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1

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An infrared spectroscopic study of lawsonite to 20 GPa (1999)

Scott, H. P. ; Williams, Q.

Springer

Physics and chemistry of minerals 26 (1999), S. 437-445

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ISSN: 1432-2021

Keywords: Key words lawsonite ; high pressure ; infrared spectroscopy ; hydrogen bonding

Source: Springer Online Journal Archives 1860-2000

Topics: Chemistry and Pharmacology , Geosciences , Physics

Notes: Abstract The infrared spectrum of CaAl2Si2O7 · H2O-lawsonite, has been characterized to pressures of 20 GPa at 300 K. Our results constrain the response to compression of the silicate tetrahedra, hydroxyl units, and water molecules in this material. The asymmetric and symmetric stretching and bending vibrations of the Si2O7 groups (at zero pressure frequencies between 600 and 1000 cm−1) increase in frequency with pressure at rates between 3.6 and 5.9 cm−1/GPa. All silicate modes appear to shift continuously with pressure to 20 GPa, although the lowest frequency stretching vibration becomes unresolvable above 18 GPa, and a splitting of the main bending vibration is observed near this pressure. The O-H stretches of the hydroxyl units exhibit a discontinuity in their mode shifts at ∼8–9 GPa, which we interpret to be produced by a pressure-induced change in hydrogen bonding. The stretching and bending vibrations of the water molecule are relatively unaffected by compression to 20 GPa, thus demonstrating that the structural cavities in which water molecules reside are relatively rigid. Significant changes in the amplitude of the O-H stretches of the hydroxyl and water units are observed at this pressure as well; nevertheless, our results demonstrate that the dominant structural units in lawsonite persist metastably at 300 K with only modest structural modifications well beyond the known stability field of this phase.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/s002690050206

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2

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Measurements of the Thermal Conductivity of HFC-125 in the Temperature Range from 300 to 515 K at Pressures up to 53 Mpa (1999)

Le Neindre, B. ; Garrabos, Y.

Springer

International journal of thermophysics 20 (1999), S. 375-399

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ISSN: 1572-9567

Keywords: coaxial cylinders ; high pressure ; refrigerants ; HFC-125 ; thermal conductivity

Source: Springer Online Journal Archives 1860-2000

Topics: Physics

Notes: Abstract Measurements of the thermal conductivity of HFC-125 that have been made by a coaxial cylinder cell operating in steady state are reported. The measurements of the thermal conductivity of HFC-125 were performed along several quasi-isotherms between 300 and 515 K in the gas phase and the liquid phase. The pressure range covered varies from 0.1 to 53 MPa. Based on the measurement of more than 600 points, an empirical equation is provided to describe the thermal conductivity outside the critical region as a function of temperature and density. A careful analysis of the various sources of error leads to an estimated uncertainty of approximately ± 1.5%.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1023/A:1022692601764

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3

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Thermodynamic Properties of Air from 60 to 2000 K at Pressures up to 2000 MPa (1999)

Panasiti, M. D. ; Lemmon, E. W. ; Penoncello, S. G. ; [et al.]

Springer

International journal of thermophysics 20 (1999), S. 217-228

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ISSN: 1572-9567

Keywords: air ; equation of state ; fundamental equation ; high pressure ; high temperature ; thermodynamic properties

Source: Springer Online Journal Archives 1860-2000

Topics: Physics

Notes: Abstract A thermodynamic property formulation for standard dry air based upon experimental P–ρ–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.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1023/A:1021450818807

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4

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Dependence of the Melting Temperature on Pressure up to 2000 Bar in Uranium Dioxide, Tungsten, and Graphite (1999)

Musella, M. ; Ronchi, C. ; Sheindlin, M.

Springer

International journal of thermophysics 20 (1999), S. 1177-1188

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ISSN: 1572-9567

Keywords: graphite ; high pressure ; laser pulse ; melting point ; tungsten ; uranium dioxide

Source: Springer Online Journal Archives 1860-2000

Topics: Physics

Notes: Abstract The melting points of uranium dioxide, tungsten, and graphite were measured as a function of the isostatic pressure up to 2000 bar (200 MPa), in a laser-heated autoclave filled with inert gas. The measured melting curves and their slopes were compared with predictions obtained from the Clausius–Clapeyron equation and existing thermochemical data of these substances. While for tungsten and graphite the results show reasonable agreement with the equilibrium thermodynamic calculations, the melting point of UO2 increases with pressure with a slope more than three times larger than expected.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1023/A:1022667206867

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5

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Melting-Point Measurements at High Static Pressures from Laser Heating Methods: Application to Uranium (1999)

Sitaud, B. ; Thévenin, Th.

