Saturated Humidity, Entropy, and Enthalpy for the Nitrogen-Water System at Elevated Temperatures and Pressures

A model is used to calculate saturated thermophysical properties (humidity, entropy, and enthalpy) of a nitrogen-water mixture at elevated temperatures and pressures. In the model, a modified Redlich–Kwong equation of state is used to calculate fugacity coefficients for the vapor phase, and the liquid phase follows Henry's law. The model has been investigated by comparing the calculated results with the available experimental data. The comparison shows that the model can be used to calculate saturated thermodynamic properties for the nitrogen-water mixture reliably up to 523.15 K and 300 bar.     

金刚石在不同温度和压力下的强度及断裂

本文利用软压头技术,测定了人造金刚石和天然金刚石在不同温度下的强度．在室温,利用软压头技术测得的金刚石强度与常规方法所得的结果一致．高温条件下,金刚石的断裂行为取决于试验温度、平均接触压力及摩擦系数.观察到两种类型的裂纹,｛111｝解理裂纹与低温、高压力有关.而应变诱发裂纹产生于｛110｝面上,与高温、低应力有关.根据试验结果,提出了金刚石在不同温度和应力状态下的强度图．     

Raman Studies of Vanadates at Low Temperatures and High Pressures

The spin and orbital ordering have been examined for high-quality SmVO₃ polycrystalline compound using Raman spectroscopy. Measurements were obtained on individual microcrystallites in the approximate y(zz)y and y(xx)y scattering configurations at low temperatures (down to 20 K) and high pressures (up to 2.75 GPa). At room temperature and ambient pressure only the A_g phonons have been observed in both polarizations examined. The decrease of temperature leads to the appearance of extra peaks in the Raman spectra related to the magnetic and structural transitions that occur in the system. We present evidence of a coexistence of the monoclinic and orthorhombic phases accompanied with the coexistence of the G- and C-type OO phases for temperatures below 100 K. However, no sign of any structural transition has been observed in the high pressure Raman spectra (1.87<P<2.75 GPa) at low temperatures T≥80 K, indicating that SmVO₃ remains orthorhombic, at least down to 80 K.     

Mechanochemical Synthesis of Intermetallic Hydrides at Elevated Hydrogen Pressures

An apparatus is described for producing gas pressures of up to 10 MPa in the grinding vessels of a planetary mill. Mechanochemical reactions are carried out for the first time at gas pressures above 1 MPa. A novel approach to the synthesis of intermetallic hydrides is proposed which involves mechanical activation of a metal mixture at a high hydrogen pressure. Using this approach, two new hydrides are synthesized: Mg₂NiH₆ and a magnesium copper hydride with the approximate composition MgCuH₂.     

Interface Interactions of Dissimilar Materials at Elevated Temperatures

This paper reviews some of the chemical interactions that occurred at the interface of ceramic/molten metal liquids. Control of interfacial reactions between dissimilar materials is an important issue in numerous technological applications, such as brazing of ceramics to metals, design of ceramic–metal composites, coatings of ceramics on metal substrates, and development of crucibles for melting of refractory metals. In ceramic/metal systems, wetting of the ceramic surface by the liquid metal is typically accompanied to some extent by interfacial reactions. The chemical incompatibility between the metal and non‐metallic materials can result in the formation of undesirable phases, due to the chemical and metallurgical reactions that take place during processing or in service. There is a need, therefore, to characterize the governing factors and reaction pathways at these interfaces. So, when the reaction products obtained during interdiffusion processing are not favorable, the diffusion pathway can be modified to control their formation.     

Calorimetric Study of Rubidium Hexafluoroarsenate at Elevated Temperatures

The heat capacity of rubidium hexafluoroarsenate, RbAsF₆, was measured from 300 to 700 K by differential scanning calorimetry. The results indicate that the structural transformation from the rhombohedral to the cubic phase occurs in the range 305–436 K through an intermediate stable phase and reaches isothermal completion in a narrow temperature range of 407–409 K. The enthalpy of the transformation is 10.90 ± 0.03 kJ/mol, and its entropy is 26.39 ± 0.08 J/(K mol) = Rln24, which suggests that this structural transition is of the order–disorder type. The heat capacity data are used to evaluate the thermodynamic properties of RbAsF₆ in the range 300–700 K.     

Experimental Investigation of the Density of Caproates at High Temperatures and Pressures

Results of experiments on investigating the density of caproates as a function of temperature and pressure are given. The equation of state of caproates in the liquid phase is composed on the basis of the P––TT data obtained.     

