摘要/Abstract

采用分子动力学模拟方法研究了Al₂O₃/聚甲基二硅氧烷(PDMS)复合材料在300 K时的传热行为, 通过分析热传导、温度梯度以及导热增强等理论数据, 讨论了不同半径以及不同浓度的Al₂O₃填料粒子对PDMS传热的影响. 结果表明随着体积分数的增大, Al₂O₃/PDMS复合材料的热传导先减小后增加. 并且当Al₂O₃填充粒子的半径为5 nm时, Al₂O₃/PDMS复合材料的热传导达到最大值. 通过考察传热过程中的Al₂O₃填料和Al₂O₃/PDMS复合材料的温度和结构变化, 添加有小半径Al₂O₃填料的Al₂O₃/PDMS复合材料在传热的过程中主要以声子的形式进行传热, 此时决定热导率的主要因素有热容c、声子的平均速度v和声子的平均自由程l. 同时, 当体积分数为15%时, 传导链形成, 热量可以顺利通过Al₂O₃填料形成的传导链传播, 有助于热传导的增加.
关键词: 分子动力学模拟, 热传导, 聚二甲基硅氧烷, Al₂O₃填料, 复合材料, 热界面材料
Molecular dynamics simulation was carried out to study the heat transfer behavior of the Al₂O₃/polydimethyl- siloxane (PDMS) composites, through analyzing the thermal conductivity, temperature gradient and the thermal conductivity enhancement, we discussed the effect of the radius and volume content on the thermal conductivity of Al₂O₃/PDMS composites. The results show that the thermal conductivity of the Al₂O₃/PDMS composites decreases first and then increases. Besides, when the particle radius is 5 nm, the thermal conductivity of Al₂O₃/PDMS composites attains the largest, which is higher than that with same volume content. In addition, by investigating the temperature and structure changes during the heat transfer behavior, we also found that the heat transfer of Al₂O₃/PDMS composites with smaller Al₂O₃fillers is mainly conducted in the form of phonons, the main influence factors that determine the thermal conductivity are heat capacity c, average velocity v and average free path l. Meanwhile, when the volume content is 15%, the conduction chains occur, the thermal can transfer successfully through the conduction chains formed by the Al₂O₃ composites, which is beneficial to the increases of the thermal conductivity. We also observed the change of the structure and surface meshes of the Al₂O₃/PDMS composites with the increasing of the volume content. The Al₂O₃ fillers increase, PDMS chains distribute separately, and the pore structure increases, promoting the rigidity of the molecules. Moreover, when the volume content is 15%, the PDMS chains are wrapped around the Al₂O₃ fillers, forming a PDMS-Al₂O₃ composite conductor, which enhances the synergistic effect of heat transfer, further explaining the conclusion that the Al₂O₃/PDMS composites with higher volume content has higher heat conduction. The whole system has similar change in the structure: i) with the increasing of the filler radius, the strip structure decreases, and the sphere structure increases. ii) the viewing of the partial enlarged drawing leads to the idea that the contribution of Al₂O₃ fillers to the conduction path increases with the increasing of the radius. iii) when the fillers are small, the distribution is more dispersed.
Key words: molecular dynamics simulation, thermal conductivity, polydimethylsiloxane, Al₂O₃ fillers, composites, thermal interface materials


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