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Zeolite supported amorphous zirconia layer with high specific surface area, abundant adsorption sites and excellent reusability hold a bright prospect in phosphate adsorption, yet it is proven to be still challenging to precisely regulate its synthesis.

To date, elemental sulfur has been considered as a prospective cathode material for exploring high-energy power systems with low cost and sustainability. However, its practical commercialization has been impeded by inherent drawbacks of notorious capacity decay, unsatisfied insulating nature, and sluggish conversion chemistry. To address these issues, for the first time, freestanding nanofibrous networks with hierarchical nanostructures are facilely constructed by inlaying electrocatalytic bimetallic chalcogenides (FexMn1-xS nanoparticles) into conductive graphene nanosheet (GN)-doped sulfurized polyacrylonitrile (SPAN) fiber matrices. Covalent-bonded SPAN featuring an insoluble mechanism serves as a reliable cathode substrate with enhanced electrostability and high sulfur utilization, while high-surface-area GN dopants promote conductivity improvement and rapid electron transfer. Meanwhile, the results prove that sulfiphilic FexMn1-xS nanoparticles with abundant electrochemically active sites facilitate construction of uniform deposition interfaces and efficient electrocatalysis conversion toward lithium polysufides. This feasible catalytic-insoluble cathode strategy drives the Li-S battery, which exhibits excellent electrochemical performances with a remarkable reversible discharge capacity of 967 mA h g-1 and a capacity retention of 623 mA h g-1 after 500 cycles. Moreover, the corresponding lithiation/delithiation mechanisms are systematically investigated through complementary morphological and spectral analyses, providing valuable insights into advanced metal-sulfur batteries.

The continuous growth of carbon nanotubes (CNTs) was realized on the surface of moving carbon fiber substrate by chemical vapor deposition (CVD). The changes in the microstructure of the catalyst precursor reduction and the catalyzed growth of CNTs during the continuous process were tracked, and the factors causing the deterioration of mechanical properties and the increase of tensile strength were discussed. The formation of catalyst nanoparticles invaded the surface of carbon fibers, cutting off the continuous graphite layer and causing a loose graphite structure. With the catalyzed growth of CNTs which have good crystallinity, the graphite cross-links between their roots and the fiber surface repaired the defects generated by the catalyst. Due to the repair of surface defects by carbon source decomposition and interface CNTs during CVD process, the tensile strength of CNTs/carbon fiber reinforcement is increased by 8.55% compared with the raw carbon fibers. This research helps to grow CNTs uniformly on the surface of carbon fibers to prepare a large number of composite reinforcements, and can maintain or even improve the overall mechanical properties.

To maintain the tendency towards lower cost and sustainability of innovative battery technologies, one challenge is the development of high-energy ecofriendly devices based on the potassium–sulfur (K–S) system using efficient sulfur-based cathodes. A free-standing flexible carbon nanotube/sulfur (CNT/S) composite cathode based on CNT film to form a conductive network on a sulfur substrate is proposed herein. The synthesized CNT/S composite takes advantages of the intercrossing microchannels of the conductive CNT networks, which clearly favors rapid charge transfer and enhanced active mass loading as well as the surface electrocatalytic effect in K–S batteries. The resulting self-supported CNT/S film cathode with high flexibility achieved high initial capacity of 585 mAh g−1 at current density of 50 mA g−1. The proposed CNT/S cathode system could thus be a promising candidate for further advancement of next-generation K–S power systems for practical applications.

The refined design of γ′-Fe4N structure plays a significant role in enhancing microwave absorption performance. γ′-Fe4N@iron oxides particles have been fabricated through an economical one-step gaseous nitriding method. The loss mechanism of the particles was studied, and the electromagnetic properties were also investigated in the frequency range of 2–18 GHz. The results show that γ′-Fe4N@iron oxides particles form a hierarchical structure with outer amorphous iron oxides, secondary outer Fe3O4, and inner γ′-Fe4N. Equipped with rugged surfaces and heterogeneities, the γ′-Fe4N@iron oxides particles feature multiple reflection and polarization characteristic, resulting in multiple relaxations in the interior of the as-fabricated particles, which enhance the microwave absorption properties. Its minimum reflection loss (RL) value can reach −38.5 dB with a thickness of 1.24 mm. We provide a facile method to fabricate particles with core-shell structure, which have great prospects for applications in microwave absorption field.

