Glycine-nitrate auto-combustion synthesis and magnetic properties of nanocrystalline NdAlxFe1-xO3 perovskites

The effect of substitution of Fe³⁺ by Al³⁺ on the structure and magnetic properties of NdAl_xFe_1-xO₃ perovskite nano-powders(x=0.0,0.1,0.2,0.3,0.4,and 0.5) prepared by the glycine-nitrate auto-combustion method was studied.All samples were characterized by X-ray diffraction(XRD),scanning electron microscopy(SEM),Fourier transform infrared spectroscopy(FT-IR),and energy dispersive X-ray spectroscopy(EDX).The magnetic properties of the samples ...     

Phosphorus fixation capacity of CaO-SiO2-Al2O3-MnO-Ce2O3 slag based on structural considerations

The phosphorus fixation capacity of some slag systems,such as Ce₂O₃-containing slag,has hardly been investigated from a thermodynamics view due to the lack of relevant thermodynamic data.Since the macroscopic properties are primarily determined by the microscopic structure,the correlation between phosphorus fixation capacity and slag structure was explored by spectroscopy(XPS),Raman spectroscopy,and ferromanganese dephosphorization experiments.The results show that the pred...     

Effects of Nd on microstructure and mechanical properties of as-cast Mg-8Li-3Al alloy

Effects of Nd on microstructure and mechanical properties of as-cast Mg-8Li-3Al alloy were investigated by OM,X-ray diffraction(XRD),EPMA,scanning electron microscopy(SEM) and energy dispersive spectroscopy(EDS).The results showed that the dendrites sizes of α phase were decreased by the Nd addition.When the amount of addition Nd was 1.6 wt.%,the alloy with the smallest α phase was obtained.The refining mechanism mainly owed to the increasing constitutional supercooling at the solidification front.Furthermore,the compound Al 2 Nd generated by the reaction of Al and Nd,which distributed at the phase boundary and inside β phase,could also restrain the growth of α phase.Nd could improve the tensile strength and elongation of Mg-8Li-3Al alloy,however,excessive Al 2 Nd might also become crack source and decrease the elongation.     

Effect of Plastic Deformation on Magnetic Properties of Fe40%Ni2%Mn Austenitic Alloy

The effects of plastic deformation on the magnetic properties of austenite structure in an Fe40%Ni2%Mn alloy is investigated by using Mssbauer spectroscopy and Differential Scanning Calorimetry (DSC) techniques The morphology of the alloy has been obtained by using Scanning Electron Microscopy (SEM). The magnetic behaviour of austenite state is ferromagnetic. After plastic deformation, a mixed magnetic structure including both paramagnetic and ferromagnetic states has been obtained at the room temperature. The volume fraction changes, the effective hyperfine fields of the ferromagnetic austenite phase and isomery shift values have also been determined by Mssbauer spectroscopy. The Curie point (TC) and the Neel temperature (TN) have been investigated by means of DSC system for nondeformed and deformed FeNiMn alloy. The plastic deformation of the alloy reduces the TN and enhances the paramagnetic character of austenitic FeNiMn alloy.     

Nitric oxide(NO) decomposition on catalysts,containing oxides of lanthanum and cerium,supported on γ-alumina

The present work was devoted to study the catalytic activity of lanthanum and cerium oxides separately,deposited on g-alumina in the reaction of decomposition of nitric oxide. The catalyst samples were prepared by the method of impregnation of g-Al_2 O_3 using solutions, containing nitrates of lanthanum and cerium. The prepared samples were calcined for 4 h at temperature 650℃ in an oven in air atmosphere. The catalysts were characterized by: chemical analysis by inductively coupled plasma atomic emission spectrometry(ICP-AES), X-ray diffraction(XRD), X-ray photoelectron spectroscopy(XPS),scanning electron microscopy(SEM) combined with energy-dispersive X-ray spectroscopy(EDS), electron paramagnetic resonance(EPR) and infrared(IR) spectroscopy, as well as measurement of the specific surface area. The results show that the catalysts based on lanthanum oxide and cerium oxide deposited on alumina display high catalytic activity over 60% conversion degree with respect to decomposition of nitric oxide in the absence of reducing agent. In the presence of reducer the activity reaches 90% conversion degree.     

