Nd-doped SnO₂:characterization and its gas sensing property

Nd-doped(2%,5%,10% in mass ratio) SnO2 powders were prepared via a facile hydrothermal procedure.The as-prepared samples were characterized by X-ray diffraction(XRD),scanning electron microscopy(SEM),and Brunauer-Emmett-Teller(BET) specific surface area analyzers.Results showed that the Nd-doped SnO2 samples had more uniform and smaller primary particles compared with the pure sample,the particle size of the doped SnO2 decreased gradually with the increase of Nd,and the specific surface area also increased with the increase of the doped Nd.When used as gas sensing materials,the 5% and 10% Nd-doped sample showed high sensitivity and selectivity to ethanol.Furthermore,the Nd-doped sample showed fast response and recovery time to ethanol gas.This could be attributed to their small diameter,large surface area and Nd element doping.     

Synthesis and photocatalytic property of Ce-doped SnO2

Pure SnO₂ and Ce-doped (1%, 4%, 7%, 10% in mass ratio) SnO₂ powders were prepared by a simple sol-gel method. The as-prepared samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and Brunauer-Emmett-Teller (BET) specific surface area analyzers. Results showed that the 7% Ce-doped sample has a particle size of 0.1-0.3 μm with a narrow particle size distribution while the pure SnO₂ was consisted of large agglomerated particles with a diameter up to several micrometers. When used as the catalyst to degrade methyl orange (MO), the 7% Ce-doped sample showed best photocatalytic property. These properties can be attributed to the large surface area and small particle size of the 7% Ce-doped sample.     

La-doped SnO₂:synthesis and its electrochemical property

Tin dioxide(SnO2) and La-doped(1%,5%,10% in mass ratio) SnO2 samples were prepared via a hydrothermal method. The as-prepared powders were characterized by X-ray diffraction(XRD) and scanning electron microscopy(SEM) . Results showed that the particle size of SnO2 decreased gradually with the increase of the doped La element. When used as anode materials of Li ion battery,the La-doped samples exhibited better cycling performance than the pure SnO2,and the cycling performance of the La-doped samples got better and better with the increase of the doped La. The better electrochemical performance of the doped material could be attributed to the doping of La element,which not only enabled SnO2 powders to have a good dispersivity but also reduced their particle size.     

Nd-doped SnO2: characterization and its gas sensing property

Nd-doped (2%, 5%, 10% in mass ratio) SnO₂ powders were prepared via a facile hydrothermal procedure. The as-prepared samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and Brunauer-Emmett-Teller (BET) specific surface area analyzers. Results showed that the Nd-doped SnO₂ samples had more uniform and smaller primary particles compared with the pure sample, the particle size of the doped SnO₂ decreased gradually with the increase of Nd, and the specific surface area also increased with the increase of the doped Nd. When used as gas sensing materials, the 5% and 10% Nd-doped sample showed high sensitivity and selectivity to ethanol. Furthermore, the Nd-doped sample showed fast response and recovery time to ethanol gas. This could be attributed to their small diameter, large surface area and Nd element doping.     

Synthesis and characterization of CaAl_xO_y:Eu²⁺ phosphors prepared using solution-combustion method

Europium-doped calcium aluminate(CaAlxOy:Eu2+) phosphors were obtained at low temperatures(500 oC) by the solution-combustion of corresponding metal nitrate-urea solution mixtures.The particle size and morphology and the structural and luminescent properties of the as-synthesized phosphors were examined by means of scanning electron microscopy(SEM),X-ray diffraction(XRD),Auger spectroscopy,transmission electron spectroscopy(TEM) and photoluminescence(PL).It was found that the Ca:Al molar ratios showed greatly influence not only on the particle size and morphology,but also on their PL spectra and structure.With the Ca:Al molar ratios increasing from 6:100 to 26:100,the structure of as-synthesized phosphor changed from CaAl12O19 to monoclinic CaAl2O4 and the dominant emitting light from red to blue,implying that the oxidation state of doped europium ions changed from trivalent to divalent due to the structure variation of host lattice.A blue phosphor with almost pure phase can be easily prepared by solution combustion method with suitable Ca:Al molar ratio.     

