Diameter Of Carbon Nanofibers Research Articles

SU8 polymer derived high capacity and performance anode material for secondary and flexible Li-ion batteries: Experimental and first principle study

This study provides a novel and sustainable protocol for the synthesis of SU8 polymer-based pattern, un-pattern carbon nanofibers (CNF) using an electrospinning process followed by a photolithography technique. Scanning electron microscopy (SEM) analysis of pattern, un-pattern CNFs shows that the average diameter of CNF is within the range of 60–140 nm. Transmission electron microscopy (TEM) studies disclose the average size of CNF exists within the range of 40–150 nm. The first-principle calculations predict that the gravimetric energy and power densities of Li/CNF half cells are 26.96 kW h g−1 and 26.96 kW g−1, respectively. The corresponding theoretical volumetric energy and power densities are 0.07 W h cm−3 and 0.07 W cm−3, respectively. Electrochemical analysis demonstrates the initial discharge capacities of pattern, un-pattern Li/CNF half cells at 100 mA g−1 are 3450 and 2429.8 mA h g−1, respectively. The gravimetric energy density of pattern, un-pattern Li/CNF half cells are within the range of 1800–1366.76 W h kg−1, and subsequent power densities are in the span of 519.63–434.22 kW g−1. The theoretical gravimetric energy and power densities of CNF/LiMn0.33Ni0.33Co0.33 (LMNC) full cells are 2.9 kWh kg−1 and ∼ 2.9 kW kg−1, respectively. Their theoretical volumetric energy and power densities are 1.96 W h cm−3 and 1.96 W cm−3, respectively. Electrochemical analysis discloses that the gravimetric energy and power densities of pattern CNF/LMNC full cells are in the range of 43.18–42.4 kW h kg−1 and 51.82–50.90 kW kg−1, respectively. The gravimetric energy and power densities of un-pattern CNF/LMNC full cells are 42.07–41.59 W h kg−1 and 50.48–49.92 kW kg−1, respectively.

Carbon nanofibers fabrication, surface modifications, and application as the innovative substrate for electrical stimulation of neural cell differentiation

Engineered nanostructures are innovative and precisely designed, synthesized, and tailored with outstanding physicochemical properties that can be applied as the game-changer in neural tissue engineering. The present study aimed to develop an innovative approach based on electrical stimulation through a conductive scaffold to differentiate neural cells from human adipose mesenchymal stem cells without the use of a specific environment for neural differentiation. Electrospun carbon nanofibers (CNFs) were obtained using heat treatment of polyacrylonitrile nanofibers and treated by nitric acid, ethylenediamine, and oxygen Plasma. SEM imaging revealed that the treated nanofibers have s diameter in the range of 120–200 nm and the treatment did not significantly change the CNFs diameter. The FTIR results showed that the treatments were able to introduce COOH, OH, and NH2 functional groups on the CNFS surface. The XRD and Raman analysis showed that the plasma treatment induced the lowest structural changes in the CNFs microstructure. The biocompatibility assessments showed that the pristine and treated CNFs were nontoxic induced proliferative effect on human adipose-derived mesenchymal stem cells. The electrical stimulation (1.5 mA current with a frequency of 500 Hz and CMOS waveform for 7 days 10 min each day) induced the expression of neural genes and proteins by the cells cultured on the treated CNFs. The Plasma-treated CNFs mediated the highest differentiation outcome. These results indicate that electrospun CNFs can be applied as the innovative interface applicable for neural tissue regeneration under electrical stimulation.

Oxidative stabilization of pitch‐polyacrylonitrile composite nanofibers electrospun by incorporating high‐percentage inexpensive pitch

