Composition Of Metal Particles Research Articles

Prediction of temperature dependent effective moduli of metal particle composites with debonding damage

Debonding is one of the most commonly observed damage mechanisms in metal particle composites, which poses additional difficulties for material characterization and performance evaluation. In this paper, the equivalent modulus of debonded particles in tension and compression was derived in accordance with the debonding configurations, respectively. The debonded particles were then incorporated into the Mori-Tanaka method as a third phase with reduced modulus but perfectly bonded to the matrix. Finally, a micromechanical model of the temperature dependent effective moduli of metal particle composites was proposed, taking into account the degradation of the matrix modulus and the evolution of percentage of debonded particles at elevated temperatures. The model predictions were in high agreement with the experimental and simulation results, demonstrating the predictive ability of the micromechanical model. This study gives a highly practical forecasting toolkit for composite modulus evaluation over a wide temperature range. In addition, parametric analyses were carried out to investigate the effects of debonding configuration, temperature, and percentage of debonded particles, which contributes to further understanding of the debonding mechanism, leading to rational material design.

Thermal Performance of Liquid Metal Pastes Containing low Content of Metal Particles for Thermal Interface Materials in IC Module Electronics

In recent years, considerable attention has been paid to gallium-based liquid metal alloys in their use as thermal interface materials for GPU, APU, and HPC in PC and super computers due to its considerably high thermal conductivity and low contact thermal resistance. Gallium-based Liquid metal paste containing low content of metal particles (LMP-MPs) to enhance thermal performance and controllable BLT of the prepared liquid metal composites for thermal interface materials (TIMs) prepared by in-situ introducing gallium oxide into the liquid metal alloys will be reported in our recent research. In this paper, we will report effect of the composition, particle size/types, and bond line thickness on thermal properties of the LMP-MPs. Thermal properties of the LMP-MPs were measured at 50o C using a thermal tester, TIMA5, based on ASTM-D5470 test methodology. It was found in the present study that the composition and types of metal particles, and BLT have significant influence on thermal conductivity, and the conductivity values increase with an increase of the content of metal particles and BLT. However, thermal resistance varies with the change of composition and BLT of LMP-MPs. Scanning electron microscope (SEM) was used to characterize microstructure of LMP-MPs with different metal particles and sizes. Micrographic morphology of the LMPs-MPs shows continuous frame structure observed with SEM, which could keep liquid metals from spreading out and stabilize the phase. We eventually found the LMP-MPs have the better wetting and adhesion properties on bare Cu, glass and bare Si surface than liquid metal alloys that endows good printability to the LMP-MPs. Continuous monitoring of thermal resistance of LMP-MPs at 45o C and 89o C using a house-made thermal tester shows stable thermal resistance after a few months, which indicates LMP-MPs have excellent thermal reliability in ambient atmosphere.

The Critical Role of βPdZn Alloy in Pd/ZnO Catalysts for the Hydrogenation of Carbon Dioxide to Methanol.

The rise in atmospheric CO2 concentration and the concomitant rise in global surface temperature have prompted massive research effort in designing catalytic routes to utilize CO2 as a feedstock. Prime among these is the hydrogenation of CO2 to make methanol, which is a key commodity chemical intermediate, a hydrogen storage molecule, and a possible future fuel for transport sectors that cannot be electrified. Pd/ZnO has been identified as an effective candidate as a catalyst for this reaction, yet there has been no attempt to gain a fundamental understanding of how this catalyst works and more importantly to establish specific design criteria for CO2 hydrogenation catalysts. Here, we show that Pd/ZnO catalysts have the same metal particle composition, irrespective of the different synthesis procedures and types of ZnO used here. We demonstrate that all of these Pd/ZnO catalysts exhibit the same activity trend. In all cases, the β-PdZn 1:1 alloy is produced and dictates the catalysis. This conclusion is further supported by the relationship between conversion and selectivity and their small variation with ZnO surface area in the range 6–80 m2g–1. Without alloying with Zn, Pd is a reverse water-gas shift catalyst and when supported on alumina and silica is much less active for CO2 conversion to methanol than on ZnO. Our approach is applicable to the discovery and design of improved catalysts for CO2 hydrogenation and will aid future catalyst discovery.

