Novel light and tough ZrB2-based functionally graded ceramics

Functionally graded materials (FGM) based on ZrB2 and containing SiC chopped fibers from 5 to 50 vol% are produced by powder metallurgy and hot pressing. An additional MoSi2-ZrB2 outermost layer is added to improve the oxidation resistance. Besides, to prevent SiC fibers from detrimental reactions with MoSi2 during sintering, a ZrB2-based buffer layer is sandwiched between the fiber-rich bulk and the outer MoSi2-containing scale. The fibers in the optimized architecture are efficaciously protected during the sintering stage and effectively toughen the matrix. The FG composite has a density as low as 3.65 g/cm(3), nearly halved compared to pure ZrB2, and fracture toughness around 5-6 MPa.root m, doubled as compared to monolithic ZrB2. In addition, preliminary oxidation tests at 1650 degrees C reveal that the outermost ZrB2 scale effectively protects the fiber from oxidation, thanks to the tailored doping with MoSi2 and Si3N4. (C) 2016 Elsevier Ltd. All rights reserved.