Abstract Phase change materials (PCMs) are promising alternative candidates for a variety of thermal energy storage and related applications. Among the PCMs, alkali carbonates have received particular attention in recent years due to their favourable thermophysical properties at high temperatures. However, the use of such carbonates as PCM requires the understanding of the structural information of the material particularly at both the solid and molten states and the composition dependence of the latent heat, which are largely lacking. Here we study, by both experiments and molecular dynamics simulations, the latent heat of the binary carbonates Na2CO3/Li2CO3. The results show that the binary carbonates can convert to LiNaCO3 within a wide concentration range. A eutectic composition (EC) region of about 51 mol. % Li2CO3 has shown the largest conversion to the LiNaCO3. Any excess loading of Na2CO3 or Li2CO3 beyond the EC region of the carbonates could lower the activation energy of diffusion. The solidification of the carbonates leads to a higher phase change resistance in the EC region with a higher activation energy Ea(pc) and a larger latent heat during the phase change.

中文翻译：

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二元碳酸盐（Na 2 CO 3 /Li 2 CO 3 ）的共晶成分依赖于潜热

摘要 相变材料 (PCM) 是各种热能储存和相关应用的有前途的替代材料。在PCMs中，碱金属碳酸盐由于其在高温下良好的热物理性质而受到特别关注。然而，将此类碳酸盐用作 PCM 需要了解材料的结构信息，特别是在固态和熔融状态下的结构信息以及潜热的组成依赖性，而这在很大程度上是缺乏的。在这里，我们通过实验和分子动力学模拟研究二元碳酸盐 Na2CO3/Li2CO3 的潜热。结果表明，二元碳酸盐可以在很宽的浓度范围内转化为 LiNaCO3。共晶成分 (EC) 区域约为 51 mol。% Li2CO3 显示出最大的转化为 LiNaCO3。任何超出碳酸盐 EC 区域的 Na2CO3 或 Li2CO3 过量加载都会降低扩散的活化能。碳酸盐的固化导致 EC 区域更高的相变阻力，具有更高的活化能 Ea(pc) 和更大的相变潜热。