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Volume 50, Issue 11
Displaying 1-41 of 41 articles from this issue
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Toshihiko Shigematsu2003 Volume 50 Issue 11 Pages 810
Published: November 15, 2003
Released on J-STAGE: May 22, 2009
JOURNAL OPEN ACCESSDownload PDF (48K) -
Ruoxin Du, Hiroshi Okamura, Ryuzo Watanabe2003 Volume 50 Issue 11 Pages 811-815
Published: November 15, 2003
Released on J-STAGE: May 22, 2009
JOURNAL OPEN ACCESSHigh energy ball milling technique is often used in synthesizing ceramic composites. In this study, in order to obtain ultrafine TiN-AlN composite powder, which can be expected to improve the sinterability, mechanical alloying was employed, using AlN, Ti powders and ammonium carbonate as starting materials. The presence of nano-sized TiN was verified by XRD and TEM.View full abstractDownload PDF (4366K) -
Hoon Chul Yang, Jong Kwang Kim, Ki Tae Kim2003 Volume 50 Issue 11 Pages 816-820
Published: November 15, 2003
Released on J-STAGE: May 22, 2009
JOURNAL OPEN ACCESSA finite element analysis for near-net-shape forming of aluminum alloy powder was performed under warm rub-ber isostatic pressing and warm die pressing. The advantages of warm compaction by rubber isostatic pressing were discussed to obtain a part with better density distributions. The shape of rubber mold was designed by determining a cavity shape that provides a desired shape of the final powder compact. To simulate densification and deformed shape of a powder compact during warm pressing, the elastoplastic constitutive equation based on yield function of Shima-Oyane was implemented into a finite element program (ABAQUS). The hyperelastic constitutive equation based on the Ogden strain energy potential was employed to analyze nonlinear elastic response of rubber. Finite element results were compared with experimental data for aluminum alloy powder compacts under warm die pressing and warm isostatic pressing.View full abstractDownload PDF (379K) -
Takeshi Yamashita, Ryuzo Watanabe2003 Volume 50 Issue 11 Pages 821-827
Published: November 15, 2003
Released on J-STAGE: May 22, 2009
JOURNAL OPEN ACCESSWhen the carbon content in the Fe phase of liquid-phase-sintered Fe-Cu alloy is graded by using solid carburization method, the microstructure of the sample has a characteristic orientated Fe and Cu phases. This microstructural orientation towards the direction of carburization and the distributed area of the oriented Fe phase depends on the diffusion distance and the carbon content. In this paper, we executed three simulation programs by using Multi-Layered Potts Model and Monte Carlo method. From the simulation result, the orientated Cu phase was observed among coalescent Fe-C particles, and also sharp dihedral angles of Fe-C particles were observed. So, these combined simulations could succeed to reproduce the microstructure characteristics of orientated Cu phase of liquid-phase-sintered Fe-Cu alloy.View full abstractDownload PDF (2418K) -
Tao Lin, Liying Zhang, Zhimeng Guo, Wenxia Li, Chengyi Wu, Qinghua Wu2003 Volume 50 Issue 11 Pages 828-831
Published: November 15, 2003
Released on J-STAGE: May 22, 2009
JOURNAL OPEN ACCESSBy means of the mercurial barometer and pore size analyzer, the effects of bridged particles on the pore volume distribution in nano-scaled cemented carbide powder and its compact were investigated. Also the apparent density, specific surface area and green density were studied before and after sedimentation separating and shear milling by BET specific surface area analyzer and SEM. The results show that there is more than one peak on pore volume distribution pattern because of the presence of bridged particles. The apparent density and green density can be greatly improved by shear milling.View full abstractDownload PDF (1840K) -
Tianjun Liu, Jeff Danaher, Linda Tremblay, Ray Guo2003 Volume 50 Issue 11 Pages 832-836
Published: November 15, 2003
Released on J-STAGE: May 22, 2009
JOURNAL OPEN ACCESSThe advantages of green machining have been well recognized, including longer cutting tool life and the ability to make complex parts with sinter-hardenable powders. The high green strength of the compacted parts also prevents green cracks and damages from handling. But, green machining is yet to be widely used since the required high green strength (in excess of about 20 MPa) cannot be readily obtained through conventional P/M techniques.
The limitation of using green machining is being removed with a newly developed high green strength (HGS) polymeric lubricant at QMP. One distinguished characteristic of this lubricant is its response to temperature. High green strength can be obtained at a compacting temperature of 55°C, which can be easily reached throughout a green part by cold compaction. Even a higher green strength up to -48MPa can be reached by a subsequent curing process for parts pressed to density of 6.8 g/cm3. This high green strength has made green machining possible for those parts fabricated through conventional P/M processes.
