Search

Bismuth sulfide (Bi2S3) is a promising anode material for high-performance potassium ion batteries due to its high theoretical capacity. However, the poor conductivity and substantial volume expansion hinder its practical application. We proposed an iodine-doped graphene encapsulated Bi2S3 nanorods composite (Bi2S3/IG) as an efficient anode for PIBs. The uniform-sized Bi2S3 nanorods evenly in-situ encapsulated in iodine-doped graphene framework, facilitating the electron transportation and structural stability. The potassium storage performance was evaluated in three electrolytes, with the best option of 5 mol/L KFSI in DME. The reversible capacity of representative Bi2S3/IG reached 453.5 mAh/g at 50 mA/g. Meanwhile, it could deliver an initial reversible capacity of 413.6 mAh/g at 100 mA/g, which maintained 256.9 mAh/g after 200 cycles. The proposed strategy contributes to improving potassium storage performance of metal sulfide anodes.

Photocatalytic ammonia generation via nitrogen reduction reaction (NRR) is a green and prospective nitrogen fixation technique. However, NRR is often hampered by the high N2 adsorption/activation energies and is accompanied by a slow kinetics oxygen evolution reaction (OER). Herein, a robust Bi2S3/OV-Bi2MoO6 S-scheme heterojunction is constructed using a simple in-situ anion exchange process, which enables oxygen vacancy (OVs) abundant Bi2MoO6 microspheres with surface deposited Bi2S3. The as-fabricated Bi2S3/OV-Bi2MoO6 functioned as an effective photocatalyst to convert N2-to-NH3 under mild conditions. The photocatalytic NH3/NH4+ production rate reached 126 μmol gcat−1 under visible light for 2.5 h with 2% of Bi2S3/OV-Bi2MoO6 photocatalyst, which was 8-fold higher than pristine Bi2MoO6. Furthermore, the as-fabricated Bi2S3/Bi2MoO6 heterojunction exhibited good selectivity, high stability and reproducibility. The excellent photocatalytic NRR performance was ascribed to the Bi2S3/Bi2MoO6 heterojunction formed subsequent to the strong interaction between Bi2S3 and Bi2MoO6. The OVs facilitated the chemical adsorption process allowing activation of N2 molecule on the Bi2S3/Bi2MoO6. Simultaneously, the S-scheme heterojunction prolonged the lifetime of photogenerated carriers, accelerated the electrons/holes spatial separation and accumulation on the Bi2S3 (reduction) and Bi2MoO6 side (oxidation), respectively, thus strengthening both OER and NRR half-reactions. This simple in-situ anion exchange method offers a novel technique for strengthening OER and NRR half-reactions in Bi-based photocatalysts for effective photocatalytic ammonia generation.

ZrSiO4 demonstrates applicability as the SiC/SiC interphase. Via a non-hydrolyzed sol-gel method, the pyrolysis product, synthesis condition, and the formation effectiveness of the ZrSiO4 coating on SiC fibers were investigated. Mini-SiC/SiC composites with two layers of ZrSiO4 interface coatings were oxidized to preliminarily verify their oxidation resistance effect.

Ti3SiC2 ceramic and SUS430 stainless steel (SS) were successfully joined by a solid diffusion bonding technique using Ni interlayers. Diffusion bonding was performed in the temperature range of 850 °C–1100 °C under vacuum. The interfacial reaction phase, morphology evolution, growth kinetics and tensile strength were systematically investigated. In all cases, the inter-diffusion and reaction between Ti3SiC2 and SS can be effectively prevented by Ni foil, and the good transition in the joint benefit to the sound joining. The interface in the joints adjacent to SS matrix was composed of γ solid solution and a small amount of σ intermetallic compound. The compounds in the Ni/Ti3SiC2 interface was Ni/Ni(Si)/Ni31Si12 + Ni16Ti6Si7 + Ti3SiC2 + TiCx/Ti2Ni + Ti3SiC2 + TiCx/Ti3SiC2, which formed by the inter-diffusion and chemical reactions between Si and Ni atoms. The diffusion mechanism and reaction mechanism were interrelated, and decided the width of each reaction zones. Furthermore, the diffusion activation energy was 113 kJ/mol. The tensile strength increases with increasing the bonding temperature. The minimum and maximum strength of 32.3 MPa and 88.8 MPa were obtained from SUS430/Ni/Ti3SiC2 joints, which bonding experiments were carried out at 850 °C and 1100 °C, respectively.

The influence of surface roughness on the interfacial dynamic recrystallization kinetics and mechanical properties of Ti-6Al-3Nb-2Zr-1Mo hot-compression bonding joints was systematically investigated. It is found that for the bonding interface of rough surfaces, elongated fine grains are formed at the bonding interface due to shear deformation of the interfacial area. As the surface roughness increases, the proportion of elongated grains drastically decreases as they further reorient to form equiaxed grains along the bonding interface of rougher surfaces resulting from severe incompatible deformation of the interface area. Meanwhile, high-density geometrically necessary dislocations accumulate around the interfacial recrystallization area to accommodate the incompatible strain and lattice rotation. A rotational dynamic recrystallization mechanism is thereby proposed to rationalize the formation of fine interfacial recrystallization grains during bonding of rough surfaces. In contrast to that of rough surfaces, bonding interface of polished surfaces exists in the form of straight interface grain boundaries without fine grains under the same deformation conditions. While with the increase of deformation strain, small grain nuclei form along the bonding interface, which is associated with discontinuous dynamic recrystallization assisted by strain-induced boundary migration of interface grain boundaries. Moreover, the bonding joints of rough surfaces show lower elongation compared with that of polished surfaces. This is because the formation of heterogeneous fine grains with low Schmid factor along the bonding interface of rough surfaces, leading to worse compatible deformation capability and thereby poor ductility of bonding joints.

