Preparation and Upeonversion Lumineseenee ofNanoerystailine Gd2O3： Er^3＋, Yb^3＋

Nanocrystalline Gd1.77Yb0.2Er0.03O3 samples were prepared by combustion and precipitation methods. Structures and upconversion luminescence properties of samples were studied. The results of XRD show that all samples are cubic structure, the average crystallite size could be calculated as 23 nm and 39 nm, respectively. The lattice constants were obtained. The FT-IR spectra were measured to investigate the vibrational feature of the samples. Upconversion luminescence spectra of samples under 980 nm laser excitation were investigated. The strong red emission of samples were observed, and attributed to 4F9/2→4I152 transitions of Er^3＋ ions, the emission intensity for sample synthesized by precipitation method is stronger compared to that of combustion method. The possible upconversion luminescence mechanisms in nanocrystalline Gd1.77Yb0.2Er0.03O3 were discussed.     

Upeonversion Luminescence of Er3＋, Tin3＋ and Yb3＋ Co-doped Gd3Ga5O12 Nanocrystals

A series of Er3+,Tm3+ and Yb3+ doped Gd3Ga5O12 nanocrystals were prepared by a combustion method.The X-ray diffraction(XRD),field emission scanning electron microscope(FESEM)and upconversion(UC)emission spectra were used to characterize the samples.The results of XRD indicate that Gd3Ga5O12:Er3+,Tm3+,Yb3+ nanocrystals with cubic phase can be obtained.Under the excitation of a 980 nm laser,the different rare earth ions doped Gd3Ga5O12 nanocrystals show upconversion luminescence involving the green emission attributed to the 2H11/2→4I15/2,4S3/2→4I15/2 transitions of Er3+ ions,respectively,the red emissions assigned to the 4F9/2→4I15/2 transitions of Er3+ ions and the 1G4→3F4 as well as 3F2,3→3H6 transitions of Tm3+ ions,respectively,the blue emission attributed to 1G4→3H6 transitions of Tm3+ions,and the near-infrared assigned to the 3H4→3H6 transitions of Tm3+ ions.The CIE coordinates for the samples are calculated.The dependence of their upconversion luminescence properties on Yb3+ ion concentration is investigated.     

Preparation and Characterization of Fe^3＋ -doped Nanometer TiO2 Photocatalysts

Fe^3＋ -doped nanometer TiO2 photocatalysts were prepared by sol-gel technique. TiO2 powders with different Fe^3＋ / Ti^4 ＋ molar ratios ranging from 0. 05% to 25% were synthesized by calcinating the gels in the temperature range of 200-600 ℃ . The effects of the content of iron ions and calcination temperature on the physical properties of the powders and their photocatalytic activities were examined by the photodecorapositon of methyl orange in sunlight. The results show that Fe dopant can decrease the temperature of nanatase-ratile transformation. The ideal photocatalytic property was achieved when the sample with an Fe^3＋ / Ti^4＋ ratio of 20 at% was calcined at about 300 ℃ for an hour, which is superior to that of commercial Degussa P-25. The optimum microstructure of the Fe-doped TiO2 for a high photocatalytic activity in sunlight is consisted of nanatase and ratile.     

Luminescent properties of BaO-La2O3-B2O3 glasses with dopant

The luminescent properties of glasses synthesized in air atmosphere by conventional high temperature process were stud{ed. The emissions spectra of Eu^2 and Eu^3 were observed in BaO-La2O3-B2O3-Eu2O3 glasses.The results show that the broad emission peaks at 430 nm correspond to 5d→4f emission transition of Eu^2 , the sharp emission peaks at 592, 616, 650 and 250 nm correspond to 5^D0→1Fj(j=1--4) emission transition of Eu^3 ,respectively, which indicates that the BaO-La2O3a-B2O3-Eu2O3 glass can convert ultraviolet and green omponents of sunlight into blue and red light so as to increase the intensity of blue and red light, respectively. The luminescent in--tensity of Eu^2 increases with increasing the molar ratio of Tb^3 in BaO-La2O3-B2O3-Eu2O3a-Tb4O3 glasses, whereas the luminescent intensity of Eua^3 decreases. So the luminescent intensity of Eu(Ⅲ,Ⅱ) is influenced by Tb^3 .These phenomena can be explained by electron transfer mechanism; Eu^3 (4f6) Tb^3 (4f^8)→Eu^2 (4f′) Tb^4 (4f′). Taking advantage of the luminescent properties of BaO-La2O3-B2O3-Eu2O3 glasses, light-conversion glass for agriculture can be produced.     

