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The progress of this research is the preparation of FeNi alloy thin films by magnetron sputtering. Each step of the experimental process is based on the electrocatalytic performance of the sample, and characterized by many characterizations means such as X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), X-ray energy spectrometry (EDS) and step gauge thickness test for morphology, structure and elemental composition, etc. The analysis of the characterization results is used as a support for the experimental process. Adjustment of various preparation process parameters for material growth and subsequent processing include doping of non-metallic elements and construction of nanostructures. Doping of C elements can make FeNi based alloy films further amorphous. Zn element is used as a pore-forming agent. The two processes of doping and high-temperature vacuum dealloying can make the film obtain a nanoporous structure, which greatly increases the specific surface area. These two strategies reduce the overpotential (η10) of oxygen evolution reaction (OER) of FeNi alloy thin films to 393 mV and 314 mV, which are reduced by 47 mV and 79 mV step by step. The electrochemical properties of the finally obtained alloy film are: overpotential of 314 mV, Tafel slope of 61.8 mV/dec and the stability of only 10% decay at a current density of 10 mA/cm2 for 12 h. In this study, low-cost transition metals were used as the main materials to design OER catalysts, and the catalytic efficiency was comparable to that of commercial noble metal catalysts. The physical preparation methods made each sample have good reproducibility. It provides the experimental basis and theoretical basis for the design and synthesis of new catalytic materials at a higher level. • The electrocatalytic thin films prepared by magnetron sputtering has the characteristics of high stability. • The addition of carbon can deepen the amorphization, thus improving the catalytic efficiency. • High-vacuum dealloying is characterized by high speed and good repeatability in preparing porous structures. [ABSTRACT FROM AUTHOR]

This work investigates the static and fatigue degradation after low-velocity impact (LVI) and the corresponding mechanisms of 3D woven carbon/epoxy composites with a fiber volume fraction of 53 %. Drop weight tests employing impact energies ranging from 6 J to 20 J are performed to introduce damage to the specimens. Quasi-static tensile tests after impact (TAI) and tension–tension fatigue tests after impact (FAI) are then carried out to study the post-impact behaviors. The results of TAI tests show that the residual strength decreases linearly by up to 62 % as impact energy increases to 20 J. Similarly, residual stiffness shows a linear decline with increasing impact energy until 15 J. However, as the impact energy increases to 20 J, the residual stiffness decreases significantly and deviates from linear decreasing trend due to the impact causing fiber breakage. The FAI test results show that LVI can reduce the fatigue life. But such effect is limited for small loading levels. It is worth noticing that even slight impact damage can reduce the static and fatigue performance significantly. To understand the mechanisms behind it, the damage evolution in TAI and FAI tests is analyzed through the CT technique. The results show that even though low energy LVI does not cause fiber fracture, the stress concentrations induced by matrix cracking and delamination still reduce the uniformity of the internal stresses, thus causing fiber fracture in sequence and reducing the mechanical and fatigue performance of 3D woven composites. [ABSTRACT FROM AUTHOR]

Hydrogen production from electrochemical water electrolysis is one of the most effective solutions to the world's energy dilemma and environmental degradation. Transition metal dichalcogenides (TMDs) have been extensively reported as effective catalysts for hydrogen production, Molybdenum disulfide (MoS 2) has particularly evoked widespread interest due to its high activity, low cost, and plentiful components. For MoS 2 , it commonly has the semiconductor phase (2H) and the metallic phase (1T) structures, and 2H is more stable but less conductive than 1T. Although more favorable for electronic transfer, 1T-MoS 2 has poor stability, complex preparation, a restricted number of active sites, low intrinsic catalytic activity, and poor interlayer conductivity. In this review, we will discuss the phase transition mechanism from 2H–MoS 2 to 1T-MoS 2 , along with recent research advances. Because it is a technical challenge to synthesize the1T-MoS 2 , we will discuss the characteristics and structure of 1T-MoS 2 in detail and its application in water electrolysis cataloging on the preparation methods. The improved intrinsic activity, increased active sites, and the improvement of conductivity are discussed in terms of several aspects including (1) doping and ionic intercalation, (2) introduction of S vacancies (Vs) and defect modification, (3) highly conductive substrates and composite structures combination, as well as (4) phase transition effect. The critical difficulties and prospects are also presented at the end of this review, providing further solutions and inspirations for the preparation of 1T-MoS 2 electrocatalysts with enhanced catalytic performance. • The characteristics, structure, preparation methods of 1T-MoS2 and its application in the HER are discussed in detail. • The "quantity" and "quality" improvement of HER performance of 1T-MoS2 based on function oriented design is discussed. • The future development strategies are put forward. [ABSTRACT FROM AUTHOR]

