Fluorine Based Superhydrophobic Coatings (original) (raw)
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Fabrication of Silica Nanoparticle-Based Transparent Superhydrophobic Coatings
Proceedings of the 2016 International Forum on Energy, Environment and Sustainable Development, 2016
One-step dip-coating process was employed to fabricate transparent superhydrophobic coating on the glass surface by using the mixture of silica nanopartilces and hexadecyltrimethoxysilane in anhydrous ethanol using triethylamine as hydrolysis catalyst. The water contact angle and optical transmittance were measured for samples using all particle-substrate combination. The results indicate that the superhydrophobicity and transparency of the obtained coatings depend on the aggregation states of silica nanoparticles, which are determined by the concentration of silica nanoparticle in the suspensions.
Silica-based superhydrophobic coating by a single-step process
Surface Innovations, 2013
Silica-based superhydrophobic coatings were produced on glass substrate by dip-coating process. Colloidal solutions containing nanoparticles of silica synthesized via seed growth method (single-and dual-sized particles) and dispersed in three different solvents, ethanol, silica sol and acidic silica sol, were used. Coatings with dual-sized particles in ethanol showed superhydrophobicity with a water contact angle of 155°. The coating adhesion was improved with the use of acidic silica sol as solvent. Coatings prepared from colloidal solution containing 30 wt.% of dual-sized silica particles of 600 and 800 nm in acidic silica sol, showed hydrophilicity with water contact angle of 45° before heat treatment due to the presence of -OH groups from acidic sol. After heat treatment at 250°C for 2 h in atmospheric ambience, the -OH groups reacted to form cross-linked Si-O-Si resulting in superhydrophobicity of the coating with water contact angle of 147°. In this work, silica based superhydrophobic coating was fabricated by adjusting the ratios of the dual-sized silica particles without carrying out any secondary step such as chemical modification or fluorination process on the coating.
A simple and time-saving approach for preparing self-cleaning superhydrophobic silica coatings using a dip-coating technique is reported in this study. Commercially available silica particles were modified with methyl groups using methyl-trichlorosilane as a modifying agent. By adopting a multi-layer deposition process, a superhydrophobic silica coating with a water contact angle of 153° ± 2° and roll-off angle of 8° ± 1° was obtained. The prepared silica coating exhibited excellent self-cleaning performance; moreover, it was able to maintain superhydrophobicity under the impact of a water jet. This method could be an effective strategy for fabricating self-cleaning superhydrophobic surfaces for promising industrial applications.
Journal of Alloys and Compounds, 2018
Fluorine free superhydrophobic coatings with stabilized air-water interface had been fabricated by utilising different particle sized silica. Coatings were formulated with various composition of different sized nanosilica's along with nanotitania and aluminium stearate embedded in a matrix of silicone resin of Mñ 1,65,000. The as-prepared coating exhibited higher contact angle (CA) 152.5 along with high mechanical properties like abrasion, adhesion and impact resistance. As particles with different sizes were incorporated in the coating, the interface was stabilized during immersion in water uptake study. In addition most of these coatings also exhibited exceptional corrosion resistance withstanding upto 1000 h of salt spray.
Progress in Organic Coatings, 2017
Both surface morphology and surface energy of solid surface conclude its wettability, either in Wenzel's hydrophobic or Cassie-Baxter's superhydrophobic wetting state. The superhydrophobic silica coatings were prepared by spin deposition technique from a mixture of hydrophobically modified silica particles and polystyrene. To enhance the adherency of the coating on the substrate and also to improve the durability of the coating, polymer is especially utilized in the coating solution. The durability of the superhydrophobic coating was confirmed by resistency towards water jet impact. The consequence of number of spin deposited layers on the wettability of the coatings was precisely studied. The static and dynamic water contact angle of 158 • and 9 • were achieved on the coating surface. Freely rolling spherical water drops on the non-wettable solid surface are favourable for the self-cleaning effect and so the prepared superhydrophobic coatings revealed superior self-cleaning performance. An anti-corrosion performance of the superhydrophobic coating was also confirmed using electrochemical corrosion experiments in 3.5% NaCl solution with long immersion time.
