• Journal of Electrochemical Science and Technology
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• 제14권2호
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• pp.105-119
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• 2023

The electrochemical chlorine evolution reaction (CER) is an important electrochemical reaction and has been widely used in chlor-alkali electrolysis, on-site generation of ClO^-, and Cl₂-mediated electrosynthesis. Although precious metal-based mixed metal oxides (MMOs) have been used as CER catalysts for more than half a century, they intrinsically suffer from a selectivity problem between the CER and parasitic oxygen evolution reaction (OER). Hence, the design of selective CER electrocatalysts is critically important. In this review, we provide an overview of the fundamental issues related to the electrocatalysis of the CER and design strategies for selective CER electrocatalysts. We present experimental and theoretical methods for assessing the active sites of MMO catalysts and the origin of the scaling relationship between the CER and the OER. We discuss kinetic analysis methods to understand the kinetics and mechanisms of CER. Next, we summarize the design strategies for new CER electrocatalysts that can enhance the reactivity of MMO-based catalysts and overcome their scaling relationship, which include the doping of MMO catalysts with foreign metals and the development of non-precious metal-based catalysts and atomically dispersed metal catalysts.

• Journal of Electrochemical Science and Technology
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• 제15권3호
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• pp.345-352
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• 2024

The synthesis of Pt nanoparticles and catalytically active materials using the electrochemical top-down approach involves dispersing Pt electrodes in an electrolyte solution containing alkali metal cations and support material powder using an alternating pulsed current. Platinum is dispersed to form particles with a predominant crystallographic orientation of Pt(100) and a particle size of approximately 7.6±1.0 nm. The dispersed platinum particles have an insignificant content of PtO_x phase (0.25±0.03 wt.%). The average formation rate was 9.7±0.5 mg cm^-2 h^-1. The nature of the support (carbon material, metal oxide, carbon-metal oxide hybrid) had almost no effect on the formation rate of the Pt nanoparticles as well as their crystallographic properties. Depending on the nature of the support material, Pt-containing catalytic materials obtained by the electrochemical top-down approach showed good functional performance in fuel cell technologies (Pt/C), catalytic oxidation of CO (Pt/Al₂O₃) and electrochemical oxidation of methanol (Pt/TiO₂-C) and ethanol (Pt/SnO₂-C).

• 한국수산과학회지
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• 제23권2호
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• pp.77-86
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• 1990

5N HCl과 5N NaOH로 부산물의 일종인 꽃게의 열수수출 잔사를 12시간 가수분해하여 각각 산 가수분해물과 알칼리 가수분해물을 제조한 후 산가 수분해물의 경우 $Na_2CO_3$, NaOH 및 5N NaOH로 분해한 알칼리가수분해물등의 3가지 중화처리구, 알칼리가수분해물인 경우 HCl과 5N NCl로 분해한산가수분해물의 2가지 중화처리구 총 5가지 중화 처리구로 중화하여 시험하였다. 산 가수분해물은 알칼리 가수분해물에 의한 중화처리가, 알칼리 가수분해물은 산 가수분해물에 의한 중화처리가 total nitrogen과 formol nitrogen함량을 서로 높일 수 있을 뿐만 아니라 염 함량을 줄일 수 있었으며, 가수분해물의 맛을 상승시킬 수 있었다. 5N HCl로 가수분해하여 $Na_2CO_3$, NaOH 및 5N NaOH로 분해한 가수분해물로 중화한 가수분해물의 구성 아미노산의 함량은 각각 $2,274mg\%,\;2,105.0mg\%$와 $2,683.5mg\%$였으며, 5N NaOH로 가수분해하여 5N HCl과 5N HCl로 분해한 가수분해물로 중화한 가수분해물의 구성아미노산의 함량은 각각 $1,352.5mg\%$와 $2,498.8mg\%$였다. 가수분해물의 탈색 및 탈취시험은 분말활성탄외 4종의 탈색제로 탈색시험을 한 결과, 분말활성탄의 탈색율이 우수하였으며, 활성탄의 농도가 높을수록 total nitrogen과 formol nitrogen 함량이 감소하였다. 탈색과 탈취의 목적으로 활성탄 사용시 적정농도는 $1\~2\%$였다. 탈염시험은 중화처리한 가수분해물을 고농도로 농축시켜 석출하는 염을 제거하는 방법으로 $39^{\circ}$ Brix이상으로 농축하면 염농도를 감소시킬 수 있었다.