• A modified method for punch shear test considering the amplification effect. • Positive correlation between failure strength and strain rate. • A full mesoscale model considering strain rate effects was established. • Damage modes are affected by hybridization and strain rates. • The high elongation of aramid fibers contributes to impact resistance. A modified theoretical method for the punch shear test is derived by considering the influence of stress wave reflections caused by cross section discontinuities in the incident and transmitted bars. The dynamic punch shear behavior of 2D plain weave carbon/aramid hybrid composites was researched. The failure strength and strain are sensitive to strain rate. The stress-strain curves were obtained by the modified method. Significant shear deformation was observed under a single loading. An effective punch shear mesoscopic simulation model that accounts for the strain rate effect of the component materials was developed using the multi-scale analysis method. The model reveals the damage characteristics in the component materials. Damage modes are affected by hybridization and strain rates. The high elongation at the fracture of aramid fibers at high strain rates plays a crucial role in absorbing impact energy. [ABSTRACT FROM AUTHOR]

• A new expression to predict the upper limit of constant strain rate. • Negative correlation between strength and strain rate of hybrid composites. • The validity of the nonlinear constitutive model to dynamic property. • The effect of hybridization and strain rates on fracture modes. Based on the analysis of stress wave propagation at both ends of the specimen, a formula for the upper limit of the constant strain rate is derived. The upper limit of constant strain rate is applicable to all the ratios of wave impedance, providing a broader applicability. The in-plane dynamic compressive behavior was obtained for 2D plain weave carbon/aramid hybrid composites at strain rates ranging from 195 to 790 s−1. The results validate the prediction of the upper limit of the constant strain rate. The strength exhibited sensitive to strain rate. A nonlinear constitutive model described the dynamic constitutive relationship effectively under different strain rates. The distribution of delamination failure significantly influenced the final failure shape of the specimens. Microscopic observations indicated that carbon fiber yarns and aramid fiber yarns exhibited different fracture modes. [ABSTRACT FROM AUTHOR]

• A micromechanics-based multiscale damage model for 3D woven composites (3DWCs) is proposed. • Interface properties exhibit different effects on tensile and compressive damage mechanisms of 3DWCs. • The interaction of different damage modes controls the overall trend of the tensile strength of 3DWCs. • In contrast, the better the interface properties, the higher the compressive strength of 3DWCs. A multiscale damage model is proposed based on a micro-mesoscale bridging model and a multiscale kinking model, which can predict the damage development processes of 3D woven composites (3DWCs) under different loading conditions using only few material parameters. At the microscale, the various mesoscopic damage modes of yarns, including tensile fiber breakage, compressive fiber kinking and transverse inter-fiber crack, can be simply divided into matrix- and fiber-dominated damage. Using this multiscale damage model, a numerical comparative study is conducted to investigate the effect of interfacial properties on the mechanical performances and damage mechanism of 3DWCs. The numerical results indicate that the interfacial properties exhibit different effects on the tensile and compressive strengths and damage mechanisms of 3DWCs. The interaction of different damage modes controls the overall trend of the tensile strength of 3DWCs. There is an optimum point for the tensile strength of 3DWCs at different interfacial fracture toughness. Beyond the optimum point, the tensile strength of 3DWCs is negatively correlated with interfacial properties. Unlike the tensile loading case, the better the interfacial properties, the later fiber kinking occurs, resulting in higher compressive strength of 3DWCs. [ABSTRACT FROM AUTHOR]

This work proposed an impact momentum flexibility (IMF) to precisely and concisely characterize the soft impact behavior of twill weave laminate based on multi-scale finite element analysis. A multi-scale finite element model taking into consideration the microstructure and properties of constituents is established for twill weave laminate. The equivalent properties of fiber tows and twill weave laminate are predicted by micro-scale model and meso-scale model, respectively. Then the soft impact behavior of the laminate is investigated by macro-scale model. The multi-scale model is validated on different scales by comparing the experimental and simulated results of quasi-static compression and soft impact. On this basis, the deformation and failure of the laminate under soft impact are analyzed. The soft impact response is categorized according to the damage morphology and impact velocity. Moreover, the IMF is proposed to depict the ability to resist soft impact deformation of the laminate, and can be further adopted to rank the soft impact property of different materials. • Established the multi-scale finite element model for the twill weave laminate. • Obtained and categorized the soft impact response of the twill weave laminate. • Proposed the impact momentum flexibility (IMF). • Characterized the soft impact behavior precisely and concisely using IMF. [ABSTRACT FROM AUTHOR]

