Equation-of-state measurements for crude oils at pressures up to 1 GPa

Equation-of-state measurements of two crude oils with different compositions and viscosity were performed at room temperature in the pressure range 0<P<1.0 GPa. We found large compressibilities and a strong dependence of the compressibility on oil content and viscosity. The bulk modulus changed with pressure from 2.0 to 12.1 GPa for one oil and from 1.3 to 9.5 GPa for the other. We discuss the possibility of detecting phase transitions in the region under investigation. The Tait and Murnaghan equations of state were fitted to the data, and residuals are presented.     

Measurement of the compressibility and sound velocity of neon up to 1 GPa

The density of neon has been determined at 298.15 K as a function of pressure from 80 MPa to 1 GPa. The precision of the measurements is 0.03%, while the estimated absolute accuracy is between 0.05 and 0.09%. The sound velocity has been measured between 98 and 298 K with intervals of 25 K and at pressures up to 1 GPa, with an accuracy generally better than 0.06%. The adiabatic compressibility and the ratio of the specific heats are calculated by combining pVT with velocity-of-sound data at 298 K. Several equations of state are fitted to the density data at 298.15 K.Paper presented at the Tenth Symposium on Thermophysical Properties, June 20–23, 1988, Gaithersburg, Maryland, U.S.A.     

Compressibility and sound velocity measurements on N2 up to 1 GPa

A gas expansion technique has been used to determine the pVT properties of N₂ up to 1 GPa at 298.15 K, with an accuracy of 0.08% in density, 1 mK in temperature, and 0.05%+0.2 MPa in pressure. The sound velocity has been measured by a phase-comparison pulse-echo technique between 123 and 298 K at intervals of 25 K and at pressures up to 1 GPa, with an accuracy of better than 0.02% in sound velocity, 10 mK in temperature, and 0.05%+0.2 MPa in pressure. An equation of state is presented that correlates the density data over the wide pressure range of 36–1000 MPa with maximum deviations between the calculated and the experimental densities of less than 0.05%.     

Measurement of the compressibility and sound velocity of helium up to 1 GPa

By using a gas expansion technique, the density of helium has been determined at 298.15 K as a function of pressure from 100 MPa to 1 GPa. The precision of the measurements is 0.02%, while the estimated absolute accuracy is about 0.08%. The sound velocity has been measured by a phase-comparison pulseecho technique between 98 and 298 K with intervals of 25 K and at pressures up to 1 GPa, with an accuracy generally better than 0.04%. By combining pVT with velocity-of-sound data at 298 K, the adiabatic compressibility and the ratio of the specific heats are calculated. The experimental sound velocities are compared with the values, predicted from an equation of state as proposed by Hansen.     

Thermoelectric power of YBa2Cu3O7−δ under pressure up to 9 GPa

Thermoelectric power (TEP) of two YBa₂Cu₃O_7−δ compounds (with δ=0·17 and 0·21) was measured as a function of quasi-hydrostatic pressure up to 9GPa at 300K on samples with low porosity. In both cases TEP decreases with increasing pressure, at a rate ∼ 0·8 μVK⁻¹/GPa. The data obtained under hydrostatic pressure up to 3 GPa are in good agreement with those under quasi-hydrostatic pressure. The TEP of both compositions is found to decrease linearly at a rate 0·8 μVK⁻¹/GPa above 1·5 GPa.     

Thermodynamic Properties of Air from 60 to 2000 K at Pressures up to 2000 MPa

A thermodynamic property formulation for standard dry air based upon experimental P––T, heat capacity, and speed of sound data and predicted values, which extends the range of prior formulations to higher pressures and temperatures, is presented. This formulation is valid for temperatures from the solidification temperature at the bubble point curve (59.75 K) to 2000 K at pressures up to 2000 MPa. In the absence of experimental air data above 873 K and 70 MPa, air properties were predicted from nitrogen data. These values were included in the fit to extend the range of the fundamental equation. Experimental shock tube measurements ensure reasonable extrapolated properties up to temperatures and pressures of 5000 K and 28 GPa. In the range from the solidification point to 873 K at pressures to 70 MPa, the estimated uncertainty of density values calculated with the fundamental equation for the vapor is ±0.1%. The uncertainty in calculated liquid densities is ±0.2%. The estimated uncertainty of calculated heat capacities is ±1% and that for calculated speed of sound values is ±0.2%. At temperatures above 873 K and 70 MPa, the estimated uncertainty of calculated density values is ±0.5%, increasing to ±1% at 2000 K and 2000 MPa.     

