Addition Of Tantalum Research Articles

Enhanced lithium electrochromic performance of flexible tungsten oxide films by tantalum addition with an atmospheric pressure plasma jet

Enhanced lithium electrochromic performance of flexible tungsten oxide films by the addition of tantalum with an atmospheric pressure plasma jet in a rapid synthesis onto flexible 40Ω/□ polyethylene terephthalate/indium tin oxide substrates was investigated. The flexible organic–inorganic hybrid composites WOyCz, WTaxOyCz and TaOyCz films were synthesized by injecting the precursors tungsten carbonyl [W(CO)6] and/or tantalum ethoxide [Ta(OC2H5)] into an air plasma jet under an atmospheric pressure and the ambient temperature (~23°C). The addition of tantalum into tungsten oxide films improves the optical modulation (ΔT) from 62.3% to 74.8% (at a wavelength of 800nm, even after 200 cycles of reversible Li+ ion intercalation/de-intercalation in a 1M LiClO4-propylene carbonate electrolyte), reduces the coloration time from 13s to 8s, and increases the diffusion coefficient of the lithium ion from 0.4×10−10cm2/s to 1.2×10−10cm2/s.

The effect of tantalum addition on the corrosion behavior of W-xTa alloys in 1 M NaOH solution

The role of tantalum addition on the corrosion behavior of the sputter-deposited nanocrystalline and amorphous W-xTa (x=8-77) alloys was studied in 1 M NaOH solution open to air at 25°C using corrosion tests and electrochemical measurements. Tungsten and tantalum metals act synergistically in enhancing the corrosion resistant properties of the W-xTa alloys and hence addition of 23 at% or more tantalum to the alloys were found to be effective to lower the corrosion rate of the alloys than those of alloy-constituting tungsten and tantalum elements. The corrosion rates of the W-xTa alloys containing 23-77 at% tantalum are nearly two orders of magnitude lower than that of tungsten and even slightly lower than that of tantalum in 1 M NaOH. Addition of tantalum metal in W-xTa alloys is effective for ennoblement of the open circuit corrosion potential of the tungsten metal in 1 M NaOH solution 25°C.DOI: http://dx.doi.org/10.3126/bibechana.v10i0.8363 BIBECHANA 10 (2014) 1-8

The production of biofuels additives on sulphonated MCF materials modified with Nb and Ta—Towards efficient solid catalysts of esterification

The aim of this work was to compare the properties of niobium (Si/Nb=118) and tantalum (Si/Ta=121) containing mesostructured cellular foams (MCF) modified with (3-mercaptopropyl) trimethoxysilane (MPTMS) in one-pot synthesis and the application of materials obtained in acetic acid esterification with glycerol. TaMCF materials were prepared for the first time. Catalysts were characterized by different techniques: N2 adsorption, XRF, elemental and thermal analyses, FTIR+pyridine adsorption and titration of acid sites. New catalysts have showed an excellent catalytic activity in the acetic acid esterification with glycerol to yield triacetylglycerol, also known as triacetin (a valuable additive for biodiesel composition). The influence of modifiers on the number and strength of acidic centres in the materials obtained was found and discussed in details in the paper. The strength of Brønsted acid centres (BAS) was estimated by the interaction of organosilane with transition metal via the use of methoxy groups from MPTMS. The highest concentration of acidic sites determined by NaOH titration was obtained on tantalum modified MCF, whereas the highest strength of BAS was observed on MP-NbMCF sample. The catalytic behaviour of MPTMS and Nb modified MCF samples was comparable to that observed for Amberlyst 15 and better than that of Nafion SAC 13. The materials obtained could be reused and showed stable catalytic features in subsequent cycles. The addition of tantalum allows obtaining a new catalyst with high efficiency of thiol species oxidation (higher than reported before for other catalysts). MPTMS modified TaMCF material appeared to be attractive for further study in different reactions requiring high concentration of acidic centres.

