Search

Cold-formed steel members are usually used as purlins in buildings to support roof cladding and thus they can be treated as beams restrained fully or partially in the lateral and torsional directions. However, when these beams are subjected to wind suction loading, their free flange is in compression, which may cause web–flange distortional buckling (WFDB). This paper presents an analytical study on the WFDB of zed-section purlins when subjected to uplift bending. A simplified model is proposed to describe the WFDB of partially restrained purlins, from which the formula for calculating the critical stress of the WFDB is derived. The present model is validated by the results obtained from the finite strip analysis.

Recent studies have shown that layered compound EuCd2As2 could exhibit diverse topological states depending on the different magnetic structures, such as Weyl semimetal, Dirac semimetal, topological insulator, etc. In order to further study the interplay between magnetism and topology of EuCd2As2, it is necessary to figure out its magnetic structure. Here, by magnetization (M) measurements and negative magnetostriction (λ) along the [001] direction measured by scanning tunneling microscope on EuCd2As2 single crystals, we observe field-induced metamagnetic phase transition from A-type antiferromagnetic (AFM) ground state to field-polarized state, with canted AFM (CAFM) state in between. Magnetization and magnetostriction are more sensitive to the in-plane field than the out-of-plane field, indicating the magnetic moments lying in the ab plane. The absence of abrupt jump on M-H and λ-H curves demonstrates the phase transition is a second-order type. In CAFM state, M increases linearly with the field and λ is proportional to M 2 . Tunneling conductance spectra show the field-induced evolution of the electronic density of states. Our results provide experimental evidence for understanding the magnetic structure of EuCd2As2.

Micro-Electro-Mechanical Systems (MEMS) micro-mirrors have shown great potential in consumer applications, such as Light Detection and Ranging (LiDAR) devices and portable laser projectors. The LiDAR based on electromagnetic MEMS micro-mirror is usually exposed to vibration loads for autonomous vehicles, which results in the necessity for the destructive reliability assessment of micromirrors under vibration environment, but such studies are rarely reported. This paper explores the destructive reliability of electromagnetic MEMS micromirror under vibration environment according to the JESD22-B103B standard. The reliability evaluation is conducted by experimental tests, finite element stress analysis and theoretical dynamic response analysis. Micromirrors are tested under sweep excitation, and they are failed with the vibration level of around 33 g. The failure and stress analysis demonstrate that the crack fracture is located at the root of the slow axis. The nonlinear relationship between the peak displacement of the balance frame and acceleration levels is investigated through theoretical analysis. The nonlinearity of stiffness hardening is induced by the axial tensile strain of the beam, which contributes to the displacement-reduction of the gimbal. This work provides some valuable suggestions for the optimization design of MEMS micromirrors to improve the acceleration tolerance level in vibration environment.

Covalent organic frameworks (COFs) characterized by structural diversity, face-to-face stacking and open channels exhibit unique advantages as photothermal materials but have rarely been applied in...

In this study, based on a closed bomb test combined with computational fluid dynamics, a structural finite element method, and an acoustic boundary element method, a fluid-solid acoustic one-way coupling calculation model is established for the combustion process of energetic materials in a closed bomb, and the effectiveness of the model is verified by experiments. It is found that the maximum peak sound pressure increases exponentially with an increase in loading doses or gas pressure. However, a change in the combustion coefficient of the energetic materials has little effect on the noise generated during the combustion process in the closed bomb. When the combustion coefficient is reduced by a multiple of 16, the maximum transient sound pressure is reduced by 1.79 dB, and the sound pressure level in the frequency band is reduced by 1.75 dB. With an increase in shell thickness, the combustion noise of the energetic materials in the closed bomb decreases, and the reduction range of the combustion noise increases with the increase in shell thickness.

The compression behavior of the lattice-walled tubes under variable strain rates are investigated by numerical simulation, and the stress-strain relationship of the structure under quasi-static loading is theoretically analyzed. The finite element software LS-DYNA is used to simulate the structure established by the beam element, and the critical impact velocity is obtained when the structure collapses layer by layer. According to the plastic hinge theory and considering the combined action of the beam's bending moment and axial force in the structure, the stress-strain relationship of the structure under quasi-static loading is derived and compared with the experimental results. The numerical simulation results reveal that the structure of the single-layer gradient tube(SGC) does not undergo shear deformation under quasi-static and low-speed impact. The critical speed of the gradient square tube(GS) is higher than that of a cylindrical tube. The theoretical model can correctly reflect the mechanical response of the structure under uniaxial compression.

Due to the massive discharge of antibiotics in water, it is an urgent matter to remove antibiotics from waste water. The photocatalysts with high stability and activity have attracted extensive attention from researchers. By an in-situ polymerization method, polypyrrole (PPy) was modified on the surface of TiO2 (named as TiO2/PPy). By one-step reduction method, NiCoP was grafted on the surface of TiO2/PPy (named as TiO2/PPy/NiCoP) to synthesize the photocatalyst of TiO2/PPy/NiCoP for degradation of tetracycline (TC) antibiotic. The characterization results revealed that NiCoP was deposited on the surface of TiO2/PPy successfully. The photocatalytic experiment results illustrated that 83.2% of TC could be degraded at natural pH with 20 mg of TiO2/PPy/NiCoP in 50 mL of TC solution (10 mg/L) under visible light irradiation. The high catalytic activity is attributed to the attachment of NiCoP on the surface of TiO2/PPy which can enlarge the light response range of TiO2 effectively. Scavenger studies revealed that the degradation of TC was dominated by •O2− and h+. The photodegradation efficiency of TC with TiO2/PPy/NiCoP still reached over 74% after 5 consecutive cycles, indicating the potential applications in practical wastewater.

