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The change of bubbles and the position of the tuyere in an oxygen coal combustion melting and separating furnace affect the flow and splash behavior of the molten pool. To analyze this problem further, a three-dimensional numerical simulation method was used to explore the behavior and change of the flow field inside the molten pool during double-row tuyere injection. In addition, the arrangement of the tuyere was changed for a more detailed understanding of the internal phase distribution and splashing in a molten pool. The results indicated that under three-dimensional numerical simulation conditions, bubbles rise after leaving the tuyere and break on the surface of the molten pool, which results in certain fluctuations in the nearby melt. During the injection process of the tuyere, the meteorological accumulation in the middle part of the molten pool formed part of the foam slag because of the influence of surface tension. When the layout of the upper and lower exhaust tuyeres was changed from staggered to symmetrical, or when the spacing of the upper and lower exhaust tuyeres changed, it had an effect on the phase distribution and splash behavior.

The particles stimulated nucleation (PSN) triggered by coarsened T1 phase (Al2CuLi) in Al–Cu–Li alloys is investigated to analyze the formation of recrystallization texture that is unusual from typical PSN. The specimens were uniaxially compressed to a series of compression amount and the recrystallization process is characterized by electron backscattered diffraction (EBSD), scanning electron microscope (SEM) and transmission electron microscope (TEM). Results showed that the recrystallization occurred by progressive rotation of the matrix units that separated by the three-dimensional arranged T1 precipitates. The rotation of the units towards was observed in the initial grains of various orientations all through the recrystallization process. The massively formed fine grains contribute to a strong fiber texture. The fraction of recrystallization is 67% and the grains are averagely 2.5 μm in the specimen received a stain of 1.61. The PSN initiated by coarsened T1 phase fosters the feasibility to obtain textured and refined structure in Al–Cu–Li alloys which will facilitate the performance improvement of the fabricated components.

Understanding the limitations of electrocatalytic activity and developing advanced catalysts with enhanced activity are of exceptional importance for future hydrogen energy applications. Due to the complexity of electrolytic hydrogen evolution in alkaline media, there are limited non-noble metal catalysts to afford large scale applications. Tungsten-based catalysts exhibit favorable stability but relatively low activity owing to their strong H* adsorption characteristics. In this work, cobalt hydroxides/cubic phase WN nanoparticles with strengthened interfaces and adjustable nitrogen vacancies anchored on multi-walled carbon nanotubes (Co(OH)2/c-WN1−x/CNTs) are exploited as highly efficient alkaline hydrogen evolution electrocatalysts, which exhibit remarkable activity with an overpotential of 78 mV at 10 mA cm−2 and a low Tafel slope of 43 mV dec−1 in 1 M KOH media. Density-functional theory calculations revealed that the interfacial combinations of Co(OH)2/c-WN1−x were tuned to facilitate the kinetics of hydrogen evolution, where Co(OH)2 promoted the adsorption of water molecules and the H–OH dissociation, and cubic phase WN with nitrogen vacancies (c-WN1−x) accelerated hydrogen generation by optimizing the hydrogen adsorption free energy.

Ferromagnetic-dielectric nanocomposites have attracted extensive interests for its high electromagnetic wave absorption (EMA) performance due to the synergetic effects between different components. Herein, we report the design of core–shell structured Co7Fe3@TiO2 composite particles, which are subsequently annealed in H2/Ar atmosphere to further improve its EMA performance. The introducing of TiO2 dielectric shell together with hydrogen annealing contributes greatly to the electromagnetic properties due to the increased conductivity and enhanced ferromagnetic resonance. Excellent EMA performance is achieved in S (2–4 GHz) and C (4–8 GHz) bands in coatings using Co7Fe3@TiO2 as absorbents. Apart from the high EMA efficiency, the location of EMA band can be tailored in a wide range through regulating the coating thickness. Specifically, an effective absorption band of 2.0 GHz in C band at a thickness of 2.62 mm, and an effective absorption band of 1.7 GHz are achieved in S band at thicknesses of 4.0–5.0 mm. The excellent electromagnetic properties are ascribed to the effective complementary between dielectric loss and ferromagnetic loss.

Lithium sulfur (Li-S) batteries are the promising power sources, but their commercialization is significantly impeded by poor energy-storage functions at high sulfur loading. Here we report that such an issue can be effectively addressed by using a mussel-inspired binder comprised of chitosan grafted with catecholic moiety for sulfur cathodes. The resulting sulfur cathodes possess a high loading up to 12.2 mg cm−2 but also exhibit one of the best electrochemical properties among their counterparts. The excellent performances are attributed to the strong adhesion of the binder to sulfur particles, conducting agent, current collector, and polysulfide. The versatile adhesion effectively increases the sulfur loading, depresses the shuttle effect, and alleviates mechanical pulverization during cycling processes. The present investigation offers a new insight into high performance sulfur cathodes through a bio-adhesion viewpoint.

Oxygen-anion redox in lithium-rich layered oxides can boost the capacity of lithium-ion battery cathodes. However, the over-oxidation of oxygen at highly charged states aggravates irreversible structure changes and deteriorates cycle performance. Here, we investigate the mechanism of surface degradation caused by oxygen oxidation and the kinetics of surface reconstruction. Considering Li2MnO3, we show through density functional theory calculations that a high energy orbital (lO2p’) at under-coordinated surface oxygen prefers over-oxidation over bulk oxygen, and that surface oxygen release is then kinetically favored during charging. We use a simple strategy of turning under-coordinated surface oxygen into polyanionic (SO4)2−, and show that these groups stabilize the surface of Li2MnO3 by depressing gas release and side reactions with the electrolyte. Experimental validation on Li1.2Ni0.2Mn0.6O2 shows that sulfur deposition enhances stability of the cathode with 99.0% capacity remaining (194 mA h g−1) after 100 cycles at 1 C. Our work reveals a promising surface treatment to address the instability of highly charged layered cathode materials., Oxygen-anion redox in lithium-rich layered oxides can boost the capacity of lithium-ion battery cathodes. Here, the authors investigate the mechanism of surface degradation caused by oxygen oxidation and the kinetics of surface reconstruction.

