• 한국재료학회지
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• 제3권3호
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• pp.245-252
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• 1993

순수 $UO_2$에 첨가량 변화 및 ball-milling 시간에 따른 (U, Ce)$O_2$ 분말의 특성과 각 조건별로 제조된 분말을 압분 및 소결하여 (U, Ce)$O_2$ 분말 특성에 따른 소결성을 비교 조사하였다. 실험 결과로 부터 ball-milling시간이 길어짐에 따라 입자들은 미세화되고, Ce$O_2$ 함량이 증가할수록 압분, 소결밀도는 저하 하였으며, $CeO_2$는 소결성을 저하시키는 산화물임을 확인하였다. 10wt%,$CeO_2$ 가 첨가된 (U, Ce)$O_2$ 분말의 경우, ball-milling 4시간 수행한 분말의 소결체가 기공의 수도 적고, 구형에 가까왔으며, 소결밀도가 가장 높았다. 이는 4시간 ball-milling한 (U, Ce)$O_2$분말이 비표면적이 크로 그의 packing ratio가 적절하였기 때문이다.

• The Korean Journal of Ceramics
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• 제4권4호
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• pp.297-303
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• 1998

The effect of aliovalent dopants, $ Nb_2O_5$ and MnO, on the phase stability of 12 mol% ceria partially-stabilized zirconia (Ce-TZP) polycrystals was studied. Both dopants (MnO and $ Nb_2O_5$) significantly increased the stability of the tetragonal zirconia phase (Mb temperature lower than liquid nitrogen temperature). The enhancement of the stability of the tetragonal phase in Ce-TZP doped with 1 mol% of Mno(Ce-TZP/MnO) andCe-TZP doped with 1 mol% of $ Nb_2O_5$(Ce-TZP/$ Nb_2O_5$) were explained by the significant reduction of the driving force, -${\Delta}$Gchem, for the tetragonal-to-mono-clinic phase transformation caused by the addition of MnO and $ Nb_2O_5$. The enhanced stability of the tetragonal phase in the Ce-TZP and Al2O3 composite (Ce-TZP/$Al_2O_3$) is believed to be caused by smaller grain size, moderate reduction in the chemical driving force and increase in the strain energy barrier to the transformation. Mechanical properties of the Ce-TZP and the Ce-TZP/$Al_2O_3$ with (i) the same grain size and (ii) the same Mb temperature were examined by measuring stress-strain behavior in 3 point bending. The Ce-TZP/$Al_2O_3$ composite doped with 1.3w% MnO (Ce-TZP/$Al_2O_3$/MnO), which had the same grain size as the Ce-TZP and De-TZP/$Al_2O_3$ showed more transformation plasticity than either the Ce-TZP or the Ce-TZP/$Al_2O_3$ composite. The Ce-TZP wihch had the same Mb temperature as that of the Ce-TZP/$Al_2O_3$/MnO did not show any transformation plasticity.

• 한국세라믹학회지
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• 제34권1호
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• pp.102-108
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• 1997

수용성 ZrOCl2.8H2O, YCl3.6H2O 및 Ce(NO3)3.6H2O를 사용하여 공침법으로 다양한 조성의 Y2O3-CeO2-ZrO2 분말을 합성하고, 이들의 압분체를 1400, 150$0^{\circ}C$에서 2시간동안 공기 중에서 상압소결하였다. 2mol%Y2O3-ZrO2 조성의 140$0^{\circ}C$ 소결체는 강도(1003MPa)와 미세경도(12.6GPa) 면에서 제일 우수하였으나, 인성은 10mol%CeO2-ZrO2의 경우가 13.3MPa.m1/2로 제일 높았다. CeO2-ZrO2에Y2O3의 첨가는 소결체의 평균 결정입자의 크기를 감소시켰고, 이로 인하여 강도와 경도는 증가하지만 인성은 감소하였다. 반면에 Y2O3-ZrO3에 CeO2의 첨가는 수열분위기에서 장시간 저온시효동안 정방정상의 안정화를 향상시키는 효과를 나타내었다.

