High-strength ZrB2-based ceramics prepared by reactive pulsed electric current sintering of ZrB2-ZrH2 powders

Fully densified ZrB 2-based ceramic composites were produced by reactive pulsed electric current sintering (PECS) of ZrB 2-ZrH 2 powders within a total thermal cycle time of only 35min. The composition of the final composite was directly influenced by the initial ZrH 2 content in the starting powder batch. With increasing ZrH 2 content, ZrB 2-ZrO 2, ZrB 2-ZrB-ZrO 2 and ZrB 2-ZrB-Zr 3O composites were obtained. The ZrB 2-ZrB-ZrO 2 composite derived from a 9.8wt% ZrH 2 starting powder exhibited an excellent flexural strength of 1382MPa combined with a Vickers hardness of 17.1GPa and a fracture toughness of 5.0MPam 1/2. The high strength was attributed to a fine grain size and the removal of B 2O 3 through reaction with Zr. Higher ZrH 2 content starting powders were densified through solution-reprecipitation resulting in the formation of coarser angular ZrB 2-ZrB composites with a Zr 3O grain boundary phase with a fracture toughness of 5.0MPam 1/2 and an acceptable strength in the 852-939MPa range. © 2012 Elsevier Ltd.status: publishe