Growth Of Carbon Nanofibers Research Articles

Synthesis of Cu catalyzed chemical vapor deposition grown Cu-CNFs on less porous graphite powder

Carbon nanomaterials are the nanostructures that can have an aspect ratio greater than 1,000,000. There are various techniques, namely, arc discharge, laser ablation, and chemical vapor deposition for the synthesis of carbon nanofibers (CNFs) with high purity. In the present study, the main focus is on the synthesis of copper nanoparticles grown carbon nanofibers (Cu-CNFs) supported on graphite powder by catalytic chemical vapor deposition (CVD) method using acetylene (C2H2) as the source of carbon to grow CNFs. Herein, we demonstrate the synthesis of CNFs on less porous (SBET = 3 m2/g) graphite powder using Cu NPs as the CVD catalyst. The synthesized CNFs were further heat treated under inert atmosphere. Transmission electron microscopic analysis revealed that the synthesis of CNFs by CVD method followed tip growth mechanism. Besides, energy dispersive spectroscopy (EDS) complemented with X-ray photoelectron spectroscopic (XPS) analysis confirmed that the synthesized material was of high purity.

Predicting the optimal field enhancement factor during the growth of arched fibers

Curved carbon-based fibers, in the form of looped fibers, have been investigated as promising field electron emitters with high mechanical stability. Recently, the growth of semicircular arched carbon nanofibers (structures when the arch is incomplete) has received increased attention due to their potential application in next-generation electronic devices. In this Letter, we theoretically investigate the field enhancement factor (FEF) during the growth of these structures. We found the conditions for the optimal FEF, γmax, as a function of the geometrical parameters. Our results show that the local characteristic FEF at the top of the arch obeys a scaling law, γC≈γmax×Ω[(ψ/ψ*)2], where Ω is a nearly quadratic function of (ψ/ψ*), where ψ is a normalized arch angle of the fiber and ψ* is the ψ-value when γC=γmax. Importantly, our results show a universal behavior for γmax, namely, γmax≈κ[(R/r)α−0.45]ρ (where r and R are the radii of the fiber and the arch, respectively), α≡Rrim/r (where Rrim is the radius of the rim at the fiber top), and κ and ρ are positive constants. We point out several advantages of the arched fiber over the fully looped fiber for field emission devices, particularly the mechanical stability of the two-stage arched structures. Finally, starting with the conditions for γmax inferred from an isolated arch, the effects of electrostatic depolarization in regular arrays of arched fibers are analyzed as a function of the lattice parameters.

Template-free and in-situ growth of LZ-276&Alkali-impregnated carbon nanofibers for efficient epoxidation of styrene

Herein, a novel composite material (LZ-276&ACNFs) combining LZ-276 zeolite with alkali impregnated carbon nanofibers (ACNFs) was prepared by electrospinning method, high-temperature calcination, temple-free and in-situ growth. The walnut-like LZ-276 zeolites are strung by intricate ACNFs. The materials were characterized by FT-IR, XRD, XPS, SEM, and N2 adsorption–desorption. The conversion of styrene and the yield of styrene oxide was 93.79% and 62.65%, respectively.

Thermal, dynamic-mechanical and electrical properties of UV-LED curable coatings containing porcupine-like carbon structures

In this work, multi-functional coatings based on a UV-LED curable epoxy-acrylate resin and different loadings (namely, 1, 2.5, 5 and 10 wt%) of carbonaceous structures having a peculiar porcupine (PuP)-like morphology were formulated and thoroughly characterized through thermal, dynamic-mechanical and electrical analyses. More specifically, biochar-based particles derived from cellulose nanocrystals were modified through the growth of carbon nanofibers onto their outer surface, aiming at combining the effects of globular and high aspect ratio structures in a single filler. The preliminary characterization of the carbonaceous structures documented the achievement of a highly carbonized material involving spherical biochar particles having an average diameter ranging from 15 to 20 µm, covered by fibers displaying length up to 100 µm. As assessed by dynamic-mechanical characterization, the UV-LED cured composite films showed a progressive increase of the storage modulus values as a function of the amount of embedded PuP structures, indicating a strong level of interfacial interactions between the polymer network and the particles. Furthermore, the introduction of increasing amounts of PuPs induced a progressive increase of the material thermal conductivity (from 0.109 W/mK for unfilled cured resin, up to 0.161 W/mK, for the composite film containing 10 wt% of filler) and a remarkable enhancement of the electrical conductivity (up to (3.1 ± 0.2)*10−2 S/m, for the composite film containing 10 wt% of filler), thus pointing out the effectiveness of the proposed approach of surface modifying biochar particles in obtaining composite coating films with superior properties.