Solid-state fluorescent switches with reversible luminescence characteristics have attracted considerable attention because of their broad applications in advanced photonics, such as anticounterfei...

Nowadays, thermal conductivity as a key parameter affecting the thermal performance of PCM has attracted much attention. However, the thermal performance evaluation of ultra-high thermal conductivity PCM is scarce, especially in field of building energy conservation. Therefore, we traversed the range of thermal conductivity that can be prepared at present and within the expected time frame, which is 0.08–49.28 W ⋅ m − 1 K − 1 . In addition, a novel index, Utilization Rate of Latent Heat (URLH), was proposed to evaluate matching degree between PCM and a certain application background in buildings, so as to explore the reason of poor energy-saving effect of PCM under some application backgrounds. We found that the thermal conductivity of PCM is not the higher the better in buildings, in other words, a turning point appears. The optimal thermal conductivity is about 0.6 W ⋅ m − 1 K − 1 and when the value is lower than 0.3 W ⋅ m − 1 K − 1 , URLH is equal to 0 in the cases of Shanghai. Therefore, we recommend PCM researchers to evaluate the URLH before using PCM to avoid the ineffective use of materials. Through the analysis of URLH, researchers can know the specific parameters that affect the thermal performance of PCM and obtain the way to optimize them.

Holes have an important influence on dynamic fracture process of brittle materials. In this paper, the influence of the hole offset distance (HOD) on the movement process of the explosive crack is studied. Polymethyl methacrylate (PMMA) is used as the experimental material, and different HOD holes are drilled on the PMMA plate. A new digital laser dynamic caustics system is employed to observe the crack tip dynamic stress intensity factor and crack growth velocity of PMMA plates with different HODs under explosive loading. The results indicate that holes reduce the peak velocity of explosive crack propagation. Moreover, the interaction between the stress wave reflected by the hole and the explosion stress wave is the main cause of crack deflection. Lastly, as the HOD increases, the crack motion trajectory is weakened by the interference of the holes, which gradually decreases corresponding stress intensity factors. With the increase of HOD/d, the crack arrest effect of empty hole decreases gradually.

The shuttling effect and sluggish redox kinetics of polysulfides are the main obstacles that restrict the practical application of lithium–sulfur (Li–S) batteries. Herein, in this work, cathode mat...

Conductive carbon structure has been considered as a promising sulfur-hosting material as the cathode of lithium-sulfur batteries. However, the issue of polysulfide shuttling requires an additional component to help restrict and convert sulfur substances. Herein, in this work, hollow and porous carbon nanospheres (HCS) are synthesized by a template method and a high-temperature carbonization treatment. A thin layer of ZnS coating is then deposited on the HCS-based sulfur (ZnS@HCS/S) cathode with controlled thickness, and the overall electrochemical properties are systematically evaluated. Results show that with 30 nm -thick ZnS coating, the cathode reveals an improved capacity of 1411 mA h g−1, and higher capacities from 0.2 to 3 C rate compared with bare HCS/S cathode. Moreover, the ZnS coating also enhances the cycling stability of ZnS@HCS/S cathode over 280 cycles at 0.5 C, with only 0.2% capacity decay per cycle. This work demonstrates potential applications for high-performance lithium-sulfur batteries.

All solid-state microchip lasers having the advantage of short cavity lengths give them tremendous potential as pulsed devices for short pulse laser generation. In this work, by constructing a compact microchip-like laser resonator, we have demonstrated continuous-wave (CW) Pr,Mg:SrAl12O19 (SRA) lasers at 622 nm and 643 nm, respectively with maximum output powers of 0.69 W and 1.18 W with excellent beam qualities, which is believed to be the highest powers that have achieved in Pr3+ microchip lasers. Based on this CW opeation, we, by using a Co:LMA saturabel absorber, have further demonstrated passively Q-switched operation of the two lasers. The shortest pulse widths reached about 28.5 ns (for the 622 nm laser) and 31.9 ns (for the 643 nm laser), which are relatively short pulse time durations for passively Q-switched Pr3+ lasers thanks to the compact laser configuration. This work has proposed a simple route for achieving compact high-power CW and short-pulse Q-switched visible lasers.

