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...     

Photocatalytic activity of Eu3＋-doped ZnO nanorods synthesized via microwave assisted technique

The doped ZnO nanorods as a photocatalyst with different Eu contents were prepared by microwave assisted method and they were characterized by means of X-ray diffraction(XRD),energy-dispersive X-ray spectroscopy(EDS),UV-Vis spectroscopy,surface area Brunauer-Emmett-Teller(BET),X-ray photoelectron spectroscopy(XPS),scanning electron microscopy(SEM) and transmission electron microscopy(TEM).The average crystallite size and band gap energy of Eu-doped ZnO were varied with the Eu content.The XRD pattern of Eu-doped ZnO indicated hexagonal crystal structure with an average crystallite size of 25 nm.The presence of europium with trivalent state and its doping successfully into the crystal lattice of ZnO matrix were confirmed by XPS technique.The photocatalytic activity of Eu-doped ZnO nanorods was evaluated for methyl orange degradation.The photocatalytic experiments showed ～91% degradation of methyl orange over 0.2 mol.% Eu doped ZnO sample within 3 h under UV light(365 nm).     

Preparation of double-walled carbon nanotubes using lanthanum as promoter

Double-walled carbon nanotubes (DWNTs) were prepared from graphite by arc discharge technique with La as promoter. The DWNTs products were characterized by scanning electron microscopy, transmission electron microscopy, energy dispersive X-ray diffraction and Raman spectroscopy. The results demonstrated that La was a suitable promoter reagent for making high purity DWNTs with narrow diameter distribution by arc discharge method. The role of La in the growth of the DWNTs was briefly discussed in terms of the...     

Zirconia modified monolithic macroporous Pt/CeO2/Al2O3 catalyst used for water-gas shift reaction

Monolithic macroporous Pt/CeO2/Al2O3 and zirconia modified Pt/CeO2/Al2O3 catalysts were prepared by using concentrated emulsions synthesis route. The catalytic performances over the platinum-based catalysts were investigated by water-gas shift (WGS) reaction in a wide temperature range (180-300 oC). The samples were characterized with thermogravimetry (TG), X-ray diffraction (XRD), scanning electron microscopy (SEM), high resolution transmission electron microscopy (HRTEM) and temperature programmed reducti...     

Fabrication and photoluminescent characteristics of one-dimensional La202S：Eu3＋ nanocrystals

One-dimensional La2O2S:Eu3+ nanowires(NWs) were fabricated with a simple hydrothermal method.The structures were characterized by X-ray diffraction and transmission electron microscopy(TEM).The photoluminescent properties including excitation and emission spectra were studied.The results indicated that in excitation spectra there existed charge transfer(CT) absorption of both O2-→Eu3+ and S2-→Eu3+,and f-f transitions absorption in NWs and corresponding sub-meter materials(SMs).The relative intensity of CT absorption of O2-→Eu3+ to S2-→Eu3+ in both samples clearly changed.The strong yellow and red emissions of Eu3+ ions in NWs were observed.     

Preparation, spectral characteristics and photocatalytic activity of Eu~(3+)-doped WO_3 nanoparticles

Eu3+-WO3 nanoparticles were successfully prepared by the modified method of Pechini. The prepared samples were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM), and UV-vis spectroscopy. Results showed that the Eu3+-WO3 nanoparticles, which had an average external diameter of 10-25 nm, were composed of the different shapes of puncheon and catenary after being pretreated by pH, pressure vessal, and surfactant. Moreover, ...     

Study on reaction mechanism of low temperature preparation of nanocrystalline LaCoO3-λ

Perovskite-type oxide nanocrystalline LaCoO3-λ was prepared using the citrate method. The structure and morphology of the sampies were characterized by powder X-ray diffraction （XRD） and transmission electron microscopy （TEM）. The intermediate products were analyzed by thermal gravimetric and differential thermal analysis （TG-DTA） technology. The results showed that nanocrystalline LaCoO3-λ with a granula of 30-50 nm had a cubic perovskite structure. The reaction mechanism of low temperature preparation was suggested as follows： the metal complex was first formed by the combination of metal ion and citric acid; and then it decomposed into an aconitic acid complex, followed by an oxycarbonate, and finally a perovskite-type oxide.     

Microstructure Evolution and Microhardness of Ultrafine-grained High Carbon Steel during Multiple Laser Shock Processing

Surface microstructure and microhardness of(ferrite+cementite)microduplex structure of the ultrafinegrained high carbon steel after laser shock processing(LSP)with different impact times were investigated by means of scanning electron microscopy(SEM),transmission electron microscopy(TEM),X-ray diffraction(XRD)and microhardness measurements.Equiaxed ferrite grains were refined from 400 to 150nm,and the cementite lamellae were fully spheroidized,with a decrease of the particle diameter from 150 to 100nm as the impact times increased.The cementite dissolution was enhanced significantly.Correspondingly,the lattice parameter ofα-Fe and microhardness increased with the impact times.     

