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Titanium carbide
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| Names | |
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| IUPAC name
titanium carbide
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| Other names
titanium(IV) carbide
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| Identifiers | |
3D model (JSmol)
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| ChemSpider | |
| ECHA InfoCard | 100.031.916 |
| EC Number |
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PubChem CID
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| UNII | |
CompTox Dashboard (EPA)
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| Properties | |
| TiC | |
| Molar mass | 59.878 g·mol−1 |
| Appearance | black crystalline powder |
| Density | 4.93 g/cm3 |
| Melting point | 3,160 °C (5,720 °F; 3,430 K) |
| Boiling point | 4,820 °C (8,710 °F; 5,090 K) |
| Insoluble | |
| +8.0·10−6 cm3/mol | |
| Structure | |
| Cubic, cF8 | |
| Fm3m, No. 225 | |
| Octahedral | |
| Related compounds | |
Related compounds
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Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Titanium carbide, TiC, is an extremely hard (Mohs 9–9.5) refractory ceramic material, similar to tungsten carbide. It has the appearance of black powder with the sodium chloride (face-centered cubic) crystal structure.
It occurs in nature as a form of the very rare mineral khamrabaevite (Russian: Хамрабаевит) - (Ti,V,Fe)C. It was discovered in 1984 on Mount Arashan in the Chatkal District,[1] USSR (modern Kyrgyzstan), near the Uzbek border. The mineral was named after Ibragim Khamrabaevich Khamrabaev, director of Geology and Geophysics of Tashkent, Uzbekistan. Its crystals as found in nature range in size from 0.1 to 0.3 mm.
Physical properties
[edit]Titanium carbide has an elastic modulus of approximately 400 GPa and a shear modulus of 188 GPa.[2]
Titanium carbide is soluble in solid titanium oxide, with a range of compositions which are collectively named "titanium oxycarbide" and created by carbothermic reduction of the oxide.[3]
Manufacturing and machining
[edit]Tool bits without tungsten content can be made of titanium carbide in nickel-cobalt matrix cermet, enhancing the cutting speed, precision, and smoothness of the workpiece.[citation needed]
The resistance to wear, corrosion, and oxidation of a tungsten carbide–cobalt material can be increased by adding 6–30% of titanium carbide to tungsten carbide. This forms a solid solution that is more brittle and susceptible to breakage.[clarification needed]
Titanium carbide can be etched with reactive-ion etching.
Applications
[edit]Titanium carbide is used in preparation of cermets, which are frequently used to machine steel materials at high cutting speed. It is also used as an abrasion-resistant surface coating on metal parts, such as tool bits and watch mechanisms.[4] Titanium carbide is also used as a heat shield coating for atmospheric reentry of spacecraft.[5]
7075 aluminium alloy (AA7075) is almost as strong as steel, but weighs one third as much. Using thin AA7075 rods with TiC nanoparticles allows larger alloys pieces to be welded without phase-segregation induced cracks.[6]
See also
[edit]- Metallocarbohedryne, a family of metal-carbon clusters including Ti8C12
References
[edit]- ^ Dunn, Pete J (1985). "New mineral names". American Mineralogist. 70: 1329–1335.
- ^ Chang, R; Graham, L (1966). "Low-Temperature Elastic Properties of ZrC and TiC". Journal of Applied Physics. 37 (10): 3778–3783. Bibcode:1966JAP....37.3778C. doi:10.1063/1.1707923.
- ^ Fatollahi-Fard, Farzin (2017-05-01). Production of Titanium Metal by an Electrochemical Molten Salt Process (thesis thesis). Carnegie Mellon University.
- ^ Gupta, P.; Fang, F.; Rubanov, S.; Loho, T.; Koo, A.; Swift, N.; Fiedler, H.; Leveneur, J.; Murmu, P.P.; Markwitz, A.; Kennedy, J. (2019). "Decorative black coatings on titanium surfaces based on hard bi-layered carbon coatings synthesized by carbon implantation". Surface and Coatings Technology. 358: 386–393. doi:10.1016/j.surfcoat.2018.11.060. hdl:2292/46133. S2CID 139179067.
- ^ Sforza, Pasquale M. (13 November 2015). Manned Spacecraft Design Principles. Elsevier. p. 406. ISBN 9780124199767. Retrieved 4 January 2017.
- ^ "New welding process opens up uses for formerly un-weldable lightweight alloy". newatlas.com. 13 February 2019. Retrieved 2019-02-18.
