Effect Of CeO2 Doping Research Articles

Effects of CeO2 doping on the mechanical, infrared radiative, and thermophysical properties of Pr2Zr2O7 ceramics for potential thermal protective coatings

A series of Ce4+-doped Pr2Zr2O7 ceramics were produced using a solid reaction method to utilize novel ceramic materials as potential candidates for thermally protective coatings. The effects of Ce4+ doping on the phase composition and mechanical, infrared radiative, and thermophysical properties were studied in detail. The results indicated the good phase stability and sintering resistance of the Pr2(Zr1−xCex)2O7 ceramics. Moreover, Ce4+-doped Pr2Zr2O7 bulk materials exhibited higher infrared emissivity (0.904) at wavelengths of 3–5 μm and 1000 °C for Pr2(Zr0.5Ce0.5)2O7) owing to the introduction of impurity energy levels. Pr2(Zr0.7Ce0.3)2O7 exhibited an appropriate average coefficient of thermal expansion of 12.4 × 10−6 K−1 and a low thermal conductivity of 1.14 W m−1 K−1 at 1000 °C, owing to the reduction of lattice energy and the presence of more oxygen vacancies and substitution atoms.

Effect of CeO2 doping on the microscopic morphology and electrical properties of ZnO-based linear resistors

Effect of CeO2 doping on the microscopic morphology and electrical properties of ZnO-based linear resistors

Effect of CeO2 doping on structural, electrical and mechanical properties of basalt fibers

Developing basalt fibers with low dielectric properties and excellent water resistance is still very challenging. To overcome this problem, basalt glass and basalt fibers with different CeO2 content were prepared in this paper by using the conventional melt cooling method and single hole drawing process. The relationship between CeO2 content (0 wt%-4 wt%), the structural, electrical and mechanical properties of basalt fibers was investigated by using XRD, Raman, dielectric properties tester and fiber strength and elongation meter. The results showed that when the weight content of CeO2 was 2 wt%, the glass had the most stable network structure with the largest degree of linkage, resulting in a 75 % increase in water resistance, the lowest values of dielectric constant (6.25) and dielectric loss (4.38 × 10−3), and a 33 % increase in tensile strength.

Effect of CeO2 doping on the coercivity of 2:17 type SmCo magnets

The effects of CeO2 doping on the magnetic properties and microstructure of 2:17 type SmCo magnets are studied. With the increase of CeO2 from 0 wt.% to 3 wt.%, the coercivity of the magnets increases from 22.22 kOe to over 29.37 kOe, which is an increase of more than 30%. When the doping content is lower than 1 wt.%, the remanence and magnetic energy product of the magnets remain almost constant. Both decrease sharply as the doping concentration further increases. After CeO2 doping, the oxide content in the magnet increases significantly and the Ce element is uniformly distributed in the magnet. Observing the magnetic domains reveals that doping with CeO2 can refine the magnetic domains and make the magnetic domain wall more stable, resulting in a significant increase in the coercivity of the magnets.

Effect of CeO2 doping on high temperature oxidation resistance of YSZ TBCs

In the present work, YSZ TBCs and 10 wt% CeO2-doped YSZ thermal barrier coatings (CeYSZ TBCs) were prepared via atmospheric plasma spraying(APS) respectively, whereupon high temperature oxidation experiment was carried out at 1100 °C to compare the high temperature oxidation behavior and mechanism of the two TBCs. The results showed that the doping of CeO2 reduced the porosity of YSZ TBCs by 23%, resulting in smaller oxidation weight gain and lower TGO growth rates for CeYSZ TBCs. Besides, the TGO generated in CeYSZ TBCs was obviously thinner and there were fewer defects inside it. For YSZ TBCs, as the oxidation process proceeded, Al, Cr, Co and Ni elements in the bonding coating were oxidized successively to form loose and porous spinel type oxides (CS), which was apt to cause the spalling failure of TBCs. While, the Al2O3 layer of the TGO generated in CeYSZ TBCs ruptured later than that in YSZ TBCs, which delayed the oxidation of Cr, Co, and Ni elements and the formation of CS accordingly. Therefore, CeO2 doping can effectively improve the high temperature oxidation resistance of YSZ TBCs.

