Effect of pH values on photocatalytic properties of Bi<Subscript>2</Subscript>WO<Subscript>6</Subscript> synthesized by hydrothermal method

Highly crystalline orthorhombic Bi₂WO₆ powders were hydrothermally synthesized from aqueous solutions of Na₂WO₄ · 2H₂O and Bi (NO₃)₃ · 5H₂O over a wide range of pH. The effect of pH on morphologies, sizes and properties of the Bi₂WO₆ crystals was investigated. The band gaps of the as-prepared Bi₂WO₆ were determined from the onset of the absorption edge of UV-vis diffuse reflectance spectra. The methyl orange photodegradation was employed as a probe reaction to test the photocatalytic activity of the as-prepared samples under visible light irradiation. The photocatalytic activities of methyl orange degradation under visible light irradiation are strongly dependent on the pH used in the synthesis. The highest efficiency is observed at pH=7. Funded by the PCSIRT, the National Natural Science Foundation of China (Nos. 50532030 and 50625206) and the Zhejiang Provincial Natural Science Foundation of China (No. Z4080021)     

Morphology controlled synthesis and characterization of Bi2WO6 photocatalysts

Nest-like and multilayered-disk-like Bi₂WO₆ photocatalysts were synthesized through a hydrothermal strategy using thiourea and acetic acid as complexing agents. The nest-like Bi₂WO₆ showed excellent visible-light-driven photocatalytic performance, and it could decompose rhodamine B(RhB) within 100 minutes. This excellent performance resulted from its special microstructure and the relatively large surface area.     

Improved Breakdown Strength in (Ba<Subscript>0.6</Subscript>Sr<Subscript>0.4</Subscript>)<Subscript>0.85</Subscript>Bi<Subscript>0.1</Subscript>TiO<Subscript>3</Subscript> Ceramics with Addition of CaZrO<Subscript>3</Subscript> for Energy Storage Application

(Ba_0.6Sr_0.4)_0.85Bi_0.1TiO₃ ceramics doped with x wt%CaZrO₃ (x= 0-10) were synthesized by solid-state reaction method. The effects of CaZrO₃ amount on the dielectric properties and structure of (Ba_0.6Sr_0.4)_0.85Bi_0.1TiO₃ ceramics were investigated. X-ray diffraction results indicated a pure cubic perovskite structure for all samples and that the lattice parameter increased till x=5 and then slightly decreased. A homogenous microstructure was observed with the addition of CaZrO₃. Dielectric measurements revealed a relaxor-like characteristic for all samples and that the diffusivity γ reached the maximum value of 1.78 at x=5. With the addition of CaZrO₃, the dielectric constant dependence on electric field was weakened, insulation resistivity enhanced and dielectric breakdown strength improved obviously and reached 19.9 kV/mm at x=7.5. In virtue of low dielectric loss (tan δ<0.001 5), moderate dielectric constant (ε_r >1 500) and high breakdown strength (E_b >17.5 kV/mm), the CaZrO₃ doped (Ba_0.6Sr_0.4)_0.85Bi_0.1TiO₃ ceramic is a potential candidate material for high power electric applications.     

Structure and Electric Properties of （1-x）（Bi1/2Na1/2） TiO3-xBaTiO3 Systems

The structural, dielectric and piezoelectric properties of （1-x）（Bi1/2Na1/2） TiO3-xBaTiO3 ceramics were investigated for the compositional range, x=0.02, 0.04, 0.06, 0.08, 0.10. The samples were synthesized by a conventional solid-state reaction technique. All compositions show a single perovskite structure, and X-ray powder diffraction patterns can be indexed using a rhombohedral structure. Lattice constants and lattice distortion increase while the amount of BaTiO3 increases. The X-ray diffraction results show the morphotropic phase boundary （MPB） of （1-x）（Bi1/2Na12） TiO3-xBaTiO3 exists in near x=0.06-0.08. Temperature dependence of dielectric constant eT33/ε0 measurement reveals that all compositions experience one structural phase and two ferroelectric phases transition below 400℃： rhombohedral （or rhombohedral plus tetragonal） ferroelectric phase ←→ tetragonal antiferroelectric phase ←→ tetragonal paraelectric phase. Relaxor behaviors exist in the course of ferroelectric to antiferroelectric phase transition. Dielectric and piezoelectric properties are enhanced in the MPB range for （ 1-x）（Bi1/2Na1/2）TiO3-xBaTiO3.     

