• Corrosion Science and Technology
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• 제21권1호
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• pp.9-20
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• 2022

The aim of this paper is to study corrosion inhibition of Aluminum with Capparis decidua extract. The study was performed in a 1.0 M solution of hydrochloric acid (HCl) and was monitored both by measuring mass loss and by using electrochemical and polarization methods. A scanning electron microscopy (SEM) technique was also applied for surface morphology analysis. The results revealed high inhibition efficiency of Capparis decidua extract. Our data also determined that efficiency is governed by temperature and concentration of extract. Optimum (88.2%) inhibitor efficiency was found with maximum extract concentration at 45 o C. The results also showed a slight diminution of aluminum dissolution when the temperature is low. Based on the Langmuir adsorption model, Capparis decidua adsorption on the aluminum surface shows a high regression coefficient value. From the results, the activation enthalpy (∆H#) and activation entropy (∆S#) were estimated and discussed. In conclusion, the study clearly shows that Capparis decidua extract acted against aluminum corrosion in acidic media by forming a protective film on top of the aluminum surface.

• 한국표면공학회지
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• 제56권4호
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• pp.250-258
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• 2023

Ceramic oxide layer was formed on the surface of high silicon aluminum alloy by using PEO (plasma electrolytic oxidation) process. The microstructure of the oxide layer was analyzed using scanning electron microscopy (SEM) and x-ray diffraction patterns (XRD). The high silicon aluminum alloy prior to PEO process consists of Al, Si and Al₂Cu phases in XRD analysis, whereas Al₂Cu phase selectively disappeared after PEO treatment. Considerable decrease of relative intensity in most of peaks in XRD results of the high silicon aluminum alloy treated by PEO process was observed. It may be attributed to the formation of amorphous phases after PEO treatment. The corrosion behavior of the high silicon aluminum alloy treated by PEO process was investigated using electrochemical impedance spectroscopy (EIS) and other electrochemical techniques (i.e., open circuit potential and polarization curve). Electroanalytical studies indicated that the high silicon aluminum alloy treated by PEO process shows greater corrosion resistance than that untreated by PEO process.

• 한국결정성장학회지
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• 제15권3호
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• pp.124-127
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• 2005

[ $Ti:LiNbO_3$ ], 광도파로 제작을 위해 큐리온도$(T_c)$ 아래에서 백금박스 내에서 알곤 과 산소 분위기 내에서 열처리 과정 동안 기판 표면의 강유전 도메인 특성 변화를 관찰하였다. 열처리 된 $LiNbO_3$ 기판의 +Z면의 경우 전체적으로 약 $1.6{\mu}m$ 두께로 도메인 반전이 이루어 졌으며, 표면에서 etch hillock이 관찰되었다. $LiNbO_3$ 결정 표면의 Li 이온이 외부로 확산 되는 영향을 감소시킬 수 있는 환경에 있는 기판 면에서 하나의 도메인이 관찰되었으며, 이때 결정 표면에서의 식각특성, 결정성 및 양이온 분포변화에 관하여 X-선 회절, AFM 및 SIMS를 이용하여 분석하였다.

• Journal of Korean Dental Science
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• 제11권2호
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• pp.71-81
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• 2018

Purpose: The purpose of this study was to investigate the corrosion behaviors of dental implant alloy after microsized surface modification in electrolytes containing Mn ion. Materials and Methods: $Mn-TiO_2$ coatings were prepared on the Ti-6Al-4V alloy for dental implants using a plasma electrolytic oxidation (PEO) method carried out in electrolytes containing different concentrations of Mn, namely, 0%, 5%, and 20%. Potentiodynamic method was employed to examine the corrosion behaviors, and the alternatingcurrent (AC) impedance behaviors were examined in 0.9% NaCl solution at $36.5^{\circ}C{\pm}1.0^{\circ}C$ using a potentiostat and an electrochemical impedance spectroscope. The potentiodynamic test was performed with a scanning rate of $1.667mV\;s^{-1}$ from -1,500 to 2,000 mV. A frequency range of $10^{-1}$ to $10^5Hz$ was used for the electrochemical impedance spectroscopy (EIS) measurements. The amplitude of the AC signal was 10 mV, and 5 points per decade were used. The morphology and structure of the samples were examined using field-emission scanning electron microscopy and thin-film X-ray diffraction. The elemental analysis was performed using energy-dispersive X-ray spectroscopy. Result: The PEO-treated surface exhibited an irregular pore shape, and the pore size and number of the pores increased with an increase in the Mn concentration. For the PEO-treated surface, a higher corrosion current density ($I_{corr}$) and a lower corrosion potential ($E_{corr}$) was obtained as compared to that of the bulk surface. However, the current density in the passive regions ($I_{pass}$) was found to be more stable for the PEO-treated surface than that of the bulk surface. As the Mn concentration increased, the capacitance values of the outer porous layer and the barrier layer decreased, and the polarization resistance of the barrier layers increased. In the case of the Mn/Ca-P coatings, the corroded surface was found to be covered with corrosion products. Conclusion: It is confirmed that corrosion resistance and polarization resistance of PEO-treated alloy increased as Mn content increased, and PEO-treated surface showed lower current density in the passive region.

