基于激光闪射法测量某内燃机铝合金活塞的热物性参数

基于激光闪射法,采用闪射法导热仪测量了不同温度下某内燃机铝合金活塞的比热容、热扩散系数及导热系数。结果表明：随着温度的升高,该内燃机铝合金活塞的热扩散系数逐渐减小,比热容逐渐升高,导热系数在一定温度范围内呈逐渐增大的趋势。     

闪光法测量粉末冶金铍材热物理参数的结果不确定度评定

利用闪光法测量粉末冶金铍材的热扩散系数、比热容、导热系数等热物理参数,分析了影响热物理参数测量不确定度的来源,并对粉末冶金铍材热物理参数测量不确定度进行评定。结果表明：在置信度95%的条件下,粉末冶金铍材热扩散系数的扩展不确定度为1.48 mm²/s,比热容的扩展不确定度为0.07 J/(kg·K),导热系数的扩展不确定度为5.80 W/(m·K)。     

纳米流体的分散性研究及其热物性测量

采用"两步法"制备了稳定性良好的γ-Al2O3-DW和CNTs-DW纳米流体,研究了分散剂对纳米流体悬浮稳定性的影响,测试了溶液的热扩散系数和比定压热容,并根据测试数据计算出导热系数.结果表明,分散剂种类和用量对纳米流体的分散有重要影响,相对于基础液体(DW),纳米流体的导热系数和热扩散系数有一定的提高,但比定压热容减小.     

Al2O3纳米粉体悬浮液热物性实验研究

分别采用瞬态热线法、比较量热法和旋转粘度计测试了不同温度、粒子浓度和粒径下的Al2O3-DW（蒸馏水）纳米流体的导热系数、比热容、粘度等热物性参数。试验结果表明,粒子浓度、粒径和温度都是影响Al2O3-DW纳米流体热物性参数的重要因素。与水相比,纳米流体导热系数和粘度增加,常温4％体积份额下增幅分别为21．5％和52．3％;纳米流体比热容随着粒子体积份额增加而降低,并推导出了常温下低浓度纳米流体比热容的预测公式。     

铸铁的热物性测定及其与显微组织的关系

用激光脉冲法和比较法测量了不同种类铸铁300-1300K的热物理参数(α,Cp,λ),并对铸铁热物性与显微组织的关系作了初步讨论。结果表明,片状石墨对铸铁导热、导温能力影响最大,蠕虫状石墨次之,球状石墨较小。石墨对铸铁的导热、导温能力的贡献最大,基体组织次之,而合金元素对热物性的影响大小则决定于其在基体中的存在形式;通常各种铸铁的导热、导温系数值按灰口铁、蠕虫铁、球铁、可锻铸铁、奥氏体铸铁和白口铸铁的顺序依次降低,且在810K以后开始趋于一致;除奥氏体铸铁和白口铸铁外大多数铸铁在1040K附近存在居里点,导温系数在该处出现最小值;除奥氏体铸铁外,多数铸铁在1040K附近比热容出现峰值,有些铸铁在490K附近存在渗碳体居里点,比热容在该处也出现峰值。     

激光闪光法测定耐火材料导热系数的原理与方法

依据激光闪光法测定导热系数的理论基础和物理模型,推导了计算导热系数所需的热扩散系数和比热容两个参数的计算公式,从而阐述了该方法的原理。以美国安特公司产FLASH—LINE-5000型热扩散系数测定仪为例,介绍了激光闪光法测定导热系数设备的主要组成,并简要说明了该设备的操作步骤及导热系数的计算方法。     

建立国家材料热物性测量标准装置的意义

材料热物性是表征材料性质的重要特征量,包括导热系数、热扩散系数、比热、热膨胀系数以及热辐射的发射率和反射率等,在航空航天、微电子技术、能源有效利用、核能技术、新材料开发等高新技术领域,以及石油化工、钢铁冶金、建筑节能、制冷空调等工业领域都具有明显的科学意义和重要的工程应用价值,是技术创新、开发和科学研究的基础.     

