Carbon Nanofiber Composites Research Articles

Microwave absorption properties of Ni-substituted cobalt ferrite-loaded carbon nanofiber composites

The NixCo1−xFe2O4 (x = 0, 0.25, 0.5, 0.75)/CNFs composites were synthesized in situ by solvothermal method. A series of characterizations of the prepared samples includes X-ray diffraction (XRD), scanning microscope (SEM), vibrating sample magnetometer (VSM) and a vector network analyzer (VNA). XRD and SEM results indicated that the particles have good crystallinity and no other impurities. With the increase of Ni ion doping, the average particle size of the sample gradually decreased, smaller microspheres were beneficial to the bonding of CNFs and Ni0.5Co0.5Fe2O4 particles, and CNFs formed a good encapsulation structure. Combined with the VSM analysis, the change of Ni2+ content results in an increase in the value of Ms, while the values of Mr and Hc decreased slightly, and its magnetic properties were optimized. The complex permittivity and permeability of the NixCo1−xFe2O4/CNFs composites at a frequency of 1–18 GHz were tested by VNA, and the reflection loss (RL) was calculated. The results illustrated that when the Ni2+ doping amount is 50 %, Ni0.5Co0.5Fe2O4/CNFs particles have considerable absorbing performance, the minimum reflection loss reached − 42.24 dB at 14.68 GHz, the effective absorbing frequency band was 4 GHz (12.39–16.40 GHz), and the corresponding matching layer thickness was only 1.5 mm. Therefore, Ni0.5Co0.5Fe2O4/CNFs particles could be used as a thin layer of strong absorbing material.

Processing, microstructure and electrochemical properties of reduced graphene oxide reinforced carbon nanofiber formed by gyration

In this paper, graphene oxide (GO) were added into polyacrylonitrile to prepare carbon nanofiber by using gyration and subsequent carbonization process as to improve their electrochemical properties. The microstructure and electrochemical properties of prepared carbon nanofiber samples were investigated by using scanning electron microscopy and electrochemical workstation, respectively. The effects of the addition amount of graphene oxide and carbonation temperature on the microstructure and electrochemical properties of composite carbon nanofibers were studied.

Fabrication of 3D ordered needle-like polyaniline@hollow carbon nanofibers composites for flexible supercapacitors

Carbon nanofiber-based supercapacitors have broad prospects in powering wearable electronics owing to their high specific capacity, fast charge/discharge process, along with long-cycling life. Herein, a poly(acrylonitrile-co-β-methylhydrogen itaconate) copolymer was prepared and used to synthesize flexible hollow carbon nanofibers (HCNFs) via an electrospinning method without breaking after multiple bending. Subsequently, the inner and outer surfaces of HCNFs were evenly covered with ordered needle-like polyaniline (PANI) through in-situ polymerization methods to obtain three-dimensional flexible HCNFs/PANI composites, which exhibited a high capacity 1196.7 F/g at 1 A/g and good cycling stability (90.1% retention at 5 A/g after 3000 cycles). The symmetrical supercapacitor based on the HCNFs/PANI composites also delivered an outstanding electrochemical performance with high energy/power density (60.28 Wh/kg at 1000 W/kg) and superior cycling durability (90% capacitance retention after at 5 A/g 3000 cycles), which confirmed that the HCNFs/PANI composites had a wide application potential in flexible energy storage devices.

Improving the cycle performance of MgFe2O4 anode material based on the spatial limiting effect

A sesame straw-like MgFe2O4/N-doped hollow porous carbon nanofiber (MFO/NPCNF) composite was first designed and synthesized successfully by electrostatic spinning and spatial confinement strategy. Spherical MgFe2O4 nanoparticles about 15 nm are in-situ spatially confined grown and well dispersed in the porous and hollow structure of NPCNF by the interaction between ultrafine MgFe2O4 nanoparticles and N-doped site, which can not only improve the conductivity, promote the penetration of electrolyte, accelerate the transfer of lithium ions and enhance the reaction kinetics, but also buffer the volume expansion and improve the cycling capacity and stability. Owing to the superior structure design, the MFO/NPCNF anode shows a high cycle capacity of 1205.8 mAh g−1 after 250 cycles at 0.5 A g−1 and excellent rate performance with 359.5 mAh g−1 at a current density up to 10 A g−1, which is near to the theoretical specific capacity of commercial graphite.

