• Proceedings of the KOSOMBE Conference
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• v.1996 no.11
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• pp.327-330
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• 1996

Poly(L-leucine)(PLL)/poly(ethylene oxide)(PEO)/poly (L-leucine)(PLL) block copolymers were synthsized by polymerization of L-leucine N-carboxyanhydride with diamine-terminated PEO for possibility of wound dressing which may have several advantages such as 1) increase of solubility, 2) control of biodegradation, 3) absorption of body fluid. 4) non-immunogenic effect than PLL homopolymer wound dressing aleady commercialized. Water content increased with an increase of PEO content in the block copolymer due to the hydrophilicity of PEO. Release of silver sulfadiazine(AgSD) from AgSD loaded wound dressing increased with an increase of PEO content in the block copolymer. It was found that the number of Pseudomonas aeruginosa decrease with an increase of PEO content due to the fast release of antibacterial agents with an increase of PEO content in the block copolymer.

• Journal of the Korean institute of surface engineering
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• v.33 no.5
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• pp.309-318
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• 2000

The 6063 Aluminium alloy were electrocolored and anodized at the same time in addition of $CoSO_4$, $FeSO_4$, in the electrolyte and investigated by AES/SAM. It was found that the thickness of anodic oxide film is increased linearly in DC type, and DC combined AC type, the more ratio of anodic Portion in AC, the more increased of anodic film thickness. The color of anodic film was changed from silver to yellow when the increase of the ratio of cathodic portion in AC. Also the increase of $CoSO_4$, $FeSO_4$ in the electrolyte, the coloring time is decreased. From the AES/SAM results, the element of anodic oxide film are Al,O and S. The result of depth profile, the most of the S distributed on the surface and the more S is in DC combined AC type than only DC type.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.08a
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• pp.341-341
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• 2011

최근 AMOLED 구동이 가능한 소자에 대한 연구가 활발히 진행중이다. AMOLED구동 가능소자는 LTPS TFT, a-Si TFT, OTFT, Oxide TFT가 있으며 그 중에서 현재 대부분 LTPS TFT를 사용하고 있다. LTPS TFT는 높은 전자 이동도와 안정성을 가지고 있기 때문에 현재 각광 받는 AMOLED에 잘 맞는다. 하지만 LTPS TFT는 고비용, 250$^{\circ}C$ 이상의 공정온도, Substrate가 Glass, Metal로 제한 된다는 문제점이 있으며, 균일성이 낮고 현재 대면적 기술이 부족한 상태이다. 해결방안으로 AMOLED를 타겟으로 하는 Oxide TFT 기술이 떠오르고 있다. Oxide TFT는 이동도가 높고 저온공정이 가능하며 Substrate로 Plastic 기판을 사용할 수가 있어 차후에 Flexible 소자로서의 적용이 가능하다. 또한 기존의 진공장비 사용대신 용액공정이 가능하여 장비사용시간 및 절차를 단축시킬 수 있어 비용적인 유리함을 가지고 있다. Oxide TFT는 단결정 산화물과 다결정 복합 산화물 두 가지 범주를 가지고 있다. Oxide TFT의 재료물질은 ZnO, ZTO, IZO, SnO2, Ga2O3, IGO, In2O3, ITO, InGaO3(ZnO)5, a-IGZO이 있다. 본 연구에서는 산화물질 중 하나인 ZTO를 이용하여 TFT 소자를 제작하였다. 산화물 특성상 열처리 온도에 따라 형성되는 결정의 정도가 다르기 때문에 온도 및 시간 변수에 따른 ZTO의 특성변화에 초점을 맞추어 연구함으로서 최적화된 조건을 찾고자 실험을 진행하였다. 실험을 위한 기판으로 n-type wafer을 사용하였다. PE-CVD 장비를 이용하여 SiNx를 120 nm 증착하고, ZTO 용액을 spin-coating을 이용하여 channel layer을 형성하였다. 균일하게 형성된 ZTO의 결정을 위하여 200$^{\circ}C$, 300$^{\circ}C$, 400$^{\circ}C$, 500$^{\circ}C$에서 1시간, 3시간, 6시간, 10시간의 온도 및 시간 변수를 두어 공기 중에서 열처리 하였다. ZTO는 약 30 nm 두께로 형성되었다. Thermal evaporator를 이용하여 Source, Drain의 알루미늄 전극을 형성하고, wafer 뒷면에는 Silver paste를 이용하여 Gate전극을 만들었다. 제작된 소자를 dark room temperature에서 측정하였다.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.07b
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• pp.735-738
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• 2003

Downsizing electronics requires precision position control with an accuracy of sub-micron order, which demands development of ultra-fine displacive devices. Piezoelectric transducer is one of devices transferring electric field energy into mechanical energy and being capable for fine displacement control. The transducer has been widely used as fine Position control device Multilayer piezoelectric actuator, one of typical piezo-transducer, is fabricated by stacking alternatively ceramic and electrode layers several hundred times followed by cofiring process. Electrode material should be tolerable in the firing process maintaining at ceramic-sintering temperatures up to $1100{\sim}1300^{\circ}C$. Ag-Pd can be used as stable electrode material in heat treatment above $960^{\circ}C$. Besides, adding small quantity ceramic powder allow the actuator to be fabricated in a good shape by diminishing shrinkage difference between ceramic and electrode layers, resulting in avoidance of crack and delamination at and/or nearby interface between ceramic an electrode layers. This study presents synthesis of nano-oxide-added Ag/Pd powders and its feasibility to candidate material tolerable at high temperature. The powders were formed in a co-precipitation process of Ag and Pd in nano-oxide-dispersed solution where Ag and Pd precursors are melted in $HNO_3$ acid.

