• Journal of the Korean Crystal Growth and Crystal Technology
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• v.21 no.5
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• pp.210-213
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• 2011

Glass-ceramics composed of $5Na_2O-36CaO-10TiO_2-xP_2O_5$ could be obtained with $P_2O_5$ content as following procedure: 1) leaching out $Ca_3(PO_4)_2$ crystals between $Ca_3(PO_4)_2$ and $NaTi_2(PO_4)_3$ selectively in 1 N HCl solution for 2 days, and 2) exchanging $Na^+$ ion to $Ag^+$ ion in Ag($NO_3$) solution for 1 day. Scanning electron microscope (SEM) and X-rat diffractometer (XRD) were measured to verify the proper synthesis of glass-ceramics. And anti-bacteria test was accomplished using Staphylococus aureus bacteria. In the results of anti-bacteria test, the bacteria were died perfectly after 3 hours.

• Korean Chemical Engineering Research
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• v.43 no.2
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• pp.206-214
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• 2005

Heterogeneously-catalyzed oxidation of aqueous phase trichloroethylene (TCE) over supported metal oxides has been conducted to establish an approach to eliminate ppm levels of organic compounds in water. A continuous flow reactor system was designed to effect predominant reaction parameters in determining catalytic activity of the catalysts for wet TCE decomposition as a model reaction. 5 wt.% $CoO_x/TiO_2$ catalyst exhibited a transient period in activity vs. on-stream time behavior, suggesting that the surface structure of the $CoO_x$ might be altered with on-stream hours; regardless, it is probable to be the most promising catalyst. Not only could the bare support be inactive for the wet decomposition reaction at $36^{\circ}C$, but no TCE removal also occurred by the process of adsorption on $TiO_2$ surface. The catalytic activity was independent of all particle sizes used, thereby representing no mass transfer limitation in intraparticle diffusion. Very low TCE conversion appeared for $TiO_2$-supported $NiO_x$ and $CrO_x$ catalysts. Wet oxidation performance of supported Cu and Fe catalysts, obtained through an incipient wetness and ion exchange technique, was dependent primarily on the kinds of the metal oxides, in addition to the acidic solid supports and the preparation routes. 5 wt.% $FeO_x/TiO_2$ catalyst gave no activity in the oxidation reaction at $36^{\circ}C$, while 1.2 wt.% Fe-MFI was active for the wet decomposition depending on time on-stream. The noticeable difference in activity of the both catalysts suggests that the Fe oxidation states involved to catalytic redox cycle during the course of reaction play a significant role in catalyzing the wet decomposition as well as in maintaining the time on-stream activity. Based on the results of different $CoO_x$ loadings and reaction temperatures for the decomposition reaction at $36^{\circ}C$ with $CoO_x/TiO_2$, the catalyst possessed an optimal $CoO_x$ amount at which higher reaction temperatures facilitated the catalytic TCE conversion. Small amounts of the active ingredient could be dissolved by acidic leaching but such a process gave no appreciable activity loss of the $CoO_x$ catalyst.

• Journal of the Korean Ceramic Society
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• v.37 no.1
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• pp.63-69
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• 2000

Electrically-induced strain(S) and polarization(P) for Pb(Sc1/2Nb1/2)O3-PbTiO3(1-x)PSN-xPT) crystalline solutions were studied. From the compositional dependence of S and P we could observe two maximum values at x=0.10 and x=0.425. It is considered that PSNT10(x=0.10) composition is the structural phase boundary to indicate the variable order-disorder[VOD] region. PSNT(x=0.425) composition is the morphotropic phase boundary[MPB] to indicate the rhombohedral to tetragonal phase transition. Higher S (0.437%) and P (0.3974$\mu$C/$\textrm{cm}^2$) values were attained by the La substitution (5 wt%) at Pb site in the MPB composition of 57.5PSN-42.5PT.

