Refractory object, glass overflow forming block, and process for glass object manufacture
A refractory object can include at least 10 wt % Al 2 O 3 . In an embodiment, the refractory object can further include a dopant including an oxide of a rare earth element, Ta, Nb, Hf, or any combination thereof. In another embodiment, the refractory object may have a property such that the averaged grain size does not increase more than 500% during sintering, an aspect ratio less than approximately 4.0, a creep rate less than approximately 1.0×10 −5 μm/(μm×hr), or any combination thereof. In a particular embodiment, the refractory object can be in the form of a refractory block or a glass overflow forming block. The glass overflow forming block can be useful in forming an Al—Si—Mg glass sheet. In a particular embodiment, a layer including Mg—Al oxide can initially form along exposed surfaces of the glass overflow forming block when forming the Al—Si—Mg glass sheet.
1. A refractory object used in forming a glass object, wherein the refractory object comprises:
at least 97 wt % Al 2 O 3 ;
at least 0.5 wt % and not greater than 3 wt % of a first dopant including Ta 2 O 5 ;
a second dopant including Zr, Hf, Y, Sc, Yb, Pr, Sm, Gd, La, Ce, Dy, or any combination thereof; and
not greater than 0.5 wt. % TiO 2 .
2. The refractory object according to claim 1 , wherein the amount of the first dopant is sufficient to keep an averaged grain size from increasing more than approximately 300% during a sintering operation.
3. The refractory object according to claim 1 , wherein the refractory object includes grains in a size distribution having a plurality of modes, wherein a first mode includes a first set of grains having a first averaged grain size of at least approximately 0.5 μm.
4. The refractory object according to claim 3 , wherein the size distribution has a second mode including a second set of grains having a second averaged grain size no greater than approximately 20 μm.
5. The refractory object according to claim 1 , wherein a creep rate of the refractory object is no greater than approximately 1.0×10 −5 μm/(μm×hr) as measured at a pressure of 2 MPa and a temperature of 1275° C.
6. A refractory object used in forming a glass object, the refractory object comprises:
at least 93% by weight Al 2 O 3 ;
at least 0.5% by weight and not greater than 5% by weight of Ta 2 O 5 ;
a second dopant including Zr, Hf, Y, Sc, Yb, Pr, Sm, Gd, La, Ce, Dy, or any combination thereof; and
not greater than 0.5 wt. % TiO 2 ;
wherein the refractory object has a property including:
a percentage of grains of the refractory object having an aspect ratio of at least 2.0 is no greater than approximately 30%; and
a percentage area occupied by the grains having an aspect ratio of at least 2.0 is no greater than approximately 30%.
7. The refractory object according to claim 6 , wherein:
a D10 value of the aspect ratio is no greater than approximately 1.2;
a D50 value of the aspect ratio is no greater than approximately 1.6;
a D90 value of the aspect ratio is no greater than approximately 2.7; or
any combination thereof.
8. The refractory object according to claim 6 , wherein:
a D10 value of a size of the grains is no greater than approximately 40 μm;
a D50 value of a size of the grains is no greater than approximately 60 μm;
a D90 value of a size of the grains is no greater than approximately 90 μm;
or any combination thereof.
9. The refractory object according to claim 6 , wherein the refractory object has a porosity of at least approximately 0.1 vol % and no greater than approximately 5.0 vol %.