Influence Of Tantalum Research Articles

Relationship between microstructure, phase transformation, and mechanical behavior in Ti–40Ta alloys for biomedical applications

Titanium and Ti alloys are important materials for scientific and technological applications, especially as biomaterials, due to their excellent corrosion resistance, biocompatibility, and mechanical properties. In this work, the influence of tantalum on the microstructure and mechanical properties of Ti–40Ta alloys were studied by X-ray diffraction (XRD), scanning electron microscopy (SEM), differential scanning calorimetry (DSC), and mechanical spectroscopy (MS) techniques. XRD and SEM analyses showed that commercially pure (CP) Ti consists of a single α-phase (hcp) with an equiaxed morphology, while Ti–40Ta alloy consists of α" (orthorhombic) and β (bcc) phases. The anelastic relaxation spectra of Ti–40Ta alloy presented characteristics combining CP Ti and pure Ta anelastic responses, where the complex anelastic relaxation peaks observed around 575 and 680 K could be resolved into matrix-interstitial and substitutional-interstitial components, corresponding to Ta–O, Ti–O, and Ta–N single interactions. The combination of thermal cycles and applied stress during the mechanical spectroscopy characterization of Ti–40Ta alloy promotes the α" → β phase transition until β phase stabilization. From flexural vibration measurements, the elastic modulus values at room temperature were: (102 ± 9) GPa for CP Ti and (71 ± 5) GPa for the Ti–40Ta alloy. These results provide a valuable contribution to a better understanding of the structure and mechanical properties of the Ti–40Ta alloy, thus allowing the optimization of its properties through thermal treatments, aiming at its potential application as a biomaterial for structural orthopedic applications.

The Effect of the addition of Ta, Zr and in on the corrosion behaviour of CuAlMn alloys prepared via powder metallurgy

CuAlMn-X (X= Ta, Zr and In) shape memory alloy was fabricated using the powder metallurgy (PM) technique. After sintering at 950 °C, the products were processed using two heat treatments (solution heat treatment at 900 °C and aging at 500 °C). The influence of Tantalum (Ta), Zirconium (Zr) and Indium (In) with three wt.% on the mechanicals properties (hardness), corrosion behaviour and microstructure of CuAlMn shape memory alloys was investigated in this paper. The effect of the addition of Ta, Zr and In alloys was investigated using X-rays diffraction (XRD), open circuit potential, electrochemical tests (Tafel extrapolation method) and Vickers micro-hardness. For the corrosion tests, a 3.5 % NaCl (chloride solution) was used as corrosion solution. The results showed that there is an increase in hardness with addition of the alloy element (Ta, Zr and In) and decrease in the size of martensite plate form, as shown in the microstructures. Furthermore, it was found that the corrosion resistance of Cu-Al-Mn after the addition improved, as shown by the increase in the corrosion potential and decrease in the corrosion current densities. The improvement percentage for CuAlMnTa, CuAlMnIn and CuAlMnZr in the corrosion rate was 97 %, 91 % and 77 %, respectively.

Influence of tantalum's crystal phase growth on the microstructural, electrical and mechanical properties of sputter-deposited tantalum thin film layer

High melting point refractory tantalum (Ta) metal is frequently grown into thin film layer for many applications in biomedical implants, microelectronic devices and micro-level mechanical systems. Tantalum growth mechanism is still in debate and the inconsistent crystal phase outcome has puzzled many, though it is certain that the properties of the grown film are highly dependent on the formed crystal phase configuration. The microstructure, surface morphology, crystal orientation and residual stress of the sputter-deposited Ta thin films using direct current (DC) magnetron sputtering technique are studied at 0.4 Pa – 2 Pa of sputtering pressure, 100 W – 250 W of DC sputtering power on bare silicon and silicon dioxide substrate and 10 min – 50 min of sputtering duration. α-phase Ta is preferably grown at high sputtering time (high thickness) and high DC sputtering power (high growth rate). The sputtering pressure affects the thin film's microstructural porosity while the sputtering power controls the crystallisation's quality. Both sputtering pressure and power affect the generated argon plasma in the DC magnetron sputterer where α-phase Ta is preferably formed at high plasma. The presence of 3 μm silicon dioxide underlayer makes no difference compared to bare silicon substrate. Our study reveals that β-phase Ta is grown first irrespective of sputtering conditions and then transformed into α-phase Ta after reaching a certain thickness. The grown major α-phase content promotes small thin film sheet resistivity (58.9 μΩcm – 86.1 μΩcm) and is suspected to be the dominant factor that increases the compressive stress within the thin film layer and reduces the adhesion of Ta layer onto the substrate surface. The study has given a new insight in controlling the conductivity and adhesion level of Ta thin film based on the grown phase layer.

