Preparation Of Paraffin/SiO₂ Core/Shell Structure Phase Change Composite

In the process of phase change materials in its phase change will absorb heat in the environment, it can store energy and control the environment temperature at the same time, which make the phase change materials in temperature control, the transformation of energy absorption and recovery of energy waste widely used. However, some kinds of phase change materials have some problems such as leakage of the melted phase change material, preparation of core/shell composite phase change materials can resolve this problem, which make it easy application and storage.A novel phase change composite of paraffin/silicon dioxide, which comprises paraffin as latent heat storage medium and SiO2 as supporting material, was prepared by direct precipitation in a paraffin emulsion. The as prepared paraffin/SiO2 composites were characterized by differential scanning calorimetry(DSC), scanning electron microscopy(SEM), fourier transformation infrared spectroscope(FT-IR), X-ray diffractometer(XRD) and thermogravimetric analysis(TGA), respectively. The results showed that paraffin was encapsulated in a SiO2 shell, the particle diameter is about 2 to 5 μm.The DSC results indicated that the paraffin/ SiO2 composites melt at 56℃ with a latent heat of 86.61 kJ/kg with a core/shell mass ratio of 5/3. Thermal cycling test showed that the paraffin/ SiO2 composites could maintain its phase transition perfectly after 50 melt-freeze cycles and no leakage of paraffin was observed at 70℃ for 1h. In general, the as prepared paraffin/SiO2 composites have the better thermal stability and storage capacity, which can be wildly applied in the aspect of thermal energy storage.The single factor experiment results show that the optimum value of the surfactant CTAB dosage is 0.8 g, emulsifying speed 4000 r·min- 1, emulsifying time 15 min, paraffin wax with silicon dioxide mass ratio 5:3, concentration of sodium silicate 0.45 mol·L-1 and hydrochloric acid 0.9 mol·L-1. Further optimizing by orthogonal experiment confirmed that the results are consistent with the results of single factor experiment.