Vaporization thermodynamics

Vapor pressures of phases in these systems were measured by the Knudsen effusion technique. Use of mass spectrometer-target collection apparatus to perform thermodynamic studies is discussed. The prominent sublimation reactions for these phases below 2000 K was shown to involve formation of elemental plutonium vapor. Thermodynamic properties determined in this study were correlated with corresponding values obtained from theoretical predictions and from previous measurements on analogous intermetallics. 

The high volatility of metallic Es makes it an ideal candidate for preparation by metallothermic reduction of its oxide (Section II,B), but the scarcity of Es prohibits its preparation in pure bulk form. Vaporization thermodynamics of Es metal have been determined, assuming that Henry s Law applies, using alloys of Es with divalent... 

Langlet J, Claverie P, Caillet J, Pullman A (1988) Improvements of the continuum model. 1. Application to the calculation of the vaporization thermodynamic quantities of nonassociated liquids. J Phys Chem 92 1617-1631... 

JANAF Joint Army, Navy, Air Force Thermochemical Tables, 2nd ed., 1971. NSRDS-NBS 37, US Government Printing Office Washington, DC. See also later supplements for 1971-1981. Kohl, F. J., Stearns, C. A., and Fryburg, G. C. "Sodium Sulfate Vaporization Thermodynamics and Role in Corrosive Flames", 1975, NASA TMX-71641. 

Rossini and coworkers (374) estimate 202° K. as the melting point, 693 cal./gram atom as the heat of melting, 211° K. as the normal boiling point, and 3920 cal./gram atom as the associated heat of vaporization. Thermodynamic properties of the ideal monatomic gas have been calculate at the National Bureau of Standards (396). 

Kazenas YeK (2004) Vaporization thermodynamics of double oxides. Nauka, Moscow (in Russian)... 

In his recently published monograph, Vaporization Thermodynamics of Double Oxides , Kazenas [57] presents a wealth of collected, systematized, and generalized material on the vapour pressure and composition of metal borates, aluminates, carbonates, silicates, nitrates, sulphates, phosphates, chromates, and other double oxides. This material is based on studies by Kazenas and his group and the results reported in the literature. In a foreword to this book, Kazenas [57] claims Observation of new t3rpes of molecules completely disproved the view on the high-temperature vapour as a medium which is poor in molecular forms. It has been established, in particular, that the molecular composition of the vapour phase for many chemical compounds is more complex and diverse than it was assumed earlier. By the use of effusion MS,... 

Okhotnikov VB, Yakobson BI, Lyakhov NZ (1983) React Kinet Catal Lett 23 125-130 Okhotnikov VB, Lyakhov NZ (1984) J Solid State Chem 53 161-167 Okhotnikov VB, Petrov SE, Yakobson BI, Lyakhov NZ (1987) React Solids 2 359-372 Kirdyashkina NA, Okhotnikov VB (1988) React Kinet Catal Lett 36 417-422 Modestov AN, Poplaukhin PV, Lyakhov NZ (2001) J Therm Anal Cal 65 121-130 Kazenas YeK (2004) Vaporization thermodynamics of double oxides. Nauka, Moscow (in Russia)... 

KEMS is a tremendously powerful technique for obtaining thermodynamic data on metals and alloys. Such information as heats of vaporization, thermodynamic activities of components, partial and integral molar heats of mixing, and phase transformation temperatures can be obtained with a high degree of accuracy. General experimental aspects of the technique have been discussed with particular emphasis on the Knudsen cell... 

The vaporization thermodynamics of EuO and EU3O4 have been reported by Haschke and Eick (1969,1968). They found AG (298) = — 581.6 kJ/gfw for EuO and AG (298)= — 2152kJ/gfw for EU3O4. In each case the gaseous species was metal vapor and the solid product was the next higher oxide. 

