• Journal of the Korean Ceramic Society
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• v.32 no.11
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• pp.1262-1268
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• 1995

Photoelectrochemical properties of p-GaAs electrode have been investigated. I-V characteristic shows that the cathodic photocurrent is observed at -0.7 V vs. SCE. The photoresponse at near 870~880nm wavelength indicates that the photogenerated carriers contibuted to the observed current. The maximum converson efficiency of 35% is obtained for a Xe lamp light source at 400nm. In C-V relation, capacitance peaks appeared at the frequencies of 100Hz and 300Hz due to the activation of the interfacial states which exist at the energy level corresponding to the one-third of the GaAs band gap. The difference of about 1.1V between flatband potential (Vfb) from the Mott-Schottky method and onset voltage from I-V curve is observed due to the trap of carriers at the interfacial states in the boundary between GaAs and electrolyte. In case of WO3 deposited p-GaAs electrode, higher positive onset current and photocurent density are obtained. This can be explained by the fact that carriers are generated by light penetrated into the WO3 thin flm as well as p-GaAs substrate and then move into the electrolyte effectively.

• Journal of the Korean Ceramic Society
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• v.37 no.3
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• pp.263-270
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• 2000

The Pt/copper oxide/n-Si electrodes were fabricated by depositing copper oxide thin film of 500${\AA}$ and very thin Pt layer on the n-type (100) Si substrate. hotoelectrochemical properties and stability profiles of the electrodes were investigated as a function of deposition time of Pt layer. As the deposition time of Pt layer increased up to 10 seconds, the photocurrent and quantum efficiency were increased and then decreased with further depositing time. The better cell stability was observed for the electrode with longer deposition time. The improvements in above photoelectrochemical properties indicate that Pt layer acts as a catalyst layer at electrode/electrolyte interface as well as a protective layer. The decreasing tendency of the photocurrent and efficiency for the electrode with Pt layer deposited above 20 seconds was explained as an increases in probbility of electron-hole pair recombination and also the absorbing photon loss at electrode surface due to the excessive thickness of Pt layer. The results were confirmed by impedance spectroscopy, mutiple cycle voltammograms and microstructural analyses.

• Journal of the Korean Ceramic Society
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• v.52 no.3
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• pp.209-214
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• 2015

Silicon nitride films were deposited at $100^{\circ}C$ by using the catalytic chemical vapor deposition technique. The source gas mixing ratio, $R_N=[NH_3]/[SiH_4]$, was varied from 10 to 30, and the hydrogen dilution ratio, $R_H=[H_2]/[SiH_4]$, was varied from 20 to 100. The breakdown field strength reached a maximum value at $R_N=20$ and $R_H=20$, whereas the resistivity decreased in the same sample. The relative permittivity had a positive correlation with the breakdown field strength. The capacitance-voltage threshold curve showed an asymmetric hysteresis loop, which became more squared as $R_H$ increased. The width of the hysteresis window showed a negative correlation with the slope of the transition region, implying that the combined effect of $R_N$ and $R_H$ overides the interface defects while creating charge storage sites in the bulk region.

• Journal of the Korean Ceramic Society
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• v.50 no.6
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• pp.518-522
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• 2013

This study investigatesthe coloration mechanism by identifying the factor that affects thered coloration of copper red glazesin traditional Korean ceramics. The characteristics of the reduction-fired copper red glaze's sections are analyzed using an optical microscope, Raman spectroscopy, scanning electron microscopy (SEM) and energy dispersive x-ray spectroscopy (EDX). The sections observed using an optical microscope are divided into domains of surface, red-bubble, and red band. According to the Raman micro spectroscopy analysis results, the major characteristic peak is identified as silicate in all three domains, and the intensity of $Cu_2O$ increases toward the red band. In addition, it is confirmed that the most abundant CuO exists in the glaze bubbles. Moreover, CuO and $Cu_2O$ exist as fine particles in a dispersed state in the surface domain. Thus, Cu combined with oxygen is distributed evenly throughout the copper red glaze, and $Cu_2O$ is more concentrated toward the interface between body and glaze. It is also confirmed that CuO is concentrated around the bubbles. Therefore, it is concluded that the red coloration of the copper red glaze is revealed not only through metallic Cu but also through $Cu_2O$ and CuO.

• Journal of the Korean Ceramic Society
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• v.53 no.6
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• pp.665-669
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• 2016

$TiO_2/BiVO_4$ layered films were prepared by sol-gel and spin coating methods. X-ray diffraction (XRD), scanning electron microscopy (SEM) and Uv-vis spectroscopy were used to investigate the crystal structure, morphology and ultraviolet-visible absorption of the $TiO_2/BiVO_4$ films. The photocatalytic activity of the prepared films was inspected according to the degradation of methylene blue. The results show that the prepared films present a net chain structure; the absorption band edge had obvious red shift. The degradation of the methylene blue solution was about 80% after 300 mins using $TiO_2/BiVO_4$ layered films under visible light, which was stronger than when using only pure $TiO_2$ film and $BiVO_4$ film.