Phonon Modes in CMR Manganites at Elevated Temperatures

Phonon modes of the colossal magnetoresistance manganites La_0.7Ca_0.3MnO₃ and La_0.8Li_0.2MnO₃ have been investigated by far-infrared (100–700 cm^–1) reflectivity spectroscopy at elevated temperatures (300–800 K). The three principal optical phonons all move systematically to lower frequency as temperature increases, in accordance with a Grüneisen relationship. The La(Ca,Li)–(MnO₃) vibration (170 cm^–1) varies with cation mass as expected. The Mn–O stretching mode (580 cm^–1) has a higher frequency in the Li-doped compound than in the Ca-doped, whereas the O–Mn–O bending mode )340 cm^–1) occurs at the same frequency in each, demonstrating that the cation strongly influences the Mn–O– length but not the bond angle.     

Search for New High-Tc Superconductors at Elevated Temperatures

Journal of Superconductivity and Novel Magnetism - One of the long-standing challenges in experimental superconductivity are the sustained efforts to achieve stable and cheap superconducting...     

Thermal Expansion and Shrinkage of Unidirectional Composites at Elevated Temperatures

Strength of Materials - The model of multiphase media analyzes the effectiveness of describing thermal expansion and shrinkage of unidirectional polymer composites at their uniform heating by...     

细颗粒掺杂石墨高温热导率的研究

通过球磨分散方法制备了具有优良热机械性能的细颗粒掺杂石墨.该掺杂石墨材料具有致密的结构,细小的碳化物颗粒均匀分布在石墨基体中.研究表明;球磨分散方法制备的掺杂石墨比常规方法制备的石墨材料具有更优良的高温热性能以及抗热震性能.同时,本文对材料的性能与其微观结构进行关联.     

Mechanisms of Fatigue in Cemented Carbides at Elevated Temperatures

Cemented carbides are mainly used as cutting tools in various fields of application. In nearly all industrial uses they have to resist wear and concurrent complex thermomechanical loading, often including alternating mechanical loads at high temperatures. It has been shown that cemented carbides suffer lifetime‐limiting fatigue under cyclic loads at 25 °C caused by subcritical crack growth. Present investigations show that strong, temperature‐dependent fatigue effects occur in cemented carbides at elevated temperatures. TEM investigations revealed temperature‐dependent processes that are responsible for the changes in the fatigue behavior: at low temperatures a phase transformation of the Co‐binder phase and at higher temperatures oxidation in the cracks and brittle–ductile transitions of cubic carbides.     

Adsorption Systems of Natural Gas Storage and Transportation at Low Pressures and Temperatures

Questions of the development and investigation of thermally regulated natural gas storage and transportation systems of a new type using sorbents are considered. The results of fullscale tests of the adsorption compressed gas cylinder system for the GAZ53 truck are described.     

High Strain Rate Deformation Behavior of Zirconium at Elevated Temperatures

High temperature mechanical behaviors of zirconium at high strain rate of 103 s-1 were studied by split Hopkinson pressure bar (SHPB).The influences of strain rate and temperature on the micro-structural evolution,as well as the occurrence of shear localization and subsequent fracture,were also investigated.It s found that the compressive stress-strain response depends sensitively on the applied strain rate and test temperature.Micro-structural observations revealed that the density of the twinning grains r...     

FeAl金属间化合物的高温变形行为

对Ｆｅ－３６．５ａｔ％Ａｌ金属间化合物进行了高温拉伸试验研究。结果表明，变形温度在６００－１０００℃范围内，这种ＦｅＡｌ合金的延伸率随温度的升高不断增加，在１０００℃时延伸率最高，达１１５％。经透射电镜分析，该合金高温变形后不仅有大量的滑移位错线，而且有一定数量的位错绻线存在。     

Viscosity of Imidazolium-Based Ionic Liquids at Elevated Pressures: Cation and Anion Effects

The viscosity of imidazolium-based ionic liquids with four different cations and three different anions was measured to pressures of 126 MPa and at three temperatures (298.15 K, 323.15 K, and 343.15 K). The high-pressure viscosity of 1-ethyl-3-methylimidazolium ([EMIm]), 1-n-hexyl-3-methylimidazolium ([HMIm]), and 1-n-decyl-3-methylimidazolium ([DMIm]) cations with a common anion, bis(trifluoromethylsulfonyl)imide ([Tf₂N]), was measured to determine the alkyl-chain length effect of the cation. An increase in the alkyl-chain length increased the viscosity at elevated pressures. [DMIm] exhibited a larger nonlinear increase with pressure over the shorter alkyl substituents. Anion effects were investigated with [HMIm] as a common cation and anions of [Tf₂N], hexafluorophosphate ([PF₆]), and tetrafluoroborate ([BF₄]). [HMIm][PF₆], with the highest viscosity, demonstrated a very nonlinear pressure dependence even at relatively moderate pressures (to 30 MPa), similar to the results for [BMIm][PF₆]. A combined Litovitz and Tait equation was utilized to describe the viscosity of the ionic liquids with pressure and temperature and demonstrated good correlation with the experimental data.