Catalyst Chemical Vapor Deposition Method Research Articles

Controlled Growth of Single-Walled Carbon Nanotube Films by Iron-assisted Floating Solid Catalyst Chemical Vapor Deposition.

Single-walled carbon nanotube (SWNT) films, with exciting electronic properties are increasingly important for next-generation technologies. Here, an Iron-assisted floating solid catalyst chemical vapor deposition (IA-FSCCVD) method is developed for the controlled growth of high-quality and high-purity SWNT films. Titanium carbide nanoparticles with a high melting point are used as the solid catalysts, which provide a stable template for SWNT growth through the perpendicular growth mode. Trace amounts of iron are introduced to increase the efficiency of SWNT growth. Gas chromatography measurements and density functional theory show that the gas-phase iron acts as a pre-cracking assistance for the carbon source, promoting the growth of SWNTs. Carbon nanotube films with a high quality (average IG/ID = 166) are successfully prepared, a small diameter deviation (mean diameter of 1.6nm), and a high content of SWNTs (97%) using the IA-FSCCVD platform. This work provides a powerful way to prepare the carbon nanotube aggregates with a controlled structure.

Tensile properties at various strain rates of flexible carbon nanotube film densified by the combination of chlorosulfuric acid and uniaxial drawing

AbstractThe quasi‐static tensile properties of carbon nanotube (CNT) films have been extensively investigated, yet research on their impact tensile properties at high strain rates remains scarce. In this article, CNT films prepared by floating catalyst chemical vapor deposition (FCCVD) method were densely arranged by chlorosulfuric acid (CSA) under wet stretching. The Instron 3365 and miniaturized split Hopkinson tension bar (SHTB) were used to conduct tensile testing at different strain rates. The findings reveal that CSA wet‐stretching markedly enhances the density and orientation of CNT films, resulting in significant improvements in tensile properties with a notable strain rate effect. Specifically, when immersed for 60 s under a draft ratio of 40% and a strain rate of 1900 s−1, the densified CNT films exhibit maximum stress and energy absorption values of 777.44 MPa and 54.79 MJ/m3, respectively, achieving a 637.1% and 425.7% increase compared with the original film. This research provides a convenient and feasible strategy to prepare CNT films with high energy absorption tolerance across various strain rates, thus expanding the practical application potential of CNT films.Highlights The study innovates a posttreatment way to produce superior FCCVD CNT films. CSA treatment and wet stretching enhance CNT films' mechanical properties. Dynamic fracture strength boosts over 600% and energy absorption raises over 400%. CSA can purify FCCVD‐prepared CNT films, greatly improving their properties. The Prep can be effectively integrated with the direct spinning process.

Structural, Electrical, and Optical Properties of Single-Walled Carbon Nanotubes Synthesized through Floating Catalyst Chemical Vapor Deposition.

Single-walled carbon nanotube (SWCNT) thin films were synthesized by using a floating catalyst chemical vapor deposition (FCCVD) method with a low flow rate (200 sccm) of mixed gases (Ar and H2). SWCNT thin films with different thicknesses can be prepared by controlling the collection time of the SWCNTs on membrane filters. Transmission electron microscopy (TEM) showed that the SWCNTs formed bundles and that they had an average diameter of 1.46 nm. The Raman spectra of the SWCNT films suggested that the synthesized SWCNTs were very well crystallized. Although the electrical properties of SWCNTs have been widely studied so far, the Hall effect of SWCNTs has not been fully studied to explore the electrical characteristics of SWCNT thin films. In this research, Hall effect measurements have been performed to investigate the important electrical characteristics of SWCNTs, such as their carrier mobility, carrier density, Hall coefficient, conductivity, and sheet resistance. The samples with transmittance between 95 and 43% showed a high carrier density of 1021-1023 cm-3. The SWCNTs were also treated using Brønsted acids (HCl, HNO3, H2SO4) to enhance their electrical properties. After the acid treatments, the samples maintained their p-type nature. The carrier mobility and conductivity increased, and the sheet resistance decreased for all treated samples. The highest mobility of 1.5 cm2/Vs was obtained with the sulfuric acid treatment at 80 °C, while the highest conductivity (30,720 S/m) and lowest sheet resistance (43 ohm/square) were achieved with the nitric acid treatment at room temperature. Different functional groups were identified in our synthesized SWCNTs before and after the acid treatments using Fourier-Transform Infrared Spectroscopy (FTIR).

