Condensation is an important research topic that ensures increased energy efficiency. Our researchers aimed to optimize heat transfer in industrial heat exchanger tubes through surface modification. We first succeeded in fabricating superhydrophilic and superhydrophobic tubes using surface modification. We observed the condensation phenomenon on the outside of the tube and evaluated the heat transfer performance through a condensation experimental facility. As a result, we found that the condensation heat transfer efficiency of superhydrophobic tubes is superior to that of conventional tubes. However, the heat transfer efficiency of the superhydrophobic tube reduced with an increase in saturation. To improve performance degradation, superhydrophilic and superhydrophobic hybrid tubes were fabricated and evaluated for their potential to improve heat transfer efficiency. As a result, we found that the liquid film generated by filmwise condensation on the superhydrophilic surface swept past the residual droplets generated by dropwise condensation on the superhydrophobic surface, resulting in the best heat transfer performance. Our results break the stereotypes of previous studies and provide a new paradigm for achieving optimal heat transfer performance on large-area curved surfaces. This research is expected to be widely applied in a variety of industries where energy efficiency is critical.

Purification of water through oil–water separation is essential for preserving the ecosystem and protecting human health. Although a conventional polypropylene depth filter can effectively purify water, modifying the wettability of a filter for oil–water separation is difficult owing to its low reactivity. In this study, we developed a superhydrophilic polypropylene filter with a hydrogel layer that could enable effective oil–water separation by using plasma treatment and dip coating, which enabled an even distribution of the coating solution across the filter. The fabricated filter was superhydrophilic with a water contact angle of 0o. It showed a high repulsive force with oil in water with an underwater oil contact angle of 142.9o. When such filter was applied to an oil–water separation device, it effectively purified water with low oil content (< 15 ppm) at a flow rate of 300 mL/min. These results demonstrate potential applications of such filters in areas such as wastewater treatment and oil spill cleanup.

Anodic aluminum oxide (AAO) is widely used in various industrial fields to increase the mechanical property or corrosion resistance of the product surface. In this study, mechanical properties were measured according to the thickness of AAO through the nanoindentation test. The maximum indentation load, elastic modulus, and hardness were measured for different thicknesses of AAO. It was confirmed that the majority of the mechanical property values increased with the thickness. Various fracture shapes based on the thickness were analyzed by observing pressure marks on the surface using FE-SEM equipment. Apparently, it is proposed that the optimum AAO thickness with desired mechanical properties can be obtained, which is expected to possess immense economic value as per the optimization of the production time of AAO based products.

In this study, aluminum, used throughout the industry and actively studied for surface modification, is selected as the test subject. Micro-structured through acid etching, nano-structured through alkali treatment to maximize surface roughness, and the superhydrophilic surfaces were fabricated by forming the surface chemicals into aluminum hydroxide (Al(OH)₃). The superhydrophobic surfaces were fabricated through the self-assembled monolayer coating on the surface, and the surface structure and components were analyzed. The superhydrophilicity and superhydrophobicity were applied on the aluminum surface at the bottom of the low speed water vehicle. For the superhydrophilic and superhydrophobic surfaces, the reasons for the drag reduction performance on the bare surface and the difference in the amount of reduction were analyzed. A coating material that strong bonds with the surface are selected for anti-corrosive performance under NaCl solution. To verify that, the contact angle was measured by exposing each prepared aluminum surface to a 3.5% NaCl solution for 14 days. Additionally, we analyzed why the superhydrophobic surfaces were robust against the NaCl solution.

A simple and rapid method of fabricating Mg(OH)2 layer by chemical immersion was developed to improve the corrosion resistance of the magnesium alloy AZ31. The fabricated surface was superhydrophobic with a self-assembled monolayer coating of silane. The surface characteristics were evaluated by Scanning Electron Microscopy (SEM), Energy Dispersive X-ray Spectroscopy (EDS) and X-ray Photoelectron Spectroscopy (XPS). The average water contact angle and sliding angle were determined to be 160° and 7° respectively as a result of wettability test. Potentiodynamic polarization indicated that both Mg(OH)2 layer and the thin layer of air were effective in improving anti-corrosion. This method which is efficient with regard to time and cost would be useful for magnesium industries and its application

Super-wettability surface has various applications and actively studied in many fields. However water droplet transmissivity on super-wettability mesh was not be studied. This work is about water droplet transmissivity of an aluminum mesh with super-wettability on its surface. The mesh which fabricated surface structures with semi-permanent and non-etching process has super-wettability without strength drop of mesh structure. With this process, water droplet transmissivity was measured along various mesh pore per inch and dropping angle. Also water droplet transmissivity along dropping height was measure with super-hydrophobic mesh. As a result, super-hydrophilic mesh shows similar transmissivity behavior with bare mesh which has hydrophilic surface at high pore per inch and high dropping angle, super-hydrophobic 120 mesh shows lowest water droplet transmissivity in various situation.

