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Lead-free Bi0.5Na0.5TiO3 piezoelectric ceramics were successfully prepared by reactive flash sintering of Bi2O3-NaCO3-TiO2 mixed powders, where phase transformation and densification occurred simultaneously. The influence of electric field strength, current density and holding time at constant current state on the phase transformation and densification were investigated. The current density had a significant influence on the extent of phase transformation and densification. The holding time had no influence on the phase transformation, but had an important effect on crystallinity of sample. The sintered bulks exhibited the maximum polarization Pm of 16.8 μC/cm2, remanent polarization Pr of 9.6 μC/cm2, coercive field Ec of 29 kV/cmm, maximum electric-field-induced strain of 0.053%, and piezoelectric coefficient d33 of 85 pC/N. The reactive flash sintering can prepare the dense and single-phase ceramics from multiphase precursor powders in one step of flash, providing a new way for rapid production of ceramic materials.

A mathematical model of the plate-fin heat exchanger filled with catalyst (CFPFHX) is established to investigate the continuous cooling process coupled with ortho-para hydrogen conversion at 42–70 K. The flow and heat transfer performance and the efficiency of ortho-para hydrogen conversion in the CFPFHX are quantitatively evaluated, and the effects of the structural parameters on the flow and heat transfer coupled with ortho-para hydrogen conversion are analyzed. The results show that the Elovich model is the best existing kinetic models of ortho-para hydrogen conversion with an average relative deviation of 1.8%. The Colburn heat transfer factor (j factor) of the hot side of the CFPFHX is 4.3 times that of the plate-fin heat exchanger (PFHX), and the thermal enhancement factor (TEF) of the hot side is 37.7% of that of the PFHX. Meanwhile, for the CFPFHX, the j factor and the TEF of the hot side under different structural parameters are always about 8–10 times and 68%–93% of that of the cold side respectively. Therefore, the CFPFHX can ensure the flow and heat transfer performance and realize the ortho-para hydrogen continuous conversion. And a fin with the larger flow area (high fin height, wide fin spacing and small fin thickness) has a better flow and heat transfer performance and ortho-para hydrogen conversion. The outlet para-hydrogen ratio youtp-H2 and the mass space velocity vm in the CFPFHX have an approximate linear trend. When mass space velocity vm ≤ 0.6589 kg/(m3·s), the outlet para-hydrogen ratio youtp-H2 can meet the requirement at 42–70 K. Above all, the mechanism of flow and heat transfer coupled with ortho-para hydrogen conversion is revealed for the first time in this study, which can provide a theoretical guidance for the application of the integrated technology in large scale hydrogen liquefaction process.

R450A is one of R134a substitutions owing to its low GWP and similar refrigeration performance. The existing researches are mostly about its performance in refrigeration systems. This paper focuses on its heat transfer characteristics in condensation. By combining the SST k-ω model with the VOF method, the condensation of R450A, and its two components, R134a and R1234ze(E), in mini-channels were explored. The mass flux ranges from 400 to 800 kg•m−2•s−1. The vapor quality is between 0.4 and 1. The tube diameters are 1mm and 2mm. The results show when the mass flux is 400, 600, and 800 kg•m−2•s−1, HTC of R134a is 11.3%-16.3%, 7.5%-15.3%, and 8.2%-14.7% higher than that of R450A, and HTC of R1234ze(E) is 5.2%-12.0%, 4.9%-12.5%, and 6.7%-14.1% higher than that of R450A. Moreover, their film thickness and axial velocity are also compared. When the vapor quality is 0.5, 0.7, and 0.9, compared with the average liquid film of R450A, that of R1234ze(E) is 1.2%, 8.8%, and 11.1% thinner and that of R134a is 4.4%, 3.6%, and 1.0% thicker, respectively. The effects of vapor quality, mass flux, channel diameter, and fluid property on the condensation of R450A are also analyzed.

Lithium dendrites, “dead lithium”, infinite volume change and fragile solid electrolyte interphase (SEI) appear indefinitely during Li plating/stripping process, which severely resist the practical application of lithium metal batteries (LMBs). Herein, by a functionalized framework, a phosphorized copper mesh as support skeleton, the lithium plating/stripping has been gridded into zoning effect, thus a desired lithium anode with excellent performance and practical application significance can be achieved. The framework-based lithium anode showed multi-functions with many advantages: enhancing lithium affinity, mitigating volume expansion, improving the current distributions, and inducing uniform deposition of Li+. Thus, a highly reversible and dendrite-free lithium anode under large capacity could be successfully realized, which has been verified by operando optical dynamic test and COMSOL simulation. As expected, symmetric-cell displays low overpotential (~210 mV) at ultra-high current density of 20 mA cm−2 and long lifespan (>1600 h) at ultra-high areal capacity of 50 mAh cm−2, moreover, full-cell delivers high cycling stability (2 C, 500 cycles) and outstanding rate performance with a lower polarization.

van der Waals (vdW) vertical p-n junctions based on two-dimensional (2D) materials have shown great potential in flexible, self-driven, high-efficiency electronic and optoelectronic applications. However, due to the complex nucleation dynamics, the controllable synthesis of vertical heterostructures remains a daunting challenge. Here, we report the controlled growth of vertical GaSe/MoS2 p-n heterojunctions via a liquid gallium (Ga)-assisted chemical vapor deposition method. The growth mechanism can be interpreted by theoretical calculations based on the Burton-Cabrera-Frank theory. By analyzing the diffusion barriers and the Ehrlich-Schwoebel barriers of adatoms, we found that the growth modes between vertical and lateral can be precisely switched by means of adjusting the amount of Ga. Based on the achieved high-quality vertical GaSe/MoS2 p-n heterojunctions, photosensing devices are further designed and systematically investigated. Upon light illumination, prominent photovoltaic effects with large open-circuit voltage (0.61 V) and broadband detection capability from 375 to 633 nm are observed, which can further be employed for self-powered photodetection with high responsivity (900 mA/W) and fast response speed (5 ms). The developed liquid-metal-assisted strategy provides an effective method for controllable synthesis of vdW heterostructures and will give impetus to their applications in high-performance optoelectronic device.