N-Doped Carbon Nanofibers Encapsulating CoO@Co <sub>9</sub>S <sub>8</sub> Nanoparticles: Preparation from Thiacalixarene-Supported Co <sub>32</sub> Cluster Precursors by Electrospinning and Application for Superior Li-Ion Storage

Thiacalixarene-supported Co32nanoclusters as precursors encapsulated in polyacrylonitrile nanofibers (Co32@PAN-NFs) by electrospinning has been utilized to fabricate N-doped CoO@Co9S8 carbon nanofibers (CoO@Co9S8@CNFs) for superior Li-ion storage. The S-riching Co32 clusters capped by organic sheets afforded the well dispersed cobalt oxide/sulfide nanoparticles embedded in carbon nanofiber composites by direct calcination. The N-doped CoO@Co9S8 @CNFs nanocomposite has been utilized as anode materials for lithium ion battery with the reversible capabilities being of 1051.8, 967.6, 894.7, 782.7, 669.5 and 525.4 mAh·g-1 at 0.1, 0.2, 0.5, 1, 2 and 3 A·g-1, respectively. The CoO@Co9S8 @CNFs also showed a relatively high stable capacity of 551.7 mAh·g-1 at the current density of 1 A·g-1 after 200 cycles of rate experiments. The as-obtained N-doped CoO@Co9S8 @CNFs nanocomposites exhibited superior reversible capacity, rate performance, coulomb efficiency (74.5% vs 63.9%) and cyclic stability comparing with CoO@Co9 S8@C derived from simple annealing of Co32 templates.

Li–fluorine codoped electrospun carbon nanofibers for enhanced hydrogen storage

Carbon materials have attracted increasing attention for hydrogen storage due to their great specific surface areas, low weights, and excellent mechanical properties. However, the performance of carbon materials for hydrogen absorption is hindered by weak physisorption. To improve the hydrogen absorption performance of carbon materials, nanoporous structures, doped heteroatoms, and decorated metal nanoparticles, among other strategies, are adopted to increase the specific surface area, number of hydrogen storage sites, and metal catalytic activity. Herein, Li–fluorine codoped porous carbon nanofibers (Li–F–PCNFs) were synthesized to enhance hydrogen storage performance. Especially, perfluorinated sulfonic acid (PFSA) polymers not only served as a fluorine precursor, but also inhibited the agglomeration of lithium nanoparticles during the carbonization process. Li–F–PCNFs showed an excellent hydrogen storage capacity, up to 2.4 wt% at 0 °C and 10 MPa, which is almost 24 times higher than that of the pure porous carbon nanofibers. It is noted that the high electronegativity gap between fluorine and lithium facilitates the electrons of the hydrogen molecules being attracted to the PCNFs, which enhanced the hydrogen adsorption capacity. In addition, Li–F–PCNFs may have huge potential for application in fuel cells.

Effect of microstructure of carbon nano-fiber dispersed pure aluminum composites on mechanical and thermal properties

Effect of microstructure of carbon nano-fiber dispersed pure aluminum composites on mechanical and thermal properties

In situ synthesis hydrophobic Co/CoO/C nanofibers with enhanced microwave absorption

Carbon nanofiber composites could be used as a microwave absorbing candidate owing to its lightweight and dielectric properties. In this work, the carbon-based nanofibers were synthesized using cobalt acetate tetrahydrate (CoAc)/poly (vinyl alcohol) (PVA) as a precursor solution via the electrospinning and vacuum carbonization at 650 °C. Co and CoO were simultaneously introduced into carbon nanofibers (CNFs). The CNFs absorber with an especially low filling ratio of 10% exhibited excellent microwave absorbing properties. The minimum reflection loss (RL) reached −43.57 dB at 10.48 GHz with a matching thickness of 3 mm, and the wideband effective absorption (RL ≤ −10 dB) reached 5.78 GHz (10.94–16.72 GHz) at 2.5 mm. The superior absorption performance of the as-prepared CNFs resulted from the formation of CoO, causing the improvement of impedance matching and interfacial polarization. Besides, the CNFs displayed good hydrophobicity due to the roughened surfaces. These newly synthesized Co/CoO/CNFs might be considered as a prospective candidate for highly efficient microwave absorption materials with a self-cleaning function.

