材料热物性测试的研究现状及发展需求

材料热物性是对特定热过程进行基础研究、分析计算和工程设计的关键参数,是材料最基本的性能之一,在科学研究、工程设计、工业生产等领域应用十分广泛,也是各行业节能技术发展的基础。通过对材料热物性发展历史、国内外研究现状的分析,比较了我国与发达国家在防护热板法导热系数装置研究上的差距,阐明了热物性测试的重要意义及我国在材料热物性测试领域仍未建全量值传递体系的不足。

激光闪光法测量材料热扩散率国际比对的实验研究与分析

本文介绍了在中国计量科学研究院激光闪光法热导仪上,根据国际计量委员会温度咨询委员会(CCT)第九工作组WG9,关于材料热物性研究比对的要求,分别对WG9提供的5个不同厚度的Armco Iron和Isotropic Graphite样品,进行了热扩散率的测量和结果分析研究,以及实验结果的不确定度分析评估。根据分析实验中发现的问题,对进一步改进现有的激光闪光法装置提出了建议。

周期热流法测试金属及合金材料高导热系数可视化测试系统的研制

根据周期热流法测试原理,结合理论分析和实验测定,设计并开发了一套测试和计算金属及其合金高导热材料热物性参数的装置和软件。利用Visual Basic6.0的编程技术,并结合数据采集装置,实现了测试系统的数据自动采集及处理可视化功能。通过对几种金属及合金热物性参数实验测定的结果和文献值比较,发现最大误差不超过6.5%,测试结果可靠。

土壤及钻孔内材料对地源热泵系统性能的影响

地源热泵技术由于其节能性得到越来越多应用，但其节能性也受到很多因素影响。本文结合工程实例，通过模拟计算程序对土壤及钻孔内材料对地源热泵系统能耗的影响进行分析，得出优化地源热泵系统设计的参考建议。

建筑陶瓷成型与烧成过程导热性能的研究

研究了彩釉砖成型与烧成过程中导热系数的变化。实验结果表明，在一定的工艺条件下，对于化学组成近似的彩釉砖坯体，其室温时导热系数随着成型压力和含湿量的增加而非线性地增大；在其烧成过程中导热系数随着温度的升高和气孔率的降低而增大，却随着玻璃相量的增加而减小；在烧结温度范围内随着气孔率出现最小值时，导热系数出现最大值。据此，导热性能的测试方法可作为优化烧成制度的一种新的实验手段。

三维针刺C/SiC刹车材料的热物理性能

通过化学气相渗透(CVI)法结合反应熔体浸渗(RMI)法制备了三维针刺C/SiC刹车材料,系统研究了三维针刺C/SiC刹车材料的热物理性能。结果表明:C/SiC刹车材料的热膨胀系数随温度升高总体呈增大趋势,但呈规律性波动;在相同温度下,垂直于摩擦面方向的热膨胀系数远大于平行方向的。从室温至1300℃,平行和垂直于摩擦面方向的平均热膨胀系数分别为1.75×10-6K-1和4.41×10-6K-1;C/SiC刹车材料的比定压热容随温度的升高而增大,但增大速率逐渐减小。温度从100℃升到1400℃,其比定压热容从1.41 J/(g.K)增大到1.92 J/(g.K);C/SiC刹车材料的热扩散率随温度的升高而降低,并趋于常量。平行于摩擦面方向的热扩散率明显大于垂直于摩擦面方向的热扩散率。

Effect of heat treatment on microstructure and thermophysical properties of diamond/2024 Al composites

