Showing papers on "Coating published in 2021"

Recent research and development status of laser cladding: A review

Abstract: In industries such as aerospace, petrochemistry and automobile, many parts of different machines are under environment which shows high temperature and high pressure, and have their proneness to wear and corrosion. Therefore, the wear resistibility and stability under high temperature need to be further improved. Nowadays, Laser cladding (LC) is widely used in machine parts repairing and functional coating due to its advantages such as lower dilution rate, small heat-affected zone and good metallurgical bonding between coating and substrate. In this paper, LC is introduced in detail from aspects of process simulation, monitoring and parameter optimization. At the same time, the paper gives a comprehensive review over LC material system as high entropy alloys (HEAs), amorphous alloy and single crystal alloy have been gradually showing their advantages over traditional metal materials in LC. In addition, the applications of LC in functional coatings and in maintenance of machine parts are also outlined. Also, the existing problems and the development trend of LC is discussed then.

Reactive boride infusion stabilizes Ni-rich cathodes for lithium-ion batteries

Abstract: Engineered polycrystalline electrodes are critical to the cycling stability and safety of lithium-ion batteries, yet it is challenging to construct high-quality coatings at both the primary- and secondary-particle levels. Here we present a room-temperature synthesis route to achieve a full surface coverage of secondary particles and facile infusion into grain boundaries, and thus offer a complete ‘coating-plus-infusion’ strategy. Cobalt boride metallic glass was successfully applied to a Ni-rich layered cathode LiNi0.8Co0.1Mn0.1O2. It dramatically improved the rate capability and cycling stability, including under high-discharge-rate and elevated-temperature conditions and in pouch full-cells. The superior performance originates from a simultaneous suppression of the microstructural degradation of the intergranular cracking and of side reactions with the electrolyte. Atomistic simulations identified the critical role of strong selective interfacial bonding, which offers not only a large chemical driving force to ensure uniform reactive wetting and facile infusion, but also lowers the surface/interface oxygen activity, which contributes to the exceptional mechanical and electrochemical stabilities of the infused electrode. Coating is commonly used to improve electrode performance in batteries, but it is challenging to achieve and maintain complete coverage of electrode particles during cycling. Here the authors present a coating-and-infusion approach on Ni-rich cathodes that effectively retards stress corrosion cracking.

An Artificial Polyacrylonitrile Coating Layer Confining Zinc Dendrite Growth for Highly Reversible Aqueous Zinc-Based Batteries

Abstract: Aqueous rechargeable zinc-metal-based batteries are an attractive alternative to lithium-ion batteries for grid-scale energy-storage systems because of their high specific capacity, low cost, eco-friendliness, and nonflammability. However, uncontrollable zinc dendrite growth limits the cycle life by piercing the separator, resulting in low zinc utilization in both alkaline and mild/neutral electrolytes. Herein, a polyacrylonitrile coating layer on a zinc anode produced by a simple drop coating approach to address the dendrite issue is reported. The coating layer not only improves the hydrophilicity of the zinc anode but also regulates zinc-ion transport, consequently facilitating the uniform deposition of zinc ions to avoid dendrite formation. A symmetrical cell with the polymer-coating-layer-modified Zn anode displays dendrite-free plating/stripping with a long cycle lifespan (>1100 h), much better than that of the bare Zn anode. The modified zinc anode coupled with a Mn-doped V2 O5 cathode forms a stable rechargeable full battery. This method is a facile and feasible way to solve the zinc dendrite problem for rechargeable aqueous zinc-metal batteries, providing a solid basis for application of aqueous rechargeable Zn batteries.