In this study, we developed a convenient method to achieve superoleophobic surfaces on zinc substrates by using anodization and self-assembled monolayer coating, and to facilitate the fabrication of superoleophobic surfaces having reentrant structures, even for lower surface tension liquids than 30 mN/m- including hexadecane (γ = 27.5 mN/m). The liquid repellency of the structured surface was validated through observable experimental results; contact angle measurement. The optimal anodizing condition was determined as a critical parameter in building the superoleophobicity. The re-entrant had nanowire/microball structures formed by anodization with a high voltage. Under an optimized morphology by re-entrant structures with fluorination treatment, the contact angle over 150o is achieved, even for hexadecane.

A study of super-hydrophobic surface originated from the analysis of lotus leaf in the nature and fabrication method of super-hydrophobic surface on copper substrate has been researched for, showed functional surfaces with anti-corrosion. However, since copper nanowires decomposed during thiol coating, it is necessary to reseach on the relation with morphology of copper nanowires and thiol coating time. In this study, the research is all about the effect of thiol coating time on wettability of copper nanowires surface. Copper hydroxide nanowires were made up by oxidation using dipping method and a polymer layer was formed on nanowires using thiol coating. Surface characteristics were assessed using scanning electron microscopy and liquid contact angles. The conclusion showed relation for wettability of thiol coated copper hydroxide nanowires with thiol coating time and proposed method would be favorable for anti-corrosion functional surface.

A study about superhydrophobic surface started from the analysis of lotus leaf, and superhydrophobic surface fabrication methods have been researched. These methods cannot be used on various metals because the fabrication methods have complex and material-selective processes. In this work, we report a simple fabrication method using abrasive blasting and a self-assembled monolayer coating to produce a superhydrophobic surface. Abrasive blasting was used to create microstructures on metal surfaces. Random peak and valley microstructures were created after abrasive blasting, and a surface profile was measured to analyze the relationship between blasting pressure and a roughness parameter. A hydrophobic material coating was performed by a self-assembled monolayer method. Six kinds of metal surfaces displayed superhydrophobic properties. This utilitarian method could be applied to diverse applications.

Since the development of anodic aluminum oxide (AAO), extensive studies have been conducted ranging from fundamental research to the applications of AAO. Most of the research on AAO structures have focused on well-aligned nanoporous structures fabricated under specific conditions. This study investigated fabricable AAO structures with anodization performed with various temperatures, electrical potentials, and basal plane surfaces. As a result, nanoporous and nanofibrous structures were fabricated. The nanopores were formed at a relatively lower temperature and potential, and the nanofibers were formed at a relatively higher temperature and potential regardless of the basal plane surface. The shape of the base surface was found to influence the structural arrangement in nanoporous morphologies. These interesting findings relating to new morphologies have the potential to broaden the possible applications of AAO materials.

Herein the water film was introduced to the hydrophilic area on the line patterned surface to solve the contradiction caused by surface roughness (high different wettability has advantage to control the droplet but high roughness for that high wettability difference causes obstruction of droplet moving). Thus the droplet on the water film could not be hindered to line direction but restricted to orthogonal direction, effectively. In addition, droplet behaviors according to droplet volume and line thickness were studied. Droplet fell off the line with narrowing the interface between the droplet and the water film on the line. When the droplet fell off the line, the plate angle was designated as a critical plate angle and it used as an indicator of surface capability to control the droplet. As a result critical plate angle increases as droplet volume decreases and line thickness increases.

Recently, it has been reported that frictional behavior at nanometer scale can be different from that at macro scale. In this article, friction and wear tests were conducted using an AFM to investigate the effect of real contact area on the coefficient of friction and wear property. SiO₂, Mica, and SiGe were used in friction test and the AFM tip was Si₃N₄.The real contact area between an AFM tip and flat surface was calculated by the Johnson-Kendall-Roberts (JKR) theory. Wear specimen was Mica, and the diamond tip was used. We found that the coefficient of friction is constant below a critical area, but it is degraded over the area. Moreover, it is found that wear depth increased rapidly from a certain load and was degraded as a function of the number of the scanning cycles. Also, the range of scanning velocity used in this study had little effect on the wear depth.

Porous anodic alumina has been used widely for corrosion protection of aluminum surfaces or as dielectric material in micro-electronics applications. It exhibits a homogeneous morphology of parallel pores which can easily be controlled between 10 and 400㎚. It has been applied as a template for fabrication of the nanometer-scale composite. In this study, mechanical properties of the AAO structures are measured by the nano indentation method.
Nano indentation technique is one of the most effective methods to measure the mechanical properties of nano-structures. Basically, hardness and elastic modulus can be obtained by the nano-indentation. Using the nano-indentation method, we investigated the mechanical properties of the AAO structure with different size of nano-holes. In results, we find the hole effect that changes the mechanical properties as size of nano hole.