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Although great progress has been made in the field of electrochemical CO2 reduction reaction (eCO2RR), inducing product selectivity is still difficult. We herein report that a thiocyanate ion (SCN-) switched the product selectivity of copper catalysts for eCO2RR in an H-cell. A cuprous thiocyanate-derived Cu catalyst was found to exhibit excellent HCOOH selectivity (faradaic efficiency = 70-88%) over a wide potential range (-0.66 to -0.95 V vs RHE). Furthermore, it was revealed that the formation of CO and C2H4 over commercial copper electrodes could be dramatically suppressed with the presence of SCN-, switching to HCOOH. Density functional theory calculations disclosed that SCN- made the formation of HCOO* easier than COOH* on Cu (211), facilitating the HCOOH generation. Our results provide a new insight into eCO2RR and will be helpful in the development of cheap electrocatalysts for specific utilization.

The grain-size-dependent microstructure evolution and overall mechanical behavior of polycrystalline NiTi thin films have not been widely studied under thermomechanical loading. We propose a non-isothermal phase field model with an additional grain boundary energy term introduced into the local energy density to take into account the contribution from the grain boundary in the polycrystalline system. We investigate the grain-size effects in the process of temperature-induced martensitic transformation, detwinning and reorientation of martensitic variants, and superelastic deformation. This multi-variant two-dimensional phase field study showed that, as the average grain size of the thin film drops from 1.5 μm to 10 nm, the temperature-induced martensitic transformation tends to be inhibited. The polytwinned martensitic microstructure tends to be replaced by single-variant martensite microstructure in the grains. The martensitic transformation will not even take place once the grain size is around 10 nm. Meanwhile, the stress-induced martensitic detwinning and reorientation are less active for all types of martensite variants. The shape memory functionality may be weakened with decreasing grain size. Regarding the superelastic behavior, the stress-induced martensitic transformation is delayed with decreasing average grain size. The stress plateau tends to be higher and less noticeable as the grain size drops. The underlying mechanism of this grain-size effect is associated with the inhibiting effect of the grain boundary, the fraction of which will noticeably increase as the average grain size drops, and thus the phase transformation area will significantly reduce in the polycrystalline thin film.

Electrostatic spraying (ES) can improve the machining and environmental effects of minimum quantity lubrication (MQL). Compared with ES, composite electrostatic spraying (CES) presents better resul...

Well-crystallized perovskite ferroelectric films usually display a bulk-like polarization response (P) under an external electric field (E), i.e., a large P-E hysteresis loop featuring a sizable remnant polarization and an early polarization saturation. Such characteristics are undesirable for capacitive energy storage applications. In this work, we demonstrate an optimal P-E behavior, i.e., a small remnant polarization and a delayed polarization saturation, in perovskite BaTiO3 films consisting of superfine columnar nanograins. In a low-temperature, nucleation-dominated sputtering deposition, an in-situ grown conductive buffer layer promotes the formation of these nanograins, which display a controllable diameter down to ~10 nm and extend throughout the film thickness. The deterioration of the remnant polarization and its delayed saturation under an electric field, can be attributed to a strong polarization-constraining effect from the densely-packed, non-ferroelectric grain boundaries, which is supported by a phase field modeling simulation. The resulted BaTiO3 film capacitors integrated on Si at 350°C display a high recyclable energy density (Wrec~135±10 J/cm3) and efficiency (η~80%±4%) which are thickness-scalable. An intrinsically high power density, a simple and stable chemical composition, and good thermal (-150°C ~ 170°C) and cycling stabilities (up to ~ 2 × 108 charge-discharge cycles) warrant a broad range of applications for these film capacitors.

Composite electrostatic spraying (CES) is a process in which the coaxial jet generates when the inner and outer fluids flowing through the coaxial nozzle are charged, and jet end is broken into charged composite droplets. This paper experimentally investigated the effects of types of inner and outer fluids, voltages, and flow rates of inner and outer fluids on cutting force and cutting temperature in CES milling of aluminum alloy. The inner fluid used included water and multi-walled carbon nanotubes (MWCNTs)-water nanofluid. The outer fluid used involved castor oil, sunflower oil, MWCNTs-castor oil nanofluid, and MWCNTs-sunflower oil nanofluid. The atomization mode, current, and droplet velocity of CES were measured under different types of inner and outer fluids, voltages, and flow rates of inner and outer fluids. Results show that from the viewpoint of reducing cutting force and temperature, MWCNTs-sunflower oil nanofluid/MWCNTs-water nanofluid and 5 ml/h were the optimal outer/inner fluid combination and flow rate due to excellent charging performance, high droplet velocity, and superior friction-reducing effects of sunflower oil and MWCNTs.

This study proposed a potentiometric non-enzymatic electrochemical sensor for glucose detection based on copper doped zinc oxide (CZO) as a sensing film. In this article, a metal oxide film was used, which was able to react catalytically with glucose. The wires of the sensor were prepared by screen printing technology, and the CZO thin film was deposited on the sensor by the radio frequency (R. F.) sputtering system. In order to make the non-enzymatic sensor more stable, Nafion layer was added to the working electrodes. The characteristics of the sensor were measured using a voltage time (V-T) measurement system. Average sensitivity and linearity of the Nafion/CZO glucose sensor was tested in glucose concentrations ranging from 2 mM - 14 mM. After experiment, it was confirmed that the sensor had good performance. Experiments confirmed that the Nafion/CZO sensor exhibited characteristics including: good selectivity for glucose, average sensitivity of 6.45 mV/mM, a linearity of 0.998, a response time of 20 sec, and a limit of detection (LOD) of 0.51 mM. The device has a low relative standard deviation (RSD) and would be suitable for further development and eventual use in biomedical applications.

