Graded Buffer Layer for CTE Mismatch in Solid Oxide Fuel Cells
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Solution Overview
Problem
Solid oxide fuel cell (SOFC) stacks face component failure due to mismatched coefficients of thermal expansion (CTE) between interconnects and electrolytes, leading to residual stress and cracking, particularly in systems with rigid bonded glass seals that cannot deform to accommodate thermal stresses.
Innovation Solution
A functionally graded composite buffer layer with a gradient in coefficient of thermal expansion (CTE) is introduced between the interconnect and electrolyte, comprising layers with varying metal and ceramic concentrations to bridge the CTE mismatch, deposited using atmospheric plasma spray processes on stainless steel interconnects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If rigid bonded glass seals are used to join interconnect and electrolyte, then strong mechanical bonding is achieved, but residual stress and cracking occur due to CTE mismatch
Solution Approach 1:
The patent applies parameter changes by modifying the CTE properties of the interconnect through coating with a functionally graded material. The coating composition varies through its thickness, transitioning from metal-rich at the interconnect interface to ceramic-rich at the electrolyte interface, thereby changing the thermal expansion parameter to match between components and eliminate residual stress
Solution Approach 2:
The patent uses composite materials by creating a functionally graded coating that combines metal and ceramic phases in varying proportions. This composite structure allows the interconnect to achieve intermediate CTE properties that bridge the gap between the metal interconnect and ceramic electrolyte, preventing stress-induced cracking while maintaining bonding strength
2Manufacturing precision
If strict CTE matching specifications are enforced for interconnects, then component compatibility is improved, but manufacturing complexity and cost increase
Solution Approach 1:
The patent introduces an intermediary solution by applying a functionally graded coating on the interconnect surface. This coating acts as a mediator that provides the required CTE match with the electrolyte, thereby relaxing the strict CTE specifications for the bulk interconnect material and simplifying manufacturing while ensuring component compatibility
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 graded buffer layer minimizes electrolyte damage, enhances the robustness of SOFC stacks, broadens interconnect manufacturing specifications, reduces costs, and allows the use of cost-effective alternative metals, while also acting as a chemical barrier and dielectric layer to reduce power loss and improve durability.
Implementation Method 1
deposited using atmospheric plasma spray processes on stainless steel interconnects
Data Source
AI summary
A buffer layer between an interconnect and an electrolyte of a solid oxide fuel cell, the buffer layer having a gradient in coefficient of thermal expansion (CTE), wherein the buffer layer minimizes electrolyte damage due to a difference in CTE between the interconnect and electrolyte.