Nonlinear optical properties in bismuth-based glasses

A series of glasses with high Bi2O3 content of Bi2O3-B2O3-WO3 ternary system were chosen and prepared .Their densities and linear refractive indices increase with increasing WO3 content. The optical band gaps Eopt of glasses obtained from ultraviolet absorption edges decreases with increase of WO3 content. Z-scan technique was carried out to investigate the third-order nonlinear optical properties of the glasses. It is found that the nonlinear refraction γ increases with decreasing the optical band gap Eopt, since an increase of WO3 content can promote the non-bridging oxygen ion content, and the highest γ value of samples is 1.173×10-14 cm2/W. The results show that these glasses are potential materials in the application of third-order nonlinear optics field.     

Preparation and characterization of CeO<Subscript>2</Subscript>-TiO<Subscript>2</Subscript>/SnO<Subscript>2</Subscript>:Sb films deposited on glass substrates by R.F. sputtering

CeO2-TiO2 films and CeO2-TiO/SnO2：Sb （6 mol%） double films were deposited on glass substrates by radio-frequency magnetron sputtering （R.F. Sputtering）, using SnO2：Sb（6 mol%） target, and CeO2- TiO2 targets with different molar ratio of CeO2 to TiO2 （CeO2：TiO2-0：1.0; 0.1：0.9; 0.2：0.8; 0.3：0.7; 0.4：0.6; 0.5：0.5; 0.6：0.4; 0.7：0.3; 0.8：0.2; 0.9：0.1; 1.0：0）. The films are characterized by UV-visible transmission and infrared reflection spectra, scanning electron microscopy （SEM）, Raman spectroscopy, X-ray photoelectron spectroscopy （XPS） and X-ray diffraction （XRD）, respectively. The obtained results show that the amorphous phases composed of CeO2-TiO2 play an important role in absorbing UV, there are Ce^3-, Ce^4- and Ti^4- on the surface of the films; the glass substrates coated with CeO2-TiO2 （Ce/Ti=0.5：0.5; 0.6：0.4）/SnO2：Sb（6 mol%） double films show high absorbing UV（〉99）, high visible light transmission （75%） and good infrared reflection （〉70%）. The sheet resistance of the films is 30-50 Ω/□. The glass substrates coated with the double functional films can be used as window glass of buildings, automobile and so on.     

Thermodynamics analysis of oxidation wear behavior of cemented carbide tools in high speed machining

The essence of oxidation wear machanism of cenmented carbide tool was studied based on thermodynamics. Standard Gibbs free energy of possible reactions in cutting process at different temperature was calculated using substance Gibbs free energy function methods, and the sequence of reaction possibility order was researched as well as characteristics of every reaction. Theoretical calculation shows that WO₃, Co₃O₄, TiO₂ and CoWO₄ are the main resultants, which are proved with the experiment results.     

Effects of atmospheres and precursors on MnO x /TiO2 catalysts for NH3-SCR at low temperature

The effects of atmospheres and precursors on MnO _x /TiO₂ catalysts were studied, which were prepared by the impregnation method and tested for their NO _x conversion activity in ammonia selective catalytic reduction (NH₃-SCR) reactions. Results showed that the manganese carbonate (MC) precursor caused mainly Mn₂O₃, while the manganese nitrate (MN) precursor resulted primarily in MnO₂ and the manganese sulfate (MS) precursor was unchanged. The manganese acetate (MA) precursor leaded obtaining a mixture of Mn₂O₃ and Mn₃O₄. NO _x conversion decreased in the following order: MA/TiO₂ > MC/TiO₂ > MN/TiO₂ > MS/TiO₂ > P25, with a calcination temperature of 773 K in air. Catalysts that were prepared by MA and calcined in oxygen performed strong interaction between Ti and Mn, while MnTiO₃ was observed. Compared to the catalysts calcined in nitrogen, those calcined in oxygen had larger diameter and smaller surface area and pore. Catalysts that were prepared by MA and calcined in nitrogen tended to gain higher denitration rates than those in air, since they could be prepared with significant specific surface areas. NO _x conversion decreased with calcination atmospheres: Nitrogen> Air> Oxygen. Meanwhile, amorphous Mn₂O₃ turned into crystalline Mn₂O₃, when the temperatures increased from 673 to 873 K.     

