Designing strong interfacial adhesion between carbon fiber and epoxy resin via dopamine towards excellent protection ability under high hydrostatic pressure and severe erosion corrosion condition

The complex marine environment in the splash zone and the deep-sea area is always raising stern challenges for the steel structures served in the offshore facilitates. Compared with other coating fillers, the carbon fiber (CF), with outstanding mechanical strength, is a suitable candidate filler for coating reinforcement. However, CF has a poor compatibility with organic resin, which could cause defects inside the coating, and result in coating failure further. Hence, we used dopamine to modify CF surface (CF-PDA) and introduced CF-PDA into the epoxy coating as reinforced additive to improve the erosion wear resistance and anti-corrosion ability of coating. The interfacial shear strength (IFSS) of CF-PDA/epoxy was increased by 32.20%, compared with CF/epoxy. After 120 h immersion under 30 MPa pressure, the |Z|0.01 Hz of the CF-PDA/EP (1.04 x 108 omega cm2) was obviously higher than EP, and the interfaces of steel/coating and CF-PDA/resin were not failure evidently. Meantime, after the erosion wear test, compared with EP, the mass loss and the volume loss of CF-PDA/EP were decreased by 19.40% and 25.72%, respectively. Then, the failure process of coatings was discussed during erosion wear test, and we explained the relationship between the erosion wear resistance of coatings and interfacial strength of CF-PDA/ epoxy resin

Ultrathin nanofiltration membrane assembled by polyethyleneimine-grafted graphene quantum dots

Embedding nanofillers into the selective layer to creating moderate nanopores is a promising strategy to obtain high-performance nanofiltration membranes. Herein, we synthesized polyethyleneimine (PEI) functionalized graphene quantum dots (GQDs) as the water phase monomers and prepared an ultrathin desalination membrane through interfacial polymerization (IP). The in situ embedded GQDs with superiorly uniform dispersion generate abundant nanopores in the membrane, and PEI chains fill the introduced nanopores, avoiding the formation of overlarge nanopores. Besides, the PEI-grafted GQDs (NGQDs) display a reduced diffusion rate during IP, rendering an ultrathin selective layer. Benefiting from the ultrathin thickness (-6.5 nm), the abundant water pathways (specific surface area: 6.73 m(2)/g), and the increased pore size (-0.82 nm), the PA-NGQD600 membrane exhibits competitive pure water permeance (38.5 L m(-2) h(-1) bar(-1)) and inorganic salt rejection (95.5% for Na2SO4). The permeance exceeds those of the most desalination membranes reported so far and is-3 times higher than that of the reported GQD-based desalination membrane. This work provides a facile strategy for creating abundant nanopores in membranes with ultrathin thickness by interfacial polymerization

Kinematics analysis and workspace optimization for a 4-DOF 3T1R parallel manipulator

A four degrees-of-freedom (DOF) Parallel Manipulator (PM) with a 4PPa-2PaR configuration has been proposed to generate 3-DOF Translational and 1-DOF Rotational (3T1R) motions in our early work. It has the advantages of symmetric geometry, simple kinematics and infinite extension of translational workspace along its linear guide direction. However, its V-type assembly mode results in a long distance between its moving platform and the base, which makes its stiffness and accuracy lower. Besides, its the other two translational workspaces are limited due to its kinematic singularities. To overcome such limitations, the PM is modified by utilizing its M-type assembly mode and placing an offset angle to the last parallelogram mechanism. To simplify the displacement analysis, a geometrical projection method is employed, while a closed-loop vector approach is used for its instantaneous kinematic analysis. Both singularity and workspace issues are investigated. An optimization algorithm based on Genetic Algorithm is proposed to maximize the reachable workspace. The optimization result indicates that the workspace is significantly increased. A prototype of the M-type PM is fabricated to validate the effectiveness of the modified design

Surface modification on copper particles toward graphene reinforced copper matrix composites for electrical engineering application

