A preliminary diffraction study of electron-beam induced decomposition in α-AlH3

α-AlH3 can be decomposed thermally and by exposure to ionizing radiations. The initial stages of the reaction are postulated to occur in the sequence: an initial rapid nucleation which produces colloidal aluminium metal followed by the growth of these colloidal-sized particles to form acicular nuclei. The nuclei cluster in randomly dispersed areas of the subsurface. Attempts to observe lattice parameter changes in these small crystallites using X-ray diffraction measurements were ruled out because the crystals were too small. However, recent careful experimentation has shown that electron-beam diffraction measurements can be carried out in situ at room temperature. The process is of sufficient duration that the entire decomposition sequence of pre-selected areas can be monitored in both the image contrast and the diffraction mode. Preliminary results are reported in this communication. (author)