Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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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.[2] 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.[3] However, it has a low oxidation resistance, with the oxidation starting at temperatures as low as 430 °C.[4] 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.[5]
Atomistic simulations conducted in 2015 predicted that a similar compound, hafnium carbonitride (HfCN), could have a melting point exceeding even that of hafnium carbide.[6] Experimental evidence gathered in 2020 confirmed that it did indeed have a higher melting point exceeding 4,000 °C,[7] with more recent ab initio molecular dynamics calculations predicting the HfC0.75N0.22 phase to have a melting point as high as 4,110 ± 62 °C, highest known for any material.[8]
Hafnium carbide is usually carbon deficient and therefore its composition is often expressed as HfCx (x = 0.5 to 1.0). It has a cubic (rock-salt) crystal structure at any value of x.[9]
Hafnium carbide powder is obtained by the reduction of hafnium(IV) oxide with carbon at 1,800 to 2,000 °C. A long processing time is required to remove all oxygen. Alternatively, high-purity HfC coatings can be obtained by chemical vapor deposition from a gas mixture of methane, hydrogen, and vaporized hafnium(IV) chloride.
Because of the technical complexity and high cost of the synthesis, HfC has a very limited use, despite its favorable properties such as high hardness (greater than 9 Mohs[10]) and melting point.[2]
The magnetic properties of HfCx change from paramagnetic for x ≤ 0.8 to diamagnetic at larger x. An inverse behavior (dia-paramagnetic transition with increasing x) is observed for TaCx, despite its having the same crystal structure as HfCx.[11]
^Physical Constants of Inorganic Compounds in Lide, D. R., ed. (2005). CRC Handbook of Chemistry and Physics (86th ed.). Boca Raton (FL): CRC Press. pp. 4–44 ff. ISBN 0-8493-0486-5.
^ abcHarry Julius Emeléus (1968). "Metal Carbides". Advances in Inorganic Chemistry and Radiochemistry. Academic Press. pp. 169–170. ISBN 978-0-12-023611-4.
^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.
^Shimada, Shiro (October 1992). "Oxidation Kinetics of Hafnium Carbide in the Temperature Range of 480° to 600°C". Journal of the American Ceramic Society. 75 (10): 2671–2678. doi:10.1111/j.1151-2916.1992.tb05487.x.
^Ushakov, Sergey V.; Navrotsky, Alexandra; Hong, Qi-Jun; van de Walle, Axel (26 August 2019). "Carbides and Nitrides of Zirconium and Hafnium". Materials. 12 (17): 2728. Bibcode:2019Mate...12.2728U. doi:10.3390/ma12172728. PMC 6747801. PMID 31454900.
^Hong, Qi-Jun; van de Walle, Axel (2015). "Prediction of the material with highest known melting point from ab initio molecular dynamics calculations". Physical Review B. 92 (2): 020104. Bibcode:2015PhRvB..92b0104H. doi:10.1103/PhysRevB.92.020104. ISSN 1098-0121.
^"Scientists Create World's Most Heat Resistant Material with Potential Use for Spaceplanes". Forbes.
^Dai, Yu; Zeng, Fanhao; Liu, Honghao; Gao, Yafang; Yang, Qiaobin; Chen, Meiyan; Huang, Rui; Gu, Yi (15 October 2023). "Controlled nitrogen content synthesis of hafnium carbonitride powders by carbonizing hafnium nitride for enhanced ablation properties". Ceramics International. 49 (20): 33265–33274. doi:10.1016/j.ceramint.2023.08.035. eISSN 1873-3956. ISSN 0272-8842. OCLC 9997899259. S2CID 260672783.
^Lavrentyev, A.A.; Gabrelian, B.V.; Vorzhev, V.B.; Nikiforov, I.Ya.; Khyzhun, O.Yu.; Rehr, J.J. (26 August 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.