The failure behaviors of 3D woven composites (3DWC) under biaxial tensile loadings are investigated through a combined experimental and numerical approach in this paper. Appropriate biaxial cruciform specimen of 3DWC is first designed according to the experimental requirements. The biaxial tensile experiments are conducted on a servo-hydraulic biaxial testing facility, and then the full-field strain distributions and crack morphologies of cruciform specimens are analyzed in detail. For the multiscale geometric reconstruction of 3DWC, a full-thickness mesoscopic RVC is first extracted from the periodic woven architecture, and then a novel full-scale geometric modeling method is developed to reconstruct the biaxial cruciform specimens of 3DWC. Particularly, in conjunction with the micromechanics of failure theory, a multiscale damage model is proposed to simulate the biaxial failure behaviors of 3DWC. With the stress amplification factor, a transfer relationship between mesoscopic and microscopic stresses is established, and then the damage states of matrix and fibers within yarns can be separately determined. By comparing the experimental and predicted results, the realistic damage mechanism of 3DWC under biaxial tensile loading can be elucidated. [Display omitted] [ABSTRACT FROM AUTHOR]

• New partially-infused Kevlar/Polycarbonate laminate to improve impact resistance. • This partially-infused structure is inexpensive and simple to manufacture. • Fiber yarns in this structure contain fully infused exterior and dry fiber core. • The fully infused exterior provides good stiffness and interlaminar toughness. • The dry fiber core provides high energy dissipating during impact. High toughness Kevlar fiber reinforced polymer composites are adopted for applications such as bulletproof shields, helmets and hard body armor that require high impact resistance as well as sufficient structural stiffness and strength. However, the impact energy absorption of fully-infused stiff composites made of Kevlar fibers and matrix is not as good as that of dry Kevlar fabrics. This study proposes a partially-infused Kevlar fiber reinforced thermoplastic laminate with significantly improved impact resistance. Unlike conventional Kevlar fiber reinforced laminates where the resin is fully infused into the fiber yarns, the fabrication process of partially-infused laminates is controlled such that only the exterior of the Kevlar fiber yarns is infused with thermoplastic resin. Consequently, the Kevlar fibers at the core of each fiber yarn are unrestricted during impact, thus, dissipating more energy. The infused exterior of Kevlar fiber yarns forms tough interlaminar interfaces that resist delamination during out-of-plane loading. The partially-infused laminate has similar static indentation resistance and slightly lower bending resistance when compared to conventional fully-infused Kevlar reinforced thermoplastic laminate, but dissipated 318% more energy in ballistic penetration tests performed with a 12 mm diameter steel spherical projectile. [ABSTRACT FROM AUTHOR]

Rare-earth doped ZnO up/down-conversion materials were prepared and introduced into photoelectrodes to enhance the photovoltaic efficiency of dye-sensitized solar cells. In this paper, we achieved a optimal efficiency of 5.13% with the incorporation of ZnO:Eu 3+ ,Tb 3+ and ZnO:Er 3+ , Yb 3+ , which is about 70% higher than that of dye-sensitized solar cells based on pure TiO 2 . This is probably due to the enhancement of light harvesting via converting ultraviolet and near infrared radiation to visible emission by downconversion and upconversion luminescence process, respectively. In addition, the ZnO:Eu 3+ ,Tb 3+ film acted as a blocking layer inhibit the charge recombination, suppressing the dark current for DSSCs. Results indicate that the ZnO:Eu 3+ ,Tb 3+ /TiO 2 :ZnO:Er 3+ , Yb 3+ double composite layers can obviously improve the efficiency of dye-sensitized solar cells, and the combine of the up and down conversion materials is an effective method to extend the response both to ultraviolet and near-infrared radiation in dye-sensitized solar cells. [ABSTRACT FROM AUTHOR]

The down conversion (DC) material ZnO: Eu 3+ , Dy 3+ are synthesized by precipitation method and used to prepare the photo anode of dye-sensitized solar cells (DSSCs). The effects of down conversion material on the photoelectric performance of the DSSC were characterized by the X-ray diffraction (XRD), photoluminescence (PL), scanning electron microscope (SEM), current–voltage ( I – V ) curve, incident-photon-to-current conversion efficiency (IPCE) and UV–vis–NIR absorption spectroscopy. In this paper, Eu 3+ , Dy 3+ codoped ZnO excited by from UV to blue light converts blue to red light emission, corresponding to the absorption region of the dye (N719). At the concentration 1.75% of ZnO: Eu 3+ , Dy 3+ (weight ratio of DC to TiO 2 ), the short-circuit current density and conversion efficiency of the DSSCs reached to the optimal values: 8.92 mA cm −2 and 4.48%, about 212% and 245% higher than with pure TiO 2 and about 91.4% and 105% higher than with TiO 2 /graphene (G) structure, respectively. The research result reveals that the application of DC material can improve the efficiency of DSSCs. [ABSTRACT FROM AUTHOR]

