Growth Of Carbon Nanofibers Research Articles

Influence of Catalytic Additives on the Formation of Nanostructured Carbon Layers on the Surface of Chlorinated Polyvinyl Chloride under a High-Power Ion Beam

The influence of catalytic additives (various organometallic and inorganometallic compounds) in chlorinated polyvinyl chloride on the formation of carbon nanofibers on its surface under a high-power ion beam of nanosecond duration is studied. Ferrocene, which provides the growth of long (up to 10 μm) nanofibers with a narrow diameter distribution and a small number of pores in the underlying polymer layer, seems to be the optimal catalyst for chlorinated polyvinyl chloride. We found that carbon nanofibers grow on the surface of chlorinated polyvinyl chloride containing zinc chloride as a catalytic additive. This fact indicates that there is a new mechanism for the growth of carbon nanofibers on the surface of chloropolymers under high-power radiation conditions.

The Effects of Geometry and Chemical Composition of Nanoparticles on The Fracture Toughness of iPP Nanocomposites

This research deals with possible hybrid effects in the fracture energy of hybrid nanocomposites while taking a critical approach toward the currently-prevailing engineering practice of applying classical composite micromechanics to nanocomposites. For this purpose, different nanoparticles were embedded in an isotactic polypropylene matrix. The particles had different geometries (fibrous and platelets) and different chemical structures (organic vapor grown carbon nanofibers (VGCF); graphene nanoplatelets (GNP); and inorganic nanoclays, SiO2 nanofibers, and ZrO2 nanofibers). Almost all the composite systems presented improvements in the fracture energy, whereas the iPP/VGCF/GNP presented a positive hybrid effect. The main conclusion was that each nanocomposite system should be analyzed individually according to the constituent properties; the quality of the dispersion; and, primarily, by the type of interaction between the particles and the matrix.

Growth of carbon nanofibers by the catalytic decomposition of methane over Ni-Cu/Al2O3 catalyst

This paper shows that the catalytic decomposition of methane over Ni-Cu/Al2O3 catalyst at pressures of up to 5 bar leads to formation of carbon nanofibers of bamboo-like morphology with a “fish bone” structure with bridges inside the channel. When increasing the pressure, the change of textural characteristics of carbon nanofibers occurs. The surface area of carbon nanofibers increases from 130 to 166 m2/g, the volume of micropores grows from 0.005 to 0.014 cm3/g, the specific surface area of mesopores ranges from 117 to 137 m2/g at the pressure increase from 1 to 5 bar.

High-yielding carbon nanofibers grown on NIPS-derived porous nickel as a flexible electrode for supercapacitors

A flexible and robust 3D nickel@carbon nanofiber electrode was prepared via modified NIPS-powder metallurgy and CVD method. 3D porous nickel membrane provides more active catalysis sites and confined space for the growth of carbon nanofibers.

Carbon nano-fiber forest foundation for ruthenium oxide pseudo-electrochemical capacitors

Effect of ruthenium oxide coating temperature on directly grown carbon nanofibers for supercapacitor application is studied.

Enhanced mechanical toughness of carbon nanofibrous‐coated surface modified Kevlar reinforced polyurethane/epoxy matrix hybrid composites

ABSTRACTHigh‐performance Kevlar fiber had extensively been explored to upgraded mechanical properties of the advanced composites. Therefore, this study aimed a challenging work to grow carbon nanofibers onto the Kevlar fiber to improve its fiber‐matrix interaction properties. It was successfully done through inexpensive flame deposition as well as modification of matrix with hybrid resin using polyurethane‐epoxy mixture. A hand‐layup method had been adopted to manufacture the composite laminates. The chemical and surface structures of the prepared laminae were examined by scanning electron microscopy, Raman spectroscopy, X‐ray diffraction, and the composite's properties were evaluated tensile test, compact tension (CT) fracture test, fractography, and differential scanning calorimetry. The surface modified Kevlar laminae with CNF were used as reinforcing layer in the epoxy and PU/epoxy hybrid resin matrices. CNF‐coated heated Kevlar reinforced laminated PU/epoxy hybrid composites (CNF‐Kev/PU‐Epoxy) showed highest elongation 47% and fracture toughness (11.7 MPa√m) along with good UTS 139 MPa. Therefore, these hybrid nanocomposites developed by simple inexpensive method would be the potential candidates for several advanced applications particularly in defense, automobile, aerospace, and spacecraft applications. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020, 137, 48802.

