Authors: Dutrizac, J.E.; Ingraham, T.R.

Source: Canadian Metallurgical Quarterly, Number 2, April-June 1969 , pp. 119-126(8)

Publisher: Maney Publishing

Abstract:

Coupons of nickel metal were sulphurized in sulphur. vapour at pressures from 0.1 to 70 torr and at temperatures from 300 to 507° C. NiS was the major, and usually the only, sulphide formed. It appeared as a porous layer adjacent to the nickel, and as a compact layer where it was in contact with the sulphur vapour.

The sulphurization reaction exhibited two separate and distinct types of kinetic behaviour. In one, the reaction was fast and the NiS layer was blistered and cracked. In the other, the rate was slow and the NiS layer was intact. In some runs the sulphide layer was intact only part of the time. During the healing stage, the rate of sulphurization was slow; during the cracking stage it was rapid. The activation enthalpies for the slow and fast reactions were 30 – 32 and 19 – 21 kcal/mole, respectively.

In both, the rate of sulphurization varied directly with the square root of the partial pressure of S₂. This, together with the observation of linear kinetics for both stages, has been interpreted as involving rate control by the dissociation of S₂ to sulphur atoms. The involvement of a fast or slow reaction is thought to be dependent on whether the dissociation occurs on the metal or sulphide interfaces.

Résumé

Du nickel a été mis en contact avec la vapeur de soufre à des pressions situées entre 0.1 et 70 torr et à des températures comprises entre 300 et 507°C. Seul le NiS s'est formé, ou presque. Il était poreux à l'interface métal et it était compact à l'interface vapeur.

La cinétique de sulfuration est dédoublable. Une réaction est rapide et elle donne un sulfure cloqué et fissuré. L'autre est lente et elle donne un sulfure compact. Au cours de certains essais le sulfure était compact une partie du temps: la sulfuration lente rendait le sulfure compact; la sulfuration rapide le rendait fissuré. L'enthalpie d'activation de la sulfuration lente est 30–32 kcal/mole; celle de la sulfuration len te est 19–21 kcal/mole.

Dans les deux cas le taux de sulfuration variait linéairement avec la racine carrée de la pression partielle de S₂. Ce qui laisse entendre que la réaction clé est celle de la dissociation du S₂ en S. La sulfuration rapide laisse entendre une dissociation du S₂ à l'interface du métal tandis que la réaction lente correspondrait à une dissociation du S₂ à l'interface vapeur.

Document Type: Research Article

DOI: http://dx.doi.org/10.1179/000844369795149362

Publication date: 1969-04-01

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