Lateral hetero-junctions are considered as potential candidate for building blocks in modern electronics and optoelectronics, however, the construction of which remains a challenge. In this work, by using a laser-assisted manufacture technique, WSe2/WO3−x hetero-junction and monolayer/trilayer WSe2 homo-junction with Schottky diode like behavior are fabricated, both of which present competitive performance for photodetection and power generation in a wide range of wavelengths from ultraviolet to infrared, with maximum photoresponsivity of 10 A/W, external quantum efficiency of 14%, and power conversion efficiency of 1.3%. Combined with Kelvin probe microscopy and electrical transport measurements, it is demonstrated that the barrier-induced built-in electric field at WSe2/WO3−x interface, and the energy band discontinuities at the monolayer/trilayer WSe2 interface facilitate the separation of photo-generated electron-hole pairs. Our work provides a solid step towards the controllable construction of lateral junctions by laser-assisted manufacture for exploiting van der Waals materials-based novel electronic and optoelectronic applications.

Copper-based metal–organic frameworks (MOFs) and their derivatives have been used for CO2 electroreduction; however, they still have obvious drawbacks like poor selectivity and durability. Here, Cu...

The electrochemical conversion of CO2 into fuels and chemicals attracts worldwide attention for tackling global warming and energy crises. However, the efficiencies and selectivities for targeted products such as formate are still far from satisfactory. Herein, core–shell structured Cu2O/Cu@C immobilized on nitrogen-doped graphene sheets (Cu2O/Cu@C/NG) is prepared and used for CO2 reduction. Cu2O/Cu@C/NG yields higher activity towards formate in terms of a lower onset potential (−0.38 V versus RHE) and higher faradaic efficiency (82.1 ± 1.2%), as well as stable performance over 30 h. The enhancements in selectivity and activity are attributed to the synergistic effects between Cu sites and N doping, simultaneously improving CO2 adsorption and the interfacial charge transfer process. Additionally, N doping restrains hydrogen evolution on the copper sites, leaving more available sites for CO2 reduction. This study provides an efficient strategy to increase the activities of electrocatalysts for CO2-to-formate electroreduction.

In the present study, the microstructure and localized corrosion behavior of three Al-Zn-Mg-X alloys with Sc addition (MSc), Cu addition (MCu) and Cu + Sc addition (MCuSc) under T74 (121 °C/6 h + 163 °C/24 h) condition have been investigated. Electron backscattered diffraction and transmission electron microscope were used to analyze the microstructure of the three alloys. Pitting corrosion, intergranular corrosion, stress corrosion cracking, ASTM B117 salt spray exposure testing, and electrochemical tests, were carried out to investigate the corrosion behavior of the three alloys. Results show that the addition of Sc and/or the removal of Cu can greatly improve the localized corrosion resistance of the Al-Zn-Mg-X alloys. The pitting corrosion in the MCu and MCuSc alloys is severer than that in the MSc alloy, which is mainly attributed to the dealloying effect occurred in the Al7Cu2Fe and Al2CuMg instead of Al3(ScxZr1-x) particles. The MSc alloy shows the highest resistance to pitting corrosion, EXCO and SCC. The modified GB features and the decreased potential difference between the GB precipitates and matrix were found to be the key factors to improve corrosion resistance of Al-Zn-Mg-X alloys. This provides a theoretical and experimental basis for the design of new Al-Zn-Mg-X alloys with excellent corrosion resistance and mechanical properties.

A microbial fuel cell (MFC) is a bio-electrochemical device that convert the chemical energy to electrical energy by the oxidation of microorganisms at bioanode, while its powder generation is largely depending on the activity and durability of cathode catalysts. In this work, we report the design and synthesis of N-doped carbon nanotubes/reduced graphene oxide (rGO) nanosheet hybrids with mixed-dimensional characteristics as high-performance oxygen reduction reaction catalyst for cost-saving MFCs. Co-glycolate nanoparticles uniformly coated on rGO nanosheets are reduced to Co nanoparticles, acting as catalysts for the catalyst mediated growth of carbon nanotubes with abundant metal-nitrogen-carbon active sites. The half-wave potential of hybrid electrocatalyst are 0.859 V (vs RHE), comparable to that of benchmark Pt/C. A maximum power density of 1329 mW cm−2, 1.37 times higher than that of commercial Pt/C catalyst, is achieved in single-chamber MFCs using optimized hybrid electrocatalysts.

Developing heat-resistant conductors with high strength and high electrical conductivity is a key issue in the electrical conductor industries, as the ever-increasing power transmission poses higher requirement on the thermal stability of electrical conductor wires. Dilute Al-Sc-Zr alloys are considered as promising candidates due to the excellent heat resistance and high electrical conductivity, but the low strength always limits their application on electrical wires. Yet, few efforts on process design have been made in dilute Al-Sc-Zr alloys to enhance the strength. Here, various kinds of processing paths via combination of cold drawing, ageing and/or annealing were conducted to improve the strength and electrical conductivity of a dilute Al-Sc-Zr alloy. Results show that enhanced strength and electrical conductivity were obtained after cold drawing + ageing or pre-ageing + cold drawing + annealing treatments processes. Optimal properties (194 MPa in ultimate tensile strength and 61% IACS in electrical conductivity) were obtained through cold drawing followed by ageing. Microstructure evolution which affects strength and electrical conductivity was systematically investigated using TEM and 3DAP. The enhanced strength was mainly attributed to the suitable interactions between strain strengthening and precipitation strengthening. The enhancement in electrical conductivity was caused by precipitation of solute atoms and recovery of defects. These results provide foundations for the processing design of Al-Sc-Zr conducting wires with good properties and push forward their potential application in heat resistant conductor industries.

An isotropic hardening elastoplastic model for soil is presented, which takes into consideration the influence of structure and overconsolidation on strength and deformation of clays. Based on the superloading concept and subloading concept, the inner structural variable ω and overconsolidation variable ρ are introduced to describe the structure and overconsolidation of soil. The present model requires three additional parameters which can be obtained by conventional triaxial test, and the other parameters are same as those of modified Cam-clay (MCC) model. The performance of the proposed model is verified by undrained and drained triaxial tests.

