MECHANISMS OF LIGHT-METAL HYDRIDE REACTIONS.

A study was made of the pyrolysis of beryllium hydride from 200 to 250 C and of the ignition and burning of the hydride at higher temperatures. At low temperatures the reaction was studied by following the rate of hydrogen evolution. The reaction is autocatalytic, involving the formation of beryllium nuclei and their subsequent growth by reaction at the Be-BeH2 interface. The activation energy for the interface reaction was approcimately 25 kcalmole. The sum of the number of dimensions in which the nuclei propagate and the number of steps involved in the nucleation process, lambda beta, was found to be at least seven. The effects of additives and treatments were investigated. Lithium-doped beryllium hydride decomposition was fitted with an average activation energy of 36.5 kca.mole and a value of about three for lambda beta. Beryllium hydride ignition and burning were studied in the arc-imaging furnace with the aid of high-speed color motion pictures, narrow band light filters, chemical analysis of the products, a pressure transducer, phototubes, and a photodiode. The ignition of beryllium hydrode in oxygen involved two gross steps, the pyrolysis of the hydride with the formation of H2O and the ignition of the beryllium residue.