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Recent research shows that flexoelectricity may prominently affect the electromechanical coupling responses of elastic dielectrics at the nanoscale. From the perspective of devices design, it is urgent to know how the input parameters affect the electromechanical coupling behaviors of flexoelectric nanostructures. In this work, global sensitivity analysis is applied to elastic dielectric nanoplates to decompose the attribution of each of the parameters. Meanwhile, the existing hierarchical regression is found not suitable for simultaneously evaluating the multicollinearity and high dimensionality problems, when global sensitivity analysis of flexoelectric nanostructures is obtained combining polynomial chaos expansion (PCE). In order to overcome the above issues, the following strategies is proposed: 1) First, an adaptive sparse scheme is employed to build the sparse PCE. The number of terms of the PCE is decreased through choosing the most related polynomials with respect to a given model output. 2) Then, the hierarchical regression can be carried out iteratively via combining with the adaptive-sparse scheme. 3) Finally, the Sobol sensitivity indices are calculated through using these procedures. Further, Sobol sensitivity indices reveal that the thickness is the decisive input parameter that strongly affects the buckling and vibration responses of the flexoelectric nanoplate; the flexoelectric coefficients is the next key parameter that affect the buckling and vibration responses of flexoelectric nanoplate. Our finding also demonstrates that the influence of the flexoelectric coefficient is much stronger than that of the piezoelectric coefficient, which revealed the domination of the flexoelectric effect in ultra-thin piezoelectric nanostructures.

Compressed hydrogen tanks are now widely used for onboard hydrogen storage in fuel cell vehicles (FCVs). However, because of the high storage pressure and the low thermal conductivity of carbon fibre reinforced polymer (CFRP), the emptying of such tanks during driving or emergency release can cause a significant temperature decrease and result in an in-tank gas temperature below the low safety temperature limit of −40 °C even in warm weather. Once the gas temperature within the tank is lower than −40 °C, the sealing elements at the boss of the tank may fail, and glass transition of the polymer liner of the type IV tank may occur; both can cause hydrogen leakage and severe safety problems. In this paper, the heat transfer correlations, thermodynamic analyses, computational fluid dynamics (CFD) simulations, experimental studies, and thermal management methods associated with the emptying process of compressed hydrogen tanks are comprehensively reviewed. Future research directions on this topic are suggested.

In this paper, we report the first example of semiconducting porphyrinylphosphonate metal–organic framework (MOF) [Co(Ni-H7TPPP)2]·8H2O and its chemical exfoliation into ultrathin metal–organic lay...

It is difficult to investigate the hydrogen-bonding dynamics of hydrogen-disordered ice VI. Here, we present a comparative method based on our previous study of its counterpart hydrogen-ordered phase, ice XV. The primitive cell of ice XV is a 10 molecule unit, and the vibrational normal modes were analyzed individually. We constructed an 80 molecule supercell of ice VI to mimic the periodic unit and performed first-principles density functional theory calculations. As the two vibrational spectra show almost identical features, we compared the molecular translation vibrations. Inspired by the phonon analysis of ice XV, we found that the vibrational modes in the translation band of ice VI are classifiable into three groups. The lowest-strength vibration modes represent vibrations between two sublattices that lack hydrogen bonding. The highest-strength vibration modes represent the vibration of four hydrogen bonds of one molecule. The middle-strength vibration modes mainly represent the molecular vibrations of only two hydrogen bonds. Although there are many overlapping stronger and middle modes, there are only two main peaks in the inelastic neutron scattering (INS) spectra. This work explains the origin of the two main peaks in the far-infrared region of ice VI and illustrates how to analyze a hydrogen-disordered ice structure.

Analysis of the intermolecular vibrational modes in a fingerprint region is always difficult. It is particularly hard to figure out the normal modes, especially in the far-infrared (IR) region, whi...

We successfully synthesize six kinds of functional conjugated microporous polymer (CMP) containing amino, hydroxyl, carboxyl and ester groups by a Sonogashira–Hagihara coupling reaction. These CMPs exhibit type-I nitrogen gas sorption isotherms, and their pore widths are approximately 1.28–1.86 nm with a relatively narrow pore size distribution that is attributed to microporous structures. By blending CMPs with TiO2 under solvothermal conditions, TiO2 is uniformly coated onto the surfaces of the CMPs, and CMP/TiO2 nanocomposites are synthesized successfully. The novel nanocomposites show excellent photocatalytic properties for the degradation of organic pollutants, such as methylene blue, ciprofloxacin and tetracycline, under visible light. The degradation rate of organic pollutants is higher than 96.8%, and after 5 recycling cycles, the degradation efficiency is still more than 93%. The effects of the different functional groups of CMPs on the photocatalytic properties are discussed for the first time. CMP/TiO2 with carboxyl groups show the smallest band gap, highest photocurrent intensity and lowest resistance compared to those of nanocomposites with amino, hydroxyl and ester groups. This result may be caused by the high electronegativity of carboxyl groups, which enhances the charge transfer rate. The photocatalytic mechanism of the CMP/TiO2 nanocomposites is investigated, and the superoxide anion (·O2−) is the main active species in the photocatalytic degradation process.

