Tantalum Impurity Research Articles

Nickel Site Modification by High-Valence Doping: Effect of Tantalum Impurities on the Alkaline Water Electro-Oxidation by NiO Probed by Operando Raman Spectroscopy.

In an effort to support the large-scale implementation of clean hydrogen in industry and society, the electrolytic decomposition of water is considered a realistically enticing prospect, provided the guarantee of affordable and durable material components. Within alkaline systems, earth-abundant electrocatalysts could provide both these requirements. However, a continued exploration of the reactivity and the causes behind different behaviors in performance are necessary to guide optimization and design. In this paper, Ta-doped NiO thin films are prepared via DC magnetron sputtering (1–2–4 at % Ta) to demonstrate the effect of surface electronic modulation by non-3d elements on the catalysis of the oxygen evolution reaction (OER). Material properties of the catalysts are analyzed via Rutherford backscattering spectrometry, X-ray diffractometry, photoelectron spectroscopy, and Raman spectroscopy. Ta impurities are shown to be directly responsible for increasing the valence state of Ni sites and enhancing reaction kinetics, resulting in performance improvements of up to 64 mV at 10 mA cm–2 relative to pristine NiO. Particularly, we show that by applying operando Raman spectroscopy, Ta enhances the ability to create high-valence Ni in γ-NiOOH at a lower overpotential compared to the undoped sample. The lowered overpotentials of the OER can thus be attributed to the energetically less hindered advent of the creation of γ-NiOOH species on the pre-catalyst surface: a phenomenon otherwise unresolved through simple voltammetry.

The First Investigation of Tantalum Impurity Influence on Deuterium Retention in W–Ta Alloy after Gas Exposure

The First Investigation of Tantalum Impurity Influence on Deuterium Retention in W–Ta Alloy after Gas Exposure

Intracenter Radiative Transitions at Tantalum Impurity Centers in Cadmium Telluride

Intracenter Radiative Transitions at Tantalum Impurity Centers in Cadmium Telluride

High-Q superconducting niobium cavities for gravitational wave detectors

The main purpose of this work is to optimize the electricQ-factor of superconducting niobium klystron cavities to be used inparametric transducers of the Mario Schenberg gravitational wave detector.Many cavities were manufactured from niobium with relatively high tantalumimpurities (1420 ppm) and they were cryogenically tested to determine theirresonance frequencies, unloaded electrical quality factors (Q0) andelectromagnetic couplings. These cavities were closed with a flat niobiumplate with tantalum impurities below 1000 ppm and an unloaded electricalquality factors of the order of 105 have been obtained. AC conductivityof the order of 1012 S/m has been found for niobiumcavities when matching experimental results with computational simulations.These values for the Q-factor would allow the detector to reach the quantumlimit of sensitivity of ∼ 10−22 Hz−1/2 in the nearfuture, making it possible to search for gravitational waves around 3.2 kHz.The experimental tests were performed at the laboratories of the NationalInstitute for Space Research (INPE) and at the Institute for AdvancedStudies (IEAv - CTA).

Preparation of ultrahigh purity cylindrical tantalum ingot by electron beam drip melting without sintering process

A two-step process was used to obtain an ultrahigh purity cylindrical tantalum ingot from tantalum powder. Generally, powders cannot be used as raw materials in processes employing electron beam (EB) drip melting. We designed a process that could indeed use powders. The first step reduced the impurities in tantalum by the repeated EB melting of tantalum buttons fabricated from tantalum powder. An ultrahigh purity tantalum ingot was then fabricated by repeated EB drip melting of the refined tantalum buttons. A cylindrical ingot (Ø80×100 mm) with purity of 99·9998% was obtained. The purity of the raw tantalum powder was 99·9944%, while those of tantalum buttons remelted twice and four times were 99·9989 and 99·9994% respectively. The concentration of gas impurities such as C, N and O was reduced to <10 ppm from an initial level of 3340 ppm.

