Design and Preparation of the Phase Change Materials Paraffin/Porous Al2O3@Graphite Foams with Enhanced Heat Storage Capacity and Thermal Conductivity

Porous Al2O3@graphite foams (PAGFs) were directly prepared by a particle-stabilized foaming method, with 40 vol % Al2O3 particles and different proportions of sucrose. The as-prepared PAGFs demonstrate three-dimensional interpenetrating structures and high porosities according to SEM images, with the porous morphology being markedly influenced by the concentration percentage of sucrose. Additionally, the PAGFs could be successfully impregnated with paraffin, reaching a maximum enclosed ratio (φ) of 66 wt % without any leakage. Differential scanning calorimetry measurement showed that the latent heat of the composites of paraffin/PAGF (PAGFPs) reach maxima of 105.76 and 105.98 J/g after 200 cycles of melting/freezing. Thermogravimetric analysis, Fourier transform infrared spectroscopy, and thermal cyclic tests demonstrated good thermal and chemical stability and good thermal reliability for the as-prepared form-stable PAGFPs. Our results also confirmed that a layer of ordered graphite film is formed on the surface of Al2O3 particles after sintering at 1600 °C. As a result, the specific surface area of PAGF is 13 times greater than that of the foams without coating graphite. Meanwhile, the thermal conductivities of the PAGFPs reached a maximum of 0.76W/m·K, which was 3.62 times that of pristine paraffin. In conclusion, we demonstrated here the design and preparation of form-stable composite phase change materials with controllable porous structures and superior thermal and chemical stabilities and reliabilities for heat energy storage applications.