substrate. Not only the surface hardness and elastic modulus are greatly enhanced due to the partial surface carbonization and the ceramic-like structure produced by the reaction between energetic Si and the carbon chain of PA66, but also the antibacterial activity is improved because of the combined effects rendered by Ag and SiC structure. Furthermore, the modified materials which exhibit good cytocompatibility upregulate bone-related genes and proteins expressions of the contacted bone mesenchymal stem cells (BMSCs). For the first time, it explores out that BMSCs osteogenesis on the antibacterial ceramic-like structure is mediated via the iNOS and nNOS signal pathways. The results reveal that in situ plasma fabrication of an antibacterial ceramic-like structure can endow PA66 with excellent surface hardness, cytocompatibility, as well as antibacterial capability. © 2016 Wiley Periodicals, Inc.

Microminiature optical waveguide structure and method for fabrication

DOEpatents

Strand, O.T.; Deri, R.J.; Pocha, M.D.

1998-12-08

A method for manufacturing low-cost, nearly circular cross section waveguides comprises starting with a substrate material that a molten waveguide material can not wet or coat. A thin layer is deposited of an opposite material that the molten waveguide material will wet and is patterned to describe the desired surface-contact path pedestals for a waveguide. A waveguide material, e.g., polymer or doped silica, is deposited. A resist material is deposited and unwanted excess is removed to form pattern masks. The waveguide material is etched away to form waveguide precursors and the masks are removed. Heat is applied to reflow the waveguide precursors into near-circular cross-section waveguides that sit atop the pedestals. The waveguide material naturally forms nearly circular cross sections due to the surface tension effects. After cooling, the waveguides will maintain the round shape. If the width and length are the same, then spherical ball lenses are formed. Alternatively, the pedestals can be patterned to taper along their lengths on the surface of the substrate. This will cause the waveguides to assume a conical taper after reflowing by heat. 32 figs.

Microminiature optical waveguide structure and method for fabrication

DOEpatents

Strand, Oliver T.; Deri, Robert J.; Pocha, Michael D.

1998-01-01

A method for manufacturing low-cost, nearly circular cross section waveguides comprises starting with a substrate material that a molten waveguide material can not wet or coat. A thin layer is deposited of an opposite material that the molten waveguide material will wet and is patterned to describe the desired surface-contact path pedestals for a waveguide. A waveguide material, e.g., polymer or doped silica, is deposited. A resist material is deposited and unwanted excess is removed to form pattern masks. The waveguide material is etched away to form waveguide precursors and the masks are removed. Heat is applied to reflow the waveguide precursors into near-circular cross-section waveguides that sit atop the pedestals. The waveguide material naturally forms nearly circular cross sections due to the surface tension effects. After cooling, the waveguides will maintain the round shape. If the width and length are the same, then spherical ball lenses are formed. Alternatively, the pedestals can be patterned to taper along their lengths on the surface of the substrate. This will cause the waveguides to assume a conical taper after reflowing by heat.

Analysis of Temperature Maps of Selected Dawn Data Over the Surface of Vesta

NASA Technical Reports Server (NTRS)

Tosi, F.; Capria, M. T.; DeSanctis, M. C.; Palomba, E.; Grassi, D.; Capaccioni, F.; Ammannito, E.; Combe, J.-Ph.; Sunshine, J. M.; McCord, T. B.;

Experimental study on surface properties of the PMMA used in high power spark gaps

NASA Astrophysics Data System (ADS)

Han, Ruoyu; Wu, Jiawei; Ding, Weidong; Liu, Yunfei; Gou, Yang

2017-10-01

This paper studies the surface properties of the Polymethylmethacrylate (PMMA) insulator samples used in high power spark gaps. Experiments on surface morphology, surface profile, surface chemical composition and surface leakage current were performed. Metal particles ejected in tangent direction of discharge spots were researched on the sample surface. Three kinds of distinct bands were found on the surface after 1500 shots: colorless and transparent sinking band, black band, and grey powdered coating band. The thickness of the coating band was tens of microns and the maximum radial erosion rate was about 10 μm/C. Surface content analysis indicated that the powdered coating was a mixture of decomposed insulator material and electrode material oxides. In addition, leakage current significantly depended on water content in the chamber and presented an U-shape curve distribution along the insulator surface, in keeping with the amount of powdered coating due to shock waves. Possible reasons of the surface property changes were discussed. Electroconductive oxides of low valence states of Cu and W produced by the reactions between electrode materials and arc plasmas were considered to be the cause of dielectric performance degradation.

Bioinspired Functional Materials

DOE PAGES

Zheng, Yongmei; Wang, Jingxia; Hou, Yongping; ...

2014-11-25

This special issue is focused on the nanoscale or micro-/nanoscale structures similar to the biological features in multilevels or hierarchy and so on. Research by mimicking biological systems has shown more impact on many applications due to the well-designed micro-/nanostructures inspired from the biological surfaces or interfaces; therefore, the materials may achieve the fascinating functionality. In conclusion, the bioinspired functional materials may be fabricated by developing novel technology or methods such as synthesis, self-assembly, and soft lithography at micro- or nanolevel or multilevels and, in addition, the multidisciplinary procedures of physical or chemical methods and nanotechnology to mimic the biologicalmore » multiscale micro-/nanostructures onto one-/two-dimensional surface materials.« less

Self-Nulling Eddy Current Probe for Surface and Subsurface Flaw Detection

NASA Technical Reports Server (NTRS)

Wincheski, B.; Fulton, J. P.; Nath, S.; Namkung, M.; Simpson, J. W.

1994-01-01

An eddy current probe which provides a null-signal in the presence of unflawed material without the need for any balancing circuitry has been developed at NASA Langley Research Center. Such a unique capability of the probe reduces set-up time, eliminates tester configuration errors, and decreases instrumentation requirements. The probe is highly sensitive to surface breaking fatigue cracks, and shows excellent resolution for the measurement of material thickness, including material loss due to corrosion damage. The presence of flaws in the material under test causes an increase in the extremely stable and reproducible output voltage of the probe. The design of the probe and some examples illustrating its flaw detection capabilities are presented.

Cost/performance of solar reflective surfaces for parabolic dish concentrators

NASA Technical Reports Server (NTRS)

Bouquet, F.

1980-01-01

Materials for highly reflective surfaces for use in parabolic dish solar concentrators are discussed. Some important factors concerning performance of the mirrors are summarized, and typical costs are treated briefly. Capital investment cost/performance ratios for various materials are computed specifically for the double curvature parabolic concentrators using a mathematical model. The results are given in terms of initial investment cost for reflective surfaces per thermal kilowatt delivered to the receiver cavity for various operating temperatures from 400 to 1400 C. Although second surface glass mirrors are emphasized, first surface, chemically brightened and anodized aluminum surfaces as well as second surface, metallized polymeric films are treated. Conventional glass mirrors have the lowest cost/performance ratios, followed closely by aluminum reflectors. Ranges in the data due to uncertainties in cost and mirror reflectance factors are given.

Biomimetic superwettable materials with structural colours.

PubMed

Wang, Zelinlan; Guo, Zhiguang

2017-12-05

Structural colours and superwettability are of great interest due to their unique characteristics. However, the application of materials with either structural colours or superwettability is limited. Moreover, materials possessing both structural colours and superwettability are crucial for many practical applications. The combination of structural colours and superwettability can result in materials for use various applications, such as in sensors, detectors, bioassays, anti-counterfeiting, and liquid actuators, by controlling surfaces to repel or absorb liquids. Regarding superwettability and structural colours, surface texture and chemical composition are two factors for the construction of materials with superwettable structural colours. This review aims at offering a comprehensive elaboration of the mechanism, recent biomimetic research, and applications of biomimetic superwettable materials with structural colours. Furthermore, this review provides significant insight into the design, fabrication, and application of biomimetic superwettable materials with structural colours.

Fabrication of polydimethylsiloxane (PDMS) - based multielectrode array for neural interface.

PubMed

Kim, Jun-Min; Oh, Da-Rong; Sanchez, Joaquin; Kim, Shang-Hyub; Seo, Jong-Mo

2013-01-01

Flexible multielectrode arrays (MEAs) are being developed with various materials, and polyimide has been widely used due to the conveniece of process. Polyimide is developed in the form of photoresist. And this enable precise and reproducible fabrication. PDMS is another good candidate for MEA base material, but it has poor surface energy and etching property. In this paper, we proposed a better fabrication process that could modify PDMS surface for a long time and open the site of electrode and pad efficiently without PDMS etching.

The Upper Limit of Energy Density of Nanoporous Materials Functionalized Liquid

NASA Astrophysics Data System (ADS)

Han, Aijie; Punyamurtula, Venkata K.; Kim, Taewan; Qiao, Yu

2008-06-01

In this article, we report the experimental result of energy dissipation of a mobil crystalline material (MCM) 41 in mercury. The MCM41 contains a large volume fraction of nanometer-sized pores. As the applied pressure is relatively high, the nanopore surfaces are exposed to mercury. Due to the large nanopore surface area and the large solid-liquid interfacial tension, the energy dissipation effectiveness of this system is ultrahigh, representing the upper limit that can be achieved by the pressure-induced infiltration technique.

Monolayered Bi2WO6 nanosheets mimicking heterojunction interface with open surfaces for photocatalysis

NASA Astrophysics Data System (ADS)

Zhou, Yangen; Zhang, Yongfan; Lin, Mousheng; Long, Jinlin; Zhang, Zizhong; Lin, Huaxiang; Wu, Jeffrey C.-S.; Wang, Xuxu

2015-09-01

Two-dimensional-layered heterojunctions have attracted extensive interest recently due to their exciting behaviours in electronic/optoelectronic devices as well as solar energy conversion systems. However, layered heterojunction materials, especially those made by stacking different monolayers together by strong chemical bonds rather than by weak van der Waal interactions, are still challenging to fabricate. Here the monolayer Bi2WO6 with a sandwich substructure of [BiO]+-[WO4]2--[BiO]+ is reported. This material may be characterized as a layered heterojunction with different monolayer oxides held together by chemical bonds. Coordinatively unsaturated Bi atoms are present as active sites on the surface. On irradiation, holes are generated directly on the active surface layer and electrons in the middle layer, which leads to the outstanding performances of the monolayer material in solar energy conversion. Our work provides a general bottom-up route for designing and preparing novel monolayer materials with ultrafast charge separation and active surface.

Monolayered Bi2WO6 nanosheets mimicking heterojunction interface with open surfaces for photocatalysis

PubMed Central

Zhou, Yangen; Zhang, Yongfan; Lin, Mousheng; Long, Jinlin; Zhang, Zizhong; Lin, Huaxiang; Wu, Jeffrey C.-S.; Wang, Xuxu

2015-01-01

Two-dimensional-layered heterojunctions have attracted extensive interest recently due to their exciting behaviours in electronic/optoelectronic devices as well as solar energy conversion systems. However, layered heterojunction materials, especially those made by stacking different monolayers together by strong chemical bonds rather than by weak van der Waal interactions, are still challenging to fabricate. Here the monolayer Bi2WO6 with a sandwich substructure of [BiO]+–[WO4]2−–[BiO]+ is reported. This material may be characterized as a layered heterojunction with different monolayer oxides held together by chemical bonds. Coordinatively unsaturated Bi atoms are present as active sites on the surface. On irradiation, holes are generated directly on the active surface layer and electrons in the middle layer, which leads to the outstanding performances of the monolayer material in solar energy conversion. Our work provides a general bottom-up route for designing and preparing novel monolayer materials with ultrafast charge separation and active surface. PMID:26359212

Cleanability evaluation of ceramic glazes with nanometer far-infrared materials using contact angle measurement.

PubMed

Wang, Lijuan; Liang, Jinsheng; Di, Xingfu; Tang, Qingguo

2014-05-01

The cleanability of easy-to-clean ceramic glazes doped with nanometer far-infrared materials was compared with that of some high-quality household ceramic glazes from the market. The cleanability was evaluated by the contact angle measurement using a sessile drop method with a Dataphysics OCA-30 contact angle analyzer. The results showed that the difference of contact angles of water on the glazes before soiling and after cleaning could be used as a parameter for evaluating the cleanability of the glazes. The relationship between cleanability and surface properties, such as surface free energy and surface topography, was investigated. The surface free energy of the samples and their components were calculated using van Oss acid-base approach. By measuring advancing and receding contact angles, the contact angle hysteresis of the ceramic glazes due to the surface topography was investigated. It was shown that the cleanability of ceramic glazes containing nanometer far-infrared materials (NFIM) is better than that of household ceramic glazes from market, due to a higher ratio of electron-acceptor parameter to electron-donor parameter, which led to the effect of water hydration as well as better hydrophilic property and increased smoothness. The contact angle measurement not only accurately evaluates the cleanability of the ceramic glazes, but also has a contribution to the study of cleanability theory. Moreover, this method is simple, convenient and less sample-consumption.

A two-stage ceramic tile grout sealing process using a high power diode laser—Grout development and materials characteristics

NASA Astrophysics Data System (ADS)

Lawrence, J.; Li, L.; Spencer, J. T.

1998-04-01

Work has been conducted using a 60 Wcw high power diode laser (HPDL) in order to determine the feasibility and characteristics of sealing the void between adjoining ceramic tiles with a specially developed grout material having an impermeable enamel surface glaze. A two-stage process has been developed using a new grout material which consists of two distinct components: an amalgamated compound substrate and a glazed enamel surface; the amalgamated compound seal providing a tough, heat resistant bulk substrate, whilst the enamel provides an impervious surface. HPDL processing has resulted in crack free seals produced in normal atmospheric conditions. The basic process phenomena are investigated and the laser effects in terms of seal morphology, composition and microstructure are presented. Also, the resultant heat affects are analysed and described, as well as the effects of the shield gases, O 2 and Ar, during laser processing. Tiles were successfully sealed with power densities as low as 500 W/cm 2 and at rates up to 600 mm/min. Contact angle measurements revealed that due to the wettability characteristics of the amalgamated oxide compound grout (AOCG), laser surface treatment was necessary in order to alter the surface from a polycrystalline to a semi-amorphous structure, thus allowing the enamel to adhere. Bonding of the enamel to the AOCG and the ceramic tiles was identified as being principally due to van der Waals forces, and on a very small scale, some of the base AOCG material dissolving into the glaze.

A review on ductile mode cutting of brittle materials

NASA Astrophysics Data System (ADS)

Antwi, Elijah Kwabena; Liu, Kui; Wang, Hao

2018-06-01

Brittle materials have been widely employed for industrial applications due to their excellent mechanical, optical, physical and chemical properties. But obtaining smooth and damage-free surface on brittle materials by traditional machining methods like grinding, lapping and polishing is very costly and extremely time consuming. Ductile mode cutting is a very promising way to achieve high quality and crack-free surfaces of brittle materials. Thus the study of ductile mode cutting of brittle materials has been attracting more and more efforts. This paper provides an overview of ductile mode cutting of brittle materials including ductile nature and plasticity of brittle materials, cutting mechanism, cutting characteristics, molecular dynamic simulation, critical undeformed chip thickness, brittle-ductile transition, subsurface damage, as well as a detailed discussion of ductile mode cutting enhancement. It is believed that ductile mode cutting of brittle materials could be achieved when both crack-free and no subsurface damage are obtained simultaneously.

Microstructures of tribologically modified surface layers in two-phase alloys

NASA Astrophysics Data System (ADS)

Figueroa, C. G.; Ortega, I.; Jacobo, V. H.; Ortiz, A.; Bravo, A. E.; Schouwenaars, R.

2014-08-01

When ductile alloys are subject to sliding wear, small increments of plastic strain accumulate into severe plastic deformation and mechanical alloying of the surface layer. The authors constructed a simple coaxial tribometer, which was used to study this phenomenon in wrought Al-Sn and cast Cu-Mg-Sn alloys. The first class of materials is ductile and consists of two immiscible phases. Tribological modification is observed in the form of a transition zone from virgin material to severely deformed grains. At the surface, mechanical mixing of both phases competes with diffusional unmixing. Vortex flow patterns are typically observed. The experimental Cu-Mg-Sn alloys are ductile for Mg-contents up to 2 wt% and consist of a- dendrites with a eutectic consisting of a brittle Cu2Mg-matrix with α-particles. In these, the observations are similar to the Al-Sn Alloys. Alloys with 5 wt% Mg are brittle due to the contiguity of the eutectic compound. Nonetheless, under sliding contact, this compound behaves in a ductile manner, showing mechanical mixing of a and Cu2Mg in the top layers and a remarkable transition from a eutectic to cellular microstructure just below, due to severe shear deformation. AFM-observations allow identifying the mechanically homogenized surface layers as a nanocrystalline material with a cell structure associated to the sliding direction.

Mechanochemical synthesis of carbon-based nanocomposites for supercapacitors

NASA Astrophysics Data System (ADS)

Mateyshina, Yuliya G.; Ulihin, Artem S.; Uvarov, Nikolai F.

2014-12-01

New nanoporous carbon-SiO2 composite materials were synthesized from organic raw materials (rice shells) and their electrochemical properties were investigated by cyclic voltammetry in liquid electrolytes (6 M KOH or 1 M H2SO4). A correlation between specific capacitance and specific surface area was observed. Due to high specific capacitance of 90 F/g the carbon materials under study may be regarded as promising electrode materials for electrochemical supercapacitors.

An evaluation of complementary approaches to elucidate fundamental interfacial phenomena driving adhesion of energetic materials

DOE PAGES

Hoss, Darby J.; Knepper, Robert; Hotchkiss, Peter J.; ...

2016-03-23

In this study, cohesive Hamaker constants of solid materials are measured via optical and dielectric properties (i.e., Lifshitz theory), inverse gas chromatography (IGC), and contact angle measurements. To date, however, a comparison across these measurement techniques for common energetic materials has not been reported. This has been due to the inability of the community to produce samples of energetic materials that are readily compatible with contact angle measurements. Here we overcome this limitation by using physical vapor deposition to produce thin films of five common energetic materials, and the contact angle measurement approach is applied to estimate the cohesive Hamakermore » constants and surface energy components of the materials. The cohesive Hamaker constants range from 85 zJ to 135 zJ across the different films. When these Hamaker constants are compared to prior work using Lifshitz theory and nonpolar probe IGC, the relative magnitudes can be ordered as follows: contact angle > Lifshitz > IGC. Furthermore, the dispersive surface energy components estimated here are in good agreement with those estimated by IGC. Due to these results, researchers and technologists will now have access to a comprehensive database of adhesion constants which describe the behavior of these energetic materials over a range of settings.« less

Carbonization in Titan Tholins: implication for low albedo on surfaces of Centaurs and trans-Neptunian objects

NASA Astrophysics Data System (ADS)

Giri, Chaitanya; McKay, Christopher P.; Goesmann, Fred; Schäfer, Nadine; Li, Xiang; Steininger, Harald; Brinckerhoff, William B.; Gautier, Thomas; Reitner, Joachim; Meierhenrich, Uwe J.

2016-07-01

Astronomical observations of Centaurs and trans-Neptunian objects (TNOs) yield two characteristic features - near-infrared (NIR) reflectance and low geometric albedo. The first feature apparently originates due to complex organic material on their surfaces, but the origin of the material contributing to low albedo is not well understood. Titan tholins synthesized to simulate aerosols in the atmosphere of Saturn's moon Titan have also been used for simulating the NIR reflectances of several Centaurs and TNOs. Here, we report novel detections of large polycyclic aromatic hydrocarbons, nanoscopic soot aggregates and cauliflower-like graphite within Titan tholins. We put forth a proof of concept stating the surfaces of Centaurs and TNOs may perhaps comprise of highly `carbonized' complex organic material, analogous to the tholins we investigated. Such material would apparently be capable of contributing to the NIR reflectances and to the low geometric albedos simultaneously.

Ultrasonic impact peening for the surface properties’ management

NASA Astrophysics Data System (ADS)

Mordyuk, Bohdan N.; Prokopenko, Georgiy I.

2007-12-01

It is demonstrated that the ultrasonic impact peening (UIP) technique is a beneficial method for essential increase in the fatigue durability of metallic materials due to the surface nanocrystallization and hardening process provided for severe plastic deformation of surface via multiple impacts of high velocity impact pins. Nano-scale grain structures were obtained in the surface layers of stainless steel, low carbon steel weld and different titanium alloys using developed equipment for the UIP. Both the surface nanostructure and compressive residual stresses are shown to attribute to the essential hardness increase. It is revealed experimentally using profilometry that new modification of the UIP apparatus providing high velocity "sliding" impacts leads to marked diminution of the surface roughness, which is another important factor affecting to the fatigue cracks initiation process. The two-dimensional finite element model is used to simulate the indent formation process during single impaction. The solid steel pin and the Al alloy plate are modeled as a rigid material and an elasto-plastic material, respectively. It is shown that the surface roughness magnitude depends on the correlation of the vertical and lateral load components.

Laser-assisted immobilization of colloid silver nanoparticles on polyethyleneterephthalate

NASA Astrophysics Data System (ADS)

Siegel, Jakub; Lyutakov, Oleksiy; Polívková, Markéta; Staszek, Marek; Hubáček, Tomáš; Švorčík, Václav

2017-10-01

Immobilization of nanoobjects on the surface of underlying material belongs to current issues of material science. Such altered materials exhibits completely exceptional properties exploitable in a broad spectrum of industrially important applications ranging from catalysts up to health-care industry. Here we present unique approach for immobilization of electrochemically synthesized silver nanoparticles on polyethyleneterephthalate (PET) foil whose essence lies in physical incorporation of particles into thin polymer surface layer induced by polarized excimer laser light. Changes in chemical composition and surface structure of polymer after particle immobilization were recorded by wide range of analytical techniques such as ARXPS, EDX, RBS, AAS, Raman, ICP-MS, DLS, UV-vis, SEM, TEM, and AFM. Thorough analysis of both nanoparticles entering the immobilization step as well as modified PET surface allowed revealing the mechanism of immobilization process itself. Silver nanoparticles were physically embedded into a thin surface layer of polymer reaching several nanometers beneath the surface rather than chemically bonded to PET macromolecules. Laser-implanted nanoparticles open up new possibilities especially in the development of the next generation cell-conform antimicrobial coatings of polymeric materials, namely due to the considerable immobilization strength which is strong enough to prevent particle release into the surrounding environment.

Pretreatment-dependent surface chemistry of wood nanocellulose for pH-sensitive hydrogels.

PubMed

Chinga-Carrasco, Gary; Syverud, Kristin

2014-09-01

Nanocellulose from wood is a promising material with potential in various technological areas. Within biomedical applications, nanocellulose has been proposed as a suitable nano-material for wound dressings. This is based on the capability of the material to self-assemble into 3D micro-porous structures, which among others have an excellent capacity of maintaining a moist environment. In addition, the surface chemistry of nanocellulose is suitable for various applications. First, OH-groups are abundant in nanocellulose materials, making the material strongly hydrophilic. Second, the surface chemistry can be modified, introducing aldehyde and carboxyl groups, which have major potential for surface functionalization. In this study, we demonstrate the production of nanocellulose with tailor-made surface chemistry, by pre-treating the raw cellulose fibres with carboxymethylation and periodate oxidation. The pre-treatments yielded a highly nanofibrillated material, with significant amounts of aldehyde and carboxyl groups. Importantly, the poly-anionic surface of the oxidized nanocellulose opens up for novel applications, i.e. micro-porous materials with pH-responsive characteristics. This is due to the swelling capacity of the 3D micro-porous structures, which have ionisable functional groups. In this study, we demonstrated that nanocellulose gels have a significantly higher swelling degree in neutral and alkaline conditions, compared to an acid environment (pH 3). Such a capability can potentially be applied in chronic wounds for controlled and intelligent release of antibacterial components into biofilms. © The Author(s) 2014 Reprints and permissions: sagepub.co.uk/journalsPermissions.nav.

Pretreatment-dependent surface chemistry of wood nanocellulose for pH-sensitive hydrogels

PubMed Central

Syverud, Kristin

2014-01-01

Nanocellulose from wood is a promising material with potential in various technological areas. Within biomedical applications, nanocellulose has been proposed as a suitable nano-material for wound dressings. This is based on the capability of the material to self-assemble into 3D micro-porous structures, which among others have an excellent capacity of maintaining a moist environment. In addition, the surface chemistry of nanocellulose is suitable for various applications. First, OH-groups are abundant in nanocellulose materials, making the material strongly hydrophilic. Second, the surface chemistry can be modified, introducing aldehyde and carboxyl groups, which have major potential for surface functionalization. In this study, we demonstrate the production of nanocellulose with tailor-made surface chemistry, by pre-treating the raw cellulose fibres with carboxymethylation and periodate oxidation. The pre-treatments yielded a highly nanofibrillated material, with significant amounts of aldehyde and carboxyl groups. Importantly, the poly-anionic surface of the oxidized nanocellulose opens up for novel applications, i.e. micro-porous materials with pH-responsive characteristics. This is due to the swelling capacity of the 3D micro-porous structures, which have ionisable functional groups. In this study, we demonstrated that nanocellulose gels have a significantly higher swelling degree in neutral and alkaline conditions, compared to an acid environment (pH 3). Such a capability can potentially be applied in chronic wounds for controlled and intelligent release of antibacterial components into biofilms. PMID:24713295

An Investigation of Porous Structure of TiNi-Based SHS-Materials Produced at Different Initial Synthesis Temperatures

NASA Astrophysics Data System (ADS)

Khodorenko, V. N.; Anikeev, S. G.; Kokorev, O. V.; Yasenchuk, Yu. F.; Gunther, V. É.

2018-02-01

An investigation of structural characteristics and behavior of TiNi-based pore-permeable materials manufactured by the methods of selfpropagating high-temperature synthesis (SHS) at the initial synthesis temperatures T = 400 and 600°C is performed. It is shown that depending on the temperature regime, the resulting structure and properties of the material can differ. It is found out that the SHS-material produced at the initial synthesis temperature T = 400°C possesses the largest number of micropores in the pore wall surface structure due to a high phase inhomogeneity of the alloy. The regime of structure optimization of the resulting materials is described and the main stages of formation of the pore wall microporous surfaces are revealed. It is demonstrated that after optimization of the surface structure of a TiNi-based fine-pore alloy by its chemical etching, the fraction of micropores measuring in size less than 50 nm increased from 59 to 68%, while the number of pores larger than 1 μm increased twofold from 11 to 22%. In addition, peculiar features of interaction between certain cell cultures with the surface of the SHS-material manufactured at different initial synthesis temperatures are revealed. It is found out that the dynamics of the cell material integration depends on the pore wall surface morphology and dimensions of macropores.

The Interaction of Bacteria with Engineered Nanostructured Polymeric Materials: A Review

PubMed Central

Armentano, Ilaria; Arciola, Carla Renata; Fortunati, Elena; Ferrari, Davide; Mattioli, Samantha; Amoroso, Concetta Floriana; Rizzo, Jessica; Kenny, Jose M.; Imbriani, Marcello; Visai, Livia

2014-01-01

Bacterial infections are a leading cause of morbidity and mortality worldwide. In spite of great advances in biomaterials research and development, a significant proportion of medical devices undergo bacterial colonization and become the target of an implant-related infection. We present a review of the two major classes of antibacterial nanostructured materials: polymeric nanocomposites and surface-engineered materials. The paper describes antibacterial effects due to the induced material properties, along with the principles of bacterial adhesion and the biofilm formation process. Methods for antimicrobial modifications of polymers using a nanocomposite approach as well as surface modification procedures are surveyed and discussed, followed by a concise examination of techniques used in estimating bacteria/material interactions. Finally, we present an outline of future sceneries and perspectives on antibacterial applications of nanostructured materials to resist or counteract implant infections. PMID:25025086

Process parameter and surface morphology of pineapple leaf electrospun nanofibers (PALF)

NASA Astrophysics Data System (ADS)

Surip, S. N.; Aziz, F. M. A.; Bonnia, N. N.; Sekak, K. A.; Zakaria, M. N.

2017-09-01

In recent times, nanofibers have attracted the attention of researchers due to their pronounced micro and nano structural characteristics that enable the development of advanced materials that have sophisticated applications. The production of nanofibers by the electrospinning process is influenced both by the electrostatic forces and the viscoelastic behavior of the polymer. Process parameters, like solution feed rate, applied voltage, nozzle-collector distance, and spinning environment, and material properties, like solution concentration, viscosity, surface tension, conductivity, and solvent vapor pressure, influence the structure and properties of electrospun nanofibers. Significant work has been done to characterize the properties of PALF nanofibers as a function of process and material parameters.

Roughness Effects on Fretting Fatigue

NASA Astrophysics Data System (ADS)

Yue, Tongyan; Abdel Wahab, Magd

2017-05-01

Fretting is a small oscillatory relative motion between two normal loaded contact surfaces. It may cause fretting fatigue, fretting wear and/or fretting corrosion damage depending on various fretting couples and working conditions. Fretting fatigue usually occurs at partial slip condition, and results in catastrophic failure at the stress levels below the fatigue limit of the material. Many parameters may affect fretting behaviour, including the applied normal load and displacement, material properties, roughness of the contact surfaces, frequency, etc. Since fretting damage is undesirable due to contacting, the effect of rough contact surfaces on fretting damage has been studied by many researchers. Experimental method on this topic is usually focusing on rough surface effects by finishing treatment and random rough surface effects in order to increase fretting fatigue life. However, most of numerical models on roughness are based on random surface. This paper reviewed both experimental and numerical methodology on the rough surface effects on fretting fatigue.

Effect of elastic excitations on the surface structure of hadfield steel under friction

NASA Astrophysics Data System (ADS)

Kolubaev, A. V.; Ivanov, Yu. F.; Sizova, O. V.; Kolubaev, E. A.; Aleshina, E. A.; Gromov, V. E.

2008-02-01

The structure of the Hadfield steel (H13) surface layer forming under dry friction is examined. The deformation of the material under the friction surface is studied at a low slip velocity and a low pressure (much smaller than the yields stress of H13 steel). The phase composition and defect substructure on the friction surface are studied using scanning, optical, and diffraction electron microscopy methods. It is shown that a thin highly deformed nanocrystalline layer arises near the friction surface that transforms into a polycrystalline layer containing deformation twins and dislocations. The nanocrystalline structure and the presence of oxides in the surface layer and friction zone indicate a high temperature and high plastic strains responsible for the formation of the layer. It is suggested that the deformation of the material observed far from the surface is due to elastic wave generation at friction.

Bone Cell–materials Interactions and Ni Ion Release of Anodized Equiatomic NiTi Alloy

PubMed Central

Bernard, Sheldon A.; Balla, Vamsi Krishna; Davies, Neal M.; Bose, Susmita; Bandyopadhyay, Amit

2011-01-01

Laser processed NiTi alloy was anodized for different durations in H2SO4 electrolyte with varying pH to create biocompatible surfaces with low Ni ion release as well as bioactive surfaces to enhance biocompatibility and bone cell-materials interactions. The anodized surfaces were assessed for their in vitro cell-materials interactions using human fetal osteoblast (hFOB) cells for 3, 7 and 11 days, and Ni ion release up to 8 weeks in simulated body fluids. The results were correlated with surface morphologies of anodized surfaces characterized using field-emission scanning electron microscopy (FESEM). The results show that the anodization creates a surface with nano/micro roughness depending on anodization conditions. The hydrophilicity of NiTi surface was found to improve after anodization due to lower contact angles in cell media, which dropped from 32° to < 5°. The improved wettability of anodized surfaces is further corroborated by their high surface energy comparable to that of cp Ti. Relatively high surface energy, especially polar component, and nano/micro surface features of anodized surfaces significantly increased the number of living cells and their adherence and growth on these surfaces. Finally, a significant drop in Ni ion release from 268 ± 11 to 136 ± 15 ppb was observed for NiTi surfaces after anodization. This work indicates that anodization of NiTi alloy has a positive influence on the surface energy and surface morphology, which in turn improve bone cell-materials interactions and reduce Ni ion release in vitro. PMID:21232641

Biochar-based functional materials in the purification of agricultural wastewater: Fabrication, application and future research needs.

PubMed

Wei, Dongning; Li, Bingyu; Huang, Hongli; Luo, Lin; Zhang, Jiachao; Yang, Yuan; Guo, Jiajun; Tang, Lin; Zeng, Guangming; Zhou, Yaoyu

2018-04-01

Nowadays, agricultural contamination is becoming more and more serious due to the rapid growth of agricultural industry, which discharged antibiotics, pesticides or toxic metals into farmlands. A large number of researchers have applied biochar-based functional materials to the treatment of agricultural wastewater contamination. Meanwhile, biochar has also proved to be a very promising and effective technology in water purification field due to its various beneficial properties (e.g., cost effective, high specific surface area, and surface reactive groups). The focus of this review is to highlight the fabrication methods and application of biochar-based functional materials with the removal of different agricultural contaminants, and discuss the underlying mechanisms. However, the application of biochar-based functional materials is currently under its infancy, with the main hindrance is identified as the gap between laboratory scale and field application, immaturity of engineered biochar production technologies, and lack of quality standards. In order to fill these knowledge gaps, more efforts should be made to pay for the relevant research in future studies. Copyright © 2018 Elsevier Ltd. All rights reserved.

A geomorphic process law for detachment-limited hillslopes

NASA Astrophysics Data System (ADS)

Turowski, Jens

2015-04-01

Geomorphic process laws are used to assess the shape evolution of structures at the Earth's surface over geological time scales, and are routinely used in landscape evolution models. There are two currently available concepts on which process laws for hillslope evolution rely. In the transport-limited concept, the evolution of a hillslope is described by a linear or a non-linear diffusion equation. In contrast, in the threshold slope concept, the hillslope is assumed to collapse to a slope equal to the internal friction angle of the material when the load due to the relief exists the material strength. Many mountains feature bedrock slopes, especially in the high mountains, and material transport along the slope is limited by the erosion of the material from the bedrock. Here, I suggest a process law for detachment-limited or threshold-dominated hillslopes, in which the erosion rate is a function of the applied stress minus the surface stress due to structural loading. The process law leads to the prediction of an equilibrium form that compares well to the shape of many mountain domes.

Application of the double paddle oscillator for quantifying environmental, surface mass variation

NASA Astrophysics Data System (ADS)

Wei, Haoyan; Pomeroy, Joshua

2016-04-01

Sub-monolayer sensitivity to controlled gas adsorption and desorption is demonstrated using a double paddle oscillator (DPO) installed within an ultra-high vacuum (UHV) environmental chamber equipped with in situ film deposition, (multi)gas admission and temperature control. This effort is intended to establish a robust framework for quantitatively comparing mass changes due to gas loading and unloading on different materials systems selected or considered for use as mass artefacts. Our apparatus is composed of a UHV chamber with gas introduction and temperature control and in situ materials deposition for future materials testing enabling in situ preparation of virgin surfaces that can be monitored during initial exposure to gasses of interest. These tools are designed to allow us to comparatively evaluate how different materials gain or lose mass due to precisely controlled environmental excursions, with a long term goal of measuring changes in absolute mass. Herein, we provide a detailed experimental description of the apparatus, an evaluation of the initial performance, and demonstration measurements using nitrogen adsorption and desorption directly on the DPO.

Application of the double paddle oscillator for quantifying environmental, surface mass variation

PubMed Central

Wei, Haoyan; Pomeroy, Joshua

2016-01-01

Sub-monolayer sensitivity to controlled gas adsorption and desorption is demonstrated using a double paddle oscillator (DPO) installed within an UHV (ultra-high vacuum) environmental chamber equipped with in situ film deposition, (multi)gas admission and temperature control. This effort is intended to establish a robust framework for quantitatively comparing mass changes due to gas loading and unloading on different materials systems selected or considered for use as mass artifacts. Our apparatus is composed of a UHV chamber with gas introduction and temperature control and in-situ materials deposition for future materials testing enabling in situ preparation of virgin surfaces that can be monitored during initial exposure to gasses of interest. These tools are designed to allow us to comparatively evaluate how different materials gain or lose mass due to precisely controlled environmental excursions, with a long term goal of measuring changes in absolute mass. Herein, we provide a detailed experimental description of the apparatus, an evaluation of the initial performance, and demonstration measurements using nitrogen adsorption and desorption directly on the DPO. PMID:27212736

Ductile and brittle transition behavior of titanium alloys in ultra-precision machining.

PubMed

Yip, W S; To, S

2018-03-02

Titanium alloys are extensively applied in biomedical industries due to their excellent material properties. However, they are recognized as difficult to cut materials due to their low thermal conductivity, which induces a complexity to their deformation mechanisms and restricts precise productions. This paper presents a new observation about the removal regime of titanium alloys. The experimental results, including the chip formation, thrust force signal and surface profile, showed that there was a critical cutting distance to achieve better surface integrity of machined surface. The machined areas with better surface roughness were located before the clear transition point, defining as the ductile to brittle transition. The machined area at the brittle region displayed the fracture deformation which showed cracks on the surface edge. The relationship between depth of cut and the ductile to brittle transaction behavior of titanium alloys in ultra-precision machining(UPM) was also revealed in this study, it showed that the ductile to brittle transaction behavior of titanium alloys occurred mainly at relatively small depth of cut. The study firstly defines the ductile to brittle transition behavior of titanium alloys in UPM, contributing the information of ductile machining as an optimal machining condition for precise productions of titanium alloys.

Surface Mechanoengineering of a Zr-based Bulk Metallic Glass via Ar-Nanobubble Doping to Probe Cell Sensitivity to Rigid Materials

DOE PAGES

Huang, Lu; Tian, Mengkun; Wu, Dong; ...

2017-11-24

In this paper, a new materials platform, utilizing the amorphous microstructure of bulk metallic glasses (BMGs) and the versatility of ion implantation, was developed for the fundamental investigation of cell responses to substrate-rigidity variations in the gigapascal modulus range, which was previously unattainable with polymeric materials. The surface rigidity of a Zr-Al- Ni-Cu-Y BMG was modulated with low-energy Ar-ion implantation owing to the impartment of Ar nanobubbles into the amorphous matrix. Surface softening was achieved due to the formation of nanobubble-doped transitional zones in the Zrbased BMG substrate. Bone-forming cell studies on this newly designed platform demonstrated that mechanical cues,more » accompanied with the potential effects of other surface properties (i.e. roughness, morphology, and chemistry), contributed to modulating cell behaviors. Cell adhesion and actin filaments were found to be less established on less stiff surfaces, especially on the surface with an elastic modulus of 51 GPa. Cell growth appeared to be affected by surface mechanical properties. A lower stiffness was generally related to a higher growth rate. Findings in this study broadened our fundamental understanding concerning the mechanosensing of bone cells on stiff substrates. It also suggests that surface mechano-engineering of metallic materials could be a potential strategy to promote osseointegration of such materials for bone-implant applications. Further investigations are proposed to fine tune the ion implantation variables in order to further distinguish the surface-mechanical effect on bone-forming cell activities from the contributions of other surface properties.« less

Surface Mechanoengineering of a Zr-based Bulk Metallic Glass via Ar-Nanobubble Doping to Probe Cell Sensitivity to Rigid Materials

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

Huang, Lu; Tian, Mengkun; Wu, Dong

In this paper, a new materials platform, utilizing the amorphous microstructure of bulk metallic glasses (BMGs) and the versatility of ion implantation, was developed for the fundamental investigation of cell responses to substrate-rigidity variations in the gigapascal modulus range, which was previously unattainable with polymeric materials. The surface rigidity of a Zr-Al- Ni-Cu-Y BMG was modulated with low-energy Ar-ion implantation owing to the impartment of Ar nanobubbles into the amorphous matrix. Surface softening was achieved due to the formation of nanobubble-doped transitional zones in the Zrbased BMG substrate. Bone-forming cell studies on this newly designed platform demonstrated that mechanical cues,more » accompanied with the potential effects of other surface properties (i.e. roughness, morphology, and chemistry), contributed to modulating cell behaviors. Cell adhesion and actin filaments were found to be less established on less stiff surfaces, especially on the surface with an elastic modulus of 51 GPa. Cell growth appeared to be affected by surface mechanical properties. A lower stiffness was generally related to a higher growth rate. Findings in this study broadened our fundamental understanding concerning the mechanosensing of bone cells on stiff substrates. It also suggests that surface mechano-engineering of metallic materials could be a potential strategy to promote osseointegration of such materials for bone-implant applications. Further investigations are proposed to fine tune the ion implantation variables in order to further distinguish the surface-mechanical effect on bone-forming cell activities from the contributions of other surface properties.« less

Reasons for Placement of Restorations on Previously Unrestored Tooth Surfaces by Dental PBRN Dentists

PubMed Central

Nascimento, Marcelle M.; Gordan, Valeria V.; Qvist, Vibeke; Litaker, Mark S.; Rindal, D. Brad; Williams, O.D.; Fellows, Jeffrey L.; Ritchie, Lloyd K.; Mjör, Ivar A.; McClelland, Jocelyn; Gilbert, Gregg H.

2010-01-01

Objective To identify and quantify the reasons for placing restorations on unrestored permanent tooth surfaces and the dental materials used by Dental Practice-Based Research Network (DPBRN; www.DentalPBRN.org) dentists. Methods A total of 229 DPBRN practitioner-investigators collected data on 9,890 consecutive restorations from 5,810 patients. Information included: (1) reasons for restoring; (2) tooth and surfaces restored; and (3) restorative materials employed. Results Primary caries (85%) and non-carious defects (15%), which included abrasion/ abfraction/ erosion lesions and tooth fracture, were the main reasons for placement of restorations. Restorations due to caries were frequently placed on occlusal surfaces (49%), followed by distal, mesial, buccal/facial, lingual/palatal, and incisal surfaces. Amalgam was used for 46% of the molar and 45% of the premolar restorations. Directly placed resin-based composite (RBC) was used for 48% of the molar, 49% of the premolar, and 92% of the anterior restorations. Conclusion Dental caries on occlusal and proximal surfaces of molar teeth are the main reasons for placing restorations on previously unrestored tooth surfaces by DPBRN practitioner-investigators. RBC is the material most commonly used for occlusal and anterior restorations. Amalgam remains the material of choice to restore proximal caries in posterior teeth, although there are significant differences by DPBRN region. PMID:20354094

Molecular dynamics simulations of hydrogen bombardment of tungsten carbide surfaces

NASA Astrophysics Data System (ADS)

Träskelin, P.; Juslin, N.; Erhart, P.; Nordlund, K.

2007-05-01

The interaction between energetic hydrogen and tungsten carbide (WC) is of interest both due to the use of hydrogen-containing plasmas in thin-film manufacturing and due to the presence of WC in the divertor of fusion reactors. In order to study this interaction, we have carried out molecular dynamics simulations of the low-energy bombardment of deuterium impinging onto crystalline as well as amorphous WC surfaces. We find that prolonged bombardment leads to the formation of an amorphous WC surface layer, regardless of the initial structure of the WC sample. Loosely bound hydrocarbons, which can erode by swift chemical sputtering, are formed at the surface. Carbon-terminated surfaces show larger sputtering yields than tungsten-terminated surfaces. In both cumulative and noncumulative simulations, C is seen to sputter preferentially. Implications for mixed material erosion in ITER are discussed.

Analysis of Helium Segregation on Surfaces of Plasma-Exposed Tungsten

NASA Astrophysics Data System (ADS)

Maroudas, Dimitrios; Hu, Lin; Hammond, Karl; Wirth, Brian

2015-11-01

We report a systematic theoretical and atomic-scale computational study of implanted helium segregation on surfaces of tungsten, which is considered as a plasma facing component in nuclear fusion reactors. We employ a hierarchy of atomic-scale simulations, including molecular statics to understand the origin of helium surface segregation, targeted molecular-dynamics (MD) simulations of near-surface cluster reactions, and large-scale MD simulations of implanted helium evolution in plasma-exposed tungsten. We find that small, mobile helium clusters (of 1-7 He atoms) in the near-surface region are attracted to the surface due to an elastic interaction force. This thermodynamic driving force induces drift fluxes of these mobile clusters toward the surface, facilitating helium segregation. Moreover, the clusters' drift toward the surface enables cluster reactions, most importantly trap mutation, at rates much higher than in the bulk material. This cluster dynamics has significant effects on the surface morphology, near-surface defect structures, and the amount of helium retained in the material upon plasma exposure.

An Integrated Tool for the Coupled Thermal and Mechanical Analysis of Pyrolyzing Heatshield Materials

NASA Technical Reports Server (NTRS)

Pronchick, Stephen W.

1998-01-01

Materials that pyrolyze at elevated temperature have been commonly used as thermal protection materials in hypersonic flight, and advanced pyrolyzing materials for this purpose continue to be developed. Because of the large temperature gradients that can arise in thermal protection materials, significant thermal stresses can develop. Advanced applications of pyrolytic materials are calling for more complex heatshield configurations, making accurate thermal stress analysis more important, and more challenging. For non-pyrolyzing materials, many finite element codes are available and capable of performing coupled thermal-mechanical analyses. These codes do not, however, have a built-in capability to perform analyses that include pyrolysis effects. When a pyrolyzing material is heated, one or more components of the original virgin material pyrolyze and create a gas. This gas flows away from the pyrolysis zone to the surface, resulting in a reduction in surface heating. A porous residue, referred to as char, remains in place of the virgin material. While the processes involved can be complex, it has been found that a simple physical model in which virgin material reacts to form char and pyrolysis gas, will yield satisfactory analytical results. Specifically, the effects that must be modeled include: (1) Variation of thermal properties (density, specific heat, thermal conductivity) as the material composition changes; (2) Energy released or absorbed by the pyrolysis reactions; (3) Energy convected by the flow of pyrolysis gas from the interior to the surface; (4) The reduction in surface heating due to surface blowing; and (5) Chemical and mass diffusion effects at the surface between the pyrolysis gas and edge gas Computational tools for the one-dimensional thermal analysis these materials exist and have proven to be reliable design tools. The objective of the present work is to extend the analysis capabilities of pyrolyzing materials to axisymmetric configurations, and to couple thermal and mechanical analyses so that thermal stresses may be efficiently and accurately calculated.

Optimization of Machining Process Parameters for Surface Roughness of Al-Composites

NASA Astrophysics Data System (ADS)

Sharma, S.

2013-10-01

Metal matrix composites (MMCs) have become a leading material among the various types of composite materials for different applications due to their excellent engineering properties. Among the various types of composites materials, aluminum MMCs have received considerable attention in automobile and aerospace applications. These materials are known as the difficult-to-machine materials because of the hardness and abrasive nature of reinforcement element-like silicon carbide particles. In the present investigation Al-SiC composite was produced by stir casting process. The Brinell hardness of the alloy after SiC addition had increased from 74 ± 2 to 95 ± 5 respectively. The composite was machined using CNC turning center under different machining parameters such as cutting speed (S), feed rate (F), depth of cut (D) and nose radius (R). The effect of machining parameters on surface roughness (Ra) was studied using response surface methodology. Face centered composite design with three levels of each factor was used for surface roughness study of the developed composite. A response surface model for surface roughness was developed in terms of main factors (S, F, D and R) and their significant interactions (SD, SR, FD and FR). The developed model was validated by conducting experiments under different conditions. Further the model was optimized for minimum surface roughness. An error of 3-7 % was observed in the modeled and experimental results. Further, it was fond that the surface roughness of Al-alloy at optimum conditions is lower than that of Al-SiC composite.

Milling induced amorphisation and recrystallization of α-lactose monohydrate.

PubMed

Badal Tejedor, Maria; Pazesh, Samaneh; Nordgren, Niklas; Schuleit, Michael; Rutland, Mark W; Alderborn, Göran; Millqvist-Fureby, Anna

2018-02-15

Preprocessing of pharmaceutical powders is a common procedure to condition the materials for a better manufacturing performance. However, such operations may induce undesired material properties modifications when conditioning particle size through milling, for example. Modification of both surface and bulk material structure will change the material properties, thus affecting the processability of the powder. Hence it is essential to control the material transformations that occur during milling. Topographical and mechanical changes in surface properties can be a preliminary indication of further material transformations. Therefore a surface evaluation of the α-lactose monohydrate after short and prolonged milling times has been performed. Unprocessed α-lactose monohydrate and spray dried lactose were evaluated in parallel to the milled samples as reference examples of the crystalline and amorphous lactose structure. Morphological differences between unprocessed α-lactose, 1 h and 20 h milled lactose and spray dried lactose were detected from SEM and AFM images. Additionally, AFM was used to simultaneously characterize particle surface amorphicity by measuring energy dissipation. Extensive surface amorphicity was detected after 1 h of milling while prolonged milling times showed only a moderate particle surface amorphisation. Bulk material characterization performed with DSC indicated a partial amorphicity for the 1 h milled lactose and a fully amorphous thermal profile for the 20 h milled lactose. The temperature profiles however, were shifted somewhat in the comparison to the amorphous reference, particularly after extended milling, suggesting a different amorphous state compared to the spray-dried material. Water loss during milling was measured with TGA, showing lower water content for the lactose amorphized through milling compared to spray dried amorphous lactose. The combined results suggest a surface-bulk propagation of the amorphicity during milling in combination with a different amorphous structural conformation to that of the amorphous spray dried lactose. The hardened surface may be due to either surface crystallization of lactose or to formation of a low-water glass transition. Copyright © 2017 Elsevier B.V. All rights reserved.

Flow accelerated corrosion of carbon steel feeder pipes from pressurized heavy water reactors

NASA Astrophysics Data System (ADS)

Singh, J. L.; Kumar, Umesh; Kumawat, N.; Kumar, Sunil; Kain, Vivekanand; Anantharaman, S.; Sinha, A. K.

2012-10-01

Detailed investigation of a number of feeder pipes received from Rajasthan Atomic Power Station Unit 2 (RAPS#2) after en-masse feeder pipe replacement after 15.67 Effective Full Power Years (EFPYs) was carried out. Investigations included ultrasonic thickness measurement by ultrasonic testing, optical microscopy, scanning electron microscopy, chemical analysis and X-ray Diffraction (XRD). Results showed that maximum thickness reduction of the feeder had occurred downstream and close to the weld in 32 NB (1.25″/32.75 mm ID) elbows. Rate of Flow Accelerated Corrosion (FAC) was measured to be higher in the lower diameter feeder pipes due to high flow velocity and turbulence. Weld regions had thinned to a lower extent than the parent material due to higher chromium content in the weld. A weld protrusion has been shown to add to the thinning due to FAC and lead to faster thinning rate at localized regions. Surface morphology of inner surface of feeder had shown different size scallop pattern over the weld and parent material. Inter-granular cracks were also observed along the weld fusion line and in the parent material in 32 NB outlet feeder elbow.

Influence of laser irradiation on deposition characteristics of cold sprayed Stellite-6 coatings

NASA Astrophysics Data System (ADS)

Li, Bo; Jin, Yan; Yao, Jianhua; Li, Zhihong; Zhang, Qunli; Zhang, Xin

2018-03-01

Depositing hard materials such as Stellite-6 solely by cold spray (CS) is challengeable due to limited ability of plastic deformation. In this study, the deposition of Stellite-6 powder was achieved by supersonic laser deposition (SLD) which combines CS with synchronous laser irradiation. The surface morphology, deposition efficiency, track shape of Stellite-6 coatings produced over a range of laser irradiation temperatures were examined so as to reveal the effects of varying laser energy inputting on the deposition process of high strength material. The microstructure, phase composition and wear/corrosion resistant properties of the as-deposited Stellite-6 coatings were also investigated. The experimental results demonstrate that the surface flatness and deposition efficiency increase with laser irradiation temperature due to the softening effect induced by laser heating. The as-deposited Stellite-6 tracks show asymmetric shapes which are influenced by the relative configuration of powder stream and laser beam. The SLD coatings can preserve the original microstructure and phase of the feedstock material due to relatively low laser energy inputting, which result in the superior wear/corrosion resistant properties as compared to the counterpart prepared by laser cladding.

Terahertz Characterization of DNA: Enabling a Novel Approach

DTIC Science & Technology

2015-11-01

DNA in a more reliable and less procedurally complicated manner. The method involves the use of terahertz surface plasmon generated on the surface of...advantages are due to overlapping resonance when the plasmon frequency generated by a foil coincides with that of the biological material. The...interference of the impinging terahertz wave and surface plasmon produces spectral graphs, which can be analyzed to identify and characterize a DNA sample

Bioactivity of plasma implanted biomaterials

NASA Astrophysics Data System (ADS)

Chu, Paul K.

2006-01-01

Plasma immersion ion implantation and deposition (PIII&D) is an effective technique to enhance the surface bioactivity of materials. In this paper, recent progress made in our laboratory on plasma surface modification of biomedical materials is described. NiTi alloys have unique super-elastic and shape memory properties and are suitable for orthopedic implants but the leaching of toxic Ni may pose health hazards in humans. We have recently investigated the use of acetylene, oxygen and nitrogen PIII&D to prevent out-diffusion of nickel and good results have been obtained. Silicon is the most important material in the microelectronics industry but its surface biocompatibility has not been investigated in details. We have recently performed hydrogen PIII into silicon to improve the surface bioactivity and observed biomimetic growth of apatite on the surface in simulated body fluids. Diamond-like carbon (DLC) is widely used in the industry due to its excellent mechanical properties and chemical inertness and by incorporation of elements such as nitrogen and phosphorus, the surface blood compatibility can be improved. The properties as well as in vitro biological test results are discussed in this article.

Analysis of Viking infrared thermal mapping data of Mars. The effects of non-ideal surfaces on the derived thermal properties of Mars

NASA Technical Reports Server (NTRS)

Muhleman, D. O.; Jakosky, B. M.

1979-01-01

The thermal interia of the surface of Mars varies spatially by a factor of eight. This is attributable to changes in the average particle size of the fine material, the surface elevation, the atmospheric opacity due to dust, and the fraction of the surface covered by rocks and fine material. The effects of these non-ideal properties on the surface temperatures and derived thermal inertias are modeled, along with the the effects of slopes, CO2 condensed onto the surface, and layering of fine material upon solid rock. The non-ideal models are capable of producing thermal behavior similar to that observed by the Viking Infrared Thermal Mapper, including a morning delay in the post-dawn temperature rise and an enhanced cooling in the afternoon relative to any ideal, homogeneous model. The enhanced afternoon cooling observed at the Viking-1 landing site is reproduced by the non-ideal models while that atop Arsia Mons volcano is not, but may be attributed to the observing geometry.

pH-dependent surface charging and points of zero charge. IV. Update and new approach.

PubMed

Kosmulski, Marek

2009-09-15

The recently published points of zero charge (PZC) and isoelectric points (IEPs) of various materials are compiled to update the previous compilation [M. Kosmulski, Surface Charging and Points of Zero Charge, CRC Press, Boca Raton, FL, 2009]. Unlike in previous compilations by the same author [Chemical Properties of Material Surfaces, Dekker, New York, 2001; J. Colloid Interface Sci. 253 (2002) 77; J. Colloid Interface Sci. 275 (2004) 214; J. Colloid Interface Sci. 298 (2006) 730], the materials are sorted not only by the chemical formula, but also by specific product, that is, by brand name (commercially available materials), and by recipe (home-synthesized materials). This new approach indicated that the relatively consistent PZC/IEP reported in the literature for materials having the same chemical formula are due to biased choice of specimens to be studied. Specimens which have PZC/IEP close to the "recommended" value are selected more often than other specimens (PZC/IEP not reported before or PZC/IEP reported, but different from the "recommended" value). Thus, the previously published PZC/IEP act as a self-fulfilling prophecy.

Electrochemical and in vitro behavior of the nanosized composites of Ti-6Al-4V and TiO2 fabricated by friction stir process

NASA Astrophysics Data System (ADS)

Zhang, Chengjian; Ding, Zihao; Xie, Lechun; Zhang, Lai-Chang; Wu, Laizhi; Fu, Yuanfei; Wang, Liqiang; Lu, Weijie

2017-11-01

Although Ti-6Al-4V has been widely used in biomaterial field. Compared with other classes of materials, it still encounters some problems such as low surface hardness and relative low biocompatibility. To solve these problems friction stir processing (FSP) was applied to fabricate a nanosized composite layer of TiO2 and Ti-6Al-4V. Uniform distribution of TiO2 particles with some clusters on the surface of alloy can be observed. Due to severe plastic deformation and stirring heat, nanocrystallines and amorphous TiO2 can be observed in stir zone. FSPed samples show significant improvement in surface microhardness and biocompatibility due to its modified structure compared with original sample. In addition, through corrosion behaviors of the samples in simulated body fluid, it is found that FSP can enhance whilst TiO2 reduces the possibility and corrosion rate of material in environment of human body.

Atomic Scale Understanding of Poly-Si/SiO2/c-Si Passivated Contacts: Passivation Degradation Due to Metallization

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

Aguiar, Jeffery A.; Young, David; Lee, Benjamin

2016-11-21

The key attributes for achieving high efficiency crystalline silicon solar cells include class leading developments in the ability to approach the theoretical limits of silicon solar technology (29.4% efficiency). The push for high efficiency devices is further compounded with the clear need for passivation to reduce recombination at the metal contacts. At the same time there is stringent requirement to retain the same material device quality, surface passivation, and performance characteristics following subsequent processing. The development of passivated silicon cell structures that retain active front and rear surface passivation and overall material cell quality is therefore a relevant and activemore » area of development. To address the potential outcomes of metallization on passivated silicon stack, we report on some common microstructural features of degradation due to metallization for a series of silicon device stacks. A fundamental materials understanding of the metallization process on retaining high-efficiency passivated Si devices is therefore gained over these series of results.« less

Jet blown PTFE for control of biocompatibility

NASA Astrophysics Data System (ADS)

Leibner, Evan Scott

The development of fully hemocompatible cardiovascular biomaterials will have a major impact on the practice of modern medicine. Current artificial surfaces, unlike native vascular surfaces, are not able to control clot and thrombus formation. Protein interactions are an important component in hemocompatibility and can result in decreased patency due to thrombus formation or surface passivation which can improve endothelization. It is believed that controlling these properties, specifically the nanometer sizes of the fibers on the material's surface, will allow for better control of biological responses. The biocompatibility of Teflon, a widely used polymer for vascular grafts, would be improved with nanostructured control of surface features. Due to the difficultly in processing polytetrafluoroethylene (PTFE), it has not been possible to create nanofibrous PTFE surfaces. The novel technique of Jet Blowing allows for the formation of nanostructured PTFE (nPTFE). A systematic investigation into controlling polymer properties by varying the processing conditions of temperature, pressure, and gas used in the Jet Blowing allows for an increased understanding of the effects of plasticization on the material's properties. This fundamental understanding of the material science behind the Jet Blowing process has enabled control of the micro and nanoscale structure of nPTFE. While protein adsorption, a key component of biocompatibility, has been widely studied, it is not fully understood. Major problems in the field of biomaterials include a lack of standard protocols to measure biocompatibility, and inconstant literature on protein adsorption. A reproducible protocol for measuring protein adsorption onto superhydrophobic surfaces (ePTFE and nPTFE) has been developed. Both degassing of PBS buffer solutions and evacuation of the air around the expanded PTFE (ePTFE) prior to contact with protein solutions are essential. Protein adsorption experiments show a four-fold difference in the measure of proteins adsorbed using radiometry (I-125 labeled human serum albumin (HSA)) and electrophoresis (unlabeled HSA). This provides evidence that the standard method of radiolabeled protein for measuring adsorption does not fully account for changes to the HSA molecules due to labeling. The differences between measured protein values can be attributed to the radiolabel affecting the HSA hydrophobicity resulting in a change in the protein's interactions with the hydrophobic surface. Additionally, our work has provided repeatable results showing that the amount of protein adsorbed onto the polymer surface, after washing, accounted for only 65% of the amount of protein that was removed from solution based on depletion analysis. This implies that measurement of the amount of strongly bound protein on the material significantly underestimates the actual amount of protein adsorbing into the surface region of the material interface. HSA adsorption isotherms demonstrate an increase in protein adsorption capacity on the nPTFE surface compared to adsorption on the same surface area of ePTFE. Preliminary cell work shows that the nPTFE surfaces had a larger number of cells growing on the surface of the material when compared to ePTFE surfaces. The research also shows that while most endothelial cells were not viable on the ePTFE surface after 96 hours, they remained alive on the nPTFE surface during that same time period. Surface functionalization using ammonia plasma has been performed. X-ray photoelectron spectroscopy (XPS) analysis revealed the presence of amine groups on the nPTFE surface. The amine groups can be used to couple polypeptides onto the PTFE surface in the future. The selection of different peptides will allow for selective control of cell adhesion. This research shows that nPTFE has potential for improved biocompatibility over standard ePTFE, based on increased protein adsorption capacity, increased viability of endothelial cells, and the ability to plasma modify the PTFE surface.