Frequency-dependent alternating current piezoresistive switching behavior in self-sensing carbon nanofiber composites

Carbon nanofillers have received much attention for piezoresistive-based self-sensing of deformation in polymeric, cementitious, and ceramic composites. To date, direct current (DC) conductivity has been overwhelmingly favored for self-sensing. This is important because alternating current (AC) methods, though much less studied, have advantages over DC methods. Therefore, we herein explore AC conductivity-strain relations for polymeric carbon nanofiber (CNF) composites. It was found that Jonscher’s power law accurately describes AC conductivity as a function of both normal and shear strain. This provides a framework by which macroscale AC piezoresistivity can be characterized. Further, it was observed that the coefficients of this power law are non-linear in strain. During this testing, it was also observed that the CNF/epoxy exhibits a frequency-dependent piezoresistive switching behavior. At low frequencies, the material exhibits positive piezoresistivity. At higher frequencies, however, the material exhibits negative piezoresistivity. A state of zero piezoresistivity also exists between these cases. Computational micro-modeling revealed that this piezoresistive switching behavior is the consequence of inter-CNF AC transport behaving like a parallel resistor-capacitor arrangement and strain affecting the parallel or tunneling resistance. This novel switching behavior opens the door to many exciting possibilities for frequency-selective piezoresistive behavior in next-generation carbon nanofiller-based sensors.

Free-Standing, Foldable V2 O3 /Multichannel Carbon Nanofibers Electrode for Flexible Li-Ion Batteries with Ultralong Lifespan.

Free-standing electrodes with high energy density and long life are of critical importance to the development of lithium-ion batteries (LIBs) for flexible/wearable electronic devices. Herein, the free-standing and foldable V2 O3 /multichannel carbon nanofibers (V2 O3 /MCCNFs) composites are prepared via electrospinning and subsequent carbonization. Such V2 O3 /MCCNFs electrode delivers a superior capacity of 881.1 mAh g-1 at 0.1 A g-1 after 240 cycles. More importantly, the ultralong lifespan is achieved with a high capacity of 487.8 mAh g-1 even after 5000 cycles at a high current density of 5 A g-1 with only 0.00323% decay rate, which shows the best performance among the reported V2 O3 -based anodes and other metal oxides based free-standing anodes. Furthermore, this flexible electrode is further applied to the pouch cell, which exhibits prominent capacity of 348.3 mAh g-1 after 500 cycles at 1 A g-1 with 0.094% decay per cycle. The unprecedented performance can be ascribed to synergetic contributions of V2 O3 and multichannel carbon nanofibers, which not only promote the penetration of electrolyte and reduce the transport length of Li+ , but also increase active material/electrolyte contact area and buffer the volume change. This work paves the way to develop free-standing electrode for flexible/wearable electronic devices with ultralong lifespan.

Rational Fabrication and Improved Lithium Ion Battery Performances of Carbon Nanofibers Incorporated with α-Fe2O3 Hollow Nanoballs

The present results contribute a facile route to prepare carbon nanofibers hybrided with hollow metal oxide nanoparticles under the assistance of Kirkendall effect. α‒Fe2O3 hollow nanoball incorporated carbon nanofibers (denoted as FOCNFs) are rationally fabricated by using electrospun composite carbon nanofibers (CNFs) as the precursors. The hollow nanoparticles are 69.8 nm in the average size with the shell thickness of 14 nm. The composite nanofibers are hierarchically porous. The mesopores are in the range of 2 ‒ 10 nm and center at 3.7 nm. The micropores center at 0.5 nm with the micropore volume of 0.02 cm3·g−1. Time dependant morphology evolutions confirm that the formation of α‒Fe2O3 hollow nanoballs is promoted by the nanoscale Kirkendall effect due to the migration difference between oxygen molecules and Fe3+ cations in the solid. This route is also successfully extended to fabricate hollow Co3O4 and NiO nanoparticles incorporated carbon nanofibers. FOCNFs exhibit improved lithium ion battery performances with enhanced capacity, rate capability and long-term cycling stability. The optimized sample of FOCNFs‒30 delivers a high initial capacitance of 1903.8 mAh·g-1 at 100 mA·g-1. A reversible capacity of 601.2 mAh·g-1 sustains at 0.1 C after 300 charge-discharge cycles. The improved electrochemical performances of FOCNFs stem from coupling the characteristics of α-Fe2O3 nanoballs and porous nanofibrous carbon matrix.

Self-supporting N, P doped Si/CNTs/CNFs composites with fiber network for high-performance lithium-ion batteries

Silicon (Si) with high theoretical capacity has attracted much attention as anode materials of lithium-ion batteries (LIBs). However, the tendency of Si particles to easily expand leads to the rapid attenuation of capacity, which greatly limits their practical applications. In this work, the nitrogen (N) and phosphorus (P) doped Si/CNTs carbon nanofibers (Si/CNTs/CNFs) composites has been fabricated and explored as electrode material for LIBs. N, P doped Si/CNTs/CNFs composites possess unique fiber network structure with suitable space, which can effective buffer volume expand during charge-discharge process. By evaluating lithium storage performances of N, P doped Si/CNTs/CNFs composites as Li-ion battery electrodes, excellent rate performance with a capacity of 529 mA h g−1 (at 5.0 A g−1) and remarkable cycling performance of 1142 m Ah g−1 after the 100 cycles (at 0.2 A g−1) are obtained. Such outstanding performances can be attributed to the unique fiber network structure and the doping of N and P, which provides a new avenue for the studies of high-performance Si based anode materials of LIBs.

