Simulations of Tapered Channel in Multilayer Graphene as Reverse Osmosis Membrane for Desalination

Pressure-driven reverse osmosis membrane has important application in seawater desalination.Inspired by the structure of aquaporin,we established and studied the mechanism of the structure of multilayer graphene with tapered channels as reverse osmosis.The water flux of multilayer graphene with tapered channels was about 20%higher than that of parallel graphene channel.The flow resistance model was established,and the relationship between flow resistance and opening angles was clarified.The relationship between flow resistance and outlet size was also described.By means of molecular dynamics simulation,slip coefficients of multilayer graphene with tapered channel were obtained and verified by the contact angle of water.Results show that the permeability of graphene with tapered channel is about three orders of magnitude higher than that of commercial reverse osmosis membrane and the desalination rate is 100%.Temperature difference between the two sides of the tapered channel will promote the water flux positively.

Research on SFLA-Based Bidirectional Coordinated Control Strategy for EV Battery Swapping Station

As a good measure to tackle the challenges from energy shortages and environmental pollution,Electric Vehicles(EVs)have entered a period of rapid growth.Battery swapping station is a very important way of energy supply to EVs,and it is urgently needed to explore a coordinated control strategy to effectively smooth the load fluctuation in order to adopt the large-scale EVs.Considering bidirectional power flow between the station and power grid,this paper proposed a SFLA-based control strategy to smooth the load profile.Finally,compared simulations were performed according to the related data.Compared to particle swarm optimization(PSO)method,the presented SFLA-based strategy can effectively lower the peak-valley difference with the faster convergence rate and higher convergence precision.It is important for the swapping station that energy exchanging mode can supply energy for large-scale EVs with a smoother load profile than one-way charging mode.

Fracture toughness and destructive mechanism of ductile nanoporous metallic glass and its crystal-impregnated nanocomposite

Nanoporous metallic glasses(NPMGs)and crystalline/amorphous nanocomposites exhibit superior ductility over bulk macroscopic metallic glasses(MGs).Their fracture behaviors remain a mystery due to experimental technical limitations.In this work,the fracture behaviors of pre-cracked NPMGs and crystal-impregnated nanoporous metallic glasses(CINPMGs)are investigated through large-scale molecular dynamics simulations,and the MG and crystal phases are amorphous Cu_(50)Zr_(50)and crystalline B2CuZr,respectively.Fracture toughness is determined by simultaneously considering the surface energy and plastic dissipated energy.Our results confirm the excellent plasticity of both the pre-cracked NPMGs and CINPMGs.The progressive necking and ductile rupture of ligaments are responsible for generating NPMGs with prominent ductility and fracture toughness.Meanwhile,secondary cracking is also triggered,which can consume energy without extending the major crack,thus further improving fracture resistance.It is also found that the fracture toughness of NPMGs can be improved by increasing the solid fraction of MG,and linear relation between fracture toughness and solid fraction can be expected.Crystal impregnation effectively inhibits global failure as the crystal phase shields the individual amorphous ligaments.Homogeneous plastic flow characterized by shear bands is observed in CINPMGs,and this homogeneous global deformation is facilitated by the crystalline/amorphous interface.Besides,the fracture toughness of CINPMGs is higher than that of the constituent single phases,regardless of the volume fraction of each phase.Ashby material charts manifest that these two types of materials demonstrate promising potential in the material selection library for advanced structural design.

Effect of radial heat conduction on effective thermal conductivity of carbon nanotube bundles

The effect of the radial heat conduction on the effective thermal conductivity of carbon nanotube(CNT) bundles is studied by the nonequilibrium molecular dynamics(NEMD) method. The hexagonal CNT bundle consists of seven(10, 10) single-walled carbon nanotubes(SWCNTs). The radial heat conduction is induced by creating the vacancy defects in some segments of the constituent CNTs. Combined with the temperature differences and the inter-tube thermal resistances at the different segments,the radial heat flow in the CNT bundle is calculated. The maximum percentage of the radial heat flow is less than 7% with the presence of four defective CNTs, while the resultant decrement of the effective thermal conductivity of the bundle is about 18%.The present results indicate that the radial heat flow can significantly diminish the axial heat conduction in the CNT bundles,which probably explains the smaller effective thermal conductivity in the CNT assemblies compared to that of the individual CNTs.

Solid-state alloying of Al-Mg alloys by accumulative roll-bonding:Microstructure and properties

In this study,a novel solid-state alloying approach was adopted to fabricate Al-Mg alloys with high Mg contents(C_(Mg)) by accumulative roll-bonding(ARB)of Al and Mg elemental materials to ultrahigh cycles.Experimental results showed that the degree of alloying increased with the increase of ARB cycles and a supersaturatedα-Al solid solution accompanied with nanoprecipitates was formed in the Al-Mg alloys by ARB to 70 cycles.The as-prepared Al-Mg alloys exhibited enhanced mechanical properties,with a maximum tensile strength of∼615 MPa and a tensile elongation of∼10%at C_(Mg)=13 wt.%.The high strength can be attributed to different mechanisms,namely solid solution strengthening,grain boundary strengthening,dislocation strengthening,and precipitation strengthening.The Al-Mg alloys showed increased work hardening with increasing C_(Mg),due to the enhanced formation of nanoprecipitates.Meanwhile,no obvious drop in the intergranular corrosion(IGC)resistance was found in the Al-Mg alloys with C_(Mg) up to 13 wt.%.Moreover,sensitization treatment was found to induce little decrease in the IGC resistance of the Al-Mg alloys with C_(Mg)≤13 wt.%.We found that the excellent IGC resistance was due to the suppression of grain boundary precipitation by the preferred formation of precipitates within the grains that were induced by ARB.Our study indicated the novelty of the present solid-state alloying approach to achieving a superior combination of high mechanical properties and IGC resistance in Al-Mg alloys.

