• The Korean Journal of Ceramics
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• v.1 no.2
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• pp.81-85
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• 1995

PST-series spcimens with stoichimetric and nonstoichimtric compositins were prepared and the effects of compositionl modification on phase formation and dielectric presponse were investigated. The phases formed on calcination were mainly perovskite and trace amount of phyrochlore(s), with an increase of the latter phase(s) as the composition became more ononstoichiometric. The sintered samples showed thermal hysteresis and diffuseness in phase transition with a small degree of frequency relaxation. Temperatures corresponding to maximum values of dielectric constant and loss were relatively insensitive to the composition change while the maximum values were very sensitive to that.

• Economic and Environmental Geology
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• v.40 no.6
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• pp.713-726
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• 2007

The Daebong deposit consists of gold-silver-bearing mesothermal massive quartz veins which fill fractures along fault zones($N10{\sim}20^{\circ}W,\;40{\sim}60^{\circ}SW$) within banded gneiss or granitic gneiss of Precambrian Gyeonggi massif. Ore mineralization of the deposit is composed of massive white quartz vein(stage I) which was formed in the same stage by multiple episodes of fracturing and healing and transparent quartz vein(stage II) which is separated by a major faulting event. The hydrothermal alteration of stage I is sericitization, chloritization, carbonitization, pyritization, silicification and argillization. Sericitic zone occurs near and at quartz vein and includes mainly sericite, quartz, and minor illite, carbonates and epidote. Chloritic zone occurs far from quartz vein and is composed of mainly chlorite, quartz and minor sericite, carbonates and epidote. Fe/(Fe+Mg) ratios of sericite and chlorite range 0.36 to 0.59($0.51{\pm}0.10$) and 0.66 to 0.73($0.70{\pm}0.02$), and belong to muscovite-petzite series and brunsvigite, respectively. Calculated $Al_{IV}-Fe/(Fe+Mg)$ diagrams of sericite and chlorite suggest that this can be a reliable indicator of alteration temperature in Au-Ag deposits. Calculated activities of chlorite end member are $a3(Fe_5Al_2Si_3O_{10}(OH){_6}=0.00964{\sim}0.0291,\;a2(Mg_5Al_2Si_3O_{10}(OH){_6}= 9.99E-07{\sim}1.87E-05,\;a1(Mg_6Si_4O_{10}(OH){_6}=5.61E-07{\sim}1.79E-05$. It suggest that chlorite from the Daebong deposit is iron-rich chlorite formed due to decreasing temperature from $T>450^{\circ}C$. Calculated $log\;{\alpha}K^+/{\alpha}H^+,\;log\;{\alpha}Na^+/{\alpha}H^+,\;log\;{\alpha}Ca^{2+}/{\alpha}^2H^+$ and pH values during wall-rock alteration are $4.6(400^{\circ}C),\;4.1(350^{\circ}C),\;4.0(400^{\circ}C),\;4.2(350^{\circ}C),\;1.8(400^{\circ}C),\;4.5(350^{\circ}C),\;5.4{\sim}6.5(400^{\circ}C)\;and\;5.1{\sim}5.5(350^{\circ}C)$, respectively. Gain elements (enrichment elements) during wallrock alteration are $K_2O,\;P_2O_5,\;Na2O$, Ba, Sr, Cr, Sc, V, Pb, Zn, Be, Ag, As, Ta and Sb. Elements(Sr, V, Pb, Zn, As, Sb) represent a potentially tools for exploration in mesothermal and epithermal gold-silver deposits.

