Synthesis of crystallized TaON and Ta3N5 by nitridation of Ta2O5 thin films grown by pulsed laser deposition

TaON and Ta₃N₅ thin films of different thicknesses were prepared by pulsed laser deposition of tantalum oxide followed by ex situ thermal nitridation under ammonia. The nitridation was carried out in flowing gas in the 600–800 °C temperature range. The dependence of tantalum oxynitride and nitride crystalline phases formation on nitridation reaction parameters was investigated. Structural and microstructural characteristics were investigated by X-ray diffraction (XRD) and scanning electron microscopy (SEM).     

Anodic formation of high aspect ratio, self-ordered Nb2O5 nanotubes

In the present work, we demonstrate the feasibility to form an aligned Nb(2)O(5) nanotube layer by self-organizing anodization of Nb in a NH(4)F-glycerol electrolyte. In order to achieve a nanotubular rather than a nanoporous layer, careful optimization of the anodization electrolyte is required. We show that only in a narrow window of electrolyte parameters highly aligned nanotubes of 50 nm inner diameter and several micrometres in length can be formed.     

Formation of PPy/Ta2O5/Ta structure by electropolymerization

Electropolymerization of pyrrole on tantalum (Ta) electrodes was carried out in buffer solutions (0.04 M phosphoric acid, 0.04 M acetic acid, 0.04 M boric acid and 0.2 M sodium hydroxide) containing 0.1 M sodium ptoluenesulfonate (TsONa) under galvanostatic conditions and it was found that a polypyrrole (PPy) and a tantalum oxide (Ta₂O₅) layer are formed on a Ta electrode by an electrochemical oxidation process. The conditions of this simultaneous formation were studied in respect to current density (i_d), pyrrole concentration ([Py]), pH and the amount of electricity. Under certain conditions ([Py] = 0.25 M, pH = 1.8, i_d = 10–20 mA cm^?2, the amount of electricity = 1 C), 6–8 μm thick PPy films were efficiently formed on homogeneous 30–50 nm thick Ta₂O₅ layers. The PPy film showed a high electrical conductivity (110 s cm^?1), adhered well and covered the Ta₂O₅ layer. The resulting PPy/Ta₂O₅/Ta system is therefore proved to have excellent properties as a capacitor.     

Preparation and characterization of microsized K2Ta2O3F6 with ellipsoidal morphology by anodization

Ellipsoidal K₂Ta₂O₃F₆ particles with an average length of 2.79 μm and a diameter of 0.63 μm were synthesized by anodization in saturated solutions of potassium chloride containing 5 wt% HF. Microstructure and composition analysis were conducted by scanning electron microscopy, X-ray diffractometry and energy dispersive spectroscopy. Formation mechanism of this special morphology was given based on the experimental results.     

复合光催化材料H3PW122O40/Ta2O5光催化降解染料的研究

采用溶胶-凝胶法制备了半导体型金属氧化物Ta2O5,并通过浸渍法与杂多酸H,PW12O40复合,获得了纳米复合光催化材料H3PW12O40/Ta2O5.通过1CP-AES、FT-lR、N2吸附、Tc等手段对其组成、结构及其表面物理化学性质进行了表征,并在可见光下考察了该复合材料对可溶性染料罗丹明B和亚甲基蓝的光催化活性.实验结果表明,该复合材料存可见光下有较好的光催化活性,其中,H3PW12O40/Ta2O5在180min内对亚甲基蓝的光催化降解转化率达到78%.     

Ideally ordered porous TiO2 prepared by anodization of pretextured Ti by nanoimprinting process

Ideally ordered anodic porous TiO₂ was fabricated through the pretexturing of Ti by nanoimprinting using a metal mold with an ordered array of convexes. The shallow concaves prepared by nanoimprinting acted as initiation sites for hole development during the subsequent anodization and generated ideally hexagonally ordered porous or nanotubular TiO₂. The hole interval of the ideally ordered TiO₂ could be controlled by changing the pretexturing pattern. This process is a key step towards the preparation of various types of functional devices requiring ideally ordered defect-free hole or pore arrangements.     