This paper presents the results of green machining tests performed on several timing sprockets. The material used was a sinter-hardenable powder mix of QMP ATOMET 4601 and the HGS lubricant. The sprockets were pressed to a density of -6.8g/cm3 by cold compaction. Green machining (turning a groove along the middle of the teeth) was performed on as-compacted and cured parts. Results showed that the HGS lubricant provided sufficient green strength for clamping and machining operations, especially after curing. The machined surfaces appeared to be smooth and the edges remained integrated. The green-machined sprockets made of sinter-hardenable powder eliminated heat treatment, providing much longer tool life and improved size tolerances.View full abstractDownload PDF (7866K) -
Zhu Chunguang, Cao Hongbin, Bao Wenhai2003 Volume 50 Issue 11 Pages 837-839
Published: November 15, 2003
Released on J-STAGE: May 22, 2009
JOURNAL OPEN ACCESSThe planetary gear seat is a key part of electric winch, a self-help equipment, in cross-country vehicle. It features a complicated form, high running load, and definitely reliable operation. It is difficult to make the part by machining. We find P/M technology is a fairly better way but never easy one, because the structure of two steps internal involute gears is very special and height of the part is comparatively high. In this paper we will introduce you how to manufacture this part by P/M technology in our company.View full abstractDownload PDF (234K) -
Tetsuji Saito2003 Volume 50 Issue 11 Pages 840-843
Published: November 15, 2003
Released on J-STAGE: May 22, 2009
JOURNAL OPEN ACCESSCo-B powders were prepared by chemical reduction. The powders had a spherical shape with an average diameter of about 0.1μm. X-ray diffraction and differential scanning calorimetry studies confirmed that the powders were amorphous. The amorphous powders showed lower saturation magnetization than the crystalline counterparts. Heat treatment of the powders above the crystallization temperature resulted in the formation of fcc Co, hcp Co, Co2B, and Co3B phases. The saturation magnetization of the annealed powders monotonically increased as the annealing temperature increased. On the other hand, the coercivity of the annealed powders rapidly increased with increasing annealing temperature. The powders annealed at 500°C had a saturation magnetization of 92 emu/g with a high coercivity of 1670 Oe.View full abstractDownload PDF (1885K) -
Koji Shimojima, Hiroyuki Hosokawa, Mamoru Mabuchi, Masaru Kawakami, Sy ...2003 Volume 50 Issue 11 Pages 844-847
Published: November 15, 2003
Released on J-STAGE: July 12, 2010
JOURNAL OPEN ACCESSBinder-free WC was fabricated at the sintering temperature of 1873 K-2023 K by pulsed current sintering (PCS) process, and the density, grain size, hardness and toughness of them were investigated. As a result, the WC sintered at 1973 K showed a very high hardness more than HV10 2700 because it was almost fully dense and no singnificant grain growth occurred during sintering process.View full abstractDownload PDF (3979K) -
Yasuo Yamada, Cui'e Wen, Mamoru Mabuchi2003 Volume 50 Issue 11 Pages 848-850
Published: November 15, 2003
Released on J-STAGE: May 22, 2009
JOURNAL OPEN ACCESSThe present paper describes processing of a lotus-structured porous Ti-Al/Ti composite by SHS with Ti powder and Al rods. Ti-Al intermetallic compound was formed in a range of 200-300μm around the pore by SHS of reaction between Ti and Al, resulting in formation of a lotus-structured porous Ti-Al/Ti composite.View full abstractDownload PDF (3069K) -
Dong Ryoul Lee, Wan Jae Lee2003 Volume 50 Issue 11 Pages 851-855
Published: November 15, 2003
Released on J-STAGE: May 22, 2009
JOURNAL OPEN ACCESSBoride cermets, especially transition metal boride base ones, are promising candidates for wear resistant applications. This study focuses on the criteria for the fabrication of W2NiB2-Ni boride cermets using W, Ni and B elemental powders. Their sintering behaviors and characteristics were examined in relation with compositions and sintering temperatures. The W2NiB2 boride particles were formed by the diffusion and reaction during sintering. It seems to be a easy way to develop the boride cermets such as W2NiB2-Ni cermets.View full abstractDownload PDF (5005K) -
Compaction and Sintering of High Speed SteelHiroyuki Y. Suzuki, Masato Fukuda, Hidenori Kuroki2003 Volume 50 Issue 11 Pages 856-864
Published: November 15, 2003
Released on J-STAGE: May 22, 2009
JOURNAL OPEN ACCESSFine (4μm) and coarse (30μm) water atomized high speed steel powders were prepared as slips and compacted by high-speed centrifugal compaction process (HCP).
