Effect Of CeO2 Research Articles

Effect of CeO2 and Y2O3 on microstructure, bioactivity and degradability of laser cladding CaO–SiO2 coating on titanium alloy

To solve the lack of strength of bulk biomaterials for load-bearing applications and improve the bioactivity of titanium alloy (Ti–6Al–4V), CaO–SiO2 coatings on titanium alloy were fabricated by laser cladding technique. The effect of CeO2 and Y2O3 on microstructure and properties of laser cladding coating was analyzed. The cross-section microstructure of ceramic layer from top to bottom gradually changes from cellular–dendrite structure to compact cellular crystal. The addition of CeO2 or Y2O3 refines the microstructure of the ceramic layer in the upper and middle regions. The refining effect on the grain is related to the kinds of additives and their content. The coating is mainly composed of CaTiO3, CaO, α-Ca2(SiO4), SiO2 and TiO2. Y2O3 inhibits the formation of CaO. After soaking in simulated body fluid (SBF), the calcium phosphate layer is formed on the coating surface, indicating the coating has bioactivity. After soaking in Tris–HCl solution, the samples doped with CeO2 or Y2O3 present a lower weight loss, indicating the addition of CeO2 or Y2O3 improves the degradability of laser cladding sample.

Effects of CeO2 on microstructure and corrosion resistance of TiC-VC reinforced Fe-based laser cladding layers

The effects of CeO2 on microstructure and corrosion resistance of TiC-VC reinforced Fe-based laser cladding layers were investigated. The results showed that carbides presented in cladding layers were TiVC2 and VC. A small quantity of CeC appeared with 2.0 wt.% CeO2 addition. The amount of lamellar pearlite increased while the amount of residual austenite decreased with increasing CeO2 addition. The corrosion resistance of cladding layers increased firstly and then decreased with the addition of CeO2 increasing. The EIS spectrum of the cladding layer without CeO2 was composed of an inductive arc at low frequency and a capacitive arc at high frequency. The cladding layer with 0.5 wt.% CeO2 addition showed the best corrosion resistance, and then the inductive arc at low frequency transformed into a capacitive arc.

Study of Synergistic Effects of Cerium Oxide on Intumescent Flame Retardant Polypropylene System

Melamine salt of pentaerythritol phosphate (PPM) was synthesized with phosphoric acid, pentaerythritol and melamine. This flame retardant polypropylene containing cerium oxide (CeO2) can be used as a synergistic agent for the flame retardancy of intumescent flame retardant polypropylene system. The pendulum impact tester and universal material machine were used to evaluate the mechanical properties of intmescent flame retardant system, the limiting oxygen index (LOI), thermogravimetric analysis (TGA) and scanning electron microscopy (SEM) were used to evaluate the synergistic effects of CeO2. The LOI value of the system increased when reasonable amount of CeO2 was added, and it reached maximum (30%) when the mass fraction of PPM was 20% and CeO2 added was 1% of the PPM/PP system. The TGA data shows that CeO2 can enhance the thermal stability of the intumescent flame retardant polypropylene system at high temperature and effectively increase the char residue formation. The morphological structures observed with SEM demonstrate that reasonable amount of CeO2 can improve the morphologies of intumescent char layer and the properties of heat insulation and barrier material. The reasonable amount of CeO2 in the system can increase its impact strength and decrease its tensile properties.

CeO2가 졸겔법으로 합성한 CeO2-TiO2계 SCR용 촉매의 활성에 미치는 물리화학적 영향

The effects of CeO2 on catalytic activity of CeO2-TiO2 for the selective catalytic reduction (SCR) of NOx were investigated in terms of structural, morphological, and physico-chemical analyseis. CeO2-TiO2 catalysts were synthesized with three different additions, 10, 20, and 30 wt% of CeO2, by the sol-gel method. The XRD peaks of all specimens were assigned to a TiO2 phase (anatase) and the peaks became broader with the addition of CeO2 because it was dispersed as an amorphous phase on the surface of TiO2 particles. The specific surface area of TiO2 increased with the addition of CeO2 from 60.6306 m 2 /g to 116.2791 m 2 /g due to suppression of TiO2 grain growth by CeO2. The 30 wt% CeO2-TiO2 catalyst, having the strongest catalytic acid sites (BrΦnsted and Lewis), showed the highest NOx conversion efficiency of 98 % at 300 o C among the specimens. It was considered that CeO2 contributes to the improvement of the NOx conversion of CeO2-

