Synthesis Of Carbon Nanotubes Research Articles

Combination of chemical vapor deposition and thermal growth methods for facile synthesis of tin oxide-doped multiwalled carbon nanotubes

Combination of chemical vapor deposition and thermal growth methods for facile synthesis of tin oxide-doped multiwalled carbon nanotubes

Synthesis of multi-walled carbon nanotubes on nichrome and nickel by using rapid thermal processing furnace

Synthesis of multi-walled carbon nanotubes on nichrome and nickel by using rapid thermal processing furnace

Impact of biogenic impurities on catalytic synthesis of multi-walled carbon nanotubes and hydrogen from polyolefin resins

Biogenic impurities are common contaminants of plastic waste. This study investigated the effects of biogenic impurities on the conversion of a polyolefin mixture (6 wt% low-density polyethylene, 24 wt% high-density polyethylene, and 70 wt% polypropylene) into multi-walled carbon nanotubes (MWCNTs) and hydrogen via pyrolysis-chemical vapor deposition (CVD). Biogenic components from diverse sources were added to the polyolefin mixture, including lignocellulosic materials (pine sawdust, coconut coir pith), biosolids from wastewater treatment (municipal sewage sludge), animal-based waste (crustaceans), and bio-based plastic (polylactic acid). At contamination levels up to 9.1 wt%, 3 out of 5 impurities (coconut coir pith, sewage sludge and crustaceans) caused a decline in the conversion efficiency of feedstock into MWCNTs (33 ± 7% for polyolefins only compared with 20 ± 6%, 16 ± 1% and 16 ± 2% for polyolefins with 9.1 wt% coconut coir pith, sewage sludge and crustaceans, respectively). According to gas analysis, impurities led to a loss of catalyst activity, resulting in a decreased concentration of H2 and increased concentrations of methane and ethylene in the CVD gas. Furthermore, for polyolefins containing 9.1 wt% coconut coir pith, sewage sludge, crustaceans and polylactic acid, microscopy data revealed changes in the growth of filamentous carbon, leading to the appearance of carbon nanofibers in MWCNT samples. On the contrary, biogenic impurities barely changed outer diameters, ID/IG ratios, interlayer spacing, crystallite sizes of graphite-like sites, and the surface chemistry of MWCNT samples. The results suggest the development of quality management system for contaminated plastic feedstock could be advantageous to ensure consistent outcomes of pyrolysis-CVD process.

Catalytic mechanism of Co-containing layered double hydroxide (Co-LDH) as a precursor in carbon nanotube (CNT) synthesis

Abstract The synthesis of carbon nanotubes (CNTs) by water-assisted chemical vapor deposition using Co-containing layered double hydroxides (Co-LDH) as catalyst precursors and the catalytic mechanism of Co-LDH catalyst precursors during CNT synthesis were investigated. Co-Al and Co-Mg-Al LDH were prepared by the hydrothermal or homogeneous precipitation method using urea. XPS analysis indicated an increase in Co0 content after a reduction process during CNT synthesis, and the TEM images show that metallic Co nanoparticles were formed while maintaining the LDH platelet-like crystal form. Consequently, these metal particles were found to act as the catalyst for the formation of CNTs. Finally, through control of the flow rate of C2H4 gas during CNT synthesis, the formation of single-walled CNTs with diameters of 4 nm or less was demonstrated.

