Excellent Contact Research Articles

Corrosion Resistance and Conductivity of Ta-Nb-N-Coated 316L Stainless Steel as Bipolar Plates for Proton Exchange Membrane Fuel Cells

The large-scale application of stainless steel (SS) bipolar plates (BPs) in proton exchange membrane fuel cells (PEMFCs) is mainly limited by insufficient corrosion resistance and electrical conductivity. In this work, Ta-Nb-N coatings were prepared on 316L SS substrates by unbalanced magnetron sputtering to improve corrosion resistance and conductivity. The Ta-Nb-N coatings had a dense structure without obvious defects. In simulated PEMFC cathode environments consisting of 0.5 M H2SO4 + 2 ppm HF at 70 ± 0.5 °C, which is harsher than the U.S. Department of Energy specification, the corrosion current density of Ta-Nb-N-coated BPs was reduced to 2.2 × 10−2 μA·cm−2. Ta-Nb-N-coated samples showed better electrical conductivity than 316L SS, which had an excellent interfacial contact resistance of 9.2 mΩ·cm2. In addition, the Ta-Nb-N-coated samples had a water contact angle of 100.7°, showing good hydrophobicity for water management. These results indicate that Ta-Nb-N coatings could be a promising material for BPs.

Substrate temperature dependent crystal structure and deep-ultraviolet photodetection of ZnGa2O4 thin films * *Project supported by This work was supported by the National Natural Science Foundation of China (No. 12074044), the Fund of State Key Laboratory of Information Photonics and Optical Communications (IPOC2021ZT05), and the Fundamental Research Funds for the Central Universities (BUPT, 2023ZCJH1).

Zinc gallate (ZnGa2O4) is a promising material for deep-ultraviolet (DUV) photodetectors, owing to its wide bandgap and high transparency. However, the effect of substrate temperature on the structural and optical properties of ZnGa2O4 thin films prepared by magnetron sputtering is not well understood. Here, we report a systematic study of the influence of substrate temperature on the crystal quality, stoichiometry, bandgap, and photodetection performance of ZnGa2O4 thin films deposited on sapphire substrates. We find that the films undergo a phase transition from amorphous to polycrystalline at 300 °C, and then to single crystalline at 500 °C, accompanied by an increase in the bandgap from 4.6 to 4.9 eV. We also fabricate metal-semiconductor–metal photodetectors based on the ZnGa2O4 thin films with Ti/Au electrodes, which exhibit excellent Ohmic contact and high light-to-dark current ratio. The photodetectors show remarkable and stable DUV response, with the highest performance achieved at a substrate temperature of 650 °C. Our results demonstrate the crucial role of substrate temperature in tailoring the crystal structure and DUV photodetection of ZnGa2O4 thin films, and provide a facile route for optimizing their performance.

Robust Synthesis of Hydrophobic Biosorbent for Effective Oil/Organic Solvent Cleanup

AbstractDifferent carbon‐based sorbents are widely used for the refinement of industrial as well as domestic effluent because of their availability, low cost, and excellent hydrophobicity. In this article, the activated biosorbent (ABs) material was prepared and applied to develop a membrane (ABs@Membrane) and sponge (ABs@Sponge) for effective oil and organic solvent cleanup from water mixtures. The one‐pot process was adopted to prepare ABs material by the simple carbonization of naturally available cotton and biowaste chitosan with sulphuric acid. The fabricated ABs@Membrane and ABs@Sponge showed excellent hydrophobicity with excellent water contact angle, i. e., 138.06° and 135.58°, respectively. Moreover, the synthesized ABs@Sponge showed excellent oil/organic solvent absorption capacity in the presence of water, i. e., 40 gm of machine oil and 62 gm of chloroform. Whereas the synthesized ABs@Membrane material showed excellent oil‐water separation efficiency (>90 %) and water flux (219.29 Lm−2 h−1) with a good oil rejection ratio (>91 %). The synthesized ABs@Membrane and ABs@Sponge material showed excellent recyclability performance up to 5th no of consecutive cycles. The straightforward synthesis and fabrication of ABs@Membrane and ABs@Sponge materials with excellent oil rejection ratio and oil/organic solvent separation performance open a new window in the effluent water treatment application.

