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971.
Tian Wen Min Liu Shumei Chen Qiaohong Li Yonghua Du Tianhua Zhou Chris Ritchie Jian Zhang 《Small (Weinheim an der Bergstrasse, Germany)》2020,16(28)
Ultrathin 2D materials possess unique properties that translate to enhanced efficiency as electrocatalysts, stimulating research toward methodologies that support their preparation. Herein, a two‐step strategy is reported that involves the preparation of the new boron imidazolate framework ( BIF‐73 ) which is subsequently utilized as a precursor to yield the crystalline 2D nanosheet material ( Fe@BIF‐73‐NS ) via post‐synthetic modification. This new electrocatalytic material stabilizes ultra‐small (Fe2O3) fragments resulting in an excellent electrocatalytic performance for the oxygen evolution reaction (OER: lower overpotential with 291 mV at the current density of 10 mA cm?2) and carbon dioxide reduction reaction (faradaic efficiency of CO reaching 88.6% at ?1.8 V vs Ag/AgCl) without the need for noble metals. Additionally, theoretical calculations and microscopy reveal that the superior OER performance can be attributed to the increased exposure of binding sites within the material to which the catalytically active Fe3+ centers are bound through a post‐synthetic modification procedure. A red‐shift of the Fermi level around the valence band is observed and is proposed to be a result of the aforementioned interactions. This work opens an avenue toward the development of 2D functional metal organic framework nanosheets for energy conversion applications. 相似文献
972.
A radiative cooling garment is proposed as a promising strategy for ordinary people to attain high thermal comfort indoors and outdoors. However, low production and poor cooling capability restrict its wide applications. Herein, a high‐performance fiber and its textile with pore and wrinkle structures are fabricated that consist of polyethylene (PE) and polyethylene oxide. This specific structure endows the fiber and textile with high IR absorbance/emissivity (90.97%) and sunlight reflectance (93.77%). Therefore, the hybrid porous PE fiber and textile show good cooling capabilities and avoid the human body overheating by 6.8 °C under direct solar irradiation. The inner temperature of the transparent house with a roof covered by the textile decreases by 20.3 and 12.5 °C compared to the states of no extra cover and cotton cover, respectively. Apart from that, the results of the simulating and real human body measurements demonstrate that the porous PE textile enables the human body to acquire the same thermal comfort as the bare state. More importantly, the porous PE fiber and textile are superlight, flexible, moisture‐permeable, and waterproof, and meanwhile, have excellent tensile strength and UV protection properties. The good comprehensive performance indicates that the textile is appealing for fabricating summer clothes. 相似文献
973.
A mode decoupling control strategy is proposed for the active Kinetic Dynamic Suspension Systems (KDSS) with electrohydrostatic actuator (EHA) to improve the roll and warp mode performances. A matrix transfer method is employed to derive the modes of body and wheel station motions for full vehicle with active KDSS. The additional mode stiffness produced by the active KDSS is obtained and quantitatively described with the typical physical parameters. A new hierarchical feedback control strategy is proposed for the active KDSS to improve the roll and warp motion performances and simultaneously accounting for nonlinear dynamics of the actuators with hydraulic uncertainties. H∞ static output‐feedback control is employed to obtain the desirable mode forces, and a new projection‐based adaptive backstepping sliding mode tracking controller is designed for EHA to deal with address the nonlinearity and parameters uncertainty. This controller is used to realize the desirable pressure difference of EHA required from the target mode forces. Numerical simulations are presented to compare the roll and warp performances between the active KDSS, conventional spring‐damper suspension, and suspension with antiroll bar under typical excitation conditions. The evaluation indices are normalized and compared with radar chart. The obtained results illustrate that the proposed active KDSS with proposed controller does not produce additional warp motion for vehicle body, and has achieved more reasonable tire force distribution among wheel stations, the roll stability, road holding, and significantly improved ride comfort simultaneously. 相似文献
974.