Перспективы переработки отвалов Крестовоздвиженской россыпи

The main features of the structure and gold content of the dumps of the Krestovozdvizhenskaya placer in the Middle Urals are considered. Infofrmation on drilling operations performed, gold concentration, morphological features, granulometric, and chemical composition of metal particles are presented. The studies revealed the presence of the dumps body areas with gold content identical to conditions for modern placers. The dimension of the most gold particles makes it possible to apply the hydraulic method for their industrial extraction. Characteristic evidence of a gold long stay in dumps (the formation of a high-grade coat, deposits and films on the surface, intergrowths and "gold" conglomerates, gold intermetallic compounds) are noted. Possible ways of organizing the processing of dumps are proposed.

Aqueous suspensions of Fuller’s earth potentiate the adsorption capacities of paraoxon and improve skin decontamination properties

Fuller’s earth (FE) is a phyllosilicate used as a powder for household or skin decontamination due to its adsorbent properties. Recent studies have shown that water suspensions exhibit similar adsorbent capacities. FE is heterogeneous due to its composition of elementary clay aggregates and heavy metal particles. Here, FE toxicity was assessed in vitro on skin cells and in vivo on Danio rerio embryos. Among the suspensions tested (5%, 9.1% and 15% w/w), only the highest one shows weak toxicity. Suspensions were tested for ex vivo dermal decontamination into pig ear skin and human abdominal skin using diffusion cells and paraoxon as organophosphorus contaminant. After 24 h of diffusion, no difference was observed in the paraoxon concentration in the receptor compartment whether the decontamination was carried out with FE in powder or in suspension form. In presence of FE suspensions, we observed the disappearance of paraoxon from the stratum corneum, the reservoir compartment, independently of the suspensions’ concentration. We suggest that water potentiates the absorbing capacities of FE powder by intercalating between clay lamellas leading to the appearance of new adsorption zones and swelling. These data support the use of FE aqueous suspensions as a safe tool for organophosphorus skin decontamination.

A new strategy of carbon – Pb composite as a bipolar plate material for unitized regenerative fuel cell system

In this study, we investigated the possibilities and combination of cost-effective materials of carbon (C) and lead (Pb) with polypropylene (PP) polymer as a new kind of bipolar plate for unitized regenerative fuel cell and polymer electrolyte membrane fuel cell systems. The homogeneous composite structure of C:Pb developed through facile mechanical milling process, and optimized. The new bipolar plate was fabricated with PP using compression molding process with hot pressing techniques. A dense and smooth surface morphology of C:Pb bipolar plate was acquired with the uniform thickness of 1.33 (±0.17) mm. Compared to C, an improved electrical properties (~20%) obtained to the powdered C:Pb composite materials because of homogeneous composition of Pb metal particles with large surface area of C. The C:Pb bipolar plate revealed an efficient water contact angle behavior than the C bipolar plate, where the water contact angle for C and C:Pb bipolar plates are 82.4° and 93.1°, respectively. A sophisticated electrochemical stability performance has obtained to the C:Pb bipolar plate in acidic condition. According to Tafel plots analysis, higher corrosion resistance has observed to the C:Pb bipolar plate than the C bipolar plate. The fabricated new kind of C:Pb bipolar plate provides the many advantageous, thus it proves the insights for further developments and applicability in the practical application. In the perspective view, the performances of C:Pb bipolar plate can be further altered through modification of different carbon structures together with impregnation of Pb nanostructured materials into the pores and/or embedded throughout the surface, and efficient conductive polymers.

Non‐Destructive Three‐Dimensional Imaging of Metal Organic Framework Mixed Matrix Membranes using Lab‐based X‐ray Computed Tomography

AbstractTwo‐dimensional composites of metal particles and polymers hold the promise to enable revolutionary applications. The research and development of these films have been ongoing for over 60 years and new manufacturing and characterization techniques keep increasing the pace of advancements. Retrieving quantitative information from these types of samples can be a difficult and time‐consuming task when using line of sight imaging modalities. In this work a mixed‐matrix membrane with Co‐containing ZIF‐67 was studied with lab‐based X‐ray computed tomography. The benefits and limitations of what the computed tomography technique has to offer are presented and discussed.

Application of graphene in electrical resistance electromagnetic shielding fabric

Graphene is a kind of material formed by Sp2 hybridization of carbon atoms, which has been widely used in various scientific research fields in recent years. In this paper, the mechanism of electromagnetic shielding on fabrics and the recent development of resistance type electromagnetic shielding materials are introduced. The effects of graphene and metal particle composites, graphene and high conductivity polymer composites, carbon nanotubes and high conductivity polymer composites on fabrics are briefly described. The optimization of electromagnetic shielding effectiveness and the future development of shielding materials is prospected.

