介孔复合材料内界面热阻及热导率

界面广泛存在于复合材料中,对介孔复合材料热物性起着决定性的影响,研究界面的导热特性对于认识和理解介孔复合材料的导热机制十分重要。利用非平衡的分子动力学模拟方法计算介孔复合材料中基材与填充物间的界面热阻,考察界面热阻随温度、材料质量差异的变化,进一步用界面热阻修正介孔复合材料的有效热导率。结果表明,界面热阻的数量级为10~(-11) m~2·K·W~(-1),并随温度升高逐渐降低。界面两端材料质量差异越大,界面热阻越高。可通过减小孔径、减小纳米线长度、增大纳米线间距、降低纳米线填充率来降低介孔复合材料的有效热导率。界面热阻能降低材料的有效热导率。孔径越小、纳米线间距越小、纳米线长度越长、填充率越高,界面热阻降低热导率效果越显著。     

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。     

热界面材料热导率和接触热阻的测试

热界面材料通常用于降低电子器件中固体界面的热阻。热界面材料的性质, 如热导率、界面材料与固体表面间的接触热阻, 对于电子器件的散热分析非常重要。然而, 这些参数通常难以获得。依据ASTM D-5470测试标准, 搭建了一个热界面测试系统。通过该系统测试了硅油和导热硅脂的热导率, 以及它们与固体基板间的接触热阻。经分析, 测试热导率和接触热阻的相对误差分别小于11.3%和41.3%。     

聚合物/介孔分子筛复合材料研究进展

介绍了聚合物/介孔复合材料的制备方法,即原位聚合法和共混法,分析了其结构与性能特点和增强机理,综述了近年来无机介孔粒子-聚合物复合材料的应用领域。     

环氧树脂/介孔SiO_2复合材料的结构与性能

分别采用水玻璃(SS)和正硅酸乙酯(TEOS)自组装制备了两种大孔径的虫状介孔二氧化硅(SiO_2)MSU-J-SS以及 MSU-J-TEOS;分别制备了介孔 SiO_2含量为2%～10%的橡胶态及玻璃态的环氧树脂介孔复合材料;对介孔SiO_2的物理结构及环氧树脂介孔复合材料的力学性能和微观结构进行了研究。结果表明:硅源及合成条件将影响介孔 SiO_2的物理结构,相对于 MSU-J-TEOS,MSU-J-SS 表现出更好的结构规整性,具有较大的平均孔径,较小的比表面积、孔容及壁厚;相对于纯环氧树脂,橡胶态和玻璃态环氧树脂介孔复合材料的拉伸强度、拉伸模量均提高,并且由平均孔径较大的 MSU-J-SS 制备的介孔复合材料的断裂伸长率没有降低,体现出增韧的效果;相对于 MSU-J-TEOS,MSU-J-SS 在环氧树脂中的分散更为均匀,其拉伸试样表现出相对韧性的断口形貌。     

玻璃纤维／环氧树脂基复合材料界面介电性能的研究

本文研究了五种偶联剂对玻璃纤维／环氧基复合材料界面介电性能的影响。结果表明,玻璃纤维经偶联剂处理后,其浸润活化能降低,从而提高了玻璃纤维／环氧基复合材料界面的介电性能,其提高的幅度大小与偶联剂的极性及化学结构有关。本文还研究了温度和水煮时间对五种偶联剂处理前后的玻璃纤维／环氧基复合材料界面介电性能的影响。结果表明,其影响的强度与界面的极化强度成正比。     

环氧树脂/纳米介孔分子筛复合材料的制备及性能研究

通过溶液共混法制备出环氧树脂（EP）／纳米介孔分子筛MCM-41（with template）（以下简称MCM-41）复合材料。研究了不同的MCM-41粒子含量对其在EP中的分散性和EP／MCM-41复合材料拉伸性能的影响。结果表明,这种具有独特的有机-无机复合结构的MCM-41直接用作填料时,能与EP形成新型网络复合结构,当MCM-41粒子的用量为1．5～2．5份时,它能均匀地分散在EP基体中,有效地提高EP／MCM-41复合材料的拉伸性能。     

接触热阻对复合材料身管热性能影响分析

采用金属内衬外部缠绕纤维增强复合材料,可减轻纯金属身管重量,提高身管刚度.为了详细分析复合材料身管分界面接触热阻对身管热性能影响,本文建立考虑复合材料身管分界面接触热阻效应的瞬态传热模型,运用有限差分法编制通用程序对接触热阻效应对复合材料身管热性能影响进行数值定量分析.结果表明,接触热阻对于复合材料身管的传热性能有较大影响,必须采取措施来减小接触热阻,这在复合材料身管的热性能设计中必须重点考虑.     

