Formation mechanism and kinetics of Ni3CuN complex nitride in solution combustion synthesis

This study investigates the formation mechanism of Ni 3 CuN complex nitride during combustion of aqueous solutions of nickel and copper nitrates and hexamethylenetetramine. The impact on the combustion process and final product formation was analyzed by varying the hexamethylenetetramine concentration. Time-temperature measurements during solution combustion synthesis (SCS) reactions coupled with X-ray diffraction (XRD), transmission electron microscopy, electron diffraction, and high-resolution element analysis of reacted materials revealed a complex reaction mechanism. Thermogravimetric analysis (TGA) provided detailed insights into the combustion dynamics, identifying several distinct stages: partial dehydration of metal nitrates, decomposition of intermediate nitrates forming oxides, metal and alloy formation, and final nitridation to produce Ni 3 CuN. The TGA results highlighted the significant influence of heating rate on reaction dynamics, with lower rates (0.083–0.25 K/s) leading to gradual weight loss and higher rates (0.33–0.5 K/s) resulting in abrupt reactions. The effective activation energy calculations from TGA data, supported by XRD and electron microscopy findings, identified nickel nitrate decomposition as the rate-limiting step, with an effective activation energy of 179 ± 27 kJ/mol for lower heating rates and 217 ± 36 kJ/mol for higher rates. These integrated analyses enhance the understanding of the SCS mechanism for synthesizing Ni 3 CuN and demonstrate the potential for producing complex nitrides with tailored properties for applications in catalysis, magnetic devices, and other advanced materials technologies.