【作者】 蔡岸；

【导师】 陈江平； 奚同庚；

【作者基本信息】 上海交通大学 ， 制冷及低温工程， 2012， 博士

【摘要】 近二十年来，随着纳米技术、微电子技术和微电子机械系统（MEMS）等许多新兴技术的迅速发展，材料研发的低维化发展趋势方兴未艾，取得了突破性进展，并已在众多高新技术和传统工业领域获得了越来越广泛的应用。低维材料包括二维材料微/纳米薄膜、一维材料纳米管/线和零维材料纳米颗粒，已涵盖了金属、无机非金属和有机高分子三大材料领域。作为二维材料的薄膜的热物理性质与三维体材料特异性更加明显，不同材质的薄膜，因方法和工艺的不同，薄膜的微结构、杂质和缺陷等不同导致热物理性质出现较大差异。薄膜材料研究和应用的快速发展，以及微纳尺度传热学的不断深入，极大地促进了薄膜材料热物理性质的行为和理论以及测试新装置的研究，其中薄膜材料热物理性质的特异性及其与材料组分、微观结构之间的关系研究也成为前沿和热点课题。本论文基于激光闪光法，采用纳秒宽度激光器提供加热脉冲，纳秒响应碲镉汞红外探测器作为非接触温度探测器并辅以精密红外聚焦系统，高速示波器作为数据采集设备，研制了测量薄膜材料热扩散率的新装置，并集成了热膨胀测量组件，构成多功能热物性测量装置。经校验，该装置实现了在-50³00℃温区、测试厚度1～500μm、包括金属、非金属、有机高分子三类薄膜材料的快速测量。以该装置为平台，结合扫描电镜、透射电镜等微观表征手段，选择目前国内微电子和国防领域有广泛应用且迫切需要热物性数据的聚酰亚胺复合薄膜、铝阳极氧化薄膜和聚乙烯纳米阵列，开展了薄膜热物性行为及其与微观结构之间关系和规律的研究。聚酰亚胺（PI）应用广泛，PI的低维化以及采用纳米材料进行杂化制备纳米复合薄膜材料来改善PI的性能，已成为近年来材料科学领域的研究热点。本工作采用新的半透明材料测试模型，简化了激光闪光法测试半透明材料的实验镀膜工艺，并通过半透明氧化铝陶瓷和PI薄膜的测试进行了验证。对聚酰亚胺（PI）复合薄膜的测试研究表明，PI/SiO₂和PI/C复合薄膜的比热随着添加物的增多而下降，符合复合材料比热加和原理；纳米颗粒的加入，限制了聚合物分子链的自由膨胀，导致复合薄膜的热膨胀系数随着添加物的增多而下降；热导率随添加物含量增加而增大，PI薄膜从0.17W/（m·K）上升到添加20wt％纳米颗粒后的0.64W/（m·K），但并没有改变热导率随温度而增大的非晶态材料的固有规律。复合薄膜的热导率随由于纳米颗粒局部聚集，导致添加物含量较高时，复合薄膜热导率增加较大。通过对复合材料热导率预测模型的研究表明，复合薄膜热导率由于纳米颗粒添加物团聚更加明显，三维体材料热导率预测模型不适合此类复合薄膜热导率的预测。采用恒压阳极氧化法制备了0.9⁵μm亚微米到微米量级4种不同厚度的的广泛应用的热控阳极氧化铝膜，实验研究了氧化铝膜在220～480K导热性能及其随温度变化的规律。结果显示，氧化铝膜在厚度较薄时，结构较为疏松，随厚度变厚，气孔率变小，从而导致热扩散率随着厚度增大。2.5μm厚度的阳极氧化铝膜220K时热导率为1.22W/（m·K），室温热导率为1.4W/（m·K），480K时为1.71W/（m·K），大大低于氧化铝体材料的热导率值。由于氧化铝膜的微观结构为无定形非晶态结构，测试结果显示的非晶态导热行为特征与最小热导率模型计算得到的热导率温度趋势一致；不同测量方法的结果比较表明非稳态方法更适合在室温附近的热导率测量。对纳米孔模板润湿技术制备的低密度聚乙烯（LDPE）和高密度聚乙烯（HDPE）纳米线阵列的实验研究证实聚合物纳米线阵列具有较高的热导率，室温热导率达到2.2W/（m·K）和10W/（m·K），大约比聚乙烯体材料的热导率高二个量级，并且纳米线阵列的热导率随温度的升高略有增大。估算得到室温下单根LDPE纳米线的热导率高于5W/（m·K），室温下直径100nm和200nm的单根HDPE纳米线的热导率分别为26.5W/（m·K）和20.5W/（m·K）。纳米线阵列的分子链拉伸之后定向排列能大大提高热导率，对基于低维效应强化聚合物纳米结构的导热性质具有重要的意义。更多还原

