• Korean Chemical Engineering Research
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• v.57 no.6
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• pp.847-852
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• 2019

In this study, the effect of additives on the performance of aqueous organic redox flow battery (AORFB) using quinoxaline and ferrocyanide as active materials in alkaline supporting electrolyte is investigated. Quinoxaline shows the lowest redox potential (-0.97 V) in KOH supporting electrolyte, while when quinoxaline and ferrocyanide are used as the target active materials, the cell voltage of this redox combination is 1.3 V. When the single cell tests of AORFBs using 0.1 M active materials in 1 M KCl supporting electrolyte and Nafion 117 membrane are implemented, it does not work properly because of the side reaction of quinoxaline. To reduce or prevent the side reaction of quinoxaline, the two types of additives are considered. They are the potassium sulfate as electrophile additive and potassium iodide as nucleophilie additive. Of them, when the single cell tests of AORFBs using potassium iodide as additive dissolved in quinoxaline solution are performed, the capacity loss rate is reduced to $0.21Ah{\cdot}L^{-1}per\;cycle$ and it is better than that of the single cell test of AORFB operated without additive ($0.29Ah{\cdot}L^{-1}per\;cycle$).

• Proceedings of the Korean Vacuum Society Conference
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• 2012.08a
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• pp.317-317
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• 2012

사파이어는 우수한 광학적, 물리적, 화학적 특성을 가지고 있는 물질 중의 하나이며, 청색 발광특성을 나타내는 GaN와 격자상수, 열팽창 계수가 가장 유사할 뿐만 아니라 가격도 상대적으로 저렴하여 GaN 성장을 위한 기판으로 사용된다. 실제로 사파이어는 프로젝터와 전자파장치, 군사용 장비 등 다양한 분야에 응용되고 있으며, 발광 다이오드(LED)를 위한 기판으로 활용됨으로써 그 수요가 급격히 증가하고 있다. 그러나 사파이어 결정의 성장 중에 생길 수 있는 전위(dislocation)와 적층결함(stacking fault) 등의 결정 결함들은 결정 내에 존재하여 역학적, 전기적 성질에 큰 영향을 미칠 수 있다. 특히 사파이어가 청색 발광소자의 기판으로 사용되는 경우, 사파이어 기판 내부의 결정 결함은 증착되는 박막 특성에 영향을 미치게 된다. 따라서 사파이어의 보다 나은 응용을 위해서는 결함의 형성 메커니즘과 결정 결함의 평가기술 등에 대한 이해가 필요하고, 특히 결함의 정량적 평가 기술의 개발은 사파이어의 상용화에 중요한 핵심요소 중 하나이다. 결정 내 결함이 위치하는 부분은 분자나 원자간의 결합이 약하거나 높은 에너지 상태이므로, 결정의 표면을 적절한 산이나 염기 등을 이용하여 에칭하면 에칭반응은 결정의 전위 위치에 해당하는 부분부터 일어나 결정의 표면에 에치핏을 형성한다. 따라서 결정 표면에 나타나는 에치핏의 개수를 관찰하면 결정의 전위 밀도 파악이 비교적 간단하고, 에칭반응의 이러한 특징은 전위의 정량적 평가에 이용이 가능하다. 본 연구는 4인치 사파이어 조각기판을 수산화칼륨(KOH)으로 습식에칭 후 표면에 나타나는 에치핏의 형성거동과 이의 시간 및 온도 의존성에 관한 연구를 진행하였다. 또한 단결정의 전위밀도를 예측하기 위해 사파이어 조각시편의 단위면적당 에치핏의 개수를 파악하여 에치핏밀도(EPD, etch pid density)를 계산하였고, 값의 불확도(uncertainty)를 계산하여 전위밀도의 신뢰도를 평가하였다. 그 결과, 사파이어 조각시편의 에치핏밀도는 단위면적($cm^2$)당 약 ${\sim}10^2$개로 확인되었고, 이 값은 약 2%의 상대불확도를 가지는 것으로 나타났다.

