Flexible transparent electrodes are critically important for the emerging flexible and stretchable electronic and optoelectronic devices. To this end, transparent polymer films coated with silver ...nanowires (AgNWs) have been intensively studied in the past decade. However, it remains a grand challenge to achieve both high conductivity and transmittance in large‐area films, mainly due to the poor alignment of AgNWs and their high junction resistance. Here, the successful attempt to realize large‐area AgNW patterns on various substrates by a 2D ice‐templating approach is reported. With a relatively low dosage of AgNWs (4 µg·cm−2), the resulted flexible electrode simultaneously achieves high optical transmittance (≈91%) and low sheet resistance (20 Ω·sq−1). In addition, the electrode exhibits excellent durability during cyclic bending (≈10 000 times) and stretching (50% strain). The potential applications of the flexible transparent electrode in both touch screen and electronic skin sensor, which can monitor the sliding pressure and direction in real‐time, are demonstrated. More importantly, it is believed that the study represents a facile and low‐cost approach to assemble various nanomaterials into large‐area functional patterns for advanced flexible devices.
A 2D ice‐templating approach has been developed to assemble silver nanowires (AgNW) into large‐area patterns for a high‐performance flexible transparent electrode. The excellent alignment of the AgNW pattern provides a high contact area, yielding a high optical transmittance (≈91%) and low sheet resistance (20 Ω sq−1) simultaneously with a relatively low dosage of AgNWs (4 µg cm−2). This 2D ice‐templating approach is versatile enough to assemble various building blocks into large‐area patterns with designable topology and function, which are strongly demanded for advanced electronic devices.
Animals living in the extremely cold environment, such as polar bears, have shown amazing capability to keep warm, benefiting from their hollow hairs. Mimicking such a strategy in synthetic fibers ...would stimulate smart textiles for efficient personal thermal management, which plays an important role in preventing heat loss and improving efficiency in house warming energy consumption. Here, a “freeze‐spinning” technique is used to realize continuous and large‐scale fabrication of fibers with aligned porous structure, mimicking polar bear hairs, which is difficult to achieve by other methods. A textile woven with such biomimetic fibers shows an excellent thermal insulation property as well as good breathability and wearability. In addition to passively insulating heat loss, the textile can also function as a wearable heater, when doped with electroheating materials such as carbon nanotubes, to induce fast thermal response and uniform electroheating while maintaining its soft and porous nature for comfortable wearing.
A textile with excellent thermal insulation capability, mimicking the porous structure of polar bear hair, is fabricated by a “freeze‐spinning” technique to continuously spin silk fibroin solution into aligned porous fibers. Doped with electroheating materials, this type of textile is beneficial for personal thermal management, thermal stealth in military applications, and wearable electronics.
To address single-phase grounding fault line selection problem in small current grounding distribution network, the paper proposes a fault line selection method based on zero-sequence current (ZSC) ...increment. The method downshift grounding transformer (GT) tap step-by-step to amplify fault current, defines the line with largest ZSC variation as fault line. The results of typical non-effectively grounding 10 kV distribution network show the rationality and applicability of the proposed method.
Highly selective and direct electroreductive ring‐opening carboxylation of epoxides with CO2 in an undivided cell is reported. This reaction shows broad substrate scopes within styrene oxides under ...mild conditions, providing practical and scalable access to important synthetic intermediate β‐hydroxy acids. Mechanistic studies show that CO2 functions not only as a carboxylative reagent in this reaction but also as a promoter to enable efficient and chemoselective transformation of epoxides under additive‐free electrochemical conditions. Cathodically generated α‐radical and α‐carbanion intermediates lead to the regioselective formation of α‐carboxylation products.
Highly selective and direct electroreductive ring‐opening carboxylation of epoxides with CO2 in an undivided cell to yield synthetically important β‐hydroxy acids is described. CO2 functions not only as a carboxylative reagent in this reaction but also as a promoter to enable efficient and chemoselective transformation of epoxides under additive‐free electrochemical conditions.
Replicating nacre's multiscale architecture represents a promising approach to design artificial materials with outstanding rigidity and toughness. It is highly desirable yet challenging to ...incorporate self-healing and shape-programming capabilities into nacre-mimetic composites due to their rigidity and high filler content. Here, we report such a composite obtained by infiltrating a thermally switchable Diels-Alder network polymer into a lamellar scaffold of alumina. The chemical bond switchability and the physical confinement by the filler endows the composite with sufficient molecular mobility without compromising its thermal dimension stability. Consequently, our composite is capable of self-healing internal damages. Additionally, in contrast to the intractable planar shape of other artificial nacres, precise control of the polymer chain dynamics allows the shape of our composite to be programmed permanently via plasticity and temporarily via shape memory effect. Our approach paves a new way for designing durable multifunctional bioinspired structural materials.
