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Synthesis and reaction sintering of WB
337
ature. High density ( •99. 7% T. D. ) was obtained by HlPing above 1950°C using powders with the mean particle size less than O. 6/am. With O. 8/am a-SiC powder, the sintered density was about 95% T. D. with slight dependence on the HIP temperature. (2) The microstracture of highly dense sintered matenals was uniform with fine grains, but that of 95 % 7".1). material was characterized by coarse grains and intra.granular isolated pores. ( 3 ) a-SiC powder sinters better than 19-SIC powder for the same mean particle size. ( 4 ) Fine SiC powders gave high Vickers hardness and low Kic value in comparison to coarse powders. [ReceivedJune 11, 1986]
HIP Sintering of Silicon Nitride without Additives Katuhiko HOMMA, Hiroshi OKADA, Takao FUJIKAWA* and Tuneo TATUNO Material R. . . . . . h Laboratory, Kobe Steel, Lad. \ 3-18, Wakihama-cho 1-chome, Chuo-ku, Kobe-shi 651 * Machinery Engineering Research Laboratory, Kobe Steel, Ltd.
)
Four kinds of SiaNd starting powders with dijferent amounts of impurities and various specific surface areas, were cold pressed isostatically, encapsulated in a Vycor glass tube, and HIPed in 150 MPa-argon gas at 1800°-2000°C. The density, flexural strength, hardness and microstructure were investigated. The results are summarized as follows : ( I ) Sintered materials with more than 99% relative density werefabmcated by HIPing above 1900°C. ( 2 ) The sintered materials were composed of equiaxed fl-Si~N, grains. A small amount of an intergranular glassy phase was detected using high resolution TEM technique. ( 3 ) The sintered materials prepared from high purity powders showed excellent mechanical properties at elevated temperature, i. e. the flexural strength at 1400°C and Vichers hardness at 1300°C were 750 MPa and 13. 2 GPa, respectively. [Recelved dune 11, 1986]
Very High Pressure Hot Pressing of Oxidized Silicon Nitride Powders without Additives Shoichi KUME. Haruo YOSHIDA and Michihide MACHIDA Government Industrial Research Institute. Nagoya] 1-1, Hirate-cho, Kita-ku, Nagoya-shi 462 /
Silicon nitride powders operated by oxidation in air at 1200°C for 70 to 210 min, in which the oxygen content was from 2. 8 to 8. 9 wt%, were sintered without additives under the pressure of 3. 0 GPa. The influence of oxygen on the characteristics of the sintered bodies was studied. Various amounts of a phase remained in sintered bodies depending on the oxygen content in the operated por~ters. Vichers microhardness of the sintered body prepared from the powder containing 2. 8 wt% oxygen was higher than that of the sintered body from the starting powder at elevated temperature up to 1300 °C. [Rect~vedJuly 23, 1986]
Synthesis and Reaction Sintering of WB Tsuneaki MATSUDAIRA, Hideaki ITOH, $higeharu NAKA, Hlroshi HAMAMOTO* and Mikio OBAYASHI* Synthetic Crystal R. . . . . . h Laboratory, Facu|ty of Engineering, Nagoya University) Furo-cho, Chikusa-ku. Nagoya-shi 464 * Toyota Central Research & Development Laboratories Ine
The conditwns for preparing WB by solid state reaction between tungsten and amorphous boron powders were investigated. The effect of added titanium or zirconium on the sinterability of the synthesized WB powder was examined under high pressure and temperature conditions. WB was obtained as a single crystalline phase, when a mixed powder containing boron 10
338 at% in excess of the stoichiometric composition WB, teas pretreated at 500°C for 60 min in a stream of hydrogen and subse, quently treated at 1400"C for 60 rain in a stream of argon. The crystallinity and the amount of WB increased with increasing both heat treatment time and temperature. The atomic ratio B / W remained constant after the heat treatment below 1500°C. Sintering of the synthesized powder at 4 GPa and 1500"C for 15 min resulted in the density of 13. 3 g/cms and microhardness of 1400 kg/mm:. For 5 at% titanium addition, higher density (14. 0 g/crns) and improve.d microhardness (2800 kg/mm z) were attained by sintering at a lower temperature of 1300"C at 4 GPa. The densification of reaction-bonded WB is promoted possibly by the formation reaction of TiB, from free amorphous boron and added titanium. Similar behavior was observed with the zirconium addition also. [ReceivedJuly 15, 1986]
