• 전기화학회지
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• 제27권3호
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• pp.88-96
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• 2024

리튬금속(Li metal)은 높은 비용량과 에너지 밀도, 낮은 표준 전극 전위로 인해 유망한 음극활 물질로 각광받아온 재료이지만, 충·방전 시 발생하는 수지상 결정인 덴드라이트(dendrite)로 인해 안전성 및 수명안정성에 한계가 있었다. 본 연구에서는 나노 파이버(Nano Fiber) 형태의 도전재인 vapor grown carbon fiber (VGCF)와 은(Ag)의 복합체가 코팅된 분리막을 개발하였으며, 해당 분리막이 리튬금속 음극의 전기화학 특성에 미치는 영향을 연구하였다. VGCF와 Ag의 시너지 효과를 확인하기 위하여 표면 처리되지 않은 분리막, VGCF만 단면 코팅 처리된 분리막을 각각 준비하여 Ag-VGCF 분리막과 비교 평가하였다. Bare 분리막의 경우, 초기 충·방전 과정에서 리튬금속 표면이 덴드라이트로 뒤덮인 반면, VGCF 분리막 및 Ag-VGCF 분리막 모두 분리막 표면에 코팅된 전도성 코팅층 내부에 리튬이 석출되는 거동을 보였다. 또한 Ag-VGCF 분리막은 VGCF 분리막 대비 더욱 균일한 형상의 석출 형태를 보였다. 그 결과 Ag-VGCF 분리막은 Bare 분리막 및 VGCF 분리막 대비 향상된 전기화학적 특성을 보였다.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2010년도 춘계학술대회 초록집
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• pp.88.1-88.1
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• 2010

Organic dyes, because of their many advantages, such as high molar extinction coefficients, convenience of customized molecular design for desired photophysical and photochemical properties, inexpensiveness with no transition metals contained, and environment-friendliness, are suitable as photosensitizers for the Dye-sensitized Solar Cell (DSSC). The efficiency of DSSC based on metal-free organic dyes is known to be much lower than that of Ru dyes generally, but a high solar energy-to-electricity conversion efficiency of up to 8% in full sunlight has been achieved by Ito et al. using an indoline dye. This result suggests that smartly designed and synthesized metal-free organic dyes are also highly competitive candidates for photosensitizers of DSSCs with their advantages mentioned above. Recently, the performance of DSSC based on metal-free organic dyes has been remarkably improved by several groups. We had reported the novel organic dye with double electron acceptor chromophore, which was a new strategy to design an efficient photosensitizer for DSSC. To verify the strategy, we synthesized organic dyes whose geometries, electronic structures and optical properties were derived from preceding density functional theory (DFT) and time-dependent density functional theory (TD-DFT) calculations. In this paper, we successfully synthesized the chromophore containing multi-acceptor push-pull system from triphenylamine with thiophene moieties as a bridge unit. Organic dyes with a single electron acceptor and double acceptor system were also synthesized for comparison purposes. The photovoltaic performances of these dyes were compared, and the recombination dark current curves and the incident photon-to-current (IPCE) efficiencies were also measured in order to characterize the effects of the multi-anchoring groups on the open-circuit voltage and the short-circuit current. In order to match specifications required for practical applications to be implemented outdoors, light soaking and thermal stability tests of these DSSCs, performed under $100mWcm^{-2}$ and $60^{\circ}C$ for 1000h.

• 전기학회논문지
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• 제56권6호
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• pp.1092-1098
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• 2007

Since one decade, the detection of HFPD (High frequency Partial Discharge) has been proposed as one of the effective method for the diagnosis of the power component under service in power grids. As a tool for HFPD detection, Metal Foil sensor based on the embedded technology has been commercialized for mainly power cable due to its advantages. Recently, for the on-site noise discrimination, several PA (Pulse analysis) methods have been reported and the related software, such as Neural Network and Fuzzy, have been proposed to separate the PD (Partial Discharge) signals from the noises since their wave shapes are completely different from each other. On the other hand, the relevant fundamental investigation has not yet clearly made while it is reported that the effectiveness of the current methods based on PA is dependant on the types of sensors. Moreover, regarding the identification of the vital defects introducible into the Power Cable, the direct identification of the nature of defects from the PD signals through Metal Foil coupler has not yet been realized. As a trial for solving above shortcomings, different types of software have been proposed and employed without any convincing probability of identification. In this regards, our novel algorithm 'PA Map' based on the pulse analysis is suggested to identify directly the defects inside the power cable from the HFPD signals which is output of the HFCT and metal foil sensors. This method enables to discriminate the noise and then to make the data analysis related to the PD signals. For the purpose, the HFPD detection and PA (Pulse Analysis) system have been developed and then the effect of noise discrimination has been investigated by use of the artificial defects using real scale mockup. Throughout these works, our system is proved to be capable of separating the small void discharges among the very large noises such as big air corona and ground floating discharges at the on-site as well as of identifying the concerned defects.

