Papers by Keyword: Cerium Oxide

Abstract: Glass doped with cerium is an attractive material for a variety of applications. The aluminium fluorophosphate glasses were made by the conventional melt-quenching technique. The glass samples were characterized by density, refractive index, FTIR and photoluminescence spectra. The density was shown to increase, but refractive and molar volume were shown to decrease. The FTIR spectra of these glasses showed mainly [PO₃] and [PO₄] structural units. Transparency of the glass samples is demonstrated by a transmission intensity in the 70-80% range. Regarding the optical properties, under 307 nm excitation, the emission peak around 348 nm of the CeF₃-doped aluminium fluorophosphate glasses was confirmed. The emission would be due to the 5d→4f transitions of Ce³⁺ ions.

Abstract: The photo-catalytic degradation of Congo red (CR) was examined in presence of visible light at various operating condition, pH and amount of catalyst and time. The CR dye degradation rate was 97% about 80 minute of exposure, respectively, indicating that pH 7 was the optimal pH for degradation. The photo degradation processes of dyes were considered to be connected to a kinetic models, which was later shown incorrect. The effective degradation process might be used to explain the degradation of congo red dye.

Abstract: Cerium oxide has been widely used in many application. One of the most important applications is for chemical mechanical application/planarization (CMP). In the current work, ceria nanoparticles have been prepared via precipitation method using ethanol/water mixture as the solvent, while cerium nitrate hexahydrate as cerium source and ammonium solution as precipitant. The effects of two different temperatures (i.e. 30 and 50°C) and two different apparatus setup (i.e. Setup A and Setup B) on the morphology and crystallite size of the ceria nanoparticles were studied. The morphology and crystallite size of the ceria were analyzed using X-Ray Diffractometer (XRD) and Tranmission Electron Microscopy (TEM). The XRD analysis results showed that the peak intensity of the ceria nanoparticles prepared by using setup B was much higher than the ones prepared by using Setup A. The XRD results revealed that the crystallinity growth and mean crystallite size of the ceria was better or higher when using Setup B. The crystallite size of the calcined ceria nanoparticles were found to be 9.8; 10.5; 14.5 nm for Ceria-1, Ceria-2, and Ceria-3 samples, respectively. In addition, the TEM images showed that Ceria-3 sample exhibited better morphology and less agglomerated compared to that of Ceria-1 and Ceria-2 samples. Futhermore, Ceria-3 sample also had better dispersion stability compared to that of Ceria-1 and Ceria-2 samples due to its better morphology.

Abstract: Al₂O₃, Al₂O₃-10%CeO₂ and Al₂O₃ – 20% CeO₂ coatings were deposited on Mg AZ91 alloy by High Velocity Oxy Fuel (HVOF) process. The microstructure of deposited coatings was characterized by scanning electron microscopy and x-ray diffraction. Nano-indentation tests were performed on deposited coatings to determine its load bearing capacity and elastic recovery. Al₂O₃ coatings exhibited coarse grain structure with porous sites. While addition of CeO₂ promoted grain refinement in the coatings. A load of 100mN was applied on all the samples for nano-indentation test. Coating with 20%CeO₂ exhibited maximum load bearing capacity of 98.7mN with elastic recovery displacement of 1000 nm.

Abstract: Cerium oxide (CeO₂) is one of potential candidates of hydrophobic coatings servicing in harsh environments. In this letter, abraded CeO₂ surface was prepared using sandblasting treatment to investigate the wetting mechanism under the condition of impact abrasive wear. The water contact angle (WCA) of the abraded surface increased from 62.8° to 93.7° after aging in ambient air for about 700 h. The hydrophobic self-optimisation mechanism of the abraded CeO₂ surface is due to the hierarchical structure formed during impact abrasive wear and the surface adsorption of airborne hydrocarbon, resulting the wetting state changed from “Wenzel state” to “Cassie-Baxter State”.

Abstract: The atomic structure and morphology of cerium oxide nanoparticles obtained by laser ablation are experimentally and theoretically investigated. Using transmission electron microscopy, X-ray diffractometry, and electron energy loss spectroscopy, it has been shown that particles are enriched in oxygen vacancies that stabilize their internal structure. The density functional method was used to study the dependence of the unit cell parameter of CeO₂ nanoparticles on their size. An analysis of the charge density distribution shows a different structural distribution of Ce³⁺ and Ce⁴⁺ atoms in nanoparticles.