Nowadays, the application of supercapacitor in energy storage is more and more extensive, and the selection and preparation of electrode material have become a formidable challenge. Polyaniline (PANI) has turned into one of the most hopeful conductive polymers due to its superior properties. In this article, conductive polyaniline was synthesized by chemical oxidative polymerization to acquire excellent electrochemical properties. Scanning electron microscopy (SEM), X-ray diffraction (XRD), cyclic voltammetry (CV), and galvanostatic charge–discharge (GCD) measurements were adopted to explore the microstructure and energy storage capacity. The PANI is in coralline network morphology with high surface area, which can supply more active sites during charge and discharge process. The PANI shows a high specific capacitance value of 790 F/g, and the highest conductivity is 15.5 S/cm. The consequence shows that PANI synthesized under certain conditions has a promising feasibility for applications in high-performance supercapacitor electrode material.

Zeolite supported amorphous metal oxide nanolayers with high specific surface area, abundant adsorption sites, and excellent reusability hold a bright prospect in the efficient removal of contaminants, yet it is proven to be still challenging to precisely regulate and control their synthesis. Herein, we reported a facile synthetic strategy for rational design and achieving the uniform and firm

Polyacrylonitrile (PAN) nascent fiber plays an important role in the structural formation and development of the precursor fibers and carbon fibers. This work is used to evaluate the effect of dryi...

Graphene (GN) is transformed into carboxylic graphene (GO-COOH) with carboxylic groups by acidizing. Carboxylic graphene/polyimide (GO-COOH/PI) composite films are prepared by in-situ polymerization. The composite films show strong intermolecular force compared to the PI films which leads to excellent tensile strength and thermal conductivity. The composite films can be transformed into carbon films and graphite films by carbonization and graphitization. The GO-COOH can induce the graphitization process and compensate the defects. The thermal conductivity of graphite films prepared by composite films graphitized at the same temperature is higher compared to that of PI films. The addition of GO-COOH has great effects on reducing carbonization and graphitization temperature and improving property of films. The graphite films treated with 2500 °C possess smoother surface and the color of graphite films turn into dark grey. The films can keep the integral state and bend to a certain extent which exhibits that the flexibility of the graphite films is improved. The thermal conductivity of graphite films prepared by composite films treated with 2500 °C is 760.386 W/mK and increases by 128% compared to that prepared by the PI films, which is suitable for the application of heat conduction.

This article provides a method for growing carbon nanotubes(CNTs) on carbon fibers(CFs) using iron and nickel as catalysts at low temperatures. This series of experiments was conducted in a vacuum chemical vapor deposition(CVD)furnace. It is found that Fe–Ni catalysts, which have a certain thickness and can be better combined with resins when manufacturing composite materials, are more ideal for the growth of CNTs than single metal catalysts. At the same time, it is proved that the CVD process worked best at 450 °C. The mechanical property test proved the reinforcing effect of CNTs on carbon fiber, the single-filament tensile strength of CFs obtained by using Fe–Ni catalyst at 450 °C was 11% higher than that of Desized CFs. The bonding strength of carbon fiber and resin has also been significantly improved. When synthesized at low temperature, CNTs exhibited a hollow multi-wall structure.

