Authors & Affiliations
Osipov A.A., Ivanov K.D., Askhadullin R.Sh.
A.I. Leypunsky Institute for Physics and Power Engineering, Obninsk, Russia
Ivanov K.D. – Leading Researcher, Dr. Sci. (Techn.), A.I. Leypunsky Institute for Physics and Power Engineering.
Askhadullin R.Sh. – Deputy Director, Cand. Sci. (Techn.), A.I. Leypunsky Institute for Physics and Power Engineering.
This paper deals with the problem of dissociation of compounds in multicomponent systems. The theory of dissociation of compounds underlies all physicochemical processes, since the degree of dissociation of compounds is a measure of their strength or thermodynamic stability. In the theory of thermal dissociation of compounds, the transition of the components of a condensed compound to the gas phase is considered. The question arises of the applicability of such an approach to the consideration of processes occurring during the interaction of condensed compounds with other condensed phases. In particular, with regard to promising nuclear power plants (NPP) with a heavy liquid metal coolant (HLMC), the question of the interaction of oxide films with a liquid metal is relevant. In this paper, we have identified some of the difficulties of applying the classical theory to the problem of dissociation of compounds in multicomponent systems consisting of condensed phases, and outlines ways to overcome them. It is shown that the use of existing approaches is limited by the lack of data on the relationship of the isobaric-isothermal potential of the formation of compounds with their composition. A method for taking into account the influence of the composition of compounds on this parameter is proposed, based on an analysis of the available experimental data on stoichiometric compounds. Using the example of a three-component compound, we consider a system of basic and additional equations for the coupling of thermodynamic parameters describing the equilibrium state of the thermodynamic system during thermal dissociation of the compound. The conditions for obtaining solutions of this system are given. For the iron-oxygen two-component system, numerical calculations of the oxygen partial pressures as a function of temperature are performed and the model can be improved by using the assumption that the dissociation process of the compound is congruent. The main result of the work is a model of the equilibrium dissociation of compounds, built on the basis of solving a system of equations of conservation of mass, the laws of effective masses and the Gibbs-Duhem equations.
thermal dissociation, chemical compound, nonstoichiometry, congruent transition, composition, Gibbs energy, thermodynamic equilibrium, model, Gibbs-Duhem equation, condensed phase, liquid metal, equilibrium displacement, phase of variable composition, activity
1. Kulikov I.S. Termicheskaya dissotsiatsiya soedineniy [Thermal dissociation of compounds]. Moscow, Metullurgiya Publ., 1966. 251 p.
2. Kulikov I.S. Termodinamika oksidov [Thermodynamics of oxides]. Moscow, Metullurgiya Publ., 1986. 344 p.
3. Kulikov I.S. Termodinamika karbidov i nitridov [Thermodynamics of carbides and nitrides]. Chelyabinsk, Metullurgiya Publ., 1988. 320 p.
4. Tretyakov Yu.D. Khimiya nestekhiometricheskikh okislov [Chemistry of non-stoichiometric oxides]. Moscow, MGU Publ., 1974. 364 p.
5. Gusev A.I. Prevrashchenie besporyadok-poryadok i fazovye ravnovesiya v sil'no nestekhiometricheskikh soedineniyakh [Disorder-order transformation and phase equilibria in highly non-stoichiometric compounds]. Uspekhi fizicheskikh nauk - Advances in the physical sciences, 2000, vol. 170, no. 1, pp. 3—40.
6. Gusev A.I., Rempel A.A. Termodinamika strukturnykh vakansiy v nestekhiometricheskikh fazakh vnedreniya [Thermodynamics of the Structural Vacancies in Nonstoichiometric Interstitial Phases]. Sverdlovsk, Ural Scientific Centre Publ., 1987. 114 p.
7. Gusev A.I. Fizicheskaya khimiya nestekhiometricheskikh tugoplavkikh soedineniy [Physical chemistry of non-stoichiometric refractory compounds]. Moscow, Nauka Publ., 1991.
8. Korobeynikova A.V., Fadeeva V.I., Reznitsky L.A. Izuchenie raspredeleniya strukturnykh vakansiy v okside zheleza [Study of the distribution of structural vacancies in iron oxide]. Zhurnal strukturnoy khimii - Journal of Structural Chemistry, 1976, vol. 17, p. 860.
