Layered Plates Research Articles

Advanced Dynamic Vibration Control Algorithms of Materials Terfenol-D Si3N4 and SUS304 Plates/Cylindrical Shells with Velocity Feedback Control Law

A numerical, generalized differential quadrature (GDQ) method is presented on applied heat vibration for a thick-thickness magnetostrictive functionally graded material (FGM) plate coupled with a cylindrical shell. A nonlinear c1 term in the z axis direction of a third-order shear deformation theory (TSDT) displacement model is applied into an advanced shear factor and equation of motions, respectively. The equilibrium partial differential equation used for the thick-thickness magnetostrictive FGM layer plate coupled with the cylindrical shell under thermal and magnetostrictive loads can be implemented into the dynamic GDQ discrete equations. Parametric effects including nonlinear term coefficient of TSDT displacement field, advanced nonlinear varied shear coefficient, environment temperature, index of FGM power law and control gain on displacement, and stress of the thick magnetostrictive FGM plate coupled with cylindrical shell are studied. The vibrations of displacement and stress can be controlled by the control gain algorithms in velocity feedback control law.

Axisymmetric forced vibration of the hydro-elastic system consisting of a pre-strained highly elastic plate and compressible viscous fluid

The paper studies the axisymmetric harmonic forced vibration of the hydro-elastic system composed of an initially strained plate made of highly elastic material, a compressible viscous fluid layer, and a rigid wall restricting the fluid flow. It is assumed that the plate is in contact with the fluid layer after the appearance of the finite axisymmetric homogeneous initial strains within which are caused by the stretching of the plate by uniformly distributed radial forces acting at infinity. Also, it is assumed that after this contact, the point located time-harmonic force begins to act on the free-face plane of the plate. Within this framework, the steady-state forced vibration of the hydro-elastic system under consideration is studied by employing the eq. and relations of the so-called three-dimensional linearized theory of elastic waves in bodies with finite initial strains to describe the motion of the plate and by employing the linearized Navier-Stokes eq. to describe the flow of the fluid. The corresponding mathematical problem is solved by employing the Hankel integral transform method, and the originals of the sought values are found numerically by employing the algorithms and PC programs composed by the authors. Numerical results are presented and discussed on the frequency response of the normal stress acting on the interface plane between the plate and fluid layer. According to these discussions, corresponding conclusions on the influence of the problem parameters on the frequency response of the interface stress are made. In particular, it is established that in the axisymmetric forced vibration case, the resonance-type phenomenon appears due to the fluid viscosity.

Exposure Test of Various Zinc-Coated Steel Sheets and Corrosion Resistance Evaluation of Zinc-Based Corrosion Products in Japan

Hot-dip zinc-coated steel sheets are widely used because of their high corrosion resistance, long-lasting effects, and low cost. In addition, aluminum and magnesium have been added to hot-dip zinc-coated steel sheets to improve corrosion resistance, and their use is expanding to supported stand of photovoltaic modules and gratings for infrastructure facilities. However, the corrosion resistance of each plated steel sheet has not been evaluated and only a few studies have compared them. Therefore, 10-year exposure tests were performed at six locations in Japan and the corrosion weight loss of each plated steel sheet was measured and compared with those of other plated steel sheets. In addition, the polarization curves of unexposed plated steel sheets and those exposed for five years were measured by linear sweep voltammetry (LSV), and the changes in corrosion resistance due to the corrosion products were verified.Exposure sites were selected based on airborne salinity, the presence or absence of highways (in industrial areas), and the presence or absence of volcanoes. Exposure began in April 2013; specimens were collected 1, 2, 3, 5, and 10 years later. The exposed specimens were hot-dip zinc-coated (Zn), hot-dip zinc-5% aluminum alloy-coated (5% AlZn), hot-dip 55% aluminum-zinc alloy-coated (55% AlZn), and hot-dip zinc-aluminum-magnesium alloy-coated steel sheets (ZnAlMg). The collected specimens were observed externally, photographed, and their corrosion weight losses and electrochemical properties measured. The corrosion weight loss was measured by immersing the collected specimen in a chromic acid-based rust-removal solution to remove the corrosion products, and subsequently comparing the weight of the specimen before and after the removal of the corrosion products. However, when the corrosion products of carbon steel as the matrix (red rust) were obtained over the entire area of the specimens, the plating layer was regarded as almost dissolved, and the corrosion weight loss was not measured. For electrochemical measurements, LSV of the collected specimens was performed in a 0.1 M Na2SO4 solution. For this measurement, an O-ring with a diameter of 1 cm was used to expose only the part of the specimen in contact with the solution.The corrosion weight loss in the various specimens increased with increasing airborne salinity; However, the corrosion weight loss at the exposure site where the volcano was located was the largest. Corrosion weight loss is assumed to be affected more by volcanoes than by airborne salinity. In addition, almost no effect of the presence or absence of highways was present (in industrial areas). The corrosion weight loss increased in the order of Zn, 55% AlZn, 5% AlZn, and ZnAlMg at several exposure sites, but increased in the order of Zn, 5% AlZn, ZnAlMg, and 55% AlZn at the volcanic exposure site. Therefore, the specimens at the exposure sites with and without volcanoes were compared where the average annual airborne salinity was 1 mg dm-2 day-1 or more. The results of LSV of these specimens in 0.1 M Na2SO4 solution are shown in Fig. 1. These results indicate that the corrosion products created at the volcanic exposure site inhibited the dissolution of the plating layer. In addition, aluminum is required to obtain an inhibitory effect on the dissolution of the plating layer owing to corrosion products, and this inhibitory effect improves with increasing aluminum content in the plating layer. Figure 1

