Effect of surface morphology on wettability conversion

Abstract

Abstract:A hierarchical structural surface of TiO 2 film with reversibly light-switchable wettability between superhydrophobicity and superhydrophilicity on metal substrate was fabricated through simply dip-coating method from TiO 2 precursor solution containing TiO 2 nanoparticles with the average diameter 25 nm (P25), followed by heat-treatment and modification with fluoroalkylsilane (FAS) molecules. The morphology, phase and crystallographic structure, and chemical composite of the as-prepared TiO 2 film were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). The wettability of TiO 2 film was characterized by a drop shape analyzer. The water contact angle of superhydrophobic TiO 2 film was up to 165.6°. Under UV irradiation, the water contact angle decreased and the superhydrophobic TiO 2 film became superhydrophilic because of hydroxyl groups absorption on the TiO 2 surface. Meanwhile, the surface morphology of TiO 2 film, which resulted from the TiO 2 nanoparticles added in TiO 2 precursor solution, had a significant effect on the wettability conversion of TiO 2 film and enhanced the switch from hydrophobicity to hydrophilicity. The wettability could be reversibly switched between superhydrophobicity and superhydrophilicity via alternation of UV exposure and dark storage.

Heterojunction Engineering and Ideal Factor Optimization Toward Efficient MINP Perovskite Solar Cells

“…As can be seen, with the increase of 5‐AVA concentration, the contact angle gradually increases, and the wettability of the substrate decreases slightly, which is related to the decrease of hydrophilic hydroxyl groups on the surface of ITO. [ 34 ] However, the slight decrease in wettability did not affect the precursor coating obviously, as all perovskite films exhibited compact and uniform full coverage with almost the same grain size shown in Figure 3f–j. From the SEM images we observed that the perovskite film deposited on the ITO/5‐AVA has slightly larger grains than pristine, which may be attributed to the decrease of nucleation density due to the slightly worse wettability and the preferential growth of perovskite induced by 5‐AVA.…”

Self-cleaning material based on superhydrophobic coatings through an environmentally friendly sol–gel method

“…However, the obtained results confirm that the presence of TiO 2 layers on the surface of coated glass, after being irradiated by UV light, did not have a significant effect on decreasing the CA value. It is due to the presence of oxygen atoms from OTS molecules can gradually replace the oxygen vacancies on TiO 2 film to maintain the hydrophobicity [21].…”

“…There are several studies that have been reported on developing superhydrophobic coating through this combination method. Kong et al have prepared superhydrophobic coating on glass substrate by fabricated a micro-/nanostructured TiO 2 film via the sol-gel dip-coating method and then modified by fluoroalkylsilane molecules [18]. The asprepared coatings not only showed a high static water CA up to 165.6°but also enhanced the reversible wettability conversion between hydrophobicity and hydrophilicity.…”

“…Based on all of these drawbacks, the fabrication of superhydrophobic coatings is quite limited for some reasons: first, methods that widely used to fabricate superhydrophobic coatings are costly and tricky [20]. Second, some chemicals that involved in the fabrication of superhydrophobic coatings such as fluorinated compounds are very hazardous due to their nondegradable and high toxic properties [21]. Third, the high surface roughness that is needed to give the superhydrophobic coatings is always contradictory with the transparency properties [22].…”

Surface energy determination of fibres for Liquid Composite Moulding processes: Method to estimate equilibrium contact angles from static and quasi-static data

“…Those parameters indeed control the final void content and interfacial properties of the composite parts. Fibre surface chemistry and morphology affect wetting properties [1]. Therefore, the surface properties of fibres affect their impregnation during manufacturing and thus directly the quality of the fibre / matrix adhesion.…”