Synthetic spinel-forsterite refractory aggregates from the sillimanite minerals

Applying the alumina-magnesia-silica equilibrium phase diagram as the fundamental basis, the three sillimanite minerals, kyanite, andalusite and sillimanite, were processed in the presence of magnesia to produce spinel-forsterite refractory aggregates. Both conventional ball milling and high-energy attrition milling were applied to reduce the particle size of the minerals and mix them. Ball milling achieved micrometer size particles, while the attrition milling reduced the particles to the nanometer scale. Firing in air between 1,200° and 1,700°C produced results that are a combination of the individual mineral decompositions and the spinel/forsterite formation. These effects were separated to address the reaction/densification processes and obtain dense spinel/forsterite refractory aggregates with fine microstructures.