Carbon-decorated diatomite stabilized lauric acid-stearic acid as composite phase change materials for photo-to-thermal conversion and storage

Diatomite is a promising supporting matrix in the preparation of composite phase change material for latent thermal energy storage. Raw diatomite has the advantages of porous space but with a shortage of thermal conductivity than carbon materials. In this work, the carbon-decorated diatomite (D_C) matrix was synthesized by a novel template-carbonization method at different calcination temperatures of 600 °C, 800 °C, and 1000 °C. Then, the matrix was used to stabilize binary lauric-stearic acid of LA-SA for the preparation of diatomite-based composite phase change material which is used to explore the application of composite in photo-to-thermal conversion/storage. Results show that the carbon-decorated process on diatomite causes an increment of specific surface area and pore space. Thus, more phase change material being loaded in the matrix leads to a larger heat storage capacity of the composite. The designed composite with a matrix carbonization temperature of 1000 °C, LA-SA/D_C-1000, has a loadage of 49.92 %, melting temperature of 31.48 °C, and latent heat of 70.07 J g-1 which is improved by 23 %. Compared with the raw diatomite-based composite, the enhancements of thermal conductivity were 90 % for that of LA-SA/D_C-1000. Moreover, the corresponding composite exhibits better photo-to-thermal conversion performance and transient temperature response.