The ocean bottom flying node (OBFN) is a special autonomous underwater vehicle (AUV) for seabed resource exploration. In this article, unmodeled uncertainties, thruster faults, and ocean disturbances are considered. The trajectory errors are constrained. Based on the directed topology, the distributed finite‐time fault‐tolerant error constraint containment control problem for multiple OBFN systems is solved, while only a part of follower OBFNs can measure the state of leaders. By using the backstepping method and a tan‐type barrier lyapunov function (BLF), a novel form of virtual controller is constructed. Neural network is employed to approximate and compensate the general disturbances. And the upper bound of the estimation error is dealt with by proposing an adaptive law. Besides, the trajectory errors can be constrained to a small neighborhood of zero in finite time. In other words, follower OBFNs can reach the convex hull consisted of leaders in finite time. The effectiveness of the designed algorithm is shown by presenting numerical experiment. 相似文献
975.
ABSTRACTThe effect of extrusion temperature on the microstructures and mechanical properties of as-extruded Zn–22Al alloys was investigated in this study. With decrease of extrusion temperature from 350 to 200°C, the elongation of as-extruded Zn–22Al alloys increases remarkably at low strain rate and has no change at high strain rate, which implies that the Zn–22Al alloys extruded at lower temperature exhibit high-ductility behaviour. X-ray diffraction and electron back-scattered diffraction analysis demonstrated that the maximum elongation of Zn–22Al alloys extruded at the extrusion temperature of 200°C can be attributed to the elimination of the lamellar structure and the refinement in grain size of the Zn-rich phase. 相似文献
976.
M. Qin Y. Zhou K. Wang G. Li Y. Tian Y. Chai 《Materialwissenschaft und Werkstofftechnik》2020,51(4):445-451
A kind of low cost, high breakage resistance ceramic proppant special for exploitation of the coal-bed methane is successfully produced. The producing conditions are optimized through orthogonal experimental design method. The breakage resistance results of the orthogonal analyses show the best condition of this kind of ceramic proppant is A4B3C3D2, which means sintering temperature of 1350 °C, manganese mineral powder content of 5 wt.%, weight ratio of 75/25 (second grade bauxite to mujie clay), and holding time of 3 h. The ceramic proppants under this very condition of A4B3C3D2 are then prepared and their phase structure and microstructure are characterized subsequently. X-ray diffraction pattern exhibits that mullite and corundum are the main crystallographic phases. Scanning electron microscopy illustrates the A4B3C3D2 sample is with non-porous morphology and small amount of corundum grains and liquid phase, which play the role of improving strength. It reveals the orthogonal experimental design is a feasible optimization method and the ceramic proppant made under the condition of A4B3C3D2 is a promising material for exploiting the coal-bed methane resources. 相似文献
977.
Giuseppe Schiavone Florian Fallegger Xiaoyang Kang Beatrice Barra Nicolas Vachicouras Evgenia Roussinova Ivan Furfaro Sébastien Jiguet Ismael Seáñez Simon Borgognon Andreas Rowald Qin Li Chuan Qin Erwan Bézard Jocelyne Bloch Grégoire Courtine Marco Capogrosso Stéphanie P. Lacour 《Advanced materials (Deerfield Beach, Fla.)》2020,32(17):1906512
The convergence of materials science, electronics, and biology, namely bioelectronic interfaces, leads novel and precise communication with biological tissue, particularly with the nervous system. However, the translation of lab-based innovation toward clinical use calls for further advances in materials, manufacturing and characterization paradigms, and design rules. Herein, a translational framework engineered to accelerate the deployment of microfabricated interfaces for translational research is proposed and applied to the soft neurotechnology called electronic dura mater, e-dura. Anatomy, implant function, and surgical procedure guide the system design. A high-yield, silicone-on-silicon wafer process is developed to ensure reproducible characteristics of the electrodes. A biomimetic multimodal platform that replicates surgical insertion in an anatomy-based model applies physiological movement, emulates therapeutic use of the electrodes, and enables advanced validation and rapid optimization in vitro of the implants. Functionality of scaled e-dura is confirmed in nonhuman primates, where epidural neuromodulation of the spinal cord activates selective groups of muscles in the upper limbs with unmet precision. Performance stability is controlled over 6 weeks in vivo. The synergistic steps of design, fabrication, and biomimetic in vitro validation and in vivo evaluation in translational animal models are of general applicability and answer needs in multiple bioelectronic designs and medical technologies. 相似文献
978.
