Network Skeleton Research Articles

Highly Flexible Fabrics/Epoxy Composites with Hybrid Carbon Nanofillers for Absorption-Dominated Electromagnetic Interference Shielding

HighlightsHighly flexible carbon ink-loaded polyester fabric/epoxy composites with outstanding mechanical durability and absorption-dominant EMI-shielding characteristics are fabricated.The fracture toughness is ~ 38.5 MPa m1/2 and electrical conductivity is maintained after 1000 bending cycles.A superior electromagnetic interference SE/t of ~ 66.8 dB mm–1 was observed in the X-band frequency with over 0.7 absorption coefficient, related to the hierarchical structures composed of macro-scaled voids from the polyester nonwoven fabric skeleton and nano-scaled networks from SWCNTs/rGO.

Sandwich-like high-efficient EMI shielding materials based on 3D conductive network and porous microfiber skeleton

High-efficient and durable electromagnetic interference (EMI) shielding materials are urgently needed to address electromagnetic wave pollution. In this study, Ti3C2TX MXene and silver nanowires (AgNWs) were integrated at a porous microfiber skeleton (PMS) via a dip-coating method to form a sandwich-like conductive network, followed by a polyurethane (PU) fixation. Firstly, PMS was dipped with AgNWs dispersion (1D AgNWs acts as the interlayer) and then immersed in Ti3C2TX MXene nanosheets suspension (2D Ti3C2TX MXene acts as the upper and lower layers). Finally, an EMI shielding material with a sandwich-like conductive network was constructed by immersing it in diluted PU solution at ambient temperature for fixation. The conductivity of the resultant shielding material is found to be 1896.7 s⸱m-1, correspondingly, the average EMI shielding effectiveness (SE) is as high as 100.1 dB. The ideal conductivity of AgNWs and Ti3C2TX MXene, combined with the porous structure of microfiber substrate are believed to impart the resultant material excellent EMI shielding characteristics. In addition, benefiting from the protective effect of the outermost PU thin layer, the coated materials still remain their high shielding performance even after ultrasonic washing for 30 min (100 W), strong acid (pH 2.0), strong base (pH 12.0), 2000 bending-releasing cycles, 2000 folding-releasing cycles, and 1000 twisting-releasing cycles, showing excellent EMI shielding durability.

Reconstruction and Removal Mechanisms of Gel-like Membrane Fouling for Seawater Desalination: Experiments and Molecular Dynamics Simulations.

Anti-gel fouling is a key problem faced by membrane desalination, especially for applications in organic acid-rich seawater. In this paper, a chemical crosslinking-based method was used to reconstruct and characterize the gel pollutants produced under the actual operating conditions of seawater desalination. In addition to the calcium alginate/calcium humate three-dimensional network skeleton, salt ions (K+, Na+, Mg2+, Cl−) in solution were also considered to ensure that the reconstructed gel was similar to pollutant gels on membranes under practical operating conditions. Characterizations showed that the reconstructed gel has high thermal insulation and stability, thus adjusting the temperature has no removal effect. Two detergents (sodium citrate and sodium hydroxide) were investigated, and their gel-removal mechanism was elucidated by molecular dynamics simulation. Numerical analysis showed that the electrostatic attraction interaction had a significant role in the gel cleaning process. Owing to the attraction of the lower electrostatic potential region in the cleaning agent, the ion exchange between Na+ in the cleaning agent and Ca2+ in the gel led to the breaking of the Ca2+-induced intermolecular bridge in the complex. As the adhesion of fouling gels decreased, the gel water solubility was increased, resulting in a decrease in weight and strength of the gel. Therefore, the integrity of the gel fouling layer was weakened and can be effectively removed. This study provides a theoretical basis for the removal of gel-like membrane fouling during actual seawater desalination.

