Polymer-derived SiC_f/SiC_m composite fabrication and microwave joining for fusion energy applications

This article reports experimental results for the very first batch of products obtained by joining silicon carbide fiber-reinforced-silicon carbide matrix composites for fusion applications. The starting point of this work has been to fabricate and join matched pairs of SiC_f/SiC_m composites. The composites were joined in a microwave heating environment using preceramic polymer slurry as the joining material. Several key properties of these composites and joints were investigated, including measurements of density, flexural stress, and thermal conductivity. Measurements of our very first batch of products showed the average flexural stress for the intrinsic material at room temperature was 287.1 MPa. The composite exhibited crack deflection during fracture at room temperature. At 1100C, the average flexural stress dropped to 103.7 MPa and the composite exhibited brittle fracture. We obtained the in-plane thermal conductivity of the intrinsic material was 13.3 W/m-K at room temperature and 8.7 W/m-K at 1000C. The cross-plane thermal conductivity was 3.8 W/m-K at room temperature and 4.1 W/m-K at 1000C. Butt-joined bend bars had an average flexural stress of 31.9 MPa. Dovetail-joined bend bars had an average flexural stress of 39.0 MPa. The maximum value obtained for the dovetail-joined bend bars was 48.1 MPa. Optimization of the process parameters and detailed characterization are in progress to build a strong database and yield high-quality products for first wall structural material.