A Simple in-situ Voltage Characterization Technique and Coating Methods for Developing Polymer Electrolyte Membrane Water Electrolysis Porous Transport Layer and Bipolar Plates

As climate change progresses, decarbonization becomes imperative, and hydrogen is gaining attention as a clean energy source alongside carbon [1]. Particularly, hydrogen obtained through electrolysis has the advantage of being carbon-free throughout the production process, known as green hydrogen. Currently, electrolysis is primarily conducted through alkaline and polymer electrolyte membrane methods. Polymer electrolyte membrane devices, operating effectively even at high pressures, offer advantages over alkaline electrolysis in efficiency and hydrogen production. Thus, polymer electrolyte membrane devices are essential for entering carbon neutrality [2]. However, the high voltage (~2V) and acidic operating environment in the operating condition causes component corrosion, forcing their uses of high price materials. The porous transport layer and bipolar plates of polymer electrolyte membrane devices utilize platinum-coated titanium [3]. Therefore, accurately measuring the voltage profile inside the device and replacing precious metal coated titanium can reduce device costs and offer commercial advantages. Although considerable research is ongoing, most studies require complex electrolyte solutions and custom membrane electrode assembly fabrication techniques.This study proposes a simple technique using commercial products to evaluate internal voltage profile in polymer electrolyte membrane devices and introduces materials that can replace titanium. Membrane Electrode Assembly from HIAT and Porous Transport Layer from Mott is utilized, and similar to Z. Kang et al. [4], voltages of the PTL, Catalyst Layer (CL), and Bipolar Plate (BP) relative to the cathode were measured. 0.001x0.005 mm² gold wire (California fine wire Co.) is used to measure voltage during the voltage. In some studies, voltage profiles of PEMWE stack were measured by applying voltage to the MEA instead of the bipolar plate [5]. In this study, voltage profiles inside of the cell and stack was measured. By simply placing a gold wire between the component, the voltage profile during device operation was observed. The measurements revealed a voltage small drop within the proton exchange membrane.On the other hand, the Ta-based stainless steel confirms the potential utilization of stainless steel coated materials as an alternative to titanium-based ones. According to Becker et al. [6], the voltage of the cathode during operation is approximately 0VvsRHE or less, and the bipolar plate's condition is electrochemically stable compared to the anode. Thus, a single-layer coating of PEALD TiN on stainless steel has been proposed for the cathode. On the contrary, the environment at the anode was harsher compared to the cathode, with a higher susceptibility to corrosion due to the application of high voltages (~2V). Therefore, a Ta based coating has been proposed for the anode. When conducting PEMWE experiments using Ta-coated stainless steel (SUS), it exhibited performance comparable to using Ti-based bipolar plates in both cell and stack performance. Moreover, in long-term performance, Ta-coated SUS demonstrated superior performance. Furthermore, coating Ta onto SUS PTL used in AEMWE confirmed the feasibility of replacing Ti-based PTL.References.[1] Y. Leng, P. Ming, D. Yang, C. Zhang, Stainless steel bipolar plates for proton exchange membrane fuel cells: Materials, flow channel design and forming processes, J. Power Sources. 451 (2020) 227783. https://doi.org/10.1016/j.jpowsour.2020.227783.[2] S.Y. Kang, J.E. Park, G.Y. Jang, C. Choi, Y.H. Cho, Y.E. Sung, Directly Coated Iridium Nickel Oxide on Porous-Transport Layer as Anode for High-Performance Proton-Exchange Membrane Water Electrolyzers, Adv. Mater. Interfaces. 10 (2023). https://doi.org/10.1002/admi.202202406.[3] H. Becker, E.J.F. Dickinson, X. Lu, U. Bexell, S. Proch, C. Moffatt, M. Stenström, G. Smith, G. Hinds, Assessing potential profiles in water electrolysers to minimise titanium use, Energy Environ. Sci. 15 (2022) 2508–2518. https://doi.org/10.1039/d2ee00876a.[4] Z. Kang, S.M. Alia, M. Carmo, G. Bender, In-situ and in-operando analysis of voltage losses using sense wires for proton exchange membrane water electrolyzers, J. Power Sources. 481 (2021) 229012. https://doi.org/10.1016/j.jpowsour.2020.229012.[5] A.J. McLeod, L. V. Bühre, B. Bensmann, O.E. Herrera, W. Mérida, Anode and cathode overpotentials under accelerated stress testing of a PEM electrolysis cell, J. Power Sources. 589 (2024). https://doi.org/10.1016/j.jpowsour.2023.233750.[6] H. Becker, E.J.F. Dickinson, X. Lu, U. Bexell, S. Proch, C. Moffatt, M. Stenström, G. Smith, G. Hinds, Assessing potential profiles in water electrolysers to minimise titanium use, Energy Environ. Sci. 15 (2022) 2508–2518. https://doi.org/10.1039/d2ee00876a.

