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Volume 52, Issue 4
April
Displaying 1-14 of 14 articles from this issue
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Paper
Paper
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Katsuhisa Tanaka, Makoto Katsuta, Seisuke Nakashima, Koji Fujita2005 Volume 52 Issue 4 Pages 221-227
Published: 2005
Released on J-STAGE: April 28, 2006
JOURNAL OPEN ACCESSMagnetic properties have been examined for zinc ferrite nanocrystals synthesized via hydrothermal reaction. The hydrothermal reaction has been carried out at 200°C using an aqueous suspension containing zinc hydroxide and iron hydroxide. X-ray diffraction analysis indicates that the resultant specimens are composed of single phase of ZnFe2O4 independent of the reaction time. The size of crystal, which is smaller than 10 nm, is apt to increase as the reaction time is increased, as revealed from transmission electron micrographs as well as linewidth at half maximum of X-ray diffraction lines. A single phase of ZnFe2O4 is still observed in X-ray diffraction patterns after heat treatment at 300°C in air. The present ZnFe2O4 nanocrystals exhibit high magnetization even at room temperature. The temperature dependence of magnetization manifests superparamagnetic behavior with a blocking temperature of several tens K under external magnetic field of 500 Oe. The magnetization is apt to decrease with a decrease in temperature below the blocking temperature even when field cooling is carried out, suggesting that there is strong magnetic interaction among nanocrystals so that the magnetization of nanocrystals is oriented randomly with each other.View full abstractDownload PDF (871K) -
Tadahiro Wada, Takaomi Toihara2005 Volume 52 Issue 4 Pages 228-232
Published: 2005
Released on J-STAGE: April 28, 2006
JOURNAL OPEN ACCESSIn this study, the tool wear of the (Ti,W)N coated cemented carbide tool, which is a new type coating film, is experimentally investigated in order to clarify the effective tool material for the turning of SCr420H. The main results obtained are as follows: (1) The (Ti,W)N coated cemented carbide has high critical scratch load. (2) In the turning of SCr420H, the wear progress of the (Ti,W)N coated cemented carbide tool is slowest.View full abstractDownload PDF (1112K) -
Mitsuya Hashii, Naoyuki Kanetake2005 Volume 52 Issue 4 Pages 233-238
Published: 2005
Released on J-STAGE: April 28, 2006
JOURNAL OPEN ACCESSThe elemental powders were milled by a dry tumbler ball-mill in the Fe-25 mol% Al system. The change in phase of the powder milled in different milling times and subsequently heat-treated at different temperatures was studied. In the thermal analysis (DSC) of the milled powder, a marked exothermic reaction occurred rapidly after a short milling time 36 ks. No remarkable reaction was observed after a long milling time over 360 ks. The milled and subsequently heat-treated powders consisted of different phases according to the milling time and heat-treatment temperature. A “Milling-Time/Heat-Treatment-Temperature/Phase” diagram was obtained from the phase observation results. A single phase of Fe3Al was formed by milling over 360 ks and annealing at 750 K.View full abstractDownload PDF (574K) -
Keizo Kobayashi, Toshiyuki Nishio, Akihiro Matsumoto, Kimihiro Ozaki2005 Volume 52 Issue 4 Pages 239-242
Published: 2005
Released on J-STAGE: April 28, 2006
JOURNAL OPEN ACCESSTi-10vol%Ti5Si3, Ti-20vol%Ti5Si3 and Ti-30vol%Ti5Si3 were prepared by mixing of Ti powder and Ti5Si3 powder synthesized by self-propagating high-temperature synthesis process. These mixtures were consolidated by a pulsed current sintering in the temperature range 1073-1273 K. The changes in the density, hardness and compressive strength of Ti/Ti5Si3 composites according to the sintering temperature were examined.
In each Ti/Ti5Si3 composites, dense compacts were obtained at high temperature sintering. The reaction between Ti and Ti5Si3 was not observed in this experimental condition. The Ti/Ti5Si3 composite with high hardness and strength was obtained as the amount of Ti5Si3 in the composite increased. The Ti-30vol%Ti5Si3 composite sintered at 1273 K by the pulsed current sintering showed Vickers hardness of 526 Hv and compressive strength of 1776 MPa at room temperature.
