ABSTRACT
Robust fluorine-free superhydrophobic films were produced from a mixture of two fatty acids (stearic acid and palmitic acid), SiO2 nanoparticles, and polydimethylsiloxane. These simple and nontoxic compounds were deposited via aerosol-assisted chemical vapor deposition to provide the rough topography required for superhydrophobicity, formed through island growth of the aggregates. The optimum conditions for well-adhered superhydrophobic films produced films with a highly textured morphology, which possessed a water contact angle of 162 ± 2° and a sliding angle of <5°. Superhydrophobicity was maintained after ultraviolet exposure (14 days at 365 nm), heat treatment (5 h at 300 °C and 5 h at 400 °C), 300 tape peel cycles, and exposure to ethanol and toluene (5 h each).
ABSTRACT
In recent decades, there has been a growing interest in the development of functional, fluorine-free superhydrophobic surfaces with improved adhesion for better applicability into real-world problems. Here, we compare two different methods, spin coating and aerosol-assisted chemical vapor deposition (AACVD), for the synthesis of transparent fluorine-free superhydrophobic coatings. The material was made from a nanocomposite of (3-aminopropyl)triethoxysilane (APTES) functional mesoporous silica nanoparticles and titanium cross-linked polydimethylsiloxane with particle concentrations between 9 to 50 wt %. The silane that was used to lower the surface energy consisted of a long hydrocarbon chain without fluorine groups to reduce the environmental impact of the composite coating. Both spin coating and AACVD resulted in the formation of superhydrophobic surfaces with advancing contact angles up to 168°, a hysteresis of 3°, and a transparency of 90% at 550 nm. AACVD has proven to produce more uniform coatings with concentrations as low as 9 wt %, reaching superhydrophobicity. The metal oxide cross-linking improves the adhesion of the coating to the glass. Overall, AACVD was the more optimal method to prepare superhydrophobic coatings compared to spin coating due to higher contact angles, adhesion, and scalability of the fabrication process.
ABSTRACT
Exceptional anti-icing and antifogging devices have been synthesized through combination of micro- and/or nanoscale hierarchical thin films followed by a modification with a surface lubricant. Aerosol assisted chemical vapor deposition (AACVD) of single source titanium and tin precursors generated titanium dioxide (TiO2)/tin dioxide (SnO2) composite thin films. Variation in solvent type and/or combination notably impacted on the resulting intricate surface morphologies, which, upon Krytox lubricant modification, generated slippery liquid infused porous surfaces (SLIPS). The surface topography had a profound effect on the degree of surface ice and fog accumulation. The highest functioning films comprised of hybrid spherical/flowery surface structures generated using a mixed ethyl acetate/dichloromethane solvent system. These films retarded ice formation for >30 min at -10 °C and maintained a high level of sample transparency upon suspension above a heated water bath.
ABSTRACT
A method for the preparation of transparent superhydrophobic silica coatings on glass substrates via aerosol-assisted chemical vapour deposition (AACVD) is described. A multi-layer process to produce dual scale silica nanoparticles films, by using different functional alkoxysilanes was investigated. A first layer of 3-methacryloxypropyltrimethoxysilane (MPS) and a second layer of tetraethylorthosilicate (TEOS) were deposited at different temperatures to generate micro and nano particles of silica. Finally, a layer of perfluorooctyltriethoxysilane was deposited on top of the two layers to achieve superhydrophobicity. The transparent superhydrophobic film showed transparency of 90% in the visible light region with a static water contact angle of 165° and a sliding angle lower than 1°. Various durability tests were performed on the transparent superhydrophobic film, showing a constant water repellency after corrosion and organic solvents tests, strong resistance under UV light, and thermal stability up to 400 °C. Sandpaper mechanical robustness durability test showed superhydrophobicity for up to 5 rubbing cycles. In this study, a novel strategy to achieve highly transparent superhydrophobic glass surfaces using AACVD of alkoxysilanes, to produce surfaces with excellent durability is described. This shows great potential to obtain silica superhydrophobic films for large-scale applications.
ABSTRACT
Surfaces that have unique wettabilities and are simultaneously superhydrophobic with water contact angles > 150°, and superoleophilic with oil contact angles < 5°, are of critical importance in the oil/solvent-water separation field. This work details the facile preparation of highly efficient oil-water separation devices that successfully combine hierarchical surface roughening particles and low surface energy components with porous substrates. Coatings were generated using TiO2 and hydrophobic-SiO2 micro/nanoparticle loadings which were then embedded within polydimethylsiloxane, commercially known as Sylgard® 184, and 1H,1H,2H,2H-perfluorooctyltriethoxysilane (FAS) polymer mixtures. The resulting slurries were dip coated onto copper meshes with varying pore diameters (30, 60 and 100 meshes had 595, 250 and 149 µm pore dimensions respectively). Functional testing proved that mesh substrates coated in the lowest Sylgard® 184 : FAS polymer ratio formulations displayed heightened water repellency and retained their superoleophilic properties upon repeat testing. The largest average water contact angle of 145 ± 1°, was recorded on a copper 30 mesh substrate with a coating comprising H-SiO2 microparticles and TiO2 nanoparticles in a 1 : 9 polymer mixture of Sylgard® and FAS. The coating's extreme oil affinity was supported by high solvent-water separation efficiencies (≥99%) which withstood numerous testing/washing cycles.
ABSTRACT
Special wettability durable coatings, with average water contact angles exceeding 140°, have been fabricated utilising functionalised hydrophobic-SiO2 (H-SiO2) particles embedded in fatty acids. The inexpensive and non-toxic H-SiO2 particles imparted delicate lotus leaf inspired hierarchical surface nano-morphologies while the fatty acid modification afforded a suitable drop in surface energy. Comparison studies were carried out to explore the effects of fatty acid chain length and pipette as opposed to spray coating deposition methods on the coatings hydrophobicity. It was determined that the longest chain length fatty acid coatings showed enhanced hydrophobic properties due to their extended hydrophobic alkyl chain. A pipette deposited suspension containing H-SiO2 nanoparticles and octadecanoic acid generated a coating with the most favourable average water contact and tilting angles of 142 ± 6° and 16 ± 2° respectively.