The monitoring of tool wear plays an important role in improving the processing efficiency and reducing the production cost of enterprises. This paper is focused on the detection of electroplated diamond mill-grinding tools by using the acoustic emission sensor. The wear stages of mill-grinding tools are divided into three parts, namely initial wear stage, normal wear stage, and severe wear stage. The characteristic parameter method and the waveform analysis method are applied to analyze the acoustic emission signals. The wear characteristics of the tool and workpiece in different wear stages are observed and analyzed. The results indicate that the acoustic emission waveform is relatively stable in the initial wear stage, and the continuous acoustic emission signal is dominated. Moreover, the diamond abrasive grains are mainly worn and slightly broken in the normal wear stage, and there are some pits on the machined workpiece surface after the initial wear stage. In the severe wear stage, most of the abrasive grains are broken or broken in a large area, and there are burst acoustic emission signals in the waveform.

A new testing methodology was developed to quantitively study galvanic corrosion of AZ31B and thermoset carbon-fiber–reinforced polymer spot-joined by a friction self-piercing riveting process. Pre-defined areas of AZ31B in the joint were exposed in 0.1 M NaCl solution over time. Massive galvanic corrosion of AZ31B was observed as exposure time increased. The measured volume loss was converted into corrosion current that was at least 48 times greater than the corrosion current of AZ31B without galvanic coupling. Ninety percent of the mechanical joint integrity was retained for corroded F-SPR joints to 200 h and then decreased because of the massive volume loss of AZ31B.

Mi-se porcelain provided a step change in the history of Chinese porcelain making and influenced kiln production of later generations as well as the aesthetic orientation of society. This work compares the microstructure of ordinary Yue celadon and Mi-se porcelain. The Mi-se porcelain glaze was found to be simpler and more uniform than ordinary Yue celadon, with only some bubbles existing in the glaze. Compared with ordinary Yue celadon, the residual quartz and pores in the Mi-se porcelain body were smaller. Mi-se porcelain production is more standardized than ordinary Yue celadon. The presence of calcium phosphate in the glaze indicates that grass wood ash was used in the Yue kiln. Our research confirms that Mi-se porcelain was not the best porcelain as selected from the Yue kiln products, but it is a type of celadon that was specially fired using fine raw material processing and certain firing techniques.

Direct encapsulation of graphene shells on noble metal nanoparticles via chemical vapor deposition (CVD) has been recently reported as a unique way to design and fabricate new plasmonic heterostructures. But currently, the fundamental nature of the growth mechanism of graphene layers on metal nanostructures is still unknown. Herein, we report a systematic investigation on the CVD growth of graphene-encapsulated Au nanoparticles (Au@G) by combining an experimental parameter study and theoretical modeling. We studied the effect of growth temperature, duration, hydrocarbon precursor concentration, and extent of reducing (H2) environment on the morphology of the products. In addition, the influence of plasma oxidation conditions for the surface oxidation of gold nanoparticles on the graphene shell growth is evaluated in combination with thermodynamic calculations. We find that these parameters critically aid in the evolution of graphene shells around gold nanoparticles and allow for controlling shell thickness, graphene shell quality and morphology, and hybrid nanoparticle diameter. An optimized condition including the growth temperature of ∼675 °C, duration of 30 min, and xylene feed rate of ∼10 mL/h with 10% H2/Ar carrier gas was finally obtained for the best morphology evolution. We further performed finite-element analysis (FEA) simulations to understand the equivalent von Mises stress distribution and discrete dipolar approximation (DDA) calculation to reveal the optical properties of such new core-shell heterostructures. This study brings new insight to the nature of CVD mechanism of Au@G and might help guiding their controlled growth and future design and application in plasmonic applications.

Modified reduced graphene oxide (rtgo) was prepared by using γ - isocyanate propyl triethoxysilane (IPTS) as modifier. Graphene / polyurethane nanocomposites were prepared by in-situ polymerization. Graphene / polyurethane composites were characterized by scanning electron microscopy, TGA, DIN abrasion and electronic universal testing machine. The effects of different reaction formulations and graphene addition on the wear resistance and mechanical properties of the composites were studied. The results show that the wear resistance and tear resistance of the composite can be greatly improved after the functional graphene is compounded with polyurethane.

The uncontrollable dendrite growth of Li metal anode leads to poor cycle stability and safety concerns, hindering its utilization in high energy density batteries. Herein, a phenoxy radical Spiro-O8 is proposed as an artificial protection film for Li metal anode owing to its excellent film-forming capability and remarkable ionic conductivity. A spontaneous redox reaction between the Spiro-O8 and Li metal results in the formation of a uniform and highly ionic conductive organic film in the bottom. Meanwhile, the phenoxy radicals on surface of Spiro-O8 facilitate the decomposition of Li salt upon exposed to the ether electrolyte and lead the formation of LiF film on the top. Arising from the synergistic effects of inner high ionic conductive film and outer rigid film, stable Li plating/stripping can be realized at a high current density (4000 cycles at 10 mA cm-2 ) and a high areal capacity of 5 mAh cm-2 for 550 h with an ultrahigh Li utilization rate of 54.6 %. As a proof of concept, this work shows a facile strategy to rationally fabricate dual-layered interfaces for Li metal anodes.

Platinum (Pt) is the most effective bench-marked catalyst for producing renewable and clean hydrogen energy by electrochemical water splitting. There is demand for high HER catalytic activity to achieve efficient utilization and minimize the loading of Pt in catalysts. In this work, we significantly boost the HER mass activity of Pt nanoparticles in Pt x /Co to 8.3 times higher than that of commercial Pt/C by using Co/NC heterojunctions as a heterogeneous version of electron donors. The highly coupled interfaces between Co/NC and Pt metal enrich the electron density of Pt nanoparticles to facilitate the adsorption of H + , the dissociation of Pt-H bonds and H 2 release, giving the lowest HER overpotential of 6.9 mV vs. RHE at 10 mA/cm 2 in acid among reported HER electrocatalysts. Given the easy scale-up synthesis due to the stabilization of ultrafine Pt nanoparticles by Co/NC solid ligands, Pt x /Co can even be a promising substitute for commercial Pt/C for practical applications.

