Increasing CeO2 Content Research Articles

Microstructure and performance of AlCoCrFeNiCu(CeO2)X high-entropy alloy coatings by plasma cladding

AlCoCrFeNiCu(CeO2)X (x=0 wt%, 0.3 wt%, 0.6 wt%, 0.9 wt%, and 1.2 wt%) HEA coatings were applied via plasma cladding technology to a 35CrMo steel surface in this investigation. Electron back-scattering diffraction (EBSD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), and X-ray diffraction (XRD) were used to analyze the phase composition and microstructure of the coatings. A microhardness meter, a nanoindenter, a wear test machine, and an electrochemical station were used to assess the coating performance. The findings demonstrate that the phase composition of the coatings is unaffected by the addition of CeO2, with all coatings consisting of FCC and BCC phases. CeO2 was added to the coatings to refine their grain size and increase their proportion of high angle grain boundaries (HAGBs), BCC phase content, and geometrically necessary dislocation (GND) density. These improvements led to significant increases in the microhardness and wear resistance of the coatings. The 0.3 wt% CeO2 coating has the best corrosion resistance, which is caused by a number of factors including the element distribution, grain size, content of each phase, and phase distribution of the coatings. The corrosion resistance of the coating increases and then decreases nonlinearly with increasing CeO2 content.

Effect of CeO2 Content on Microstructure and Wear Resistance of Laser-Cladded Ni-Based Composite Coating

In order to improve the wear resistance of 45 steel, in this study, WC/Ni60 composite coatings with different CeO2 additions (0, 1, 2, and 3 wt%) were prepared on 45 steel by the laser cladding technique; the experimental analysis was carried out by means of scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS), X-ray diffraction (XRD), a Vickers hardness tester, and a friction and wear tester. The results show that CeO2 had little effect on the phase composition of the coatings; however, with the increase in CeO2 content, the CeO2 played a key role in refining the grains of the coating, thus reducing the generation of cracks. In addition, CeO2 could effectively strengthen the internal structure of the coating and improve its microhardness and wear resistance. Particularly noteworthy is the observed reduction in both the friction coefficient and mass loss of the coating when the CeO2 addition reached 2%. This suggests an enhancement in the tribological performance of the coating at this concentration.

Nano cerium oxide addition enhancing the degradation resistance of biomedical Mg alloy produced by selective laser melting

Magnesium (Mg) alloys are one of the promising bone implant materials on account of their excellent biocompatibilities, suitable mechanical properties and a distinctive degradability. However, their clinical application is hindered by their too rapid degradation rate under physiological conditions. In this study, nano cerium oxide (CeO2) was incorporated into AZ61 (Mg–6Al–1Zn, wt.%) via selective laser melting to improve the degradation behavior. The results indicated that the degradation rate of AZ61 was slowed down by about 64%, with CeO2 containing up to 2 wt %. This was mainly attributed to: 1) in the selective laser melting process of AZ61-CeO2, a part of CeO2 was reduced to cerium (Ce), and Ce reacted with aluminum (Al) in AZ61 to form acicular Al4Ce phase and hinder island Mg17Al12 phase precipitation, which caused the reduction of galvanic corrosion; 2) the other part of CeO2 was uniformly dispersed in the Mg matrix. It could enter the degradation product film as the matrix degraded, which was conducive to increasing the relative density and positive charge quantity of the degradation product film, then improving the degradation product film resistance against corrosive solution penetration. Meanwhile, the compression strength of AZ61-CeO2 increased with increasing CeO2 content and reached the maximum value of 241 ± 12.0 MPa when CeO2 content was 2 wt%, which was principally put down to the refined crystalline strengthening and nano CeO2 dispersion strengthening. In addition, the results of cytocompatibility assessment showed that the AZ61-2CeO2 exhibited the best cytocompatibility. These results showed that the AZ61-2CeO2 produced by selective laser melting was a promising bone implant biomaterial.

