Lithium containing glass with high oxidized iron content and specified redox ratio
A low infrared absorbing lithium glass includes FeO in the range of 0.0005-0.015 wt %, more preferably 0.001-0.010 wt %, and a redox ratio in the range of 0.005-0.15, more preferably in the range of 0.005-010. The glass can be chemically tempered and used to provide a ballistic viewing cover for night vision goggles or scope. A method is provided to change a glass making process from making a high infrared absorbing lithium glass having FeO in the range of 0.02 to 0.04 wt % and a redox ratio in the range of 0.2 to 0.4 to the low infrared absorbing lithium glass by adding additional oxidizers to the batch materials. A second method is provided to change a glass making process from making a low infrared absorbing lithium glass to the high infrared absorbing lithium glass by adding additional reducers to the batch material. In one embodiment of the invention the oxidizer is CeO 2 . An embodiment of the invention covers a glass made according to the method.
1. A low infrared absorbing (LIRA) glass composition comprising:
Component
Range
SiO 2
60-63
wt %
Na 2 O
10-12
wt %
Li 2 O
4-5.5
wt %
Al 2 O 3
17-19
wt %
ZrO 2
2-5
wt %
(Al 2 O 3 + ZrO 2 )
21.5-24
wt %
FeO
0.0005-0.015
wt %
Fe 2 O 3 (total iron)
50-1200
ppm;
an oxidizer selected from the group of cerium oxide in the range of greater than 0 to 0.50 wt % and/or manganese oxide in the range of greater than 0 to 0.75 wt %;
less than 5 wt % of additional glass forming materials and glass modifiers or colorants, selected from the group of MgO, CaO, MnO, TiO 2 , Sb 2 O 3 , As 2 O 3 , K 2 O, PbO, SO 3 , colorants and mixtures thereof; and
a redox ratio in the range of 0.005-0.15, wherein glass formed from the glass composition and having a thickness of 0.223 inch (5.7 millimeters) has:
a visible transmission over a wavelength range of 380 to 780 nm of equal to or greater than 88%;
an infrared transmission over a wavelength range of 800 to 2100 nm of equal to or greater than 80%; and
an infrared viewing transmission over the wavelength range of 400 to 920 nm of equal to or greater than 80%.
2. The glass composition according to claim 1 , wherein the glass composition comprises cerium oxide in the range of 0.02 to 0.45 wt %.
3. The glass composition according to claim 1 , comprising FeO in the range of 0.001-0.010 wt %.
4. The glass composition according to claim 1 , wherein the redox ratio is in the range of 0.005-0.10.
5. An aircraft windshield formed from the glass composition according to claim 1 .
6. A device for viewing radiated infrared energy, the device comprising:
a housing having at least one passageway, the passageway having a first open end and a second open end,
a lens system for viewing radiated infrared energy,
a chemically tempered ballistic glass lens mounted adjacent to one end of the passageway, the ballistic glass lens comprising a first surface, an opposite second surface and a glass segment between the first and the second surfaces of the ballistic glass lens, and
the glass segment formed from the glass composition according to claim 1 .
7. A viewing window for infrared equipment comprising glass formed from the glass composition according to claim 1 .
8. The viewing window of claim 7 , wherein the infrared equipment comprises infrared night goggles and/or scopes.