Forms Of Cerium Research Articles

Comparison of the cytotoxic effects of bulk and nanosized CeO2 on lymphocyte cells

Cerium(IV) oxide (CeO2) is widely used in industrial fields such as biomedical, glass, electronics, automotive, and pharmacology. In this study, the cytotoxic effects on human peripheral blood cultures of two forms of cerium(IV) oxide with different particle sizes (Bulk-sized Cerium(IV) oxide: BC and Nano-sized Cerium(IV) oxide: NC) in concentrations range of 0.001-200 ppm were investigated. 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay were used to determine the cytotoxicity of these forms. According to the test results, it was determined that both forms caused severe cytotoxicity at all concentrations studied. It was observed that cytotoxicity increased with increasing concentration. NCs are more toxic at all concentrations except 100 and 200 ppm concentrations.

Sol-gel Synthesis of Ce0.8Sr0.2Co1-(x+y)NixFeyO3-δ (x = 0.1, 0.2, and y = 0.2, 0.5, 0.7)—a Nanocomposite-Type Electrocatalyst for the Oxygen Evolution Reaction in Alkaline Media

We report on nanocomposite materials that are both active and stable for the oxygen evolution reaction (OER) in alkaline media. Ce0.8Sr0.2Co0.6Ni0.2Fe0.2O3-δ (CSCNF1), Ce0.8Sr0.2Co0.3Ni0.2Fe0.5O3-δ (CSCNF2), and Ce0.8Sr0.2Co0.2Ni0.1Fe0.7O3-δ (CSCNF3) that contain a lanthanide, in the form of Cerium (Ce) in the A site and varied compositions of Co, Ni, and Fe in the B site, were synthesized by a typical sol-gel route and compared with a benchmark nanocomposite, i.e. Ba0.5Sr0.5Co0.8F0.2O3-δ, synthesized by the same method. The crystal structure was examined employing X-ray diffraction (XRD) and the textural properties were examined using Fourier transform infrared spectroscopy (FTIR). The morphology and microstructure were examined employing scanning electron microscopy (SEM) and high-resolution transmission electron microscopy (HRTEM). The CSCNF1 (n = 1, 2, or 3) nanocomposite materials exhibited high intrinsic activities, by displaying overpotentials of 0.290 V, 0.470 V, and 0.350 V for CSCNF1, CSCNF2, and CSCNF3, respectively, at 10 mA cm−2, and Tafel slopes of 54.1 mV dec−1, 71.3 mV dec−1, and 62.8 mV dec−1, respectively. CSCNFn (n = 1–3) nanocomposites compared with BSCF nanocomposite established its viability as a good electrocatalyst. They exhibited good electrocatalytic performance and stability and deserve further investigation as electrocatalysts for the OER in alkaline solution.

Investigation on the influence of cerium doping form on the luminescence properties of Lu0.8Sc0.2BO3 scintillation crystals

Transparent Lu0.8Sc0.2BO3:Ce single crystals doped with different forms of cerium [CeF3, CeO2 or Ce(NO3)3] were grown by the Czochralski method. The influence of cerium doping form on the luminescence mechanism, point defect and scintillation efficiency of Lu0.8Sc0.2BO3:Ce was investigated and discussed in detail. We found that the cerium doping form had no influence on the luminescence mechanism and the type of point defects in Lu0.8Sc0.2BO3:Ce host. The underlying reason for the scintillation efficiency discrepancy in these singlecrystall samples was revealed by XANES technique. Based on the Ce LIII-edge XANES spectra, it can be concluded that the Ce3+/Ce4+ ratio in the crystal resulted in the scintillation emission discrepancy. More importantly, our research demonstrates that it is possible to qualitatively identify the cerium oxidation state in single crystal scintillator doped with trace amounts of Ce ions by the XANES method and that the scintillation efficiency of single crystals could be tailored by manipulating the content of the contributed valence state, such as Ce3+ for Ce ions.

Study on the cerium oxidation state in a Lu0.8Sc0.2BO3 host

Lu0.8Sc0.2BO3:Ce powders doped with different forms of cerium [CeF3, CeO2 or Ce(NO3)3] were synthesized by solid-state methods under different conditions (carbon powders, nitrogen or air) and studied by a combination of X-ray excited luminescence spectra, optical diffuse reflectance spectra, fluorescence decay curves and X-ray absorption near edge spectroscopy. The optical diffuse reflectance spectra and fluorescence decay curves confirmed the different Ce3+/Ce4+ ratios in the samples of interest. Based on the Ce LIII-edge XANES spectra, we finally concluded that the differences in the scintillation intensities of the samples of interest originate from the varied Ce3+/Ce4+ ratios, which explains why the sample doped with CeF3 and synthesized under carbon powder conditions shows an optimal scintillation emission. The specific Ce3+/Ce4+ ratio was also qualitatively determined by fitting the Ce LIII-edge XANES spectra. More importantly, this study further demonstrates the effectiveness of using XANES spectroscopy to investigate the cerium oxidation state in cerium-doped scintillators.

Cerium (IV) molybdate cation exchanger: Synthesis, properties and ion separation capabilities

A description of the preparation and properties of an H + form of cerium (IV) molybdate ion exchanger prepared at different pH values is given. The material was characterized by inductively coupled plasma (ICP) elemental analysis, IR spectrometry and thermo-gravimetry and titration curve analysis; its composition was found to be Ce(OH) 2(HMoO 4) 2· nH 2O. It was also observed that the exchange capacity of the ion exchanger depends upon the pH value of the ceric solutions used and its value was lowered after gamma irradiation. Furthermore, the absorption of 99Mo and the distribution coefficient of this ion exchanger for Mg(II), Ba(II), Ca(II), Ni(II), Mo(VI), Cr(VI) and Th(IV) were investigated. It was found that cerium (IV) molybdate had the highest absorption for Th(IV) and Ba(II), while Mg(II) and Ca(II) showed the lowest absorption, respectively. Finally, gamma irradiation, in general, lowered the absorption of the cations being investigated in this study.

