China
Africa
Explore chapters and articles related to this topic
Thin Films for Surface Protection
Published in Fredrick Madaraka Mwema, Tien-Chien Jen, Lin Zhu, Thin Film Coatings, 2022
Fredrick Madaraka Mwema, Tien-Chien Jen, Lin Zhu
Whereas hydrophobic thin films repel water, hydrophilic thin films attract and absorb water and moisture. As stated earlier, hydrophobic surfaces have a contact angle greater than 90°, whereas hydrophilic surface has a contact angle less than 90°. A contact angle refers to the angle between the solid–liquid interface and liquid-vapour interface and is dependent on the water droplet volume and the inertial force imposed by gravity. A hydrophobic surface has poor adhesiveness to water, poor wettability, and low solid surface free energy. A hydrophilic surface, on the other hand, has good adhesiveness to water, good wettability, and high solid surface free energy [44]. Superhydrophobic surfaces are highly water repellent, whereas superhydrophilic are highly water absorbers. These two concepts are applied to the coated thin films depending on the desired operating condition [43].
Hydrophobic and Hydrophilic Polymer Coatings
Published in Sanjay Mavinkere Rangappa, Jyotishkumar Parameswaranpillai, Suchart Siengchin, Polymer Coatings, 2020
Sanjay Remanan, Harikrishnan Pulikkalparambil, Sanjay Mavinkere Rangappa, Suchart Siengchin, Jyotishkumar Parameswaranpillai, Narayan Chandra Das
Superhydrophilic or superwetting surfaces have the tendency to spread out water (liquid) present on the surface, and this is mostly in the form of films than droplets. For such surfaces, the roughness factor in the Wenzel equation is always greater than 1 (r >1) and the water spread over the surfaces helps in the application of removal of dirt and staining materials, and oil-in-water separation, biomedical, anti-fogging, anti-corrosive, and pervaporation applications. Tuning the surface chemistry to increase the surface energy and making the pattern to increase the surface roughness is the key feature to achieve the desired hydrophilicity. There are different preparation methods to fabricate superhydrophilic coatings, such as plasma treatment, ultraviolet and laser irradiation, sol–gel, phase inversion, anodization, and etching, the details of which can be found in a recent review article (Otitoju, Ahmad, and Ooi 2017).
Numerical modeling of impact, runoff and drying of wind-driven rain on a window glass surface
Published in Paul Fazio, Hua Ge, Jiwu Rao, Guylaine Desmarais, Research in Building Physics and Building Engineering, 2020
J. Carmeliet, M. Rychtáriková, B. Blocken
However, a wide range of glass-type surfaces exist, with coatings that exhibit behavior ranging from super-hydrophylic to superhydrophobic. Further research is needed for different types of glass surfaces. An assumption made in the present model is that rain is present at the surface as individual drops, and not as a water film. This assumption is justified for hydrophobic surfaces and canbe justified for regular hydrophilic surfaces. At superhydrophilic surfaces however, water films will occur at the surface rather than individual drops.
Exploration of the performance of iron-based superhydrophilic meshes for oil-water separation
Published in Journal of Environmental Science and Health, Part A, 2023
V. Preethi, Shradha Nair, S. T. Ramesh, R. Gandhimathi
In this study, the oil-water separation performance of iron based superhydrophilic meshes is explored and found to exhibit a good response. The cooperative effect of the micro/nano structures and the hydrophilic nature of iron/iron oxide coating on the stainless steel mesh are responsible for oil-water separation. The average separation efficiency of 150 mesh for the oil-water mixtures is about 83%, and for 400 mesh, it is around 95%. For 300 mesh, the average separation efficiency for all the oil-water mixtures tested is around 93%, with satisfactory intrusion pressure and flux values. For practical considerations, a balance between separation efficiency, flux, and intrusion pressure is required. Hence, compared to the other two mesh sizes (150 mesh-less separation efficiency and 400 mesh-low flux), mesh 300 is observed to be superior. Designated superhydrophilic mesh is also tested to have pronounced reusability with separation effectiveness above 90% even at the third cycle and good strength in harsh conditions. The efficiency of separation for the locomotive wash effluent using superhydrophilic meshes is in accord with the earlier test result that the 300 mesh can bring efficient oil-water separation. The separation efficiency of 94.7%, along with reasonable flux and intrusion pressure values of 73.28 Lm−2min−1 and 0.848 kPa, respectively, is achieved by applying the designated superhydrophilic mesh for oil-water separation of the locomotive wash effluent. In addition, it is seen that the permeate has a reduced value of turbidity of 21.8 NTU, and chemical oxygen demand of around 70 ppm. This study, therefore, also exhibits a promising potential of superhydrophilic mesh for practical application.
Hydrophilic and hydrophobic materials and their applications
Published in Energy Sources, Part A: Recovery, Utilization, and Environmental Effects, 2018
Darem Ahmad, Inge van den Boogaert, Jeremey Miller, Roy Presswell, Hussam Jouhara
The superhydrophilic property is capable to prevent pollutants from adhering to the substrate through the formation of a uniform water film over the solid surface. The synergism of hydrophilic and photocatalytic results could maintain esthetical properties; improve surface maintenance and reduce degrading processes (Fujishima, Rao, and Tryk 2000a).
Novel method of obtaining textile fabrics with self-cleaning and antimicrobial properties
Published in The Journal of The Textile Institute, 2022
Iwona Masłowska-Lipowicz, Anna Słubik
The self-cleaning effect is related to the following concepts developed by scientists: TiO2-based superhydrophilic self-cleaning, lotus effect self-cleaning, gecko setae–inspired self-cleaning, and underwater organisms–inspired antifouling self-cleaning. The self-cleaning mechanism depends on the superhydrophilicity or superhydrophobicity of the surface. In the case of the superhydrophilic surface, water droplets can spread and form a thin layer on the surface that washes away contaminants as it flows off. The self-cleaning mechanism caused by superhydrophobicity, on the example of the so-called the lotus effect, is associated with the presence of numerous microtubes on the modified surface. The presence of microtubes results in a smaller contact area between the surface and the water droplets, allowing the water droplets to roll over the surface, collecting the contaminants from the surface (Chan-Juan et al., 2018; Hasan & Nosonovsky, 2020; Liu & Jiang, 2012; Shao et al., 2020). The self-cleaning properties of the surface are of great interest due to the wide range of applications in various industries (textiles, construction, sanitary appliances, car parts—car body, mirrors, photovoltaic panels, cameras, mobile phones, cosmonautics, etc.) (Han & Min, 2020). In the textile industry, self-cleaning fabrics are mainly based on surface modification with TiO2 or SiO2 nanoparticles. One of the methods of applying nanoparticles (nano-TiO2 or nano-SiO2) to fabrics is the sol-gel method. Nanoparticles are produced by acidic or alkaline hydrolysis in the presence of the so-called precursors. Precursors are most often organic salts of the appropriate metals (e.g. titanium isopropoxide, tetraethyl orthosilicate). The produced nanoparticles have a high surface area to volume ratio and high surface energy, thanks to which they show a high affinity for fabrics (Krifa & Prichard, 2020). Additionally, the use of photocatalytic nano-TiO2 gives textiles the function of photocatalytic cleaning. In this type of fabric, contaminations are broken down by UV radiation (Altangerel et al., 2020; Diaa & Hassabo, 2022; Wan et al., 2021; Wu et al., 2021).