聚合物基复合材料导热性的研究

讨论了聚合物基高导热高绝缘纳米复合材料的导热机理与常用的导热理论模型。考虑到填充率、温度等的影响，采用不同理论模型计算了用氧化铝纳米颗粒填充环氧树脂时材料的热导率，并结合相关研究实验对不同导热理论模型进行了分析比较。     

聚合物复合材料导热性能的研究

论述了填充聚合物复合材料的导热性及其变化规律；总结了复合材料导热的理论模型和导热系数预测方程，对比研究了各种导热模型的区别与联系；分析了影响复合材料导热特性的因素。     

氮化硼填充导热绝缘复合材料的研究进展

近来,通过添加导热填料制备高导热绝缘聚合物基复合材料成为学者们研究的热点。文中综述了以氮化硼(BN)为填料的导热塑料、导热橡胶的研究现状。发现对无机填料进行表面处理,可以提高基体与填料间的相容性,减小两者间的热传导阻力;采用多模式的填料以适当的比例混杂填充聚合物基体,可以使填料间接触面积增大,从而有效提高聚合物基体的热导率。文中还简述了填充型导热复合材料的导热机理和典型理论模型,并提出了提高复合材料导热性的关键所在。     

固相纳米复合材料的导热系数预测

研究了分散剂和纳米颗粒对固相纳米复合材料导热系数的影响。假设纳米颗粒在纳米流体中均匀分布,构建了一个考虑纳米颗粒尺度和分散介质影响的物理分析模型;并由此利用最小热阻力法则和比等效导热系数相等法则,建立了一个固相纳米复合材料的导热系数理论模型。计算结果表明,颗粒的体积分数和导热系数、以及分散剂导热系数的增大,都会引起复合材料导热系数的增大。     

碳纤维随机填充橡胶复合材料导热性能的数值模拟

运用随机顺序添加算法RSA(Random sequential addition method),基于均匀化理论建立了碳纤维填充橡胶复合材料代表体积单元RVE(Representative volume element)模型,利用有限元方法数值模拟研究了碳纤维对橡胶复合材料导热性能的影响。结果表明:在相同的填充分数下,碳纤维根数对复合材料导热性能的影响较小;合理安排碳纤维空间分布及纤维取向能有效提高复合材料的导热性能;复合材料的导热性随着碳纤维填料含量及长径比的增加而增大;与理论模型相比,基于碳纤维填料随机分布模型所得模拟结果与实验值较接近,尤其在高填充分数时与实验值吻合较好,可以更好地预测纤维填料填充复合材料的导热性能,对制备具有高填充分数的高导热复合材料具有一定的指导意义。     

高导热云母胶制备工艺研究

采用无机纳米氮化铝粉体填充改性环氧树脂,获得所需的高导热云母胶。针对氮化铝粉体的表面改性、粉体掺杂方式对云母胶导热系数的影响进行了系统分析。经导热系数测试,确定了粉体的表面改性工艺,得到了最佳的粉体分散工艺。     

导热高分子材料研究进展

讨论了提高聚合物导热性能的途径－合成高导热系数的结构聚合物，用高导热无机填料对聚合物进行填充复合。综述了导热高分子材料的研究成果：聚合物导热的基本概念和影响其导热性能的因素及导热系数的预测理论；聚合物基导热复合材料的选材、复合技术及其应用。指出了导热高分子材料的研究方向－－纳米导热填料的研究和开发；聚合物树脂基体的物理化学改性；聚合物基体与导热填料复合新技术的研究和开发；复合材料导热模型的建立、导热机理（特别是聚合物基体与导热填料界面的结构与性能对材料导热性能的影响）及导热通路的形成等；探索高导热本体聚合物材料的制备方法和途径等。对导热高分子材料的研究和开发有重要意义。     

氮化硼和纳米金刚石混杂填充聚酰亚胺导热复合材料的制备与表征

以二维六方氮化硼和三维纳米金刚石为导热填料通过原位聚合方式杂化填充到聚酰亚胺(PI)基体中制备导热绝缘复合材料。采用聚芳酰胺和4,4-二氨基二苯醚分别对氮化硼和纳米金刚石进行表面接枝改性,以提高有机-无机两相界面的相容性。通过扫描电子显微镜、导热仪、热重分析等方法对复合材料的结构和性能进行了表征。结果表明,不同粒径的导热填料混杂填充聚合物,利用协同效应可以提高堆砌密度,降低界面热阻,形成导热网络。当填料总质量分数为30%,改性氮化硼和纳米金刚石的质量比为9∶1时,复合材料的热导率达0.596 W/(m·K),是纯PI的3.5倍,同时复合材料仍具有较好的热稳定性和电绝缘性,满足微电子领域的应用需求。     