Microporous polymer membranes hold great promise in carbon capture. However, engineering a continuous CO2-selective microporous network to achieve ultrahigh gas permeance and desirable selectivity remains a grand challenge. Aiming to manipulate the pore architecture and pore chemistry to implement efficient separation, knitted microporous polymer membranes are fabricated by in situ knitting composite membranes comprised of polyphenylene oxide (PPO) polymer and benzyl alcohol (BnOH). Specifically, the crosslinkers, formaldehyde dimethylacetal, bridge the neighboring aromatic backbones of PPO chains and BnOH to construct a highly crosslinked network with microporosity. By increasing the structural bridge density, the BET surface area of membranes increases from 4 to 538 m2 g−1. The formation of a highly interconnected microporous network provides remarkably increased permeability. Meanwhile, BnOH as a hydroxyl-containing functional building unit is knitted into micropore skeletons, which can directly tune the pore size and improve the CO2-philicity for enhanced selectivity. The resulting membrane displays an ultrahigh permeability of 4651.2 barrer with a CO2/CH4 selectivity of 27, and demonstrated good resistance to plasticization (up to 30 bar) and aging (for 190 days). This knitting strategy enabling versatile combination of building units with different structures and special functionalities may set up an innovative platform for fabricating a broad range of advanced membranes.

Molecular separations that enable selective transport of target molecules from gas and liquid molecular mixtures, such as CO2 capture, olefin/paraffin separations, and organic solvent nanofiltration, represent the most energy sensitive and significant demands. Membranes are favored for molecular separations owing to the advantages of energy efficiency, simplicity, scalability, and small environmental footprint. A number of emerging microporous organic materials have displayed great potential as building blocks of molecular separation membranes, which not only integrate the rigid, engineered pore structures and desirable stability of inorganic molecular sieve membranes, but also exhibit a high degree of freedom to create chemically rich combinations/sequences. To gain a deep insight into the intrinsic connections and characteristics of these microporous organic material-based membranes, in this review, for the first time, we propose the concept of organic molecular sieve membranes (OMSMs) with a focus on the precise construction of membrane structures and efficient intensification of membrane processes. The platform chemistries, designing principles, and assembly methods for the precise construction of OMSMs are elaborated. Conventional mass transport mechanisms are analyzed based on the interactions between OMSMs and penetrate(s). Particularly, the 'STEM' guidelines of OMSMs are highlighted to guide the precise construction of OMSM structures and efficient intensification of OMSM processes. Emerging mass transport mechanisms are elucidated inspired by the phenomena and principles of the mass transport processes in the biological realm. The representative applications of OMSMs in gas and liquid molecular mixture separations are highlighted. The major challenges and brief perspectives for the fundamental science and practical applications of OMSMs are tentatively identified.

Highly conductive, conformable and gel-free electrodes are desirable in human electrophysiology. Besides, intimately coupling with human skin, wearable strain sensors can detect numerous physiological signals, such as wrist pulse and breath. In this study, a multilayer graphene nanosheet film (MGNF) with high conductivity was prepared by the Marangoni self-assembly for using in tattoo dry electrodes (TDEs) and in a graphene tattoo strain sensor (GTSS). Compared to commercial Ag/AgCl gel electrodes, TDEs have lower skin-electrode contact impedance and could detect human electrocardiogram for 24-hour wearing more accurately as well as electromyogram. Through designing a slim serpentine ribbon structure, a resistance-type GTSS, without deterioration even after 2000 cycles, is well demonstrated for human wrist pulse and breath sensing. With the advantages of high conductivity and conformability, MGNF provides support to fabricate low-cost, customizable, and high-performance electronic tattoos for human electrophysiology and strain sensing.

An analytical hydrodynamics model for a piezoelectric micro-robotic fish with double caudal fins is presented in this paper. The relation between displacement of the piezoelectric actuator and oscillating angle of the caudal fin is established based on the analysis of the flexible four-bar linkage transmission. The hydrodynamics of caudal fins are described by airfoil and blade element theories. Furthermore, the dynamics and kinetics of the whole micro-robotic fish are analyzed and validated by experiments.

A vapor–liquid–solid horizontal circulating fluidized bed evaporation setup was constructed to study the thermal-exchange properties and pressure change. The influences of the operating variables, including the amount of added particles, heat flux, and circulating flow velocity, were systematically inspected using resistance temperature detectors and pressure sensors. The results showed that the heat transfer effect was improved with the increase in the amount of added particles, circulating flow velocity, and particle diameter, but decreased with increasing heat flux. The pressure drop fluctuated with the increase in operating parameters, except circulating flow velocity. The enhancing factor reached up to 71.5%. The enhancing factor initially increased and then decreased with the increase in the amount of added particles and circulating flow velocity, fluctuated with increasing particle diameter, and decreased with increasing heat flux. Phase diagrams showing the variation ranges of the operation variables for the enhancing factor were constructed.

