| Revision as of 12:34, 24 May 2014 editBduke (talk | contribs)Extended confirmed users, Pending changes reviewers, Rollbackers34,082 edits Reverted 1 edit by Plasmic Physics (talk): No, you are the person doing a controversial rewrite. (TW)← Previous edit | Revision as of 14:29, 25 May 2014 edit undoSmokefoot (talk | contribs)Autopatrolled, Extended confirmed users, Pending changes reviewers, Rollbackers74,701 edits secondary source for its lab prep, it has been used to generate pure H2, updated the Ullmann citation to the more recent edition, appsNext edit → | ||
| Line 27: | Line 27: | ||
| }} | }} | ||
| '''Titanium hydride''' normally refers to the ] TiH<sub> |
'''Titanium hydride''' normally refers to the ] TiH<sub>2</sub> and closely related nonstoichiometric materials. It is commercially available as a stable grey/black powder, which is used as an additive in the production of ] sintered magnets, in the sintering of powdered metals, the production of ], the production of powdered titanium metal and in pyrotechnics.<ref name = "Ullmanns"/> | ||
| ==Production and reactions of |
==Production and reactions of TiH<sub>(2-x)</sub>== | ||
| In the commercial process for producing non-stoichiometric TiH<sub>(2-x)</sub> titanium metal sponge is |
In the commercial process for producing non-stoichiometric TiH<sub>(2-x)</sub>, 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 TiH<sub>1.95</sub>.<ref name = "Ullmanns">{{cite book |last1=Rittmeyer |first1=Peter |last2=Weitelmann |first2=Ulrich |title=Ullmann's Encyclopedia of Industrial Chemistry |publisher=Wiley-VCH|date= 2005 |chapter=Hydrides |doi=10.1002/14356007.a13_199 }}</ref> The laboratory, titanium hydride is produced by heating titanium powder under flowing hydrogen at 700 C, the idealized equation being:<ref name=Brauer>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.</ref> | ||
| :Ti + H<sub>2</sub> → TiH<sub>2</sub> | |||
| ⚫ | Other methods of producing titanium hydride |
||
| ⚫ | Other methods of producing titanium hydride include electrochemical and ball milling methods.<ref name=Millenbach1982>{{cite journal|last=Millenbach|first=Pauline|coauthors=Givon, Meir|title=The electrochemical formation of titanium hydride|journal=Journal of the Less Common Metals|date=1 October 1982|volume=87|issue=2|pages=179–184|doi=10.1016/0022-5088(82)90086-8|url=http://www.sciencedirect.com/science/article/pii/0022508882900868|accessdate=10 March 2013}}</ref><ref name="ZhangKisi1997">{{cite journal|last1=Zhang|first1=Heng|last2=Kisi|first2=Erich H|title=Formation of titanium hydride at room temperature by ball milling|journal=Journal of Physics: Condensed Matter|volume=9|issue=11|year=1997|pages=L185–L190|issn=0953-8984|doi=10.1088/0953-8984/9/11/005}}</ref> | ||
| ⚫ | TiH<sub>1.95</sub> is unaffected by water and air |
||
| ===Reactions=== | |||
| To produce powdered titanium the hydride is heated to 600 °C under vacuum to remove hydrogen.<ref name = "Ullmanns"/> | |||
| ⚫ | TiH<sub>1.95</sub> is unaffected by water and air. It is slowly attacked by strong acids, but is degraded by hydrofluoric and hot sulfuric acids. It reacts rapidly with oxidising agents. | ||
| The material has been used to produce highly pure hydrogen, which is released upon heating the solid starting at 300 °C.<ref name=Brauer/> Only at the melting point of titanium is dissociation finally complete.<ref name = "Ullmanns"/> | |||
| ==Titanium - hydrogen system== | |||
| ==Structure== | |||
| ⚫ | Titanium has an ] structure at room temperature, (α- form). Hydrogen is absorbed exothermically. The initial absorption involves hydrogen atoms forming a solid solution in α titanium, occupying tetrahedral interstitial sites in the metal lattice. Solubility is limited. Dissolution of hydrogen reduces the transition temperature from the ] α- form to the ] β- form by over 500 °C and as more hydrogen is absorbed the metal lattice starts to change to the β-. As more H atoms enter the metal the lattice then converts from the β- form to a ], δ- form, the H atoms eventually filling all the tetrahedral sites to give the limiting stoichiometry of TiH<sub>2</sub> |
||