• Proceedings of the Plant Resources Society of Korea Conference
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• 2018.10a
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• pp.107-107
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• 2018

양파는 백합과에 속하는 여러해살이풀로 서남아시아의 페르시아가 원산인데 세계 각국의 온대지방에서 많이 재배하고 있다. 양파의 생약명은 옥총(玉憁)으로 피 속의 콜레스테롤을 떨어뜨리고 심장혈관의 혈류량을 증가시켜 성인병 예방에 좋다. 철원지역은 내륙지방이면서도 고도가 높아 기온차가 큰 대륙성 기후의 성격이 강하기 때문에 이 지역에서 재배한 양파는 남부지방에서 재배된 양파보다 당도가 높고 맛도 좋다고 알려져 있다. 인산질 성분은 특히 근의 발육을 촉진시키는 중요한 성분이다. 하지만 토양부의 인산성분이 수확 시까지 다량 지속되면 양분의 경합으로 뿌리부의 부패를 초래하기 쉽다. 따라서 수확기에 환원형 인산질을 중심으로 엽면시비 방법으로 영양균형을 유도하여 양파의 품질과 저장성을 향상시키는 것이 중요하다. 본 연구는 아인산(H3PO3)과 수산화칼륨(KOH)을 희석하여 산도조절 후, 아인산염으로 철원양파에 엽면 처리한 후 성분을 비교분석하였다. 본 연구에서 아인산염의 농도를 500, 1000, 1500배 희석하여 철원양파에 2018년 5월에 분무기를 이용하여 3회 엽면살포 한 후 6월 말경 수확한 후 HPLC를 이용하여 페놀화합물을 분석하였다. 그 결과 양파에서 중요한 물질 중의 하나인 큐에르세틴(quercetin)함량은 대조구(96.39 ug/g)에 비해 500배(179.70 ug/g), 1000배(150.27 ug/g), 1500배(105.95 ug/g) 처리구에서 높은 함량을 보였다. 또한 caffeic acid, p-coumaric acid, ferulic acid, rutin, kaempferol, 당도 함량은 처리구에서 대조구보다 높은 함량을 보였다. 따라서 아인산염 처리는 철원양파에서 페놀화합물의 함량을 높이는데 중요한 역할을 한다는 것을 알 수 있었다. 본 연구를 통하여 아인산염과 같은 환원형 엽면시비법을 이용하여 재배한다면 고품질의 기능성 양파를 생산할 수 있을 것이라 생각한다.

• Journal of the Korea institute for structural maintenance and inspection
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• v.19 no.3
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• pp.39-47
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• 2015

In this study, the properties of strength and drying shrinkage of alkali-activated slag cement (AASC) with magnesium oxide (MgO) contents between 0 and 16 wt% were investigated. The ground granulated furnace blast slag (GGBFS) was activated by potassium hydroxide (KOH) and dosage of activator was 2M and 4M. The MgO was replaced with 2% to 16% of GGBFS by weight. The water-binder ratio (w/b) was 0.5. In the result, the higher MgO content leads to a slightly higher degree of reaction and thus to a higher compressive strength at all ages. The compressive strength and ultra sonic velocity (UPV) increased with increases MgO contents. The drying shrinkage of AASC was decreased as the contents of MgO increases. The results from SEM confirmed that there were densified reaction product of higher MgO content specimens.

• Clean Technology
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• v.21 no.1
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• pp.62-67
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• 2015

We have developed a versatile method for the preparation of chemically linked graphene/multi-walled carbon nanotubes (MWNTs) hybrid materials via simple acid-catalyzed dehydration reaction between graphene oxide (GO) and amine-functionalized MWNTs (af-MWNTs). In this condition, ketone (-C=O) groups in GO and primary amine (-NH₂) moieties in af-MWNTs readily react to form imine (-C=N-) linkage. The chemical structures of graphene/MWNTs hybrid materials have been investigated using various microscopic and spectroscopic measurements. As a result of the synergetic effects of hybrid materials such as improved surface area and the superior structural restoration of graphitic networks, the hybrid materials demonstrate improved capacitance with excellent long-term stability. Furthermore, controlled experiments were conducted to optimize the weight ratio of graphene/MWNTs in hybrid materials. The highest capacitance of 132.4 F/g was obtained from the GM7.5 material, in which the weight ratio between graphene and MWNTs was adjusted to 7.5/1, in 1M KOH electrolyte at a scan rate of 100 mV/s.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.4
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• pp.641-647
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• 2017

In order to meet the stricter emission regulations, the proportion of after-treatments for vehicles and vessels has been increasing gradually. The objective of this study is to investigate the physicochemical properties according to ash cleaning agents of CDPF for Diesel Engines. Penetrating agents with strong penetration into ash and a surfactant component to mix water and oil were prepared properly. The cleaning characteristics of S1 sample were good. Washcoat loss rate of S1 sample was lower by about 2.2% because of less KOH component and lower Na2SiO3 content. Washcoat loss rate of S4 sample with an added KOH and Na2SiO3 components by penetration agents was increased by about 13%. In terms of less than about 13% of CDPF's washcoat loss rate, it was able to reduce the harmful gas components.

