연신 조건에 따른 그래핀/PVDF-HFP 복합 필름의 미세구조 및 물성 분석

김혜림,이선희,Kim, Hyelim,Lee, Sunhee 한국섬유공학회 2017 한국섬유공학회지 Vol.54 No.2

Graphene/poly(vinylidene fluoride-co-hexafluoropropylene)(PVDF-HFP) composite films were prepared by the solution casting method. The resultant 2 wt% graphene/ PVDF-HFP composite films were uniaxially drawn at $50^{\circ}C$, $75^{\circ}C$, and $100^{\circ}C$. Investigation of the surface morphology of these films confirmed that the orientation of the polymer matrix. The XRD results showed ${\alpha}$-phase crystals. With increasing drawing temperature, the (002) reflections of graphene decreased and the (100) and (020) planes of the ${\alpha}$-phase of PVDF-HFP increased. DSC thermograms indicated no change in the melting temperature but a slight increase in crystallinity with increasing drawing temperatures. The surface resistivity of the graphene/PVDF-HFP composite films in the case of $75^{\circ}C$ drawing temperature were slightly lower than those in the case of the other two temperatures.

Au/YBCO 박막의 크기가 퀜치 거동에 미치는 영향

김혜림,임성우,오성용,현옥배,Kim, H.R.,Yim, S.W.,Oh, S.Y.,Hyun, O.B. 한국초전도학회 2008 Progress in superconductivity Vol.9 No.2

We investigated the size effect on quench development in $Au/YBa_2Cu_3O_7$ (YBCO) thin film meander lines on sapphire substrates. The meander lines were fabricated by patterning YBCO films coated with gold layers. The lines were subjected to simulated AC fault current, and immersed in liquid nitrogen during the experiment. After the initial rapid rise, the resistance increased moderately and then slowly. In 4 inch-diameter meander lines, the period during which the resistance increased moderately was considerably longer than in 2 inch-diameter line. Moderate increase of resistance was originated from quench propagation. The film temperature was about 180 K at the point when the propagation was completed. The rate of resistance increase after the quench completion was not affected by the film size.

Quench Development in Coated Conductors

김혜림,박충렬,임성우,유승덕,오성용,현옥배,Kim, H.R.,Park, C.R.,Yim, S.W.,Yoo, S.D.,Oh, S.Y.,Hyun, O.B. The Korean Superconductivity Society 2009 Progress in superconductivity Vol.10 No.2

We measured and analyzed the quench development in coated conductor(CC) tapes. The CC was grown on hastelloy substrates and has an Ag protection layer. The tapes were subjected to simulated AC fault currents for quench development measurement. They were immersed in liquid nitrogen during the experiment. The quench resistance increased rapidly first, and the increase slowed down afterwards. It increased linearly with applied voltage at lower voltages, and depended less strongly on applied voltage at higher voltages. The resistance was compared with that of Au/YBCO films grown on sapphire substrates, and found to increase more monotonously than the latter. Data were analyzed quantitatively with the concept of heat transfer within the tape and the surrounding liquid nitrogen. A heat balance equation was derived and solved, taking into consideration temperature dependence of thermal parameters of the tapes. Solutions, together with values of thermal parameters taken from the literature, explained the data well. Cooling by liquid nitrogen affected the quench development considerably at lower applied voltages. Dependence on applied voltages could be also understood quantitatively.

3원색 분산염료를 이용한 PET 섬유의 Black 염색

김혜림,장혜경,이정진,Kim, Hae-Rim,Jang, Hae-Kyoung,Lee, Jung-Jin 한국섬유공학회 2008 한국섬유공학회지 Vol.45 No.6

In black dyeing of PET fabric, high concentrations of disperse dyes of three primary color are generally required, which leads low exhaustion level of dyes and discharge of unfixed dye into dyehouse effluent. In this study, the effect of combination ratio of dye concentration, liquor ratio, and dyeing pH on dyeing and color property of black dyed PET fabric was investigated. From the results, high K/S values and low lightness $(L^*)$ of PET fabric could be obtained with relatively small amount (1%owf) of yellow dye on condition that red and blue dye were used in high concentration. The dyeing results of red dye were consistent with those of yellow dye while blue dye did not follow the trend. Use of small amount of blue dye and large amount of yellow and red dyes resulted in PET fabric of grayish red color instead of black. Dyeing and color property of black dyed PET fabric were found to be dependent upon dyeing pH while not on liquor ratio.

Temperature Behavior of Superconducting Fault Current Limiters during Quenches

김혜림,심정욱,현옥배,Kim H.-R.,Sim J.,Hyun O.-B. The Korean Superconductivity Society 2005 Progress in superconductivity Vol.6 No.2

We investigated temperature behavior of superconducting fault current limiters (SFCLs) during quenches. Knowledge on temperature behavior during quenches is important to the design of SFCLs, because the temperature of SFCLs is related to their stability. SFCLs were fabricated by patterning $Au/YBa_2Cu_3O_7$ thin films grown on sapphire substrates into meander lines by photolithography. A gold film grown on the back side of the substrate was patterned into a meander line, and used as a temperature sensor. The front meander line was subjected to simulated AC fault currents, and the back line to DC current. They were immersed in liquid nitrogen during the experiment for effective cooling. Overall, temperature at the back side of SFCLs was close to that at the front side. It was closer at the beginning of faults, and at lower applied voltages. Temperature distribution at the back side was even except at the edge, as at the front side. These results tell that the whole SFCL was heated to similar degree during quenches, and that effective cooling of SFCLs at the back side is as important to the stability of SFCLs as at the front side. The results could be explained with the concept of heat transfer within the film.