Effects of aluminum co-doping on photoluminescence properties of Ce³⁺-doped SiO₂ glasses

SiO2 glasses co-doped with Al3+ ions were prepared by a sol-gel method by holding 0.5% of Ce3+ ions constant and varying the Al3+ ions concentrations.Thermal stability,the structural,chemical and the optical properties of the samples were studied by using differential scanning calorimetric(DSC),thermo gravimetric analysis(TGA),X-ray diffraction(XRD),scanning electron microscopy(SEM),energy dispersive spectroscopy(EDS),UV-vis spectroscopy and photoluminescence spectroscopy(PL).The DSC and TGA of samples depicted that the presence of dopant and co-dopant decreased the endothermic peak temperature and the yield respectively.SEM images showed that the particles were in the nano-range and spherical in shape.The XRD showed that all the samples were amorphous.The UV absorption measurements indicated that the presence of Al3+ ions significantly reduced the SiO2 absorption band,increased the absorbance intensity of SiO2 and decreased the transmittance as compared to the presence of the Ce3+ ions alone.The photoluminescence results displayed an optimum increase in luminescence intensity when the ratio of Al:Ce was 10:1 and further increase in aluminum content quenched the luminous intensity.     

Effects of Cu on Corrosion Resistance of Low Alloyed Steels in Acid Chloride Media

The corrosion resistance of two kinds of low alloyed steels was studied according to the test procedures for qualification of corrosion resistant steel for cargo oil tanks issued by International Maritime Organization.The results indicated that the addition of Cu improved the corrosion resistance of the NS-D36 steel to more than three times that of the conventional D36 steel in the strong acid solution containing chloride(10% NaCl,pH=0.85).The anodic polarization behavior of the copper-bearing steel was studied by polarization curves and electrochemical impedance spectroscopy(EIS),and alloying element Cu showed beneficial effects including an active potential range,low current density and high transfer resistance of electric charge.The rust layer was analyzed by scanning electron microscopy(SEM)and Auger electron spectroscopy(AES),and the results pointed out that the mechanism of copper′s beneficial effects was based on the suppression of anodic dissolution by metallic copper re-deposition on the steel surface immersed in the strong acid chloride media.     

Luminescence properties and energy transfer of host sensitized CaMoO4：Tb^3＋ green phosphors

A series of CaMoO 4 :xTb 3+(x=0.01,0.03,0.05,0.07,0.09,0.15 and 0.20) phosphors in pure phase were prepared via high temperature solid-state reaction approach.The crystal structure of the phosphors was investigated by X-ray diffraction(XRD),and the optical properties were investigated by Fourier transform infrared spectroscopy(FT-IR),ultraviolet-visible spectroscopy(UV-Vis) and photoluminescence(PL) spectroscopy.The PL spectra illustrated that these phosphors could be efficiently excited by the charge transfer band of the host and the energy transfer efficiency from the host to the doped activator reached 60% when the doping concentration of the activator Tb 3+ was 20 mol.%.The concentration quenching occurred at x=10 mol.%,from which the critical distance of activator was calculated to be about 1.14 nm.The CIE coordinates were estimated to be close to the standard green value.The host sensitized samples had potential application as green phosphors.     

Sonication method synergism with rare earth based nanocatalyst:preparation of NiFe_(2–x)Eu_xO_4 nanostructures and its catalytic applications for the synthesis of benzimidazoles,benzoxazoles,and benzothiazoles under ultrasonic irradiation

A simple and practical ultrasonically synthetic strategy for the preparation of rare-earth based catalyst, nanostructured NiFe_(2–x)Eu_xO_4 was developed. The structure of NiFe_(2–x)Eu_xO_4 was characterized by various analyses such as X-ray diffraction(XRD), scanning electron microscopy(SEM) and fourier transform infrared spectroscopy(FT-IR). The catalytic performance of NiFe_(2–x)Eu_xO_4 was evaluated for the synthesis of benzimidazoles, benzoxazoles and benzothiazoles under ultrasonic irradiation. All reactions were completed in short times and all products were obtained in good to excellent yields in presence of the rare-earth based catalyst. Besides, NiFe_(2–x)Eu_xO_4 could be recovered for 6 times without noticeably decreasing the catalytic activity.     

Preparation of CeO2 abrasives by reducing atmosphere-assisted molten salt method for enhancing their chemical mechanical polishing performance on SiO2 substrates

Ce³⁺as the active site on the CeO₂ abrasive surface is the key to enhancing the material removal rate(MRR).The CeO₂ abrasives with high chemical activity were prepared by the molten salt method under a reducing atmosphere.The crystal structure and morphology of CeO₂ abrasive s were characterized by X-ray diffraction(XRD),scanning electron microscopy(SEM),transmission electron microscopy(TEM),Fourier transform infrared spectroscopy(FT-IR),ultraviolet—vi...     