Mussel-Inspired Self-Adhesive and Tough Hydrogels for Effectively Cooling Solar Cells and Thermoelectric Generators.

Adhesive hydrogel-based evaporative cooling, which necessitates no electricity input, holds promise for reducing energy consumption in thermal management. Herein, inspired by the surface attachment of mussel adhesive proteins via abundant dynamic covalent bonds and noncovalent interactions, we propose a facile strategy to fabricate a self-adhesive cooling hydrogel (Li-AA-TA-PAM) using a copolymer of acrylamide (AM) and acrylic acid (AA) as the primary framework. The monomers formed hydrogen bonds between their carboxyl and amide groups, while tannic acid (TA), rich in catechol groups, enhances the adhesion of the hydrogel through hydrogen bonding. The hydrogel demonstrated strong adhesion to various material surfaces, including plastic, ceramic, glass, and metal. Even under high-speed rotation, it still maintains robust adhesion. The adhesion strength of the Li-AA-TA-PAM hydrogel to aluminum foil reached an impressive value of 296.875 kPa. Interestingly, the excellent contact caused by robust adhesion accelerates heat transfer, resulting in a rapid cooling performance, which mimics the perspiration of mammals. Lithium bromide (LiBr) with hydroactively sorptive sites is introduced to enhance sorption kinetics, thereby extending the effective cooling period. Consequently, the operation temperature of commercial polycrystalline silicon solar cells was reduced by 16 °C under an illumination of 1 kW m-2, and the corresponding efficiency of energy conversion was increased by 1.14%, thereby enhancing the output properties and life span of solar cells. The strategy demonstrates the potential for refrigeration applications using viscous gels.

Low-temperature fabrication of boron-doped amorphous silicon passivating contact as a local selective emitter for high-efficiency n-type TOPCon solar cells

Tunnel oxide passivating contact (TOPCon) solar cells (SCs) currently dominate the photovoltaic industry but grapple with efficiency challenges. A primary concern is the direct contact between front-sided metal electrodes and boron emitters, resulting in substantial carrier recombination losses and limiting further efficiency improvements. Here, we introduce a low-temperature approach to deposit a local boron-doped amorphous silicon [a-Si:H(p)] between front-sided metal electrodes and boron emitters. This method, avoiding issues associated with high-temperature processes, demonstrates excellent passivation and contact properties, featuring the lowest contact resistivity (< 1 mΩ·cm2) and a low saturation current density (< 400 fA/cm2). The outstanding passivation and contact properties remain robust even with variations in diborane flow rates during a-Si:H(p) fabrication, annealing temperatures, and sheet resistances of boron emitters. We elucidate the factors contributing to the enhanced passivation observed in boron emitters with a-Si:H(p) through a combination of simulations and experiments. The a-Si:H(p) layer between boron emitters and metal electrodes acts as a protective barrier, preventing the diffusion of metal atoms and suppressing carrier recombination. A heterojunction is formed between a-Si:H(p) and the boron emitter, facilitating electric-field passivation. Consequently, the TOPCon SCs incorporating a-Si:H(p) achieve an efficiency of 24.50%, surpassing their counterparts without a-Si:H(p) (23.11%). This work utilizes low-temperature technology to achieve fully passivated contact, providing insights for the development of high-efficiency TOPCon SCs.

Flat-tube solid oxide stack with high performance for power generation and hydrogen production

This study presents the design, fabrication, and evaluation of a high-performance flat-tube solid oxide cell (FT-SOC) stack, which demonstrates exceptional power generation and hydrogen production capabilities. Comprising three large-sized FT-SOCs, each with an active area of 60 cm2, the stack was tested at 750 °C. It achieved a peak power density of 1.222 W/cm2 in fuel cell (FC) mode and an electrolysis current density of 1.283 A/cm2 at an average voltage of 1.3 V in electrolysis cell (EC) mode, marking the highest reported values for FT-SOC stacks to date. These results surpass the performance of most large-sized planar SOC stacks. Post-operation analysis revealed excellent interfacial contact between components, contributing to the stack's high performance. This study underscores the potential of FT-SOCs in efficient power generation and electrolytic energy storage applications, providing insights that could facilitate their industrial application.

