All issues
Volume 39, Issue 6
Displaying 1-17 of 17 articles from this issue
- |<
- <
- 1
- >
- >|
-
[in Japanese]1992 Volume 39 Issue 6 Pages 440
Published: June 15, 1992
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSDownload PDF (65K) -
Kiyohito Okamura1992 Volume 39 Issue 6 Pages 441-446
Published: June 15, 1992
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSPrecursor-SiC fibers with high tensile strength are produced by the conversion process of polycarbosilane under an inert atmosphere. The fibers consist of SiCxOy(x=1.2-1.4, y=0.3-0.4), and
are amorphous. The fibers are actively applied as the reinforcements of inorganic composites. The fibers decompose by heat treatment at temperatures above 1573K in N2 or Ar atmosphere, and the evolution of SiO and CO gas occurs. The morphology and crystal structure of the fibers change and the tensile strength rapidly decreases. In order to improve the tensile strength at high temperatures, it is necessary to reduce the oxygen content. The oxygen control in the fibers is studied using radiationchemical reactions, and the tensile strength has been removed. On the other hand, polycarbosilane is converted to silicon nitride by the heat treatment in NH3 gas flow.On the basis of this nitridation process, Si3N4 or Si-N-O fibers are synthesized.View full abstractDownload PDF (352K) -
Toshio Shimoo, Kiyohito Okamura1992 Volume 39 Issue 6 Pages 447-450
Published: June 15, 1992
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSThe chemical stability of Si-C-O fiber at high temperatures was investigated. The amorphous fiber was pyrolyzed to crystallize to β-SiC under an atmosphere of inert gas at 1473K and higher. During the pyrolysis, both SiO and CO were evolved. The pyrolytic rate was described by the Avrami-Erofeev equation, and was determined by the crystal growth of SiC controlled by the diffusion of carbon in fiber. The oxide film, which was formed around the fiber by heating in O2 gas stream, was amorphous silica at the biginning of the oxidation and low temperatures, and changed to cristobalite at longer time and at high temperatures. The temperature dependence of the oxidation rate was complicated, because of wide variation in the morphology of the oxide film. The oxidation rate was analyzed by the parabolic rate law. The oxidation was controlled by the gaseous diffusion through the pores in the oxide film. This film suppressed the pyrolysis of the amorphous core of the fiber.View full abstractDownload PDF (250K) -
Ken-ichi Kakimoto, Yoshiharu Kakehi, Toshio Shimoo, Kiyohito Okamura1992 Volume 39 Issue 6 Pages 451-454
Published: June 15, 1992
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSThe pyrolytic process of amorphous Si-Ti-C-O fiber (Tyranno) containing 17.8mass%0 was investigated in argon and oxygen atomospheres at temperatures from 1473 to 1673K. The amorphous fiber crystallizes rapidly to β-SiC and TiC by the pyrolysis in an argon atomosphere. By this pyrolysis, the mechanical properties of the fiber deteriorate remarkably at temperatures above 1573K. On the other hand, the dense oxide film consisted of cristobalite and rutile was formed on the surface of the fiber by the oxidation, which suppresses the pyrolysis in the inner area of the fiber. After the oxide film was formed on the surface of the fiber in an oxygen atomosphere at 1673K, therefore, the pyrolysis of the fiber decreased significantly in an argon atomosphere. Finally, thermal-resistant characteristics of the fiber were found to be improved by the form of the oxide film.View full abstractDownload PDF (186K) -
Hiroyasu Taguchi1992 Volume 39 Issue 6 Pages 455-458
Published: June 15, 1992
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSSince the advent of high-strength, high modulus, low-density boron fiber, the role of fibers produced by chemical vapor deposition (CVD) in the field of high-performance composites has been well established. Although best known for its use as a reinforcement in resin-matrix composites, boron fiber has also received considerable attention in the field of metal matrix composites. Boron/aluminum was employed for tube-shaped truss members to reinforce the Space Shuttle orbiter structure, and has been investigated as a fan blade material for turbofan jet engines. There are drawbacks, however, in the use of boron in a metal matrix. The rapid reaction of boron fiber with molten aluminum and long-term degradation of the mechanical properties of diffusion-bonded boron /aluminum at temperatures greater than 480°C (900°F) preclude its use both for high-temperature applications and for potentially more economically feasible fabrication methods such as casting or low-pressure, high-temperature pressing. These drawbacks have led to the development of the silicon carbide (SiC) fiber.View full abstractDownload PDF (3410K) -