Evaluation of the Contribution Rates of Different Phases on Pavement Performance of Cement-Casting Asphalt Mixture

Cement-casting asphalt mixture (CCAM) exhibits excellent antirutting properties and has been widely used to address the severe rutting distress across the world. However, CCAM’s failure mechanism has not been comprehensively understood. To this end, the contribution rates of porous asphalt mixture (PAM), cementitious network, and asphalt-cement interface phases to CCAM’s pavement performance are evaluated. A novel method was developed to fabricate the cementitious network with the aid of plastic balls. Abrasion loss, strength, peak force, and fracture energy of PAM, cement samples, and CCAM samples are obtained through different tests. Analysis results show that the contribution rate of cementitious network to Cantabro loss is around 60% and that of the interface phase is around 30%. Interface phase and PAM phase approximately contribute 90% to the overall strength and fracture energy of CCAM. With the increase of polymer contents in asphalt binder, the contribution rate of PAM phase increases and the contribution rate of interface decreases. Contribution rates results together with samples’ fracture surface observation verify that the interaction between asphalt skeleton and cement network plays a vital role during CCAM’s failure process. Attention should be given to the physical-chemical interactions between asphalt and cement in the future study.

Multi-functional bilayer carbon structures with micrometer-level physical encapsulation as a flexible cathode host for high-performance lithium-sulfur batteries

With the exceptional merits of high energy density, low cost, and environmental friendliness, lithium-sulfur batteries are considered to be one of the most promising next-generation flexible rechargeable batteries. However, the notorious “shuttle effect” has seriously hindered their practical applications. Herein, a strategy for designing multi-functional bilayer carbon structures is proposed, specifically, by employing a micrometer-thick graphene nanoflowers (GF) layer to encapsulate a micrometer-scale hybrid network skeleton composed of metallic Co and carbon nanotubes (CNT) as a flexible sulfur cathode host (Co/CNT@GF). Beneficial from the merits of chemical adsorption, electrocatalysis and volume expansion mitigation from the internal skeleton as well as the micrometer-level physical domain confinement by the external GF layer, the developed host could chemically trap, electrochemically catalyze, physically block and storage the lithium polysulfides. Due to the synergistic effect of these functions, the Co/CNT@GF-S delivers a superior discharge capacity of 799 mAh g−1 with a decay rate as low as 0.08 % per cycle after 400 cycles at 1 C. Even at a high sulfur loading of 8.16 mg cm−2, the average discharge capacity is as high as 5.05 mAh cm−2 in 100 cycles. This work does not only contribute to the rational design of multi-functional bilayer structures but also offers a novel design method for the commercialization of flexible lithium-sulfur batteries with high-energy–density.

Flexible Aluminum-Air Battery Based on Ionic Liquid-Gel Polymer Electrolyte.

There is an urgent demand to develop high-performance flexible batteries for a wide range of contemporary emerging fields, including flexible electronics, wearable sensors, and implantable medical devices. However, the inherent safety and stability issues of traditional organic liquid-based electrolytes make their application in flexible batteries unsatisfactory. Therefore, exploring gel electrolytes with superior ionic conductivity and safety is considered to be the key to the development of flexible batteries. In this paper, two types of high-quality ionic liquid-based gel polymer electrolyte membranes (PVDF-ILs) are created by a conventional solution-casting method, which are further integrated into flexible aluminum-air batteries to guide the interface and process research, and the related discharge properties of two ionic liquid-based electrolyte membrane (PVDF-[C4mpyr]Cl, PVDF-[BMIM]Cl) in different bending states are discussed. The results show that PVDF-ILs have a rich pore structure and interwoven skeleton network, leading to relatively high ionic conductivity (2.97 × 10-3 S cm-1). Moreover, two types of batteries can meet the needs of flexibility, although there is a slight loss of power density under various bending conditions. In general, a PVDF-[C4mpyr]Cl-based flexible aluminum-air battery is suitable for the working conditions of high power and low bending angle, while the PVDF-[BMIM]Cl-based flexible aluminum-air battery is favored for microwatt low-power devices with high flexibility requirements.

Contribution of κ-/ι-carrageenan on the gelling properties of shrimp myofibrillar protein and their interaction mechanism exploration.

