Synergetic effects of SiC and Csf in ZrB2-based ceramic composites. Part II: Grain growth

The synergetic effects SiC particles and short carbon fibers (C-sf) as well as hot pressing parameters (sintering temperature, dwell time and applied pressure) on the grain growth of ZrB2-based composites were investigated. Taguchi methodology was employed for the design of experiments to study the microstructure and grain growth of ZrB2-SiC-C-sf ceramic composites. Three hot pressing parameters and SiC/C-sf ratio were selected as the scrutinized variables. The sintering temperature and SiC/C-sf ratio were identified by ANOVA as the most effective variables on the gain growth of ZrB2-based samples. Removal of oxide impurities from the surface of starting particles by the reactant C-sf, not only hindered the extraordinary grain growth of ZrB2 matrix, but also improved the sinterability of the ceramics. A fully dense ceramic with an average grain size of 8.3 mu m was obtained by hot pressing at 1850 degrees C for 30 min under 16 MPa through adding 20 vol% SiC and 10 vol% C-sf to the ZrB2 matrix. SEM observations and EDS analysis verified the in-situ formation of ZrC which can restrain the growth of ZrB2 particles, similar to the role of SiC, by the pinning of grain boundaries as another stationary secondary phase. (C) 2016 Elsevier Ltd and Techna Group S.r.l. All rights reserved.