Atomically thin two‐dimensional (2D) bismuth oxychalcogenides (Bi2O2X, X = S, Se, Te) have recently attracted extensive attention in the material research community due to their unique structure, outstanding long‐term ambient stability, and high carrier mobility, which enable them as promising candidates for high‐performance electronic and optoelectronic applications. Herein, we present a comprehensive review on the recent advances of 2D bismuth oxychalcogenides research. We start with an introduction of their fundamental properties including crystal structure and electronic band structure. Next, we summarize the common techniques for synthesizing these 2D structures with high crystallinity and large lateral size. Furthermore, we elaborate on their device applications including transistors, artificial synapses, optical switch and photodetectors. The last but not the least, we summarize the existing challenges and prospects for this emerging 2D bismuth oxychalcogenides field.

Rare earth–Mg–Ni-based alloys with superlattice structures are new generation negative electrode materials for the nickel metal hydride batteries. Among them, the novel AB4-type superlattice structure alloy is supposed to have superior cycling stability and rate capability. Yet its preparation is hindered by the crucial requirement of temperature and the special composition which is close to the other superlattice structure. Here, we prepare rare earth–Mg–Ni-based alloy and study the phase transformation of alloys to make clear the formation of AB4-type phase. It is found Pr5Co19-type phase is converted from Ce5Co19-type phase and shows good stability at higher temperature compared to the Ce5Co19-type phase in the range of 930–970 °C. Afterwards, with further 5 °C increasing, AB4-type superlattice structure forms at a temperature of 975 °C by consuming Pr5Co19-type phase. In contrast with A5B19-type alloy, AB4-type alloy has superior rate capability owing to the dominant advantages of charge transfer and hydrogen diffusion. Besides, AB4-type alloy shows long lifespan whose capacity retention rates are 89.2% at the 100th cycle and 82.8% at the 200th cycle, respectively. AB4-type alloy delivers 1.53 wt% hydrogen storage capacity at room temperature and exhibits higher plateau pressure than Pr5Co19-type alloy. The work provides novel AB4-type alloy with preferable electrochemical performance as negative electrode material to inspire the development of nickel metal hydride batteries.

This paper investigates the effect of varying solid alkali activators on the fresh and hardened properties and microstructural changes of one-part geopolymers (OPGs). Single and binary solid alkali activators were used to activate high calcium fly ash. The alkali activators were either solely sodium metasilicate (Na2SiO3) or a combination of sodium aluminate (NaAlO2) and sodium metasilicate (Na2SiO3). The OPG activated with anhydrous Na2SiO3 achieved an excellent 28-day compressive strength of 83.6 MPa while OPG activated with NaAlO2 and Na2SiO3 attained a compressive strength of 45.1 MPa. The Na2SiO3-activated OPG demonstrated better fluidity than the OPG activated with NaAlO2 and Na2SiO3 due to the thixotropic behaviour caused by the NaAlO2. The Na2SiO3-activated OPG consisted of sodium-calcium aluminium silicate hydrate ((N,C)-A-S-H) gel phase, while the OPG activated with NaAlO2 and Na2SiO3 comprised of the coexistence of sodium aluminium silicate hydrate (N-A-S-H) and calcium aluminium silicate hydrate (C-A-S-H) gel phases. Regardless of the distinctive properties, the OPGs are adequate for building materials applications.

We propose a GaN-based superjunction current-aperture vertical electron transistor (CAVET) with a dipole layer (DL-SJ CAVET) and demonstrated two-dimensional numerical simulations by Silvaco-Atlas. The dipole layer (DL) formed by Al0.1Ga0.9N is attached to the Al0.15Ga0.85N barrier layer and located in the passivation layer between the source and the gate electrodes. The simulated results of the proposed device exhibit high breakdown voltage (BV) and low specific on-resistance (RonA).The BV can reach 2453 V and the RonA reach 2.23 mΩ·cm2.Compared with the conventional GaN SJ CAVET, the improvement of RonA and BV can realized in DL-SJ CAVET based on the special structure features. To improve the RonA, we proposed a novel DL-SJ CAVET with step-doping p-pillars and n-pillars (DS-SJ CAVET). Compared with DL-SJ CAVET under the same aspect ratio, DS-SJ CAVET can further decrease RonA by increasing differently doped layers in p-pillars and n-pillars. The RonA reaches 1.76 mΩ·cm2 while BV reaches 2640 V. Further reduction in RonA can be achieved by adding differently doped layers and differently doped concentrations in n-pillars and p-pillars with decreasing BV. The proposed devices can be fabricated by selective area growth (SAG) technology and it shows significant potential in microwave power applications.

To improve the cracking behavior of hydrocarbon, Ni–Mo/SiO2 bimetallic catalysts were synthesized by different preparation methods (sol-gel, co-impregnation and single-impregnation) and added the additives (citric acid, polyethylene glycol and cetyltrimethylammonium bromide) based on the most suitable method above. The cracking reaction of methylcyclohexane under supercritical conditions was performed as the probe reaction to estimate the catalytic performance, and the properties of Ni–Mo/SiO2 catalyst were characterized by N2 absorption-desorption, XRD, XPS, H2-TPR, NH3-TPD, in-situ IR of NH3 desorption, HRTEM and STEM-mapping so as to study the structure-activity relationship. The catalyst synthesized via sol-gel method showed the best conversion and heat sink, being 81.8% and 3.81 MJ/kg, which was closely related to strong mutual effect between active components and SiO2 as well as strong acid sites. Besides, the introduction of additives by sol-gel method has an affirmative influence on properties of Ni–Mo/SiO2 catalysts, being that the acidity (more L and B acid sites) was modulated and organic groups interact with metal to suppress the aggregation of metal species (Ni and Mo), thereby enhancing the catalytic activity. At 750 °C, the conversion (89.3%) as well as heat sink (3.99 MJ/kg) of MCH cracking obtained an optimum over Ni–Mo/SiO2 catalyst with addition of citric acid.