Two kinds of Fe/C nanofibers were prepared by electrospinning and calcination under the same process conditions. A simple way was used to adjust the size of the Fe nanoparticles by using different spinning solvents. The one was prepared by a mixture of water and anhydrous alcohol as solvents (named as CNFwater) and the other by N,N-Dimethylformamide and anhydrous alcohol (named as CNFDMF). Due to the higher solubility to iron salts and larger surface tension of water, CNFwater gained a larger size of Fe nanoparticles and average diameter. In addition, the graphite layers wrapped on Fe nanoparticles which were formed during calcination were thinner in CNFwater than CNFDMF. These factors endowed CNFwater better microwave absorption performance. The results of XRD, SEM, HRTEM, Raman, magnetostatic and electromagnetic properties analysis revealed the influence mechanisms of solvents on the formation, microstructure and properties of Fe/C nanofibers.

This paper aims to develop a catalyst for highly efficient growth of carbon nanotubes (CNTs) on carbon fibers (CFs) with improved tensile strength by chemical vapor deposition (CVD). The effect of the composition of Fex-Co1-x catalysts on the morphology of the synthesized CNTs and the tensile properties of the CFs at different stages of the CVD process were explored. It was found that the bimetallic catalysts possessed better catalytic effect than monometallic catalysts at low temperature. The detailed study of the tensile properties of CFs at different stages of CVD process manifested that the composition of catalysts affected the catalytic activity. When the atomic fraction of Fe was 50%, the bimetallic catalyst among Fex-Co1-x family was considered to hold the highest catalytic efficiency due to the least damage to the fibers and the ability to generate more carbon atoms to repair and reinforce CFs. The corresponding tensile strength of the final CNTs-grafted CFs was 11.53% higher than that of the desized CFs.

The effect of spinning speed on the microstructures and mechanical properties of polyacrylonitrile (PAN) fibers and carbon fibers was investigated. The microstructures and mechanical properties of PAN fibers and resulted carbon fibers were characterized. When winding speed increased from 63m/min to 95m/min, the fibers still exhibited smooth surfaces, and the diameter and aspect ratio of fibrils increased. In early spinning stages, the lamellae were arranged orderly and PAN fibers had larger crystallinity at low spinning speed. After densifying process, the crystal layers were stacked regularly and their crystallinity was larger at high spinning speed, and the resulted precursor fibers had big thermal stability and large dimethylsulfoxide (DMSO) residue value. Meanwhile, the tendency of mechanical strengths of PAN fibers was in accord with their crystallinity changes. Increasing spinning speed brought the negative influence on microstructures and mechanical properties of the resulted carbon fibers, and the carbon fibers owned low tensile strength due to relatively poor crystallinity and graphitic structures.

Coagulation process is one of the most important stages of the microstructure formation and evolution in polyacrylonitrile (PAN) fibers during the spinning process. The network and lamellae were fu...

This paper focuses on improving the out-of-plane properties of carbon fiber/epoxy composites to extend their applications. Carbon nanotubes (CNTs) were introduced on carbon fiber surface by a novel one-step chemical vapor deposition (CVD) method at ultra-low temperature and hybrid composites were fabricated by molding technology. Mechanical and dielectric tests were conducted to figure out the changes in out-of-plane properties after grafting CNTs. The results of single-fiber tensile strength indicated that both the strength and the Weibull modulus of the CNTs-coated carbon fiber increased due to the less damage caused to the fiber by catalysts at low temperature and the repairing effect of the CNTs. Compared with the properties of desized fiber based composites, both interfacial shear strength (IFSS) and interlaminar shear strength (ILSS) of CNTs-coated fiber/epoxy composites increased by 30.73% and 32.29%, respectively, as well as the dielectric properties were also improved. The fracture mechanisms of CNTs were investigated based on the morphology observation on the interface. The improved out-of-plane properties were associated with the improved stress transfer between the carbon fibers and surrounding matrix through the newly formed interphase induced by CNT layer.

