Preparation of NiCo by Solution Combustion Synthesis Method

In this study, NiCo composite materials were synthesized via the solution combustion synthesis (SCS) method using nickel and cobalt nitrates with hexamethylenetetramine as fuel. Thermodynamic calculations were first conducted to identify optimal fuel-to-oxidizer ratios (φ) and water content, revealing that the maximum adiabatic temperature (2670 K) occurs at φ = 1.25. Experimental results showed that combustion could not be initiated at φ = 0.5, while φ = 1.5 yielded the highest combustion temperature (1580 K) and a pure NiCo composite phase, as confirmed by XRD analysis. The synthesized materials exhibited a porous sintered microstructure with an average crystallite size of ~25 nm. Pressure variation from 0.1 to 1.5 MPa had negligible influence on the phase composition but significantly affected combustion wave velocity, which increased by two orders of magnitude. SEM analysis confirmed that all samples retain porous and sintered morphology, with higher pressures leading to more pronounced sintering. These results demonstrate that the SCS method enables the rapid and effective synthesis of structurally uniform NiCo composites with tunable properties.