碳纳米管/聚合物复合材料的导热模型进展

综述了以聚合物为基体的碳纳米管复合材料导热模型,分析了复合材料热传导体系中碳纳米管(CNTs)填料的作用机制,归纳了混合规则导热模型、均质模型、有效介质模型、非均质模型和随机分散模型等,并总结了导热模型常用的数值计算方法。这些模型丰富了导热理论,可以对复合材料导热系数进行初步预测,但在数值上都存在近似或者简化处理,对碳纳米管/聚合物复合材料预测广谱性较差。未来需要对分子尺寸和界面热阻等影响导热系数的关键因素深入探究,改善数值和表征分析方法,以期为碳纳米管/聚合物复合材料的导热性能的研究和设计提供参考,为其他复合材料导热性能的研究提供借鉴。     

碳纳米管/氮化硼配比对聚乙烯复合材料性能的影响

以高密度聚乙烯为基体材料,以碳纳米管和氮化硼颗粒为导热填料,通过熔融共混法制备了导热聚乙烯复合材料;研究了碳纳米管和氮化硼颗粒的配比和添加量时复合材料力学性能、导热率、流动性、耐热性的影响。结果表明:当碳纳米管和氮化硼的质量比为1:1时,复合材料导热率最高;当碳纳米管和氮化硼含量均为10%时,复合材料的导热率提高了62.64%(100℃)。     

碳纳米管材料导热性能的实验研究

本文对碳纳米管与环氧树脂(Epoxy-EP)复合材料的导热性能进行了定量的研究,探索了CNTs/EP复合材料的制备方法,运用Hotdisk热常数分析仪研究了CNTs/EP复合材料的导热系数;利用CNTs/EP两相复合材料的导热理论模型得到了室温下单壁碳纳米管(Single-Wall Carbon Nanotubes-SWCNTs)的导热系数为3980 W/(m.K),双壁碳纳米管的导热系数(Double-Wall Carbon Nanotubes-DWCNTs)为3580 W/(m.K),以及多壁碳纳米管(Multi-Wall Carbon Nanotubes-MWCNTs)的导热系数为2860 W/(m.K)。     

单向C／C复合材料导热系数的计算

针对实验室制备的单向C/C复合材料,利用平板导热模型对复合材料中炭纤维和基体炭的导热系数进行了计算,并对单向C/C复合材料的整体导热系数进行了模拟和预测.结果显示:平板导热的并、串联模型能对单向C/C复合材料沿纤维方向和垂直纤维方向的导热性能进行较为准确的模拟和预测.     

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。     

3D打印技术在高导热复合材料中的应用研究

分析了3D打印技术在制备导热复合材料上的发展过程，介绍了不同种类的3D打印技术制备的高导热复合材料，包括碳纤维型、石墨烯型、碳纳米管型、氮化硼型、氮化铝型等，概述了不同类型的成型过程并归纳和总结了其导热性能。最后，对3D打印技术制备导热复合材料进行了总结与展望。     

碳纳米管／Al2O3／硅橡胶导热复合材料结构和性能的研究

将碳纳米管混入Al2O3 /硅橡胶复合材料中,制得了导热硅橡胶复合材料并对其进行了研究。结果表明：随着碳纳米管用量的增加,材料导热性能逐渐增加;碳纳米管有助于填料网络结构的形成．达到了协同增加导热性能的效果;原预想碳纳米管在体系中伸展后能形成导热通路,可大幅提高导热效率．但由于开炼共混时未能保存住其高长径比的特点,增益效果不够显著。     

硅橡胶/三氧化二铝复合材料导热率的预测

应用最小热阻力法则和比等效导热率法则,建立了颗粒填充聚合物基复合材料导热模型,推导出了等效导热率公式,并对硅橡胶/三氧化二铝复合材料导热率进行了估算。结果表明,复合材料导热率预测曲线与实测曲线大致相似;当三氧化二铝颗粒体积分数较小时,采用已发表理论模型计算的导热率与本模型预测值之间有较好的一致性。     