金属化合物@介孔碳硅复合材料的制备和表征

发展了一种以金属无机盐为前躯体,蔗糖为碳源,介孔二氧化硅SBA-15为模板原位合成金属化合物@介孔碳硅复合材料(M@CS)的方法。采用SEM、TEM、EDS和XRD等手段对材料进行了表征。结果表明不同的原位合成过程对材料的组成和颗粒尺寸有比较重要的影响。本文结果对高稳定嵌入式介孔复合催化剂的制备具有较好的指导意义。     

Temperature dependence of effective thermal conductivity and thermal diffusivity of treated and untreated polymer composites

Thermal properties, such as thermal conductivity, thermal diffusivity, and specific heat, of treated and untreated oil palm fiber–reinforced PF composites were measured simultaneously at room temperature and normal pressure using the transient plane source (TPS) technique. An increase in thermal conductivity was observed in the fiber‐treated and resin‐treated composites. Surface modifications of fibers by prealkali, potassium permanganate, and peroxide treatments increased the fiber–matrix adhesion by increasing porosity and pore size of the fiber surfaces. The increase in crosslinking enhanced the thermal conductivity of a composite of resin treated with peroxide compared to other composites. Also an attempt was made to explain the temperature dependence of thermal conductivity and thermal diffusivity of amorphous polymer samples using the same technique. It was observed that at the glass‐transition peak of the polymer, thermal conductivity and diffusivity were maximum. Below and above this temperature their values decreased. This has been explained on the basis of predominant scattering processes. An empirical relationship was established for the theoretical prediction of thermal conductivity and diffusivity. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 1708–1714, 2003     

Preparation and properties of polystyrene/SiCw/SiCp thermal conductivity composites

The silicon carbide whisker (SiCw) and silicon carbide particle (SiCp) were employed to prepare polystyrene/silicon carbide whisker/silicon carbide particle (PS/SiCw/SiCp) thermal conductivity composites, and the titanate coupling reagent of NDZ‐105 was introduced to functionalize the surface of fillers. The thermal conductive coefficient λ improved from 0.18 W/mK for native PS to 1.29 W/mK for the composites with 40% volume fraction of SiCw/SiCp (volume fraction, 3 : 1) hybrid fillers. Both the thermal decomposition temperature and dielectric constant of the composites increased with the addition of SiCw/SiCp hybrid fillers. At the same addition of SiCw/SiCp hybrid fillers, the surface modification of hybrid fillers by NDZ‐105 could improve the thermal conductivity and the mechanical properties of the composites. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

聚合物基导热复合材料的研究进展

阐述了聚合物基导热复合材料的导热机制。综述了国内外导热胶粘剂、导热橡胶和导热塑料等研究进展。介绍了提高复合材料导热性能的途径,并在此基础上,展望了聚合物基导热复合材料的应用前景和未来的发展方向。     

