Tantalum Wire Research Articles

Drawing Tantalum Encapsulated in the Cooper Pipe

Tantalum has characteristics such as excellent ductility, high corrosion resistance, high mechanical strength at high temperatures and high resistance to etching of acids and bases. Its high ductility allows the realization of large reductions without the need for intermediate heat treatment. A process for the production of tantalum wire is drawing. However, when using this process, the high ductility of the tantalum (Ta) metal causes a retention/accumulation of the Ta in the spinneret. Therefore, to be drawn is necessary that the tantalum is encapsulated in a copper tube. In this work was produced a Ta wire by means of rotary forging and drawing process. In the drawing process of the tantalum encapsulated in copper tube, was the appearance of striation on the surface of tantalum, when applied to an area reduction (AR) of approximately 22%. This fact is possibly related to the different sliding systems with consequent formation of non-hydrostatic stress fields at the interface Cu / Ta. After an area reduction (AR) of 94% the Cu was removed from the surface of the wire, through chemical etching, and this wire was drawn up to 0.43mm without retention/accumulation of the Ta in the spinneret.

Effect of doping on microstructure and technical usage property of tantalum wire

Effect of different dopants and various dopants quantity at different annealing temperatures on microstructure of tantalum wire, bending of tantalum wire after sintering and bending after pressing into tantalum powder and sintering were investigated through observation of microstructure and testing of bending of tantalum wire after sintering and bending after pressing into tantalum powder and sintering. The results show that the recrystallization temperature of tantalum wire increases and the grain of microstructure can be reduced with the increase of dopants quantity. At the same time, the effect of dopant Ce on reduction of the grain is more obvious than that of dopant Ge. The bending time of tantalum wire after sintering increases with the increase of dopant Ge or Ce quantity. Under the same condition, the bending time of tantalum wire after pressing into tantalum powder and sintering worsens with the increase of oxygen content in tantalum powder. The bending time of tantalum wire doped with Ge and Ce after pressing into tantalum powder and sintering is better than that of tantalum wire doped with Ge, while that of tantalum wire doped with Ge is better than that of pure one when oxygen content in tantalum powder is not too high.

Spin Hall effect clocking of nanomagnetic logic without a magnetic field

Spin-based computing schemes could enable new functionalities beyond those of charge-based approaches. Examples include nanomagnetic logic, where information can be processed using dipole coupled nanomagnets, as demonstrated by multi-bit computing gates. One fundamental benefit of using magnets is the possibility of a significant reduction in the energy per bit compared with conventional transistors. However, so far, practical implementations of nanomagnetic logic have been limited by the necessity to apply a magnetic field for clocking. Although the energy associated with magnetic switching itself could be very small, the energy necessary to generate the magnetic field renders the overall logic scheme uncompetitive when compared with complementary metal-oxide-semiconductor (CMOS) counterparts. Here, we demonstrate a nanomagnetic logic scheme at room temperature where the necessity for using a magnetic field clock can be completely removed by using spin-orbit torques. We construct a chain of three perpendicularly polarized CoFeB nanomagnets on top of a tantalum wire and show that an unpolarized current flowing through the wire can 'clock' the perpendicular magnetization to a metastable state. An input magnet can then drive the nanomagnetic chain deterministically to one of two dipole-coupled states, '2 up 1 down' or '2 down 1 up', depending on its own polarization. Thus, information can flow along the chain, dictated by the input magnet and clocked solely by a charge current in tantalum, without any magnetic field. A three to four order of magnitude reduction in energy dissipation is expected for our scheme when compared with state-of-the-art nanomagnetic logic.

Latent Cracking of Tantalum-Titanium Welds Due to Hydrogen Embrittlement

Establishing electrical interconnects in implantable electronic medical devices frequently requires joining of dissimilar materials. A weld between a tantalum wire and titanium sheet metal on a contact module is presented as an example for dissimilar joining. Latent, brittle cracking was observed in the proximity of the weld upon pull testing. The weld cracking occurs by the mechanism known as hydrogen stress cracking (HSC) and is due to titanium hydride formation. Diffusion facilitated hydrogen transport into the weld area. Diffusing hydrogen accumulates preferably in regions of high stress, causing latent titanium hydride formation and embrittlement of the weld. A broad array of analytical tools such as scanning electron microscopy (SEM), transmission electron microscopy, electron backscattered diffraction, dynamic secondary ion mass spectroscopy, and nanoindentation were utilized to identify the root cause for HSC.

