Tantalum carbide

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Tantalum carbide
ZrN-polyhedral.png
Tantalum carbide TaC.JPG
Names
IUPAC name
Tantalum carbide
Other names
Tantalum(IV) carbide
Identifiers
3D model (JSmol)
ChemSpider
ECHA InfoCard 100.031.914 OOjs UI icon edit-ltr-progressive.svg
EC Number
  • (TaC):235-118-3
  • (TaC0.5):235-119-9
PubChem CID
UNII
  • (TaC):InChI=1S/C.Ta/q-1;+1
    Key: DUMHRFXBHXIRTD-UHFFFAOYSA-N
  • (TaC0.5):InChI=1S/C.2Ta
    Key: VDBAWDHDCVOEAA-UHFFFAOYSA-N
  • (TaC):[Ta+]#[C-]
  • (TaC0.5):[C].[Ta].[Ta]
Properties
TaC
Molar mass 192.96 g/mol
AppearanceBrown-gray powder
Odor Odorless
Density 14.3–14.65 g/cm3 (TaC)
15.1 g/cm3 (TaC0.5) [1]
Melting point 3,768 °C (6,814 °F; 4,041 K)
(TaC) [2]
3,327 °C (6,021 °F; 3,600 K)
(TaC0.5) [1]
Boiling point 4,780–5,470 °C (8,640–9,880 °F; 5,050–5,740 K)
(TaC) [1] [3]
Insoluble
Solubility Soluble in HF-HNO3 mixture [1]
Thermal conductivity 21 W/m·K [3]
Thermochemistry
36.71 J/mol·K [4]
Std molar
entropy (S⦵298)
42.29 J/mol·K
−144.1 kJ/mol
Related compounds
Related refractory ceramic materials
 Zirconium nitride
Niobium carbide
Zirconium carbide
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Tantalum carbides (TaC) form a family of binary chemical compounds of tantalum and carbon with the empirical formula TaCx, where x usually varies between 0.4 and 1. They are extremely hard, brittle, refractory ceramic materials with metallic electrical conductivity. They appear as brown-gray powders, which are usually processed by sintering.

Contents

Being important cermet materials, tantalum carbides are commercially used in tool bits for cutting applications and are sometimes added to tungsten carbide alloys. [5]

The melting points of tantalum carbides was previously estimated to be about 3,880 °C (4,150 K; 7,020 °F) depending on the purity and measurement conditions; this value is among the highest for binary compounds. [6] [7] And only tantalum hafnium carbide was estimated to have a higher melting point of 3,942 °C (4,215 K; 7,128 °F). [8] However new tests have conclusively proven that TaC actually has a melting point of 3,768 °C and both tantalum hafnium carbide and hafnium carbide have higher melting points. [9]

Preparation

TaCx powders of desired composition are prepared by heating a mixture of tantalum and graphite powders in vacuum or inert-gas atmosphere (argon). The heating is performed at a temperature of about 2,000 °C (2,270 K; 3,630 °F) using a furnace or an arc-melting setup. [10] [11] An alternative technique is reduction of tantalum pentoxide by carbon in vacuum or hydrogen atmosphere at a temperature of 1,500–1,700 °C (1,770–1,970 K; 2,730–3,090 °F). This method was used to obtain tantalum carbide in 1876, [12] but it lacks control over the stoichiometry of the product. [7] Production of TaC directly from the elements has been reported through self-propagating high-temperature synthesis. [13]

Crystal structure

b-TaC0.5 with the unit cell, blue color is tantalum B-Ta2C-bas.png
β-TaC0.5 with the unit cell, blue color is tantalum

TaCx compounds have a cubic (rock-salt) crystal structure for x = 0.7–1.0; [14] the lattice parameter increases with x. [15] TaC0.5 has two major crystalline forms. The more stable one has an anti-cadmium iodide-type trigonal structure, which transforms upon heating to about 2,000 °C into a hexagonal lattice with no long-range order for the carbon atoms. [10]

FormulaSymmetryType Pearson symbol Space group NoZρ (g/cm3)a (nm)c (nm)
TaCCubicNaCl [15] cF8Fm3m225414.60.4427
TaC0.75Trigonal [16] hR24R3m1661215.010.31163
TaC0.5Trigonal [17] anti-CdI2hP3P3m1164115.080.31030.4938
TaC0.5Hexagonal [11] hP4P63/mmc194215.030.31050.4935

Here Z is the number of formula units per unit cell, ρ is the density calculated from lattice parameters.

