Superhydrophobic surfaces have attracted wide attention due to their excellent waterproof performance. However, the micro-nano structural superhydrophobic surfaces are always fragile due to the poor mechanical stability. We demonstrate robust superhydrophobic surfaces with fine mechanical stability by spraying superhydrophobic coatings on rough substrates. Compared with the superhydrophobic coatings on smooth substrates (SCSS), the superhydrophobic coatings on rough substrates (SCRS) exhibit better mechanical durability because that the microstructures of the rough substrates can effectively protect superhydrophobic coatings from being destroyed under external force. The water contact angles (WCAs) of the SCRSs maintain at 152.1° ± 1.2° after 100 g sand scouring and at 139.5° ± 3.1° after 1000 g sand scouring, while the corresponding WCAs of the SCSSs will drop to 131.8° ± 2.2° and 102.6° ± 5.8°, respectively. Meanwhile, the influence of spraying process parameters on coating morphology, thickness, hydrophobicity and durability has been studied. The ratio of TiO2 and ethyl cellulose in the coatings has been optimized, and the effects of the surface average roughness (Ra) and the coating thickness on the durability of the SCRSs have been studied. The SCRSs possess the best durability when the coating thickness is around 2/3 of the Ra of the substrate surface. The Ra of the substrate surface is fixed at 15.3μm, the durability of the SCRSs increases with the coating thickness at first. As the coating thickness exceeds 2/3 of the substrate Ra, the durability of the SCRSs decreases gradually if the coating thickness increases further. The conclusion is also verified by the SCRSs with aluminum alloys substrates under different Ra. Our work provides a feasible approach for the fabrication of robust superhydrophobic surfaces with excellent durability.
Zeolite membranes with unique physical and chemical properties are emerging as attractive candidates for membrane separation. However, defects in the zeolite layer seriously affect their molecular sieving performance. In this study, a novel strategy for preparing compact zeolite membranes on rough supports with the assistance of a reticulated hydrotalcite layer was developed. The reticulated hydrotalcite layer was grown on the inner surface of a 170 mm length ceramic tube by an in situ hydrothermal method, and a NaA zeolite membrane was prepared on this reticulated layer by the microwave-heating method. The hydrotalcite interlayer could not only improve the smoothness and regularity of the surface of the support but also fix the Si/Al active ingredients using its reticulate structure, finally effectively improving the quality and stability of the zeolite layer. The optimal molar ratio of the synthesis solution for the synthesis of the zeolite membrane was 3Na2O : 2SiO2 : Al2O3 : 200H2O. The permeance flux of H2 through the zeolite membrane synthesized under the optimal conditions was high as 0.47 × 10−6 mol m−2 s−1 Pa−1, and its permselectivity for H2 over N2 was 4.7, which was higher than the corresponding Knudsen diffusion coefficient. This study provides a new idea for the preparation of defect-free membranes on rough supports.
Dielectrics fabrication on rough substrates, always leading to microstructural defects and detrimental dielectric properties eventually, is a great challenge for academic endeavors in this field. We report here on self-flattening AlO x :Y dielectric thin films processed by a facile aqueous solution method. The obtained AlO x :Y dielectrics are dense, large-area uniform, and amenable to accurate control of film thickness by repeating the deposition cycles. In particular, an atomically smooth surface with a RMS of 0.10 nm was realized for the AlO x :Y film with a thickness of 14.5 nm on Si wafer, yielding a low leakage current density of 7.9 × 10 -8 A cm -2 @2 MV/cm, a dielectric constant of 8.8 @100 Hz, and an attenuated dielectric dispersion property. The interactions between pre-baked YO x underlayer and later-dropped AlO x precursor were comprehensively investigated, in order to understand the film growth mechanism and the origin of self-flattening effect. Fortunately, this self-flattening effect is also applicable to other substrates. A RMS of 0.81 nm was achieved on ITO glasses , and the height distribution profile of the film surface was found to follow symmetric Gaussian distribution. This preparation routine was also examined by device verification in the fully-transparent thin-film transistors. The combination of ease of preparation and attractive physical properties would provide a green-route solution platform for dielectric synthesis, for interface engineering, and for well-performed devices on rough substrates.
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