One-step aerosol synthesis of iron nanoparticles coated single-walled carbon nanotubes (Fe@SWCNT) for multifunctional composite textiles with electromagnetic interference shielding properties

Single-walled carbon nanotubes (SWCNTs) based nanocomposites demonstrate remarkable electromagnetic interference (EMI) shielding potential. However, the efficient and rapid fabrication of SWCNT-based nanocomposite remains a technical challenge. This study successfully one-step synthesizes iron (Fe) nanoparticle-enriched SWCNTs (Fe@SWCNT) using the floating catalyst chemical vapor deposition (FCCVD) method in the aerosol phase. The aerosol-synthesized Fe@SWCNTs were directly integrated with carbon cloth (CC) and polydimethylsiloxane (PDMS) to develop a compelling nanocomposite film for multifunctional EMI shielding. The composite film exhibits exceptional shielding effectiveness of 50.2 dB in the X-band (8.2–12.4 GHz) with absolute shielding effectiveness (SSEt) of 3279.3 dB cm²/g. Notably, the film also displays rapid and uniform electrical heating at low voltages, reaching a temperature of 110.4 °C under a 1.0 V. Overall, this study reveals the potential applications of multifunctional textiles in fields such as EMI shielding, hydrophobicity, and thermal management.

Molecular dynamics simulation of carbon nanotube growth under a tensile strain

We performed molecular dynamics simulations of carbon nanotube (CNT) to elucidate the growth process in the floating catalyst chemical vapor deposition method (FCCVD). FCCVD has two features: a nanometer-sized cementite (Fe3\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$_3$$\\end{document}C) particle whose melting point is depressed because of the larger surface-to-volume ratio and tensile strain between the growing CNT and the catalyst. The simulations, including these effects, demonstrated that the number of 6-membered rings of the (6,4) chiral CNT constantly increased at a speed of 1mm/s\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${1}\\,{\ extrm{mm}/\ extrm{s}}$$\\end{document} at 1273K\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${1273}\\,{\ extrm{K}}$$\\end{document}, whereas those of the armchair and zigzag CNTs were stopped in the simulations and only reached half of the numbers for chiral CNT. Both the temperature and CNT chirality significantly affected CNT growth under tensile strain.

A new method for evaluation of nanotube growth kinetics in aerosol CVD

Aerosol chemical vapor deposition (CVD) – a particular case of floating catalyst CVD method with an extreme dilution of catalyst – has been demonstrated to be one of the most advanced one-stage and continuous techniques for the production of single-walled carbon nanotubes (SWCNTs) for various applications in electronics, optics, energy storage, etc. Nevertheless, rational scaling of the aerosol CVD reactor is often limited by a fundamental problem of tracking the growth kinetics, in particular, the nanotube growth rate and the catalyst deactivation rate. We propose a robust method for the assessment of nanotube growth kinetics (growth rate and catalyst lifetime) based on the analysis of the SWCNT film equivalent sheet resistance (R90) versus residence time (τ) dependencies. We have demonstrated identical trends of R90-vs-τ and length-vs-τ curves at different concentrations of CO2 used as a promoter in the Boudouard reaction- (CO-) based synthesis. As a result, we have revealed the mechanisms behind the CO2 effect on the catalyst deactivation rate not reported before. In particular, we observed an increase in CO2 concentration to provide a faster growth rate but an earlier catalyst deactivation. We believe this work might be useful for researchers from both academia and industry and facilitate more active development of aerosol CVD methods for the production of new materials.

