Tantalum Carbide Particles Research Articles

Effects of impurities on stability of TiC, TaC and ZrC particles in tungsten

Titanium carbide (TiC), tantalum carbide (TaC) and zirconium carbide (ZrC) in form of particles are widely added in W to improve its mechanical and anti-irradiation properties. However, TiC, TaC and ZrC particles are decomposed to Ti-C-O, Ta-C-O and Zr-C-O in W, respectively. To understand the micro-mechanisms, we carry out systematical simulations and find that the presence of impurities such as O, N, and P has great influence on the bond length and bond strength of Ti-C, Ta-C and Zr-C in W. The bond lengths of Ti-C, Ta-C and Zr-C are generally increased when O meets Ti-C, Ta-C and Zr-C. The bond strength of O to Ti-C, Ta-C and Zr-C is much larger than that of C to Ti-O, Ta-O and Zr-O. In contrast, N has little effect on the Ti-C bond, but has great influence on the Ta-C bond. P significantly increases Ta-C bond length, while its influence on Zr-C bond is negligible. The kinetics calculations elucidate that the diffusion barriers of C away from TiO are significantly increased by about 1 eV. It is very difficult for C to escape from TiO and ZrO, and it is also extremely difficult for O to escape from TiC, TaC and ZrC. This may be the reason why Ti-C-O, Ta-C-O, and Zr-C-O particles are found in W when TiC TaC and ZrC compounds are dispersed in W.

Highly dispersed TaC nanowire cathodes via template-assisted electrolysis for enhanced lithium–oxygen batteries

High efficiency oxygen electrode is essential to achieve long cycle life of lithium–oxygen battery. In this study, we present a novel approach involving the fabrication of porous, interwoven tantalum carbide (TaC) nanowires via molten salt electrolysis, with multi-walled carbon nanotubes (MWCNTs) serving both as a carbon source and as a structural template. In contrast, using carbon nanoparticles as carbon source results in severe agglomeration of TaC particles. These TaC nanowires offer sufficient storage space for discharge products, establish efficient ions and O2 diffusion pathways, and expose numerous catalytic active sites to effectively mitigating the formation of carbonate byproducts. The lithium–oxygen battery with TaC nanowires oxygen electrode demonstrates a high specific discharge capacity of 11,856.69 mAh g−1, a stable cycle life of 120 cycles at 500 mA g−1 with the limited capacity of 1000 mAh g−1, and a discharge/charge overvoltage gap of 1.13 V. This study introduces a promising approach for the development of new catalysts based on transition metal carbides for lithium–oxygen batteries.

Effect of gamma dose rate in the crosslinking of PVC composites used for radiation protection in radiology

Flexible PVC composites loaded with various levels of tantalum carbide (TaC) were gamma irradiated at two different dose rates and their effect on crosslinking level, thermal stability and mechanical properties evaluated. The shielding properties of composites against X-Rays at radiodiagnosis energies were also evaluated. Gel percentage results indicate a relatively stable crosslinking level after irradiation, only some reduction was observed for highly loaded composite treated at a low dose rate, although thermal stability observed by TGA was maintained. TaC particles were properly dispersed within the PVC material, as seen by SEM and toughness increased when both E' and E'' Moduli were enhanced after irradiation; even Tg, followed by Tanδ DMA curves, increased noticeably after treatment and for the higher TaC loaded composites, particularly when treated at low dose rate irradiation. Density measurements indicated lighter and manageable materials with respect to traditional shielding items. The shielding properties for composites, evaluated in a clinical X-Ray apparatus, in the 50–129 kV interval, show mass attenuation coefficients close to the ones reported for lead, even higher for 50% TaC loaded composite and a very competitive half-value layer (HVL) for all of them.

Wear behavior analysis of vitallium metal matrix composite

At present, the applications of composites are gradually increased due to its performances and admirable substance properties. Through this research work, the vitallium composite were reinforcement with tantalum carbide particles through stir casting technique and the morphology was investigated with scanning electron microscope (SEM). Energy dispersive analyses of X-rays (EDAX) were applied to inspect the composition of various alloying elements. Cobalt and chromium were the major alloy in vitallium composite and these alloys used to enhance the substance properties. In addition to that the hardness of the vitallium composite were augmented by tantalum carbide. A pin on disc tribometer was used to analyze the wear resistance of the material. The wear resistance of the material was highly improved. The casting defect was analyzed through acoustic emission method.