Metallic sodium is considered the most likely anode material to replace metallic lithium owing to its high theoretical capacity, abundant reserves, and low cost. However, the uneven deposition and agglomerate deposition of Na often result in low coulombic efficiency and inferior lifetime during cycling. Here, by phosphorizing treatment, a sodiophilic phosphorized copper mesh (PCM) has been achieved as the metallic sodium-host current collector for the first time; then through in situ electrochemical reaction construct, sodiophilic Na–Cu–P composite layer, which has a fast electronic/ionic conductivity and strong adsorption ability with sodium, thereby greatly mitigating electrodeposition overpotential for improving Na plating/stripping behaviors. Meanwhile, the cross-linked mesh skeleton significantly diminishes the local current density, thus achieving highly reversible Na plating/stripping behavior with dendrite-free and “dead Na”-free. Consequently, the PCM electrode can maintain a high coulombic efficiency (∼99.96%) over 1000 cycles at 5 mA cm−2 and exhibit an ultra-low electrodeposition overpotential from 0.5 mA cm−2 to 10 mA cm−2 in a half-cell. Similarly, the symmetrical cell displays superior cycling stability with low overpotential. Furthermore, the PCM@Na anode delivers excellent cycling/rate performance when paired with Prussian blue (PB) cathode in full-cell.

An egg white-derived carbon/magnetic nanoparticles/water-soluble graphene oxide composite absorber (EWC/MNPs/WSGO) was specially designed and synthesized via a facile sol–gel process with subsequent high-temperature pyrolysis. Magnetic nanoparticles (MNPs) were used to bring magnetic loss ability and improve the electromagnetic matching condition. Water-soluble graphene oxide (WSGO) was also used to adjust the absorption properties of the composite absorber. Moreover, egg white, which is liquid biomass, enables uniform dispersion of MNPs and WSGO within the absorber, allowing full use of the synergistic effect of each component. Benefiting from the excellent homogeneous structure, moderate dielectric loss and magnetic loss, strongly matched impedance, and multiple polarization are achieved. The as-synthesized optimal sample (EWC/MNPs/WSGO-1.0) exhibits superior electromagnetic wave absorption properties. The minimum reflection loss (RLmin) reaches −51.5 dB, and the effective absorption bandwidth (EAB, RL < −10 dB) is 3.4 GHz at a thickness of 1.6 mm. Compared with the reported bio-derived carbonaceous composite absorbers, EWC/MNPs/WSGO has great potential to be a lightweight and efficient electromagnetic wave absorption material in the frequency range of 2 to 18 GHz.

The emerging applications of electrochemical gas sensors (EGSs) in Internet of Things-enabled smart city and personal health electronics bring out a new challenge for common EGSs, such as alcohol fuel cell sensors (AFCSs) to reduce the dependence on a pricy Pt catalyst. Here, for the first time, we propose a low-cost novel N,S-codoped metal catalyst (FeNSC) to accelerate oxygen reduction reaction (ORR) and replace the Pt catalyst in the cathode of an AFCS. The optimal FeNSC shows high ORR activity, stability, and alcohol tolerance. Furthermore, the FeNSC-based AFCS not only demonstrates excellent linearity, low detection limit, high stability, and superior sensitivity to that of the commercial Pt/C-based AFCS but also outperforms commercial Pt/C-based AFCS in the exposed cell regarding great linearity, high sensitivity, and great stability. Such a promising sensor performance not just proves the concept of the FeNSC-based ACFS but enlightens the next-generation designs toward low-cost, highly sensitive, and durable EGSs.

The shuttle effect of dissolved polysulfides produced during the operation of lithium–sulfur batteries is the most serious and fundamental problem among many challenges. We propose a strategy via i...

In this work, various photocatalysts were synthesized with an impregnation-precipitation process to in situ decorate Ag-based nanoparticles (NPs, including Ag3PO4, AgCl, Ag2O, and Ag2CO3) on the cellulosic paper. The structure and properties of the Ag-based composites were characterized by scanning electron microscopy, X-ray diffraction, transmitting electron microscopy, UV-vis diffuse reflectance spectra, and photocatalysis testing. The results showed that cellulosic paper is an efficient carrier which is feasible to grasp NPs due to the cellulosic nanofiber-network microstructure. Among the obtained samples, Ag2CO3 and AgCl NPs on cellulosic paper displayed high photocatalytic activity for the degradation of methyl orange under ultraviolet and visible light. However, photo lability of Ag2CO3 limits its recyclable. AgCl showed a better reutilization with the assistance of a surface plasmon resonance effect by Ag NPs that were grown in situ on the AgCl NPs, which formed Ag@AgCl nanocomposite structure. The photocatalytic activity of the AgCl/cellulosic paper decreased only slightly after three runs of photodegradation of methyl orange. The possible mechanism for photocatalysis was proposed. This work may provide a new method for the design of silver-based NPs/cellulosic paper nanocomposite photoreactors with favorable photocatalytic activities for industrial applications.