Gamma-ray irradiation to achieve high tensile performance of unidirectional CNT yarn laminates

Continuous carbon nanotube (CNT) yarn fabricated from a floating catalyst chemical vapor deposition (FCCVD) method is treated under gamma-ray irradiation to enhance the mechanical properties of the CNT yarn and its unidirectional composite laminates. Gammy-ray doses varying from 50 kGy to 1200 kGy are used to irradiate CNT yarns and their microstructures, tensile properties and surface characterizations are studied. The graphitic structure change is not clear from the transmission electron microscopy, however, the specific tensile strength and modulus of yarn vary slightly within 10 % as the dose increased. This modulus trend coincides with mesoscopic distinct element modeling (mDEM) simulation results. Surface characterization shows additional oxygen functional groups and smaller contact angles after irradiation. Interestingly, the specific tensile properties of composite laminates also increase relative to the yarns, and the unidirectional laminate from CNT yarn treated with the optimal dose of 700 kGy achieves specific strength and modulus as high as 1.89 GPa/gcm−3 and 258 GPa/gcm−3, respectively, which are 30.9 % and 37 % increases compared to the control laminate. The results indicate that radiation-induced crosslinking among the CNTs and the formation of surface-active sites leads to enhanced load transfer in the yarns and promote CNT/resin interfacial bonding.

Boosting CO-based synthesis of single-walled carbon nanotubes with hydrogen

Aerosol (floating catalyst) chemical vapor deposition method based on CO disproportionation (the Boudouard reaction) is one of the most promising techniques for the synthesis of single-walled carbon nanotubes (SWCNTs), especially in the form of thin films. However, despite its advantages (i.e., high quality of nanotubes, absence of double- or multi-walled nanotubes, and high controllability of the process), synthesis based on CO disproportionation fails to provide high-yield production. In this work, we examined the effect of hydrogen, admixed to the CO atmosphere as a growth promoter, on the synthesis and properties of SWCNTs. Using optical spectroscopy techniques, conductivity tests, TEM and SEM analysis, and thermodynamic calculations, we revealed hydrogen affects both catalyst activation and nanotube growth. We found a positive H2 effect in two different temperature regimes: the yield increased by a factor of ∼15 at a low temperature (880 °C), which, after doping, led to one of the lowest ratios of the equivalent sheet resistance (R90) and yield (i) and SWCNT lengthening by a factor of 2.4 leading to a 3-fold decrease in an R90 coupled with a noticeable increase in the yield at a high temperature (1000 °C) (ii). We believe the presented results are fruitful for the fundamental understanding of the mechanism for nanotube growth and practical opportunity to fine-tune the production rate of SWCNT films.

Thermal energy compensation strategy to achieve rambutan-like CoFe@C-CNTs composites with controllable cross-linked networks for broadband microwave absorption

Combining carbon nanotubes (CNTs) with dielectric/magnetic materials is an attractive strategy to obtain high-performance microwave absorbing materials. However, it remains great challenges to overcome the agglomeration of CNTs and balance magnetic components to achieve impedance matching and broadband absorption. Herein, a thermal energy compensation strategy is designed to construct rambutan-like CoFe@C-CNTs composites with excellent microwave absorption performances via a catalyst chemical vapor deposition method and the subsequent reduction process. This strategy fully utilizes the thermal energy released during the C2H2 carbonization process, allowing the cracking of C2H2 and the growth of CNTs to continue at a temperature of lower than 430 °C. By adjusting the C2H2 introduction time in the cooling process of preheated cobalt iron oxide (CoFeO) nanoparticles, the number and length of CNTs on the carbon shells covering the surface of CoFeO cores can be controlled without forming metal carbides. The abundant interfaces, defects and grain boundaries in CoFe@C-CNTs composites contribute to enhancing the polarization loss via various polarizations and relaxations. Meanwhile, the appropriate 3D conductive network constructed by properly controlled CNTs provides remarkable additional conductivity loss. Furthermore, the effective retention of magnetic components greatly improves the impedance matching of the composites and offers considerable magnetic loss. Therefore, the optimized CoFe@C-CNTs-3 composite shows an effective absorption bandwidth of 9.00 GHz with a thickness of 2.1 mm. The proposed thermal energy compensation strategy provides a novel insight into developing magnetic metal-CNTs composites with potential practical applications.

