Carbon nanotube/titanium carbide sol-gel coated zirconium diboride composites prepared by spark plasma sintering

With combination of a powder processing technique and a sol-gel process, carbon nanotube/titanium carbide coated zirconium diboride matrix composite was fabricated. Zirconium diboride (ZrB2) powders were coated with a functionalized carbon nanotubes (CNTs) mixed titanium carbide (TiC) sol-gel precursor. As the results suggests, the carbothermal reduction produced nanosized TiC grains at the surface of the ZrB2 particles with a homogenous distribution of CNTs. The densification of the CNT/TiC coated ZrB2 matrix composite was achieved via 1900 °C spark plasma sintering(SPS). The TiC grains and the CNTs were primarily concentrated in the grain boundaries of the ZrB2 and showed the pinning effects that restrained the growth of ZrB2 grain. The TiC grain diffusion in the sintering coarsened the grains from nanosizes to 1-2 µm, which improved the densification of the ZrB2. Due to the difference in coefficient of thermal expansion, CNTs bridged the gaps between the TiC and the ZrB2 matrix, which formed a weak-bonding interface. The major toughening mechanism found was crack deflection via the TiC grains on the ZrB2 matrix.