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Electrochemical Discharge Machining
Published in V. K. Jain, Advanced Machining Science, 2023
Dileep Kumar Mishra, Julfekar Arab, Pradeep Dixit
Heterogeneous nucleation at the gas-evolving electrode requires much less dissolved gas supersaturation than required in the bulk liquid. The presence of an electrode surface reduces the energy barrier for the nucleation process due to variation in the contact angle θ. The contact angle determines the wettability of liquid over the solid surface and is defined as the angle between the plane of the solid surface and the tangent to the liquid surface at the contact line. Thus, in the case of heterogeneous nucleation, the surface tension (σ) is multiplied by a factor f (θ), which is given below by Equation 13.3. f(θ)=1+cosθ22−cosθ4
Traditional and Advanced Characterization Techniques for Reinforced Polymer Composites
Published in Shishir Sinha, G. L. Devnani, Natural Fiber Composites, 2022
Amit Pandey, G. L. Devnani, Dhanajay Singh
Wetting properties of fluids on a fiber surface plays a key role in polymer composite engineering. A significant amount of research has been done to study the interfacial properties of a fiber matrix system that includes the wetting property of a fiber surface along with the interface bonding strength between matrix and fibers. The toughening ofa composite material and the damage mechanisms involved during fiber reinforcement of composites are greatly affected by the interfacial properties of a fiber matrix system (Wu & Dzenis, 2006). Natural fibers are generally hydrophilic in nature and when they are made to interact with some hydrophobic thermoplastic matrix like polyethylene or polypropylene, they produce very low interfacial interactions. This leads to a poor interfacial strength and with that comes the need to study all the aspects related to the composite interface (Fuentes et al., 2014). The wetting property of the droplet defines the geometry of a droplet on a fiber. The wetting property of microdroplets on monofilaments has drawn a significant amount of attention in the past. The wetting shape of a microdroplet on a flat surface is defined as a partial sphere, but in case a fiber it does not exhibit the same geometry. Wettability studies basically revolve around the measurement of contact angles. Contact angles act as an important tool to describe the degree of wetting during a solid liquid interaction. Small contact angles (<<90°) signify high wettability; on the other hand, large contact angles (>>90°) can be associated with low wettability.
Case Studies
Published in Giorgio Luciano, Statistical and Multivariate Analysis in Material Science, 2021
The wettability behavior of surfaces was determined by the surface free energy and topographical structure. Contact angle hysteresis is the important parameter for evaluating the wetting behavior of surfaces. Generally, the Wenzel and Cassie-Baxter states are two main models that are used to describe the wettability properties of surfaces 52. The important assumption of the Wenzel model is that the water droplet can fully penetrate to the rough features and adhere more strongly to the surface 32. In contrast, in the Cassie-Baxter state, the droplet suspends on the groove-texture of solid surfaces, and the air pocket entrapment on the solid-liquid contact occurs 54. This property leads to minimizing the water adhesion and decreasing the CAH value. So, the Wenzel model is usually applied to define the wettability properties of surfaces with CAH higher than 20.
Thermal conductivity and shear strength characterisation of hybrid GNPs and silane functionalised BN as thermal conductive adhesive
Published in The Journal of Adhesion, 2023
S. Jasmee, M Ramli, S.S. Othaman, G. Omar
Based on these studies, treated BN exhibits a lower epoxy contact angle than untreated BN, which aids in filler dispersion inside the polymer matrix. The contact angle describes the wettability of a material or the ability of a liquid to wet the surface of a solid. The variation in the contact angle with respect to the filler content will provide insight into the hydrophilicity or hydrophobicity of the nanoparticles on the surface of the polymeric matrix.[77] Additionally, the compatibility between the two substances can be determined using a quantitative method known as the Hansen solubility parameter (HSP). The concept was previously used to forecast the compatibility of two materials with epoxy resin, and it expresses the cohesive energy density depending on the intensity of the interaction forces between its molecules.[78] The HSP can be calculated using the group contribution approach, where the structure of the substance is divided into chemical groups, and the HSP is calculated using the parameters assigned to each group. Parameters can be assigned using several estimation methods.[79–82] However, among the available methods, Fedor’s method has been extensively used for polymers and organic solvents because it only requires knowledge of the chemical structure of the substances.[83]
Nitric acid oxidation and urea modification of carbon fibres as biofilm carriers
Published in Environmental Technology, 2023
Qijie Liu, Ling Shao, Zhenzhong Liu, Yingwei Chen, Guangze Dai, Jialei Ying
Table 3 summarizes the radius, zeta potential, and van der Waals energy components of E. coli and S. aureus. The diiodiomethane contact angle, zeta potential, energy component and Hamaker constant of the CF supports are summarised in Table 4. The contact angle of the surface of a material is affected by the surface roughness [38]. With a contact angle of less than 90°, an increase in surface roughness reduced the contact angle, whereas when with a contact angle greater than 90°, an increase in surface roughness increased the contact angle [39, 40]. The diiodiomethane contact angle of CF-0 was less than 90°. CF-H had a lower contact angle than CF-0 because nitric acid oxidation of the CF increased its surface roughness. As shown in Table 4, the zeta potential of CF-U is higher than that of CF-0. This can be explained by the introduction of amino groups on the surface through urea modification. Amino groups can acquire a positive charge by combining with hydrogen ions, thereby increasing the zeta potential on the carbon fibre surface [41]. Some studies have also shown that the introduction of amino groups can increase the zeta potential of a material [42–44].
Titania-silica Composite with Photocatalytic Properties and Its Application on Brazilian Granite and Sandstone
Published in International Journal of Architectural Heritage, 2023
Danielle Grossi, Dolores Ribeiro Ricci Lazar, Eliane Aparecida Del Lama, Valter Ussui
Results show that the hydrophilic characteristic of TiO2 can be observed on both stones. The greater the concentration of the product, the smaller the contact angle. This trend was also found in the literature (Pinho and Mosquera 2013). It could also be observed that — provided the product is the same — the lower the stone’s porosity, the wider the contact angle, thus corroborating the results found in the literature (Carrascosa, Facio, and Mosquera 2016). The surface roughness also influences the contact angle. The rougher the surface, the smaller the contact angle (Gherardi, Goidanish, and Toniolo 2018). The product was expected to be hydrophobic, according to one of the articles consulted for this study (Pinho and Mosquera 2013). However, there are differences between the products used, as the silica source used in the work cited contained 41% SiO2, whereas the source used in the present study had 29% SiO2. Although silica is hydrophilic, the hypothesis that the difference in concentration could be the reason for the different results was put forward. To test this hypothesis, silica and silicic acid were synthesised in the laboratory to obtain a higher concentration (62.5%). However, this new composite proved to be superhydrophilic, showing that the higher concentration of silica did not make the composite hydrophobic. Nevertheless, commercial products are known to use mixtures in their formulations that are not disclosed and are protected by patent law. The content of such a mixture could be the reason for the hydrophobicity encountered in the work cited.