Fluorine-doped TiO2 powders prepared by spray pyrolysis and their improved photocatalytic activity for decomposition of gas-phase acetaldehyde

F-doped TiO₂ (FTO) powders were synthesized by spray pyrolysis (SP) from an aqueous solution of H₂TiF₆. The resulting FTO powders possessed spherical particles with a rough surface morphology and a strong surface acidity. The fluorine concentrations in the FTO powders calculated from XPS spectra significantly depended on SP temperature and ranged from 2.76 to 9.40 at.%. The FTO powder prepared at SP temperature of 1173 K demonstrated the highest photocatalytic activity for the decomposition of gas-phase acetaldehyde under both ultraviolet (UV) and visible light (vis) irradiations, and it was higher than that of commercial P 25. This high photocatalytic activity was ascribed to several beneficial effects produced by F-doping: enhancement of surface acidity, creation of oxygen vacancies, and increase of active sites. It was interesting to point out that the vis photocatalytic activity of FTO powders was achieved by the creation of surface oxygen vacancies rather than the improvement of optical absorption property of bulk TiO₂ in vis region.     

Fabrication of mesoporous SiO2–C–Fe3O4/γ–Fe2O3 and SiO2–C–Fe magnetic composites

A synthetic method for the fabrication of silica-based mesoporous magnetic (Fe or iron oxide spinel) nanocomposites with enhanced adsorption and magnetic capabilities is presented. The successful in situ synthesis of magnetic nanoparticles is a consequence of the incorporation of a small amount of carbon into the pores of the silica, this step being essential for the generation of relatively large iron oxide magnetic nanocrystals (10 ± 3 nm) and for the formation of iron nanoparticles. These composites combine good magnetic properties (superparamagnetic behaviour in the case of SiO₂–C–Fe₃O₄/γ–Fe₂O₃ samples) with a large and accessible porosity made up of wide mesopores (>9 nm). In the present work, we have demonstrated the usefulness of this kind of composite for the adsorption of a globular protein (hemoglobin). The results obtained show that a significant amount of hemoglobin can be immobilized within the pores of these materials (up to 180 mg g⁻¹ for some of the samples). Moreover, we have proved that the composite loaded with hemoglobin can be easily manipulated by means of an external magnetic field.     

磁光Fe3O4@SiO2@CdS复合材料的制备及表征

采用水解三氯化铁得到Fe₃O₄磁核,然后水解四乙氧基硅烷(TEOS)得到Fe₃O₄@SiO₂,再在其表面包覆半导体CdS即可得到良好的磁性光电信标Fe₃O₄@SiO₂@CdS。材料形貌、组成分析及光电化学测试表明成功地合成了具有超顺磁性的Fe₃O₄@SiO₂@CdS纳米复合材料。该材料分散均匀、具有良好的光学性能、在光电化学传感及光电催化等领域具有良好的应用前景。     

Synthesis and Characterization of TiO2 Doped ZnO Microtubes

The TiO₂-doped ZnO microtubes have been successfully fabricated via a wet chemicalmethod, using zinc chloride and titanium sulphate as the starting materials. The as-synthesized products were characterized by X-ray diffraction, field emission scanning electronmicroscopy and room temperature photoluminescence measurement. The photocatalytic ac-tivity in degrading methyl orange was measured with a UV-Vis spectrophotometer. The pure ZnO microtubes exhibit an exact hexangular hollow structure with a diameter of about 700 nm, a length of 3 μm and a wall thickness of about 40 nm. The TiO₂-doped ZnO microtubes with TiO₂/ZnO ratio less than 5% have the same dimension with the pure ZnO microtubes, a smooth column shape, not a hexangular structure. The growth of ZnO may be inhibited by the more Ti⁴⁺ doped into ZnO structure to achieve a small dimension or a multiphase. The crystallinity of ZnO microtubes decreases with increasing TiO₂ content, and then a multiphase containing ZnO, Ti₃O₅ and TiO occur when the TiO₂/ZnO ratio is more than 5%. The UV emission intensity of the TiO₂-doped ZnO obviously increases and then tends to decrease with TiO₂/ZnO ratio increasing. The photocatalytic properties of the TiO₂-doped ZnO microtubes are very effcient in degrading organic dyes of methyl orange and are well identical with its PL properties and the crystallinity.     

