• 한국주조공학회지
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• 제43권2호
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• pp.55-63
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• 2023

Due to the importance of the surface on the final slab quality, it is essential to maintain a smooth segment roll surface that is in touch with the thin solid shell during solidification. In this paper, the surface of the used continuous casting guide roll was analyzed to realize the mechanism of its surface deterioration. Surface analysis has revealed severe corrosion at two distinct areas leading to deep roughness occurring on the guide roll. Firstly, the severe corrosion follows prior austenite grain boundary due to exposure with acidic environment. Also, in heat affected zone (HAZ) where two cladding beads overlap, more severe corrosion takes place. The overheat input results in local ferritization without full melting which increases retained δ-ferrite content almost 10 times higher than surrounding area. Corrosion was observed to happen at the δ-γ interface where Cr depletion takes place.

• 한국전기전자재료학회논문지
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• 제31권4호
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• pp.244-248
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• 2018

We propose a method for improving the reliability of a solar cell by applying a fluorinated surface coating to protect the cell from the outdoor environment using an atmospheric pressure plasma (APP) treatment. An APP source is operated by radio frequency (RF) power, Ar gas, and $O_2gas$. APP treatment can remove organic contaminants from the surface and improve other surface properties such as the surface free energy. We determined the optimal APP parameters to maximize the surface free energy by using the dyne pen test. Then we used the scratch test in order to confirm the correlation between the APP parameters and the surface properties by measuring the surface free energy and adhesive characteristics of the coating. Consequently, an increase in the surface free energy of the cover glass caused an improvement in the adhesion between the coating layer and the cover glass. After treatment, adhesion between the coating and cover glass was improved by 35%.

• 한국재료학회지
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• 제32권2호
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• pp.107-113
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• 2022

Fibrous supercapacitors (FSs), owing to their high power density, good safety characteristic, and high flexibility, have recently been in the spotlight as energy storage devices for wearable electronics. However, despite these advantages, FCs face many challenges related to their active material of carbon fiber (CF). CF has low surface area and poor wettability between electrode and electrolyte, which result in low capacitance and poor long-term stability at high current densities. To overcome these limits, fibrous supercapacitors made using surface-activated CF (FS-SACF) are here suggested; these materials have improved specific surface area and better wettability, obtained by introducing porous structure and oxygen-containing functional groups on the CF surface, respectively, through surface engineering. The FS-SACF shows an improved ion diffusion coefficient and better electrochemical performance, including high specific capacity of 223.6 mF cm^-2 at current density of 10 ㎂ cm^-2, high-rate performance of 171.2 mF cm^-2 at current density of 50.0 ㎂ cm^-2, and remarkable, ultrafast cycling stability (96.2 % after 1,000 cycles at current density of 250.0 ㎂ cm^-2). The excellent electrochemical performance is definitely due to the effects of surface functionalization on CF, leading to improved specific surface area and superior ion diffusion capability.

• International Journal of CAD/CAM
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• 제5권1호
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• pp.11-18
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• 2005

The traditional method of manipulation of knots and degrees gives poor quality of surface, if compatibility of input curves is not good enough. In this work, a new algorithm of multiple refitting of curves has been developed using minimum energy based formulation to get compatible curves for skinning. The present technique first reduces the number of control points and gives smoother surface for given accuracy and the surface obtained is then skinned by compatible curves. This technique is very useful to reduce data size when a large number of data have to be handled. Energy based technique is suitable for approximating the missing data. The volumetric information can also be obtained from the surface data for analysis.

• 대한설비공학회:학술대회논문집
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• 대한설비공학회 2007년도 동계학술발표대회 논문집
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• pp.635-639
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• 2007

In this study, optimal design and test of flat-plate heat pipe were carried out in order to improve both thermal response and surface temperature uniformity of heating plate. Experimental results show that the thermal response of flat-plate heat pipe is faster than that of a conventional heating type ones along with less weight and cost. The surface temperature uniformity is also improved.