Characterization and photoluminescence of Lu_2O_3-Eu~（3＋） nano-phosphor prepared by modified solution combustion method

Nanoscale Lu2O3:Eu3+ phosphor was prepared by a modified solution combustion method using urea and acrylamide monomer.The particle sizes and photoluminescent properties of nano-phosphor were closely related to the molar ratio of urea-to-RE nitrates and acrylamide monomer-to-RE nitrates.The as-prepared samples with the sizes of 9.6-11.6 nm were characterized by X-ray diffraction,scanning electron microscopy,transmission electron microscopy and energy dispersive spectrometer.Lu2O3:Eu3+ nano-phosphor that depicted high photoluminescence in the size around 10 nm was reported.Compared with the sample prepared by solid state reaction,the photoluminescence of sample was increased sufficiently to be 45.1%.The emission spectra of the samples presented the typical emission from 5D0 level to 7FJ(J=0,1,2,3,4) level of the Eu3+ ion.     

Biogenic synthesis and catalysis of porous CeO2 hollow microspheres

Porous CeO2 hollow microspheres were successfully prepared through a facile process by using the rape pollen as the biotem-plate. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), the N2 adsorption and desorption, X-ray diffraction (XRD), UV-vis diffuse reflectance spectra, and hydrogen temperature-programmed reduction (H2-TPR) were used for their characterization. The results showed that the obtained materials exhibited the same morphology as that of the pollen template, with a diameter of ca. 10 μm, and the surface was evenly covered with a special network-like structure with mesh size of about 0.3 μm, and the Brunauer-Emmett-Teller (BET) surface area was measured to be 156 m2/g. The detailed property investigation inferred that the product exhibited better photocatalytic activity in acid fuchsine decolorization under daylight because of higher surface area, smaller crystallite size and higher oxygen capacity.     

Sol-gel synthesis and photoluminescence properties of BaSO_4/Y_2O_3:Eu~(3+) core-shell submicrospheres

Europium-doped nanocrystalline Y2O3 phosphor layers were coated on the surface of preformed submicron BaSO4 spheres via the sol-gel process.The obtained BaSO4/Y2O3:Eu3+ core-shell phosphors were characterized by X-ray diffraction(XRD),scanning electron microscopy(SEM),transmission electron microscopy(TEM),energy dispersive spectroscopy(EDS) and photoluminescence spectra.The results showed that the obtained BaSO4/Y2O3:Eu3+ core-shell phosphors consisted of well-dispersed submicron spherical particles with na...     

Luminescence of EPDM rubber ultrafine fibers containing nanodispersed Eu-complexes

Polyvinylpyrrolidone/ethylene-propylene-diene terpolymer (PVP/EPDM) sheath/core fibers, with the incorporation of Eu(TTA) 3 Phen (TTA=2-thenoyltrifluoroacetone, Phen=1,10-phenanthroline) complex (Eu-complex) in EPDM, were prepared by coaxial electrospinning. The composite fibers were further vulcanized by peroxide. Scanning electron microscopy (SEM) observations showed that the composite fibers had an average diameter of about 200 nm and a smooth surface. The dispersion of Eu-complexes in the fibers was characterized by transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDS), and X-ray diffraction (XRD). The studies revealed that the Eu-complex was dispersed in the EPDM fibers in the form of molecular clusters and/or nanoparticles with a diameter smaller than 10 nm. Fluorescence spectra and Judd-Ofelt parameters analysis showed that the luminescent quantum efficiency of the composite fibers was greatly improved when the Eu-complex content was 15 wt.%, because the fine dispersion of Eu-complex in EPDM facilitated the increase of radiative transition rate of the composite fibers over that of the neat complex powder.     

Phase and microstructure of TbCuT-type SmFe melt-spun powders

The SmxZr0.3Fe9.1-xCo0.6(x=0.8,0.9,1.0) powders were prepared by melt-spun method with different quenching velocities.The phase and microstructure were studied by X-ray diffraction(XRD),scanning electron microscopy(SEM) and transmission electron microscopy(TEM).The Th2Zn17-type structure of the as-cast state changed to TbCu7-type after quenching to a rotating molybdenum roll under certain velocity,and the formation of TbCu7-type phase was strictly depending on the Sm content and roll speed.The SEM morphology showed that the Fe-rich zone was typically fish-bone structure and TEM diffraction pattern indicated the nano-scale crystal size with TbCu7-structure when x=0.9,and FCC type γ-Fe on the basis of α-Fe formed in the non-equilibrium solidification could be detected by selected area electron diffraction(SAED) indexing in the x=0.8 samples.     

A controllable hydrothermal method to prepare La（OH）3 nanorods using new precursors

Using the hydrothermal method, lanthanum hydroxide nanorods were synthesized by the reaction of La Cl3·7H2O, ethylenediamine, and hydrazine. According to SEM results, ethylenediamine and hydrazine with p H management could control the particle growth and played an important role in formation of lanthanum hydroxide nanorods. The morphology and microstructure of the obtained products were characterized by X-ray diffraction(XRD) spectra, energy-dispersive X-ray spectroscopy(EDX), Fourier transformed infrared(FTIR) spectrum, transmission electron microscopy(TEM), and scanning electron microscopy(SEM). Furthermore, the effects of the molar ratio of the precursors as well as the reaction temperature and time on the morphology and particle size of the products were investigated.     