Green synthesis of carbon nanotubes functionalized with iron nanoparticles and coffee husk biomass for efficient removal of losartan and diclofenac: Adsorption kinetics and ANN modeling studies

The presence of emerging contaminants in wastewater poses a global environmental challenge, requiring the development of innovative materials or methods for their treatment. This study focused on the production of green functionalized carbon nanotubes (CNTs) and using them in the adsorption of the pharmaceuticals Losartan (LOS) and Diclofenac (DIC). The efficiency of the methodology was verified by characterization techniques. Elemental composition analysis indicated a significant increase in the iron content after the green functionalization, proving the effectiveness of the method. Thermogravimetric analysis showed similar thermal degradation profiles for pristine CNTs and functionalized CNTs, indicating better post-functionalization thermal stability. BET analysis revealed mesoporous characteristics of CNTs, with increased surface area and pore volumes after functionalization. X-Ray diffraction confirmed the preservation of the lattice structure of the CNTs post-functionalization and post-adsorption, with changes in peak broadening suggesting surface modifications. LOS and DIC adsorption were evaluated via kinetic studies at four different concentrations (0.1–0.4 mmol/L) that were best represented by the pseudo-second order model, suggesting chemisorption mechanisms, with faster and higher uptakes for DIC (0.084–0.261 mmol/g; teq = 5 min) when compared to LOS (0.058–0.235 mmol/g; teq = 20 min). The curves were also studied via artificial neural networks (ANN) and revealed that the best ANN architecture for representing the experimental data is a network with [3 5 5 2] neurons trained using the Bayesian-Regularization algorithm and the Log-sigmoid (hidden layers) and Linear (output layer) transfer functions. The desorption study showed that CaCl2 had better performance in CNT regeneration, reaching its removal capacity above 50% up to 3 cycles, for both pharmaceuticals. These findings reveal the potential of the developed material as a promising adsorbent for targeted removal of pollutants, contributing to advances in the remediation of emerging contaminants and the application of artificial intelligence in adsorption research.

Enhancing the Thermal Conductivity of CNT/AlN/Silicone Rubber Composites by Using CNTs Directly Grown on AlN to Achieve a Reduced Filler Filling Ratio.

Achieving the thermal conductivity required for efficient heat management in semiconductors and other devices requires the integration of thermally conductive ceramic fillers at concentrations of 60 vol% or higher. However, an increased filler content often negatively affects the mechanical properties of the composite matrix, limiting its practical applicability. To address this issue, in this paper, we present a new strategy to reduce the required ceramic filler content: the use of a thermally conductive ceramic composite filler with carbon nanotubes (CNTs) grown on aluminum nitride (AlN). We combined catalyst coating technology with vacuum filtration to ensure that the catalyst was uniformly applied to micrometer-sized AlN particles, followed by the efficient and uniform synthesis of CNTs using a water-assisted process in a vertical furnace. By carefully controlling the number of vacuum filtration cycles and the growth time of the CNTs, we achieved precise control over the number and length of the CNT layers, thereby adjusting the properties of the composite to the intended specifications. When AlN/CNT hybrid fillers are incorporated into silicone rubber, while maintaining the mechanical properties of rubber, the thermal diffusivity achieved at reduced filler levels exceeds that of composites using AlN-only or simultaneous AlN and CNTs formulations. This demonstrates the critical influence of CNTs on AlN surfaces. Our study represents a significant advancement in the design of thermally conductive materials, with potential implications for a wide range of applications.

Innovative multiwall carbon nanotubes synthesis on 3D nickel surface: a comparative study

The article presents the synthesis of multi-walled carbon nanotubes (MWCNTs) on the porous nickel foam (3D-Ni) surface using the chemical vapor deposition (CVD) method, followed by the field emission characteristics of the resulting 3D-Ni/MWCNT nanocomposite structures. The characterization of the 3D-Ni/MWCNT morphology showed a uniform distribution of the “moss-like” CNT coating on the walls of the porous 3D-Ni. TEM images showed a high number of walls in MWCNTs, which made such a material resistant to destruction under conditions of strong electric fields during the field emission process. The studies also showed a high degree of chemical purity of the synthesized MWCNTs under the presented technological conditions. An increase in the emission current due to the introduction of CNTs into the structure of porous 3D-Ni is shown. 3D-Ni/MWCNTs field emitter showed a low turn-on field of 5.41 V/μm; a field enhancement factor of 915; and high operating stability. For the first time, the current mode of 3D-Ni-MWCNTs cathode was tested for compliance with the classical field emission law using the Forbes “orthodoxy” test.