Synthesis and characterization of yttrium and antimony codoped SnO₂ conductive nanoparticles

Y was used as a dopant in preparing conductive powder to improve its performance. Y and Sb co-doped SnO2 conductive nanoparticles were prepared by the complexation-coprecipitation method with Sn,Sb2O3 and Y2O3 as the raw materials. Crystal phase,thermal behavior and structure of the prepared conductive nanoparticles were characterized by X-ray diffraction(XRD) ,thermal analysis(TG-DSC) ,Fourier transform infrared(FTIR) and transmission electron microscopy(TEM) techniques,respectively. The Y and Sb co-doped SnO2 conductive nanoparticles with a structure of tetragonal rutile had intense absorption in 4000-2500 cm-1,and the diameter ranged from 10 to 30 nm. The resistivity of Y and Sb co-doped SnO2 conductive nanoparticles was as low as 0.09 Ω·cm which was 4.6 times lower than that of Sb doped SnO2 conductive nanoparticles.     

Facile synthesis of visible light excited La_1-xGd_xF₃:Eu³⁺ micro-meter sphere using polyvinylpyrrolidone as a template

Lanthanide fluorides exhibited unique luminescent properties in terms of their low phonon energy can restrict the luminescence quenching and extend luminescent lifetimes.Here,a room-temperature co-precipitation method was used to synthesize europium(III) activated La1-xGdxF3 solid phosphors.X-ray diffraction(XRD) data confirmed the crystalline phases of synthesized sample belongs to orthorhombic system.All the as-derived materials exhibited red luminescence(5D0→7F1) under the excitation at longer wavelengths(394 and 466 nm).The powder with the most intense emission was achieved in terms of 10 mol.% doping concentration(Eu content,La/Gd=1/9) and sample sintered at 700 oC.Scanning electron microscopy(SEM) investigated the morphology and crystalline of the samples,showing that many regular and large balls(5-10 μmol/L) were dispersed within the micro-meter scale composites.We proved that the above crystal growth structures were controllable and predicable based on the surface functionalization by polyvinylpyrrolidone ligand.     

Size dependence of up-conversion luminescence of NaYF₄:Yb³⁺/Tm³⁺

Tm3+/Yb3+ codoped NaYF4 microcrystals were synthesized using a hydrothermal method.The bright upconversion light was observed under 980 nm excitation.The upconversion luminescence was systematically investigated at different Yb3+ concentrations and different reaction temperatures and time.The sample with 60% Yb3+ concentration and reacting at 180 oC for 24 h possessed the highest luminescent efficiency.The higher luminescent efficiency was contributed to a large surface area.The large surface area induced the large vibration mode by absorbed H2O and CO2.The larger vibration mode could enhance the energy transfer efficiency from the excited Yb3+ to Tm3+ by the process of phonon assisted energy transfer.     

Electrospinning synthesis and luminescent properties of Lu₂O₃:Eu³⁺ nanofibers

One-dimensional Lu2O3:Eu3+ nanofibers were prepared by electrospinning followed by high-temperature calcinations.Thermogravimetric and differential thermal analysis,X-ray powder diffraction,Fourier transform infrared spectroscopy,scanning electron microscopy,photoluminescent spectra and decay curves were used to characterize the samples.Results showed that samples began to crystallize at ～500 oC and crystallized completely around 1000 oC.The average diameter of nanofibers(1000 oC annealed) was about 55 nm and the particle size of Lu2O3:Eu3+ increased with increasing annealing temperature.Under ultraviolet excitation,nanofibers exhibited typical red emission of Eu3+ in Lu2O3.The effect of heat-treatment temperature on luminescent properties of nanofibers was also discussed.     

Magnetic properties and magnetocaloric effects of manganite (La_0.8Ho_0.2)_2/3Ca_1/3MnO₃ and (La_0.5Ho_0.5)_2/3Ca_1/3MnO₃

We reported the magnetic properties and magnetocaloric effects(MCE) of(La0.8Ho0.2)2/3Ca1/3MnO3 and(La0.5Ho0.5)2/3Ca1/3MnO3 nanoparticles by sol-gel technique.With this method,we were able to obtain the samples with particle diameters ranging from 50 to 200 nm.In the(La1-xHox)2/3Ca1/3MnO3 compound,an external magnetic field induced a magnetic transition from an paramagnetic phase to a ferromagnetic phase above Ts=105-135 K,leading to magnetocaloric effects.The maximum value of ΔSM was 1.19 J/(kg·K) at 100 K and 2.03 J/(kg·K) at 152 K for a magnetic field change of 5 T.Because both samples had large relative cooling power(RCP) and wide δTFWHM,the study on systems with the(La1-xHox)2/3Ca1/3MnO3-related magnetic transitions may open an important field in searching good magnetic materials.     

