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Volume 55, Issue 4
April
Displaying 1-8 of 8 articles from this issue
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Paper
Paper
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Kiyotaka Katou, Tadasi Asahina, Tsutomu Sonoda, Akihiro Matsumoto, Koj ...2008 Volume 55 Issue 4 Pages 233-238
Published: 2008
Released on J-STAGE: October 22, 2008
JOURNAL OPEN ACCESSTo improve sintering-ability on MIM aluminum compact, liquid phase sintering were tried by addition of elemental powder. Mixed powders which were composed of 1 mass.%Si or 4 mass.%Cu powder and pure Al powders (average particle size: 35μm, 20μm, 11μm) were starting materials. Then, sintered Al-1Si and Al-4Cu compacts were prepared by MIM. The densities, microstructures and tensile properties at room temperature were investigated for obtained compacts. The results obtained were summarized as follows. (1) Regardless of Al powder size, the addition of these elemenal powders widely enhanced the density of sintered Al compacts. Using the roughest Al powder of 35μm, the relative density of the pure-Al compact was only 66%, while that of both the Al-1Si and Al-4Cu compacts went up to 89%. When 11μm Al powder was used, both the Al-1Si and Al-4Cu compacts had the relative density more than 95%. (2) The tensile properties of Al-1Si compacts were close to those of annealed wrought pure-Al. The Al-4Cu compact showed lower elongation but higher tensile strength than the Al-1Si compact.View full abstractDownload PDF (1457K) -
Yuji Kawakami, Toru Tanaka, Takashi Enjoji, Kazuki Takashima, Masaaki ...2008 Volume 55 Issue 4 Pages 239-243
Published: 2008
Released on J-STAGE: October 22, 2008
JOURNAL OPEN ACCESSIn order to improve wear properties of austenite stainless steel, we applied powder composite process to obtain thick hard layer on stainless steel. The raw alloy powder was prepared by planetary ball milled tungsten carbide (WC) powder and SUS316L stainless steel powder. Sintering process was performed by pulsed current sintering (PCS) method. Wear properties were evaluated by pin-on-disk wear testing machine, and a remarkable improvement was confirmed in wear resistance property. In this investigation, we applied micro-sized testing technique to evaluate mechanical properties of WC layer and Stainless interface of layer. Micro-sized cantilever specimens with a size of 10×20×50μm3 were prepared by focused ion beam machining system. Micro-sized bending tests were successfully completed using a mechanical testing machine for micro-sized specimens. The maximum bending stresses were different for stainless matrix, interface layer, and SUS/WC composite. Ductile rapture surface was observed at stainless matrix, and brittle rapture surfaces at interface of WC layer and Stainless layer and SUS/WC composite layer.View full abstractDownload PDF (948K) -
Keitaro Enami, Yukitoshi Fujita, Yoshitsugu Motoe, Masaki Ohara, Takan ...2008 Volume 55 Issue 4 Pages 244-249
Published: 2008
Released on J-STAGE: October 22, 2008
JOURNAL OPEN ACCESSThe new bulk mechanical alloying process (Equal Channel Angular Bulk Mechanical Alloying process: ECABMA) was developed in this research. Magnesium alloy chip (AM60) mixed with 5-weight percent titanium powder was processed into a magnesium composite billet via ECABMA process. The magnesium composite billet was extruded into round bar, and several mechanical properties were investigated. It was found that the ECABMA process was effective for the mechanical fragmentation of the magnesium chip and titanium powder into small pieces and the uniform mixture of their input materials. The extruded composite had micro-scale magnesium grains finely dispersed with refined titanium powders. It had 370 MPa-0.2% proof stress, 400 MPa-tensile strength and 10%-elongation at room temperature. The ECABMA process was effective to increase 0.2% proof stress due to the grain refinement via dynamic recrystallization.View full abstractDownload PDF (1451K)
Special Issue:Highly-Ordered Structural Assembly Materials
Summarization
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Junichi Hojo2008 Volume 55 Issue 4 Pages 252