Tunneled Intergrowth Structures in the Ga2O3–In2O3–SnO2 System

The structures of several Ga₂O₃–In₂O₃–SnO₂ phases were investigated using high-resolution electron microscopy, X-ray diffraction, and Rietveld analysis of time-of-flight neutron diffraction data. The phases, expressed as Ga_4−4xIn_4xSn_n−4O_2n−2 (n=6 and 7–17, odd), are intergrowths between the β-gallia structure of (Ga,In)₂O₃ and the rutile structure of SnO₂. Samples prepared with n≥9 crystallize in C2/m and are isostructural with intergrowths in the Ga₂O₃–TiO₂ system. Samples prepared with n=6 and n=7 are members of an alternative intergrowth series that crystallizes in P2/m. Both intergrowth series are similar in that their members possess 1-D tunnels along the b axis. The difference between the two series is described in terms of different crystallographic shear plane operations (CSP) on the parent rutile structure.     

富表面氧空位Fe2O3/ZnO催化剂在光催化合成氨中的应用

光催化合成氨是一种绿色节能的合成氨技术,设计制造丰富的表面氧空位和异质结构是促进氮分子活化和抑制电子-空穴复合的重要方法。我们以乙二醇作为还原剂,采用溶剂热法制备合成了Fe2O3/ZnO光催化剂,利用X射线衍射(XRD)、透射电镜(TEM)、电子顺磁共振(EPR)、紫外-可见漫反射(UV-Vis DRS)、荧光光谱(PL)及光电流(PC)对Fe2O3/ZnO催化剂进行表征,并考察了Fe2O3/ZnO催化剂在常温、常压下的光催化合成氨的性能。4%Fe2O3/ZnO催化剂在无牺牲剂下用于光催化合成氨,有较好的光催化效率和稳定性,其合成氨效率达到2059μmol·L-1·g-1·h-1。其高催化效率归因于:可见光区域吸收的提高、氮分子在表面氧空位与Fe3+活性中心上的协同活化及光生电子与空穴的高分离效率。     

Phase Relations at 1500°C in the Ternary System ZrO2–Gd2O3–TiO2

Phase relations at 1500°C in the ternary system ZrO₂–Gd₂O₃–TiO₂ have been determined by the powder X-ray diffraction of samples prepared by standard solid state reaction. A large area of this ternary oxide system centered on the Gd₂Ti₂O₇–Gd₂Zr₂O₇ join was shown to exhibit the pyrochlore and defect fluorite structures. The pyrochlore structure was observed for stoichiometries as far from the ideal M₄O₇ as M₄O_6.7 and M₄O_7.4, although the degree of disorder seemed much higher at these stoichiometries. On further deviation from the ideal M₄O₇ stoichiometry a smooth transition to fluorite average structure was observed for Zr-rich compositions. None of the other binary phases were observed to show significant extent of solid solution into the ternary region.     

Selective Catalytic Reduction of NO with Propene over Au/Fe2O3/Al2O3 Catalysts

A series of Au/Fe₂O₃/Al₂O₃ catalysts were prepared by the homogeneous deposition-precipitation method. The catalytic activity of the catalyst samples for selective catalytic reduction of NO by propene under oxygen-rich atmosphere was evaluated. The results showed that 2%Au/10%Fe₂O₃/Al₂O₃ exhibited good low-temperature activity. The maximum of NO conversion reached 43% at 300 °C, while it was only 21% over the 2%Au/Al₂O₃ catalyst at the same temperature. The addition of 2% steam to the feed gas had little effect on the catalytic activity. X-ray diffraction results indicated that both Au and Fe₂O₃ particles were highly dispersed over Al₂O₃. H₂-temperature-programmed reduction results indicated that there was strong interaction between Au and Fe₂O₃, which made the reduction of Fe₂O₃ easy. The synergistic effect between Au and Fe₂O₃ was probably responsible for the good catalytic performance of the Au/Fe₂O₃/Al₂O₃ catalyst at low temperature.     