Preparation of Ultra-Fine Spherical Particles of 7-A1203 by Burning of Aluminum Powder Tsukasa HIRAYAMA Research Development Corporation of Japan Now with R & D Dept. 1, Nippondettso Co.,Ltd.I 1-1, Showa-cho, Kariya-shi 448 /
A new methodfor preparing ultra-fine alumina powders consistingof sphericalparticles basedon combustion has beendeveloped. A mixture of fuel gas, H,+ CH,, and aluminum powder with particle size of several micrometers is burnt in a conventional burner for glass blowing. Examination of obtained products by electron microscopyand X- ray diffraction shoumt that they were alumina with two types of structures, 8- and & AIjQ. The present note describes an economical and efficient method for tile production of alumina sphericalparticles. [ReceivedJuly 11, 1986]
Preparation of Silicon Oxynitride Fiber and its Mechanical Properties Mitsuhiko SATO, Yoshio HASEGAWA" and Kiyohito OKAMURA The Oarai Branch, The Research Institute for Iron, Steel and Other Metals, Tohoku University\ Oarai, Higashi-Ibaraki-gun 311-13 * The Research Institute for Special Inorganic Materials
)
The nitridation of polycarbosilane started at 400* to 500°C in the heat treatment of polycarbosilane in NEe gas and was almost completed at about 800"C. Above 1000°C, the obtained nitride changed from amorphous to crystalline state, and at 1400"C, the crystalline phase was a-SisN,. On the basis of the nitridation of polycarbosilane, oxidation-cured polycarbosilane fibers mere heated in NH, gas between 1000° and 1400"C to obtain silicon oxynitride fibers. The silicon oxynitride fibers were in the amorphous state and transparent to visible light. The tensile strength and Youn~s modulus of the fibers obtained at 1300"C were 1.80±0. 37 GPa and 139 ~ 17 GFa, respectively. The fibers obtained at 1400"C were heat-treated between 1000" and 1400"C in Ar gas and in air to examine the heat resistance of the fibers. The fibers retained their tensile strength and Youn~ s modulus up to 1400"C in Ar gas and up to 1200"C in air. [ReceivedJuly 15, 1986]
Microstructural Change of Polycrystalline Ba-Ferrite (BaO'6FesO~) by Hot-Extrusion Processing Tomozo NISHIKAWA, Toshihiko NISHIDA, Takeshi SHIONO, lwao UENO and Harunobu SANO Department of Industrial Chemistry, Faculty of Engineering and Design, Kyoto Institute of Technology~ ] Matangasaki, Sakyo-ku, Kyoto-shi 606
The hot.working processes such as rolling, forging, extrusion etc. are widely used for metallic materials to make their shape and improve their properties. For ceramics, theseprocesses are seldom carried out because of the lack of their plastic property. However, it is also well known that ceramics can deform plastically at high temperature. In this study r o e tried to examine the possibility of the hot-extrusion process for polyerystalline Ba-ferrite ( BaO.6 FejOj) that is easier to deform plash. cally than other oxide ceramics. Polycrystalline Ba-ferrite samples capsulated in stainless steel (SUS304) were pre, keated
ature. High density ( •99. 7% T. D. ) was obtained by HlPing above 1950°C using powders with the mean particle size less than O. 6/am. With O. 8/am a-SiC powder, the sintered density was about 95% T. D. with slight dependence on the HIP temperature. (2) The microstracture of highly dense sintered matenals was uniform with fine grains, but that of 95 % 7".1). material was characterized by coarse grains and intra.granular isolated pores. ( 3 ) a-SiC powder sinters better than 19-SIC powder for the same mean particle size. ( 4 ) Fine SiC powders gave high Vickers hardness and low Kic value in comparison to coarse powders. [ReceivedJune 11, 1986]
HIP Sintering of Silicon Nitride without Additives Katuhiko HOMMA, Hiroshi OKADA, Takao FUJIKAWA* and Tuneo TATUNO Material R. . . . . . h Laboratory, Kobe Steel, Lad. \ 3-18, Wakihama-cho 1-chome, Chuo-ku, Kobe-shi 651 * Machinery Engineering Research Laboratory, Kobe Steel, Ltd.
