• Journal of Korean Society of Environmental Engineers
• /
• v.27 no.3
• /
• pp.253-261
• /
• 2005

Catalytic wet oxidation of ppm levels of trichloroethylene (TCE) in water has been conducted using $TiO_2$-supported cobalt oxides at a given temperature and weight hourly space velocity. 5% $CoO_x/TiO_2$ might be the most promising catalyst for the wet oxidation at $36^{\circ}C$ although it exhibited a transient behavior in time on-stream activity. Not only could the bare support be inactive for the wet decomposition reaction, 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. Characterization of the $CoO_x$ catalyst by acquiring XPS spectra of both fresh and used Co surfaces gave different surface spectral features of each $CoO_x$. Co $2p_{3/2}$ binding energy of Co species exposed predominantly onto the outermost surface of the fresh catalyst appeared at 781.3 eV, which is very similar to the chemical states of $CoTiO_x$ such as $Co_2TiO_4$ and $CoTiO_3$. The spent catalyst possessed a 780.3 eV main peak with a satellite structure at 795.8 eV. Based on XPS spectra of reference Co compound, the TCE-exposed Co surfaces could be assigned to be in the form of mainly $Co_3O_4$. XRD measurements indicated that the phase structure of Co species in 5% $CoO_x/TiO_2$ catalyst even before reaction is quite comparable to the diffraction lines of external $Co_3O_4$ standard. A model structure of $CoO_x$ present on titania surfaces would be $Co_3O_4$, encapsulated in thin-film $CoTiO_x$ species consisting of $Co_2TiO_4$ and $CoTiO_3$, which may be active for the decomposition of TCE in a flow of water.

• Journal of the Korean Ceramic Society
• /
• v.34 no.8
• /
• pp.897-907
• /
• 1997

Thin films of Bi4-xSmxTi3O12(0$\leq$x$\leq$2) were prepared on Pt/Ti/SiO2/Si(100) at $700^{\circ}C$ using spin-coating with sols derived from Bi-Sm-Ti complex alkoxides. From X-ray diffraction analysis, it was observed that Sm-substituted phases resembled ferroelectric Bi4Ti3O12 in structure. Variations of their lattice parameters depending on the amount of Sm-substitution showed that an anomalous structural distortion might exist at x=1. The grain sizes of the thin films decreased from 0.115 ${\mu}{\textrm}{m}$ to 0.078${\mu}{\textrm}{m}$ with increasing the amount of Sm-substitution. The dielectric constants and the remanent polarizations of the thin films decreased with increasing the amount of the Sm-substitution, which were related to decrease of the stereo-active Bi3+ ion contributing to polarization. However, these values were exceptionally high at x=1, compared to those of the other substituted phases. Such an anomaly suggests that the phase of x=1 has 1:1 chemical ordering between Sm and Bi in structure. The thin films of all compositions except x=2 showed ferroelectricity. The thin film of x=2 was paraelectric, whose grains were too fine to exhibit ferroelectricity.

• Journal of the Korean Ceramic Society
• /
• v.30 no.11
• /
• pp.891-896
• /
• 1993

Pb(Fe1/2Nb1/2)O3 and (1-x)Pb(Fe1/2Nb1/2)O3-xPbTiO3 ceramics were prepared by the precalcination method. Their structural and dielectric properties were investigated. The amount of perovsikte phase was increased by the precalcination and the dielectric properties of ceramics were improved. Additions of PbTiO3 were found to increase the tetragonality (c/a) of crystal lattice and Tc. In the middle region of (1-x)Pb(Fe1/2Nb1/2)O3-xPbTiO3, duffuse phase transitions (DPT) were observed.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2005.07a
• /
• pp.338-339
• /
• 2005

본 연구에서는 $Fe_2O_3$를 첨가한 $Pb(Ni_{1/3}Nb_{2/3})O_3-Pb(Zr_xTi_{1-x})O_3$ 세라믹스에서 Zr/Ti 비 변화에 따른 소결 및 압전, 유전특성을 조사하였다. $0.4Pb(Ni_{1/3}Nb_{2/3})O_3-0.6Pb(Zr_xTi_{1-x})O_3$+0.25Wt% $Fe_2O_3$ 계에서 Zr/(Ti+Zr)비(x)를 0.39에서 0.42까지 변화시킨 조성을 1100 - $1250^{\circ}C$ 온도에서 2시간 소결하여 이의 결정구조 및 미세조직을 분석하였고, 압전, 유전 특성 및 RAINBOW 액츄에이터로의 응용을 조사하였다. $1150^{\circ}C$에서 소결한 0.405 조성(x)에서 유전상수(${\varepsilon}r$) = 4669, 전기기계결합계수(kp) = 0.75, 압전상수($d_{33}$) = 810 pC/N의 우수한 특성 값을 나타내었으며, 닥터블레이드법에 의해 RAINBOW 액츄에이터를 제작하여 변위특성을 조사하였다.