Diffusion mechanism and ion exchange equilibria of some heavy metal ions on cerium(IV) antimonate as cation exchanger

Abstract The kinetics and mechanism of diffusion of Zn 2+ , Sr 2+ , Co 2+ and Eu 3+ in the H + -form of cerium(IV) antimonate (CeSb) have been studied as a function of particle sizes, reaction temperatures and solution concentrations of the exchanging ions. The exchange rate was controlled by particle diffusion mechanism as a limited batch technique. The physical thermodynamic parameters such as, activation energies and entropies of activation have been evaluated. The mobility of these ions inside the particles of the exchanger decrease in the order: Zn 2+ >Sr 2+ >Co 2+ >Eu 3+

The β to γ transformation in cerium—A twenty year study

Cerium has four allotropic modifications at one atmosphere pressure: {alpha}-Ce -- the so called ``collapsed fcc`` phase; {beta}-Ce -- the double hexagonal close packed phase; {gamma}-Ce -- the normal fcc phase; and {delta}-Ce -- the high temperature bcc phase. The phase relationships are transformations between the {alpha}, {beta} and {gamma} forms of cerium are complex and temperature hysteretic in nature, and these are described in great detail by Koskenmaki and Gschneidner. Recently, however, the authors decided to make heat capacity measurements on allotropically pure {beta}-Ce and {gamma}-Ce below 350 K, since the data obtained in the 1950`s were made on samples which contained two or more of the low temperature phases of cerium. The {beta}-Ce sample which was initially used had been prepared in May 1975. When the heat capacity was measured on this sample after it had been cooled down to 77 K to start the run (December 13, 1994), a large peak in the heat capacity was observed at {approximately}180 K, indicating that {alpha}-Ce was transforming primarily to {gamma}-Ce (and perhaps to {beta}-Ce). Since {beta}-Ce is stable down to {approximately}45 K before it transforms to {alpha}-Ce, the question was, where did the {alpha}-Ce come from? The most likely more » answer was that in the 19.6 years since the {beta}-Ce had been prepared, some of it must have transformed to {gamma}Ce while sitting at room temperature (295 {+-} 2 K), and the {gamma}-Ce phase present in the sample transformed to {alpha}-Ce when cooled down below {approximately}110 K. Another piece of the {beta}-Ce starting material was examined by x-rays, which confirmed that this sample contained {approximately}25% {gamma}-Ce. These measurements indicate that at room temperature the true equilibrium phase is {gamma}-Ce, and that the {beta} {l_equilibrium} {gamma} equilibrium temperature must be less than 295 {+-} 2 K. « less

Determination of different valence forms of cerium in glasses using potentiometric titration

This paper describes a potentiometric method for the quantitative determination of two cerium oxide forms--cerium dioxide and dicerium trioxide--in glasses where the oxides form a major constituent. The method uses hydroquinone as a reducing agent. Cerium valences are also determined. The sensitivity of the method is tested by analyzing known synthetic mixtures simulating the composition of the glasses. The method has been used to determine the total concentration of cerium and to monitor the redox regime in glass melting furnaces during the melting of cerium-containing glasses.

Crystal structure of triclinic CeP 5O 14: A new type of ultraphosphate

The new form of cerium(III) ultraphosphate, CeP 5O 14 described here is triclinic with a = 9.227(5), b = 8.890(5), c = 7.219(4)Å, α = 110.12(5)°, β = 102.68(5)°, γ = 82.13(5)°. Space group is P1. Z = 2. D x = 3.186 mg/m 3. Crystal structure of this salt has been solved by using 4587 independent reflections with a final R value 0.029. The atomic arrangement can be described as [P 10O 28] sheets spreading in (110) planes. The internal structure of these sheets is mainly a linkage of (P 12O 36) rings in which 40% of the phosphorus atoms are branching phosphorus.

A New Allotropic form of Cerium Due to its Transition Under Pressure to the Tetravalent State

An x-ray structural analysis on cerium under pressure was made in order to investigate its valence behavior in the metallic state. A new form, ${\ensuremath{\alpha}}^{\ensuremath{'}}\ensuremath{-}\mathrm{Ce}$, always fcc but strongly collapsed, was found to exist at pressures higher than 50 kbar. It was deduced that Ce is tetravalent in the ${\ensuremath{\alpha}}^{\ensuremath{'}}$ form. The atomic radius of ${\mathrm{Ce}}^{\mathrm{IV}}$ was calculated, and the probable values of the valency in $\ensuremath{\gamma}\ensuremath{-}\mathrm{Ce}$ and $\ensuremath{\alpha}\ensuremath{-}\mathrm{Ce}$ are also estimated.

Ceric ion equilibrium in aqueous acetic acid

Ceric ion equilibrium in aqueous acetic acid

Radioisotopes as Aids to Metallography

Variations in two radiotracer techniques are described and compared in their application to Problems involving the distribution and chemical form of cerium and titanium in steel. The relative advantages of macroautoradiography, microautoradiography, radioactivity measurements of surfaces, and radiometric analysis of thin samples are discussed.