Transition metal sulfides are promising non-noble metal catalysts for water oxidation, a vital half reaction of electrocatalytic water splitting. However, the realization of tunable electronic structure and synergetic catalysis of cobalt sulfides is still a challenge. In this work, a salt-templating route was adopted to embed uniform Co9S8 nanoparticles into high-conductive N, S co-doped carbon nanosheets (Co9S8/N,S-CNs). Benefiting from the abundant catalytic active sites and optimized electronic structure, the as-prepared Co9S8/N,S-CNs exhibited high efficiency with a low overpotential of 325 mV to afford current density of 10 mA cm−2 and low Tafel slope of 86.3 mV dec−1 towards oxygen evolution in 1 M KOH alkaline electrolyte.

The combination of mixed-dimensional semiconducting materials can provide additional freedom to construct integrated nanoscale electronic and optoelectronic devices with diverse functionalities. In this work, we report a high-performance dual-channel phototransistor based on one-dimensional (1D)/two-dimensional (2D) trigonal selenium (t-Se)/ReS2 heterostructures grown by chemical vapor deposition. The injection and separation efficiency of photogenerated electron–hole pairs can be greatly improved due to the high-quality interfacial contact between t-Se nanobelts and ReS2 films. Compared with bare ReS2 film devices, the dual-channel phototransistor based on t-Se/ReS2 heterostructure exhibits considerable enhancement with the responsivity (R) and detectivity (D*) up to 98 A·W–1 and 6 × 1010 Jones at 400 nm illumination with an intensity of 1.7 mW·cm−2, respectively. Besides, the response time can also be reduced by three times of magnitude to less than 50 ms due to the type-II band alignment at the interface. This study opens up a promising avenue for high-performance photodetectors by constructing mixed-dimensional heterostructures.

With the improving voltage grade for high-temperature superconducting (HTS) power devices, the surface flashover phenomenon in liquid nitrogen has become an important factor that makes the HTS devices break down. So, the study on surface flashover characteristics in liquid nitrogen has become more important. This paper studied the polarity effect of standard lightning impulse surface flashover under the extremely nonuniform electric field in liquid nitrogen by experiment. It is found that flashover voltages under positive impulses are generally higher than that under negative polarity, which is opposite to the results in gas gaps breakdown and on solid-SF6 gas and solid-transformer oil interface. By the analysis of flashover traces and electric field distribution between the triangle-plane electrodes, combining the related surface flashover theory in liquid nitrogen, it is assumed that surface flashover in liquid nitrogen is started from the electron emission from cathode triple junction. Because of the nonuniformity of electric field distribution, the initial voltages of the electron emission from cathode triple junction and the forces suffered on the head of flashover streamers have differed. It is the main reason that the polarity effect in liquid nitrogen is formed. The results could provide a reference for the dielectric design of HTS devices.

The addition of minor Mg (~0.4 wt%) to Al-Cu-Li alloy could not only modify the precipitation path but also promote the precipitation of T1 (Al2CuLi) phase, however, the influence of higher Mg addition on the microstructures during ageing is still not clear. In this work, the influence of high Mg addition (>0.4 wt%) on the precipitation sequence, precipitation kinetics and the corresponding strengthening of an Al-Cu-Li alloy has been investigated by atom probe tomography (APT), transmission electron microscopy (TEM), differential scanning calorimetry (DSC) and tensile testing. For an Al-Cu-Li-0.4 wt% Mg alloy in the peak-aged condition, the microstructure contains a high density of fine T1 precipitates along with some non-negligible θ' phase (Al2Cu). When adding larger amount of Mg (0.8 wt%) to the alloy, however, the precipitation of S′ phase (Al2CuMg) is strongly accelerated at the expense of T1 and θ' phases. Much more Mg clusters are observed by APT at the early ageing stages of the high Mg-containing alloy, leading to more rapid hardening response. The precipitation kinetics for T1 phase become somewhat sluggish due to decreased nucleation sites and shortage of available solutes caused by formation of more S′ precipitates. The precipitation of coarse T1 and S′ phases is significantly detrimental to the ductility and toughness in the peak-aged condition for the high Mg-containing alloy.

Rational design of high-performance electrocatalysts with low cost and large abundance is highly desirable for water splitting technology. Here we report the synthesis of Ni3S2 pyramids coated with crimped graphene (Ni3S2@G), the unique configuration of which endows Ni3S2@G with large roughness, creating much more active sites along the edges. Moreover, the coupling of graphene enhances the electrical conductivity of the nanocomposite, and thus improves the electrocatalytic activity due to synergistic effect between graphene and Ni3S2. Ni3S2@G hybrid shows outstanding performance toward both hydrogen evolution reactions (HER) and oxygen evolution reactions (OER) with low overpotentials (η10 = 103 mV for HER and η20 = 294 mV for OER) and small Tafel slope. Ni3S2@G electrode also exhibits superior full water splitting ability with a low cell voltage of 1.66 V.

The quench-induced precipitation and subsequent aging response in 2A97 aluminum alloy was investigated based on the systematic microstructure characterization. Specifically, the influence on precipitation from grain structure was examined. The results indicated the evident influence from the cooling rate of the quenching process. Precipitation of T1 and δ′ phase can hardly occur in the specimen exposed to water quenching while become noticeable in the case of air cooling. The yield strength of 2A97-T6 alloy de-graded by 234 MPa along with a comparable elongation when water quenching was replaced by air cooling. Sub-grains exhibited a much higher sensitivity to the precipitation during quenching. The presence of dislocations in sub-grains promoted the quench-induced precipitation by acting as nucleation sites and enhancing the diffusion of the solute. A quenching rate of 3 °C/s is tolerable for recrystallized grains in 2A97 Al alloy but is inadequate for sub-grains to inhibit precipitation. The study fosters the feasibility of alleviating quench-induced precipitation through cultivating the recrystallization structure in highly alloyed Al–Cu–Li alloys.

