유체가 흐르는 원통형 관내의 최적 전기도금을 위한 전류분포의 예측

朱宰伯,鄭在益 弘益大學校 科學技術硏究所 1996 科學技術硏究論文集 Vol.7 No.1

The methmatical model of the tertiary current distribution for the optimum conditions of electroplating inside a cylindrical tube with fluid flows, was stuied. With the assumption of fully developed flow, in the diffusion layer region the steady state equation of laminar convective diffusion was used, in the bulk region the Laplace's equation in cylindrical coordinates was used. The optimum condition of electroplating considered parameters that decide current distribution, was predicted.

정방 Cavity형 전극내 물질전달 분포의 이론적 예측

朱宰伯,李鎭宇 弘益大學校 科學基術硏究所 1999 科學技術硏究論文集 Vol.10 No.2

Prediction of mass transfer rates between the interior surface of small rectangular cavities and the solution glowing past the cavity opening, was investigated by theoretical method. The boundary integral method was used to calculate the viscous shear stress along the cavity surface under the assumption of Stokes flow for aspect ratios(width:depth) between 0.5:1 and 5:1. Based on the distribution of shear stress, the local mass transfer rate was calculated using the Lighthill integral method. The distribution of shear stress was symmetric because of its Stokes flow regime. However the distribution of local mass transfer rate was not symmetric and the largest mass transfer rate was occurred at the right corner of cavity. The mass transfer rate was proportional to the Re⅓ and this is in good agreement with experimental results previously known. The mass transfer rate increased with the increase of aspect ratio, but the method used in this study showed some errors when the aspect ratio exceeded the value of 3.

구리 미소 전극의 전기화학적 용해에 대한 과도기적 특성 변화의 이론적 해석

朱宰伯,鄭容錫 弘益大學校 科學技術硏究所 1998 科學技術硏究論文集 Vol.9 No.2

A transient behavior of a copper micro-band electrode dissolved electrochemically in hydrochloric acid has been solved by BIEM. The indirect method involving the Laplace transformation was used to analyze the system. The local current distribution becomes nonuniform when the dissolution time is proceeded. Especially the current density was increased sharply at the edge of electrode. It was found that the Tafel slope increased as the dissolution time was proceeded. Theoretical results shows that Tafel slope becomes constant value at steady state and the electrochemical dissolution behavior of copper in hydrochloric acid was mass transfer controlled.

졸겔법에 의해 제조된 결정질 LiMn₂O₄의 전기화학적 반응 특성연구

朱宰伯,曺星美 弘益大學校 科學技術硏究所 2001 科學技術硏究論文集 Vol.12 No.-

Lithium secondary batteries is expected to be highlighted as the future mobile electric power source since it is more outstanding in energy density and many other properties compared with the existing secondary batteries. Among the cathode materials of lithium secondary battery, LiMn₂O₄ consists of spinel structure and shows the highest level of operative voltage. The citric acid method, one of the moisture present methods, is easy to control the composition rate and gets less amount of inflow impurities and even the grain size is adjustable in microscopic level so that possibly obtains the sample powder with large surface area and evenly distributed grains, subsequently a lot of research proceeded so far. The initial discharge capacity was 110Ah/g which is corresponding to 74.2% of the theoretical capacity of LiMn₂O₄, 148.21mAh/g. After 20 cycle, it showed 92mAh/g and after 30 cycle, it became 75mAh/g that is a large capacity fading of 31.8%.

단일 충돌 분사법을 이용한 고속 전기도금 시스템의 반응특성 연구

朱宰伯,鄭在益 弘益大學校 科學技術硏究所 1997 科學技術硏究論文集 Vol.8 No.-

For an unsubmerged impinging slot-jet electroplating system, a theoretical model of the current and potential distribution was developed. It was found that hydrodynamic conditions exert a strong effect on performance at high current densities since flow influences mass transfer and also the shape of the free surface that confines the potential field. The capability of achieving selective reaction in the impingement region was found to improve with increased current density and flow rate. Dimensionless criteria for the upper limit of such improvements were established. Also the value of dimensionless parameters to represent the physical characteristics of the system gave significant effects for the determination of electroplating characteristics such as uniformity and selectivity of plating layer.

코발트 회전전극을 이용한 부식 반응 기구 및 산소의 영향에 관한 고찰

朱宰伯 弘益大學校 科學技術硏究所 1994 科學技術硏究論文集 Vol.5 No.-

Electrochemical dissolution behavior of cobalt in sulfate solutions was investigated. Tafel kinetic behavior of cobalt dissolution and hydrogen reduction were measured in acid and alkaline solutions containing sulfate ions at several pH values. Rotating disc electrode was used in order to eliminate the mass transport limitations at the electrode surface. The increase of pH resulted the shift of corrosion potential and the decrease of corrosion current. Also the kinetic mechanism of cobalt dissolution in acid solution was examined. The effect of dissolved oxygen in acidic solution on the corrosion and electrodissolution of cobalt and the oxygen reduction on cobalt were studied with rotating disc electrode. The increase of dissolved oxygen concentration enhanced the corrosion current. The number of electrons consumed in the oxygen reduction process was determined as about 2 in hydrochloric acid and about 4 in sulfuric acid. This indicates that the primary product is hydrogen peroxide in chloride solution and water in sulfate solution in the process of oxygen reduction.

