Glass-Ceramic Seal Composition for CTE-Matched SOC Sealing
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Solution Overview
Problem
Existing glass-ceramic sealants for solid oxide cells (SOC) face challenges such as the formation of undesirable crystalline phases with coefficients of thermal expansion (CTE) significantly different from other SOC components, high porosity, chemical reactivity, and thermal instability at high temperatures.
Innovation Solution
A glass-ceramic sealing composition with a specific formulation of SiO2 (40-60 mol%), B2O3 (3-12 mol%), SrO (30-50 mol%), CaO (1-12 mol%), MgO (0-5 mol%), and Al2O3 (1-6 mol%), which forms SrSiO3 and/or Sr2SiO4 as main crystalline phases, minimizing the formation of low-CTE phases and ensuring thermal and chemical stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional glass-ceramic compositions are used as sealants, then electrical insulation and gas tightness are provided, but formation of undesirable crystalline phases with incompatible CTE occurs
Solution Approach 1:
The patent modifies the chemical composition parameters of the glass-ceramic sealant by incorporating specific amounts of SrO (10-30 wt%), CaO (5-20 wt%), MgO (2-10 wt%), and controlling SiO2 (20-40 wt%), B2O3 (5-15 wt%), and Al2O3 (5-15 wt%). These parameter changes are designed to control crystallization behavior and achieve desired CTE matching with SOC components while maintaining electrical insulation and gas tightness properties.
Solution Approach 2:
The patent creates a composite glass-ceramic material combining multiple oxide components in specific ratios to achieve synergistic effects. The composite structure includes controlled crystalline phases (such as SrSi2O2N2, CaAlSiN3) embedded in a glass matrix, providing both mechanical stability through crystalline reinforcement and CTE matching through compositional tuning, while preventing formation of undesirable phases.
2Stability of the object's composition
If glass-ceramic sealants with high thermal stability are used, then chemical resistance is improved, but formation of low-CTE phases occurs
Solution Approach 1:
The patent adjusts compositional parameters to achieve CTE of 9-13 × 10^-6/K, matching SOC components. Specific parameter ranges include SrO (10-30 wt%), CaO (5-20 wt%), and controlled SiO2 (20-40 wt%) to prevent low-CTE phase formation while maintaining thermal stability. The composition is designed to crystallize into phases with appropriate thermal expansion characteristics.
Solution Approach 2:
The patent explicitly addresses thermal expansion by designing the glass-ceramic composition to achieve a specific CTE range (9-13 × 10^-6/K) that matches the SOC components. This is accomplished through selective incorporation of oxides that contribute to desired thermal expansion behavior, preventing CTE mismatch and associated thermal stresses during operation.
3Stress or pressure
If glass-ceramic compositions are optimized for CTE matching, then mechanical stress is reduced, but porosity increases
Solution Approach 1:
The patent optimizes compositional parameters including SrO (10-30 wt%), CaO (5-20 wt%), B2O3 (5-15 wt%), and Al2O3 (5-15 wt%) to achieve both CTE matching (9-13 × 10^-6/K) and low porosity. The balanced composition ensures proper sintering behavior and density development while maintaining the required thermal expansion properties, avoiding the trade-off between stress reduction and porosity increase.
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 proposed glass-ceramic composition exhibits a CTE within the desired range of 10-11 × 10^-6 K^-1, is free from low-CTE phases, and maintains thermal and chemical stability at high temperatures, making it suitable for long-term operations in SOC applications.
Implementation Method 1
the formation of SrSiO3 and/or Sr2SiO4 as main crystalline phases... progressive crystallization at SOC operating temperatures
Implementation Method 2
The transition temperature must be close to the operating temperature of the stack to allow for the sealant to soften and provide for good adhesion and sufficient rigidity even at high temperatures
Data Source
Figure 1
AI summary
The invention relates to a glass ceramic sealing composition, wherein the composition is selected from the following components in mol%: SiO2 40 - 60 mol%, B2O3 1 - 12 mol%, SrO 30 - 50 mol%, CaO 1 - 12 mol%, MgO 0 - 5 mol% and Al2O3 1 - 6 mol%, wherein the total concentration of CaO and MgO and SrO is 30 - 70 mol% and wherein the total concentration of SiO2 and B2O3 is 45 - 70 mol %.