Thermophysical Properties of NZP Ceramics (A Review)

Data on the thermophysical properties of NZP ceramics with the NaZr₂(PO₄)₃-type structure are summarized. A system of thermal expansion regularities is proposed making it possible to predict NZP materials with controllable thermal expansion, including ultralow expansion with near-zero anisotropy. The thermodynamic functions of the reactions of synthesis of NZP phosphates are calculated and the applicability of ceramic technology is justified. It is proposed to use NZP ceramics as heat-insulating materials capable of working under abrupt temperature shifts.     

Thermophysical Properties of Stone Fruit

The thermophysical properties of the stone fruits plum, peach, and nectarine were modeled from experimental data as functions of moisture content. Samples were dried to preset moistures in a laboratory cabinet dryer, and the thermal conductivity, specific heat, apparent density, bulk density, and porosity of the fruit were determined. The thermal conductivity and specific heat were found to be linear functions of moisture content, whereas apparent bulk density and porosity followed second-order polynomials. Temperature dependence was not found to be significant.     

High-Temperature Thermophysical Properties of Zirconium Carbide

An apparatus based on the method of Jain and Krishnan was developed for property measurements in the temperature range from measurable radiant emission to the thermal stability limit of metallic materials. Apparatus and experimental techniques for cylindrical specimens with length-to-diameter ratios >4 are described. The theory of the method is reviewed, practical formulations are developed, and error sources are analyzed. The following properties were determined for zirconium carbide in the range 1000° to 2500°K: thermal conductivity, spectral thermal emittance at 0.65μ spectral thermal emittance at 0.65μ as a function of time in vacuum, electrical resistivity, and total thermal emittance. A compilation of experimental values for other physical properties of ZrC is given.     

High-Temperature Thermophysical Properties of Uranium Monocarbide

Thermal conductivity ( k ), electrical resistivity ( p ), total hemispherical emittance (ε_t), and normal spectral emittance (ε_0.65μ) of dense, arc-cast uranium monocarbide (5.3 wt % total carbon) were measured in the temperature range 1150° to 2050°K. The results were as follows: k , 0.057 cal/sec-cm-deg, 1200° < T < 2050°K, probable error ± 0.002; p, 20.4 × 10⁻⁶+ 114.8 T × 10⁻⁹ ohm-cm, 1175° < T < 2050°K, probable error ± 1.7 × 10⁻⁶; ε_t0.42, 1250° < T < 1980°K, probable error ± 0.02; ε_0.65 0.539 – 0.02 T × 10⁻³ 1150° < T < 1890°K, probable error ± 0.02. Experimental methods are discussed and error sources are analyzed. Uranium monocarbide exhibited typical metallic behavior in its thermophysical properties.     

Thermophysical Properties of Perovskite-Type Strontium Cerate and Zirconate

Polycrystalline samples of strontium series perovskite-type oxides, SrCeO₃ and SrZrO₃, were prepared and the thermophysical properties were measured. The chemical compositions of the samples do not deviate from the stoichiometric composition. The oxygen-to-metal (O/M) ratios of SrCeO₃ and SrZrO₃ are 3.00±0.03 and 2.98±0.01, respectively. The average linear thermal expansion coefficients are 1.11 × 10⁻⁵ K⁻¹ for SrCeO₃ and 9.69 × 10⁻⁶ K⁻¹ for SrZrO₃ in the temperature range between 300 and 1000 K. The melting temperatures T _m of SrCeO₃ and SrZrO₃ are 2266 and 2883 K, respectively. The longitudinal and shear sound velocities were measured by an ultrasonic pulse–echo method at room temperature in air, which enables to evaluate the elastic moduli and Debye temperature. The heat capacity was measured by using a differential scanning calorimeter in high-purity argon atmosphere. The thermal diffusivity was measured by a laser flash method in vacuum. The thermal conductivities of SrCeO₃ and SrZrO₃ at room temperature are 2.95 and 4.06 W·m⁻¹·K⁻¹, respectively.     

Thermophysical Properties of α-Tungsten Carbide

Upper and lower bounds for the thermal expansion of polycrystalline tungsten carbide (α-WC) are predicted at ultrahigh temperatures from low-temperature experimental data. The lower bound is obtained from an α _VK_TV model, where α _V is the volume thermal expansion, K_T the isothermal bulk modulus for a randomly oriented polycrystalline sample, and V the molar volume. For many materials, the α _VK_TV product approaches a constant value that is similar to the specific heat at the highest temperatures. The upper bound uses Grüneisen's rule with a constant Grüneisen parameter gamma at temperatures >1.3θ_D (where θ_D is the Debye temperature) and experimental data below that temperature. Literature data for the thermophysical properties of α-WC have been reviewed and used in our α _VK_TV model to calculate a lower bound for the thermal expansion at temperatures >2θ_D and to calculate the temperature dependence of the bulk modulus. The ultrahigh-pressure thermal expansion has been calculated from the lower bound. Model predictions of the thermophysical properties of WC are given for an extended temperature range.     

温度对环氧树脂热物性影响的研究

环氧树脂是工业生产中一种典型的高粘度流体。文章采用Hot-disk、DSC、DV-I+等仪器,研究温度对其比热容、粘度、导热系数、密度等热物性的影响。热容、粘度、导热系数等在温度的影响下都有明显的变化趋势。实验结果对高粘度流体的传热传质具有重要指导意义。     

Thermophysical Parameters of Fibre-Forming Polymer Macromolecules. A Review

In studying the statistics of molecular vibrations, it was found that the quantum statistics of molecular vibrations must be taken into consideration in the entire temperature range of the existence of polymers in the solid state. It was shown that two vibrations of the carbon skeleton make the basic contribution to the thermophysical parameters of the molecules; their frequencies and vibrational level population were determined. The concentration of regular sequences of conformers in the amorphous regions of polymers was determined. The thermal and quantum expansion of the carbon skeleton of the molecules was measured.     