The Phase Relations in the System In2O3–TiO2–MgO at 1100 and 1350°C

The phase relations in the system In₂O₃–TiO₂–MgO at 1100 and 1350°C are determined by a classical quenching method. In this system, there are four pseudobinary compounds, In₂TiO₅, MgTi₂O₅ (pseudobrookite type), MgTiO₃ (ilmenite type), and Mg₂TiO₄ (spinel type) at 1100°C. At 1350°C, in addition to these compounds there exist a spinel-type solid solution Mg_2−xIn_2xTi_1−xO₄ (0≤x≤1) and a compound In₆Ti₆MgO₂₂ with lattice constants a=5.9236(7) Å, b=3.3862(4) Å, c=6.3609(7) Å, β=108.15(1)°, and q=0.369, which is isostructural with the monoclinic In₃Ti₂FeO₁₀ in the system In₂O₃–TiO₂–MgO. The relation between the lattice constants of the spinel phase and the composition nearly satisfies Vegard's law. In₆Ti₆MgO₂₂ extends a solid solution range to In₂₀Ti₁₇Mg₃O₆₇ with lattice constants of a=5.9230(5) Å, b=3.3823(3) Å, c=6.3698(6) Å, β=108.10(5)°, and q=0.360. The distributions of constituent cations in the solid solutions are discussed in terms of their ionic radius and site preference effect.     

First-principles investigation of R2O3(ZnO)3 (R=Al, Ga, and In) in homologous series of compounds

Atomic and electronic structures of R₂O₃(ZnO)₃ (R=Al, Ga, and In), which are included in homologous series of compounds, are investigated using first-principles calculations based on density functional theory. Three models with different R atom arrangements in the five-fold and four-fold coordination sites are examined. Al and Ga prefer the five-fold coordination sites. The formation energies are much larger than those of the competing phases, ZnR₂O₄, with a normal spinel structure. On the other hand, In₂O₃(ZnO)₃ shows no clear site preference and can be more stable than the spinel at high temperatures when configurational entropy contribution is taken into account. Electronic states near the conduction band bottom are mainly composed of Zn-4s orbital in Al₂O₃(ZnO)₃, while the contributions of Ga-4s and In-5s are comparable to Zn-4s in Ga₂O₃(ZnO)₃ and In₂O₃(ZnO)₃.     

Preparation of crack-free ZrO2 membrane on Al2O3 support with ZrO2–Al2O3 composite intermediate layers

To develop porous alumina supported MF ZrO₂ membranes, ZrO₂–Al₂O₃ composite intermediate layers are considered in order to decrease stress creation during the processing and avoid cracks formation. The relation between distortion stress and sintering shrinkage was experimentally studied. And the cracks formation mechanism was qualitatively evaluated and discussed. Finally, crack-free YSZ membrane with pore size of 0.16 μm on the two ZrO₂–Al₂O₃ intermediate layers possessing a gradient composition was successfully prepared and characterized.     

Solid Solutions of WO3into Zirconia in WO3-ZrO2 Catalysts

Catalysts in the WO₃-ZrO₂ system were produced by coprecipitation of aqueous solutions of zirconium oxynitrate and ammonium metatungstate. Samples were characterized by X-ray powder diffraction, thermogravimetry, and refinement of their crystalline structures with the Rietveld method. This coprecipitation gave rise to solid solutions of tungsten oxide into zirconia; the initial phase was amorphous and crystallized into two tetragonal crystalline phases, T1 and T2, when samples were annealed at 560°C. The main difference between both phases was the oxygen position along the c axis. In the phase with higher symmetry, T2, an oxygen atom was at one-half of the unit cell, 0.50(2), producing flat crystallite surfaces perpendicular to the c axis, while in the phase with the lower symmetry, T1, it was at 0.447(2), and gave rise to rough crystallite surfaces parallel to (100) planes. The interpenetrating tetrahedra forming the representative polyhedron of the crystalline structure were almost nondeformed in the phase with higher symmetry, because all Zr-O atom bond lengths were very similar. As the annealing temperature of the sample was increased, the dissolved tungsten atoms in the phase with higher symmetry segregated to the crystallite's surface.     

