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Volume 37, Issue 2
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[in Japanese]1990 Volume 37 Issue 2 Pages 182
Published: February 25, 1990
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSDownload PDF (47K) -
Junjiro Takekawa1990 Volume 37 Issue 2 Pages 183-186
Published: February 25, 1990
Released on J-STAGE: December 04, 2009
JOURNAL FREE ACCESSParmendur(Fe-50%Co alloy), the highest magnetic saturation material, was fabricated using the metal injection molding process. The sintering behaviors of injection molded Fe-50%Co powder compacts and the properties of the sintered compacts were investigated.
The main results obtained were as follows:
1) In the sintering of injection molded compacts the silane agent was effective only when added directly to the organic. binder. 2)The sintered structure of Fe-50%Co injection molded compacts showed uniformly distributed fine( < 5μm )spherical. pores.
3) Magnetic properties ( B20, He and μmax )of the parmendur fabricated by metal injection molding were rather inferior to those of wrought materials except for B20.View full abstractDownload PDF (308K) -
Hidetaka Uraoka, Yasunari Kaneko, Hiromichi Iwasaki, Yoshimitsu Kankaw ...1990 Volume 37 Issue 2 Pages 187-190
Published: February 25, 1990
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSThe injection molding of Cu powder by four kinds of binder systems(A, B, C, D) was investigated. The binder system(A) consisted of special-acrylate copolymer(AC), atactic polypropylene(APP), paraffin wax(Wax), and di-n-butyl phthalate(DBP); (B) consisted of ethylene-vinylacetate copolymer(EVA), polybutylmethacrylate(PBMA), Wax and DBP; (C) consisted of polyethylene(PE), special-polyvinylalcohol copolymer, Wax and stearic acid (St); (D) consisted of polystyrene(PS), PBMA, APP, Wax and DBP. The green body buried in sand was debinded during heating from room temperature to 300(B) or 320°C(A, C, D) in the air. The debinded part was sintered at 950(A), 970 and 1020°C(B, C, D) in H2 and Ar gas. The sintered part used the binder system(A) and the sintered part at 1020°C used the binder systems(B, D) had a relative density of over 95%. The density of sintered part relates to debinding process. The sintered part used the binder system(A) showed tensile strength of 28.27kgf/mm2, elongation of 48.5%.View full abstractDownload PDF (2147K) -
Yasunari Kaneko, Norio Kasahara, Kei Ameyama, Shigeya Sakaguchi, Takas ...1990 Volume 37 Issue 2 Pages 191-193
Published: February 25, 1990
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSThe injection molding of Mo powder using a Acrylate-APP(atactic-polypropyrene)-Wax binder system was carried out. The molding composition was 54.8%Mo powder, 18.8%Acrylate, 10.9%APP, 11.6%Wax and 3.9%dibutyl phtalate in volume.The green parts were debinded in air, and then specimens were sintered at 1700°C for 19hr in hydrogen gas.The relative density of sintered specimen was 93.0-93.5%.The carbon and oxygen content of sintered specimen were 46 and 224ppm.View full abstractDownload PDF (2219K) -
Yoshimitsu Kankawa, Katsuyoshi Saitou, Yasunari Kaneko, Hiromichi Iwas ...1990 Volume 37 Issue 2 Pages 194-197
Published: February 25, 1990
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSThe molding of calcium phosphate compound was tried using injection molding of ceramics powder. The composition changes and the physical properties of the sintered product in calcium phosphate compounds were discussed. Rod like test-piece(φ6×501)was produced by the injection molding with two compounds : (A) calcium secondary phosphate and several organic binders ; (B) calcium secondary phosphate, calcium carbonate and several organic bainders.After the binder extraction process, the test-pieces of Wand(B) were heated up to 1000°C-1300°C at the rate of 100°C of a hour. As the results of sintered process, it was found onthe basis of x-ray diffraction that (A) consists of calcium pyrophosphoric acidand calcium tertiary phosphate, whereas it was found on the basis of it that (B) consists of hydroxylapatite and calcium oxide.View full abstractDownload PDF (2546K) -
Tohru Takeda, Kazumi Minagawa1990 Volume 37 Issue 2 Pages 198-202
Published: February 25, 1990
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSStainless steel powders with the composition of 23% Cr-equivalent and 11% Ni-equivalent were produced by the water atomization using the pressure of 82 MPa and the flow rate of 1.9 m3/ks. Under size powders sieved with 25μm screen had the mean particle size of 5/μm and the tap density of 4 Mg/m3.
The slip containing 16 mass% water and 0.3 mass% ammonium alginate as the binder had the good flowability. The apparent viscosity showed the minimum value at the range of PH 9-10 and the value decreased with reducing the oxygen content of powders. With the rise of ammonium alginate contents from 0.2 to 0.5%, the strength of green bodys after drying at 420 K in vacuum increased from 3.2 to 5.1 MPa respectively.
