Preparation of alumina/silica/exfoliated graphite nanoplatelets composite aerogels and its application as supporting material for erythritol based form-stable phase change materials

Abstract

Alumina-silica (Al-Si) and Al-Si/exfoliated graphite nanoplatelets (xGnPs) composite aerogels were prepared via a novel epoxide method followed by ambient pressure drying (APD) and heat treatment. Epichlorohydrin (ECH) was applied as proton scavenger to control the hydrolysis of AlCl3·6H2O to obtain the composite gel. Then the ring-opening products of ECH acted as drying control chemical additives to prevent the gel from high volume shrinkage during APD and was then removed by heat treatment at 800 °C to obtain composite aerogels. Doping the Al-Si aerogel with xGnPs was in favor of obtaining composite aerogels with high specific area and low volume shrinkage. The specific surface area of the prepared Al-Si/xGnP aerogels could attain 350 m2/g with a pore volume of 1.156 cm3/g. The synthesized aerogels were then vacuum infiltrated with erythritol (ET) to obtain form-stable phase change materials (FSPCMs). The loading of ET in the prepared FSPCMs attained 90 wt%, and the latent heat storage capacity attained 279 J/g. In addition, the thermal conductivity of the FSPCMs could be enhanced to 49.8 % higher than pristine ET with the help of 0.6 wt% xGnPs, and the supercooling of ET in the FSPCMs could be suppressed to 59 °C. Moreover, the FSPCMs supported by Al-Si/xGnP aerogels possessed greatly enhanced light-to-thermal conversion efficiency than the pristine ET and the Al-Si aerogel supported FSPCM. More importantly, the FSPCMs possessed very good long-term thermal reliability.