This work presents the dynamic response of piezoelectric and flexoelectric Euler–Bernoulli beams subjected to mechanical loads by means of Green’s functions. Exact solutions in closed form for the electromechanical coupling behaviors are derived. The present solutions will reduce to those of classical piezoelectric beam models by neglecting the flexoelectric effect. Numerical results for a $${\text {BaTiO}}_{3}$$ cantilever show that the tip deflection of the beam will be separated when the beam thickness reduces to one micrometer; therefore, pure mechanical experiments can be used to determine the flexoelectric effect by a bending test under different electrical boundary conditions. In addition, the dynamic output voltage under open-circuit condition and the dynamic output charge under short-circuit condition are dominated by the flexoelectric effect. The dynamic output voltage and charge become negligible when the beam thickness reduces to one micrometer. By reducing the length–thickness ratio or introducing the effective piezoelectric coefficient, the electric response can be more easily detected at microscale. These results demonstrate that the flexoelectric effect can be strong enough to dominate the electromechanical coupling behavior, coordinating with the ‘ever green’ trend to miniaturization, and the flexoelectric effect can be applicable for energy harvesters, sensing, and others.

A comprehensive design methodology is required to maximize the power capacity, the efficiency, and the power density of medium-frequency transformer (MFT), while complying with material, insulation, leakage inductance, and temperature limits. Different from the previous work, an analytical expression for the optimum conductor size of rectangular litz-wire conducting harmonic currents, which ensures best use of the available copper is proposed. A method to tune the leakage inductance with different winding configurations is presented. An insulation design scheme considering the influence of short-term power frequency sinusoidal wave and long-term square wave voltage excitations is put forward. Method to acquire the optimal dimension of fin array heat exchanger under forced air-cooling condition is presented. On this basis, the design methodology is established using the multiobjective nondominated sorting genetic algorithm II. A 1 kV, 200 kVA, 10 kHz nanocrystalline core MFT is designed and prototyped for a 10 kV, 2.5 MW solid-state transformer. The optimal design achieves an efficiency of 99.45%, a power density of 8 MW/m3, and a forced air-cooling temperature of 62 °C.

In order to further develop efficient ultraviolet light-driven photocatalysts for environmental application, α-zirconium phosphate (α-ZrP) and carbon nitride (C3N4) were synthesized, respectively. Then, C3N4–ZrP compositing nanomaterials were prepared by compositing α-ZrP nanocrystals and C3N4 with different mass ratios. C3N4–ZrP compositing nanomaterials were characterized by X-ray diffraction, scanning electron microscopy, Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy. The results illustrated that α-ZrP and C3N4 were successfully composited, and the polarization of the compositing nanomaterials was reduced compared with raw materials. The photocatalytic performances of C3N4–ZrP compositing nanomaterials with different mass ratios were studied by photodegradation of RhB under ultraviolet irradiation. All of the degradation rates of the C3N4–ZrP compositing nanomaterials system were achieved more than 90% after 18 min. When the mass ratio of C3N4–ZrP compositing nanomaterials is 2:1, the degradation efficiency achieved 99.95%, which is more efficient than other tested mass ratios. The result indicated the possibility of utilizing C3N4–ZrP compositing nanomaterials for environmental pollutants degradation.

Flexible and wearable energy storage microdevice systems with high performance and safety are promising candidates for the electronics of on-chip integration. Herein, we demonstrate inkjet-printed ...

Two-dimensional (2D) network polymers with nano-sized pores are generally insoluble, and therefore, it is difficult to determine their molecular structures and to fabricate their membranes. Soluble...

This paper carries out the transient behaviors of a thin rectangular plate considering different boundary conditions, Pasternak foundation, and thermal environment simultaneously. The governing differential equations of the system are derived by employing the Kirchhoff’s classical plate theory and Hamilton’s principle. This paper proposes a novel semi-analytical methodology, which integrates Laplace transform, the one-dimensional differential quadrature method, Fourier series expansion technique, and Laplace numerical inversion to analyze plates’ transient response. The proposed method can obtain dynamic response of the rectangular efficiently and accurately, which fills the gap of transient behaviors in semi-analytical method. A comparison between semi-analytical results and numerical solutions from the publication on this subject is presented to verify the method. Specifically, the results also agree well with the data generated by the Navier’s method. The convergence tests indicate that the semi-analytical algorithm is a quick convergence method. The effects of various variables, such as geometry, boundary conditions, temperature, and the coefficients of the Pasternak foundation, are further studied. The parametric studies show that geometry and temperature change are significant factors that affect the dynamic response of the plate.

The effect of evaporation section setting on the thermal performance of a closed thermosyphon combined with the fluidized bed heat transfer technology is experimentally investigated by varying the solid holdup (10–20%) and input power (50–300 W). Pure water and glass beads are chosen as the working media in a smooth copper tube. The results show that the particle addition may enhance the heat transfer of the thermosyphons under different evaporation section settings. The maximum reduction rate of the overall thermal resistance is 23.5% with a evaporation section length of 200 mm at solid holdup of 15% and input power of 300 W. The overall thermal resistances of the two-phase and three-phase thermosyphons decrease with the increase in evaporation section length. The upward movement of the evaporation section is beneficial to the heat transfer of the two-phase closed thermosyphon, but is not conducive to that of the three-phase closed thermosyphon.

