* Corresponding author. Tel.: #81-75-753-5593; fax: #81-75-761- 7695. E-mail address: kawase@cheme.kyoto-u.ac.jp (M. Kawase). Chemical Engineering Science 56 (2001) 2161}2170 Numerical simulation of the thermal-gradient chemical vapor in"ltration process for production of "ber-reinforced ceramic composite Teruoki Tago, Motoaki Kawase*, Yoshiaki Ikuta, Kenji Hashimoto Department of Chemical Engineering, Graduate School of Engineering, Kyoto University, Yoshida-Honmachi, Sakyo-Ku, Kyoto 606-8317, Japan Received 2 May 2000; received in revised form 22 August 2000; accepted 6 October 2000 Abstract A numerical model was developed in order to describe the thermal-gradient chemical vapor in"ltration (CVI) for the production of SiC  /Al  O  composite. The proposed model considered reaction, di!usion and deposition of alumina within the porous preform. The cubic array of disconnected cylinders model was proposed in order to represent the porous structure of the preform and the composite. The experimental results of CVI were in good agreement with the calculated results. The e!ects of total pressure, heating temperature and initial surface temperature on the "nal residual porosity and the in"ltration time were investigated. The heating temperature and the initial surface temperature had a larger e!ect on the porosity and the in"ltration time than did the total pressure. In order to produce a dense composite, the initial surface temperature must decrease with increasing heating temperature.  2001 Elsevier Science Ltd. All rights reserved. Keywords: Composites; Materials processing; Mathematical modeling; Reaction engineering; Chemical vapor in"ltration; Thermal gradient 1. Introduction Ceramic materials have increasing importance in high-temperature applications because of their high strength at high temperatures, as well as their low density and resistance to corrosion and erosion. Fiber-reinforced ceramic composites have improved toughness and strength compared to monolithic ceramics. One of the most common ways to produce ceramic composites is chemical vapor in"ltration (CVI), which can fabricate the composites without damaging the reinforcing whiskers and allows a near-net-shape production. In the CVI, a porous substrate (preform) is made from "bers or whiskers, and a CVD reaction and di!usion of gaseous reactants occur within the substrate simultaneously. The deposition of matrix component resulting from the CVD reaction a!ects the substrate porosity, which in#uences the di!usion and the reaction. A numerical model in which the change in the porous structure, the reaction and the di!usion rate in the voids must be taken into consideration in order to gain a better understanding of the in"ltration process. Several mathematical models for the CVI have been developed (Starr, 1988; Currier, 1990; Sotirchos, 1991). The numerical model for isothermal-CVI, which was based on the single-pore model (Gupte & Tsamopoulos, 1989), was developed, and the deposition pro"le was calculated within a single pore. Chung, McCoy, Smith, Cagliostro, and Carswell (1991), Chung, McCoy, Smith, and Cagliostro (1992) and Chung, McCoy, and Smith (1993) simulated isothermal-CVI taking into account the three-dimensional geometry of a woven fabric preform. Ofori and Sotirchos (1996, 1997) analyzed forced #ow CVI using the randomly overlapping "ber model to de- scribe the evolution of the porous structure, and Vaidyaraman, Lackey, Agrawal, and Starr (1996) and Lewis, Lackey, and Vaidyaraman (1997) developed a one-dimensional model for forced #ow-thermal gradi- ent CVI. Comparison between the calculated results and the experimental results was reported by McAllister and Wolf (1991) and Kawase et al. (1994). McAllister and Wolf reported a porous structure described by the random pore model in modeling isothermal-CVI. The 0009-2509/01/$- see front matter  2001 Elsevier Science Ltd. All rights reserved. PII:S0009-2509(00)00492-9