• Environmental Analysis Health and Toxicology
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• v.23 no.2
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• pp.87-91
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• 2008

In this study, three different sizes of cerium oxide ($CeO_2$) nanoparticles were synthesized and exposed to Caenorhabditis elegans to investigate the potential harmful effect of $CeO_2$ nanoparticles on the environment. The effects of the $CeO_2$ nanoparticles on C. elegans were assessed at multiple levels, such as with respect to stress response gene expression, growth, reproduction and mortality. Moreover, to test the ecotoxicological relevance of $CeO_2$-induced gene expression. The overall results suggest that $CeO_2$ nanoparticles may provoke ecotoxicity in C. elegans especially with respect to gene expression, reproduction and survival, which can comprise an important contribution to knowledge on the ecotoxicity of $CeO_2$ nanoparticles, about which little data are available. This is particularly valuable in the biomarker research on ecotoxicology, as ecological relevance is a crucial criterion for the applicability of the biomarker in field biomonitoring and ecological risk assessment.

• The Korean Journal of Ceramics
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• v.5 no.1
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• pp.1-11
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• 1999

The effect of aliovalent dopents, $Nb_3O_5$ and MnO, on the grain growth kinetics of 12 mol% ceria stabilized tetragonal zirconia polycrystals (Ce-TZP) was studied. All specimens were sintered at $1550^{\circ}C$ for 20 minutes prior to annealing at different temperatures to study grain growth kinetics. Grain growth kinetics of Ce-TZP and 1 mol% $Nb_2O_5$ doped Ce-TZP (Ce-TZP/$Nb_3O_5$) during annealing at 1475, 1550, and $1600^{\circ}C$ adequately matched with square law $(D^2-D_\;o^2=k_at)$. However, grain growth in 1 mol% MnO suppressed grain growth in Ce-TZP by drag force exerted by $Mn^{+2}$ ions which segregated strongly to the positively-charged grain boundaries of Ce-TZP, $Nb_2O_5$ enhanced grain growth by increasing the concentration of vacancies of $Zr^{+4}$ ion and $Ce^{+4}$ ions. Surface analysis with X-ray photoelectron spectroscopy (XPS) showed the segregation of Mn+2 ions to grain boundaries. The kinetics of grain growth obtained in the base Ce-TZP and the Ce-TZPs with the aliovalent dopants were examined in the context of impurity drag effect and space charge effect.

• Journal of the Korean Ceramic Society
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• v.37 no.10
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• pp.1014-1020
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• 2000

RF 마크네트론 스퍼터법으로 Ce의 일부를 희토류 원소로 치환한 Ce$_{1-x}$RE$_{x}$O$_{2-y}$(0.1$\leq$x$\leq$0.4, RE=Y, Nd) 박막을 Si(111), $Al_2$O$_3$(1012) 기판 위에 1450~1$600^{\circ}C$로 소결한 target을 이용하여 성장시켰다. Ce$_{1-x}$RE$_{x}$O$_{2-y}$ 박막의 성장시 기판온도 및 증착시간 등을 변화시켜 성장시켰으며, 성장된 박막의 특성분석은 XRD, SEM, TEM으로 행하였다. 증착된 박막의 방향성 및 결정성장 거동은 증착온도 및 시간에 따라 차이를 보였다. Si(111) 기판 위에 증착된 Ce$_{1-x}$Y$_{x}$O$_{2-y}$(x=0.3) 박막의 경우, 80$0^{\circ}C$에 비해 7$50^{\circ}C$에서 증착 시간에 따른 (111) 우선배향성의 정도가 나은 결과를 보였으며, $Al_2$O$_3$(1012) 기판 위에 증착한 Ce$_{1-x}$Nd$_{x}$O$_{2-y}$(x=0.3) 박막 또는 (111) 우선배향성을 나타내었다.을 나타내었다.