Polyhydroxyl-aluminum pillaring improved adsorption capacities of Pb^2＋ and Cd^2＋ onto diatomite

In order to greatly improve adsorption capacity, the diatomite was pillared by polyhydroxyl-aluminum.A series of adsorption tests were conducted to obtain the optimum condition for pillared diatomite synthesis. The scanning electron microscopy （SEM）, Fourier transform infrared spectroscopy （FTIR）, surface area and porosity analyzer and micro-electrophoresis were used to determine pore structure and surface property.The pillared diatomite attaining the optimal adsorption densities （qe） of Pb^2＋ and Cd^2＋ was synthesized with the following conditions： Addition of pillaring solution containing Al3＋-oligomers with a concentration range of 0.1-0.2 mol/L to a suspension containing Na＋-diatomite to obtain the required Al/diatomite ratio of 10 mmol/g; synthesis temperature of 80 ℃ for 120 min; aging at a temperature of 105 ℃ for 16 h. The adsorption capacities of Pb^2＋ and Cd^2＋ on pillared diatomite increase by 23.79% and 27.36% compared with natural diatomite, respectively. The surface property of pillared diatomite is more favorable for ion adsorption than natural diatomite. The result suggests that diatomite can be modified by pillaring with polyhydroxyl-aluminum to improve its adsorption properties greatly.     

One new photon avalanche phenomenon of Er^3＋ at 976 nm excitation

A photon avalanche phenomenon was observed in Er^3＋ and Li^ ＋ eodoped ZnO nanocrystals at room temperature under excitation around 976 nm. When the excitation power was over 120 mW/mm^2 , we found that the upconversion of red emission was generated by a four-photon absorption process and might be caused by intense interaction between neighboring Er^3 ＋ ions ： ^4 F7/2 ＋ ^4 I11/2 → 2^4 F9/2. When the excitation power was over the threshold of 240 mW/mm^2, the green emission avalanche upconversion was generated through an excitedstate absorption process ： ^4 F9/2 ＋ photon →^2 H9/2. The study extends the knowledge of this ion to a wider range of upconversion application.     

Influence of addition of B2O3 on properties of Yb^3＋-doped phosphate laser glass

The three host glasses doped with Yb^3＋ were prepared by means of conventional melt quenching technology, and the influence on physical and spectral properties of phosphate glass due to addition of B2O3 was investigated and compared with silicate glass. The results show that due to the existence of OH^- impurities which induce the non-radiative route, the fluorescence lifetime of phosphate glass is shorter, so silicate glass has better spectral properties than phosphate glass. Silicate glass has more excellent thermal-mechanical properties than phosphate glass, but with the addition of B2O3, thermal-mechanical properties of phosphate glass are improved greatly without fluorescence quenching effect, and this kind of borophosphate glass will be the candidate to be used in high average power solid state laser.     

Removal of Pb^2＋ and Cd^2＋ by adsorption on clay-solidified grouting curtain for waste landfills

Pb^2＋ and Cd^2＋ in leachate were adsorbed on clay-solidified grouting curtain for waste landfills with equilibrium experiment. The cation exchange capacity was determined with ammonium acetate. And the concentration of heavy metal cations in leachate was determined with atomic absorption spectrophotometer. Their equilibrium isotherms were measured, and the experimental isotherm data were analyzed by using Freundlich and Langmuir models. The results show that the adsorption capacities of the heavy metal cations are closely related to the compositions of clay-solidified grouting curtain, and the maximum adsorption appears at the ratio of cement to clay of 2 ： 4 in the experimental conditions. At their maximum adsorption and pH 5.0, the adsorption capacities of Pb^2＋ and Cd^2＋ are 16.19 mg/g and 1.21 mg/g. The competitive adsorption coefficients indicate that the adsorption of clay-solidified grouting curtain for Pb^2＋ is stronger than that for Cd^2＋. The adsorption process conforms to Freundlich＇s model with related coefficient higher than 0. 996.     