Synthesis and electrochemical performance of TiO2-B as anode material

TiO₂-B was synthesized by solid-state reaction. The structures, surface morphologies and electrochemical performances of TiO₂-B were characterized by X-ray diffractometry (XRD), scanning electron microscopy (SEM) and electrochemical measurement, respectively. The effects of calcining temperature, molar ratio of K₂O to TiO₂ and calcining time on the characteristics of TiO₂-B were investigated. The results show that the calcining time exerts a significant influence on the electrochemical performances of TiO₂-B. The TiO₂-B is obtained with good crystal structure and suitable size by using K₂Ti₄O₉, which is prepared at 950°C for 24 h under the condition of x(K₂O)/x(TiO₂)=1:3.5. The TiO₂-B delivers all initial discharge capacity of 231.6 mA·h/g. And the rate capacity is 73.2 mA·h/g at 1 675 mA/g, which suggests that TiO₂-B is a promising anode material for the lithium ion batteries.     

Preparation, characterization and photocatalytic behavior of WO3-TiO2/Nb2O5 catalysts

TiO2/Nb2O5 photocatalyst loaded with WO3 (WO3-TiO2/Nb2O5) was prepared by a modified hydrolysis process, and characterized by X-ray diffractometry, transmission electron microscopy, Raman spectra and UV-Vis diffuse refraction spectroscopy. The photocatalytic activity of WO3-TiO2/Nb2O5 was investigated by employing splitting of water for O2 evolution. The results indicate that WO3 loading can pronouncedly improve the photocatalytic activity of TiO2/Nb2O5 by using Fe3 as an electron acceptor under UV irradiation. The optimum molar fraction of the loaded WO3 is 2%, and the largest speed of O2 evolution for 2% WO3-TiO2/Nb2O5 catalyst is 151.8 μmol/(L·h).     

Asymmetric synthesis of 3β-acetoxy-17,17-ethylendioxy-15β, 16β-methylene-5-androsten-7β-ol

3β-acetoxy-17, 17-ethylendioxy-15β, 16β-methylene-5-androsten-7β-ol(I) was prepared by 3 steps from 3β-acetoxy-15β, 16β-methylene-5-androsten-17-one (II) with overall yield of 52.7%. Thus, interaction of ethylene glycol and material (II) gave 3β-acetoxy- 17, 17-ethylendioxy-15β, 16β-methylene-5-androsten (III) which was subsequently oxidated and stereoselectively reduced to produce compound(I). The normal influencing factors, such as the types of oxidants and reductives, the mole ratio of reactants, the reaction temperature, and the addition ways of reactants, in oxidation and reduction were discussed. The results show that the oxidation rate order is CrO₃-C₅H₅N (1:1, mole fraction)>CrO₃-C₅H₅N(1:2)>(C₅H₅NH)₂Cr₂O₇ in terms of the oxidant, the yield of the oxidation becomes higher with increasing the oxidant stoichiometry and raising the reaction temperature. And the optimum condition is that the reaction temperature is at 30 °C, and n(III)/n(CrO₃-C₅H₅N(1:2))=1:20. The yield of the −7β alcohol order with Li[Al(OC(CH₃)₃)₃H] (e. g. 78.6%) is more than that with NaBH₄ (e. g. 14.5%) in terms of the reductive agent and the reduction rate decreases in the course of reaction. The compound (I) is characterized by IR and MS. Foundation item: Project (1357) supported by the Excellent Young Teachers Program of the Ministry of Education of China     

Effect of doped Mn on piezoelectric properties of （Na0.5Bi0.5 ）0.92 Ba0.08 TiO3 lead-free ceramics

Piezoelectric ceramics (Na0.5Bi0.5)0.92Ba0.05TiO3 x%MnCO3(BNBT-Mn, x=0-1.6,mass fraction)were synthesized by conventional solid state reaction. The results show that when the addition of MnCO3 is 0-1.4%, BNBT-Mn ceramics exhibit a single-phase perovskite structure. With the increase of content of MnCO3, piezoelectric constant and electromechanical coupling factor increase rapidly when x is lower than 0.3. Then they both decrease when x is in the range of 0.3 and 1.6. When x=0.3, piezoelectric constant and electromechanical coupling factor reach the maximum value of 160 pC/N and 58.5% respectively, which can improve the temperature stability of BNBT-Mn.     

