I. Yu. Zavalii

New Metal-Hydride Electrode Materials Based On R1–xMgxNi3–4 Alloys for Chemical Current Sources

We present a brief survey of works on the structure and hydrogen-sorption properties of some R–Mg–Ni alloys. It is shown that R–Mg–Ni alloys can be regarded as promising electrode materials for Ni/MH rechargeable batteries. Main attention is focused on the analysis of the properties of R1–xMgxNi3–4 alloys. The relationship between the composition of these alloys, character of isotherms, and electrochemical characteristics is discussed.

Metal-Hydride Systems for Processing Hydrogen Isotopes for Power Plants

We consider the main approaches and designs of using metal hydrides in supply systems of vacuum power plants with hydrogen isotopes as a working medium. By analyzing the results of investigations and developments in this field, we show that the most promising method is connected with the creation of multifunctional metal-hydride elements, which are a part of the structural units of the working zone of a vacuum chamber (e.g., the electrodes of a device supporting plasma) and are made of hydride-forming materials that are reversible absorbers of low-pressure hydrogen. In this case, in addition to the complex solution of auxiliary problems of compact storage, purification, and programmed bleeding-in of hydrogen isotopes into the vacuum chamber of a power plant, efficient pumping-out and improved operation of the plant as a whole can be ensured in certain cases.

Characteristic Features of the Sorption–Desorption of Hydrogen by Mg–M–Ni (M = Al, Mn, Ti) Ternary Alloys

By the method of high-energy milling in a ball mill, we obtain new alloys of Mg–M−Ni (M = Al, Mn, Ti) ternary systems. The properties of hydrogen sorption of the Mg3AlNi2 compound (Ti2Ni-type structure) are investigated and compared with the properties of Mg3MNi2 (M = Mn, Ti) isostructural compounds. The sorption–desorption of hydrogen by Mg88M4Ni8 (M = Al, Mn, Ti) alloys is studied. The catalytic influence of Mg3MNi2 ternary phases on the hydrogenation of magnesium is established.

Investigation of Ti(Zr–Ni) Hydrogen-Sorbing Alloys as Electrode Materials for Nickel–Metal-Hydride Storage Batteries

We studied cyclic charge–discharge characteristics of partially substituted and oxygen-containing derivatives of a Ti2Ni alloy by using specially designed equipment based on PI-50-1 potentiostats and a computer. For Ti3.8Zr0.2Ni2Ox alloys, a twofold increase in the discharge capacity was detected as the oxygen content increased from x = 0 to x = 0.3. It was established that the effect of the hydrogenation–desorption–disproportionation–recombination process on the homogeneity of the Ti4Ni2O0.3 alloy and its electrochemical charge–discharge parameters in alkaline electrolytes is positive.

Zr-V-Fe alloys as efficient hydrogen getters

SummaryResults are presented on phase equilibria and hydrogen uptake characteristics for alloys in the Zr-V-Fe system. Effects have been determined from combining these alloys with scandium, lanthanum, and aluminum oxide. The hydrogenation uptake kinetics can be improved if the alloy contains Zr3V3O, and the hydrogen capacity is increased if lanthanum or scandium is added. The thermal decomposition conditions for the hydrogenated alloys have been examined.One can use a Zr-V-Fe alloy as a basic element in a metal hydride system to support ion sources in accelerators, which enables one to combine all the necessary functions in such a system: storage, purification, and inlet before transfer to the pump, with improved gas economy in the ion source.

Hydrogenation of Zr6MeX2 intermetallic compounds: Absorption and desorption characteristics, crystal structure, and magnetic properties (Me-Fe, Co, Ni; X-Al, Ga, Sn)

We study the process of formation of the hydrides of Zr6MeX2 ternary intermetallic compounds (Me-Fe, Co, Ni; X-Al, Ga, Sn). It is shown that they are characterized by high hydrogen-storage capacity (9.4–10.8 atoms of hydrogen per formula unit). In the process hydrogenation, by the method of X-ray powder diffraction analysis, we revealed the transition of the crystal structure of Zr6MeX2 from the {ie528-1} space group of symmetries into {ie528-2} with doubling of the unit cell in the [001]-direction. The analysis of the crystal structure of Zr6NiAl(Sn)2Hx hydrides by using the Rietveld improvement of the data of X-ray powder diffraction analysis shows that it is identical to the structure of Zr6FeAl2D10 deuteride studied earlier by the method of neutron diffraction analysis. The thermal desorption of hydrogen from the synthesized Zr6MeX2 hydrides was observed in the temperature range 400–900°K. The dependence of the magnetic susceptibility of the Zr6FeAl2 compound on temperature is characterized by the presence of a peak at 50°K. The character of these curves undergoes significant changes in the processes of hydrogenation and dehydrogenation of the specimen.

Hydrogenation and the magnetic and electrochemical parameters of Nd2Fe12.6T1.4B intermetallides with Nd2Fe14B structures (T series 1 transition metal)

Conclusions1.Solid solutions are formed with the Nd2Fe14B structure type when 10% of the iron atoms in the Nd2Fe14B are replaced by series 1 transition metals (Sc, V, Cr, Mn, Co, Ni) or silicon to give Nd2Fe12.6T1.4B. The tetragonal unit cell of the initial structure is almost unaltered.2.The chemical nature of the alloying component affects the activity in the interaction with hydrogen for the initial intermetallides, as well as the adsorption capacity and the thermal stability in the hydrides formed. The highest rate of hydride formation occurs for alloys rich in neodymium, which is due to the catalysis by the solid solution of iron in neodymium.3.Hydrogenation is accompanied by a rise in Curie temperture of 70–100 K with a simultaneous slight rise in the specific magnetization and a subtantial reduction in the anisotropy field.4.The Nd2Fe12.6T1.4B intermetallides are embrittled by hydrogen saturation, which is due to the expansion of the structure by 2–3%, and which enables one to make fine powders with clean unoxidized surfaces. There are thus appreciable increases in the magnetic characteristics of permanent magnets: coercive force, residual magnetization and magnetic energy, which enables one to make high-quality permanent magnets.