Tetradecanol/expanded graphite composite form-stable phase change material for thermal energy storage

• Tetradecanol (TD)/expanded graphite (EG) composite form-stable PCMs were prepared.
• The loading of TD in the composite PCMs with good form-stability could attain 93 wt%.
• The phase change enthalpy of the composite PCMs could attain 202.6 J/g.
• The thermal conductivity of the PCM containing 7 wt% EG is 5.37 times higher than that of TD.
• The solid–solid transition of TD in the composite PCMs was constrained.

Natural flake graphite was chemically intercalated to prepare expandable graphite. The expandable graphite was then expanded by means of microwave irradiation to obtain expanded graphite (EG). Tetradecanol (TD)/EG composite form-stable phase change materials (PCMs) were prepared by mixing TD with EG through an autoclave method. The highest loading of TD in the composite form-stable PCMs with good form-stability was 93 wt%. The composite form-stable PCMs exhibited excellent thermal energy storage capacity. The melting enthalpy (ΔHm) and crystallization enthalpy (ΔHc) of the composite form-stable PCM containing 93 wt% TD were 202.6 and 201.2 J/g, respectively. However, the solid–solid phase transition of TD in the composite form-stable PCMs was hindered as TD was strongly absorbed by EG. As a result, the ΔHm and ΔHc of the composite form-stable PCMs were slightly lower than the theoretical value. The thermal conductivity of the composite form-stable PCMs was greatly enhanced by EG and was increased with the increasing of EG loading. The thermal conductivity of the composite form-stable PCM containing 7 wt% EG attained 2.76 W/m K. Besides, effects of the prepared EG on properties of the composite form-stable PCMs were compared with those of EG derived from commercially obtained expandable graphite.