The contribution and mechanism of κ-/ι-carrageenan (CG) with different hydration characteristics on the gelling properties of shrimp myofibrillar protein (MP) gelation was studied. The gel strength, water-holding capacity and viscoelastic properties of MP gels were significantly enhanced by 1.0% κ-/ι-CG (P < 0.05), but the microstructure showed that excessive carrageenan caused fragmentation of the gel network and a corresponding decrease in gel properties. Compared to MP-ιCG, MP-κCG showed larger breaking force and shorter breaking distance, thus enhancing the hardness and brittleness of the gel, which might be ascribed to a reinforced network skeleton and a tighter binding of κCG-myosin. However, MP-ιCG stabilized more moisture in the gel network, thereby improving the tenderness of the gel, which might be related to the electrostatic repulsion observed between the sulfate groups of ιCG and the myosin observed by molecular docking. In addition, the β-sheet content and intermolecular interactions might be positively correlated with gel properties. In this study, a composite gel system was constructed based on the interaction of MP and CG. The quality differences of two kinds of CG-MP gels were clarified, which will provide guidance for the application of different kinds of carrageenan and the development of recombinant meat products with specific quality. © 2022 Society of Chemical Industry.

Reversibly Compressible Supramolecular Aerogels with Low Density and Sound Insulation Performance

AbstractIt is still a great challenge for supramolecular materials to be used as polymer systems. Here, reversibly compressible supramolecular aerogels with low density and sound insulation performance are reported, which are exclusively composed of small molecules. It is found that the mixture of melamine and isonicotinic acid can form supramolecular hydrogel. Then it could be transformed into aerogel via a simple freeze‐drying method to allow gas to replace the position of water in the 3D network skeleton pores of the hydrogel. This supramolecular aerogel is characterized of low density (1.2 mg cm‐3), high porosity (99.9%), and no volume shrinkage. In addition, the supramolecular aerogel exhibits intrinsically elastic and strong fatigue resistance under compress loading/unloading cycles. The mechanical efficiency of the supramolecular aerogel can be maintained in a wide density range without significant stiffness degradation. Remarkably, such supramolecular aerogel can be used as a sound insulator and exhibits a good sound insulation performance. Compared with the polymeric foam insulation materials, the supramolecular aerogel is environmentally friendly, easy to be fabricated and disposed. This work demonstrates the fabrication of supramolecular aerogel and expands the application of self‐assembled supramolecular materials.

Efficient cellulose aerogel biosorbents functionalized by nanosized zero-valent iron: Isotherms, kinetics, thermodynamics and mechanism of tellurium adsorption

Fabrication of eco-friendly and efficient biosorbents played a crucial role in adsorbing tellurium from wastewater, yet which was confronted with large obstacles to achieve a high adsorption capacity and biocompatibility simultaneously. Herein, a simple and economical strategy for adsorbing tellurium by nanosized zero-valent iron/ cellulose fiber hybrid aerogel (nZVI/CFA) is proposed. Cellulose fiber aerogel (CFA) was firstly fabricated by freeze-drying the cellulose fibers that were extracted from agricultural waste maize bracts. Then, the nZVI was uniformly anchored on the porous network skeleton structure of CFA by liquid-phase reduction. The nZVI/CFA exhibited mesoporous structure with a large specific surface area (399.85 m2/g), uniform pore size (3.92 nm) and pore volume (0.47 cm3/g). According to the kinetics and isothermal model, the tellurium adsorption by nZVI/CFA was uniform and endothermic-chemical on the monolayer surface. Due to the highly exposed specific surface area, more active sites and the synergistic effect of electrostatic attraction, reduction and substitution, nZVI/CFA has a high adsorption capacity (119.32 mg/g). As a low-cost and efficient biosorbent, nZVI/CFA provided a new idea for the treatment with other abandoned photovoltaic materials and agricultural waste.

Text Detection Algorithm for Natural Scenes under Attention Supervision Strategy

The existing scene text detection algorithms will include redundant background area when dealing with arbitrary shape text regions. In order to automatically learn to focus on arbitrary shape text regions, a text detection algorithm is proposed under attention supervision strategy. Firstly, deep residual network is used as the skeleton network to extract feature maps containing multi-scale information, and then the fused feature maps are converted to generate attention masks through the attention mask generation module, and through the background suppression module, the next level feature map is generated by attention mask. Finally, the segmentation masks are generated through a series of convolution operations, and the final text detection results are obtained after post-processing optimization. Experimental results show that the proposed algorithm has superior multi-index comprehensive performance on the ICDAR2015 dataset, and the <italic>F</italic>-measure is 2.1% ahead of the comparison algorithm.