Properties

The bonding between tantalum and carbon atoms in tantalum carbides is a complex mixture of ionic, metallic and covalent contributions, and because of the strong covalent component, these carbides are very hard and brittle materials. For example, TaC has a microhardness of 1,600–2,000 kg/mm2 [18] (~9 Mohs) and an elastic modulus of 285 GPa, whereas the corresponding values for tantalum are 110 kg/mm2 and 186 GPa. [19]

Tantalum carbides have metallic electrical conductivity, both in terms of its magnitude and temperature dependence. TaC is a superconductor with a relatively high transition temperature of TC = 10.35 K. [15]

The magnetic properties of TaCx change from diamagnetic for x ≤ 0.9 to paramagnetic at larger x. An inverse behavior (para-diamagnetic transition with increasing x) is observed for HfCx, despite that it has the same crystal structure as TaCx. [20]

Application

Tantalum carbide is widely used as sintering additive in ultra-high temperature ceramics (UHTCs) or as a ceramic reinforcement in high-entropy alloys (HEAs) due to its excellent physical properties in melting point, hardness, elastic modulus, thermal conductivity, thermal shock resistance, and chemical stability, which makes it a desirable material for aircraft and rockets in aerospace industries.

Wang et al. have synthesized SiBCN ceramic matrix with TaC addition by mechanical alloying plus reactive hot-pressing sintering methods, in which BN, graphite and TaC powders were mixed with ball-milling and sintered at 1,900 °C (2,170 K; 3,450 °F) to obtain SiBCN-TaC composites. For the synthesis, the ball-milling process refined the TaC powders down to 5 nm without reacting with other components, allowing to form agglomerates that are composed of spherical clusters with a diameter of 100 nm-200 nm. TEM analysis showed that TaC is distributed either randomly in the form of nanoparticles with sizes of 10-20 nm within the matrix or distributed in BN with smaller size of 3-5 nm. As a result, the composite with 10 wt% addition of TaC improved the fracture toughness of the matrix, reaching 399.5 MPa compared to 127.9 MPa of pristine SiBCN ceramics. This is mainly due to the mismatch of thermal expansion coefficients between TaC and SiBCN ceramic matrix. Since TaC has a larger coefficient of thermal expansion than that of SiBCN matrix, TaC particles endures tensile stress while the matrix endures tensile stress in radial direction and compressive stress in tangential direction. This makes the cracks to bypass the particles and absorbs some energy to achieve toughening. In addition, the uniform distribution of TaC particles contributes to the yield stress explained by Hall-Petch relationship due to a decrease in grain size. [21]

Wei et al. have synthesized novel refractory MoNbRe0.5W(TaC)x HEA matrix using vacuum arc melting. XRD patterns showed that the resulting material is mainly composed of a single BCC crystal structure in the base alloy MoNbRe0.5W and a multi-component (MC) type carbide of (Nb, Ta, Mo, W)C to form a lamellar eutectic structure, with the amount of MC phase proportional to TaC addition. TEM analysis showed that the lamellar interface between BCC and MC phase presents a smooth and curvy morphology which exhibits good bonding with no lattice misfit dislocations. As a result, the grain size decreases with increasing TaC addition which improves the yield stress explained by Hall-Petch relationship. The formation of lamellar structure is because at elevated temperature, the decomposition reaction occurs in the MoNbRe0.5W(TaC)x composites: (Mo, Nb, W, Ta)2C → (Mo, Nb, W, Ta) + (Mo, Nb, W, Ta)C in which Re is dissolved in both components to nucleate BCC phase first and MC phase in the following, according to the phase diagrams. [22] In addition, the MC phase also improves the strength of composites, due to its stiffer and more elastic property compared to BCC phase. [23]