Study on the law and mechanism of anisotropic conductivity of carbon nanotubes film prepared by floating catalytic chemical vapor deposition method

Carbon nanotubes (CNTs) film has attracted extensive attention in the field of electronics, sensors, and other potential applications due to their excellent electrical conductivity. The conductivity of CNTs film is one of the most important aspects of engineering applications. This study investigates the conductivity of CNTs film with varying areal density, prepared using the floating catalyst chemical vapor deposition (FCCVD) method and densified by rolling. The square resistance of pre- and post-rolling films was measured to characterize the electrical properties. Experimental results indicate that square resistance decreases with increasing areal density and stabilizes eventually. A mathematical formula was derived to explain the relationship between areal density and square resistance, incorporating volume and areal density formulas. Experimental data curves of pre- and post-rolling films were fitted, yielding mathematical relations consistent with the derived formulas. The electrical conductivity of post-rolling CNTs film was superior to pre-rolling in experiment and calculation. The charge carrier transport mechanism in CNTs film was studied by analyzing its internal structure and electrical properties. Surface conductivity was over 1000 times higher than volume conductivity, attributed to the distribution of CNTs bundles in collection and thickness directions. Charge carrier transport capacity decreased with increasing layers in thickness direction due to contact resistance and large resistance at tube–tube junctions. Layers of CNTs near the current application surface significantly contribute to charge carrier transport at high areal density levels.

The improvement of yield and thermal stability of single-walled carbon nanotubes fabricated by Gd-assisted FCCVD

In this work, single-walled carbon nanotubes (SWNTs) were synthesized by a scalable floating catalyst chemical vapor deposition (FCCVD) method, in which Gd was used as growth promotor to improve the yield and quality of SWNTs. Based on the characterization results of electron microscope, thermogravimetric analysis and Raman spectroscopy, the application of Gd leads to a great increase in the production of large-diameter SWNTs with a narrow diameter distribution and an enhanced thermal stability. The newly developed FCCVD technique makes it possible to produce large-diameter SWNTs at a low cost, and the generated structurally homogenous SWNTs are suitable for their applications in the fields of electronic systems and electromagnetic shielding, etc.

Facile fabrication of SWCNT film-based superhydrophobic cotton fabrics for oil/water separation and self-cleaning

With the increase of oily waste, oil-water separation has become an urgent and difficult task. However, the current challenge is to fabricate such efficient membrane materials for oil-water separation. Herein, superhydrophobic single-walled carbon nanotubes (SWCNTs)/cotton fabric (CF) was prepared via a dry process. In which the ultrathin SWCNT films with a low content of hydrophilic groups were prepared by a facile floating catalyst chemical vapor deposition method and directly deposited on CF without solvent dispersion. The obtained SWCNT@CF was further treated by 1 H,1 H,2 H,2 H-perfluorooctyltriethoxysilane (POTS). Due to the synergistic effect of SWCNTs and POTS, the POTS-modified SWCNT@CF displayed excellent superhydrophobicity with a water contact angle（WCA）of ∼163.3°, and consequently can be further used as a membrane for oil-water separation. These superhydrophobic fabrics have high oil/water separation efficiency (99.2% for dichloromethane/water) and high oil flux (28.71 ×103 L·m−2·h−1 for dichloromethane/water). Even after 25 separation cycles, oil/water separation efficiency and oil flux maintain 98.8% and 25.15 × 103 L·m−2·h−1, respectively. In addition, it exhibits high separation efficiency (∼99%) for water-in-oil emulsion. Moreover, under extreme environmental conditions, the contact angle of the obtained POTS-modified SWCNT/CF was maintained at ∼155°, keeping stable superhydrophobicity. This reported preparation strategy of superhydrophobic fabrics is environmentally friendly, low cost, sustainable, and easy to scale up, thereby exhibiting great potential in practical applications.

Defect-Induced Adsorption Switching (p- to n- Type) in Conducting Bare Carbon Nanotube Film for the Development of Highly Sensitive and Flexible Chemiresistive-Based Methanol and NO2 Sensor.

Lightweight and flexible gas sensors are essentially required for the fast detection of toxic gases to pass on the early warning to deter accident situations caused by gas leakage. In view of this, we have fabricated a thin paper-like free-standing, flexible, and sensitive carbon nanotube (CNT) aerogel gas sensor. The CNT aerogel film synthesized by the floating catalyst chemical vapor deposition method consists of a tiny network of long CNTs and ∼20% amorphous carbon. The pores and defect density of the CNT aerogel film were tuned by heating at 700 °C to obtain a sensor film, which showed excellent sensitivity for toxic NO2 and methanol gas in the concentration range of 1-100 ppm with a remarkable limit of detection ∼90 ppb. This sensor has consistently responded to toxic gas even after bending and crumpling the film. Moreover, the film heat-treated at 900 °C showed a lower response with opposite sensing characteristics due to switching of the semiconductor nature of the CNT aerogel film to n-type from p-type. The annealing temperature-based adsorption switching can be related to a type of carbon defect in the CNT aerogel film. Therefore, the developed free-standing, highly sensitive, and flexible CNT aerogel sensor paves the way for a reliable, robust, and switchable toxic gas sensor.

