Estudo Experimental da Difusão do Níquel no Cr2O3 por Espectrometria de Massa de Íons Secundários

AUTOR(ES)
DATA DE PUBLICAÇÃO

2007

RESUMO

Many industrial alloys, that are submited the high temperatures, contain the element chromium, that it oxidates preferential forming a very adherent film. This film acts as a barrier of protection against the corrosion of the alloys in oxidant environment. Example of these alloys is the stainless steel and other alloys contend chromium and nickel. The interpretation of the mechanisms of formation and growth of this film of chromia requires the knowledge of the diffusion processes that occur in this material. Beyond the diffusion of the oxygen and chromium, the diffusion of the too much component elements of the metallic alloys also must be know, such as the Fe, Mn, Ni and others. These elements still spread out through the film of chromia affecting its properties, being able, in determined alloys, to give origin to the formation other phases, either in the inward of the film, either in the outward surface of oxide. In this work, we experimentally determine the diffusion coefficients of Ni in chromia in synthetics single crystal and polycrystal. In the chromia single crystal, the study of the diffusion was carried through in bulk. Whereas in the chromia polycrystals these diffusion studies had been carried through as much in bulk much grain boundaries. A nickel film with about 35nm of thickness was deposited on the surface duly prepared of the samples of chromia. The diffusion experiments were carried out in range temperatures 900 to 1100C, under a partial oxygen pressure of 10Pa. The profiles of diffusion of nickel had been determined by spectrometry of mass of secondary ions (SIMS). These experiments had lead to the determination of the bulk and grain boundary diffusion coefficients in the chromia, with appropriate solutions of the second law of Fick, Le Claires model and the Harts equation. The variations of these coefficients of diffusion had been described by Arrhenius equations. In the experimental conditions of this work the differences between the diffusion coefficients of nickel in the chromia single crystal and the bulk diffusion in the chromia polycrystals they had not been significant. Using the results of this work and others previous ones a comparison was made between the diffusion of nickel, chromium, iron and manganese in the chromia.

ASSUNTO(S)

engenharias 1. difusão - teses. 2. níquel - teses. 3. oxidação - teses. 4. Óxido de cromo - teses. i. universidade federal de ouro preto. ii. título.

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