探针法测量低温下猪主动脉导热系数研究

低温下导热系数测定对生物器官的低温保存、低温外科医学及数值模拟计算至关重要.在分析探针法测量原理的基础上,用探针法对低温下猪主动脉的导热系数进行了测量研究.实验表明探针在用甘油和蒸馏水进行标定后,可以方便准确地测量-90～-35℃温区下猪主动脉的导热系数.     

热探针法测定含湿土壤的导热系数

根据线热源瞬态导热模型,设计制作了用于测定含湿土壤导热系数的热探针,研究了加热功率、加热时间、探针壁厚对导热系数测定的影响。对不同含水量的土壤导热系数进行测定,得出纯土、河沙含水量～导热系数拟合关系式。结果表明,热探针法测定含湿土壤的导热系数具有便捷、准确的特点。     

金属反射型保温材料导热系数的测定

根据稳态法测量导热系数原理,设计了一套稳态导热系数测量装置,利用自动控制技术实现实验过程的可控性。通过与导热系数参比块的测量校对,该装置测量结果的准确度达到标准要求。并利用此测量装置对压力容器金属反射型保温层试样的导热系数进行了测定,测定温度在80～220 ℃范围内,测量误差小于1.3%,导热系数值由0.040 W/(m·K)变化到0.053W/(m·K)。     

高分子聚合材料的导热系数测定

讨论了平板法测量导热系数的原理。介绍了导热仪的结构。给出了对新型高导热性能有机高分子材料的导热系数测试结果。测试表明,此导热仪可对不良导热材料进行低于０℃的测量,填补了国内这方面的空白。     

热探针测定装置参数实验研究

针对线热源理论自制的热探针在实际测定导热系数过程中所得结果受实验参数影响显著的问题,该文对加热时间、电压、试样直径3个实验参数展开研究,在不同的装置参数下测定乙二醇的导热系数,以探究三者对导热系数测定结果的影响及参数选取的最优区间。实验结果表明:热探针的最佳加热时间为40~60 s,最佳电压为1~2 V;电压2 V时可忽略试样直径对测定结果的影响;实验过程温度变化5℃时可显著降低试样对流引起的实验误差。研究结果可为热探针测定导热系数参数的选取提供可靠的数据参考,所得规律能有效降低热探针测定导热系数的误差。     

热线法测量固体材料的导热系数：新的近似及分析

开发出一种使用热线法测量和确定高温下固体材料导热系数的新方法，本文介绍了测量温度可达到１５００℃的实验设备，应用“热四极子法”建立的数学模型，基于参数估计方法的参数识别技术以及一些陶瓷材料导热系数新的实验结果。     

固化吸附剂导热系数测量参数选择

在开发高导热吸附剂过程中经常需要测量材料的导热系数,稳态平板法测量导热系数因方法简单直接而应用广泛.通过数值模拟和实验发现侧面散热对导热系数测量影响很大,采用大空间自然对流换热实验关联式对试验数据处理公式进行修正,可得到较满意的实验结果,并进一步研究了热源温度、样品厚度、试样导热系数对侧面散热的影响.为减少侧面散热以及热电偶波动对测量结果的影响,并考虑到试样加工难易程度,就所用实验装置而言,试样厚度在12mm较为适宜,热源温度选用55℃较为适宜.     

石墨烯及其复合材料导热系数测量的研究进展

石墨烯是当下材料学研究的热点和难点,其优越的导热性能,超越了绝大多数的材料,具有广泛的运用前景。近10年来,石墨烯产业的快速发展对其导热系数准确测量的需求越来越迫切。对石墨烯及其复合材料的定义、制备方法和在散热上的应用进行了综述;介绍了传统的导热系数测量方法,以及适用于石墨烯导热系数测量的激光闪光-拉曼光谱法和电热微桥法,对比了部分文献报道的石墨烯导热系数测量值;对熔融注塑法制备的还原氧化石墨烯和聚丙烯复合材料样品的导热系数和热扩散系数进行了测量,从热扩散系数测量结果发现其导热性能存在严重的各向异性;根据测量研究进展指出当前石墨烯及其复合材料导热系数测量存在的问题,并分析了导致这些问题的原因;最后,对石墨烯及其复合材料导热系数测量的研究进展进行总结和展望。     

热线法测量保温材料的导热系数

本文在分析热线法测量导热系数原理的基础上，应用热线法测定了几种保温材料不同温度下的导热系数。并通过Origin 7．0对测量结果进行了数据线性拟合，可快捷、精确的获得测量结果。     

微型制冷机做冷源的固体材料导热系数测量装置设计

基于一维轴向稳态热流法,采用微型脉冲管制冷机作为冷源,研究建立了一台可连续测量60-300 K下固体材料的导热系数的装置.该装置采用集成化设计,各组件密集排布,整体结构精简有序,其测量方法采用两探针形式,适用于测量导热系数较小的样品.在高真空的环境下,进一步对该装置制冷机冷头的漏热和样品的漏热进行了分析和计算,得出样品...     