An arcuate multi–orifice distributor is designed and fixed in the front shell cover of a horizontal liquid–solid circulating fluidized bed heat exchanger to inhibit the particle deposition in the front shell cover and improve the particle distribution in the tube bundle. Polyformaldehyde (POM) particles and water are selected as the working mediums. The influence of the inclination angle of the distributor (−34–42°) and the operating parameters such as the amount of added particles (0.5%–2.0%), circulation flow rate (7.9–19.9 m3/h), and particle diameter (3.15–5.5 mm) on the effect of the distributor is investigated by a charge–coupled device (CCD) system. The results show that the distributor can improve the particle distribution by 41%–90% at the optimal inclination angle of 27°, with a small increment in pressure drop. The findings are beneficial to the application of the fluidized bed heat transfer technology to the heat exchanger with horizontal tube bundle.

Copper is the most common interconnected materials in the field of microelectronic packaging, and it is widely used in various advanced package technologies, such as redistribution layer (RDL), copper pillar (CuP) and under bump metallization (UBM) etc. However, the rapid development of packaging technology, decreasing size and increasing Joule heat make a great challenge on the mechanical properties and thermal stability of copper interconnected materials. It was widely reported that the nanotwinned copper had very high strength and excellent conductivity, which was quite suitable for the next generation interconnected materials. However, different from electroplating thin films, the achievement of uniformity and flatness for electroplating ultra-fine pitch nanotwinned RDLs would be difficult since the line width was as low as 1.5µm. Through the study of growth mechanism and additives effect, we had invented an acid nanotwinned copper electrolyte as reported previously. So in our study, the evaluation of modified nanotwinned copper electrolyte was conducted in order to clarify its performance of on the electroplating ultra-fine pitch RDLs. Also, three kinds of commercial RDL electrolytes were served as comparisons. In detail, different electrolytes were evaluated from the aspect of microstructure, hardness, thermal stability, uniformity and flatness. Firstly, the morphology of electroplating copper film was characterized by focus ion beam (FIB), and then the hardness was measured. The thermal stability was revealed by the hardness evolution before and after heat treatment test. Finally, the 1.5µm, 4pm and 1.5µm RDLs were electroplated on a patterned wafer, and their uniformity and flatness were calculated. Both uniformity and flatness showed a decreasing tendency basically when the line width kept decreasing. The uniformity and flatness were 6.73~13.89% and 2.32~4.17% respectively for nanotwinned copper electrolyte, which was at the upper level compared to the commercial RDL electrolytes.

Thermal degradation of the composite constituted by high density polyethylene (HDPE) and microencapsulated red phosphorus (MRP) were studied using thermogravimetric (TG) data obtained at different heating rates. The kinetic models and parameters of the thermal degradation of MRP/HDPE composite were evaluated by FWO, KAS and IKP method. It indicates that the activation energy E of 4 % MRP/HDPE composite is higher than HDPE for three methods. MRP could improve the thermal stability and slow down the thermal degradation of HDPE. With adding MRP, the degradation mechanism of HDPE is changed and the degradation rate decreases.

Diamond particle with tungsten boride (WB) coating was synthesized by the molten salt method. Three different diamond/Fe-Ni composites made from pristine diamond, B4C coated diamond and WB coated diamond with Fe-Ni powders were prepared by powder metallurgy. The composition and microstructure of the tungsten boride coating were investigated. Both bending strength and cutting performance of the composites were investigated. Addition of the WB coating provided an increased bending strength (871.2 MPa) and relative density (93.54%), compared with the composites consist of uncoated diamond and Fe-Ni (746.8 MPa, 92.81%). Three different Fe-Ni-based impregnated diamond drill bits contained 20 vol.% pristine diamond, B4C coated diamond and WB coated diamond were manufactured by powder metallurgy, respectively. Drilling rate of bits was measured by XY-4 geological core drill on granite. The test results show that the drilling rate of bits with WB coated diamond (2.42 m/h) was 40% higher than that with pristine uncoated diamond (1.72 m/h).

A facile and eco-friendly way for fabrication of CuO is developed based on an one-step chemical precipitation route without calcination procedure or use of surfactant. The structure features of as-prepared CuO are characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy and N2 adsorption-desorption experiment. X-ray diffraction analysis shows that CuO with particle size of 13.5–19.2 nm and crystallinity of 67.0–72.9% can be fabricated by the transformation of Cu(OH)2 precursor at bath temperature above 50 °C. By adjusting the oil bath temperature and the content of ammonium hydroxide, we demonstrate a formation mechanism to control CuO to be 2D leaf-like structure with large specific surface area of 33.4 m2/g and pore volume of 0.226 cm3/g, or 3D flower-like ones with specific surface area of 7.45–18.7 m2/g and pore volume of 0.0249–0.0850 cm3/g. The catalytic performances of as-prepared CuO are evaluated by monitoring degradation of methylene blue in the presence of hydrogen peroxide. Almost 100% methylene blue degradation rate can be reached after reaction for 210 min on 3D flower-like CuO synthesized with 10 mL ammonia content in oil bath of 50 °C. The high activity can be correlated with the morphology and pore volume of CuO. The present synthetic strategy is an inexpensive and convenient way suitable for large-scale fabrication of copper oxides, which are potential catalysts for organic compounds degradation.

