Microstructure, Mechanical Property and Thermal Conductivity of Porous TiCO Ceramic Fabricated by In Situ Carbothermal Reduction of Phenolic Resin and Titania

The porous TiCO ceramic was synthesized through a one-step sintering method, utilizing phenolic resin, TiO2 powder, and KCl foaming agent as raw materials. Ni(NO3)2·6H2O was incorporated as a catalyst to facilitate the carbothermal reaction between the pyrolytic carbon and TiO2 powder. The influence of Ni(NO3)2·6H2O catalyst content (0, 5, 10 wt.% of the TiO2 powder) on the microstructure, compressive strength, and thermal conductivity of the resultant porous TiCO ceramic was examined. X-ray diffraction and X-ray photoelectron spectroscopy results confirmed the formation of TiC and TiO in all samples, with an increase in the peak of TiC and a decrease in that of TiO as the Ni(NO3)2·6H2O content increased from 0% to 10%. Scanning electron microscopy results demonstrated a morphological change in the pore wall, transforming from a honeycomb-like porous structure composed of well-dispersed carbon and TiC-TiO particles to rod-shaped TiC whiskers, interconnected with each other as the catalyst content increased from 0% to 10%. Mercury intrusion porosimetry results proved a dual modal pore-size distribution of the samples, comprising nano-scale pores and micro-scale pores. The micro-scale pore size of the samples minorly changed, while the nano-scale pore size escalated from 52 nm to 138 nm as the catalyst content increased from 0 to 10%. The morphology of the pore wall and nano-scale pore size primarily influenced the compressive strength and thermal conductivity of the samples by affecting the load-bearing capability and solid heat-transfer conduction path, respectively.