Binder-free Cu1.9Bi0.1Se@SWCNT hybrid anodes for lithium-ion and sodium-ion batteries

The rapid growth of portable electronic devices, electric vehicles, and grid-scale energy storage systems has accelerated the demand for enhancing existing materials and innovating new materials in rechargeable battery technologies. Li-ion batteries have dominated the energy storage field among the various battery systems. Na-ion batteries have emerged as promising candidates due to their similarities to Li-ion battery chemistry, low cost, and environmental sustainability. This study explores the potential advantages of synthesizing the binder-free Cu1.9Bi0.1Se@SWCNT heterostructure directly on the copper collector surface. A crucial aspect of this research is the intentional use of nanostructuring during synthesis. This technique capitalizes on the benefits of greater surface area, enhanced electron transport, and superior ionic conductivity. The synthesis method not only ensures excellent electrical and mechanical contact with the collector but also omits the need for a binder, offering a potential for improved overall performance in Li-ion and Na-ion batteries. The electrodes were synthesized using a simple and cost-effective physical vapor deposition method. The structural, morphological, and electrochemical properties of the electrodes were characterized. The binder-free Cu1.9Bi0.1Se@SWCNT electrode with 25 % SWCNT content exhibits excellent performance in Li-ion half cells, maintaining a high energy capacity of 556 mAh g−1 at 0.1 A g−1 over 100 cycles and 244 mAh g−1 at 0.5 A g−1 over 750 cycles. However, in the Na-ion battery system, the performance is notably poorer, revealing challenges and limitations. Most likely, the larger size of sodium ions posed difficulties in intercalation within the anode material structure.

High Energy Density Solid‐State Lithium Metal Batteries Enabled by In Situ Polymerized Integrated Ultrathin Solid Electrolyte/Cathode

AbstractSolid‐state batteries (SSBs) are regarded as the most promising next‐generation energy storage devices due to their potential to achieve higher safety performance and energy density. However, the troubles in the preparation of ultrathin solid‐state electrolytes (SEs) as well as the resultant compromise in mechanical strength greatly limit the safety application of SSBs. Herein, a novel in situ polymerized integrated ultrathin SE/cathode design is developed. The ultrathin ceramic layer supported on the cathode serves not only as a rigid scaffold to prevent direct contact between the cathode and anode but also as active inorganic fillers to enhance the mechanical properties of in situ polymerized SE film. The unique Li‐ion coordination environments as well as the Li hopping mechanism profoundly promote fast ion transport in composite SEs. The in situ polymerized SEs simultaneously achieve the balance in ultrathin thickness (10 µm), fast ion transport (0.65 mS cm−1), superior Young's modulus (66.8 GPa), and excellent interface contact. The pouch cells with practical Li||LiNi0.8Co0.1Mn0.1O2 configuration achieve an ultrahigh volumetric energy density of 1018 Wh L−1 and safety performance. The in situ polymerized integrated ultrathin SE/cathode design exhibits great promise for the practical application of SSBs with high energy density and safety performance.

Phase-separated stretchable conductive nanocomposite to reduce contact resistance of skin electronics

Skin electronics, facilitating a high-quality interface between external devices and human skin for recording physiological and/or electrophysiological signals as well as delivering external electrical and/or mechanical energy into the human body, has shown significant progress. However, achieving mechanically conformal contact and electrically low contact resistance at the device-skin interface remains challenging. Here, we propose a material strategy to potentially address such an issue by using phase separation of silver nanowires and silver nanoparticles (Ag NWs and Ag NPs) within a stretchable conductive nanocomposite (NC). This phase-separated NC ensures low contact resistance and high conductivity, which are key requirements in skin electronics, while maintaining excellent mechanical contact with the skin. To achieve phase separation, we hydrophobically treated the surfaces of Ag NWs and Ag NPs. Then, as the NC solidified, the solvent contained in the NC was slowly evaporated to sufficiently precipitate Ag NPs within the NC. As a result, the phase-separated NC exhibited high conductivity (~ 18,535 S cm−1), excellent stretchability (~ 80%), and low contact resistance on both the top and bottom NC surfaces (average ~ 0.132 Ω). The phase-separated NC has enabled implementation of high performance skin-mounted devices, including strain sensors, electrophysiological sensors, and a wearable heater.