【Abstract】 In recent decades, with the rapid development of nanotechnology, microelectronics and mechanical systems (mems) and many new technologies, materials’low-dimensional development trend is catching on and has obtained wide applications in traditional industrial sectors and high-tech areas. Thermophysical properties of two dimensional thin films are different from buck materials, which are caused by size effects, fabrication process, microstructure, impurities and defects. The rapid progress of thin films’research and application, plus research of micro/nano-size heat transfer, deepens the research of thermophysical properties and its measuring apparatus of thin films materials, in which the characteristics of thin films and its relationship to chemical component and microstructure have become focus topics.By using a nanosecond laser, nanosecond response MCT infrared detector and high speed oscilloscope, laser flash method is utilized to construct an apparatus to measure the thermal diffusivity of thin films. Integreating thermal expansion component, a multifunctional apparatus measuring thermphysical properties of thin films is developed. The apparatus can measure three different kinds of thin films with thickness1-500microns in the temperature range-50～300℃. By utilizing this apparatus, SEM, TEM and other charactrizaion method, the thermophysical properties of polyimide composite films, anodic alumina films and polyethelene nanowire arrays films related to its microstructure and other influencial effects are researched.Polyimide (PI) films has got wide spread applications due to its excellent properties and PI based composite films using ceramic nanoparticles to modify its properties have become a hot subject. A new test model has been developed to simplify the pretreatment procedure and improve the precision of semi-transparent sample such as PI films tested by laser flash method. Thermophysical properties of Pi/Silica composite films with different silica content and PI/C films are investigated. Specific heat of composite films comply with addition principle of composite materials. Thermal expansion decreases with the addition of silica nanoparticles to suppress the extension of polyer molecular chains. The thermal conductivity of composite films increases with temperature increasing, which means the thermal conductivity behavior of PI films does not change with the addition of silica nanoparticles. Themal conductivity of PI increases from0.17W/(m-K) to0.64W/(m-K) after20wt%silica is added. Thermal conductivity of PI composite films increases with increase of silica content and is much higher than values predicted by composite materials prediction models, which indicates the prediction models for bulk composite materials may not apply to thin films’thermal conductivity prediction because of the aggregation of nanoparticles.Anodic alumina films are widely used as bio-sensors, fabrication templates and thermal control coatings in aeroplanes. Anodic alumina films with thickness of900nm-5μm are grown from aluminum foil by anodic oxidation. Thermal properties of anodic films in temperature range220～480K are researched. The film with thiner thickness has more porosity, which explains thermal diffusivity increases with thickness increasing. Thermal conductivity of film with2.5μm thickness is1.22W/(m-K) at220K,1.4W/(m-K) at RT and1.71W/(m-K) at480K which is much lower than bulk alumina material. This temperature dependence is coherent with calculated results of minimum thermal conductivity model. The comparison results show that non-steady method is more suitable for measurement of thermal conductivity around room temperature range.Polymers can have larger thermal conductivity by stretching polymer’s moleculars. High-density polyethylene (HDPE) nanowire arrays with diameter of100nm and200nm and low-density polyethylene (LDPE) nanowire arrays with diameter of200nm are fabricated by using a nanoporous template wetting technique, which have a room thermal conductivity of10and2.2W/(m-K) respectively, which are about2orders of magnitude higher than their bulk counterparts. Estimated thermal conductivity of a single HDPE nanowire and LDPE nanowire is as high as26.5W/(m-K) and5W/(m-K) respectively at room temperature. This enhancement may be attributed to transformation from ramdom orientation to high chain orientation of the nanowire arrays.更多还原