Lithium metal is the most promising anode candidate because of its ultrahigh theoretical specific capacity. Unfortunately, its high reactivity, uncontrolled dendrites, “dead lithium” formation, and infinite volume expansion hinder its commercial application. Herein, by in-situ constructing a multifunctional lithium-pinned array (m-LPA) endowed with functions of lithiophilicity, zoning effect and riveting effect on a surfacely phosphorized three-dimensional (3D) copper foam, a high reversible Li plating/stripping electrochemistry can be achieved. Benefiting from the m-LPA, lithium can uniformly plate/strip both on the surface and in the inner space of the 3D skeletons with improved morphology. Consequently, a high Coulombic efficiency (~98.41%) could be achieved at 1 ​mA ​cm−2 with 1 ​mA ​h cm−2 for over 600 cycles (1200 ​h). Moreover, at a higher current density of 10 ​mA ​cm−2 with 0.5 ​mA ​h cm−2, a symmetric cell with m-LPA@Li electrode could still stably cycle for 900 cycles. Finally, a full cell coupled with LiFePO4 cathode displayed excellent rate performance with a lower overpotential. The conception and strategy of m-LPA, which were first proposed here, are a promising way to realize large-scale application of Li anode.

Li–S batteries have received unprecedented attention owing to their exceptionally high energy density and low cost. Nevertheless, the daunting challenges of insulating properties, soluble polysulfide shuttling, drastic volume change and sluggish polysulfide conversion kinetics, still hinder their application towards commercialization. Very recently, exciting progresses have been made on inorganic/organic polar hosts as either polysulfide immobilizers or polysulfide redox accelerators, targeting durable Li–S batteries. Herein, self-assembled NiCo2S4 granules comprising secondary open-hole tubular structures are first devised as highly-efficient host materials for high-sulfur-loading and durable Li–S batteries. NiCo2S4 hosts are featured with their large porosity, high electronic conductivity, rapid ion conduction, strong polysulfide immobilization capability and catalytic effect on polysulfide redox, thus greatly ameliorating the polysulfide-shuttle issue and accelerating the polysulfide conversion kinetics. Therefore, the NiCo2S4/S cathode shows a reversible capacity of 1387 ​mAh g−1 at 0.2C and retains a value of 543 ​mAh g−1 after 500 cycles at 2 ​C. Impressively, the NiCo2S4/S cathode with a sulfur loading of 8.9 ​mg ​cm−2 exhibits high areal capacity of 8.3 ​mAh cm−2, low polarization and high cycling stability. Moreover, the as-derived soft-package battery with a 4.5 ​mg ​cm−2 sulfur loading can power 169 light-emitting diodes, verifying its great potential for practical application.

Li-rich Mn-based materials, as high-energy-density and low-cost cathode materials for Li-ion batteries, suffer severe irreversible voltage fading and capacity loss during cycling, associated with the instability of crystal structure at high voltage, which greatly reduces the specific energy density after cycling and thus impedes their commercialization. Here, we introduce a new strategy to mitigate voltage fading and improve the cycling performance of Li-rich Mn-based cathode materials by simply introducing MgSO4 in the cathode during its preparation process. The results show that cycling stability and voltage fading of corresponding batteries were dramatically improved due to the high Li+ retention at the initial charge process and the stable cathode electrolyte interface (CEI) layer. After 100 cycles at 1C, the average discharge voltage decay is only 0.115 V (1.15 mV per cycle), with a high voltage retention of 96.7%, and the capacity remains at 91.5% after 300 cycles at 1C.

Lithium (Li) is a metallic element possessing the most negative electrode potential and the lowest electrochemical equivalent, which make it one of the key materials for the development of the next-generation Li batteries with high specific energy. However, the heterogeneous deposition, volume expansion, solid-electrolyte interphase (SEI) fracture, and high reactivity of metallic Li make its commercialized development difficult. Herein, a novel polyaniline (PANI) decorated three-dimensional (3D) copper mesh (3DCMP) skeleton for a Li metal anode is proposed, which was prepared by in situ polymerizing aniline on the surface of a copper mesh (3DCM). The lithiophilic PANI micro-sheets could induce ordered Li deposition on the mesh and facilitate the formation of a more available SEI film, which could effectively alleviate the formation of Li dendrites and highly promote the utilization of Li during long-term cycling. The symmetrical-cell displayed an excellent Li plating/stripping performance, in which it maintained an overpotential of less than 20 mV at a current density of 2 mA cm−2 over 4000 h. Furthermore, the full-cell coupled with the LiFePO4 cathode exhibited a high capacity retention of 84.8% at 4C after 550 cycles and when coupled with the rGO/S cathode exhibited a capacity retention of 94.4% at 1C after 100 cycles. Hence, it demonstrates a promising potential to be applied in large-scale manufacturing.