Preparation and properties of excellent performance W–Cu alloy with a variety of strengthening mechanisms

In this paper, using the ultrafine W-27.5 wt%Cu-2wt.%Mo-1.75 wt%Ni-0.75 wt%Fe-(0–1)wt.%CeO2 alloy powders as raw materials, W–Cu–Mo–Ni–Fe–CeO2 alloys with excellent performances were prepared by low temperature sintering. Two-step reduction method consisting of carbothermic pre-reduction and hydrogen deep deoxidation was used to produce ultrafine W–Cu–Mo–Ni–Fe–CeO2 alloy powders with uniform distributed composition. All sintered blocks obtained relatively high densification degree (97.1 %∼99.2 %) to ensure the excellent comprehensive properties. Moreover, the existences of γ-(Cu, Ni, Fe) and W–Mo solid solutions ensured the alloy possessed a high mechanical strength. More importantly, the introduction of CeO2 inhibited the growth of W–Mo grains. With increasing CeO2 content from 0 wt% to 1 wt%, the W–Mo grain size decreased from 1.76 μm to 1.44 μm. Especially, alloy sample with the highest tensile and compressive strengths was obtained by adding 0.5 wt% CeO2, which were 602 MPa and 3187 MPa, respectively. Furthermore, owing to finer W–Mo grain size, this sample also possessed the maximum micro-hardness and bending strength of 482 H V and 1685 MPa, respectively. Nevertheless, the existences of Ni, Fe and CeO2 also destroyed the electrical conductivities of the samples to some extent. Specifically, with increasing CeO2 content from 0 wt% to 1 wt%, the electrical conductivity of the sample decreases from 32.56 %IACS to 30.16 %IACS.

Rare earth oxide CeO2 enhanced reactive air brazing of YSZ ceramics

Cerium oxide (CeO2) in the range of 0–16 mol.% is used to enhance the joint of Ag-based filler for brazing yttria-stabilized zirconia (YSZ) ceramic in the air. Ag–CeO2 filler is first adopted to braze YSZ ceramic (3 mol.% yttria). The CeO2 is found to cluster at the interface of YSZ and Ag seam, improving the wetting behavior of Ag-based fillers. The maximum shear strength of YSZ joints can reach 35.1 MPa using Ag–1CeO2 fillers at 1050 °C/30 min. Moreover, CeO2 is used to enhance the Ag–CuO filler for brazing YSZ ceramic. As the increase of CeO2 content, the contact angle of Ag–CuO on the YSZ surface decreases first and then increases. The average shear strength could reach 76.5 MPa using Ag–CuO–8CeO2 at 1050 °C/30 min. The CeO2 could decrease residual stress by adjusting the linear expansion coefficient of Ag-based fillers. Therefore, this study provides a new strategy for exploring air brazing fillers.

OH-PLIF study on the mechanism regulating flame-wall interaction with catalytically active CeO2-ZrO2 coatings

Technically, using catalytically active coatings regulate flame-wall interactions to enhance flame stability in small-scale burners, such as the common ZrO2-based ceramics with doping CeO2 which benefit to improve the high-temperature mobility and reactivity of lattice oxygen as an oxygen source to promote gas phase combustion. Probing by OH-PLIF laser diagnosis, the aim of this study was to investigate the dopant content effect (0–20 wt.% CeO2) on the flame characteristics of methane-air mixtures of varying equivalence ratio (0.9, 1.0, and 1.2) in an adjustable-gap narrow channel (2–12 mm) at a wall temperature range of 373 K to 973 K, including the dynamic flame morphology, flame quenching performance, and near-wall spatial distribution of OH radicals. Results show that the flame-wall distances are strongly correlated with wall temperature, equivalence ratio, and channel scale. After doping CeO2, the measured quenching distances can significantly drop, but do not show a linear downward trend with increasing CeO2 content. The case of 5%CeO2-ZrO2 coating demonstrates a small critical quenching Peclet number at high wall temperatures. The maximum OH fluorescence intensity in flame core areas increases with CeO2 doping into CeO2-ZrO2 at 973 K when the channel clearance is less than 4 mm. However, the absolute concentration of near-wall surviving OH radicals in the presence of 20%CeO2-ZrO2 coating is substantially lower than in the 5%CeO2-ZrO2 case due to differences in the redox properties. In situ diffuse reflectance infrared Fourier transformations spectroscopy tests further indicate that the adsorption quantities of C2H4 and C2H6 species on the coating surface also show a non-monotonous CeO2 dependence, as they are important intermediates in the low-temperature C2 chain reaction of methane.

