两种相变复合材料的制备及其储热性能研究

发布时间：2018-03-07 19:08

本文选题：聚丙烯　切入点：氮化硼　出处：《兰州理工大学》2017年硕士论文　论文类型：学位论文

【摘要】：相变材料(PCMs)能在相转变时吸收或释放大量的潜热,从而使其被大量的应用于建筑节能、室内保暖、可调温纺织品、军事和航天领域等。本文以聚丙烯和氮化硼为基体材料,制备了两类相变复合材料。全文共分为三个部分:第一部分,将聚丙烯溶于对二甲苯,借助冷冻干燥的方法制备了聚丙烯的气凝胶。通过吸附相变物质,如石蜡、硬脂酸(SA)、肉豆蔻酸(MA)等,制备了聚丙烯基相变复合材料。通过SEM,表明聚丙烯气凝胶内部是多孔结构,相变物质被吸附到了聚丙烯的多孔结构中。通过EDS,表明聚丙烯气凝胶吸附相变物质是比较均匀的。BET分析结果表明聚丙烯气凝胶的比表面积为38.66 m2g-1,在相对压力P/Po为0.97时测试得到的孔体积为0.17 cm3g-1,孔径分布主要集中在22.54 nm。DSC测试结果表明聚丙烯气凝胶不论吸附石蜡,还是硬脂酸、肉豆蔻酸等相变物质,均能达到相变物质本身75%左右的储能密度,经过30次的冷热循环,测得聚丙烯气凝胶对石蜡的吸附质量分数达到了900%;经过50次冷热循环的聚丙烯/石蜡(PP/Paraffin)相变复合材料的熔融焓也没有明显的降低,且他们的DSC曲线几乎重合。导热分析测试结果表明聚丙烯/石蜡相变复合物的热导率比纯石蜡的至少提高了一倍,说明聚丙烯气凝胶有助于增强热导率。第二部分,利用异丙醇充分溶解硬脂酸和不同比例的氮化硼,得到了几种比例的二元相变复合材料。通过SEM和TEM可以清晰的观察到氮化硼的片层结构,FTIR表明了混合后的相变复合物没有发生化学反应。XRD结果表明了氮化硼的相变复合材料仍然保持着良好的结晶性能。DSC测试结果表明氮化硼的相变复合材料的放热温度均在50℃,适当的添加氮化硼对于提高相变潜热是非常有利的。过冷度分析表明,氮化硼的添加使复合材料的过冷度都降至10℃以下,说明其对于降低相变物质的过冷度很有帮助。通过测试样品的热导率,结果表明添加少量的氮化硼对于热导率的提高明显。第三部分,通过化学还原法制备了氮化硼/石墨烯(BG)的凝胶,再用冷冻干燥制备了气凝胶,最后对相变物质进行吸附制备了氮化硼-石墨烯-硬脂酸(BGS)三元相变复合物材料。通过SEM观察,石墨烯气凝胶的内部呈疏松多孔结构,二维的石墨烯片层发生了扭曲并联结到一起,石墨烯气凝胶与硬脂酸复合后,内部几乎没有孔隙,与氮化硼复合后则依然有许多孔隙存在。通过FTIR测试表明氮化硼和硬脂酸的特征吸收峰明显,且石墨烯和氮化硼复合后没有新的吸收峰。XRD测试结果说明氮化硼和石墨烯的添加对硬脂酸的两个特征峰没有影响。吸附性能测试发现石墨烯气凝胶的吸附倍率为15.11倍,而少量氮化硼添加的三元相变复合材料拥有更高的吸附倍率,达到了18.52倍。DSC结果表明氮化硼-石墨烯-硬脂酸相变复合物和纯相变物质的相变温度相差很小,少量添加氮化硼时其储能密度达180 J g-1,其它三元复合物的储能密度大多在150-160 J g-1左右,并且添加少量氮化硼的三元相变复合物的潜热值要比未添加的石墨烯/硬脂酸的潜热值高出15%左右。热导率测试结果表明,三元相变复合材料的热导率随着氮化硼含量的增加而增加,说明氮化硼有利于提高复合物的热导率。
[Abstract]:Phase change material (PCMs) can absorb or release large amount of latent heat in phase transition, which is widely used in building energy saving, indoor warm, thermostat textiles, military and aerospace fields. In this paper, polypropylene and boron nitride as matrix materials, preparation of two kinds of phase change composite material. It consists of into three parts: the first part, the polypropylene is soluble in xylene and aerogel was prepared by polypropylene freeze-drying method. The adsorption phase change material, such as wax, stearic acid (SA), myristic acid (MA), polypropylene based phase change composites were prepared by SEM, showed that the internal polypropylene aerogels are porous structure, phase change material is adsorbed onto the porous structure of the polypropylene. By EDS, it is proved that polypropylene aerogel adsorption phase change material is.BET compared to the results of the analysis show that the uniform polypropylene aerogel surface area is 38.66 m2g-1, the relative Pressure P/Po 0.97 test pore volume obtained is 0.17 cm3g-1, the pore size distribution mainly concentrated in the 22.54 nm.DSC test results show that the polypropylene aerogel regardless of adsorption or paraffin, stearic acid, myristic acid as phase change material, can achieve the transformation material itself about 75% of the energy density, after 30 cycles of adsorption, mass fraction the measured aerogel of polypropylene wax reached 900%; after 50 thermal cycles of polypropylene / paraffin (PP/Paraffin) without obvious loss of the melting enthalpy of phase change composite material, and the curve of their DSC weighs almost. Thermal analysis test