Microstructure refinement and mechanical properties improvement of HfB2-SiC composites with the incorporation of HfC

HfB2 and HfB2-10 vol% HfC fine powders were synthesized by carbo/boronthermal reduction of HfO2, which showed high sinterability. Using the as-synthesized powders and commercially available SiC as starting powders, nearly full dense HfB2-20 vol% SiC (HS) and HfB2-8 vol% HfC-20 vol% SiC (HHS) ceramics were obtained by hot pressing at 2000 degrees C/30 MPa. With the incorporation of HfC, the grain size of HHS was much finer than HS. As well, the fracture toughness and bending strength of HHS (5.09 MPa m(1/2), 863 MPa) increased significantly compared with HS (3.95 MPa m(1/2), 654 MPa). Therefore, it could be concluded that the incorporation of HfC refined the microstructure and improved the mechanical properties of HfB2-SiC ceramics. (C) 2012 Elsevier Ltd. All rights reserved.