• 암석학회지
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• 제6권3호
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• pp.185-209
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• 1997

청산지역의 화강암류는 기재적인 특징으로부터 백록 화강섬록암, 청산 반상 화강암 및 청산복운모 화강암으로 분류할 수 있다. 백록 화강섬록암의 각섬석은 외각섬석군에 속하고, 중심부의 Mg- 보통각섬석에서 주변부의 양기석질 보통각섬석으로 조성적 변화를 보인다. 청산 지역 화강암류의 흑운모는 금운모와 애나이트의 중간 조성을 나타낸다. 복운모 화강암에서 산출되는 백운모는 그 산출상태와 조성으로부터 마그마 정출의 1차적인 백운모로 판단된다. 주성분 산화물의 변화 경향에서 각각의 화강암류는 체계적인 변화를 나타낸다. 백록 화강섬록암은 청산 반상 화강암 및 복운모 화강암과는 주성분의 변화 경향에서 매우 뚜렷한 차이를 보인다. 반상 화강암과 복운모 화강암의 경우 일부 성분에서는 연속성이 관찰되지만, 몇몇 원소에서는 뚜렷한 차이를 보인다. 따라서 청산 지역의 세 화강암류는 각각 이질적 성인의 다른 조성의 마그마로부터 형성된 것으로 판단된다. 화강암류의 전암 화학조성으로부터 청산 지역 화강암류는 칼크-알칼리질임을 알 수 있다. 한편, 백록 화강섬록암과 청산 반상 화강암은 그 전암 조성이 I-타입과 메타알루미나질임에 비해, 청산 복운모 화강암은 I-/S-타입 양쪽과 과알루미나질을 나타낸다. 불투명광물의 함량과 전암 대자율값으로부터 청산지역 화강암륜느 모도 티탄철석계열에 속해 비교적 환원적인 환경에서 관입·고결되었음을 알 수 있다. 또한 세 화강암류는 활동성 대륙연변부에서 일어난 화성활동의 결과로 형성되었음이 추정된다. 청산 반상 화강암에 나타나는 알칼리장석의 거정은 그 결정의 크기, 형태, 배열 및 포유물의 분포 양상 등으로부터 마그마 기원임을 추정할 수 있다. 반상 화강암의 조직적 특징은 2단계 정출작용으로 설명된다. 즉, 알칼리장석 거정의 크기와 형태는 과냉각 정도가 적은 상태에서 결정의 느린 핵형성과 빠른 성장속도로 말미암아 형성된 반면, 석기는 과냉각 정도가 큰 상태에서 핵형성 밀도와 속도가 증가하여 형성된 것으로 판단된다.

• 펄프종이기술
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• 제37권3호
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• pp.66-73
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• 2005