A T-joint with two welds in the same welding direction was successfully connected for an α titanium alloy using friction stir welding (FSW). The texture and joint properties under different stress ...

The dependence of interfacial contact resistance (ICR) on contact materials between cathode and interconnect is systematically studied under both isothermal oxidation and thermal cycling conditions. Three kinds of cathode current-collecting layer (CCCL) are used, (La,Sr) (Co,Fe)O3 (LSCF), LSCF+10%Ag, and Ag, and tested in a SUS430/CCCL/SUS430 sandwich structure to simulate the actual operation of the solid oxide fuel cells (SOFCs). Experimental results show that the ICR of LSCF+10%Ag exhibits the smallest value, in comparison with the specimens with LSCF and Ag paste, as well as the sample without a CCCL. For LSCF+10%Ag contact, the ICR increases from 0.0069 mΩ cm2 to 3.74 mΩ cm2 under an isothermal condition for 150 h, then increases from 3.74 mΩ cm2 to 10.79 mΩ cm2 after 15 thermal cycles. This work provides information for the understanding of possible mechanisms of performance degradation of SOFCs.

A Polycrystalline sample of Pb2NiOsO6 was synthesized by high-pressure (6 GPa) and high-temperature (1575 K) conditions. Pb2NiOsO6 crystallizes in a monoclinic double perovskite structure with a centrosymmetric space group P21/n at room temperature. Pb2NiOsO6 is metallic down to 2 K and shows a single antiferromagnetic (AFM) transition at TN = 58 K. Pb2NiOsO6 is a new example of a metallic and antiferromagnetic oxide with three-dimensional connectivity. Neutron powder diffraction and first-principle calculation studies indicate that both Ni and Os moments are ordered below TN and the antiferromagnetic magnetic order breaks inversion symmetry. This loss of inversion symmetry driven by antiferromagnetic order is unusual in metallic systems and the 3d-5d double-perovskite oxides represent a new class of noncentrosymmetric AFM metallic oxides.

In this work, we, for the first time, observed the remarkable thermoelectric properties of a few high-quality PtSe2 layered films fabricated by a post selenization of Pt thin films. An excellent po...

The size of graphene nanofillers and the ambient temperature are two important factors for the effective thermal conductivity of graphene nanocomposites. However, these two issues together are seldom considered in theoretical evaluation of the overall thermal property. By introducing the size-dependent thermal transport mechanisms (quasi-ballistic heat flow and diffusive heat transport) to the Landauer-like theory, we established a new method to calculate the in-plane size and temperature dependence of the thermal conductivity of graphene nanofillers from the nanoscale perspective, which is crucial for the overall thermal conductivity of the nanocomposites. The validity of this approach was confirmed by nonequilibrium molecular dynamics simulation. Then the filler-size- and temperature-dependent thermal conductivity of graphene nanocomposites was calculated via an effective-medium approximation based on Maxwell’s far-field matching at a microscopic level. We highlight this multiscale approach with its implementation in the estimation of the overall thermal conductivity of graphene-polymer nanocomposites. The results are shown to be in close agreement with the experimental observations over the average filler size from 200 to 1000 nm and over the temperature from 300 to 360 K, respectively. This study revealed the significant effects of the graphene-filler size and the ambient temperature on the thermal conductivity of the nanocomposites.

Solid-state lithium metal batteries (SSLBs) contain various kinds of interfaces, among which the solid electrode|solid electrolyte (ED|SE) interface plays a decisive role in the battery’s power density and cycling stability. However, it is still lack of comprehensive knowledge and understanding about various interfacial physical/chemical processes so far. Although tremendous efforts have been dedicated to investigate the origin of large interfacial resistance and sluggish charge (electron/ion) transfer process, many scientific and technological challenges still remain to be clarified. In this review, we detach and discuss the critical individual challenge, including charge transfer process, chemical and electrochemical instability, space charge layers, physical contact and mechanical instability. The fundamental concepts, individual effects on the charge transfer and potential solutions are summarized based on material’s thermodynamics, electrode kinetics and mechanical effects. It is anticipated that future research should focus on quantitative analysis, modeling analysis and in-situ microstructure characterizations in order to obtain an efficient manipulation about the complex interfacial behaviors in all solid-state Li batteries.

In this study, the characteristics and stability of the nickel oxide (NiO) based uric acid biosensors modified with graphene and magnetic beads (MBs) were investigated. The sensitivity and linearity of the different membranes were compared by using the voltage-time (V-T) measurement system. Then, the electrochemical impedance spectroscopy (EIS) was used to prove that adding the modification could reduce the impedance of the thin films and improve the electron transfer feature. Furthermore, we successfully fabricated the MBs-uricase/rGO/NiO films as a sensing membrane for the NiO based biosensor, which was suitable for measuring the uric acid in this study. Thus, the NiO based uric acid biosensor showed the relatively higher average sensitivity and linearity of 38.279 mV/(mg/dL) and 0.966, respectively. Finally, in terms of stability, an investigated into both the interference effect and lifetime of the uric acid biosensor was conducted, and the satisfying stability in this regard was also shown.

