Titanium Alloy Separator Surface Conductivity
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Solution Overview
Problem
Current titanium and titanium alloy materials for fuel cell separators face challenges in achieving low contact resistance and durability, particularly in corrosive environments with fluoride ions and under applied voltage, which affects the longevity of fuel cells.
Innovation Solution
A titanium material with a titanium hydride layer formed on the surface, followed by a passivation treatment and stabilization treatment using specific aqueous solutions, resulting in a titanium oxide film with a composition ratio of titanium hydride exceeding 60%, enhancing contact-to-carbon electrical conductivity and corrosion resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a passive film is present on the titanium surface, then corrosion resistance is improved, but contact-to-carbon electrical conductivity deteriorates
Solution Approach 1:
The invention applies different surface treatments to different regions or aspects of the titanium surface. The oxide film provides corrosion resistance while conductive substance particles (carbon, metal, or carbonitride) are added to specific surface regions to enhance electrical conductivity. This local differentiation allows the surface to simultaneously achieve both corrosion resistance from the oxide film and low contact resistance from the conductive particles at the interface with carbon materials.
Solution Approach 2:
The invention creates a composite surface structure combining titanium oxide (for corrosion resistance) with conductive substance particles such as carbon particles, metal particles, or carbonitride particles. This composite surface layer maintains the protective function of the oxide film while introducing highly conductive phases that bridge the electrical resistance gap between titanium and carbon materials in the membrane electrode assembly.
2Manufacturing precision
If the contact resistance with MEA is reduced by adding conductive substances, then electrical conductivity is improved, but durability in corrosive environment deteriorates
Solution Approach 1:
The titanium oxide film serves as an intermediary layer between the base titanium material and the conductive substance particles, and between the metal separator and the corrosive fuel cell environment. The oxide film protects the conductive particles and the underlying titanium from direct exposure to fluoride ions and other corrosive species, while still allowing the conductive particles to provide electrical pathways. This mediator approach enables low contact resistance without sacrificing corrosion resistance.
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 provides a titanium material with low and stable contact resistance, even in corrosive environments, significantly prolonging the fuel cell's lifespan by maintaining excellent durability and electrical conductivity.
Implementation Method 1
a passivation treatment and stabilization treatment using specific aqueous solutions, resulting in a titanium oxide film
Implementation Method 2
A titanium material with a titanium hydride layer formed on the surface
Data Source
Figure 1
Figure 2(a)~2(b)
Figure 3~4
AI summary
The composition ratio of a titanium hydride [ITi-H/(ITi + ITi-H)] × 100 found from the maximum intensity of metal titanium (ITi) and the maximum intensity of the titanium hydride (ITi-H) of the X-ray diffraction peaks measured at a surface of a titanium or a titanium alloy at an incident angle to the surface of 0.3° is 55% or more, a titanium oxide film is formed on an outermost surface of the titanium or the titanium alloy, and C is at 10 atomic% or less, N is at 1 atomic% or less, and B is at 1 atomic% or less in a position where the surface has been subjected to sputtering of 5 nm with argon. The titanium oxide film is formed by performing stabilization treatment after performing passivation treatment in prescribed aqueous solutions, and has a thickness of 3 to 10 nm.