CeO2 Particles Research Articles

Development of polystyrene/polyaniline/ceria (PS/PANI/CeO2) multi-component abrasives for photochemical mechanical polishing/planarization applications

Tri-layer nanostructured polystyrene/polyaniline/ceria (PS/PANI/CeO2) multi-component composites were developed as functionalized particle abrasives for improved photochemical mechanical polishing/planarization (PCMP) applications. The physicochemical characteristics of the PS/PANI/CeO2 and PS/CeO2 samples were examined by X-ray diffraction, transmission electron microscopy, scanning electron microscopy, Flourier-transform infrared spectroscopy, UV–visible spectrophotometer, photoluminescence spectroscopy, and thermogravimetric analysis. Ultra-smooth and defect-free surfaces with ultra-low roughness (0.12 nm Ra, 0.16 nm RMS) were achieved after PCMP with polymer/CeO2 hybrid abrasives. It might be attributed to the enlarged contact area and the decreased indention depth between the particle and the surface, possibly originating from the elastic polymer cores. The synergy of the PANI conductive polymer and the CeO2 particle photocatalyst contributed to improving the separation efficiency of photo-generated carriers, thereby enhancing the photochemical oxidation activity. As expected, the tri-layer PS/PANI/CeO2 abrasives achieved a ca. 69% increment of material removal rate compared to the PS/CeO2. The interfacial contact model and material modification/removal mechanism of the PS/PANI/CeO2 multi-component tri-layer abrasives during PCMP processes were also discussed. The aim of this work is expected to provide guidance for the design and promising applications of novel polymer/CeO2 composite abrasives in advanced CMP, PCMP, electrochemical mechanical polishing (ECMP), and photoelectrochemically combined mechanical polishing (PECMP).

Phyto-mediated green synthesis of CeO2–ZnO nanoparticles using glycosmis mauritiana leaf extract: Antibacterial activity and photodegradative applications

A simple novel green synthesis of the nano compound cerium oxide doped with zinc oxides (CeO2–ZnO) was produced with a reduction agent of glycosmis mauritiana leaf extracted. The compounds synthesized are characterized by × - ray diffraction, UV, DRS and TEM. The results show that the prepared materials were superior in performance as compared to unoped ZnO and CeO2 particles, due to alternation in band gap, surface adsorption and enhanced photoresponsive. The photocatalytic efficiency of the CeO2-ZnO series was evaluated against Acid black 1 and the antibacterial properties were checked against the clinical bacteria strains. All findings showed that CeO2-ZnOs' photocatalytical and antibacterial activities with various CeO2 material are superior to the pure ZnO activities.

High‐temperature oxidation resistance and antifailure mechanism of MAO‐SG composite coating on TC4 titanium alloy

AbstractTo refine microarc oxidation (MAO) coating surface micropores, and enhance the coating's toughness and oxidation resistance. In the process of MAO, negatively charged CeO2 particles are adsorbed and deposited into the coating under the action of electrophoresis, and a 6 g/L CeO2 doped MAO coating is prepared. Then, the Al2O3‐SiO2 composite sol‐gel seal coating was used to obtain the microarc oxidation‐sol‐gel composite coating (MAO‐SG). The TC4 substrate, undoped MAO coating, CeO2 doped MAO coating, and MAO‐SG composite coating were subjected to high‐temperature oxidation at 650, 750, and 850°C, respectively. The results show that the composite coating exhibits excellent high‐temperature oxidation resistance at three temperatures. Compared with the undoped MAO coating, the maximum oxidation weight gain per unit area of the MAO‐SG coating was reduced by 13.44%, 23.87%, and 38.16%, and the average oxidation rate was reduced by 17.15%, 50.98%, and 69.37%, respectively. The sol‐gel layer on the surface of the composite coating will decompose α‐Al2O3 at high temperatures, and form a dense protective layer on the surface of the MAO coating and protect the MAO coating, which greatly improves the high‐temperature oxidation resistance of the TC4 titanium alloy.

