Rare Earth Oxide CeO2 Research Articles

Effect of CeO2 on the preparation of functional ceramsite and the adsorption effect of ammonia-nitrogen wastewater treatment

This study investigates the effect of rare earth oxide CeO2 on the physical properties of ceramsite and its efficiency in treating ammonia-nitrogen wastewater. Ceramsite was prepared from solid waste with 10 % coal gangue added as a pore-forming agent. Ceramsite sample I with CeO2 and sample II without CeO2 were prepared using pure reagents. The process parameters for both samples were optimized using an orthogonal test. Additionally, the effects of CeO2 on ceramsite performance and the treatment of ammonia-nitrogen wastewater were studied, and the adsorption mechanism of CeO2 on ammonia-nitrogen wastewater was clarified. The process parameters for preparing ceramsite sample Ⅰ were: preheating for 30 min at 600 °C, followed by roasting for 20 min at 1090 °C. The parameters for preparing ceramsite sample Ⅱ were: preheating for 30 min at 600 °C, followed by roasting time for 15 min at 1090 °C. The presence of CeO2 increased the porosity of the ceramsite by 0.89 % and the specific surface area by 0.66 m2/g. Under neutral environmental conditions of water samples, CeO2 increased the removal rate of ammonia nitrogen by 1.85 %. Ceramsite has a high porosity and specific surface area, indicating that it has abundant internal pores, a large contact area with ammonia-nitrogen, a strong ability to remove ammonia nitrogen, and resistance to erosion and water flow shear, which are conducive to the treatment of ammonia-nitrogen wastewater.

Effect of CeO2 on the microstructure and properties of AlCoCrFeNi2.1 laser cladding coatings

In the process of strengthening the substrate’s surface properties, it is easy to produce cracks or air holes and other defects between the coatings and the substrate, and rare earth elements can improve the microstructure and properties of the metal surface coatings. Using laser cladding(LC) technology, the effect of the addition of rare earth oxides CeO2 on the properties of AlCoCrFeNi2.1 coatings is investigated to find the optimal amount of CeO2 added. AlCoCrFeNi2.1 alloy powder doped with Xwt% (X = 0–3) rare-earth oxide CeO2 was clad on the surface of the H13 steel substrate by laser cladding process using RFL-C3000 laser. The macroscopic morphology, microstructure, hardness, and corrosion resistance of specimens were analyzed and studied by optical microscope (OM), scanning electron microscope (SEM), X-ray diffractometer (XRD), hardness tester, and other equipment. The results show that the addition of the appropriate amount of rare earth oxide CeO2 (3 %) can effectively reduce the cracks, air holes, and inclusions in the composite layer, and promote grain refinement. The addition of 3 wt%CeO2 to AlCoCrFeNi2.1 can improve the microstructure uniformity and surface hardness of the coatings, and significantly improve the wear and corrosion resistance of the composite coatings.

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.

Polymer dispersed liquid crystals doped with CeO2 nanoparticles for the smart window

ABSTRACT In this paper, rare earth oxide CeO2 nanoparticle-doped polymer dispersed liquid crystal (PDLC) films were prepared by the polymerisation induced phase separation (PIPS) process. The effects of the crosslinking agent TMPTA content, liquid crystal (LC) content and the CeO2 content on the polymer structures and electro-optical properties of the as-made PDLC films were investigated systematically. It has been found that by changing the TMPTA content, LC content and doping a small amount of CeO2 nanoparticles, the electro-optical properties of PDLC films can be optimised. After adding a low concentration of CeO2 nanoparticles, the electro-optical properties of the PDLC film have been well optimised: after adding 0.8% CeO2, Vth decreased from 26.6 V to 16.8 V, and CR increased from 89.5 to 137.6. Consequently, this work offers a meaningful approach to optimise the electro-optical properties of PDLC films, which indeed can form a wonderful footstone for the wide application of PDLC.

Influence of CeO2 content on WC morphology and mechanical properties of WC/Ni matrix composites coating prepared by laser in-situ synthesis method

Improving the mechanical properties of metal matrix composites (MMCs) by the addition of a ceramic phase is one of the present studying hot spots. Understanding the morphology evolution rule of the ceramic phase during laser cladding is a critical issue to its wider industrial applications. In the present paper, different CeO2 contents with WC reinforced Ni matrix composite coatings were prepared by laser in-situ synthesis technology. The influence of CeO2 content on the WC morphology and the attendant mechanical properties was investigated by using scanning electron microscopy (SEM), X-ray diffraction (XRD), energy disperse X-ray (EDX) spectroscopy, hardmeter and frictional tester. The result shows that the shape of WC particles has a close relation to the addition of rare earth oxide CeO2. Specifically, at first, with the increasing CeO2 additions, the aspect ratio of WC particles reaches the minimum value when 2 wt. % CeO2 is added. Then, the aspect ratio increases with further increasing CeO2 additions. In addition, the effect of CeO2 on macroscopic morphology of laser cladding coating and the mechanism of CeO2 on the morphology evolution of WC particle were investigated. Finally, microhardness and wear results show that the coating with 2 wt. % CeO2 has the best mechanical properties.