Titanium carbide
View on GrokipediaChemical and Structural Characteristics
Composition and Nomenclature
Titanium carbide is represented by the chemical formula TiC, indicating a stoichiometric 1:1 ratio of titanium atoms to carbon atoms.[7] This composition reflects the compound's basic structure as a binary interstitial carbide, where carbon atoms occupy octahedral voids in a titanium lattice.[7] The molar mass of TiC is 59.878 g/mol, derived from the standard atomic weights of titanium (47.867 g/mol) and carbon (12.011 g/mol).[7] This value is consistent across authoritative chemical databases and underscores the compound's lightweight nature relative to other transition metal carbides.[8] In nomenclature, the IUPAC name for TiC is titanium carbide, with the alternative designation titanium(IV) carbide emphasizing the +4 oxidation state of titanium.[9] It is commonly abbreviated as TiC and referred to as titanium monocarbide to distinguish it from other titanium-carbon phases, such as the sesquicarbide Ti₂C.[9] These naming conventions align with systematic inorganic chemistry standards for metal carbides.[4] Titanium carbide frequently exhibits non-stoichiometric compositions, expressed as , where (typically 0.01 to 0.5) denotes vacancies in the carbon sublattice.[10] These deviations from ideal stoichiometry arise during synthesis and significantly impact properties, including enhanced ductility and altered electronic characteristics due to the increased vacancy concentration.[11] Such variability allows tailoring of TiC for specific applications while maintaining its core refractory nature.[10]Crystal Structure
Titanium carbide (TiC) adopts a face-centered cubic (FCC) crystal structure, classified as the halite or rock salt type, with the space group Fmm (No. 225).[12] In this arrangement, titanium atoms form the FCC lattice, while carbon atoms occupy all octahedral interstitial sites, resulting in each titanium atom being octahedrally coordinated to six carbon atoms and vice versa.[13] The lattice parameter is approximately 4.327 Å at room temperature for near-stoichiometric TiC, though it varies slightly with composition due to non-stoichiometry.[14] The bonding in TiC combines strong covalent interactions between Ti and C atoms with metallic bonding among neighboring Ti atoms, contributing to its unique combination of ceramic hardness and metallic conductivity.[15] This hybrid nature arises from the directional charge density in Ti-C bonds and delocalized d-electrons facilitating Ti-Ti interactions, as revealed by cluster model analyses.[15] TiC is typically non-stoichiometric, with a homogeneity range from TiC to TiC, primarily due to carbon vacancies that act as constitutional defects.[13] These vacancies are predominantly located in the carbon sublattice and can be randomly distributed in most compositions, though ordered arrangements may emerge at lower carbon contents, influencing lattice stability and electronic properties.[16] Structurally, TiC resembles the rock salt (NaCl) configuration, where the anion and cation sublattices are interpenetrating FCC arrays, but it exhibits metallic characteristics absent in ionic NaCl, such as high electrical conductivity stemming from partially filled d-bands.[17]Physical and Mechanical Properties
Thermal and Electrical Properties
Titanium carbide (TiC) possesses remarkable thermal stability, characterized by a high melting point of 3140 °C and a boiling point of 4820 °C, making it suitable for extreme high-temperature applications.[1] Its thermal conductivity ranges from approximately 20 to 30 W/(m·K) at room temperature, though this value decreases with rising temperature due to enhanced phonon scattering in its lattice.[18] The coefficient of thermal expansion is about 7.5–8.5 × 10^{-6} /K, which reflects the material's ability to withstand thermal stresses without significant dimensional changes.[5] Additionally, the specific heat capacity lies in the range of 30–40 J/(mol·K), indicating moderate energy absorption per unit mass under heating conditions.[2] Electrically, titanium carbide behaves as a metallic conductor, with an electrical resistivity of approximately 68–120 μΩ·cm at room temperature, a property influenced by its rock-salt crystal structure that facilitates electron mobility.[18][19] This conductivity level supports its use in applications requiring both thermal resilience and electrical performance. In terms of oxidation resistance, TiC begins to oxidize in air above approximately 600–800 °C, forming a protective titanium dioxide (TiO₂) layer that slows further degradation, though prolonged exposure above 900 °C leads to progressive scale formation.[20][21]Hardness and Elastic Properties
Titanium carbide exhibits a black-gray appearance in its crystalline powder or solid form. Its theoretical density is 4.93 g/cm³.[5] The material demonstrates exceptional hardness, ranking 9–9.5 on the Mohs scale, with Vickers hardness values ranging from approximately 2,800 to 3,200 HV and Knoop hardness from 2,500 to 3,000 kg/mm².[22][5][23] In terms of elastic properties, titanium carbide possesses a Young's modulus of approximately 400–450 GPa, a shear modulus of about 188 GPa, and a Poisson's ratio between 0.19 and 0.25.[2][24] Despite its high stiffness, titanium carbide is brittle, with a low fracture toughness of approximately 3–4 MPa·m^{1/2}, rendering it susceptible to cleavage fracture under tensile loading.[18] This brittleness limits its tensile strength to around 250–350 MPa, while compressive strength reaches 3,000–4,000 MPa.[5]| Property | Value/Range | Measurement Type |
|---|---|---|
| Density | 4.93 g/cm³ | Theoretical |
| Mohs Hardness | 9–9.5 | Scratch resistance |
| Vickers Hardness | 2,800–3,200 HV | Indentation (load-dependent) |
| Knoop Hardness | 2,500–3,000 kg/mm² | Microindentation |
| Young's Modulus | 400–450 GPa | Uniaxial tension |
| Shear Modulus | 188 GPa | Torsional deformation |
| Poisson's Ratio | 0.19–0.25 | Lateral strain ratio |
| Fracture Toughness | 3–4 MPa·m^{1/2} | Critical stress intensity |
| Compressive Strength | 3,000–4,000 MPa | Uniaxial compression |
| Tensile Strength | 250–350 MPa | Uniaxial tension |