Galvanic Corrosion Behavior of CFRP/Galvannealed Steel Coupling and Corrosion Inhibition

In recent years, environmental regulations for automobiles are getting stronger every year. To comply with these regulations, there is a strong need to reduce the weight of automobiles, which will lead to improve fuel economy and increase cruising range. Carbon fiber reinforced plastics (CFRP), a lightweight and high-strength material, is attracting attention as a material for the next generation of vehicles. A multi-material car body using CFRP in combination with conventional metal materials is effective in reducing the weight of automobiles. However, galvanic corrosion occurs when different materials come into electrical contact in a corrosive environment. Therefore, Inhibition of galvanic corrosion is essential for practical use of CFRP. In this study, galvanic corrosion behavior of CFRP/galvannealed steel coupling was investigated, and galvanic corrosion inhibition technology was developed. CFRP (3K plain weave, epoxy resin) and galvannealed steel (GA) were prepared. CFRP was used on the surface and cross-section. GA was used on the surface as received and the surface of base-steel where the plating layer was removed by polishing. Galvanic corrosion tests were measured in 0.1 M NaCl saturated with air. A scanning electron microscope equipped with an energy dispersive X-ray spectroscopy system was used to observe the surface of the specimens.

Investigation on Corrosion Behavior of Nickel Plated Steel in Copper Sulfate Solution and It's Applicability As a Defect Inspection

The effects of defect on the corrosion behavior of electrolytically Ni-plated steel in copper sulfate solution were investigated using electrochemical methods and surface characterization techniques. The results show that copper is deposited on the Ni surface not on steel exposed through defect. In the case of incompletely-open defects, weight gain on the Ni surface due to the copper deposition is decreased with immersion time and levelled off within 3 hours. However, the copper deposition on the Ni surface with fully-open defects exhibits continuous weight gain by vertical growth of copper layer. This is because copper deposition proceeds in the lateral direction preferentially until exposure of steel to the corrosive environment is blocked in incompletely-open defects where connection between copper deposition layers on separate Ni plating is accomplished. In contrast, in fully-open defects, vertical growth of copper deposition layers on separate Ni plating is observed. The vertical growth of the copper deposition layer in fully-open defects means that the interface between the substrate and nickel plating layers is continuously exposed to a corrosive environment, which eventually leads to delamination of the Ni plating layer from its substrate.The difference between incomplete and complete opening of defects is related to the defect area of the Ni plating layer, but verification of further electrochemical factors is required to distinguish the structural difference. These defects vary depending on the substrate and Ni plating process, but are inevitably accompanied by the subsequent forming process of Ni-plated steel. Since these defects are a major factor in determining the durability of the final products related to corrosion, it is important for manufacturers to identify and screen for these defects before moving on to the next step. Therefore, this study aims to identify the differences in copper sulfate test results according to the defect types and the correlation with product's durability due to corrosion. To verify this, analysis of the interfacial reaction through EIS (electrochemical impedance analysis) and current density and its overvoltage according to cathodic polarization related to the reaction of the copper deposition are in progress.

Corrosion Behavior of Al-Zn Alloys Fabricated By Spark Plasma Sintering

Hot-Dip Al-Zn plated steel sheets are essential materials for societal infrastructure, utilized in construction materials and conveying equipment. To further enhance the durability, a balance between the dissolution resistance of the plating layer and sacrificial corrosion protection for the base steel is crucial. In this study, we fabricated Al-Zn alloys, to analyze the influence of the microstructure refinement on the dissolution behavior.Using the planetary ball milling, powders of 65at%Al-Zn,75at%Al-Zn and 50at%Al-Zn were prepared. Powders were sintered by plasma sintering. As a comparative reference, a Hot-Dip 55mass%Al-Zn steel was prepared. To investigate corrosion behavior, immersion potential, polarization curves, and galvanic current measurements were conducted using the three-electrode method.The sintered bodies constitute a complex microstructure consisting of nano-scaled Al-rich and Zn-rich phases. Measurements of the immersion potential revealed that the sintered bodies exhibited dissolution behavior different from the conventionally used Al-Zn plating layer. The base steel was protected after the galvanic current measurements, as observed through surface analysis.

Niobium Interlayer Coating: Is it a Practical Approach to Tune the Protective Pt Loading in PEM Water Electrolyzers?

