Browsing by Subject "THERMODYNAMIC PROPERTIES"

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  • Krieger, Ulrich K.; Siegrist, Franziska; Marcolli, Claudia; Emanuelsson, Eva U.; Gobel, Freya M.; Bilde, Merete; Marsh, Aleksandra; Reid, Jonathan P.; Huisman, Andrew J.; Riipinen, Ilona; Hyttinen, Noora; Myllys, Nanna; Kurten, Theo; Bannan, Thomas; Percival, Carl J.; Topping, David (2018)
    To predict atmospheric partitioning of organic compounds between gas and aerosol particle phase based on explicit models for gas phase chemistry, saturation vapor pressures of the compounds need to be estimated. Estimation methods based on functional group contributions require training sets of compounds with well-established saturation vapor pressures. However, vapor pressures of semivolatile and low-volatility organic molecules at atmospheric temperatures reported in the literature often differ by several orders of magnitude between measurement techniques. These discrepancies exceed the stated uncertainty of each technique which is generally reported to be smaller than a factor of 2. At present, there is no general reference technique for measuring saturation vapor pressures of atmospherically relevant compounds with low vapor pressures at atmospheric temperatures. To address this problem, we measured vapor pressures with different techniques over a wide temperature range for intercomparison and to establish a reliable training set. We determined saturation vapor pressures for the homologous series of polyethylene glycols (H-(O-CH2-CH2)(n)-OH) for n = 3 to n = 8 ranging in vapor pressure at 298 K from 10(-7) to 5 x 10(-2) Pa and compare them with quantum chemistry calculations. Such a homologous series provides a reference set that covers several orders of magnitude in saturation vapor pressure, allowing a critical assessment of the lower limits of detection of vapor pressures for the different techniques as well as permitting the identification of potential sources of systematic error. Also, internal consistency within the series allows outlying data to be rejected more easily. Most of the measured vapor pressures agreed within the stated uncertainty range. Deviations mostly occurred for vapor pressure values approaching the lower detection limit of a technique. The good agreement between the measurement techniques (some of which are sensitive to the mass accommodation coefficient and some not) suggests that the mass accommodation coefficients of the studied compounds are close to unity. The quantum chemistry calculations were about 1 order of magnitude higher than the measurements. We find that extrapolation of vapor pressures from elevated to atmospheric temperatures is permissible over a range of about 100 K for these compounds, suggesting that measurements should be performed best at temperatures yielding the highest-accuracy data, allowing subsequent extrapolation to atmospheric temperatures.
  • Maksimova, A. A.; Petrova, E. V.; Chukin, A. V.; Karabanalov, M. S.; Felner, I.; Gritsevich, M.; Oshtrakh, M. I. (2020)
    We studied the interior and the fusion crust of the recently recovered Ozerki L6 meteorite using optical microscopy, scanning electron microscopy (SEM) with energy dispersive spectroscopy, X-ray diffraction (XRD), magnetization measurements, and Mossbauer spectroscopy. The phase composition of the interior and of the fusion crust was determined by means of SEM, XRD, and Mossbauer spectroscopy. The unit cell parameters for silicate crystals were evaluated from the X-ray diffractograms and were found the same for the interior and the fusion crust. Magnetization measurements revealed a decrease of the saturation magnetic moment in the fusion crust due to a decrease of Fe-Ni-Co alloy content. Both XRD and Mossbauer spectroscopy show the presence of magnesioferrite in the fusion crust. The temperatures of cation equilibrium distribution between the M1 and M2 sites in silicates calculated using the data obtained from XRD and Mossbauer spectroscopy appeared to be in a good consistency: 553 and 479 K for olivine and 1213 and 1202 K for orthopyroxene.
