Growth Of Carbon Nanomaterials Research Articles

Template synthesis and characterization of carbon nanomaterials from ferrocene crystals

Filamentous ribbon-like structures of highly disordered carbon of thickness 10–100 nm built from merged individual carbon nanofibers were synthesised by chemical vapour deposition from saturated ferrocene–benzene solution at 950 K. The materials obtained were characterized by electron microscopy, x-ray and electron diffraction, Raman spectroscopy and a possible growth mechanism for their formation was proposed and discussed. The synthesis demonstrates the possibility of a template growth of carbon nanomaterials and supports the vapour–solid–solid growth model of carbon materials because the catalysing metal particles are solid under the experimental conditions. Due to the large number of structural defects, filamentous structure, submicrometer thickness and low intraparticle diffusion of the nanomaterials, they can find application in catalysis as catalyst supports and sorbents.

Investigation of Carbon Nanomaterials Growth on Anode Surface by Arc Discharge Method

Investigation of Carbon Nanomaterials Growth on Anode Surface by Arc Discharge Method

Effect of Metal Catalysts on Synthesis of Carbon Nanomaterials by Alcohol Catalytic Chemical Vapor Deposition

Carbon nanomaterials (CNMs) were synthesized by alcohol catalytic chemical vapor deposition (CVD) at atmospheric pressure using different metal catalysts (Ni, Co and Fe) at growth temperature of 700◦C. Ni and Fe exhibited as active catalysts for multi-walled carbon nanotubes (MWNTs) growth, while Co acted as an active catalyst for bamboo-like MWNTs and carbon nanofibers (CNFs). The CNMs synthesized from Ni catalyst showed the highest crystallinity with a small amount of byproducts. These results imply that metal catalyst is key parameter to the structure, morphology and crystallinity of CNMs. The different effect of metal catalyst on growth of CNMs can be described in term of the difference in the change in Gibbs free energy for metal carbide formation.

The Effect of Substrate on the Low-Temperature Carbon Nanomaterials Growth by Microwave Excited Surface-wave Plasma Chemical Vapor Deposition

Multi-walled carbon nanotubes (CNTs) have been successfully grown on Si and polyimide substrates at temperature of 230~260°C by the microwave-excited surface wave plasma technique. Graphene-encapsulated nickel nanoparticles have been used as the catalyst for growing CNTs in NH3/CH4 plasma. The optimal gas flow mixture ratio and bias voltage for this type of plasma were investigated. High-resolution transmission electron microscopy and Raman spectroscopy investigations show similar results for CNTs grown on the Si and polyimide substrates.

The development of a ‘process map’ for the growth of carbon nanomaterials from ferrocene by injection CVD

Ferrocene was used as a catalyst in a hydrocarbon solution to carry out injection chemical vapour deposition (CVD) growth of carbon nanomaterials in a horizontal tube furnace. The presence and quality of various carbon materials was determined using Raman spectroscopy, thermogravimetric analysis, and electron microscopy. Products ranged from amorphous carbon (a-C), multi walled carbon nanotubes (MWNTs) and vapour grown fibers (VGFs). Catalyst concentration, growth temperature, injection rate, carrier gas flow rate, and the choice of hydrocarbon were found to influence the product outcome. Slower injection rates gave higher isolated yield. High catalyst concentrations were found to produce less pure carbon materials with iron oxides impurities. Higher temperatures were favourable to nanotube formation. The use of benzene was found to increase yield compared with the other hydrocarbons. In this work we developed a process map to chart the various carbon nanomaterial allotropes that were created according to reaction parameters.