Different from other alloys, the observation in this work on the dendritic mushy zone shows that the freckles are formed in two different regions before and after peritectic reaction in directional solidification of Sn–Ni peritectic alloys. In addition, the experimental results demonstrate that the dendritic morphology is influenced by the temperature gradient zone melting and Gibbs–Thomson effects. A new Rayleigh number (RaP) is proposed in consideration of both effects and peritectic reaction. The prediction of RaP confirms the freckle formation in two regions during peritectic solidification. Besides, heavier thermosolutal convection in samples with larger diameter is also demonstrated.

Most organic semiconductors have closed-shell electronic structures, however, studies have revealed open-shell character emanating from design paradigms such as narrowing the bandgap and controlling the quinoidal-aromatic resonance of the π-system. A fundamental challenge is understanding and identifying the molecular and electronic basis for the transition from a closed- to open-shell electronic structure and connecting the physicochemical properties with (opto)electronic functionality. Here, we report donor-acceptor organic semiconductors comprised of diketopyrrolopyrrole and naphthobisthiadiazole acceptors and various electron-rich donors commonly utilized in constructing high-performance organic semiconductors. Nuclear magnetic resonance, electron spin resonance, magnetic susceptibility measurements, single-crystal X-ray studies, and computational investigations connect the bandgap, π-extension, structural, and electronic features with the emergence of various degrees of diradical character. This work systematically demonstrates the widespread diradical character in the classical donor-acceptor organic semiconductors and provides distinctive insights into their ground state structure-property relationship., The classical narrow bandgap donor-acceptor organic semiconductors show great application potential in organic electronics, bio-imaging and other fields. Here, the authors systematically and rigorously demonstrate their open-shell diradical character via experimental and theoretical investigation.

Platinum group elements are invaluable tracers for planetary accretion and differentiation and the formation of PGE sulfide deposits. Previous laboratory determinations of the sulfide liquid–basaltic melt partition coefficients of PGE (\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${D}_{PGE}^{SL/SM}$$\end{document}DPGESL/SM) yielded values of 102–109, and values of >105 have been accepted by the geochemical and cosmochemical society. Here we perform measurements of \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${D}_{Pt,\,Pd}^{SL/SM}$$\end{document}DPt,PdSL/SM at 1 GPa and 1,400 °C, and find that \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${D}_{Pt,\,Pd}^{SL/SM}$$\end{document}DPt,PdSL/SM increase respectively from 3,500 to 3.5 × 105 and 1,800 to 7 × 105, as the Pt and Pd concentration in the sulfide liquid increases from 60 to 21,000 ppm and 26 to 7,000 ppm, respectively, implying non-Henrian behavior of the Pt and Pd partitioning. The use of \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${D}_{Pt,\,Pd}^{SL/SM}$$\end{document}DPt,PdSL/SM values of 2,000–6,000 well explains the Pt and Pd systematics of Earth’s mantle peridotites and mid-ocean ridge basalts. Our findings suggest that the behavior of PGE needs to be reevaluated when using them to trace planetary magmatic processes., Platinum group elements are used as tracers for planetary and PGE sulfide deposit formation. Here, the authors, through the measurements of Pt and Pd partition coefficients between sulfide liquid and basaltic melt, demonstrate that the partitioning of Pt and Pd does not obey Henry’s law.

As a secondary Li-ion battery with high energy density, lithium-sulfur (Li-S) batteries possess high potential development prospects. One of the important ingredients to improve the safety and energy density in Li-S batteries is the solid-state electrolyte. However, the poor ionic conductivity largely limits its application for the commercial market. At present, the gel electrolyte prepared by combining the electrolyte or ionic liquid with the all-solid electrolyte is an effective method to solve the low ion conductivity of the solid electrolyte. We present a cross-linked gel polymer electrolyte with fluoroethylene carbonate (FEC) as a solid electrolyte interface (SEI) film formed for Li-S quasi-solid-state batteries, which can be simply synthesized without initiators. This gel polymer electrolyte with FEC as an additive (GPE@FEC) possesses high ionic conductivity (0.830 × 10-3 S/cm at 25 °C and 1.577 × 10-3 S/cm at 85 °C) and extremely high Li-ion transference number (tLi+ = 0.674). In addition, the strong ability toward anchoring polysulfides resulting in the high electrochemical performance of Li-S batteries was confirmed in GPE@FEC by the diffusion experiment, X-ray photoelectron spectroscopy analysis (XPS), and scanning electron microscopy (SEM) mapping of the S element. Such a high ion conductivity (IC) gel polymer electrolyte enables a competitive specific capacity of 940 mAh/g at 0.2C and supreme cycling performance for 180 cycles at 0.5C, which is far beyond that of conventional poly(ethylene oxide)-based quasi-solid-state Li-S batteries.

The cylinder head is one of the most complex and concentrated load components of the engine, playing an important role in the safety and reliability of the engine. In this paper, the finite element method is used to simulate the casting and heat treatment process of cylinder head. The distribution characteristics of microstructure, shrinkage porosity defects as well as mechanical properties are analyzed, and the mechanical properties simulation results were verified by experimental data. The results show that the microstructure varies significantly at different regions and is related to local cooling rate. The shrinkage porosity defects are mainly distributed in the thick walls and thin–thick wall junctions, but the porosity value is small and the effect on the mechanical properties could be ignored. The mechanical properties of different cylinders are similar, but there are obvious differences at the top plate, force wall and bottom plate in each cylinder, with a maximum difference of 12%. The large discrepancies of microstructure, shrinkage porosity defects as well as mechanical properties in cylinder head are caused by the different local filling and cooling conditions in the casting process.