Magnetoelectric effect is one of the most important features in multiferroic composites which is absent in either ferromagnetic or ferroelectric composites. In this paper, a two-level micromechanics model is developed to study the nonlinear magnetoelectric (ME) effects of multiferroic composites consisting both ferromagnetic (or magneto-strictive) and ferroelectric (or piezoelectric) materials. At the first level, the model involves a thermodynamically based evolution of the product domain from the parent one in ferromagnetic phase which provides the nonlinear response of the system under the external loading. And at the second level, it treats the ferromagnetic and ferroelectric as a two-phase composite, and Eshelby based micromechanics is applied to obtain the overall effective properties of the composite. Then the two-level model is used to study the nonlinear magnetoelectric effects of Terfenol-D/PZT/Terfenol-D laminated system under the applied magnetic field first, and then under the combined mechanical and magnetic field in different directions. To verify the model, the theoretical calculations have been compared with the existing experimental data for both single phase Terfenol-D at the first level and the two-phase Terfenol-D/PZT/Terfenol-D multiferroic composite at the second level. The comparisons between the theory and experiment are in a good agreement.

In this study, coffee gunny which is made of jute fiber (Jf) hybrid woven cloth was used to reinforce polypropylene (PP). Maleic anhydride grafted polypropylene (MAPP) was added as a compatibilizer. Moreover, Jf was chemically treated by various methods to enhance the compatibility between fiber and the PP matrix. The results of Fourier transform infrared spectroscopy (FTIR), Polarized optical microscopy (POM), and Differential scanning calorimetry (DSC) showed that Jf is composed of jute yarn, PE fiber, and PP/PE hybrid fiber. Scanning electron microscopy (SEM) analysis showed that the compatibility between Jf and PP was improved by the chemical treatment of Jf. The results of tensile and impact tests showed that PP composite containing MAPP and the Jf after alkaline treatment (PP/MAPP/BJf) exhibited the best tensile and impact strengths. Its increments of tensile and impact strengths were 25% and 29% as compared to the untreated Jf-containing composite (PP/Jf). Apart from enhancing the mechanical properties of PP, the incorporation of coffee gunny can reduce the production cost of materials while meeting the demands of environmental protection agencies.

The effects of rotation speed and plunge depth on macro/microstructures and mechanical properties of dissimilar 2195/2219 aluminum alloy joints produced by refill friction stir spot welding (RFSSW) were investigated. The results show that some shallow annular grooves present on the joint surfaces depending on the process parameters. Besides, hook defects are in the form of downward bending due to the higher strength of 2195 aluminum alloy. The change of rotating speed has no apparent influence on hook defect, while the increase of plunge depth makes the height of the hook defect increase significantly. The higher tensile-shear strength is associated with increased rotation speed. However, as the plunge depth increases, the tensile-shear strength rises first and then decreases. The highest tensile-shear strength measured is 6480 N, for a rotation speed of 1600 rpm, and plunge depth of 2.5 mm. Besides, there are two kinds of fracture modes present: the plug fracture and the shear-plug fracture.

In this work, the flexible arrayed urea biosensor is composed of silver paste electrodes by screen printing technology. The sensing film is made of the nickel oxide (NiO) by radio frequency (R.F.) sputtering system and then modified by Au nanoparticles (Au NPs) and graphene oxide (GO). The average sensitivity, response time, interference effect, and electrochemical impedance of urea biosensors are analyzed by the voltage–time ( ${V}$ – ${T}$ ) measurement system and electrochemical impedance spectroscopy (EIS). The surface morphology of the biosensor is analyzed by scanning electron microscope (SEM). The results show that the flexible arrayed urea biosensor has excellent average sensitivity over a wide concentration range (0.01–100 mM) of 57.16 mV/decade, linearity of 0.998, a response time of 25 s, a limit of detection (LOD) of $7.64~\mu \text{M}$ , and an excellent selectivity.

Electrostatic spraying is a new generation of green and efficient cooling/lubrication technique in machining. Critical heat flux reflects the heat transfer potential of electrostatic spraying. In this paper, an evaluation device for cooling capacity of electrostatic spraying is developed to study the effects of voltage, target distance, flow rate of nanofluids, and volume fraction of nanoparticles on critical heat flux by transient heat transfer tests. The electrostatic field between the nozzle and the heat transfer surface is simulated to analyze the heat transfer mechanism. The results show that the critical heat flux is greatly affected by the thermophysical properties of nanofluids, the electric field strength, and the deposition of nanoparticles on the heat transfer surface. Under the cone-jet mode, increasing voltage, flow rate of nanofluids, and volume fraction of nanoparticles and reducing target distance can considerably increase critical heat flux. The maximum critical heat flux can be obtained when the voltage, target distance, flow rate of nanofluids, and volume fraction of nanoparticles are taken as − 8.4 kV, 15 mm, 0.63 ml/min, and 0.15%, respectively.

In this work, we used radio frequency (RF) system and screen printing technology to fabricate urea biosensor based on urease-maghemite nanoparticles ( $\gamma $ -Fe2O3 NPs)/graphene oxide (GO)/nickel oxide (NiO) sensing membrane on silver conductive wire printed polyethylene terephthalate (PET) substrate. The ${V}$ – ${T}$ measurement system was used to investigate the sensing characteristics of urea biosensors based on GO/NiO sensing membrane modified by $\gamma $ -Fe2O3 NPs. The sensing membrane was modified by adding different contents of $\gamma $ -Fe2O3 NPs. The concentration of $\gamma $ -Fe2O3 NPs was 1 mg/mL. When the volume ratio of urease/ $\gamma $ -Fe2O3 NPs was 1/1, it had the best sensitivity. The average sensitivity, the linearity, and the limit of detection of (LOD) of the best urea biosensor in this work were 52.36 mV/decade ± 0.22 mV/decade, 0.996, and $7.91~{\mu }\text{M}$ , respectively. The effect of temperature on the urea biosensor was investigated from 25 °C to 65 °C. The stability of urea biosensors was evaluated by the effect of hysteresis and long-term storage stability. After 29 days, the average sensitivity remained 80.62% of the initial value. Compared with other urea biosensors, our urea biosensor based on urease- $\gamma $ -Fe2O3 NPs/GO/NiO sensing membrane has better average sensitivity.

