石蜡/TOCNF相变气凝胶的制备及结构性能调控

Preparation and structure performance regulation of paraffins/TOCNF phase change aerogels

为了防止固-液相变材料在相变过程中的液体泄漏,提高相变材料的稳定性,减少团聚,增加传热表面积,以TEMPO氧化纤维素纳米纤维(TEMPO-oxidized cellulose nanofibers,TOCNF)作为稳定剂,以石蜡作为油相,经过高速分散得到石蜡/TOCNF Pickering乳液(paraffins/TOCNF Pickering emulsion,PTPE),并将其与作为气凝胶主体的TOCNF混合,通过冷冻干燥制备石蜡/TOCNF相变气凝胶(paraffins/TOCNF phase change aerogels,PTA);分析TOCNF质量分数、溶液pH值对Pickering乳液尺寸形貌及稳定性的影响,探讨不同Pickering乳液添加量下所得PTA的形貌结构、储热容量、热稳定性和力学性能等。结果表明:当稳定剂TOCNF质量分数为0.5%、pH值为7~11时,所得Pickering乳液粒径较小且尺寸均一,平均粒径分布在8.3~14.8μm,具有优异的稳定性;经乳化分散后,石蜡颗粒均匀镶嵌在PTA孔壁表面,无液体泄漏。所得PTA潜热值可高达225.8J/g,并具有良好的机械性能。该文以TOCNF作为乳化剂和气凝胶的骨架,通过Pickering乳液模板法制备的具有三维多孔网络结构的相变气凝胶,一定程度上解决了目前纤维素复合相变气凝胶存在的液体泄漏、潜热低与机械强度差等难题。

To prevent liquid leakage in solid-liquid phase change materials,improve the stability of phase change materials,reduce the agglomeration and increase the heat transfer surface area,the article,took TEMPO-oxidized cellulose nanofibers(TOCNF)as the stabilizer and paraffins as the oil phase,prepared the paraffins/TOCNF phase change aerogels(PTA)by freeze-drying after obtaining paraffins/TOCNF Pickering emulsion(PTPE)at high speed and mixing it with TOCNF,the main body of the aerogel.The effects of TOCNF concentration and solution pH value on the morphology and stability of the Pickering emulsion,the morphology structure,heat storage capacity,thermal stability and mechanical properties of PTA with different amounts of Pickering emulsion were studied.The results showed that when the mass fraction of TOCNF emulsifier was 0.5%and pH was within 7-11,the Pickering emulsion had small and uniform size,with the average particle size distribution ranging from 8.3μm to 14.8μm,indicating excellent stability.After emulsification and dispersion,paraffin particles were evenly embedded on the surface of PTA hole wall without liquid leakage.The latent heat value of PTA could be as high as 225.8J/g indicating good mechanical properties.It can be seen that the phase change aerogel with a threedimensional porous network structure prepared by the Pickering emulsion template method using TOCNF as the emulsifier and the skeleton of aerogels solves the problems of liquid leakage,low latent heat,and poor mechanical strength existing in the current cellulose composite phase change aerogels to some extent.