Solubilities, Vapor Pressures, and Heat Capacities of the Water + Lithium Bromide + Lithium Nitrate + Lithium Iodide + Lithium Chloride System

The optimum mole ratio of lithium salts in the H₂O + LiBr + LiNO₃ + LiI + LiCl system was experimentally determined to be LiBr : LiNO₃ : LiI : LiCl = 5 : 1 : 1 : 2. The solubilities were measured at temperatures from 252.02 to 336.75 K. Regression equations on the solubility data were obtained with a least-squares method. Average absolute deviations of the calculated values from the experimental data were 0.15% at temperatures <285.18 K and 0.05% at temperatures 285.18 K. The vapor pressures were measured at concentrations ranging from 50.0 to 70.0 mass% and at temperatures from 330.13 to 434.88 K. The experimental data were correlated with an Antoine-type equation, and the average absolute deviation of the calculated values from the experimental data was 2.25%. The heat capacities were measured at concentrations from 50.0 to 65.0 mass% and temperatures from 298.15 to 328.15 K. The average absolute deviation of the values calculated by the regression equation from the experimental data was 0.24%.     

Design of a high-pressure ebulliometer,with vapor-liquid equilibrium results for the systems CHF2 Cl + CF3 CH3 and CF3 CH2 F + CH2F2

We describe the design and operation of a new high-pressure metal ebulliometer which can operate at pressures to at least 3 MPa in the range 220–400 K. Infinite-dilution activity coefficients are presented for the system CHF₂Cl + CF₃-CH, at 275 K and for the system CF₃-CH₂F + CH₂F₂, at 260, 230, and 300 K. The Wilson activity coellicient model and a virial coefficient model are applied to these systems, and the phase equilibrium conditions are calculated. The results are shown to agree well with predicted and with published measured values. The excess enthalpy is calculated and compared with results from a Peng Robinson equation of state. Vapor densities on the dew curves are given.     

Phase equilibrium and critical lines in n-pentane + water and n-hexane + water systems

Results are given of experimental investigation of the thermal properties of n-pentane + water and n-hexane + water binary systems in the temperature range from 300 to 680 K at pressures up to 60 MPa in a wide density range. Measurements are performed for several values of concentration. The investigations cover the region of liquid-liquid, liquid-vapor, and gas-gas phase equilibria and extend to the homogeneous region. Lines of phase equilibrium and critical lines of these systems are obtained.     

Solubilities and vapor pressures of the lithium bromide+calcium nitrate+water system

Solubilities and vapor pressures of the lithium bromide+calcium nitrate+water system [LiBr/Ca(NO₃)₂ mass ratio=1.0] were measured in various absorbent (lithium bromide+calcium nitrate) concentration and temperature ranges. Solubilities were measured by a visual polythermal method in the temperature range from 282.55 to 343.45 K and the experimental values were correlated with two least-squares regression equations as a function of temperature. The average absolute deviation between the experimental and the calculated solubilities was 0.23%. Vapor pressures were measured by the boiling point method in the temperature range from 334.65 to 385.85 K and in the absorbent concentration range from 44.9 to 70.3 mass%. The experimental values were correlated with an Antoine-type equation and the overall average absolute deviation was found to be 1.06%.     

Vapor Pressure of the 1,1,1,2-Tetrafluoroethane (R-134a) + Polyalkylene Glycol System

Vapor pressures of the 1,1,1,2-tetrafluoroethane + polyalkylene glycol system were obtained at 72 points over the temperature range from 253.15 to 333.15 K at 10 K intervals and the composition range from 0 to 90 mass % polyalkylene glycol. It was found that below 273.15 K, the effect of the polyalkylene glycol on the vapor pressure was negligible up to 30 mass % polyalkylene glycol. The vapor pressure of the 1,1,1,2-tetrafluoroethane + polyalkylene glycol system decreased as the concentration of polyalkylene glycol increased. Raoults model and Flory–Huggins model were used for data reduction. Raoults model gave reasonable predictions for the vapor pressure of the system below 30 mass % polyalkylene glycol. The Flory–Huggins model gave reasonable predictions for the vapor pressure over the complete composition range. An empirical vapor pressure equation was obtained in terms of temperature and mass fraction polyalkylene glycol. The empirical equation was the most convenient way to calculate the vapor pressure.     

