非晶态TiO_2薄膜用于HMP45D温湿传感器的Pt100电阻保护层

用Pt100薄膜电阻代替金属铂电阻可提高HMP45D温度传感器的精度和响应速度,但面临稳定性下降的问题。我们采用溶胶-凝胶方法在Pt100薄膜电阻表面生成TiO_2保护膜,研究表明,非晶态TiO_2保护膜具有良好的光催化活性,镀了TiO_2保护膜的Pt100电阻可获得逼近Callendar-Van Dusen方程的电阻-温度特性,其温度系数在使用180天后仍能保持原来的97.79%。因此,非晶态TiO_2保护膜在提高Pt100薄膜电阻工作稳定性和使用耐久性方面具有很高的应用价值。     

活化温度对Pt/YSZ电极性能影响

借助交流阻抗谱测试技术、扫描电镜和超声波处理,研究了Pt/YSZ电极烧制工艺(活化温度)对电极性能的影响。研究表明,随着活化温度的升高,Pt/YSZ电极的固体电解质电阻不变,而电极界面电阻和响应时间变化显著,电极层附着性增强。1 050℃为最佳活化温度,Pt/YSZ电极的界面电阻最小,Pt/YSZ电极响应时间为0.5 s,响应最快,活性最高,电极层附着牢固。     

钇稳定氧化锆铂电极活化时间对氧化锆氧传感器性能的影响

为解决钇稳定氧化锆铂(Pt/YSZ)电极易脱落的问题,采用氯铂酸分解法制备了Pt/YSZ电极,并在烧制过程中对其进行高温活化。采用交流阻抗谱、扫描电镜和超声波冲击研究了Pt/YSZ电极烧制工艺中活化时间对电极性能的影响。将Pt/YSZ电极装入氧化锆氧传感器,测试其响应时间。结果表明:随着活化时间的增加,Pt/YSZ电极的固体电解质电阻不变、电极界面电阻和氧化锆氧传感器响应时间均先减小后增大,电极层附着性增强,传感器寿命得以延长;1 050℃活化最佳时间为1.0 h,此时,Pt/YSZ电极的界面电阻最小,活性最高,附着性良好,氧化锆氧传感器反应最快。     

高压点火装置接触点材料的应用研究

本文叙述了Pt Ir25、Pt Ir25 Ru0.75、Pt Ru10、W、WRe5、WRel(六个牌号合金接触点的金属转移、金属损失、熔焊及接触电阻等性能以及金属转移、金属损失的测量方法,通过高压点火装置接触点工作寿命试验证明Pt Ru10合金自行配对的接触点工作性能最佳。其金属转移高度的最大值为0.31mm,比目前广泛使用的Pt Ir25合金接触点金属转移高度的最大值0.70mm减少一倍以上,其金属损失也比Pt Ir25合金接触点为小。如果将使用性能同经济价值结合考虑时,用Pt Ru10合金做固定接触点、WRe10合金做活动接触点配对使用,不仅可保证航空发动机高压点火装置接触点可靠工作1000小时(即比原Pt Ir25合金接触点工作寿命延长一倍),而且可以取得良好的经济效果。为开展接触点材料以贱代贵的应用研究工作提出了方向。     

Pt/TiO2表面状态对气敏特性的影响

通过浸渍法用H2PtCl6溶液修饰TiO2厚膜,经过不同的处理工艺,获得表面负载Pt粒子的Pt/TiO2厚膜.采用XRD和SEM分析了Pt/TiO2的物相结构和表面形貌,并通过电阻氧分压关系计算Pt/TiO2厚膜活化能.然后分别通过静态和动态测试法,表征了Pt/TiO2厚膜在H2/O2中的稳态阻值和动态响应时间.结果表明:受"spill-over"机制影响,Pt/TiO2厚膜在H2/O2气氛下的稳态电阻与Pt的散布状态有关.而样品响应时间不仅与Pt粒子的分布有关,还受表面活化能的影响,在Pt散布基本相同情况下,活化能越低,样品响应速度越快.     

