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Environmentally friendly microencapsulated phase change materials (MEPCMs) with calcium carbonate (CaCO3) shells were modified with graphene oxide (GO), and the effects of GO content and methodology on MEPCMs were examined. The core–shell structure of MEPCMs and crystal structure of CaCO3 shells were confirmed by scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FTIR), and X-ray diffractometer (XRD). The thermal properties and stability of MEPCMs were investigated by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA), suggesting that the addition of GO contributed to improving the heat storage capacity and thermal stability of MEPCMs. When the GO content was 1.0 wt %, the encapsulation ratio of MEPCMs was as high as 73.19%, and the leakage rate was reduced by 89.6% compared to the MEPCMs without GO. Furthermore, the thermal conductivity and mechanical properties of GO modified MEPCMs were improved significantly. The considerable latent heat storage, thermal stability, thermal conductivity, leakageprevention, and mechanical properties of GO modified paraffin@CaCO3 MEPCMs offer potential in green energy applications.

A series of microencapsulated phase-change materials (MEPCMs) based on paraffin core and calcium carbonate (CaCO 3 ) shell were synthesized, and the effect of emulsifier type and pH value on morphology, structure, and properties of paraffin@CaCO 3 MEPCMs were investigated. The results showed that CaCO 3 shell was formed in vaterite and calcite crystalline phase when emulsifier was sodium dodecyl benzene sulfonate and styrene-maleic anhydride (SMA), respectively. When sodium dodecyl sulfate was used as an emulsifier, both vaterite and calcite CaCO 3 were formed. The forming mechanism of emulsifier type on CaCO 3 crystalline phase was studied. Furthermore, phase-change enthalpy and leakage rate of MEPCMs were related with the type of emulsifier and the pH value of the emulsion. With optimum condition of SMA as emulsifier and pH value of 7, paraffin@CaCO 3 MEPCMs had an encapsulation ratio at 56.6% and leakage rate at 2.88%, illustrating its considerable heat storage capability and leakage-prevention property. The 50 heating−cooling cycles test indicated that the MEPCMs owned excellent thermal reliability. The thermal conductivity of MEPCMs was significantly improved due to the existence of CaCO 3 shell. In addition to excellent thermal storage ability, the paraffin@CaCO 3 MEPCMs also owned good mechanical property and light-to-heat energy conversion efficiency. The characteristics of MEPCMs indicated its potential application in solar energy resource.

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Summary Novel microencapsulated phase change materials (MEPCMs) composed of the lead tungstate (PbWO4) shell and paraffin core were designed for shielding of gamma radiation as well as thermal energy storage. Such MEPCMs were prepared via self‐assembly methods and in‐situ precipitation. The PbWO4 shell with excellent photon attenuation can give the resulting MEPCMs an acceptable gamma radiation shielding capability. The chemical composition and structure of microcapsules samples were studied by X‐ray diffractometer (XRD) and Fourier‐transform infrared spectroscopy (FTIR). The effects of different core/shell mass ratios on the surface morphology and microstructure of the MEPCMs were determined by scanning electron microscopy (SEM), energy‐dispersive spectrometer (EDS), and transmission electronic microscopy (TEM). It was confirmed that the microcapsules exhibit a distinct core‐shell structure and a perfect spherical shape. Differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) were used to present thermal stability and thermal‐storage capability of MEPCMs. A high‐purity germanium gamma spectrometer to measure the attenuation coefficient of the microcapsules for gamma rays showed that the MECPMs has good γ‐rays‐shielding property. The multifunction microcapsules in this study have great potential applications for building energy conservation as well as wearable personal protection in nuclear energy engineering.

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The negatively charged phase change latex (PCL) was obtained by simultaneously emulsifying paraffin and ethylene propylene diene monomer (EPDM) into water. Graphene (GE) was positively modified using cetyltrimethylammonium bromide and was then introduced into the PCL. Because of electrostatic attraction, the positively charged graphene was tightly bonded with the negatively charged PCL particles. Paraffin/EPDM@graphene thermally conductive and shape-stabilized phase change materials (TSPCMs) were obtained by hot press vulcanization. The thermal conductivity of TSPCMs was up to 1.451 W·m–1·K–1, with an increase of 294% compared to that without graphene. The error between the actual enthalpy and the theoretical value of TSPCMs was −1.00%, and the leakage rate was only 0.621% after being heated for 48 h. Because of the combination of EPDM and GE, the prepared TSPCM exhibits excellent comprehensive performance, so it has great application potential in the field of thermal energy storage and thermal management of electronic devices.