预测复合材料导热系数的热阻网络法

借助计算机模拟复合材料的空间结构,直接迭代求解热阻网络,得到复合材料的导热系数。分析了在随机分布条件下取样尺度对导热系数的影响,以及二维和三维条件下导热的差别。与文献中实验数据的比较表明,所述方法能够较好地预示颗粒弥散型复合材料的导热系数。     

航天复合材料热导率测量的实验研究

通过实验研究了复合材料中玻璃纤维和碳纤维的不同配比对热导率影响。采用瞬态平面热源法,使用Hotdisk热常数分析仪获得了不同配比下玻璃纤维-碳纤维复合材料热导率与温度变化曲线。实验结果表明:随着温度降低,复合材料热导率减小;复合材料的热导率都随着碳纤维布含量的增加而升高。     

真空绝热板热工性能的研究

介绍真空绝热板的构造及加工工艺，对其高效绝热热工性能进行理论分析及实验数据测试，运用数理统计及计算机数值模拟的方法分析其热工性能随自身参数及制造工艺的变化规律，提出产品生产、施工及使用中应注意的问题和改进的意见。     

Measurement of thermal properties of iron oxide pellets

The thermal properties of iron oxide pellets of different porosity and prepared by reduction at different rates were investigated in the range of room temperature to about 800°C. The thermal diffusivity a was measured by a laser flash method and the specific heat C _p was measured by adiabatic scanning calorimetry. The thermal conductivity was calculated from the relation =aC p, where is the density of the specimen.For nonreduced iron oxide pellets, the thermal diffusivity and thermal conductivity decreased with increase in temperature and porosity. The specific heat increased with increasing temperature and there was a transformation point at which the specific heat reached a maximum. In prereduced iron oxide pellets, the thermal diffusivity and thermal conductivity were very small compared with the nonreduced pellets and they gradually increased with increasing temperature. The specific heat had a minimum and a maximum at about 300 and 600°C, respectively, and the scale of these features became smaller with increase in the reduction rate.Paper presented at the Fourth Japan Symposium on Thermophysical Properties, October 20–22, 1983, Yokohama, Japan.     

GNP法制备固体氧化物燃料电池复合阳极材料CuxCo1-x-SDC的研究

采用甘氨酸-硝酸盐法制备了CuxCo1-xO-SDC复合阳极材料。利用电化学工作站测试了其电化学性能,使用SEM、电导率、红外、差热-热重分析仪对CuxCo1-xO-SDC进行表征。研究结果表明,在Cu基阳极中加入一种具有高催化活性的金属钴,阳极表现出很好的催化活性,提高了电池的电化学性能。     

A Multiscale Model for the Effective Thermal Conductivity Tensor of a Stratified Composite Material

Thermal modeling of composites has three essential objectives: (i) comprehension of their thermal behavior; (ii) composite scaling in order to satisfy specific requirements; and (iii) optimal analysis of experimental results from thermal characterization. For a complete study of the material, each of these three points must be taken into account at the fiber scale ( 10m), the yarn scale ( 1 mm), and the composite scale ( 10 cm). This work presents multi-scale modeling of the effective thermal conductivity tensor of a stratified composite material made from carbon fibers, phenolic resin, and carbon loads. The longitudinal and transverse thermal conductivities of the yarn are computed from optical microscopic imaging of the material. The isotropic thermal conductivity of the loaded matrix is computed by the Bruggeman model. Then, the thermal conductivity tensor is determined by a finite element method taking into account the morphology of the fabric. Computed values are close to experimental values measured by classical methods. Finally, analytical relations are proposed to obtain an efficient model which can be used in a multiphenomenon simulation of the composite structure.Paper presented at the Fifteenth Symposium on Thermophysical Properties, June 22--27, 2003, Boulder, Colorado, U.S.A.     

钾明矾热传导性能的研究与改善

钾明矾作为固-液相变材料存在热传导性能差的缺点.目前应用高导热性能的石墨进行改进的研究中存在石墨用量过大(一般10%～20%)的问题.通过改性石墨与相变材料的复合使相变材料的热传导性能得到提高,并使改性石墨的用量降低到5%,可将相变时间缩短72.8%.     