离子液体改性石墨烯的制备及其对ABS复合材料导热性能的影响

合成了一种氨基功能化离子液体[HAIM]BF4,并将其应用于石墨烯的改性。通过绿色直接的球磨法,将G粉与1-己基-3-氨乙基咪唑四氟硼酸离子液体[HAIM]BF4相结合,制备出离子液体功能改性石墨烯（G@ILs）。所得G@ILs使用熔融共混法加入丙烯腈-丁二烯-苯乙烯共聚物（ABS）中,制备G@ILs/ABS复合材料。使用X射线衍射分析（XRD）,X射线光电子能谱（XPS）,扫描电子显微镜（SEM）,透射电子显微镜（TEM）和拉曼测试等多种手段对G@ILs的结构和性质进行分析。结果表明,[HAIM]BF4通过阳离子-π相互作用对石墨烯进行了有效修饰,保持了石墨烯的结构完整性。由于G@ILs的独特性能,G@ILs/ABS复合材料在机械性能方面表现出相当大的改善。加入1 wt.%G@ILs的G@ILs/ABS复合材料的拉伸强度和弯曲模量为42.4 MPa和2145.1 MPa,比ABS提高了8.36%和12.76%。此外,在加入1 wt.%G@ILs的G@ILs/ABS复合材料的导热系数为0.249 W·m-1·k-1,比纯ABS提高了21.5%。     

Effect of initial density on thermal conductivity of new micro-pipeline heat conduction C/SiC composites

C/SiC composites prepared by chemical vapor infiltration technique (CVI) have been regarded as thermal structural materials widely. However, these composites still suffer from poor functional properties like low thermal conductivity, especially in thickness direction of the composites, limiting their large-scale applications. Herein, mesophase pitch based carbon fiber (MPCF) and continuous wave laser machining were utilized to construct highly effective heat conductive micro-pipelines within CVI C/SiC composite. The effect of initial density on the final density and thermal conductivity of the as-obtained MPCF-C/SiC composites were investigated. The results revealed that higher initial density would directly enhance the thermal conductivity and reduce the negative impact of the bottle-neck effect. At temperatures between 100°C and 500°C, MPCF-C/SiC composites preserved more than threefold of the thermal conductivity (340%) when compared to reference C/SiC composites. This work provides a highly effective route for enhancing the thermal conductivity of C/SiC, which would broaden their future applications.     

Optimized ablation resistance behavior and mechanism of C/SiC composites with high thermal conductive channels

Aimed to enhance the high-temperature service performance of C/SiC composites in high-speed aircraft thermal protection system, in this article, pitch-based carbon fibers were used to construct high thermal conductive channels to improve the heat transfer capability of C/SiC composites. The results revealed that the as-prepared composites equipped with 4.7 times higher thermal conductivity than that of conventional C/SiC composites. The oxyacetylene flame ablation test confirmed that the constructed high thermal conductive channels, which quickly conducted the heat flow from the ablation center area to other areas is the main reason of as-prepared composites exhibiting a very impressive ablation resistance property. Briefly, the ablation temperature of the as-prepared composite surfaces considerably dropped by about 300°C compared with conventional C/SiC composites, while the linear ablation rate and mass ablation rate of the composites are 1.27 μm/s and 0.61 mg/s respectively, which is superior to many recent reports, demonstrating that this article provides a simple but highly effective measure to improve the ablation resistance property of C/SiC composites.     

氮化硼纳米片改性复合材料导热性能的研究进展

氮化硼纳米片（BNNSs）是一种二维片状纳米材料，具有较高的导热性和热稳定性。将其作为填料加入聚合物中，可显著提高复合材料的导热性能。本文基于近年来对BNNSs改性复合材料的导热性能的研究进展，总结了BNNSs制备和改性的方法以及建立导热路径的方法，介绍了该体系复合材料的导热机理，分析了影响复合材料导热性能的因素，最后对提高复合材料的导热性能进行了展望。     

聚合物基热界面材料与导热性能研究进展

随着电子产品的小型化、集成化和功能化发展,功率密度及热流密度急剧上升,器件内巨大的散热和温压压力使电子设备的寿命和可靠性受到影响,因此对器件在运行过程中如何有效散热提出了更为苛刻的要求。开发及使用高性能导热基复合材料（热界面材料,TIM）降低接触热阻是解决电子设备散热问题的有效途径之一,热界面材料创新与优化备受关注。本文从基本的导热机理出发,阐述聚合物基热界面材料结构及导热强化方面最新进展,讨论导热填料和聚合物基体对复合材料性能的影响。重点对微纳结构的导热强化（协同）作用、构筑3D高导热微结构、导热填料和基质间的界面微结构和导热互穿网络结构等进行讨论,为设计高性能导热结构、制备开发新型高性能TIM提供参考。