Mechanics and Wave Propagation Characterization of Chiral S-Shaped Auxetic Metastructure

Auxetic metastructures have attracted tremendous attention because of their robust multifunctional properties and promising potential industrial applications.This paper studies the in-plane mechanical behaviors of a chiral S-shaped metastructure subjected to tensile loading in both X-direction and Y-direction and wave propagation properties using the finite element(FE)method.The relationships between structural parameters and elastic behaviors are also discussed.The results indicate that the orientation of chiral S-shaped metastructure under tensile loading in the X-direction exhibits higher auxeticity and stiffness.Then,the band structures and the edge modes of each band gap of the chiral S-shaped metastructure are explored,and the relations between band gap properties and structural parameters are also systematically analyzed.Moreover,we explore the wave mitigation of the chiral S-shaped metastructures by regulating the structural parameters.Finally,the transmission properties of the finite chiral S-shaped periodic metastructures are studied to confirm the results of band gap simulation.This study promotes the engineering application of vibration isolation of chiral structures based on the band gap theory.

Promoting catalysis activity with optimizable self-generated Co-Fe alloy nanoparticles for efficient CO_(2)electrolysis performance upgrade

Stable and flexible metal nanoparticles(NPs)with regeneration ability are critical for long-term operation of solid oxide electrolysis cells(SOECs).Herein,a novel perovskite electrode with stoichiometric Pr_(0.4)Sr_(0.6)Co_(0.125)Fe_(0.75)Mo_(0.125)O_(3)−δ(PSFCM)is synthesized and studied,which undergoes multiple redox cycles to validate its structural stability and NPs reversibility.The Co-Fe alloy has exsolved from the parent bulk under reducing atmosphere,and is capable of reincorporation into the parent oxide after re-oxidation treatment.During the redox process,we successfully manipulate the size and population density of the exsolved NPs,and find that the average particle size significantly reduces but the population density increases correspondingly.The electrode polarization resistance of the symmetric cell remains stable for 450 h,and even activates after the redox cycling,which may be attributed to the higher quantity and larger specific surface area of the regenerated Co-Fe alloy NPs.Moreover,the electrochemical performance towards carbon dioxide reduction reaction(CO_(2)RR)is evaluated,and the CO_(2)electrolyzer consisting of CoFe@PSCFM-Ce_(0.8)Sm_(0.2)O_(1.9)(SDC)dual-phase electrode exhibits an excellent current density of 1.42 A·cm^(−2)at 1.6 V,which reaches 1.7 times higher than 0.83 A·cm^(−2)for the pristine PSCFM electrode.Overall,with this flexible and reversible high-performance SOEC cathode material,new options and perspectives are provided for the efficient and durable CO_(2)electrolysis.

Robust Ruddlesden-Popper phase Sr_(3)Fe_(1.3)Mo_(0.5)Ni_(0.2)O_(7-δ)decorated with in-situ exsolved Ni nanoparticles as an efficient anode for hydrocarbon fueled solid oxide fuel cells

A highly efficient Ruddlesden-Popper structure anode material with a formula of Sr_(3)Fe_(1.3)Mo_(0.5)Ni_(0.2)O_(7-δ)(RP-SFMN)has been developed for hydrocarbon fueled solid oxide fuel cells(HF-SOFC)application.It is demonstrated that a nanostructured RP-SFMN anode decorated with in-situ exsolved Ni nanoparticles(Ni@RP-SFMN)has been successfully prepared by annealing the anode in reducing atmosphere similar to the operating conditions.The phase compositions,valence states,morphologies,and electrocatalytic activities of RP-SFMN material have been characterized in detail.In addition,the in-situ exsolution mechanism of the metallic Ni phase from the parent oxide is clearly explained by using density function theory calculation.The peak output power density at 800℃ is significantly enhanced from 0.163 to 0.409 W/cm^(2)while the electrode polarization resistance is effectively lowered from 0.96 to 0.30Ωcm^(2)by the substitution of B-site Fe by Ni,which is attributed to the improved electrocatalytic activities induced by the in-situ exsolved Ni nanocatalysts.Moreover,the single cell with RP-SFMN anode exhibits good stability in 3%H_(2)O humidified H_(2)and syngas for 110 and 60 h at 800℃,respectively.Our findings indicate that RP-SFMN is a greatly promising anode candidate of HF-SOFCs due to its good electrochemical performance and stability during the operation.