• 한국진공학회:학술대회논문집
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• 한국진공학회 2011년도 제40회 동계학술대회 초록집
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• pp.335-335
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• 2011

Instability of a thin film attached to a compliant substrate often leads to emergence of exquisite wrinkle patterns with length scales that depend on the system geometry and applied stresses. However, the patterns that are created using the current techniques in polymer surface engineering, generally have low aspect ratio of undulation amplitude to wavelength, thus, limiting their application. Here, we present a novel and effective method that enables us to create wrinkles with a desired wavelength and high aspect ratio of amplitude over wavelength as large as to 2.5:1. First, we create buckle patterns with high aspect ratio of amplitude to wavelength by deposition of an amorphous carbon film on a surface of a soft polymer poly(dimethylsiloxane) (PDMS). Amorphous carbon films are used as a protective layer in structural systems and biomedical components, due to their low friction coefficient, strong wear resistance against, and high elastic modulus and hardness. The deposited carbon layer is generally under high residual compressive stresses (~1 GPa), making it susceptible to buckle delamination on a hard substrate (e.g. silicon or glass) and to wrinkle on a flexible or soft substrate. Then, we employ glancing angle deposition (GLAD) for deposition of a high aspect ratio patterns with amorphous carbon coating on a PDMS surface. Using this method, pattern amplitudes of several nm to submicron size can be achieved by varying the carbon deposition time, allowing us to harness patterned polymers substrates for variety of application. Specifically, we demonstrate a potential application of the high aspect wrinkles for changing the surface structures with low surface energy materials of amorphous carbon coatings, increasing the water wettability.

• 한국표면공학회:학술대회논문집
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• 한국표면공학회 2012년도 추계총회 및 학술대회 논문집
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• pp.16-16
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• 2012

Mg and its alloys have been of great interest because of their low density of 1.7, 30% lighter than Al, but their wide applications have been limited because of their poor resistances against corrosion and/or abrasion. Corrosion resistance of Mg alloys can be improved by formation of anodic films using anodic oxidation method in aqueous electrolytes. Plasma electrolytic oxidation (PEO) is one of anodic oxidation methods by which hard anodic films can be formed as a result of micro-arc generation under high electric field. PEO method utilize not only substrate elements but also chemical components in electrolytes to form anodic films on Mg alloys. PEO films formed on AM50 magnesium alloy in an acidic fluozirconate electrolyte were observed to consist of mainly $ZrO_2$ and $MgF_2$. Liu et al reported that PEO coating on AM30 Mg alloy consists of $MgF_2$-rich outer porous layer and an MgO-rich dense inner layer. PEO films prepared on ACM522 Mg die-casting alloy in an aqueous phosphate solution were also reported to be composed of monoclinic $Mg_3(PO_4)_2$. $CeO_2$-incorporated PEO coatings were also reported to be formed on AZ31 Mg alloys in $CeO_2$ particle-containing $Na_2SiO_3$-based electrolytes. Magnesium tin hydroxide ($MgSn(OH)_6$) was also produced on AZ91D alloy by PEO process in stannate-containing electrolyte. Effects of $OH^-$, $F^-$, $PO{_4}^{3-}$ and $SiO{_3}^{2-}$ ions and alloying elements of Al and Sn on the formation of PEO films on pure Mg and Mg alloys and their protective properties against corrosion have been investigated in this work. $PO{_4}^{3-}$, $F^-$ and $SiO{_3}^{2-}$ ions were observed to contribute to the formation of PEO films but $OH^-$ ions were found to break down the surface films under high electric field. The effect of pulse current on the formation of PEO films will be also reported.

• 박물관보존과학
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• 제19권
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• pp.69-82
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• 2018

국립청주박물관 소장 충북 영동 영국사 출토 금동여래입상과 동제여래입상의 과학적 조사와 보존처리를 하였다. 성분분석 결과, 금동여래입상은 구리, 주석, 납의 삼원계, 동제여래입상은 구리, 주석의 이원계 합금으로 확인되었다. 동제여래입상 성분분석 결과 금이 확인되어 금동여래입상으로 명칭이 수정되어야 할 것이다. 금동여래입상은 국내에서 생산된 납을 원료로 하여 제작되었을 것으로 유추할 수 있었고, 표면에 존재하는 개금을 위한 접착제로 보이는 물질은 분석을 통해 옻으로 추정되었다. 보존처리는 상태를 확인하여 물리적, 화학적 방법으로 최소한의 이물질을 제거하고, 안정화처리 및 보호 코팅의 과정을 거쳤다.