• Electrical & Electronic Materials
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• v.10 no.7
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• pp.674-681
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• 1997

Ternary compound ceramics, (1-y-x) BaTiO$_3$-y SrTiO$_3$-x MgTiO$_3$(0.00 x 0.20), were fabricated by the conventional ceramic process. The structural and dielectric properties of specimens were investigated while varying the composition and sintering temperature(1,200~1,45$0^{\circ}C$) in order to obtain the optimum condition of capacitor. As is well known, Curie temperature(T$_{c}$) of high dielectric-based ceramic(BaTiO$_3$) was shifted and temperature of capacitance was decreased in according to increase of solid solution with (Sr, Mg)TiO$_3$. As a result, a suitable condition of compound rate for capacitor was obtained such as the BSM-11(0.8BaTiO$_3$-0.1SrTiO$_3$-0.1MgTiO$_3$), and sintering temperature was sintered at 1,25$0^{\circ}C$ for two hours. In this case, dielectric constant<1,300, dielectric loss(tan$\delta$)<0.03, and the variation rate of capacitance had less than 3% in the range -10~7$0^{\circ}C$.>.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.11a
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• pp.91-92
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• 2007

An anomalous positive temperature coefficient of electrical resistivity (PTCR) was investigated in a ferroelectric lead-free perovskite-type compound $(Bi_{0.5}Na_{0.5})TiO_3$ within $BaTiO_3$-based solid solution ceramics. The effect of $Nb_2O_5$ content on the electrical properties and the microstructure of (1 - x) $BaTiO_3-x\;(Bi_{0.5}Na_{0.5})TiO_3$ (BNT) ceramics made using a conventional mixed oxide process also has been studied. The Curie temperature was obviously increased with the increasing of $(Bi_{0.5}Na_{0.5})TIO_3$ content. The Nb - doped BNT ceramics (x=0.01) display low resistivity values of $10^{1{\circ}}C-10^{2{\circ}}C$ ohm.cm at room temperature and the Curie Temperature of $T_c=160^{\circ}C$.

• Korean Journal of Materials Research
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• v.10 no.9
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• pp.607-611
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• 2000

Zr modified $(Ba_{1-x},Sr_x)TiO_3$ thin films as capacitor for high density DRAM were deposited by r.f. magnetron sputtering. The films deposited at various chamber pressure exhibited a polycrystalline structure. The Zr/Ti ratio of the films increased significantly with decreasing the chamber pressure and this variation affected the microstructure and surface roughness of films When chamber pressure increased dielectric constant of the films effected due to decrease of Zr. The thin films prepared in this study show dielectric constant of 380 to 525 at 100KHz. The variation of capacitance and polarization measured as a function of bias voltage suggested that all films were paraelectric phases. Leakage current exhibited smaller value as chamber pressure decrease and the leakage current density of the films deposited above 10mTorr was $10^{-7}~10^{-8}A/cm^2$ order at 200kV/cm. $(Ba_{1-x},Sr_x)(Ti_{1-y},Zr_y)O_3$ thin films in this study appeared to be potential thin film capacitor for high density DRAM.

• Journal of the Microelectronics and Packaging Society
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• v.12 no.2 s.35
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• pp.161-166
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• 2005

Glass formation, thermal property and crystallization behavior were investigated in $xK_2O-(33.3-x)BaO-16.7TiO_2-50SiO_2(mole\%)$ with fresnoite($Ba_2TiSi_2O_8$) crystal by replacement BaO for $K_2O$. As x(0$\le$x$\le$20) contents increased, glass formation became easy, and crystallization temperature moved on to the low temperature. Crystal phase of the $Ba_2TiSi_2O_8$ was confirmed by XRD, and the replaced x was not effected on the formation of new crystals. The kinetics of crystallization of fresnoite were studied by applying the DTA measurements carried out at different heating rates. The average avrami exponent(n) and activation energy were changed $2.26 {\pm}0.1,\;2.03 {\pm}0.1,\;1.93{\pm}0.15$, $279 {\pm}12kJ/mole,\;302{\pm}7kJ/ mole,\;319{\pm}1kJ/mole$ according to x contents, respectively. The replaced x improved the orientation of crystal growth.