微波敏化强化芬顿试剂催化氧化NO机理研究

微波结合活性炭的微波敏化方式可大幅提高Fenton试剂氧化能力,为研究产物的生成路径及微波、活性炭、H2O2之间的关联性,自制不同孔隙材料及不同Fe含量的碳材料,采用多组对照实验验证产物O2、CO、NO2的可能生成路径及微波、活性炭的作用,最终得到微波敏化下的芬顿试剂催化氧化NO的反应机理.结果表明:采用活性炭加微波的敏化方式后,NO脱除效率可从33.1%提高至46.3%,O2生成量从6.9%增加到18.6%,同时伴随着体积分数68×10-6的CO生成; O2可通过活性炭的吸附作用及Fe2+的催化作用产生; C及NO只能被芬顿反应过程中生成的·OH、HO2·氧化成CO及NO2;微波可强化体系内所有可发生反应,活性炭能进一步提高微波敏化的前提是发达的孔隙,同时活性炭中存在的部分Fe元素参与到了芬顿反应.     

Photocatalytic activity of lanthanum and sulfur co-doped TiO<Subscript>2</Subscript> photocatalyst under visible light

A novel lanthanum and sulfur co-doped TiO2 photocatalyst was synthesized by precipitation- dipping method, and characterized by X-ray diffraction（XRD）, transmission electron microscopy（TEM） and UV-Vis diffuse reflectance spectroscopy. Compared with the S-doped TiO, La-doped TiO2 and the standard Degussa P25 photocatalysts, the lanthanum and sulfur co-doped TiO2 photocatalyst （the molar percentage of La is 3.0%） calcined at 450 ℃ for 2 h showed the strongest absorption for visible light and highest activities for degradation of reactive blue 19 dye in aqueous solution under visible light（λ〉400 nm） irradiation. It was also discovered that the co-doping of lanthanum and sulfur hindered the aggregation and growth of TiO2 particles, and the doping of lanthanum reduced slightly the phase transition temperature ofTiO2 from anatase to rutile.     

Thermodynamic equilibrium of bismuth hydrometallurgy in chloride and nitrate solutions

Simultaneous equilibrium was applied to the thermodynamic analysis and calculation of Bi( Ⅲ )-X(Cl- ,NO3- )-H2O systems, based on which the diagrams of the logarithm of equilibrium concentration of Bi( Ⅲ ) of series precipitation vs pH value of these two systems at 25 ℃ were obtained, and the pH ranges of the stable zones of various precipitations were analyzed and determined. In Bi( Ⅲ )-Cl -H2O system, the variations of c0 (Bi3 ) and c0 (Cl-) have little effect on the equilibria of Bi(OH)3-solution and BiOOH-solution, but has great influence on the equilibrium of BiOCl-solution. However, in Bi( Ⅲ )-NO3-H2O system, the variations of c0 (Bi3 ) and C0 (NO3-)have little effect on equilibria of Bi(OH)3-solution, BiOOH-solution and Bi2O3-solution. When pH value is high,Bi2O3 is the thermodynamic stable phase, its stable zone is the widest, almost including the stable zones of BiOCl or BiONO3, Bi(OH)3 and BiOOH. Bi(OH)3 cannot be obtained from Bi( Ⅲ )-Cl--H2O system, even strong alkaline media. Bi2O3 can be obtained from the solution directly, and highly pure BiOCl or BiONO3 can also be obtained through strictly controlling pH value.     

Process optimization of reaction of acid leaching residue of asbestos tailing and sodium hydroxide aqueous solution

Silica is the major component of the acid leaching residue of asbestos tailing. The waterglass solution can be prepared by the reaction of the residue with sodium hydroxide aqueous solution. Compared to the high temperature reaction method, this process is environmental friendly and low cost. In this paper, the reaction process of the residue and the sodium hydroxide aqueous solution is optimized. The optimum reaction process parameters are as follows: the usage of sodium hydroxide is 26.4 g/100 g acid leaching residue, the reaction temperature is 90℃, the reaction time is 1 h, and the ratio of the liquid/solid is 2.0. The significance sequence of the process parameters to the alkali leaching reaction effect is the usage of sodium hydroxide > the ratio of the liquid/solid > the reaction time > the reaction temperature. The significance sequence to the leaching ratio of SiO2 is the ratio of the liquid/solid > the usage of sodium hydroxide > the reaction time > the reaction temperature. The significance sequence to the modulus of the sodium silicate is the ratio of the liquid/solid > the usage of sodium hydroxide > the reaction time > the reaction temperature. Under the optimum conditions, the leaching ratio of the SiO2 is 77.5%, and the modulus of the sodium silicate is 3.15. The XRD analysis result indicates that the major components of the alkali leaching residue are serpentine, talc, quartz and some albite.     