| <ref name="Fukai">{{cite book |last=Fukai |first=Y |year=2005 |title=The Metal-Hydrogen System, Basic Bulk Properties, 2d edition|publisher=Springer|isbn=978-3-540-00494-3}}</ref> | TiH<sub>2</sub> has the ] structure, with tetrahedral four-coordinate hydride ligand]]s linking eight-coordinate Ti(II) centres.<ref name="Fukai">{{cite book |last=Fukai |first=Y |year=2005 |title=The Metal-Hydrogen System, Basic Bulk Properties, 2d edition|publisher=Springer|isbn=978-3-540-00494-3}}</ref> | ||
| ⚫ | The evolution of the dihydride from titanium metal and hydrogen has been examined in some detail. Titanium has an ] structure at room temperature, (α- form). Hydrogen is absorbed exothermically. The initial absorption involves hydrogen atoms forming a solid solution in α titanium, occupying tetrahedral interstitial sites in the metal lattice. Solubility is limited. Dissolution of hydrogen reduces the transition temperature from the ] α- form to the ] β- form by over 500 °C and as more hydrogen is absorbed the metal lattice starts to change to the β-form. As more H atoms enter the metal the lattice then converts from the β- form to a ], δ- form, the H atoms eventually filling all the tetrahedral sites to give the limiting stoichiometry of TiH<sub>2</sub>. | ||
| {|class="wikitable" style="text-align:center" | {|class="wikitable" style="text-align:center" | ||
| Line 67: | Line 69: | ||
| == Uses == | == Uses == | ||
| Common applications include ]s, ], ], as a laboratory ], as a ], and as a |
Common applications include ]s, ], ], as a laboratory ], as a ], and as a precursor to porous titanium. When heated as a mixture with other metals in ], titanium hydride releases hydrogen which serves to remove carbon and oxygen, producing a strong alloy.<ref name = "Ullmanns"/> | ||
| As of 1988, titanium hydride was considered to be a leading candidate as a form of long-term ] storage.<ref name=Brown1988>{{cite journal|last=Brown|first=Charles C.|coauthors=Buxbaum, Robert E.|title=Kinetics of hydrogen absorption in alpha titanium|journal=Metallurgical Transactions A|date=June 1988|volume=19|issue=6|pages=1425–1427|url=http://link.springer.com/article/10.1007%2FBF02674016?LI=true#|accessdate=16 February 2013|doi=10.1007/bf02674016}}</ref> | As of 1988, titanium hydride was considered to be a leading candidate as a form of long-term ] storage.<ref name=Brown1988>{{cite journal|last=Brown|first=Charles C.|coauthors=Buxbaum, Robert E.|title=Kinetics of hydrogen absorption in alpha titanium|journal=Metallurgical Transactions A|date=June 1988|volume=19|issue=6|pages=1425–1427|url=http://link.springer.com/article/10.1007%2FBF02674016?LI=true#|accessdate=16 February 2013|doi=10.1007/bf02674016}}</ref> | ||
Revision as of 14:29, 25 May 2014
This article is about the stable titanium hydride. For the unstable molecular chemical compound, see Titanium(IV) hydride. Titanium hydride powder | |
| Names | |
|---|---|
| IUPAC name titanium dihydride (hydrogen deficient) | |
| Identifiers | |
| CAS Number | |
| ECHA InfoCard | 100.028.843 
|
| PubChem CID | |
| CompTox Dashboard (EPA) | |
| Properties | |
| Chemical formula | TiH2-x |
| Molar mass | 49.88 g/mol (TiH2) |
| Appearance | black powder (commercial form) |
| Density | 3.76 g/cm (typical commercial form) |
| Melting point | 350 °C approx |
Except where otherwise noted, data are given for materials in their standard state (at 25 °C , 100 kPa).
 Y verify (what is ?)
Infobox references
| |
Titanium hydride normally refers to the inorganic compound TiH2 and closely related nonstoichiometric materials. 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.
Production and reactions of TiH(2-x)
In the commercial process for producing non-stoichiometric TiH(2-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. The laboratory, titanium hydride is produced by heating titanium powder under flowing hydrogen at 700 C, the idealized equation being:
- Ti + H2 → TiH2
Other methods of producing titanium hydride include electrochemical and ball milling methods.
Reactions
TiH1.95 is unaffected by water and air. It is slowly attacked by strong acids, but is degraded by hydrofluoric and hot sulfuric acids. It reacts rapidly with oxidising agents.
The material has been used to produce highly pure hydrogen, which is released upon heating the solid starting at 300 °C. Only at the melting point of titanium is dissociation finally complete.