Robust network topologies for temperature-inducible bioswitches

BackgroundThermoinducible bioswitches are unique in that the all-or-none switch response is triggered by temperature, which is a global factor that impacts all biochemical reaction processes. To date, temperature-inducible bioswitches rely exclusively on special thermal sensing biomolecules of DNA, RNA, proteins and lipids whose conformations are critically temperature dependent.MethodThis paper extends the traditional thermal switch by utilizing purposely designed network topologies of biomolecular interactions to achieve the switching function. By assuming the general Arrhenius law for biochemical reactions, we explore the full space of all three-node genetic interaction networks to screen topologies capable of thermal bioswitches. Three target bioswitches, i.e., thermal-inducible Off–On, cold-inducible On–Off, and hybrid Off–On-Off double switches, are considered separately.ConclusionsWe identify the minimal and core network skeletons that are basic and essential for building robust high-performance bioswitches: three Off–On motifs, three On–Off motifs, and an incoherent feedforward motif for an Off–On-Off double switch. Functional topologies are implicitly preferential in choosing parameter values to achieve the target functions. The scenario of the topology-based bioswitch we propose here is an extension of molecule-based bioswitches and would be valuable in aiding the rational design and synthesis of efficient high-performance thermal bioswitches.

Dendrobium officinale Enzyme Changing the Structure and Behaviors of Chitosan/γ-poly(glutamic acid) Hydrogel for Potential Skin Care.

Hydrogels have been widespreadly used in various fields. But weak toughness has limited their further applications. In this study, Dendrobium officinale enzyme (DOE) was explored to improve chitosan/γ-poly(glutamic acid) (CS/γ-PGA) hydrogel in the structure and properties. The results indicated that DOE with various sizes of ingredients can make multiple noncovalent crosslinks with the skeleton network of CS/γ-PGA, significantly changing the self-assembly of CS/γ-PGA/DOE hydrogel to form regular protuberance nanostructures, which exhibits stronger toughness and better behaviors for skin care. Particularly, 4% DOE enhanced the toughness of CS/γ-PGA/DOE hydrogel, increasing it by 116%. Meanwhile, water absorption, antioxygenation, antibacterial behavior and air permeability were increased by 39%, 97%, 27% and 52%.

Highly-stretchable porous thermoplastic polyurethane/carbon nanotubes composites as a multimodal sensor

Conductive polymer composites (CPCs) can be designed into stretchable sensors because of their flexibility and responses to external stimuli. However, sensors based on traditional CPCs normally exhibit unsatisfactory detection limits and narrow sensing ranges, which astrict their practical applications. Herein, we designed a new multimodal sensor based on porous CPCs composed of thermoplastic polyurethane (TPU) and carbon nanotubes (CNTs). The sensor can be used to detect the stimuli of strain, pressure, and temperature. As a strain sensor, ultra-low detection limit (0.01%) and ultrawide sensing range (0.01%–900%) are achieved simultaneously, owing to the highly stretchable TPU skeleton anchored with a microcracked CNT conductive layer. To our knowledge, the strain sensor possesses the lowest detection limit and the widest sensing range compared to previously reported CPC-based strain sensors. Meanwhile, this sensor can also output repeatable electrical responses to different pressure stimuli due to the reversible variation of the porous TPU skeleton and CNT networks during cyclic compression and release process. More interestingly, the as-prepared sensor is also capable of monitoring respiration because of its excellent linear negative temperature coefficient effect. It is credible that this highly stretchable sensor possesses tremendous potentials in human motion monitoring, personal healthcare monitoring, and human-computer interaction.

Construction of CoP/Co2P Coexisting Bifunctional Self-Supporting Electrocatalysts for High-Efficiency Oxygen Evolution and Hydrogen Evolution.

Development of a low cost, high activity, and stable nonprecious metal bifunctional catalyst for electrocatalytic water cracking is a hot topic and big challenge. In this paper, we prepared a nitrogen-doped carbon nanotube (NCNT)-enhanced three-dimensional self-supported electrocatalyst with CoP and Co2P coexistence by a two-step strategy of high-temperature carbonization and low-temperature phosphorylation. Furthermore, the induced three-dimensional carbon network skeleton facilitates rapid charge transfer. In addition, the active sites of the carbon foam (CF) are greatly increased by the construction of hollow structures. As a bifunctional electrocatalyst, CoP/Co2P/NCNT@CF exhibited excellent catalytic activity for both hydrogen evolution reaction and oxygen evolution reaction in alkaline media, requiring low overpotentials of 133 and 289 mV to obtain a current density of 10 mA cm–2, respectively. Additionally, the synthesized catalysts also exhibit good long-term stability, maintaining high catalytic activity after 20 h of continuous operation. We also confirmed the main driving force to improve the electron transfer between the heterostructures of Co and P by XPS spectra. The excellent electrocatalytic performance can be attributed to the close synergy between the highly active CoP/Co2P/NCNT and CF. This study provides a new strategy for the design of highly active bifunctional self-supporting electrocatalysts.