Wu et al. have also synthesized Ti(C, N)-based cermets with TaC addition with ball-milling and sintering at 1,683 K (1,410 °C; 2,570 °F). TEM analysis showed that TaC helps dissolution of carbonitride phase and converts to TaC-binder phase. The resulting is a formation of “black-core-white rim” structure with decreasing grain size in the region of 3-5 wt% TaC addition and increasing transverse rupture strength (TRS). 0-3 wt% TaC region showed a decrease in the TRS because the TaC addition decreases the wettability between binder and carbonitride phase and creates pores. Further addition of TaC beyond 5 wt% also decreases TRS because TaC agglomerates during sintering and porosity again forms. The best TRS is found at 5wt% addition where fine grains and homogeneous microstructure are achieved for less grain boundary sliding. [24]

Natural occurrence

Tantalcarbide is a natural form of tantalum carbide. It is a cubic, extremely rare mineral. [25]

See also

Related Research Articles

<span class="mw-page-title-main">Sintering</span> Process of forming and bonding material by heat or pressure

Sintering or frittage is the process of compacting and forming a solid mass of material by pressure or heat without melting it to the point of liquefaction. Sintering happens as part of a manufacturing process used with metals, ceramics, plastics, and other materials. The nanoparticles in the sintered material diffuse across the boundaries of the particles, fusing the particles together and creating a solid piece.

Refractory metals are a class of metals that are extraordinarily resistant to heat and wear. The expression is mostly used in the context of materials science, metallurgy and engineering. The definition of which elements belong to this group differs. The most common definition includes five elements: two of the fifth period and three of the sixth period. They all share some properties, including a melting point above 2000 °C and high hardness at room temperature. They are chemically inert and have a relatively high density. Their high melting points make powder metallurgy the method of choice for fabricating components from these metals. Some of their applications include tools to work metals at high temperatures, wire filaments, casting molds, and chemical reaction vessels in corrosive environments. Partly due to the high melting point, refractory metals are stable against creep deformation to very high temperatures.

<span class="mw-page-title-main">Tungsten carbide</span> Hard, dense and stiff chemical compound

Tungsten carbide is a chemical compound containing equal parts of tungsten and carbon atoms. In its most basic form, tungsten carbide is a fine gray powder, but it can be pressed and formed into shapes through sintering for use in industrial machinery, cutting tools, chisels, abrasives, armor-piercing shells and jewelry.

A cermet is a composite material composed of ceramic and metal materials.

<span class="mw-page-title-main">Refractory</span> Materials resistant to decomposition under high temperatures

In materials science, a refractory is a material that is resistant to decomposition by heat or chemical attack that retains its strength and rigidity at high temperatures. They are inorganic, non-metallic compounds that may be porous or non-porous, and their crystallinity varies widely: they may be crystalline, polycrystalline, amorphous, or composite. They are typically composed of oxides, carbides or nitrides of the following elements: silicon, aluminium, magnesium, calcium, boron, chromium and zirconium. Many refractories are ceramics, but some such as graphite are not, and some ceramics such as clay pottery are not considered refractory. Refractories are distinguished from the refractory metals, which are elemental metals and their alloys that have high melting temperatures.

<span class="mw-page-title-main">Titanium diboride</span> Chemical compound

Titanium diboride (TiB2) is an extremely hard ceramic which has excellent heat conductivity, oxidation stability and wear resistance. TiB2 is also a reasonable electrical conductor, so it can be used as a cathode material in aluminium smelting and can be shaped by electrical discharge machining.

<span class="mw-page-title-main">Hafnium diboride</span> Chemical compound

Hafnium diboride is a type of ceramic composed of hafnium and boron that belongs to the class of ultra-high temperature ceramics. It has a melting temperature of about 3250 °C. It is an unusual ceramic, having relatively high thermal and electrical conductivities, properties it shares with isostructural titanium diboride and zirconium diboride. It is a grey, metallic looking material. Hafnium diboride has a hexagonal crystal structure, a molar mass of 200.11 grams per mole, and a density of 11.2 g/cm3.

