Resistance of Superhydrophobic Surface-Functionalized TiO2 Nanotubes to Corrosion and Intense Cavitation (original) (raw)
Related papers
2019
n-type, wide bandgap titanium dioxide (TiO2) nanostructures have a great number of engineering applications such as electron transport layers in solar cells and light emitting diodes, photocatalysts, filtration membranes, biomedical implants, drug eluting coatings, superhydrophobic coatings, self-cleaning coatings and chemical sensors. The high Preface This Master thesis includes the result of my research, which is carried out at University of Alberta, Department of Electrical and Computer Engineering. Certainly, this research would not go further without the non-stop help of Professor Karthik Shankar, who supervised me during this period. I also thank Dr. Pawan Kumar who co-supervised my thesis and helped me in the last year of my master studies. Each chapter of this paper-based thesis is either published or prepared as a manuscript draft for submission to a journal. Results of the research presented in Chapter 2 were presented as a poster at the ATUMS annual meeting, Jasper, 12-17 November 2017and at Photonics North, Montreal, June 2012 respectively. A more detailed manuscript of this study titled, "TiO2 Nanotube-Seeded TiO2 Nanowires: Hierarchical Structures for Stable Wetting & Antifouling Studies" has been generated containing Arezoo Hosseini as first author.
Journal of the Brazilian Chemical Society, 2013
Superfícies super-hidrofóbicas com ângulos de contacto maiores ou iguais a 159 o foram preparadas utilizando nanopartículas de dióxido de titânio e trimetoxipropil silano (TMPSi) em solventes aquosos ou não aquosos. A superfície super-hidrofóbica preparada em solvente aquoso mostrou uma histerese angular alta. Por outro lado, a superfície super-hidrofóbica preparada em solvente não aquoso teve uma histerese angular baixa e propriedades auto-limpantes. O uso da espectroscopia NEXAFS (Near Edge X-ray Absorption Fine Structure) é demonstrado e justificado no estudo de superfícies super-hidrofóbicas com a ajuda da espectroscopia no infravermelho com transformada de Fourier no modo de refletância total atenuada (FTIR-ATR). O presente estudo realça a importância da heterogeneidade química de uma superfície sobre as propriedades finais de uma superfície super-hidrofóbica. As propriedades autolimpantes de uma superfície super-hidrofóbica somente são obtidas com um completo recobrimento da superfície com TMPSi quando um solvente não aquoso é utilizado. Esse resultado é sustentado por dados detalhados de NEXAFS e FTIR-ATR. Superhydrophobic surfaces with static water contact angles higher or equal to 159 o were fabricated using titanium dioxide nanoparticules and trimethoxypropyl silane (TMPSi) in aqueous or non-aqueous solvents. The superhydrophobic surface fabricated in aqueous solvent showed high contact angle hysteresis. On the other hand, the superhydrophobic surface fabricated in non-aqueous solvent showed low contact angle hysteresis and self-cleaning properties. The application of near edge X-ray absorption fine structure (NEXAFS) spectroscopy in surface analysis of superhydrophobic surface is demonstrated and justified with the help of Fourier transform infrared spectroscopy by attenuated total reflectance (FTIR-ATR). The present work highlights the importance of chemical heterogeneity of the surface on the final properties of a superhydrophobic surface. The self cleaning superhydrophobic surface is obtained only with a complete coverage of the surface with TMPSi in a non-aqueous solvent. This finding is supported by detailed NEXAFS and FTIR-ATR data.
Improving oleophobicity and hydrophilicity of superhydrophobic surface by TiO2-based coatings
Materials Research Express, 2018
Stability and hydrophilicity of TiO 2 nano-coating was improved in this work. TiO 2 nanoparticles were prepared via conventional, microwave radiation, surfactant, refrigerating, and silica-assisted sol-gel processes. The coated rock plates were obtained by impregnating the plates with nanofluids. The modified TiO 2-based coatings shows to be more effective for wettability alteration purposes compared to the conventional TiO 2 coating. The un-coated surface was superhydrophobic where the n-heptane and water droplets contact angles on the rock surface were 0° and 168° respectively. The n-heptane contact angle on the rock treated via conventional, microwave radiation, surfactant, refrigerating, and silica-assisted sol-gel synthesized nanoparticles changed to 128°, 159°, 156.8°, 151° and 163° respectively. While water contact angle was 53.5°, 0°, 24.1°, 28.6°, and 0° applying the above processes. This confirms that the superhydrophilic coatings were formed on a superhydrophobic surface. The fabricated nano-coatings exhibited high thermal, mechanical and salinity stability. The rock surface before and after treatment as well as the synthesized nanoparticles were characterized by SEM, XRD, and FTIR analyses. Moreover, the surface charge of the nanoparticles in the solution was evaluated using Zeta potential analysis. Applications of these nanocoatings vary from self-cleaning surfaces, protection of building facades and public monuments from weathering however, results of this study indicate possibility of using the materials for wettability alteration of oil-wet carbonate rock in enhanced oil recovery (EOR) process.