Morphology-control synthesis of polyaniline decorative porous carbon with remarkable electromagnetic wave absorption capabilities

Abstract: Porous carbon materials have been widely reported on dealing with the electromagnetic (EM) wave interference. However, monotonous EM loss mechanism still performed an obstacle to achieve exceptional absorption. In this paper, a series of three-dimensional porous carbon·@PANI (polyaniline) composites were synthesized via facile roasting and subsequent coating process. The morphology, nanostructure and EM wave absorption properties of porous carbon@PANI (PC@PANI) were discussed in detail. Obviously, porous carbon derived from EDTA-2Na coated by PANI (PC@PANI-2) composites exhibited significantly enhanced EM wave absorption performance compared to pure porous carbon. The widest absorption bandwidth (RL

A Patternable and In Situ Formed Polymeric Zinc Blanket for a Reversible Zinc Anode in a Skin-Mountable Microbattery.

Abstract: Owing to their high safety and reversibility, aqueous microbatteries using zinc anodes and an acid electrolyte have emerged as promising candidates for wearable electronics. However, a critical limitation that prevents implementing zinc chemistry at the microscale lies in its spontaneous corrosion in an acidic electrolyte that causes a capacity loss of 40% after a ten-hour rest. Widespread anti-corrosion techniques, such as polymer coating, often retard the kinetics of zinc plating/stripping and lack spatial control at the microscale. Here, a polyimide coating that resolves this dilemma is reported. The coating prevents corrosion and hence reduces the capacity loss of a standby microbattery to 10%. The coordination of carbonyl oxygen in the polyimide with zinc ions builds up over cycling, creating a zinc blanket that minimizes the concentration gradient through the electrode/electrolyte interface and thus allows for fast kinetics and low plating/stripping overpotential. The polyimide's patternable feature energizes microbatteries in both aqueous and hydrogel electrolytes, delivering a supercapacitor-level rate performance and 400 stable cycles in the hydrogel electrolyte. Moreover, the microbattery is able to be attached to human skin and offers strong resistance to deformations, splashing, and external shock. The skin-mountable microbattery demonstrates an excellent combination of anti-corrosion, reversibility, and durability in wearables.

Ultrasensitive strain sensor based on superhydrophobic microcracked conductive Ti3C2Tx MXene/paper for human-motion monitoring and E-skin

Abstract: With the rapid development of wearable intelligent devices, low-cost wearable strain sensors with high sensitivity and low detection limit are urgently demanded. Meanwhile, sensing stability of sensor in wet or corrosive environments should also be considered in practical applications. Here, superhydrophobic microcracked conductive paper-based strain sensor was fabricated by coating conductive Ti3C2Tx MXene on printing paper via dip-coating process and followed by depositing superhydrophobic candle soot layer on its surface. Owing to the ultrasensitive microcrack structure in the conductive coating layer induced by the mismatch of elastic modulus and thermal expansion coefficient between conductive coating layer and paper substrate during the drying process, the prepared paper-based strain sensor exhibited a high sensitivity (gauge factor, GF = 17.4) in the strain range of 0–0.6%, ultralow detection limit (0.1% strain) and good fatigue resistance over 1000 cycles towards bending deformation. Interestingly, it was also applicable for torsion deformation detection, showing excellent torsion angle dependent, repeatable and stable sensing performances. Meanwhile, it displayed brilliant waterproof, self-cleaning and corrosion-resistant properties due to the existence of micro/nano-structured and the low surface energy candle soot layer. As a result, the prepared paper-based strain sensor can effectively monitor a series of large-scale and small-scale human motions even under water environment, showing the great promising in practical harsh outdoor environments. Importantly, it also demonstrated good applicability for spatial strain distribution detection of skin upon body movement when assembled into electronic-skin (E-skin). This study will provide great guidance for the design of next generation wearable strain sensor.

Functional hydrogel coatings.

Abstract: Hydrogels-natural or synthetic polymer networks that swell in water-can be made mechanically, chemically and electrically compatible with living tissues. There has been intense research and development of hydrogels for medical applications since the invention of hydrogel contact lenses in 1960. More recently, functional hydrogel coatings with controlled thickness and tough adhesion have been achieved on various substrates. Hydrogel-coated substrates combine the advantages of hydrogels, such as lubricity, biocompatibility and anti-biofouling properties, with the advantages of substrates, such as stiffness, toughness and strength. In this review, we focus on three aspects of functional hydrogel coatings: (i) applications and functions enabled by hydrogel coatings, (ii) methods of coating various substrates with different functional hydrogels with tough adhesion, and (iii) tests to evaluate the adhesion between functional hydrogel coatings and substrates. Conclusions and outlook are given at the end of this review.