钙钛矿氧化物H1.9K0.3La0.5Bi0.1Ta2O7和Pt/WO3组成的Z体系下完全光解水性能

以质子化层状钙钛矿氧化物H_1.9K_0.3La_0.5Bi_0.1Ta₂O₇ (HKLBT)作为产氢催化剂, Pt/WO₃作为产氧催化材料进行Z 型体系下完全分解水反应. 考察了不同载流子传递介质及不同载流子浓度对反应活性的影响. 结果表明, 以Fe²⁺/Fe³⁺为载流子传递介质时可以实现水的完全分解(H₂/O₂体积比为2:1), 8 mmol·L^-1的FeCl₃作为初始载流子传递介质时, 产氢、产氧活性分别为66.8和31.8 μmol·h^-1, 氢氧体积比为2.1:1. 受光催化材料对载流子传递介质氧化还原速度的限制, 过高的载流子传递介质浓度并不能提高光催化活性.     

The effects of ZnGa2O4 formation on structural and optical properties of ZnO:Ga powders

Gallium-doped zinc oxide (ZnO:Ga 1, 2, 3, 4 and 5 at%) samples were prepared in powder form by modifying the Pechini method. The formation of zinc gallate (ZnGa₂O₄) with the spinel crystal structure was observed even in ZnO:Ga 1 at% by X-ray diffraction. The presence of ZnGa₂O₄ in ZnO:Ga samples was also evidenced by luminescence spectroscopy through its blue emission at 430 nm, assigned to charge transfer between Ga³⁺ at regular octahedral symmetry and its surrounding O²⁻ ions. The amount of ZnGa₂O₄ increases as the dopant concentration increases, as observed by the quantitative phase analysis by the Rietveld method.     

Kinetics of adsorption of Saccharomyces cerevisiae mandelated dehydrogenase on magnetic Fe3O4–chitosan nanoparticles

The adsorption of Saccharomyces cerevisiae mandelated dehydrogenase (SCMD) protein on the surface-modified magnetic nanoparticles coated with chitosan was studied in a batch adsorption system. Functionalization of surface-modified magnetic particles was performed by the covalent binding of chitosan onto the surface of magnetic Fe₃O₄ nanoparticles. Characterization of these particles was carried out using FTIR spectra, transmission electron micrography (TEM), X-ray diffraction (XRD) and vibrating sample magnetometry (VSM). Magnetic measurement revealed that the magnetic Fe₃O₄–chitosan nanoparticles were superparamagnetic and the saturation magnetization was about 37.3 emu g⁻¹. The adsorption capacities and rates of SCMD protein onto the magnetic Fe₃O₄–chitosan nanoparticles were evaluated. The adsorption capacity was influenced by pH, and it reached a maximum value around pH 8.0. The adsorption capacity increased with the increase in temperature. The adsorption isothermal data could be well interpreted by the Freundlich isotherm model. The kinetic experimental data properly correlated with the first-order kinetic model, which indicated that the reaction is the adsorption control step. The apparent adsorption activation energy was 27.62 kJ mol⁻¹ and the first-order constant for SCMD protein was 0.01254 min⁻¹ at 293 K.     

Effect of TiO2 addition on the crystallization and tribological properties of MgO–CaO–SiO2–P2O5–F glasses

The kinetic parameters including the activation energy for crystallization (E), the Avrami parameter (n) and frequency factor (υ) of a glass in the MgO–CaO–SiO₂–P₂O₅–F system were studied using non-isothermal differential thermal analysis (DTA) with regard to small amount of TiO₂ additions. It has been shown that the role of TiO₂ changes from a glass network former to a glass network modifier with increasing TiO₂ content in this system. The kinetic parameters of the crystallizing phases, apatite and wollastonite, indicated changes accompanied with TiO₂ additions, implying that the TiO₂ is an effective nucleating agent for promoting the crystallization of apatite and wollastonite. The most effective addition is of about 4 wt% TiO₂ in this system. The wear rate and friction coefficient decreased from 1.8 ± 0.1 to 0.9 ± 0.2 and 0.87 to 0.77, respectively, when 4 wt% TiO₂ was incorporated to the base glass.     

CuO/ZnO/Y2O3/γ-Al2O3双功能催化剂上二甲醚水蒸气重整制氢

将沉积-沉淀法制备的CuO/ZnO/Y2O3催化剂同γ-Al2O3进行机械混合, 制备了CuO/ZnO/Y2O3/γ-Al2O3双功能催化剂, 用于二甲醚水蒸气重整制氢反应, 实验结果表明其活性、稳定性等均优于常用的CuO/ZnO/Al2O3/γ-Al2O3催化剂. 结合N2吸附-脱附(BET)、N2O化学吸附(N2O chemisorption)、NH3程序升温脱附(NH3-TPD)、X射线衍射(XRD)、H2程序升温还原(H2-TPR)等表征手段研究了两种催化剂在表面酸性及微观结构上的差异, 发现CuO/ZnO/Y2O3催化剂具有相对较高的铜分散度, 铜晶粒更加细小化, 并且具有高温稳定性的Y2O3可能起到隔离铜的作用, 在一定程度上防止了铜晶粒的团聚, 从而改善了重整组分的性能, 提高了双功能催化剂的重整制氢活性及稳定性.     