The influence of pre-stretch on the mechanical properties of 2219 Al alloys sheets were systematically investigated, with the aim of examining the age-strengthening in parts draw-formed from as-quenched sheets. The precipitation was characterized based on differential scanning calorimetry (DSC) analysis and transmission electron microscope (TEM) observation of specimens of as-quenched and quenched-stretched condition to address the influence of pre-stretching. A tensile test was performed to evaluate the effect on mechanical properties. The introduction of pre-stretching endues increased yield strength (YS) and thus can be helpful to exert the potential of the alloy. Peak YS of 387.5 and 376.8 MPa are obtained when specimens pre-stretched for 10% are aged at 150 and 170 °C, respectively, much higher than that obtained in the non-stretched specimens (319.2 MPa). The precipitation of Guinier-Preston zone (G.P. zones) and the transition to θ″ shifts to a lower temperature when pre-stretched is performed. The high density of dislocations developed during the stretching contributes to the acceleration in precipitation. Quench-stretched specimens present a much quicker age-hardening response at the beginning stage, which endue higher peaked yield strength. The yield strength, however, decrease much more quickly due to the recovery that occurs during the aging processes. The study suggested the feasibility of aging draw-formed components of 2219 Al alloy to obtain high strength.

In van der Waals (vdWs) materials and heterostructures, the interlayers are bonded by weak vdWs interactions due to the lack of dangling bonds. The vdWs gap at the homo- or heterointerface provides great freedom to enrich the tunability of electronic structures by external intercalation of foreign ions or atoms at the interface, leading to the discovery of new physics and functionalities. Herein, the recent progress on electrochemical intercalation of foreign species into atomically thin vdWs materials for structural phase transition and device applications is reviewed and future opportunities are discussed. First, several kinds of electrochemical intercalation platforms to achieve the intercalation in vdWs materials and heterostructures are introduced. Next, the in situ characterization of electrochemical intercalation dynamics by state-of-the-art techniques is summarized, including optical techniques, scanning probe techniques, and electrical transport. Moreover, particular attention is paid on the experimentally reported phase transition and multifunctional applications of intercalated devices. Finally, future applications and challenges of intercalation in vdWs materials and heterostructures are proposed, including the intrinsic intercalation mechanism of solid ion conductors, exact identification of intercalated foreign species by near-field optical techniques, and the tunability of intercalation kinetics for ultrafast switching.

The practical application of sulfur cathodes in traditional lithium–sulfur batteries has been hindered by the substantial deterioration of the sulfur electrode due to the polysulfide shuttling effect and the large volume expansion of the electrode during charge/discharge cycling. The resolving of this issue demands for a robust binder to hold the polysulfide/sulfur particles, but without causing severe disintegration of the electrode. A polar polymeric binder with high mechanical strength was designed and synthesized for use in high-performance sulfur cathodes. The complementary multiple hydrogen bonds formed in the polymeric binder significantly enhanced the adhesive strength of the binder, and buffered the dramatic volume expansion of the sulfur cathode during cycling. The strong physical and chemical interactions between the functional groups (e.g. carboxyl and tertiary amine groups) of the binder and the polysulfides effectively mitigated the shuttling effect in the Li–S batteries. As a consequence, the sulfur cathode exhibited excellent electrochemical performance at a high sulfur loading, yielding an initial discharge capacity of 627.8 mA h g−1 with sulfur loading up to 9.610 mg cm−2 at a rate of 0.2C, corresponding to an aerial capacity of 6.03 mA h cm−1. The present work opens a new avenue for constructing a high-performance Li–S battery using a simple and effective binder.

In this work, an effective method was developed to prepare novel PEO-b-PPO-b-PEO (EPE)/α-cyclodextrin (α-CD) supramolecular hydrogels containing exfoliated graphite nanoplates (xGNPs) by mi...

Atomically thin monolayer molybdenum disulfides (MoS2) with tunable electronic structure has promising applications in opto-electronic devices and sensors. In this work, unique nano-patterning and surface oxidation of monolayer MoS2 was achieved based on hydrogen peroxide (H2O2) treatment. It was found that the exfoliated monolayer MoS2 can be uniformly oxidized when exposed to low-concentration H2O2, forming an intermediate phase composed of MoSxOy. In addition, patterned triangular pits with well-defined edges can be formed under high-concentration H2O2 condition. The band gap of monolayer MoS2 could be effectively modulated by H2O2 treatment as verified by photoluminescence spectra. This work shows that simple H2O2 treatment can be an alternative approach for both surface functionalization and band gap modulation of MoS2 flake, and it also provides an alternatively simple way to obtain patterned MoS2 nanostructures without complicated standard lithography processes.

Polyimide films are widely used in space with extreme environments, where high energy beam irradiation and corresponding coupling treatment could occur. The combined effect of high energy electrons (1.2 MeV) and high tensile stress (50 MPa) on the degradation behavior of polyimide films was studied by means of scanning electron microscopy, atomic force microscopy, X-ray diffraction, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy and mechanical testing. The degradation of polyimide films was evaluated by analyzing the microstructure and mechanical properties. The results indicated that the external tensile stress and irradiation coupling treatment resulted in the breakage of a larger number of chemical bonds and greater deterioration of the surface quality when compared with the irradiated polyimide samples. After irradiation-load coupling treatment, numerous micro-cracks were formed on the polyimide surface, facilitating the diffusion of oxygen into polyimide films and thus increasing the probability of free radical reactions. Moreover, the coupling treatment led to a more significant decrease in tensile strength and elongation of polyimide films by 10% and 35%, respectively. The mechanism of molecular chains' scission and crosslinking as well as correlations between molecular chains and mechanical performances were discussed. The obtained results indicated that the external tensile stress accelerates the degradation process during electron beam irradiation; thus, the tensile stress potentially seriously deteriorates polyimide film properties in irradiated environments.

