Coatings for glass-shaping molds and molds comprising the same
Described are glass-forming molds made of a graphite mold body and a coating formed by atomic layer deposition, with the coating being made of alumina or a combination of alumina and yttria.
1. A glass-forming mold comprising:
a fine-grained graphite mold body having one or more mold features, wherein the fine-grained graphite has a grain size that is not greater than 10 microns; and
a coating on the one or more mold features, the coating consisting essentially of alternating layers of alumina and yttria.
2. The glass-forming mold of claim 1 , wherein the coating has a coefficient of thermal expansion that is within 1 part per million/° C. of the coefficient of thermal expansion of the fine-grained graphite mold body.
3. The glass-forming mold of claim 1 , wherein a thickness of the coating is between 10 nanometers and 500,000 nanometers.
4. The glass-forming mold of claim 1 , wherein the glass-forming mold is free of surface discontinuities that are greater than about 25 microns from the average surface plane of the glass-forming mold.
5. A method of making a glass-forming mold comprising:
providing a fine-grained graphite mold body, wherein the fine-grained graphite has a grain size that is not greater than 10 microns; and
depositing a coating on the fine-grained graphite mold body by atomic layer deposition, the coating consisting essentially of alternating layers of alumina and yttria.
6. The method of claim 5 , wherein the coating has a coefficient of thermal expansion that is within 1 part per million/° C. of the coefficient of thermal expansion of the fine-grained graphite mold body.
7. The method of claim 5 , wherein a thickness of the coating is between 10 nanometers and 500,000 nanometers.
8. The method of claim 5 , wherein the glass-forming mold is free of surface discontinuities that are greater than about 25 microns from the average surface plane of the glass-forming mold.
9. A method of forming a glass article comprising:
providing a fine-grained graphite mold body, wherein the fine-grained graphite has a grain size that is not greater than 10 microns;
depositing a coating on the fine-grained graphite mold body by atomic layer deposition, the coating consisting essentially of alternating layers of alumina and yttria; and
contacting a surface of the fine-grained graphite mold body with softened glass.
10. The method of claim 9 , wherein the softened glass is softened alumino-silicate glass.