Enhanced thermal properties of polyethylene glycol/modified rice husk ash eco-friendly form-stable phase change material via optimizing support pore structure

In this work, a novel eco-friendly form-stable phase change material (PCM) was synthetized based on latent heat storage material of polyethylene glycol (PEG) and supporting material of rice husk ash (RHA). To enhance the thermal properties of the form-stable PCM, rough RHA (rRHA) was modified by an ultrasonic hydrochloric acid treatment to unblock the pores stacked by non-crystal silica. The modified RHA (mRHA) behaved an optimized pore structures, in which the BJH pore volume and the BET surface area showed 24.8% and 12.8% increases compared with rRHA. The latent heat of 119.3 J/g for PEG/mRHA form-stable PCM was 20.9% higher than that of PEG/rRHA form-stable PCM due to deep filling of PEG into the non-crystal silica stacked pores of mRHA. Moreover, Frenkel-Halsey-Hill (FHH) theory was introduced to quantitatively characterize the surface complexities of rRHA and mRHA. The result showed the increased surface complexity of mRHA, leading to greater nucleation promotion for PEG. Thus, PEG/mRHA achieved the improved crystallization behaviors. In addition, PEG/mRHA showed favorable thermal cycling reliability after 300 thermal cycles. Therefore, PEG/mRHA provides a new insight into the improved resource utilization and functionality of RHA in terms of eco-friendly form-stable PCM for thermal energy storage.