Thermophysical Properties of Zirconium Alloy E110 (Zr-0.01Nb) After Oxidation in Air Atmosphere

The subsecond resistive pulse heating technique has been used to study the temperature dependence of the heat capacity and spectral emissivity (for the wavelength of 0.65 µm) of the zirconium alloy E110 (Zr-0.01Nb) after oxidation in air atmosphere. The tubular samples were oxidized at multiple pulse heating cycles up to different maximum temperatures (1200, 1300, 1400, 1500, and 1600 K) and subsequent cooling. It is shown that the thermophysical properties of the oxidized samples depend on the maximum temperature of oxidation.     

Thermophysical Properties of Solid Phase Zirconium at High Temperatures

This paper presents experimental results on the thermophysical properties of relatively pure polycrystalline zirconium samples in the solid phase from room temperature up to near the melting point. The specific heat capacity and specific electrical resistivity were measured from 290 to 1970 K, the hemispherical total emissivity from 1400 to 2000 K, the normal spectral emissivity from 1480 to 1940 K, and the thermal diffusivity in the range from 290 to 1470 K. From these data, the thermal conductivity and Lorentz number were computed in the range from 290 to 1470 K. For necessary corrections the most recent values of the linear thermal expansion from the literature have been used. Subsecond pulse calorimetry for measuring heat capacity, specific electrical resistivity, and both emissivities and the laser flash method for measuring thermal diffusivity were applied. Samples in the form of a thin rod and in the form of a thin disk were used in the first and second methods, respectively. Measurement uncertainties were generally about 3% for heat capacity, 1.6% for specific electrical resistivity, 3–10% for the two emissivities, and from less than 1% up to 6% for thermal diffusivity. All the results are discussed in reference to available literature data.Paper presented at the Seventeenth European Conference on Thermophysical Properties, September 5–8, 2005, Bratislava, Slovak Republic.     

Thermophysical Properties of Solid Phase Hafnium at High Temperatures

The thermophysical properties of several hafnium samples with a content of zirconium below 1% were experimentally studied over a wide temperature range. The specific heat capacity and specific electrical resistivity were measured from 300 to 2340 K, the hemispherical total emissivity from 1000 to 2130 K, while the thermal diffusivity was measured in the range from 300 to 1470 K. The thermal conductivity and Lorentz number were computed from measured properties for the range from 300 to 1470 K. The specific heat capacity, specific electrical resistivity, and hemispherical total emissivity were measured by subsecond pulse calorimetry, and the thermal diffusivity using the laser flash method. Samples in the form of a thin rod or wire, and in the form of a thin disk were used in the first and second methods, respectively. For data reduction and computation of relevant parameters, recent literature values of the linear thermal expansion were used. The results are compared with literature data and discussed.     

Non-Contact Measurements of the Thermophysical Properties of Hafnium-3 Mass% Zirconium at High Temperature

Several thermophysical properties of hafnium-3 mass % zirconium, namely the density, the thermal expansion coefficient, the constant pressure heat capacity, the hemispherical total emissivity, the surface tension and the viscosity are reported. These properties were measured over wide temperature ranges, including overheated and undercooled states, using an electrostatic levitation furnace developed by the National Space Development Agency of Japan. Over the 2220 to 2875 K temperature span, the density of the liquid can be expressed as _L (T)=1.20×10⁴–0.44(T–T _m ) (kgm^–3) with T _m =2504 K, yielding a volume expansion coefficient _L (T)=3.7×10^–5 (K^–1). Similarly, over the 1950 to 2500 K span, the density of the high temperature and undercooled solid -phase can be fitted as _S (T)=1.22×10⁴–0.41(T–T _m ), giving a volume expansion coefficient _S (T)=3.4×10^–5. The constant pressure heat capacity of the liquid phase can be estimated as C _PL (T)=33.47+7.92×10^–4(T–T _m ) (Jmol^–1K^–1) if the hemispherical total emissivity of the liquid phase remains constant at 0.25 over the 2250 K to 2650 K temperature interval. Over the 1850 to 2500 K temperature span, the hemispherical total emissivity of the solid -phase can be represented as _TS (T)=0.32+4.79×10^–5(T–T _m ). The latent heat of fusion has also been measured as 15.1 kJmol^–1. In addition, the surface tension can be expressed as (T)=1.614×10³–0.100(T–T _m ) (mNm^–1) and the viscosity as h(T)=0.495 exp [48.65×10³/(RT)] (mPas) over the 2220 to 2675 K temperature range.     

锆合金在焦磷酸钠电解液中的微弧氧化

目前锆合金表面处理存在周期长、装置复杂,得到的膜层质量不理想的问题,为此,开发了以焦磷酸钠为主要成分的电解液,研究了锆合金Zircaloy-4的直流微弧氧化(MAO)行为.采用扫描电镜和XRD对膜层的微观结构和相组成进行了分析.结果表明:微弧氧化膜层的生长符合线性规律,生长速度可达2.1μm/min;膜层的主要相组成为...     

