Photocatalytic performance of nano-photocatalyst from TiO2 and Fe2O3 by mechanochemical synthesis

Nano-particles of homogeneous solid solution between TiO₂ and Fe₂O₃ (up to 10 mol%) have been prepared by mechanochemical milling of TiO₂ and yellow Fe₂O₃/red Fe₂O₃/precipitated Fe (OH)₃ using a planetary ball mill. Such novel solid solution cannot be prepared by conventional co-precipitation technique. A preliminary investigation of photocatalytic activity of mixed oxide (TiO₂/Fe₂O₃) on photo-oxidation of different organic dyes like Rhodamine B (RB), Methyl orange (MO), Thymol blue (TB) and Bromocresol green (BG) under visible light (300-W Xe lamp; λ > 420 nm) showed that TiO₂ having 5 mol% of Fe₂O₃ (YFT1) is 3-5 times higher photoactive than that of P25 TiO₂. The XRD result did not show the peaks assigned to the Fe components (for example Fe₂O₃, Fe₃O₄, FeO₃, and Fe metal) on the external surface of the anatase structure in the Fe₂O₃/TiO₂ attained through mechanochemical treatment. This meant that Fe components were well incorporated into the TiO₂ anatase structure. The average crystallite size and particle size of YFT1 were found to be 12 nm and 30 ± 5 nm respectively measured from XRD and TEM conforming to nanodimensions. Together with the Fe component, they absorbed wavelength of above 387 nm. The band slightly shifted to the right without tail broadness, which was the UV absorption of Fe oxide in the Fe₂O₃/TiO₂ particle attained through mechanochemical method. This meant that Fe components were well inserted into the framework of the TiO₂ anatase structure. EPR and magnetic susceptibility show that Fe³⁺ is in low spin state corresponding to μ_B = 1.8 BM. The temperature variation of μ_B shows that Fe³⁺ is well separated from each other and does not have any antiferromagnetic or ferromagnetic interaction. The evidence of Fe³⁺ in TiO₂/Fe₂O₃ alloy is also proved by a new method that is redox titration which is again support by the XPS spectrum.     

气液爆轰控制合成多晶纳米二氧化钛

以氢气、氧气和四氯化钛为混合前驱体,通过气液爆轰法合成了多晶纳米二氧化钛.研究了不同摩尔比例的前驱体和初始反应压力对纳米二氧化钛晶相结构的影响.采用X射线衍射及透射电子显微镜对产物的纳米结构、成分、颗粒大小和形态进行了表征.结果 表明:获得的二氧化钛存在纯净的锐钛矿相、纯净的金红石相和混合相,其中混合相的球形或者类球形...     

Glass fibers templated preparation of TiO2 microtubes assembled from nano/micro hierarchical TiO2 crystals

The unique rutile TiO₂ microtubes with the larger specific surface area and the distinct external/internal surface morphology have been fabricated in large-scale by a sol-gel-hydrothermal method via the readily available glass fibers as templates. The crystal phase, morphology and surface area of as-obtained samples were measured by XRD, SEM, TEM and BET. The results indicate that these microtubes with the inner diameter of ca. 8 μm and the wall thickness of 2-3 μm have a novel double-layer structure, which is built from closely associated TiO₂ rod arrays and TiO₂ gel film. Detailed electric microscopy investigations on such TiO₂ rod arrays exhibit that they are mainly constructed by flower-like rod clusters, and each TiO₂ rod derives from the assembly of the parallel-growth TiO₂ nanowires with the diameter of ca. 10 nm. Such unique hierarchical nano/micro TiO₂ structure enhances the specific surface area of these microtubes effectively, which makes them have more potential applications in the fields of catalysis, sensors, and drug delivery.     

常压干燥法制备CNTs掺杂TiO2气凝胶

以钛酸丁酯为原料,乙酸为有机配体,甲酰胺为干燥控制化学添加剂(DCCA),采用溶胶凝胶法制备碳纳米管(CNTs)掺杂TiO2复合醇凝胶,并结合常压干燥等后续工艺,制备了CNTs掺杂TiO2块体气凝胶。采用XRD、BET、TEM、SEM、EDS、DSC及FT-IR等对样品进行表征。结果表明:制备态CNTs掺杂TiO2气凝胶晶型为无定型,比表面积为601.7 m2/g;在氮气保护下,经950℃热处理后,比表面积为136.8 m2/g,TiO2以锐钛矿相存在,且均匀密集包覆在CNTs表面,对甲基橙光降解具有较高光催化活性。     