Long-life MnO-based anodes with high power density for lithium ion batteries (LIBs) is still a great challenge due to the inferior electrical conductivity and drastic volume change of MnO during the lithiation/delithiation process. Herein, to achieve high rate capacity and long cycle life simultaneously, MnO nanoparticles were encapsulated within a foam-like carbon nanosheet matrix through a confined phase transition process. By annealing polydopamine (PDA) coated porous ZnMnO3 nanosheets in a reducing atmosphere, MnO nanoparticles and surrounding in-situ formed pores could be encapsulated in the PDA-derived carbon nanosheets synchronously, forming MnO@C nanosheets with ball-in-pore structure (MnO@C-BP). The internal voids originating from Zn evaporation can not only accommodate the huge volume expansion of MnO nanoparticles, but also significantly enlarge the specific surface area, leading to an enhanced pseudocapacitive Li-storage behavior. Moreover, the as-prepared sheet-shaped MnO@C-BP with thickness of about 30 nm can provide a short path for fast Li-ion diffusion, while the continuous carbon framework promotes the charge transfer between the encapsulated MnO nanoparticles. Because of these merits, MnO@C-BP electrode exhibits superior rate performance (514 mAh g−1 at 10 A g−1, 383 mAh g−1 at 15 A g−1), outstanding cycling performance (1212 mAh g−1 after 1000 cycles at 2 A g−1, capacity retention of 127%), as well as a high reversible capacity of 1178 mAh g−1 at 0.1 A g−1.

Near-infrared (NIR) light absorbing nanomaterials, which can convert light to heat energy, have great prospects in biomedical applications. In the current work, Fe3+–TA (Tannic Acid) coordination complex formed by simple mixing of tannic acid and FeCl3 solutions was explored as a novel photothermal agent. Due to the strong absorbance in the near-infrared region induced by the coordination effect between TA molecule and Fe3+ ion, the as-prepared Fe3+–TA complex exhibited excellent photothermal performance with high photothermal conversion efficiency of 77.3% and high photothermal stability. Upon the exposure to Fe3+–TA aqueous dispersions with a concentration of 0.125 mg/mL, the cell mortality of HeLa cells was more than 85% after being irradiated for 10 min under NIR light (808 nm, 6 W cm−2). Besides, the Fe3+–TA complex exhibited ultralow cytotoxicity since only biocompatible tannic acid and iron ions were used as raw materials. Therefore, the merits of simple and convenient fabrication method, high photothermal conversion efficiency and excellent biocompatibility endow the high potential of Fe3+–TA complex as a photothermal agent for biomedical applications.

Smart miniaturized aquatic devices have many important applications, but their locomotion at different interfaces remains a challenge. Here, we report a smart miniaturized submarine moving at various air/liquid or oil/water interfaces. The microsubmarine is fabricated by a CO2-responsive superhydrophobic copper mesh and is driven by the Marangoni effect. The microsubmarine can not only transfer among different interfaces reversibly but also move horizontally at the interfaces freely. The unique locomotion of the device is attributed to a CO2-triggered switch between superhydrophobicity and underwater superoleophobicity. Moreover, the microsubmarine exhibits good stability and excellent oil repellence at the oil/water interface. Our study provides a strategy for fabricating smart aquatic devices that have potential applications in environment monitoring, water purification, channel-free microfluidics, and so on.

Transition metal dichalcogenides two-dimensional materials are of great importance for future electronic and optoelectronic applications. In this work, triangular WS2 monolayers with size up to 130 μm were prepared via chemical vapor deposition method. WS2 monolayers presented uniform Raman intensity, while quenched photoluminescence (PL) was observed in the center. The PL quenching in the central part of WS2 monolayer flakes was attributed to the gradually increasing sulfur vacancies toward the center. The proportion of negative trion (X−) in PL spectrum increases with increasing sulfur vacancies in WS2. The enhanced binding energy of X− suggests higher Fermi level and n-doping level with larger sulfur vacancy concentration. Our findings may be beneficial to the development of integrated devices, and also explore the defect-induced optical and electrical properties for nanophotonics.

Cu-based composites are considered as one of the high performance and cost-effective materials to replace the noble metal-based electrical contact materials used in low-voltage electrical apparatus. However, the oxidation resistance of Cu-based electrical contact materials at high temperatures is still the major challenge that limits their applications. In this study, CuZr/Zn2SnO4 composites were prepared through powder metallurgy method. The air arc erosion resistance of the composites under AC 380 V and 20 A was evaluated through the mass loss and the electrical contact resistance after experienced over 10,000 arc discharge cycles. The microstructure evolution, which reflected the deterioration process of the composites, was demonstrated through SEM analysis. The results indicated that the oxidation of Zr occurred along with the oxidation of Cu at high temperature, which considerably consumed the oxygen and thus significantly enhanced the oxidation resistance of Cu-based composites. In addition, TEM result showed a smooth and clear interface between Cu and Zn2SnO4 phases, suggesting that the addition of Zn2SnO4 phases was beneficial to enhance the durability of the composite. This work will not only merit the design and development of Cu-based electrical contact materials but also expand the applications of Cu-based composites in the air at high temperature.

The application of MnO as anode material for lithium-ion batteries has been largely hindered by its unsatisfied rate capacity and short cycle life. To address this problem, yolk-shell MnO@C nanodiscs were successfully prepared through a novel carbothermal reduction approach. Polydopamine coated Zn0.5Mn0.5CO3 nanodiscs were annealed at 700 °C in Ar atmosphere, during which polydopamine-derived amorphous carbon was utilized to reduce Zn2+ to Zn0, leading to the evaporation of Zn. As a result, large void space between the MnO cores and carbon shells was formed, which could effectively accommodate the volume expansion of MnO during cycling. Benefited from the improved electronic conductivity by the uniform carbon shells, as well as the enhanced structural stability ensured by large void space, the yolk-shell MnO@C nanodiscs electrode exhibited a high reversible capacity of 910 mAh g−1 at 0.1 A g−1 and delivered a specific capacity of 605 mAh g−1 (with a capacity increase of only 11%) without noticable capacity fading after 600 cycles at a current density of 1 A g−1.