In addition, weight gains of Ti/Ti5Si3 composites by the oxidation at high temperature were measured. The weight gains of the Ti/Ti5Si3 composites at 1273 K in the air were 1/3 or less of that of Ti. The obtained Ti/Ti5Si3 composites were lightweight materials suitable for high temperature applications.View full abstractDownload PDF (821K) -
Yukio Makino, Shoji Miyake, Saburo Sano, Bunkei Kyoh2005 Volume 52 Issue 4 Pages 243-246
Published: 2005
Released on J-STAGE: April 28, 2006
JOURNAL OPEN ACCESSDensification behavior and crystallite growth were investigated for alumina-YSZ composites by examining sintering behavior under 28 GHz millimeter-wave radiation. Enhancement of sintering in the intermediate stage by millimeter-wave radiation was suggested from the analysis on densification behaviors for alumina-YSZ composites as well as alumina. These ceramic composites under millimeter-wave radiation have been proved to densify with suppressing crystallite growth of alumina, compared with those by conventional sintering method.View full abstractDownload PDF (412K)
Special Issue: Simultaneous Control of Multiple Properties of Fine Particulate Materials
Summarization
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Mamoru Senna2005 Volume 52 Issue 4 Pages 248
Published: 2005
Released on J-STAGE: April 28, 2006
JOURNAL OPEN ACCESSDownload PDF (116K)
Review
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Kenji Sumiyama, Dong-Liang Peng, Hirohisa Yamada, Takehiko Hihara, Tet ...2005 Volume 52 Issue 4 Pages 249-254
Published: 2005
Released on J-STAGE: April 28, 2006
JOURNAL OPEN ACCESSElectrically charged and neutral clusters whose average sizes ranged from 6 to 16 nm were accelerated and deposited onto the substrate with a bias voltage, Va, using a plasma-gas-condensation cluster deposition system. Fe cluster-assembled films thus obtained have flat and lustrous surfaces, being remarkably prevented from oxidation. With increasing Va, the saturation magnetization, Ms, and packing fraction, P, of these films increase, while the magnetic coercivity, HC, rapidly decreases: Ms = 1.78 Wb/m2, P = 86% of bulk Fe and HC<80 A/m at Va = -20 kV. The electrical resistivity of Fe cluster-assembled film prepared at Va = -20 kV is 0.6-0.8 μΩm (for temperature, T = 20-300 K), which is an order of magnitude larger than that of bulk Fe. These results demonstrate that the dense Fe cluster assembly is a candidate of soft magnetic materials for high frequency uses.View full abstractDownload PDF (1474K)
Paper
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Jin Amagai, Yuzo Kato, Akira Ueki, Noriko Saito, Naoki Ohashi, Hajime ...2005 Volume 52 Issue 4 Pages 255-260
Published: 2005
Released on J-STAGE: April 28, 2006
JOURNAL OPEN ACCESSEffects of CaCO3 powder sizes on syntheses and characteristics of CaZrO3 powders and (Ba,Ca)(Ti,Zr)O3 (BCTZ) ceramics have been examined in a low-temperature co-firing technique. For the solid state reaction between CaCO3 and ZrO2 to synthesize CaZrO3, the calcination temperature is decreased by applying ultra-fine CaCO3 powders. Moreover, the lowering of calcination temperature enabled to obtain highly dispersed CaZrO3 powders with fine grain (80 nm). For the solid state reaction between CaZrO3 and BaTiO3 powder, the intermediate products depend on the initial grain size of CaZrO3 powders (80, 200 and 300 nm), indicating that reaction kinetics is obviously affected by the powder size of CaZrO3. The dielectric constants of BCTZ ceramics more markedly depend on the CaZrO3 powder sizes and the reaction behavior between CaZrO3 and BaTiO3.View full abstractDownload PDF (1237K) -
Kazuharu Iwasaki, Kazuhiro Sakai, Makoto Inoue, Yuichi Sasaki2005 Volume 52 Issue 4 Pages 261-266
Published: 2005
Released on J-STAGE: April 28, 2006
JOURNAL OPEN ACCESSThe amorphous BaTiO3 fine particles were synthesized by the sol-gel method of aqueous solution. The morphology and the structure of the formed particles have been investigating by TEM, SAED, DSC and XRD. The mean size of the particles formed at the aging temperature of 27°C was 27 nm, however those particles were joined each other and the monodispersed particles were not obtained. The only monodispersed particles of 0.1∼1.3 μm diameter were obtained by the synthesis conditions: pH9.0 or the mole ratio of EDTA/(Ba+Ti) = 10.0 of mother liquids. It is assumed that the formation of the monodispersed particles is carried by the dissolution-recrystallization process in the mother liquids. The phase of the produced fine particles was transformed from amorphous to tetragonal BaTiO3 at 600°C.View full abstractDownload PDF (1692K) -
Kouji Tokita, Shigeki Sato2005 Volume 52 Issue 4 Pages 267-270
Published: 2005
Released on J-STAGE: April 28, 2006
JOURNAL OPEN ACCESSBarium titanate (BaTiO3) nano-particles with high crystalinity were synthesized by hydrothermal process using Ba(OH)2 · 8H2O and TiO2 as source materials. The average size of the synthesized BaTiO3 particles decreased as the TiO2 particle size decreased. The amount of hydroxide ions incorporated into the perovskite lattice decreased as the BaTiO3 particle size increased and then became constant above 50 nm. Moreover, the ratio of the c- to a-axis length increased when the BaTiO3 particle size was above 50 nm. Sintered ceramics with a grain size smaller than 100 nm were obtained by using highly crystallized hydrothermal BaTiO3 particles.View full abstractDownload PDF (562K) -