Effects of Addition of Ta and Y Ions to InZnO Thin Film Transistors by Sol–Gel Process

We have investigated the effects of the addition of tantalum (Ta) and yttrium (Y) ions to InZnO thin film transistors (TFTs) using the sol-gel process. TaInZnO and YInZnO TFTs had significantly lower off current and higher on-to-off current ratio than InZnO TFTs. Ta and Y ions have strong affinity to oxygen and so suppress the formation of free electron carriers in thin films; they play an important role in enhancing the electrical characteristic due to their high oxygen bonding ability. The optimized TaInZnO and YInZnO TFTs showed high on/off ratio and low subthreshold swing.

X-ray Photoelectron Spectroscopic Study on the Anodic Passivity of Sputterdeposited W-Ta Alloys in 12 M HCl

The role of a simultaneous additions of tungsten and tantalum on the anodic passivity of the passive films of the sputter-deposited nanocrystalline W-xTa alloys was studied using immersion tests, electrochemical measurements and X-ray photoelectron spectroscopic (XPS) analysis. The formation of spontaneous passive film on the alloys, which is composed of double oxyhydroxide of tungsten and tantalum ions are responsible for their higher corrosion resistance than those of the alloy-constituting elements in 12 M HCl solution open to air at 30°C. The quantitative surface analysis by XPS is clarified that the improved anodic passivity of the alloys than those of alloy-constituting elements is based on the formation of new anodic passive oxyhydroxide films composed of W6+ and Ta5+ ions. These films have higher protectiveness and stability than those of passive oxyhydroxide films of alloy-constituting elements, that is, oxyhydroxides of hexavalent tungsten and pentavalent tantalum after potentiostatic polarization for 1 h in 12 M HCl.DOI: http://dx.doi.org/10.3126/njst.v12i0.6492 Nepal Journal of Science and Technology 12 (2011) 139-148

Influence of Contact Materials on Phenomena in a Short Electrical Arc

Investigation of transition phenomena accompanying the evolution of metallic phase of electric arc into gaseous phase is very important for the further progress in such fields as plasma technologies, electrical apparatus, plasmatrons and other technical applications. Some aspects of this transition are considered in presented paper on the base of mathematical model described dynamics of phenomena in the arc column, near-electrode zones, anode and cathode solids. Cathode and anode phenomena such as ion bombardment, thermionic emission, inverse electron flux, evaporation, radiation, heat conduction etc. are considered in dependence on time, current, opening velocity, parameters of the gas and contact materials. The conditions of the arc transition from one phase to another are formulated in terms of above characteristics and increasing of gas ionization level. Special experiments with two contacts materials, and have been carried to verify the mathematical model. The results of calculation and experimental data enables us to conclude that in metallic arc phase (short arc length), which is characterized by material transfer from the anode to the cathode, the erosion of contacts is considerably small than erosion of contacts both for resistive and inductive circuits, while in gaseous arc phase (long arc length) with opposite material transfer the rate of erosion depends on the inductance. If the inductance, then contacts have smaller erosion in comparison with contacts, however for inductive circuits situation is quite different, thus use of contacts in the case of long arcs burning in gaseous phase is more preferable. It was found also that the addition of niobium diselenide (1%) and tantalum (5%) into silver contact material which are sublimating into arc plasma enables to change ionization potential, that leads to decreasing of the arc temperature, arc duration and contact erosion.

Synthesis and characterization of sub-micron sized copper–ruthenium–tantalum composites for interconnection application

Sub-micron sized ruthenium and tantalum reinforced copper composites as suitable material for electronic interconnection applications was synthesized using high temperature high pressure technique. High purity sub-micron starting powders were blended in a turbula mixer at varying compositions and consolidated at temperature of 850°C and pressure of 30MPa for 30min. The density, phase composition, microstructure, hardness and electrical conductivity of the resulting materials were investigated. The addition of 2.5vol% ruthenium improved the density of the pure sintered Cu from 97.20% of the theoretical to 99.89% and increased the Vickers hardness value from 114.2HV to 127.8HV. Tantalum addition was found to inhibit copper grain growth during sintering. The electrical resistivity of copper based composites remained relatively low with the addition of reinforcement materials.