石墨烯/聚丙烯复合材料导热性能测量分析研究

针对现有文献报道的石墨烯/PP复合材料导热系数测量结果差异较大,该文对相应测量方法、仪器、样品尺寸和测量结果等进行分析和评价。制备质量分数为5%至30%的石墨烯/PP复合材料块状和薄片状等样品,分别通过QTM500型、TC3000型和DRE-Ⅲ型3种瞬态导热系数测试仪对块状样品导热系数进行直接测量,并通过LFA467型激光闪光法导热仪、DSC3+型差示扫描量热仪和ZB603C型电子天平和密度组件分别对各质量分数石墨烯/PP复合材料样品的热扩散系数、比热容和密度进行测量后计算获得导热系数。结果表明：3种瞬态导热系数测试仪测量纯PP、5%和10%质量分数石墨烯/PP复合样块导热系数偏差在2.6%～8.7%范围内,大于各仪器声称测量偏差;直接测量法与间接测量法获得的导热系数偏差大于36%,且随石墨烯质量分数的增加而变大。因此,在测量复合材料导热系数时应选择适用尺寸和量程的直接测量法,导热系数等热物性参数的量值传递体系仍需进一步建立和完善来提高直接测量法的准确性和间接测量法的可靠性。     

高碳钢的热物性与显微组织的关系

采用激光脉冲法和比较法测量了不同组织状态下的高碳钢的导温系数a、比热容Cp和导热系数λ等热物性参数。并对高碳钢的热物性与显微组织、力学性能之间存在的某些对应关系做了初步讨论。结果表明,高碳钢的a和A值按珠光体、回火索氏体、回火马氏体和淬火马氏体的顺序依次减小,且在500℃以后趋于一致,这恰好与硬度、强度值随回火温度变化的规律吻合。通常随着含碳量的增加,高碳钢的a和λ值降低。碳以固溶形式存在于基体时对钢导热能力的损害比以第二相形式存在时大。与强度和塑性等力学性能不同,高碳钢的晶粒越小,其a和λ值越低。淬火后的高碳钢在100℃附近回火,a和λ值出现最小值与硬度出现峰值相对应,在750℃附近存在居里点,比热容出现最大值。     

激光闪射法测试耐火材料导热系数的原理与方法

介绍了激光闪射法测定材料导热系数的理论基础,通过对热扩散系数和比热容计算公式的推导,阐述了该方法的基本原理.以德国耐驰仪器制造有限公司生产的LFA-427型激光闪射导热仪为例,介绍了激光闪射法测定导热系数设备的主要组成,并简要说明了该设备的操作步骤以及计算方法.     

Intercomparison of Thermophysical Property Measurements on an Austenitic Stainless Steel

The results of an inter laboratory comparison of thermal conductivity, thermal diffusivity, specific heat capacity, and thermal expansion measurements on austenitic stainless steel in the temperature range between 20 and 1000°C are presented here. Mean values are presented for the physical properties studied. Reliable relative expanded uncertainties can be stated for the properties determined, which were achieved by applying good measurement practice, i.e., 3% for thermal expansion, 5% for specific heat capacity and thermal diffusivity, and 6% for thermal conductivity. The mean values derived from this intercomparison agree well with the results of a previous intercomparison in 1990. An erratum to this article is availabale at .     

Measurement and Analysis of Thermophysical Properties of Diorites in the Temperature Range from 253 to 333 K

Thermal conductivity and thermal diffusivity are simultaneously measured for a collection of diorite samples taken from Shewa-Shahbaz Garhi volcanic complex near Mardan, Pakistan by using the transient plane source (TPS) technique. The temperature dependence of the transport properties of these samples is studied in the temperature range from 253 to 333 K. Different relationships for the temperature dependence of the thermal conductivity and thermal diffusivity are tested. The samples are also characterized by their chemical composition, density, porosity, and specific gravity at room temperature and atmospheric pressure. Theoretical calculation of the specific gravity parameter based on the chemical composition is in good agreement with the experimental observation. No correlation was found for the temperature dependence of the thermal transport behavior on porosity, chemical composition, and density.     

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.     

Thermophysical Parameters of Optical Glass BK 7 Measured by the Pulse Transient Method

This paper is focused on the pulse transient method. The theory of the method and the measuring regime (time window) are analyzed. The results of the analysis are verified on borosilicate crown glass BK7, which is a candidate for a standard for thermal conductivity. Thermal contact and surface effects affect the length of the time window in which the evaluation procedure is applied. The one-point evaluation technique is compared with the results of the fitting procedure that uses the time window found by difference analysis. The values of the thermal conductivity, thermal diffusivity, and specific heat were found to be 1.05 W· m^–1 · K^–1, 0.548 × 10^–6m ^{– 2} · s^–1, and 767 J· kg^–1 · K^–1, respectively, using the one-point evaluation technique.Paper presented at the Sixteenth European Conference on Thermophysical Properties, September 1–4, 2002, London, United Kingdom.     