• Journal of the Korean Chemical Society
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• v.29 no.6
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• pp.582-591
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• 1985

The thin films of Ti$O_{2-x}$, were prepared by vapor oxidation and Ti$O_2$ single crystal was reduced by heating in argon atmosphere. The photo-electrochemical properties of these samples were studied. When the photocurrent was scanned in 1M NaOH electrolyte solution, several peaks were observed in the vicinity of 320nm in the UV-region and in the vicinity of 520nm, 620nm, and 740nm in the visible-region. Contrary to the previous suppositions, those peaks were produced by the second-order lines from the grating monochromator.

• Korean Journal of Materials Research
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• v.25 no.8
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• pp.423-428
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• 2015

Impedancemetric $NO_x$ (NO and $NO_2$) gas sensors were designed with a stacked-layer structure and fabricated using $LaCr_xCo_{1-x}O_3$ (x = 0, 0.2, 0.5, 0.8 and 1) as the receptor material and $Li_{1.3}Al_{0.3}Ti_{1.7}(PO_4)_3$ plates as the solid-electrolyte transducer material. The $LaCr_xCo_{1-x}O_3$ layers were prepared with a polymeric precursor method that used ethylene glycol as the solvent, acetyl acetone as the chelating agent, and polyvinylpyrrolidone as the polymer additive. The effects of the Co concentration on the structural, morphological, and $NO_x$ sensing properties of the $LaCr_xCo_{1-x}O_3$ powders were investigated with powder X-ray diffraction, field emission scanning electron microscopy, and its response to 20~250 ppm of $NO_x$ at $400^{\circ}C$ (for 1 kHz and 0.5 V), respectively. When the as-prepared precursors were calcined at $700^{\circ}C$, only a single phase was detected, which corresponded to a perovskite-type structure. The XRD results showed that as the Co concentration of the $LaCr_xCo_{1-x}O_3$powders increased, the crystal structure was transformed from an orthorhombic phase to a rhombohedral phase. Moreover, the $LaCr_xCo_{1-x}O_3$ powders with $0{\leq}x<0.8$ had a rhombohedral symmetry. The size of the particles in the $LaCr_xCo_{1-x}O_3$powders increased from 0.1 to $0.5{\mu}m$ as the Co concentration increased. The sensing performance of the stack-structured $LaCr_xCo_{1-x}O_3/Li_{1.3}Al_{0.3}Ti_{1.7}(PO_4)_3$ sensors was found to divide the impedance component between the resistance and capacitance. The response of these sensors to NO gas was more sensitive than that to $NO_2$ gas. Compared to other impedancemetric sensors, the $LaCr_{0.8}Co_{0.2}O_3/Li_{1.3}Al_{0.3}Ti_{1.7}(PO_4)_3$ sensor exhibited good reversibility and reliable sensingresponse properties for $NO_x$ gases.

• Journal of Korean Society for Atmospheric Environment
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• v.26 no.1
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• pp.1-9
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• 2010

In this study, the selective catalytic reduction of $NO_x$ with ammonia was carried out in a filter bag support reactor. The experiments were performed by powder type $MnO_x$ and $V_2O_5$/$TiO_2$ catalyst at low temperature between 130 and $250^{\circ}C$. Also, the effect of $SO_2$ and $H_2O$ on the NO conversion was investigated under our test conditions. The powder type catalysts were analyzed by X-ray photoelectron spectrum (XPS), X-ray diffraction(XRD), scanning electron microscopy (SEM) and thermal gravimetric analysis (TGA). It was observed that NO removal efficiency of the powder type $V_2O_5$/$TiO_2$ catalyst was 85% at low temperature($200^{\circ}C$) under presence of oxygen and that of $MnO_x$ was 50% at the same condition. The powder type $V_2O_5$/$TiO_2$ catalyst, in conclusion, was found to be available for SCR reaction in a filter bag support system.