Surface morphology, nano-indentation and TEM analysis of tantalum carbide–graphite composite film synthesized by hot-filament chemical vapor deposition

Hot-filament chemical vapor deposition was used to deposit tantalum carbide–graphite composite films on etched silicon. Thermal evaporation from heated tantalum wires provided tantalum while carbon was obtained from methane diluted with hydrogen. Resulting films were characterized and analyzed by field emission scanning electron microscope, high-resolution transmission electron microscopy and nano-indentation. The results indicate that surface morphology of coatings and their hardness are greatly influenced by the process parameters. The grain distribution obtained is more homogenous at moderate pressure rather than at lower or higher pressures. Average grain size at 60 Torr is 30 nm, while at low pressure it is 15 nm and at high pressure nano-scale grains coalesced and formed cauliflower structure and secondary nucleation. With increase in methane concentration grains coalesce and become coarse. The films grown at 100 Torr and higher methane concentration show higher porosity but better growth rate compared to others. Elemental composition analysis and nano-indentation results reveal that higher the graphite content lower is the hardness.

A compact and efficient strontium oven for laser-cooling experiments

Here we describe a compact and efficient strontium oven well suited for laser-cooling experiments. Novel design solutions allowed us to produce a collimated strontium atomic beam with a flux of 1.0 × 10(13) s(-1) cm(-2) at the oven temperature of 450 °C, reached with an electrical power consumption of 36 W. The oven is based on a stainless-steel reservoir, filled with 6 g of metallic strontium, electrically heated in a vacuum environment by a tantalum wire threaded through an alumina multi-bore tube. The oven can be hosted in a standard DN40CF cube and has an estimated continuous operation lifetime of 10 years. This oven can be used for other alkali and alkaline earth metals with essentially no modifications.

Fabrication of a-Si:H/c-Si Hetero-Junction Solar Cells by Dual Hot Wire Chemical Vapor Deposition

The a-Si:H/c-Si hetero-junction (HJ) solar cells have a variety of advantages in efficiency and fabrication processes. It has already demonstrated about 23% in R&D scale and more than 20% in commercial production. In order to further reduce the fabrication cost of HJ solar cells, fabrication processes should be simplified more than conventional methods which accompany separate processes of front and rear sides of the cells. In this study, we propose a simultaneous deposition of intrinsic thin a-Si:H layers on both sides of a wafer by dual hot wire CVD (HWVCD). In this system, wafers are located between tantalum wires, and a-Si:H layers are simultaneously deposited on both sides of the wafer. By using this scheme, we can reduce the process steps and time and improve the efficiency of HJ solar cells by removing surface contamination of the wafers. We achieved about 16% efficiency in HJ solar cells incorporating intrinsic a-Si:H buffers by dual HWCVD and p/n layers by PECVD.

Infiltration casting and in situ fabrication of tantalum carbide particulate-reinforced iron matrix composites

Reinforced tantalum carbide particles were synthesized between tantalum wires and graphite in gray cast iron by heat treatment; the effects of different heat treatment times on the phase evolution, microstructure, and micro-hardness of the composites were investigated. The particles obtained were small and square-shaped, 1–2 µm in size, and evenly distributed through the cast iron. The maximum micro-hardness of the composite region was 1832 HV0.1. After 20 min heat treatment, the micro-hardness decreased to approximately 1077 HV0.1, between about four and five times that of the matrix. The resulting composites also presented higher wear resistance compared with unreinforced gray cast iron.

Quantum Cascade Laser Spectroscopy and Photoinduced Chemistry of Al–(CO)n Clusters in Helium Nanodroplets

Helium nanodroplet isolation and a tunable quantum cascade laser are used to probe the fundamental CO stretch bands of aluminum carbonyl complexes, Al-(CO)(n) (n ≤ 5). The droplets are doped with single aluminum atoms via the resistive heating of an aluminum wetted tantalum wire. The downstream sequential pick-up of CO molecules leads to the rapid formation and cooling of Al-(CO)(n) clusters within the droplets. Near 1900 cm(-1), rotational fine structure is resolved in bands that are assigned to the CO stretch of a linear (2)Π(1/2) Al-CO species and the asymmetric and symmetric CO stretch vibrations of a planar C(2v) Al-(CO)(2) complex in a (2)B(1) electronic state. Bands corresponding to clusters with n ≥ 3 lack resolved rotational fine structure; nevertheless, the small frequency shifts from the n = 2 bands indicate that these clusters consist of an Al-(CO)(2) core with additional CO molecules attached via van der Waals interactions. A second n = 2 band is observed near the CO stretch of Al-CO, indicating a local minimum on the n = 2 potential consisting of an "unreacted" (Al-CO)-CO cluster. The line width of this band is ∼0.3 cm(-1), which is about 30 times broader than the transitions within the Al-CO band. The additional broadening is consistent with a homogeneous mechanism corresponding to a rapid vibrational excitation induced reaction within the (Al-CO)-CO cluster to form the covalently bonded Al-(CO)(2) complex. Ab initio CCSD(T) calculations and natural bond orbital (NBO) analyses are carried out to investigate the nature of the bonding in the n = 1, 2 complexes. The NBO calculations show that both π-donation (from the occupied aluminum p orbital into a π* antibonding CO orbital) and σ-donation (from CO into the empty aluminum p orbitals) play a significant role in the bonding, analogous to transition-metal carbonyl complexes. The large red shift observed for the CO stretch vibrations is consistent with this bonding analysis.

