Stainless Steel Fuel Cell Separator Surface Texturing
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Solution Overview
Problem
Stainless steel sheets for fuel cell separators exhibit high contact resistance due to the growth of passive films during the fuel cell stack production process, which hinders the achievement of desired power generation performance.
Innovation Solution
A stainless steel sheet with a textured surface structure and increased atomic concentration of Cr in chemical form other than metal, formed through etching treatment and subsequent condensation, maintains low contact resistance even under heat treatment conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If stainless steel separators are used to enhance durability and corrosion resistance, then reliability is improved, but contact resistance increases due to passive film formation
Solution Approach 1:
The patent applies preliminary action by forming a textured structure on the stainless steel separator surface before the fuel cell stack production process. This pre-formed texture prevents excessive passive film growth during subsequent heat treatment, thereby maintaining low contact resistance while preserving the corrosion resistance benefits of stainless steel.
Solution Approach 2:
The patent changes the surface parameter of the stainless steel separator by creating a textured structure with specific surface roughness and morphology. This parameter change modifies how the passive film forms and grows, limiting its thickness and electrical resistance while maintaining the protective corrosion-resistant properties of the stainless steel material.
2Ease of manufacture
If heat treatment is applied during fuel cell stack production, then manufacturing process is completed, but passive film grows excessively causing contact resistance to increase
Solution Approach 1:
The textured structure is formed preliminarily before heat treatment, creating a surface morphology that controls passive film growth during the subsequent heat treatment process. This preliminary surface preparation allows the heat treatment to proceed without causing excessive contact resistance.
Solution Approach 2:
The textured structure acts as a preliminary anti-action by pre-establishing surface features that counteract the harmful effect of excessive passive film growth during heat treatment. The texture creates physical constraints and chemical conditions that limit film thickening, thereby preventing the increase in contact resistance that would otherwise occur during manufacturing heat treatment.
3Object-affected harmful factors
If graphite is used as separator material to achieve low contact resistance, then electrical conductivity is improved, but mechanical strength and durability deteriorate
Solution Approach 1:
The patent creates a composite surface structure on the stainless steel separator, combining the bulk stainless steel material (providing strength and corrosion resistance) with a textured surface layer (controlling passive film formation and reducing contact resistance). This composite approach integrates the advantages of both material types.
Solution Approach 2:
The patent applies local quality by modifying only the surface properties of the stainless steel separator through texturing, while maintaining the bulk material properties (strength and corrosion resistance) of the stainless steel. The surface texture provides low contact resistance locally, while the bulk material provides mechanical strength.
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 effectively reduces contact resistance and enhances durability, ensuring stable power generation performance and practical usability of stainless steel sheets as fuel cell separators.
Implementation Method 1
subjecting the stainless steel sheet to etching treatment
Implementation Method 2
subjecting the stainless steel sheet subjected to the etching treatment, to condensation treatment for Cr existing in chemical form other than metal at a surface of the stainless steel sheet
Implementation Method 3
the growth of the passive film causes an increase in contact resistance
Implementation Method 4
The durability depends on corrosion resistance
Data Source
AI summary
A stainless steel sheet for fuel cell separators comprises a predetermined chemical composition, wherein the stainless steel sheet has a textured structure at a surface thereof, an average interval between projected parts of the textured structure being 20 nm or more and 200 nm or less, and a ratio [Cr]/[Fe] of an atomic concentration of Cr existing in chemical form other than metal to an atomic concentration of Fe existing in chemical form other than metal at the surface of the stainless steel sheet is 2.0 or more.