巻号一覧
55 巻, 9 号
September
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研究
研究
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清水 博幸, 堀田 勝喜2008 年 55 巻 9 号 p. 617-622
発行日: 2008年
公開日: 2008/12/02
ジャーナル オープンアクセスA composite consisting of the powder of Bi system and resin was produced to discuss the absorption effect on the X band microwave. Prior to the production of the absorber, the method of measuring, calculating and thickness on the material constant were discussed, followed by the preparation of the material. Then, the absorption performance for the microwave was evaluated. The experimental results showed that the composite produced tends to increase the reflection loss in accordance with the increase of the content of the powder of the system at room temperature. On the other hand, it weas found that the composite does not absorb the microwave at the temperature of liquid nitrogen because of its superdiamagnetism. Then, it was concluded that the composite prepared can be used as the microwave absorber at room temperature while it can be used as the shielding medium of the microwave at the temperature of liquid nitrogen.抄録全体を表示PDF形式でダウンロード (906K) -
和田 任弘, 岩本 晃二2008 年 55 巻 9 号 p. 623-628
発行日: 2008年
公開日: 2008/12/02
ジャーナル オープンアクセスUsing polycrystalline cubic boron nitride compact (cBN) tools, which had the different cBN contents, the influences of both cBN contents and cutting speed on tool life in turning of hardened steel (SKD11, 60HRC) were investigated. Four types of cBN tools (cBN contents of 45 %, 55 %, 65 % and 75 % respectively) and a coated cBN tool (cBN contents of 55 %) were tested. In order to find out the wear mechanism of cBN tool, the SEM observation and the EDS analysis were carried out on the worn surface of cBN tool. The main results obtained are as follows: (1) The most suitable cBN contents of cBN tool was 55 % from the standpoint of tool life. (2) The wear progress of coated cBN tool was slightly slower than that of un-coated cBN tool.抄録全体を表示PDF形式でダウンロード (1521K) -
藤村 研悟, 加藤 将樹, 廣田 健2008 年 55 巻 9 号 p. 629-636
発行日: 2008年
公開日: 2008/12/02
ジャーナル オープンアクセスFabrication of MgFe2O4/Fe-Ni alloy bulk composites, in which Fe-Ni grains (∼5 μm in diameter) are fully surrounded with thin MgFe2O4 layer (∼0.3 μm in thick), has been tried by adopting high-pressure sintering for two powders: "Composite Powder I" and "Composite Powder II". The former was prepared as follows; fine MgO particle-coated Fe-Ni powders were heat-treated under various oxygen partial pressures at 600° and 700°C. The latter was fine MgO+α-Fe2O3 mixed powder particles-coated Fe-Ni powders. For the composite powders, two sintering processes were tried; i.e., pulsed-electric current pressure sintering PECPS (800°C/30 MPa/3 min) and HIP (950°-1250°C/196 MPa/2 h). Phase identification by XRD and SEM observations revealed that dense microstructure consisting of two phases (spinel MgFe2O4 and Fe-Ni alloy) was attained from the combination of composite powders II, PECPS and a re-oxidation process. However, other process resulted in formation of Wüsteit phase of Mg1-xFexO and FeO in addition to Fe-Ni due to highly reductive atmosphere during the sintering. Thus obtained composite materials consisting two phases showed good magnetic properties at room temperature as expected from their compositions and microstructures: saturation magnetization density Bs of 1.20 T, and permeability μ∼15-30 at 1 MHz, and a Curie point above 460°C.抄録全体を表示PDF形式でダウンロード (1542K) -
笠井 奈緒子, 山本 真平, 島川 祐一2008 年 55 巻 9 号 p. 637-642
発行日: 2008年
公開日: 2008/12/02
ジャーナル オープンアクセスWe studied effects of pyridine and H2O on the synthesis of monodisperse and spherical V2O5 fine particles by hydrolysis of vanadium isopropoxide (VO(OiPr)3) in acetone/pyridine mixture solutions. The average size of the V2O5 fine particles strongly depends on the concentration of pyridine but shows little dependence on the concentration of H2O. The size distribution of the V2O5 fine particles, on the other hand, is affected by the concentration of both pyridine and H2O: The size distribution increases with increasing the concentration of H2O while it decreases with increasing the concentration of pyridine. We succeeded in synthesizing the spherical V2O5 fine particles with the sizes from 100 to 700 nm by adjusting the concentration of pyridine and H2O while keeping the narrow size distribution. These V2O5 fine particles could be self-assembled to form three-dimensionally ordered colloidal crystals.抄録全体を表示PDF形式でダウンロード (1478K) -
Takayuki Kondo, Taku Kuramoto, Yasuhiro Kodera, Manshi Ohyanagi, Zuhai ...2008 年 55 巻 9 号 p. 643-650
発行日: 2008年
公開日: 2008/12/02
ジャーナル オープンアクセスThe effect of pulsed DC current (current density of up to 1476 A/cm2) on the growth of Mo2C layer formed in Mo-C system using spark plasma sintering method was investigated at temperature ranging from 1798 to 2140 K. The phase of product formed between Mo and C was identified only as Mo2C. The thickness of the Mo2C layer increased in the presence of the current, and also the growth rate was significantly enhanced with current densities. The activation energy for the growth of the product layer also decreased above current density of 600 A/cm2. When the current density was approximately 1476 A/cm2, the activation energy for growth of the product layer was calculated to be 182 ± 4 kJ/mol in the presence of the current which was much smaller than the activation energy of 320 ± 3 kJ/mol in the absence of the current.抄録全体を表示PDF形式でダウンロード (1146K)
特集：自動車用焼結材料の高機能化とそれを支える基盤技術
総報
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藤根 学2008 年 55 巻 9 号 p. 652
発行日: 2008年
公開日: 2008/12/02
ジャーナル オープンアクセスPDF形式でダウンロード (108K)
受賞記念講演
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鍛冶 俊彦, 徳岡 輝和, 西岡 隆夫, 井上 明久2008 年 55 巻 9 号 p. 653-660
発行日: 2008年
公開日: 2008/12/02
ジャーナル オープンアクセスA new alloy is made from rapid solidified Al-Ni-Zr-Ce aluminum alloy powder, and has the following unique mechanical characteristics: (1) The stress-strain curve shows a yield point which is not appeared in the conventional aluminum alloys; (2) The alloy shows high heat resistance. The hardness does not deteriorate until the annealing temperature reaches roughly 673 K; (3) Although the alloy has submicron diameter of crystal grain size, it shows excellent creep resistance.
