Concentration-Dominated Temperature-Dependence of Upconversion Luminescence in Gd6WO12 Nanophosphor Co-Doped with Er3+ and Yb3+

2016 ◽  
Vol 16 (4) ◽  
pp. 3534-3541
Author(s):  
Yanqiu Zhang ◽  
Baojiu Chen ◽  
Xiangping Li ◽  
Jiashi Sun ◽  
Jinsu Zhang ◽  
...  
Keyword(s):  
Upconversion Luminescence ◽  
Thermal Quenching ◽  
Precipitation Method ◽  
X Ray Diffraction ◽  
X Ray ◽  
Two Photon ◽  
Microscopic Morphology ◽  
Co Precipitation ◽  
Co Doped ◽  
Scanning Electron

Nanosized Gd6WO12 phosphors containing various Er3+ concentrations and fixed Yb3+ concentration were synthesized by a co-precipitation method. The crystal structure and microscopic morphology of the obtained nanophosphors were characterized by means of X-ray diffraction (XRD) and field emission scanning electron microscopy (FE-SEM). Two-photon processes for both the green and red upconversion (UC) emissions were confirmed by analyzing the dependence of UC intensities on 980 nm laser working current. UC emission intensity changing with temperature displays different trends for the samples with different Er3+ concentrations. The experimental results indicated that thermal quenching behavior of UC luminescence could not be simply explained by crossover mechanism. The enhancement for green UC emission in the sample with higher Er3+ concentration was discussed. Finally, the Er3+ concentration dependence of UC luminescence was experimentally observed, and its mechanisms were analyzed.

Synthesis and Luminescence Properties of Yb3+/Ho3+ Co-Doped Lu2O3 Nanocrystalline Powders

2007 ◽  
Vol 280-283 ◽  
pp. 521-524
Author(s):  
Li Qiong An ◽  
Jian Zhang ◽  
Min Liu ◽  
Sheng Wu Wang
Keyword(s):  
Electron Microscopy ◽  
Upconversion Luminescence ◽  
Nanocrystalline Powders ◽  
Precipitation Method ◽  
X Ray Diffraction ◽  
Excitation Spectra ◽  
X Ray ◽  
Transmission Electron ◽  
Co Precipitation ◽  
Co Doped

Yb3+ and Ho3+ co-doped Lu2O3 nanocrystalline powders were synthesized by a reversestrike co-precipitation method. The as-prepared powders were examined by the X-ray diffraction and transmission electron microscopy. The phase composition of the powders was cubic and the particle size was in the range of 30~50 nm. Emission and excitation spectra of the powders were measured by a spectrofluorometer and the possible upconversion luminescence mechanism was also discussed.

Synthesis of Magnetic Modified Organobentonite as Adsorbent for Degradation of Orange II

2013 ◽  
Vol 838-841 ◽  
pp. 2306-2309
Author(s):  
Guang Hua Wang ◽  
Kun Chen ◽  
Wen Bing Li ◽  
Dong Wan ◽  
Qin Hu ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Reaction Medium ◽  
Precipitation Method ◽  
Basal Spacing ◽  
Orange Ii ◽  
X Ray Diffraction ◽  
X Ray ◽  
Ft Ir ◽  
Co Precipitation ◽  
Scanning Electron

Magnetic modified organobentonite (Fe3O4/CTAB–Bent) was synthesized by chemical co-precipitation method in which CTAB–Bent was firstly achieved via ion–exchange.The composite materials have been characterized by powder X–ray diffraction (XRD), Fourier transform infrared spectroscopy (FT–IR) and Scanning electron microscopy (SEM) . The results revealed that basal spacing of bentonite was increased through organic modification and the Fe3O4 particles synthesized which covering the surfaces of bentonite .Compared with natural bentonite, the adsorption capacity of Fe3O4/CTAB–Bent for Orange II was greatly enhanced and can be easily separated from the reaction medium by an external magnetic field after the treatment.

Effects of Aging and Temperature on the Oriental Growth of Hydroxyapatite

2011 ◽  
Vol 308-310 ◽  
pp. 2180-2186
Author(s):  
Hui Yang ◽  
Fei Fei Huang ◽  
Ke Wei Xu
Keyword(s):  
Sem Analysis ◽  
Precipitation Method ◽  
X Ray Diffraction ◽  
Directional Growth ◽  
X Ray ◽  
Preparation Conditions ◽  
A Value ◽  
Co Precipitation ◽  
Effects Of Aging ◽  
Scanning Electron

In order to find a simple way to prepare oriental HA, only by controlling the preparation conditions, a co-precipitation method was used to prepare an oriented HA. The influences of temperature and aging on its directional growth were investigated kinetically and thermodynamically. The chemical composition was characterized by X-Ray diffraction and Fourier transform infrared. The morphologies were observed by scanning electron microscopy (SEM). The oriented parameters of HA (c/a) were calculated by Scherrer equation. The results show that the temperature rise in the process of synthesis, aging or calcining inhibited the growth of HA crystal in the direction of c-axis. Aging for 24 h benefited the growth along c-axis, whereas aging for 36 h was in favor of the decreasing of the c/a value. The supernatant-replacement during aging exerted the same effect on the growth with the rising of temperature. The SEM analysis result shows that the morphology of the produced HA particles looked like a uniform needle shape and had a good dispersion.