On the limit of superhydrophobicity: defining the minimum amount of TiO2 nanoparticle coating
Materials research express, 2018
Fabrication of superhydrophobic surfaces in large scale has been in high interest for several years, also titanium oxide nanostructures having been applied for the purpose. Optimizing the amount and structure of the TiO2 material in the coating will play a key role when considering upscaling. Here, we take a look at fabricating the superhydrophobic surface in a one-step rollto-roll pilot scale process by depositing TiO2 nanoparticles from a Liquid Flame Spray onto a moving paperboard substrate. In order to find the minimum amount of nanomaterial still sufficient for creating superhydrophobicity, we varied nanoparticle production rate, flame distance from the substrate and line speed. Since the deposited amount of material sideways from the flame path was seen to decrease gradually, spatial analysis enabled us to consistently determine the minimum amount of TiO2 nanoparticles on the substrate needed to achieve superhydrophobicity. Amount as low as 20-30 mg/m 2 of TiO2 nanoparticles was observed to be sufficient. The scanning electron microscopy revealed that at this amount, the surface was covered with nanoparticles only partially, but still sufficiently to create a hierarchical structure to affect wetting significantly. Based on XPS analysis, it became apparent that TiO2 gathers hydrocarbons on the surface to develop the surface chemistry towards hydrophobic, but below the critical amount of TiO2 nanoparticles, the chemistry could not enable superhydrophobicity anymore. While varying the deposited amount of TiO2, besides the local spatial variance of the coating amount, also the overall yield was studied. Within the text matrix, a yield up to 44 % was achieved. In conclusion, superhydrophobicity was achieved at all tested line speeds (50 to 300 m/min), even if the amount of TiO2 varied significantly (20 to 230 mg/m 2).
Recent advances in the mechanical durability of superhydrophobic materials
Advances in colloid and interface science, 2016
Large majority of superhydrophobic surfaces have very limited mechanical wear robustness and long-term durability. This problem has restricted their utilization in commercial or industrial applications and resulted in extensive research efforts on improving resistance against various types of wear damage. In this review, advances and developments since 2011 in this field will be covered. As such, we summarize progress on fabrication, design and understanding of mechanically durable superhydrophobic surfaces. This includes an overview of recently published diagnostic techniques for probing and demonstrating tribo-mechanical durability against wear and abrasion as well as other effects such as solid/liquid spray or jet impact and underwater resistance. The review is organized in terms of various types of mechanical wear ranging from substrate adhesion, tangential surface abrasion, and dynamic impact to ultrasonic processing underwater. In each of these categories, we highlight the mos...
Langmuir, 2004
We report on the photoinduced superhydrophilicity of the surface of amorphous TiO2. Amorphous TiO2 thin films were prepared on self-assembled monolayers by the peroxotitanate-complex deposition (PCD) and liquid-phase deposition (LPD) methods. The surface morphology and topography were characterized in detail. The contact angles were 34°and 66°for the as-deposited thin films through the PCD and LPD methods, respectively, which slowly increased to about 70°and 73°after being stored in air. After irradiation by UV light, the contact angle vanished and the surface exhibited superhydrophilicity. The superhydrophilicity and hydrophobicity could be switched by alternatively exposing the surface to UV light and drying in an atmosphere filled with organic gases. Although the oxidation of the contamination on the surface has effects on the increase in hydrophilicity, the X-ray photoelectron spectroscopy results suggested that the superhydrophilicity was also related to the transformation of the Ti-OH groups to groups that have dangling bonds. This paper indicates that an amorphous TiO2 thin film does not need to be heated to obtain superhydrophilicity; such a self-cleaning surface can be achieved at room temperature by our newly developed environmentally friendly method.
