scholarly journals Assessment of Super-Hydrophobic Textured Coatings on AA6082 Aluminum Alloy

Coatings ◽  
2019 ◽  
Vol 9 (6) ◽  
pp. 352 ◽  
Author(s):  
Luigi Calabrese ◽  
Amani Khaskhoussi ◽  
Salvatore Patane ◽  
Edoardo Proverbio
Keyword(s):  
Contact Angle ◽  
Surface Morphology ◽  
In Situ Polymerization ◽  
Contact Angles ◽  
Measuring System ◽  
Hydrophobic Surfaces ◽  
Short Term Treatment ◽  
Water Contact ◽  
Water Separation ◽  
Wide Range

Superhydrophobicity is one of the most required surface properties for a wide range of application such as self-cleaning, anti-corrosion, oil-water separation, anti-icing, and anti-bioadhesion. Recently, several methods have been developed to produce nature inspired super-hydrophobic surfaces. Nevertheless, these methods require a complicated process and expensive equipment. In order to overcome these issues, we propose three different methods to obtain nature-inspired super-hydrophobic surfaces: short-term treatment with boiling water, HF/HCl and HNO3/HCl concentrated solution etching. Afterwards, a thin layer of octadecylsilane was applied by in situ polymerization on all pre-treated surfaces. Eventually, all substrates were dried for 3 h at 100 °C to complete the silane curing. Scanning electron microscopy (SEM), contact angle measuring system and atomic force microscope (AFM) were used to characterize the surfaces. Surface morphology analysis showed that each method results in a specific dual hierarchical nano-/micro-structure. The corresponding water contact angles ranged from 160° to nearly 180°. The best results were observed for HF etched Al 6082 surface were water contact angle above 175° was achieved. Furthermore, a scheme able to assess the relationship between hydrophobic behavior and surface morphology was finally proposed.

Preparation of Super Hydrophobic Surfaces by the Stainless Steel Wire Mesh as Templates

2012 ◽  
Vol 562-564 ◽  
pp. 56-59 ◽  
Author(s):  
Jian Zhuang ◽  
Meng Meng Du ◽  
Heng Zhi Cai ◽  
Ya Jun Zhang ◽  
Da Ming Wu
Keyword(s):  
Contact Angle ◽  
Stainless Steel ◽  
Steel Wire ◽  
Contact Angles ◽  
Wire Mesh ◽  
Stainless Steel Wire ◽  
Hydrophobic Surfaces ◽  
Water Contact ◽  
Stainless Steel Wire Mesh ◽  
Steel Wire Mesh

A facile method for manufacturing super hydrophobic surfaces is presented using the stainless steel wire mesh as templates. The rough surfaces of polymers including polycarbonate, polypropylene and PMMA are prepared with hot embossing on different specifications of stainless steel wire mesh. Scanning electron microscopy (SEM) results reveal that the surfaces roughness of the polymers can be controlled by selecting templates. Contact angle measurement shows that the water contact angles(WCA) rise with the increase of surface roughness, especially, the water contact angle on the PC surfaces prepared with specifications of 635mesh screen can reach to 152.3°, alias super hydrophobic surfaces.

An Easy Approach for Obtaining Superhydrophobic Surfaces and their Applications

2019 ◽  
Vol 813 ◽  
pp. 37-42
Author(s):  
Amani Khaskhoussi ◽  
Luigi Calabrese ◽  
Edoardo Proverbio
Keyword(s):  
Surface Morphology ◽  
Large Scale ◽  
Adhesion Force ◽  
Industrial Applications ◽  
Contact Angles ◽  
Boiling Water ◽  
Superhydrophobic Surfaces ◽  
Acid Mixture ◽  
Short Term Treatment ◽  
Water Contact

Three different methods were used to obtain nature-inspired superhydrophobic surfaces on aluminum alloys: short-term treatment with boiling water, HF/HCl and HNO3/HCl concentrated solution etching. Afterwards a thin octadecylsilane film was deposited on all pre-treated surfaces. The surface morphology analysis showed that each method allow to obtain a specific dual nano/micro-structure. The corresponding water contact angles ranged from 160° to nearly 180°. The adhesion force between the water droplets and superhydrophobic surfaces were evaluated. The specimen etched with HF/HCl acid mixture solution showed the lowest adhesion. However, the boiling water treatment sample was characterized by the highest adhesion. Furthermore, the relationship between hydrophobic behavior and surface morphology was discussed compressively. In addition, the electrochemical measurements show that the different superhydrophobic surfaces have an excellent anti-corrosion performance evidencing promising results suitable to obtain large-scale nature-inspired superhydrophobic surfaces for several industrial applications.

