Nickel hydride

Edit links
Source: Wikipedia, the free encyclopedia.
For Nickel–hydride battery, see Nickel–hydrogen battery.

Nickel hydride is either an inorganic compound of the formula NiHx or any of a variety of coordination complexes. It was discovered by Polish chemist Bogdan Baranowski in 1958.[1]

Binary nickel hydrides and related materials

"The existence of definite hydrides of

catalyst
. Experimental studies on nickel hydrides are rare and principally theoretical.

Hydrogen hardens nickel (as it does most metals), inhibiting

ductile than nickel. Loss of ductility occurs due to cracks maintaining sharp points due to suppression of elastic deformation by the hydrogen, and voids forming under tension due to decomposition of the hydride.[3] Hydrogen embrittlement can be a problem in nickel in use in turbines at high temperatures.[4]

In the narrow range of stoichiometries adopted by nickel hydride, distinct structures are claimed. At room temperature, the most stable form of nickel is the face-centred cubic (FCC) structure α-nickel. It is a relatively soft metallic material that can dissolve only a very small concentration of hydrogen, no more than 0.002 wt% at 1,455 °C (2,651 °F), and only 0.00005% at 25 °C (77 °F). The solid solution phase with dissolved hydrogen, that maintains the same structure as the original nickel is termed the α-phase. At 25°C, 6 kbar of hydrogen pressure is needed to dissolve in β-nickel, but the hydrogen desorbs at pressures below 3.4 kbar.[5]

Surface

Hydrogen dissociates on nickel surfaces. The dissociation energies on Ni(111), Ni(100), and Ni(11O) crystal faces are respectively 46, 52, and 36 kJ/mol. The H2 dissociates from each of these surfaces at distinct temperatures: 320–380, 220–360, and 230–430 K.[5]

High pressure phases

Crystallographically distinct phases of nickel hydride are produced with hydrogen gas at 600 MPa;

face-centred cubic or β-nickel hydride. Hydrogen to nickel atomic ratios are up to one, with hydrogen occupying an octahedral site.[7] The density of the β-hydride is 7.74 g/cm3. It is grey.[7] At a current density of 1 amp per square decimeter, in 0.5 mol/liter of sulfuric acid and thiourea a surface layer of nickel will be converted to nickel hydride. This surface is replete with cracks up to millimeters long. The direction of cracking is in the {001} plane of the original nickel crystals. The lattice constant of nickel hydride is 3.731 Å, which is 5.7% more than that of nickel.[6]

The near-stoichiometric NiH is unstable and loses hydrogen at pressures below 340 MPa.[5]

Molecular nickel hydrides

A large number of nickel

hydride complexes are known. Illustrative is the complex trans-NiH(Cl)(P(C6H11)3)2.[8]

References

  1. ^ Stanislaw M. Filipek, Izabella Grzegory, Janusz Lipkowski, Stanislaw Sieniutycz. "In Memoriam: Professor Bogdan Baranowski". researchgate.net. Retrieved 8 November 2023.{{cite web}}: CS1 maint: multiple names: authors list (link)
  2. ISBN 978-0-08-037941-8
    .
  3. doi:10.1016/s0927-0256(01)00217-8
    .
  4. ISSN 1345-9678
    .
  5. ^
    ISBN 9789085704171. Retrieved 11 February 2013. {{cite book}}: |work= ignored (help
    )
  6. ^
    doi:10.2355/isijinternational.52.263
    .
  7. ^ a b Travares, S. S. M.; A. Lafuente; S. Miraglia; D. Fruchart; S. Pairis (2003). "SEM Characterization of Hydrogenated Nickel". Acta Microscopia. 12 (1).
  8. PMID 27437790
    .

See also
Retrieved from "https://en.wikipedia.org/w/index.php?title=Nickel_hydride&oldid=1218028790"