Relations Among Particle Size, Shape, and Surface Area of Mg(OH)2 and Its Calcination Product |
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| Authors: | V A PHILLIPS H OPPERHAUSER J L KOLBE |
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| Affiliation: | Martin Marietta Laboratories, 1450 South Rolling Road, Baltimore, Maryland 21227 |
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| Abstract: | Precipitated Mg(OH)2 particles 0.05 to 1 μm in diam. and of various shapes were calcined in air for 1/2 h at 704°, 816°, 954°, 1093°, or 1232°C. At 704°C, BET surface areas, initially 11 to 32 m2/g, increased 1.4- to 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 to 260 Å 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° and 1232°C, but one sample retained single-layer pseudomorphs containing cubic crystallites. One observation indicated that sodium cation impurity decreased the surface area of oxide formed at 704°C. |
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