Improved wear behaviors of lead-free electroless Ni B and Ni-B/CeO2 composite coatings

NiB and Ni-B/CeO2 coatings were deposited by the electroless deposition method using a bath containing nickel sulfate hexahydrate, dimethylamine borane, and sodium acetate. Instead of lead and tantalum-based stabilizers, thiourea was used as the stabilizing agent for an environmentally friendly and cost-effective process. Different amounts of submicron CeO2 particles were used as reinforcement for composite coatings. The main aim is to investigate the effects of CeO2 particles on the structural properties, hardness, crystallite size, strain, and tribological behavior of coatings. Surface analysis of pure NiB and Ni-B/CeO2 composite coatings was performed by scanning electron microscope (SEM) device equipped with energy-dispersive spectroscopy (EDS) attachment. Cross-section examinations were carried out by field emission scanning electron microscopy (FESEM). Inductively coupled plasma optical emission spectroscopy (ICP-OES) was used to obtain the nickel and boron percentages in the coating. X-ray diffraction (XRD) was applied to analyze phase structures of the coatings, nanohardness measurements of coatings were performed by nanoindenter, and wear tests were performed with a ball-on-disc test device. Roughness measurements and worn surface analyses were performed using a 3D profilometer. Experimental results showed that the CeO2 particle concentration in the plating bath of 10 g/l is the optimum amount to provide a noticeable enhancement in hardness and wear resistance compared to the other composites.

Influence of CeO2 reinforcement on microstructure, mechanical and wear behaviour of AA2219 squeeze cast composites

The present investigation deals with development of AA2219 composites with different weight fractions of Cerium oxide (CeO2) reinforcement and characterizing the microstructure and mechanical properties thereof. XRD and SEM micrograph confirm the presence of CeO2 particles and Al2Cu precipitate. The grain size of 0, 0.5, 1.0, 1.5 and 2 wt% CeO2 composites are 483, 453, 411, 362 and 328 μm, respectively. Addition of CeO2 significantly reduces the dendritic morphology and refines the α-Al grain structure. 2 wt% CeO2 addition has yielded the maximum hardness of 124 HV and yield strength of 87 MPa in all the composites developed. Additionally, the developed composites were evaluated by examining the wear characteristics with the co-efficient of friction (COF) and the specific wear rate. In this study, Taguchi's L25 orthogonal array was used to optimize the parameters like reinforcement fraction, load and sliding distance. Signal-to-noise ratio (S/N ratio) and analysis of variance (ANOVA) are used to obtain the parameters highly influencing the wear behaviour. Adhesive wear is exhibited by ploughing at lower loads and delamination is observed with increasing load. Deep shallow ploughs with embarked abrasion are observed at higher loads.

Facile in-situ synthesis of floating CeO2@ expanded graphite composites with efficient adsorption and visible light photocatalytic degradation of phenol

A facile solution to obtain efficient, stable and cheap photocatalysts was conducted in this work. CeO2@ expanded graphite (CeO2/EG) composites were in-situ synthesized with a new strategy, in which CeCl3 molecules inserted the graphite intercalation compound (GIC) and converted into CeO2 as GIC changed into EG via instant calcination. The introduction of EG has accelerated the adsorption of contaminant molecules, promoted the charge transfer and improved the photocatalytic efficiency. The best sample, containing 80.75 wt% CeO2 particles of nanometer scale, has achieved the highest pollutant removal efficiency of 97.3% for phenol, displaying the highest reaction rate constant of 0.0262 min−1, which was 35.4 times higher than CeO2. Besides, it possesses good stability and keeps floating in water pollution treatment, showing great advantages to work in natural water body. Phenol and its degradation intermediates were identified using HPLC/MS, and appropriate reaction pathways were proposed.

Antioxidant Properties of Stabilized CeO2 Nanoparticles

Ceria particles of nanodispersed composition have been obtained by laser ablation and subsequent treatment in an aqueous solution. Using techniques (TEM, XRD, Raman, EELS) of the nanostructural and electronic analysis, it is shown that the produced particles have structural defects that stabilize their internal structure. It is established that when the particle size decreases from 100 to 10 nm, the crystal lattice parameter lowers from 5.41 to 5.39 Å, and the elemental O/Ce composition changes from 1:1.83 to 1:1.76. The stabilized CeO2 particles of nanodispersed composition exhibit high antioxidant activity due to the high concentration of functional defects on the surface of nanoparticles.

