A method to in-situ synthesize surface coating of SiC nanowhiskers on cordierite honeycombs by combining aluminothermic, silicothermic and carbothermic reduction reactions

Abstract

A simple in-situ method was proposed to synthesize surface coating of SiC nanowhiskers on cordierite honeycombs by aluminothermic, silicothermic, and carbothermic reduction reactions. The surface coating of SiC nanowhiskers was synthesized by controlling the partial pressure of SiO gas on the surface of honeycombs, based on the pore-forming process using aluminium(Al) agent. Increasing the porosity of the honeycombs provided aisles to volatilize SiO gas, and the growth of SiC nanowhiskers changed from inside the honeycomb wall to on the honeycomb surface. SEM and TEM observations revealed that the relatively high porosity (≥45%) and sintering temperature (1250–1300 °C) were necessary for obtaining surface coating of SiC nanowhiskers, and the nanowhisker-coating having the smooth morphology and a thickness of ∼150 µm was obtained at 1250 °C. Compared with cordierite honeycombs without SiC nanowhiskers, SiC nanowhiskers inside the honeycomb walls could improve the compressive strength and thermal conductivity with increasing rates of 121% and 123%, respectively, and the surface coating of SiC nanowhiskers increased the specific surface area of the honeycombs by 241 times.