Cryogenic thermal conductivity measurements on candidate materials for space missions

Spacecraft and instruments on space missions are built using a wide variety of carefully-chosen materials. It is common for NASA engineers to propose new candidate materials which have not been totally characterized at cryogenic temperatures. In many cases a material’s cryogenic thermal conductivity must be known before selecting it for a specific space-flight application. We developed a test facility in 2004 at NASA’s Goddard Space Flight Center to measure the longitudinal thermal conductivity of materials at temperatures between 4 and 300 K, and we have characterized many candidate materials since then. The measurement technique is not extremely complex, but proper care to details of the setup, data acquisition and data reduction is necessary for high precision and accuracy. We describe the thermal conductivity measurement process and present results for ten engineered materials, including alloys, polymers, composites, and a ceramic.     

Thermal conductivity of Torlon between 4.2 and 300 K

Torlon is an organic polymer (polyamide-imide) which exhibits room temperature good mechanical and thermal properties and high chemical resistance. The thermal conductivity of Torlon 4203 was measured in the range of temperature 4.2-300 K. These data complete existing measurement in the temperature range 0.1-5 K. The thermal conductivity shows a linear behavior between 30 K and 250 K and a plateau, typical of many amorphous materials, around 7 K.     

耐热和导电铜合金发展现状

铜和铜合金具有优异的导电、导热及其它性能，是重要的工业材料之一。笔者就其发展现状和今后的开发与利用提出了看法。     

一种绝热材料热物性参数λ、α和c的瞬态测算法

本介绍了无限大平板冷却过程中表面及中心的瞬态温度场的测量以及同时确定物体导热系数λ,导温系数α和比热容ｃ的原理及方法,并对测量误差进行了分析与计算。结果表明在置信概率为９５％时,α、和λｃ的扩展不确定度分别不大于３％、５％和７％。     

A Method for Thermal Diffusivity Determination of Thermal Insulators

A so-called “three-point” (3P) method has been developed for thermal diffusivity measurements of thermal insulating materials. One side of a cylindrical specimen, sandwiched between two thin metal plates, is subjected to intense light from an incandescent lamp to generate a thermal perturbance. The temperature response is measured in three locations along the test specimen. Thermocouples are located at the front and rear faces of the specimen, and the third is placed inside the specimen at a known location. The two outside temperatures are used as boundary conditions, and the unknown thermal diffusivity is calculated from the third temperature versus time curve. The method combines the advantages of rapid transient non-contact heating methods with the well-defined boundary conditions of steady-state methods. The results of the 3P method are compared with those from steady-state methods for a micro-porous insulation material and for a honeycomb structure.     

掺杂石墨导热性能的研究

制备了一系列掺杂石墨并研究了其导热性能,实验结果表明,与相同条件下制得的纯石墨相比,掺杂石墨的导热系数均有较大的提高,掺杂钛组元可使石墨材料的导热性能有所提高,而硅组元的加入可大大提高石墨材料的导热性能,硼组元的加入则使石墨材料的导热性能明显下降,这与硼原子可溶入石墨晶格而造成晶格缺陷有关,XRD分析结果表明掺杂石墨都具有大的晶格尺寸,高的石墨化程度,这与掺杂组元的催化石墨化作用有关。     

Direct measurements of the thermal conductivity of various pyrolytic graphite samples (PG,TPG) used as thermal dissipation agents in detector applications

We performed model measurements on heat conduction in graphite-based structures, using several configurations. We describe our method for the direct measurement of thermal conductivity both in-plane and out-of-plane, for TPG and PG samples. Our results for the in-plane thermal conductivity coefficient, K_ab were obtained with two different sets of boundary conditions; they are in good mutual agreement. Those for the transverse coefficient, K_c, differ by a significant factor from the values published by the producers of the material.     

Comments on the measurement of thermal conductivity and presentation of a thermal conductivity integral method

A discussion is presented regarding the significance of the spatial temperature gradient approximation normally used in thermal conductivity measurement. Examples are presented illustrating the magnitude of temperature differences allowed for conductivity integral (TCI) method of analysis is presented as an alternative method which totally eliminates the need to impose temperature difference restrictions on the measurement process, so long as other errors, such as radiative heat losses, do not become excessive.     

Thermoelectric properties of graphene nanosheets-modified polyaniline hybrid nanocomposites by an in situ chemical polymerization

A hybrid material of polyaniline protonated with hydrochloric acid and conductive graphene nanosheets (PANi/GNs) has been prepared by an in situ chemical polymerization method. The interactions between PANi and GNs in the hybrid composites are investigated by utilizing XRD, FT-IR, UV–vis and Raman. It is found that the PANi are adsorbed on the surface of the GNs, and the morphology of PANi transforms from twist structure to extended structure after the GNs are introduced. The thermoelectric (TE) properties of PANi/GNs composites have been investigated in the range from 323 K to 453 K. The electrical conductivity and the Seebeck coefficient of PANi/GNs composites are obviously higher than those of the PANi, while the thermal conductivity of the composites still keeps relatively low values even with high GNs content, resulting in the increase in dimensionless figure of merit (ZT). A highest ZT value of 1.95 × 10⁻³ has been obtained for the composite containing 30 wt % GNs at 453 K, which is about 70 times higher than that obtained from the PANi.