• 자원환경지질
• /
• 제37권4호
• /
• pp.375-381
• /
• 2004

장주기 방사성 폐기물인 악티나이드 원소들을 고정화시킬 수 있는 파이로클로어 (pyrochlore; CaCeH$f_xTi_{2-x}O_7$=0.2, 0.6, 1.0, 1.4, 1.8, 2.0)를 합성하여 상평형 관계 및 특성을 연구하였다. 혼합된 시료는 상온에서 400kg/$cm^2$의 압력으로 성형한 후, 산소분위기에서 1200∼1$600^{\circ}C$ 범위로 소결온도를 변화시키면서 소성하였다. 합성된 시료는 XRD를 사용하여 상분석을 실시하였다. 실험결과, 파이로클로어의 최적 합성조건은 산소분위기 하에서, 각각의 조성에 따라, 1300∼150$0^{\circ}C$로 매우 다양하였다. 합성시 생성된 상으로는 페롭스카이트, 파이로클로어 및 $A_{2}BO_{5}$산화물 등이 있으며, 본 계의 특성은 Hf의 함량증가에 따라 페롭스카이트 및 파이로클로어의 격자상수가 증가한다는 점이다. 이같은 현상은 육배위 자리를 차지하고 있는 Hf와 Ti의 이온반경의 차이에서 비롯된 것이다.

• 한국세라믹학회:학술대회논문집
• /
• 한국세라믹학회 2003년도 추계총회 및 연구발표회 초록집
• /
• pp.100.2-100
• /
• 2003

• 한국환경과학회지
• /
• 제28권1호
• /
• pp.65-73
• /
• 2019

The catalytic activity of Ni-0.2%YSZ (Yttria-Stabilized Zirconia) with different promoters was evaluated for $CO_2$ methanation. The catalysts were weighed for mixing and they were dried at $110^{\circ}C$ for molding into disks. The concentration of $CO_2$ and $CH_4$ for conducting of $CO_2$ methanation were analyzed by gas chromatography and the physical characteristics of the disk-type catalyst formed were analyzed by X-ray diffraction, scanning electron microscope and energy dispersive x-ray spectrometer. The addition of $CeO_2$ as a promoter for Ni-0.2%YSZ (denoted as Ni-5%Ce-0.2%YSZ) resulted in the highest $CO_2$ methanation. It also showed catalytic activity at a low temperature($200^{\circ}C$). Following this, $ZrO_2$, $SiO_2$, $Al_2O_3$ and $TiO_2$ were added to Ni-5%Ce-0.2%YSZ to compare the $CO_2$ methanation, and the highest efficiency was found for. Ni-1%Ti-5%Ce-0.2%YSZ Then, the concentration of Ti was increased to 10% and the catalytic activity was estimated using seven different types of commercial $TiO_2$. In conclusion, ST-01 $TiO_2$ showed the highest efficiency for $CO_2$ methanation.

• 한국세라믹학회지
• /
• 제21권4호
• /
• pp.373-381
• /
• 1984

The coloration of the $Nd_2O_3$ contained $R_2O-BaO-SrO-ZrO_2-SiO_2$ glass added the various amount of $CeO_2$ $MnO_2$, $Fe_2O_3$ and $As_2O_3$ alone or together by the irradiation of X-ray irradiation,. The glasses added $CeO_2$ in proportion to amount were more effective on preventing coloration by X-ray irradiation but the addition of $MnO_2$ produced different color according to the amount of addition. The addition of the $Fe_2O_3$, $TiO_2$ and $As_2O_3$ did not give much effects to the transmission changes of $Nd_2O_3$ contained glass by X-ray irradiation but the glass added $CeO_2$ , $Fe_2O_3$, $TiO_2$ together was most effective to prevent coloration and transmisson changes.

• Journal of Electrical Engineering and Technology
• /
• 제13권1호
• /
• pp.413-417
• /
• 2018

The $Li_4Ti_5O_{12}$ of anode material for the hybrid capacitor was coated using $CePO_4$, $M_3(PO_4)_2$ (M=Mg, Zn). The capacitance of phosphate coated $Li_4Ti_5O_{12}$ was found to be lower than that of $Li_4Ti_5O_{12}$, whereas the equivalent series resistance was higher than that of $Li_4Ti_5O_{12}$. With an increase in cycle number, the base of cylindrical cell exhibited swelling due to gas generated from the reaction between $Li_4Ti_5O_{12}$ and electrolyte. The swelling cycle number of phosphate coated $Li_4Ti_5O_{12}$ was higher than that of $Li_4Ti_5O_{12}$ due to improvement in electrochemical stability. Based on the results, it is proposed that phosphate coating can be employed as a barrier layer to control the gassing reaction by isolating the $Li_4Ti_5O_{12}$ particle from electrolyte solution.