• 한국구조물진단유지관리공학회 논문집
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• 제12권6호
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• pp.97-108
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• 2008

시멘트 대체 재료로서 플라이애쉬의 사용은 시멘트 생산비용을 절감시키는 효과를 창출하였다. 반면에 플라이애쉬 혼입콘크리트는 OPC에 비해 상대적으로 긴 양생시간과 초기강도의 발현 저하를 들 수 있어 이의 해결을 위해 물리적 방법, 온도 및 화학적 방법 등과 같은 다양한 활성화 기술의 적용을 통하여 플라이애쉬 혼입 콘크리트의 수화를 가속시킬 수 있고, 콘크리트의 부식 저항성을 향상시킬 수가 있다. 본 연구에서는 10~40%의 치환률을 가진 활성화된 플라이애쉬 시편을 통해 개방 회로형 전위측정(Open circuit potential measurement)을 수행하였고, 투수시험, 급속염화물침투시험 및 SEM(Scanning electron microscopy)촬영을 통해 OPC 콘크리트와 비교 분석 하였다. 또한, 치환률의 임계범위 20~30%의 경우에 있어서 활성화된 플라이애쉬를 사용한 콘크리트가 열화저항성에 있어서 개선효과가 나타나고 있음을 확인하였다. 또한 플라이애쉬를 화학적으로 활성화시킨 경우가 본 연구에서 수행된 다른 활성화 방법들에 비해 더욱 좋은 결과를 나타나고 있음도 확인하였다.

• 문화기술의 융합
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• 제9권1호
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• pp.539-544
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• 2023

연구 대상은 경상북도 ◯◯시 ◯◯동에 위치한 마애여래입상 암반으로서 안정성이 우려되는 중생대 백악기 화강섬록암 마애불상이다. 안정성 해석을 위해 마애불 암반의 3차원 face mapping과 절리의 지질공학적 특성, 3차원 스캐닝, 초음파속도, 편광현미경 분석, 전자현미경 분석 및 XRD 분석을 수행하였다. 더불어 손상상태 조사, 평사투영해석, 암반분류 및 한계평형해석으로 마애불 암반의 안전율을 산정하였다. 구간별로 손상 및 가능한 붕괴의 유형과 규모는 암석의 풍화도와 절리면의 배향과 특성에 따라 다르나 쐐기파괴와 전도파괴가 소규모로 예상된다. face-mapping 자료, RMR, 암석의 물성·역학시험, 평사투영해석 및 한계평형해석으로 종합·검토한 결과, 마애불 암반의 건기 시와 우기 시의 허용안전율 1.2에 미달하여 안정성이 우려된다. 손상유형은 박리, 균열, 입상분해 및 초목생장, 균열 방향별 점유율은 전면이 가장 우세한 것으로 나타난다. 마애불 암석은 화강섬록암이며, 표면 변색의 물질은 K, Fe, Mg로 판명되었고, 4조의 절리 중 J1은 인장절리이고 나머지는 전단절리이다. 초음파탐사로 추정한 일축압축강도는 514kgf/cm2로서 대부분 연암과 일부 풍화암에 해당한다. 암반분류 결과 5등급으로 추산되며, 마애여래입상 전면부 불안정성이 예상된다. 기존의 문화재 안전진단의 방법과 더불어 이들 기법은 석조문화재의 객관적인 해석 및 안정성 검토의 합리적인 도구가 될 것으로 예상한다.

• 한국세라믹학회지
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• 제52권4호
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• pp.237-242
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• 2015

$Bi_{0.5}(Na_{0.78}K_{0.22})_{0.5}TiO_3$ (BNKT) lead-free piezoelectric ceramics modified by $LaMnO_3$ (LM) were fabricated by conventional solid-state method. The crystal structure and the morphology of the lead free ceramics were analyzed by XRD (X-ray diffraction) and FE-SEM (Field Emission Scanning Electron Microscopy). The LM modified BNKT ceramics have a phase transition from ferroelectric tetragonal to non-polar pseudo-cubic. Despite decreases in the remnant polarization ($P_r$) and coercive field ($E_c$) in the P-E hysteresis loops, the electric-field induced strain properties were significantly enhanced by the LM modification. The highest value of $S_{max}/E_{max}=412pm/V$ at an applied electric field of 5 kV/mm was found in BNKT-0.01LM ceramic.

