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Microstructural characterization, mechanical properties, and corrosion resistance of the CaO–TiO2 system

Published online by Cambridge University Press:  31 January 2011

P.S. Maiya ,
R. Russell ,
D.S. Poa ,
A.S. Wagh  and
R.B. Poeppel
P.S. Maiya
Affiliation:
Materials and Components Technology Division, Argonne National Laboratory, Argonne, Illinois 60439
R. Russell
Affiliation:
Materials and Components Technology Division, Argonne National Laboratory, Argonne, Illinois 60439
D.S. Poa
Affiliation:
Materials and Components Technology Division, Argonne National Laboratory, Argonne, Illinois 60439
A.S. Wagh
Affiliation:
Materials and Components Technology Division, Argonne National Laboratory, Argonne, Illinois 60439
R.B. Poeppel
Affiliation:
Materials and Components Technology Division, Argonne National Laboratory, Argonne, Illinois 60439
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Abstract

Ceramic materials with chemical compositions of CaO–X mole % TiO2, where X ranges from 3 to 40, have been prepared for the evaluation of microstructures, mechanical properties, thermal shock resistance, resistance to hydration in air, and resistance to corrosion in molten salt saturated with calcium. When the TiO2 content is less than 40.3 mole %, the CaO forms two-phase microstructures consisting of CaO and Ca3Ti2O7, and the composition CaO−40.3 mole % TiO2 corresponds to the (single-phase) compound Ca3Ti2O7. The data on mechanical properties suggest that the single-phase material has better flexural strength and fracture toughness than do the two-phase materials. It is also demonstrated that the stabilizing effect of TiO2 on CaO imparts resistance to atmospheric hydration. Both scanning electron microscopy and energy-dispersive x-ray analysis of the specimens exposed to molten CaCl2−20 mole % CaF2 saturated with calcium at 900 °C show that corrosion resistance increases with an increase in TiO2 content, but that corrosion does occur in all materials. On the basis of experimental observations and thermodynamic considerations, the degradation of Ca3Ti2O7 is shown to be associated with the reduction of Ca3Ti2O7 by calcium to form CaO and metallic titanium followed by the dissolution of the reaction product CaO in the molten salt.

Type
Articles
Information
Journal of Materials Research , Volume 8 , Issue 6 , June 1993 , pp. 1387 - 1393
Copyright
Copyright © Materials Research Society 1993

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References

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