Sintering was drastically promoted by the presence of 15-40% δ-ferrite in γ matrix-By sintering at 1400 K and above for 7.2ks, green bodys having the density ratio of 49% were densified to 98% and over. Specimens sintered at 1470 K showed the ultimate tensile strength of 660 MPa and the elongation of 40%.View full abstractDownload PDF (2135K) -
Masatomo Kamada, Shinya Ozaki, Youichi Tokunaga1990 Volume 37 Issue 2 Pages 203-208
Published: February 25, 1990
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSThe effect of compact density and aging condition on the tensile property was investigated for sintered precipitation hardening stainless steel (PH stainless steel) which was characterized by high tensile strength and high corrosion resistance. Two types powders of 17-7PH and 17-10P stainless steel were prepared by water atomizing process. The compact density does not increase greatly during sintering process because the powders are austenitic at sintering temperature. Addition of lwt%CrB to the stainless powder produces liquid phase at the sintering temperature, leading to an increase in compact density from 6.5 Mg/m3 (no addition of CrB) to 7.3 Mg/m3 . A sintered compact treated under optimum condition has high tensile strength above 900MPa for 17-7PH and 500MPa for 17-10P stainless steel.View full abstractDownload PDF (1387K) -
Yasushi Nishikura, Tohru Kohno1990 Volume 37 Issue 2 Pages 209-213
Published: February 25, 1990
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSHigh speed steels (JIS SKH51) have been produced by sinter forging using high-pressure water atomized powders ( ?? 10μm). The mechanical properties such as bend strength and hardness have been measured and optical and electron microscopic observation have been carried out. The properties of the forged steels have been compared with those of conventional sinterd steels. The results obtained can be summarized as follows:
1) The grain of sinter-forged high speed steels is very fine and carbides ( ?? 1μm) distributed uniformly are observed.
2) Carbide particle size is dependent upon powder size and sintering temperature, but not upon austenitizing temperature.
3) Bend strength of sinter forged steels is 450kg/mm2, whereas that of conventional products is 200kg/mm2.View full abstractDownload PDF (2692K) -
Akira Fujiki, Masashi Arita, Wataru Nojiri, Teruhisa Watanabe1990 Volume 37 Issue 2 Pages 214-218
Published: February 25, 1990
Released on J-STAGE: December 04, 2009
JOURNAL FREE ACCESSElements in Infiltrant on Mechanical Properties of Copper-alloy Infiltrated P/M High Speed Steels
Mechanical properties of copper-alloy infiltrated M42, T42 P/M high speed steels were studied.The green compacts were sintered in vacuum at 1433, 1443, 1453 K to make skeletons. The skeletons were infiltrated with Cu-Cr, Cu-Co and Cu-Fe-Mn alloy infiltrants in hydrogen or argon at 1423 K for 1.8 ks.The result obtained were summarized as follows.
1)All the infiltrated specimens shrinked.The Cu-Fe-Mn infiltrated M42, T42 P/M high speed steels had the least amount of dimentional change values during infiltration.The Cu-Fe-Mn infiltrated M42, T42 P/M steels had comparatively high hardness, but low strength.
2)Cu-Cr, Cu-Co infiltrated P/M high speed steels showed high strength, especially the P/M M42 steel having a skeleton sintered at 1453 k in vacuum and infiltrated with the Cu-Co alloy infiltrant in hydrogen had 2450 MPa of transverse rupture strength and HRC 48 of hardness as infiltrated.View full abstractDownload PDF (326K) -
Kuniaki Miyazaki, Shigeru Ito, Nobuyuki Koura, Noboru Yoneda, Kazuo As ...1990 Volume 37 Issue 2 Pages 219-224
Published: February 25, 1990
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSFe-WC composite consisted of average grain sizes of 90, 110μm, respectively, was prepared by HIP technique. Although iron is easy to react with WC at high temperature about 1200°C, the reaction was successfully controlled at 800°C below 13% under hipping pressure. Therefore, dense and pore free composites with the compositions of Fe-5wt%WC and Fe-20wt%WC were obtained at 800°C, applying 50-200MPa and 200MPa, respectively, for 30min. The reaction layer around the WC grain was about 5μm in thickness, according to the EPMA observation of the cross section of the composite. The growth rate of the reaction layer largely decreased with an increase in hipping pressure. The Fe-WC composite exhibited an excellent wear resistance, which was also increased under higher hipping pressure.View full abstractDownload PDF (2384K) -
Dsamu Furukimi, Keiichi Maruta, Teruyoshi Abe, Shigeaki Takajo1990 Volume 37 Issue 2 Pages 225-228
Published: February 25, 1990
Released on J-STAGE: December 04, 2009
JOURNAL FREE ACCESSThe composition of Ni and Mo containing composite-type alloyed steel powders was optimized for the production of ultra high strength, high toughness sintered components via compaction, sintering and heat treatment. A powder with 2%Ni and 1%Mo attained a high tensile strength of 1500MPa and a high unnotched Charpy impact value of 21J, when single-pressed, single-sintered and case hardened. Double-pressed, double-sintered and heat treated compacts made from the same powder showed an extremely high tensile strength of 1920MPa and a high unnotched Charpy impact value of 53J. The sintered compacts before heat treatment remained relatively soft and allowed machining and sizing. The strengthening was attributed to the strain-induced martensitic transformation of Ni-rich austenite.View full abstractDownload PDF (230K) -
[in Japanese], [in Japanese], [in Japanese], [in Japanese]1990 Volume 37 Issue 2 Pages 229-234
Published: February 25, 1990
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSThe results were summarized as follow:
(1)The granulated powder had higher compressibility than conventional water-atomized powder of-100 mesh. It showed the maximum green density when 10wt% fine powder was added.