Carbon films prepared by polyimide (PI) films treated under 1500°C exhibit favorable thermal conductivity. However, the bonds of carbon films will fracture and recombine which will cause shrinking and forming defects. The flexibility of the carbon films will be greatly reduced, and then affect the application of the carbon films in the field of thermal conduction. When the films prepared by the graphene oxide/polyimide (GO/PI) composite films and the reduced graphene oxide/polyimide (rGO/PI) composite films, respectively, rGO and GO can fill the defects, then increasing the flexibility of the carbon films and inducing the carbonation process. Because of the high thermal conductivity and the six-membered ring structure of rGO and GO, the carbonization temperature will decrease and save costs. When the composite films treated under 1500°C, the thermal conductivity increases with the content of rGO and GO. There are connections between PI and graphene. As the amount of rGO and GO increases, the strong interactions between the rGO or GO and PI lead to contact that enhances its thermal conductivity. However, the rGO and GO have different effects on the films flexibility and thermal conductivity and the differences will be described in the article.

The microfibrils served as the structural elements in polyacrylonitrile (PAN) fiber, which played an important role in the quality of the PAN precursor fibers. Their morphologies were examined by the scanning electron microscopy (SEM), atomic force microscopy (AFM) and high-resolution transmission electron microscope (HRTEM). The microfibrils existed in all of PAN fibers and arranged evenly in the cross-sections. Furthermore, the pores existed between the microfibrils. The unoriented microfibrillar network was already formed in nascent fiber during coagulated process. Although the microfibrillar network was elongated and the microfibrils oriented along the fiber longitudinal direction during the spinning process, the interconnected microfibrillar network was still existed in the fiber transverse section. Furthermore, the transverse connection of the microfibrils was reinforced and the small microfibrils were tended to aggregate into the large fibrils. For mechanical performance of PAN fibers, their tensile strength increased to 708 MPa and the elongation at break decreased to 15.5%. PAN fibers exhibited ductile rupture during the mechanical test and the microfibrils served as reinforcing elements.

The dry-jet wet spinning polyacrylonitrile fibers (PAN fibers) were preoxidized in six gradient-elevated temperature zones and the internal structure changed greatly. Ultrathin sections for electron microscopy were used to study the internal structure of the fibers, and the fibril structure in the fibers was first observed by ultrasonic etching under a high-resolution transmission microscope. The fibers were ultrasonically etched in dimethyl sulfoxide (DMSO) solution to separate the fibril structure. The fibril structure is parallel to the fiber axis and the lamellar-plate structure is arranged perpendicular to the fiber axis.

To date, elemental sulfur has been considered as a prospective cathode material for exploring high-energy power systems with low cost and sustainability. However, its practical commercialization has been impeded by inherent drawbacks of notorious capacity decay, unsatisfied insulating nature, and sluggish conversion chemistry. To address these issues, for the first time, freestanding nanofibrous networks with hierarchical nanostructures are facilely constructed by inlaying electrocatalytic bimetallic chalcogenides (Fe

Owing to the insoluble organosulfur mechanism and stable cycling life, sulfurized polyacrylonitrile (SPAN) developed as a promising cathode material for high-energy potassium–sulfur batteries (KSBs). However, it is yet a major challenge to achieve fast catalytic kinetics and high reversible capacity in SPAN-based cathodes. Here, one-step electrospun SPAN nanofibers embedded with Fe[Formula: see text]Nb[Formula: see text]O metal oxide nanoparticles (FeNb@SPAN) have been successfully developed to construct sulfur electrodes with high electrochemical activity, high sulfur utilization, and high cycling stability. The as-prepared freestanding FeNb@SPAN composite cathode, which featuring interwoven nanofibers with Fe[Formula: see text]Nb[Formula: see text]O nanoparticles homogeneously implanted, possesses high storage space for volume expansion and suppresses polysulfide dissolution during potassiation/depotassiation. Benefiting from its unique structure and composition in electrode design, the FeNb@SPAN cathode is endowed with outstanding energy storage performances with a high initial specific capacity of 776 mAh [Formula: see text] g[Formula: see text] under 50 mA [Formula: see text] g[Formula: see text] and an excellent cycling capability of 201 mAh [Formula: see text] g[Formula: see text] after 80 charge/discharge processes. This work heralds a feasible strategy toward SPAN-based sulfur host materials in the structural design of next-generation high-performance cathode materials for KSBs and other metal–sulfur batteries.