Structure and electrical properties of Ce-modified Ca1-Ce Bi2Nb1.75(Cu0.25W0.75)0.25O9 high Curie point piezoelectric ceramics

Ca1-xCexBi2Nb1.975(Cu0.25W0.75)0.025O9 (CBNCW-xCe: x = 0.00, 0.02, 0.04, 0.06, and 0.09) lead-free piezoelectric ceramics with improved piezoelectric properties were prepared by the traditional solid-state reaction method. The effects of CeO2 doping on the microstructure and electrical properties were investigated in detail. XRD patterns and Rietveld refinement show that the crystal structures of the samples transform from the orthorhombic phase into the pseudotetragonal phase and that the lattice distortion is weakened. Raman and XPS spectra indicate that Ce ions exist with +3 and + 4 valences in the air sintered ceramics, in which Ce4+ replaces Nb5+, causing the weakened NbO6 octahedral vibration of torsional and tensile and an increase in oxygen vacancies in the doped ceramics. When x = 0.04, it shows excellent comprehensive properties with a high d33 value of 18.1 pC/N, a Tc value of 900 °C, and a ρdc value of 2.8 × 105 Ω cm at 500 °C. Our results suggest that the CBNCW-0.04Ce ceramic is a promising candidate in high-temperature piezoelectric applications.

A EFFECT OF CeO2 DOPING ON THE MICROSTRUCTURE AND CORROSION BEHAVIOR OF CoCuNiTi HIGH-ENTROPY ALLOY COATINGS

CoCuNiTi high-entropy alloy coatings with an equal molar ratio were prepared on 45 steel substrates using the laser-cladding method. The effect of CeO2 doping on phase structure, microstructure and corrosion behavior of CoCuNiTi coatings were investigated by X-ray diffraction, optical microscope, scanning electron microscope, and electrochemical workstation. The results show that the phase structure of CoCuNiTi coating doped with 1 w/% CeO2 is transformed from the original dual-phase structure of FCC main phase and BCC phase to the dual-phase structure of BCC main phase and FCC phase, mainly because CeO2 addition helps to improve the temperature gradient and solidification rate during solidification, reduce the nucleation resistance and the diffusion distance of the alloying elements, and provide a liquid environment with longer time, lower viscosity and higher diffusion rate. The microstructure of the two coatings is composed of BCC-phase dendrite and FCC-phase interdendrite. The widths of the primary dendrites of the columnar dendrites in CoCuNiTi cladding layer before and after CeO2 doping are about 8.10 µm and 6.51 µm, respectively. The CoCuNiTi coating doped with 1 w/% CeO2 has the smallest corrosion current density, the largest capacitive reactance arc radius and polarization resistance, and the best corrosion resistance in 3.5 w/% NaCl solution, which is mainly due to making the alloy structure refined and the element distribution uniform after the CeO2 addition.

Effect of CeO2 Doping on the Structure and Properties of Titanium Barium Silicate Glass

Glasses with the composition 50SiO2 · 20TiO2 · 15BaO · 7.5SrO · 7.5CaO doped with the varied content of CeO2 were prepared by conventional melt quenching technique. The effect of CeO2 on the structure of glasses was investigated by X-ray photoelectron spectroscopy and Raman spectroscopy. The density, thermal stability, dielectric properties and acid resistance of glasses were studied by Archimedes method, differential thermal scanning analysis and X-ray diffraction, dielectric measuring as well as the powder method. The results showed that the coordination of Ti, which existed in glasses as [TiO4], did not change. An increase in the content of non-bridging oxygen atoms and a corresponding decrease in the content of bridging oxygens correlated. The depolymerization of the glass network was attributed to an increase in the number of Si–O–Ti bonds and the change of the Qn distribution. With an increase in the CeO2 content, the thermal stability and acid resistance of glass first increased and then decreased, and the dielectric constant and dielectric loss of glass decreased first and then increased.

In situ studies on ceria promoted cobalt oxide for CO oxidation

In situ studies of catalysts play valuable roles in observing phase transformation, understanding the corresponding surface chemistry and the mechanism of the reaction. In this paper, ceria promoted cobalt oxide was prepared by the calcination method and investigated for the CO oxidation. The microstructure and morphology of CeO2-Co3O4 were investigated by the Scanning Electron Microscope, High-resolution transmission electron microscopy, Raman and X-ray photoelectron spectroscopy characterization. The effect of CeO2 doping on Co3O4 for CO oxidation was characterized by in situ X-ray Diffraction (in situ XRD) and in situ diffuse reflectance infrared Fourier transform spectroscopy (in situ DRIFTS). In situ XRD was carried out under H2 atmosphere to evaluate the redox property of catalysts. The results indicated that the ceria doping can enhance the reducibility of Co2+ and promote the Co3+—Co2+—Co3+ cycle, owing to the oxygen replenish property of CeO2. Furthermore, adsorbed carbonate species on the surface of CeO2-Co3O4 were investigated by in situ-DRIFTS experiment. It was turned out that carbonate species on ceria promoted cobalt oxide catalysts showed different IR peaks compared with pure cobalt oxide. The carbonate species on ceria promoted catalyst are more active, and similar to free state carbonate species with weak bonding to catalyst surface, which can effectively inhibit catalyst inactivation. This study revealed the mechanism of ceria promoting CO oxidation over cobalt oxide, which will provide theoretical support for the design of efficient CO oxidation catalysts.