Effect of CeO2 Content on Microstructure and Properties of SiCp/Al-Si Composites Prepared by Powder Metallurgy.

The effect of CeO2 content on the microstructure and properties of SiCp/Al-Si composites prepared by powder metallurgy was studied, and the mechanism of CeO2 in composites was deeply analyzed. The results show that the addition of the appropriate amount of CeO2 can refine the Si particles and improve the tensile properties of the SiCp/Al-Si composites. As the CeO2 content increases from 0 to 0.4 vol%, the particle size of the Si phase shows a tendency to decrease first and then increase, while the tensile strength, yield strength, and elongation of the composites show a trend of first increasing and then decreasing. When the CeO2 content is 0.2 vol%, the refining effect of CeO2 and the tensile properties of composites are the best. The fracture mode of SiCp/Al-Si composites with a rare earth addition is a mixed fracture. There are three main mechanisms for CeO2 in SiCp/Al-Si composites. One is when CeO2 serves as the nucleation substrate of Si phase to refine Si particles. The second is when CeO2 reacts with the alloying elements in the aluminum matrix to form a new phase, CeCu2Si2, which can not only play a role of dispersion strengthening, but also improve the bonding strength between Al matrix and Si particles. The third is the pinning effect of CeO2 and CeCu2Si2 particles on grain boundaries or phase boundaries to refine aluminum grains.

Preparation and Properties of Modified Graphene Reinforced Aluminum Matrix Composites

In order to solve the problem of agglomeration of graphene in preparation of composites, GN-CeO2 powders with even dispersion were obtained by a hydrothermal reduction method, which involved modifying the surface of acidified graphene by cerium nitrate. Then, Al/GN-CeO2 composite powders and materials were prepared by high-energy ball milling and vacuum hot pressing, respectively. The details were investigated, including the effect of modification process on the surface morphology and functional groups of graphene and modification time on the properties of Al/GN-CeO2 composites. The result shows that the functional groups and defects of graphene were added by the treatment of acidification process, which is beneficial to the composite of graphene and CeO2 particles. The quantity of CeO2 deposition on graphene surface increased with the duration of hydrothermal reduction time. After 6 h modification, the properties of the composites performed best. Compared with Al/GN composites, the tensile strength of the modified composites was increased from 284 MPa to 321 MPa; and the tensile strain rate of the modified composites was increased to 12.3%；the hardness of the modified composites was increased from 97.1 Hv to 99.5 Hv；the conductivity of the modified composites was increased from 29.84%IACS to 33.21%IACS.

Study on mechanical and tribological properties of cerium oxide/fluorine rubber composites

In order to study the effect of nanoscale cerium oxide (CeO2) on the basic mechanical properties of binary fluorine rubber (FKM), especially the tribological properties at different temperatures, CeO2/FKM composites were prepared by mechanical blending and hot molding process. The hardness test, tear test, uniaxial tension test, room-temperature rotational friction test and high-temperature reciprocating friction test of FKM and CeO2/FKM were performed. The surface morphology of the two materials after being rubbed was observed, and the rubber surface changes were analyzed by scanning electron microscope (SEM) and energy dispersive spectroscopy (EDS). The results show that CeO2 particles can increase the hardness, matrix strength and resistance to external damage of rubber. Compared with pristine FKM, the tensile strength, elongation at break, anti-wear and anti-friction properties of CeO2/FKM composites have been effectively improved, and the enhancement of anti-wear properties of CeO2 reinforced FKM is more obvious under the condition of high temperature (200 °C). Therefore, the composites prepared by blending CeO2 with FKM can effectively improve the basic mechanical properties and tribological properties of FKM.