Piezoelectrics interconvert mechanical energy and electric charge and are widely used in actuators and sensors. The best performing materials are ferroelectrics at a morphotropic phase boundary, where several phases coexist. Switching between these phases by electric field produces a large electromechanical response. In ferroelectric BiFeO3, strain can create a morphotropic-phase-boundary-like phase mixture and thus generate large electric-field-dependent strains. However, this enhanced response occurs at localized, randomly positioned regions of the film. Here, we use epitaxial strain and orientation engineering in tandem-anisotropic epitaxy-to craft a low-symmetry phase of BiFeO3 that acts as a structural bridge between the rhombohedral-like and tetragonal-like polymorphs. Interferometric displacement sensor measurements reveal that this phase has an enhanced piezoelectric coefficient of ×2.4 compared with typical rhombohedral-like BiFeO3. Band-excitation frequency response measurements and first-principles calculations provide evidence that this phase undergoes a transition to the tetragonal-like polymorph under electric field, generating an enhanced piezoelectric response throughout the film and associated field-induced reversible strains. These results offer a route to engineer thin-film piezoelectrics with improved functionalities, with broader perspectives for other functional oxides.

Circularly polarized luminescence (CPL) materials have potential applications in 3D optical displays, information security encryption, sensors, and photoelectric devices because of their inherent a...

ZnS has great potentials as an anode for lithium storage because of its high theoretical capacity and resource abundance; however, the large volume expansion accompanied with structural collapse and low conductivity of ZnS cause severe capacity fading and inferior rate capability during lithium storage. Herein, 0D-2D ZnS nanodots/Ti3C2Tx MXene hybrids are prepared by anchoring ZnS nanodots on Ti3C2Tx MXene nanosheets through coordination modulation between MXene and MOF precursor (ZIF-8) followed with sulfidation. The MXene substrate coupled with the ZnS nanodots can synergistically accommodate volume variation of ZnS over charge–discharge to realize stable cyclability. As revealed by XPS characterizations and DFT calculations, the strong interfacial interaction between ZnS nanodots and MXene nanosheets can boost fast electron/lithium-ion transfer to achieve excellent electrochemical activity and kinetics for lithium storage. Thereby, the as-prepared ZnS nanodots/MXene hybrid exhibits a high capacity of 726.8 mAh g−1 at 30 mA g−1, superior cyclic stability (462.8 mAh g−1 after 1000 cycles at 0.5 A g−1), and excellent rate performance. The present results provide new insights into the understanding of the lithium storage mechanism of ZnS and the revealing of the effects of interfacial interaction on lithium storage performance enhancement.

To study the formation and stability of the O/W and reverse W/O microemulsion, dissipative particle dynamics (DPD) simulation was utilized to investigate the system composed of oil, water and Gemin...

Titanium alloy has been widely applied in industrial fields because of its excellent material properties. Electrical discharge machining (EDM) is commonly technology for processing titanium alloy. When titanium alloy was processed by EDM, a recast layer was inevitably be produced on its surface, which can adversely affect the surface quality and working life. Focus on the above problem, this paper proposed to add B4C powders into the spark oil and cooperate with the tool electrode sloshing for powder mixed electrical discharge machining (PMEDM) of titanium alloy, which can reduce the thickness of the recast layer and thereby improve the quality of the machined surface. Firstly, B4C powders were mixed in the spark oil and the PMEDM of the titanium alloy was carried out. In this step, the thickness of recast layer was preliminarily reduced and the quality of machined surface was improved. Secondly, when the PMEDM of the titanium alloy was nearly completed, the tool electrode sloshed along the machine tool spindle within the EDM gap. Combining PMEDM with the tool electrode sloshing, the recast layer on the machined surface was further eliminated and the quality of machined surface was further improved. By adding 3000 mesh B4C powders into the spark oil, the paper carried out the PMEDM of titanium alloy combining with the tool electrode sloshing. Under the action of appropriate process parameters, the micro-groove structure with surface roughness Ra of 0.205 μm was obtained in the titanium alloy and the recast layer on the machined surface was almost invisible.

Ti-6Al-4V alloy has been widely used in industrial fields. Electrical discharge machining (EDM) is a commonly used technology for machining Ti-6Al-4V alloy. During EDM of Ti-6Al-4V alloy, the thermal and physical characteristics of tool electrode have an important influence on processing characteristics. In order to study the influence of different electrode materials on the processing characteristics of Ti-6Al-4V alloy, brass electrode, copper tungsten electrode, and tungsten electrode were used to perform EDM of Ti-6Al-4V alloy. In this paper, electrodes with V-groove array structures were designed to carry out powder mixed electrical discharge machining (PMEDM) of Ti-6Al-4V alloy, and the machining results were evaluated based on four indicators: microstructures morphology, tool electrode wear (TEW), material removal rate (MRR), and recast layer thickness (RLT). The processing results show that copper tungsten electrode is recommended to machine Ti-6Al-4V alloy because it has the highest reproduction rate (75.2%), a smaller TEW (139 μm), the highest MRR (255.39 mm3/min), and a thinner RLT (3.35 μm).

