• Journal of the Korean institute of surface engineering
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• v.40 no.1
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• pp.11-15
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• 2007

Stable metallic Cu/Zn nanoparticles were prepared in the base oil phase by hydrothermal method. The physical properties, such as crystal structure, crystallite size and crystallinity according to synthesis conditions have been investigated by XRD, FT-IR and TEM. In addition, 4-ball test has been performed in order to investigate the frictional wear properties of prepared nanosized Cu/Zn particles. The peaks of the X-ray diffraction pattern indicate that the particle size was very small and crystallinity of Cu/Zn particles was good. The micrographs of TEM showed that nanosized Cu/Zn particles possessed a spherical morphology with a narrow size distribution. The crystallite size of the Cu/Zn particles synthesized in base oils was 23-30 nm. It was found that the antiwear capacity increases with increasing Cu/Zn concentration. When the concentration of Cu/Zn was 5.0 wt%, the wear scar diameters was 0.38 mm.

• Journal of Microbiology and Biotechnology
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• v.12 no.3
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• pp.437-443
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• 2002

A number of soil and wastewater samples were collected from the vicinity of an effluent treatment plant for the chemical industry. Several microorganisms were screened fur their ability to decolorize the triphenylmethane group of dyes. As a result, a novel crystal violet dye-degrading strain LK-24 was isolated. Taxonomic identification including 16S rDNA sequencing and phylogenetic analysis indicated that the isolate had a $99.5\%$ homology in its 16S rDNA base sequence with Stenotrophomonas maltophilia. The triphenylmethane dye, crystal violet, was degraded extensively by growing cells of Stenotrophomonas maltophilia LK-24 in agitated liquid cultures, although their growth was strongly inhibited in the initial stage of incubation. This group of dyes is toxic, depending on the concentration used. The dye was significantly degraded at a relatively lower concentration, below $100{\mu}g\;ml^-1$, yet the growth of the cells was totally suppressed at a dye concentration of $250{\mu}g\;ml^-1$. The degradation products of crystal violet were identified as 4,4'-bis(dimethylamino)-benzophenone and ${\rho}$-dimethylaminophenol by Gas chromatography-Mass spectrometry. The 4,4'-bis(dimethylamino)-benzophenone was easily obtained in a reasonable yield, as it was not metabolized further by S. maltophilia LK-24; however, the ${\rho}$-dimethylaminophenol was not easily identifiable, as it was further metabolized.

• Proceedings of the Korea Association of Crystal Growth Conference
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• 1996.06a
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• pp.508-508
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• 1996

;The growth of films have considerable interest in the field of superlattice structured multi-layer epitaxy led to realization of new devices concepts. Molecular beam epitaxy (MBE) with in situ observation by reflection high-energy electron diffraction (RHEED) is a key technology for controlled layered growth on the atomic scale in oxide crystal thin films. Also, the combination of radical oxygen source and MBE will certainly accelerate the progress of applications of oxides. In this study, the growth process of single crystal films using by MBE method is discussed taking the oxide materials of Bi-Sr-Ca-Cu family. Oxidation was provided by a flux density of activated oxygen (oxygen radicals) from an rf-excited discharge. Generation of oxygen radicals is obtained in a specially designed radical sources with different types (coil and electrode types). Molecular oxygen was introduced into a quartz tube through a variable leak valve with mass flowmeter. Corresponding to the oxygen flow rate, the pressure of the system ranged from $1{\;}{\times}{\;}10^{-6}{\;}Torr{\;}to{\;}5{\;}{\times}{\;}10^{-5}$ Torr. The base pressure was $1{\;}{\times}{\;}10^{-10}$ Torr. The growth of Bi-oxides was achieved by coevaporation of metal elements and oxygen. In this way a Bi-oxide multilayer structure was prepared on a basal-plane MgO or $SrTiO_3$ substrate. The grown films compiled using RHEED patterns during and after the growth. Futher, the exact observation of oxygen radicals with MBE is an important technology for a approach of growth conditions on stoichiometry and perfection on the atomic scale in oxide. The oxidization degree, which is determined and controlled by the number of activated oxygen when using radical sources of two types, are utilized by voltage locked loop (VLL) method. Coil type is suitable for oxygen radical source than electrode type. The relationship between the flux of oxygen radical and the rf power or oxygen partial pressure estimated. The flux of radicals increases as the rf power increases, and indicates to the frequency change having the the value of about $2{\times}10^{14}{\;}atoms{\;}{\cdots}{\;}cm^{-2}{\;}{\cdots}{\;}S^{-I}$ when the oxygen flow rate of 2.0 seem and rf power 150 W.150 W.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.25 no.1
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• pp.1-5
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• 2015