Nuclear quadrupole interaction at 181Ta in hafnium dioxide fiber: Time differential perturbed angular correlation measurements and ab initio calculations

The thermal behavior of hafnium dioxide fiber has been investigated with the aid of time differential perturbed angular correlation (TDPAC) technique along with XRD and SEM measurements. This study has proved a good thermal stability of the fibrous material up to 1173K and the fiber loses its crystallinity to a meager extent at 1673K. No phase transition has been observed up to 1673K in this fiber. TDPAC parameters for the HfO2 fiber annealed at 1173K are ωQ=124.6 (3) Mrad/s and η=0.36 (1). These values remain unaltered for the HfO2 fiber annealed even at 1673K. Electronic structure calculations based on the density functional theory (DFT) for HfO2 doped with tantalum impurity have been performed and the calculated EFG parameters are in reasonable agreement with the experimental values.

O K-energy loss near-edge structure change induced by tantalum impurity in monoclinic hafnium oxide

The present paper reports the energy loss near-edge structure (ELNES) study of monoclinic HfO2 (m-HfO2) and tantalum doped m-HfO2 (Ta0.1Hf0.9O2) thin films prepared by radio frequency magnetron co-sputtering method. A change in the O K-ELNES spectra was observed as the amount of dopant increases. In order to precise the common features and the differences as a function of Ta defect nature (substitutional or interstitial) in HfO2, the O K-ELNES were commented with respect to density functional theory calculations implemented in Vienna ab initio simulation package code. The calculated Ta doped HfO2 band structure showed that substitutional tantalum is the dominant defect and the spectral differences between doped and non-doped HfO2 are mainly originated from the change in the local cation distribution around the oxygen atoms.

水素透過膜用 Nb-W-Ta 合金の水素雰囲気中における機械的性質と水素透過能

Pressure-Composition-Isotherm (PCT) measurements, in-situ small punch (SP) tests in hydrogen gas atmosphere and hydrogen permeation tests are conducted for Nb-W-Ta ternary alloys in order to investigate the alloying effects of tantalum on the hydrogen solubility, the mechanical properties and hydrogen permeability of Nb-5 mol%W alloy. It is found that the hydrogen solubilities of Nb-5 mol%W-Xmol%Ta (X=5, 10) alloys are very similar with that of Nb-5 mol%W alloy. Also, the mechanical properties in hydrogen gas atmosphere and hydrogen permeability of the alloys are comparable with Nb-5 mol%W alloy. Therefore, the addition of tantalum scarcely modifies the properties of Nb-5 mol%W alloys. Thus, it is not necessary to take into account the amount of tantalum in Nb-W alloys for hydrogen permeable membrane. In other words, it is not needed to remove tantalum impurity from niobium mineral ores in the course of the refinery process of niobium metal. This means that niobium mineral ore containing high tantalum impurity can be used to reduce the material cost of Nb-W-based hydrogen permeable membranes.

Preparation of 5N grade tantalum by electron beam melting

Abstract The commercial Na-reduced tantalum powder was purified using electron beam melting (EBM) by four successive melt cycles. Nearly 60 impurity elements (Li to U) in the tantalum was analyzed using glow discharge mass spectrometry (GDMS). Vickers hardness on the surface of the electron beam (EB)-melted tantalum piece was decreased by ∼43% after first melting and the change in hardness was feeble in the subsequent melt cycles, indicating a quick vaporization of impurities during the first melt cycle itself. The behaviour of Na, K, S, Ti, Mo, Zr, Nb, W, C, N, and O impurities in tantalum at the end of each melt cycle were analyzed and found to be in ppm/ppb level. The overall purity of tantalum by EBM was increased from 2N8 to 5N at the end of three melt cycles. GDMS analysis results on EB-melted tantalum, showed excellent removal effect of interstitial and metallic impurities. The metallic and gaseous impurities present in high purity of tantalum prepared by EBM and plasma arc melting (PAM) were compared. The removal degree of impurities in tantalum using EBM was much higher, when compared to Ar/Ar–H 2 plasma arc melting.