Novel humidity sensors based on nanomodified Portland cement

Commonly used humidity sensors are based on metal oxides, polymers or carbon. Their sensing accuracy often deteriorates with time, especially when exposed to higher temperatures or very high humidity. An alternative solution based on the utilization of Portland cement-based mortars containing in-situ grown carbon nanofibers (CNFs) was evaluated in this study. The relationship between the electrical resistivity, CNF content and humidity were determined. The highest sensitivity was observed for samples containing 10 wt.% of the nanomodified cement which corresponded to 0.27 wt.% of CNFs. The highest calculated sensitivity was approximately 0.01024 per 1% change in relative humidity (RH). The measured electrical resistivity is a linear function of the RH in the humidity range between 11 and 97%. The percolation threshold value was estimated to be at around 7 wt.% of the nanomodified cement, corresponding to ~ 0.19 wt.% of CNFs.

Hydrophilic graphitic carbon nitride-supported Cu-CNFs: An efficient adsorbent for aqueous cationic dye molecules

The current study describes the synthesis of chemical vapor deposition (CVD)-grown carbon nanofibers (CNFs) over the graphitic carbon nitride (g-C3N4) used as the substrate, and copper (Cu) as the CVD catalyst. The synthesized thermally treated Cu-CNFs/g-C3N4 composite shows a porous and hydrophilic characteristics, and is successfully used as an efficient adsorbent for aqueous methylene blue (MB). The high adsorption capacity (165 mg g−1) of MB over Cu-CNFs/g-C3N4-HT is attributed to the combined effects of the negatively electrostatic surface charge, hydrophilic characteristics, and a high BET surface area (162 m2g−1) of the material. The data clearly indicate the synthesized material in this study to be an efficient adsorbent for the removal of cationic molecules from wastewater.

Degradation and mineralization of oxalic acid using catalytic wet oxidation over carbon coated ceramic monoliths

Carbon coated ceramic monoliths were prepared by two strategies: (i) washcoating with N-doped carbon nanotubes (CNTs) using an active binder and (ii) chemical vapour deposition (CVD) growing carbon nanofibers (CNFs). In both cases the material was well adhered to the monoliths. These materials were tested in the catalytic wet oxidation of oxalic acid (1000 mg L−1) under continuous operation.For the washcoating method, the oxalic acid removal was not improved by adding the N-doped CNTs, most likely due to the CNTs coverage by the binder. However, a high temperature of the final thermal treatment (900 °C), was found to be important not only to achieve high oxalic acid conversions (over 55%), but also to improve the stability (less than 10% reduction in conversion in 24 h). Regarding the materials prepared by CVD, the dimensions of the CNFs were dependent on the presence of an alumina coating before their growth. The presence of NH3 during the carbon growth resulted in a steep decline in the amount of carbon formed, decreasing the activity of the monolith. However, the removal of oxalic acid per mass of carbon was much higher in this case, around 22 mg L−1 mgcarbon−1, due to the nitrogen groups.The highest removal was reached with the monolith produced by washcoating without the N-doped CNTs, thermally treated at 900 °C, achieving over 55% conversion of oxalic acid for 48 h on stream at 140 °C and 8 bar of oxygen partial pressure.

Direct synthesis of carbon nanomaterials via surface activation of bulk copper

A facile and novel surface activation approach using a strong-base solution enables the synthesis of carbon nanomaterials (CNMs) directly from bulk copper substrates via chemical vapor deposition. Amorphous carbon nanofibers (CNFs) were grown at temperatures as low as 250 °C, whereas at 600 °C the nanofibers were observed to be turbostratic, and at 700 °C turbostratic CNFs were synthesized together with a new aerogel-like 3D porous turbostratic CNM. A mechanistic model for the observed growth of CNMs from surface activated bulk copper is proposed. Our process is shown to yield conformal CNF growth on various complex-shaped copper substrates, such as meshes and wires, as well as copper-coated materials including carbon fibers and polymer films.