The HCP green compacts of the both fine and coarse powders can be sintered to almost full density at 1448K to 1498K without any pressure assistance during sintering. Their sintering behavior, however, were quite different. While the compact of coarse powder needed to form a liquid phase to densify and resulted in a coarse microstructure, that of fine powders densified in solid phase so that fine microstructures were obtained. A homogeneous packing of fine several micron powder by the HCP was essential to solid state sintering of high speed steel. The HCP compact of fine powders showed a comparable hardness and strength to wrought materials.View full abstractDownload PDF (7148K) -
Hiroshi Yamamoto, Taichi Mori2003 Volume 50 Issue 11 Pages 865-869
Published: November 15, 2003
Released on J-STAGE: May 22, 2009
JOURNAL OPEN ACCESSExperiments were carried out to investigate the effect of composition, heat-treatment and nitrogenation conditions on the magnetic properties of Sm-Fe-Co-Ti-N compounds with TbCu7-type structure. The optimum preparation conditions of the compounds were as follows: composition: {Sm10(Fe0.95CO0.05)89.7Ti0.3}82.0N18.0, roller velocity: 50 m/s, heat treatment: 680°C for 60min in high-purity Ar gas, and nitrogenation condition: 420°C for 15h in high-purity N2 gas. Typical magnetic properties of the obtained compound powders were as follows: Jr=0.99 T, Hcj=736.5 kA/m, HcB=540.4 kA/m, (BH)max=140.9 kJ/m3 (17.7 MGOe), and Tc=488°C. It was found that this sample was an exchange spring magnet from recoil loops of the hysteresis curve, TEM photographs and X-ray analysis. The value of (BH)max for the compression-molding isotropic bonded magnet prepared by using from {Sm10(Fe0.95Co0.05)89.7Ti0.3}82.0N18.0 powder was 103.2 kJ/m3 (13.0 MGOe), when the density of bonded magnet was 6.04 Mg/m3. And the average reversible temperature coefficient of Jr was a(Jr)ave.=-0.04%/°C, the temperature coefficient of Hcj in the range from 25°C to 125°C obtained by a linear extrapolation was a (HcJ) =-0.44 %/°C.View full abstractDownload PDF (1713K) -
Hiroshi Yamamoto, Hiroaki Nishio, Natsuki Wakamura2003 Volume 50 Issue 11 Pages 870-874
Published: November 15, 2003
Released on J-STAGE: December 04, 2009
JOURNAL OPEN ACCESSThis experiment was carried out to investigate the effect of ZnO substitution on the magnetic and physical properties of Co-Ni ferrite fine particle prepared by the chemical coprecipitation method without post-annealing process. The chemical coprecipitation compositions were chosen according to the formula (CoO)0.5(NiO)0.5-x(ZnO)x⋅n/2(Fe2O3), where x was varied between 0 and 0.5, and n between 2.0 and 3.0. The saturation magnetization σs, has a tendency to increase up to x=0.3, however decrease when x is above 0.3. On the other hand, the coercivity HcJ decreases as x increases. Optimum magnetic properties were achieved with materials of composition (CoO)0.05(NiO)0.45(ZnO)0.05⋅1.25(Fe2O3). The typical magnetic and physical properties are saturation magnetization σs=61.9×10-6 Wb⋅m/kg (49.3 emu/g), coercivity HcJ=372.5kA/m (4.68 kOe), the lattice constant a= 0.8379 run, and the average particle size = 38 nm. The rotational hysteresis integral Rh, which is related to the magnetization mechanism of these fine particles, is 1.80, and it is found that the magnetization mechanism is an incoherent rotation mode. Crystalline magnetic anisotropy constants are K11=+6.7×104 J/m3 (+6.7×105 erg /cm3) and K2=-16.8×104J/m3 (-16.8×105 erg/cm3).View full abstractDownload PDF (1759K) -
Wei Zhang, Hiroto Ohta, Kazuyoshi Yoshimura, N. V. Mushnikov, Tsuneaki ...2003 Volume 50 Issue 11 Pages 875-879
Published: November 15, 2003
Released on J-STAGE: May 22, 2009
JOURNAL OPEN ACCESSWe report experimental results of magnetic susceptibility and the high-field magnetization of Yb1-xYxInCu4 under various fixed temperatures, most of which are found to be explained by the calculation according to the modified Falicov-Kiwball model, although the observed sharp transition in substituted YbInCu4 is unexpected by this model. By proper scaling of the (Hv Tv) data extracted from the high-field magnetization measurements, we can collect all of the data from the system of Yb1-xYxInCu4 onto a universal H-T phase diagram, but it is shifted from the relationship expected by Falicov-Kimball model.View full abstractDownload PDF (379K) -
Yoshihiro Takitani, Toshirou Matuki, Jin-Feng Li, Ryuzou Watanabe2003 Volume 50 Issue 11 Pages 880-884
Published: November 15, 2003
Released on J-STAGE: May 22, 2009
JOURNAL OPEN ACCESSThe synthesis of Ti3SiC2 powder by mechanical alloying (MA) from elemental Ti, Si and C powders and evaluation of some properties of the sintered compacts of the MA powder were conducted. MA was carried out by vibratory ball milling and planetary ball milling. The influence of parameters, such as running time, ball size and rotation speed on MA powder were examined. The annealing of the MA powder was done at various temperatures and holding times. The MA powders could be sintered to dense Ti3SiC2-based ceramics which contained TiC as a secondary phase. Mechanical, thermal and electrical properties of sintered compacts were evaluated. The Ti3SiC2-based compact showed low hardness, high Young's modulus, and plastic behavior at high temperatures over 1373 K, And the compact showed high thermal expansion, high thermal conductivity, and higher electrical conductivity than other conventional ceramics.View full abstractDownload PDF (4876K) -