Deformation and relaxation of an incompressible viscoelastic body with surface viscoelasticity

NASA Astrophysics Data System (ADS)

Liu, Liping; Yu, Miao; Lin, Hao; Foty, Ramsey

2017-01-01

Measuring mechanical properties of cells or cell aggregates has proven to be an involved process due to their geometrical and structural complexity. Past measurements are based on material models that completely neglect the elasticity of either the surface membrane or the interior bulk. In this work, we consider general material models to account for both surface and bulk viscoelasticity. The boundary value problems are formulated for deformations and relaxations of a closed viscoelastic surface coupled with viscoelastic media inside and outside of the surface. The linearized surface elasticity models are derived for the constant surface tension model and the Helfrich-Canham bending model for coupling with the bulk viscoelasticity. For quasi-spherical surfaces, explicit solutions are obtained for the deformation, stress-strain and relaxation behaviors under a variety of loading conditions. These solutions can be applied to extract the intrinsic surface and bulk viscoelastic properties of biological cells or cell aggregates in the indentation, electro-deformation and relaxation experiments.

Graphite intercalated polyaniline composite with superior anticorrosive and hydrophobic properties, as protective coating material on steel surfaces

NASA Astrophysics Data System (ADS)

Rathnayake, R. M. N. M.; Mantilaka, M. M. M. G. P. G.; Hara, Masanori; Huang, Hsin-Hui; Wijayasinghe, H. W. M. A. C.; Yoshimura, Masamichi; Pitawala, H. M. T. G. A.

2017-07-01

Solid polymer composite systems are widely being used for potential technological applications in secondary energy sources and electrochromic devices. In this study, we synthesized and characterized a composite material composed of polyaniline (PANI) and natural needle platy (NPG) vein graphite. Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), cyclic voltammetry (CV), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), micro-Raman analysis, thermogravimetric and differential thermal analysis (TGA/DTA), transmission electron microscopy (TEM) were used to study the structural and electrochemical properties of the prepared PANI/NPG graphite composite. XPS, FTIR, and micro-Raman analysis confirmed the existence of relevant functional groups and bonding in the prepared PANI/NPG composite material. The composite shows a very low corrosion rate, approximately 29 μm per year, and high hydrophobicity on steel surfaces, which helps to prevent the corrosion due to O2 penetration towards the metal surface. It indicates that the composite can be used as a high potential surface coating material to anticorrosion. The specific capacitance of PANI/NPG composite is 833.3 F g-1, which is higher than that of PANI. This synergistic electrical performance result proves the prepared PANI/NPG graphite composite as a suitable protective coating material for steel surfaces.

Cavitation Erosion in Hydraulic Turbine Components and Mitigation by Coatings: Current Status and Future Needs

NASA Astrophysics Data System (ADS)

Singh, Raghuvir; Tiwari, S. K.; Mishra, Suman K.

2012-07-01

Cavitation erosion is a frequently observed phenomenon in underwater engineering materials and is the primary reason for component failure. The damage due to cavitation erosion is not yet fully understood, as it is influenced by several parameters, such as hydrodynamics, component design, environment, and material chemistry. This article gives an overview of the current state of understanding of cavitation erosion of materials used in hydroturbines, coatings and coating methodologies for combating cavitation erosion, and methods to characterize cavitation erosion. No single material property fully characterizes the resistance to cavitation erosion. The combination of ultimate resilience, hardness, and toughness rather may be useful to estimate the cavitation erosion resistance of material. Improved hydrodynamic design and appropriate surface engineering practices reduce damage due to cavitation erosion. The coatings suggested for combating the cavitation erosion encompasses carbides (WC Cr2C3, Cr3C2, 20CrC-80WC), cermets of different compositions (e.g., 56W2C/Ni/Cr, 41WC/Ni/Cr/Co), intermetallic composites, intermetallic matrix composites with TiC reinforcement, composite nitrides such as TiAlN and elastomers. A few of them have also been used commercially. Thermal spraying, arc plasma spraying, and high velocity oxy-fuel (HVOF) processes have been used commercially to apply the coatings. Boronizing, laser surface hardening and cladding, chemical vapor deposition, physical vapor deposition, and plasma nitriding have been tried for surface treatments at laboratory levels and have shown promise to be used on actual components.

Metal-organic frameworks for lithium ion batteries and supercapacitors

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

Ke, Fu-Sheng; Wu, Yu-Shan; Deng, Hexiang, E-mail: hdeng@whu.edu.cn

2015-03-15

Porous materials have been widely used in batteries and supercapacitors attribute to their large internal surface area (usually 100–1000 m{sup 2} g{sup −1}) and porosity that can favor the electrochemical reaction, interfacial charge transport, and provide short diffusion paths for ions. As a new type of porous crystalline materials, metal-organic frameworks (MOFs) have received huge attention in the past decade due to their unique properties, i.e. huge surface area (up to 7000 m{sup 2} g{sup −1}), high porosity, low density, controllable structure and tunable pore size. A wide range of applications including gas separation, storage, catalysis, and drug delivery benefitmore » from the recent fast development of MOFs. However, their potential in electrochemical energy storage has not been fully revealed. Herein, the present mini review appraises recent and significant development of MOFs and MOF-derived materials for rechargeable lithium ion batteries and supercapacitors, to give a glimpse into these potential applications of MOFs. - Graphical abstract: MOFs with large surface area and high porosity can offer more reaction sites and charge carriers diffusion path. Thus MOFs are used as cathode, anode, electrolyte, matrix and precursor materials for lithium ion battery, and also as electrode and precursor materials for supercapacitors. - Highlights: • MOFs have potential in electrochemical area due to their high porosity and diversity. • We summarized and compared works on MOFs for lithium ion battery and supercapacitor. • We pointed out critical challenges and provided possible solutions for future study.« less

Material removal and surface figure during pad polishing of fused silica

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

Suratwala, T I; Feit, M D; Steele, W A

2009-05-04

The material removal and surface figure after ceria pad polishing of fused silica glass have been measured and analyzed as a function of kinematics, loading conditions, and polishing time. Also, the friction at the workpiece/lap interface, the slope of the workpiece relative to the lap plane, and lap viscoelastic properties have been measured and correlated to material removal. The results show that the relative velocity between the workpiece & lap (determined by the kinematics) and the pressure distribution determine the spatial and temporal material removal and hence the final surface figure of the workpiece. In the case where the appliedmore » loading and relative velocity distribution over the workpiece are spatially uniform, a significant non-uniform spatial material removal from the workpiece surface is observed. This is due to a non-uniform pressure distribution resulting from: (1) a moment caused by a pivot point and interface friction forces; (2) viscoelastic relaxation of the polyurethane lap; and (3) a physical workpiece/lap interface mismatch. Both the kinematics and these contributions to the pressure distribution are quantitatively described, and then combined to form a spatial and temporal Preston model & code for material removal (called Surface Figure or SurF{copyright}). The surface figure simulations are consistent with the experiment for a wide variety of polishing conditions. This study is an important step towards deterministic full-aperture polishing, which would allow optical glass fabrication to be performed in a more repeatable, less iterative, and hence more economical manner.« less

Mechanic and surface properties of central-venous port catheters after removal: A comparison of polyurethane and silicon rubber materials.

PubMed

Braun, Ulrike; Lorenz, Edelgard; Weimann, Christiane; Sturm, Heinz; Karimov, Ilham; Ettl, Johannes; Meier, Reinhard; Wohlgemuth, Walter A; Berger, Hermann; Wildgruber, Moritz

2016-12-01

Central venous port devices made of two different polymeric materials, thermoplastic polyurethane (TPU) and silicone rubber (SiR), were compared due their material properties. Both naïve catheters as well as catheters after removal from patients were investigated. In lab experiments the influence of various chemo-therapeutic solutions on material properties was investigated, whereas the samples after removal were compared according to the implanted time in patient. The macroscopic, mechanical performance was assessed with dynamic, specially adapted tests for elasticity. The degradation status of the materials was determined with common tools of polymer characterisation, such as infrared spectroscopy, molecular weight measurements and various methods of thermal analysis. The surface morphology was analysed using scanning electron microscopy. A correlation between material properties and clinical performance was proposed. The surface morphology and chemical composition of the polyurethane catheter materials can potentially result in increased susceptibility of the catheter to bloodstream infections and thrombotic complications. The higher mechanic failure, especially with increasing implantation time of the silicone catheters is related to the lower mechanical performance compared to the polyurethane material as well as loss of barium sulphate filler particles near the surface of the catheter. This results in preformed microscopic notches, which act as predetermined sites of fracture. Copyright © 2016 Elsevier Ltd. All rights reserved.

Constraining the physical properties of compositionally distinctive surfaces on Mars from overlapping THEMIS observations

NASA Astrophysics Data System (ADS)

Ahern, A.; Rogers, D.

2017-12-01

Better constraints on the physical properties (e.g. grain size, rock abundance, cohesion, porosity and amount of induration) of Martian surface materials can lead to greater understanding of outcrop origin (e.g. via sedimentary, effusive volcanic, pyroclastic processes). Many outcrop surfaces on Mars likely contain near-surface (<3 cm) vertical heterogeneity in physical properties due to thin sediment cover, induration, and physical weathering, that can obscure measurement of the bulk thermal conductivity of the outcrop materials just below. Fortunately, vertical heterogeneity within near-surface materials can result in unique, and possibly predictable, diurnal and seasonal temperature patterns. The KRC thermal model has been utilized in a number of previous studies to predict thermal inertia of surface materials on Mars. Here we use KRC to model surface temperatures from overlapping Mars Odyssey THEMIS surface temperature observations that span multiple seasons and local times, in order to constrain both the nature of vertical heterogeneity and the underlying outcrop thermal inertia for various spectrally distinctive outcrops on Mars. We utilize spectral observations from TES and CRISM to constrain the particle size of the uppermost surface. For this presentation, we will focus specifically on chloride-bearing units in Terra Sirenum and Meridiani Planum, as well as mafic and feldspathic bedrock locations with distinct spectral properties, yet uncertain origins, in Noachis Terra and Nili Fossae. We find that many of these surfaces exhibit variations in apparent thermal inertia with season and local time that are consistent with low thermal inertia materials overlying higher thermal inertia substrates. Work is ongoing to compare surface temperature measurements with modeled two-layer scenarios in order to constrain the top layer thickness and bottom layer thermal inertia. The information will be used to better interpret the origins of these distinctive outcrops.

Physicochemical properties affect the synthesis, controlled delivery, degradation and pharmacokinetics of inorganic nanoporous materials.

PubMed

Yazdi, Iman K; Ziemys, Arturas; Evangelopoulos, Michael; Martinez, Jonathan O; Kojic, Milos; Tasciotti, Ennio

2015-10-01

Controlling size, shape and uniformity of porous constructs remains a major focus of the development of porous materials. Over the past two decades, we have seen significant developments in the fabrication of new, porous-ordered structures using a wide range of materials, resulting in properties well beyond their traditional use. Porous materials have been considered appealing, due to attractive properties such as pore size length, morphology and surface chemistry. Furthermore, their utilization within the life sciences and medicine has resulted in significant developments in pharmaceutics and medical diagnosis. This article focuses on various classes of porous materials, providing an overview of principle concepts with regard to design and fabrication, surface chemistry and loading and release kinetics. Furthermore, predictions from a multiscale mathematical model revealed the role pore length and diameter could have on payload release kinetics.

Fracture Surface Morphology and Impact Strength of Cellulose/PLA Composites.

PubMed

Gao, Honghong; Qiang, Tao

2017-06-07

Polylactide (PLA)-based composite materials reinforced with ball-milled celluloses were manufactured by extrusion blending followed by injection molding. Their surface morphology from impact fracture were imaged with scanning electron microscopy (SEM) and investigated by calculating their fractal dimensions. Then, linear regression was used to explore the relationship between fractal dimension and impact strength of the resultant cellulose/PLA composite materials. The results show that filling the ball-milled celluloses into PLA can improve the impact toughness of PLA by a minimum of 38%. It was demonstrated that the fracture pattern of the cellulose/PLA composite materials is different from that of pristine PLA. For the resultant composite materials, the fractal dimension of the impact fractured surfaces increased with increasing filling content and decreasing particle size of the ball-milled cellulose particles. There were highly positive correlations between fractal dimension of the fractured surfaces and impact strength of the cellulose/PLA composites. However, the linearity between fractal dimension and impact strength were different for the different methods, due to their different R-squared values. The approach presented in this work will help to understand the structure-property relationships of composite materials from a new perspective.

Fracture Surface Morphology and Impact Strength of Cellulose/PLA Composites

PubMed Central

Gao, Honghong; Qiang, Tao

2017-01-01

Polylactide (PLA)-based composite materials reinforced with ball-milled celluloses were manufactured by extrusion blending followed by injection molding. Their surface morphology from impact fracture were imaged with scanning electron microscopy (SEM) and investigated by calculating their fractal dimensions. Then, linear regression was used to explore the relationship between fractal dimension and impact strength of the resultant cellulose/PLA composite materials. The results show that filling the ball-milled celluloses into PLA can improve the impact toughness of PLA by a minimum of 38%. It was demonstrated that the fracture pattern of the cellulose/PLA composite materials is different from that of pristine PLA. For the resultant composite materials, the fractal dimension of the impact fractured surfaces increased with increasing filling content and decreasing particle size of the ball-milled cellulose particles. There were highly positive correlations between fractal dimension of the fractured surfaces and impact strength of the cellulose/PLA composites. However, the linearity between fractal dimension and impact strength were different for the different methods, due to their different R-squared values. The approach presented in this work will help to understand the structure–property relationships of composite materials from a new perspective. PMID:28772983

Surface modifications on InAs decrease indium and arsenic leaching under physiological conditions

NASA Astrophysics Data System (ADS)

Jewett, Scott A.; Yoder, Jeffrey A.; Ivanisevic, Albena

2012-11-01

Devices containing III-V semiconductors such as InAs are increasingly being used in the electronic industry for a variety of optoelectronic applications. Furthermore, the attractive chemical, material, electronic properties make such materials appealing for use in devices designed for biological applications, such as biosensors. However, in biological applications the leaching of toxic materials from these devices could cause harm to cells or tissue. Additionally, after disposal, toxic inorganic materials can leach from devices and buildup in the environment, causing long-term ecological harm. Therefore, the toxicity of these materials along with their stability in physiological conditions are important factors to consider. Surface modifications are one common method of stabilizing semiconductor materials in order to chemically and electronically passivate them. Such surface modifications could also prevent the leaching of toxic materials by preventing the regrowth of the unstable surface oxide layer and by creating an effective barrier between the semiconductor surface and the surrounding environment. In this study, various surface modifications on InAs are developed with the goal of decreasing the leaching of indium and arsenic. The leaching of indium and arsenic from modified substrates was assessed in physiological conditions using inductively coupled plasma mass spectrometry (ICP-MS). Substrates modified with 11-mercapto-1-undecanol (MU) and graft polymerized with poly(ethylene) glycol (PEG) were most effective at preventing indium and arsenic leaching. These surfaces were characterized using contact angle analysis, ellipsometry, atomic force microscopy (AFM), and X-ray photoelectron spectroscopy (XPS). Substrates modified with collagen and synthetic polyelectrolytes were least effective, due to the destructive nature of acidic environments on InAs. The toxicity of modified and unmodified InAs, along with raw indium, arsenic, and PEG components was assessed using zebrafish embryos.

United Kingdom Infrared Telescope's Spectrograph Observations of Human-Made Space Objects

NASA Technical Reports Server (NTRS)

Buckalew, Brent; Abercromby, Kira; Lederer, Susan; Frith, James; Cowardin, Heather

2017-01-01

Presented here are the results of the United Kingdom Infrared Telescope (UKIRT) spectral observations of human-made space objects taken from 2014 to 2015. The data collected using the UIST infrared spectrograph cover the wavelength range 0.7-2.5 micrometers. Overall, data were collected on 18 different orbiting objects at or near the geosynchronous (GEO) regime. Thirteen of the objects are spacecraft, one is a rocket body, and four are cataloged as debris pieces. The remotely collected data are compared to the laboratory-collected reflectance data on typical spacecraft materials; thereby general materials are identified but not specific types. These results highlight the usefulness of observations in the infrared by focusing on features from hydrocarbons and silicon. The spacecraft show distinct features due to the presence of solar panels. Signature variations between rocket bodies, due to the presence of various metals and paints on their surfaces, show a clear distinction from those objects with solar panels, demonstrating that one can distinguish most spacecraft from rocket bodies through infrared spectrum analysis. Finally, the debris pieces tend to show featureless, dark spectra. These results show that the laboratory data in its current state give excellent indications as to the nature of the surface materials on the objects. Further telescopic data collection and model updates to include more materials, noise, surface roughness, and material degradation are necessary to make better assessments of orbital object material types. A comparison conducted between objects observed previously with the NASA Infrared Telescope Facility (IRTF) shows similar materials and trends from the two telescopes and from the two distinct data sets. However, based on the current state of the model, infrared spectroscopic data are adequate to classify objects in GEO as spacecraft, rocket bodies, or debris.

Study of multiple hologram recording in lithium niobate

NASA Technical Reports Server (NTRS)

Gaylord, T. K.; Callen, W. R.

1974-01-01

The results of detailed experimental and theoretical considerations relating to multiple hologram recording in lithium niobate are reported. The following problem areas are identified and discussed: (1) the angular selectivity of the stored holograms, (2) interference effects due to the crystal surfaces, (3) beam divergence effects, (4) material recording sensitivity, and (5) scattered light from material inhomogeneities.

Strain characterization of embedded aerospace smart materials using shearography

NASA Astrophysics Data System (ADS)

Anisimov, Andrei G.; Müller, Bernhard; Sinke, Jos; Groves, Roger M.

2015-04-01

The development of smart materials for embedding in aerospace composites provides enhanced functionality for future aircraft structures. Critical flight conditions like icing of the leading edges can affect the aircraft functionality and controllability. Hence, anti-icing and de-icing capabilities are used. In case of leading edges made of fibre metal laminates heater elements can be embedded between composite layers. However this local heating causes strains and stresses in the structure due to the different thermal expansion coefficients of the different laminated materials. In order to characterize the structural behaviour during thermal loading full-field strain and shape measurement can be used. In this research, a shearography instrument with three spatially-distributed shearing cameras is used to measure surface displacement gradients which give a quantitative estimation of the in- and out-of-plane surface strain components. For the experimental part, two GLARE (Glass Laminate Aluminum Reinforced Epoxy) specimens with six different embedded copper heater elements were manufactured: two copper mesh shapes (straight and S-shape), three connection techniques (soldered, spot welded and overlapped) and one straight heater element with delaminations. The surface strain behaviour of the specimens due to thermal loading was measured and analysed. The comparison of the connection techniques of heater element parts showed that the overlapped connection has the smallest effect on the surface strain distribution. Furthermore, the possibility of defect detection and defect depth characterisation close to the heater elements was also investigated.

Fabrication and condensation characteristics of metallic superhydrophobic surface with hierarchical micro-nano structures

NASA Astrophysics Data System (ADS)

Chu, Fuqiang; Wu, Xiaomin

2016-05-01

Metallic superhydrophobic surfaces have various applications in aerospace, refrigeration and other engineering fields due to their excellent water repellent characteristics. This study considers a simple but widely applicable fabrication method using a two simultaneous chemical reactions method to prepare the acid-salt mixed solutions to process the metal surfaces with surface deposition and surface etching to construct hierarchical micro-nano structures on the surface and then modify the surface with low surface-energy materials. Al-based and Cu-based superhydrophobic surfaces were fabricated using this method. The Al-based superhydrophobic surface had a water contact angle of 164° with hierarchical micro-nano structures similar to the lotus leaves. The Cu-based surface had a water contact angle of 157° with moss-like hierarchical micro-nano structures. Droplet condensation experiments were also performed on these two superhydrophobic surfaces to investigate their condensation characteristics. The results show that the Al-based superhydrophobic surface has lower droplet density, higher droplet jumping probability, slower droplet growth rate and lower surface coverage due to the more structured hierarchical structures.

Thermal characteristics of carbon fiber reinforced epoxy containing multi-walled carbon nanotubes

NASA Astrophysics Data System (ADS)

Lee, Jin-woo; Park, Soo-Jeong; Kim, Yun-hae; Riichi-Murakami

2018-06-01

The material with irregular atomic structures such as polymer material exhibits low thermal conductivity because of the complex structural properties. Even materials with same atomic configurations, thermal conductivity may be different based on their structural properties. It is expected that nanoparticles with conductivity will change non-conductive polymer base materials to electrical conductors, and improve the thermal conductivity even with extremely small filling amount. Nano-composite materials contain nanoparticles with a higher surface ratio which makes the higher interface percentage to the total surface of nanoparticles. Therefore, thermal resistance of the interface becomes a dominating factor determines the effective thermal conductivity in nano-composite materials. Carbon fiber has characteristic of resistance or magnetic induction and Also, Carbon nanotube (CNT) has electronic and thermal property. It can be applied for heating system. These characteristic are used as heating composite. In this research, the exothermic characteristics of Carbon fiber reinforced composite added CNT were evaluated depend on CNT length and particle size. It was found that the CNT dispersed in the resin reduces the resistance between the interfaces due to the decrease in the total resistance of the heating element due to the addition of CNTs. It is expected to improve the life and performance of the carbon fiber composite material as a result of the heating element resulting from this paper.

Advances for the Topographic Characterisation of SMC Materials

PubMed Central

Calvimontes, Alfredo; Grundke, Karina; Müller, Anett; Stamm, Manfred

2009-01-01

For a comprehensive study of Sheet Moulding Compound (SMC) surfaces, topographical data obtained by a contact-free optical method (chromatic aberration confocal imaging) were systematically acquired to characterise these surfaces with regard to their statistical, functional and volumetrical properties. Optimal sampling conditions (cut-off length and resolution) were obtained by a topographical-statistical procedure proposed in the present work. By using different length scales specific morphologies due to the influence of moulding conditions, metallic mould topography, glass fibre content and glass fibre orientation can be characterized. The aim of this study is to suggest a systematic topographical characterization procedure for composite materials in order to study and recognize the influence of production conditions on their surface quality.

Exoelectronic emission of particles of lunar surface material

NASA Technical Reports Server (NTRS)

Mints, R. I.; Alimov, V. I.; Melekhin, V. P.; Milman, I. I.; Kryuk, V. I.; Kunin, L. L.; Tarasov, L. S.

1974-01-01

A secondary electron multiplier was used to study the thermostimulated exoelectronic emission of particles of lunar surface material returned by the Soviet Luna 16 automatic station. The natural exoemission from fragments of slag, glass, anorthosite, and a metallic particle was recorded in the isochronic and isothermal thermostimulation regimes. The temperature of emission onset depended on the type of regolith fragment. For the first three particles the isothermal drop in emission is described by first-order kinetic equations. For the anorthosite fragment, exoemission at constant temperature is characterized by a symmetric curve with a maximum. These data indicate the presence of active surface defects, whose nature can be due to the prehistory of the particles.

Recent advances of mesoporous materials in sample preparation.

PubMed

Zhao, Liang; Qin, Hongqiang; Wu, Ren'an; Zou, Hanfa

2012-03-09

Sample preparation has been playing an important role in the analysis of complex samples. Mesoporous materials as the promising adsorbents have gained increasing research interest in sample preparation due to their desirable characteristics of high surface area, large pore volume, tunable mesoporous channels with well defined pore-size distribution, controllable wall composition, as well as modifiable surface properties. The aim of this paper is to review the recent advances of mesoporous materials in sample preparation with emphases on extraction of metal ions, adsorption of organic compounds, size selective enrichment of peptides/proteins, specific capture of post-translational peptides/proteins and enzymatic reactor for protein digestion. Copyright © 2011 Elsevier B.V. All rights reserved.

Lateral-drag propulsion forces induced by anisotropy.

PubMed

Nefedov, Igor S; Rubi, J Miguel

2017-07-21

We predict the existence of lateral drag forces near the flat surface of an absorbing slab made of an anisotropic material. The forces originate from the fluctuations of the electromagnetic field, when the anisotropy axis of the material forms a certain angle with the surface. In this situation, the spatial spectra of the fluctuating electromagnetic fields becomes asymmetric, different for positive and negative transverse wave vectors components. Differently from the case of van der Waals interactions in which the forward-backward symmetry is broken due to the particle movement, in our case the lateral motion results merely from the anisotropy of the slab. This new effect, of particular significance in hyperbolic materials, could be used for the manipulation of nanoparticles.

Activated alumina preparation and characterization: The review on recent advancement

NASA Astrophysics Data System (ADS)

Rabia, A. R.; Ibrahim, A. H.; Zulkepli, N. N.

2018-03-01

Aluminum and aluminum based material are significant industrial materials synthesis because of their abandonment, low weight and high-quality corrosion resistance. The most advances in aluminum processing are the ability to synthesize it's under suitable chemical composition and conditions, a porous structure can be formed on the surface. Activated alumina particles (AAP) synthesized by the electrochemically process from aluminum have gained serious attention, inexpensive material that can be employed for water filtration due to its active surface. Thus, the paper present a review study based on recent progress and advances in synthesizing activated alumina, various techniques currently being used in preparing activated alumina and its characteristics are studied and summarized

Development of novel antibiofouling materials from natural phenol compounds

NASA Astrophysics Data System (ADS)

Chelikani, Rahul; Kim, Dong Shik

2007-03-01

Biofilms consist of a gelatinous matrix formed on a solid surface by microbial organisms.Biofilm is caused due to the adhesion of microbes to solid surfaces with production of extracellular polymers and the process of the biofilm formation is reffered to as biofouling.Biofouling causes serious problems in chemical, medical and pharmaceutical industries.Although there have been some antibiofouling materials developed over the years,no plausible results have been found yet.Natural polyphenolic compounds like flavanoids,cathechins have strong antioxidant and antimicrobial properties.Recently,apocynin,a phenol derivative,was polymerized to form oligomers,which can regulate intracellular pathways in cancer cells preventing cell proliferation and migration.These natural phenolic compounds have never been applied to solid surfaces to prevent biofouling.It is thought that probably because of the difficulty to crosslink them to form a stable coating.In this study,some novel polyphenolic compounds synthesized using enzymatic technique from cashew nut shell liquid,a cheap and renewable byproduct of the cashew industry are used as coating materials to prevent biofouling.The interaction of these materials with microbes preventing fouling on surfaces and the chemico-physical properties of the materials causing the antibiofouling effect will be discussed.It is critical to understand the antibiofouling mechanism of these materials for better design and application in various fields.

Microbe-surface interactions in biofouling and biocorrosion processes.

PubMed

Beech, Iwona B; Sunner, Jan A; Hiraoka, Kenzo

2005-09-01

The presence of microorganisms on material surfaces can have a profound effect on materials performance. Surface-associated microbial growth, i.e. a biofilm, is known to instigate biofouling. The presence of biofilms may promote interfacial physico-chemical reactions that are not favored under abiotic conditions. In the case of metallic materials, undesirable changes in material properties due to a biofilm (or a biofouling layer) are referred to as biocorrosion or microbially influenced corrosion (MIC). Biofouling and biocorrosion occur in aquatic and terrestrial habitats varying in nutrient content, temperature, pressure and pH. Interfacial chemistry in such systems reflects a wide variety of physiological activities carried out by diverse microbial populations thriving within biofilms. Biocorrosion can be viewed as a consequence of coupled biological and abiotic electron-transfer reactions, i.e. redox reactions of metals, enabled by microbial ecology. Microbially produced extracellular polymeric substances (EPS), which comprise different macromolecules, mediate initial cell adhesion to the material surface and constitute a biofilm matrix. Despite their unquestionable importance in biofilm development, the extent to which EPS contribute to biocorrosion is not well-understood. This review offers a current perspective on material/microbe interactions pertinent to biocorrosion and biofouling, with EPS as a focal point, while emphasizing the role atomic force spectroscopy and mass spectrometry techniques can play in elucidating such interactions.

On Critical States, Rupture States and Interlocking Strength of Granular Materials.

PubMed

Szalwinski, Chris M

2017-07-27

The Mohr-Coulomb theory of strength identifies cohesion and internal friction as the two principal contributions to the shear strength of a granular material. The contribution of cohesion in over-compacted granular materials has been challenged and replacing cohesion with interlocking has been proposed. A theory of rupture strength that includes interlocking is derived herein. The physics-chemistry concept of critical state is elaborated to accommodate granular materials, based on empirical definitions established in the fields of soil mechanics and bulk solids' flow. A surface in state space, called the critical compaction surface, separates over-compacted states from lightly compacted states. The intersection of this surface with the Mohr-Coulomb envelope forms the critical state surface for a granular material. The rupture strength of an over-compacted granular material is expressed as the sum of cohesion, internal friction and interlocking strength. Interlocking strength is the shear strength contribution due to over-compaction and vanishes at critical state. The theory allows migrations from one critical state to another. Changes in specific volume during such migrations are related to changes in mean-normal effective stress and uncoupled from changes in shearing strain. The theory is reviewed with respect to two established research programs and underlying assumptions are identified.

Titanium as a Reconstruction and Implant Material in Dentistry: Advantages and Pitfalls

PubMed Central

Özcan, Mutlu; Hämmerle, Christoph

2012-01-01

Commercial pure titanium (cpTi) has been the material of choice in several disciplines of dentistry due to its biocompatibility, resistance to corrosion and mechanical properties. Despite a number of favorable characteristics, cpTi as a reconstruction and oral implant material has several shortcomings. This paper highlights current knowledge on material properties, passive oxidation film formation, corrosion, surface activation, cell interactions, biofilm development, allergy, casting and machining properties of cpTi for better understanding and potential improvement of this material for its clinical applications.

Mass-produced multi-walled carbon nanotubes as catalyst supports for direct methanol fuel cells.

PubMed

Jang, In Young; Park, Ki Chul; Jung, Yong Chae; Lee, Sun Hyung; Song, Sung Moo; Muramatsu, Hiroyuki; Kim, Yong Jung; Endo, Morinobu

2011-01-01

Commercially mass-produced multi-walled carbon nanotubes, i.e., VGNF (Showa Denko Co.), were applied to support materials for platinum-ruthenium (PtRu) nanoparticles as anode catalysts for direct methanol fuel cells. The original VGNFs are composed of high-crystalline graphitic shells, which hinder the favorable surface deposition of the PtRu nanoparticles that are formed via borohydride reduction. The chemical treatment of VGNFs with potassium hydroxide (KOH), however, enables highly dispersed and dense deposition of PtRu nanoparticles on the VGNF surface. This capability becomes more remarkable depending on the KOH amount. The electrochemical evaluation of the PtRu-deposited VGNF catalysts showed enhanced active surface areas and methanol oxidation, due to the high dispersion and dense deposition of the PtRu nanoparticles. The improvement of the surface deposition states of the PtRu nanoparticles was significantly due to the high surface area and mesorporous surface structure of the KOH-activated VGNFs.

Surface passivation of nano-textured fluorescent SiC by atomic layer deposited TiO2

NASA Astrophysics Data System (ADS)

Lu, Weifang; Ou, Yiyu; Jokubavicius, Valdas; Fadil, Ahmed; Syväjärvi, Mikael; Petersen, Paul Michael; Ou, Haiyan

2016-07-01

Nano-textured surfaces have played a key role in optoelectronic materials to enhance the light extraction efficiency. In this work, morphology and optical properties of nano-textured SiC covered with atomic layer deposited (ALD) TiO2 were investigated. In order to obtain a high quality surface for TiO2 deposition, a three-step cleaning procedure was introduced after RIE etching. The morphology of anatase TiO2 indicates that the nano-textured substrate has a much higher surface nucleated grain density than a flat substrate at the beginning of the deposition process. The corresponding reflectance increases with TiO2 thickness due to increased surface diffuse reflection. The passivation effect of ALD TiO2 thin film on the nano-textured fluorescent 6H-SiC sample was also investigated and a PL intensity improvement of 8.05% was obtained due to the surface passivation.

Terahertz NDE for Metallic Surface Roughness Evaluation

NASA Technical Reports Server (NTRS)

Madaras, Eric I.; Anastasi, Robert F.

2006-01-01

Metallic surface roughness in a nominally smooth surface is a potential indication of material degradation or damage. When the surface is coated or covered with an opaque dielectric material, such as paint or insulation, then inspecting for surface changes becomes almost impossible. Terahertz NDE is a method capable of penetrating the coating and inspecting the metallic surface. The terahertz frequency regime is between 100 GHz and 10 THz and has a free space wavelength of 300 micrometers at 1 THz. Pulsed terahertz radiation, can be generated and detected using optical excitation of biased semiconductors with femtosecond laser pulses. The resulting time domain signal is 320 picoseconds in duration. In this application, samples are inspected with a commercial terahertz NDE system that scans the sample and generates a set of time-domain signals that are a function of the backscatter from the metallic surface. Post processing is then performed in the time and frequency domains to generate C-scan type images that show scattering effects due to surface non-uniformity.

Detecting Unknown Artificial Urban Surface Materials Based on Spectral Dissimilarity Analysis.

PubMed

Jilge, Marianne; Heiden, Uta; Habermeyer, Martin; Mende, André; Juergens, Carsten

2017-08-08

High resolution imaging spectroscopy data have been recognised as a valuable data resource for augmenting detailed material inventories that serve as input for various urban applications. Image-specific urban spectral libraries are successfully used in urban imaging spectroscopy studies. However, the regional- and sensor-specific transferability of such libraries is limited due to the wide range of different surface materials. With the developed methodology, incomplete urban spectral libraries can be utilised by assuming that unknown surface material spectra are dissimilar to the known spectra in a basic spectral library (BSL). The similarity measure SID-SCA (Spectral Information Divergence-Spectral Correlation Angle) is applied to detect image-specific unknown urban surfaces while avoiding spectral mixtures. These detected unknown materials are categorised into distinct and identifiable material classes based on their spectral and spatial metrics. Experimental results demonstrate a successful redetection of material classes that had been previously erased in order to simulate an incomplete BSL. Additionally, completely new materials e.g., solar panels were identified in the data. It is further shown that the level of incompleteness of the BSL and the defined dissimilarity threshold are decisive for the detection of unknown material classes and the degree of spectral intra-class variability. A detailed accuracy assessment of the pre-classification results, aiming to separate natural and artificial materials, demonstrates spectral confusions between spectrally similar materials utilizing SID-SCA. However, most spectral confusions occur between natural or artificial materials which are not affecting the overall aim. The dissimilarity analysis overcomes the limitations of working with incomplete urban spectral libraries and enables the generation of image-specific training databases.

Detecting Unknown Artificial Urban Surface Materials Based on Spectral Dissimilarity Analysis

PubMed Central

Jilge, Marianne; Heiden, Uta; Habermeyer, Martin; Mende, André; Juergens, Carsten

2017-01-01

High resolution imaging spectroscopy data have been recognised as a valuable data resource for augmenting detailed material inventories that serve as input for various urban applications. Image-specific urban spectral libraries are successfully used in urban imaging spectroscopy studies. However, the regional- and sensor-specific transferability of such libraries is limited due to the wide range of different surface materials. With the developed methodology, incomplete urban spectral libraries can be utilised by assuming that unknown surface material spectra are dissimilar to the known spectra in a basic spectral library (BSL). The similarity measure SID-SCA (Spectral Information Divergence-Spectral Correlation Angle) is applied to detect image-specific unknown urban surfaces while avoiding spectral mixtures. These detected unknown materials are categorised into distinct and identifiable material classes based on their spectral and spatial metrics. Experimental results demonstrate a successful redetection of material classes that had been previously erased in order to simulate an incomplete BSL. Additionally, completely new materials e.g., solar panels were identified in the data. It is further shown that the level of incompleteness of the BSL and the defined dissimilarity threshold are decisive for the detection of unknown material classes and the degree of spectral intra-class variability. A detailed accuracy assessment of the pre-classification results, aiming to separate natural and artificial materials, demonstrates spectral confusions between spectrally similar materials utilizing SID-SCA. However, most spectral confusions occur between natural or artificial materials which are not affecting the overall aim. The dissimilarity analysis overcomes the limitations of working with incomplete urban spectral libraries and enables the generation of image-specific training databases. PMID:28786947

Improved Composites Using Crosslinked, Surface-Modified Carbon Nanotube Materials

NASA Technical Reports Server (NTRS)

Baker, James Stewart

2014-01-01

Individual carbon nanotubes (CNTs) exhibit exceptional tensile strength and stiffness; however, these properties have not translated well to the macroscopic scale. Premature failure of bulk CNT materials under tensile loading occurs due to the relatively weak frictional forces between adjacent CNTs, leading to poor load transfer through the material. When used in polymer matrix composites (PMCs), the weak nanotube-matrix interaction leads to the CNTs providing less than optimal reinforcement.Our group is examining the use of covalent crosslinking and surface modification as a means to improve the tensile properties of PMCs containing carbon nanotubes. Sheet material comprised of unaligned multi-walled carbon nanotubes (MWCNT) was used as a drop-in replacement for carbon fiber in the composites. A variety of post-processing methods have been examined for covalently crosslinking the CNTs to overcome the weak inter-nanotube shear interactions, resulting in improved tensile strength and modulus for the bulk sheet material. Residual functional groups from the crosslinking chemistry may have the added benefit of improving the nanotube-matrix interaction. Composites prepared using these crosslinked, surface-modified nanotube sheet materials exhibit superior tensile properties to composites using the as received CNT sheet material.

Characterizing the effects of regolith surface roughness on photoemission from surfaces in space

NASA Astrophysics Data System (ADS)

Dove, A.; Horanyi, M.; Wang, X.

2017-12-01

Surfaces of airless bodies and spacecraft in space are exposed to a variety of charging environments. A balance of currents due to plasma bombardment, photoemission, electron and ion emission and collection, and secondary electron emission determines the surface's charge. Photoelectron emission is the dominant charging process on sunlit surfaces in the inner solar system due to the intense solar UV radiation. This can result in a net positive surface potential, with a cloud of photoelectrons immediately above the surface, called the photoelectron sheath. Conversely, the unlit side of the body will charge negatively due the collection of the fast-moving solar wind electrons. The interaction of charged dust grains with these positively and negatively charged surfaces, and within the photoelectron and plasma sheaths may explain the occurrence of dust lofting, levitation and transport above the lunar surface. The surface potential of exposed objects is also dependent on the material properties of their surfaces. Composition and particle size primarily affect the quantum efficiency of photoelectron generation; however, surface roughness can also control the charging process. In order to characterize these effects, we have conducted laboratory experiments to examine the role of surface roughness in generating photoelectrons in dedicated laboratory experiments using solid and dusty surfaces of the same composition (CeO2), and initial comparisons with JSC-1 lunar simulant. Using Langmuir probe measurements, we explore the measured potentials above insulating surfaces exposed to UV and an electric field, and we show that the photoemission current from a dusty surface is largely reduced due to its higher surface roughness, which causes a significant fraction of the emitted photoelectrons to be re-absorbed within the surface. We will discuss these results in context of similar situations on planetary surfaces.

An experimental study on soft PDMS materials for aircraft icing mitigation

NASA Astrophysics Data System (ADS)

Liu, Yang; Ma, Liqun; Wang, Wei; Kota, Arun K.; Hu, Hui

2018-07-01

A series of experiments were conducted to characterize the anti-/de-icing performances of soft PDMS materials with different shear modulus and to explore their potentials for aircraft icing mitigation. In the present study, a new class of soft PDMS materials with adjustable shear modulus were fabricated by adding different amounts and different molecular weights of non-reactive trimethyl-terminated PDMS (t-PDMS) into the hydrosilylation mixture of vinyl-terminated PDMS (v-PDMS) and hydride-terminated PDMS (h-PDMS). While the soft PDMS materials were found to be hydrophobic with the contact angle of water droplets over the PDMS surfaces being about 110°, the ice adhesion strength over the soft PDMS materials was found to be extremely low (i.e., being less than 10 kPa at -5 °C or two orders of magnitude smaller), in comparison to those of the conventional rigid surface (i.e., being greater than 1000 kPa for Aluminum or the hard plastic material used to make the airfoil/wing model used in the present study). Upon the dynamic impacting of water droplets at relatively high weber number levels pertinent to aircraft inflight icing phenomena (e.g., We = 4000), the soft PDMS surfaces were found to deform dynamically due to the elastic nature of the PDMS materials, which cause the soft PDMS materials acting as "trampolines" to bounce off most of the impinged water mass away from the impacted surfaces. By applying the soft PDMS materials to coat/cover the surface of a NACA 0012 airfoil/wing model, an explorative study was also performed in an Icing Research Tunnel available at Iowa State University (i.e., ISU-IRT) to demonstrate the feasibility of using the soft PDMS materials to mitigate the impact ice accretion process pertinent to aircraft inflight icing phenomena.

Wireless Metal Detection and Surface Coverage Sensing for All-Surface Induction Heating

PubMed Central

Kilic, Veli Tayfun; Unal, Emre; Demir, Hilmi Volkan

2016-01-01

All-surface induction heating systems, typically comprising small-area coils, face a major challenge in detecting the presence of a metallic vessel and identifying its partial surface coverage over the coils to determine which of the coils to power up. The difficulty arises due to the fact that the user can heat vessels made of a wide variety of metals (and their alloys). To address this problem, we propose and demonstrate a new wireless detection methodology that allows for detecting the presence of metallic vessels together with uniquely sensing their surface coverages while also identifying their effective material type in all-surface induction heating systems. The proposed method is based on telemetrically measuring simultaneously inductance and resistance of the induction coil coupled with the vessel in the heating system. Here, variations in the inductance and resistance values for an all-surface heating coil loaded by vessels (made of stainless steel and aluminum) at different positions were systematically investigated at different frequencies. Results show that, independent of the metal material type, unique identification of the surface coverage is possible at all freqeuncies. Additionally, using the magnitude and phase information extracted from the coupled coil impedance, unique identification of the vessel effective material is also achievable, this time independent of its surface coverage. PMID:26978367

Outstanding catalytic activity of ultra-pure platinum nanoparticles.

PubMed

Januszewska, Aneta; Dercz, Grzegorz; Piwowar, Justyna; Jurczakowski, Rafal; Lewera, Adam

2013-12-09

Small (4 nm) nanoparticles with a narrow size distribution, exceptional surface purity, and increased surface order, which exhibits itself as an increased presence of basal crystallographic planes, can be obtained without the use of any surfactant. These nanoparticles can be used in many applications in an as-received state and are threefold more active towards a model catalytic reaction (oxidation of ethylene glycol). Furthermore, the superior properties of this material are interesting not only due to the increase in their intrinsic catalytic activity, but also due to the exceptional surface purity itself. The nanoparticles can be used directly (i.e., as-received, without any cleaning steps) in biomedical applications (i.e., as more efficient drug carriers due to an increased number of adsorption sites) and in energy-harvesting/data-storage devices. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Impact of plasma treatment under atmospheric pressure on surface chemistry and surface morphology of extruded and injection-molded wood-polymer composites (WPC)

NASA Astrophysics Data System (ADS)

Hünnekens, Benedikt; Avramidis, Georg; Ohms, Gisela; Krause, Andreas; Viöl, Wolfgang; Militz, Holger

2018-05-01

The influence of plasma treatment performed at atmospheric pressure and ambient air as process gas by a dielectric barrier discharge (DBD) on the morphological and chemical surface characteristics of wood-polymer composites (WPC) was investigated by applying several surface-sensitive analytical methods. The surface free energy showed a distinct increase after plasma treatment for all tested materials. The analyzing methods for surface topography-laser scanning microscopy (LSM) and atomic force microscopy (AFM)-revealed a roughening induced by the treatment which is likely due to a degradation of the polymeric surface. This was accompanied by the formation of low-molecular-weight oxidized materials (LMWOMs), appearing as small globular structures. With increasing discharge time, the nodules increase in size and the material degradation proceeds. The surface degradation seems to be more serious for injection-molded samples, whereas the formation of nodules became more apparent and were evenly distributed on extruded surfaces. These phenomena could also be confirmed by scanning electron microscopy (SEM). In addition, differences between extruded and injection-molded surfaces could be observed. Besides the morphological changes, the chemical composition of the substrates' surfaces was affected by the plasma discharge. Infrared spectroscopy (ATR-FTIR) and X-ray photoelectron spectroscopy (XPS) indicated the formation of new oxygen containing polar groups on the modified surfaces.

High-Strain-Rate Material Behavior and Adiabatic Material Instability in Impact of Micron-Scale Al-6061 Particles

NASA Astrophysics Data System (ADS)

Chen, Qiyong; Alizadeh, Arash; Xie, Wanting; Wang, Xuemei; Champagne, Victor; Gouldstone, Andrew; Lee, Jae-Hwang; Müftü, Sinan

2018-04-01

Impact of spherical particles onto a flat sapphire surface was investigated in 50-950 m/s impact speed range experimentally and theoretically. Material parameters of the bilinear Johnson-Cook model were determined based on comparison of deformed particle shapes from experiment and simulation. Effects of high-strain-rate plastic flow, heat generation due to plasticity, material damage, interfacial friction and heat transfer were modeled. Four distinct regions were identified inside the particle by analyzing temporal variation of material flow. A relatively small volume of material near the impact zone becomes unstable due to plasticity-induced heating, accompanied by severe drop in the flow stress for impact velocity that exceeds 500 m/s. Outside of this region, flow stress is reduced due to temperature effects without the instability. Load carrying capacity of the material degrades and the material expands horizontally leading to jetting. The increase in overall plastic and frictional dissipation with impact velocity was found to be inherently lower than the increase in the kinetic energy at high speeds, leading to the instability. This work introduces a novel method to characterize HSR (109 s-1) material properties and also explains coupling between HSR material behavior and mechanics that lead to extreme deformation.

Surface engineered porous silicon for stable, high performance electrochemical supercapacitors

PubMed Central

Oakes, Landon; Westover, Andrew; Mares, Jeremy W.; Chatterjee, Shahana; Erwin, William R.; Bardhan, Rizia; Weiss, Sharon M.; Pint, Cary L.

2013-01-01

Silicon materials remain unused for supercapacitors due to extreme reactivity of silicon with electrolytes. However, doped silicon materials boast a low mass density, excellent conductivity, a controllably etched nanoporous structure, and combined earth abundance and technological presence appealing to diverse energy storage frameworks. Here, we demonstrate a universal route to transform porous silicon (P-Si) into stable electrodes for electrochemical devices through growth of an ultra-thin, conformal graphene coating on the P-Si surface. This graphene coating simultaneously passivates surface charge traps and provides an ideal electrode-electrolyte electrochemical interface. This leads to 10–40X improvement in energy density, and a 2X wider electrochemical window compared to identically-structured unpassivated P-Si. This work demonstrates a technique generalizable to mesoporous and nanoporous materials that decouples the engineering of electrode structure and electrochemical surface stability to engineer performance in electrochemical environments. Specifically, we demonstrate P-Si as a promising new platform for grid-scale and integrated electrochemical energy storage. PMID:24145684

Surface engineered porous silicon for stable, high performance electrochemical supercapacitors.

PubMed

Oakes, Landon; Westover, Andrew; Mares, Jeremy W; Chatterjee, Shahana; Erwin, William R; Bardhan, Rizia; Weiss, Sharon M; Pint, Cary L

2013-10-22

Silicon materials remain unused for supercapacitors due to extreme reactivity of silicon with electrolytes. However, doped silicon materials boast a low mass density, excellent conductivity, a controllably etched nanoporous structure, and combined earth abundance and technological presence appealing to diverse energy storage frameworks. Here, we demonstrate a universal route to transform porous silicon (P-Si) into stable electrodes for electrochemical devices through growth of an ultra-thin, conformal graphene coating on the P-Si surface. This graphene coating simultaneously passivates surface charge traps and provides an ideal electrode-electrolyte electrochemical interface. This leads to 10-40X improvement in energy density, and a 2X wider electrochemical window compared to identically-structured unpassivated P-Si. This work demonstrates a technique generalizable to mesoporous and nanoporous materials that decouples the engineering of electrode structure and electrochemical surface stability to engineer performance in electrochemical environments. Specifically, we demonstrate P-Si as a promising new platform for grid-scale and integrated electrochemical energy storage.

Surface engineered porous silicon for stable, high performance electrochemical supercapacitors

NASA Astrophysics Data System (ADS)

Oakes, Landon; Westover, Andrew; Mares, Jeremy W.; Chatterjee, Shahana; Erwin, William R.; Bardhan, Rizia; Weiss, Sharon M.; Pint, Cary L.

2013-10-01

Silicon materials remain unused for supercapacitors due to extreme reactivity of silicon with electrolytes. However, doped silicon materials boast a low mass density, excellent conductivity, a controllably etched nanoporous structure, and combined earth abundance and technological presence appealing to diverse energy storage frameworks. Here, we demonstrate a universal route to transform porous silicon (P-Si) into stable electrodes for electrochemical devices through growth of an ultra-thin, conformal graphene coating on the P-Si surface. This graphene coating simultaneously passivates surface charge traps and provides an ideal electrode-electrolyte electrochemical interface. This leads to 10-40X improvement in energy density, and a 2X wider electrochemical window compared to identically-structured unpassivated P-Si. This work demonstrates a technique generalizable to mesoporous and nanoporous materials that decouples the engineering of electrode structure and electrochemical surface stability to engineer performance in electrochemical environments. Specifically, we demonstrate P-Si as a promising new platform for grid-scale and integrated electrochemical energy storage.

Enhanced Locomotion Efficiency of a Bio-inspired Walking Robot using Contact Surfaces with Frictional Anisotropy

NASA Astrophysics Data System (ADS)

Manoonpong, Poramate; Petersen, Dennis; Kovalev, Alexander; Wörgötter, Florentin; Gorb, Stanislav N.; Spinner, Marlene; Heepe, Lars

2016-12-01

Based on the principles of morphological computation, we propose a novel approach that exploits the interaction between a passive anisotropic scale-like material (e.g., shark skin) and a non-smooth substrate to enhance locomotion efficiency of a robot walking on inclines. Real robot experiments show that passive tribologically-enhanced surfaces of the robot belly or foot allow the robot to grip on specific surfaces and move effectively with reduced energy consumption. Supplementing the robot experiments, we investigated tribological properties of the shark skin as well as its mechanical stability. It shows high frictional anisotropy due to an array of sloped denticles. The orientation of the denticles to the underlying collagenous material also strongly influences their mechanical interlocking with the substrate. This study not only opens up a new way of achieving energy-efficient legged robot locomotion but also provides a better understanding of the functionalities and mechanical properties of anisotropic surfaces. That understanding will assist developing new types of material for other real-world applications.

Enhanced Locomotion Efficiency of a Bio-inspired Walking Robot using Contact Surfaces with Frictional Anisotropy

PubMed Central

Manoonpong, Poramate; Petersen, Dennis; Kovalev, Alexander; Wörgötter, Florentin; Gorb, Stanislav N.; Spinner, Marlene; Heepe, Lars

2016-01-01

Based on the principles of morphological computation, we propose a novel approach that exploits the interaction between a passive anisotropic scale-like material (e.g., shark skin) and a non-smooth substrate to enhance locomotion efficiency of a robot walking on inclines. Real robot experiments show that passive tribologically-enhanced surfaces of the robot belly or foot allow the robot to grip on specific surfaces and move effectively with reduced energy consumption. Supplementing the robot experiments, we investigated tribological properties of the shark skin as well as its mechanical stability. It shows high frictional anisotropy due to an array of sloped denticles. The orientation of the denticles to the underlying collagenous material also strongly influences their mechanical interlocking with the substrate. This study not only opens up a new way of achieving energy-efficient legged robot locomotion but also provides a better understanding of the functionalities and mechanical properties of anisotropic surfaces. That understanding will assist developing new types of material for other real-world applications. PMID:28008936

Non-Equilibrium Plasma Processing for the Preparation of Antibacterial Surfaces

PubMed Central

Sardella, Eloisa; Palumbo, Fabio; Camporeale, Giuseppe; Favia, Pietro

2016-01-01

Non-equilibrium plasmas offer several strategies for developing antibacterial surfaces that are able to repel and/or to kill bacteria. Due to the variety of devices, implants, and materials in general, as well as of bacteria and applications, plasma assisted antibacterial strategies need to be tailored to each specific surface. Nano-composite coatings containing inorganic (metals and metal oxides) or organic (drugs and biomolecules) compounds can be deposited in one step, and used as drug delivery systems. On the other hand, functional coatings can be plasma-deposited and used to bind antibacterial molecules, for synthesizing surfaces with long lasting antibacterial activity. In addition, non-fouling coatings can be produced to inhibit the adhesion of bacteria and reduce the formation of biofilm. This paper reviews plasma-based strategies aimed to reduce bacterial attachment and proliferation on biomedical materials and devices, but also onto materials used in other fields. Most of the activities described have been developed in the lab of the authors. PMID:28773637

Launch vehicle flight control augmentation using smart materials and advanced composites (CDDF Project 93-05)

NASA Technical Reports Server (NTRS)

Barret, C.

1995-01-01

The Marshall Space Flight Center has a rich heritage of launch vehicles that have used aerodynamic surfaces for flight stability such as the Saturn vehicles and flight control such as on the Redstone. Recently, due to aft center-of-gravity locations on launch vehicles currently being studied, the need has arisen for the vehicle control augmentation that is provided by these flight controls. Aerodynamic flight control can also reduce engine gimbaling requirements, provide actuator failure protection, enhance crew safety, and increase vehicle reliability, and payload capability. In the Saturn era, NASA went to the Moon with 300 sq ft of aerodynamic surfaces on the Saturn V. Since those days, the wealth of smart materials and advanced composites that have been developed allow for the design of very lightweight, strong, and innovative launch vehicle flight control surfaces. This paper presents an overview of the advanced composites and smart materials that are directly applicable to launch vehicle control surfaces.

Visible light guided manipulation of liquid wettability on photoresponsive surfaces

PubMed Central

Kwon, Gibum; Panchanathan, Divya; Mahmoudi, Seyed Reza; Gondal, Mohammed A.; McKinley, Gareth H.; Varanasi, Kripa K.

2017-01-01

Photoresponsive titania surfaces are of great interest due to their unique wettability change upon ultraviolet light illumination. However, their applications are often limited either by the inability to respond to visible light or the need for special treatment to recover the original wettability. Sensitizing TiO2 surfaces with visible light-absorbing materials has been utilized in photovoltaic applications. Here we demonstrate that a dye-sensitized TiO2 surface can selectively change the wettability towards contacting liquids upon visible light illumination due to a photo-induced voltage across the liquid and the underlying surface. The photo-induced wettability change of our surfaces enables external manipulation of liquid droplet motion upon illumination. We show demulsification of surfactant-stabilized brine-in-oil emulsions via coalescence of brine droplets on our dye-sensitized TiO2 surface upon visible light illumination. We anticipate that our surfaces will have a wide range of applications including microfluidic devices with customizable wettability, solar-driven oil–water clean-up and demulsification technologies. PMID:28440292

Tribological properties of multifunctional coatings with Shape Memory Effect in abrasive wear

NASA Astrophysics Data System (ADS)

Blednova, Zh. M.; Dmitrenko, D. V.; Balaev, E. U. O.

2018-01-01

The article gives research results of the abrasive wear process on samples made of Steel 1045, U10 and with applied composite surface layer "Nickel-Multicomponent material with Shape Memory Effect (SME) based on TiNi". For the tests we have chosen TiNiZr, which is in the martensite state and TiNiHfCu, which is in the austenitic state at the test temperature. The formation of the surface layer was carried out by high-speed oxygen-fuel deposition in a protective atmosphere of argon. In the wear test, Al2O3 corundum powder was used as an abrasive. It is shown that the wear rate of samples with a composite surface layer of multicomponent materials with SME is significantly reduced in comparison with the base, which is explained by reversible phase transformations of the surface layer with SME. After carrying out the additional surface plastic deformation (SPD), the resistance of the laminated composition to abrasion wear has greatly enhanced, due to the reinforcing effect of the SPD. It is recommended for products working in conditions of abrasive wear and high temperatures to use the complex formation technology of the surface composition "steel-nickel-material with high-temperature SME", including preparation of the substrate surface and the deposited material, high-speed spraying in the protective atmosphere of argon, followed by SPD.

Modeling quantum yield, emittance, and surface roughness effects from metallic photocathodes

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

Dimitrov, D. A.; Bell, G. I.; Smedley, J.

Here, detailed measurements of momentum distributions of emitted electrons have allowed the investigation of the thermal limit of the transverse emittance from metal photocathodes. Furthermore, recent developments in material design and growth have resulted in photocathodes that can deliver high quantum efficiency and are sufficiently robust to use in high electric field gradient photoinjectors and free electron lasers. The growth process usually produces photoemissive material layers with rough surface profiles that lead to transverse accelerating fields and possible work function variations, resulting in emittance growth. To better understand the effects of temperature, density of states, and surface roughness on themore » properties of emitted electrons, we have developed realistic three-dimensional models for photocathode materials with grated surface structures. They include general modeling of electron excitation due to photon absorption, charge transport, and emission from flat and rough metallic surfaces. The models also include image charge and field enhancement effects. We report results from simulations with flat and rough surfaces to investigate how electron scattering, controlled roughness, work function variation, and field enhancement affect emission properties. Comparison of simulation results with measurements of the quantum yield and transverse emittance from flat Sb emission surfaces shows the importance of including efficient modeling of photon absorption, temperature effects, and the material density of states to achieve agreement with the experimental data.« less

Modeling quantum yield, emittance, and surface roughness effects from metallic photocathodes

DOE PAGES

Dimitrov, D. A.; Bell, G. I.; Smedley, J.; ...