To promote the development and application of ultra-thin heat dissipation devices, Cu/grapheme (GR) composite foils with hierarchical microscale structure were prepared by ultrasonic-assisted composite electrodeposition, and chemical etching and plasma oxidation treatment were applied to obtain superhydrophilic. The study found that the hierarchical multi-scale structure on the mold electrode surface can be replicated on the foil surface. Ultrasonic refines the grains and reduces the internal defects, while an increase in the GR content not only further refines the grains but also makes the microstructure multi-directional. The combined effect of ultrasonic and GR significantly improves the microhardness of the foils up to 125 HV0.01. Without any surface treatment, the contact angle (CA) of foil gradually increased with the introduction of ultrasonic and GR, the wettability developed towards hydrophobic, and the highest CA reached 98.43°. Chemical etching can change the submicron-scale structure of the foil surface, and then make the wettability towards to hydrophilic, but not enough to reach the superhydrophilic state. After plasma oxidation treatment, a large number of nanoscale CuO and Cu2O particles are generated on the surface of the chemical etching foils, which not only further enriches the multi-scale structure, but also improves the surface energy. As a result, the wettability of foil surface is further improved, showing a superhydrophilic state, and the CA is less than 5°. Moreover, with the introduction of ultrasonic and the increase of GR content, the hydrophily of the foil surface also tends to improve, and the minimum CA can reach 1.89°.

A comprehensive CFD study was conducted to understand the hydrodynamics characteristics in a top-covered unbaffled stirred tank. The turbulent flow in the tank was described by the Reynolds stress turbulence (RST) model, and the impeller rotation was simulated using a single reference frame (SRF) approach. The flow field and power number in the tank stirred by a Rushton turbine were investigated firstly. It is found that circumferential flow is dominant in the unabffled tank, and the flow field can be divided into forced and free vortex zones. A weak two-loop flow pattern forms in the vertical plane, and would evolve into one single-loop when impeller was equipped very close to the bottom of the tank. In general, impeller off-bottom clearance and blade thickness have small effects on flow field in the unbaffled tank. With increasing of rotational speed, the dimensionless liquid velocity rises, especially near the critical radius of two zones. Critical radius is larger for larger impeller, while the variation range of critical radius to impeller diameter ratio is narrow. The effects of operational and geometric parameters on impeller power number (Np) in unbafffled tank are far different from those in baffled tank. In the unbaffled stirred tank, rotational speed, blade thickness and impeller off-bottom clearance have small effects on power number, while impeller diameter has a significant effect on power number. Under the same operating condition, the larger the impeller diameter, the smaller the power number is. Finally, the hydrodynamics characteristics in the tank stirred by four common impellers were investigated and compared.

So far, many investigations have reported that Zr-based bulk metallic glasses (BMGs) could be precisely and flexibly shaped by electrical discharge machining (EDM). However, EDM induced crystallization and roughness is still a bottleneck. In this research, bench-mode electrochemical surface smoothing (ESS) in the NaCl-ethylene glycol (EG) electrolyte has been proposed to post-process the spark erosion treated Zr-based BMGs in order to solve the abovementioned problems. The utilization of the NaCl-EG electrolyte overcomes the difference in electrochemical dissolution mechanisms of multiple components contained in Zr-based BMGs. Taking a sort of Zr-based BMGs, Vit1 (Zr41.2Ti13.8Cu12.5Ni10.0Be22.5), as an example, voltammetry and chronoamperometry methods have been performed on the BMG surface before and after wire-EDM, respectively, in the NaCl-EG electrolyte to reveal the steady and transient electrochemical behaviors. In order to achieve high-efficiency and high-quality ESS of Zr-based BMGs, a 3D printed setup with lateral flushing has been developed, combined with the micron sized inter-electrode gap (IEG) and the pulse current. The surface morphologies after ESS have been compared to evaluate the effects of the initial surface morphologies, dwell time, and pulse parameters. The surface material properties and mechanical performance before and after ESS have also been investigated by EDS, XRD, XPS, and nanoindentation. The results suggests that the proposed ESS method is capable of quickly eliminating the crystalline layer induced by the thermal shock and reducing roughness caused by the discharge craters, which has been finally validated by fast ESS of two Zr-based BMG molds with ruled surfaces in the NaCl-EG solution.

Semi-solid metal forming processes cover a wide variety of technologies in manufacturing, generally leading to non-dendritic microstructures typified by rosette-like or spherical grains. With the contemporary experimental methods, researchers still cannot completely understand the formation of such microstructures. However, as a process coupled with dendritic growth, deformation and flow, the microstructural evolution during the semi-solid deformation has been scarcely simulated. With the vector-valued phase-field method, two-phase flow model and an innovative design of boundary conditions, the current research numerically compressed a single dendrite into a less dendritic polycrystalline structure. The resulting microstructure was consistent with the metallographic analysis and the simulation enables a clear observation of the whole process: the ripening transformed the highly branched shape into a less dendritic one; the subsequent deformation crushed the dendrite into a stubby structure; eventually, the deformation caused the boundaries inside this structure, dividing the solid into multiple grains. The analysis on the boundaries inside the deformed solid offered further insight into the formation of non-dendritic structures. These boundaries showed a tendency towards melting with increasing misorientation, demonstrating the possibility of the grain boundary wetting, which was considered as the source of the fragmentation when the dendrite undergoes deformation, but is hard to validate in situ even with the cutting-edge X-ray imaging technique.