Fabrication of ideally ordered anodic porous TiO2 by anodization of pretextured two-layered metals

Ideally ordered anodic porous TiO₂ was fabricated by anodizing an Al/Ti layered specimen. A two-layered specimen composed of an Al top layer and a Ti underlying layer was prepared and then processed by nanoimprinting. The Al top layer was easily pretextured by nanoimprinting owing to its softness and it was straightforward to introduce an ideally ordered pore arrangement by anodization. This pore arrangement was transferred to the underlying Ti layer, resulting in ideally ordered porous structures in TiO₂. This process can be applied to the high-throughput fabrication of ideally ordered anodic porous oxides other than TiO₂ and also to other metals with high hardness.     

Physicochemical Study of Ta2O5 and SiO2-Ta2O5 Film Formation from Film-Forming Solutions

In order to study physicochemical processes of formation of Ta₂O₅ and SiO₂-Ta₂O₅ films from film-forming solutions, the properties of these solutions, and also the thermal-oxidative breakdown and the properties of the obtained films, were studied.     

Improvement of electrochemical properties of lithium-rich manganese-based cathode materials by Ta2O5

Journal of Solid State Electrochemistry - As one of the most promising cathodes for next-generation lithium-ion batteries, lithium-rich materials have been widely studied because of their excellent...     

Enhancement of green-light photoluminescence of Ta2O5 nanoblock stacks

In this study we have explored the structural, electronic, and photoluminescence (PL) properties of Ta(2)O(5) nanoblock stacks. The Ta(2)O(5) nanoblocks were synthesized by the hot filament metal-oxide vapor deposition (HFMOVD) technique and randomly arranged in large-area stacks. Field-emission scanning electron microscopy (FESEM) showed most of the stacking Ta(2)O(5) nanoblocks to be 21 nm wide. Energy dispersive spectroscopy (EDS) analysis verified the presence of only the elements Ta and O. X-Ray photoemission spectroscopy (XPS) not only revealed the electronic structures and chemical properties of the stacking Ta(2)O(5) nanoblocks but also their stoichiometric Ta/O ratio of ～0.416 (i.e. Ta:O = 2.08?:?5). Photoluminescence (PL) spectroscopy showed very strong green-light emissions, which emerged from the trap-levels of the oxygen vacancies within the Ta(2)O(5) bandgap. The PL intensities were linearly enhanced by increasing the laser power and the excitation time. The PL results suggest that the nanoblocks are excellent visible-light emitters.     

Neue Phasen in den Systemen Nb2O5-WO3 und Ta2O5-WO3

Zusammenfassung Bei Untersuchungen im WO₃-ärmeren Bereich der Systeme Nb₂O₅-WO₃ und Ta₂O₅-WO₃ bis zum Molverhältnis Me₂O₅:WO₃=1:2 wurden folgende Phasen neu gefunden: 40 Nb₂O₅·WO₃–20 Nb₂O₅·WO₃ (Phasenbreite), 13 Nb₂O₅· ·4 WO₃, 9 Nb₂O₅·8 WO₃ (Tieftemperaturphase), 9 Ta₂O₅· ·8 WO₃; ferner eine Mischphase des T-Ta₂O₅, die bis zur Zusammensetzung 13 Ta₂O₅·4 WO₃ (bei 1300° C) reicht. Weitere Phasen wurden im System Nb₂O₅-WO₃ bei den Molverhältnissen 8:1–6: 1, 7:3, 8:5 und 9:8 (Hochtemperaturphase) beobachtet.49. Mitt.:H. Schäfer, R. Gruehn undF. Schulte, Angew. Chemie, im Druck.     