Simple photocleavable indoline-based materials for surface wettability patterning

Surface wettability is controlled through UV light-induced photocleavage of indoline-based small molecules. Simple, solution-based deposition enables photopatterning with excellent spatial control and contact angle changes up to 61°.

High-energy sputtering for the deposition of a conductive and adherent single molybdenum layer for solar cell applications

Molybdenum (Mo) thin films are thought to be an excellent back contact for CuIn1-xGaxSe2 (CIGS) solar cells. Mo films require high conductivity and good adhesion to glass substrates; however, these characteristics cannot be combined in sputtered Mo under the same deposition conditions. Direct current Magnetron Sputtering (DcMS) and High-Power Impulse Magnetron Sputtering (HiPIMS) were used to deposit Mo films on glass substrates, and the effects of working pressure and substrate bias on their characteristics were investigated. To begin, single layers of Mo were produced at pressures ranging from 0.2 to 1.4 Pa. The Mo films deposited at the lowest working pressure of 0.2 Pa were then subjected to a negative substrate bias varying from -50 to -200 V. All of the HiPIMS films adhered well to the glass substrate, whereas the DcMS films deposited at various pressures showed poor adhesion. Furthermore, our findings demonstrated that applying a negative substrate bias reduced the resistivity of Mo films to the lowest values of 2.56 × 10−5 Ω.cm and 2.771 × 10−5 Ω.cm, respectively, for the HiPIMS and DcMS-deposited films, while improving the adhesion of the DcMS-samples due to the development of films with homogenous stress distribution.

Ductile adhesive elastomers with force-triggered ultra-high adhesion strength.

Elastomers play a vital role in many forthcoming advanced technologies in which their adhesive properties determine materials' interface performance. Despite great success in improving the adhesive properties of elastomers, permanent adhesives tend to stick to the surfaces prematurely or result in poor contact depending on the installation method. Thus, elastomers with on-demand adhesion that is not limited to being triggered by UV light or heat, which may not be practical for scenarios that do not allow an additional external source, provide a solution to various challenges in conventional adhesive elastomers. Herein, we report a novel, ready-to-use, ultra high-strength, ductile adhesive elastomer with an on-demand adhesion feature that can be easily triggered by a compression force. The precursor is mainly composed of a capsule-separated, two-component curing system. After a force-trigger and curing process, the ductile adhesive elastomer exhibits a peel strength and a lap shear strength of 1.2 × 104 N m-1 and 7.8 × 103 kPa, respectively, which exceed the reported values for advanced ductile adhesive elastomers. The ultra-high adhesion force is attributed to the excellent surface contact of the liquid-like precursor and to the high elastic modulus of the cured elastomer that is reinforced by a two-phase design. Incorporation of such on-demand adhesion into an elastomer enables a controlled delay between installation and curing so that these can take place under their individual ideal conditions, effectively reducing the energy cost, preventing failures, and improving installation processes.

Design and transmission performance analysis of planthopper hip joint gear

To enhance the efficiency and load-carrying capacity of the jumping robot’s transmission system, the transmission characteristics of the planthopper hip gear were analyzed. The analysis revealed that the gear pair exhibited low transmission errors, high transmission efficiency, and significant torque capacity, making it suitable for high-speed, high-precision, and high-power density transmissions. A bionic design study of the jumping robot’s gear was conducted, drawing inspiration from the planthopper hip gear’s tooth shape and profile. A logarithmic spiral was assumed as the tooth profile based on its consistent pitch angle and curvature gradient characteristics. Parameters of the tooth profile of the bionic gear were calculated, and equations for the tooth surface were derived. A three-dimensional model of the bionic gear was constructed, and both its transmission efficiency and error were calculated. Using the finite element method, theoretical formulas for contact stress and bending stress in the bionic gear were deduced. The distribution characteristics of both bending and contact stress were analyzed, demonstrating that the bionic gear used in high-performance jumping robots possesses low transmission error, high transmission efficiency, and excellent contact strength, providing a theoretical foundation for enhancing their jumping capabilities.