Tailoring Surface Hydrophobicity of Commercial Polyimide by Laser-Induced Nanocarbon Texturing

2020 ◽  
Vol 8 (3) ◽  
Author(s):  
Moataz Abdulhafez ◽  
Angela J. McComb ◽  
Mostafa Bedewy
Keyword(s):  
Contact Angle ◽  
Surface Characterization ◽  
Surface Engineering ◽  
Processing Parameters ◽  
Surface Hydrophobicity ◽  
Spot Size ◽  
Contact Angles ◽  
Water Contact ◽  
Wide Range ◽  
Surface Nanostructure

Abstract The growth of laser-induced nanocarbons, referred to here as laser-induced nanocarbon (LINC) for short, directly on polymeric surfaces is a promising route toward surface engineering of commercial polymers. This paper aims to demonstrate how this new approach can enable achieving varied surface properties based on tuning the nanostructured morphology of the formed graphitic material on commercial polyimide (Kapton) films. We elucidate the effects of tuning laser processing parameters on the achieved nanoscale morphology and the resulting surface hydrophobicity or hydrophilicity. Our results show that by varying lasing power, rastering speed, laser spot size, and line-to-line gap sizes, a wide range of water contact angles are possible, i.e., from below 20 deg to above 110 deg. Combining water contact angle measurements from an optical tensiometer with LINC surface characterization using optical microscopy, electron microscopy, and Raman spectroscopy enables building the process–structur–property relationship. Our findings reveal that both the value of contact angle and the anisotropic wetting behavior of LINC on polyimide are dependent on their hierarchical surface nanostructure which ranges from isotropic nanoporous morphology to fibrous morphology. Results also show that increasing gap sizes lead to an increase in contact angles and thus an increase in the hydrophobicity of the surface. Hence, our work highlight the potential of this approach for manufacturing flexible devices with tailored surfaces.

The Wetting of Insect Cuticles by Water

1955 ◽  
Vol 32 (3) ◽  
pp. 591-617 ◽  
Author(s):  
M. W. HOLDGATE
Keyword(s):  
Surface Roughness ◽  
Contact Angle ◽  
Surface Properties ◽  
Surface Composition ◽  
Contact Angles ◽  
Aquatic Species ◽  
Water Contact ◽  
Calliphora Erythrocephala ◽  
Wetting Properties ◽  
Wide Range

1. The water contact angles of insects show a wide range of variation, which is broadly correlated with surface roughness and with habitat. 2. The contact angles of species inhabiting stored products or carrion are greatly modified by contamination. This produces large variations between apparently similar individuals. 3. In terrestrial insects surface roughness increases the contact angles to very large apparent values. Detailed analyses of its effect have been made in the pupa of Tenebrio molitor and the adult Calliphora erythrocephala. In some aquatic insects surface roughness leads to a reduction in the contact angles; this has been studied in the nymph of Anax imperator. 4. Prolonged immersion in water causes a lowering of the contact angles of all the insects examined, and the low angles of many aquatic species may therefore be the direct effect of their environment. In some aquatic species there is evidence of the active maintenance of a large contact angle during life. 5. Changes in contact angle accompany processes of cuticle secretion and will occur at any moult if changes in roughness or habitat take place. 6. The observed variations of surface properties can be explained without assuming any variation in the chemical composition of the cuticle surface. Wetting properties are of little value as indicators of cuticle surface composition. 7. The biological aspects of insect surface properties are briefly discussed.

Effects of Air Exposure Time and Annealing Temperature on Superhydrophobic Surface of Titanium Dioxide Films

2017 ◽  
Vol 751 ◽  
pp. 137-142
Author(s):  
S.Tipawan Khlayboonme ◽  
Warawoot Thowladda
Keyword(s):  
Contact Angle ◽  
Surface Morphology ◽  
Exposure Time ◽  
Annealing Temperature ◽  
Sol Gel ◽  
Contact Angles ◽  
Angle Measurement ◽  
Elemental Distribution ◽  
Water Contact ◽  
Air Exposure

TiO2 thin films coated on glass substrates for self-cleaning applications were prepared by sol-gel dip-coating technique. The influence of annealing temperature and air exposure time on wettability was investigated by a water contact-angle measurement. Thermal annealing at temperatures of 100, 200 and 300 °C in air were conducted to the films. Surface morphology of the films was observed by FE-SEM. Elemental distribution and optical properties were examined by EDX mapping and UV-Vis transmission spectroscopy, respectively. Atomic bonding was confirmed by FTIR. The contact angle reached a maximum when the films were annealed at 200 °C. The contact angles of the as-synthesized films were 61.4±2.7°. During storage in air for 20 days, the contact angles increased to 143.1±2.1°. The films were further reannealed with 100 °C for 20 min, the contact angles were enhanced to 153.1±1.3°. The association of contact angle among the surface morphology, elemental distribution and atomic bonding of the films will be discussed.