Takashi Ishikawa, Atsushi Kawamoto, Kenji Ohmori2003 Volume 50 Issue 11 Pages 885-888
Published: November 15, 2003
Released on J-STAGE: May 22, 2009
JOURNAL OPEN ACCESSA reduction and diffusion method (R/D) is used to make a mother alloy of Sm-Fe-N anisotropic magnets. Reduction of 0.5 wt% of samarium content compared to conventional powder increases magnetization. Milling and surface treatment improve the squareness of demagnetization curve, the aging property and the heat resistance quality. Maximum energy product of 292 kJ/m3 is obtained with the powder. High coercive force is maintainable even if the powder is exposed for 300 h in 80°C and 90 %RH. The maximum energy product of 141 kJ/m3 is obtained with an injection molded anisotropic magnet. The aging property estimated by irreversible flux loss is comparable to the conventional MQP-B magnets. The heat resistance temperature (T-5%) at which the initial irreversible flux loss becomes -5% is 125-more than 150°C for Sm-Fe-N magnets and 150-170°C for hybrid magnets.View full abstractDownload PDF (312K) -
Taesuk Jang, Dae-Hoon Lee, Tae-Whan Lim, C.J. Choi, B.K. Kim2003 Volume 50 Issue 11 Pages 889-893
Published: November 15, 2003
Released on J-STAGE: May 22, 2009
JOURNAL OPEN ACCESSFabrication of Nd-Fe-B magnetic powders by R-D process using spray-dried precursors was tried. Due to stable formation of a-Fe as a primary phase as same as that in ingots, the hard magnetic Nd2Fe14B phase was not formed in the alloy powder with the composition of stoichiometric Nd2Fe14B unless excessive amount of Nd precursor or Ca was added in the process. However, this excessive addition, especially for Ca, led to abnormal grain growth of Nd2Fe14B. On the contrary, Nd2Fe14B was successfully obtained as a major phase from the alloy powder with the composition of Nd15Fe77B8 without such excessive addition. The size of spherical shape Nd2Fe14B particles mostly consisted of one or more subgrains was less than 1, um. The coercivity measured from this powder was relatively low (-3 kOe) mostly due to residual CaO and soft magnetic phases.View full abstractDownload PDF (1995K) -
Yuichi Ogawa, Hisato Tokoro, Shigeho Tanigawa2003 Volume 50 Issue 11 Pages 894-898
Published: November 15, 2003
Released on J-STAGE: May 22, 2009
JOURNAL OPEN ACCESSProduction of R-Fe-B type permanent magnets has been rapidly increased since its discovery in 1983. This type of permanent magnets is used various applications today. The application for electric motors is one of the expanding field of R-Fe-B magnets in future. We studied the improvement of particular characteristics of R-Fe-B magnets required in motor applicant. In this paper, improvement of high temperature stability, mechanical strength and magnetizability will be reported. By refinement of microstructure, R-Fe-B sintered magnets with high temperature stability comparable to Sm-Co type sintered magnets was obtained. This material also showed high mechanical strength because of its fine microstructure.View full abstractDownload PDF (1633K) -
Xuanhui Qu, Jianxiang Gao, Mingli Qin, Changming Lei2003 Volume 50 Issue 11 Pages 899-902
Published: November 15, 2003
Released on J-STAGE: May 22, 2009
JOURNAL OPEN ACCESSAn improved wax-based binder was developed for powder injection molding of WC-TiC-Co cemented carbides. The critical powder loading and the flow behavior of the feedstock were determined. I was found that the critical powder loading could achieve up to 62.5 Vol% and the feedstock exhibited a pseudo-plastic flow behavior. The injection molding, debinding and sintering processes were studied. The dimension deviation of the sintered samples could be controlled in the range of ±0.2% with the optimized processing parameters and the mechanical properties were equivalent to those of the same alloy made by conventional press-sintering process.View full abstractDownload PDF (4814K) -
Hideki Kyogoku, Shinichiro Komatsu, Masahiro Shinzawa, Takashi Matsuok ...2003 Volume 50 Issue 11 Pages 903-907
Published: November 15, 2003
Released on J-STAGE: May 22, 2009
JOURNAL OPEN ACCESSThe purpose of this study is to investigate the influence of powder characteristics on the mechanical properties, especially fatigue and impact strengths, of the austenitic stainless steel compacts made by powder injection molding. The specimens were made of water-atomized (WA) and gas-atomized powders which were blended with a polyamide binder system. The compacts were debound in air and then sintered in vacuum at various temperatures for various times. The powder characteristics influenced significantly on the density, microstructure and mechanical properties of the sintered compacts. The fatigue limits of the WA and GA powder compacts were approximately 300MPa and 310 MPa, respectively. The fatigue strength of these compacts was slightly lower than that of the wrought material. The impact value of the sintered compacts increased lineally with increasing density.View full abstractDownload PDF (6637K) -