(2)Maximum pereability and coercive force were improved as compared with water-atomized powder in the range of less than 50wt% fine powder.View full abstractDownload PDF (3700K) -
[in Japanese]1990 Volume 37 Issue 2 Pages 240
Published: February 25, 1990
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSDownload PDF (76K) -
Masayuki Niino1990 Volume 37 Issue 2 Pages 241-244
Published: February 25, 1990
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSThis paper discribes the development of Functionally Gradient Material (FGM) which is promoted by Science and Technology Agency with "special coordination funds for promoting science and. technology" from 1987. FGM is an advanced metal/ceramic compositional gradient from a metal side to a ceramic side to obtain the function of the thermal stress reduction In the high temperatur circumstance such as aerodynamic heating or combustion chamber of space plane. The aim of the development Is completion of FGM with the function to withstand 2000 K In the ceramic side and the difference of 1000 K between both sides. which are generated by the high temperature gas and the active cooling system. The small-sized FGM with a diameter of 30 mm and a thickness of 1-10 mm is scheduled to be completed by March, 1990 and the large-sized FGM of 300 mm by 300 mm with 1-10 mm in thickness by March. 1992. The development is shared by three research groups such as material designing, fabrication and evaluation, which consist of 30 research Institutes including national institues, universities and private companies. Material design group developed expert system. Fabrication group produced small FGM test pieces by physical-chemical combination vapor deposition process, thin sheet lamination method, low pressure plasma spray method and self-propagating high temperature synthesis process. Evaluation group developed various techniques for thermal barrier performance, thermal fatigue properties, thermal shock resistance and etc.View full abstractDownload PDF (253K) -
Shoji Noda, Tatsumi Hioki, Haruo Doi1990 Volume 37 Issue 2 Pages 245-252
Published: February 25, 1990
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSHigh energy ion irradiation is an emergent process to modify materials surface. This irradiation results in implantation of foreign atoms as well as many displacements of atoms in a materials surface layer at low temperatures at which the diffusion of atoms is limited. So, the ion irradiation often generates metastable amorphous phase in the surface layer. The ion irradaition also generates high residual compressive stress in the surface layer. The amorphous layer and the compressively stressed layer are demonstrated to be beneficial to improvement of mechanical properties of ceramics. Ion beam mixing also causes improvement of adhesion strength of a metal thin film on ceramics. Ion beam mixed ceramics are found to have high resistivity against abrasive wear.View full abstractDownload PDF (453K) -
Akira Kawasaki, Ryuzo Watanabe1990 Volume 37 Issue 2 Pages 253-258
Published: February 25, 1990
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSThe fabrication of disk shaped functionally gradient material with an optimum distribution of composition for thermal stress reduction in a specific material combination of PSZ/Stainless Steel is described. The thermal stress generated during cooling from sintering temperature was analized by finite element method as a function of conpositional distribution and sample size.