Tai Cheng Chuanjiang Qin Satoru Watanabe Toshinori Matsushima Chihaya Adachi 《Advanced functional materials》2020,30(24)
Quasi‐2D metal halide perovskite films are promising for efficient light‐emitting diodes (LEDs), because of their efficient radiative recombination and suppressed trap‐assisted quenching compared with pure 3D perovskites. However, because of the multidomain polycrystalline nature of solution‐processed quasi‐2D perovskite films, the composition engineering always impacts the emitting properties with complicated mechanisms. Here, defect passivation and domain distribution of quasi‐2D perovskite films prepared with various precursor compositions are systematically studied. As a result, in perovskite films prepared from stoichiometric quasi‐2D precursor compositions, large organic ammonium cations function well as passivators. In comparison, precursor compositions of simply adding large organic halide salt into a 3D perovskite precursor ensure not only the defect passivation but also the effective formation of quasi‐2D perovskite domains, avoiding unfavorable appearance of low‐order domains. Quasi‐2D perovskite films fabricated with a well‐designed precursor composition achieve a high photoluminescence quantum yield of 95.3% and an external quantum efficiency of 14.7% in LEDs. 相似文献
979.
Anisotropic 1D contraction motion of polymeric actuating materials has drawn growing interests in fields ranging from soft robotics to biomimetic muscles. Although light‐driven liquid crystal polymers (LCPs) represent promising candidates to realize contraction (<20%) triggered remotely and spatially, there remain multitudes of challenges to develop an LCP system possessing ultralarge contraction rate. Here, a novel strategy combining shape memory effect and photochemical phase transition is presented to realize light‐driven contraction as large as 81% in a newly designed linear liquid crystal copolymer, where the eutectic mesogens of azobenzene and phenyl benzoate self‐organize into the smectic B phase. Importantly, this highly ordered structure as the switching segment firmly locks the stress‐induced strain energy, which is rapidly released by reversible trans–cis photoisomerization that destroys the lamellar liquid crystal phase, therefore leading to such ultralarge contraction. Fibers serve as light‐driven building blocks to achieve precise origami, to mimic the recovery of a “broken” spider web and to screen objects in different sizes, laying new ground for advanced applications of light‐driven LCPs from biomimetic robots to human assists. 相似文献
980.
Runsheng Gao Jie Tang Xiaoliang Yu Shiqi Lin Kun Zhang Lu‐Chang Qin 《Advanced functional materials》2020,30(27)
Silicon‐based materials have shown great potential and been widely studied in various fields. Unlike its unparalleled theoretical capacity as anodes for batteries, few investigations have been reported on silicon‐based materials for applications in supercapacitors. Here, an electrode composed of layered silicon‐based nanosheets, obtained through oxidation and exfoliation, for a supercapacitor operated up to 4 V is reported. These silicon‐based nanosheets show an areal specific capacitance of 4.43 mF cm?2 at 10 mV s?1 while still retaining a specific capacitance of 834 µF cm?2 even at an ultrahigh scan rate of 50 000 mV s?1. The volumetric energy and power density of the supercapacitor are 7.65 mWh cm?3 and 9312 mW cm?3, respectively, and the electrode can operate for 12000 cycles in a potential window of 4 V at 2 A g?1, while retaining 90.6% capacitance. These results indicate that the silicon‐based nanosheets can be a competitive candidate as the supercapacitor electrode material. 相似文献