Carbon/silicon composites were synthesized by mixing silicon powders with petroleum pitch and subsequent heat-treatment. The resultant composites were composed of carbon and nano-size crystalline silicon identified by XRD and EDX. FIB images and SEM images were taken respectively to detect the existence of silicon impregnated in carbon and the distribution of silicon on the carbon surface. The obtained carbon/silicon materials were assembled as half cell anodes for lithium ion secondary battery and their electrochemical properties were tested. The pitch/silicon composite (3 : 1 wt. ratio) heat treated at 1000℃ and mixed with 55.5 wt.% of graphite showed relatively good electrochemical properties such as the initial efficiency of 78%, the initial discharge capacity of 605 mAh/g, and the discharge capacity of 500 mAh/g after 20 cycles.

Aluminum was anodized in a H2SO4 solution, and titanium (IV) oxide (TiO2) was electrodeposited into nanopores of anodic porous alumina in a mixed solution of TiOSO4 and (COOH)2. The photocatalytic activity of the prepared film was analyzed for photodegradation of methylene blue aqueous solution. Consequently, we found it was possible to electrodeposit TiO2 onto anodic porous alumina, and synthesized it into the nanopores by hydrolysis of a titanium complex ion under AC 8-9 V when film thickness was about 15-20μm. The photocatalytic activity of TiO2-loaded anodic porous alumina (TiO2/Al2O3) at an impressed voltage of 9 V was the highest in every condition, being about 12 times as high as sol-gel TiO2 on anodic porous alumina. The results revealed that anodic porous alumina is effective as a substrate for photocatalytic film and that high-activity TiO2 film can be prepared at low cost.

In this work, activated carbons (ACs) were prepared from polystyrene-based cation-exchangeable resin (PSI) by a chemical activation with KOH as an activating agent. The surface morphologies were observed by using SEM, and the textural properties were investigated by using nitrogen adsorption at 77 K. From the experimental results, it was found that the well-developed micro- and mesopores were produced by a chemical activation, and the textural properties including specific surface areas and pore volumes were greatly enhanced. The electrochemical behaviors of the ACs showed similar phenomena with that of textural properties. These results indicated that KOH activation played an important role in the changes of surface, and pore structures, resulting in enhancing the electrochemical properties of the ACs prepared in present work.

전기변색(electrochromism, EC)소자는 여러 가지 색으로 발색이 가능하고, 낮은 구동전압과 메모리성이 좋은 특징을 갖고 있으나, 내구성이 부족하고 발색 및 소색 속도의 감소, 반복에 따른 완전한 소색과 응답성이 떨어져 실용화에 문제점를 나타내고 있다. 따라서 본 연구에서는 viologen 유도체와 leuco dyes의 안정성 및 내구성을 향상시키기 위하여 이들 색소들의 산화환 원전위와 산화방지제(AO-60)를 사용하였을 때의 cyclic voltammetry와 chronocoulometry를 비교 측정하였다. 그 결과 leuco dye인 CVL과 ODB-2에서는 charge값의 안정성이 10% 이상 증가하였고 Orange-DCF, Red-DCF, Green-DCF에서는 charge값이 5% 이상 상승한 결과를 나타내었다. 모든 색소가 산화방지제를 첨가하였을 경우가 안정한 상태로 내구성을 유지하는 것이 확인 되었다. Benzyl viologen의 경우 AO-60 첨가에 의하여 불안정한 산화상태를 안정화시키는 것을 확인하였다. 따라서 본 연구결과 leuco dye에 의한 EC 소자의 가능성과 칼라화에 대한 가능성을 보임을 확인하였다.

크로노포텐시오미터(CP)와 전류-전압곡선(I-V)을 사용하여 음/양 이온 교환 층의 영향을 하전 모자이크 막에서 조사하였다. 역시 전해질과 음/양이온의 계면에서 이온수송을 실험하였다. 결과 음/양이온 교환 막은 전류범위에서 점점 전압강하가 나타났고, 특히 저 농도의 KCl 전위는 일정하였다. 한편 복합 하전 모자이크 막은 여러 전해질 수용액의 종류와 농도에 관계없이 전위의 변화는 없었다. CP와 I-V의 측정은 이온교환 막 계면에서 일어나는 이온수송에 대한 기초해석으로 대단히 유효하였다.