AbstractPolyacrylonitrile (PAN)‐based composite nanofibers incorporated with high‐percentage inexpensive pitch were successfully prepared by a simple electrospinning technique. Low‐softening‐point naphthalene pitch (NP) has the merit of high solubility but inevitably brings about preoxidation problem. Thus the influence of different preoxidation strategies on the morphology, composition, and structure of composite nanofibers was systematically investigated. The results show that there exists a ternary phase diagram consisting of PAN‐pitch‐solvent and a suitable apparent viscosity of homogeneous solution, which favors the smooth electrospinning and good adjustment for the diameter of carbon nanofibers (100–500 nm). The crystallinity, crystalline order, and electrical conduction of composite nanofibers are enhanced by incorporating graphitizable NP, for example, the electrical resistance of 50% NP‐PAN composite nanofiber films after 800°C carbonization decreases about 30%. Both increasing the oxidation temperature and extending the oxidation time are beneficial to the oxidative stabilization of composite nanofibers with a suitable NP percentage below 50%. Gradient heating (240–340°C) and pressurized (0.08 MPa) preoxidations could accelerate the oxidative stabilization of composite nanofibers with a high NP percentage up to 110% and significantly shorten the oxidation time by half. Therefore, this study paves the road for facile preparation of cost‐competitive carbon nanofibers with controllable morphology, structure, and properties.

Synthesis, characterization and mechanism of electrospun carbon nanofibers decorated with ZnO nanoparticles for flexible ammonia gas sensors at room temperature

A flexible gas sensor based on ZnO nanoparticles decorated carbon nanofibers (ZnO@CNF) was fabricated by electrospinning, preoxidation, oxidation and carbonization to detect ammonia at room temperature. SEM, TEM, EDS, XPS, XRD and Raman spectra were used to analyze the morphology, structure and composition of the composite. By using electrospinning technology, preoxidation at 220 °C in air, oxidation at 410 °C and carbonization at 600 °C in argon, ZnO@CNF with a diameter of about 200 nm were synthesized. The preoxidation stage includes cyclization, dehydrogenation and oxidation of PAN, while the carbonization was contributed to the decreasing of carbon nanofiber diameter. The gas sensing test results show that ZnO@CNF has higher response, better selectivity than CNF to ammonia at room temperature, while greatly reducing the optimum working temperature of pure ZnO. The flexibility test of ZnO@CNF shows that the composite of metal oxides and carbon materials has a certain degree of flexibility. With the advantages of flexibility, room temperature operation and good response to ammonia, gas sensors based on ZnO@CNF are expected to become a potential candidate for the detection of ammonia in exhaled gas of patients with gastrointestinal diseases or kidney diseases in the future.

Tailoring diameters of carbon nanofibers with optimal mesopores to remarkably promote hemin adsorption toward ultrasensitive detection of bisphenol A

Bisphenol A (BPA) is a worldwide used endocrine disrupting chemical that can migration from food containers and packaging, resulting in bioaccumulation of BPA in humans and causing adverse health effects. Porous electrodes have been proved with large surface areas and high sensing abilities in electrochemical detection of BPA. However, how to tailor the pore sizes to further improve the sensing performance is still a great challenge. Here, we delicately tailored the diameters of carbon nanofibers (CNFs) by adjusting electrospinning parameters to have optimal mesopore structure for strong adsorption of hemin that has been demonstrated with high electrocatalytic activity for BPA sensing. Benefiting from the optimal mesopores structure of CNFs and the synergistic effect of hemin and CNFs, this hemin@CNFs based sensor achieves an ultrahigh sensitivity of 40.97 μA cm−2 μM−1, a low detection limit of 3.1 nM and satisfactory recoveries from 90.2% to 104.2% in the direct detection of BPA in liquors. This work offers a promising sensing platform for ultrasensitive monitoring of BPA.

Effect of microstructural features on the thermal conducting behavior of carbon nanofiber–reinforced styrene-based shape memory polymer composites

This article presents a novel hierarchical micromechanics approach to carefully investigate the thermal conductivities of styrene-based shape memory polymer composites containing carbon nanofibers. The research is mainly focused on the simulation of carbon nanofiber/shape memory polymer interfacial thermal resistance and carbon nanofiber agglomeration as two critical microstructural features of carbon nanofiber–shape memory polymer composite materials. The computed results are compared with the available experimental measurements. It is found that both of those microstructural factors along with carbon nanofiber non-straight shape significantly affecting the thermal conducting behavior must be incorporated in the analysis to have a more realistic prediction. The thermal conductivity of carbon nanofiber–reinforced shape memory polymer composites reduces significantly due to the effects of carbon nanofiber/shape memory polymer interfacial resistance and carbon nanofiber agglomeration and waviness. It is suggested to uniformly disperse carbon nanofibers into the shape memory polymers and reduce interfacial resistance for improving the carbon nanofiber–styrene composite thermal properties. In addition, the present study reveals that the effective thermal conductivities of the shape memory polymer composites reinforced by aligned carbon nanofibers are greatly enhanced over those of the shape memory polymer composites containing randomly dispersed carbon nanofibers. The effects of percentage, waviness parameters, degree of agglomeration, material properties, length and diameter of carbon nanofibers as well as interfacial thermal resistance value on the thermal behavior of carbon nanofiber–reinforced styrene-based shape memory polymer composites are investigated.