Effect of CeO2 on the Crystalline Structure of Forsterite Synthesized from Low-Grade Magnesite

The influence of CeO2 on the crystalline structure of forsterite synthesized from low-grade magnesite and natural silica is discussed in this paper. X-ray diffraction (XRD) and scanning electron microscopy (SEM) were used to study the crystalline structure and microstructure of each specimen, while X’ Pert Plus software was used to determine each specimen’s lattice parameters. The bulk density, apparent porosity, water absorption, and cold crushing strength of the specimens were determined in accordance with standards issued by the Ministry. The results show that forsterite can be synthesized from low-grade magnesite and natural silica through solid reaction. The synthesis process is facilitated by addition of the appropriate amount of CeO2. A defect caused by Ce2O in active magnesia accelerates diffusion of the ions. The results obtained by XRD, SEM, and property analysis show that the optimum addition of CeO2 is 0.8 – 1.2%. The forsterite has a microstructure with a homogeneous grain size, a bulk density of 2.15 – 1.18 g/cm3, apparent porosity of 29.5 – 30.1%, water absorption of 13.5 – 14.0%, and cold crushing strength of 13.4 – 14.2 MPa.

Effect of CeO2 and Y2O3 as Catalysts on Hydrogen Desorption Properties of NaAlH4

Abstract The effect of two rare earth oxides (0, 0.5, 1, 2, 3, 4, 5 mol% CeO 2 and 0, 0.5, 1, 2, 3, 4 mol% Y 2 O 3 ) on hydrogen desorption of NaAlH 4 by mechanical milling under an atmosphere of argon was studied. The PCT result reveals that increasing content of CeO 2 and Y 2 O 3 causes a similar effect trends on the maximum dehydrogenation amount and the dehydrogenation rate which increases firstly and then decreases under the same moderate conditions. CeO 2 as the catalyst for NaAlH 4 presents superior catalytic activity to Y 2 O 3 . For the same amount of 4.8 wt%, the dehydrogenation rate of that of 1 mol% CeO 2 -NaAlH 4 is obviously faster than that of 1 mol% Y 2 O 3 -NaAlH 4 . SEM analysis shows that with the increasing of catalyst content, the microscopic surface morphology of all the samples changes from homogeneous to flocculent. Besides, the dispersive particle structure may have a bigger reaction area than the flocculent structure and heating could make NaAlH 4 form a kind of porous structure like honeycomb.

Effects of CeO2 on the XPS valence band spectra of coal under the combustion initialization stage at 400°C

In order to get the catalytic mechanism of CeO2 on graphite and coal at 400°C, the morphologies of coal, graphite, and CeO2 before and after combustion were analyzed through X-ray photoelectron spectroscopy (XPS). It is found that the particle size of coal is mostly between 11.727 and 64.79 μm, while the particle size of CeO2 is between 1.937 and 11.79 μm. The agglomeration of coal and CeO2 can be seen by scanning electron microscopy (SEM) after reaction. XPS results show that with the addition of CeO2, the intensity of binding energy gets stronger, but there is no energy peak transition. Comparing the character of coal with and without the addition of CeO2, it can be seen that the C-C bond fractures first at 400°C, while the C-H energy-band takes electrons at the same time to be far away from the Fermi level, and the O 2s, O 2p, and C sp hybrid orbitals are all excited. Adding CeO2 can enhance the activity of the whole coal. In addition, through XPS analysis, combined with the oxygen transfer theory and the electron transfer theory, the catalytic mechanism of CeO2 for pulverized coal combustion could be obtained.