Transport properties of nonelectrolyte liquid mixtures—VII. Viscosity coefficients for isooctane and for equimolar mixtures of isooctane + n-octane and isooctane + n-dodecane from 25 to 100°C at pressures up to 500 MPa or to the freezing pressure

Changes in the high-pressure self-centering falling-body viscometer system, and the new automated data logging system, are described. Viscosity coefficient measurements made with an estimated accuracy of ± 2 % are reported for isooctane and for equimolar mixtures of isooctane + n-octane and isooctane + n-dodecane at 25, 50, 75, and 100°C at pressures up to 500 MPa or to the freezing pressure. The pressure dependence of the results is found to be represented equally well by the recent equation of Makita and by a free-volume form of equation. The Grunberg and Nissan equation gives a good fit to the mixture viscosity coefficient data.     

Solid-liquid phase equilibria of benzene + 2-methyl-2-propanol system under high pressures

Solid-liquid phase equilibria of the benzene + 2-methyl-2-propanol system have been investigated at temperatures from 278 to 323 K and pressures up to 300 MPa using a high-pressure optical vessel. The uncertainties of the measurements of temperature, pressure and composition are within ±0.1 K, ±0.5 MPa, and ±0.001 mole fraction, respectively. The freezing pressure at a constant composition increases monotonously with pressure. The eutectic point shifts to a higher temperature and benzene-rich composition with increasing pressure. In order to describe the pressure-temperature-composition relation of high-pressure solid-liquid phase equilibria, a new simple equation has been proposed as follows:

Study on Isochoric Specific Heat Capacity of Liquid R-410A and HFE-347pcf2

The isochoric heat capacity (c _v ) of R-410A [a mixture of 49.81 mass% difluoromethane (HFC-32) + 50.19 mass% pentafluoroethane (HFC-125)] and 1,1,2,2-tetrafluoroethyl-2,2,2-trifluoroethylether (HFE-347pcf2) was measured at temperatures from 277 K to 400 K and at pressures up to 30 MPa. The reported density measurements for R-410A and HFE-347pcf2 are in the single-phase region and cover a density range above 0.92 g·cm^?3 and 1.33 g·cm^?3, respectively. The measured data of R-410A are compared with data reported by other researchers. Also, the measured data of R-410A are examined with an available equation of state. As a result, it is found that the present c _v data for R-410A agree well with those by other researchers and the calculated values with the equation of state in the measurement range except near the critical isochore.     

Effect of pressure on the solid-liquid phase equilibria of (carbon tetrachloride + p-xylene) and (carbon tetrachloride+benzene) systems

Solid-liquid phase equilibria of the carbon tetrachloride + p-xylene and the carbon tetrachloride+benzene systems have been investigated at temperatures from 278 to 323 K and pressures up to 500 MPa using a high-pressure optical vessel. The uncertainties in the measurements of temperature, pressure, and composition are within ±0.1 K, ±0.5 MPa, and ±0.001 mole fraction, respectively. In the former system, which has an intermolecular compound with a congruent melting point, the freezing temperature at a constant composition increases monotonously with increasing pressure. The two eutectic points of this system shift to higher temperatures and richer compositions of the compound with increasing pressure. In the latter system, which has two intermolecular compounds with incongruent melting points, the one compound disappears under the present experimental conditions and the incongruent melting point of the other compound changes to the congruent melting point under high pressures. The solid-liquid coexistence curves of these systems can be correlated satisfactorily by the equation previously proposed.     

Optical and electrical properties of ZnGa2O4/Mn2+ powder electroluminescent device

We developed a powder electroluminescent device using ZnGa₂O₄/Mn²⁺ phosphor with particle size of 2 μm. Optical and electrical properties of powder electroluminescent device were investigated. This device emits green color of 505 nm with a half width of 25 nm. The green emission occurs at the falling edge of applied voltage. The origin of green color is explained in terms of the energy transfer from hot carriers to Mn²⁺ centers via self-activated Ga–O centers. The relationship between luminance (L)-applied voltages (V) matches well-known equation of L=L_oexp(−bV^−1/2). Luminance is linearly dependent on frequency due to the increase of excitation chances of host lattice or Mn²⁺ ions with increasing frequency. The emission color of ZnGa₂O₄/Mn²⁺-based EL device is not influenced by both frequency and applied voltage. The luminance and luminous efficiency at sinusoidal voltage of 180 V and frequency of 400 Hz are about 1.0 cd/m² and 15 lm/W, respectively. Thus, our fabricated powder electroluminescent device with ZnGa₂O₄/Mn²⁺ phosphor shows chemical stability along longer lifetime in comparison with the existing ZnS powder electroluminescent device.     

