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Selected AbstractsTribological Studies of a Zr-Based Glass-Forming Alloy with Different States,ADVANCED ENGINEERING MATERIALS, Issue 11 2009Feng Jiang Abstract The tribological characteristics of a glass-forming alloy, Zr52.5Cu17.9Ni14.6Al10.0Ti5.0, in atomic percent (at.%, Vit 105), with different microstructural states have been investigated. Friction and wear studies were conducted using a ball-on-flat reciprocating sliding apparatus against an AISI E52100 bearing steel under dry condition. The observed wear resistance in an ascending order is: the deformed, creep-tested, and as-cast states. Wear analyses suggested that the wear processes of glass-forming alloys involved abrasion, adhesion, and oxidation. The differences in hardness, free volume, and brittleness in different states significantly affected the friction and wear behaviors of the glass-forming alloys. [source] Nanocomposite Hard Coatings: Deposition Issues and Validation of their Mechanical Properties,ADVANCED ENGINEERING MATERIALS, Issue 5 2005P. Schwaller Abstract The limitations of conventional coatings due to inferior hardness or poor oxidation stability can be overcome by nanocomposite hard coatings such as nc-TiN/a-SiNx, which consists of nanocrystalline TiN and a non-crystalline tissue phase of SiNx which are mutually immiscible. The properties of nanocomposite coatings, especially their increased hardness, can be explained by their nanostructure, which leads to a maximum hardness at typically 80 atomic percent of the crystalline phase. We show that enhanced hardness can only be attained when the silicon nitride phase is sufficiently nitrided. The accurate and reliable measurement of the hardness and elastic modulus requires the use of appropriate nanoindentation equipment and a careful tip correction with periodical validation. It is shown that for a correct hardness determination of a few microns thick nanocomposite coatings, an indentation depth of 100,nm is sufficient. The maximum hardness of our nc-TiN/a-SiNx coatings deposited by a hybrid UBM/arc-PVD process is about 40,GPa. This value represents a global hardness value, due to the nanocomposite structure there may be a local hardness variation of about ±10,%. [source] Aliovalent Substitutions in Olivine Lithium Iron Phosphate and Impact on Structure and PropertiesADVANCED FUNCTIONAL MATERIALS, Issue 7 2009Nonglak Meethong Abstract Lithium transition metal phosphate olivines are enabling a new generation of high power, thermally stable, long-life rechargeable lithium batteries that may prove instrumental in the worldwide effort to develop cleaner and more sustainable energy. Nanoscale (<100,nm) derivatives of the olivine family LiMPO4 (M,=,Fe, Mn, Co, Ni) are being adopted in applications ranging in size scale from hybrid and plug-in hybrid electric vehicles to utilities-scale power regulation. Following the previous paradigm set with intercalation oxides, most studies have focused on the pure ordered compounds and isovalent substitutions. In contrast, even the possibility for, and role of, aliovalent doping has been widely debated. Here, critical tests of plausible defect compensation mechanisms using compositions designed to accommodate Mg2+, Al3+, Zr4+, Nb5+ ions on the M1,and/or M2 sites of LiFePO4 with appropriate charge-compensating defects are carried out, and conclusive crystallographic evidence for lattice doping, e.g., up to at least 12 atomic percent added Zr, is obtained. Structural and electrochemical analyses show that doping can reduce the lithium miscibility gap, increase phase transformation kinetics during cycling, and expand Li diffusion channels in the structure. Aliovalent modifications may be effective for introducing controlled atomic disorder into the ordered olivine structure to improve battery performance. [source] Nanoanalysis by a high-resolution energy filtering transmission electron microscopeMICROSCOPY RESEARCH AND TECHNIQUE, Issue 3 2004Masanori Mitome Abstract An energy-filtering transmission electron microscope with 300 kV acceleration voltage was developed and the spatial resolution of elemental distribution images was improved. Observing oxygen monolayers in Al11O3N9, it was shown that the actual resolution attained is up to 0.5 nm. Surface plasmon loss images of silver particles were taken with a resolution of better than 0.4 nm. Furthermore, the sensitivity is sufficiently high to distinguish indium content differences of 2.5 atomic percent in InxAl1-xAs. This performance is good enough to analyze elemental distribution with atomic-level resolution. Furthermore, since analysis with the energy-filtering microscope is easy and practical, nanoanalysis may come into wide use not only in academic fields but also in industry. Microsc. Res. Tech. 63:140,148, 2004. © 2004 Wiley-Liss, Inc. [source] Oxygen induced band-gap reduction in ZnOxSe1,x alloysPHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 3 2004W. Shan Abstract The effect of alloying a small amount of ZnO with ZnSe on the electronic band structure has been studied. Optical transitions in MBE-grown ZnOxSe1,x epitaxial films (0 , x , 0.0135) were investigated using photoreflectance and photoluminescence spectroscopies. The fundamental band-gap energy of the alloys was found to decrease at a rate of about 0.1 eV per atomic percent of oxygen. The pressure dependence of the band gap was also found to be strongly affected by the O incorporation. Both effects can be quantitatively explained by an anticrossing interaction between the extended states of the conduction band of ZnSe and the highly localized oxygen states located at approximately 0.22 eV above the conduction band edge. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] |