In-Situ Flame-Synthesized Carbon Nanomaterials via an Impinging Swirl Flow with an N-Butanol Pool

ABSTRACT This study aims to investigate the impact of flow rotation and oxygen concentration on the synthesis of carbon nanomaterials using n-butanol diffusion flames in a rotating stagnation flow with a liquid pool and a catalytic Ni substrate. With increasing angular velocity (ω), the diffusion flame shifts slightly toward the upper oxidizer nozzle, experiences a lower strain rate, and becomes stronger with a higher maximum flame temperature at a fixed oxygen concentration (ΩO). Meanwhile, the soot layer thickens and gradually turns yellowish. Field Emission Scanning Electron Microscopy (FESEM) analyses confirm that carbon nanotubes (CNTs) can only be fabricated at ω = 2 or 3 rps when ΩO = 21%, highlighting the critical role of flow rotation. Interestingly, the optimal positions for CNT synthesis consistently occur at the same sampling position (1.5 mm below the upper edge of the blue flame) for all values of oxygen concentration (ΩO). The corresponding temperature ranges for ΩO = 19%, 18%, and 17% are approximately 950°C, 820–920°C, and 800–850°C, respectively, which align with existing literature. High-resolution transmission electron microscopy (HRTEM) images reveal both typical straight tubular and bamboo-like CNT structures. Raman spectra indicate superior graphitization at high angular velocities (ω). Notably, at ω = 0 rps, the intensity ratio of the D- and G-bands is greater than 1 (ID/IG >1); however, as ω increases, the opposite holds (ID/IG <1), with its value gradually decreasing. This suggests that the swirl effect enhances graphite layer crystallization. Importantly, the strain rate controlled by flow rotation significantly influences CNT fabrication, considering both residence time and carbon source. The key finding of this study is that swirl flow enhances both the quality and quantity of CNTs synthesized via n-butanol diffusion flames.

Efficiency of green synthesised carbon nanotubes from Moringa oleifera leaf extract as potential toxic metals adsorbent in polluted water

Abstract Among the many drawbacks of the current wastewater treatment systems are their high energy consumption and creation of harmful sludge. Carbon nanotubes (CNTs) are advantageous for the treatment of water due to their strong adsorption capacity and selectivity towards various pollutants. Thus, creating methods for treating water by producing CNTs from Moringa oleifera leaf extract can greatly help with the clean water problem. The synthesised material’s Ultra Visible (260–385 nm), FTIR (764–3295 cm−1) and Scanning Electron Microscope (SEM) characterizations have demonstrated their CNTs characteristics. The repeatability testing yielded the %RSD values for Ca = 0.4, Cu = 0.24, Mg = 0.9, Pb = 1.06 and Zn = 0.36 which suggest that the AES approach demonstrated a high degree of precision. The findings show that the quantity of recovered metals increases with retention period. Mg &gt; Cu &gt; Zn &gt; Ca &gt; Pb was the order of the metal adsorption capacity throughout retention durations of 3, 6, 24, and 48 h. As the initial concentrations of the components under research were doubled and tripled, so were the removal capacities of CNTs increased which may be as a result of an increase in metal ions in the solution. The outcomes show how well the synthetic CNTs can remove heavy metals from wastewater.

