无机相变材料CaCl2·6H2O的过冷特性

CaCl₂·6H₂O作为一种常见的常温无机水合盐相变材料，由于成本低、易获取、蓄热强而受到广泛的关注。按无水CaCl₂与H₂O的质量比为1.027：1制备了CaCl₂·6H₂O，经X射线衍射（XRD）表征其晶体结构；通过添加成核剂SrCl2·6H₂O和Ba（OH）₂对CaCl₂·6H₂O改性，发现两者的联合作用可抑制过冷，10次熔化-冷却循环平均过冷度1.07℃。采用差示扫描量热仪（DSC）测定CaCl₂·6H₂O添加成核剂前后相变潜热，发现潜热由223.54 J·g^-1降至160.41 J·g^-1；为了扩大CaCl₂·6H₂O相变温度的范围，通过添加质量分数分别为5%、10%、15%、20%和25%的MgCl₂·6H₂O，发现相变温度随MgCl₂·6H₂O质量分数的升高呈线性降低，但不宜超过20%；选取CaCl₂·6H₂O-20% MgCl₂·6H₂O二元共晶盐相变储热体系为改性目标，通过添加1% SrCl2·6H₂O和0.5% CMC，过冷度降至0.57℃，相变潜热为141.09 J·g^-1，低于单独组成盐CaCl₂·6H₂O的潜热223.54 J·g^-1和MgCl₂·6H₂O的潜热163.35 J·g^-1。研究表明，CaCl₂·6H₂O作为无机相变材料具有显著的应用价值。

Supercooling characteristics of inorganic phase change material CaCl2·6H2O

As a common room temperature inorganic hydrated salt phase change material(PCM), calcium chloride hexahydrate(CaCl₂·6H₂O) is being widely focused due to its low cost, easy availability and high thermal energy storage. CaCl₂·6H₂O was prepared in terms of mass ratio of anhydrous CaCl₂ and H₂O as 1.027:1, whose crystal structure was characterized by X-ray diffraction(XRD). CaCl₂·6H₂O was modified by adding nucleating agents SrCl2·6H₂O and Ba(OH)₂. The results showed that the combination of SrCl2·6H₂O and Ba(OH)₂ could suppress supercooling phenomenon. The average supercooling degree was 1.07℃ in the process of melting-cooling for 10 cycles. The phase change latent heat of CaCl₂·6H₂O before and after adding nucleating agents, characterized by differential scanning calorimetry(DSC), decreased from 223.54 J·g^-1 to 160.41 J·g^-1. In order to enlarge the scope of phase change temperature of CaCl₂·6H₂O, 5%, 10%, 15%, 20% and 25%(mass) magnesium chloride hexahydrate(MgCl₂·6H₂O) was added into CaCl₂·6H₂O respectively, which indicated the phase change temperature of CaCl₂·6H₂O decreased linearly with the increase of MgCl₂·6H₂O content, however, not exceeding 20%(mass). The modification of CaCl₂·6H₂O-20% MgCl₂·6H₂O binary eutectic salt phase change thermal energy storage material was designed by adding 1% SrCl2·6H₂O and 0.5% CMC, and the results suggested that the degree of supercooling was reduced to 0.57℃. The phase change latent heat of this material was 141.09 J·g^-1, which was lower than that of CaCl₂·6H₂O(223.54 J·g^-1) and MgCl₂·6H₂O(163.35 J·g^-1). The above study showed that inorganic hydrated salt CaCl₂·6H₂O had significant application value as an inorganic PCM.