본 논문은 지하매설 철 구조물의 전기적 부식방지를 위해 Mg 희생양극을 사용하는 부식방지 기술에 대한 연구 또한 활발히 진행되고 있다. Mg 희생양극은 지하에 매설되는 철 구조물(파이프, 탱크, 파일, 고정 앵커 등)을 부식으로부터 보호하기 위하여 사용되는 것이다. 본 연구에서는 종래의 산화 소화용 표면 보호재로 이용되고 있는 비교적 값이 싼 CaCl2 염화물을 이용하여 마그네슘 합금제조 시 CaCl2 염화물의 표면보호 효과 및 제조된 Mg-Ca 합금들의 전기화학적 특성을 조사하였다 금속 Ca가 아닌 산화방지 및 소화 용제로 이용되고 있는 염화물(CaCl2)을 이용하여 자연부식 전위 값이 -1.695VSCE 이하, 사용효율도 59% 이상인 Mg-Mn-Ca 희생양극제의 제조기술을 확립하였다.

In the development of new hydrogen absorbing materials for a next generation of metal hydride electrodes for rechargeable batteries, metastable Mg-Ni-based compounds find currently special attention. Amor phous-nanocrystalline and alloys were produced by mechanical alloying and melt-spinning and characterized by means of XRD, TEM and DSC. On basis of mechanically alloyed Mg-Ni-Y powders, complex hydride electrodes were fabricated and their electrochemical behaviour in 6M KOH (pH=14,8) was investigated. The electrodes made from powders, which were prepared under use of a SPEX shaker mill, with a major fraction of nanocrystalline phase reveal a higher electrochemical activity far hydrogen reduction and a higher maximum discharge capacity (247 mAh/g) than the electrodes from alloy powder with predominantly amorphous microstructure (216 mAh/g) obtained when using a Retsch planetary ball mill at low temperatures. Those discharge capacities are higher that those fur nanocrystalline electrodes. However, the cyclic stability of those alloy powder electrodes was low. Therefore, fundamental stability studies were performed on and ribbon samples in the as-quenched state and after cathodic hydrogen charging by means of anodic and cathodic polarisation measurements. Gradual oxidation and dissolution of nickel governs the anodic behaviour before a passive state is attained. A stabilizing effect of higher fractions of yttrium in the alloy on the passivation was detected. During the cathodic hydrogen charging process the alloys exhibit a change in the surface state chemistry, i.e. an enrichment of nickel-species, causing preferential oxidation and dissolution during subsequent anodization. The effect of chemical pre-treatments in 1% HF and in solution on the surface degradation processes was investigated. A HF treatment can improve their anodic passivation behavior by inhibiting a preferential nickel oxidation-dissolution at low polarisation, whereas a treatment has the opposite effect. Both pre-treatment methods lead to an enhancement of cathodically induced surface degradation processes.

The electrochemical properties of novel metal powders were investigated for the electrode materias of polymer electrolyte memebrane electrolysis. Two types of Pt black and powder electrodes were hot-pressed on the polymer electrolyte membrane to form membrane electrode assembly. The galvanodynamic polarization methode was used to characterize the electrochemical properties of both electrodes. From the experimental results, we concluded that the powder electrode exhibits better electrochemical performance than Pt black as cathode material for the electrolysis.

Solid Oxide Fuel Cell technology uses powder processes to produce electrodes with residual porosity by partially sintering a mixture of electronically and ionically conducting particles. We model porous fuel cell electrodes with 3D packings of monosized spherical particles. These packings are created by numerical sintering. Each particle-particle contact is characteristic for an ionic, electronic or electrochemical resistance. The numerical packing is then discretized into a resistor network which is solved by using Kirchhoff's current law to evaluate the electrode's electrochemical performance. We investigate in particular percolation effects in functionally graded electrodes as compared to other types of electrodes.