A new type of water-soluble coal dust suppressant (later called MA) with excellent performance was prepared by modified starch, styrene, methyl methacrylate, Butyl acrylate (as the main monomers) and acrylic acid (as the functional monomer) via mixed the emulsifiers of Sodium dodecyl sulfate (SDS)/octylphenol polyoxyethylene(10)ether (OP-10) and ammonium persulfate served as initiator. The properties of anti-wind erosion, water retention and coal quality impact were investigated. The MA was characterized by viscosity measurements and scanning electron microscopy. The results show that the spraying of MA has no effect on coal quality, and the water loss rate of MA is slightly lower than that of water, which has certain moisture retention. After spraying MA on the surface of coal sample for 120 hours, the coal sample is swept by six-stage wind (wind speed is 10.8-13.8 m/s), and the erosion rate is only 1.8%. The MA and coal samples are closely bonded to form a dense soft film, which has a excellent dust suppression effect.

Welding properties of three alloys with different Cu contents (0.1, 0.4 and 0.9 wt.%) is studied by means of melt inert-gas welding (MIG). The results showed that, with the increase of Cu content from 0.1 wt.% to 0.9 wt.%, the strength and elongation increased obviously. When the Cu content was 0.9 wt.%, the strength and elongation reached 375MPa and 15%, respectively, which is a better match for bearing structure part of vehicles application. Besides, the adding of Cu element provided an increase limit for welding joint strength. Due to abundant coarse phases in fusion zone (FZ) and welding zone (WZ), the strength slightly increased and the failure fracture was different compared with that of 0.1Cu and 0.4Cu alloy. Present result was meaningful and valuable for pushing aluminum application automobile structural parts and other engineering components.

Lithium-sulfur (Li-S) batteries have great potential in next-generation energy storage due to its high theoretical specific capacity and energy density. However, there are several challenges to the practical application of Li-S batteries including the growth of lithium dendrites and the shuttle effect of polysulfide. Introducing interlayeres (freestanding or coated on the separator) is an effective approach to reduce these obstacles and improve the electrochemical performance of Li-S batteries. In this review, we briefly summarize the interlayer materials and structures modified on both cathodic and anodic sides including (i) carbon-based materials, (ii) polymers, (iii) inorganic metal compounds, (iv) metal–organic frameworks, as well as (v) the novel separators in recent years. We also systematically address the fabrication processes, assembling methods, and functions of interlayers for enhancing the performance of Li-S batteries. Furthermore, the prospects and outlooks of the future development of advanced interlayers and separators are also presented.

Non-dendritic microstructures are generally obtained in metals after semi-solid deformation (deformation during solidification); however, dendritic growth is preferred without deformation. The fragmentation of dendrites is recognized as an essential contributing factor to non-dendritic microstructures. However, the underlying mechanism of fragmentation needs to be clarified in depth. It is infamously hard for researchers to carry out a direct observation of this process. Moreover, a comprehensive numerical survey of this process is not trivial. The present research reported a new method to model dendritic growth during semi-solid deformation. The motion and deformation of the solid coupled with liquid flow in the melt were treated as the two-phase flow because plastic materials could be formulated as non-Newtonian fluids. The vector-valued phase-field formulation and the self-constructed Navier–Stokes solver made it possible to simulate the growth, motion, deformation, fragmentation and agglomeration of two dendrites coupled with liquid flow in the melt. Computational results suggest that fragmentation can occur when the grain boundary is wet and penetrated by the melt, giving new supporting evidence to a previously proposed mechanism for the fragmentation of dendrites.

Sodium-ion batteries (SIBs) have attracted significant attentions as promising alternatives to lithium-ion batteries for large-scale energy storage applications. Here carbon materials are considered as the most competitive anodes for SIBs based on their low-cost, abundant availability and excellent structural stability. Pitch, with high carbon content and low cost, is an ideal raw precursor to prepare carbon materials for large-scale applications. Nevertheless, the microstructures of pitch-based carbon are highly ordered with smaller interlayer distances, which are unfavorable for Na ion storage. Many efforts have been made to improve the sodium storage performance of pitch-based carbon materials. This review summarizes the recent progress about the application of pitch-based carbons for SIBs anodes in the context of carbon's morphology and structure regulation strategies, including morphology adjustment, heteroatoms doping, fabricating heterostructures, and the increase of the degree of disorder. Besides, the advantages, present challenges, and possible solutions to current issues in pitch-based carbon anode are discussed, with the highlight of future research directions. This review will provide a deep insight into the development of low-cost and high-performance pitch-based carbon anode for SIBs.

The growing energy concern all over the world has recognized hydrogen energy as the most promising renewable energy sources. Recently, electrocatalytic hydrogen evolution reaction (HER) by water splitting has been extensively studied with a focus on developing efficient electrocatalysts that can afford HER at overpotential with minimum power consumption. The two-dimensional transition metal carbides and nitride, also known as MXenes, are becoming the rising star in developing efficient electrocatalysts for HER, owing to their integrated chemical and electronic properties, e.g., metallic conductivity, variety of redox-active transition metals, high hydrophilicity, and tunable surface functionalities. In this review, the recent progress about the fundamental understanding and materials engineering of MXenes-based electrocatalysts is summarized in concern with two aspects: i) the regulation of the intrinsic properties of MXenes, which include the composition, surface functionality, and defects; and ii) MXenes-based composites for HER process. In the end, we summarize the present challenges concerning the efficiency of MXenes-based HER electrocatalysts and propose the directions of future research efforts.