Synthesis and Characterization of ZnO-TiO2/Carbon Fiber Composite with Enhanced Photocatalytic Properties.

Herein, we prepared a novel photocatalytic ZnO-TiO2 loaded carbon nanofibers composites (ZnO-TiO2-CNFs) via electrospinning technique followed by a hydrothermal process. At first, the electrospun TiO2 NP-embedded carbon nanofibers (TiO2-CNFs) were achieved using electrospinning and a carbonization process. Next, the ZnO particles were grown into the TiO2-CNFs via hydrothermal treatment. The morphology, structure, and chemical compositions were studied using state-of-the-art techniques. The photocatalytic performance of the ZnO-TiO2-CNFs composite was studied using degrading methylene blue (MB) under UV-light irradiation for three successive cycles. It was noticed that the ZnO-TiO2-CNFs nanocomposite showed better MB removal properties than that of other formulations, which might be due to the synergistic effects of carbon nanofibers and utilized metal oxides (ZnO and TiO2). The adsorption characteristic of carbon fibers and matched band potentials of ZnO and TiO2 combinedly help to boost the overall photocatalytic performance of the ZnO-TiO2-CNFs composite. The obtained results from this study indicated that it can be an economical and environmentally friendly photocatalyst.

Setaria Viridis-Inspired Electrode with Polyaniline Decorated on Porous Heteroatom-Doped Carbon Nanofibers for Flexible Supercapacitors.

Carbon nanofibers are promising as primary electrode materials for supercapacitors on account of high specific surface area, lightweight, superior physicochemical stability, rich resource, and renewability. However, constructing porous and flexible carbon electrode materials with high capacitance for practical applications remains challenging. Here, heteroatom-decorated hierarchical porous carbon nanofiber composites containing phosphazene [N3P3(p-OC6H4-p-CHO)6, HAPCP], polymethyl methacrylate (PMMA), and graphene oxide (GO) are prepared through one-step electrospinning and subsequent thermal treatment. The alternant phosphorus-nitrogen structure links to the carbon backbones to improve flexibility and electrochemical performance. Inspired by a biomimetic Setaria viridis-like structure, the polyaniline (PANI)-decorated porous hybrid electrodes are prepared. The PANI@GO/PMMA/HAPCP/PAN carbon nanofibers (400P@0.1GPHCNFs) covered by PANI nanofibers as a novel free-standing flexible electrode exhibit an excellent electrochemical performance of 680.8 F g-1 at 0.5 A g-1 with a good capacitance retention of 93.5% after 3000 cycles. Moreover, the symmetric flexible all-solid-state supercapacitor assembled by the novel and delicate electrodes exhibits a high energy density of 27.70 W h kg-1 (at a power density of 231.08 W kg-1) and favorable cycling stability (84.50% retention of the capacitance after 1000 charge-discharge cycles), which indicates that the 400P@0.1GPHCNFs have great potential as a high-performance flexible supercapacitor electrode.

Optimization of cyclodextrin content for highly porous carbon nanofibers with enhanced electrocapacitive performance

Polyacrylonitrile/phenylsilane/cyclodextrin-derived carbon nanofiber composites (PPSCD) are prepared by one-step electrospinning using α-cyclodextrin (CD) and phenylsilane (PS) as the pore generator, because many organic molecules are easily decomposed by a self-activation process during heat treatment. We optimize the effects of different α-CD contents on the electrochemical performance of the PPSCD derived from the inclusion complex of PS/α-CD. The PPSCD electrode exhibits a high specific capacitance of 193 F g−1 at 1 mA cm−2 and a high energy density of 23.5–16.21 Wh kg−1 at power densities ranging from 400 to 10,000 W kg−1 in an aqueous solution. The superior electrochemical properties of PPSCD are favorable for ion storage and transfer due to the synergistic effects of high specific surface area and well-balanced micro/mesoporosity. Hence, PPSCD electrodes have a promising potential as a supercapacitor electrode material in the development of high performance energy storage systems.