2017-10-26

Here, detailed measurements of momentum distributions of emitted electrons have allowed the investigation of the thermal limit of the transverse emittance from metal photocathodes. Furthermore, recent developments in material design and growth have resulted in photocathodes that can deliver high quantum efficiency and are sufficiently robust to use in high electric field gradient photoinjectors and free electron lasers. The growth process usually produces photoemissive material layers with rough surface profiles that lead to transverse accelerating fields and possible work function variations, resulting in emittance growth. To better understand the effects of temperature, density of states, and surface roughness on themore » properties of emitted electrons, we have developed realistic three-dimensional models for photocathode materials with grated surface structures. They include general modeling of electron excitation due to photon absorption, charge transport, and emission from flat and rough metallic surfaces. The models also include image charge and field enhancement effects. We report results from simulations with flat and rough surfaces to investigate how electron scattering, controlled roughness, work function variation, and field enhancement affect emission properties. Comparison of simulation results with measurements of the quantum yield and transverse emittance from flat Sb emission surfaces shows the importance of including efficient modeling of photon absorption, temperature effects, and the material density of states to achieve agreement with the experimental data.« less

Spectroscopic imaging scanning tunneling microscopy of a Dirac line node material ZrSiS

NASA Astrophysics Data System (ADS)

Zhou, Lihui; He, Qingyu; Queiroz, Raquel; Grüneis, Andreas; Schnyder, Andreas; Ast, Christian; Schoop, Leslie; Takagi, Hide; Rost, Andreas

3D Dirac materials are an intensive area of current condensed matter research. The related Dirac line node materials have come into focus due to many shared properties such as unconventional magneto-transport and the potential to host topologically nontrivial phases. ZrSiS is one of the first discovered materials of this new family, hosting a nodal line and an unconventional surface state. Spectroscopic imaging scanning tunneling microscopy (SI-STM) detects quasiparticle interference and has been extensively used to study the scattering mechanism and the band structures of exotic materials with high energy resolution at the atomic scale. Here in this presentation, we report the investigation of ZrSiS by SI-STM at the atomic scale, in combination with DFT calculations. We succeeded in visualizing the Dirac nodal line both in real and momentum space, adding key pieces of evidences confirming the existence of a nodal line in this material and highlighting its exceptional properties. The breaking of a non-symmorphic symmetry at the surface induces an unusual surface state whose dispersion was mapped. In particular, we observed spectroscopic signatures of a type-II Dirac fermion hosted by the surface state. Our data as seen by SI-STM has impact beyond ZrSiS providing crucial insights into the properties of Dirac line node materials in particular and non-symmorphic crystals in general.

Rayleigh-wave diffractions due to a void in the layered half space

USGS Publications Warehouse

Xia, J.; Xu, Y.; Miller, R.D.; Nyquist, Jonathan E.

2006-01-01

Void detection is challenging due to the complexity of near-surface materials and the limited resolution of geophysical methods. Although multichannel, high-frequency, surface-wave techniques can provide reliable shear (S)-wave velocities in different geological settings, they are not suitable for detecting voids directly based on anomalies of the S-wave velocity because of limitations on the resolution of S-wave velocity profiles inverted from surface-wave phase velocities. Xia et al. (2006a) derived a Rayleigh-wave diffraction traveltime equation due to a void in the homogeneous half space. Encouraging results of directly detecting a void from Rayleigh-wave diffractions were presented (Xia et al., 2006a). In this paper we used four two-dimensional square voids in the layered half space to demonstrate the feasibility of detecting a void with Rayleigh-wave diffractions. Rayleigh-wave diffractions were recognizable for all these models after removing direct surface waves by F-K filtering. We evaluate the feasibility of applying the Rayleigh-wave diffraction traveltime equation to a void in the layered earth model. The phase velocity of diffracted Rayleigh waves is predominately determined by surrounding materials of a void. The modeling results demonstrate that the Rayleigh-wave diffraction traveltime equation due to a void in the homogeneous half space can be applied to the case of a void in the layered half space. In practice, only two diffraction times are necessary to define the depth to the top of a void and the average velocity of diffracted Rayleigh waves. ?? 2005 Society of Exploration Geophysicists.

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

Biassoni, M.; Brofferio, C.; Bucci, C.

Due to their excellent energy resolution values and the vast choice of possible materials, bolometric detectors are currently widely used in the physics of rare events. A limiting aspect for bolometers rises from their inability to discriminate among radiation types or surface from bulk events. It has been demonstrated that the main limitation to sensitivity for purely bolometric detectors is represented by surface alpha contaminations, causing a continuous background that cannot be discriminated. A new scintillation based technique for the rejection of surface alpha background in non- scintillating bolometric experiments is proposed in this work. The idea is to combinemore » a scintillating and a high sensitivity photon detector with a non- scintillating absorber. Finally, we present results showing the possibility to reject events due to alpha decay at or nearby the surface of the crystal.« less

Degradation phenomena of magnetic attachments used clinically in the oral environment

NASA Astrophysics Data System (ADS)

Chung, Chae-Heon; Choe, Han-Cheol; Kwak, Jong-Ha

2006-08-01

The purpose of this study was to investigate the mechanisms involved in the failure of magnetic attachments used to retain dental prostheses. Dyna magnets were retrieved from dentures that had failed after 34 months of clinical use. These magnetic attachments were prepared and sectioned so as to observe the corrosion surface and layer in order to analyze the corrosion behaviors of the attachments. The corroded surface was observed under a field emission scanning electron microscope (FE-SEM) (JSM 840A, JEOL, Japan). An X-ray diffractometer (XRD) was used to analyze the corrosion product formed due to corrosion in the oral environment. Erosion-corrosion started in the uneven portion of the stainless steel cover in the magnetic attachments composed with Nd-Fe-B alloy. Corrosion was initiated on the worn stainless steel surface, followed by spalling of magnetic material due to corrosive solution. The corrosion rate increased drastically after the corrosion product caused spalling in Nd-Fe-B alloy. Corrosion initiated in the uneven stainless steel surface as well as in the welded zone. In conclusion, the failure of magnetic attachments may occur by either welding failure or breakdown of the encapsulating material. Thus, we believe that treating the surface of magnetic attachments would resolve the corrosion problem seen in magnetic attachments to some extent.

Second NATO Workshop on Passive Infrared Optical Materials and Coatings

DTIC Science & Technology

1987-12-01

sponsor, NATO AC/243 ( Panel III tion is sprayed through a furnace at RSG 2). This is an abridged version of about 1000*C. A 7-hour operation yields the...strength, generate high-quality optical surfaces Cl, of the monocrystalline material is 4 162 MPa at a load increase rate of 18 MPa due to removal of water

Mechanisms of biochar assisted immobilization of Pb2+ by bioapatite in aqueous solution.

PubMed

Shen, Zhengtao; Tian, Da; Zhang, Xinyu; Tang, Lingyi; Su, Mu; Zhang, Li; Li, Zhen; Hu, Shuijin; Hou, Deyi

2018-01-01

Bioapatite (BAp) is regarded as an effective material to immobilize lead (Pb 2+ ) via the formation of stable pyromorphite. However, when applied in contaminated soil, due to its low surface area and low adsorption capacity, BAp might not sufficiently contact and react with Pb 2+ . Biochar, a carbon storage material, typically has high surface area and high adsorption capacity. This study investigated the feasibility of using biochar as a reaction platform to enhance BAp immobilization of Pb 2+ . An alkaline biochar produced from wheat straw pellets (WSP) and a slightly acidic biochar produced from hardwood (SB) were selected. The results of aqueous adsorption showed the combination of biochar (WSP or SB) and BAp effectively removed Pb 2+ from the aqueous solution containing 1000 ppm Pb 2+ . XRD, ATR-IR, and SEM/EDX results revealed the formation of hydroxypyromorphite on both biochars' surfaces. This study demonstrates that biochars could act as an efficient reaction platform for BAp and Pb 2+ in aqueous solution due to their high surface area, porous structure, and high adsorption capacity. Therefore, it is mechanistically feasible to apply biochar to enhance BAp immobilization of Pb 2+ in contaminated soil. Copyright © 2017 Elsevier Ltd. All rights reserved.

New Route for Synthesis of Fluorescent SnO₂ Nanoparticles for Selective Sensing of Fe(III) in Aqueous Media.

PubMed

Vyas, Gaurav; Kumar, Anshu; Bhatt, Madhuri; Bhatt, Shreya; Paul, Parimal

2018-06-01

A simple new route for synthesis of fluorescent SnO2 and its application as an efficient sensing material for Fe3+ in aqueous media is reported. The fluorescent SnO2 nanoparticles were obtained by oxidation of SnCl2, which when used as reducing agent for the reduction of organic nitro compounds to corresponding amino compounds in ethanol. The SnO2 nanoparticles have been characterized on the basis of powder-XRD, IR, UV-Vis, TEM, FESEM and EDX analysis and found that this material is highly fluorescent in aqueous media. Detail study revealed that this material functions as a selective probe for Fe3+ out of a large number of metal ions used. The oxygen vacancies (defects) generated on the surface of the SnO2 during synthesis, are the source of emission due to recombination of electrons with the photo-excited hole in the valance bond. The quenching of emission intensity in presence of Fe3+ is due to the nonradiative recombination of electrons and holes at the surface. This material is used for estimation of Fe3+ in real samples such as drinking water, tap water and soil.

A New Thermal Treatment Process of Low Value Volcanic Glass towards the Production of Expanded Material and its Use on CNTs’ Synthesis as Substrate Material

NASA Astrophysics Data System (ADS)

Angelopoulos, Panagiotis M.; Samouhos, Michail; Taxiarchou, Maria; Tsakiridis, P.; Haggman, John; Joyce, Paul

2018-05-01

Pitchstone is a naturally occurring volcanic glass that contains considerable amount of chemically bound water (> 6 % wt). Due to its high water content, its direct thermal processing in conventional expansion furnaces towards the production of lightweight material, similar to expanded perlite, is practically impossible. In the current research paper a sophisticated 2 stage process is presented that consists of a partial dehydration and an expansion stage towards the production of high quality expanded material. After proper treatment, low-value volcanic glass is transformed to frothy, lightweight material of closed external surface and apparent density of 52 kg·m-3 that can be used in various branches of the industry. The material produced is used as substrate for the development of multiwall CNTs through CVD method. Dense multiwall CNT clusters were identified on expanded pitchstone surface, thus rendering the material suitable for such application.

Cutting Materials in Half: A Graph Theory Approach for Generating Crystal Surfaces and Its Prediction of 2D Zeolites

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

Witman, Matthew; Ling, Sanliang; Boyd, Peter

Scientific interest in two-dimensional (2D) materials, ranging from graphene and other single layer materials to atomically thin crystals, is quickly increasing for a large variety of technological applications. While in silico design approaches have made a large impact in the study of 3D crystals, algorithms designed to discover atomically thin 2D materials from their parent 3D materials are by comparison more sparse. Here, we hypothesize that determining how to cut a 3D material in half (i.e., which Miller surface is formed) by severing a minimal number of bonds or a minimal amount of total bond energy per unit area canmore » yield insight into preferred crystal faces. We answer this question by implementing a graph theory technique to mathematically formalize the enumeration of minimum cut surfaces of crystals. While the algorithm is generally applicable to different classes of materials, we focus on zeolitic materials due to their diverse structural topology and because 2D zeolites have promising catalytic and separation performance compared to their 3D counterparts. We report here a simple descriptor based only on structural information that predicts whether a zeolite is likely to be synthesizable in the 2D form and correctly identifies the expressed surface in known layered 2D zeolites. The discovery of this descriptor allows us to highlight other zeolites that may also be synthesized in the 2D form that have not been experimentally realized yet. Finally, our method is general since the mathematical formalism can be applied to find the minimum cut surfaces of other crystallographic materials such as metal-organic frameworks, covalent-organic frameworks, zeolitic-imidazolate frameworks, metal oxides, etc.« less

Cutting Materials in Half: A Graph Theory Approach for Generating Crystal Surfaces and Its Prediction of 2D Zeolites.

PubMed

Witman, Matthew; Ling, Sanliang; Boyd, Peter; Barthel, Senja; Haranczyk, Maciej; Slater, Ben; Smit, Berend

2018-02-28

Scientific interest in two-dimensional (2D) materials, ranging from graphene and other single layer materials to atomically thin crystals, is quickly increasing for a large variety of technological applications. While in silico design approaches have made a large impact in the study of 3D crystals, algorithms designed to discover atomically thin 2D materials from their parent 3D materials are by comparison more sparse. We hypothesize that determining how to cut a 3D material in half (i.e., which Miller surface is formed) by severing a minimal number of bonds or a minimal amount of total bond energy per unit area can yield insight into preferred crystal faces. We answer this question by implementing a graph theory technique to mathematically formalize the enumeration of minimum cut surfaces of crystals. While the algorithm is generally applicable to different classes of materials, we focus on zeolitic materials due to their diverse structural topology and because 2D zeolites have promising catalytic and separation performance compared to their 3D counterparts. We report here a simple descriptor based only on structural information that predicts whether a zeolite is likely to be synthesizable in the 2D form and correctly identifies the expressed surface in known layered 2D zeolites. The discovery of this descriptor allows us to highlight other zeolites that may also be synthesized in the 2D form that have not been experimentally realized yet. Finally, our method is general since the mathematical formalism can be applied to find the minimum cut surfaces of other crystallographic materials such as metal-organic frameworks, covalent-organic frameworks, zeolitic-imidazolate frameworks, metal oxides, etc.

Cutting Materials in Half: A Graph Theory Approach for Generating Crystal Surfaces and Its Prediction of 2D Zeolites

PubMed Central

2018-01-01

Scientific interest in two-dimensional (2D) materials, ranging from graphene and other single layer materials to atomically thin crystals, is quickly increasing for a large variety of technological applications. While in silico design approaches have made a large impact in the study of 3D crystals, algorithms designed to discover atomically thin 2D materials from their parent 3D materials are by comparison more sparse. We hypothesize that determining how to cut a 3D material in half (i.e., which Miller surface is formed) by severing a minimal number of bonds or a minimal amount of total bond energy per unit area can yield insight into preferred crystal faces. We answer this question by implementing a graph theory technique to mathematically formalize the enumeration of minimum cut surfaces of crystals. While the algorithm is generally applicable to different classes of materials, we focus on zeolitic materials due to their diverse structural topology and because 2D zeolites have promising catalytic and separation performance compared to their 3D counterparts. We report here a simple descriptor based only on structural information that predicts whether a zeolite is likely to be synthesizable in the 2D form and correctly identifies the expressed surface in known layered 2D zeolites. The discovery of this descriptor allows us to highlight other zeolites that may also be synthesized in the 2D form that have not been experimentally realized yet. Finally, our method is general since the mathematical formalism can be applied to find the minimum cut surfaces of other crystallographic materials such as metal–organic frameworks, covalent-organic frameworks, zeolitic-imidazolate frameworks, metal oxides, etc. PMID:29532024

Cutting Materials in Half: A Graph Theory Approach for Generating Crystal Surfaces and Its Prediction of 2D Zeolites

DOE PAGES

Witman, Matthew; Ling, Sanliang; Boyd, Peter; ...

2018-02-06

Scientific interest in two-dimensional (2D) materials, ranging from graphene and other single layer materials to atomically thin crystals, is quickly increasing for a large variety of technological applications. While in silico design approaches have made a large impact in the study of 3D crystals, algorithms designed to discover atomically thin 2D materials from their parent 3D materials are by comparison more sparse. Here, we hypothesize that determining how to cut a 3D material in half (i.e., which Miller surface is formed) by severing a minimal number of bonds or a minimal amount of total bond energy per unit area canmore » yield insight into preferred crystal faces. We answer this question by implementing a graph theory technique to mathematically formalize the enumeration of minimum cut surfaces of crystals. While the algorithm is generally applicable to different classes of materials, we focus on zeolitic materials due to their diverse structural topology and because 2D zeolites have promising catalytic and separation performance compared to their 3D counterparts. We report here a simple descriptor based only on structural information that predicts whether a zeolite is likely to be synthesizable in the 2D form and correctly identifies the expressed surface in known layered 2D zeolites. The discovery of this descriptor allows us to highlight other zeolites that may also be synthesized in the 2D form that have not been experimentally realized yet. Finally, our method is general since the mathematical formalism can be applied to find the minimum cut surfaces of other crystallographic materials such as metal-organic frameworks, covalent-organic frameworks, zeolitic-imidazolate frameworks, metal oxides, etc.« less

Strongly Modulated Friction of a Film-Terminated Ridge-Channel Structure.

PubMed

He, Zhenping; Hui, Chung-Yuen; Levrard, Benjamin; Bai, Ying; Jagota, Anand

2016-05-26

Natural contacting surfaces have remarkable surface mechanical properties, which has led to the development of bioinspired surface structures using rubbery materials with strongly enhanced adhesion and static friction. However, sliding friction of structured rubbery surfaces is almost always significantly lower than that of a flat control, often due to significant loss of contact. Here we show that a film-terminated ridge-channel structure can strongly enhance sliding friction. We show that with properly chosen materials and geometrical parameters the near surface structure undergoes mechanical instabilities along with complex folding and sliding of internal interfaces, which is responsible for the enhancement of sliding friction. Because this structure shows no enhancement of adhesion under normal indentation by a sphere, it breaks the connection between energy loss during normal and shear loading. This makes it potentially interesting in many applications, for instance in tires, where one wishes to minimize rolling resistance (normal loading) while maximizing sliding friction (shear loading).

Synchronized femtosecond laser pulse switching system based nano-patterning technology

NASA Astrophysics Data System (ADS)

Sohn, Ik-Bu; Choi, Hun-Kook; Yoo, Dongyoon; Noh, Young-Chul; Sung, Jae-Hee; Lee, Seong-Ku; Ahsan, Md. Shamim; Lee, Ho

2017-07-01

This paper demonstrates the design and development of a synchronized femtosecond laser pulse switching system and its applications in nano-patterning of transparent materials. Due to synchronization, we are able to control the location of each irradiated laser pulse in any kind of substrate. The control over the scanning speed and scanning step of the laser beam enables us to pattern periodic micro/nano-metric holes, voids, and/or lines in various materials. Using the synchronized laser system, we pattern synchronized nano-holes on the surface of and inside various transparent materials including fused silica glass and polymethyl methacrylate to replicate any image or pattern on the surface of or inside (transparent) materials. We also investigate the application areas of the proposed synchronized femtosecond laser pulse switching system in a diverse field of science and technology, especially in optical memory, color marking, and synchronized micro/nano-scale patterning of materials.

Some wear studies on aircraft brake systems

NASA Technical Reports Server (NTRS)

Ho, T. L.

1975-01-01

An initial investigation of worn surfaces in friction pads and steel rotors used in current aircraft brakes was carried out using electron microprobe and X-ray diffraction analysis. It consists of the topographical study and the analysis of chemical element distribution. Based upon this initial examination, two approaches, microscopic and macroscopic have been conducted to interpret and formulate the wear mechanism of the aircraft brake materials. Microscopically, the wear particles were examined. The initiation and growth of surface cracks and the oxidation were emphasized in this investigation. Macroscopically, it has been found that, for the current copper based brake material sliding against 17-22 AS steel in a caliper brake, the surface temperature raised due to frictional heat is nonlinearly proportional to the load applied and slide time with speed at 1750 rpm. The wear of brake materials is then proportional to this temperature and is also a function of the melting temperature for copper.

Complex permittivity measurements during high temperature recycling of space shuttle antenna window and dielectric heat shield materials

NASA Technical Reports Server (NTRS)

Bassett, H. L.; Bomar, S. H., Jr.

1973-01-01

The research performed and the data obtained on candidate space shuttle antenna window and heat shield materials are presented. The measurement technique employs a free-space focused beam microwave bridge for obtaining RF transmission data, and a device which rotates a sample holder which is heated on one side by natural gas-air flames. The surface temperature of each sample is monitored by IR pyrometry; embedded and rear surface thermocouples are also used in obtaining temperature data. The surface of the sample undergoing test is subjected to approximately the same temperature/time profile that occurs at a proposed antenna position on the space shuttle as it re-enters. The samples are cycled through ten of these temperature profiles to determine the recycling effects. Very little change was noted in the materials due to the recycling.

Tritium saturation in plasma-facing materials surfaces1

NASA Astrophysics Data System (ADS)

Longhurst, Glen R.; Anderl, Robert A.; Causey, Rion A.; Federici, Gianfranco; Haasz, Anthony A.; Pawelko, Robert J.

1998-10-01

Plasma-facing components in the International Thermonuclear Experimental Reactor (ITER) will experience high heat loads and intense plasma fluxes of order 10 20-10 23 particles/m 2s. Experiments on Be and W, two of the materials considered for use in ITER, have revealed that a tritium saturation phenomenon can take place under these conditions in which damage to the surface results that enhances the return of implanted tritium to the plasma and inhibits uptake of tritium. This phenomenon is important because it implies that tritium inventories due to implantation in these plasma-facing materials will probably be lower than was previously estimated using classical recombination-limited release at the plasma surface. Similarly, permeation through these components to the coolant streams should be reduced. In this paper we discuss evidences for the existence of this phenomenon, describe techniques for modeling it, and present results of the application of such modeling to prior experiments.

Nanoscale definition of substrate materials to direct human adult stem cells towards tissue specific populations.

PubMed

Curran, Judith M; Chen, Rui; Stokes, Robert; Irvine, Eleanor; Graham, Duncan; Gubbins, Earl; Delaney, Deany; Amro, Nabil; Sanedrin, Raymond; Jamil, Haris; Hunt, John A

2010-03-01

The development of homogenously nano-patterned chemically modified surfaces that can be used to initiate a cellular response, particularly stem cell differentiation, in a highly controlled manner without the need for exogenous biological factors has never been reported, due to that fact that precisely defined and reproducible systems have not been available that can be used to study cell/material interactions and unlock the potential of a material driven cell response. Until now material driven stem cell (furthermore any cell) responses have been variable due to the limitations in definition and reproducibility of the underlying substrate and the lack of true homogeneity of modifications that can dictate a cellular response at a sub-micron level that can effectively control initial cell interactions of all cells that contact the surface. Here we report the successful design and use of homogenously molecularly nanopatterned surfaces to control initial stem cell adhesion and hence function. The highly specified nano-patterned arrays were compared directly to silane modified bulk coated substrates that have previously been proven to initiate mesenchymal stem cell (MSC) differentiation in a heterogenous manner, the aim of this study was to prove the efficiency of these previously observed cell responses could be enhanced by the incorporation of nano-patterns. Nano-patterned surfaces were prepared by Dip Pen Nanolithography (DPN) to produce arrays of 70 nm sized dots separated by defined spacings of 140, 280 and 1000 nm with terminal functionalities of carboxyl, amino, methyl and hydroxyl and used to control cell growth. These nanopatterned surfaces exhibited unprecedented control of initial cell interactions and will change the capabilities for stem cell definition in vitro and then cell based medical therapies. In addition to highlighting the ability of the materials to control stem cell functionality on an unprecedented scale this research also introduces the successful scale-up of DPN and the novel chemistries and systems to facilitate the production of homogeneously patterned substrates (5 mm2) that are applicable for use in in vitro cell conditions over prolonged periods for complete control of material driven cell responses.

Internal and surface waves in vibrofluidized granular materials: Role of cohesion

NASA Astrophysics Data System (ADS)

Huang, Kai

2018-05-01

Wave phenomena in vibrofluidized dry and partially wet granular materials confined in a quasi-two-dimensional geometry are investigated with numerical simulations considering individual particles as hard spheres. Short-ranged cohesive interactions arising from the formation of liquid bridges between adjacent particles are modeled by changing the velocity-dependent coefficient of restitution. Such a change effectively suppresses the formation of surface waves, in agreement with previous experimental observations. The difference in pattern creation arises from the suppressed momentum transfer due to wetting and it can be quantitatively understood from an analysis of binary impacts.

Assessing the Increase in Specific Surface Area for Electrospun Fibrous Network due to Pore Induction.

PubMed

Katsogiannis, Konstantinos Alexandros G; Vladisavljević, Goran T; Georgiadou, Stella; Rahmani, Ramin

2016-10-26

The effect of pore induction on increasing electrospun fibrous network specific surface area was investigated in this study. Theoretical models based on the available surface area of the fibrous network and exclusion of the surface area lost due to fiber-to-fiber contacts were developed. The models for calculation of the excluded area are based on Hertzian, Derjaguin-Muller-Toporov (DMT), and Johnson-Kendall-Roberts (JKR) contact models. Overall, the theoretical models correlated the network specific surface area to the material properties including density, surface tension, Young's modulus, Poisson's ratio, as well as network physical properties, such as density and geometrical characteristics including fiber radius, fiber aspect ratio and network thickness. Pore induction proved to increase the network specific surface area up to 52%, compared to the maximum surface area that could be achieved by nonporous fiber network with the same physical properties and geometrical characteristics. The model based on Johnson-Kendall-Roberts contact model describes accurately the fiber-to-fiber contact area under the experimental conditions used for pore generation. The experimental results and the theoretical model based on Johnson-Kendall-Roberts contact model show that the increase in network surface area due to pore induction can reach to up to 58%.

Relaxation dynamics of femtosecond-laser-induced temperature modulation on the surfaces of metals and semiconductors

NASA Astrophysics Data System (ADS)

Levy, Yoann; Derrien, Thibault J.-Y.; Bulgakova, Nadezhda M.; Gurevich, Evgeny L.; Mocek, Tomáš

2016-06-01

Formation of laser-induced periodic surface structures (LIPSS) is a complicated phenomenon which involves periodic spatial modulation of laser energy absorption on the irradiated surface, transient changes in optical response, surface layer melting and/or ablation. The listed processes strongly depend on laser fluence and pulse duration as well as on material properties. This paper is aimed at studying the spatiotemporal evolution of a periodic modulation of the deposited laser energy, once formed upon irradiation of metal (Ti) and semiconductor (Si) surfaces. Assuming that the incoming laser pulse interferes with a surface electromagnetic wave, the resulting sinusoidal modulation of the absorbed laser energy is introduced into a two-dimensional two-temperature model developed for titanium and silicon. Simulations reveal that the lattice temperature modulation on the surfaces of both materials following from the modulated absorption remains significant for longer than 50 ps after the laser pulse. In the cases considered here, the partially molten phase exists 10 ps in Ti and more than 50 ps in Si, suggesting that molten matter can be subjected to temperature-driven relocation toward LIPSS formation, due to the modulated temperature profile on the material surfaces. Molten phase at nanometric distances (nano-melting) is also revealed.

Surface properties of the Mars Science Laboratory candidate landing sites: characterization from orbit and predictions

USGS Publications Warehouse

Fergason, R.L.; Christensen, P.R.; Golombek, M.P.; Parker, T.J.

2012-01-01

This work describes the interpretation of THEMIS-derived thermal inertia data at the Eberswalde, Gale, Holden, and Mawrth Vallis Mars Science Laboratory (MSL) candidate landing sites and determines how thermophysical variations correspond to morphology and, when apparent, mineralogical diversity. At Eberswalde, the proportion of likely unconsolidated material relative to exposed bedrock or highly indurated surfaces controls the thermal inertia of a given region. At Gale, the majority of the landing site region has a moderate thermal inertia (250 to 410 J m-2 K-1 s-1/2), which is likely an indurated surface mixed with unconsolidated materials. The primary difference between higher and moderate thermal inertia surfaces may be due to the amount of mantling material present. Within the mound of stratified material in Gale, layers are distinguished in the thermal inertia data; the MSL rover could be traversing through materials that are both thermophysically and compositionally diverse. The majority of the Holden ellipse has a thermal inertia of 340 to 475 J m-2 K-1 s-1/2 and consists of bed forms with some consolidated material intermixed. Mawrth Vallis has a mean thermal inertia of 310 J m-2 K-1 s-1/2 and a wide variety of materials is present contributing to the moderate thermal inertia surfaces, including a mixture of bedrock, indurated surfaces, bed forms, and unconsolidated fines. Phyllosilicates have been identified at all four candidate landing sites, and these clay-bearing units typically have a similar thermal inertia value (400 to 500 J m-2 K-1 s-1/2), suggesting physical properties that are also similar.

Enhanced Photocatalytic Activity of Bismuth Precursor by Rapid Phase and Surface Transformation Using Structure-Guided Combustion Waves.

PubMed

Lee, Kang Yeol; Hwang, Hayoung; Kim, Tae Ho; Choi, Wonjoon

2016-02-10

The development of an efficient method for manipulating phase and surface transformations would facilitate the improvement of catalytic materials for use in a diverse range of applications. Herein, we present the first instance of a submicrosecond time frame direct phase and surface transformation of Bi(NO3)3 rods to nanoporous β-Bi2O3 rods via structure-guided combustion waves. Hybrid composites of the prepared Bi(NO3)3·H2O rods and organic fuel were fabricated by a facile preparation method. The anisotropic propagation of combustion waves along the interfacial boundaries of Bi(NO3)3·H2O rods induced direct phase transformation to β-Bi2O3 rods in the original structure due to the rapid pyrolysis, while the release of gas molecules enabled the formation of nanoporous structures on the surfaces of rods. The developed β-Bi2O3 rods showed improved photocatalytic activity for the photodegradation of rhodamine B in comparison with Bi(NO3)3·H2O rods and α-Bi2O3 rods due to the more suitable interdistance and the large contact areas of the porous surfaces. This new method of using structure-guided combustion waves for phase and surface transformation may contribute to the development of new catalysts as well as the precise manipulation of diverse micronanostructured materials.

Direct laser interference patterning of metallic sleeves for roll-to-roll hot embossing

NASA Astrophysics Data System (ADS)

Lang, Valentin; Rank, Andreas; Lasagni, Andrés. F.

2017-03-01

Surfaces equipped with periodic patterns with feature sizes in the micrometer, submicrometer and nanometer range present outstanding surface properties. Many of these surfaces can be found on different plants and animals. However, there are few methods capable to produce such patterns in a one-step process on relevant technological materials. Direct laser interference patterning (DLIP) provides both high resolution as well as high throughput. Recently, fabrication rates up to 1 m2·min-1 could be achieved. However, resolution was limited to a few micrometers due to typical thermal effects that arise when nanosecond pulsed laser systems are used. Therefore, this study introduces an alternative to ns-DLIP for the fabrication of multi-scaled micrometer and submicrometer structures on nickel surfaces using picosecond pulses (10 ps at a wavelength of 1064 nm). Due to the nature of the interaction process of the metallic surfaces with the ultrashort laser pulses, it was not only possible to directly transfer the shape of the interference pattern intensity distribution to the material (with spatial periods ranging from 1.5 μm to 5.7 μm), but also to selectively obtain laser induce periodic surface structures with feature sizes in the submicrometer and nanometer range. Finally, the structured nickel sleeves are utilized in a roll-to-roll hot embossing unit for structuring of polymer foils. Processing speeds up to 25 m·min-1 are reported.

An adapted yield criterion for the evolution of subsequent yield surfaces

NASA Astrophysics Data System (ADS)

Küsters, N.; Brosius, A.

2017-09-01

In numerical analysis of sheet metal forming processes, the anisotropic material behaviour is often modelled with isotropic work hardening and an average Lankford coefficient. In contrast, experimental observations show an evolution of the Lankford coefficients, which can be associated with a yield surface change due to kinematic and distortional hardening. Commonly, extensive efforts are carried out to describe these phenomena. In this paper an isotropic material model based on the Yld2000-2d criterion is adapted with an evolving yield exponent in order to change the yield surface shape. The yield exponent is linked to the accumulative plastic strain. This change has the effect of a rotating yield surface normal. As the normal is directly related to the Lankford coefficient, the change can be used to model the evolution of the Lankford coefficient during yielding. The paper will focus on the numerical implementation of the adapted material model for the FE-code LS-Dyna, mpi-version R7.1.2-d. A recently introduced identification scheme [1] is used to obtain the parameters for the evolving yield surface and will be briefly described for the proposed model. The suitability for numerical analysis will be discussed for deep drawing processes in general. Efforts for material characterization and modelling will be compared to other common yield surface descriptions. Besides experimental efforts and achieved accuracy, the potential of flexibility in material models and the risk of ambiguity during identification are of major interest in this paper.

Development of barrier coatings for cellulosic-based materials by cold plasma methods

NASA Astrophysics Data System (ADS)

Denes, Agnes Reka

Cellulose-based materials are ideal candidates for future industries that need to be based on environmentally safe technologies and renewable resources. Wood represents an important raw material and its application as construction material is well established. Cellophane is one of the most important cellulosic material and it is widely used as packaging material in the food industry. Outdoor exposure of wood causes a combination of physical and chemical degradation processes due to the combined effects of sunlight, moisture, fungi, and bacteria. Cold-plasma-induced surface modifications are an attractive way for tailoring the characteristics of lignocellulosic substrates to prevent weathering degradation. Plasma-polymerized hexamethyldisiloxane (PPHMDSO) was deposited onto wood surfaces to create water repellent characteristics. The presence of a crosslinked macromolecular structure was detected. The plasma coated samples exhibited very high water contact angle values indicating the existence of hydrophobic surfaces. Reflective and electromagnetic radiation-absorbent substances were incorporated with a high-molecular-weight polydimethylsiloxane polymer in liquid phase and deposited as thin layers on wood surfaces. The macromolecular films, containing the dispersed materials, were then converted into a three dimensional solid state network by exposure to a oxygen-plasma. It was demonstrated that both UV-absorbent and reflectant components incorporated into the plasma-generated PDMSO matrix protected the wood from weathering degradation. Reduced oxidation and less degradation was observed after simulated weathering. High water contact angle values indicated a strong hydrophobic character of the oxygen plasma-treated PDMSO-coated samples. Plasma-enhanced surface modifications and coatings were employed to create water-vapor barrier layers on cellophane substrate surfaces. HMDSO was selected as a plasma gas and oxygen was used to ablate amorphous regions. Oxygen plasma treated cellophane and oxygen plasma treated and PPHMDSO coated cellophane surfaces were comparatively analyzed and the corresponding surface wettability characteristics were evaluated. The plasma generated surface topographies controlled the morphology of the PPHMDSO layers. Higher temperature HMDSO plasma-state environments lead to insoluble, crosslinked layers. Continuous and pulsed Csb2Fsb6 plasmas were also used for surface modification and excellent surface fluorination was achieved under the pulsed plasma conditions.

Preparation of c-axis perpendicularly oriented ultra-thin L10-FePt films on MgO and VN underlayers

NASA Astrophysics Data System (ADS)

Futamoto, Masaaki; Shimizu, Tomoki; Ohtake, Mitsuru

2018-05-01

Ultra-thin L10-FePt films of 2 nm average thickness are prepared on (001) oriented MgO and VN underlayers epitaxially grown on base substrate of SrTiO3(001) single crystal. Detailed cross-sectional structures are observed by high-resolution transmission electron microscopy. Continuous L10-FePt(001) thin films with very flat surface are prepared on VN(001) underlayer whereas the films prepared on MgO(001) underlayer consist of isolated L10-FePt(001) crystal islands. Presence of misfit dislocation and lattice bending in L10-FePt material is reducing the effective lattice mismatch with respect to the underlayer to be less than 0.5 %. Formation of very flat and continuous FePt layer on VN underlayer is due to the large surface energy of VN material where de-wetting of FePt material at high temperature annealing process is suppressed under a force balance between the surface and interface energies of FePt and VN materials. An employment of underlayer or substrate material with the lattice constant and the surface energy larger than those of L10-FePt is important for the preparation of very thin FePt epitaxial thin continuous film with the c-axis controlled to be perpendicular to the substrate surface.

Prospects of DLC coating as environment friendly surface treatment process.

PubMed

Kim, S W; Kim, S G

2011-06-01

After first commercialization in 90's, the applications of diamond-like carbon (DLC) have been significantly expanded to tool, automobile parts, machineries and moulds to enhance wear and friction properties. Although DLC has many advantages like high hardness, low friction electrical insulating and chemical stability and has the possible market, its application in the field is still very limited due to the gaps of understanding between end-user and developer of its advantage of costing. Recently, one of the most popular issues in the surface modification is providing the long lasting super-hydrophilic or -hydrophobic properties on the material surface for the outdoor usage. A lot of material loss is caused due to water corrosion which has to do with the flow and contacts of water like fuel cell separator and air conditioner parts. The consequence of development of functional surface based on the hydrophilic or hydrophobic design for the important parts would be really helpful for materials to be cleaner and more energy effective. Here, we first reviewed the DLC technology and then examined the kind of surface modification as well as its merits and disadvantage. We also looked at how we can improve super-hydrophilic and super hydrophobic for the DLC coating layer as well as current status of technology and arts of DLC. In the end, we would like to suggest it as one of the environmental friendly industrial technology. Copyright © 2011 The Research Centre for Eco-Environmental Sciences, Chinese Academy of Sciences. Published by Elsevier B.V. All rights reserved.

Seasonal signatures in SFG vibrational spectra of the sea surface nanolayer at Boknis Eck Time Series Station (SW Baltic Sea)

NASA Astrophysics Data System (ADS)

Laß, K.; Bange, H. W.; Friedrichs, G.

2013-02-01

The very thin sea surface nanolayer on top of the sea surface microlayer, sometimes just one monomolecular layer thick, forms the interface between ocean and atmosphere. Due to the small dimension and tiny amount of substance, knowledge about the development of the layer in the course of the year is scarce. In this work, the sea surface nanolayer at Boknis Eck Time Series Station (BE), southwestern Baltic Sea, has been investigated over a period of three and a half years. Surface water samples were taken monthly by screen sampling and were analyzed in terms of organic content and composition by sum frequency generation spectroscopy, which is specifically sensitive to interfacial layers. A yearly periodicity has been observed with a pronounced abundance of sea surface nanolayer material (such as carbohydrate-rich material) during the summer months. On the basis of our results we conclude that the abundance of organic material in the nanolayer at Boknis Eck is not directly related to phytoplankton abundance. We suggest that indeed sloppy feeding of zooplankton together with photochemical and/or microbial processing of organic precursor compounds are responsible for the pronounced seasonality.

Seasonal signatures in SFG vibrational spectra of the sea surface nanolayer at Boknis Eck Time Series Station (SW Baltic Sea)

NASA Astrophysics Data System (ADS)

Laß, K.; Bange, H. W.; Friedrichs, G.

2013-08-01

The very thin sea surface nanolayer on top of the sea surface microlayer, sometimes just one monomolecular layer thick, forms the interface between ocean and atmosphere. Due to the small dimension and tiny amount of substance, knowledge about the development of the layer in the course of the year is scarce. In this work, the sea surface nanolayer at Boknis Eck Time Series Station (BE), southwestern Baltic Sea, has been investigated over a period of three and a half years. Surface water samples were taken monthly by screen sampling and were analyzed in terms of organic content and composition by sum frequency generation spectroscopy, which is specifically sensitive to interfacial layers. A yearly periodicity has been observed with a pronounced abundance of sea surface nanolayer material (such as carbohydrate-rich material) during the summer months. On the basis of our results we conclude that the abundance of organic material in the nanolayer at Boknis Eck is not directly related to phytoplankton abundance alone. We speculate that indeed sloppy feeding of zooplankton together with photochemical and/or microbial processing of organic precursor compounds is responsible for the pronounced seasonality.

Ultrashort pulse laser machining of metals and alloys

DOEpatents

Perry, Michael D.; Stuart, Brent C.

2003-09-16

The invention consists of a method for high precision machining (cutting, drilling, sculpting) of metals and alloys. By using pulses of a duration in the range of 10 femtoseconds to 100 picoseconds, extremely precise machining can be achieved with essentially no heat or shock affected zone. Because the pulses are so short, there is negligible thermal conduction beyond the region removed resulting in negligible thermal stress or shock to the material beyond approximately 0.1-1 micron (dependent upon the particular material) from the laser machined surface. Due to the short duration, the high intensity (>10.sup.12 W/cm.sup.2) associated with the interaction converts the material directly from the solid-state into an ionized plasma. Hydrodynamic expansion of the plasma eliminates the need for any ancillary techniques to remove material and produces extremely high quality machined surfaces with negligible redeposition either within the kerf or on the surface. Since there is negligible heating beyond the depth of material removed, the composition of the remaining material is unaffected by the laser machining process. This enables high precision machining of alloys and even pure metals with no change in grain structure.

Effect of Powder-Suspended Dielectric on the EDM Characteristics of Inconel 625

NASA Astrophysics Data System (ADS)

Talla, Gangadharudu; Gangopadhyay, S.; Biswas, C. K.

2016-02-01

The current work attempts to establish the criteria for powder material selection by investigating the influence of various powder-suspended dielectrics and machining parameters on various EDM characteristics of Inconel 625 (a nickel-based super alloy) which is nowadays regularly used in aerospace, chemical, and marine industries. The powders include aluminum (Al), graphite, and silicon (Si) that have significant variation in their thermo-physical characteristics. Results showed that powder properties like electrical conductivity, thermal conductivity, density, and hardness play a significant role in changing the machining performance and the quality of the machined surface. Among the three powders, highest material removal rate was observed for graphite powder due to its high electrical and thermal conductivities. Best surface finish and least radial overcut (ROC) were attained using Si powder. Maximum microhardness was found for Si due to its low thermal conductivity and high hardness. It is followed by graphite and aluminum powders. Addition of powder to the dielectric has increased the crater diameter due to expansion of plasma channel. Powder-mixed EDM (PMEDM) was also effective in lowering the density of surface cracks with least number of cracks obtained with graphite powder. X-ray diffraction analysis indicated possible formation of metal carbides along with grain growth phenomenon of Inconel 625 after PMEDM.

Study of Fresh and Hardening Process Properties of Gypsum with Three Different PCM Inclusion Methods

PubMed Central

Serrano, Susana; Barreneche, Camila; Navarro, Antonia; Haurie, Laia; Fernandez, A. Inés; Cabeza, Luisa F.

2015-01-01

Gypsum has two important states (fresh and hardened states), and the addition of phase change materials (PCM) can vary the properties of the material. Many authors have extensively studied properties in the hardened state; however, the variation of fresh state properties due to the addition of Micronal® DS 5001 X PCM into gypsum has been the object of few investigations. Properties in fresh state define the workability, setting time, adherence and shrinkage, and, therefore the possibility of implementing the material in building walls. The aim of the study is to analyze, compare and evaluate the variability of fresh state properties after the inclusion of 10% PCM. PCM are added into a common gypsum matrix by three different methods: adding microencapsulated PCM, making a suspension of PCM/water, and incorporating PCM through a vacuum impregnation method. Results demonstrate that the inclusion of PCM change completely the water required by the gypsum to achieve good workability, especially the formulation containing Micronal® DS 5001 X: the water required is higher, the retraction is lower (50% less) due to the organic nature of the PCM with high elasticity and, the adherence is reduced (up to 45%) due to the difference between the porosity of the different surfaces as well as the surface tension difference. PMID:28793584

Laser Ablation Surface-Enhanced Raman Spectroscopy (LA-SERS) for the Characterization of Organic Colorants in Cultural Heritage

NASA Astrophysics Data System (ADS)

Londero, Pablo

The characterization of artistic practice throughout history often requires measurements of material composition with microscopic resolution, either due to the fine detail of the material composition or to the amount of sample available. This problem is exacerbated for the detection of organic colorants, which are often embedded in a complex matrix (e.g. oil, natural fibers) and in low concentration due to their high tinting strength. Surface-Enhanced Raman Spectroscopy (SERS) is increasingly used in detection of organic colorants in cultural heritage due to its high sensitivity and inherent preferential sensitivity to small organic molecules. This talk will discuss recent results from a new SERS measurement technique, in which laser ablation is used as a micro-sampling method onto a SERS-active film to characterize art samples with microscopic precision and sensitivity comparable to many mass spectrometry measurements. Furthermore, the nature of the sampling method provides built-in benefits to other SERS-based techniques, such as more quantitative characterization of mixtures, improved sensitivity to some analytes, and reduced background interference. Examples will be shown for measurements of reference materials and art objects, including a restored 16th-century dish and a Renaissance fresco, The Incredulity of San Thomas, by Luca Signorelli. Supported by the National Science Foundation (NSF-CHE-1402750).

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

Choi, Hyekyoung; Kim, Sungwoo; Luther, Joseph M.

Silver dimetal chalcogenide (Ag-V-VI 2) ternary quantum dots (QDs) are emerging lead-free materials for optoelectronic devices due to their NIR band gaps, large absorption coefficients, and superior electronic properties. However, thin film-based devices of the ternary QDs still lag behind due to the lack of understanding of the surface chemistry, compared to that of lead chalcogenide QDs even with the same crystal structure. Here in this paper, the surface ligand interactions of AgSbS 2 QDs, synthesized with 1-dodecanethiol used as a stabilizer, are studied. For nonpolar (1 0 0) surfaces, it is suggested that the thiolate ligands are associated withmore » the crystal lattices, thus preventing surface oxidation by protecting sulfur after air-exposure, as confirmed through optical and surface chemical analysis. Otherwise, silver rich (1 1 1) surfaces are passivated by thiolate ligands, allowing ligand exchange processes for the conductive films. This in-depth investigation of the surface chemistry of ternary QDs will prompt the performance enhancement of their optoelectronic devices.« less

Calcium phosphate-titanium composites for articulating surfaces of load-bearing implants.

PubMed

Bandyopadhyay, Amit; Dittrick, Stanley; Gualtieri, Thomas; Wu, Jeffrey; Bose, Susmita

2016-04-01

Calcium phosphate (CaP)-titanium (Ti) composites were processed using a commercial laser engineered net shaping (LENS™) machine to increase wear resistance of articulating surfaces of load-bearing implants. Such composites could be used to cover the surface of titanium implants and potentially increase the lifetime of a joint replacement. It was hypothesized that adding calcium phosphate to commercially pure titanium (CP-Ti) and Ti6Al4V alloy via laser processing would decrease the material loss when subjected to wear. This added protection would be due to the in situ formation of a CaP tribofilm. Different amounts of CaP were mixed by weight with pure Ti and Ti6Al4V powders. The mixed powders were then made into cylindrical samples using a commercial LENS™-750 system. Microstructures were observed and it was found the CaP had integrated into the titanium metal matrix. Compression test revealed that CaP significantly increased the 0.2% offset yield strength as well as the ultimate compressive strength of CP-Ti. It was found that the addition of CaP to pure titanium reduced the material loss and increased wear resistance. This was due to the formation of CaP tribofilm on the articulating surface. The in situ formed tribofilm also lowered the coefficient of friction and acted as a solid lubricant between the two interacting metal surfaces. Overall, CaP addition to Ti and its alloy Ti6Al4V show an effective way to minimize wear induced damage due to the formation of in situ tribofilm at the articulating surface, a strategy that can be utilized in various biomedical devices. Copyright © 2015 Elsevier Ltd. All rights reserved.

Rejection of Alpha Surface Background in Non-scintillating Bolometric Detectors: The ABSuRD Project

DOE PAGES

Biassoni, M.; Brofferio, C.; Bucci, C.; ...

2016-01-14

Due to their excellent energy resolution values and the vast choice of possible materials, bolometric detectors are currently widely used in the physics of rare events. A limiting aspect for bolometers rises from their inability to discriminate among radiation types or surface from bulk events. It has been demonstrated that the main limitation to sensitivity for purely bolometric detectors is represented by surface alpha contaminations, causing a continuous background that cannot be discriminated. A new scintillation based technique for the rejection of surface alpha background in non- scintillating bolometric experiments is proposed in this work. The idea is to combinemore » a scintillating and a high sensitivity photon detector with a non- scintillating absorber. Finally, we present results showing the possibility to reject events due to alpha decay at or nearby the surface of the crystal.« less

Surface plasticity: theory and computation

NASA Astrophysics Data System (ADS)

Esmaeili, A.; Steinmann, P.; Javili, A.

2017-11-01

Surfaces of solids behave differently from the bulk due to different atomic rearrangements and processes such as oxidation or aging. Such behavior can become markedly dominant at the nanoscale due to the large ratio of surface area to bulk volume. The surface elasticity theory (Gurtin and Murdoch in Arch Ration Mech Anal 57(4):291-323, 1975) has proven to be a powerful strategy to capture the size-dependent response of nano-materials. While the surface elasticity theory is well-established to date, surface plasticity still remains elusive and poorly understood. The objective of this contribution is to establish a thermodynamically consistent surface elastoplasticity theory for finite deformations. A phenomenological isotropic plasticity model for the surface is developed based on the postulated elastoplastic multiplicative decomposition of the surface superficial deformation gradient. The non-linear governing equations and the weak forms thereof are derived. The numerical implementation is carried out using the finite element method and the consistent elastoplastic tangent of the surface contribution is derived. Finally, a series of numerical examples provide further insight into the problem and elucidate the key features of the proposed theory.

Biodegradable Magnesium Alloys Developed as Bone Repair Materials: A Review

PubMed Central

Liu, Chen; Ren, Zheng; Xu, Yongdong; Pang, Song; Zhao, Xinbing

2018-01-01

Bone repair materials are rapidly becoming a hot topic in the field of biomedical materials due to being an important means of repairing human bony deficiencies and replacing hard tissue. Magnesium (Mg) alloys are potentially biocompatible, osteoconductive, and biodegradable metallic materials that can be used in bone repair due to their in situ degradation in the body, mechanical properties similar to those of bones, and ability to positively stimulate the formation of new bones. However, rapid degradation of these materials in physiological environments may lead to gas cavities, hemolysis, and osteolysis and thus, hinder their clinical orthopedic applications. This paper reviews recent work on the use of Mg alloy implants in bone repair. Research to date on alloy design, surface modification, and biological performance of Mg alloys is comprehensively summarized. Future challenges for and developments in biomedical Mg alloys for use in bone repair are also discussed. PMID:29725492

A position-aware linear solid constitutive model for peridynamics

DOE PAGES

Mitchell, John A.; Silling, Stewart A.; Littlewood, David J.

2015-11-06

A position-aware linear solid (PALS) peridynamic constitutive model is proposed for isotropic elastic solids. The PALS model addresses problems that arise, in ordinary peridynamic material models such as the linear peridynamic solid (LPS), due to incomplete neighborhoods near the surface of a body. We improved model behavior in the vicinity of free surfaces through the application of two influence functions that correspond, respectively, to the volumetric and deviatoric parts of the deformation. Furthermore, the model is position-aware in that the influence functions vary over the body and reflect the proximity of each material point to free surfaces. Demonstration calculations onmore » simple benchmark problems show a sharp reduction in error relative to the LPS model.« less

A position-aware linear solid constitutive model for peridynamics

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

Mitchell, John A.; Silling, Stewart A.; Littlewood, David J.

A position-aware linear solid (PALS) peridynamic constitutive model is proposed for isotropic elastic solids. The PALS model addresses problems that arise, in ordinary peridynamic material models such as the linear peridynamic solid (LPS), due to incomplete neighborhoods near the surface of a body. We improved model behavior in the vicinity of free surfaces through the application of two influence functions that correspond, respectively, to the volumetric and deviatoric parts of the deformation. Furthermore, the model is position-aware in that the influence functions vary over the body and reflect the proximity of each material point to free surfaces. Demonstration calculations onmore » simple benchmark problems show a sharp reduction in error relative to the LPS model.« less

Influence of the Cutting Conditions in the Surface Finishing of Turned Pieces of Titanium Alloys

NASA Astrophysics Data System (ADS)

Huerta, M.; Arroyo, P.; Sánchez Carrilero, M.; Álvarez, M.; Salguero, J.; Marcos, M.

2009-11-01

Titanium is a material that, despite its high cost, is increasingly being introduced in the aerospace industry due to both, its weight, its mechanical properties and its corrosion potential, very close to that of carbon fiber based composite material. This fact allows using Ti to form Fiber Metal Laminates Machining operations are usually used in the manufacturing processes of Ti based aerospace structural elements. These elements must be machined under high surface finish requirements. Previous works have shown the relationship between the surface roughness and the tool changes in the first instants of turning processes. From these results, new tests have been performed in an aeronautical factory, in order to analyse roughness in final pieces.

Fabrication of p-n heterostructure ZnO/Si moth-eye structures: Antireflection, enhanced charge separation and photocatalytic properties

NASA Astrophysics Data System (ADS)

Zeng, Yu; Chen, XiFang; Yi, Zao; Yi, Yougen; Xu, Xibin

2018-05-01

The pyramidal silicon substrate is formed by wet etching, then ZnO nanorods are grown on the surface of the pyramidal microstructure by a hydrothermal method to form a moth-eye composite heterostructure. The composite heterostructure of this material determines its excellent anti-reflection properties and ability to absorb light from all angles. In addition, due to the effective heterojunction binding area, the composite micro/nano structure has excellent photoelectric conversion performance. Its surface structure and the large specific surface area gives the material super hydrophilicity, excellent gas sensing characteristic, and photocatalytic properties. Based on the above characteristics, the micro/nano heterostructure can be used in solar cells, sensors, light-emitting devices, and photocatalytic fields.

The Diverse Surface Compositions of the Galilean Satellites

NASA Technical Reports Server (NTRS)

Carlson, R. W.

2002-01-01

The galilean satellites represent a diverse collection, ranging from the volcanic moon Io, with a surface that is changing yearly, to Callisto, with a dark, ancient surface overlying ice. The composition of these surfaces are also quite different due to a variety of processes and influences, including tidal heating, radiolysis, gardening, a magnetic field (Ganymede), and meteoritic infall. Io's surface contains large quantities of sulfur dioxide (SO2) and colorful sulfur allotropes, both originating in plumes and flows from the tidally driven volcanoes. A broad, 1-micron band is found at high latitudes and may be due to absorption by long-chain sulfur polymers produced by SO2 radiolysis, although iron and iron sulfide compounds are candidates. An unidentified 3.15 micron absorber is equatorially distributed while a 4.62 micron band, perhaps due to a sulfate compound, exhibits a non-uniform distribution. Hot spots are generally dark, and some exhibit negative reflectance slopes (i.e., blue). The composition of these lavas has not been established spectroscopically, but the high temperatures of some volcanoes suggest ultramafic silicates or perhaps more refractory material such as oxides.

Antifouling Properties of Fluoropolymer Brushes toward Organic Polymers: The Influence of Composition, Thickness, Brush Architecture, and Annealing.

PubMed

Wang, Zhanhua; Zuilhof, Han

2016-07-05

Fluoropolymer brushes are widely used to prevent nonspecific adsorption of commercial polymeric or biological materials due to their strongly hydrophobic character. Herein, a series of fluoropolymer brushes with different compositions, thicknesses and molecular architectures was prepared via surface-initiated atom transfer radical polymerization (ATRP). Subsequently, the antifouling properties of these fluoropolymer brushes against organic polymers were studied in detail using X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM) measurements and polystyrene as a representative fouling polymer. Among all of the molecular architectures studied, homopolymerized methacrylate-based fluoropolymer brushes (PMAF17) show the best antifouling properties. Annealing the fluoropolymer brushes improves the antifouling property dramatically due to the reregulated surface composition. These fluoropolymer brushes can be combined with, e.g., micro- and nanostructuring and other advanced materials properties to yield even better long-term antifouling behavior under harsh environments.

Molecular dynamics modeling of periodic nanostructuring of metals with a short UV laser pulse under spatial confinement by a water layer

NASA Astrophysics Data System (ADS)

Ivanov, D. S.; Blumenstein, A.; Ihlemann, J.; Simon, P.; Garcia, M. E.; Rethfeld, B.

2017-12-01

The possibility of material surfaces restructuring on the nanoscale due to ultrashort laser pulses has recently found a number of practical applications. It was found experimentally that under spatial confinement due to a liquid layer atop the surface, one can achieve even finer and cleaner structures as compared to that in air or in vacuum. The mechanism of the materials restructuring under the liquid confinement, however, is not clear and its experimental study is limited by the extreme conditions realized during the intense and localized laser energy deposition that takes place on nanometer spatial and picosecond time-scales. In this theoretical work, we suggest a molecular dynamics-based approach that is capable of simulating the processes of periodic nanostructuring with ultrashort UV laser pulse on metals. The theoretical results of the simulations are directly compared with the experimental data on the same spatial and temporal scales.

Investigating the thermophysical properties of indurated materials on Mars

NASA Astrophysics Data System (ADS)

Murphy, Nathaniel William

Indurated materials have been observed on the surface of Mars at every landing site and inferred from orbital remote-sensing data by the Viking, Mars Global Surveyor, and Mars Odyssey spacecraft. However, indurated materials on Mars are poorly understood because there is no ground truth for the indurated surfaces inferred from thermal remote-sensing data. I adopted two approaches to investigate indurated materials on Mars: (1) remote-sensing analysis of the Isidis basin, which shows some of the highest thermal inertia values derived from TES 1 observations, and (2) laboratory analyses of terrestrial indurated materials. To characterize the surface of the Isidis basin, I combined a variety of remote-sensing datasets, including thermal inertia data derived from TES and MO-THEMIS, TES albedo, THEMIS thermal and visible imaging, and Earth-based radar observations. From these observations I concluded that the thermal inertia values in the Isidis basin are likely the result of variations in the degree of cementation of indurated materials. To examine the thermophysical properties of indurated materials I collected four examples of terrestrial indurated materials. These included two types of gypcrete collected from a gypcrete deposit near Upham Hills, NM, clay-materials from Lunar Lake Playa, NV, and a pyroclastic material from the Bandelier Tuff near Los Alamos, NM. Despite significant differences in their physical properties and origins, all of these materials have thermal inertia values consistent with inferred indurated surfaces on Mars. There are no strong correlations between the thermal and physical properties of the collected samples due to thermal effects of the fabrics of the indurated materials. 1 Thermal Emission Spectrometer onboard the Mars Global Surveyor spacecraft. 2 Thermal Emission Imaging System onboard the Mars Odyssey spacecraft

Comments on the interaction of materials with atomic oxygen

NASA Technical Reports Server (NTRS)

Torre, Larry P.; Pippin, H. Gary

1987-01-01

An explanation of the relative resistance of various materials to attack by atomic oxygen is presented. Data from both ground based and on-orbit experiments is interpreted. The results indicate the importance of bond strengths, size and structure of pendant groups, and fluorination to the resistance of certain polymers to atomic oxygen. A theory which provides a partial explanation of the degradation of materials in low Earth orbit due to surface recombination of oxygen atoms is also included. Finally, a section commenting on mechanisms of material degradation is provided.

Characterization and optimization of polycrystalline Si70%Ge30% for surface micromachined thermopiles in human body applications

NASA Astrophysics Data System (ADS)

Wang, Ziyang; Fiorini, Paolo; Leonov, Vladimir; Van Hoof, Chris

2009-09-01

This paper presents the material characterization methods, characterization results and the optimization scheme for polycrystalline Si70%Ge30% (poly-SiGe) from the perspective of its application in a surface micromachined thermopile. Due to its comparative advantages, such as lower thermal conductivity and ease of processing, over other materials, poly-SiGe is chosen to fabricate a surface micromachined thermopile and eventually a wearable thermoelectric generator (TEG) to be used on a human body. To enable optimal design of advanced thermocouple microstructures, poly-SiGe sample materials prepared by two different techniques, namely low-pressure chemical vapor deposition (LPCVD) with in situ doping and rapid thermal chemical vapor deposition (RTCVD) with ion implantation, have been characterized. Relevant material properties, including electrical resistivity, Seebeck coefficient, thermal conductivity and specific contact resistance, have been reported. For the determination of thermal conductivity, a novel surface-micromachined test structure based on the Seebeck effect is designed, fabricated and measured. Compared to the traditional test structures, it is more advantageous for sample materials with a relatively large Seebeck coefficient, such as poly-SiGe. Based on the characterization results, a further optimization scheme is suggested to allow independent respective optimization of the figure of merit and the specific contact resistance.

