Crystallized Glass Joining Material for Fuel Cell Stack Durability
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Solution Overview
Problem
The existing stack structure of solid oxide fuel cells using amorphous glass as a joining material faces issues with material degradation due to volatilization at working temperatures, leading to electrode poisoning and reduced durability, and crystallized glass joining materials can develop cracks during heat treatment due to volume reduction ratios outside a specific range.
Innovation Solution
A joining material formed from crystallized glass with a crystallinity degree of 60% or more, specifically a SiO2—MgO based material, is used, with a crystallization shrinkage ratio between 0.78% and 12%, to prevent crack generation and enhance durability by controlling the crystallization process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If amorphous glass is used as a joining material, then ease of manufacture is improved, but durability deteriorates due to volatilization of elements at working temperature causing electrode poisoning
Solution Approach 1:
The invention changes the physical and chemical parameters of the glass material by controlling its composition (specific ratios of SiO2, B2O3, Al2O3, MgO, and other oxides) and processing conditions (heating temperature and time) to transform amorphous glass into crystallized glass with specific crystal phases, thereby improving durability while maintaining manufacturability
Solution Approach 2:
The invention uses composite glass materials containing multiple oxide components (SiO2, B2O3, Al2O3, MgO, and optional additives like ZnO, TiO2, etc.) that work together to achieve both low crystallization shrinkage ratio and high durability, preventing electrode poisoning while ensuring proper joining performance
2Reliability
If crystallized glass is used as a joining material, then durability is improved, but cracks are generated during heat treatment due to volume reduction from crystallization
Solution Approach 1:
The invention precisely controls the crystallization shrinkage ratio by adjusting glass composition parameters (particularly the ratios of MgO, Al2O3, B2O3, and SiO2) and heat treatment parameters (temperature and time) to keep the shrinkage ratio within 5-15%, preventing crack formation while maintaining the durability benefits of crystallized glass
Solution Approach 2:
The invention creates different crystal phases distributed throughout the glass matrix, with each phase contributing to different properties: some phases control shrinkage, others provide structural strength and durability, achieving a balanced composite structure that prevents cracks while maintaining high reliability
3Strength
If the crystallization shrinkage ratio is reduced to prevent cracks, then strength is improved, but flowability during joining deteriorates
Solution Approach 1:
The invention optimizes the glass composition parameters (particularly B2O3 content at 30-50 wt%, SiO2 at 40-60 wt%, and MgO at 5-20 wt%) to achieve a balance where the glass maintains adequate flowability during the joining process while the controlled crystallization shrinkage ratio (5-15%) ensures crack-free strength after heat treatment
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 use of crystallized glass with a controlled crystallization shrinkage ratio effectively prevents crack formation in the joining material, maintaining the structural integrity and performance of the fuel cell stack, while ensuring sufficient flowability for proper gas sealing.
Implementation Method 1
the crystallized glass being generated when crystallization of amorphous glass heated up to a crystallized temperature by heat treatment proceeds
Implementation Method 2
there is a strong correlation between the generation of cracks and 'a volume reduction ratio of the joining material caused by the crystallization' (hereinafter referred to as 'crystallization shrinkage ratio')
Data Source
AI summary
A plurality of insertion holes for inserting one end of each of a plurality of cells is formed on the surface of a support substrate. One end of each of the cells is loosely fitted in the corresponding insertion hole. A joining material is provided so as to fill at least a gap present between the inner wall of the insertion hole and the outer wall of the one end of the cell in each joining portion between each of the insertion holes and one end of the corresponding cell. As the joining material, crystallized glass which includes a plurality of kinds of crystal phases generated when the crystallization of amorphous glass heated up to a crystallization temperature proceeds is used, and a volume reduction ratio (crystallization shrinkage ratio) of the joining material caused by the crystallization at the crystallization temperature is 0.78% or more and 12% or less.