A nickel oxide-decorated in situ grown 3-D graphitic forest engrained carbon foam electrode for microbial fuel cells.

A facile and single-step nickel oxide-dispersed in situ grown 3-D graphitic forest engrained carbon foam (NiO-CNF-CF)-based electrode was fabricated for high-performance microbial fuel cells (MFCs). The metal oxide, graphitic contents, biocompatibility, stability and large surface area available in the material for biofilm formation rendered the prepared electrode competent for wastewater treatment and bioenergy (0.79 V and 1.955 W m-2) generation with a coulombic efficiency of 85.66%.

Mechanical analysis of conductive polymer nanocomposite

Polymers are widely appreciated for the development of electronic devices due to their light weight and design flexibility. Therefore, studying the approximate values of failures during displacement and deformation in the polymer nanocomposite is very important for medical devices. The present work deals with the development of polymer nanocomposite (PNC) using the Polyvinylidene fluoride (PVDF) as host polymer with vapour grown carbon nano fibers (VGCNF) and ionic liquid (IL) as the filler particles using solution casting technique. The tensile test has been done experimentally using the Ultimate Tensile Machine (UTM) for determining the deformation behaviour in the specimen samples of PNC. Further, the specimen models were developed using the Finite Element Analysis (FEA) to compare with the experimental results. The experimental samples were prepared using the solvent casting technique with ASTM 3039 standard dimensions. The uni-axial load (0.5, 1 2, 3, 4 and 5 N) was applied to one end of the specimen while keeping another end fixed for simulating the data with ANSYS. The results obtained by the FEM showed favourable results with an acceptable margin of errors.

Nickel oxide on directly grown carbon nanofibers for energy storage applications

Nickel oxide on directly grown carbon nanofibers (CNF-NiO) electrodes were fabricated and used as cathodes for hydrogen production by water electrolysis and as electrode materials for supercapacitors. Tafel polarization from the CNF-NiO electrodes showed an improvement in the hydrogen evolution reaction. This was attributed to the increment of the electrochemically active surface area, conductivity, and the synergy effects between the nickel oxide, carbon nanofibers, and nickel foam substrate. When used for supercapacitor applications, these electrodes showed a specific capacitance of ca. 776.20 ± 26 mF cm−2 at a current density 3 mA cm−2. These electrodes prepared using a facile method also exhibited a capacitance retention of 89% even after 3000 cycles with a coulombic efficiency of 89% when cycled at 20 mA cm−2. Considering the simplistic approach of the electrode preparation, the stability, and the capacitance, this method opens an avenue to try various metal oxide deposit on the directly grown CNF template.

Vapor grown carbon nanofiber based cotton fabrics with negative thermoelectric power

Vapor grown carbon nanofiber (CNF) based ink dispersions were used to dip-coat woven cotton fabrics with different constructional parameters, and their thermoelectric (TE) properties studied at room temperature. Unlike the positive thermoelectric power (TEP) observed in TE textile fabrics produced with similar carbon-based nanostructures, the CNF-based cotton fabrics showed negative TEP, caused by the compensated semimetal character of the CNFs and the highly graphitic nature of their outer layers, which hinders the p-type doping with oxygen groups onto them. A dependence of the electrical conductivity (σ) and TEP as a function of the woven cotton fabric was also observed. The cotton fabric with the largest linear density (tex) showed the best performance with negative TEP values around − 8 μV K−1, a power factor of 1.65 × 10−3 μW m−1 K−2, and a figure of merit of 1.14 × 10−6. Moreover, the possibility of a slight e− charge transfer or n-doping from the cellulose onto the most external CNF graphitic shells was also analysed by computer modelling. This study presents n-type carbon-based TE textile fabrics produced easily and without any functionalization processes to prevent the inherent doping with oxygen, which causes the typical p-type character found in most carbon-based TE materials.