PRODUCTION OF CARBON COMPOSITE NANOFIBERS BASED ON COAL TAR AND TEXTILE CORD

The article conducted experiments on the production of carbon nanofibers based on coal tar andtextile cord by method electrospinning in a laboratory setup. Carbon nanofibers (CNFs) were obtained from textilecord carbonizate (TC) and coal tar (CT) from the Shubarkol deposit, and polymethylmethacrylate (PMMA) was usedas a binder. The elemental composition was determined and the surface morphology of the samples was studied. As aresult of energy dispersive X-ray spectroscopy and SEM microscopy, the chemical compositions of the CNF basedon TC + PMMA were determined, which amounted to C-82.69%, O-1.72%, Si-0.46%, Al-15.14%, TC + CT +PMMA: C-88.43%, O-4.06%, Al-7.32%, S-0.19%, the diameter of carbon nanofibers ranged from 64.2 nm to539.3 nm.

Preparation and characterization of Ni/Al2O3 for carbon nanofiber fabrication from CO2 hydrogenation

In this study, Ni/Al2O3 was prepared with an impregnation method for CO2 hydrogenation into carbon nanofibers (CNFs). High purity CNFs were acquired from CO2 hydrogenation at 500 °C and 1 atm over Ni/Al2O3 catalyst after a liquid phase extraction process, removing the used catalysts and by-products. The particle properties of as-prepared Ni/Al2O3 have been well characterized for comparison with the commercial ones. The results of XPS spectra and XRPD patterns indicated that the commercial, as-prepared, and used Ni/Al2O3 were multicomponent with various crystal phases. The as-prepared Ni/Al2O3 can be sufficiently exposed in CO2 atmosphere for higher catalytic performances owing to its unique microstructure with higher specific surface area (429.2 m2/g). Both EXAFS and XANES spectra have shown that the first shell of Ni atom in commercial, as-prepared, and used Ni/Al2O3 were NiO with bond distances of 1.61, 1.63, and 1.62 Å, respectively. The configuration of fabricated CNFs was characterized by its unique ID/IG (Intensities of D-band/G-band) ratio of 0.23 in the Raman spectrum. Solid tubular shape with 30 nm diameter of CNFs was observed using FE–SEM and HR–TEM. Thermodynamic analyses indicate that CO2 hydrogenation into CNFs is a spontaneous and exothermic reaction with an optimal temperature of 500 °C.

Lignin-derived nitrogen-doped polyacrylonitrile/polyaniline carbon nanofibers by electrospun method for energy storage

Herein, we employed the lignin as sustainable carbon precursor with polyacrylonitrile (PAN) to synthesize the carbon nanofibers (CNFs), and coated the polyaniline (PANI) to acquire the high N-doped CNFs. The as-obtained lignin-derived nitrogen-doped polyacrylonitrile/polyaniline carbon nanofibers (LCNFs/PANI/N-9) displayed excellent properties, such as the large specific surface areas of 483.1 m2 g−1, uniform pore size distributions of 9.1 nm, high graphitic structure, and high nitrogen doping content of 6.31 wt%. The uniform diameter of CNFs could allow a short ion diffusion path with efficient electron transport. And the highest specific capacitance of the LCNFs/PANI/N-9 increased to 199.5 F g−1 at 1 A g−1. Besides, the N-doped CNFs presented excellent cycling stability with 82% capacitance retention after 1000 charge-discharge cycles at the current density of 4 A g−1. This research opened the new promising of high-value applications for inexpensive and renewable biomass.