Langmuir
One-dimensional (1D) nanostructured surfaces based on high-density arrays of nanowires and nanotubes of photoactive titanium dioxide (TiO2) present a tunable wetting behavior from superhydrophobic to superhydrophilic states. These situations are depicted in a reversible way by simply irradiating with ultraviolet light (superhydrophobic to superhydrophilic) and storage in dark. In this article, we combine in-situ Environmental Scanning Electron Microscopy (ESEM) and Near Ambient Pressure Photoemission analysis (NAPP) to understand this transition. These experiments reveal complementary information at microscopic and atomic level reflecting the surface wettability and chemical state modifications experienced by these 1D surfaces upon irradiation. We pay a special attention to the role of the water condensation mechanisms and try to elucidate the relationship between apparent water contact angles of sessile drops under ambient conditions at the macroscale with the formation of droplets by water condensation at low temperature and increasing humidity on the nanotubes surfaces. Thus, for the as-grown nanotubes, we reveal a metastable and superhydrophobic Cassie state for sessile drops that tunes towards water dropwise condensation at the microscale compatible with a partial hydrophobic Wenzel state. For the UV irradiated surfaces, a filmwise wetting behavior is observed for both condensed water and sessile droplets. NAPP analyses show a hydroxyl accumulation on the as-grown nanotubes surfaces during the exposure to water condensation conditions, whereas the water filmwise condensation on a previously hydroxyl enriched surface is proved for the superhydrophilic counterpart.
Multifunctional superhydrophobic nanocomposite surfaces based on photocatalytic materials, such as fluorosilane modified TiO 2 , have generated significant research interest. However, there are two challenges to forming such multifunctional surfaces with stable superhydrophobic properties: the photocatalytic oxidation of the hydrophobic functional groups, which leads to the permanent loss of superhydrophobicity, as well as the photoinduced reversible hydrolysis of the catalytic particle surface. Herein, we report a simple and inexpensive template lamination method to fabricate multifunctional TiO 2 −high-density polyethylene (HDPE) nanocomposite surfaces exhibiting superhydrophobicity, UV-induced reversible wettability, and self-cleaning properties. The laminated surface possesses a hierarchical roughness spanning the micro-to nanoscale range. This was achieved by using a wire mesh template to emboss the HDPE surface creating an array of polymeric posts while partially embedding untreated TiO 2 nanoparticles selectively into the top surface of these features. The surface exhibits excellent superhydrophobic properties immediately after lamination without any chemical surface modification to the TiO 2 nanoparticles. Exposure to UV light causes the surface to become hydrophilic. This change in wettability can be reversed by heating the surface to restore superhydrophobicity. The effect of TiO 2 nanoparticle surface coverage and chemical composition on the mechanism and magnitude of wettability changes was studied by EDX and XPS. In addition, the ability of the surface to shed impacting water droplets as well as the ability of such droplets to clean away particulate contaminants was demonstrated.
Superhydrophobicity through Coatings Prepared by Chemical Methods
Superhydrophobic Surfaces - Fabrications to Practical Applications, 2020
Superhydrophobic surfaces were first observed in nature like on a lotus leaf. The surfaces need to have hierarchical micro-and nanoscale roughness and low surface energy to achieve superhydrophobicity. Their unique behavior against water leads to various applications like corrosion resistance, oil-water separation, self-cleaning properties, anti-icing properties, drag reduction, and antibacterial properties. To investigate the wetting behavior of the coating, water contact angle, contact angle hysteresis and sliding angle must be measured. If WCA is higher than 150 and sliding angle and contact angle hysteresis are below 10 , then it can be concluded that the surface is superhydrophobic. Various fabrication methods including lithography, templating, chemical vapor deposition, layer-by-layer deposition, colloidal aggregation, and electrospinning and electrospraying especially wet chemical method are thoroughly studied. Among all fabrication methods, the wet chemical technique is one of the promising methods due to its low cost and capability of largescale production and also the substrate shape and dimensions having a minimal effect on the process. Superhydrophobic coatings still lack sufficient mechanical endurance. Also, in all traditional superhydrophobic coatings, it is necessary to lower the surface energy by a low-energy polymeric material that does not have suitable bonding and stability in harsh environments.