TaC Precipitation Kinetics During Cooling of Co−Re‐Based Alloys

Cobalt−rhenium (Co−Re) alloys are developed for high‐temperature applications at ≈1200 °C and are strengthened by dispersion of nanosized tantalum carbide (TaC) precipitates. Herein, the precipitation behavior during cooling from supersolution depending on the cooling rate and the addition of chromium is presented. The phase composition (matrix phases and TaC) is analyzed from the wide‐angle neutron diffraction patterns measured in situ during temperature cycling. The precipitation of nanosized TaC particles is measured by in situ and ex situ neutron and X‐ray small‐angle scattering. The in situ measurements are used to extract the temperature‐dependent volume fraction of the precipitates; the final size distribution after cooling is extracted from the ex situ measurements. A Kampmann−Wagner's numerical (KWN) model is adapted to isochronal cooling processes. The in situ measurements give the unique possibility to calibrate the model parameters, whereas the ex situ measurements are used to assess the model predictions.

Material Characterization and Parametric Optimization of Unconventional Machining of TiN and TaC reinforced Stir Casted Vitallium Metal Matrix Composite

In this work, influence of machining parameters of the electro discharge machining (EDM) and Abrasive-water jet machining (AWJM) processes on the material removal rate, tool wear rate and surface roughness of the composites were investigated. Titanium nitride and tantalum carbide particles reinforced vitallium composite material was synthesized by stir casting method. The machining characteristics were analyzed through Taguchi and ANOVA methods. The Taguchi optimization technique was used to find the optimal level of parameters while the percentage of contribution for each input parameter on the responses was computed by ANOVA. Scanning electron microscope (SEM) was employed to examine the surface morphology.

Microstructural and electrochemical corrosion properties of electroless Ni-P-TaC composite coating

Ceramic particles are frequently used as reinforcements in electroless Ni-P coating to enhance the mechanical and electrochemical properties. Tantalum carbide (TaC) is a well-known refractory ceramic material, with excellent mechanical properties such as high hardness and fracture toughness. However, its performance as a composite additive has not yet been investigated in the electroless Ni-P coating system. A detailed surface and microstructural analysis have been carried out to explain the mechanical hardness, as well as corrosion-resistant behavior of as-plated and heat treated Ni-P and Ni-P-TaC coating systems. Nanocrystallites of Ni and Ni3P phases along with incorporated TaC particles are distributed in heat treated composite coating as revealed by XRD and TEM analysis. A unique amorphous interface between TaC particle and coating matrix is observed in the Ni-P-TaC composite coating that has provided a protective layer to the corrosion attack at the grain boundaries and defects presented in the coatings. The phase and thermal oxidation behavior of Ni-P and Ni-P-TaC system studied via temperature-dependent Raman measurement show that the coating systems are stable in ambient environment up to 500 °C. The electrochemical corrosion test suggests good corrosion resistance properties of the heat treated Ni-P-TaC composite coating over as-plated Ni-P coating.

Metal Carbide as A Light-Harvesting and Anticoking Catalysis Support for Dry Reforming of Methane.

Dry reforming of methane (DRM) is one of the most attractive chemical reactions, since it converts global‐warming gases into valuable syngas including hydrogen and carbon monoxide. Numerous previous studies used metal oxides catalysis supports, such as Al2O3, but their operating temperature was very high and severe coking occurred and deteriorated their catalytic activities. The present study reports that a metal carbide like tantalum carbide (TaC) acts as a multifunctional catalyst support for the DRM reaction, including light‐harvesting properties for saving energy operation as well as an anticoking property for long‐term stability. Nickel nanoparticles loaded on tantalum carbide (Ni/TaC) are prepared by impregnation and reductive hydrogen treatment. TaC particles act as a light‐harvesting support to promote the DRM reaction by photon irradiation through plasmonic photothermal energy conversion in TaC. Furthermore, Ni/TaC exhibits an excellent long‐term anticoking property, as compared to Ni loaded on conventional metal oxide supports such as Al2O3 or Ta2O5. According to the sole gas condition's experiment, and secondary ion mass spectroscopy, the oxy‐carbide layer near the interface between TaC and Ni plays an essential role in imparting the efficient anticoking property of Ni/TaC.

