Enhancement of through-thickness thermal conductivity in adhesively bonded joints using aligned carbon nanotubes

A concept of incorporating aligned multi-walled carbon nanotubes (MWCNTs) in the adhesive layer has been demonstrated to enhance the through-thickness thermal conductivity in the adhesively bonded joints. Both numerical and experimental studies were performed to determine key components in improving the through-thickness thermal conductivity and to realize the improvement in an adhesively-jointed system. The numerical analysis indicated that the key components to improve the through-thickness thermal conductivity in the adhesive joints are using highly conductive vertically aligned nanotubes as well as the thermal conductivity and the size of a transition zone between the nanotube ends and surrounding matrix materials in the form of either the adhesive or adherends. Therefore, the thermal contact of the conductive phase (the MWNT in this case) with the adherent surfaces is essential to achieve the desirable through-thickness thermal conductivity in joints. This theoretical observation was demonstrated experimentally by using conductive graphite facesheets as adherends and the polymer adhesive layer with the aligned MWCNTs. To ensure the ends of the MWCNTs make thermal contact with the adherent surfaces, the surface of the adhesive with the MWCNTs were plasma-etched and coated with thin An layer, along with the surface of the graphite facesheet coated with thin Au-Pd layer. The measured value of the through-thickness thermal conductivity of the modified adhesive joint with the MWNCT was over 250 W/m K, which superseded the thermal conductivity of neat adhesive joint by several order of magnitudes. Thus the study demonstrates a new approach as well as opportunities of much needed thermal property tailoring in structural joints. (c) 2007 Elsevier Ltd. All rights reserved.

一种在胶粘剂层中加入定向多壁碳纳米管（MWCNTs）的概念已被证明可提高胶接接头的厚度方向热导率。为了确定提高厚度方向热导率的关键因素，并在胶接系统中实现这种提高，进行了数值研究和实验研究。数值分析表明，提高胶接接头厚度方向热导率的关键因素是使用高导电性的垂直定向纳米管，以及纳米管端部与周围基体材料（以胶粘剂或被粘物的形式存在）之间过渡区的热导率和尺寸。因此，导电相（在此情况下为MWNT）与被粘表面的热接触对于在接头中实现理想的厚度方向热导率至关重要。通过使用导电石墨面板作为被粘物以及含有定向MWCNTs的聚合物胶粘剂层，这一理论观察在实验中得到了验证。为确保MWCNTs的端部与被粘表面热接触，对含有MWCNTs的胶粘剂表面进行了等离子蚀刻并涂覆了一层薄的银层，同时对石墨面板表面涂覆了一层薄的金 - 钯层。含有MWNCT的改性胶接接头的厚度方向热导率测量值超过250 W/m·K，比纯胶接接头的热导率高出几个数量级。因此，该研究展示了一种新方法以及在结构接头中进行急需的热性能调整的机会。（c）2007爱思唯尔有限公司。保留所有权利。