纳米氧化石墨烯/芒硝基复合相变材料的制备及其热性能

Preparation and Thermal Performance of Nano-Graphene Oxide/Mirabilite Composite Phase Change Materials

针对芒硝相变材料因过冷度大、相分层严重导致相变潜热存储循环寿命缩短的问题,以Na_(2)SO_(4)·10H_(2)ONa_(2)CO_(3)·10H_(2)O-NaCl相变材料体系为基体、改进的Hummers法结合冷冻干燥和球磨工艺改性制备的亲水性纳米氧化石墨烯(Nano-GO)为添加剂,制得纳米氧化石墨烯/芒硝基复合相变材料(GO-MCPCMs)。结果表明:氧化处理过的纳米氧化石墨烯中O/C比例增加了65.75%,结构缺陷水平由0.224增至1.088,无团聚现象;纳米氧化石墨烯/芒硝基复合相变材料的结晶相变温度增至约23℃、过冷度减小至0℃、相分层消除,该复合相变体系中Na_(2)SO_(4)结晶体全部结晶为晶粒长度尺寸近于2 cm的Na_(2)SO_(4)·10H_(2)O;500次固-液循环前后含氧化石墨烯质量分数为0.075%的GO-MCPCMs结晶潜热值分别为156.7 J/g和149.9 J/g,衰减率为4.3%,Nano-GO的加入明显改善了芒硝基复合相变体系的热稳定性。纳米氧化石墨烯/芒硝基复合相变材料具有良好的热循环稳定性和较长的使用寿命。

To solve the problem of the shortened cycle life of phase-change latent heat storage due to the large subcooling degree and serious phase stratification of mirabilite phase-change materials,a graphene oxide/mirabilite composite phase-change material(GO-MCPCM)was prepared with Na_(2)SO_(4)·10H_(2)ONa_(2)CO_(3)·10H_(2)O-NaCl phase-change composite as a matrix and graphene oxide(GO)as additives.The microstructure and properties of GO and GO-MCPCMs were characterized by scanning electron microscopy,transmission electron microscopy Raman spectroscopy,Fourier transform infrared spectroscopy,X-ray photoelectron spectroscopy,and thermogravimetry-Differential scanning calorimetry,respectively.The results show that the O/C ratio in oxidized graphene oxide is increased by 65.75%,the structural defect level is increased from 0.224 to 1.088,indicating that the oxidation-treated graphene has no agglomeration phenomenon and has good hydrophilicity and compatibility.The crystalline phase transition temperature of GO-MCPCMs is 23℃,the degree of subcooling reduces to 0℃,only sodium sulfate decahydrate releases heat,and the crystalline hydrate is Na_(2)SO_(4)·10H_(2)O with a grain length of approximately 2 cm.The maximum latent heat of GO-MCPCMs crystallization at a mass fraction of 0.075%is 156.7 J/g,and the attenuation rate of the latent heat of GO-MCPCMs crystallization at a mass fraction of 0.075%is 4.3%after 500 solid-liquid cycles.Therefore,the addition of GO can improve the thermal stability of the mirabilite composite phase-change material,and graphene oxide/mirabilite composite phase-change material prepared has a good thermal cycle stability and a long service life.