Low-Temperature Glass-Ceramic Joining Material for Fuel Cells
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Solution Overview
Problem
Current glass-ceramic joining materials for fuel cells and electrolysis cells require high joining temperatures, exceeding 800°C, which is impractical and costly, and existing materials with lower SiO2 content have coefficients of thermal expansion that do not match the components, leading to unstable bonds and potential corrosion issues.
Innovation Solution
A glass-ceramic joining material with a SiO2 content of 3-9.5 mol%, B2O3 content of 16-34 mol%, and CaO content of 8-40 mol%, which crystallizes to form BaAl2Si2O8 as the main crystal phase, allowing for bonds at temperatures not exceeding 800°C with a coefficient of thermal expansion of 9.5-12.5·10−6 K−1, ensuring chemical stability and matching thermal expansion with components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If glass-ceramic joining materials with high SiO2 content are used to achieve stable thermal expansion matching, then the coefficient of thermal expansion matches the components, but the joining temperature becomes excessively high (exceeding 800°C)
Solution Approach 1:
The patent applies parameter changes by precisely controlling the SiO2 content within a specific range (3-9.5 mol%) rather than using high SiO2 content. This quantitative parameter adjustment allows the glass-ceramic to achieve the required coefficient of thermal expansion (9.5-12.5·10−6 K−1) while maintaining a low joining temperature not exceeding 800°C, directly resolving the contradiction between thermal expansion stability and joining temperature
Solution Approach 2:
The patent creates a composite glass-ceramic material with a specific composition including SiO2 (3-9.5 mol%), B2O3 (16-34 mol%), CaO (8-40 mol%), and other oxides. This composite formulation enables the material to simultaneously achieve low joining temperature, appropriate thermal expansion coefficient, and chemical stability, resolving the contradiction by combining multiple components in optimized proportions
2Ease of operation
If amorphous glass joining materials are used, then the joining operation is simple, but the operating temperature must be significantly below the joining temperature to prevent bond failure
Solution Approach 1:
The patent utilizes phase transition by transforming the amorphous glass material into a glass-ceramic through controlled crystallization. This phase transition fundamentally changes the material properties: the crystalline structure provides thermal stability that allows the bond to withstand operating temperatures much closer to the joining temperature, eliminating the severe operating temperature limitation while maintaining ease of operation
Solution Approach 2:
The patent changes the physical state parameter of the joining material from amorphous to crystalline (glass-ceramic). This parameter change in the material's structural state enables the bond to maintain integrity at higher operating temperatures without requiring the operating temperature to be significantly below the joining temperature, thus resolving the contradiction
3Temperature
If glass-ceramic joining materials are used to enable high operating temperatures, then the bond can withstand higher temperatures, but the crystallization process requires precise control of heating and cooling curves
Solution Approach 1:
The patent optimizes the chemical composition parameters of the glass-ceramic (specific ratios of SiO2, B2O3, CaO, and other oxides) to create a material with inherent crystallization characteristics that simplify the heating and cooling curve requirements. This parameter optimization in the material composition reduces the complexity of the thermal processing procedure while maintaining the ability to withstand high operating temperatures
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
Enables the production of stable, hermetic, and electrically insulating bonds at low temperatures, reducing corrosion and energy costs, and extending the lifespan of fuel cells and electrolysis units by avoiding excessive thermal stresses and chemical instability.
Implementation Method 1
the amorphous base glass crystallizes at least partly or else completely in the course of the joining operation
Implementation Method 2
the coefficient of thermal expansion of the joining materials corresponds approximately to that of the components to be bonded
Data Source
AI summary
The glass-ceramic joining material, which is suitable for bonding or joining at low processing temperatures, especially less than 800° C., is composed of a BaO—SiO2—CaO—B2O3—Al2O3 system and has a coefficient of thermal expansion α(20-300)≧9.5·10−6 K−1.