표면막과 표면거칠기가 접촉 저항에 미치는 영향

이현철,이보라,유용훈,조용주 한국트라이볼로지학회 2019 한국윤활학회지(윤활학회지) Vol.35 No.1

In this study, we aim to analyze the effects of both contact layer properties and surface roughness on contact resistance. The contact has a great influence on performance in terms of electrical conduction and heat transfer. The two biggest factors determining contact resistance are the presence of surface roughness and the surface layer. For this reason we calculated the contact resistance by considering both factors simultaneously. The model of this study to calculate contact resistance is as follows. First, the three representative surface parameters for the GW model are obtained by Nayak's random process. Then, the apparent contact area, real contact area, and contact number of asperities are calculated using the GW model with the surface parameters. The contact resistance of a single surface layer is calculated using Mikic's constriction equation. The total contact resistance is approximated by the parallel connection between the same asperity contact resistances. The results of this study are as follows. The appropriate thickness with reduction effect for contact resistance is determined according to the difference in conductivity between the base layer and surface layer. It was confirmed that the standard deviation of surface roughness has the greatest influence on surface roughness parameters. The results of this study will be useful for selecting the surface material and surface roughness when the design considering the contact resistance is needed.

Correlations between electrochemical resistances and surface properties of acid-treated fuel in coal fuel cells

Eom, Seongyong,Ahn, Seongyool,Kang, Kijoong,Choi, Gyungmin Elsevier 2017 ENERGY Vol.140 No.1

<P><B>Abstract</B></P> <P>Herein, we investigate the relationship between fuel surface properties and inner resistances of direct carbon fuel cells (DCFCs) by subjecting raw coal to a liquid-phase chemical treatment and correlating its surface property changes (e.g., degree of oxidation, surface area, and ash composition) with those of electrochemical resistances. Fuel surface characteristics are analyzed by thermogravimetry, gas adsorption, and X-ray photoelectron spectroscopy, with correlations established using the Pearson correlation analysis. The obtained results show that the surface Si content is strongly correlated with electrolyte resistance due to influencing the concentration of carbonate ions. Moreover, charge transfer resistance is strongly negatively correlated with the surface oxygen content, since oxygenated functional groups (e.g., carbonyl and quinone moieties) enhance the oxidation of solid carbon by increasing its reactivity and wettability.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Effects of surface properties on resistances are investigated in carbon fuel cell. </LI> <LI> The performance and resistance of raw coal and treated coals are compared. </LI> <LI> Si content on the fuel surface has a correlation with the electrolyte resistance. </LI> <LI> The charge transfer resistance is affected by surface oxygen groups. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Corrosion resistance of water repellent aluminum surfaces with various wetting morphologies

Song, Kyounghwan,Kim, Inkyu,Bang, Soosik,Jung, Jung-Yeul,Nam, Youngsuk Elsevier 2019 APPLIED SURFACE SCIENCE - Vol.467 No.-

<P><B>Abstract</B></P> <P>We investigated the improved corrosion resistance of micro/nanostructured aluminum surfaces by varying wetting morphologies. By combining the wet-chemical oxidation schemes and low surface energy coating, we induced three different wetting morphologies including superhydrophilic, Cassie-mode superhydrophobic and Wenzel-mode hydrophobic on micro/nanostructured aluminum surfaces. The superhydrophilic oxide layers provided approximately 30–76% improvement in the corrosion resistance compared to untreated ones. When a hydrophobic coating was added to the oxide layers and Cassie-mode superhydrophobicity was induced, all types of samples showed over 95% increase in the corrosion resistance compared with untreated ones. When the air trapped on the superhydrophobic surfaces was removed in a vacuum environment, the corrosion resistance decreased but still provided 70–98% increase compared with untreated ones. The present work showed that the superhydrophobic treatment is a very effective way to improve the corrosion resistance but the proper choice of the passivation layer and hydrophobic coating can provide a meaningful increase in the corrosion resistance. The present work further clarified the high corrosion resistance of superhydrophobic aluminum surfaces and will help to develop practical anti-corrosion resistance surfaces.</P> <P><B>Highlights</B></P> <P> <UL> <LI> The effects of various wetting morphologies on the corrosion resistance were quantified. </LI> <LI> The importance of the air trapping was clarified by forcing the Cassie-to-Wenzel wetting transition. </LI> <LI> The effects of oxide barriers, hydrophobic coating and air layer on the corrosion resistance were analyzed. </LI> <LI> This work helps to estimate the effects of the surface degradation of anti-corrosion surfaces. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

