Search

Thermal storage ceramics using metals as phase change materials (PCMs) have both high thermal conductivity and high heat storage density. However, in the process of use is very easy to occur in the metal phase change material leakage, will seriously affect the service life of the thermal storage ceramics. In this study, ceramic composite phase change heat storage materials with Al-12Si alloy as phase change material were prepared. Firstly, Al-12Si was pretreated by sol-gel method and high temperature heat treatment to obtain the pretreated Al-12Si alloy powder with dense alumina shell layer. Afterthat, the pretreated Al-12Si alloy powder was mixed and pressed with alumina, silicon dioxide, magnesium oxide, and mullite respectively, and sintered at 1,100°C, 1,200°C, or 1,300°C. The experimental results show that the metal phase change materials and the four ceramic materials show good chemical compatibility, and pretreated Al-12Si essentially retains its initial shape and is uniformly dispersed in the heat storage material. Among all the samples, the pre-treated Al-12Si/mullite ceramic thermal storage materials with a sintering temperature of 1,200°C showed the best thermal storage performance. The thermal conductivity of the samples was up to 17.94 W/(m-K). The latent heat storage value was 139.51 J/g before thermal cycling, 138.27 J/g after 100 thermal cycling, which was only decreased by 0.89%, and there was almost no alloy leakage. This study has successfully realized that the ceramic thermal storage material possesses high thermal conductivity, high thermal storage density and excellent thermal cycling performance at the same time, and provides a new method for the production and preparation of Al-12Si/ ceramic heat storage materials, which has great potential for application in heat storage systems. [ABSTRACT FROM AUTHOR]

In recent years, heat storage technology has attracted wide attention in the fields of renewable energy storage for its relatively high melting point, high heat storage capacity and economy, Na2CO3 and eutectic salt mixtures containing Na2CO3 are promising candidates in the field of solar energy storage. In this paper, a molecular dynamics (MD) simulation of Na2CO3 was conducted with the Born–Mayer potential function. The simulated solid–liquid phase change temperature is 1200 K, and the error is 5.4%. The heat capacity at constant pressure (Cp) is higher in liquid than in solid, the average Cp of solid is 1.45 J/g and that of liquid is 1.79 J/g, and the minimum error is 2.8%. The simulation results revealed the change rules of density and thermal expansion coefficient of Na2CO3 in the process of heating up, and these changes were analyzed by radial distribution functions (RDF) and angular distribution functions (ADF). Moreover, the RDF and ADF results show that the atomic spacing of Na2CO3 increases, the coordination number decreases, and the angle distribution between atoms becomes wider as the temperature rises. Finally, this paper examined the microscopic changes of ions during the phase transition of Na2CO3 from solid to liquid. It is concluded that the angle change of CO 3 2 − in the liquid state is more sharply. This study improves the understanding of the thermodynamic properties and local structure of Na2CO3 and provides theoretical support for Na2CO3 heat storage materials. [ABSTRACT FROM AUTHOR]