Formation of rare earth hydroxide nanotubes and whiskers as corrosion product of LaNi5-type alloys in aqueous KOH

Mm(OH)(3) (Mm = mischmetal) single crystalline needles with [001] growth ax is form upon exposure of MmNi(5)-substituted alloys to aqueous KOH. Crystal structure, chemical composition and morphology of the needles are studied by means of scanning electron microscopy and quantitative transmission elec tron microscopy. The needles can be either solid (whiskers) or hollow (nano tubes). Their morphology and growth kinetics are studied as a function of i mmersion temperature, stirring rate of the aqueous KOH electrolyte and pres ence of tracer. Based on the observations, a model mechanism is developed f or their growth.