동결융해 환경에서의 제설염 종류와 표면강화제 처리에 따른 콘크리트의 표면박리 저항성 및 평가방법에 관한 연구

이현기(Lee, Hyeongi),이인희(Lee, Inhee),이종미(Lee, Jongmi),오홍섭(Oh, Hongseob) 한국방재학회 2017 한국방재학회논문집 Vol.17 No.4

본 연구의 목적은 제설염의 종류 및 구체강화제의 처리 유무에 따른 콘크리트 표면 박리저항성을 평가하고, 3D 스캐닝에 의해 표면상태를 평가하는 기법을 제안하고자 하였다. 본 연구에서는 국내에서 많이 사용되고 있는 다양한 습염식 제설염을 국외의 스케일링 시험법에 따라 콘크리트 표면에 표면강화제를 변수로 하여 박리실험을 실시하였다. 실험결과 무기질계 구체강화제를 사용한 경우 스케일링 저항성이 크게 향상되는 것으로 나타났으며, 규산나트륨계열의 강화제의 경우에는 박리가 상대적으로 많이 진행되었다. 또한 본 연구에서는 콘크리트 표면 박리를 평가하기 위하여 3D 스캐닝을 사용하여 박리량을 평가하는 법을 제안하고자 하였다. The objectives of this research study were to evaluate and discuss the scaling resistance of concrete surface due to freeze-thaw effect according to both the type of saline solution that was applied in compliance with overseas standards, and the treatment of the concrete surface hardener. Further, the accuracy of the evaluation method was assessed utilizing 3-D imaging technologies to determine the scaling resistance of concrete surface. This research study comparatively analyzed the scaling resistance of concrete surfacefor deicing agents that are currently used in domestic pre-wetting spray systems. Comparisons were made according to the saline solution that is used in compliance with overseas scaling resistance evaluation standards, the type of concrete surface hardener used, and whether the concrete had undergone a surface treatment. The results based on the concrete surface hardener treatment manifested superior results when mineral silane-based treatment agents were used. In order to provide a more quantitatively reliable evaluation, a concrete surface scaling resistance evaluation method utilizing 3-D scanning technologies was proposed in this research study.

Effect of Free Surface Based on Submergence Depth of Underwater Vehicle

Taek-Geun Youn,Min-Jae Kim,Moon-Chan Kim,Jin-Gu Kang 한국해양공학회 2022 韓國海洋工學會誌 Vol.36 No.2

This paper presents the minimum submergence depth of an underwater vehicle that can remove the effect of free surface on the resistance of the underwater vehicle. The total resistance of the underwater vehicle in fully submerged modes comprises only viscous pressure and friction resistances, and no wave resistance should be present, based on the free surface effect. In a model test performed in this study, the resistance is measured in the range of 2 to 10 kn (1.03–5.14 m/s) under depth conditions of 850 mm (2.6D) and 1250 mm (3.8D), respectively, and the residual resistance coefficients are compared. Subsequently, resistance analysis is performed via computational fluid dynamics (CFD) simulation to investigate the free surface effect based on various submergence depths. First, the numerical analysis results in the absence of free surface conditions and the model test results are compared to show the tendency of the resistance coefficients and the reliability of the CFD simulation results. Subsequently, numerical analysis results of submergence depth presented in a reference paper are compared with the model test results. These two sets of results confirm that the resistance increased due to the free surface effect as the high speed and depth approach the free surface. Therefore, to identify a fully submerged depth that is not affected by the free surface effect, case studies for various depths are conducted via numerical analysis, and a correlation for the fully submerged depth based on the Froude number of an underwater vehicle is derived.