The influence of tantalum on human cell lineages important for healing in soft-tissue reattachment surgery: an in-vitro analysis

BackgroundPorous tantalum is currently used in orthopaedic surgery for a variety of indications including soft tissue re-attachment. However, the clinical results have been variable and a previous laboratory study has suggested that tantalum may actually inhibit chick tendon fibroblasts. The influence of tantalum on human cell-types involved in soft tissue re-attachment has not been defined.MethodsHuman fibroblasts, human osteoblasts and human mesenchymal stem cells were plated on glass cover slips, half of which were coated with tantalum. Cell numbers were assessed at 1, 2, 7 and 14 days using Cyquant® assay. Cell adhesion and morphology were assessed using light microscopy at 7, 14 and 28 days. To reduce the effect of an expected rate of error, n = 4 was utilised for each cell type and the experiment was repeated twice.ResultsStatistically similar numbers of human osteoblasts and human mesenchymal stem cells were present at 14 days on tantalum-coated and uncoated glass cover slips, revealing no inhibitory effect on cell proliferation. More than double the number of human fibroblasts was seen on tantalum-coated cover slips at that time point (compared to controls), which was statistically significant (p < 0.0001). Morphological assessment revealed normal cell spreading and adhesion on both substrates at all time points.ConclusionsIn vitro study demonstrates that Tantalum causes a significant increase in the proliferation of human fibroblasts with no quantifiable negative effects seen on fibroblast behaviour after 28 days culture. Furthermore, tantalum does not exert any inhibitory effects on the proliferation or behaviour of human osteoblasts or human mesenchymal stem cells. Tantalum could be an appropriate biomaterial for use in situations where soft tissue requires direct reattachment to implants and may stimulate soft tissue healing.

Influence of Tantalum on phase stability and mechanical properties of WB2

Abstract

Influence of tantalum on mechanical, ferroelectric and dielectric properties of Bi-excess Bi3.25La0.75Ti3O12 thin film

The Bi-excess Bi3.25La0.75Ti3O12 (BLT) and Bi3.25La0.75Ti2.91Ta0.09O12 (BLTT) thin films were deposited on Pt(1 1 1)/Ti/SiO2/Si substrates using rf-magnetron sputtering method. The effect of tantalum on mechanical, ferroelectric and dielectric properties of BLT thin films was investigated. XRD patterns reveal that BLT and BLTT thin films have a same second crystalline phase Bi12TiO20, but the former has a randomly oriented major Bi4Ti3O12 phase while the major phase in the later is preferentially oriented along 〈1 1 7〉 direction. XPS analysis shows that the substitution of Ta5+ has a significant influence on Ti3+ defects. Mechanical response of thin films is discussed in the light of nano indentation analysis which shows that both the hardness and modulus are reduced with the addition of Ta5+. Ferroelectric properties were improved significantly by Ta5+ doping due to the reduction of Ti3+ defects, and an enhanced remnant polarization (2Pr) of 32.5 μC/cm2 and a decreased coercive field (2Ec) of 260 kV/cm were obtained. In addition, the Ta substitution elevated the dielectric constant and slightly raised the Curie temperature.

Influence of tantalum on the microstructure and properties of Ti(C,N)-Ni cermets

Several (Ti,Ta)(C,N) cermets were prepared from Ti(C,N) and Ta powder with or without Ni. For comparison, Ti(C,N) with Ni were also prepared. The mixed powders were sintered at 1400–1500°C by FAST/SPS up to a density higher than 99% theoretical density. The addition of Ta delays densification of Ti(C,N)-Ni cermets due to the formation of intermetallic phases. During sintering, the Ta was incorporated into the Ti(C,N), forming solid solution, thus changing the core-rim structure of the Ti(C,N) cermets. On the other hand, the Ta additions result in grain refinement and improved hardness (from 16.1GPa to 17.8GPa) and fracture toughness (from 5.5MPa.m1/2 to 6.9MPa.m1/2).

