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The thermodynamic knowledge of accurate phase equilibrium data plays an important role in the design and optimization of separation processes in chemical and engineering industries. Vapour-liquid equilibrium data are essential for the design of efficient separation processes such as distillation. The presented research study is mainly focused on the vapour-liquid equilibrium data measurement of fluorochemical and hydrocarbon binary systems at various temperatures and at high pressures. A new static analytical apparatus was constructed and commissioned for the measurement of accurate and precise vapour-liquid equilibrium data at temperatures and absolute pressures ranging from low temperatures to 323.15 K and 0 to 10 MPa respectively. The new apparatus incorporates the ROLSI TM sampler, a sampling technique developed by the CEP/TEP laboratory in Fontainebleau, France. Isothermal high pressure VLE data were measured for three binary systems comprising of hexafluoroethane (R116) + propane, HFPO + propane and ethane + octafluoropropane (R218). The R116 + propane system at 263.15 K was measured as a test system using the new static apparatus. These measurements helped to confirm the functioning of the experimental apparatus. The reliability and the reproducibility of the experimental procedure were also checked. The data obtained were in excellent agreement with data in the literature. Thereafter, measurements of previously unmeasured systems were undertaken. Isothermal vapour-liquid equilibrium data measurements for the ethane + octafluoropropane system were performed at five isotherms with temperatures and pressures ranging from 264.05 to 308.04 K and 0.298 to 4.600 MPa respectively. The five isotherms constitute new experimental data. The HFPO + propane system was also investigated and vapour-liquid equilibrium data were measured at three isotherms (283.05, 303.05 and 323.05 K) with pressures ranging from 0.437 to 2.000 MPa. The data measured also constitute a set of a new HPVLE data. The uncertainties in the measurement for both systems were within ± 0.09 K, ± 0.0016 MPa and less than 2% for temperatures, pressures and mole fractions, respectively. All experimental data were correlated via the direct method using the Peng-Robinson equation of state with the Mathias-Copeman alpha function and the Wong-Sandler mixing rules incorporating the NRTL activity coefficient model. The consistency of the measured VLE data was tested using the Van Ness point test which yielded few points of difference between the measured and calculated data, suggesting a low error rate. / Thesis (M.Sc.Eng.)-University of KwaZulu-Natal, Durban, 2010.

Modifications were undertaken to a static high pressure vapour-liquid equilibrium (VLE) apparatus described by Naidoo [2004]. The alterations were made to improve the sample analysis technique. These modifications included the incorporation of the ROLSITM sampling device into the equilibrium cell, a re-design of the air bath which improved the temperature profile and further alterations described in the text. The equipment has an operating temperature range of 278.15 K to 473.15 K and pressure range of absolute vacuum to 150 bars. The apparatus consisted of an agitated cell in an air-bath. The uncertainties in the temperature and pressure measurements were ±0.02 K and ±4 kPa respectively. A Shimadzu Gas Chromatograph, Model 2010 was used for sample analysis. An initial test of the apparatus was carried out to measure the pure component vapour pressure data for propane and ethane in the temperature range of 279.24 – 360.18K and the results concurred with literature data (absolute relative deviation <0.153%) The experimental procedure used in this study was developed from the technique used by Ramjugernath [2000], with some minor changes implemented only to achieve some requirements for problems encountered during the project. Isothermal binary measurements for the hexafluoroethane (R116) + propane system were used as test system to investigate the accuracy and reliability of the equipment. Three binary isotherms were measured at 291.22 K, 296.23 K and 308.21 K. The measured data compared well with literature data. Particular attention was placed on the fluorinated hydrocarbons. Specific properties of fluorinated hydrocarbons give them many applications in industry, such as solvents, refrigerants, propellants, anaesthetics, etc. Hence, a phase equilibria study of a fluorinated hydrocarbons system was carried out in this project. The commissioning of the equipment was successfully undertaken and the equipment was found to be efficient and reliable. As a consequence measurements were made on the hexafluoropropylene oxide (HFPO) + ethane system. No data has been previously published in literature for this system. Measurements were undertaken at five different temperatures, 283.15 K, 290.15 K, 298.15 K, 308.15 K and 318.15 K. The isotherms were chosen in order to have measurements below and above the critical temperature of ethane, in order to see the transition at the critical temperature. The experimental data were modelled via the direct (phi-phi) method. The Peng-Robinson equation of state was applied, including the Mathias-Copeman alpha correlation with the Wong- Sandler mixing rules incorporating the NRTL activity coefficient model. Good agreement was found between the correlated and the measured data. / Thesis (M.Sc.Eng.)-University of KwaZulu-Natal, Durban, 2010.

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Thesis (Ph. D.)--Auburn University, 2005. / Abstract. Vita. Includes bibliographical references.

Thesis (M.S.)--Mississippi State University. Department of Aerospace Engineering. / Title from title screen. Includes bibliographical references.

Thesis (Ph. D.)--University of Texas at Austin, 2004. / Supervisors: Keith P. Johnston and William J. Koros. Vita. Includes bibliographical references.

TiP4N8 was obtained from the binary nitrides TiN and P3N5 upon addition of NH4F as a mineralizer at 8 GPa and 1400 °C. An intricate interplay of disorder and polymorphism was elucidated by in situ temperature- dependent single-crystal X-ray diffraction, STEMHAADF, and the investigation of annealed samples. This revealed two polymorphs, which consist of dense networks of PN4 tetrahedra (degree of condensation k= 0.5) and either augmented triangular TiN7 prisms or triangular TiN6 prisms for α- and β-TiP4N8, respectively. The structures of TiP4N8 exhibit body-centered tetragonal (bct) framework topology. DFT calculations confirm the measured band gaps of α- and β-TiP4N8 (1.6–1.8 eV) and predict the thermochemistry of the polymorphs in agreement with the experiments.