Materials Processing Technology ELSEVIER Joumal of Materials Processing Technology 190(2007)358-362 www.elsevier.com/locate/jmatprotec Rapid fabrication of c/C/Sic composite by Plp of HMds Jiehua Zhong Shengru Qiao a, Guofeng Lu, Yuebing Zhang a Ultra-high-temperature structural composites laboratory, Northwestern Polytechnical University, Xi'an 710072, PR China National Key Laboratory for Precision Hot Processing of Metals, Harbin Institute of Technology, Harbin 150001, PR China Received 9 July 2006: received in revised form 10 December 2006: accepted 3 February 2007 Abstract The C/C/SiC composite was fabricated within several days by the method of precursor impregnation and pyrolysis(PlP)using hexamethyldis- ilazane(HMDS)as the precursor. The carbon fiber plates, woven and punctured with two-dimensional orthogonal continuous carbon bundle and short carbon fiber, were used as the reinforced preforms. The characters of the C/C/SiC composite were analyzed using XRD, EDS and SEM, and three-point-bending test. The results indicated that pyrolyzed substance of the precursor contained excessive carbon, followed by silicon, and small amount of nitrogen. There were micro-cracks on the massive matrix. The phase composition was difficult to distinguish, primarily considered as the Si-C-N composite. The structure of C/C/SiC was dense and homogeneous with some pores whose sizes were less than 5 um between fibers and less than 100 um between the carbon fiber bundles, respectively Fiber pull-out was observed on the bending fracture surface. The stress-strain curve of both at room temperature and 1300 C appeared ascendin zigzag Flexural strength was 150 MPa at 1300C, higher than 121 MPa at room temperature o 2007 Published by Elsevier B.V. Keywords: PIP: HMDS; C/C/SiC; Flexural strength 1. Introduction Liquid precursor infiltration and pyrolysis(PIP) route to fab- ricate ceramic matrix composites is being actively studied for Continuous carbon fiber reinforced ceramic matrix com- its low processing temperature, short manufacturing time and posites(CFCCs) have many potential applications in high- simple demand for equipment [5,6]. Common precursors for temperature structural components because of their high strength fabricating C/SiC composites are such high molecular weight at elevated temperature, low density, superior toughness and polymers as polycarbosilane(PCs)and polymethlsilane(PMs brasive properties. Among CFCCs, carbon fiber reinforced However, their prices are high because they are not commer- silicon carbide composite(C/SiC) have been extensively investi- cial production at present. So, it is essential to look for a new gated and obtained certain practical application[1-3]. Currently, available precursor the main method for fabricating C/SiC composites in industry In this paper, HMDS, a cheap commercial organic substance, is the isothermal chemical vapor infiltration(CVD) technique. is selected. Feasibility of using it as precursor to fabricate C/Sic However, there was a limitation for its further development and composite is investigated and typical properties of as-prepare application because of its long price and long processing period C/C/SiC composite are analyzed [4]. In order to shorten processing period, several developments were done on CVI, including thermal-gradient chemical vapor 2. Material preparation analytical methods infiltration, forced-flow chemical vapor infiltration, pulse chem- ical vapor infiltration and so on. Those techniques need further In present work, the HMDS was used as precursor. The plates, woven and development although their processing time can be shortened. carbon fiber, were usedas the reinforced preform. The main characters of HMDS and the physical parameters of carbon fiber preform were given in Table 1.At preform was immersed in the container that was filled with molten low sponding author.Tel:+862988492084:fax:+862988492084 temperature coal pitch, and infiltrated with a pressure nailaddresses:zhongjiehua1981@mailnwpu.edu.cn, was taken out as the temperature dropped slightly and then put in a steel box. blao@nwpu.edu.cn(.Zhong) The preform, covered with a graphite powder layer with a thickness of 0.01 0924-0136/S-see front matter o 2007 Published by Elsevier B.V. doi: 10. 