【作者】 高智芳；

【导师】 万怡灶；

【作者基本信息】 天津大学 ， 材料学， 2013， 博士

【摘要】 开发导热高分子复合材料对改善微型电子元器件散热问题，保证其使用的安全性，延长使用寿命具有重要意义。目前，获得导热高分子复合材料主要依靠填充高导热的无机陶瓷粉体材料。大量粉体材料加入虽然提高了复合材料的导热性能，但降低了复合材料的力学性能，增大了其密度。因此，研究具有优良综合性能的导热高分子复合材料才能进一步扩大其应用的领域。本文制备了新型纳米填料，并研究了不同填料以及不同填充方式对PA6导热复合材料导热性能、力学性能、电绝缘性、加工性能等的影响；采用有限元技术分析了填料对复合材料热传导过程的影响。首先，采用尿素法制备了纳米AlN、纳米AlN/CNTs和AlN/GE杂化材料作为新型纳米导热填料，通过SEM、XRD、TEM、FTIR、TG和XPS等手段对材料进行了表征，然后分别将三种纳米填料按相同配比与微米Al2O3混合，获得了填充导热环氧复合材料，并对复合材料导热性能、密度和热稳定性进行了分析与比较。结果表明，与只添加微米Al2O3的复合材料相比，纳米填料的加入明显提高复合材料的导热性能，导热系数由大到小分别是添加了AlN/CNTs、AlN/GE和纳米AlN填料的复合材料。此外，纳米填料的加入还降低了复合材料的密度，提高了复合材料初始分解温度和完全分解温度。其次，研究了Al2O3、AlN、BN、SiC和石墨几种不同填料单一颗粒、颗粒混杂和纤维与颗粒混杂三种填充方式对PA6复合材料导热性能、力学性能、电绝缘性、密度、热变形温度和加工性能的影响。结果表明，单一无机陶瓷颗粒填充的复合材料力学性能较好、导热性能稍差，石墨填充的具有高导热性能，但力学性能差；而通过颗粒混杂填充得到的复合材料兼具了陶瓷颗粒填充时的良好力学性能和石墨填充的高导热性能，纤维的加入还可以进一步提高复合材料的综合性能。最后，采用有限元软件分析了网格密度、填料种类以及树脂种类等对复合材料导热性能的影响。结果显示，模拟结果和实验结果接近，很好的反应了填料粒径、体积分数和种类以及树脂基体对导热复合材料的导热系数、温度场和热流分布的影响，可以为导热高分子复合材料的导热性能设计提供相应的参考依据。更多还原

【Abstract】 For the aim of improving heat dissipation problem of micro-electroniccomponents, guaranteeing the security and extending the serviced lives of components,it is crucial to develop the polymer composites with high thermal conductivity. As arule, the high thermal conductivity polymer composites are fabricated by filling withthe high thermal conductivity inorganic ceramic materials. However, a high content offiller materials can improve the thermal conductively but simultaneously can result inthe poor mechanical properties and a high density of polymers. Therefore, the study ofthe thermal conductivity of polymer composites with excellent overall performance,such as light weight, appropriate mechanical properties and ease of processing, will bebenefit to expand their application fields. In this paper, the new nano-fillers wereprepared and then the effects of fillers type and filler systems on thermal conductivity,mechanical properties, electrical insulation, processing performance of compositeswere investigated. In addition, the effect of filler content on the heat conductionprocess of composites was also analyzed using finite element method.Firstly, the nano-AlN, AlN/CNTs and AlN/GE hybrid materials were prepared bysimple urea method to be employed as new nano thermal conductive filler materialand then were characterized by SEM, XRD, TEM, FTIR, TG and XPS. After that,these three types of nano-fillers were mixed with micro-Al2O3at the same proportionto prepare the thermal conductive epoxy composite. Furthermore, the influence ofthree type nanoparticles on thermal conductivity, density and thermal stability ofepoxy composites was investigated. The results revealed that the thermal conductivityof composite was significantly improved by adding nano-fillers. In addition, nanofiller was also helpful to reduce the density and improve initial decompositiontemperature and IPDT temperature of epoxy composites.Secondly, the Al2O3, AlN, BN, SiC, and graphite were selected as thermalconductivity fillers for PA6composites, respectively. The influences of compositesystems such as single type of particle fillers, hybrid particle fillers, and hybridparticle and fiber fillers on thermal conductivity, mechanical properties, electricalinsulation, density, heat distortion temperature and processing performance of PA6composites were investigated. The results revealed that PA6composites with singleinorganic ceramic particles had excellent mechanical properties and inferior thermal conductivity while the composites with single graphite particles had high thermalconductivity and inferior mechanical properties. The PA6composites with hybridparticle fillers exhibited a combination of excellent thermal conductivity andmechanical properties. Besides, the addition of fibers could improve thecomprehensive performances of the PA6composite further.Finally, the influences of fillers (particle size, volume fraction and types of fillers)and resin matrix on the thermal conductivity, temperature fields and heat fluxdistributions of the composites were obtained by finite element method. The thermalconductivity of composites obtained from finite element method exhibited agreementwith experimental results. It meant that this approach could be employed to providethe appropriate references for designing and fabricating polymer composite materialswith high thermal conductivity.更多还原