• 청정기술
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• 제19권2호
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• pp.128-133
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• 2013

$CeO_2$에 담지된 구리산화물에서 벤젠의 촉매연소 반응에 대해 연구하였다. 담지된 구리산화물 촉매들은 볼밀법과 함침법으로 제조하였고, XRD, FT-IR, TEM 및 TPR에 의해 특성분석을 하였다. 볼밀법으로 제조된 CuO/$CeO_2$ 촉매는 높은 담지량에서도 잘 분산된 CuO를 얻었다. 볼밀법으로 제조된 CuO/$CeO_2$ 촉매는 함침법으로 제조된 촉매에 비해 높은 활성을 보여주었다. CuO의 담지량이 증가할수록 촉매 활성이 증가하였으며, 10 wt%로 담지된 촉매에서 가장 높은 활성을 나타내었다. 또한, 10 wt% CuO/$CeO_2$ 촉매에 소량의 $Fe_2O_3$와 CoO의 조촉매 첨가는 CuO의 분산도를 높여 반응활성을 증가시켰다.

• 한국결정성장학회지
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• 제23권6호
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• pp.320-324
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• 2013

$CeO_2$의 첨가가 $CeO_2-TiO_2$계 SCR촉매 활성에 미치는 영향을 구조적, 형상학적, 물리화학적 분석을 통해 규명하였다. 순수한 $TiO_2$ 분말과 10, 20, 30 wt%의 $CeO_2$를 첨가한 $CeO_2-TiO_2$ 분말을 졸겔법으로 합성한 결과, 분말 모두 $TiO_2$의 아나타제 (anatase)상을 나타내었고 $CeO_2$를 첨가할수록 $TiO_2$ 표면에 결정성이 낮은 $CeO_2$가 분산되어 피크강도가 낮아짐을 확인하였다. 순수한 $TiO_2$의 비표면적이 $60.6306m^2/g$인데 반해 $CeO_2-TiO_2$의 비표면적은 30 wt%의 $CeO_2$를 첨가한 경우 $116.2791m^2/g$으로 비표면적이 증가하였고 따라서 첨가된 $CeO_2$가 $TiO_2$의 응집을 억제한 것으로 예상된다. $NO_x$ 제거효율은 30 wt% $CeO_2-TiO_2$ 촉매가 $300^{\circ}C$에서 98 %로 다른 분말보다 높은 효율을 나타내는데 이는 FT-IR을 이용하여 촉매의 산점 변화를 확인한 결과 30 wt% $CeO_2-TiO_2$ 분말의 경우가 다른 분말들에 비해 산점이 상대적으로 많았기 때문이다. 따라서 졸겔법으로 합성한 SCR용 $CeO_2-TiO_2$계 촉매에서 $CeO_2$의 첨가는 $TiO_2$의 입성장을 억제하여 비표면적을 증가시키고 $Br{\Phi}nsted$ 및 Lewis 산점을 증가시킴으로써 촉매 효율을 향상시켰다고 판단된다.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2001년도 추계학술대회 논문집 Vol.14 No.1
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• pp.430-433
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• 2001

The $0.96MgTiO_{3}-0.04SrTiO_{3}+xCe(x=0{\sim}1.6wt%)$ ceramics were fabricated by the conventional mixed oxide method. The sintering temperature and time were $1300^{\circ}C$, 2hr., respectively. From the X-ray diffraction patterns, it was found that the perovskite $SrTiO_{3}$ and ilmenite $MgTiO_{3}$ structures were coexisted in the $0.96MgTiO_{3}-0.04SrTiO_{3}+xCe(x=0{\sim}1.6wt%)$ ceramics. The dielectric constant$(\varepsilon_{r})$ was increased with addition of Ce. The temperature coefficient of resonant frequency$(\Gamma_{f})$ was gradually varied from positive value to the negative value with increasing the Ce. The temperature coefficient of resonant frequency of the $0.96MgTiO_{3}-0.04SrTiO_{3}+0.2Ce$ ceramics was near zero, where the dielectric constant, quality factor, and $\Gamma_{f}$ were 20.68, 50,272 and ${-0.5ppm/^{\circ}C}$, respectively.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2001년도 추계학술대회 논문집
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• pp.430-433
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• 2001