Effect of the Rare Earth Oxide CeO2 on the Microstructure and Properties of the Nano-WC-Reinforced Ni-Based Composite Coating

In this study, the addition of the rare earth oxide CeO2 was investigated to alter the microstructural properties of the nano-WC-reinforced Ni-based composite coatings. The reinforced composite was prepared on the 42CrMo steel surface using a semiconductor laser. The morphology and microstructure of coatings were analyzed using a scanning electron microscope (SEM), energy dispersive spectroscopy (EDS), and X-ray diffraction (XRD). Further, the digital microhardness tester and high-temperature friction and wear tester were used to observe the mechanical properties. The results indicated that the addition of CeO2 eliminated the cracks from the surface of the coatings and effectively reduced the number of pores. The phases were mainly observed as γ-Ni(Fe) in a solid solution, and some residual WC and W2C phases were observed. In addition, Fe3C, Cr23C6, M6C (M = W, Fe, and Ni), SiC and Cr7C3 composite carbides, Si2W and NiW tungsten compounds, and CeFe2- and CeNi2-containing Ce complex compounds were formed on the coating. The rare earth oxide CeO2 composite-modified coating mainly comprised dendrites, crystal cells, strips, and massive microstructures. The reinforced phases of the modified coating presented uniform dispersion distribution with the addition of 1% CeO2, and the structures were significantly refined. The maximum microhardness of the modified coating was approximately 1560 HV0.2, which was approximately 20% higher than that of the unmodified composite coating. The minimum wear loss of the modified coating was 6.1 mg and the minimum frictional coefficient was approximately 0.23, which were better than those of the unmodified coating. The wear mechanism of the nano-WC-reinforced Ni-based coating was primarily adhesive, whereas that of the CeO2 composite modified coating was mainly abrasive particle wear, which accompanied adhesive wear.

Effect of CeO2 on High‐Temperature Oxidation Performance of Electron Beam Cladding NiCoCrAlY Coating on Ni‐Based Alloy

In order to enhance the high‐temperature oxidation resistance properties of Inconel 617 alloy, NiCoCrAlY and NiCoCrAlY CeO2 composite powder coatings metallurgically bonded to substrate were prepared on the surface of Inconel 617 alloy by electron beam cladding. The effect of rare earth oxide CeO2 on the oxidation resistance of NiCoCrAlY coating was investigated. The isothermal oxidation behavior of the substrate and NiCoCrAlY cladding layer with different CeO2 contents (1%, 2%, 3%, and 4%) and without CeO2 oxidized at 1050°C for 20 h, 40 h, 60 h, and 100 h was analyzed. The microstructure and phase composition of the coating after electron beam treatment were tested. The results show that the self‐repair of Al2O3 and Cr2O3 oxide film can be improved under a high‐temperature oxidation environment with the addition of CeO2, and the oxidation resistance of NiCoCrAlY coating can be effectively strengthened by adding CeO2. The improvement effect is most obvious when the content of CeO2 is 2%.

Effect of rare earth oxide CeO2 on microstructure and surface properties of laser cladded CoFeCrNiSiB high-entropy alloy coatings

CoFeCrNiSiB high-entropy alloy coatings with different content of REO (rare earth oxide) CeO2 were fabricated on the surface of corrosion-resistance steel plates by using laser cladding process. The surface properties of the cladded coatings including wear and corrosion resistance were evaluated by friction wear equipment and electrochemical workstation, respectively, while the microstructure was observed by scanning electron microscope, energy dispersive spectrometer, x-ray diffractor and transmission electron microscope. When the CeO2 content was not higher than 2%, the wear resistance and corrosion resistance of cladded coating was improved with the increased of CeO2 content. However, when the CeO2 content was between 2% and 4%, the wear resistance and corrosion resistance of cladded coatings decreased with the increased of CeO2 content. The corrosion resistance evaluation environment included 2 N(1 mol l−1) H2SO4 and 5 wt% NaCl solutions. Equi-axed grains of the cladded coatings got refined by adding CeO2, the grains were most refined at 2% in the range of 0%–4% CeO2 content. However, when too much CeO2 (>2%) was added, CeO2 would exist as an oxide in the intergranular area. Therefore, grain refinement could improve the surface properties of coatings, while the presence of intergranular oxides would make the surface properties of coatings worse.

