Synthesis and densification of zirconium diboride prepared by carbothermal reduction

Abstract

Using boron powder as additive, the preparation of zirconium diboride (ZrB2) by carbothermal reduction was investigated. The results show that the carbothermal reduction cannot be completely done until the temperature is more than 1900 °C. The ZrB2 particles prepared without boron (B) additive at 1900 °C for 3 h are rodlike and show a preferential grain growth along [001] direction. B additive changes the heat effect of the raw materials. With B additive, the morphology of ZrB2 particles turns to be regular shape. The average particle size is about 3.6 μm with 2.5 wt% B additives. With more B additive, the shape of particles turns to be round like and the average particle size is decreased to 2.3 μm when 5 wt% B is added. The existence of oxides in grain boundary is a key factor to keep ZrB2 ceramic from deep densification. Using ZrB2 powder prepared with 5 wt% B additives, by controlling carbon content in ZrB2 powder, ZrB2 ceramic with 93% relative density is hot-pressed.