Given the increasing concern regarding the global decline in rare earth reserves and the environmental burden from current wet-process recycling techniques, it is urgent to develop an efficient recycling technique for leftover sludge from the manufacturing process of neodymium–iron–boron (Nd–Fe–B) sintered magnets. In the present study, centerless grinding sludge from the Nd–Fe–B sintered magnet machining process was selected as the starting material. The sludge was subjected to a reduction–diffusion (RD) process in order to synthesize recycled neodymium magnet (Nd2Fe14B) powder; during this process, most of the valuable elements, including neodymium (Nd), praseodymium (Pr), gadolinium (Gd), dysprosium (Dy), holmium (Ho), and cobalt (Co), were recovered simultaneously. Calcium chloride (CaCl2) powder with a lower melting point was introduced into the RD process to reduce recycling cost and improve recycling efficiency. The mechanism of the reactions was investigated systematically by adjusting the reaction temperature and calcium/sludge weight ratio. It was found that single-phase Nd2Fe14B particles with good crystallinity were obtained when the calcium weight ratio (calcium/sludge) and reaction temperature were 40 wt% and 1050 °C, respectively. The recovered Nd2Fe14B particles were blended with 37.7 wt% Nd4Fe14B powder to fabricate Nd–Fe–B sintered magnets with a remanence of 12.1 kG (1 G = 1 × 10−4 T), and a coercivity of 14.6 kOe (1 Oe = 79.6 A·m−1), resulting in an energy product of 34.5 MGOe. This recycling route promises a great advantage in recycling efficiency as well as in cost. Keywords: Nd–Fe–B grinding sludge, Recycled sintered magnets, Calcium reduction–diffusion, Rare-earth-rich alloy doping

The hydrogen-disordered structure of ice, Ic, makes it difficult to analyze the vibrational normal modes in the far-infrared region (i.e., the molecular translation band). To clarify the origin of the energy-splitting of hydrogen bond vibrations in this area, a 64-molecule supercell was constructed and calculated using first-principles density functional theory. The results were in good agreement with inelastic neutron scattering experiments and our previous study of a hydrogen-ordered ice Ic model. Assisted by analytic equations, we concluded that the origin of the two hydrogen bond peaks in real ice Ic is consistent with that of hydrogen-ordered ice Ic: the peaks originate from two kinds of normal mode vibration. We categorize the four peaks in the far-infrared region recorded from inelastic neutron scattering experiments as the acoustic peak, the superposition peak, the two-hydrogen bond peak and the four-hydrogen bond peak. We conclude that the existence of two intrinsic hydrogen bond vibration modes represents a general rule among the ice family, except ice X.

The application of optical microscopy in four-dimensional (spatial and temporal) super-resolution imaging poses challenges because of the requirement of a long acquisition time or high illumination intensity. In this paper, we introduce simultaneous two-angle axial ratiometry (STARII) for

For liquid water in the far-infrared spectrum, phonons of molecular vibrations constitute two bands with a narrow gap at around 30 meV. Interestingly, there are two distinct peaks for ice in this g...

Highly crystalline α-zirconium phosphate (α-ZrP) nanoparticles were synthesized and exfoliated into nanosheets, and then the hydrophilic nanosheets were modified into hydrophobic nanosheets with octadecyltrichlorosilane (OTS). Scanning electron microscopy, Fourier transform infrared spectroscopy, X-ray diffraction, and thermogravimetric analysis were applied to confirm the morphology and chemical structure of the nanosheets. Contact angle measurement was conducted to explore the wettability alteration of the hydrophobically modified α-ZrP nanosheets, and the result showed that the wettability of the core was changed into hydrophobicity. When ZrP-OTS nanosheets were injected during water-flooding, a Pickering emulsion will be formed. The droplet diameters and viscosities of the Pickering emulsions were measured. The hydrophobically modified α-ZrP nanosheets were applied in low-permeability sandstone cores and various concentrations were tested. The injectivity of the hydrophobically modified α-ZrP nanosheets was also studied and the result indicated that the nanosheets exhibit good injectivity. The mechanisms for enhancing oil recovery by utilizing hydrophobic α-ZrP nanosheets were analyzed: forming Pickering emulsions and increasing the viscosity of the displacing phase. Forming emulsions and increasing the viscosity of the flooding phase can enhance the microdisplacement efficiency, while good injectivity can also enhance the macrodisplacement efficiency. The result indicated the possibility of using hydrophobically modified α-ZrP nanosheets for enhancing oil recovery in a low-permeability reservoir.