Preparation and Characterization of Ag and Co Doped ZnO Nano Particles

2012 ◽  
Vol 584 ◽  
pp. 248-252
Author(s):  
B. Sankara Reddy ◽  
S. Venkatramana Reddy ◽  
R.P. Vijaya Lakshmi ◽  
N. Koteeswara Reddy
Keyword(s):  
Blue Emission ◽  
Photo Luminescence ◽  
Hexagonal Structure ◽  
Nano Particles ◽  
Precipitation Method ◽  
X Ray Diffraction ◽  
X Ray ◽  
Doped Zno ◽  
Co Precipitation ◽  
Co Doped

Pure ZnO and Ag, Co doped ZnO nano particles [Zn1-xAgxCoyO, where x = 0.00 and 0.05, y = 0.05] were synthesized by chemical co precipitation method without use of surfactant. All the prepared samples calcinated in 1 hour at 500oC, after that the morphology of the samples were evaluated by Scanning Electron Microscope (SEM). The X- ray diffraction (XRD) results indicated that the synthesized co-doped ZnO nano crystals had the pure hexagonal structure without any significant change in the structure affected by Ag and Co substitution. Dopant elements Ag and Co are present in the ZnO host material and conformed by Energy Dispersive Analysis of X-ray Spectra (EDAX). The incorporation of Ag+ in the place of Zn2+ has made a considerable decrease in the size of nano crystals as compared to pure ZnO nano particles (It is to be noted that Co should be kept constant at 5 mol %). Blue emission was observed by Photo Luminescence (PL) Spectra.

Study on Preparation of LiNi0.5Co0.2Mn0.3O2 Precursor-Spherical Ni0.5Co0.2Mn0.3O2(OH)2

2015 ◽  
Vol 816 ◽  
pp. 676-681 ◽  
Author(s):  
Xiao Long Qu ◽  
Zheng Fu Zhang ◽  
Jin Cheng ◽  
Xiao Yan Wang
Keyword(s):  
Particle Size ◽  
Electron Microscope ◽  
Scanning Electron Microscope ◽  
Precipitation Method ◽  
X Ray Diffraction ◽  
X Ray ◽  
Tap Density ◽  
Homogeneous Particle ◽  
Co Precipitation ◽  
Scanning Electron

The spherical Ni0.5Co0.2Mn0.3(OH)2 powders were prepared by ammonia-hydroxide co-precipitation method. The influence of different synthesizing factors on the precursors characteristic were investigated. The product prepared with optimized condition has tap density of D≥1.7g·cm-3, and middle particle size D50≈3.6μm. The X-ray diffraction (XRD) results showed that the precursor can be indexed by a hexagonal β-Ni (OH)2 structure. The scanning electron microscope (SEM) results showed that the powders had quasi-spherical pattern and homogeneous particle size distribution.

scholarly journals Method for preventing air pollution: Methane oxidation by two types of catalysts

2014 ◽  
Vol 25 (1) ◽  
pp. 43-46
Author(s):  
Cristina Ileana Covaliu ◽  
Gina Alina Traistaru ◽  
Gigel Paraschiv
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Air Pollution ◽  
Methane Oxidation ◽  
Sol Gel ◽  
Precipitation Method ◽  
X Ray Diffraction ◽  
X Ray ◽  
Co Precipitation ◽  
Scanning Electron

Abstract Methane oxidation using different catalysts is an useful process for preventing air pollution. This study presents the methane oxidation by two types of catalysts: Pd-Sn/Al2O3 and spinel mixed oxide, CuFe2O4. The Pd-Sn/Al2O3 was successfully prepared by sol-gel method and CuFe2O4 by co-precipitation method. The catalysts obtained have been characterized structurally, morphologically and texturally by X-ray diffraction (XRD), scanning electron microscopy (SEM) and specific surface area (BET). The catalytic activity tests regarding methane oxidation were also performed.