Growth of carbon nanofibers through chemical vapor deposition for enhanced sodium ion storage

Innovation of carbon anodes plays a significant role in the commercialization of Sodium-ion batteries. In this work, we report hybrid carbon nanofibers synthesized by a facile chemical vapor deposition method and explore their application potential as anode for sodium ion storage. The designed hybrid carbon nanofibers have diameters of 50−150 nm and show linear and spiral structures. Impressively, the carbon nanofibers anode exhibits good electrochemical performance with a high initial Coulombic efficiency of 87.6 % and excellent cycling stability with a capacity retention of 75.4 % at the 100th cycle. The improved Na-ion storage performance is attributed to the carbon nanofiber structure with considerable defect concentration and shortened transfer length for ions and electrons. Moreover, the fibrous structure is interconnected with cross-linked pores, contributing to good mechanical stability and reduced contact resistance. Our work may provide valuable inspiration for developing advanced electrodes for advanced alkali ion energy storage.

CVD grown carbon nanofibers: an efficient DSPE sorbent for cleanup of multi-class pesticide residue in high fat and low water commodities by QuEChERS using GC-ECD.

An inexpensive, effective, and efficient dispersive solid-phase extraction (DSPE) sorbent was developed as an alternative totraditionally used sorbents (primary secondary amine and C18) for fatty matrices using theQuEChERS method. Catalytic chemical vapor deposition grown carbon nanofibers dispersed on activated carbon fibers (Ni-ACF/CNF) having aBET specific surface area of738 (m2/g) were for thefirst time evaluated as a DSPE material for sample cleanup before gas chromatographic analysis. Based on cleanup performance and recoveries, 10mg of Ni-ACF/CNF was found optimalfor the determination of twenty-seven multi-class pesticides in high fat and low water commodities/matrices (peanut, soybean, sesame, and flaxseed). The recoveries obtained for all analytes were in the range ~ 72 to ~ 117%, with relative standard deviation values ≤ 15%. The limits of detection and quantification values were 0.7-4.2ng/g and 2.3-13.9ng/g, respectively. The matrix match calibration curve was linear in the range 20-500ng/g with a correlation coefficient of ≥ 0.993. The results reveal thatthe Ni-ACF/CNF is a competent DSPE sorbent, similar to primary secondary amines and C18sorbent materials, for pesticide determination by QuEChERS methods in high fat and low water commodities. Graphical abstract.

A dual photoelectrode-based double-chambered microbial fuel cell applied for simultaneous COD and Cr (VI) reduction in wastewater

Cerium oxide (CeO2) and cuprous oxide (Cu2O) were used for the first time as photoanode and photocathode, respectively, in a microbial fuel cell (MFC) for simultaneous reduction of chemical oxygen demand (COD) and Cr(VI) in wastewater. The photoelectrodes, viz. Photoanode and photocathode were separately prepared by impregnating activated carbon fiber (ACF) with the respective metal oxide nanoparticles, followed by growing carbon nanofibers (CNFs) on the ACF substrate using catalytic chemical vapor deposition. The MFC, operated under visible light irradiation, showed reduction in COD and Cr(VI) by approximately 94 and 97%, respectively. The MFC also generated high bioelectricity with a current density of ~6918 mA/m2 and a power density of ~1107 mW/m2. The enhanced performance of the MFC developed in this study was attributed to the combined effects of the metal oxide photocatalysts, the graphitic CNFs, and the microporous ACF substrate. The MFC based on the inexpensive transition metal oxides-based photoelectrodes developed in this study has a potential to be used at a large scale for treating the industrial aqueous effluents co-contaminated with organics and toxic Cr(VI).

Site-Specific Controlled Growth of Coiled Lambda-Shaped Carbon Nanofibers for Potential Application in Catalyst Support and Nanoelectronics

Carbon nanofibers (CNFs), in particular branched ones, raise high interest because of their potential for nanoelectronics, catalyst presentation, and applicability as dry adhesives. Here, we presen...