Two-dimensional nanosheets and their assembles have attracted considerable attention as high-performance anode materials for Li-ion batteries because of their short transport lengths and robust structures. In this work, Fe3O4 hierarchical structures assembled by porous ultrathin nanosheets are prepared from the topochemical conversion of Fe-glycolate precursor obtained via a facile refluxing process. The flower-like hierarchical nanostructures have a size of ~ 2.5 µm constructed from ultrathin nanosheet building blocks with thickness of ca. 10 nm. When used as an anode electrode, the as-prepared Fe3O4 hierarchical nanostructures demonstrate excellent electrochemical properties with a reversible and stable capacity as high as 964.3 mAh g−1 at 500 mA g−1 after 100 cycles, and superior rate capability of 487 mAh g−1 at a high current density of 8 A g−1.

The degradation behavior of polyimide in extreme environments, especially under coupling treatment, directly determines the service life of several key components in spacecraft. In this research, the combined effect of a high energy electron beam (1.2 MeV), heavy tensile stress (50 MPa) and constant high temperature (150 °C) was taken into account to study the surface modification and degradation behavior of polyimide films. By analyzing surface morphology, microstructural evolution and mechanical behavior of polyimide films after coupling treatment, the results indicated that the coupling treatment led to severe breakage of chemical bonds and decrease of surface quality. Meanwhile, new chemical bonds of C–C, CH2–O and CN formed after coupling treatment. Additionally, a high dose of electron beam during coupling experiments contributed to the formation of an oxide layer, surface defects and even volatile gases in the outer layer of the polyimide film. This was attributed to the significant scissioning of molecular chains in polyimide films and corresponding chemical reactions between free radicals and oxygen in air. Consequently, the irradiation-load-heating coupling treatment led to a remarkable drop in viscoelastic properties and mechanical performance of polyimide films.

Integrating two-dimensional (2D) materials with ferroelectric thin films may result in unique characteristics and novel applications due to the coupling between their intrinsic characters. Here, we observed the ferroelectric resistive switching behavior in both graphene/BFO and MoS2/BFO heterojunctions, which stems from the modulation of contact barriers and depletion width at the hetero-interface induced by the ferroelectric polarization. Besides, the ferroelectric resistive switching behavior in both graphene/BFO and MoS2/BFO depends on the thicknesses of the corresponding 2D materials, because the thickness-dependent work function or conductivity of 2D materials could change the contact barrier heights and widths at the interface of 2D materials and ferroelectrics. Our results will widen the memristive applications of 2D/ferroelectrics hetero-junctions and provide a pathway for the novel memory devices based on hetero-structures with 2D/3D materials in the future.

Doping has been adopted as a versatile approach for tuning the adhesion of metal oxide/metal interfaces. Understanding the mechanism of doping at the interface adhesion on the atomic and electronic scale is crucial for the rational design and optimization of metal oxide/metal composites. In this work, we have investigated the effects of dopants on the adhesion of SnO2/Cu interfaces through first-principles calculations. Firstly, O-terminated a SnO2(110)/Cu(111) interface (denoted as I) was considered and the work of separation values of the interfaces with various dopants (Mo, Sb, Ti, Zn and Cu) were calculated to evaluate the interface adhesion strength. It was demonstrated that low-valence dopants (Zn2+ and Cu2+) enhance the adhesion strength of interface I, while high-valence dopants (Mo6+ and Sb5+) play the opposite role. Secondly, the strengthening effects of low-valence dopants were further verified in four candidate interfacial models with different atomic structures (denoted as II-V). The work of separation values indicated that the adhesion of all of the interfaces involved could be enhanced by low-valence doping. The electronic structure of the interface was demonstrated through density of states, charge density and charge density difference analyses. The results revealed that upon low-valence doping, the holes facilitate charge transfer between Cu and SnO2, which generates strong covalent bonds across the interface and thus significantly enhances the interface adhesion. This work not only provides insight into rational doping to enhance the adhesion of SnO2/Cu composites but can also be expanded upon for the design of other metal oxide/metal composites with strong interface adhesion.

CO2 electroreduction is regarded as a potential way to mitigate CO2 level and produce value-added chemicals. Although Cu-Sn bimetallic electrodes show an excellent selectivity towards targeted formate or CO, the better performance is only achieved in a narrow potential range. Herein, porous Cu6.26Sn5 electrode is prepared. Alloying Cu with Sn atoms tunes the electronic structure of catalyst, which balances the adsorption and protonation of CO2*– intermediate. The unique rice spike-like microstructure intensifies the local electric field to raise the CO2 concentration at the reaction sites. As a result, it exhibits a superior selectivity towards formate with the maximum faradaic efficiency (FEformate) of 97.8 ± 2.4 %. The better selectivity (FEformate over 80 %) is maintained over a wider potential range of 600 mV, which outperforms the majority of reported Cu-Sn bimetallic electrodes. This research provides a promising way to concurrently regulate morphological and electronic structure of alloy electrodes for efficient CO2 electroreduction.

ReS2 films are considered as a promising candidate for optoelectronic applications due to their direct band gap character and optical/electrical anisotropy. However, the direct band gap in a narrow spectrum and the low absorption of atomically thin flakes weaken the prospect for light-harvesting applications. Here, we developed an efficient approach to enhance the performance of a ReS2-based phototransistor by coupling CdSe–CdS–ZnS core–shell quantum dots. Under 589 nm laser irradiation, the responsivity of the ReS2 phototransistor decorated with quantum dots could be enhanced by more than 25 times (up to ∼654 A/W) and the rising and recovery time can be also reduced to 3.2 and 2.8 s, respectively. The excellent optoelectronic performance is originated from the coupling effect of quantum dots light absorber and cross-linker ligands 1,2-ethanedithiol. Photoexcited electron–hole pairs in quantum dots can separate and transfer efficiently due to the type-II band alignment and charge exchange process at the i...

xLi2MnO3·(1−x)LiMO2 (LLO)/spinel nanocomposites are of substantial interest as cathodes with high capacity and enhanced conductivity. However, their electrochemical properties are significantly influenced by the complex phase constitutions, and undesired by-products such as rock salt phase could not be efficiently avoided. By ex-/in-situ XRD, we revealed the three phase transitions during the decomposition reaction of spinel phase, namely, Li-rich spinel (SL) to LLO (L), normal spinel (SN) to rock salt (R) and rock salt to LLO. Density functional theory calculations suggest that Li migrates from the 8a tetrahedral site to the interstitial 16c octahedral site as oxygen is released from SL and SN, forming quasi-Li2MnO3 and quasi-rock salt crystals, respectively. The dynamic priority of each reaction determined by experiments and calculations was utilized to design the LLO/spinel composites, and a composite with more spinel phase (7.6%) demonstrated high capacity retention at high rates. Our study sheds light on the mechanism of phase transitions among the spinel-layered-rock salt system and reveal the thermodynamic and dynamic priority of each reaction, facilitating the rational design of LLO/spinel composites.