纳米碳管强化水合物导热的研究

实验研究了不同温度（258．15K～270．15K）、不同纳米碳管含量（0．1wt％～10wt％）以及有无分散剂十二烷基硫酸钠（Sodium Dodecyl Sulfate，SDS）情况下四氢呋喃（Tetrahydrafuran，THF）水合物的导热系数。结果表明：THF水合物的导热系数随纳米碳管含量的增加而显著增加，纳米碳管的加入并没有改变THF水合物导热系数随温度的玻璃体变化特性。在纳米碳管质量分数一定时，随着温度的升高，THF水合物导热系数增大的速率越来越快。对于含纳米碳管的THF水合物，不加分散剂时的导热系数比加分散剂的导热系数低，但高于纯THF水合物的导热系数。     

高导热环氧树脂的研究进展

封装是电气工程和电子工业的重要组成部分,封装材料是决定封装成败和产品性能的关键因素之一,聚合物封装材料因可靠性与金属和陶瓷相当,成型工艺简单,且具有明显的价格优势,从而成为目前的主流封装材料.环氧树脂(EP)因收缩率小、耐热性好、密封性好及电绝缘性优良等特点,在电子封装材料领域的使用量达90％以上.近些年,随着电力设备功率密度的不断提升,电子器件的微型化以及向高温、高压、高频领域转变的发展趋势,纯环氧树脂0.2 W?m-1?K-1的低热导率使封装后的微细化超大规模集成电路以及电机运行等产生的热量难于释放,导致器件可靠性降低、寿命变短.发展高导热的环氧树脂封装材料成为必然选择.高导热环氧树脂具体包括本征型导热环氧树脂和填充型导热环氧树脂复合材料.当前,有关本征型导热环氧树脂的研究热点是通过化学合成刚性分子链或者容易结晶的小分子单体以及在分子链上引入液晶结构来提高环氧树脂的结晶度,减少声子散射.对于填充型导热环氧树脂而言,主要通过向环氧基体中添加高导热填料以构建导热通路,进而提高复合材料的热导率.但在低填充含量下往往无法构建有效的导热通路,而提高填充量又将影响材料的加工性与力学性能.与简单的共混相比,用高导热纳米填料构建3D框架可以极大地提高聚合物的热传递性能,但一般需要使用特殊工艺去除模板.本文综述了近些年关于环氧树脂导热性能的研究现状,给出了两种类型导热环氧树脂的制备方法,重点分析了提升其热导率的机制.进一步阐述了高导热填料的尺寸、形状、分布形态对填充型导热环氧树脂热导率的影响.最后,结合环氧树脂导热性能研究中存在的一些问题,展望了其未来的发展方向.     

Numerical Investigation of Heat Transfer of Silver-Coated Glass Particles Dispersed in Ethylene Vinyl Acetate Matrix

The effective thermal conductivity of silver-coated glass spheres dispersed in an ethylene vinyl acetate matrix was investigated numerically as a function of filler concentration. The finite-element method was carried out for modeling the thermal heat transport and to calculate the effective thermal conductivity of the composite for three elementary cells; simple cubic (SC), body-centered cubic (BCC), and face-centered cubic (FCC). The effect of the inclusion/matrix thermal contact resistance and the ratio of thermal conductivities of the filler-to-matrix material are also taken into account. The numerical results are compared with previously published experimental data and some theoretical models. The calculated values of the thermal conductivity of the SC model are in good agreement with the measured results for all the filler volume fractions. Numerical results for FCC and BCC models were found to be in good agreement with analytical models. The results show that the filler/matrix contact resistance has an important effect on the effective thermal conductivity.     

聚合物基复合材料导热模型的研究现状及应用

综述了描述聚合物基复合材料导热性能的经典模型和新模型,详细列举了各模型的特点,比较了模型之间的区别,具体分析了影响复合体系导热性能的各种因素.结合对碳纳米管复合材料的研究给出了一些常用模型的应用建议,同时提出了当前研究中存在的模型通用性差的问题,指出今后聚合物基导热复合材料的研究趋势应为开发新的高导热纳米填充物和纳米复合技术以使填充物在基体中能形成有效的导热通路,从而改善复合体系的导热性能.     

