Study on preparation and properties of CeO2/epoxy resin composite coating on sintered NdFeB magnet

The CeO₂/epoxy resin composite coating was deposited on NdFeB substrate by cathode electrophoresis method for enhancing the anticorrosion and anti-wear performances. The morphologies and structures were characterized by a scanning electron microscope and an X-ray diffractometer. The micro hardness of the composite coating was evaluated by a microhardness tester. The corrosive behaviors of the coatings were studied by potentiodynamic polarization curve, electrochemical impedance spectroscopy and neutral salt spray tests. The concentration of CeO₂ nanoparticles (NPs) in the electrophoresis bath was optimized according to the coating structures and anticorrosion performances. The results show that CeO₂ NPs can enhance the microhardness of the composite coatings. Moreover, the nanoparticles disperse uniformly in the matrix when the concentration is lower than 30 g/L. The microhardness of CeO₂/epoxy resin (30 g/L) composite coating is about 63% higher than that of the blank epoxy resin coating. And the NSS time of the CeO₂/epoxy resin (30 g/L) composite coated sample can reach 1248 h. Meanwhile, the composite coatings possess no deteriorate influence on the magnetic properties of NdFeB substrates. The anticorrosion mechanisms of the composite coatings on the NdFeB substrate are deeply discussed.     

Electrochemical Impedance Spectroscopy and Corrosion Behavior of Co/CeO2 Nanocomposite Coatings in Simulating Body Fluid Solution

A series of Co/CeO₂ (25 nm) nanocomposite coating materials by electrodeposition were successfully prepared containing different cerium oxide composition in the cobalt-plating bath. Stainless steel (304L) was used as support material for nanocomposite coatings. The nano-CeO₂ is uniformly incorporated into cobalt matrix, and the effect on surface morphologies was identified by scanning electron microscopy with energy-dispersive X-ray analysis. Codeposition of nano-CeO₂ particles with cobalt disturbs the regular surface morphology of the cobalt coatings. It should be noted that the as-prepared Co/CeO₂ nanocomposite coatings were found to be much superior in corrosion resistance over those of pure cobalt coatings materials based on a series of electrochemical impedance spectroscopy measurements in simulating body fluid solution. With increase in the nano-CeO₂ particles concentration in the cobalt electrolyte, it is observed that the corrosion resistance of Co/CeO₂ increases. Co/CeO₂ nanocomposite coatings have higher polarization resistance as compared with pure cobalt layers in simulating body fluid solution.     

Development of CeO2 nanorods reinforced electrodeposited nickel nanocomposite coating and its tribological and corrosion resistance properties

A simple electrodeposition technique was used to prepare Ni-CeO_2 nanorods composite coating(Ni-CeO_2 NRs) using Watt's nickel plating bath containing CeO_2 nanorods(NRs) as the reinforcement phase under optimized process conditions. The X-ray diffraction analysis(XRD) was used for the structural analysis of Ni-CeO_2 NRs composite coatings and their average crystalline size is ～22 nm for pure Ni and ～18 nm,respectively. The crystalline structure is fcc for the Ni-CeO_2 nanocomposite coatings. The surface morphology of the electrodeposited Ni-CeO_2 NRs composite coatings was analyzed by scanning electron microscopy(SEM). Microhardness of pure Ni and Ni-CeO_2 NRs composite coatings are found to be 253 HV and 824 HV, respectively. The inclusion of CeO_2 NRs increases the microhardness of Ni-CeO_2 NRs composite coatings. The corrosion resistance behavior of Ni-CeO_2 NRs composite coating was evaluated by Tafel polarization and AC impedance methods. It is revealed that CeO_2 NRs reinforced Ni matrix shows higher microhardness and corrosion resistance than existing reported electrodeposited pure Ni and CeO_2 nanoparticles reinforced Ni coatings.     