Yasuharu Miyauchi, Tomohiro Arashi2005 Volume 52 Issue 4 Pages 271-275
Published: 2005
Released on J-STAGE: April 28, 2006
JOURNAL OPEN ACCESSThe influence of TiO2 filler particle size on sintering behavior was investigated in glass-ceramics designed for low temperature co-fired ceramics (LTCC). The composition consisted of: 0.15 volAl2O3-0.15volTiO2-0.70vol glass (Sr-Mg-Ca-Si-Al-B-O), with Al2O3 and TiO2 being used as filler. Several average particle sizes of TiO2 were used while the average sizes of the Al2O3 and the glass were kept constant. As the particle size of TiO2 decreased, the sintering temperature increased. The origin of this effect formed the basis for this investigation. The density and crystal phases of the glass ceramics were not affected by a change in the TiO2 particle size. However, a change in viscosity was observed; as the TiO2 average particle size decreased, the viscosity of the glass-ceramics increased. This effect was explained by the ability of the smaller particles to more effectively obstruct glass liquidity.View full abstractDownload PDF (944K) -
Takashi Yamaguchi, Katsuyoshi Kondoh, Tadashi Serikawa, Momoko Henmi, ...2005 Volume 52 Issue 4 Pages 276-281
Published: 2005
Released on J-STAGE: April 28, 2006
JOURNAL OPEN ACCESSCoating technology by using magnesium silicide intermetallics (Mg2Si) was developed to improve the surface properties of magnesium alloys. This is because they have superior corrosion resistance to the conventional stainless steel and high Young's modulus and hardness. In this study, Mg-Si thin film deposited on AZ31 magnesium alloys by using a high frequency sputtering method was examined when employing the sintered Mg2Si bulky materials as sputtering targets. The change in the sputtering Ar gas pressure enables the structure control of Mg-Si thin film; crystal structures at lower pressure and amorphous one over 4 Pa. Some results of SST to evaluate the corrosion resistance indicated that AZ31 substrate with Mg-Si coating showed no damage after 240 h. On the other hand, that with no coating was corroded within only 1 h, and showed remarkably damaged surfaces. Pin on disk type wear test under oil lubricant indicated that a friction coefficient, μ was low and stable in using AZ31 alloy disk specimen coated by Mg-Si film. The disk specimen with no coating showed severely damaged surface including seizure or sticking phenomena with S35C pin specimens. In particular, the amorphous Mg-Si film showed superior anti-seizure properties to the crystalline one because of higher hardness and Young's modulus.View full abstractDownload PDF (1517K) -
Hideki Oginuma, Katsuyoshi Kondoh, Masaki Sumida, Eiji Yuasa2005 Volume 52 Issue 4 Pages 282-286
Published: 2005
Released on J-STAGE: April 28, 2006
JOURNAL OPEN ACCESSMg-Si alloys have high potential as heat resistant light metals because Mg2Si dispersoids exhibit a high melting temperature, low density, low thermal expansion coefficient, and a reasonably high elastic modulus.
In this study, Mg2Si compounds are formed in the solid-state by spark plasma sintering process, in employing the elemental powder mixture of Mg-33.33 mol% Si. The magnesium composite alloys including a large amount of Mg2Si particles were fabricated. The relative density of the composite alloys decreases with increase in the amount of Mg2Si particles because the dispersoids cause not only pores at primary particle boundaries, but poor sinterability between magnesium alloy powder due to their thermal stability. The elastic coefficient, however, increases in increasing the Mg2Si content of the composite alloys.View full abstractDownload PDF (1333K) -
Keijiro Terashita, Nobuyuki Nanba, Takuya Nagato, Susumu Natsuyama2005 Volume 52 Issue 4 Pages 287-292
Published: 2005
Released on J-STAGE: April 28, 2006
JOURNAL OPEN ACCESSA new fluidized bed particle coating equipment has been developed by combining following unique features of two different processing equipments:
1. A fluidized bed processor has ideal particle circulation movement and drying capability.
2. A commuting mill has a good dispersing ability of agglomerated particles.
Using this newly developed fluidized bed processor, we first carried out coating experiments of fine particles under various conditions, and particle size distribution and dissolution profile of coated particles were measured.
Coated particles were compressed into tablets and the dissolution profile of each tablet was also studied.
The above study showed that the newly developed fluidized bed could coat each particle with sharp particle size distribution but without agglomeration. And uniform film layer was obtained.
Moreover, it is confirmed that coated particles can be compressed into tablets without being damaged.View full abstractDownload PDF (1403K)
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