Due to high theoretical capacity, lithium sulfur (Li–S) batteries are regarded as aussichtsreich batteries for future energy storage devices. Several factors, such as low usage effectiveness of ...sulfur and “shuttle effect” of polysulfides, restrain the development of Li–S batteries. Porous sulfur carriers have been developed to remit these shortcomings to some extent. In this paper, a simple strategy is reported to prepare porous Ni3S2 hollow microspheres as sulfur hosts for Li–S batteries by an easy hydrothermal and calcination method. The as-fabricated Ni3S2/S cathodes present excellent cycling performance (959.7 mA h g−1 at 0.1 C after 100 cycles) as well as good rate property and cyclability (557.5 mA h g−1 at 1 C after 400 cycles). Such excellent energy storage properties can be ascribed to the unique hollow microsphere structure with high specific surface area, which is conducive to the capture of polysulfides during cycling. The study also provides a simple route to develop transition metal sulfide with hollow structures as superior sulfur hosts which may promote the development of various hollow structures for Li–S batteries application.
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•Porous Ni3S2 hollow microspheres are prepared as sulfur hosts for Li–S batteries.•Ni3S2/S exhibit good electrochemical performance as Li–S battery cathodes.•Porous Ni3S2 hollow structure is conducive to capture polysulfide.•Large specific surface area of electrode can well adapt volume change of S.
Cu xO(x = 1,2)/amorphous compounds have been successfully synthesized by chemical free dealloying and spontaneous oxidation method. Technological parameters, such as the acid concentration and ...dealloying time strongly influence the crystal type, size and morphology of coppery oxide. The further study shows that with the increase of HCl concentration, the surface coverage rate of Cu2O micro-flowers increases and the sizes of Cu2O micro-flowers get bigger. Moreover, it is observed that cracks are formed on the etched ribbon surface and plentiful Cu2O/CuO particles grow up from these crack walls if the dealloying time extends to long enough. Considering many fascinating properties of Cu2O/CuO particles and the amorphous alloy carrier, potential application fields of these amazing compounds will be developed in future.
Various secondary structures, for example, β-sheet hydrogen bonds formed by oligopeptides exhibiting high directionality and selectivity provide a new avenue to regulate optoelectronic performances ...of supramolecular assemblies constructed by π-conjugated chromophores. In this work, oligopeptide-perylene diimides (AUPDIs) are synthesized to generate β-sheet strands which guide the formation of chiral supramolecular polymers with a diversity of morphologies in combination with the π–π stacking even in aqueous media. Complex morphology transitions are successfully controlled by simply adjusting the water volume fraction in the binary solvent of water and tetrahydrofuran from spherical hollow aggregates to long helical nanowires and to short nanofibers. The mechanism of the assembly changes from cooperative to the isodesmic model relying on AUPDI concentrations. This originates from the transformation in the β-sheet that regulates profoundly the arrangement of the AUPDI molecules. Prominently efficient and positive electronic sensing to triethylamine for highly helical nanowires engenders due to the highly ordered helical arrangement within the nanowires, fourfold of the short nanofibers.
An interesting biomass-derived shape memory polymer (SMP) based on cross-linked poly(l-malic acid) (PMA), with reconfigurable permanent shape and tunable shape memory transition temperature (Ttrans), ...was developed in this work. The amorphous cross-linked network was constructed in PMA using eco-friendly 1,8-octanediol as the cross-linker through a catalyst-free two-step way. The relations between crosslinking density (d) and glass transition temperature (Tg), as well as the mechanical strengths of as-obtained cross-linked PMA (CPMA) were then evaluated. Both the strengths and the Ttrans are easily tunable by controlling curing times. Moreover, the permanent shape of CPMA is reconfigurable due to additional crosslinking in the heat treatment process. It also shows good diversity of processing approaches. This work is the first report to achieve good strengths on the biodegradable PMA and to activate its shape memory effect, opening up a window of application of PMA as the smart material or even as the common plastics.
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•Developing a green and very simple SMP based on the cross-linked PMA.•The permanent shape is reconfigurable because of the solid state plasticity.•Shape memory transition temperature is tunable by controlling curing times.
