Thermodynamic functions of thorium–cerium mixed oxides

Journal of Thermal Analysis and Calorimetry - Thorium–cerium mixed oxides (Th1?xCex)O2 (x?=?0.25, 0.5, 0.75) were prepared by the citrate gel combustion technique. X-ray...     

Oxidative bisdecarboxylation of α-alkoxymalonic acids with cerium(IV)

Ceric ammonium nitrate is an excellent reagent for preparing carboxylic esters from α-alkoxymalonic acids by oxidative bisdecarboxylation.     

Electrochemical separation of uranium and cerium in molten LiCl–KCl

The electrochemical separation of uranium from cerium in LiCl–KCl eutectic and the electrochemical behavior of Ce(III) were studied. According to the cyclic voltammogram of Ce(III) and the former result of U(III), electrodeposition potential was determined at ?1.65 V (vs Ag/AgCl). The uranium metal was successfully deposited and separated from cerium. The morphology of deposit and cross section of electrode were investigated by SEM, firstly uranium deposit alloys with stainless steel and forms a thin transition layer, and secondly the uranium metal layer grows from the transition layer. The separation factors of uranium/cerium on different recovery ratios were determined through a series of steps. It was found that the content of cerium in the deposit and separation factors declined with increasing the initial concentration of U³⁺ in molten salts; the separation factors remained stable at around 20 in different uranium recovery ratios.     

Activity of copper–cerium–zirconium catalysts in oxidation of hydrogen

We have studied the catalytic properties in oxidation of hydrogen for copper–cerium oxide systems deposited on supports obtained by calcination of yttrium-stabilized zirconium dioxide at 300–1000 °C. We have shown that the catalytic activity of the samples obtained depends on the specific surface area of the original supports and the amount of reduced copper within the composition of the catalyst. In samples whose support has high specific surface area, the content of reduced metallic copper is greater and the catalytic activity is higher.     

Synthesis and electrocatalytic reactivity for water oxidation of two cerium complexes

Two cerium complexes with and without manganese ion, [MnCe₄(dipic)₆(H₂O)₂₀][Ce(dipic)₃]₂·7H₂O (dipic = dipicolinate) (1) and [Ce₂(H₂O)₄(O₂CMe)₆][Ce(H₂O)₄(NO₃)₂(O₂CMe)]₂·2H₂O·2MeOH (2), have been prepared, and their electrocatalytic reactivity for water oxidation has been investigated. Compound 1 is a heterometallic 3d-4f compound which possesses four Ce(IV) ions, two Ce(III) ions, and one Mn(II). Compound 2 is composed of three neutral parts, one of which is a dinuclear cerium molecule lying on an inversion center, and the other two are symmetric monomer units; the four cerium ions in 2 are all Ce(III). Electrochemical studies of 1 and 2 show that 1 can catalyze water oxidation at the potential ~1.5 V with an overpotential of ca. 900 mV versus NHE. Control potential electrolysis (CPE) experiments at 1.50 V of 1 displayed a stable current density of 2.5 mA/cm², and the calculated Faradaic efficiency is 60%. However, no electrocatalytic reactivity was observed for 2. By comparison experiments, it was found that the electrocatalysis of 1 may result from the cooperative catalytic effect of the 4f cerium ion and 3d transition metal manganese ion.     

Enrichment of trace cerium subgroup rare earths by means of ion flotation

The possibility of ion flotation of cerium subgroup rare earths (Ce-subgroup) wasexplored. Various factors affecting the flotation efficiency were investigated. The results showedthat, by using sodium tetradecyl sulfate as the collector of trace Ce-subgroup and frother, over 95%of Ce-subgroup at ng/g levels could be separated from pH 2.3 media in 10--15 min. The proposedmethod has been applied to the determination of Ce-subgroup in a polluted farmland soil referencematerial (GBW 08303) with satisfactory results.     

