In Situ Observation of Nanocrystal Formation Via Dehydroxylation

Abstract

Recently, a promising new route to prepare nano phase composites with fine transition metal particles (2 - 50nm) has been proposed via dehydroxylation and dehydration process. Thermal and mechanical dehydroxylation process has also been used to form ultra fine powders of NiO-Ni(OH). We have found a substantially increased carbonation rate at room temperature (RT) for partially dehydroxylated brucite (Mg(OH)2) single crystal fragments. BET measurements confirm the increase in the surface area of partially dehydroxylated (90%) single-crystal Mg(OH)2 fragments, which directly contributes to the increase in carbonation reactivity. As dehydroxylation proceeds rapidly in a TEM column, due to high vacuum and electron beam effects, the atomic level nature of the process has not been understood until recently.6 We have observed the development of nanocrystals during in situdehydroxylation of Mg(OH)2.Experiments were performed using a PHILIPS-430 electron microscope operated at 300KV, fitted with a differentially pumped environmental-cell (E-cell) and a Gatan Imaging Filter (GIF).