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용액법을 이용한 [C12mim][TFSI] 용매에서의 Alq3 결정 성장 메커니즘
박세연 ( Se Yeon Park ),최세원 ( Se Won Choi ),오용택 ( Yong Taeg Oh ),신동찬 ( Dong Chan Shin ) 조선대학교 공학기술연구원 2016 공학기술논문지 Vol.9 No.2
The organic semiconductor is promising material for flexible electronics due to many advantages such as simple manufacturing process, inexpensive, and flexibility. The high purity single crystal of the organic semiconductor, however, is not easily obtained and thus degradation of electrical property is a big hurdle for organic electronics applications. We have investigated the growth mechanism of Alq3 single-crystal using a [C12mim][TFSI] ionic liquid as a solvent. Isothermal heat-treatment has been carried out at 100℃ for 1h, 3h, 24h, and 120h with 9 mol% composition. We can make high quality single crystal of Alq3 via just one time process using ionic liquid. The shape of Alq3 single-crystal changes from hollow structure to filled hexagonal-rod shape. Now we are trying to measure the electrical properties of the Alq3 single crystal. Our research could be promising process to improve electrical properties of organic semiconductor such as Organic Light Emitting Diode (OLED), Organic Thin Film Transistor (OTFT), and Organic Solar Cell.
김기현 ( Kim Ki-hyun ),최세원 ( Choi Se-won ),박세연 ( Park Se-yeon ),오용택 ( Oh Yong-taeg ),신동찬 ( Shin Dong-chan ) 조선대학교 공학기술연구원 2016 공학기술논문지 Vol.9 No.3
We investigated thermostability of imidazolium based ionic liquids according to temperature and atmosphere. Mass variation of the ionic liquid corresponding to the temperature was analyzed by thermogravimetric analyzer(TGA). Imidazolium based ionic liquids of [C2mim][TFSI], [C8mim][TFSI], [C12mim][TFSI], which have different alkyl chain length, were used. The color change was evaluated by UV-visible spectrophotometer. The structure change was verified by pH measurements. As the temperature and oxygen concentration increase, the color of the ionic liquid turns to dark brown. The pH number was lowered according to color darkening. [C8mim][TFSI] showed faster color change compared to [C2mim][TFSI]. Color change of [C12mim][TFSI] was slower and to light brown despite long alkyl chain than [C8mim][TFSI]. The color change is strongly related to the thermal stability. Coulombic packing by symmetry affects the thermal stability larger than Van der Waals force generated by the alkyl chain.
소뼈를 원료로 하여 스폰지법으로 제작한 다공성 하이드록시아파타이트 생체 세라믹스
이종국 ( Jong Kook Lee ),음상철 ( Sang Cheol Eum ),최세원 ( Se Won Choi ) 조선대학교 공학기술연구원 2016 공학기술논문지 Vol.9 No.4
Natural hydroxyapatite powder was obtained from the calcination of bovine bones and porous hydroxyapatite bioceramics were fabricated by a polymeric sponge method and pressureless sintering. Slurry for sponge filling was prepared by the mixing of hydroxyapatite powder (47.4wt%), distilled water(49.5wt%), Davan C as a dispersant and PVA 1500 as a binder (0.6 wrt%). Melanin sponge was selected as a porous scaffold, which had large pore size of 50∼200 μm and the porosity about 94%. Sponge filling into pores by slurry was performed by a dipping method. After sintering at 1250 °C for 2 hours, porous hydroxyapatite could be obtained by the burning out of sponge polymer and the forming of new bonding between particles. Porous hydroxyapatite compact was composed of sphere particles 1∼2 μm and had the sintered density of 26% and the porosity of 74%. Two kinds of pores were observed in porous hydroxyapatite compact. Large pores about 100∼500μm had a spherical shape and dispersed with irregular distribution. On the contrary, small pores with 2∼3 μm between particles were homogeneously existed on all of regions.
공업용 순알루미늄의 전기전도도에 미치는 스크랩비율 및 GBF처리조건의 영향
황남규 ( Nam Gyu Hwang ),김영찬 ( Young Chan Kim ),최세원 ( Se Won Choi ),강창석 ( Chang Seok Kang ),홍성길 ( Sung Kil Hong ) 한국주조공학회 2011 한국주조공학회지 Vol.31 No.3
Effects of GBF (gas bubbling filtration) treatment conditions and scrap ratio on the electric conductivity of a commercial pure aluminum for diecasting were investigated using by specific gravity and electrical conductivity measurement system, hydrogen gas analyzer, XRD, and EDS. Electrical conductivities of specimen mixed Al scrap ratio until 60% from 0% were decreased with increasing the precipitates amount and size of AlFeSi ternary intermetallic compound on the grain boundary as well as amount of porosity in the grain. On the other hand, electrical conductivities was reincreased gradually in spite of scrap ratio increase from 80% to 100%. Size of AlFeSi compound formed on the grain boundary were coarsened with the increament of scrap ratios untill 80% and GBF treatment time simultaneously.