Ti/La_(0.7)Ca_(0.3)MnO_3/Pt结构器件中“负”电阻开关特性研究

以Pt/Ti/SiO2/Si为衬底,制备了具有电阻转变特性的Ti/La0.7Ca0.3MnO3(LCMO)/Pt结构器件.X射线衍射分析表明LCMO薄膜呈纳米晶或非晶态,扫描电子显微镜及原子力显微镜分析表明LCMO薄膜表面平整、光滑致密.电学测试结果表明Ti/LCMO/Pt结构具有明显的双极型"负"电阻转变特性,低电阻态的导电过程为空间电荷限制电流机制,高电阻态的导电过程为Poole-Frenkel发射机制.利用氧化还原反应的随机性和TiOx中间层空间分布的不均匀性,定性地解释了高电阻态的不稳定性以及电流-电压曲线上的电流突变现象.     

配热电阻用数字温度指示仪表示值误差测量结果的不确定度评定

配热电阻用数字温度指示仪表在工业生产中有着广泛的应用,其检定、校准结果的不确定度分析与评定,有着重要的意义。本文主要对工业生产中经常用到的配Pt100热电阻的数字温度指示仪表的检定结果的不确定度进行了分析。     

Pt/YSZ氧传感器的电极电阻和响应特性

应用两电极直流极化法测定了氧传感器在380～800℃中的Pt,空气／YSZ电极电阻,从交流低频阻抗测量外推法测得YSZ的体电阻,可以将YSZ的直流极化从电极的过电位中区分出来．Pt,空气｜（ZrO2）_0．93（Y₂O₃）_0．07｜空气,Pt,电池的直流极化1gI-η作图得出,电极电荷传递系数为2．YSZ体电阻、Pt,空气／YSZ电极电阻和电极交换电流对温度的Arrhenius图,在600℃和570℃附近存在着类似的活化能变化．测量表明;700℃时,氧传感器的测量响应时间≤2．5s．     

Al2O3保护层对高温下Pt/ZnO/Al2O3电极导电稳定性的影响

本工作研究了Al₂O₃保护层的厚度对高温下声表面波器件电极导电稳定性的影响, 采用激光分子束外延方法在Pt/ZnO/Al₂O₃电极上制备了不同厚度的Al₂O₃保护层。通过测量样品高温环境中的实时电阻, 发现Al₂O₃缓冲层的厚度对电极在高温下的导电稳定性的影响非常大。结果表明, 没有Al₂O₃保护层时, Pt/ZnO/Al₂O₃电极的电阻升温至800 ℃时开始急剧地增加。当包覆40 nm的Al₂O₃保护层时, 电极在升温至900 ℃以上才出现电阻值剧烈增加的现象。而随着Al₂O₃保护层厚度的增加, 电极的电阻在高温下的导电性能也更加稳定。SEM测试结果表明, 经过1000 ℃、1 h的高温测试后, Al₂O₃保护层越薄的Pt/ZnO/Al₂O₃电极, 结块形成的Pt颗粒越大与不连续的Pt空洞更多。这些结果为制备高温下稳定工作的声表面波器件提供了一条新的思路。     

Pt/C催化剂制备及CO催化氧化性能研究

采用大气压介质阻挡放电辅助氢气热还原方法和氢气热还原方法制备Pt/C催化剂,考察了制备方法及Pt负载量对Pt/C催化性能的影响。采用X-射线衍射(XRD)、循环伏安法、CO催化氧化反应研究Pt/C催化剂的晶相结构、电催化性能和CO催化氧化活性。结果表明:大气压介质阻挡放电辅助氢气热还原所制备的样品具有更高的电化学活性和CO催化氧化活性。当Pt负载量在2%到10%之间变化时,Pt/C-PC催化活性随负载量增加而增加。XRD测试结果显示当Pt负载量为2%,5%和10%时,Pt粒径分别为:10.6 nm,9.1 nm和6.4 nm,说明采用等离子体辅助氢气热还原方法制备的Pt/C-PC催化剂,Pt负载量越大,Pt粒径越小,CO催化氧化活性更高。     

梯度热障涂层热冲击性能研究

采用等离子喷涂的方法,分别获得了２ｍｍ ＺｒＯ２－ＮｉＣｒＡｌ和ＺｒＯ２－Ｎｉ／Ａｌ系梯度热障涂层。热冲击实验结果表明,两种涂层具有不同的失效机理。ＺｒＯ２－ＮｉＣｒＡｌ系的失效是由于基于基体氧化引起的涂层整体脱落;而ＺｒＯ２－Ｎｉ／Ａｌ系的失效是支径向裂纹扩展到Ｎｉ／Ａｌ底层氧化共同作用的结果。     

