Interaction of periclase with spinellides saturated with iron oxide

Conclusions

The redistribution of iron oxides between the spinellide and periclase portions at temperatures up to 1200°C depends on the partial decay of the Mg(Al_1−XCr_X)₂O₄+ 30% Fe₂O₃ solid solution.

The transfer of the iron oxides to the periclase at high temperatures depends chiefly on the degree of reduction of Fe³⁺ to Fe²⁺. This process leads to the formation of magnesiowustite and magnomagnetite, which enter the periclase. During this, the magnomagnetite yield decreases in the sequence MgAl₂O₄→ MgCr₂O₄. The transfer of the iron oxides from the spinellide (particularly from the compositions MgCr₂O₄+30% Fe₂O₃ and MgAlCrO₄+30% Fe₂O₃) to the periclase is chiefly associated with the dissolution of the same spinellide in the periclase.

A combination of phase conversions, decay of the Mg(Al_1−XCr_X)₂O₄ +30%Fe₂O₃ solid solution, and transfer of the iron oxides from the spinel portion to the periclase and back, determines the properties of the anneal products. The best properties are exhibited by compositions in which the spinellide portion consists of a solid solution of magnesio-alumina spinels and iron oxides, as opposed to solid solutions of magnesio-chromite and iron oxides.

An increase in periclase content in all cases promotes an improvement in the properties of the anneal products. The advantage of the compositions with a predominating magnesio-alumina spinel phase is preserved.