• Corrosion Science and Technology
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• 제4권4호
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• pp.140-146
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• 2005

Fossil fired power plant produces the electric energy by using a thermal energy by the combustion of fossil fuels as like oil, gas and coal. The exhausted flue gas by the combustion of oil etc. contains usually many contaminated species, and especially sulfur-content has been controlled strictly and then FGD (Flue Gas Desulfurization) facility should be installed in every fossil fired power plant. To minimize the content of contaminations in final exhaust gas, high corrosive environment including sulfuric acid (it was formed during the process which $SO_2$ gas combined with $Mg(OH)_2$ solution) can be formed in cooling zone of FGD facility and severe corrosion damage is reported in this zone. These conditions are formed when duct materials are immersed in fluid that flows on the duct floors or when exhausted gas is condensed into thin layered medium and contacts with materials of the duct walls and roofs. These environments make troublesome corrosion and air pollution problems that are occurred from the leakage of those ducts. The frequent shut down and repairing works of the FGD systems also demand costs and low efficiencies of those facilities. In general, high corrosion resistant materials have been used to solve this problem. However, corrosion problems have severely occurred in a cooling zone even though high corrosion resistant materials were used. In this work, a new technology has been proposed to solve the corrosion problem in the cooling zone of FGD facility. This electrochemical protection system contains cathodic protection method and protection by coating film, and remote monitoring-control system.

• Journal of Magnetics
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• 제7권3호
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• pp.63-71
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• 2002

Three fabrication techniques for forming thin barrier layer with uniform thickness and large barrier height in magnetic tunnel junction (MTJ) are discussed. First, the effect of immiscible element addition to Cu layer, a high conducting layer generally placed under the MTJ, is investigated in order to reduce the surface roughness of the bottom ferromagnetic layer, on which the barrier is formed. The Ag addition to the Cu layer successfully realizes the smooth surface of the ferromagnetic layer because of the suppression of the grain growth of Cu. Second, a new plasma source, characterized as low electron energy of 1 eV and high density of $10^{12}$ $cm^{-3}$, is introduced to the Al oxidation process in MTJ fabrication in order to reduce damages to the barrier layer by the ion-bombardment. The magnetotransport properties of the MTJs are investigated as a function of the annealing temperature. As a peculiar feature, the monotonous decrease of resistance area product (RA) is observed with increasing the annealing temperature. The decrease of the RA is due to the decrease of the effective barrier width. Third, the influence of the mixed inert gas species for plasma oxidization process of metallic Al layer on the tunnel magnetoresistance (TMR) was investigated. By the use of Kr-O$_2$ plasma for Al oxidation process, a 58.8 % of MR ratio was obtained at room temperature after annealing the junction at $300{^{\circ}C}$, while the achieved TMR ratio of the MTJ fabricated with usual Ar-$0_2$ plasma remained 48.4%. A faster oxidization rate of the Al layer by using Kr-O$_2$ plasma is a possible cause to prevent the over oxidization of Al layer and to realize a large magnetoresistance.

• 공업화학
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• 제27권4호
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• pp.358-365
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• 2016

수자원의 효과적 활용을 위해 유해물질을 제거하는 기술이 중요하며 흡착이 하나의 경쟁력 있는 기술로 검토/개발되고 있다. 흡착공정이 경쟁력을 가지기 위해서는 뛰어난 성능의 흡착제 개발이 중요하다. 유기물과 무기물 모두를 함유한 금속-유기 골격체(metal-organic frameworks, MOFs)는 큰 표면적, 세공부피, 잘 정의된 세공 구조 및 용이한 기능화 등으로 인해 다양한 흡착에 활용되고 있다. 본 고에서는 MOFs를 이용하여 물로부터 유해한 유기물을 흡착제거하는 기술을 요약, 정리하였다. 단순히 흡착량이나 속도를 증가하는 연구 대신에 흡착질과 흡착제 간의 상호작용의 메커니즘을 요약하였고 이를 위해 MOFs를 수정/기능화한 연구를 정리하였다. 이러한 요약으로부터 독자들은 유해물질의 흡착제거를 위한 흡착제의 필요 물성 및 수정에 대해 이해를 하게 될 것이며 흡착 외에 유기물들의 저장 및 전달에 대한 새로운 아이디어를 얻을 수 있을 것으로 기대된다.

