Papers by Keyword: Ceria

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).

Abstract: Crystalline ceria nanomaterials have been successfully synthesized through ionothermal treatment method. Morphology of the ceria nanoparticles are confirmed with scanning electron microscopy (SEM), transmission electron microscopy (TEM) with an average size of 6-30 nm and with the N₂ adsoprtion-desorption technique in the range of 46-62 m²g^-1 in the presence of ionic liquid as base on acetate anion, trifluoroacetate anion, dicyanamide anion as organic linker, cerium nitrate hexahydrate as precursor and ammonia. It was found that the cerium oxide synthesized by acetate anion based ionic liquid has cube shape morphology and gradually form belt shape as elevated the hydrothermal treatment temperature. Cerium oxide synthesized by trifluoroacetate anion based ionic liquid remains its cubic morphology even at elevated temperature. Whereas, cerium oxide synthesized by dicyanamide anion based ionic liquid, ceria particles agglomerate and form irregular structures. The synthesized ceria nanocrystals show better performance for the degradation of methylene blue.

Abstract: Biomophic ceria with nanocrystalline was successfully synthesized using crucian fish scales as template. Unique biomorphic microstructures were characterized by X-ray diffraction (XRD), field emission scanning electron microscope (FESEM), transmission electron microscopy (TEM) and nitrogen absorption-desorption technique. The obtained ceria material shows the repetitious biomimetic structure consisting of sheet with thickness of ca. 80-100 nm and nanopores which had 2-10 nm apertures. The surface oxygen activity of fish scale-templated CeO₂ was enhanced revealed by hydrogen temperature-programmed reduction (H₂-TPR) mesurements, because of the higher surface area (113.5 m²/g) and smaller particle size (average of 8.2 nm). Those detailed investigation could infer that the biotemplate product exhibit better catalytic activity in CO oxidation reaction.

Abstract: Solution combustion synthesis technique is one of the novel techniques used to prepare nanoparticles, multi-component ceramic oxides and nanocomposites with properties better than conventionally prepared one and these materials have been used for various applications such as sensors, catalysts, and materials for solid oxide fuel cell (SOFCs). In the present work, the method has been used to prepare nanoparticles of 10 mol% Gd doped ceria (GDC) and Cu and its oxides. The oxidant to fuel (O/F) ratio is found to affect the powder properties and even compositional homogeneity. In glycine-nitrate combustion synthesis of GDC, as revealed by XRD studies, phase pure nanoparticles with crystallite size in the range 9-12nm were obtained for all the O/F ratios. TEM measurements of calcined powder showed hexagonal shaped particles of roughly 20nm size. The exothermicity was increased with the oxidant to fuel ratio resulting in high surface area and soft agglomerates. A slightly lean O/F ratio gives surface area of 73 m²/g and soft agglomerates (D₅₀ = 5.34 mm), which eventually results into high sintering density at low temperature. Raman Spectra of GDC showed a sharp and intense peak at 467 cm⁻¹ which corresponds to CeO₂ due to F_2g symmetry of the cubic phase. In combustion synthesis of copper nitrate and citirc acid, the compositional homogenity and phase purity was affected by the oxidant to fuel ratio. The combustion at stoichiometric O/F ratio gives Cu nano particles, lean O/F ratio gives nanoparticles of Cu, CuO and Cu₂O and rich ratio gives pure CuO nanoparticles. These nanoparticles have been studied with different characterization techniques like XRD, TG-DTA, SEM, TEM, FT-IR and Raman.

Abstract: Hierarchical porous ceria with nanocrystalline was successfully synthesized using filter paper as biotemplate. Unique biomorphic microstructures were characterized by Field Emission Scanning Electron Microscope (FESEM), transmission electron microscopy (TEM) and nitrogen absorption-desorption technique. The obtained ceria material showed the repetitious biomimetic structure consisting of fibre with diameter of ca. 1-3 μm and nanopores which had 2-4 nm apertures. The small crystallite diameter (6-8 nm) and the high specific surface area (71.3 m²·g^-1) of porous CeO₂ were measured by wide-angle X-ray Diffraction (XRD), high resolution TEM (HRTEM) and the BET method. While the concentration of acid fuchsine was 20 mg/L, the porous sample had a higher decoloring rate in a shorter time than others. The decoloring rate can reach 100% after 200 min.

Abstract: The present investigation is about fabrication of single-crystalline ceria (CeO₂) nanoparticle by a hydrothermal route. High surface area CeO₂ was synthesized with transformation of morphology from nanofibers to nanocubes in response to processing conditions. A steady variation of average nanocrystallite size ca. in the range 3.0-16.9 nm and a range of band gap energy from 2.6 to 2.9 eV were measured. The surface area of the nanoparticles varied in the range 16.0136.1 m²/g and the variation in surface area is attributed to the nature of packing of particles. The ceria nanofibers could generate 870.5 µmol of H₂ in 3 h of irradiation.

Abstract: The aim this work is to synthesize the CeO₂ in the ceramic powder form through three different methods of synthesis, they are: method of combustion, Pechini method and hydrothermal method. Will be evaluated the influence exerted by these methods of preparing of the metallic oxide on the structural features presented in the same. Three samples of CeO₂ were synthesized in this work, they were analysed by x-ray diffraction, SEM and adsorption and desorption of N₂ by BET method. According to the results has been observed that the synthesis method has great influence on the structural characteristics of CeO₂ obtained. The sample of CeO₂ synthesized by Pechini method showed a structure with a higher percentage of crystallinity and average pore diameter smaller when compared to samples of CeO₂ synthesized by means of the combustion method and of the hydrothermal method. The sample synthesized by the combustion reaction method presented larger agglomerated of unitary particles.

Abstract: Nanocrystalline ceria powder was prepared through homogeneous precipitation method, orthogonal experiment was designed to figure out the most important factor that influence the particle size of the resultant and the optimum condition. X-ray diffraction revealed that the as-prepared nanoscale ceria powder had cubic fluorite structure, TEM image showed that the ceria powder was weakly agglomerated with a particle size of about 10 nm.

Abstract: A series of CuO-ZnO-CeO₂-ZrO₂/HZSM-5 catalysts were prepared and characterized by XRD, H₂-TPR. CO₂ hydrogenation to DME was carried out in a fixed bed reactor to test the catalytic performance of Ce-modified CuO-ZnO-ZrO₂/HZSM-5 catalyst under the condition of GHSV=1800 h^-1, p=3.0 MPa and T=250°C. The results indicate that the added CeO₂ improved the performance of the bifunctional catalysts, the CO₂ conversion and DME selectivity were obviously improved. CuO-ZnO-CeO₂-ZrO₂/HZSM-5 catalyst with Ce to Zr molar ratio of 1/1 showed the highest activity for DME synthesis from CO₂ hydrogenation.

Abstract: CuO/TiO₂, CuO/Ti_0.9Ce_0.1O₂ and CuO/CeO₂/TiO₂ composite catalysts were prepared and tested for their application in selective catalytic reduction (SCR) of NO with C₃H₆. The effect of CeO₂ species on the catalytic performance was further evaluated. Catalyst characterization including BET surface area, XRD and temperature-programmed reduction of H₂ (H₂-TPR) suggested that the addition of CeO₂ species changed the physicochemical properties of the catalysts obtained. Compared to the impregnation method, the homogeneous precipitation method was an effective approach to preparing the CeO₂ doped catalyst, which could promote the activation of C₃H₆ to react with NO.