No abstract

No abstract

Fhdeld‐assisted and ordinary diffusion ion exchange of K+, Rb+hd Cs+, and Ag+ from nitrate salts with Na+ in soda‐lime glass tubes were investigated between 700 and 735 K by application of various currents between 0 and 20.0 mA. An analysis of the field‐assisted process with both a forward and a reverse field allowed calculation of the conductivity of the exchanged layer from the change of potential difference with time. Good agreement with experiment was found in both directions but anomalously high conductivities were observed in the Rb and Cs layers. Photoelastic measurements on rings sliced from the ion‐exchanged tubes were used to calculate the residual stress arising from the ion exchange with the different cations. These results showed that other factors in addition to the ion size influence the magnitude of residual stress after exchange. The voltage‐current relation during field‐assisted ion exchange, along with the Nernst‐Einstein equation, permitted calculation of the self‐discussion coefficient of the exchanged cation in the exchanged layer. The self‐diffusion coefficient was also estimated by applying the Nernst‐Planck equation to results from unassisted ion‐exchange experiments.