La_0.6Ba_0.4In_1-yM_yO_3-δ(M=Ga³⁺ , Sc³⁺, Yb³⁺)계 조성의 상생성과 Proton 전도

김혜림,김신,이홍림,Kim, Hye-Lim,Kim, Shin,Lee, Hong-Lim 한국세라믹학회 2002 한국세라믹학회지 Vol.39 No.6

Perovskite 구조를 나타내는 L $a_{0.6}$B $a_{0.4}$I $n_{1-y}$ $M_{y}$ $O_{3{\delta}}$(M=G $a^{3+}$ , S $c^{3+}$ , Y $b^{3+}$ )계 조성의 생성상과 proton 전도성을 관찰하였다. G $a^{3+}$ 이온이 25at% 첨가된 조성은 입방정 단일상을 나타낸 반면 50at% 첨가된 조성에서는 입방정상과 이차상이 함께 생성되었다. S $c^{3+}$ 이온 및 Y $b^{3+}$ 이온이 25at%와 50at%씩 첨가된 조성은 모두 입방정 단일상을 나타내었다. 양이온을 25at% 첨가한 조성에 대해 wet $N_2$ 분위기(P $h_{H_2O}$=6.1hPa)에서 전도도를 측정한 결과, S $c^{3+}$ 이온 및 Y $b^{3+}$ 이온이 첨가된 조성은 proton 전도를 나타내었다. Phase formation and proton conduction of L $a_{0.6}$B $a_{0.4}$I $n_{1-y}$ $M_{y}$ $O_{3-{\delta}}$(M=G $a^{3+}$, S $c^{3+}$, Y $b^{3+}$) system were studied. A cubic perovskite structure with a single phase was formed in all of the compositions of this work except for the composition off=G $a^{3+}$ with y=0.5, viz,L $a_{0.6}$B $a_{0.4}$I $n_{1-y}$G $a_{0.5}$ $O_{3-{\delta}}$ For the compositions of M=S $c^{3+}$and Y $b^{3+}$with y=0.25, proton conduction occurred in wet $N_2$ atmosphere(P $h_{H_2O}$=6.1hPa).X>/=6.1hPa).Pa).

Analysis on Recovery in Au/YBCO thin Film Meander Lines

김혜림,임성우,오성용,현옥배,Kim, H.R.,Yim, S.W.,Oh, S.Y.,Hyun, O.B. The Korean Superconductivity Society 2007 Progress in superconductivity Vol.9 No.1

We investigated recovery in $Au/YBa_2Cu_3O_7$ (YBCO) thin film meander lines on sapphire substrates. The meander lines were fabricated by patterning YBCO films coated with gold layers. The lines were subjected to simulated AC fault current and then small current was applied for recovery measurements. The samples were immersed in liquid nitrogen during the experiment. After the fault, the resistance decreased linearly, first slowly and then fast to zero. The initial slow decrease was due to the decrease of the meander line temperature, whereas the fast decrease was originated from the transition from the normal state to the superconducting state. The recovery speed depended on the size of samples, and was faster in the smaller samples during the whole period of recovery. The experimental results were analyzed quantitatively with the concept of heat transfer within the sample and to the surrounding liquid nitrogen. A heat balance equation was solved for the initial phase of recovery, and an expression for the time dependence of resistance was obtained. The result agreed with data well.

충북 제천 남천초등학교 발명공작교실

김혜림,Kim, Hye-Rim 한국발명진흥회 2006 發明特許 Vol.31 No.2

Scintillation properties of the Gd3Al2Ga3O12 : Ce crystal

김혜림,김홍주,장은정,이원근,기문광,Heun-Duk Kim,전구식,Vladimir Kochurikhin 한양대학교 세라믹연구소 2015 Journal of Ceramic Processing Research Vol.16 No.1

We investigated luminescence and scintillation properties of the Gd3Al2Ga3O12 : Ce (GAGG) crystal grown in TPS(Total Polishing Solution) Co.. The GAGG crystal has the highest light yield among oxide crystal at room temperature and fast decay time for the detection of radioactivity and in nuclear and particle physics experiments and medical imaging. The scintillation properties of the GAGG crystal were studied by comparing the GAGG crystals grown by two companies. We measured an X-ray induced emission spectra, an energy resolution, an absolute light yield and a decay time. A pulse shape discrimination capability for a and g-ray was also demonstrated.

Resistance Development in Au/YBCO Thin Film Meander Lines under High-Power Fault Conditions

김혜림,심정욱,최인지,임성우,현옥배,Kim, H.R.,Sim, J.,Choi, I.J.,Yim, S.W.,Hyun, O.B. The Korean Superconductivity Society 2006 Progress in superconductivity Vol.8 No.1

We investigated resistance development in $Au/YBa_2Cu_3O_7(YBCO)$ thin film meander lines during high-power faults. The meander lines were fabricated by patterning 300 nm thick YBCO films coated with 200 nm thick gold layers into meander lines. A gold film grown on the back side of the substrate was also patterned into a meander line. The front meander line was connected to a high-power fault-test circuit and the back line to a DC power supply. Resistance of both lines was measured during the fault. They were immersed in liquid nitrogen during the experiment. Behavior of the resistance development prior to quench completion could be understood better by comparing resistance of the front meander lines with that of the back. Quench completion point could be determined clearly. Resistance and temperature at the quench completion point were not affected by applied field strength. The experimental results were analyzed quantitatively with the concept of heat transfer within the meander lines/substrate and to the surrounding liquid nitrogen. In analysis, the fault period was divided into three regions: flux-flow region, region prior to quench completion, and region after quench completion. Resistance was calculated for each region, reflecting the observation for quench completion. The calculated resistance in three regions was joined seamlessly and agreed well with data.