聚合物/导热金属复合材料的研究进展

综述了聚合物/金属粒子导热复合材料的最新研究进展,重点探讨了金属粒子的种类、形状及大小、用量、加工方式及核壳结构等对复合材料热导率的调控及影响机理。在低填料用量时采用特殊加工手段在基体内构筑有利于声子传递的连续导热粒子通道,可得到优良综合性能的高导热聚合物复合材料;适应于可穿戴电子及柔性电子器件散热的液体合金/弹性聚合物在大尺度形变下具有良好的导热能力,是导热聚合物未来发展的重要方向。     

聚合物/新型导热填料复合电介质的研究进展

综述了非常规新型导热粒子如纳米金刚石、碳化物、铁电陶瓷及其他无机功能粒子及其填充聚合物电介质的最新研究进展，重点探讨了新型导热粒子的含量、表面改性、加工方式等对聚合物复合材料的导热及介电性能的影响。介绍和分析了基于有机分子晶体为连续声子传递通路改性聚合物导热性能的研究及机理;在基体树脂内利用无机导热粒子及有机分子晶体可构筑连续的声子导热通路，从而达到降低界面热阻、提高体系热导率的目的。相比传统导热粒子，新型导热粒子在提高绝缘聚合物热导率的同时，还赋予体系其他物理性能如磁性、优良介电性能及储能等性能。     

碳系填料构筑具有隔离结构导热复合材料进展

导热途径不均匀导致导热效率较低是制备高导热聚合物复合材料的重点难题,制备具有优良导热性能的复合材料仍面临巨大的挑战。制备具有三维导热网络结构的复合材料,有效地提高了热导率,是目前导热复合材料研究的热点。隔离结构的导热复合材料具有独特的导热网络结构,为声子提供了有效的传播途径,并且能降低填料-基体、填料-填料间的界面热阻,在低负载下能获得高热导率。综述了近年来碳系填料构筑隔离结构的导热复合材料的研究进展,分析了具有隔离结构复合材料的导热机理及制备方法,对各类方法制备复合材料的性能、特点缺陷进行概括对比,并且对能提升热导率的方法进行简要分析。     

聚合物基复合材料导热模型及热导率方程的研究

根据导热填料在聚合物基体中的分布，提出了导热聚合物基复合材料两相体系的“海岛-网络”模型；并结合逾渗理论及其在导电复合材料中的应用，建立了导热复合材料的逾渗热导率方程。实验证明，该模型及热导率方程符合实际而且适用于高含量填充型导热聚合物基复合材料热导率的预测。     

碳纳米填料几何形状和界面热阻对复合材料热导率的影响

以管状碳纳米填料[如多壁碳纳米管(MWCNTs)、碳纳米纤维(Pyrograf纤维)和碳晶须(丝状-VGCF)等]作为聚合物基复合材料的导热填料,探讨了MWCNTs-COOH(氧化功能化改性MWCNTs)、MWCNTs及Pyrograf纤维和丝状-VGCF的热导率、几何形状和界面热阻(R k)等对填料/聚合物基复合材料热性能的影响。研究结果表明:MWCNTs-COOH/基体、Pyrograf纤维/基体的热导率增幅相对较大;采用有效热介质理论模拟法确定了填料/基体的R k,碳纳米填料的几何形状和R k是影响复合材料热导率的重要因素,而碳纳米填料本身的热导率对复合材料热导率的影响并不大。     

聚合物基导热绝缘复合材料的制备及逾渗模型的应用

采用乙烯一醋酸乙烯a共聚物和无机导热填料制备聚合物基导热绝缘复合材料,概述了以逾渗理论为基础的热导率计算模型,并应用所制备的导热绝缘复合材料讨论了逾渗模型的准确性。结果表明,SiC填充的复合材料具有较好的导热性能;填料体积分数达0.5时,复合材料的热导率可达1.86 W/(m0K)。研究表明,简单地运用逾渗理论在预测导热复合材料体系的热导率方面准确性不足,需要进一步考虑实际填料粒子分布与理论假设的差异以及界面相的存在等因素的影响。     

三氧化二铝/硅橡胶复合材料热导率的预测

应用最小热阻力法则和比等效热导率法则,建立颗粒填充聚合物基复合材料的导热模型并推导出等效热导率公式,并对三氧化二铝/硅橡胶复合材料热导率进行预测.结果表明,复合材料热导率预测值与实测值接近;三氧化二铝粒径较小时,预测值与实测值更为接近;三氧化二铝体积分数相同时,大粒子填充硅橡胶复合材料热导率更高.     