Post-fire mulching and soil hydrological response

NASA Astrophysics Data System (ADS)

Jordán, Antonio; Zavala, Lorena M.; Gordillo-Rivero, Ángel J.; Muñoz-Rojas, Miriam; Keesstra, Saskia; Cerdà, Artemi

2017-04-01

In general, one of the major threats after a forest fire is the increased erosion. This can occur due to the erosive impact of rainfall after a drastic reduction of vegetation cover or to changes in soil surface properties that contribute to enhanced runoff flow. There is a consensus among researchers that one of the best ways to reduce this risk is to apply a mulch cover (straw, shredded wood or other materials) immediately after fire. In this study, we studied the effectiveness of various types of mulch materials for the reduction of runoff and soil loss during the first 3 years after a forest fire, in plots of different sizes, with special attention to water repellency and physical properties of the soil surface. In general, straw mulch reduced both runoff and erosion rate more than other treatments. However, the effect was much more important on larger plots. This may be due to specific processes and impacts on sediment connectivity and surface water flow. Therefore, the effect of the scale seems to be an important factor in the management of burnt soils.

A model for the origin of Martian polygonal terrain

NASA Technical Reports Server (NTRS)

Mcgill, G. E.

1993-01-01

Extensive areas of the Martian northern plains in Utopia and Acidalia Planitiae are characterized by 'polygonal terrain.' Polygonal terrain consists of material cut by complex troughs defining a pattern resembling mudcracks, columnar joints, or frost-wedge polygons on the Earth. However, the Martian polygons are orders of magnitude larger than these potential Earth analogs, leading to severe mechanical difficulties for genetic models based on simple analogy arguments. Stratigraphic studies show that the polygonally fractured material in Utopia Planitia was deposited on a land surface with significant topography, including scattered knobs and mesas, fragments of ancient crater rims, and fresh younger craters. Sediments or volcanics deposited over topographically irregular surfaces can experience differential compaction producing drape folds. Bending stresses due to these drape folds would be superposed on the pervasive tensile stresses due to desiccation or cooling, such that the probability of fracturing is enhanced above buried topographic highs and suppressed above buried topographic lows. Thus it was proposed that the scale of the Martian polygons is controlled by the spacing of topographic highs on the buried surface rather than by the physics of the shrinkage process.

Casimir forces from conductive silicon carbide surfaces

NASA Astrophysics Data System (ADS)

Sedighi, M.; Svetovoy, V. B.; Broer, W. H.; Palasantzas, G.

2014-05-01

Samples of conductive silicon carbide (SiC), which is a promising material due to its excellent properties for devices operating in severe environments, were characterized with the atomic force microscope for roughness, and the optical properties were measured with ellipsometry in a wide range of frequencies. The samples show significant far-infrared absorption due to concentration of charge carriers and a sharp surface phonon-polariton peak. The Casimir interaction of SiC with different materials is calculated and discussed. As a result of the infrared structure and beyond to low frequencies, the Casimir force for SiC-SiC and SiC-Au approaches very slowly the limit of ideal metals, while it saturates significantly below this limit if interaction with insulators takes place (SiC-SiO2). At short separations (<10 nm) analysis of the van der Waals force yielded Hamaker constants for SiC-SiC interactions lower but comparable to those of metals, which is of significance to adhesion and surface assembly processes. Finally, bifurcation analysis of microelectromechanical system actuation indicated that SiC can enhance the regime of stable equilibria against stiction.

Educational Brief: Using Space for a Better Foundation on Earth Mechanics of Granular Materials

NASA Technical Reports Server (NTRS)

Dooling, Dave (Editor)

2002-01-01

Soils are three-phase composite materials that consist of soil, solid particles, and voids filled with water and/or air. Based on the particle-size distribution, they are generally classified as fine-grained (clays and plastic silts) and coarse-grained soils (nonplastic silts, sand, and gravel). Soil's resistance to external loadings is mainly derived from friction between particles and cohesion. Friction resistance is due to particles' surface-to-surface friction, interlocking, crushing, rearrangement, and dilation (or expansion) during shearing. Cohesion can be due to chemical cementation between particles, electrostatic and electromagnetic forces, and soil-water reaction and equilibrium. The basic factor responsible for the strength of coarse-grained soils is friction. Cohesion can be ignored. This educational brief focuses on measuring shear strength of sands (typical example of coarse-grained soils) where, for the same material, packing density is a main factor to be considered when one asks about the shear strength value. As the external load is applied, the soil's resistance is attained through shearing resistance, which causes the soil volume to increase (expand) or decrease (compress) depending on the initial packing density.

Flammability of self-extinguishing kenaf/ABS nanoclays composite for aircraft secondary structure

NASA Astrophysics Data System (ADS)

Karunakaran, S.; Majid, D. L.; Mohd Tawil, M. L.

2016-10-01

This study investigates the flammability properties of kenaf fiber reinforced acrylonitrile butadiene styrene (ABS) with nanoclays composites. Natural fiber is one of the potential materials to be used with thermoplastic as a composite due to its attractive properties such as lightweight and strong. In this paper, flammability properties of this material are evaluated through Underwriters Laboratory 94 Horizontal Burning (UL94 HB), which has been conducted for both controlled and uncontrolled conditions, smoke density and limiting oxygen index tests (LOI). These flammability tests are in compliance with the Federal Aviation Regulation (FAR) requirement. The results from UL94 HB and smoke density tests show that the presence of nanoclays with effective composition of kenaf fiber reinforced ABS has enhanced the burning characteristics of the material by hindering propagation of flame spread over the surface of the material through char formation. Consequently, this decreases the burning rate and produces low amount of smoke during burning. On contrary, through LOI test, this material requires less oxygen to burn when exposed to fire, which hinders the enhancement of burning characteristics. This is due to burning mechanism exhibited by nanoclays that catalyzes barrier formation and flame propagation rate over the surface of the biocomposite material. Overall, these experimental results suggest that this biocomposite material is capable of self-extinguishing and possesses effective fire extinction. The observed novel synergism from the result obtained is promising to be implemented in secondary structures of aircraft with significant benefits such as cost-effective, lightweight and biodegradable self-extinguishing biocomposite.

Improve electrochemical performance of CeO2 surface modification LiNi0.80Co0.15Al0.05O2 cathode material

NASA Astrophysics Data System (ADS)

Xia, Shubiao; Zhang, Yingjie; Dong, Peng; Zhang, Yannan

2014-06-01

Lithium ion battery cathode material LiNi0.8Co0.15Al0.05O2 cathode has successfully prepared by co-precipitation. CeO2 surface modification has improved LiNi0.80Co0.15Al0.05O2 electrochemical performance use sol-gel method and subsequent heat treatment at 600 °C for 5 h. Different to other conventional coating material, CeO2 coating layer can not only inhibit the reaction of the electrode and the electrolyte, but also can reduce the impedance of electron transfer due to its high conductivity, and inhibit the production of Ni2+ because of its high oxidation. The surface-modified and pristine LiNi0.80Co0.15Al0.05O2 powders are characterized by XRD, SEM, TEM, XPS, CV and DSC. When CeO2 coating is 0.02% (mole ratio), contrast to pristine NCA, the CeO2-coated NCA cathode exhibits no decrease in its initial specific capacity of 184 mAh g -1 (at 0.2 C) and excellent capacity retention (86% of its initial capacity at 1 C) between 2.75 and 4.3 V after 100 cycles. The results indicate that the CeO2 surface treatment should be an effective way to improve cycle properties due to CeO2 inhibit the electrodes and the electrolyte side effects.

New chemical approach to obtain dense layer phosphate-based ionic conductor coating on negative electrode material surface: Synthesis way, outgassing and improvement of C-rate capability

NASA Astrophysics Data System (ADS)

Fleutot, Benoit; Davoisne, Carine; Gachot, Grégory; Cavalaglio, Sébastien; Grugeon, Sylvie; Viallet, Virginie

2017-04-01

Li4Ti5O12 (LTO) based batteries have severe gassing behavior during charge/discharge and storage process, due to interfacial reactions between active material and electrolyte solution. In the same time, the electronic and ionic conductivity of pristine LTO is very poor and induces the use of nanoparticles which increase the outgassing phenomena. The coating of LTO particles could be a solution. For this the LTO spinel particles are modified with ionic conductor Li3PO4 coating using a spray-drying method. For the first time a homogeneous thin dense layer phosphate based conductor is obtained without nanoparticles, as a thin film material. It is so possible to study the influence of ionic conductor deposited on the negative electrode material on performances by the controlled layer thickness. This coating was characterized by XRD, SEM, XPS and TEM. The electrochemical performance of Li3PO4 coated Li4Ti5O12 is improved at high C-rate by the surface modification (improvement of 30 mAh g-1 at 5 C-rate compared to pristine LTO for 5 nm of coating), inducing by a modification of surface energy. An optimum coating thickness was studied. This type of coating allows a significant decrease of outgassing phenomena due the conformal coating and opens the way to a great number of studies and new technologies.

Design and performance of a Near Ultra High Vacuum Helium Ion Microscope

NASA Astrophysics Data System (ADS)

Poelsema, Bene; van Gastel, Raoul; Hlawacek, Gregor; Zandvliet, Harold J. W.

2012-02-01

The advent of He Ion Microscopy (HIM) as a new nanoscopic technique to image materials has enabled a new look at materials that is based on the interaction of swift light ions with matter. Initial HIM instruments have demonstrated high-resolution imaging, combined with great surface sensitivity, the ability to neutralize charge very efficiently, and with enhanced materials contrast when ion induced secondary electrons are used for imaging. To achieve ultimate performance, the chamber vacuum of the existing platform may be improved. For instance, carbon deposits due to beam interaction are readily seen due to the surface sensitivity of the technique. At high current densities the sharply focused beam may very efficiently decompose residual hydrocarbons. Not only can this obscure a clear view of the sample, thereby negating the benefits of the small spot size, it also limits the available acquisition time. This has proven extremely useful for nanopatterning for sensors, and other device fabrication applications at the sub-10nm level. However, it is undesirable when the instrument is used for materials characterization. We will discuss the basic considerations that went into the design of a Near-UHV He Ion Microscope [1]. First applications that the instrument was used for will be highlighted and its impact in surface physics and other research areas that require increased imaging sensitivity will be discussed. [4pt] [1] R.van Gastel et al, Microscopy and Microanalysis 17, 928-929 (2011)

Physicochemical characterizations of nano-palm oil fuel ash

NASA Astrophysics Data System (ADS)

Rajak, Mohd Azrul Abdul; Majid, Zaiton Abdul; Ismail, Mohammad

2015-07-01

Palm Oil Fuel Ash (POFA) is known as a good supplementary cementing material due to its siliceous-rich content. The application of nanotechnology in the pozzolanic materials could invent new functions in the efficiency of physical and chemical properties of materials. Thus, the present study aims to generate nano-sized POFA and characterize the physicochemical properties of nano-palm oil fuel ash (nPOFA). The nPOFA was prepared by mechanically grinding micro POFA using a high intensity ball milling for 6 hours. The physicochemical properties of nPOFA were characterized via X-Ray Fluoresence (XRF), Scanning Emission microscopy- Energy Dispersive X-Ray (SEM-EDX), Transmission Electron Microscope (TEM) and X-Ray Diffraction (XRD). The particle size of nPOFA acquired from TEM analysis was in the range of 20 nm to 90 nm, while the average crystallite size calculated from XRD diffractogram was 61.5 nm. The resulting nPOFA has a BET surface area of 145.35 m2/g, which is more than 85% increment in surface area compared to micro-sized POFA. The morphology and elemental studies showed the presence of spherical as well as irregularly shaped and fine nPOFA particles contains with high silicon content. The presence of α-quartz as the major phase of the nPOFA was identified through XRD analysis. The study concludes that nPOFA has the potential as a supplementary cementing material due to the high silica content, high surface area and the unique behaviors of nano-structured particles.

Amine–mixed oxide hybrid materials for carbon dioxide adsorption from CO2/H2 mixture

NASA Astrophysics Data System (ADS)

Ravi, Navin; Aishah Anuar, Siti; Yusuf, Nur Yusra Mt; Isahak, Wan Nor Roslam Wan; Shahbudin Masdar, Mohd

2018-05-01

Bio-hydrogen mainly contains hydrogen and high level of carbon dioxide (CO2). High concentration of CO2 lead to a limitation especially in fuel cell application. In this study, the amine-mixed oxide hybrid materials for CO2 separation from bio-hydrogen model (50% CO2:50% H2) have been studied. Fourier-transform infrared spectroscopy (FTIR) and x-ray diffraction (XRD) characterizations showed that the amine–mixed oxide hybrid materials successfully adsorbed CO2 physically with no chemical adsorption evidence. The dry gas of CO2/H2 mixture adsorbed physically on amine–CuO–MgO hybrid material. No carbonates were detected after several times of adsorption, which indicated the good recyclability of adsorbents. The adsorbent system of diethanolamine (DEA)/15% CuO–75% MgO showed the highest CO2 adsorption capacity of 21.2 wt% due to the presence of polar substance on MgO surface, which can adsorb CO2 at ambient condition. The alcohol group of DEA can enhance the CO2 solubility on the adsorbent surface. In the 20% CuO–50% MgO adsorbent system, DEA as amine type showed a high CO2 adsorption of 19.4 wt%. The 10% amine loading system showed that the DEA adsorption system provided high CO2 adsorption. The BET analysis confirmed that a high amine loading contributed to the decrease in CO2 adsorption due to the low surface area of the adsorbent system.

Surface Functionalized Nanostructured Ceramic Sorbents for the Effective Collection and Recovery of Uranium from Seawater

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

Chouyyok, Wilaiwan; Pittman, Jonathan W.; Warner, Marvin G.

2016-05-02

The ability to collect uranium from seawater offers the potential for a nearly limitless fuel supply for nuclear energy. We evaluated the use of functionalized nanostructured sorbents for the collection and recovery of uranium from seawater. Extraction of trace minerals from seawater and brines is challenging due to the high ionic strength of seawater, low mineral concentrations, and fouling of surfaces over time. We demonstrate that rationally assembled sorbent materials that integrate high affinity surface chemistry and high surface area nanostructures into an application relevant micro/macro structure enables collection performance that far exceeds typical sorbent materials. High surface area nanostructuredmore » silica with surface chemistries composed of phosphonic acid, phosphonates, 3,4 hydroxypyridinone, and EDTA showed superior performance for uranium collection. A few phosphorous-based commercial resins, specifically Diphonix and Ln Resin, also performed well. We demonstrate an effective and environmentally benign method of stripping the uranium from the high affinity sorbents using inexpensive nontoxic carbonate solutions. The cyclic use of preferred sorbents and acidic reconditioning of materials was shown to improve performance. Composite thin films composed of the nanostructured sorbents and a porous polymer binder are shown to have excellent kinetics and good capacity while providing an effective processing configuration for trace mineral recovery from solutions. Initial work using the composite thin films shows significant improvements in processing capacity over the previously reported sorbent materials.« less

Inhibition of bacterial and leukocyte adhesion under shear stress conditions by material surface chemistry.

PubMed

Patel, Jasmine D; Ebert, Michael; Stokes, Ken; Ward, Robert; Anderson, James M

2003-01-01

Biomaterial-centered infections, initiated by bacterial adhesion, persist due to a compromised host immune response. Altering implant materials with surface modifying endgroups (SMEs) may enhance their biocompatibility by reducing bacterial and inflammatory cell adhesion. A rotating disc model, which generates shear stress within physiological ranges, was used to characterize adhesion of leukocytes and Staphylococcus epidermidis on polycarbonate-urethanes and polyetherurethanes modified with SMEs (polyethylene oxide, fluorocarbon and dimethylsiloxane) under dynamic flow conditions. Bacterial adhesion in the absence of serum was found to be mediated by shear stress and surface chemistry, with reduced adhesion exhibited on materials modified with polydimethylsiloxane and polyethylene oxide SMEs. In contrast, bacterial adhesion was enhanced on materials modified with fluorocarbon SMEs. In the presence of serum, bacterial adhesion was primarily neither material nor shear dependent. However, bacterial adhesion in serum was significantly reduced to < or = 10% compared to adhesion in serum-free media. Leukocyte adhesion in serum exhibited a shear dependency with increased adhesion occurring in regions exposed to lower shear-stress levels of < or = 7 dyne/cm2. Additionally, polydimethylsiloxane and polyethylene oxide SMEs reduced leukocyte adhesion on polyether-urethanes. In conclusion, these results suggest that surface chemistry and shear stress can mediate bacterial and cellular adhesion. Furthermore, materials modified with polyethylene oxide SMEs are capable of inhibiting bacterial adhesion, consequently minimizing the probability of biomaterial-centered infections.

Decontamination of clothing and building materials associated with the clandestine production of methamphetamine.

PubMed

Serrano, Kate A; Martyny, John W; Kofford, Shalece; Contreras, John R; Van Dyke, Mike V

2012-01-01

This study was designed to determine how easily methamphetamine can be removed from clothing and building materials, utilizing different cleaning materials and methods. The study also addressed the penetration of methamphetamine into drywall and the ability of paints to encapsulate the methamphetamine on drywall. Clothing and building materials were contaminated in a stainless steel chamber by aerosolizing methamphetamine in a beaker heater. The amount of methamphetamine surface contamination was determined by sampling a grid pattern on the material prior to attempting to clean the materials. After cleaning, the materials were again sampled, and the degree of decontamination noted. We found that household clothing and response gear worn by first responders was easily decontaminated using a household detergent in a household washing machine. A single wash removed over 95% of the methamphetamine from these materials. The study also indicated that methamphetamine-contaminated, smooth non-porous surfaces can be easily cleaned to below detectable levels using only mild cleaners. More porous surfaces such as plywood and drywall were unlikely to be decontaminated to below regulatory levels even with three washes using a mild cleaner. This may be due to methamphetamine penetration into the paint on these surfaces. Evaluation of methamphetamine contamination on drywall indicated that approximately 40% of the methamphetamine was removed using a wipe, while another 60% remained in the paint layer. Stronger cleaners such as those with active ingredients including sodium hypochlorite or quaternary ammonia and commercial decontamination agents were more effective than mild detergent-based cleaners and may reduce methamphetamine contamination to below regulatory levels. Results from the encapsulation studies indicate that sprayed on oil-based paint will encapsulate methamphetamine on drywall and plywood surfaces up to 4.5 months, while latex paints were less effective.

Solution Based Functionalization of Nanostructured Oxides with Organic Molecules

NASA Astrophysics Data System (ADS)

Pearce, Brady Lawrence

The surface modification of wide bandgap semiconductors with organic molecules provides novel functionalities to the composite material. These functionalities can include tuning of the optical properties, providing solution stability of the inorganic material, as well as many others. The use of an in-situ functionalization method for surface attachment of phosphonic group containing molecules to the surface of gallium nitride (GaN) has shown promise. This technique is particularly advantageous due to the etching and functionalization steps occurring at the same time, in the same beaker, as well as not being reliant on organic solvents or high temperatures. In this functionalization process, surface hydroxide groups are preferentially grown on the surface of GaN, which serve as attachment sites for phosphonic groups on organic moieties. Molecules with these hydroxyl groups available natively on their surface, such as AlOOH and GaOOH, provide a unique advantage. The requirement for an etching step is removed, and the functionalization process could be performed in a simple one-step modification. The work in this dissertation seeks to address the possibility of using these materials as the inorganic component in organic/inorganic composite material in devices. Of particular importance in solar cell and bioelectronic devices is the ability to withstand varying pH environments, and to avoid the leaching of toxic ionic species. Lysine has shown to reduce the leaching of ionic species, when particles of inorganic molecules are cross-linking agents for the amino acid. In this work, the aqueous stability of both AlOOH and GaOOH in a lysine environment will be explored. The optical and size characteristics observed in nanostructured forms of the mixed composition AlxGa1-xOOH material system is of interest, due optical tunability providing a distinct advantage in optoelectronic devices containing these organic/inorganic hybrids. Immobilizing phosphonic group containing organic dyes on the surface of GaN, GaOOH, AlOOH and mixed compositions of AlGaOOH using surface bonding sites, and possible covalent attachments mechanisms, seeks to provide an improvement in the long term stability of the inorganic/organic interface for devices. Future work in this area will test device efficiency using these hybrids, explore additional mixed oxyhydroxide composition systems and continue the advancement of the understanding of the important role of phosphonic groups in organic/inorganic devices. The nature of chemical and surface species in these materials will be characterized with Fourier Transformed-Infrared Spectroscopy (FT-IR) and X-Ray Photoelectric Spectroscopy (XPS). The optical properties of the materials were tested with photoluminescence (PL) spectroscopy, and the stability was examined with fluorescence spectroscopy. The crystallographic nature of the nanostructured inorganic materials before and after functionalization was determined with X-Ray Diffraction (XRD). Images of the nanostructures were obtained with mainly Scanning Electron Microscopy (SEM) as well as Transmission Electron Microscopy (TEM). The work in this dissertation seeks to address the improvement of the development of nanostructured inorganic/organic hybrid materials, the investigation of novel composites for these applications and the improvement of the long term stability in aqueous medium as well as of the organic/inorganic interface itself.

Detecting Damage in Composite Material Using Nonlinear Elastic Wave Spectroscopy Methods

NASA Astrophysics Data System (ADS)

Meo, Michele; Polimeno, Umberto; Zumpano, Giuseppe

2008-05-01

Modern aerospace structures make increasing use of fibre reinforced plastic composites, due to their high specific mechanical properties. However, due to their brittleness, low velocity impact can cause delaminations beneath the surface, while the surface may appear to be undamaged upon visual inspection. Such damage is called barely visible impact damage (BVID). Such internal damages lead to significant reduction in local strengths and ultimately could lead to catastrophic failures. It is therefore important to detect and monitor damages in high loaded composite components to receive an early warning for a well timed maintenance of the aircraft. Non-linear ultrasonic spectroscopy methods are promising damage detection and material characterization tools. In this paper, two different non-linear elastic wave spectroscopy (NEWS) methods are presented: single mode nonlinear resonance ultrasound (NRUS) and nonlinear wave modulation technique (NWMS). The NEWS methods were applied to detect delamination damage due to low velocity impact (<12 J) on various composite plates. The results showed that the proposed methodology appear to be highly sensitive to the presence of damage with very promising future NDT and structural health monitoring applications.

Dynamics at a Peptide-TiO2 Anatase (101) Interface.

PubMed

Polimeni, Marco; Petridis, Loukas; Smith, Jeremy C; Arcangeli, Caterina

2017-09-28

The interface between biological matter and inorganic materials is a widely investigated research topic due to possible applications in biomedicine and nanotechnology. In this context, the molecular level adsorption mechanism that drives specific recognition between small peptide sequences and inorganic surfaces represents an important topic likely to provide much information useful for designing bioderived materials. Here, we investigate the dynamics at the interface between a Ti-binding peptide sequence (AMRKLPDAPGMHC) and a TiO 2 anatase surface by using molecular dynamics (MD) simulations. In the simulations the adsorption mechanism is characterized by diffusion of the peptide from the bulk water phase toward the TiO 2 surface, followed by the anchoring of the peptide to the surface. The anchoring is mediated by the interfacial water layers by means of the charged groups of the side chains of the peptide. The peptide samples anchored and dissociated states from the surface and its conformation is not affected by the surface when anchored.

Dynamics at a Peptide–TiO 2 Anatase (101) Interface

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

Polimeni, Marco; Petridis, Loukas; Smith, Jeremy C.

The interface between biological matter and inorganic materials is a widely investigated research topic due to possible applications in biomedicine and nanotechnology. In this context, the molecular level adsorption mechanism that drives specific recognition between small peptide sequences and inorganic surfaces represents an important topic likely to provide much information useful for designing bioderived materials. In this paper, we investigate the dynamics at the interface between a Ti-binding peptide sequence (AMRKLPDAPGMHC) and a TiO 2 anatase surface by using molecular dynamics (MD) simulations. In the simulations the adsorption mechanism is characterized by diffusion of the peptide from the bulk watermore » phase toward the TiO 2 surface, followed by the anchoring of the peptide to the surface. The anchoring is mediated by the interfacial water layers by means of the charged groups of the side chains of the peptide. Finally, the peptide samples anchored and dissociated states from the surface and its conformation is not affected by the surface when anchored.« less

Dynamics at a Peptide–TiO 2 Anatase (101) Interface

DOE PAGES

Polimeni, Marco; Petridis, Loukas; Smith, Jeremy C.; ...

2017-08-29

The interface between biological matter and inorganic materials is a widely investigated research topic due to possible applications in biomedicine and nanotechnology. In this context, the molecular level adsorption mechanism that drives specific recognition between small peptide sequences and inorganic surfaces represents an important topic likely to provide much information useful for designing bioderived materials. In this paper, we investigate the dynamics at the interface between a Ti-binding peptide sequence (AMRKLPDAPGMHC) and a TiO 2 anatase surface by using molecular dynamics (MD) simulations. In the simulations the adsorption mechanism is characterized by diffusion of the peptide from the bulk watermore » phase toward the TiO 2 surface, followed by the anchoring of the peptide to the surface. The anchoring is mediated by the interfacial water layers by means of the charged groups of the side chains of the peptide. Finally, the peptide samples anchored and dissociated states from the surface and its conformation is not affected by the surface when anchored.« less

Estimation of surface temperature variations due to changes in sky and solar flux with elevation.

USGS Publications Warehouse

Hummer-Miller, S.

1981-01-01

Sky and solar radiance are of major importance in determining the ground temperature. Knowledge of their behavior is a fundamental part of surface temperature models. These 2 fluxes vary with elevation and this variation produces temperature changes. Therefore, when using thermal-property differences to discriminate geologic materials, these flux variations with elevation need to be considered. -from Author

Thermal stability of electron-irradiated poly(tetrafluoroethylene) - X-ray photoelectron and mass spectroscopic study

NASA Technical Reports Server (NTRS)

Wheeler, Donald R.; Pepper, Stephen V.

1990-01-01

Polytetrafluoroethylene (PTFE) was subjected to 3 keV electron bombardment and then heated in vacuum to 300 C. The behavior of the material as a function of radiation dose and temperature was studied by X-ray photoelectron spectroscopy (XPS) of the surface and mass spectroscopy of the species evolved. Lightly damaged material heated to 300 C evolved saturated fluorocarbon species, whereas unsaturated fluorocarbon species were evolved from heavily damaged material. After heating the heavily damaged material, those features in the XPS spectrum that were associated with damage diminished, giving the appearance that the radiation damage had annealed. The observations were interpreted by incorporating mass transport of severed chain fragments and thermal decomposition of severely damaged material into the branched and cross-linked network model of irradiated PTFE. The apparent annealing of the radiation damage was due to covering of the network by saturated fragments that easily diffused through the decomposed material to the surface region upon heating.

Graphene-Based Materials for Lithium-Ion Hybrid Supercapacitors.

PubMed

Ma, Yanfeng; Chang, Huicong; Zhang, Miao; Chen, Yongsheng

2015-09-23

Lithium-ion hybrid supercapacitors (LIHSs), also called Li-ion capacitors, have attracted much attention due to the combination of the rapid charge-discharge and long cycle life of supercapacitors and the high energy-storage capacity of lithium-ion batteries. Thus, LIHSs are expected to become the ultimate power source for hybrid and all-electric vehicles in the near future. As an electrode material, graphene has many advantages, including high surface area and porous structure, high electric conductivity, and high chemical and thermal stability, etc. Compared with other electrode materials, such as activated carbon, graphite, and metal oxides, graphene-based materials with 3D open frameworks show higher effective specific surface area, better control of channels, and higher conductivity, which make them better candidates for LIHS applications. Here, the latest advances in electrode materials for LIHSs are briefly summarized, with an emphasis on graphene-based electrode materials (including 3D graphene networks) for LIHS applications. An outlook is also presented to highlight some future directions. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Adsorbent materials from paper industry waste materials and their use in Cu(II) removal from water.

PubMed

Méndez, A; Barriga, S; Fidalgo, J M; Gascó, G

2009-06-15

This paper deals with the removal of Cu(2+) from water using adsorbent materials prepared from paper industry waste materials (one de-inking paper sludge and other sludge from virgin pulp mill). Experimental results showed that de-inking paper sludge leads to mesoporous materials (V(mic)/V(T)=0.13 and 0.14), whereas the sludge from virgin pulp mill produces high microporous adsorbents (V(mic)/V(T)=0.39 and 0.41). Adsorbent materials were then used for Cu(2+) removal from water at acid pH. During water treatment, heavy metals lixiviation from adsorbent materials was not produced. However, important Ca and Mg leaching was observed. Final pH significantly increases after treatment of water with adsorbent materials probably due to their elevated CaCO(3) content. In general, highest Cu(2+) removal was obtained using adsorbent materials from de-inking paper sludge. This result could be due to their higher content in oxygenated surface groups, high average pore diameter, elevated superficial charge density, high CaCO(3) amount and high Ca and Mg exchange content.

Drying of pulverized material with heated condensible vapor

DOEpatents

Carlson, Larry W.

1986-01-01

Apparatus for drying pulverized material utilizes a high enthalpy condensable vapor such as steam for removing moisture from the individual particles of the pulverized material. The initially wet particulate material is tangentially delivered by a carrier vapor flow to an upper portion of a generally vertical cylindrical separation drum. The lateral wall of the separation drum is provided with a plurality of flow guides for directing the vapor tangentially therein in the direction of particulate material flow. Positioned concentrically within the separation drum and along the longitudinal axis thereof is a water-cooled condensation cylinder which is provided with a plurality of collection plates, or fins, on the outer lateral surface thereof. The cooled collection fins are aligned counter to the flow of the pulverized material and high enthalpy vapor mixture to maximize water vapor condensation thereon. The condensed liquid which includes moisture removed from the pulverized material then flows downward along the outer surface of the coolant cylinder and is collected and removed. The particles travel in a shallow helix due to respective centrifugal and vertical acceleration forces applied thereto. The individual particles of the pulverized material are directed outwardly by the vortex flow where they contact the inner cylindrical surface of the separation drum and are then deposited at the bottom thereof for easy collection and removal. The pulverized material drying apparatus is particularly adapted for drying coal fines and facilitates the recovery of the pulverized coal.

Raman detection of improvised explosive device (IED) material fabricated using drop-on-demand inkjet technology on several real world surfaces

NASA Astrophysics Data System (ADS)

Farrell, Mikella E.; Holthoff, Ellen L.; Pellegrino, Paul M.

2015-05-01

The requirement to detect hazardous materials (i.e., chemical, biological, and explosive) on a host of materials has led to the development of hazard detection systems. These new technologies and their capabilities could have immediate uses for the US military, national security agencies, and environmental response teams in efforts to keep people secure and safe. In particular, due to the increasing use by terrorists, the detection of common explosives and improvised explosive device (IED) materials have motivated research efforts toward detecting trace (i.e., particle level) quantities on multiple commonly encountered surfaces (e.g., textiles, metals, plastics, natural products, and even people). Non-destructive detection techniques can detect trace quantities of explosive materials; however, it can be challenging in the presence of a complex chemical background. One spectroscopic technique gaining increased attention for detection is Raman. One popular explosive precursor material is ammonium nitrate (AN). The material AN has many agricultural applications, however it can also be used in the fabrication of IEDs or homemade explosives (HMEs). In this paper, known amounts of AN will be deposited using an inkjet printer into several different common material surfaces (e.g., wood, human hair, textiles, metals, plastics). The materials are characterized with microscope images and by collecting Raman spectral data. In this report the detection and identification of AN will be demonstrated.

Recent Advances in Biohybrid Materials for Tissue Engineering and Regenerative Medicine

NASA Astrophysics Data System (ADS)

Wan, Ying; Li, Xing; Wang, Shenqi

2016-07-01

Biohybrid materials play an important role in tissue engineering, artificial organs and regenerative medicine due to their regulation of cell function through specific cell-matrix interactions involving integrins, mostly those of fibroblasts and myofibroblasts, and ligands on the matrix surface, which have become current research focus. In this paper, recent progress of biohybrid materials, mainly including main types of biohybrid materials, rapid prototype (RP) technique for construction of 3D biohybrid materials, was reviewed in detail; moreover, their applications in tissue engineering, artificial organs and regenerative medicine were also reviewed in detail. At last, we address the challenges biohybrid materials may face.

Tool life and surface integrity aspects when drilling nickel alloy

NASA Astrophysics Data System (ADS)

Kannan, S.; Pervaiz, S.; Vincent, S.; Karthikeyan, R.

2018-04-01

Nickel based super alloys manufactured through powder metallurgy (PM) route are required to increase the operational efficiency of gas turbine engines. They are material of choice for high pressure components due to their superior high temperature strength, excellent corrosion, oxidation and creep resistance. This unique combination of mechanical and thermal properties makes them even more difficult-to-machine. In this paper, the hole making process using coated carbide inserts by drilling and plunge milling for a nickel-based powder metallurgy super alloy has been investigated. Tool life and process capability studies were conducted using optimized process parameters using high pressure coolants. The experimental trials were directed towards an assessment of the tendency for surface malformations and detrimental residual stress profiles. Residual stresses in both the radial and circumferential directions have been evaluated as a function of depth from the machined surface using the target strain gauge / center hole drilling method. Circumferential stresses near workpiece surface and at depth of 512 µm in the starting material was primarily circumferential compression which was measured to be average of –404 MPa. However, the radial stresses near workpiece surface was tensile and transformed to be compressive in nature at depth of 512 µm in the starting material (average: -87 Mpa). The magnitude and the depth below the machined surface in both radial and circumferential directions were primarily tensile in nature which increased with hole number due to a rise of temperature at the tool–workpiece interface with increasing tool wear. These profiles are of critical importance for the selection of cutting strategies to ensure avoidance/minimization of tensile residual stresses that can be detrimental to the fatigue performance of the components. These results clearly show a tendency for the circumferential stresses to be more tensile than the radial stresses. Overall the results indicate that the effect of drilling and milling parameters is most marked in terms of surface quality in the circumferential direction. Material removal rates and tool flank wear must be maintained within the control limits to maintain hole integrity.

Material removal in magnetorheological finishing of optics.

PubMed

Kordonski, William; Gorodkin, Sergei

2011-05-10

A concept of material removal based on the principle of conservation of particles momentum in a binary suspension is applied to analyze material removal in magnetorheological finishing and magnetorheological jet processes widely used in precision optics fabrication. According to this concept, a load for surface indentation by abrasive particles is provided at their interaction near the wall with heavier basic (magnetic) particles, which fluctuate (due to collision) in the shear flow of concentrated suspension. The model is in good qualitative and quantitative agreement with experimental results.

Modeling and Analysis of Composite Wing Sections for Improved Aeroelastic and Vibration Characteristics Using Smart Materials

NASA Technical Reports Server (NTRS)

Chattopadhyay, Aditi

1996-01-01

The objective of this research is to develop analysis procedures to investigate the coupling of composite and smart materials to improve aeroelastic and vibratory response of aerospace structures. The structural modeling must account for arbitrarily thick geometries, embedded and surface bonded sensors and actuators and imperfections, such as delamination. Changes in the dynamic response due to the presence of smart materials and delaminations is investigated. Experiments are to be performed to validate the proposed mathematical model.

Hydroxylation of organic polymer surface: method and application.

PubMed

Yang, Peng; Yang, Wantai

2014-03-26

It may be hardly believable that inert C-H bonds on a polymeric material surface could be quickly and efficiently transformed into C-OH by a simple and mild way. Thanks to the approaches developed recently, it is now possible to transform surface H atoms of a polymeric substrate into monolayer OH groups by a simple/mild photochemical reaction. Herein the method and application of this small-molecular interfacial chemistry is highlighted. The existence of hydroxyl groups on material surfaces not only determines the physical and chemical properties of materials but also provides effective reaction sites for postsynthetic sequential modification to fulfill the requirements of various applications. However, organic synthetic materials based on petroleum, especially polyolefins comprise mainly C and H atoms and thus present serious surface problems due to low surface energy and inertness in reactivity. These limitations make it challenging to perform postsynthetic surface sequential chemical derivatization toward enhanced functionalities and properties and also cause serious interfacial problems when bonding or integrating polymer substrates with natural or inorganic materials. Polymer surface hydroxylation based on direct conversion of C-H bonds on polymer surfaces is thus of significant importance for academic and practical industrial applications. Although highly active research results have reported on small-molecular C-H bond activation in solution (thus homogeneous), most of them, featuring the use of a variety of transition metals as catalysts, present a slow reaction rate, a low atom economy and an obvious environmental pollution. In sharp contrast to these conventional C-H activation strategies, the present Spotlight describes a universal confined photocatalytic oxidation (CPO) system that is able to directly convert polymer surface C-H bonds to C-OSO3(-) and, subsequently, to C-OH through a simple hydrolysis. Generally speaking, these newly implanted hydroxyl groups preserve their own reactivity toward other complementary compounds, thus creating a novel base with distinct surface properties. Thanks to this functionalized platform, a wide range of organic, inorganic and metal materials have been attached to conventional organic polymer substrates through the rational engineering of surface molecular templates from small functional groups to macromolecules. It is expected that the proposed novel CPO method and its versatile usages in advanced material applications will offer new opportunities for a variety of scientific communities, especially for those working on surface/interface modulation.

Surface Texture-Induced Enhancement of Optical and Photoelectrochemical Activity of Cu2ZnSnS4 Photocathodes

NASA Astrophysics Data System (ADS)

Sarswat, Prashant K.; Deka, Nipon; Jagan Mohan Rao, S.; Free, Michael L.; Kumar, Gagan

2017-08-01

The objective of this work is to understand and improve the photocatalytic activity of Cu2ZnSnS4 (CZTS) through postgrowth modification techniques to create surface textures. This objective can be achieved using a combination of solvents, etching agents, and anodization techniques. One of the most effective surface treatments for enhancing the surface properties of photovoltaic materials is formation of nanoscale flakes, although other surface modifications were also evaluated. The superior performance of textured films can be attributed to enhanced surface area of absorber material exposed to electrolyte, ZnS deficiency, and high catalytic activity due to reduced charge-transfer resistance. Fine-tuning of ion flux and electrolyte stoichiometry can be used to create a controlled growth algorithm for CZTS thin films. The resulting information can be utilized to optimize film properties. The utility of nanostructured or engineered surfaces was evaluated using photoelectrochemical measurements. Finite-difference time-domain (FDTD)-assisted simulations were conducted for selected texturing, revealing enhanced surface area of absorbing medium that ultimately resulted in greater power loss of light in the medium.

Comparison of Observed Surface Temperatures of 4 Vesta to the KRC Thermal Model

NASA Technical Reports Server (NTRS)

Titus, T. N.; Becker, K. J.; Anderson, J. A.; Capria, M. T.; Tosi, F.; DeSanctis, M. C.; Palomba, E.; Grassi, D.; Capaccioni, F.; Ammannito, E.;

Advanced Nanoporous Materials for Micro-Gravimetric Sensing to Trace-Level Bio/Chemical Molecules

PubMed Central

Xu, Pengcheng; Li, Xinxin; Yu, Haitao; Xu, Tiegang

2014-01-01

Functionalized nanoporous materials have been developed recently as bio/chemical sensing materials. Due to the huge specific surface of the nano-materials for molecular adsorption, high hopes have been placed on gravimetric detection with micro/nano resonant cantilevers for ultra-sensitive sensing of low-concentration bio/chemical substances. In order to enhance selectivity of the gravimetric resonant sensors to the target molecules, it is crucial to modify specific groups onto the pore-surface of the nano-materials. By loading the nanoporous sensing material onto the desired region of the mass-type transducers like resonant cantilevers, the micro-gravimetric bio/chemical sensors can be formed. Recently, such micro-gravimetric bio/chemical sensors have been successfully applied for rapid or on-the-spot detection of various bio/chemical molecules at the trace-concentration level. The applicable nanoporous sensing materials include mesoporous silica, zeolite, nanoporous graphene oxide (GO) and so on. This review article focuses on the recent achievements in design, preparation, functionalization and characterization of advanced nanoporous sensing materials for micro-gravimetric bio/chemical sensing. PMID:25313499

Geology of 243 Ida

USGS Publications Warehouse

Sullivan, R.; Greeley, R.; Pappalardo, R.; Asphaug, E.; Moore, Johnnie N.; Morrison, D.; Belton, M.J.S.; Carr, M.; Chapman, C.R.; Geissler, P.; Greenberg, R.; Granahan, J.; Head, J. W.; Kirk, R.; McEwen, A.; Lee, P.; Thomas, P.C.; Veverka, J.

1996-01-01

The surface of 243 Ida is dominated by the effects of impacts. No complex crater morphologies are observed. A complete range of crater degradation states is present, which also reveals optical maturation of the surface (darkening and reddening of materials with increasing exposure age). Regions of bright material associated with the freshest craters might be ballistically emplaced deposits or the result of seismic disturbance of loosely-bound surface materials. Diameter/depth ratios for fresh craters on Ida are ???1:6.5, similar to Gaspra results, but greater than the 1:5 ratios common on other rocky bodies. Contributing causes include rim degradation by whole-body "ringing," relatively thin ejecta blankets around crater rims, or an extended strength gradient in near-surface materials due to low gravitational self-packing. Grooves probably represent expressions in surface debris of reactivated fractures in the deeper interior. Isolated positive relief features as large as 150 m are probably ejecta blocks related to large impacts. Evidence for the presence of debris on the surface includes resolved ejecta blocks, mass-wasting scars, contrasts in color and albedo of fresh crater materials, and albedo streaks oriented down local slopes. Color data indicate relatively uniform calcium abundance in pyroxenes and constant pyroxene/olivine ratio. A large, relatively blue unit across the northern polar area is probably related to regolith processes involving ejecta from Azzurra rather than representing internal compositional heterogeneity. A small number of bluer, brighter craters are randomly distributed across the surface, unlike on Gaspra where these features are concentrated along ridges. This implies that debris on Ida is less mobile and/or consistently thicker than on Gaspra. Estimates of the average depth of mobile materials derived from chute depths (20-60 m), grooves (???30 m), and shallowing of the largest degraded craters (20-50 m minimum, ???100 m maximum) suggest a thickness of potentially mobile materials of ???50 m, and a typical thickness for the debris layer of 50-100 m. ?? 1996 Academic Press, Inc.

Surface characterization of anodized zirconium for biomedical applications

NASA Astrophysics Data System (ADS)

Sanchez, A. Gomez; Schreiner, W.; Duffó, G.; Ceré, S.

2011-05-01

Mechanical properties and corrosion resistance of zirconium make this material suitable for biomedical implants. Its good in vivo performance is mainly due to the presence of a protective oxide layer that minimizes corrosion rate, diminishes the amount of metallic ions released to the biological media and facilitates the osseointegration process. Since the implant surface is the region in contact with living tissues, the characteristics of the surface film are of great interest. Surface modification is a route to enhance both biocompatibility and corrosion resistance of permanent implant materials. Anodizing is presented as an interesting process to modify metal surfaces with good reproducibility and independence of the geometry. In this work the surface of zirconium before and after anodizing in 1 mol/L phosphoric acid solution at a fixed potential between 3 and 30 V, was characterized by means of several surface techniques. It was found that during anodization the surface oxide grows with an inhomogeneous coverage on zirconium surface, modifying the topography. The incorporation of P from the electrolyte to the surface oxide during the anodizing process changes the surface chemistry. After 30 days of immersion in Simulated Body Fluid (SBF) solution, Ca-P rich compounds were present on anodized zirconium.

Nanostructural Evolution of Hard Turning Layers in Carburized Steel

NASA Astrophysics Data System (ADS)

Bedekar, Vikram

The mechanisms of failure for components subjected to contact fatigue are sensitive to the structure and properties of the material surface. Although, the bulk material properties are determined by the steel making, forming and the heat treatment; the near surface material properties are altered during final material removal processes such as hard turning or grinding. Therefore, the ability to optimize, modulate and predict the near surface properties during final metal removal operations would be extremely useful in the enhancement of service life of a component. Hard machining is known to induce severely deformed layers causing dramatic microstructural transformations. These transformations occur via grain refinement or thermal phenomena depending upon cutting conditions. The aim of this work is to engineer the near surface nanoscale structure and properties during hard turning by altering strain, strain rate, temperature and incoming microstructure. The near surface material transformations due to hard turning were studied on carburized SAE 8620 bearing steel. Variations in parent material microstructures were introduced by altering the retained austenite content. The strain, strain rate and temperature achieved during final metal cutting were altered by varying insert geometry, insert wear and cutting speed. The subsurface evolution was quantified by a series of advanced characterization techniques such as transmission electron microscopy (TEM), glancing angle X-ray diffraction (GAXRD), X-ray stress evaluation and nanoindentation which were coupled with numerical modeling. Results showed that the grain size of the nanocrystalline near surface microstructure can be effectively controlled by altering the insert geometry, insert wear, cutting speed and the incoming microstructure. It was also evident that the near surface retained austenite decreased at lower cutting speed indicating transformation due to plastic deformation, while it increased at higher cutting speed indicated thermal transformation. Nanoindentation tests showed that the substructures produced by plastic deformation follow the Hall-Petch relationship while the structures produced by thermal transformation did not. This indicated a change in the hardness driver from dislocation hardening to phase transformation, both of which have a significant impact on fatigue life. Using hardness based flow stress numerical model, these relationships between the processing conditions and structural parameters were further explored. Results indicated that the hard turning process design space can be partitioned into three regions based on thermal phase transformations, plastic grain refinement, and a third regime where both mechanisms are active. It was found that the Zener-Holloman parameter can not only be used to predict post-turning grain size but also to partition the process space into regions of dominant microstructural mechanisms.

Ozone-surface interactions: Investigations of mechanisms, kinetics, mass transport, and implications for indoor air quality

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

Morrison, Glenn Charles

1999-12-01

In this dissertation, results are presented of laboratory investigations and mathematical modeling efforts designed to better understand the interactions of ozone with surfaces. In the laboratory, carpet and duct materials were exposed to ozone and measured ozone uptake kinetics and the ozone induced emissions of volatile organic compounds. To understand the results of the experiments, mathematical methods were developed to describe dynamic indoor aldehyde concentrations, mass transport of reactive species to smooth surfaces, the equivalent reaction probability of whole carpet due to the surface reactivity of fibers and carpet backing, and ozone aging of surfaces. Carpets, separated carpet fibers, andmore » separated carpet backing all tended to release aldehydes when exposed to ozone. Secondary emissions were mostly n-nonanal and several other smaller aldehydes. The pattern of emissions suggested that vegetable oils may be precursors for these oxidized emissions. Several possible precursors and experiments in which linseed and tung oils were tested for their secondary emission potential were discussed. Dynamic emission rates of 2-nonenal from a residential carpet may indicate that intermediate species in the oxidation of conjugated olefins can significantly delay aldehyde emissions and act as reservoir for these compounds. The ozone induced emission rate of 2-nonenal, a very odorous compound, can result in odorous indoor concentrations for several years. Surface ozone reactivity is a key parameter in determining the flux of ozone to a surface, is parameterized by the reaction probability, which is simply the probability that an ozone molecule will be irreversibly consumed when it strikes a surface. In laboratory studies of two residential and two commercial carpets, the ozone reaction probability for carpet fibers, carpet backing and the equivalent reaction probability for whole carpet were determined. Typically reaction probability values for these materials were 10 -7, 10 -5, and 10 -5 respectively. To understand how internal surface area influences the equivalent reaction probability of whole carpet, a model of ozone diffusion into and reaction with internal carpet components was developed. This was then used to predict apparent reaction probabilities for carpet. He combines this with a modified model of turbulent mass transfer developed by Liu, et al. to predict deposition rates and indoor ozone concentrations. The model predicts that carpet should have an equivalent reaction probability of about 10 -5, matching laboratory measurements of the reaction probability. For both carpet and duct materials, surfaces become progressively quenched (aging), losing the ability to react or otherwise take up ozone. He evaluated the functional form of aging and find that the reaction probability follows a power function with respect to the cumulative uptake of ozone. To understand ozone aging of surfaces, he developed several mathematical descriptions of aging based on two different mechanisms. The observed functional form of aging is mimicked by a model which describes ozone diffusion with internal reaction in a solid. He shows that the fleecy nature of carpet materials in combination with the model of ozone diffusion below a fiber surface and internal reaction may explain the functional form and the magnitude of power function parameters observed due to ozone interactions with carpet. The ozone induced aldehyde emissions, measured from duct materials, were combined with an indoor air quality model to show that concentrations of aldehydes indoors may approach odorous levels. He shows that ducts are unlikely to be a significant sink for ozone due to the low reaction probability in combination with the short residence time of air in ducts.« less

Jovian magnetospheric weathering of Europa's nonice surface material

NASA Astrophysics Data System (ADS)

Hibbitts, Charles A.; Paranicas, Christopher; Blaney, Diana L.; Murchie, Scott; Seelos, Frank

2016-10-01

Jovian plasma and energetic charged particles bombard the Galilean satellites. These satellites vary from volcanically active (Io) to a nearly primordial surface (Callisto). These satellites are imbedded in a harsh and complex particle radiation environment that weathers their surfaces, and thus are virtual laboratories for understanding how particle bombardment alters the surfaces of airless bodies. Europa orbits deeply in the Jovian radiation belts and may have an active surface, where space weathering and geologic processes can interact in complex ways with a range of timescales. At Europa's surface temperature of 80K to 130K, the hydrated nonice material and to a lesser extent, water ice, will be thermally stable over geologic times and will exhibit the effects of weathering. The ice on the surface of Europa is amorphous and contains trace products such as H2O2 [1] due to weathering. The nonice material, which likely has an endogenic component [2] may also be partially amorphous and chemically altered as a result of being weathered by electrons, Iogenic sulfur, or other agents [3]. This hydrated salt or frozen brine likely compositionally 'matures' over time as the more weakly bound constituents are preferentially removed compared with Ca and Mg [4]. Electron bombardment induces chemical reactions through deposition of energy (e.g., ionizations) possibly explaining some of the nonice material's redness [5,6]. Concurrently, micrometeroid gardening mixes the upper surface burying weathered and altered material while exposing both fresh material and previous altered material, potentially with astrobiological implications. Our investigation of the spectral alteration of nonice analog materials irradiated by 10s keV electrons demonstrates the prevalence of this alteration and we discuss relevance to potential measurements by the Europa MISE instrument.References: [1] Moore, M. and R. Hudson, (2000), Icarus, 145, 282-288; [2] McCord et al., (1998), Science, 280, 1242; [3] Carlson et al., (2002), Icarus, 157, 456-463; [4] McCord et al., (2001), JGR, 106, E2, 3311-3319; [5] Hand, K. and R. Carlson, (2015), GRL, 10.1002/2015GRL063559. [6] Hibbitts, C.A. and Paranicas, C., ACS conference, Aug., 2016.

Surface magnetism in a chiral d -wave superconductor with hexagonal symmetry

NASA Astrophysics Data System (ADS)

Goryo, Jun; Imai, Yoshiki; Rui, W. B.; Sigrist, Manfred; Schnyder, Andreas P.

2017-10-01

Surface properties are examined in a chiral d -wave superconductor with hexagonal symmetry, whose one-body Hamiltonian possesses intrinsic spin-orbit coupling identical to the one characterizing the topological nature of the Kane-Mele honeycomb insulator. In the normal state, spin-orbit coupling gives rise to spontaneous surface spin currents, whereas in the superconducting state, besides the spin currents, there exist also charge surface currents, due to chiral pairing symmetry. Interestingly, the combination of these two currents results in a surface spin polarization, whose spatial dependence is markedly different on the zigzag and armchair surfaces. We discuss various potential candidate materials, such as SrPtAs, which may exhibit these surface properties.

Duplex stainless steel fracture surface analysis using X-ray fractography

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

Rajanna, K.; Pathiraj, B.; Kolster, B.H.

1997-02-01

The fatigue fracture surface of a duplex stainless steel was analyzed using x-ray fractography. A lower than average austenite content was observed at the fracture surface due to the transformation of austenite into deformation-induced martensite. The influence of fatigue cycling on the transformation was confined to a depth of about 30 {micro}m below the fracture surface. X-ray analyses of both the ferrite-martensite and the austenite phases indicated residual stresses ({sigma}{sub r}) increasing with depth from the fracture surface and reaching a maximum some tens of microns below the fracture surface. The lower {sigma}{sub r} observed at the fracture surface hasmore » been attributed to the stress relaxation effects caused by the new fracture surfaces created in the crack growth process. The observed decrease in full width at half maximum (FWHM) in the ferrite-martensite phase was presumed to be due to the dynamic recovery effect that was likely to occur within the material close to the crack tip as a consequence of fatigue cycling.« less

Graphene oxide: surface activity and two-dimensional assembly.

PubMed

Kim, Franklin; Cote, Laura J; Huang, Jiaxing

2010-05-04

Graphene oxide (GO) is a promising precursor for preparing graphene-based composites and electronics applications. Like graphene, GO is essentially one-atom thick but can be as wide as tens of micrometers, resulting in a unique type of material building block, characterized by two very different length scales. Due to this highly anisotropic structure, the collective material properties are highly dependent on how these sheets are assembled. Therefore, understanding and controlling the assembly behavior of GO has become an important subject of research. In this Research News article the surface activity of GO and how it can be employed to create two-dimensional assemblies over large areas is discussed.

Evanescent field Sensors Based on Tantalum Pentoxide Waveguides – A Review

PubMed Central

Schmitt, Katrin; Oehse, Kerstin; Sulz, Gerd; Hoffmann, Christian

2008-01-01

Evanescent field sensors based on waveguide surfaces play an important role where high sensitivity is required. Particularly tantalum pentoxide (Ta2O5) is a suitable material for thin-film waveguides due to its high refractive index and low attenuation. Many label-free biosensor systems such as grating couplers and interferometric sensors as well as fluorescence-based systems benefit from this waveguide material leading to extremely high sensitivity. Some biosensor systems based on Ta2O5 waveguides already took the step into commercialization. This report reviews the various detection systems in terms of limit of detection, the applications, and the suitable surface chemistry. PMID:27879731

False-Negative Rate and Recovery Efficiency Performance of a Validated Sponge Wipe Sampling Method

PubMed Central

Piepel, Greg F.; Boucher, Raymond; Tezak, Matt; Amidan, Brett G.; Einfeld, Wayne

2012-01-01

Recovery of spores from environmental surfaces varies due to sampling and analysis methods, spore size and characteristics, surface materials, and environmental conditions. Tests were performed to evaluate a new, validated sponge wipe method using Bacillus atrophaeus spores. Testing evaluated the effects of spore concentration and surface material on recovery efficiency (RE), false-negative rate (FNR), limit of detection (LOD), and their uncertainties. Ceramic tile and stainless steel had the highest mean RE values (48.9 and 48.1%, respectively). Faux leather, vinyl tile, and painted wood had mean RE values of 30.3, 25.6, and 25.5, respectively, while plastic had the lowest mean RE (9.8%). Results show roughly linear dependences of RE and FNR on surface roughness, with smoother surfaces resulting in higher mean REs and lower FNRs. REs were not influenced by the low spore concentrations tested (3.10 × 10−3 to 1.86 CFU/cm2). Stainless steel had the lowest mean FNR (0.123), and plastic had the highest mean FNR (0.479). The LOD90 (≥1 CFU detected 90% of the time) varied with surface material, from 0.015 CFU/cm2 on stainless steel up to 0.039 on plastic. It may be possible to improve sampling results by considering surface roughness in selecting sampling locations and interpreting spore recovery data. Further, FNR values (calculated as a function of concentration and surface material) can be used presampling to calculate the numbers of samples for statistical sampling plans with desired performance and postsampling to calculate the confidence in characterization and clearance decisions. PMID:22138998

Controlling cation segregation in perovskite-based electrodes for high electro-catalytic activity and durability.

PubMed

Li, Yifeng; Zhang, Wenqiang; Zheng, Yun; Chen, Jing; Yu, Bo; Chen, Yan; Liu, Meilin

2017-10-16

Solid oxide cell (SOC) based energy conversion systems have the potential to become the cleanest and most efficient systems for reversible conversion between electricity and chemical fuels due to their high efficiency, low emission, and excellent fuel flexibility. Broad implementation of this technology is however hindered by the lack of high-performance electrode materials. While many perovskite-based materials have shown remarkable promise as electrodes for SOCs, cation enrichment or segregation near the surface or interfaces is often observed, which greatly impacts not only electrode kinetics but also their durability and operational lifespan. Since the chemical and structural variations associated with surface enrichment or segregation are typically confined to the nanoscale, advanced experimental and computational tools are required to probe the detailed composition, structure, and nanostructure of these near-surface regions in real time with high spatial and temporal resolutions. In this review article, an overview of the recent progress made in this area is presented, highlighting the thermodynamic driving forces, kinetics, and various configurations of surface enrichment and segregation in several widely studied perovskite-based material systems. A profound understanding of the correlation between the surface nanostructure and the electro-catalytic activity and stability of the electrodes is then emphasized, which is vital to achieving the rational design of more efficient SOC electrode materials with excellent durability. Furthermore, the methodology and mechanistic understanding of the surface processes are applicable to other materials systems in a wide range of applications, including thermo-chemical photo-assisted splitting of H 2 O/CO 2 and metal-air batteries.

LEVELS OF SYNTHETIC MUSKS COMPOUNDS IN AQUATIC ENVIRONMENT

EPA Science Inventory

Synthetic musk compounds are consumer chemicals manufactured as fragrance materials Due to their high worldwide usage and release, they frequently occur in the aquatic and marine environments. The U.S. EPA (ORD, Las Vegas) developed surface-water monitoring methodology and conduc...

Integrated polymer-based Mach-Zehnder interferometer label-free streptavidin biosensor compatible with injection molding.

PubMed

Bruck, R; Melnik, E; Muellner, P; Hainberger, R; Lämmerhofer, M

2011-05-15

We report the development of a Mach-Zehnder interferometer biosensor based on a high index contrast polymer material system and the demonstration of label-free online measurement of biotin-streptavidin binding on the sensor surface. The surface of the polyimide waveguide core layer was functionalized with 3-mercaptopropyl trimethoxy silane and malemide tagged biotin. Several concentrations of Chromeon 642-streptavidin dissolved in phosphate buffered saline solution were rinsed over the functionalized sensor surface by means of a fluidic system and the biotin-streptavidin binding process was observed in the output signal of the interferometer at a wavelength of 1310 nm. Despite the large wavelength and the comparatively low surface sensitivity of the sensor system due to the low index contrast in polymer material systems compared to inorganic material systems, we were able to resolve streptavidin concentrations of down to 0.1 μg/ml. The polymer-based optical sensor design is fully compatible with cost-efficient mass production technologies such as injection molding and spin coating, which makes it an attractive alternative to inorganic optical sensors. Copyright © 2011 Elsevier B.V. All rights reserved.

Nanoscale surface analysis on second generation advanced high strength steel after hot dip galvanizing.

PubMed

Arndt, M; Duchoslav, J; Preis, K; Samek, L; Stifter, D

2013-09-01

Second generation advanced high strength steel is one promising material of choice for modern automotive structural parts because of its outstanding maximal elongation and tensile strength. Nonetheless there is still a lack of corrosion protection for this material due to the fact that cost efficient hot dip galvanizing cannot be applied. The reason for the insufficient coatability with zinc is found in the segregation of manganese to the surface during annealing and the formation of manganese oxides prior coating. This work analyses the structure and chemical composition of the surface oxides on so called nano-TWIP (twinning induced plasticity) steel on the nanoscopic scale after hot dip galvanizing in a simulator with employed analytical methods comprising scanning Auger electron spectroscopy (SAES), energy dispersive X-ray spectroscopy (EDX), and focused ion beam (FIB) for cross section preparation. By the combination of these methods, it was possible to obtain detailed chemical images serving a better understanding which processes exactly occur on the surface of this novel kind of steel and how to promote in the future for this material system galvanic protection.

