Nanosized n-tetracosane as heat storage media: adjustable phase transition temperature and thermal property

Normal alkane tetracosane (C 24 ) as a representative compound containing alkyl chains was loaded into various porous materials to obtain form-stable phase change materials (PCMs). In the pores of controlled porous glasses (CPGs), silica gels (SGs), SBA-15 and KIT-6, C 24 acquired tunable phase transition temperatures. By changing the pore sizes, C 24 displayed regulated temperature windows of around 6 K (via melting) and 10 K (via solid phase transition) in the CPGs, 9 K in the SG pores (via melting) and about 13 K in SBA-15 (via melting). Phase transition temperatures, degree of supercooling and enthalpies of phase transitions exhibited linear dependence on the reverse pore diameter. The transition temperature and enthalpy change also had relevance to pore geometries. The phase sequences and solid structures of C 24 in the pores changed largely. The study provides an insight into thermal properties of nano-sized PCMs.