Takahiko Sakaue, Katsuhiko Yoshimaru2003 Volume 50 Issue 11 Pages 908-911
Published: November 15, 2003
Released on J-STAGE: May 22, 2009
JOURNAL OPEN ACCESSConventional copper powder used to form terminations of MLCC generally contains large flakes with high aspect ratios and large agglomerate spherical particles. The use of agglomerate powder and large flakes results in low dry film density, and thus a thicker film. In our research, we focused on highly dispersed, uniform, and fine flakes and powder that did not contain coarse particles, and examined the paste characteristics and their effect on firing conditions. We found that a smaller particle size would increase the thixotropic value and result in an earlier start to firing. We also discovered that the agglomerate condition of powder had a significant influence on the rheology of the paste. A higher degree of agglomeration would result in higher viscosity and a higher thixotropic value, but would not have a major effect on the firing condition.View full abstractDownload PDF (4574K) -
Liying Zhang, Yuxin Tan, Tao Lin, Zhimeng Guo, Chengyi Wu, Qinghua Wu2003 Volume 50 Issue 11 Pages 912-915
Published: November 15, 2003
Released on J-STAGE: May 22, 2009
JOURNAL OPEN ACCESSThe characteristics of shrinkage kinetics curve of compacts of W-(Ni-Fe)10% with particle size less than 200 nm sintered in hydrogen atmosphere was researched by high temperature dilatometer. And the influence of the particle size of W and green density on commence shrinkage temperature, sharp shrinkage temperature and shrinkage rate were also investigated. It shows that the commence shrinkage temperature and sharp shrinkage temperature of the compact with ultrafine grain are 970°C and 1240°C respectively. The maximum shrinkage rate is 0.11%/°C. The shrinkage ratio decreases with the increase of green density and increases with the increase of sintering temperature.View full abstractDownload PDF (272K) -
Takashi Yoshioka, Yukio Makino, Shoji Miyake2003 Volume 50 Issue 11 Pages 916-920
Published: November 15, 2003
Released on J-STAGE: December 04, 2009
JOURNAL OPEN ACCESSThe relationship between thermal conductivity and intergranular oxide phase variation in AlN sintered by millimeter-wave heating was investigated. The thermal conductivity was increased with the decrease of a ratio of Al2O3 to Yb203+Al2O3 in the intergranular phase. When a high thermal conductivity of 210 W/(m⋅K) was obtained at 1973 K for 3 hrs under a mixed gas atmosphere of N2 with 3 vol% H2, Yb2O3 phase was observed as an intergranular phase, unlike conventional sintering.View full abstractDownload PDF (2264K) -
Koki Kanno, Yoshinobu Takeda, Ricardo Canto Leyton2003 Volume 50 Issue 11 Pages 921-926
Published: November 15, 2003
Released on J-STAGE: May 22, 2009
JOURNAL OPEN ACCESSAt present, most stainless steel materials are sintered at high temperatures to achieve the desired mechanical, corrosion and high-temperature properties through densification. Although this method of processing achieves the desired properties, the resulting dimensional change can be difficult to control. A potential alternative to reduce the amount of densification required would be stainless steel powders with higher compressibility, which can reach higher green densities at reasonable compaction pressures. The purpose of this paper will be to compare different techniques to attain the desired sintered properties. The mechanical properties and green and sintered densities reached with these techniques will also be discussed.View full abstractDownload PDF (2072K) -
Takahiro Inoue, Isao Shimazoe, Izumi Sato2003 Volume 50 Issue 11 Pages 927-930
Published: November 15, 2003
Released on J-STAGE: May 22, 2009
JOURNAL OPEN ACCESSThe machining of green compacts can lead to manufacturing cost reductions through longer tool life, equipment downsizing, decreased processing times etc. Cost benefits can be gained in particular with materials that are hard to cut, such as sinter hardening materials. We have succeeded in changing product processes for sintered parts with drilled holes, by optimizing processing conditions and tools for improvements in cut surface finish and dimensional accuracy.View full abstractDownload PDF (4564K) -
Jun-ichi Yamamoto, Yasuo Shimizu, Hajime Ohtani, Keisuke Shiozaki, Kaz ...2003 Volume 50 Issue 11 Pages 931-936
Published: November 15, 2003
Released on J-STAGE: May 22, 2009
JOURNAL OPEN ACCESSP-type and n-type β-FeSi2 was produced by utilizing the process of mechanical alloying(MA)and spark plasma sintering(SPS)technique. Raw powders of pure iron, silicon, manganese and cobalt were mixed and mechanically alloyed for 72ks using planetary ball mill. The mixing fractions of the powders were in accordance with the mole fractions of the Fe0.92Mn0.08Si2 (p-type) and Fe0.98Co0.02Si2 (n-type), respectively. The SPS temperature for producing p-type β-FeSi2 was 1073-1153 K and n-type β-FeSi2 was 1073-1173 K, and the holding time was 0.3ks. When the sintering temperature was over these temperatures, α-FeSi2 was produced and thermoelectric properties were reduced. The density of p-type β-FeSi2 sintered at 1153 K was 4.64g/cm3(the relative density was 94.1%), and the maximum power factor was 0.30mW/mK2 at 850 K. The density of n-type β-FeSi2 sintered at 1173K was 4.71 g/cm3(the relative density was 95.5%), and the maximum power factor was 0.058 mW/mK2 at 650K.View full abstractDownload PDF (4292K) -