Published: 2008
Released on J-STAGE: October 22, 2008
JOURNAL OPEN ACCESSDownload PDF (124K)
Review
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Chigusa Sato, Mohamed Ahmed El-Toni, Shu Yin, Tsugio Sato2008 Volume 55 Issue 4 Pages 253-258
Published: 2008
Released on J-STAGE: October 22, 2008
JOURNAL OPEN ACCESSAlthough nanoparticles of semiconductors are used as inorganic UV-shielding materials, the comfort of nanoparticles are modest because of their agglomeration. In order to fabricate UV-shielding materials with better comfort, calcia-doped ceria (Ce0.8Ca0.2O1.8) nanoparticles were coated on plate-like titanate (lepidocrocite type K0.8Li0.27Ti1.73O4), 10-20μm in diameter. Such panoscopic assembling combined nanoparticles with microparticles successfully improved the comfort of the product when wearing it on the skin without compromising the UV-shielding ability, meanwhile greatly reducing the oxidation catalytic activity, resulting in the fabrication of safe, comfort and high performance UV-shielding material.View full abstractDownload PDF (1400K)
Paper
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Miki Inada, Kei Mizue, Junichi Hojo2008 Volume 55 Issue 4 Pages 259-262
Published: 2008
Released on J-STAGE: October 22, 2008
JOURNAL OPEN ACCESSRutile TiO2 nanoparticles were synthesized by self-hydrolysis of TiOCl2. Rutile phase was detected by XRD at 50°C. As the reacting temperature became higher, the XRD peaks of anatase appeared and the peak intensity of both phases became larger. The roundish agglomerates surrounded by acicular particles were observed by SEM at 50°C and acicular particles grew with elevating temperature. These results indicate that the crystal growth of rutile was promoted at high temperatures. When the pH value of starting solution became lower by addition of HCl, only rutile phase was detected by XRD even at high temperatures. This is because the deprotonation was suppressed under low pH value, leading to predominant formation of rutile. In this study, we obtained small acicular particles of rutile crystalline by addition of HNO3.View full abstractDownload PDF (1101K) -
Kimitoshi Sato, Ji-Guang Li, Hidehiro Kamiya, Takamasa Ishigaki2008 Volume 55 Issue 4 Pages 263-269
Published: 2008
Released on J-STAGE: October 22, 2008
JOURNAL OPEN ACCESSDispersion behavior of aqueous suspensions of TiO2 nanoparticles were investigated by putting polyacrylic acids, PAA, with various molecular weights ranging from 1200 to 30000. Suspensions with solid fraction of 15 vol% were prepared by ultrasonication and milling with 5-mm balls. The dispersion stability was evaluated by sedimentation test and re-dispersion behavior of sediment as well as mesurement of slurry viscosity and aggregate size. The dispersion stability in suspensions after ultrasonic treatment was much higher than those by ball milling. Sediments from ultrasonicated slurry could easily return to the condition of original slurry even by slow stirring, however, sediments from ball milled one could not recover. The optimum molecular weight of PAA for re-dispersion behavior of the sediment by ultrasonic treatment was 8000 g/mol.View full abstractDownload PDF (1379K) -
Kazuhiro Umezawa, Toshio Kimura2008 Volume 55 Issue 4 Pages 270-275
Published: 2008
Released on J-STAGE: October 22, 2008
JOURNAL OPEN ACCESSTextured CaBi4Ti4O15 and SrBi4Ti4O15 ceramics have been prepared by the reactive-templated grain growth process. When slurries for tape casting are prepared using a solvent, binder, and plasticizer, large agglomerates are formed in the slurries by heterocoagulation between Bi2O3 and CaCO3 or SrCO3 particles. These agglomerates melt between 800° and 850°C, and the melt penetrates into surrounding powder layers, leaving large voids. Sintering at high temperatures cannot eliminate these voids, resulting in a low density. Furthermore, the voids disturb the alignment of platelike particles surrounding the voids. The use of dispersant in the preparation of the slurries suppresses the formation of the agglomerates, and dense, highly-textured materials are obtained.View full abstractDownload PDF (1561K)
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