Surface Analysis Of Float Glass Using Surface Ablation Cell (Sac). Part 2. Determination Of The Diffusion Characteristics Of K+-Na+Ion Exchange

The surface ablation cell (SAC), a laboratory equipment for determining surface concentration profiles, has been utilised to characterise surface ion exchange processes in float glass. In this paper, single side ion exchange is reported. Data on the ion concentration profiles were used to calculate diffusion coefficients as well as the activation energy for K+-Na+ion exchange. The air sides for float glass samples were treated with two different salt mixtures, (I) 2:1 KNO3:KCl, and (II) 1:2 KNO3:KCl, (both by weight), and heated to different temperatures below Tg, 460-520 degrees C. The diffusion coefficients calculated using a Greens function approach were in the ranges (I) 1.4x10-12 and (II) 1.8x10-12 cm2/s while those calculated using Bolzmann-Matano were in the ranges (I) 5.7 x 10-11 and (II) 3.4x10-12 to 6.0x10-12cm2/s. Average values of the activation obtained through the greens function were (I) 111.0 kJ/mol and (II) 99.8 kJ/mol for the different salt mixtures.