Photoelectrochemical properties of Fe2O3-Nb2O5 films prepared by sol-gel method

Fe2O3-Nb2O5 coating films of various Nb/(Fe + Nb) mole ratios were prepared on nesa silica glass substrates from Fe(NO3)3.9H2O - NbCl5 - CH3(CH2)2CH2OH - CH3COOH solutions by the sol-gel method. The photoanodic properties were studied in a three-electrode cell with an aqueous buffer solution of pH = 7 as the supporting electrolyte. The crystalline phases identified were alpha-Fe2O3 (Nb/(Fe + Nb) = 0), alpha-Fe2O3 + FeNbO4 (Nb/(Fe + Nb) = 0.25), FeNbO4 (Nb/(Fe + Nb) = 0.5), FeNbO4 + Nb2O5 (Nb/(Fe + Nb) = 0.75), and Nb2O5 (Nb/(Fe + Nb) = 1). When the Nb/(Fe + Nb) mole ratio increased from 0 to 0.25, the crystalline phases changed from alpha-Fe2O3 to alpha-Fe2O3 + FeNbO4, the photoanodic current under white light illumination increased, and the photoanodic current under monochromatized light illumination increased in both visible and ultraviolet regions. When the Nb/(Fe + Nb) ratio increased over 0.25, the crystalline phases changed to FeNbO4, FeNbO4 + Nb2O5, or Nb2O5, and the photoanodic current decreased. The sample consisting of alpha-Fe2O3 and FeNbO4 (Nb/(Fe + Nb) = 0.25) exhibited photoresponse extending to 600 nm and an IPCE of 18% at a wavelength of 325 nm.     

Phase distribution in the HfO2Er2O3Ta2O5 system

Phase relationships obtained by heating coprecipitated oxide powders in the HfO₂Er₂O₃Ta₂O₅ system were investigated by X-ray diffractometry. Partial isothermal sections at 1100 and 1500°C are presented.     

New Compounds in the IMb2O6(Ta2O5)-V2O6 Systems

Tetraphenyl Imidodiphosphate as Ligand in Fluoro Complexes. 3. Fluoro Complexes of Niobium, Tantalum, and Antimony Tetraphenyl imidodiphosphate forms with NbF₅, TaF₅, and SbF₅ the addition complexes MF₅ · LH and (MF₅)₂(μ-LH). The imidodiphosphate acts in the latter as bidentately bridging ligand. Furtheron, it reacts with NbF₅ and TaF₅ by replacing fluoride forming tetrafloro and trifluoro complexes: [MF₄(μ-L)]₂ and MF₃(η²-L)(OPh) or μ-O[MF₃(η²-L)]₂, resp., (M ? Nb, Ta). SbF₅ does not form substitution complexes. The constitution and conformation of the complexes have been concluded from n.m.r. spectroscopic data.     

Preillumination of TiO2 and Ta2O5 photoactive thin films as a tool to tailor the synthesis of composite materials

Illumination of TiO 2 thin films with UV light is known to induce the transformation of the surface of this material from partially hydrophobic into fully hydrophilic. The present work shows that this transformation is accompanied by other effects that may be used to control the synthesis of composite materials. For this purpose, TiO 2 and Ta 2O 5 transparent thin films with a columnar structure and open pores were prepared by electron evaporation at glancing angles. Transparent TiO 2 thin films with micropores (i.e., pores smaller than 2 nm) prepared by plasma enhanced chemical vapor deposition (PECVD) were also used. All these films became hydrophilic upon UV illumination. Rhodamine 6G and Rhodamine 800 dyes were irreversibly adsorbed within the columns of the TiO 2 and Ta 2O 5 thin films by immersion into a water solution of these molecules. Isolated and aggregated molecules of these two dyes were detected by visible absorption spectroscopy. The infiltration adsorption efficiency was directly correlated with the acidity of the medium, increasing at basic pHs as expected from simple considerations based on the concepts of the point of zero charge (PZC) in colloidal oxides. The infiltration experiments were repeated with columnar TiO 2 and Ta 2O 5 thin films that were subjected to preillumination with UV light. It was found that this treatment produced a modification in the type (isolated or aggregated) and amount of dye molecules incorporated into the pores. Moreover, the selective adsorption of a given dye in preilluminated areas of the films permitted the lithographic coloring of the films. Preillumination also controls the UV induced deposition of silver on the surface of the microporous TiO 2 thin films. It was found that the size distribution of the formed silver nanoparticles was dependent on the preillumination treatment and that a well-resolved surface plasmon resonance at around 500 nm was only monitored in the preilluminated films. A model is proposed to account for the effects induced by UV preillumination on the TiO 2 and Ta 2O 5 oxide surfaces. The possibilities of this type of light treatment for the tailored synthesis of nanocomposite thin films (i.e., dye-oxide, metal nanoparticles-oxide) are highlighted.