THE EFFECT OF CeO2 NANOPARTICLE DOPING ON REFINEMENT OF Y-211 PARTICLES IN POIG PROCESSED YBCO COMPOSITES

Doping of non-interacting nanoparticles in YBCO superconductors in order to get fine microstructure defects has been studied. Y-211 inclusion, itself has large potential to create structural defects without affecting Y-123 matrix phase. Nanoparticles of grain refining agent like CeO2/Pt/PtO2 are interesting dopants, especially CeO2 for being cheaper than Pt. POIG process, as is one of the advance processing techniques to get uniform distribution of fine Y-211 particles of the order of 1-2 μm, throughout the YBCO composites. Finer Y-211 particles can drastically increase the pinning centers. Introduction of fine sized CeO2 as grain refining agent to reduce the size of Y-211 particles would create additional pinning centers. In the present work, the effect of CeO2 on Y-211size and distribution in POIG processed YBCO composite was studied. It was observed that with increase in CeO2 content Y-211 particle size decreases below 1μm and even less than 0.5μm for 10 weight percent CeO2 doping. The mechanism for refinement appears to be the formation of BaCeO3 on the surface of Y-211 during liquid phase infiltration that leads to splitting of Y-211 into smaller particles.

Effect of CeO2 on the crystallization behavior and magnetic properties of Zn-ferrite glass ceramics

In this study CeO2 was added to Zn-ferrite glass ceramic. Glass–ceramic with a composition (Fe2O3–ZnO–SiO2–CaO–CeO2) was prepared by a glass ceramic method and the effect of partial replacement of 10, 20 and 30mol.% of Fe2O3 with CeO2 was studied. Based on the obtained results, it can be observed that the solubility limit of Ce3+ ions in this Ce-substituted glass ceramic, in an ordinary atmosphere, was approximately 10%. When the Ce3+ content exceeded the solution limit for Zn-ferrite glass ceramic, a foreign CeO2 phase was residual in the glass ceramic, which led to impurity in the final materials. An excessive addition of CeO2 (20% and 30%) reduced the remanent magnetization and the saturation magnetization, opposite to what occurs with a small addition of CeO2 (10%). Consequently, the addition of CeO2 into the Zn-ferrite glass ceramic material should be controlled carefully.

Effect of Different Contents of CeO<sub>2</sub> on Microstructure and Properties of Roller Surface Alloyed by Laser

To improve the service life of roller, a kind of alloying powder materials with CeO2 was designed. And the surface of roller was alloyed by a 5kW CO2 laser. The effect of CeO2 on microstructure and properties was studied by means of OM, Micro-hardness Testing Machine, Friction and Wear Tester. The experimental results indicate that addition of CeO2 into coating materials can refine and purify microstructure. Microstructure in alloying layer is coarse without CeO2, when CeO2 is up to 2.0wt.%, microstructure in alloying layer becomes finest. And microhardness and wear resistance become largest.

Partial oxidation of methane on Ni and Pd catalysts: Influence of active phase and CeO2 modification

Ni/Al2O3, Pd/Al2O3, Ni/CeO2/Al2O3 and Pd/CeO2/Al2O3 catalysts were synthesized in order to investigate the influence of the active phase on the partial oxidation of methane (POM) and the effect of CeO2 on the catalytic properties of these systems. The catalysts were characterized by XRD, XRF, BET, XPS, H2-TPR and catalytic activity was evaluated by TPSR experiments and catalytic activity tests over 24h on stream. The results indicated that over Ni catalysts the reaction occurs in two distinct steps: the total combustion of CH4 followed by reforming with H2O and CO2. Over Pd catalysts, the reaction follows a direct mechanism, with simultaneous formation of H2, CO, CO2 and H2O. Regarding CeO2 effect, the results indicated it improved the CH4 conversion, CO and H2 selectivity and catalytic activity and the resistance to deactivation.

Effects of CeO2 on the microstructure and hydrogen evolution property of Ni–Zn coatings

In this work, high-performance Ni–Zn/CeO2 composite electrodes are prepared for hydrogen evolution reaction (HER) in alkaline solutions using a composite electrodeposition technique in a Ni–Zn bath containing suspended micro- or nano-sized CeO2 particles. The composite electrodes containing more CeO2 particles are dominant with laminate morphology. The addition of CeO2 particles can alter the electrode phase composition. Optimization of the concentration of CeO2 particles leads to a significant enhancement of HER activity on the composite electrodes, relative to Ni–Zn coating. The exchange current density of the composite electrode is 2 times higher than that of the Ni–Zn coating when the nano-CeO2 concentration is 1 g L−1. Electrochemical impedance spectroscopy results suggest that a possible synergetic effect on HER may exist between CeO2 particles and Ni–Zn matrix.

