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Structural Instability of the Ceramic Coating in a Metal-Ceramic Composite Induced Through Control of Chemistry of the Bonding Atmosphere

Published online by Cambridge University Press:  25 February 2011

Abhijit Ray*
Affiliation:
Mechanical Engineering Department, University of Nevada-Reno, NV-89557.
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Abstract

A novel processing technique has been developed to coat Al2O3 on Nb in an argon atmosphere with very low O2 content. It has been proposed1 that the low O2 content helped to increase the defect concentration in the ceramic phase resulting in an enhanced diffusion of Nb into Al2O3 at the metal-ceramic interface at a relatively low bonding temperature. A mathematical model has been developed1 to understand the effect of purified bonding atmosphere on interfacial diffusion. While diffraction studies in the transmission electron microscope revealed1 extensive amorphization at the metal-ceramic interface, EDX analysis showed1 that the interfacial amorphous phase has a very high concentration of O. Additionally, this phase is found to contain Al and Nb. The interfacial phase is formed due to the diffusion of Nb into the ceramic phase. The paradoxical phenomenon of O enrichment of the interfacial amorphous phase in a low O2 containing bonding atmosphere is due to the loss of gaseous oxides of Al from this phase. These oxides have relatively less proportion of O compared to Al2O3. Continuous loss of such oxides from the amorphous phase to the gaseous phase will, therefore, result in an O to Al ratio (in the amorphous phase) far exceeding that in Al2O3 (3:2).

Type
Research Article
Copyright
Copyright © Materials Research Society 1993

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References

REFERENCES

Ray, A., and Samanta, S.K., Submitted to Phil. Mag., 1991.Google Scholar
2. Saunders, S.R.J. and Nicholls, J.R., Material Science and Technology, vol. 5, p. 780.Google Scholar
3. Barin, I., Knacke, O., Thermochemical Properties of Inorganic Substances, (New York: Springer-Verlag and Dusseldorf: Verlag Stahleisen m.b.H., 1973), Vol. 1, pp. 2933.Google Scholar
4. Barin, I., Knacke, O., and Kubaschewski, O., Thermochemical Properties of Inorganic Substances: suppliment, (New York: Springer-Verlag and Dusseldorf: Verlag Stahleisen m.b.H., 1977), Vol. 2, pp. 2426.CrossRefGoogle Scholar
5. Langmuir, I., Phys. Rev., 2, 329 (1913).CrossRefGoogle Scholar