• 한국군사과학기술학회지
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• 제19권5호
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• pp.618-628
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• 2016

The development of new concepts of liners is required in order to effectively neutralize the enemy's attack power concealed in the armored vehicles. A multiple-layer liner is one of possibilities and has a mechanism for explosion after penetrating the target which is known as "Behind Armor Effect." The multiple-layer explosive liner should have sufficient kinetic energy to penetrate the protective structure and explosive material react after target penetration. With this in mind, double-layer liner materials were obtained by cold spray coating methods and these material properties were experimentally characterized and used in this simulation for double-layer liners. In this study, numerical simulations in the three different layer types, i.e., single, A/B, A/B/A in terms of the layer location were verified in terms of finite element mesh sizes and numerical results for the jet tip velocity, kinetic energy, and the corresponding jet deformation characteristics were analysed in detail depending on the structure of layer types.

• 멤브레인
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• 제16권1호
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• pp.1-8
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• 2006

나노섬유란 $1{\mu}m$ 이하의 섬유를 의미하며 멜트블로운(Melt blown), 복합방사, 분할방사, 전기방사 등의 방법으로 제조된다. 나노섬유는 초극세 섬유로서 섬유의 생성과 동시에 3차원의 네트워크로 융착되어 적층된 형태의 다공성 웹은 초박막, 초경량이며 기존 섬유에 비해 부피 대비 표면적비가 지극히 높고, 높은 기공도를 지니고 있다. 이러한 특성으로 인해 가스나 액체로부터 미세입자를 분리하는 고효율 초기능성 필터 소재로 활용될 수 있으며, 나노섬유로 구성된 필터는 여과 효율이 높고 공극율이 매우 높아 필터에서 발생하는 압력강하가 적다. 또한 공정의 적용이 용이하여 기존의 부직포 등의 소재에 코팅이 가능하므로, 나노섬유 필터는 기존 부직포 필터 시장의 대부분을 대체할 것으로 기대되어 진다. 본 총설에서는 나노섬유 필터의 연구개발 동향과 공업적 제조기술의 문제점 및 향후 시장성에 대해서 고찰하였다.

• 한국재료학회지
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• 제8권8호
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• pp.685-692
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• 1998

용융탄산염 연료전지는 $650^{\circ}C$의 부식성이 강한 용융탄산염내에서 작동되므로, 분리판 재료로 사용되고 있는 316L 스테인레스강의 부식은 용융탄산염 연료전지의 수명을 단축시키는 주요한 원인이다. 특히 분리판 wet-seal부의 부식은 보다 심각한 것으로 알려져 있다. 이를 해결하기 위하여 AI계 합금이 피복재료로 사용되어 왔지만, 본 연구에서는 보다 우수한 분리판 wet-seal부의 내식 피복재료 개발을 위하여 피복재료인 NiAI 합금에 산화 활성화 원소인 yttrium을 최고 1.5 at%까지 첨가하였다. $650^{\circ}C$의 용융탄산염내에서 yttium 함량에 따른 NiAI/Y 합금의 침지부식실험 및 분극실험을 통하여 내식성을 평가하고 부식 억제를 위해 가장 적절한 NiAI/Y 피복 재료의조성을 결정한 결과 최소의 yttrium 조성은 0.7 at% 임을 알 수 있었다.

• 박물관보존과학
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• 제18권
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• pp.51-64
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• 2017

숭실대학교 한국기독교박물관이 소장한 자명종을 특별전 전시를 위해 보존처리 하였다. 보존처리를 위해 성분 분석을 하였으며 그 결과 본체는 황동에 아말감도금법으로 금을 도금하였고, 문자판은 순구리에 법랑을 씌운 것을 확인하였다. 그리고 시계 바늘의 재질은 철이었다. 이물질 제거를 통해 문자판의 테이프 자국 등을 없앴으며, 안정화를 위해 보호 코팅을 하였다. 원래의 형상에 가깝게 복원하기 위해 황동으로 부품을 제작하여 시계 바늘과 문자판을 연결하고, 아크릴 지지대를 만들어 문자판을 본체에 접합하였다. 재질 분석과 보존처리를 통하여 안정한 상태로 전시와 연구에 활용할 수 있도록 하였다.