Thermophysical Properties of Carbon-Carbon Materials Based on Graphite Foam

Refractories and Industrial Ceramics - Low density heat-conducting carbon-carbon materials containing coke from 2.8 to 40 wt.% and with density varying in the range from 0.065 to 0.81 g/cm3 are...     

C/PyC/Si-C-N复合材料的热物理性能研究

本研究采用CVI方法制备出了以Si-C-N陶瓷为基体以热解碳为界面的碳纤维增强陶瓷基复合材料(C/PyC/Si-C-N).用热膨胀仪和激光导热仪分别测试了C/PyC/Si-C-N的热膨胀性能和热扩散性能.研究结果表明:在25～1200℃范围内,C/PyC/Si-C-N复合材料的平均热膨胀系数为0.638×106 K-1;而热扩散率则随温度的升高而减小,并与温度呈一种指数关系,常温下的热扩散率约为0.00925 cm2·s-1.     

Thermophysical Properties of Alumina Particle Reinforced Glass Matrix Composites

Alumina particles incorporated glass matrix composites, which showed good prospect to be used as coating materials for high‐temperature corrosion protection on intermetallics or titanium alloys, were prepared via pressureless sintering. With increasing alumina content, the Young's modulus, fracture strength, Vickers hardness, indentation toughness, softening point, and thermal shock resistance of the composites increased monotonically. A similar increasing trend could be found for the thermal expansion coefficient of the composites, except for an abnormal drop at small amount of incorporation, which closely correlated with the Al³⁺ dissolution into the glass matrix.     

利用T-history曲线法求解三水醋酸钠热物性

三水醋酸钠(CH3COONa·3H2O)经过添加增稠剂和成核剂后具有广阔的应用前景,而其热物性参数影响着蓄热器的设计计算。T-history曲线法(Temperature History Method)简单实用,方便快捷。经水浴实验后,求得混合材料的固态导热系数为0.77 W/(m·℃),液态导热系数为1.12 W/(m·℃),相变潜热为247.6 k J/kg,与利用差示扫描量热法(Differential Scanning Calorimetry)测得混合材料在循环过程中的相变潜热值误差维持在7.2%内,能够满足实际使用要求。     

Analysis of the Thermophysical and Chemical-Technological Properties of Mining and Processing Waste Materials

Theoretical Foundations of Chemical Engineering - Results of a system analysis of volumes and physical, chemical, granulometric, lithological, and thermophysical characteristics of waste materials...     

Calculating the Parameters of Heat Transfer between Countercurrent Flows with Variable Thermophysical Properties

A method is developed for calculating the parameters of heat transfer between heat-transfer media with highly variable properties in a countercurrent heat exchanger. It is based on a stable converging algorithm that minimizes a given functional and is similar to the shooting method for solving ordinary differential equations. Heat-transfer parameters are calculated for sub- and supercritical pressures. The calculated results are compared with observed data.     

Thermophysical and Tribological Properties of Composite Materials Reinforced with Polyoxadiazole Fibres

The effect of the technology for manufacture of a composite material on the coefficient of linear thermal expansion is examined. The low- and high-temperature extrema of the dilatometric curve are found. The effect of physicochemical transformations both in the phenol—formaldehyde binder and in the Arselon reinforcing fibre is demonstrated. The important decrease in the friction coefficient of polymer composite materials with respect to steel in reinforcement with polyoxadiazole fibre in comparison to cotton fibre is demonstrated. __________ Translated from Khimicheskie Volokna, No. 3, pp. 50–53, May–June, 2005.     

Thermophysical Properties of Multiphase Borosilicate Glass‐Ceramic Waste Forms

Multiphase borosilicate glass‐ceramics represent one candidate to contain radioactive nuclear waste separated from used nuclear fuel. In this work, the thermophysical properties from room temperature to 1273 K were investigated for four different borosilicate glass‐ceramic compositions containing waste loadings from 42 to 60 wt% to determine the sensitivity of these properties to waste loading, as‐fabricated microstructure, and potential evolutions in microstructure brought about by temperature transients. The thermal expansion, specific heat capacity, thermal diffusivity, and thermal conductivity are presented. The impact of increasing waste loading is shown to have a small but measurable effect on the thermophysical properties between the four compositions, contrasted to a much greater impact observed when transitioning from predominantly crystalline to amorphous systems. Thermal cycling below 1273 K was not found to measurably impact the thermophysical properties of the compositions investigated here.     

Production and Thermophysical Properties of BeO Ceramics with the Addition of Nanocrystalline Titanium Dioxide

Refractories and Industrial Ceramics - A slip casting method was used to produce samples of BeO-based composite ceramics with additions of 5 – 30 wt.% of nanocrystalline TiO2 powder. It was...     

Critical Properties of Hydrocarbon Systems

The main objective of this article is to provide a model for predicting critical properties of heavy and nonboiling hydrocarbon fractions. For this purpose, the methods available today are discussed. The procedures for application to complex mixtures are of empirical nature, and most of them are limited to distillates. The detailed information required for application of group contribution methods is usually not available for complex heavy mixtures. A new procedure is presented which takes up the concept of group contributions. The critical properties are predicted on the basis of the molecular weight and the double-bond equivalent (DBE). Since the DBE can be calculated from molecular weight and elemental composition, even nonboiling fractions can be characterized. The exactness of the model depends on the available analytical information.