Influence of Iron Nanoparticle and Multifaceted Endophytic Fungus Piriformospora indica on Zea mays L. - A Novel Approach toward Innovative Yet Sustainable Farming

The amalgamation of nanotechnology and biotechnology holds immense potential for developing innovative and essential products beneficial to mankind. Nanoparticles, particularly iron nanoparticles, exhibit the capacity to enhance plant growth and yield in various crops. Rather than employing nanomaterials alone, combining them with beneficial microorganisms can offer a more effective approach to promoting plant growth and yield. Piriformospora indica, a versatile endophytic fungus serves as a biofertilizer, bioregulator, stimulant, and biocontrol agent upon colonizing plant roots. The present study focuses on the synthesis and characterization of iron-modified multiwalled carbon nanotubes, mesoporous carbon, and alumina materials and their impact on the growth and yield of Zea mays L. in conjunction with Piriformospora indica under greenhouse conditions. The nanomaterials were prepared using the impregnation method and were characterized to confirm their nano size. Under greenhouse conditions, plants treated with nanomaterials and colonized by Piriformospora indica exhibited improvements in root length (≌2.5 times), shoot length (≌1.8 times), root biomass (≌3.5 times), shoot biomass (≌ 2.3 times), chlorophyll content (≌ 3 times), proline accumulation (≌ 2.5 times), and a reduction in lipid peroxidation compared to untreated Zea mays L. plants. This suggests that the combined application of nanomaterials and the multifaceted fungus can positively influence plant growth and yield.

Field emission characterization of field-aligned carbon nanotubes synthesized in an environmental transmission electron microscope

Optimizing the synthesis of carbon nanotubes (CNTs) for applications like field emission (FE) sources requires a fundamental understanding of the growth kinetics of individual CNTs. In this article, we explore how applying electric fields during CNT synthesis influences the as-grown nanotubes and their FE performance. We observe growth and undertake FE measurements in real time using an environmental transmission electron microscope. This is achieved through a polarizable capacitor gap within a microchip sample heater specifically designed for this purpose. Individual nanotubes are easily resolved and are predominantly single-wall CNTs. At low-applied fields, the growing nanotubes can span the gap and link with the opposite electrode, albeit with some loss due to mechanical failure. With a high-applied field and positive bias for FE, we continue to observe the oriented growth of nanotubes. However, this growth is constrained within the gap due to the possibility of FE occurring during the growth process, which can result in either saturation or damage. At any given time, we have the flexibility to halt the growth process and conduct in situ FE experiments. This approach enables us to comprehensively track the complete development of the CNTs and gain insights into the various mechanisms responsible for limiting the performance of CNT cathodes. Interestingly, we report an original self-oscillation induced destruction mechanism that has not been reported before.

Arc Discharge Synthesis and Multistep Purification of Multiwall Carbon Nanotubes

This research work describes the cost-effective synthesis and purification of multiwall carbon nanotubes (MWCNTs). Synthesis of CNTs was carried out in distilled water between two electrodes using the electric arc discharge (EAD) method. EAD is a simple and straightforward route in which an electric arc is generated between graphite electrodes through DC power source to produce soot which contains MWCNTs along with impurities. The deposited soot containing MWCNTs was then chipped off and purified. In this case, multistep purification scheme was opted to remove unwanted impurities from produced MWCNTs. Purification route comprised thermal treatment, chemical treatment and a combination of both to yield pure MWCNTs. Thermal treatments were carried out in normal air and under controlled flow of oxygen at different temperatures whereas chemical treatment was performed using acidic solution. Thermo gravimetric analysis (TGA), field emission scanning electron microscopy (FE-SEM) and X-ray diffraction (XRD) were carried out before and after purification treatments to investigate the outcome of employed treatments. Results showed that the thermal or chemical treatment alone is not sufficient to remove impurities from soot. Moreover, the introduction of an oxide group through chemical treatment reduces the oxidization temperature of graphitic particles. It was found that the chemical treatment followed by thermal annealing under the controlled flow of oxygen is the most appropriate method for successful purification of MWCNTs synthesized via EAD method.

