• Journal of the Korean Electrochemical Society
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• v.13 no.4
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• pp.270-276
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• 2010

Nickel-copper foam electrodes with pore gradient micro framework and nano-ramified wall have been prepared by using an electrochemical deposition process. Growth habit of nickel-copper co-deposits was quite different from that of pure nickel deposit. In particular, the ramified structure of the individual particles was getting clear with chloride ion content in the electrolyte. The ratio of nickel to copper in the deposits decreased with the distance away from the substrate and the more chloride ions in the electrolyte led to the more nickel content throughout the deposits. Compositional analysis for the cross section of a ramified branch, together with tactical selective copper etching, proved that the copper content increased with approaching central region of the cross section. Such a composition gradient actually disappeared after heat treatment. It is anticipated that the pore gradient nickel-copper nanostructured foams presented in this work might be a promising option for the high-performance electrode in functional electrochemical devices.

• Applied Chemistry for Engineering
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• v.7 no.2
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• pp.362-370
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• 1996

The performance of The performance of $Li/V_6O_{13}$ cell and the electrochemical properties of polymer electrolyte based on poly(acrylonitrile)[PAN] was investigated. The ionic conductivity of polymer electrolyte showed $2.3{\times}10^{-3}S/cm$ and the compatibility with lithium electrode was excellent. Also, it showed the electrochemical stability up to 4.3V(vs. $Li^+/Li$). The cell reaction of $Li/V_6O_{13}$ was dominated by the interfacial resistance between $V_6O_{13}$ electrode and polymer electrolyte. The diffusion coefficient of lithium ion within $V_6O_{13}$ was $2.7{\times}10^{-9}{\sim}4.2{\times}10^{-8}cm^2/sec$. The utilization of $V_6O_{13}$ active material was 95% at C/8($50{\mu}A/cm^2$) and 82% at C/4($100{\mu}A/cm^2$), respectively.

• KSBB Journal
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• v.6 no.3
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• pp.241-247
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• 1991

The Poly (4-vinyipyridine-co-styrene) membrane containing Pyridine as fixed carrier was synthesized and characterized. And the active transport mechanism of Cl- and $CCl_3COO^-$ with changing concentration of $H^+$ and $OH^-$ was investigated. $CCl_3COO^-$ was transported not only by a symport mechanism with $H^+$ transfer but also by an antiport mechanism with $OH^-$transfer, while $Cl^-$ was transported only by a symport mechanism with $H^+$ transfer. Observing the initial flux of anions, salt formation constant between ions and membrane (K), and diffusion coefficient in membrane (D) were calculated as follows: for $Cl^-, \;K=4.60{\times}10^2\;mol^{-1}{\cdot}\textrm{cm}^3, \;D=1.57{\times}10^{-3}{\textrm{cm}^2/h$ and for $CCl_3COO^-, \;K=1.l0{\times}10^4\;mol^{-1}{\cdot}\textrm{cm}^3, \;D=1.14{\times}10^{-4}{\textrm{cm}^2}/h$.

• Journal of the Korean Ceramic Society
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• v.41 no.12 s.271
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• pp.900-906
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• 2004

Solid oxide fuel cells have a limitation in their low-temperature application due to the low ionic conductivity of electrolyte materials and difficulties in thin film formation on porous gas diffusion layer. These problems can be solved by improvement of ionic conductivity through controlled nanostructure of electrolyte and adopting nanoporous electrodes as substrates which have homogeneous submicron pore size and highly flattened surface. In this study, ultra-thin oxide films having submicron thickness without gas leakage are deposited on nanoporous substrates. By oxidation of metal thin films deposited onto nanoporous anodic alumina substrates with pore size of $20nm{\sim}200nm$ using dc-magnetron sputtering at room temperature, ultra-thin and dense ionic conducting oxide films with submicron thickness are realized. The specific material properties of the thin films including gas permeation, grain/gran boundaries formation, change of crystalline structure/microstructure by phase transition are investigated for optimization of ultra thin film deposition process.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.4 no.1
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• pp.63-70
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• 1994

Single crystals of the superionic conductor ${\beta}-Ag_3SI$ were prepared by thermal treatmentr from the reactant mixture of AgI and $Ag_2S$. The growing single crystals were made to spherical shape of $200{mu}m$ in diameter. The detailed structures analyses revealed that $Ag^+$ in ${\beta}-Ag_3SI$ distribute on 12h site of 4-coordination inpreference to 3c site of 6-coordination. The effective one-particle potential (o.p.p.). of $Ag^+$ along [110] direction was evaluated from the probability density function(p.d.f.) Activation energy calculated from the o.p.p. curve has been found to be 0.012 eV for the diffusion of $Ag^+$ on (001) plane in the ${\beta}-Ag_3SI$ structure.

• Journal of Sensor Science and Technology
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• v.5 no.2
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• pp.15-20
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• 1996

The diffusion of hydrogen ions into a sensing membrane causes the output voltage of pH-ISFET to vary with time, which might be considered to be drift in this sensor. We tried to deposit ultra-thin film for minimizing tile drift that has been considered to be main obstacle for putting pH-ISFET to practical use. In this paper, tantalum pentoxide, known as a good pH sensing membrane, was formed to about $70{\AA}$ thick by sol-gel method on $Si_{3}N_{4}/SiO_{2}$-gate of pH-ISFET. The fabricated $Ta_{2}O_{5}$-gate pH-ISFET showed good sensitivity(about 59mV/ pH) and good lineality in the range of pH $3{\sim}11$, and had relatively small average pH drift of about 0.06 pH/day.