• 한국재료학회:학술대회논문집
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• 한국재료학회 2011년도 추계학술발표대회
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• pp.18.1-18.1
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• 2011

Some applications of carbon nanotubes (CNTs) as field emitters, such as x-ray tubes and microwave amplifiers, require high current emission from a small emitter area. To emit the high current density, CNT emitters should be optimally fabricated in terms of material properties and morphological aspects including high crystallinity, aspect ratio, distribution density, height uniformity, adhesion on a substrate, low outgassing rate during electron emission in vacuum, etc. In particular, adhesion of emitters on the substrate is one of the most important parameters to be secured for high current field emission from CNTs. So, we attempted a novel approach to improve the adhesion of CNT emitters by incorporating metal oxide layers between CNT emitters. In our previous study, CNT emitters were fabricated on a metal mesh by filtrating the aqueous suspensions containing both highly crystalline thin multiwalled CNTs and thick entangled multiwalled CNTs. However, the adhesion of CNT film was not enough to produce a high emission current for an extended period of time even after adopting the metal mesh as a fixing substrate of the CNT film. While a high current was emitted, some part of the film was shown to delaminate. In order to strengthen the CNT networks, cobalt-nickel oxides were incorporated into the film. After coating the oxide layer, the CNT tips seemed to be more strongly adhered on the CNT bush. Without the oxide layer, the field emission voltage-current curve moved fast to a high voltage side as increasing the number of voltage sweeps. With the cobalt-nickel oxide incorporated, however, the curve does not move after the second voltage sweep. Such improvement of emission properties seemed to be attributed to stronger adhesion of the CNT film which was imparted by the cobalt-nickel oxide layer between CNT networks. Observed after field emission for an extended period of time, the CNT film with the oxide layer showed less damage on the surface caused by high current emission.

• 한국통신학회논문지
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• 제28권7A호
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• pp.433-439
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• 2003

본 논문에서는 광섬유 브래그 격자와 Cr/Au 박막이 단면에 증착된 광섬유를 이용하여 위상 배열 안테나를 광학적으로 구동할 수 있는 새로운 구조의 광 실시간 지연 선로를 제안하였다. 이 구조는 각 안테나 소자에 연결된 광 지연선로에서 금속 박막이 광섬유 브래그 격자 한 개를 대체하기 때문에 광섬유 브래그 격자들로만 구성된 종래의 실시간 지연선로 구조들에 비해 적은 수의 광섬유 브래그 격자를 사용하며, 금속 박막의 반사율이 광범위한 파장대역에서 일정하므로 금속 박막으로부터 반사되는 파장을 선택하기 용이한 장점을 갖고 있다. 0$^{\circ}$와 $\pm$30$^{\circ}$로 빔 주사가 가능한 10 GHz 선형 위상 배열 안테나를 위한 실시간 지연선로를 구현하였으며, 모든 빔 주사각에서 시간 지연 측정 결과는 계산치와 일치하였다. 또한, 제안된 실시간 지연선로로 구동되는 8개의 안테나 소자로 구성된 10 GHz 선형 배열 안테나를 설계하였으며, 이 안테나의 원거리 방사패턴을 시뮬레이션을 통해 구하였다.

• Bulletin of the Korean Chemical Society
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• 제34권12호
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• pp.3681-3689
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• 2013

This study explored a direct SET-photochemical strategy to construct a new family of thioene conjugated-naphthalamide fluorophore based lariat-crown ethers which show strong binding properties towards heavy metal ions. Irradiations of designed nitrogen branched (trimethylsilyl)methylthio-terminated polyethylenoxy-tethered naphthalimides in acidic methanol solutions have led to highly efficient photocyclization reactions to generate naphthalamide based lariat type thiadiazacrown ethers directly in chemo- and regio-selective manners which undergo very facile secondary dehydration reactions during separation processes to produce their corresponding amidoenethio ether cyclic products tethered with electron donating diethyleneoxy- and diethyenethio-side arm chains. Fluorescence and metal cation binding properties of the lariat type enamidothio products were examined. The photocyclized amidoenethio products, thioene conjugated naphthalamide fluorophore containing lariat-thiadiazacrowns exhibited strong fluorescence emissions in region of 330-450 nm along with intramolecular exciplex emissions in region of 450-560 nm with their maxima at 508 nm. Divalent cation $Hg^{2+}$ and $Pb^{2+}$ showed strong binding to sulfur atom(s) in side arm chain and atoms in enethiadiazacrown ether rings which led to significant enhancement of fluorescence from its chromophore singlet excited state and concomitant quenching of exciplex emission. The dual fluorescence emission responses towards divalent cations might provide a new guide for design and development of fluorescence sensors for detecting those metals.

