Crown ether interlayer-modulated polyamide membrane with nanoscale structures for efficient desalination

Nanoscale thin-film composite(TFC)polyamide membranes are highly desirable for desalination owing to their excellent separation performance.It is a permanent pursuit to further improve the water flux of membrane without deteriorating the salt rejection.Herein,we fabricated a high-performance polyamide membrane with nanoscale structures through introducing multifunctional crown ether interlayer on the porous substrate impregnated with m-phenylenediamine.The crown ether interlayer can reduce the diffusion of amine monomers to reaction interface influenced by its interaction with m-phenylenediamine and the spatial shielding effect,leading to a controlled interfacial polymerization(IP)reaction.Besides,crown ether with intrinsic cavity is also favorable to adjust the IP process and the microstructure of polyamide layer.Since the outer surface of the nanocavity is lipophilic,crown ether has good solvency with the organic phase,thus attracting more trimesoyl chloride molecules to the interlayer and promoting the IP reaction in the confined space.As a result,a nanoscale polyamide membrane with an ultrathin selective layer of around 50 nm is obtained.The optimal TFC polyamide membrane at crown ether concentration of 0.25 wt.%exhibits a water flux of 61.2 L·m^(−2)·h^(−1),which is 364%of the pristine TFC membrane,while maintaining a rejection of above 97%to NaCl.The development of the tailor-made nanoscale polyamide membrane via constructing multifunctional crown ether interlayer provides a straightforward route to fabricate competitive membranes for highly efficient desalination.

Atomically self-healing of structural defects in monolayer WSe_(2)

Minimizing disorder and defects is crucial for realizing the full potential of two-dimensional transition metal dichalcogenides(TMDs) materials and improving device performance to desired properties. However, the methods in defect controlcurrently face challenges with overly large operational areas and a lack of precision in targeting specific defects. Therefore,we propose a new method for the precise and universal defect healing of TMD materials, integrating real-time imaging withscanning transmission electron microscopy (STEM). This method employs electron beam irradiation to stimulate the diffusionmigration of surface-adsorbed adatoms on TMD materials grown by low-temperature molecular beam epitaxy (MBE),and heal defects within the diffusion range. This approach covers defect repairs ranging from zero-dimensional vacancydefects to two-dimensional grain orientation alignment, demonstrating its universality in terms of the types of samples anddefects. These findings offer insights into the use of atomic-level focused electron beams at appropriate voltages in STEMfor defect healing, providing valuable experience for achieving atomic-level precise fabrication of TMD materials.

Study of Quantitative and Qualitative Characteristics of Nickel Clusters and Semiconductor Structures

The possibility of building of clusters of impurity atoms of Ni in silicon and controlling their parameters is currently investigated in the present research article. Our group develops a special technique for doping, the so-called “low-temperature doping” of semiconductors. This method of doping is based upon the diffusion process which is carried out in stages by gradually increasing temperature ranging from room temperature to the diffusion temperature.

Achieving High Strength-plasticity of Nanoscale Lamellar Grain Extracted from Gradient Lamellar Nickel

Traditional metallic materials usually face a dilemma between high strength and poor strain hardening capacity.However,heterogeneous structured metallic materials have been found to obviously overcome the trade-of.Herein,gradient lamellar structure was fabricated through ultrasound-aided deep rolling technique in pure Ni with high stacking fault energy after heat treatment.The gradient lamellar Ni was successively divided into the four regions.In-situ micropillar compression tests were conducted in diferent regions to reveal the corresponding microscopic mechanical properties.Microscopic characterization techniques were performed to explore underlying deformation mechanisms and the efects of microstructural parameters on deformation behaviors.This work demonstrates that the micropillar with near nanoscale lamellar thickness possesses excellent strength and plasticity.On one hand,the reason for high strength of near nanoscale micropillar is that the strength of micropillar increases with the decrease of lamellar thickness according to the Hall-Petch efect.On the other hand,numerous lamellar grain boundaries perpendicular to the loading direction is found to hinder the motion of slip bands,resulting in great strain hardening capacity in the near nanoscale lamellar micropillar.