Topological morphology that dominates the surface electronic properties of nanostructures plays a key role in producing desired materials for versatile functions and applications in many fields, but its modulation for specific functions remains a big challenge. Herein, we report an acid-induced method to prepare S-doped graphitic carbon nitride/graphitic carbon nitride (S-CN/CN) homojunction by simply pyrolyzing a supramolecular precursor synthesized from melamine and H2SO4. The topological morphology and electronic structure of CN homojunction can be easily adjusted only by changing the ratio of raw materials. Moreover, the topological morphology of S-CN/CN homojunction can be further adjusted from hollow cocoon to 2D nanosheets by changing the annealing conditions. The optimized S-CN/CN homojunction shows highly efficient in charge transfer and separation and exhibits superior OER activity and high ability to degrade organic pollutants. Impressively, S-CN/CN nanosheets only demand low overpotential of 301 mV to drive a current density of 10 mAcm−2 in 1 M KOH media, and the corresponding Tafel slope is only 57.71 mV/dec, which is superior to the most advanced precious metal IrO2 catalyst. Moreover, under visible light irradiation, its photodegradation kinetic rate of RhB is 2.38, which is 47.6 times higher than that of bulk CN. This work provides useful guidance for designing and developing efficient multifunctional metal-free catalysts.

The cell migration and invasion behaviors play pivotal roles in tissue regeneration. For the skin repair process, a directed inflammatory response that regulates fibroblasts is critical for efficient wound healing. In this study, the authors present the design and fabrication of a microfluidic-based three-dimensional (3D) microphysiological system and how it impacts in controlling fibroblast migration and invasion under the induction of differently polarized macrophages. The microfluidic device had two chambers on opposite sides of a 1 mm micochannel, providing directed induction and sufficient width for long-term observation. The test cells could be seeded with or without matrix gel, cultured in a 2D or 3D microenvironment according to experiment settings. The microchannel allowed for any sorts of matrix filling and was on-demanding for continuous surveillance. Herein, our microfluidic device reserved the advantages of traditional methods using transwell chamber or scratch wound healing assay. In addition, it even came with more superiority such as retrievability, dynamic observation, and 3D environment simulation. The migration and invasion pattern of NIH3T3 modulated by RAW264.7 macrophages in different polarization status was demonstrated as an example. The results of the migration assay corresponded with that of the proliferation and gene expression experiments, verifying that our device was fully capable of restoring in vivo microenvironment and presenting cellular motility behaviors.

The interfacial microstructure evolution of 12Cr1MoV/TP347H dissimilar steel welded joints with a nickel-based filler metal during aging was studied in detail to elucidate the mechanism of premature failures of this kind of joints. The results showed that not only a band of granular Cr23C6 carbides were formed along the fusion boundary in the ferritic steel during aging, but also a large number of granular or platelike Cr23C6 carbides, which have a cube-cube orientation relationship with the matrix, were also precipitated on the weld metal side of the fusion boundary, making this zone be etched more easily than the other zone and become a dark etched band. Stacking faults were found in some Cr23C6 carbides. In the as-welded state, deformation twins were observed in the weld metal with a fully austenitic structure. The peak micro-hardness was shifted from the ferritic steel side to the weld metal side of the fusion boundary after aging and the peak value increased significantly. Based on the experimental results, a mechanism of premature failures of the joints was proposed.

Additive doping is one of the effective methods to overcome the shortcomings of MgH2 on the aspect of relatively high operating temperatures and slow desorption kinetics. In this paper, hollow g-C3N4 (TCN) tubes with a diameter of 2 μm are synthesized through the hydrothermal and high-temperature pyrolysis methods, and then nickel is chemically reduced onto TCN to form Ni/TCN composite at 278 K. Ni/TCN is then introduced into the MgH2/Mg system by means of hydriding combustion and ball milling. The MgH2–Ni/TCN composite starts to release hydrogen at 535 K, which is 116 K lower than the as-milled MgH2 (651 K). The MgH2–Ni/TCN composite absorbs 5.24 wt% H2 within 3500 s at 423 K, and takes up 3.56 wt% H2 within 3500 s, even at a temperature as low as 373 K. The apparent activation energy (Ea) of the MgH2 decreases from 161.1 to 82.6 kJ/mol by the addition of Ni/TCN. Moreover, the MgH2–Ni/TCN sample shows excellent cycle stability, with a dehydrogenation capacity retention rate of 98.0% after 10 cycles. The carbon material enhances sorption kinetics by dispersing and stabilizating MgH2. Otherwise, the phase transformation between Mg2NiH4 and Mg2NiH0.3 accelerates the re/dehydrogenation reaction of the composite.

NOx- reduction acts a pivotal part in sustaining globally balanced nitrogen cycle and restoring ecological environment, ammonia (NH3) is an excellent energy carrier and the most valuable product among all the products of NOx- reduction reaction, the selectivity of which is far from satisfaction due to the intrinsic complexity of multiple-electron NOx--to-NH3 process. Here, we utilize the Schottky barrier-induced surface electric field, by the construction of high density of electron-deficient Ni nanoparticles inside nitrogen-rich carbons, to facilitate the enrichment and fixation of all NO x - anions on the electrode surface, including NO 3 - and NO 2 - , and thus ensure the final selectivity to NH 3 . Both theoretical and experimental results demonstrate that NO x - anions were continuously captured by the electrode with largely enhanced surface electric field, providing excellent Faradaic efficiency of 99 % from both electrocatalytic NO 3 - and NO 2 - reduction. Remarkably, the NH 3 yield rate could reach the maximum of 25.1 mg h -1 cm -2 in electrocatalytic NO 2 - reduction reaction, outperforming the maximum in the literature by a factor of 6.3 in neutral solution. With the universality of our electrocatalyst, all sorts of available electrolytes containing NO x - pollutants, including seawater or waste water, could be directly used for ammonia production in potential through sustainable electrochemical technology.