NiO-Fe_2O_3/PG-γ-Al_2O_3催化剂的制备及其在秸秆热解中的应用

通过沉积沉淀法与均匀沉淀法制备以坡缕石与伽马氧化铝(Palygorskite-Gamma Alumina,PG-γ-Al_2O_3)为复合载体的负载型NiO-Fe_2O_3/PG-γ-Al_2O_3催化剂,采用了EDX、XRD、SEM、N2等温吸附-脱附等手段对催化剂进行了表征与分析。同时利用管式炉考察了NiO-Fe_2O_3/PG-γ-Al_2O_3催化剂在作物秸秆热解中的催化性能和再生使用寿命及抗积炭能力,并与两种单载体催化剂(NiO-Fe_2O_3/PG,NiO-Fe_2O_3/γ-Al_2O_3)进行了比较。结果表明,PG-γ-Al_2O_3复合载体比表面积达134.21 m2/g,平均孔径为39.65 nm。NiO-Fe_2O_3/PG-γ-Al_2O_3催化剂活性组分负载均匀,分散较好且催化剂中同时存在镍铁合金与镍铝尖晶石结构。催化剂活性测试显示,NiO-Fe_2O_3/PG-γ-Al_2O_3催化剂用于作物秸秆热解具有极高的催化活性,能够显著提高产品燃气品质、燃气中的CO与H2含量和燃气热值;相比单载体催化剂其催化活性好,再生效果佳,抗积炭能力较强。     

Fe2O3 transformation to iron chlorides in radical chain gas-phase chlorination of methane

It has been established that the formation of iron chlorides in chain gas-phase reaction of methane chlorination is observed starting with T650 K. At Cl₂:CH₄=4:1, Fe₂O₃ is transformed to FeCl₃. With increasing methane concentration (Cl₂:CH₄=1:1), besides FeCl₃, FeCl₂ is also formed. Kinetic regularities of the reaction have been studied at 600–1200 for both gaseous mixtures.

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, 650 . : 41, Fe₂O₃ FeCl₃. (Cl₂CH₄=11) , FeCl₃ FeCl₂. 600–1200 -.

     

Application of Fe2O3/Al2O3 Composite Particles as Oxygen Carrier of Chemical Looping Combustion

Chemical looping combustion (CLC) of carbonaceous compounds has been proposed, in the past decade, as an efficient method for CO2 capture without cost of extra energy penalties. The technique involves the use of a metal oxide as an oxygen carrier that transfers oxygen from combustion air to fuels. The combustion is carried out in a two-step process: in the fuel reactor, the fuel is oxidized by a metal oxide, and in the air reactor, the reduced metal is oxidized back to the original phase. The use of iron oxide as an oxygen carrier has been investigated in this article. Particles composed of 80 wt% Fe2O3, together with Al2O3 as binder, have been prepared by impregnation methods. X-ray diffraction (XRD) analysis reveals that Fe2O3 does not interact with the Al2O3 binder after multi-cycles. The reactivity of the oxygen carrier particles has been studied in twenty-cycle reduction-oxidation tests in a thermal gravimetrical analysis (TGA) reactor. The components in the outlet gas have been analyzed. It has been observed that about 85% of CH4 converted to CO2 and H2O during most of the reduction periods. The oxygen carrier has kept quite a high reactivity in the twenty-cycle reactions. In the first twenty reaction cycles, the reaction rates became slightly higher with the number of cyclic reactions increasing, which was confirmed by the scanning electron microscopy (SEM) test results. The SEM analysis revealed that the pore size inside the particle had been enlarged by the thermal stress during the reaction, which was favorable for diffusion of the gaseous reactants into the particles. The experimental results suggested that the Fe2O3/Al2O3 oxygen carrier was a promising candidate for a CLC system.