Abstract: In this paper, the two methods, electroluminescence in frequency domain and electrochemical impedance spectroscopy, have been applied to investigate the carrier mobility in single layer polymer light-emitting diode employing the polymer MEH-PPV (Poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene]) as the light-emitting layer. The carrier mobility μ is 1.64×10−6 cm2/Vs under the electric field 8.3×105 V/cm measured by the method of electroluminescence in frequency domain. The electrochemical impedance spectroscopy results indicate that the carrier mobility μ is 1.08×10−6 cm2/Vs under the electric field 7.5×105 V/cm. A significant advantage of the two methods is that both of them can be applied to measure the carrier mobility in the thin film. [Copyright &y& Elsevier]

• The tension–compression fatigue damage mechanisms of 3D woven composites. • A multi-information research method for fatigue damage of 3D woven composites. • A novel anti-buckling device which can be used with the measuring equipment. • The critical damage which causes rapid stiffness degradation and final failure. The fatigue damage mechanisms of 3D woven composites are very complex. In this work the tension–compression (T-C) fatigue damage evolution of 3D woven composites is investigated using a multi-scale method. To avoid the buckling failure during the T-C fatigue tests, a novel anti-buckling device is designed. The authors combine the macro damage information (i.e., axial stiffness and surface temperature) and the meso -damage information (i.e., detection results by synchrotron radiation computed tomography (SRCT)) to investigate the fatigue damage evolution. The results show that the T-C fatigue process can be divided into two stages. The stiffness decreases slowly in a linear form in Stage I, and then decreases rapidly to final failure in Stage II. Most of the fatigue damage occurs in Stage II. The SRCT results can reveal the damage modes in either fatigue stage, in which the warp yarn breakage is the critical damage mode. [ABSTRACT FROM AUTHOR]

Abstract: Photoexcited energy transfer in organic multilayer well structure devices in which Alq3 is the well layer material is discussed in terms of the different barrier layer materials, the well number, the wavelength of excitation light and the thickness of well layer. The photoluminescence intensity from the Alq3 layer is enhanced and that from the barrier layer is weakened in the devices with the multilayer well structure compared with the conventional double-layer structure as a result of effective Förster energy transfer from the barrier to the well. The photoluminescence characteristics of organic multilayer well structure devices are investigated in detail. [Copyright &y& Elsevier]

Abstract: In this work, organic/inorganic heterostructure electroluminescence devices are fabricated, in which the inorganic layers (ZnO, ZnS) act as the electron transfer layer and the hole blocking layer. Compared to single-organic-layer (MEH-PPV) devices, the heterostructure devices have a significantly enhanced luminous efficiency. The influences of the electric field and the barrier potential on the improvements in performance are analyzed in detail. The results are: (i) the introduction of the inorganic layer makes the injection of electrons easier; (ii) the hole current density is enhanced by the increase of the electric field in the organic layer due to a high dielectric constant of the inorganic layer and accumulation of electrons at the inorganic/organic interface; (iii) the electron–hole current density balance is improved. [Copyright &y& Elsevier]

• A novel method based on SRCT for the fatigue damage of 3D woven composites. • The relationship between the stiffness degradation and temperature variation. • The damage mechanisms at every fatigue stages for 3D woven carbon/epoxy composites. • The effects of the yarns' undulation and twist on the fatigue damage. A method combining mechanical testing, infrared thermography (IRT) and synchrotron radiation computed tomography (SRCT) is proposed for the damage evolution of 3D woven carbon/epoxy composites under tension-tension (T-T) fatigue loading. To study the relationship between the damage evolution and the stiffness degradation, fatigue tests of six specimens are carried out to different stages before detection by SRCT and optical microscope. The detected results have revealed how cracks initiate, distribute and develop with increasing fatigue cycles. Particularly, the effects of fiber yarn undulation and twist caused during the manufacturing process are discussed. [ABSTRACT FROM AUTHOR]