According to the optimum compositional gradient, the sintered compact of the PSZ /SUS304 functionally gradient material was successfully fabricated.View full abstractDownload PDF (1014K) -
Toshihiko Nishida, Hideaki Fujioka, Tomozo Nishikawa1990 Volume 37 Issue 2 Pages 259-262
Published: February 25, 1990
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSA homogeneous mixture of ultrafine MgO powder and SUS304 atomized powder was press-formed under a pressure of 500 kgf/cm2. The obtained green compacts were sintered at 1250°- 1430°C for2 hr in Ar. The composition along the cross section of the bodies sintered at 1300°- 1400°C was not uniform; the results of EPMA and XMDA showed that the Mg and MgO content decreased gradually from the center to the surface of the bodies. Possible mechanism for the appearance of the compositional gradience was discussed on the basis of the partial vaporization of MgO and chemical reaction associated with it.View full abstractDownload PDF (2956K) -
Akira Takahashi, Kimiaki Tanihata, Yoshinari Miyamoto, Manshi Oyanagi, ...1990 Volume 37 Issue 2 Pages 263-266
Published: February 25, 1990
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSThe NbN ceramic plate was formed very quickly by nitriding Nb metal plate in a chemical furnace utilizing the combustion synthesis reaction. Very high heat of 2700K can be supplied to the sample by igniting the combustion agent of Nb+NbN powders charged in the furnace in pressurized nitrogen atmosphere below 10MPa. When the Nb metal is thin within 100μm, it was fully converted into B1 phase NbN. For thick Nb metal as much as 1mm, the NbN ceramic layer was formed for several ten μm at the surface. In this case, nitrogen atoms diffused gradually into the metal plate and the graded structure of NbN-Nb2N-Nb was formed. The Vickers microhardness gradually decreased from the surface to the inside. B1 phase NbN is a superconducting material. The nitrided plate showed the critical temperature of 16.2K. Complicated shape components of NbN-Nb can be easily formed by this new nitriding method.View full abstractDownload PDF (874K) -
Yucong Wang, Makoto Sasaki, Toshio Hirai1990 Volume 37 Issue 2 Pages 267-270
Published: February 25, 1990
Released on J-STAGE: July 12, 2010
JOURNAL FREE ACCESSAs a fundamental study for the preparation of CVD⋅SiC/C functionally gradient materials, SiC-C nano-composites were prepared by chemical vapor deposition using SiCl4-C3H8-H2 system. Thermal conductivity and thermal expansion of the composites were measured. Consistently with the results of thermodynamic calculation, SiC-C nano-composites from C to SiC were prepared by controlling Si/C ratio in input gas. Thermal properties of the composites were affected by the morphology of C phase. The thermal conductivity of the composites changed accompanying with the composition and micro-structure. In the composition range <5mol%SiC, deposits showed strong anisotropy in thermal expansion. However, the thermal expansion of CVD⋅SiC-C nano-composites having C content up to 73.5mol% nearly equal to that of CVD⋅SiC.View full abstractDownload PDF (1406K) -
Makoto Sasaki, Yucong Wang, Akira Ohkubo, Toshiyuki Hashida, Toshio Hi ...1990 Volume 37 Issue 2 Pages 271-274
Published: February 25, 1990
Released on J-STAGE: July 12, 2010
JOURNAL FREE ACCESSThermal stress calculated in SiC/C⋅FGM was considerably smaller than that of SiC monolith. The preparation of SiC/C⋅FGM, having the graded concentration predicted from the calculation, was tried by using CVD technique under the following conditions; a SiCl4-CH4-H2 system, a deposition temperature of 1773K, total gas pressure of 1.3kPa. The film(thickness of 0.4mm) having a compositional gradient from C to SiC was obtained on a graphite substrate by changing the Si/C ratio in the gas phase during the deposition. Many small pores were observed in the range of 40-60 mol%C. SiC/C⋅FGM was not broken under cyclic high temperature heat flow conditions (heat flux=0.7MW⋅m-2), but SiC monolith was broken under the same conditions.View full abstractDownload PDF (1438K) -
Seiichi Uemura, Yoshio Sohda, Yukinori Kude, Toshio Hirai, Makoto Sasa ...1990 Volume 37 Issue 2 Pages 275-282
Published: February 25, 1990
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSSiC/C Functionally Gradient Materials(FGM) were prepared by chemical vapor deposition (CVD). SiCl4, CH4 and H2 were used as source gases. Non-FGM of SiC/C molar ratio with 0-1 were obtained by changing the ratio of SiCl4/CH4 in a temperature range of 1300-1500°C and in a pressure range of 10-100 Torr. Several non-FGM with various SiC/C ratio were subjected to the evaluation of mechanical properties and thermal properties. Modified SP test showed that fracture stress and Young's moduli of non-FGM changed with SiC/C ratio. Relationship between mechanical properties and SiC/C ratio, however, did not follow the rule of mixture(R.O.M.).Coefficient of thermal expansion of non-FGM did not change widely within a range of C=0-80mol%.Non-FGM with carbon content of 90-100mol% showed anisotropy. Thermal conductvity of non-FGM also did not follow R.O.M.. The reasons for the non-R.O.M. tendency seemed to be (1) Porosity in SiC/C mixture (2) Preferred orientation of carbon (3) SiC skelton structure even in non-FGM with low SiC/C ratio. Finally FGM of SiC/C were prepared by changing the ratio of SiCl4/CH4 stepwisely or conteniously. FGM or step FGM could be deposited not only on graphite plate, but also on carbon fibers and also cylindrical graphite tube. Microscopic observation revealed that CVD technique could be useful for the preparation of FGM on the substrate with complex shape.View full abstractDownload PDF (4674K) -
Masao Murakawa, Shuichi Watanabe, Yasujiro Sugimoto1990 Volume 37 Issue 2 Pages 283-286
