Synthesis and research of phase composition of alloys Nb2O5: Fe3+ and Ta2O5: Fe3+

The conditions were studied for the synthesis of niobium and tantalum pentoxide containing iron impurity introduced into the strip liquor after extraction separation of niobium and tantalum and subsequent precipitation of metal hydroxides with ammonia. A phase composition of the synthesized alloys was examined by X-ray diffraction and infrared spectroscopy.     

Die Phasen Nb3Ga2, Ta5Ga3 und Ta5Al3Bx

Zusammenfassung Die Phasen Nb₃Ga₂, Ta₅Ga₃ und Ta₅Al₃B_x werden aus den Komponenten hergestellt. Nb₃Ga₂ kristallisiert im U₃Si₂-Typ, Ta₅Ga₃ hat Cr₅Br₃-Struktur (T 2) und Ta₅Al₃B_x ist mit Mn₅Si₃ (teilweise aufgefüllt) isotyp.     

Optical properties of a perfluorosulfonic membrane modified with Co2+ cations

A perfluorosulfonic membrane was modified with Co²⁺ cations. A comparative study of the thermal stabilities of the starting (hydrogen) and cobalt(II)-containing forms of the membrane was carried out. Optical electronic spectroscopy was used to characterize color transformations accompanying sorption-desorption of water by the modified membrane.     

On two alternative mechanisms of ethane activation over ZSM-5 zeolite modified by Zn2+ and Ga1+ cations

The activation of ethane over zinc- and gallium-modified HZSM-5 dehydrogenation catalysts was studied by diffuse reflectance infrared spectroscopy. Hydrocarbon activation on HZSM-5 modified by bivalent Zn and univalent Ga cations proceeds via two distinctly different mechanisms. The stronger molecular adsorption of ethane by the acid-base pairs formed by distantly separated cationic Zn2+ and basic oxygen sites results already at room temperature in strong polarizability of adsorbed ethane and subsequent heterolytic dissociative adsorption at moderate temperatures. In contrast, molecular adsorption of ethane on Ga+ cations is weak. At high temperatures dissociative hydrocarbon adsorption takes place, resulting in the formation of ethyl and hydride fragments coordinating to the cationic gallium species. Whereas in the zinc case a Br?nsted acid proton is formed upon ethane dissociation, decomposition of the ethyl fragment on gallium results in gallium dihydride species and does not lead to Br?nsted acid protons. This difference in alkane activation has direct consequences for hydrocarbon conversions involving dehydrogenation.     

Improvement of lithium-ion conductivity in A-site-disordered lithium lanthanum titanates by V5+/Nb5+ substitution

The V⁵⁺/Nb⁵⁺-substituted lithium lanthaum titanates are synthesized by a conventional solid-state reaction method at high temperature in air. The structural and conductivity studies of the obtained perovskite oxide samples are investigated by x-ray diffraction (XRD), SEM, and impedance spectroscopy. From the powder XRD patterns, it is clearly observed that the synthesized samples exhibit a well-defined cubic structure with the Pm3m (Z = 1) space group. The lattice parameter is decreased with increasing vanadium content in Li_0.5?x La_0.5Ti_1?x V _x O₃, but increased with the increasing niobium content in Li_0.5?x La_0.5Ti_1?x Nb _x O₃. The scanning electron microscope measurements confirmed that these materials consist of fairly ordered grains throughout the surface area. The conductivity variations with the substitution of vanadium/niobium are also reported. The bulk ionic conductivity measured in the temperature range from room temperature to 150 °C is about the same as reported earlier for the related lithium lanthanum titanate. However, the low activation energies for ionic conduction observed for these samples encourage further investigations for better conductors in this system.     

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.     

Spectral and fluorescent kinetics features of Nd3+ ion in Nb2O5, Ta2O5 and La2O3 mixed lithium zirconium silicate glasses

A sensitive competitive flow injection chemiluminescence (CL-FIA) immunoassay for immunoglobulin G (IgG) was developed using gold nanoparticle as CL label. In the configuration, anti-IgG antibody was immobilized on a glass capillary column surface by 3-(aminopropyl)-triethoxysilane and glutaraldehyde to form immunoaffinity column. Analyte IgG and gold nanoparticle labeled IgG were passed through the immunoaffinity column mounted in a flow system and competed for the surface-confined anti-IgG antibody. CL emission was generated from the reaction between luminol and hydrogen peroxide in the presence of Au (III), generated from chemically oxidative dissolution of gold nanoparticle by an injection of 0.10 mol L⁻¹ HCl–0.10 mol L⁻¹ NaCl solution containing 0.10 mmol L⁻¹ Br₂. The concentration of analyte IgG was inversely related to the amount of bound gold nanoparticle labeled IgG and the CL intensity was linear with the concentration of analyte IgG from 1.0 ng mL⁻¹ to 40 ng mL⁻¹ with a detection limit of 5.2 × 10⁻¹⁰ g mL⁻¹. The whole assay time including the injections and washing steps was only 30 min for one sample, which was competitive with CL immunoassays based on a gold nanoparticle label and magnetic separation. This work demonstrates that the CL immunoassay incorporation of nanoparticle label and flow injection is promising for clinical assay with sensitivity and high-speed.     