Characterization and electrochemical performance of CeO2 and Eu-doped CeO2 films as a manganese redox flow battery component

Hexagonal CeO_2 and Eu-doped CeO_2 nanoparticles were obtained using a facile microwave-hydro thermal method under mild conditions and their application towards manganese redox flow battery component were studied. The structural properties were studied by X-ray diffraction and indicate that samples present a fluorite structure. Raman spectroscopy shows Eu3+ ions substitute Ce~(4+) and generate oxygen vacancies. Electrochemical properties of pure and Eu-doped CeO_2 films deposited at graphite substrates investigated by cyclic voltammetry and galvanostatic charge—discharge indicate that dopant concentration affects the electrochemical properties of CeO_2. The increase in the reversibility redox of electrochemical systems observed is attributed to coexistence of Ce~(4+)/Ce~(3+) redox couple confirmed by XPS.Charge—discharge tests display coulombic and voltage efficiency values of above 80% and 90%, respectively. The obtained specific capacity for Ce_(0.99)Eu_(0.01)O_2(372.49 mAh/g) and pure oxide(334.84 mAh/g)indicates that both samples are promising for application in Mn-batteries.     

Understanding the role of tungsten on Pt/CeO2 for vinyl chloride catalytic combustion

Spherical CeO₂ synthesized by the hydrothermal process was used as support to prepare Pt/WO₃/CeO₂,and the effects of tungsten(W) contents on activity,stability and polychlorinated by-products were investigated to understand the role of W for vinyl chloride(VC) catalytic oxidation.The introduction of12 wt% W to Pt/CeO₂(P12 WC) exhibits the highest catalytic activity with 90% conversion of VC at 250℃,meanwhile the stability improves and the polychlorinat...     

Constructing a high concentration CuO/CeO2 interface for complete oxidation of toluene: The fantastic application of spatial confinement strategy

In this paper,CeO₂ substrate was prepared by the sol-gel method,further CuO was introduced by adding the copper complexes with chelating agents into the sol-gel precursors of CeO₂,in which different chelating agents(β-cyclodextrin,glucose and trimesic acid) were tried.This synthesis method helps the CuO species to disperse very uniformly in the CeO₂ substrates.When the amount of copper oxide is up to33 mol%,the CuO/CeO₂ samples can still maintain a hig...     

Reaction between tetravalent cerium ion and chloride ion and effect of thiourea using cyclic voltammetry

To monitor the reaction between Ce⁴⁺ ion and Cl^– ion at the electron level, an electrochemical experiment was designed in this work. Herein, the intermediate and final products that may be produced during the redox reaction are directly tracked by using cyclic voltammetry, and the influences of Ce⁴⁺ ion concentration, temperature and F^– ion on the reduction peak potential of Ce⁴⁺ ion were investigated. The results show that Ce⁴⁺ ion reacts with Cl^– ion through an irreversible reaction without any intermediate products, and the rate-determining step of the reaction is diffusion during the electrode reaction. The effects of temperature (20–40 °C) and Ce⁴⁺ ion concentration (0.04–0.12 mol/L) on the reduction peak potential of Ce⁴⁺ ion can be ignored, but the higher the molar ratio of F^– to Ce⁴⁺ (0–3 mol/mol), the more easily the reduction of Ce⁴⁺ ion to Ce³⁺ ion occurs. Additionally, the Ce⁴⁺ ions are preferentially reduced by thiourea when thiourea is added in the HCl solution, and thiourea inhibits the oxidation of Cl^– ions to Cl₂ by forming a complex with Cl^– ions. This work provides a theoretical basis for the role of thiourea in inhibiting Cl₂ production and offers a new way to find new reductants.     

Catalytic action of rare earth oxide (La2O3, CeO2, Pr6O11) on electrochemical oxidation of activated carbon in molten KOH–NaOH

The oxidation of anode carbon fuel directly affects the electrochemical performance of molten hydroxide direct carbon fuel cell (MHDCFC). In general, the anode carbon fuel can be oxidized at high temperature, thus the direct carbon fuel cell (DCFC) can show great electrochemical performance. In this study, rare earth oxides (La₂O₃, CeO₂, Pr₆O₁₁) were prepared by the method of precipitation. Activated carbon was prepared by pretreatment of lignite. Rare earth oxides and activated carbon were mixed as anode carbon fuel, and rare earth oxides were used to catalyze the electrochemical oxidation of anode carbon fuel. The results show that CeO₂ has better electrocatalytic activity compared with La₂O₃ and Pr₆O₁₁ in the MHDCFC. The electrochemical test results show that the current density (at 0.4 V) increases from 81.02 to 112.90 mA/cm² and the maximum power density increases from 34.78 to 47.05 mW/cm² at 450 °C, when the mass fraction of CeO₂ is increased from 0 to 40%. When the mass fraction of CeO₂ is 30%, the current density (82.55 mA/cm² at 0.4 V) at 400 °C is higher than that (81.02 mA/cm² at 0.4 V) without CeO₂ at 450 °C. The electrochemical oxidation mechanism of CeO₂ catalyzed anode carbon fuel is discussed.     