Perfect GMR effect in gapped graphene-based ferromagnetic normal ferromagnetic junctions

We investigate the quantum transport property in gapped graphene-based ferromagnetic/normal/ferromagnetic （FG/NG/FG） junctions by using the Dirac-Bogoliubov-de Gennes equation. The graphene is fabricated on SiC and BN substrates separately, so carders in FG/NG/FG structures are considered as massive relativistic particles. Transmission prob- ability, charge, and spin conductances are studied as a function of exchange energy of ferromagnets （h）, size of graphene gap, and thickness of normal graphene region （L） respectively. Using the experimental values of Fermi energy in the normal graphene part （EFN - 400 meV） and energy gap in graphene （260 meV for SiC and 50 meV for BN substrate）, it is shown that this structure can be used for both spin-up and spin-down polarized current. The latter case has different behavior of gapped FG/NG/FG from that of gapless FG/NG/FG structures. Also perfect charge giant magnetoresistance is observed in a range of E FN - mv 2 F〈h〈E FN＋mv 2 F.

Mechanical Reinforcement and Piezoelectric Properties of PZT Ceramics Embedded with Nano-Crystalline

The double-scale lead zirconate titanate （PZT） piezoelectric ceramics were prepared by the solid state processing with PZT nano-crystalline and micro-powder. The microstructures, electrical and mechanical properties of the double-scale PZT are investigated. All the sintered ceramics exhibit a single perovskite structure and the grain size of the dou ble-scale PZT reduces due to the incorporation of PZT nano-crystalline. Compared to normal PZT, the mechanical properties increase significantly and the piezoelectric properties decrease slightly. Mechanisms responsible for the reinforcement of the double-scale PZT are discussed.

High Characteristic Temperature 1.3μm InAs/GaAs Quantum-Dot Lasers Grown by Molecular Beam Epitaxy

We report the molecular beam epitaxy growth of 1.3 μm InAs/GaAs quantum-dot （QD） lasers with high characteristic temperature T0. The active region of the lasers consists of five-layer InAs QDs with p-type modulation doping. Devices with a stripe width of 4 μm and a cavity length of 1200 μm are fabricated and tested in the pulsed regime under different temperatures. It is found that T0 of the QD lasers is as high as 532 K in the temperature range from 10°C to 60°C. In addition, the aging test for the lasers under continuous wave operation at 100°C for 72 h shows almost no degradation, indicating the high crystal quality of the devices.

Irradiation Effects of Femtosecond Pulses on Refractive Index of Ag-Embedded Nanocomposite Glasses

The irradiation effects of femtosecond pulses on Ag-embedded composite glasses fabricated by ion-exchange are investigated using z-scan measurement. Both changes of the refractive index caused by the laser irradiation effect and the third-order optical nonlinearity are observed in the experiment. Taking the change of the linear and nonlinear refractive index into consideration, the fitting results are in agreement with the experimental results.

Thermionic electron emission in the 1D edge-to-edge limit

Thermionic emission is a tunneling phenomenon,which depicts that electrons on the surface of a conductor can be pulled out into the vacuum when they are subjected to high electrical tensions while being heated hot enough to overtake their work functions.This principle has led to the great success of the so-called vacuum tubes in the early 20 th century.To date,major challenges still remain in the miniaturization of a vacuum channel transistor for on-chip integration in modern solid-state integrated circuits.Here,by introducing nano-sized vacuum gaps(~200 nm)in a van der Waals heterostructure,we successfully fabricated a one-dimensional(1 D)edge-to-edge thermionic emission vacuum tube using graphene as the filament.With the increasing collector voltage,the emitted current exhibits a typical rectifying behavior,with the maximum emission current reaching 200 p A and an ON-OFF ratio of 10;.In addition,it is found that the maximum emission current is proportional to the number of the layers of graphene.Our results expand the research of nano-sized vacuum tubes to an unexplored physical limit of 1 D edge-to-edge emission,and hold great promise for future nano-electronic systems based on it.

Rules essential for water molecular undercoordination

A sequential of concepts developed in the last decade has enabled a resolution to multiple anomalies of water ice and its low-dimensionality,particularly.Developed concepts include the coupled hydrogen bond(O:H–O)oscillator pair,segmental specific heat,three-body coupling potentials,quasisolidity,and supersolidity.Resolved anomalies include ice buoyancy,ice slipperiness,water skin toughness,supercooling and superheating at the nanoscale,etc.Evidence shows consistently that molecular undercoordination shortens the H–O bond and stiffens its phonon while undercoordination does the O:H nonbond contrastingly associated with strong lone pair“:”polarization,which endows the low-dimensional water ice with supersolidity.The supersolid phase is hydrophobic,less dense,viscoelastic,thermally more diffusive,and stable,having longer electron and phonon lifetime.The equal number of lone pairs and protons reserves the configuration and orientation of the coupled O:H–O bonds and restricts molecular rotation and proton hopping,which entitles water the simplest,ordered,tetrahedrally-coordinated,fluctuating molecular crystal covered with a supersolid skin.The O:H–O segmental cooperativity and specific-heat disparity form the soul dictate the extraordinary adaptivity,reactivity,recoverability,and sensitivity of water ice when subjecting to physical perturbation.It is recommended that the premise of“hydrogen bonding and electronic dynamics”would deepen the insight into the core physics and chemistry of water ice.

