Preparation and Properties of ZrB_2-SiC Ceramic Composites Reinforced by Carbon Nanotubes

ZrB_2-SiC-xwt% carbon nanotubes(x=0,1.0,2.5,4.0)ceramic composites were fabricated by the hot-pressing sintering.The prepared conditions,mechanical properties and microstructure were also investigated.TEM was used to observe the microstructure and SEM was used to analyze the fracture surface and crack propagation.Then,the strengthening and toughening mechanism of carbon nanotubes were discussed.Results show that carbon nanotubes can deposit in the ZrB_2 crystal grain and form intragranular structure.When the carbon nanotubes content is 2.5wt%,the flexural strength and toughness reach 542MPa and 6.10MPa.m~(1/2)respectively,with the relative density of 99.6% and Vickers hardness value of 21.7GPa.The reasons of the mechanical properties improvement are the increased compactness,grain refining and the intragranular structure caused by the introduction of carbon nanotubes.