Springer

International journal of thermophysics 20 (1999), S. 1189-1198

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ISSN: 1572-9567

Keywords: diamond anvil cell ; emissivity ; high pressure ; laser heating ; melting ; uranium

Source: Springer Online Journal Archives 1860-2000

Topics: Physics

Notes: Abstract Two experimental approaches dealing with the determination of melting at high static pressures are described and analyzed. With the sample squeezed inside a diamond anvil cell, high temperatures up to the solid–liquid transition are obtained using Nd:YAG laser heating. Two methods have been investigated. In the first technique, the heating is accomplished with a pulsed laser and the brief radiation variations (t〈10 ms) emitted from the sample are recorded with two high-speed infrared detectors. The melting location is defined by a plateau or changes of slope of the signals, and the temperatures are calculated by assuming a constant value of emissivity factor at the end of the transition over the studied pressure range. The second system employs a continuous laser and a two-dimensional CCD detector to measure temperatures using multispectral pyrometry. Melting is detected from criteria related either to textural change in the sample involving interference contrast under a laser illumination or to the specific variations of temperature and emissivity as a function of laser power. Thermal radiation is fitted to Planck's law with temperature and emissivity as the free parameters. Advantages and drawbacks are presented from results obtained on pure uranium.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1023/A:1022619323705

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6

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Relative Permittivity and Resistivity of Liquid HFC Refrigerants Under High Pressure (1999)

Tanaka, Y. ; Matsuo, S. ; Sotani, T. ; [et al.]

Springer

International journal of thermophysics 20 (1999), S. 107-117

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ISSN: 1572-9567

Keywords: dielectric constant ; electrical resistivity ; HFC-236ea ; HFC-245fa ; hydrofluorocarbon ; permittivity ; high pressure ; refrigerants

Source: Springer Online Journal Archives 1860-2000

Topics: Physics

Notes: Abstract The static relative permittivity (dielectric constant) and the resistivity of HFC-236ea (CF3–CHF–CHF2) and HFC-245fa (CF3–CH2–CHF2) in the liquid phase were studied at temperatures from 293 to 343 K and pressures from 0.1 to 50 MPa. The relative permittivity was measured by a concentric-cylinder-type capacitance cell with an LCR meter with an uncertainty of less than 0.1%. The resistivity was measured by a high resistance meter using plane-parallel platinum electrodes installed in a borosilicate glass syringe. It was found that the relative permittivities and the resistivities of liquid HFC-236ea and HFC-245fa at 303 K and 0.101325 MPa are about 5.13 and 6.54 and 1.5×1010 and 0.2×1010 Ω·cm, respectively. The relative permittivity and the resistivity increase monotonically with increasing pressure and decreasing temperature.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1023/A:1021430214264

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7

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Thermal Conductivity Measurements of Aqueous SrCl2 and Sr(NO3)2 Solutions in the Temperature Range Between 293 and 473 K at Pressures up to 100 MPa (1999)

Abdulagatov, I. M. ; Magomedov, U. B.

Springer

International journal of thermophysics 20 (1999), S. 187-196

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ISSN: 1572-9567

Keywords: aqueous solutions ; density ; high pressure ; parallel-plate method ; salt ; thermal conductivity ; water

Source: Springer Online Journal Archives 1860-2000

Topics: Physics

Notes: Abstract Accurate high-pressure thermal conductivity measurements have been performed on H2O+SrCl2 and H2O+Sr(NO3)2 mixtures at pressures up to 100 MPa over a temperature range between 293 and 473 K using a parallel-plate apparatus. The concentrations studied were 0.025, 0.05, 0.10, 0.15, and 0.20 mass fraction of the salts. The estimated accuracy of the method is about ±1.6%. The pressure, temperature, and concentration dependences of the thermal conductivity have been studied. Measurements were made on six isobars, namely, 0.1, 20, 40, 60, 80, and 100 MPa. The thermal conductivity shows a linear dependence on pressure and concentration for all isotherms. Along each isobar, a given concentration shows the thermal-conductivity maximum at a temperature of about 413 K. The measured values of thermal conductivity at atmospheric pressure are compared with the results of other investigators. Literature data at atmospheric pressure reported by Ridel and by Zaitzev and Aseev agree with our thermal conductivity values within the estimated uncertainty.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1023/A:1021494601060

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8

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Viscosity of twelve hydrocarbon liquids in the temperature range 298–348 K at pressures up to 110 MPa (1982)

Kashiwagi, H. ; Makita, T.

