Lithium Glass Redox Control for Infrared Transmission
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Solution Overview
Problem
The challenge lies in efficiently transitioning between producing high infrared absorbing (HIRA) and low infrared absorbing (LIRA) lithium aluminosilicate glasses, as existing methods result in significant waste and increased costs due to the discarding of glass sheets that are out of specifications during campaign changes.
Innovation Solution
The use of cerium oxide and manganese oxide as oxidizers to control the redox ratio, allowing for the rapid conversion of ferrous iron to ferric iron within the glass composition, enabling the production of HIRA or LIRA glasses without the need for extensive batch ingredient changes, thereby minimizing waste and reducing production time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If batch ingredients are changed extensively to transition between HIRA and LIRA glass production, then glass composition specifications are met, but production time increases and waste increases
Solution Approach 1:
The patent applies parameter changes by adjusting the redox ratio (FeO/Fe2O3) through controlled oxidation rather than changing batch ingredients. By adding oxidizers like manganese dioxide or cerium oxide to the existing glass batch, the iron content transitions from ferrous (FeO) to ferric (Fe2O3) state, enabling conversion between HIRA and LIRA glass types without extensive batch reformulation. This maintains manufacturing precision while significantly reducing transition time and waste.
2Manufacturing precision
If batch ingredients are changed extensively to transition between HIRA and LIRA glass production, then glass composition specifications are met, but material waste increases
Solution Approach 1:
The patent changes the chemical state parameter of iron (from FeO to Fe2O3) through oxidation rather than discarding and replacing batch ingredients. This allows the same glass batch to be reused for producing different glass types (HIRA or LIRA) by simply adjusting the oxidation level, thereby eliminating material waste while maintaining composition specifications.
Solution Approach 2:
The patent converts the potentially harmful effect of excess ferrous iron (which causes infrared absorption) into a beneficial feature by controlling its oxidation state. Through adding oxidizers, the ferrous iron is converted to ferric iron, transforming a defect into a controllable property that enables production of LIRA glass without wasting materials.
3Manufacturing precision
If ferrous iron is not converted to ferric iron rapidly, then redox ratio control is achieved, but production efficiency decreases
Solution Approach 1:
The patent employs strong oxidants such as manganese dioxide (MnO2) or cerium oxide (CeO2) to rapidly convert ferrous iron to ferric iron during glass melting. These oxidizers accelerate the oxidation reaction, achieving precise redox ratio control within the normal production cycle, thereby maintaining both manufacturing precision and high productivity without extending production time.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach allows for a swift and cost-effective transition between HIRA and LIRA glass production, reducing waste and optimizing glass properties for infrared transmission and absorption, while maintaining acceptable liquidus temperatures for float glass processes.
Implementation Method 1
The use of cerium oxide and manganese oxide as oxidizers to control the redox ratio, allowing for the rapid conversion of ferrous iron to ferric iron within the glass composition
Implementation Method 2
ferrous oxide, FeO, is a strong infrared radiation absorber and operates as a blue colorant in the glass
Implementation Method 3
The ferric oxide, Fe2O3, is a strong ultraviolet radiation absorber and operates as a yellow colorant in the glass
Data Source
AI summary
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 0.005-0.10. 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 CeO2. An embodiment of the invention covers a glass made according to the method.