Compositions: ceramic – Ceramic compositions – Glass compositions – compositions containing glass other than...
Reexamination Certificate
1998-12-30
2001-02-20
Group, Karl (Department: 1755)
Compositions: ceramic
Ceramic compositions
Glass compositions, compositions containing glass other than...
C501S071000, C428S426000, C428S428000
Reexamination Certificate
active
06191059
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention is directed to performance modifiers for silicate based glass compositions, more particularly to metal silicides as performance modifiers for silicate based glass compositions, and even more particularly to metal silicides in silicate based glass compositions for the improvement of properties such as the absorption of infrared energy or the transmittance of color. The present invention is also directed to both a method of producing a glass composition and the finished glass composition resulting from the admixing, heating, and melting of a metal silicide in the batch glass composition.
2. Background of the Invention
Base glass compositions generally include one primary ion as a network former. A network former is the primary cation in the glass composition that bonds with oxygen to create an amorphous network. Other cations may also be present in the amorphous network. However, a primary cation is generally considered one which is present in an amount of about 25 weight percent or greater in the glass composition. Silicon is one cation which serves as a network former to provide silicate based glasses. The silicon is generally added to a batch glass composition as silica (SiO
2
).
Performance modifiers are often added to a base glass composition to impart specific color and energy absorbance properties in the finished glass. The absorption of energy at specific wavelengths is often desirable to enable various uses for the glass compositions. Additionally, certain colors are preferred for various glasses for aesthetic reasons.
There are limitations within specific glasses that must be balanced or optimized when attempting to achieve desired color and energy transmittance properties. For example, certain ingredients may improve the absorption of near infrared energy while imparting an undesirable color or reducing the light transmittance. Thus, the optimization of a specific color or energy transmittance property often negatively impacts other desirable transmittance properties.
The glass industry is continuously seeking ways to improve solar attenuation properties in glass and thereby to improve the efficiency, and expand the use, of the resulting glass articles. Infrared absorbing, or heat reducing, silicate glasses are recognized within the art. In general, infrared absorbing silicate glasses involve the addition of specific colorants that impact the color and energy transmittance properties of the glass.
One method generally recognized for manufacturing heat or infrared radiation absorbing silicate glass is through the incorporation therein of iron. The iron is generally present in the glass as both ferrous oxide (FeO) and ferric oxide (Fe
2
O
3
). The balance between ferrous and ferric oxide has a direct and material effect on the color and transmittance properties of the glass. As the ferrous oxide content is increased (as a result of chemically reducing ferric oxide), the infrared absorption increases and the ultraviolet absorption decreases. The shift toward a higher concentration of FeO in relation to the Fe
2
O
3
causes a change in the color of the glass from a yellow-green to a blue-green, which reduces the visible transmittance of the glass.
Thus, it is desirable in the glass industry to provide additional performance modifiers that provide a high degree of selectivity between the visible region and the infrared region of the spectrum. Selectivity is generally referred to as the difference between the transmittance of visible light and the attenuation of infrared energy. Additionally, it is important to balance a high degree of selectivity in the finished glass composition with a desired color.
SUMMARY OF THE INVENTION
According to the present invention, there is provided a metal silicide compound suitable for use in a silicate batch glass composition as a performance modifier to impart desirable color or improve energy absorbance properties over conventional silicate glasses.
The metal silicide compound is added to the batch glass composition prior to melting. The present invention also includes a process for melting the glass batch composition and the articles produced therefrom. The utilization of a metal silicide results in the unexpected improvement of color or energy absorbance properties when added to conventional silicate based glass compositions.
The glasses produced in accordance with the present invention may have various different colors and optical properties. The metal silicide is utilized to produce glasses with a visible light transmittance (IllA) of 10% or greater, depending upon additional colorants utilized in the glass batch composition. Additionally, specific applications may require the use of the metal silicide in glasses needing a high degree of selectivity. For example, the performance modifiers of the present invention enable the production of a silicate glass composition having a visible light transmittance in excess of 70% with a high degree of absorption of near infrared energy.
The preferred metal silicides suitable for use in the present invention are selected from the group consisting of lithium silicide, sodium silicide, potassium silicide, rubidium silicide, cesium silicide, lanthanum silicide, magnesium silicide, calcium silicide, strontium silicide, barium silicide, cerium silicide, thorium silicide, scandium silicide, yttrium silicide, titanium silicide, vanadium silicide, chromium silicide, manganese silicide, iron silicide, cobalt silicide, nickel silicide, copper silicide, zirconium silicide, niobium silicide, molybdenum silicide, ruthenium silicide, rhodium silicide, palladium silicide, hafnium silicide, tantalum silicide, tungsten silicide, rhenium silicide, osmium silicide, iridium silicide, platinum silicide, praseodymium silicide, neodymium silicide, samarium silicide, europium silicide, gadolinium silicide, terbium silicide, dysprosium silicide, holmium silicide, erbium silicide, thulium silicide, ytterbium silicide, lutetium silicide, uranium silicide, neptunium silicide, plutonium silicide, and combinations thereof.
Each of the metal suicides may impart different characteristics to the finished silicate glass. Therefore, the selection of the metal silicide is dependent upon the desired color and energy absorbance properties of the finished glass as well as the base glass composition and other colorants included in the base glass composition. Additionally, several of the noted performance modifiers may be utilized in combination in the glass batch composition.
In accordance with the present invention, the most preferred silicides include iron silicide, titanium silicide, and molybdenum silicide. A finished silicate glass containing iron, and produced with the preferred silicide compounds, can exhibit improved absorption of near infrared energy over iron containing glasses without the noted metal silicides.
It would be an advantage to provide a performance modifier for use in silicate batch glass compositions that significantly improves either the color or energy absorbance properties of the finished glass composition. The metal silicide of the present invention is a suitable performance modifier that is capable if improving the energy absorbance of the glass over conventional silicate glasses. Additionally, the metal silicide of the present invention is capable of achieving a high degree of selectivity.
It would be an additional advantage to provide a performance modifier that is suitable for use in batch glass compositions in a float glass production process.
DETAILED DESCRIPTION
In accordance with the present invention, it has been discovered that a metal silicide compound may be included in a silicate based batch glass composition as a performance modifier to improve color or energy absorbance properties of the finished glass. The metal silicide compound is added to conventional silicate glass compositions. It is desirable to improve solar attenuation properties in glass to improve the efficiency and expand the use of the resulting glass art
Group Karl
Libbey-Owens-Ford Co.
Marshall & Melhorn
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