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AAO 두께 및 표면 형상에 따른 고체-고체 마찰 대전 기반 에너지 하베스팅 발전 성능에 관한 연구
이광석,황운봉,Kwangseok Lee,Woonbong Hwang 한국복합재료학회 2023 Composites research Vol.36 No.3
Due to the increasing demand for wearable devices and miniaturization of various electronic devices, the trend of nanofabrication in IT devices is underway. In order to overcome the limitations of battery size and capacity, there has been a lot of research interest in energy harvesting technology, also known as triboelectric nanogenerator. AAO(Anodic Aluminum oxide) coated with fluoride is a structure that includes an anode layer with high properties in the triboelectric series, an dielectric layer that helps transfer the triboelectrically generated charges to the electrode without loss, and the electrode. For these reasons, AAO has been a lot of research on its application to frictional energy harvesting nanogenerators. In this work, we analyzed the correlation of AAO between the surface morphology and thickness of the insulating layer by utilizing aluminum oxide, which is advantageous for the application of triboelectric nanogenerators, and adjusting the thickness of the insulating layer.
김영애(Yeongae Kim),황운봉(Woonbong Hwang) Korean Society for Precision Engineering 2016 한국정밀공학회지 Vol.33 No.3
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.
원자 현미경을 이용한 접촉 면적에 따른 마찰 및 마멸 특성 분석
최덕현(Dukhyun Choi),황운봉(Woonbong Hwang) Korean Society for Precision Engineering 2004 한국정밀공학회지 Vol.21 No.12
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.
곽원식(Wonshik Kwak),황운봉(Woonbong Hwang) Korean Society for Precision Engineering 2018 한국정밀공학회지 Vol.35 No.5
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.
양극산화기법을 이용한 나노딤플구조물 제조 및 젖음성 연구
김동현(Dong Hyun Kim),황운봉(Woonbong Hwang),김준원(Joonwon Kim),이건홍(Kun Hong Lee) 대한기계학회 2005 대한기계학회 춘추학술대회 Vol.2005 No.5
this paper, a wetting phenomenon of nanodimple structured surfaces was investigated, with particular attention devoted to the relation of the apparent contact angle and the fraction of contact area. For this purpose, Nanodimple structures which had various dimple sizes were fabricated by using an anodizing method and two types wetting test were performed. One is a hydrophilic type wetting test, and the other is a hydrophobic type test. Test results were deferent with existing wetting theories. The nanodimple surface made the apparent contact angle of the hydrophilic aluminum increase and made the apparent contact angle of the hydrophobic coated aluminum decrease. To verify these results, the modified Cassie & Boxter’s equation for the dimple geometry was induced and compared with test results.
박병락(Byungrak Park),황운봉(Woonbong Hwang) Korean Society for Precision Engineering 2018 한국정밀공학회지 Vol.35 No.2
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.
박홍렬 ( Hong Ryul Park ),황운봉 ( Woonbong Hwang ),최덕현 ( Dukhyun Choi ) 한국복합재료학회 2023 Composites research Vol.36 No.2
유수분리는 석유 생산, 폐수 처리 및 식품 가공을 포함한 다양한 산업 응용 분야와 해양 기름 유출과 같은 환경 분야에서 중요한 과정이다. 물-기름 혼합물의 분리 효율은 혼합물의 유형, 기름과 물의 상태, 적용하고자 하는 기술을 포함한 여러 요인에 의해 영향을 받을 수 있으며, 수년에 걸쳐 물리적, 화학적 및 생물학적 방법으로 물과 기름을 분리하기 위한 다양한 기술이 개발되어 오고 있다. 본 논문은 중력에 의한 분리, 원심 분리, 흡착재, 필터 등을 이용한 유수분리를 포함하여 물-기름 분리에 사용할 수 있는 다양한 방법과 기술에 대해 개략적으로 설명하고자 한다. 각 방법의 장점과 한계를 최근 연구 동향 및 향후 전망과 함께 논의한다. 또한 본 논문에서는 지속 가능하고 환경 친화적인 접근 방식에 특히 중점을 두고 유수분리 분야의 향후 연구와 산업 적용을 위한 방향성을 제시하고자 한다. 결론적으로 본 논문에서는 유수분리 분야의 연구자 및 산업 종사자에게 유용할 수 있는 최근 유수 분리 기술에 대한 포괄적인 개요를 제공하고자 한다. Oil-water separation is a critical process for several industrial applications, including oil production, wastewater treatment, food processing, and environmental area such as marine oil spills. The separation efficiency of oil-water mixtures can be influenced by various factors such as mixture composition, oil and water conditions, and the separation technology used. Over the years, various technologies have been developed to separate water and oil by physical, chemical and biological methods. This paper presents an overview of the various methods and technologies available for oil-water separation, including gravity separation, centrifugal separation, and separation using adsorbents, filters. The strengths and limitations of each method are discussed, along with recent research trends and future prospects. Furthermore, this paper aims to provide direction for future research and industrial application of sustainable and environmentally friendly oil-water separation technologies. In conclusion, we provide a comprehensive overview of recent oil-water separation technologies that will be beneficial to researchers and industrialists in the field of oil-water separation.
A Study of Droplet Transmissivity Change by Characteristic of Mesh
박진영(Jinyoung Park),황운봉(Woonbong Hwang) Korean Society for Precision Engineering 2018 한국정밀공학회지 Vol.35 No.6
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.