The sluggish kinetics of the sulfur conversion reactions in Li–S batteries is a critical challenge for their application. Thus, many studies have been dedicated to promoting the conversion process by including either functionalized matrix materials in the cathode or redox mediators in the electrolyte. Herein, by embedding a solid auxiliary redox species, we designed and prepared a composite that can be used as a matrix for a sulfur cathode. Differing from the conventional method, in which all the so-called redox mediators utilized are dissolved in the electrolyte, we employed a solid auxiliary redox species, a cobalt phthalocyanine complex supported on graphene structures, as skeleton materials of sulfur to promote the conversion kinetics in Li–S batteries. The graphene–cobalt phthalocyanine hybrid played a prominent role in promoting the kinetics of polysulfide conversion with multiple functions of reducing the activation energy hill, transferring electrons, suppressing the shuttle effect, etc. Consequently, the Li–S battery with the graphene–cobalt phthalocyanine–sulfur cathode showed better electrochemical performance than the battery with the graphene–sulfur cathode. Typically, a high initial capacity of 1400 mA h g−1 was achieved at 0.1C during the initial activation cycle, and the 1st and 300th cycle capacities at 0.5C were 1116 and 860 mA h g−1, respectively. Additionally, at a rate of 0.3C, high capacities of 1182 and 869 mA h g−1 were obtained during the 1st and 500th cycles, respectively. Furthermore, enhanced rate capability was achieved, delivering a capacity of 874 mA h g−1 at a rate of 2C.

Three-dimensional (3D) printing of Cu items is a new way to build up the structured Cu materials, but 3D printing of Cu items is usually a challenge because of the high melting point, high thermal ...

The storage of sodium ions with carbon materials has huge potential for large-scale application due to its resource-rich and environmental advantages. However, how to realize high power density, high energy density and long cycle life are the bottlenecks restricting its development. Herein, by using a facile synthesis strategy, a carbon-based framework with a hierarchical structure and intrinsic heteroatom sites which are the characteristics contributing to ultrahigh rate and capacity has been achieved. As a result, the hierarchical carbon-based material exhibits excellent performance when used as both the anode and cathode for sodium-ion capacitors (SICs), which can deliver a high energy density of 224 W h kg−1 (at 180 W kg−1), an ultrahigh power density of 17 160 W kg−1 (at 128 W h kg−1) and ultralong cycle life (91% capacity retention after 10 000 cycles at 2 A g−1), outperforming most of the previously reported SICs with other configurations.

The unipolar n‐type polymeric semiconductors are crucial for the development of complementary inverters and complementary logic circuits. To achieve this target, the polymer skeleton should be electron‐deficient, which guarantees the energy‐level alignment between the lowest unoccupied molecular orbital energy level of polymeric materials and the work function of electrode, further permitting effective electron injection. Different from the introduction of the sp2‐hybridized nitrogen atoms and fluorine atoms, cyano‐substituted aromatic blocks are synthesized and further copolymerized with naphthalene diimide (NDI) unit, affording a series of copolymers of PNDI‐BTCN, PNDI‐TVTCN, and PNDI‐SVSCN. The photophysical, electrochemical, and thermal properties of all the copolymers are systematically investigated, and their semiconducting performance is studied by fabricating field‐effect transistors and tested under atmosphere. All the polymers exhibit unipolar n‐type semiconducting performance because of the synergetic effect of strong electron‐withdrawing NDI units and cyano‐substituted aromatic blocks. The highest mobility of 0.20 cm2 V−1 s−1 is obtained. Moreover, theoretical simulation and thin‐film characterization are conducted to reveal the difference in semiconducting performance among the three polymeric materials.

The sluggish kinetics and shuttle effect of lithium polysulfide intermediates are the major issues that retard the practical applications of lithium-sulfur (Li-S) batteries. Herein, we introduce a defect engineering strategy to construct a defected-UiO-66-NH2-4/graphene electrocatalytic membrane (D-UiO-66-NH2-4/G EM) which could accelerate the conversion of lithium polysulfides in high sulfur loadings and low electrolyte/sulfur (E/S) ratio Li-S batteries. Metal-organic frameworks (UiO-66-NH2) can be directionally chemical engraved to form concave octahedra with abundant defects. According to electrocatalytic kinetics and DFT calculations studies, the D-UiO-66-NH2-4 architecture effectively provides ample sites to capture polysulfides via strong chemical affinity and effectively delivers electrocatalytic activity of polysulfide conversion. As a result, a Li-S battery with such an electrocatalytic membrane delivers a high capacity of 12.3 mAh cm-2 (1013 mAh g-1) at a sulfur loading up to 12.2 mg·S cm-2 under a lean electrolyte condition (E/S = 5 μL mg-1-sulfur) at 2.1 mA cm-2 (0.1 C). Moreover, a prototype soft package battery also exhibits excellent cycling stability with a maintained capacity of 996 mAh g-1 upon 100 cycles.

The mandrel frame is the most commonly used sensitizing structure for scalar fiber hydrophones, and its material properties and structure directly affect hydrophone performance. The finite element simulation model of a hydrophone is established based on the principle of acoustic-structure interaction. Additionally, the influences of the material and structure on hydrophone sensitivity and the working bandwidth are analyzed in detail. The results show that the sensitivity and bandwidth of the hydrophone restrict each other, and the inner mandrel resonance exerts the main limitation on the bandwidth. Increasing the inner mandrel thickness and reducing the inner mandrel radius can widen the working bandwidth while maintaining sensitivity. The accuracy of the model is verified by via experiments in a lake.

Different from the ion intercalation/deintercalation, conversion-based reactions are a promising way to achieve high capacity of storage materials. However, their too much volume change and poor re...