50%diamond particle （5μm） reinforced 2024 aluminum matrix （diamond/2024 Al） composites were prepared by pressure infiltration method. Diamond particles were distributed uniformly without any particle clustering, and no apparent porosities or significant casting defects were observed in the composites. The diamond-Al interfaces of as-cast and annealed diamond/2024 Al composites were clean, smooth and free from interfacial reaction product. However, a large number of Al2Cu precipitates were found at diamond-Al interface after aging treatment. Moreover, needle-shaped Al2MgCu precipitates in Al matrix were observed after aging treatment. The coefficient of thermal expansion （CTE） of diamond/2024 Al composites was about 8.5×10-6 °C-1 between 20 and 100 °C, which was compatible with that with chip materials. Annealing treatment showed little effect on thermal expansion behavior, and aging treatment could further decrease the CTE of the composites. The thermal conductivity of obtained diamond/2024 Al composites was about 100 W/（m？K）, and it was slightly increased after annealing while decreased after aging treatment.

Laser-weldable Si_p-SiC_p/Al hybrid composites with bilayer structure for electronic packaging

Laser-weldable Sip-SiCp/Al hybrid composites with high volume fraction （60%-65%） of SiC reinforcement were fabricated by compression moulding and vacuum gas pressure infiltration technology. Microscopic observation displayed that the Sip-SiCp/Al hybrid composites with bilayer structure were compact without gas pores and the intergradation between Sip/Al layer and SiCp/Al layer was homogeneous and continuous. Further investigation revealed that the Sip-SiCp/Al hybrid composites possessed low density （2.96 g/cm^3）, high gas tightness （1.0 mPa·cm^3）/s）, excellent thermal management function as a result of high thermal conductivity （194 W/（m·K） and low coefficient of thermal expansion （7.0×10^-6 K-1）. Additionally, Sip-SiCp/Al hybrid composites had outstanding laser welding adaptability, which is significantly important for electronic packaging applications. The gas tightness of components after laser welding （48 mPa·cm^3）/s） can well match the requirement of advanced electronic packaging. Several kinds of these precision components passed tests and were put into production.

Prediction of the thermo-elastic properties of knitted structural composites using FEM

It is a very important and complex task to estimate the thermo-elasticproperties of a textile structural composite. In this paper, the finite element method (FEM) wasused for the prediction of the orthotropic thermo-elastic properties of a composite reinforced byglass fiber knitted fabric. In order to define the final 3-D configuration of the loop reinforcingstructure, the interactions between the adjacent loops, the large displacement and the contactelements without friction were considered. The values predicted were compared with the experimentalresults.

Mechanical and thermo-physical properties of rapidly solidified Al-50Si-Cu(Mg) alloys for thermal management application

Al-high Si alloys were designed by the addition of Cu or Mg alloying elements to improve the mechanical properties. It is found that the addition of 1 wt.% Cu or 1 wt.% Mg as strengthening elements significantly improves the tensile strength by 27.2% and 24.5%, respectively. This phenomenon is attributed to the formation of uniformly dispersed fine particles(Al2Cu and Mg2Si secondary phases) in the Al matrix during hot press sintering of the rapidly solidified(gas atomization) powder. The thermal conductivity of the Al-50 Si alloys is reduced with the addition of Cu or Mg, by only 7.3% and 6.8%, respectively. Therefore, the strength of the Al-50 Si alloys is enhanced while maintaining their excellent thermo-physical properties by adding 1% Cu(Mg).

Hydrogenation reaction characteristics and properties of its hydrides for magnetic regenerative material HoCu_2

The hydrogenation reaction characteristics and the properties of its hydrides for the magnetic regenerative material HoCu_2(CeCu_2-type) of a cryocooler were investigated. The XRD testing reveals that the hydrides of HoCu_2 were a mixture of Cu, unknown hydride Ⅰ, and unknown hydride Ⅱ. Based on the PCT(pressure-concentration-temperature) curves under different reaction temperatures, the relationships among reaction temperature, equilibrium pressure, and maximum hydrogen absorption capacity were analyzed and discussed. The enthalpy change ΔH and entropy change ΔS as a result of the whole hydrogenation process were also calculated from the PCT curves. The magnetization and volumetric specific heat capacity of the hydride were also measured by SQUID magnetometer and PPMS, respectively.

