Solid Oxide Fuel Cell Single Sintering Process
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Solution Overview
Problem
Solid oxide fuel cells (SOFCs) are susceptible to damage from temperature fluctuations, leading to mechanical stress and limited thermal shock resistance, which hampers production yield and operational reliability, particularly in stacked configurations.
Innovation Solution
A single, free-sintering process is employed to form a solid oxide fuel cell unit cell with a green electrolyte layer, interconnect layer, and electrode layer, where diffusion bonds are formed between the components, allowing for improved thermal expansion matching and reduced mechanical stress.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If multi-step firing processes or hot-pressing are used to form SOFC stacks, then the layers can be bonded together, but the thermal shock resistance deteriorates and mechanical stress increases
Solution Approach 1:
The patent combines multiple sintering operations into a single simultaneous sintering process where the electrolyte layer, anode layer, and interconnect layer are sintered together in one step. This merging of processes eliminates the thermal cycling and mechanical stress associated with multi-step firing, while still achieving strong diffusion bonds between layers through the controlled formation of metallurgical bonds at the interfaces.
Solution Approach 2:
The patent changes the sintering parameters by conducting the process at a controlled temperature range (900-1100°C) with specific hold times, and by controlling the atmosphere conditions. This allows the formation of strong bonds between layers while minimizing thermal stress and improving thermal shock resistance compared to conventional high-temperature hot-pressing methods.
2Strength
If conventional multi-step sintering processes are used, then layers can be bonded, but production efficiency decreases and yield is limited
Solution Approach 1:
The patent merges the sintering of electrolyte, anode, and interconnect layers into a single simultaneous process, eliminating multiple heating and cooling cycles. This reduces production time and increases throughput while maintaining strong interlayer bonding through diffusion bonding mechanisms that occur during the unified sintering process.
Solution Approach 2:
The patent applies preliminary actions by pre-forming the green layers with appropriate compositions and structures before the final sintering step. The green layers are prepared with controlled particle size distributions and layer configurations that enable successful simultaneous sintering and strong bond formation in a single process step.
3Ease of operation
If stacks of individual fuel cells are assembled, then electrical interconnects can be disposed between stacks, but mechanical stress from temperature fluctuations increases and failure risk heightens
Solution Approach 1:
The patent merges the interconnect layer with the electrode and electrolyte layers in a single integrated structure formed through simultaneous sintering. This eliminates the need for separate assembly of stacks with interconnects disposed between them, and the integrated structure has matched thermal expansion properties that reduce mechanical stress from temperature fluctuations.
Solution Approach 2:
The patent achieves homogeneity in thermal expansion properties by using similar ceramic materials (calcium or zirconium oxide) for all layers - electrolyte, anode, and interconnect. This material homogeneity ensures that all layers expand and contract at similar rates during temperature changes, minimizing mechanical stress and improving reliability of the assembled structure.
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
This approach enhances the mechanical and electrical characteristics of SOFCs, reducing the risk of failure and improving production efficiency by integrating the layers in a unified, crack-free structure with minimal warpage and high thermal resilience.
Implementation Method 1
sintering the green SOFC unit cell in a single sintering process to form a sintered SOFC unit cell
Implementation Method 2
diffusion bonds are formed between the components of the interconnect layer and the first electrode layer
Data Source
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AI summary
A method for forming a solid oxide fuel cell (SOFC) article includes forming a SOFC unit cell in a single, free-sintering process, wherein the SOFC unit cell is made of an electrolyte layer, an interconnect layer, a first electrode layer disposed between the electrolyte layer and the interconnect layer. The electrolyte layer of the SOFC unit cell is in compression after forming.