Abstract

In this paper, the porous SiC preforms•were prepared by compression molding and sintering with SiC particles of 100μm and 12μm, NH 4 HCO 3 as pore-forming agent and NH 4 H 2 PO 4 as binder. The NH 4 HCO 3 is an excellent pore forming agent because of its no residual impurities. The pore-forming mechanism of NH 4 HCO 3 were studied, it shows that NH 4 HCO 3 decomposes at high temperature and forms pores at corresponding positions. In a certain range, with the increase of NH 4 HCO 3 content, the number of pores in the preform increases and the pore connectivity becomes better. Through the study of the volume ratio of coarse and fine SiC particles, it shows that the volume fraction of preform can be effectively adjusted by changing the ratio of 100μm and 12μm SiC. Additionally, this work verified the feasibility of ultrasonic cleaning SiC process and preform thermal debinding and sintering process. It shows that the preform with ideal appearance, porosity and strength can be well prepared by controlling these process parameters.

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