Efficient Fabrication of High-Quality Single-Walled Carbon Nanotubes and Their Macroscopic Conductive Fibers.

High-purity and well-graphitized single-walled carbon nanotubes (SWCNTs) with excellent physiochemical properties are ideal building blocks for the assembly of various CNT macrostructures for a wide range of applications. We report the preparation of high-quality SWCNTs on a large scale using a floating catalyst chemical vapor deposition (FCCVD) method. Under the optimum conditions, the conversion rate of the carbon source to SWCNTs reached 28.8%, and 20.4% of the metal nanoparticles were active for SWCNT growth, which are 15% and ∼400 times higher than those previously reported for FCCVD synthesis, respectively. As a result, the prepared SWCNTs have a very low residual catalyst content of ∼1.9 wt % and a high rapid oxidation temperature of 717 °C. Using these high-quality SWCNTs, we spun macroscopic SWCNT fibers by a wet-spinning process. The resulting fibers had a high electrical conductivity of 6.67 MS/m, which is 32% higher than the best value previously reported for SWCNT fibers.

Effective Self-Support Growth of Spring-Like Carbon Nanotube Arrays with Ultra-Large Specific Surface Area

Carbon nanotube (CNT) long array with higher aspect ratio is an ideal electrode material for high performance supercapacitors due to its excellent conductivity and high specific surface area (SSA). How to quickly and concisely prepare high-quality CNT long-arrays is the key to achieving large-scale application. Herein, high-quality spring-like CNT (tube diameter 5–8[Formula: see text]nm) long arrays (100–400[Formula: see text][Formula: see text]m) with high purity (96.2% after purification) and ultrahigh graphitization ([Formula: see text]) were fabricated in a high yield (eight times) by a self-supporting catalyst chemical vapor deposition (CVD) method, and its formation process was first investigated under specific conditions of iron content in catalyst, growth temperature and carbon source species. The SSAs can reach 728[Formula: see text]m2/g, which is more than twice that of MWCNTs on the market. The high graphitization and ultra-large SSAs of this spring-like CNT arrays as electrodes exhibit potential electrochemical performance.

MnO2 nanosheets synthesized on nitrogen-doped vertically aligned carbon nanotubes as a supercapacitor electrode material

In the present study, nitrogen-doped vertically aligned carbon nanotubes (N-VACNTs) were synthesized on carbon cloth (CC) using the floating catalyst chemical vapor deposition (FCCVD) method, and MnO2 nanosheets were grown on them using the hydrothermal method to produce an N-VACNT@MnO2 nanocomposite structure. In this structure, a synergistic effect was obtained by combining N-VACNTs, which allow high electrical conductivity and fast ion transfer. In the galvanostatic charge-discharge (GCD) measurements performed separately in a three-electrode test cell using 1 M of Na2SO4 electrolyte, the specific capacitance of the N-VACNTs was found to be 53.7 F g−1 at a current density of 0.5 A g−1, and the specific capacitance of the N-VACNT@MnO2 electrode structure was found to be 497 F g−1. In addition, after 10,000 charge-discharge cycles at a current density of 10 A g−1, the N-VACNT electrode retained 99 % of its initial specific capacitance, while the N-VACNT@MnO2 electrode exhibited outstanding cyclic stability with 76 % of its initial specific capacitance. Moreover, in the as-fabricated asymmetric supercapacitor (ASC) using N-VACNTs and N-VACNTs@MnO2, the negative and positive electrodes achieved a stable voltage window of 0–1.7 V, with a specific capacitance of 59.4 F g−1 at a current density of 1 A g−1. Additionally, this ASC showed good cycling stability retaining 84 % of its specific capacitance at the end of 10,000 cycles. Therefore, this ASC structure with an energy density of 24.7 Wh kg−1 and a power density of 15.7 kW kg−1 are promising electrode materials for energy storage.

