Formation Of Tantalum Carbide Research Articles

The formation mechanism of in-situ TaC/Ni0.9Ta0.1 composites prepared by pressureless reactive sintering

The in-situ Tantalum Carbide (TaC)/Ni0.9Ta0.1 composite was fabricated by pressureless reactive sintering method using Nickel (Ni), Tantalum (Ta) and graphite as raw materials. The formation mechanism was investigated through analyzing the phase and morphology evolution process during the reactive sintering process. Results showed that Ni, Ta and graphite completely reacted and dense TaC/Ni0.9Ta0.1 composite was obtained. With the increase of temperature, the solid-phase diffusion of atoms occurs at the interface of Ni, Ta and graphite, leading to the formation of Ni3C, Ni2Ta, Ni3Ta, Ni0.9Ta0.1 and TaC. Meanwhile, the reaction [Ta] (Ta atoms in Ni3Ta) + [C] (C atoms in Ni3Ta)TaC in Ni3Ta takes place, due to the high affinity between Ta and C atoms. The intermediate products Ni3C, Ni2Ta and Ni3Ta vanish, and the composite is consisted of Ni0.9Ta0.1 and TaC before the appearance of liquid phase. The formation of TaC included two ways, namely the diffusion of C into Ta particles and the reaction [Ta]+[C] = TaC in Ni3Ta. Ni0.9Ta0.1 was also generated through two ways, i.e., the diffusion of Ta into Ni and the transformation of Ni3Ta. The liquid phase sintering of composite occurs at about 1320 °C, and the optimum sintering temperature was about 1380 °C.

Low Shrinkage, Coarse‐Grained Tantalum–Alumina Refractory Composites via Cold Isostatic Pressing

Alumina–tantalum composites are produced in a two‐step synthesis via cold isostatic pressing (CIP) from commercially available raw materials without any addition of organic additives. The highest densification for fine‐grained composites is found with a maximum pressure of 150 MPa, whereby a cyclic pressure increase or at maximum pressure showed no measurable influence. The increase of the sintering temperature from 1600 to 1700 °C led to a higher densification up to a relative density of . Aggregates received by jawbreaking show a blocky morphology, rounded corners, and edges with porosities of . The formation of tantalum carbide and the incorporation of oxygen into the tantalum lattice are verified during sintering. The coarse‐grained composites produced from these aggregates show open porosities of and shrinkage . Determined splitting tensile strenghts are in the range between 8.4 and 9.1 MPa.

Growth of graphene on tantalum and its protective properties

The mechanism of graphene growth on tantalum has been studied. It has been demonstrated that graphene growth occurs through the formation of tantalum carbide, which exhibits catalytic properties towards cracking of hydrocarbons. We found that excessive carbon, not involved in carbide formation, forms self-limiting layer of graphene on the surface. The layer of tantalum carbide and graphene provides an efficient protective layer against chemical corrosion and high temperature oxidation.

Synthesis of ultra-fine tantalum carbide powders by a combinational method of sol–gel and spark plasma sintering

Tantalum carbide (TaC) nanopowders were synthesized by a novel method combining the sol–gel and spark plasma sintering (SPS) processes using tantalum pentachloride (TaCl5) and phenolic resin as the sources of tantalum (Ta) and carbon (C), respectively. Gels of Ta-containing chelate with good uniformity and high stability were prepared by solution-based processing. The products with the structure of carbon-coated tantalum pentoxide (Ta2O5) were obtained after pyrolysis at 800 °C. Further heat treatment by SPS resulted in the fast formation of TaC at a relatively low temperature. The effects of the C/Ta molar ratio in the raw materials and the heat treatment temperature on the prepared powders were investigated. With increase in the C/Ta molar ratio from 3.75 to 4.25, the synthesis temperature, oxygen content and average crystallite size of the TaC powders decreased. Furthermore, the oxygen content of the powders prepared at the C/Ta molar ratio of 4.25 could be reduce by increasing the heat treatment temperature from 1400° to 1600°C, which unfortunately also induced a mean crystallite size increase from 30 to 100 nm. The TaC powders obtained at a comparatively low C/Ta molar ratios of 4.25 at 1500 °C had an average particle size of about 50 nm and a low oxygen content of about 0.43 wt%.

Analysis of interaction between reactants and substrate materials during the growth of tantalum coatings

We have analyzed interaction between reactants and substrate materials during the reduction of tantalum bromide with cadmium in the course of tantalum deposition on Cu, Fe, Mo, and Ni metallic substrates and the 25Kh3M3NBTsA, Ni3Al, VKNA, and ZhS32 alloys. The results indicate that molybdenum and nickel substrates are the most stable to the reactants used in this study; copper and iron experience etching; and aluminum, chromium, and titanium are capable of competing with cadmium as a reducing agent. The presence of carbon in the substrate material leads to the formation of tantalum carbide in the metal–coating interfacial layer. In the absence of aluminum, oxygen impurities are likely to be removed as oxybromides. Optimal materials for the fabrication of reaction chambers for tantalum deposition are nickel-coated high-temperature steels.