Published: February 25, 1990
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSThe authors have investigated that a cubic boron nitride (c-BN) film with stoichiometric composition can be synthesized on a Si wafer by the use of hot cathode plasma discharged within a parallel magnetic field in an activated reactive evaporation process. The c-BN film prepared by this method, however, initially did not show good adhesion because of the internal stress within the film. Thus, in an effort to obtain good adhesion of the film, the effect of gradual control in N content across the film thickness on the adhesion was examined in expectation that the internal stress can be reduced. The results show that it is possible to deposit, with good adhesion, a c-BN film onto a Si wafer by providing a multilayer film structure, i.e., the one comprising a thin B layer, a gradually controlled BN one and a c-BN one.View full abstractDownload PDF (1418K) -
Akira Kawasaki, Ryuzo Watanabe1990 Volume 37 Issue 2 Pages 287-291
Published: February 25, 1990
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSFabrication of piezoelectric functionally gradient material by temperature gradient sintering is described. The temperature gradient was given by an infrared-rays lamp beam and a controlled auxiliary heater. Cylindrical PZT powder compacts were air-sintered lhr with a temperature difference of about 150K in the distance of 5mm from the sample surface. The variation of relative density along the axial direction was found to be well corresponding to the local temperature gradient within the sample. It was found that a flexural vibration mode was generated due to the density gradient along the axial direction.View full abstractDownload PDF (2188K) -
Kenji Higashi, Munetake Satoh, Fumiaki Hamano, Kei Miyanami, Shinji Ta ...1990 Volume 37 Issue 2 Pages 292-295
Published: February 25, 1990
Released on J-STAGE: December 04, 2009
JOURNAL FREE ACCESSThe new method has been developed to produce composite powder that was dispersed homogeneously by silicon carbide particles along grain boundaries in matrix powder of Aluminium-Lithium alloy. This composite powder can be obtain in combination with a high-speed/high-shear type mill and superplasticity of matrix powder. The model of compounding process has been proposed from metallographic observation.of powder. This new method might be useful for designing the new composite materials.View full abstractDownload PDF (2736K) -
Osamu Kimura, Toshio Kawashima1990 Volume 37 Issue 2 Pages 296-299
Published: February 25, 1990
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSIn this paper, we apply our theory hitherto developed to a ceramic-metal joint with an interlayer of functional gradient materials. Thermal stress occuring in the ceramic part of the joint is discussed as a function of the layer thickness. The effect of the layer is found remarkable to diminish thermal stresses, when it is sufficiently thick.View full abstractDownload PDF (217K) -
Masahiro Saito, Hee Don Jeong, Hideaki Takahashi, Akira Kawasaki, Ryuz ...1990 Volume 37 Issue 2 Pages 300-306
Published: February 25, 1990
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSFracture toughness test and Modified Small Punch(MSP) test by use of Acoustic Emission(AE) Technique were performed on Y2O3 stabilized ZrO2, 3mol% Y2O3 - ZrO2 (PSZ)/SUS composite materials, and Macor which is a machinable ceramics. MSP testing method(miniaturized test technique) was developed to determine fracture strength, and fracture strain with high accuracy and good reproducibility, where AE monitoring was also made. From these results, AE characteristics of various materials were compared, and microscopic fracture mechanism was discussed on the basis of the AE results. Furthermore, the AE for stress induced transformation in 3, 4 mol% Y2O3 - ZrO2 were also examined.View full abstractDownload PDF (1299K) -
Toshiyuki Hashida, Hideaki Takahashi, Kazuhiko Miyawaki1990 Volume 37 Issue 2 Pages 307-312
Published: February 25, 1990
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSThis paper presents some results of laser heating thermal shock tests performed on plasmasprayed thermal barrier coatings. The coatings tested were single-layer ZrO2 (stabilized with 8% Y2O3), and Functionally Gradient Materials (FGMs) which consisted of multi-layer with varying mixture ratios of ZrO2 and Ni-based superalloy (NiCrAlY). FGMs are recently proposed coating materials which are aimed at mitigating thermally induced stresses in the coating. A CO2 laser was used for the thermal shock tests, where a laser beam with a preset spot size, duration and intensity was irradiated onto the coating surfaces. Concurrently with the laser experiments acoustic-emission (AE) monitoring was made to defect the onset of the thermal shock fracture. In order to evaluate the stress state of coatings induced by the laser heating and to discuss the fracture process, numerical computations of transient thermal stresses was made using the finite element method. Based on the results, critical laser power density at the onset of coating failure was defined in order to characterize the thermal shock resistance of the coatings. It was shown that the critical power density of the FGMs is significantly higher than that of the single-layer coating, indicating the effectiveness of the FGMs to reduce the thermal expansion mismatch stress.View full abstractDownload PDF (2017K) -
Akinaga Kumakawa, Masaki Sasaki, Shuhei Maeda, Naohito Adachi1990 Volume 37 Issue 2 Pages 313-316
Published: February 25, 1990
Released on J-STAGE: December 04, 2009
