Preparation and properties of thorium nitrides

In order to prepare pure Th3N4 powder of high crystallinity, a considerable amount of experimental work has been expended, and it is found that the reaction of powdered Th4H15 with a stream of N2 at 800deg C gives a satisfactory method for preparing powdered Th3N4 of the desired quality. Preparation of ThN has been performed by thermal decomposition of Th3N4 at temperatures from 1250 to 1400deg C for various periods of time in vacuum and in a stream of H2 or He gas. The stabiltiy of ThN has also been evaluated from thermodynamic calculation using the reported values for the free energies of formation of the related compounds in the Th-N-O system. The oxidation of Th3N4 has also been studied around room temperature. X-ray diffraction analysis has revealed that air-oxidation of Th3N4 may yield poorly crystallized ThO2, its degree of crystallinity depending upon the oxidation temperature. Moreover, the solid phase precipitating from the solution prepared by the reaction of Th3N4 with HNO3 has been examined by X-ray diffraction method, chemical analysis, IR spectroscopy and DTA-TG analysis. The precipitate has been identified to be H2Th(NO3)6·3H2O. Furthermore, the precipitate from the solution prepared by dissolving H2Th(NO3)6·3H2O in HNO3 has been found to be presumably (NH4)2Th(NO3)6. (author)