• Journal of the Korean Chemical Society
• /
• v.54 no.3
• /
• pp.291-294
• /
• 2010

In this study, we demonstrated high-efficiency blue organic light-emitting diodes (OLEDs) employing BCzVBi as a blue fluorescent dye doped into blue host material, DPVBi with various concentration. The optimized blue OLED device having high-efficiency was constructed with structure of NPB (500 ${\AA}$) / DPVBi:BCzVBi-6% (150 ${\AA}$)/$Alq_3$(300 ${\AA}$) / Liq (20 ${\AA}$) / Al (1000 ${\AA}$). The maximum luminescence of blue OLED was 13200 cd/$m^2$ at 13.8 V and current density and maximum efficiency were 26.4 mA/$cm^2$ at 1000 cd/$m^2$ and 4.24 cd/A at 3.9 V, respectively. Luminous efficiency shows two times higher than comparing with non-doped BCzVBi blue OLED whereas $CIE_{x,y}$ coordinate was similar with bare DPVBi blue OLED such as (0.16, 0.19). Electroluminescence of BCzVBi-6% doped blue OLED has two major peaks at 445 nm and 470 nm whereas pure DPVBi's blue peak appears at 456 nm and it is happened through endothermic Forster energy transfer by molecule's vibration between LUMO of DPVBi as host material and LUMO of BCzVBi as dopant in device.

• Applied Chemistry for Engineering
• /
• v.8 no.3
• /
• pp.489-501
• /
• 1997

Electropolymerization of 2-vinylnaphthalene (2-VN) and methylmethacrylate (MMA) with high radiation resistance property was conducted on the surfaces of carbon fibers by using a nonaqueous solution of comonomers dissolved in N,N-dimethylformamide containing sodium nitrate as a supporting electrolyte. The fabrication of carbon fiber/2-VN/MMA prepreg was performed electrochemically in 1:1 comonomer solution. Electropolymerization was conduced by changing the current density, initial comonomer concentration, and reaction time. The weight gain on the surface of the carbon fibers was measured by thermogravimetric analyser (TGA). The highest weight gain of 50 wt% was obtained at 600mA/g~800mA/g current density range, but the weight gain was rapidly decreased above 800mA/g current density. The weight gain was increased with the concentration of comonomer, while the concentration of electrolyte had almost no effect on the weight gain. At 300mA/g current density, weight gain rate was increased abruptly to the initial 30 minutes of reaction time. After that the rate was decreased due to the generation of gas bubbles. In order to check the effect of coated polymers on the radiation resistance, morphology changes before and after $\gamma$-ray irradiation was investigated for the composites.

• Applied Chemistry for Engineering
• /
• v.24 no.4
• /
• pp.396-401
• /
• 2013

Alternating copolymers, poly[9-(2-octyl-dodecyl)-9H-carbazole-alt-4,7-di-thiophen-2-yl-benzo[1,2,5]thiadiazole] (PCD20TBT) and poly[9,10-bis-(2-octyl-dodecyloxy)-phenanthrene-alt-4,7-di-thiophen-2-yl-benzo[1,2,5]thiadiazole] (PN40TBT), were synthesized by the Suzuki coupling reaction. The copolymers were soluble in common organic solvents such as chloroform, chlorobenzene, 1,2-dichlorobenzene, tetrahydrofuran and toluene. The maximum absorption wavelength and the band gap of PCD20TBT were 535 nm and 1.75 eV, respectively. The maximum absorption wavelength and the band gap of PN40TBT were 560 nm and 1.97 eV, respectively. The HOMO and the LUMO energy level of PCD20TBT were -5.11 eV and -3.36 eV, respectively. As for PN40TBT, the HOMO and the LUMO energy level of PCD20TBT were -5.31 eV and -3.34 eV, respectively. The polymer solar cells (PSCs) based on the blend of copolymer and PCBM (1 : 2 by weight ratio) were fabricated. The power conversion efficiencies of PSCs based on PCD20TBT and PN40TBT were 0.52% and 0.60%, respectively. The short circuit current density ($J_{SC}$), fill factor (FF) and open circuit voltage ($V_{OC}$) of the device with PCD20TBT were $-1.97mA/cm^2$, 38.2% and 0.69 V. For PN40TBT, the $J_{SC}$, FF, and $V_{OC}$ were $-1.77mA/cm^2$, 42.9%, and 0.79 V, respectively.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2005.07a
• /
• pp.294-295
• /
• 2005