Structure
TiH2 has the fluorite structure, with tetrahedral four-coordinate hydride ligand]]s linking eight-coordinate Ti(II) centres.
The evolution of the dihydride from titanium metal and hydrogen has been examined in some detail. Titanium has an hexagonal close packed (hcp) structure at room temperature, (α- form). Hydrogen is absorbed exothermically. The initial absorption involves hydrogen atoms forming a solid solution in α titanium, occupying tetrahedral interstitial sites in the metal lattice. Solubility is limited. Dissolution of hydrogen reduces the transition temperature from the hcp α- form to the bcc β- form by over 500 °C and as more hydrogen is absorbed the metal lattice starts to change to the β-form. As more H atoms enter the metal the lattice then converts from the β- form to a face centred cubic (fcc), δ- form, the H atoms eventually filling all the tetrahedral sites to give the limiting stoichiometry of TiH2.
| Phase | Weight % H | Atomic % H | TiHx | Metal lattice |
|---|---|---|---|---|
| α- | 0 - 0.2 | 0 - 8 | hcp | |
| α- & β- | 0.2 - 1.1 | 8 - 34 | TiH0.1 - TiH0.5 | |
| β- | 1.1 - 1.8 | 34 - 47 | TiH0.5 - TiH0.9 | bcc |
| β- & δ | 1.8 - 2.5 | 47 - 57 | TiH0.9 - TiH1.32 | |
| δ- | 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 ε-titanium.
When titanium hydrides with less than 1.3% hydrogen, known as hypoeutectoid titanium hydride are cooled, the β-titanium phase of the mixture attempts to revert to the α-titanium phase, resulting in an excess of hydrogen. One way for hydrogen to leave the β-titanium phase is for the titanium to partially transform into δ-titanium, leaving behind titanium that is low enough in hydrogen to take the form of α-titanium, resulting in an α-titanium matrix with δ-titanium inclusions.
A metastable γ-titanium hydride phase has been reported. When α-titanium hydride with a hydrogen content of 0.02-0.06% is quenched rapidly, it forms into γ-titanium hydride, as the atoms "freeze" in place when the cell structure changes from hcp to fcc. γ-Titanium takes a body centred tetragonal (bct) structure. Moreover, there is no compositional change so the atoms generally retain their same neighbours.
Hydrogen embrittlement of "CP" (commercially pure) titanium and titanium alloys
The absorption of hydrogen and the formation of titanium hydride are a source of damage to titanium and titanium alloys (Ti /Ti alloys). One obvious example of physical is spalling of the surface due to hydride formation at low temperatures. The effect of hydrogen is to a large extent determined by the composition, metallurgical history and handling of the Ti /Ti alloy. Ti /Ti alloys are often coated with oxide, Ti(II) , Ti(III) and Ti(IV) oxides have been observed, and this layer offers a degree of protection to hydrogen entering the bulk. Ti /Ti alloys 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 sometimes used to clean the surface can be a source of hydrogen. CP-titanium (commercially pure less than about 99.55% Ti content) is more susceptible to hydrogen attack than pure α-titanium. Embrittlement, observed as a reduction in ductility and caused by the formation of a solid solution of hydrogen, can occur in CP-titanium at concentrations as low as 30-40 ppm. Hydride formation has been linked to the presence of iron in the surface of a Ti alloy. Hydride particles are observed in specimens of Ti /Ti alloys that have been welded, and because of this welding is often carried out under an inert gas shield to reduce the possibility of hydride formation.
Uses
Common 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.
As of 1988, titanium hydride was considered to be a leading candidate as a form of long-term tritium storage.
References
- ^ Rittmeyer, Peter; Weitelmann, Ulrich (2005). "Hydrides". Ullmann's Encyclopedia of Industrial Chemistry. Wiley-VCH. doi:10.1002/14356007.a13_199.
- ^ 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 (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.
{{cite journal}}: Unknown parameter|coauthors=ignored (|author=suggested) (help) - 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. doi:10.1088/0953-8984/9/11/005. ISSN 0953-8984.
- ^ 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.
- ^ Donachie, Matthew J. (2000). Titanium: A Technical Guide. ASM International. ISBN 0-87170-686-5.
- 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.
- Brown, Charles C. (June 1988). "Kinetics of hydrogen absorption in alpha titanium". Metallurgical Transactions A. 19 (6): 1425–1427. doi:10.1007/bf02674016. Retrieved 16 February 2013.
{{cite journal}}: Unknown parameter|coauthors=ignored (|author=suggested) (help)