The present work deals with a poly(vinyl alcohol)‐based membrane mixed with poly(4‐styrenesulfonic acid) to be used as a proton‐conducting solid‐state electrolyte in an electrochemical gas sensor for the detection of alcohol. A cross‐linking bonding semi‐interpenetrating network is formed between the polymer backbones, providing the membrane with superior mechanical property and excellent water retention. Meanwhile, the graphene oxide nanosheets are incorporated into the polymer fibrous backbones, creating impermeable block layers to limit ethanol gas penetration. Importantly, the modification of graphene oxide facilitates the protons transportation in both in‐plane and through‐plane channels of the membrane, boosting excellent conductivities of 0.13 S cm−1 (in‐plane) and 22.6 mS cm−1 (through‐plane) at 75°C, respectively. An alcohol fuel cell sensor assembled with this semi‐interpenetrating network solid electrolyte membrane is fabricated based on direct ethanol fuel cell principle, exhibiting excellent sensitivity, linearity, as well as low ethanol detection limits of 25 ppm.

Uniform temperature distribution within solid catalyst particles is important to achieving low coke formation in a high-temperature reaction. However, the issue of uneven temperature distribution exists in most fixed-bed catalytic reaction systems. Here, we developed a microwave-assisted system and used it in catalytic dehydration of glycerol for sustainable production of acrolein. A coated microwave absorbing catalyst WO3/ZrO2@SiC was prepared and employed in the catalytic reactions. The effects of reaction temperature, ZrO2/SiC ratio, and weight hourly space velocity (WHSV) on glycerol conversion and arcolein selectivity were examined. Experimental results showed that the microwave heating proved to be more effective than the conventional electric heating for glycerol dehydration to acrolein at lower temperature. The acrolein selectivity reached over 70% with complete glycerol conversion at 250 oC by microwave heating. The catalyst acidity was greatly influenced by ZrO2/SiC ratio, which in turn determined the acrolein selectivity. More importantly, much better catalyst stability was obtained in the microwave-heating process than the electric-heating process. In addition, the microwave-heating system was effective for the in-situ regeneration of deactivated catalyst.

A super long and stable laminar plasma jet was used in the atmospheric plasma spray process in this work. Microstructures evolution and properties of alumina coatings that were obtained using a long spraying distance ranging from 200 mm to 350 mm in an atmospheric environment were studied in this work. These processes were carried out by using a total gas flow rate of 14 slpm with 70% nitrogen and 30% argon in volume and output power of 25.4 kW (current of 160 A). A long particle residence time was obtained in this study, which compared with other current atmospheric plasma spray methods. The microstructures of coatings showed the multi-island protrusions on the top surfaces and overlapped lamellar splats at the fracture surfaces. The microstructural evolution was significantly affected by the heating and motion behaviors of alumina particles when these were flowing in the long laminar plasma jet at different spraying distances.

For Li-S batteries, the interlayer between the separator and sulfur cathode preventing lithium polysulfide (LiPS) travel across the membrane is a research hotspot. The good blocking ability for LiPSs indicates that these interlayers can promote the electrochemistry performance with high S loading. However, most of these interlayers are just used as a simple blocking wall. Such a blocking wall, for example, the lower Li+ ion conductivity, would often reduce the electrochemical performance, especially under large current density. Here, we report a multifunctional ion-sieve made by three two-dimensional (2D) sheets, graphitic carbon nitride (g-C3N4), boron nitride (BN), and graphene. A g-C3N4 sheet which possesses orderly channels with a size of 3 A in the crystalline structure can effectively prevent polysulfides from passing through but allow lithium ions to pass freely, whereas a BN sheet acts as an excellent catalyst for sulfur redox, and graphene acts as an extended collector, which can promote the conductivity of the sulfur electrode region. Benefiting from the synergistic effect among these 2D materials, the ion-sieve interlayer makes the Li-S battery show excellent performance at a large rate with both high sulfur loadings and high sulfur content. In addition, the host materials are not necessary in these cells. The ion-sieve liberated a discharge capacity of about 600 mA h g-1 after 500 cycles at 1 C, and the capacity attenuation was less than 0.01% per cycle with a 6 mg cm-2 areal S-loading (pure S as the active material). The reversible capacity could be maintained at more than 400 mA h g-1 at 2 C, which amounts to an area current density of 26.88 mA cm-2.

A series of double perovskite Sr2MgTeO6:Sm3+/Dy3+ phosphors for solid-state lighting application were successfully synthesized by the solid-state reaction process. The phase structure, photoluminescence, thermal quenching, and decay behavior of the prepared phosphors were investigated. The photoluminescence of Sr2MgTeO6:Sm3+ exhibits red emission (640 nm) due to the transition from the 4G5/2 → 6H7/2 under 404 nm excitation. Sr2MgTeO6:Dy3+ exhibits two emission bands under 390 nm excitation. They are due to 4F9/2 → 6H15/2 (blue) and 4F9/2 → 6H13/2 (yellow) transitions of Dy3+, respectively. Sr2MgTeO6:0.10Sm3+ phosphor shows excellent thermal stability. Therefore, Sr2MgTeO6:Sm3+/Dy3+ phosphors are a promising candidate for UV chip-based WLED and solid-state lighting.

The recent criteria to evaluate electromagnetic wave absorber include low density, strong absorbency, wide absorption bandwidth and thin absorber thickness, but its performance at low frequencies is always ignored. In this paper, the porous magnetic carbon nanofibers (P-CNF/Fe) for high-efficient electromagnetic wave absorption at low frequencies were fabricated by electrospinning followed by stabilization and carbonization. With the introduction of porous nanostructure, the permittivity of carbon nanofibers was decreased at low frequency and the impedance matching of permittivity and permeability was realized. The electromagnetic absorbing properties were investigated in detail. The minimum reflection coefficient reaches −44.86 dB at 4.42 GHz, and the widest effective absorption bandwidth (EAB) in the frequency was 3.28 range from 12.96 to 16.24 GHz. Consequently, considering the EM wave absorption performance, P-CNF/Fe synthesized in this work can be a promising candidate in the field of EM wave attenuation.