1016/j- jmatprotec 2007.02.008Journal of Materials Processing Technology 190 (2007) 358–362 Rapid fabrication of C/C/SiC composite by PIP of HMDS Jiehua Zhong a, Shengru Qiao a,∗, Guofeng Lu a, Yuebing Zhang b, Wenbo Han b, Dechang Jia b a Ultra-high-temperature structural composites laboratory, Northwestern Polytechnical University, Xi’an 710072, PR China b National Key Laboratory for Precision Hot Processing of Metals, Harbin Institute of Technology, Harbin 150001, PR China Received 9 July 2006; received in revised form 10 December 2006; accepted 3 February 2007 Abstract The C/C/SiC composite was fabricated within several days by the method of precursor impregnation and pyrolysis (PIP) using hexamethyldis￾ilazane (HMDS) as the precursor. The carbon fiber plates, woven and punctured with two-dimensional orthogonal continuous carbon bundle and short carbon fiber, were used as the reinforced preforms. The characters of the C/C/SiC composite were analyzed using XRD, EDS and SEM, and three-point-bending test. The results indicated that pyrolyzed substance of the precursor contained excessive carbon, followed by silicon, and a small amount of nitrogen. There were micro-cracks on the massive matrix. The phase composition was difficult to distinguish, primarily considered as the Si–C–N composite. The structure of C/C/SiC was dense and homogeneous with some pores whose sizes were less than 5 m between fibers and less than 100 m between the carbon fiber bundles, respectively. Fiber pull-out was observed on the bending fracture surface. The stress–strain curve of both at room temperature and 1300 ◦C appeared ascending zigzag. Flexural strength was 150 MPa at 1300 ◦C, higher than 121 MPa at room temperature. © 2007 Published by Elsevier B.V. Keywords: PIP; HMDS; C/C/SiC; Flexural strength 1. Introduction Continuous carbon fiber reinforced ceramic matrix com￾posites (CFCCs) have many potential applications in high￾temperature structural components because of their high strength at elevated temperature, low density, superior toughness and abrasive properties. Among CFCCs, carbon fiber reinforced silicon carbide composite (C/SiC) have been extensively investi￾gated and obtained certain practical application [1–3]. Currently, the main method for fabricating C/SiC composites in industry is the isothermal chemical vapor infiltration (CVI) technique. However, there was a limitation for its further development and application because of its long price and long processing period [4]. In order to shorten processing period, several developments were done on CVI, including thermal-gradient chemical vapor infiltration, forced-flow chemical vapor infiltration, pulse chem￾ical vapor infiltration and so on. Those techniques need further development although their processing time can be shortened. ∗ Corresponding author. Tel.: +86 29 88492084; fax: +86 29 88492084. E-mail addresses: zhongjiehua1981@mail.nwpu.edu.cn, blao@nwpu.edu.cn (J. Zhong). Liquid precursor infiltration and pyrolysis (PIP) route to fab￾ricate ceramic matrix composites is being actively studied for its low processing temperature, short manufacturing time and simple demand for equipment [5,6]. Common precursors for fabricating C/SiC composites are such high molecular weight polymers as polycarbosilane (PCS) and polymethlsilane (PMS). However, their prices are high because they are not commer￾cial production at present. So, it is essential to look for a new available precursor. In this paper, HMDS, a cheap commercial organic substance, is selected. Feasibility of using it as precursor to fabricate C/SiC composite is investigated and typical properties of as-prepared C/C/SiC composite are analyzed. 2. Material preparation analytical methods In present work, the HMDS was used as precursor. The plates, woven and punctured with two-dimensional orthogonal continuous carbon bundle and short carbon fiber, were used as the reinforced preform. The main characters of HMDS and the physical parameters of carbon fiber preform were given in Table 1. At first, the preform was immersed in the container that was filled with molten low￾temperature coal pitch, and infiltrated with a pressure of 1 MPa. The preform was taken out as the temperature dropped slightly and then put in a steel box. The preform, covered with a graphite powder layer with a thickness of 0.01 mm 0924-0136/$ – see front matter © 2007 Published by Elsevier B.V. doi:10.1016/j.jmatprotec.2007.02.008