Commensurate Nb2Zr5O15: Accessible Within the Field Nb2ZrxO2x+5 After All

Doped niobium zirconium oxides are applied in field-effect transistors and as special-purpose coatings. Whereas their material properties are sufficiently known, their crystal structures remain widely uncharacterized. Herein, we report on the comparably mild sol-gel synthesis of Nb₂Zr₅O₁₅ and the elucidation of its commensurately modulated structure via neutron diffraction. We describe the structure using the most appropriate superspace as well as the convenient supercell approach. It is part of an α-PbO₂-homeotypic field with the formula Nb₂Zr_xO_2x+5, which has previously been reported only for x≥5.1, and is closely related to the structure of Hf₃Ta₂O₁₁. The results, supported by X-ray diffraction and additional synthesis experiments, are contextualized within the existing literature. Via the sol-gel route, metastable Nb−Zr−O compounds and their heavier congeners are accessible that shed light on possible structures of these commercially utilized materials.     

Drei Wege zur Oxydation von [Ta6Cl12]2+ ([Ta6Br12]2+ und [Nb6Cl12]2+)

Three Oxidation Paths of [Ta₆Cl₁₂]²⁺ ([Ta₆Br₁₂]²⁺ and [Nb₆Cl₁₂]²⁺) [Ta₆Cl₁₂]²⁺ is oxidized autocatalytically to [Ta₆Cl₁₂]⁴⁺ by HNO₃. The titration of [Ta₆Cl₁₂]²⁺ with KBrO₃ (in HBr-containing solutions) or with Ce⁴⁺ or K₂Cr₂O₇ (in HNO₃-containing solutions) leads to a clear [Ta₆Cl₁₂]³⁺ step. The further titration leads beside [Ta₆Cl₁₂]⁴⁺ to the formation of Ta₂O₅(· xH₂O). [Ta₆Cl₁₂]²⁺ behaves with KBrO₃(+ HBr) equally, but the formation of [Ta₂O₅](· xH₂O) is only small. [Nb₆Cl₁₂]²⁺ (22°C) titrated with Ce(ClO₄)₄ in 2n HClO₄ gives the first potential step nearby exact ([Nb₆Cl₁₂]³⁺) and at a very slow titration in a second step a precipitation of Nb₂O₅(· xH₂O) occurs, which adsorbed Ce⁴⁺ additionally. At ?15°C with Ce(ClO₄)₄ the first potential step was exactly at [Nb₆Cl₁₂]^2+→3+, while the second step needs a distinct additional consumption of titer. (Formation of [Nb₆Cl₁₂]⁴⁺ and beside it [Nb₂O₅](· xH₂O)). From the titration curves and sections of its normal progress in all cases we get the normal potentials 2+/3+ and 3+/4+ with an accuracy of ± 0.01 volt. In alkaline solution the complexes are oxidized with air-oxygen to [M₆X₁₂](OH)₆^2?, while the Br-containing complexes suffer hydrolysis afterwards.     

Spectroscopic study of the complexation of an aza-15-crown-5 containing chromofluoroionophore with Ba2+ and Ca2+ cations

The complexation of 1-[(4-benzothiazolyl)phenyl]-4,7,10,13-tetraoxa-1-aza-cyclopenta-decane with Ba²⁺ and Ca²⁺ cations was investigated spectrophotometrically and spectrofluorometrically. The stability constants of the complexes formed are: for Ba²⁺ logK _st=3.17±0.01 (absorption) and logK _st=2.95±0.03 (fluorescence); for Ca²⁺ logK _st=3.71±0.02 (absorption) and logK _st=3.58±0.05 (fluorescence). Protonation of the ligand leads to fluorescence quenching. AM1 and PPP quantum chemical calculations were used to predict molecular geometry, proton affinities and the spectra of the compounds studied.Dedicated to Prof. Dr. Karl-Heinz Drexhage on the occasion of his 60th birthday     

Preparation of new photosensitive Nb2O5 gel films modified with benzoylacetone and properties of heat-treated films

In this study, in order to develop a new photosensitive gel film, Nb₂O₅ gel films including a chelate ring were prepared by the sol?Cgel method. Photosensitive and patterning properties of the gel films were investigated. Properties such as refractive index for annealed films were also evaluated. In the electronic absorption spectra of the gel films, the absorption peak assigned a chelate ring was observed at 353?nm, this peak intensity decreased by UV irradiation. From this result, the obtained gel films exhibit photosensitivity. Fine patterns (minimal width of about 2???m) could be fabricated. It was found that the value of refractive index reaches a maximum of 2.25 for the film heat-treated at 800?°C.     