Fluorine-Free Transparent Superhydrophobic Nanocomposite Coatings from Mesoporous Silica
Langmuir, 2020
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 crosslinked polydimethylsiloxane with particle concentrations between 9 wt% 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 crosslinking 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. Inclusion of nanoparticles is a well-established approach to achieve morphology control and superhydrophobicity. 26,27 Whilst there have been several studies on the control of particle morphology and size in synthesis, this paper focuses on the use of mesoporous particles with the aim of reducing particle density and increasing hierarchical roughness. The Stöber reaction and sol-gel process are still the main synthetic routes with many examples and reviews reported, 28-30 including modifications that have shown the rise of various particle structures including the use of surfactants and templates to dictate the porosity and inner structure, 31,32 and organic solvents for morphology modification. 31 This paper bases synthesis on a previously reported method, 31 for ex situ morphology control for aerosol assisted chemical vapour deposition and spin coating. One of the many challenges of working with nanoparticles is agglomeration, which this paper addresses through silanization to increase steric hindrance and reduce surface energy. Silica particles have been previously utilized in the fabrication of superhydrophobic coatings with a vast array of approaches. 33-39 However, studies show that the addition of this inorganic filler to polymers to form nanocomposites often results in loss of transparency due to increased scattering. Alternative particle structures have been utilized to overcome this such as hollow, dendritic and mesoporous particles. Works by done on understanding the effect of the particle concentration such as by Vo et al, 40 demonstrate that particles with porous morphology reduce the impact on transparency of the coatings as the pores allow for the polymer to penetrate the particle. They also reported that lower concentrations also improve transparency. 40 Polydimethylsiloxane (PDMS) has often been used as the polymer of choice for superhydrophobic coatings 41-44 because of its hydrophobic nature as well as
Superhydrophobic durable coating based on UV-photoreactive silica nanoparticles
Journal of Applied Polymer Science, 2014
Superhydrophobic surfaces can be obtained by tailoring both the chemistry and roughness topography, mimicking the Lotus leaf characteristics. Most of the synthetic superhydrophobic surfaces reported have been composed of micro and nanoparticles (NPs) embedded in polymer-based coatings. The particles which tailor the topography are bonded to the base polymers by weak secondary forces. Consequently, the topography integrity is highly affected by handling and surface drag making them unsuitable for long term applications. This work is focused on promoting covalent bonding between the NPs and the base polymer to obtain durable superhydrophobic surfaces. The rough topography was achieved by ultraviolet (UV) curing of SiO 2 NPs containing a photoreactive benzophenone moiety in addition to methylated fumed silica NPs which can bind covalently to the polymer base coating, on UV radiation. The hydrophobic chemistry was obtained by fluoroalkylsilane top coating. Coating durability was evaluated using surface air drag and accelerated weathering conditions (UV radiation, humidity and temperature). Results indicated that the proposed approach resulted in superhydrophobic surfaces having high contact angle (>150 ) and low sliding angle (<10 ) with improved long term durability.
3rd International Conference on Communication and Electronics Systems (ICCES 2018) IEEE sponsored, Coimbatore, India, October 2018., 2018
This work explores the superhydrophobic effect of functionalized silica nanoparticles on multiple surfaces. Glass, Polysheet, Metal and Wooden materials are coated with functionalized silica nanoparticles by drop casting and chemical bath coating. Challenges and limitations of coated nanoparticles on various materials have been investigated. UV-visible spectroscopy and Scanning electron microscopy have been used in analyzing the absorption spectra and morphology of functionalized silica nanoparticles.
Surface innovation superhydrophobic coating
Silica-based superhydrophobic coatings were produced on glass substrate by dip-coating process. Colloidal solutions containing nanoparticles of silica synthesized via seed growth method (single-and dual-sized particles) and dispersed in three different solvents, ethanol, silica sol and acidic silica sol, were used. Coatings with dual-sized particles in ethanol showed superhydrophobicity with a water contact angle of 155°. The coating adhesion was improved with the use of acidic silica sol as solvent. Coatings prepared from colloidal solution containing 30 wt.% of dual-sized silica particles of 600 and 800 nm in acidic silica sol, showed hydrophilicity with water contact angle of 45° before heat treatment due to the presence of -OH groups from acidic sol. After heat treatment at 250°C for 2 h in atmospheric ambience, the -OH groups reacted to form cross-linked Si-O-Si resulting in superhydrophobicity of the coating with water contact angle of 147°. In this work, silica based superhydrophobic coating was fabricated by adjusting the ratios of the dual-sized silica particles without carrying out any secondary step such as chemical modification or fluorination process on the coating.
Effect of Structural Features on the Superhydrophobicity of SiO2-Based Coatings
Langmuir, 2020
A detailed correlation between topographical features and wettability of chemically modified coatings based on silica nanoparticles (SiO 2) was performed. In this study, hierarchical structures were prepared by the layer-by-layer (LbL) technique using two different approaches: random roughened surfaces were obtained by exploring stacking defects spontaneously arisen after 15, 30, and 45 assembly cycles of 22 nm SiO 2 , and a particular structure, commonly known as raspberry-like, was obtained by depositing 22 nm SiO 2 over the first deposited 400 nm SiO 2. As an intrinsic attribute of the assembly process, the average slope of random roughened surfaces seems to be constant and virtually independent of the number of deposited layers. Additionally, the local slopes are always lower than a critical value (Φ crit) required to stabilize the solid−liquid−air interface; thus, a fully wetted Wenzel state is invariably observed with water contact angles (WCAs) ∼130°. On the other hand, since the local slopes of the raspberry-like structure follow a nearly spherical curvature, small SiO 2 can stabilize the solid−liquid−air interface by increasing the local contact angle and avoid the deep penetration of water into the surface asperities, resulting in a WCA ∼167°. The results also suggest that nanoroughness might also play an important role in the pinning effect of the solid−liquid−air contact line, favoring the maintenance of superhydrophobicity of raspberry-like surfaces.