巻号一覧
56 巻, 8 号
August
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研究
研究
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Yoichi Okamoto, Kazuhiko Kato, Kenshiro Asai, Jun Morimoto, Toru Miyak ...2009 年 56 巻 8 号 p. 477-483
発行日: 2009年
公開日: 2009/09/25
ジャーナル オープンアクセスMeasurements of electrical resistivity, thermoelectric power and thermal conductivity were made on sintered SiC semiconductors as a function of both Cu doping concentration (in the range 0.1∼5.0 mass%) and temperature (from room temperature to around 1000 K). In addition, Hall coefficient measurements, X-ray crystallography, EPMA and ICP analysis were performed. The electrical resistivity of n-type (electron) conduction was found to decrease drastically by Cu addition. At a Cu concentration of 0.5 mass% and at around 1000 K, the figure of merit Z was estimated to reach 1.4×10-4 K-1. We conclude that Cu is an effective dopant for reducing electrical resistivity and that sintered SiC/Cu is a promising candidate material for use in conventional thermoelectric power generation in addition to self-cooling devices.抄録全体を表示PDF形式でダウンロード (897K) -
中山 英樹, 岡谷 昌平, 京極 秀樹2009 年 56 巻 8 号 p. 484-489
発行日: 2009年
公開日: 2009/09/25
ジャーナル オープンアクセスThe effect of debinding conditions on the mechanical properties of martensitic stainless steel fabricated by metal injection molding process was investigated. The specimens were made by injecting the mixture of water-atomized powder and polyamide binder into a metallic mold. The compacts were debound in air at a temperature between 533 K and 593 K for 7.2 ks, and then sintered in vacuum at 1573 K and 1623 K for 7.2 ks. The carbon content of the sintered compacts decreased linearly with elevating debinding temperature. This means that the carbon content of sintered compacts can be successfully controlled by the debinding temperature. The mechanical properties of the sintered compacts were strongly affected by strengthening of matrix by carbon and formation of NbC. The sintered compact of 5 μm powder showed ductility, while the sintered compact of 10 μm powder showed high strength.抄録全体を表示PDF形式でダウンロード (829K) -
田中 俊行, 多田 大, 中川 貴, 阿部 正紀2009 年 56 巻 8 号 p. 490-494
発行日: 2009年
公開日: 2009/09/25
ジャーナル オープンアクセスBy "flow tubular reactor method", spherical ferrite nanoparticles with 210±30 nm diameter and composition intermediate between Fe3O4 and γ-Fe2O3 were synthesized from an aqueous solution. A reaction solution of FeCl2 and an oxidizing solution of NaOH and NaNO3 added with sucrose, which shapes spheres, together with ferrite seed crystals, which narrow the size distribution, were mixed and injected into a flow tubular reactor kept at 90°C. The tubular reactor had 3 mm inner diameter, 4 mm outer diameter, and 50 m length. We extended the method to a sequential flow process by which we could fabricate ferrite nanoparticles coated with citrate; the output stream of the tubular reactor containing the as-synthesized ferrite particles was mixed with a trisodium citrate solution, which was then injected into another tubular reactor at room temperature. The obtained ferrite particles coated with citrate were stably dispersed in a distilled water for as long as 24 hours. They were separated from the water by a magnet in two minutes. Since the yield of the flow tubular reactor method is easily multiplied by multiplying the number of the reactors, producing ferrite particles by the flow tubular reactor method will give new impetus to mass production of ferrite particles.抄録全体を表示PDF形式でダウンロード (744K) -
荒牧 正俊, 中尾 友紀, 宇波 繁, 古君 修2009 年 56 巻 8 号 p. 495-501
発行日: 2009年
公開日: 2009/09/25
ジャーナル オープンアクセスIt is well known that the pore morphology has a direct effect on the strength of sintered material. On the other hand, the strength of sintered material is influenced by the microstructure. In this study, the effects of graphite powder diameter on the pore morphology and the microstructure of Fe-2%Cu-C sintered materials, where the graphite powder amount added was 0.6, 0.8 and 1.0 mass%, were examined. The main results are as follows; (1) With decrease in the graphite powder diameter from 17 to 1.5 μm, the pore size after sintering was reduced. (2) The tensile strength of sintered materials indicated a peak at 4.2 μm of the graphite particle diameter. (3) The tensile strength was correlated to the area fraction of pearlite.抄録全体を表示PDF形式でダウンロード (1159K)
特集：硬質材料技術の新たな展開と課題
総報
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松原 秀彰2009 年 56 巻 8 号 p. 504
発行日: 2009年
公開日: 2009/09/25
ジャーナル オープンアクセスPDF形式でダウンロード (101K)
受賞記念講演
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坂口 茂也2009 年 56 巻 8 号 p. 505-511
発行日: 2009年
公開日: 2009/09/25
