Investigation On Surface Wettability Of Common And Nano-crystal Fe

The wettability of a solid material, which is determined by the combined effects of thesurface composition and surface morphology, is one of its most important properties whichdeserve considerable research. To date, some groups have prepared materials withsuperhydrophobicity and superhydrophilicity, but reports on materials with tunable surfacewettability are rare, which made it essential to seek a specific material with superiorhydrophilicity. Moreover, it is an important to seek an easy and effective way to control thewettability of materials. As is known, Nano-crystal metals exhibit both great mechanicalproperties including high hardness, superior strength, as well as good plasticity and toughness,and excellent chemical properties such as good corrosion resistance and high activity.Therefore, this paper was devoted to Conventional polycrystalline ingot iron and Bulknanocrystalline ingot iron, with an emphasis on the effects of surface morphology, electronicstructure and aging on the wettability of iron surfaces. The relationship underlying the surfacestructure and surface wettability was aim to explore good theoretical foundation for thedevelopment of next surface coatings.Conventional polycrystalline ingot iron and Bulk nanocrystalline ingot iron sampleswere prepared, and their water contact angles were measured in sessile drop method (DSA100,Kruss Co.). The scanning electron microscope (SEM) and white light interferometry contourequipment were employed to determine the surface morphology and surface roughness of thesamples, respectively. X-ray photoelectron spectroscopy (XPS) was conducted toanalyze surface composition of the samples, and the surface free energy was calculated by theembedded software in DSA100 device with the help of the static contact angles results.The experiments show that, for Conventional polycrystalline ingot iron and Bulknanocrystalline ingot iron samples under the same experimental condition after one day ofaging, their contact angles both decrease with increase of surface roughness, and Bulknanocrystalline ingot iron exhibited better wettability. The measurements for the samples after24 days of aging, however, show that the larger the surface roughness, the greater the watercontact angle. The water contact angle hysteresis is caused by the surface heterogeneity, withthe static contact angle almost amount to the receding contact angle for hydrophilic surfacesand the static contact angle closing to the advancing contact angle for hydrophobic surfaces. We also reveal that the relationship between contact angle and surface roughness falls inagreement with Wenzel model. Conventional polycrystalline ingot iron is oxidized more easilythan Bulk nanocrystalline ingot iron after the same time of aging, which is proved by thesurface free energy calculation of the different surfaces, that Bulk nanocrystalline ingot ironhas greater surface free energy than Conventional polycrystalline ingot iron when otherconditions remain constant.