Glass Surface Prestress via Composition Gradient
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Solution Overview
Problem
Current methods for imparting compressive prestress to glass surfaces, such as chemical and thermal tempering, require additional process steps and significant chemical or engineering effort, and there is a need for a more efficient method to achieve compressive prestress in glass products like tubes and panes.
Innovation Solution
A production method that modifies the surface composition of glass articles by targeted removal of components, creating a surface layer with a lower coefficient of thermal expansion than the core, resulting in a compressive prestress at the surface through a quasi-inline process, where the surface glass is present down to a depth of less than 20 nm and the core glass is at least 500 nm deep, with specific constituent phases and compositions optimized for thermal expansion differences.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If chemical tempering is used to create compressive prestress at the glass surface, then the mechanical strength is improved, but additional process steps and chemical effort are required
Solution Approach 1:
The patent changes the chemical composition parameters of the glass surface by creating a specific concentration gradient of alkali metal oxides (Na2O, K2O) in the surface layer. This composition modification results in a lower coefficient of thermal expansion at the surface compared to the core, generating compressive prestress when the glass is cooled. This approach achieves strength improvement through parameter optimization rather than additional tempering processes.
Solution Approach 2:
The patent creates a composite glass structure with a surface layer having different chemical composition and properties than the core material. The surface layer contains specific concentrations of alkali metal oxides that create a gradient structure, forming a composite material system where the surface layer and core interact to produce compressive prestress, eliminating the need for separate chemical tempering steps.
2Strength
If thermal tempering is used to create compressive prestress at the glass surface, then the mechanical strength is improved, but additional process steps and engineering effort are required
Solution Approach 1:
The patent modifies the thermal expansion parameters by creating a composition gradient in the glass surface layer. The surface layer has a lower coefficient of thermal expansion than the core due to controlled concentrations of alkali metal oxides. This parameter difference generates compressive prestress during cooling without requiring the complex heating and rapid cooling cycles of traditional thermal tempering.
Solution Approach 2:
The patent performs preliminary composition modification during the glass manufacturing process itself, creating the desired concentration gradient of alkali metal oxides in the surface layer before the glass is fully formed and cooled. This preliminary action embeds the prestress-generating structure directly into the manufacturing process, eliminating the need for subsequent thermal tempering steps.
3Reliability
If a surface layer with modified composition is created to achieve compressive prestress, then the mechanical resistance is enhanced, but the manufacturing process becomes more complex
Solution Approach 1:
The patent achieves enhanced mechanical resistance by optimizing the concentration parameters of alkali metal oxides in the glass surface layer. By controlling the amounts of Na2O and K2O within specific ranges (0.1-10 mol% and 0.1-5 mol% respectively), the surface layer develops appropriate compressive prestress that improves reliability while maintaining manufacturing simplicity through direct composition control.
Solution Approach 2:
The patent applies local quality modification by creating a surface layer with specific compositional characteristics different from the core. The surface layer contains controlled concentrations of alkali metal oxides that provide localized compressive prestress, enhancing mechanical resistance at the surface where it is most needed, while the core maintains its original composition and properties.
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 method effectively imparts compressive prestress to glass surfaces, enhancing mechanical resistance and strength by creating a compressive stress zone at the surface, which can compress cracks, thereby increasing the durability of glass products without the need for additional process steps or high effort.
Implementation Method 1
the coefficient of thermal expansion at the surface and in the core is different
Data Source
AI summary
The invention relates to glass articles, such as for example glass tubes or flat glasses, where the material at the surface by a targeted process control has gradient material properties which in turn result in a compressive prestress of the surface. The invention also relates to a method for the production of the glass articles as well as their use.