Free and Forced Convective Heat Transfer through a Nanofluid with Two Dimensions past Stretching Vertical Plate

The present study focus on both free and forced convective heat transfer through a nanofluid in two dimensions past stretching vertical plate. This free and forced convective heat transfer in Cu–water Nanofluid past permeable flat vertical semi-infinite plate was due to high conductivity and its occurrence. In this paper magnetic field and also heat source were considered. In graphs the effect on various parameters such as Reynolds number (Re) , solid volume fraction (φ), magnetic field parameter (M), inclination angle of the plate (γ ), heat source parameter (Qh), on linear velocity (U), vertical velocity (V) and temperature (θ) were exhibited. The profile of every governing parameter is displayed for natural as well as forced convection by considering the Ar >> 1 and Ar << 1 respectively. This rate of heat transfer in forced convection is more than equivalent in free convection. So these problems have several applications in engineering and petroleum industries such as electroplating, chemical processing of heavy metals and solar water heaters. Inertial force reducing the heat transfer rate in natural convection but the enhancement of Nu observed in forced convection. The composition of metal particles enhances the heat transfer rate in both convections, which emphasizes the nanofluid significance. Lorentz force is enhancing the heat transfer rate slightly. Heat source obviously increase the rate of heat transfer in both convections. The present paper aims to study the convective high temperature transfer of nanofluids into which viscosity proposed by Einstein and thermal conductivity proposed by Corcione were used.

The variations of chemical composition and features of the distribution of rare elements in chondrites of fragments of the Chelyabinsk meteorite

Research subject. This paper reports the results of a series of experiments carried out to study the mineral and geoche mical features of 10 Chelyabinsk meteorite fragments. In addition, these fragments were analysed in terms of their chemical composition.Materials and methods. The fragments under study were represented by light-grey granular rocks of the chondrite structure having either isometric or elongated shape. Their surface was largely covered with a black-brownish fusion crust with a thickness of approximately 1 mm. The petrogenic components of the meteorite and the content of rare elements were studied using the methods of chemical silicate analysis and ICP MS respectively. All measurements were carried out using an Agilent 7700x quadrupole mass spectrometer produced by the Agilent Technologies company. The composition of sulphides and metal particles was determined by electron probe microanalysis (PCMA) usinga JXA8200 microanalyzer (Jeol, Japan).Results. The chondri and cementing matrix are found to be primarily composed of olivine and orthopyroxene. The inter-chondruli matrixis shown to consist of a pyroxene-olivine aggregate with inclusions of plagioclase, apatite, fused glass and ore minerals (tenite, kamasite, troilite, rarely pyrrhotine, pentlandite, single grains of chromite and ilmenite). The concentration of the majority of rare and ore elements in the Chelyabinsk meteorite samples is established to be close to their average values for LL-chondrite. When normalizing to coaly chondrite, the substance of the meteorite fragments and the average LL-chondrite were closest to coaly chondrite in terms of the content of siderophile elements (Mo, Ni, Cr, Co, V and Cu). At the same time, the studied meteorite fragments are shown to contain a significantly lower (nearly by one order) concentration of chalcophyle elements (Zn, Pb and Sn) with regard to С1.Conclusion. A comparison of the obtained and published analytical data (ICP MS) has allowed us to make a conclusion on the geochemical heterogeneity of different meteorite remainst hat were scattered over a wide area of the Chelyabinsk Region. The acquired evidence suggests the differentiation of meteorite substance at early stages of the formation of terrestrial planets, which is likely to have occurred due to impact processes.

Embedded electrical tracks in 3D printed objects by fused filament fabrication of highly conductive composites

The incorporation of electrical components into 3D printed products such as sensors or printing of circuits requires the use of 3D printable conductive materials. However, most conductive materials available for fused filament fabrication (FFF) have conductivities of less than 1000 S/m. Here, we describe the study of conductive thermoplastic composites comprising either nylon – 6 or polyethylene (PE) matrix. The fillers used were nickel and Sn95Ag4Cu1, a low melting point metal alloy. The combination of nickel metal particles and tin alloy allows for higher metal loading at lower melt viscosity, compared to composites of nickel metal particles alone. Conductivities of 31,000 S/m were achieved, and 30 vol. % metal loading was processable by a single screw extruder. Embedded conductive tracks of various geometries were easily printed via FFF. Electrical conductivity of embedded conductive track has been investigated as a function of geometrical variation, where conductive tracks printed along a horizontal axis show resistance of ≤ 1 Ω. Porosity of the printed track is shown to increase with prints along the vertical axis, leading to a reduction in electrical conductivity of more than two orders of magnitude.