Synthesis, structure, and characterization of two new layered mixed-metal phosphates, BaTeMO4(PO4) (M = Nb5+ or Ta5+

Two new isostructural mixed-metal phosphates, BaTeMO(4)(PO(4)) (M = Nb(5+) or Ta(5+)), have been synthesized as bulk phase powders and single crystals by standard solid-state techniques using BaCO(3), TeO(2), Nb(2)O(5) (or Ta(2)O(5)), and NH(4)H(2)PO(4) as reagents. The materials have novel layered crystal structures consisting of [M(5+)O(6/2)](-) corner-sharing octahedral chains that are connected to [Te(4+)O(4/2)](0) polyhedra and [P(5+)O(2/1)O(2/2)](-) tetrahedra. The Ba(2+) cations reside between the layers and maintain charge balance. The Te(4+) cations are in asymmetric coordination environments attributable to their lone pairs. The Nb(5+) distorts along the local C(4) direction of its octahedron resulting in a "short-long-short-long" Nb-O-Nb bond motif. The Nb(5+) cation displaces away from the oxide ligands that are bonded to Te(4+) or P(5+) cations, attributable to the structural rigidity of the TeO(4) and PO(4) polyhedra. Thus, the TeO(4) and PO(4) polyhedra support and reinforce the intraoctahedral distortion observed within the NbO(6) octahedra. Infrared and Raman spectroscopy, thermogravimetric analysis, and ion-exchange experiments are also presented. Crystal data: BaTeNbO(4)(PO(4)), orthorhombic, space group Pbca (No. 61), with a = 6.7351(9) A, b = 7.5540(10) A, c = 27.455(4) A, V = 1396.8(3) A(3), and Z = 8; BaTeTaO(4)(PO(4)), orthorhombic, space group Pbca (No. 61), with a = 6.734(2) A, b = 7.565(3) A, c = 27.435(9) A, V = 1372.6(8) A(3), and Z = 8.     

Die H-Phasen Ti2TlC,Ti2PbC,Nb2InC,Nb2SnC und Ta2GaC

Zusammenfassung Die Verbindungen Ti₂TlC, Ti₂PbC, Nb₂InC, Nb₂SnC und Ta₂GaC werden hergestellt. Die Bestimmung der Kristallstruktur zeigt Isotypie mit Cr₂AlC (H-Phase).     

Thermochemistry of interaction between cellulose modified with 2-aminomethylpyridine and divalent cations

Cellulose, a biopolymer seemingly inert, was chlorinated initially by reaction with thionyl chloride and then after it becomes more reactive, reacted with 2-aminomethylpyridine molecule for increasing its capacity of removal of divalent cations from an aqueous medium. These materials were characterized by means of elemental analysis, ¹³C NMR, and FTIR techniques, which have proved that a successful modification has occurred. The final material (Celamp), after being characterized was submitted to adsorption assays to evaluate its interaction with cations, whose affinity was found to be Cu²⁺ > Co²⁺ > Ni²⁺ > Zn²⁺. The quantitative cation/base center interactions were calorimetrically determined and showed exothermic enthalpies of ?(13.25 ± 0.12), ?(15.11 ± 0.22), ?(17.23 ± 0.15), and ?(14.66 ± 0.27) kJ mol^?1; negative Gibbs energies of ?(16.3 ± 0.7), ?(14.7 ± 0.7), ?(14.4 ± 0.7), and ?(13.3 ± 0.7) kJ mol^?1; and entropies of 10 ± 2, ?1 ± 1, ?10 ± 1, and ?5 ± 1 J mol^?1 K^?1 for the same sequence of cations. These favorable thermodynamic data suggest that the synthesis involving cellulose produces a new useful material for cation removal from the environment.     

Ein weiteres Gemischtvalentes Oxoniobat: Sr5Nb34+Nb25+O16

About a Mixed Valence Oxoniobate: Sr₅Nb₃⁴⁺Nb₂⁵⁺O₁₆ The hitherto unknown compound Sr₅Nb₅O₁₆ was prepared and examined by X-ray single crystal work. It crystallizes with orthorhombic symmetry (space group D–Pmn2₁, a = 3.992(1), b = 32.476(10), c = 5.677(2) Å; Z = 2). Sr₅Nb₅O₁₆ consists of stacked perovskite-like blocks cut by a plane perpendicular to the cube face diagonal of the perovskite structure. The coordination relations of the intersections between those blocks and the distribution of Nb⁵⁺ and Nb⁴⁺ are discussed.