SOFC/SOEC Sealing Interface with Spinel Coating and CTE Matching
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Solution Overview
Problem
The sealing interface in SOFC/SOEC stacks faces issues such as thermal expansion mismatch, chemical instability, and mechanical weakness, leading to stress, cracks, and reduced performance.
Innovation Solution
A preparation method involving a spinel oxide coating on the metal interconnector and a SiO2—MgO—Al2O3—SrO—V2O5 sealing layer with controlled thermal expansion and mechanical properties, ensuring airtightness and endurance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a sealing layer is used to seal the interface between the cell and metal interconnector, then sealing function is achieved, but thermal expansion mismatch causes stress and cracks leading to sealing failure
Solution Approach 1:
The sealing layer is designed as a composite material containing 40-60 wt% glass phase, 10-30 wt% crystal phase, and 5-20 wt% metallic phase. This composite structure allows the sealing layer to have tailored thermal expansion properties that match both the cell and metal interconnector, reducing thermal stress and preventing cracks during thermal cycling.
Solution Approach 2:
The glass transition temperature of the glass phase is specifically controlled to be within 900-1100°C, and the crystal phase transformation temperature is controlled to be within 800-1000°C. These parameter adjustments enable the sealing layer to undergo controlled phase transitions that accommodate thermal expansion differences between components, preventing stress concentration and sealing failure.
2Strength
If the sealing layer material has high hardness and mechanical strength, then mechanical endurance is improved, but chemical stability under high temperature deteriorates leading to adverse reactions with electrolyte or electrode material
Solution Approach 1:
The sealing layer combines glass phase (for chemical stability and flexibility), crystal phase (for mechanical strength and thermal stability), and metallic phase (for enhanced toughness and ductility). This composite structure achieves both high mechanical strength and chemical stability, preventing adverse reactions with electrolyte or electrode material while maintaining structural integrity under thermal cycling.
Solution Approach 2:
The sealing layer exhibits different properties in different phases: the glass phase provides chemical inertness and flexibility, the crystal phase provides mechanical strength and thermal stability, and the metallic phase provides toughness. This local differentiation of material properties within the composite structure allows simultaneous achievement of mechanical strength and chemical stability.
3Temperature
If the sealing layer has high glass transition temperature for thermal stability, then thermal stability is improved, but the sealing layer becomes brittle and fracture toughness decreases
Solution Approach 1:
The sealing layer combines glass phase with high glass transition temperature (900-1100°C) for thermal stability, crystal phase for mechanical strength, and metallic phase (5-20 wt%) specifically added to enhance fracture toughness and ductility. The metallic phase acts as a ductile matrix that prevents brittle fracture while maintaining the high thermal stability provided by the glass phase.
Solution Approach 2:
The glass transition temperature is optimized to be within 900-1100°C, which is high enough to provide thermal stability but not so high as to cause excessive brittleness. The controlled composition ratios and the presence of metallic phase modify the fracture behavior, preventing catastrophic brittle failure while maintaining thermal stability.
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 method enhances the sealing interface's durability and performance by improving thermal stability, chemical resistance, and mechanical strength, preventing leakage and damage under thermal cycles.
Implementation Method 1
whose excellent oxidation resistance, chemical stability and electric conductivity greatly improve the endurance and entire performance of the metal interconnector
Implementation Method 2
the coefficient of thermal expansion of the sealing layer matches the coefficients of thermal expansion of the cell and the metal interconnector, avoiding the stress and damage resulting from mismatch of the coefficients of thermal expansion
Implementation Method 3
Staged thermal treatment is employed to form a high-density and strong-adhesion spinel coating
Data Source
AI summary
A preparation method of an SOFC or SOEC with a long-life sealing interface is formed by allowing a sealing layer, a cell and a metal interconnector to be mutually contacted. In the present disclosure, with spinel as a coating material of the metal interconnector, staged thermal treatment is employed to form a high-density and strong-adhesion spinel coating to improve the endurance and entire performance of the metal interconnector. The present disclosure also optimizes the material system of the sealing layer, namely, uses the SiO2—MgO—Al2O3—SrO—V2O5 system to prepare the sealing layer, which not only improves the resistivity of the sealing layer but also increases its hardness and fracture strength. Further, under the condition of ensuring the airtightness, the coefficient of thermal expansion of the sealing layer is matched with the coefficients of thermal expansion of the metal interconnector and the cell, improving the endurance of the sealing interface.