• JSTS:Journal of Semiconductor Technology and Science
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• v.3 no.1
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• pp.13-20
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• 2003

Both MgO and $Sc_2O_3$ are shown to provide low interface state densities (in the $10^{11}{\;}eV^{-1}{\;}cm{\;}^{-2}$ range)on n-and p-GaN, making them useful for gate dielectrics for metal-oxide semiconductor(MOS) devices and also as surface passivation layers to mitigate current collapse in GaN/AlGaN high electron mobility transistors(HEMTs).Clear evidence of inversion has been demonstrated in gate-controlled MOS p-GaN diodes using both types of oxide. Charge pumping measurements on diodes undergoing a high temperature implant activation anneal show a total surface state density of $~3{\;}{\times}{\;}10^{12}{\;}cm^{-2}$. On HEMT structures, both oxides provide effective passivation of surface states and these devices show improved output power. The MgO/GaN structures are also found to be quite radiation-resistant, making them attractive for satellite and terrestrial communication systems requiring a high tolerance to high energy(40MeV) protons.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.29 no.3
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• pp.192-197
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• 2016

A novel heteroleptic ruthenium(II) complex bearing a 4-picolinic acid unit as anchoring ligands (trans-dithiocyanato bis(4-picolinic acid)ruthenium(II) (trans-H1)) was synthesized and its chemical structure was identified by $^1H$-NMR, FT-IR and mass spectroscopy. The optical, thermal, electrochemical and dye adsorption properties of trans-H1 dye were investigated and compared with those of the gold standard ruthenium complex, Ru(4,4'-dicarboxy-2,2'-bipyridine)$_2cis(NCS)_2$ (N3). DSSCs based on trans-H1 dyes were examined under the illumination of AM 1.5 G, $100mWcm^{-2}$ and exhibited typical photovoltaic properties with an open-circuit voltage ($V_{OC}$) of 0.46 V, a short-circuit current ($J_{SC}$) of $4.10mA{\cdot}cm^{-2}$, a fill factor (FF) of 60.4%, and a conversion efficiency (PCE) of 1.14%.

• JSTS:Journal of Semiconductor Technology and Science
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• v.5 no.2
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• pp.131-135
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• 2005

The effect of different surface passivation films on blue or green (465-505 nm) InGaN/GaN multi-quantum well light-emitting diodes (LEDs) die were examined. $SiO_2$ or $SiN_x$ deposited by plasma enhanced chemical vapor deposition, or $Sc_2O_3$ or MgO deposited by rf plasma enhanced molecular beam epitaxy all show excellent passivation qualities. The forward current-voltage (I-V) characteristics were all independent of the passivation film used, even though the MBE-deposited films have lower interface state densities ($3-5{\times}10^{12}\;eV^{-1}\;cm^{-2}$) compared to the PECVD films (${\sim}10^{12}\;eV^{-1}\;cm^{-2}$), The reverse I-V characteristics showed more variation, hut there was no systematic difference for any of the passivation films, The results suggest that simple PECVD processes are effective for providing robust surface protection for InGaN/GaN LEDs.

• Solar Energy
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• v.10 no.3
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• pp.60-65
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• 1990

[ $n^+-p^+$ ] InP homojunction solar cells were fabricated by thermal diffusion of sulphur into a $p^+$-InP wafer($p=4{\times}10^{18}cm^{-3}$), and a SiO film($600{\AA}$ thick) was coated on the $n^+$ layer as an antireflection(AR) coating by an e-beam evaporator. The volume of the cells were $5{\times}5{\times}0.3mm^3$. The front contact grids of the cells with 16 finger pattern of which width and space were $20{\mu}m$ and $300{\mu}m$ respectively, were formed by photo-lithography technique. The junction depth of sulphur were as shallow as about 0.4r m We found out the fabricated solar cells that, with increasing the diffusion time, short circuit current densities($J_{sc}$), series resistances($R_s$) and energy conversion efficiencies(${\eta}$) were increased. The cells show good spectral responses in the region of $5,000-9,000{\AA}$. The short circuit current density, the open circuit voltage( $V_{oc}$), the fill factor(F.F) and the energy conversion efficiency of the cell were $13.16mA/cm^2$, 0.38V, 53.74% and 10.1% respectively.