Before approaching the problem of dynamics of contact line, we shall briefly review the equilibrium properties of gas-liquid interfaces and their dependence on the proximity to solid surfaces. We shall consider the simplest one-component system a liquid in equilibrium with its vapor. Thermodynamic equilibrium in a two-phase system implies equilibrium of the interphase boundary, which tends to minimize its area. The thermodynamic quantity that expresses additional energy carried by the interface is surface tension, defined as the derivative of the Helmholtz or Gibbs free energy with respect to interfacial area E ... 

Vaporization data have also been obtained for several reduced halide systems. An independent study of the Yb-F system (Petzel and Greis, 1976) confirm the results of a study cited previously (cf. section 4.4.3). The congruently vaporizing composition is YbF2.37(Yb27F64). The vaporization thermodynamics of EuBr2 (cf. section 4.4.3) have been remeasured (Haschke, 1977) the revised values =... 

Pdipets, O.V., Shlykov, S.A., Girichev, G.V., Giricheva, N.I., 2003. Vaporization thermodynamics of europium dichloride and europium dibromide. In Proceedings of the II International Symposium on High Temperature Mass Spectrometry (Plyos, 2003), Ivanovo, pp. 140-141. 

Haschke and Eick (1969) have studied the vaporization thermodynamics of EuO using a Knudsen effusion technique. The reaction... 

Extensive studies have been performed for the determination of the vapor pressures and the vaporization thermodynamics of rare-earth fluorides. The majority of the data are based on mass spectrometric work and originate from the laboratories of Suvorov, Margrave and Searcy. Table 1 summarizes the reported vapor pressures and thermodynamic functions of sublimation, vaporization and (in two cases) dimerization of rare-earth fluorides. The data are not in full agreement in those cases that the same compound has been studied by different research groups. The reader should also refer to the articles of Myers and Graves (1977a,b) for selected third-law values for the enthalpy of sublimation, A//5298-... 

Vapor pressures and vaporization thermodynamics of rare-earth fluorides... 

Among the rare-earth halides, bromides constitute the group of systems which are studied to a much lesser extend compared to fluorides, chlorides and iodides. It is noteworthy that after Makhmadmurodov et al. (1975a,b) published their results on vaporization thermodynamics of some rare-earth bromides it was very recently that an extensive well-documented Knudsen effusion mass spectrometric investigation of the DyBr3 vaporization appeared in the literature (Hilpert et al. 1995). The successful characterization of the thermochemical properties of the dimer homocomplex Dy2Br6(g) by Hilpert et al. is taken as an indication that further vaporization studies are required for most rare-earth bromide systems with a view to establish the probable existence of vapor dimer homocomplexes and determine their thermochemical properties. Table 8 summarizes the vapor pressures and vaporization thermodynamics of rare-earth bromides. Most likely the vapor pressures reported so far could be in considerable error since the formation of dimers has not been taken into account. 

A summary of the available data on vaporization thermodynamics of rare-earth iodides is presented in table 10. Scandium iodide is by far the most extensively studied system due to its wide use in lamps. However, it was from a mass spectrometric study of Hirayama et al. (1976) on Lal3, where the detection of appreciable amounts of La2le(g) made evident that chemical interaction occurred in the gas phase between the monomers and that the presumption of congruent vaporization for the rare-earth iodides should... 

Before closing this section it should be pointed out that the present review of the vaporization thermodynamics and structural trends of rare-earth halides reveals that several of the single-component systems should be reinvestigated with a view both to establishing the existence of dimer species in the equilibrium vapors, if they exist, and to refine the relevant vapor pressure data. Furthermore, the thermochemical properties of the vapors need to be studied more thoroughly in order to identify possible trends in the vaporization thermodynamics. Finally, a clear, unambiguous high-temperature and/or matrix isolation spectroscopic (Raman and IR) characterization of the vibrational properties of the rare-earth halide vapors still remains to be realized before their structural picture is fully settled and a reliable third-law treatment of the data is attempted. 

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