The surge in energy demand, along with global warming emissions from natural energy sources, has accelerated the transition towards renewable energies at an unprecedented rate. Among the array of potential candidates, green hydrogen stands out as a particularly promising alternative. In this regard, proton exchange membrane water electrolyzers (PEMWE) have gained widespread acceptance for green hydrogen generation due to their high efficiency and low operating temperatures. However, the relatively high cost of PEMWE components like catalysts, porous transport layer (PTL) and bipolar plates remains a challenge. For instance, commercial PTLs, comprising over 20% of the total PEM stack, often incorporate precious metal coatings to prevent passivation. In this study, we aimed to address the cost issue by replacing precious metal with non-precious metals. Niobium is known for its corrosion resistivity within acidic electrolytes [1]. Here, niobium thin films were deposited onto commercial titanium felt PTLs using pulsed laser deposition (PLD), a technique that allows precise control over film thickness and composition. Corrosion tests were conducted using an electrochemical potentiostat, with end-of-life tests employed for comparison. Results showed improvements in the performance of niobium-supported titanium felts compared to uncoated felts, indicating promise for cost optimization in PEM stacks.To deposit niobium thin films, a pulsed KrF laser with a wavelength of 248 nm was employed. Prior to each deposition, the chamber was evacuated to 5 × 10−5 mbar, followed by the introduction of specific gases such as N2 or He into the chamber during deposition. The choice of background gas is presumed to impact the composition of the niobium based thin films on PTL [2]. The corrosion resistivity of the produced niobium-coated titanium PTLs using two different gases were evaluated using a three electrodes cell. An ex-situ electrochemical setup was designed and 0.5 M H2SO4 electrolyte was used to simulate the electrolyzer media. The temperature was set at 70 °C. Chronopotentiometry was employed to assess the end-of-life characteristics of the samples over a period of at least 10 hours.The thickness of each sample was controlled by X-ray reflectivity (XRR) accompanied by the cross-section scanning electron microscopy (SEM). Corrosion tests were performed on Nb-based thin films with a thickness of 120 nm. Figure 1(a) demonstrate the chronopotentiometry results of niobium-coated samples using nitrogen and helium in compared to bare PTL. In these tests, a constant current density of 400 mA/cm² was applied for an extended duration, allowing the potential to change within the 0-10 V range. These graphs show that with the same current density, the electrochemical potential was found to be lower in niobium-coated Ti PTLs compared to the uncoated counterpart, indicative of enhanced surface conductivity post-coating. It is observed that the potential of uncoated titanium PTL rises after 3 hours of this test. In contrast, both niobium-coated films demonstrated prolonged test duration, with no cessation even after 10 hours, underscoring the advantage of niobium-coated films over bare titanium PTLs. Intriguingly, niobium films subjected to nitrogen gas exhibited a lower potential than counterparts grown in helium, suggesting the potential presence of nitride compounds replacing oxides within the thin film structure of niobium. Given that the electrical conductivity of NbN is higher than that of the NbO structure [3], it can be inferred that the presence of nitrogen may enhance both the electrical conductivity and corrosion resistance of the PTL. Figure 1 (b)-(d) reveals the SEM images of these samples after three hours of the corrosion tests. These results confirm that the surface of the niobium thin film grown in nitrogen exhibited less peeling compared to other niobium-coated and uncoated titanium PTLs. Hence, it is inferred that niobium thin films grown in a nitrogen-rich environment exhibit noteworthy potential for prolonged stability when contrasted with both the uncoated PTL and the niobium-coated PTL developed under nitrogen-deficient conditions.Fig. 1 (a) Chronopotentiometry curve obtained for different coated and uncoated titanium PTLs. The SEM images of the (b) Nb:He, (c) Nb: N2, and (d) uncoated titanium PTLs after three hours of corrosionWe would like to acknowledge the support of the Natural Sciences and Engineering Research Council of Canada, Canada Research Chair and PRIMA Québec and Niobay team for their constant support.

(Invited) Development of Novel Coatings on Stainless Steel based Bipolar Plates for Proton Exchange Membrane (PEM) Water Electrolyzer Application