Optimization of spectroscopic properties of ytterbium-doped laser glasses

Four laser glasses with high emission cross sections are experimentally obtained. The laser performance parameters are determined from the spectroscopic parameters of these glasses and compared with those of developing laser glasses abroad. It is shown that Yb~(3-)-doped telluorogermanate, Yb~(3 )-doped niobosilicate glasses have the highest emission cross section and gain coefficient, the smallest minimum pumping intensity and saturation pumping intensity, and the lowest minimum fraction of excited ions. Yb~(3 )-doped borate glass follows just behind them. These glasses have some spectroscopic advantages over laser glasses developed recently elsewhere. Yb~(3 )-doped phosphate glass is comparable to phosphate laser glass which had high emission cross section and was developed recently by HOYA Corporation in Japan.The domestic glasses with optimum spectroscopic properties may be promising candidates for applications in high-average power and high-peak power solid state lasers, especially laser for the ne     

EXAFS STUDY OF THE LOCAL STRUCTURE OF Ga IN Ga_2O_3-P_2O_5 GLASSES

Room temperature EXAFS spectra of a series ofgallium phosphate glasses have been obtained in alaboratory EXAFS facility.Fourier transform isemployed for EXAFS data analysis.Low-cristobalitetype GaPO_4 crystal is used as a standard specimento extract the local structure parameters of Gaatoms in Ga_2O3-P_2O_5 glasses.The Ga-O average bondlength is 1.75-1.86 and Ga atoms can form both[GaO_4] tetrahedra and [GaO_6] octahedra in some ofthese glasses.The coordination number of Ga atomschanges from six to four with the increase of Ga_2O_3content,and this change becomes more significantwhen the Ga_2O_3 content exceeds 30mol%.The anomalouschange of the refractive index at 30mol% Ga_2O_3 iscaused by the change of the local structure of Gafrom [GaO_6] octahedra to [GaO_4] tetrahedra.A simpleformula to estimate the concentration of six foldcoordinated Ga atoms in glasses is derived based onaverage bond length measured from the EXAFS.     

Mechanism and behaviors of Cr3+-doped TiO2

TiO₂ powder and TiO₂ thin film on the surface of glazed ceramic tile were prepared by sol-gel method. The influences of different doping Cr³⁺ concentration on the photocatalytic activity of TiO₂ were discussed, UV-visible and X-ray diffraction analysis were used to test the performance of TiO₂ powder and film. The results indicate that photocatalytic activity of doping Cr³⁺-TiO₂ thin film is higher than that of powder, and the interaction between Cr³⁺-doped and substrate can greatly enhance the photocatalytic activity. The results of X-ray diffraction and photoabsorption show that the Cr³⁺-doped energy level in TiO₂ is 0.62 eV high from the top of valence band, which belongs to the type of deep energy level doping. On the basis of the semiconductor energy level theory and Cr³⁺ dopant energy level, the semiconductor energy level model of Cr³⁺ in TiO₂ powder and thin film were established, and the doping mechanisms of Cr³⁺-doped in TiO₂ powder and thin film were analyzed. Foundation item: Project (20466001) supported by the National Natural Science Foundation of China     

Frequency up-conversion luminescence properties and mechanism of Tm<Superscript>3+</Superscript>/Er<Superscript>3+</Superscript>/Yb<Superscript>3+</Superscript> co-doped oxyfluorogermanate glasses

Oxyfluoride glasses were developed with composition 60GeO 2 ·10AlF 3 ·25BaF 2 ·(1.95-x)GdF 3 · 3YbF 3 ·0.05TmF 3 ·xErF 3 (x=0.02,0.05,0.08,0.11,0.14,0.17)in mole percent.Intense blue(476 nm),green(524 and 546 nm)and red(658 nm)emissions which identified from the 1G 4 →3H 6 transition of Tm3+and the(2H 11/2 ,4S 3/2 )→4I 15/2 ,4F 9/2 →4I 15/2 transitions of Er3+,respectively,were simultaneously observed under 980 nm excitation at room temperature.The results show that multicolor luminescence including white l...     