Improve creep properties of reduced activation steels by controlling precipitation behaviors

Abstract Effect of a new heat treatment and tantalum content on precipitation behaviors and mechanical properties of reduced activation was studied in this paper. The results indicated that the combined application of adding 0.26 wt.% tantalum content and the new heat treatment in the modified steel caused a decrease in the minimum creep rate of an order of magnitude and an increase in the rupture time of nearly an order of magnitude than the traditional reduced activation steel, because the former obtained a number of the finer MX and M23C6 carbides. The prior precipitation of MX by addition of tantalum or intermediate heat treatment that caused a decrease of the growth rate and mean size of M23C6 carbides. Both adding 0.26 wt.% tantalum content and intermediate heat treatment at 850 °C were proposed for an improvement of creep properties in reduced activation steels.

Pseudoelasticity of thermo-mechanically treated Fe–Mn–Si–Cr–Ta alloys

Abstract The effects of slight Tantalum (Ta) addition on the microstructures, martensitic transformation and pseudoelasticity of Fe–28Mn–6Si–5Cr alloy were investigated. Experimental results show that the slight addition of 0.1 wt% Ta can effectively inhibit the slip deformation, increase the M d temperature and hence improve the pseudoelasticity of Fe–28Mn–6Si–5Cr alloy. Meanwhile, the cold rolling can also significantly increase the alloy's pseudoelasticity, especially when the specimens are tested at near M d temperature. The pseudoelasticity can reach 62% at the sixth loading–unloading cycle for the 30% cold-rolled Fe–28Mn–6Si–5Cr–0.1Ta alloy.

A non–destructive compositional analysis of thin surface films formed on W–xTa alloys by angle resolved X–ray photoelectron spectroscopy

Synergistic effect of the simultaneous additions of tungsten and tantalum in the extremely high corrosion resistance properties of the spontaneously passivated sputter–deposited W–xTa alloys was investigated using a non-destructive angle resolved X-ray photoelectron spectroscopy (angle resolved XPS) techniques in this study. In-depth surface analyses of the thin passive films formed on the spontaneously passivated amorphous/nanocrystalline W–xTA alloys using angle resolved XPS analyses revealed that the high corrosion resistance of the alloys is mostly due to the formation of homogeneous passive double oxyhydroxide films consisting of Wox and Ta4+ cations with a small concentration gradients in–depth particularly after immersion between 20–168 h in 12 M HCl solution open to air at 30°C. Consequently, tantalum metal acts synergistically with tungsten in enhancing the spontaneous passivity as well as the high corrosion resistance of the sputter–deposited binary W–xTa alloys in 12 M HCl solution.Keywords: Sputter deposition; W–xTa alloys; 12 M HCl; Take-off angleDOI: http://dx.doi.org/10.3126/bibechana.v8i0.4784BIBECHANA 8 (2012) 8-16

The Effect of Ta and Ti Additions on the Strain Sensitivity of Bulk Niobium-Tin

The effect of tantalum and titanium additions on the composition, the superconducting properties, and their sensitivity to strain of bulk Nb3Sn is investigated. Using heat capacity analysis and Scanning Electron Microscopy with Energy Dispersive X-ray Spectroscopy (SEM-EDX), it is found that the binary Nb3Sn bulk and Nb3Sn bulk with added titanium and tantalum consist of stoichiometric Nb3Sn and niobium(-oxide). Furthermore, it is found that the niobium-to-tin ratio decreases in the presence of tantalum and increases in the presence of titanium, which suggests that tantalum is replacing niobium and titanium is replacing tin in the A15 crystal structure. Using a 10% resistivity criterion, it is observed that the critical magnetic field of unstrained binary bulk is 26.7 T, while the presence of tantalum and titanium raises the critical magnetic field to 29.3 and 30.1 T, respectively. The curves of normalized critical magnetic field as function of strain of all three samples nearly overlap, a strong indication that the variation in strain sensitivity observed in wires is not caused by the titanium and tantalum additions. Understanding the effect of additions on the composition, superconducting properties, and strain sensitivity of Nb3Sn is important for optimizing Nb3Sn conductor technology

