CeO2 Particles Research Articles

Effect of flame temperature on structure and CO oxidation properties of Pt/CeO2 catalyst by flame-assisted spray pyrolysis

Flame synthesis offers the potential for the synthesis of structure-controlled catalysts. In this study, Pt/CeO2 nanoparticles were synthesized via flame-assisted spray pyrolysis (FASP) and used as CO oxidation catalysts. The catalysts were synthesized using a burner diffusion flame at three different flame temperatures (maximum flame temperatures, Tf = 1556, 1785, and 2026 K), and their particle structure and CO oxidation activity were evaluated. The synthesized Pt/CeO2 catalysts had a bimodal structure containing 100 nm-scale CeO2 loaded with 10 nm-scale Pt and fine CeO2 less than 10 nm loaded with highly dispersed Pt (less than 1 nm). As the flame temperature increases from 1556 to 2026 K, the formation of fine CeO2 particles dominates, resulting in an increase in BET specific surface area from 7.97 to 112 m2/g and Pt dispersion from 4.67 to 20.6%. Insight into the particle formation routes that determine the catalyst structure is provided by numerical simulation of droplet evaporation in a burner flame. CO oxidation experiments showed that the temperature at which CO conversion reached 100% (T100) decreased from 513 to 378 K with increasing flame temperature in FASP. In addition, the thermal stability test showed that the Pt dispersion after thermal degradation was higher for Pt/CeO2 catalyst made by FASP at Tf = 2026 K than that prepared by the impregnation method, and the T100 for CO oxidation was lower by 20 K.

In situ synthesis of nano-CeO2 and chitosan composite

Nanosized cerium oxide (CeO2) particles were prepared by co-precipitation method using chitosan as a template, cerium (III) nitrate and cerium (IV) sulfate as starting materials and aqueous ammonia solution as a precipitating agent. XRD data indicate that cerianite with face-centered cubic phase is formed in the reaction systems. The size of the coherent scattering regions is about 3 nm or less. FTIR spectroscopy data indicate the interaction of polymer molecules with the inorganic component. The shift of absorption bands related to N-H bonds for composites with Ce(III) and Ce(IV) compared to chitosan indicates the interaction of amino groups with CeO2 particles. The application of chitosan as a matrix for the synthesis of CeO2 nanoparticles showed that this approach is more economical and easier to produce nanomaterials for various applications.

The influence of CeO2 on the oxidation resistance of TaC/Ni composites

The in-situ TaC/Ni composites with different CeO2 content (0 wt%, 1 wt%, 2 wt%) were prepared by reactive sintering method, and their oxidation behavior in air at 1073 K was analyzed by static cyclic oxidation method to investigate the influence mechanism of CeO2 on the oxidation resistance of composites. The results show that the CeO2 particles are distributed around the TaC particles in the Ni matrix, and the oxidation behavior of composites with different CeO2 content conforms to the linear kinetic law. The oxide film is mainly composed of NiTa2O6 and a small amount of NiO. The generation reactions of Ta2O5 and NiTa2O6 induce a high expansion and compressive stress in oxide scale, leading to the formation of nonprotective oxide film with pores and cracks on the surface. As the addition of CeO2 increases from 0 wt% to 2 wt%, the thickness of oxide scale on composites obviously reduces from 505 μm to 122 μm, and the Ni and Ta oxides content decreases, leading to the reduction of pores and cracks in oxide scale. The Ce ion generated from the dissolution of CeO2 particles mainly distributes in the Ta oxides during the oxidation process, which hinders the outward diffusion of Ni and Ta ions, resulted in the improved oxidation resistance of TaC/Ni composites.

Enhanced mechanical properties of molybdenum alloy originating from composite strengthening of Re and CeO2

To enhance the mechanical properties of molybdenum alloys at both room and high temperatures, Mo−14Re−1CeO2 alloy was synthesized using the powder metallurgy method, and the corresponding microstructure and mechanical properties were characterized. The results indicate that the ultimate tensile strength of Mo−14Re−1CeO2 reaches 657 MPa, with a total elongation of 35.2%, significantly higher than those of pure molybdenum (453 MPa, and 7.01%). Furthermore, the compression strength of Mo−14Re−1CeO2 at high temperature (1200 °C) achieves 355 MPa, which is still larger than that of pure molybdenum (221 MPa). It is revealed that there is a coherent interface between CeO2 and the Mo−14Re matrix with CeO2 particles uniformly distributed in both intergranular and intragranular regions. The improvements in mechanical properties are primarily attributed to the formation of Mo−Re solid solution, grain refinement, and dispersion strengthening effect of CeO2.

