Sintering studies on ultrafine ZrB2 powder produced by a self-propagating high-temperature synthesis process

A detailed study on the sintering behavior of zirconium diboride powder pro duced by the self-propagating high-temperature synthesis (SHS) process was carried out in the temperature range of 1500-1800 degreesC. The fine powder prepared by the SHS process exhibited excellent sinterability and could be sintered at 1800 degreesC for 1 h to approximately 94% of the theoretical density. The apparent activation energy of densification in the range of 15 00-1800 degreesC was estimated to be 248 +/- 4 kJ mol(-1). A zirconium diox ide layer formed on the surface of the sintered body and was attributed to boron oxide formation during sintering and concurrent surface oxidation by the oxygen generated from the reduction of boron oxide in the carbonaceous atmosphere. Sintering aids like Fe and Cr appeared to help in densification of ZrB2 powder.