Springer

International journal of thermophysics 3 (1982), S. 289-305

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ISSN: 1572-9567

Keywords: aromatic hydrocarbons ; cyclohexane ; free volume expression ; hard-sphere theory ; high pressure ; n-alkanes ; torsionally vibrating crystal method ; viscosity

Source: Springer Online Journal Archives 1860-2000

Topics: Physics

Notes: Abstract New experimental data on the viscosity of 12 organic liquids are presented at temperatures of 25, 30, 50, and 75°C and at pressures up to 110 MPa. The liquids measured are five n-alkanes (C6, C7, C8, C10, C12), cyclohexane, and six aromatic hydrocarbons (benzene, toluene, ethylbenzene, o-, m-, p-xylenes). The measurements were performed using a torsionally vibrating crystal method on a relative basis with an uncertainty less than 2%. A linear relationship between fluidity and molar volume, which is predicted from the hard-sphere theory, fails at pressures above 50 MPa. The rough hard-sphere model proposed by Chandler provides a reasonable representation of the data for aromatic hydrocarbons, while for n-alkanes the agreement is not satisfactory because of an aspherical shape of molecules. The viscosity data can be correlated well with the molar volume by a free-volume expression and also can be represented as a function of pressure by a similar expression to the Tait equation.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF00502346

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9

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Vibrational Spectra of Nitrogen in Simple Mixtures at High Pressures (1999)

Kooi, M. E. ; Ulivi, L. ; Schouten, J. A.

Springer

International journal of thermophysics 20 (1999), S. 867-876

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ISSN: 1572-9567

Keywords: dilute mixtures ; high pressure ; high-resolution Raman spectroscopy ; line width ; nitrogen

Source: Springer Online Journal Archives 1860-2000

Topics: Physics

Notes: Abstract Previous investigations have revealed a considerable difference between the spectral behavior of a molecule in a pure substance and that in a mixture. To gain more insight into the influence of the intermolecular interaction and of the mass of the molecules, we performed high-resolution measurements of the linewidths and peak positions of the vibrational Raman spectrum of pure nitrogen, nitrogen in argon, and nitrogen in helium. The research was carried out at room temperature and at pressures up to the melting line. It turns out that, in contrast with expectation, the linewidth as well as the frequency shift is essentially the same for pure nitrogen as for nitrogen diluted in argon, although both the mass and the potential well depth are quite different. The experimental results show the same tendency as recent computer simulations.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1023/A:1022635203155

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10

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Determination of the Critical Point of Gold (1999)

Boboridis, K. ; Pottlacher, G. ; Jäger, H.

Springer

International journal of thermophysics 20 (1999), S. 1289-1297

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ISSN: 1572-9567

Keywords: critical point ; electrical resistivity ; enthalpy ; gold ; high pressure ; high temperature ; liquid metals

Source: Springer Online Journal Archives 1860-2000

Topics: Physics

Notes: Abstract Wire-shaped gold specimens are placed in a new, improved high-pressure vessel, which is part of a fast capacitor-discharge circuit and in which static pressures above 600 MPa can be reached with distilled water as the pressure-transmitting medium. The specimens are self-heated resistively by a current pulse. The current through the specimen, the voltage drop across it, and its temperature are recorded as a function of time with submicrosecond resolution. The radial expansion of the specimen is determined with a CCD camera, Experiments are performed at different pressures. When the critical pressure is exceeded, there is no liquid–gas phase transition; hence, no sudden change in the thermal expansion rate is observed. The results for temperature, pressure, and specific volume at the critical point of gold are as follows: T c =7400±1100 K, p c=530±20 MPa, and v c=0.13±0.03 × 10−3m3·kg−1.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1023/A:1022687811410

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