Controlled synthesis of TiO2 mesoporous microspheres via chemical vapor deposition

Anatase titanium dioxide (TiO₂) mesoporous microspheres with core-shell and hollow structure were successfully prepared on a large scale by a one-step template-free chemical vapor deposition method. The effects of various reaction conditions on the morphology, composition and structure of the products were investigated by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Brunauer-Emmett-Teller (BET) technique and photoluminescence (PL) method. The results indicate that the product near the source was composed of core-shell structure TiO₂ microspheres with diameters from 3 to 5 μm. With increasing the distance between the source materials and the substrate, the hollow TiO₂ spheres with 1-2 μm dominant the products. A localized Ostwald ripening can be use to explain the formation of core-shell and hollow structures, and the size of the initial TiO₂ solid nanoparticles plays an important role in determining the evacuation manner of the solid in the ripening-induced hollowing process. The surface area of TiO₂ hollow microspheres determined by the adsorption isotherms was measured to be 74.67 m²/g. X-ray photoelectron spectroscopy (XPS) analysis revealed that the O-H peaks of hollow structures have a chemical shift compared with the core-shell structures. The optical property of the products was also discussed.     

钛渣制备二氧化钛技术发展现状

我国钛资源丰富,但钛矿品位低,钙、镁等杂质含量高,且有一半的钛资源是以类质同象形式赋存于钒钛磁铁矿中,难以利用,因此需通过冶炼形成钛渣后再用于提取二氧化钛。同时,钛铁矿直接用于硫酸法生产钛白粉会产生大量硫酸亚铁,造成资源浪费和环境污染,而通过制备钛渣后再用于提取二氧化钛则可综合利用钛铁矿中的铁,减少硫酸亚铁的产生和硫酸消耗,是未来的发展趋势。目前钛渣制备二氧化钛的方法主要有盐酸法、氯化法、传统硫酸法、混合法、加碱活化焙烧法、磷酸活化焙烧法、硫酸氢铵活化焙烧法和微波法等。     

Structure differences between TiO2 and phosphorus implanted TiO2 films caused by thermal treatment

The titanium oxide film has been deposited on Si wafers (110) by unbalance reactive magnetron sputtering and modified by phosphorus ion implantation and succeeding vacuum annealing. The structural, states of surface chemistry and surface morphology of the films have been investigated by X-ray diffraction (XRD), X-ray photoelectric spectroscopy (XPS), atomic force microscope (AFM) and Scanning Electron Microscope (SEM), respectively. The results of XRD show rutile structure of as-deposited film, which is not changed by phosphorus implantation and vacuum annealing. However, a slightly shift of the peaks position to higher degree and the half width increases after ion implanted and vacuum annealing represent that the variety of the structure film caused by these treatments. The surface roughness is inclined to increase with the rising of annealing temperature for both undoped and P doped titanium oxide films. The surface chemistry presents significant difference between undoped and phosphorus doped films after a vacuum annealing, it may be attributed to the different evolvement of the surface defects existing in the film, which may be considered as an important influencing factor in the blood compatibility of the titanium oxide film.     

Self-organized porous TiO2 and ZrO2 produced by anodization

The present work investigates the electrochemical formation of self-organized high aspect ratio TiO₂ and ZrO₂ nanotube layers. The formation and growth of a self-organized porous layer can be achieved directly by anodization without any templates in fluoride containing electrolytes. The morphology of the porous layers is affected by the electrochemical conditions such as the electrolyte composition, the pH and the exact polarization treatment (such as the potential sweep rate from the open-circuit potential to the anodizing potential). For Ti, nanotube layers are formed with diameters varying from approx. 20 nm to 100 nm and lengths from approx. 0.25 μm to 2.5 μm depending on the electrolytes and pH. On the other hand, for Zr, tubes of 50 nm in diameter and up to approx. 17 μm in length can be grown—a key parameter in this case is the potential sweep rate. The large difference between Ti and Zr in the achievable thickness of nanotube layers indicates a difference in the growth mechanism which may be based on the different chemical dissolution rates of electrochemically formed oxides.     