JOURNAL FREE ACCESSThe Fuctionally Gradient Materials(FGM) comprise with different material components such as ceramics and metals with continuously varying mixture ratio and micro structure in conformance with the actual environments in order to relax the thermal stress due to high temperature gradients. This evaluation method was developed to determine the performance of the FGM related with thermal resistance and thermal fatigue. High temperature gradient condition was accomplished by heating one side of specimen with Xenon lamp while cooling the other surface with liquid hydrogen or nitrogen in vacuum. The evaluation of the samples were available for metallographic examination and the variation of the effective thermal conductivity dependent upon the delamination damage and subcritical cracks. Some samples fabricated by several method were examined under several conditions. With some results that it was evident the FGM was quite promising for decreasing the thermal stress under high heat loads.View full abstractDownload PDF (220K) -
[in Japanese]1990 Volume 37 Issue 2 Pages 318
Published: February 25, 1990
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSDownload PDF (85K) -
Teruya Shinjo1990 Volume 37 Issue 2 Pages 319-323
Published: February 25, 1990
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSRecent topics in multilayer studies relating to surface anisotropy are introduced. In Fe/Mg and Mn/Sb multilayers, ferromagnetic monolayer samples were fabricated, which show perpendicular easy directions but have lower Tc than room temperature. It was found that Co/Pt multilayers have a potentiality as magnetic recording media since their perpendicular magnetization is stable at room temperature. The giant magnetoresistance found in Fe/Cr multilayers is another recent topic in this field.View full abstractDownload PDF (1347K) -
Tadashi Kokubo1990 Volume 37 Issue 2 Pages 324-328
Published: February 25, 1990
Released on J-STAGE: December 04, 2009
JOURNAL FREE ACCESSIt was shown that composite ceramics with special biomedical functions can be obtained by a process of crystallization of glasses. A heat treatment of a glass in the system 3CaO⋅P2O5-CaO⋅SiO2-MgO⋅CaO⋅2SiO2 gave a composite ceramic containing fine-grained apatite and wollastonite in a glassy matrix, which was characterized with a high mechanical strength as well as high bioactivity. It is useful for artificial bones. A heat treatment of a glass in the system (FeO, Fe2O3)-CaO⋅SiO2 gave a composite ceramic containing fine-grained magnetite in a CaO⋅SiO2 crystalline and glassy matrix, which was characterized with a ferromagnetism as well as a bioactivity. It is expected to be useful for a thermoseed for hyperthermia of cancer. The properties of the obtained composite ceramics were discussed in terms of their microstructures.View full abstractDownload PDF (2319K) -
Hiroshi Sakakima1990 Volume 37 Issue 2 Pages 329-332
Published: February 25, 1990
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSSuperstructured alloy films composed of non-nitride layers and nitride layers such as Co-Nb-Z r/Co-Nb-Zr-N and Fe-Nb-B/Fe-Nb-B-N are prepared by N2 reactive R F sputtering. S oft magnetic properties are obtained when the layer thickness is less than 15 nm for the films comprizing metal-metalloid elements and less than 30 nm for the films comprizing metal-metal elements. Layered structures of the obtained films remained even after annnealing up to 600 °C in the metal-metalloid alloy films, while they changed into weakly compositionally modulated structures in the metal-metal alloy films. These films show high permeabilities (>2000 at1 MHz) and high saturation magnetizations (4π Ms=13-15 kG) and are promizing magnetic core materials for VTR or computer heads.View full abstractDownload PDF (252K) -
Koichi Kugimiya, Ken Hirota, Mitsuo Satomi, Osamu Inoue1990 Volume 37 Issue 2 Pages 333-336
Published: February 25, 1990
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSA new family of materials, nano-structure controlled(NANOCON) metals with very high resistivity of 1011Ωcm, has been developed. Nanocon metals compose with 95-99.5% metals and 0.5-5% dielectrics and have a porosity of less than 1%. Pure metal powders are coated with very thin dielectric films of an order of 10nm. Coated powders are hotpress-sintered to a final density. A newly developed rate controlled sintering technique has resulted in a unique microstructure: dielectrics completely fill out grainboundaries without allowing any direct contacts between metal grains.View full abstractDownload PDF (983K) -
Nobuyuki Aoki, Keiichi Ochiai, Hideaki Komoda1990 Volume 37 Issue 2 Pages 337-340
Published: February 25, 1990
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSThe application to magnetic recording of Ba-ferrite epitaxially coated with Spinel-ferrite, which is called SEB particles, was investigated. The results obtained are as follows: The lattice images of SEB particles showed that the Spinel-ferrite(Co-ferrite) was epitaxially crystallized on the surface of Ba-ferrites.
The saturation magnetization of the SEB powders was increased about 10% for that of the Ba-ferrite powders before reaction.
The output voltage in short wavelength of the tapes with SEB powders was lower than that of the oter tapes, MP tapes and Baferrite tapes. We considered this is probably due to the mixture formation by an incomplete SEB reaction, particle distribution and formation distribution of any particles etc.View full abstractDownload PDF (2314K) -
Shigeo Inoue, Tetsuo Uchiyama, Koichi Niihara1990 Volume 37 Issue 2 Pages 341-347
Published: February 25, 1990
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSThe reasons for high toughness in Al2O3/SiC whisker/ZrO2 ceramic composite were elucidated by each toughening mechanims such as crack deflection and whisker pull out.
