• Journal of the Korea Academia-Industrial cooperation Society
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• v.4 no.3
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• pp.139-144
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• 2003

A flat type micro gas sensor was fabricated on the p-type silicon wafer with low stress Si$_3$N$_4$, whose thickness is 2 ${\mu}{\textrm}{m}$, using MEMS technology. WO$_3$ thin film as a sensing material for detection of NO$_2$ gas was deposited using a tungsten target by sputtering method, followed by thermal oxidation at several temperatures (40$0^{\circ}C$-$600^{\circ}C$) for one hour. NO$_2$ sensitivities were investigated for the WO$_3$ thin films with different annealing temperatures. The highest sensitivity was obtained for the samples annealed at $600^{\circ}C$ when it was operated at 20$0^{\circ}C$. The results of XRD analysis showed the annealed samples had polycrystalline phase mixed with triclinic and orthorhombic structures. The sample exhibits higher sensitivity when the system has less triclinic structure. The sensitivities, $R_{gas}/R_{air},$ operating at 20$0^{\circ}C$ to 5 ppm NO$_2$ of the sample annealed at $600^{\circ}C$ were approximately 90.

• Advances in materials Research
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• v.13 no.3
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• pp.161-171
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• 2024

This study aimed to investigate the effect of physicochemical properties and mix ratios of iron ore (oxide feed): coke (reductant) on the carbothermic reductions of iron ore. Coke size was fixed at ≤63 ㎛ while iron ore size varied between 150-63 ㎛ and ≤63 ㎛ respectively. Mix ratios were changed from 100:0 (reference) to 80:20 and 60:40 while the temperature, heating rate and soaking duration in muffle furnace were fixed at 1100 ℃, 10 ℃/min and 1 hour. Particle size analyzer, XRF, CHNS and XRD analyses were used for determination of raw feed characteristics. The occurrence of phase transformations from various forms of iron oxides to iron during the carbothermal reductions were identified through XRD profiles and supported with weight loss (%). XRF analysis proved that iron ore is of high grade with 93.4% of Fe₂O₃ content. Other oxides present in minor amounts are 2% Al₂O₃ and 1.8% SiO₂ with negligible amounts of other compounds such as MnO, K₂O and CuO. Composite pellet with finer size iron particles (≤63 ㎛) and higher carbon content of 60:40 exhibited 45.13% weight lost compared to 32.30% and 3.88% respectively for 80:20 and 100:0 ratios. It is evident that reduction reactions can only occur with the presence of coke, the carbon supply. The small weight loss of 3.88% at 100:0 ratio occurs due to the removal of moisture and volatiles and oxidations of iron ore. Higher carbon supply at 60:40 leads into better heat and mass transfer and diffusivity during carbothermic reductions. Overall, finer particle size and higher carbon supply improves reactivity and gas-solid interactions resulting in increased reductions and phase transformations.

• Journal of the Society of Cosmetic Scientists of Korea
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• v.30 no.2
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• pp.173-180
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• 2004

Nano sized ZnO particle as 20-30nm applies for material, pigments, rubber additives, gas sensors, varistors, fluorescent substance as well as new material such as photo-catalyst, sensitizer, fluorescent material. ZnO with a particle size in the range 20-30nm has provided to be an excellent UV blocking material in the cosmetics industry, which can be used in sunscreen product to enhance the sun protection factor and natural makeup effect. But pure ZnO particles application limits for getting worse wearing feeling. We make high-functional inorganic-composite that coated with nano-ZnO on the plate-type particle such as sericite, boron nitride and bismuthoxychloride. In this experiment, we synthesized composite powder using hydrothermal precipitation method. The starting material was ZnCl$_2$ Precipitation materials were used hexamethylenetetramine(HMT) and urea. We make an experiment with changing as synthesis factors that are concentrations of starting material, precipitation materials, nuclear formation material, reaction time, and reaction temperature. We analyzed composite powder's shape, crystallization and UV-blocking ability with FE-SEM, XRD, FT-IR, TGA-DTA, In vitro SPF test. The user test was conducted by product's formulator. In the results of this study, nanometer sized ZnD was coated regardless of the type of plate-powder at fixed condition range. When the coated plate-powders were applied in pressed powder product, the glaze of powder itself decreased, but natural make-up effect, spreadability, and adhesionability were increased.

• Journal of the Korean institute of surface engineering
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• v.56 no.2
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• pp.147-151
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• 2023

Transparent ZnO (100 nm thick) and ZnO/Ti/ZnO (ZTZ) films were prepared with radio frequency (RF) and direct current (DC) magnetron sputtering on the glass substrate at room temperature. During the ZTZ film deposition, the thickness of the Ti interlayer was varied, such as 6, 9, 12, and 15 nm, while the thickness of ZnO films was kept at 50 nm to investigate the effect of the Ti interlayer on the crystallization and opto-electrical performance of the films. From the XRD pattern, it is concluded that the 9 nm thick Ti interlayer showed some characteristic peaks of Ti (200) and (220), and the grain size of the ZnO (002) enlarged from 13.32 to 15.28 nm as Ti interlayer thickness increased. In an opto-electrical performance observation, ZnO single-layer films show a figure of merit of 1.4×10^-11 Ω^-1, while ZTZ films with a 9 nm-thick Ti interlayer show a higher figure of merit of 2.0×10^-5 Ω^-1.