Low Temperature Growth of Carbon Nanomaterials on the Polymer Substrates by Microwave Plasma Technique

Low Temperature Growth of Carbon Nanomaterials on the Polymer Substrates by Microwave Plasma Technique

Synthesis of various carbon nanomaterials (CNMs) on powdered activated carbon

Carbon nanomaterials (CNMs) are promising in many potential applications for their attractive physical and chemical properties. Chemical vapor deposition technique (CVD) is used to synthesize CNMs on fixed substrate. Powdered activated carbon (PAC) was used as a successful substrate for CNMs growth in CVD reaction process. Iron clustered nano particles Fe3+ was impregnated successfully on PAC surface under sonication. EDX characterization results showed the evidence of impregnation and growth of CNMs on PAC surface. The optimum weight percentage of Fe3+ impregnation on PAC was found to be 5%. The CVD reactor used in thisstudy was locally fabricated and modified to reduce the process time and cost. CNMs were synthesized at different temperatures (850, 750, 650 and 550°C) and the maximum yield was obtained at 550°C with majority of CNFs. Various types of CNMs were grown: carbon nanotubes (CNTs), carbon nanofibers (CNFs), CN spheres and CN-coils. Field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM) images were studied for all the samples to investigate the nanostructures for CNMs. Key words: Carbon nanomaterials, carbon nanotube, carbon nanofibers, nanotechnology, chemical vapor deposition, catalyst impregnation, activated carbon

The effect of substituted alkynes on nickel catalyst morphology and carbon fiber growth

The growth of shaped carbon nanomaterials from a range of substituted alkynes over a NiO catalyst was investigated. It was found that the structure of the substituted alkyne affected both catalyst morphology and carbon fiber growth. For linear alkynes (1-pentyne to 1-octyne) the fiber morphology and yield varied with the type of alkyne used. It was also found that hetero-atoms (Cl, Br, OH and NH 2) greatly impacted carbon fiber growth and structure. An analysis of the catalyst particles associated with the carbon fibers grown from various alkynes showed that different alkynes gave differently shaped Ni catalyst particles. It was found that pre-treatment of the catalyst with an alkyne such as trimethylsilyl acetylene or ethynyl aniline (that did not give fiber growth), followed by treatment with acetylene initiated fiber growth morphologies (Y-junction, helical or straight fibers) different from that observed after direct treatment with acetylene. Further, sequential fiber growth from two alkynes that were both capable of producing fibers (e.g. methyl prop-2-ynoate followed by prop-2-yn-1-amine) resulted in ‘co-block’ fiber growth. These results highlight the dynamic relationships that exists between carbon source, catalyst morphology and carbon nanomaterial growth.

Growth of Carbon Nanomaterials on Granular Activated Carbon

Since the discovery of carbon nanotubes (CNT) and subsequent Carbon Nanomaterials (CNMs), there has been an ever increased academic and industrial interest on there various fields of application due to their exceptional mechanical and electrical properties. In this work, granular activated carbon (GAC) made from palm Kernel shell (PKS) of mesh size 8x12 was impregnated with nickel as substrate catalyst for the growth of Carbon Nanomaterials (CNMs) in a chemical decomposition (CVD) reactor. Various percentages by weight of the nickel (1%, 3%, 5% and 7%) were impregnated on the GAC surface for CNM growth. The CNM growth took place at a fixed reaction temperature and gas flow rates for both the hydrogen gas and carbon source. Characterization of the novel composite material was carried out by using SEM, FESEM and TEM. The results show that growth was successful as at 1% nickel impregnation, while a denser network distribution and rougher surface of CNM was observed at 7% nickel. The growth of CNMs on a larger substrate GAC should make handling of the CNMs easier and it is expected to also open new doors of application in water treatment and oil refining.

