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Microstructure, transport properties and chemical reactions in ceramics and composities: application to superconductor based composites.

Gavarii J.R., Kopia-Zastawa A., Fremy M.A., Pischedda M.H., Suliga I., Jasieńska S.

Inżynieria Materiałowa

1998

R. XIX, nr 4

813-818

In this review, we deal with active two-phase composites made of one superconducting constituent (S) and of an additional phase (F) having a mechanical or electrical role. To interpret the effects of sintering processes, two types of modelling approaches are discussed: firstly, the modelling of the chemical diffusions and, secondly, the chemical reactivity which conditions both electrical and mechanical properties of the resulting F/S composites. The chemical reactions at the interfaces of the F/S composites are firstly described by a simplified Fick law approach: each element can be characterized by one apparent chemical diffusion coefficient D. Then expressing the chemical reaction following the classical form: F + n.S -> P, and considering elemental kinetics laws (d[F]/dt = -k1. [F][S]), we propose to determine two new parameters characteristic of the degradation of the system during the sintering process. Finally, three types of parameters (D, n, k1) are available to describe the chemical evolutions in composites.