• Proceedings of the Korean Ceranic Society Conference
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• 2003.10a
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• pp.189.1-189
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• 2003

• Proceedings of the Korean Ceranic Society Conference
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• 2003.10a
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• pp.190.1-190
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• 2003

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2002.10b
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• pp.439-440
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• 2002

Nano-Crystalline $CeO_2$ particles were dispersed in deionized water with controlled slurry chemicals for CMP test. According to the CMP test, the removal rate of $SiO_2$ layer was mainly controlled by the size and crystallinity of $CeO_2$ particles which can be controlled by the heat-treatment condition during $CeO_2$ synthesis. In contrast, the removal rate of $Si_3N_4$ layer was significantly influenced by the passivation reagent which protects the $Si_3N_4$ surface layer from excessive dissolution during CMP.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.28 no.3
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• pp.118-122
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• 2018

Ceria ($CeO_2$) is a rare earth oxide, which has been widely investigated to improve the property. It is important to increase the surface area of $CeO_2$, because high surface area of $CeO_2$ can improve the catalytic ability. $CeO_2$ nanoparticles were synthesized by a solvothermal process. A discussion on the influence of solvent ratio and precursors on $CeO_2$ nanoparticles was performed. The size and degree of the agglomeration of the synthesized $CeO_2$ could be tuned by controlling those parameters. The average size and distribution of prepared $CeO_2$ powders was in the range of 3 to 13 nm and narrow, respectively. The XRD pattern showed that the synthesized $CeO_2$ powders were crystalline with cubic phase of $CeO_2$. The average particle size was calculated by Scherrer equation and FE-TEM images. The morphology of the synthesized $CeO_2$ particle was objected using FE-TEM and FE-SEM. Specific surface area of the synthesized $CeO_2$ was determined using BET (Brunauer-Emmett-Teller) equation.

• Transactions of the Korean hydrogen and new energy society
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• v.25 no.6
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• pp.561-569
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• 2014

Ceria ($CeO_2$) was used to increase the durability of the membrane in the polymer electrolyte membrane water electrolysis (PEMWE) circumstance. The sulfonated polyether ether ketone (SPEEK) as polymer matrix was prepared in the sulfonation reaction of polyether ether ketone (PEEK) to improve electrochemical characteristics. After sulfonation reaction, the organic-inorganic blended composite membranes were prepared by means of sol-gel casting method with loading the highly dispersed $CeO_2$ and Cs-substituted molybdophosphoric acid (Cs-MoPA) with cross-linking agent (tetrapropyl orthosilicate). Consequently, the composite membrane CL-SPEEK/Silane 4wt%/Cs-MoPA/Ceria(1%) showed the improved characteristics such as 82% of water content, 0.11136 S/cm of proton conductivity at $80^{\circ}C$, 55.50 MPa of tensile strength and 4.37% of breeding out of MoPA.

• Journal of the Korean Ceramic Society
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• v.36 no.11
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• pp.1205-1210
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• 1999

Ceria based electrolytes were fabricated by a plasma spraying method. The porosity which was crated during the plasma spraying process was infiltrated with Ce0.8Gd0.2O2 sol by ultrasonic treatment and heat treatment at 90$0^{\circ}C$ in order to improve physical and electrical properties. The porosity decreased from 9.8% to 6.5% and gas permeability at 80$0^{\circ}C$ decreased from 16.7$\times$10-3 to 5.7$\times$10-3 cm3(STP)/cm2.s.cmHg as the number of treatment increased 10 cycles. The ionic conductivity was also increased about 30% after 10 times of sealing.

• 한국신재생에너지학회:학술대회논문집
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• 2007.06a
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• pp.49-52
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• 2007

We investigated hydrogen storage and production properties using redox system of iron oxide($Fe_{3}O_{4}$ + $4H_{2}$ ${\leftrightarrows}$ 3Fe + $4H_{2}O$) modified with rhodium, ceria and zirconia under atmospheric pressure. Reduction of iron oxide with hydrogen(hydrogen storage) and re-oxidation of reduced iron oxide with steam(hydrogen evolution) was carried out using a temperature programmed reaction(TPR) technique. On the temperature programmed studies, the effects of amounts of cerium and zirconium on the re-oxidation rate of partial reduced iron oxides were increased with increasing metal additives amount, but the rhodium amount showed little effect on the re-oxidation rate. On the thermal studies, the re-oxidation rates were enhanced with increasing temperature(300 $^{\circ}C$ < 350 $^{\circ}C$).