The condition required for SiC whisker to obtain ceramic composite was analysed by fracture mechanics and was found that diamater of SiC whisker must be lowered under a critical size. Toughening mechanisms by SiC whisker such as crack deflection and whisker pull out were also discussed. Importance of diameter, length and strength of SiC whisker was made clear. On the other hand contributions of UP ZrO2 to high toughness were also explained by grain refining and transformation toughening. Finally, additional effect of each toughening mechanism, which is called multiple toughening, was shown to be important to obtain high toughness ceramic composite.View full abstractDownload PDF (2563K) -
Koichi Niihara1990 Volume 37 Issue 2 Pages 348-351
Published: February 25, 1990
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSStructural ceramic composites can be divided into three categories: microcomposites, nanocomposites and nanocomposites combined with microcomposites. In the microcomposites, the second-phase micrometer-size dispersions such as particulates, plateletes, whiskers and fibres are dispersed at the grain boundaries of the matrix, while in the nanocomposites the second-phase nanometer-size dispersions such as particulates and whisker are incorporated within the matrix grains. The main advantage of the microcomposites is to improve the fracture toughness (and then fracture strength). On the other hand, the nanocomposites such as Al2O3/SiC, Al2O3/Si3N4, MgO/SiC and Si3N4/SiC, in which the second phase particulate dispersions are dispersed within Al2O3, MgO and Si3N4 matrix grains, were recently developed in our laboratory. In these nanocomposites, the fracture toughness and strength were approximately 2-4 times improved by dispersing the nano-size second phase particles into the matrix grains. The remarked improvement of hardness and strength were also observed even at high temperatures. In this paper, the toughening and strengthening mechanisms of various nanocomposites will be reviewed briefly, and the possibility of the nanocomposites combined with microcomposites for developing the strong and tough ceramics even at high temperatures will be also discussed.View full abstractDownload PDF (220K) -
Koichi Niihara, Kansei Izaki, Atsushi Nakahira1990 Volume 37 Issue 2 Pages 352-356
Published: February 25, 1990
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSEffects of nano-size dispersions on mechanical properties such as hardness, fracture toughness and strength were investigated for the Si3N4-SiC nanocomposite system. The Si3N, -SiC nanocomposites were fabricated by hot-pressing the mixtures of amorphous Si-C-N precursor powder with various C/N ratio and sintering additives. Transmisson electron microscopic observation indicated that the Sic particles less than approximately 0.1μm in diameter were dispersed whithin the Si3N4, matrix grains. No apparent impurity phases was observed at the intertfaces of Si3N4 and Sic. The grain morphology of Si3N4 was strongly influenced by the Sic dispersion, indicating that the formation of elongated and equiaxed Si3N4 grains was acceralated at the lower and higher SiC volume fractions, respectively. As expected from this change of grain morphology, the fracture toughness and strength were showed the maxmima, 155OMPa and 6.5MPam1/2, at the certain volume fraction of SiC. The high-temperature strength was also improved by the Sic dispersion and the high strength of over 1GPa was observed even at 1400°C.View full abstractDownload PDF (2745K) -
Ryoichi Shikata, Yoshinori Urata, Takeshi Shiono, Tomozo Nishikawa1990 Volume 37 Issue 2 Pages 357-361
Published: February 25, 1990
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSZirconia raw powder containing 2 or 3 mol% of Y2O3 prepared by a hydrolytic precipitation method and Al2O3 raw powder were mixed with ethanol using a pot-mill. The homogeneously mixed powder was mold-pressed at 35 MPa, and then, it was further isostatically pressed at 98 MPa. The moldings were sintered at 1300°-1600°C for 3 hr in air, and these densely sintered bodies were isostatically hot-pressed at 1450°or 1550°C for 1 hr in Ar under a pressure of 98 MPa.
An addition of 20-40 wt% of Al2O3 to Y-PSZ was remarkably effective for the enhancement of the fracture strength of the obtained composite ceramics to give the average bending strength about 3GPa. The fabrication conditions which produced the composite ceramics with high strength and their microstructural features were discussed in this paper.View full abstractDownload PDF (1165K) -
Chitake Yamagishi, Hideto Yoshida, Hideto Kamiaka, Junji Asaumi, Nobor ...1990 Volume 37 Issue 2 Pages 362-366
Published: February 25, 1990
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSA fabrication process has been developed for incorporating X-phase into mullite by the reaction of β-Sialon and mullite under firing. The composites were made by pressureless sintering at 1600-1750°C in vacuum atmosphere, covered with packing powder of mullite. The firing temperature was optimized to be 1700°C because the decomposition of X-phase occurs above 1720°C.