聚合物/碳基导热复合材料研究进展

碳家族主要包括石墨、碳纤维、碳纳米管、富勒烯、石墨烯以及无定形碳等。其中石墨、碳纤维、碳纳米管以及石墨烯具有良好的导热性能,最近被广泛研究的石墨烯是1种很有前景的导热填料。综述近年来国内外以碳材料为填料的导热复合材料研究进展,阐述了碳材料及其纳米导热复合材料导热性的影响因素,最后对碳材料的发展方向进行了展望。     

碳纳米管/聚乙烯导热系数分子动力学模拟

采用平衡分子动力学模拟方法研究了碳纳米管(CNT)/聚乙烯(PE)复合材料的导热系数。结果表明,使用长度为0.738nm的单壁CNT填充,CNT/PE复合材料的导热系数可达7.2 W/(m·K),增加CNT的填充量,复合材料的导热系数值随之增大;由于官能团改性造成的CNT缺陷阻碍了CNT自身热传导过程中声子的传播,官能团改性CNT填充虽然也能很大程度地提高了复合材料的导热系数,但其效果却不及CNT,模拟结果表明,CNT可成为提高PE导热性能的优良添加剂。     

Thermal conductivity of polymer filled with carbon materials: Effect of conductive particle chains on thermal conductivity

Thermal and electric conductivities of polyethylene and poly(vinyl chloride) filled with carbon materials over a wide range are measured in order to study the effect of formed conductive particle chains on thermal conductivities of the composites. With increase of content of carbon particles, the amount of formed conductive chains exponentially increases and the conductive chains tend largely to increase thermal conductivity of a composite. Some models proposed to predict thermal conductivity of a composite in a two-phase system could not be applied to the system with high volume content of particles. In this study, a new thermal conduction model is proposed to correctly predict thermal conductivity of a composite which contains various amounts of particles ranging from a small content, to the region in which conductive chains largely effect a thermal conductivity of a composite. Thermal conductivity of a polymer filled with high volume content of particles largely decreased with a rise in temperature. This phenomenon can be referred to as a PTC phenomenon in thermal resistance.     

基于导热形状因子的泡沫金属导热特性分析

通过理论分析引入用于定向计算泡沫金属等效热导率的导热形状因子（m）,并基于文献报道的大量实验数据对m进行了计算和分析。研究发现,m随泡沫金属材质、孔隙率及孔密度变化呈显著随机波动现象,无固定趋势或规律可循;泡沫金属等效热导率的准确预测需纳入多孔泡沫结构定向形变效应影响。鉴于此,通过直接数值模拟获得了m随孔胞形变参数（即沿泡沫金属宏观传热方向与其垂直方向的胞径比）变化的无量纲准则关联式,进而提出了基于m定向预测泡沫金属等效热导率的新方法。对比文献报道实验数据及基于各向同性结构假设的理论模型预测结果发现,上述方法可提高等效热导率的预测精度（平均偏差为0.77%）。     

甲基乙烯基硅橡胶导热复合材料的研究与制备

以甲基乙烯基硅橡胶为基体树脂,不同粒径碳化硅(SiC)和碳纤维(CF)复配作为填料,经开炼后模压硫化成型制得高导热复合材料。利用热流法导热系数测试仪(DRL-II)、扫描电子显微镜(SEM)对复合材料的导热性能、微观结构、力学性能进行了表征。结果表明：碳化硅和碳纤维能够均匀的分散在基体树脂中,不同粒径的碳化硅复配能使复合材料的导热性能进一步提高,导热系数达到1.28w/(m.k)。加入碳纤维不仅能使基体内部形成串联的导热网链,进一步提高基体树脂的导热性能,使复合材料的导热系数达到1.88w/(m.k),同时提高了复合材料的拉伸强度。     

PP/AlN复合材料导热机理研究

以氮化铝(AlN)粉末、聚丙烯(PP)为原料,通过共混-模压法制备了PP/AlN导热复合材料,并对其导热性能进行检测。研究发现,该复合材料的导热系数与AlN添加量之间不是线性关系而是呈幂函数关系,与介电逾渗理论基本吻合。根据检测数据并参考介电逾渗理论,提出了导热逾渗模型,并利用该模型和其他导热预测模型对PP/AlN复合材料的导热系数进行了计算。结果表明:复合材料的导热系数随AlN质量分数的增加呈幂函数增加趋势;实际检测结果与导热逾渗模型的预测结果基本相符,使该理论得到了验证。     

