• Journal of the Korean Society of Safety
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• v.19 no.1
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• pp.12-17
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• 2004

By using an experimental approach recently developed to determine the torque-tension relationship for bearing frictional characteristics of several typical bolted joints were studied. The experimental approach allows the direct determination of the bearing friction between the nut and its bearing surface. Detailed friction studies were made on the influences of the size and shape of the hole, the use of a slot in a bolted joint, contact area and position, and other factors such as turning speed, coating, and the use of wax on the bearing surface. The contact area and position of the washer have a marginal effect on the bearing friction. The organic coating on the nuts reduces the bearing friction significantly. Nuts with organic coating over a washer with zinc finish provide the smallest and the most consistent bearing friction. The results from the experimental investigation will be helpful for the better design of bolted joints bearing friction. The results from the experimental investigation Will be helpful for the better design of bolted joints.

• Corrosion Science and Technology
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• v.18 no.5
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• pp.168-174
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• 2019

The sol-gel methodology has been applied successfully in the synthesis of a novel hybrid coating based on dimethoxymethyl-n-octadecylsilane precursor. The newly synthesized parent coating was functionalized further with two commercially-available corrosion-inhibitive pigments Moly-$white^{(R)}$ 101-ED and Hfucophos $Zapp^{(R)}$, applied to mild steel panels, and immersed continuously in 3.5% NaCl electrolytic solution for 288 h. The corrosion protection performance of the prepared functional coatings was evaluated using electrochemical impedance spectroscopy (EIS) and DC polarization techniques. An enhancement in the barrier properties has been revealed from the electrochemical characterization data of the hybrid films, in comparison with untreated mild steel substrates following long-term immersion in 3.5% NaCl. The corrosion resistance properties of the newly developed coatings over mild steel substrates found to be largely dependent on the type of the loaded inhibitive pigment in which the Moly-white inhibitor has a positive impact on the corrosion protection performance of the parent coating, while an opposite behavior was observed upon mixing the base polymeric matrix with the commercially-available Zapp corrosion inhibitor.

• Journal of the Korea Safety Management & Science
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• v.19 no.4
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• pp.317-322
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• 2017

When the heat flux on the heating surface following changing heat condition in the boiling heat transfer system exceeds critical heat flux, the critical heat flux phenomenon is going over to immediately the film boiling area and then it is occurred the physical destruction phenomenon of various heat transfer systems. In order to maximize the safe operation and performance of the heat transfer system, it is essential to improve the CHF(Critical Heat Flux) of the system. Therefore, we have analysis the effect of improving CHF and characteristics of heat transfer following the nanoparticle coating thickness. As the results, copper nanocoating time are increased to CHF, and in case of nano-coatings are increased spray-deposited coating times more than in the fure water; copper nanopowder is increased up to 6.40%. The boiling heat transfer coefficients of the pure water are increased up to 5.79% respectively. Also, the contact angle is decreased and surface roughness is increased when nano-coating time is increasingly going up.

• Korean Journal of Metals and Materials
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• v.48 no.5
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• pp.401-409
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• 2010

This study was performed to develop an antibacterial film that can be dried at room temperature. A nanosized TiO$_2$ particle-dispersed solution was prepared by the hydrothermal treatment of peroxo-titanic acid at 160${^{\circ}C}$ for 4h. The binder was synthesized through the hydrolysis and condensation reactions of TEOS (10cc) and GPTS (3.5cc) in the mixture of H$_2$O (30cc) and EtOH (30cc). The synthesized binder was mixed with 0.1 M of TiO$_2$ solution in a volume ratio of binder/TiO$_2$ solution=0.25~0.5. The glass substrate was coated after using the dip coating method, which was then followed by drying for over 2h at room temperature. Although the TiO$_2$ particles did not chemically-bond to the binder, the coating layer strongly adhered to the substrate and displayed good antibacterial properties.

• Journal of the Microelectronics and Packaging Society
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• v.29 no.1
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• pp.61-66
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• 2022

This study is to increase the surface area and maximize the effect of the catalyst by coating a nanometersized metal catalyst material on the anode layer using atomic layer deposition (ALD) technology. ALD process is known to produce uniform films with well-controlled thickness at the atomic level on substrates. We measured the performance by coating metals (Ni) on Ni/YSZ, which is the most widely known anode material for solid oxide fuel cells. ALD coatings began to show a decrease in cell performance over 3 nm coatings.

• Journal of Electrochemical Science and Technology
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• v.14 no.3
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• pp.283-292
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• 2023

Currently, spray coating has attracted interest in the mass production of anode catalyst layers for proton exchange membrane water electrolysis (PEMWE). The solvent in the spray ink is a critical factor for the catalyst dispersion in ink, the microstructure of the catalyst layer, and the PEMWE performance. Herein, various pure organic solvents were examined as a substitute for conventional isopropanol-deionized water (IPA-DIW) mixture for ink solvent. Among the polar solvents that exhibited better IrO₂ dispersion over nonpolar solvents, 2-butanol (2-BuOH) was selected as a suitable candidate. The PEMWE single cells were fabricated using 2-BuOH at various ionomer contents, spray nozzle types, and drying temperatures, and their performance was compared to the cells fabricated using a conventional IPA-DIW mixture. The PEMWE single cells with 2-BuOH solvent showed good performances comparable to the conventional IPA-DIW mixture case and highly durable performances under accelerated degradation tests.