Microstructure and Properties of Direct Laser-Deposited CeO2-Modified Cobalt-Based Composite Coatings

The seawater circulation pump is a significant piece of equipment in coastal nuclear power plants that is susceptible to erosion and corrosion in the seawater. In this work, CeO2-modified cobalt-based composite coatings were prepared on the surface of martensitic stainless steel by direct laser deposition. The effect of CeO2 on the phase composition, microstructure, microhardness, corrosion resistance, and erosion properties of the cobalt-based composite coatings was systematically investigated. While the addition of CeO2 did not affect the phase composition of the coatings that comprised γ-Co, γ-Ni, M7C3, and M23C6 (M = Cr, W, Fe) metallic carbides, the eutectic organization showed an obvious phenomenon of contiguous aggregation. Microscopic pores were found in the coatings with 2 wt.% CeO2, and the number of pores increased with the increase in CeO2 content. Despite the higher self-corrosion potential (−0.27668 V) of cobalt-based alloy coating compared to the substrate (−0.37019 V), indicating enhanced corrosion resistance, the difference in self-corrosion potential among coatings with varying CeO2 addition amounts is small (0.027 V), and the corrosion current densities are within one order of magnitude (10−8 A/cm2). These findings suggest that the addition of CeO2 has no significant impact on the coating’s corrosion resistance.

Effect of CeO2 Content on Melting Performance and Microstructure of CaO-Al2O3-SiO2-MgO Refining Slag

CeO2 can be applied to refining slag to minimize the size of inclusions, speed up the deoxidization process, and adsorb Al2O3 inclusions. The impact through which CeO2 content affects slag’s melting efficiency is still uncertain. The thermal analyzer was used to measure the thermogravimetric analysis (TG) and differential scanning calorimetry (DSC) curves of the slag melting process. According to the study results, with the increase in CeO2 content, the melting temperature of slag decreased first and then increased. The slag’s melting point fell from 1364 °C to 1324 °C and then rose to 1503 °C. XRD and SEM were used to analyze the CaO-Al2O3-SiO2-MgO-CeO2 slag’s microstructure. The mineral-phase structure of CeO2-containing refining slag was primarily composed of Ca2SiO4 and 3CaO·Al2O3, MgO, SiO2, CaO·Al2O3, and Ca8Ce6Al6O26. The proportion of 3CaO·Al2O3, CaO·Al2O3, and Ca2SiO4 decreased as the rare-earth-oxide content increased, while the proportion of Ca8Ce6Al6O26 increased. FactSage was used to estimate the equilibrium-phase compositions of slags with various compositions, and a model for predicting melting points was carried out by a linear regression model. Results were obtained through the analysis of equilibrium-phase composition and crystal structure transformation. The main reasons for the melting point decrease were the change of degree of polymerization and the decrease in contents and complete melting temperature of high-melting-point Ca3Al2O6 and Ca2SiO4 compounds. The latter increase in melting point was due to the number of Ca8Ce6Al6O26 compounds and precipitation temperature increases and the complexity of the structural-network increases.

Design of hybrid La1-xCexCoO3-δ catalysts for lean methane combustion via creating active Co and Ce species

The catalytic activity of perovskite-typed catalysts depends on both the surface properties and bulk structure. Herein, we report a facile strategy to induce surface reconstruction and lattice distortion of the La1-xCexCoO3-δ catalysts via acid-etching pretreatment, ultimately realizing superior performance for catalytic combustion of lean methane, even in the presence of steam and hydrogen sulfide. The exsolution of small Ce and Co oxides (ca. 5 nm) from the perovskite were found on the surface of the La1-xCexCoO3-δ catalysts to form a hybrid structure after the acid-etching, which interact with the perovskite bulk to create more Co3+ and surface absorbed oxygen as active sites for methane combustion. It is also found that Ce species can be embedded in the crystal lattice and decorated on the surface of the catalysts after the acid-etching, which may enhance the formation of surface absorbed oxygen and the redox ability of Co3+/Co2+ pair. This results in high catalytic activity (T90 = 486 ℃) with a space velocity of 30,000 mL·g−1·h−1. Otherwise, the weak ability of hydroxyl species adsorbed on the surface of acid-etched catalysts restrain further adsorption of water molecules, improving the stability of methane combustion in the presence of water vapour. The increase in CeO2 content on the surface due to acid etching also contributes to the catalyst’s resistance to sulfur poisoning. The present work may provide a new strategy for the synthesis of hybrid perovskite catalysts with excellent catalytic performance, stability and resistance to impurities poisoning.