The coercivity, microstructure, and magnetic domain structure of Nd–Fe–B sintered magnets by grain boundary diffusion process (GBDP) with TbH3 nanoparticles were systematically investigated. Compared to the original magnet, the coercivity (Hci) of the GBDP magnets improved from 1702 to 2374 kA·m−1 with few remanence reduced from 1.338 to 1.281 T. Electron probe micro-analysis (EPMA) analysis showed that Tb diffused along grain boundary, mainly concentrated in the boundary layer of the main phase, and formed a core–shell structure. Magneto-optical Kerr optical microscope (MOKE) analysis showed that there were two types of magnetic domain reversal in one grain: gradual reversal (GR) and abrupt reversal (AR). When the applied field decreased from saturated magnetic field, the reversal magnetic domain nucleated and then spread over the whole grain gradually, which was called GR. However, some grains kept the single domain state until Hh which was a value of reverse direction applied field in second quadrant in hysteresis loops. When the applied field increased above Hh, reversed magnetic domain would suddenly appear and occupy most of the area of the grain, which was called AR. That is because AR grains have higher reversed magnetic domain nucleation field (HRN2) than GR grains (HRN1). After GBDP, the area of AR region increased obviously and GR region decreased accordingly, indicating that the core–shell structure could change GR grain into AR grain. The core–shell structure could suppress flipping of the magnetization of the grains due to the large magnetic anisotropy of Tb-rich shell. Therefore, large AR area led to high coercivity.

In this study, an experimental device is designed and built to investigate the heat transfer characteristics in a downflow circulating fluidized bed evaporator. The tested downer has a length of 1200 mm and a dimension of Ф38 mm × 3 mm. Polyformaldehyde (POM), SiC and glass bead particles are used as the inert solid particles. A range of experimental investigations are performed by varying the amount of added particles (0.5–2.0%), heat flux (8–16 kW·m−2) and circulation flow velocity (0.56–1.78 m/s). Results show that as the addition of the particles destroys the laminar sublayer and increases nucleate sites, the boiling heat transfer coefficient of the three-phase flow is higher than that of the two-phase flow. All three kinds of particles added can enhance the heat transfer. The maximum enhancing factors are 78.5%, 68.8%, and 72.1% within the range of experiments for POM, glass bead and SiC particles, respectively. The flow boiling heat transfer coefficient initially increases and then decreases or fluctuates with the increase in the amount of added particles. The circulation flow velocity has two aspects of influence on the flow boiling heat transfer. The enhancing factor increases with the increase in circulation flow velocity at low heat flux, but initially increases and then decreases at high heat flux. The enhancing factor decreases with the increase in heat flux because of the generation of vapor film on the heating wall. Three dimensional diagrams are established to determine the optimum particles. The results can provide some references for the industrial application of the circulating fluidized bed heat transfer technology.

Summary Interfacial polymerization (IP) is a platform technology for ultrathin membranes. However, most efforts in regulating the IP process have been focused on short-range H-bond interaction, often leading to low-permselective membranes. Herein, we report an electrostatic-modulated interfacial polymerization (eIP) via supercharged phosphate-rich substrates toward ultra-permselective polyamide membranes. Phytate, a natural strongly charged organophosphate, confers high-density long-range electrostatic attraction to aqueous monomers and affords tunable charge density by flexible metal-organophosphate coordination. The electrostatic attraction spatially enriches amine monomers and temporally decelerates their diffusion into organic phase to be polymerized with acyl chloride monomers, triggering membrane sealing and inhibiting membrane growth, thus generating polyamide membranes with reduced thickness and enhanced cross-linking. The optimized nearly 10-nm-thick and highly cross-linked polyamide membrane displays superior water permeance and ionic selectivity. This eIP approach is applicable to the majority of conventional IP processes and can be extended to fabricate a variety of advanced membranes from polymers, supermolecules, and organic framework materials., Graphical abstract, Highlights • Electrostatic-modulated interfacial polymerization is proposed for the first time • Electrostatic attraction regulates the spatial-temporal distribution of amine monomers • Monomer regulation leads to reduced thickness and enhanced cross-linking of membrane • Ultrathin and highly cross-linked polyamide membrane displays superior permselectivity, Supramolecular Materials; Materials Science; Materials Chemistry; Materials Synthesis; Polymers

According to a report, the existence of two characteristic hydrogen bond (H-bond) peaks in the translational band of ice does not occur in high-pressure ice VIII. To test this, a comparative analys...

In this paper, a direct co-precipitation method was used to prepare antimony-doped calcium fluoride nanopowders (NPs). The effects of reaction concentration, reaction medium and lanthanum doping on the properties of calcium fluoride NPs were investigatedviaa control variable method and the best preparation conditions was identified. The structural analysis of the powder materials prepared in this work were carried out by XRD, SEM, ICP and other test methods. By analyzing the experimental data, we found that the best performance of Eu-doped CaF2NPs can be acquired under the reaction concentration of 1 mol/L in aqueous solution. In the same time, the NPs possess a high degree of dispersion with an average diameter of 22 nm, which is beneficial to the preparation of transparent Eu3+: CaF2ceramics with excellent up-conversion luminescence. The results show that the grain size, the crystallinity of the NPs and the amount of Eu infiltration have a decreasing tendency with the increasing reaction concentration, while the degree of agglomeration of the NPs can be enhanced by increasing the reaction concentration.