기판내 홀의 전기도금 전류분포에 관한 이론적 연구

朱宰佰 弘益大學校 科學技術硏究所 2005 科學技術硏究論文集 Vol.16 No.-

A theoretical model was developed for the calculation of current distribution problems. The problem in this study is the electroplating through a hole in circuit board. We assumed that the flow pattern was tubular laminar flow through a hole. With use of commercial partial differential equation solver, The model equations was solved successfully. The results of secondary and tertiary current distribution problems showed that the value of applied potential or current was important to determine the uniformity of current distribution rather than the direction of fluid flow.

RuO₂계 슈퍼캐패시터의 전기화학적 특성에 관한 연구

權大哲,朱宰伯 弘益大學校 科學技術硏究所 2004 科學技術硏究論文集 Vol.15 No.-

Recently RuO₂·xH₂O is one of the best candidates for use as a pseudocapacitance material, but ruthenium is a very expensive material compared to activated carbon. In this work, the ruthenium-carbon electrodes were prepared with sol-gel process by dipping the carbon in various concentrations of ruthenium and annealing. Their physical properties were analyzed by BET, SEM, XRD, etc. Prepared electrode was tested by cyclic voltammetry and the specfic capacitances were calculated. The effect of ruthenium content on carbon were observed. Ruthenium-carbon electrode were used for the evaluation of various aqueous electrolytes and the adequate electrolyte were selected. Carbon electrode was prepared and used for the test of nonaqueous electrolyte. The charge-dischage cycle was examined for the performance of EDLC (electric double layer capacitor) cell fabricted in this study. As a result, electrodes with various contents of ruthenium oxide on carbon show good performace as a capacitor electrode. The 10 wt% ruthenium-carbon electrode was tested in various electrolytes such as HCl, NaOH, HNO₃, LiCl, LiOH, H₂SO₄, etc. by cyclic voltammetry method and the specific capacitances in H₂SO₄ and HNO3 solution show the 203 F/g and 157 F/g, respecively, which are about 2-3 times larger than the other electrolytes.

Electrodeposition of palladium on the copper lead frame: Electrode reaction characteristics and the effects of primary additives

Jeh-Beck Ju,이진우,Joong-Do Kim 한국화학공학회 2007 Korean Journal of Chemical Engineering Vol.24 No.6

This study is mainly concerned with the electrodeposition of palladium on the copper alloy lead frame used for semiconductor assembly process. The role and effect of additives on palladium electrodeposition were studied by using various electrochemical methods. Ortho-formylbenzenesulfonic acid as a primary additive was used in palladium plating on the lead frame in this study. The electrochemical characteristics of electrode reaction were measured by the hanging mercury drop electrode for electrochemical system and the qualities of the plated surface of lead frames were also examined. The additive agent in Pd solution could have been classified as the grain refiner. It acted as the electroactive species, which increased the polarization and decreased the roughness, by adsorption on the electrode in palladium pre-plated process. The reduction of palladium ion was identified to be an irreversible reaction and the diffusion coefficient of palladium ion and the reaction rate constant were obtained from chronopotentiometry experiment.

Change of Electrochemical Characteristics Due to the Fe Doping in Lithium Manganese Oxide Electrode

Ju Jeh Beck,Kang Tae Young,Cho Sung Jin,Sohn Tae Won The Korean Electrochemical Society 2004 한국전기화학회지 Vol.7 No.3

Sol-gel method which provides better electrochemical and physiochemical properties compared to the solid-state method was used to synthesize the material of $LiFe_yMn_{2-y}O_4$. Fe was substituted to increase the structural stability so that the effects of the substitution amount and sintering temperature were analyzed. XRD was used for the structural analysis of produced material, which in turn, showed the same cubic spinel structure as $LiMn_2O_4$ despite the substitution of $Fe^{3+}$. During the synthesis of $LiFe_yMn_{2-y}O_4$, as the sintering temperature and the doping amount of Fe(y=0.05, 0.1, 0.2)were increased, grain growth proceeded which in turn, showed a high crystalline and a large grain size, certain morphology with narrow specific surface area and large pore volume distribution was observed. In order to examine the ability for the practical use of the battery, charge-discharge tests were undertaken. When the substitution amount of $Fe^{3+}\;into\;LiMn_2O_4$ increased, the initial discharge capacity showed a tendency to decrease within the region of $3.0\~4.2V$ but when charge-discharge processes were repeated, other capacity maintenance properties turned out to be outstanding. In addition, when the sintering temperature was $800\~850^{\circ}C$, the initial capacity was small but showed very stable cycle performance. According to EVS(electrochemical voltage spectroscopy) test, $LiFe_yMn_{2-y}O_4(y=0,\;0.05,\;0.1,\;0.2)$ showed two plateau region and the typical peaks of manganese spinel structure when the substitution amount of $Fe^{3+}$ increased, the peak value at about 4.15V during the charge-discharge process showed a tendency to decrease. From the previous results, the local distortion due to the biphase within the region near 4.15V during the lithium extraction gave a phase transition to a more suitable single phase. When the transition was derived, the discharge capacity decreased. However the cycle performance showed an outstanding result.