• Journal of the Korean Ceramic Society
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• v.29 no.2
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• pp.152-160
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• 1992

High-Tc superconductor thick films of YBa2Cu$\chi$O7-y (X=3, 3.5, 4) of which thickness varies from 100 $\mu\textrm{m}$ to 200 $\mu\textrm{m}$ were successfully prepared by plasma spraying method, and the characteristics of thick film depending on copper content and heat treatment conditions were investigated. Regardless of heat-treated temperature, the specimens with X=3 were composed of YBa2Cu$\chi$O7-y, Y2BaCuO5 and BaCuO3 phases. The specimens with X=4, however, were composed of YBa2Cu$\chi$O7-y phase at all heat treatment conditions. The specimens with X=4 composition showed the best superconducting characteristics after heat treatment at 925$^{\circ}C$, and the superconducting transition temperature with zero resistivity (Tc,zero) was 87K. The thick film lost superconductivity when the specimens were heat-treated at 950$^{\circ}C$ because of interdiffusion between superconductor elements and bond coating elements and Y2BaCuO5 phase was found was found to be main phase at the interface.

• Journal of the Korean Ceramic Society
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• v.37 no.4
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• pp.368-375
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• 2000

Fracture toughness of particulate composites of Al2O3/SiC, Al2O3/ZrO2 and Al2O3/ZrO2/SiC was analysed theoretically. According to the suggested particle bridging model for obtaining the R-curve height, the crack extension resistance for the long crack was linearly proportional to the residual calmping stress at the interface between the second phase and the matrix. It was also a function of the particle size and the content. It was confirmed that the rising R-curve behavior of Al2O3 containing 30 vol% SiC particles of 3${\mu}{\textrm}{m}$ was owing to the strong crack bridging by SiC particles. For Al2O3/ZrO2/SiC composites, the tensional stress from the 3${\mu}{\textrm}{m}$ SiC particles was large enough to activate the spontaneous transformation of the ZrO2. The crack extension resistance due to the particle bridging mechanism did not seem to be affected much by the coupled toughening, but its resultant toughness increase could be significantly smaller due to the dependency on the matrix toughness.

• Journal of the Korean Ceramic Society
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• v.33 no.7
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• pp.793-801
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• 1996

The effect of catalysts which was catalyzed by acid($HNO_3$) and base ($NH_4OH$) or not on the surface microst-ructures and consequent dielectric characteristics of the $PbTiO_3$ thin films prepared by sol-gel method were investigated. The result indicated that bse catalyst promoted the phase transformation of perovskite phase while acid catalyst was found to produce most uniform surface microstructure and improved dielectric properties However degradation of properties due to secondary phase formation and non-uniform microstructure at high annealing temperature (>75$0^{\circ}C$) by rapid diffusion of lead was unavoidable in any case as long as $Si_{(100)}$ \ $SiO_2$ \Pt substrate used.

• Journal of the Korean Ceramic Society
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• v.47 no.5
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• pp.357-364
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• 2010

This study was performed to get basic information about properties of high blaine slag cement(HSC) to use shotcrete(or sprayed concrete and mortar). Particle size distribution, setting time and compressive strength test, analysis like as SEM, DSC thermal analysis, XRD was carried out to investigate principle properties of HSC. Setting time of HSC was delayed slightly, but influence of accelerators was more bigger than ordinary portland cement(OPC). Compressive strength of HSC at 28 days was more higher than OPC regardless of using accelerators. Results of analysis showed early period hydration products of HSC is more small and located widely, because of the interface of between cement particle and water is increased as specific surface of cement increase. From the SEM observation and analysis of DSC and XRD results, aluminates accelerators bring on some hydration products like as calcium aluminium hydrates, alkali free accelerators increases ettringite and monosulfates. Aluminates accelerators has a advantage of setting time and early strength, alkali free accelerators increases strength after 7 days.

• Journal of Ceramic Processing Research
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• v.19 no.5
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• pp.413-418
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• 2018

All-solid-state lithium batteries (ASSBs) using inorganic sulfide-based solid electrolytes are considered prospective alternatives to existing liquid electrolyte-based batteries owing to benefits such as non-flammability. However, it is difficult to form a favorable solid-solid interface among electrode constituents because all the constituents are solid particles. It is important to form an effective electron conduction network in composite cathode while increasing utilization of active materials and not blocking the lithium ion path, resulting in excellent cell performance. In this study, a mixture of fibrous VGCF and spherical nano-sized Super P was used to improve rate performance by fabricating valid conduction paths in composite cathodes. Then, composite cathodes of ASSBs containing 70% and 80% active materials ($LiNi_{0.6}Co_{0.2}Mn_{0.2}O_2$) were prepared by a solution-based process to achieve uniform dispersion of the electrode components in the slurry. We investigated the influence of binary carbon additives in the cathode of all-solid-state batteries to improve rate performance by constructing an effective electron conduction network.