• 한국버섯학회지
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• 제16권4호
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• pp.331-333
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• 2018

The incorporation of Shiitake culture into sawdust is a widely utilized technique that can assist in reducing the cost and time consumption associated with oak cultivation. In sawdust cultivation, browning of the surface mycelia is an important stage with respect to the utility and longevity of the sawdust media. Surface browning forms a protective coating on the substrate, which can inhibit the invasion of pathogens and suppress water evaporation. Several different light sources (red LED, white LED, blue LED, and fluorescent light) were used and the intensity of illumination was carefully controlled (1.5, 10.5, $20.5{\mu}mol/m^2s$ for LEDs and 10, 100, 300 lux for the fluorescent light) to induce browning. The light sources were regulated via a 1 h on/off cycle in a controlled room environment at a temperature of $20^{\circ}C$, 60% humidity, and 1200 ppm $CO_2$ concentration for 60days. The browning effect varied depending on the source and the intensity of illumination. This effect was most effectively induced at $1.5{\mu}mol/m^2s$ for the red and blue LEDs. All light sources induced less browning at the highest intensity of illumination. This indicates that intensity values higher than $20.5{\mu}mol/m^2s$ in the case of the LEDs and 300 lux for the fluorescent light are not effective. After harvesting of the fruit bodies, we measured the weight, length, and width of the pileus and stipe in addition to their chromaticity and hardness. Treatment with $1.5{\mu}mol/m^2s$ blue LED produced the best harvest with the highest average chromaticity, weight (21.2 g), stipe length (30.8 mm), and hardness (377.9 g), with a fine length and width of the pileus.

• Corrosion Science and Technology
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• 제18권2호
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• pp.61-71
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• 2019

Flow-Accelerated Corrosion (FAC) is a phenomenon in which a protective coating on a metal surface is dissolved by a flow of fluid in a metal pipe, leading to continuous wall-thinning. Recently, many countries have developed computer codes to manage FAC in power plants, and the FAC prediction model in these computer codes plays an important role in predictive performance. Herein, the FAC prediction model was developed by applying a machine learning method and the conventional nonlinear regression method. The random forest, a widely used machine learning technique in predictive modeling led to easy calculation of FAC tendency for five input variables: flow rate, temperature, pH, Cr content, and dissolved oxygen concentration. However, the model showed significant errors in some input conditions, and it was difficult to obtain proper regression results without using additional data points. In contrast, nonlinear regression analysis predicted robust estimation even with relatively insufficient data by assuming an empirical equation and the model showed better predictive power when the interaction between DO and pH was considered. The comparative analysis of this study is believed to provide important insights for developing a more sophisticated FAC prediction model.

• Computers and Concrete
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• 제32권2호
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• pp.119-138
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• 2023

Concrete carbonation is a prevalent phenomenon that leads to steel reinforcement corrosion in reinforced concrete (RC) structures, thereby decreasing their service life as well as durability. The process of carbonation results in a lower pH level of concrete, resulting in an acidic environment with a pH value below 12. This acidic environment initiates and accelerates the corrosion of steel reinforcement in concrete, rendering it more susceptible to damage and ultimately weakening the overall structural integrity of the RC system. Lower pH values might cause damage to the protective coating of steel, also known as the passive film, thus speeding up the process of corrosion. It is essential to estimate the carbonation factor to reduce the deterioration in concrete structures. A lot of work has gone into developing a carbonation model that is precise and efficient that takes both internal and external factors into account. This study presents an ML-based adaptive-neuro fuzzy inference system (ANFIS) approach to predict the carbonation depth of fly ash (FA)-based concrete structures. Cement content, FA, water-cement ratio, relative humidity, duration, and CO2 level have been used as input parameters to develop the ANFIS model. Six performance indices have been used for finding the accuracy of the developed model and two analytical models. The outcome of the ANFIS model has also been compared with the other models used in this study. The prediction results show that the ANFIS model outperforms analytical models with R-value, MAE, RMSE, and Nash-Sutcliffe efficiency index values of 0.9951, 0.7255 mm, 1.2346 mm, and 0.9957, respectively. Surface plots and sensitivity analysis have also been performed to identify the repercussion of individual features on the carbonation depth of FA-based concrete structures. The developed ANFIS-based model is simple, easy to use, and cost-effective with good accuracy as compared to existing models.