• Journal of the Korean Ceramic Society
• /
• v.38 no.7
• /
• pp.615-620
• /
• 2001

E $r_2$ $O_3$-MgO 복합 첨가가 BaTi $O_3$계 내환원성 X7R 재질의 유전특성에 미치는 영향에 대하여 환원성 분위기에서 연구하였다. (B $a_{1-x}$ E $r_{x}$)( $Ti_{1-y}$M $g_{y}$ ) $O_3$첨가계에서 1.0 mol% 이상 MgO의 복합첨가로 E $r_{Ba}$ 도너 불순물과 $Mg_{Ti}$ 억셉터 불순물이 전기적으로 보상되어, 환원성분위기 소결 후에도 $10^{10}$Ωcm 이상의 높은 절연저항을 나타내었다. E $r_2$ $O_3$가 첨가된 시편에서 MgO가 2.0 mol% 이상 첨가될 경우, 유전율의 온도안정성이 향상되어 X7R 규격을 만족시켰으며 1.0$mu extrm{m}$ 이하의 작고 균일한 입자가 관찰되었다. 한편, E $r_2$ $O_3$의 첨가량이 3.0 mol%로 증가함에 따라 유전율의 온도안정성이 향상되었으나 상대적으로 상온 유전상수값이 현저히 감소하였다.였다.다.

• Proceedings of the Materials Research Society of Korea Conference
• /
• 1997.10a
• /
• pp.130-130
• /
• 1997

• Journal of the Korean Ceramic Society
• /
• v.40 no.2
• /
• pp.178-183
• /
• 2003

Electrical conductivity of$50Li_2O-xTiO_2-(50-x)P_2O_5$ glasses has been studied with an increase of the intermediate$TiO_2$content. Thermal properties were observed from TG-DTA measurement and the variation of glass structure was investigated by FT-IR. The density and glass transition temperature increased with an increase of the $TiO_2$ content. These results were attributed to the fact that bond strengthening was occurred because of the formation of P-O-Ti cross linkages in the glass. The ionic conductivity increased with $TiO_2$ content and a maximum value, $1.2{imes}10^{-6}$S/cm showed at x=20. The ionic conductivity showed a large increasement as a result that the pyrophosphate group become the predominant structural unit. This result can explain that Li ions mobility increased as a number of non-bridging oxygen on phosphate units increased.

• Korean Journal of Materials Research
• /
• v.7 no.10
• /
• pp.871-871
• /
• 1997

(1-x)CaTiO/sub 3/-xLa(Zn/sub 1/2/Ti/sub 1/2/)O/sub 3/의 마이크로 유전특성을 조사하였다. x가 증가함에 따라 비유전율과 공진주파수의 온도계수는 감소하였으며, Qㆍf/sub 0/는 증가하였다. 그 결과 x=0.5인 (Ca/sub 0.5/La/sub 0.5/)(Ti/sub 0.75/Zn/sub 0.25/)O/sub 3/의 조성에서 ε/sub r/=51, Qㆍf/sub 0/=38,000 (at 7 GHz), τ/sub f/=+5ppm/℃의 유전특성이 나타났다. (Ca/sub 0.5/La/sub 0.5/)(Ti/sub 0.75/Zn/sub 0.25/) O/sub 3/조성의 소결온도를 저하시키기 위하여 Bi/sub 2/O/sub 3/를 주조성으로한 소결체를 첨가하여 소결 및 유전특성을 조사하였다. 1wt% 0.76Bi/sub 2/O/sub 3/-0.24NiO가 첨가된 경우 소결온도는 150℃ 낮아졌으며, 비유전율 (ε/sub r/), 공진주파수의 온도계수(τ/sub f), Qㆍf/sub 0/가 각각 50+5ppm/℃, 35,000인 마이크로파 유전특성이 얻어졌다. 또한 3wt%의 0.76Bi/sub 2/O/sub 3/-0.24NiO가 첨가된 경우 소결온도는 200℃ 저하되었고, 비유전율 (ε/sub r/)과 공진주파수의 온도계수 (τ/sub f)는 변하기 않았으나, Qㆍf/sub 0/값이 38,000에서 25,000으로 저하되었다.

• The Transactions of the Korean Institute of Electrical Engineers C
• /
• v.48 no.6
• /
• pp.410-415
• /
• 1999

$Ba_{1-x}Sr_xTiO_3$ thin films with various ratio of Sr (X = 0.4, 0.5, 0.6) were grown $Pt/TiN/SiO_2/Si$ subastrate by RF magnetron sputtering deposition. As, Ag, and Cu films were deposited on $Ba_{1-x}Sr_xTiO_3$ thin films as top electrodes by using a thermal evaporator. The electrical properties of $Ba_{1-x}Sr_xTiO_3$ thin films for various compositions were characterized and the physical properties at interface between $Ba_{1-x}Sr_xTiO_3$ thin films and top electrodes were evaluated in terms of the work function difference. At x =0.5, the degradation of capacitance is lower to the other compositions. As negative biasapplied, the specimen with Cu top electrode has board saturation region and low leakage current since work function of Cu is bigger than other electrodes.$ Ba_{0.5}Sr_{0.5}TiO_3$ thin films with Cu top electrode, the dielectric constant was measured to the value of 354 at 1 kHz and the leakage current was obtained to the value of $5.26\times10^{-6}A/cm2$ at the forward bias of 2 V.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2000.07a
• /
• pp.865-868
• /
• 2000

It was examined that the relationship between microstructures, electrical properties and crystal structure of (1-x)CaMnO$_3$-xCaTiO$_3$solid solution system which was made by mixing a semiconducting material CaMnO$_3$of low resistance and a dielectric material CaTiO$_3$of high resistance with variable ratios (x=0, 0.1, 0.3, 0.5, 0.7, 0.9, 1.0). As the CaTiO$_3$increased, the resistance, B constant and lattice constant were increased, but the grain size was decreased. On particular, above 50wt% of CaTiO$_3$, the resistance at 2 5$^{\circ}C$ was rapidly increased due to the correlation in connectivity of the lattices between the conductive Mn$^{+4}$ octahedron and the insulative Ti$^{+4}$ octahedron.ron.