Chemical Properties
Gray-black metallic powder. Stable
toward air and water.
Uses
Zirconium hydride is a powerful reducing agent in acid solution or at high temperatures; hydrogenation catalyst; in the vacuum tube industry.Also, it is used as a source of pure hydrogen and a catalyst in hydrogenation reactions. Some other applications are in powder metallurgy; as a moderator in nuclear reactors; and as a metal-foaming agent
Hazard
Flammable, dangerous fire risk, especially
in the presence of oxidizers.
Description
Zirconium(II) hydride, ZrH2, is a molecular chemical compound, which has been produced by laser ablation and isolated at low temperature. Zirconium(II) hydride has a dihedral (C2v) structure. In zirconium(II) hydride, the formal oxidation states of hydrogen and zirconium are 21 and 12, respectively, since the electronegativity of zirconium is lower than that of hydrogen. The stability of metal hydrides with the formula MH2 (M 5 Ti-Hf) decreases as the atomic number increases.
Physical properties
Grayish-black powder; density 5.60 g/cm3; stable in water; soluble in dilute hydrofluoric acid; soluble in concentrated acids.
Preparation
Zirconium hydride may be prepared by heating zirconium oxide with magnesium in the presence of hydrogen: ZrO2 + 2Mg + H2 → ZrH2 + 2MgO
Alternatively, hydride may be made by heating zirconium oxide with calcium hydride in the presence of hydrogen
Hydride also may be obtained by combining zirconium metal with hydrogen at elevated temperature.
Production Methods
Zirconium hydride in powder form was produced by the reduction of zirconium oxide with calcium hydride in a bomb reactor. However, the workup was hazardous and many fires and explosions occurred when the calcium oxide was dissolved with hydrochloric acid to recover the hydride powder. With the ready availability of zirconium metal via the Kroll process, zirconium hydride can be obtained by exothermic absorption of hydrogen by pure zirconium, usually highly porous sponge. The heat of formation is 167.4 J/mol (40 kcal/mol) hydrogen absorbed.
General Description
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Flammability and Explosibility
Flammable