The overuse of synthetic colorants may result in hepatocellular damage, renal failure, and potential immunotoxicity. Therefore, the content of synthetic colorants in foods must be strictly controlled. A simple sensor based on 1-butylpyridinium hexafluorophosphate@glassy carbon microspheres composites electrode (GCILE) was constructed for the rapid and sensitive detection of sunset yellow (SY) and tartrazine (TZ). Composite materials were investigated using scanning electron microscopy and Fourier transform infrared spectroscopy. Then the electrochemical properties of the sensors were characterized using cyclic voltammetry. Furthermore, the electrochemical behaviors of SY and TZ were studied at the GCILE using differential pulse voltammetry. The effects of pH value, the different ratios of glassy carbon microspheres and ionic liquid, accumulation time, and accumulation potential on current responses of SY and TZ were discussed in detail. The GCILE displayed favorable electrocatalytic activity to SY and TZ. Under the optimum experimental conditions, the linear ranges of SY and TZ were 0.02–5 μM and 0.5–15 μM, respectively. When the noise–signal ratio (S/N) was 3, the detection limits of SY and TZ were 0.01 and 0.1 μM, respectively. Interference studies showed that common interfering substances did not affect the detection of SY and TZ. The proposed method was applied for analyzing azo dyes in beverages.

Frequency Loss Induced Quench (FLIQ) is an active protection system designed to generate heat from AC losses to uniformly and safely quench a superconducting coil. It drives an imbalance in the transport current between two or more sections of the magnet using the H-bridge design with Insulated Gate Bipolar Transistor (IGBT)s, whose gates are controlled based on the current feedback within its loop. This allows FLIQ to operate at resonance with the frequency of the load. The performance of FLIQ circuit was characterized using simulations to assess the relative effectiveness of the key parameters of voltage, frequency, and time. The results show that the voltage is the most effective parameter. It was shown that with the selection of appropriate values of the parameters, the FLIQ system released sufficient energy into the coil to quench it.

Highlights A general layered 2D materials-derived atomic substitution conversion strategy is proposed to achieve the synthesis of large-size ultrathin nonlayered 2D materials.Using low-melting-point CdI2 flakes via a simple hot plate assisted vertical vapor deposition method as precursor, large-size ultrathin CdS flakes were successfully converted from layered to nonlayered nanostructures through a facile low-temperature chemical sulfurization process.The size and thickness of CdS flakes can be controlled by the CdI2 precursor. The growth mechanism is ascribed to the chemical substitution reaction from I to S atoms between CdI2 and CdS, which has been evidenced by experiments and theoretical calculations. Supplementary Information The online version contains supplementary material available at 10.1007/s40820-021-00692-6., Nonlayered two-dimensional (2D) materials have attracted increasing attention, due to novel physical properties, unique surface structure, and high compatibility with microfabrication technique. However, owing to the inherent strong covalent bonds, the direct synthesis of 2D planar structure from nonlayered materials, especially for the realization of large-size ultrathin 2D nonlayered materials, is still a huge challenge. Here, a general atomic substitution conversion strategy is proposed to synthesize large-size, ultrathin nonlayered 2D materials. Taking nonlayered CdS as a typical example, large-size ultrathin nonlayered CdS single-crystalline flakes are successfully achieved via a facile low-temperature chemical sulfurization method, where pre-grown layered CdI2 flakes are employed as the precursor via a simple hot plate assisted vertical vapor deposition method. The size and thickness of CdS flakes can be controlled by the CdI2 precursor. The growth mechanism is ascribed to the chemical substitution reaction from I to S atoms between CdI2 and CdS, which has been evidenced by experiments and theoretical calculations. The atomic substitution conversion strategy demonstrates that the existing 2D layered materials can serve as the precursor for difficult-to-synthesize nonlayered 2D materials, providing a bridge between layered and nonlayered materials, meanwhile realizing the fabrication of large-size ultrathin nonlayered 2D materials. Supplementary Information The online version contains supplementary material available at 10.1007/s40820-021-00692-6.

The Huang-Pair is a novel hybrid diode concept based on the integration of a low forward voltage drop, low voltage rating diode with a high voltage majority carrier switch, such as a silicon carbide (SiC) Junction gate field-effect transistor (JFET). A 1200 V Huang-Pair is developed to demonstrate the concept in which a low voltage Si diode is paired with a 1200 V SiC JEFT, resulting in a low-forward voltage, low reverse recovery high voltage diode. The Huang-Pair is a two terminal device and its performance tradeoff between forward voltage drop, leakage current, and reverse recovery can be conducted between two discrete devices, which is more flexible. The Huang-Pair concept can also be realized by SiC MOSFET and gallium nitride MOSFET, and it can be applied to different voltage classes.

This article presents the experimental characterization of SiC MOSFETs exposed to heavy-ion irradiation. Different leakage paths related to the drain bias used during the tests are observed, suggesting different damage sites in the devices, which can be further verified through the post-irradiation measurements. TCAD simulations are utilized to explore the underlying failure mechanisms. Based on the evolution of the gate oxide field, it is shown that the damage first occurs in the middle of the JFET region, while gradually spreads to the channel region with the increase of drain bias, but terminates at the source region. A preliminary model to roughly emulate the drain bias dependence of such degradation behaviors is developed, and the simulation results match the experiments well. Additionally, the emission microscope (EMMI) is carried out so as to detect the latent damage at the die level. The findings in this article demonstrate that more attention should be paid to the damaged gate oxide induced by the heavy-ion strike before SiC MOSFETs could act as a drop-in replacement of Si-based counterparts in avionic applications.