Graphene has been demonstrated as an effective reinforcement for metal matrix composites, due to its excellent mechanical properties, robust chemical inertness, thermal stability, and self-lubricating. Nevertheless, the limiting factor for its further use in metal matrix composites, is to realize the homogeneous dispersion of graphene for taking advantage of its exceptional and fascinating properties, because of the poor wettability and density contrast between metal matrix and graphene. Herein, we design a gel assisted route to synthesize high-quality graphene nanoplatelets modified monodispersed copper particles, followed by hot pressing to fabricate graphene reinforced copper matrix composites bulk. This simple route with high efficiency and low cost, offers a new solution for the mass-production of graphene reinforced copper matrix composites and other graphene-based composites on an industrial scale. Significantly enhanced tensile strength of 253 MPa, and yield strength of 145 MPa, accompanied by the low friction coefficient and improved wear resistance, can be simultaneously achieved in the composites. For the real electrical contact performance test, the service life of electrical contacts made of graphene reinforced copper matrix composites, is 10 times longer as that of the commercial pure copper electrical contacts and almost comparable to CuAg20 contacts, demonstrating its superior ability to solve the electrical contact issues in electrical engineering systems. (c) 2021 Elsevier B.V. All rights reserved

Ultrathin polyamide nanofiltration membranes with tunable chargeability for multivalent cation removal

Positively charged nanofiltration membranes are promising in water softening and heavy metal ion removal. However, facile modulation on their chargeability remains a great challenge. Here, we proposed a charged monomer-engineered interfacial polymerization toward positively charged polyamide membranes. In particular, branched amino macromolecules (BAMs) with different charged group numbers and molecular sizes were selected as aqueous monomers, allowing for wide-range-tunable membrane chargeability. We found that larger BAMs tend to form intramolecularly crosslinked networks with more amino residues, conferring membrane chargeability up to +5.53 mC m(-2). Besides, the slower diffusion of larger BAMs also led to ultrathin membranes down to 9.0 nm in thickness. The optimal composite nanofiltration membrane displayed a high rejection to multivalent cations (e.g., MgCl2 rejection of 98.7%) with ultrahigh pure water permeance of 31.5 L m(-2) h(-1) bar(-1), which was around 2-10 times higher than that of the reported positively charged nanofiltration membranes. Our monomer design strategy for interfacial polymerization may evolve into a facile approach to constructing advanced charged membranes

Neel-type antiferromagnetic skyrmionic crystals on two-dimensional square lattices investigated with optimized quantum Monte Carlo method

The formations of individual antiferromagnetic (AF) skyrmions and AF skyrmionic lattices on two-dimensional (2D) magnets with square crystal structure are debatable in recent years, for only an isolated skyrmion can be generated in such systems if classical Monte Carlo (CMC) method is employed. For the sake, we apply here an optimized quantum Monte Carlo approach to a 2D square magnet where the AF Heisenberg exchange (HE) and Dzyaloshinskii-Moriya (DM) interactions co-exist. Consequently, the computing program converges to the equilibrium states with appreciable computational speed, and the results obtained in the last one iteration are able to accurately produce well symmetric and periodic AF skyrmionic lattices (SLs) at elevated temperatures when a considerably strong external magnetic field is exerted perpendicular to the 2D monolayer. Moreover, each of these AF SLs can be decomposed into two almost identical ferromagnetic (FM) SLs, and the distribution of topological charge density also forms symmetric lattice with the same periodicity as the AF SL, dividing the AF SL into several areas of distinct spin configurations. The reasons why the OQMC approach can work beyond CMC method are explained in the Discussion Section

Laser beam welding of AlCoCrFeNi2.1 eutectic high-entropy alloy

To determine the potential of an AlCoCrFeNi2.1 eutectic high entropy alloy (EHEA) as a structural material, its laser beam welding (LBW) performance was evaluated, and the microstructure and mechanical properties of weld joint were studied. A fully penetrated, defect-free joint was obtained, in which the fusion zone (FZ) exhibited a eutectic lamellar microstructure containing FCC(L1(2))/BCC(B2) solid solution phases. The FZ contained refined columnar grains, which grown with the preferential 111 orientation induced by the rapid cooling during LBW. The tensile strength of the FZ was superior than that of the base metal (BM), which was attributed to grain refinement and higher dislocation density. LBW is a suitable process for joining AlCoCrFeNi2.1 EHEAs

