近藤半導体CeT2Al10 (T = Ru, Os)の特異な反強磁性秩序に対するSi置換と一軸圧力の効果

広島大学(Hiroshima University)博士(理学)Doctor of Sciencedoctora

Crystallographic orientation control of pure chromium via laser powder bed fusion and improved high temperature oxidation resistance

This is the first comprehensive study on the development of a cubic crystallographic texture in pure chromium (Cr) manufactured using laser powder bed fusion (LPBF) with different laser energy densities to alter its microstructure and high-temperature oxidation behavior. An increase in the laser energy density led to the formation of a strong crystallographic texture, which was preferentially oriented in the (100) plane, and there were microstructural improvements in the pure Cr. The grain size of the (100)-oriented Cr was larger than that of the randomly oriented Cr. In addition, the high-angle grain boundary and coincident site lattice (CSL) boundary characteristics were altered. The (100)-oriented Cr exhibited a decrease in the oxide thickness that was due to the decrease in the grain boundary density with a larger grain size and an increase in the CSL boundary ratio. In contrast, the Cr with a random texture showed higher oxidation kinetics and spallation of the oxide layer. The oxidation kinetics of the pure Cr manufactured using LPBF obeyed the parabolic rate law. However, the crystal orientation affected the oxidation of the Cr as the (100)-oriented pure Cr displayed a lower parabolic rate constant, indicating that the (100)-oriented Cr was oxidation-resistant. This is the first report to demonstrate the cubic crystallographic texture formation and the improvement of high-temperature oxidation resistance in Cr manufactured using LPBF.Gokcekaya O., Hayashi N., Ishimoto T., et al. Crystallographic orientation control of pure chromium via laser powder bed fusion and improved high temperature oxidation resistance. Additive Manufacturing, 36, 101624. https://doi.org/10.1016/j.addma.2020.101624

Synthesis of a bowl-type dodecavanadate by the coupling reaction of alkoxohexavanadate and discovery of a chiral octadecavanadate

金沢大学理工研究域物質化学系A new route to an alkoxohexavanadate species leads to the isolation of a bowl-type dodecavanadate without a guest molecule in the cavity. The 1D tetravanadate, [V4O11]2-, is a good precursor for the alkoxohexavanadate, [V6O13(OCH3)6]2-, which is then utilized for the [V6 + V6] coupling reaction to form the dodecavanadate, [V12O42]4-, with a capped dichloromethane molecule at the cavity entrance. We also obtained structural information on a newly discovered octadecavanadate, [V18O46(NO3)]5-, in both the solid and solution states through extended X-ray absorption fine structure (EXAFS) studies. The existence of the chiral inorganic species in acetonitrile with double-stranded V8 chains was confirmed through EXAFS oscillations. © 2009 IUPAC