Laser-Induced Nanocarbon Formation for Tuning Surface Properties of Commercial Polymers

2020 ◽  
Author(s):  
Moataz Abdulhafez ◽  
Angela J. McComb ◽  
Mostafa Bedewy
Keyword(s):  
Contact Angle ◽  
Surface Properties ◽  
Surface Characterization ◽  
Surface Engineering ◽  
Surface Hydrophobicity ◽  
Contact Angles ◽  
Structure Property ◽  
Water Contact ◽  
Wide Range ◽  
Commercial Polymers

Abstract The growth of laser-induced nanocarbons, referred to here are LINC for short, directly on polymeric surfaces is a promising route toward surface engineering of commercial polymers. This paper aims to demonstrate how this new approach can enable achieving varied surface properties based on tuning the nanostructured morphology of the formed graphitic material on commercial polyimide (Kapton) films. We elucidate the effects of tuning laser processing parameters on the achieved nanoscale morphology and the resulting surface hydrophobicity or hydrophilicity. Our results show that by varying lasing power, rastering speed, laser spot size, and line-to-line gap sizes, a wide range of water contact angles are possible, i.e. from below 20° to above 110°. Combining water contact angle measurements from an optical tensiometer with LINC surface characterization using optical microscopy, electron microscopy, and Raman spectroscopy enables building the process-structure-property relationship. Our findings reveal that both the value of contact angle and the anisotropic wetting behavior of LINC on polyimide are dependent on their hierarchical surface nanostructure which ranges for isotropic nanoporous morphology to fibrous morphology. Results also show that increasing gap sizes lead to an increase in contact angles and thus an increase in the hydrophobicity of the surface. Hence, our work highlight the potential of this approach for manufacturing flexible devices with tailored surfaces.

scholarly journals Is contact angle a cause or an effect? – A cautionary tale

2020 ◽  
Vol 146 ◽  
pp. 03004
Author(s):  
Douglas Ruth
Keyword(s):  
Contact Angle ◽  
Solid Surface ◽  
Contact Angles ◽  
Two Dimensions ◽  
Experimental Results ◽  
Flow In Porous Media ◽  
Two Dimensional ◽  
Wide Range ◽  
Fluid Drop ◽  
Surrounding Fluid

The most influential parameter on the behavior of two-component flow in porous media is “wettability”. When wettability is being characterized, the most frequently used parameter is the “contact angle”. When a fluid-drop is placed on a solid surface, in the presence of a second, surrounding fluid, the fluid-fluid surface contacts the solid-surface at an angle that is typically measured through the fluid-drop. If this angle is less than 90°, the fluid in the drop is said to “wet” the surface. If this angle is greater than 90°, the surrounding fluid is said to “wet” the surface. This definition is universally accepted and appears to be scientifically justifiable, at least for a static situation where the solid surface is horizontal. Recently, this concept has been extended to characterize wettability in non-static situations using high-resolution, two-dimensional digital images of multi-component systems. Using simple thought experiments and published experimental results, many of them decades old, it will be demonstrated that contact angles are not primary parameters – their values depend on many other parameters. Using these arguments, it will be demonstrated that contact angles are not the cause of wettability behavior but the effect of wettability behavior and other parameters. The result of this is that the contact angle cannot be used as a primary indicator of wettability except in very restricted situations. Furthermore, it will be demonstrated that even for the simple case of a capillary interface in a vertical tube, attempting to use simply a two-dimensional image to determine the contact angle can result in a wide range of measured values. This observation is consistent with some published experimental results. It follows that contact angles measured in two-dimensions cannot be trusted to provide accurate values and these values should not be used to characterize the wettability of the system.

scholarly journals Facile Fabrication of Multifunctional ZnO Urchins on Surfaces

2018 ◽  
Vol 2 (4) ◽  
pp. 74 ◽  
Author(s):  
Abinash Tripathy ◽  
Patryk Wąsik ◽  
Syama Sreedharan ◽  
Dipankar Nandi ◽  
Oier Bikondoa ◽  
...  
Keyword(s):  
Contact Angle ◽  
Water Contact Angle ◽  
Surface Density ◽  
Room Temperature ◽  
High Surface ◽  
Secondary Growth ◽  
Water Contact ◽  
Growth Step ◽  
Si Substrates ◽  
Wide Range