Solid-liquid phase equilibria of benzene + cyclohexane system under high pressures

Solid-liquid phase equilibria of the benzene + cyclohexane system have been investigated experimentally at temperatures from 278 to 323 K and pressures up to 500 MPa using a newly designed optical vessel. The uncertainties of the measurements of temperature, pressure, and composition are within ±0.1 K, ±0.5 MPa, and ±0.001 mole fraction, respectively. The solid-liquid equilibrium pressure at a constant composition increases almost linearly with increasin temperature. The eutectic point shifts to a higher temperature and to a benzenerich composition with increasing pressure. This trend is found to agree with the direction predicted by the van Laar equation. The solid-liquid coexistence curves can be expressed by the Wilson equation with a mean deviation of 0.007 and a maximum deviation of 0.029 in mole fraction.     

Superconductivity of FeSr2YCu2O6+δ

Resistivity measurements of polycrystalline FeSr₂YCu₂O_6+δ under magnetic fields up to 160 kOe were made to study the superconductivity of FeSr₂YCu₂O_6+δ in detail. The resistivity began to decrease at 64 K and dropped to zero at 38 K under zero magnetic field. The superconductivity in inter grain was affected by the magnetic field and zero resistivity was observed below 12 K under H=10 kOe. Above 20 kOe, the superconductivity in the grain began to be affected. Even with increasing magnetic field up to 160 kOe, zero resistivity was persisted below 10 K.     

Bubble-point pressures and liquid densities of binary R-125 + R-143a System

Bubble-point pressures and saturated-liquid densities of the binary R-135 (pentafuoroethane) + R- 143a ( 1, 1, 1-trifluoroethane) system have been measured for several compositions at temperatures from 280 to 330 K by means of a magnetic densimeter coupled with a variable-volume cell mounted with a metallic bellows. The experimental uncertainties of the temperature, pressure. and density measurements and the composition determination were estimated to be within ±15 mK, ±13 k Pa, ±0.2%, and ±0.1 wt%, respectively. The purities of the samples used throughout the measurements are 99.98 wt% for R-125 and 99.0 mol % for R- 143a. Based on the present data, the thermodynamic behavior of the vapor-liquid equilibria of this binary refrigerant mixture has been evaluated by using the Peng-Robinson equation for the bubble-point pressures, and the modified Hankinson-Brobst-Thomson equation for the saturated-liquid densities. This was done to identify the optimized binary interaction parameters.Paper presented at the Twelfth Symposium on Thermophysical Properties, June 19–24, 1994, Boulder, Colorado, U.S.A.     

The equation of state for solutions of the sunflower oil+isomerhexane system

The article presents the results of an experimental investigation into the density of solutions of the sunflower oil+isomerhexane system (from 23 to 75%) at temperatures of from 293 to 450 K and pressures of from 0.101 to 98.1 MPa. An equation of state is obtained.K. Sh. Dzhuraev Dushanbe State Pedagogical University, Tadzhikistan. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 68, No. 6, pp. 914–916, November–December 1996.     

Bubble-Point Pressures and Saturated- and Compressed-Liquid Densities of the Binary R-125 + R-143a System

Bubble-point pressures and saturated- and compressed-liquid densities of the binary R-125 (pentafluoroethane) + R-143a (1,1,1 -trifluoroethane) system have been measured for several compositions at temperatures from 280 to 330 K by means of a magnetic densimeter coupled with a variable-volume cell mounted with a metallic bellows. The experimental uncertainties of the temperature, pressure, density, and composition were estimated to be within ±10mK, ± 12 kPa, ±0.2%, and ±0.2mass%, respectively. The purities of the samples used throughout the measurements are 99.96 area% for R-125 and 99.94 area% for R-143a. Based on these measurements, the thermodynamic behavior of the vapor-liquid equilibria of this binary refrigerant mixture has been represented using the Peng–Robinson equation for the bubble-point pressures, a correlation for the saturated-liquid densities, and an equation of state for the compressed-liquid densities.     