We investigated the electrochemical properties for Langmuir-Blodgett (LB) films mixed with fatty acid (8A5H) and phospholipid (DLPE, DMPC, and DPPA). LB films of 8A5H monolayer and 8A5H-phospholipid mixture were deposited using the Langmuir-Blodgett method on the indium tin oxide(ITO) glass. The electrochemical properties measured using cyclic voltammetry with three-electrode system, an Ag/AgCl reference electrode, a platinum wire counter electrode and LB film-coated ITO working electrode at various concentrations(0.1, 0.5, and 1.0 mol/L) of NaClO4 solution. A measuring range was reduced from initial potential to -1350 mV, continuously oxidized to 1650 mV and measured to the initial point. The scan rate was 50, 100, 150 and 200 mV/s, respectively. As a result, LB films of fatty acid and phospholipid (8A5H/DLPE and DPPA) appeared irreversible process were caused by only the reduction current from the cyclic voltammogram and LB film of 8A5H-DMPC mixture was found to be caused by a reversible oxidation-reduction process.

Synthesis of iron nanopowder by room-temperature electrochemical reduction process of nanopowder was investigated in terms of phase evolution and microstructure. As process variables, reduction time and applied voltage were changed in the range of h and V, respectively. From XRD analyses, it was found that volume of Fe phase increased with increasing reduction time and applied voltage, respectively. The crystallite size of Fe phase in all powder samples was less than 30 nm, implying that particle growth was inhibited by the reaction at room temperature. Based on the distinct equilibrium shape of crystalline particle, phase composition of nanoparticles was identified by TEM observation.

이트리아 안정화 지르코니아(yttria stabilized zirconia, YSZ)를 전해질로 선정하여 소결조건에 따른 열적 안정성과 전기적인 특성을 분석하였다. SEM사진으로 소결온도가 증가할수록 입자가 커지므로 상대적으로 기공은 줄어드는 것을 보였고 입자크기에 따른 영향을 확인하였다. 전기적 특성을 알아보고자 2단자법(2-probe method)으로 800~1000℃의 오도에서 교류 임피던스 측정을 통하여 전해질 내의 저항과 전기전도도 측정으로 입자 내부 저항 및 전기적 성능을 평가하였다. 소결온도가 1400℃일 때 건식법과 습식법에서 밀도는 각각 6.13, 6.25 g/cm3이며, 상대밀도는 각각 98, 99%였다. 소결온도가 올라갈수록 저항은 낮아지고, 전도도는 커지는 것을 확인할 수 있으며, 건식 및 습식법으로 제작한 전해질의 전기전도도는 10000℃에서 각각 8.8×10-2,;11×10-2 S/cm이었다.

We investigated the electrochemical properties for Langmuir-Blodgett (LB) films mixed with 4-octyl-4'-(5-carboxylpentamethyleneoxy)azobenzene (denoted as 8A5H) and phospholipid(L-α-dimyristoylphosphatidylcholine, denoted as DMPC). LB films of 8A5H monolayer and 8A5H-DMPC were deposited by using the Langmuir-Blodgett method on the indium tin oxide(ITO) glass. The electrochemical properties measured by using cyclic voltammetry with a threeelectrode system, an Ag/AgCl reference electrode, a platinum wire counter electrode and LB film-coated ITO working electrode at various concentrations(0.1, 0.5, and 1.0mol/L) of NaClO4 solution. A measuring range was reduced from initial potential to -1350mV, continuously oxidized to 1650mV and measured to the initial point. The scan rates were 50, 100, 150 and 200mV/s, respectively. As a result, LB films of 8A5H monolayer appeared irreversible process caused by only the oxidation current from the cyclic voltammogram and LB films of 8A5H-DMPC mixture were found to be caused by a reversible oxidation-reduction process.