For high-performance mixed-matrix membranes (MMMs), it is crucial to design gas transport channels in fillers to rationally manipulate the structure-property relationship. In this study, the novel porous organosilicon nanotubes (PSiNTs) were incorporated into Pebax to prepare MMMs for biogas purification (CO2/CH4 separation). After comparing the separation performance of MMMs containing PSiNTs and MMMs containing non-porous organosilicon nanotubes (SiNTs)，it can be found that the porous structure on wall of organosilicon nanotubes had a significant effect on the improvement of the gas permeability. In addition, the amino-modified PSiNTs (N-PSiNTs) were prepared and introduced into membranes to significantly enhance the CO2 permeability and CO2/CH4 selectivity. Firstly, the porosity of N-PSiNTs afforded rapid gas transport channels in MMMs and intensified the diffusion mechanism, increasing the CO2 permeability. Secondly, the reversible reaction between amino groups and CO2 in MMMs intensified the facilitated transport mechanism, increasing the CO2/CH4 selectivity. In particular, the Pebax-N-PSiNTs with 0.5 wt% and 1 wt% N-PSiNTs exhibited the optimal separation performance, which surpassed 2008 upper bound and were superior to the MMMs incorporated with other kinds of nanotubes.

The polycrystal CuO curved nanowires on Cu mesh were synthesized by a facile alkalization method. This visible light-driven CuO curved nanowires were observed to have highly sensitivity for non-enzymatic ethanol sensing in solution and fast antibacterial property under flashlight irradiation. In order to reveal the mechanism of polycrystal CuO curved nanowires, the comparison between polycrystal CuO nanowires and single-crystal CuO nanowires were investigated based on the analysis of the morphology, nanostructure, theoretical modeling and photoelectrochemical performance. As a result, the highest photocurrent densities were obtained by polycrystal CuO curved nanowires, as the facet heterojunction in curved nanowires played a key role, which existed in the interface between facets CuO (111) and CuO (110) resulting in the effectively separation of photoelectron-holes, thereby increasing of the charge carrier density. Herein, the CuO curved nanowires were assembled as a photoelectrochemical sensor to detect the low concentration ethanol ranging from 10 to 100 nM, and then showed a highly sensitivity. The fast antibacterial performance of CuO curved nanowires was found to completely kill 107 CFU ml−1 E. coli under flashlight irradiation in 20 min. The proposed CuO curved nanowires electrode with self-cleaning performance can be ideal for monitoring the low concentration ethanol in real-time at room temperature as photoelectrodes.

As a promising alternative to the toxic PbTe-based thermoelectric materials, eco-friendly SnTe has attracted considerable attention. Here, we use a facile solvothermal method to in-situ synthesize MXene/SnTe nanocomposites. Comprehensive characterization results indicate that the incorporation of two-dimensional MXene in SnTe matrix can suppress Sn vacancies to result in a reduced carrier concentration and induce abundant MXene/SnTe interfaces, which simultaneously optimizes the electrical and thermal transport properties. As a result, with the optimized MXene content, the maximum figure of merit of ∼0.63 ​at 823 ​K is obtained in SnTe with 0.6 ​wt% MXene, which shows a 60% enhancement compared to pristine SnTe. This work explores a new strategy to introduce two-dimensional MXene into SnTe-based materials with improved thermoelectric properties, which can inspire new pathways into designing and synthesizing high-performance thermoelectric materials.

The safe and efficient operation of submarine high-voltage cables depends on their thermal performance. Based on the electromagnetic heat coupling and heat transfer theory, the cables’ heat dissipation in multi-layered sediments is simulated using FEM. The proposed models are validated by comparing with the results of IEC 60287 and illustrated the limitation of IEC 60287 which ignores convective heat transfer. Further, the width of the cable embedding layers greater than 9 m can promote heat dissipation when the permeability of the cable embedding layer is relatively high, but the effect of depth is less pronounced. Also, the cable temperatures increase with the decrease of sediments thermal conductivity and increase of the buried depth when permeability is below 10−12 m2. The temperature decreases as the permeability increases, the range of decay is between 10% and 55% when the permeability reaches 10−9 m2. The heat dissipation is great when the permeability is greater than 10−11 m2. When the characteristic of the cable embedding layers is different from its upper and lower layers, the high permeability of the upper layers reduces the cable conductor temperature more efficiently than the lower layers. The findings give some reference in improving the transmission efficiency of cables.

A series of four chiral, diimide-bonded Zn(II)porphyrin-perylene-Zn(II)porphyrin hybrids and the four free-base derivatives H2Porphyrin-perylene-H2Porphyrin hybrids were prepared, determined and characterized by various spectroscopies including circular dichroism (cd) spectra. A detailed analysis of the optical and redox properties was carried out by comparing the results obtained via optical spectroscopy and electrochemistry. Interestingly, these chiral perylene-porphyrin hybrids have significant expansion in both UV–vis absorption, fluorescence and circular dichroism spectra, especially in the visible-region.

Three fused-ring-expanded rubyrins with modified macrocyclic core have been synthesized and characterized. A series of spectroscopic, electrochemical measurements and a set of theoretical calculations demonstrate that the core-modification of the inner core of rubyrins has a large influence on the electronic structure. Colorimetric changes are observe that demonstrate that these core-modified rubyrins could be used as selective Hg2+ ion sensors. These properties can be fine-tuned by introducing lipophilic substituents on the meso-aryl rings.