9. Gusev A.I., Shveikin G.P. Calculation of state diagrams of solid solutions based on transition metal carbides. News of the USSR Academy of Sciences. Inorganic materials, 1977, vol. 13, no. 1, pp. 67—69.
10. Gusev A.I. Statistical description of vacancy formation in compounds of variable composition such as zirconium nitride and carbide. Russ. J. of Phys.Chemistry, 1979, vol. 53, no. 6, pp. 780—782.
11. Gusev A.I. Calculation of some thermodynamic characteristics of structural vacancies in high-melting compounds of the type of zirconium and niobium carbides. High Temperature, 1979, vol. 17, no. 6, pp. 1020—1023.
12. Gillot В., Bouton F.J. Correlation between IR spectra, X-ray diffraction, and distribution of structural vacancies in Fe3O4-type spinels. Solid State Chem., 1980, vol. 32, no. 3, pp. 303.
13. Gusev A.I. Characteristics of the formation of structural vacancies in vanadium carbide and thermodynamic properties of defect-free vanadium carbide. Russ. J. Phys. Chem., 1983, vol. 57, no. 6, pp. 837—839.
14. Gubanov V.A. et al. Vacancies and the Energy Spectrum of Refractory Metal Compounds: TiC and TiO. Journal of Physics and Chemistry of Solids, 1984, vol. 45, no. 7, pp. 719.
15. Gusev A.I. Structural vacancies in nonstoichiometric compounds at high pressure. Thermodynamic model. Physica status solidi(a), 1984, vol. 85, no. 1, pp. 159—166.
16. Gusev A.I., Alyamovskii S.I., Zainulin Yu.G., Shveikin G.P. Structural vacancies in compounds of variable composition. Russian Chemical Review, 1986, vol. 55, no. 12, pp. 1175—1185.
17. Novikov D.L., Ivanovsky A.L., Gubanov V.A. The influence of structural vacancies and impurities on the electronic structure of TiC(100). Philosophical Magazine B, 1991, vol. 63, pp. 1409.
18. Gusev A.I., Rempel A.A. Strukturnye fazovye perekhody v nestekhiometricheskikh soedineniyakh [Structural Phase Transitions in Nonstoichiometric Compounds]. Moscow, Nauka Publ., 1988. 308 p.
19. Ivanchenko V.I. et al. Fazovye ravnovesiya i termodinamika splavov v sisteme khrom-azot [Phase equilibria and thermodynamics of alloys in the chromium-nitrogen system]. Metallofizika - Metal Physics, 1990, vol. 12, no. 1, pp. 14.
20. Tsurekawa S., Yoshinaga Н. Indentification of Long Range Ordered Structure in TiC0.59 by Transmission Electron Microscopy. Journal of the Japan Institute of Metals, 1992, vol. 56, no. 2, pp. 133.
21. Rempel A.A. Effekty uporyadocheniya v nestekhiometricheskikh soedineniyakh vnedreniya [Ordering effects in non-stoichiometric implantation compounds]. Yekaterinburg, Nauka Publ., 1992.
22. Puska M.J. et al. First principles calculation of positron lifetimes and affinities in perfect and imperfect transition metal carbides and nitrides. Physical Review B, 1994, vol. 49, pp. 10947.
23. Brauer G. et al. Positron studies of polycrystalline TiC. Materials Chemistry and Physics, 1995, no. 17, pp. 9091.
24. Illyasov V.V., Nikiforov I.Ya. Vliyanie stepeni uporyadocheniya strukturnykh vakansiy na tonkuyu strukturu vershiny valentnoy polosy kubicheskogo nitrida bora [The effect of the degree of ordering of structural vacancies on the fine structure of the top of the valence band of cubic boron nitride]. Fizika tverdogo tela - Solid state physics, 1997, vol. 39, pp. 1064.
25. Ogawa T. et al. Thermodynamic assessment of the Fe—U, U—Zr and Fe—U—Zr systems. Journal of Alloys and Compounds, 1998, vol. 347, pp. 271—273.
26. Andersson S. et al. Phase Analysis Studies on the Titanium-Oxygen System. Acta Chemica Scandinavica, 1957, vol. 11, pp. 1641.
27. Westman S. Nordmark C. Phase Analysis Studies on the Vanadium-Oxygen System within the VO0.25-VO1.5 Region at 800 degrees C. Acta Chemica Scandinavica, 1960, vol. 14, no. 6, pp. 465.