Synthesis of Helical and Straight Carbon Nanofibers on Water Soluble Sodium Chloride Supported Catalyst

Carbon nanofibers are synthesised via chemical vapour deposition of acetylene as carbon source through using water soluble catalysts. The new water soluble catalyst is prepared by supporting the copper on sodium chloride salt. Copper acetate and copper nitrate salts are used for preparing catalysts through impregnation method. The yield of carbon deposits using the catalyst prepared by copper acetate is almost twenty times higher than the one prepared by copper nitrate precursor. The X-ray diffraction pattern and field emission scanning electron microscopy (FESEM) images confirm the formation of CuO in the catalyst after calcination process. The growth time for carbon material is 15 min. The FESEM images show the growth of helical and straight carbon nanofibers on the catalysts with metal loading of 5 wt% at 600, 650 and 680 °C. The results showed that the morphology of the carbon deposited on the catalyst depends on both the amount of metal loaded on the catalyst and reaction temperature, while there is a significant interaction between them. However, fishbone carbon nanofibers with diameters less than 100 nm are deposited on the catalysts with metal loading of 1 wt% at 650 °C.

One-pot conversion of carbon dioxide to CNT-grafted graphene bifunctional for sulfur cathode and thin interlayer of Li–S battery

Gaseous carbon dioxide (CO2) was converted into few-layered graphene sheets grafted by carbon nanofibers (G-CNFs) at the atmospheric pressure. The synthesis was performed in a one-pot route by the thermal Mg-aided reduction of CO2 in the presence of nickel nanoparticles that have a crucial role in the growth of carbon nanofibers. The produced G-CNF was bifunctionally applied as a cathode supporter for elemental sulfur and a thin interlayer for the separator in the Li–S battery. The graphene layers exfoliated by the carbon nanofibers enabled the formation of semi-freestanding membrane through sonication in a surfactant solution. They were attached on the separator to be used as a several micron-thick interlayer. The G-CNF employed as both cathode and interlayer materials enhanced the charge-discharge capacity and stability due to its low electrical resistivity and its role as a barrier to the polysulfides shuttle. As a result, a high capacity of 820 mAhg−1 and 640 mA h g−1 after 100 and 500 cycles were acquired at 0.5 C, respectively. The results suggest not only the facile one-step conversion of atmospheric CO2 to the exfoliated graphene grafted by carbon nanofibers, but also its outstanding electrochemical performance in the Li–S battery.

One-step synthesis of carbon nanotubes with secondary growth of carbon nanofibers: effect of chlorine, synthesis time and temperature

Applications of carbon nanotubes (CNTs) in nanoscale electronic, filtration and adsorption platforms, requires the production of a high density network structure of the CNTs, which are intermeshed and/or chemically connected to each other. Strong network structures can be created if a stable connection is established through cross-linked CNTs. In a previous preliminary study, we reported the secondary growth of carbon nanofibers (CNFs) that grew on top of the CNTs during the CNT synthesis through decomposition of 1,2-dichlorobenzene (DCB). In the current study, we studied in detail the effect of synthesis time and temperature on the secondary growth of CNFs on CNTs as well as the morphology of CNFs that were grown. The amount of CNFs that grew onto the main CNTs increased with an increase in the synthesis time for reactions performed at 60 and 90 min but decreased with a 120 min growth time. It is proposed that decomposition of the DCB let to Cl/carbon radicals that either (i) eroded the CNT surface or (ii) deposited on the CNT surface, depending on the synthesis parameters. The CNFs grew at defective sites of the CNT walls. A synthesis temperature of 700 °C and synthesis time of 90 min were the growth conditions that resulted in the highest formation of the CNFs, presumably due to formation of defects that were uncovered by carbon deposition and allowed for the secondary growth of CNFs. The types of defects created were identified as on-site defects in the graphene sheet by Raman spectroscopy. All other studied synthesis temperatures (i.e. 600, 650, and 750) were unfavorable for growth of secondary CNFs.

