THE BREAK POINT IN THE PRESSURE DENSITY CURVE OF MAGNESIA PREPARED BY THE SEA-WATER MAGNESIA PROCESS

Uniaxial compacting behaviour of MgO powders calcined at a temperature between 900 and 1200-degrees-C in air was investigated; the break point which appeared in the pressure-density curve of MgO powder was effective in elucidating the agglomeration state in the powder. The packing density of MgO powder as a function of calcination temperature was measured before and after milling operations. The plots of relative density versus logarithmic pressure also exhibited a break point indicating the pressure at which the contact points in porous agglomerates began to be destroyed. The agglomerate strength of MgO powders calcined at low and high temperatures (900 and 1200-degrees-C) only were measured. The microstructural differences between agglomerates in MgO powder and the surface of a compressed powder (applied pressure 150 MPa) were examined by scanning electron microscopy.