Additive effect in salt bath for glass strengthening

Abstract

We introduce the additives effect in the molten salts such as commercially pure KNO₃ and polluted KNO₃. The results showed that in case of the commercial purity KNO₃, only KOH improved the compressive stress (CS) of ion-exchanged glasses up to ∼50 MPa, and the others additives did not make the CS improvement. Rather than the CS was diminished by additive contamination. In case of the contaminated KNO₃, the additives K₃PO₄, K₂CO₃, and K₂SO₄ successfully removed the impurities, Na⁺, Ca²⁺, Mg²⁺, by precipitating chemical compounds in molten bath and recovered the CS up to ∼97 %. X-ray diffraction (XRD) results proved how the harmful ions in molten salt was removed by adding additives.