随着5G时代到来及半导体和电子技术的快速发展，电子设备朝着小型化、高集成度、高频率和大功率方向日益发展，其产生的热量将呈指数级增长，随之带来严峻的散热问题。不能及时有效的散热将会导致设备的性能下降，降低工作稳定性和精度，缩短使用寿命。环氧树脂(EP)具有易加工、优异电绝缘和良好机械性能等综合特性已被广泛应用于微电子和电力设备封装等热管理材料领域。然而，由固化环氧的无序性诱发的声子散射使其热导率很低，这无法满足高性能电子设备和电力装备的散热发展需求。

通过向EP中添加高导热填料以制备具有高导热性和优异综合性能的环氧导热复合材料是一种有效的应对策略。但高导热的获得往往需要填充高含量的导热填料，这导致材料的加工性能、力学和电性能明显下降和劣化。因此，如何以更少的填料构建更高效的热传导路径来提升导热性能同时保证复合材料的良好综合性能，这对面向电子器件热管理的封装材料具有重要意义。

针对此，本文基于在EP内构建三维导热粒子的热传导网络的基础上，实现了综合性能良好的导热环氧复合材料的制备，主要研究内容如下：

(1) 以石墨相氮化碳(g-CN)为原料，采用高温氧化法制备了g-CN纳米片(g-CNNS)，通过对g-CNNS进行了扫描电镜(SEM)、X射线衍射(XRD)和接触角的测试表明所制备的g-CNNS尺寸相比原始g-CN尺寸有所减少，且亲水性更强。随后以纤维素(CNF)水溶液为分散剂，通过冰模板法制备了g-CNNS/CNF骨架网络，最后采用真空浸渍法制备了相应的g-CNNS/CNF/EP复合材料。研究了g-CN与g-CNNS填料含量对环氧复合材料的导热与介电性能，结果表明，随着骨架中g-CNNS含量增加，g-CNNS/CNF/EP复合材料的导热性能显著提升。当填料量为10.4 wt%时，热导率为0.76 W/(m·K)，相比纯EP(0.2 W/(m·K))明显提高。归因于冰晶的体积排斥效应和CNF、g-CNNS分子间作用力，最终形成垂直方向上的有序导热网络结构，导热网络的构筑有利于声子传输，提升了导热性能。此外，g-CNNS/CNF/EP复合材料具有良好的介电常数及损耗，如在10.4 wt%填料时，10⁴ Hz下体系的介电常数和损耗分别为2.4和0.01。

(2) 以六方氮化硼(BN)为原料，通过机械球磨法制备了BN纳米片(BNNS)，通过SEM、XRD等手段分析其剥离效果，证明了BNNS剥离成功。以聚偏氟乙烯(PVDF)为胶粘剂，采用牺牲盐模板法制备了BNNS/PVDF骨架，最后通过真空辅助浸渍策略制备了环氧复合材(BNNS/PVDF/EP)。研究了该材料的导热与介电性能，结果表明，复合材料的热导率随着填料量的增加而显著升高，当填料含量为55.0 wt%时，导热性能增大至2.21 W/(m·K)，相比纯EP(0.2 W/(m·K))提升10倍。微观结构分析表明，成功制备了有序导热通道，归因于氯化钾盐颗粒的体积排斥效应和PVDF、BNNS分子间相互作用力两个因素。以制备的复合材料作为LED灯的热界面材料，考察动态散热性能，结果表明，BNNS/PVDF/EP具有优异的散热性能。此外，该复合材料具有较低的介电常数与介电损耗，如55.0 wt%填料时，体系在10⁴ Hz下的介电常数和损耗分别为1.46和0.007。

本文通过两种方法制备了不同三维导热网络，研究了网络结构对环氧性能的影响，揭示了粒子尺寸与网络结构对环氧导热性能与介电性能的影响。所制备的环氧基复合材料具有较高热导率，较低介电常数以及高电绝缘性能，在热管理材料领域具有潜在的应用价值。

With the advent of the 5G era and the rapid development of semiconductor and electronic technologies, electronic devices are increasingly moving towards miniaturization, high integration, high frequency, and high power, resulting in an exponential increase in heat generation and posing severe heat dissipation problems. Failure to dissipate heat in a timely and effective manner will result in decreased device performance, reduced work stability and accuracy, and shortened lifespan. Epoxy resin (EP), with its comprehensive properties such as easy processing, excellent electrical insulation, and good mechanical performance, has been widely applied in the field of thermal management materials such as microelectronics and power equipment packaging. However, the phonon scattering induced by the disorder of cured epoxy results in a low thermal conductivity, which cannot meet the heat dissipation requirements of high-performance electronic devices and power equipment.