results show that the thermal conductivity of polypropylene / paraffin composite rate than pure paraffin at least doubled that polypropylene aerogel helps to enhance the thermal conductivity. The second part, boron nitride using isopropanol to fully dissolve stearic acid and different proportion, get some proportion The two element composite phase change material. By SEM and TEM can clear the boron nitride layer structures were observed, FTIR shows that the composite phase change mixture did not produce chemical reaction of.XRD results show that the composite phase change material of boron nitride still keeps the crystalline properties of.DSC good test results show that the exothermic temperature of phase change composite boron nitride the above 50 DEG C, adding boron nitride appropriate to improve the latent heat is very favorable. Undercooling analysis showed that adding boron nitride composite undercooling are reduced to below 10 DEG C, indicating the decrease of phase change material undercooling helpful. Through thermal test samples. The rate, the results show that the addition of a small amount of boron nitride for thermal conductivity increased significantly. The third part, were prepared by chemical reduction of boron nitride / graphene (BG) gel, gel was prepared by freeze drying gas, the most After the phase change material was prepared by adsorption of boron nitride graphene - stearic acid (BGS) three phase change composites. Observed by SEM, interior is a porous structure of graphene aerogel, two-dimensional graphene layer is distorted and joined together, graphene aerogel and stearic acid composite after almost no internal pore, and boron nitride composite is still a lot of pores exist. Through the FTIR test showed that the boron nitride and stearic acid characteristic absorption peaks, and graphene and boron nitride composite after no new absorption peak of.XRD test results show that the addition of boron nitride and graphene have no influence on the two features the peak of stearic acid. The adsorption test showed that the adsorption rate of graphene aerogel is 15.11 times, and three yuan a small amount of boron nitride composite phase change material added with higher adsorption rate reached 18.52 times,.DSC results show that boron nitride The phase transition temperature of graphene - stearic acid phase change composites and pure phase change material is very small, adding a small amount of boron nitride when the energy density of 180 J g-1, the other three yuan compound energy density mostly in 150-160 J g-1, three yuan compound and phase change latent heat added value to boron nitride compared with the graphene / latent heat without adding stearic acid value higher than about 15%. Thermal conductivity test results show that the three phase change thermal conductivity of composites increased with the increase of boron nitride, boron nitride that is beneficial to improve the thermal conductivity of the composite.

【学位授予单位】：兰州理工大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TB33

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