Papers by Keyword: Contact Angle

Abstract: The paper deals with an experimental determination of the temperature dependence of the contact angle of wetting of the tungsten substrate by liquid tin using the sessile drop method. Unlike the traditional method of heating of one drop of melt on a solid substrate, here a new similar drop of liquid tin was supplied through the capillary as the temperature increased. It was found that the values of the contact angle decreased with the growing temperature, but these values increased again at higher temperatures. Our findings indicate that, as applied to the tin–tungsten system, the curve of temperature dependence of the contact angle shows the sections of an anomalous increase in values of the contact angle as the temperature rises. We observed this effect earlier in the tin–steel system, and it was given a theoretical explanation from the standpoint of the quantum-mechanical model of Wentzel–Kramers–Brillouin quasiclassical representations.

Abstract: The noise and vibrations generated by equipment and machinery during everyday life and industrial activities can affect both human and machine operations. Specifically, research aimed at suppressing vibrations and noise to enhance the energy efficiency of machinery is becoming increasingly active. In this study, magnesium was selected as the material for vibration damping. The detrimental effects of magnesium are improved by the addition of small amounts of Mn and Zn. A composite material was fabricated using magnesium, which has excellent vibration damping properties, and carbon steel (S45), which has superior mechanical properties. Magnesium alloys with Zn additions of 1, 3, and 5 wt.% were produced to enhance the corrosion resistance and strength of magnesium. Contact angle experiments were conducted to measure the wettability of the magnesium alloys. The contact angle was measured using the sessile drop method. The magnesium alloys showed a decreasing trend in contact angle with increasing zinc content. To explain the decrease in contact angle in Mg-Zn alloys, microstructure and compositional analyses were performed. First, Mg-Fe and Zn-Fe phase diagrams were investigated. The Mg-Fe system was found to contain no intermetallic compounds. In Zn-Fe interactions, Zn appears to form a metallic bond with Fe. The presence of the Γ phase at the interface between the magnesium alloy and S45 indicates that Zn has diffused from the magnesium alloy into both the magnesium alloy and S45. The Γ phase, considered a compound of Fe₃Zn₁₀, improves wettability between particles due to the formation of intermetallic compounds. Therefore, it was inferred that the wettability of the magnesium alloy improved. Additionally, improved wettability is expected to contribute to better adhesion processes and potentially increase interfacial shear strength.

Abstract: Hydro turbines are the key features of the developing globe for utilizing one of the important renewable energies, namely hydro power. The longevity of these hydro machineries links directly to the surface properties of critical component like impellers, as these components are exposed to slurry and cavitation erosion during their use and should be addressed by the properly designed material surfaces for consistent efficiency. The surface properties can be altered and improved by developing coating in conventional steels that are used for impellers. A recommended hard coating for such applications involves titanium carbide (TiC) with Ni and Cr binders. Along with hardness, an increase in surface hydrophobicity can also reduce wear. High velocity oxygen fuel (HVOF) spraying process comes under the umbrella of thermal spray process that utilizes melting of powders via burning of fuel and these molten powders were bombarded on the surface with supersonic velocity to generate a coating. In this paper, HVOF thermal sprayed coating consisting of TiC and NiCr has been utilized for SS410 steel. In addition, a thin layer of polytetrafluoroethylene (PTFE) has also been investigated on the HVOF sprayed surface to enhance its hydrophobicity. The developed surface has been characterized by static contact angle, hardness, porosity, surface roughness, and coating thickness. Variable impingement parameters, namely sand concentration (20000 & 40000 ppm), angle of impingement (45 & 90°) for slurry testing, stand-off-distance (4 & 8 cm), and flow velocity (15 and 30 m/sec) for cavitation testing were opted for analysis the wear resistance of candidate specimens. From the results, it has been observed that the implementation of a PTFE layer leads to super hydrophobicity. However, the hardness and surface roughness have been reduced with the assistance of PTFE layer. Meanwhile, the slurry and cavitation erosion resistance were also found to be improved by the PTFE layer due to the increase in static contact angle. In the case of cavitation erosion, maximum jet velocity and stand-off distance contribute to more wear, owing to sufficient bubble generation. Next, in case of slurry erosion testing, mixed aspect of erosion wear with respect of influence of parameters was observed for coated and uncoated samples. Ductile mode of failure was observed for SS410, and PTFE sprayed specimens, on the other side, HVOF sprayed TiC+50%NiCr coating showed mixed mode of erosion.

