Simple tweak could cut fuel cell costs without sacrificing durability
Researchers found that how you coat fuel cell components matters far less than how much coating you apply. By adjusting carbon content in protective titanium coatings, manufacturers can now dial in the exact hardness and conductivity needed—potentially reducing production complexity and costs while maintaining performance for fuel cell makers worldwide.
Originaltitel: Magnetron sputtering of titanium carbonitride nanocomposite coatings: Does the choice of carbon source affect film properties?
<p>We report on a study of titanium carbonitride coatings, with potential applications as protective coatings on bipolar plates in fuel cells. Two series of Ti-C-N coatings with a carbon concentration varying between 8 and 34 at.% were deposited by magnetron sputtering, using a graphite target or methane gas as carbon source. Characterisation with X-ray diffraction, ion beam analysis, Raman spectroscopy and electron microscopy shows that the coatings consist of a crystalline titanium carbonitride phase and an amorphous carbon tissue phase: nc-Ti(C,N)/a-C(:N). It was found that the mechanical and electrical properties are primarily dependent on the carbon content and not the choice of carbon source. An increase in C content leads to a decreasing crystallite size and an increasing amount of amorphous carbon. Thus, the phase content and microstructure and thereby the properties are controlled by the carbon content, making the nc-Ti(C,N)/a-C(:N) coatings highly tuneable. Depending on C content hardness of 11-38 GPa and resistivity of 150-623 mu ohm cm was observed. Additionally, the coatings were found to exhibit a contact resistance against silver that was 10 times lower than that of a stainless steel reference. This makes titanium carbonitride nanocomposite coatings promising candidates for the use on bipolar plates in fuel cells.</p>