Float-reaction between liquid bronze and magnesium aluminosilicate and ZnO-doped magnesium aluminosilicate glass-ceramic-forming glassmelts

Wavelength-dispersive X-ray spectroscopy (WDS) was used to characterize the morphology of the reactions between a liquid bronze alloy (Cu-36 at.%Sn) and two magnesium aluminosilicate, glass-ceramic-forming glassmelts, one of which was doped significantly with ZnO. Two suites of experiments were pursued for each glassmelt, an isochronal series (30-min reactions with temperatures ranging from ∼1300 to 1400 °C) and an isothermal series (1350 °C reactions with durations ranging from 5 to 60 min). The reactions are decidedly complex. Transient behavior sees initially rapid incorporation of Cu^+,2+ into the glassmelts, effected primarily by a redox couple involving the SiO₂ component of the aluminosilicate. This behavior gives way to a more dominant kinetic response in which Sn^2+,4+ is incorporated into the glassmelt in a reaction and chemical diffusion process that, in part, pulls the early-incorporated ionic copper back out of the aluminosilicate. In the case of the ZnO-doped glassmelt, coupled redox and interdiffusion of ionic Sn and ionic Zn is important in the longer-time response, giving rise to a Liesegang-band morphology. The extent of metal-silicate reaction diminishes as the temperature is increased, a thermodynamic effect related to the solution thermodynamics of the liquid bronze alloy. The reaction kinetics are interpreted following the Wagner-Schmalzried formalism for diffusion-effected redox reactions.