In this work, a graphene-based planar terahertz electromagnetically induced transparency-like (EIT-like) metamaterial, composed of two horizontally symmetric mono-layer graphene micro-ring resonators (MRR) and a vertical mono-layer graphene micro-strip resonator (MSR), has been proposed. The transparent window was observed in the y polarization direction. By changing the carrier mobility of the graphene, the transparent window could be opened and closed while the position of the EIT-like window remained unchanged. The physical mechanism of the EIT-like effect was explained by the distribution of the electric field on E z and the three-level $\Lambda $ -type system. The theoretical fitting results based on the Lorentz oscillator model and the S-parameter inversion method were consistent with the numerical simulation results. In addition, the performance of the metamaterial for detecting the refractive index of the surrounding medium was analyzed. Numerical simulation showed that when the FOM exceeded 8.0, the sensitivity was 1.6 THz/RIU. Finally, as the graphene carrier mobility increased, the group delay of the device increased. The delay time reached 1.49 ps, and the group index was as high as 400. The proposed design provides a feasible method for the development of optical switches, biochemical molecular detection, and slow light equipment.

A new technique for preparing semisolid slurry, namely, distributary-confluence runner (DCR), was combined with die-casting (DC) to conduct rheological die-casting (R-DC) of A356 alloy. The mechanism of DCR for semisolid slurry preparation was determined via numerical simulations and experiments. The microstructure and mechanical properties of A356 alloys prepared via DC and R-DC were studied. High-quality slurry containing numerous primary α-Al (α1-Al) with an average size of 49 μm and a shape factor of 0.81 could be prepared via DCR. Simulation results indicated that the unique flow state and physical field changes during slurry preparation were conducive to accelerating the uniformity of melt temperature and composition fields, nucleation exfoliation, and spherical growth. Compared with the alloy prepared via DC, the tensile strength, yield strength, and elongation of A356 alloy prepared via R-DC increased by 19%, 15%, and 107%, respectively.

Herein, we report facile synthesis and multiple inherent properties of low-bandgap mesoporous C 4 N particles and showcase its previously-unexplored use as universal responsive bifunctional oxygen catalysts for constructing visible-light-sensitive (VLS) rechargeable Zn-air battery (RZAB) and polymer-air battery (RPAB) towards solar energy conversion/storage. Compared to widely-studied g-C 3 N 4 , as-obtained C 4 N shows a smaller bandgap of 1.99 eV with larger photocurrent response and can function simultaneously as visible-light-harvesting antenna and bifunctional oxygen reduction/evolution (ORR/OER) catalyst, enabling effective photo-coupling to tune oxygen catalysis. In addition to good energy storage performance, the C 4 N-enabled VLS-RZAB displays a low charge voltage of 1.35 V under visible light - below the theoretical RZAB voltage of 1.65 V, corresponding to a high energy efficiency of 97.78 %. Pairing C 4 N cathode with polymer anode also endows an entirely-new all-polymer VLS-RPAB with light-boosted charge performance, implying the generality of our strategy. Combined theoretical and experimental studies unveil that the ORR and OER active sites in C 4 N are separate carbon sites near pyrazine-nitrogen atoms and photo-generated energetic holes can activate OER for improved reaction kinetics. This study not only highlights a rarely-explored carbon nitride polymer and its new property and application but also opens new opportunities to develop organic semiconductors for photo-coupled rechargeable batteries towards solar energy utilization.

In this work, we first report the facile synthesis of porous waist drum-like α-Fe2O3 nanocrystals in high yield by hydrothermal method for supercapacitor application. The as-prepared porous waist drum-like α-Fe2O3 nanocrystals have an equatorial diameter of 100–130 nm and length of 150–200 nm, which are self-assembled by numerous nanoparticles. The formation mechanism of the porous waist drum-like α-Fe2O3 nanocrystals was proposed according to a series of time-dependent experiments. The specific surface area and pore size of the porous waist drum-like α-Fe2O3 nanocrystals were measured to be 28.6 m2 g−1 and 1.7 nm, respectively. Electrochemical measurements indicate that the porous waist drum-like α-Fe2O3 nanocrystals electrode exhibits noticeable pseudocapacitive properties with a high specific capacitance up to 234 F g−1 at 2 A g−1 as well as good cycling stability and high capacitance retention of 84.6% after 2000 charge–discharge cycles. The excellent pseudocapacitive performance could be due to the unique nanostructure of the porous waist drum-like α-Fe2O3 nanocrystals, which can provide fast ion/electron transfer.

We have investigated computationally the effect of π-conjugated extension on the charge transfer properties of triphenylene and coronene; where we have added fused benzene or triazole rings in the ...

Perovskite solar cells exhibit great potential to become commercial photovoltaic technology due to their high power conversion efficiency, low cost, solution processability, and facile large-area device manufacture. Interface engineering plays a significant role to optimize device performance. For the anode in the inverted devices, this review introduces the progress on the modification of poly(3,4-ethylenedioxythiophene): poly(styrene sulfonate) including chemical structure alteration, physical doping, and solution treatment. We present the recent advances of dopant-free hole transport materials widely applied in mesoporous and conventional devices, outlining their innovation with novel molecular design concepts toward promising material properties, and device performance. For the cathode, various metal oxide and organic electron transport materials are covered and the different modification strategies and related mechanisms are highlighted. Most importantly, simple synthesis process, inexpensive raw materials and highly reproducible photovoltaic performance are the main consideration for the design of all the interface materials. Finally, an outlook and some suggestions regarding the future interface engineering are proposed based on the summary of the current development status and working mechanism of interface materials.

