本文選題：聚丙烯　切入點：氮化硼　出處：《蘭州理工大學》2017年碩士論文　論文類型：學位論文

【摘要】：相變材料(PCMs)能在相轉變時吸收或釋放大量的潛熱,從而使其被大量的應用于建筑節(jié)能、室內保暖、可調溫紡織品、軍事和航天領域等。本文以聚丙烯和氮化硼為基體材料,制備了兩類相變復合材料。全文共分為三個部分:第一部分,將聚丙烯溶于對二甲苯,借助冷凍干燥的方法制備了聚丙烯的氣凝膠。通過吸附相變物質,如石蠟、硬脂酸(SA)、肉豆蔻酸(MA)等,制備了聚丙烯基相變復合材料。通過SEM,表明聚丙烯氣凝膠內部是多孔結構,相變物質被吸附到了聚丙烯的多孔結構中。通過EDS,表明聚丙烯氣凝膠吸附相變物質是比較均勻的。BET分析結果表明聚丙烯氣凝膠的比表面積為38.66 m2g-1,在相對壓力P/Po為0.97時測試得到的孔體積為0.17 cm3g-1,孔徑分布主要集中在22.54 nm。DSC測試結果表明聚丙烯氣凝膠不論吸附石蠟,還是硬脂酸、肉豆蔻酸等相變物質,均能達到相變物質本身75%左右的儲能密度,經過30次的冷熱循環(huán),測得聚丙烯氣凝膠對石蠟的吸附質量分數達到了900%;經過50次冷熱循環(huán)的聚丙烯/石蠟(PP/Paraffin)相變復合材料的熔融焓也沒有明顯的降低,且他們的DSC曲線幾乎重合。導熱分析測試結果表明聚丙烯/石蠟相變復合物的熱導率比純石蠟的至少提高了一倍,說明聚丙烯氣凝膠有助于增強熱導率。第二部分,利用異丙醇充分溶解硬脂酸和不同比例的氮化硼,得到了幾種比例的二元相變復合材料。通過SEM和TEM可以清晰的觀察到氮化硼的片層結構,FTIR表明了混合后的相變復合物沒有發(fā)生化學反應。XRD結果表明了氮化硼的相變復合材料仍然保持著良好的結晶性能。DSC測試結果表明氮化硼的相變復合材料的放熱溫度均在50℃,適當的添加氮化硼對于提高相變潛熱是非常有利的。過冷度分析表明,氮化硼的添加使復合材料的過冷度都降至10℃以下,說明其對于降低相變物質的過冷度很有幫助。通過測試樣品的熱導率,結果表明添加少量的氮化硼對于熱導率的提高明顯。第三部分,通過化學還原法制備了氮化硼/石墨烯(BG)的凝膠,再用冷凍干燥制備了氣凝膠,最后對相變物質進行吸附制備了氮化硼-石墨烯-硬脂酸(BGS)三元相變復合物材料。通過SEM觀察,石墨烯氣凝膠的內部呈疏松多孔結構,二維的石墨烯片層發(fā)生了扭曲并聯(lián)結到一起,石墨烯氣凝膠與硬脂酸復合后,內部幾乎沒有孔隙,與氮化硼復合后則依然有許多孔隙存在。通過FTIR測試表明氮化硼和硬脂酸的特征吸收峰明顯,且石墨烯和氮化硼復合后沒有新的吸收峰。XRD測試結果說明氮化硼和石墨烯的添加對硬脂酸的兩個特征峰沒有影響。吸附性能測試發(fā)現(xiàn)石墨烯氣凝膠的吸附倍率為15.11倍,而少量氮化硼添加的三元相變復合材料擁有更高的吸附倍率,達到了18.52倍。DSC結果表明氮化硼-石墨烯-硬脂酸相變復合物和純相變物質的相變溫度相差很小,少量添加氮化硼時其儲能密度達180 J g-1,其它三元復合物的儲能密度大多在150-160 J g-1左右,并且添加少量氮化硼的三元相變復合物的潛熱值要比未添加的石墨烯/硬脂酸的潛熱值高出15%左右。熱導率測試結果表明,三元相變復合材料的熱導率隨著氮化硼含量的增加而增加,說明氮化硼有利于提高復合物的熱導率。
[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.

【學位授予單位】：蘭州理工大學
【學位級別】：碩士
【學位授予年份】：2017
【分類號】：TB33

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