ジャーナル オープンアクセスTi-Mo alloy have difficulties in manufacturing by melting-casting process because of its heavy gravitational segregation. Sintered Ti-Mo, Ti-Mo-TiC, Ti-Mo-W-C alloys were developed by the powder metallurgical process, and their microstructures, mechanical properties and corrosion behaviors were investigated. Ti-30mass%Mo alloy was consisted of β-Ti phase, its corrosion resistance in 35%HCl solution was far better than that of pure titanium; this was thought to be caused by the spontaneously passivated film, in which molybdenum was enriched by preferential dissolution of titanium, suppressing the anodic reaction. Ti-Mo-(33-80)mass% TiC alloy had two phases of TiCx and β-Ti phases, and increasing the TiC content increased the hardness, and maximum hardness of HRC 66 was obtained in Ti-Mo-45mass%TiC alloy, but slightly decreased the transverse-rupture-strength. Its potentiodynamic curve revealed also same as that of Ti-30mass%Mo alloy. In this alloy, the spontaneously passivated film adopting to each environment was formed, causing the alloy to show an excellent corrosion resistance in every test solutions. In consequence of these results, this alloy was thought to have both wear resistance and corrosion resistance.抄録全体を表示PDF形式でダウンロード (1202K) -
山本 勉2009 年 56 巻 8 号 p. 512-518
発行日: 2009年
公開日: 2009/09/25
ジャーナル オープンアクセスEngineering development of cemented carbides treated by various surface improvement and machining were carried out as follows: (1) The residual stresses of coated layer and WC phase of substrate for cemented carbides coated with TiN by CVD and PVD processes were investigated by X-ray diffraction method to explain the difference of the cutting performance between the CVD-coated and PVD-coated carbide tools. (2) The effects of HIP, grinding and coating treatments on bending and compressive fatigue characteristics of cemented carbides were investigated relating to structural defects, surface residual stress or fatigue hardening in Co phase. (3) The effects of various blasting treatments on surface residual stress and bending strength of cemented carbides were investigated to improve the mechanical properties of them with their sintered surface. (4) The variation of surface properties and bending strength of cemented carbides machined by wire EDM were investigated comparing with those of the as-ground carbides. The above-mentioned results were discussed and summarized.抄録全体を表示PDF形式でダウンロード (1462K)
研究
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竹田 容大, 河野 信一, 山本 勉, 細田 幸宏, 砂田 聡2009 年 56 巻 8 号 p. 519-522
発行日: 2009年
公開日: 2009/09/25
ジャーナル オープンアクセスIn order to evaluate corrosion characteristics of cemented carbides in wide pH range of aqueous solutions from strong acidity to strong alkalinity, the effects of carbon content in the alloy and Cr3C2 addition on corrosion characteristics of WC-10%Co alloys were investigated by mainly measuring potentiodynamic polarization curves of them. The results obtained were as follows; (1) In the case of aqueous solutions of strong acidity and weak acidity close to neutrality, corrosion speed in pseudo-passive region decreased with the decrease of carbon content in the alloy. (2) The effect of corrosion repression by Cr3C2 addition was small in the strong acid solution, but so big in the weak acid one. (3) The corrosion in the strong and weak acid solutions was mainly due to the dissolution of the cobalt phase. (4) In the case of strong alkali solution, the alloys showed almost same polarization curves with no relation to carbon content in the alloy and Cr3C2 addition because the corrosion was due to the dissolution of WC phase.抄録全体を表示PDF形式でダウンロード (594K) -
小林 慶三, 尾崎 公洋, 多田 周二, 中山 博行2009 年 56 巻 8 号 p. 523-528
発行日: 2009年
公開日: 2009/09/25
ジャーナル オープンアクセスWC-23%TiC-6%Ni-8%Co powder was prepared by a mechanical alloying for a short time. When the MA powder was consolidated by a pulsed current sintering process, the hard composite material with the hardness of 92.1 HRA and the transverse rapture strength of 1455 MPa was obtained. When Ti powder and graphite powder were used for mechanical alloying as starting materials instead of TiC powder, TiC particles were synthesized during the pulsed current sintering. Although the obtained sintered body had fine structure, the transverse rapture strength of it was lower than that of the case with TiC powder used. It would be attributable to the remaining pores and the unstable metallic binder phases in the sintered WC-23%TiC-6%Ni-8%Co body. The new process of the mechanical alloying for a short time combined with the pulsed current sintering was effective to obtain a hard composite material with higher strength than that of ordinary vacuum sintering process because of its fine microstructure.抄録全体を表示PDF形式でダウンロード (742K) -
長江 正寛, 伊勢 直子, 桑原 秀行, 高田 潤2009 年 56 巻 8 号 p. 529-533
発行日: 2009年
公開日: 2009/09/25
ジャーナル オープンアクセスFor Mo-Cr nitride layer prepared by NH3 gas nitriding of pure Mo subjected to Cr-diffusion treatment, the oxidation behavior in air and corrosion behavior in boiling sulfuric acid were investigated. The surface nitride layer consisted of γ-Mo2N type solid solution of which Mo-Cr ratio was almost 1 : 1 on the surface. Although γ-Mo2N layer obtained by nitriding pure Mo was oxidized at temperatures above 773 K, Mo-Cr nitride layer exhibited superior oxidation resistance up to 1073 K. The corrosion resistance of Mo-Cr nitride layer in boiling sulfuric acid was as excellent as that of γ-Mo2N layer.抄録全体を表示PDF形式でダウンロード (1336K)
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