Highly enhanced electrochemical cycling stabilities of hierarchical partially-embedded MnO/carbon nanofiber composites as supercapacitor electrodes

Post-grown hierarchical pseudocapacitive nanostructures often suffer from their bad long-term cycling stability. In this work, a type of hierarchical partially-embedded MnO nanocube/electrospun carbon nanofiber composites (pe-MnO/ECNFs) was designed. Results show the MnO nanocubes are partially embedded into the ECNFs skeletons, showing a strong joint between them. The pe-MnO/ECNFs electrodes exhibit a high specific capacitance of 146 F g−1 (to the whole electrode mass) at scan rate of 5 mV s−1, and an ultralow decay rate of 0.004‰ per cycle for 20,000 cycles at 10 A g−1, which is much better than those of the MnO2/ECNF ones (96 F g−1, decay rate of 0.015‰ per cycle). Furthermore, the assembled flexible symmetric supercapacitors show an high energy density of 6.8 W h kg−1, a high dynamic bending stability, and a robust long cycling stability (low decay rate of 0.003‰ per cycle for 6000 cycles at 1 A g−1).

Effect of different phenylsilane contents on the electrochemical behavior of cyclodextrin/phenylsilane-W. dela Cruzderived carbon nanofiber composites

Highly porous carbon nanofiber composites (PPSCD) are prepared through one-step electrospinning using a mixture of polyacrylonitrile (PAN), phenylsilane (PS), and α-cyclodextrin (CD) in a carbonization process without any additional physical/chemical activation step. Their capacitive performance is well optimized by adjusting the PS concentration. The PS concentration of 3 wt% in a PAN and CD polymer solution provides a large specific surface area of 563 m2g−1, which is advantageous for double layer capacitance for charge storage and rapid ion transport in charge–discharge processes. The PPSCD electrode shows a maximum specific capacitance (189 Fg−1 at a current density of 1 mAcm−2) and high energy density (22–15 Whkg−1 at power densities ranging from 400 to 10,000 Wkg−1) in a 6 M KOH aqueous solution.

Ultra-small MnCo2O4 nanocrystals decorated on nitrogen-enriched carbon nanofibers as oxygen cathode for Li-O2 batteries

Ultra-small MnCo2O4 nanocrystals/nitrogen enriched carbon nanofiber composites, with particle size as small as 2–4[Formula: see text]nm and nitrogen content as high as [Formula: see text][Formula: see text]at.%, were designed and used as oxygen cathode materials for Li-O2 batteries, with an aprotic electrolyte. Via an in-situ nucleation and growth, the morphology, size and distribution of MnCo2O4 nanocrystals were well controlled on surface of nanofibers, with strong interfacial interactions between the two components. Benefitting from the unique microstructure and high-level nitrogen doping, the MnCo2O4/NCF composite can deliver discharge and charge capacities of 4147.8 and 3842.8[Formula: see text]mAh/g as oxygen cathode materials, and columbic efficiencies are about 92.6%. More importantly, the discharge products can completely decompose in charging process as evidenced by an ex-situ FESEM investigation, while for pure NCF cathode, particle and plate-like Li2O2 were still observed on its surface, which confirmed that the MnCo2O4/NCF composite has a superior electrocatalytic activity that that of NCF.

Fe3C composite carbon nanofiber interlayer for efficient trapping and conversion of polysulfides in lithium-sulfur batteries

The poor electrical conductivity of the sulfur electrode and the severe shuttle effect limit the practical application of current lithium-sulfur (Li–S) batteries. Therefore, we demonstrate a methodology to design and develop a multifunctional interlayer based on carbon nanofiber (CNF) with Fe3C nanoparticles (Fe3C–CNF), which can simultaneously improve the electrical conductivity and reduce the shuttling effect by entrapping soluble polysulfides. The three-dimensional network-like structure of the Fe3C–CNF interlayer with uniformly distributed Fe3C nanoparticles not only enables the efficient deposition of active materials but also enhances the electron transfer of sulfur species. The Fe3C nanoparticles can effectively reduce the interfacial resistance and enhance the kinetics of the redox reaction of the sulfur material as a catalyst. A Li–S battery with a Fe3C–CNF interlayer and a conventional cathode (prepared by merely blending sulfur and conductive carbon) exhibits a capacity of 941 mAh g−1 and average Coulombic efficiency of 98.0% at 0.2 C. Even after 250 cycles at 1.0 C, the Li–S battery with the Fe3C–CNF interlayer exhibits a reversible discharge capacity of 804 mAh g−1, with an average capacity decay of 0.091% per cycle. The methodology proposed herein aids in the development of next-generation Li–S batteries.

A Technology for Producing Polymeric Composites Based on Carbon Nanofibers

Technologies for producing liquid-phase polymer composites of carbon nanofibers and their modifications are presented: carboxylated carbon nanotubes, polyaniline-modified nanotubes, supercondensate of multiwalled carbon nanotubes in epoxy phenol–formaldehyde resins. Polymeric composites with microwave absorption capabilities are considered.