Uranium(III) hydride
Uranium(III) hydride, with the formula UH3, is a binary inorganic chemical compound consisting of uranium and hydrogen. It is a black, pyrophoric powder, meaning it can spontaneously ignite in air. This material is a metallic, albeit brittle, compound exhibiting ferromagnetism below approximately 180 K.
UH3 exists in two allotropic forms, designated α-UH3 and β-UH3. The α-form possesses a body-centered cubic structure (space group Pm3m), while the β-form has a cubic structure with a higher symmetry (space group Fm3m). The two forms are thought to be related to different particle sizes of the uranium used in its synthesis.
The most common method of preparation involves the direct reaction of finely divided uranium metal with hydrogen gas at elevated temperatures (typically around 200-300 °C). The reaction is reversible, and heating UH3 under vacuum will decompose it back into uranium metal and hydrogen gas. This property is utilized for the purification of uranium.
Uranium(III) hydride is primarily used as a starting material in the synthesis of other uranium compounds. It reacts with various elements and compounds, allowing for the controlled introduction of uranium into complex molecules. It is also used in the preparation of finely divided uranium metal, useful in catalysis and other applications. Due to its pyrophoric nature, it requires careful handling and storage under an inert atmosphere to prevent spontaneous combustion.