The influence of tantalum on the high temperature characteristics of lamellar gamma + alpha 2 titanium aluminide

Abstract The high temperature behavior of as-cast Ti–46Al, Ti–45Al–7Nb and Ti–45Al–7Ta (in at.%) alloys at 800 °C was investigated in this work. The structure, hardness and bending strength of the as-cast alloys were characterized. During long-term (460 h) annealing of the alloys at 800 °C, the structural changes were examined, and the development of hardness was monitored. The creep behavior at 800 °C was studied in the three-point bending mode at bending stresses of 200, 400 and 600 MPa. The oxidation rate of the alloys in air at 800 °C was monitored by measuring the weight gain as a function of oxidation time. It was found that tantalum did not modify the lamellar γ + α 2 structure of titanium aluminides, but it negatively influenced the bending strength at room temperature in comparison to niobium. The formation of metastable Ta-supersaturated γ and α 2 phases was also revealed to occur in the Ti–45Al–7Ta alloy. During annealing at 800 °C, the Ta-rich τ phase precipitated, which led to hardening of the Ti–45Al–7Ta alloy. The creep resistance of the Ti–45Al–7Ta alloy was shown to be the best of all the investigated materials, and the influence of Ta is discussed in relation to its diffusivity and creep mechanism.

Influence of Tantalum on the Rates of High Temperature Oxidation and Chromia Volatilization for Cast (Fe and/or Ni)-30Cr-0.4C Alloys

Four cast superalloys, Fe-base and (Fe,Ni)-base alloys, all containing 30%Cr and 0.4%C, were elaborated with addition of 3% and 6% of tantalum. Their oxidation behaviours were studied at 1000, 1100 and 1200°C during 50 hours. The oxidized surfaces of the samples were quantitatively characterized by measurements of thicknesses and surface fractions of internal oxides. The thermogravimetry files were treated according to the {m×(dm/dt) = Kp - Kv×m} equation, to obtain simultaneously the parabolic constant and the chromia volatilization constant. The internal tantalum oxides are more present in the Fe-base alloys and the carbide-free zones are less developed for the (Fe,Ni)-base alloys than for the others. The Fe-base alloys oxidize faster than the (Fe,Ni)-base and Ni-base alloys. The comparison with the corresponding Ta-free ternary alloys shows that the presence of Ta tends to accelerate the oxidation.

Growth of highly c-axis oriented aluminum nitride thin films on β-tantalum bottom electrodes

We have investigated the influence of tantalum (Ta) bottom electrodes on the crystallinity and crystal orientation of aluminum nitride (AlN) thin films. AlN thin films and Ta electrodes were prepared by using rf magnetron sputtering method. The crystal structure of the Ta electrodes was tetragonal (β-Ta, a metastable phase) at room temperature. The crystallinity and orientation of the AlN thin films and Ta electrodes strongly depended on sputtering conditions. Especially, the crystallinity and crystal orientation of the Ta electrodes were influenced by their film thickness and the substrate temperature. When the thickness of the Ta bottom electrodes was 200 nm and the substrate temperature was 100 °C, the AlN thin films indicated high c-axis orientation (the full width at half maximum of rocking curve of 3.9°). The crystal orientation of the AlN film was comparable to that of AlN thin films deposited on face centered cubic (fcc) lattice structure metal, such as Au, Pt and Al, bottom electrodes.

Influence of tantalum and silver interlayers on thermal stress evolution in copper thin films on silicon substrates

Cu thin films with Ta or Ag interlayers exhibited similar stress amplitudes during thermal cycling. However, the Ta interlayer, which was expected to enhance Cu adhesion, led to significantly higher 500 °C stresses than did Ag. Interlayer stress, which was substantial for Ta, was subtracted to calculate true Cu stresses.

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.

Influence of tantalum and nitrogen contents, normalizing condition and TMCP process on the mechanical properties of low-activation 9Cr–2W–0.2V–Ta steels for fusion application

For clarifying the reason of good creep and mechanical properties and improving the mechanical properties of the low-activation 9Cr–2W–0.2V–Ta steels (JLF-1 steels), the influence of Ta, N contents, normalizing condition and thermo-mechanical controlled processes (TMCP) on the mechanical properties of the 9Cr–2W–0.2V–Ta steels was investigated in contrast with conventional 9Cr–1Mo–0.2V–Nb steels. The creep strength of the 9Cr–2W–0.2V–Ta steels increases with increasing amount of Ta and N contents irrespective of the manufacturing processes. An increase in the normalizing temperature or the application of TMCP processes can also improve creep strength. It is hypothesized that the increase in creep strength due to an increase in normalizing temperature or the application of TMCP processes is attributed to the uniform distribution of fine (Ta,V)(C,N) precipitates. Furthermore, the 9Cr–2W–0.2V–Ta steels demonstrate good toughness mainly due to a fine austenite grain size. The 9Cr–2W–0.2V–Ta steels have equivalent or better creep strength and better toughness compared with 9Cr–1Mo–0.2V–Nb steels.