Nanocasting synthesis of mesoporous CeO2 particle abrasives from mesoporous SiO2 hard templates for enhanced chemical mechanical polishing performance

Mesoporous abrasive particles exhibit superior chemical mechanical polishing/planarization (CMP) performance, as compared with the corresponding bulk materials. Nevertheless, the lack of control over the shape and particle size or distribution extremely restricts the development of mesoporous abrasives and their potential applications. To overwhelm these drawbacks, pure and ytterbium-doped mesoporous ceria (mCeO2 and mCeYbO2) spheres with well-defined morphology and good uniformity were synthesized via a straightforward nanocasting strategy using high-quality mesoporous silica spheres as hard templates and metal nitrates as precursors. The resulting samples were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, selected area electron diffraction, X-ray photoelectron spectroscopy, Raman spectroscopy, UV–vis diffuse reflectance spectroscopy, photoluminescence spectroscopy, Zeta potential, and N2 adsorption-desorption measurements. The as-prepared mCeO2 and mCeYbO2 products exhibited enriched surface defects (trivalent Ce, vacancy oxygen, hydroxyls) and polycrystalline porous frameworks with a surface area of up to 160 m2/g and pore size of 4–7 nm. Benefiting from these synergistic attributes, the flexible and defective particle abrasives enabled significant improvements in both surface quality and removal efficiency during oxide-CMP, as compared to commercial CeO2. A possible CMP mechanism was proposed on the basis of the physical contact state, adsorption and adhesion behavior, as well as tribochemical interaction occurred at CeO2–SiO2 interfaces. This work demonstrates highly promising abrasive materials advancement combining architecture and defect engineering towards high-performance oxide-CMP.

Elevating dimethyl oxalate hydrogenation activity over core–shell Cu/SiO2@CeO2 catalysts

Increasing dimethyl oxalate (DMO) hydrogenation activity remains a challenge. A Cu catalyst was designed by creating Cu nanoparticles (NPs) over SiO2 layer formed on the CeO2 particles (SiO2@CeO2) using the ammonia evaporation method followed by the calcination and reduction step. The optimized 30Cu/SiO2@5CeO2 catalyst shows good performance in the micro-packed bed reactor (100 % DMO conversion, 95.9 % ethylene glycol (EG) selectivity, 200 h stability) under the condition of the ratio of H2 to DMO (H2/DMO) = 30, 190 °C and 2 MPa in the run, and CeO2 was proved to be effective in the DMO hydrogenation process. The exposed CeO2 on the surface of catalyst was found to facilitate the formation of Cu+ by its interaction between adjacent Cu nanoparticles, resulting in the faster adsorption and dissociation of C=O bond on the catalyst surface, according to the characterization results obtained by the XRD, XPS and in situ FT-IR, etc.

