Multicomponent 3d transition-metal nanoparticles supported on Al 2 O 3 were prepared using a complex polymerization process and a post H 2 -reduction treatment at 900 °C. Catalysts in a binary system were divided into two groups: single-phase alloys (NiCu and FeNi) and immiscible two-phase mixtures (FeCu and CoCu), whereas ternary (FeNiCu and CoNiCu) and quaternary (FeCoNiCu) catalysts produced single-alloy nanoparticles. The ternary and quaternary alloy catalysts achieved high NO reduction in a stoichiometric NO−CO−C 3 H 6 −O 2 reaction under wet conditions (5% H 2 O), which simulates automotive three-way catalysis (TWC). In contrast, the activity of unary and binary systems of these metal elements significantly deteriorated in the presence of H 2 O. Cu-based metal catalysts are efficient for NO reduction, but they are easily deactivated by oxidation to less active oxides in the presence of O 2 and/or H 2 O. The superiority of the multinary alloy catalysts is a result of the higher stability and regenerability of the metallic Cu species. Therefore, increasing the number of metal elements in alloy nanoparticles can provide a phase stabilization against oxidation under TWC conditions.

Tensile tests of single crystalline and polycrystalline Mg-Y alloys were carried out at room temperature to investigate the in uence of yttrium on activation of slip systems and to clarify the relationship between ductility of magnesium and the activation of slip systems. Tensile directions of single crystals and polycrystals were parallel to (0001) and their rolling direction, respectively. Mg-(0.6-1.1)at%Y alloy single crystals yielded due to the rst order pyramidal slip (FPCS). Yield stress and ductility of Mg-(0.6-1.1)at%Y alloy single crystals were higher than those of pure magnesium. Mg-0.9at%Y alloy polycrystals showed higher ductility than pure magnesium. The number of grains where second order pyramidal slips were activated was the largest in those where non-basal slips were activated in pure magnesium, while those where FPCS were activated increased with increasing strain in Mg-0.9at%Y alloy. High ductility of Mg-0.9at%Y alloy would be caused by activation of FPCS due to yttrium addition.

Single-phase quaternary spinel solid solutions, Cu 0.05 Ni 0.95 Al y Cr 2−y O 4 (0 ≤ y ≤ 2.0), were prepared over the whole range of y by a polymerized complex method to study as platinum group metal-free three-way catalysts (TWC). Most conventional binary and/or ternary spinel oxides lose their NO reduction activity in the presence of water vapor and/or after hightemperature aging. In contrast, the present quaternary system with y = 1.8, which was aged at 900 °C for 25 h, preserved high activity even under a wet gas stream (5% H 2 O) simulating real TWC conditions. Comprehensive structural analyses via X-ray absorption fine structure and Xray Rietveld analysis showed that, in the quaternary system, Cu and Cr prefer to occupy the tetrahedral site and the octahedral site, respectively, whereas Ni and Al are distributed across both sites. The partial replacement of Cr by Al increased the specific surface area from 7 m 2 g −1 (y = 0) to 36 m 2 g −1 (y = 1.8), which is a common feature of the NiAl 2 O 4 -based spinel platform. The replacement also yielded monovalent Cu on the surface, which plays a key role in the catalytic NO reduction via the Mars−van Krevelen mechanism. Cr and Ni are beneficial for promoting CO−H 2 O and C 3 H 6 −O 2 reactions, respectively. A positive synergy between these different functionalities arising from each metal element affords high NO reduction activity under a wet gas stream. Furthermore, single-phase quaternary spinel solid solutions seem to provide an entropy-mediated phase-stabilization effect under stoichiometric TWC conditions where ternary Cu x Ni 1−x Cr 2 O 4 (0 ≤ x ≤ 1.0) solid solutions are less stable and decompose because of the low equilibrium O 2 pressure.

Gold-coated silver nanoplates, when subjected to pulsed laser irradiation, changed their shape from triangular to spherical, accompanied by a shift of their extinction spectra. The simple single crystal structure of the silver nanoplates changed to multiple small crystal domains. The ratio of silver to gold of the particles also changed from 22 : 1 to 4.5 : 1, enabling more silver to be released. As a result, the antibacterial activity of the gold-coated silver nanoplates was significantly increased after pulsed laser irradiation.