Papers by Keyword: Dip-Coating

Abstract: Kapok fiber has been known for its hydrophobic-oleophilic characteristics and exhibits a great potential as oil sorbent. Methods in enhancing its hydrophobicity have been explored to improve its sorption performance in oil-in-water applications. This study investigates the oil sorption performance and hydrophobicity of kapok fibers coated with calcium stearate, a known waterproofing agent. The calcium stearate solution was prepared by mixing known amounts of stearic acid and calcium chloride in an ethanol solution. This was followed by hydrolysis using 0.12 M sodium hydroxide solution. The calcium stearate-coated kapok fibers exhibited higher hydrophobicity compared to raw kapok fibers with a water contact angle of ~137°. It achieved the highest oil sorption capacity and reusability of 50 g/g and 65% for viscous motor oil, respectively.

Abstract: Perovskite CsPbBr₃ has a band gap energy of 2.3 eV which has the potential for solar cell applications. The issue regarding the relationship between the different coating methods and the concentration has not been studied further. Therefore, this study focuses on analyzing the effect of variations in the concentration of CsPbBr₃ 20 mM and 40 mM as well as different coating methods, spin-coating, dip-coating and drop-casting on the morphology of the thin film. The ligand assisted reprecipitation LARP method was used to synthesize CsPbBr₃ using control ligands, octylamine and oleic acid to obtain CsPbBr₃ orthorhombic. Scanning Electron Microscopy (SEM) observations show that increasing the concentration resulted in larger particle size, and the Drop Casting method resulted in a more fully coverage on thin film. Drop Casting and a 40 mM solution produced the highest solar cell efficiency of 1.4 %.

Abstract: Metallic materials including stainless steel, cobalt-chromium alloys, titanium and its alloys, and nickel-titanium (NiTi) shape memory alloys have been used in biomedical applications since the 1940s due to their favorable mechanical properties. Classified as a smart material, NiTi alloy has gained noticeable popularity in biomedical fields such as orthopedic, dental, and cardiovascular applications as it retains reasonable corrosion resistance and biocompatibility along with unique shape memory properties. However, several studies have shown their limits in medical applications due to the risk of Ni ions release from the NiTi implant surface. In order to prevent Ni release, ceramic-based surface coatings such as hydroxyapatite, alumina, and titanium dioxide have been proposed applied by various methods such as electrophoretic deposition, sol-gel, biomimetic and dip coating. In this work, HA coatings on NiTi wire samples were obtained by using biomimetic and dip-coating methods. The biomimetic coating consisted of immersing the NiTi wire samples into simulated body fluid for 24 and 48 h periods, whereas dip coating was accomplished by placing the NiTi wire samples into the HA suspension and retracting the sample with a controlled speed. The effects of the two coating methods on coating quality, surface characteristics and corrosion behavior of NiTi wire samples were investigated. Dip coating method was shown to be a more favorable technique for the NiTi wire samples used throughout this study.

Abstract: In this work, we studied the effect of pre-heating temperature on the structural and optical properties of ZnO nanorods grown by free template sol-gel dip-coating technique. The prepared films were pre-heated at different temperatures: 240, 260, 280 and 300 °C, then annealed at 500 °C for one hour. The structural properties of the prepared samples were investigated by X-ray diffraction (XRD) and the surface morphologies were studied by scanning electron microscope (SEM). The optical properties were studied by means of UV-Visible spectrophotometer. The XRD diffraction spectra show that all the prepared samples have a ZnO wurtzite structure with a preferential orientation along (002) axis. SEM micrographs revealed the formation of well-aligned ZnO nanorods for the sample preheated at 280 °C. The prepared ZnO nanorod structured thin films are highly transparent in the visible region with an average transmittance above 85 % in the 400–800 nm wavelength range.

Abstract: Fiber coatings for BN/SiC-and BN/Si₃N₄-bilayer systems were developed for the use in SiC/SiC composites. All coatings were produced with high process velocities of 500 m/h by a continuous roll-to-roll dip-coating process. The fiber surface was fully covered with a homogeneous coating and without fiber bridging. Tensile tests of fiber bundles were used to examine potential degradation of the fiber properties due to the application of the coatings. The coated fiber bundles showed a reduction of the maximum tensile load to 90.0 % for the BN/Si₃N₄ and to 86.7 % for the BN/SiC coating in comparison to the fiber bundle in the as-received state. A thermal treatment of the coated fiber bundles up to 1650 °C led to no reduction of their maximum tensile load. SiC/SiC composites were fabricated by polymer infiltration and pyrolysis. The flexural strength and strain of composites with BN/SiC fiber coating were improved to 467 MPa and 0.42 % in comparison to the composites without fiber coating. The composites with BN/SiC coating showed toughened fracture behavior with fiber pull-out effects.