• Journal of the Korean Chemical Society
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• v.45 no.6
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• pp.549-554
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• 2001

For the development of new COX-2 inhibitor, novel compound were synthesized through induction an arylsulfonyl group to 1-position, an arylcarboxamidyl group to 2-position and an alkyl group to 4-position of L-proline. We started from 4-hydroxy-L-proline, the 4-methylphenylsulfonyl of 1-position was introduced through N-tosylation and the carboxylic acid group was protected by esterification. We sucessfully converted to a various derivatives 4b-d for O-alkyl-(or aralkyl)ation of 4-position using silver oxide as catalysis. The 4-alkyloxy-1-tosyl L-prolines 5b-d were synthesized through base-hydrolysis for the deprotection of carboxylic acid. Final compound 1,2,4-substituted pyrrolidines, 4-alkyloxy-2-phenylcarboxamidyl-1-tosyl pyrrolidines 6a-d were synthesized through the condensation of arylamine with 3 and 5b-d using DCC.

• Applied Chemistry for Engineering
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• v.2 no.2
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• pp.165-174
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• 1991

The kinetics and the mechanism for the selective oxidation of ethylene on the supported monolithic silver catalyst were experimentally investigated in a fixed bed tubular reactor. The formation rates of ethylene oxide and carbon dioxide were measured at the atmospheric pressure with various combinations of partial pressures of ethylene and oxygen at temperature range of $225-300^{\circ}C$, conversion with 1.2-7.5 %, and then the mechanism of the selective oxidation of ethylene was verified. Their formation rates fitted with the Langmuir-Hinshelwood mechnism. The ethylene oxide and carbon dioxide are produced by reation of adsorbed ethylene with monoatomic oxygen adsorbed on the active sites of Ag-surface, and their formation rate equation are expressed as : $R_{EO}={\frac{k_1K_0{^{1/2}}K_EK_SP_{02}{^{3/2}}P_E}{(1+{\sqrt{K_0P_{02}}}+K_EP_E+K_PP_P)^2(1+{\sqrt{K_SP_{02}})^2}}$ $R_C={\frac{k_2K_0{^3}K_EK_S{^{7/2}}P_{02}{^{13/2}}P_E}{(1+{\sqrt{K_0P_{02}}}+K_EP_E+K_PP_P)^7(1+{\sqrt{K_SP_{02}})^7}}$ The activation energies of ethylene oxide and dioxide and carbon dioxide formations can be estimated to be 12.25 and 17.85 Kcal/mol, respectively.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.31 no.1
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• pp.55-60
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• 2018

Transparent conductive thin films (TCFs) are essential materials for solar cells, organic light-emitting diodes, and display panels. Indium tin oxide (ITO) is one of the most widely used commercial materials to create TCFs'; however, new materials that can possibly replace ITO at a lower cost and/or those possessing mechanical flexibility are urgently needed. Silver nanowire (AgNW) is one of those promising materials, as it is less expensive and possesses superior mechanical flexibility as compared to ITO. We used AgNW and sol-gel ZnO to fabricate composite thin films by spray coating. We propose two spray-coating methods: the 'metal-organic chemical vapor deposition (MOCVD)/AgNW' method and the Mixture method. These two methods are expected to be commercialized for high-quality and low-cost products, respectively.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.23 no.7
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• pp.521-524
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• 2010

Low loss perovskite niobates and tantalates have been placed on a short list of functional materials for future technologies. In this study, we fabricated Ag(Ta,Nb)$O_3$ thick films on the $Al_2O_3$ substrates by the screen printing method. The Ag(Ta,Nb)$O_3$ powders were fabricated by the mixed oxide method. The sintering temperature and time were $1150^{\circ}C$ and 2 hrs, respectively. The results of XRD analysis showed that the specimens employed in this study had the pesudo cubic structure. The dielectric permittivity and loss tangent of the films have been characterized from 1 kHz to 1 MHz. Also the dielectric permittivity and loss tangent were measured from 303 K to 393 K. The electrical properties of the film are also discussed.

• Journal of the Optical Society of Korea
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• v.19 no.3
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• pp.217-221
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• 2015

Developing a metallization that has low cost and high efficiency is essential in solar-cell industries, to replace expensive silver-based metallization. Ni/Cu two-step metallization is one way to reduce the cost of solar cells, because the price of copper is about 100 times less than that of silver. Alkaline electroless plating was used for depositing nickel seed layers on the front electrode area. Prior to the nickel deposition process, 2% HF solution was used to remove native oxide, which disturbs uniform nickel plating. In the subsequent step, a nickel sintering process was carried out in $N_2$ gas atmosphere; however, copper was plated by light-induced plating (LIP). Plated nickel has different properties under different bath conditions because nickel electroless plating is a completely chemical process. In this paper, plating bath conditions such as pH and temperature were varied, and the metal layer's structure was analyzed to investigate the adhesion of Ni/Cu metallization. Average adhesion values in the range of 0.2-0.49 N/mm were achieved for samples with no nickel sintering process.

• Journal of Powder Materials
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• v.15 no.3
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• pp.221-226
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• 2008

Silver coated copper composite powders were prepared by electroless plating method by controlling the activation and deposition process variables such as feeding rate of silver ions solution, concentration of reductant and molar ratio of activation solution $(NH_4OH/(NH_4)_2SO_4)$ at room temperature. The characteristics of the product were verified by using a scanning electron microscopy (SEM), X-ray diffraction (XRD) and atomic absorption (A.A.). It is noted that completely cleansing the copper oxide layers and protecting the copper particles surface from hydrolysis were important to obtain high quality Ag-Cu composite powders. The optimum conditions of Ag-Cu composite powder synthesis were $NH_4OH/(NH_4)_2SO_4$ molar ratio 4, concentration of reductant 15g/l and feeding rate of silver ions solution 2 ml/min.