• Journal of Industrial and Engineering Chemistry
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• v.68
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• pp.387-392
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• 2018

Various technical approaches and concepts have been proposed to develop conductive super-hydrophobic (SH) surfaces. However, most of these approaches are not usable in practical applications because of insufficient adhesion and cost issues. Additionally, durability and uniformity issues are still in need of improvement. The goal of this research is to produce a large-area conductive SH surface with improved adhesion performance and uniformity. To this end, carbon nanotubes (CNT) with a high aspect ratio and elastomeric polymer were utilized as a conductive filler and matrix, respectively, to form a coating layer. Additionally, nanoscale silica particles were utilized for stable implementation of the conductive SH surface. To improve the adhesion properties between the SH coating layer and substrate, pretreatment of the substrate was conducted by utilizing both wet and dry etching processes to create specific organic functional groups on the substrate. Following pretreatment of the surface, a zirco-aluminate coupling agent was utilized to enhance adhesion properties between the substrate and the SH coating layer. Raman spectroscopy revealed that adhesion was greatly improved by the formation of a chemical bond between the substrate and the SH coating layer at an optimal coupling agent concentration. The developed conductive SH coating attained a high electromagnetic interference (EMI) shielding effectiveness, which is advantageous in self-cleaning EMI shielding applications.

• Transactions of the Korean Society of Mechanical Engineers
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• v.17 no.12
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• pp.3083-3093
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• 1993

Friction and wear at ceramic coated surfaces of aluminum alloy were experimentally studied using a Ring-on-Block wear test machine. Ceramic materials coated on aluminum alloy surfaces were WC, CrC, $Al_{2}O_{3}$ by a plasma spray; and $Al_{2}O_{3}$,$Al_{2}SiO_{5}$, $Na_{2}B_{4}O_{7}$,$Na_{4}P_{2}O_{7}$, and $Al_{2}O_{3}-ZrO_{2}$ composite coating by an Anodic Spark Depositon. They were tested under the sliding wet contact and compared with aluminum alloys and steels. Test results showed that ceramic coated surfaces, in general, have better anti-wear property than those of aluminum alloys due to increase in the surface hardness ; however, they also showed higher coefficients of friction and changes in wear mechanisms, resulting in brittle fractures.

• Journal of Ocean Engineering and Technology
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• v.18 no.1
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• pp.75-79
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• 2004

Organic coatings are widely used to control of the corrosion of a steel structure. The water in coatings may cause the coatings to swell, leading to the degradation of the coatings. In addition, water affects the permeation of oxygen and other corrosive agents, and consequently, the presence of such substances at coating-metal interface promotes corrosion of the metal substrate. In this study, the anticorrosive properties of 4 types of coating, such as epoxy-epoxy, epoxy-urethane, urethane-epoxy, urethane-urethane, were evaluated. The evaluation tests were conducted under cyclic water-absorption/desorption conditions, consisting of alternative exposure to diluted 0.001M-LiCl(a$H_2O$≒1) and concentrated 10M-LiCl(a$H_2O$≒0.15). The anticorrosive performance of coatings was found to decrease in the order of urethane-urethane > urethane-epoxy > epoxy-epoxy coating.

• Journal of the Korean Ceramic Society
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• v.53 no.5
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• pp.541-547
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• 2016

In developing high temperature molds with advantages of the sand and precision (investment) castings, mechanical properties of the mold were improved through homogeneous coating of starting powders with an inorganic binder and improvement of fabrication process. Beads with mullite composition were employed for properties of the mold under high temperature, which was compared with artificial sands. Precursors of silica and sodium oxide were used as starting materials for an inorganic binder to achieve homogeneous coating on the starting powders. Strength was enhanced by the glass phase converted from the inorganic binder through heat treatment process. Also, two kinds of process, wet and dry processes, were incorporated to prepare mold specimens. Consequently, fabrication process of the mold with superior strength and high temperature applicability, compared with the previous molds for sand casting, could be suggested through control of the starting material and enhancement of the vitrification efficiency.

• Transactions of Materials Processing
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• v.28 no.2
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• pp.77-82
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• 2019

Corrosion occurs well on surface of roll formed and Zn alloy subsequently electro-deposited on steel bolt under wet condition. In this study, variations in corrosion resistance were investigated through the measurement of polarization curves on steel bolts which were roll formed and subsequently coated with various types of coating methods. According to the measured polarization curve, Ni-P electroless deposits on roll formed steel increased the resistance to corrosion. The corrosion resistance of Zn alloy powder coated steel bolt was found to be better than that of Zn-Ni electro-deposited sample.