Hiroaki Suzuki, Hiroshi Okamura, Ryuzo Watanabe2003 Volume 50 Issue 11 Pages 937-943
Published: November 15, 2003
Released on J-STAGE: May 22, 2009
JOURNAL OPEN ACCESSThe (Zn0.98Al0.02)O ceramic is known to show high dimensionless figure of merit(ZT)at high temperature among the n-type oxide materials. But it has problem of the large lattice thermal conductivity compared with other thermoelectric materials. However the lattice thermal conductivity can be decreased by grain refining, and further improvement in the ZT value is possible. Thus we have tried to synthesize homogeneous (Zn0.98Al0.02)O powders with fine particles size by mechanical alloying(MA), and make the fine grained and dense (Zn0.98Al0.02)O ceramic under several sintering conditions, expeceting the increase of ZT value due to the decrease in lattice thermal conductivity. We found an optimum MA condition for grain refinement, but homogeneous (Zn0.98Al0.02)O powders could not be obtained under present MA conditions. The fine grained and dense (Zn0.98Al0.02)O ceramic obtained by MA/HP process shows the decrease in lattice thermal conductivity. Hot pressing was found to decrease the absolute value of Seebeck coefficient and increase the electrical conductivity as compared with the normal sintering (NS). MA/HP process will increase the amount of the substituted Al for Zn. The ZT value became the maximum by the MA/NS; ZT=0.13 at 1073K.View full abstractDownload PDF (3672K) -
Shigeru Katsuyama, Yoshiki Takagi, Mikio Ito, Shigeta Hara2003 Volume 50 Issue 11 Pages 944-947
Published: November 15, 2003
Released on J-STAGE: May 22, 2009
JOURNAL OPEN ACCESSWe have synthesized ZnO ceramics added with Ag or Y by the polymerized complex method. The microscopic structure and the thermoelectric properties such as Seebeck coefficient, electrical resistivity and thermal conductivity of the materials are much affected by the added elements. Ag metal or Y2O3 oxide was observed as a second phase in the sintered Ag-or Y-added samples, respectively. The crystal grain size of the Ag-or Y-added samples is much smaller than that of the non-added samples. The absolute values of the Seebeck coefficient and electrical resistivity for the Y-added samples increase with an increase of the Y content, while those for the Ag-added samples are almost constant independent of the Ag content. More reduction in the thermal conductivity was observed in the Y-added samples. These behaviors are ascribed to the physical properties of the precipitated second phases.View full abstractDownload PDF (2365K) -
Hiroshi Okamura, Ryuzo Watanabe2003 Volume 50 Issue 11 Pages 948-951
Published: November 15, 2003
Released on J-STAGE: May 22, 2009
JOURNAL OPEN ACCESSSynthesis of AgSbTe2/Ag2Te composite by mechanical alloying from elemental powders is described. Mechanical alloying was done by vibratory ball milling with a ball-to-powder ratio of 100:1. The studied composition range was Sb2Te3-xmol%Ag2Te (x=43-70); the (β+Ag2Te) region in the Sb2Te3-Ag2Te phase diagram. XRD analysis showed that after sufficient milling β compound AgSbTe2 was found to be formed for x=43. The composites of various compositions were formed depending on the initial mixing ratios. The sintered compacts of the mechanically alloyed powders had homogeneous composite microstructures and exhibited the increase in the connectivity of the second phase Ag2Te in the AgSbTe2 matrix with increase in the Ag2Te content.View full abstractDownload PDF (5042K) -
Mikio Ito, Yoshimitsu Oda, Shigeta Hara2003 Volume 50 Issue 11 Pages 952-957
Published: November 15, 2003
Released on J-STAGE: May 22, 2009
JOURNAL OPEN ACCESSThe citric acid complex (CAC) process and subsequent pressureless sintering were explored towards the synthesis of a c-axis oriented NaxCo2O4 thermoelectric polycrystal. The effects of the CAC process on the shape of powder precursor, crystallographic anisotropy of a sintered compact and its thermoelectric properties were investigated. The CAC process provided a plate-like powder precursor composed of the γ-NaxCo2O4 phase, reflecting its layered crystal structure. During compacting and sintering of this powder, the plate-like grains were well aligned along the pressed plane because of their specific shape, resulting in the sintered body with large crystallographic anisotropy. The CAC method was also effective for synthesizing the sample with compositional homogeneity and fine microstructure. The electrical resistivity of the CAC sample was almost the same as that of the sample prepared by the conventional solid state reaction method in spite of the fine microstructure, because of its high degree of c-axis orientation. The Seebeck coefficient was significantly improved by adopting the CAC method, resulting in the large enhancement of the power factor.View full abstractDownload PDF (1996K) -