Anisotropic Thermal Diffusivities of Plasma-Sprayed Thermal Barrier Coatings

Thermal barrier coatings (TBCs) are used to shield the blades of gas turbines from heat and wear. There is a pressing need to evaluate the thermal conductivity of TBCs in the thermal design of advanced gas turbines with high energy efficiency. These TBCs consist of a ceramic-based top coat and a bond coat on a superalloy substrate. Usually, the focus is on the thermal conductivity in the thickness direction of the TBC because heat tends to diffuse from the surface of the top coat to the substrate. However, the in-plane thermal conductivity is also important in the thermal design of gas turbines because the temperature distribution within the turbine cannot be ignored. Accordingly, a method is developed in this study for measuring the in-plane thermal diffusivity of the top coat. Yttria-stabilized zirconia top coats are prepared by thermal spraying under different conditions. The in-plane and cross-plane thermal diffusivities of the top coats are measured by the flash method to investigate the anisotropy of thermal conduction in a TBC. It is found that the in-plane thermal diffusivity is higher than the cross-plane one for each top coat and that the top coats have significantly anisotropic thermal diffusivity. The cross-sectional and in-plane microstructures of the top coats are observed, from which their porosities are evaluated. The thermal diffusivity and its anisotropy are discussed in detail in relation to microstructure and porosity.     

车室内人体热舒适性的计算模型

在车室内热环境计算的基础上,借助于人体热调节系统以及人体生物热方程计算了人体温度场的分布,并且利用当量温度Teq去评价不同环境下人体的热舒适性。文中完成了一个典型算例,预测了司机与乘客的热舒适性问题,并与国外提供的热舒适范围作了比较,结果令人满意。显然,这一研究对进一步改进车室内环境的控制方法具有重要的指导意义。     

Characterization of Thermal Barrier Coatings Using Thermal Methods

Although low thermal conductivity was one of the major reasons for the development of thermal barrier coatings (TBCs) based on yttria stablilized zirconia (YSZ), its mechanical properties are often considered crucial in failure analysis and assessment of coatings. Thermal properties usually are treated as just basic material parameters and have not been utilized widely in TBC characterization and failure analysis. In fact, thermal transport properties such as thermal conductivity and thermal diffusivity are closely related to the microstructural changes of the TBC. In this paper, a brief overview of characterization of TBCs using thermal thermophysical properties and temperature mapping is presented.     

热障涂层热导率的研究进展

简要回顾了热障涂层体系的发展,讨论了氧化锆陶瓷材料的传热规律,包括涂层微观结构、陶瓷成分等因素的影响.同时指出了改进陶瓷涂层热导率的方法和开发适用于更高温度下的陶瓷涂层材料的指导原则,并详细介绍了改善热障涂层热导率的研究现状.     

Influence of Thermal Strain on Thermal Properties of Composites

The temperature dependence of the thermal expansion characteristics of the AS21 magnesium alloy, AS21–25 vol% Saffil fiber composite and the Mg-10 vol% Saffil fiber composite has been measured in the temperature range from 20 to 380°C. The expansion characteristics were influenced by the residual and thermal strains. The residual strain was removed within the first thermal cycle. The relative elongation of the tensile pre-deformed AS21–25 vol% Saffil fiber composite is lower than that for the sample without deformation and for the composite pre-deformed in compression. The anisotropy of the thermal expansion is demonstrated on the Mg-10 vol% Saffil fiber composite. The coefficient of thermal expansion (CTE) in the transverse direction (TD) (the planes of the short Saffil fibers are laid perpendicular to the axis of the sample) is higher than the CTE in the longitudinal direction (LD) (the planes of the short Saffil fibers are laid parallel to the axis of the sample). The anisotropy and the thermal strain influence the thermal diffusivity for AS21 composites investigated at temperatures between 20 and 380°C.Paper presented at the Seventeenth European Conference on Thermophysical Properties, September 5-8, 2005, Bratislava, Slovak Republic.     

基于暖体假人的热环境评价指标

由于暖体假人的对流及辐射散热特性与实际人体非常接近，因此，在热环境工效学研究中发挥着突出的作用。该文介绍了几种通过暖体假人实验得到的热环境评价指标，提出了用暖体假人测定湿球黑球温度的好处，给出了各指标的计算公式，并对它们作了简单的分析。最后，将各指标与平均辐射温度进行了列表对比。     

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.