• Composites Research
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• 제31권4호
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• pp.122-127
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• 2018

섬유강화고분자복합재료(CFRP, Carbon Fiber Reinforced Plastics)의 경량화는 자동차 및 항공 분야에서 끊임없이 요구되고 있으며, 구조용 폼과 CFRP를 혼합하여 샌드위치 복합재료로 사용되고 있다. 본 연구에서는 열경화성 소재인 에폭시 폼과 폴리우레탄 폼 및 열가소성 소재인 PET 폼과 PVC 폼의 조성 차이에 따른 폼의 형상 및 열 노화를 통해 변화되는 기계적 특성 변화를 관찰하였다. 성형한 에폭시 폼, 폴리우레탄 폼 및 상용화된 PET 폼과 PVC폼을 180도에서 열 노화시켰으며, 30, 60, 120, 180분의 노화시간에 따라 구조용 폼의 변화를 광학 현미경 및 만능시험기로 폼 셀의 형상 및 압축강도를 평가하였다. 궁극적으로 에폭시 폼이 가장 높은 2.6 MPa의 압축강도를 가졌으며, 열 노화 조건에서도 물성저하나 형상의 변화가 거의 발생되지 않았다. 이는 에폭시 폼이 타 구조용 폼에 비해 열 노화 조건에서 후경화되어 강직한 조성을 이루며, 타 구조용 폼과는 다르게 내열 특성이 우수하기 때문에 고온용 구조용 폼으로 적용하기 적합한 소재임을 확인하였다.

• 한국전기전자재료학회논문지
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• 제25권12호
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• pp.1009-1014
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• 2012

Hydrogenated amorphous silicon (${\alpha}$-Si:H) layers deposited by plasma enhanced chemical vapor deposition (PECVD) are investigated for use in silicon hetero-junction solar cells employing n-type crystalline silicon (c-Si) substrates. The optical and structural properties of silicon hetero-junction devices have been characterized using spectroscopy ellipsometry and high resolution cross-sectional transmission electron micrograph (HRTEM). In addition, the effective carrier lifetime is measured by the quasi-steady-state photocoductance (QSSPC) method. We have studied on the correlation between the order of ${\alpha}$-Si:H and the passivation quality at the interface of ${\alpha}$-Si:H/c-Si. Base on the result, we have fabricated a silicon hetero-junction solar cell incorporating the ${\alpha}$-Si:H passivation layer with on open circuit voltage ($V_{oc}$) of 637 mV.

• 한국응용과학기술학회지
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• 제15권3호
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• pp.13-19
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• 1998

This study was carried out to investigate characteristics and Pb(II) removal effect of natural Muan, Seosan, Kangjin clays in the batch mode test to develope the low-priced treatment agent of wastewater which contain heavy metals in order structural, optical properties and chemical compositions of natural clays from domestic have been investigated to have high specific surface area and have minerals such as $SiO_2$ and $Al_2O_3$. As a result, removal effects of Pb(II) ions on clays were reached at equilibrium in aqueous solutions by stirring about 20minutes. The removal effect of Pb(II) ions was best for Seosan clay than Muan or Kangjin clays in terms of fixed time. The results show the possibility of continuous treatment system of wastewater which contain heavy metals by using natural clays from domestic.

• 한국고분자학회:학술대회논문집
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• 한국고분자학회 2006년도 IUPAC International Symposium on Advanced Polymers for Emerging Technologies
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• pp.228-228
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• 2006

Conjugated oligomers, used as models for fluorene-thiophene copolymers, are compared in terms of the microscopic morphology of thin deposits and the optical properties. The AFM images and the solid-state absorption and emission spectra are interpreted in line with the structural data, in terms of the assembly of the conjugated molecules. The compound with a terthiophene central unit and fluorene end-groups shows well-defined monolayer-by-monolayer assembly into micrometer-long strip-like structures, with a crystalline herringbone-type organization within the monolayers. Polarized confocal microscopy indicates a strong orientation of the crystalline domains within the stripes. In contrast, the compound with a terfluorene central unit and thiophene end groups forms no textured aggregates. The difference in behavior between the two compounds most probably originates from their different capability of forming densely-packed assemblies of ${\pi-pi}$ interacting molecules. These assemblies are used as active elements in organic field effect transistors designed by using soft lithography technique.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2008년도 추계학술대회 논문집 Vol.21
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• pp.248-249
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• 2008

ZnO (Zinc Oxide) thin film can be applied to various devices. Recently, ZnO film has been promoted in transparent TFTs (thin film transistors) because of high transparency and low temperature process. In this paper, ZnO thin films were grown on glass with the three conditions of RF sputtering power, which are 50W, 75W, 100W. Their structural, electrical and optical properties were investigated by using XRD, UV-Visible spectrometer and 4-point probes. In the ZnO film with 50W process, good crystallinity, high transmittance, and high sheet resistance were shown. In conclusion, the ZnO film with 50W can be an optimal channel layer of TFTs.