Comparison of room-temperature multiferroics in Bi4Fe2TiO12 film and bulk

It was reported that both dielectricity and magnetism at room temperature were appreciably improved in Bi₄Fe₂TiO₁₂ film compared with Bi₄Fe₂TiO₁₂ bulk. X-ray diffraction profiles reveal similar crystalline nature and random orientation of the two, but X-ray photoelectron spectroscopy (XPS) experiments indicate that it is 1.4 eV lower binding energy of core-state O1s in the film relative to that of the bulk, so the improvement of multiferroics in the film is attributed to oxygen vacancies and high fraction of interface. The results have promising applications in multifunctional integrated devices.     

Synthesis and Piezoelectric Properties of Lead-free （ Bi0.5 Na0.5 ）1-x（BaaSrb）xTiO3 Ceramics

A new group of lead-free piezoelectric ceramics,（Bi0.5 Na0.5）1-x（BaaSrb）xTiO3（abbreviated as BNBST[100x-100a/100b],0〈x〈1,a＋b=1）,was synthesized.The ceramics were prepared by conventional ceramic sintering technique,and the ceramics with density of 95% of the theoretical one can be sintered without the atmosphere control during the sintering process.The results of the X-ray diffraction（XRD） data show that the ceramics possess a single perovskite phase.The measurements of dielectric and piezoelectric properties reveal that the ceramics provide relatively high piezoelectric charge constant d33 and high planar electromechanical coupling factor kp.For the BNBST6-95/5 ceramics,d33 is equal to 170pC/N,and kp is equal to 32.0%.The fabrication technique for these ceramics is conventional and stable.     

Electronic band structures of TiO<Subscript>2</Subscript> with heavy nitrogen doping

The first-principles density-functional calculation was conducted to investigate the electronic band structures of titanium dioxide with heavy nitrogen doping （TiO2-xNx）.The calculation results indicate that when x≤0.25,isolated N 2p states appear above the valence-band maximum of TiO2 without a band-gap narrowing between O 2p and Ti 3d states.When x≥0.50,an obvious band gap narrowing between O 2p and Ti 3d states was observed along with the existence of isolated N 2p states above the valence-band of TiO2,indicating that the mechanism proposed by Asahi et al operates under heavy nitrogen doping condition.     

Heat treatment temperature effect on the microstructure and optical properties of Dy2(WO4)3 powders

Dy₂(WO₄)₃ powders were synthesized through liquid-phase reaction. The structure transformation of Dy₂(WO₄)₃ powders were analyzed by differential scanning calorimetry (DSC), X-ray diffractometer (XRD) and Fourier transform infrared spectroscopy (FTIR). The optical absorption and photoluminescence properties were characterized by UV-vis-infra diffuse reflectance spectra and fluorescence spectra. The Dy₂(WO₄)₃ host could absorb deep UV light and transfer the energy of UV light to Dy³⁺ ions, which convert the high-energy UV light to blue light (482 nm, ⁴ F _9/2→⁶ H _15/2) and yellow light (547 nm, ⁴ F _9/2→⁶ H _13/2). The Dy₂(WO₄)₃ powders could also absorb near UV light and exhibit blue and yellow emissions near 482 and 547 nm, respectively. Heat treating promoted the crystallization and regulated the micro-structure of Dy₂(WO₄)₃ hosts. The bands of W-O_d anti-symmetric stretching vibration exhibited red shift with the increasing of sintering temperature. The W-O_b-W groups tended to combine with each other to form W-O_c-W groups after heat treating. These regulation of micro-structure had influence on the luminescent color of Dy₂(WO₄)₃. The samples could emit yellow-green, white-yellow and white light under the excitation of 350 nm after being treated at 600, 800 and 1 000 °C, respectively. The prepared Dy₂(WO₄)₃ powders have potential to act as UV absorber for solar cell to improve the conversion efficiency and also exhibit potential for white light LED.