An attempt of improving LSI SiC/SiC temperature tolerance through adjusting C-Si reaction to regulate the matrix structure and composition

Residual Si softens or melts at elevated temperatures, compromising the ability of matrix to transmit stress and thereby limiting the maximum service temperature of LSI SiC/SiC composites, despite their many advantages. To address this limitation, a strategy involving Si encapsulated by SiC has been proposed in this work. This structure can be fabricated by combining a three-dimensional C network composed of C spheres with a segmented heat-preservation infiltration process. The graphitized C spheres react with Si to produce a large amount of granular SiC. Additionally, the segmented heat preservation approach allows for precise control over the C-Si reaction and growth of SiC, ultimately yielding a matrix structure in which SiC forms an interconnected network that encapsulates residual Si. The SiC/SiC composites show flexural strengths of 473 ± 28 MPa at 1315 °C and 461 ± 34 MPa at 1400 °C, with only a 2.54 % decrease. In comparison, composites with a dispersed SiC-reinforced continuous Si matrix retain only 75.25 % of their strength when the temperature rises from 1315 °C to 1400 °C.