Influence of B-site substituent Ce on thermophysical, oxygen diffusion, and mechanical properties of La2Zr2O7

Pyrochlore-type La2Zr2O7 (LZ) is a promising candidate for high-temperature thermal barrier coatings (TBCs). However, its thermal expansion coefficient and low fracture toughness are not optimal for such application and thus, need to be improved. In this study, we systematically report the effect of CeO2 addition on phase formation, oxygen-ion diffusion, and thermophysical and mechanical properties of full compositions La2(Zr1−xCex)2O7 (x = 0, 0.1, 0.3, 0.5, 0.7, 0.9, 1). La2(Zr1−xCex)2O7 exhibits a pyrochlore structure at x ≤ 0.3, while a fluorite structure is observed outside this range. With the increase in CeO2 content, thermal expansion coefficient and oxygen-ion diffusivity in La2(Zr1−xCex)2O7 are increased. Oxygen-ion diffusivity of La2(Zr1−xCex)2O7 is two orders of magnitude less than that of classical 8YSZ. Among La2(Zr1−xCex)2O7 compounds, La2(Zr0.7Ce0.3)2O7 and La2(Zr0.5Ce0.5)2O7 exhibit relatively low oxygen diffusivities. The composition La2(Zr0.5Ce0.5)2O7 presents the lowest thermal conductivity due to the strongest phonon scattering and also the highest fracture toughness due to the solid-solution toughening. The highest sintering resistance is achieved by the composition La2(Zr0.7Ce0.3)2O7 because of its ordered pyrochlore structure and high atomic mass of Ce. Based on these results, the compositions La2(Zr0.5Ce0.5)2O7 and La2(Zr0.7Ce0.3)2O7 are alternatives for classical 8YSZ for TBC materials operating at ultrahigh temperatures.

Hydrodesulfurization of Dibenzothiophene over Ni-Mo-W Sulfide Catalysts Supported on Sol-Gel Al2O3-CeO2.

To achieve sulfur content in gas oil at a near-zero level, new catalysts with improved hydrogenation functions are needed. In this work, new Ni-Mo-Mo hydrodesulfurization (HDS) catalysts supported by Al2O3-CeO2 materials were synthesized to evaluate their efficiency in the reaction of HDS with dibenzothiophene (DBT). Al2O3-CeO2 supports different CeO2 loadings (0, 5, 10 and 15 wt.%) and supported NiMoW catalysts were synthesized by sol-gel and impregnation methods, respectively. The physicochemical properties of the supports and catalysts were determined by a variety of techniques (chemical analysis, XRD, N2 physisorption, DRS UV-Vis, XPS, and HRTEM). In the DBT HDS reaction carried out in a batch reactor at 320 °C and a H2 pressure of 5.5 MPa, the sulfide catalysts showed a dramatic increase in activity with increasing CeO2 content in the support. Nearly complete DBT conversion (97%) and enhanced hydrogenation function (HYD) were achieved on the catalyst with the highest CeO2 loading. The improved DBT conversion and selectivity towards the hydrogenation products (HYD/DDS ratio = 1.6) of this catalyst were attributed to the combination of the following causes: (i) the positive effect of CeO2 in forcing the formation of the onion-shaped Mo(W)S2 layers with a large number of active phases, (ii) the inhibition of the formation of the undesired NiAlO4 spinel phase, (iii) the appropriate textural properties, (iv) the additional ability for heterolytic dissociation of H2 on the CeO2 surfaces, and (v) the increase in Brønsted acidity.

