• The Korean Journal of Ceramics
• /
• v.5 no.2
• /
• pp.131-136
• /
• 1999

Yttria stabilized zirconia(YSZ) films were deposited on porous NiO substrates and quartz plates by the thermal CVD using $ZrCl_4, YCl_3$ as precursors, and $O_2$ as a reactive gas at atmospheric pressure. The evaporation temperature of $ZrCl_4$ was varied from $250^{\circ}C$ to $550^{\circ}C$ while the temperatures of $YCl_3$ and the substrate were varied from $1000^{\circ}C$ to $1030^{\circ}C$. As the evaporation temperature of $ZrCl_4$ increased, the deposition rate of $ZrO_2$ decreased, contrary to our expectation. As a result of the decreased deposition rate of $ZrO_2$, the yttria content increase. The high evaporation temperature of $ZrCl_4$ makes the well-faceted crystal while the low evaporation temperature leads to the cauliflower-shaped structure. The dependence of the evaporation temperature on the growth rate and the morphological evolution was interpreted by the charged cluster model.

• Journal of the Korean Ceramic Society
• /
• v.26 no.3
• /
• pp.315-322
• /
• 1989

Li2O-Al2O3-SiO2 system glasses contained P2O5, TiO2 and ZrO2as the nucleating agents were melted and formed. The glass was subsequently heated first to nucleate and then to grow the crystals. At constant nucleating agent content the base glass compositions were varied and the influences of these variations on the crystallization behaviour were investigated. The study was made by measurement of thermal expansion coefficient, differential thermal analysis, X-ray diffraction analysis, scanning electron microscope observation and transmission measurement of crystallized glass specimen in visible region. It was shown that the content of crystalline phase decreased with increasing SiO2 content as well as decresing Li2O in the base glass compositions. As the result of X-ray diffrection analysis, the major crystal was $\beta$-quartz solid solution. The degree of crystallinity which was calculated using the noncrystalline scattering methods increased in S-shape with increasing heat treatment time. This change was similar to that in thermal expansion coefficient. The transmissions of 5mm thick samples were 80-90% in visible ray region.

• Journal of Electrical Engineering and Technology
• /
• v.4 no.1
• /
• pp.106-110
• /
• 2009

An amperometric glucose biosensor has been developed using viologen derivatives as a charge transfer mediator between a glucose oxidase (GOD) and a gold electrode. A highly stable self-assembled monolayer (SAM) of thiol-based viologen was immobilized onto the gold electrode of a quartz crystal microbalance (QCM) and GOD was immobilized onto the viologen modified electrode. This biosensor response to glucose was evaluated amperometrically in the potential of -300mV. Upon immobilization of the glucose oxidase onto the viologen modified electrode, the biosensor showed rapid response towards glucose. Experimental conditions influencing the biosensor performance, such as pH potential, were optimized and assessed. This biosensor offered excellent electrochemical responses for glucose concentration below ${\mu}$ mol level with high sensitivity and selectivity and short response time. The levels of the RSDs (<5%) for the entire analyses reflected the highly reproducible sensor performance. A linear calibration range between the current and the glucose concentration was obtained up to $4.5{\times}10^{-4}M$. The detection limit was determined to be $3.0{\times}10^{-6}M$.

• Proceedings of the Korean Institute of Surface Engineering Conference
• /
• 2011.05a
• /
• pp.47-48
• /
• 2011

The effect of solution acidity and organic additives, polyethylene glycol (PEG), on the trivalent chromium electroplating was systematically investigated in the view point of solution stability, electroreduction of trivalent chromium ions and characterization of deposition layer. It was found that, the concentration of fraction chromium complexes in the trivalent chromium bath containing formic acid is strongly depended on pH value. PEG molecules were stable in trivalent chromium bath containing formic acid via studies on electrospray ionization mass spectrometry (ESI-MS) and UV-Vis. However, the presence of PEG molecules decreased the reductive current of hydrogen evolution, increasing of current efficiency higher about 10 % compared with solutions without PEG. Moreover, PEG additives developed the nodular morphology during electroreduction of trivalent chromium ions with the increase of solution acidity and enhanced its current efficiency by maintaining the consumption of complexant, formic acid, at a low speed. In this study, the effect of solution acidity was emphasized important, there, it controlled the formation of complexes in the solution, cathodic film (CF) during deposition, and properties of deposited layer. By electrochemical quartz crystal microbalance (EQCM), studies show that chromium electrodeposition occurs via the formation of intermediate complexes and adsorption on the cathode surface, which hinder the penetration of ions from bulk solution to the cathode surface.

• Proceedings of the KIEE Conference
• /
• 2006.07c
• /
• pp.1305-1306
• /
• 2006

A monolayer assembly of anthracene-viologen linked thiol ($AMVC_{8}SH$) was fabricated on a gold electrode by self-assembly method. Structural property of the self-assembled monolayers (SAMs) was carried out by optical and electrochemical method. Firstly, we investigated PL spectrum and UV/visible absorption for the optical properties in solution state. Secondly, we determined the characteristics of charge transfer in different electrolyte solutions by electrochemical quartz crystal microbalance (EQCM). From the data, the PL spectrum and UV/visible absorption were observed and the well-defined shape peaks were nearly equal charges during redox reactions and existed to an excellent linear relationship between the scan rates and existed to currents. The mass change was determined during redox reaction. The mass change behavior of SAMs was not only governed by the mobility of the ion in the viologen but the valence of the ion in the electrolyte solution.