Properties of TiO2 support and the performance of Au/TiO2 Catalyst for CO oxidation reaction

Gold catalysts were prepared on TiO₂ supports of different phase structures (i.e., anatase, rutile and biphasic), TiO₂ crystal size (i.e., 9–23 nm), surface and textural properties (i.e., hydration and surface area). The CO oxidation on the gold catalysts was carried out in an operando-DRIFTS set-up equipped with DRIFTS reactor cell connected on-line to CO gas analyser and gas chromatograph enabling real time monitoring of surface reaction and simultaneous reaction rate measurements. Gold catalysts supported on pure anatase TiO₂ were more resistant to sintering compared to catalysts supported on rutile and bi-phasic TiO₂. Besides catalyst sintering, deposition of surface carbonates is an important cause of catalyst deactivation. The best gold catalyst was prepared on 13 nm anatase TiO₂. It displays both increased activity and stability for CO oxidation reaction at room temperature. Surface and textural properties of TiO₂ also play a role on the performance of the Au/TiO₂ catalyst.     

TiO2掺杂SmTaO4陶瓷热物理性能研究

热障涂层是燃气轮机高温部件保护的重要材料之一,SmTaO4陶瓷具有优异的高温相稳定性和力学性能,有望成为新型热障涂层材料。本研究采用固相法制备TiO2掺杂SmTaO4陶瓷,研究结果表明：掺杂TiO2未改变SmTaO4陶瓷晶体结构,样品均为单斜相,掺杂2% mol TiO2的SmTaO4陶瓷烧结过程中出现的第二相为Sm0.33TaO3;随着TiO2含量增加,SmTaO4陶瓷的热导率先下降后上升,当TiO2掺杂含量为2%时,热导率最低为1.42W?m?1?K?1,低于SmTaO4（1.59W?m-1?K-1,900℃）,与7-8YSZ相比（2.1~2.7 W?m?1?K?1,100~900℃）下降了近30%。掺杂2%TiO2的SmTaO4陶瓷热膨胀性系数最大值为10.8×10-6K-1,大于YSZ（~10.0×10-6K-1）和SmTaO4（9.62×10-6K-1,1200℃）,与纯SmTaO4相比,TiO2掺杂提高了SmTaO4陶瓷的热膨胀系数。因此,TiO2掺杂SmTaO4陶瓷有望作为新型热障涂层材料使用。     

Anatase TiO2 sols derived from peroxotitanium acid and to form transparent TiO2 compact film for dye-sensitized solar cells

Transparent and surfactant-free TiO₂ sols containing anatase nanocrystals were prepared by the hydrothermal treatment of water-soluble peroxotitanium acid (PTA) at a temperature of 120 °C. The TiO₂ nanocrystals were characterized by transmission electron microscopy (TEM). The TEM results indicated that the TiO₂ nanocrystals were nanorod-like with diameters of less than 7 nm after the subsequently hydrothermal treatment. A gradient layer between the transparent fluorine doped SnO₂ (FTO) layer and the porous titanium dioxide nanocrystalline film for dye-sensitized solar cells (DSSCs) photoelectrodes, was made with the as-prepared TiO₂ sols. The TiO₂ gradient layers were characterized by field-emission scanning electron microscopy and UV-vis absorption spectrometry. After the gradient layer deposition on the FTO coated glass, the composite multilayer film exhibited the visible light transmittance of 80% which approached to that of bare FTO glass. The photo-to-electric energy conversion efficiency of the N719 dye-sensitized solar cell had significantly improved from 4.2% to 5.6% in the presence of the compact layer between FTO and the porous TiO₂ nanocrystalline film under of AM1.5 illumination (100 mW/cm²). The remarkable improvements in short-circuit current for the DSSCs was due to the effective gradient layer at the FTO-TiO₂ interface which prevented direct contact of electrolytes with FTO and consequently reduced charge recombination losses.     

Fast synthesis of monodisperse TiO2 submicrospheres via a modified sol-gel approach

Monodisperse titania glycolate submicrospheres were synthesized by a modified sol-gel route,in which ultrasonic treatment was introduced to improve the reaction efficiency.The as-prepared products were characterized by means of Fourier transform infrared spectrum (FT-IR),transmission electron microscopy (TEM),powder X-ray diffraction (XRD),and scanning electron microscopy (SEM).The results indicate that the as-prepared products are titania glycolate submicrospheres with diameters of 230-330 nm.The average particle diameter is estimated to be about 280 nm.Ultrasonic treatment has an important influence on the morphology of the produced titania glycolates.After calcination at 450℃ for 2 h,these titania glycolates were completely converted into anatase TiO2.The morphology of TiO2 particles was well reserved during the calcination process except for a reduction of 18% in the average particle size.     

