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A micromechanistic model of the combustion synthesis process: Mechanism of ignition

Published online by Cambridge University Press:  31 January 2011

Cheng He
Affiliation:
School of Ceramic Engineering and Sciences, New York State College of Ceramics at Alfred University, Alfred, New York 14802
Gregory C. Stangle
Affiliation:
School of Ceramic Engineering and Sciences, New York State College of Ceramics at Alfred University, Alfred, New York 14802
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Extract

A micromechanistic model of the combustion synthesis has been extended to study the detailed mechanism and influential parameters of a combustion synthesis process, as well as the development of ignition criteria in the Nb–C system. The case of constant heat-flux ignition conditions has been used to illustrate the details of the ignition process, in order to elucidate the various physical and chemical processes that take place during the initial stages of the combustion synthesis process; however, the results of this study can be generally extended to the other modes of the ignition process. The results showed that the ignition criteria for the Nb–C system corresponded to the establishment of a proper balance between the rates of enthalpy redistribution within the sample, and to the establishment of a kind of positive feedback loop during the ignition process that is necessary for self-propagation to occur. If the heat supplied from an external source to initiate the combustion synthesis process is less than a certain critical value, the combustion wave stops at a certain short distance from the ignition surface. Otherwise, the reaction proceeds in a self-propagating manner.

Type
Articles
Copyright
Copyright © Materials Research Society 1998

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