Synthesis of carbon nanofibers over lanthanum supported on radially aligned nanorutile: A parametric study

Radially aligned nano-rutile (RANR) was synthesized using the hydrothermal technique. This material was used as catalyst support for Lanthanum (La) nanoparticles which were loaded onto the RANR support by a deposition-precipitation method using urea (DPU) to form La/RANR catalysts. It was observed from TEM images that the width of the nanorods making up the RANR support is ca. 9 nm and the actual RANR is heterogeneously sized, with spherical microstructures that have radii ranging between 1.2 and 1.6 μm. The La nanoparticles were loaded onto RANR at weight percentages ranging from 0.5 to 10 wt%. The as-synthesized La/RANR catalyst was used to catalyze the synthesis of carbon nanofibers (CNFs) by chemical vapor deposition (CVD), using acetylene as a carbon source and hydrogen as a reducing gas. A parametric study was conducted to investigate how gas flow rate, synthesis temperature, reaction time, and La loading on La/RANR affected the growth of CNFs by monitoring the morphology, graphicity and thermal properties of the products. It was observed that 5 wt% La/RANR yielded CNFs with the lowest width and highest graphicity and thermal stability, particularly for the ones synthesized at 700 °C. These CNFs were used as an adsorbent and were observed to have adsorbed over 90% of methyl red within 5 min.

Development of Steel Matrix Composites Used for Metal Die

In this study, we show the development of the steel matrix composites used for metal die. Matrix used is 40CrMoV5 (ISO standard) steel, which is used as press and die-casting dies. The dispersants used are vapor grown carbon nanofiber (VGCF), which is one of carbon nanofiber (CNF) and titanium die-bride (TiB2) particle powder. After mixing 40CrMoV5 powder and the dispersants by ball milling, the composites was prepared by spark plasma sintering (SPS) process. For VGCF, 1.9 and 3.8 vol. % was added to 40CrMoV5 powder in order to obtain the composites. The thermal conductivity of the VGCF/40CrMoV5 alloy composites improved about 20% compared with the 40CrMoV5 monolithic alloy. The tensile strength of the composites with 1.9 vol. % VGCF is about 1980MPa, which is higher than the monolithic alloy with 1250 MPa. For TiB2 particle, 4.0, 8.0 20.0 vol. % powders was added to 40CrMoV5 powder. By adding 8.0 vol. % TiB2, the thermal conductivity improved about 40% compared with the monolithic alloy, but tensile strength decreased to 612 MPa in 8.0 vol. % VGCF composites, which are caused by the aggregation of TiB2 powders. It seems the strength of the composites will improve by controlling the dispersibility of TiB2 powders.

Raman investigations on gamma irradiated iPP-VGCNF nanocomposites: The polymer's tale

Raman investigations on nanocomposites obtained by loading various amounts of vapor grown carbon nanofibers within an isotactic polypropylene matrix, and gamma irradiated in air, at various integral doses ranging between 0 and 27 kGy, are reported. The analysis is focused on the polymer's answers as revealed by Raman spectroscopy and investigate in detail the effect of ionizing radiation on the position of the Raman line originating from the polymer. The as-obtained data are correlated to the elastic features of the nanocomposites. A competition between gamma irradiation and loading by carbon nanofiber, resulting in the stretching of the polymeric matrix and revealed as a displacement of Raman lines towards smaller wavenumber is reported. It is concluded that side groups (CH3) are less affected by the loading with carbon nanofibers,

Cerium oxide-catalyzed chemical vapor deposition grown carbon nanofibers for electrochemical detection of Pb(II) and Cu(II)

