High fracture toughness of HfC through nano‐scale templating and novel sintering aids

Abstract An approach to improve the sintering ability and the fracture toughness of hafnium carbide (HfC) ceramic by designing a unique composite structure is reported. The uniform and ultra‐fine HfC nanoparticles (~300 nm) are synthesized at 1450°C by vacuum carbonization reaction with the glucose‐derived hydrothermal precursor as a carbon source and template. HfC ceramic sintered with a SiCN sintering aid of 15 vol. % possesses a beneficial three‐dimensional network microstructure composed of inter‐penetrating phases of carbon, SiC and HfC with varied stoichiometry at multi‐length scales. The obtained HfC exhibits a higher fracture toughness of 5.5 MPa m 1/2 , which can be attributed to the unique composite structure able to promote stress releases in the crack tip and enhance the resistance to crack propagation.