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Silver based composites with varying concentration of graphite and/or MoS2 were prepared by powder metallurgy method. Impacts of composition on the tribological performance of the composites in ambient air and vacuum were investigated. The lowest friction in air was achieved by Ag-20G (vol.-%) composite, while Ag-20MoS2 exhibited the best lubricity in vacuum. XPS evaluation revealed the oxidation of MoS2 in air and a decrease concentration of graphite on the surface of the wear tracks under vacuum. As the proportion of graphite to MoS2 increased, the friction coefficient and the wear rates ascended gradually in air while decreased sharply under vacuum. As compared with other compositions, Ag-15MoS2-5G exhibited a comparable stable and good tribological performance as the environmental condition changed for its friction coefficient and wear rate remained around 0.14 and 5 x 10-6 mm³ N-1 m-1. [ABSTRACT FROM AUTHOR]

Polyoxypropylene diamine has been used as shale hydration inhibitor in drilling fluid and exhibited outstanding performance. The authors describe the inhibition characteristics of KCl and polyoxypropylene diamine and provided a comparative assessment. Through bentonite inhibition test, bulk hardness test, hot-rolling dispersion test, slake durability test, fluid loss test, linear swelling test and X-ray diffraction test, the inhibitive properties of potassium chloride, and polyoxypropylene diamine were evaluated. The results indicate that polyoxypropylene diamine is superior to potassium chloride in shale stabilization, which can effectively suppress the hydration and swelling of clay and play an important role in permanent stabilization with a relatively low concentration. Moreover, the mechanisms of the two inhibitors are briefly analyzed. [ABSTRACT FROM PUBLISHER]

Effect of the particle size of TiC and TiN on the microstructure and mechanical properties of Ti(C,N) based cermets has been evaluated. Ti(C,N)–WC–Co cermets made from four groups of mixed raw powders of different sizes were manufactured by vacuum sintering. The microstructure and composition were studied using X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive X-ray spectrum (EDX). The result shows that the four samples have the typical microstructures of 'black core/grey rim'. The mechanical properties of the cermet manufactured from submicron TiC and nano TiN are the best among the four samples. [ABSTRACT FROM AUTHOR]

The structure, hydrogen storage property, and electrochemical characteristics of the La0.7Mg0.3Ni5.5-x (Al0.5Mo0.5)x (x = 0, 0.2, 0.4, 0.6, 0.8) hydrogen storage alloys have been investigated systematically. It has been found by X-ray powder diffraction and Rietveld analysis that the alloys are multiphase and consist of impurity Ni phase and two main crystallographic phases, namely, the La(La, Mg)2Ni9 phase and the LaNi5 phase, and the lattice parameters and the cell volumes of both the La(La, Mg)2Ni9 phase and the LaNi5 phase increase with increasing Al and Mo content in the alloys. The P-C isotherm curves indicated that the hydrogen storage capacity of the alloy first increases and then decreases with increasing x, and the equilibrium pressure decreases with increasing x. The electrochemical measurements show that the maximum discharge capacity first increases from 298.5 (x = 0) to 328.3 mAh/g (x = 0.6) and then decreases to 304.7 mAh/g (x = 0.8). The high rate dischargeability (HRD) of the alloy electrodes increases lineally from 65.4 pct (x = 0) to 86.6 pct (x = 0.8) at the discharge current density of 1200 mA/g. Moreover, the exchange current density of the alloy electrodes also increases monotonously with increasing x by the linear polarization curves. The hydrogen diffusion coefficient in the alloy bulk, D, increases with increasing Al and Mo content and thus enhances the low-temperature dischargeability (LTD) of the alloy electrodes. [ABSTRACT FROM AUTHOR]

InAs/GaSb type-II superlattices (SLs) were grown on (001) GaSb substrates by metal organic chemical vapor deposition. Besides the expected tensile stress introduced by the InAs layers in the SLs, additional tensile stress is found in the InAs/GaSb SLs from the simulation of x-ray diffraction (XRD) curves of the SLs. High-resolution transmission electron microscopy and XRD of the SLs grown with different interface gas switching procedures suggest that the additional tensile stress is mainly located at the GaSb→InAs interface. To compensate for the tensile stress in the SL structures, we show that introducing ∼2-ML-thick InAs0.8Sb0.2 layer at the interfaces of the SL improves the morphology and the structural properties of the SLs significantly. [ABSTRACT FROM AUTHOR]

Lattice-matched In0.49Ga0.51P/GaAs superlattices were grown on (001) GaAs substrates using metalorganic chemical vapor deposition. The interface properties were characterized by photoluminescence, transmission electron microscopy, and x-ray diffraction. By varying the growth temperature, the precursor flow rates, and the growth interruption at the interfaces, we found that, while arsenic and phosphorus carry over have some effect on the formation of a low-bandgap InGaAsP quaternary layer at the interfaces, the In surface segregation seems to play an important role in the formation of the interface quaternary layer. Evidence of this indium segregation comes from x-ray and photoluminescence studies of samples grown at different temperatures. These studies show that the formation of an interfacial layer is more prominent when the growth temperature is higher. Growing a thin (∼1 monolayer thick) GaP intentional interfacial layer on top of the InGaP before the growth of the GaAs layer at the P→As transition effectively suppresses the formation of the low-bandgap unintentional interface layer. On the other hand, the growth of a thin GaAsP (or GaP) layer before the growth of the InGaP layer, at the As→P transition increases the formation of a low-bandgap interfacial layer. This nonequivalent effect of a GaP layer at the two interfaces on the PL properties is discussed. [ABSTRACT FROM AUTHOR]

Abstract: The II–VI materials lattice matched to GaSb substrates are desirable for ultrahigh-efficiency multijunction solar cells. This paper reports the growth of ZnTe and ZnCdTe/ZnTe quantum wells on undoped GaSb (100) substrates using molecular beam epitaxy. During growth, in situ reflection high-energy electron diffraction shows fast and smooth transition from GaSb surface to ZnTe surface. Post-growth structural characterization using X-ray diffraction and high-resolution transmission electron microscopy reveals very low-defect density, i.e. high crystalline quality. Visible photoluminescence is observed from 10 to 300K. [Copyright &y& Elsevier]