• Polymer(Korea)
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• v.35 no.1
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• pp.35-39
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• 2011

In this work, mesoporous carbons (CMK-3) were prepared by a conventional templating method using mesoporous silica (SBA-15) for using catalyst supports in polymer electrolyte membrane fuel cells (PEMFCs). The CMK-3 were chemically activated to obtain high surface area and small pore diameter with different potassium hydroxide (KOH) amounts, i.e., 0, 1, 3, and 4 g as an activating agent. And then Pt-Ru was deposited onto activated CMK-3 (K-CMK-3) by a chemical reduction method. The characteristics of Pt-Ru catalysts deposited onto K-CMK-3 were determined by surface area and pore size analysis, X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and inductive coupled plasma-mass spectrometry (ICP-MS). The electrochemical properties of Pt-Ru/K-CMK-3 catalysts were also analyzed by cyclic voltammetry (CV). From the results, the K3g-CMK-3 carbon supports activated with 3 g KOH showed the highest specific surface areas. In addition, the K3g-CMK-3 led to uniform dispersion of Pt-Ru onto K-CMK-3, resulted in the enhancement of elelctro-catalystic activity of Pt-Ru catalysts.

• Clean Technology
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• v.13 no.4
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• pp.266-273
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• 2007

The adsorption properties of the activated carbon-based adsorbents were studied to remove COS emitted from $SO_2$ catalytic reduction process on the integrated gasification combined cycle (IGCC) system in this work. Transition metal supported catalysts and mixed metal oxide catalysts were used for the $SO_2$ catalytic reduction. The mechanism of COS produced from the $SO_2$ reduction and the COS concentration s according to the reaction temperature were investigated. In this study, an activated carbon and a modified activated carbon doped with KOH were used to remove the very low concentration of COS effectively. The adsorption rate and the breakthrough time of COS were measured by a thermo gravity analyzer (TGA, Cahn Balance) and a fixed bed flow reactor equipped with GC-pulsed flammable photometric detector (PFPD), respectively. It was confirmed that the COS breakthrough time of the activated carbon doped with KOH was longer than that of an activated carbon. In conclusion, the modified-activated carbon having a high surface area showed a high adsorption rate of COS produced from the $SO_2$ reduction.

• Applied Chemistry for Engineering
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• v.33 no.6
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• pp.636-645
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• 2022

In this study, we investigated the adsorption characteristics of methyl orange (MO), an anionic dye, on ginkgo shell-based activated carbon (AC). For this purpose, ACs (GS-1, GS-2, and GS-4) with different textural properties were prepared using ginkgo shells and potassium hydroxide (KOH), a representative chemical activating agent. The correlation between the textural characteristics of AC prepared and the mixing ratio of KOH was investigated using nitrogen adsorption/desorption isotherms. The MO adsorption equilibrium experiment on the prepared ACs was conducted under different pH (pH 3~11) and temperature (298~318 K) conditions, and the results were investigated by Langmuir, Freundlich, Sips and temperature-dependent Sips equations. The feasibility of the MO adsorption treatment process of the prepared AC was also investigated using the dimensionless Langmuir separation factor. The heterogeneous adsorption properties of MO for the prepared AC examined using the adsorption energy distribution function (AED) were closely related to the system temperature and textural characteristics of AC. The kinetic results of the batch adsorption performed at different temperatures can be satisfactorily explained by the homogeneous surface diffusion model (HSDM), which takes into account the external mass transfer, intraparticle diffusion, and active site adsorption. The relationship between the activation energy value obtained by the Arrhenius plot and the adsorption energy distribution function value was also investigated. In addition, the adsorption process mechanism of MO on the prepared AC was evaluated using Biot number.

• Clinical and Experimental Pediatrics
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• v.52 no.3
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• pp.376-379
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• 2009

We report a case of a premature newborn baby who presented with hyponatremia, hyperkalemia, and metabolic acidosis accompanied by severe polyhydramnios in utero. The baby was diagnosed with pseudohypoaldosteronism on the basis of normal 17-hydroxyprogesterone levels, elevated aldosterone, and clinical symptoms. His serum electrolyte levels were corrected with sodium chloride supplementation. Sodium supplementation was reduced gradually and discontinued at 5 months of age. At 5 months, the child was able to maintain normal serum electrolyte levels without oral sodium chloride supplementation, and showed normal physical and neurological development. This case illustrates that pseudohypoaldosteronism must be considered if a newborn infant with an antenatal history of severe polyhydramnios shows excessive salt loss with normal levels of 17-hydroxyprogesterone.