Improved fracture toughness of CNTs/SiC composites by HF treatment

Highlights: • A HF treatment to raw SiC powder was proposed to fabricate CNTs/SiC composites. • More structural damage of CNTs in untreated SiC matrix was caused. • With HF treatment, the fracture toughness of the CNTs/SiC composites was improved. Residual oxide impurities in high-temperature structural ceramics containing carbon-based reinforcements can react with the reinforcements during sintering to weaken their toughening effect. To eliminate such effect, a simple HF treatment technique is proposed. In this work, SiC ceramics and carbon nanotubes (CNTs)/SiC ceramic composites were fabricated by spark plasma sintering. The results showed that, after HF treatment, the structure of incorporated CNTs in the composites was unaffected and a slight improvement of relative density was fulfilled. The fracture toughness improvement of the composites from 4.4 ± 0.4 MPa m^1/2 to 5.4 ± 0.5 MPa m^1/2 with indentation method (IM) after HF treatment was also observed due to crack branching, CNT pull-out and crack bridging.