Solid Cerium Research Articles

Numerical simulations of solid cerium ejecta transporting in vacuum and in non-reactive and reactive gases

When a shock wave impacts a roughened metal/gas interface, metal ejecta particles emit and transport in the gas. The exchanges of momentum and energy between ejecta particles and the gas occur. If active metal particles transport in the reactive gas, the heat released by a chemical reaction could change these exchanges. In this paper, we use numerical simulations to study solid cerium ejecta transporting in a vacuum, and in non-reactive and reactive gases. In vacuum, the emitted ejecta could self-similarly expand neglecting the particle interaction. In the non-reactive gas (He), ejecta particles slow down by the gas resistance and have the exchanges of momentum and energy with the gas. In the reactive gas (D2), the ejecta particles also slow down. The exothermic reaction could induce the temperature rise of the ejecta and the gas, which could induce changes in physical property values of the gas after the shock wave and the velocity of the shock wave. The numerical result shows that the maximum temperature of the ejecta may appear in the middle of the mixture zone, which may result from the ejecta temperature being controlled by two competitive effects. Furthermore, the maximum ejecta temperature increases rapidly in the beginning and then becomes steady. Finally, the ejecta with a different initial size distribution is investigated. The ejecta with a smaller maximum size has a larger maximum particle temperature, a larger gas temperature after the shock wave, and a larger chemical reaction function of the ejecta at the same moment.

High Efficient Construction and Comprehensive Evaluation of Superhydrophobic Filter Screen Coatings

The preparation of environment-friendly and efficient superhydrophobic filter screen still faces great challenges. Herein, a compact, solid cerium stearate superhydrophobic-coated stainless steel mesh (SSSM) was prepared by a simple, efficient, and environmentally friendly one-step electrodeposition process. Fourier transform infrared (FTIR) spectroscopy, energy-dispersive X-ray spectroscopy (EDS), scanning electron microscopy (SEM), and contact angle measurement were used to characterize the surface coating (composition, morphology, and contact angle) of SSSM. The results show that the SSSM surface is a dense mastoid cerium stearate micronanostructure coating, and its static contact angle with water can reach 162.73°. In addition, it has excellent self-cleaning performance for conventional simulated pollutants, and the contact angle can still reach 161° after 28 days of storage. In the wear resistance and corrosion resistance tests, the contact angle can still be kept above 150° after 600 mm abrasion under the load of 19.6 kPa, the corrosion current of SSSM is reduced by two orders of magnitude, and its corrosion inhibition efficiency reaches 99.74%. In addition, the oil/water separation performance of SSSM is also very good, and the separation efficiency for different oil/water mixtures exceeds 97%. This study will provide important data support and method reference for the preparation of metal anticorrosion superhydrophobic material coating and the development of environment-friendly and efficient oil–water separation materials.

Confinement and Electrocatalysis of Cerium Fluoride Nanocages to Boost the Lithium–Sulfur Batteries Performance

Lithium–sulfur batteries (LSBs) are beset by the polysulfides shuttling and the sluggish conversion kinetics, leading to fast capacity fading and inferior rate capability. A feasible solution is to confine the active species and/or electrocatalytically boost the polysulfides conversion by suitable host materials. Herein, hollow cerium fluoride nanocages (h‐CeF3) are employed as the host, which not only suppressed polysulfides shuttling via physical confinement and chemisorption, but also exhibited remarkable catalytic promotion to the polysulfide conversion, much superior to the counterparts of solid cerium fluoride nanodiscs (s‐CeF3) and hollow ceria nanospheres (h‐CeO2). Consequently, the sulfur‐filled h‐CeF3 cathode delivers an outstanding capacity of 544 mAh g−1 at 5 A g−1, demonstrating a high rate capability. With an areal sulfur loading of ≈3.5 mg cm−2, the LSB exhibits a reversible capacity of 429.5 mAh g−1 at 1 A g−1 after 200 cycles under a low electrolyte/sulfur (E/S) ratio of 10 μL mg−1. This study demonstrates the promise of the h‐CeF3 host in Li–S batteries, shedding light in developing advanced sulfur hosts of metal fluorides.

Preparation and Tribological of 8-Hydroxyquinolinato Cerium

A new solid cerium complex, was synthesized by 8-hydroxyquinoline and cerium nitrate in the ethanol-aqueous solution. The complex was characterized by elemental analysis and FTIR. The results indicate that the complex is Ce(C9H6NO)3. The tribological properties of the Ce(C9H6NO)3particles as additive in paraffin oil was investigatedon MRS-10A four-ball tester, the results indicate that Ce(C9H6NO)3particles as additive can be effective in improving anti-wear ability, in enhancing extreme-pressure capacity. The wear scar width can be decreased 0.3mm when the additive in paraffin oil is about 0.25wt.%, when the additive in paraffin oil is about 0.5wt.%, load-carrying capacity can improve 29%. The morphologies, typical element distribution of the worn surfaces were characterized by SEM and EDS, respectively. Its anti-wear mechanism as follows: A permeating layer with rare earth elements was produced in the frictional sub-surface, the layer modified the microstructure and the lubricating state of the frictional surface.