^James F. Shackelford; William Alexander, eds. (2001). CRC Materials Science and Engineering Handbook (3rd ed.). CRC Press. ISBN 978-0-849-32696-7.
^Aleksandr Ivanovich Gusev; Andreĭ Andreevich Rempel; Andreas J. Magerl (2001). Disorder and Order in Strongly Nonstoichiometric Compounds: Transition Metal Carbides, Nitrides, and Oxides. Springer. pp. 513–516. ISBN 978-3-540-41817-7.
Hafniumcarbide (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...
hafniumcarbide is a refractory chemical compound with a general formula TaxHfyCx+y, which can be considered as a solid solution of tantalum carbide and...
actually has a melting point of 3,768 °C and both tantalum hafniumcarbide and hafniumcarbide have higher melting points. TaCx powders of desired composition...
Hafnium is a chemical element; it has symbol Hf and atomic number 72. A lustrous, silvery gray, tetravalent transition metal, hafnium chemically resembles...
a carbide usually describes a compound composed of carbon and a metal. In metallurgy, carbiding or carburizing is the process for producing carbide coatings...
zirconium carbide and tantalum carbide is an important cermet material.[citation needed] Hafnium-free zirconium carbide and niobium carbide can be used...
Hafnium compounds are compounds containing the element hafnium (Hf). Due to the lanthanide contraction, the ionic radius of hafnium(IV) (0.78 ångström)...
and burn. Binary compounds such as tungsten carbide or boron nitride can be very refractory. Hafniumcarbide is the most refractory binary compound known...
The hafnium nitrides are the various salts produced from combining hafnium and nitrogen. The two most important such are hafnium(III) nitride, HfN; and...
Hafnium carbonitride (HfCN) is an ultra-high temperature ceramic (UHTC) mixed anion compound composed of hafnium (Hf), carbon (C) and nitrogen (N). Ab...
combined with carbon, boron, silicon, silicon carbide, and/or nickel to improve the consolidation of the hafnium diboride powder (sintering). It is commonly...
monochloride: HfO2 + 2 Cl2 + C → HfCl4 + CO2 Chlorination of hafniumcarbide above 250 °C. Hafnium and zirconium occur together in minerals such as zircon...
a lustrous, grey-white, strong transition metal that closely resembles hafnium and, to a lesser extent, titanium. Zirconium forms a variety of inorganic...
Bayarjargal, Lkhamsuren (2011). "Synthesis of Binary Transition Metal Nitrides, Carbides and Borides from the Elements in the Laser-Heated Diamond Anvil Cell and...
theoretical possible up to the highest crystal material, such as tantalum hafniumcarbide 4215 °C.) Allotropy – Property of some chemical elements to exist in...
Chuen, Hong Kong, China Heng Fa Chuen station (by MTR station code) Hafniumcarbide Hydrofluorocarbons High frequency content measure, of a signal Hybrid...
periodic table. It contains the four elements titanium (Ti), zirconium (Zr), hafnium (Hf), and rutherfordium (Rf). The group is also called the titanium group...
other direct heating designs by using a retained seed (tantalum carbide or hafniumcarbide) approach. The propellant flows through the porous walls of a...
compounds such as molybdenum boride, hafnium diboride, titanium diboride, dysprosium titanate and gadolinium titanate. Hafnium absorbs neutrons avidly and it...
Carbohydrides (or carbide hydrides) are solid compounds in one phase composed of a metal with carbon and hydrogen in the form of carbide and hydride ions...
180W. Theoretically, all five can decay into isotopes of element 72 (hafnium) by alpha emission, but only 180W has been observed to do so, with a half-life...
tungsten (melting point 3695 K, boiling point 6203 K) or tantalum hafniumcarbide (melting point 4263 K, boiling point some unknown higher temperature)...
A.E.; de Boer, J.H. (1925). "Preparation of pure titanium, zirconium, hafnium, and thorium metal". Zeitschrift für anorganische und allgemeine Chemie...
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