Effect of CeO2 and Al2O3 on the activity of Pd/Co3O4/cordierite catalyst in the three-way catalysis reactions (CO/NO/CnHm)

The present article studies the effect of CeO2 and Al2O3 on the activity of Pd/Co3O4/cordierite catalyst in conversion of NO, CO, CnHm. The catalysts were characterized by temperature programmed reduction with hydrogen, X-ray diffraction, X-ray photoelectron spectroscopy and transmission electron microscopy. It is shown that the effect of CeO2 on the properties of Pd/Co3O4/cordierite catalyst depends on preparation method. The catalyst obtained by co-deposition of cerium and cobalt oxides has higher activity in CO oxidation (CO + O2 and CO + NO) and total hexane oxidation (C6H14 + O2). Such phenomenon is probably caused by more than stoichiometric amount of formed oxygen vacancies, an increase in both mobility of surface oxygen and dispersity of components in the catalytic composition. It is demonstrated that CeO2 addition promotes the SO2 resistance of Pd/Co3O4/cordierite. The second support decreases the activity of Pd/Co3O4/cordierite catalyst in the reactions of CO and C6H14 with oxygen because of CoAl2O4 formation.

CeO2 doped ZnO flower-like nanostructure sensor selective to ethanol in presence of CO and CH4

CeO2-doped ZnO nanostructures, with different Ce/Zn ratios, were synthesized via a very fast microwave-assisted method using zinc acetate dihydrate and cerium nitrate as starting materials and water as solvent. The samples were characterized via SEM, EDX, XRD, and BET analyses. Gas sensitivity of the fabricated sensor was studied for selective detection of ethanol in presence of CO and CH4 and effect of CeO2 with different concentrations as a dopant was investigated. 5wt% CeO2 doped sample was shown to improve the sensor response to 500ppm ethanol with high selectivity in presence of CO and CH4. Furthermore presence of ceria reduced the recovery time of the sensor significantly. The CeO2-doped ZnO may be considered a promising sensing material for selective detection of ethanol.

Effect of CeO2 on Microstructure and Hardness of Roller Surface Alloyed by Laser

To improve the service performance of roller. The surface of roller was alloyed by a 5kW CO2 laser. The effect of CeO2 on microstructure and hardness was studied by means of OM, Micro-hardness Testing Machine and Rockwell hardness tester. The results indicate that addition of CeO2 into coating materials can enhance the fluidity of molten liquid, refine and purify microstructure and increase microhardness and surface hardness of alloying coating.

The investigation of active Ni/YSZ interlayer for Cu-based direct-methane solid oxide fuel cells

In this study, dense YSZ (d_YSZ)–Ni/YSZ–porous YSZ (p_YSZ) double-layer anode structures were prepared by the tape casting–lamination–co-sintering (TLC) method to improve the stability of the cells due to the cracking reaction of methane. Cu was infiltrated into all cells as an electronic conductive material. The effect of CeO2 and SDC (samarium-doped ceria) loadings were also investigated. Stable operation was obtained by using a Ni-interlayered Cu-based anode structure for dry methane fuel at 800°C for 72h. No carbonization was observed after the addition of Cu to the cell. An interesting finding was that a highly loaded secondary material (CeO2 and SDC) leads to a regional break of the electronic conduction network, which decreases the number of active TPB regions. Therefore, carbonization occurred inside the cell in the Ni-containing interlayer zone. At the end of 72h of cell operation, carbonization was observed inside the Ni-containing and Ni-free regions in the SDC-containing cell. In addition to conducting cell tests, the behavior of powder SDC was studied under a dry methane environment by temperature-programmed surface reaction (TPR) and temperature-programmed oxidation (TPO) analysis.

