Ryo Kasuya

Synthesis of submicron sized Fe20Ni80 particles and their magnetic properties

Fe–Ni alloy nanoparticles were synthesized by polyol process using hydrazine as a reduction assist reagent. Particle size, crystallite size, and crystal phases varied with the type of polyol. The saturation magnetizations of the as-synthesized Fe–Ni particles synthesized in ethylene glycol (EG) and 1-heptanol were similar to the bulk and were 73 emu/g and 83 emu/g, respectively. On the other hand, the coercivities of the same were 41 and 123 Oe. The coercivity of the Fe–Ni particles synthesized in EG decreased to 27 Oe after heat treatment. Though the magnetic properties were very similar irrespective of the polyol used in this study, the Mossbauer spectroscopic measurements revealed that Fe–Ni particles with single permalloy phase was synthesized only when EG was used.

Synthesis and magnetic properties of platelet Fe–Co particles

The synthesis scheme for hexagonal shaped Fe–Co platelets with magnetic properties comparable to the bulk is reported for the first time. The hexagonal Fe–Co platelets with the size of about 8u2002μm and an aspect ratio of about 5.4 were prepared by reducing the platelet shaped intermediate obtained in ethylene glycol-metal salts-sodium hydroxide system. The saturation magnetization and coercivity of the Fe–Co hexagonal platelets obtained by reducing the solid intermediate at 673 K in hydrogen atmosphere were above 220 emu/g and 25 Oe, respectively. Since the use of such particles in high frequency applications demand further reduction in size and increment in aspect ratio, a synthesis scheme for particle morphology control was devised. The proposed synthesis scheme using nucleating agents clearly demonstrated that the shape, size, and aspect ratio of the platelets can be controlled freely. Consequently, platelets with elongated shape and thickness of about few hundred nanometers were produced. Though further...

Potential of sub-micron-sized Fe-Co particles for antenna applications

High frequency properties of (a) as-synthesized and (b) flattened by ball milling Fe-based alloys particles and their potential as antenna materials is reported. The high frequency properties of Fe-Co nanoparticles exhibited a resonance peak in the range of a few gigahertz (GHz), and the resonance peak shifted to a higher region for decreasing particle size. However, magnetic permeability was not high enough to be used as high performing electromagnetic wave absorbers. On the other hand, the permeability of Fe-Ni particles at 1u2009GHz was 2.5 and the magnetic loss was 0.36. However, permeability was enhanced to a value of more than 3 and the magnetic loss decreased by more than half, when the dispersibility and planular aggregates were realized through ball milling. Additional experiments suggested that the particle aggregation had greater influence in the high frequency properties than the composition and magnetic properties. Similarly, when Fe50Co50 particles were also subjected to ball milling, their magn...

Dissolution Process of Palladium in Hydrochloric Acid: A Route via Alkali Metal Palladates

To improve the safety of the Pd recovery processes that use toxic oxidizers, dissolution of Pd in hydrochloric acid with alkali metal palladates was investigated. Alkali metal palladates were prepared by calcining a mixture of Pd black and alkali metal (Li, Na, and K) carbonates in air. Almost the entire amount of Pd was converted into Li2PdO2 after calcination at 1073xa0K (800xa0°C) using Li2CO3. In contrast, PdO was obtained by calcination at 1073xa0K (800xa0°C) using Na and K carbonates. Our results indicated that Li2CO3 is the most active reagent among the examined alkali metal carbonates for the formation of palladates. In addition, dissolution of the resulting Li2PdO2 in HCl solutions was evaluated under various conditions. In particular, Li2PdO2 rapidly dissolved in diluted (0.1xa0M) HCl at ambient temperature. Solubility of Pd of Li2PdO2 was found to be 99xa0pct or larger after dissolution treatment at 353xa0K (80xa0°C) for 5xa0minutes; in contrast, PdO hardly dissolved in 0.1xa0M HCl. The dissolution mechanism of Li2PdO2 in HCl was also elucidated by analysis of crystal structures and particulate properties. Since our process is completely free from toxic oxidizers, the dissolution process via alkali metal palladates is much safer than currently employed methods.