<span class="mw-page-title-main">Superalloy</span> Alloy with higher durability than normal metals

A superalloy, or high-performance alloy, is an alloy with the ability to operate at a high fraction of its melting point. Key characteristics of a superalloy include mechanical strength, thermal creep deformation resistance, surface stability, and corrosion and oxidation resistance.

<span class="mw-page-title-main">Zirconium carbide</span> Chemical compound

Zirconium carbide (ZrC) is an extremely hard refractory ceramic material, commercially used in tool bits for cutting tools. It is usually processed by sintering.

<span class="mw-page-title-main">Ceramic engineering</span> Science and technology of creating objects from inorganic, non-metallic materials

Ceramic engineering is the science and technology of creating objects from inorganic, non-metallic materials. This is done either by the action of heat, or at lower temperatures using precipitation reactions from high-purity chemical solutions. The term includes the purification of raw materials, the study and production of the chemical compounds concerned, their formation into components and the study of their structure, composition and properties.

<span class="mw-page-title-main">Hafnium carbide</span> Chemical compound

Hafnium carbide (HfC) is a chemical compound of hafnium and carbon. Previously the material was estimated to have a melting point of about 3,900 °C. More recent tests have been able to conclusively prove that the substance has an even higher melting point of 3,958 °C exceeding those of tantalum carbide and tantalum hafnium carbide which were both previously estimated to be higher. However, it has a low oxidation resistance, with the oxidation starting at temperatures as low as 430 °C. Experimental testing in 2018 confirmed the higher melting point yielding a result of 3,982 (±30°C) with a small possibility that the melting point may even exceed 4,000°C.

Tantalum hafnium carbide is a refractory chemical compound with a general formula TaxHfyCx+y, which can be considered as a solid solution of tantalum carbide and hafnium carbide. It was originally thought to have the highest melting of any known substance but new research has proven that hafnium carbonitride has a higher melting point.

<span class="mw-page-title-main">Zirconium diboride</span> Chemical compound

Zirconium diboride (ZrB2) is a highly covalent refractory ceramic material with a hexagonal crystal structure. ZrB2 is an ultra-high temperature ceramic (UHTC) with a melting point of 3246 °C. This along with its relatively low density of ~6.09 g/cm3 (measured density may be higher due to hafnium impurities) and good high temperature strength makes it a candidate for high temperature aerospace applications such as hypersonic flight or rocket propulsion systems. It is an unusual ceramic, having relatively high thermal and electrical conductivities, properties it shares with isostructural titanium diboride and hafnium diboride.

<span class="mw-page-title-main">Cemented carbide</span> Type of composite material

Cemented carbides are a class of hard materials used extensively for cutting tools, as well as in other industrial applications. It consists of fine particles of carbide cemented into a composite by a binder metal. Cemented carbides commonly use tungsten carbide (WC), titanium carbide (TiC), or tantalum carbide (TaC) as the aggregate. Mentions of "carbide" or "tungsten carbide" in industrial contexts usually refer to these cemented composites.

Dymalloy is a metal matrix composite of 20% copper and 80% silver alloy matrix with type I diamond. It has a very high thermal conductivity of 420 W/(m·K), and its thermal expansion can be adjusted to match other materials, e.g., silicon and gallium arsenide chips. It is chiefly used in microelectronics as a substrate for high-power and high-density multi-chip modules, where it aids with removing waste heat.

<span class="mw-page-title-main">MAX phases</span>

The MAX phases are layered, hexagonal carbides and nitrides which have the general formula: Mn+1AXn, (MAX) where n = 1 to 4, and M is an early transition metal, A is an A-group (mostly IIIA and IVA, or groups 13 and 14) element and X is either carbon and/or nitrogen. The layered structure consists of edge-sharing, distorted XM6 octahedra interleaved by single planar layers of the A-group element.

Ultra-high-temperature ceramics (UHTCs) are a type of refractory ceramics that can withstand extremely high temperatures without degrading, often above 2,000 °C. They also often have high thermal conductivities and are highly resistant to thermal shock, meaning they can withstand sudden and extreme changes in temperature without cracking or breaking. Chemically, they are usually borides, carbides, nitrides, and oxides of early transition metals.