An improved tool was designed to enhance weld formation for adjustable-gap bobbin-tool friction stir welding. No macro defects are observed as the welding speed increases from 120 to 240 mm/min. Microstructure analysis shows the maximum density of geometrically-necessary dislocations reaches 2.52 × 10 13 m - 2 presenting at the stir zone (SZ). The Guinier-Preston-Bagaryatsky zones in heat affected zone (HAZ) and SZ are partially dissolved, and the relative volume fraction of S and θ phases in SZ is larger than that in HAZ. The hardness of the joints exhibits a W-shaped distribution. The minimum hardness is obtained at the HAZ. As the welding speed increases, the tensile strength initially increases up to 400 MPa at 180 mm/min, and then decreases. Poor mechanical properties at 60 mm/min and 300 mm/min are related to void defect.

Scripta materialia 186, 268 - 271 (2020). doi:10.1016/j.scriptamat.2020.05.002, We reveal a slow-to-fast dynamics transition in the as-cast Cu$_{46}$Zr$_{46}$Al$_8$ (at.%) metallic glass (MG) at a temperature below the glass transition upon heating, which depends on the competition between free volume annihilation and thermally-activated atomic mobility, well consistent with the bond-length change of Cu-Cu pairs. The activation of $��$-relaxation at high temperatures could be related to the bond-length extension of Cu-Cu and Zr-Zr like-atom pairs together with the shortening of Cu-Zr unlike-atom pairs. Our results provide new insights into the correlation of dynamics with atomic structure in MGs and will be helpful to the understanding of ageing behaviors in MGs., Published by Elsevier Science, Amsterdam [u.a.]

Different thermal responses of local atomic packing structures in a Pd43Cu27Ni10P20 alloy from glass to liquid have been studied by in situ high-energy X-ray diffraction together with ab initio mol...

Compared with minimum quantity lubrication, electrostatic spraying can greatly improve machining and environmental performances. However, the cooling and lubricating performance of electrostatic spraying needs to be further improved. In this paper, the composite electrostatic spray cutting approach is proposed, and the environment-friendly machining of titanium alloy by using this approach is investigated. An atomization test device for composite electrostatic spray cutting and a composite electrostatic spray milling system are developed. The atomization tests for composite electrostatic spray cutting are performed to study its atomization morphology and to determine the atomization parameters that guarantee a stable composite electrostatic spraying. The atomization current is measured by using a picoammeter under stable composite electrostatic spraying conditions, and the charging performance and atomizing stability of composite electrostatic spraying are evaluated. Milling experiments of titanium alloy and ambient oil mist concentration tests are also carried out under electrostatic and composite electrostatic spraying conditions. The effects of composite electrostatic spraying on milling force, tool wear, chip morphology, and oil mist concentration are analyzed. Results show that compared with electrostatic spraying, composite electrostatic spraying can effectively reduce tool wear and oil mist concentration. Under composite electrostatic spraying condition, an increase in the flow rates of internal and external fluids can further reduce tool wear. An increase in the flow rate of internal fluid does not affect ambient oil mist concentration. But an increase in the flow rate of external fluid significantly increases ambient oil mist concentration.

Transition metal dichalcogenides (TMDCs) have recently attracted a tremendous amount of attention owing to their superior optical and electrical properties as well as the interesting and various na...

An eye-safe white-lighting source configured with violet laser diode (VLD) and an ultrafast color convertor using the BEHP-PPV + MEH-PPV polymer blend is demonstrated for optical wireless communica...

In this study, the Ti-4Al-0.005B (TA5, Chinese brand) titanium alloy was used in a specially designed T-joint joined by friction stir welding, where two plates served as the skins and one plate served as the stringer with two separate welds. The base material (BM) has a typical rolling microstructure, consisting of α grains deformed along the rolling direction. The grains in the heat-affected zone (HAZ) are coarser than those in the BM, while the grains in the thermo-mechanically affected zone are deformed along the shear direction. When the temperature is higher than the β transus in the welding process, there are lamellar α phase structures in the stir zone (SZ). When the temperature is lower than the β transus in the welding process, there are fine equiaxed grains in the SZ due to sufficient dynamic recrystallization, while the grains in the first weld are slightly larger than those in the second weld due to their longer exposure to the thermal cycle of the second weld. The microhardness of the first weld decreases following the second weld, and the area of lowest microhardness occurs in the HAZ on the advancing side near the first weld. The microhardness of SZ at the position of 0.5 mm from the upper surface is slightly higher in the thickness direction. In the tensile tests, the initial position of the fracture occurs in the area where the skin and the stringer are joined by FSW. With the increase of tool rotation speed from 450 rpm to 850 rpm, the tensile strength increases first and then decreases along the direction of skin and stringer. In addition, a coupled Eulerian-Lagrangian (CEL) numerical model is developed to investigate the temperature distribution and material flow during FSW, showing stronger correlation with the experiments.

