Graphene modified octadecane/diatomite composite phase change materials for developing high-performance thermal energy storage concrete

The thermal energy storage concrete (TESC) incorporating phase change materials (PCM) exhibits promising prospects for building energy conservation due to its exceptional thermal inertia and high thermal mass. However, challenges such as PCM leakage, low conductivity, and poor mechanical properties restrict its widespread application. To overcome these issues, a novel shape-stabilized PCM was developed by impregnating n-octadecane as the PCM into diatomite and wrapping it with graphene nanoplatelets. DSC analysis results revealed that the graphene nanoplatelets-coated octadecane/diatomite composite (GNP-OC/D) possessed a latent heat of 55.68 J/g. The GNP coating can effectively prevent leakage while enhancing thermal conductivity. Moreover, ultra-high performance concrete was used as the matrix for preparing high-performance thermal energy storage concrete (HP-TESC). SEM results demonstrated that GNP-OC/D exhibited excellent dispersion in UHPC with remarkable compatibility. Moreover, even with a content of 75 % GNP-OC/D, the cement mortar still achieved impressive flexural strength of up to 12.5 MPa and compressive strength of 73.1 MPa respectively. It is worth noting that higher amounts of OC/D inclusion resulted in a lower thermal conductivity but an increased thermal energy storage capacity; thus HP-TESC has shown potential in reducing indoor temperature fluctuations.