Thermal conductivity and thermal diffusivity of SiO2 nanopowder

A 3ω approach for the simultaneous determination of the effective thermal conductivity and thermal diffusivity of nanopowder materials was developed. A 3ω experimental system was established, and the thermal properties of water and alcohol were measured to validate and estimate the accuracy of the current experimental system. The effective thermal conductivity and thermal diffusivity of the SiO₂ nanopowder with 375, 475, and 575 nm diameters were measured at 290–490 K and at different densities. At room temperature, the effective thermal conductivity and thermal diffusivity of the SiO₂ nanopowder increased with temperature; however, both values decreased as the particle diameter was reduced. An optimum SiO₂ powder density that decreased with decreasing diameter was also observed within the measurement range. The minimum effective thermal conductivity and maximum effective thermal diffusivity were obtained at 85 × 10⁻³ kg/L, when the particle diameter was 575 nm. The optimum densities of the particles with 375 and 475 nm diameters were less than 50.23 × 10⁻³ and 64.82 × 10⁻³ kg/L, respectively.