다중 코어를 이용한 대전류 변압기용 Mn-Zn ferrite를 제조하고 전자기적 특성을 분석하였으며, 제조된 자심재료를 이용하여 변압기를 제조하고 전원장치에 탑재하여 효율특성을 분석하였다. ZnO의 몰비가 증가할수록 혼합 스피넬의 형성을 통한 보아 자자의 증가로 인해 투자율은 증가하고 상대적으로 전력손실이 감소하여 $Fe_2O_3$ : MnO : ZnO = 53 : 36 : 11 mo\% 일 때 가장 우수한 특성을 나타냈고, 열처리 공정의 승온 과정에서부터 산소 분압을 제어하고 최적의 대기압 상수를 산출함으로써 Zn-loss 현상을 최소화하여 ZnO 11 mol%, 대기압 상수 7.7일 때 투자율 2350, 밀도 4.9 $g/cm^3$, 비저항 480 ${\Omega}cm$, 300 mT의 최대 자속 밀도 특성을 갖는 우수한 자심 재료를 개발하였다. 그리고 최소 손실 온도를 $90^{\circ}C$ 이하로 감소시켰으며 100 kHz에서 250 $kW/m^3$의 낮은 전력손실을 나타냈다. 또한 개발된 자심재료를 이용하여 제조된 전원장치는 30~80A의 출력 전류에서 85% 이상의 고효율을 얻었다.

• Applied Chemistry for Engineering
• /
• v.8 no.3
• /
• pp.482-488
• /
• 1997

Copper recovery from waste water of electronic industry has been conducted effectively in a fluidized bed reactor. Initial concentration of copper in the waste water, liquid flow rate in the reactor, reaction temperature and time and current density between the cathode and anode in the reactor have been selected as operating variables. The effects of operating variables on the recovery of copper have been studied. It has found that the copper resolved in the waste water can be recovered continuously by means of a fluidized bed reactor The recovery of copper decreased with an increase in the initial concentration of copper in the waste water, while it increased with increasing reaction time and current density, however, it exhibited its maximum value with the variations of liquid flow rate and reaction temperature. The optimum reaction condition to maintain the copper recovery around 85% is as follows ; $X_o=3wt%$, $U_L=0.5cm/s$, $T=25^{\circ}C$, $I=7A/dm^2$ and t=2hrs within this experimental condition.

• Proceedings of the KWS Conference
• /
• 2009.11a
• /
• pp.30-30
• /
• 2009

GTA 용접에서 용입, 용접부의 크기와 형상이 형성되는 아크 물리학적 현상을 이해함에 있어서 에너지 분포특성은 매우 중요한 인자이다. GTA 용접에서 아크 길이의 변화와 사용된 실드 가스 종류에 따라 음극인 텅스텐 전극 팁의 아크 루트 직경에 큰 변화를 주며, 양극인 모재 쪽의 에너지 분포에 영향을 미치며 된다. 기존의 연구자들은 저전류나 중전류 영역의 GTA 용접에서 텅스텐 전극의 선단각과 용입 형태와 의 관계를 plasma 기류 등에 의해 고찰하거나, 최대 아크압력에 미치는 전극형상의 영향에 대하여 연구하였다. 용접부에 작용하는 아크 압력의 분포는 결국 운동 에너지의 분포이다. 기존의 연구자들에 비하여 보다 간편한 실험을 통하여 양극 모재위의 아크 압력에 의한 에너지 분포특성을 규명하는 연구가 필요하다. 본 연구의 목적은 GTA 용접의 용접전류 100A~200A 영역에서 아크 길이 변화와 Ar 가스에 $H_2$ 혼합에 따른 측정된 아크 압력으로부터 기존연구자들의 아크 물리학적 결과들을 활용하여 양극 모재 위에 작용하는 전류밀도 분포를 유도하는 것이다. GTA 용접에서 아크 길이의 변화와 Ar 가스에 $H_2$ 혼합은 아크 압력분포에 큰 영향을 미치며, 이에 따라 에너지 분포특성에 많은 영향을 미친다. 아크 길이가 증가함에 따라 Ar가스와 $H_2$ 혼합가스의 에너지 분포는 감소하였고, Ar가스에 $H_2$ 혼합에 의해 아크 에너지가 증가하여 용입형상에 큰 영향을 미칠 것으로 판단된다. 이에 대한 연구는 향후 GTA 용접 응용분야 확대 적용될 것이며, 아크 물리학 연구에 기초적이고 아주 중요한 과학적인 자료가 될 것으로 판단된다.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
• /
• v.13 no.4
• /
• pp.160-169
• /
• 1999

Linear pulse rootor (LPM) be suitable a field where smooth linear rootion of high precision is required, because it's structured with minute teeth pitch in airgap of between and stator and roover(forcer). Force and position of LPM are effected sensitively by the teeth pitch, air gap, permanent magnet and excitation current. So, LPM is much important to analyze the force characteristics. llis paper was awlied to perrreance roothed for force calculation at airgap. The airgap of LPM is maintained from the pressure generated by an air-bearing. Simplified airflow and permeance methods will be used to calculate the air gap under static conditions. Therefore, the maximum available force is then derived using the coenergy method with variable air gap, also normal force and linear thrust was acquired from variable minute displacement 1[mm]. 1[mm].