Study of Tantalum impurity in HfO2 based on DFT

Study of Tantalum impurity in HfO2 based on DFT

Electrical and nonlinear optical properties of KTiOPO4 single crystals doped with niobium, antimony, and tantalum

Single crystals of K1 − xTi1 − xNbxOPO4 (KTP: Nb), K1 − xTi1 − xSbxOPO4 (KTP: Sb), and K1 − xTi1 − xTaxOPO4 (KTP: Ta) solid solutions are grown and their dielectric, conducting, and nonlinear optical properties are investigated. The maximum contents x of niobium, antimony, and tantalum impurities in the crystals are equal to 0.11, 0.23, and 0.25, respectively. The doping of the KTiOPO4 crystals with niobium, antimony, and tantalum brings about the formation of additional potassium vacancies and additional potassium positions and, as a consequence, an increase in the ionic conductivity σ33. An increase in the doping level leads to a smearing of the ferroelectric phase transitions and a decrease in the phase transition temperatures. The permittivity of the doped crystals exhibits a broad relaxation peak in the temperature range 200–600°C.

Impurity and Intrinsic Defects in Barium Titanate Ceramics and Their Influence on PTCR Effect

An electron spin resonance (ESR) study of BaTiO 3 ceramics doped by niobium or tantalum is presented. In both series of the samples six intensive lines corresponded to Mn 2+ spectrum was observed. The intensity of the spectra increases with tantalum or niobium concentration increases. Besides Mn 2+ spectrum we observed a single line with g = 1.971. The intensity of this line depends on the impurity concentration. The mechanism of excess positive charge compensation of Nb 5+ or Ta 5+ ions substituted for Ti 4+ in perovskite type lattice is analyzed. The influence of tantalum and niobium impurities, their charge states and position in the lattice on PTCR effect is discussed as well.

Effect of Ta-doping on dielectric properties of yPbMg 1/3(Nb (1− x) Ta x) 2/3O 3–(1− y)PbTiO 3

Lead magnesium niobate–lead titanate (referred to PMN–PT or PMNT) is a very attractive material for the applications in multi-layer capacitors and electro-mechanical transducers. This material has unusually high dielectric permittivity, low dielectric loss and high strain around Curie temperatures. Niobium oxide, one of the components for fabricating PMNT, always contains tantalum impurity. It was originally thought that to make high quality PMNT, it was necessary to use high purity niobium oxide. High purity niobium oxide is very costly. Therefore, it limits massive application of this material. If Ta-doping in PMN–PT does not significantly degrade the properties, it will lower the cost for large-scale industrial production and make the materials more applicable. Our previous work shows that an appropriate amount of tantalum doping in 0.9PMN–0.1PT significantly increases the dielectric constant and refine the grain size. In this work we extend the investigation to 0.65PMN–0.35PT and 0.70PMN–0.30PT that are more close to the morphotropic phase boundary (MPB).

Extraction of Tantalum(V) Impurities from Niobium(V) Fluoride Solutions with Octanol

Fine purification of niobium(V) to remove tantalum(V) by extraction was studied at various compositions of solutions and ratios of phase volumes. Washing of tantalum(V) and niobium(V) extracts with aqueous solutions of their fluorides was considered.

GDouble-focusing Sector Field Inductively Coupled Plasma Mass Spectrometry for Highly Sensitive Multi-element and Isotopic Analysis

The different areas of application in double-focusing sector field ICP-MS are described, such as the determination of trace and ultratrace elements in environmental and materials research and for the characterisation of long-lived radionuclides in environmental and radioactive waste samples. Analytical methods using double-focusing sector field ICP-MS allow the determination at low mass resolution of ultratrace elements ( e.g ., rare earth elements) and some radionuclides in the µg l -1 and pg l -1 concentration ranges ( e.g. , for U, Th, Pu and 129 I) in aqueous solutions and at the ng g -1 level and lower in solid samples after a digestion step. Some examples of trace analysis of solid samples after matrix separation are discussed. For the determination of spallation nuclides and impurities in irradiated tantalum (with an 800 MeV proton beam) from a spallation neutron source, double-focusing sector field ICP-MS was used after liquid–liquid extraction of the tantalum matrix. Further, the results of the analysis of high-purity GaAs by double-focusing ICP-MS after dissolution with and without matrix separation are compared with those of quadrupole ICP-MS.

