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Metal bipolar plates are prone to corrosion in the acid environment of fuel cells. It is necessary to deposit protective films with excellent corrosion resistance on the surface of metal bipolar plates. In this study, LaB 6 -doped carbon films with strong corrosion resistance were deposited on 316L stainless steel by magnetron sputtering ion plating using graphite composite targets with different contents of LaB 6. The effects of bias voltage and content adjusting on the corrosion resistance of obtained films were investigated. The results show that doping LaB 6 is benefit to adjust the structure and improve the corrosion resistance of a-C matrix. The carbon film with moderate LaB 6 doping possesses compact structure with no columnar defects and exhibits excellent corrosion resistance, providing good protection for 316L stainless steel bipolar plates. • LaB 6 can emit abundant energetic particles, which give higher energy to the plasma during magnetron sputtering process and thus suppress the growth of columnar structure in a-C matrix. • Doping LaB 6 is benefit to promote the graphitization of carbon films and increase the content of sp2-C in a-C matrix. • The most compact structure with no columnar defects is observed for the La-5-100 film, which inhibit the corrosion solution invading into substrates and provide good protection. • The corrosion current density of La-5 films is less than 1 µA·cm-2, and the lowest value can reach 0.33 µA·cm-2. [ABSTRACT FROM AUTHOR]

Polymer-based piezoelectric motors have excellent properties, such as lightweight and corrosion resistance. In addition, 3D printing and customized additive manufacturing of polymers provide new opportunities for the development of piezoelectric motors with complex or special structures. In this paper, a 3D printed polymer-based sandwich-type piezoelectric motor operating in a single longitudinal mode is developed. A vibration decomposition model of the motor and an analytical model considering polymer viscoelasticity are established to analyze the dynamic characteristics and to determine the geometric structure of the motor. To increase the coefficient of friction, a polymer surface texture is utilized on the contacts. The experimental results show that the friction coefficient of the contact tip with surface texture is about 0.16, which increased by 45.5% compared to a smooth surface. The resonance frequency is 28.648 kHz, and the maximum no-load speed under 300 Vp-p is 54 r/min. Our study shows the promise of polymer-based materials in the development of the piezoelectric motor. [ABSTRACT FROM AUTHOR]

Proton exchange membrane fuel cell has attracted much attention in recent years due to their advantages of environmental protection and high resource utilization, which is important for improving the global environment. Bipolar plates are the important components of fuel cell, which accounts for most of the weight and high cost. Compared with graphite bipolar plates, metal bipolar plates are easier to machining and have lower cost because of its good mechanical properties. However, in the acidic environment of proton exchange membrane fuel cell operation, metal bipolar plates are prone to corrosion, which leads to lower output efficiency of fuel cell and seriously affected the application. Applying a protective coating to the metal bipolar plates is an effective way to improve its corrosion resistance. This paper mainly introduces the research progress of several anti-corrosion coatings for metal bipolar plates in recent years, and summarizes the challenges and future requirements of metal bipolar plates. • Metal nitride and carbon based coating are suitable for metal bipolar plates. • Environmental standard of bipolar plates corrosion test should be unified. • High potential and long-term corrosion test of bipolar plates should be valued. • Multilayer coating and element doping are feasible for metal bipolar plates. [ABSTRACT FROM AUTHOR]

[Display omitted] • CrN films prepared by HiPIMS exhibit good interface conductivity. The lowest interface contact resistance can reach 6.14 mΩ·cm2 at 1.4 MPa. • The high energy density during magnetron sputtering is beneficial to inhibition the growth of columnar structure and formation Cr 2 N films with high metallicity and stability. • The corrosion current density of all CrN films prepared by HiPIMS is less than 1 µA·cm−2, and the lowest value can reach 0.086 µA·cm−2. • The space network structure of amorphous wrapped Cr 2 N nanoclusters inhibited corrosion solution invading into Ti substrates, which greatly improves the corrosion resistance of CrN films. Films for bipolar plates deposited from PVD are always restricted by narrow parameters' widow, which restrict the robust quality of high conductivity and anticorrosion due to the fluctuation of deposition plasma naturally. In this study, CrN films with high conductivity and strong corrosion resistance was deposited on Ti plates by high power impulse magnetron sputtering in wider Ar/N 2 ratios. The results show that the CrN film prepared by this method effectively inhibits the columnar structure and forms a dense structure of amorphous wrapped nano Cr 2 N clusters, providing good protection for Ti plate. Meanwhile, First-principal calculations shown Cr 2 N has stronger metallicity than CrN, resulting in lower ICR. This work has opened up a new way for the large-scale preparation of metal bipolar plate films. [ABSTRACT FROM AUTHOR]

