Effect of high‐temperature direct‐current electrolysis on properties of hydrous aluminosilicates

A method which has been developed for thermogravimetric study of solids in the presence of applied electric fields has been used in a study of kaolinite dehydroxylation in a controlled inert atmosphere. Electric fields of ~10 ~ V/m lower the initiation temperature for dehydroxylation by as much as 60 ~ in some cases; the activation energy for dehydroxylation is reduced by 3--12 kcal/mole. The rate constants" for electrolysed samples (based arbitrarily on a first-order Saw) are increased by electrolysis but this effect falls off at higher temperatures as the normal thermal processes begin to predominate. The effect of the field on the various processes of ionic migration in the lattice is discussed.In previous papers [1,2] it has been shown qualitatively that the application of an a.c. or d.c. electric field to hydroxyl-containing solids such as kaolinite [A12Si2Os(OH)a ] above the dehydroxylation temperature results in an enhancement of the high-temperature reactions and a significant improvement in the physical and crystallochemical properties of the product at a given temperature. In the case of the applied d.c. field these results have been attributed to the removal of residual protons present in kaolinite even after dehydroxylation is substantially complete [1]. The operation of such a proton-elimination mechanism during the high temperature reactions suggests that electrolysis of inorganic hydroxylcontaining solids at lower temperatures might also influence the course of their dehydroxylation reactions.The purpose of this work was to investigate the manner in which d.c. electric fields interact with solids during their thermal dehydroxylation. The course of the dehydroxylation reaction was followed directly by weight-loss measurements made during the electrolysis. Although this was not primarily a kinetic study, a kinetic analysis was made of the resulting weight-loss curves since this was the most convenient means of comparing the behaviour of the electrolysed solid hydroxides with the unelectrolysed control samples.Previous TG kinetic investigations of kaolinite dehydroxylation have often resulted in differing conclusions; earlier workers generally interpreted their weightloss data in terms of first-order kinetics [3,4] which were taken to indicate a random nucleation process. More recent work in vacuo [5,6] and controlled

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Temperature dependence of DC electrical conductivity of kaolin

Podoba

Štubňa

Trnovcová³

et al. 2013

J Therm Anal Calorim

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Effect of high‐temperature direct‐current electrolysis on properties of hydrous aluminosilicates

Cited by 8 publications

References 10 publications

Devitrification of aluminosilicate glasses under applied electric fields

Devitrification of aluminosilicate glasses under applied electric fields

Thermal reactions of inorganic hydroxy-compounds under applied electric fields, I

Temperature dependence of DC electrical conductivity of kaolin

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