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Volume 51, Issue 9
Displaying 1-12 of 12 articles from this issue
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Takaaki Tanaka, Tomohiro Inoue, Hirofumi Inoue, Harushige Tsubakino2004 Volume 51 Issue 9 Pages 641-645
Published: September 15, 2004
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSEffect of 5-30 mol% alumina addition on the tetragonal(T)-to-monoclinic(M) (Martensitic) phase transformation in zirconia-2 and 3 mol% yttria ceramics was investigated. Powders were compressed at 100MPa, and sintered at 1923 K for 54ks. The sintered specimens were aged at 573 K. Mean grain sizes were increased by alumina addition. The amount of expansion and contraction during heating and cooling accompanied with transformation were increased by the addition of alumina. The amount of transformation increased with aging time as a sigmoidal curve and the curve sifted to shorter aging time by the addition of alumina. In higher alumina, long time was required for saturation in transformation, although the transformation started occurred earlier. Aged 2Y specimen has a texture of (111)M, while in the alumina added specimen such tendency became to be weak. AFM observations show that, after aging in 3Y-5A specimen, the transformation accompanied by aging time developed in the various directions with many branch compared with those in 3Y.View full abstractDownload PDF (3221K) -
Satoshi Masuda, Kenta Takagi, Yang-Sheng Kang, Akira Kawasaki2004 Volume 51 Issue 9 Pages 646-654
Published: September 15, 2004
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSGermanium spherical particles were prepared by pulsed orifice ejection method. The apparatus was divised for ejecting molten droplet from a small orifice by a reciprocating action of a rod given by piezoelectric actuator. Germanium particles with diameter of several hundreds micrometer could be formed by optimizing process parameters of feeder cross-section area, rod position, supplied pressure and rod displacement. The obtained particles were polycrystal and had microstructure derived either from dendritic growth at a high undercooling or lateral growth at a low undercooling. The latter particles exhibited smaller number of grains than the former ones, and these grain boundaries were twin planes. Finally, solidification mechanisms for the particles were estimated.View full abstractDownload PDF (8042K) -
Part 1, Formation of Amorphous Materials and Their lon Conducting PropertiesNobuya Machida, Naoko Tomei, Toshihiko Shigematsu2004 Volume 51 Issue 9 Pages 655-661
Published: September 15, 2004
Released on J-STAGE: December 04, 2009
JOURNAL FREE ACCESSSilver-ion-conducting amorphous materials in the system AgI-Ag2WO4 were prepared by use of a high-energy ball-milling process. The amorphous materials were obtained over the wide composition range of 30 to 70 mol% AgI content. The composition range in which the amorphous materials were obtained by the ball-milling process was much wider than the glass-forming region by conventional melt-quenching methods. Raman spectra revealed that the tungsten ions in the amorphous samples were octahedrally coordinated by oxygens as in crystalline α-Ag2WO4. The silver-ion conductivities of the obtained amorphous materials increased with an increase in the AgI content. The amorphous 70AgI-30Ag2WO4(mol%) sample showed the maximum conductivity 1.8×10-2Scm-1 at 298 K among the amorphous samples obtaining by the ball-milling process.View full abstractDownload PDF (545K) -
Part 2, Vitrification Process by the Ball MillingNobuya Machida, Naoko Tomei, Toshihiko Shigematsu2004 Volume 51 Issue 9 Pages 662-667
Published: September 15, 2004
Released on J-STAGE: December 04, 2009
JOURNAL FREE ACCESSVitrification process induced by a ball milling was investigated for silver-ion-conducting materials in the system AgI-Ag2WO4. The amorphous materials were obtained over the wide composition range of 30 to 70mol%AgI content. The silver-ion conductivities of a ball-milled sample showed the maximum at a milling time at which the sample was composed of an amorphous phase and a-Ag2WO4 crystalline phase. This result suggested that the amorphous phase was containing a large amount of AgI content and the amorphous phase was a high ion conductive phase. The maximum conductivity 4.8×10-2 Scm-1 at 298 K was observed for the 70AgI⋅0Ag2WO4(mol%) sample ball-milled for 20 h. This conductivity was higher than that of the completely amorphous sample with the same composition.View full abstractDownload PDF (567K) -
[in Japanese]2004 Volume 51 Issue 9 Pages 670
Published: September 15, 2004
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSDownload PDF (76K) -
Masahiko Abe, Hideki Sakai2004 Volume 51 Issue 9 Pages 671-679
Published: September 15, 2004
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSMost of chemical reactions proceed at the interface between two different phases except some gas and liquid phase reactions. The precise control of the interfaces thus allows us to tune the microstructure and properties of materials obtained. In this report, preparation methods of nano-functional powders utilizing interfacial reactions are described. First, a novel preparation method of titanium boride powders by tuning solid/solid interface is described. Preparations of silica nanoporous materials and polystyrene latex particles utilizing nano-tuned liquid/liquid interfaces are also described.View full abstractDownload PDF (6758K) -
Takao A. Yamamoto, Takuya Kinoshita, Satoshi Seino, Yohei Otome, Takas ...2004 Volume 51 Issue 9 Pages 680-684
Published: September 15, 2004