The preparation of epoxy thermal conductive composites with high thermal conductivity and excellent comprehensive properties by adding high thermal conductivity fillers to EP is an effective coping strategy. However, obtaining high thermal conductivity requires filling with a high content of thermal conductivity fillers, which leads to a significant reduction and deterioration in the material's processing performance, mechanical and electrical properties. Therefore, how to construct a more efficient heat conduction path with less filler to improve the thermal conductivity while ensuring the good comprehensive performance of the composite material is of great significance for the packaging materials for thermal management of electronic devices.

Based on constructing a three-dimensional thermal conductive network of particles within EP, this thesis realizes the preparation of thermally conductive epoxy composites with good comprehensive performance. The main research contents are as follows.

(1) When graphite carbon nitride (g-CN) was used as the raw material, g-CN nanosheets (g-CNNS) was prepared by a high-temperature oxidation method. Scanning electron microscopy (SEM), X-ray diffraction (XRD) and contact angle tests were carried out on g-CNNS, indicating that the prepared g-CNNS had smaller particle size and stronger hydrophilicity than that of the original g-CN. Then, g-CNNS/CNF skeleton was designed by ice-templating method using cellulose nanofibril (CNF) water solution as a dispersant, and corresponding g-CNNS/CNF/EP composite material was designed by a vacuum impregnation method. The effect of g-CN and g-CNNS filler content on the thermal and dielectric properties of epoxy composites was investigated, and the results showed that the thermal conductivity of the g-CNNS/CNF/EP composite material significantly increased with the increase of g-CNNS content in the skeleton. When the filler content was 10.4 wt%, the thermal conductivity was 0.76 W/(m·K), which was significantly higher than that of pure EP (0.2 W/(m·K)). Through the volume repulsion effect of ice crystals and the force between the CNF and g-CNNS molecules, an ordered thermal conductivity network structure is eventually formed in the vertical direction. The construction of the thermal conductivity network facilitates phonon transport and enhances the thermal conductivity. In addition, the g-CNNS/CNF/EP composite material had suitable dielectric constants and losses. For example, at 10.4 wt% filler content, the dielectric constant and loss of the system at 10⁴ Hz were 2.4 and 0.01, respectively.

(2) When hexagonal boron nitride (BN) was used as a raw material, BN nanosheets (BNNS) was prepared through mechanical ball milling. The peeling effect of BNNS was analyzed by SEM, XRD, and other methods, which proved the successful exfoliation of BNNS. The BNNS/PVDF skeleton was prepared by the sacrificial salt template method using polyvinylidene fluoride (PVDF) as the adhesive, and finally the epoxy composite (BNNS/PVDF/EP) was prepared with a vacuum-assisted impregnation strategy. The thermal and dielectric properties of the material were investigated, and the results showed that the thermal conductivity of the composite increased significantly with the amount of filler, increasing to 2.21 W/(m·K) at a filler content of 55.0 wt%, a 10 times improvement compared to pure EP (0.2 W/(m·K)). Microstructural analysis showed that ordered thermal channels were successfully prepared, which was attributed to the volume exclusion effect of KCl salt particles and the interaction force between PVDF and BNNS molecules. The prepared composite material was used as a thermal interface material for LED lamps, and its dynamic heat dissipation performance was investigated, which showed excellent heat dissipation performance of BNNS/PVDF/EP. In addition, the composite material had low dielectric constant and dielectric loss. For example, at 55.0 wt% filler content, the dielectric constant and loss of the system at 10⁴ Hz were distributed as 1.46 and 0.007, respectively.

In this thesis, different three-dimensional thermally conductive networks were prepared by two methods, and the effects of network structure on epoxy properties were investigated to reveal the effects of particle size and network structure on epoxy thermal conductivity and dielectric properties. The prepared epoxy composites have high thermal conductivity, low dielectric constant and high electrical insulation properties, which have potential application value in the field of thermal management materials.

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