Impact of counter-rotating-wave term on quantum heat transfer and phonon statistics in nonequilibrium qubit–phonon hybrid system

Counter-rotating-wave terms(CRWTs)are traditionally viewed to be crucial in open small quantum systems with strong system–bath dissipation.Here by exemplifying in a nonequilibrium qubit–phonon hybrid model,we show that CRWTs can play the significant role in quantum heat transfer even with weak system–bath dissipation.By using extended coherent phonon states,we obtain the quantum master equation with heat exchange rates contributed by rotating-waveterms(RWTs)and CRWTs,respectively.We find that including only RWTs,the steady state heat current and current fluctuations will be significantly suppressed at large temperature bias,whereas they are strongly enhanced by considering CRWTs in addition.Furthermore,for the phonon statistics,the average phonon number and two-phonon correlation are nearly insensitive to strong qubit–phonon hybridization with only RWTs,whereas they will be dramatically cooled down via the cooperative transitions based on CRWTs in addition.Therefore,CRWTs in quantum heat transfer system should be treated carefully.

A polaron theory of quantum thermal transistor in nonequilibrium three-level systems

We investigate the quantum thermal transistor effect in nonequilibrium three-level systems by applying the polarontransformed Redfield equation combined with full counting statistics.The steady state heat currents are obtained via this unified approach over a wide region of system–bath coupling,and can be analytically reduced to the Redfield and nonequilibrium noninteracting blip approximation results in the weak and strong coupling limits,respectively.A giant heat amplification phenomenon emerges in the strong system–bath coupling limit,where transitions mediated by the middle thermal bath are found to be crucial to unravel the underlying mechanism.Moreover,the heat amplification is also exhibited with moderate coupling strength,which can be properly explained within the polaron framework.

Mechanical Behavior of Nanometer Ni by Simulating Nanoindentation

An indentation simulation of the crystal Ni is carried out by a molecular dynamics technique （MD） to study the mechanical behavior at nanometer scales. Indenter tips with both sphere shape and conical shape with 60° cone angle are used, and simulation samples with different crystal orientations are adopted. Some defects such as dislocations and point defects are observed. It is found that nucleated defects （dislocations, amorphous atoms） are from the local region near the pin tip or the sample surface. The temperature distribution of the local region is analyzed and it can explain our MD simulation results.

Damage Performance of Multilayer Films under Simultaneous Exposure to Multi-Wavelength Pulses

Laser damage performance of multilayer films with combined irradiation of 1ω and 2ω is studied to probe the damage mechanisms during wavelength division. The laser induced damage thresholds （LIDTs） of the samples are obtained and tested with only 2ω with various energy densities of 1ω. Different 1ω; polarization directions combined with the 2ω case are also investigated. The result suggests that lw can raise the damage probability of multilayer mirrors when two light wavelengths are present simultaneously; the increasing number of sensitive defects for 2ω can be related to the decline of the LIDTs of the multilayer mirrors.

Band structure properties of elastic waves propagating in the nanoscaled nearly periodic layered phononic crystals

The localization factor is used to describe the band structures for P wave propagating normally in the nanoscaled nearly periodic layered phononic crystals. The localization factor is calculated by the transfer matrix method based on the nonlocal elastic continuum theory.Three kinds of nearly periodic arrangements are concerned, i.e., random disorder, quasiperiodicity and defects. The influences of randomly disordered degree of the sub-layer＇s thickness and mass density, the arrangement of quasi-periodicity and the location of defect on the band structures and cut-off frequency are analyzed in detail.