Combinatorial Investigation of ZrO2-Based Dielectric Materials for Dynamic Random-Access Memory Capacitors

We investigated zirconia (ZrO2)-based material libraries in search of new dielectric materials for dynamic random-access memory (DRAM) by combinatorial-pulsed laser deposition (combi-PLD). We found that the substitution of yttrium (Y) to Zr sites in the ZrO2 system suppressed the leakage current effectively. The metal–insulator–metal (MIM) capacitor property of this system showed a leakage current density of less than 5×10-7 A/cm2 and the dielectric constant was 20. Moreover, the addition of titanium (Ti) or tantalum (Ta) to this system caused the dielectric constant to increase to ∼25 within the allowed leakage level of 5×10-7 A/cm2. Therefore, Zr–Y–Ti–O and Zr–Y–Ta–O systems have good potentials for use as new materials with high dielectric constants of DRAM capacitors instead of silicon dioxides (SiO2).

Effects of Ta on microstructure and microhardness of Ni based laser clad coating

Through addition of Tantalum, fine TaC particles were in situ synthesized in a NiCrBSi alloy laser clad composite coating. Microstructure, microhardness and abrasive wear resistance of the composite coating were investigated. The result showed that TaC particles were dispersed in Ni based alloy composite coating, refining the microstructure of the coating after laser cladding. Amount of coarse primary carbides such as M7C3 and eutectic of γ-Ni + M23C6 substantially decreased because the formation of TaC particles suppressed the formation of M7C3 and M23C6. On the one hand, fine TaC particles acted as hard phase, which improved the microhardness of the composite coating; on the other hand, a decrease in amount of the coarse M7C3 and eutectic of γ-Ni + M23C6 reduced the crack susceptibility of the Ni based composite coating. Also, Ta element improved the abrasive wear resistance of the Ni based coating.

Quarternary and Quinary Additions to Directionally-Solidified X-X3Si Eutectics of Chromium and Vanadium

ABSTRACTAn alternative high temperature structural alloy system based on the X-X3Si eutectic compositions of chromium and vanadium is put forward. These low-density (~6g/cm3) eutectics have a bcc solid-solution to increase alloy fracture toughness, and a A15 X3Si as the high temperature load-bearing phase. (½Cr,½V)-(½Cr,½V)3Si was used as the base alloy for further element additions, and is represented by the symbol 山 10at.% tantalum and aluminium were substituted for vanadium as quaternary and quinary alloy additions.Microstructure, elemental phase partitioning, compression creep and oxidation results will be discussed. Cr-Cr3Si has a tidy, fine lamellar microstructure. Vanadium coarsens and destabilises the lamellae to a limited extent. Tantalum addition causes two distinct populations of eutectic to form; one population having finer lamellae than the other. Aluminium does not coarsen or destabilise the lamellar microstructure. High temperature compression tests at 1200°C and 1300°C show that 山 is stronger than the binary alloys, and of similar strength to the quaternary and quinary alloys.

Improvement of shape memory effect in Fe–Mn–Si alloy by slight tantalum addition

The effects of slight tantalum (Ta) addition on the microstructures, precipitates, martensitic transformation and shape memory performance of Fe–30Mn–6Si-based alloys were investigated. Experimental results show that the slight Ta addition will increase the c/ a ratio of ɛ martensite, reduce the M s temperature and improve the alloy's shape recovery ability. After TMT at 650 °C, the alloy's M s temperature is reduced and lots of (Fe, Mn) 3Si and TaC precipitates form. The effective nuclei and well-aligned precipitates within the grain interior after TMT will improve significantly the alloy's shape memory performance.