Electrochemical extraction kinetics of Nd on reactive electrodes

Pyroprocessing technology with molten salt electrolysis as the core is a promising technology for the reprocessing of spent fuel. In this work, the electrochemical reduction mechanism and kinetic properties of Nd3+ on various electrodes (inert W and reactive Al, Ga, Bi, Cd, Zn, Pb, and Sn electrodes) were systematically investigated and compared in LiCl-KCl eutectic melts using cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and Tafel techniques. The electrochemical reduction of Nd3+ was a two-step process on the W electrode including Nd3+-> Nd2+ and Nd2+-> Nd, while it became a one-step process involving three electrons on the reactive electrodes with obvious depolarization effects. Furthermore, the connections between the reduction potentials of Nd3+ on these reactive cathodes and the formation energies of the electrode-rich alloy phases (Al11Nd3, Cd11Nd, Pb3Nd, Zn17Nd2, Ga6Nd, Sn3Nd, BiNd2) were established. After evaluating the physico-chemical, depolarization and kinetic properties of these reactive electrodes, liquid Cd was considered as the most favorable material for the electrochemical extraction of Nd. In addition, Al, Cd, and Bi are also promising candidates for An / Ln separation

Interfacial assembled mesoporous polydopamine nanoparticles reduced graphene oxide for high performance of waterborne epoxy-based anticorrosive coatings

Embedding two-dimension micro/nanocontainers containing corrosion inhibitors into organic coating is a well-established concept to impart the coating with enhanced barrier and self-healing feature. Herein, a versatile nanoemulsion assembly approach was used to synthesis nanocarriers combing mesoporous polydopamine nanoparticles (MPDA) with reduced graphene oxide (GO), which was employed to encapsulate corrosion inhibitors (benzotriazole, BTA) to improve the anticorrosion performance of waterborne epoxy coating. The BTA release profiles from synthesized GO with MPDA (PDAG) demonstrated the rapid pH-triggered activities to acidic corrosion environment. With the addition of BTA-loaded PDAG, the composited epoxy coatings presented self-repairing behavior and enhanced corrosion resistance during longterm immersion. The outstanding anticorrosion performance is attributed to dual-protection mechanism provided by BTA-loaded PDAG: (1) MPDA endows GO with satisfactory interface compatibilities and thus provides impermeable barrier to delay the penetration process of corrosive electrolyte; (2) corrosion inhibitors including BTA and polydopamine form the adsorption layers on bare steel surface to resist con-tinuous corrosion at metal/coating interface. (c) 2021 Elsevier Inc. All rights reserved

In-situ structural health self-monitoring and diagnosing of glass fiber reinforced plastics with embedded nickel coated carbon fiber

In this study, a nickel coated carbon fiber (Ni-CF) tow is used to enable glass fiber reinforced plastics (GFRPs) to exhibit multi-functional properties with self-diagnosing function. The experimental results indicate that the NiCF exhibits desirable interfacial compatibility with the matrix resin and has no negative effect on the performance of GFRPs, thereby the loading conditions can be effectively monitored without deterioration. The electromechanical response suggests that the changes in resistance can be further divided into two stages corresponding to the two different safety states based on the strain under uniaxial tensile loading. At the same time, the composites were examined under cyclic loading conditions to confirm the stability and robustness of the Ni-CF as a sensing element. Moreover, the safety factor and reliability of composites were calculated based on the stress corresponding to the transition point of the safety states and the ultimate stress of the composites. Consequently, the results show that the reliability is close to 100% when the maximum safety factor of Ni-CF/GFRP is 1.5. In addition, we also suggest two different solutions for manufacturing self-diagnosing composites which can be individually applied in the development of the structures with low failure risk or with high safety requirements