Chemical vapor deposition (CVD) grown cerium oxide catalyzed 1-D carbon nanofibers (Ce-CNFs) were synthesized first time via tip growth mechanism for the sensitive, selective and simultaneous determination of heavy metals/ions, i.e., Pb (II) and Cu (II). Acetylene and cerium oxide was used for growing the Ce-CNFs via CVD process as carbon source and catalyst for decomposing the acetylene respectively. Inexpensive polymethyl vinyl ether-alt-maleic anhydride (PMMVEA) was used as a binder rather than expensive Nafion solution. Ce-CNFs modified glassy carbon electrode was used as working electrode in three electrode assembly for simultaneous selective detection of Pb (II) and Cu (II) using cyclic voltammetry (CV) and differential pulse voltammetry (DPV). The fabricated Ce-CNF electrode exhibited a linear behavior with Pb (II) and Cu (II), and the limit of detection was found to be 0.6 ppb and 0.3 ppb respectively. The electrode material was efficaciously tested against real water sample (Gomti river, Lucknow, India), for checking its practical applications. The prepared Ce-CNFs modified electrode is relatively nontoxic and low-cost. Consequently, it could be directly employed as a real-time electrochemical sensor for simultaneous determination of Pb (II) and Cu (II) ions.

Enhanced Supercapacitor Performance By Tuning the Wettability of Vapor Grown Carbon Nanofibers Using Oxygen Plasma Treatment

Carbon based materials have been explored widely for supercapacitor applications in commercial perspective. Despite that their poor performance in terms of volumetric and gravimetric capacitance seems bottleneck in high performance supercapacitor device applications. The major reason for the same is their poor wettability. Generally, carbon based materials are found to be hydrophobic which limits their electrode – electrolyte interfacial interaction and hence, suppresses the charge storage performance. In this work, we report vapor grown carbon nano fibers (CNF) at large scale using chemical vapor deposition adopting simple catalytic approach. CVD grown CNF showed crystalline 1 D morphology confirmed by detailed electron microscopy. As grown CNF shows hydrophobic nature. Supercapacitor measurements revealed 14.6 mF/cm2 aerial capacitance. In order to improve electrode - electrolyte interfacial interaction, the wettability factor has to be improved and hence O2 plasma treatment has been adopted to convert hydrophobic CNF into hydrophilic. Time dependent contact angle measurements revealed the absence of ageing effect due to changes in microstructure after plasma treatment which was confirmed by electron microscopic investigations. Further, comparative electrochemical measurements proved remarkable enhancement in supercapacitor performance of plasma treated CNF in terms of aerial capacitance (162.5 mF/cm2) compared to as grown CNF. The change in wettability led to superior supercapacitor performance along with high Coulombic efficiency. Taking this work to one step further CNF were uniformly encapsulated with MoO3 in 1 D core – shell fashion where CNF acts as core and MoO3 acts as shell in the subsequent CVD process. This approach provides a path in developing low cost - high energy density supercapacitor using simple methods.

Dynamic modeling of carbon nanofiber growth in strong electric fields via plasma-enhanced chemical vapor deposition

Plasma enhanced chemical vapor deposition is an important method in the synthesis of carbon nanofibers which have been widely used in many technologies. Previous work devoted to the theoretical modeling of this process focused only on kinetics, i.e., the steady-state growth rate and its dependence on experimental conditions. This paper develops a dynamic model of a single carbon nanofiber grown in the cathode layer of a weakly ionized C2H2 glow discharge plasma. The model takes into account all main processes, including chemical kinetics, heat transfer, and the dynamics of electric field distribution. Specifically, the model considers the effects of a strong electric field on nanofiber growth: the field enhanced neutral particle flux and heat flux toward the catalyst and the increased catalyst temperature as a result of the thermal field emission current (along with its accompanying Nottingham effect). Numerical simulation shows that the increased fluxes caused by a strong electric field are unlikely to lead to a substantial acceleration of nanofiber growth. The growth tends to saturate, up to a complete stop, caused by the catalyst heating, which starts around the same time the field enhanced fluxes become significant. This serves as an alternate termination mechanism of nanofiber growth to the commonly-known catalyst poisoning. The competition and transition of the two mechanisms when changing the characteristic time of catalyst poisoning are shown. The results of this work help to improve the physical understanding of nanofiber growth and lay the foundation for further studies on other types of plasma-assisted nanofabrication.