• Korean Journal of Food Science and Technology
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• v.26 no.5
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• pp.644-648
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• 1994

Lactic acid bacteria(LAB) and its metabolites were tested for their inhibitory effect on the growth of Staphylococcus aureus in vitro. When S. aureus and LAB were incubated simultaneously in MRS broth, the growth of S. aureus began to be suppressed after 12 hour of incubation, completely inactivated within 24 hour of incubation by L. lactis and 48 hour by L. casei, L. acidophilus, and Sc. thermophilus. The pH values of media incubated by S. aureus and LAB were about 4.5 at 12 hour of incubation and 3.5 at 48 hour. The metabolites of the four LAB all exerted antibacterial activity on the growth of S. aureus in TS broth, but is got lost the antibacterial activity by heating ($100^{\circ}C,\;20\;min$). On treating metabolites with catalase, only L. lactis were lost its antibacterial activity. Organic acids (acetate, lactate) showed more active inhibition than inorganic acid (HCl) at pH 3.5, 4.5 but there is no significant differance at pH 5.5, 6.5.

• Journal of the Korean Electrochemical Society
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• v.10 no.4
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• pp.288-294
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• 2007

The LSCF cathode far Solid Oxide Fuel Cell was investigated to develop high performance unit cell at intermediate temperature by modified oxalate method with different electrolytes and different pH. The LSCF powders employed La, Sr, Co and Fe oxides, oxalic acid, ethanol and $NH_4OH$ solution were synthesized with pH controlled as 2, 6, 7, 8, 9 and 10 at $80^{\circ}C$ Single crystalline phase was obtained from pH $2{\sim}9$. on the other hand, $La_2O_3$ appeared from pH 10. Very fine powder with particle size of 50 nm was obtained at calcination temperature of $800^{\circ}C$ for 4 hours. LSCF cathode synthesized at pH 7 showed the highest electric conductivity in the temperature range of $600^{\circ}C$ to $900^{\circ}C$ its value was 950 S/cm at $900^{\circ}C$ Under same synthesis conditions, polarization resistance of each LSCF cathode was changed with different calcination temperatures. As-prepared powder presented 2.52, 1.54 and $2.58\;{\Omega}$ at $600^{\circ}C$ with ScSZ, 8Y-YSZ and GDC as its electrolyte respectively after calcination at $800^{\circ}C$ for 4 hours.

• Journal of the Korean earth science society
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• v.25 no.6
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• pp.443-473
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• 2004

In northern Gohung granitic gneiss, porphyroblastic gneiss and migmatitic gneiss are widely distributed. Gneisses were plotted in granodiorite domain on an lUGS silica-alkali diagram. The amounts of trace elements (Li, Zn, Sc, Sr, Ni, V Y etc.) vs. $SiO_2$, somewhat decreased. Plagioclase showed a wide compositional range ($An_{32-48}$). $X_{alm}$ and $X_{sps}$ were higher in garnet rim and $X_{pyp}$ in garnet core. The rocks in the study area were formed from S and I-type magmas which generated from syn-collision and the late to post-orogenic tectonic environment. Metamorphic P-T conditions u·ere low to medium pressure, high temperature (803-913$^{\circ}C$, 6.1-7.3 kb) and overprinted by retrograde metamorphism (570-726$^{\circ}C$, 2.2-5.1 kb) and chloritization.

• Journal of the Korean institute of surface engineering
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• v.55 no.6
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• pp.368-375
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• 2022

YSZ (Yttria Stabilized Zirconia) is used as a thermal barrier coating material for gas turbines due to its low thermal conductivity and high fracture toughness. However, the operating temperature of the gas turbine is rising according to the market demand, and the problem that the coating layer of YSZ is peeled off due to the volume change due to the phase transformation at a high temperature of 1400℃ or higher is emerging. To solve this problem, various studies have been carried out to have phase stability, low thermal conductivity, and high fracture toughness in a high temperature environment of 1400℃ or higher by doping trivalent and tetravalent oxides to YSZ. In this study, the monoclinic phase formation behavior and crystallinity were comparatively analyzed according to the total doping amount of oxides by controlling the doping amounts of Sc₂O₃ and Gd₂O₃, which are trivalent oxides, and TiO₂, which are tetravalent oxides, in YSZ. Through comparative analysis of monoclinic phase formation and crystallinity, the thermal conductivity of the thermal barrier coating layer according to the amount of doping was predicted.