Coaxial 3D-printing constructing all-in-one fibrous lithium-, sodium-, and zinc-ion batteries

For battery manufacturing, 3D printing has merits of the unique intelligent and continuous characteristics. To construct the battery anode, cathode, and electrolyte network skeletons simultaneously via one-step 3D printing is a promising development direction. Here, a universal coaxial 3D printing approach was applied to construct the all-in-one fibrous lithium-ion batteries (LIBs), sodium-ion batteries (SIBs), and aqueous zinc-ion batteries (AZIBs) skeletons in one-step. The obtained anode, cathode, and separator inks can be scaled up to kilograms scale and have the obvious shear thinning characteristics, which are conducive to the large-scale coaxial 3D printing. Moreover, all the 3D printing constructed all-in-one fibrous LIBs, SIBs, and AZIBs have good electrochemical performances. The obtained all-in-one fibrous LIBs exhibit the capacity of 60 mAh g−1, high-rate capability up-to 510 mA g−1 with 33 mAh g−1, and long cycle stability up-to 1000 cycles. Meanwhile, the all-in-one fibrous SIBs deliver the high capacity (50 mAh g−1), high-rate capability (31 mAh g−1 at 500 mA g−1), and long cycle stability (2000 cycles). Similarly, the prepared AZIBs reveal the high capacity (121 mAh g−1), high-rate capability (68 mAh g−1 at 1600 mA g−1), and long cycle stability. This coaxial 3D printing strategy to construct all-in-one fibrous filaments provides a new method for the functional fibrous energy storage system.

Co-pyrolysis of industrial sludge and rice straw: Synergistic effects of biomass on reaction characteristics, biochar properties and heavy metals solidification

Co-pyrolysis of sludge and biomass was conducted to produce biochar with heavy metals solidification. The synergistic coupling mechanism and the surface functional groups and pore structure characteristics of co-pyrolytic biochar were studied. The solidification characteristics and mechanism of heavy metals were also investigated. Biomass composition in the co-pyrolysis system provided energy, solidified heavy metals and improved product quality. Compared with the weighted calculated value of two individual materials, the secondary decomposition process of co-pyrolysis was prolonged by approximately 80 °C and enhanced by 29%. OH bond, CH bond, and CO bond of co-pyrolytic biochar obtained at 500 °C increased significantly, and the carbon network structure and skeleton were enhanced, and the specific surface area increased by 102.8%, comparing with that of sludge biochar. The solidification effect of Cu and Cd in co-pyrolytic biochar was 29% and 50% higher than that in sludge biochar, respectively. The leaching rates of Cu and Cd in co-pyrolytic biochar were only 38.22% and 39.54% of that from sludge biochar. This study demonstrated that high-quality biochar with low heavy metal risk can be obtained by co-pyrolysis technology, which provides a potential way for the comprehensive utilization of industrial sludge and biomass.

Co[sbnd]Fe hydroxyoxalate nanosheets chemically bonded with reduced graphene oxide as High-performance anode for lithium-ion batteries