• 공업화학
• /
• 제21권4호
• /
• pp.391-395
• /
• 2010

본 연구는 Pt/$TiO_2$ 촉매를 이용한 $H_2$ SCR 반응에서 배가스 중 CO에 대한 영향을 조사하였다. 반응가스 중 공존하는 CO는 촉매표면의 활성점에서 환원제인 $H_2$와의 경쟁흡착을 유발하여 반응활성을 감소시키는 결과를 나타내었다. 또한 경쟁흡착은 반응활성의 감소와 함께 미반응 $H_2$ 및 CO의 생성을 야기하였으며 주입되는 CO의 농도가 증가할수록 이러한 현상들은 극심한 양상을 보였다. CO에 의한 inhibition을 최소화하기 위하여 $PdO_2$, $CeO_2$를 첨가하였으며 $CeO_2$를 첨가한 촉매가 100 ppm 이하의 공존 CO에 대한 내구성을 나타내었다.

• Advances in materials Research
• /
• 제3권2호
• /
• pp.105-116
• /
• 2014

The microwave dielectric properties of $CeO_2$ nanoparticles (0.5, 1.0 & 1.5wt%) doped $Mg_2TiO_4$ (MTO) ceramics have been investigated at cryogenic temperatures. The XRD patterns of the samples were refined using the full proof program reveal the inverse spinel structure without any secondary phases. The addition of $CeO_2$ nanoparticles lowered the sintering temperature with enhancement in density and grain size as compared to pure MTO ceramics. This is attributed to the higher sintering velocity of the fine particles. Further, the microwave dielectric properties of the MTO ceramics were measured at cryogenic temperatures in the temperature range of 6.5-295 K. It is observed that the loss tangent ($tan{\delta}$) of all the samples increased with temperature. However, the $CeO_2$ nanoparticles doped MTO ceramics manifested lower loss tangents as compared to the pure MTO ceramics. The loss tangents of the pure and MTO ceramics doped with 1.5 wt% of $CeO_2$ nanoparticles measured at 6.5K are found to be $6.6{\times}10^{-5}$ and $5.4{\times}10^{-5}$, respectively. The addition of $CeO_2$ nanoparticles did not cause any changes on the temperature stability of the MTO ceramics at cryogenic temperatures. On the other hand, the temperature coefficient of the permittivity increased with rise in temperature and with the wt% of $CeO_2$ nanoparticles. The obtained lower loss tangent values at cryogenic temperatures can be attributed to the decrease in both intrinsic and extrinsic losses in the MTO ceramics.

• 한국전기전자재료학회:학술대회논문집
• /
• 한국전기전자재료학회 1992년도 춘계학술대회 논문집
• /
• pp.137-139
• /
• 1992

By addition of 1～5mol% CeO$_2$to powders with composition in the BaO-Nd$_2$O$_3$-TiO$_2$, temperature coefficient of permittivity of sintered ceramics may be decreased from approximately-140ppm/$^{\circ}C$～-65ppm/$^{\circ}C$. Dense, fine grained ceramics were prepared with permitivity within the range of 78～92 and Q above 1000.

• 한국전기전자재료학회:학술대회논문집
• /
• 한국전기전자재료학회 2001년도 추계학술대회 논문집
• /
• pp.442-445
• /
• 2001

In this study, microstructural and dielectric properties of P $b_{0.83}$(L $a_{0.2}$C $e_{0.8}$)$_{0.08}$Ti $O_3$PCT ceramics as a function of Mn $O_2$ addition were investigated for 30MHz ceramic resonator application. Grain size was gradually increased according to the increase of Mn $O_2$ addition amount and showed the highest value of 1.502${\mu}{\textrm}{m}$ at the 0.9wt% Mn $O_2$. Moreover, density showed the highest value of 7.582 g/$\textrm{cm}^2$ at the 0.7wt% Mn $O_2$. All the composition ceramics, curie temperature was nearly constant around 33$0^{\circ}C$.EX>.>.>.

• International Journal of Oral Biology
• /
• 제46권3호
• /
• pp.105-110
• /
• 2021

The physicochemical properties of crystalline titanium dioxide nanoparticles (TiO₂ NPs) were investigated by comparing amorphous (amTiO₂), anatase (aTiO₂), metaphase of anatase-rutile (arTiO₂), and rutile (rTiO₂) NPs, which were prepared at various calcination temperatures (100℃, 400℃, 600℃, and 900℃). X-ray diffraction (XRD) and scanning electron microscopy (SEM) analyses confirmed that the phase-transformed TiO₂ had the characteristic features of crystallinity and average size. The surface chemical properties of the crystalline phases were different in the spectral analysis. As anatase transformed to the rutile phase, the band of the hydroxyl group at 3,600-3,100 cm^-1 decreased gradually, as assessed using Fourier transform infrared spectroscopy (FT-IR). For ultraviolet-visible (UV-Vis) spectra, the maximum absorbance of anatase TiO₂ NPs at 309 nm was blue-shifted to 290 nm at the rutile phase with reduced absorbance. Under the electric field of capillary electrophoresis (CE), TiO₂ NPs in anatase migrated and detected as a broaden peak, whereas the rutile NPs did not. In addition, anatase showed the highest photocatalytic activity in an UV-irradiated dye degradation assay in the following order: aTiO₂ > arTiO₂ > rTiO₂. Overall, the phases of TiO₂ NPs showed characteristic physicochemical properties regarding size, surface chemical properties, UV absorbance, CE migration, and photocatalytic activity.