Synergistic catalytic ozonation of toluene with manganese and cerium varies at low temperature

The temperature of waste gas in refuse transfer station, airport smoking area, and RTO terminal is low,which needs deep oxidation. Catalytic ozonation is one of the most effective treatment techniques in these scenarios. In this study, we reported that catalysts were modified under the condition of magnetic field to simulate the low temperature dynamic conditions of low concentration toluene for catalytic ozonation. This paper aims to explore the relationship between oxygen vacancy and active ox...     

Triclinic structural isomer of cerium(III)–picrate complexes with triethylene glycol

Two new isomers of [Ce(NO₃)(Pic)(H₂O)₂(EO3)](Pic) complex (where EO3 = triethylene glycol and Pic = picrate anion) have been synthesized by one-pot reaction and structurally characterized. Both isomers, orange and yellow in color, respectively, have a triclinic P-1 crystal lattice with different unit cell dimension, and Ce(III) adopts a different coordination number. In orange isomer, the Pic anion is chelated to Ce(III) via phenolic and ortho-nitro oxygens in a bidentate mode, while in yellow isomer the Pic anion is chelated only monodentate through the phenolic oxygen. Coordination geometries can be described as a distorted bicapped square antiprism and a distorted tricapped trigonal prism for 1 and 2, respectively. Alcohol groups from EO3 form a 1-D chain with symmetry direction [1 0 0] through intermolecular O–H ··· O hydrogen bonding. Photoluminescence spectra of the complexes showed a broad band at 515–540 nm due to the 5d → 4f transition from the Ce(III) with electric dipole allowed.     

Topological evolution of cerium(Ⅲ) molybdate microflake assemblies induced by amino acids

In this work, cerium(Ⅲ) molybdate microspheres configured as microflakes were synthesized in the presence of lysine via a hydrothermal process. We studied the role of lysine and other amino acids on the morphologic control of cerium(Ⅲ) molybdate crystals. First, with the increase of lysine, thinner microflakes and smaller microspheres are obtained. Moreover, a transformation in topology of cerium(Ⅲ) molybdate assemblies from three-dimensional(3D) into two-dimensional(2D) can be ascribed to controlled nucleation and growth of cerium(Ⅲ) molybdate induced by lysine. Second, amino acids with strong hydrophilic ‘‘R' groups tend to induce nucleation and result in spherical assemblies formed by nanoparticles or nanoflakes, while those with weaker hydrophilic ‘‘R' groups tend to induce growth and yield spherical assemblies of microflakes.     

Environmentally benign sol–gel derived nanocrystalline rod shaped calcium doped cerium phosphate yellow-green pigment

Nanocrystalline rod shaped calcium doped cerium phosphate yellow-green pigment particles having an average length of ~100 nm and aspect ratio 10 even after calcination at 600 °C have been realized through an aqueous sol–gel process. The morphology, particle size and identification of the phase are determined by using different analytical tools such as transmission electron microscopy (TEM), photon correlation spectroscopy (PCS), Fourier-transform IR (FTIR) and X-ray diffraction (XRD). Brunauer–Emmett–Teller (BET) nitrogen adsorption analysis showed the pigment particles are mesoporous texture having specific surface area 42 m² g^?1 and average pore size 153 Å. Thermogravimetric (TG) analysis is used to explain the thermal phase stability of the pigment. UV–Visible spectroscopy and colorimetric analysis are also done. The typical yellow-green color has been obtained even after heating to as low as 600 °C, which is 300 °C lesser than reported. Systematic study on synthesis and effect of temperature on color are presented.     

Influence of cerium concentration on the structure and properties of silica-methacrylate sol–gel coatings

The aim of this work was to study the effect of the incorporation of cerium nitrate in a silica-methacrylate sol–gel hybrid matrix reinforced with silica nanoparticles. Sols, coatings and powders have been studied, focusing specially in the determination of the redox ratio Ce³⁺/Ce⁴⁺ and films structure. Sols have been characterised using viscosity measurements and FT-IR spectroscopy, and powders and coatings obtained with different Ce contents through UV–Vis and FT-IR spectroscopy, TGA, TEM, AFM and FE-SEM. The goal was to reach the best compromise between maximum cerium concentration and coating stability to better understand the mechanisms acting in active anti-corrosive processes.     