Effect of heat treatment temperature on energy storage performance of PAN co‐MMA based carbon nanofibers as freestanding lithium ion batteries anode

AbstractPolyacrylonitrile co methyl methacrylate (PAN co‐MMA) based nanofibers were synthesized by electrospinning technique and were converted into carbon nanofibers (CNFs) by heating at 1000°C (PAN‐1000), 1800°C (PAN‐1800), and 2200°C (PAN‐2200). Various characterizations such as SEM, TEM, Raman, FT‐IR have been carried out to study the effect of heat temperature on the microstructure of carbon fibers. The carbon nanofiber diameter varies in the range 600‐120 nm for different heat temperatures. Further, these CNFs were evaluated as freestanding anode in Li‐ion batteries. The PAN‐1000 and PAN‐1800 CNFs show stable capacity up to 150 cycles and specific capacity of 254 and 238 mAh g−1 at high discharge rate of 1C; however PAN‐2200 despite of better microstructure and surface area (~60m2/g) shows low specific capacity of 105 mAh g−1mAh/g, that is probably due to distribution of pore structures present in fibers as well as low electrolyte wetting through the carbon fibers electrode observed in post‐cycling SEM analysis. In addition, at higher discharge rate of 3C, PAN‐1000 shows stable cyclability and high capacity of 198 mAh g−1 over 450 cycles and 238 mAh g−1at 1C rate over 500 cycles. The microstructure and pore structure all affect the energy storage performance of PAN‐co MMA based CNFs.

Extinction Capability of Carbon Nanofibers to Millimeter Wave

Carbon nanofibers, whose diameter is between carbon nanotubes and conventional carbon fibers, is a new type of nanomaterials with features of good absorbing performance, small size and low density, and is easy to meet the requirements of passive interference materials.To study the interference properties of carbon nanofibers to millimeter wave, the interaction model of carbon nanofibers and electromagnetic field is established in this paper. The integral equation of the carbon nanofibers inductive current is established and solved by using of the method of moment, and the formula of mass extinction coefficient is obtained. The relationships between the mass extinction coefficient of carbon nanofibers and the millimeter wavelength, the diameter and length of fibers are analyzed via programming by Matlab. It is revealed that the extinction capability of carbon nanofibers decreases as the wavelength of millimeter wave increases. The larger the ratio of length to diameter of carbon nanofibers, the better its extinction capability to millimeter wave will be.

Energy Storage in a Transition Metal Doped MOF Derived Carbon Nanostructure

We illustrate a novel concept in tailoring the architecture of MOF-derived carbons by doping MOF crystals with transition metal ions prior to carbon structure growth via chemical vapor deposition (CVD). MOF-5 was isomorphously doped with various concentrations of Ni2+ during synthesis and was subsequently subjected to CVD to grow a labyrinth of carbon nanofibers (CNF) with high electrical conductivity and higher surface area than that of the parent MOF. TEM of the inner structure of the CNFs revealed a chevron arrangement with ~0.34 nm visible fringe spacing. The CNF diameters increased with increasing Ni concentration. This is attributed to the decreasing distance between Ni dopants with increasing Ni concentration, which may facilitate coalescence of the Ni catalyst during the heat treatment and thereby increase the diameter of the resultant CNF. However, Ni doping concentration greater than 30% led to large agglomerations of Ni particles which eventually ceased CNF growth. The electrical conductivity and the electrochemical double layer capacitance of the CNFs also increased with increasing Ni concentrations. The highest electrochemical double layer capacitance and the lowest resistance was observed at a Ni doping concentration of 30%. An alkaline electrolyte was used to engage the Ni particles inside the CNFs to participate in a reversible redox reaction shuttling between Ni and Ni(OH)2, which resulted in a specific capacitance as high as 349 F/g. The possibility of doping transition metals into a wide variety of MOF structures can provide a new method to synthesize novel carbon structures with high energy storage capabilities.