Hideharu Fukunaga, Yeoh Guan Keat1992 Volume 39 Issue 6 Pages 459-463
Published: June 15, 1992
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSThe discontinuous ceramic fiber reinforced aluminum alloy composites have been put into practical use, such as the piston and cylinder liner for automobile engines, the vane for rotary compressor and so on. However, they are requested to improve the high temperature strength over 200t and the wear resistivity. One of authers proposed reaction squeeze casting process to introduce intermatallic compounds into matrix aluminum by utilizing positively the reaction between fibers and molten aluminum. The reaction squeeze casting using the anatase type of TiO2 with molten aluminum showed that the mixed structure with very high hardness of α-Al2O3, TiAl and TiAl3 was formed, but it was not a homogenous microstructure. In the present paper, the reaction squeeze casting using the rutile type of TiO2 with molten aluminum was carting out to prepare the intermetallic compounds distributed matrix composites. The process temperatures and the hardness of composites with intermetallics are discussed.View full abstractDownload PDF (2594K) -
Moritaka Hida, Akira Sakakibara, Yoshito Takemoto, Hiroyuki Okada, Sei ...1992 Volume 39 Issue 6 Pages 464-467
Published: June 15, 1992
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSTensile property of cast Ti-fiber-reinforced Mg composite was tested and swaging effect of cast Mg covered with Al or Ti plate was examined. Strong interfacial bonding between Ti and Mg was confirmed by the pull-out test and excellent wettability was observed by the scanning electron microscope. Tensile strength of the cast Ti-fiber-reinforced Mg increased with increasing volume fraction of the fiber from 1 to 14%, while the increase of elongation was restricted within 10% of the volume fraction. Interfacial condition between Al and Mg was rather good after the swaging for the three-layer clad prepared free from intermetallic compound. Contact situation of the cast Mg to the Ti cover was once lowered by swaging but became improved by further swaging.View full abstractDownload PDF (2511K) -
Hiroshi Mabuchi, Hiroshi Tsuda, Yutaka Nakayama1992 Volume 39 Issue 6 Pages 468-473
Published: June 15, 1992
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSThe potential of TiAl as an elevated temperature material is well investigated. However, negligible room-temperature toughness and low high-temperature strength have limited its practical applications. To improve these properties, this compound was made as a composite material containing a second phase such as ceramics.
In the present study, using powder mixtures, combustion reaction was carried out to form in-situ intermetallic/ceramic composites in the Al-Ti-C, and Al-Ti-BN systems. As a result, the compact of Ti and Al with C(or BN) powder reacted exothermically to form TiAl and Ti2AlC(or Ti2AlN+TiB2). The resulting composites had a fine distribution of the Ti2AlC(or Ti2AlN+TiB2) in the matrix TiAl with a small amount of Ti3Al, and the volume fraction of these particles depended on the amount of C(or BN) present. Therefore, the processing technique in the present investigation is of interest as a new combustion reaction process to make in-situ intermetallic-based composite materials.View full abstractDownload PDF (3868K) -
Kenzo Fukaura, Nobumitsu Takase, Hisakichi Sunada, Hisashi Izumi, Kanj ...1992 Volume 39 Issue 6 Pages 474-478
Published: June 15, 1992
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSAl2O3 fiber reinforced Ni3Al composites were fabricated by vacuum hot pressing the mixtures of nickel, aluminium, boron powder and Al2O3 fiber. The high temperature tensile properties of the composites were discussed in connection with the microstructure.
