Glass-ceramic plate
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Solution Overview
Problem
Existing transparent, colorless, and non-diffusing glass-ceramics used in cooking devices and fireplace inserts face challenges with toxicity and cost issues due to the use of arsenic and antimony oxides, and neodymium oxide, which can cause yellow coloration and reduce light transmission.
Innovation Solution
A lithium aluminosilicate glass-ceramic plate with a specific chemical composition excluding arsenic and antimony oxides, containing SiO2, Al2O3, Li2O, Na2O+K2O, CaO, MgO, BaO, ZnO, TiO2, and ZrO2, optimized to achieve high light transmission, low thermal expansion, and minimal yellow coloration, using a ceramization process to form β-quartz crystals with controlled sizes for reduced light scattering.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If arsenic or antimony oxides are used as refining agents, then glass refining effectiveness is improved, but toxicity increases
Solution Approach 1:
The patent extracts and removes toxic arsenic and antimony oxides from the glass composition, replacing them with non-toxic alternatives. The claimed composition explicitly excludes these toxic refining agents while maintaining effective glass refinement through alternative mechanisms.
Solution Approach 2:
The patent employs tin oxide as a replaceable, non-toxic refining agent that can be effectively used and then removed or stabilized in the final glass-ceramic product, replacing persistent toxic substances with safer alternatives.
2Illumination intensity
If neodymium oxide is added to decolorize glass-ceramic, then yellow coloration is reduced, but light transmission decreases and cost increases
Solution Approach 1:
The patent removes neodymium oxide from the composition entirely, achieving decolorization through alternative means - specifically by controlling the oxidation states of transition metal impurities and using appropriate refining agents that prevent yellow coloration without sacrificing light transmission.
Solution Approach 2:
The patent changes the chemical parameters of the glass system by adjusting oxide ratios and controlling oxidation-reduction conditions during melting, which alters the color properties of trace impurities without requiring additional decolorizing agents that would reduce light transmission.
3Strength
If β-spodumene crystals are formed through high-temperature ceramicization, then light diffusion increases, but transparency is reduced
Solution Approach 1:
The patent creates local variations in crystal distribution and size within the glass-ceramic matrix, controlling that crystals are formed in specific patterns and size ranges that minimize light diffusion while maintaining thermal resistance properties in critical areas.
Solution Approach 2:
The patent changes the ceramicization temperature parameters and holding times to control crystal nucleation and growth, producing a crystal size distribution that optimizes the balance between thermal resistance and optical transparency rather than forming large diffusing crystals.
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
The solution provides a glass-ceramic with high light transmission (>75%), low thermal expansion, and minimal yellow coloration, ensuring excellent visibility and thermal resistance while avoiding toxic materials, thus meeting the requirements for applications like oven doors and fireplace inserts.
Implementation Method 1
These glass-ceramics are produced by a two-step process: in the first step, precursor glass plates are obtained, which then undergo a controlled crystallization treatment in the second step. This heat treatment, called 'ceramicization,' allows the growth of β-quartz or β-spodumene crystals (depending on the ceramization temperature) within the glass.
Implementation Method 2
These crystals generally have negative coefficients of thermal expansion, resulting in a final glass-ceramic with a very low coefficient of thermal expansion.
Implementation Method 3
tinted glass-ceramics typically contain β-quartz crystals, while diffusing glass-ceramics generally contain β-spodumene (or keatite) crystals, generated by a higher-temperature ceramicization process. Their larger diameter causes light diffusion.
Data Source
AI summary
The invention relates to a non-diffusing, colorless, transparent lithium aluminosilicate vitroceramic plate containing β-quartz crystals, the chemical composition of which does not contain arsenic, antimony, or neodymium oxides. Said vitroceramic plate also includes the following components within the defined limits, hereinafter expressed in wt%: 55-75% SiO2, particularly 60-70%; 12-25% A12O3, particularly 19-24%; 2-5% Li2O, particularly 3-4%; 0-<2% Na2O+ K2O, particularly 0-1%; 0-<7% Li2O+Na2O+K2O, particularly 0-5%; 0.3-5% CaO; 0-5% MgO, particularly 0-1%; 0-5% SrO, particularly 0-1%; 0.5-10% BaO, particularly 1-5%; >1% CaO+BaO, particularly 3-5%; 0-5% ZnO, particularly 1-2%; ≤1.9% TiO2; ≤3% ZrO2, particularly 2-3%; >3.80% TiO2+ZrO2; >0.1% SnO2; and <0.1 SnO2/(SnO2+ZrO2+TiO2), particularly <0.06.