Titanium hydride normally refers to the inorganic compound TiH2 and related nonstoichiometric materials.[1][2] It is commercially available as a stable grey/black powder, which is used as an additive in the production of Alnico sintered magnets, in the sintering of powdered metals, the production of metal foam, the production of powdered titanium metal and in pyrotechnics.[3]
![]() Titanium hydride powder
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Names | |
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IUPAC name
titanium dihydride (hydrogen deficient)
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Identifiers | |
ECHA InfoCard | 100.028.843 |
PubChem CID
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UNII | |
CompTox Dashboard (EPA)
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Properties | |
TiH2−x | |
Molar mass | 49.88 g/mol (TiH2) |
Appearance | black powder (commercial form) |
Density | 3.76 g/cm3 (typical commercial form) |
Melting point | Decomposes |
insoluble | |
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Also known as titanium–hydrogen alloy,[4][5] it is an alloy[6] of titanium, hydrogen, and possibly other elements. When hydrogen is the main alloying element, its content in the titanium hydride is between 0.02% and 4.0% by weight. Alloying elements intentionally added to modify the characteristics of titanium hydride include gallium, iron, vanadium, and aluminium.
Production
editIn the commercial process for producing non-stoichiometric TiH2−x, titanium metal sponge is treated with hydrogen gas at atmospheric pressure at between 300-500 °C. Absorption of hydrogen is exothermic and rapid, changing the color of the sponge grey/black. The brittle product is ground to a powder, which has a composition around TiH1.95.[3] In the laboratory, titanium hydride is produced by heating titanium powder under flowing hydrogen at 700 °C, the idealized equation being:[7]
- Ti + H2 → TiH2
Other methods of producing titanium hydride include electrochemical and ball milling methods.[8][9]
Reactions
editTiH1.95 is unaffected by water and air.[citation needed] It is slowly attacked by strong acids and is degraded by hydrofluoric and hot sulfuric acids. It reacts rapidly with oxidizing agents, this reactivity leading to the use of titanium hydride in pyrotechnics.[3]
The material has been used to produce highly pure hydrogen, which is released upon heating the solid.[7] Hydrogen release in TiH~2 starts just above 400 °C but may not be complete until the melting point of titanium metal.[10][3] Titanium tritide (Ti3Hx) has been proposed for long-term storage of tritium gas.[11]
Structure
editAs TiHx approaches stoichiometry, it adopts a distorted body-centered tetragonal structure, termed the
The evolution of the dihydride from titanium metal and hydrogen has been examined in some detail.
Phase | Weight % H | Atomic % H | TiHx | Metal lattice |
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0 – 0.2 | 0 – 8 | TiH0 – TiH0.1 | hcp | |
0.2 – 1.1 | 8 – 34 | TiH0.1 – TiH0.5 | ||
1.1 – 1.8 | 34 – 47 | TiH0.5 – TiH0.9 | bcc | |
1.8 – 2.5 | 47 – 57 | TiH0.9 – TiH1.32 | ||
2.7 – 4.1 | 57 – 67 | TiH1.32 – TiH2 | fcc |
If titanium hydride contains 4.0% hydrogen at less than around 40 °C then it transforms into a body-centred tetragonal (bct) structure called
When titanium hydrides with less than 1.3% hydrogen, known as hypoeutectoid titanium hydride are cooled, the
A metastable
Hydrogen embrittlement in titanium and titanium alloys
editThe absorption of hydrogen and the formation of titanium hydride are a source of damage to titanium and titanium alloys. This hydrogen embrittlement process is of particular concern when titanium and alloys are used as structural materials, as in nuclear reactors.
Hydrogen embrittlement manifests as a reduction in ductility and eventually spalling of titanium surfaces. The effect of hydrogen is to a large extent determined by the composition, metallurgical history and handling of the Ti and Ti alloy.[14] CP-titanium (commercially pure: ≤99.55% Ti content) is more susceptible to hydrogen attack than pure
Ti and Ti alloys form a surface oxide layer, composed of a mixture of Ti(II), Ti(III) and Ti(IV) oxides,[15] which offers a degree of protection to hydrogen entering the bulk.[14] The thickness of this can be increased by anodizing, a process which also results in a distinctive colouration of the material. Ti and Ti alloys are often used in hydrogen containing environments and in conditions where hydrogen is reduced electrolytically on the surface. Pickling, an acid bath treatment which is used to clean the surface can be a source of hydrogen.
Uses
editCommon applications include ceramics, pyrotechnics, sports equipment, as a laboratory reagent, as a blowing agent, and as a precursor to porous titanium. When heated as a mixture with other metals in powder metallurgy, titanium hydride releases hydrogen which serves to remove carbon and oxygen, producing a strong alloy.[3]
The density of titanium hydride varies based on the alloying constituents, but for pure titanium hydride it ranges between 3.76 and 4.51 g/cm3.
