• 한국결정성장학회지
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• 제20권1호
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• pp.1-6
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• 2010

혼합소스 hydride vapor phase epitaxy(HVPE) 방법으로 CuInGaSe(CIGS) 혼합 소스를 형성하였다. 각 금속들은 일정 비율로 혼합하였고, $1090^{\circ}C$에서 1시간 30분간 soaking 하였다. 혼합된 소스를 분말형태로 만든 후, 직경 10 mm 크기의 pellet을 만들었다. 시료는 혼합소스 HVPE 에서 소성 한 후 e-beam 으로 Mo이 증착된 기판 위에 증착하였다. Scanning electron microscope(SEM), Energy dispersive X-ray spectrum(EDS) 그리고 X-ray diffraction(XRD) 측정을 통하여 그 특성을 분석하였으며 박막의 특성은 (112), (204)/(220), (116)/(312)그리고 (400) 방향 등의 다결정 특성을 나타내었다.

• Journal of Periodontal and Implant Science
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• 제37권4호
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• pp.719-732
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• 2007

Purpose: Various bone graft materials are being used for periodontal tissue regeneration. Th materials are being developed continuously for ideal clinical effects. Therefore, it is necessary to identify the clinical characteristics of each bone graft material through comparing the various bone graft materials statistically and in doing so, proposing a more efficient bone graft material. In this study, the following results were attained through comparing the clinical effects among the bone graft materials, using the statistical method based on the clinical studies published at the department of periodontology of Yonsei hospital. Materials and Method: 6 selected studies of department of Periodontology at Yonsei University Hospital were based on clinical study of bone grafting in intrabony defects. It was compared the clinical parameters among the 6 clinical studies, using the statistical META analysis. Result: When comparing the probing depth reduction, there was a relatively great amount of decease when using the xenograft, Anorganic Bovine Derived Hydroxapatite Bone Matrix/Cell Binding Peptide(ABM/P-15: PepGen $P-15^{(R)}$) and the autogenous bone and absorbable membrane, d, 1-alctide/glycolide copolymer(GC: $Biomesh^{(R)}$). The allogfrafts showed a relatively low decrease in the probing depth and clinical attachment change. It also showed a slight decrease in the bone probing depth. The allografts showed various results according to different bone graft materials. When comparing the ABM/P-15 and bovine bone $powder(BBP^{(R)})$, ABM/P-15 showed a relatively high clinical attachment level and the bovine bone powder showed a relatively high clinical attachment level. The probing depth change and gingival recession change showed a lower value than the mean value between the two bone graft materials. The synthetic bone showed a relatively high decrease in clinical attachment level and periodontal probing depth change. There was a relatively larger amount of gingival recession when using Bioactive Glass(BG) but a relatively low bone regeneration effect was seen. Conclusion: Good restorative results of the periodontal tissue can be attained by applying the various bone graft materials being used today after identifying the accurate clinical effects.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2012년도 제43회 하계 정기 학술대회 초록집
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• pp.218-218
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• 2012

Recently, hexagonal manganites have attracted much attention because of the coexistence of ferroelectricity and antiferromagnetic (AFM) order. The crystal structure of hexagonal manganites consists of $MnO_5$ polyhedra in which $Mn^{3+}$ ion is surrounded by three oxygen atoms in plane and two apical oxygen ions. The Mn ions within Mn-O plane form a triangular lattice and couple the spins through the AFM superexchange interaction. Due to incomplete AFM coupling between neighboring Mn ions in the triangular lattice, the system forms a geometrically-frustrated magnetic state. Among hexagonal manganites, $YMnO_3$, in particular, is the best known experimentally since the f states are empty. In addition, for applications, $YMnO_3$ thin films have been known as promising candidates for non-volatile ferroelectric random access memories. However, $YMnO_3$ has low magnetic order temperature (~70 K) and A-type AFM structure, which hinders its applications. We have synthesized $YMn1_{-x}Cr_xO_3$ (x = 0, 0.05 and 0.1) samples by the conventional solid-state reaction. The powders of stoichiometric proportions were mixed, and calcined at $900^{\circ}C$ for $YMn1_{-x}Cr_xO_3$ for 24 h. The obtained powders were ground, and pressed into 5-mm-thick disks of 1/2-inch diameter. The disks were directly put into the oven, and heated up to $1,300^{\circ}C$ and sintered in air for 24 h. The phase of samples was checked at room temperature by powder x-ray diffraction using a Rigaku Miniflex diffractometer with Cu $K{\alpha}$ radiation. All the magnetization measurements were carried out with a superconducting quantum-interference-device magnetometer. Our experiments point out that the Cr-doped samples show the characteristics of a spin-glass state at low temperatures.