Efficient photocatalytic hydrogen evolution based on a Z-scheme 2D LaVO4/2D Mo-doped SV-ZnIn2S4 heterojunction

2D ultrathin Z-scheme heterojunctions with excellent contact interfaces and robust internal electric fields are synthesized based on LaVO4 and ZnIn2S4 (ZIS) and exhibit outstanding photocatalytic hydrogen evolution performance.

Insights into the ecotoxicological effects associated with imidacloprid: A Review

Imidaclopridis a neonicotinoid insecticide contently used in agricultural fields with excellent systemic and contact activity, used in the largest volume worldwide against sucking pests of Diptera, Coleoptera and Lepidoptera in chilly, cotton, grapes, groundnut, okra, paddy, sugarcane, sunflower and tomato. It functions as an agonist at the acetylcholine receptors of the pest, affecting invertebrate movements, leading to palsy and mortality. It has an approbative toxicity profile, due to its poor penetration of the blood–brain barrier in vertebrates. Moreover, it does not exhibit any mutagenic, carcinogenic, teratogenicor immunotoxic properties. Besides these boons of imidacloprid, several studies reported the high leaching potential and persistence of imidacloprid in the ecosystem, creating threat to non-targeted organisms by altering their biochemical and reproductive processes.

Electrical and ionic conductivity of Li2O-B2O3-Al2O3 glass electrolyte for solid-state batteries

Solid-state electrolyte is a key component for all-solid-state lithium-ion batteries. The Li2O-B2O3-Al2O3 has been prepared, which is co-sinterable with electrode due to its low sintering temperature (520 °C). The as-prepared Li2O-B2O3-Al2O3 reveals glass transition temperature of 420 °C and crystallization temperature of 462 °C. The Li2O-B2O3-Al2O3 possess the reasonable electrochemical performances such as lithium-ion conductivity of 3.075 × 10−5 S/cm, activation energy of 0.72 eV, electronic conductivity of 4.102 × 10−5 S/cm. It is attributed to the particle morphology, grain-to-grain bonding and non-bridging oxygen. Our finding demonstrates that Li2O-B2O3-Al2O3 is an effective breakthrough in solid electrolyte for good electrochemical performances as well as excellent interfacial contact through co-sintering.

Consequences of thermite welding on the microstructure of the heat affected zone of a carbide-free bainitic steel rail

Due to their excellent Rolling Contact Fatigue (RCF) resistance, Carbide-Free Bainitic (CFB) steels rails have recently received increasing attention to replace pearlitic steels in the railways sector. This is mainly attributed to the TRansformation Induced Plasticity (TRIP) effect, which mechanically transforms austenite into martensite during wheel/rail contact. However, the welding of these carbide-free bainitic steels could lead to a local decrease in mechanical properties, as well as RCF resistance, inside the Heat Affected Zone, which limits the use of these steels. The present work aims to explain the reason of the loss of RCF resistance of these steels after welding. To do so, the microstructure evolution along the Heat Affected Zone is investigated thoroughly, and is linked with its thermal history.In the most critical areas in terms of RCF resistance, the consumption of all retained austenite has been evidenced, thus suppressing TRIP effect. This loss of austenite is mainly observed in a critical range of temperatures and has been linked to the low thermal stability of austenite. The microstructural investigations performed lead to a proposal of improvements in terms of rail chemical composition and/or heat treatments, in such a way that carbide-free bainitic steels rails could be less sensitive to RCF resistance loss after welding.