Formation of Nanostructured Ni-TaC and Fe-TaC Composite Powders via Mechanical Alloying

In this study, mixtures of 25 wt.% of tantalum carbide (TaC) and iron (Fe) or nickel (Ni) powders were mechanical alloyed against time in order to investigate the interactions between the reinforcement (harder TaC particles) and surrounding ductile metallic matrixes (Fe and Ni). After mechanical alloying, apparent densities and particle size and distribution (PSD) of the powders were measured and morphological observations were realized via scanning electron microscopy (SEM). X-ray diffraction (XRD) was applied for phase analysis and with increasing mechanical alloying time certain shifts were observed for the two theta values of the samples. These data used for characterization of strain rates and crystallite sizes by fundamentals parameters approach applied with Lorentzian function and Williamson-Hall plot analysis.

Microstructure and kinetics study on tantalum carbide coating produced on gray cast iron in situ

Abstract Tantalum carbide (TaC) coatings were produced in this study on gray cast iron samples by a combination of casting and heat treatment at 1115–1155 °C. The microstructure and growth kinetics of TaC coatings were investigated. Scanning electron microscopy, transmission electron microscopy, and X-ray diffraction were conducted to analyze macrostructure and the thickness of layer, microstructure, and phase composition. Results show that TaC coating thickness ranges from 14.4 ± 1.59 to 354.3 ± 2.89 μm depending upon the treatment time and temperature. The presence of Ta, TaC, α-Fe, G (graphite), and Fe 3 C phases on the iron matrix surface was detected. From the surface to the substrate, the TaC particles gradually increased from 100–300 nm to 1–2 μm at 1155 °C for different times. The kinetics of TaC coating in situ showed a parabolic relationship between carbide layer thickness and treatment time, and the activation energy for the process was 388.68 kJ/mol.

Laser ablation synthesis of tantalum carbide particles with specific phase assemblage and special interface

Pulsed laser ablation of bulk TaC in vacuum under a high power density was used to fabricate fine-sized tantalum carbide particles, i.e., γ-TaC1−x with varied extent of carbon deficiency and α-Ta2C surrounded by an amorphous phase of Ta-doped carbon clusters or lamellae according to X-ray and electron diffraction. The predominant γ-TaC1−x has a high x value (~0.4) and almost spherical shape when rapidly solidified as submicron-sized particulates, whereas x ~ 0.2 and facetted with occasional {111} coalescence twin when condensed as nanoparticles. The minor α-Ta2C occurred either as nanocondensates with hexagonal crystal form or as a stable epitaxial intergrowth with the γ-TaC1−x particulate having close-packed planes in parallel with the precipitation process. The γ-TaC1−x and α-Ta2C nanocondensates were also coalesced approaching a secondary relationship, i.e., [011]TaC1−x//[01\( \overline{ 1} \)0]Ta2C and (100)TaC1−x//(0001)Ta2C having a fair coincidence site lattice at the interface. The refractory materials have a bimodal minimum band gap (ca. 3.8 and 2.3 eV) for potential optocatalytic and tribology applications at high temperatures.