We propose and demonstrate a high-frequency interferometric optical fiber hydrophone based on acoustic resonance isolation. Novel air chambers are introduced into common type of mandrel sensitization structure to prevent acoustic resonance which occurs inside the inner cylindrical cavity of hydrophone frame at specific high frequency acoustic filed. 1kHz-30kHz frequency response of this new kind of hydrophone is measured in a lake. Experiment shows that, by this acoustic structure optimization, the working frequency bandwidth of optical fiber hydrophone, whose acoustic pressure sensitivity is-147dB, is expanded from 10kHz to above 30kHz.

With the rapid development of electronic devices and wireless communication tools, it is urgent to design and fabricate low-cost, lightweight and effective electromagnetic absorption materials to solve interference of electromagnetic waves. Herein, a new strategy toward porous carbon/graphite nanosheet/ferromagnetic nanoparticle (PC/GNS/Fe) composites was designed to investigate the influence of crystalline carbon on electromagnetic wave absorption. To begin with, graphite nanosheets (GNSs) were incorporated into the porous polyimide by in situ polymerization, and Fe were added as a magnetic particle source and an agent to regulate the pore size. A series of PC/GNS/Fe composite absorbents were obtained. The direct carbonization of porous polymer precursors was beneficial to the design of the pore structure of materials. A hierarchically porous structure derived from the phase separation process was well maintained in the polyimide pyrolysis process. The results demonstrated that the presence of crystalline carbon could influence the reflection loss value and the frequency range. Hence, the absorbing performance can be optimized by adjusting the pore structure and the content of crystalline carbon in materials, which is conducive to obtaining electromagnetic wave absorption materials with excellent comprehensive performance.

Plane wave imaging (PWI) is attracting more attention in industrial nondestructive testing and evaluation (NDT&E). To further improve imaging quality and reduce reconstruction time in ultrasonic imaging with a limited active aperture, an optimized PWI algorithm was proposed for rapid ultrasonic inspection, with the comparison of the total focusing method (TFM). The effective area of plane waves and the space weighting factor were defined in order to balance the amplitude of the imaging area. Experiments were carried out to contrast the image quality, with great agreement to the simulation results. Compared with TFM imaging, the space-optimized PWI algorithm demonstrated a wider dynamic detection range and a higher defects amplitude, where the maximum defect amplitude attenuation declined by 6.7 dB and average attenuation on 12 defects decreased by 3.1 dB. In addition, the effects of plane wave numbers on attenuation and reconstruction time were focused on, achieving more than 10 times reduction of reconstruction times over TFM.

Sodium metal anodes combine low redox potential (−2.71 V versus SHE) and high theoretical capacity (1165 mAh g−1), becoming a promising anode material for sodium‐ion batteries. Due to the infinite volume change, unstable SEI films, and Na dendrite growth, it is arduous to achieve a long lifespan. Herein, an oxygen‐doped carbon foam (OCF) derived from starch is reported. Heteroatom doping can significantly reduce the nucleation resistance of sodium metal; combined with its rich pore structure and large specific surface area, OCF provides abundant nucleation sites to effectively guide the nucleation and subsequent growth of sodium metal, and the nature of this foam can accommodate the deposited sodium. Furthermore, a more uniform, robust, and stable SEI layer is observed on the surface of OCF electrode, so it can maintain ultra‐high reversibility and excellent integrity for a long time without dendritic growth. As a result, when the current density is 10 mA cm−2, the electrode can maintain stable 2000 cycles and the coulombic efficiency can reach to 99.83%. Na@OCF||Na3V2(PO4)3 full cell also has extremely high capacity retention of about 97.53% over 150 cycles. These results provide a simple but effective method for achieving the safety and commercialization of sodium metal anode., An O‐doped carbon foam with a sodiophilic surface is constructed and applied to the sodium metal anode. The excellent sodiophilic property, abundant porous structure, and large specific surface make the material stable during multiple plating/stripping processes, and no sodium dendrites are formed. Consequently, the sodium metal battery exhibits excellent electrochemical performance.

Ab initio potentials available in the literature are used to investigate the internal energy and pρT properties of helium, neon, argon, krypton, and xenon by molecular dynamics simulations. The total uncertainty of the simulation data is evaluated by reasonably quantifying the contributions from both the simulation method and the potential models. The theoretical predictions of this work are compared with recent experimental pρT data as well as the NIST data for the gas and supercritical phases to check the quality of this work. In most cases, agreement is found between the internal energy and pρT property values of this work and the literature data and the differences are smaller than the corresponding simulation uncertainty. It is concluded that the simulation data of this work are accurate enough to be used with confidence in different technical and practical applications over a wide temperature and density range.