Shoko Kikuchi, Kenta Takagi, Jing-Feng Li, Ryuzo Watanabe2003 Volume 50 Issue 11 Pages 958-962
Published: November 15, 2003
Released on J-STAGE: May 22, 2009
JOURNAL OPEN ACCESSLanthanum-modified lead zirconate titanate (PLZT) ceramics possess photostrictive effect that is applicable to photo-driven and wireless actuators. The photo-induced strain is expressed in a product of piezoelectric constant and anomalous photovoltage, and it is theoretically explained that grain size reduction enhances photovoltage. Finegrained PLZT ceramics that have mean grain sizes of 2.0-0.2μm were prepared through the mechanical alloying (MA) synthesis and normal or hot-press sintering process. Their piezoelectric constant, dielectric constant and electric resistivity up to a grain size of 0.5μm were not dependent on grain size and agreed with the conventional one. The photovoltage significantly increased with a decrease in grain size. These results suggested that a lowering of grain size by MA leads to a remarkable improvement of the photo-induced strain value without a decline in strain response. However, the photo-induced strain value within grain size less than 0.5μm extremely declined due to a little remnant polarization. The photo-induced strain with illumination of 15mWcm-2 intense was maximally estimated to be 1×10-4.View full abstractDownload PDF (1996K) -
Tomio Satoh, Hua-Nan Liu, Michiru Sakamoto, Yuji Kawakami, Keisaku Ogi2003 Volume 50 Issue 11 Pages 963-967
Published: November 15, 2003
Released on J-STAGE: May 22, 2009
JOURNAL OPEN ACCESSThe MA-SPS (mechanical alloying followed by spark plasma sintering) process was adopted to further improve the high temperature properties of a newly developed 36Cr white cast iron (a eutectic Fe-36Cr-9Ni-5Mo-0.45Si-2.2C alloy). α-Al2O3 powder with a mean diameter of 0.4μm was used as reinforcement for the MA material, and the volume fractions of Al2O3 in the composites were 10% and 30%. The results show that the microstructures of the MA materials were greatly refined compared to those of the conventionally solidified ingot and that their high temperature hardness and high temperature abrasive resistance were considerably improved. Also found was that the increase in the volume fraction of the Al2O3 powder increased both the hardness and the abrasive resistance of the composite materials.View full abstractDownload PDF (3545K) -
Hirotaka Kato, Masahiro Takama, Kazuo Washida, Yoshinori Sasaki, Setsu ...2003 Volume 50 Issue 11 Pages 968-972
Published: November 15, 2003
Released on J-STAGE: May 22, 2009
JOURNAL OPEN ACCESSMechanical properties and sliding wear characteristics of Cu-10mass%Sn composites containing graphite or molybdenum disulfide (MoS2) produced by powder metallurgy techniques were investigated in order to develop a suitable self-lubricating and anti-wear material for use under dry sliding conditions. Graphite and MoS2 powders were coated with copper for the purpose of promoting the bonding between a copper particle and the lubricant particle during the sintering process. The hardness, microstructure, bending strength, wear and coefficient of friction of the sintered specimens were examined. It was found that the mechanical properties of the composites decreased with increase of the amount of addition of graphite or MoS2. However, the use of the copper-coated lubricant powders improved the strength. Graphite addition was very effective in reducing the wear and friction. Moreover the wear rate of the copper-coated graphite specimens was much smaller than that of the uncoated graphite specimens. By contrast, the wear rates of the MoS2 composites increased considerably with the amount of MoS2 addition. This behavior is thought to be due to the absence of MoS2 and the presence of brittle CuMo2S3 compounds in the sintered composites.View full abstractDownload PDF (1713K) -
Kiyoshi Nomura2003 Volume 50 Issue 11 Pages 973-975
Published: November 15, 2003
Released on J-STAGE: May 22, 2009
JOURNAL OPEN ACCESSPerovskite related oxides such as (Ba, Ca)(Fe, Co)O3-δ, (Sr, Ca)(Fe, Co)O3-δ and (Ba, Ca)(Fe, Mg)O3-δ have been developed as safety materials for quick solidification of CO2 at high temperatures. The CO2 solidification properties and microstructures were investigated. Perovskite oxides (ABO3) become active for CO2 accommodation due to the lattice distortion produced by mixing different alkaline earth ions in site A and the mixed valence states by substitution of Fe ions by Cc and Mg ions in site B. The mechanism of rapid CO2 accommodation was taken into consideration.View full abstractDownload PDF (281K) -
Nurul Taufiqu Rochman, Hidekazu Sueyoshi2003 Volume 50 Issue 11 Pages 976-980
Published: November 15, 2003
Released on J-STAGE: May 22, 2009
