Preparation and characterization of a heat storage ceramic with Al-12 wt% Si as the phase change material

Abstract While the high thermal conductivity, latent heat storage and excellent thermal cycling performance are all important for ceramics used in heat storage, it is difficult to obtain these properties in a single material. In the present study, the heat storage ceramic based on Al-12 wt% Si alloy particles was prepared to achieve these three goals. The alloy particles were pretreated into microcapsules precursor (pre-microcapsules), then mixed with mullite powder and ball clay to prepare green body followed by firing at 1000, 1100, 1200 and 1300 °C. Phase analysis and microstructure observation of the samples after sintering at different temperatures showed that mullite, alumina and Al–Si alloy were the main phases and that the Al-12 wt% Si alloy particles were found in their initial shapes due to their wrapping by the ceramic shell formed during sintering. The test results showed that the sample sintered at 1300 °C with 45 wt % pre-microcapsule content displayed the best performance with a cold crushing strength and a cold modulus of rupture were more than 120 MPa and 65 MPa, respectively. Even after five thermal shock tests, the cold modulus of rupture of the sample was still higher than 50 MPa. More importantly, the thermal conductivity of the sample was as high as 9.36 W m−1 K-1, the latent heat was 90.84 J g−1 and the latent heat was maintained at 93.4% of the initial value after 3000 thermal cycles. The results meant that these three goals were achieved simultaneously. Moreover, the sensible heat storage capacity was improved by 1.7 times owing to the addition of pre-microcapsules. This heat storage ceramic with Al-12 wt% Si alloy as the phase change material has high potential for use in thermal energy storage systems.