Effect of CeO2 on Microstructure and Properties of Wear and Corrosion Resistance Martensitic Stainless Steel‐Based Coating on Laser Cladding

The effects of CeO2 on the quantity, morphology, and distribution of carbides, the microhardness, friction and wear properties, and corrosion resistance of 0.3C–16Cr martensitic stainless steel‐based cladding layer are investigated. The results show that the addition of CeO2 inhibits the dendrite growth and improves the morphology, size, and distribution of carbides in the cladding layer. The hardness shows a peak with the increase in CeO2 content, the wear rate of the cladding layer with CeO2 decreases, and the wear resistance increases. In addition, CeO2 significantly improves the corrosion resistance of the cladding layer, causing the pitting potential to increase and the blunt current density to decrease. Compared with the original sample, the wear amount and dimensional blunt current density of the sample with 0.3% CeO2 content are reduced by 55.36% and 35.32%, respectively, and the pitting potential is increased by 2.71 times. The comprehensive performance of the cladding layer is the best. This is mainly because CeO2 can increase the latent heat of crystallization during the cooling process of the cladding layer, reduce the constitutional supercooling, inhibit the directional growth of dendrites, improve the uniformity of the microstructure and composition, and thereby improve the wear resistance and corrosion resistance.

Effect of CeO2 and VC co-doping on the microstructure and properties of WC-10Co cemented carbide

Combining spray drying and in-situ synthesized technology, WC-10Co cemented carbides with uniform composition was prepared by vacuum sintering to investigate the effects of different CeO2 contents (0 wt%, 0.5 wt%, 1 wt%, 2 wt%, 4 wt%) as well as co-doping with CeO2 and VC on the microstructure and mechanical properties. With increasing CeO2 addition from 0 wt% to 0.5 wt%, the WC grain size decreased from 0.79 ± 0.35 μm to 0.62 ± 0.24 μm. The hardness, fracture toughness and transverse rupture strength (TRS) of the alloy with 0.5 wt% CeO2 all reached the maximum values of 1752 ± 28 HV30, 18.50 ± 0.35 MPa·m1/2 and 2245 ± 35 MPa, respectively, which indicated that the mechanical properties of cemented carbide could be simultaneously improved by adding 0.5 wt% CeO2 to refine the WC grains. However, as the CeO2 content increased to 4 wt%, the hardness gradually decreased, while the fracture and TRS all slightly decreased first and then tended to be stable. Moreover, the corrosion resistance of alloys first increased and then decreased with the increase of CeO2 content. The 0.5 wt% CeO2 alloy had the best corrosion resistance. After adding 0.5 wt% VC, the grain size of alloys became smaller and distribution of Co binder was more uniform. Compared to the samples with only added CeO2, the alloy with co-addition of 0.5 wt% CeO2 and 0.5 wt% VC exhibited the best comprehensive mechanical properties. The hardness, fracture toughness and TRS of the alloy with co-addition of 0.5 wt% CeO2 and 0.5 wt% VC were 1987 ± 44 HV30, 16.10 ± 0.34 MPa·m1/2 and 2023 ± 78 MPa, respectively.

Bacterial Cellulose-Based Nanocomposites Containing Ceria and Their Use in the Process of Stem Cell Proliferation

A technique for the fabrication of bacterial cellulose-based films with CeO2 nanofiller has been developed. The structural and morphological characteristics of the materials have been studied, their thermal and mechanical properties in dry and swollen states having been determined. The preparation methodology makes it possible to obtain composites with a uniform distribution of nanoparticles. The catalytic effect of ceria, regarding the thermal oxidative destruction of cellulose, has been confirmed by TGA and DTA methods. An increase in CeO2 content led to an increase in the elastic modulus (a 1.27-fold increase caused by the introduction of 5 wt.% of the nanofiller into the polymer) and strength of the films. This effect is explained by the formation of additional links between polymer macro-chains via the nanoparticles’ surface. The materials fabricated were characterized by a limited ability to swell in water. Swelling caused a 20- to 30-fold reduction in the stiffness of the material, the mechanical properties of the films in a swollen state remaining germane to their practical use. The application of the composite films in cell engineering as substrates for the stem cells’ proliferation has been studied. The increase in CeO2 content in the films enhanced the proliferative activity of embryonic mouse stem cells. The cells cultured on the scaffold containing 5 wt.% of ceria demonstrated increased cell survival and migration activity. An analysis of gene expression confirmed improved cultivation conditions on CeO2-containing scaffolds.

Synthesis, Optical, Chemical and Thermal Characterizations of PMMA-PS/CeO2 Nanoparticles Thin Film.