CeO2/SWCNT nanocomposite coating: A novel approach for corrosion application

AbstractThe coatings were prepared by blending different concentrations of SWCNTs and CeO2 particles with an epoxy resin by hydrothermal method, which was then applied to the substrate through the doctor blade technique. The mixtures were transferred into a 1‐L capacity autoclave with a teflon‐lined flange type and subjected to hydrothermal treatment at 100°C for 3 h. The surface coatings were applied using a doctor blade. Subsequently, the coated materials were placed in an oven and dried for 12 h at 50°C under vacuum conditions. The samples' structural analysis was examined through x‐ray diffraction (XRD). XRD analysis verified the CeO2/SWCNT composite coating, and Fourier transform infrared spectroscopy (FTIR) was utilized to assess the presence of functional groups. Thermodynamic properties and thermal stability of composite coatings that were modified with SWCNTs and CeO2 particles were studied by thermogravimetric analysis (TGA). The impact of the CeO2/SWCNT composite on the anticorrosion capabilities of the epoxy coating was examined through electrochemical impedance spectroscopy (EIS), Nyquist curve, and Tafel slope characterization. Corrosion tests were conducted on the CeO2/SWCNT composite coatings in a 3.5 wt% sodium chloride (NaCl) solution at 25°C to improve corrosion resistance. The concentration of 0.4 wt% CeO2 was found to be optimal for achieving effective corrosion resistance. The composite coating CNT0.6‐C0.4 exhibited significantly higher Ecorr (−426 V) and lower Icorr (2.96 × 10−6 A cm−2) values compared to samples from the CNT0, CNT0.2, and CNT0.6 groups. The paper presents a viable solution with CeO2/SWCNT composite coating for the engineering application of corrosive‐inhibiting coatings.

Preparation and investigation of Ni-W/CeO2 composite coating and its structure and anti-corrosion properties with different ceria content and deposition time

In the current work, CeO2 nanoparticles were embedded in Ni-W alloy matrix by pulse electrochemical deposition on copper substrate to optimize their microstructure and corrosion resistance. The effects of CeO2 concentration and deposition time on Ni-W/CeO2 composite coating were investigated for optimized structure and improved corrosion resistance. The composite coatings present nodular-like surfaces with dense and compact growth profiles, containing 63.03–67.88 wt% Ni, 28.73–31.87 wt% W and 0.25–8.24 wt% Ce. The content of incorporated CeO2 in coatings increased with the increase of CeO2 concentration in electrolyte. The addition of CeO2 particles has refined the grains of the prepared coating. The surface became rougher with the extension of electrodeposition time. Ni-W/CeO2 composite coating electrodeposited at 10 g L−1 CeO2 for 60 min possessed the highest corrosion resistance, indicating enhanced corrosion protection and long-term stability. This premium coating can be applied in harsh environments to prolong the lifespan of machinery, equipment, and parts in marine, vehicle, aerospace, and chemical industries.

Effect of CeO2@Ni on the Oxidation Resistance of in Situ TiC/Ni Composite Applied for Intermediate Temperature Solid Oxide Fuel Cell Interconnects

The TiC/Ni composites with different CeO2 or CeO2@Ni content are fabricated by pressureless reactive sintering, and the CeO2@Ni particles are prepared by electroless plating technique. The results show that the continuous Ni layer is prepared on CeO2 particles, leading to the decrease of contact angle between CeO2 and Ni from about 116° to 65°. The relative density of composites with 1 wt% CeO2 increases from 85.79% to 96.45% by Ni layer on CeO2 particles. The CeO2 or CeO2@Ni particles exhibit no obvious influence on the microstructure of composites, and Ce atoms of CeO2 diffuse into TiC particles during the reactive sintering process. The mass gain of composite decreases from 7.4709 to 4.9075 mg cm−2 by addition of 1 wt% CeO2@Ni. The Ce‐doped in NiO and TiO2 would restrict the inward diffusion of O atoms and outward diffusion of Ni atoms, resulting in the improvement of oxidation resistance of composite. With the increase of CeO2@Ni content from 0 to 1 wt%, the surface specific resistance of composite decreases from 3.16 to 0.56 Ω cm2 at 800 °C due to the thinner oxide scale and lower bandgap of TiO2 by Ce doping.

Synthetic opal decorated by Co and Ce oxides as a nanoreactor for the catalytic CO oxidation

Macroporous synthetic opal grown from non-porous silica nanoparticles and decorated by Co and Ce oxides was applied for the catalytic CO oxidation in the inert (TOX) and H2-rich (PROX) gas mixtures. Prepared materials were studied by methods of SEM, TEM, EDX, XRD, XPS and FTIR spectroscopy. The relationship between synthesis conditions, structure, and catalytic behavior of composites is discussed. The best Co-O-Ce interaction and the highest activity in the CO-TOX and PROX are achieved when cerium oxide was added prior to the addition of cobalt oxide. In this case highly dispersed particles of Co3O4 and CeO2 are located in close proximity on the silica surface and anchored between the opal spheres. The use of Co/Ce decorated synthetic opal as a nanoreactor for the catalytic oxidation of CO in the H2 excess makes it possible to achieve 99.5 % conversion of CO at 150°C, the high efficiency and selectivity of the process are maintained in multiple cyclic tests in heating and cooling modes. The synergistic activity of Co and Ce oxides was observed when they both were located together on the outer surface of non-porous SiO2 nanospheres. These results are superior to known data for other catalysts based on Co and Ce oxides.