Experimental Study on Catalytic Reduction of SO2 by Rare Earth Compound in the Presence of Oxygen

Compared with a great deal of traditional desulphurization crafts, the catalytic reduction of SO2 with CO to elemental sulfur is considered to be the best technology for the removal of CO2 from flue gas. Adding rare earth oxide CeO2 with variable valences to La2O3formes a mixture of rare earth oxides. By means of dipping CeO2, La2O3 and their mixture, whose carriers are allγ-Al2O3, are used as the catalyst for the reduction of CO2 by CO. Under the condition of oxygen, all kinds of catalyst will be poisoned to some extent. However, the oxygen resistance of the catalyst can be improved by changing the composition of the catalyst. It is found through experiments that this poisoning effect is partially reversible. The structure of the catalyst is not completely destroyed. There is still a great distance from the actual application.

Synergistic effects of CeO2 and Y2O3 on the properties of glass-diamond composites

In this study, effects of rare earth oxide CeO2 and Y2O3 on the structure and properties of glass-diamond composites were systematically researched. The thermal analysis of the borosilicate glass was performed by TG-DSC curves. Phase composition of the glass-diamond composites was analyzed by XRD. SEM images showed the microstructure of the composites. Thermal properties of the composites were characterized by thermal conductivity and coefficient of thermal expansion. Bending strength was measured to explain the mechanical properties. Results showed that the addition of CeO2 and Y2O3 improved the mechanical and thermal properties of the glass-diamond composites and CeO2/Y2O3 compound additive had greater impacts on the composites than single additive. When the content of CeO2/Y2O3 additive reached 4 wt % (1.07 vol %), the thermal conductivity and bending strength of the glass-diamond composites increased by 69.77% and 35.13%, respectively.

Experimental Study on Catalytic Reduction of SO<sub>2</sub> by Rare Earth Compound

Compared with a great deal of traditional desulphurization crafts, the catalytic reduction of SO2 with CO to elemental sulfur is considered to be the best technology for the removal of SO2 from flue gas. Adding rare earth oxide CeO2 with variable valences to La2O3 formed a mixture of rare earth oxides. By means of dipping CeO2, La2O3 and their mixture, whose carriers are allγ-Al2O3, are used as the catalyst for the reduction of SO2 by CO. The activation process of this catalyst without O2 was investigated. The result shows that the rare earth oxide mixture composing of CeO2 and La2O3, as the catalyst for the reduction of SO2 by CO, can remove SO2 mostly without O2.

Effect of rare earth (RE) on pack boronising process of titanium alloy

The pack boronising experiments were carried out on the TC21 titanium alloy using monomer boron powder as the boriding agent with and without rare earth oxide CeO2 respectively. The friction and wear behaviour of boride coated TC21 samples were evaluated using a pin on disc friction tester. The boride layers were investigated by means of X-ray diffraction, X-ray photoelectron spectroscopy, SEM and optical microscopy. The results show that the boride layers grown on TC21 consist of continuous top layer TiB2 and sublayer TiB whiskers; with the addition of CeO2 in the boriding agent, the grain size of boride layers is refined, the diffusion efficiency is increased and more TiB changes to TiB2; the microhardness of the top layer is ∼3200 HV(10 g); without CeO2, the friction coefficient of boride coated TC21 sample is ∼0·56, while with the addition of CeO2, it is <0·2. The boride coated TC21 samples show a much better wear resistance than the TC21 substrate.

Microstructure and Abrasive-Wear Behavior under High Temperature of Laser Clad Ni-Based WC Ceramic Coating

The laser cladding is used on the surface of 4Cr14Ni14NW2Mo heat-resisting steel, In the laser cladding added 0. 5% CeO2,Ni-based WC coating can be formed. The effects of rare-earth oxide CeO2 on the microstructure and microhardness and wear-resistance and corrosion-resistance of Ni-based metal-ceramic coatings are investigated. Observing and analying the microstructure, Measuring microhardness, Checking the dry friction and wear properties of high-temperature of the coating in different temperature. The results showed that the microstructure of Ni21+20%Wc+0.5%CeO2 cladding layer is even small, Hardness is more uniform and gentle. Wear mechanism of the laser cladding layer changes with temperature changes.Abrasion is the main mode under Low temperature , it was transformed into Adhesive wear and Oxidation wear along with the increase of the temperature.dry friction and wear properties of high-temperature is excellent.

