Thermal Decomposition of Brucite: II, Kinetics of Decomposition in Vacuum

Polycrystalline samples, thin single crystals, and—325 mesh powders of brucite decomposed according to a first‐order rate equation consistent with a random nucleation process in beds of micron‐sized particles formed by disruption during the very early stages of the process and consistent with electron and optical microscope observations. Kinetic data for the decomposition of thick single crystals were more complex but could be fitted to an interface‐model equation which predicts that decomposition will be controlled by the movement of an interface reaction along the basal plane. Physical disruption of these crystals was confined initially to the outer edges of the crystals and proceeded along the basal plane in the form of a contracting disk. Since the decomposition occurs in cracked material and not at a strict interface, the fit of the data to the interface model may be fortuitous.