Float reaction between sodium aluminoborosilicate glassmelts and copper-base liquid metal alloys

Wavelength-dispersive X-ray spectroscopy (WDS) has been utilized in a study of redox chemical diffusion dynamics in reaction couples of two sodium aluminoborosilicate glassmelts – both lightly doped with Fe3+ – with two copper-base liquid metal alloys: Cu–37 at.%Ge and Cu–36 at.%Sn. The glassmelts were floated on the alloys for 30 min in a controlled, reducing atmosphere at temperatures in the range 1200–1350 °C. Despite there being a significant driving potential to incorporate Cu+,2+ into the glassmelt, such does not occur: ionic Cu concentration in the glassmelts was below the detection limits of WDS (i.e., XCu < 100 ppm atomic). As a generalization, the Ge2+,4+ and Sn2+,4+ diffused into the glassmelt to a depth of ∼50 μm, a distance similar to that seen for ionic Sn in the soda-lime silicate on pure Sn float process that is operated at notably lower temperatures and for dramatically shorter reaction times. For reactions with Cu–37 at.%Ge, doping the glass with ferric iron had a profound effect on the depth of penetration of ionic Ge, decreasing it significantly: Fe3+ acts as an electron acceptor from Ge2+; the resultant tetravalent cation (Ge4+, a network former) is all-but immobile. A similar result was not seen for reactions with the Cu–Sn alloy, a consequence of considerable reduction of the glassmelt by its pre-reaction with molybdenum components of a delivery system. The reaction morphologies seen are consistent with the Wagner/Schmalzried formulation for dynamic redox reactions.