• Bulletin of the Korean Chemical Society
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• 제28권10호
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• pp.1751-1755
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• 2007

The interaction of ammonium hydroxide (NH4OH) with zircaloy-4 (Zry-4) was investigated using X-ray photoelectron spectroscopy (XPS) and Auger electron spectroscopy (AES) methods. In order to study the surface chemistry of NH4OH/Zry-4 system, the binding energies of N1s, O1s and Zr3d electrons were monitored. The N1s peak intensity was remarkably increased by following cycles of Ar+ sputtering of NH4OH dosed Zry-4 surface at room temperature. Because the nitrogen stayed under the subsurface region was diffused out onto the Zry-4 surface after oxygen concentration was decreased. These could be occurred after the surface oxygen was diffused into the bulk or desorbed out from the surface until Ar+ fluence was 6.0 × 1016 Ar+/cm2 then the surface was relatively atomic deficient state. The O1s peak intensity was decreased by stepwise Ar+ sputtering. After many cycles of Ar+ sputtering, the peak intensities of Zr3d peaks did not change much but the shape of the peak clearly did change. This implies that the oxidation state of zirconium was changed during stepwise Ar+ sputtering of NH4OH/Zry-4. The Zr3d peak intensity of zirconium nitride (ZrNx) increased as the intensity of N1s (from zirconium nitride) increased but the Zr3d peak intensity of zirconium oxide (ZrOx) decreased due to the depopulation of the oxygen species on the surface region. We also observed that the peak intensity of Zr4+ was nearly same after Ar+ sputtering processes but the peak intensity of metallic zirconium increased compared to that of before the sputtering process was performed.

• 한국산학기술학회논문지
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• 제15권11호
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• pp.6952-6957
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• 2014

광촉매 반응에서 $TiO_2$에 금속물질을 첨가하면 촉매표면이 변화되며, 이러한 금속물질은 광분해반응의 속도를 증가시킨다. 본 연구에서는 $TiO_2$ 광촉매의 광분해능력을 향상시키기 위해 다양한 방법을 이용하여 개질하였으며, 개질된 광촉매의 광분해특성은 회분식 광반응기를 이용하여 조사하였다. 우수한 $TiO_2$ 광촉매용액을 얻기 위해 여러 종류의 분산제와 안정제를 조사하였으며, 분산제로는 isoproply alcohol, 안정제로는 sodium silicate가 적합하였다. 톨루엔 분해반응을 향상시키기 위해 다양한 금속물질을 $TiO_2$ 광촉매에 첨가하여 광분해효율을 조사한 결과 Pd가 가장 우수하였으며, Cu와 W도 우수하였다. Pd를 첨가한 경우 25%의 제거효율 향상이 있었다. 그러나 Fe의 경우 광촉매분해반응을 상당히 저해하는 것으로 나타났다. $Pd/TiO_2$ 광촉매에 Cu 또는 W를 부가적으로 첨가하여도 촉매의 광분해효율에는 증가가 없었다.

• 한국추진공학회지
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• 제24권2호
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• pp.1-13
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• 2020

Zr을 원료로하는 점화제와 ZrNi를 원료로 하는 지연제로 구성된 파이로테크닉스의 노화현상을 열적/화학적/광학적으로 분석하였다. 열적 분석에는 Differential Scanning Calorimetry (DSC) 와 Thermogravimetry Analysis(TGA)를 통해 열 기반의 반응식을 규명했다. DSC의 결과로 수행한 픽 분석기법 (peak deconvolution)을 통해 각 연료의 노화에 따른 열적 변화를 분석하였다. 화학종 변화 분석에는 Laser Induced Breakdown Spectroscopy (LIBS)와 X-ray Photoelectron Spectroscopy (XPS)를 사용하였다. 수분에 의한 산화제의 분해가 연료의 노화에 크게 영향을 미쳤으며, 열에너지 감소의 원인은 연료 표면의 산화막 형성과 산화금속의 형성으로 나타났다.

• 자원환경지질
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• 제29권1호
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• pp.87-103
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• 1996

The purposes of this research are to investigate the pollution level of heavy metals due to the urbanization and industrialization in the satellite cities of Seoul, and to assess the chemical species and the sources of heavy metals in highly contaminated soils and dusts. Soil and dust samples were collected from the Uijeongbu and the Koyang cities, which are northern and the northwestern satellite cities of Seoul metropolitan city, respectively. Relatively high pH values($6.3{\sim}9.9$) were found in roadside soils compared with agricultural and forest soils. Difference in pH values of soils was not identified between before and after rainy seasons. In spite of no specific pollution sources in the above cities, the contents of Cu, Pb, and Zn in soils and dusts were much higher than the world average contents. The metal levels in dusts were higher than those in soils, but the metal concentration in dusts was significantly decreased after rainy season. Pollution index was high(> 1.0) in the areas of heavy traffic, industrial complex, and city centres. There is an appreciable proportion of total Zn in exchangeable/water-acid soluble fraction. Copper is predominantly associated with reducible and oxidizable phases, whereas Pb is largely in reducible association. It is concluded that the mobility and bioavailability of metals are high in the order of Zn >> Cu > Pb, on the basis of characteristic particle morphology and chemical composition, Pb-containing particles are originated probably from the automobile exhaust, particularly in heavy traffic areas. The metallic forms and iron-oxide associated forms of Cr, Ni, Cu, Zn, and Pb can be assessed as industrial origin.