The evolution of heterogeneous microstructure and mechanical properties of a 12Cr–10Ni–Mo–Ti maraging steel was investigated at different aging temperatures. As the aging temperature increases, more reversed austenite forms with the recovery of martensite matrix. When aging temperature is up to 560 °C, more lath-like reversed austenite coalesces together and leads to the formation of martensite and austenite dual-phase microstructure. Fine η-Ni3(Ti, Al) particles initially precipitate at 440 °C and grow up with increased aging temperature. Notably, it was found that η-precipitates can be encompassed in reversed austenite at 500 °C. Thermodynamic calculations further verify the austenite reversion, and nanoprecipitation can occur independently of each other though there is competition of Ni element. However, it leads to the coarsening and dissolution of η-precipitates as the aging temperature further increases. The desirable heterogeneous microstructure of the aged martensite matrix, soft reversed austenite and stable η-precipitates at 500 °C contributes to a high yield strength (~ 1 GPa, 25 °C; ~ 1.4 GPa, -196 °C) and a reasonable cryogenic impact toughness (~ 60 J, − 196 °C), which is mainly ascribed to the precipitation strengthening of η-precipitates, transformation-induced plasticity (TRIP) toughening effect from the lath-like reversed austenite and the increased misorientation toward high-angle grain boundary.

Thermal effect in absorbing composite is concerned gradually due to electromagnetic environment tends to high power, high frequency and wide bandwidth. Microstructure characteristics and some basic material properties of carbonyl iron powder/silicone rubber (CIP/SR) are obtained by experiments method. Complex permittivity and permeability of CIP/SR composite as an absorbing material is measured by the vector network analyzer. CIP/SR composite with 78 wt% particles filling exhibits excellent absorption performance in C and X band. A numerical model coupled with electromagnetic wave, heat transfer and mechanics theory is presented to study the thermal effect and mechanical damage of absorbing composite under microwave radiation. Microwave heating and attenuation mechanism of CIP/SR composite are discussed. Electric field, temperature, stress and deformation in CIP/SR composite are quantitatively characterized. The results indicate temperature distribution relates to electric polarization and hysteresis loss. Temperature of CIP/SR composite increases by 36 °C as microwave radiation lasts 2 s at 9.37 GHz. Thermal expansion and stress concentration will be aggravated as frequency increases.

We report on the fabrication of circular cladding waveguides with cross-section diameters of 60−120 μm in Pr:YAG crystal by applying femtosecond laser inscription. The fabricated waveguides present 2D guidance on the cross-section and fairly low propagation losses. Multiple high-order guiding modes are observed in waveguides with different diameters. Corresponding simulation results reveal the origin of a specific kind of guiding modes. Confocal micro-Raman (μ-Raman) experiments demonstrate the modification effects in femtosecond laser affected areas and ascertain the refractive index induced guiding mechanism. In addition, luminescence emission properties of Pr3+ ions at waveguide volume are well preserved during the femtosecond laser inscription process, which may result in a potential high-power visible waveguide laser.

Fluorescence probes with strong near-infrared (NIR) emission and water solubility are considered useful visualization tools for localization marking as well as investigating cell migration and tran...

Luminescent conjugated network polymer is one of the most promising chemo-sensors owing to their good chemical/optical stability and multiple functionalization. Herein, three conjugated network polymers were prepared by using aggregation-induced emission active 1,1,2,2-tetrakis(4-formyl-(1,1′-biphenyl))-ethane (TFBE) unit as monomer and hydrazine as linker. Through regulating the synthetical condition, the polymeric network can form either uniform two-dimensional azine-linked nanosheets (A-NS), conjugated microporous polymers (A-CMP) or covalent organic frameworks (A-COF). All of these polymers exhibited good stability and high fluorescence quantum efficiency with the quantum yield of 6.31% for A-NS, 5.26% for A-CMP, and 5.80% for A-COF, as well as fast and selective fluorescence quenching response to 2,4,6-trinitrophenol (TNP). And the best TNP sensing performance with the Stern-Volmer constants (Ksv) values up to 8 × 105 L/mol and a detection limit of 0.09 μmol/L was obtained for A-NS. The study explores various strategies to construct conjugated polymers with different nanoarchitectures based on the same building block for sensitive detection of explosives.

Fe–10Cr–10Ni cryogenic maraging steel is one of the key candidate materials applied in harsh cryogenic condition due to its high strength and good cryogenic toughness. In this study, the effect of aging temperature on its microstructure and mechanical properties was systematically studied based on austenite reversion and nano-precipitation. It shows that a desirable combination of high strength (834 MPa, 25 °C) and excellent cryogenic impact toughness (164 J, −196 °C) can be obtained by aging treatment at 500 °C. Multi-scale characterizations were conducted to reveal the microstructure characteristics of the steel. It was found that obvious film-like reversed austenite nucleate and grow at the high-angle grain boundaries of martensite matrix in the steel aged at 500 °C, whereas the higher aging temperature resulted in a larger content of blocky reversed austenite in martensite blocks. Austenite reversion mechanism was proposed based on the double-spherical-cap model and diffusion kinetics of Ni element. Besides, it was found that the precipitation sites of Ti-rich particles are not only distributed in matrix but also located at the dislocations, and they were identified as the clusters of Ni3Ti precipitates. Finally, the origin of the above cryogenic toughness includes the transformation-induced plasticity (TRIP) effect from the soft film-like austenite, higher density of high angle grain boundaries of martensite and fine nanoscale precipitates. Moreover, the precipitation strengthening from the clusters of Ni3Ti precipitates contributes to the high strength of the steel aged at 500 °C.