Thermal conductivity of polystyrene–aluminum nitride composite

The thermal conductivity of polymer composites having a matrix of polystyrene (PS) containing aluminum nitride (AlN) reinforcement has been investigated under a special dispersion state of filler in the composites: aluminum nitride filler particles surrounding polystyrene matrix particles. Data for the thermal conductivity of the composites are discussed as a function of composition parameters (aluminum nitride concentration, polystyrene particle size) and temperature. It is found that the thermal conductivity of composites is higher for a polystyrene particle size of 2 mm than that for a particle size of 0.15 mm. The thermal conductivity of the composite is five times that of pure polystyrene at about 20% volume fraction of AlN for the composite containing 2 mm polystyrene particle size. The relationship between thermal conductivity of composites and AlN filler concentrations has been compared with the predictions of two theoretical models from the literature.     

高比例SiC_p/Al复合材料的有效热导率模型

有效热导率是铝基复合材料在电子封装、热控方面应用的重要性能指标.结合复合材料广义自洽微观力学模型,并在Maxwell理论的基础上,初步建立了适合高体积分数SiCp/Al复合材料的有效热导率预测模型.模型不仅考虑了颗粒与颗粒、颗粒与基体间的界面效应,而且在一定程度上也考虑了增强体颗粒的形状.其理论计算结果与实测值吻合较好.     

导热型碳纤维增强聚合物基复合材料的研究进展

综述了导热型连续碳纤维增强聚合物基复合材料(CFRP)的研究与应用现状和进展,阐述了CFRP的声子导热和光子导热机理,介绍了不同铺层角度和铺层比的CFRP面内和厚度方向热导率计算模型及测试方法,分析了环氧树脂、氰酸酯、双马来酰亚胺等3类树脂体系和聚丙烯腈基(PAN)碳纤维、中间相沥青基碳纤维、气相生长碳纤维、碳纳米管纤维等4类增强体以及工艺方法等因素对CFRP热导率的影响。     

Analytical and Numerical Investigation on Effective Thermal Conductivity of Polymer Composites Filled with Conductive Hollow Particles

The thermal behavior of hollow conductive particles filled in epoxy resin has been investigated using 3D finite element computation. The effect of the filler concentrations associated with the particle/matrix interfacial resistance on the effective thermal conductivity of the composites was considered. The relationship between the out-of-plane effective thermal conductivity, the wall thickness of the hollow particles, and the ratio of the thermal conductivities of the filler to the matrix material were also taken into account. The numerical results show an increase of the effective thermal conductivity with increasing wall thickness of the hollow particles. However, for a large contact resistance and/or for a high effective thermal conductivity, it is shown that the contact resistance has a dominant influence on the effective thermal conductivity of the composites. The numerical results were also compared to some well-known analytical effective thermal conductivity models.     

Transient Characteristics of Thermal Conduction in Dispersed Composites

The effective thermal conductivity of dispersed composites with a hot-melt-adhesive matrix, measured using the steady-state method, is compared with the apparent thermal conductivity calculated from the average heat capacity and from the thermal diffusivity measured by the laser-flash method. The transient effect has been observed obviously at higher volume percentages for various dispersed particle sizes and ratios of the thermal conductivity values of dispersed and continuous phases. All of the experimental results are compared with those calculated by existing models and by the finite element method (FEM). An attempt has been made to show how the criterion for the homogeneity of dispersed composites under transient conditions is affected by the percentages of dispersed phase, dispersed particle size, and ratio of the thermal conductivity values of dispersed and continuous phases.     

Predictions of the thermal conductivity of multiphase nanocomposites with complex structures

Multiphase nanocomposites have drawn substantial attention due to their advanced functionality, including high thermal conductivity. Herein, theoretical models are developed based on modifications of the effective medium theory and then validated to predict the effective thermal conductivity (K_eff) of three common multiphase nanocomposites: nanosheet/nanoparticle/polymer, nanotube/nanoparticle/polymer, and nanosheet/nanotube/polymer. Case studies showed that the predicted K_eff agreed well with available experimental data, validating the developed models. Moreover, quantifiable material properties, like the thermal conductivity of nanofillers, the morphology of nanofillers, and the interfacial thermal resistance around nanofillers, were used to investigate their effects on the K_eff of multiphase nanocomposites. This quantitative study not only can provide simplified strategy to predict the K_eff for diverse multiphase nanocomposites, but it can also guide the design of multiphase nanocomposites with enhanced thermal conductivity.     

热传导聚合物基复合材料的研究进展

本文主要介绍了聚合物基复合材料的导热机理 ,以及预测二相体系复合材料热导率的理论模型方程。同时介绍了聚合物基导热材料的 3种类型及其具体应用 ,并提出聚合物基导热材料现阶段值得开发的课题和研究方向