Preparation and morphology of nano-size ceria by a stripping precipitation using oxalic acid as a precipitating agent

The precursors organic cerium deposits were obtained by a stripping precipitation method from cerium-loaded P507 organic phase using oxalic acid as a precipitating agent and nano-sized ceria particles were prepared by calcining the precursors at 500 °C. The morpholo-gies, phase structure of the precursors and ceria particles were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), thermogravimetric analysis (TG-DSC) and infrared spectroscopy analysis (FTIR). The results indicated that the concentration of oxalic acid had a little impact on the morphology of the precursors, which was blocky-shape Ce2(C2O4)3·10H2O with a monoclinic lattice structure. With the volume ratio of organic phase and oxalic acid aqueous solution (aqueous phase) varied from 1:3 to 1:6, the morphologies of the precursors Ce2(C2O4)3·10H2O precipitates gradually changed from inhomogeneous blocky-shape to uniform spherical particles. The precursors could be turned to CeO2 crystal particles with a fluorite structure by calcining, and the products ceria particles were similar in the size and morphology to the precursors.     

Influence of La2O3 addition on microstructure and wear resistance of Fe-Cr-C cladding formed by arc surface welding

The Fe-Cr-C claddings formed by arc surface welding with different La2O3 additions were investigated. The microstructures were observed by optical microscopy (OM), field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM). The phase structures were measured by X-ray diffraction (XRD). The wear resistances of the claddings were tested by friction and wear experiment. On this basis, the carbide refinement mechanism by inclusion enriched with La was discussed theoretically. The results showed that, the microstructure of the Fe-Cr-C cladding consisted of primary (Cr,Fe)7C3 carbides and eutectic (γ-Fe+(Cr,Fe)7C3 ) structure. With La2O3 addition increasing, the primary carbides were refined, and the mass loss of the cladding decreased gradually. The Fe-Cr-C cladding with 4wt.% La2O3 addition had a best wear resistance behaviour. The RE inclusion LaAlO3 as heterogeneous nuclei of the primary M7C3 was medium effective, and could refine the M7C3 carbides. Besides, the wear resistance could be improved by adding La2O3 in the claddings.     

Influence of preparation method on performance of a metal supported perovskite catalyst for combustion of methane

A different method was employed for the preparation of a metal supported perovskite catalyst for the catalytic combustion of methane.The prepared metallic catalysts were characterized by means of X-ray diffractometer(XRD),scanning electron microscopy(SEM),transmission electron microscopy(TEM),and also by ultrasonic and thermal shock tests and catalytic activity.It was found that the process factors during the preparation,e.g.the preparation of the catalyst precursor and the coating slurry,the calcination te...     

Influence of dispersant on Y_2O_3:Eu~(3+) powders synthesized by combustion method

Y2O3:Eu3+ powders were synthesized by combustion method and the influence of dispersant was investigated.XRD analysis indicated that the particle size increased with a small amount of dispersant firstly and then decreased with a further increase of dispersant.The morphologies of the powders were studied by scanning electron microscopy(SEM) and high-resolution transmission electron microscopy(HRTEM).SEM images revealed that an appropriate amount of dispersant could reduce the agglomeration significantly.Due ...     

Preparation and photoluminescence enhancement of Li＋ and Eu3＋ co-doped YPO4 hollow microspheres

Li+ and Eu3+ co-doped YPO4 hollow microspheres were successfully synthesized by a sacrificial template method using polystyrene (PS) as template. Techniques of X-ray diffraction (XRD), scanning electron microscopy (SEM), as well as transmission electron microscopy (TEM) were employed to characterize the as-synthesized sample. Furthermore, the photoluminescence (PL) characterization of the Li+ and Eu3+ co-doped YPO4 microsphere was carried out and the effects of the doping concentration of Li+ and Eu3+ active center concentration as well as calcination temperature on the PL properties were studied in detail. The results showed that the incorporation of Li+ ions into the YPO4 :Eu3+ lattice could induce a remarkable improvement of the PL intensity. The highest emission intensity was observed with the compound of 5%Li+ and 5%Eu3+ co-doped YPO4 , whose brightness was increased by a factor of more than 2.2 in comparison with that of the YPO4 :5%Eu3+.     

Comparison of Microstructures and Properties Obtained After Different Heat Treatment Strategies of High Strength Low Alloyed Steel

The influence of different heat treatment strategies on the microstructure and properties of 42SiCr steel was investigated.To compare the benefit of innovative treatment methods with more conventional ones,several strategies based on a new quenching and partitioning (Q-P) process were designed together with several strategies using more traditional quenching and tempering process.Different combinations of mechanical properties were obtained with ultimate strengths in the range of 1818-2120 MPa and ductility between 10% and 24%.Resulting microstructures were martensitic with 0-12% of retained austenite and they were analyzed by laser scanning confocal microscopy,transmission electron microscopy and X-ray diffraction phase analysis.