A Cu-1.5 wt.%Ti/Diamond (55 vol.%) composite was fabricated by hot forging from powder mixture of copper, titanium and diamond powders at 1050 °C. A nano-thick TiC interfacial layer was formed between the diamond particle and copper matrix during forging, and it has an orientation relationship of (111)TiC//(002)Cu&[1 1 ¯ 0]TiC//[1 1 ¯ 0]Cu with the copper matrix. HRTEM analysis suggests that TiC is semi-coherently bond with copper matrix, which helps reduce phonon scattering at the TiC/Cu interface and facilitates the heat transfer, further leading to the hot-forged copper/diamond composite (referred as to Cu-Ti/Dia-0) has a thermal conductivity of 410 W/mK, and this is about 74 % of theoretical thermal conductivity of hot-forged copper/composite (552 W/mK). However, the formation of thin amorphous carbon layer in diamond particle (next to the interfacial TiC layer) and deformed structure in the copper matrix have adverse effect on the thermal conductivity of Cu-Ti/Dia-0 composite. 800 °C-annealing eliminates the discrepancy in TiC interface morphology between the diamond-{100} and -{111} facets of Cu-Ti/Dia-0 composite, but causes TiC particles coarsening and agglomerating for the Cu-Ti/Dia-2 composite and interfacial layer cracking and spallation for the Cu-Ti/Dia-1 composite. In addition, a large amount of graphite was formed by titanium-induced diamond graphitization in the Cu-Ti/Dia-2 composite. All these factors deteriorate the heat transfer behavior for the annealed Cu-Ti/Dia composites. Appropriate heat treatment needs to be continually investigated to improve the thermal conductivity of hot-forged Cu-Ti/Dia composite by eliminating deformed structure in the copper matrix with limit/without impacts on the formed TiC interfacial layer.

PurposeThe coefficient of thermal expansion (CTE) and modulus of elasticity (ME) values of mortar and stone from room temperature to cryogenic temperatures provide an experimental basis for the design of liquefied natural gas (LNG) storage tanks.Design/methodology/approachThe CTE and ME of mortar and limestone were measured by resistance strain gauge testing technology at cryogenic temperatures.FindingsThe test results showed that CTE values of mortar and stone decreased with the decrease of temperature and CTE values of mortar was greater than that of stone from 0 °C to −165 °C. The ME values of mortar increased significantly at cryogenic temperatures, and less change in stone.Originality/valueThe material at cryogenic temperatures may continue to work in the elastic phase due to the continuous increase of elastic modulus. Therefore, the study of material in the elastic stage may be more important than in the ultimate bearing capacity stage, and it is necessary to carry out further study surrounding the deformation properties of materials at cryogenic temperatures. The CTE and ME values of mortar and stone from room temperature to cryogenic temperatures provide an experimental basis for the design of LNG storage tanks.

Structural, electronic and optical properties of Nb and F co-doped SnO2 were mainly investigated using density functional theory (DFT). Hybrid density functional theory was employed to obtain band structure, density of states (DOS) and optical properties. The calculated lattice parameters of pure SnO2 by PBEsol functional (a = 4.774 A and c = 3.218 A) are in good agreement with experimental date (a = 4.742 A and c = 3.206 A). When co-doping with Nb&F, the length of octahedron (4.136 A) closely matches with pure SnO2 (4.112 A) in direction of perpendicular to the c-axis. The direct band gaps of 3.80 eV, 3.38 eV 3.63 eV, 3.23 eV, 3.06 eV have been obtained for pure, F, Nb, Nb&F and Nb&2F doped SnO2 respectively, and the dispersed conduction band after doping does not significantly affect the electron effective mass of the conduction band minimum (CBM). A study of band alignment shows the clearly increasing valence band maximum (VBM) and the slightly decreasing CBM occur after doping. Analyses of the charge density difference and Bader charge suggest that Sn–O bond shows covalent characteristic, but the degree of ionization decreases in following order: Nb > Nb&F > Nb&2F > SnO2 > F. In terms of optical properties after doping, the optical absorption side slightly red or blue shift, and the reflectivity in the visible spectrum is greatly low.

In this work, we demonstrated nano-scaled Laue diffractions by a focused polychromatic synchrotron radiation beam to discover what happens in MoS2 when van der Waals epitaxy is locally invalid. A stronger exciton recombination with a local charge depletion in the density of 1 × 1013 cm-2, extrapolated by Raman scattering and photoluminescence, occurs in grains, which exhibits a preferred orientation of 30° rotation with respect to the c-plane of a sapphire substrate. Else, the charge doping and trion recombination dominate instead. In addition to the breakthrough in extrapolating mesoscopic crystallographic characteristics, this work opens the feasibility to manipulate charge density by the selection of the substrate-induced disturbances without external treatment and doping. Practically, the 30° rotated orientation in bilayer MoS2 films is promoted on inclined facets in the patterned sapphire substrate, which exhibits a periodic array of charge depletion of about 1.65 × 1013 cm-2. The built-in manipulation of carrier concentrations could be a potential candidate to lateral and large-area electronics based on 2D materials.

Aluminum-sulfur batteries (ASBs) have attracted substantial interest due to their high theoretical specific energy density, low cost, and environmental friendliness, while the traditional sulfur cathode and ionic liquid have very fast capacity decay, limiting cycling performance because of the sluggishly electrochemical reaction and side reactions with the electrolyte. Herein, we demonstrate, for the first time, excellent rechargeable aluminum-selenium batteries (ASeBs) using a new deep eutectic solvent, thiourea-AlCl3, as an electrolyte and Se nanowires grown directly on a flexible carbon cloth substrate (Se NWs@CC) by a low-temperature selenization process as a cathode. Selenium (Se) is a chemical analogue of sulfur with higher electronic conductivity and lower ionization potential that can improve the battery kinetics on the sluggishly electrochemical reaction and the reduction of the polarization where the thiourea-AlCl3 electrolyte can stabilize the side reaction during the reversible conversion reaction of Al-Se alloying processes during the charge-discharge process, yielding a high specific capacity of 260 mAh g-1 at 50 mA g-1 and a long cycling life of 100 times with a high Coulombic efficiency of nearly 93% at 100 mA g-1. The working mechanism based on the reversible conversion reaction of the Al-Se alloying processes, confirmed by the ex situ Raman, XRD, and XPS measurements, was proposed. This work provides new insights into the development of rechargeable aluminum-chalcogenide (S, Se, and Te) batteries.