Surface and interface characteristics of CeO2 doped Al2O3 coating on solution treated and peak aged AZ91 Mg alloy

The present study deals with the development of a ceramic based coating on AZ91 Mg alloy. D-gun thermal spray technique is used to deposit these coatings. The work is divided into two explorations; (i) the effect of substrate (AZ91 alloy) microstructure and (ii) the effect of CeO2 doping in Al2O3 coating. The coating quality is judged by recording hardness (H), elastic modulus (E) and H/E ratio. The microstructural, metallurgical and mechanical properties were recorded using SEM/EDS, XRD and nanoindenter, respectively. The results indicate that there is optimality in the doping concentration of CeO2 in Al2O3. Moreover the coatings deposited on solution treated alloy exhibit superior properties. The improved mechanical response is attributed to the development of new phases.

Crystallization kinetics and glass transition kinetics of iron borophosphate glass and CeO2-doped iron borophosphate compounds

Effects of CeO2 doping and the preexisting formed CePO4 crystallite on the crystallization kinetics and glass transition kinetics of the 36Fe2O310B2O354P2O5 glass (IBP glass) have been investigated by differential thermal analysis (DTA). The results reveal that a well defined glass transition peak and two crystallization peaks are observed in DTA curve of the IBP glass. The crystallization activation energies for the first crystallization peak (Ec for P1) and the second crystallization peak (Ec for P2) of the IBP glass are 211.77 KJ mol−1 and 564.31 KJ mol−1 respectively. And CeO2 doping insignificantly affects the Ec for P1 but increases the Ec for P2. Moreover, the preexisting CePO4 crystallite increases the Ec for P1 and the activation energies of glass transition peak (Eg). However, the CePO4 crystallite obviously decreases the Ec for P2. In addition, the crystal growth in the IBP glass occurs in two dimensions. Due to the preexisting CePO4, the dimensions of crystal growth in CeO2-doped IBP compounds change to three. The conclusions offer some useful information for the disposal of high-level radioactive wastes using iron borophosphate glasses and iron borophosphate based glass-ceramics.

Microstructure and Electrical Properties of Cerium-Doped Bismuth-Layer 0.9Bi4Ti3O12-0.1K0.5Na0.5NbO3 Piezoelectric Ceramics

The cerium doped 0.9Bi4Ti3O12-0.1K0.5Na0.5NbO3 (BTO-KNN) piezoelectric ceramics were synthesized using conventional solid state processing. The effects of CeO2 doping on the microstructure and the electrical properties of BTO-KNN ceramics were investigated. It is found that the ceramics possess a pure phase of bismuth oxide layer-type structure. The piezoelectric properties of BTO-KNN-based ceramics are significantly improved after cerium doping. The piezoelectric constant d33, dielectric loss tan δ, mechanical quality factor Qm and remanent polarization Pr for the BTO-KNN ceramics with 0.75 wt% CeO2 dopant are found to be 28 pC/N, 0.29%, 2897, 11.83 µC/cm2, respectively, and with high Curie temperature TC (∼615 °C) and stable piezoelectric properties, demonstrating that the cerium doped BTO-KNN piezoelectric ceramics are the promising candidates for high-temperature applications.

Effect of CeO2 Doping on Properties of PCrNi-4 Piezoelectric Ceramics

The piezoelectric ceramic Pb0.94Sr0.06(Zr0.53Ti0.47)O3 + 0.1 wt% (Ni2O3 + Cr2O3) + x wt%CeO2 (PCrNi-4) was prepared using a traditional solid state sintered method. The effects of CeO2 doping on phase structure, microstructure, piezoelectric, and dielectric properties were analyzed by means of XRD, SEM, and electrical property measurements. The results indicate that when CeO2 doping content is 0.3 wt% and sintering temperature is 1,280 °C, the dielectric loss value of the ceramic is the least with a value of 0.00238, and the dielectric factor $$ \varepsilon_{33}^{\text{T}} $$ , piezoelectric strain factor d 33, planar electromechanical coupling coefficient K p and mechanical quality factor Q m of the ceramic is 1400, 375 pCN−1, 0.68, and 460, respectively.