<span class="mw-page-title-main">High-entropy alloy</span> Alloys with high proportions of several metals

High-entropy alloys (HEAs) are alloys that are formed by mixing equal or relatively large proportions of (usually) five or more elements. Prior to the synthesis of these substances, typical metal alloys comprised one or two major components with smaller amounts of other elements. For example, additional elements can be added to iron to improve its properties, thereby creating an iron-based alloy, but typically in fairly low proportions, such as the proportions of carbon, manganese, and others in various steels. Hence, high-entropy alloys are a novel class of materials. The term "high-entropy alloys" was coined by Taiwanese scientist Jien-Wei Yeh because the entropy increase of mixing is substantially higher when there is a larger number of elements in the mix, and their proportions are more nearly equal. Some alternative names, such as multi-component alloys, compositionally complex alloys and multi-principal-element alloys are also suggested by other researchers.

<span class="mw-page-title-main">Niobium diboride</span> Chemical compound

Niobium diboride (NbB2) is a highly covalent refractory ceramic material with a hexagonal crystal structure.

Hafnium compounds are compounds containing the element hafnium (Hf). Due to the lanthanide contraction, the ionic radius of hafnium(IV) (0.78 ångström) is almost the same as that of zirconium(IV) (0.79 angstroms). Consequently, compounds of hafnium(IV) and zirconium(IV) have very similar chemical and physical properties. Hafnium and zirconium tend to occur together in nature and the similarity of their ionic radii makes their chemical separation rather difficult. Hafnium tends to form inorganic compounds in the oxidation state of +4. Halogens react with it to form hafnium tetrahalides. At higher temperatures, hafnium reacts with oxygen, nitrogen, carbon, boron, sulfur, and silicon. Some compounds of hafnium in lower oxidation states are known.

