Salt bath compositions for strengthening glass articles, methods for using the salt bath compositions to strengthen glass articles, and glass articles strengthened thereby
The methods generally include contacting an alkali-containing glass article having a first alkali metal cation with a molten salt bath including from 0.1 wt. % to 3 wt. % nanoparticles and at least one alkali metal salt having a second alkali metal cation that has an atomic radius larger than an atomic radius of the first alkali metal cation. The nanoparticles may include at least one of metalloid oxide nanoparticles and metal oxide nanoparticles. The methods also include maintaining contact of the glass article with the molten salt bath to allow the first alkali metal cations to be exchanged with the second alkali metal cations of the molten salt bath. Further, the methods may include removing the glass article from contact with the molten salt bath to produce a strengthened glass article. A Surface Hydrolytic Resistance titration volume of the strengthened glass article may be less than 1.5 mL.
1. A method of strengthening an alkali-containing glass article comprising a first alkali metal cation, the method comprising:
contacting at least a portion of the glass article with a molten salt bath comprising from 0.1 wt. % to 3 wt. % of nanoparticles, the nanoparticles comprising at least one of metalloid oxide nanoparticles and metal oxide nanoparticles, and at least one alkali metal salt comprising a second alkali metal cation, wherein an atomic radius of the second alkali metal cation is larger than an atomic radius of the first alkali metal cation;
maintaining contact of the at least a portion of the glass article with the molten salt bath to allow the first alkali metal cations in the glass article to be exchanged with the second alkali metal cations of the molten salt bath; and
removing the at least a portion of the glass article from contact with the molten salt bath to produce a strengthened glass article, wherein a Surface Hydrolytic Resistance titration volume of the strengthened glass article is less than 1.5 mL,
wherein the molten salt bath comprises a combination of NaNO 3 and KNO 3 , and
wherein the nanoparticles comprise a combination of SiO 2 , Al 2 O 3 , and at least one of TiO 2 and BeO.
2. The method of claim 1 , wherein the metal oxide nanoparticles have an average surface area of from 300 m 2 /g to 600 m 2 /g.
3. The method of claim 1 , wherein the nanoparticles have an average particle size of from 1 nm to 25 nm.
4. The method of claim 1 , wherein a pH of the molten salt bath is from 6 to 8.
5. The method of claim 1 , wherein the glass article is at least one of a glass pharmaceutical package and a glass vial.
6. The method of claim 1 , wherein a temperature of the salt bath is from 350° C. to 500° C.
7. The method of claim 1 , further comprising washing the strengthened glass article to remove at least a portion of the metal oxide nanoparticles.