We report the synthesis of hybrid thin films based on polymethyl methacrylate) (PMMA) and polystyrene (PS) doped with 1%, 3%, 5%, and 7% of cerium dioxide nanoparticles (CeO2 NPs). The As-prepared thin films of (PMMA-PS) incorporated with CeO2 NPs are deposited on a glass substrate. The transmittance T% (λ) and reflectance R% (λ) of PMMA-PS/CeO2 NPs thin films are measured at room temperature in the spectral range (250–700) nm. High transmittance of 87% is observed in the low-energy regions. However, transmittance decreases sharply to a vanishing value in the high-energy region. In addition, as the CeO2 NPs concentration is increased, a red shift of the absorption edge is clearly observed suggesting a considerable decrease in the band gap energy of PMMA-PS/CeO2 NPs thin film. The optical constants (n and k) and related key optical and optoelectronic parameters of PMMA-PS/Ce NPs thin films are reported and interpreted. Furthermore, Tauc and Urbach models are employed to elucidate optical behavior and calculate the band gaps of the as-synthesized nanocomposite thin films. The optical band gap energy of PMMA-PS thin film is found to be 4.03 eV. Optical band gap engineering is found to be possible upon introducing CeO2 NPs into PMMA-PS polymeric thin films as demonstrated clearly by the continuous decrease of optical band gap upon increasing CeO2 content. Fourier-transform infrared spectroscopy (FTIR) analysis is conducted to identify the major vibrational modes of the nanocomposite. The peak at 541.42 cm−1 is assigned to Ce–O and indicates the incorporation of CeO2 NPs into the copolymers matrices. There were drastic changes to the width and intensity of the vibrational bands of PMMA-PS upon addition of CeO2 NPs. To examine the chemical and thermal stability, thermogravimetric (TGA) thermograms are measured. We found that (PMMA-PVA)/CeO2 NPs nanocomposite thin films are thermally stable below 110 °C. Therefore, they could be key candidate materials for a wide range of scaled multifunctional smart optical and optoelectronic devices.

Preparation of Y2O3–ZrO2–CeO2 solid solution by co-precipitation and its electrical property

{(Y2O3)0·08(ZrO2)0.92}1-x (CeO2)x (0 ≤ x ≤ 0.6) is synthesized by co-precipitation method. Thermal analysis, phase structure, lattice constant, micro-morphology, elements distribution, density, open porosity and electrical conductivity are measured by TG, DSC, XRD, GSAS, SEM, EDS, Archimedes method and EIS respectively, and the influence of CeO2 content on the above properties are investigated. TG-DSC results show that the weight loss of the sample is mainly due to the decomposition of the initial powder, forming a solid solution above ~600 °C. XRD results show that {(Y2O3)0·08(ZrO2)0.92}1-x (CeO2)x (0 ≤ x ≤ 0.6) is a cubic solid solution, and the lattice parameters and volume increase with the increase of CeO2 content. SEM results show that YZC is a dense sintered body. Density and open porosity of YZC sample are ~4.5 g cm−3 and ~0.12, respectively. The electrical conductivity results show that the conductivity of {(Y2O3)0·08(ZrO2)0.92}1-x (CeO2)x (0 ≤ x ≤ 0.2) is equivalent, and then the conductivity decreases due to defect association with the increase of CeO2 content.

Active sites adjustable phosphorus promoted CeO2/TiO2 catalysts for selective catalytic reduction of NOx by NH3

Highly-efficient CeO2-TiO2-based catalyst is an attractive alternative to traditional V2O5-based catalysts for selective catalytic reduction of NOx by NH3 (NH3-SCR). Herein, we construct an efficient and stable P-doped CeO2/TiO2 (yCeTi-Px) catalyst by dispersing CeO2 on strongly acidic and highly stable mesoporous P-doped TiO2 (Ti-Px). The characteristic structure of Ti-Px causes highly dispersed CeO2, strong active component-support interaction, and abundant surface active oxygen and acid sites on CeTi-P catalyst. Therefore, yCeTi-Px catalyst exhibits much higher catalytic activity than yCeTi catalyst at temperature of 200–450 °C. The yCeTi-Px catalysts show high activity in the presence of H2O and strong resistance to H2O + SO2 at medium-high temperature, implying that they have great industrial application prospects. Different P/Ti ratio and CeO2 loading content were investigated. Excessive P doping can block the Ce4+/Ce3+ redox couple, and suppress redox sites on yCeTi-Px catalyst. Additionally, increasing CeO2 content can reduce the NH3 capacity of yCeTi-Px catalyst. By controlling the P/Ti ratio and CeO2 loading content, surface acid sites and redox sites on yCeTi-Px catalyst can be balanced to obtain the best catalytic activity. This work demonstrates a feasible method in adjusting acid sites and redox sites on CeTi catalyst, which ultimately contributes to the new design of CeO2-TiO2-based catalyst.