Influence of the fuel structure on the flame synthesis of carbon nanomaterials

Carbon nanomaterials (CNMs) were grown on nickel-coated stainless-steel mesh grids using a combustion synthesis method. Three fuel feedstocks of dissimilar chemical structures, ethylene, ethyl benzene and ethyl alcohol, were burned at fuel-rich equivalence ratios to generate disparate combustion products. The chemical compositions of these products were assessed to identify and contrast the species that contribute to the growth of CNMs. The generated CNMs were characterized using SEM and TEM. Each set of conditions produced a distinct distribution (bi-modal or mono-modal) of CNMs, including carbon nanotubes and carbon nanofibers, both of varying diameters and lengths. The effects of combustion-generated light aliphatic hydrocarbons and light aromatic hydrocarbons on CNM growth and structure were ascertained. It was found that ethylene and ethyl alcohol generated tubular CNMs under all tested conditions, whereas ethyl benzene generated only small amounts of CNMs and under much more limited conditions. It was also determined that concentrations of aliphatic species, notably methane and acetylene, at mole fractions as low as 500 ppm have a thickening effect on the resulting CNMs. Linear correlations were found between the concentrations of these species and the mean diameter of the CNMs.

Effect of growth of carbon nanofibers on the electrical conductivity of carbon fibers

Recently, research on various carbon materials such as carbon fibers (CFs), carbon black (CB), carbon nanofibers (CNFs), carbon nanotubes (CNTs), fullerenes, and graphene has received considerable attention. In particular, CFs that exhibit a graphite-layered structure have a strong structural anisotropy, and the alignment of CFs along the direction of an applied electrochemical application field (antistatic material, electromagnetic interference shielding material, sensing elements, heating elements, and packing of electronic components and equipment) has been attempted by utilizing their mechanically strong, durable and electrically conductive properties. Most recently, there have been many studies of the improvement of electrical conductivity of CFs. Its electrical conductivity strongly depends on the thermal treatment, microtexture, hybridization, surface treatments, content of heteroatoms, length. A number of studies have shown that the various methods for the enhancement of electrical conductivity of CFs such as plating with conductive metals electrochemical or plasma oxidation, fluorination, and the growth of carbon nanomaterials on its surfaces, etc. For example, Park et al. prepared the activated carbon fibers (ACFs) coated with CNFs for enhancement electrical conductivity of ACFs due to the CNFs have unique electrical properties. Jiang et al. reported that the use of Ag as a metallic film is coated onto the surface of chopped CFs or ACFs to increase the conductivity of conductive fillers. Zeng et al. synthesized the CNTs on CFs substrate by the floating catalyst method for field electron emission material. The catalytic chemical vapor deposition (CCVD) was a most common method for the synthesis of carbon nanomaterials on the different substrates. However, there are some problems in the synthesis of carbon nanomaterials (CNFs or CNTs) on CF surfaces by CCVD method: (a) the ununiformly dispersed-metal catalysts (such as Fe, Ni, and Co catalyst) on CF surfaces due to its low specific surface area; (b) the metal catalysts were easily diffused into the CFs; (c) the metal catalysts were easily aggregated into large particles and formed mixed phases of carbon materials (CNFs, CNTs, and amorphous carbon); (d) the products require the purity process. So, the uniform dispersion of catalysts is a critical process to get uniformly grown CNFs on CF surfaces. As few research reported, the mesoporous silica films are excellent catalyst supports and have been used in the growth of carbon nanomaterials. Zheng et al. reported that ordered meso silica films can direct the growth of CNTs from perpendicular to parallel to the substrate surface through control of the distribution of catalysts. In this work, we have synthesized CNFs on CF surfaces by using Ni-doped mesoporous silica film at different temperatures, and the density of CNFs on CF surfaces is uniform and densely. The Ni-doped mesoporous silica film was used to control the distribution of catalysts on CF surfaces. We examined the microstructure of CNFs coated CFs, physical properties, electrical conductivity, of the paper.

General rules governing carbon nanomaterial growth directly on metal support by chemical vapor deposition

Growing carbon nanotubes and relative nanomaterials directly on metal support has attracted increasing attention due to its applications in nanoelectronics and composites. In order to reveal the effect of metal support on the catalytic property of the catalyst, several metal powders were selected as catalyst carrier for carbon nanomaterial growth by chemical vapor deposition (CVD). The results show that the interaction between metal support and catalyst plays a key role for the activity of the catalyst, while, the metal support itself has a relative little effect. By critically controlling their interactions, all metal powders are extrapolated to be used as catalyst supports for the carbon nanomaterial growth by CVD.