Magnetic composite Fe3O4/CeO2 for adsorption of azo dye

In this paper, magnetic composite Fe₃O₄/CeO₂ (MC Fe/Ce) was synthesized via CeO₂ covered onto the surface of Fe₃O₄ by sol-precipitation method. The as-synthesized samples were characterized by FE-SEM, XRD, SEM-EDS and FT-IR spectrum. The pseudo-second-order (PSO) kinetic can describe well the adsorption of Acid black 210 (AB210) onto the as-obtained MC Fe/Ce of which the adsorption isotherm fits the Langmuir adsorption model better than Freundlich adsorption model. Furthermore, the maximum monolayer adsorption capacity of MC Fe/Ce is about 93 mg/g, which is 6 times more than that of commercial CeO₂ for AB210. Moreover, the removal rate of the adsorbates for AB210 is 82.3% after first adsorption and still about 70% the fourth forth adsorption experiments within 120 min, which demonstrates that the obtained MC Fe/Ce has outstanding adsorption capacity and good stability. Additionally, the composite can be easily separated from aqueous solution in a few seconds with an external magnetic field due to its magnetic property, which is vital and has potential for its practical applications.     

CeO2 nanoscale particles: Synthesis,characterization and photocatalytic activity under UVA light irradiation

CeO_2 nanoparticles(NPs) were synthesized in alkaline medium via the homogeneous precipitation method and were subsequently calcined at 80 ℃/24 h(assigned as CeO_2-80) and 500 ℃/2 h(assigned as CeO_2-500). The as-prepared materials and the commercial ceria(assigned as CeO_2-com) were characterized using TGA-MS, XRD, SEM-EDX, UV-vis DRS and IEP techniques. The photocatalytic performances of all obtained photocatalysts were assessed by the degradation of Congo red azo-dye(CR) under UVAlight irradiation at various environmental key factors(e.g., reaction time and calcination temperature).Results reveal that CeO_2 compounds crystalize with cubic phase, CeO_2-500 exhibits smaller crystallite size(9 nm vs 117 nm) than that of bare CeO_2-com. SEM analysis shows that the materials are sphericallike in shape NPs with strong assembly of CeO_2 NPs observed in the CeO_2-500 NPs. EDX analysis confirms the stoichiometry of CeO_2 NPs. UV-vis DRS measurement reveals that, CeO_2-500 NPs exhibits a red-shift of absorption band and a more narrow bandgap(2.6 eV vs 3.20 eV) than that of bare CeO_2-com. On the contrary, Urbach energy of Eu is found to be increased from 0.12 eV(CeO_2-com) to 0.17 eV(CeO_2-500),highlighting an increase of crystalline size and internal microstrain in the CeO_2-500 NPs sample. Zeta potential(IEP) of CeO_2-500 NPs is found to be 7.2. UVA-light-responsive photocatalytic activity is observed with CeO_2-500 NPs at a rate constant of 10×10~(-3) min~(-1), which is four times higher than that of CeO_2-com(K_(app)=2.4×10~(-3) min~(-1)) for the degradation of CR. Pseudo-first-order kinetic model gives the best fit. On the basis of the energy band diagram positions, the enhanced photocatalytic performance of CeO_2-500 nano-catalyst can be ascribed to O_2~-, 'OH and R'~+ as the primary oxidative species involved in the degradation of RC under UVA-light irradiation.     

Synthesis and Properties of Pulse Electrodeposited Ni-CeO2 Nanocomposite

Ni-CeO₂ nanocomposite coatings were pulse electrodeposited from the Watt??s electrolyte containing different concentrations of nanosized CeO₂ particles (10, 20, 30, 40, and 50?g/L). The microhardness, thermal stability, and corrosion resistance of these coatings were evaluated and compared with those of pure nanocrystalline Ni deposited under the same conditions. The results show that the Ni-CeO₂ nanocomposite coating, synthesized from the electrolyte containing 30?g/L CeO₂, has significantly higher hardness, thermal stability, and corrosion resistance than those of the pure nanocrystalline Ni and other Ni-CeO₂ nanocomposite coatings.     