  • Moreau, Juulia-Gabrielle; Kohout, Tomas; Wünnemann, Kai (2018)
    We studied shock-darkening in ordinary chondrites by observing the propagation of shock waves and melting through mixtures of metals and iron sulfides. We used the shock physics code iSALE at the mesoscale to simulate shock compression of modeled ordinary chondrites (using olivine, iron and troilite). We introduced FeS-FeNi eutectic properties and partial melting in a series of chosen configurations of iron and troilite grains mixtures in a sample plate. We observed, at a nominal pressure of 45 GPa, partial melting of troilite in all models. Only few of the models showed partial melting of iron (a phase difficult to melt in shock heating) due to the eutectic properties of the mixtures. Iron melting only occurred in models presenting either strong shock wave concentration effects or effects of heating by pore crushing, for which we provided more details. Further effects are discussed such as the frictional heating between iron and troilite and the heat diffusion in scenarios with strongly heated troilite. We also characterized troilite melting in the 32-60 GPa nominal pressure range. We concluded that specific dispositions of the iron and troilite grains in mixtures exist that lead to melting of iron and explain why it is possible to find a mix of metals and iron sulfides in shock-darkened ordinary chondrites.
  • Baird, Zachariah Steven; Dahlberg, Artur; Uusi-Kyyny, Petri; Osmanbegovic, Nahla; Witos, Joanna; Helminen, Jussi; Cederkrantz, Daniel; Hyväri, Paulus; Alopaeus, Ville; Kilpeläinen, Ilkka; Wiedmer, Susanne K.; Sixta, Herbert (2019)
    7-Methyl-1,5,7-triazabicyclo[4.4.0]dec-5-ene (mTBD) has useful catalytic properties and can form an ionic liquid when mixed with an acid. Despite its potential usefulness, no data on its thermodynamic and transport properties are currently available in the literature. Here we present the first reliable public data on the liquid vapor pressure (temperature from 318.23K to 451.2K and pressure from 11.1Pa to 10000Pa), liquid compressed density (293.15K to 473.15K and 0.092MPa to 15.788MPa), liquid isobaric heat capacity (312.48K to 391.50K), melting properties, liquid thermal conductivity (299.0K to 372.9K), liquid refractive index (293.15K to 343.15K), liquid viscosity (290.79K to 363.00K), liquid-vapor enthalpy of vaporization (318.23K to 451.2K), liquid thermal expansion coefficient (293.15K to 473.15K), and liquid isothermal compressibility of mTBD (293.15K to 473.15). The properties of mTBD were compared with those of other relevant compounds, including 1,5-diazabicyclo(4.3.0)non-5-ene (DBN), 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU), and 1,1,3,3-tetramethylguanidine (TMG). We used the PC-SAFT equation of state to model the thermodynamic properties of mTBD, DBN, DBU, and TMG. The PC-SAFT parameters were optimized using experimental data.
  • Baird, Zachariah Steven; Uusi-Kyyny, Petri; Witos, Joanna; Rantamäki, Antti H.; Sixta, Herbert; Wiedmer, Susanne K.; Alopaeus, Ville (2020)
    Ionic liquids have the potential to be used for extracting valuable chemicals from raw materials. These processes often involve water, and after extraction, the water or other chemicals must be removed from the ionic liquid, so it can be reused. To help in designing such processes, we present data on the vapor-liquid equilibrium of the system containing protic ionic liquid 7-methyl-1,5,7-triazabicyclo [ 4.4.0 ] dec-5-enium acetate, water, acetic acid, and 7-methyl-1,5,7-triazabicyclo [4.4.0] dec-5-ene. Earlier studies have only focused on mixtures of water and an ionic liquid with a stoichiometric ratio of the ions. Here, we also investigated mixtures containing an excess of the acid or base component because in real systems with protic ionic liquids, the amount of acid and base in the mixture can vary. We modeled the data using both the ePC-SAFT and NRTL models, and we compared the performance of different modeling strategies. We also experimentally determined the vapor composition for a few of the samples, but none of the modeling strategies tested could accurately predict the concentration of the acid and base components in the vapor phase.