Pressure effects on the Raman spectra of 3-deutero-ammonia,lattica dynamics and vibrons up to 40 GPa

High-pressure Raman studies up to 40 GPa have been made on solid ND₃ at room temperature. Features of external and internal modes are compared to that of solid NH₃ and mode assignments are proposed in solid phase IV (p3.8 GPa). In contrast with NH₃, which transforms to a cubie phase at 15 GPa, solid IV ND₃ was observed to be stable up to 40 GPa, the upper limit of the present investigation. It is concluded that bond symmetrization in ND₃ will occur above that of NH₃.Paper presented at the Tenth Symposium on Thermophysical Properties, June 20–23, 1988, Gaithersburg, Maryland, U.S.A.     

Thermal conductivity of benzene and cyclohexane in the temperature range 36–90°C at pressures up to 0.33 GPa

The paper describes new, accurate measurements of the thermal conductivity of benzene and cyclohexane in the temperature range 36–88°C and at pressures up to 0.33 GPa. The experimental data have an estimated accuracy of ±0.3%. The density dependence of the thermal conductivity for both liquids is well represented by a simple power law relationship which is almost independent of temperature. The connection of this correlation to one previously established for normal alkanes is examined.     

Measurements of the compressibility and sound velocity in methane up to 1 GPa,revisited

New density measurements of methane (CH₄) at 298.15 K up to 1 GPa are reported. The precision of the measurements is 0.03%, while the estimated accuracy is between 0.05 and 0.1%. Velocities of sound have been remeasured between 148.15 and 298.15 K at intervals of 25 K and at pressures up to 1 GPa, with an estimated accuracy of 0.12% at 100 M Pa, 0.10% at 150 MPa, and 0.08% above 150 MPa. Comparisons with experimental results and equations of state of other workers are presented. The isothermal and the adiabatic compressibility and the ratio of specific heats have been calculated at 298.15 K.     

热处理对金属薄膜压阻灵敏度的影响

采用磁控溅射法制备锰铜薄膜,溅射和真空蒸发法制备镱薄膜.对热处理前后薄膜的电学性能、微观形貌和结构进行了表征,并采用轻气炮和对顶砧装置对薄膜传感器进行了压阻性能测试,结果表明热处理后薄膜的压阻系数有很大提高.SEM和XRD的分析表明,压阻系数的提高是由于热处理后薄膜晶粒长大、缺陷减少、电阻率下降所致.敏感薄膜的电阻率与传感器的灵敏度直接相关.热处理后,薄膜压阻计的灵敏度已接近箔式传感器的水平,热处理是提高薄膜压阻计灵敏度的有效手段.     

Resistivity and Hall Coefficient of Zinc Diarsenide at Hydrostatic Pressures of up to 9 GPa

The electrical properties of ZnAs₂ single crystals were measured along the [001] direction in the pressure range from 0 to 9 GPa. The electrical resistivity of the crystals was found to decrease by one order of magnitude as the pressure increases from 0 to 7 GPa, without significant changes at higher pressures. The Hall coefficient drops by two orders of magnitude as the pressure increases from 0 to 7 GPa and remains constant in the range from 7 to 9 GPa.     

Velocity of sound in supercritical water up to 700°C and 300 MPa

The velocity of sound in water was measured up to 700°C and 300 MPa. A classical pulse method has been used. The frequency was typically 5 MHz. The mean accuracy of the data is 0.5% of the velocity. The greatest error in velocity is due to the uncertainty in the temperature measurements at high pressures.     

差分飞行时间法精密测量高压液体声速的研究

基于差分飞行时间法建立了一套可直接测量高压液体声速的实验装置,自主设计和研制了双超声腔体,建立了精密声速测量系统、高压液体充注系统、精密压力和温度测量系统以及数据采集和分析系统。在此系统上,开展了303～353K,压力高至10MPa的纯水声速测量研究,声速测量相对标准不确定度为0.018% (k=1),纯水声速测量结果与国际标准状态方程及已有实验数据具有良好的一致性。研究成果为后续开展其他液体如海水、新型燃料等工质的精密声速测量奠定了基础。     

Accurate measurements of the PVT properties of methane from —20 to 150 °C and to 690 MPa

The density of methane has been measured in the temperature range -20 to 150°C and in the pressure range 130–690 MPa, using a substitution method. The overall uncertainty in the results of 0.03% at the 95% confidence level. The data are presented in the form of a modified Benedict-Webb-Rubin equation of state and are compared with the results of other workers.     

Thermal conductivity of oct-1-ene in the temperature range 307 to 360 K at pressures up to 0.5 GPa

New measurements of the thermal conductivity of liquid oct-1-ene in the temperature range 307 to 360 K at pressures up to 0.5 GPa have been performed. The experimental data have an estimated uncertainty of ±0.3%. Within the limited range of pressures for which data for the density of the liquid are available, it has proved possible to represent all of the thermal conductivity results by means of a single equation with just one temperature-dependent parameter. This representation is based on the ideas of the hard-sphere theory of fluids and is consistent with that employed earlier for alkanes.     