Efficient fish-scale CeO2/NiFeCo composite material as electrocatalyst for oxygen evolution reaction

An electrochemical catalyst with efficient, stable, inexpensive energy storage for oxygen evolution and hydrogen evolution has raised global concerns on energy, calling for high-performance materials for effective treatments. In this paper, novel amorphous polymetallic doped CeO2 particles were prepared for an electrochemical catalyst via homogeneous phase precipitation at room temperature. Metal ions can be easily embedded into the oxygen vacancies formed by CeO2, and the the electron transport capacity of the CeO2/NiFeCo electrocatalyst is improved owing to the increase in active sites. In addition, the amorphous CeO2/NiFeCo composite material is in a metastable state and will transform into different active states in a reducing or oxidizing environment. Furthermore, the amorphous material drives oxygen evolution reaction (OER) through the lattice oxygen oxidation mechanism (LOM), while LOM can effectively bypass the adsorption of strongly related intermediates in the adsorbate release mechanism, thus promoting OER procedure in a timely manner. As a result, CeO2/NiFeCo exhibits a lower oxygen evolution overpotential of 260 mV at 10 mA cm−2 current density, which shows a predatorily competitive advantage compared with commercially available RuO2 and the reported catalysts.

In vitro cellular activity of maghemite/cerium oxide magnetic nanoparticles with antioxidant properties

Magnetic γ-Fe2O3/CeO2 nanoparticles were obtained by precipitation of Ce(NO3)3 with ammonia in the presence of γ-Fe2O3 seeds. The formation of CeO2 nanoparticles on the seeds was confirmed by transmission electron microscopy linked with selected area electron diffraction, energy-dispersive X-ray spectroscopy, electron energy loss spectroscopy, and dynamic light scattering. The γ-Fe2O3/CeO2 particle surface was functionalized with PEG-neridronate to improve the colloidal stability in PBS and biocompatibility. Chemical and in vitro biological assays proved that the nanoparticles, due to the presence of cerium oxide, effectively scavenged radicals, thus decreasing oxidative stress in the model cell line. PEG functionalization of the nanoparticles diminished their in vitro aggregation and facilitated lysosomal cargo degradation in cancer cells during autophagy, which resulted in concentration-dependent cytotoxicity of the nanoparticles. Finally, the iron oxide core allowed easy magnetic separation of the particles from liquid media and may enable monitoring of nanoparticle biodistribution in organisms using magnetic resonance imaging.

Analysis of surface tension for nano-fuels containing disparate types of suspended nanoparticles

Nano-fuel, as an appealing alternative, provides a new opportunity to promote engine performances. The surface tension is a vital factor affecting spray and evaporation of fuel. In this study, fuel blends containing 20 and 50 nm particles of CNT, CeO2 and Co3O4 with different mass concentrations (i.e. 50, 100 and 150 mg/L) were prepared by the two-step method, in which diesel worked as the base fuel and CTAB served as the surfactant. The surface tension of nano-fuel was determined experimentally at 10–140 °C based on the pendant drop method, and the effects of mass concentration, particle size, nanoparticle types and temperature on the surface tension of nano-fuel were analyzed. It is revealed that the nano-fuel had higher surface tension than diesel and it increased with the increase in mass concentration or particle size, while decreased linearly with the rise of temperature. Among three types of nano-fuels, CNT nano-fuels had the maximum surface tension, which is followed by CeO2 nano-fuels and then Co3O4 nano-fuels.

Tuning the interactions among Ce, Pd and Rh over Ce-modified Pd-Rh three-way catalyst for exhaust treatment of natural gas vehicles

Three Ce-modified Pd-Rh bimetallic catalysts for exhaust purification of natural gas vehicles (NGVs) under stoichiometric conditions were prepared by deposition-precipitation (DP), stepwise impregnation (SI) and co-impregnation (CI) methods, respectively. It demonstrated that before and after aging the catalyst prepared by DP technique displayed much higher activity for the conversions of CH4 and NO than the other two catalysts, especially at high temperatures (about 410–550 °C). X-ray diffraction, CO-chemisorption, hydrogen temperature-programmed reduction and X-ray photoelectron spectroscopy analyzes demonstrated that there were smaller CeO2 particles, higher metal dispersion, stronger reducibility and more surface metallic Pd species over the catalyst prepared by DP method. This might be due to the stronger Pd-Ce but weaker Pd-Rh interactions over the catalyst prepared by DP mean. Moreover, in situ diffuse reflectance infrared Fourier transform spectroscopy of CO adsorption analysis implied that the electronic structures of Pd in the three catalysts were different, which may be also induced by the different interactions among Rh, Ce and Pd in these catalysts. The results indicated that the performance of Pd-Rh three-way catalyst for NGVs exhaust purification can be enhanced by modulating the interactions of Pd-Rh and Pd-Ce. Our work may provide a new strategy for the preparation of three-way catalyst with high efficiency for NGVs.