Cobalt-doped β-Ni(OH)2 electrode fabricated by in-situ chemical corrosion for photo-assisted supercapacitor with low-temperature operation

The integration of photosensitive electrode materials with excellent electron and ion transfer dynamics provides an effective strategy to address the unsatisfactory low temperature tolerance of energy storage devices. Here, the surface morphology reconstruction derived from the in-situ chemical corrosion of nickel foam (NF) endow the Co-doped β-Ni(OH)2 electrode material excellent electrolyte contact and more exposed active surface, showing the super area specific capacity under illumination (15.01 F/cm2 at 60 mA/cm2), which is three times higher than that without illumination (5.29 F/cm2 at 60 mA/cm2) at room temperature. The energy density of the assembled asymmetric photoassisted supercapacitor (ASC) reaches 1.85 mWh/cm2 at a power density of 36.01 mW/cm2 under illumination, increased by 94.7 % compared to that without illumination at room temperature. Benefiting from the excellent photoelectric and photothermal conversion ability of the electrodes, the energy density of ASC can reach up to 0.63 mWh/cm2 with a power density of 34.94 mW/cm2 under illumination even at a low temperature of −40 °C, demonstrating the potential application of the wide temperature range of the supercapacitor.

Flexible Si/PEDOT:PSS heterojunction photodetectors with excellent interface contact quality for NIR detection

Flexible Si/PEDOT:PSS heterojunction photodetectors have gained widespread attention due to their excellent performance and low preparation cost, however, the presence of defects on the Si surface that generate surface states and the poor hydrophilicity of PEDOT:PSS that leads to poor contact between Si and PEDOT:PSS have been limiting the performance of the devices; In this study, an inverted pyramidal structure Si substrate with the smaller specific surface area was selected and the Si to PEDOT:PSS interface quality was improved by doping the PEDOT:PSS solution with the fluorosurfactant FC4430 and vinyltrimethoxysilane (VTMO). It was found that the doping of fluorosurfactant FC4430 could reduce the contact angle of PEDOT:PSS solution on IP substrate from 104.5° to 23°, which greatly enhanced the hydrophilicity of PEDOT:PSS without affecting the electrical properties of the films. The doping of VTMO forms Si-O-Si bonds at the Si/PEDOT:PSS interface, which passivates the defects on the silicon surface and at the same time forms a cross-linking network to improve the adhesion of the PEDOT:PSS, which enables the device to exhibit an extremely low dark current of 4.08 × 10−8 mA. Meanwhile, the prepared flexible Si/PEDOT:PSS photodetector exhibits excellent performance, with a responsivity of 8.74 mA/W, a detectivity of 1.21 × 1012 Jones, and a response speed of 120/480 μs under 0 V bias voltage and laser irradiation at a wavelength of 980 nm. Finally, the bending stability of the device was evaluated and the device performance remained above 95 % of the initial value after 50 bending cycles.

The effect of Ti-based surface layer on AlSi thin film as a high-performance anode for the lithium-ion battery

Significant volume changes during cycling and the instability of the solid electrolyte interphase (SEI) are the main challenges that limit the practical application of silicon-based anodes. TiN and TiO2 were selected as surface layers and deposited on the HCl-etched AlSi (AlSi’) thin films by atomic layer deposition (ALD) to enhance the electrochemical performance of the anode. The surface layers with excellent mechanical strength can effectively suppress the volume expansion of the AlSi thin film and maintain excellent electrical contact between the film and the substrate during cycling. The effects of TiN and TiO2 surface layers on the composition and growth of the SEI layer on the AlSi’ film anode have been discussed in detail. The TiO2 surface layer was found to inhibit the continuous growth of the SEI layer and promote the formation of a mechanically robust and stable SEI layer. The AlSi’/TiO2(8 nm) anode shows a high initial discharge capacity of 2802 mA h g-1 with an initial coulomb efficiency (ICE) of 88% at 0.8 A g-1, and it maintains a capacity retention rate of 83% after 500 cycles. Moreover, the AlSi’/TiO2(8 nm) anode exhibits outstanding rate performance, as it sustains a capacity of 1710 mA h g-1 after 500 cycles at 5 A g-1, and maintains a capacity above 1032 mA h g-1 even at 30 A g-1.