치과용 임플란트 나사의 풀림에 미치는 표면코팅 효과

구철인,정재헌,최한철,Koo Cheol-In,Chung Chae-Heon,Choe Han-Cheol 대한치과보철학회 2004 대한치과보철학회지 Vol.42 No.2

Statement of problem: Implant screw loosening has been remained problem in restorative practices. Surface treatment of screw plays a role of preventing screw from loosening in implant screw mechanism. Purpose : The purpose of this study was to investigate surface characteristics of TiN and ZrN film ion plated screw with titanium and gold alloy screw and to evaluate wear resistance, surface roughness, and film adhesion on screw surface using various instruments. Material and methods : GoldTite screws and titanium screws provided by 3i (Implant Innovation, USA) and TorqTite screws or titanium screws by Steri-Oss (Nobel Biocare, USA) and gold screws and titanium screws by AVANA (Osstem Implant, korea) were selected. Ion plating which is much superior to other surface modification techniques was carried out for gold screws and titanium screws using Ti and Zr coating materials with nitrogen gas. Ion nitrided surface of each abutment screw was observed with field emission scanning electron microscopy (FE-SEM, micro-diamond scratch tester, vickers hardness tester, and surface roughness tester. Results : 1) The surface of gold screw and GoldTite is more smooth than ones of other kinds of non coated screw. 2) The ZrN and TiN coated surface is the more smooth than ones of other kinds of screw. 3) The hardness of TiN and ZrN coated surface showed higher than that of non coated surface. 4) The TiN coated titanium screw and ZrN coated gold screw have a good wear resistance and adhesion on the surface. 5) The surface of ZrN coated screw showed low surface roughness compared with the surface of TiN coated screw. Conclusion : It is considered that the TiN and ZrN coated screw which would prevent a screw from loosening can be applicable to implant system and confirmed that TiN and ZrN film act as lubricant on surface of screw due to decrease of friction for recycled tightening and loosening.