Supported nickel catalysts for low temperature methane steam reforming: comparison between metal additives and support modification

The effect of Ag (1 wt%) and Au (1 wt%) on the catalytic properties of Ni/Al2O3 (7 wt% Ni) for methane steam reforming (MSR) was studied in parallel with the effect of CeO2 (6 wt%) and La2O3 (6 wt%) addition. The addition of 1 wt% Ag to the alumina supported nickel catalyst drastically decreased its catalytic properties at temperatures lower than 600 °C, due to the blockage of metal catalytic centers by silver deposition. The addition of Au and CeO2 (La2O3) to the nickel catalyst improved the methane conversion, CO2 selectivity and hydrogen production at low reaction temperatures (t < 600 °C). At 700 °C under our working conditions, the additives have no important effect in hydrogen production by MSR. The best hydrogen production at low temperatures was obtained for Ni–Au/Al2O3, due to the higher CO2 selectivity, cumulated with slightly higher methane conversion in comparison with Ni/CeO2–Al2O3. At high temperature, Ni/CeO2–Al2O3 is stable for 48 h on stream. Ni–Au/Al2O3 and Ni–Ag/Al2O3 are mainly deactivated due to the temperature effect on Au and Ag nanoparticles and less through coke formation. On Ni/Al2O3 and Ni/La2O3–Al2O3, crystalline, graphitic carbon was deposited after 48 h of reaction leading to catalyst partial deactivation. On the Ni/CeO2–Al2O3 surface, a porous amorphous form of deposited carbon was found, which does not decrease its catalytic activity after 48 h of reaction.

Effects of CeO2 coating on oxidation behavior of T91 steel in water vapor

Oxidation behaviors of blank and CeO2 coated T91 steel were investigated at 600 ℃ in water vapor for up to 150 h. Gold marker was used to define the mass transport direction. The oxide scales were studied with X-ray diffractometry (XRD), scanning electron microscopy (SEM) and electron probe microanalyzer (EPMA). The oxidation resistance of the steel is improved by CeO2 coating, though the improvement is not remarkable. Ce-rich oxide band is located at the interface of the inner equiaxed layer and the outer columnar layer after oxidation, which is not consistent with the original surface. The results show that outward iron transport is blocked by the Ce-rich band. A new oxide nucleating and growing site (reaction front) is induced at the inner surface of the Ce rich band.

The Compaction, Sintering, and Mechanical Properties of Al2O3–CeO2 Composite Nanopowders

In the present work, compaction, sintering behavior, and mechanical properties of Al2O3–CeO2 composite nanopowders were investigated. Al2O3 and Al2O3–CeO2 composite nanopowders were prepared by a sol–gel method. The effect of CeO2 on compressibility, sintering rate, final density, and mechanical properties was studied. The aggregation strength of nanopowders reduced from 158 to 101 MPa by adding 5 wt% CeO2. The amount of CeO2 had a strong effect on the sintering behavior and final microstructure of nanopowders and it inhibited alumina grain growth and suppressed densification process. The activation energy for grain growth increased from 428 to 554 kJ/mol by adding 5 wt% CeO2 to the nanopowders. The addition of 5 wt% CeO2 improved fracture toughness (by 28%) and flexural strength (by 17%) with respect to monolithic Al2O3.

Wear Characterization of Thermal Sprayed and Fused Fe-Ni-Cr Alloy Coatings with the Addition of CeO&lt;sub&gt;2&lt;/sub&gt;

Fe-Ni-Cr alloy powders with CeO2 were flame sprayed and fused on the surface of 1045 carbon steel substrate. The effect of CeO2 on microstructure and tribological behavior of coatings were studied experimentally by means of scanning electron microscopy (SEM), field emission gun scanning electron microscopy (FEGSEM), energy dispersive spectroscopy (EDS) and wear tests. The results show that an adhered oxide debris layer was formed on the worn surface in friction which contributed to decreased wear. Wear rate of the material increased with the load, but dramatically decreased at first and then slightly decreased the sliding speed. The friction coefficient of the material decreased slightly with the load, but increased with sliding speed at first, and then tended to be a constant value. Wear mechanism of the coatings was oxidation wear and a large amount of counterpart material was transferred to the coatings, the RE oxide in the debris layer contributes to the improvement in wear resistance.