The main results obtained were summarized as follows:
(1) The Al2O3/Ni3Al composites displayed no evidence of chemical reaction at the interface and it was considered that they had intimate relationship between Ni3Al matrix and Al2O3 fiber.
(2) The yield stress of the composites increased with increasing temperature up to about 800K.
(3) The effect of Al2O3 fiber on the strength of the composites was obscure, because Al2O3 fibers were randomly oriented and pores existed within the cluster of Al2O3 fibers.View full abstractDownload PDF (2951K) -
Sennosuke Takahashi, Masatoshi Ono, Yoshiya Ueda1992 Volume 39 Issue 6 Pages 479-483
Published: June 15, 1992
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSNi-Mo-liC samples were prepared by mixing powders and hot pressing them in vacuum. The sample was melted and pressed under microgravity conditions by a sounding rocket. The electron microstructures of this sample showed the uniform distribution and the globular configuration of liC particles in Ni-Ho matrix. The distribution of elements of Ni, Mo, Ti and C was measured by micro Auger electron spectroscopy for three parts;TiC particles in matrix, the boundary of TiC particles and their matrix, and the matrix. the obtained results suggest the molten state of the sample was kept static during rocket fright without the influence of thermal convection and gravity segregation.View full abstractDownload PDF (1418K) -
Masahiro Inoue, Atsushi Nakahira, Koichi Niihara1992 Volume 39 Issue 6 Pages 484-487
Published: June 15, 1992
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSThe sintering mechanism of Al2O3/SiC nanocomposites was investigated by microstructural observation using scanning and transmission electron microscopy. The sintering process in hot-pressing of γ-Al2O3/5vol% SiC powder mixture was divided into 3 stages. In the first stage (1000°-1350°C), γ→α phase transformation of Al2O3 occurred. The grain growth mechanism in the second stage (1350°-1450°C) was the subgrain rotation and coalescence. The subgrain domain was formed in this stage. In the final stage (1450°-1600°C), the larger subgrain domain was confirmed to grow by grain boundary migration.View full abstractDownload PDF (4284K) -
Mamoru Omori, Taro Koide, Toshio Hirai1992 Volume 39 Issue 6 Pages 488-491
Published: June 15, 1992
Released on J-STAGE: December 04, 2009
JOURNAL FREE ACCESSThe fine powder of β -SIC (50 mass%) and 50 mass% of oxide powders, 2 mole of Yb2O3 and 1 mole of Al2O3, were mixed and sintered at 1825°C in N2 gas. A dense composite can be obtained. The composite is constituted of β-SIC and Yb4Al2O9 mainly. It is not clear whether the Yb4Al2O9 matrix makes a martensitic transformation. The strength is more than 500 MPa. The thermal expansion coefficient is 6.1×10-6/°C.View full abstractDownload PDF (1243K) -
Hideto Yoshida, Noboru Miyata, Masaaki Sagawa, Shigeki Ishikawa, Junji ...1992 Volume 39 Issue 6 Pages 492-496
Published: June 15, 1992
Released on J-STAGE: December 04, 2009
JOURNAL FREE ACCESSSiC composites (Cf/SiC) reinforced with unidirectionally oriented carbon fibers are fabricated by Hot press sintering method. Five kinds of carbon fibers are used for the reinforcement. Tensile strengths of carbon mono-filaments after filament winding (FW) treatment, press treatment and heat treatment are measured to estimate the damages of them under the Cf/SiC fabrication. The mechanical properties of Cf/SiC composites are classified by two groups. One group shows high fracture toughness (13.4 - 21.4 MPa√m) and high flexural strength (360-540 MPa) and the other group shows low fracture toughness (3.4-6.3 MPa√m) and low flexural strengh (240-290 MPa). From tensile strength measurments of carbon mono-filament, it is turned out that two kinds of carbon fibers are easily deteriorated by (FW treatment)+(Press treatment)+(Heat treatment), and Cf/SiC composites fabricated by the fibers shows low fracture toughness and low flexural strength.View full abstractDownload PDF (1327K) -
Tomoyuki Awazu, Osamu Komura, Masaya Miyake1992 Volume 39 Issue 6 Pages 499-503
Published: June 15, 1992
