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Reaction rate modeling in noncatalytic gas‐solid systems: Species transport and mechanical stress
Author(s) -
Rode Hitmar,
Orlicki Dariusz,
Hlavacek Vladimir
Publication year - 1995
Publication title -
aiche journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.958
H-Index - 167
eISSN - 1547-5905
pISSN - 0001-1541
DOI - 10.1002/aic.690411210
Subject(s) - diffusion , stress (linguistics) , electric field , ion , chemical physics , thermal , product (mathematics) , charge (physics) , field (mathematics) , particle (ecology) , transport phenomena , chemistry , materials science , thermodynamics , physics , organic chemistry , mathematics , linguistics , philosophy , geometry , oceanography , quantum mechanics , pure mathematics , geology
A detailed model to describe the overall reaction rate of the oxidation of titanium is developed. The mathematical model consists of two facets, the first of which involves a detailed description of species transport that accounts for the formation of charged species. This is augmented by a description of the occurrence of mechanical stress due to a Pilling ‐ Bedworth ratio that differs significantly from I as well as differences between precursor and product thermal expansion coefficients. A self imposed electric field is formed across the oxide layer due to different mobilities of the species considered. This field opposes the transport of electrons and enhances the transport of anion vacancies, thus increasing the overall reaction rate compared to a pure diffusion process, while also ensuring that electrical charge is conserved. Large growth stresses result from the unmatched precursor and product volumes, significantly affecting the overall process. These results show that the incorporation of a consistent treatment of mechanical stress forms a necessay part of any accurate description of the overall behavior of a reacting particle.