Model for thermal conductivities in spun yarn carbon fabric composites

A study on the thermal conductivities of spun yarn‐type carbon/phenolic (spun C/P) composites using a thermal‐electrical analogy method is presented. This method is based on the similarity between the partial differential equation that governs the thermal potential and electrical potential distribution. The unit cell of a laminate composite is divided into several conduction elements. By constructing an equivalent thermal resistance network in series, and in parallel based on analogy, we were able to predict the thermal conductivity of the composite. The prediction values obtained from the model are compared with known thermal conductivities on a carbon/epoxy composite with an eight‐harness satin (8HS) texture. It is shown that the model provides a good estimate of the thermal conductivity of the spun yarn fabric‐reinforced composite. With the use of this model, the thermal conductivity of the spun C/P composites with 8HS was validated experimentally. Good agreement was found between the present approach and the experimental results. POLYM. COMPOS., 26:791–798, 2005. © 2005 Society of Plastics Engineers     

Thermal conductivity augmentation of composite polymer materials with artificially controlled filler shapes

Plastics or polymers of high thermal conductivity are highly desired in various industries. Adding fillers of high thermal conductivity to the base materials is a solution to make composite plastics of high thermal conductivity. Previous researches were focused on increasing the thermal conductivity of the composite materials by increasing the filler content and the thermal conductivity of the fillers. Relatively little attention was paid to the optimization of filler shapes. In this study, the effects of the filler shapes on the thermal conductivity of the composite materials are investigated, where the filler shapes are artificially designed. Heat conduction between the base materials and the artificially designed fillers is modeled. It is found that the filler shapes have great impacts on the effective thermal conductivity of the composite materials. Of the various shapes, the double Y shaped fillers are found to be the best choice for composite materials in which the fillers are distributed randomly. In future industrial applications, new filler shapes, such as double Y, Y, quad Y shaped, I and T shapes should be specially produced to replace the traditional fillers shapes: particles, fibers or slices. At last, composite materials made of paraffin wax and steel fillers of ten shapes are fabricated to simulate and validate the results. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 39550.     

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。     

Role of Interfacial Carbon layer in the Thermal Diffusivity/Conductivity of Silicon Carbide Fiber-Reinforced Reaction-Bonded Silicon Nitride Matrix Composites

The role of an interfacial carbon coating in the heat conduction behavior of a uniaxial silicon carbide nitride was investigated. For such a composite without an interfacial carbon coating the values for the thermal conductivity transverse to the fiber direction agreed very well with the values calculated from composite theory using experimental data parallel to the fiber direction, regardless of the ambient atmosphere. However, for a composite made with carbon-coated fibers the experimental values for the thermal conductivity transverse to the fiber direction under vacuum at room temperature were about a factor of 2 lower than those calculated from composite theory assuming perfect interfacial thermal contact. This discrepancy was attributed to the formation of an interfacial gap, resulting from the thermal expansion mismatch between the fibers and the matrix in combination with the low adhesive strength of the carbon coating. In nitrogen or helium the thermal conductivity was found to be higher because of the contribution of gaseous conduction across the interfacial gap. On switching from vacuum to nitrogen a transient effect in the thermal diffusivity was observed, attributed to the diffusion-limited entry of the gas phase into the interfacial gap. These effects decreased with increasing temperature, due to gap closure, to be virtually absent at 1000°C.     

Thermal conductivity of polymer nanocomposites made with carbon nanofibers

An internal mixer was used to prepare polycarbonate (PC)‐based nanocomposites containing carbon fibers, carbon nanofibers (CNF), and mixtures of the two fillers. The influence of the filler volume fraction, the relative amounts of the two fillers, and the filler orientation relative to the direction of heat flow on the thermal conductivity was examined. Filler orientation was obtained by the extrusion of strands of the nanocomposite. The thermal conductivity was measured using a steady‐state heat conduction technique. The CNF were fragile, and their aspect ratio could be decreased during processing. In general, the composite thermal conductivity increased with increasing filler content. Fiber alignment in the heat flux direction resulted in a significant increase in thermal conductivity. Mixing of nanofibers with microfibers resulted contacts between the microfibers. This, together with fiber alignment provided large increases in the thermal conductivity. POLYM. ENG. SCI., 2008. © 2008 Society of Plastics Engineers