Abstract: Cerium (Ce) doped ZnO is a promising material for advanced photocatalysis. It is useful for inducing the treatment of many organic pollutants in water. However, the stability of its performance under varying temperature and saline condition has never been not fully assessed. In this study, powder form photocatalyst comprising 99.0 mol% ZnO and 1 mol% CeO₂ has been synthesized via modified citrate gelation technique and solid-state sintering at 1200 °C for 5 hours. The conversion of Ce doped ZnO from its precursors has been confirmed using XRD, SEM, and EDX techniques. The photocatalytic efficiency of the synthesized Ce doped ZnO under UV-C light (λ=265 nm) was determined. In the experiment, the operating temperature was varied between 25 to 40 °C, and the salinity of the treated solution was increased from 0 to 40 g/L NaCl. The findings revealed that the photocatalytic efficiency of Ce doped ZnO under UV light improved from 78.2% to 88.6% as the temperature increased from 25 to 40 °C. The performance of Ce doped ZnO decreased from 86.7% to 36.7% when the salinity increased from 0 g/L to 40 g/L. The elevation of temperature encouraged the photogeneration of electron-hole pairs on catalyst surface while the presence of chloride ions in treated medium caused scavenging of hydroxyl radicals or hole.

Abstract: Cerium oxide and tin oxide nanocomposites (CeO₂-SnO₂ NCs) were successfully synthesized via a simple co-precipitation method. The structure and properties of the synthesized materials were characterized using several X-ray and electron-based techniques including XRD, FE-SEM, TEM, EDS and BET to unravel the structure, morphology, element composition and specific surface area. The XRD and BET results showed that the NCs have the characteristic crystalline structures of SnO₂ and CeO₂-SnO₂ NCs, and high specific surface area (66.45 and 86.29 m²/g), respectively. Amorphous phase of CeO₂ and SnO₂ were not found in XRD patterns. EDS analysis confirms the absence of all element composition and the FE-SEM and TEM analysis observed as particles having the clear spherical morphologies with the average particle size of of SnO₂ and CeO₂-SnO₂ NCs was about 13 and 10 nm, respectively.

Abstract: In the present work, the impact of the rhodium deposition on the thermal stability of ceria-based catalysts was studied. The samples were prepared by an incipient wetness impregnation of the support with aqueous solution of rhodium nitrate. The loading of Rh was 0.1 and 1 wt.%. The textural characteristics of the samples were examined by a low-temperature nitrogen adsorption. It was shown that the addition of rhodium intensifies the process of ceria agglomeration, which leads to the lower values of specific surface area along with increased average pore diameter after the aging at 1000 °C. Stability of the catalysts was investigated by means of a prompt thermal aging procedure. The high-loaded catalyst (1 wt.% Rh/CeO₂) was more active than the 0.1 wt.% Rh/CeO₂ sample, while the stability of both the catalysts was excellent. It should be emphasized that the alumina-based reference samples with the similar rhodium loading were significantly less active and poorly stable.

Abstract: A sample thermal treatment technique was utilised to synthesis cerium dioxide (CeO₂) nanoparticles, using cerium (111) nitrate as a precursor, Polyvinylpyrrolidone as a capping agent, and deionized water as a solvent. The product underwent calcination treatment of 500, 550, 600, and 650 1C to crystallize the nanoparticles and to remove organic compounds. It was verified by XRD that by varying the calcination temperature, the cubic fluorite structure of CeO₂ nanoparticles with pure products was achieved. Furthermore, the crystal sizes of the CeO₂ nanoparticles were assessed to be 4 nm for the lowest calcination temperature and 23 nm for the highest calcination temperature. The FESEM micrographs of the CeO₂ nanoparticles revealed a structure of CeO₂ nanospherical that exhibited a tendency to amalgamate at higher calcination temperatures. The optical characteristics that were evaluated with the help of a UV-Vis spectrophotometer indicated a decrease in the band gap energy with an increase in calcination temperature as a result of the increase in the crystal sizes.