For electrically conductive adhesives (ECAs), high electrical conductivity generally conflicts with excellent mechanical properties because electrical conductivity increases while desirable mechanical properties decrease with the increase in loading of conductive fillers or removal of lubricants on the silver filler surface. In this work, a method was developed to improve both the electrical conductivity and mechanical properties of the ECAs by introducing double bonds. Itaconic acid (IA) was used to replace the lubricant on the silver flake (Ag-F) surface, and acrylic acid (AA) was used as part of the ECA resin matrix. IA can replace the lubricant on the Ag-F surface, similar to other short-chain dibasic acids, to improve the ECA electrical conductivity. Furthermore, IA can be polymerized with AA to form covalent bonds between the silver flakes and the resin matrix, enhancing the mechanical properties of ECA. Compared with ECA filled with commercial silver flakes, the electrical conductivity of ECA filled with IA-treated silver flakes increased by ~ 21%, and the lap shear strength increased by ~ 29%.

Efficient Fe/N/C electrocatalysts for oxygen reduction reaction (ORR) have been prepared from a nonporous 8-fold interpenetrated metal–organic framework (Fe–Zn-TTPA) bearing dense Zn(II)–carboxylat...

Temperature and the alignment state of nanofillers are two important factors that can greatly affect the thermal conductivity of graphene nanocomposites, but the simultaneous influence of these two issues have never been considered in any theoretical treatment. In this work we incorporate the contributions of electron-phonon coupling and phonon-phonon interaction into the diffuse mismatch model to establish the temperature dependence of filler-matrix interfacial thermal resistance and filler-filler contact resistance, both crucial for thermal conduction in graphene nanocomposites. The electron and phonon transport mechanisms, suitable for metal and nonmetal matrices respectively, are both taken into account. Then through an effective-medium approximation based on Maxwell's far-field matching, the temperature-dependent thermal conductivity of both metal and nonmetal-based graphene nanocomposites is derived. By further introducing a confinement angle with respect to the main alignment direction wherein the graphene nanofillers are supposed to be dispersed, the influence of the alignment state of graphene nanofillers is also investigated. We highlight this newly developed theory with direct comparisons to several sets of experimental data, and demonstrate the significant effects of temperature level and alignment state in thermal conductivity of graphene metal and nonmetal nanocomposites.

Three-dimensional (3D) CuO/TiO2 hybrid heterostructure nanorod arrays (NRs) with noble-metal-free composition, fabricated by template-assisted low-cost processes, were used as the photo-Fenton-like catalyst for dye degradation. Here, CuO NRs were deposited into anodic aluminum oxide templates by electrodeposition method annealed at various temperatures, followed by deposition of TiO2 thin films through E-gun evaporation, resulting in the formation of CuO/TiO2 p-n heterojunction. The distribution of elements and compositions of the CuO/TiO2 p-n heterojunction were analyzed by EDS mapping and EELS profiles, respectively. In the presence of H2O2, CuO/TiO2 hybrid structure performed more efficiently than CuO NRs for Rhodamine B degradation under the irradiation of 500-W mercury-xenon arc lamp. This study demonstrated the effect of length of CuO NRs, on the photo-degradation performance of CuO NRs as well as CuO/TiO2 heterostructure. The optimized CuO/TiO2 hybrid NR array structure exhibited the highest photo-degradation activity, and the mechanism and role of photo-Fenton acting as the catalyst in photo-degradation of dye was also investigated.

The degree of shape recovery in shape memory alloys is highly associated with their deformation due to martensitic detwinning. In this work, we studied the microstructural evolution of the martensitic variants in NiTi shape memory alloys under applied tension or compression. We first carried out a phase-field simulation based on the Landau-type energy function to investigate the nucleation and growth of the B19$$'$$ variants that form a polytwinned structure right after the material is cooled below the martensitic transformation temperature. Then, the detwinning of the polytwinned martensites was studied under a uniaxially applied tensile or compressive strain. The simulation was run in a 2-variant system to confirm the applicability of the approach, and then, it was performed in a 6-variant system to highlight the microstructure-based mechanism for the overall mechanical response with a higher degree of microstructure complexity. The detwinning simulation confirms many features found by micrograph observation. What was not experimentally reported is the continuing martensitic reorientation in the early stage of the subsequent unloading, which caused the nonlinear stress–strain behavior. Although dislocation was not considered in our model, we still found tension–compression asymmetry in the calculated stress–strain behavior. It is due to the initial configuration of the unevenly distributed polytwinned martensitic structure and the separate evolution paths under tension or compression. Finally, we carried out the sensitivity study of the numerical results to the applied strain rate and the kinetic coefficient and we found that the two effects are interrelated in the framework of the current model.

Unlike common TMDCs such as MoS2, PtSe2 can be fabricated at temperatures below 600 °C, or even as low as 300 °C, while still maintaining high quality. By varying the selenization temperature from 300 °C to 600 °C, the electrical properties were changed significantly, resulting in superior gas sensing performance. Through comprehensive material analysis, an interesting phenomenon was found, namely that strain along the [001] direction existed in films grown at a low temperature rather than at a high temperature. Moreover, due to the layer-dependent property of PtSe2, a phase transition from metal-to-semiconductor occurs as the thickness is reduced. Hybridization of phase engineering and thermal strain engineering significantly enhances the gas sensing performance, resulting in PtSe2 with a dramatic increase in the response to 1 ppm NO2 from 25% to 550% once the thickness was reduced from 10 to 5 layers. In addition, PtSe2 showed good stability during exposure to not only 1 ppm but also 50 ppb NO2 for more than 5 cycles with responses of over 550% and 60%, respectively.