Asymmetric material impact: Achieving free surfaces velocities nearly double that of the projectile

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

Aslam, Tariq; Dattelbaum, Dana; Gustavsen, Richard

Hypervelocity impact speeds are often limited by practical considerations in guns and explosive driven systems. In particular, for gas guns (both powder driven and light gas guns), there is the general trend that higher projectile speeds often come at the expense of smaller diameters, and thus less time for examining shock phenomena prior to two dimensional release waves affecting the observed quantities of interest. Similarly, explosive driven systems have their own set of limiting conditions due to limitations in explosive energy and size of devices required as engineering dimensions increase. The focus in this study is to present a methodologymore » of obtaining free surface velocities well in excess of the projectile velocity. The key to this approach is in using a high impedance projectile that impacts a series of progressively lower impedance materials. The free surface velocity (if they were separated) of each of the progressively lower impedance materials would increase for each material. The theory behind this approach, as well as experimental results are presented.« less

Asymmetric material impact: Achieving free surfaces velocities nearly double that of the projectile

DOE PAGES

Aslam, Tariq; Dattelbaum, Dana; Gustavsen, Richard; ...

2015-05-19

Hypervelocity impact speeds are often limited by practical considerations in guns and explosive driven systems. In particular, for gas guns (both powder driven and light gas guns), there is the general trend that higher projectile speeds often come at the expense of smaller diameters, and thus less time for examining shock phenomena prior to two dimensional release waves affecting the observed quantities of interest. Similarly, explosive driven systems have their own set of limiting conditions due to limitations in explosive energy and size of devices required as engineering dimensions increase. The focus in this study is to present a methodologymore » of obtaining free surface velocities well in excess of the projectile velocity. The key to this approach is in using a high impedance projectile that impacts a series of progressively lower impedance materials. The free surface velocity (if they were separated) of each of the progressively lower impedance materials would increase for each material. The theory behind this approach, as well as experimental results are presented.« less

Spectral behavior of hydrated sulfate salts: implications for Europa mission spectrometer design

NASA Technical Reports Server (NTRS)

Dalton, James Bradley 3rd

2003-01-01

Remote sensing of the surface of Europa with near-infrared instruments has suggested the presence of hydrated materials, including sulfate salts. Attention has been focused on these salts for the information they might yield regarding the evolution of a putative interior ocean, and the evaluation of its astrobiological potential. These materials exhibit distinct infrared absorption features due to bound water. The interactions of this water with the host molecules lead to fine structure that can be used to discriminate among these materials on the basis of their spectral behavior. This fine structure is even more pronounced at the low temperatures prevalent on icy satellites. Examination of hydrated sulfate salt spectra measured under cryogenic temperature conditions provides realistic constraints for future remote-sensing missions to Europa. In particular, it suggests that a spectrometer system capable of 2-5 nm spectral resolution or better, with a spatial resolution approaching 100 m, would be able to differentiate among proposed hydrated surface materials, if present, and constrain their distributions across the surface. Such information would provide valuable insights into the evolutionary history of Europa.

Spectral behavior of hydrated sulfate salts: implications for Europa mission spectrometer design.

PubMed

Dalton, James Bradley

2003-01-01

Remote sensing of the surface of Europa with near-infrared instruments has suggested the presence of hydrated materials, including sulfate salts. Attention has been focused on these salts for the information they might yield regarding the evolution of a putative interior ocean, and the evaluation of its astrobiological potential. These materials exhibit distinct infrared absorption features due to bound water. The interactions of this water with the host molecules lead to fine structure that can be used to discriminate among these materials on the basis of their spectral behavior. This fine structure is even more pronounced at the low temperatures prevalent on icy satellites. Examination of hydrated sulfate salt spectra measured under cryogenic temperature conditions provides realistic constraints for future remote-sensing missions to Europa. In particular, it suggests that a spectrometer system capable of 2-5 nm spectral resolution or better, with a spatial resolution approaching 100 m, would be able to differentiate among proposed hydrated surface materials, if present, and constrain their distributions across the surface. Such information would provide valuable insights into the evolutionary history of Europa.

Dispersion, spatial growth rate, and start current of a Cherenkov free-electron laser with negative-index material

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

Wang, Yuanyuan; Wei, Yanyu; Jiang, Xuebing

We present an analysis of a Cherenkov free-electron laser based on a single slab made from negative-index materials. In this system, a flat electron beam with finite thickness travelling close to the surface of the slab interacts with the copropagating electromagnetic surface mode. The dispersion equation for a finitely thick slab is worked out and solved numerically to study the dispersion relation of surface modes supported by negative-index materials, and the calculations are in good agreement with the simulation results from a finite difference time domain code. We find that under suitable conditions there is inherent feedback in such amore » scheme due to the characteristics of negative-index materials, which means that the system can oscillate without external reflectors when the beam current exceeds a threshold value, i.e., start current. Using the hydrodynamic approach, we setup coupled equations for this system, and solve these equations analytically in the small signal regime to obtain formulas for the spatial growth rate and start current.« less

[Adhesion loss of syrups in a metering glass which consists of a low surface free energy material].

PubMed

Yamamoto, Yoshihisa; Suzuki, Toyofumi; Hashizaki, Kaname; Ogura, Masao; Umeda, Yukiko; Hidaka, Shinji; Fukami, Toshiro; Tomono, Kazuo

2010-08-01

We previously reported a strong positive correlation between syrup viscosity and the rate of syrup loss due to adhesion to a glass metering device. In this study, we examined differences in the surface free energies of metering devices made of different polymeric materials, since reducing adhesion loss to metering devices could improve the efficiency of drug preparation involving highly viscous syrups. Among metering devices made of glass only, glass with a silicone coating (SLC), polypropylene (PP), and polymethylpentene (PMP) the surface free energy of the glass-only metering device was the highest (49.2 mN/m). The adhesion loss obtained for highly viscous syrups in the PP and PMP metering devices was significantly lower than that of the glass metering device. Measurements of syrup contact angles suggested that in metering devices made of PP and PMP, which have low surface free energies, a decrease in the spreading wetting of syrups was a factor in reducing the rate of adhesion loss. Thus irrespective of the syrup viscosity being measured, metering devices produced from materials with low surface free energies can reduce the time required to prepare prescriptions without compromising the accuracy of drug preparation.

Modified silicon carbide whiskers

DOEpatents

Tiegs, Terry N.; Lindemer, Terrence B.

1991-01-01

Silicon carbide whisker-reinforced ceramic composites are fabricated in a highly reproducible manner by beneficating the surfaces of the silicon carbide whiskers prior to their usage in the ceramic composites. The silicon carbide whiskers which contain considerable concentrations of surface oxides and other impurities which interact with the ceramic composite material to form a chemical bond are significantly reduced so that only a relatively weak chemical bond is formed between the whisker and the ceramic material. Thus, when the whiskers interact with a crack propagating into the composite the crack is diverted or deflected along the whisker-matrix interface due to the weak chemical bonding so as to deter the crack propagation through the composite. The depletion of the oxygen-containing compounds and other impurities on the whisker surfaces and near surface region is effected by heat treating the whiskers in a suitable oxygen sparaging atmosphere at elevated temperatures. Additionally, a sedimentation technique may be utilized to remove whiskers which suffer structural and physical anomalies which render them undesirable for use in the composite. Also, a layer of carbon may be provided on the surface of the whiskers to further inhibit chemical bonding of the whiskers to the ceramic composite material.

Modified silicon carbide whiskers

DOEpatents

Tiegs, T.N.; Lindemer, T.B.

1991-05-21

Silicon carbide whisker-reinforced ceramic composites are fabricated in a highly reproducible manner by beneficating the surfaces of the silicon carbide whiskers prior to their usage in the ceramic composites. The silicon carbide whiskers which contain considerable concentrations of surface oxides and other impurities which interact with the ceramic composite material to form a chemical bond are significantly reduced so that only a relatively weak chemical bond is formed between the whisker and the ceramic material. Thus, when the whiskers interact with a crack propagating into the composite the crack is diverted or deflected along the whisker-matrix interface due to the weak chemical bonding so as to deter the crack propagation through the composite. The depletion of the oxygen-containing compounds and other impurities on the whisker surfaces and near surface region is effected by heat treating the whiskers in a suitable oxygen sparging atmosphere at elevated temperatures. Additionally, a sedimentation technique may be utilized to remove whiskers which suffer structural and physical anomalies which render them undesirable for use in the composite. Also, a layer of carbon may be provided on the surface of the whiskers to further inhibit chemical bonding of the whiskers to the ceramic composite material.

Ceramic composites reinforced with modified silicon carbide whiskers and method for modifying the whiskers

DOEpatents

Tiegs, Terry N.; Lindemer, Terrence B.

1991-01-01

Silicon carbide whisker-reinforced ceramic composites are fabricated in a highly reproducible manner by beneficating the surfaces of the silicon carbide whiskers prior to their usage in the ceramic composites. The silicon carbide whiskers which contain considerable concentrations of surface oxides and other impurities which interact with the ceramic composite material to form a chemical bond are significantly reduced so that only a relatively weak chemical bond is formed between the whisker and the ceramic material. Thus, when the whiskers interact with a crack propagating into the composite the crack is diverted or deflected along the whisker-matrix interface due to the weak chemical bonding so as to deter the crack propagation through the composite. The depletion of the oxygen-containing compounds and other impurities on the whisker surfaces and near surface region is effected by heat treating the whiskers in a suitable oxygen sparaging atmosphere at elevated temperatures. Additionally, a sedimentation technique may be utilized to remove whiskers which suffer structural and physical anomalies which render them undesirable for use in the composite. Also, a layer of carbon may be provided on the surface of the whiskers to further inhibit chemical bonding of the whiskers to the ceramic composite material.

Ceramic composites reinforced with modified silicon carbide whiskers and method for modifying the whiskers

DOEpatents

Tiegs, T.N.; Lindemer, T.B.

1991-02-19

Silicon carbide whisker-reinforced ceramic composites are fabricated in a highly reproducible manner by beneficating the surfaces of the silicon carbide whiskers prior to their usage in the ceramic composites. The silicon carbide whiskers which contain considerable concentrations of surface oxides and other impurities which interact with the ceramic composite material to form a chemical bond are significantly reduced so that only a relatively weak chemical bond is formed between the whisker and the ceramic material. Thus, when the whiskers interact with a crack propagating into the composite the crack is diverted or deflected along the whisker-matrix interface due to the weak chemical bonding so as to deter the crack propagation through the composite. The depletion of the oxygen-containing compounds and other impurities on the whisker surfaces and near surface region is effected by heat treating the whiskers in a suitable oxygen sparging atmosphere at elevated temperatures. Additionally, a sedimentation technique may be utilized to remove whiskers which suffer structural and physical anomalies which render them undesirable for use in the composite. Also, a layer of carbon may be provided on the surface of the whiskers to further inhibit chemical bonding of the whiskers to the ceramic composite material.

Ceramic composites reinforced with modified silicon carbide whiskers

DOEpatents

Tiegs, Terry N.; Lindemer, Terrence B.

1990-01-01

Silicon carbide whisker-reinforced ceramic composites are fabricated in a highly reproducible manner by beneficating the surfaces of the silicon carbide whiskers prior to their usage in the ceramic composites. The silicon carbide whiskers which contain considerable concentrations of surface oxides and other impurities which interact with the ceramic composite material to form a chemical bond are significantly reduced so that only a relatively weak chemical bond is formed between the whisker and the ceramic material. Thus, when the whiskers interact with a crack propagating into the composite the crack is diverted or deflected along the whisker-matrix interface due to the weak chemical bonding so as to deter the crack propagation through the composite. The depletion of the oxygen-containing compounds and other impurities on the whisker surfaces and near surface region is effected by heat treating the whiskers in a suitable oxygen sparaging atmosphere at elevated temperatures. Additionally, a sedimentation technique may be utilized to remove whiskers which suffer structural and physical anomalies which render them undesirable for use in the composite. Also, a layer of carbon may be provided on the surface of the whiskers to further inhibit chemical bonding of the whiskers to the ceramic composite material.

Modeling of surface temperature effects on mixed material migration in NSTX-U

NASA Astrophysics Data System (ADS)

Nichols, J. H.; Jaworski, M. A.; Schmid, K.

2016-10-01

NSTX-U will initially operate with graphite walls, periodically coated with thin lithium films to improve plasma performance. However, the spatial and temporal evolution of these films during and after plasma exposure is poorly understood. The WallDYN global mixed-material surface evolution model has recently been applied to the NSTX-U geometry to simulate the evolution of poloidally inhomogenous mixed C/Li/O plasma-facing surfaces. The WallDYN model couples local erosion and deposition processes with plasma impurity transport in a non-iterative, self-consistent manner that maintains overall material balance. Temperature-dependent sputtering of lithium has been added to WallDYN, utilizing an adatom sputtering model developed from test stand experimental data. Additionally, a simplified temperature-dependent diffusion model has been added to WallDYN so as to capture the intercalation of lithium into a graphite bulk matrix. The sensitivity of global lithium migration patterns to changes in surface temperature magnitude and distribution will be examined. The effect of intra-discharge increases in surface temperature due to plasma heating, such as those observed during NSTX Liquid Lithium Divertor experiments, will also be examined. Work supported by US DOE contract DE-AC02-09CH11466.

Parameters effects study on pulse laser for the generation of surface acoustic waves in human skin detection applications

NASA Astrophysics Data System (ADS)

Li, Tingting; Fu, Xing; Dorantes-Gonzalez, Dante J.; Chen, Kun; Li, Yanning; Wu, Sen

2015-10-01

Laser-induced Surface Acoustic Waves (LSAWs) has been promisingly and widely used in recent years due to its rapid, high accuracy and non-contact evaluation potential of layered and thin film materials. For now, researchers have applied this technology on the characterization of materials' physical parameters, like Young's Modulus, density, and Poisson's ratio; or mechanical changes such as surface cracks and skin feature like a melanoma. While so far, little research has been done on providing practical guidelines on pulse laser parameters to best generate SAWs. In this paper finite element simulations of the thermos-elastic process based on human skin model for the generation of LSAWs were conducted to give the effects of pulse laser parameters have on the generated SAWs. And recommendations on the parameters to generate strong SAWs for detection and surface characterization without cause any damage to skin are given.

Chain alignment for improved properties - Optimization of PLA and PHB-V by crystallization and reinforcement

NASA Astrophysics Data System (ADS)

Moser, K.; Bergmann, B.; Diemert, J.; Elsner, P.

2014-05-01

In this paper two promising ways to improve the material characteristics of PLA and PHB-V are presented by showing their positive effects on mechanical, optical, and thermal properties. The optimization is achieved by increasing the crystallization from the melt of the polymer chains and the other by means of a reinforcement of the matrices by bio-based materials. In the case of crystallization specific nucleating agents and optimized process parameters promote optimized crystallization conditions and lead particularly in toughness to significant improvements. In addition to crystallization the introduction of cellulose-based reinforcing materials is also a good alternative to improve the ductility of a biopolymer matrix considerably. Due to their polar surface structure cellulose fibres are favouring a very good interaction to the also polar biopolymers. In addition, the polar surfaces of both materials results in very homogeneous dispersion within the compound.

Tuning graphitic oxide for initiator- and metal-free aerobic epoxidation of linear alkenes

NASA Astrophysics Data System (ADS)

Pattisson, Samuel; Nowicka, Ewa; Gupta, Upendra N.; Shaw, Greg; Jenkins, Robert L.; Morgan, David J.; Knight, David W.; Hutchings, Graham J.

2016-09-01

Graphitic oxide has potential as a carbocatalyst for a wide range of reactions. Interest in this material has risen enormously due to it being a precursor to graphene via the chemical oxidation of graphite. Despite some studies suggesting that the chosen method of graphite oxidation can influence the physical properties of the graphitic oxide, the preparation method and extent of oxidation remain unresolved for catalytic applications. Here we show that tuning the graphitic oxide surface can be achieved by varying the amount and type of oxidant. The resulting materials differ in level of oxidation, surface oxygen content and functionality. Most importantly, we show that these graphitic oxide materials are active as unique carbocatalysts for low-temperature aerobic epoxidation of linear alkenes in the absence of initiator or metal. An optimum level of oxidation is necessary and materials produced via conventional permanganate-based methods are far from optimal.

Temperature Measurement of Ceramic Materials Using a Multiwavelength Pyrometer

NASA Technical Reports Server (NTRS)

Ng, Daniel; Fralick, Gustave

1999-01-01

The surface temperatures of several pure ceramic materials (alumina, beryllia, magnesia, yittria and spinel) in the shape of pellets were measured using a multiwavelength pyrometer. In one of the measurements, radiation signal collection is provided simply by an optical fiber. In the other experiments, a 4.75 inch (12 cm) parabolic mirror collects the signal for the spectrometer. Temperature measurement using the traditional one- and two-color pyrometer for these ceramic materials is difficult because of their complex optical properties, such as low emissivity which varies with both temperature and wavelength. In at least one of the materials, yittria, the detected optical emission increased as the temperature was decreased due to such emissivity variation. The reasons for such changes are not known. The multiwavelength pyrometer has demonstrated its ability to measure surface temperatures under such conditions. Platinum electrodes were embedded in the ceramic pellets for resistance measurements as the temperature changed.

Effect of flowing sodium on corrosion and tensile properties of AISI type 316LN stainless steel at 823 K

NASA Astrophysics Data System (ADS)

Sivai Bharasi, N.; Thyagarajan, K.; Shaikh, H.; Balamurugan, A. K.; Bera, Santanu; Kalavathy, S.; Gurumurthy, K.; Tyagi, A. K.; Dayal, R. K.; Rajan, K. K.; Khatak, H. S.

2008-07-01

AISI type 316LN stainless steel was exposed to flowing sodium in mass transfer loop (MTL) at 823 K for 16 000 h and then examined for changes in the tensile properties due to the mass transfer and corrosion effects. Comparisons in microstructural and mechanical properties were made between annealed, thermally aged and sodium exposed materials. Microstructural examination of thermally aged and sodium exposed materials revealed precipitation of carbides at the grain boundaries. The sodium exposed samples contained a degraded layer at the surface up to a depth of around 10 μm and a surface carburized layer of about 30 μm. There was about 15% increase in yield strength and a decrease of about 20% in ductility for the sodium exposed material vis-a-vis thermally aged material and this was attributed to carburization effects and microstructural changes.

Corrosion-resistant catalyst supports for phosphoric acid fuel cells

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

Kosek, J.A.; Cropley, C.C.; LaConti, A.B.

High-surface-area carbon blacks such as Vulcan XC-72 (Cabot Corp.) and graphitized carbon blacks such as 2700{degree}C heat-treated Black Pearls 2000 (HTBP) (Cabot Corp.) have found widespread applications as catalyst supports in phosphoric acid fuel cells (PAFCs). However, due to the operating temperatures and pressures being utilized in PAFCs currently under development, the carbon-based cathode catalyst supports suffer from corrosion, which decreases the performance and life span of a PAFC stack. The feasibility of using alternative, low-cost, corrosion-resistant catalyst support (CRCS) materials as replacements for the cathode carbon support materials was investigated. The objectives of the program were to prepare high-surface-areamore » alternative supports and to evaluate the physical characteristics and the electrochemical stability of these materials. The O{sub 2} reduction activity of the platinized CRCS materials was also evaluated. 2 refs., 3 figs.« less

Impact of surface porosity and topography on the mechanical behavior of high strength biomedical polymers.

PubMed

Evans, Nathan T; Irvin, Cameron W; Safranski, David L; Gall, Ken

2016-06-01

The ability to control the surface topography of orthopedic implant materials is desired to improve osseointegration but is often at the expense of mechanical performance in load bearing environments. Here we investigate the effects of surface modifications, roughness and porosity, on the mechanical properties of a set of polymers with diverse chemistry and structure. Both roughness and surface porosity resulted in samples with lower strength, failure strain and fatigue life due to stress concentrations at the surface; however, the decrease in ductility and fatigue strength were greater than the decrease in monotonic strength. The fatigue properties of the injection molded polymers did not correlate with yield strength as would be traditionally observed in metals. Rather, the fatigue properties and the capacity to maintain properties with the introduction of surface porosity correlated with the fracture toughness of the polymers. Polymer structure impacted the materials relative capacity to maintain monotonic and cyclic properties in the face of surface texture and porosity. Generally, amorphous polymers with large ratios of upper to lower yield points demonstrated a more significant drop in ductility and fatigue strength with the introduction of porosity compared to crystalline polymers with smaller ratios in their upper to lower yield strength. The latter materials have more effective dissipation mechanisms to minimize the impact of surface porosity on both monotonic and cyclic damage. Copyright © 2016 Elsevier Ltd. All rights reserved.

Nanostructuring of Palladium with Low-Temperature Helium Plasma

PubMed Central

Fiflis, P.; Christenson, M.P.; Connolly, N.; Ruzic, D.N.

2015-01-01

Impingement of high fluxes of helium ions upon metals at elevated temperatures has given rise to the growth of nanostructured layers on the surface of several metals, such as tungsten and molybdenum. These nanostructured layers grow from the bulk material and have greatly increased surface area over that of a not nanostructured surface. They are also superior to deposited nanostructures due to a lack of worries over adhesion and differences in material properties. Several palladium samples of varying thickness were biased and exposed to a helium helicon plasma. The nanostructures were characterized as a function of the thickness of the palladium layer and of temperature. Bubbles of ~100 nm in diameter appear to be integral to the nanostructuring process. Nanostructured palladium is also shown to have better catalytic activity than not nanostructured palladium. PMID:28347109

Nanostructuring of Palladium with Low-Temperature Helium Plasma.

PubMed

Fiflis, P; Christenson, M P; Connolly, N; Ruzic, D N

2015-11-25

Impingement of high fluxes of helium ions upon metals at elevated temperatures has given rise to the growth of nanostructured layers on the surface of several metals, such as tungsten and molybdenum. These nanostructured layers grow from the bulk material and have greatly increased surface area over that of a not nanostructured surface. They are also superior to deposited nanostructures due to a lack of worries over adhesion and differences in material properties. Several palladium samples of varying thickness were biased and exposed to a helium helicon plasma. The nanostructures were characterized as a function of the thickness of the palladium layer and of temperature. Bubbles of ~100 nm in diameter appear to be integral to the nanostructuring process. Nanostructured palladium is also shown to have better catalytic activity than not nanostructured palladium.

Colloidal aluminum nanoparticles with tunable localized surface plasmon resonances for energy applications

NASA Astrophysics Data System (ADS)

Cheng, Yan; Smith, Kenneth; Arinze, Ebuka; Nyirjesy, Gabrielle; Bragg, Arthur; Thon, Susanna

Localized surface plasmon resonances (LSPRs) of noble metal nanoparticles are of interest for energy applications due to their visible and near infrared wavelength sensitivity. However, application of these materials in optoelectronic devices is limited by their rarity and high cost. Earth-abundant, inexpensive and non-toxic aluminum is a promising alternative material with a plasmon resonance that can also be tuned via size-, shape- and surface-oxide-control. Here, we employ solution-processed methods to synthesize stable colloidal aluminum nanoparticles. We systematically investigate parameters in the synthesis that control size, shape and oxidation of the aluminum nanoparticles and tune their LSPRs over the ultraviolet and visible spectral regions. We optically characterize the nanoparticle solutions and evaluate their potential for future integration into photovoltaic, photocatalytic and photosensing systems.

Surface modification by carbon ion implantation for the application of ni-based amorphous alloys as bipolar plate in proton exchange membrane fuel cells

NASA Astrophysics Data System (ADS)

Kim, Min-Uk; Kim, Do-Hyang; Han, Seung-hee; Fleury, Eric; Seok, Hyun-Kwang; Cha, Pil-Ryung; Kim, Yu-Chan

2011-04-01

Ni-based amorphous alloys with surface modification by carbon ion implantation are proposed as an alternative bipolar plate material for polymer electrolyte membrane fuel cells (PEMFCs). Both Ni60Nb20Ti10Zr10 alloys with and without carbon ion implantation have corrosion resistance as good as graphite as well as much lower contact resistance than 316L stainless steel in the PEMFC environment. The formation of conductive surface carbide due to carbon ion implantation results in a decrease in the contact resistance to a level comparable to that of graphite. This combination of excellent properties indicates that carbon ion implanted Ni-based amorphous alloys can be potential candidate materials for bipolar plates in PEMFCs.

Few layered vanadyl phosphate nano sheets-MWCNT hybrid as an electrode material for supercapacitor application

NASA Astrophysics Data System (ADS)

Dutta, Shibsankar; De, Sukanta

2016-05-01

It have been already seen that 2-dimensional nano materials are the suitable choice for the supercapacitor application due to their large specific surface area, electrochemical active sites, micromechanical flexibility, expedite ion migration channel properties. Free standing hybrid films of functionalized MWCNT (- COOH group) and α-Vanadyl phosphates (VOPO42H2O) are prepared by vacuum filtering. The surface morphology and microstructure of the samples are studied by transmission electron microscope, field emission scanning electron microscope, XRD, Electrochemical properties of hybrid films have been investigated systematically in 1M Na2SO4 aqueous electrolyte. The hybrid material exhibits a high specific capacitance 236 F/g with high energy density of 65.6 Wh/Kg and a power density of 1476 W/Kg.

Topological insulators double perovskites: A2TePoO6 (A = Ca, Sr, Ba)

NASA Astrophysics Data System (ADS)

Lee, Po-Han; Zhou, Jian; Pi, Shu-Ting; Wang, Yin-Kuo

2017-12-01

Based on first-principle calculations and direct density functional theory calculations of surface bands, we predict a new class of three-dimensional (3D) Z2 topological insulators (TIs) with larger bulk bandgaps up to 0.4 eV in double perovskite materials A2TePoO6 (A = Ca, Sr, and Ba). The larger nontrivial gaps are induced by the symmetry-protected band contact along with band inversion occurring in the absence of spin-orbit coupling (SOC) making the SOC more effective than conventional TIs. The proposed materials are chemically inert and more robust to surface perturbations due to its intrinsic protection layer. This study provides the double perovskite material as a rich platform to design new TI-based electronic devices.

Ultrasonic Surface Measurements for the investigation of superficial alteration of natural stones

NASA Astrophysics Data System (ADS)

Meier, Thomas; Auras, Michael; Bilgili, Filiz; Christen, Sandra; Cristiano, Luigia; Krompholz, Rolf; Mosca, Ilaria; Rose, David

2013-04-01

Seismic waveform analysis is applicable also to the centimeter and decimeter scale for non-destructive testing of pavement, facades, plaster, sculptures, or load-bearing structures like pillars. Mostly transmission measurements are performed and travel-times of first arriving P-waves are considered that have limited resolution for the upper centimeters of an object. In contrast, surface measurements are well suited to quantify superficial alterations of material properties e.g. due to weathering. A number of surface measurements have been carried out in the laboratory as well as on real structures in order to study systematically the information content of ultrasonic waveforms and their variability under real conditions. As a preposition for ultrasonic waveform analysis, reproducible, broad-band measurements have to be carried out with a definite radiation pattern and an about 1 mm accuracy of the measurement geometry. We used special coupling devices for effective ultrasonic surface measurements in the laboratory as well as at real objects. Samples of concrete with varying composition and samples of natural stone - marble, tuff, and sandstone - were repeatedly weathered and tested by ultrasonic measurements. The resistance of the samples to weathering and the penetration depth of the weathering are analyzed. Furthermore, material specific calibration curves for changes in velocities of elastic waves due to weathering can be obtained by these tests. Tests on real structures have been carried out for marble (Schlossbrücke, Berlin) and sandstone (Porta Nigra, Trier). Altogether, these test measurements show clearly that despite of the internal inhomogeneity of many real objects, their surface roughness and topography especially ultrasonic Rayleigh waves are well suited to study material alterations in the upper centimeters. Dispersion of Rayleigh waves may be inverted for shear-wave velocity as a function of depth.

Enhanced Detection of Surface-Associated Bacteria in Indoor Environments by Quantitative PCR

PubMed Central

Buttner, Mark P.; Cruz-Perez, Patricia; Stetzenbach, Linda D.

2001-01-01

Methods for detecting microorganisms on surfaces are needed to locate biocontamination sources and to relate surface and airborne concentrations. Research was conducted in an experimental room to evaluate surface sampling methods and quantitative PCR (QPCR) for enhanced detection of a target biocontaminant present on flooring materials. QPCR and culture analyses were used to quantitate Bacillus subtilis (Bacillus globigii) endospores on vinyl tile, commercial carpet, and new and soiled residential carpet with samples obtained by four surface sampling methods: a swab kit, a sponge swipe, a cotton swab, and a bulk method. The initial data showed that greater overall sensitivity was obtained with the QPCR than with culture analysis; however, the QPCR results for bulk samples from residential carpet were negative. The swab kit and the sponge swipe methods were then tested with two levels of background biological contamination consisting of Penicillium chrysogenum spores. The B. subtilis values obtained by the QPCR method were greater than those obtained by culture analysis. The differences between the QPCR and culture data were significant for the samples obtained with the swab kit for all flooring materials except soiled residential carpet and with the sponge swipe for commercial carpet. The QPCR data showed that there were no significant differences between the swab kit and sponge swipe sampling methods for any of the flooring materials. Inhibition of QPCR due solely to biological contamination of flooring materials was not evident. However, some degree of inhibition was observed with the soiled residential carpet, which may have been caused by the presence of abiotic contaminants, alone or in combination with biological contaminants. The results of this research demonstrate the ability of QPCR to enhance detection and enumeration of biocontaminants on surface materials and provide information concerning the comparability of currently available surface sampling methods. PMID:11375164

Helium Ion Microscope: A New Tool for Sub-nanometer Imaging of Soft Materials

NASA Astrophysics Data System (ADS)

Shutthanandan, V.; Arey, B.; Smallwood, C. R.; Evans, J. E.

2017-12-01

High-resolution inspection of surface details is needed in many biological and environmental researches to understand the Soil organic material (SOM)-mineral interactions along with identifying microbial communities and their interactions. SOM shares many imaging characteristics with biological samples and getting true surface details from these materials are challenging since they consist of low atomic number materials. FE-SEM imaging is the main imagining technique used to image these materials in the past. These SEM images often show loss of resolution and increase noise due to beam damage and charging issues. Newly developed Helium Ion Microscope (HIM), on the other hand can overcome these difficulties and give very fine details. HIM is very similar to scanning electron microscopy (SEM) but instead of using electrons as a probe beam, HIM uses helium ions with energy ranges from 5 to 40 keV. HIM offers a series of advantages compared to SEM such as nanometer and sub-nanometer image resolutions (about 0.35 nm), detailed surface topography, high surface sensitivity, low Z material imaging (especially for polymers and biological samples), high image contrast, and large depth of field. In addition, HIM also has the ability to image insulating materials without any conductive coatings so that surface details are not modified. In this presentation, several scientific applications across biology and geochemistry will be presented to highlight the effectiveness of this powerful microscope. Acknowledgements: Research was performed using the Environmental Molecular Sciences Laboratory (EMSL), a national scientific user facility sponsored by the Department of Energy's Office of Biological and Environmental Research and located at PNNL. Work was supported by DOE-BER Mesoscale to Molecules Bioimaging Project FWP# 66382.

Infrared Telescope Facility's Spectrograph Observations of Human-Made Space Objects

NASA Technical Reports Server (NTRS)

Abercromby, K.; Buckalew, B.; Abell, P.; Cowardin, H.

2015-01-01

Presented here are the results of the Infrared Telescope Facility (IRTF) spectral observations of human-made space objects taken from 2006 to 2008. The data collected using the SpeX infrared spectrograph cover the wavelength range 0.7-2.5 micrometers. Overall, data were collected on 20 different orbiting objects at or near the geosynchronous (GEO) regime. Four of the objects were controlled spacecraft, seven were non-controlled spacecraft, five were rocket bodies, and the final four were cataloged as debris pieces. The remotely collected data are compared to the laboratory-collected reflectance data on typical spacecraft materials, thereby general materials are identified but not specific types. These results highlight the usefulness of observations in the infrared by focusing on features from hydrocarbons, silicon, and thermal emission. The spacecraft, both the controlled and non-controlled, show distinct features due to the presence of solar panels, whereas the rocket bodies do not. Signature variations between rocket bodies, due to the presence of various metals and paints on their surfaces, show a clear distinction from those objects with solar panels, demonstrating that one can distinguish most spacecraft from rocket bodies through infrared spectrum analysis. Finally, the debris pieces tend to show featureless, dark spectra. These results show that the laboratory data in its current state give excellent indications as to the nature of the surface materials on the objects. Further telescopic data collection and model updates to include noise, surface roughness, and material degradation are necessary to make better assessments of orbital object material types. However, based on the current state of the comparison between the observations and the laboratory data, infrared spectroscopic data are adequate to classify objects in GEO as spacecraft, rocket bodies, or debris.

Temperature responses of carbon monoxide and hydrogen uptake by vegetated and unvegetated volcanic cinders

PubMed Central

King, Caitlin E; King, Gary M

2012-01-01

Ecosystem succession on a large deposit of volcanic cinders emplaced on Kilauea Volcano in 1959 has resulted in a mosaic of closed-canopy forested patches and contiguous unvegetated patches. Unvegetated and unshaded surface cinders (Bare) experience substantial diurnal temperature oscillations ranging from moderate (16 °C) to extreme (55 °C) conditions. The surface material of adjacent vegetated patches (Canopy) experiences much smaller fluctuations (14–25 °C) due to shading. To determine whether surface material from these sites showed adaptations by carbon monoxide (CO) and hydrogen (H2) consumption to changes in ambient temperature regimes accompanying succession, we measured responses of CO and H2 uptake to short-term variations in temperature and long-term incubations at elevated temperature. Based on its broader temperature optimum and lower activation energy, Canopy H2 uptake was less sensitive than Bare H2 uptake to temperature changes. In contrast, Bare and Canopy CO uptake responded similarly to temperature during short-term incubations, indicating no differences in temperature sensitivity. However, during extended incubations at 55 °C, CO uptake increased for Canopy but not Bare material, which indicated that the former was capable of thermal adaptation. H2 uptake for material from both sites was completely inhibited at 55 °C throughout extended incubations. These results indicated that plant development during succession did not elicit differences in short-term temperature responses for Bare and Canopy CO uptake, in spite of previously reported differences in CO oxidizer community composition, and differences in average daily and extreme temperatures. Differences associated with vegetation due to succession did, however, lead to a notable capacity for thermophilic CO uptake by Canopy but not Bare material. PMID:22258097

Temperature responses of carbon monoxide and hydrogen uptake by vegetated and unvegetated volcanic cinders.

PubMed

King, Caitlin E; King, Gary M

2012-08-01

Ecosystem succession on a large deposit of volcanic cinders emplaced on Kilauea Volcano in 1959 has resulted in a mosaic of closed-canopy forested patches and contiguous unvegetated patches. Unvegetated and unshaded surface cinders (Bare) experience substantial diurnal temperature oscillations ranging from moderate (16 °C) to extreme (55 °C) conditions. The surface material of adjacent vegetated patches (Canopy) experiences much smaller fluctuations (14-25 °C) due to shading. To determine whether surface material from these sites showed adaptations by carbon monoxide (CO) and hydrogen (H(2)) consumption to changes in ambient temperature regimes accompanying succession, we measured responses of CO and H(2) uptake to short-term variations in temperature and long-term incubations at elevated temperature. Based on its broader temperature optimum and lower activation energy, Canopy H(2) uptake was less sensitive than Bare H(2) uptake to temperature changes. In contrast, Bare and Canopy CO uptake responded similarly to temperature during short-term incubations, indicating no differences in temperature sensitivity. However, during extended incubations at 55 °C, CO uptake increased for Canopy but not Bare material, which indicated that the former was capable of thermal adaptation. H(2) uptake for material from both sites was completely inhibited at 55 °C throughout extended incubations. These results indicated that plant development during succession did not elicit differences in short-term temperature responses for Bare and Canopy CO uptake, in spite of previously reported differences in CO oxidizer community composition, and differences in average daily and extreme temperatures. Differences associated with vegetation due to succession did, however, lead to a notable capacity for thermophilic CO uptake by Canopy but not Bare material.

Adhesion Between Volcanic Glass and Spacecraft Materials in an Airless Body Environment

NASA Technical Reports Server (NTRS)

Berkebile, Stephen; Street, Kenneth W., Jr.; Gaier, James R.

2012-01-01

The successful exploration of airless bodies, such as the Earth s moon, many smaller moons of the outer planets (including those of Mars) and asteroids, will depend on the development and implementation of effective dust mitigation strategies. The ultrahigh vacuum environment (UHV) on the surfaces of these bodies, coupled with constant ion and photon bombardment from the Sun and micrometeorite impacts (space weathering), makes dust adhesion to critical spacecraft systems a severe problem. As a result, the performance of thermal control surfaces, photovoltaics and mechanical systems can be seriously degraded even to the point of failure. The severe dust adhesion experienced in these environments is thought to be primarily due to two physical mechanisms, electrostatic attraction and high surface energies, but the dominant of these has yet to be determined. The experiments presented here aim to address which of these two mechanisms is dominant by quantifying the adhesion between common spacecraft materials (polycarbonate, FEP and PTFE Teflon, (DuPont) Ti-6-4) and a synthetic noritic volcanic glass, as a function of surface cleanliness and triboelectric charge transfer in a UHV environment. Adhesion force has been measured between pins of spacecraft materials and a plate of synthetic volcanic glass by determining the pull-off force with a torsion balance. Although no significant adhesion is observed directly as a result of high surface energies, the adhesion due to induced electrostatic charge is observed to increase with spacecraft material cleanliness, in some cases by over a factor of 10, although the increase is dependent on the particular material pair. The knowledge gained by these studies is envisioned to aid the development of new dust mitigation strategies and improve existing strategies by helping to identify and characterize mechanisms of glass to spacecraft adhesion for norite volcanic glass particles. Furthermore, the experience of the Apollo missions revealed that dust mitigation strategies must be subjected to high fidelity tests. To facilitate the effectiveness of ground-based testing of mitigation strategies, the issue of a pressure limit for high fidelity tests will be addressed.

Lithium effects on the mechanical and electronic properties of germanium nanowires

NASA Astrophysics Data System (ADS)

González-Macías, A.; Salazar, F.; Miranda, A.; Trejo-Baños, A.; Pérez, L. A.; Carvajal, E.; Cruz-Irisson, M.

2018-04-01

Semiconductor nanowire arrays promise rapid development of a new generation of lithium (Li) batteries because they can store more Li atoms than conventional crystals due to their large surface areas. During the charge-discharge process, the electrodes experience internal stresses that fatigue the material and limit the useful life of the battery. The theoretical study of electronic and mechanical properties of lithiated nanowire arrays allows the designing of electrode materials that could improve battery performance. In this work, we present a density functional theory study of the electronic band structure, formation energy, binding energy, and Young’s modulus (Y) of hydrogen passivated germanium nanowires (H-GeNWs) grown along the [111] and [001] crystallographic directions with surface and interstitial Li atoms. The results show that the germanium nanowires (GeNWs) with surface Li atoms maintain their semiconducting behavior but their energy gap size decreases when the Li concentration grows. In contrast, the GeNWs can have semiconductor or metallic behavior depending on the concentration of the interstitial Li atoms. On the other hand, Y is an indicator of the structural changes that GeNWs suffer due to the concentration of Li atoms. For surface Li atoms, Y stays almost constant, whereas for interstitial Li atoms, the Y values indicate important structural changes in the GeNWs.

Graphene as a Coating for Plasma Facing Components

NASA Astrophysics Data System (ADS)

Navarro, Marcos; Zamiri, Marziyeh; Kulcinski, Gerald; Lagally, Max; Santarius, John

2017-10-01

This research explores the protection by graphene of plasma facing materials bombarded with energetic ions of helium. Few studies have shown that graphene can act as a protective layer against sputtering due to energetic ions. In the presence of such irradiation, plasma facing components (PFC's) tend to develop surface morphologies that lead to the sputtering of wall material, potentially diminishing the lifetime of the PFC's and plasma performance. Since plasmas have broad applications and the quality of transferred and grown graphene is different, we have used a chemical vapor deposition method to grow on other substrates. We have also shown that graphene can reduce changes on surface morphology due to energetic helium. After irradiation, in the case of graphene-covered tungsten, our results show that, compared to the uncovered W, graphene suppresses these morphologies that form on the surface of hot W. Using Raman spectroscopy as a diagnostic, the graphene coating shows little sign of damage after being irradiated, indicating that there is little to no sputtering of carbon impurities from the surface. We have determined that the mass losses in W have been reduced significantly, which may lead to an improved plasma performance and longer PFC lifetimes. Supported by DHS Project 2015-DN-077-ARI095 and the Grainger Foundation.

Electric treatment for hydrophilic ink deinking.

PubMed

Du, Xiaotang; Hsieh, Jeffery S

2017-09-01

Hydrophilic inks have been widely used due to higher printing speed, competitive cost and being healthy non-organic solvents. However, they cause problems in both product quality and process runnability due to their hydrophilic surface wettability, strong negative surface charge and sub-micron size. Electric treatment was shown to be able to increase the ink sizes from 60 nm to 700 nm through electrocoagulation and electrophoresis. In addition, electric treatment assisted flotation could reduce effective residual ink concentration (ERIC) by 90 ppm, compared with only 20 ppm by traditional flotation. Furthermore, the effect of electric treatment alone on ink separation was investigated by two anode materials, graphite and stainless steel. Both of them could remove hydrophilic inks with less than 1% yield loss via electroflotation and electrophoresis. But graphite is a better material as the anode because graphite reduced ERIC by an additional 100 ppm. The yield loss of flotation following electric treatment was also lower by 17% if graphite was the anode material. The difference between the two electrode materials resulted from electrocoagulation and ink redeposition during electric treatment. An electric pretreatment-flotation-hyperwashing process was conducted to understand the deinking performance in conditions similar to a paper mill, and the ERIC was reduced from 950 ppm to less than 400 ppm.

Development of Novel Fe-Based Coating Systems for Internal Combustion Engines

NASA Astrophysics Data System (ADS)

Bobzin, K.; Öte, M.; Königstein, T.; Dröder, K.; Hoffmeister, H.-W.; Mahlfeld, G.; Schläfer, T.

2018-04-01

Nowadays, combustion engines are the most common way to power vehicles. Thereby, losses occur due to cooling, exhaust gas and friction. With regard to frictional losses, highest potentials for optimization can be found in the tribological system of the inner surface of combustion chamber and piston ring. Besides friction, corrosive stress increases, e.g., due to utilization of exhaust gas recovery. In order to save energy, reduce emissions and enhance the life span of combustion engines, the demand for innovative coating material systems, especially for the inner surface of combustion chamber, increases. This study focuses on the development of innovative iron-based coating materials for the combustion chamber. As a first step, the plasma transferred wire arc and rotating single wire arc (RSW) technologies were compared using 0.8% C-steel as a reference. Subsequently, RSW was used for coating deposition using an innovative iron-based feedstock material. In order to improve wear and corrosion resistance, boron and chromium were added to the feedstock material. After deposition, different honing topographies were manufactured and compared under tribological load. Furthermore, electrochemical corrosion tests were conducted using an electrolyte simulating the exhaust gas concentrate. Especially with regard to corrosion, the novel coating system FeCrBMn showed promising results.

SEM viewing of gypsiferous material and study of their influence on electrical resistivity

NASA Astrophysics Data System (ADS)

Dafalla, M.; Fouzan, F. Al

2012-04-01

The gypsum rich material is often linked to the cavity formation due to the high solubility of cal-cium carbonate in the presence of acidic media. This work is dedicated to a close-up look to the structure of materials rich of gypsum and material of less or traces of sulfate ions. Electrical resistivity measurements were conducted along extended lines on sections involving cavities and the resulting profiles were examined for any changes. Forms and features of gypsum and minerals containing sulfates were studied and compared to sam-ples tested using SEM (scanning electron microscope). The chemical analyses (EDAX) using electron beam was carried out and the elements present within these samples were established. Quantitative chemical testing for some parameters including sulfate ions was carried out. Structural forms variation and changes are studied in view of the chemical composition. The electrical resistivity was measured using Syscal R1 electerical resis-tivity equipment for several spots near surface. Statistical correlations between sulfate ions content and elec-trical resistivity, for near surface soils, is presented. This study is aiming at utilizing the geophysical testing methods of sulfate rich soils and predicting future cavity formation in areas of high risk to cavities due to chemical weathering.

Photonic surface waves on metamaterial interfaces

NASA Astrophysics Data System (ADS)

Takayama, O.; Bogdanov, A. A.; Lavrinenko, A. V.

2017-11-01

A surface wave (SW) in optics is a light wave, which is supported at an interface of two dissimilar media and propagates along the interface with its field amplitude exponentially decaying away from the boundary. Research on surface waves has been flourishing in the last few decades due to their unique properties of surface sensitivity and field localization. These features have resulted in applications in nano-guiding, sensing, light-trapping and imaging based on near-field techniques, contributing to the establishment of nanophotonics as a field of research. Up to now, a wide variety of surface waves has been investigated in numerous material and structure settings. This article reviews the recent progress and development in the physics of SWs localized at metamaterial interfaces, as well as bulk media in order to provide broader perspectives on optical surface waves in general. For each type of surface wave, we discuss the material and structural platforms. We mainly focus on experimental realizations in the visible and near-infrared wavelength ranges. We also address existing and potential application of SWs in chemical and biological sensing, and experimental excitation and characterization methods.

Optical Properties and Plasmonic Performance of Titanium Nitride

PubMed Central

Patsalas, Panos; Kalfagiannis, Nikolaos; Kassavetis, Spyros

2015-01-01

Titanium nitride (TiN) is one of the most well-established engineering materials nowadays. TiN can overcome most of the drawbacks of palsmonic metals due to its high electron conductivity and mobility, high melting point and due to the compatibility of its growth with Complementary Metal Oxide Semiconductor (CMOS) technology. In this work, we review the dielectric function spectra of TiN and we evaluate the plasmonic performance of TiN by calculating (i) the Surface Plasmon Polariton (SPP) dispersion relations and (ii) the Localized Surface Plasmon Resonance (LSPR) band of TiN nanoparticles, and we demonstrate a significant plasmonic performance of TiN.

Positron and nanoindentation study of helium implanted high chromium ODS steels

NASA Astrophysics Data System (ADS)

Veternikova, Jana Simeg; Fides, Martin; Degmova, Jarmila; Sojak, Stanislav; Petriska, Martin; Slugen, Vladimir

2017-12-01

Three oxide dispersion strengthened (ODS) steels with different chromium content (MA 956, MA 957 and ODM 751) were studied as candidate materials for new nuclear reactors in term of their radiation stability. The radiation damage was experimentally simulated by helium ion implantation with energy of ions up to 500 keV. The study was focused on surface and sub-surface structural change due to the ion implantation observed by mostly non-destructive techniques: positron annihilation lifetime spectroscopy and nanoindentation. The applied techniques demonstrated the best radiation stability of the steel ODM 751. Blistering effect occurred due to high implantation dose (mostly in MA 956) was studied in details.

Surface of the comet 67P from PHILAE/CIVA images as clues to the formation of the comet nucleus

NASA Astrophysics Data System (ADS)

Poulet, Francois; Bibring, Jean-Pierre; Carter, John; Eng, Pascal; Gondet, Brigitte; Jorda, Laurent; Langevin, Yves; Le Mouélic, Stéphane; Pilorget, Cédric

2015-04-01

The CIVA cameras onboard PHILAE provided the first ever in situ images of the surface of a comet (Bibring et al., this conf). The panorama acquired by CIVA at the landing site reveals a rough terrain dominated by agglomerates of consolidated materials similar to cm-sized pebbles. While the composition of these materials is unknown, their nature will be discussed in relation to both endogenic and exogenic processes that may sculpted the landscape of the landing site. These processes includes erosion (spatially non-uniform) by sublimation, redeposition of particles after ejection, fluidization and transport of cometary material on the surface, sintering effect, thermal fatigue, thermal stress, size segregation due to shaking, eolian erosion due to local outflow of cometary vapor and impact cratering at various scales. Recent advancements in planet formation theory suggest that the initial planetesimals (or cometestimals) may grow directly from the gravitational collapse of aerodynamically concentrated small particles, often referred to as "pebbles" (Johansen et al. 2007, Nature 448, 1022; Cuzzi et al. 2008, AJ 687, 1432). We will then discuss the possibility that the observed pebble pile structures are indicative of the formation process from which the initial nucleus formed, and how we can use this idea to learn about protoplanetary disks and the early processes involved in the Solar System formation.

Thermostructural Analysis of Carbon Cloth Phenolics "Ply Lifting" and Correlation to LHMEL Test Results

NASA Technical Reports Server (NTRS)

Clayton, Louie

2004-01-01

This paper provides a discussion of the history of Carbon Cloth Phenolic (CCP) ply lifting in the Redesigned Solid Rocket Motor (RSRM) Program, a brief presentation of theoretical methods used for analytical evaluation, and results of parametric analyses of CCP material subject to test conditions of the Laser Hardened Material Evaluation Laboratory. CCP ply lift can occur in regions of the RSRM nozzle where ply angle to flame surface is generally less than about 20 degrees. There is a heat rate dependence on likelihood and severity of the condition with the higher heating rates generally producing more ply lift. The event occurs in-depth, near the heated surface, where the load necessary to mechanically separate the CCP plies is produced by the initial stages of pyrolysis gas generation due to the thermal decomposition of the phenolic resin matrix. Due to the shallow lay-up angle of the composite, normal components of the indepth mechanical load, due to "pore pressure", are imparted primarily as a cross-ply tensile force on the interlaminar ply boundaries. Tensile capability in the cross-ply (out of plane) direction is solely determined by the matrix material capability. The elevated temperature matrix material capabilities are overcome by pressure induced mechanical normal stress and ply-lift occurs. A theoretical model used for CCP in-depth temperature, pressure, and normal stress prediction, based on first principles, is briefly discussed followed by a parametric evaluation of response variables subject to boundary conditions typical of on-going test programs at the LHMEL facility. Model response demonstrates general trends observed in test and provides insight into the interactivity of material properties and constitutive relationships.

Interactions on External MOF Surfaces: Desorption of Water and Ethanol from CuBDC Nanosheets.

PubMed

Elder, Alexander C; Aleksandrov, Alexandr B; Nair, Sankar; Orlando, Thomas M

2017-10-03

The external surfaces of metal-organic framework (MOF) materials are difficult to experimentally isolate due to the high porosities of these materials. MOF surface surrogates in the form of copper benzenedicarboxylate (CuBDC) nanosheets were synthesized using a bottom-up approach, and the surface interactions of water and ethanol were investigated by temperature-programmed desorption (TPD). A method of analysis of diffusion-influenced TPD was developed to measure the desorption properties of these porous materials. This approach also allows the extraction of diffusion coefficients from TPD data. The transmission Fourier transform infrared spectra, powder X-ray diffraction patterns, and TPD data indicate that water desorbs from CuBDC nanosheets with activation energies of 44 ± 2 kJ/mol at edge sites and 58 ± 1 kJ/mol at external surface and internal and pore sites. Ethanol desorbs with activation energies of 58 ± 1 kJ/mol at internal pore sites and 66 ± 0.4 kJ/mol at external surface sites. Co-adsorption of water and ethanol was also investigated. The presence of ethanol was found to inhibit the desorption of water, resulting in a water desorption process with an activation energy of 68 ± 0.7 kJ/mol.

Surface functionalization of 3D glass-ceramic porous scaffolds for enhanced mineralization in vitro

NASA Astrophysics Data System (ADS)

Ferraris, Sara; Vitale-Brovarone, Chiara; Bretcanu, Oana; Cassinelli, Clara; Vernè, Enrica

2013-04-01

Bone reconstruction after tissue loosening due to traumatic, pathological or surgical causes is in increasing demand. 3D scaffolds are a widely studied solution for supporting new bone growth. Bioactive glass-ceramic porous materials can offer a three-dimensional structure that is able to chemically bond to bone. The ability to surface modify these devices by grafting biologically active molecules represents a challenge, with the aim of stimulating physiological bone regeneration with both inorganic and organic signals. In this research work glass ceramic scaffolds with very high mechanical properties and moderate bioactivity have been functionalized with the enzyme alkaline phosphatase (ALP). The material surface was activated in order to expose hydroxyl groups. The activated surface was further grafted with ALP both via silanization and also via direct grafting to the surface active hydroxyl groups. Enzymatic activity of grafted samples were measured by means of UV-vis spectroscopy before and after ultrasonic washing in TRIS-HCl buffer solution. In vitro inorganic bioactivity was investigated by soaking the scaffolds after the different steps of functionalization in a simulated body fluid (SBF). SEM observations allowed the monitoring of the scaffold morphology and surface chemical composition after soaking in SBF. The presence of ALP enhanced the in vitro inorganic bioactivity of the tested material.

Beeswax as phase change material to improve solar panel’s performance

NASA Astrophysics Data System (ADS)

Thaib, R.; Rizal, S.; Riza, M.; Mahlia, T. M. I.; Rizal, T. A.

2018-02-01

One of the main obstacles faced during the operation of photovoltaic (PV) panels was overheating due to excessive solar radiation and high ambient temperatures. In this research, investigates the use of beeswax phase change materials (PCM) to maintain the temperature of the panels close to ambient. Solar panels used in this study has 839 mm length, 537 mm wide, and 50 mm thick, with maximum output power at 50 W. During the study, there were two solar panels was evaluated, one without phase change material while the other one was using beeswax phase change material. Solar panels were mounted at 15° slope. Variables observed was the temperature of solar panel’s surface, output voltage and current that produced by PV panels, wind speed around solar panels, and solar radiation. The observation was started at 07:00 am and ended at 06:00 pm. The research shows that maximum temperature of solar panels surface without phase change material is ranging between 46-49 °C, and electrical efficiency is about 7.2-8.8%. Meanwhile, for solar panels with beeswax phase change material, the maximum temperature solar panels surface is relatively low ranging between 33-34 °C, and its electrical efficiency seems to increase about 9.1-9.3%.

Analysis of different materials subjected to open-air explosions in search of explosive traces by Raman microscopy.

PubMed

Zapata, Félix; García-Ruiz, Carmen

2017-06-01

Post-explosion scenes offer such chaos and destruction that evidence recovery and detection of post-blast residues from the explosive in the surrounding materials is highly challenging and difficult. The suitability of materials to retain explosives residues and their subsequent analysis has been scarcely investigated. Particularly, the use of explosive mixtures containing inorganic oxidizing salts to make improvised explosive devices (IEDs) is a current security concern due to their wide availability and lax control. In this work, a wide variety of materials such as glass, steel, plywood, plastic bag, brick, cardboard or cotton subjected to open-air explosions were examined using confocal Raman microscopy, aiming to detect the inorganic oxidizing salts contained in explosives as black powder, chloratite, dynamite, ammonium nitrate fuel oil and ammonal. Post-blast residues were detected through microscopic examination of materials surfaces. In general, the more homogeneous and smoother the surface was, the less difficulties and better results in terms of identification were obtained. However, those highly irregular surfaces were the most unsuitable collectors for the posterior identification of explosive traces by Raman microscopy. The findings, difficulties and some recommendations related to the identification of post-blast particles in the different materials studied are thoroughly discussed. Copyright © 2017 Elsevier B.V. All rights reserved.

Measurement of the properties of lossy materials inside a finite conducting cylinder

NASA Technical Reports Server (NTRS)

Dominek, A.; Park, A.; Caldecott, R.

1988-01-01

Broadband, swept frequency measurement techniques were investigated for the evaluation of the electrical performance of thin, high temperature material coatings. Reflections and transmission measurements using an HP8510B Network Analyzer were developed for an existing high temperature test rig at NASA Lewis Research Center. Reflection measurements will be the initial approach used due to fixture simplicity even though surface wave transmission measurements would be more sensitive. The minimum goal is to monitor the electrical change of the material's performance as a function of temperature. If possible, the materials constitutive parameters, epsilon and muon will be found.

Size-Dependent Materials Properties Toward a Universal Equation

PubMed Central

2010-01-01

Due to the lack of experimental values concerning some material properties at the nanoscale, it is interesting to evaluate this theoretically. Through a “top–down” approach, a universal equation is developed here which is particularly helpful when experiments are difficult to lead on a specific material property. It only requires the knowledge of the surface area to volume ratio of the nanomaterial, its size as well as the statistic (Fermi–Dirac or Bose–Einstein) followed by the particles involved in the considered material property. Comparison between different existing theoretical models and the proposed equation is done. PMID:20596422

Solar-collector materials exposure to the IPH site environment. Task 5.0

NASA Astrophysics Data System (ADS)

Morris, V. L.

1982-07-01

An environmental exposure test was conducted at a site which utilizes solar energy for enhanced oil recovery procedures. Two types of reflector materials were evaluated for survivability in this environment: second surface silvered glass and aluminized acrylic (FEK-244) on an aluminum substrate. Black chrome absorber material and low iron float glass were evaluated for thermal, photochemical and environmental degradation. The reflector specimens were monitored for decreases in specular and hemispherical reflectance due to soil buildup. The absorber material is evaluated for changes in solar absorptivity and emissivity and the glass cover plates is evaluated for changes in transmissivity.

Behaviour of a ZnO thin film as MSG for biosensing material in sub-wavelength regime

NASA Astrophysics Data System (ADS)

Iftimie, N.; Steigmann, R.; Danila, N. A.; Iacomi, F.; Faktorova, D.; Savin, A.

2016-11-01

Zinc oxide nanostructured materials, such as films and nanoparticles, could provide a suitable platform for development of high performance biosensing material due to their unique fundamental material properties. In this study, the enzyme biosensing consisting of a zinc oxide (ZnO) nanoparticles were grown on SiO2/Si substrates by vacuum thermal evaporation method and their sensing characteristics are examined in air and investigated. The film morphology is characterized by X-ray diffraction (XRD) the film crystalline quality and by scanning electron microscopy (SEM). Also, the interest in surface waves appeared due to evanescent waves in the metallic strip grating structure (MSG-Ag/ZnO/SiO2/Si) in sub-wavelength regime. Before testing the sensor with metamaterials (MMs) lens in the sub-wavelength regime, a simulation of the evanescent wave's formation has been performed at the edge of Ag strips, with thicknesses in the range of micrometers.

The Electric Propulsion Interactions Code (EPIC)

NASA Technical Reports Server (NTRS)

Mikellides, I. G.; Mandell, M. J.; Kuharski, R. A.; Davis, V. A.; Gardner, B. M.; Minor, J.

2004-01-01

Science Applications International Corporation is currently developing the Electric Propulsion Interactions Code, EPIC, as part of a project sponsored by the Space Environments and Effects Program at the NASA Marshall Space Flight Center. Now in its second year of development, EPIC is an interactive computer tool that allows the construction of a 3-D spacecraft model, and the assessment of a variety of interactions between its subsystems and the plume from an electric thruster. These interactions may include erosion of surfaces due to sputtering and re-deposition of sputtered materials, surface heating, torque on the spacecraft, and changes in surface properties due to erosion and deposition. This paper describes the overall capability of EPIC and provides an outline of the physics and algorithms that comprise many of its computational modules.