Efficient electrocatalyst for alkaline oxygen evolution reaction is the critical core to the wide application of metal-air energy storage and water electrolysis hydrogen energy. Therefore, appropriate design of highly active and stable non-noble metal oxygen evolution electrocatalyst with good electronic structure and multilevel structure is both a goal and a challenge. Here, we report a Fe–Ni 2 P electrocatalyst (NiFeP-MOF) with multilevel structure, which was obtained by anion exchange on the basis of Fe–Ni(OH) 2 (NiFe-MOF) grown on nickel foam in situ by solvothermal method. As expected, Fe substitution regulates the Ni oxidation state in the NiFeP-MOF and realizes electronic structure coupling, showing a highly active and stable oxygen evolution reaction (OER) in alkaline electrolyte solution. Specifically, the NiFeP-MOF demonstrates an ultralow overpotentials (232 mV, 10 mA cm−2; 267 mV 100 mA cm−2), respectively, an extremely small Tafel slope (34 mV dec−1). Separately, the electrocatalyst shows an excellent cycle stability at 10 mA cm−2 for 12 h (43,200 s). More importantly, this work come up with an available policy for the preparation of excellent alkaline hydrolysis electrolysis catalysts and air cathodes with excellent performance. • Fe–Ni 2 P (NiFeP-MOF) electrocatalyst with multilevel structure is obtained. • The synthesized catalysts have excellent OER performance and catalytic stability. • The catalyst with Ni:Fe ratio of 2:1 has high activity and good stability. • Fe substitution regulates the Ni oxidation state realizes electronic structure coupling. [ABSTRACT FROM AUTHOR]

To effectively balance the accuracy and efficiency in solving high-dimensional damage problems, a self-consistent clustering analysis framework with field refinement capability (RESCA) incorporating a mesoscale damage model, is developed to investigate the mesoscale failure behavior of 3D woven composites (3DWCs). The RESCA method includes three stages: offline stage, online stage and field refinement stage integrating damage information. In the third stage, a damage-related field refinement framework is proposed to achieve cluster-based field dehomogenization and efficiently reconstruct the voxel-based field information. The results indicate that the RESCA method can accurately predict the local stress concentration, the voxel-based damage field distribution and the damage accumulation process, which are not available with the traditional SCA method. Importantly, the RESCA method can improve the computational efficiency by 25∼55 times compared to the finite element analysis (FEA) method. The RESCA method has double advantages in the efficiency and accuracy for the damage analysis of 3DWCs. [Display omitted] [ABSTRACT FROM AUTHOR]

Electrocatalytic water splitting is a promising route for the generation of clean hydrogen. However, the anodic oxygen evolution reaction (OER) suffers greatly from low reaction kinetics and thereby hampers the energy efficiency of alkaline water electrolysers. In recent years, tremendous efforts have been dedicated to the pursuit of highly efficient, low cost and stable electrocatalysts for oxygen evolution reaction. Herein, an amorphous FeOOH roughened capillary-liked CoAl layered double hydroxide (LDH) catalyst grown on nickel foam (denoted as FeOOH–CoAl LDH/NF) was reported for OER electrolysis. The developed FeOOH–CoAl LDH/NF electrode shows excellent OER activity with overpotentials of 228 mV and 250 mV to deliver a current density of 50 mA cm−2 and 100 mA cm−2 in 1.0 M KOH solution, respectively, ranking it one of the most promising OER catalysts based on transition-metal-based LDH. This is owed to the formed capillary-liked hierarchy structure with high-porosity as well as the strong electronic interaction between FeOOH and CoAl LDH. The developed morphological engineering approach to build hierarchal porous structures together with facile amorphous FeOOH modification may be extended to other layered double hydroxide catalyst for enhanced OER activities. [Display omitted] • Amorphous FeOOH decorated capillary-liked CoAl LDH structure was synthesized. • The amorphous structure induces sufficient active sites for water oxidation. • The interfacial interaction facilitates the mass transport and charge transfer. [ABSTRACT FROM AUTHOR]

In this paper, a novel mesoscopic progressive damage model is proposed to investigate the effective properties and damage mechanisms of 3D angle-interlock woven composites. The damage activation is based on the three-dimensional version of Puck criterion. Given that there may be multiple cracks in the transverse direction of the fiber yarns, a set of fracture angle-dependent damage variables are introduced to eliminate the stress abnormal phenomenon. In addition, an innovative exponential damage evolvement scheme, based on the equivalent displacement and stress, characteristic element length and fracture toughness, is proposed to govern the damage variables. Furthermore, a representative mesoscopic volume cell model, accounting for the fluctuation, distortion and actual cross-section size of fiber yarns, is constructed to represent the realistic interlaced architecture of the woven composites. The anisotropic damage model is applied to investigate the failure behavior of the 3D woven composites subjected to uniaxial tensile loading along the warp and weft directions. Some typical quasi-static tension experiments are performed to validate the accuracy of the simulations. The numerical predictions including failure strength and damage accumulation process are coincident with the corresponding experimental results. [ABSTRACT FROM AUTHOR]