IN-SITU REACTED TIB2-REINFORCED MULLITE

In situ formation of TiB2 in mullite matrix through the reaction of TiO2, boron and ca rbon has been studied. In hot-pressed and pressureless-sintered samples, in addition to TiB2, TiC was also found to be dispersed phases in mullite matrix. However, in the case of pressureless-sintered samples, mullite/Ti(B)2 composite With 98% relative density can be obtained through a preheating step held at 1300 degrees C for longer than 3 h and then sintering at a temperature above 1600 degrees C. Hot-pressed composite containing 30 vol % TIB2 gives a flexural strength of 427 MPa and a fracture toughness of 4.3 MPam(1/2). Pressureless-sintered composite containing 20 vol % TiB2 gives a flexural strength of 384 MPa and a fracture toughness of 3.87 MPam(1/2).