SYNTHESIS OF COPPER METAL/SALTS FROM COPPER BLEED SOLUTION OF A COPPER PLANT

Copper bleed solution (CBS) generated during the electrorefining of anode copper contains 40 g/L Cu, 10–20 g/L Ni, and 170–200 g/L H₂SO₄, along with other impurities in different quantities. In order to get the valuable metals from this CBS, studies have been carried out to crystallize and recover metal salts on bench scale with/without partial decopperization from the point of view of reuse and the recycling of the sulphate salts and the acid recovered back to the system. Studies showed the possibility of recovering copper sulphate salt without affecting its purity with respect to nickel by controlling the extent of evaporation. In an alternative approach, a part of copper metal of purity 99.85% produced during partial decopperization of copper from 39.8 to 9.64 g/L Cu without affecting the current efficiency at a current density of 100 A/m². Subsequently, mixed salt containing 9.80% Cu and 13.19% Ni has also been produced from the partially decopperized solution. The mixed salt could be processed for metal recovery by solvent extraction. The mother and wash liquor could be recycled in the electrorefining plant for acid and copper make-up.     

Effect of grain size on thermal stability and oxygen storage capacity of Ce0.17Zr0.73La0.02Nd0.04Y0.04O2 solid solutions

Nanostructured CeO_2-ZrO_2 materials are an irreplaceable constituent in catalytic systems for automobile exhaust purification due to their unique oxygen storage capacity(OSC). However, traditional CeO_2-ZrO_2 materials are easy to sinter at high temperature, which causes a sharp decrease of OSC. In this paper,La~(3+) , Nd~(3+) and Y~(3+) are chosen as dopants for CeO_2-ZrO_2 to improve anti-sintering and OSC properties.The Ce_(0.17) Zr_(0.73) La_(0.02) Nd_(0.04) Y_(0.04) O_2 powders(CZLNY) were prepared by co-precipitation method. The effects of grain sizes with different mixed chlorinated solution concentrations on performances were investigated. X-ray diffraction(XRD) and transmission electron micrograph(TEM) were performed to calculate the grain sizes of CZLNY. The specific surfaces, OSC and redox properties were investigated by N_2 adsorption/desorption and temperature programmed reduction(H2-TPR). The results show that introducing La~(3+) , Nd~(3+) and Y~(3+) into CeO_2-ZrO_2 lattice can improve the stability of phase structure and anti-sintering ability. Moreover, low concentration of mixed chlorinated solution remarkably improves structural and textural properties of CZLNY. Relatively large fresh grain exhibits superior thermal stability and OSC under the condition of being calcined at 800℃ for 3 h. The specific surface and OSC are42.37 m~2/g and 333.13 mmol/g after calcining at 1000℃ for 10 h, respectively. This is owing to the low sintered driving force of large grain and long-range migration energy of large pores during the sintering process, which are beneficial to the stability of structure in CZLNY materials.     

Nanosized CeO<Subscript>2</Subscript> Particles Obtained by Mechanical Solid-State Reaction Combined with Sol–Gel Method

The synthesis of cerium dioxide (CeO₂) nanopowders via mechanical solid-state reaction combined with sol–gel method was studied. Cerium(III) nitrate hexahydrate, dihydrate oxalate, NH₄F, along with stearic acid or glycol, were mechanically milled. Calcination of the as-milled mixtures in air at 400 °C resulted in the formation of CeO₂ nanoparticles. The dispersity and uniformity in particle size and morphology were greatly improved by both physical and chemical effects of the stearic acid or glycol brought in: on one hand, they had the space steric hindrance effect; on the other hand, they might act as complexing agents, letting the whole process being carried out in highly homogeneous dispersed circumstance. The CeO₂ particles showed best dispersity and uniformity in particle size and morphology when the content of stearic acid was 20 g, along with 10 wt% NH₄F. As-obtained, near spherical CeO₂ particles were controlled to the size of 30–60 nm.     

