Reaction of polycrystalline Na β″ -alumina with CO2 and H2O and the formation of hydroxyl groups
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The reactions of polycrystalline Na β″-alumina with CO2 and H2O were investigated using infrared reflectance methods. These reactions result in the replacement of Na+ ions with H3O+ ions and the formation of a scale of NaHCO3 or hydrated Na2CO3 on the surfaces of ceramic specimens. The composition of the scale formed depends on the pressures of CO2 and H2O: NaHCO3 forms at high CO2 pressure while Na2CO3 · XH2O forms at low CO2 pressures. The H3O+ ions dislocate by an endothermic process to produce OH− species in the conduction layers of the grains. The removal of these species by H2O evolution at high temperature implies that an irreversible change occurs in the composition of the surface region of the ceramic.
KeywordsReflection Spectrum Conduction Layer Ceramic Specimen Effective Path Length Multiple Internal Reflection
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- 1.J. T. Kummer, in “Progress in Solid State Chemistry”, Vol. 7, edited by H. Reiss and J. O. McCaldin (Pergamon, New York, 1972) p. 141.Google Scholar
- 8.J. B. Bates and D. Dohy, unpublished (1983).Google Scholar
- 12.N. J. Harrick, “Internal Reflection Spectroscopy” (John Wiley, New York, 1967).Google Scholar
- 19.“JANAF Thermochemical Tables”, 2nd Edn, NSRDS-NBS 37 (US Government Printing Office, Washington, D.C.).Google Scholar
- 21.W. B. White, in “The Infrared Spectra of Minerals”, edited by V. C. Farmer (Mineralogical Society, London, 1974).Google Scholar
- 22.D. Eisenberg and W. Kauzmann, “The Structure and Properties of Water” (Oxford University Press, Oxford, 1969).Google Scholar
- 23.J. D. Hodge, Amer. Ceram. Soc. Bull. 62 (1983) 244.Google Scholar
- 24.T. A. Hunt, N. Weber and T. Cole, in “Fast Ion Transport in Solids”, edited by P. Vashishta, J. N. Mundy, and G. K. Shenoy (North Holland, Amsterdam, 1979) p. 95.Google Scholar