The objective of this paper is to experimentally and numerically investigate the transient cavitation flow during the startup process of mixed flow pump with emphasis on studying the influence of blade numbers. The transient cavitation simulation was studied based on the improved SST k–ω turbulence model and the Zwart cavitation model. Firstly, in order to obtain the relationship between transient flow rate and the variation of rotational speed at startup, a theoretical analysis based on the fast transients of centrifugal pump was first applied to mixed flow pump and was verified by the current experiment study. Subsequently, the influence of blade number on the cavitation flow in the startup was studied. It is found that the transient cavitation could be classified into four stages regardless of the number of blades: no cavitation stage, the cavitation growth stage, the cavitation reduction stage and the cavitation stabilization stage. However, the blade number does have an impact on the spatial-temporal evolution of cavitation. More specifically, when the blade number increases, the initial cavitation appeared lately, the coverage area of the triangular cavitation cloud and sheet cavitation both decreased, and the increase in blade number has a better inhibitory effect on the sheet cavitation at the cavitation growth stage, and can make sheet cavitation disappear more quickly at the cavitation reduction stage.

The creation of drag-reducing surfaces in deformed tubes is of vital importance to thermal management, energy, and environmental applications. However, it remains a great challenge to tailor the surface structure and wettability inside the deformed tubes of slim and complicated feature. Here, we describe an electrochemical anodization strategy to achieve uniform and superhydrophobic coating of TiO2 nanotube arrays throughout the inner surface in deformed/bend titanium tubes. Guided by a hybrid carbon fibre cathode, conformal electric field can be generated to adaptatively fit the complex geometries in the deformed tube, where the structural design with rigid insulating beads can self-stabilize the hybrid cathode at the coaxial position of the tube with the electrolyte flow. As a result, we obtain a superhydrophobic coating with a water contact angle of 157° and contact angle hysteresis of less than 10°. Substantial drag reduction can be realised with an overall reduction up to 25.8 % for the anodized U-shaped tube. Furthermore, we demonstrate to spatially coat tubes with complex geometries, to achieve energy-saving liquid transportation. This facile coating strategy has great implications in liquid transport processes with the user-friendly approach to engineer surface regardless of the deformation of tube/pipe.

This study proposes a material microstructure topology optimization model for a piezoelectric composite beam subject to initial disturbance. The optimization model is built through the Solid Isotropic Material with Penalization interpolation subject to the material volume fraction on the microlevel. And the objective function is to minimize the time integral about local structural response. By introducing the Lyapunov second equation, this time integral is simplified and does not need any numerical integration technique. It can also be used to measure the global vibration response instead of short time gap. Besides, different objectives such as a regional structural response can also be obtained by only changing the weight matrix form. And the sensitivity of the objective function with respect to the design variables are also deduced by solving the Lyapunov equation. A bidirectional evolutionary structural optimization algorithm is used to acquire the optimal results. Four numerical examples including multiphase material microstructure topology optimization verify the developed method that can effectively suppress local structural vibration level and obtain lighter structure.

Printed circuit board (PCB) can provide assembly support and electrical connection for components in electronic systems. The machining of micro-holes in PCB is a necessary process and key step for its application in electronic components. Therefore, micro-holes are the key structures of PCB. At present, high-speed drilling based on micro-bit is the key supporting technology for machining PCB micro-holes. However, when the copper foil layer in PCB is machined by this technology, the micro-holes are prone to defects such as hole mouth burr and hole nail head, which could seriously affect the performance of PCB. Focusing on the above problems, this paper proposed to use micro electro-discharge machining (micro-EDM) for assisted machining of PCB micro-holes. With this method, the copper foil layer in PCB was machined by micro-EDM, so as to remove hole mouth burr and hole nail head. The paper detailedly studied the influence of micro-EDM voltage, pulse width and pulse interval on hole mouth burr and hole nail head. Finally, under the effects of 10,000 rpm rotational speed, 40 V voltage, 80 ns pulse width and 160 ns pulse interval, the micro-bit with diameter of 200 μm was used to carry out micro-EDM-assisted machining of the copper foil in PCB. From the machining results, it can be found that the hole mouth burr and the hole nail head were basically eliminated and PCB micro-holes with good quality were obtained by the proposed method.

Excellent crystallinity and uniform composition distribution of the Cu2ZnSn(S,Se)4 (CZTSSe) absorber are indispensable factors for the fabrication of photovoltaic device with excellent performance. Here, a facile and effective method is developed to improve the composition uniformity of CZTSSe absorber. It is inspiring that by replacing the acetates with chlorides as the solutes in the precursor solution, the issue of the composition non-uniformity especially for the distribution of Cu and Sn, which is ascribed to the rich-carbon in the acetate-based CZTSSe absorber, is able to be avoided. Due to less organic residues and composition uniformity, the grain size and the crystallinity of absorber could be significantly enhanced, and the photovoltaic performance of chloride-based CZTSSe solar cell is improved remarkably. Furthermore, substituting CuCl2 with CuCl as the copper source in the precursor solution is able to obtain a stable solution, and the quality of CZTSSe absorber is further improved. As a consequence, 8.48% efficient CZTSSe solar cell has been yield.

