Template-assisted fabrication of macroporous NiFe2O4 films with tunable microstructural, magnetic and interfacial properties

Nickel ferrite (NiFe2O4) films with macroporous frameworks are successfully fabricated on silicon substrates via a novel template-assisted route. The fabrication approach mainly involves the formation of two-phase composite (desired nickel ferrite and nickel oxide phases) films by thermal conversion of Ni-Fe layered double hydroxide precursor films followed by a selective leaching of self-generated NiO template from the two-phase composite films. The microstructural, magnetic and interfacial properties of the resulting films were characterized by means of X-ray diffraction (XRD), chemical analyses, scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX) and atomic force microscopy (AFM). The results revealed that the microstructures (e.g. particle sizes and spacing among particles), magnetism and surface hydrophobic property of as-fabricated NiFe2O4 films could be finely tuned by varying the composition of precursor films. The increasing Ni/Fe ratio in precursor films leads to reduced particle sizes and enlarged spacing among ferrite particles in NiFe2O4 films. Furthermore, the as-fabricated NiFe2O4 films show tunable saturation magnetization varying from 36 to 55 emu/g and excellent surface hydrophobicity ranging from 139 to 152 degrees after surface modification of films. We believe that such unique macroporous NiFe2O4 films can open up new opportunities for a wide range of advanced applications.