Combustion Characteristics of Ramjet Fuel Grains with Boron and Aluminum Additives

An experimental investigation of the effect of boron (B) and aluminum (Al) additives to fuel-rich propellant for a solid fuel ramjet application was performed. In this research, depending on the composition of metal particles, three types of fuel grains with 15 wt % ammonium perchlorate particles were prepared and tested. To provide a short ignition delay, an ignition support material consisting of and a composite propellant were coated on the fuel grain. For the test, an oxidant gas having a controlled temperature and pressure and an oxygen composition close to that of the air in a ramjet combustor was supplied using an ethanol-blended hydrogen peroxide () gas generator. Air simulant gas was supplied with an average mass flow rate near and a Mach number of 0.21 in the fuel grain port. Through the test, the noticeable effect of B particles on combustion was confirmed by a high regression rate over and combustion efficiency over 80%. Al particles were not effective additives individually; however, Al particles contributed to the ignition of B. In addition, metal oxide particle deposits on the nozzle confirmed the existence of a two-phase flow.

Identification of Metallic Trace Particles of Injuring Fe-Mn Steel Hammer from Body Trauma

We describe an effective method for extracting metallic trace particles from injured tissue. As a validation test, we used scanning electron microscopy with energy-dispersive X-ray spectrometry with the INCAFeature software package to analyze metallic trace particles deposited by different Fe-Mn steel hammers. Our results demonstrate the feasibility of the proposed method. Based on the proposed method, an effective index is suggested for evaluating elemental composition. This index can be used for determining the nature and composition of residue metallic particles, which is likely to be of importance to forensic pathologists.

Characteristics of soil particles in the Xiaohulishan deposit, Inner Mongolia, China

In this paper, we used transmission electron microscopy (TEM) to study metal-bearing particles in the Gobi Desert soil of the concealed Xiaohulishan deposit in north-western Inner Mongolia. By analysing the category, size, shape, and chemical composition of metal particles in soil samples, as well as their co-occurrence with soil mineral particles in the surface overburden, we determined the characteristics of the metal particles that are related to mineralization. Along with the geological setting, this information can provide insight into prospecting the concealed ore body based on the surface overburden particles. In addition, studying the association between metal particles and soil mineral particles allows us to summarize the adsorption properties of soil minerals for metal particles, and analysing the metal particles carried by ascending gas helps us determine the mechanism by which metal particles are transported by ascending gas flow in the surface overburden. This paper discusses both the natural metal particles and the soil mineral particles that contain metals. We propose that it is possible to prospect a concealed ore body using the characteristics of surface overburden particles, and we summarize the preferences and behaviour of metal particles (mainly Fe-, Mo-, Cu-, Pb- and Zn-bearing particles) adsorbed by soil minerals such as Ca sulphates, silicates, carbonate minerals, and clay minerals. This knowledge is significant because it can help explain the migration mechanisms of metal particles in the soil-covered areas of the Gobi Desert. These findings will also help to explore concealed deposits by facilitating the use of elemental concentrations, as well as the characteristics of metal particles carried by ascending gas flow.

Interfacial characteristic, thermal conductivity, and modeling of graphite flakes/Si/Al composites fabricated by vacuum gas pressure infiltration

Abstract

A role of Au-content in performance of Pd-Au/SiO2 and Pd-Au/Al2O3 catalyst in the hydrogen and oxygen recombination reaction. The microcalorimetric and DFT studies