Negative thermoelectric power of melt mixed vapor grown carbon nanofiber polypropylene composites

In this work, commercial vapor grown carbon nanofibers (CNF), produced by chemical vapor deposition (CVD), were melt extruded with polypropylene (PP) with the aim of analyzing their thermoelectric properties (i.e., electrical conductivity, thermoelectric power, power factor and figure of merit). Unexpectedly, all PP/CNF composites showed negative thermoelectric power (TEP) values instead of showing the typical positive TEP observed for this type of carbon-based polymer composites. These results can be attributed to the double layer structure surrounding the tubular core of the carbon nanofiber grown by the CVD method at 1100 °C, which may lead the intrinsically negative TEP contribution from the larger inner layer to counteract the positive TEP contribution from the smaller outer layer due to common oxygen doping. Overall, all composites showed negative TEP values around −8.5 μVK−1 and a maximum power factor of 1.75 × 10-3 μW m-1 K−2, corresponding to a figure of merit of 1.2 × 10-6 at room temperature. This study demonstrates that melt mixed polymer composites with large-diameter tubular carbon nanostructures and negative Seebeck coefficients can be directly produced with large-scale processing methods without requiring specific additives and/or deoxygenation treatments.

Effect of Ni incorporation in cobalt oxide lattice on carbon formation during ethanol decomposition reaction

In this work, we report the results of catalytic decomposition of ethanol over a porous mixed metal oxide of Ni-Co (NiCoO2) and analyze the effect of Ni incorporation in Co3O4 lattice on the activity and hydrogen selectivity from ethanol decomposition reaction. In-situ FTIR analysis was conducted between 50 °C to 400 °C for both, Co3O4 and NiCoO2, catalysts to understand the reaction mechanism leading to gas phase product distribution. On cobalt surface the reaction pathway proceeds via the formation of surface ethoxy intermediate that subsequently transforms to aldehyde and acetate intermediates before decomposing to release CO2, H2 and CH4 gases at high temperature. A similar pathway is followed on NiCoO2 surface, leading to aldehyde intermediate, which is relatively unstable and decomposes to release CO along with CH4 and H2 at 400 °C. The NiCoO2 catalyst shows relatively low selectivity for CO2, possibly due to the unstable aldehyde species providing little acetate intermediate that decomposes to release gaseous CO2. The addition of Ni improves the activity for ethanol decomposition by achieving a complete ethanol conversion at 350 °C as compared to 420 °C for cobalt alone. The crystallinity, morphology and particle analysis of the spent catalyst after the reaction was studied using XRD, SEM, and TEM respectively. The XRD shows a phase change of porous NiCoO2 to NiCo alloy, whereas SEM indicates the presence of fibrous structure on the surface with 91.7% of carbon while keeping 1:1 ratio of Ni and Co after the reaction. The detailed analysis of carbon structure using HRTEM-STEM shows the simultaneous growth of carbon nanofibers (CNFs) and multiwalled carbon nanotubes (MWCNTs) that were favored by larger and smaller crystallites respectively. A detailed mechanism of carbon deposition is also proposed.