This study reports a preliminary mix design of the geopolymer-based ultra-high-performance concrete (G-UHPC) developed using the alkaline activated alumino-silicate source materials. A combination of the sodium silicate (Na2SiO3) solution and sodium hydroxide (NaOH) was used as the alkaline activator, and the alumino-silicate source materials included the granulated blast furnace slag (GGBFS), fly ash and silica fume. The effect of the sodium silicate modulus, fly ash, GGBFS, Si/Al ratio, Ca/(Si + Al) ratio and steel fiber on the flowability of the fresh mixture and mechanical behavior of G-UHPC was comprehensively investigated via a series of flowability, compression and flexure tests. The X-ray diffraction (XRD) and scanning electron microscopy (SEM) analyses were conducted to reveal the performance enhancement mechanism based on the reaction products and micromorphology. It was observed that an increase in the sodium silicate modulus, GGBFS and Si/Al ratio negatively impacted the flowability of the fresh G-UHPC mixture, whereas a significantly positive effect on the flowability was observed on incorporating the fly ash. Overall, the compressive and flexural strength of G-UHPC exhibited an increasing trend, followed by a decline, on increasing the sodium silicate modulus, fly ash, GGBFS and Ca/(Si + Al) fractions. The compressive and flexural strength demonstrated an identical trend on increasing the Si/Al fraction at a CaO fraction of 0.1 or 0.2. On the other hand, an increment in the Si/Al fraction exhibited a negative impact on the compressive and flexural strength as the CaO fraction increased to 0.3. The steel fiber dosage negatively affected the flowability, whereas an increase in the steel fiber dosage enhanced the compressive and flexural strength. Further, the flowability and flexural strength could be effectively estimated from the length (Lf) -to-dimeter (Df) ratio (Lf / Df), whereas 1/(LfDf)could be used to estimate the compressive strength. The XRD and SEM analyses revealed the fundamental contribution of the mentioned factors on the reaction products and micromorphology of G-UHPCs. Eventually, suggestions have been made for the effective preliminary mix design of G-UHPC for the civil engineers.

Single-crystal LiNi0.8Co0.1Mn0.1O2 (S-NCM811) with an electrochemomechanically compliant microstructure has attracted great attention in all-solid-state batteries (ASSBs) for its superior electrochemical performance compared to the polycrystalline counterpart. However, the undesired side reactions on the cathode/solid-state electrolyte (SSE) interface causes inferior capacity and rate capability than lithium-ion batteries, limiting the practical application of S-NCM811 in the ASSB technology. Herein, it shows that S-NCM811 delivers a high capacity (205 mAh g-1, 0.1C) with outstanding rate capability (175 mAh g-1 at 0.3C and 116 mAh g-1 at 1C) in ASSBs by the coating of a nano-lithium niobium oxide (LNO) layer via the atomic layer deposition technique combined with optimized post-annealing treatment. The working mechanism is verified as the nano-LNO layer effectively suppresses the decomposition of sulfide SSE and stabilizes the cathode/SSE interface. The post-annealing of the LNO layer at 400 °C improves the coating uniformity, eliminates the residual lithium salts, and leads to small impedance increasing and less electrochemical polarization during cycling compared with pristine materials. This work highlights the critical role of the post-annealed nano-LNO layer in the applications of a high-nickel cathode and offers some new insights into the designing of high-performance cathode materials for ASSBs.

For compact ultrahigh‐power lighting and high‐speed optical wireless communication (OWC) purposes, the red/green/violet laser diodes (R/G/V‐LDs) moduled with specific Subminiature A (SMA) connectors are used for cold white‐light mixing and direct digital encoding. Even with hybridizing a high‐power yellow light‐emitting diode (LED) for high color‐rendering index lighting, such a R/G/V/Y design can miniaturize its volume to W × L × H = 6 × 5.4 × 2 cm3 (only 1/310 of the conventional bulky setup). The R/G/V‐LDs are individually encoded by 16 quadrature amplitude modulation orthogonal frequency‐division multiplexing (16‐QAM OFDM) data to demonstrate the visible wavelength division multiplexing (VWDM). Such R/G/V‐LD VWDM transmitters provide 8.8/5.2/7.2 Gbps modulation to achieve the total data rate as high as 21.2 Gbps after employing the power preleveling technique. Such high‐power R/G/V‐LDs under optimized bias currents deliver an output power of 102/97/129 mW, which can offer a high illuminance of 12 800 lux within a divergent angle of 54° at a distance of 0.5 m. To date, such ultrahigh‐power compact R/G/V‐LDs with lighting VWDM capability beyond 20 Gbps also enable the possibility of network coverage for B5G/6 G and Industry 4.0 applications.

Potentiometric biosensors based on flexible arrayed silver paste electrode and copper-doped zinc oxide sensing film modified by iron-platinum nanoparticles (FePt NPs) are designed and manufactured to detect lactate in human. The sensing film is made of copper-doped zinc oxide (CZO) by a radio frequency (RF) sputtering system, and then modified by iron-platinum nanoparticles (FePt NPs). The surface morphology of copper-doped zinc oxide (CZO) is analyzed by scanning electron microscope (SEM). FePt NPs are analyzed by X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR). The average sensitivity, response time, and interference effect of the lactate biosensors are analyzed by voltage-time (V-T) measurement system. The electrochemical impedance is analyzed by electrochemical impedance spectroscopy (EIS). The average sensitivity and linearity over the concentration range 0.2–5 mM are 25.32 mV/mM and 0.977 mV/mM, respectively. The response time of the lactate biosensor is 16 s, with excellent selectivity.