Sulfur Polymer를 사용한 콘크리트 구조물용 내화학성 표면보호재의 성능 평가

이병재,이의성,정우성,김윤용 한국구조물진단유지관리공학회 2014 한국구조물진단유지관리공학회 논문집 Vol.18 No.5

본 연구에서는 유황을 폴리머화하여 내화학성능이 요구되는 구조물의 콘크리트 표면보호재로 활용할 수 있도록 성능을 검토하였다.평가 결과, 유황폴리머 표면도포재의 중력식 스프레이가 적절한 것으로 나타났으며, 도포횟수는 왕복 3회 이상 도포했을 때 1MPa 이상의 부착강도 확보가 가능하였다. 표면보호재가 도포될 콘크리트 표면조건은 상온조건 (20~30℃) 이상에서 높은 부착강도를 나타내었으며,온도가 높을수록 부착강도가 증가하였다. 표면보호재의 채움재 혼입량에 따른 강도특성 평가결과, 20~40% 정도 혼입된 채움재는 유황폴리머의 수축을 저감시키는 효과를 나타내어 강도 향상에 기여하였다. 또한, 플라이애시 보다는 규사 혼입시 부착강도가 높았고, 동시 혼입시가장 우수한 부착강도 특성을 나타내었다. 화학저항성은 플라이애시 및 규사를 각각 20% 대체한 배합에서 부착강도 저하가 최소로 되어우수한 내화학성을 나타내었다. 염소이온 침투에 대한 성능평가를 수행한 결과, 표면보호재를 도포하지 않은 시험체에 비하여 유황폴리머표면보호재를 도포한 경우, 29~48% 정도 염소이온침투저항성이 증대되었다. 표면보호재의 도포조건, 압축강도, 부착강도, 화학저항성, 염해저항성 등을 모두 고려하여 볼 때, 본 연구범위에서는 유황폴리머에 채움재로서 규사와 플라이애시를 각각 20%씩 대체하는 것이 적절한수준인 것으로 판단된다. Structures requiring chemical resistance are usually coated with surface protecting agents, but the cost for maintenance and re-construction is incurred due to the low durability. Therefore, in this study, sulfur was polymerized and the performance was examined so that it could be used as the concrete surface protecting agents for structures requiring chemical resistance.The evaluation results indicated that for the spray of the sulfur polymer surface coating agents, the application of the gravitytype was appropriate; and for the number of coating times, about 3 cycle spray gave the best results. For the surface condition ofthe concrete to be coated with the surface protecting agents, outstanding quality was obtained above room temperature (20~30℃),and the bond strength increased as the temperature increased. The evaluation results of the strength characteristics depending on the filler content of the surface protecting agents indicated that about 20~40% filler mixing contributed to the strength improvementas it reduced the shrinkage of the sulfur polymer. Also, the mixing of silica showed larger increase in the bond strength than the mixing of fly ash, and the most outstanding bond strength characteristics could be obtained by the mixing of both silica and flyash. In the case of the chemical resistance, the strength reduction was minimized and outstanding chemical resistance was obtained when the fly ash and silica were substituted by 20%, respectively. The performance evaluation of the chloride ion penetration indicated that for the specimens coated with the sulfur polymer surface protecting agents, the chloride ion penetration resistance increased by 29~48% compared to the specimen without the coating of the surface protecting agent. The examination of the coating condition of the surface protecting agents, compressive strength, bond strength, chemical resistance, and salt damage resistance indicated that in the range of this study, the optimal level was when the silica and fly ash were substituted by 20%, respectively, as the filler for the sulfur polymer.

실란-에폭시 다층 표면개질을 통한 역삼투막의 내오염성 향상

권세이,이용택 한국막학회 2015 멤브레인 Vol.25 No.4

본 연구는 역삼투막의 막오염을 해결하기 위하여 실란-에폭시 층을 형성시킨 다층 표면개질법을 이용하여 역삼투막의 내오염성을 향상시키고자 하였다. Sol-gel법을 이용하여 Octyltrimethoxysilane (OcTES)을 막 표면에 가교를 통해 고분자화 하였으며 n = 8인 OcTES의 알킬기가 자발적인 self-assembly를 통하여 막 표면에 가지구조를 형성시켰다. 그 위에 ethylene glycol diglycidyl ether (EGDE)의 ether기를 ring-opening을 통해 막 표면에 친수성을 부여하여 역삼투막의 내오염성을향상시키고자 하였다. FE-TEM, AFM을 이용하여 막의 단면 및 표면구조 분석을 하였고 막 표면의 ridge and valley 구조와OcTES, EGDE의 다층 표면개질로 인한 bridge 구조를 확인하였으며, 거칠기의 증가를 통해 막 표면의 가지가 잘 형성되었음을 확인하였다. XPS를 통하여 막 표면의 화학구조에 대한 관찰과 표면개질이 잘 이루어졌음을 확인하였으며, contact angle 분석을 통해 표면개질막의 표면에 친수성이 부여되었음을 확인하였다. EGDE 표면개질 조건 최적화를 진행한 결과 EGDE 농도는 0.5 wt%, ring-opening 온도는 70°C가 가장 적합하였고, 내오염성 실험 결과 및 막오염지수(MFI)는 SUL-H10, PA-OcTES1.0, PA-OcTES1.0-EGDE0.5이 68.7, 60.4, 5.4 (10E-8 hr/mL2)로 나타나 다층 표면 개질막의 내오염성이 매우 향상되었음을 확인할 수 있었다. In this study, to solve the major problem of reverse osmosis (RO) membrane, surface of reverse osmosis membrane was modified by silane-epoxy multi layer. Octyltrimethoxysilane (OcTES) was polymerized to membrane surface via cross-linking by Sol-gel method. n = 8 alkylgroup of OcTES formed the branch structure by self assembly. And for improve fouling resistance of RO membrane, Ether group of ethylene glycol diglycidyl ether (EGDE) was given to improve hydrophilicity of RO membrane surface by ring-opening. To analyze structure of RO membrane surface with FE-TEM and AFM. Membrane surface of the ridge and valley structure and the bridge structure was confirmed due to the multi-layer surface modification of OcTES and EGDE. And through the increase of the roughness, the branch structure was formed well on membrane surface. Through the XPS analysis was identified chemical structure of membrane surface. And confirmed that the hydrophilic surface modification is given to the surface of the film through a Contact angle analysis. In optimization of EGDE surface modification condition, was suitable 0.5 wt% EGDE concentraion and 70°C ring-opening temperature. In result of fouling resistance test and MFI is SUL-H10, PA-OcTES1.0, PA-OcTES1.0-EGDE0.5 68.7, 60.4, 5.4 (10E-8 hr/mL2), multi-layer surface modified membrane improved fouling resistance.

