Ti and TiC co-toughened Al2O3 composites by in-situ synthesis from reaction of Ti and MWCNT

This study aims to toughen brittle Al2O3 ceramics by preparing Al2O3–Ti–TiC multi-phase composites from Al2O3, TiH2 and multi-walled carbon nanotube (MWCNT) mixed powders. Co-toughened effects of soft Ti phase and hard TiC phase which was in-situ formed by reaction of Ti and MWCNT were studied. For this purpose, Ti and MWCNT with different content were added into Al2O3 matrix to fabricate multi-phase composites of Al2O3–Ti–TiC and their microstructure, mechanical and electrical properties were investigated. Energy-dispersive X-ray spectroscopy (EDX) and X-ray diffraction (XRD) analysis indicated the successful synthesis of Al2O3–Ti–TiC multi-phase composites and the compositions were calculated by Rietveld method based on X-ray diffraction patterns. Due to the absence of MWCNT phase, the addition of MWCNT didn't improve electrical properties and these Al2O3–Ti–TiC multi-phase composites exhibited quite high electrical resistivity of ̴ 1011 Ωcm. On the other hand, the combination of Ti and TiC phases showed greater toughening effects than any single one. Fracture toughness of 0.5 vol% CNT added (Al2O3-2.4 vlo% Ti-7.9 vol% TiC) composite reached to the maximum which increased by 37% compared to monolithic Al2O3. The toughening mechanism was demonstrated as crack deflection and bridging by both Ti and TiC particles. In addition, it was found that when TiC which was in-situ formed from reactive Ti and MWCNT was employed to toughen Al2O3, owning to refined mi...
Source: Materials Science and Engineering: A - Category: Materials Science Source Type: research