SU‐E‐T‐326: Investigating the Use of Tantalum Mesh Bolus in Electron Beams

Purpose: In order to achieve a higher surface dose for electron beams of less than 15 MeV, tantalum wire mesh bolus has been investigated in the past. Despite an increase in surface dose as seen by a depth dose (DD) curve, these investigations did not quantify variation in surface dose over the radiation field. Thus quantifications of surface dose variations are given along with an investigation into the effect of randomized mesh placements over several treatment fractions. Method and Materials:A tantalum wire mesh of 0.02 inch (0.51 mm) thickness and a mesh spacing of eight meshes per inch was used as bolus for a 6 MeV electron beam. DD curves were measured using a Scaditronix EFD3G electron diode in a water tank and profiles were measured with EBT2™ Gafchromic films in Solid Water™. The EBT2™ films were scanned using an Epson Expressions 10000XL flatbed scanner correcting for scanner non‐uniformities. Results: Despite a very flat surface dose as seen by one DD measurement, another DD measurement taken with the electron diode at a lateral offset of 2mm showed a 17% increase in surface dose. In general, high spatial frequency variations in the surface dose of nearly 70% were seen in the EBT2™ film due to the scattering and absorption of electrons in the tantalum mesh bolus. However, through the randomized placement of the tantalum mesh bolus on the surface over the course of ten fractions, the variations in surface dose were reduced to around 34%.Conclusion: Tantalum wire mesh bolus has been shown to increase the surface dose of 6 MeV electrons, but with significant variations over the full radiation field. By randomly placing the mesh bolus on the surface, the large surface dose variations can be reduced to around 34%.

Lifetime and strength tests of tantalum and tungsten under thermal shock for a Neutrino Factory target

A description is given of tests on tantalum and tungsten wires to evaluate their lifetime and strength under the thermal shock that will be experienced when a solid target is bombarded with short pulses of high energy protons in a Neutrino Factory. The results of lifetime tests and measurements of dynamic strength characteristics at high temperatures, stresses and strain rates using a laser Doppler vibrometer are given. The tests show that a solid tungsten target will have a life of at least 3 years, which, with other beneficial characteristics, make it an excellent candidate for the Neutrino Factory.

Absolute measurement of thermal conductivity of poly (acrylic acid) by transient hot wire technique

The transient hot-wire method is considered the most accurate technique to measure the thermal conductivity of fluids. In this study, a transient hot wire instrument which employs 25.4-μm-diameter tantalum wire with an insulating tantalum pentoxide coating has been used. This hot-wire cell with a thin insulating layer is suitable for measurement of the thermal conductivity of electrically conducting and polar liquids. Measurements of the thermal conductivity of 50 wt% solution of PAA [poly (acrylic acid)] in water and PAA–Na in 50 wt% water are reported here. These measurements were obtained in the temperature range of 299–368 K at 1 atmospheric pressure. The measurement of thermal conductivity is estimated to be accurate within ±4%.

Relation between doping and texture and property of tantalum bar and wire

Relation between doping and texture and property of tantalum bar and wire was carefully investigated by optical microscope, SEM fractograph, electron microprobe analysis, density test, observation of TEM and mechanical property test at room temperature. It is illustrated that the grain of tantalum bar after sintering reduces with the increasing of dopant quantity, and the effect of dopant Ce on reduction of the grain is more obvious than that of dopant Ge, even that sintering is becoming insufficient and the density of tantalum bar tends to be lower with the increaseing of dopant Ce. The recrystallization temperature of tantalum wire increases and the grain of texture reduces with the increaseing of dopants quantity. The tensile strength of tantalum wire at room temperature increases with the increasing of dopants quantity, while its elongation decreases with the increase of dopant Ge quantity and rises with theincrease of dopant Ce quantity. And the strengthening effect of dopant Ce is clearer than that of dopant Ge.

Thermal conductivity and thermal diffusivity of poly(acrylic acid) by transient hot wire technique

The paper describes a new transient hot wire instrument which employs 25.4 μm diameter tantalum wire with an insulating tantalum pentoxide coating. This hot-wire cell with a thin insulating layer is suitable for measurement of the thermal conductivity and the thermal diffusivity of electrically conducting and polar liquids. This instrument has been used for experimental measurement of the thermal conductivity and the thermal diffusivity of poly(acrylic acid) solution (50 mass%) in the temperature range of 299 to 368 K at atmospheric pressure. The thermal conductivity data is estimated to be accurate within ±4%. Thermal diffusivity measurements have a much higher uncertainty (±30%) and need further refinement.