Surface-controlled CuOx/rGO nanocomposite has been successfully fabricated in this study using a simple hydrothermal method. In addition to the characterization by X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and N2 adsorption/desorption, the catalytic conversions of 4-nitrophenol (4-NP), methylene blue (MB) or rhodamine B by the CuOx/rGO nanocomposite in the presence of NaBH4 were carried out. The results demonstrate that all the selected probe reactants show no adsorption on the as-prepared CuOx/rGO nanocomposite, however, their conversions are close to 100% and can be carried out within several minutes. The excellent catalytic activities may be associated with the multi-valenced copper species and the controlled surface of the CuOx/rGO nanocomposite. In the meantime, the CuOx/rGO nanocomposite has a better stability and can be reused for many times without obvious decrease in activity, suggesting a great potential of the as-prepared CuOx/rGO nanocomposite for catalytic degradation of organic pollutants.

The counter-gravity casting methods have been developed to remove the casting defects of Mg based alloys. However, the effects of different counter-gravity casting methods on the microstructure and mechanical properties have not been studied in detail. ZM5 alloys were prepared by gravity casting, low-pressure casting and counter-pressure casting, respectively. The mechanical properties, microstructure and fracture morphologies were examined and compared by means of optical microscopy, scanning electron microscopy methods and tensile testing. Results show that casting defects such as gas pore, shrinkage porosity and cavity can be eliminated by counter-pressure casting. The grain size of α-Mg is decreased signifi cantly by counterpressure casting. Moreover, the precipitated particles are more uniform and fi ner in the counter-pressure casting sample. As a result, the mechanical properties of the alloys are greatly improved. The tensile strength and elongation of the samples by counter-pressure casting are 285 MPa and 13.9%, respectively, which are much higher than those of the low pressure casting and gravity casting.

We report on the design and implementation of an integrated dual-color stimulated emission depletion (STED) microscopy and fluorescence emission difference (FED) microscopy. This highly integrated system combines the respective advantages of STED and FED microscopies, enabling acquisition of super-resolution STED images with specific fluorophores and high laser power, or resolution-enhanced FED imaging for ordinary fluorescent dyes and other materials with moderate demand for laser power. The functional integration enables researchers to select the more appropriate microscopy according to practical scenario and requirements, giving full play to their respective strengths and satisfying the imaging demands maximally. The system’s resolution is characterized by dual-color imaging of fluorescent particles. Its practical applicability is verified through imaging various kinds of samples, including several fixed cells stained with different organic dyes and a given organic material—organometallic halide perovskite.

Conjugate heat transfer of air and steam in a rectangular channel with 90° ribs along two opposite walls was investigated experimentally and numerically. The stainless steel test section was 80 mm × 40 mm × 2.5 mm and the ribs were 80 mm × 2.5 mm × 2.5 mm with 25 mm between ribs. The tests investigated the effects of coolant mass flow rate (the corresponding Reynolds numbers in the range of 10,000-50,000) on the conjugate heat transfer enhancement with the ribs. Two conjugate heat transfer calculation methods with different models were developed. For the first model (CHT-Q model) solid domain was viewed as a uniform internal heat source with the adiabatic exterior surfaces, while for the second model (CHT-T model) the outwall temperature was specified by the fitting polynomials of measured data with the zero internal heat. Comparisons between the experimental and numerical results showed that the SST k–ω turbulence model was more suitable for the conjugate heat transfer in such channels. Regardless of numerical error, an approximation of heat loss was specified by the successive trial calculations of the CHT-Q model, while a relatively accurate heat loss was evaluated by the post-processing of the CHT-T calculation. Local heat transfer coefficient can be determined accurately by the quantified heat loss of test system. The critical impact of conjugate heat transfer was demonstrated. Furthermore, the steam coolant compared to air exhibited a higher heat transfer performance by 12–25% for both the ribbed and smooth walls at the same Reynolds number.

Flexible power packs combining a flexible photovoltaic part with a wearable all-solid-state supercapacitor as the self-sustaining energy system to power wearable device have attracted great interest due to the increasing demands for green energy and the tendency for multi-functionalization in electronics industry. To meet this energy requirement, we report an asymmetric all-solid-state supercapacitor, then integrate with commercial flexible solar cells to develop a self-sustaining power pack. In view of comfort for wearable electronics, cotton-textile radiation-proof clothes commonly used for pregnant woman cloth (PWC) are selected as the flexible substrate to construct wearable energy storage devices, which have the properties of flexible, green, renewable, breathable and excellent conductivity. Experimental tests demonstrate that the wearable asymmetric supercapacitors with high power density and relatively large energy density, fast charge/discharge capability, light-weight, excellent reliability and flexibility can enable the solar energy captured from the environment to afford a continuous and stable output of electric power and diminish the solar energy fluctuations. The supercapacitor is assembled with the Co–Ni layered double hydroxides (Co-Ni LDH) nanosheets as the positive electrode and the FeOOH as the negative electrode. Furthermore, the fabricated self-sustaining power pack as the energy source can continuously power the press sensor for monitoring the human physiological signals regardless of the sunlight fluctuation, demonstrating its potential usage in future wearable and portable electronic devices.