6061 aluminium was treated by Plasma electrolytic oxidation (PEO) where a new experimental method was introduced: the applied voltage of the PEO process was quickly increased to 486 V by different ...

Hierarchically ordered structures with low tortuosity, excellent mechanical flexibility, high optical transparency, and outstanding electrical conductivity are critically important in developing flexible transparent supercapacitor electrodes for innovative applications in electronics and displays. Here a CVD process is employed to fabricate leaf-skeleton inspired electrodes, which are reticulated monolithic networks consisting of carbon nanostructures serving as a 3D spongy core and graphene-based films as a protective/conductive shell. The network electrodes show optical transmittance of 85–88%, an electrical sheet resistance of ~1.8 Ω/sq, and an areal capacitance of 7.06 mF cm−2 (at 0.78 mA cm−2 in a three-electrode cell) in Na2SO4 aqueous electrolyte. Flexible transparent and symmetric supercapacitors, based on PVA/H3PO4 gel and the network electrodes, possess a stable working voltage of 1.6 V, energy and power density of 0.068 μWh cm−2 and 47.08 μW cm−2 at an optical transparency of ~80%, and no capacitance loss over 30,000 flat-bend-release cycles. Flexible, transparent supercapacitor electrodes are promising materials for innovative electronic and display applications. Here, the authors report a leaf-skeleton inspired core-shell network that exhibits up to 88% optical transmittance and is stable over 30000 bend-release cycles while retaining competitive electrochemical performance.

Temperature-dependent short-range structural evolution of Au44Ga56 liquid eutectic alloy has been studied by in situ extended X-ray absorption fine structure (EXAFS), in situ high-energy X-ray diffraction (HEXRD) together with first-principles molecular dynamics (FPMD) simulations. It is found that the short-range structure of Au44Ga56 liquid strongly inherits the local atomic packing of the AuGa compound. A short-range structural change in Ga-centered clusters is revealed by in situ EXAFS data at the Ga K-edge at about 970 K, while no such change in Au-centered clusters appears at the Au LIII-edge. The in situ HEXRD and FPMD simulations also confirm the existence of a liquid-to-liquid crossover (LLC) in the Au44Ga56 liquid at a temperature range of about 1000–1100 K, mainly lying in the local structural change around Ga atoms. Indeed, the alloys quenched from the liquid phases below 1000 K and above 1100 K exhibit differences in structure and magnetic properties, which opens a possibility to fabricate ne...

Various plasma electrolytic oxidation (PEO) ceramic coatings were fabricated on aluminum in the electrolytes with different concentrations of Na2SiO3·9H2O. The morphology of fractured cross-section and coating/substrate (C/S) interface, phase compositions, and corrosion behavior of these ceramic coatings were characterized employing field emission scanning electron microscopy (SEM) equipped with energy dispersive X-ray spectroscopy (EDS), X-ray diffractometer (XRD), potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) measurements. The results showed that adding Na2SiO3·9H2O in the electrolyte could reduce the decrease amplitude of the voltage-time curve, and it can affect the types of the anodic film before the beginning of plasma discharges. A novel phenomenon was recorded as PEO treatment was carried out in the electrolyte with 1.85 g l−1 Na2SiO3·9H2O that the substrate was first covered by a barrier-type anodic film, and then a porous-type anodic film appeared after the barrier-type anodic film was broken down. The anodic film continued to grow for a long duration in the PEO process after being broken down. Characteristics of PEO ceramic coatings with a similar thickness acquired in various electrolytes were also evaluated. XRD results indicated that these ceramic coatings of similar thickness were mainly composed of α-Al2O3 and γ-Al2O3, and the α-Al2O3 proportion decreased with increasing Na2SiO3·9H2O concentration. The electrochemical data showed that the corrosion resistance of these PEO ceramic coatings of similar thickness decreased by adding Na2SiO3·9H2O in the electrolyte.

In this study, AA5083 aluminum alloy T-joints were properly welded, where both of the corners were successfully joined with stationary shoulder friction stir welding. According to the microstructur...

Exploring highly efficient electrode materials is crucial for advancing clean energy storage devices such as pseudocapacitors (PCs). Transition-metal sulfides (TMSs), typically involving conventionally stoichiometric ternary components (such as NiCo2S4 and Ni2CoS4), are suggested as promising electrode nanomaterials for PCs. Herein, a large-specific-surface-area NiS2/CoS2 composite anchored on three-dimensional reduced graphene oxide (NiS2/CoS2/3DGO) is prepared by the sulfuration of a needle-like NiCo-hydroxycarbonate precursor grown on the 3DGO support. The NiS2/CoS2/3DGO composite is endowed with the following advantages: CoS2 and NiS2 composite, a large specific surface area (200.48 m2 g−1) and narrow mesoporous size distribution, as well as high conductivity. The composite electrode indeed delivers a highly attractive capacitance of 2451 F g−1 at 1 A g−1, which is comparable or superior to most TMS electrodes reported previously. Furthermore, the all-solid-state NiS2/CoS2/3DGO//activated carbon for PCs achieves a decent energy density and power density at 1 A g−1, and an attractive reversible capacitance retention of 97.2% after 5000 cycles at the high current density of 20 A g−1. Such an improvement strategy can be extended for constructing diverse transition-metal sulfides and phosphides as electrode materials for energy storage.