• Membrane Journal
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• v.20 no.1
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• pp.13-20
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• 2010

Using poly(ethylene oxide) (PEO) as a polymer host, poly(ethylene glycol) (PEG) as a plasticizer, potassium iodide and iodine as sources of $I^-/{I_3}^-$ PEO-PEG-KI/$I_2$ polymer gel electrolytes were prepared. Based on the polymer gel electrolytes, solid-state dye-sensitized solar cell(DSSC)s were fabricated. The content of PEG in the electrolyte was changed from 0 to 85%. The electrolyte showed self-supporting form through whole range of the PEG content. As the PEG content increased, the ionic conductivity and ${I_3}^-$ diffusivity increased and the light-to electrical energy conversion efficiency increased under irradiation of 100 $mWcm^{-2}$ simulated sunlight.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.16 no.5
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• pp.181-188
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• 2006

Rutile single crystals grown by skull melting method were cut parallel and perpendicular to growth axis, and both sides of the cut wafers (${\phi}5.5mmx1.0mm$) were then polished to be mirror surfaces. The black wafers were changed into pale yellow color by annealing in air at 1200 and $1300^{\circ}C$ for $3{\sim}15\;and\;10{\sim}50$ hours, respectively. After annealing, structural and optical properties were examined by specific gravity (S.G), SEM-electron backscattered pattern (SEM-EBSP), X-ray diffraction (XRD), FT-IR transmittance spectra, laser Raman spectroscopy (LRS), photoluminescence (PL) and X-ray photoelectron spectroscopy (XPS). These results are analyzed increase of weight in air, decrease of weight in water and specific gravity, shown secondary phase of needle shape, diffusion of oxygen ion and increase of $Ti^{3+}$. From the above results, we suggest that the skull melting method grown rutile single crystals contain defect centers such as $O_v,\;Ti^{3+},\;O_v-Ti^{3+}$ interstitials and $F^+-H^+$.

• Journal of the Korean Chemical Society
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• v.18 no.6
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• pp.400-407
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• 1974

Steady-state anodic and cathodic polarization curves were developed for the Al electrode in 60 mole %$AlCl_3$-40 mole % NaCl at $180^{\circ}C$$453^{\circ}K$). Ohmic resistance contributed substantially to the anodic polarization at current densities greater than 50 mA/$CM^2$ even with capillary tip placed close to the electrode. This could not be rationalized from the resistivity of the melt, which would lead to a much smaller polarization. It was therefore concluded that a layer of high resistance $AlCl_3$ (or $AlCl_3$-rich melt) formed close to the anode surface. From the IR-corrected anodic Tafel and Allen-Hickling plots an apparent anodic charge-transfer coefficient of ${\alpha}_a$ = (2.3 RT/F)(d log i/d${\eta}$) = $1.5{\pm}0.25$ was obtained. At cathodic current densities greater than approximately 30 mA/$cm^2$, slow ion diffusion and dendrite growth both interfered with the measurement of kinetic parameters.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 1999.10a
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• pp.105-105
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• 1999

핵연료 피복관은 핵연료에서 방사성 핵분열생성물의 방출을 저지하는 가장 뚱요한 방어막인데, 현재 지르칼로이 4가 피복관의 재료로 사용되고 있다. 사용후 핵연료는 원자력발전소내 습식 저장조에 저장되고 있으나, 지속적인 관리와 장소확보의 용이 성으로 인해 건식 저장조를 사용하는 추세에 있다. 본 연구에선 건식 저장조에 장 기간 저장되는 핵연료 피복관에 주변 환경으로부터 오염될 수 있는 소금기나 기름 등이 지르칼로이의 공기중 산화에 미치는 영향의 존재를 밝히려 한다. 현재 고리 원자력발전소에서 사용중인 핵연료 피복관을 1cm정도 높이로 자르고, 피복관 표면 을 ASTM -G2-88 방법으로 처리한 후 산화실험을 수행하였다. 산화정도는 간헐적 (intermittent) 방법을 사용하여 시편의 무게를 측정하여 구하였으며, 산화온도는 $400-500^{\circ}C$로 하였다. 소금이 흡착이 된 경우, 산화 속도는 흡착이 안된 시편보다 가속되었으며, 거의 이차법칙을 따르고 있다. 산화막 위의 흡착물의 영향을 알아보기 위해, 지르칼로이를 $500^{\circ}C$ 수증기에 $5g/m^2$ 두께로 산화시킨 후, 다시 산화실험을 수행하였다. 사용한 흡착물은 LiF, NaF, KF, NaCI 이다. 흡착물들은 산화를 대체로 가속시켰으며, NaF, KF, NaCI 순으로 그 영향력이 컸다. 그러나, LiF는 산화에 전혀 영향을 미치지 않았다. SIMS를 사용하여 각 시편의 두께에 따른 흡착물의 분포 를 알아보았다. 음이온(CI, F)과 양이온(Na, Li, K)이 산화막과 금속 경계면까지 관 찰되었으며, 음이온과 양이온의 분포는 대게 동일하였다. LiF의 경우 산화막에서 이들의 농도가 급격히 떨어지고 있음을 알 수 있었다. 산화막 내에서 이들 흡착물의 확산이 산화속도 가속의 원인이며 이들 흡착물중 CI과 F는 산화막과 금속 겸계면 에서 새로 생성되는 산화막의 강도에 영향을 미쳐, 일찍 미세균열을 만들기 시작하여 산화를 가속시키는 것으로 판단된다.