Determination of trace impurities in tantalum by inductively coupled plasma mass spectrometry after removal of the matrix by liquid-liquid extraction

Trace impurities in tantalum have been isolated by extracting the tantalum matrix from aqueous solutions containing hydrofluoric and hydrochloric acid into methyl isobutyl ketone. A study on the extractability of the fluoride complex by methyl isobutyl ketone and diisopropyl ketone indicated that the former was much more effective. The extractability of tantalum was higher in a HCl medium as compared to HNO 3. Tantalum was easily extracted into the organic phase while most impurities usually accompanying tantalum, e.g. V, Nb, Zr, Hf and W, remained almost completely in the aqueous phase. Trace impurities were analyzed in the aqueous phase by inductively coupled plasma mass spectrometry (ICP-MS) after evaporating the excess acids. The detection limits for most impurities in tantalum were in the sub-μg/g range. The procedure could be applied to the determination of spallation products in a tantalum target irradiated with 800 MeV proton especially in combination with the sensitive ICP-MS.

Oxygen‐Tantalum Interaction in Niobium

AbstractThis article deals with results of the investigation of oxygen dissolution in niobium foil containing tantalum impurity. Experimental data show spatial separation of oxygen and tantalum in niobium if the oxygen concentration is near to the oxygen solibility limit in niobium at room temperature. Tantalum atoms move to the foil surface, and there is more oxygen in the foil volume than near the foil surface. Enrichment of niobium foil surface by tantalum influences strongly the oxygen diffusion across the foil and foil surface ability to electron injection.

Resolution of discrepant analytical data in the certification of platinum in two automobile catalyst SRMs

The National Institute of Standards and Technology (NIST) recently developed two recycled automobile catalyst materials as standard reference materials (SRMs), in response to a request from the International Precious Metals Institute. Results of analyses for platinum by two different analytical techniques did not agree well, with the means differing up to 6%. The palladium results for these same two techniques in the same materials showed much better agreement. Finally, it was determined that one technique (instrumental neutron activation analysis — INAA) had a small, random interference due to a tantalum impurity in/on the acid washed polyethylene bag used to hold the finely powdered sample. This Ta was not present in any of the empty bags used to evaluate the bag blank. Once this problem was identified, the unique characteristics of the INAA technique allowed the magnitude of the interference to be accurately determined for each sample, data recalculated, and a final result obtained which agreed well with the second technique.

Influence of indium and tantalum as an impurity on the normal and superconducting state properties of in situ prepared CuNb composite wires

The influence of impurities on the normal and superconducting state properties of CuNb composite wires prepared by in situ technique have been studied. The results show an increase in the normal state resistivity, resistivity ratio, critical current density and upper critical field — important parameters for device application of superconducting composite wires with the addition of indium and tantalum impurities. There is, however, a decrease in the transition temperature and the transition width of the wires.

Characterization of tantalum impurities in hot-filament diamond layers

During hot-filament diamond deposition metal impurities ( e.g. tantalum) can evaporate from the filament. The incorporation of tantalum in diamond films was studied as a function of process conditions using secondary ion mass spectrometry, Rutherford backscattering spectrometry and transmission electron microscopy. It was found that the tantalum concentration depends on the initial carburization status of the filament, its temperature and the diamond growth rate. If diamond deposition is started with metallic tantalum filaments, TaC nanoprecipitates are formed at the interface.