Preparation of isolated semiconducting single-wall carbon nanotubes by oxygen-assisted floating catalyst chemical vapor deposition

Semiconducting single-wall carbon nanotubes (s-SWCNTs) are promising for use in flexible electronics as a channel material. However, it remains a big challenge to directly grow high purity, high-quality s-SWCNTs in large scale. Here we report the synthesis of isolated s-SWCNTs by an oxygen-assisted floating catalyst chemical vapor deposition method. By controlling the density of nucleated SWCNTs, isolated or small-bundled, rather than large-bundled SWCNTs were generated in a floating state, so that the oxygen introduced could more efficiently selectively etch the metallic-SWCNTs formed. In addition, it was found that the oxygen also functions in limiting the size of Fe catalyst nanoparticles in a narrow range of 5–8 nm. As a result, isolated s-SWCNTs with a narrow diameter distribution were synthesized. The content of s-SWCNTs reached ∼96%, and the percentage of isolated tubes was estimated to be ∼83%. Thin-film transistors (TFTs) constructed using the s-SWCNT film showed high on/off ratios ranging from 2.1 × 104 to 1.2 × 106, verifying the effective enrichment of s-SWCNTs.

Vertical carbon nanotubes arrays with controlled morphology on silicon carbide fibers for electromagnetic wave absorption

Silicon carbide fiber-Carbon nanotubes arrays (SiCf-CNTs) hybrids with controllable morphologies were successfully synthesized by a floating catalyst chemical vapor deposition method (CVD). As the reaction duration prolonged from 2 min to 15 min, the length of CNTs was elongated from 2 μm to 50 μm, and moreover the content of CNTs in the hybrids increased from 1.5 wt% to 3.7 wt%. By filling this chopped SiCf-CNTs (20 wt%) hybrids into paraffin, the composite with 3 mm in thickness presented the minimum reflection loss (RLmin = −56.2 dB) and the maximum effective absorption wideband (EAB, RL ≤ −10 dB) of 4.3 GHz (8.5–12.8 GHz). The dielectric performance of this hybrid synthesized by optimized CNT's length and growth density has presented high potential in the application of electromagnetic wave absorption.

Large-area synthesis of vertically aligned carbon nanotubes growth on the aluminum foil via FCCVD method

In this study, VA-CNTs were synthesized homogeneously on Al foil at 610 oC temperature by Floating Catalyst Chemical Vapor Deposition (FCCVD) method in a horizontal tube furnace. While ethanol was used as the carbon source, ferrocene was used as the catalyst. VA-CNTs with diameters in the range of ~10-15 nm and lengths in the range of ~30-35 µm were obtained. Structural and morphological analyzes of VA-CNTs were determined using X-Ray Diffraction (XRD), Field Emission Scanning Electron Microscopy (FESEM), Energy Dispersion X-Ray Spectroscopy (EDS), Raman Spectroscopy and X-Ray Photoelectron Spectroscopy (XPS). These VA-CNTs, synthesized by the FCCVD method on an Al foil in a large area, have the potential applications to be used especially in energy storage, optoelectronic, and sensor.

Effect of a Metallocene Catalyst Mixture on CNT Yield Using the FC-CVD Process

This work studies synthesis of carbon nanotube (CNT) sheet using the high temperature (1400 °C) floating catalyst chemical vapor deposition (FC-CVD) method. Three metallocenes—ferrocene, nickelocene, cobaltocene—and their combinations are used as precursors for metal catalysts in the synthesis process. For the carbon source, an alcohol fuel, a combination of methanol and n-hexane (9:1), is used. First, the metallocenes were dissolved in the alcohol fuel. Then, the fuel mixture was injected into a tube furnace using an ultrasonic atomizer with Ar/H2 carrier gas in a ratio of about 12/1. The synthesis of CNTs from a combination of two or three metallocenes reduces the percentage of metal catalyst impurity in the CNT sheet. However, there is an increase in structural defects in the CNTs when using mixtures of two or three metallocenes as catalysts. Furthermore, the specific electrical conductivity of the CNT sheet was highest when using a mixture of ferrocene and cobaltocene as the catalyst. Overall, the multi-catalyst method described enables tailoring certain properties of the CNT sheet. However, the standard ferrocene catalyst seems most appropriate for large-scale manufacturing at the lowest cost.