ZIRCONIUM HYDRIDE

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.

Chemical Properties

Gray-black metallic powder. Stable toward air and water.

Physical properties

Grayish-black powder; density 5.60 g/cm³; stable in water; soluble in dilute hydrofluoric acid; soluble in concentrated acids.

Uses

Zirconium Hydride, ZrH2, is a brittle, metallicgray solid that is stable in air and water, and has a density of 5.6 g/cm3. The chemical properties of ZrH2 closely resemble those of titanium hydride. Commercial uses are as a getter in the manufacture of vacuum tubes and other systems; as a hydrogen source for foaming metals; as a hydrogen reservoir; for the introduction of zirconium into powdered alloys; for metal–ceramic and metal–metal bonding; as a moderator in nuclear reactors; and as a source of Zr metal powder and alloys.

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

Uses

Zirconium(II) hydride (ZrH₂) can be used as a precursor for:

• Reactive hot-pressing synthesis of Zr₂SC ceramics by displacement reaction with the mixture of ZrC and ZrS₂.,·
• The synthesis of Mg-Zr hydrides by treating with MgH₂ for hydrogen storage.
• The preparation of layer structured β-zirconium nitride chloride (ZrNCl) by reacting with NH₄Cl.

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.

Definition

Contains 1.7–2.1% combined hydrogen which can be driven off in a vacuum above 600C.

General Description

This product has been enhanced for energy efficiency.

Hazard

Flammable, dangerous fire risk, especially in the presence of oxidizers.

Flammability and Explosibility

Flammable

reaction suitability

core: zirconium
reagent type: catalyst
reaction type: Reductions
reagent type: reductant

Safety Profile

A powerful reducing agent. Flammable when dry or wet. Very dangerous to handle; can explode. Incandesces when heated in air. See also HYDRIDES and ZIRCONIUM COMPOUNDS.