Solid-state regioselective nitration of activated hydroxyaromatics and hydroxycoumarins with cerium (IV) ammonium nitrate

Predominant ortho-selective mononitration of low-melting and liquid phenols and hydroxycoumarins in moderate to high yields has been accomplished upon grinding with solid cerium (IV) ammonium nitrate (CAN). Microwave-assisted expeditious CAN-mediated nitration of relatively high melting phenols and hydroxycoumarins with high efficiency and selectively under solvent-free conditions has been also developed to address the problems of sluggishness and low yield for these reluctant substrates.

Preliminary Studies of the Obtaining of Solid Metallic Cerium from Fluoride Melts

The present study deals with the obtaining of solid cerium by molten salt electrolysis of a 46.74 - 48.26 - 5wt% LiF-NaF-NaCeF4 mixture, in the temperature range 700 - 730 °C and with a current efficiency of ~ 75%. For this purpose NaCeF4 was obtained, characterized and it’s cubic form was identified. The solubility and decomposition potential of this compound in the molten electrolyte 49.2 - 50.8% LiF-NaF was also studied.

X-ray Spectrum Emitted by a Laser-Produced Cerium Plasma in the 7.5 to 12 Å Wavelength Range

A highly stripped cerium (Z = 58) plasma is produced by irradiating a solid cerium target with an intense short laser pulse. The x-ray spectrum emitted from the plasma is recorded in the 7.5–12 Å wavelength range using a flat RAP crystal spectrometer. Ab-initio calculations using the RELAC relativistic computer code, as well as isoelectronic trends deduced from previous works, together with spectra obtained under different laser beam focusing conditions, are all employed for the identification of the spectral lines and features emitted by various ions from Fe-like Ce32+ to As-like Ce25+. The technique of comparing spectra obtained using different laser intensities is also employed to confirm or to resolve some ambiguous identifications of spectral features in the spectrum of a laser-produced lanthanum plasma studied in a previous work.

Investigation of a laser-produced cerium plasma by the analysis of the high-resolution x-ray spectrum

A highly stripped cerium $(Z=58)$ plasma is produced by irradiating a solid cerium target with a short pulse laser. The x-ray spectrum emitted from the plasma is recorded in the limited wavelength range 9.0--9.3 \AA{} using a high-resolution curved mica crystal spectrometer. The high-resolution spectrum, which corresponds to the $3d\ensuremath{-}5f$ transitions in Ni-, Cu-, and Zn-like cerium ions, is analyzed by means of a detailed collisional-radiative model that includes autoionization and dielectronic capture processes. The intensity ratio of the Ni-like $3d\ensuremath{-}5f$ resonant line at 9.045 \AA{} to the features emitted from satellite transitions of Cu-like ions provides an estimate for the mean electron temperature and density of 230 eV and ${10}^{22} {\mathrm{cm}}^{\mathrm{\ensuremath{-}}3},$ respectively. The deduced mean electron temperature is higher than that obtained in a similar experiment on laser-produced barium plasma. The origin of the higher mean electron temperature deduced in the present experiment is explained by the different type of transition employed for the temperature diagnostics, which might reflect a different phase of the plasma evolution.

Study of cerium species in molten Li2CO3-Na2CO3 in the conditions used in molten carbonate fuel cells. Part II : Potentiometric and voltammetric behaviour

The electrochemical behaviour of metallic cerium and cerium dioxide is analysed in molten Li2CO3–Na2CO3 under the anodic and cathodic conditions used for the molten carbonate fuel cells (MCFC). Chronopotentiometric measurements on metallic cerium rods or foils show the influence of CeO2 growth and the deviation from its stoichiometric composition. A study of the voltammetric characteristics of dissolved cerium at a gold electrode, of metallic cerium and cerium oxide is carried out in both oxidising and reducing MCFC atmospheres. Experimental evidence is given for the existence of a solid–solid cerium system: Ce2O3(s)|CeO2(s) and a system relative to dissolved cerium species Ce2O3(l)|CeO2(l). These systems are in agreement with thermodynamic predictions. Other more complex phenomena involving interactions with alkali species are discussed.

Determination of Trace Amounts of Rare Earth Elements in High-purity Cerium Oxide by Inductively Coupled Plasma Mass Spectrometry After Separation by Solvent Extraction

A method was developed for the determination of trace amounts of REEs in high-purity cerium oxide by ICP-MS after separation by solvent extraction. Based on the specificity of 2-ethylhexyl hydrogen-2-ethylhexylphosphonate, the Ce matrix in a tetravalent ionic state was separated from all other trivalent ionic state REEs. After removal of the matrix, the polyatomic interferences in ICP-MS were negligible. More than 99.5% of the Ce matrix was removed with 94–102% recoveries for 14 REE impurities in a spiked sample. The precision was 0.7–2.7% (RSD). The detection limits for 14 rare earth elements were 0.026–0.003 ng cm - 3 in solution and the limits of quantification were 0.02–0.09 µg g - 1 in solid cerium oxide. The method is rapid, precise and reliable and is well suited for the determination of REE impurities in high-purity cerium oxide.