The usage of elemental sulfur (S8) for constructing sulfur‐containing polymers is of great significance in terms of sulfur resource utilization or fabrication of high‐performance polymers. Currently, ...the random disassembly of S8 hinders its direct use in the precise synthesis of sulfur‐containing polymers. Herein, we provide an effective strategy for controlling the dismantlement of S8 to synthesize polydisulfides, a promising category of dynamic bonds containing polymers. In this strategy, the completely alternating copolymerization of one sulfur atom, which is orderly derived from S8, with episulfides is achieved with MTBD (7‐methyl‐1,5,7‐triazabicyclo4.4.0dec‐5‐ene) as catalyst and PPNSbF6 (PPN+ is bis(triphenylphosphine)iminium) as cocatalyst. Delightedly, the living‐ polymerization feature, and the good monomer compatibility allows for the access to diverse polydisulfides. Furthermore, the density functional theory (DFT) was employed to elaborate the copolymerization process.
A strategy for controlling the orderly disassembly of elemental sulfur (S8) in the presence of MTBD (a hindered organic base) and PPNSbF6 (an ammonium salt) is described for constructing polydisulfides by copolymerizing with episulfides. The “living polymerization” feature and good monomer compatibility of this copolymerization allows for the access to diverse polydisulfides with well‐defined structures and excellent optical properties.
The operation efficiency evaluation for distribution network line is helpful to improve the management level of power grid enterprises. The paper presents an analysis model for optimal operation ...efficiency of line in distribution network considering reliability and economy. Firstly, the operation efficiency of line in distribution network is defined, and its calculation method is proposed in combination with safety and economy. Then reliability assessment with different load components is executed. Finally, the actual load rate is optimized to improve operation efficiency of line in distribution network. The proposed analysis model is tested in distribution system.
Polymeric materials possessing both high refractive indices and high Abbe numbers are much in demand for the development of advanced optical devices. However, the synthesis of such functional ...materials is a challenge because of the trade‐off between these two properties. Herein, a synthetic strategy is presented for enhancing the optical properties of CO2‐based polycarbonates by modifying the polymer's topological structure. Terpolymers with thiocarbonate and carbonate units randomly distributed in the polymers’ main chain were synthesized via the terpolymerization of cyclohexene oxide with a mixture of CO2 and COS in the presence of metal catalysts, most notably a dinuclear aluminum complex. DFT calculations were employed to explain why different structural sequence were obtained with distinct bimetallic catalysts. Varying the CO2 pressure made it possible to obtain terpolymers with tunable carbonate linkages in the polymer chain. More importantly, optical property studies revealed that terpolymers with comparable thiocarbonate and carbonate units exhibited a refractive index of 1.501 with an enhanced Abbe number as high as 48.6, much higher than the corresponding polycarbonates or polythiocarbonates. Additionally, all terpolymers containing varying thiocarbonate content displayed good thermal properties with Tg>109 °C and Td>260 °C, suggesting little loss in the thermal stability compared to the polycarbonate. Hence, modification of the topological structure of the polycarbonate is an efficient method of obtaining polymeric materials with enhanced optical properties without compromising thermal performance.
Terpolymers with randomly distributed sulfur atoms were synthesized via terpolymerization of cyclohexene oxide with a mixture of CO2 and COS in the presence of a dinuclear aluminum complex. Varying the CO2 pressure made tunable carbonate linkages possible. Terpolymers with comparable thiocarbonate and carbonate units exhibited a much higher Abbe number than the corresponding polycarbonates or polythiocarbonates.
In the past few decades, the arcing‐high‐impedance fault (arcing‐HIF) detection problems have become an important issue in the effectively grounded distribution network. Many solutions have been ...proposed to address this problem. The most attractive way is artificial intelligence (AI) method. The paper gives a comprehensive review of arcing‐HIF detection in distribution network‐based AI. First, characteristics and models of arcing‐HIF are analysed, the arcing‐HIF database construction method is also explained; this part is a foundation work for arcing‐HIF detection. Next, arcing‐HIF detection methods based AI are summarised in details including data acquisition, feature extraction and classifier selection. Then, a set of criteria are proposed to evaluate the reliability of arcing‐HIF detection algorithm. Finally, the future trends and challenges to arcing‐HIF detection are also fully accounted. This review can be a valuable guide for researchers who are interested in arcing‐HIF detection‐based AI.
Liquid absorption and recycling play a crucial role in many industrial and environmental applications, such as oil spill cleanup and recovery, hemostasis, astronauts' urine recycling, and so on. ...Although many liquid absorbing materials have been developed, it still remains a grand challenge to achieve both fast absorption and efficient recycling in a cost‐effective and energy‐saving manner, especially for viscous liquids such as crude oil. A smart polyurethane‐based porous sponge with aligned channel structure is prepared by directional freezing. Compared to common sponges with random porous structure, the as‐prepared smart sponge has larger liquid absorption speed due to its lower tortuosity and stronger capillary (“tortuosity effect”). More importantly, the absorbed liquid can be remotely squeezed out due to a thermally responsive shape memory effect when the sponge is heated up. Such smart sponges with well‐defined porous structure and thermal responsive self‐squeezing capability have great potential in efficient liquid absorption and recycling.
A smart porous sponge with aligned channel structure is fabricated by directional freezing. Compared to sponges with random porous structure, the as‐prepared sponge has larger liquid absorption speed due to its lower tortuosity. The absorbed liquid can be remotely squeezed out due to thermally responsive shape memory effect. Such sponges have great potential in efficient liquid absorption and recycling.
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