Effects of key factors on the densification and grain growth behaviour of sintered magnesia from magnesite

Giving magnesia a denser microstructure is a goal relentlessly pursued by refractory scientists and related entrepreneurs. In this study, the effects of the key factors of ball milling, calcination temperature, and starting raw material (high-purity magnesite) size on the densification and grain growth behaviour of sintered magnesia were systematically investigated using a typical two-step sintering method. The results revealed that ball milling reduces the size of light-burned magnesia (pre-calcination product) to a certain extent, which is reflected in a higher tap density; moreover, both the density and grain size of the magnesia samples rise with increasing calcination temperature, implying that the activity of light-burned magnesia is not the only controlling factor for densification; in addition, the smaller magnesite particle size improves the density and grain size of the magnesia samples by weakening the negative effect of the pseudomorphic aggregates. More adequate ball milling, more moderate calcination temperature, and smaller size of magnesite (also for other magnesium salts), therefore, can be the preferred process for the two-step sintering preparation of sintered magnesia.