Synthesis of CeO2 Coupling rGO Material Oriented to Rhodamine B Degradation under Optical Irradiation

In the present work, CeO2 with different loading were embedded on reduced graphene oxide (rGO) by a simple one-pot hydrothermal method. The synthesized samples were characterized using XRD, EDX mapping, FESEM and UV-Vis DRS techniques. The photocatalytic activity of the as-synthesized CeO2, rGO, and 0,5% (1,5% and 5,0% wt )CeO2/rGO was studied by monitoring the degradation of Rhodamine B dye (denotes RhB) under xenon light irradiation. The analyses show that CeO2 particles were evenly dispersed on rGO and the optical properties of the xCeO2/Rgo (x = 0,5; 1,5; and 5,0%wt)/rGO material were significantly enhanced due to the interaction between CeO2 anf rGO. The effects of CeO2 loading, initial RhB concentration and pH were thoroughly investigated. Under the irradiation, the RhB degradation reached 100% over 1.5%CeO2/rGO. tThe high performance of the synthesized composites was attributed to the significant suppression of the recombination rate of photo-generated electron - hole pairs due to charge transfer between rGO sheets and CeO2 particles and the smaller optical band-gap in the CeO2/rGO nanocomposite.

Comparative first-principles analysis of crystalline versus amorphous CeO2 particles: implications for chemical mechanical planarization

Comparative first-principles analysis of crystalline versus amorphous CeO2 particles: implications for chemical mechanical planarization

The Effect of Calcination Temperature on the Characteristics of CeO2 Synthesized Using the Precipitation Method

Cerium oxide (CeO2) was synthesized using the precipitation method at various calcination temperatures ranging from 500 to 700°C. Cerium(III) nitrate hexahydrate (Ce(NO)3.6H2O) was used as the precursor for cerium, while Cetyltrimethylammonium bromide (CTAB) acted as the morphology-directing agent. Characterization results indicated that pure CeO2 was obtained at all calcination temperature variations. Calcination temperature influences crystallinity, crystal size, and CeO2 crystal parameters. The crystallinity and crystal size of CeO2 increased with the rising calcination temperature, reaching values of 81.1–84.5% and 15.58–23.12 nm, respectively, along with larger crystal parameters as the temperature increased (a = 5.406–5.410 Å). Surface morphology showed irregular shapes of CeO2 particles, with decreasing sizes as the calcination temperature increased, ranging from 0.2-5.6 μm at 600°C to 0.12-2.9 μm at 700°C. The Ce/O ratio on the surface increased with the rising calcination temperature, reaching a range of 0.48–0.57. CeO2 obtained from calcination at 600°C exhibited the highest fluorescence emission intensity (λ= 496 nm), indicating the least oxygen vacancies presence. Therefore, for antioxidant and catalyst applications, it is preferable to calcinate CeO2 at 700°C.

Enhancing photocatalytic tetracycline degradation through the fabrication of high surface area CeO2 from a cerium-organic framework.

Water pollution is a global environmental issue, and the presence of pharmaceutical compounds, such as tetracyclines (TCs), in aquatic ecosystems has raised growing concerns due to the potential risks to both the environment and human health. A high surface area CeO2 was prepared via atmospheric thermal treatment of a metal-organic framework of cerium and benzene-1,3,5-tricarboxylate. The effects of calcination temperature on the morphology, structure, light absorption properties and tetracycline removal efficiency were studied. The best activity of the photocatalysts could be achieved when the heat treatment temperature is 300 °C, which enhances the photocatalytic degradation performance towards tetracycline under visible light. The resulting CeO2 particles have high capacity for adsorbing TCs from aqueous solution: 90 mg g-1 for 60 mg L-1 TCs. As a result, 98% of the initial TC can be removed under simulated sunlight irradiation. The cooperation of moderate defect concentration and disordered structure showed tetracycline removal activity about 10 times higher than the initial Ce-MOF. An embryotoxicity assessment on zebrafish revealed that treatment with CeO2 particles significantly decreased the toxicity of TC solutions.