• 한국정밀공학회지
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• 제27권8호
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• pp.76-83
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• 2010

Metallic sandwich panels with pyramidal truss structures are high-stiffness and high-strength materials with low weight. In particular, bulk structures have enough space for additional multi-functionalities. In this work, in order to fabricate 3-D structures efficiently, Layered Manufacturing Method (LMM) which was composed of three steps, including crimping process, stacking process and bonding process using rapid infrared brazing, was proposed. The joining time was drastically reduced by employing infrared brazing of which heating rate and cooling rate were faster than those of conventional furnace brazing. By controlling the initial cooling rate slowly, the bonding strength was improved up to the level of strength by conventional vacuum brazing. The observation of infrared brazed specimens by optical microscope and SEM showed no defect on the joining sections. The experiments of 1-layered pyramidal structures and 2-layered pyramidal structures subject to 3-point bending were conducted to determine structural advantages of multilayered structures. From the results, the multi-layered structure has superior mechanical properties to the single-layered structure.

• 한국재료학회지
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• 제30권9호
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• pp.441-446
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• 2020

Synthesizing nanostructured thin films of oxide semiconductors is a promising approach to fabricate highly efficient photoelectrodes for hydrogen production via photoelectrochemical (PEC) water splitting. In this work, we investigate the feasibility as an efficient photoanode for PEC water oxidation of zinc oxide (ZnO) nanostructured thin films synthesized via a simple method combined with sputtering Zn metallic films on a fluorine-doped tin oxide (FTO) coated glass substrate and subsequent thermal oxidation of the sputtered Zn metallic films in dry air. Characterization of the structural, optical, and PEC properties of the ZnO nanostructured thin film synthesized at varying Zn sputtering powers reveals that we can obtain an optimum ZnO nanostructured thin film as PEC photoanode at a sputtering power of 40 W. The photocurrent density and optimal photocurrent conversion efficiency for the optimum ZnO nanostructured thin film photoanode are found to be 0.1 mA/㎠ and 0.51 %, respectively, at a potential of 0.72 V vs. RHE. Our results illustrate that the ZnO nanostructured thin film has promising potential as an efficient photoanode for PEC water splitting.

• Bulletin of the Korean Chemical Society
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• 제34권12호
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• pp.3615-3620
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• 2013

Two novel copper(II) bromide complexes with pyridine containing Schiff base ligands, $Cu(pmed)Br_2$ and $Cu(pmed)Br_2$ where pmed = N'-((pyridin-2-yl)methylene)ethane-1,2-diamine (pmed) and dpmed = N,N-diethyl-N'-((pyridin-2-yl)methylene)ethane-1,2-diamine (dpmed) were synthesized and characterized using X-ray single crystal structure analysis, optical and magnetic susceptibility measurements. Crystal structural analysis of $Cu(pmed)Br_2$ showed that the copper(II) ion has a distorted square-pyramidal geometry with the trigonality index of ${\tau}=0.35$ and two intermolecular hydrogen bonds, which result in the formation of two dimensional networks in the ab plane. On the other hand, $Cu(pmed)Br_2$ displayed a near square-pyramidal geometry with the value of ${\tau}=0.06$. In both compounds, the NNN Schiff base and one Br atom occupy the basal plane, whereas the fifth apical position is occupied by the other Br atom at a greater Cu-Br apical distance. The reported complexes show $g_{\mid}$ > $g_{\perp}$ > 2.0023 with a $d_{x2-y2}$ ground state and a penta-coordinated square pyramidal geometry. Variable temperature magnetic susceptibility measurements showed that the developed copper(II) complexes follow the Curie-Weiss law, that is there are no magnetic interactions between the copper(II) ions since the Cu--Cu distance is too far for magnetic contact.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2008년도 춘계학술대회 논문집 센서 박막재료연구회 및 광주 전남지부
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• pp.58-61
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• 2008

$TiO_2$ is a wide band-gap semiconductor (3.4 eV) and can only absorb about 5% of sun light in the ultraviolet light region, which largely limits its practical applications because of the lower utility of sun light and quantum yield. In order to move the absorption edge of $TiO_2$ fims to visible spectrum range, we have made the impurity level within a band-gap of $TiO_2$ thin film by introduction of oxygen vacancy. Oxygen-defected $TiO_2$ thin film have prepared by reactive sputtering with the partial pressure of $Ar:O_2=10:90{\sim}99.33:0.66$ ratio. As a result, we could have the impurity level of about 2.75 eV on condition that oxygen partial pressure is below 7%.

• E2M - 전기 전자와 첨단 소재
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• 제10권9호
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• pp.930-937
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• 1997

Polycrystalline CdTe thin films have been studied for photovoltaic application because of their high absorption coefficient and optimal band energy(1.45 eV) for solar energy conversion. In this study CdTe thin films were deposited on CdS(chemical bath deposition)/ITO(indium tin oxide) substrate by rf-magnetron sputtering under various conditions. Structural optical and electrical properties are investigated with XRD UV-Visible spectrophotometer SEM and solar simulator respectively. The fabricated CdTe/CdS solar cell exhibited open circuit voltage( $V_{oc}$ ) of 610 mV short circuit current density( $J_{sc}$ ) of 17.2 mA/c $m^2$and conversion efficiency of about 5% at optimal sputtering conditions.