This study was performed to understand the changes in wood extractives, mainly acetone extracts, in pine woods (Pinus densiflora and Pinus rigida) treated by three blue stain fungi (BSF) such as native BSF in Korea, Leptographium sp., screened Albino strain(BSFcs-1) and commercial Cartapip and fungicide, Wood guard. In addition their pulping and bleaching properties were investigated. BSF treatment has significantly reduced acetone extracts, $25.1{\sim}30.4%$ decreasing in red pine and $22.9{\sim}28.1%$ in pitch pine. Three week aging treatment showed about 20% decreasing in red pine and 19.3% in pitch pine. There were not so significant differences in extracts reduction among native BSF and Albino-type strains (Albino strain, BSFcs-1, and commercial Cartapip). But fungicide, Wood guard, treated wood showed relatively lower decreasing rates of extractives, 14% in red pine and 10.1% in pitch pine. Therefore it is understandable that the fungicide could protect the wood from blue stain fungi attack, but has no effect on its extractive reduction. Concerned to pulping properties of BSF and fungicide treated woods, red pine and pitch pine, optimum pulping condition was 20% active alkali, wood to liquor ratio 1 to 6, $170^{\circ}C$, and 2.5 hr. In the case of BSF woods, optimum pulping condition was same as the sound wood, $43.5{\sim}45%$ of pulp yields and $1.3{\sim}1.45%$ of rejects. Screened pulp yield of fungicide treated wood was lower than those of BSF treated woods. Rejects in pulps were higher in fungicide-treated wood than BSF treated woods. Bleaching pulp yields were ranged of 92 to 93.5%. BSF, Cartapip and fungicide treated woods resulted in lower brightness of $55{\sim}58%$, but Albino-type strain(BSFcs-1) $61.3{\sim}62.3%$, very similar to untreated one. Therefore bleaching chemicals could be saved in the processing of chemical pulping.

• 한국자기공명학회논문지
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• 제19권2호
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• pp.67-73
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• 2015

The microcystin is a cyclic heptapeptide from metabolites of cyanobacteria in the genera mycrocystis, anabaeba as a result of eutrophication. It has been known that microcystin-LR is a potent inhibitor of the catalytic subunits of protein phosphatase-1 (PP-1) as well as powerful tumor promoter. The active site of microcystin actually has two metal ions $Fe^{2+}/Zn^{2+}$ close to the nucleophilic portion of PP-1-microcystin complex. We report the isolation and purification of this microcystin-LR from cyanobacteria (blue-green algae) obtained from Daechung Dam in Chung-cheong Do, Korea. Microcystin-LR was extracted from solid-phase extraction (SPE) sample preparation using a CN cartridge. The cyanobacteria extract was purified to obtain microcystin-LR by HPLC method and identified by LC/MS. The detail structural studies that can elucidate the possible role of monovalent and divalent metal ions in PP-1-microcystin complexation were carried out by utilizing molecular dynamics. Conformational changes in metal binding for ligands were monitored by molecular dynamic computation and potential of mean force (PMF) using the method of the free energy perturbation. The microcystin-metal binding PMF simulation results exhibit that microcystin can have very stable binding free energy of -10.95 kcal/mol by adopting the $Mg^{2+}$ ion at broad geometrical distribution of $0.5{\sim}4.5{\AA}$, and show that the $K^+$ ion can form a stable metal complex rather than other monovalent alkali metal ions.

• 한국재료학회지
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• 제20권9호
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• pp.488-493
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• 2010

Geopolymer is a term covering a class of synthetic aluminosilicate materials with potential use in a number of areas, but mainly as a replacement for Portland cement. In this study, geopolymers with fly ash and meta kaolin were prepared using KOH as an alkali activator and water glass. The effect of water glass on the microstructures and the compressive strength of the geopolymer was investigated. As the amount of water glass increased, the dissolved inorganic binder particles in the geopolymers increased due to polymerization, resulting in a dense microstructure. The meta kaolin-based geopolymer showed a better extent of polymerization and densification than that of the fly ash-based geopolymer. XRD data also suggested that polymerization in meta kaolin-based geopolymers should be active resulting in the formation of an amorphous phase with an increasing amount of water glass. The compressive strength of the geopolymer was also dependent on the amount of water glass. The compressive strength of the geopolymers from both fly ash and meta kaolin increased with an increasing amount of water glass because water glass improved the extent of polymerization of the inorganic binder and resulted in a dense microstructure. However, the addition of water glass to the geopolymer did not seem to be effective for the improvement of compressive strength because the meta kaolin-based geopolymer mainly consisted of a clay component. For this reason, the fly ash-based geopolymer showed a higher value of compressive strength than the meta-kaolin geopolymer.