High-Temperature Cyclic Oxidation Behavior and Microstructure Evolution of W- and Ce-Containing 18Cr-Mo Type Ferritic Stainless Steel.

Due to the recurrent starting and stopping operations of automobiles during service, their engines' hot ends are continually subjected to high-temperature cyclic oxidation. Therefore, it is crucial to develop ferritic stainless steels with better high-temperature oxidation resistance. This study focuses on improving the high-temperature cyclic oxidation performance of 18Cr-Mo (444-type) ferritic stainless steel by alloying with high-melting-point metal W and the rare earth element Ce. For this purpose, a high-temperature cyclic oxidation experiment was designed to simulate the actual service environment and investigate the high-temperature cyclic oxidation behavior and microstructure evolution of 444-type ferritic stainless steel alloyed with W and Ce. The oxide structure and composition formed during this process were analyzed and characterized using scanning electron microscopy/energy dispersive spectroscopy (SEM-EDS) and electron probe X-ray micro-analyzer (EPMA), in order to reveal the mechanism of action of W and Ce in the cyclic oxidation process. The results show that 18Cr-Mo ferritic stainless steel alloyed with W and Ce exhibits an excellent resistance to high-temperature cyclic oxidation. The element W can promote the precipitation of the Laves phase between the matrix and the oxide film, and the small-sized Laves phase can inhibit the interfacial diffusion of oxidation reaction elements and prevent the inward growth of the oxide film. The element Ce can refine oxide particles and reduce the thickness of the oxide film. CeO2 particles within the oxide film can serve as nucleation sites for the formation of oxide particles from reactive elements, and they also contribute to pinning the oxide film, thereby enhancing its adhesion.

Effect of CeO2 nanoparticles on hydroxyl radicals in EPR studies of the photodegradation of methylene blue under influence of red light

The antioxidant properties of cerium dioxide nanoparticles synthesized by the hydrothermal method are studied both by optical photometry and by EPR spectroscopy. It was found that with increasing intensity of irradiation of methylene blue with red light, the antioxidant activity of CeO2 nanoparticles improve. The greatest antioxidant activity is achieved at a concentration of CeO2 particles in solution from 5 mM to 10 mM. Increasing a concentration of CeO2 nanoparticles above 20 mM leads to deterioration in their antioxidant properties. It has been shown that in an alkaline medium the antioxidant activity of nanoparticles increases significantly, but with a decrease in pH to 3, CeO2 nanoparticles exhibit weak pro-oxidant properties due to more active generation of O2− radicals.

Preparation of CeO2 particles via ionothermal synthesis and its application to chemical mechanical polishing

CeO2 is a widely used abrasive for the chemical mechanical polishing of silicon during chip manufacturing. CeO2 can be synthesized via traditional coprecipitation, hydrothermal, and solvothermal methods; however, these methods have some issues, including high vapor pressure, flammability, toxicity, volatile solvents, and narrow heating temperature range. To overcome these issues, we developed a new ionothermal synthesis approach for high-quality CeO2 particles using 1-ethyl-3-methylimidazolium tetrafluoroborate as an imidazole ionic liquid without a template. Based on the scanning electron microscopy and particle size distribution, CeO2 particles synthesized at a reaction temperature of 210 °C for 16 h displayed sizes ranging between 0.1 and 0.3 μm. Additionally, the spherical shapes exhibited good crystallinity, regular morphology, and uniform dispersion. The results of CMP experiments indicated that the abrasives could reduce the surface roughness from 1.63 to 0.29 nm (scanning area is 5 μm × 5 μm). The obtained synthesized CeO2 particles demonstrated promising performance in Si polishing, achieving removal rates of up to 255.5 nm/min. It found that the removal rate of the abrasive prepared by ionic thermal synthesis in Si polishing was twice as much as other abrasives. Further, a possible mechanism was put forward to explain the formation of CeO2 structures with various morphologies. The proposed method presents a new approach for synthesizing CeO2 particles with uniform morphology and excellent polishing properties.