Re-determination of the crystal structure of Ca₂Y₈Si₆O₂₆ and study on the luminescent properties of Ca₂Y₈Si₆O₂₆:Tb³⁺

The crystal structure of silicate oxyapatite Ca2Y8Si6O26 was indexed as hexagonal,space group P63/m,a=0.93515 nm,c=0.67872 nm,α=β=90°,γ=120°,V=0.5138692 nm3.Three strong peaks located at 32.079o,32.595o,and 50.104o with d=2.7903,2.74649,1.8194 was in accordance with,(112),and(213) planes.The optimum concentration of Tb3+ in Ca2Y8Si6O26 to yield highest photoluminescence intensity was 10 mol.% of Y3+.The corresponding excitation spectrum consisted of an intense broad band from 220 to 260 nm.The photoluminescence measurements showed that the green emission originated from 5D4-7F5 was predominant in the measured range with strong doublet lines at 543 and 549 nm.     

Photoluminescence study of SiO₂ coated Eu³⁺:Y₂O₃ core-shells under high pressure

Uniform core-shell Eu3+:Y2O3/SiO2 spheres were synthesized via precipitation and the Stber method.The structural transition of core-shell Eu3+:Y2O3/SiO2 was studied by using high pressure photoluminescence spectra.With pressure increasing,the emission intensities of 5D0→7F0,1,2 transitions of Eu3+ ions decreased and the transition lines showed a red shift.The relative luminescence intensity ratio of 5D0→7F2 to 5D0→7F1 transitions decreased with increasing pressure,indicating lowering asymmetry around Eu3+ ions.During compression,structural transformation for cores in the present core-shell Eu3+:Y2O3/SiO2 sample from cubic to monoclinic took place at 7.5 GPa,and then the monoclinic structure turned into hexagonal above 15.2 GPa.After the pressure was released,the hexagonal structure transformed back to monoclinic and the monoclinic structure was kept stable to ambient pressure.     

Ultraviolet-shielding and conductive double functional films coated on glass substrates by sol-gel process

Ultraviolet-shielding and conductive double functional films were composed of CeO2-TiO2 film and SnO2:Sb film deposited on glass substrates using sol-gel process.Ce(NO3)3·6H2O and Ti(C4H9O4),SnCl4 and SbCl3 were used as precursors of the two different functional films respectively.The CeO2-TiO2 films were deposited on glass substrates by sol-gel dip coating method,and then the SnO2:Sb films with different thickness were deposited on the pre-coated CeO2-TiO2 thin film glass substrates,finally,the substrates coated with double functional films were annealed at different temperatures.The optical and electrical properties of the CeO2-TiO2 films and the double films were measured by UV-Vis spectrometer and four probe resistance measuring instrument.The crystal structures and surface morphology of the films were characterized using XRD and optical microscope,respectively.The obtained results show that the ultraviolet-shielding rate of the glass substrates with CeO2-TiO2 films is not less than 90%,and transmittance in visible lights can reach 65%.With the thickness of the SnO2:Sb film increasing,its conductivity became better,and the surface resistance is about 260 Ω/ when the SnO2:Sb films were deposited 11 cycles of the dip on the pre-coated CeO2-TiO2 glass.The ultraviolet-shielding rate of the glass substrates with double functional films is higher than 97%,and the peak transmittance in the visible lights is 72%.Additionally,with increasing the heat treatment time,the Na+ of the glass substrates diffuses into the films,resulting in the particle size of SnO2 crystal smaller.     

Preparation and Characterization of CeO2-ZrO2 Solid Solution Ultrafine Particles Using Reversed Microemulsion

The development of the TWCs (three-way cata-lysts) was dictated bythe need to si multaneously con-vert the three main pollutants inthe exhaust gases ,i .e .,hydrocarbons (HCs) ,COand NOxpresent in theautomotive exhaust to H2O, CO2and N2[1]. Highestconvers…     

Study on analysis of crystal structure in CeO₂ doped with Er₂O₃ or Gd₂O₃

To simulate the effects of burnable poison doping in nuclear fuel UO2,Er2O3(or Gd2O3)-doped CeO2 pellets were prepared. Changes in lattice constant and atomic disordering for CeO2 due to the Er2O3 and Gd2O3 doping were measured by means of XRD and XAFS. By the Er2O3 doping,the lattice constant decreased,and a disordering of lattice structure was induced in the samples. The doping with Er2O3 also induced the disordering of atomic arrangement around Er atoms,which was observed through the change in XAFS spectra. In contrast,the effect of Gd2O3 doping was smaller than that of Er2O3 doping. The result was discussed in terms of ionic size of dopants in CeO2 crystal.     