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.     

Optical and electrical conductivity properties of rare earth elements (Sm,Y, La,Er) co-doped CeO2

In this research, un-doped CeO₂ and Ce_0.85La_0.10M_0.05O₂ (M: Sm, Er, Y) compounds were synthesized by hydrothermal method and the multi-functional properties are reported. Oxygen defects were created with the additives of rare earth ions. The electrical and luminescence behaviors of the synthesized compounds were investigated in accord with the types of additives. The synthesized products were characterized by X-ray diffraction (XRD) analysis, Brunauer–Emmett–Teller (BET) measurement, UV–vis diffuse reflectance spectroscopy (DRS), scanning electron microscopy (SEM), photoluminescence (PL) spectroscopy and electrochemical impedance spectroscopic (EIS). All synthesized compounds are found to be nano-structured and have cubic phase. The total conductivity of all samples was calculated. Hence, the total conductivity of un-doped CeO₂, Ce_0.85La_0.10Y_0.05O₂, Ce_0.85La_0.10Er_0.05O₂ and Ce_0.85La_0.10Sm_0.05O₂ is found to be 2.07 × 10^?10, 5.70 × 10^?4, 1.0 × 10^?3 and 0.0747 S/cm, respectively. Also, bandgap energy (E_g) of these samples calculated from UV visible absorption spectra is discussed, and the optical results show variation between 3.2 and 2.15 eV. Additionally, the luminescence properties of the compounds were investigated and different emissions occur depending on the additive type. Accordingly, photoluminescent emission spectra of Ce_0.85La_0.10Y_0.05O₂, Ce_0.85La_0.10Er_0.05O₂ and Ce_0.85La_0.10Sm_0.05O₂ phosphors indicate that these phosphors have red, green and orange-red colors, respectively.     

CeO2 and CeO2-based nanomaterials for photocatalytic,antioxidant and antimicrobial activities

Cerium oxide(CeO₂),one of the most significant rare-earth oxides,has attracted considerable interest over the past decades.This is primarily due to the ease in Ce³⁺/Ce⁴⁺ redox ability as well as other factors that affect the efficacy of CeO₂ and CeO₂-based materials.CeO₂ and CeO₂-based materials have shown enhanced responses in catalytic and photocatalytic activities for environmental and biological applications.In addi...     

Catalytic combustion of toluene on Pt/Al2O3 and Pd/Al2O3 catalysts with CeO2,CeO2-Y2O3 and La2O3 as coatings

CeO₂,La₂O₃,and CeO₂-Y₂O₃ oxides were coated on the surface of spherical granular AI₂O₃(3-5 mm)through impregnation method,and proved as better supports of Pd and Pt catalysts.The influences of rare earth metal doping on the adsorption rates of Pd and Pt ions,as well as the catalytic performance,were investigated.Results show that the H₂PtCl₆·6H₂O adsorption rates of the Al     

Synthesis and characterization of manganese doped CeO2 nanopowders from hydrolysis and oxidation of Ce37Mn18C45

The Mn-doped CeO 2 nanopowders with high catalysis activity were successfully fabricated through a simple hydrolyzed-oxidized approach.Firstly,the alloy Ce 37 Mn 18 C 45 was prepared in vacuum induction melting furnace.Subsequently,Mn-doped CeO 2 nanopowders with 142 m 2 /g of specific surface area were obtained through a simple hydrolyzed-oxidized procedure of the alloy.Those nanopowders were heat treated at different temperatures.The obtained materials were characterized by X-ray diffraction(XRD),transmission electron microscopy(TEM),high-resolution transmission electron microscopy(HRTEM) and energy dispersive spectroscopy(EDS).And the catalytic activity on vinyl chloride(VC) emission combustion was investigated.The results showed that those nanopowders after hydrolyzed-oxidized from Ce 37 Mn 18 C 45 mainly consisted of CeO 2 and Mn 3 O 4.Manganese element increased the thermal stability of CeO 2 nanopowders.The Mn-doped CeO 2 nanopowders had three morphologies.Small particles were Mn-doped CeO 2,square particles were Mn 3 O 4 and the rods were Mn 3 O 4 and Mn 2 O 3.The Mn-doped CeO 2 nanopowders had good vinyl chloride(VC) emission catalytic performance.