• 대한전기학회논문지
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• 제40권9호
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• pp.883-892
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• 1991

This paper presnets the characteristics of electropolymerization and electrochemicla propoerties of polyaniline(PAn). From the morphology study on the PAn surface, it seems that coagulation of the fibrils on the surface proceeds as the PAn grows, resulting in fibril clusters with new branches and more extensive voids. While PAn/Li cell is cycled at potential range between 2.9V and 3.7V in which the first strong reduction peak of 2.75V does not appear, its oxidation reduction capacities were increased up to about tenth cycle. Electricity efficiency of stable charge-discharge to deep discharge in PAn/Li cell was 42.9%. Average charge potential, avergae discharge potential, energy density, and charge-discharge energy efficiency of the PAn/Li cell were 3.4V, 3.25V, 132.9Wh/kg, and 95.6%, respectively.

• Journal of Mechanical Science and Technology
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• 제18권4호
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• pp.640-648
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• 2004

This paper describes a new magnetization method for non-destructive testing with magneto-optical sensor (denoted as MO sensor) which have the following characteristic : high observation sensitivity, independence of the crack orientation, and precise imaging of a complex crack geometry such as multiple cracks. When a magnetic field is applied normally to the surface of a specimen which is significantly larger than its defects, approximately the same magnetic charge per unit area occurs on the surface of the specimen. If there is a crack in the specimen, magnetic charge per unit area has the same value at the bottom of the crack. The distribution of the vertical component of the magnetic flux density, B$\_$Z/, is almost uniform over the no-crack area (denoted as B$\_$Z,BASE/), while the magnetic flux density is smaller in the surroundings of the crack(denoted as B$\_$Z,CRACK/) If B$\_$Z, BASE/ is a bit larger than the saturated magnetic flux density of the MO sensor (B$\_$s/) , then small magnetic domains occur over the crack area and a large domain over the non-crack area because B$\_$Z,CRACK/ is smaller than B$\_$s/.

• 한국재료학회지
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• 제21권12호
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• pp.703-707
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• 2011

The electrochromic properties of tungsten oxide films grown by RF sputtering were investigated. Among the sputter parameters, first the $Ar:O_2$ ratios were controlled with division into only an $O_2$ environment, 1:1 and 4:1. The structure of each film prepared by these conditions was studied by X-ray diffraction, X-ray photoelectron spectroscopy and Rutherford backscattering spectroscopy. The sputter-deposited tungsten oxide films had an amorphous structure regardless of the $Ar:O_2$ ratios. The chemical compositions, however, were different from each other. The stoichiometric structure and low-density film was obtained at higher $O_2$ contents. Electrochemical tests were performed by cyclic voltammetry and chronoamperometry at 0.05 M $H_2SO_4$ solutions. The current density and charge ratio was estimated during the continuous potential and pulse potential cycling at -0.5 V and 1.8 V, respectively. The film grown in a higher oxygen environment had a higher current density and a reversible charge reaction during intercalation and deintercalation. The in-situ transmittance tests were performed by He-Ne laser (633 nm). At higher oxygen contents, a big transmittance difference was observed but the response speed was too slow. This was likely caused by higher film resistivity. Furthermore, the effect of sputtering pressure was also investigated. The structure and surface morphology of each film was observed by X-ray diffraction and scanning electron microscopy. A rough surface was observed at higher sputtering pressure, and this affected the higher transmittance difference and coloration efficiency.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2009년도 제38회 동계학술대회 초록집
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• pp.357-357
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• 2010

Using ab initio density functional theory, we study the structural and electronic properties of interface between Cu surface and highly electron withdrawing hexaazatriphenylene-hexanitrile (HAT-CN) known as an efficient hole injection layer for organic light emitting diodes (OLEDs). We calculate the equilibrium geometries of the interface with different HAT-CN coverages. Usually, some of C-N bonds located at the edge of the HAT-CN molecule are deformed toward Cu atoms resulting in the reconstruction of Cu surface. By analyzing the electron charge and the potential distributions over the interface, we observe the formation of surface dipoles, which modify the work function at the interface. Such dipole formation is attributed to two origins, one of which is a geometrical nature and the other is a bond dipole. The former is related to structural deformation mentioned above, whereas the latter is due to charge transfer between organic and metal surface.

• Journal of Electrochemical Science and Technology
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• 제8권3호
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• pp.197-205
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• 2017

Lead dioxide thin films were electrodeposited on nickel substrate from acidic lead nitrate solution. Current efficiency and thickness measurements, cyclic voltammetry, AFM, SEM, and X-ray diffraction experiments were conducted on $PbO_2$ surface to elucidate the effect of lead nitrate concentration, current density, temperature on the morphology, chemical behavior, and crystal structure. Experimental results showed that deposition efficiency was affected by the current density and solution concentration. The film thickness was independent of current density when deposition from high $Pb(NO_3)_2$ concentration, while it decreased for low concentration and high current density deposition. On the other hand, deposition temperature had negative effect on current efficiency more for lower current density deposition. Cyclic voltammetric study revealed that comparatively more ${\beta}-PbO_2$ produced compact deposits when deposition was carried out from high $Pb(NO_3)_2$ concentration. Such compact films gave lower charge discharge current density during cycling. SEM and AFM studies showed that deposition of regular-size sharp-edge grains occurred for all deposition conditions. The grain size for high temperature and low concentration $Pb(NO_3)_2$ deposition was bigger than from low temperature and high concentration deposition conditions. While cycling converted all grains into loosely adhered flappy deposit with numerous pores. X-ray diffraction measurement indicates that high concentration, high temperature, and high current density favored ${\beta}-PbO_2$ deposition while ${\alpha}-PbO_2$ converted to ${\beta}-PbO_2$ together with some unconverted $PbSO_4$ during cycling in $H_2SO_4$.