The thermal effects and activity of silica and alumina supported bimetallic Pd-Au catalysts (of various Pd/Au ratio) in the exothermic H2 and O2 recombination reaction have been investigated in view of their potential use in the industrial passive autocatalytic recombiners (PAR). The catalysts were prepared by the colloid-based reverse “water-in-oil” microemulsion method which provided metal particles of size in a very narrow range (4–7nm). In both SiO2 and Al2O3 − series catalysts the Pd-Au particles aggregated to some extent, especially strongly in alumina-series samples. The H2+O2 reaction has been monitored using Microscal gas-flow through microcalorimeter at temperature of 22°C and atmospheric pressure. The observed pattern of changes in both the heat evolution and the conversion of hydrogen seem to reflect the effect of water and/or other oxygen-containing surface species (like OH) on the activity/deactivation of catalysts. The nature of support and the composition of metal particles (Pd/Au ratio) played a role. Deactivation of alumina supported catalysts was stronger than silica supported counterparts. Among all studied catalysts, the best behavior was offered by low Au content-containing Pd-Au-0.1/SiO2 (Pd90Au10) catalyst. Its almost stable activity during the catalytic run may be attributed to relatively weak interactions with water molecules and/or other oxygen-containing species (like OH), intermediates formed in the hydrogen oxidation. It may be supposed that electronic modification of palladium sites by gold assisted by the surface composition of Pd-Au particles reflecting in “surface arrangement of Pd and Au-atoms” are decisive. This experimental observation seems to correlated with the DFT calculation indicating that besides the number of Au atoms, their location with respect to the Pd, e.g “surface arrangement of Au” is more important for the energy/strength of interaction with water molecules.

Cu-Containing Carbon Nanocomposites Based on Cellulose

Structural transitions of Fe-containing fibrous and microcrystalline flax and hemp cellulose during heat treatment in an inert medium were studied using IR spectroscopy, x-ray diffraction, electron microscopy, thermogravimetric analysis, and N2 adsorption. Mesoporous ferromagnetic graphitecontaining carbon composites with specific surface area 280-550 m2/g were produced. The nature and shape of the cellulose matrix and the iron-salt anion were found to affect the composition, shape, and size of metal particles and the catalytic graphitization process.

Investigation on FTU dust and on the origin of ferromagnetic and lithiated grains

A comprehensive analysis of composition and morphology of metallic micrometric particles collected in FTU during the 2013 shut-down is presented. The data-set analyzed is the result of years of experimental activity in FTU which is a full metal machine since the beginning of operation and with a liquid lithium limiter (LLL) from 2005. It was found that the metallic population, consisting of flakes, smashed and spheroidally shaped particles from plasma facing components (mainly SS and Mo), exhibits an unexpectedly high, up to 70 wt%, fraction of magnetic grains. The change of crystalline phase from γ to α/δ of the iron component contained in the particles coming from stainless steel is suggested as the mechanism responsible for magnetic dust production. This phase change can be ascribed to the particle temperature quench and/or to the presence of a strong magnetic field during the re-solidification of molten stainless steel droplets. In connection to the dust collected close to the LLL, consisting mainly of lithium carbonate spherical-like particles up to a few mm, the mechanism of Li2CO3 formation and its role as a source of C and O impurities are discussed.

Role of Metal–Support Interactions, Particle Size, and Metal–Metal Synergy in CuNi Nanocatalysts for H2 Generation

Efficient bimetallic nanocatalysts based on non-noble metals are highly desired for the development of new energy storage materials. In this work, we report a simple method for the synthesis of highly dispersed CuNi catalysts supported on mesoporous carbon or silica nanospheres using low-cost metal nitrate precursors. The mesoporous carbon-supported Cu0.5Ni0.5 nanocatalysts exhibit excellent catalytic performance for the hydrolysis of ammonia borane and decomposition of hydrous hydrazine with 100% hydrogen selectivity in aqueous alkaline solution at 60 °C. The chemical composition and size of the metal particles, which have a significant influence on the catalytic properties of the supported bimetallic CuNi materials, can readily be controlled by adjusting the metal loading and ratio of metal precursors. An exceedingly high turnover frequency of 3288 (molH2 molmetal–1 h–1) and complete reaction within 1 min in dehydrogenation of ammonia-borane were achieved over a tailored-made catalyst obtained through precise monitoring of metal particle size, composition, and support properties.

Lycurgus Cup: inverse problem using photographs for characterization of matter.

Photographs of the Lycurgus Cup with a source light inside and outside exhibit purple and green colors, respectively (dichroism). A model relying on the scattering of light to colors in the photographs is proposed and used within an inverse problem algorithm, to deduce radius and composition of metallic particles, and the refractive index of the surrounding glass medium. The inverse problem algorithm is based on a hybridization of particle swarm optimization and of the simulated annealing methods. The results are compared to experimental measurements on a small sample of glass. The linear laws that are deduced from sets of possible parameters producing the same color in the photographs help simplify the understanding of phenomena. The proportion of silver to gold in nanoparticles is found to be in agreement, but a large proportion of copper is also found. The retrieved refractive index of the surrounding glass is close to 2.