A comparative study on microstructure and properties of traditional laser cladding and high-speed laser cladding of Ni45 alloy coatings

Abstract: High-speed laser cladding technology can significantly improve the efficiency of coating preparation and effectively widen the application range of laser cladding. In this study, the Ni45 powders were deposited on steel substrate by traditional low speed laser cladding and high-speed laser cladding process, respectively. The cladding efficiency, surface forming, cross-sectional microstructure, microhardness, wear and corrosion resistance properties of the traditional and high-speed laser cladded Ni45 alloy coatings were compared. It can be seen that the thickness of the high-speed laser cladding coating was much thinner than that of the traditional laser cladding coating. Compared with traditional laser cladding, high-speed laser cladding could achieve a cladding speed of 76.86 m/min and a cladding efficiency of 156.79 cm2/min. The microstructure of the two kinds of coatings shows the same growth law, but the microstructure in high-speed laser cladding was smaller and denser, and the columnar crystal interval was narrower, only about 6 μm. It is found that the cooling rate of the traditional laser cladding coating was smaller than that of the high-speed laser cladding, and as the cladding speed increased, the cooling rate became higher and higher. The cross-section microhardness of the traditional laser cladding coating was relatively uniform of 337 HV0.2, while the microhardness of high-speed laser cladding surface increased to about 543 HV0.2. In addition, the wear and corrosion resistance of high-speed laser cladded coatings were better than that of traditional laser cladded coatings. As the cladding speed increased, the wear and corrosion resistance of the cladded coatings became better.

A Universal Strategy for the Preparation of Dual Superlyophobic Surfaces in Oil-Water Systems

Abstract: There are some methods to prepare superwetting surfaces with underwater superoleophobicity (UWSOB) or underoil superhydrophobicity (UOSHB), but it is still thorny to put forward a universal strategy for constructing dual superlyophobic surfaces in oil-water systems due to a thermodynamic contradiction. Herein, a universal strategy was proposed to prepare the dual superlyophobic surfaces in oil-water systems only via delicately controlling surface chemistry, that is, adjusting the ratios of superhydrophilic and superhydrophobic counterparts in the spray solution. Three types of materials, attapulgite (APT), TiO2, and loess, were chosen to prepare a diverse series of mixed coatings (mass gradient of superhydrophobic counterparts from 0 to 100 wt %). With the proportion of each superhydrophobic counterpart increasing, the underwater oil contact angle (θo/w*) of each mixed coating slightly decreased but still was more than 150°, that is, UWSOB. In contrast, the underoil water contact angle (θw/o*) was significantly improved, realizing the transformation from UOHL (or UOHB) to UOSHB. More importantly, the respective mass ratios of superhydrophobic counterparts in the resulting mixed coatings of APT, TiO2, and loess were finally determined to be 0.3, 0.4, and 0.2, respectively. Taking APT as a model, a train of mixed APT coatings with different superhydrophobic components were systematically characterized and analyzed. Finally, the prepared superlyophobic separation mesh in oil-water systems was applied to the separation of various surfactant-stabilized oil-water emulsions. We envision that this universal strategy we proposed will show a significant application potential in addressing scientific and technological challenges in the field of interfacial chemistry such as oil-water separation, microfluidics, microdroplet manipulation, antifogging/icing, cell engineering, drag reduction, and so forth.