Hydrothermal synthesis,structure study and luminescent properties of YbPO₄:Tb³⁺ nanoparticles

YbPO4:Tb3+ were synthesized by mild hydrothermal method.The luminescent properties,morphologies and structure of the obtained powders were characterized by photoluminescence(PL) spectra,FESEM,X-ray diffractometer(XRD) and FTIR.The results showed that the prepared YbPO4:Tb3+ nanoparticles were pure tetragonal phase and the average grain size varied with increasing of Tb3+ concentration.Hydrothermal temperature was revealed to be the key factor to enhance the emission intensity of YbPO4:Tb3+ phosphors.The spherical nanoparticles could be effectively excited by near UV(369 nm) light and exhibited green performance at 543 nm(5D4→7F5),489 nm(5D4→7F6) and 586 nm(5D4→7F4).The CIE chromaticity was calculated to be x=0.298,y=0.560.The YbPO4:Tb3+ nanoparticles exhibited potential to act as UV absorber for solar cells to enhance the conversion efficiency.     

Study on Transformation of CaO-Al₂O₃-SiO₂-MgO System Inclusions in ZG06Cr13Ni4Mo Stainless Steel

This paper aims at generally studying on the inclusions of ZGG06Cr13Ni4Mo ultra-low carbon stainless steel used for large scale hydraulic turbine sets. On the basis of analysis the industrial test samples, thermodynamic software FactSage is used to study inclusions transformation process in CaO-SiO2-Al2O3-MgO system while stainless steel is been smelting. The results illustrate the inclusions melting points and plasticity variation law. The reasonable inclusions plasticity controlling area is found out in low melting point. The melting point is up to 1280℃ While MgO weight concentration is 10% in CaO-SiO2-Al2O3-MgO system, SiO2, Al2O3 and CaO in inclusions are in weight concentration range of 50-70%, 10-20% and 10-40%, respectively. For purpose of gaining low melting point inclusions, silicon alumina radio in deoxidant should be controlled between 2-5 for ultra-low carbon stainless steel refining in industry.     

SiC粒径比对SiC_p/Al基复合材料组织及性能的影响

采用高压扭转(high pressure torsion)法将粒径比分别为1:1,1:7,1:21的SiC颗粒和纯铝粉末的混合物固结成金属基复合材料。利用金相显微镜、显微维氏硬度计、万能试验机和扫描电镜研究不同SiC粒径比对SiCp/Al复合材料显微组织和力学性能的影响。结果表明,与SiC粒径比1:1的试样相比,粒径比为1:7和1:21的试样中SiC颗粒分布更加均匀,颗粒间无明显团聚现象;大颗粒加入后对材料硬度的影响较为复杂,1:21试样硬度值最低;材料伸长率分别提高130%和113%,致密度也高于1:1的试样,材料断裂形式为韧性断裂。SiC粒径比为1:7试样的致密度、伸长率高于粒径比为1:21试样,综合性能较好。     

Optimization of BaMgAl₁₀O₁₇:Eu²⁺ phosphors by the substitution of Si-N bonds for Al-O bonds

We proposed a simple method to improve the thermal stability of BaMgAl10O17:Eu2+(BAM) phosphors by the substitution of Si-N bonds for Al-O bonds in the host lattice.Both photoluminescence properties and thermal stability under ultraviolet(UV) and vacuum ultraviolet(VUV) excitation could be significantly improved through Si-N incorporation.After thermal degradation at 600 °C for 1 h in air atmosphere,the Si-N doped sample(Ba0.88Eu0.12MgAl9.97Si0.03O16.97N0.03) had the highest emission intensity which was 22% and 40% stronger than that of as-received sample under UV and VUV excitation,respectively.This could be attributed to the stable local structure surrounding the Eu2+ ions and the lower electronegativity of nitrogen.     

约束弧等离子体制备铝纳米粉体的研究

利用自行研制的约束弧等离子体制备金属纳米粉试验装置,成功制备了平均粒度为44nm的铝纳米粉体。利用X射线衍射(XRD)、BET吸附法、透射电子显微镜(TEM)和相应选区电子衍射(SAED)等测试手段对所制备样品的晶体结构、形貌、粒度及其分布、比表面积进行性能表征。试验结果表明:约束弧等离子体法制备的铝纳米粉晶体结构为fcc结构的晶态,与体材料相比晶格常数发生膨胀。比表面积为41m2.g-1,粒径范围分布在20~70nm之间,平均粒径为44nm,粒度均匀,分散性好,呈规则球形链状分布。