Abstract:
Investigations into both 1-step and 2-step ion exchange strengthening techniques in mixed alkali glasses were examined. A "high" temperature 1-step exchange (Li+→Na+), which was conducted above the glass transition temperature to strengthen the rods by way of mismatch thermal expansion coefficients. Further a 2-step exchange was conducted by taking previously exchanged (Li+→Na+) rods and "stuffing" them below the glass transition temperature (Na+→Li+ and K+→Li+), resulting in a compressive layer in the surface of the glass structure. The effects of ion exchanges were examined by WDS, mass change analysis, and strength data. The effect of a mixed alkali glass being exchanged with multiple exchange mediums and treatments were examined and explained through this data. Strength increases of 85% were reported for 1-step exchanges with Li+, 100% for 2-step exchange with Na+, and 160% for 2-step exchanges with K+. Diffusion coefficients between multiple ion pairs were also calculated where possible. Also, some strange phenomena explained by the mixed alkali effect were observed for both the high temperature exchange and the low temperature exchanges.
Description:
Thesis completed in partial fulfillment of the requirements for the degree of Master of Science in Materials Science at the Inamori School of Engineering, New York State College of Ceramics at Alfred University