LaB 6 have been using as hot electron emission materials to serve as hollow cathode ions source, which can help to enhance forming densen films. Besides, La can easy oxide to form La 2 O 3 which can hinder penetration of water to improve the anti-corrosion properties. Thus, we embed LaB 6 in carbon which can be employed as sputtering target, expecting to hot the plasma to get more sp2 carbon involved in growth a-C films. As a result, the LaBC film show higher I D /I G values, which improves the graphitization of the carbon matrix, thus partially solving the contradiction between electrical conductivity and corrosion resistance of the LaBC film. The corrosion current density of the LaBC film coated SS316L reduced by one and two orders of magnitude compared to the a-C film coated and uncoated SS316L, respectively, which can be attributed to the formation of boron oxide and lanthanum oxide on the surface of the film. Boron oxide is a waxy substance, and under the dual obstruction of boron oxide and lanthanide oxide, the corrosive solution is difficult to penetrate into the surface and reach the substrate, which greatly delays the oxidation and corrosion of the substrate. Therefore, the LaBC film are expected to be effective bipolar plate coatings for proton exchange membrane fuel cells. [Display omitted] [ABSTRACT FROM AUTHOR]

TiN coatings were deposited by HiPIMS at different N 2 flow rate to improve the corrosion resistance and conductivity of metallic bipolar plates. The results show that the surface microstructure of TiN coating depends strongly on the N 2 flow rate, all the samples (N 2 flow rate: 4 to10 sccm) meet the DOE 2025 standard and exhibit good hydrophobicity, which has great potential for industrial application. Among them, at the N 2 flow rate of 8 sccm, the TiN coating shows high compactness and the optimum surface microstructure with the lowest surface roughness of 1.083 nm and the highest hardness of 31.172 GPa. The optimized TiN coating exhibits excellent corrosion resistance with corrosion current density of 0.278 μA cm−2 and a low interfacial contact resistance value of 3.51 mΩ cm2. This work has opened a new way for the large-scale preparation of high-performance metal bipolar plate coatings. • HiPIMS was employed for TiN coatings deposition for bipolar plates. • The electric conductivity and corrosion properties rely on the surface roughness and relatively compactness. • The optimized TiN coating under 8 sccm N 2 exhibits excellent corrosion resistance and electric conductivity. [ABSTRACT FROM AUTHOR]

Benefited from the high-power impulse magnetron sputtering (HiPIMS) method with small targets (most of them in 2–4 in.) in labs, many published works reported that excellent anti-corrosion and interface conductivity CrN films were obtained in a wide processing window, which is favor in the coating industry. However, a paramount concern is whether this technology could achieve industrial mass production in large vacuum coating equipment with high loading capacity. To assure this, in the present work, a series of CrN films were prepared under different sputtering currents of Cr target by HiPIMS using Cr cylindrical targets with height and diameter of 675 mm and 100 mm, respectively. The effects of sputtering current on the electrical conductivity, corrosion resistance and mechanical properties were investigated. However, often stated as fact that the wide process window in labs turns narrow under industrial scale depending on HiPIMS. Only that the CrN film deposited at the Cr target current of 500 A showing best anti-corrosion and interface conductivity. Our results show that beautiful data obtained under lab scale cannot directly be generalized under industrial scale, which should be carried out in a more serious light. • Compared to the 2-inch target, none of the films prepared meet DOE standards. • Beautiful data obtained under lab scale cannot directly be generalized to others, which should be carried out in a more serious light. • A home-made industrial sclae sputterting system was employed for HiPIMS deposition. [ABSTRACT FROM AUTHOR]