• Corrosion Science and Technology
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• v.7 no.6
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• pp.332-337
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• 2008

A reaction and evaporation types of cerium based conversion coatings were developed for galvanized steel sheet. The corrosion loss Q(Cb/cm2) and protection efficiency P(%) were obtained using a polarization technique for cerium based conversion coatings on galvanized steel exposed to 0.5N NaCl for 7 days. The microstructure of coating layer was observed using SEM. An excellent corrosion reistnce of galvanized steel was obtained by two types of cerium basd conversion coating. Salt spray test was done to evaluate the corrosion resistance of three samples by visual inspection. The corrosion ranking of three samples-untreated and two treatedby electrochemical data was matched well with the results of salt spray test.

• Resources Recycling
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• v.28 no.6
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• pp.18-25
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• 2019

In order to recover the cerium contained in the spent nickel metal hydride batteries (NiMH battery), the recovered rare earth complex precipitates from NIMH were converted into rare earth hydroxides through ion exchange reaction to react with NaOH aqueous solution at a reaction temperature of 70 ℃, for 4 hours. Rare earth hydroxides were oxidized by injecting air at 80 ℃ for 4 hours to oxidize Ce³⁺ to Ce⁴⁺. The oxidation rate of cerium was confirmed to be about 25 % through XPS, and the oxidized powder was separated from the rest of the rare earth using the difference in solubility in dilute sulfuric acid. The finally recovered powder has a crystal phase of cerium hydroxide (Ce(OH)₄). The cerium purity of the final product was about 94.6 %, and the recovery rate was 97.3 %.

• Applied Chemistry for Engineering
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• v.29 no.4
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• pp.425-431
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• 2018

Composite particles of porous silica and cerium oxide nanoparticles blocking UV/blue light were prepared through a dry coating process. Various composite particles were prepared by varying conditions such as the mixing ratio of cerium oxide and silica, and the chamber rotating speed of mechano fusion system. The surface morphology of the composite particles was observed with SEM and the composition was analyzed using X-ray fluorescence (XRF). When the cerium oxide/silica composite particles were dispersed in water, the transparency and dispersion stability of the colloidal solution were improved. In addition, the fluidity and spreadability of the particle powder were enhanced by making composite particles. These results show that cerium oxide/silica composite particles can be used as functional cosmetic ingredients for UV/blue light protection.

• Applied Science and Convergence Technology
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• v.25 no.1
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• pp.19-24
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• 2016

In this study, we evaluated the change of electronic structure during redox process in cerium-doped $ZrO_2$ grown by sol gel method. By sol-gel method, we could obtain cerium-doped $ZrO_2$ in high oxygen partial pressure and low temperature. After post annealing process in nitrogen ambient, the film is deoxidized. We used spectroscopic and theoretical methods to analysis change of electronic structure. X-ray absorption spectroscopy (XAS) for O K1-edge and Density Functional Theory (DFT) calculation using VASP code were performed to verify the electronic structure of the film. Also, high resolution x-ray photoelectron spectroscopy (HRXPS) for Ce 3d was carried out to confirm chemical bond of cerium doped $ZrO_2$. Through the investigation of the electronic structure, we verified as followings. (1) During reduction process, binding energy of oxygen is increase. Simultaneously, oxidation state of cerium was change to 4+ to 3+. (2) Cerium 4+ and cerium 3+ states were generated at different energy level. (3) Absorption states in O K edge were mainly originated by Ce 4+ $f_0$ and Ce 3+, while occupied states in valance band were mainly originated from Ce 4+ $f_2$.

• Bulletin of the Korean Chemical Society
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• v.31 no.4
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• pp.1058-1060
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• 2010

• Toxicological Research
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• v.25 no.2
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• pp.79-84
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• 2009

Cerium oxide nanoparticles (size: 30 nm) were prepared by the supercritical synthesis method, Acute oral toxicity and tissue distribution of the nanoparticles were evaluated by a single administration in rats. Oral administration of the nanoparticles to the rats did not lead to death when the animals were treated by a dose of 5 g/kg (high dose) as well as 100 mg/kg (low dose). Abnormal clinical signs, changes in serum biochemistry and hematology were not observed in high-dose treated group compared to the vehicle control group. Lesions in liver, lung and kidney were not observed in high-dose treated group by histopathological examination. Tissue distribution analysis in liver, kidney, spleen, lung, testis and brain was performed on day 1, day 7 and day 14 after treatment. The average values of the accumulated cerium oxide nanoparticles were elevated in all tissues but statistical significance was only shown in lung. Low levels of tissue distributions after a single oral administration seem to be the low bioavailability of the nanoparticles.