From the micro-structures of this new alloy, it was thought that the above mechanical characteristics are based on the following reasons: (1) Appearance of the yield point is considered to be a result of the fact that the dislocation strongly adheres to the alloy's many crystal boundaries; (2) Microstructural change is not occured up to 673 K, which seems to be due to the small diffusion coefficient of the added alloying elements in aluminum; (3) The strong creep resistance is thought to the result from the presence of tiny inter-metallic compound particles (approximately 100 to 200 nm) at the grain boundary of this alloy, which inhibits the grain-boundary slip.抄録全体を表示PDF形式でダウンロード (1404K) -
石原 千生, 浅香 一夫, 嶋 治郎, 渡邉 篤2008 年 55 巻 9 号 p. 661-665
発行日: 2008年
公開日: 2008/12/02
ジャーナル オープンアクセスIn recent years, melted electromagnetic stainless steels containing a small amount of lead (Pb) have been used in the majority of magnetic parts in which corrosion resistance is required, beginning with solenoid valves and also including injectors for fuel injection systems and various other types of actuators. In these fields, the development of various types of sintered magnetic cores using the powder metallurgy method has been attempted in the past. But because it was not, however, possible to solve problems such as low magnetic flux density and excessive core loss, etc., these products have not reached application. This is attributable to the low density at 7.0 Mg/m3 of the conventional sintered electromagnetic stainless steel, SUS410, which made it impossible to obtain high magnetic flux density and satisfactory suction. Therefore, the authors developed a new sintered electromagnetic stainless steel with greatly improved compactibility and sinterability by optimizing the powder composition and annealing treatment. The developed sintered electromagnetic stainless steel has an Fe-6.5Cr-3Si composition with no Pb, considering the environment. Satisfactory compactibility is maintained in spite of the high content of Si at 3 mass%, and a high density ratio of more than 95% (7.4 Mg/m3) can be obtained after sintering. As a result, the developed material realized a sintered electromagnetic stainless steel with both a high magnetic flux density of B2500A/m: 1.4 T and satisfactory permeability of μm: 5000, which are necessary in actuators, as well as airtightness, which is important as a functional property in injectors. The mass production of the injectors core for LPG engines began in September 2005.抄録全体を表示PDF形式でダウンロード (893K)
研究
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伊藤 芳典, 植松 俊明, 佐藤 憲治, 三浦 秀士2008 年 55 巻 9 号 p. 666-670
発行日: 2008年
公開日: 2008/12/02
ジャーナル オープンアクセスThe metal injection molding process was applied to produce the Ti-6Al-4V alloy compacts using Ti and 3 types of Al-40V alloy powders. The first Al-40V alloy powder is a fine irregular powder, the second one is a coarse irregular powder, and the third one is a spherical powder obtained by gas atomization which particle size is same as the coarse irregular powder. The effect of particle size or shape of Al-40V alloy powder and sintering conditions on the relative density, mechanical properties and oxygen content of the sintered compacts were mainly investigated.
The sintered compacts using fine irregular Al-40V alloy powder showed highest density, the compacts using coarse irregular Al-40V alloy powder showed slightly higher density than the compacts using spherical atomized Al-40V alloy powder. This seemed to be due to the enhancement of sintering by using fine particle sizes or irregular particle shape of Al-40V alloy powder. The tensile strength of sintered compacts using fine irregular Al-40V alloy powders was about 70MPa higher than the compacts using other 2 types of Al-40V alloy powders. This was mainly affected by oxygen content of the sintered compacts derived from fine Al-40V alloy powder which had originally high oxygen content.抄録全体を表示PDF形式でダウンロード (1173K)
研究速報
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沖本 邦郎, 小路 和弘2008 年 55 巻 9 号 p. 671-675
発行日: 2008年
公開日: 2008/12/02
ジャーナル オープンアクセスIt is well known that the resin impregnation improves the machinability of sintered iron. The generally accepted view of this improvement is that the resin impregnation changes the cutting status of sintered iron from interrupted cutting to continuous cutting. According to other reports, resin impregnation is considered not only to reduce the friction between tool and material, but also to induce the material embrittlement. However, further research is still required to determine the reasons for improved machinability by resin impregnation. In this study, the influence of resin impregnation on the friction coefficient of sintered iron was investigated using ring compression tests. The friction coefficient was decreased by resin impregnation. However, the decrease was small compared to using a commercially available lubricant. Therefore, the reduction of friction by resin impregnation is unlikely to be the main cause for improved machinability.抄録全体を表示PDF形式でダウンロード (462K)
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