Papers by Keyword: CeO₂

Abstract: The CeO₂/rGO composites were prepared by hydrothermal method. The microscopic phase structure and microstructure of the samples were characterized by SEM, XRD and FTIR. The cyclic voltammetry (CV) and constant current charge and discharge tests were used to study the electrochemical stability and cycle ability of the CeO₂/rGO composite electrode. The results show that the incorporation of graphene effectively increases the reversibility of CeO₂ as an electrode material. The special structure of graphene provides a continuous network and more active sites for redox reactions. In the 6mol/L KOH electrolyte, the specific capacitance of CeO₂/rGO composite reached 114F·g^-1 when the current density was 0.5A/g. After 1000 cycles, the specific capacitance only decreased by 12.66%, which proves that this material has good cycle performance.

Abstract: Addition of CeO₂ into ZTA and its effects on microstructure and mechanical properties were investigated. CeO₂ was detected with significant amounts only above 10 wt%. Viscosity was measured for slurry preparartions and characterization of mechanical properties of ZTA. Additions of CeO₂ of more than 10 wt% surpassed the solubility limit and formed Ce₂Zr₃O_10. Ce₂Zr₃O₁₀ increased the tetragonality factor, prevented excessive grain growth through a pinning effect, which is attributed to the segregation of Ce₂Zr₃O₁₀ to the grain boundaries and showed a peak in fracture toughness with a value of 9.3 MPam^1/2 with 10 wt% additions of CeO₂. Further additions of CeO₂ reduced ZTA’s mechanical strength. Maximum value of H_v was 17700 MPa with 10 wt% CeO₂. Porosities have been attributed as the underlying reason as to why theoretical density were always higher than measured densities.

Abstract: It is well known that sol-gel technique is a simple method to produce nano sized ceramic powders. In this study, cerium oxide doped zirconia samples, with 10 mol%-12mol% and14mol% CeO₂, were synthesized by sol-gel technique and characterized. The surface morphology, elemental composition, microstructure, and phase analysis, of the sintered CeO₂ doped ZrO₂ ceramics were characterized by field emission scanning electron microscopy (FE-SEM), energy dispersive X-ray (EDS) analysis, and X-ray diffraction (XRD) respectively. X-ray diffraction for samples sintered at 1550 °C for 4h revealed that the zirconia ceramics have a tetragonal phase structure. The addition of CeO₂ can raise the content of the tetragonal phase, but the minor monoclinic phase exists even at the CeO₂ content of 10 mol%. The effect of dopant concentration on the lattice parameter, average primary crystallite size and micro-strain was studied. Relative densities for CeO₂ doped ZrO₂ bulk ceramics varied between 95% and 99 %, depending on the CeO₂ addition.

Abstract: Pure CeO₂ and Cu-doped CeO₂ nanoparticles with different doping amounts of Cu in the range of 0.5-2.0 wt.% were synthesized by the combination of homogeneous precipitation and impregnation methods. The effect of Cu on the correlation of structural, optical and photocatalytic properties of CeO₂ were studied. The XRD results indicated that phase structures of pure CeO₂ and Cu-doped CeO₂ nanoparticles were cubic fluorite phase and no other characteristic peaks related to Cu were detected. TEM images revealed that all samples were spherical in shape with the size less than 10 nm. The shift of absorption edge of Cu-doped CeO₂ catalysts, corresponding to a decrease of band gap energies from 3.2 to 2.8 eV, was also observed as the amount of Cu dopant increased. The photocatalytic performances of the Cu-doped CeO₂ exhibited higher activity than pure CeO₂ for photocatalytic degradation of methylene blue under visible light irradiation, and the CeO₂ doped with 1.0 wt.% Cu exhibited the highest photocatalytic activity.