碳包钴纳米颗粒/聚二甲基硅氧烷复合热界面材料的制备和性能

为了制备具有良好的热导率、热稳定性、导电性和柔顺性的纳米颗粒填充硅树脂复合材料,首先以乙基封端聚二甲基硅氧烷(PDMS)为基体材料,以碳包钴纳米颗粒(C@Co)为填料,采用研磨共混法制备了C@Co/PDMS复合热界面材料。然后,运用TEM、XRD、Raman和SEM分别对C@Co的微观结构、物相、石墨化程度和分散性进行了研究。最后,研究了C@Co含量对复合热界面材料的热导率、热稳定性、导电性和柔顺性的影响。结果表明:该复合热界面材料的热导率随着C@Co含量的增加而增大,当C@Co的含量为24wt%时,复合材料的热导率达到最大值1.64 W/(m·K),比纯PDMS的提高了10.7倍;TG分析表明,添加24wt%的C@Co后,复合材料的起始分解温度和最终分解温度比纯PDMS的分别提高了约70℃和80℃,说明C@Co能提高复合材料的热稳定性;随着C@Co含量的增加,复合热界面材料的电导率非线性增大,拟合试差计算的逾渗阀值为10wt%,即C@Co含量小于10wt%时复合材料的绝缘性良好,而填充24wt%的C@Co时复合材料的电导率为9.38×10-3 S·m-1;复合材料的硬度适中,处于17.6~26.8HA范围内,表明该复合材料的柔顺性较好。因此,24wt%C@Co/PDMS复合材料不仅能满足热界面材料电性能的基本要求,且具有良好的热导率、热稳定性和柔顺性。     

热传导聚合物基复合材料的研究进展

本文主要介绍了聚合物基复合材料的导热机理 ,以及预测二相体系复合材料热导率的理论模型方程。同时介绍了聚合物基导热材料的 3种类型及其具体应用 ,并提出聚合物基导热材料现阶段值得开发的课题和研究方向     

具有木材结构Al/C、Al/(SiC+C)复合材料的制备及热学性能

该研究以柳桉木材结构为模板,通过对木材的碳化、硅树脂的浸渍与反应、铝合金的浸渍处理,制备了具有木材结构的Al/C、Al/(SiC C)两种复合材料,并对复合材料的微观结构、热膨胀性能及导热性能进行了研究.结果表明:该复合材料保持了所选木材的天然结构特征,并且其热膨胀系数明显低于铝合金,导热系数远高于由木材转化的多孔碳.     

粉煤灰-硅藻土复合相变储能材料制备及导热强化

固废资源化利用是实现节能减排的重要途径,以月桂酸为相变工作介质,以粉煤灰-硅藻土二元载体为封装材料,碳纳米管为导热剂,采用直接熔融共混法制备出月桂酸/粉煤灰-硅藻土/碳纳米管复合相变储能材料。采用热扩散渗透测试、傅里叶红外光谱仪(FTIR)、差示扫描量热仪(DSC)、热重分析仪(TGA)、无纸记录仪等分别考察了定形复合相变储能材料的承载性能、微观结构和热物性。结果表明:粉煤灰-硅藻土二元载体可有效防止月桂酸的泄漏,当二元载体中月桂酸的质量分数为28%时可制得无泄漏复合相变储能材料,且原样粉煤灰利用率为55%;FTIR结果表明复合材料中各组分之间相容性好;DSC测得其熔化相变温度为45.79℃,相变潜热为51.06 J/g;TGA分析显示月桂酸/粉煤灰-硅藻土/碳纳米管热稳定性较好;储/放热性能曲线显示加入质量分数为5%的碳纳米管时,复合相变储能材料的熔化与凝固时间分别减少60%和62.5%,传热效率得到显著改善。     

相变材料的复合及其热性能研究

针对相变材料应用领域中对相变温度和相变焓的具体要求,采用复合的方法重点对相变材料的相变温度进行调节,复合出具有特定相变温度和较高相变焓的相变材料.论述了相变材料的复合原理,研究了4种相变材料的复合及其热性能,通过理论计算与实际测试相比较,筛选出复合物的最佳配比.研究表明:通过相变材料的复合可以调节材料的相变温度至所需要的范围,并具有较高的相变焓,可保持良好吸收或释放能量的能力.     

有机玻璃热物性准稳态法实验研究

基于准稳态法实验原理,运用精密温度采集设备,得到有机玻璃试件的热、冷端温升曲线及温差曲线,由此计算出其导热系数和比热。应用数值方法对测试结果进行了修正。修正后的导热系数和比热均在相关文献推荐范围之内。     

Establishment of accuracy limits and standards for comparative thermal conductivity measurements

New techniques have been developed for reducing thermal conductivity data from thermal comparative measurements. The first of these techniques is based on making a Taylor-series expansion of the stack centerline temperature profile. The result is an expression giving the ratio of sample to reference conductivities at any temperature as a function of measured quantities, the stack thermocouple readings and stack element thicknesses. The conventional formula presently used to reduce comparative conductivity data is shown to be a special result of the general analysis. A second technique involves the use of linear least-squares (LS) techniques to derive both the sample and the reference conductivities from the measured data. The LS technique provides the coefficients for a polynomial temperature expansion of the reference and sample conductivities directly. Use of the new techniques is illustrated in a reduction of some comparative data on the conductivities of Pyrex 7740 and Pyroceram 9606. It is shown that a highly self-consistent pair of conductivity functions can be derived for these two commonly used reference materials if the conductivity vs temperature relation for Pyrex is modified slightly from its recommended value. The Pyroceram conductivity results from the comparative measurements are in good agreement with a conductivity derived from pulse diffusivity and differential scanning calorimetry measurements and also in good agreement with the recommended Pyroceram conductivity function.Paper presented at the Ninth Symposium on Thermophysical Properties, June 24–27, 1985, Boulder, Colorado, U.S.A.     