Realizing high-power and high-capacity zinc/sodium metal anodes through interfacial chemistry regulation

Abstract: Stable plating/stripping of metal electrodes under high power and high capacity remains a great challenge. Tailoring the deposition behavior on the substrate could partly resolve dendrites’ formation, but it usually works only under low current densities and limited capacities. Here we turn to regulate the separator’s interfacial chemistry through tin coating with decent conductivity and excellent zincophilicity. The former homogenizes the electric field distribution for smooth zinc metal on the substrate, while the latter enables the concurrent zinc deposition on the separator with a face-to-face growth. Consequently, dendrite-free zinc morphologies and superior cycling stability are achieved at simultaneous high current densities and large cycling capacities (1000 h at 5 mA/cm2 for 5 mAh/cm2 and 500 h at 10 mA/cm2 for 10 mAh/cm2). Furthermore, the concept could be readily extended to sodium metal anodes, demonstrating the interfacial chemistry regulation of separator is a promising route to circumvent the metal anode challenges. Zinc metal anodes suffer from severe dendrites’ growth. Herewith authors construct electrically conductive and zincophilic tin coating on separator to suppress dendrites initiation and eliminate the inevitably formed dendrites.

Facile Fabrication of Densely Packed Ti3C2 MXene/Nanocellulose Composite Films for Enhancing Electromagnetic Interference Shielding and Electro-/Photothermal Performance.

Abstract: The development of modern electronics has raised great demand for multifunctional materials to protect electronic instruments against electromagnetic interference (EMI) radiation and ice accretion in cold weather. However, it is still a great challenge to prepare high-performance multifunctional films with excellent flexibilty, mechanical strength, and durability. Here, we propose a layer-by-layer assembly of cellulose nanofiber (CNF)/Ti3C2Tx nanocomposites (TM) on a bacterial cellulose (BC) substrate via repeated spray coating. CNFs are hybridized with Ti3C2Tx nanoflakes to improve the mechanical properties of the functional coating layer and its adhesion with the BC substrate. The densely packed hierarchical structure and strong interfacial interactions endows the TM/BC films with good flexibility, ultrahigh mechanical strength (>250 MPa), and desirable toughness (>20 MJ cm-3). Furthermore, benefiting from the densely packed hierarchical structure, the resultant TM/BC films present outstanding EMI shielding effictiveness of 60 dB and efficient electro-/photothermal heating performance. Silicone encapsulation further imparts high hydrophobicity and exceptional durability against solutions and deformations to the multifunctional films. Impressively, the silicone-coated TM/BC film (Si-TM/BC) exhibits desirable low voltage-driven Joule heating and excellent photoresponsive heating performance, which demonstrates great feasibility for efficient thermal deicing under actual conditions. Therefore, we believe that the Si-TM/BC film with excellent mechanical properties and durability holds great promise for the practical applications of EMI shielding and ice accretion elimination.

Cathode-Electrolyte Interphase in Lithium Batteries Revealed by Cryogenic Electron Microscopy

Abstract: Summary Cathode electrolyte interphase (CEI), the intimate coating layer formed on the positive electrode, has been thought to be critical. However, many aspects of CEI remain unclear. This originates from the lack of effective tools to characterize structural and chemical properties of these sensitive interphases at nanoscale. Here, we develop a protocol to preserve the native state and directly visualize the interface on the positive electrode using cryogenic electron microscopy. We find that under normal operation conditions, there does not exist an intimate coating layer at the single-particle level in carbonate-based electrolyte. However, upon brief external electrical shorting, a solid-electrolyte interphase, which usually forms on anodes, could form on cathodes and be electrochemically converted into a stable, conformal CEI in situ. The conformal CEI helps improve Coulombic efficiency and overall capacity retention of the battery. This generates a different perspective of CEI in commercial carbonate-based electrolytes than previously understood.

Uniform Zn Deposition Achieved by Ag Coating for Improved Aqueous Zinc-Ion Batteries.

Abstract: Aqueous zinc-ion batteries (ZIBs) are considered as a promising energy storage system due to their low cost and high safety merits. However, they suffer from the challenge of uncontrollable dendrit...