Characterization of various Eu2+ sites in Ca2SiO4:Eu2+ and Ba2SiO4:Eu2+ by high-pressure spectroscopy

Photoluminescence of Ba₂SiO₄ and Ca₂SiO₄ activated with Eu²⁺ was investigated at various temperatures (from 10 K to 300 K) and pressures (from ambient to 200 kbar). At ambient pressure and room temperature, under UV excitation both phosphors yielded a green emission band with maxima at 505 nm and 510 nm for Ba₂SiO₄ and Ca₂SiO₄, respectively. The energies of these bands depended on pressure; the pressure shifts were ?12:55 cm^?1/kbar for Ba₂SiO₄:Eu²⁺; and ?5:59 cm^?1/kbar for Ca₂SiO₄:Eu²⁺. In the case of Ca₂SiO₄:Eu²⁺, we observed additional broadband emission at lower energies with a maximum at 610 nm (orange band). The orange and green emission in Ca₂SiO₄:Eu²⁺ had different excitation spectra: the green band could be excited at wavelengths shorter than 470 nm, whereas the orange band — at wavelengths shorter than 520 nm. The pressure caused a red shift of orange emission of 7.83 cm^?1/kbar. The emission peaked at 510 nm was attributed to the 4f⁶5d→4f⁷(⁸S₇₌₂) transition of Eu²⁺ in the β — Ca₂SiO₄:Eu²⁺ phase, whereas the emission peaked at 610 nm — to the γ — Ca₂SiO₄:Eu²⁺ phase. The emission of Ba₂SiO₄:Eu²⁺ peaked at 505 nm was attributed to the 4f⁶5d→ 4f⁷(⁸S_7/2) transition of Eu²⁺ in the β — Ba₂SiO₄ phase.     

NpO 2 + -UO 2 2+ cation-cation interaction in NaCl-KCl-CsCl and LiCl-KCl-CsCl eutectic melts

Absorption spectra of the NpO ₂ ⁺ ion in UO ₂ ²⁺ -containing NaCl-KCl-CsCl (0.300:0.245:0.455) and LiCl-KCl-CsCl (0.575:0.165:0.260) eutectic melts in the region of the 5f-5f transitions, 700–2000 nm, were studied at 650 and 500°C, respectively. Processing of the spectra allowed the previously discovered phenomenon, cation-cation interaction of actinides in melts, to be interpreted for the first time in terms of the mass action law. It was shown that, at the concentrations of the interacting components studied (C _Np = 0.2 M and C _U = 0.1–2 M), a 1: 1 NpO ₂ ⁺ ·UO ₂ ²⁺ cation-cation complex is formed. Its concentration stability constant was estimated at 0.06(6) and 0.11 1 mol^?1 for the NaCl-KCl-CsCl and LiCl-KCl-CsCl systems, respectively.     

Thermal Property Measurements and Enthalpy Calculation of the Lithium Bromide+Lithium Iodide+1,3-Propanediol+Water System

The lithium bromide+lithium iodide+1,3-propanediol+water [LiBr/LiI mole ratio=4 and (LiBr+LiI)/HO(CH₂)₃ OH mass ratio=4] solution is being considered as a potential working fluid for an absorption chiller. Heat capacities at four temperatures, 283.15, 298.15, 313.15, and 333.15 K, were measured in the range from 50 to 70 mass%. In addition, the differential heats of dilution at 298.15 K were measured in the range from 45.3 to 71.8 mass%. Each individual data set was correlated with a proper regression equation with a high accuracy. A new enthalpy calculation method for the working fluids containing organics was proposed. The calculation method correlated the heat capacity (at various temperatures and concentrations) and the differential heat of dilution (at ambient temperature and various concentrations). The present method was applied for the construction of enthalpy–concentration (H–T–X) diagrams with high confidence.     

Up-conversion luminescence properties of Y2O2S:Yb3+,Er3+ nanophosphors

Up-converting yttrium oxysulfide nanomaterials doped with ytterbium and erbium (Y₂O₂S:Yb³⁺,Er³⁺) were prepared with the flux method. The precursor oxide materials were prepared using the combustion synthesis. The morphology of the oxysulfides was characterized with transmission electron microscopy (TEM). The particle size distribution was 10–110 nm, depending on the heating temperature. According to the X-ray powder diffraction (XPD), the crystal structure was found hexagonal and the particle sizes estimated with the Scherrer equation agreeded with the TEM images. Upon the 970 nm infrared (IR) laser excitation, the materials yield moderate green ((²H_11/2, ⁴S_3/2) → ⁴I_15/2 transition) and strong red (⁴F_9/2 → ⁴I_15/2) luminescence. The green luminescence was enhanced with respect to the red one by an increase in both the crystallite size and erbium concentration due to the cross-relaxation (CR) processes. The most intense up-conversion luminescence was achieved with x_Yb and x_Er equal to 0.10 and 0.005, respectively. Above these concentrations, concentration quenching occurred.