نتایج جستجو برای: niobium
تعداد نتایج: 3152 فیلتر نتایج به سال:
A new niobium-doped inorganic scintillating oxyfluoride, Rb4Ge5O9F6:Nb, was synthesized in single crystal form by high-temperature flux growth. The host structure, Rb4Ge5O9F6, crystallizes the orthorhombic space group Pbcn with lattice parameters a = 6.98430(10) Å, b 11.7265(2) and c 19.2732(3) consisting of germanium oxyfluoride layers made up Ge3O9 units connected GeO3F3 octahedra. In its pur...
In this work the effects of controlled rolling parameters and adding of Niobium have been studied. In this order two steel grades with and without Niobium are planed and after steelmaking and continuous casting, rolling process are done. Then, laboratory investigations such as microstructure, mechanical properties and grain size analysis were performed Tensile and Charpy impact tests specimens ...
The accelerating gradient performance of superconducting niobium cavities is rapidly progressing as a result of reduced field emission due to improvement in surface preparation techniques. Beyond the field emission limitation, there exists a fundamental limit imposed by the critical magnetic field of niobium. One way to tackle this limit is to reduce the ratio of the peak magnetic field to the ...
The decomposition reaction of niobium(V) oxytrichloride ammoniate to the oxynitride of niobium in the 5+ oxidation state was developed in a methodological way. By combining elemental analysis, Rietveld refinements of X-ray and neutron diffraction data, SEM and TEM, the sample compound was identified as approximately 5 nm-diameter particles of NbO(1.3(1))N(0.7(1)) crystallizing with baddeleyite-...
To achieve optimal mechanical properties in high manganese steels, the precipitation of nanoprecipitates of vanadium and niobium carbides is under investigation. It is shown that under controlled heat treatments between 850°C and 950°C following hot deformation, few-nanometre precipitates of either carbide can be produced in test steels with suitable contents of vanadium or niobium. The structu...
We have designed and constructed a custom far-infrared Fourier transform spectrometer using an antenna-coupled bolometer as a detector. The active element of the detector is a superconducting niobium microbridge, and the far-infrared signal is coupled to the microbridge via a planar antenna mounted on a hyperhemispherical silicon lens. The spectrometer uses a broadband blackbody source with fre...
While the superconducting community has developed various techniques for the fabrication of nanoscale hot electron bolometers (HEB), the basic structure of an HEB microbridge has been fairly consistent. A typical HEB used in a cryogenic terahertz mixer consists of a thin strip of superconductor contacted on opposite ends by small metal contact pads in a planar configuration. Both the physics an...
A niobium and tantalum co-doped perovskite cathode for solid oxide fuel cells operating below 500 °C
The slow activity of cathode materials is one of the most significant barriers to realizing the operation of solid oxide fuel cells below 500 °C. Here we report a niobium and tantalum co-substituted perovskite SrCo0.8Nb0.1Ta0.1O3-δ as a cathode, which exhibits high electroactivity. This cathode has an area-specific polarization resistance as low as ∼0.16 and ∼0.68 Ω cm2 in a symmetrical cell an...
Superconductors with periodically ordered mesoporous structures are expected to have properties very different from those of their bulk counterparts. Systematic studies of such phenomena to date are sparse, however, because of a lack of versatile synthetic approaches to such materials. We demonstrate the formation of three-dimensionally continuous gyroidal mesoporous niobium nitride (NbN) super...
Vanadium-niobium oxide catalysts containing variable amounts of vanadium and prepared by coprecipitation were investigated using 51V solid-state NMR. It was found that, in samples containing less than about 8 mol % V2O5, vanadium occurs in three different oxygen environments: in isolated tetrahedra, in comer-sharing tetrahedra (pyrovanadate), and in distorted octahedra. The number of octahedral...
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