Effect of CeO 2-doping on surface and catalytic properties of CuO–ZnO system

The effect of doping CuO–ZnO system with CeO 2 on its surface and catalytic properties was investigated using nitrogen adsorption at −196 °C, EDX technique and catalysis of CO oxidation by O 2 at 100–200 °C. Pure mixed solids were prepared by thermal decomposition of copper/zinc mixed hydroxides at 400 °C. The doped solids were obtained by impregnating a known mass of mixed hydroxides with calculated amount of cerium ammonium nitrate followed by drying then calcination at 400 °C. The dopant concentration was 1.5, 3.0 and 4.5 mol% CeO 2. The results revealed that CeO 2-doping modified the surface atomic Cu/Zn ratio of the system investigated and changed the crystallite size of both CuO and ZnO phases. The increase of the amount of dopant added changed the major phase present. This treatment decreased the specific surface area of doped solids. The doping process modified also the catalytic activity in a manner dependent on both mode of preparation and dopant concentration. However, CeO 2-doping did not modify the mechanism of the catalytic reaction but changed the concentration of catalytically active sites involved in the catalyzed reactions.

Effect of CeO2 Doping on Structure and Catalytic Performance of Co3O4 Catalyst for Low-Temperature CO Oxidation

The effect of CeO2 doping on structure and catalytic performance of Co3O4 catalyst was studied for low-temperature CO oxidation. The Co3O4 catalyst was prepared by a precipitation method and the CeO2/Co3O4 catalyst was prepared by an impregnation method. Their catalytic performance had been studied with a continuous flowing micro-reactor. The results reveal that the CeO2/Co3O4 catalyst exhibits much better resistance to water vapor poisoning than the Co3O4 catalyst for CO oxidation. The CeO2/Co3O4 catalyst can maintain CO complete conversion at least 8,400 min at 110 °C with 0.6% water vapor in the feed gas, while the Co3O4 catalyst can maintain at 100% for only 100 min. Characterizations with XRD, TEM and TPR suggest that the CeO2/Co3O4 catalyst possesses higher dispersion degree, smaller particles and larger SBET, due to the doping of Ceria, and exists the interaction between CeO2 and Co3O4, which may contribute to the excellent water resistance for low-temperature CO oxidation. Furthermore, the H2 detected in the reactor outlet gas seems to indicate that the water–gas shift reaction is the more direct reason.

Effects of CeO2 Doping on Electrical Properties of Lead Metaniobate Based Ceramics

Pb 0.97 Ca 0.03 Nb 2 O 6 + xwt% CeO2 (x = 0, 0.3) bulk ceramics were fabricated by conventional solid state reaction route. The structures of the specimen were investigated by XRD and SEM. The dielectric, piezoelectric properties were also measured, the results indicate that CeO 2 doping can improve the piezoelectric properties. The specimen of x = 0.3 showed the main electrical properties as follows: K p = 0.06, K t = 0.40, Q m = 25, tanδ = 0.36%, ϵ 33 T /ϵ0 = 243 and d 33 = 71 pC/N. The Curie temperature of the specimen x = 0.3 is 526°C, it can be potentially applied for high temperature and high frequency wideband ultrasonic transducers and detectors.

Effects of CeO 2-doping on surface and catalytic properties of CuO/Al 2O 3 solids

The effects of doping of CuO/Al 2O 3 solids with CeO 2 on their surface and catalytic properties were investigated using nitrogen adsorption measurements at −196°C and oxidation of CO by O 2 at 100–175°C. The dopant concentrations were varied between on 0.75–4.5 mol% CeO 2 and the amount of copper was fixed at 16.7 mol% CuO. Pure and variously doped solids were prepared by wet impregnation method using finely-powdered Al(OH) 3 and solutions containing different amounts of cerium nitrate. The impregnated solid samples were dried at 100°C and calcined at 400°C. The obtained solids were treated with solutions containing fixed amounts of copper nitrate, drying then calcination at 300, 500 and 700°C. The results showed that the doping process resulted in a measurable increase in the BET-surface area of the treated solids. The maximum increase in the S BET attained 51, 22.5 and 5% for the solids precalcined at 300, 500 and 700°C, respectively. The doping process brought about a considerable increase in the catalytic activity of the treated catalysts. Furthermore, the catalytic activity of pure solids decreased considerably (about 60%) by increasing the precalcination temperature from 300 to 700°C. On the other hand, the catalytic activity of doped samples remained almost unchanged or increased slightly (about 22%) upon increasing the temperature of heat treatment from 300 to 700°C. The maximum increase in the catalytic activity, expressed as reaction rate constant per unit surface area measured at 125°C attained 27, 150 and 422% for the catalysts doped with 3 mol% CeO 2 and precalcined at 300, 500, and 700°C, respectively. The doping process did not modify the activation energy of the catalyzed reaction i.e. doping of CuO/Al 2O 3 solids with CeO 2 followed by heating at 300–700°C did not alter the mechanism of the catalytic reaction but increased the concentration of catalytically active constituents taking part in the catalytic process without changing their energetic nature.