To accurately obtain the tensile strength of rock and fully understand the evolution process of rock failure is one of the key issues to the research of rock mechanics theories and rock mass engineering applications. Using direct tensile, Brazilian splitting, and three-point bending test methods, we performed indoor and numerical simulation experiments on marble, granite, and diabase and investigated the tensile strength and damage evolution process of several typical rocks in the three different tests. Our experiments demonstrate that (1) the strength is about 10% greater in the Brazilian splitting than in the direct tensile, while the tensile modulus is lower; it is the highest in the three-point bending, which is actually subjected to the bending moment and suggested as one of the indexes to evaluate the tensile strength of rock; (2) the strength in splitting tests is strikingly different, while the strain law is basically similar; the direct tensile test with precut slits is more attainable than that with no-cut slits, with an uninfluenced strength; (3) the failure modes of rocks using different methods are featured by different lithology, while their final modes are basically the same under the same method; (4) PFC and RFPA numerical simulation tests are effective to analyze the internal crack multiplication and acoustic emission changes in the rock as well as the damage evolution process of rock in different tests.

The influence of pyrolytic carbon (PyC) interphase and different pyrolysis temperatures on the mechanical and tribological properties of Cf/SiC fabricated via polymer infiltration and pyrolysis after heat treatment at 1800 °C was investigated in this study. It was shown that the PyC interphase and high pyrolysis temperature were beneficial for protecting the carbon fibres and reducing the oxygen content in the matrix. Composites with PyC interphase and high pyrolysis temperature exhibited high flexural strength and fracture toughness after heat treatment. In addition, the results of reciprocating sliding tests showed that the tribological properties of composites with PyC interphase and high pyrolysis temperature were improved, and the high-strength fibres in the composite were beneficial to the formation and stabilisation of friction film at high frequencies.

A novel catalyst with a yolk-shell structure was designed to overcome the leaching of noble metals in heterogeneous catalysis. Through a template method, palladium (Pd) nanoparticles were encapsulated by hollow spherical covalent organic frameworks (COFs) consisting of 2,4,6-trihydroxybenzene-1,3,5-tricarbaldehyde (Tp) and p-phenylenediamine (Pa). The final catalyst with a yolk-shell structure was denoted as (Pd/C)@TpPa COFs. The unique morphology and chemical structure of this novel composite (Pd/C)@TpPa COFs were confirmed by a transmission electron microscope (TEM), a laser particle analyzer, X-ray diffraction (XRD), and N2 adsorption and desorption. Subsequently, to demonstrate its catalytic performance brought by structural design, this novel catalyst was applied to catalyze the Suzuki reaction. Interestingly, this catalyst exhibited a brilliant size cutoff efficiency for aryl benzene amounting to 100% and achieved a high conversion with only 0.05 mol% Pd loading. Besides, this catalyst could be readily recovered via filtration and reused for at least five consecutive cycles without any significant loss in its activity.

To constrain the behavior of chalcophile (sulfide-loving) elements during arc magmatic differentiation and to understand the formation conditions of Earth’s continental crust, the partition coefficients (D) of Mn, Co, Cu, Zn, As, Se, Mo, Ag, Cd, Sn, Sb, Te, Re, Au, Pb, and Bi between monosulfide-solid-solution (MSS), Cu-rich sulfide liquid (SL; containing 11–45 wt.% Cu), and hydrous silicate melt (SM) of basaltic to dacitic compositions were determined at 1000–1200 °C, 0.5–1.0 GPa, and fO2 1–1.5 log units above the fayalite–magnetite–quartz (FMQ) buffer. The D SL / S M values are 16–160 for Co, 1100–8400 for Cu, 50–220 for Se, 1200–5900 for Ag, 50–1800 for Cd, 700–3300 for Te, 15–510 for Re, 5700–90,000 for Au, 20–440 for Pb, and 140–3300 for Bi. The D SL / S M values for Mn, Zn, As, Mo, Sn, and Sb are below 1–40. The D MSS / S M values are 55–260 for Co, 530–1700 for Cu, 74–110 for Se, 30–110 for Ag, 4–40 for Cd, 15–70 for Te, 200–5900 for Re, and 140–270 for Au. The D MSS / S M values for Mn, Zn, As, Mo, Sn, Sb, Pb, and Bi are below 1–3. The D SL / S M of Au increase with increasing Cu content of the sulfide liquid, but the D SL / S M of the other elements little affected by the Cu concentration in the sulfide liquid. Because of their distinct dissolution mechanisms in the silicate melt, the D SL / S M and D MSS / S M of Mn, Co, Zn, Cd, Sn, and Pb are mainly controlled by the silicate melt FeOtot content ([FeOtot]); the D SL / S M and D MSS / S M for Re, Mo, As, Sb, and Bi are mainly controlled by [FeOtot] and fO2; the D SL / S M and D MSS / S M for Cu, Ag, and Au are mainly controlled by [FeOtot] and the content of reduced sulfur in the silicate melt; and the D SL / S M and D MSS / S M for Se and Te are mainly controlled by fO2. Using all available D SL / S M and D MSS / S M data, a partitioning model was developed for predicting D SL / S M and D MSS / S M of chalcophile elements as a multi-function of temperature, pressure, fO2, and silicate melt and sulfide compositions. Sulfide phase relations suggest that the sulfides precipitating from arc magmas containing >100 µg/g Cu in the silicate melt occur as Cu-rich sulfide liquid, whereas the sulfides precipitating from arc magmas containing 30–70 µg/g Cu in the silicate melt occur as mixed MSS and Cu-rich sulfide liquid. Modeling the Cu evolution trends of global arc magmas illustrates that the precipitating sulfides are dominantly MSS in continental arcs with a crustal thickness of >30 km, with the proportion of sulfide liquid being less than 20%; whereas, in island arcs with a crustal thickness of