In this study, a sapphire-derived fiber (SDF)-based Fabry-Pérot interferometer (FPI) is proposed and experimentally demonstrated as a high-temperature sensor using the arc discharge crystallization ...process, forming a region with disordered mullite grains. This shows that the disordered mullite grains are related to the gradual temperature distribution during the arc discharge process, which results in a larger refractive index (RI) modulation of the SDF near the fusing area, forming a reflection mirror. An FPI was obtained by combining the optical fiber end facet. Considering the high-temperature resistance of the fiber, the fabricated FPI was used for high-temperature sensing. This shows that the device can operate at temperatures of up to 1200 °C with a sensitivity of 15.47 pm/°C, demonstrating that the proposed devices have potential applications in high-temperature environments.
With the aim of studying the properties of SBS/CR modified asphalt with CR directional distributed in SBS, SBS/CR composites were prepared in advance by method of melt blending in this work, and then ...the SBS/CR composite modified asphalts were prepared by the traditional wet process. The effect of the content of CR and the compatibility between SBS and CR on modified asphalts were discussed in details. The results show that the increasing blending temperature is conducive to improving the compatibility between SBS and CR, but it led to degradation of polymer modifiers. The hot storage stability of modified asphalt decreases with the growth content of CR, while increases with the increasing blending temperature. The conventional properties, elastoplastic relaxation behavior, temperature-sensitivity and rheological behaviors of modified asphalts were evaluated by the test of cyclic tension, rotational viscosity, dynamic shear rheometer (DSR) and blending beam rheometer (BBR). The results indicate that SBS combined with CR in advance have positive effect on the properties of modified asphalt, which is related to the directional distribution of CR and the improved compatibility between SBS and CR. Furthermore, the pre-blending of CR with SBS enhances the resistance of modified asphalts to thermal-oxidation aging. This work provides further guidance for understanding the modification mechanism of SBS/CR composite modified asphalt and improving the properties of SBS/CR modified asphalt.
•SBS/CR modified asphalt with CR selective distribution were prepared.•The distribution state of CR has impact on the properties of modified asphalt.•The pre-combined SBS and CR can improve the storage stability of modified asphalt.•The better compatibility between SBS and CR, the better performance of modified asphalt.
Along with China entering an aging society, the percentage of people that over 60 will reach 34.9% in 2050, resulted in a significant increase in stroke patients.
This paper proposes a rehabilitation ...robotic walker for walking assistance during the daily life, and a control method for the motor relearning during the gait training. The walker consists of an omni-directional mobile platform (OMP) which ensures the walker can move on the ground, a body weight support system (BWS) which is capable of providing the desired unloading force, and a pelvic assist mechanism (PAM) to provide the user with four degrees of freedom and avoid the rigid impact. The study goal is to gain a better understanding of the assist-as-needed control strategy during the gait training.
For the man-machine interaction control, the assist-as-needed control strategy is adopted to guide the users' motions and improve the interaction experience. To build the force field in the three-dimensional space, the dynamics of the system is derived to increase the accuracy of force control.
The simulation results show that the force field around the motion trajectory was generated in the three-dimensional space. In order to understand the force field, we designed the simulation on sagittal plane and the controller can generate the appropriate force field. The preliminary experiment results were consistent with the simulation results.
Based on the mathematical simulation and the preliminary test, the results demonstrate that the proposed system can provide the guide force around the target trajectory, the accuracy of force control still remains to be improved.
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•Dipole-dipole interactions between C-F bonds benefit the mechanical properties.•The introduction of MEA can reduce the Tg and promote healing and stretchability.•These CF3…CF3 and ...C=O…C=O interactions make fast, repeatable, and tough adhesion.
Integration of high toughness, fracture resistance, and fast self-healing, as well as robust adhesion is critically required for flexible electronics, healthcare monitoring, and electronic skins. However, it still remains a critical challenge to combine these significant functions into one material. Here, we synthesize an elastomer by copolymerizing two acrylate monomers containing functional groups and established hierarchical dipolar interactions and hydrogen bonds between C-F, C=O, -O-CH3, and C-H groups with different bonding strengths, which successfully not only combines with high toughness (31.41 ± 1.12 MJ m−3), outstanding crack resistance (fracture energy: 10252 ± 208 J m−2), fast self-healing (completely restore within 30 min at room temperature), but also with fast, repeatable, and toughness adhesion to different substrates, e.g. PMMA, Aluminum, glass, steel, and PTFE. The PF4M6 demonstrates great sensing performance in detecting human motion. Overall, this work provides some insights for preparing high-performance, healing, and adhesive elastomer materials applied in electronics, adhesives, and interface materials.
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