Abstract: The surface wettability of metallic biomaterials significantly influences the biological response of biomedical implants. However, the optimal degree of wettability depends on the specific coating or surface treatment applied to the biomaterial. Researchers have widely utilised hydroxyapatite coatings to modify implant surfaces to enhance bioactivity, biocompatibility, and osseointegration. This review article discussed the impact of hydroxyapatite-doped coatings on the surface wettability of metallic biomaterials. A systematic search of Scopus and Web of Science databases was conducted to review recent studies investigating the wettability and biological response of hydroxyapatite-doped coatings applied through standard implant surface deposition techniques. Results reveal that hydroxyapatite-doped coatings are typically hydrophilic and have higher surface energy than uncoated hydrophobic metallic surfaces. The hydrophilic nature promotes better interaction with biological fluids, resulting in cell adhesion and proliferation. The rough and porous surface increases wettability as fluid can easily penetrate the craters. Further research may elucidate the complex connectivity of deposition method process parameters with surface wettability and biological outcomes. This review briefly overviews current research on hydroxyapatite-doped coatings and their effects on surface wettability and biointegration.

Abstract: Investigating the electrowetting behavior of droplets on structured surfaces provides insight in developing electric-driven microfluidic substrates and membranes. Microstructures and patterns inspired by nature could result in interestingly unique wettability and electrowetting phenomenon. In this work, the electrowetting of water droplets on a superhydrophobic leaf of desmodium (Desmodium spp) and its elastomeric replica were explored. An open electrowetting system consisted of an optical camera, platinum wire, and DC power supply with water microdroplets as test liquid was used to investigate the electrowetting behavior on the leaf. Soft lithography using elastomer was used to produce replica of the leaves. Natural cell-like patterns, including central protrusions and microhairs, contribute to the leaf's superhydrophobic properties (contact angle > 150°). The negative copy of the natural patterns generated via soft lithography produced a microstructured elastomeric film, showing a static contact angle of ~128°. Optical microscope images of the elastomeric copy revealed the successful duplication of the leaf’s surface features. Subsequent electrowetting experiments demonstrated a contact angle reduction of up to 15° and 9.5° for the natural leaf and its elastomeric replica, respectively. A pronounced electrowetting-driven droplet motion was observed on the leaf while droplet pinning was noted in the elastomer. These results offer new insights into the electrowetting phenomenon of microstructured surfaces for potential self-cleaning and water-trapping applications.

Abstract: The application of membrane technology in the separation process has led to the technology's present rapid development. Nylon 6.6 polyamide membrane has hydrophilic properties and has advantages such as low fouling tendency and resistance to high temperatures. This research aims to determine the effect of pectin on the characteristics of nylon 6.6 membranes. In this study, the membrane was made from nylon 6.6 using the phase inversion technique. Modification was carried out by adding pectin at variations of 0, 0.25, 0.5, and 0.75% by weight. The IR structure characterization results of the nylon6.6-pectin membrane show the same peak for the-NH group and the OH, C-H, amide I, amide II, amide III, CH₂, and C-C groups. Membrane contact angle measurements P0, P0.25, P0.5, and P0.75 were 59.37°, 67.70°, 63.48°, and 58.00° respectively, indicating hydrophilic properties. Meanwhile, the degree of swelling after the membrane was soaked in distilled water for 24 hours showed values of 55.32%, 44.44%, 60.38%, and 63.16% for membranes P0, P0.25, P0.5, and P0.75. The P0.75 membrane has the lowest contact angle which is increasingly hydrophilic and the highest swelling value which indicates the highest absorption level compared to other variations.