Transient liquid phase sintering of tantalum carbide ceramics by using silicon as the sintering aid and its effects on microstructure and mechanical properties

Tantalum carbide composites with 0.76–8.85 wt.% elemental silicon as a sintering aid were fabricated by spark plasma sintering (SPS) at 1700 °C and 30 MPa for 5 min. The transient-liquid-phase sintering behavior, the microstructures and the mechanical properties of the tantalum carbide composites were investigated. Oxide impurities present on the surfaces of the tantalum carbide particles were eliminated by reactions with the elemental silicon in a temperature range from 1271 °C to 1503 °C to benefit densification. Then the silicon melted at its melting point temperature of 1413 °C to facilitate rearrangement of the tantalum carbide particles. By the end of the densification, the elemental silicon transformed into more refractory TaSi2 and SiC in the consolidated ceramics by reactions with the tantalum carbide at temperatures lower than 1773 °C. Both TaSi2 and SiC particles improved densification by physically pinning growth of the tantalum carbide grains. Further densification was resulted from creep flow of the silicides after brittle-to-ductile transformation of the silicides at temperatures <1650 °C. Due to the good effects of using elemental silicon as the sintering aid, all the compositions reached densities >96.7% theoretical. The average grain sizes in the consolidated materials decreased with the silicon addition from about 19 μm in the 0.76 wt.% Si composition to about 9 μm in the 8.85 wt.% Si composition. A good flexural strength up to ∼709 MPa was reached in the 8.85 wt.% Si material due to full density and fine microstructure.

High Cr-Ni Cast Iron Base Deposits with Tantalum Carbide Particles Produced by Plasma Spraying

Fe-C-Ta-Cr-Ni alloy powder in diameter of 32-53 μm made by argon atomization was low-pressure plasma sprayed to produce high Cr-Ni cast iron base deposits with finely dispersed tantalum carbide particles. The as-sprayed deposit formed on a water-cooled substrate consisted of γFe, αFe and carbide. The fine precipitates of approximately 0.1 μm in the as-sprayed deposit formed on a water-cooled substrate were carbide. With increasing heat treatment temperature up to 1273 K, the carbide particles coarsened. The hardness of deposit decreases with increasing heat treatment temperature. The wear resistance of as-sprayed deposit formed on a non-cooled substrate was higher than that of the deposit heat-treated at 1273 K. The as-sprayed deposit and deposit heat-treated at 1273 K hade higher wear resistance than a commercial stainless steel.

Origin Analyses of Obtuse Triangular Defects in 4deg.-Off 4H-SiC Epitaxial Wafers by Electron Microscopy and by Synchrotron X-Ray Topography

Triangular shaped defects with obtuse-angles at tops and long bases are often observed in surfaces of epitaxial films. We have investigated the origins of them, and it became clear that these defects without clear origins were formed by contaminations of tantalum carbide particles. Formations of micro-order pipes at the origin points of these defects were also observed. These micro-order pipes did not accompany strain and dislocations around them, though their appearances were very similar to the ones so-called micro-pipes.

A study on in situ growth of TaC whiskers in Al2O3 matrix powder for ceramic cutting tools

In situ growth of tantalum carbide (TaC) whiskers was synthesized in an α-Al2O3 matrix powder via a carbothermal reduction technique within a temperature range of 1350–1500°C in an argon atmosphere. The starting materials consisted of Ta2O5, C, Ni and NaCl powders. Different mixing methods and various reaction temperatures were employed. Most of the prepared whiskers were 0.2–0.5μm in diameter and 5–15μm in length. The reaction temperature of 1400–1450°C was suitable for the growth of TaC whiskers and a wet mixing method was beneficial to increase the whisker yield. Some of the whiskers exhibited the needle shape while others exhibited the screw shape. The growth mechanism of the whiskers was a complex mechanism involving a helical screw dislocation mechanism and a vapor–liquid–solid process. No obvious influences of the Al2O3 matrix powder on the growth of TaC whiskers were found and the major impurities in the obtained powder were TaC particles, nickel and unreacted carbon.

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.

Microstructure of Carbide-Dispersed Nanocrystalline Fe&amp;ndash;Ta&amp;ndash;C Films

Nanocrystalline structure of soft magnetic Fe-Ta-C films crystallized from an amorphous state has been investigated. High-resolution transmission electron microscopy (HRTEM) revealed that tantalum carbide particles much smaller than iron grains are dispersed at the grain boundaries (mostly at tripple junctions) of iron grains. Such a configuration of the carbides hardly interrupts the intergranular magnetic coupling which reduces the effective magnetocrystalline anisotropy