Hydrogen is one of the most efficient energy carriers and can be produced by different methods. Among all the production methods, the proton exchange membrane water electrolyzer (PEMWE) is considered as the most promising technique to produce highly pure hydrogen from renewable energy sources with pure oxygen as by-products with no carbon emissions. The PEMWE technology has reached the early stages of commercial deployment while the mass production is tied to cost reduction. A PEMWE single cell comprises a membrane electrode assembly which considered as a core component where the electrochemical reactions take places in three phase boundaries. It also includes a titanium based porous transport layer (PTL) in anode side and carbon-based gas diffusion layer (GDL) in cathode side for the transportation of water and gas into and out of the cell. Additionally, bipolar plates (BPPs) with grooves provide mechanical support for the cell and distribute the water inside the cell and remove generated gases to the outlet trough flow field distribution channels. PTLs and BPPs, which are metallic components, are designed to endure the corrosive conditions present in the electrolyzer and they both needs protective coatings to stand at high voltage (<2 V), acidic media, temperature (60–80 °C) and oxygen saturated environment (anode).In this research, a modified electroplating process is used to deposit gold thin film as a protective film on both stainless steel (SS) and titanium based BPPs and PTLs, respectively. The electroplating of gold is a mature technology and easy to implement for large scale coating. This process will be impacted by many factors, such as the ingredient of plating solution, arrangement of electrodes, current distribution, and operating parameters. In addition, pre-treating the surface plays an important role to develop the durable thin films with proper adhesion. The gold striking underlayer on the SS substrate passivated the surface oxides and facilitated a dense electroplated chromium layer. Furthermore, a uniform gold protective layer was electroplated on the chromium coated substrate to achieve a promising anti-corrosive property. To evaluate the impact of pre-treatment and the anti-corrosion properties of the developed coating, different physical and electrochemical characterization techniques are conducted. As a result, The Au/Cr/Au coating on the SS substrate showed corrosion current density of 0.84 µA/cm2 and lower degradation as compared to without gold striking underlayer.The surface morphology and the crystallinity and phase analysis are investigated by scanning electron microscopy and X-ray diffraction (XRD), respectively. X-ray photoelectron spectroscopy (XPS) is used to study the surface properties and the bonds between the elements. The contact resistance also is studied under different pressures. In addition, traditional lab-scale durability analysis, using stagnant liquid electrolyte and three-electrode cell setups, might not provide such a precise information for PEM water electrolyzer. The three-electrode setup does not include crucial parameters relating to real cell-operating conditions or contributions to the PTL by other key cell components such as the membrane, catalyst layer, ionomer, and bipolar plates. Flow electrochemical setup is developed in our lab and is used to run the accelerate stress test to check the durability of the coated samples. Potentiodynamic, chronoamperometry and impedance also used to evaluate the samples. Figure 1. (a) Schematic of gold electroplating on the SS substrate, (b) SEM image and EDX analysis of Au/Cr/Au coating.We would like to acknowledge the support of the Natural Sciences and Engineering Research Council of Canada, Canada Research Chair and Mitacs Accelerate program and Intlvac Thin Film for their constant support. Figure 1

Anodic Dissolution of Stainless Steel Covered with Oxide Thin Film in PEFC Simulated Environment

Stainless steels have been considered for the bipolar plate materials in fuel cell stack components to reduce the cost of the fuel cell vehicles (FCVs). However, the contact resistance between the gas diffusion layer (GDL) and bipolar plates fabricated by the stainless steels may show large values due to the formation of passive film on the stainless steels 1,2). Further, the anodic dissolution of stainless steels may occur in FC operation, leading to the increase of the contact resistance between the GDL and bipolar plates. In the present study, we developed the surface treatment method for bipolar plates fabricated by the stainless steels using oxide thin film. The dissolution behavior of stainless steels with oxide thin film was investigated in the polymer electrolyte fuel cell (PEFC) simulated environment. In addition, the contact resistance between the GDL and stainless steels with oxide thin film was evaluated before and after corrosion test. In the present study, the stainless steel sheets covered with oxide thin film were fabricated by the vacuum evaporation. The dissolution behavior of these samples was investigated by an electrochemical measurement by a three-electrode system. To simulate PEFC environment, the test solution containing 3 ppm NaF and 10 ppm NaCl was used as the electrolyte solution. The pH of the test solution was adjusted at pH 3. The stainless steel sheet or stainless steel sheet covered with oxide thin film was used as the working electrode. The platinum wire and the KCl-saturated Ag/AgCl electrode were used as the counter electrode and reference electrode, respectively. The potentiostanic polarization was performed at an arbitrary potential. The electrochemical impedance was measured under potentiostanic polarization. In this measurement, the AC potential amplitude was 10 mV and the frequency range was 100 kHz to 0.01 Hz at 5 frequencies per decade. The potentiostatic polarization of the stainless steel sheets and stainless steel sheet covered with oxide thin film was carried out at an arbitrary potential to evaluate the corrosion behavior of each sample. In the stainless steel sheet, the increase and the decrease in the current density were observed under potentiostatic polarization, implying the dissolution of Fe ions or the dissolution and repassivation of the passive film. The time variation of the current density for stainless steel sheet covered with oxide thin film under potentiostanic polarization suggested that the dissolution rate of Fe ions was small under potentiostatic polarization. Based on these results, we measured the impedance spectra of the stainless steel sheet covered with oxide thin film under potentiostanic polarization. In this case, the time variation of impedance was investigated by 3D plots of impedance to determine the instantaneous impedance at arbitrary measurement time 3,4). The charge transfer resistance of each sample, which was estimated by curve fitting using equivalent circuit, at arbitrary measurement time was discussed to examine the corrosion mechanisms. References (1) A.Miyazawa, T. Himeno, A. Nishikata, J. Power Sources, 220, 199 (2012).(2) A.Miyazawa, E Tada, A. Nishikata, J. Power Sources, 231, 226 (2013).(3) Z.B. Stoynov, B.S. Savova-Stoynov, J. Electroanal. Chem. 183, 133 (1985).(4) Y.Hoshi et al., Corros. Sci., 232, 112018 (2024). Acknowledgement This is based on results obtained from a project, JPNP20003, subsidized by the New Energy and Industrial Technology Development Organization (NEDO).

