改性硅藻土/脂肪酸定形相变材料的制备及性能

Preparation and characterization of modified diatomite/fatty acid form-stable phase change material

采用癸酸和月桂酸的二元低共熔混合脂肪酸为相变芯材,以经过高温焙烧和酸浸法进行改性处理的硅藻土作为基体材料,通过真空浸渍法制备改性硅藻土/脂肪酸定形相变材料,并采用不同的固-液分离工艺对定形相变材料进行干燥。利用扫描电镜(SEM)、X射线衍射仪(XRD)、差示扫描量热法(DSC)、热重分析法(TG)和热循环实验等方法对改性硅藻土以及定形相变材料的物质成分、化学结构、热性能及稳定性等进行表征。结果表明,500℃高温焙烧5h和50%硫酸酸浸5h对硅藻土的改性效果良好,改性硅藻土的孔隙率和吸附性能明显提高;经抽滤干燥处理的定形相变材料热性能最优,改性硅藻土对脂肪酸相变材料的吸附率为42.7%,定形相变材料相变温度为17.68℃,相变潜热为66.65J/g,改性硅藻土能够对脂肪酸产生吸附和固定作用,定形相变材料表现出良好的热稳定性,可以用作保温、蓄热建筑材料。

A kind of form-stable phase change material （PCM） was prepared by vacuum impregnation method using binary eutectic of capric acid and lauric acid as thermal absorbing core material and diatomite modified by high-temperature roasting and sulfuric acid leaching as the supporting matrix. Different solid-liquid separation methods were conducted for desiccation of the form-stable PCMs to obtain the best one. The compositions, structural characteristics, thermal properties and thermal stability of the composite PCM were investigated by scanning electron microscopy （SEM）, X-ray diffraction （XRD）, differential scanning calorimeter （DSC）, thermogravimetric analysis （TG） and thermal cycling test. The results showed that the porosity and absorptive property of the modified diatomite was promoted significantly after being roasted at 500℃ for 5 h and acid leached in 50% sulfuric acid for 5 h. The modified diatomite/fatty acid composite PCM had the optimal thermal properties after the single suction filtration treatment. The absorption capacity of fatty acid in the composite was 42.7% （mass fraction） and the latent heat of the composite PCM was 66.65 J/g with a phase change temperature of 17.68℃. The modified diatomite was able to absorb and constrain the fatty acid in the pores and behaved good thermal stability. It was concluded that the prepared modified diatomite/fatty acid form-stable PCM was a potential material for thermal insulation and thermal storage building material applications.