• Journal of the Korean Applied Science and Technology
• /
• v.14 no.3
• /
• pp.89-95
• /
• 1997

It is well known that the metallo-phthalocyanine(MPcs) are sensitive to toxic gaseous molecules such as $NO_2$ and also chemically and thermally stable. Therefore, lots of MPcs have been studied for the potential chemical sensor for $NO_2$ gas using quartz crystal microbalance or electrical conductivity. In this study, 2,3,9,10,16,17,23,24-[octa-(dodecyloxy)] copper phthalocyanine and 2,3,9,10,16,17,23,24-[octa-(octyloxy)] copper phthalocyanine were synthesized and their possibility of LB film preparation were tested. It was confirmed by using FT-IR, DSC, NMR, UV-Vis absorption spectroscopy and Elemental Analysis that CuPc derivatives were successfully synthesized. From the ${\pi}$-A characteristics and limiting areas of two CuPc derivatives it was found that the preparation of LB films with these CuPc derivatives is possible.

• Journal of the Korean Physical Society
• /
• v.73 no.12
• /
• pp.1834-1839
• /
• 2018

A tabletop ultrafast soft x-ray has been generated from the laser-produce plasma with a femtosecond pulsed Ti:Sapphire laser. The estimated total flux of Al $K{\alpha}$ is of $2.2{\times}10^9photons/sec$ in $4{\pi}$ radian and the parameters related to the optical performance were obtained. The tungsten/silicon multilayer, flat quartz and bent thallium acid phthalate (TLAP) crystal were used for monochromatization of soft x-ray to refine the aluminum $K{\alpha}$ radiation and compared the respective value of $E/{\Delta}E$. To estimate the size of the x-ray source beam generated by a fs laser, the approximation using the FWHM obtained from the x-ray beam scan near the focal point was discussed, and the size of the diameter was about $9.76{\mu}m$.

• Journal of the Korean Crystal Growth and Crystal Technology
• /
• v.31 no.2
• /
• pp.89-95
• /
• 2021

Research on the production of lithium hydroxide (LiOH) has been actively conducted in response to the increasing demand for high nickel-based positive electrode materials for lithium-ion batteries. Herein we studied the conversion of lithium oxide (Li2O) through thermal decomposition of lithium carbonate for the production of lithium hydroxide from lithium carbonate (Li2CO3). The reaction mechanism of lithium carbonate with alumina, quartz and graphite crucible during heat treatment was confirmed. When graphite crucible was used, complete lithium oxide powder was obtained. Based on the TG analysis results, reagent-grade lithium carbonate was heat-treated at 700℃, 900℃ and 1100℃ for various time and atmosphere conditions. XRD analysis showed the produced lithium oxide showed high crystallinity at 1100℃ for 1 hour in a nitrogen atmosphere. In addition, several reagent-grade lithium oxides were reacted at 100℃ to convert to lithium hydroxide. XRD analysis confirmed that lithium hydroxide (LiOH) and lithium hydroxide monohydrate (LiOH·H2O) were produced.

• Journal of the Korean Crystal Growth and Crystal Technology
• /
• v.33 no.5
• /
• pp.174-180
• /
• 2023

Porcelain (white ware, celadon ware) coated with a ferrous sulfate and ferrous/cobalt sulfate was sintered at 1250℃. The specimens were investigated by HR-XRD, FE-SEM, HR-EDS, and UV-vis spectrophotometer. Through X-ray rietveld quantitative analysis, quartz and mullite were found to be the main phases for white ware, and mullite and plagioclase were found to be the main phases for celadon ware. When the pigment of ferrous/cobalt sulfate was applied, were identified as an andradite phase for celadon ware and a spinel phase for the white ware, and the amorphous phase, respectively. The L^* value, which was the brightness of the specimen, was 72.01, 60.92 for white ware and celadon ware, respectively. The ferrous and ferrous/cobalt pigment coated porcelain had L^* values of 44.89, 52.27 for white ware and celadon ware, respectively; with a^* values of 2.12, 1.40, an d at b^* values of 1.45 and 13.79. As for the color of the specimens, it was found that the L^* value was greatly affected by the white ware, and the b^* value differed greatly depending on the clay. It was thought to be closely related to the production of the secondary phase such as Fe₂O₃ and andradite phase produced in the surface layer.

• Journal of the Korean Crystal Growth and Crystal Technology
• /
• v.34 no.4
• /
• pp.131-138
• /
• 2024

In this study, the microstructure and plasma resistance characteristics of 35Bi₂O₃-15Al₂O₃-50SiO₂ (BiAl SiO) and 35Bi₂O₃-7.5Al₂O₃-50SiO₂-7.5AlF₃ (BiAlSiOF) glass layers coated on sintered alumina substrates were investigated according to the sintering conditions. The coated layers were formed using the bar coating method and then sintered at a temperature in the range of 700~900℃, which corresponds to the temperature before and after the hemisphere forming temperature, after a debinding process. The plasma resistance of the two coated glasses was approximately 2~3 times higher than that of the quartz glass, and in particular, the BiAlSiOF glass film with F added showed higher plasma resistance than BiAlSiO. It is thought to be due to the effect of suppressing the reaction with fluorine gas by adding fluorine to the glass. When the sintering time was increased at 700℃ and 800℃, the plasma resistance of both glasses improved, but when the sintering temperature was increased to 900℃, the plasma resistance decreased again (i.e., the etching rate increased). This phenomenon is thought to be related to the crystallization behavior of both glasses. The change in plasma resistance depending on the sintering conditions is thought to be related to the appearance of Al and Bi-rich phases.