Abstract: Several zeolite membrane types, including Mordenite (MOR), Linde Type A (LTA), and Faujasite (FAU), have been developed. Among these membranes, FAU zeolite membranes have a variety of applications, especially in the separation of mixtures that contain large molecules. The goal of this study is to use zeolite membranes (Y/alumina) to separate suspensions of oil-in-water emulsion. Two ceramic supports were prepared from the alumina at different sintering temperatures (700°C and 1200°C) to obtain gamma-alumina and alpha-alumina, respectively. The materials prepared, zeolite Y membranes/alpha-alumina and Y/gamma-alumina, were characterized using X-ray diffraction (XRD) and Scanning Electron Microscopy (SEM). The powder pressing method was used to compact the alpha-alumina and gamma-alumina ceramic support and the dip-coating method was used to prepare the zeolite Y membranes. The XRD pattern showed that the zeolite Y membrane/alumina obtained by the secondary growth dip-coating method, independent of the ceramic support used, showed no trace of the phases characterized as impurities. It was possible to observe a significant reduction in the concentration of oil in the permeate for the zeolite Y membranes, thus showing their potential for use in this application.

Abstract: Recently, the performance of solid oxide fuel cell is focused on lowering operating temperature (400°C-650°C). To achieve the goal, the thickness of commonly used electrolyte, YSZ was reduced. The dip-coating technique was used for preparing dense YSZ electrolyte thin films on glass substrate. The suspensions were prepared by sol-gel method. Polyvinyl alcohol (PVA) and polyethylene glycol (PEG) was used as a ceramic binder and plasticizer, respectively. Crystalline structure and morphology of thin films were analyze by X-ray diffraction (XRD) and Atomic Force Microscope (AFM). The XRD reveals that crystallization of YSZ phase does not occur at any sintering temperature but can only have a small peak at 2θ = 30° as the thickness of layer increase. The roughness and morphology of the film with different thickness were observed. The roughness increased as the thickness increased.

Abstract: In this work, synthesis of ZIF-8 membranes via in situ and secondary seeded growth methods was conducted at the preliminary stage. Synthesis durations were varied at 4 h and 36 h using in situ growth method. For secondary growth, the seeding procedure was applied through rubbing and dip-coating of the seeds on the support. The resultant membranes were characterized using X-ray diffraction (XRD) and scanning electron microscope (SEM). Subsequently, the defects of the resultant membranes were determined using nitrogen gas permeation test. The results showed that, ZIF-8 membrane synthesized using in situ growth method for 4 h exhibited highest crystallinity and lower defects with the nitrogen gas permeance of 5.09 × 10^-7 mol/m²·s·Pa. Besides, in situ growth method has shown its potential in synthesizing high quality ZIF-8 membrane through an easy and faster route.

Abstract: Porous Al₂O₃-SiO₂-ZrO₂ ceramic composite membranes were fabricated by the sol-gel method. The effects of constitution of the composite sol, dip-coating parameters and calcination parameters on the morphology, phase composition, pore size distribution and BET surface area of the membranes were investigated extensively. The thermogravimetric analysis (TGA)/differential scanning calorimeters (TG/DSC), scanning Electron Microscopy (SEM), XRD analysis and N₂ adsorption-desorption analysis was employed for the membranes characterization. TG/DSC curve shows that the suitable calcination temperature of Al₂O₃-SiO₂-ZrO₂ membranes is 1000°C. The SEM morphology displays a smooth and free-crack layer of Al₂O₃-SiO₂-ZrO₂ composite membranes on the surface of the support after calcination at 1000°C. Furthermore, the membranes were also successfully coated with a good adhesion to the support. The optimal composite membranes were obtained when the moral ratio of Al₂O₃-SiO₂-ZrO₂ was 10:2.3:1, the dip-coating parameters were four times dip-coating with every time of 60s respectively.

Abstract: Tin doped zinc oxide (Sn:ZnO) thin films were prepared on glass substrates via sol-gel dip-coating technique starting from zinc acetate dehydrate, (CH₃CO₂)₂Zn⋅2H₂O and tin chloride, SnCl₂. The consequences of various Sn doping on the behavior of the film was investigated. The atomic percentages of dopant in ZnO-based solution were [Sn⁴⁺]/[Zn²⁺] which is between 0% and 4%. The thin films were characterized using Field Emission Scanning Electron Microscope (FESEM) and UV-Vis-NIR spectrophotometer.