Sulfur Polymer를 사용한 콘크리트 구조물용 내화학성 표면보호재의 성능 평가

이병재,이의성,정우정,김윤용 한국구조물진단유지관리공학회 2014 한국구조물진단유지관리공학회 논문집 Vol.18 No.5

Structures requiring chemical resistance are usually coated with surface protecting agents, but the cost for maintenance andre-construction is incurred due to the low durability. Therefore, in this study, sulfur was polymerized and the performance wasexamined so that it could be used as the concrete surface protecting agents for structures requiring chemical resistance. The evaluation results indicated that for the spray of the sulfur polymer surface coating agents, the application of the gravitytype was appropriate; and for the number of coating times, about 3 cycle spray gave the best results. For the surface condition ofthe concrete to be coated with the surface protecting agents, outstanding quality was obtained above room temperature (20~30℃),and the bond strength increased as the temperature increased. The evaluation results of the strength characteristics depending on thefiller content of the surface protecting agents indicated that about 20~40% filler mixing contributed to the strength improvementas it reduced the shrinkage of the sulfur polymer. Also, the mixing of silica showed larger increase in the bond strength than themixing of fly ash, and the most outstanding bond strength characteristics could be obtained by the mixing of both silica and flyash. In the case of the chemical resistance, the strength reduction was minimized and outstanding chemical resistance was obtainedwhen the fly ash and silica were substituted by 20%, respectively. The performance evaluation of the chloride ion penetrationindicated that for the specimens coated with the sulfur polymer surface protecting agents, the chloride ion penetration resistanceincreased by 29~48% compared to the specimen without the coating of the surface protecting agent. The examination of thecoating condition of the surface protecting agents, compressive strength, bond strength, chemical resistance, and salt damageresistance indicated that in the range of this study, the optimal level was when the silica and fly ash were substituted by 20%,respectively, as the filler for the sulfur polymer. 본 연구에서는 유황을 폴리머화하여 내화학성능이 요구되는 구조물의 콘크리트 표면보호재로 활용할 수 있도록 성능을 검토하였다. 평가 결과, 유황폴리머 표면도포재의 중력식 스프레이가 적절한 것으로 나타났으며, 도포횟수는 왕복 3회 이상 도포했을 때 1MPa 이상의 부착강도 확보가 가능하였다. 표면보호재가 도포될 콘크리트 표면조건은 상온조건 (20~30℃) 이상에서 높은 부착강도를 나타내었으며,온도가 높을수록 부착강도가 증가하였다. 표면보호재의 채움재 혼입량에 따른 강도특성 평가결과, 20~40% 정도 혼입된 채움재는 유황폴리머의 수축을 저감시키는 효과를 나타내어 강도 향상에 기여하였다. 또한, 플라이애시 보다는 규사 혼입시 부착강도가 높았고, 동시 혼입시가장 우수한 부착강도 특성을 나타내었다. 화학저항성은 플라이애시 및 규사를 각각 20% 대체한 배합에서 부착강도 저하가 최소로 되어우수한 내화학성을 나타내었다. 염소이온 침투에 대한 성능평가를 수행한 결과, 표면보호재를 도포하지 않은 시험체에 비하여 유황폴리머표면보호재를 도포한 경우, 29~48% 정도 염소이온침투저항성이 증대되었다. 표면보호재의 도포조건, 압축강도, 부착강도, 화학저항성, 염해저항성 등을 모두 고려하여 볼 때, 본 연구범위에서는 유황폴리머에 채움재로서 규사와 플라이애시를 각각 20%씩 대체하는 것이 적절한수준인 것으로 판단된다.

