Additive-free hot-pressed silicon carbide ceramics-A material with exceptional mechanical properties

Densification of silicon carbide without any sintering aids by hot-pressing and rapid hot pressing was investigated. Full density (>99% t.d.) has been reached at 1850 degrees C, a temperature of at least 150-200 degrees C lower compared to the up to now known solid state sintered silicon carbide powders. Silicon carbide was freeze granulated and heat treated prior the densification. Evolution of microstructure, mechanical properties and creep behavior were evaluated and compared to reference ceramics from as received silicon carbide powder as well as those of commercial one. Novel method results in dense ceramics with Vickers hardness and indentation fracture toughness of 29.0 GPa and 5.25 MPam(1/2), respectively. Moreover, the creep rate of 3.8 x 10(-9) s(-1) at 1450 degrees C and the load of 100 MPa is comparable to the commercial alpha-SiC solid state sintered at 2150 degrees C. (C) 2015 Elsevier Ltd. All rights reserved.