For the special usage, the effort of developing AlN single crystals has been very hot in the world. The AlN-base UV LEDs are used on the field of sterilization, purification, curing and analyzing, which can advance human's living and medical processes etc.. AlN single crystals were grown by the PVT (Physical vapor transport) method. On the growing process, carbon crucibles with three different types such as normal size, taller than normal and wider than normal were used for comparison. The processing temperature was in the range of $1900{\sim}2100^{\circ}C$ and ambient pressure was 200~1 Torr. When the taller crucible was used, the sublimation mass was greater than normal dimension one but the best condition of growth changes widely. However the wider one gave much sublimation mass and growing condition was more stable than normal dimension. On limited growing furnace system, the changes of crucible dimension of PVT method provide the change of best condition for growth rate, as-grown crystal quality and growth condition stability.

• Journal of the Korean Institute of Telematics and Electronics A
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• v.30A no.12
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• pp.51-59
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• 1993

A 4${\times}10^{19}cm^{3}$ carbon-doped base AlGaAs/GaAs HBY was grown using carbontetracholoride(CCl$_4$) by atmospheric pressure MOCVD. Abruptness of emitter-base junction was characterized by SIMS(secondary ion mass spectorscopy) and the doping concentration of base layer was confirmed by DXRD(double crystal X-ray diffractometry). Mesa-type HBTs were fabricated using wet etching and lift-off technique. The base sheet resistance of R$_{sheet}$=550${\Omega}$/square was measured using TLM(transmission line model) method. The fabricated transistor achieved a collector-base junction breakdown voltage of BV$_{CBO}$=25V and a critical collector current density of J$_{O}$=40kA/cm$^2$ at V$_{CE}$=2V. The 50$\times$100$\mu$$^2$ emitter transistor showed a common emitter DC current gain of h$_{FE}$=30 at a collector current density of JS1CT=5kA/cm$^2$ and a base current ideality factor of ηS1EBT=1.4. The high frequency characterization of 5$\times$50$\mu$m$^2$ emitter transistor was carried out by on-wafer S-parameter measurement at 0.1~18.1GHz. Current gain cutoff frequency of f$_{T}$=27GHz and maximum oscillation frequency of f$_{max}$=16GHz were obtained from the measured Sparameter and device parameters of small-signal lumped-element equivalent network were extracted using Libra software. The fabricated HBT was proved to be useful to high speed and power spplications.

• Journal of the Korean Ceramic Society
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• v.16 no.3
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• pp.135-141
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• 1979

This study seeks to find optimum conditions for the heating schedule of the Diopside-Devitrite system, to find the amounts and the kinds of nucleus which effect the crystal growth and forming nucleus. Generally, crystallization in the glass depends on the number of nucleus growing in the internal system and the rate of crystal growth. In order to obtain homogeneous polystalline phae, Diopside as MgO source and $ZrO_2$.$P_2O_5$, $TiO_2$, NaF, $CaF_2$ as nucleating agents were added to the $Na_2O$.CaO.$6SiO_2$ glass. The results obtained were Summarized as follows. 1) Optimum Batch Composition of base glass is 76.82 wt.% $SiO_2$, 5.84 wt.% CaO, 4.54 wt.% MgO and 9.80 wt.% $Na_2O$. 2) Best heating schedule.140$0^{\circ}C$(Melting)coolinglongrightarrow95$0^{\circ}C$reheatinglongrightarrow$1100^{\circ}C$coolinglongrightarrowRoom Temp. 3) The optimum amounts of $ZrO_2$.$P_2O_5$, $TiO_2$ and $CaF_2$ are 3wt.% and that of NaF is 4 wt.% as a nucleating agents.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.1 no.2
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• pp.94-103
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• 1991

