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Novel fibrillar carbon nanotube heat transfer gels with enhanced thermal conductivities.

机译：具有增强的热导率的新型纤维状碳纳米管传热凝胶。

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摘要

Lubricants and cooling agents such as oil, ethylene glycol, and water are often used as traditional heat transfer fluids (HTFs) in engines, radiators, heat pumps, and other equipment which require cooling and/or energy maintenance. The United States of America (USA) spends over {dollar}80 billion on energy maintenance and increasing the thermal efficiency of HTFs by 25% could annually save over {dollar}20 billion. This study was aimed at improving the thermal conductivity (TC) of synthetic and vegetable oil heat transfer fluids (HTFs) by using Single-Walled Carbon Nanotubes (SWNTs) additives that resulted in a semi-solid lubricant that was a nanotube-HTF (n-HTF). The n-HTFs were processed with nitrogen containing additives that coupled with toluene and acetone solvent processing promoted the gelation of the carbon nanotube fibers in the oil. Such processing improved the nanotube dispersion due to hydrogen bonding (H bonding) and micelle formation of the amine groups around the carbon nanotube rod-like fibers and the additive-oil matrix. This allowed for high weight percent (Wt %) loadings of carbon nanotubes in the oil.; Characterization via thermal graviometric analysis (TGA) and Fourier Infrared Transform (FTIR) showed that high temperature radical mechanisms breakdown both the oil and nanotubes, and optical microscopy showed that sonication-homogenizing-mixing affects the coagulation-flocculation-aggregation-agglomeration of the nanotubes. Additionally we used two new TC instruments, the Mathis-Hot Disk and KD2 systems, to provide accurate and reproducible data with a 10% and 4% error margin for the Mathis and KD2, respectively. Raman and FTIR spectroscopies suggest that the TC enhancements result from SWNT phonon mechanisms, these being phonon-phonon, phonon-defect, and phonon-interface, all of which are present at room temperature with the absence of ballistic and superconductivity phenomena. Additional vibrations in the oil that occur due to Brownian motion and electron-phonon and H bonding from the additives would have also contributed to the TC mechanism and were evidenced via Raman spectroscopy and FTIR.; The optical microscopy, Raman, FTIR, and TC values indicated that the n-HTFs had a three-dimensional (3D) SWNT networked structure due to the inclusion of the oleylamine additive and the toluene-acetone processing. This would have resulted in the formation of oleylamine-nanotube micelles that were suspended in the oil-additive mixture. Raman spectroscopy evidenced a percolation effect that was coupled with fluid vibrations and Brownian motion, which led to the absence of the one- or two-dimensional (1D, 2D) ballistic or superconductivity phenomena that is often associated with aligned and single SWNTs and other 1D or 2D media, and this was reflected in the TC values. Nevertheless, the TC of the resulting n-HTFs was improved by over 80-96% when compared to other HTFs and the dispersion of the nanotubes in the oil-additive mixture was greatly enhanced. Applications of the n-HTFs include: mechanical-frictional damping, semiconductor packaging, thin-films, hydraulic oil lubricant use, thermoelectric power, thermo-sensing, fuel cells, additive-antioxidant-viscosity modifiers, and filtration.
机译：润滑剂和冷却剂（例如油，乙二醇和水）通常用作发动机，散热器，热泵和其他需要冷却和/或维护能量的设备中的传统传热流体（HTF）。美利坚合众国（美国）在能源维护上花费了超过800亿美元，将HTF的热效率提高25％每年可以节省超过200亿美元。这项研究旨在通过使用单壁碳纳米管（SWNTs）添加剂来改善合成和植物油传热流体（HTF）的导热系数（TC），从而产生一种半固体润滑剂，即纳米管-HTF（n -HTF）。 n-HTFs用含氮添加剂处理，再与甲苯和丙酮溶剂处理相结合，促进了油中碳纳米管纤维的凝胶化。由于氢键（H键）和在碳纳米管棒状纤维和添加剂油基体周围的胺基团的胶束形成，这种处理改善了纳米管的分散性。这允许油中碳纳米管的高重量百分比（Wt％）负载。通过热重量分析（TGA）和傅立叶红外变换（FTIR）进行的表征表明，高温自由基机制会破坏油和纳米管，光学显微镜表明，超声-均质化-混合会影响纳米管的凝结-絮凝-聚集-凝聚。此外，我们使用了两种新的TC仪器，即Mathis-Hot Disk和KD2系统，以Mathis和KD2分别提供10％和4％的误差幅度的准确且可重复的数据。拉曼光谱和FTIR光谱表明，TC增强是由SWNT声子机制引起的，它们是声子-声子，声子缺陷和声子界面，所有这些均存在于室温下，而没有弹道和超导现象。油中由于布朗运动以及添加剂产生的电子声子和氢键而引起的其他振动也将有助于TC机理，并通过拉曼光谱和FTIR进行了证明。光学显微镜，拉曼光谱，FTIR和TC值表明，由于包含油胺添加剂和甲苯-丙酮处理，n-HTFs具有三维（3D）SWNT网络结构。这将导致形成油胺-纳米管胶束的悬浮在油添加剂混合物中。拉曼光谱法证明了渗流效应与流体振动和布朗运动相结合，导致缺乏一维或二维（1D，2D）弹道或超导现象，该现象通常与对准和单个SWNT和其他1D相关或2D媒体，这在TC值中得到了体现。然而，与其他HTF相比，所得n-HTF的TC提高了80-96％以上，并且大大增强了纳米管在油添加剂混合物中的分散性。 n-HTF的应用包括：机械摩擦阻尼，半导体封装，薄膜，液压油润滑剂的使用，热电功率，热敏，燃料电池，添加剂-抗氧化剂-粘度调节剂和过滤。

著录项

  • 作者

    Rostro, Betty Catalina.;

  • 作者单位

    Rice University.;

  • 授予单位 Rice University.;
  • 学科 Engineering Materials Science.
  • 学位 M.S.
  • 年度 2007
  • 页码 186 p.
  • 总页数 186
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类 工程材料学;
  • 关键词

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