Single-stage preparation and formation mechanism of Ni-Co alloy by solution combustion synthesis
摘要
In this study, an effective approach has been proposed for the single-stage preparation of fine powders of а Ni-Co alloy by application of the solution combustion synthesis (SCS) method, based on heating an aqueous solution containing metal nitrates and organic reducers, urea, and glycine. It has been established that only a combination of the selected reducing compounds, can led to a virtually single-phase nickel-cobalt alloy. Scanning electron microscopy, powder X-ray diffraction, EDS and XPS analyses were used to characterize the obtained material. Application of these methods allowed to reveal that trace amounts of the two main impurities, carbon and nitrogen, are distributed homogeneously in the alloy as a result of decomposition of the used reducers, and oxygen is present basically on the surface of the alloy in the form of physically and chemically absorbed molecules of water, metal hydroxide, or oxide. Using differential scanning calorimetry in combination with the thermogravimetric analysis, possible mechanisms of chemical transformations during the SCS process yielding the target Ni-Co alloy were discussed. The role of individual organic reducers at different stages of SCS was assessed.
Graphical Abstract