Metallographic investigations of the La-N-C system

In the course of an investigation into the phases occurring in the little known La-N-C system, both X-ray investigations and chemical analyses were carried out. Manipulation of the specimens during preparation, analysis and metallographic examination is difficult because of the susceptibility of the rare earth nitrides and carbides to atmospheric moisture and oxygen. In order to prevent falsification of the analysis results by hydrolysis and oxidation, all the preparative stages must be carried out in the absence of air in a glove box filled with dry argon or nitrogen. Although the preparation for the analytical and X-ray determinations can easily be undertaken in a protective atmosphere, the production of polished sections for metallographic phase analysis is fraught with difficulties on account of the apparatus required and the preparative technique. Investigations have however shown that it is possible to prepare sections of these easily hydrolysed specimens from the La-N-C system in air if certain precautions are taken. (orig.)