STUDY OF STRUCTURAL AND MAGNETIC PROPERTIES OF Co-DOPED In2O3 NANOPARTICLES

2011 ◽  
Vol 10 (04n05) ◽  
pp. 961-965 ◽  
Author(s):  
RAM PRAKASH ◽  
JUNG IL SONG ◽  
SHALENDRA KUMAR ◽  
CHAN GYU LEE
Keyword(s):  
Room Temperature Ferromagnetism ◽  
Precipitation Method ◽  
X Ray Diffraction ◽  
Xrd Pattern ◽  
Dc Magnetization ◽  
X Ray ◽  
Sem Micrograph ◽  
Magnetization Hysteresis Loop ◽  
Co Precipitation ◽  
Co Doped

In the present work, we have prepared Co doped In2O3 nanoparticles using co-precipitation method. The prepared nanoparticles were characterized by the X-ray diffraction, scanning electron microscopy and dc magnetization hysteresis loop measurements. From the X-ray diffraction analysis it observed that all sample exhibits single phase polycrystalline nature. All the diffraction lines correspond to the bixbyite cubic structure. The full width half maximum (FWHM) calculated from XRD pattern has been found to decrease with increase in the Co contents, indicating that particle size decreases with increase in the Co concentration. FE–SEM micrograph reflects the nanocrystalline behavior of all the samples and shows that doping of Co ions hinders growth of the particles. DC magnetization measurements reveal that Co -DOPED In2O3 samples exhibits room temperature ferromagnetism.

Fabrication, Properties and Laser Performance of Indium-Substituted YAG:Ho Phosphor by Co-Precipitation Method

2013 ◽  
Vol 320 ◽  
pp. 40-43 ◽  
Author(s):  
Shi Xing Liu ◽  
Wei Zhang ◽  
Zheng Fa Hu ◽  
Hao Yi Wu ◽  
Xia Sheng
Keyword(s):  
Photoluminescence Property ◽  
Critical Distance ◽  
Precipitation Method ◽  
X Ray Diffraction ◽  
X Ray ◽  
Garnet Phase ◽  
Yttrium Aluminum ◽  
Method Effects ◽  
Co Precipitation ◽  
Scanning Electron

Ho-doped Yttrium aluminum indium garnet, Y3Al4.5In0.5O12 (YAIG), was synthesized by co-precipitation method. Effects of Ho concentration, reaction mechanism, crystallinity and luminescence properties of the phosphor powders were studied using the X-ray diffraction, thermo-gravimetry Analyzer,scanning electron microscopy and photoluminescence. The performances of samples were analyzed by changing the concentration of Ho3+ and the substitution of indium for aluminum. The results showed that pure cubic garnet phase was formed in the Indium-substituted samples, and the critical distance of the energy transfer was 1.41 nm. Both the excitation and emission intensities increased firstly and then decreased with the increasing of Ho3+ concentration. When the concentration of Ho3+ reached 15%, the photoluminescence property of the sample was best.

Synthesis of LiFePO4 Cathode Materials by a Chemical Method

2011 ◽  
Vol 675-677 ◽  
pp. 57-60
Author(s):  
Yuan Sun ◽  
Xiu Juan Zhao ◽  
Rui Ming Ren
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Chemical Method ◽  
Single Phase ◽  
Raw Materials ◽  
Precipitation Method ◽  
X Ray Diffraction ◽  
X Ray ◽  
Co Precipitation ◽  
Scanning Electron

The olivine-type LiFePO4 powder was prepared by a chemical method using the synthesized FePO4⋅2H2O, LiOH and glucose as raw materials. The synthesized FePO4⋅2H2O powder was obtained by co-precipitation method. FePO4⋅2H2O and LiFePO4 powders were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The results showed the synthesized FePO4⋅2H2O powder at pH of 2.05 was in a single phase and nearly spherical in shape. Using the synthesized powders to prepared LiFePO4 at 600 °C in vacuum for 2 h was nearly spherical in shape and whose size was in the range of 0.1-0.5μm.

Magnetically recyclable silica-coated magnetite-molybdate nanocatalyst and its applications in N-formylation reactions under solvent-free conditions-

2022 ◽  
Vol 19 ◽  
Author(s):  
Runjhun Tandon ◽  
Shripad Patil ◽  
Nitin Tandon ◽  
Pushpendra Kumar
Keyword(s):  
Catalytic Activity ◽  
Solvent Free ◽  
Precipitation Method ◽  
X Ray Diffraction ◽  
X Ray ◽  
Solvent Free Conditions ◽  
Ft Ir ◽  
Co Precipitation ◽  
Coated Nanoparticle ◽  
Scanning Electron

Abstract: A novel magnetite silica-coated nanoparticle-supported molybdate nanocatalyst has been prepared successfully by a simple co-precipitation method. Prepared nanocatalyst has been characterized by different techniques like Fourier Transmission Infrared Spectroscopy (FT-IR), X-ray diffraction (XRD), Field Emission Scanning Electron Microscope (FE-SEM) and Energy Dispersive X-ray Spectroscopy (EDX). Further, the catalytic activity of the nanocatalyst was explored for N-formylation reactions under solvent-free conditions. Interestingly, the catalyst could be reused for 10 cycles and only 2 mol % of the catalyst was sufficient to catalyze the N-formylation reaction at 700C under solvent-free conditions.

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