Composition, surface structure, and thermal behavior of ZrO2 + TiO2/Ti and ZrO2 + CeOx + TiO2 composites formed by plasma-electrolytic oxidation

Specific surface structures of ZrO₂ + TiO₂ (I) and ZrO₂ +CeO_x + TiO₂ (II) coatings on titanium before and after annealing at 850°C for 24 h in air are studied. Whiskers are found on the surface of type-I coatings before annealing, and perfectly edged crystals composed of TiO₂ and ZrO₂ oxides are found upon annealing. Pores in both coatings have a multilevel structure. In the case of type-I coatings, orifices of pores are covered with titanium. In type-II coatings, pore orifices contain titanium, zirconium, and oxygen. Oxygen deficiency implies that titanium and zirconium are present in pore orifices in metallic state. In type-II coatings, the surface distribution of cerium is heterogeneous. Mechanical treatment of the annealed coatings causes their exfoliation from the substrate metal. In the case of both coatings, the exfoliating surfaces are composed of TiO₂ blocks containing excess oxygen.     

保护渣对铝钛系夹杂物溶解的吸收规律

以CaO-SiO₂-Al₂O₃-Na₂O-CaF₂-MgO为基础渣系,采用旋转动力学方法研究了不同碱度、BaO质量分数(0~15%)、B₂O₃质量分数(0~15%)对连铸保护渣吸收Al₂O₃或TiO₂速率的影响以及吸收前后矿相变化。结果表明,保护渣吸收TiO₂的速率要远大于吸收Al₂O₃的速率;添加BaO或B₂O₃后均能提高保护渣吸收Al₂O₃和TiO₂的能力;保护渣主要物相为钙镁黄长石(2CaO·MgO·2SiO₂)、钙铝黄长石(2CaO·Al₂O₃·2SiO₂)、枪晶石(3CaO·2SiO₂·CaF₂)及玻璃相(Na₂O·Al₂O₃·SiO₂);添加BaO后,钙镁黄长石转变为重硅酸钡钙镁(2CaO·MgO·2SiO₂·BaO),并抑制黄长石和枪晶石晶体长大;当添加B₂O₃的质量分数不低于10%,保护渣形成的物相为玻璃相。试验条件下,不同碱度的保护渣和添加B₂O₃的保护渣中TiO₂仍以TiO₂形式存在,而在添加BaO的保护渣中,TiO₂形成钙钛矿。     

Performance Enhancement in Dye-Sensitized Solar Cells with Composite Mixtures of TiO2 Nanoparticles and TiO2 Nanotubes

In the present investigation,a new composite nanostructured photoanodes were prepared using TiO₂ nanotubes（TNTs） with TiO₂ nanoparticles（TNPs）.TNPs were synthesized by sol-gel method,and TNTs were prepared through alkali hydrothermal method.Dye-sensitized solar cells（DSSCs） were fabricated with different photoanodes comprising of various ratios of TNTs + TNPs,synthetic indigo dye as photosensitizer,PMII（l-propyl-3-methylimidazolium iodide） as ionic liquid electrolyte and cobalt sulfide as counter electrode.The structures and morphologies of TNPs and TNTs were analyzed through X-ray diffractometer,transmission electron microscope and scanning electron microscopes.The results of the investigation showed that the DSSC-4 made with composite photoanode structure（TNTs/TNPs）（90% of TNPs + 10% of TNTs） had improved photocurrent efficiency（2.11%） than pure TNPs（1.00%） and TNT film（0.78%）.Electrochemical impedance spectra revealed that the composite TNTs/TNPs film-based DSSCs possessed the lowest charge-transfer resistances and longest electron lifetime.Hence,it could be concluded that the composite TNTs/TNPs photoanode facilitates the charge transport rate and enhances the efficiencies of DSSCs.     

Dissociation of Ti2O3 from titania slag under mechanical activation

In this present study, the effects of mechanical activation on the characterization of titania slag were systematically investigated. The crystal structures, surface chemical functional groups, and microstructure of the samples were characterized before and after mechanical activation using XRD, FT-IR, and Raman spectroscopy techniques, respectively. It was found that untreated titania slag under mechanical activation was mainly composed of Fe₃Ti₃O₁₀ and rutile TiO₂, but that of being treated by mechanical activation was mainly composed of Fe₃Ti₃O₁₀, Ti₂O₃ and rutile TiO₂. Ti₂O₃ is transformed partially from Fe₃Ti₃O₁₀ under moderate mechanical activation conditions for 12 h. The demonstration of mechanical activation techniques can be applied effectively and efficiently to the treatment processing of titania slag.     

