PHOTOLYTIC DECOMPOSITION OF LITHIUM ALUMINUM-HYDRIDE POWDER

The ultraviolet photolysis of powdered LiAlH4 has been investigated at room temperature by using pristine material and material subjected to 60Co γ-ray irradiation. In all samples, similar shaped pressure vs. time curves are obtained that comprise an initial deceleratory period followed by a constant rate of hydrogen gas evolution. The data curves can be resolved into one saturating-exponential component and one linear component. The final (linear) stage approximates a second-order dependence on light intensity. This dependence indicates that two excited sites are required to produce a decomposition center. For a 1.0 × 106 rd γ-ray dose the irradiation increases the deviation from almost second-order dependence. This is consistent with a previously developed phenomenological theory. In addition, low γ-ray doses (below 7.0 × 103 rd) produce a decrease in the magnitude of the exponential component, a decrease in time required to reach the final stage and the steady state rate. In the γ-ray dose range from 7.0 × 103 to 1.0 × 107 rd the effect is reversed. These results are interpreted to be produced by an increase in the concentration of radiolysis product with increasing dose. © 1979 American Chemical Society.