Preparation of In-doped SnO2 hollow spheres and the solar-heat insulation properties of polyvinylidene fluoride film containing prepared spheres

Abstract

In-doped SnO2 hollow spheres of submicron size were prepared with carbon ball substrate via the hydrothermal method and heat treatment process. The micromorphology and microstructure of the spheres were examined with XRD, SEM, EDS and TEM. And their absorption and diffuse reflection characteristics were also characterized. The prepared spheres were then introduced to polyvinylidene fluoride (PVDF) to form composite films with the spin coater. UV-Vis-NIR spectrophotometer and confined thermal insulation device were used to study the optical and solar-heat insulation properties of the film, respectively. The results show that In3+ doping increases the lattice constant, results in lattice distortion, generates oxygen vacancies and narrows the forbidden band, leading to significant increase in the diffuse reflectance of PVDF film in the visible and infrared regions. Moreover, In3+ doping has no negative effect on the high transmittance of SnO2, and the hollow structure of SnO2 is beneficial to the heat insulation of PVDF film. In addition, when the loading content of SnO2 spheres is in a range of 15–25 wt%, the thermal conductivity and heat insulation performance of the PVDF film show little change, possibly caused by local agglomeration. This study indicates that PVDF film containing In-doped SnO2 hollow spheres is a promising material for energy conservation.