The final publication is available at Elsevier via https://doi.org/10.1016/j.nanoen.2018.07.031. © 2018. This manuscript version is made available under the CC-BY-NC-ND 4.0 license http://creativecommons.org/licenses/by-nc-nd/4.0/

We report in this paper a miniature adjustable-focus camera module integrated with a solid tunable lens driven by MEMS-thermal actuators. Thanks to the compact structures of the MEMS actuators and the optical-power-variation capability of such solid tunable lenses, such a camera module shows great potential in various applications, especially in tiny underwater imaging systems where an optical zoom or focus-tuning function is required. The camera module presented in this paper consists of a solid tunable lens for optical power tuning, two identical MEMS-thermal actuators for lens component driving and one commercial CMOS chip for image recording, assisted with necessary mechanical parts for supporting and housing. We first introduce the optimal design of the solid tunable lens which consists of two freeform components moving in the direction perpendicular to the optical axis, and subsequently, the MEMS thermal actuators which consist of V-shaped micro beams. The lens components are fabricated by the technique of single-point diamond turning followed by the PMDS modelling process while the MEMS-thermal actuators are materialized by a commercial MUMPS process. The static performance of the designed system, including the temperature distribution, displacement-versus-voltage curve and the optical tuning capability, is characterized in detail, together with the dynamic responding speed, hysteresis and imaging performance stability during tuning. Results show that a maximum output displacement of 135 μm is achieved by the optimized MEMS-thermal actuator with a driving voltage of 10V, and consequently a focal length tuning range from 9.2 to 7.9 mm with a responding speed of about 90 ms is realized by the solid tunable lens. The highest temperate on the actuator is about 690 K during the operation while the temperate increase on the lens components is found to be about 30 K, which guarantees the optical performance stability. Targets placed at different object distances are clearly focused by the assembled miniature camera module with various driving voltages, which demonstrate its adjustable focus capability. Such miniature adjustable-focus camera modules show promising future in underwater applications due to their compact structures and optical-power-variation capability.

A novel structure of yttria stabilized zirconia coatings was developed in this study by a newly laminar plasma spraying technology in atmospheric environment. The unique microstructures of coatings showed the multi-island protrusions feature at the top surface, quasi-columnar structures along the cross-section distributed as a certain interval and hybrid droplet/vapor deposited structures at the fracture surface. The distributions of particle velocity and surface temperature along the axial direction of long laminar plasma jet were investigated and compared with other plasma spraying methods. The effects of different microstructures to thermal conductivities comparing with other current plasma spray methods were also demonstrated.

The powder flowability of pulverized coal and glass bead powders were characterized by using different testing methods, including fluidization test, packing properties test, AOR test and shear test, which correspond to different stress levels of the powders, from the highly dispersed state in fluidized beds to the highly consolidated state in shear testers. The data obtained from these testing methods were compared and evaluated to establish internal relationships between them. The results show that the results of these testing methods are highly dependent on particle size, as powder particle size increases, the values of HR, CI, AOR, c decrease, while the value of FF increases gradually, which indicates a decrease of powder cohesiveness, and the powder flowability becomes better. Meanwhile, there exists a good linear relationship between tan AOR and 1/ρpdp. The empirical correlation equations describing the quantitative relationship between tan AOR and 1/ρpdp were proposed for pulverized coal and glass bead powders, respectively. The results of testing methods which measure flow behavior at relatively similar degrees of stress state can be transferred between each other; otherwise, the results cannot be correlated well. It was found that there exists a non-linear relationship between AOR and HR within our experimental range.

A novel direct current non-transferred arc plasma torch that can generate long, silent and stable laminar plasma jet in air is applied to thermal spraying process in this article. Such long laminar plasma jet, making a low level of noise (

Long-term results of implants in small animal models can be used to optimize the design of grafts to further promote tissue regeneration. In previous study, we fabricated a poly(ɛ-caprolactone) (PCL) bi-layered vascular graft consisting of an internal layer with circumferentially aligned microfibers and an external layer with random nanofibers. The circumferentially oriented vascular smooth muscle cells (VSMCs) were successfully regenerated after the grafts were implanted in rat abdominal aorta for 3 months. Here we investigated the long-term (18 months) performance of the bi-layered grafts in the same model. All the grafts were patent. No thrombosis, aneurysm, or stenosis occurred. The endothelium maintained complete. However, most of circumferentially oriented VSMCs migrated to luminal surface of the grafts to form a neointima with uniform thickness. Accordingly, extracellular matrix including collagen, elastin, and glycosaminoglycan displayed high density in neointima layer while with low density in the grafts wall because of the incomplete degradation of PCL. A small amounts of calcification occurred in the grafts. The contraction and relaxation function of regenerated neoartery almost disappeared. These data indicated that based on the structure design, many other factors of grafts should be considered to achieve the regenerated neoartery similar to the native vessels after long-term implantation. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 106B: 2596-2604, 2018.

The synthesis and growth of CH3NH3PbI3 films with controlled nucleation is a key issue for the high efficiency and stability of solar cells. Here, 4-tert-butylpyridine (tBP) was introduced into a CH3NH3PbI3 antisolvent to obtain high quality perovskite layers. In situ optical microscopy and X-ray diffraction patterns were used to prove that tBP significantly suppressed perovskite nucleation by forming an intermediate phase. In addition, a gradient perovskite structure was obtained by this method, which greatly improved the efficiency and stability of perovskites. An effective power conversion efficiency (PCE) of 17.41% was achieved via the tBP treatment, and the high-efficiency device could maintain over 89% of the initial PCE after 30 days at room temperature.

Morphology regulation is vital to obtain high-performance perovskite films. Vapor-assisted deposition provides a simple approach to prepare perovskite films with controlled vapor–solid reaction. However, dense PbI2 precursor films with large crystal grains make it difficult for organic molecules to diffuse and interact with inner PbI2 frame. Here, a surface modification process is developed to optimize the surface layer morphology of PbI2 precursor films and lower the resistance of the induced period in crystallization. The vapor optimization time is shortened to several seconds, and the intermediate phase forms on the surface layer of PbI2 films. We achieve porous PbI2 surface with smaller grains through dimethyl sulfoxide vapor treatment, which promotes the migration and reaction rate between CH3NH3I vapor and PbI2 layer. The PbI2 precursor films undergo dramatic morphological evolution due to the formed intermediate phase on PbI2 surface layer. Taking advantage of the proposed surface modification proc...