실란-에폭시 다층 표면개질을 통한 역삼투막의 내오염성 향상

권세이,이용택 한국막학회 2015 멤브레인 Vol.25 No.4

본 연구는 역삼투막의 막오염을 해결하기 위하여 실란-에폭시 층을 형성시킨 다층 표면개질법을 이용하여 역삼투막의 내오염성을 향상시키고자 하였다. Sol-gel법을 이용하여 Octyltrimethoxysilane (OcTES)을 막 표면에 가교를 통해 고분자화 하였으며 n = 8인 OcTES의 알킬기가 자발적인 self-assembly를 통하여 막 표면에 가지구조를 형성시켰다. 그 위에 ethylene glycol diglycidyl ether (EGDE)의 ether기를 ring-opening을 통해 막 표면에 친수성을 부여하여 역삼투막의 내오염성을 향상시키고자 하였다. FE-TEM, AFM을 이용하여 막의 단면 및 표면구조 분석을 하였고 막 표면의 ridge and valley 구조와 OcTES, EGDE의 다층 표면개질로 인한 bridge 구조를 확인하였으며, 거칠기의 증가를 통해 막 표면의 가지가 잘 형성되었음을 확인하였다. XPS를 통하여 막 표면의 화학구조에 대한 관찰과 표면개질이 잘 이루어졌음을 확인하였으며, contact angle 분석을 통해 표면개질막의 표면에 친수성이 부여되었음을 확인하였다. EGDE 표면개질 조건 최적화를 진행한 결과 EGDE 농도는 0.5 wt%, ring-opening 온도는 70°C가 가장 적합하였고, 내오염성 실험 결과 및 막오염지수(MFI)는 SUL-H10, PA-OcTES1.0, PA-OcTES1.0-EGDE0.5이 68.7, 60.4, 5.4 (10E-8 hr/mL2)로 나타나 다층 표면 개질막의 내오염성이 매우 향상되었음을 확인할 수 있었다. In this study, to solve the major problem of reverse osmosis (RO) membrane, surface of reverse osmosis membrane was modified by silane-epoxy multi layer. Octyltrimethoxysilane (OcTES) was polymerized to membrane surface via cross-linking by Sol-gel method. n = 8 alkylgroup of OcTES formed the branch structure by self assembly. And for improve fouling resistance of RO membrane, Ether group of ethylene glycol diglycidyl ether (EGDE) was given to improve hydrophilicity of RO membrane surface by ring-opening. To analyze structure of RO membrane surface with FE-TEM and AFM. Membrane surface of the ridge and valley structure and the bridge structure was confirmed due to the multi-layer surface modification of OcTES and EGDE. And through the increase of the roughness, the branch structure was formed well on membrane surface. Through the XPS analysis was identified chemical structure of membrane surface. And confirmed that the hydrophilic surface modification is given to the surface of the film through a Contact angle analysis. In optimization of EGDE surface modification condition, was suitable 0.5 wt% EGDE concentraion and 70°C ring-opening temperature. In result of fouling resistance test and MFI is SUL-H10, PA-OcTES1.0, PA-OcTES1.0-EGDE0.5 68.7, 60.4, 5.4 (10E-8 hr/mL2), multi-layer surface modified membrane improved fouling resistance.