A vibrating tube flow densitometer for measurements with corrosive solutions at temperatures up to 723 K and pressures up to 40 MPa

A new version of a vibrating tube flow densitometer has been designed permitting measurements of density differences between two fluids in the temperature range from 298 to 723 K and at pressures up to 40 MPa. The instrument is equipped with a Pt/Rh20 vibrating tube (1.6-mm o.d.) and a Pt/Rh10 transporting tube (1.2-mm o.d.) permitting measurements with highly corrosive liquids. The period of oscillation of the tube is about 7.5 ms, with a typical stability better than 10⁻⁴% over about a 1-h period over the entire temperature interval. The calibration constantK at room temperature is about 530 kg·m⁻³·ms⁻², with a temperature coefficient of approximately −0.13kg·m⁻³·ms⁻²·K⁻¹, and is practically pressure independent. It can be determined by calibration with a reproducibility generally better than 0.1%. The instrument was tested with NaCl(aq) solutions in the temperature range from 373 to 690 K for density differences between sample and reference liquid ranging from 200 to 2 kg·m⁻³; the corresponding errors are believed to be below 0.3 and 5%, respectively. A highly automated temperature control maintains the temperature of the tube stable to within ±0.02 K.     

Determination of oxygen to metal ratio of U-Pu mixed oxides by x-ray diffraction

The possibility of measuring the oxygen-metal ratio (O/M) of U-Pu mixed oxides by x-ray diffraction technique has been explored. In single-phase U-Pu mixed oxides, the lattice parameter vs O/M plots for different plutonium concentrations are drawn by interpolation of lattice parameter values between those of UO₂, PuO₂ and Pu₂O₃. These plots are then used for determining the O/Ms of unknown samples against their experimentally measured lattice parameter values. In two-phase mixed oxides, the mole fractions of the two phases are determined from the intensities of their selected diffraction lines. The O/M of the mixed oxide is then given by the mole average of the individual O/Ms of the two phases.     

Thermal conductivity and thermal diffusivity of xylene isomers in the temperature range 308–360 K at pressures up to 0.38 GPa

New, absolute measurements of the thermal conductivity of the three xylene isomers within the temperature range 308–360 K for pressures up to 0.38 GPa are reported. In addition, for two of the isomers, m-xylene and p-xylene, it has been possible to measure the thermal diffusivity simultaneously within the same range of conditions. The accuracy of the thermal conductivity data reported is one of ±0.3%, whereas for the thermal diffusivity the estimated accuracy is ±6%. It is found that the density dependence of the thermal conductivity for all of the xylenes can be well represented by one equation based on a rigid-sphere model in the same way that has proved successful for normal alkanes. The thermal diffusivity data have been employed to derive heat capacities for the xylenes over a range of pressures.     

Magnetic and structural phase transitions of MnBi under high magnetic fields

Abstract

High-field x-ray diffraction and magnetization measurements and differential thermal analysis (DTA) were carried out for polycrystalline MnBi with an NiAs-type hexagonal structure to investigate its magnetic and structural phase transitions. The lattice parameter a rapidly decreases below the spin reorientation temperature T_SR(=90 K) in a zero magnetic field. The parameter c decreases gradually with decreasing temperature and exhibits an anomaly in the vicinity of T_SR. By applying a magnetic field of 5 T, the parameter a increases by ～0.05% when T<T_SR and varies smoothly when 8≤T≤300 K. DTA data show that the magnetic phase transition temperature from the ferromagnetic state to the paramagnetic state increases linearly at a rate of 2 KT^?1 with increasing magnetic field up to 14 T.     

Bi_8Nb_2O_(17)材料的电传导率测定

δ-Bi2O3是性能优异的氧离子导体,但是相变制约了它的应用。本研究利用固相烧结法制备Bi8Nb2O17材料,使之在低温下仍能保持传导性能好的立方相,采用X射线衍射分析表征了该材料的组成和结构,并利用交流阻抗技术测定了材料的电导率。结果表明,这种材料从室温到832℃不发生相变,但电导率随着温度的升高有较大的提升,832℃时达6.16S·m-1。另外,不同氧分压(20kPa~91.2kPa)条件下测定电导率,发现Bi8Nb2O17材料的氧离子电导率不随氧分压而变化,700℃和800℃下分别稳定于2.30S·m-1和3.89S·m-1,表明该材料在高温环境中是一种优良的氧离子导体,具有较大的应用潜能。