• 한국환경과학회지
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• 제21권4호
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• pp.421-435
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• 2012

Novel $N_2O_2$ tetradentate ligands, H-3BPD and H-2BPD were synthesized. Hydrochloric acid salts of Br-3BPD, Cl-3BPD, Br-2BPD and Cl-2BPD having Br and Cl substituents at the $para$ position of the phenol hydroxyl group, were synthesized. The ligands were characterized by C. H. N atomic analysis, $^1H$ NMR, $^{13}C$ NMR, UV-visible, and mass spectra. The proton dissociation constants ($logK_n{^H}$) of the phenol hydroxyl group and secondary amine of the synthesized $N_2O_2$ ligands were shown by four step wise values. The orders of the calculated overall proton dissociation constants ($log{\beta}_p$) were Br-3BPD < Cl-3BPD < H-3BPD in case of 3BPD and Br-2BPD < Cl-2BPD < H-2BPD in case of 2BPD respectively. The order agreed well with that of $para$ Hammett substituent constants(${\delta}_p$). The stability constants($logK_{ML}$) of the complexes between the synthesized ligands and transition metal(II) ions agreed with the order of $log{\beta}_p$ of the ligands. The order of the $logK_{ML}$ value of the each transition metal (II) ion was Co(II) < Ni(II) < Cu(II) > Zn(II) > Cd(II) > Pb(II), which agreed well with that of Iriving-Williams series.

• 한국분말재료학회지
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• 제20권6호
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• pp.467-473
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• 2013

This research presents a preparation method of dental components by metal injection molding process (MIM process) using titanium scrap. About $20{\mu}m$ sized spherical titanium powders for MIM process were successfully prepared by a novel dehydrogenation and spheroidization method using in-situ radio frequency thermal plasma treatment. The effects of MIM process parameters on the mechanical and biological properties of dental components were investigated and the optimum condition was obtained. After sintering at $1250^{\circ}C$ for 1 hour in vacuum, the hardness and the tensile strength of MIMed titanium components were 289 Hv and 584 MPa, respectively. Prepared titanium dental components were not cytotoxic and they showed a good cell proliferation property.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2004년도 춘계학술대회 논문집
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• pp.21-23
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• 2004

We report experimental results demonstrating a novel metal defined polymer optical waveguide with a low loss in electro-optic polymers for the first time. The polymer optical waveguides are created using a metal film on the top of upper cladding without any conventional etching process. The fabricated waveguides have an excellent lateral optical mode confinement at both 1.31 ${\square}m$ and 1.55 ${\square}m$ wavelength, resulting in a fiber-to lens optical insertion loss of ~ 7 dB at 1.55 ${\square}m$ and ~4.5 dB at 1.31 ${\square}m$ wavelength in a 3.5cm total length for TM polarizations, respectively. We also present the optical loss dependence of the waveguide as a function of optical wavelengths. These results may be used in the complex design of integrated polymer optical circuits that need simpler and cheaper fabrication process.

• 자원리싸이클링
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• 제20권4호
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• pp.58-64
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• 2011

고온에서 PCB 처리를 통한 Au, Ag와 같은 귀금속뿐 아니라 Ni과 같은 주요 회유금속을 회수하기 위한 기초연구로서 CaO-$Al_2O_3$(-$SiO_2$) 및 CaO-$SiO_2$-$CaF_2$ 슬래그를 이용하여 Au, Ag, Ni의 회수거동올 관찰하였다. 슬래그 투입 없이 PCB만으로 용융실험을 수행한 결과 PCB는 거의 용융되지 않았으며, 이로부터 유도전류를 이용한 용융을 촉진할 뿐 아니라 유가금속의 회수를 위해서는 Cu와 갇은 적절한 base metal이 필요함을 확인하였다. 본 연구결과, PCB/Cu ratio는 1 이하가 바람직할 것으로 생각된다. CaO-$Al_2O_3$(-$SiO_2$) 및 CaO-$SiO_2$-$CaF_2$ 슬래그를 투입한 결과, $CaF_2$를 함유하는 fluorosilicate계 슬래그가 calcium aluminate계 슬래그보다 융점과 점도가 낮게 제어되었으며, 이로부터 Au, Ag, Ni의 높은 분배비를 얻을 수 있었다. 점도가 낮은 $CaF_2$ 함유 슬래그 적용 시 높은 유가금속 회수율은 슬래그 내에서 각 금속입자의 등속침강속도가 상승하기 때문인 것으로 평가되었다.