• Transactions of the Korean hydrogen and new energy society
• /
• v.35 no.1
• /
• pp.48-55
• /
• 2024

The electrochemically active site of mixed ionic and electronic conductor (MIEC) as a cathode material is restricted to the triple phase boundary in protonic ceramic fuel cells (PCFCs) due to the insufficient of proton-conducting properties of MIEC. This study primarily focused on expanding the electrochemically active site by La_0.6Sr_0.4Co_0.2Fe_0.8O_3-δ(LSCF6428)-BaZr_0.4Ce_0.4Y_0.1Yb_0.1O_3-δ (BZCYYb4411) composite cathode. The electrochemical properties of the composite cathode were evaluated using anode-supported PCFC single cells. In comparison to the LSCF6428 cathode, the peak power density of the LSCF6428-BZCYYb4411 composite cathode is much enhanced by the reduction in both ohmic and non-ohmic resistance, possibly due to the increased electrochemically active site.

• Journal of the Korean Vacuum Society
• /
• v.10 no.1
• /
• pp.112-118
• /
• 2001

Magnetic field is commonly used in low temperature processing plasmas to enhance the performance of the plasma reactors. E$\times$B magnetron or surface multipole configuration is the most popular. However, the properties of capacitively coupled rf plasma confined by axial static magnetic field have rarely been studied. With these background, the effect of magnetic field on the characteristics of capacitively coupled 13.56 MHz/40 KHz argon plasma was studied, Ion saturation current, electron temperature and plasma potential were measured by Langmuir probe and emissive probe. At low pressure region (~10 mTorr), ion current increases by a factor of 3-4 due to reduction of diffusion loss of charged particles to the wall. Electron temperature slightly increases with magnetic field for 13.56 MHz discharge. However, for 40 KHz discharge, electron temperature decreased from 1.8 eV to 0.8 eV with magnetic field. It was observed that the magnetic field induces large temporal variation of the plasma potential. Particle in cell simulation was performed to examine the behaviors of the space potential. Experimental and simulation results agreed qualitatively.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2010.08a
• /
• pp.236-236
• /
• 2010

단일접합 $n^+-p/p^+$ (p-emitter) 및 $p^+-n/n^+$ (n-emitter) GaAs 태양전지 (Solar Cell)를 각각 제작하여, 그 소자특성을 비교 분석하였다. AM 1.5 (1 sun, $100\;mW/cm^2$) 표준광을 조사할 경우, p-emitter/n-emitter 소자의 개방회로전압 (Voc), 단락회로전류 (Jsc), 충전율 (FF), 효율 (Eff)은 각각 0.910/0.917 V, $15.9/16.1\;mA/cm^2$, 78.7/78.9, 11.4/12.1%로서, n-emitter 소자가 다소 크지만 거의 비슷한 값을 가지고 있었다. 태양전지의 집광 특성을 분석하기 위하여 조사광의 출력에 따른 태양전지의 소자 특성을 측정하였다. 조사광 강도가 높아짐에 따라 p-emitter 소자의 특성은 점진적으로 증가하는 반면, n-emitter는 1.3 sun에서 약 1.4 배의 최대 효율 (17%)을 나타내고 조사광이 더 증가함에 따라 급격히 감소하는 특성을 보여 주었다. (그림 참고) 본 연구에서 사용한 2종류 소자의 층구조는 서로 반대되는 대칭구조로서, 모두 가까이에 위치하고 있는 표면전극 (surface finger) 방향으로 소수전하 (minority carrier)가 이동하고 다수전하 (majority carrier)는 기판 (두께 $350\;{\mu}m$)을 통한 먼 거리의 후면전극 (back electrode)으로 표류 (drift)되도록 설계되어 있다. 이때, n-emitter에서는 이동도 (mobility)와 확산길이 (diffusion length)가 높은 전자가 후면전극으로 이동하기 때문에 적정밀도의 전자-정공 쌍 (EHP)이 여기될 경우에는 Jsc와 Eff가 극대화되지만, 조사광 강도 또는 EHP가 더 높아질 경우에는 직렬저항의 증가와 함께 전류-전압 (I-V)의 이상인자 (ideality factor)가 커짐으로서 FF와 효율이 급격히 감소한 결과로 분석된다. 현재 전산모사를 통한 자세한 분석을 진행하고 있으며, 본 결과는 효율 극대화를 위한 최적 층구조 및 도핑 밀도 설계에 활용할 수 있을 것으로 판단된다.