Writing in Foreign Language Contexts: Learning, Teaching, and Research, Rosa Manchón (Ed.). Multilingual Matters, Bristol, UK (2009). 296 pp.

A series of micro-disperse Ni-Mo alloys with the sponge-like structure was prepared by a simultaneous precipitation method followed by sintering of the sediment in H2 atmosphere at 800 °C. According to XRD data, the formation of single-phase solid solution Ni1-xMox took place for the samples with Mo content of 0.6–8.3 wt.%. Synthesized samples were studied in a process of the catalytic CVD of C2H4Cl2 at 550–700 °C. In situ kinetic studies of carbon deposition process were carried out in a flow gravimetric setup equipped with McBain balances. An interaction of Ni-Mo alloys with C2H4Cl2 is accompanied by their rapid disintegration with formation of disperse active particles catalyzing the growth of carbon nanomaterials (CNM). The strong boosting effect of Mo on the catalytic performance of Ni was revealed. The maximum yield of CNM product (8.3 wt.% Mo, 600 °C, 120 min) was as high as 45 g/gM. The study on effect of the reaction temperature on the CNM yield allowed one to define an optimal temperature regime. The impact of Mo concentration upon the morphology, structural features and textural properties of the produced carbon fibers was investigated by means of SEM, TEM, Raman spectroscopy and low-temperature nitrogen adsorption. The role of chemisorbed chlorine species in a pulse-to-pulse regime of the segmented carbon filaments formation was discussed.

Effects of total CH 4/Ar gas pressure on the structures and field electron emission properties of carbon nanomaterials grown by plasma-enhanced chemical vapor deposition

The effects of total CH 4/Ar gas pressure on the growth of carbon nanomaterials on Si (1 0 0) substrate covered with CoO nanoparticles, using plasma-enhanced chemical vapor deposition (PECVD), were investigated. The structures of obtained products were correlated with the total gas pressure and changed from pure carbon nanotubes (CNTs) through hybrid CNTs/graphene sheets (GSs), to pure GSs as the total gas pressure changed from 20 to 4 Torr. The total gas pressure influenced the density of hydrogen radicals and Ar ions in chamber, which in turn determined the degree of how CoO nanoparticles were deoxidized and ion bombardment energy that governed the final carbon nanomaterials. Moreover, the obtained hybrid CNTs/GSs exhibited a lower turn-on field (1.4 V/μm) emission, compared to either 2.7 V/μm for pure CNTs or 2.2 V/μm for pure GSs, at current density of 10 μA/cm 2.

The effect of carbon microfiber substrate pretreatment on the growth of carbon nanomaterials

The floating catalyst method was used to obtain carbon nanotubes, carbon submicrotubes and other carbon nanomaterials by changing the pretreatment conditions of carbon microfiber substrate. The morphology and microstructure of the obtained products were characterized by field emission scanning electron microscopy, high-resolution transmission electron microscopy and Raman spectroscopy. The results showed that on untreated carbon microfiber surface, only some carbon particles and several carbon nanotubes were deposited. However, after carbon microfibers were boiled in the solution of H 2SO 4/HNO 3 and were immersed in the solutions of Fe(NO 3) 3/xylene, Fe(NO 3) 3/acetone, ferrocene/acetone and Fe(NO 3) 3/ferrocene/acetone, the obtained products were a high-density carbon nanotubes, carbon nanotubes with many carbon particles, carbon submicrotubes and a mixture of carbon nanomaterial, respectively. Thus the pretreatment of the carbon microfiber substrate greatly influenced the morphology and microstructure of the synthesized products.

