COMPOSITES SCIENCE AND TECHNOLOGY ELSEⅤIER Composites Science and Technology 62(2002)2179-2188 www.elsevier.com/locate/compscitech Consolidation of polymer-derived Sic matrix composites processing and microstructure Masaki Kotania,*. I, Takahiro Inoue, Akira Kohyama, Kiyohito Okamura Yutai Katoh Graduate School of Energy Science, Kyoto Univ Yoshidahonmachi, Sakyo-ku, Kyoto 606-8501, Japan bNational Institute of Advanced Industrial Science and Technology, 1-2-1 Namiki, Tsukuba, Ibaraki, 305-8942 Jape Institute of Advanced Energy, Kyoto University, Gokasho, Uji, Kyoto, 611-0011 Japan dOsaka prefecture University, 1-1 Gakuen-cho, Sakai, Osaka, 599-8531 Japan Received 19 October 2001: received in revised form 26 July 2002: accepted 27 July 2002 Abstract SiC fiber reinforced Sic matrix composite(SiC/SiC composite) has been developed by polymer impregnation and pyrolysis (PIP) method, which consists of impregnation, curing, consolidation, and re-impregnation and pyrolysis. As a prospective approach to fabricate a high performance composite, consolidation conditions, such as curing temperature to make a green body, pressure and heating rate during consolidation, were systematically controlled for effective consolidation. Because of its advantage in controlling hysical characteristic, polyvinylsilane(pvs) that is liquid thermosetting organo-silicic compound was utilized as the matrix pre- cursor. Based on the pyrolytic behavior of PVs, effects of the process conditions on microstructure of the consolidated bodies were accurately characterized. To relate those microstructure with mechanical property, flexural tests were performed for the composites fter multiple PIP processing. Consequently, process conditions to make a high performance composite could be appeared. Struc- C 2002 Elsevier Science Ltd. All rights reserved. er tural conditions to be optimized for further improvement in mechanical and environmental properties were also discussed Keywords: A Ceramic-matrix composites(CMCs): A. Preceramic polymer; B Curing: B Porosity: B Mechanical properties 1. Introduct shape and geometry, microstructural control, and cost Since silicon carbide possesses such superior proper Main challenge of this process has been made to ties as strength at elevated temperature, oxidation resis- reduce pores and cracks which were formed due to gas tance and microstructural stability under irradiation, evolution and volumetric shrinkage of a preceramic there have been many efforts on r& d of Sic/Sic polymer during pyrolysis [8-11]. Gas evolution causes composite for use in aerospace vehicles and fusion the inhomogenization of matrix. Volumetric shrinkage power reactor [1-5]. Among potential fabrication pro- directly gives rise to the formation of pores. After a cesses of ceramics matrix composites (CMCs), PIP polymer is hardened, both events lead to crack initia- method is one of most promising methods because of its tion. At that time, fiber distribution is determined advantages in the viewpoints of impregnation efficiency Although repetition of PIP processing is much useful to among fibers, large-scale fabrication with complicated fill such defects with polymer-pyrolyzed product microstructure produced in first PIP processing would be influential on final microstructure. Therefore, effec- Corresponding author at present address. Tel: +81-298-68-2336: tive consolidation to yield minimum amount of crack initiation and appropriate fiber distribution are very and Development, National Space Development Agency e Present address: Thermal Engineering Group, Office important technical issue a high per mance SiC/Sic composite Tsukuba Space Center 2-1-1 Sengen, Tsukuba, Ibaraki, n order to control the distribution of fibers and pores, utilization of high volumetric yield polymer, fille 0266-3538/02/S. see front matter C 2002 Elsevier Science Ltd. All rights reserved. PII:S0266-3538(02)00151-3Consolidation of polymer-derived SiC matrix composites: processing and microstructure Masaki Kotania,*,1, Takahiro Inoueb, Akira Kohyamac , Kiyohito Okamurad, Yutai Katohc a Graduate School of Energy Science, Kyoto University, Yoshidahonmachi, Sakyo-ku, Kyoto 606-8501, Japan bNational Institute of Advanced Industrial Science and Technology, 1-2-1 Namiki, Tsukuba, Ibaraki, 305-8942 Japan c Institute of Advanced Energy, Kyoto University, Gokasho, Uji, Kyoto, 611-0011 Japan dOsaka Prefecture University, 1-1 Gakuen-cho, Sakai, Osaka, 599-8531 Japan Received 19 October 2001; received in revised form 26 July 2002; accepted 27 July 2002 Abstract SiC fiber reinforced SiC matrix composite (SiC/SiC composite) has been developed by polymer impregnation and pyrolysis (PIP) method, which consists of impregnation, curing, consolidation, and re-impregnation and pyrolysis. As a prospective approach to fabricate a high performance composite, consolidation conditions, such as curing temperature to make a green body, pressure and heating rate during consolidation, were systematically controlled for effective consolidation. Because of its advantage in controlling physical characteristic, polyvinylsilane (PVS) that is liquid thermosetting organo-silicic compound was utilized as the matrix pre￾cursor. Based on the pyrolytic behavior of PVS, effects of the process conditions on microstructure of the consolidated bodies were accurately characterized. To relate those microstructure with mechanical property, flexural tests were performed for the composites after multiple PIP processing. Consequently, process conditions to make a high performance composite could be appeared. Struc￾tural conditions to be optimized for further improvement in mechanical and environmental properties were also discussed. # 2002 Elsevier Science Ltd. All rights reserved. Keywords: A. Ceramic-matrix composites (CMCs); A. Preceramic polymer; B. Curing; B. Porosity; B. Mechanical properties 1. Introduction Since silicon carbide possesses such superior proper￾ties as strength at elevated temperature, oxidation resis￾tance and microstructural stability under irradiation, there have been many efforts on R & D of SiC/SiC composite for use in aerospace vehicles and fusion power reactor [1–5]. Among potential fabrication pro￾cesses of ceramics matrix composites (CMCs), PIP method is one of most promising methods because of its advantages in the viewpoints of impregnation efficiency among fibers, large-scale fabrication with complicated shape and geometry, microstructural control, and cost [6,7]. Main challenge of this process has been made to reduce pores and cracks which were formed due to gas evolution and volumetric shrinkage of a preceramic polymer during pyrolysis [8–11]. Gas evolution causes the inhomogenization of matrix. Volumetric shrinkage directly gives rise to the formation of pores. After a polymer is hardened, both events lead to crack initia￾tion. At that time, fiber distribution is determined. Although repetition of PIP processing is much useful to fill such defects with polymer-pyrolyzed product, microstructure produced in first PIP processing would be influential on final microstructure. Therefore, effec￾tive consolidation to yield minimum amount of crack initiation and appropriate fiber distribution are very important technical issue for making a high perfor￾mance SiC/SiC composite. In order to control the distribution of fibers and pores, utilization of high volumetric yield polymer, filler 0266-3538/02/$ - see front matter # 2002 Elsevier Science Ltd. All rights reserved. PII: S0266-3538(02)00151-3 Composites Science and Technology 62 (2002) 2179–2188 www.elsevier.com/locate/compscitech * Corresponding author at present address. Tel.: +81-298-68-2336; fax: +81-298-68-2968. E-mail address: kotani.masaki@nasda.go.jp (M. Kotani). 1 Present address: Thermal Engineering Group, Office of Research and Development, National Space Development Agency of Japan, Tsukuba Space Center 2-1-1 Sengen, Tsukuba, Ibaraki, 305-8505 Japan