Ferromagnetic metal/alloy nanoparticles have attracted extensive interest for electromagnetic wave-absorbing applications. However, ferromagnetic nanoparticles are prone to oxidization and producing eddy currents, leading to the deterioration of electromagnetic properties. In this work, a simple and scalable liquid-phase reduction method was employed to synthesize uniform Co7Fe3 nanospheres with diameters ranging from 350 to 650 nm for high-performance microwave absorption application. Co7Fe3@SiO2 core–shell nanospheres with SiO2 shell thicknesses of 30 nm were then fabricated via a modified Stober method. When tested as microwave absorbers, bare Co7Fe3 nanospheres with a diameter of 350 nm have a maximum reflection loss (RL) of 78.4 dB and an effective absorption with RL > 10 dB from 10 to 16.7 GHz at a small thickness of 1.59 mm. Co7Fe3@SiO2 nanospheres showed a significantly enhanced microwave absorption capability for an effective absorption bandwidth and a shift toward a lower frequency, which is asc...

The surface microstructure and its evolution during long-term room-temperature storage were studied using transmission electron microscopy for an Al-Zn-Mg-Cu alloy processed by surface abrasion with grinding paper. An altered surface layer (ASL) with thickness of 0.4–0.8 μm was present on the alloy after abrasion. Ultrafine subgrains with width of about 50–120 nm and a high density of dislocations were observed in the ASL. The pre-existing aging-induced η′ and η precipitates dissolved during surface abrasion. During room-temperature aging, relatively pure Zn, Al 2 Cu and AlCu phases were observed to precipitate at the extreme surface and subgrain boundaries in the ASL. These phases are very unusual in that they are typically not formed in Al-Zn-Mg-Cu alloys. Mg was not found in these particles, as it remained dissolved in the solid solution of the ASL. Al 2 Cu and AlCu phases also precipitated at the grain boundaries in the underlying substrate right below the ASL, as far as 6 μm in depth from the extreme surface. Considerable growth and coarsening of these phases occurred during natural aging over a period of 42 months. The enhanced diffusion accelerated by vacancies, dislocations, and subgrain/grain boundaries was considered to be mainly responsible for the accelerated precipitation and growth of these atypical phases.

V2O5 nanoneedle arrays were grown directly on titanium (Ti) substrate by a facile solvothermal route followed with calcination at 350 °C for 2 h. The as-prepared V2O5 nanoneedles are about 50 nm in diameter and 800 nm in length. The electrochemical behavior of V2O5 nanoarrays as binder-free cathode for lithium-ion batteries (LIBs) was evaluated by cyclic voltammetry and galvanostatic discharge/charge tests. Compared with V2O5 powder electrode, V2O5 nanoneedle arrays electrode exhibited improved electrochemical performance in terms of high discharge capacity of 262.5 mA h g−1 between 2.0 and 4.0 V at 0.2 C, and high capacity retention up to 77.1% after 100 cycles. Under a high current rate of 2 C, a discharge capacity of about 175.6 mA h g−1 can be maintained. The enhanced performance are mainly due to the intimate contact between V2O5 nanoneedle active material and current collector, which enable shortened electron transfer pathway and improved charge transfer kinetics, demonstrating their potential applications in high rate electrochemical storage devices.

Substitutional doping of transition metal dichalcogenide two-dimensional materials has proven to be effective in tuning their intrinsic properties, such as band gap, transport characteristics, and magnetism. In this study, we realized substitutional doping of monolayer rhenium disulfide (ReS2) with Mo via chemical vapor deposition. Scanning transmission electron microscopy demonstrated that Mo atoms are successfully doped into ReS2 by substitutionally replacing Re atoms in the lattice. Electrical measurements revealed the degenerate p-type semiconductor behavior of Mo-doped ReS2 field effect transistors, in agreement with density functional theory calculations. The p–n diode device based on a doped ReS2 and ReS2 homojunction exhibited gate-tunable current rectification behaviors, and the maximum rectification ratio could reach up to 150 at Vd = −2/+2 V. The successful synthesis of p-type ReS2 in this study could largely promote its application in novel electronic and optoelectronic devices.

A novel pressure-responsive polymer composite film was developed based on Ag@Au composite nanoplates (NPLs) and polyvinylpyrrolidone (PVP) by using Au nanoparticles as concentration reference. The orientation change of Ag@Au NPLs is impelled by the deformation of polymer matrix under pressure, resulting in its localized surface plasmon resonance (LSPR) intensity change of in-plane dipolar peak. The intensity ratio between plasmon peak of Au nanoparticles and in-plane dipolar peak of Ag@Au NPLs relies on the intensity and duration of pressure. By adjusting the viscosity of the polymer, the orientation change of LSPR may respond to a wide range of stresses. This pressure sensitive film can be utilized to record the magnitude and distribution of pressure between two contacting surfaces via optical information.