Preparation and electrical properties of BaPbO3 thin film

BaPbO3 thin films were deposited on Al2O3 substrates by sol-gel spin-coating and rapid thermal annealing. The microstructure and phase of BaPbO3 thin films were determined by X-ray diffractometry, scanning electrons microscopy and energy dispersive X-ray spectrometry. The influence of annealing temperature and annealing time on sheet resistance of the thin films was investigated. The results show that heat treatment, including annealing temperature and time, causes notable change in molar ratio of Pb to Ba, resulting in the variations of sheet resistance. The variation of electrical properties demonstrates that the surface state of the film changes from two-dimensional behavior to three-dimensional behavior with the increase of film thickness. Crack-free BaPbO3 thin films with grain size of 90 nm can be obtained by a rapid thermal annealing at 700 ℃ for 10 min. And the BaPbO3 films with a thickness of 2.5 μm has a sheet resistance of 35 Ω·-1.     

Leaching kinetics of low grade zinc oxide ore in NH3-NH4Cl-H2O system

The leaching kinetics of low grade zinc oxide ore in NH3-NH4Cl-H2O system was studied. The effects of ore particle size, reaction temperature and the sum concentration of ammonium ion and ammonia on the leaching efficiency of zinc were examined. The leaching kinetics of low-grade zinc oxide ore in NH3-NH4Cl-H2O system follows the kinetic law of shrinking-core model. The results show that diffusion through the inert particle pores is the leaching kinetics rate controlling step. The calculated apparent activation energy of the process is about 7.057 kJ/mol. The leaching efficiency of zinc is 92.1% under the conditions of ore particle size of 69μm, holding at 80℃ for 60 min, sum ammonia concentration of 7.5 mol/L, the molar ratio of ammonium to ammonia being 2：1, and the ratio （g/mL） of solid to liquid being 1：10.     

Retention of clay-solidified grouting curtain to Cd^2＋ , Pb^2＋ and Hg^2＋ in landfill of municipal solid waste

The effects of components and their ratio of groups on anti-seepage capability of clay-solidified grouting curtain and its permeability of heavy metal cations were investigated by permeating experiments, using reactive solute transport model to study the permeation of heavy metals (Cd²⁺, Pb²⁺ and Hg²⁺). The study of permeating for different mixture ratios of cement and clay indicates that hydraulic conductivity of clay-solidified groupting curtain with different ratios of solid to liquid or with the same ratio of solid to liquid but with different ratios of cement to clay is changed. The laboratory simulation test results also show that precipitates produced in heavy metal cation migration process in curtain block up water flowing passage which makes the hydraulic conductivity of the solution-permeated curtain decrease with the leakage time. The permeation velocities for different heavy metal cations vary with ionic concentration, exchange capacity and ion radius etc. The test results indicate that the permeation rapidity order of heavy metals cations in clay-solidified grouting curtain is Hg²⁺ > Pb²⁺ in the same experimental circumstance. In addition, permeability for different mixture ratios and antisepsis capabilities of clay-solidified grouting curtain were studied in tests. Foundation item: Project (2000-65) supported by the Fund for University Key Teacher by the Ministry of Education of China     

Near-infrared quantum cutting in Pr3+-Yb3+ Co-doped oxyfluoride glass ceramics containing CaF2 nanocrystals

The Pr³⁺-Yb³⁺ co-doped oxyfluoride glass-ceramics containing CaF₂ nanocrystals were obtained by thermal treatment on the as-made glasses. The structure of fluoride nanocrystals was investigated. The light-emitting mechanism of Pr³⁺-Yb³⁺ in the near infrared region was proposed and the fluorescence lifetime and quantum efficiency was calculated. The results indicate that the main phase in the oxyfluoride glassceramics is CaF₂ nanocrystal sized at 30 nm. Energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD) have proved the incorporation of Pr³⁺ and Yb³⁺ into CaF₂ nanocrystal lattice. Near-infrared quantum cutting involving Yb³⁺ 980 nm and 1 015 nm (²F_5/2→² F _7/2) emission has been achieved upon the excitation of the ³ P ₀ energy level of Pr³⁺ at 482 nm. The fluorescence lifetime decreases sharply and quantum efficiency increases with increasing Yb³⁺ concentration, and the optimal quantum efficiency reaches 191%.