Microstructure and Mechanical Properties of B<sub<4</sub<C-TiB<sub<2</sub<-SiC Ceramics Fabricated by Spark Plasma Sintering

A new preparation method of B<sub<4</sub<C-based composite ceramics was proposed to improve sintering performance and decrease preparation cost of B<sub<4</sub<C ceramics. Taking B<sub<4</sub<C, Ti<sub<3</sub<SiC<sub<2</sub<, and Si mixtures as raw powders, B<sub<4</sub<C-TiB<sub<2</sub<-SiC composite ceramics with 30 wt. % (TiB<sub<2</sub<+SiC) second phase were fabricated based on spark plasma sintering (SPS) method. Taking advantage of special sintering mechanism of SPS and in situ exothermic reaction during the sintering process, the new method was arranged to improve the sintering property and reduce the preparation cost of B<sub<4</sub<C ceramics. The results indicate that composite ceramics with high relative density (98.5%) can be obtained at 1650 °C and 50 MPa for 5 min. With the increasing of sintering pressure, hardness of B<sub<4</sub<C-TiB<sub<2</sub<-SiC composite ceramics gradually increases, fracture toughness decreases, while flexural strength shows a trend of rise slowly at first and then rise rapidly.