• 공업화학
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• 제25권6호
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• pp.553-558
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• 2014

미세조류는 통상적인 에너지 작물에 비하여 빠른 성장속도와 높은 오일함량으로 바이오디젤 생산의 원료로 관심을 받고 있다. 미세조류의 지질은 주로 트리글리세라이드인 중성지방으로 에스테르교환반응을 통하여 바이오디젤인 지방산 메틸에스테르로 전환할 수 있다. 본 논문에서는 영양분의 제한, 염도 및 금속 성분의 변화와 같이 미세조류의 지질 생산을 촉진할 수 있는 배양환경 스트레스 조건의 영향들을 비교 고찰하였다. 사용하는 미세조류 종에 따라 스트레스에 대응하여 지질의 양이 변하거나 구성하는 지방산의 조성이 변화될 수 있다. 비록 질소원 제한 조건이 가장 많이 사용되는 지질생산 촉진조건이긴 하지만, 미세조류로부터 바이오디젤 생산성의 향상을 위해서는 그 외에도 영양분 과잉 조건, 염도의 변화, pH, 온도, 금속 성분 농도 변화 등의 다른 조건들도 고려되어야 한다.

• 한국표면공학회:학술대회논문집
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• 한국표면공학회 2016년도 추계학술대회 논문집
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• pp.105-105
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• 2016

Recently, high power impulse magnetron sputtering (HIPIMS) has attracted considerable attentions due to its high potential for industrial applications. By pulsing the sputtering target with high power density and short duration pulses, a high plasma density and high ionization of the sputtered species can be obtained. HIPIMS has exhibited several merits such as increased coating density, good adhesion, microparticle-free and smooth surface, which make the HIPIMS technique desirable for synthesizing hard coatings. However, hard coatings present intrinsic defects (columnar structures, pinholes, pores, discontinuities) which can affect the corrosion behavior, especially when substrates are active alloys like steel or in a wear-corrosion process. Atomic layer deposition (ALD), a CVD derived method with a broad spectrum of applications, has shown great potential for corrosion protection of high-precision metallic parts or systems. In ALD deposition, the growth proceeds through cyclic repetition of self-limiting surface reactions, which leads to the thin films possess high quality, low defect density, uniformity, low-temperature processing and exquisite thickness control. These merits make ALD an ideal candidate for the fabrication of excellent oxide barrier layer which can block the pinhole and other defects left in the coating structure to improve the corrosion protection of hard coatings. In this work, CrN/Al2O3/CrN multilayered coatings were synthesized by a hybrid process of HIPIMS and ALD techniques, aiming to improve the CrN hard coating properties. The influence of the Al2O3 interlayer addition, the thickness and intercalation position of the Al2O3 layer in the coatings on the microstructure, surface roughness, mechanical properties and corrosion behaviors were investigated. The results indicated that the dense Al2O3 interlayer addition by ALD lead to a significant decrease of the average grain size and surface roughness and greatly improved the mechanical properties and corrosion resistance of the CrN coatings. The thickness increase of the Al2O3 layer and intercalation position change to near the coating surface resulted in improved mechanical properties and corrosion resistance. The mechanism can be explained by that the dense Al2O3 interlayer acted as an excellent barrier for dislocation motion and diffusion of the corrosive substance.

• Nano
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• 제13권11호
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• pp.1850127.1-1850127.13
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• 2018

Bi metal deposited on $Bi_2MoO_6$ composite photocatalysts have been successfully synthesized via a simple reduction method at room temperature with using $NaBH_4$ as the reducing agent. The photocatalytic activity of the composite was evaluated by degradation of rhodamine B (RhB) and bisphenol A (BPA) solution under visible light. The rate constant of $Bi/Bi_2MoO_6$ composite to RhB is 10.8 times that of $Bi_2MoO_6$, and the degradation rate constant of BPA is 6.9 times of that of $Bi_2MoO_6$. Nitrogen absorption-desorption isotherm proved that the increase of specific surface area is one of the reasons for the improvement of photocatalytic degradation activity of $Bi/Bi_2MoO_6$ composites. The higher charge transfer efficiency of $Bi/Bi_2MoO_6$ is found through the characterization of the photocurrent and impedance, which are attributed to the surface plasmon resonance (SPR) effect produced by the introduction of the metal Bi monomer in the composite. Free radical capture experiments proved that cavitation is the main active species. Based on the above conclusions, a possible mechanism of photocatalytic degradation is proposed.