• 한국환경보건학회지
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• 제29권1호
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• pp.51-61
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• 2003

Pollution purification using titanium dioxide (TiO$_2$) photocatalyst has attracted a great deal of attention with increasing number of relent environmental problems. Currently, the application of TiO$_2$ photocatalyst has been focused on purification and treatment of waste water. However. the use of conventional TiO$_2$ powder photocatalyst results in disadvantage of stirring during the reaction and of separation after the reaction. And the usage of artificial UV lamp has made the cost of photocatalyst treatment system high. Consequently, we herein studied the pilot-scale design to aid in optimization of the energy-saving process for more through development and reactor design by solar light/UV lamp/ TiO$_2$system. In this study, we manufactured the TiO$_2$sol by sol-gel method. According to analysis by XRD, SEM and TEM, characterization of TiO$_2$ sol were nano-size (5-6 nm) and anatase type. Inorganic binder (SiO$_2$) was added to TiO$_2$ lot to be coated for support strongly, and support of ceramic bead was used to lower separation rate that of glass bead The influences were studied of various experimental parameters such as TiO$_2$ quantity, pH, flow rate. additives, pollutants concentration, climate condition and reflection plate by means of reaction time of the main chararteristics of the obtained materials. In water treatment system, variable realtor as solar light/ or UV lamp according to climate condition such as sunny and cloudy days treated the phenol and E-coli(Escherichia coli) effectively.

• 한국재료학회지
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• 제22권9호
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• pp.494-498
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• 2012

Geopolymer cements and geopolymer resins are newly advanced mineral binders that are used in order to reduce the carbon dioxide generation that accompanies cement production. The effect of additives on the compressive strength of geopolymerized class-F fly ash was investigated. Blast furnace slag, calcium hydroxide($Ca(OH)_2$), and silica fume powders were added to fly ash. A geopolymeric reaction was initiated by adding a solution of water glass and sodium hydroxide(NaOH) to the powder mixtures. The compressive strength of pure fly ash cured at room temperature for 28 days was found to be as low as 291 $kgf/cm^{-2}$, which was not a suitable value for use in engineering materials. On the contrary, addition of 20 wt% and 40 wt% of blast furnace slag powders to fly ash increased the compressive strength to 458 $kgf/cm^{-2}$ and 750 $kgf/cm^{-2}$, respectively. 5 wt% addition of $Ca(OH)_2$ increased the compressive strength up to 640 $kgf/cm^{-2}$; further addition of $Ca(OH)_2$ further increased the compressive strength. When 2 wt% of silica fume was added, the compressive strength increased to 577 $kgf/cm^{-2}$; the maximum strength was obtained at 6 wt% addition of silica fume. It was confirmed that the addition of CaO and $SiO_2$ to the fly ash powders was effective at increasing the compressive strength of geopolymerized fly ash.

• 한국지구과학회지
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• 제38권6호
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• pp.421-426
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• 2017

본 연구에서는 국내 암석을 대표할 수 있는 한국산 지질 표준물질을 제작하기 위해 대상이 되는 시료를 선정하고 암석학적 연구를 실시하였다. 지질 표준물질 대상 암석으로 쥐라기 화강암인 KJG-1와 KJG-2와 함께 백악기 화강암인 KCG-1을 선정하였다. 표준적인 분쇄 과정을 통하여 분말시료를 제조하고, X-선 형광을 위한 유리 비드를 제작하였으며, 최종적으로 시료들의 주성분 원소함량을 구하였다. 분석 자료에는 평균, 표준편차 및 상대 표준편차를 함께 제시하였다. 미국지질조사소(USGS)와 일본지질조사소(GSJ)의 지질표준물질을 함께 분석하여 그들의 참값과의 비교를 통해 5% 내의 정확도를 확인하였으며, 세 시료에 대한 XRF 분석결과 상대표준편차가 3% 내외의 높은 정밀도 역시 확인하였다.