• Korean Journal of Environment and Ecology
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• v.20 no.4
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• pp.436-447
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• 2006

Recently, there is increasing demand on enhancing the efficiency of hydro-seed spraying in afforestation for damaged or degraded land including forest road slopes. In this study, we focus on how seed coating and molding may affect seed germination and seedling growth. Plant species used in the study are Lespedeza cyrtobotrya, Indigofera pseudotinctoria, Arudineila hirta, Poa pratensis, and Lolium perenne. The results of seed germination and seedling growth with and without seed coating and molding are analyzed as follows: 1. For all the species and in both seeding with molding covered with soil and seeding without molding in which seeds were over sown, the increment of germination ratio by seed coating method is greater than by non·coating one. Seed coating increases average germination ratios observed in seeding with molding and without molding by 11.2% and 21.4%, respectively. Germination force may decrease from 0.8 to 3.7 days depending on the plant species and the treatments. The $LD_{50}$ decreased by $0.8{\sim}2.6$ days. However, seed coating delays the start of germination by approximate 1 day for all of the observed plants. 2. Seed coating may have the effect of accelerating the growth of stem and leaf and root. The experimental result shows that seed coating leads to 21.7% and 34.8% increment of average stem and leaf growth by seeding with molding and without molding, respectively. In terms of root growth, seeding with molding results in 22.0% increment while seeding without molding produces 26.2% increased root growth. 3: Compared to seeding without molding, germination starts on an average of 1.3 days later in seeding coated seeds with molding. However. the germination ratio is increased by 5%, and germination force and $LD_{50}$ are observed to shorten by 1.0 day and 1.4 days, respectively. Meanwhile, whether seeds are coated or not may be more related with germination and seedling growth in seeding without molding than with those in seeding with molding. 4. In this study, coating materials are examined to look at which ones are better in each treatment. Coating with Vermiculite+Talcum is the most effective in germination and seedling growth for overall plants. Seed coating using Bentonite, Calcium Carbonate, and Calcium Hydroxide shows better results than non-coating does. 5. When seeds are coated, the greatest enhancement of seed germinations was observed in Indigofera pseudotinctoria and, in the case of seedling growth, Lespedeza cyrtobotrya has the most increasing observation value among the 5 examined species. These results may indicate that woody plant seeds, having greater sizes of seeds than ones of grass seeds, may have greater relation with seed coating than grass plant seeds may have. 6. Therefore, if seeds cannot be molded up after hydro-seeding on forest road slopes, it is recommended that seeds for restoration be pre-coated with Vermiculite+Talcum and then be sowed, in order to quickly stabilize the damaged slope and achieve successful afforestation.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2007.05a
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• pp.375-378
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• 2007

Abrasive wear between piston ring face and cylinder liner is an extremely unpredictable and hard-to-reproduce phenomenon that significantly decreases engine performance. Wear by abrasion are forms of wear caused by contact between a particle and solid material. Abrasive wear is the loss of material by the passage of hard particles over a surface. From the pin-on-disk test, particle dent test and scuffing test, abrasive wear characteristics of diesel engine cylinder liner-piston ring have been investigated. Pin-on-disk test results indicate that abrasive wear resistance is not simply related to the hardness of materials, but is influenced also by the microstructure, temperature, lubricity and micro- fracture properties. In particle dent test, dent resistance stress decreases with increasing temperature. From the scuffing test by using pin-on-disk tester, scuffing mechanisms for the soft coating and hard coating were proposed and experimentally confirmed.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.08a
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• pp.414-414
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• 2012

차세대 플렉시블 디스플레이 소재로서, 탄소나노뷰브(CNT) 기반의 투명전도막은 기존의 ITO 박막보다 우수한 유연성을 갖기 때문에 많은 관심을 모으고 있다. 특히 낮은 저항과 투과도를 유지하면서 투명 전도막의 내구성을 향상시키는 연구는 상업화에 가장 필요한 연구 분야이다. 본 연구에서는 다층벽 탄소나노튜브(MWCNT)를 이용하여 제작된 투명 전도막의 내구성을 개선하기 위하여 오버 코팅을 통한 물성 개선을 연구하였다. 투명전도막은 PET기판 위에 스프레이 방식을 이용하여 균일하게 코팅하였다. 오버 코팅 물질로는 실리콘계 유무기하이브리드 투명하드 코팅을 적용하였다. 연구결과 오버 코팅층과 CNT 코팅층과의 젖음성이 물성 향상에 가장 많은 영향을 끼치는 것을 관찰하였고, 특히 젖음성이 증가할수록 투과도와 전기전도도가 향상되는 것을 확인하였다. 또한 고온 고습 환경에서 240시간 이상 내구성 테스트 결과, 저항률 변화가 1.1 이하인 것을 확인하였다.

• Journal of the Korean Society of Safety
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• v.23 no.3
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• pp.8-11
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• 2008

In the present work, the measurement method of residual stresses in thermal barrier coatings(TBCs) which are received the thermal shock is performed numerically. For this, the internal residual stresses are predicted by commercial FEM software ABAQUS because the hole drilling strain gage method measures residual stresses only near the surface of a material. As the results of this study, the residual stresses are linearly increased when the surface temperatures are over $1,200^{\circ}C$. It is also found that the values of residual stress are increased as the coating thickness is thin.