• 한국산업보건학회지
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• 제21권4호
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• pp.201-208
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• 2011

Objectives: According to the compliance of the asbestos-related regulation, every building has to be inspected for asbestos presence before its abatement work. This study was performed for identifying the types and contents of asbestos in building bulk samples. Materials and Methods: Bulk samples were collected during the asbestos inspection in 2010. We grouped the bulk samples into the regulated asbestos containing materials(RACM), presumed asbestos containing materials(PACM), and construction products. Additionally, the types of asbestos in all bulk samples were identified by polarization microscopy(PLM). Results: The RACMs were from building, house, pipe and facility. The RACMs were found mainly building (72.1%) and house (93.7%). The contents of chrysotile in building, house and facility were 66.9% (1-90%), 89.7% (2-90%) and 11.0% (2-90%), respectively. PACMs were surfacing material, thermal system insulation (TSI), and miscellaneous material. The miscellaneous materials that showed a high detection rate (79.2%) were ceiling, roofing and wall materials. Among them, the roofing materials had high chrysotile content(9.7%, 2-21%), followed by wall (8.7%, 2-21%) and ceiling (3.4%, 1-17%). In the construction products, asbestos was found mainly in slate (92.6%, 2-21%), including chrysotile. The slate had high asbestos content (9.7%, 2-21%), followed by cement flat board (8.7%, 2-19%) and textile (3.4%, 1-17%) Conclusions: Utilizing these results, it would be contributed to construct a useful ACM database and prevent from asbestos exposure to workers in the asbestos abatement and maintenance works.

• 공업화학
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• 제19권6호
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• pp.661-667
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• 2008

본 연구에서는 LCD 백라이트용 휘도향상 편광필름으로 사용하기 위해, 콜레스테릭 액정(CLC)을 합성하여 네미틱 액정과 혼합한 다음 이들이 충진된 모듈을 제작하였다. 광확산필름에 의해 면광원화된 빛을 통과시킬 때, LCD 백라이트상에서 이들의 투과광 증폭 및 편광능력에 대한 특성을 연구하였다. 합성된 콜레스테릭 액정의 특성은 UV/Visible 스펙트럼과 편광현미경(POM) 등으로 평가하였다. 여러 종류의 선형 카르복실산을 콜레스테롤 분자에 도입하여 콜레스테릭 메소젠 사이의 유연격자를 이루도록 유도하여 각 층에서 일정한 방향성을 유지하도록 하였다. 또한 CLC필름을 적층하여 가시광선대에서 편광능력, 휘도향상 및 투과파장영역을 넓히고 백라이트 유니트의 밝기를 향상시키는 모듈로 적용할 수 있었다.

• Journal of Advanced Marine Engineering and Technology
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• 제20권5호
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• pp.103-113
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• 1996

The properties of the deposited film depend on the deposition condition and these, in turn depend critically on the morphology and crystal orientation of the films. Therefore, it is important to clarify the nucleation occurrence and growth stage of the morphology and orientation of the film affected by deposition parameters, e.g. the gas pressure and bias voltage etc. In this work, magnesium thin flims were prepared on cold-rolled steel substrates by a thermo-eletron activation ion plating technique. The influence of nitrogen gas pressure and substrate bias voltage on their crystal orientation and morphology of the coated films were investigated by scanning electron microscopy (SEM) and X-ray diffraction, respectively. The diffraction peaks of magnesium film became less sharp and broadened with the increase of nitrogen gas pressure. With an increase in nitrogen gas pressure, flim morphology changed from colum nar to granular structure, and surface crystal grain-size decreased. The morphology of films depended not only on gas pressure but also on bias voltage, i.e., the effect of increasing bias voltage was similar to that of decreasing gas pressure. The effect of crystal orientation and morphology of magnesium films on corrosion behaviors was estimated by measuring anodic polarization curves in deaerated 3%NaCl solution. Magnesium, in general, has not a good corrosion resistance in all environments. However, these magnesium films prepared by changing nitrogen gas pressure showed good corrosion resistance. Among the films, magnesium films which exhibited granular structure had the highest corrosion resistance. The above phenomena can be explained by applying the effects of adsorption, occlusion and ion sputter of nitrogen gas.