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 (Csf), were studied. A design of experiment approach, Taguchi methodology, was used to investigate the characteristics of ZrB2–SiC–Csf composites concentrated upon the hot pressing parameters (sintering temperature, dwell time and applied pressure) as well as the composition (vol% SiC/vol% Csf). The analysis of variance recognized the sintering temperature and SiC/Csf ratio as the most effective variables on the relative density of hot pressed composites. The microstructural investigations showed that Csf 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% Csf and 20 vol% SiC to the ZrB2 matrix via hot pressing at 1850 °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.