Development of a high-performance green Fe–Al2O3 composites using Bayan Obo minerals: Enhancement effects of CeO2

With the deepening understanding for the concept of sustainable development, the utilization of minerals is no longer limited to the traditional way. In this study, an environment friendly method for preparing Fe–Al₂O₃ composites by using natural minerals was investigated. Additionally, the effects of CeO₂ on the properties of composites were studied. The mechanical properties of Fe–Al₂O₃ composites prepared by natural minerals are affected by the brittleness of glass phase. The strength and toughness of the glass phase in the composite are improved successfully by using rare earth oxides, indicating that the natural rare earths in Bayan Obo minerals have an enhanced influence on the properties of composite materials. The results show that the properties of glass phase can be significantly improved by addition of CeO₂. At the optimal addition of 3 wt% CeO₂, the composite achieves the density of 4.21 g/cm³, flexural strength of 401 MPa, Vickers hardness of 13.07 GPa and fracture toughness of 6.58 MPa⋅m^1/2. The composite has excellent mechanical properties, which can be used in engineering as a cheap structural material. This study aims at reducing waste emissions, improving energy efficiencies and avoiding waste of rare earth resources during the preparation of composite materials.     

Low-temperature thermocatalytic particulate carbon decomposition via urea solution-combustion derived CeO_2 nanostructures

A facile,one-pot,urea solution combustion route was utilized to synthesize highly catalytic CeO_2 nanostructures.CeO_2 prepared under varying thermal conditions was characterized by electron microscopy,energy dispersive X-ray spectroscopy,X-ray diffraction,X-ray photoelectron spectroscopy,infrared and Raman techniques.As the synthesis temperature is raised from 400 to 1000℃,the crystallite size and dspacing of nanoparticles are observed to reduce while cell parameters remain in the same range.Particle size exhibits an accession from ～20 to ～50 nm along the process.Initial CeO_2 nanoparticles are detected as a composite structure of CeO_2 and graphitic carbon nitride(g-C_3 N_4) produced by the pyrolysis of urea.Concerning the solid carbon particulate oxidation capacity,an outstanding performance is exhibited by CeO_2 synthesized at 800℃ where the oxidation onset temperature is reduced by 27% compared with the others.The superior performance is attributed to the carbon nitride-generated unique CeO_2 nanomorphology consolidating ample reactive sites and facilitated oxygen delivery for a highly efficient thermocatalytic process.Concerning atmospheric pollution mitigation,synthesis of these CeO_2 nanostructures represents a cost effective and convenient abatement technique for carbon particulates in comparison to cost-intensive,environmentally detrimental and noble-metal based techniques.     

Ce(Ⅲ)-modulation over non-enzymatic Pt/CeO2/GO biosensor with outstanding sensitivity and stability for lactic acid detection

A series of non-enzymatic graphene functionalized biosensors was developed via deposition precipitation method for lactic acid(LA) detection,which we re characterized by transmission electron micro scopy(TEM),Raman spectroscopy,X-ray photoelectron spectroscopy(XPS),gas chromatography-mass spectrometry,liquid chromatography-mass spectro metry,and proton nuclear magnetic re sonance(¹H NMR).The electrochemical performances of the non-enzymatic biosensors were measured by means of the ele...     

Fabrication of Cerium Oxide Nanoparticles by Solution Combustion Synthesis and Their Cytotoxicity Evaluation

The diverse abilities such as the antioxidant effect of cerium oxide nanoparticles (CeO₂-NPs) have encouraged researchers to pursue CeO₂-NPs as a therapeutic agent to treat a number of diseases, including cancer and diabetes. The synthesis method of CeO₂-NPs affected on its abilities. In this study, nanosize ceria powders were synthesized by combustion of aqueous containing corresponding cerium nitrate, ammonium nitrate, and glycine redox mixtures. Solution combustion synthesis is a fast and cost-efficient process with high purity product. The crystallite structures were characterized by various methods, including X-ray diffraction technique, high-resolution scanning electron microscopy, transmission electron microscopy, and UV–vis spectroscopy technique. The combustion was flaming and yields voluminous oxides with nano size (20–30 nm). In addition, no diffraction patterns that are characteristic of impurities were observed, indicating the purity of the CeO₂-NPs. In vitro cytotoxicity studies on L929 cells, a non-toxic effect in all concentration (up to 1000 μg/mL) was indicated and it can be believed that this nanoparticle will have viable applications in different medical fields.     