Preconcentration technique for manganese by adsorption onto a tantalum wire for tungsten tube atomizer electrothermal atomization atomic absorption spectrometry

A preconcentration technique for manganese in water samples by adsorption on a tantalum wire was investigated for tungsten tube atomizer electrothermal atomization atomic absorption spectrometry. After preconcentration, the tantalum wire was directly inserted into the tungsten tube atomizer. In the preconcentration (adsorption) process for manganese, the optimal immersion time was 60 sec and the best pH was 9. Under the optimal conditions, the detection limit for manganese by the tantalum wire preconcentration method was 6.3 pg mL−1 (3S/N) and the relative standard deviation was 7.6%. The influences of concomitants on the preconcentration of manganese were evaluated. Even though 103 to 104-fold excess of matrix elements existed in aqueous solution, the manganese absorption signal was not significantly affected by the matrix elements. The method with preconcentration on a tantalum wire was applied to the determination of manganese in river waters and proved to be sensitive, simple, and convenient. Because this preconcentration method can be utilized in the in-situ treatment of trace manganese in environmental water samples, it was unnecessary to carry the water samples to the analytical work place. The technique was shown to be useful for the determination of manganese in environmental water samples at 0.1–1 g L−1 levels.

Preconcentration of trace lead by adsorption onto a tantalum wire for electrothermal atomization atomic absorption spectrometry with a tungsten tube atomizer

A preconcentration method of lead in waters by adsorption on a tantalum wire was developed for electrothermal atomization atomic absorption spectrometry with a tungsten tube atomizer. After the preconcentration, the tantalum wire was directly inserted into the tungsten tube atomizer. In the preconcentration (adsorption) process for lead, the optimal immersing time was 90 s and the best pH was 4. Under the optimal conditions, the detection limit for lead by the tantalum wire preconcentration method was 6.0 pg mL − 1 (3S/N) and the relative standard deviation was 6.1%. The influences of large amounts of concomitants on the preconcentration of lead were evaluated. Even though 10 3 to 10 4-fold excess of matrix elements existed in aqueous solution, the lead absorption signal was not significantly affected by the matrix elements. The method with preconcentration on a tantalum wire was applied to the determination of lead in river waters and proved to be sensitive, simple, and convenient. Because this preconcentration method can be utilized in the in-situ treatment of trace lead in environmental water samples, it was unnecessary to carry the water samples to the analytical work place. The present technique was shown to be useful for the determination of lead in environmental water samples at 0.1−1 μg L − 1 .

Double-vacuum crucible for temperatures upto 1600°C

A new design of dual-vacuum crucible (Staudacher type) is described. The lower and upper part of the crucible is made of tantalum and titanium, respectively. The lower part is heated by a tantalum wire coil inserted into a helix furrow made in a thick-walled insulating cylinder. This cylinder was made from a machineable boron nitride ceramic. By means of this, the crucible may be safely heated in vacuum up to 1600°C.

LS-DYNA calculations of shocks in solids

This paper concentrates on numerical studies of thermally induced shock waves in a tantalum target using the commercial LS-Dyna code. Initial calculations of the stresses induced in the Neutrino Factory target are presented as well as an estimation of the shock stresses resulting from pulsed heating of a tantalum wire using an electric current.

Fabrication of diamond thin films with high quality on microcylindrical substrates

The study on deposition of diamond thin films on tungsten wire substrate with a gas mixture of acetone and hydrogen by using bias-enhanced hot filament CVD with the tantalum wires being optimised was carried out. The quality of the diamond film was tested by Scanning Electron Microscopy (SEM) and Raman spectroscopy. The effect of deposition technology on the nucleation and growth of diamond crystals was analysed. The results show that the cylindrical diamond thin films with good quality and uniform thickness have been obtained on microtungsten wires, which laid a foundation for subsequent fabrication of self-supported diamond tubes and deposition of diamond coatings on the rotating tools.

알루미나/산화아연/이산화티타늄 나노유체의 열전도율 측정

The thermal conductivity of water- and ethylene glycol-based nanofluids containing alumina (Al₂O₃), zinc oxide (ZnO) and titanium dioxide (TiO₂) nanoparticles is measured by varying the particle diameter and volume fraction. The transient hot-wire method using an anodized tantalum wire for electrical insulation is employed for the measurement. The experimental results show that nanofluids have substantially higher thermal conductivities than those of the base fluid and the ratio of thermal conductivity enhancement increases linearly with the volume fraction. It has been found that the ratio of thermal conductivity enhancement increases with decreasing particle size but no empirical or theoretical correlation can explain the particle-size dependence of the thermal conductivity. This work provides, for the first time to our knowledge, a set of consistent experimental data over a wide range of nanofluid conditions and can therefore serve as a basis for developing theoretical models to predict thermal conduction phenomena in nanofluids.