Abstract
Antioxidation mechanism of a newly developed oxidation inhibitor composed of a refractory powder-SiO2-aluminum-synthetic mica-colloidal silica-coking bond has been investigated.
During heating, the metallic silicon is formed after the reduction by the metallic aluminum of both mullite (3Al2O3·2SiO2) containing in refractory powder and SiO2. This is oxidized again so as to change gradually to protective amorphous SiO2 layer which acts as an excellent diffusion barrier to oxigen from atmosphere. Aluminum, in turn, is oxidized to form the protective films composed of α-Al2O3 and FeO·Al2O3. In addition, a spinel (FeO·Al2O3) prevents effectively the formation of low melting fayalite (2FeO·SiO2), and consequently the protective films remain stable even after prolonged heating at high temperatures.
On the other hand, a lot of pores are formed by the volume reduction due to the melting of aluminum, the oxidation of aluminum and the reduction of SiO2, by which the diffusion of Fe2+ and O2- is effectively inhibited.
