Ruilong Wen

Enhanced thermal properties of novel shape-stabilized PEG composite phase change materials with radial mesoporous silica sphere for thermal energy storage.

Radial mesoporous silica (RMS) sphere was tailor-made for further applications in producing shape-stabilized composite phase change materials (ss-CPCMs) through a facile self-assembly process using CTAB as the main template and TEOS as SiO2 precursor. Novel ss-CPCMs composed of polyethylene glycol (PEG) and RMS were prepared through vacuum impregnating method. Various techniques were employed to characterize the structural and thermal properties of the ss-CPCMs. The DSC results indicated that the PEG/RMS ss-CPCM was a promising candidate for building thermal energy storage applications due to its large latent heat, suitable phase change temperature, good thermal reliability, as well as the excellent chemical compatibility and thermal stability. Importantly, the possible formation mechanisms of both RMS sphere and PEG/RMS composite have also been proposed. The results also indicated that the properties of the PEG/RMS ss-CPCMs are influenced by the adsorption limitation of the PEG molecule from RMS sphere with mesoporous structure and the effect of RMS, as the impurities, on the perfect crystallization of PEG.

Polyethylene glycol/Cu/SiO2 form stable composite phase change materials: preparation, characterization, and thermal conductivity enhancement

Novel form-stable composite phase change materials (FS-CPCMs) of polyethylene glycol (PEG)/Cu/SiO2 were prepared by adding Cu powder to PEG and SiO2 via the ultrasound-assisted sol–gel method. This method ensured the uniform distribution of Cu powder in the FS-CPCMs, thus providing an important method to develop composite phase change materials (CPCMs) with a high thermal conductivity. The FS-CPCMs were characterized by various techniques. The results showed that the FS-CPCMs remained in the solid state without leakage above the melting point of PEG. The XRD and FTIR results indicated that no new chemical bond was formed between the constituents of FS-CPCMs: Cu, PEG, and SiO2. The DSC and TGA analyses showed that the FS-CPCMs had an optimum phase-change temperature, a high enthalpy of phase change, an excellent thermal stability, and a good form-stable performance. The thermal conductivity was 0.431 W m−1 K−1 for 3.45 wt% Cu powder in the FS-CPCMs, an increase of 49.13% compared to pure PEG.

Preparation and thermal properties of phase change materials based on paraffin with expanded graphite and carbon foams prepared from sucroses

Carbon foam/expanded graphite composite (CEC) was prepared from a sucrose-expandable graphite resin using a thermal foaming method. This CEC was impregnated through its pores with paraffin to obtain a paraffin/carbon foam/expanded graphite composite (PCEC). In the case of CECs, when the amount of added expandable graphite reached 10 wt% to 15 wt%, the microstructure of the CEC was damaged because of the expansion in volume of the expandable graphite. Fourier transform infra-red spectroscopy and X-ray diffraction analysis of PCECs showed that there was no chemical interaction between the paraffin and CECs. With an increase in the amount of expandable graphite in CECs, the adsorption capacity of paraffin and the latent heat first showed an increase and then decreased. The heat transfer capability of the paraffin was truly improved by the CECs. The processes for the preparation of the CECs and PCECs were environmentally friendly, convenient, and inexpensive. The PCECs, with good thermal properties and chemical stabilities, are suitable for low temperature (40–50 °C) thermal energy storage applications.