• Current Applied Physics
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• 제18권12호
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• pp.1528-1533
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• 2018

The trajectories of adsorption and dissociation process of $O_2$ on the Al (111) surface were studied by the spinpolarized ab initio molecular dynamics method, and the adsorption activation energy was clarified by the NEB method with hybrid functionals. Three typical dissociation trajectories were found through simulation of $O_2$ molecule at different initial positions. When vertically approaches to the Al surface, the $O_2$ molecule tends to rotate, and the activation energy is 0.66eV. If $O_2$ molecule does not rotate, the activation energy will increase to 1.43 eV, and it makes the O atom enter the Al sublayer eventually. When the $O_2$ molecules parallel approach to the Al surface, there is no activation energy, due to the huge energy released during the adsorption process.

• 풍력에너지저널
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• 제14권4호
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• pp.43-49
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• 2023

We have studied biofouling in Korea's offshore wind farms by using image analysis through monitoring and surface energy analysis. To observe the biofouling characteristics, samples were fabricated using Micron extra 2 and PropOne, which have a self-polishing property, and Hempathane HS 55610, which is used in substructure coatings. The manufactured samples were installed at the bottom of a ladder in a substructure, and monitored for 10 months. The most biofouling occurred in the sample without the self-polishing property, and algae, barnacles and corallinales were observed. The surface energy analysis used the Owens-Wendt-Rabel and Kaelble (OWRK) model, which uses the contact angles of two standard fluids. As a result of calculating the surface energy using contact angle measurement, the sample without the self-polishing property showed the highest value. This result was consistent with the biofouling incidence observed through monitoring.

• 전기화학회지
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• 제7권4호
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• pp.211-219
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• 2004

A classical Lippmann equation valid for liquid electrodes can not describe the interfacial properties of solid electrodes due to the elastic surface strain on solid electrodes. Although there have been many attempts to derive the thermodynamic equations for solid electrodes Outing the past few decades, their validity has been still questioned by many researchers. In practice, although there are various experimental techniques to measure surface energy of solid electrodes, the results obtained by each technique are rather inconsistent due to the complexity of the surface strain on solid electrodes. This article covers these controversial issues in surface energy of solid electrodes. After giving brief summaries of the definition of the important thermodynamic parameters and the derivation of the thermodynamic equations for solid electrodes, the several experimental methods were introduced for the measurement of surface energy of solid electrodes. And then we discussed in detail the inconsistent results in the measurement of the potential of zero charge (pac) and the potential of electrocapillary maximum (ecm).

• 접착 및 계면
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• 제4권4호
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• pp.1-6
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• 2003

대기압 플라즈마를 이용하여 폴리프로필렌 필름의 표면을 처리한 후 각각 극성 용매(water)와 비극성 용매(diiodomethane)를 사용한 접촉각 측정기로 필름 표면의 접촉각을 측정하였다. 측정된 접촉각을 이용해 표면 자유에너지 변화를 계산한 후 대기압 플라즈마 처리 전후의 폴리프로필렌 필름의 접촉각과 표면 자유에너지 상태를 비교, 분석하였다. 또한 대기압 플라즈마의 처리 조건을 바꿔가며 폴리프로필렌 필름 표면을 처리함으로써 접촉각과 표면 자유에너지가 각각의 처리 조건에 따라 어떠한 영향을 받는지 연구하였다. 대기압 플라즈마 처리 조건에 따라 접촉각 및 표면 자유에너지는 최적값을 보여주거나 일정한 값에 도달하는 경향을 보여 주었다.

• Nuclear Engineering and Technology
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• 제28권4호
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• pp.366-372
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• 1996

The simulated spent PWR fuel pellet which is corresponding to the turnup of 33,000 MWD/MTU is prepared by adding 11 fission-product elements to UO$_2$. The simulated spent fuel pellet is treated at 40$0^{\circ}C$ in air (oxidation), at 110$0^{\circ}C$ in air (high-temperature treatment), and at $600^{\circ}C$ in hydrogen (reduction). The product is treated through additional addition and reduction up to 3 cycles. Pellets are completely pulverized by the first oxidation, and the high-temperature treatment causes particle and crystallite to grow and surface to be smooth, and thus particle size significantly increases and surface area decreases. The reduction following the high-temperature treatment decreases much the particle size by means of the formation of intercrystalline cracks. The particle size decreases a little during the second oxidation and reduction cycle and then remains nearly constant during the third and fourth cycles. Surface area of pounder increases progressively with the repetition of oxidation and reduction cycles, mainly due to the formation of Surface cracks. The degradation of surface area resulting from high-temperature treatment is restored by too subsequent resulting oxidation and reduction cycles.