Rapid In Situ Investigation of Nitride Synthesis: Ambient Atmospheric Nitridation of 3d Metal Oxides Using Dicyandiamide

Abstract

The synthesis of metal nitrides, which are a class of functional materials, generally requires an air-free atmosphere, hindering their efficient exploration and production. In this study, we demonstrate the rapid screening of the nitridation conditions of 3d transition metal oxides under an ambient atmosphere via in situ synchrotron X-ray diffraction (XRD). Among V₂O₅, NaVO₃, and a mixture of NH₄VO₃ and NaHCO₃ as the precursors and Dicyandiamide as the nitrogen source, in situ XRD analysis shows that NaVO₃ is a suitable precursor to form a single-phase rock salt structure, which is an anion-rich oxynitride, V_0.69N_0.53O_0.47. The nitridation of NaFeO₂ with Dicyandiamide results in the formation of Fe₃N through FeNCN, which is converted to Fe₃C after further heating. The reaction of NaMnO₂ affords MnNCN, while NaCrO₂ does not produce chromium nitride/carbodiimide. Guided by the in situ XRD results, these metal oxides and Dicyandiamide are placed in an alumina crucible and heated in a box furnace under an ambient atmosphere to synthesize nitride/carbodiimide/carbide on a gram scale without a gas cylinder. This study presents a novel and efficient method for synthesizing various nitrides, oxynitrides, carbodiimides, and carbides under ambient conditions using in situ synchrotron XRD and box furnace, thereby significantly simplifying the nitride synthesis process.