KINETICS OF IRON - SODIUM DISILICATE REACTIONS AND WETTING

Thermogravimetric and sessile drop measurements were used to study kinetics of redox reactions between sodium disilicate glass and iron. Two redox reaction sequences were identified; both introduced ferrous oxide into the glass at the interface. One consists of formation of ferrous oxide at the interface by reduction of sodium ions in the glass; this is primarily dependent on the a(FeO) in the metal being less than one. The second consists of oxidation of ferrous ions in the glass by the reduction of sodium ions to form ferric ions which subsequently react with the iron to form ferrous oxide. The reaction rates were shown to be sensitive to temperature, time, total ambient pressure, partial pressure of sodium and oxygen in the atmosphere, and the a(FeO) in the iron. Decrease of contact angles and spreading occur with the redox reaction in which the metal plays an active role, i.e. whose a(FeO) is less than one and whose composition undergoes a change