Low-temperature hydrogen production from waste polyethylene by nonthermal plasma (NTP)-assisted catalytic pyrolysis using NiCeOx/β catalyst

Conventional catalytic pyrolysis of waste plastics for H2 production faces challenges due to excessively high reaction temperatures. This study introduced a NiCeOx/β catalyst for low-temperature H2 production from polyethylene (PE), aiming to enhance H2 yield through nonthermal plasma (NTP) and catalytic active sites. Experimental results confirmed the efficacy of NTP in promoting collision between high-potential-energies active species and plasma-catalyst interactions, identifying acidic sites as primary catalytic active sites. Both experiments and density functional theory (DFT) calculations confirmed NiO and CeO2 particles as metallic active sites, exhibiting thermodynamic and kinetic benefits for primary products from PE pyrolysis. Under optimal conditions, the highest H2 yield and selectivity respectively reached 32.71 mmol/g and 82.10 % at a PE/(NiCeOx/β) ratio of 1:4, reaction temperature of 400 °C, and NTP discharge power of 210 W. The NiCeOx/β catalyst facilitated low-temperature pyrolysis of waste plastics, enhancing H2 selectivity and yield.

Influence of Cerium Oxide Abrasive Particle Morphologies on Polishing Performance

AbstractIn this study, two morphologies of cerium oxide (CeO2) abrasive particles, octahedral and spheroidal, are synthesized by solvothermal method using cerium nitrate hexahydrate (Ce(NO3)3‐6H2O) as raw material. Fourier infrared spectroscopy, X‐ray diffractometer (XRD) and scanning electron microscopy (SEM) are used to characterize the composition and morphology of CeO2 abrasive particles. The synthesized CeO2 is used for chemical mechanical polishing (CMP) of the Si surface of 6H‐SiC wafers, and the surface morphology of the polished wafers are observed using atomic force microscopy (AFM). After polishing with octahedral and spheroidal abrasive particles, the surface roughness of the wafers are 0.327 and 0.287 nm, and the material removal rates (MRR) are 870 and 742 nm h−1, respectively. Calculations comparing the ultraviolet absorption spectra and bandgap energies of the two types of abrasive particles as well as molecular dynamics (MD) simulations reveal that the synthesized octahedral CeO2 particles possessed stronger surface chemical activity and material removal performance.

MgAl Oxide Coatings Modified with CeO2 Particles Formed by Plasma Electrolytic Oxidation of AZ31 Magnesium Alloy: Photoluminescent and Photocatalytic Properties

MgAl oxide coatings composed of MgO and MgAl2O4 phases were doped with CeO2 particles via plasma electrolytic oxidation (PEO) of AZ31 magnesium alloy in a 5 g/L NaAlO2 water solution. Subsequently, particles of CeO2 up to 8 g/L were added. Extensive investigations were conducted to examine the morphology, the chemical and phase compositions, and, most importantly, the photoluminescent (PL) properties and photocatalytic activity (PA) during the photodegradation of methyl orange. The number of CeO2 particles incorporated into MgAl oxide coatings depends on the concentration of CeO2 particles in the aluminate electrolyte. However, the CeO2 particles do not significantly affect the thickness, phase structure, or surface morphology of the coatings. The PL emission spectrum of MgAl oxide coatings is divided into two bands: one in the 350–600 nm range related to structural defects in MgO, and another much more intense band in the 600–775 nm range attributed to the F+ centres in MgAl2O4. The incorporated CeO2 particles do not have a significant effect on the PL intensity of the band in the red spectral region, but the PL intensity of the first band increases with the concentration of CeO2 particles. The PA of MgAl/CeO2 oxide coatings is higher than that of pure MgAl oxide coatings. The MgAl/CeO2 oxide coating developed in aluminate electrolyte with a concentration of 2 g/L CeO2 particles exhibited the highest PA. The MgAl/CeO2 oxide coatings remained chemically and physically stable across multiple cycles, indicating their potential for applications.