• Proceedings of the Korean Ceranic Society Conference
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• 2000.10a
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• pp.204.2-204
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• 2000

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.07a
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• pp.901-904
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• 2001

For the c-axis oriented epitaxial YBa$_2$Cu$_3$O$_{7-{\delta}}$ thin film on r-cut sapphire substrate it is necessary to deposit buffer layers. The CeO$_2$buffer layer was deposited on sapphire substrate using RF magnetron sputtering system. We investigated XRD pattern of CeO$_2$thin films at various sputtering conditions such as sputtering gas ratio, sputtering power, target to substrate distance, sputtering pressure and substrate temperature. The optimum condition was 15 mTorr with deposition pressure, 1:1.2 with $O_2$and Ar ratio and 9cm with target to substrate distance. The CeO$_2$(200) peak was notable for a deposition temperature above 75$0^{\circ}C$. The YBa$_2$Cu$_3$O$_{7-{\delta}}$ was deposited on CeO$_2$buffered r-cut sapphire substrate using pulsed laser ablation. The YBa$_2$Cu$_3$O$_{7-{\delta}}$CeO$_2$(200)/A1$_2$O$_3$thin film was exhibited a critical temperature of 89K.xhibited a critical temperature of 89K.

• Journal of the Korean Electrochemical Society
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• v.11 no.2
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• pp.95-99
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• 2008

This study has made the electrode that is coated zirconium oxide on the titanium by ESD(Electrostatic spray deposition) coating methode. It has investigated the effects of the etching method of a Ti substrate as the preparation, making of zirconium oxide film and electrochemical characteristics of the electrode that is etched on the titanium. The HCl etching develops a fine and homogeneous roughness on the Ti substrate. Fabrication and material properties of the metal oxide electrode, which is known to be so effective to generate ozone and hypochlorous acid (HOCl) as power oxidant, were studied. A proper metal oxide material is focus zirconium oxide through reference. A coating method to enhance the fabrication reproducibility of the zirconium oxide electrode was used ESD coating method by zirconium oxychloride. Zirconium oxide films on the Ti substrate were tested using SEM, XRD, Cyclic voltammetry.

• Journal of the Korean Society of Radiology
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• v.9 no.7
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• pp.439-443
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• 2015

An electrical signals of a conventional radiation medical imaging sensor are obtained by charge integration method. In this study, the polycrystalline cadmium telluride(p-CdTe) film was fabricated by a thermal evaporation method for the photon counting sensor development with excellent resolution in low exposure dose. From the fabricated p-CdTe sensor, the physical properties(SEM, XRD) and the electrical properties(leakage current, x-ray sensitivity, SNR) were evaluated. As a result, the leakage current of below $5nA/cm^2$ and $7{\mu}C/cm^2-R$ of the X-ray sensitivity were showed in below $1V/{\mu}m$. In addition, the signal to noise ratio showed the values of above 5000 at operating voltage.

• Journal of the Korean Ceramic Society
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• v.38 no.12
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• pp.1104-1109
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• 2001

Samples with the nominal composition, B $i_{1.84}$P $b_{0.34}$S $r_{1.91}$C $a_{2.03}$C $u_{3.06}$ $O_{10+}$$\delta$/ high $T_{c}$ superconductors containing As as an additive were fabricated by a solid-state reaction method. Samples with Ag of 10wt%, 30 wt% and 50 wt% each were sintered at 86$0^{\circ}C$~875$^{\circ}C$ for 24 hours. The structural characteristics, critical temperature and grain size with respect to Ag contents were analyzed by XRD(X-ray Diffraction) and SEM(Scanning Electron Microscope), respectively. As Ag contents increased, XRD peaks of g in Bi-2223 phase superconductors intensified and the proportion of the phase transition from Bi-2223 to Bi-2212 was increased.increased.

• Analytical Science and Technology
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• v.26 no.3
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• pp.211-221
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• 2013

This research aims to examine compositional and microstructural properties of grayish-blue-powdered celadon in Wonju Beopcheon-temple site. X-ray fluorescence sequential spectroscopy (XRF) with micro-point analysis, scanning electron microscopy (SEM) with energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD) were applied to determine the chemical composition, microstructure and crystallinity of samples, respectively. As a result, the average compositions of bodies were low silica ($RO_2$) and high flux (RO+$R_2O$). Owing to the high content of calcium oxide the glaze is considered lime type between limealkali type. The body of celdon sheard was found quarts, mullite, microcline, albite. Especially, the body's chemical compositions were compared to the results of previous studies by using a Seger formula. The compositional properties of Grayish-blue-powdered celadon in Wonju Beopcheon-temple site showed diffrently from the the other grayish-blue-powdered celadon.