Investigations of glasses with matrix properties for gradient elements using the electrical measurements

Influence of tantalum and niobium oxide on the electrical conductivity of alkali silicate glasses was investigated. The electrical measurements were performed for three types of alkali silicate glasses containing different amounts of tantalum, niobium and alkali. These glasses are promising materials for gradient elements produced by ion-exchange process.

The role of tantalum in TiC-WC-TaC-Co sintered carbides. II. Influence of tantalum content on the structure and properties of TiC-WC-TaC-Co three-phase sintered carbides

This work is devoted to a study of the influence of tantalum on the structure and properties of three-phase alloys. The investigations were made with a constant weight ratio of Ti:WC = 35:65% and an unchanged carbon content. The alloys were prepared by mixing of the (T, W, Ta)C carbides with cobalt and tungsten carbide. The pressed specimens were given a preliminary sinter in hydrogen at 923-973 K and a final one in a vacuum furnace at 1773 K. The microstructure, density, and bend and compressive strengths at room and increased temperatures, coeffiecients of cutting life and strength (in comparison with a standard taken as unity), and adhesion interaction were determined. The coefficient of cutting life was determined by transverse machining of steel. The coefficient of strength was determined by the method of breaking feed in milling of 50 steel with a single-tooth cutter. The adhesion interaction of TiC-WC-TaC-Co alloys with the material being machined (50 steel) was determined in vacuum (which eliminated the additional influence of oxidation of the alloy) at 873 K with a load of 1000N. Tantalum carbide additions have a favorable influence on the physicomechanical and service properties of TiC-WC-Co alloys. Their bend strength at roommore » and increased temperatures increases and there is an increase in the total deformation and the work for deformation at increased temperatures, a reduction in oxidation and adhesion interaction with the material being machined, and a significant increase in wear resistance in cutting. Graphs and tables are included.« less

The effect of the purity and of the materials used for adapters on the purification of yttrium by solid state electrotransport

The influence of tantalum, molybdenum and virconium adapters on the efficiency of the solid state electrotransport process is investigated with a view to increasing the vuality and purity of yttrium. The degree and direction of metallic impurity electromigration in the given metals were studied. The impurities in vuestion were shown to move in different directions depending on the type of adapter. Recommendations for the application of adapters according to their purity are given. The application of high purity tantalum as anode and cathode adapters in three-stage solid state electrotransport enabled us to obtain yttrium single crystals with a ratio of resistance at room temperature to that at helium temperatures of 1200.

High-temperature strength of nickel alloys based on γ′-phase

AbstractAn investigation has been made of the influence of tantalum, hafnium, and carbon on the strength of Ni3Al (γ′). Ternary and quaternary alloys have been studied, based on the Ni-Al-Ta and Ni-Al-Hf systems, with aluminium contents in the range ∼20–25 at.-%, tantalum or hafnium contents up to 5 at.-%, and carbon up to 1·4 at.-%. These alloys consisted wholly or predominantly of γ′, with compositions on the (Al + Ta, Hf)-rich side of γ′-stoichiometry. Also, a multicomponent alloy (Ni-Al-Ta-Hf-W-Cr-Co-Zr-B-C) on the nickel-rich side of stoichiometry has been studied. Structural observations have been made, together with measurements of yield stress and of secondary-creep rates at temperatures up to ∼1000°C. Tantalum and hafnium conferred substantial solid-solution strengthening on γ′; however, with carbon additions, carbide formation significantly reduced the matrix strength as a result of solute depletion. The strength and creep resistance of the multicomponent alloy consisting of γ + γ′ + carbide wer...

Paramagnetic Susceptibility, Electrical Resistivity, and Lattice Parameters of Nickel-Rich Nickel-Tantalum Alloys

The paramagnetic susceptibility, electrical resistivity, and lattice parameters of nickel-rich nickel-tantalum solid solutions (10 compositions) have been studied. The paramagnetic measurements extend to about 1500°K. The resistivities have been obtained at 4.2°, 77.2,° and 297.0°K. The lattice parameters of samples quenched from 1473°K were determined at 298°K. All these data indicate that the influence of tantalum on the physical properties of nickel is very similar to that of niobium. It is demonstrated by means of the magnetic susceptibility measurements that the generally accepted Curie-Weiss law, with an additive temperature-independent susceptibility term, is not applicable to the solid solutions of tantalum in nickel. The susceptibility and resistivity data are briefly discussed from the viewpoint of recent theoretical and experimental developments. The lattice parameters are analyzed using the previously suggested atomic volume scheme and elasticity theory. The agreement between the experimental values and the predictions is satisfactory.