Thermophysical Properties of U–Mo/Al Alloy Dispersion Fuel Meats

Uranium–molybdenum alloy dispersion fuel meats are being studied for utilization as a research reactor fuel. Thermophysical properties of U–Mo/Al dispersion fuel, where U–Mo was dispersed in aluminum in research reactor fuel for the study, were determined by computing the thermal conductivity through measurements of the specific heat capacity and thermal diffusivity. Uranium molybdenum powder was first fabricated and utilized as U–Mo/Al dispersion fuel; the molybdenum-to-uranium ratios were 6, 8, and 10 mass% to produce the initial powder, which was then combined with aluminum (Al 1060). The volume fractions of U–Mo powder to aluminum were 10, 30, 40, and 50 vol.% to fabricate the dispersion fuel. The thermal diffusivity and specific heat capacity were measured by the laser-flash and differential scanning calorimetry (DSC) methods, respectively. Although the thermal diffusivity showed a decreasing trend with the U–Mo volume fraction when the dispersion quantity was insignificant, the trend reversed with a higher dispersion level. The specific heat capacity increases monotonically with temperature; its value is larger for a smaller dispersion level. Additionally, the overall thermal conductivity increases with temperature. Finally, the thermal conductivity decreases with an increase in the amount of U–Mo powder in the dispersion fuel. Paper presented at the Seventeenth European Conference on Thermophysical Properties, September 5–8, 2005, Bratislava, Slovak Republic.     

锆合金织构对腐蚀性能影响的研究进展

锆的晶体结构是密排六方,其腐蚀各向异性比较显著。另外,锆合金在加工成材的过程中会产生织构,这将影响锆合金的耐腐蚀性能。论述了锆合金腐蚀各向异性的研究方法、结果和进展,并讨论了织构对锆合金耐腐蚀性能的影响,为认识锆合金的腐蚀行为、研究其腐蚀机理提供参考。     

Thermophysical and Thermal Optical Properties of Vanadium by Millisecond Calorimetry Between 300 and 1900 K

A variant of millisecond-resolution pulse calorimetry in use at the Institute of Nuclear Sciences Vina since 1983 involves measuring the specific heat and electrical resistivity of electrical conductors from room temperature to 2500 K and the hemispherical total emissivity and normal spectral emissivity from about 1300 K to the same maximum operating temperature. The method was applied successfully to different materials: pure metals, ferrous and nickel-base alloys, reactor materials, and refractory metals in thermal characterization of candidates for thermophysical property standard reference materials. This paper presents and discusses new data obtained in the study of thermophysical and thermal optical properties of vanadium.     

Thermophysical Properties by a Pulse-Heating Reflectometric Technique: Niobium, 1100 to 2700 K

Pulse-heating experiments were performed on niobium strips, taking the specimens from room temperature to the melting point is less than one second. The normal spectral emissivity of the strips was measured by integrating sphere reflectometry, and, simultaneously, experimental data (radiance temperature, current, voltage drop) for thermophysical properties were collected with sub-millisecond time resolution. The normal spectral emissivity results were used to compute the true temperature of the niobium strips; the heat capacity, electrical resistivity, and hemispherical total emissivity were evaluated in the temperature range 1100 to 2700 K. The results are compared with literature data obtained in pulse-heating experiments. It is concluded that combined measurements of normal spectral emissivity and of thermophysical properties on strip specimens provide results of the same quality as obtained using tubular specimens with a blackbody. The thermophysical property results on niobium also validate the normal spectral emissivity measurements by integrating sphere reflectometry.     

Investigation of the Temperature Limits of Polymorphous Transformation in Zr-1%Nb Alloy under Different Thermal Conditions

The method of pulsed resistive heating is used to investigate the structural transformation in low-alloy zirconium. The dependence of the transformation temperature on the direction of the process is revealed: in the cooling stage, the transformation occurs at lower temperatures than in the case of heating the sample. Experiments are performed which involve the interruption of heating in the region of two-phase state. A delay of return to the low-temperature phase is revealed, which leads to a temperature drop immediately after the heating current is switched off, irrespective of the completion of the process of structural transformation.     

Specific heat capacity and emissivity measurements of ribbon-shaped graphite using pulse current heating

A measurement method for specific heat capacity and hemispherical total emissivity of electrically conductive materials with pulse current heating is investigated, in which a ribbon-shaped sample is heated up to 3000K in a subsecond-duration experiment. Specific heat capacity and hemispherical total emissivity of the sample are calculated from the time variations of heat generations and surtace temperature of the sample measured during heating and cooling phases. The true surface temperature of the rihhon-shaped samples is obtained with a radiation thermometer: the directional spectral emissivity of the sample surface is measured using a hemisplicrical mirror centered at the sample surface. Measurements are performed for POCO AXM-5Ql graphite in the temperature range from 1500 to 3000 K.Paper presented at the Twelfth Symposium on Thermophysical Properties. June 19–34, 1994 Boulder, Colorado, U.S.A.     