集成电路封装用GNPs/CNTs/HDPE导热高分子复合材料的研究

本文以高密度聚乙烯(HDPE)为基体,以自制的h-G-C-2/1体系杂化填料为导热填料,制备了GNPs/CNTs/HDPE导热高分子复合材料,重点对比了杂化填料和复配填料对GNPs/CNTs/HDPE复合材料在导热、导电及力学性能方面的影响。结果表明,GNPs/CNTs/HDPE导热高分子复合材料的拉伸强度为31.9 MPa,冲击强度为22.1 kJ/m^2,体积电阻率为690 MΩ·cm,热导率为0.759 W/(m·K),满足集成电路封装用技术参数要求。杂化填料的分散性优于复配填料,杂化填料在提高复合材料的拉伸性能方面优于复配填料,复配填料在提高复合材料的热导率方面优于杂化填料。本文所获得的研究成果为制备新型综合性能优异的集成电路封装用导热高分子复合材料提供了一条新的思路。     

改善聚合物热导率的研究进展

分别从导热填料粒子性质、聚合物基体、两相界面结构性质,以及材料加工工艺等角度出发,深入探讨了影响聚合物热导率的因素和机制,总结了提高和改善聚合物导热性能的方法。提高导热粒子和基体的热导率,在聚合物基体内形成稳定的最大化导热粒子通路等措施均可有效改善聚合物热导率。     

热传导高分子复合材料的导热机理、类型及应用

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Maxwell-Eucken,Bruggemen,Cheng-Vochen,Ziebland,Lewis-Nielsen,Y.Agari-Uno方程。同时介结了聚合物基导热材料的三种类型及其具体应用。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。     

Thermal conductivity of carbon nanotubes and their polymer nanocomposites: A review

Thermally conductive polymer composites offer new possibilities for replacing metal parts in several applications, including power electronics, electric motors and generators, heat exchangers, etc., thanks to the polymer advantages such as light weight, corrosion resistance and ease of processing. Current interest to improve the thermal conductivity of polymers is focused on the selective addition of nanofillers with high thermal conductivity. Unusually high thermal conductivity makes carbon nanotube (CNT) the best promising candidate material for thermally conductive composites. However, the thermal conductivities of polymer/CNT nanocomposites are relatively low compared with expectations from the intrinsic thermal conductivity of CNTs. The challenge primarily comes from the large interfacial thermal resistance between the CNT and the surrounding polymer matrix, which hinders the transfer of phonon dominating heat conduction in polymer and CNT.This article reviews the status of worldwide research in the thermal conductivity of CNTs and their polymer nanocomposites. The dependence of thermal conductivity of nanotubes on the atomic structure, the tube size, the morphology, the defect and the purification is reviewed. The roles of particle/polymer and particle/particle interfaces on the thermal conductivity of polymer/CNT nanocomposites are discussed in detail, as well as the relationship between the thermal conductivity and the micro- and nano-structure of the composites.     

石墨烯导热高分子复合材料的制备、性能与机理

石墨烯是一种具有超大的比表面积、良好的热和化学稳定性、超高的热导率以及易于化学修饰的蜂窝状单层碳材料,已作为填料广泛应用于导热高分子复合材料领域。近年来石墨烯导热高分子材料的研究重点是改善石墨烯在聚合物基体中的界面相容性和分散性能。阐述了近年来石墨烯导热高分子复合材料的制备方法及其热性能,并重点对石墨烯导热高分子复合材料的导热机理进行综述,同时结合研究现状对石墨烯导热高分子复合材料的研究方向进行展望。     

导热高分子复合材料的研究进展

随着电子信息技术的快速发展，电子设备的散热问题面临严峻的挑战，亟须研发高性能导热复合材料。高分子复合材料因其轻质、高强度和良好的柔韧性，在导热材料领域得到了广泛应用。简要介绍了导热高分子复合材料的导热机理、导热填料以及影响导热率的因素。综述了通过表面功能化、杂化粒子、填料取向和构建3D互联骨架结构等方法提高复合材料导热性能的研究现状。总结了导热材料当前面临的问题，并对未来导热高分子复合材料的发展方向进行了展望。     

聚合物/碳纳米管复合导电材料的研究进展

基于碳纳米管(CNTs)的导电性能,对以碳纳米管为导电填料的复合导电材料的制备方法及国内外研究进展进行了综述。重点介绍了几种常见聚合物/CNTs复合导电材料的研究现状。展望了此类导电材料的发展前景。     

A review of vapor grown carbon nanofiber/polymer conductive composites

Vapor grown carbon nanofiber (VGCNF)/polymer conductive composites are elegant materials that exhibit superior electrical, electromagnetic interference (EMI) shielding effectiveness (SE) and thermal properties compared to conventional conductive polymer composites. This article reviews recent developments in VGCNF/polymer conductive composites. The article starts with a concise and general background about VGCNF production, applications, structure, dimension, and electrical, thermal and mechanical properties. Next composites of VGCNF/polymer are discussed. Composite electrical, EMI SE and thermal properties are elaborated in terms of nanofibers dispersion, distribution and aspect ratio. Special emphasis is paid to dispersion of nanofibers by melt mixing. Influence of other processing methods such as in-situ polymerization, spinning, and solution processing on final properties of VGCNF/polymer composite is also reviewed. We present properties of CNTs and CFs, which are competitive fillers to VGCNFs, and the most significant properties of their composites compared to those of VGCNF/polymer composites. At the conclusion of the article, we summarize the most significant achievements and address the future challenges and tasks in the area related to characterizing VGCNF aspect ratio and dispersion, determining the influence of processing methods and conditions on VGCNF/polymer composites and understanding the structure/property relationship in VGCNF/polymer composites.     