Experimental investigation into effect of cutting parameters on surface integrity of hardened tool steel

NASA Astrophysics Data System (ADS)

Bashir, K.; Alkali, A. U.; Elmunafi, M. H. S.; Yusof, N. M.

2018-04-01

Recent trend in turning hardened materials have gained popularity because of its immense machinability benefits. However, several machining processes like thermal assisted machining and cryogenic machining have reveal superior machinability benefits over conventional dry turning of hardened materials. Various engineering materials have been studied. However, investigations on AISI O1 tool steel have not been widely reported. In this paper, surface finish and surface integrity dominant when hard turning AISI O1 tool steel is analysed. The study is focused on the performance of wiper coated ceramic tool with respect to surface roughness and surface integrity of hardened tool steel. Hard turned tool steel was machined at varying cutting speed of 100, 155 and 210 m/min and feed rate of 0.05, 0.125 and 0.20mm/rev. The depth of cut of 0.2mm was maintained constant throughout the machining trials. Machining was conducted using dry turning on 200E-axis CNC lathe. The experimental study revealed that the surface finish is relatively superior at higher cutting speed of 210m/min. The surface finish increases when cutting speed increases whereas surface finish is generally better at lower feed rate of 0.05mm/rev. The experimental study conducted have revealed that phenomena such as work piece vibration due to poor or improper mounting on the spindle also contributed to higher surface roughness value of 0.66Ra during turning at 0.2mm/rev. Traces of white layer was observed when viewed with optical microscope which shows evidence of cutting effects on the turned work material at feed rate of 0.2 rev/min

A Combined Model of Charging of the Surface and Bulk of a Dielectric Target by Electrons with the Energies 10-30 keV

NASA Astrophysics Data System (ADS)

Zykov, V. M.; Neiman, D. A.

2018-04-01

A physico-mathematical model of the processes of radiation-induced charging of dielectric materials with open surfaces, irradiated with monoenergetic electrons in the energy range 10-30 keV, is described. The model takes into account the relationship between the processes of surface and bulk charging for the given conditions of the experimental design, which accounts for the effect of anomalously long charging of dielectrics after the incident energy of primary electrons during charging is reduced to below the second critical energy for the secondary electronic emission coefficient. The initial fast phase of charging a high-resistivity dielectric material (Al2O3) is investigated. It is shown that as the incident electron energy is approaching the second critical energy during charging, the secondary electronic emission is partially suppressed due to negative charging of the open surface of the dielectric and formation of a near-surface inversion electrical field retarding the electronic emission yield.

Evaluation of cellular glasses for solar mirror panel applications

NASA Technical Reports Server (NTRS)

Giovan, M.; Adams, M.

1979-01-01

An analytic technique was developed to compare the structural and environmental performance of various materials considered for backing of second surface glass solar mirrors. Cellular glass was determined to be a prime candidate due to its low cost, high stiffness-to-weight ratio, thermal expansion match to mirror glass, evident minimal environmental impact and chemical and dimensional stability under conditions of use. The current state of the art and anticipated developments in cellular glass technology are discussed; material properties are correlated to design requirements. A mathematical model is presented which suggests a design approach which allows minimization of life cost; and, a mechanical and environmental testing program is outlined, designed to provide a material property basis for development of cellular glass hardware, together with methodology for collecting lifetime predictive data. Preliminary material property data from measurements are given. Microstructure of several cellular materials is shown, and sensitivity of cellular glass to freeze-thaw degradation and to slow crack growth is discussed. The effect of surface coating is addressed.

X-ray photoelectron and mass spectroscopic study of electron irradiation and thermal stability of polytetrafluoroethylene

NASA Technical Reports Server (NTRS)

Wheeler, Donald R.; Pepper, Stephen V.

1990-01-01

Polytetrafluoroethylene (PTFE) was subjected to 3 keV electron bombardment and then heated in vacuum to 300 C. The behavior of the material as a function of radiation dose and temperature was studied by X-ray photoelectron spectroscopy (XPS) of the surface and mass spectroscopy of the species evolved. A quantitative comparison of the radiation dose rate with that in other reported studies showed that, for a given total dose, the damage observed by XPS is greater for higher dose rates. Lightly damaged material heated to 300 C evolved saturated fluorocarbon species, whereas unsaturated fluorocarbon species evolved from heavily damaged material. After heating the heavily damaged material, those features in the XPS that were associated with damage diminished, giving the appearance that the radiation damage annealed. The apparent annealing of the radiation damage was found to be due to the covering of the network by saturated fragments that easily diffused through the decomposed material to the surface region upon heating.

Properties of the "Orgamax" osteoplastic material made of a demineralized allograft bone

NASA Astrophysics Data System (ADS)

Podorognaya, V. T.; Kirilova, I. A.; Sharkeev, Yu. P.; Uvarkin, P. V.; Zhelezny, P. A.; Zheleznaya, A. P.; Akimova, S. E.; Novoselov, V. P.; Tupikova, L. N.

2016-08-01

We investigated properties of the "Orgamax" osteoplastic material, which was produced from a demineralized bone, in the treatment of extensive caries, in particular chronic pulpitis of the permanent teeth with unformed roots in children. The "Orgamax" osteoplastic material consists of demineralized bone chips, a collagen additive, and antibiotics. The surface morphology of the "Orgamax" osteoplastic material is macroporous, with the maximum pore size of 250 µm, whereas the surface morphology of the major component of "Orgamax", demineralized bone chips, is microporous, with a pore size of 10-20 µm. Material "Orgamax" is used in the treatment of complicated caries, particularly chronic pulpitis of permanent teeth with unformed roots in children. "Orgamax" filling a formed cavity exhibits antimicrobial properties, eliminates inflammation in the dental pulp, and, due to its osteoconductive and osteoinductive properties, undergoes gradual resorption, stimulates regeneration, and provides replacement of the defect with newly formed tissue. The dental pulp viability is completely restored, which ensures the complete formation of tooth roots with root apex closure in the long-term period.

Ballistic Performance Model of Crater Formation in Monolithic, Porous Thermal Protection Systems

NASA Technical Reports Server (NTRS)

Miller, J. E.; Christiansen, E. L.; Deighton, K. D.

2014-01-01

Porous monolithic ablative systems insulate atmospheric reentry vehicles from reentry plasmas generated by atmospheric braking from orbital and exo-orbital velocities. Due to the necessity that these materials create a temperature gradient up to several thousand Kelvin over their thickness, it is important that these materials are near their pristine state prior to reentry. These materials may also be on exposed surfaces to space environment threats like orbital debris and meteoroids leaving a probability that these exposed surfaces will be below their prescribed values. Owing to the typical small size of impact craters in these materials, the local flow fields over these craters and the ablative process afford some margin in thermal protection designs for these locally reduced performance values. In this work, tests to develop ballistic performance models for thermal protection materials typical of those being used on Orion are discussed. A density profile as a function of depth of a typical monolithic ablator and substructure system is shown in Figure 1a.

Design of ice-free nanostructured surfaces based on repulsion of impacting water droplets.

PubMed

Mishchenko, Lidiya; Hatton, Benjamin; Bahadur, Vaibhav; Taylor, J Ashley; Krupenkin, Tom; Aizenberg, Joanna

2010-12-28

Materials that control ice accumulation are important to aircraft efficiency, highway and powerline maintenance, and building construction. Most current deicing systems include either physical or chemical removal of ice, both energy and resource-intensive. A more desirable approach would be to prevent ice formation rather than to fight its build-up. Much attention has been given recently to freezing of static water droplets resting on supercooled surfaces. Ice accretion, however, begins with the droplet/substrate collision followed by freezing. Here we focus on the behavior of dynamic droplets impacting supercooled nano- and microstructured surfaces. Detailed experimental analysis of the temperature-dependent droplet/surface interaction shows that highly ordered superhydrophobic materials can be designed to remain entirely ice-free down to ca. -25 to -30 °C, due to their ability to repel impacting water before ice nucleation occurs. Ice accumulated below these temperatures can be easily removed. Factors contributing to droplet retraction, pinning and freezing are addressed by combining classical nucleation theory with heat transfer and wetting dynamics, forming the foundation for the development of rationally designed ice-preventive materials. In particular, we emphasize the potential of hydrophobic polymeric coatings bearing closed-cell surface microstructures for their improved mechanical and pressure stability, amenability to facile replication and large-scale fabrication, and opportunities for greater tuning of their material and chemical properties.

Effect of cutting edge radius on surface roughness in diamond tool turning of transparent MgAl2O4 spinel ceramic

NASA Astrophysics Data System (ADS)

Yue, Xiaobin; Xu, Min; Du, Wenhao; Chu, Chong

2017-09-01

Transparent magnesium aluminate spinel (MgAl2O4) ceramic is one of an important optical materials. However, due to its pronounced hardness and brittleness, the optical machining of this material is very difficult. Diamond turning has advantages over the grinding process in flexibility and material removal rate. However, there is a lack of research that could support the use of diamond turning technology in the machining of MgAl2O4 spinel ceramic. Using brittle-ductile transition theory of brittle material machining, this work provides critical information that may help to realize ductile-regime turning of MgAl2O4 spinel ceramic. A characterization method of determination the cutting edge radius is introduced here. Suitable diamond tools were measured for sharpness and then chosen from a large number of candidate tools. The influence of rounded cutting edges on surface roughness of the MgAl2O4 spinel ceramic is also investigated. These results indicate that surface quality of MgAl2O4 spinel is relate to the radius of diamond tool's cutting edge, cutting speed, and feed rate. Sharp diamond tools (small radius of cutting edge) facilitated ductile-regime turning of MgAl2O4 spinel and shows great potential to reduce surface roughness and produce smoother final surface.

The Southwest Research Institute ultraviolet reflectance chamber (SwURC): a far ultraviolet reflectometer

NASA Astrophysics Data System (ADS)

Winters, Gregory S.; Retherford, Kurt D.; Davis, Michael W.; Escobedo, Stephen M.; Bassett, Eric C.; Patrick, Edward L.; Nagengast, Maggie E.; Fairbanks, Matthew H.; Miles, Paul F.; Parker, Joel W.; Gladstone, G. Randall; Slater, David C.; Stern, S. Alan

2012-10-01

We designed and assembled a highly capable UV reflectometer chamber and data acquisition system to provide bidirectional scattering data of various surfaces and materials. This chamber was initially conceived to create laboratory-based UV reflectance measurements of water frost on lunar soil/regolith simulants, to support interpretation of UV reflectance data from the Lyman Alpha Mapping Project ("LAMP") instrument on-board the NASA Lunar Reconnaissance Orbiter spacecraft. A deuterium lamp illuminates surfaces and materials at a fixed 45° incident beam angle over the 115 to 200 nm range via a monochromator, while a photomultiplier tube detector is scanned to cover emission angles -85° to +85° (with a gap from -60° to -30°, due to the detector blocking the incident beam). Liquid nitrogen cools the material/sample mount when desired. The chamber can be configured to test a wide range of samples and materials using sample trays and holders. Test surfaces to date include aluminum mirrors, water ice, reflectance standards, and frozen mixtures of water and lunar soil/regolith stimulant. Future UV measurements planned include Apollo lunar samples, meteorite samples, other ices, minerals, and optical surfaces. Since this chamber may well be able to provide useful research data for groups outside Southwest Research Institute, we plan to take requests from and collaborate with others in the UV and surface reflection research community.

Tested Demonstrations: Diffusion of Gases--Kinetic Molecular Theory of Gases.

ERIC Educational Resources Information Center

Gilbert, George L., Ed.

1984-01-01

Provided are procedures and list of materials needed to demonstrate that the pressure inside a container with a porous surface can be changed due to the rate of diffusion of low molecular weight gases. Typical results obtained are included. (JN)

Use of pre-pulse in laser spot welding of materials with high optical reflection

NASA Astrophysics Data System (ADS)

Mys, Ihor; Geiger, Manfred

2003-11-01

Laser micro welding has become a standard manufacturing technique, particularly in industry sectors, such as automotive and aerospace electronics or medical devices, where the requirements for strength, miniaturization and temperature resistance are constantly rising. So far the use of laser micro welding is limited due to the fluctuation of the quality of the welded joints, because the welding results for material with high optical reflection and thermal conductivity, such as copper and copper alloys, depend very strongly on the condition of the material surface. This paper presents investigations on the use of a laser pre-pulse in spot welding of electronic materials with Nd:YAG laser. In order to achieve reproducible joining results two strategies are followed-up. The first one utilizes a reflection-based process control for measuring the reflection during the short pre-pulse. The intensity of the reflected light is used to calculate an appropriated welding pulse power, which corresponds to the measured relative absorption. Adjustment of laser parameters according to the condition of the surface is done in real time before laser main pulse. A second possibility for the stabilization of copper welding is the employment of a short and powerful laser pre-pulse before laser main pulse. This pre-pulse affects the workpiece surface and creates more reproducible absorption conditions for the main pulse, independent from the initial situation on material surface.

Review of Recent Progress of Plasmonic Materials and Nano-Structures for Surface-Enhanced Raman Scattering

PubMed Central

Wang, Alan X.; Kong, Xianming

2015-01-01

Surface-enhanced Raman scattering (SERS) has demonstrated single-molecule sensitivity and is becoming intensively investigated due to its significant potential in chemical and biomedical applications. SERS sensing is highly dependent on the substrate, where excitation of the localized surface plasmons (LSPs) enhances the Raman scattering signals of proximate analyte molecules. This paper reviews research progress of SERS substrates based on both plasmonic materials and nano-photonic structures. We first discuss basic plasmonic materials, such as metallic nanoparticles and nano-rods prepared by conventional bottom-up chemical synthesis processes. Then, we review rationally-designed plasmonic nano-structures created by top-down approaches or fine-controlled synthesis with high-density hot-spots to provide large SERS enhancement factors (EFs). Finally, we discuss the research progress of hybrid SERS substrates through the integration of plasmonic nano-structures with other nano-photonic devices, such as photonic crystals, bio-enabled nanomaterials, guided-wave systems, micro-fluidics and graphene. PMID:26900428

LiNbO3 coating on concrete surface: a new and environmentally friendly route for artificial photosynthesis.

PubMed

Nath, Ranjit K; Zain, M F M; Kadhum, Abdul Amir H

2013-01-01

The addition of a photocatalyst to ordinary building materials such as concrete creates environmentally friendly materials by which air pollution or pollution of the surface can be diminished. The use of LiNbO3 photocatalyst in concrete material would be more beneficial since it can produce artificial photosynthesis in concrete. In these research photoassisted solid-gas phases reduction of carbon dioxide (artificial photosynthesis) was performed using a photocatalyst, LiNbO3, coated on concrete surface under illumination of UV-visible or sunlight and showed that LiNbO3 achieved high conversion of CO2 into products despite the low levels of band-gap light available. The high reaction efficiency of LiNbO3 is explained by its strong remnant polarization (70 µC/cm(2)), allowing a longer lifetime of photoinduced carriers as well as an alternative reaction pathway. Due to the ease of usage and good photocatalytic efficiency, the research work done showed its potential application in pollution prevention.

The Challenge of Peat Substitution in Organic Seedling Production: Optimization of Growing Media Formulation through Mixture Design and Response Surface Analysis

PubMed Central

Ceglie, Francesco Giovanni; Bustamante, Maria Angeles; Ben Amara, Mouna; Tittarelli, Fabio

2015-01-01

Peat replacement is an increasing demand in containerized and transplant production, due to the environmental constraints associated to peat use. However, despite the wide information concerning the use of alternative materials as substrates, it is very complex to establish the best materials and mixtures. This work evaluates the use of mixture design and surface response methodology in a peat substitution experiment using two alternative materials (green compost and palm fibre trunk waste) for transplant production of tomato (Lycopersicon esculentum Mill.); melon, (Cucumis melo L.); and lettuce (Lactuca sativa L.) in organic farming conditions. In general, the substrates showed suitable properties for their use in seedling production, showing the best plant response the mixture of 20% green compost, 39% palm fibre and 31% peat. The mixture design and applied response surface methodology has shown to be an useful approach to optimize substrate formulations in peat substitution experiments to standardize plant responses. PMID:26070163

High-performance shape-engineerable thermoelectric painting

PubMed Central

Park, Sung Hoon; Jo, Seungki; Kwon, Beomjin; Kim, Fredrick; Ban, Hyeong Woo; Lee, Ji Eun; Gu, Da Hwi; Lee, Se Hwa; Hwang, Younghun; Kim, Jin-Sang; Hyun, Dow-Bin; Lee, Sukbin; Choi, Kyoung Jin; Jo, Wook; Son, Jae Sung

2016-01-01

Output power of thermoelectric generators depends on device engineering minimizing heat loss as well as inherent material properties. However, the device engineering has been largely neglected due to the limited flat or angular shape of devices. Considering that the surface of most heat sources where these planar devices are attached is curved, a considerable amount of heat loss is inevitable. To address this issue, here, we present the shape-engineerable thermoelectric painting, geometrically compatible to surfaces of any shape. We prepared Bi2Te3-based inorganic paints using the molecular Sb2Te3 chalcogenidometalate as a sintering aid for thermoelectric particles, with ZT values of 0.67 for n-type and 1.21 for p-type painted materials that compete the bulk values. Devices directly brush-painted onto curved surfaces produced the high output power of 4.0 mW cm−2. This approach paves the way to designing materials and devices that can be easily transferred to other applications. PMID:27834369

Review of Recent Progress of Plasmonic Materials and Nano-Structures for Surface-Enhanced Raman Scattering.

PubMed

Wang, Alan X; Kong, Xianming

2015-06-01

Surface-enhanced Raman scattering (SERS) has demonstrated single-molecule sensitivity and is becoming intensively investigated due to its significant potential in chemical and biomedical applications. SERS sensing is highly dependent on the substrate, where excitation of the localized surface plasmons (LSPs) enhances the Raman scattering signals of proximate analyte molecules. This paper reviews research progress of SERS substrates based on both plasmonic materials and nano-photonic structures. We first discuss basic plasmonic materials, such as metallic nanoparticles and nano-rods prepared by conventional bottom-up chemical synthesis processes. Then, we review rationally-designed plasmonic nano-structures created by top-down approaches or fine-controlled synthesis with high-density hot-spots to provide large SERS enhancement factors (EFs). Finally, we discuss the research progress of hybrid SERS substrates through the integration of plasmonic nano-structures with other nano-photonic devices, such as photonic crystals, bio-enabled nanomaterials, guided-wave systems, micro-fluidics and graphene.

Laser-induced Self-organizing Microstructures on Steel for Joining with Polymers

NASA Astrophysics Data System (ADS)

van der Straeten, Kira; Burkhardt, Irmela; Olowinsky, Alexander; Gillner, Arnold

The combination of different materials such as thermoplastic composites and metals is an important way to improve lightweight construction. As direct connections between these materials fail due to their physical and chemical properties, other joining techniques are required. A new joining approach besides fastening and adhesive joining is a laser-based two-step process. Within the first step the metal surface is modified by laser-microstructuring. In order to enlarge the boundary surface and create undercuts, random self-organizing microstructures are generated on stainless steel substrates. In a second process step both joining partners, metal and composite, are clamped together, the steel surface is heated up with laser radiation and through heat conduction the thermoplastic matrix is melted and flows into the structures. After cooling-down a firm joint between both materials is created. The presented work shows the influence of different laser parameters on the generation of the microstructures. The joint strength is investigated through tensile shear strength tests.

Modifying the anti-wetting property of butterfly wings and water strider legs by atomic layer deposition coating: surface materials versus geometry.

PubMed

Ding, Yong; Xu, Sheng; Zhang, Yue; Wang, Aurelia C; Wang, Melissa H; Xiu, Yonghao; Wong, Ching Ping; Wang, Zhong Lin

2008-09-03

Although butterfly wings and water strider legs have an anti-wetting property, their working conditions are quite different. Water striders, for example, live in a wet environment and their legs need to support their weight and bear the high pressure during motion. In this work, we have focused on the importance of the surface geometrical structures in determining their performance. We have applied an atomic layer deposition technique to coat the surfaces of both butterfly wings and water strider legs with a uniform 30 nm thick hydrophilic Al(2)O(3) film. By keeping the surface material the same, we have studied the effect of different surface roughness/structure on their hydrophobic property. After the surface coating, the butterfly wings changed to become hydrophilic, while the water strider legs still remained super-hydrophobic. We suggest that the super-hydrophobic property of the water strider is due to the special shape of the long inclining spindly cone-shaped setae at the surface. The roughness in the surface can enhance the natural tendency to be hydrophobic or hydrophilic, while the roughness in the normal direction of the surface is favorable for forming a composite interface.

Fatigue strength degradation of metals in corrosive environments

NASA Astrophysics Data System (ADS)

Adasooriya, N. D.; Hemmingsen, T.; Pavlou, D.

2017-12-01

Structures exposed to aggressive environmental conditions are often subjected to time-dependent loss of coating and loss of material due to corrosion; this causes reduction in the cross-sectional properties of the members, increased surface roughness, surface irregularities and corrosion pits, and degradation of material strengths. These effects have been identified and simulated in different research studies. However, time and corrosive media dependent fatigue strength curves for materials have not been discussed in the design or assessment guidelines for structures. This paper attempts to review the corrosion degradation process and available approaches/models used to determine the fatigue strength of corroded materials and to interpolate corrosion deterioration data. High cycle fatigue and full range fatigue life formulae for fatigue strength of corroded materials are proposed. The above formulae depend on the endurance limit of corroded material, in addition to the stress-life fatigue curve parameters of the uncorroded material. The endurance limit of corroded material can either be determined by a limited number of tests in the very high-cycle fatigue region or predicted by an analytical approach. Comparison with experimentally measured corrosion fatigue behavior of several materials is provided and discussed.

Evaluation of Toluene Adsorption Performance of Mortar Adhesives Using Porous Carbon Material as Adsorbent.

PubMed

Wi, Seunghwan; Chang, Seong Jin; Jeong, Su-Gwang; Lee, Jongki; Kim, Taeyeon; Park, Kyung-Won; Lee, Dong Ryeol; Kim, Sumin

2017-07-26

Porous carbon materials are advantageous in adsorbing pollutants due to their wide range of specific surface areas, pore diameter, and pore volume. Among the porous carbon materials in the current study, expanded graphite, xGnP, xGnP C-300, xGnP C-500, and xGnP C-750 were prepared as adsorbent materials. Brunauer-Emmett-Teller (BET) analysis was conducted to select the adsorbent material through the analysis of the specific surface area, pore size, and pore volume of the prepared porous carbon materials. Morphological analysis using SEM was also performed. The xGnP C-500 as adsorbent material was applied to a mortar adhesive that is widely used in the installation of interior building materials. The toluene adsorption performances of the specimens were evaluated using 20 L small chamber. Furthermore, the performance of the mortar adhesive, as indicated by the shear bond strength, length change rate, and water retention rate, was analyzed according to the required test method specified in the Korean standards. It was confirmed that for the mortar adhesives prepared using the xGnP C-500 as adsorbent material, the toluene adsorption performance was excellent and satisfied the required physical properties.

Facet-Specific Ligand Interactions on Ternary AgSbS 2 Colloidal Quantum Dots

DOE PAGES

Choi, Hyekyoung; Kim, Sungwoo; Luther, Joseph M.; ...

2017-11-07

Silver dimetal chalcogenide (Ag-V-VI 2) ternary quantum dots (QDs) are emerging lead-free materials for optoelectronic devices due to their NIR band gaps, large absorption coefficients, and superior electronic properties. However, thin film-based devices of the ternary QDs still lag behind due to the lack of understanding of the surface chemistry, compared to that of lead chalcogenide QDs even with the same crystal structure. Here in this paper, the surface ligand interactions of AgSbS 2 QDs, synthesized with 1-dodecanethiol used as a stabilizer, are studied. For nonpolar (1 0 0) surfaces, it is suggested that the thiolate ligands are associated withmore » the crystal lattices, thus preventing surface oxidation by protecting sulfur after air-exposure, as confirmed through optical and surface chemical analysis. Otherwise, silver rich (1 1 1) surfaces are passivated by thiolate ligands, allowing ligand exchange processes for the conductive films. This in-depth investigation of the surface chemistry of ternary QDs will prompt the performance enhancement of their optoelectronic devices.« less

Mechanical properties of friction stir welded butt joint of steel/aluminium alloys: effect of tool geometry

NASA Astrophysics Data System (ADS)

Syafiq, W. M.; Afendi, M.; Daud, R.; Mazlee, M. N.; Majid, M. S. Abdul; Lee, Y. S.

2017-10-01

This paper described the mechanical properties from hardness testing and tensile testing of Friction Stir Welded (FSW) materials. In this project, two materials of aluminium and steel are welded using conventional milling machine and tool designed with different profile and shoulder size. During welding the temperature along the weld line is collected using thermocouples. Threaded pins was found to produce stronger joints than cylindrical pins. 20 mm diameter shoulder tool welded a slightly stronger joint than 18 mm diameter one, as well as softer nugget zone due to higher heat input. Threaded pins also contributed to higher weld temperature than cylindrical pins due to increase in pin contact surface. Generally, higher temperatures were recorded in aluminium side due to pin offset away from steel.

Development of an attached microalgal growth system for biofuel production.

PubMed

Johnson, Michael B; Wen, Zhiyou

2010-01-01

Algal biofuel production has gained a renewed interest in recent years but is still not economically feasible due to several limitations related to algal culture. The objective of this study is to explore a novel attached culture system for growing the alga Chlorella sp. as biodiesel feedstock, with dairy manure wastewater being used as growth medium. Among supporting materials tested for algal attachment, polystyrene foam led to a firm attachment, high biomass yield (25.65 g/m(2), dry basis), and high fatty acid yield (2.31 g/m(2)). The biomass attached on the supporting material surface was harvested by scraping; the residual colonies left on the surface served as inoculum for regrowth. The algae regrowth on the colony-established surface resulted in a higher biomass yield than that from the initial growth on fresh surface due to the downtime saved for initial algal attachment. The 10-day regrowth culture resulted in a high biodiesel production potential with a fatty acid methyl esters yield of 2.59 g/m(2) and a productivity of 0.26 g/m(-2) day(-1). The attached algal culture also removed 61-79% total nitrogen and 62-93% total phosphorus from dairy manure wastewater, depending on different culture conditions. The biomass harvested from the attached growth system (through scraping) had a water content of 93.75%, similar to that harvested from suspended culture system (through centrifugation). Collectively, the attached algal culture system with polystyrene foam as a supporting material demonstrated a good performance in terms of biomass yield, biodiesel production potential, ease to harvest biomass, and physical robustness for reuse.

Physicochemical characterizations of nano-palm oil fuel ash

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

Rajak, Mohd Azrul Abdul, E-mail: azrulrajak88@gmail.com; Preparatory Centre of Science and Technology, Universiti Malaysia Sabah, Jalan UMS, 88400, Kota Kinabalu, Sabah; Majid, Zaiton Abdul, E-mail: zaiton@kimia.fs.utm.my

2015-07-22

Palm Oil Fuel Ash (POFA) is known as a good supplementary cementing material due to its siliceous-rich content. The application of nanotechnology in the pozzolanic materials could invent new functions in the efficiency of physical and chemical properties of materials. Thus, the present study aims to generate nano-sized POFA and characterize the physicochemical properties of nano-palm oil fuel ash (nPOFA). The nPOFA was prepared by mechanically grinding micro POFA using a high intensity ball milling for 6 hours. The physicochemical properties of nPOFA were characterized via X-Ray Fluoresence (XRF), Scanning Emission microscopy- Energy Dispersive X-Ray (SEM-EDX), Transmission Electron Microscope (TEM)more » and X-Ray Diffraction (XRD). The particle size of nPOFA acquired from TEM analysis was in the range of 20 nm to 90 nm, while the average crystallite size calculated from XRD diffractogram was 61.5 nm. The resulting nPOFA has a BET surface area of 145.35 m{sup 2}/g, which is more than 85% increment in surface area compared to micro-sized POFA. The morphology and elemental studies showed the presence of spherical as well as irregularly shaped and fine nPOFA particles contains with high silicon content. The presence of α-quartz as the major phase of the nPOFA was identified through XRD analysis. The study concludes that nPOFA has the potential as a supplementary cementing material due to the high silica content, high surface area and the unique behaviors of nano-structured particles.« less

Flat-plate solar array project process development area, process research of non-CZ silicon material

NASA Technical Reports Server (NTRS)

Campbell, R. B.

1984-01-01

The program is designed to investigate the fabrication of solar cells on N-type base material by a simultaneous diffusion of N-type and P-type dopants to form an P(+)NN(+) structure. The results of simultaneous diffusion experiments are being compared to cells fabricated using sequential diffusion of dopants into N-base material in the same resistivity range. The process used for the fabrication of the simultaneously diffused P(+)NN(+) cells follows the standard Westinghouse baseline sequence for P-base material except that the two diffusion processes (boron and phosphorus) are replaced by a single diffusion step. All experiments are carried out on N-type dendritic web grown in the Westinghouse pre-pilot facility. The resistivities vary from 0.5 (UC OMEGA)cm to 5 (UC OMEGA)cm. The dopant sources used for both the simultaneous and sequential diffusion experiments are commercial metallorganic solutions with phosphorus or boron components. After these liquids are applied to the web surface, they are baked to form a hard glass which acts as a diffusion source at elevated temperatures. In experiments performed thus far, cells produced in sequential diffusion tests have properties essentially equal to the baseline N(+)PP(+) cells. However, the simultaneous diffusions have produced cells with much lower IV characteristics mainly due to cross-doping of the sources at the diffusion temperature. This cross-doping is due to the high vapor pressure phosphorus (applied as a metallorganic to the back surface) diffusion through the SiO2 mask and then acting as a diffusant source for the front surface.

Understanding the ballistic event : Methodology and observations relevant to ceramic armour

NASA Astrophysics Data System (ADS)

Healey, Adam

The only widely-accepted method of gauging the ballistic performance of a material is to carry out ballistic testing; due to the large volume of material required for a statistically robust test, this process is very expensive. Therefore a new test, or suite of tests, that employ widely-available and economically viable characterisation methods to screen candidate armour materials is highly desirable; in order to design such a test, more information on the armour/projectile interaction is required. This work presents the design process and results of using an adapted specimen configuration to increase the amount of information obtained from a ballistic test. By using a block of ballistic gel attached to the ceramic, the fragmentation generated during the ballistic event was captured and analysed. In parallel, quasi-static tests were carried out using ring-on-ring biaxial disc testing to investigate relationships between quasi-static and ballistic fragment fracture surfaces. Three contemporary ceramic armour materials were used to design the test and to act as a baseline; Sintox FA alumina, Hexoloy SA silicon carbide and 3M boron carbide. Attempts to analyse the post-test ballistic sample non-destructively using X-ray computed tomography (XCT) were unsuccessful due to the difference in the density of the materials and the compaction of fragments. However, the results of qualitative and quantitative fracture surface analysis using scanning electron microscopy showed similarities between the fracture surfaces of ballistic fragments at the edges of the tile and biaxial fragments; this suggests a relationship between quasi-static and ballistic fragments created away from the centre of impact, although additional research will be required to determine the reason for this. Ballistic event-induced porosity was observed and quantified on the fracture surfaces of silicon carbide samples, which decreased as distance from centre of impact increased; upon further analysis this porosity was linked to the loss of a boron-rich second phase. Investigating why these inclusions are lost and the extent of the effect of this on ballistic behaviour may have important implications for the use of multi-phase ceramic materials as armour.

Mussel-inspired functionalization of graphene for synthesizing Ag-polydopamine-graphene nanosheets as antibacterial materials

NASA Astrophysics Data System (ADS)

Zhang, Zhe; Zhang, Jing; Zhang, Bailin; Tang, Jilin

2012-12-01

Mussels have been shown to attach to virtually all types of inorganic and organic surfaces via their adhesive proteins. The adhesive proteins secreted by mussels contain high concentrations of catechol and amine functional groups, which have similar functional groups with polydopamine (PDA). Inspired by mussels, a mild and environmentally friendly method was used to synthesize Ag nanoparticles (Ag NPs) on functionalized PDA-graphene nanosheets (PDA-GNS) with uniform and high dispersion. First, a uniform layer of PDA was coated on graphene oxide (GO) by polymerizing dopamine (DA) at room temperature. During the process GO was reduced by the DA. The PDA layer on the surface of GNS can be used as a nanoscale guide to form uniform Ag NPs on the surface of PDA-GNS. The obtained Ag-PDA-GNS hybrid materials are characterized by atomic force microscopy, transmission electron microscopy, UV-vis spectroscopy, Raman spectroscopy, X-ray photo-electron spectroscopy, X-ray diffraction, and thermal gravimetric analysis. The resultant Ag-PDA-GNS hybrid materials exhibited strong antibacterial properties to both Gram-negative and Gram-positive bacteria due to the synergistic effect of GNS and Ag NPs.Mussels have been shown to attach to virtually all types of inorganic and organic surfaces via their adhesive proteins. The adhesive proteins secreted by mussels contain high concentrations of catechol and amine functional groups, which have similar functional groups with polydopamine (PDA). Inspired by mussels, a mild and environmentally friendly method was used to synthesize Ag nanoparticles (Ag NPs) on functionalized PDA-graphene nanosheets (PDA-GNS) with uniform and high dispersion. First, a uniform layer of PDA was coated on graphene oxide (GO) by polymerizing dopamine (DA) at room temperature. During the process GO was reduced by the DA. The PDA layer on the surface of GNS can be used as a nanoscale guide to form uniform Ag NPs on the surface of PDA-GNS. The obtained Ag-PDA-GNS hybrid materials are characterized by atomic force microscopy, transmission electron microscopy, UV-vis spectroscopy, Raman spectroscopy, X-ray photo-electron spectroscopy, X-ray diffraction, and thermal gravimetric analysis. The resultant Ag-PDA-GNS hybrid materials exhibited strong antibacterial properties to both Gram-negative and Gram-positive bacteria due to the synergistic effect of GNS and Ag NPs. Electronic supplementary information (ESI) available. See DOI: 10.1039/c2nr32092d

Synthesis and characterization of titanium oxide supported silica materials

NASA Astrophysics Data System (ADS)

Schrijnemakers, Koen

2002-01-01

Titania-silica materials are interesting materials for use in catalysis, both as a catalyst support as well as a catalyst itself. Titania-silica materials combine the excellent support and photocatalytic properties of titania with the high thermal and mechanical stability of silica. Moreover, the interaction of titania with silica leads to new active sites, such as acid and redox sites, that are not found on the single oxides. In this Ph.D. two recently developed deposition methods were studied and evaluated for their use to create titanium oxide supported silica materials, the Chemical Surface Coating (CSC) and the Molecular Designed Dispersion (MDD). These methods were applied to two structurally different silica supports, an amorphous silica gel and the highly ordered MCM-48. Both methods are based on the specific interaction between a titanium source and the functional groups on the silica surface. With the CSC method high amounts of titanium can be obtained. However, clustering of the titania phase is observed in most cases. The MDD method allows much lower titanium amounts to be deposited without the formation of crystallites. Only at the highest Ti loading very small crystallites are formed after calcination. MCM-48 and silica gel are both pure SiO2 materials and therefore chemically similar to each other. However, they possess a different morphology and are synthesized in a different way. As such, some authors have reported that the MCM-48 surface would be more reactive than the surface of silica gel. In our experiments however no differences could be observed that confirmed this hypothesis. In the CSC method, the same reactions were observed and similar amounts of Ti and Cl were deposited. In the case of the MDD method, no difference in the reaction mechanism was observed. However, due to the lower thermal and hydrothermal stability of the MCM-48 structure compared to silica gel, partial incorporation of Ti atoms in the pore walls of MCM-48 took place. This incorporation manifested itself in both pore size as well as unit cell size increase and had a stabilizing effect on the titanium oxide coating prepared by the CSC method. Due to the incorporation of Ti in MCM-48, the coating was more firmly bound to the surface and no clustering was observed during the calcination in contrast to the silica gel support where no incorporation has taken place.

Surface modifications induced by pulsed-laser texturing—Influence of laser impact on the surface properties

NASA Astrophysics Data System (ADS)

Costil, S.; Lamraoui, A.; Langlade, C.; Heintz, O.; Oltra, R.

2014-01-01

Laser cleaning technology provides a safe, environmentally friendly and very cost effective way to improve cleaning and surface preparation of metallic materials. Compared with efficient cleaning processes, it can avoid the disadvantages of ductile materials prepared by conventional technologies (cracks induced by sand-blasting for example) and treat only some selected areas (due to the optical fibers). By this way, laser technology could have several advantages and expand the range of thermal spraying. Moreover, new generations of lasers (fiber laser, disc laser) allow the development of new methods. Besides a significant bulk reduction, no maintenance, low operating cost, laser fibers can introduce alternative treatments. Combining a short-pulse laser with a scanner allows new applications in terms of surface preparation. By multiplying impacts using scanning laser, it is possible to shape the substrate surface to improve the coating adhesion as well as the mechanical behaviour. In addition, during the interactions of the laser beam with metallic surfaces, several modifications can be induced and particularly thermal effects. Indeed, under ambient conditions, a limited oxidation of the clean surface can occur. This phenomenon has been investigated in detail for silicon but few works have been reported concerning metallic materials. This paper aims at studying the surface modifications induced on aluminium alloy substrates after laser texturing. After morphological observations (SEM), a deeper surface analysis will be performed using XPS (X-ray photoelectron spectroscopy) measures and microhardness testing.

Drying of pulverized material with heated condensible vapor

DOEpatents

Carlson, L.W.

1984-08-16

Apparatus for drying pulverized material utilizes a high enthalpy condensable vapor such as steam for removing moisture from the individual particles of the pulverized material. The initially wet particulate material is tangentially delivered by a carrier vapor flow to an upper portion of a generally vertical cylindrical separation drum. The lateral wall of the separation drum is provided with a plurality of flow guides for directing the vapor tangentially therein in the direction of particulate material flow. Positioned concentrically within the separation drum and along the longitudinal axis thereof is a water-cooled condensation cylinder which is provided with a plurality of collection plates, or fines, on the outer lateral surface thereof. The cooled collection fines are aligned counter to the flow of the pulverized material and high enthalpy vapor mixture to maximize water vapor condensation thereon. The condensed liquid which includes moisture removed from the pulverized materials then flows downward along the outer surface of the coolant cylinder and is collected and removed. The particles travel in a shallow helix due to respective centrifugal and vertical acceleration forces applied thereto. The individual particles of the pulverized material are directed outwardly by the vortex flow where they contact the inner cylindrical surface of the separation drum and are then deposited at the bottom thereof for easy collection and removal. The pulverized material drying apparatus is particularly adapted for drying coal fines and facilitates the recovery of the pulverized coal. 2 figs.

Optical Fluorescence Microscopy for Spatially Characterizing Electron Transfer across a Solid-Liquid Interface on Heterogeneous Electrodes.

PubMed

Choudhary, Eric; Velmurugan, Jeyavel; Marr, James M; Liddle, James A; Szalai, Veronika

2016-01-01

Heterogeneous catalytic materials and electrodes are used for (electro)chemical transformations, including those important for energy storage and utilization. 1, 2 Due to the heterogeneous nature of these materials, activity measurements with sufficient spatial resolution are needed to obtain structure/activity correlations across the different surface features (exposed facets, step edges, lattice defects, grain boundaries, etc.). These measurements will help lead to an understanding of the underlying reaction mechanisms and enable engineering of more active materials. Because (electro)catalytic surfaces restructure with changing environments, 1 it is important to perform measurements in operando . Sub-diffraction fluorescence microscopy is well suited for these requirements because it can operate in solution with resolution down to a few nm. We have applied sub-diffraction fluorescence microscopy to a thin cell containing an electrocatalyst and a solution containing the redox sensitive dye p-aminophenyl fluorescein to characterize reaction at the solid-liquid interface. Our chosen dye switches between a nonfluorescent reduced state and a one-electron oxidized bright state, a process that occurs at the electrode surface. This scheme is used to investigate the activity differences on the surface of polycrystalline Pt, in particular to differentiate reactivity at grain faces and grain boundaries. Ultimately, this method will be extended to study other dye systems and electrode materials.

Osseointegration improvement by plasma electrolytic oxidation of modified titanium alloys surfaces.

PubMed

Echeverry-Rendón, Mónica; Galvis, Oscar; Quintero Giraldo, David; Pavón, Juan; López-Lacomba, José Luis; Jiménez-Piqué, Emilio; Anglada, Marc; Robledo, Sara M; Castaño, Juan G; Echeverría, Félix

2015-02-01

Titanium (Ti) is a material frequently used in orthopedic applications, due to its good mechanical properties and high corrosion resistance. However, formation of a non-adherent fibrous tissue between material and bone drastically could affect the osseointegration process and, therefore, the mechanical stability of the implant. Modifications of topography and configuration of the tissue/material interface is one of the mechanisms to improve that process by manipulating parameters such as morphology and roughness. There are different techniques that can be used to modify the titanium surface; plasma electrolytic oxidation (PEO) is one of those alternatives, which consists of obtaining porous anodic coatings by controlling parameters such as voltage, current, anodizing solution and time of the reaction. From all of the above factors, and based on previous studies that demonstrated that bone cells sense substrates features to grow new tissue, in this work commercially pure Ti (c.p Ti) and Ti6Al4V alloy samples were modified at their surface by PEO in different anodizing solutions composed of H2SO4 and H3PO4 mixtures. Treated surfaces were characterized and used as platforms to grow osteoblasts; subsequently, cell behavior parameters like adhesion, proliferation and differentiation were also studied. Although the results showed no significant differences in proliferation, differentiation and cell biological activity, overall results showed an important influence of topography of the modified surfaces compared with polished untreated surfaces. Finally, this study offers an alternative protocol to modify surfaces of Ti and their alloys in a controlled and reproducible way in which biocompatibility of the material is not compromised and osseointegration would be improved.

Peroxides and the survivability of microorganisms on the surface of Mars.

PubMed

Mancinelli, R L

1989-01-01

Results of the Viking mission seem to indicate that there is a ubiquitous layer of highly oxidizing aeolian material covering the Martian surface. This layer is thought to oxidize organic material that may settle on it, and is therefore responsible for the lack of detection of organic matter on the planet's surface by Viking. The mechanism that creates the oxidizing condition is not well understood, nor is the extent of the oxidation potential of this material. It has been suggested that the oxidizing nature of the soil is due to photochemical reactions which create hydrogen peroxide and superoxides in the surface soil. One question of importance to planetary protection regarding this material is, what is its potential for destroying terrestrial microorganisms, thus making the surface of Mars "self-sterilizing"? Using data obtained by the gas exchange experiment on Viking, and for simplicity assuming that all of the O2 released came from H2O2, the concentration range for H2O2 on the surface of Mars can be calculated to be 25-250 ppm. The microbial disinfection rate by H2O2 is concentration dependent, and is highly variable within the microbial community. Data from our laboratory indicate that certain soil bacteria survive and grow to stationary phase in 30,000 ppm H2O2. However, the total number of organisms decreases in the presence of H2O2. These results indicate that it is doubtful that the presence of H2O2 alone on Mars would make the surface "self-sterilizing".

Influence of the post-weld surface treatment on the corrosion resistance of the duplex stainless steel 1.4062

NASA Astrophysics Data System (ADS)

Rosemann, P.; Müller, C.; Baumann, O.; Modersohn, W.; Halle, T.

2017-03-01

The duplex stainless steel 1.4062 (X2CrNiN22-2) is used as alternative material to austenitic stainless steels in the construction industry. The corrosion resistance of welded seams is influenced by the base material, the weld filler material, the welding process and also by the final surface treatment. The scale layer next to the weld seam can be removed by grinding, pickling, electro-polished or blasting depending on the application and the requested corrosion resistance. Blasted surfaces are often used in industrial practice due to the easier and cheaper manufacturing process compared to pickled or electro-polished surfaces. Furthermore blasting with corundum-grain is more effective than blasting with glass-beads which also lower the process costs. In recent years, stainless steel surfaces showed an unusually high susceptibility to pitting corrosion after grinding with corundum. For this reason, it is now also questioned critically whether the corrosion resistance is influenced by the applied blasting agent. This question was specifically investigated by comparing grinded, pickled, corundum-grain- and glass-bead-blasted welding seams. Results of the SEM analyses of the blasting agents and the blasted surfaces will be presented and correlated with the different performed corrosion tests (potential measurement, KorroPad-test and pitting potential) on welding seams with different surface treatments.

Solar-Wind Protons and Heavy Ions Sputtering of Lunar Surface Materials

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

Barghouty, N.; Meyer, Fred W; Harris, Peter R

2011-01-01

Lunar surface materials are exposed to {approx}1 keV/amu solar-wind protons and heavy ions on almost continuous basis. As the lunar surface consists of mostly oxides, these materials suffer, in principle, both kinetic and potential sputtering due to the actions of the solar-wind ions. Sputtering is an important mechanism affecting the composition of both the lunar surface and its tenuous exosphere. While the contribution of kinetic sputtering to the changes in the composition of the surface layer of these oxides is well understood and modeled, the role and implications of potential sputtering remain unclear. As new potential-sputtering data from multi-charged ionsmore » impacting lunar regolith simulants are becoming available from Oak Ridge National Laboratory's MIRF, we examine the role and possible implications of potential sputtering of Lunar KREEP soil. Using a non-equilibrium model we demonstrate that solar-wind heavy ions induced sputtering is critical in establishing the timescale of the overall solar-wind sputtering process of the lunar surface. We also show that potential sputtering leads to a more pronounced and significant differentiation between depleted and enriched surface elements. We briefly discuss the impacts of enhanced sputtering on the composition of the regolith and the exosphere, as well as of solar-wind sputtering as a source of hydrogen and water on the moon.« less

Improved sensitivity of polychlorinated-biphenyl-orientated porous-ZnO surface photovoltage sensors from chemisorption-formed ZnO-CuPc composites

PubMed Central

Li, Mingtao; Meng, Guowen; Huang, Qing; Zhang, Shile

2014-01-01

We report a new mechanism for the enhancement of porous-ZnO surface photovoltage (SPV) response to polychlorinated biphenyls (PCBs, a notorious class of persistent organic pollutants as global environmental hazard) based on copper phthalocyanine (CuPc) chemisorptive bonding on porous-ZnO. A new ZnO-CuPc composite is formed on the porous-ZnO surface due to the interaction between the surface ZnO and CuPc, with its valence band (VB) energy level being higher than that of the pristine porous-ZnO. So that the efficiency of the photogenerated-electron transfer from the composite VB to the adjacent ZnO's surface states is drastically increased due to the reduced energy gap between the transition states. As a result, the sensitivity of the PCB-orientated SPV sensor is much improved by showing amplified variation of the SPV-signals perturbed by PCBs adsorbed on the ZnO-CuPc@porous-ZnO sensitive material. PMID:24594662

Sci-Sat AM: Radiation Dosimetry and Practical Therapy Solutions - 02: Dosimetric effects of gold nanoparticle surface coatings

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

Koger, Brandon; Kirkby, Charles

2016-08-15

Introduction: Gold nanoparticles (GNPs) can enhance radiation therapy within a tumour, increasing local energy deposition under irradiation, but experimental evidence suggests the enhancement is not as large as predicted by dose enhancement alone. Many studies neglect to account for surface coatings that are frequently used to optimize GNP uptake and biological distribution. This study uses Monte Carlo methods to investigate the consequences on local dose enhancement due to including these surface coatings. Methods: Using the PENELOPE Monte Carlo code system, GNP irradiation was simulated both with and without surface coatings of polyethylene glycol (PEG) of various molecular weights. Dose wasmore » scored to the gold, coating, and surrounding water, and the dosimetric differences between these scenarios were examined. Results: The simulated PEG coating absorbs a large portion of the energy that would otherwise be deposited in the medium. The mean dose to water was reduced by up to 2.5, 3.5, and 4.5% for GNPs of diameters 50, 20, and 10 nm, respectively. This effect was more pronounced for smaller GNPs, thicker coatings, and low photon source energies where the enhancement due to GNPs is the greatest. The molecular weight of the coating material did not have a significant impact on the dose. Conclusions: The inclusion of a coating material in GNP enhanced radiation may reduce the dose enhancement due to the nanoparticles. Both the composition and size of the coating play a role in the level of this reduction and should be considered carefully.« less

LiFePO4 Nanostructures Fabricated from Iron(III) Phosphate (FePO4 x 2H2O) by Hydrothermal Method.

PubMed

Saji, Viswanathan S; Song, Hyun-Kon

2015-01-01

Electrode materials having nanometer scale dimensions are expected to have property enhancements due to enhanced surface area and mass/charge transport kinetics. This is particularly relevant to intrinsically low electronically conductive materials such as lithium iron phosphate (LiFePO4), which is of recent research interest as a high performance intercalation electrode material for Li-ion batteries. Many of the reported works on LiFePO4 synthesis are unattractive either due to the high cost of raw materials or due to the complex synthesis technique. In this direction, synthesis of LiFePO4 directly from inexpensive FePO4 shows promise.The present study reports LiFePO4 nanostructures prepared from iron (III) phosphate (FePO4 x 2H2O) by precipitation-hydrothermal method. The sintered powder was characterized by X-ray diffractometry (XRD), X-ray photoelectron spectroscopy (XPS), Inductive coupled plasma-optical emission spectroscopy (ICP-OES), and Electron microscopy (SEM and TEM). Two synthesis methods, viz. bulk synthesis and anodized aluminum oxide (AAO) template-assisted synthesis are reported. By bulk synthesis, micro-sized particles having peculiar surface nanostructuring were formed at precipitation pH of 6.0 to 7.5 whereas typical nanosized LiFePO4 resulted at pH ≥ 8.0. An in-situ precipitation strategy inside the pores of AAO utilizing the spin coating was utilized for the AAO-template-assisted synthesis. The template with pores filled with the precipitate was subsequently subjected to hydrothermal process and high temperature sintering to fabricate compact rod-like structures.

PHOTONICS AND NANOTECHNOLOGY Laser generation of nanostructures on the surface and in the bulk of solids

NASA Astrophysics Data System (ADS)

Bityurin, N. M.

2010-12-01

This paper considers nanostructuring of solid surfaces by nano-optical techniques, primarily by laser particle nanolithography. Threshold processes are examined that can be used for laser structuring of solid surfaces, with particular attention to laser swelling of materials. Fundamental spatial resolution issues in three-dimensional (3D) laser nanostructuring are analysed with application to laser nanopolymerisation and 3D optical information recording. The formation of nanostructures in the bulk of solids due to their structural instability under irradiation is exemplified by photoinduced formation of nanocomposites.

New Technologies for Repairing Aging Cables in Nuclear Power Plants: M3LW-14OR0404015 Cable Rejuvenation Report

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

Simmons, Kevin L.; Fifield, Leonard S.; Westman, Matthew P.

The goal of this project is to conceptually demonstrate techniques to repair cables that have degraded through subjection to long-term thermal and radiation exposure in nuclear power plants. In fiscal year 2014 (FY14) we focused on commercially available ethylene-propylene rubber (EPR) as the relevant test material, isolated a high surface area form of the EPR material to facilitate chemical treatment screening and charaterization, and measured chemical changes in the material due to aging and treatment using Fourier Transfrom Infrared (FTIR) spectroscopy.

Thermal and visible studies of Mars using the Termoskan data set

NASA Astrophysics Data System (ADS)

Betts, Bruce Harold

1994-01-01

In 1989, the Soviet Phobos '88 Termoskan instrument acquired the highest spatial resolution thermal data ever for Mars, (300 m to 3 km per pixel), and simultaneous broad band visible data. The panoramas cover a large portion of the equatorial region from 30 deg S to 6 deg N. This thesis presents new and unique analyses facilitated by Termoskan and describes the instrument, data, and validation. Ejecta blankets distinct in the thermal infrared (EDITHs), a newly recognized type of feature, show a strong dependence upon Hesperian aged terrains. I postulate that most of the observed EDITHs are due to excavation of thermally distinctive Noachian age material from beneath a relatively thin layer of younger, more consolidated Hesperian volcanic material. EDITHs are excellent targets for future landers and orbiters because of relatively dust free surface exposures of material excavated from depth. Most observed channels have higher inertias than their surroundings. Channel inertia lower bounds range from 8.4 to 12.5 (10-3 cal/sq cm s-1/2/K. Channel floor inertia enhancements are strongly associated with channels showing fretted morphologies such as wide, flat floors. Fretting may have emplaced more blocks on channel floors or caused increased bonding of fines due to increased availability of water. The coupling to morphology of EDITH and channel inertias is unlike most Martian inertia variations. Termoskan observed fine thermal structure at the limit of its spatial resolution, implying there cannot be global scale dust blanketing deeper than about one centimeter. Morning limb brightening in the thermal channel is likely due to a water ice or dust hare that is warmer than the surface at the time of the observations. In the visible channel, scattering is significant to 70 km and localized high altitude stratospheric clouds are observed. Termoskan obtained the first ever thermal images of Phobos' shadow on the surface of Mars. I used the observed cooling to calculate thermal inertias in the upper mm of the Martian surface. Most of the derived inertias on the flanks of Arsia Mons fall within the range 0.9 to 1.4, corresponding to 5 to 10 micron dust particles for a homogeneous surface.

Multifunctional clickable and protein-repellent magnetic silica nanoparticles

NASA Astrophysics Data System (ADS)

Estupiñán, Diego; Bannwarth, Markus B.; Mylon, Steven E.; Landfester, Katharina; Muñoz-Espí, Rafael; Crespy, Daniel

2016-01-01

Silica nanoparticles are versatile materials whose physicochemical surface properties can be precisely adjusted. Because it is possible to combine several functionalities in a single carrier, silica-based materials are excellent candidates for biomedical applications. However, the functionality of the nanoparticles can get lost upon exposure to biological media due to uncontrolled biomolecule adsorption. Therefore, it is important to develop strategies that reduce non-specific protein-particle interactions without losing the introduced surface functionality. Herein, organosilane chemistry is employed to produce magnetic silica nanoparticles bearing differing amounts of amino and alkene functional groups on their surface as orthogonally addressable chemical functionalities. Simultaneously, a short-chain zwitterion is added to decrease the non-specific adsorption of biomolecules on the nanoparticles surface. The multifunctional particles display reduced protein adsorption after incubation in undiluted fetal bovine serum as well as in single protein solutions (serum albumin and lysozyme). Besides, the particles retain their capacity to selectively react with biomolecules. Thus, they can be covalently bio-functionalized with an antibody by means of orthogonal click reactions. These features make the described multifunctional silica nanoparticles a promising system for the study of surface interactions with biomolecules, targeting, and bio-sensing.Silica nanoparticles are versatile materials whose physicochemical surface properties can be precisely adjusted. Because it is possible to combine several functionalities in a single carrier, silica-based materials are excellent candidates for biomedical applications. However, the functionality of the nanoparticles can get lost upon exposure to biological media due to uncontrolled biomolecule adsorption. Therefore, it is important to develop strategies that reduce non-specific protein-particle interactions without losing the introduced surface functionality. Herein, organosilane chemistry is employed to produce magnetic silica nanoparticles bearing differing amounts of amino and alkene functional groups on their surface as orthogonally addressable chemical functionalities. Simultaneously, a short-chain zwitterion is added to decrease the non-specific adsorption of biomolecules on the nanoparticles surface. The multifunctional particles display reduced protein adsorption after incubation in undiluted fetal bovine serum as well as in single protein solutions (serum albumin and lysozyme). Besides, the particles retain their capacity to selectively react with biomolecules. Thus, they can be covalently bio-functionalized with an antibody by means of orthogonal click reactions. These features make the described multifunctional silica nanoparticles a promising system for the study of surface interactions with biomolecules, targeting, and bio-sensing. Electronic supplementary information (ESI) available: Detailed synthetic procedures and additional experimental light scattering and zeta-potential data. See DOI: 10.1039/c5nr08258g

First principles study of surface stability and segregation of PdRuRh ternary metal alloy system

NASA Astrophysics Data System (ADS)

Aspera, Susan Meñez; Arevalo, Ryan Lacdao; Nakanishi, Hiroshi; Kasai, Hideaki

2018-05-01

The recognized importance on the studies of alloyed materials is due to the high possibility of forming designer materials that caters to different applications. In any reaction and application, the stability and configuration of the alloy combination are important. In this study, we analyzed the surface stability and segregation of ternary metal alloy system PdRuRh through first principles calculation using density functional theory (DFT). We considered the possibility of forming phases as observed in the binary combinations of elements, i.e., completely miscible, and separating phases. With that, the model we analyzed for the ternary metal alloy slabs considers forming complete atomic miscibility, segregation of each component, and segregation of one component with mixing of the two other. Our results show that for the ternary combination of Pd, Rh and Ru, the Pd atoms have high tendency to segregate at the surface, while due to the high tendency of Ru and Rh to mix, core formation of a mixed RuRh is possible. Also, we determined that the trend of stability in the binary alloy system is a good determinant of stability in the ternary alloy system.

Van der Waals epitaxy and photoresponse of hexagonal tellurium nanoplates on flexible mica sheets.

PubMed

Wang, Qisheng; Safdar, Muhammad; Xu, Kai; Mirza, Misbah; Wang, Zhenxing; He, Jun

2014-07-22

Van der Waals epitaxy (vdWE) is of great interest due to its extensive applications in the synthesis of ultrathin two-dimensional (2D) layered materials. However, vdWE of nonlayered functional materials is still not very well documented. Here, although tellurium has a strong tendency to grow into one-dimensional nanoarchitecture due to its chain-like structure, we successfully realize 2D hexagonal tellurium nanoplates on flexible mica sheets via vdWE. Chemically inert mica surface is found to be crucial for the lateral growth of hexagonal tellurium nanoplates since it (1) facilitates the migration of tellurium adatoms along mica surface and (2) allows a large lattice mismatch. Furthermore, 2D tellurium hexagonal nanoplates-based photodetectors are in situ fabricated on flexible mica sheets. Efficient photoresponse is obtained even after bending the device for 100 times, indicating 2D tellurium hexagonal nanoplates-based photodetectors on mica sheets have a great application potential in flexible and wearable optoelectronic devices. We believe the fundamental understanding of vdWE effect on the growth of 2D tellurium hexagonal nanoplate can pave the way toward leveraging vdWE as a useful channel to realize the 2D geometry of other nonlayered materials.

Solvent evaporation induced graphene powder with high volumetric capacitance and outstanding rate capability for supercapacitors

NASA Astrophysics Data System (ADS)

Zhang, Xiaozhe; Raj, Devaraj Vasanth; Zhou, Xufeng; Liu, Zhaoping

2018-04-01

Graphene-based electrode materials for supercapacitors usually suffer from poor volumetric performance due to the low density. The enhancement of volumetric capacitance by densification of graphene materials, however, is usually accompanied by deterioration of rate capability, as the huge contraction of pore size hinders rapid diffusion of electrolytes. Thus, it is important to develop suitable pore size in graphene materials, which can sustain fast ion diffusion and avoid excessive voids to acquire high density simultaneously for supercapacitor applications. Accordingly, we propose a simple solvent evaporation method to control the pore size of graphene powders by adjusting the surface tension of solvents. Ethanol is used instead of water to reduce the shrinkage degree of graphene powder during solvent evaporation process, due to its lower surface tension comparing with water. Followed by the assistance of mechanical compression, graphene powder having high compaction density of 1.30 g cm-3 and a large proportion of mesopores in the pore size range of 2-30 nm is obtained, which delivers high volumetric capacitance of 162 F cm-3 and exhibits outstanding rate performance of 76% capacity retention at a high current density of 100 A g-1 simultaneously.

