Formation and reactivity of nitrides. IV. Titanium and zirconium nitrides

The reactivities of the interstitial titanium and zirconium nitrides have been compared. Samples of these nitrides have been converted to oxides by being calcined in air. Changes in phase composition, surface area, crystallite and aggregate sizes have been correlated with oxidation time and temperature. Crystallites of rutile, TiO2, split off from the remaining titanium nitride before they sinter, and inhibit further oxidation. Zirconium nitride oxidation is complicated by formation of tetragonal ZrO2 at higher temperatures, particularly over 1200°, and monoclinic ZrO2 at lower temperatures. The nitride initially forms the so‐called ‘amorphous’ cubic ZrO2, notably between 400–600°, which may be stabilised somewhat by the remaining cubic ZrN. Subsequently, there is a further fractional volume increase while formation of monoclinic ZrO2 is being completed.