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Volume 54, Issue 1
January
Displaying 1-11 of 11 articles from this issue
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Paper
Paper
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Noboru Shikatani, Tatsuya Misawa, Yasunori Ohtsu, Hiroharu Fujita, Yuj ...2007 Volume 54 Issue 1 Pages 3-9
Published: 2007
Released on J-STAGE: May 15, 2007
JOURNAL OPEN ACCESSWe sintered a material composed of the raw material ZnO, the doping agent Al2O3 for resistivity reduction, and a sintering aid in which TiO2 and CoO are mixed at a predetermined ratio by pulse current sintering at 80 MPa and 1373-1423 K for 10 min, and studied its thermoelectric properties and microstructure. From the microstructures of a sintered material, we confirmed that TiO2 suppresses the grain growth, CoO promotes the grain growth and the development of intergrain neck connections. Because a decrease in resistivity of the material was observed when CoO was added to the specimen, the decrease in resistivity is considered to be caused by intergrain neck connections which seem to form a conduction channel. Moreover, from the analysis of EPMA, Al2O3 was localized in 100ZnO-2Al2O3 (ZA); however, Al2O3 was observed in the entire region of 100ZnO-2TiO2-2CoO-2Al2O3 (ZTCA). From the XRD analysis of these two specimens, the spinel phase of ZnAl2O4, which causes high resisitivity, was more prominent in ZA than in ZTCA. Among the materials studied, ZTCA showed the best thermoelectric properties and a dimensionless figure of merit (ZT) of approximately 0.28 was obtained at 1073 K.View full abstractDownload PDF (2060K) -
Satoshi Hirosawa, Hiroyuki Tomizawa, Katsunori Bekki2007 Volume 54 Issue 1 Pages 10-14
Published: 2007
Released on J-STAGE: May 15, 2007
JOURNAL OPEN ACCESSLa(Fe1-xSix)13 alloys with the NaZn13-type structure were prepared from rapidly solidified ribbons via a short annealing treatment. The rapid solidification process was realized by using a laboratory scale melt-spinning apparatus and a large strip-casting facility. The rapidly solidified ribbons contained a large amount of the NaZn13-type phase together with an α-(Fe-Si) phase and a La-rich phase. The finely dispersed α-(Fe-Si) and La-rich phases readily combine to form the NaZn13-type phase upon a short-time annealing. The magnetic part of the entropy change near the Curie temperature at about 190 K was estimated from magnetization vs. temperature measurements to be about −20 J/K/kg for a field change between zero and one T. The process developed in this work may be applied to a mass production of thin slabs of La(Fe1-xSix)13 alloys of thickness around 100μm as the starting material for production of coarse powder of hydrogenated La(Fe1-xSix)13 alloy.View full abstractDownload PDF (1312K) -
Shigeru Katsuyama, Hiroshi Nishimura2007 Volume 54 Issue 1 Pages 15-19
Published: 2007
Released on J-STAGE: May 15, 2007
JOURNAL OPEN ACCESSWe have prepared a sintered CeFe3CoSb12-FeSb2 composite and investigated the Seebeck coefficient, electrical resistivity, and thermal conductivity in order to estimate the corresponding figure of merit. The thermal conductivity of the composite whose molar ratio of CeFe3CoSb12 to FeSb2 is 0.9:0.1 is as large as that of CeFe3CoSb12 while the lattice contribution of the thermal conductivity of the composite is somewhat smaller than that of CeFe3CoSb12, which is ascribed to the enhancement of the phonon scattering caused by the additive material. With increasing FeSb2 content the thermal conductivity of the composite is enhanced. The Seebeck coefficient and electrical resistivity of the composite generally decrease with increasing FeSb2 content. These behaviors in the thermal conductivity, Seebeck coefficient and electrical resistivity with increasing FeS2 content is considered to be ascribed to the physical properties of FeSb2. As a result, the composite whose molar ratio of CeFe3CoSb12 to FeSb2 is 0.9:0.1 shows somewhat larger figure of merit than CeFe3CoSb12 in the whole temperature range from 373K to 773K.View full abstractDownload PDF (701K)
Special Issue:Synthesis of Powder Materials
Summarization
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Yuichi Shimakawa2007 Volume 54 Issue 1 Pages 22
Published: 2007
Released on J-STAGE: May 15, 2007
JOURNAL OPEN ACCESSDownload PDF (109K)
Memorial Lecture of JSPM Award
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Takamasa Ishigaki2007 Volume 54 Issue 1 Pages 23-31
Published: 2007
Released on J-STAGE: May 15, 2007
JOURNAL OPEN ACCESSSynthesis of functional nano-structured powders has been developed through the reactive thermal plasma processing. Spherical carbon powders, such as phenolic resin, glassy carbon and graphite powders, were treated in reactive thermal plasma. Crystallinity, chemical composition, and surface morphology were changed in plasma-treated carbon powders depending on the plasma conditions. Plasma-treated powders were applied to the anode of lithium-ion rechargeable battery, and improvement of the discharge capacity and the discharge efficiency was recognized. Also, the synthesis of nano-size titanium oxide powders has been performed by the oxidation of solid and liquid precursors. Plasma-synthesized TiO2 nano-particles showed the different phase preference from those synthesized by conventional wet processes. The nano-size particles of high crystallinity and non-equilibrium chemical composition were formed by one-step processing.View full abstractDownload PDF (1869K) -
Masato Kakihana2007 Volume 54 Issue 1 Pages 32-38
Published: 2007
Released on J-STAGE: May 15, 2007