Redox flow batteries are of particular interest because of the flexible power and energy storage originating from their unique architecture, but their low energy density has inhibited their widespread dissemination. In this work, a novel strategy of tuning the pH of the electrolyte environment is put forward to enhance the battery voltage, and eventually achieve the goal of high energy density for all-aqueous redox flow batteries. With this strategy, a hybrid alkaline zinc–iodine redox flow battery has been designed with a 0.47 V potential enhancement by switching the anolyte from acidic to basic, thus inspiring an experimental high energy density of 330.5 W h L−1. This is an unprecedented record to date for an all-aqueous redox flow battery.

Nanoscale architecturing of platinum group metal-free (PGM-free) electrocatalysts is expected to dramatically improve the overall catalytic performance for oxygen reduction reaction (ORR). Desired structures and morphologies for boosting active site density and enhancing mass and charge transfer are essential for developing next-generation PGM-free electrocatalysts. Herein, we report the design of a M-N-C type catalyst consisting of 3-dimensional graphitic meso-porous carbon spheres wrapped with 2-dimensional graphenized sheets. This heterostructure comprises resultant large electroactive surface area, abundant pore channels, and tuned chemical structures, which provide improved electrocatalytic performance. Meanwhile, these pore structures can be regarded as nano-channel reactors to catalyze ORR with easily accessible active sites, effective mass transfer, and smooth charge transfer. The obtained catalyst delivers a high maximum power density of 0.83 W cm−2 in a single H2–O2 fuel cell measurement, ranking it as one of the most promising PGM-free catalysts in proton exchange membrane fuel cells (PEMFCs). Moreover, reasonable fuel cell stability was also observed through accelerated degradation testing. This work provides a new avenue for PGM-free catalysts design that can be a step towards practical commercial of PEMFCs.

As a favorable candidate for the next-generation anode materials, metallic lithium is faced with two crucial problems: uncontrollable lithium plating/stripping process and huge volume expansion during cycling. Herein, a 3D lithiophilic skeleton modified with nanoscale Bi sheets (Ni@Bi Foam, i.e., NBF) through one-step facile substitution reaction is constructed. Benefiting from the nanoscale modification, smooth and dense lithiophilic Li3 Bi layer is in situ formed, which improves the uniform deposition of Li subsequently. Meanwhile, the 3D structure inhibits the growth of Li dendrites effectively by reducing local areal current density. Consequently, the NBF exhibits outstanding cycling stability with a high average Coulombic efficiency of 98.46% at 1 mA cm-2 with 1 mAh cm-2 (>500 cycles). Symmetrical cell with NBF exhibits a high reversibility at 1 mA cm-2 with 1 mAh cm-2 (>2000 h). Moreover, superior long-term cycling and rate performance of NBF@Li anode are also acquired when assembled with high areal loading of LiFePO4 (10.1 mg cm-2 ) cathode (Negative/Positive ratio: 2.91). Even in anode-free metal lithium batteries, NBF has higher capacity during cycling compared with NF. To conclude, NBF shows excellent electrochemical performance and provides an idea of facile preparation method which can be extend to other metal batteries.

A mathematical model is developed to investigate the effects of working media, operating conditions and fin structural parameters on the flow and heat transfer performance of sub-atmospheric and low-temperature helium in serrated fin. For helium, nitrogen and air, when the Reynolds number (Re) is less than 2500, the Colburn heat transfer factor (j factor) of helium is in the middle, while that is the lowest when Re is higher than 2500. The Fanning friction factor (f factor) of helium under the working condition is much higher than those of air and nitrogen under corresponding working conditions. The results show that short fin height is selected for high Re and high fin height is selected for low Re. The overall performance can be improved by increasing the fin spacing and decreasing the fin thickness. Small fin length can improve the overall performance, but the effect is poor at high Re. The Kriging response surface is used to fit the flow and heat transfer correlations of serrated fin. The fitting degrees of j and f factors are 0.963 and 0.978 respectively, and the average relative errors are 4.31% and 8.79% respectively. The two correlations have good prediction performance, which can provide a theoretical reference for the design of sub-atmospheric and low-temperature plate-fin heat exchanger.

As the increasing discharge of industrial oily wastewater posed a severe threat to the ecological environment and human health, various oil/water separation technology has been proposed all over the world. In recent years, superhydrophobic film for oil/water separation has gained much more attention. A simple method was explored in this paper to prepare superhydrophobic TiO2/SiO2 nanoparticle coating with varied particle size and ratio. Superhydrophobic metal mesh, sponge and loofah were fabricated by simple spraying method. The topological structure and surface wettability of the prepared coating was characterized by SEM, TEM as well as contact angle measurements. The nano-scale pore structure and the convex nano-nipple structure were observed on the surface of the coating, which supply the microstructure evidence to explain its superhydrophobic characteristics, water contact angle (WCA) ≥ 155° and oil contact angle (OCA) ≈ 0°. The oil/water separation efficiency of the superhydrophobic coating with different substrates was around 95% during a series of experimental investigation for varied oil/water mixtures. In addition, the separation efficiency can remain above 90% after 60 separation cycles, which indicated the better sustainability of the coating. The developed materials with their stable hydrophobicity, recyclability, durable oil resistance and water resistance displayed potential application for oil/water separation in industry and daily life.