Effect of the chelating agent contents on the topography, composition and phase of SPPS-deposited cobalt ferrite splats

Cobalt ferrite solution was deposited onto mild steel substrates to form single splats employing a solution precursor plasma spray (SPPS) process. It was revealed that the thermal oxidation of cobalt and iron salts into cobalt monoxide (CoO), maghemite (γ-Fe2O3), cobalt oxide (Co3O4), cobalt oxyhydroxide (CoOOH), goethite (α-FeOOH), hematite (α-Fe2O3), magnetite (Fe3O4), and cobalt ferrite (CoFe2O4) occurred mainly within the deposited splats. The surface topographies of the splats exhibited unmolten, partially molten, and completely molten splats. All splat diameters were in the range of 2–5 μm, while the thicknesses were 0.3–2.0 μm. The citric acid (CA) concentration of the chelating agent significantly affected the percentage of the cobalt ferrite phase and the equivalent diameter of the splats. More than 90% of cobalt ferrite phase was formed when using 20% CA.