Growth and Annealing Properties of Carbon Nanofibers on Carbon Black By Using Chemical Vapour Deposition

Various nanocarbon materials, such as fullerenes [1], carbon nanotubes (CNTs) [2], graphene [3], carbon nanofibers (CNFs) [4,5,6] and carbon nanospheres [7], have potential applications in next-generation electrical [8,9] and electrochemical devices [10–13] due to their excellent physical (e.g., crystal, semi-crystal, amorphous structures) and chemical properties (e.g., high specific surface area, large pore volume). The nanostructures depend on the catalysts, hydrocarbon sources, temperature, etc., and the growth mechanism has been extensively studied [5,6,14]. Nanocarbon composite materials are expected to exhibit synergistic effects not only in the bulk but also in composites. Amorphous carbon blacks (CBs), such as Vulcan XC-72R (Cabot Co.) and Ketjen (Akzonobel, Lion speciality chemicals Co., Ltd.), are used widely as electrode supporting nanocarbon materials due to their excellent electronic conducting properties and high specific surface areas. Recently, for renewable energy conversion technology, high performance nanocarbon materials are still required. In this study, we investigated the growth and annealing properties of CNFs on CB by using chemical vapour deposition with a Ni catalyst. The as-grown CNF-CB composites were annealed at different temperatures. The crystallinity and thermal properties of the CNF-CB composite increased with an increase in the annealing temperature. The micropore and mesopore areas of the CNF-CB composites decreased and increased, respectively, as compared to those of CB only. The CNF-CB composite annealed at 1600 °C had a higher current density than only CB did, as determined by using cyclic voltammetry (CV). The CNF-CB composites should be extremely useful in various energy applications, such as fuel cells, capacitors, and batteries. Acknowledgements This work was partially supported by the MEXT program for development of environmental technology using nanotechnology.

Fractionation of direct dyes using modified vapor grown carbon nanofibers and zirconia in cellulose acetate blend membranes

In the textile industry, membrane technology has been widely employed for the exclusion of direct dyes. In this research paper, firstly vapor grown carbon nanofibers (VGCNFs) were functionalized with carboxylates group via piranha oxidation, and then series of CA/PEO-PPO-PEO triblock copolymers were prepared by blending with varying weight percentages of modified VGCNFs and Zirconia (ZrO2). The structural morphologies of membranes were visualized by scanning electron microscope (SEM), atomic force microscopy (AFM) and transmission electron microscopy (TEM), which exhibits the dispersity of dual fillers in polymer matrix thus improving the microstructure of resultant membranes. The experimental data indicates that the modified VGCNF and ZrO2 nanoparticles were shown increase hydrophilic character. The direct dyes rejection were successfully after filler addition, which were 96% (for Direct Red), 99% (for Direct Blue) and 93% (for Direct Orange). The membranes showed a better antifouling property even after several washing cycles along with improved biofouling property, both of these properties showed a better membrane life. As an outcome, this research could have been a great potential to be used to treat dyes in textile industry.

Activated carbon surface modification by catalytic chemical vapor deposition of natural gas for enhancing adsorption of greenhouse gases

Activated Carbon (AC) was modified by Catalytic Chemical Vapor Deposition (CCVD) of Urban Natural Gas (UNG) using microwave irradiation. Pretreatment of the as-prepared activated carbon was performed by washing with nitric acid and Ni impregnation by nickel nitrate solution (with 1.5–3.5 wt.% Ni/AC) followed by N2 thermal treatment at 450 °C. Modification of the AC surface was carried out by carbon source flow through the surface under microwave irradiation. Carbon nanofibers (CNFs) growth was observed on the surface of AC by FESEM analysis. The properties of the surface were characterized by FTIR, FESEM, EDX and BET analysis. The effect of the carbon source and the content of Ni/AC were investigated on the CNF quality. Among three carbon sources (pure methane, methane-ethane mixture, and UNG), the fibers formed under UNG flow possessed the best surface characteristics. Presence of Ni improved the rate of nanofiber formation at lower temperatures and shortened the run time. It was observed that specific surface area and total pore volume of the modified AC increased by 12% and 41% after CNF growth, respectively. Pore volume distribution indicated a slight reduction of the micropores while the number of mesopores increased with fiber formation. Equilibrium adsorption experiments were conducted on the samples for CO2, CH4, CO, and H2. The adsorption capacity and selectivity of the greenhouse gases have been improved up to 15% and 60%, respectively, whereas hydrogen adsorption capacity was negligible and remained unchanged after surface modification.