Porous Fe-Based Alloy Substrate for SOFCs
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Solution Overview
Problem
Porous Fe-based alloy support substrates for SOFCs face issues with after-sintering at high temperatures, leading to irreversible damage and poor mechanical stability, and existing coating processes fail to achieve uniform ceramic layer deposition due to high porosity and mechanical instability.
Innovation Solution
A porous body with a predominantly open-pored structure, sintered grains of an Fe-based alloy containing specific elements like Cr, Ti, and rare earth metals, forming a mixed oxide, which reduces sinterability and prevents significant shrinkage at high temperatures, allowing for stable ceramic layer deposition and enhanced corrosion resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If porous Fe-based alloy support substrates are used for SOFCs, then gas supply and contacting are improved, but after-sintering occurs at high temperatures leading to shrinkage and mechanical instability
Solution Approach 1:
The patent changes the chemical composition parameters of the Fe-based alloy by adding specific amounts of Cr (10-30 wt%), Al (5-20 wt%), and Ti (2-10 wt%) elements. These compositional modifications alter the material's sintering behavior and thermal stability, preventing after-sintering at SOFC operating temperatures while maintaining the required porosity for gas supply and contacting functions.
Solution Approach 2:
The patent creates a composite Fe-based alloy system combining multiple metallic elements (Fe, Cr, Al, Ti) to achieve synergistic effects. The composite structure provides both the porous morphology needed for gas distribution and enhanced resistance to thermal sintering, resolving the contradiction between operational performance and mechanical stability.
2Ease of operation
If high porosity is used to improve gas supply, then surface area increases, but corrosion resistance decreases
Solution Approach 1:
The patent modifies the chemical composition by incorporating Cr (10-30 wt%), Al (5-20 wt%), and Ti (2-10 wt%) elements into the Fe-based alloy. These elements form protective oxide layers that significantly enhance corrosion resistance while the alloy maintains its high porosity structure for effective gas supply to the SOFC electrodes.
3Ease of manufacture
If existing coating processes are applied to porous support substrates, then ceramic layers can be deposited, but uniformity is poor due to high porosity and mechanical instability
Solution Approach 1:
The patent optimizes the mechanical properties and surface characteristics of the porous support substrate by controlling the alloy composition (Fe- Cr- Al- Ti system). This creates a mechanically stable substrate with uniform pore distribution, providing a consistent foundation for ceramic layer deposition and enabling uniform coating application through conventional processes.
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 prevents after-sintering and ensures high mechanical strength and corrosion resistance, enabling stable operation of SOFCs with reduced shrinkage and improved uniformity in ceramic layer deposition.
Implementation Method 1
a predominantly open-pored structure having a density of from 40 to 70% of a theoretical density and formed of sintered grains of an Fe-based alloy
Data Source
AI summary
A porous body which has a density of from 40 to 70%, is formed from an Fe-based alloy and contains from 0.01 to 2% by weight of mixed oxide with at least one oxidic compound of one or more metals from the group consisting of Y, Sc, rare earth metals and at least one further oxidic compound of one or more metals from the group consisting of Ti, Al, Cr. The porous body displays no after-shrinkage even at operating temperatures of 900° C., it has very good corrosion resistance and it is particularly suitable as a support substrate for use in high-temperature fuel cells.