Review of Anti-Icing/Ice Release Systems

DTIC Science & Technology

2014-01-29

be superhydrophobic and tend to be fragile, Figure 3. Note if the water completely wets the surface then the adhesion energy can be much higher due...to the increase in surface area. γSV γLV γSL θ 3 Figure 3: Water drops on a superhydrophobic coating [11]. Freezing of a drop... Superhydrophobic coatings. • Other: Phase change materials that change shape/volume may reduce the adhesive strength of the ice-coating bond. 4

Development of Silicon-Coated Superparamagnetic Iron Oxide Nanoparticles for Targeted Molecular Imaging and Hyperthermic Therapy of Prostate Cancer

DTIC Science & Technology

2016-07-01

their biocompatibility, biodegradability , and simple surface chemistry that is amenable to drug loading and targeting20. Because of this, they are... Biodegradable luminescent porous silicon nanoparticles for in vivo applications. Nature Materials 8, 331–336 (2009). 21. Yen, Y.-F., Nagasawa, K...ideally suited as biomedical imaging agents, due to their biocompatibility, biodegradability , and simple surface chemistry that is amenable to drug

Heterogenous Material Integration and Band Engineering With Type II Superlattice

DTIC Science & Technology

2015-10-26

tunneling or surface effects. A careful variable area diode study is needed to investigate the effect of surfaces in this low temperature regime. In the mid...theoretically predicted advantages of T2SL over bulk MCT detectors, including lower tunneling currents [1] and suppressed Auger recombination rates [2...The tunneling currents are also reduced due to significant reduction in field drop. Thus the device can be made diffusion limited over wide range of

The Influence of Marine Microfouling on the Corrosion Behaviour of Passive Materials and Copper Alloys

DTIC Science & Technology

2008-01-02

to organometallic catalysis, acidification of the electrode surface, the combined effects of elevated H20 2 and decreased pH and the production of...Ennoblement in marine waters has been ascribed to depolarization of the oxygen reduction reaction due to organometallic catalysis, acidification of the...organometallic catalysis, acidification of the electrode surface, the combined effects of elevated hydrogen peroxide (H202) and decreased pH and the production

Anomalous Faraday effect of a system with extraordinary optical transmittance.

PubMed

Khanikaev, Alexander B; Baryshev, Alexander V; Fedyanin, Andrey A; Granovsky, Alexander B; Inoue, Mitsuteru

2007-05-28

It is shown theoretically that the Faraday rotation becomes anomalously large and exhibits extraordinary behavior near the frequencies of the extraordinary optical transmittance through optically thick perforated metal film with holes filled with a magneto-optically active material. This phenomenon is explained as result of strong confinement of the evanescent electromagnetic field within magnetic material, which occurs due to excitation of the coupled plasmon-polaritons on the opposite surfaces of the film.

Changes In Mechanical Properties Of Heat Resisting Alloy For A Satellite Propulsion System After A Nitriding Process

NASA Astrophysics Data System (ADS)

Kagawa, Hideshi; Fujii, Go; Kajiwara, Kenichi; Kuroda, Daisuke; Suzuki, Takuya; Yamabe-Mitarai, Yoko; Murakami, Hideyuki; Ono, Yoshinori

2012-07-01

Haynes25 (L-605) is a common heat resistant alloy used in mono-propellant structures and screen materials for catalyst beds. The lifetime requirements for thrusters have expanded dramatically after studies conducted in the 1970s on mono-propellant materials used to extend the service life. The material design had long remained unchanged, and the L-605 was still used as thruster material due to its good heritage. However, some important incidents involving degradation were found during the test-unit break-up inspection following the thruster life tests. The Japanese research team focused on the L-605 degradations found on the catalyst bed screen mesh used for mono-propellant thruster and analysed the surface of the wire material and the cross- section of the wire screen mesh used in the life tests. The investigation showed that the degradation was caused by nitriding L-605 component elements. The team suggested that the brittle fracture was attributable to tungsten (W) carbides, which formed primarily in the grain boundaries, and chromium (Cr) nitride, which formed mainly in the parts in contact with the hot firing gas. The team also suggested the installation of a platinum coating on the material surface as a countermeasure L-605 nitric degradation. Inconel 625 is now selected as a mono-propellant structure material due to its marginal raw material characters and cost. The team believes that Inconel 625 does not form W carbides since it contains no tungsten component, but does contain Cr and Fe, which form nitrides easily. Therefore, the team agreed that for the Inconel 625, there was a need to evaluate changes in the microstructure and mechanical properties following exposure to hot nitrogen gases. This paper will describe these changes of Inconel 625.

Irreversible Capacities of Graphite in Low Temperature Electrolytes for Lithium-Ion Batteries

NASA Technical Reports Server (NTRS)

Ratnakumar, B.; Smart, M.; Surampudi, S.; Wang, Y.; Zhang, X.; Greenbaum, S.; Hightower, A.; Ahn, C.; Fultz, B.

1999-01-01

Carbonaceous anode materials in lithium ion rechargeable cells experience irreversible capacity, mainly due to a consumption of lithium in the formation of surface passive films. The stability and kinetics of lithium intercalation into the carbon anodes are dictated by these films.

Laboratory study of SO2 dry deposition on limestone and marble: Effects of humidity and surface variables

USGS Publications Warehouse

Spiker, E. C.; Hosker, R.P.; Weintraub, V.C.; Sherwood, S.I.

1995-01-01

The dry deposition of gaseous air pollutants on stone and other materials is influenced by atmospheric processes and the chemical characteristics of the deposited gas species and of the specific receptor material. Previous studies have shown that relative humidity, surface moisture, and acid buffering capability of the receptor surface are very important factors. To better quantify this behavior, a special recirculating wind tunnel/environmental chamber was constructed, in which wind speed, turbulence, air temperature, relative humidity, and concentrations of several pollutants (SO2, O3, nitrogen oxides) can be held constant. An airfoil sample holder holds up to eight stone samples (3.8 cm in diameter and 1 cm thick) in nearly identical exposure conditions. SO2 deposition on limestone was found to increase exponentially with increasing relative humidity (RH). Marble behaves similarly, but with a much lower deposition rate. Trends indicate there is little deposition below 20% RH on clean limestone and below 60% RH on clean marble. This large difference is due to the limestone's greater porosity, surface roughness, and effective surface area. These results indicate surface variables generally limit SO2 deposition below about 70% RH on limestone and below at least 95% RH on marble. Aerodynamic variables generally limit deposition at higher relative humidity or when the surface is wet.The dry deposition of gaseous air pollutants on stone and other materials is influenced by atmospheric processes and the chemical characteristics of the deposited gas species and of the specific receptor material. Previous studies have shown that relative humidity, surface moisture, and acid buffering capability of the receptor surface are very important factors. To better quantify this behavior, a special recirculating wind tunnel/environmental chamber was constructed, in which wind speed, turbulence, air temperature, relative humidity, and concentrations of several pollutants (SO2, O3, nitrogen oxides) can be held constant. An airfoil sample holder holds up to eight stone samples (3.8 cm in diameter and 1 cm thick) in nearly identical exposure conditions. SO2 deposition on limestone was found to increase exponentially with increasing relative humidity (RH). Marble behaves similarly, but with a much lower deposition rate. Trends indicate there is little deposition below 20% RH on clean limestone and below 60% RH on clean marble. This large difference is due to the limestone's greater porosity, surface roughness, and effective surface area. These results indicate surface variables generally limit SO2 deposition below about 70% RH on limestone and below at least 95% RH on marble. Aerodynamic variables generally limit deposition at higher relative humidity or when the surface is wet.

How accelerated biological aging can affect solar reflective polymeric based building materials

NASA Astrophysics Data System (ADS)

Ferrari, C.; Santunione, G.; Libbra, A.; Muscio, A.; Sgarbi, E.

2017-11-01

Among the main issues concerning building materials, in particular outdoor ones, one can identify the colonization by microorganisms referred to as biological aggression. This can affect not only the aesthetical aspect but also the thermal performance of solar reflective materials. In order to improve the reliability of tests aimed to assess the resistance to biological aggression and contextually reduce the test duration, an accelerated test method has been developed. It is based on a lab reproducible setup where specific and controlled environmental and boundary conditions are imposed to accelerate as much as possible biological growth on building materials. Due to their widespread use, polymeric materials have been selected for the present analysis, in the aim of reaching an advanced bio-aged level in a relatively short time (8 weeks or less) and at the same time comparatively evaluate different materials under a given set of ageing conditions. Surface properties before, during and after ageing have been investigated by surface, microstructural and chemical analyses, as well as by examination of time progressive images to assess bacterial and algal growth rate.

Effects of Hydrocarbon-Based Grease on Rapid Prototype Material Used for Grease Retention Shrouds

NASA Technical Reports Server (NTRS)

Zakrajsek, Andrew J.; Valco, Daniel J.; Street, Kenneth W., Jr.

2010-01-01

Effects of hydrocarbon-based greases on specific rapid prototype (RP) materials used to fabricate grease retention shrouds (GRS) were explored in this study. Grease retention shrouds are being considered as a way to maintain adequate grease lubrication at the gear mesh in a prototype research transmission system. Due to their design and manufacturing flexibility, rapid prototype materials were chosen for the grease retention shrouds. In order to gain a better understanding of the short and long term effects grease pose on RP materials, research was conducted on the interaction of hydrocarbon-based grease with RP materials. The materials used in this study were durable polyamide (nylon), acrylonitrile butadiene styrene (ABS), and WaterClear 10120. Testing was conducted using Mobilgrease 28 and Syn-Tech 3913G grease (gear coupling grease). These greases were selected due to their regular use with mechanical components. To investigate the effect that grease has on RP materials, the following methods were used to obtain qualitative and quantitative data: Fourier transform infrared spectroscopy (FT-IR), interference profilometer measurements, digital camera imaging, physical shape measurement, and visual observations. To record the changes in the RP materials due to contact with the grease, data was taken before and after the grease application. Results showed that the WaterClear 10120 RP material provided the best resistance to grease penetration as compared to nylon and ABS RP materials. The manufacturing process, and thus resulting surface conditions of the RP material, played a key role in the grease penetration properties and resilience of these materials.

Efficiency of Cs-free materials for negative ion production in H2 and D2 plasmas

NASA Astrophysics Data System (ADS)

Friedl, R.; Kurutz, U.; Fantz, U.

2017-08-01

High power negative ion sources use caesium to reduce the work function of the converter surface which significantly increases the negative ion yield. Caesium, however, is a very reactive alkali-metal and shows complex redistribution dynamics in consequence of plasma-surface-interaction. Thus, maintaining a stable and homogenous low work function surface is a demanding task, which is not easily compatible with the RAMI issues (reliability, availability, maintainability, inspectability) for a future DEMO fusion reactor. Hence, Cs-free alternative materials for efficient negative ion formation are desirable. At the laboratory experiment HOMER materials which are referred to as promising are investigated under identical and ion source relevant parameters: the refractory metals Ta and W, non-doped and boron-doped diamond as well as materials with inherent low work function (lanthanum-doped molybdenum, MoLa and lanthanum hexaboride, LaB6). The results are compared to the effect of in-situ caesiation, which at HOMER leads to a maximal increase of the negative ion density by a factor of 2.5. Among the examined samples low work function materials are most efficient. In particular, MoLa leads to an increase of almost 50 % compared to pure volume formation. The difference to a caesiated surface can be attributed to the still higher work function of MoLa, which is expected to be slightly below 3 eV. Using deuterium instead of hydrogen leads to increased atomic and positive ion densities, while comparable negative ion densities are achieved. In contrast to the low work function materials, bulk samples of the refractory metals as well as carbon based materials have no enhancing effect on H-, where the latter materials furthermore show severe erosion due to the hydrogen plasma.

Persistent free radicals in carbon-based materials on transformation of refractory organic contaminants (ROCs) in water: A critical review.

PubMed

Qin, Yaxin; Li, Guiying; Gao, Yanpeng; Zhang, Lizhi; Ok, Yong Sik; An, Taicheng

2018-06-15

With the increased concentrations and kinds of refractory organic contaminants (ROCs) in aquatic environments, many previous reviews systematically summarized the applications of carbon-based materials in the adsorption and catalytic degradation of ROCs for their economically viable and environmentally friendly behavior. Interestingly, recent studies indicated that carbon-based materials in natural environment can also mediate the transformation of ROCs directly or indirectly due to their abundant persistent free radicals (PFRs). Understanding the formation mechanisms of PFRs in carbo-based materials and their interactions with ROCs is essential to develop their further applications in environment remediation. However, there is no comprehensive review so far about the direct and indirect removal of ROCs mediated by PFRs in amorphous, porous and crystalline carbon-based materials. The review aims to evaluate the formation mechanisms of PFRs in carbon-based materials synthesized through pyrolysis and hydrothermal carbonization processes. The influence of synthesis conditions (temperature and time) and carbon sources on the types as well as the concentrations of PFRs in carbon-based materials are also discussed. In particular, the effects of metals on the concentrations and types of PFRs in carbon-based materials are highlighted because they are considered as the catalysts for the formation of PFRs. The formation mechanisms of reactive species and the further transformation mechanisms of ROCs are briefly summarized, and the surface properties of carbon-based materials including surface area, types and number of functional groups, etc. are found to be the key parameters controlling their activities. However, due to diversity and complexity of carbon-based materials, the exact relationships between the activities of carbon-based materials and PFRs are still uncertain. Finally, the existing problems and current challenges for the ROCs transformation with carbon-based materials are also pointed out. Copyright © 2018 Elsevier Ltd. All rights reserved.

A Review: Fundamental Aspects of Silicate Mesoporous Materials

PubMed Central

ALOthman, Zeid A.

2012-01-01

Silicate mesoporous materials have received widespread interest because of their potential applications as supports for catalysis, separation, selective adsorption, novel functional materials, and use as hosts to confine guest molecules, due to their extremely high surface areas combined with large and uniform pore sizes. Over time a constant demand has developed for larger pores with well-defined pore structures. Silicate materials, with well-defined pore sizes of about 2.0–10.0 nm, surpass the pore-size constraint (<2.0 nm) of microporous zeolites. They also possess extremely high surface areas (>700 m2 g−1) and narrow pore size distributions. Instead of using small organic molecules as templating compounds, as in the case of zeolites, long chain surfactant molecules were employed as the structure-directing agent during the synthesis of these highly ordered materials. The structure, composition, and pore size of these materials can be tailored during synthesis by variation of the reactant stoichiometry, the nature of the surfactant molecule, the auxiliary chemicals, the reaction conditions, or by post-synthesis functionalization techniques. This review focuses mainly on a concise overview of silicate mesoporous materials together with their applications. Perusal of the review will enable researchers to obtain succinct information about microporous and mesoporous materials.

Ultrasound beam transmission using a discretely orthogonal Gaussian aperture basis

NASA Astrophysics Data System (ADS)

Roberts, R. A.

2018-04-01

Work is reported on development of a computational model for ultrasound beam transmission at an arbitrary geometry transmission interface for generally anisotropic materials. The work addresses problems encountered when the fundamental assumptions of ray theory do not hold, thereby introducing errors into ray-theory-based transmission models. Specifically, problems occur when the asymptotic integral analysis underlying ray theory encounters multiple stationary phase points in close proximity, due to focusing caused by concavity on either the entry surface or a material slowness surface. The approach presented here projects integrands over both the transducer aperture and the entry surface beam footprint onto a Gaussian-derived basis set, thereby distributing the integral over a summation of second-order phase integrals which are amenable to single stationary phase point analysis. Significantly, convergence is assured provided a sufficiently fine distribution of basis functions is used.

Polyethylenimine-impregnated mesoporous silica: effect of amine loading and surface alkyl chains on CO2 adsorption.

PubMed

Heydari-Gorji, Aliakbar; Belmabkhout, Youssef; Sayari, Abdelhamid

2011-10-18

Poly(ethyleneimine) (PEI) supported on pore-expanded MCM-41 whose surface is covered with a layer of long-alkyl chains was found to be a more efficient CO(2) adsorbent than PEI supported on the corresponding calcined silica and all PEI-impregnated materials reported in the literature. The layer of surface alkyl chains plays an important role in enhancing the dispersion of PEI, thus decreasing the diffusion resistance. It was also found that at low temperature, adsorbents with relatively low PEI contents are more efficient than their highly loaded counterparts because of the increased adsorption rate. Extensive CO(2) adsorption-desorption cycling showed that the use of humidified feed and purge gases affords materials with enhanced stability, despite limited loss due to amine evaporation. © 2011 American Chemical Society

Dirac cone and pseudogapped density of states in the topological half-Heusler compound YPtBi

NASA Astrophysics Data System (ADS)

Kronenberg, A.; Braun, J.; Minár, J.; Elmers, H.-J.; Kutnyakhov, D.; Zaporozhchenko, A. V.; Wallauer, R.; Chernov, S.; Medjanik, K.; Schönhense, G.; Kläui, M.; Chadov, S.; Ebert, H.; Jourdan, M.

2016-10-01

Topological insulators (TIs) are exciting materials, which exhibit unprecedented properties, such as helical spin-momentum locking, which leads to large torques for magnetic switching and highly efficient spin current detection. Here we explore the compound YPtBi, an example from the class of half-Heusler materials, for which the typical band inversion of topological insulators was predicted. We prepared this material as thin films by conventional cosputtering from elementary targets. By in situ time-of-flight momentum microscopy, a Dirac conelike surface state with a Dirac point ≃300 meV below the Fermi energy was observed, in agreement with electronic structure-photoemission calculations. Only little additional spectral weight due to other states was observed at EF, which corroborates the identification of the topologically protected surface state and is highly relevant for spintronics applications.

Few layered vanadyl phosphate nano sheets-MWCNT hybrid as an electrode material for supercapacitor application

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

Dutta, Shibsankar; De, Sukanta, E-mail: sukanta.physics@presiuniv.ac.in

It have been already seen that 2-dimensional nano materials are the suitable choice for the supercapacitor application due to their large specific surface area, electrochemical active sites, micromechanical flexibility, expedite ion migration channel properties. Free standing hybrid films of functionalized MWCNT (– COOH group) and α-Vanadyl phosphates (VOPO{sub 4}2H{sub 2}O) are prepared by vacuum filtering. The surface morphology and microstructure of the samples are studied by transmission electron microscope, field emission scanning electron microscope, XRD, Electrochemical properties of hybrid films have been investigated systematically in 1M Na{sub 2}SO{sub 4} aqueous electrolyte. The hybrid material exhibits a high specific capacitance 236more » F/g with high energy density of 65.6 Wh/Kg and a power density of 1476 W/Kg.« less

Galvanostatic interruption of lithium insertion into magnetite: Evidence of surface layer formation

DOE PAGES

Nicholas W. Brady; Takeuchi, Esther S.; Knehr, K. W.; ...

2016-04-24

Magnetite is a known lithium intercalation material, and the loss of active, nanocrystalline magnetite can be inferred from the open-circuit potential relaxation. Specifically, for current interruption after relatively small amounts of lithium insertion, the potential first increases and then decreases, and the decrease is hypothesized to be due to a formation of a surface layer, which increases the solid-state lithium concentration in the remaining active material. Comparisons of simulation to experiment suggest that the reactions with the electrolyte result in the formation of a thin layer of electrochemically inactive material, which is best described by a nucleation and growth mechanism.more » Simulations are consistent with experimental results observed for 6, 8 and 32-nm crystals. As a result, simulations capture the experimental differences in lithiation behavior between the first and second cycles.« less

Effect of heat treatment of wood on the morphology, surface roughness and penetration of simulated and human blood.

PubMed

Rekola, J; Lassila, L V J; Nganga, S; Ylä-Soininmäki, A; Fleming, G J P; Grenman, R; Aho, A J; Vallittu, P K

2014-01-01

Wood has been used as a model material for the development of novel fiber-reinforced composite bone substitute biomaterials. In previous studies heat treatment of wood was perceived to significantly increase the osteoconductivity of implanted wood material. The objective of this study was to examine some of the changing attributes of wood materials that may contribute to improved biological responses gained with heat treatment. Untreated and 140°C and 200°C heat-treated downy birch (Betula pubescens Ehrh.) were used as the wood materials. Surface roughness and the effect of pre-measurement grinding were measured with contact and non-contact profilometry. Liquid interaction was assessed with a dipping test using two manufactured liquids (simulated blood) as well as human blood. SEM was used to visualize possible heat treatment-induced changes in the hierarchical structure of wood. The surface roughness was observed to significantly decrease with heat treatment. Grinding methods had more influence on the surface contour and roughness than heat treatment. The penetration of the human blood in the 200°C heat-treated exceeded that in the untreated and 140°C heat-treated materials. SEM showed no significant change due to heat treatment in the dry-state morphology of the wood. The results of the liquid penetration test support previous findings in literature concerning the effects of heat treatment on the biological response to implanted wood. Heat-treatment has only a marginal effect on the surface contour of wood. The highly specialized liquid conveyance system of wood may serve as a biomimetic model for the further development of tailored fiber-composite materials.

Ion beam figuring of silicon aspheres

NASA Astrophysics Data System (ADS)

Demmler, Marcel; Zeuner, Michael; Luca, Alfonz; Dunger, Thoralf; Rost, Dirk; Kiontke, Sven; Krüger, Marcus

2011-03-01

Silicon lenses are widely used for infrared applications. Especially for portable devices the size and weight of the optical system are very important factors. The use of aspherical silicon lenses instead of spherical silicon lenses results in a significant reduction of weight and size. The manufacture of silicon lenses is more challenging than the manufacture of standard glass lenses. Typically conventional methods like diamond turning, grinding and polishing are used. However, due to the high hardness of silicon, diamond turning is very difficult and requires a lot of experience. To achieve surfaces of a high quality a polishing step is mandatory within the manufacturing process. Nevertheless, the required surface form accuracy cannot be achieved through the use of conventional polishing methods because of the unpredictable behavior of the polishing tools, which leads to an unstable removal rate. To overcome these disadvantages a method called Ion Beam Figuring can be used to manufacture silicon lenses with high surface form accuracies. The general advantage of the Ion Beam Figuring technology is a contactless polishing process without any aging effects of the tool. Due to this an excellent stability of the removal rate without any mechanical surface damage is achieved. The related physical process - called sputtering - can be applied to any material and is therefore also applicable to materials of high hardness like Silicon (SiC, WC). The process is realized through the commercially available ion beam figuring system IonScan 3D. During the process, the substrate is moved in front of a focused broad ion beam. The local milling rate is controlled via a modulated velocity profile, which is calculated specifically for each surface topology in order to mill the material at the associated positions to the target geometry. The authors will present aspherical silicon lenses with very high surface form accuracies compared to conventionally manufactured lenses.

Composition of bands in Argadnel Regio, Europa: Implications for Volcanic Resurfacing.

NASA Astrophysics Data System (ADS)

Prockter, L. M.; Shirley, J. H.; Dalton, J. B.; Kamp, L. W.

2012-04-01

Bands on Europa are dark or grey features which formed as a result of the pulling apart of cracks in Europa's surface, allowing new cryovolcanic material to be emplaced into the newly formed gaps. Bands have been shown to be sites of extensive resurfacing, and appear to have brightened over time, although the exact cause is not known. Thus the relative albedo of a band can be used as a proxy for age, as has been observed on Europa's surface, where the darkest bands crosscut, and are therefore younger than, lighter, or "grey" bands. We here combine Galileo Near-Infrared Mapping Spectrometer (NIMS) and Solid State Imager (SSI) data, using the methods of Shirley et al., [2010], to determine the surface compositions and water ice grain sizes of dark and grey bands in Europa's anti-Jovian Argadnel Regio, and to understand their relative histories. Preliminary results show that the total amount of hydrated salts modeled in the grey bands tends to be less than that seen in the dark bands (from ~19 to ~38% and ~38 to 47% respectively). One dark band contains hydrated sulfuric acid which is >5% lower than that of the surrounding ridged plains, as well as only 9% water ice of small grain size. These observations are interpreted as evidence that this band has been less processed by radiolysis, and so is relatively young or has been recently resurfaced. Relatively larger ice grain sizes are observed in the grey bands, as might be expected if they are older than the dark bands, and all the bands contain less large-grained ice than the surrounding ridged plains, thought to be the oldest unit on Europa's surface. We also find a wedge-shaped band that exhibits a different composition across its northern part, and appears to have undergone resurfacing as the result of the formation of a large, shallow trough that cuts diagonally across the band. We speculate that this resurfacing could be due to processes such as (1) the removal of frost due to surface shaking during the tectonic event, resulting in lower albedo material being revealed; (2) the emplacement of fine-grained plume or similar material due to a cryovolcanic eruption on the wedge floor; or (3) because the fault forming the southwestern wall of the depression intersected a near-surface briny reservoir, such as has been suggested to exist on Europa, enabling low-albedo material to be emplaced onto the floor of the depression, thereby darkening the wedge and modifying its surface composition. Reference: [1] Shirley J.H. et al. (2010) Icarus, 210, 358-384.

United Kingdom Infrared Telescope's Spectrograph Observations of Human-Made Space Objects

NASA Technical Reports Server (NTRS)

Buckalew, Brent; Abercromby, Kira; Lederer, Susan; Cowardin, Heather; Frith, James

2017-01-01

Presented here are the results of the United Kingdom Infrared Telescope (UKIRT) spectral observations of human-made space objects taken from 2014 to 2015. The data collected using the UKIRT 1-5 micron Imager Spectrometer (UIST) cover the wavelength range 0.7-2.5 micrometers. Overall, data were collected on 18 different orbiting objects at or near geosynchronous orbit (GEO). Two of the objects are controlled spacecraft, twelve are non-controlled spacecraft, one is a rocket body, and three are cataloged as debris. The remotely collected data are compared to the laboratory-collected reflectance data on typical spacecraft materials; thereby general materials are identified but not specific types. These results highlight the usefulness of observations in the infrared by focusing on features from hydrocarbons and silicon. The spacecraft, both the controlled and non-controlled, show distinct features due to the presence of solar panels whereas the rocket bodies do not. Signature variations between rocket bodies, due to the presence of various metals and paints on their surfaces, show a clear distinction from those objects with solar panels, demonstrating that one can distinguish most spacecraft from rocket bodies through infrared spectrum analysis. Finally, the debris pieces tend to show featureless, dark spectra. These results show that the laboratory data in its current state give well-correlated indications as to the nature of the surface materials on the objects. Further telescopic data collection and model updates to include noise, surface roughness, and material degradation are necessary to make better assessments of orbital object material types. A comparison conducted between objects observed previously with the NASA Infrared Telescope Facility (IRTF) shows similar materials and trends from the two telescopes and different times. However, based on the current state of the model, infrared spectroscopic data are adequate to classify objects in GEO as spacecraft, rocket bodies, or debris.

Quantum Corrections in Nanoplasmonics: Shape, Scale, and Material

NASA Astrophysics Data System (ADS)

Christensen, Thomas; Yan, Wei; Jauho, Antti-Pekka; Soljačić, Marin; Mortensen, N. Asger

2017-04-01

The classical treatment of plasmonics is insufficient at the nanometer-scale due to quantum mechanical surface phenomena. Here, an extension of the classical paradigm is reported which rigorously remedies this deficiency through the incorporation of first-principles surface response functions—the Feibelman d parameters—in general geometries. Several analytical results for the leading-order plasmonic quantum corrections are obtained in a first-principles setting; particularly, a clear separation of the roles of shape, scale, and material is established. The utility of the formalism is illustrated by the derivation of a modified sum rule for complementary structures, a rigorous reformulation of Kreibig's phenomenological damping prescription, and an account of the small-scale resonance shifting of simple and noble metal nanostructures.

A nuclear method to measure spallation by thermal cycling of protective surface layers

NASA Astrophysics Data System (ADS)

Stroosnijder, M. F.; Macchi, G.

1995-05-01

After a general introduction on spallation by thermal cycling, the principle of Thin Layer Activation (TLA) is outlined. A practical setup to measure spallation of protective surface layers by thermal cycling using TLA is discussed. Its use is illustrated with the study of the spallation behaviour of an advanced thermal barrier coating. It is shown that among the various benefits, TLA has a direct relation to material loss and shows a significant increase in sensitivity over other test methods. Due to its intrinsic properties, TLA can contribute to a greater scientific understanding of material degradation by thermal cycling and it can provide a more reliable assessment of the service lives of technical components.

Effect of mechanical properties on erosion resistance of ductile materials

NASA Astrophysics Data System (ADS)

Levin, Boris Feliksovih

Solid particle erosion (SPE) resistance of ductile Fe, Ni, and Co-based alloys as well as commercially pure Ni and Cu was studied. A model for SPE behavior of ductile materials is presented. The model incorporates the mechanical properties of the materials at the deformation conditions associated with SPE process, as well as the evolution of these properties during the erosion induced deformation. An erosion parameter was formulated based on consideration of the energy loss during erosion, and incorporates the material's hardness and toughness at high strain rates. The erosion model predicts that materials combining high hardness and toughness can exhibit good erosion resistance. To measure mechanical properties of materials, high strain rate compression tests using Hopkinson bar technique were conducted at strain rates similar to those during erosion. From these tests, failure strength and strain during erosion were estimated and used to calculate toughness of the materials. The proposed erosion parameter shows good correlation with experimentally measured erosion rates for all tested materials. To analyze subsurface deformation during erosion, microhardness and nanoindentation tests were performed on the cross-sections of the eroded materials and the size of the plastically deformed zone and the increase in materials hardness due to erosion were determined. A nanoindentation method was developed to estimate the restitution coefficient within plastically deformed regions of the eroded samples which provides a measure of the rebounding ability of a material during particle impact. An increase in hardness near the eroded surface led to an increase in restitution coefficient. Also, the stress rates imposed below the eroded surface were comparable to those measured during high strain-rate compression tests (10sp3-10sp4 ssp{-1}). A new parameter, "area under the microhardness curve" was developed that represents the ability of a material to absorb impact energy. By incorporating this parameter into a new erosion model, good correlation was observed with experimentally measured erosion rates. An increase in area under the microhardness curve led to an increase in erosion resistance. It was shown that an increase in hardness below the eroded surface occurs mainly due to the strain-rate hardening effect. Strain-rate sensitivities of tested materials were estimated from the nanoindentation tests and showed a decrease with an increase in materials hardness. Also, materials combining high hardness and strain-rate sensitivity may offer good erosion resistance. A methodology is presented to determine the proper mechanical properties to incorporate into the erosion parameter based on the physical model of the erosion mechanism in ductile materials.

Effect of professional dental prophylaxis on the surface gloss and roughness of CAD/CAM restorative materials

PubMed Central

Sugiyama, Toshiko; Enokuchi, Tomoka; Haruyama, Akiko; Chiba, Aoi; Sugiyama, Setsuko; Hosaka, Makoto; Takahashi, Toshiyuki

2017-01-01

Background This study aimed to evaluate the effect of dental prophylaxis on the surface gloss and roughness of different indirect restorative materials for computer-aided design/computer-aided manufacturing (CAD/CAM): two types of CAD/CAM composite resin blocks (Shofu Block HC and Estelite Block) and two types of CAD/CAM ceramic blocks (IPS Empress CAD and Celtra DUO). Material and Methods After polishing the CAD/CAM blocks and applying prophylaxis pastes, professional dental prophylaxis was performed using four different experimental protocols (n = 5 each): mechanical cleaning with Merssage Regular for 10 s four times (Group 1); four cycles of mechanical cleaning with Merssage Regular for 10 s and Merssage Fine for 10 s (Group 2); four cycles of mechanical cleaning with Merssage Regular for 10 s and Merssage Fine for 30 s (Group 3); and mechanical cleaning with Merssage Fine for 10 s four times (Group 4). A glossmeter was used to measure surface gloss before and after mechanical cleaning, and a contact stylus profilometer was used to measure surface roughness (Ra). Results Polishing with prophylactic paste led to a significant reduction in surface gloss and increase in surface roughness among resin composite blocks, whereas the polishing-related change in surface gloss or roughness was smaller in Celtra DUO, a zirconia-reinforced lithium silicate block. Conclusions Changes in surface gloss and roughness due to polishing with a prophylactic paste containing large particles were not improved by subsequent polishing with a prophylactic paste containing fine particles. Key words:CAD/CAM, professional dental prophylaxis, prophylactic paste, surface gloss, surface roughness. PMID:28638554

Functionalization of graphene for efficient energy conversion and storage.

PubMed

Dai, Liming

2013-01-15

As global energy consumption accelerates at an alarming rate, the development of clean and renewable energy conversion and storage systems has become more important than ever. Although the efficiency of energy conversion and storage devices depends on a variety of factors, their overall performance strongly relies on the structure and properties of the component materials. Nanotechnology has opened up new frontiers in materials science and engineering to meet this challenge by creating new materials, particularly carbon nanomaterials, for efficient energy conversion and storage. As a building block for carbon materials of all other dimensionalities (such as 0D buckyball, 1D nanotube, 3D graphite), the two-dimensional (2D) single atomic carbon sheet of graphene has emerged as an attractive candidate for energy applications due to its unique structure and properties. Like other materials, however, a graphene-based material that possesses desirable bulk properties rarely features the surface characteristics required for certain specific applications. Therefore, surface functionalization is essential, and researchers have devised various covalent and noncovalent chemistries for making graphene materials with the bulk and surface properties needed for efficient energy conversion and storage. In this Account, I summarize some of our new ideas and strategies for the controlled functionalization of graphene for the development of efficient energy conversion and storage devices, such as solar cells, fuel cells, supercapacitors, and batteries. The dangling bonds at the edge of graphene can be used for the covalent attachment of various chemical moieties while the graphene basal plane can be modified via either covalent or noncovalent functionalization. The asymmetric functionalization of the two opposite surfaces of individual graphene sheets with different moieties can lead to the self-assembly of graphene sheets into hierarchically structured materials. Judicious application of these site-selective reactions to graphene sheets has opened up a rich field of graphene-based energy materials with enhanced performance in energy conversion and storage. These results reveal the versatility of surface functionalization for making sophisticated graphene materials for energy applications. Even though many covalent and noncovalent functionalization methods have already been reported, vast opportunities remain for developing novel graphene materials for highly efficient energy conversion and storage systems.

Creation of wettability contrast patterns on metallic surfaces via pen drawn masks

NASA Astrophysics Data System (ADS)

Choi, Won Tae; Yang, Xiaolong; Breedveld, Victor; Hess, Dennis W.

2017-12-01

Micropatterned surfaces with wettability contrast have attracted considerable attention due to potential applications in 2D microfluidics, bioassays, and water harvesting. A simple method to develop wettability contrast patterns on metallic surfaces by using a commercial marker is described. A marker-drawn ink pattern on a copper surface displays chemical resistance to an aqueous solution of sodium bicarbonate and ammonium persulfate, thereby enabling selective nanowire growth in areas where ink is absent. Subsequent ink removal by an organic solvent followed by fluorocarbon film deposition yields a stable hydrophobic/super-hydrophobic patterned copper surface. Using this approach, hydrophobic dot and line patterns were constructed. The adhesion force of water droplets to the dots was controlled by adjusting pattern size, thus enabling controlled droplet transfer between two surfaces. Anisotropy of water droplet adhesion to line patterns can serve as a basis for directional control of water droplet motion. This general approach has also been employed to generate wettability contrast on aluminum surfaces, thereby demonstrating versatility. Due to its simplicity, low cost, and virtual independence of solid surface material, ink marker pens can be employed to create wettability patterns for a variety of applications, in fields as diverse as biomedicine and energy.

Effect of Intermolecular Distance on Surface-Plasmon-Assisted Catalysis.

PubMed

Wu, Shiwei; Liu, Yu; Ma, Caiqing; Wang, Jing; Zhang, Yao; Song, Peng; Xia, Lixin

2018-06-26

4-Aminothiophenol (PATP) and 4-aminophenyl disulfide (APDS) in contact with silver will form H 2 N-C 6 H 4 -S-Ag (PATP-Ag), and under the conditions of surface-enhanced Raman spectroscopy (SERS), a coupling reaction will generate 4,4-dimercaptoazobenzene (DMAB). DMAB is strongly Raman-active, showing strong peaks at ν ≈ 1140, 1390, and 1432 cm -1 , and is widely used in surface-plasmon-assisted catalysis. Using APDS, PATP, p-nitrothiophenol (PNTP), and p-nitrodiphenyl disulfide (NPDS) as probe molecules, Raman spectroscopy and imaging techniques have been used to study the effect of intermolecular distance on surface-plasmon-assisted catalysis. Theoretically, PATP-Ag formed from APDS will be bound at proximal Ag atoms on the Ag surface due to S-S bond cleavage. The results show that APDS is more prone to surface-plasmon-assisted catalytic coupling due to the smaller distance between surface PATP-Ag moieties than those derived from PATP. Therefore, APDS has a higher reaction efficiency, better Raman activity, and better Raman imaging than does PATP. Analogous experiments with PNTP and NPDS gave similar results. Thus, this technique has great application prospects in the fields of surface chemistry and materials chemistry.

Computational design of surfaces, nanostructures and optoelectronic materials

NASA Astrophysics Data System (ADS)

Choudhary, Kamal

Properties of engineering materials are generally influenced by defects such as point defects (vacancies, interstitials, substitutional defects), line defects (dislocations), planar defects (grain boundaries, free surfaces/nanostructures, interfaces, stacking faults) and volume defects (voids). Classical physics based molecular dynamics and quantum physics based density functional theory can be useful in designing materials with controlled defect properties. In this thesis, empirical potential based molecular dynamics was used to study the surface modification of polymers due to energetic polyatomic ion, thermodynamics and mechanics of metal-ceramic interfaces and nanostructures, while density functional theory was used to screen substituents in optoelectronic materials. Firstly, polyatomic ion-beams were deposited on polymer surfaces and the resulting chemical modifications of the surface were examined. In particular, S, SC and SH were deposited on amorphous polystyrene (PS), and C2H, CH3, and C3H5 were deposited on amorphous poly (methyl methacrylate) (PMMA) using molecular dynamics simulations with classical reactive empirical many-body (REBO) potentials. The objective of this work was to elucidate the mechanisms by which the polymer surface modification took place. The results of the work could be used in tailoring the incident energy and/or constituents of ion beam for obtaining a particular chemistry inside the polymer surface. Secondly, a new Al-O-N empirical potential was developed within the charge optimized many body (COMB) formalism. This potential was then used to examine the thermodynamic stability of interfaces and mechanical properties of nanostructures composed of aluminum, its oxide and its nitride. The potentials were tested for these materials based on surface energies, defect energies, bulk phase stability, the mechanical properties of the most stable bulk phase, its phonon properties as well as with a genetic algorithm based evolution theory of the materials to ensure that no spurious phases had a lower cohesive energy. Thirdly, lanthanide doped and co-doped Y3Al5O 12 were examined using density functional theory (DFT) with semi-local and local functional. Theoretical results were compared and validated with experimental data and new co-doped materials with high efficiency were predicted. Finally, Transition element doped CH3NH3PbI3 were studied with DFT for validation of the model with experimental data and replacement materials for toxic Pb were predicted.

Characterization of nanoporous shales with gas sorption

NASA Astrophysics Data System (ADS)

Joewondo, N.; Prasad, M.

2017-12-01

The understanding of the fluid flow in porous media requires the knowledge of the pore system involved. Fluid flow in fine grained shales falls under different regime than transport regime in conventional reservoir due to the different average pore sizes in the two materials; the average pore diameter of conventional sandstones is on the micrometer scale, while of shales can be as small as several nanometers. Mercury intrusion porosimetry is normally used to characterize the pores of conventional reservoir, however with increasingly small pores, the injection pressure required to imbibe the pores becomes infinitely large due to surface tension. Characterization of pores can be expressed by a pore size distribution (PSD) plot, which reflects distribution of pore volume or surface area with respect to pore size. For the case of nanoporous materials, the surface area, which serves as the interface between the rock matrix and fluid, becomes increasingly large and important. Physisorption of gas has been extensively studied as a method of nanoporous solid characterization (particularly for the application of catalysis, metal organic frameworks, etc). The PSD is obtained by matching the experimental result to the calculated theoretical result (using Density Functional Theory (DFT), a quantum mechanics based modelling method for molecular scale interactions). We present the challenges and experimental result of Nitrogen and CO2 gas sorption on shales with various mineralogy and the interpreted PSD obtained by DFT method. Our result shows significant surface area contributed by the nanopores of shales, hence the importance of surface area measurements for the characterization of shales.

Numerical study of surface plasmon enhanced nonlinear absorption and refraction.

PubMed

Kohlgraf-Owens, Dana C; Kik, Pieter G

2008-07-07

Maxwell Garnett effective medium theory is used to study the influence of silver nanoparticle induced field enhancement on the nonlinear response of a Kerr-type nonlinear host. We show that the composite nonlinear absorption coefficient, beta(c), can be enhanced relative to the host nonlinear absorption coefficient near the surface plasmon resonance of silver nanoparticles. This enhancement is not due to a resonant enhancement of the host nonlinear absorption, but rather due to a phase shifted enhancement of the host nonlinear refractive response. The enhancement occurs at the expense of introducing linear absorption, alpha(c), which leads to an overall reduced figure of merit beta(c)/alpha(c) for nonlinear absorption. For thin (< 1 microm) composites, the use of surface plasmons is found to result in an increased nonlinear absorption response compared to that of the host material.

Simulation of gross and net erosion of high-Z materials in the DIII-D divertor

DOE PAGES

Wampler, William R.; Ding, R.; Stangeby, P. C.; ...

2015-12-17

The three-dimensional Monte Carlo code ERO has been used to simulate dedicated DIII-D experiments in which Mo and W samples with different sizes were exposed to controlled and well-diagnosed divertor plasma conditions to measure the gross and net erosion rates. Experimentally, the net erosion rate is significantly reduced due to the high local redeposition probability of eroded high-Z materials, which according to the modelling is mainly controlled by the electric field and plasma density within the Chodura sheath. Similar redeposition ratios were obtained from ERO modelling with three different sheath models for small angles between the magnetic field and themore » material surface, mainly because of their similar mean ionization lengths. The modelled redeposition ratios are close to the measured value. Decreasing the potential drop across the sheath can suppress both gross and net erosion because sputtering yield is decreased due to lower incident energy while the redeposition ratio is not reduced owing to the higher electron density in the Chodura sheath. Taking into account material mixing in the ERO surface model, the net erosion rate of high-Z materials is shown to be strongly dependent on the carbon impurity concentration in the background plasma; higher carbon concentration can suppress net erosion. As a result, the principal experimental results such as net erosion rate and profile and redeposition ratio are well reproduced by the ERO simulations.« less

Photoconductivity in Dirac materials

NASA Astrophysics Data System (ADS)

Shao, J. M.; Yang, G. W.

2015-11-01

Two-dimensional (2D) Dirac materials including graphene and the surface of a three-dimensional (3D) topological insulator, and 3D Dirac materials including 3D Dirac semimetal and Weyl semimetal have attracted great attention due to their linear Dirac nodes and exotic properties. Here, we use the Fermi's golden rule and Boltzmann equation within the relaxation time approximation to study and compare the photoconductivity of Dirac materials under different far- or mid-infrared irradiation. Theoretical results show that the photoconductivity exhibits the anisotropic property under the polarized irradiation, but the anisotropic strength is different between 2D and 3D Dirac materials. The photoconductivity depends strongly on the relaxation time for different scattering mechanism, just like the dark conductivity.

(abstract) Effect of Electrolyte Composition on Carbon Electrode Performance

NASA Technical Reports Server (NTRS)

Huang, C-K.; Surampudi, S.; Shen, D. H.; Halpert, G.

1993-01-01

Rechargeable lithium cells containing lithium foil anodes are reported to have limited cycle life (at 100% DOD) performance and safety problems. These limitations are understood to be due to the high reactivity of elemental Li with the electrolyte and the formation of high surface area Li during cycling. To mitigate these problems, several lithium alloys and lithium intercalation compounds are being investigated as alternate lithium anode materials. Li(sub x)C has been identified as a promising lithium anode material due to its low equivalent weight, low voltage vs. Li, and improved stability towards various electrolytes. In this paper, we report the results of our studies on the electrolyte evaluation for the Li(sub x)C anode.

Development of Superhydrophobic Material SS 17-4 PH for Bracket Orthodontic Application by Metal Injection Molding

NASA Astrophysics Data System (ADS)

Supriadi, S.; Suharno, B.; Widjaya, T.; Ayuningtyas, S. T.; Baek, E. R.

2018-01-01

Dental’s plaque is a common problem that encountered during orthodontic treatment using bracket. It is caused by demineralization of enamel due to the activity of bacteria. The bacteria increase with remaining excess food which trapped in teeth and bracket. A hydrophobic surface could reduce food attachment on the bracket because of extremely low wettability properties that make it easy to clean with water. There are several methods to obtain hydrophobic surfaces, which are sol-gel, template replica and also etching. The propose of this work is to compare etching treatment and surface modification on sintered SS 17-4 PH as bracket material using CuCl2 and HCl as an etchant while stearic acid was used for surface modification. Hydrophobic surfaces were produced under various etching time i.e 15, 30, 45 and 60 seconds for CuCl2 and 40, 50, 60 and 70 minutes for HCl and also HCl concentration i.e 1,2 and 3 mol/L at room temperature. The hydrophobicity is observed using contact angle measurement while the microstructures observed by Scanning Electron Microscope. The result shows the contact angle could be achieved up to 60% higher than the as-sintered material. Hydrophobic structure has successfully fabricated using etching technique that might be applied to the orthodontic bracket.

The development of peptide-based interfacial biomaterials for generating biological functionality on the surface of bioinert materials.

PubMed

Meyers, Steven R; Khoo, Xiaojuan; Huang, Xin; Walsh, Elisabeth B; Grinstaff, Mark W; Kenan, Daniel J

2009-01-01

Biomaterials used in implants have traditionally been selected based on their mechanical properties, chemical stability, and biocompatibility. However, the durability and clinical efficacy of implantable biomedical devices remain limited in part due to the absence of appropriate biological interactions at the implant interface and the lack of integration into adjacent tissues. Herein, we describe a robust peptide-based coating technology capable of modifying the surface of existing biomaterials and medical devices through the non-covalent binding of modular biofunctional peptides. These peptides contain at least one material binding sequence and at least one biologically active sequence and thus are termed, "Interfacial Biomaterials" (IFBMs). IFBMs can simultaneously bind the biomaterial surface while endowing it with desired biological functionalities at the interface between the material and biological realms. We demonstrate the capabilities of model IFBMs to convert native polystyrene, a bioinert surface, into a bioactive surface that can support a range of cell activities. We further distinguish between simple cell attachment with insufficient integrin interactions, which in some cases can adversely impact downstream biology, versus biologically appropriate adhesion, cell spreading, and cell survival mediated by IFBMs. Moreover, we show that we can use the coating technology to create spatially resolved patterns of fluorophores and cells on substrates and that these patterns retain their borders in culture.

Persistently Auxetic Materials: Engineering the Poisson Ratio of 2D Self-Avoiding Membranes under Conditions of Non-Zero Anisotropic Strain.

PubMed

Ulissi, Zachary W; Govind Rajan, Ananth; Strano, Michael S

2016-08-23

Entropic surfaces represented by fluctuating two-dimensional (2D) membranes are predicted to have desirable mechanical properties when unstressed, including a negative Poisson's ratio ("auxetic" behavior). Herein, we present calculations of the strain-dependent Poisson ratio of self-avoiding 2D membranes demonstrating desirable auxetic properties over a range of mechanical strain. Finite-size membranes with unclamped boundary conditions have positive Poisson's ratio due to spontaneous non-zero mean curvature, which can be suppressed with an explicit bending rigidity in agreement with prior findings. Applying longitudinal strain along a singular axis to this system suppresses this mean curvature and the entropic out-of-plane fluctuations, resulting in a molecular-scale mechanism for realizing a negative Poisson's ratio above a critical strain, with values significantly more negative than the previously observed zero-strain limit for infinite sheets. We find that auxetic behavior persists over surprisingly high strains of more than 20% for the smallest surfaces, with desirable finite-size scaling producing surfaces with negative Poisson's ratio over a wide range of strains. These results promise the design of surfaces and composite materials with tunable Poisson's ratio by prestressing platelet inclusions or controlling the surface rigidity of a matrix of 2D materials.

Effects of materials surface preparation for use in spacecraft potable water storage tanks

NASA Astrophysics Data System (ADS)

Wallace, William T.; Wallace, Sarah L.; Loh, Leslie J.; Kuo, C. K. Mike; Hudson, Edgar K.; Marlar, Tyler J.; Gazda, Daniel B.

2017-12-01

Maintaining a safe supply of potable water is of utmost importance when preparing for long-duration spaceflight missions, with the minimization of microbial growth being one major aspect. While biocides, such as ionic silver, historically have been used for microbial control in spaceflight, their effectiveness is sometimes limited due to surface reactions with the materials of the storage containers that reduce their concentrations below the effective range. For the Multi-Purpose Crew Vehicle, the primary wetted materials of the water storage system are stainless steel and a titanium alloy, and ionic silver has been chosen to serve as the biocide. As an attempt to understand what processes might reduce the known losses of silver, different treatment processes were attempted and samples of the wetted materials were tested, individually and together, to determine the relative loss of biocide under representative surface area-to-volume ratios. The results of testing presented here showed that the materials could be treated by a nitric acid rinse or a high-concentration silver spike to reduce the loss of silver and bacterial growth. It was also found that the minimum biocidal concentration could be maintained for over 28 days. These results have pointed to approaches that could be used to successfully maintain silver in spacecraft water systems for long-duration missions.

Polyimide encapsulated lithium-rich cathode material for high voltage lithium-ion battery.

PubMed

Zhang, Jie; Lu, Qingwen; Fang, Jianhua; Wang, Jiulin; Yang, Jun; NuLi, Yanna

2014-10-22

Lithium-rich materials represented by xLi2MnO3·(1 - x)LiMO2 (M = Mn, Co, Ni) are attractive cathode materials for lithium-ion battery due to their high specific energy and low cost. However, some drawbacks of these materials such as poor cycle and rate capability remain to be addressed before applications. In this study, a thin polyimide (PI) layer is coated on the surface of Li1.2Ni0.13Mn0.54Co0.13O2 (LNMCO) by a polyamic acid (PAA) precursor with subsequently thermal imidization process. X-ray diffraction (XRD), scanning electron microscopy (SEM), and high-resolution transmission electron microscopy (HR-TEM) results confirm the successful formation of a PI layer (∼3 nm) on the surface of LNMCO without destruction of its main structure. X-ray photoelectron spectroscopy (XPS) spectra show a slight shift of the Mn valence state from Mn(IV) to Mn(III) in the PI-LNMCO treated at 450 °C, elucidating that charge transfer takes place between the PI layer and LNMCO surface. Electrochemical performances of LNMCO including cyclic stability and rate capability are evidently improved by coating a PI nanolayer, which effectively separates the cathode material from the electrolyte and stabilizes their interface at high voltage.

Topological surface states in nodal superconductors.

PubMed

Schnyder, Andreas P; Brydon, Philip M R

2015-06-24

Topological superconductors have become a subject of intense research due to their potential use for technical applications in device fabrication and quantum information. Besides fully gapped superconductors, unconventional superconductors with point or line nodes in their order parameter can also exhibit nontrivial topological characteristics. This article reviews recent progress in the theoretical understanding of nodal topological superconductors, with a focus on Weyl and noncentrosymmetric superconductors and their protected surface states. Using selected examples, we review the bulk topological properties of these systems, study different types of topological surface states, and examine their unusual properties. Furthermore, we survey some candidate materials for topological superconductivity and discuss different experimental signatures of topological surface states.

A molecular dynamics study on the adsorption of a mussel protein on two different films: Polymer film and a SAM

NASA Astrophysics Data System (ADS)

He, Cunxue; Zhang, Heng; Lin, Cunguo; Wang, Li; Yuan, Shiling

2017-05-01

The adhesion of marine life would produce a certain degree of corrosion effect on the hull surface. Shellfish organisms, such as barnacles and mussels, were always used to research the impediment of coating material to protein adsorption. In this work, the adsorbed behaviors of mussel protein on the PDMS and C7F16-SAM surfaces were explored by molecular dynamics (MD) simulations. Simulation results showed that protein was strongly adsorbed onto the hydrophobic surface, as reflected by the large interaction energy; while the adsorption onto the hydrophilic PDMS surface was weak due to two strongly adhered water layers.

Surface Diagnostics in Tribology Technology and Advanced Coatings Development

NASA Technical Reports Server (NTRS)

Miyoshi, Kazuhisa

1999-01-01

This paper discusses the methodologies used for surface property measurement of thin films and coatings, lubricants, and materials in the field of tribology. Surface diagnostic techniques include scanning electron microscopy, transmission electron microscopy, atomic force microscopy, stylus profilometry, x-ray diffraction, electron diffraction, Raman spectroscopy, Rutherford backscattering, elastic recoil spectroscopy, and tribology examination. Each diagnostic technique provides specific measurement results in its own unique way. In due course it should be possible to coordinate the different pieces of information provided by these diagnostic techniques into a coherent self-consistent description of the surface properties. Examples are given on the nature and character of thin diamond films.

An analysis of LDEF-exposed silvered FEP teflon thermal blanket material

NASA Technical Reports Server (NTRS)

Young, Philip R.; Slemp, Wayne S.

1991-01-01

The characterization of selected silvered fluorinated ethylene propylene (FEP) teflon thermal blanket material which received 5 years and 9 months of exposure to the LEO environment on the Long Duration Exposure Facility is reported. X-ray photoelectron spectroscopy, infrared, and thermal analyses did not detect a significant change at the molecular level as the result of this exposure. However, various microscopic analyses revealed a roughening of the coating surface due to atomic oxygen erosion which resulted in some materials changing from specular reflectors of visible radiation to diffuse reflectors. The potential effect of silicon-containing molecular contamination on these materials is addressed.

Friedel oscillation near a van Hove singularity in two-dimensional Dirac materials

NASA Astrophysics Data System (ADS)

Lu, Chi-Ken

2016-02-01

We consider Friedel oscillation in the two-dimensional Dirac materials when the Fermi level is near the van Hove singularity. Twisted graphene bilayer and the surface state of topological crystalline insulator are the representative materials which show low-energy saddle points that are feasible to probe by gating. We approximate the Fermi surface near saddle point with a hyperbola and calculate the static Lindhard response function. Employing a theorem of Lighthill, the induced charge density δ n due to an impurity is obtained and the algebraic decay of δ n is determined by the singularity of the static response function. Although a hyperbolic Fermi surface is rather different from a circular one, the static Lindhard response function in the present case shows a singularity similar with the response function associated with circular Fermi surface, which leads to the δ n\\propto {{R}-2} at large distance R. The dependences of charge density on the Fermi energy are different. Consequently, it is possible to observe in twisted graphene bilayer the evolution that δ n\\propto {{R}-3} near Dirac point changes to δ n\\propto {{R}-2} above the saddle point. Measurements using scanning tunnelling microscopy around the impurity sites could verify the prediction.

Performance of fast-setting impression materials in the reproduction of subgingival tooth surfaces without soft tissue retraction.

PubMed

Rudolph, Heike; Röhl, Andreas; Walter, Michael H; Luthardt, Ralph G; Quaas, Sebastian

2014-01-01

Fast-setting impression materials may be prone to inaccuracies due to accidental divergence from the recommended mixing protocol. This prospective randomized clinical trial aimed to assess three-dimensional (3D) deviations in the reproduction of subgingival tooth surfaces and to determine the effect of either following or purposely diverging from the recommended mixing procedure for a fast-setting addition-curing silicone (AS) and fast-setting polyether (PE). After three impressions each were taken from 96 participants, sawcut gypsum casts were fabricated with a standardized procedure and then optically digitized. Data were assessed with a computer-aided 3D analysis. For AS impressions, multivariate analysis of variance revealed a significant influence of the individual tooth and the degree to which the recommended mixing protocol was violated. For PE impressions, the ambient air temperature and individual tooth showed significant effects, while divergence from the recommended mixing protocol was not of significance. The fast-setting PE material was not affected by changes in the recommended mixing protocol. For the two fast-setting materials examined, no divergences from the recommended mixing protocol of less than 2 minutes led to failures in the reproduction of the subgingival tooth surfaces.

Conductive Polymer Binder for High-Tap-Density Nanosilicon Material for Lithium-Ion Battery Negative Electrode Application.

PubMed

Zhao, Hui; Wei, Yang; Qiao, Ruimin; Zhu, Chenhui; Zheng, Ziyan; Ling, Min; Jia, Zhe; Bai, Ying; Fu, Yanbao; Lei, Jinglei; Song, Xiangyun; Battaglia, Vincent S; Yang, Wanli; Messersmith, Phillip B; Liu, Gao

2015-12-09

High-tap-density silicon nanomaterials are highly desirable as anodes for lithium ion batteries, due to their small surface area and minimum first-cycle loss. However, this material poses formidable challenges to polymeric binder design. Binders adhere on to the small surface area to sustain the drastic volume changes during cycling; also the low porosities and small pore size resulting from this material are detrimental to lithium ion transport. This study introduces a new binder, poly(1-pyrenemethyl methacrylate-co-methacrylic acid) (PPyMAA), for a high-tap-density nanosilicon electrode cycled in a stable manner with a first cycle efficiency of 82%-a value that is further improved to 87% when combined with graphite material. Incorporating the MAA acid functionalities does not change the lowest unoccupied molecular orbital (LUMO) features or lower the adhesion performance of the PPy homopolymer. Our single-molecule force microscopy measurement of PPyMAA reveals similar adhesion strength between polymer binder and anode surface when compared with conventional polymer such as homopolyacrylic acid (PAA), while being electronically conductive. The combined conductivity and adhesion afforded by the MAA and pyrene copolymer results in good cycling performance for the high-tap-density Si electrode.

Influence of nanohydroxyapatite surface properties on Staphylococcus epidermidis biofilm formation.

PubMed

Barros, J; Grenho, L; Manuel, C M; Ferreira, C; Melo, L; Nunes, O C; Monteiro, F J; Ferraz, M P

2014-05-01

Nanohydroxyapatite (nanoHA), due to its chemical properties, has appeared as an exceptionally promising bioceramic to be used as bone regeneration material. Staphylococcus epidermidis have emerged as major nosocomial pathogens associated with infections of implanted medical devices. In this work, the purpose was to study the influence of the nanoHA surface characteristics on S. epidermidis RP62A biofilm formation. Therefore, two different initial inoculum concentrations (Ci) were used in order to check if these would affect the biofilm formed on the nanoHA surfaces. Biofilm formation was followed by the enumeration of cultivable cells and by scanning electron microscopy. Surface topography, contact angle, total surface area and porosimetry of the biomaterials were studied and correlated with the biofilm data. The surface of nanoHA sintered at 830 (nanoHA830) showed to be more resistant to S. epidermidis attachment and accumulation than that of nanoHA sintered at 1000 (nanoHA1000). The biofilm formed on nanoHA830 presented differences in terms of structure, surface coverage and EPS production when compared to the one formed on nanoHA1000 surface. It was observed that topography and surface area of nanoHA surfaces had influence on the bacterial attachment and accumulation. Ci influenced bacteria attachment and accumulation on nanoHA surfaces over time. The choice of the initial inoculum concentration was relevant proving to have an effect on the extent of adherence thus being a critical point for human health if these materials are used in implantable devices. This study showed that the initial inoculum concentration and surface material properties determine the rate of microbial attachment to substrata and consequently are related to biofilm-associated infections in biomaterials.

