石蜡(PA)作为相变储能的储能介质因导热系数低限制了其在工业领域的应用,重点探究不同功能化石墨烯与石蜡共掺对复合相变材料(CPCM)热导率及玻璃化转变温度的影响,建立了纯十八烷体系模型、未功能化石墨烯(GN)以及分别接枝羟基(—OH)、氨基(—NH2)和羧基(—COOH)官能团的石蜡/功能化石墨烯复合体系模型。使用非平衡分子动力学方法得出了材料的热导率、玻璃化转变温度。通过计算体系结构参数,从均方位移、径向分布函数分子层面阐释了材料热力学性能增强的内在机理。结果表明:各项石蜡复合相变材料体系热性能均有不同幅度的提升,其中PA/GN-NH2在热力学性能上较其他掺杂体系提升最为明显,其热导率较掺杂前提升了69.19%、玻璃化转变温度提升了2.3%;从均方位移(MSD)可以看出,GN的引入提高了玻璃化转变温度,增强了体系的稳定性,尤其以GN-NH2最为明显,玻璃化温度达到307K,从径向分布函数看出,添加GN可以显著改变烷烃分子有序度,改善热输运效果。所得结果可为复合相变材料的掺杂设计、性能调控提供理论支持。
Paraffin wax (PA),as an energy storage medium for phase change energy storage,is limited in industrial applications due to its low thermal conductivity.This paper focused on exploring the effects of co-doping of different functional graphene and paraffin on the thermal conductivity and glass transition temperature of CPCM.The models of pure octadecane,unfunctionalized graphene (GN) and paraffin/functionalized graphene composite systems grafted with hydroxyl (—OH),amino (—NH2) and carboxyl (—COOH) functional groups were established.The thermal conductivity and glass transition temperature of the material were obtained by non-equilibrium molecular dynamics method.By calculating the structural parameters of the system,the internal mechanism of the enhancement of the material's thermodynamic properties was explained from the molecular level of mean azimuth shift and radial distribution function.The results showed that the thermal properties of each paraffin CPCM system was improved in different amplitude,and the thermodynamic properties of PA/GN-NH2 were the most obvious improvement compared with other doping systems,the thermal conductivity was increased by 69.19%,and the glass transition temperature was increased by 2.3%.It could be seen from the mean azimuth shift (MSD) that the introduction of GN improved the glass transition temperature and enhanced the stability of the system.Especially for GN-NH2,its glass transition temperature reached 307K.The radial distribution function revealed that the addition of GN significantly changed the order degree of alkane molecules and improved the heat transport effect.The findings could provide theoretical support for doping design and property control of CPCM.
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基金资助
河南省中原科技创新领军人才项目(234200510011);河南省重点研发计划项目(241111320900,231111320900);郑州市协同创新专项(校重大重点项目培育)(2021ZDPY0107)
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