Advancing PEMFC Bipolar Plate Design: Biomimetics, Simulation, and Surrogate Modeling By Deep Neural Networks for Optimized Performance

Proton exchange membrane fuel cells (PEMFC) represent a promising solution in the transition to cleaner and more sustainable energy sources. Their efficient and environmentally friendly operation relies in part on the performance of bipolar plates. These key components play a crucial role in the uniform distribution of reactants and the evacuation of products, directly impacting the overall efficiency of the fuel cell. By optimizing the design of bipolar plates, particularly through simulation, it is possible to significantly improve the operation of these cells. The use of biomimetics design in bipolar plate design offers an innovative approach to maximize active species concentration, facilitate product evacuation, and reduce pressure drop. Drawing inspiration from natural structures and mechanisms, such as leaf vascular networks, optimized channel configurations can be designed to promote uniform and efficient flow of reactants and products across the plate. This approach not only enhances overall fuel cell performance but also reduces environmental footprint by optimizing resource utilization. The use of multiphysics simulation provides a valuable tool to predict the behavior of PEMFCs based on operational parameters such as gas fluxes and operating voltage/current density. Focusing on the operating power per unit area of the bipolar plate's active surface, as well as the distribution of partial pressures in gas, water, and temperature within the cell, simulation allows for a thorough understanding of the complex interactions within the system. This enables optimization of operating conditions to enhance energy efficiency and durability of PEMFCs. Developing a surrogate model, with Comsol Multiphysics, for bipolar plate design holds significant interest in creating an application able of real-time prediction of the impact of minor geometry modifications on local concentration distributions within the channels of the bipolar plate and gas diffusion layers (GDLs) using deep neural networks. This approach enables rapid assessment of design variations, facilitating optimization efforts and informed decision-making. By harnessing the power of deep learning, the surrogate model enhances efficiency in the design process, streamlining iterations and minimizing experimental testing requirements. This innovative approach accelerates the development of high-performance fuel cell systems. The developed strategy combines biomimetics for designing optimized bipolar plates, multiphysics simulation to predict PEMFC behavior, and the development of a surrogate model to accelerate prototyping phase.

Evaluation of Corrosion Resistance of Au-Plated Titanium Bipolar Plates for Polymer Electrolyte Membrane Water Electrolysis

Polymer Electrolyte Membrane Water Electrolysis (PEMWE) is one of the most promising on-site hydrogen production methods using renewable energy because of its fast start-up and higher current density compared to alkaline water electrolysis (AWE). The urgent issues related to the widespread use of PEMWE are cost reduction of components and durability. Currently, titanium (Ti) is the most common material for bipolar plates for PEMWE and is coated with gold (Au) or platinum (Pt) to reduce contact resistance and improve corrosion resistance. Therefore, it is a very expensive component, accounting for about 50% of the PEMWE stack cost. Optimizing the amount of noble metal used in the coating is one way to reduce the cost of bipolar plates. In this study, the corrosion resistance and contact resistance of Ti bipolar plates with different Au plating thicknesses are compared to determine the optimal amount of Au used in coatings for bipolar plates.Commercial pure Ti plate (Ti 99.5%) was used as a test specimen. The Ti plate with 0.1 mm thickness was machined into a rectangular shape (20 mm x 50 mm) and electroplated with Au of different thicknesses (plating thickness: 0, 0.1, 0.3, 1.0 μm). The corrosion resistance of Au-plated Ti bipolar plates was evaluated by potentiostatic polarization at 2.0 V (vs. RHE) for 24 hours in a sulfuric acid solution (H2SO4, pH 3.0) at 353 K simulating the PEMWE anode environment. After the polarization test, the concentration of Ti in the test solution was determined by Inductively Coupled Plasma Mass Spectrometry (ICP-MS). The contact resistance was measured according to the four-terminal method between Au-plated Ti bipolar plates and the porous transport layer (PTL) before and after the potentiostatic polarization test. Pt-plated titanium sintered fiber (2GDL-06N-030-PT05, Becart Co. Ltd.) with a Pt-plating thickness of 0.5 μm was used as the PTL. The surfaces of the specimens before and after the potentiostatic polarization were observed using the Ultra-Low Voltage Scanning Electron Microscope (ULV-SEM) to calculate the coverage of Au plating. Elemental qualitative analysis of the specimen surfaces was also carried out by Energy Dispersive X-ray Spectroscopy (EDX).The Ti concentration determined by ICP-MS after the potentiostatic polarization test was 4 μg dm-3 for the unplated Ti and 2 μg dm-3 for the Au plated-Ti (0.1 μm), while it was below the limit of quantification (<1 μg dm-3) when the Au plating thickness was 0.3 μm or higher. The contact resistance of unplated Ti increased by 22.0 mΩ cm2 at 2.0 MPa after polarization. On the other hand, the increase in contact resistance of Au-plated Ti was less than 0.1 mΩ cm2, regardless of the Au-plating thickness. Fig.1 shows SEM images (a) and EDX spectra (b)-(c) of the surface of the Au-plated Ti(0.1 μm) after polarization. It can be seen that there is a plating defect with a diameter of about 1 μm on the surface. EDX analysis results revealed that almost the entire Ti surface was coated with a straight Au plating layer, with only the defective areas of the underlying Ti exposed. The coverage of the Au-plated Ti (0.1 μm) was 99.86%, calculated from an area of 1 mm2 by binarizing the multiple backscattered electron images. The coverage of the Au-plated Ti (0.3 μm) is 99.98%, which indicates fewer plating defects than the Au-plated Ti (0.1 μm). Therefore, it is considered that the plating defects in the Au-plated Ti (0.1 μm) preferentially corroded and Ti was leached out. On the other hand, the contact resistance is almost the same regardless of the Au plating thickness or coverage and does not increase immediately provided that most the Ti surface is covered with Au plating. These results indicate that thinner Au coating with higher coverage on Ti bipolar plates for PEMWE can reduce the amount of Au used in the coating. Figure 1

