V–VO₂ core–shell structure for potential thermal switching

The efficiency of internal combustion engine is vey low at cold start than when the engine is warm. By using thermal switching material, the engine can be warm up quickly after the engine starts. In this work, we discuss about the potential thermal switching material V-VO₂ core-shell structure. The V-VO₂ core-shell structure was formed by converting the outer surface of V particles into VO₂ by controlled thermal annealing in air. In such core-shell structure, in insulator phase of VO₂ electrons confine inside the vanadium particles and in metallic phase electrons will be transfered from V into VO₂, which resulted in electrical conductivity increased from 2.1 × 10⁵ to 5.1 × 10⁵ S m⁻¹ through the insulator-to-metal transition. Due to the increase in electrical conductivity, corresponding electrical thermal conductivity increased from 1.51 to 4.87 W m^-1 K^-1 which finally resulted on switching of total thermal conducitivity by 22% across the phase transition temperature.