Preparation And Properties Of Superhydrophobic Ferric Oxide Films Through Hydrothermal Method

With remarkable surface properties, superhydrophobic materials have received muchattention not only for their significance to fundamental research but also for their importantapplications in fields ranging from self-cleaning coatings, mico-fluidic devices, andfriction-reduction coatings to national defence field, industry and agriculture production, andpeople’s daily lives. Therefore, both academic and practical research attention has been focused onthe preparation technology and performance research of superhydrophobic surfaces. Meanwhile,iron oxide has attracted a great deal of attention owing to its excellent electrical, optical, magneticand catalytic properties. Hematite (α-Fe2O3), which has weak ferromagnetism at room temperature,has a seductive application prospects in gas-sensitive sensors, lithium batteries, magnetic devicesand other emerging areas. Demands of functional applications have been driven the research ofsuperhydrophobic to move forward and keep going. Under this trend, combining the propertieslisted above with superhydrophobicity could open up new possibilities for the use of α-Fe2O3invarious fields. However, up to date, the simple fabrication of a superhydrophobic Fe2O3hierarchical structure has been barely reported in the literature. Here we present simple andinexpensive ways to achieve superhydrophobic α-Fe2O3nanostructured films throughhydrothermal procedures in this paper. The main research contents and conclusions of this paperare as follows:1. With potassium ferricyanide as reactants, three kinds of α-Fe2O3coatings with differentsurface topographies were prepared on copper sheet, aluminium sheet, and glass slidesrespectively, using a simple hydrothermal process. These films were all surperhydrophobic withhierarchical micro-nanostructures. In particular, coatings on copper and aluminium sheets hadexcellent surperhydrophobicity with very high water contact angles, the smallest sliding anglesand the smaller surface water adhesion. However, all the coatings were not firmly attached to thesubstrates. Their abrasion resistance and superhydrophobic durability need to be further improved.2. With hydrous ferric chloride and polyvinylpyrrolidone as reactants, stearic acids-modifiedα-Fe2O3nanorod films with a hierarchical micro-nanostructure were prepared on glass slides usinga simple hydrothermal process and heat treatment. These films were surperhydrophobic with ahigh water contact angle. The relationship between the surface topographies and the hydrothermalreaction time was studied and the possible formation behavior mechanism of rod-like FeOOHcrystal was proposed. In the formation mechanism, PVP acted as a surface-regulating polymer toresult in the rod-like morphology of the FeOOH crystal with spatial effect, electrostatic andhydrogen bond effects. 3. We studied the water wettability of the α-Fe2O3nanorod films and found that reaction timecould strongly affect the morphology of the nanorod film, leading to differentsuperhydrophobicities and the water adhesion. The surface adhesion forces could be effectivelytuned by solid-liquid contact ways at the nanoscale, which chang with the surface microstructuresresulted from different treatments. The mechanical durability of the α-Fe2O3nanorod surfaces wasevaluated by scratch and friction tests, and the tests showed that the nanorod films possessed goodabrasion resistance and superhydrophobic durability. The magnetic property of α-Fe2O3nanorodpowders was investigated and the magnetization measurement exhibited a hysteretic feature withthe remanent magnetization (Mr) of0.062emu/g and coercivity (Hc) of1173.7Oe, suggesting thatthe α-Fe2O3nanorods exhibit ferromagnetic behaviors at room temperature.