JOURNAL OPEN ACCESSFe-C system alloys were prepared by mechanical alloying and powder metallurgy (MA-PM). Elemental powders of iron and graphite with various carbon concentrations were mechanically alloyed (MAed) by using a planetary ball mill in argon atmosphere. The MAed powders were then characterized by X-ray diffraction (XRD), differential thermal analysis (DTA) and scanning electron microscopy (SEM). During MA, the particle refinement, formation of super-saturated solid solution and Fe/C amorphous occur and their degrees are influenced by carbon concentration in the mixed powders. The MAed powders with 4-10 mass% carbon concentration were hot isostatic pressed (HIPed) and with 0.4-2 mass% were hot pressed (HPed) at both lower and higher temperatures than the eutectoid transformation point A1. The sintered compacts were characterized by Vickers hardness test, tensile test and scanning electron microscopy (SEM). Both the HIPed and HPed compacts obtained in the present study have very fine microstructures in which very fine cementite dispersed in very fine ferrite matrix. Mechanical properties of the HPed compacts of Fe-C system with hypo-eutectoid composition are comparable with those of standard steels. Thus, MA and PM is a new technique of near net-shape to gain steels with excellent mechanical properties without thermal refining and alloying elements.View full abstractDownload PDF (1978K) -
David L. Bourell, Joseph J. Beaman2003 Volume 50 Issue 11 Pages 981-991
Published: November 15, 2003
Released on J-STAGE: May 22, 2009
JOURNAL OPEN ACCESSFreeform fabrication as a technology is 25 years old, although its antecedents date back over 100 years. A brief historical context for freeform fabrication will be presented. Included is an introduction to current techniques and overview of the processes. The presentation will close with a review of current applications and future possibilities.View full abstractDownload PDF (7839K) -
Kenji Doi, Kazuki Hanami, Tsuneo Teraoka, Syuntaro Terauchi, Takashi S ...2003 Volume 50 Issue 11 Pages 992-995
Published: November 15, 2003
Released on J-STAGE: May 22, 2009
JOURNAL OPEN ACCESSHigh cycle fatigue properties of Metal Injection Molded (MIM) cold work tool steel and wrought steel (JIS SKD11) were investigated via ultrasonic fatigue test. The wrought steel specimens were tempered at 423 K for 1 hour. On the other hand, the MIM steel specimens were tempered at various temperatures in order to evaluate effect of tempering temperature on fatigue property. The ultrasonic fatigue tests were performed in the fatigue life range of N=103-108. Fatigue strength of the MIM steel specimens was equivalent to that of the wrought steel specimens. Fatigue strength of the MIM specimens declined with increasing tempering temperature. The results of microstructure observation showed that the diameter and shape of carbide of the MIM specimens were more uniform than those of the wrought steel specimens.View full abstractDownload PDF (3395K) -
Xuanhui Qu, Xinbo He2003 Volume 50 Issue 11 Pages 996-1000
Published: November 15, 2003
Released on J-STAGE: May 22, 2009
JOURNAL OPEN ACCESSUniversity of Science and Technology Beijing (USTB) is one of the key universities that are directly under the guidance of China Ministry of Education. Powder metallurgy activities have been carried out at USTB for about 50 years. Beijing Key Laboratory for Advanced Powder Metallurgy and Particulate Materials, which was founded on the base of Department of Powder Metallurgy at USTB, is a comprehensive base for PM education, research and development in China. In this paper, some of the current research activities and achievements in this laboratory are introduced, including ultra-fine grained cemented carbides made from nanometer powders, W-Cu and Mo-Cu alloys for electronic packages, SHS process and its applications, warm compaction, and powder injection molding.View full abstractDownload PDF (5175K) -
Yang Cao2003 Volume 50 Issue 11 Pages 1001-1003
Published: November 15, 2003
Released on J-STAGE: May 22, 2009
JOURNAL OPEN ACCESSNingbo Tongmuo New Materials Co., Ltd. (NBTM), which specializes in manufacturing PM components, has been enjoying rapid growth since 1995. This article gives a brief introduction of NBTM, as one of the largest manufacturers of sintered metal structural components in China.View full abstractDownload PDF (5012K) -
Kuan-Hong Lin, Chen-Sheng Hsu, Shun-Tian Lin2003 Volume 50 Issue 11 Pages 1004-1008
Published: November 15, 2003
Released on J-STAGE: May 22, 2009
JOURNAL OPEN ACCESSAlloying Mo into W-Ni-Fe heavy alloys results in solid solution strengthening of the matrix phase and yields smaller tungsten grains. However, a high alloying concentration of Ma causes a high concentration of Mo in the matrix phase at the final stage of liquid phase sintering. When the concentration of Mo in the liquid phase exceeds a critical value, a MoNi type intermetallic phase heterogeneously nucleates and grows on the surface of W-Mo grains during cooling, which imparts brittleness to the alloys. This article summarizes the recent studies regarding the effect of Mo on the microstructural evolution and mechanical properties of tungsten heavy alloy. In addition, the mechanism behind the formation of the intermetallic phase is emphasized.View full abstractDownload PDF (5482K)
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