• 한국전기전자재료학회논문지
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• 제25권2호
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• pp.114-120
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• 2012

In this research, we prepared Ga doped zinc oxide(ZnO:Ga, GZO) targets each difference sintering temperature $700^{\circ}C$, $800^{\circ}C$, and doping rate 1 wt.%, 2 wt.%, 3 wt.%. The characteristics of thin film on glass substrates which deposited by facing target sputtering in pure Ar atmosphere are reported. Ga doped zinc oxide film is attracted material through low resistivity, high transmittance, etc. When prepared target powder's structure was investigated by scanning electron microscope, densification and coarsening by driving force was observed. For each ZnO:Ga films with a $Ga_2O_3$ content of 3 wt.% at input power of 45W, the lowest resistivity of $9.967{\times}10^{-4}{\Omega}{\cdot}cm$ ($700^{\circ}C$) and $9.846{\times}10^{-4}{\Omega}{\cdot}cm$ ($800^{\circ}C$) was obtained. the carrier concentration and mobility were $4.09{\times}10^{20}cm^{-3}$($700^{\circ}C$), $4.12{\times}10^{20}cm^{-3}$($800^{\circ}C$) and $15.31cm^2/V{\cdot}s(700^{\circ}C)$, $12.51cm^2/V{\cdot}s(800^{\circ}C)$, respectively. And except 1 wt.% Ga doped ZnO thin film, average transmittance of these samples in the range 350-800 nm was over 80%.

• Current Photovoltaic Research
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• 제2권4호
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• pp.177-181
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• 2014

$Cu_2ZnSn(S_xSe_{1-x})_4$ (CZTSSe) absorber thin films were prepared on Mo coated soda lime glass substrates by sulfo-selenization of sputtered stacked Zn-Sn-Cu precursor thin films. The Zn-Sn-Cu precursor thin films were sulfo-selenized inside a graphite box containing S and Se powder using rapid thermal processing furnace at $540^{\circ}C$ in Ar atmosphere with pre-treatment at $300^{\circ}C$. The effect of different S/Se ratio on the structural, compositional, morphological and electrical properties of the CZTSSe thin films were studied using XRD (X-ray diffraction), XRF (X-ray fluorescence analysis), FE-SEM (field-emission scanning electron microscopy), respectively. The XRD, FE-SEM, XRF results indicated that the properties of sulfo-selenized CZTSSe thin films were strongly related to the S/Se composition ratio. In particular, the CZTS thin film solar cells with S/(S+Se)=0.25 shows best conversion efficiency of 4.6% ($V_{oc}$ : 348 mV, $J_{sc}$ : $26.71mA/cm^2$, FF : 50%, and active area : $0.31cm^2$). Further detailed analysis and discussion for effect of S/Se composition ratio on the properties CZTSSe thin films will be discussed.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2002년도 하계학술대회 논문집 Vol.3 No.2
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• pp.869-873
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• 2002

$Cu_2ZnSnS_4$ (CZTS) thin film is one of the candidate materials for the solar cell. It has an excellent optical absorption coefficient as well as appropriate 1.4~1.5eV band gap. The purpose of this study is replacing a half of high-cost Indium(In) atoms with low-cost Zinc(Zn) atoms and the other half with low-cost Tin(Sn) atoms in the lattice of CIS. In annealing process of thin films deposited with mixture target, the thin films were appeared the peeling. The resistivity was decreased. Thin films were deposited on ITO glass substrates using a compound target which were made by $CU_2S$, ZnS, $SnS_2$ powder were sintered in the atmosphere of Al at room temperature by rf magnetron sputtering We investigated potentialities of a low-cost material for the solar cell by measuring of thin film composition, the structure and optical properties. We could get an appropriate $Cu_2ZnSnS_4$ composition A (112) preferred orientation was appeared without annealing temperature as shown in the diffraction peaks of the CIS cells and was available for photovoltaic thin film materials. The band gap increased from 1.4 to 1.7eV as the composition ratio of Zn/Sn.. The optical absorption coefficient of the thin film was above $10^4cm^{-1}$.

• 한국세라믹학회지
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• 제42권8호
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• pp.554-560
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• 2005

The engineering ceramic needs the properties of high strength, hardness, corrosion-resistance and heat-resistance in order to withstand thermal shock or applied nonuniform stresses without failure. The densely coated porous ceramics can be used for machine component, electromagnetic component, bio-system component and energy-system component by their high-performances from superior coating properties and light-weight characteristics due to the structure including pore by itself. In this study we controlled the porosity of silica and alumina, $8.2\~25.4\%$ and $23.4\~36.0\%$, respectively, by the control of sintering temperature and starting powder size. We made bilayer structures, consisting of a transparent glass coating layer bonded to a thick substrate of different porous ceramics by a thin layer of epoxy adhesive, facilitated observations of crack initiation and propagation. The elastic modulus mismatch could be controlled using different porous ceramics as the substrate layer. Then we applied 150 N force using WC sphere with a radius of 3.18 mm by Hertzian indentation. As a result, the crack initiation in the coating layer was delayed at lower porosity in the substrate layer, and the damage in the coating layer was relatively smaller at the bilayer structure coated on higher elastic substrate.