Transition metal layered double hydroxide (LDHs) materials are promising anodes for high-energy lithium-ion batteries (LIBs) due to their high specific capacities. However, the conductivity and the influence of intercalated anions are key issues for improving their electrochemical performances. Herein, a C2O42− intercalated CoFe-LDH nanosheets anchored on reduced graphene oxide (Co0.83Fe0.17(OH)2(C2O4)0.085·0.08H2O/rGO, CFO) composite was successfully synthesized for the first time by a two-step hydrothermal process. Graphene provides abundant nucleation sites for CoFe-LDH and forms the interconnected porous network skeleton. The intercalated C2O42− ions widen the interlayer spacing of CoFe-LDH to 0.92 nm, which can enhance the transportation of lithium ions. The lithium storage mechanism was proved that the CFO was transformed into a heterostructure nanocomposite (metal hydroxide and lithium oxalate) after discharge, and the high-valent carbon in lithium oxalate was electrocatalytically converted into low-valent carbon. This results in fast electrochemical reactions and high capacity. What’s more, the CFO shows a high reversible capacity (1603 mAh g−1 after 120 cycles), and long-term cycle stability under high current density (CFO delivers a reversible capacity of 860 mAh·g−1 after 1000 cycles at 4 A·g−1). This work provides a new anodes material for application in high-energy LIBs.

Two-Stage MILP Model for Optimal Skeleton-Network Reconfiguration of Power System for Grid-Resilience Enhancement

Skeleton-network reconfiguration is an important task and plays a most important role during power system restoration (PSR) after a blackout. By determining the skeleton network, the power system can be restored as soon as possible to minimize the burden of network reconfiguration. In this paper, a resilience-based skeleton-network reconfiguration (NR) strategy, i.e., a two-stage mixed-integer linear programming (MILP)–based NR strategy for grid-resilience enhancement, is proposed to minimize the impact of emergency power outages on power systems. The start-up sequence for non-black-start generators (NBSGs) and line energization sequences are determined in the first-stage optimization model. A serial restoration constraint and a transient frequency constraint are considered to achieve the serial restoration scheme of NBSGs. Except for the generator power, all the variables attained during the first stage are assumed fixed in the second stage. The second-stage optimization model determines the optimal skeleton network by determining the target transmission lines and critical load pickup during the NR phase. Furthermore, the sets of metrics (i.e., system flexibility, power loss ratio, and recovery time resilience) are presented to determine the grid operational resilience in the skeleton-network reconfiguration. Then, two stages of skeleton-NR are formulated as MILP, and the branch-and-bound method is presented to solve both models. Finally, simulation studies are performed on the two modified power system test cases and the results validate that the proposed strategy can efficiently determine the robust skeleton network for practical and detailed PSR planning.

Application of imine covalent organic frameworks in sample pretreatment

亚胺类共价有机骨架(I-COFs)是有机单体根据席夫碱(Schiff-base)反应原理缩合形成的一类新型多孔晶体有机材料。I-COFs具有骨架密度低、比表面积大、孔隙率高、单体种类丰富、孔径尺寸可控、结构可功能化、合成方法多样和物化稳定性好等优点。近年来,I-COFs已成为材料科学领域的研究前沿,并广泛用于气体吸附、存储、催化、传感、光电材料等方面。I-COFs材料优异的物理化学性能使其非常适于用作复杂样品中痕量目标物的分离富集介质,其高比表面积、高孔隙率性能赋予了它极高的吸附负载量,这些性能使得目标分析物可被高效富集;通过控制有机单体的链段长度、几何结构、掺杂元素、取代基团等方面精确调控I-COFs的孔洞结构和功能化基团,从而实现目标痕量物质的选择性富集。目前,I-COFs材料在样品前处理领域作为新型萃取介质已引起了极大关注。该文综述了近年来I-COFs材料的主要类型、合成方法及其在固相萃取、磁性固相萃取、分散固相萃取和固相微萃取方面的研究进展,同时展望了I-COFs在样品前处理领域的发展前景。

Laser Curve Extraction of Wheelset Based on Deep Learning Skeleton Extraction Network.

In this paper, a new algorithm for extracting the laser fringe center is proposed. Based on a deep learning skeleton extraction network, the laser stripe center can be extracted quickly and accurately. Skeleton extraction is the process of reducing the shape image to its approximate central axis representation while maintaining the image’s topological and geometric shape. Skeleton extraction is an important step in topological and geometric shape analysis. According to the characteristics of the wheelset laser curve dataset, a new skeleton extraction network, a hierarchical skeleton network (LuoNet), is proposed. The proposed architecture has three levels of the encoder–decoder network, and YE Module interconnection is designed between each level of the encoder and decoder network. In the wheelset laser curve dataset, the F1_score can reach 0.714. Compared with the traditional laser curve center extraction algorithm, the proposed LuoNet algorithm has the advantages of short running time, high accuracy, and stable extraction results.