Abstract: Polyurethane coating has been widely used as a protective coating due to its wide range of mechanical strength, excellent abrasion resistance, toughness, low-temperature flexibility, and chemical resistance, simplicity in production and application, and superior protection on corrosion to mild steel. No studies have been reported utilizing coconut-based/PPG blend polyols to produce polyurethane-based protective coatings on mild steel. Therefore, in this work, we fabricated polyurethane-based protective coating using coconut-based/PPG blend polyols for anti-corrosion application. Due to low adhesion strength of Polyurethane-based protective coating, the incorporation of nano-fillers into the polymer matrix improved the adhesion strength of the coating due to its functional benefits and its effects gave rise to increased intermolecular bonding, hydrogen bonding, van der waals, magnetism, and surface energy. Therefore, we fabricated PANI/PU composite coatings with varied amounts of polyaniline nanoparticles on mild steel using coconut-based/PPG blend polyols exposed in 3.5 wt% NaCl aqueous solution for anti-corrosion application. Characterizations like Fourier Transform Infrared Spectroscopy (FTIR), Potentiodynamic Polarization (Tafel plot), contact angle, adhesion test, FESEM, XRD, and UV-VIS were used in this study. Tafel plot revealed that PU-based and PANI/PU composite coatings exhibited a significant reduction in corrosion current density (I_corr), perhaps due to the adsorption of inhibitor in the surface of the mild steel which reduced corrosion rate of the metal by retarding the anodic process and impeding the corrosive species from the surroundings. Among all fabricated coatings, 0.5-PANI/PU composite coating was the best, having a less corrosion rate of 5.66x10^-5 mmpy compared to others. In addition, its surface was more compact, smooth, rigid, and no voids present at the interface according to the result of FESEM, suggesting better corrosion protection to mild steel. Hence, PU-based protective coating and PANI/PU composite coatings using coconut-based/PPG blend polyols inhibited the penetration of the corrosive species and served as an adequate barrier protection against corrosion for mild steel.

Abstract: Among the numerous metal oxide semiconductors, zinc oxide (ZnO) is one of the most widely used materials in various fields due to its non-toxic nature, tunable electric and optical properties, and good thermal and chemical stability. This research aims to study the tuning of optical, electrical, and surface properties of ZnO film treated with dielectric barrier discharge (DBD) plasma produced at atmospheric pressure. The result revealed a significant decrease in its optical band gap, but there was an increase in conductivity. The results of contact angle measurement clearly showed the change of surface nature from hydrophobic to hydrophilic for DBD-treated ZnO film.

Abstract: Naturally-occurring saturated fatty acids have been classified as the interesting biomaterials. Typically, the interfacial tension and wettability relying on intermolecular forces relate to the well-fitted performance with any target sites of in situ forming matrix. This research aimed to determine surface tension/contact angle of several saturated fatty acids in selected aprotic solvents commonly used in in situ forming system by varying fatty acid concentrations and molecular weights. Six fatty acids were dissolved in the aprotic solvents, namely 2-pyrrolidone (PYR), N-methyl-2-pyrrolidone (NMP) and dimethyl sulfoxide (DMSO). As fatty acid concentrations in binary mixtures increased, surface tension and contact angle became diminished except where DMSO was used as a solvent. The longer chain of fatty acid, the lower the surface tension except when C_14-16 fatty acid was dissolved in NMP. Contact angle was also decreased as the chain of fatty acid increased except for C_14-16 fatty acid-based preparation due to their viscosity. Understanding these fatty acid solution's surface tension/contact angle behaviors is useful for designing the suitable fatty acid-based in situ forming system.

Abstract: This research study focused on the fabrication and characterization of sodium alginate incorporated with iron (III) oxide in the form of beads and biofilm for biomedical application. The fabrication of the samples was carried out by using solution casting method and syringe pump extrusion technique. Beads and biofilm of sodium alginate incorporated with iron oxide were characterized by several characterization testing such as XRD, FTIR and contact angle measurement. From the XRD testing shows the diffraction peak that confirmed the cubic structure of Maghemite. Then, FTIR analysis shows the presence of several intermolecular and intramolecular bond stretching of sodium alginate. Lastly, contact angle measurement exhibits that alginate incorporated with iron oxide has hydrophilic behavior due to the contact angle less than 90Also, it was found that as the contact angle reduced as the weight of iron oxide increased.