Preparation of thermally stable anatase TiO2 photocatalyst from TiOF2 precursor and its photocatalytic activity

Preparation of anatase TiO₂ with high themal stability is of great importance for its environmental application. In this work, TiOF₂ was first synthesized by a simple microwave-assisted hydrothermal route using tetrabutyl titanate and hydrofluoric acid as precursors at 200 °C for 20 min. Then the resulted precipitates were calcined at different temperatures (300-1000 °C) for 2 h. The as-prepared samples were characterized by X-ray diffraction, Raman spectrum, scanning electron microscopy, N₂ adsorption-desorption isotherms and X-ray photoelectron spectroscopy. The photocatalytic activity was evaluated using Brilliant Red X3B, an anionic azo dye, as the target organic molecule under UV light irradiation. The results showed that the prepared TiOF₂ exhibited weak or no photocatalytic activity. The phase transformation of TiOF₂ to anatase TiO₂ occurred at about 300 °C. The prepared anatase TiO₂ from TiOF₂ showed very high thermal stability and the anatase-to-rutile phase transformation temperature was up to 1000 °C. Fluoride ions played an important role in the improvement of thermal stability of anatase TiO₂ by strongly adsorbing on the crystal planes of anatase to stabilize the anatase structure. The 700 °C-calcined sample showed the highest photocatalytic activity due to its relative good crystallization and high specific surface areas.     

Characterization of TiO2 coatings prepared by a modified electric arc-physical vapour deposition system

TiO₂ thin coatings were prepared, on various substrates, through evaporation of metallic titanium in an oxidizing atmosphere by modified electric arc-physical vapor deposition (EA-PVD). The coatings were characterized chemically (by means of XPS and SIMS) and from the structural point of view (by means of XRD and Raman spectroscopy), in order to understand the factors which lead to homogeneous coatings with high anatase content. The type of substrate is the main parameter that influences the crystal structure of the coatings: when stainless steel is used as substrate the coatings consist essentially of rutile, while on glass substrates coatings containing mainly anatase are obtained. The photocatalytic activity of the samples upon UVA irradiation was tested by using phenol as the target molecule. Phenol in the solution can be photocatalytically and rapidly degraded through the EA-PVD anatase TiO₂ coatings.     

TiO2纳米管薄膜的屈曲图样（英文）

采用基体应变测试方法研究TiO2纳米管薄膜的屈曲图样。结果表明：TiO2纳米管薄膜室温样、250℃退火样和 400℃退火样的屈曲应变依次为2.5%、8.9%和7.8%,说明退火改善了纳米管薄膜/Ti 基体界面状况。从 SEM 观察可以看出,TiO2纳米管薄膜室温样、250℃退火样和400℃退火样的临界屈曲应力分别为180.4、410.2 和 619.5MPa;从 AFM 观察可以看出,TiO2纳米管薄膜 250℃退火样的临界屈曲应力为470.2MPa,两者吻合得很好。采用AFM计算250℃退火样的真实应力和能量释放率分别为840.3MPa和77.2J/m2,此结果与从裂纹角度计算出的250℃退火样的能量释放率102.6 J/m2吻合得很好。     

TiO2纳米管薄膜的脱层现象（英文）

分别通过曲率法和基体拉伸应变测试方法研究TiO2纳米管薄膜的残余应力和脱层行为。结果表明:TiO2纳米管薄膜的内残余应力为-54MPa。TiO2纳米管薄膜室温样、250°C退火样和400°C退火样的脱层出现点的应变依次为2.6%、5.1%和8.6%,半径依次为27.5、17.1和19.4μm。TiO2纳米管薄膜室温样、250°C退火样和400°C退火样的真实临界脱层应力为220.4、394.5和627.9MPa。在脱层条件下,对界面剪滞模型进行修订,并对TiO2纳米管薄膜界面剪切强度进行多项式拟合。由于拟合结果与裂纹密度的分析结果能很好吻合,因此界面剪滞模型的修订方程和多项式拟合方程均为可信的。