Papers by Author: Kiyonori Suzuki

Abstract: It is well known that catalytic additives and mechanical milling are effective in improving hydrogen desorption kinetics of MgH2. In this study, the effect of catalytic additives including BaCa1-xNdxO3-δ (BCN) on the desorption behavior of MgH2 was investigated. It was found that BCN can improve the desorption kinetics, but not as effective as other known additives such as Nb2O5. The effect of milling temperature was also studied. It was found that the cryogenic milling is not as effective as room temperature milling primarily due to the inhomogeneous particle size distribution.

Abstract: Zn1-xCoxO thin films ( ) have been grown on Si (100) substrates by pulsed laser deposition. The as-prepared films showed paramagnetic characteristics at room temperature, while the films after annealing in a H2 atmosphere exhibited clear ferromagnetic behaviors. Raman scattering has been used to study the influence of the post-deposition H2 annealing on the structural properties and consequently on the magnetic properties of Co-doped ZnO films. It is found that the post-deposition annealing increases defect oxygen vacancies in the host lattice and induces an additional Raman vibration mode. The ferromagnetism of Zn1-xCoxO is believed to be strongly related to the oxygen deficiency in ZnO.

Abstract: The magnetic and optical properties of regioregular poly(3-hexylthiophene)-capped Au nanoparticles (NPs) have been investigated in order to clarify the effectiveness of polythiophene capping on the induction of ferromagnetism in Au. The room-temperature magnetization curve of the polythiophene-capped Au NPs exhibits a clear hysteresis behavior with a spontaneous magnetization of 8.5 x 10-3 emu/g. The average magnetic moment of the surface Au atoms is estimated to be 2.6 x 10-3 B. The ultraviolet-visible spectrum shows a clear sign of the surface plasmon absorbance of metallic Au which reflects the week character of the chemical bond between the Au and S atoms on capping surface. Our results show clearly that Au NPs capped with polythiophene can be ferromagnetic.

Abstract: A physically-based model is proposed for the competitive precipitation of multiple phases (bcc-Fe, Fe3B, Nd2Fe14B, Nd2Fe23B3, NdFe4B4 and Fe2B) from an amorphous Fe-B-Nd matrix. These materials form the basis of a class of nanocomposite hard magnets. The nucleation and growth of the different phases are calculated using computational thermodynamics and kinetics tools with input from a thermodynamic assessment of this system. In some alloy compositions, the phase formation sequence during crystallization shows significant sensitivity to the heating-rate. Model calculations illustrate that this effect cannot be explained by homogeneous nucleation and growth of the phases. The possible role of heterogeneous nucleation is briefly discussed.