Determination of the Thermophysical Properties of Halogenated Hydrocarbons in a Heat-Conducting Calorimeter

The values of the coefficients of thermal expansion and compressibility, isobaric heat capacity and thermal diffusivity of three brominated saturated hydrocarbons of butyl bromide, hexyl bromide and heptyl bromide are measured in a heat-conducting calorimeter at a temperature of 298–363 K in the pressure range of 0.098–147 MPa. The experimental data on the isobaric heat capacity are compared to the calculation results. Generalized dependences are suggested to determine the heat capacity and thermal diffusivity.     

Thermophysical properties of tungsten electrodes by subsecond pulse calorimetry

Prediction of the behavior of tungsten electrode material in high-temperature plasma generators requires knowledge of its thermophysical properties over a wide temperature range. For determination of its relevant thermophysical properties, the direct pulse heating calorimetry technique was chosen as the most appropriate, as it meets requirements of both high-speed measurements and the widest temperature range. As a high-temperature sensor, the method used simultaneously a fine-gauge thermocouple and an optical pyrometer. Such a combination enables coverage of a few thousand degrees within a second, with a time resolution of less than 1 ms. The measurement technique and details of the apparatus as well as experimental results for specific heat, electrical resistivity, normal spectral, and hemispherical total emittance in the temperature range from 300 to 2500 K are presented.Paper presented at the Fourth International Workshop on Subsecond Thermophysics, June 27–29, 1995, Köln, Germany.     

氢对TC21钛合金热物理性能的影响

目的 获得氢含量对TC21钛合金密度、热扩散系数、比热容和热导率等热物理性能的影响规律.方法 利用固态置氢法对TC21钛合金进行氢处理,利用固体密度测试仪、激光导热仪和差示扫描量热仪等设备测定原始及含有不同氢含量TC21钛合金的热物理性能.结果 随着氢含量的增加,TC21钛合金的密度呈线性降低趋势;TC21钛合金在不同...     

A combined transient and brief steady-state technique for measuring hemispherical total emissivity of electrical conductors at high temperatures: Application to tantalum

A new method for measuring hemispherical total emissivity of electrically conducting materials at high temperatures (above 1500 K) using a feedback-controlled pulse-heating technique has been developed. The technique is based on rapid resistive self-heating of a solid cylindrical specimen in vacuum up to a preset high temperature in a short time (about 200 ms) and then keeping the specimen at that temperature under steady-state conditions for a brief period (about 500 ms) before switching off the current through the specimen. The specimen is maintained at constant temperature with a feedback control system which controls the current through the specimen. The computer-controlled feedback system operates a solid-state switch (composed of field-effect transistors). The sensing signal for the feedback is provided by a high-speed optical pyrometer. Hemispherical total emissivity is determined at the temperature plateau from the data on current through the specimen, the voltage drop across the middle portion of the specimen, and the specimen temperature using the steady-state heat balance equation based on the Stefan-Boltzmann law. The true temperature of the specimen is determined from the measured radiance temperature and the normal spectral emissivity: the latter is obtained from laser polarimetric measurements. The experimental quantities are measured and recorded every 0.2 ms with a 12-bit digital oscilloscope. To demonstrate the feasibility of the technique, experiments were conducted on a tantalum specimen in the temperature range 2000 to 2800 K. The results on hemispherical total emissivity are presented and are compared with the data given in the literature.     

High-Temperature Strength of KTTs-110 Zirconium Alloy

We describe the methods and results of investigation of the characteristics of strength and plasticity of a pilot batch of tubes made of KTTs-110 zirconium alloy under the conditions of short- and long-term static loading. The obtained results are compared with the same characteristics of É-110 alloy extensively used in the active zones of WWÉR-1000-type nuclear reactors.     

铝合金表面锆盐转化膜的制备及其性能

为提高铝合金涂膜的结合力及耐蚀性,在铝合金表面制备了锆盐转化膜.通过盐雾试验、电化学试验、膜微观结构与涂膜结合力测试,研究了锆盐转化膜的耐蚀性与漆膜的结合力,并与通用的铬酸盐转化膜和无铬转化膜进行对比.结果表明:锆盐转化膜120 h盐雾试验的耐蚀等级达8级,在3.5%NaCl溶液中铝合金的自腐蚀电位明显正移,腐蚀电流密度大大降低;转化膜层均匀多孔,含有Al,O,Zr和Mg元素,且与漆膜结合力良好.