• 한국토양비료학회지
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• 제34권4호
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• pp.237-244
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• 2001

토양의 하전특성을 평가하는 데 이용되는 이온흡착법에서 지표이온이 달라졌을 때 측정되는 표면전하량의 차이를 파악하기 위하여, 화강암을 모재로 하는 논토양(지산통, 사촌통)과 밭토양(상주통, 백산통)에 $Na^+$와 $K^+$ 이온을 지표이온으로 하는 이온흡착법을 적용하였다. 표면 음전하는 모든 pH에서 직선적으로 증가하는 경향을 보였고, 표면 양전하는 pH6 이하에서만 미량으로 발현되고 중성 이상에서는 거의 발현되지 않았다. 또, NaCl이 지표이온종인 경우 KCl을 사용하여 측정한 표면전하량에 비해 측정된 모든 pH 범위에서 상대적으로 낮은 전하밀도값을 나타내었다. 이러한 차이는 지표이온종의 수화반경에 따른 표면 흡착강도 차에 기인하는 것으로 판단된다. 지산, 사촌, 백산통의 표면전하량은 pH에 따라 $0.21{\sim}9.01cmol_c{\cdot}kg^{-1}$의 범위 내에 존재하였으며, 통일한 pH에서는 백산통의 표면전하 밀도가 다른 토양에 비하여 가장 높게 나타났다. 본 연구에서 분석된 토양의 pH 변화에 따른 전하변화량(dCEC/dpH)은 가변전하를 발현시키는 토양구성물 중 유기물에 의하여 가장 크게 변화하는 것으로 나타났다.

• 펄프종이기술
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• 제34권1호
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• pp.7-11
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• 2002

The print quality of a ink jet printer is generally affected by three major components of the printing process: printer, ink formulation, and paper. The result of this study indicated that the surface sized paper with oxidized starch and cationic starch differed ink jet print quality in terms of ink spread and black optical density of the print image. Paper properties, like air permeability and siting degree, which may influence the ink jet printing were also measured. It was found that black print quality was controlled by starch level and ionic charge on the paper surface. Cationic surface sizing starch improved black ink jet print quality.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1992년도 하계학술대회 논문집 B
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• pp.829-831
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• 1992

Ultrathin metal-oxide-semiconductor(MOS) gate dielectrics have been fabricated by conventional thermal oxidation in $N_2O$ ambient. Compared to oxides grown in $O_2$, $N_2O$ oxides exhibit significantly low flatband voltage and small shift in flatband voltage. $N_2O$ oxidation induces a slight decrease in mobile ionic charge density($N_m$), fixed charge density($N_f$) and surface state charge density($N_{ss}$). This study establishes that $N_2O$ oxides may have a great impact on future MOS ULSI technology in which ultrathin gate dielectrics are required.

• 펄프종이기술
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• 제29권4호
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• pp.45-52
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• 1997

This study was carried out to investigate the adsorption characteristics of cationic starches onto BKP, BCTMP and talc. Concentration of the unadsorbed cationic starch contained in the supernatant of the pulp or talc slurries was determined using a spectoscopy method and the adsorption isotherm of cationc starch was constructed. When the equilibrium concentration of the cationic starch was low, almost complete adsorption of the starch onto BKP and BCTMP was observed. This indicates that electrostatic attraction is the main driving force for the adsorption of cationc starches onto pulps. BCTMP adsorbed greater amount of cationic starches than BKP since it contained more anionc functional groups on its surface. The adsorption amount of the cationic starch increased as the cationicity of the starches decreased. Surface charge density of the pulp and starch adsorption increased as the pH of the pulp slurry increased. Adsorption amount of the cationic starch onto talc was lower than that onto the pulp due to its low charge density and hydrophobic surface property.

• Korean Chemical Engineering Research
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• 제49권5호
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• pp.554-559
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• 2011

리튬금속을 음전극으로 사용할 때의 안전성과 전극 특성을 개선하기 위해, 리튬금속 표면에 각기 종류가 다른 3가지의 탄소분말을 리튬금속 표면에 물리적으로 코팅한 전극을 제조하고 이를 리튬 2차전지의 음전극으로 채택하여 충방전 특성을 조사하였다. 일차입자의 입경이 작고 비표면적이 큰 탄소분말로 코팅한 음전극을 채택하는 경우가 충진밀도가 높고 표면 거칠기가 낮으며, 충방전 특성도 우수하게 나타났다. 이러한 탄소분말 코팅 효과는 소형 셀일수록 더욱 유리하게 나타났다.