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CRTA for the thermoanalytical screening of volatile compounds

1. Calibration of standard Q-derivatograph sample holders vs. vapor partial pressures during quasi-isobaric quasi-isothermal heating

Journal of Thermal Analysis and Calorimetry
Authors: V. Logvinenko, G. Gavrilova, I. Karpova and P. Stabnikov

Abstract  

Quasi-equilibrium thermogravimetry (variant of CRTA) is utilized as a thermoanalytical screening method for volatile compounds, standard Q-derivatograph sample holders (platelike holder, open crucible, crucible with lid, and conical holder) were calibrated against the partial pressures of metal β-diketonate vapor (in sublimation and evaporation processes) in the range 0.0006–0.11 atm. The mathematical relationship between the vapor partial pressure, the holder construction, the vapor molecular mass, and the mutual diffusion coefficient of the gas was derived and considered. It is possible to obtain a roughp-T relationship for volatile compounds by using stabilized temperatures of sublimation (evaporation) processes in four pressure-calibrated sample holders.

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Abstract  

Volatile compounds of iridium(I): (acetylacetonato)(1,5-cyclooctadiene)iridium(I) Ir(acac)(cod), (methylcyclopentadienyl) (1,5-cyclooctadiene)iridium(I) Ir(Cp’)(cod), (pentamethylcyclopentadienyl)(dicarbonyl) iridium(I) Ir(Cp*)(CO)2 and (acetylacetonato)(dicarbonyl)iridium(I) Ir(acac)(CO)2 were synthesized and identified by means of element analysis, NMR-spectroscopy, mass spectrometry. Thermal properties in solid phase for synthesized iridium(I) complexes were studied by means of thermogravimetric analysis in inert atmosphere (He). By effusion Knudsen method with mass spectrometric registration of gas phase composition the temperature dependencies of saturated vapor pressure were measured for iridium(I) compounds and the thermodynamic characteristics of vaporization processes enthalpy ΔH T* and entropy ΔS T 0 were determined. The energy of intermolecular interaction in the crystals of complexes was calculated.

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Abstract

Volatile palladium(II) β-iminoketonates of the general formula Pd(R–C(NH)–CH–CO–R1),where R and R1 are CH3, CF3, C(CH3)3 in various combinations, were synthesized and identified. Thermal properties of the resulting palladium(II) complexes in the solid phase were studied by thermogravimetric analysis under an argon atmosphere. The temperature dependence of the saturated vapor pressure was measured for the compounds by the flow method and thermodynamic characteristics of vaporization processes, enthalpy ΔH T and entropy ΔS T o, were determined. The atom-atomic potential calculation of the van der Waals energy (E cryst) of the crystal lattice was performed and the results were compared to the experimental values of the sublimation enthalpy for the complexes under study.

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