ZnO-$P_2O_5$ system glasses containing 45 to 60 mol% ZnO have been melted at$1200^{\circ}C$and crystallized through controlled heat treatment. The properties of the base glass and crystallized glass were examined with XRD. FTIR. density. thermal expansion, electric conductivity, hardness. The principal crystalline phase was identified as zinc metaphosphate [$Zn(PO_3)_2$ in crystallized glasses containing 45-55mol% ZnO and zinc pyrophosphate ($Zn_2P_2O_7$) in the sample of 60mol% ZnO with X - ray diffraction analysis. Thermal expansion coefficient and DC electrical conductivity were varied with direction of oriented crystalline in the samples containing 50-60mol% ZnO. This suggests the existance of the oriented crystalline.

• Journal of the Korean Ceramic Society
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• v.23 no.5
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• pp.9-16
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• 1986

The effect of $TiO_2$ addition to the 90wt% Cordierite-10wt% Enstatite base glass was investi-gated to understand the crystallization behavior of the glass. Glasses with addition of $TiO_2$ less than 7, 5wt% had a tendency of surface crystallization and were cracked when heat treated and in this case the crystalline phase formed was indialite. glasses with addition of $TiO_2$ more than 10wt% to 15wt% were crystallized in bulk when heat treated and were suitable for glass-ceramics. The highest microhardness 1640kg/$mm^2$ was obtained when the glass of 12.5wt% $TiO_2$ addition was heat treated at 762$^{\circ}C$ for 60 minutes for nucleation and at 1135$^{\circ}C$ for 20 minutes for crystal growth and in general higher microhardness was obtained when crystalline phase of magnesium aluminum titanate and $\mu$-cordierite were developed. Avrami equation for crystal growth kinetics was applicable in glasses of less than 7.5 wt% $TiO_2$ addition and in case of glasses of more than 10wt% $TiO_2$ addition it was not applicable because of too fast crystal growth.

• Korean Journal of Veterinary Research
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• v.50 no.4
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• pp.259-264
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• 2010

Melamine is an organic base and a trimer of cyanamide which contains 66% nitrogen by mass, but it was sometimes illegally added to food products in order to enhance the apparent protein content for the bigger profit. Many Chinese infants and pet animals fed melamine-containing formulas suffered acute kidney failure with renal crystal formation. Fish feeds were also recently found to be contaminated with melamine. This experiment has been designed to determine whether renal crystals can be experimentally induced in crucian carp (Carassius carassius) fed melamine and cyanuric acid (each at 400 mg/kg/day for 3 days) in combination, and to compare experimentally induced crystals with those from pet animals with triazine related renal failure. The results showed that all fish developed gold brown renal crystals arranged in radial spherulites in the renal tubules, similar to those detected in the pet animals.

• Journal of the Korean Applied Science and Technology
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• v.13 no.3
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• pp.51-60
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• 1996

A new one series of chiral schiff's base containing benzylidene aniline moieties was synthesized and characterized by IR, $^1H$ NMR. elementary analysis, and polarized optical microscopy(POM). The yield of these synthetic compounds was in the range of $62{\sim}67^{\circ}C$. The results showed that most of the synthetic compounds were monotropic liquid crystal and exhibited chiral smectic C($Sc^{\ast}$) liquid crystal phases, and the range of phase transition temperature was to $71.4^{\circ}C$ from $45.0^{\circ}C$.