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.

Oxidation Resistance of Fully Dense ZrB2 with SiC, TaB2, and TaSi2 Additives

Specimens of ZrB2 containing various concentrations of B4C, SiC, TaB2, and TaSi2 were pressureless‐sintered and post‐hot isostatic pressed to their theoretical densities. Oxidation resistances were studied by scanning thermogravimetry over the range 1150°–1550°C. SiC additions improved oxidation resistance over a broadening range of temperatures with increasing SiC content. Tantalum additions to ZrB2–B4C–SiC in the form of TaB2 and/or TaSi2 increased oxidation resistance over the entire evaluated spectrum of temperatures. TaSi2 proved to be a more effective additive than TaB2. Silicon‐containing compositions formed a glassy surface layer, covering an interior oxide layer. This interior layer was less porous in tantalum‐containing compositions.

Combustion and structure formation in the Ti-Ta-C-Ca3(PO4)2 system

Biocompatible composites (Ti, Ta)Cx + Ca3(PO4)2 for deposition of nanofilms onto load-bearing implants by ion-plasma sputtering were prepared from Ti + Ta + C + Ca3(PO4)2 mixtures by forced SHS compaction. The effect of Ta + C addition to green mixtures (characterized by parameter z) on the structure/phase formation in combustion products was explored. The addition of tantalum and carbon was found to have little or no influence on the burning velocity U and combustion temperature Tc. Two thermal spikes exhibited by thermograms were associated with the occurrence of two consecutive reactions leading to formation of titanium and tantalum carbides. With increasing z, the grain size of (Ti, Ta)C was found to diminish, its relative density to decrease, while the hardness to markedly grow.

Phase Diagram and Precipitation Behaviour in Ni-Rich Region of Ni-Ta-Al Ternary System

Tantalum (Ta) addition is one of the promising method for increasing the strength of Ni-based wrought alloys such as Inconel 718, because Ta is an element having a high melting temperature. For wrought alloys, it is necessary to make clear the phase relationships at 700~1000°C, but there is a few report on phase diagrams of Ni-Ta and Ni-Ta-Al systems at those temperatures. In this study, the phase diagram in Ni-rich region of Ni-Ta-Al system at 800°C, which is the important temperature for the practical use of the wrought alloys, was investigated. The equilibrium relations of each phase were examined by a conventional XRD, SEM/EDX and TEM observations. It was found that the γ-phase region expanded considerably towards Ta-rich compositional region in Ni-Ta-Al system at 800°C. Also, it was observed that the γ phase precipitated secondarily in the primary precipitated γ’ phase in Ni-10.5mol%Ta-5.5mol%Al alloy. Ni8Ta phase was not detected even in Ni-Ta binary system in this study, although this phase was reported previously.

Effect of tantalum addition on anatase phase stability and photoactivity of aqueous sol–gel derived mesoporous titania

The effect of the addition of tantalum to nanocrystalline titania matrix on the photocatalytic activity is presented. The tantalum addition increases the anatase phase stability to above 1000 °C by inhibiting the increase in crystallite size of titania. All the tantalum added titania compositions have higher surface area than pure titania. Transmission electron micrograph images support the reduction in crystallite size of titanium oxide in presence of tantalum. Addition of tantalum above 1 mole percentage increases photocatalytic activity considerably and the activity is much higher than that of commercially available Hombikat UV 100 titania. All the compositions containing tantalum have higher photoactivity than pure titania. The synergistic effect of high surface area and small crystallite size is found to be responsible for the observed photocatalytic activity rates. The aqueous sol–gel method adopted for the preparation of tantalum added titania from cheaper salt precursors and the resultant highly photoactive titania make this investigation promising for various technological applications.