Even in the narrow range of concentrations that make up titanium hydride, mixtures of hydrogen and titanium can form a number of different structures, with very different properties. Understanding such properties is essential to making quality titanium hydride. At room temperature, the most stable form of titanium is the hexagonal close-packed (HCP) structure
There are many types of heat treating processes available to titanium hydride. The most common are annealing and quenching. Annealing is the process of heating the titanium hydride to a sufficiently high temperature to soften it. This process occurs through three phases: recovery, recrystallization, and grain growth. The temperature required to anneal titanium hydride depends on the type of annealing. Annealing must be done under a hydrogen atmosphere to prevent outgassing.
See also
editReferences
edit- ^ Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. ISBN 978-0-08-037941-8.
- ^ Holleman, A. F.; Wiberg, E. "Inorganic Chemistry" Academic Press: San Diego, 2001. ISBN 0-12-352651-5.
- ^ a b c d e Rittmeyer, Peter; Weitelmann, Ulrich (2005). "Hydrides". Ullmann's Encyclopedia of Industrial Chemistry. Wiley-VCH. doi:10.1002/14356007.a13_199. ISBN 978-3-527-30673-2.
- ^ McQuillan, A. D. (22 December 1950). "An experimental and thermodynamic investigation of the hydrogen-titanium system". Proceedings of the Royal Society A. 204 (1078): 309–323. Bibcode:1950RSPSA.204..309M. doi:10.1098/rspa.1950.0176. S2CID 135759594. Retrieved 10 March 2013.
- ^ Bennett, L. H. (1980). "Nuclear magnetic resonance in alloys". MRS Proceedings. 3. doi:10.1557/PROC-3-3. Retrieved 10 March 2013.
- ^ Wang, Xin-Quan; Wang, Jian-Tao (15 June 2010). "Structural stability and hydrogen diffusion in TiHx alloys". Solid State Communications. 150 (35–36): 1715–1718. Bibcode:2010SSCom.150.1715W. doi:10.1016/j.ssc.2010.06.004. Retrieved 10 March 2013.
- ^ a b M. Baudler "Hydrogen, Deuterium, Water" in Handbook of Preparative Inorganic Chemistry, 2nd Ed. Edited by G. Brauer, Academic Press, 1963, NY. Vol. 1. p. 114-115.
- ^ Millenbach, Pauline; Givon, Meir (1 October 1982). "The electrochemical formation of titanium hydride". Journal of the Less Common Metals. 87 (2): 179–184. doi:10.1016/0022-5088(82)90086-8. Retrieved 10 March 2013.
- ^ Zhang, Heng; Kisi, Erich H (1997). "Formation of titanium hydride at room temperature by ball milling". Journal of Physics: Condensed Matter. 9 (11): L185–L190. Bibcode:1997JPCM....9L.185Z. doi:10.1088/0953-8984/9/11/005. ISSN 0953-8984. S2CID 250853926.
- ^ Paulin, Irena; Donik, Črtomir; Mandrino, Djordje; Vončina, Maja; Jenko, Monika (January 2012). "Surface characterization of titanium hydride powder". Vacuum. 86 (6): 608–613. doi:10.1016/j.vacuum.2011.07.054.
- ^ Brown, Charles C.; Buxbaum, Robert E. (June 1988). "Kinetics of hydrogen absorption in alpha titanium". Metallurgical Transactions A. 19 (6): 1425–1427. Bibcode:1988MTA....19.1425B. doi:10.1007/bf02674016. S2CID 95614680.
- ^ a b Fukai, Y (2005). The Metal-Hydrogen System, Basic Bulk Properties, 2d edition. Springer. ISBN 978-3-540-00494-3.
- ^ Numakura, H; Koiwa, M; Asano, H; Izumi, F (1988). "Neutron diffraction study of the metastable
γ titanium deuteride". Acta Metallurgica. 36 (8): 2267–2273. doi:10.1016/0001-6160(88)90326-4. ISSN 0001-6160. - ^ a b c Donachie, Matthew J. (2000). Titanium: A Technical Guide. ASM International. ISBN 978-0-87170-686-7.
- ^ Lu, Gang; Bernasek, Steven L.; Schwartz, Jeffrey (2000). "Oxidation of a polycrystalline titanium surface by oxygen and water". Surface Science. 458 (1–3): 80–90. Bibcode:2000SurSc.458...80L. doi:10.1016/S0039-6028(00)00420-9. ISSN 0039-6028.
- ^ Setoyama, Daigo; Matsunaga, Junji; Muta, Hiroaki; Uno, Masayohi; Yamanaka, Shinsuke (3 November 2004). "Mechanical properties of titanium hydride". Journal of Alloys and Compounds. 381 (1–2): 215–220. doi:10.1016/j.jallcom.2004.04.073.
External links
edit- Media related to Titanium hydride at Wikimedia Commons