Study of Molecular and Ionic Vapor Composition over CeI3 by Knudsen Effusion Mass Spectrometry

The molecular and ionic composition of vapor over cerium triiodide was studied by Knudsen effusion mass spectrometry. In the saturated vapor over CeI3 the monomer, dimer, and trimer molecules and the negative ions I−, CeI4−, and Ce2I7− were identified in the temperature range of 753–994 K. The partial pressures of CeI3, Ce2 I6, and Ce3I9 were determined and the enthalpies of sublimation, Δ

Thermodynamic Properties of Al-Cr-Fe Alloys: Experimental Investigation by Knudsen Effusion Mass Spectrometry

Vaporization of ternary Al-Cr-Fe and binary Al-Fe, and Cr-Fe alloys has been investigated in the temperature range 1234-1608 K by Knudsen effusion mass spectrometry (KEMS). The atoms Al, Cr, and Fe were found to be the only vapor species. Partial pressures of the elements were evaluated from the measured ion intensities and thermodynamic activities of the alloy components were determined by pressure ratio method (p/p°). Reliable partial and integral molar enthalpies, entropies and Gibbs energies for all the components have been obtained for the systems under investigation. The partial molar enthalpies and entropies were found to be nearly temperature independent over the wide temperature range investigated.</jats:p

Experimental Thermodynamics of New Electrode Materials for Li-Ion Batteries

Vaporization of five liquid binary Li-Sn alloys (molar fractions x Li = 0.1; 0.2; 0.3; 0.4; and 0.5) as well as pure Li have been investigated in the temperature range 576-1040 K by Knudsen effusion mass spectrometry (KEMS). The Thermodynamic activity of lithium was determined by the ratio of ion current intensities measured over the alloy and the pure metal. The activity of tin was determined by Gibbs-Duhem integration. The results were approximated by Redlich-Kister sub-regular solution model and compared with the available literature data.</jats:p

Thermal Emission of Alkali Metal Ions from Al30-Pillared Montmorillonite Studied by Mass Spectrometric Method

The thermal emission of alkali metal ions from Al30-pillared montmorillonite in comparison with its natural form was studied by mass spectrometry in the temperature range 770–930 K. The measurements were carried out on a magnetic mass spectrometer MI-1201. For natural montmorillonite, the densities of the emission currents (j) decrease in the mass spectrum in the following sequence (T = 805 K, A/cm2): K+ (4.55 · 10−14), Cs+ (9.72 · 10−15), Rb+ (1.13 · 10−15), Na+ (1.75 · 10−16), Li+ (3.37 · 10−17). For Al30-pillared montmorillonite, thermionic emission undergoes temperature-time changes. In the low-temperature section of the investigated range (770–805 K), the value of j increases substantially for all ions in comparison with natural montmorillonite (T = 805 K, A/cm2): Cs+ (6.47 · 10−13), K+ (9.44 · 10−14), Na+ (3.34 · 10−15), Rb+ (1.77 · 10−15), and Li+ (4.59 · 10−16). A reversible anomaly is observed in the temperature range 805–832 K: with increasing temperature, the value of j of alkaline ions falls abruptly. This effect increases with increasing ionic radius of M+. After a long heating-up period, this anomaly disappears and the lnj-1/T dependence acquires a classical linear form. The results are interpreted from the point of view of the dependence of the efficiency of thermionic emission on the phase transformations of pillars

Activity Determination in the Alumina-Dysprosia System by Knudsen Effusion Mass Spectrometry

The vaporization of Al-Dy-O mixtures has been investigated by the Knudsen effusion mass spectrometry technique. The saturated vapor has been found to consist of the atoms Al, O and the molecules AlO, Al2O, DyO. At the initial stage the vaporization of Dy2O3 and Al2O3-Dy2O3 mixtures was found to be incongruent and accompanied by some loss of oxygen. An attainment of congruently vaporizing composition and equilibrium state takes quite a long time. The activities of binary oxides have been measured at T = 2130 K. The Gibbs energies and enthalpies have been derived for formation of the compounds Dy4Al2O9, DyAlO3 and Dy3Al5O12 from sesquioxides.</jats:p

DOI:10.1068/htwu144

Thermodynamic properties of neutral and charged species in high-temperature vapour over terbium and thulium trichloride

Vapor Composition and Vaporization Thermodynamics of 1-Ethyl-3-methylimidazolium Hexafluorophosphate Ionic Liquid

The processes of the sublimation and thermal decomposition of the 1-ethyl-3-methylimidazolium hexafluorophosphate ionic liquid (EMImPF6) were studied by a complex approach including Knudsen effusion mass spectrometry, IR and NMR spectroscopy, and quantum chemical calculations. It was established that the vapor over the liquid phase primarily consists of decomposition products under equilibrium conditions. Otherwise, the neutral ion pairs are the only vapor components under Langmuir conditions. To identify the nature of the decomposition products, an experiment on the distillation of the ionic liquid was performed and the collected distillate was analyzed. It was revealed by the IR and NMR spectroscopy that EMImPF6 decomposes to substituted imidazole-2-ylidene (C6N2H10PF5) and HF. The measured vapor pressure of C6N2H10PF5 reveals a very low activity of the decomposition products (−4) in the liquid phase. The absence of a significant accumulation of decomposition products in the condensed phase makes it possible to determine the enthalpy of sublimation of the ionic liquid assuming its unchanged activity. The thermodynamics of the EMImPF6 sublimation was studied by Knudsen effusion mass spectrometry. The formation enthalpy of EMImPF6 in the ideal gas state was found from a combination of the sublimation enthalpy and formation enthalpy of the ionic liquid in the condensed state. The obtained value is in good agreement with those calculated by quantum chemical methods