Über die Stickstoffbestimmung in hochtemperaturstabilen Metallnitriden und -carbonitriden

A report is given on the determination of nitrogen content in nitrides and carbonitrides of transition metals. In detail several methods are compared:

1. The interference of CuO with the reaction mechanism is examined by the Dumas method. By thermodynamic calculations and experimental investigations as well as by X-ray diffraction analysis it has been verified that the release of nitrogen is only possible by the use of a CO₂ carrier gas. The modified Dumas method is the best suitable method for a precise and reproducable nitrogen analysis in thermally high-stable nitrides and carbonitrides. Especially the high capacity of indication is of interest, so for instance, it is still possible to analyse 0.5 ppm by using samples of 1 g.
2. In decomposing nitrides not easily to dissolve the Kjeldahl method fails because of the oxidation effect of special solvents which at higher temperatures and extended time of analysation leads to a considerable decrease in verification.
3. The method of hot extraction with steel, cobalt, and nickel leads also without a carbon saturated prefusion at a temperature of 2000°C to a decrease in verification. The precipitation of graphite in the melt is clearly responsible for this effect. By means of the electron beam microprobe analysis it could be proved that the remaining nitrogen was in the graphite needles, but not as an undecomposed metallic nitride. In general the results of the platin flux method were in good agreement with the results of the methods compared. An analysis without a bath metal is always successful, if the nitride is easily to dissolve, reacts quickly with the carbon of the graphite crucible, and if the melting point of the nitrides or carbides is near working temperature.