Corrugated Green Sheets for Flat Large Ceramic Electrolytes
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Solution Overview
Problem
The challenge in solid oxide cell technology is the formation of bulges and burrs at the edges of large-sized ceramic sheets during sintering, which leads to cell defects and cracking, and the existing methods fail to effectively address this issue, resulting in poor process yield and increased material costs.
Innovation Solution
A non-sintered green sheet or tape with a corrugated surface, featuring alternating crests and troughs arranged at specific angles, is used to minimize adhesion and movement during sintering, thereby compensating for horizontal shrinkage and reducing bulging at the edges, ensuring flatness and mechanical strength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of moving object
If the cell dimensions are increased to reduce stack costs per kW, then the footprint of SOCs is enlarged and material costs are reduced, but the sintered sheets develop bulges and burrs at edges that increase in amplitude towards the center, leading to cell defects and cracking
Solution Approach 1:
The green sheets are pre-corrugated with a sinusoidal profile before sintering. This preliminary structural modification compensates for the expected shrinkage during sintering, preventing bulge formation at the edges while maintaining large cell dimensions for cost-effective stack design
Solution Approach 2:
The invention changes the geometric parameters of the green sheets by introducing corrugations with specific amplitudes and wavelengths. This structural parameter modification allows the sheets to maintain flatness after sintering by pre-compensating for shrinkage effects that would otherwise cause edge bulging
2Ease of manufacture
If flat green sheets are used for sintering, then the manufacturing process is simple, but the sheets undergo substantial shrinkage and form bulges at the center portion and edge curls, increasing in amplitude towards the center of the edges
Solution Approach 1:
The green sheets are pre-corrugated with a sinusoidal profile before sintering. This preliminary structural modification compensates for the expected shrinkage during sintering, preventing bulge formation at the edges while maintaining large cell dimensions for cost-effective stack design
Solution Approach 2:
The invention applies a sinusoidal corrugation profile to the green sheets, transforming the flat surface into a curved, wavy structure. This curvature pre-compensates for the uniform shrinkage during sintering, ensuring the final sintered sheet remains flat without edge curls or central bulges
3Productivity
If the green sheet area is increased to reduce the number of stacks required, then the material costs decrease, but the edge curls become larger and the sheets often have to be cut to size, resulting in poor process yield
Solution Approach 1:
The green sheets are pre-corrugated with a sinusoidal profile before sintering. This preliminary structural modification compensates for the expected shrinkage during sintering, preventing bulge formation at the edges while maintaining large cell dimensions for cost-effective stack design
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 corrugated green sheet approach results in flat ceramic sheets without substantial bulges or burrs, even at large dimensions, enhancing the SOC cell footprint, reducing stack costs, and improving manufacturing yield by preventing cracking and maintaining mechanical strength.
Implementation Method 1
the corrugation of the green sheet allows for the shrinkage of the green sheet during the sintering step, wherein movement of the green sheet on the sintering substance is minimized
Data Source
AI summary
This invention relates a non-sintered green sheet or tape comprising a corrugated surface having alternating crests and troughs arranged along both a first direction of the surface and a second direction of the surface, the second direction forming an angle of between 60° to 120° to the first direction, wherein the corrugation periods and/or corrugation amplitudes in the first direction differ from those in the second direction. The invention enables preparation of a reliable, large-sized ceramic sheet material, e.g. as a ceramic electrolyte layer for use in solid oxide cells, as a ceramic sheet for filter or membrane applications, or as sintering substrate or setter. In addition, sintered ceramic sheets and electrolytes, methods of preparation, and solid oxide cells (SOCs) making use of the non-sintered green sheet or tape are described.