• Journal of Powder Materials
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• v.18 no.3
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• pp.250-255
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• 2011

The potential application of ultrafine cerium oxide (ceria, $CeO_2$) as an oxygen gas sensor has been investigated. Ceria was synthesized by a thermochemical process: first, a precursor powder was prepared by spray drying cerium-nitrate solution. Heat treatment in air was then performed to evaporate the volatile components in the precursor, thereby forming nanostructured $CeO_2$ having a size of approximately 20 nm and specific surface area of 100 $m^2/g$. After sintering with loosely compacted samples, hydrogen-reduction heat treatment was performed at 773K to increase the degree of non-stoichiometry, x, in $CeO_{2-x}$. In this manner, the electrical conductivity and oxygen-response ability could be enhanced by increasing the number of oxygen vacancies. After the hydrogen reduction at 773K, $CeO_{1.5}$ was obtained with nearly the same initial crystalline size and surface. The response time $t_{90}$ measured at room temperature was extremely short at 4 s as compared to 14 s for normally sintered $CeO_2$. We believe that this hydrogen-reduced ceria can perform capably as a high-performance oxygen sensor with good response abilities even at room temperature.

• Bulletin of the Korean Chemical Society
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• v.28 no.8
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• pp.1329-1334
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• 2007

The electrochemical oxidation of cerium(III) was carried out using divided and undivided electrochemical cells in nitric acid medium. It was found that divided cell with Nafion 324 as the separator gave good conversion yield with high current efficiency compared to the undivided cell. The efficiency of the divided electrochemical cell was further optimized in terms of cell voltage, temperature, flow rate of solution recirculation, concentrations of Ce(III) and nitric acid. The better conditions for 1 M Ce(III) in 3 M nitric acid were found to be 2.5 V, 363 K and 100 mL/min recirculation flow rate based on the current efficiency under the experimental conditions investigated. The Ce(IV) oxidant produced was used as a mediator for the mineralization of phenol. The mineralization efficiency of the cerium mediated electrochemical oxidation was found rapid and higher compared to the direct electrochemical oxidation based on CO2 evolution under the same conditions.

• Proceedings of the Korean Vacuum Society Conference
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• 1999.07a
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• pp.104-104
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• 1999

Cerium dioxide 박막의 포토루미네슨에 관해서는 Cerium 4f band에서 oxygen 2p band로의 transition에 의한 발광(400nm) 현상이 보고되었다. 또한 Indium Oxide 박막의 발광(637nm0 현상이 보고되었다. 본 연구에서는 3족인 Indium을 Si/In/CeO2/Si 구조와 CeO2/Si 구조에 도핑하여 포토루미네슨스 현상을 관찰하였다. E-beam evaporator를 사용하여 Silicon(111) 기판에 Cerium dioxcide 박막을 성장시킨 경우의 두가지 시료를 분석하였다. 포토루미네슨스 관찰을 위해서 Ge-Cd laser (325nm)가 사용되었으며 Indium의 도핑양과 분포 상태를 알기 위해 SIMS와 ADP를 이용하여 분석하였다. Indium양에 대한 포토루미네슨스 변화와 열처리 후의 indium의 분포의 변화에 의한 포토루미네슨스 변화를 관찰하였다. 상온에서 In/CeO2/Si 시료와 Si/In/CeO2/Si 시료에 대한 포토루미네슨스 현상을 관찰한 결과 Si/In/CeO2/Si 시료에서만 500nm(2.5eV)에서 발광 현상이 관찰되었다. 도핑된 indium은 ADP에서는 검출되지 않고 SIMS에서만 검출되어 ADP의 detection range(1-0.1%) 이하의 양이 도핑된 것으로 추측된다. 도핑된 Indium의 양이 증가할수록 포토루미네슨스의 Intensity가 증가하였다. 또한 열처리(110$0^{\circ}C$, 1min) 후 포토루미네슨스의 peak위치가 390nm(3.18eV)로 변화하였다. Si/In/CeO2/Si에서 포토루미네슨스 현상이 관측되고 Intensity가 indium의 양에 의존하므로 완전하지 못한 Cerium dioxide의 CeOx 구조와 indium과의 결합이 포토루미네슨스의 원인으로 추측된다. 열처리 후 SIMS의 분석결과 indium의 분포가 변화하였으며 이는 포토루미네슨스의 변화의 원인으로 판단된다.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2006.12a
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• pp.33-34
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• 2006

The effects of Ba and Ce addition has been investigated in YBCO prepared by trifluoroacetate (TFA) metalorganic depostition (MOD) method. Precursor solutions with cation ratios of Y:Ba:Cu:Ce = 1:2+x:3:x (x = 0, 0.05, 0.1 and 1.5) have been prepared by adding an excess amount of cerium and barium. Coated film was calcined at lower temperature and conversion heat treatment at temperature of $780{\sim}810^{\circ}C$. It has been shown that the critical current (Ic) of YBCO film was degraded by doping of Ba and Ce atoms. But Ic was increased as the amount of doped Ba and Ce content increased from 5 % to 15 %. It was observed that there was little increase of a flux pinning force with Ba and Ce addition in YBCO film prepared by TFA-MOD process.