An interfacial survey on microstructure of ZrB2-based ceramics codoped with carbon fibers and SiC whiskers

The objective of this paper was to study the impact of carbon fiber (C-f) addition on the densification behavior and the microstructure formation of ZrB2 reinforced with SiC whiskers (SiCw). The spark plasma sintering (SPS) performed at 1900 degrees C led to a near fully dense composite as a result of the synergetic effect between SiCw and C-f on the sintering behavior of ZrB2. The field emission scanning electron microscopy (FESEM), field emission electron probe micro-analyzer (FEEPMA), and X-ray diffraction (XRD) analyses verified the unreactivity of the ZrB2-SiCw-C-f system under the applied sintering conditions. The thermodynamic study proposed the in-situ generation of B4C and ZrC compounds, although any proof could be found in neither X-ray photoelectron spectroscopy (XPS) patterns nor high-resolution transmission electron microscopy (HRTEM) images. Additionally, thanks to the nucleation and growth of new SiC and graphite phases, barely any whisker/fiber form of such additives could be observed in the micrographs. Many dislocations, originating from the plastic deformation during the SPS process and the mismatch between the thermal expansion coefficients of adjacent phases, were found in the microstructure.