ISSN:
1573-9139
Quelle:
Springer Online Journal Archives 1860-2000
Thema:
Maschinenbau
Notizen:
Conclusions It was shown in an investigation of the kinetics of the heat-induced shrinkage and deformation of magnesite and chromite and their mixtures that the kinetics is proportional to 1/t2 and that the sintering of the mixtures at a temperature up to 1750°C proceeds by virtue of the elimination of open pores. Chromite added to the magnesite intensifies sintering only when the proportion of chromite is small and is reduced with an increase in the temperature. This decrease depends on the quantity of chrome-spinel (about 2.5% on the maximum practicable concentration) dissolved in the periclase under the conditions concerned. When this proportion of dissolved chrome-spinel is high, the degree of sintering of the mixture decreases. However, at 1750°C the porosity of specimens containing 20% chromite is adequately low, viz. 2.5–3%. A proportion of 20% chromite in the mixture reduces the deformation but the latter increases with a further increase in the chromite content and is at a maximum with 40% chromite. This variation of the deformation arises from changes in the number of phases and in the total length of the interphase boundaries in the specimen. The calculated diffusion coefficients of magnesite, chromite, and a 20/80 mixture of these materials provide evidence that the sintering and deformation of chromite and its mixtures with magnesite proceed by virtue of the diffusion of vacancies, the rate of diffusion being dictated by the mobility of the oxygen ion which diffuses more slowly than the other ions.
Materialart:
Digitale Medien
URL:
http://dx.doi.org/10.1007/BF01285678
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