Relations among particle size, shape, and surface area of Mg(OH) sub 2 and its calcination product

Precipitated Mg(OH) sub 2 particles 0.05-1 Micro m diam. of various shapes were calcined in air for 1/2 h at 704, 816, 954, 1093, or 1232 Degrees C. At 704 Degrees, BET surface areas, initially 11-32 m sup 2/g, increased 1.4-7.6-fold, and TEM observations showed pseudomorphs. Depending on the parent crystal size and shape, these particles contained either single layers or multilayers of MgO crystallites 40-260 Angstroms in diam., roughly perpendicular to the original c axis. Pseudomorph stability varied greatly, even between particles of different shape in the same sample. Coalescence into single or linked angular particles occurred at 1093 Degrees and 1232 Degrees, but one sample retained single-layer pseudomorphs containing cubic crystallites. One observation indicated that Na cation impurity decreased the surface area of oxide formed at 704 Degrees.