In this work, a novel microencapsulated phase change composite of paraffin@SiO2 was prepared by in situ emulsion interfacial hydrolysis and polycondensation of tetraethyl orthosilicate (TEOS). The as-prepared paraffin@SiO2 composite was determined by Fourier transformation infrared spectroscope (FT-IR), X-ray diffractometer (XRD), scanning electronic microscope (SEM), and transmission electron microscopy (TEM), respectively. The results showed that the paraffin@SiO2 composite is composed of quasi-spherical particles with diameters of 200–500 nm. The paraffin is encapsulated in a SiO2 shell, and there is no chemical reaction between them. The DSC results indicate that the melting temperature and latent heat of the composite are 56.5 °C and 45.5 J/g, respectively. The encapsulation ratio of paraffin was calculated to be 31.7% from the results of the DSC measurements, slightly lower than the loading content (32.5%) of paraffin in the microencapsulated composite from the TGA measurements. The as-prepared paraffin@SiO2 composite could maintain its phase transition perfectly after 30 melting–freezing cycles, and no leakage of paraffin was observed at 70 °C for 20 min. Moreover, the high heat storage capability and good thermal stability of the composite enable it to be a potential material to store thermal energy in practical applications.

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The ceramics with complex porous structures were fabricated by a combination of impregnating and freeze-casting process. The polyurethane sponge was impregnated in the mold with 20 vol% of aqueous alumina slurry, and then the bottom of the cast body was kept at a constant cooling rate of 61C/min to induce unidirectional solidification. After drying and sintering of the green part, porous ceramic with obvious lamellar architectures was prepared. The lamellae thickness and interlayer distance were as large as B9 and B15 lm, respectively. The large pores, which resulted from the burn-up of sponge struts were homogeneously distributed in the sample. The use of the porous template introduced some local interruption of the lamellar structures. However, high compression strength for the porous ceramic can still be obtained. Fig. 1. Scanning electron micrographs of (a) SPS and (b) BPS polyurethane sponges.