JOURNAL OPEN ACCESSThe "polymerizable complex (PC)" method has been developed to prepare copper based high-Tc superconductors with outstandingly high purity, photocatalysts for water decomposition with high activity and phosphor materials with excellent emission intensities. The PC method is based upon formation of metal complexes and subsequent polyesterification between a hydroxy-caroboxylic acid such as citric acid and a glycol such as propylene glycol, keeping metal species homogeneous on the molecular scale inside the polyester resin precursor. The PC method is also an efficient methodology for testing promising compounds with less tailoring efforts of synthesis for each candidate; a scheme to search for potential phosphors has been demonstrated as a representative example.View full abstractDownload PDF (987K)
Paper
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Norio Kobayashi, Yuji Kawakami, Keiji Kamada, Ji-Guang Li, Takayuki Wa ...2007 Volume 54 Issue 1 Pages 39-43
Published: 2007
Released on J-STAGE: May 15, 2007
JOURNAL OPEN ACCESSSpherical submicron copper particles were synthesized through evaporation and subsequent condensation of copper powders in Ar-H2 thermal plasma. Copper powders of ∼40μm in size injected into the plasma, evaporated instantly and fine particles were formed through homogeneous nucleation and subsequent heterogeneous condensation. Particle size and the distribution in the synthesized powders were changed depending on the powder feed rate. Formation of submicron size spherical powders attributed to a significantly high degree of supersaturation in a vapor phase. Particle sizes of the as-produced powders range from submicron to several tens of micrometers. A simple sedimentation treatment was successfully applied to separate the as-formed powders with alcohol solvent to give uniform spherical submicron-size particles with monomodal size distributions. Cu-W composite powders were synthesized through the Ar-H2 plasma treatment of Cu-WO3 composite powders. The starting temperature of shrinkage was made significantly higher than pure Cu powders by mixing with several wt% of W.View full abstractDownload PDF (1836K) -
Yoshihito Suzuki, Masato Kakihana, Yasuo Shimomura, Naoto Kijima2007 Volume 54 Issue 1 Pages 44-47
Published: 2007
Released on J-STAGE: May 15, 2007
JOURNAL OPEN ACCESSCa3Sc2Si3O12:Ce3+ is a green emission phosphor, which can be excited by blue light. This compound may find application as the green component of a white lamp based on downconversion of blue light of LED excitation. Although the use of single-phase Ca3Sc2Si3O12:Ce3+ results in an increase in the materials fluorescence intensity, Sc2O3 has low chemical reactivity and remains in the mixture as an unreacted impurity.
A polymerizable complex method based on polyester formation between metal-citricacid complexes and propylene glycol was applied to synthesis Ca3Sc2Si3O12:Ce3+.
The Ca3Sc2Si3O12:Ce3+ contained only trace of Sc2O3 and showed over twice fluorescent intensity than when compared than with that of the solid state reaction samples.View full abstractDownload PDF (588K) -
Satoshi Ohara, Naoki Hayashi, Jing Zhang, Mitsuo Umetsu, Takashi Naka, ...2007 Volume 54 Issue 1 Pages 48-52
Published: 2007
Released on J-STAGE: May 15, 2007
JOURNAL OPEN ACCESSWe propose a new method to synthesize organic-inorganic hybrid nanoparticles using supercritical hydrothermal synthesis. By introducing organic species, e.g., carboxylic acids, during supercritical hydrothermal synthesis, CeO2 nanoparticles whose surface was chemically bonded with organic molecules were synthesized. Particle size was about 5nm and its particle size distribution was very narrow. The hybrid nanoparticles were dispersed perfectly in organic solvent. After the drying of this colloid, we obtained self-assembly structure of nanocrystals.View full abstractDownload PDF (827K) -
Kengo Oka, Masaki Azuma, Yasuo Narumi, Koichi Kindo, Naoaki Hayashi, Y ...2007 Volume 54 Issue 1 Pages 53-57
Published: 2007
Released on J-STAGE: May 15, 2007
JOURNAL OPEN ACCESSMagnetic and electrical properties of InFe2O4 were investigated. InFe2O4 belongs to the RFe2O4 family where R is trivalent cation (R= In, Yb, Lu, Er, or Y). In the rhombohedral crystal structure of this compound, the double layers of FeO5 bipyramids make two-dimensional triangular lattices and are separated by RO6 octahedra. Since the numbers of Fe2+ and Fe3+ ions are equal in the triangular lattice, the coexistence of charge and magnetic frustrations is expected. We succeeded in preparing high-quality InFe2O4 samples by a solid state reaction from In2O3, Fe and Fe2O3 in a vacuum sealed tube. A small amount of Fe3O4 was magnetically separated. The dielectric constant, magnetic susceptibility, high-field magetization, Mössbauer spectroscopy, and the specific heat data suggested that charge and ferrimagnetic ordering took place simultaneously at 240K in this compound.View full abstractDownload PDF (670K) -
Masanori Kawai, Takashi Saito, Naoaki Hayashi, Masaki Azuma, Mikio Tak ...2007 Volume 54 Issue 1 Pages 58-63
Published: 2007
Released on J-STAGE: May 15, 2007
JOURNAL OPEN ACCESSBaFe6-xMnxO11 (x=2.0, 3.0 and 3.5) and SrFe3Mn3O11 were prepared by high-pressure method, and their crystal structures and physical properties were investigated. The materials crystallize in R-type hexagonal ferrite structure, in which Fe3+ ions mainly occupy B(2) and B(3) sites, while Mn ions mainly occupy B(1) site. The compounds show Collinear Gorter-type ferrimagnetic structure, and saturation magnetization and Curie temperature decrease with increasing x. They also show Arrhenius-type semiconducting behaviors.View full abstractDownload PDF (967K)
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