Direct Epitaxial Growth of Polycrystalline MOF Membranes on Cu Foils for Uniform Li Deposition in Long‐life Anode‐free Li Metal Batteries

AbstractAnode‐free Li‐metal battery (AFLMB) is being developed as the next generation of advanced energy storage devices. However, the low plating and stripping reversibility of Li on Cu foil prevents its widespread application. A promising avenue for further improvement is to enhance the lithophilicity of Cu foils and optimise their surfaces through a metal–organic framework (MOF) functional layer. However, excessive binder usage in the current approaches obscures the active plane of the MOF, severely limiting its performance. In response to this challenge, MOF polycrystalline membrane technology has been integrated into the field of AFLMB in this work. The dense and seamless HKUST‐1 polycrystalline membrane was deposited on Cu foil (HKUST‐1 M@Cu) via an epitaxial growth strategy. In contrast to traditional MOF functional layers, this binder‐free polycrystalline membrane fully exposes lithophilic sites, effectively reducing the nucleation overpotential and optimising the deposition quality of Li. Consequently, the Li plating layer becomes denser, eliminating the effects of dendrites. When coupled with LiFePO4 cathodes, the battery based on the HKUST‐1 membrane exhibits excellent rate performance and cycling stability, achieving a high reversible capacity of approximately 160 mAh g−1 and maintaining a capacity retention of 80.9 % after 1100 cycles.

Direct Epitaxial Growth of Polycrystalline MOF Membranes on Cu Foils for Uniform Li Deposition in Long-life Anode-free Li Metal Batteries.

Anode-free Li-metal battery (AFLMB) is being developed as the next generation of advanced energy storage devices. However, the low plating and stripping reversibility of Li on Cu foil prevents its widespread application. A promising avenue for further improvement is to enhance the lithophilicity of Cu foils and optimise their surfaces through a metal-organic framework (MOF) functional layer. However, excessive binder usage in the current approaches obscures the active plane of the MOF, severely limiting its performance. In response to this challenge, MOF polycrystalline membrane technology has been integrated into the field of AFLMB in this work. The dense and seamless HKUST-1 polycrystalline membrane was deposited on Cu foil (HKUST-1 M@Cu) via an epitaxial growth strategy. In contrast to traditional MOF functional layers, this binder-free polycrystalline membrane fully exposes lithophilic sites, effectively reducing the nucleation overpotential and optimising the deposition quality of Li. Consequently, the Li plating layer becomes denser, eliminating the effects of dendrites. When coupled with LiFePO4 cathodes, the battery based on the HKUST-1 membrane exhibits excellent rate performance and cycling stability, achieving a high reversible capacity of approximately 160 mAh g-1 and maintaining a capacity retention of 80.9 % after 1100 cycles.

