Laser-Treated Fuel Cell Separator Surface
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Solution Overview
Problem
Fuel cell separators face challenges in achieving high electrical conductivity, hydrophilicity, and low leachability due to issues with surface treatment methods, such as incomplete removal of mold release agents and resin components, which lead to contamination and increased contact resistance.
Innovation Solution
A method involving laser treatment of a composition comprising graphite powder, epoxy resin, phenolic resin, and an internal mold release agent, with specific power and pulse duration conditions to achieve a fuel cell separator with low surface residues, optimal roughness, and improved electrical conductivity and hydrophilicity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If blasting treatment is used to hydrophilize the separator surface, then hydrophilicity is improved, but mold release agents and resin components cannot be fully removed causing contamination
Solution Approach 1:
The patent replaces the mechanical blasting treatment with laser irradiation treatment. The laser beam (optical energy) directly ablates and removes mold release agents and resin components from the separator surface while simultaneously creating hydrophilic groups, eliminating the contamination problem that occurs with blasting treatment where such substances cannot be fully removed.
Solution Approach 2:
The patent changes the treatment parameters by using laser irradiation with specific power (10-50 W) and pulse duration (10-100 ns) conditions. This allows precise control of the surface treatment to achieve both complete removal of contaminants and introduction of hydrophilic groups, resolving the contradiction between hydrophilicity improvement and contamination prevention.
2Reliability
If plasma treatment is used to introduce hydrophilic groups, then hydrophilicity is improved, but hydrophilic groups vanish when separators are bonded together or when fluoroplastic gasket is molded
Solution Approach 1:
The patent replaces plasma treatment with laser irradiation treatment. The laser directly ablates the resin components and carbonizes them on the separator surface, creating permanent hydrophilic groups that do not vanish during subsequent bonding or molding processes, thus resolving the stability issue of hydrophilic groups.
Solution Approach 2:
The patent utilizes the phase transition of resin components from solid to gas through laser-induced pyrolysis and carbonization. This phase transition permanently alters the surface chemistry, creating stable hydrophilic groups that remain intact during subsequent processing, unlike plasma-treated groups that can vanish.
3Reliability
If YAG laser treatment is used to carbonize resin layer, then electrical conductivity is improved, but resin remains at spot periphery causing increased contact resistance and leaching
Solution Approach 1:
The patent changes the laser parameters by using lower power (10-50 W, compared to higher power YAG laser) and shorter pulse duration (10-100 ns). This parameter adjustment allows complete removal and carbonization of resin components including the periphery areas, preventing resin residue formation while maintaining electrical conductivity improvement.
Solution Approach 2:
The patent uses pulsed laser irradiation with specific pulse duration (10-100 ns) to treat the separator surface. This periodic action allows complete carbonization of resin components at each pulse while the short duration prevents heat accumulation that would cause resin to remain at the spot periphery, resolving the contradiction between conductivity improvement and resin residue prevention.
4Reliability
If laser with long pulse duration (50 μs) is used to introduce hydrophilic groups, then hydrophilicity is improved, but treatment time increases causing separator heating and warping
Solution Approach 1:
The patent changes the pulse duration parameter to a shorter range (10-100 ns, compared to 50 μs). This parameter change reduces the treatment time significantly while still achieving effective introduction of hydrophilic groups, preventing separator heating and warping that occur with longer pulse durations.
Solution Approach 2:
The patent uses ultra-short pulsed laser irradiation (10-100 ns pulse duration) to treat the separator surface. This periodic action with very short pulses introduces hydrophilic groups efficiently without allowing heat to accumulate in the separator, thus preventing warping while maintaining hydrophilicity improvement.
5Reliability
If infrared laser treatment is applied only to groove inner surfaces, then hydrophilicity of grooves is improved, but contact surface with gas diffusion electrode lacks treatment causing water blockage
Solution Approach 1:
The patent applies laser irradiation treatment to the entire separator surface including both groove inner surfaces and the contact surface with the gas diffusion electrode. This universal treatment ensures hydrophilicity is improved in all areas, preventing water blockage at the electrode-separator interface while maintaining the benefits of groove hydrophilicity.
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 method results in a fuel cell separator with high electrical conductivity, low leachability, and stable performance over extended periods, maintaining efficient power generation and reducing contact resistance.
Implementation Method 1
subjecting a surface of the molded article to laser irradiation treatment wherein the laser irradiation conditions are a power of 100 to 200 W and a pulse duration of 30 to 200 ns
Implementation Method 2
subjecting a surface of the molded article to laser irradiation treatment wherein the laser irradiation conditions are a power of 100 to 200 W and a pulse duration of 30 to 200 ns
Data Source
Figure 1~2
Figure 3~4
Figure 5
AI summary
This fuel cell separator is obtained by irradiating the surface of a molded article formed by molding a composition containing graphite powder, an epoxy resin, a phenol resin, a curing accelerator, and an internal mold lubricant and is provided with the following characteristics (1)-(6). Accordingly, the conductivity and hydrophilicity of a fuel cell separator provided with grooves that form flow paths for gas supply and exhausting on the surface thereof can be improved, and also elutability can be reduced. (1) Residue from laser irradiation of the surface is 5% or less by area ratio (2) Arithmetic average roughness (Ra) of surface is 0.80-1.50 µm (3) Surface static contact angle is 15-60° (4) Surface contact resistance is 3-7 mΩ·cm2 (5) Ion exchanged water: under a condition of separator = 9:1 (mass ratio), the conductivity after the separator has been immersed in ion exchanged water at 90°C for 168 hours is 1.2 µS/cm or less (6) The change in the surface roughness with immersion for 2000 hours each in 90°C ion exchanged water and 150°C ion exchanged water is within 0.3 µm of that prior to immersion.