Mechanical and Wear Properties of Al–Al<Subscript>2</Subscript>O<Subscript>3</Subscript> Metal Matrix Composites Fabricated by the Combined Effect of Stir and Squeeze Casting Method

The effects of nano particles on double shear strength and tribological properties of A356 alloy reinforced with Al₂O₃ nano particles of size 30 nm were investigated. The percentage inclusions of Al₂O₃ were varied from 0.5 to 1.5 wt%. The particles were added with stirring at 400 rpm and squeeze casting at 750 °C and pressure of 600 MPa in a squeeze casting machine. Comparison of the performance of as cast samples of A356/Al₂O₃ nano composite was conducted. The tribological properties of the samples were also investigated by pin-on-disk tests at 10, 30 and 50 N load, sliding speed 0.534 m/s and sliding distance 1100 m in dry condition. SEM images of microstructure analysis of the composite, Al₂O₃ (0.5 and 1 %) particles were well dispersed in the A356 alloy matrix. Partial agglomeration was observed in metal matrix composite with higher (1.5 %) Al₂O₃ particle contents. The nano dispersed composites containing 0.5 and 1 wt% of Al₂O₃ nano particles exhibited the highest double shear strength, lesser wear loss and coefficient of friction.     

Mechanism of CeO_2 synthesized by thermal decomposition of Ce-MOF and its performance of benzene catalytic combustion

In this paper,the formation mechanism of mesoporous CeO_2 synthesized by thermal decomposition of Ce-MOF and its performance of benzene catalytic combustion,as well as the structure-activity relationship between them were studied in depth.The self-assembly process and physicochemical properties of CeO_2 were characterized by thermogravimetry analysis,powder X-ray diffraction,N_2 adsorption/desorption,high-resolution transmission electron microscopy and X-ray photoelectron spectroscopy techniques.Characterization results show that Ce-MOF is completely decomposed into pure mesoporous CeO_2 when the decomposition temperature is higher than 400℃.At this threshold temperature,CeO_2(400) has the largest specific surface area and pore volume of 114 m~2/g and 0.152 cm3/g,respectively.CeO_2(400) exhibits very high catalytic activity for benzene combustion,which can completely catalyze the degradation of benzene at 260℃.Meanwhile,the mesoporous CeO_2(400) supported Pt nanocrystalline catalysts were prepared by high temperature solution-phase reduction method.Pt/CeO_2(400)can completely degrade benzene at about 200℃ and represents high durability and good waterresistance for benzene combustion during 100 h of continuous reaction.     

Synthesis of CeO_2/fly ash cenospheres composites as novel photocatalysts by modified pyrolysis process

A novel fly ash cenospheres(FACs)-supported CeO2 composite(CeO2/FACs) was successfully synthesized by the modified pyrolysis process.The prepared composites were characterized by X-ray diffraction(XRD), scanning electron microscopy(SEM), X-ray photoelectron spectroscopy(XPS), and diffuse reflection spectra(DRS) techniques.XRD results indicated that the CeO2 film coated on cenospheres was a face-centered cubic structure.SEM images confirmed that the CeO2 film was relatively compact.XPS results showed that Ce was present as both Ce4+ and Ce3+ oxidation states in CeO2 film coated on FACs substrate.The bandgap of the composite was narrower compared with the pure CeO2.The as-prepared material exhibited good photocatalytic activity for the decolorization of methylene blue(MB) under visible light irradiation, and the first-order reaction rate constant(k) of 0.0028 min–1 for CeO2/FACs composite was higher than 0.0015 min–1 of pure CeO2.The fact that they floated on water meant that CeO2/FACs composites were easily recovered from water by filtration after the reaction.The recycling test revealed that the composites were quite stable during the MB photocatalytic decolorization.The CeO2/ FACs catalyst was therefore promising for practical use in the degradation of pollutants or water cleanup.     