• Proceedings of the Materials Research Society of Korea Conference
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• 2012.05a
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• pp.111.2-111.2
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• 2012

정보 기술 시대에 맞춰 광전소자의 연구가 활발해지면서 투명전극으로 사용될 수 있는 Transparent Conductive Oxide (TCO) 재료에 대한 관심이 높아지고 있다. 하지만 TCO의 대표적인 물질인 Indium Tin Oxide (ITO)의 경우 In의 가격 상승으로 인해 최근에는 낮은 전도도와 높은 투과도를 가질 수 있는 대체 물질에 대한 연구가 활발히 진행되고 있다. 그 중에서 3.2 eV 의 높은 밴드갭을 갖는 ZnO 는 가시광선 영역에서 높은 투과율을 나타낼 뿐만 아니라 Al, Ga을 도핑함으로써 낮은 전도도를 가질 수 있다. 이러한 TCO 재료는 surface texturing을 통하여 optical region 에서 반사를 억제 시킴으로서 빛을 모으는 역할을 하여 태양전지의 효율을 향상 시킬 수 있기 때문에 PV (Photovoltaics) Cell의 anti-reflective coating에 적용 할 수 있다. 본 연구에서는 pulsed DC magnetron sputtering을 이용하여 Ga-doped ZnO (GZO) 박막을 증착하였고, HCl 0.5 wt %로 wet etching을 통하여 surface texturing을 진행하였다. 결정성은 X-ray diffractometer (XRD)로 분석하였으며, 표면 형상은 Scanning Electron Microscope (SEM)을 통해 확인하였다. Van der Pauw 방법을 통해 resistivity, carrier concentration, hall mobility 등의 전기적 특성을 분석하였고 UV-Vis spectrophotometer 를 통해 투과도 및 반사도를 측정하였다.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.28 no.12
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• pp.826-830
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• 2015

Transparent Ag nanowire conducting thin films with high surface hardness were fabricated by bar coating method. When coating speed was changed from 35 mm/sec to 50 mm/sec, the transmittance of coated glass increased from 65.3% to 80.8% in visible light range and the surface resistance was changed from $10.1{\Omega}/sq$ to $23.3{\Omega}/sq$. The surface hardness and adhesion of thin film were 5H and 5B.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2018.11a
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• pp.31-32
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• 2018

Lately, cement mixed siliceous powder waterproofing coating has been used as a waterproofing material in the wet environment condition of an underground concrete structure. Underground is exposed to environmental influences such as pressure of ground water, pressure of soil. However, the quality standard for pressure (water pressure, earth pressure) is not specified in the specification of the cement mixed siliceous powder waterproofing coating. Therefore, in this study, the permeability test was carried out based on the assumption that the durability should be verified in consideration of the environmental aspects of the material in actual field. As a result of the test, the permeability was generated from the inorganic single type material, but it was caused by the sealing failure and the test error, and the permeability was not generated in most of the materials. The results of this study will be analyzed by reviewing the physical properties of the material, and the research direction will be resumed.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2006.06a
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• pp.192-193
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• 2006

The wet coating process could easily be made from large area film with printing paste mixed with semiconductor and binder material at room temperature. Semiconductor film fabricated about 25mm thickness was evaluated by field emissions-canning electron microscopy (FE-SEM). X-ray performance data such as dark current, sensitivity and signal to noise ratio (SNR) were evaluated. The $Hgl_2$ semiconductor was shown in much lower dark current than the others, but the best sensitivity. In this paper, reactivity and combination character of semiconductor and binder material that affect electrical and X-ray detection properties would prove out though experimental results.

• Journal of the Korean Chemical Society
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• v.63 no.2
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• pp.94-101
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• 2019

Nb, Mo-doped and Nb/Mo-codoped $VO_2(M)$ nanocrystallites with various doping levels were synthesized for the first time by a hydrothermal and post thermal transformation method. The reversible phase transition characteristics of those doped $VO_2(M)$ was comparatively investigated. Nb-doping of $VO_2(M)$ by this method resulted in a very efficient lowering of the transition temperature ($T_c$) with a rate of $-16.7^{\circ}C/at.%$ that is comparable to W-doping, while Mo-doping did not give a serious reduction of $T_c$ with only a rate of $-5.1^{\circ}C/at.%$. Nb/Mo-codoping gave a similar result to Nb-doping without a noticeable difference. The thin films of Nb-doped and Nb/Mo-codoped $VO_2(M)$ with a thickness of ca. 120 nm were prepared by a wet-coating of the nanoparticle-dispersed solutions. Those films showed a good thermochromic modulation of near infrared radiation with 30-35% for Nb-doped $VO_2(M)$ and 37-40% for Nb/Mo-codoped ones. Nb/Mo-codoped $VO_2(M)$ film showed slightly enhanced thermochromic performance compared with Nb-doped $VO_2(M)$ film.