)
Four kinds of SiaNd starting powders with dijferent amounts of impurities and various specific surface areas, were cold pressed isostatically, encapsulated in a Vycor glass tube, and HIPed in 150 MPa-argon gas at 1800°-2000°C. The density, flexural strength, hardness and microstructure were investigated. The results are summarized as follows : ( I ) Sintered materials with more than 99% relative density werefabmcated by HIPing above 1900°C. ( 2 ) The sintered materials were composed of equiaxed fl-Si~N, grains. A small amount of an intergranular glassy phase was detected using high resolution TEM technique. ( 3 ) The sintered materials prepared from high purity powders showed excellent mechanical properties at elevated temperature, i. e. the flexural strength at 1400°C and Vichers hardness at 1300°C were 750 MPa and 13. 2 GPa, respectively. [Recelved dune 11, 1986]
Very High Pressure Hot Pressing of Oxidized Silicon Nitride Powders without Additives Shoichi KUME. Haruo YOSHIDA and Michihide MACHIDA Government Industrial Research Institute. Nagoya] 1-1, Hirate-cho, Kita-ku, Nagoya-shi 462 /
Silicon nitride powders operated by oxidation in air at 1200°C for 70 to 210 min, in which the oxygen content was from 2. 8 to 8. 9 wt%, were sintered without additives under the pressure of 3. 0 GPa. The influence of oxygen on the characteristics of the sintered bodies was studied. Various amounts of a phase remained in sintered bodies depending on the oxygen content in the operated por~ters. Vichers microhardness of the sintered body prepared from the powder containing 2. 8 wt% oxygen was higher than that of the sintered body from the starting powder at elevated temperature up to 1300 °C. [Rect~vedJuly 23, 1986]
Synthesis and Reaction Sintering of WB Tsuneaki MATSUDAIRA, Hideaki ITOH, $higeharu NAKA, Hlroshi HAMAMOTO* and Mikio OBAYASHI* Synthetic Crystal R. . . . . . h Laboratory, Facu|ty of Engineering, Nagoya University) Furo-cho, Chikusa-ku. Nagoya-shi 464 * Toyota Central Research & Development Laboratories Ine
The conditwns for preparing WB by solid state reaction between tungsten and amorphous boron powders were investigated. The effect of added titanium or zirconium on the sinterability of the synthesized WB powder was examined under high pressure and temperature conditions. WB was obtained as a single crystalline phase, when a mixed powder containing boron 10
338 at% in excess of the stoichiometric composition WB, teas pretreated at 500°C for 60 min in a stream of hydrogen and subse, quently treated at 1400"C for 60 rain in a stream of argon. The crystallinity and the amount of WB increased with increasing both heat treatment time and temperature. The atomic ratio B / W remained constant after the heat treatment below 1500°C. Sintering of the synthesized powder at 4 GPa and 1500"C for 15 min resulted in the density of 13. 3 g/cms and microhardness of 1400 kg/mm:. For 5 at% titanium addition, higher density (14. 0 g/crns) and improve.d microhardness (2800 kg/mm z) were attained by sintering at a lower temperature of 1300"C at 4 GPa. The densification of reaction-bonded WB is promoted possibly by the formation reaction of TiB, from free amorphous boron and added titanium. Similar behavior was observed with the zirconium addition also. [ReceivedJuly 15, 1986]
Preparation of Ultra-Fine Spherical Particles of 7-A1203 by Burning of Aluminum Powder Tsukasa HIRAYAMA Research Development Corporation of Japan Now with R & D Dept. 1, Nippondettso Co.,Ltd.I 1-1, Showa-cho, Kariya-shi 448 /
A new methodfor preparing ultra-fine alumina powders consistingof sphericalparticles basedon combustion has beendeveloped. A mixture of fuel gas, H,+ CH,, and aluminum powder with particle size of several micrometers is burnt in a conventional burner for glass blowing. Examination of obtained products by electron microscopyand X- ray diffraction shoumt that they were alumina with two types of structures, 8- and & AIjQ. The present note describes an economical and efficient method for tile production of alumina sphericalparticles. [ReceivedJuly 11, 1986]
Preparation of Silicon Oxynitride Fiber and its Mechanical Properties Mitsuhiko SATO, Yoshio HASEGAWA" and Kiyohito OKAMURA The Oarai Branch, The Research Institute for Iron, Steel and Other Metals, Tohoku University\ Oarai, Higashi-Ibaraki-gun 311-13 * The Research Institute for Special Inorganic Materials
)
The nitridation of polycarbosilane started at 400* to 500°C in the heat treatment of polycarbosilane in NEe gas and was almost completed at about 800"C. Above 1000°C, the obtained nitride changed from amorphous to crystalline state, and at 1400"C, the crystalline phase was a-SisN,. On the basis of the nitridation of polycarbosilane, oxidation-cured polycarbosilane fibers mere heated in NH, gas between 1000° and 1400"C to obtain silicon oxynitride fibers. The silicon oxynitride fibers were in the amorphous state and transparent to visible light. The tensile strength and Youn~s modulus of the fibers obtained at 1300"C were 1.80±0. 37 GPa and 139 ~ 17 GFa, respectively. The fibers obtained at 1400"C were heat-treated between 1000" and 1400"C in Ar gas and in air to examine the heat resistance of the fibers. The fibers retained their tensile strength and Youn~ s modulus up to 1400"C in Ar gas and up to 1200"C in air. [ReceivedJuly 15, 1986]
Microstructural Change of Polycrystalline Ba-Ferrite (BaO'6FesO~) by Hot-Extrusion Processing Tomozo NISHIKAWA, Toshihiko NISHIDA, Takeshi SHIONO, lwao UENO and Harunobu SANO Department of Industrial Chemistry, Faculty of Engineering and Design, Kyoto Institute of Technology~ ] Matangasaki, Sakyo-ku, Kyoto-shi 606
The hot.working processes such as rolling, forging, extrusion etc. are widely used for metallic materials to make their shape and improve their properties. For ceramics, theseprocesses are seldom carried out because of the lack of their plastic property. However, it is also well known that ceramics can deform plastically at high temperature. In this study r o e tried to examine the possibility of the hot-extrusion process for polyerystalline Ba-ferrite ( BaO.6 FejOj) that is easier to deform plash. cally than other oxide ceramics. Polycrystalline Ba-ferrite samples capsulated in stainless steel (SUS304) were pre, keated