Hot Corrosion Behaviour of Refractory and Rare Earth Oxide Reinforced CoCrAlY APS Coatings at 700 °C

This paper investigates cyclic hot corrosion of plasma sprayed CoCrAlY?+?Al₂O₃?+?YSZ (C1) and CoCrAlY?+?CeO₂ (C2) composite coatings on MDN 321 and Superni 76 substrates in molten salt (Na₂SO₄-60%V₂O₅) environment exposed to 700 °C. Weight change technique is used to evaluate the corrosion performance. Both C1 and C2 coatings showed better corrosion resistance than uncoated alloy. Both the coatings showed linear weight gain during the initial cycles and parabolic weight gain nature with subsequent hot corrosion cycles. The parabolic rate constant (K_p) of C1 and C2 coating was observed to be in the range 0.29–0.32?×?10^?10 g² cm^?4 s^?1 and 1.0–1.13?×?10^?10 g² cm^?4 s^?1 respectively. In C1 coating, the globular and continuously packed structure on the corroded surface having CoO, Cr₂O₃, CoCr₂O₄ and CoAl₂O₄ spinel oxides provided superior hot corrosion resistance. While in case of C2 coating, the outward growth of CeVO₄ irregular crystals as a corrosion product of CeO₂ and V₂O₅ salt deteriorated the oxide scales resulting in higher corrosion rate.     

One-step solution combustion synthesis of micro-nano-scale porous Cu/CeO2 with enhanced photocatalytic properties

The Cu/CeO₂ nanoporous composite material was prepared via a one-step and energy-saving method of solution combustion synthesis(SCS).The phase composition,surface morphology and optical characteristics of Cu/CeO₂ were studied.The results show that the SCS products are composed of cubic fluorite CeO₂ and Cu.Due to the generation and escape of gas during the synthetic reaction,the SCS CeO₂ shows porous structure,in which the mesopores(diameter 10-17 nm) ...     

Formation of ZrO<Subscript>2</Subscript>–SiC Composite Coating on Zirconium by Plasma Electrolytic Oxidation in Different Electrolyte Systems Comprising of SiC Nanoparticles

Plasma electrolytic oxidation (PEO) coupled with electrophoretic deposition (EPD) was used to fabricate ZrO₂/SiC composite coating on the zirconium metal. The PEO–EPD process was carried out in three different electrolyte systems consisting of 5 g/l sodium aluminate or trisodium orthophosphate or sodium metasilicate with 4 g/l SiC nanoparticles. The X-ray diffraction results indicate monoclinic zirconia is the major phase in phosphate and silicate electrolyte while the coating produced in aluminate electrolyte is composed of tetragonal zirconia. The potentiodynamic polarization studies (PDP) indicate that composite coating produced in phosphate?+?SiC nanoparticle containing electrolyte exhibit superior resistance to corrosion, which can be attributed to the pore-free morphology of the coating. All the PEO–EPD coatings show exceptionally good adhesion strength (L_c ?> 40 N). The coating fabricated in phosphate?+?SiC nanoparticles is found to be the best coating because of its superior resistance to corrosion and reasonably good adhesion strength.     

Effect of active oxygen on the performance of Pt/CeO2 catalysts for CO oxidation

This study was focused on the influence of active oxygen on the performance of Pt/CeO_2 catalysts for CO oxidation. A series of CeO_2 supports with different contents of active oxygen were obtained by adding surfactant at different synthesis steps. 0.25 wt% Pt was loaded on these CeO_2 supports by incipientwetness impregnation methods. The catalysts were characterized by N2 adsorption, X-ray diffraction(XRD), high-resolution transmission electron microscopy(HRTEM), H_2 temperature-programmed reduction(H_2-TPR), dynamic oxygen storage capacity(DOSC) and in-situ DRIFTS technologies. For S-f supports, the surfactant was added into the solution before spray-drying in the synthesis process, which facilitates more active oxygen formation on the surface of CeO_2. After loading Pt, the more active oxygen on CeO_2 contributes to dispersing Pt species and enhancing the CO oxidation activity. As for the aged samples,Pt-R-h shows the highest activity above 190 ℃ because of the presence of more partly oxidized Pt~(δ+) species. Thus the activity is also influenced by the states of Pt and the Pt~(δ+) species may contribute to the high activity at elevated temperature.