The production of carbon nano-materials by arc discharge under water or liquid nitrogen

The growth mechanism of carbon nano-materials by arc discharge in water or liquid nitrogen was investigated using a special arc discharge apparatus. High-resolution transmission electron microscopy was used to observe and analyze the products. Results indicated that multi-walled carbon nanotubes (MWCNTs) and carbon onions can be produced by arc discharge in water and liquid nitrogen respectively. Single-walled carbon nanohorns can be produced by arc discharge in liquid nitrogen, and cobalt encapsulated carbon nano-particles can be produced by cobalt catalyzed carbon arc discharge in water. The liquids acted as quenching walls for the nucleation and growth of carbon nano-materials, resulting in the formation of different forms of carbon nano-materials. A cross alternating magnetic field with a frequency 5 Hz can affect the nucleation of nano-materials to form MWCNTs or carbon onions because nucleation time is longer than the periodicity of the magnetic field. Based on the experimental phenomena, a primary physical model was proposed to interpret the growth of nano-materials by arc discharge in liquids.

Magnetic properties and transmission electron microscopy studies of Ni nanoparticles encapsulated in carbon nanocages and carbon nanotubes

Three types of carbon nanomaterials, including bamboo-shaped carbon nanotubes with Ni encapsulated and hollow and Ni catalytic particles filled carbon nanocages, have been prepared by methane catalytic decomposition at a relatively low temperature. Transmission electron microscopy observations showed that fascinating fullerene-like Ni–C (graphitic) core–shell nanostructures predominated. Detailed examination of high-resolution transmission electron microscopy showed that the walls of bamboo-shaped carbon nanotubes with quasi-cone catalytic particles encapsulated consisted of oblique graphene planes with respect to the tube axis. The Ni particles encapsulated in the carbon nanocages were larger than that encapsulated in carbon nanotubes, but the diameters of the cores of hollow carbon nanocages were less than that of Ni particles encapsulated in carbon nanotubes, suggesting that the sizes of catalyst particles played an important role during carbon nanomaterial growth. The magnetic properties of the carbon nanomaterials were measured, which showed relatively large coercive force ( H c = 138.4 O e) and good ferromagnetism ( M r/ M s = 0.325).

Effects of ion bombardment on the morphology and microstructure of carbon nanomaterials grown by microwave plasma chemical vapor deposition

Effects of ion bombardment on the growth of carbon nanomaterials on Fe substrates in microwave plasma chemical vapor deposition were investigated. The product morphologies are directly correlated with the kinetic energy of bombarding ions and range from nanosheets, through cones, to aligned nanotubes for bias voltages from 0to−250V, respectively. A change in growth mechanism from a base growth to tip growth induced by the competition between etching and growth is responsible for the observed changes. These findings bring insights into the growth mechanism and provide a strong tool to control the structure of carbon nanomaterials.

Bamboo-shaped carbon nanotubes produced by catalytic decomposition of methane over nickel nanoparticles supported on aluminum

Bamboo-shaped carbon nanotubes (CNTs) and herringbone nanofibers were catalytically synthesized by a decomposition of methane over Ni/Al catalyst under N 2 at the low temperature (500–600 °C). Transmission electron microscopy (TEM) was used to investigate the bamboo-shaped CNTs and the nanofibers. High-resolution TEM analysis revealed that two species of bamboo-shaped tubes with different morphologies and structures, categorized according to the shape and participation of the encapsulated catalytic nanoparticles, coexist in one sample. It is found that the morphology and structure of the catalytic particles play very important roles during carbon nanomaterial growth. The growth mechanisms for the bamboo-shaped CNTs and nanofibers are proposed in detail, especially the formation process of compartments of the bamboo-shaped CNTs.

Y-Junction Multibranched Carbon Nanofibers

Multibranched carbon nanofiber (CNF) is produced by a thermal chemical vapor deposition method using camphor as precursor. Nickel and cobalt catalyst was deposited on silicon substrate by e-beam evaporation and used as substrate for the growth of carbon nanomaterials. Branched carbon nanofibers were grown on the nickel thin film at 900 degrees C, whereas spherical carbon beads formed on the cobalt thin film. These fibers followed base growth mechanism devoid of any catalyst particle at the tip of fibers.