References

  1. 1 2 3 4 Lide, David R., ed. (2009). CRC Handbook of Chemistry and Physics (90th ed.). Boca Raton, Florida: CRC Press. ISBN   978-1-4200-9084-0.
  2. ↑ Cedillos-Barraza, Omar; Manara, Dario; Boboridis, K.; Watkins, Tyson; Grasso, Salvatore; Jayaseelan, Daniel D.; Konings, Rudy J. M.; Reece, Michael J.; Lee, William E. (2016). "Investigating the highest melting temperature materials: A laser melting study of the TaC-HFC system". Scientific Reports. 6: 37962. Bibcode:2016NatSR...637962C. doi:10.1038/srep37962. PMC   5131352 . PMID   27905481.
  3. 1 2 US 5196273,Tsantrizos, Peter; Mavropoulos, Lakis T.& Shanker, Kartiket al.,"Tantalum carbide composite materials",published 1993-03-23, assigned to Noranda Inc.
  4. ↑ Tantalum carbide in Linstrom, Peter J.; Mallard, William G. (eds.); NIST Chemistry WebBook, NIST Standard Reference Database Number 69, National Institute of Standards and Technology, Gaithersburg (MD) (retrieved 2014-07-02)
  5. ↑ Emsley, John (11 August 2003). Nature's building blocks: an A-Z guide to the elements . Oxford University Press. pp.  421–. ISBN   978-0-19-850340-8 . Retrieved 2 May 2011.
  6. ↑ The claim of melting point of 4,000 °C (4,270 K; 7,230 °F) in TaC0.89 is based not on actual measurement but on an extrapolation of the phase diagram, using an analogy with NbC, see Emeléus
  7. 1 2 Emeléus, Harry (1968). Advances in Inorganic Chemistry and Radiochemistry. Academic Press. pp. 174–176. ISBN   978-0-12-023611-4 . Retrieved 3 May 2011.
  8. ↑ Agte, C.; Alterthum, H. (1930). "Researches on Systems with Carbides at High Melting Point and Contributions to the Problem of Carbon Fusion". Zeitschrift für technische Physik. 11: 182–191. ISSN   0373-0093.
  9. ↑ "New record set for world's most heat resistant material".
  10. 1 2 Lonnberg, B; Lundstrom, T; Tellgren, R (1986). "A neutron powder diffraction study of Ta2C and W2C". Journal of the Less Common Metals. 120 (2): 239–245. doi:10.1016/0022-5088(86)90648-X.
  11. 1 2 Rudy, Erwin; Brukl, C. E.; Windisch, Stephan (1968). "Constitution of Ternary Ta-Mo-C Alloys". Journal of the American Ceramic Society. 51 (5): 239–250. doi:10.1111/j.1151-2916.1968.tb13850.x.
  12. ↑ Joly, A. (1876). "Sur les azotures et carbures de niobium et de tantale". Compt. Rend. (in French). 82: 1195.
  13. ↑ Shuck, Christopher E.; Manukyan, Khachatur V.; Rouvimov, Sergei; Rogachev, Alexander S.; Mukasyan, Alexander S. (January 2016). "Solid-flame: Experimental validation". Combustion and Flame. 163: 487–493. Bibcode:2016CoFl..163..487S. doi: 10.1016/j.combustflame.2015.10.025 .
  14. ↑ Lavrentyev, A; Gabrelian, B; Vorzhev, V; Nikiforov, I; Khyzhun, O; Rehr, J (2008). "Electronic structure of cubic HfxTa1–xCy carbides from X-ray spectroscopy studies and cluster self-consistent calculations". Journal of Alloys and Compounds. 462 (1–2): 4–10. doi:10.1016/j.jallcom.2007.08.018.
  15. 1 2 3 Valvoda, V. (1981). "X-ray diffraction study of Debye temperature and charge distribution in tantalum monocarbide". Physica Status Solidi A. 64 (1): 133–142. Bibcode:1981PSSAR..64..133V. doi:10.1002/pssa.2210640114.
  16. ↑ Yvon, K.; Parthé, E. (1970). "On the crystal chemistry of the close-packed transition-metal carbides. I. The crystal structure of the [zeta]-V, Nb and Ta carbides". Acta Crystallographica Section B. 26 (2): 149–153. Bibcode:1970AcCrB..26..149Y. doi:10.1107/S0567740870002091.
  17. ↑ Bowman, A. L.; Wallace, T. C.; Yarnell, J. L.; Wenzel, R. G.; Storms, E. K. (1965). "The crystal structures of V2C and Ta2C". Acta Crystallographica. 19 (1): 6–9. Bibcode:1965AcCry..19....6B. doi:10.1107/S0365110X65002670.
  18. ↑ Kurt H. Stern (1996). Metallurgical and Ceramic Protective Coatings. Chapman & Hall.
  19. ↑ Oyama, S. T. (1996-01-31). The Chemistry of Transition Metal Carbides and Nitrides. Springer Science & Business Media. ISBN   978-0-7514-0365-7.
  20. ↑ Gusev, Aleksandr; Rempel, Andrey; Magerl, Andreas (2001). Disorder and order in strongly nonstoichiometric compounds: transition metal carbides, nitrides, and oxides. Springer. pp. 513–516. ISBN   978-3-540-41817-7 . Retrieved 3 May 2011.
  21. ↑ Wang, Bingzhu, et al. "Effects of TaC addition on microstructure and mechanical properties of SiBCN composite ceramics." Ceramics International 45.17 (2019): 22138-22147
  22. ↑ E. Rudy, S. Windisch, C.E. Brukl, Technical Report No. AFML-TR-65-2, Part II, Ternary Phase Equilibria in Transition Metal Boron-carbon-silicon Systems, vol. XVII, 1967
  23. ↑ Wei, Qinqin, et al. "Microstructure evolution, mechanical properties and strengthening mechanism of refractory high-entropy alloy matrix composites with addition of TaC." Journal of Alloys and Compounds 777 (2019): 1168-1175
  24. ↑ Wu, Peng, et al. "Effect of TaC addition on the microstructures and mechanical properties of Ti (C, N)-based cermets." Materials & Design 31.7 (2010): 3537-3541
  25. ↑ Mindat, http://www.mindat.org/min-7327.html
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