The amount of X-phase increased with the addition of β-Sialon(Z=2) powder, and there was no β-Sialon in the composite. It was guessed that the liquid phase in the mullite reacted with β-Sialon to produce X-phase. It was found that the composites (3-10% β-Sialon addition) were almost densified after firing for 2 hours at 1700°C.View full abstractDownload PDF (780K) -
Chitake Yamagishi, Hideto Yoshida, Hideto Kamiaka, Junji Asaumi, Nobor ...1990 Volume 37 Issue 2 Pages 367-370
Published: February 25, 1990
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSMicrostructure of the mullite - X-phase composites made by reaction of β-Sialon and mullite is the mixture of needle shaped particles (15μm) and fine particles (1μm). The amount of liquid phase in the composites decrease with increasing the amount of X-phase. Neither cracks nor liquid phase is obserbed at the boundary between X-phase and mullite. The flexural strength of the composites at 1300°C increases in proportion to the amount of β-Sialon addition and the composite with 10vol% β-Sialon keeps the same flexu ral strength thatmullite shows at room temparature. The fracture toughness of the composites at room temperature does not improved compered with that of mullite.View full abstractDownload PDF (1720K) -
Shin-ichi Hirano, Takashi Hayashi, Chikage Kato1990 Volume 37 Issue 2 Pages 371-375
Published: February 25, 1990
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSProcessing of mullite and mullite/ 4Y.ZrO2 composites compacts was investigated through a colloidal filtration route to consolidation. The green compacts consolidated from a powder suspension by a colloidal filtration method did exhibit uniformly-packed microstructure with a smaller particle size and a narrower particle-size distribution, compared with those of the compacts fabricated by a uniaxially pressing technique. The dispersion states of powder suspensions were controlled by adjusting pH and/or by adding a surfactant. The filtration rate and strength of the colloidal-filtered compacts were improved by the addition of an optimum amount of the surfactant, which was determined by a zeta-potential technique. A higher sinterability and superior mechanical property of mullite/4Y.Zr02 composites can be achieved by using the colloidal filtration method relative to the uniaxial pressing technique, reflecting the uniformity of the green compact microstructure.View full abstractDownload PDF (947K) -
Mitsuhiko Sato, Okamura Okamura, Tadao Seguchi1990 Volume 37 Issue 2 Pages 376-380
Published: February 25, 1990
Released on J-STAGE: December 04, 2009
JOURNAL FREE ACCESSSi-C-O fibers have been prepared from cured polycarbosilane fibers. The curing of polycarbosilane fibers was carried out by thermal oxidation and electron beam irradiation. Si-C-O fibers prepared at 1473K from the thermal-oxidized polycarbosilane fibers contained oxygen by 10.8wt % . The structure of the fibers was amorphous and changed to crystalline of β-SiC with increase of the heat treatment temperature. At 1773K, the crystalline size (L(111)) of β-SiC was about 25nm. On the other hand, Si-C-O fibers prepared at 1473K from the electron beam cured polycarbosilane fibers contained oxygen by 2.2wt%. The fiber structure was microcrystalline of β-SiC and scarcely changed by increase of the heat treatment up to 1773K, and L(111) of β-SiC was about 4.5nm even at 1773K.
The change of the fiber structure affected the tensile strength of these fibers. The tensile strength of the fibers contained a large amount of oxygen, which prepared from the thermal-oxidized polycarbosilane fibers, were almost nil at 1773K. But the fibers contained a small amount of oxygen, which prepared from the polycarbosilane fibers cured with electron beam, still remained the tensile strength of about 1.8GPa.View full abstractDownload PDF (3017K) -
Tomoyoshi Motohiro, Shoji Noda1990 Volume 37 Issue 2 Pages 381-383
Published: February 25, 1990
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSAn Obliquely deposited thin film has a unique microstructure; a nano-composite of void and an inclined 'platelet' of deposited material. Obliquely deposited oxide thin films of the inclined platelet microstructure have been demonstrated to have birefringence. Oblique deposition process was computer-simulated and the platelet microstructure was shown to be explained basically in terms of the self-shadowing effect.View full abstractDownload PDF (216K) -
Hideroh Takahashi, Takashi Ohta, Takaaki Matsuoka, Kenzo Fukumori, Tos ...1990 Volume 37 Issue 2 Pages 384-388
Published: February 25, 1990
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSOriginally incompatible blends of SAN 30% and PC 70% were extruded with extremely high shear rate up to 107 s-1 as a typical example of the blends. The.blends are of binary systems microscopically in the first run of extruding, where SAN is present as small spherical particles in PC matrix. The apparent volume fraction of the spherical SAN estimated from the microscopic photographs decreases with the shear rate. The fraction is decreased also with the repeated runs. The blend appears uniform or structureless at the fifth run. Dynamic loss tangent gives two peaks corresponding to T ?? of SAN and PC, respectively. The latter shifts to lower temperatures with the number of extruding run. It is considered that some of SAN is mixed with PC in a compatible form. The pulsed NMR analysis supports the conclusion.View full abstractDownload PDF (2962K)
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