Effect of flash-Ni plating layer on interfacial behavior of Zn-Al-Mg coating/DH780 steel

The Zn-Al-Mg coated DH780 high-strength steel with a flash-Ni plating layer was used in this study. The occurrence state of Ni element at the coating/steel interface was investigated, and the relationship between Mn and Si elements and the internal oxidation at the interface was discussed. The results show that Ni existed between the Fe2Al5 layer and the steel substrate in the form of Fe(Ni) solid solution and Ni elemental substance. The mutual diffusion rate between Fe and Al was greatly reduced after flash-Ni plating, and the continuity of Fe2Al5 layer of the flash-Ni-plated steel was slightly lower than that of the Ni-free steel. Moreover, the diffusion coefficients of Mn and Si in the Ni layer were lower than those in the steel substrate, which indicated that the Ni layer significantly inhibited the diffusion of Mn and Si to the surface. The average depth of internal oxidation was reduced by 70.8 % after flash-Ni plating, the average Mn, Si and O contents at the interface after flash-Ni plating were reduced by 19.6 %, 6.1 % and 22.7 %, respectively, which indicated that the flash-Ni plating layer can isolate the steel substrate from the annealing atmosphere, inhibit the internal oxidation and interfacial enrichment of Mn and Si, especially for Mn. Therefore, the flash-Ni plating layer can improve the wettability of high-strength steel sheets during continuous annealing.

Recycled industrial waste silicon steel as high-performance electrode for oxygen evolution reaction using electroless plating surface modification

Exploring the large-area, cost-effective, and high-performance electrocatalyticoxygen evolution reaction (OER) electrode for water splitting is of great significance. Inspiring from the ‘waste to resource’ toward the circular economy, herein, the waste silicon steels (SS) were transformed into high-performance CoxFe3-xP/SS OER electrode through a facile electroless plating method. The plating layer of CoxFe3-xP not only endows the CoxFe3-xP/SS with outstanding electrocatalytic OER activity but also improves the corrosion resistance and stability of CoxFe3-xP/SS. The obtained Co2Fe1P/SS electrode exhibits the lowest overpotential of 244 mV at a current density of 10 mA/cm2 in 1 M KOH with a low Tafel slope of 48.7 mV/dec. Even at high current densities and in 6 M KOH and alkaline seawater (seawater + 1 M KOH), the Co2Fe1P/SS electrode also shows relatively low overpotentials, as well as high long-term durability. Specially, a large-area Co2Fe1P/SS OER electrode(40 × 40 cm2)was successfully prepared via the electroless plating approach. Toward the CoxFe3-xP/SS, the bimetallic Co-Fe synergies and phosphating effect promote the exposure of active sites and charge transfer. In addition, generated M(OH)x/MOOH (M = Co or Fe) species during OER activation could synergize with CoxFe3-xP and contribute excellent catalytic activity and stability.

Examining the Role of Surface Temperature on Boundary Layer Stability and Transition to Turbulence

This study investigates the influence of varying surface temperature on the critical Reynolds number to understand the onset of turbulence in the boundary layer of a flat plate. Computational Fluid Dynamics (CFD) simulations in ANSYS Fluent have been utilized for the purpose of this study. The study systematically varies surface temperature to measure its impact on flow stability. The research demonstrates that an increase in surface temperature results in a lower critical Reynolds number (leading to an earlier transition from laminar to turbulent flow) by modeling air as the working fluid and applying the k-ω SST turbulence model. The results align with theoretical predictions which highlight the destabilizing effect of temperature-induced viscosity changes. This finding has practical implications for aerospace engineering, HVAC systems, and environmental modeling where controlling turbulence can optimize performance and energy efficiency. The study acknowledges limitations due to the use of a 2D model and suggests future work using 3D simulations and other flow conditions to expand the applicability of the findings.

Overdamping of vibration resonances by liquid crystal elastomers

This work aims to compare the capability of vibration attenuation by standard elastomeric polymers, and by the new anomalously damping nematic liquid crystal elastomer. We use the most mainstream materials in both categories, and design two testing platforms: the ASTM-standard constrained layer plate resonance geometry, and the attenuation of resonances in a commercial device (electric drill) where the damping polymers were inserted into the casing. In the standard plate resonance testing, we find that LCE outperforms all standard damping materials, moreover, it brings the vibrating plate into the overdamped condition, which is unique for a non-fluid dissipative system. In the attenuation of high-frequency vibrations of a device, we also found LCE dissipates these vibrations much better, although we did not find the optimal insertion configuration for the damping polymer, and did not reach overdamping.

Prediction of non-magnetic metal sphere radius using real part slope of inductance

The existing eddy current measurement thickness technology is mainly for one or more layers of metal plate. However, in real life, the radius of spherical metal is also a critical parameter, so using an eddy current sensor to measure it is also an important research topic. In this paper, real part slope of inductance is used as the characteristic value to characterize the radius of the non-magnetic metal sphere. Compared with the traditional real part of inductance, the addition of slope improves the accuracy and stability of detection data. The experimental results show that the maximum error rate of radius measurement is less than 2%, and the overall data stability is good, which can meet the measurement requirements.

Analysis of the thermomechanical behavior of a three-layer rectangular plate of the ceramic-metal-ceramic structure due to non-stationary convective heating

A rectangular isotropic layered plate is considered, which is convectively heated by the external environment. The thermal stress state of the plate is determined in two stages. At the first stage, the nonstationary temperature field is determined from the ratios of the non-stationary thermal conductivity problem. At the second stage, using the five-modal mathematical model of the shear theory of thermoelasticity, the parameters of the stress-strain state are determined.