Corrosion of Si3N4-ceramics in aqueous solutions Part I: Characterisation of starting materials and corrosion in 1 NH2SO4

The corrosion behaviour of silicon nitride materials in acids strongly depends on the composition and amount of the grain boundary. But there exist no systematic investigations of the relation between the corrosion behaviour and the composition and amount of the grain-boundary phase. The aim of the series of these papers is the systematic investigation of these relations. In the first part the methods of determination of the amorphous grain-boundary phases are described in detail. Additionally, the correlation between the corrosion behaviour and the composition of the grain-boundary phases are given. The structural reasons and the mechanisms behind the observed changes in the corrosion behaviour will be given in part II of this paper.