Porous IrO2-Ta2O5 Coating Modified with Carbon Nanotubes for Oxygen Evolution Reaction

A novel porous coating consisting of iridium oxide (IrO2) and tantalum oxide (Ta2O5), modified with multiwalled carbon nanotubes (CNT) was prepared on a titanium (Ti) substrate. The Ta2O5 was obtained by the oxidation of tantalum chloride (TaCl5), and followed by the formation of tantalum carbide (TaC) through the reduction of Ta2O5 with CNT, which generated the intermediate layer of Ta2O5-CNT-TaC. The presence of TaC inhibited the grain growth and refined the particle sizes in the intermediate layer, enhancing the adhesion between the particles, while the introduction of CNT promoted the growth of IrO2 columnar nanocrystal arrayed particles on the active layer, which strengthened the adhesion between the active coating and the substrate. Four characteristic processes involving initiated, continuous, intercrossing and complete coating growths were identified, and further correlated to the electrochemical performance, life and failure behaviors of the coatings. The life of the novel IrO2-Ta2O5-CNT coated Ti electrode was three times longer than that of the conventional IrO2-Ta2O5 coated Ti electrode in sulfuric acid solutions. The electrode failure was mainly caused by the consumption of Ta2O5 at the coating, which damaged the porous structures and destroyed the pore channels.

Interaction Between Sputtered <I>β</I>-Ta Films and Diamond-Like Carbon with Ru Intermediate Layer

Interaction between beta-tantalum film and Diamond-like Carbon (DLC) film was studied with and without ruthenium intermediate barrier layer. Phase identification using X-ray Diffraction showed that the phase transformation of tantalum film from beta to alpha crystalline structure was delayed by 100 degrees C and the formation of tantalum carbide was also hindered when ruthenium interlayer is present. X-ray reflectivity measurements indicate that the surface and interfacial area of C/Ta film was maintained to achieve desired magnetic and tribological performance even after N2 annealing at 400 degrees C. In C/Ru/Ta film there is minimum intermixing between tantalum and DLC. In C/Ta film, severe reaction between tantalum and carbon took place. Raman spectroscopy analysis revealed the as-deposited carbon film possessed amorphous structure regardless of the existence of Ru interlayer. Graphitization of carbon film was observed in both structures, upon annealing, however the films with Ru layer was thermodynamically more stable thus desirable in magnetic recording.

Formation of Tantalum Carbide and Nitride Phases in Atomic Layer Deposition Using Hydrogen Plasma and tert‐Butylimido‐tris(diethylamido)‐tantalum (TBTDET), and its Effect on Material Properties

AbstractTaCN films are deposited with plasma‐enhanced atomic layer deposition (PEALD) using tert‐butylimido‐tris(diethylamido)‐tantalum and hydrogen. It is confirmed that the film is a homogeneous mixture of TaC, TaN, Ta3N5, and Ta2O5 with the oxide phase formed from the post‐deposition uptake of oxygen from the air. It is shown that the electrical properties of TaCN film are affected by the phase composition in the film. The effects of process parameters, such as deposition temperature, plasma power, and cycle time, on the film composition and electronic properties are evaluated. With the increase of the TaC and TaN phases over the Ta3N5 phase, the resistivity of the film is decreased. As the deposition temperature, plasma power, and plasma cycle time are increased, the carbide and TaN phases in the film are increased and the film resistivity is decreased. The uptake of oxygen after deposition is up to 10 at.‐%, and the resistivity of TaCN film deposited using PEALD is as low as 350 µΩ · cm.

One simple synthesis route to nanocrystalline tantalum carbide via the reaction of tantalum pentachloride and sodium carbonate with metallic magnesium

Nanocrystalline tantalum carbide (TaC) was synthesized via a simple route by the reaction of metallic magnesium with sodium carbonate and tantalum pentachloride in an autoclave at 600 °C. X-ray powder diffraction pattern indicated that the product was cubic TaC, and the cell constant was a = 4.451 Å. Field emission scanning electron microscopy image showed that it consisted of particles with an average size of 40 nm. The product was also studied by TGA in the flowing air. It had good thermal stability and oxidation resistance below 450 °C in air. The mechanism of the formation of TaC was also discussed in this paper.