Influence of cerium oxide on properties of glass–ceramic sealants for solid oxide fuel cells

The influence of the cerium oxide concentration on the properties of glasses and glass ceramics of the SiO₂–Al₂O₃–CaO–Na₂O–MgO–K₂O–B₂O₃–CeO₂ system as potential adhesive and sealing materials for solid oxide fuel cells was studied. According to the data of differential scanning calorimetry, variation of the CeO₂ concentration does not appreciably influence the glass transition and crystallization temperatures of glasses. As the cerium oxide concentration is increased, the linear thermal expansion coefficient increases for the glasses but decreases for the partially crystalline samples. The gluing temperature of the glass sealants prepared allows their use for joining YSZ solid electrolytes with interconnectors of Crofer22APU type in solid oxide fuel cells..     

Production of monodisperse cerium oxide microspheres with diameters near 100 µm by internal-gelation sol–gel methods

Internal-gelation sol–gel methods have used a variety of sphere-forming methods in the past to produce metal oxide microspheres, but typically with poor control over the size uniformity at diameters near 100?µm. This work describes efforts to make and measure internal-gelation, sol–gel microspheres with very uniform diameters in the 100–200-µm size range using a two-fluid nozzle. A custom apparatus was used to form aqueous droplets of sol–gel feed solutions in silicone oil and heat them to cause gelation of the spheres. Gelled spheres were washed, dried, and sintered prior to mounting them on glass slides for optical imaging and analysis. Microsphere diameters and shape factors were determined as a function of silicone oil flow rate in a two-fluid nozzle and the size of a needle dispensing the aqueous sol–gel solution. Nine batches of microspheres were analyzed and had diameters ranging from 65.5?±?2.4?µm for the smallest needle and the fastest silicone oil flow rate to 211?±?4.7?µm for the largest needle and the slowest silicone oil flow rate. Standard deviations for measured diameters were less than 8% for all samples and most of them were less than 4%. Microspheres had excellent circularity with measured shape factors of 0.9–1. However, processing of optical images was complicated by shadow effects in the photoresist layer on glass slides and by overlapping microspheres. Based on the calculated flow parameters, microspheres were produced in a simple dripping mode in the two-fluid nozzle. Using flow rates consistent with a simple dripping mode in a two-fluid nozzle configuration allows for very uniform oxide microspheres to be produced using the internal-gelation sol–gel method.

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Chromatographic separation of cerium(Ⅲ) in L-valine medium using poly[dibenzo-18-crown-6]

A column chromatographic method has been developed for the separation and determination of cerium(Ⅲ) using poly[dibenzo-18-crown-6]. The separation was carried out in L-valine medium. The adsorption of cerium(Ⅲ) was quantitative from 1×10-1 to 1×10-4 mol/L L-valine. Amongst the various eluents, 1.0-8.0 mol/L hydrochloric acid, 1.0-8.0 mol/L hydrobromic acid, 1.0-8.0 mol/L perchloric acid, 1.0-2.0 mol/L sulfuric acid and 4.0-5.0 mol/L acetic acid, were found to be the efficient eluents for cerium(Ⅲ). The capacity of poly[dibenzo-18-crown-6] for cerium(Ⅲ) was (0.428±0.01) mmol/g. The method was applied to the separation of cerium(Ⅲ) from associated elements link uranium(Ⅵ) and thorium(Ⅳ). It was also applied for the determination of cerium(Ⅲ) in geological samples. The method is simple, rapid and selective with good reproducibility (approximately±2% ).     