Released on J-STAGE: December 04, 2009
JOURNAL FREE ACCESSSince silicon nitride is fabricated using liquid phase sintering, sintering additives usually remain between Si3N4 grains as grain boundary phases. The grain boundary phases are softened and suddenly reduce the strength of sintered body under high temperature. This phenomenon occurs more notably when grain boundary phases contain glassy ones. The condition of grain boundary phases also influences the creep property under high temperature. This paper investigates the internal friction of Si3N4 sintered body, which relates to grain boundary slip and diffusion of atoms. This investigation will clarify the relationship between the conditions of grain boundary phases (ex. crystallization) and the internal friction changes. The creep properties of sintered body are also studied by analyzing the results of internal friction measurements. This will allow us to fully consider the relationship between the composition of sintering additives and the effects of heat treatment for crystallization.View full abstractDownload PDF (3542K) -
Mitsuo Ueki, Osamu Terada, Minoru Saito, Satoshi Kinoshita, Hisashi Su ...1992 Volume 39 Issue 6 Pages 504-509
Published: June 15, 1992
Released on J-STAGE: December 04, 2009
JOURNAL FREE ACCESSStructure changes of TiC-10vol%Mo2C-10vol%Ni and TiC-20vol%TiN-10vol%Mo2C-10vol%Ni cermets occurring during short-time bending creep tests were mainly studied to elucidate the reason why the creep strength of nitrogen(N) contained cermets was superior to that of the other. It was found that micro-cracks formed in both cermets In the early stage of creep tests and the number of cracks increased with increasing creep strain or testing time, showing that creep curves obtained were by no means steady-state ones, and the creep strength of those cermets could not be now discussed from the viewpoint of steady-state creep. It was suggested that the superior creep strength of N contained cermets was caused by the fact that the uniform plastic flow during the tests was highly suppressed owing to the increased carbonitride/carbonitride interfaces, and moreover micro-cracks formation needed for Increasing creep strain was much more difficult comparing with N free cermets.View full abstractDownload PDF (5050K) -
Masahiro Anzai, Toru Sudo, Hisanori Otaki, Takuya Obana, Takeo Nakagaw ...1992 Volume 39 Issue 6 Pages 510-514
Published: June 15, 1992
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSSolid magnetic abrasive has been ever used in the field of magnetic finishing.In this study, the compound (liquid abrasive) of diamond paste and iron powder was used for magnetic abrasive and using this liquid abrasive, was attempted a magnetic finishing of WC-Co alloy. WC-Co alloy can be finished comfortably in comparison with steel under a similar finishing condition and it's surface roughness is under Rmax 0.1 μm. Magnetic finishing may contribute to the finishing of die or punch which were made of hard metal.View full abstractDownload PDF (5138K) -
Yoshihide Kotera, Michiko Yonemura1992 Volume 39 Issue 6 Pages 515-518
Published: June 15, 1992
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSZinc oxide, prepared by oxidation of zinc vapor at the temperature above 1500°C, contains metallic zinc or oxygen vacancy. When it isprepared by decomposition of zinc carbonate at the temperature below 500°C, it seems to be stoichiometric. Zinc oxide changed its color, when heated at 1400°C for 3 hours, to yellow with the addition of 1-5 wt% of aluminum oxide, or to brown with gallium oxide. X-ray diffraction analysis shows no peak shift of zinc oxide pattern, while zinc aluminate or zinc gallate was formed, ascertained from their peak positions. The addition of aluminum oxide had the complicated influence upon the optical properties of zinc oxide, while that of gallium oxide causes new absorption band. The results would be explained by the assumption, that color center was formed in zinc oxide and the model of imperfections in zinc oxide containing color center was proposed.View full abstractDownload PDF (239K)
- |<
- <
- 1
- >
- >|