Enhancing thermal conductivity of C/SiC composites containing heat transfer channels

In this study, CNTs/SiC micro-pillars at controlled content ratios were introduced into C/SiC composites as heat transfer channels to improve the thermal conductivity in the thickness direction. The thermal conductivities and bending strengths before and after heat treatment at 1650 °C were investigated and the results were discussed. The theoretical calculations and finite element analyses confirmed that CNTs/SiC micro-pillars successfully worked as heat transfer channels. The theoretical thermal conductivity calculated by effective medium theory (EMT) model was 19.25 W/m⋅k and agreed-well with the experimental value. The measured thermal conductivity was estimated to 20.69 W/m⋅k and improved to 22.36 W/m⋅k after heat treatment. The latter was 3.56-fold higher than that of traditional C/SiC and attributed to increased grain growth during heat treatment. The optimal bending strength before heat treatment was recorded as 324.5 ± 23.74 MPa due to microstructure evolution caused by CNTs. After heat treatment, the bending strength improved by 138 % with ductile fracture mode attributed to ordered layer structure of PyC interphase and complex phase composition of the composites. These features benefited the abundant propagation of cracks and energy consumption. In sum, introduction of heat transfer channels into C/SiC composites provided a new way to improve the thermal conductivity in thickness direction of ceramic matrix composites.     

Joule effect self-heating of epoxy composites reinforced with graphitic nanofillers

Self-heating of conductive nanofilled resins due to the Joule effect is interesting for numerous applications, including computing, self-reparation, self-post-curing treatment of resins, fabrication of adhesive joints, de-icing coatings and so on. In this work, we study the effect of the nature and amount of graphitic nanofiller on the self-heating of epoxy composites.The addition of graphitic nanofillers induced an increase in the thermal conductivity of the epoxy resins, directly proportional to the nanofiller content. Percolation was not observed because of the heat transport through phonons. In contrast, the electrical conductivity curves present a clear percolation threshold, due to the necessity of an electrical percolation network. The electrical threshold is much lower for composites reinforced with carbon nanotubes (CNTs, 0.1 wt.%) than for the resin filled with graphene nanoplatelets (GNPs, 5 %). This fact is due to their very different specific areas.The composites filled with CNTs reach higher temperatures than the ones reinforced with GNPs, applying low electrical voltage because of their higher electrical conductivity. In contrast, the self-heating is more homogeneous for the GNP/epoxy resins due to their higher thermal conductivity. It was also confirmed that the self-heating is repetitive in several cycles, reaching the same temperature when the same voltage is applied.     

Improved dispersion of carbon nanotubes in poly(vinylidene fluoride) composites by hybrids with core–shell structure

Core–shell structure hybrids of carbon nanotubes (CNTs)/BaTiO₃ (H‐CNT‐BT) and commercial multi‐wall CNTs are respectively incorporated into poly(vinylidene fluoride) (PVDF) for preparing the composites near the percolation thresholds. A comprehensive investigation for CNT's dispersion and composite's conductivity is conducted between H‐CNT‐BT/PVDF and CNT/PVDF at different depths vertical to the injection's direction. Gradual increases of the conductivity in two composites are observed from the out‐layer to the core part which infers an inhomogeneous CNT's dispersion in the interior of composites due to their migration under flow during the injection. However, the use of H‐CNT‐BT fillers with core–shell structure enables to reduce this inhomogeneous dispersion in the composite. Furthermore, the conductive network of CNTs in H‐CNT‐BT/PVDF is less sensitive to the thermal treatment than the one in CNT/PVDF composite, which infers the core–shell structure of hybrids can ameliorate the sensitivity of the conductive network. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45693.     

环氧树脂/碳纳米管导热复合材料的制备与性能研究

采用先酸化再空气氧化的方法对碳纳米管（CNTs）进行了纯化处理,并制备了2种环氧树脂(EP)/CNTs导热复合材料。研究了不同含量的CNTs及纯化CNTs对复合材料的导热性能、冲击性能及弯曲性能的影响。结果表明,纯化处理后,CNTs表面的催化剂粒子和无定形碳被去除,得到了纯净CNTs;当纯化CNTs含量为1.5 %时(质量分数,下同),材料的冲击强度和弯曲强度最高,分别为24.95 kJ/m2、127.2 MPa;当纯化CNTs含量为1.5 %时,复合材料的热导率可达1.237 W/（m·℃）。