Preparation and performance evaluation of expanded vermiculite-based phase change materials for building thermal insulation and energy saving

Abstract

To meet the demand for building envelope materials with efficient heat storage and release capabilities in the harsh climate of Northwest China, this study reports the development of a novel ternary composite phase change material (CEV@SiC). The material was prepared by vacuum impregnation, encapsulating calcium chloride hexahydrate into highly porous expanded vermiculite and further incorporating silicon carbide nanoparticles as thermal conductivity enhancers. Thermal analysis showed that the sample with 5% SiC doping exhibited the highest enthalpy of fusion (90.3 J g⁻¹) and retained 95% of its enthalpy after 100 thermal cycles, demonstrating excellent cycling stability. A microscale heat transfer model of phase change mortar was established through simulation, and test modules incorporating CEV@SiC as a partial replacement for aggregate in cement mortar were constructed. Compared with ordinary modules, the CEV@SiC-modified modules reduced the indoor peak temperature by 2.04 °C and delayed the occurrence of the peak temperature by 1 h, confirming their significant energy-saving and temperature-regulation potential. This study provides crucial insights into component design and process optimization for developing high-performance phase change materials tailored for building envelopes in Northwest China. The developed material effectively fulfils the dual requirements of high thermal storage density and rapid thermal response under the region's unique climatic conditions.