Is the surface oxygen exchange rate linked to bulk ion diffusivity in mixed conducting Ruddlesden–Popper phases?

DOE PAGES

Tomkiewicz, Alex C.; Tamimi, Mazin A.; Huq, Ashfia; ...

2015-03-02

There is a possible link between oxygen surface exchange rate and bulk oxygen anion diffusivity in mixed ionic and electronic conducting oxides; it is a topic of great interest and debate. While a large body of experimental evidence and theoretical analyses support a link, observed differences between bulk and surface composition of these materials are hard to reconcile with this observation. This is further compounded by potential problems with simultaneous measurement of both parameters. Here we utilize separate techniques, in situ neutron diffraction and pulsed isotopic surface exchange, to examine bulk ion mobility and surface oxygen exchange rates of threemore » Ruddlesden-Popper phases, general form A n-1A 2'BnO 3n+1, A n-1A 2'BnX 3n+1; LaSrCo 0.5Fe 0.5O 4-δ (n = 1), La 0.3Sr 2.7CoFeO 7-δ (n = 2) and LaSr 3Co 1.5Fe 1.5O 10-δ (n = 3). These measurements are complemented by surface composition determination via high sensitivity-low energy ion scattering. We observe a correlation between bulk ion mobility and surface exchange rate between materials. The surface exchange rates vary by more than one order of magnitude with high anion mobility in the bulk of an oxygen vacancy-rich n = 2 Ruddlesden-Popper material correlating with rapid oxygen exchange. Furthermore this is in contrast with the similar surface exchange rates which we may expect due to similar surface compositions across all three samples. This paper conclude that experimental limitations lead to inherent convolution of surface and bulk rates, and that surface exchange steps are not likely to be rate limiting in oxygen incorporation.« less

Magnetotransport in Dirac metals: Chiral magnetic effect and quantum oscillations

DOE PAGES

Monteiro, Gustavo M.; Abanov, Alexander G.; Kharzeev, Dmitri E.

2015-10-08

Dirac metals are characterized by the linear dispersion of fermionic quasiparticles, with the Dirac point hidden inside a Fermi surface. We study the magnetotransport in these materials using chiral kinetic theory to describe within the same framework both the negative magnetoresistance caused by the chiral magnetic effect and quantum oscillations in the magnetoresistance due to the existence of the Fermi surface. Lastly, we discuss the relevance of obtained results to recent measurements on Cd 3As 2.

Changes in surface figure due to thermal hysteresis

NASA Astrophysics Data System (ADS)

Jacobs, S. F.; Johnston, S. C.; Sasian, J. M.; Watson, M.; Targove, J. D.

1987-01-01

Thermal cycling hysteresis affects surface figure in low-expansivity mirror substrates. Zerodur, ULE, and Cer-Vit 8-in.-diameter mirrors and dilatometer samples were thermally cycled at uniform rates of 6 K/hr and 60 K/hr, and somewhat faster for nonuniform heating. Figure distortions as large as lambda/10 were observed following nonuniform heating of standard Zerodur, which was the only material exhibiting thermal hysteresis. A new experimental Zerodur appears to be free of this problem.

Surface figure changes due to thermal cycling hysteresis.

PubMed

Jacobs, S F; Johnston, S C; Sasian, J M; Watson, M; Targove, J D; Bass, D

1987-10-15

How does thermal cycling hysteresis affect surface figure in low expansivity mirror substrates? Zerodur, ULE, and Cer-Vit 20.3-cm (8-in.) diam mirrors and dilatometer samples were thermally cycled at 6 and 60 K/h with uniform and nonuniform heating. Figure distortions as large as lambda/10 were observed only with nonuniform heating of standard Zerodur, which was the only material exhibiting thermal hysteresis. A new experimental Zerodur appears to be free of this problem.

Surface characteristics, biocompatibility, and mechanical properties of nickel-titanium plasma-implanted with nitrogen at different implantation voltages.

PubMed

Liu, X M; Wu, S L; Chan, Y L; Chu, Paul K; Chung, C Y; Chu, C L; Yeung, K W K; Lu, W W; Cheung, K M C; Luk, K D K

2007-08-01

NiTi shape memory alloy is one of the promising orthopedic materials due to the unique shape memory effect and superelasticity. However, the large amount of Ni in the alloy may cause allergic reactions and toxic effects thereby limiting its applications. In this work, the surface of NiTi alloy was modified by nitrogen plasma immersion ion implantation (N-PIII) at various voltages. The materials were characterized by X-ray photoelectron spectroscopy (XPS). The topography and roughness before and after N-PIII were measured by atomic force microscope. The effects of the modified surfaces on nickel release and cytotoxicity were assessed by immersion tests and cell cultures. The XPS results reveal that near-surface Ni concentration is significantly reduced by PIII and the surface TiN layer suppresses nickel release and favors osteoblast proliferation, especially for samples implanted at higher voltages. The surfaces produced at higher voltages of 30 and 40 kV show better adhesion ability to osteoblasts compared to the unimplanted and 20 kV PIII samples. The effects of heating during PIII on the phase transformation behavior and cyclic deformation response of the materials were investigated by differential scanning calorimetry and three-point bending tests. Our results show that N-PIII conducted using the proper conditions improves the biocompatibility and mechanical properties of the NiTi alloy significantly.

Spectroscopic and Computational Investigation of Room-Temperature Decomposition of a Chemical Warfare Agent Simulant on Polycrystalline Cupric Oxide

DOE PAGES

Trotochaud, Lena; Tsyshevsky, Roman; Holdren, Scott; ...

2017-08-21

Certain organophosphorus molecules are infamous due to their use as highly toxic nerve agents. The filtration materials currently in common use for protection against chemical warfare agents were designed before organophosphorus compounds were used as chemical weapons. A better understanding of the surface chemistry between simulant molecules and the individual filtration-material components is a critical precursor to the development of more effective materials for filtration, destruction, decontamination, and/or sensing of nerve agents. Here, we report on the surface adsorption and reactions of a sarin simulant molecule, dimethyl methylphosphonate (DMMP), with cupric oxide surfaces. In situ ambient pressure X-ray photoelectron andmore » infrared spectroscopies are coupled with density functional calculations to propose mechanisms for DMMP decomposition on CuO. We find extensive room temperature decomposition of DMMP on CuO, with the majority of decomposition fragments bound to the CuO surface. We observe breaking of PO-CH3, P-OCH3, and P-CH3bonds at room temperature. On the basis of these results, we identify specific DMMP decomposition mechanisms not seen on other metal oxides. Participation of lattice oxygen in the decomposition mechanism leads to significant changes in chemical and electronic surface environment, which are manifest in the spectroscopic and computational data. This study establishes a computational baseline for the study of highly toxic organophosphorous compounds on metal oxide surfaces.« less

Spectroscopic and Computational Investigation of Room-Temperature Decomposition of a Chemical Warfare Agent Simulant on Polycrystalline Cupric Oxide

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

Trotochaud, Lena; Tsyshevsky, Roman; Holdren, Scott

Certain organophosphorus molecules are infamous due to their use as highly toxic nerve agents. The filtration materials currently in common use for protection against chemical warfare agents were designed before organophosphorus compounds were used as chemical weapons. A better understanding of the surface chemistry between simulant molecules and the individual filtration-material components is a critical precursor to the development of more effective materials for filtration, destruction, decontamination, and/or sensing of nerve agents. Here, we report on the surface adsorption and reactions of a sarin simulant molecule, dimethyl methylphosphonate (DMMP), with cupric oxide surfaces. In situ ambient pressure X-ray photoelectron andmore » infrared spectroscopies are coupled with density functional calculations to propose mechanisms for DMMP decomposition on CuO. We find extensive room temperature decomposition of DMMP on CuO, with the majority of decomposition fragments bound to the CuO surface. We observe breaking of PO-CH3, P-OCH3, and P-CH3bonds at room temperature. On the basis of these results, we identify specific DMMP decomposition mechanisms not seen on other metal oxides. Participation of lattice oxygen in the decomposition mechanism leads to significant changes in chemical and electronic surface environment, which are manifest in the spectroscopic and computational data. This study establishes a computational baseline for the study of highly toxic organophosphorous compounds on metal oxide surfaces.« less

SEM and TEM Observation of the Surfaces of the Fine-Grained Particles Retrieved from the Muses-C Regio on the Asteroid 25413 Itokawa

NASA Technical Reports Server (NTRS)

Noguchi, T.; Nakamura, T.; Zolensky, Michael E.; Tanaka, M.; Hashimoto, T.; Konno, M.; Nakato, A.; Ogami, T.; Fujimura, A.; Abe, M.;

Combination of Functional Nanoengineering and Nanosecond Laser Texturing for Design of Superhydrophobic Aluminum Alloy with Exceptional Mechanical and Chemical Properties.

PubMed

Boinovich, Ludmila B; Modin, Evgeny B; Sayfutdinova, Adeliya R; Emelyanenko, Kirill A; Vasiliev, Alexander L; Emelyanenko, Alexandre M

2017-10-24

Industrial application of metallic materials is hindered by several shortcomings, such as proneness to corrosion, erosion under abrasive loads, damage due to poor cold resistance, or weak resistance to thermal shock stresses, etc. In this study, using the aluminum-magnesium alloy as an example of widely spread metallic materials, we show that a combination of functional nanoengineering and nanosecond laser texturing with the appropriate treatment regimes can be successfully used to transform a metal into a superhydrophobic material with exceptional mechanical and chemical properties. It is demonstrated that laser chemical processing of the surface may be simultaneously used to impart multimodal roughness and to modify the composition and physicochemical properties of a thick surface layer of the substrate itself. Such integration of topographical and physicochemical modification leads to specific surface nanostructures such as nanocavities filled with hydrophobic agent and hard oxynitride nanoinclusions. The combination of superhydrophobic state, nano- and micro features of the hierarchical surface, and the appropriate composition of the surface textured layer allowed us to provide the surface with the outstanding level of resistance of superhydrophobic coatings to external chemical and mechanical impacts. In particular, experimental data presented in this study indicate high resistance of the fabricated coatings to pitting corrosion, superheated water vapor, sand abrasive wear, and rapid temperature cycling from liquid nitrogen to room temperatures, without notable degradation of superhydrophobic performance.

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

Wampler, William R.; Ding, R.; Stangeby, P. C.

The three-dimensional Monte Carlo code ERO has been used to simulate dedicated DIII-D experiments in which Mo and W samples with different sizes were exposed to controlled and well-diagnosed divertor plasma conditions to measure the gross and net erosion rates. Experimentally, the net erosion rate is significantly reduced due to the high local redeposition probability of eroded high-Z materials, which according to the modelling is mainly controlled by the electric field and plasma density within the Chodura sheath. Similar redeposition ratios were obtained from ERO modelling with three different sheath models for small angles between the magnetic field and themore » material surface, mainly because of their similar mean ionization lengths. The modelled redeposition ratios are close to the measured value. Decreasing the potential drop across the sheath can suppress both gross and net erosion because sputtering yield is decreased due to lower incident energy while the redeposition ratio is not reduced owing to the higher electron density in the Chodura sheath. Taking into account material mixing in the ERO surface model, the net erosion rate of high-Z materials is shown to be strongly dependent on the carbon impurity concentration in the background plasma; higher carbon concentration can suppress net erosion. As a result, the principal experimental results such as net erosion rate and profile and redeposition ratio are well reproduced by the ERO simulations.« less

Peculiar behavior of MWW materials in aldol condensation of furfural and acetone.

PubMed

Kikhtyanin, Oleg; Chlubná, Pavla; Jindrová, Tereza; Kubička, David

2014-07-21

MWW family of different structural types (MCM-22, MCM-49, MCM-56 and MCM-36) was used as catalysts for aldol condensation of furfural and acetone studied in a batch reactor at 100 °C, autogenous pressure and a reaction time of 0-4 h. To establish a relation between physico-chemical and catalytic properties of microporous materials, the samples were characterized by XRD, SEM, N2 adsorption, FTIR and TGA. It was found that the acidic solids possessed appreciable activity in the reaction and resulted in the formation of products of aldehyde-ketone interaction. Surprisingly, MCM-22 and MCM-49, i.e. three-dimensional materials containing internal supercages, exhibited higher activity than two MCM-36 catalysts with two-dimensional character having larger accessible external surface area due to expansion of the interlayer space by swelling and pillaring treatments. Moreover, all MWW family catalysts gave higher conversion than the large-pore zeolite BEA. Nevertheless, furfural conversion decreased rapidly for all the studied materials due to coke formation. Unexpectedly, the deactivation was found to be more severe for MCM-36 catalysts than for MCM-22 and MCM-49, which was attributed to the reaction taking place also in supercages that are protected by 10-ring channels from severe coking. In contrast the cups located on the external surface were coked rapidly.

Surface erosion and sedimentation caused by ejecta from the lunar crater Tycho

NASA Astrophysics Data System (ADS)

Shkuratov, Y.; Basilevsky, A.; Kaydash, V.; Ivanov, B.; Korokhin, V.; Videen, G.

2018-02-01

We use Kaguya MI images acquired at wavelengths 415, 750, and 950 nm to map TiO2 and FeO content and the parameter of optical maturity OMAT in lunar regions Lubiniezky E and Taurus-Littrow with a spatial resolution of 20 m using the Lucey method [Lucey et al., JGR 2000, 105. 20,297]. We show that some ejecta from large craters, such as Tycho and Copernicus may cause lunar surface erosion, transportation of the eroded material and its sedimentation. The traces of the erosion resemble wind tails observed on Earth, Mars, and Venus, although the Moon has no atmosphere. The highland material of the local topographic prominences could be mobilized by Tycho's granolometrically fine ejecta and caused by its transportation along the ejecta way to adjacent mare areas and subsequent deposition. The tails of mobilized material reveal lower abundances of Ti and Fe than the surrounding mare surface. We have concluded that high-Ti streaks also seen in the Lubiniezky E site, which show unusual combinations of the TiO2 and FeO content on the correlation diagram, could be the result of erosion by Tycho's ejecta too. In these locations, Tycho's material did not form a consolidated deposit, but resulted in erosion of the mare surface material that became intermixed, consequently, diluting the ejecta. The Taurus-Littrow did provide evidence of the mechanical effect of Tycho's ejecta on the local landforms (landslide, secondary craters) and do not show the compositional signature of Tycho's ejecta probably due to intermixing with local materials and dilution.

Platelet Surface-Associated Activation and Secretion-Mediated Inhibition of Coagulation Factor XII

PubMed Central

Zakharova, Natalia V.; Artemenko, Elena O.; Podoplelova, Nadezhda A.; Sveshnikova, Anastasia N.; Demina, Irina A.; Ataullakhanov, Fazly I.; Panteleev, Mikhail A.

2015-01-01

Coagulation factor XII (fXII) is important for arterial thrombosis, but its physiological activation mechanisms are unclear. In this study, we elucidated the role of platelets and platelet-derived material in fXII activation. FXII activation was only observed upon potent platelet stimulation (with thrombin, collagen-related peptide, or calcium ionophore, but not ADP) accompanied by phosphatidylserine exposure and was localised to the platelet surface. Platelets from three patients with grey platelet syndrome did not activate fXII, which suggests that platelet-associated fXII-activating material might be released from α-granules. FXII was preferentially bound by phosphotidylserine-positive platelets and annexin V abrogated platelet-dependent fXII activation; however, artificial phosphotidylserine/phosphatidylcholine microvesicles did not support fXII activation under the conditions herein. Confocal microscopy using DAPI as a poly-phosphate marker did not reveal poly-phosphates associated with an activated platelet surface. Experimental data for fXII activation indicates an auto-inhibition mechanism (k i/k a = 180 molecules/platelet). Unlike surface-associated fXII activation, platelet secretion inhibited activated fXII (fXIIa), particularly due to a released C1-inhibitor. Platelet surface-associated fXIIa formation triggered contact pathway-dependent clotting in recalcified plasma. Computer modelling suggests that fXIIa inactivation was greatly decreased in thrombi under high blood flow due to inhibitor washout. Combined, the surface-associated fXII activation and its inhibition in solution herein may be regarded as a flow-sensitive regulator that can shift the balance between surface-associated clotting and plasma-dependent inhibition, which may explain the role of fXII at high shear and why fXII is important for thrombosis but negligible in haemostasis. PMID:25688860

Chimeric Peptides as Implant Functionalization Agents for Titanium Alloy Implants with Antimicrobial Properties

NASA Astrophysics Data System (ADS)

Yucesoy, Deniz T.; Hnilova, Marketa; Boone, Kyle; Arnold, Paul M.; Snead, Malcolm L.; Tamerler, Candan

2015-04-01

Implant-associated infections can have severe effects on the longevity of implant devices and they also represent a major cause of implant failures. Treating these infections associated with implants by antibiotics is not always an effective strategy due to poor penetration rates of antibiotics into biofilms. Additionally, emerging antibiotic resistance poses serious concerns. There is an urge to develop effective antibacterial surfaces that prevent bacterial adhesion and proliferation. A novel class of bacterial therapeutic agents, known as antimicrobial peptides (AMPs), are receiving increasing attention as an unconventional option to treat septic infection, partly due to their capacity to stimulate innate immune responses and for the difficulty of microorganisms to develop resistance towards them. While host and bacterial cells compete in determining the ultimate fate of the implant, functionalization of implant surfaces with AMPs can shift the balance and prevent implant infections. In the present study, we developed a novel chimeric peptide to functionalize the implant material surface. The chimeric peptide simultaneously presents two functionalities, with one domain binding to a titanium alloy implant surface through a titanium-binding domain while the other domain displays an antimicrobial property. This approach gains strength through control over the bio-material interfaces, a property built upon molecular recognition and self-assembly through a titanium alloy binding domain in the chimeric peptide. The efficiency of chimeric peptide both in-solution and absorbed onto titanium alloy surface was evaluated in vitro against three common human host infectious bacteria, Streptococcus mutans, Staphylococcus epidermidis, and Escherichia coli. In biological interactions such as occur on implants, it is the surface and the interface that dictate the ultimate outcome. Controlling the implant surface by creating an interface composed chimeric peptides may therefore open up new possibilities to modify the implant site and tailor it to a desirable bioactivity.

Optimization of Electropolishing on NiTi Alloy Stents and Its Influence on Corrosion Behavior.

PubMed

Kim, Jinwoo; Park, Jun-Kyu; Kim, Han Ki; Unnithan, Afeesh Rajan; Kim, Cheol Sang; Park, Chan Hee

2017-04-01

Nitinol or NiTi alloys are well-known as an attractive biomedical material due to their unique properties such as the shape memory effect, super-elasticity and biocompatibility. These characteristics enable them to be best candidates for implant materials such as stent. One of the major factors that strongly affect the performance of nitinol stent is its unique surface properties. In this study, the influence of electropolishing on nitinol stents and its corrosion behavior were observed. Electropolishing is an effective method for surface treatment, which not only controls the surface state but also helps to produce uniform surface layers. Therefore, to improve the surface quality of nitinol stents, we conducted an electropolishing under various conditions from 30–40 V and 10–30 s as a post heat treatment for nitinol stent manufacturing process. In order to find the optimal surface state of NiTi stents, various electropolished samples were explored using various characterization techniques. Furthermore, the potentiodynamic polarization tests were also performed to determine the corrosion resistance. The electropolished nitinol stents under the condition of 40 V for 10 s exhibited the best corrosion performance as well as surface quality.

Surface modification of polymers for biocompatibility via exposure to extreme ultraviolet radiation.

PubMed

Inam Ul Ahad; Bartnik, Andrzej; Fiedorowicz, Henryk; Kostecki, Jerzy; Korczyc, Barbara; Ciach, Tomasz; Brabazon, Dermot

2014-09-01

Polymeric biomaterials are being widely used for the treatment of various traumata, diseases and defects in human beings due to ease in their synthesis. As biomaterials have direct interaction with the extracellular environment in the biological world, biocompatibility is a topic of great significance. The introduction or enhancement of biocompatibility in certain polymers is still a challenge to overcome. Polymer biocompatibility can be controlled by surface modification. Various physical and chemical methods (e.g., chemical and plasma treatment, ion implantation, and ultraviolet irradiation etc.) are in use or being developed for the modification of polymer surfaces. However an important limitation in their employment is the alteration of bulk material. Different surface and bulk properties of biomaterials are often desirable for biomedical applications. Because extreme ultraviolet (EUV) radiation penetration is quite limited even in low density mediums, it could be possible to use it for surface modification without influencing the bulk material. This article reviews the degree of biocompatibility of different polymeric biomaterials being currently employed in various biomedical applications, the surface properties required to be modified for biocompatibility control, plasma and laser ablation based surface modification techniques, and research studies indicating possible use of EUV for enhancing biocompatibility. © 2013 Wiley Periodicals, Inc.

Recent advances based on the synergetic effect of adsorption for removal of dyes from waste water using photocatalytic process.

PubMed

Natarajan, Subramanian; Bajaj, Hari C; Tayade, Rajesh J

2018-03-01

The problem of textile dye pollution has been addressed by various methods, mainly physical, chemical, biological, and acoustical. These methods mainly separate and/or remove the dye present in water. Recently, advanced oxidation processes (AOP) have been focused for removal of dye from waste water due to their advantages such as ecofriendly, economic and capable to degrade many dyes or organic pollutant present in water. Photocatalysis is one of the advance oxidation processes, mainly carried out under irradiation of light and suitable photocatalytic materials. The photocatalytic activity of the photocatalytic materials mainly depends on the band gap, surface area, and generation of electron-hole pair for degradation dyes present in water. It has been observed that the surface area plays a major role in photocatalytic degradation of dyes, by providing higher surface area, which leads to the higher adsorption of dye molecule on the surface of photocatalyst and enhances the photocatalytic activity. This present review discusses the synergic effect of adsorption of dyes on the photocatalytic efficiency of various nanostructured high surface area photocatalysts. In addition, it also provides the properties of the water polluting dyes, their mechanism and various photocatalytic materials; and their morphology used for the dye degradation under irradiation of light along with the future prospects of highly adsorptive photocatalytic material and their application in photocatalytic removal of dye from waste water. Copyright © 2017. Published by Elsevier B.V.

Ultrasonic grinding of optical materials

NASA Astrophysics Data System (ADS)

Cahill, Michael; Bechtold, Michael; Fess, Edward; Stephan, Thomas; Bechtold, Rob

2017-10-01

Hard ceramic optical materials such as sapphire, ALON, Spinel, PCA, or Silicon Carbide can present a significant challenge in manufacturing precision optical components due to their tough mechanical properties. These are also the same mechanical properties that make them desirable materials when used in harsh environments. Slow processing speeds, premature tool wear, and poor surface quality are common results of the tough mechanical properties of these materials. Often, as a preparatory stage for polishing, the finish of the ground surface greatly influences the polishing process and the resulting finished product. To overcome these challenges, OptiPro Systems has developed an ultrasonic assisted grinding technology, OptiSonic, which has been designed for the precision optics and ceramics industry. OptiSonic utilizes a custom tool holder designed to produce oscillations, in microns of amplitude, in line with the rotating spindle. A software package, IntelliSonic, is integral to the function of this platform. IntelliSonic can automatically characterize tooling during setup to identify and select the ideal resonant peak which to operate at. Then, while grinding, IntelliSonic continuously adjusts the output frequency for optimal grinding efficiency while in contact with the part. This helps maintain a highly consistent process under changing load conditions for a more precise surface. Utilizing a variety of instruments, tests have proven to show a reduction in force between tool and part by up to 50%, while increasing the surface quality and reducing tool wear. This paper will present the challenges associated with these materials and solutions created to overcome them.

Cavitation resistance of surface composition "Steel-Ni-TiNi-TiNiZr-cBNCo", formed by High-Velocity Oxygen-Fuel spraying

NASA Astrophysics Data System (ADS)

Blednova, Zh. M.; Dmitrenko, D. V.; Balaev, E. U. O.

2018-01-01

The object of the study is a multilayered surface composition "Steel - a Multicomponent material with Shape Memory Effect - a wear-resistant layer" under conditions of cavitation effects in sea water. Multicomponent TiNi-based coatings with addition of alloying elements such as Zr in an amount up to 10% mass, allow to create a composite material with a gradient of properties at the interface of layers, which gives new properties to coatings and improves their performance significantly. The use of materials with shape memory effect (SME) as surface layers or in the composition of surface layered compositions allows to provide an effective reaction of materials to the influence of external factors and adaptation to external influences. The surface composite layer cBN-10%Co has high hardness and strength, which ensures its resistance to shock cyclic influences of collapsing caverns. The increased roughness of the surface of a solid surface composite in the form of strong columnar structures ensures the crushing of vacuum voids, redistributing their effect on the entire surface, and not concentrating them in certain zones. In addition, the gradient structure of the multilayer composite coating TiNi-Ti33Ni49Zr18-cBN-10%Co Co makes it possible to create conditions for the relaxation of stresses created by the variable impact load of cavitation caverns and the manifestation of compensating internal forces due to thermo-elastic martensitic transformations of SME materials. The cavitation resistance of the coating TiNi-Ti33Ni49Zr18-cBN-10%Co according to the criterion of mass wear is 15-20 times higher than that of the base material without coating and 10-12 times higher than that of the TiNi-TiNiZr coating. The proposed architecture of the multifunctional gradient composition, "steel-Ni-TiNi- Ti33Ni49Zr18-cBN-10%Co", each layer of which has its functional purpose, allows to increase the service life of parts operating under conditions of cavitation-fatigue loading in corrosive environments.

Synthesis and Characterization of Chitosan-p-t-Butylcalix[4]arene acid

NASA Astrophysics Data System (ADS)

Handayani, D. S.; Frimadasi, W.; Kusumaningsih, T.; Pranoto

2018-03-01

The synthesis of chitosan-p-t-butylcalix[4]arene acid was done with DIC (N, N’-diisopropylcarbodiimide) as the coupling agent. The structural analysis of the chitosan-p-t-butylcalix[4]arene acid was conducted by spectrophotometer Fourier Transform Infra Red (FTIR) and X-Ray Diffraction (XRD). Meanwhile, the surface area was investigated by Surface Area Analysis, the Scanning Electrone Microscope (SEM) analysed the surface morphology, and also the melting point temperature was determined. FTIR analysis on Chitosan-p-t-butylcalix[4]arene provides an overlapped absorption of -OH and -NH groups at 3438.26 cm-1. Meanwhile, a C = C aromatic bond present at 1480.43 cm-1. XRD analysis shows some broaden peaks due to the amorphous phase of the prepared material. The prepared material is a brownish yellow solid, odorless and porous. The melting point, surface area, and the average pore radius are above 300 °C, 9.42 m2 / g, and 52.5938 Å, respectively.

Effects of surface topography on magnetization reversal of magnetic thin films.

PubMed

Girgis, E; Pogossian, S P; Benkhedar, M L

2006-04-01

The influence of the created surface roughness on the coercivity of magnetic thin films has been investigated. The magnetic thin films (CoFe and alternatively NiFe) are sputtered on top of smooth substrates that were previously covered with an array of considerably rougher lines with one of these materials Pt, Cu, CoFe, and NiFe. The lines have been patterned using optical lithography into arrays that are deposited with different thicknesses varying between 5 nm-15 nm. The lines have been designed to have a very rough edge and seated in two different angles relative to the wafer edge (zero and 45 degrees). Magneto-optic Kerr effect (MOKE) measurements showed two distinct switching fields in the hysteresis loops that are due to magnetic domain wall trapping created by the surface roughness. The magnetization reversal showed a strong dependence on the height, the orientation angle, and the material's type of the created surface roughness (the lines).

The influence of surface area, porous structure, and surface state on the supercapacitor performance of titanium oxynitride: implications for a nanostructuring strategy.

PubMed

Lee, Eun Joo; Lee, Lanlee; Abbas, Muhammad Awais; Bang, Jin Ho

2017-08-09

A recent surge of interest in metal (oxy)nitride materials for energy storage devices has given rise to the rapid development of various nanostructuring strategies for these materials. In supercapacitor applications, early transition metal (oxy)nitrides have been extensively explored, among which titanium oxynitride stands out due to its great potential for charge storage. Despite recent advances in supercapacitors based on titanium oxynitride, many underlying factors governing their capacitive performance remain elusive. In this work, nanostructured titanium oxynitride is prepared by firing an organic-inorganic hybrid precursor under a hot ammonia atmosphere, and the influence of its physical characteristics on the supercapacitor performance is investigated. New insights into the effects of surface area, porous structure, and surface state of titanium oxynitride on the supercapacitor performance are revealed through which a comprehensive understanding about the capacitive behavior of titanium oxynitride is provided. In addition, the implications of these insights for a nanostructuring strategy striving for higher capacitance and improved stability are discussed.

Effect of Ion Escape Velocity and Conversion Surface Material on H- Production

NASA Astrophysics Data System (ADS)

Tarvainen, O.; Kalvas, T.; Komppula, J.; Koivisto, H.; Geros, E.; Stelzer, J.; Rouleau, G.; Johnson, K. F.; Carmichael, J.

2011-09-01

According to generally accepted models surface production of negative ions depends on ion escape velocity and work function of the surface. We have conducted an experimental study addressing the role of the ion escape velocity on H- production. A converter-type ion source at Los Alamos Neutron Science Center was employed for the experiment. The ion escape velocity was affected by varying the bias voltage of the converter electrode. It was observed that due to enhanced stripping of H- no direct gain of extracted beam current can be achieved by increasing the converter voltage. The conversion efficiency of H- was observed to vary with converter voltage and follow the existing theories in qualitative manner. We present calculations predicting relative H- yields from different cesiated surfaces with comparison to experimental observations from different types of H- ion sources. Utilizing materials exhibiting negative electron affinity and exposed to UV-light is considered for Cesium-free H-/D- production.

Phase conjugate Twyman-Green interferometer for testing spherical surfaces and lenses and for measuring refractive indices of liquids or solid transparent materials

NASA Technical Reports Server (NTRS)

Shukla, R. P.; Dokhanian, Mostafa; Venkateswarlu, Putcha; George, M. C.

1990-01-01

The present paper describes an application of a phase conjugate Twyman-Green interferometer using barium titanate as a self-pumping mirror for testing optical components like concave and convex spherical mirrors and lenses. The aberrations introduced by the beam splitter while testing concave or convex spherical mirrors of large aperture are automatically eliminated due to self-focussing property of the phase conjugate mirror. There is no necessity for a good spherical surface as a reference surface unlike in classical Twyman-Green interferometer or Williams interferometer. The phase conjugate Twyman Green interferometer with a divergent illumination can be used as a test plate for checking spherical surfaces. A nondestructive technique for measuring the refractive indices of a Fabry Perot etalon by using a phase conjugate interferometer is also suggested. The interferometer is found to be useful for measuring the refractive indices of liquids and solid transparent materials with an accuracy of the order of + or - 0.0004.

Graphene-Like 2D Porous Carbon Nanosheets Derived from Cornstalk Pith for Energy Storage Materials

NASA Astrophysics Data System (ADS)

Gao, Kezheng; Niu, Qingyuan; Tang, Qiheng; Guo, Yaqing; Wang, Lizhen

2018-01-01

Biomass materials from different organisms or different parts (even different periods) of the same organism have different microscopic morphologies, hierarchical pore structures and even elemental compositions. Therefore, carbon materials inheriting the unique hierarchical microstructure of different biomass materials may exhibit significantly different electrochemical properties. Cornstalk pith and cornstalk skin (dried by freeze-drying) exhibit significantly different microstructures due to their different biological functions. The cornstalk skin-based carbon (S-carbon) exhibits a thick planar morphology, and the Barrett-Emmett-Teller (BET) surface area is only about 332.07 m2 g-1. However, cornstalk pith-based carbon (P-carbon) exhibits a graphene-like 2D porous nanosheet structure with a rough, wrinkled morphology, and the BET surface area is about 805.17 m2 g-1. In addition, a P-carbon supercapacitor exhibits much higher specific capacitance and much better rate capability than an S-carbon supercapacitor in 6 M potassium hydroxide (KOH) electrolyte.

Polysaccharide-derived mesoporous materials (Starbon®) for sustainable separation of complex mixtures.

PubMed

Zuin, Vânia G; Budarin, Vitaliy L; De Bruyn, Mario; Shuttleworth, Peter S; Hunt, Andrew J; Pluciennik, Camille; Borisova, Aleksandra; Dodson, Jennifer; Parker, Helen L; Clark, James H

2017-09-21

The recovery and separation of high value and low volume extractives are a considerable challenge for the commercial realisation of zero-waste biorefineries. Using solid-phase extractions (SPE) based on sustainable sorbents is a promising method to enable efficient, green and selective separation of these complex extractive mixtures. Mesoporous carbonaceous solids derived from renewable polysaccharides are ideal stationary phases due to their tuneable functionality and surface structure. In this study, the structure-separation relationships of thirteen polysaccharide-derived mesoporous materials and two modified types as sorbents for ten naturally-occurring bioactive phenolic compounds were investigated. For the first time, a comprehensive statistical analysis of the key molecular and surface properties influencing the recovery of these species was carried out. The obtained results show the possibility of developing tailored materials for purification, separation or extraction, depending on the molecular composition of the analyte. The wide versatility and application span of these polysaccharide-derived mesoporous materials offer new sustainable and inexpensive alternatives to traditional silica-based stationary phases.

Colour Changes on the Surface of the Rock Materials Due to UV-A and UV-B Rays

NASA Astrophysics Data System (ADS)

Binal, Adil; Ayderman, Aykut; Sel, Aylin

2015-04-01

The colour of the rocks used in the current buildings, and historical monuments is an important parameter in architecture and engineering. In addition, engineering geologists use the colour in order to identify the weathering class of rock material. The main colour of the stone, especially, are affected by the mineral size, the colour of the primary minerals and matrix material, as well as the colour of the accessory minerals. Due to atmospheric effects, changes in the outer surface colour of the rocks used as siding materials occur with over time. Factors causing the colour change are carbon dioxide (CO2), ozone (O3), sulphate (SO2, SO3) and nitrate (NOx) from the atmosphere with aerosols as well as UV rays from the sun. There is no more work in the literature on colour changes caused by UV-A and UV-B rays. In this study, the effects of ultraviolet in the colour of the surfaces of basalt, limestone, ignimbrite, travertine and sandstone have been simulated with a new experimental device in the laboratory medium. Lutron colour analyser (RGB-1002) was used for the measurements of RGB colours. Colour differences between the beginning and end of tests were determined with the standard practice for calculation of colour tolerances and colour differences from instrumentally measured colour coordinates (ASTM D2244). As a result of the experiments performed, lighten that seem on dark-grey micritic limestone (colour change ratio, CCR: 17.06) and basalt samples (CCR: 8.24) become even visually noticeable. Black and red ignimbrite samples having high porosity were presented the lower rate of colour changes. Finally, colour darkening has been observed in the light-coloured travertine (CCR: 13.8) and sandstone samples (CCR: 20.99).

Effect of Glucose Concentration on Electrochemical Corrosion Behavior of Pure Titanium TA2 in Hanks’ Simulated Body Fluid

PubMed Central

Liu, Shuyue; Wang, Bing; Zhang, Peirong

2016-01-01

Titanium and its alloys have been widely used as implant materials due to their excellent mechanical property and biocompatibility. In the present study, the effect of glucose concentration on corrosion behavior of pure titanium TA2 in Hanks’ simulated body fluid is investigated by the electrochemical impedance spectrum (EIS) and potentiodynamic polarization methods. The range of glucose concentrations investigated in this research includes 5 mmol/L (limosis for healthy people), 7 mmol/L (after diet for healthy people), 10 mmol/L (limosis for hyperglycemia patient), and 12 mmol/L (after diet for hyperglycemia patient), as well as, 15 mmol/L and 20 mmol/L, which represent different body fluid environments. The results indicate that the pure titanium TA2 demonstrates the best corrosion resistance when the glucose concentration is less than 10 mmol/L, which shows that the pure titanium TA2 as implant material can play an effective role in the body fluids with normal and slight high glucose concentrations. Comparatively, the corrosion for the pure titanium implant is more probable when the glucose concentration is over 10 mmol/L due to the premature penetration through passive film on the material surface. Corrosion defects of pitting and crevice exist on the corroded surface, and the depth of corrosion is limited to three microns with a low corrosion rate. The oxidation film on the surface of pure titanium TA2 has a protective effect on the corrosion behavior of the implant inner material. The corrosion behavior of pure titanium TA2 will happen easily once the passive film has been penetrated through. The corrosion rate for TA2 implant will accelerate quickly and a pure titanium implant cannot be used. PMID:28773993

Effect of organic materials used in the synthesis on the emission from CdSe quantum dots

NASA Astrophysics Data System (ADS)

Lee, Jae-Won; Yang, Ho-Soon; Hong, K. S.; Kim, S. M.

2013-12-01

Quantum-dot nanocrystals have particular optical properties due to the quantum confinement effect and the surface effect. This study focuses on the effect of surface conditions on the emission from quantum dots. The quantum dots prepared with 1-hexadecylamine (HDA) in the synthesis show strong emission while the quantum dots prepared without HDA show weak emission, as well as emission from surface energy traps. The comparison of the X-ray patterns of these two sets of quantum dots reveals that HDA forms a layer on the surface of quantum dot during the synthesis. This surface passivation with a layer of HDA reduces surface energy traps, therefore the emission from surface trap levels is suppressed in the quantum dots synthesized with HDA.

Environmental isolation task

NASA Technical Reports Server (NTRS)

Coulbert, C. D.

1982-01-01

The failure-analysis process was organized into a more specific set of long-term degradation steps so that material property change can be differentiated from module damage and module failure. Increasing module performance and life are discussed. A polymeric aging computer model is discussed. Early detection of polymer surface reactions due to aging is reported.

DETERMINATION OF SYNTHETIC MUSK COMPOUNDS IN MUNICIPAL WASTEWATER AND ESTIMATING BIOTA EXPOSURE IN THE RECEIVING WATERS

EPA Science Inventory

Synthetic musk compounds are consumer chemicals manufactured as fragrance materials and consumed in very large quantities worldwide. Due to their high usage and release, they have become ubiquitous in the environment. The U.S. EPA (Las Vegas) developed surface water monitoring me...

Use of high-volume reclaimed asphalt pavement for asphalt pavement rehabilitation due to increasing highway truck traffic from freight transportation.

DOT National Transportation Integrated Search

2012-06-01

The objective of this research was to examine the effects that different methods of RAP stockpile fractionation had on : the volumetric mix design properties for high-RAP content surface mixes. The processing of RAP materials resulted in : the degrad...

The capture of lunar materials in low lunar orbit

NASA Technical Reports Server (NTRS)

Floyd, M. A.

1981-01-01

A scenario is presented for the retrieval of lunar materials sent into lunar orbit to be used as raw materials in space manufacturing operations. The proposal is based on the launch of material from the lunar surface by an electromagnetic mass driver and the capture of this material in low lunar orbit by a fleet of mass catchers which ferry the material to processing facilities when full. Material trajectories are analyzed using the two-body equations of motion, and intercept requirements and the sensitivity of the system to launch errors are determined. The present scenario is shown to be superior to scenarios that place a single mass catcher at the L2 libration point due to increased operations flexibility, decreased mass driver performance requirements and centralized catcher servicing.

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

Kobayashi, Takehiko; Nojima, Toshio; Yamada, Kenji

A dry phantom material having the same electric properties in the UHF band as biological tissues is developed. The new composite material is composed of microwave ceramic powder, graphite powder, and bonding resin. This material overcomes the various problems inherent in the conventional jelly phantom material, such as dehydration and deterioration due to invasion of bacteria or mold. This innovation of the phantom material makes it possible to accomplish highly reliable and precise estimation of specific absorption rate (SAR) in biological systems. Dry phantom models of spheres and human heads are fabricated. Experiments are performed to estimate the SAR ofmore » human heads exposed to microwave sources by using the thermography method. Since this material removes the necessity of the phantom shell indispensable with the conventional jelly material, the surface SAR distribution can be readily obtained.« less

Laser surface processing with controlled nitrogen-argon concentration levels for regulated surface life time

NASA Astrophysics Data System (ADS)

Obeidi, M. Ahmed; McCarthy, E.; Brabazon, D.

2018-03-01

Laser surface modification can be used to enhance the mechanical properties of a material, such as hardness, toughness, fatigue strength, and corrosion resistance. Surface nitriding is a widely used thermochemical method of surface modification, in which nitrogen is introduced into a metal or other material at an elevated temperature within a furnace. It is used on parts where there is a need for increased wear resistance, corrosion resistance, fatigue life, and hardness. Laser nitriding is a novel method of nitriding where the surface is heated locally by a laser, either in an atmosphere of nitrogen or with a jet of nitrogen delivered to the laser heated site. It combines the benefits of laser modification with those of nitriding. Recent work on high toughness tool steel samples has shown promising results due to the increased nitrogen gas impingement onto the laser heated region. Increased surface activity and nitrogen adsorption was achieved which resulted in a deeper and harder surface compared to conventional hardening methods. In this work, the effects of the laser power, pulse repetition frequency, and overlap percentage on laser surface treatment of 316 L SST steel samples with an argon-nitrogen jet will be presented. Resulting microstructure, phase type, microhardness, and wear resistance are presented.

Synthesis of graphene and related two-dimensional materials for bioelectronics devices.

PubMed

Zhang, Tao; Liu, Jilun; Wang, Cheng; Leng, Xuanye; Xiao, Yao; Fu, Lei

2017-03-15

In recent years, graphene and related two-dimensional (2D) materials have emerged as exotic materials in nearly every fields of fundamental science and applied engineering. The latest progress has shown that these 2D materials could have a profound impact on bioelectronics devices. For the construction of these bioelectronics devices, these 2D materials were generally synthesized by the processes of exfoliation and chemical vapor deposition. In particular, the macrostructures of these 2D materials have also been realized by these two processes, which have shown great potentials in the self-supported and special-purpose biosensors. Due to the high specific surface area, subtle electron properties, abundant surface atoms of these 2D materials, the as-constructed bioelectronics devices have exhibited enhanced performance in the sensing of small biomolecules, heavy metals, pH, protein and DNA. The aim of this review article is to provide a comprehensive scientific progress in the synthesis of 2D materials for the construction of five typical bioelectronics devices (electrochemical biosensors, FET-based biosensors, piezoelectric devices, electrochemiluminescence devices and supercapacitors) and to overview the present status and future perspective of the applications of these bioelectronics devices based on 2D materials. Copyright © 2016 Elsevier B.V. All rights reserved.

Evaluation of Toluene Adsorption Performance of Mortar Adhesives Using Porous Carbon Material as Adsorbent

PubMed Central

Chang, Seong Jin; Jeong, Su-Gwang; Lee, Jongki; Kim, Taeyeon; Park, Kyung-Won; Lee, Dong Ryeol; Kim, Sumin

2017-01-01

Porous carbon materials are advantageous in adsorbing pollutants due to their wide range of specific surface areas, pore diameter, and pore volume. Among the porous carbon materials in the current study, expanded graphite, xGnP, xGnP C-300, xGnP C-500, and xGnP C-750 were prepared as adsorbent materials. Brunauer–Emmett–Teller (BET) analysis was conducted to select the adsorbent material through the analysis of the specific surface area, pore size, and pore volume of the prepared porous carbon materials. Morphological analysis using SEM was also performed. The xGnP C-500 as adsorbent material was applied to a mortar adhesive that is widely used in the installation of interior building materials. The toluene adsorption performances of the specimens were evaluated using 20 L small chamber. Furthermore, the performance of the mortar adhesive, as indicated by the shear bond strength, length change rate, and water retention rate, was analyzed according to the required test method specified in the Korean standards. It was confirmed that for the mortar adhesives prepared using the xGnP C-500 as adsorbent material, the toluene adsorption performance was excellent and satisfied the required physical properties. PMID:28773214

Effects of in situ dual ion beam (He+ and D+) irradiation with simultaneous pulsed heat loading on surface morphology evolution of tungsten-tantalum alloys

NASA Astrophysics Data System (ADS)

Gonderman, S.; Tripathi, J. K.; Sinclair, G.; Novakowski, T. J.; Sizyuk, T.; Hassanein, A.

2018-02-01

The strong thermal and mechanical properties of tungsten (W) are well suited for the harsh fusion environment. However, increasing interest in using tungsten as plasma-facing components (PFCs) has revealed several key issues. These potential roadblocks necessitate more investigation of W and other alternative W based materials exposed to realistic fusion conditions. In this work, W and tungsten-tantalum (W-Ta) alloys were exposed to single (He+) and dual (He+  +  D+) ion irradiations with simultaneous pulsed heat loading to elucidate PFCs response under more realistic conditions. Laser only exposer revealed significantly more damage in W-Ta samples as compared to pure W samples. This was due to the difference in the mechanical properties of the two different materials. Further erosion studies were conducted to evaluate the material degradation due to transient heat loading in both the presence and absence of He+ and/or D+ ions. We concluded that erosion of PFC materials was significantly enhanced due to the presence of ion irradiation. This is important as it demonstrates that there are key synergistic effects resulting from more realistic fusion loading conditions that need to be considered when evaluating the response of plasma facing materials.

Organic pi-stacking Semiconducting Material: Design, Synthesis and the Analysis of Structure and Properties

NASA Astrophysics Data System (ADS)

Wilkinson, Taylor Marie

Oil shales are naturally occurring heterogeneous composites with micro-scale, micro-structural variations. They may be found throughout the world, with large deposits located in the United States; shales are composed of organic matter known as kerogen, clays, calcite, quartz, and other minerals. Typically their microstructure consists of a composite network where the organic matter is housed in open and closed pores between different mineral phases that range in size from sub-micron to several microns. Currently, it is unknown how the micro-scale heterogeneity of the shale will impact hydraulic fracture, which is the key extraction technique used for these materials. In this thesis, high-resolution topographic and modulus maps were collected from oil shales with the use of new nanoindentation techniques in order to characterize the micro-scale, micro-structural variations that are typical for these materials. Dynamic modulus mapping allows for substantially higher spatial resolution of properties across grains and intragranular regions of kerogen than has previously been produced with standard quasistatic indentation methods. For accurate scanning, surface variations were minimized to maintain uniform contact of the tip and appropriate quasi-static and dynamic forces were used to maintain displacement amplitudes that avoid plastic deformation of the sample. Sample preparation to minimize surface roughness was completed with the use of focused ion beam milling, however, some variation was still noted. Due to the large changes in modulus values between the constituents of the shale, there were variations in the recorded displacement amplitude values as well. In order to distinguish biased data due to surface topography or a lack of displacement amplitude, filtering techniques were developed, optimization and implemented. Variations in surface topography, which resulted in the indenter tip not being able to accurately resolve surface features, and inadequate displacement amplitude values that prohibit differentiation between material changes and the noise floor of the machine, were removed. These filters resulted in a more valid interpretation of the micro-scale, micro-structural features and arrangement, as well as the mechanical properties, that are common to oil shales.

Lifetime Predictions of a Titanium Silicate Glass with Machined Flaws

NASA Technical Reports Server (NTRS)

Tucker, Dennis S.; Nettles, Alan T.; Cagle, Holly

2003-01-01

A dynamic fatigue study was performed on a Titanium Silicate glass to assess its susceptibility to delayed failure and to compare the results with those of a previous study. Fracture mechanics techniques were used to analyze the results for the purpose of making lifetime predictions. The material strength and lifetime was seen to increase due to the removal of residual stress through grinding and polishing. Influence on time-to-failure is addressed for the case with and without residual stress present. Titanium silicate glass otherwise known as ultra-low expansion (ULE)* glass is a candidate for use in applications requiring low thermal expansion characteristics such as telescope mirrors. The Hubble Space Telescope s primary mirror was manufactured from ULE glass. ULE contains 7.5% titanium dioxide which in combination with silica results in a homogenous glass with a linear expansion coefficient near zero. delayed failure . This previous study was based on a 230/270 grit surface. The grinding and polishing process reduces the surface flaw size and subsurface damage, and relieves residual stress by removing the material with successively smaller grinding media. This results in an increase in strength of the optic during the grinding and polishing sequence. Thus, a second study was undertaken using samples with a surface finish typically achieved for mirror elements, to observe the effects of surface finishing on the time-to-failure predictions. An allowable stress can be calculated for this material based upon modulus of rupture data; however, this does not take into account the problem of delayed failure, most likely due to stress corrosion, which can significantly shorten lifetime. Fortunately, a theory based on fracture mechanics has been developed enabling lifetime predictions to be made for brittle materials susceptible to delayed failure. Knowledge of the factors governing the rate of subcritical flaw growth in a given environment enables the development of relations between lifetime, applied stress and failure probability for the material under study. Dynamic fatigue is one method of obtaining the necessary information to develop these relationships. In this study, the dynamic fatigue method was used to construct a time-to-failure diagram for polished ULE glass.

Amine Enrichment of Thin-Film Composite Membranes via Low Pressure Plasma Polymerization for Antimicrobial Adhesion.

PubMed

Reis, Rackel; Dumée, Ludovic F; He, Li; She, Fenghua; Orbell, John D; Winther-Jensen, Bjorn; Duke, Mikel C

2015-07-15

Thin-film composite membranes, primarily based on poly(amide) (PA) semipermeable materials, are nowadays the dominant technology used in pressure driven water desalination systems. Despite offering superior water permeation and salt selectivity, their surface properties, such as their charge and roughness, cannot be extensively tuned due to the intrinsic fabrication process of the membranes by interfacial polymerization. The alteration of these properties would lead to a better control of the materials surface zeta potential, which is critical to finely tune selectivity and enhance the membrane materials stability when exposed to complex industrial waste streams. Low pressure plasma was employed to introduce amine functionalities onto the PA surface of commercially available thin-film composite (TFC) membranes. Morphological changes after plasma polymerization were analyzed by SEM and AFM, and average surface roughness decreased by 29%. Amine enrichment provided isoelectric point changes from pH 3.7 to 5.2 for 5 to 15 min of plasma polymerization time. Synchrotron FTIR mappings of the amine-modified surface indicated the addition of a discrete 60 nm film to the PA layer. Furthermore, metal affinity was confirmed by the enhanced binding of silver to the modified surface, supported by an increased antimicrobial functionality with demonstrable elimination of E. coli growth. Essential salt rejection was shown minimally compromised for faster polymerization processes. Plasma polymerization is therefore a viable route to producing functional amine enriched thin-film composite PA membrane surfaces.

Prediction of Failure Due to Thermal Aging, Corrosion and Environmental Fracture in Amorphous and Titanium Alloys

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

Farmer, J C

2003-04-15

DARPA is exploring a number of advanced materials for military applications, including amorphous metals and titanium-based alloys. Equipment made from these materials can undergo degradation due to thermal aging, uniform corrosion, pitting, crevice corrosion, denting, stress corrosion cracking, corrosion fatigue, hydrogen induced cracking and microbial influenced corrosion. Amorphous alloys have exceptional resistance to corrosion, due in part to the absence of grain boundaries, but can undergo crystallization and other phase instabilities during heating and welding. Titanium alloys are extremely corrosion resistant due to the formation of a tenacious passive film of titanium oxide, but is prone to hydrogen absorption inmore » crevices, and hydrogen induced cracking after hydrogen absorption. Accurate predictions of equipment reliability, necessary for strategic planning, requires integrated models that account for all relevant modes of attack, and that can make probabilistic predictions. Once developed, model parameters must be determined experimentally, and the validity of models must be established through careful laboratory and field tests. Such validation testing requires state-of-the-art surface analytical techniques, as well as electrochemical and fracture mechanics tests. The interaction between those processes that perturb the local environment on a surface and those that alter metallurgical condition must be integrated in predictive models. The material and environment come together to drive various modes of corrosive attack (Figure 1). Models must be supported through comprehensive materials testing capabilities. Such capabilities are available at LLNL and include: the Long Term Corrosion Test Facility (LTCTF) where large numbers of standard samples can be exposed to realistic test media at several temperature levels; a reverse DC machine that can be used to monitor the propagation of stress corrosion cracking (SCC) in situ; and banks of potentiostats with temperature controlled cells for potentiostatic and potentiodynamic testing (Figure 2).« less

“Feathered” fractal surfaces to minimize secondary electron emission for a wide range of incident angles

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

Swanson, Charles; Kaganovich, Igor D.

Complex structures on a material surface can significantly reduce the total secondary electron emission from that surface. The reduction occurs due to the capture of low-energy, true secondary electrons emitted at one point of the structure and intersecting another. We performed Monte Carlo calculations to demonstrate that fractal surfaces can reduce net secondary electron emission produced by the surface as compared to the flat surface. Specifically, we describe one surface, a “feathered” surface, which reduces the secondary electron emission yield more effectively than other previously considered configurations. Specifically, feathers grown onto a surface suppress secondary electron emission from shallow anglesmore » of incidence more effectively than velvet. Here, we find that, for the surface simulated, secondary electron emission yield remains below 20% of its un-suppressed value, even for shallow incident angles, where the velvet-only surface gives reduction factor of only 50%.« less

“Feathered” fractal surfaces to minimize secondary electron emission for a wide range of incident angles

DOE PAGES

Swanson, Charles; Kaganovich, Igor D.

2017-07-24

Complex structures on a material surface can significantly reduce the total secondary electron emission from that surface. The reduction occurs due to the capture of low-energy, true secondary electrons emitted at one point of the structure and intersecting another. We performed Monte Carlo calculations to demonstrate that fractal surfaces can reduce net secondary electron emission produced by the surface as compared to the flat surface. Specifically, we describe one surface, a “feathered” surface, which reduces the secondary electron emission yield more effectively than other previously considered configurations. Specifically, feathers grown onto a surface suppress secondary electron emission from shallow anglesmore » of incidence more effectively than velvet. Here, we find that, for the surface simulated, secondary electron emission yield remains below 20% of its un-suppressed value, even for shallow incident angles, where the velvet-only surface gives reduction factor of only 50%.« less

Surface Texture-Based Surface Treatments on Ti6Al4V Titanium Alloys for Tribological and Biological Applications: A Mini Review

PubMed Central

Li, Dali; Zou, Jiaojuan; Xie, Ruizhen; Wang, Zhihua; Tang, Bin

2018-01-01

Surface texture (ST) has been confirmed as an effective and economical surface treatment technique that can be applied to a great range of materials and presents growing interests in various engineering fields. Ti6Al4V which is the most frequently and successfully used titanium alloy has long been restricted in tribological-related operations due to the shortcomings of low surface hardness, high friction coefficient, and poor abrasive wear resistance. Ti6Al4V has benefited from surface texture-based surface treatments over the last decade. This review begins with a brief introduction, analysis approaches, and processing methods of surface texture. The specific applications of the surface texture-based surface treatments for improving surface performance of Ti6Al4V are thoroughly reviewed from the point of view of tribology and biology. PMID:29587358

"Feathered" fractal surfaces to minimize secondary electron emission for a wide range of incident angles

NASA Astrophysics Data System (ADS)

Swanson, Charles; Kaganovich, Igor D.

2017-07-01

Complex structures on a material surface can significantly reduce the total secondary electron emission from that surface. The reduction occurs due to the capture of low-energy, true secondary electrons emitted at one point of the structure and intersecting another. We performed Monte Carlo calculations to demonstrate that fractal surfaces can reduce net secondary electron emission produced by the surface as compared to the flat surface. Specifically, we describe one surface, a "feathered" surface, which reduces the secondary electron emission yield more effectively than other previously considered configurations. Specifically, feathers grown onto a surface suppress secondary electron emission from shallow angles of incidence more effectively than velvet. We find that, for the surface simulated, secondary electron emission yield remains below 20% of its un-suppressed value, even for shallow incident angles, where the velvet-only surface gives reduction factor of only 50%.

Structure and properties of polymeric composite materials during 1501 days outer space exposure at Salyut-7 orbital station

NASA Technical Reports Server (NTRS)

Startsev, Oleg V.; Nikishin, Eugene F.

1995-01-01

Specimens of polymeric composite materials for aviation and space applications such as glass fiber reinforced plastics (GFRP), carbon fiber reinforced plastics (CFRP), organic fiber reinforced plastics (OFRP), and hybrid plastics (HP) based on epoxy compounds were exposed to the space environment on the surface of Salyut-7 orbital station. The space exposure lasted 1501 days as a maximum. The data relating to the change in mechanical properties, mass losses, glass transition temperature, linear thermal expansion coefficient, and microstructure after various periods of exposure are given. It has been found that the change in properties is caused by the processes of binder postcuring and microerosion of the exposed surface of plastics. The phenomenon of strengthening of the surface layer of hybrid composites, due to which the nature of destruction changes at bending loads, has been revealed.

Cursory examination of the zeta potential behaviors of two optical materials

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

Tesar, A.; Oja, T.

1992-01-02

When an oxide surface is placed in water, a difference in potential across the interface occurs due to dipole orientation. Hydroxyl groups or bound oxygen atoms on the oxide surface will orient adjacent water molecules which balance the dipole charge. This occurs over some small distance called the electrical double layer. Trace amounts of high field strength ions present in the vicinity of the double layer can have significant effects on the double layer. When there is movement of the oxide surface with respect to the water, a shearing of the double layer occurs. The electrical potential at this surfacemore » of shear is termed the zeta potential. The impetus for this study was to document the zeta potential behavior in water of two optical materials. (1) a multicomponent phosphate glass; and (2) Zerodur, a silicate glass-ceramic.« less

Biodeterioration of medical-grade silicone rubber used for voice prostheses: a SEM study.

PubMed

Neu, T R; Van der Mei, H C; Busscher, H J; Dijk, F; Verkerke, G J

1993-05-01

Silicone voice prostheses used for rehabilitation of speech after total laryngectomy are inserted in an non-sterile habitat. Deposits on explanted Groningen Button voice prostheses revealed a biofilm, due to heavy colonization of the silicone surface by bacteria and yeasts. Furthermore, it was demonstrated by scanning electron microscopy on sectioned explants that the silicone material was deteriorated by filamentous and vegetative yeast cells. The different explants showed a variety of sharp-edged, discrete yeast colonies. The yeasts grew just under the silicone surface and up to 700 microns into the silicone material. Finally, nine different types of defects in the silicone material created by the yeasts are described. This deterioration of the silicone by yeasts seems to be the main reason for the failure and the frequent replacement of the prostheses. The mechanisms of silicone deterioration are still hypothetical.

Patched bimetallic surfaces are active catalysts for ammonia decomposition.

PubMed

Guo, Wei; Vlachos, Dionisios G

2015-10-07

Ammonia decomposition is often used as an archetypical reaction for predicting new catalytic materials and understanding the very reason of why some reactions are sensitive on material's structure. Core-shell or surface-segregated bimetallic nanoparticles expose outstanding activity for many heterogeneously catalysed reactions but the reasons remain elusive owing to the difficulties in experimentally characterizing active sites. Here by performing multiscale simulations in ammonia decomposition on various nickel loadings on platinum (111), we show that the very high activity of core-shell structures requires patches of the guest metal to create and sustain dual active sites: nickel terraces catalyse N-H bond breaking and nickel edge sites drive atomic nitrogen association. The structure sensitivity on these active catalysts depends profoundly on reaction conditions due to kinetically competing relevant elementary reaction steps. We expose a remarkable difference in active sites between transient and steady-state studies and provide insights into optimal material design.