Functional ZnO nanostructured surfaces are important in a wide range of applications. Here we report the simple fabrication of ZnO surface structures at near room temperature with morphology resembling that of sea urchins, with densely packed, μm-long, tapered nanoneedles radiating from the urchin center. The ZnO urchin structures were successfully formed on several different substrates with high surface density and coverage, including silicon (Si), glass, polydimethylsiloxane (PDMS), and copper (Cu) sheets, as well as Si seeded with ZnO nanocrystals. Time-resolved SEM revealed growth kinetics of the ZnO nanostructures on Si, capturing the emergence of “infant” urchins at the early growth stage and subsequent progressive increases in the urchin nanoneedle length and density, whilst the spiky nanoneedle morphology was retained throughout the growth. ε-Zn(OH)2 orthorhombic crystals were also observed alongside the urchins. The crystal structures of the nanostructures at different growth times were confirmed by synchrotron X-ray diffraction measurements. On seeded Si substrates, a two-stage growth mechanism was identified, with a primary growth step of vertically aligned ZnO nanoneedle arrays preceding the secondary growth of the urchins atop the nanoneedle array. The antibacterial, anti-reflective, and wetting functionality of the ZnO urchins—with spiky nanoneedles and at high surface density—on Si substrates was demonstrated. First, bacteria colonization was found to be suppressed on the surface after 24 h incubation in gram-negative Escherichia coli (E. coli) culture, in contrast to control substrates (bare Si and Si sputtered with a 20 nm ZnO thin film). Secondly, the ZnO urchin surface, exhibiting superhydrophilic property with a water contact angle ~ 0°, could be rendered superhydrophobic with a simple silanization step, characterized by an apparent water contact angle θ of 159° ± 1.4° and contact angle hysteresis ∆θ < 7°. The dynamic superhydrophobicity of the surface was demonstrated by the bouncing-off of a falling 10 μL water droplet, with a contact time of 15.3 milliseconds (ms), captured using a high-speed camera. Thirdly, it was shown that the presence of dense spiky ZnO nanoneedles and urchins on the seeded Si substrate exhibited a reflectance R < 1% over the wavelength range λ = 200–800 nm. The ZnO urchins with a unique morphology fabricated via a simple route at room temperature, and readily implementable on different substrates, may be further exploited for multifunctional surfaces and product formulations.

Effects of Continuous and Discontinuous Deposition Time in Reactive Direct Current Magnetron Sputtering of Titanium Dioxide Thin Films

2015 ◽  
Vol 1131 ◽  
pp. 251-254
Author(s):  
Montri Aiempanakit ◽  
Chantana Salawan ◽  
Kamon Aiempanakit
Keyword(s):  
Thin Films ◽  
Grain Size ◽  
Surface Morphology ◽  
Magnetron Sputtering ◽  
Direct Current ◽  
Deposition Time ◽  
Spherical Shape ◽  
Contact Angles ◽  
Water Contact ◽  
Direct Current Magnetron Sputtering

The effect of continuous and discontinuous deposition time on the properties of TiO2 thin films deposited by reactive direct current magnetron sputtering (DCMS) on glass substrates was investigated. The deposition processes were designed for a condition of continuous deposition time D1 (60 min) and three conditions of discontinuous deposition time D2 (30 min × 2 times), D3 (15 min × 4 times), and D4 (1 min × 60 times). The crystal structure, surface morphology, and hydrophilicity of TiO2 thin films were characterized by X-ray diffraction, atomic force microscope, and water contact angle method, respectively. It was found that the increasing of discontinuous deposition time (conditions from D1 to D4) shows the changing of grain size from big grain size with spherical shape to small grain size with oval shape. The crystallinity of TiO2 films decrease with increasing the discontinuous deposition time. The water contact angles also decrease as a function of increasing discontinuous deposition time. These results may be explained from the accumulation of heat on the substrate which affected the phase composition and surface morphology of TiO2 thin films.

Design and fabrication of polydopamine based superhydrophobic fabrics for efficient oil-water separation

Soft Matter ◽  
2021 ◽  
Author(s):  
Jixi Zhang ◽  
Ligui Zhang ◽  
Xiao Gong
Keyword(s):  
Contact Angle ◽  
Water Contact Angle ◽  
Sol Gel ◽  
High Water ◽  
Water Contact ◽  
Water Separation ◽  
Oil Water Separation ◽  
Oil Water ◽  
Fabric Surface

In this work, we prepare a PDMS-SiO2-PDA@fabric with high water contact angle (WCA=155o). Combining dopamine self-polymerization and sol-gel method, SiO2 is in situ grown on a PDA-modified fabric surface to...

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