【作者】 程立媛；

【导师】 马烽；

【作者基本信息】 山东轻工业学院 ， 应用化学， 2009， 硕士

【摘要】 面临能源日益枯竭的现状,如何有效提高能源的利用率成为众多科学家研究的主要问题。相变储能是利用相变材料的相变潜热进行能量贮存的一项新型环保节能技术。为了解决相变材料低热导性和运输、储存的问题,提出了相变材料与高导热性的多孔石墨基体相结合,制备出新型的定形相变材料。多孔石墨基体通过对天然鳞片状石墨进行插层处理,对插层化合物进行微波膨化制备。该方法制备的多孔石墨具有丰富的孔道结构,膨胀体积为170.72ml/g。通过N2吸附和脱附测得其比表面积分别为29.157 m2/g和48.5424 m2/g, N2吸脱附表明多孔石墨基体中孔比例占到了68.8 %。对石墨基体进行SEM扫描,发现孔道结构大多为封闭孔和半封闭孔;进行EDS元素分析,得知其中仅有C和O两种元素。选用相变温度比较适宜的脂肪酸类和烷烃类进行分子合金的制备。这类相变材料具有无腐蚀性,无毒性的,价格便宜,高存储密度,相变焓值较大的特性。根据“相似相容”原理,脂肪酸在一定的比例范围可以形成具有最低共熔点的分子合金。在熔融状态下,烷烃具有良好溶剂性能,可以和部分脂肪酸形成最低共熔物。分子合金材料在真空浸透的作用下和多孔石墨基体进行复合,制备出十八烷-月桂酸/石墨基(OC-LA/EG)、十八烷-棕榈酸/石墨基(OC-PA/EG)、癸酸-月桂酸/石墨基(CA-LA/EG)、月桂酸-棕榈酸/石墨基(LA-PA/EG)定形相变材料。基于多孔石墨基体表面张力和毛细吸附的作用,相变材料在相变过程中不会从多孔石墨基体中渗出。通过DSC分析,得出相变材料和基体的复合情况较好,分子合金在基体内的质量最高可达93.28 %;从SEM表征可以看出,相变材料被较多的吸附于多孔石墨基体中;利用对分子合金以及定形相变材料进行冷热循环分析材料的导热性能,定形相变材料的导热性能较分子合金相变材料有一定程度的提高。制备的定形相变材料焓值较大,导热性能和热稳定性能均较好。制备的定形相变材料易于储存和运输,且相变焓值和相变温度适宜,热稳定好,导热性能优良,可应用于储能和热能回收系统中。更多还原

【Abstract】 Facing with the growing depletion of the energy status, how to improve the energy efficiency has become the major question that numerous scientists now focus on. It is a new environment-friendly energy-saving technology to use phase change materials for latent heat energy storage. The porous graphite matrix which owns high thermal conducitivity could be combined with phase change materials to prepare the novel shape-stabilized phase change materials. And the same time, the problem of transportation and storage could be solved out.The porous graphite matrix was prepared from the microwave expansion of intercalated compounds which was obtianed from the chemical oxidation intercalation of the natural flake graphite. The abundant porous structure was found in the inner of expanded graphite, and the inflation volume was 170.72 ml/g. From the analysis of N2 Adsorption and Desorption, the surface for the Adsorption and Desorption was 29.157 m2/g and 48.5424 m2/g, respectively. According to the analysis of N2 Adsorption and Desorption, the proportion of mesoporous is up to 68.6 %. The closed pore structure and enclosed was found from the SEM images. Through the EDS element analysis, only C and O was found in the expanded graphite.The fatty acids and alkane with appropriate phase change temperature were selected for the preparation of molecular alloys. The good performance PCMs are of non-corrosive, non-toxic, cheap price, high energy storage density, larger phase change enthalpy. According to the pricinple of similar dissolve mutually theory, the fatty acids could be formed into the eutectic molecular alloys with minimum melting point after some simple physical treatment at the certain proportion. In the process of melting, the good solvent of alkane make it possible to form the eutectic molecular alloys with some of fatty acids.Using the method of vacuum impregnation, the novel shape-stabilized phase change materials-the Octadecane-Lauric acid/EG, Octadecane-Palmitic acid/EG palmitic acid, Capric acid-Lauric acid/EG and Lauric acid-Palmitic acid/EG were prepared through the combination of the molecular alloys and the porous graphite matrix. Thanks to the surface tension and capillary force of the expanded graphite, the phase change materials could not leak out from the porous matrix.From the analysis of DSC, the well combination between the phase change materials and porous matrix was shown. The biggest molecular alloys weight in the inner pore of expanded graphite could reach to 93.28 %. From the characterization of SEM, the molecular alloys was absorbed into the internal of expanded graphite. The melting and solidification process indicated that the addition of expanded graphite to the molecular alloys phase change matreials could enhance the thermal conductivity of the molecular alloys to a certain extent. The novel shape-stabilized phase change materials were in the possession of high phase change enthalpy, low weight loss and good thermal stabilities.The novel shape-stabilized PCMs with appropriate phase change enthalpy and temperature, good thermal stabilities, high thermal conductivity could be easily stored and transported, and meanwhile could be applied to the storage and heat recovery system.更多还原