Direct growth of carbon nanofiber forest on nickel foam without any external catalyst

Interest in the direct growth of carbon nanostructures on metal substrates is growing, especially in the field of supercapacitors, fuel cells, batteries and sensors. This paper presents results on the growth of carbon nanofibers (CNF) without the requirement of an external catalyst directly on nickel foam (Ni-foam) at a relatively low temperature of 400°C. Etching of Ni-foam leads to the growth of CNF forests covering entirely the internal surfaces of the Ni-foam, with CNF diameters that can be tuned between 78±32nm and 375±35nm through a change in the growth temperature between 400 and 700°C. Etching was found to be important to obtain a uniform surface CNF coverage and growth, particularly at higher temperatures. These CNF/Ni-foam composites yield 3D nano-scale internal forest structures in good contact with the micro-scale porosity of the metallic foam electrode. This work provides a foundation to use binderless CNF composite electrodes to obtain higher capacitance.

Carbon nanofibers prepared by electrospinning accompanied with phase-separation method for supercapacitors: Effect of thermal treatment temperature

Abstract

Direct growth of coiled carbon nanofibers without nanocatalyst

The paper presents the coiled carbon nanofibers growth on bulk metals without use of nanocatalyst on indigenously developed custom build Chemical Vapour Deposition (CVD) set-up. Transition metal and alloys as substrate were investigated for their effect on morphology during growth of carbon nanofibers. The application of Inconel proved as a very good substrate for homogenous coiled nanofibers growth. Effects of variation in temperature and gas flow ratio were studied on diameter and helix angle of synthesized carbon nanofibers on Inconel as substrate. Experimental results reveal that the range of diameter of carbon nanofibers was 80–150nm. Transmission electron microscopy (TEM) analysis shows stacked-cup type structure with amorphous carbon deposits on carbon nanofibers. As the CVD process is very simple and economical, hence, this process can be effectively used for direct growth of carbon nanofibers.

Quantitative crystallographic analysis of individual carbon nanofibers using high resolution transmission electron microscopy and electron diffraction

High resolution transmission electron microscopy (HRTEM) and electron diffraction allow for a thorough crystallographic characterization of the herringbone structure of carbon nanofibers (CNF). A newly developed method for an extended quantitative structural evaluation of single carbon nanofibers is applied. The method is based on quantitative analysis of radial and azimuthal profiles extracted from selected area electron diffraction (SAED) patterns, nano beam electron diffraction (NBED) patterns or power spectra obtained by Fourier transformation of HRTEM images. Precise quantification of structural parameters, in particular cone apex angle, interlayer spacing and undulation of graphene layers is carried out. For the first time a profound interpretation of CNF diffraction patterns is given, proving the rotational disorder of the turbostratic structure and suggesting a random rotation between successive graphene cones. A series of crystallographic analyses along the axis of a single CNF reveal a continuous increase of the interlayer spacing during CNF growth. Additionally, the different techniques HRTEM, SAED, and NBED are evaluated in terms of attainable structural information, precision and applicability to different diameters of CNFs.

Influence of structural and textural parameters of carbon nanofibers on their capacitive behavior

Herringbone, platelet, and tubular carbon nanofibers (CNFs) were synthesized by catalytic chemical vapor deposition using methane, propane, and ethylene as carbon precursors. Alumina-supported nickel and iron catalysts were used for the syntheses. The resultant CNFs were characterized by scanning electron microscopy, transmission electron microscopy, and nitrogen sorption at 77 K. The performance of a CNF-based supercapacitor working in 6 mol L−1 KOH was analyzed using cyclic voltammetry, galvanostatic charge/discharge, and electrochemical impedance spectroscopy techniques. The Brunauer–Emmett–Teller (BET) surface area of the CNFs ranged between 150 and 296 m2 g−1. An increase in the CNF diameter was accompanied by a decrease in the BET surface area. A comparison of the porous textures and the structure types of the CNFs demonstrated that the performance of the CNF-based supercapacitor is enhanced primarily by the exposed edges of the graphitic layers on the CNF surface, followed by the specific surface area. Among the studied CNFs, the highest capacitance value, 26 F g−1 at 0.2 A g−1, was obtained for the platelet-type CNFs. Tubular CNFs exhibited the lowest capacitance value, which increased from 4 to 33 F g−1 at 0.2 A g−1 upon air treatment at 450 °C. The presence of exposed graphitic edges on the air-treated CNT surface and an increase in the specific surface area are considered to be responsible for the enhancement of the capacitor performance.

