Field-Assisted Ion Exchange of Borosilicate Glass
Due to the relatively low failure strength of untreated glass, surface flaws generated during processing or through handling can limit the useful lifetimes of glass-based components, such as display panels for cellular phones, windows, and transparent armor. Field-assisted ion exchange (FAIE) is a glass strengthening technique being studied to overcome the inherently poor tensile properties of glass and to better control fracture properties. During FAIE, smaller ions in the glass (Na+) exchange positions with larger ions (K+) from a molten bath of potassium nitrate. The ion exchange process creates compressive stresses at the glass surface, thereby increasing the strength of the glass. The relationship between FAIE parameters – time (10-90 min), temperature (370-420 °C), and applied voltage (40-500 VDC) – on the strength of borosilicate glass tubes is under investigation. Four-point bend tests and nanoindentation will be performed to quantify the fracture strength, hardness, and elastic modulus of the ion exchanged glass. The results are expected to show that the fracture strength of common glass materials can be significantly enhanced and controlled through FAIE.