Effect of CeO2 dispersion on the oxidation behavior of Ni-Al/Ni-Re coating in dry and wet CO2 gas at 650 °C

A CeO2-dispersed nickel-aluminide coating was deposited by aluminizing a Ni-CeO2 electroplating film with a Ni-Re interlayer pre-electroplated sequentially. The CeO2-dispersed coating was exposed to dry and wet CO2 gas at 650 °C for 1300 h. Internal oxidation and cavities were observed in the coating centralized around CeO2 particles, which became more aggravated with the presence of H2O in CO2 gas. The activity of CeO2/Ni2Al3 interface for CO2 and H2O dissociation and oxygen diffusion was studied by first-principle calculations. The effect of CeO2 dispersion on the coating oxidation in dry and wet CO2 gas was discussed.

Highly Active and Stable Palladium Catalysts on Novel Ceria-Alumina Supports for Efficient Oxidation of Carbon Monoxide and Hydrocarbons.

Precious metal catalysts with superior low-temperature activity and excellent thermal stability are highly needed in environmental catalysis field. In this work, a novel two-step incipient wetness impregnation (T-IWI) method was developed for the fabrication of a unique and highly stable CeO2/Al2O3 support (CA-T). Pd anchored on CA-T exhibited a much higher low-temperature catalytic activity and superior thermal stability in carbon monoxide (CO) and hydrocarbon (HC) oxidations, compared to Pd anchored on conventional CeO2/Al2O3 (CA), which was prepared by a one-step IWI method. After aging treatment at 800 °C, the CO oxidation rate on Pd/CA-T (1.69 mmol/(gPd s)) at 120 °C was 4.1 and 84.5 times of those on Pd/CA (0.41 mmol/(gPd s)) and Pd/Al2O3 (0.02 mmol/(gPd s)), respectively. It was revealed that the CA-T support with well-controlled small CeO2 particles (ca. 12 nm) possessed abundant defects for Pd anchoring, which created rich Pd-CeO2 interfaces with strengthened interaction between Pd and CeO2 where oxygen could be efficiently activated. This resulted in the significantly improved oxidation activity and thermal stability of Pd/CA-T catalysts. The T-IWI method developed herein can be applied as a universal approach to prepare highly stable metal oxide-alumina-based supports, which have broad application in environmental catalyst design, especially for automobile exhaust aftertreatment.

Microstructure and properties of cerium oxide/polyurethane elastomer composites

In general, inorganic filler/polyurethane elastomer (PUE) composites possess favorable properties, such as modulus, chemical resistance, and heat stability, are promising for broadening the application area of polyurethanes (PU). For the experiments, a series of cerium oxide (CeO2)/PUE composites were prepared with different sizes and appearance of CeO2, and different mixing methods as well. CeO2 particles with different sizes were added into PUs during the formation of urethane linkage and the chain-extend process, respectively. The morphology along with mechanical properties, thermal properties of the composites were studied. The results suggest that the size of CeO2 and mixing methods influence the microstructure of PUs which has profound effect on properties of these composites. The composites tend to form more quantity of hard domains (HDs) with small size when CeO2 particles were added before the formation of urethane linkage, whereas CeO2 particles increase the size of HDs when added with chain extender into PU prepolymer.

