Alloys hydriding

M. A. Gutjahr, H. Buchner, K. Beccu, Proc. 8th Ini. Symp. of a new reversible negative electrode for alkaline storage batteries based on metal alloy hydrides, 1974, p. 79. 

Metal foils used as catalysts in the experiments described above turned out to be ill-fitted to these investigations. The electrolytic transformation of alloy foils into alloy hydrides did not guarantee a sufficient purity of the samples. Copper rich alloys should be excluded from the experiments because they could not be hydrogen treated in the same manner as the other alloys, and consequently no active microcrystalline layer was developed on their surface. 

The alloy hydride has been investigated as a useful hydrogenation catalyst for a wide variety of substrates under mild conditions. It is however pyrophoric in air, and an experimental procedure has been developed to avoid this hazard. A related hydride, LaNi4.5Alo.5H5 has similar properties. 

See LANTHANIDE-TRANSITION METAL ALLOY HYDRIDES See Poly(tetralluoroethylene) Metal hydrides... 

Sodium-antimony alloy, 4797 Sodium germanide, 4418 Sodium-zinc alloy, 4798 Titanium-zirconium alloys, 4921 See also LANTHANIDE-TRANSITION METAL ALLOY HYDRIDES... 

Several lanthanide-transition metal alloys (LaNi5, PrCo5, SmCo5) readily absorb large volumes of hydrogen under mild conditions, and some of these alloy hydrides function as active hydrogenation catalysts e.g., the title structures, which are pyrophoric in air. Analogous hydrides may be expected to behave similarly. 

Virtually all of the reported structural data on titanium alloy hydrides and deuterides indicate that the solute atoms occupy tetrahedral interstitial sites in the metal lattice. Neutron diffraction data obtained for deuterium in Ti/34 atom % Zr and in Ti/34 atom % Nb (17) indicate tetrahedral site occupancy in the bcc /3-phase. Similarly, data reported for deuterium in Ti/19 atom % V and in Ti/67 atom % Nb (18) indicate tetrahedral site occupancy in the fee 7-phase. Crystallographic examination of the 7-phase Ti-Nb-H system (19) reveals that increasing niobium content linearly increases the lattice parameter of the fee 7-phase for Nb contents ranging from 0 to 70.2 atom %. Vanadium, on the other hand, exerts the opposite effect (6) at H/M = 1.85, the 7-phase lattice parameter decreases with increasing vanadium contents. 

The anode material, MH, is a transition metal hydride or rare earth alloy hydride. Explain why the voltage remains nearly constant during the entire discharge cycle. 

See also LANTHANIDE—TRANSITION METAL ALLOY HYDRIDES... 

Magnesium—nickel hydride, 4458 Plutonium(III) hydride, 4504 Poly(germanium dihydride), 4409 Poly(germanium monohydride), 4407 Potassium hydride, 4421 Rubidium hydride, 4444 Sodium hydride, 4438 f Stibine, 4505 Thorium dihydride, 4483 Thorium hydride, 4535 Titanium dihydride, 4484 Titanium—zirconium hydride, 4485 Trigermane, 4415 Uranium(III) hydride, 4506 Uranium(IV) hydride, 4536 Zinc hydride, 4486 Zirconium hydride , 4487 See COMPLEX HYDRIDES, PYROPHORIC MATERIALS See entry LANTHANIDE—TRANSITION METAL ALLOY HYDRIDES... 

Lanthanide iodide silicides, 200 Lanthanide metals, 200 Lanthanide nitrobenzoates, 200 Lanthanide—transition metal alloy hydrides, 201 Lassaigne test, 201 Lead salts of nitro compounds, 201 Lecture demonstrations, 202 Light alloys, 202 Lime fusion, 202 Linseed oil, 202 Liquefied gases, 203 Liquefied natural gas, 203 Liquefied petroleum gases, 203 Liquid air, 204 Liquid nitrogen cooling, 205 Lithium peralkyluranates, 205 Lubricants, 205 Lycopodium powder, 205... 

P. V. Geld, R. A. Ryabov, L. P. Mokhracheva, Hydrogen and the Physical Properties of Metals and Alloys Hydrides of the Transition Metals, Nauka, Moscow, 1985. 

Reilly, J. J. and Johnson, J. R., Titanium Alloy Hydrides and Their Applications, "Proc. 1st World Hydrogen Energy Conf.", 1976, Miami Beach, International Assoc, of Hydrogen Energy, II, 8B-6. 

A metal hydride battery similar to the nickel-cadmium battery has been developed by Sharp corporation. The battery is shaped in the form of a button of 20 mm diameter and can give 1.2 V. The anode in the battery is made of La-Ni-Sn alloy hydride, and the cathode is nickel oxide. Potassium hydroxide solution in polyamide-resin is the electrolyte. The battery exhibits high energy density (i.e.) 1.5 to 2.0 times that of the Ni-Cd battery, good cycling life and superior low temperature behaviours. 

The absorption of H by alloys poses even more complicated and less well understood problems. None of the theoretical models currently available can account satisfactorily for the fact that H can distinguish between interstitial sites surrounded by different types of metal atoms, although Switendick has commented on the need to allow for substantial local effects in calculations of the band structure of alloy hydrides. 

KEYWORDS electronic structure, hydrogen storage alloys hydride stability, alloy design... 

---