Synergetic effects of SiC and Csf in ZrB2-based ceramic composites. Part I: Densification behavior

The effects of processing variables on densification behavior of hot pressed ZrB2-based composites, reinforced with SiC particles and short carbon fibers (C-sf), were studied. A design of experiment approach, Taguchi methodology, was used to investigate the characteristics of ZrB2-SiC-C-sf composites concentrated upon the hot pressing parameters (sintering temperature, dwell time and applied pressure) as well as the composition (vol% SiC/vol% C-sf). The analysis of variance recognized the sintering temperature and SiC/C-sf ratio as the most effective variables on the relative density of hot pressed composites. The microstructural investigations showed that C-sf can act as a sintering aid and eliminate the oxide impurities (e.g. B2O3, ZrO2 and SiO2) from the surfaces of raw materials. A fully dense composite was achieved by adding 10 vol% C-sf and 20 vol% SIC to the ZrB2 matrix via hot pressing at 1850 degrees C for 30 min under a pressure of 16 MPa. Moreover, the in -situ formation of interfacial ZrC, which also improves the sinterability of ZrB2-based composites, was studied by energy -dispersive X-ray spectroscopy analysis and verified thermodynamically. (C) 2015 Elsevier Ltd and Techna Group S.r.l. All rights reserved.