Controlling the synthesis of TaC nanopowders by injecting liquid precursor into RF induction plasma

Thermal plasma processing has been used to synthesize nano-size powders through the condensation of reactant species from a vapor phase. Further development of this synthesis method will require the careful selection of an appropriate precursor and precise control of products species and their particle sizes. Direct introduction of liquid mist into thermal plasma gives us a wider choice of precursors than does vapor-phase precursor injection and lets us inject the precursors in larger amounts. In the present work, nano-size tantalum carbide powder was prepared from a liquid precursor, tantalum ethoxide Ta(OC2H5)5, by using r.f. thermal plasma. The liquid precursor was atomized to generate micron-sized mist droplets, and the mist was introduced into plasma. This atomized precursor evaporated quickly in the high-temperature plasma flame, and nanoparticles were formed as temperature decreased. The process was controlled by changing the hydrogen addition, process pressure, carrier gas flow rate for mist injection, and quenching condition. Adding hydrogen improved the powder quality by removing solid carbon, but excess hydrogen suppressed the formation of tantalum carbide. The quenching conditions gave significant effects on the reduction of particles size by two thirds and yielded average particle sizes as small as 8 nm.

An electrochemically prepared precursor for the formation of tantalum carbide

Metallic tantalum was electrochemically dissolved in an organic electrolyte containing n-propylamine. This resulted in the formation of a viscous fluid. Heating of the solution resulted in the formation of a glassy amorphous solid. Calcination of this precursor in an atmosphere of argon or ammonia resulted in the formation of tantalum carbide, with nitrogen contents in the range 0.6 to 2.5 wt %. Calcination at comparably low temperatures led to products with extremely broadened X-ray diffraction (XRD) patterns. Tantalum carbide has some remarkable properties such as an excellent resistance against oxidation and hydrolysis as well as an extremely high melting point of 3985 °C [1, 2]. Its main current use is as a hard coating on hard metals, such as tungsten carbide, to increase the corrosion and wear resistance [1, 2]. Coating tantalum nitride on various materials, such as carbon fibres, should drastically increase their oxidation resistance. By contrast to titanium, for example, different tantalum-nitride phases with the stoichiometries Ta2N, TaN and Ta3Ns, and different titanium-carbide phases with the stoichiometries Ta2C and TaC are known [3]. TaC and TaN both possess a cubic crystal structure; the solubility of TaN in the TaC lattice is around 45% [4]. Tantalumcarbide and nitride coatings have been solely obtainable, up to now, by physical means [1, 2] or by chemical vapour deposition [5]. This letter describes the formation of an oxygen-free tantalum-carbide precursor, by an electrochemical route, and its calcination behaviour. Electrochemically prepared polymeric precursors have already been used for the formation of aluminium nitride [6-13], titanium nitride and titanium carbide [12-15], and chromium nitride and chromium carbide [16]. This route also enables the formation of coatings [11-14] on various substrates and fibres and it is possibly applicable to all metal nitrides and many carbides relevant in materials science. Metallic tantalum was anodically dissolved in a purely organic electrolyte. This consisted of an organic amine (400 mL n-propylamine), acetonitrile (150 mL) to increase the polarity, and tetrabutylammonium bromide (11 g) as a supporting electrolyte to achieve sufficient ionic conductivity. A doublewalled glass vessel contained the electrodes and the electrolyte. Both the cathodes and the anodes were formed by sheets of metallic tantalum (3 mm thick). The distance between two electrodes was about 2 mm. A condenser, fixed at the top of the vessel,

An electrochemically prepared precursor for the formation of tantalum carbide

An electrochemically prepared precursor for the formation of tantalum carbide

ChemInform Abstract: TANTALUM CARBIDE FORMED BY THE CARBONIZATION OF TA2O5 IN AN ARGON PLASMA ARC

The formation of tantalum carbide by the carbonization of Ta2O5 with graphite by heating in an argon plasma arc was studied. Chemical and X-ray analyses showed that the product obtained was either stoichiometric or a defect carbide with the formula of TaC1−X. The products were found to be superconductors.

Tantalum Carbide Formed by the Carbonization of Ta2O5 in an Argon Plasma Arc

Abstract The formation of tantalum carbide by the carbonization of Ta2O5 with graphite by heating in an argon plasma arc was studied. Chemical and X-ray analyses showed that the product obtained was either stoichiometric or a defect carbide with the formula of TaC1−X. The products were found to be superconductors.

Some properties of tantalum carbide powder produced by synthesis from the elements

1. A study was made of the preparation of tantalum carbide by synthesis from tantalum powder and carbon. It was established that synthesis for 1 hat 2000°C in a graphite tube resistance furnace results in the formation of tantalum carbide with a total carbon content of 6.39%. 2. The effects of milling for various periods of time upon the particle size and shape and the apparent and tap densities of the tantalum carbide powder produced were determined.