Hierarchical structures assembled by two-dimensional (2D) nanosheets could inherit the characteristics of nanosheets and acquire additional advantages from the unique secondary architectures, which would have important influences on the photocatalytic properties of semiconductor nanomaterials. In this work, we successfully synthesized Ca(II) doped β-In2S3 hierarchical structures stacked by thin nanosheets by a simple solution chemical process. The effects of reaction temperature and Ca2+ concentration on the size and morphology of the products were systematically investigated. The photocatalytic applications of the β-In2S3 hierarchical structures were evaluated for hydrogen production and degradation of Rhodamine B (RhB) under visible light irradiation (λ>420nm). The β-In2S3 hierarchical structures showed promising activity towards photocatalytic hydrogen production (145.0μmolg-1h-1) and RhB solution (1×10-5M) was completely degraded within 100min under visible light irradiation.

Transition metal-based compounds are promising alternative nonprecious electrocatalysts for oxygen evolution to noble metals-based materials. Nanosheet-constructed hollow structures can efficiently promote the electrocatalystic activity, mainly because of their largely exposed active sites. Herein, hierarchical Co9S8 hollow microplates with nanosheet building units are fabricated via sulfurization and subsequent calcination of preformed Co-glycolate microplates. Benefiting from the advantages of a hollow structure, nanosheet units and high Co3+ content, Co9S8 hollow microplates exhibit remarkable catalytic property for oxygen evolution reaction (OER) with low overpotential of 278 mV to reach a current density of 10 mA cm–2, a low Tafel slope of 53 mV dec–1, and satisfied stability. This construction method of Co9S8 hierarchical hollow microplates composed of a nanosheet structure is an effective tactic for promoting OER performance of water splitting electrocatalysts.

Nickel sulfides have been widely employed as high-performance electrocatalysts for the hydrogen evolution reaction (HER) with high activity and low cost, and their performance could be tremendously promoted by elaborate design. Herein, we report a simple solvothermal route for the in situ growth of a three-dimensional network structure of Sn-doped Ni3S2, assembled by using ultrathin nanosheets on Ni foam. The ultrathin nanosheets with thicknesses of approximately 5–9 nm could provide more exposed active edges and a shorter electron transfer path. The Sn-doped sample exhibited efficient and durable electrocatalytic HER activity both in acid and alkaline conditions, much better than that of undoped Ni3S2 nanorods. Nyquist plots indicated that the electrochemical impendence reduced with the introduction of elemental Sn, which was another critical factor for the enhanced catalytic performance.

Cobalt microspheres with diameters of 1.5–3.5 µm were synthesized by a liquid phase reduction method. The effects of hydrogen annealing on microstructure evolution and electromagnetic properties of Co microspheres were investigated. The influence of filling ratio on the electromagnetic properties of specimens containing Co microspheres as fillers was also examined. The results indicated that the annealing leads to increase in Co microspheres' permittivity as the improved conductivity that developed during annealing contributes to enhanced dielectric relaxation. High filling ratio is found to be favorable for achieving high electromagnetic properties and thus higher electromagnetic absorbing performances, which is of technical significant for application in low frequency band. Coatings containing 30, 45 and 50 vol% Co particles as fillers present excellent EMA performance, even very thin thickness is applied. High electromagnetic wave absorbing efficiency of −10 dB was observed at thickness of 1.5 mm in C band and the electromagnetic wave absorption bandwidth reaches up to 6.3 GHz (6.7–13 GHz) when the filling volume is 45 vol%.

The development of highly efficient water oxidation electrocatalysts made of low-cost and earth-abundant elements is a prerequisite. Sluggish kinetics in the reaction of water splitting is the major obstacle. Herein, we report the fabrication of a robust catalyst for the oxygen evolution reaction (OER) based on the hybrid of N-doped graphene coupled metallic NiSe2 pyramids (NG/NiSe2/NF). The reaction kinetics has greatly increased due to the synergistic effects of the two components providing enhanced electroconductibility and increased active sites. The NG/NiSe2/NF electrode exhibits superior water oxidation ability and cycle stability. This approach opens ways to design effective oxygen evolution electrodes.

Li2MnSiO4 is a promising high capacity cathode material due to the potential to extract two Li ions per formula unit. In practice, however, the use of Li2MnSiO4 is restricted by a low discharge capacity, which has been attributed to an irreversible structural change in the first charge cycle. In this work, we use density functional theory calculations to explore the details of this structural change, and our results reveal that the structural change during delithiation has two components. First, we find that the material undergoes a structural collapse upon partial delithiation, which is characterized by distortion of the MnO4 tetrahedron. Remarkably, while this transformation results in a disordered structure, our calculations show that it is reversible upon relithiation and that the transformation does not strongly impede Li de/intercalation. The calculated reversibility of the phase change is consistent with recent experimental X-ray diffraction measurements showing that peaks associated with the crystalline MnO4 order, which disappear upon delithiation, are restored upon lithiation. Additional experiments are conducted showing the reversibility of the material during cycling as a function of charging cutoff voltages. Second, we argue that, the irreversible structural degradation is primarily caused by oxygen evolution in the highly delithiated state; the oxygen deficient structure can only reincorporate half of the total Li when discharged to 1.5 V. Experimentally observed voltage profile shifts of Li2MnSiO4 during the first few cycles as well as the different electrochemical behavior exhibited by Li2FeSiO4 can be explained by this two-component structural change model.

Rhenium disulfide (ReS2) has attracted scientists' attention for its unique physical properties and potential applications in high-efficiency photodetector devices. Although lots of works have been done to obtain high-quality ReS2 nanoflakes, in-plane uniform growth is still challenging due to its unique decoupling property between layers. In this work, we successfully realized the epitaxial growth of continuous monolayer ReS2 films on mica substrate by chemical vapour deposition (CVD). By prolonging the growth time, continuous multilayer ReS2 films can also be obtained. The growth mechanism of ReS2 films is proposed based on Stranski–Krastanov theory. Filed effect transistors (FETs) based on multilayer ReS2 films exhibit typical n-type semiconducting behaviour with a carrier density of 0.27 cm2 V−1 s−1 and ON/OFF ratio of about 4 × 103. The photoresponsivity of the phototransistor could reach up to 0.98 A W−1 with a light intensity of 0.56 mW cm−2, suggesting that ReS2 is a promising material for electronic and optoelectronic applications.