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Author Rode, H. ♦ Hlavacek, V.
Source United States Department of Energy Office of Scientific and Technical Information
Content type Text
Language English
Subject Keyword MATERIALS SCIENCE ♦ CHEMISTRY ♦ TITANIUM ♦ NITRATION ♦ OXIDATION ♦ POWDER METALLURGY ♦ MATHEMATICAL MODELS ♦ TITANIUM NITRIDES ♦ TITANIUM OXIDES ♦ CHEMICAL REACTION KINETICS ♦ STRESSES
Abstract The reaction rate in gas-solid systems can be affected by mechanical stresses that arise as the reaction proceeds. Stresses develop due to differences between precursor and product molar volumes and thermal expansion coefficients. Experimental evidence on the interaction of reaction rate and mechanical stress for the Ti/N{sub 2} and Ti/O{sub 2} systems is provided. A detailed and consistent mathematical model is developed for the reaction taking place at the constrained precursor/product interface. An elastic formulation for the stresses is adopted, and stress generation due to mismatches in linear thermal expansion coefficients and equivalent volume (Pilling-Bedworth ratio) for the precursor and product are considered. The effect of surface energy, which becomes significant for particle sizes below 1 {mu}m, is also included in the model. Both experimentally and theoretically, conditions exist where the mechanical stresses exceed the strength of the material, leading to mechanical breakdown of the product layer, thus causing a discontinuity in the observed reaction rate. The entire process history, including the reaction, temperature, and pressure profiles, play an important role in determining the overall reaction kinetics of the powder.
ISSN 00011541
Educational Use Research
Learning Resource Type Article
Publisher Date 1995-05-01
Publisher Place United States
Journal AIChE Journal
Volume Number 41
Issue Number 5


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