Effect of the Preliminary Heat Treatment of Chlorinated Polyvinyl Chloride on the Formation of Carbon Nanofibers on its Surface under High-Power Ion-Beam Irradiation

The effect of a high-power ion beam of nanosecond duration on layers of chlorinated polyvinyl chloride with a catalytic additive (ferrocene), which preliminarily underwent treatment in air or an inert medium in the temperature range 100–400°C, is studied. Heat treatment at 150°C for 1 h is shown to reduce the length of the formed carbon nanofibers by ~20 times. Disk-shaped depressions are observed on the surface of the polymer irradiated after treatment at 200°C due to the removal of a part of the surface layer. These depressions are likely associated with polymer embrittlement during heat treatment. A net-like structure is observed between these depressions. An increase in the treatment temperature to 400°C (in an inert medium) results in the formation of nanofibers with a length not exceeding 0.5 μm. The effect of preliminary heat treatment on the growth of carbon nanofibers and possible mechanisms of their growth under the influence of a high-power ion beam on a chloropolymer containing a catalytic additive is discussed.

Parametric Study of Plasma Characteristics and Carbon Nanofibers Growth in PECVD System: Numerical Modeling

The aim of the present work is to develop a numerical model to understand and optimize the process parameters for the growth of carbon nanofibers (CNFs) inside the plasma enhanced chemical vapor deposition system containing acetylene, hydrogen, and argon gases. Two-dimensional axis-symmetrical inductive couple plasma module is implemented using COMSOL Multiphysics 5.2 simulation software to analyze the density profiles and temperatures of electrons, ions, and neutral species in the plasma at different gas pressures and input plasma powers. The outcomes of the COMSOL computational model show that the electron density in the plasma decreases with increase in gas pressure and increases with increase in plasma power. Other than the computational model, an analytical model is developed in the present paper that accounts the plasma sheath equations to study the fluxes and energies of the plasma species. The results obtained from the plasma sheath model at the catalyst-substrate surface boundary are fed as the input parameters to surface deposition model to investigate the growth characteristics of carbon nanofibers, i.e., poisoning of the catalyst nanoparticle, height, and diameter of carbon nanofiber at different gas pressures and input plasma powers. It is found that electron density decays at the faster rate when gas pressure is increased and decays at slower rate when input plasma power is raised. Moreover, it is also found that growth rate of CNFs increases with increase in gas pressure and plasma power. However, the significant drop in CNF growth rate is observed when the gas pressure is high enough (above and around 50 Torr). From the results obtained, it can be concluded that the CNFs having good growth characteristics can be obtained at some optimum pressure range, i.e., one order of the magnitude in the units of Torr. A good comparison between numerical simulation results and analytical results with each other and with existing experimental results confirms the adequacy of the computational and analytical approach.

Mechanochemical Synthesis, Structure, and Catalytic Activity of Ni-Cu, Ni-Fe, and Ni-Mo Alloys in the Preparation OF Carbon Nanofibers During the Decomposition of Chlorohydrocarbons

A series of Ni-M (M = Cu, Fe, Mo)-based alloys is synthesized using mechanochemical alloying of metal powders. The phase composition and structure of Ni-M samples are analyzed by powder X-ray diffraction. The catalytic activity of Ni-M B is studied in the synthesis of carbon nanofibers (CNFs) by decomposing a C2H4Cl2/H2/Ar mixture at 600 °C. It is shown that as a result of the interaction of alloys with the reaction medium, their rapid disintegration occurs with the formation of active particles catalyzing the growth of CNFs. The highest yield (22.2 g(CNF)/g(Ni)) is obtained for Ni-Mo alloy (in 2 h). The structural and morphological features of carbon materials are investigated. SEM and TEM data indicate the formation of carbon fibers with a pronounced segmented structure. The specific surface of the carbon material is 250–400 m2/g.

Study of the in-situ growth of carbon nanofibers on cement clinker

Because fibres are difficult to disperse evenly in cement-based materials, we attempted to grow carbon nanofibers (CNFs) in situ on Portland cement clinker particles using chemical vapor deposition (CVD). The results show that the phase compositions and alite polymorph didn’t change for the Portland cement clinker treated at 600 °C in the atmosphere of blended gas containing argon (Ar), hydrogen (H2) and acetylene (C2H2). The CNFs was successfully grown in situ on the Portland cement clinker due to the reaction of C2H2 in the presence of H2. The diameter and length of the CNFs were 20–30 nm and 0.6–0.9 μm respectively. C3S is the main component of cement clinker. The hydration of C3S plays a crucial role in the performance of cementitious composites. The hydration of C3S was significantly delayed and reduced due to the incorporation of CNFs.