Flame retardancy properties of ammonium polyphosphate with crystalline form II by non-P2O5 process

Ammonium polyphosphate (APP) produced by non-P2O5 process and traditional P2O5 process were used in an intumescent flame retardant (IFR) polypropylene (PP) composition (IFR–PP). Rare earth oxide CeO2, in different amounts was added to study its synergistic effects in the IFR–PP material by limiting oxygen index (LOI), UL-94 and mechanical properties. TGA and SEM were used to study the decomposition processes of CeO2 added IFR–PP compositions, and to investigate its synergistic mechanism. Results showed that CeO2 could increase the LOI value of IFR–PP, maximum LOI values were found with certain amounts of CeO2. SEM demonstrated that CeO2 could promote formation of a homogenous and compact intumescent char layer. It was shown that APP by non-P2O5 process had similar IFR properties as APP by traditional P2O5 process.

Absorption Spectra and Bioactivity Behavior of Gamma Irradiated CeO2-Doped Bioglasses

The synthesis and characterization of some bioglasses based on Hench’s Bioglass® 45S5 with additions of CeO2 (1.0, 2.0, or 3.0%) have been carried out. Two objectives have been focused upon; first, the effect of successive ionizing gamma irradiation on the undoped and CeO2-doped bioglass samples has been evaluated with the aim of justifying the role of the rare earth oxide CeO2 on gamma irradiation. The second objective was directed to test the bioactivity of such prepared CeO2-doped samples after soaking for 1 month in a simulated body fluid at 37 °C. The results indicate that the additions of CeO2 suppress, to a marked extent, the generation of radiation induced defects especially in the visible region. The bioactivity results show that the studied CeO2-doped bioglass samples gave rise to a calcium phosphate surface layer upon immersion in a simulated body fluid for 1 month at 37 °C and the bioactivity extent was almost identical in the CeO2 doping interval limit (1 → 3% CeO2) to that of the undoped base Hench’s Bioglass. The presence of both Ce3+ and Ce4+ ions were confirmed by optical absorption spectra. Electron spin resonance (ESR) studies of gamma irradiated CeO2-doped glasses indicate and confirm the dominance of Ce4+ in the bioglass compositions and its transformation to Ce3+ by high gamma irradiation.

Morphology and Electrical Characteristics of (PEO)&lt;sub&gt;10&lt;/sub&gt;LiClO&lt;sub&gt;4&lt;/sub&gt; Electrolyte with Nanosized CeO&lt;sub&gt;2&lt;/sub&gt;

In the present work, using nanosized rare earth oxide CeO2 as filler and acetonitrile as organic solvent, a novel solid-state composite polymer electrolyte (CPE) films (PEO)10LiClO4-x wt.%CeO2 (x=0,2,6,9,12,15) was prepared by solution-casting technique. The effect of CeO2 filler concentration on morphology and electrical characteristics of CPE films has been investigated and analyzed. The AC impedance measurements show that the ionic conductivity of CPE can be efficiently enhanced by adding appropriate CeO2. The highest room temperature (25OC) ionic conductivity of 1.71×10-5S•cm-1 is achieved with the CeO2 content of 9 wt.%. With the CeO2 content continues to increase, CPE ionic conductivity begin to decline. This is because appropriate CeO2 can disorder the chain structure and effectively inhibit the crystallization of PEO, which expands the amorphous region required for the lithium-ion transport.

Characterisation of HVOF sprayed NiCrAlY–0˙4 wt-%CeO2 coatings on superalloys

In the present work, metallurgical and mechanical properties of high velocity oxy fuel thermal sprayed NiCrAlY–0˙4 wt-%CeO2 coatings on Ni and Fe based superalloys have been investigated. The microstructural morphologies, composition, and phases of the coatings were characterised using the techniques such as optical microscopy, field emission scanning electron microscopy /energy dispersive spectroscopy and X-ray diffraction. The mechanical properties of coatings such as microhardness and adhesion strength were measured. The coatings exhibited characteristic splat like, layered morphologies due to the deposition and resolidification of successive molten or semimolten powder particles. The coatings contained less than 1˙4% porosity and showed the measured hardness values in the range of 649–753 HV. Average bond strength of the coating was found to be 45 MPa. The observed higher values of microhardness of the coated samples might be attributed to the addition of small amount of rare earth oxide CeO2 in the coatings.

Preparation and characterization of three-dimensional ordered macroporous rare earth oxide—CeO2

Three-dimensional ordered macroporous (3DOM) rare earth oxide—CeO2 was prepared by colloid crystal template. Cerous nitrate in the presence of citric acid was used as precursor and polystyrene (PS) beads as template. The effect and mechanism between citric acid and cerous nitrate was studied. The introduction of citric acid as chelator could overcome the disadvantage from the low melting point of single cerous nitrate and played an important role to the formation of 3DOM structure. The resulted CeO2 had three-dimensional ordered structure, uniform pore distribution, and interconnected macropores through small holes, which makes CeO2 probably become a new-type catalyst or catalyst support in future.