Spectroscopic, Structural, Thermal, and Mechanical Properties of B2O3-CeO2-PbO2 Glasses

The melt-quenching method has been used to fabricate a PbO2–B2O3–CeO2 glass system. The XRD diffractometer procedure was used to check the status of these samples. It can be concluded, from the X-ray diffraction curves, that the tested samples have high levels of glassiness. As the CeO2 concentration increased most of the [BO4] are converted into [BO3] structural units with the formation of non-bridging oxygen ions in the borate matrix. It can be cross verified with the decrease of the N4 fraction from 0.654 to 0.239. This decrease may be attributed to the formation of [CeO7] structural units that needs more oxygen atoms. The ultrasonic velocities of the prepared glasses are decreased with the increase of CeO2 content. Different types of elastic modules were evaluated (experimental and theoretical) for the prepared glasses are increases with the increase of CeO2 content. Glass transition temperature (Tg), crystallization temperature (Tc), the peak of crystallization temperature (Tp) and thermal stability values decreases with the increase of CeO2 content. The refractive index of these samples is increasing with the increase in the reflection and the density.

Effects of CeO2 Content on Friction and Wear Properties of SiCp/Al-Si Composite Prepared by Powder Metallurgy.

SiCp/Al-Si composites with different CeO2 contents were prepared by a powder metallurgy method. The effect of CeO2 content on mechanical properties, friction and wear properties of the composites was studied. The results show that with the increase in CeO2 content from 0 to 1.8 wt%, the density, hardness, friction coefficient of the composites first increases and then decreases, the coefficient of thermal expansion (CTE) and wear rate of the composites first decreases and then increases. When the content of CeO2 was 0.6 wt%, the density and hardness of the composite reached the maximum value of 98.54% and 113.7 HBW, respectively, the CTE of the composite reached the minimum value of 11.1 × 10−6 K−1, the friction coefficient and wear rate of the composite reached the maximum value of 0.32 and the minimum value of 1.02 mg/m, respectively. CeO2 has little effect on the wear mechanism of composites, and the wear mechanism of composites with different CeO2 content is mainly abrasive wear under the load of 550 N. Compared with the content of CeO2, load has a great influence on the wear properties of the composites. The wear mechanism of the composites is mainly oxidation wear and abrasive wear under low load. With the increase in load, the wear degree of abrasive particles is aggravated, and adhesive wear occurs under higher load.

Effects of CeO2 on the Si Precipitation Mechanism of SiCp/Al-Si Composite Prepared by Powder Metallurgy.

SiCp/Al-Si composites with different CeO2 contents were prepared by a powder metallurgy method. The effect of CeO2 content on the microstructure of the composites was studied. The mechanism of CeO2 on the precipitation of Si during sintering was analyzed by theoretical calculations. The results show that the appropriate amount of CeO2 can significantly refine the size of precipitated Si particles in the composite and increase the number of Si particles. With the increase of CeO2 content from 0 to 0.6 wt%, the number of Si particles precipitated in the composites increases gradually, and the average particle size of Si particles decreases gradually. When the CeO2 content is 0.6 wt%, the number of Si particles precipitated in the composites reaches the maximum, and the average particle size reaches the minimum. However, with the increase of CeO2 content from 0.6 wt% to 1.8 wt%, the number of Si particles precipitated in the composites began to decrease, and the average size of Si particles gradually increased. CeO2 can be used as heterogeneous nucleation substrate of precipitated Si, and the nucleation rate of precipitated Si on a CeO2 substrate is higher than that on an aluminum substrate. The proper addition of CeO2 can improve the nucleation efficiency of precipitated Si, thus increasing the amount and refining the size of precipitated Si.