Low-activation joining of SiC/SiC composites for fusion applications

Research at PNNL has been directed at high-strength, low-activation joints using solid-state displacement reactions. This paper reports on further development and optimization of displacement reaction joints for the TITAN collaboration. The results reveal that fully dense and high-quality joints between SiC-composite bars are fabricated at 1623 K–1723 K using 30 MPa pressure in purified argon atmospheres. Scanning electron micrographs reveal typical interpenetrating phase microstructures in the joints, which are about 10 μm thick. Blocky SiC particles are observed to nucleate preferentially at the SiC-joint interface but are more plate-like within the joint. X-ray spectroscopy reveals a uniform distribution of constituent elements consistent with the interpenetrating phases.