Noncatalytic gas‐solid reactions and mechanical stress generation

Rode, Hilmar; Orlicki, Dariusz; Hlaváček, Vladimír

doi:10.1002/aic.690410519

Cited by 14 publications

(13 citation statements)

References 39 publications

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“…While early studies considered charged species moving through the oxide in a pairwise manner (Wagner, 1930, 1933, 1975), current theories take into account movement of a set of charge carriers (Fromhold, 1976, 1980; Fromm, 1989; Kapila and Plawsky, 1993). Rode et al (1995a, b) showed that the electrical field might affect the elastic stresses within the oxidized layer. The theoretical predictions were made assuming local electrochemical equilibrium inside the electrolyte and chemical equilibrium on the oxide surface.…”

Section: Introductionmentioning

confidence: 99%

“…The theoretical predictions were made assuming local electrochemical equilibrium inside the electrolyte and chemical equilibrium on the oxide surface. These assumptions are valid only at low oxidation temperatures having a characteristic time of the order of hours and days (Fromhold, 1976, 1980; Fromm, 1989; Kapila and Plawsky, 1993; Rode et al, 1995a, b). However, these assumptions and corresponding predictions are invalid during very fast, high‐temperature reactions.…”

Section: Introductionmentioning

confidence: 99%

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Electric‐field generation by gas–solid combustion

2004

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Electric‐field generation by gas–solid combustion

2004

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“…Possible changes in the parameters as the reaction proceeds also should be investigated. In addition, a stress analysis of a reacting RBAO sample, such as that which has been developed in the literature, 10 would help to identify the exact conditions that cause sample cracking and indicate how cracking might be avoided.…”

Section: Discussionmentioning

confidence: 99%

“…Stresses often develop because of differences between the precursor and product molar volumes and the thermal expansion coefficients. 10,11 The Pilling-Bedworth ratio-the ratio of the volume of product to the volume of precursor from which it is formed-is often used to determine if stresses will occur because of differences in the precursor and product molar volumes. 10 In general, if the Pilling-Bedworth ratio deviates from a value of 1, the product is formed at a constrained interface and growth stresses will develop.…”

Section: Introductionmentioning

confidence: 99%

Controlled Firing of Reaction‐Bonded Aluminum Oxide (RBAO) Ceramics: Part I, Continuum‐Model Predictions

Gaus

Harmer

Chan

et al. 1999

Journal of the American Ceramic Society

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The reaction‐bonded aluminum oxide (RBAO) process is a novel, reaction‐forming technique for producing monolithic, alumina‐based ceramics. Although there has been extensive work on the RBAO process, it is often difficult to reproduce the process and avoid sample cracking. To solve the problems that are associated with the RBAO process, it is necessary to have a fundamental understanding of the reaction‐bonding process and the effects of various processing parameters on the reaction behavior. To gain some insight into the process, a continuum model has been developed. The model, which considers the interaction between the macroscopic material and energy balances, is used to predict conditions under which RBAO bodies may be fired in a controlled manner, i.e., avoiding the runaway reaction. In particular, the effects of the oxygen content of the atmosphere, the heat loss by convection and radiation, the heating cycle, and scale (sample size) have been investigated. For small sample sizes, model predictions indicate that the reaction may be controlled by reducing the oxygen content of the atmosphere, increasing the heat loss, and/or incorporating an isothermal hold into the heating cycle at a temperature just below the ignition temperature. For larger sample sizes, model predictions indicate the need for multiple low‐temperature holds at increasing temperatures. It is believed that firing RBAO bodies in a controlled manner will allow one to avoid sample cracking. Part II of this work presents a complementary experimental study that investigates the reaction behavior and structural integrity of samples that have been fired under the predicted conditions.

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“…Recently, Pigeon and Varma (1993) took the expansion of the product layer into account during their quantitative analysis of silicon nitridation. Rode et al (1995a) developed a general model which describes the evolution of stresses in reactive gas-solid powder systems. The thermoelastic model accounts for the generation of stresses due to the Pilling-Bedworth ratio and different thermal expansion coefficients of the precursor core and product shell.…”

Section: Reactionmentioning

confidence: 99%