42CrMo钢齿轮轴断裂原因分析

采用化学成分分析、断口分析、金相检验和力学性能测试等方法,对42CrMo钢齿轮轴断裂的原因进行了分析。结果表明:由于齿轮轴制造过程中的热处理工艺或方法不当,导致齿轮轴的力学性能偏低,在使用过程中发生了疲劳断裂。     

Measurement of Selected Thermophysical Properties of the NPL Certified Reference Material Stainless Steel 310

Flash methods have become one of the most commonly used techniques for measuring the thermal diffusivity and thermal conductivity of various kinds of solids and liquids such as metals, carbon materials, ceramics, and polymers. Easy sample preparation, small sample dimensions, fast measurement times, and high accuracy are only some of the advantages of this non-destructive measurement technique. However, the accuracy of measurement and level of uncertainty of the resulting data are becoming increasingly important for countless industrial applications. Instruments must be checked to determine the uncertainty of the system at different temperature and application ranges. One way of checking the accuracy of the results is to cross-check the unit with certified reference materials. However, there is a lack of standard materials for thermal diffusivity/thermal conductivity all over the world. Furthermore, for some available standards, the thermophysical properties are known only over a limited temperature range. Presented in this work are thermophysical property measurements on a certified thermal conductivity standard, Stainless Steel 310. Tests were carried out between −125 and 1000°C.     

Measurement of thermophysical properties of molten salts: Mixtures of alkaline carbonate salts

The purpose of this study is to develop measuring methods for the thermal diffusivity, the specific heat capacity, and the density of molten salts, as well as to measure these properties of mixtures of alkaline carbonate salts. The thermal diffusivity is measured by the stepwise heating method. The sample salt is poured into a thin container, and as a result, a three-layered cell is formed. The thermal diffusivity is obtained from the ratio of temperature rises at different times measured at the rear surface of the cell when the front surface is heated by the stepwise energy from an iodine lamp. The specific heat capacity is measured using an adiabatic scanning calorimeter. The density is measured by Archimedes' principle. Thermal conductivity is determined from the above properties. Measured samples are Li₂CO₃-K₂CO₃ (42.7–57.3, 50.0-50.0, and 62.0-38.0 mol%).Invited paper presented at the Tenth Symposium on Thermophysical Properties, June 20–23, 1988, Gaithersburg, Maryland, U.S.A.     

Nd3+:Gd3Ga5O12晶体的热物理性能研究

提拉法生长了Nd^3＋：Gd3Ga5O12（Nd：GGG）单晶，用差示扫描量热法（DSC）和激光脉冲法分别测量了Nd：GGG激光晶体的比热和热扩散系数，计算得到晶体的导热系数，与用PPMS测量得到的导热系数相吻合．实验结果表明：Nd：GGG激光晶体具有较大的比热和导热系数，具有良好的热物理性能；Nd：GGG晶体的热扩散系数和导热系数随着温度的升高而减小；计算得到晶体的德拜温度为711K．     

Some research activities on thermophysical properties in China

Various aspects of the importance of thermophysical property (TPP) studies to science and technology in China are discussed. Several stages of the development of experimental principles and equipment are described. Some examples of TPP applications in economic practice are presented. Theoretical and methodological studies in this field are summarized. The presentations are limited mostly to work on solids.Invited paper presented at the Ninth Symposium on Thermophysical Properties, June 24–27, 1985, Boulder, Colorado, U.S.A.     

稀土对42CrMo钢等离子体氮碳共渗表层组织的影响

对42CrMo钢在不同温度和时间下进行有、无稀土添加的脉冲等离子体氮碳共渗的工艺进行研究。通过金相检验和XRD分析,归纳出稀土对等离子体氮碳共渗的影响。结果表明：稀土的添加改善了渗层的显微组织,并降低了渗氮初期的化合物层厚度;使渗层的e相含量降低,γ＇相含量增加;并且使表面氮含量提高。