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSA composite nanoparticle material was synthesized by gamma-ray irradiation of an aqueous solution containing gold ions and dispersing iron-oxide nanoparticles. Gamma-ray irradiation induces reduction of gold ions in the solution to form metallic gold, which are stabilized at the surface of iron-oxide particles. TEM observation indicated that many gold grains of 5 run surround each iron oxide particle. A reddish color due to the surface plasmon resonance of nano-sized gold was seen in an aqueous dispersion of the composite particles and attracted by a magnet, which indicates a connection of gold and iron-oxide in the nanoscale. The surface of gold in the composite particles was found reactive with the mercapto group and to adsorb glutathione and two amino acids possessing sulfur preferably out of seventeen amino acids. The iron oxide surface was substantially covered up with gold grains grown from the seed grains initially deposited by the gamma-rays. The synthesis procedure, characterization, and the tests of the molecule adsorption are described.View full abstractDownload PDF (3303K) -
Kenji Sumiyama, Ryoji Katoh, Takehiko Hihara, Dong-Liang Peng2004 Volume 51 Issue 9 Pages 685-690
Published: September 15, 2004
Released on J-STAGE: December 04, 2009
JOURNAL FREE ACCESSA plasma-gas condensation cluster deposition system with two sources has been applied for preparing Co/Si clusters assemblies. When a separation plate is inserted between two glow-discharge-rooms, a mixture of Co and Si clusters is obtained: small Co clusters are distributed at random, while the Si clusters are aggregated to form large secondary particles. Without a separation plate, on the other hand, core-shell clusters are obtained: a Co core is covered by small Si crystallites. The magnetization measurement at 5 K shows that the magnetic coercive force of Co/Si cluster assemblies is much smaller than that of Co cluster assemblies. Since the Si shell prevents Co cluster surfaces from their oxidation, such core-shell clusters will be used as building blocks for novel nano-structure-controlled materials.View full abstractDownload PDF (3580K) -
Ryohei Kobayashi, Satoshi Sugimoto, Toshio Kagotani, Koichiro Inomata, ...2004 Volume 51 Issue 9 Pages 691-697
Published: September 15, 2004
Released on J-STAGE: November 19, 2010
JOURNAL FREE ACCESSThe Aerosol Deposition Method (ADM) has the possibility for fabrication of thick films at a high deposition rate at room temperature and under low vacuum. Therefore, Ni-Zn ferrite thick films, which possess high permeability at high frequencies, deposited by ADM are expected to be applied as noise suppressors in the quasi-microwave band. This paper describes the preparation and the high frequency properties of Ni-Zn-Cu ferrite thick films deposited by ADM. The powder for ADM was the calcined Ni-Zn-Cu ferrite powder with composition Ni0.25Zn0.65Cu0.12Fe1.98O4 prepared by the usual ceramics technique. The film with thickness of 10.7μm was obtained by the deposition for 4min and the deposition rate was estimated as 2.8μm/min. The relative density of the films was over 90%. The saturation magnetization of film after annealing at 1200°C was 6.33×10-5 Wb⋅m/kg and the coercvity was 0.94kA/m. These values were approximately equal to the values of the sintered body made from the powder. The maximum values of μr′ and μr″ were 200 and 70, respectively. The microwave absorption capabilities estimated by the product of μr″ and f (μr″⋅f) was 28 GHz (at 1 GHz) with the film annealed at 1200°C and this value was 75% larger than Fe-Si-Al flakes-polymer composite (16 GHz at 1 GHz), which is now used as a noise suppressor.View full abstractDownload PDF (583K) -
Futoshi Kuniyoshi, Koji Nakahara, Yuji Kaneko2004 Volume 51 Issue 9 Pages 698-702
Published: September 15, 2004
Released on J-STAGE: December 04, 2009
JOURNAL FREE ACCESSThe theoretical value of the maximum energy products of the Nd2Fe14B compound is calculated to be 512 kJ/m3. Day and day, every researcher investigates to achieve higher maximum energy products. In order to obtain realize this theme, not only improving on alignment of the 2-14-1 grains, but also increasing the coercive force is very important. So, we have been investigating on controlling the microstructure to be fine with an excellent alignment.
As a result, we have succeeded in developing higher performance magnets having Br=1.533 T, HcJ=784kA/m, (BH)max=460kJ/m3. New techniques to achieve at this record are as follows; (1) Reduction of impurities such as oxygen, (2) Improvement of microstructure of the strip cast alloy, (3) Development of alignment method "Inclined magnetic pulsing".View full abstractDownload PDF (1904K) -
Computer Simulation vs. Experimental ObservationsSatoshi Kawamura, Koichi Haneda2004 Volume 51 Issue 9 Pages 703-707
Published: September 15, 2004
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSA computer simulation has been made for a calculation of technical magnetization curves of magnetic small particles in nanometer scale by assuming surface anisotropy acting in addition to existing magneto-crystalline anisotropy in bulk (a particle body). A particle shape modeled is a cylinder, in which a variable particle size of 30, 40, 50 and 60 rim in diameter with a fixed height of 30 nm for each is considered. Micro-magnetic calculations, based on Landau-Lifshitz-Gilbert equation, indicate an enhanced coercivity for a magnetic single-domain particle with the smaller particle size and also with the stronger surface anisotropy acting there, in accord with the existing coercivity data for various materials in small particle forms.View full abstractDownload PDF (365K) -
Keishi Sato, Kenji Kamishima, Koichi Kakizaki, Nobuyuki Hiratsuka2004 Volume 51 Issue 9 Pages 708-712
Published: September 15, 2004
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSPolycrystalline Cu1-xFe2+xO4(x=0, 0.25, 0.50, 0.75, 0.90) samples with spinel structure were prepared by the conventional ceramic process. The samples were sintered in N2at 1100-1400°C for 2 hours. The resistivity of all the samples is in 10-2 10Ωcm, which is low as a ferrite. This originates in the hopping conduction between Cu1+ and Cue2+, and between Fe2+ and Fe3+ in all the samples. MR ratio at room temperature in Cu0.50Fe2.50O4 became maximum 10.4%. This value is large twice compared with that of Fe3O4 reported before. The curves of MR and magnetization of Cu0.05Fe2.50O4 have correlation, in which resistance decreases as magnetization increases. The MR effect is coused by magnetic scattering.View full abstractDownload PDF (1663K)
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