Growth and Characterization of Carbon Nanofibers on Fe/C-Fiber Textiles Coated by Deposition-Precipitation and Dip-Coating.

This research was conducted to synthesize carbon nanofibers on C-fiber textiles, by thermal chemical vapor deposition (CVD) using Fe catalyst. The substrate, which was a carbon textile consisting of non-woven carbon fibers and attached graphite particles, was oxidized by nitric acid, before the deposition process. Hydroxyl groups were created on the C-fiber textile, due to the oxidization step. Fe(III) hydroxide was subsequently deposited on the oxidized surface of the C-fiber textile. To deposit ferric particles, two different methods were tested: (i) deposition-precipitation, and (ii) dip-coating. For the experiments using both types of catalyst deposition, the weight ratio of Fe to C-fiber textile was also varied. Ferric particles were reduced to iron after deposition, by using H2/N2 gas, and carbon nanofibers (CNFs) were grown by flowing ethylene gas. Properties of carbon nanofibers created like this were analyzed through Scanning Electron Microscopy (SEM), Energy Dispersive Spectroscopy (EDS), N2-sorption (BET), X-ray Diffraction (XRD), X-ray Photoelectron Spectoscopy (XPS), Thermal analysis (TG/DTA), and Raman spectroscopy. In the case of the deposition-precipitation method, the results show that the diameter of carbon nanofibers grew up to 40-60 nm and 30-55 nm, at which the weight ratios of Fe catalyst to C-fiber textiles were 1:30 and 1:70, respectively. When Fe particles were deposited by the dip-coating method, the diameter of carbon nanofibers grew up to 40-60 nm and 25-30 nm, for the ratios of Fe catalyst to C-fiber textiles of 1:10 and 1:30, respectively.

Bicontinuous Structure of Li₃V₂(PO₄)₃ Clustered via Carbon Nanofiber as High-Performance Cathode Material of Li-Ion Batteries.

In this work, the composite structure of Li3V2(PO4)3 (LVP) nanoparticles with carbon nanofibers (CNF) is designed. The size and location of LVP particles, and the degree of graphitization and diameter of carbon nanofibers, are optimized by electrospinning and heat treatment. The bicontinuous morphologies of LVP/CNF are dependent on the carbonization of PVP and simultaneous growing of LVP, with the fibers shrunk and the LVP crystals grown toward the outside. LVP nanocystals clustered via carbon nanofibers guarantee improving the diffusion ability of Li(+), and the carbon fiber simultaneously guarantees the effective electron conductivity. Compared with the simple carbon-coated LVP and pure LVP, the particle-clustered structure guarantees high rate capability and long-life cycling stability of NF-LVP as cathode for LIBs. At 20 C rate in the range 3.0-4.3 V, NF-LVP delivers the initial capacity of 122.6 mAh g(-1) close to the theoretical value of 133 mAh g(-1), and maintains 97% of the initial capacity at the 1000th cycle. The bead-like structure of cathode material clustered via carbon nanofibers via electrospinning will be further applied to high-performance LIBs.

Diameter‐Controlled Synthesis and Capacitive Performance of Mesoporous Dual‐Layer MnO2 Nanotubes

AbstractMesoporous dual‐layer MnO2 nanotubes assembled from well‐aligned MnO2 nanosheets are synthesized via a facile and efficient sacrificial template method. To begin with, the self‐standing carbon nanofibrous membranes are prepared via electrospinning and high‐temperature carbonization, followed by an in situ redox reaction in KMnO4 solution to coat the carbon nanofiber (CNF) template with MnO2 nanosheets until the CNFs are consumed. The synthesized dual‐layer MnO2 nanotubes are composed of an inner shell of packed MnO2, and an outer shell of mesoporous sheet‐like MnO2. Importantly, the dimensions of the MnO2 nanotubes can be easily controlled by tuning parameters including CNF diameter and redox reaction temperature. The MnO2 nanotube electrode thus prepared manifests excellent cycling stability with a specific capacitance of 231 F g−1 and an areal capacitance of 309 mF cm−2 for supercapacitors. This approach opens up a new way for designing MnO2 nanostructures as promising electrode materials.