Abstract: Hydrothermal processes have the potential for the direct preparation of crystalline ceramic powders and offer a low-temperature alternative to conventional powder synthesis techniques in the production of oxide powders. These processes can produce fine, high-purity, stoichiometric particles of single and multi-component metal oxides. Furthermore, if process conditions such as solute concentration, reaction temperature, reaction time and the type of solvent are carefully controlled, the desired shape and size of particles can be produced. Uniform distribution of the particles is key for optimal control of grain size and microstructure in order to maintain high reliability. It has been demonstrated that such powders are composed of much softer agglomerates and sinter much better than those prepared by calcination decomposition of the same oxides. These powders could be sintered at low temperature without calcination and milling steps. The objective of this study was to synthesis TiO₂-CeO₂ nanosized crystalline particles by a hydrothermal process.TiO₂-CeO₂ nanosized powders were prepared under high temperature and pressure conditions by precipitation from metal nitrates with aqueous potassium hydroxide. The TiO₂-CeO₂ nanosized powder was obtained at 185°C and 6 h. The average size and size distribution of the synthesized particles were below 10±5 nm and narrow, respectively. The XRD diffraction pattern shows that the synthesized particles were crystalline. This study has shown that the synthesis of TiO₂-CeO₂ nanosized crystalline particles is possible under hydrothermal conditions in aqueous solution.

Abstract: The dynamic behavior of bed for regeneration of cerium oxide high temperature gas desulfurization sorbent under the atmosphere of O₂ was investigated in the fixed bed micro-reactor. O₂ concentration during the regeneration can be detected by an oxygen analyzer, and the sulfur content of sorbent in the bed was test using sulfur analyzer. The effects of O₂ concentration, regeneration temperature on the dynamic behavior of bed for regeneration of CeO₂ desulfurization sorbent were discussed. According to the experimental results, the length and movement speed of regeneration zone are calculated. The results showed that the increase of O₂ concentration in inlet gas obviously improves the movement speed of regeneration zone in bed for CeO₂ desulfurization sorbent, and the increase of regeneration temperature can decreased the length of the regeneration zone and improved the movement speed of the regeneration zone. The increase of regeneration temperature had a better effect on the improvement of bed utilization of sorbent than that of O₂ concentration.

Abstract: This work examined improvements in cutting efficiency obtained during the slicing of sapphire workpieces when adding CeO₂ to the cutting fluid. Various machining parameters, including the cutting temperature, machining surface tolerance, surface quality and tool wear, were assessed. It was confirmed that both the cutting temperature and the machining surface tolerance are reduced by the presence of CeO₂ in the cutting fluid. Observations of the machined surfaces and the cutting tool also demonstrated that both brittle fracturing of the surface and loss of abrasive grains were suppressed following the addition of CeO₂. These results suggest that the cutting temperature likely affects the accuracy of the cutting process and that CeO₂ appears to improve cutting efficiency by reducing the workpiece temperature and by stabilizing the cutting process.

Abstract: Ultrafine CeO₂ nanoparticles were prepared through a calcination method. The photocatalyst was characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM). The performance of photocatalytic antibacterial was investigated by inactivation of E.coli. and S.aureus.

Abstract: Hydrogen zeolite was modified with CeO₂ by impregnation - filtration - heat treatment. Hydrogen-zeolite samples before and after modification were characterized by XRD and SEM. The catalytic efficiency of modified hydrogen-zeolite was investigated. Such modification conditions were explored: as the CeO₂ percentage, calcination temperature, calcination time, impregnation temperature. The results show that the optimal CeO₂ percentage is 0.5%, calcination temperature is 600°C, calcination time is 2h, impregnation temperature is 75°C. The aspirin yield reaches 78.3% under the optimal conditions, compared with that (64.8%) catalyzed by sulfuric acid and that (70.4%) catalyzed by unmodified zeolite. XRD, SEM characterizations show that Ce ions can be doped into the zeolite framework. And the modification makes the zeolite particle size become smaller, which is reduced to 50.5nm from 56.76nm. A high efficient and eco-enviromently catalyst was got by modification.

Abstract: Cerium Oxide (CeO₂) nanocubes are synthesized by using hydrothermal treatment method in the presence of four different types of ionic liquid such as acetate anion, phosphate anion, and dicyanamide anion. Ceria nanocubes has been consisted with average size of 16 to 31 nm in diameter and characterized by transmission electron microscope (TEM), X-ray diffraction (XRD), and surface analyzer and porosimetry analysis (ASAP). Ceria nanocubes have higher photocatalytical ability in the degradation of methylene blue as compared to commercial ceria nanoparticles which are confirmed through ultraviolet-visible spectroscopy (UV/Vis).