Evolution of Structural and Magnetic Properties of BaFe12O19 with B2O3 Addition

We investigate the effects of B2O3 addition on structural and magnetic properties of hard magnetic BaFe12O19 particles. The conventional solid state reaction method is used as the synthesis route. Single phase BaFe12O19 could be synthesized with very small amounts of B2O3 addition and with calcination at low temperatures （850°C） in short times （1 h）. B2O3 addition also improves the magnetic parameters significantly. Remanence magnetization and specific magnetization at 1.5 T increase by ～40% in magnitude although no significant variations on coercivity is observed.

Competition between Radiative Power and Dissipation Power in the Refrigeration Process in Oxide Multifilms

The maximum refrigeration power dependence on the doping density in the p-BaTiO3/BaTiO3/SrTiO3/BaTiO3/ n-BaTiO3 system and in the p-AlGaAs/AlGaAs/GaAs/AlGaAs/n-AlGaAs system is obtained respectively based on the opto-thermionic refrigeration model. The results show that the maximum refrigeration power in the p-BaTiO3/BaTiO3/SrTiO3/BaTiO3/n-BaTiO3 system increases dramatically with the increase of doping density from 1.0×1018 cm-3 to 5.0×1019 cm-3 while that in the p-AlGaAs/AlGaAs/GaAs/AlGaAs/n-AlGaAs system is nearly a constant. It is found that the different Auger coefficients and the competition between radiative power and dissipation power lead to the different behavior of the maximum refrigeration power dependence on the doping density of the two systems.

A Study on Porosity Distribution in Nanoporous TiO2 Photoelectrodes for Output Performance of Dye-Sensitized Solar Cells

Porosity as one of the crucial factors to film morphology affects the overall electrical current-voltage characteristics of dye-sensitized solar cell （DSC）. We search for the short-circuit current density, the open-circuit voltage and the maximum power output as the main functional parameters of DSC closely related to porosity under different film thickness. The theoretical analyses show some exciting results. As porosity changes from 0.41 to 0.75, the short-circuit current density shows the optimal value when the film thickness is 8-10 μm. The open-circuit voltage presents different variation tendencies for the film thicknesses within 1-8 μm and within 10-30 μm. The porosity is near 0.41 and the film thickness is about 10 μm, DSC will have the maximum power output. The theoretical studies also illustrate that given a good porosity distribution, DSC can obtain an excellent short-circuit current characteristic, which agrees well with the experimental results reported in previous literature.

Fine description of unconventional clastic oil reservoirs

The latest researches reveal that studies on unconventional clastic oil reservoirs in China generally lag far behind those in other countries in respect of content and methodology.This study presents the definition and classification of unconventional oil reservoirs and analyzes the problems in the fine description of unconventional oil reservoirs.The key content of the fine description of unconventional oil reservoirs is summarized from four aspects:fine fracture characterization based on fine structure interpretation,reservoir architecture characterization based on sedimentary facies,characteristics of nanoscale microscopic pore structure of reservoir,and evaluation of source rock and“sweet spot zone”.Finally,this study suggests that development of fine description of unconventional clastic oil reservoirs in the future should focus on rock brittleness analysis and fracture modeling,geophysical characterization of unconventional clastic oil reservoirs,fluid description of tight reservoirs,and physical/numerical simulation experiments of unconventional oil reservoirs.

Nonlinear buckling and postbuckling behavior of cylindrical shear deformable nanoshells subjected to radial compression including surface free energy effects

The objective of the present investigation is to predict the nonlinear buckling and postbuckling characteristics of cylindrical shear deformable nanoshells with and without initial imperfection under hydrostatic pressure load in the presence of surface free energy effects.To this end, Gurtin-Murdoch elasticity theory is implemented into the irst-order shear deformation shell theory to develop a size-dependent shell model which has an excellent capability to take surface free energy effects into account. A linear variation through the shell thickness is assumed for the normal stress component of the bulk to satisfy the equilibrium conditions on the surfaces of nanoshell. On the basis of variational approach and using von Karman-Donnell-type of kinematic nonlinearity, the non-classical governing differential equations are derived. Then a boundary layer theory of shell buckling is employed incorporating the effects of surface free energy in conjunction with nonlinear prebuckling deformations, large delections in the postbuckling domain and initial geometric imperfection. Finally, an eficient solution methodology based on a two-stepped singular perturbation technique is put into use in order to obtain the critical buckling loads and postbuckling equilibrium paths corresponding to various geometric parameters. It is demonstrated that the surface free energy effects cause increases in both the critical buckling pressure and critical end-shortening of a nanoshell made of silicon.