Study On Graphite-like Carbon Film Coated Metallic Bipolar Plate By Magnetron Sputtering

Bipolar plate is one of the key components in proton exchange membrane fuel cell（PEMFC）,the research focus on coatings on stainless steel as metallic bipolar plate has been one of the hots in recent years.In this paper,the unbalanced magnetron sputtering system SP0806SI,which is developed by lanzhou institute of chemical physics with medium frequency AC pair target combined with DC magnetron single target,and the new generation of unbalanced magnetron magnetron sputtering system CF-800 developed by Teer coating company were used to deposit a series of GLC as bipolar plates on 304SS stainless steel.The results showed that A_D/A_G in the pure GLC structure prepared by SP0806SI could reach a maximum of 4.76,while A_D/A_G in the pure GLC structure prepared by CF-800 was lower,but its A_D/A_G could be significantly improved by doping Cr and optimizing bias voltage.Finally,the influence of modulation ratio on CF-800 preparation of multilayer structure GLC is also explored.The specific research content is as follows:（1）GLC series with different pulse duty cycles and bias voltages were deposited on304SS stainless steel by SP0806SI coating equipment.Duty cycle series results showed that the preparation of GLC at the duty cycle of 40%with the highest sp2/sp3 has the lowest contact resistance of 10.2 mΩcm²,at this point the corrosion current density is 5.20×10^-7Acm^-2;Bias voltage series results showed that the preparation of GLC at-75 V has the lowest contact resistance of 8.4 mΩcm²because of the densest morphology though the sp2/sp3 isn’t the highest,at this point the corrosion current density is 2.78×10^-77 Acm^-2.The properties of the optimized samples were stable before and after potentiostatic polarization,and the hardness reached 10.159 GPa,water contact angle reaches 87.8°.（2）Cr-doped GLC series were deposited on 304SS stainless steel by CF-800 coating equipment and the effects of Cr target current and bias voltages on the structure and performance of the composite were studied.The results of Cr target current series showed that doping Cr could promote the increase of sp2/sp3 and thus improve the conductivity,but had an adverse effect on the corrosion resistance.When meet the standard of DOE,the GLC:Cr prepared at the Cr target of 0.8 A has the lowest contact resistance of 7.4 mΩcm²,at this point the corrosion current density is 5.89×10^-77 Acm^-2;Bias voltage series results showed that the GLC:Cr prepared at-80 V has the lowest contact resistance of 6.3 mΩcm² because of highest sp2/sp3,at this time the corrosion current density is 4.39×10^-7Acm^-2,and water contact angle reaches 95.9°.（3）Cr/GLC:Cr/GLC multilayer graphite-like carbon films with different ratios were deposited by CF-800 coating equipment,and the influence of time adjustment on the structure and properties of the interlayer and the surface layer was studied.The results showed that the GLC prepared at the ratio of 40:80 had the best electrical conductivity and corrosion resistance because of the densest morphology.