Thermal Shock Characteristics of C-B-Ti Composite Materials

Abstract

C-B-Ti composite ceramic materials have some preferable properties including high melting point as the inner wall materials of nuclear fusion devices, but their thermal shock resistances are not well known. In this experiment, those materials were fabricated by sintering carbon, boron and titanium powders, and then characterized by X-ray diffraction, X-ray micro-analysis, scanning electron microscopy and density measurement. Thermal shock tests of these samples were performed using a hollow-cathode type electronbeam apparatus.
Thermal-stress fracture was more infrequent in samples containing higher carbon and lower titanium contents. The investigation of relations between the microstructures and the atomic concentration ratios revealed that samples with high titanium and low carbon concentrations had polycrystals of TiC and TiB₂, while those containing high carbon and low titanium consisted of TiC, TiB₂ and graphite polycrystals, and exhibited complex microstructures of the ceramics and the graphite. Higher resistance to thermal-stress fracture of samples with high carbon and low titanium contents may be highly related to the constituent graphite for it has high thermal-shock resistance and complex microstructures with high crack-propagation resistances.