Thermal conductivity enhancement and shape stability of composite phase change materials using MIL-101(Cr)-NH2/expanded graphite/multi-walled carbon nanotubes

Abstract

Low heat conductivity and leakage much restrict the effective use of phase changing materials (PCMs) in heat energy management. Here, an expanded graphite (EG)/ multi-walled carbon nanotube (MWCNT) / metal organic framework (MOF: MIL-101(Cr)-NH2) composite was developed to solve these issues. The porous MOF can avoid the loss of liquid paraffin wax (PW). The heat conductivity of composite PCMs (CPCMs) was improved using EG/MWCNT with a mass ratio of 4:1. The thermophysical properties, heat stability and chemical compatibility of CPCMs were comprehensively investigated. Results demonstrate the successful preparation of CPCMs without any chemical reaction. The MOF (35 %)/EG(4 %)/MWCNT(1 %)/PW(60 %) CPCM exhibits superior thermophysical properties and its melting enthalpy (74.59 J/g) is near the theoretical level after 500 heating/cooling cycles. It exhibits a 792 % increment in heat conductivity from pure PW.