Modified graphite filled natural rubber composites with good thermal conductivity

The rubber composites with good thermal conductivity contribute to heat dissipation of tires. Graphite filled natural rubber composites were developed in this study to provide good thermal conductivity. Graphite was coated with polyacrylate polymerized by monomers including methyl methacrylate, n-butyl acrylate and acrylic acid. The ratios between a filler and acrylate polymerization emulsion and those between monomers were varied. Eight types of surface modification formulas were experimentally investigated. Modification formula can affect coating results and composite properties greatly. The best coating type was achieved by a ratio of1:1 between methyl methacrylate and n-butyl acrylate. The coating of graphite was thermally stable in a running tire. Filled with modified graphite, the tire thermal conductivity reached up to 0.517–0.569 W·m-1·K-1. In addition, the mechanical performance was improved with increased crosslink density, extended scorch time and short vulcanization time.

既有建筑围护结构内保温墙体热湿性能研究——以天津和广州地区为例

我国既有建筑存量大,能耗高,改善既有建筑围护墙体的热工性能是实现建筑节能的重要举措。湿气是影响建筑耐久性的主要因素之一,因此在进行既有建筑围护墙体节能改造时需要综合考虑墙体的热湿特性。本文首先实验测量了历史青砖、烧结红砖和硅酸钙保温板3种建筑材料的热湿物性。其次,在天津气候条件下,模拟分析了以青砖和红砖为砌体材料的外墙在加装硅酸钙内保温系统前后的热湿性能,结果表明内保温外墙墙角内表面不存在表面结露和霉菌生长风险。最后,模拟研究了广州气候条件下典型红砖墙体加装硅酸钙内保温系统的可行性,发现该内保温系统同样适用于这一地区既有建筑围护墙体的节能改造。

Copper chalcogenide thermoelectric materials

Cu-based chalcogenides have received increasing attention as promising thermoelectric materials due to their high efficiency,tunable transport properties,high elemental abundance and low toxicity.In this review,we summarize the recent research progress on this large family compounds covering diamond-like chalcogenides and liquid-like Cu2X (X=S,Se,Te)binary compounds as well as their multinary derivatives.These materials have the general features of two sublattices to decouple electron and phonon transport properties.On the one hand,the complex crystal structure and the disordered or even liquid-like sublattice bring about an intrinsically low lattice thermal conductivity.On the other hand, the rigid sublattice constitutes the charge-transport network, maintaining a decent electrical performance.For specific material systems,we demonstrate their unique structural features and outline the structure-performance correlation. Various design strategies including doping,alloying,band engineering and nanostructure architecture,covering nearly all the material scale,are also presented.Finally,the potential of the application of Cu-based chalcogenides as high-performance thermoelectric materials is briefly discussed from material design to device development.

Optimization of the thermoelectric properties of poly(nickel-ethylenetetrathiolate) synthesized via potentiostatic deposition

The coordination polymer poly（nickel-ethylenetetrathiolate） （poly（Ni-ett））, formed by nickel（Ⅱ） and 1,1,2,2-ethenetetrathiolate （ett）, is the most promising N-type organic thermoelectric material ever reported; it is synthesized via potentiostatic deposition, and the effect of different applied potentials on the optimal performance of the polymers is investigated. The optimal thermoelectric property ofpoly（Ni-ett） synthesized at 0.6 V is remarkably greater than that of the polymers synthesized at 1 and 1.6 V, exhibiting a maximum power factor of up to 131.6μW/mK2 at 360 K. Furthermore, the structure-property correlation ofpoly（Ni-ett） is also extensively investigated. X-ray diffraction （XRD） and X-ray photoelectron spectroscopy （XPS） analyses revealed that the larger size of crystalline domains and the higher oxidation state of poly（Ni-ett） synthesized at 0.6 V possibly results in the higher bulk mobility and carrier concentration in the polymer chains, respectively, accounting for the enhanced power factor.