STUDY OF THERMAL CO-DECOMPOSITION OF MANGANESE AND CERIUM OXALATES IN AIR AND IN INERT MEDIA

Controlled thermal decomposition of oxalate salts is a promising method for the preparation of highly dispersed materials. In this work, co-decomposition of Mn and Ce salts is studied upon variations of the cation ratio and the gas atmosphere of the process (air and inert gas). To this aim, a series of Mn and Ce oxalates is prepared by co-precipitation from aqueous solutions of nitrates with Mn:Ce ratios varying from 0:1 to 1:0. It is shown by X-ray powder diffraction and by scanning electron microscopy that cerium Ce(C2O4)3·10H2O and manganese MnC2O4·2H2O oxalates are formed. Also, increasing manganese content increases the amount of the corresponding salts and affects the morphology of the particles. It was shown by a number of physicochemical methods such as thermal analysis, in situ X-ray diffraction, and mass spectrometry shows that the oxalate decomposition proceeds in two stages and depends on the cation ratio and the decomposition atmosphere. The first stage is a weight loss accompanied by removal of structural water; this process is accelerated in a flow of an inert gas. The second stage is the formation of oxides from the anhydrous salt accompanied by CO2 or CO/CO2 release. Due to exothermic oxidation reaction, the decomposition occurs at lower temperatures in air than in an inert gas. The introduction of manganese does not significantly affect the temperature ranges of the first and second stages of salt decomposition. However, the addition of the second cation affects the decomposition product: as the manganese content increases, the size of CeO2 particles decreases and simple manganese oxides Mn3O4 and MnO are formed in air and in the inert atmosphere, respectively. The catalytic properties in the oxidation of CO, Mn and Ce oxides obtained by the decomposition of oxalates in an inert gas and in air are studied. It is shown that the catalysts formed in the oxidizing environment are more active.

Graphene oxide–cerium oxide hybrids for enhancement of mechanical properties and corrosion resistance of epoxy coatings

In this study, graphene oxide–cerium oxide (GO–CeO2) hybrids were synthesized through an in situ hydrothermal approach and were incorporated into epoxy resin to prepare a robust coating for aluminum alloy protection. The mechanical properties of the GO–CeO2-loaded coating were characterized by nano-indentation, friction-wear test and pull-off adhesion test, using pristine epoxy coating and GO-loaded epoxy coating for comparison. Results revealed that GO–CeO2 addition could increase the hardness, elastic modulus and the wear resistance and decrease the friction coefficient of the composite coating. Compared with pristine epoxy coating, the adhesion strength of GO–CeO2/epoxy coating increased from 7.3 MPa to 12.2 MPa. Such improvement in the mechanical properties can be explained by the good dispersion of GO–CeO2 in the composite coating. In addition, salt spray and electrochemical impedance spectroscopy (EIS) measurement results showed that the corrosion resistance of the GO–CeO2-loaded coating was significantly enhanced. After 30 days of salt spray test, the coating resistance of the GO–CeO2/epoxy coating was 17.8 and 3.5 times higher compared with that of the blank epoxy coating and GO/epoxy coating, respectively. The superior barrier performance of the composite coating was mainly ascribed to the synergistic effects of the prolonged pathway against corrosive media permeation and the corrosion inhibition effect of CeO2 particles.

Comprehensive Characterization of a Mesoporous Cerium Oxide Nanomaterial with High Surface Area and High Thermal Stability.

In the present study, the pore space of a mesoporous cerium oxide material is investigated, which forms by the self-assembly of primary particles into a spherical secondary structure possessing a disordered mesopore space. The material under study exhibits quite stable mesoporosity upon aging at high temperatures (800 °C) and is, thus, of potential interest in high-temperature catalysis. Here, different characterization techniques were applied to elucidate the structural evolution taking place between heat treatment at 400 °C and aging at 800 °C, i.e., in a water-containing atmosphere, which is usually detrimental to nanoscaled porosity. The changes in the mesoporosity were monitored by advanced physisorption experiments, including hysteresis scanning, and electron tomography analysis coupled with a 3D reconstruction of the mesopore space. These methods indicate that the 3D spatial arrangement of the primary particles during the synthesis under hydrothermal conditions via thermal hydrolysis is related to the thermal stability of the hierarchical mesopore structure. The assembly of the primary CeO2 particles (∼4 nm in size) results in an interparticulate space constituting an open 3D mesopore network, as revealed by skeleton analysis of tomography data, being in conformity with hysteresis scanning. At elevated temperatures (800 °C), sinter processes occur resulting in the growth of the primary particles, but the 3D mesopore network and the spherical secondary structure are preserved.