Gel reactive melt infiltration: A new method for large-sized complex-shaped C/C components ceramic modification

摘要

To widen the applications of conventional reactive melt infiltration (RMI) in large-sized complex-shaped C/C components, an ingenious process of gel-RMI (GRMI) was proposed in this study. The arching C/C-SiC composite was prepared successfully using GRMI method with polycarbosilane (PCS)-Si90Zr10 (Si: 90 at.%; Zr:10 at.%) sol. The porosity rate of the C/C preform decreased from 18.5% to 2.9%, while the density was raised from 1.40 g.cm(-3) to 2.05 g.cm(-3) after GRMI. The reason why C/C preform has been significantly densified is as follow: the PCS in PCS-Si90Zr10 sol formed SiC aerogel skeleton after pyrolysis, and then the Si90Zr10 powders were melted and released from the SiC aerogel into the C/C preform body when the temperature reached the melting point of Si90Zr10 alloy. The obtained C/C-SiC composite showed a pseudo-ductile rupture characteristic distinguished from that of the C/C preform, and its bending strength was significantly improved from 104.2 MPa of the C/C preform to 258.8 MPa. The C/C-SiC composite had a far lower mass ablation rate of 0.75 rugs(-1) than that of C/C preform, 23.30 mg.s(-1). Moreover, the GRMI was preliminarily applied in ceramic modifying nozzle-like C/C preform, and the result showed that the nozzle-like C/C preform was successfully densified from 1.3 g cm(-3 )to 1.96 g cm(-3). The GRMI process has great potential in ceramic modifying large-sized complex-shaped C/C components.