Role of hydroxyl group in cerium hydroxycinnamate on corrosion inhibition of mild steel in 0.6 M NaCl solution

The corrosion inhibition mechanism of cerium hydroxycinnamate compounds has been studied and compared as an effective corrosion inhibitor for steel in an aqueous 0.6?M NaCl solution. Surface analysis results showed that the surface of steel coupons exposed to solutions containing cerium hydroxycinnamate compounds has less signs of corrosion attack due to a formation of the protective film, while the surface of mild steel coupons exposed to 0.6?M chloride solution without inhibitor additions was severely corroded due to pitting. Electrochemical results performed a good inhibition performance and information of the formed protective deposit that hinders the electrochemical corrosion reactions with a dominance of anodic inhibition mechanism. The results also indicated that the addition of cerium hydroxycinnamate compounds to 0.6?M NaCl solution could mitigate electrochemical corrosion reactions, reduce protective and double layer CPE magnitudes, and improve protective and charge transfer resistances. Furthermore, cerium 2-hydroxycinnamate showed better efficient corrosion inhibitor in comparison with cerium 4-hydroxycinnamate for steel in aqueous media containing 0.6?M chloride ion.     

Determination of lanthanum and cerium in cmsx-4 nickel-based superalloys by inductively coupled plasma mass spectrometryEI北大核心CSCD

CMSX-4 is the second-generation nickel-based single crystal superalloy used widely in the world. The oxidation resistance and corrosion resistance of CMSX-4 alloy can be improved by adding trace lanthanum (La), cerium (Ce) and other rare earth elements. A method for the simultaneous determination of La and Ce in CMSX-4 nickel-based superalloy by wet dissolution-inductively coupled plasma mass spectrometry was established. The sample was heated and dissolved under normal pressure by aqua regia and hydrofluoric acid, and the interference of fluorine ion was eliminated by using perchloric acid. The amount of dissolved acid and the digestion conditions were optimized. The limits of detection were 0.23 μg/g for La and 0.85 μg/g for Ce under optimized conditions. The spiked recoveries were 95.0%–98.9% with the relative standard deviations of 1.3%–3.9%, which can meet the requirements of accurate and rapid determination of La and Ce in CMSX-4 nickel-based superalloy. © 2023, Youke Publishing Co.,Ltd. All rights reserved.     

Promoting effect of potassium and calcium additives to cerium–zirconium oxide catalysts for the complete oxidation of carbon monoxide

The effect of potassium and calcium additives on the catalytic activity of the Ce_0.8Zr_0.2O₂ system in the reaction of CO oxidation was studied. With the use of X-ray diffraction analysis, it was found that the Ce_0.8Zr_0.2O₂ and Ce_0.8Zr_0.2O₂–Ca,K samples contained a mixed oxide of cerium and zirconium; the presence of the independent phases of potassium and calcium compounds in the modified system was not detected. With the use of the low-temperature adsorption–desorption of nitrogen, X-ray photoelectron spectroscopy, and temperature-programmed reduction, it was established that the Ce_0.8Zr_0.2O₂–Ca,K system (in spite of the fact that its specific surface area was lower than that of Ce_0.8Zr_0.2O₂) contained more active oxygen on the surface; peroxide and superoxide complexes formed upon the chemisorption of O₂ can act as active oxygen species. This can be the reason for a higher efficiency of the Ce_0.8Zr_0.2O₂–Ca,K system in comparison with that of the unmodified oxide. The results obtained indicate that the ash impurities of Ca and K can increase the catalytic activity of the biomorphic mixed oxides Ce_0.8Zr_0.2O₂ prepared with the use of sawdust as a template.     

Adsorptive desulfurization of model diesel fuel over mono-functionalized nickel/γ-alumina and bi-functionalized nickel/cerium/γ-alumina adsorbents

Research on Chemical Intermediates - In this study, the S–M direct interaction and π-complexation mechanisms for selective adsorption of 4,6-dimethyldibenzothiophene (4,6-DMDBT) onto the...