填料型高导热复合材料的研究现状与发展趋势

填料型导热复合材料是LED等半导体在封装及使用过程中一种常见的散热材料,它利用高导热填料填充具有密度小、可加工性能好、成本低廉等优点的高分子聚合物制备而成,对降低半导体器件的结温、增强其综合特性大有裨益。简要概述了近年来填料型导热复合材料的研究现状,并对其发展趋势进行了预测,以期为LED的实际散热需要提供技术参考,进而推动LED产业的发展。     

Calorimetric and transport properties of Zircalloy 2, Zircalloy 4, and Inconel 625

This paper presents the measurements and the results on thermal and electrical transport properties of three nuclear reactor cladding materials: Zircalloy 2, Zircalloy 4, and Inconel 625. Study of these materials constituted a part of the IAEA coordinated research program aimed at the generation and establishment of a reliable and complete database of the thermal properties of reactor materials. Measured properties include thermal diffusivity, specific heat, and electrical resistivity. Thermal diffusivity was measured by the laser pulse technique. Specific heat and electrical resistivity were measured using a millisecond-resolution direct electrical pulse heating technique. Thermal conductivity was computed from the experimentally determined thermal difusivity and specific heat functions and the room temperature density values. Measurements were performed in the 20 to 1500°C temperature range, depending on the material and property concerned.     

颗粒随机分布复合材料的细观构造对有效热传导系数的影响

结合建立的颗粒随机分布复合材料的微结构模型和基于均匀化理论统计的双尺度计算方法, 针对氮化硼颗粒增强高密度聚乙烯(BN/HDPE)复合材料, 研究了颗粒形状、体积分数和空间分布参数等微结构特征对复合材料有效热传导系数的影响。结果表明: 颗粒体积分数的增加将导致有效热传导系数升高; 球形颗粒的位置参数、长椭球颗粒的取向程度都对有效热传导系数有重要影响。数值试验表明, 材料的微结构特征对复合材料的有效热传导系数具有极大影响。     

Preparation and thermal properties of layered porous carbon nanotube/epoxy resin composite films

A floating-catalyst spray pyrolysis method was used to synthesize carbon nanotube (CNT) thin films. With the use of ammonium chloride as a pore-former and epoxy resin (EP) as an adhesive, CNT/EP composite films with a porous structure were prepared through the post-heat treatment. These films have excellent thermal insulation (0.029--0.048 W·m⁻¹·K⁻¹) at the thickness direction as well as a good thermal conductivity (40--60 W·m⁻¹·K⁻¹) in the film plane. This study provides a new film material for thermal control systems that demand a good thermal conductivity in the plane but outstanding thermal insulation at the thickness direction.     

静电纺丝制备金刚石/聚丙烯腈杂化复合纤维

为了改善金刚石在聚合物中的均匀分散性,并提高导热性能,以不同粒度的金刚石和聚丙烯腈（PAN）共聚物为原料,采用静电纺丝方法制备得到金刚石/PAN杂化复合纤维。通过改变纺丝溶液中金刚石的添加量,研究了不同金刚石含量及不同粒度的金刚石对金刚石/PAN杂化复合纤维形态和热性能的影响。研究结果表明,静电纺丝可以有效解决微米级金刚石在PAN聚合物中的分散问题,金刚石的粒度对纺丝的稳定性和连续性影响很大,粒度为0.5~1 μm的金刚石经过纺丝可以有效地包覆在纤维中。当金刚石的粒度大于1~2 μm时,纺丝时稳定性差,纤维中很少或几乎没有包覆金刚石颗粒。当金刚石粒度为0.5~1 μm、实际质量分数为38.5wt%时,金刚石/PAN杂化复合纤维热导率最高,达到1.923 W/（m·K）。     

复合相变储冷材料的制备及性能研究

以十二烷基苯磺酸钠(SDBS)作为分散剂,多层石墨烯、TiO₂/石墨烯(m(TiO₂):m(石墨烯)=25∶75)和TiO₂颗粒作为导热添加剂,加入到二元复合有机储冷材料中(m(壬酸):m(葵醇)=60:40),制备了复合相变储冷材料。通过吸光度、DSC和热导率测试等手段,对复合相变储冷材料的稳定性、相变温度、相变潜热及热导率进行了评价分析。结果表明,分散剂和导热添加剂的加入,对储冷材料的相变温度和相变潜热影响不大,但对热导率影响较大。当分散剂SDBS浓度为0.2 g/L,导热添加剂(分别为TiO₂/石墨烯和TiO₂颗粒)浓度为0.5 g/L时,复合相变储冷材料具有较好的稳定性,其热导率分别为为0.2211和0.2096 W/(m·K),相比没有加入任何导热添加剂的储冷材料的热导率(0.1738 W/(m·K)),分别提高了27.22%和20.61%;当分散剂SDBS浓度为0.3 g/L,导热添加剂多层石墨烯浓度为0.3 g/L时,复合相变储冷材料处于稳定状态,其热导率为0.2...