Abstract The shape stable phase change materials (SSPCMs) consisting of coal fly ash (CFA) and potassium carbonate (K2CO3) are promising candidates for high temperature thermal storage applications, owing to their low price, high melting enthalpy and low corrosivity of K2CO3. Nevertheless, the chemical reactions between K2CO3 and CFA at high temperature limit its application. To solve this problem, in this work, a new two-step method for preparing SSPCMs containing K2CO3 and CFA was proposed. Firstly, the CFA was successfully modified by K2CO3 with a mass ratio of 3:2. The main phase of the modified CFA was changed into potassium aluminum silicate (KAlSiO4). Then the SSPCMs were synthesized using the modified CFA and K2CO3. The latent heat and thermal conductivity of the prepared SSPCMS increased with the increase of salt content. The SSPCMs with potassium carbonate contents of 50 wt% (SSPCM-55) and 60 wt% (SSPCM-46) maintained good shape without cracks after the sintering processes. In addition, they showed a good cyclic stability in the 150 times thermal cycle tests in terms of mass, latent heat and chemical compatibility. The SSPCM-46 showed the best performance considering both heat transfer and energy storage density, and is promising to be used as a low-cost high-temperature PCM.

中文翻译：

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基于粉煤灰和 K2CO3 的新型低成本高温形状稳定相变材料

摘要 由粉煤灰 (CFA) 和碳酸钾 (K2CO3) 组成的形状稳定相变材料 (SSPCMs) 具有价格低廉、熔融焓高和 K2CO3 腐蚀性低等优点，是高温蓄热应用的有希望的候选材料。然而，K2CO3与CFA在高温下的化学反应限制了其应用。为了解决这个问题，在这项工作中，提出了一种新的两步法制备含有 K2CO3 和 CFA 的 SSPCMs。首先，CFA 被 K2CO3 以 3:2 的质量比成功改性。改性CFA的主相变为硅酸铝钾（KAlSiO4）。然后使用改性的 CFA 和 K2CO3 合成 SSPCM。制备的 SSPCMS 的潜热和热导率随着盐含量的增加而增加。碳酸钾含量为 50 wt% (SSPCM-55) 和 60 wt% (SSPCM-46) 的 SSPCM 在烧结过程后保持良好的形状而没有裂纹。此外，它们在150次热循环试验中在质量、潜热和化学相容性方面表现出良好的循环稳定性。SSPCM-46 在传热和储能密度方面均表现出最佳性能，有望用作低成本高温 PCM。