The 0.96MgTiO$_3$-0.04SrTiO$_3$+xCe(x=0∼1.6 wt%) ceramics were fabricated by the conventional mixed oxide method. The sintering temperature and time were 1300$^{\circ}C$, 2hr., respectively. From the X-ray diffraction patterns, it was found that the perovskite SrTiO$_3$ and ilmenite MgTiO$_3$ structures were coexisted in the 0.96MgTiO$_3$-0.04SrTiO$_3$+xCe(x=0∼1.6 wt%) ceramics. The dielectric constant($\varepsilon$$\sub$r/) was increased with addition of Ce. The temperature coefficient of resonant frequency($\tau$$\sub$f/) was gradually varied from positive value to the negative value with increasing the Ce. The temperature coefficient of resonant frequency of the 0.96MgTiO$_3$-0.04SrTiO$_3$+0.2Ce ceramics was near zero, where the dielectric constant, quality factor, and $\tau$$\sub$f/ were 20.68, 50, 272 and -0.5pm/$^{\circ}C$, respectively.

• Bulletin of the Korean Chemical Society
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• 제27권12호
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• pp.1989-1996
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• 2006

The $NiSO_4/CeO_2-ZrO_2 $catalysts containing different nickel sulfate and $CeO_2$ contents were prepared by the impregnation method, where support, $CeO_2-ZrO_2$was prepared by the coprecipitation method using a mixed aqueous solution of zirconium oxychloride and cerium nitrate solution followed by adding an aqueous ammonia solution. No diffraction line of nickel sulfate was observed up to 20 wt %, indicating good dispersion of nickel sulfate on the surface of $CeO_2-ZrO_2$. The addition of nickel sulfate (or $CeO_2$) to $ZrO_2$ shifted the phase transition of $ZrO_2$ from amorphous to tetragonal to higher temperatures because of the interaction between nickel sulfate (or $CeO_2$) and $ZrO_2$. A catalyst (10-$NiSO_4/1-CeO_2-ZrO_2$) containing 10 wt % $NiSO_4$ and 1 mole % $CeO_2$, and calcined at $600{^{\circ}C}$ exhibited a maximum catalytic activity for ethylene dimerization. The catalytic activities were correlated with the acidity of catalysts measured by the ammonia chemisorption method. The role of $CeO_2$was to form a thermally stable solid solution with zirconia and consequently to give high surface area, thermal stability and acidity of the sample.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2001년도 추계학술대회 논문집 Vol.14 No.1
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• pp.442-445
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• 2001

In this study, microstructural and dielectric properties of $Pb_{0.83}(La_{0.2}Ce_{0.8})_{0.08}TiO_3$(PCT) ceramics as a function of $MnO_2$ addition were investigated for 30MHz ceramic resonator application. Grain size was gradually increased according to the increase of $MnO_2$ addition amount and showed the highest value of $1.502{\mu}m$ at the 0.9wt% $MnO_2$. Moreover, density showed the highest value of $7.582 g/cm^3$ at the 0.7wt% $MnO_2$.All the composition ceramics,curie temperature was nearly constant around $330^{\circ}C$

• Bulletin of the Korean Chemical Society
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• 제34권8호
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• pp.2461-2465
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• 2013

Pd-$Ce/{\gamma}-Al_2O_3-TiO_2$ catalysts were prepared by combined sol-gel and impregnation methods. Transmission electron microscopy, X-ray diffraction, $H_2$-temperature-programmed reduction, $O_2$-temperature-programmed desorption, and ethanol oxidation experiments were conducted to determine the properties of the catalysts. Addition of an optimal amount of Ce improved the performance of the $Pd/{\gamma}-Al_2O_3-TiO_2$ catalyst in promoting the complete oxidation of ethanol. The catalyst with 1% Ce exhibited the highest activity, and catalyzed complete oxidation of ethanol at $175^{\circ}C$; its selectivity to $CO_2$ reached 87%. Characterization results show that addition of appropriate amount of Ce could enrich the PdO species, and weaken the Pd-O bonds, thus enhancing oxidation ability of the catalyst. Meanwhile, the introduction of $CeO_2$ could make PdO better dispersed on ${\gamma}-Al_2O_3-TiO_2$, which is beneficial for the improvement of the catalytic oxidation activity.