• Archives of Pharmacal Research
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• 제17권1호
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• pp.26-30
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• 1994

Some ammonium oxalate soluble pectic fragments prepared from cultured cell wall of Ephycla distrahya elicited the accumulation of p-coumarocylamino acids (p-CAA) in E. distachya cultures while water soluble and alkali soluble fractions had no activity. Partial purification of the pectic fragments fraction using DEAE-cellulose chromatography afforded two active fractions (PS-I and PS-II) which were composed of mainly uronic acids (98-99 w/w %). They elicited the accumulation of p-CAA in an amount of 52-60 nmol per gram fresh weight of cultures. The acidic sugar compositions of PS-I and PS-II were found to be galacturonic acid and glucuronic acid by TLC analysis. They were supposed to act as endogenous elicitors of p-CAA accumulation. In order to investigate the effect of ethylene on p-CAA accumulation, Ethrel, which is known as ethylene generator, and ACC(1-aminocyclopropane-1-carboxylic acid), a direct precusor of ethylene biosynthesis, were added to the culture. However, they did not glycopeptide elicitor [(Con A-II)], either. Consequently, no relationships between ethylene and p-CAA accumulation were recognized. Several tentative elicitors were teted for their activity. Commercial yeast glucan, $CuCl_2$, laminarin and laminariheptaose had slight activity whereas ${\alpha}$-methylmannopyranoside and commercial yeast mannan had no elicitor activity. ${\alpha}$-methylmannopyranoside which has been known as a tentative inhibitor of glucan elicitor in Glycine max did not affect on the elicitor activity of Con A-II.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2011년도 제40회 동계학술대회 초록집
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• pp.207-207
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• 2011

Amorphous transparent oxide semiconductors (a-TOS) have been widely studied for many optoelectronic devices such as AM-OLED (active-matrix organic light emitting diodes). Recently, Nomura et al. demonstrated high performance amorphous IGZO (In-Ga-Zn-O) TFTs.1 Despite the amorphous structure, due to the conduction band minimum (CBM) that made of spherically extended s-orbitals of the constituent metals, an a-IGZO TFT shows high mobility.2,3 But IGZO films contain high cost rare metals. Therefore, we need to investigate the alternatives. Because Aluminum has a high bond enthalpy with oxygen atom and Alumina has a high lattice energy, we try to replace Gallium with Aluminum that is high reserve low cost material. In this study, we focused on the electrical properties of IZO:Al thin films as a channel layer of TFTs. IZO:Al were deposited on unheated non-alkali glass substrates (5 cm ${\times}$ 5 cm) by magnetron co-sputtering system with two cathodes equipped with IZO target and Al target, respectively. The sintered ceramic IZO disc (3 inch ${\phi}$, 5 mm t) and metal Al target (3 inch ${\phi}$, 5 mm t) are used for deposition. The O2 gas was used as the reactive gas to control carrier concentration and mobility. Deposition was carried out under various sputtering conditions to investigate the effect of sputtering process on the characteristics of IZO:Al thin films. Correlation between sputtering factors and electronic properties of the film will be discussed in detail.

• Korean Chemical Engineering Research
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• 제50권1호
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• pp.182-185
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• 2012

$TiCl_4$와 히드라진/암모니아수를 사용하여 졸겔 및 강알칼리 수열합성법의 신규 2단 합성법을 통해 N도핑된 $TiO_2$ 나노튜브를 제조하였다. 제조된 나노튜브는 튜브형상의 손상이 없이 10 nm 전후의 직경과 3 nm 이하의 벽두께를 가지며, 잘발달된 아나타제 결정상을 나타내었다. 또한 N이 도핑되어 일반 도핑되지 않은 $TiO_2$ 나노튜브와 아나타제상입자에 비해 각각 ~35 nm, ~25 nm 정도 적색편이 된 우수한 가시광 흡수능과 노란색 색상을 보여 주었다.