Surface analysis of float glass using surface ablation cell (SAC)--Part 2. Determination of the diffusion characteristics of K~+-Na~+ ion exchange

摘要

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 of float glass samples were treated with two different salt mixtures, (I) 2:1 KNO_3:KCl, and (II) 1:2 KNO_3:KCI, (both by weight), and heated to different temperatures below T_g, 460-520°C. The diffusion coefficients calculated using a Green's function approach were in the ranges (I) 1.4×10~(-11) to 6.8 × 10~(-11) and (II) 1.8×10~(-11) to 6.0 ×10~(-11) cm~2/s while those calculated using Boltzmann-Matano were in the ranges (I) 5.7 ×10~(-12) to 1.4×10~(-11) and (II) 3.4 ×10~(-12) to 6.0 ×10~(-12) cm~2/s. Average values of the activation energies obtained through the Green's function were (I) 111.0 kJ/mol and (II) 99.8 kJ/mol for the different salt mixtures.