Loading patent…
AssigneeCorning Glass Works
InventorsAndre Andrieu, Marie J. M. Comte, Frederic J. M. Ferry, Jean-Pierre Mazeau
Estimating the term…
This invention relates to the preparation of glass-ceramic articles in which potassium fluorrichterite and/or a related fluormica constitutes the predominant crystal phase(s). The precursor glasses can be crystallized in situ very rapidly and exhibit very little thermal deformation during the crystallization heat treatment. The base glasses are essentially free of Li.sub.2 O and consist essentially, expressed in terms of weight percent on the oxide basis, of: ______________________________________ SiO.sub.2 61-70 Na.sub.2 O 0.5-3 BaO 0-3.5 Al.sub.2 O.sub.3 2.75-7 K.sub.2 O 2.5-5.5 P.sub.2 O.sub.5 0-2.5 MgO 11-16 Na.sub.2 O + K.sub.2 O <6.8 CaO 4.75-9 F 2-3.25 ______________________________________
A glass-ceramic article containing potassium fluorrichterite and/or a related fluormica as the predominant crystal phase(s) which, in the form of bars measuring 9 cm.times.1 cm.times.5 mm, will exhibit sagging during the crystallization heat treatment not greater than 0.75 mm over a span of 6.8 cm, and which displays such opacity that the diffuse transmittance of a sample of 2.75 mm thickness is in the 40-180 range, said glass-ceramic article having a composition essentially free of Li.sub.2 O and consisting essentially, as expressed in terms of weight percent on the oxide basis, of:
A thermally crystallized glass characterized in that it is capable of being crystallized in situ in a period of two hours to form a highly crystalline glass-ceramic article containing potassium fluorrichterite and/or a related fluormica as the predominant crystal phase(s) and which, in the form of bars measuring 9 cm.times.1 cm.times.5 mm, will exhibit sagging during the crystallization heat treatment not greater than 0.75 mm over a span of 6.8 cm, said glass-ceramic article having a composition essentially free of Li.sub.2 O and consisting essentially, as expressed in terms of weight percent on the oxide basis, of:
Dependencies are inferred from the claim text.