セリウムの酸素溶解度

Solubilities of oxygen in liquid and solid cerium were determined by metal-oxide equilibrium method: Solubility in liquid ceriumlog (Co/mass %) liquid Ce=-4600 (±500)/T+6.3 (±0.4)(1, 123-1, 573 K)Solubility in solid cerium log (Co/mass %) solid Ce (γ) =-3200 (±600)/T+5.9 (±0.7)(923-1, 023 K)Ce2O3 was identified by the X-ray diffraction analysis as the oxide phase in equilibria with cerium from 923 to 1, 573 K.Based on the results, the partial phase diagram of Ce-O system was determined.

An electrochemical investigation of the thermodynamic properties of cerium stannide (CeSn 3) and liquid tincerium alloys

The thermodynamic properties of the intermetallic compound CeSn 3 and the tin-rich liquid tincerium alloys in equilibrium with CeSn 3 were studied by a high-temperature galvanic cell technique using the reversible concentration cell Ta, Ce∥CeCl 3, LiClKCl (eutectic)∥CeSn (two-phase alloy), Ta in the temperature range 723–873 K. The standard Gibbs energy of formation of CeSn 3 from pure solid cerium and pure liquid tin varies with temperature according to the equation ΔG f(CeSn 3) 0 = −260.08 + 0.0476 T (±2) kJ mol −1 The activity coefficients, excess partial molar free energies, enthalpies and entropies of cerium in the saturated liquid alloys have been computed from the e.m.f. data obtained in this study and the data for the solubility of cerium in liquid tin. The activity coefficients of cerium in liquid tin with reference to solid cerium can be expressed as G Ce xs = RT ln τ Ce = −249 + 0.059 T (±2) kJ mol −1

Vaporization study of solid CeTe by the Knudsen effusion mass spectrometric method

A thermodynamic study of the vaporization of solid cerium monotelluride, CeTe(s), was performed by using the Knudsen effusion mass spectrometric method in the temperature range of 1925–2060 K. As the vapor species over CeTe(s), Ce(g), Te(g) and CeTe(g) were identified and their partial vapor pressures were obtained. The reaction equilibria were established such as CeTe(g) a ́ i Ce(g) + Te(g) , CeTe(s) a ́ i Ce(g) + Te(g) and CeTe(s) a ́ i CeTe(g) . The enthalpies of these reactions were obtained by using the slope method. The dissociation energy of CeTe(g) was obtained by the second and third law treatments. The standard Gibbs energy of formation of CeTe(s) was evaluated as ΔG f o(T) = 134.2T − 5.342 × 10 5 (J/mol) in the temperature range of 1925–2060 K.

ChemInform Abstract: THERMODYNAMIC STUDY OF THE VAPORIZATION OF CERIUM ORTHOPHOSPHATE

AbstractDie Verdampfung von CePO4 im Temperaturbereich 1700‐1850 K wird massenspektroskopisch unter Verwendung einer Knudsen‐Zelle untersucht.

Thermodynamic study of the vaporization of cerium orthophosphate

The high temperature Knudsen cell mass spectrometric technique has been used to study the vaporization behaviour of solid cerium orthophosphate over the temperature range 1700–1850 K.From the second- and third-law analyses of the equilibrium reaction: CePO4(s)= CeO2(g)+ PO2(g), the following standard heat of formation of CePO4(s) has been derived: ΔH°298,f[CePO4(s)]=–1898.5 ± 31.5 kJ mol–1. These results are discussed and compared with those obtained by other authors for other LnPO4 compounds.

Thermodynamics of Rare-Earth–Carbon Systems. I. The Cerium–Carbon System

The gaseous phase in thermodynamic equilibrium with the condensed cerium–carbon system has been investigated by means of the combined Knudsen-cell–mass-spectrometric technique in the temperature range 1990°–2300°K. In addition to cerium atoms, the gaseous carbide molecules CeC2 and CeC4 were identified and their partial pressures measured. Using this information, the following dissociation and atomization energies were derived: D0° = 162 ± 2 kcal/mole for the Ce–C2 bond energy in CeC2; ΔH0° = 304.5 ± 1.5 kcal/mole for the atomization energy of CeC2; ΔH0° = 609 ± 5 kcal/mole for the atomization energy of CeC4. A heat of formation for the solid cerium dicarbide was also obtained.

Electrolytic Conduction in Calcium-Doped Solid Cerium Oxide

At 460°C the passage of direct current through ceramic pellets of cerium dioxide containing one weight percent calcium oxide caused distinct volume discolorations to appear. The current at constant applied bias increased gradually from its initial value during the formation of the discolored regions, finally reaching a new, stable, higher level if sufficient time elapsed. In the latter case, both anode and cathode surfaces were discolored and the discoloration extended completely through the body of a pellet. When insufficient time was allowed for the current to reach a new, stable level, only the cathode surface was discolored and the discoloration extended only part way through the material. The discolorations could always be removed by heating the pellets for one hour in air at 600°C and the entire process could be repeated many times. These effects are interpreted to indicate that a significant fraction of the current in this material at this temperature is carried by oxygen ions which move to the anode where they are ``plated-out'' leaving reduced, discolored material.