Synthesis and Rapid Sintering of Ultra Fine TiB2-ZrO2 Composite

Abstract

TiB₂ is considered candidate materials for ultra-high temperature ceramics and cutting tools because of its a high thermal conductivity, a low coefficient of thermal expansion, a high hardness and high melting temperature. Despite these attractive properties, TiB2 applications are limited because it has a low fracture toughness below the brittle-ductile transition temperature. To improve on its mechanical properties, the approach universally utilized has been to add secondary materials to form a composite and to fabricate an ultra - fine material. A dense ultra - fine TiB₂- ZrO₂ composite was rapidly sintered using pulsed high current activated heating (PHCAH) methods within 3 min in one step from the mechanically synthesized the powders of TiB₂ and ZrO₂ . Consolidation was reached using an effective combination of mechanical pressure and the pulsed high current. A highly dense TiB₂-ZrO₂ material with relative density of 97.2% was made by the simultaneous application of 75 MPa pressure and a pulsed 2500 A current. The grain sizes of TiB₂ and ZrO₂ in the composite were 135 nm and 84 nm, respectively. The fracture toughness and hardness of the TiB₂ -ZrO₂ composite were 11.2 MPa.m^1/2 and 957 kg/mm² , respectively. The fracture toughness of the TiB₂ -ZrO₂ composite was three times higher than that of monolithic TiB₂ .