Micro-milling is a flexible and promising fabrication process. Based on the analysis of the surface formation process in micro-end milling, the theoretical surface model was established to investigate the influence of seven identified factors, i.e., minimum cut thickness (MCT), elastic recovery, plastic side flow, radial and axial runout, tool wear (corner radius and unbalanced wear coefficient), and vibration on the frequency spectrum characteristics. The increase of MCT coefficient and plastic side flow height could increase the amplitude of the sft and 2sft frequency, while the scenario for the elastic recovery coefficient witnessed a reverse trend. The amplitude of the 0.5sft frequency decreased with the increase of the radial runout offset, while the amplitude of sft frequency increased as the radial runout offset increased; the scenario for the influence of the radial runout angle was opposite. The increase of the axial runout offset could lead to the increase of the amplitude of both 0.5sft and sft frequency. The increase of corner radius could lead to a slight reduction of the amplitude of the 0.5sft and sft frequency. The occurrence of the vibration with high frequency leaded to a low spatial frequency. The corresponding tool wear experiment was conducted, and the frequency-spectrum characteristics of the micro-milled surface were compared with the simulated results to validate the established profile models. The paper successfully correlated the relative importance of the identified individual factors to the corresponding frequency spectrum characteristics, and it had potential applications in predicting and controlling the spatial content of machined surfaces.

Fluorescent photoswitches are highly attractive, because they hold great promises for photonic devices and imaging. However, a limited number of reversible switches with a response to light have been achieved in the solid state. Here, we report reversible dual fluorescent photoswitching characteristics in the solid state of spiropyran (SP)-functionalized tetraphenylethene (TPE) derivatives. These photoswitches exhibit two distinct and selectively addressable states, a cyan fluorescence and a red fluorescence, which can be conveyed into each other in a reversible feature upon irradiation with alternating UV and visible light. Detailed spectroscopic and theoretical studies suggest that the nonplanar molecular conformation of TPE moieties leads to large free volumes, which facilitates the reversible photoisomerization of SP. The excellent reversibility and high-contrast fluorescence of solid-state photoswitches enable great applications in multimodality anticounterfeiting and optical writing and erasing fluorescent devices.

Microemulsion and reverse microemulsion exhibited important applications in many fields. Bola-surfactant as a specific type of surfactants has a certain impact on the formation and stability of the...

Organic mechanochromic materials(also known as piezochromic materials), whose color or emission changes under mechanical force, have attracted great interest owing to their potential applications in pressure sensors, rewritable materials, optical storage, and security ink. Organic mechanochromic materials with aggregation-induced emission(AIE) features have better development prospects and research value owing to their excellent optical properties. To date, mechanochromism has mostly been realized by means of mechanical grinding. Nevertheless, the magnitude of the grinding force is usually uncontrollable and its direction is anisotropic, making it awkward to study the mechanism of mechanochromic materials. On the contrary, hydrostatic pressure, whose magnitude and direction are controllable, is a more valid and governable method to investigate the mechanism of mechanochromic materials, which can help us to construct a meaningful structure-property relationship and understand the latent origin of the mechanochromism. Furthermore, it is conducive to developing other mechanochromic material systems with desired chemical and physical properties. In this review, we focus on the recent progress in the mechanism of organic mechanochromic materials with AIE features under hydrostatic pressure. Four types of mechanisms are included: intermolecular interaction change, intramolecular conformation change, transformation from locally excited state to intramolecular charge-transfer state, and intra- and inter-molecular effects induced by hydrostatic pressure, respectively.

Materials that can produce large controllable strains are widely used in shape memory devices, actuators and sensors. Great efforts have been made to improve the strain outputs of various material systems. Among them, ferroelastic transitions underpin giant reversible strains in electrically-driven ferro/piezoelectrics and thermally- or magneticallydriven shape memory alloys. However, large-strain ferroelastic switching in conventional ferroelectrics is very challenging while magnetic and thermal controls are not desirable for applications. Here, we demonstrate an unprecedentedly large shear strain up to 21.5 % in a hybrid ferroelectric, C6H5N(CH3)3CdCl3. The strain response is about two orders of magnitude higher than those of top-performing conventional ferroelectric polymers and oxides. It is achieved via inorganic bond switching and facilitated by the structural confinement of the large organic moieties, which prevents the undesired 180-degree polarization switching. Furthermore, Br substitution can effectively soften the bonds and result in giant shear piezoelectric coefficient (d35 ~ 4800 pm/V) in Br-rich end of the solid solution, C6H5N(CH3)3CdBr3xCl3(1-x). The superior electromechanical properties of the compounds promise their potential in lightweight and high energy density devices, and the strategy described here should inspire the development of next-generation piezoelectrics and electroactive materials based on hybrid ferroelectrics., 32 pages, 14 figures, 5 tables