PROMOTION OF ZNAL2O4 FORMATION BY LIF .1. EFFECT OF ALUMINA AND COMPACTION PRESSURE ON ZINC ALUMINATE FORMATION IN THE PRESENCE OF LITHIUM-FLUORIDE

The formation of ZnAl//2O//4 in the presence of LiF was affected by the various states of Al//2O//3 and by the compaction pressure. The rate curves showed a typical sigmoid form and were analysed by the Hancock and Sharp method. The results indicated a main process controlled by nucleation which is followed by a diffusion-controlled process. The effects of the aggregation or agglomeration state of Al//2O//3 powder were examined with compaction pressures of up to 60 MPa. The amount of ZnAl//2O//4 decreased with an increase in the degree of agglomeration or aggregation when the firing temperature was around 600 degree C but no effect was observed at higher temperatures. Similar effects were also observed for the compaction pressures. These effects are the result of the degree of formation of a liquid intermediate phase.