Thermo-oxidative degradation of carbon nanotubes and related nanostructures: role of acidic environment and chloride ions

It is shown that acid activation of ultralong carbon nanotubes synthesis products increases their reactivity during subsequent thermochemical treatment in air at 480 °C. Such an integrated approach of CNTs processing provides high purity and maximum yield of the target product. For example, the non-CNT fraction decreases by 3.2 times, while the residual iron content decreases by 17–24 times in comparison with thermochemical treatment without acid. Raman spectroscopy and low-temperature nitrogen adsorption showed that acid activation does not lead to extra surface defects, which could initiate further oxidation of carbon matrix in air. It is suggested that the increased reactivity of CNT synthesis products after acid activation during thermo-oxidative degradation may be due to the formation of an “adduct” of carboxyl groups on the surface of nanotube carbon matrix with hydrogen chloride. It was shown by thermogravimetric studies coupled with mass-spectra investigation of gas evolved, that under the constant heating, at the temperatures of the beginning of intensive oxidation (500–600 °C), the decomposition of the “adduct” occurs, bypassing the stage of formation of more temperature-resistant phenolic groups, which can inhibit further oxidation. Water released during the decomposition of the “adduct” can also accelerate the process of thermal oxidation.

Catalytic pyrolysis of plastic waste using metal-incorporated activated carbons for monomer recovery and carbon nanotube synthesis

As the global plastic waste crisis intensifies, innovative and sustainable solutions are urgently needed. This study evaluated waste-derived metal-incorporated activated carbon (AC) catalysts for the pyrolysis of mixed plastic waste to generate value-added products, focusing on product yield distribution, composition, hydrogen, and carbon nanotube (CNT) formation. Pyrolysis-catalysis experiments were conducted using a two-stage fixed-bed reactor, wherein the temperature was maintained at 500 °C in first stage (pyrolysis) and varied (500, 600, and 700 °C) in the second stage (catalysis). The tested ACs were incorporated with nickel (Ni-AC), iron (Fe-AC), and zinc (Zn-AC) to assess the impact of metal particles distributed on the carbonaceous support in the second stage. The results from the ACs were compared to those obtained using zeolite (H-ZSM-5), Raw-AC, and non-catalytic runs. The Ni-AC and Fe-AC demonstrated superior catalytic activity, with Ni-AC being more efficient in producing hydrogen (4.24 wt%) and CNTs (34.5 wt%) with diameters of approximately 30 nm, and Fe-AC leading to higher gas yields (68.8 wt%) and CNTs (12.4 wt%) of around 60 nm. In contrast, Zn-AC and Raw-AC presented limited effectiveness, although Raw-AC moderately outperformed Zn-AC with enhanced gas yields and reduced oil/wax yields. The zeolite H-ZSM-5 exhibited the highest gas yields (78 wt%), converting heavy fractions into lighter molecules, notably the monomers ethylene and propylene. These findings provide valuable insights into catalyst selection and optimization for plastic waste pyrolysis processes, with H-ZSM-5 being the most effective catalyst for monomer recovery, and Ni-AC and Fe-AC demonstrating promising results.

Chirality Engineering of Carbon Nanotubes, Modeling and Photons Density Improvement for Solar cell Applications

Carbon nanotubes and fullerenes offer exceptional mechanical and electrical qualities due to their cylindrical and hollow spherical molecular structures. Their extensive range of applications, which includes field emission displays, impregnated metal composites, battery storage media, and nanoelectronics devices, demonstrates their exceptional adaptability. The combination of simple materials, variable behavior, and simplicity of manufacture makes these materials a focal point of contemporary research. Due to the low bias transmission at a few nanometers, they have a wide range of applications in electronic devices, and finding their potential applications is a complicated process. Due to the fact that the valance and conduction bands are symmetric, they have a straight band gap and can be exploited for optical emission. Three processes, including arc discharge, laser ablation, and chemical vapor deposition, can be used to generate carbon nanotubes (CNTs), although chemical vapor deposition (CVD) is the most used method since it yields CNTs that are more than 98% pure. Multiple chirality of 100% pure MWCNTs results in enhanced optical properties and improved use as a light harvesting material. Using CNT composites and functionalized nanotubes, the dye-sensitized solar cells are constructed. In this brief review, the synthesis of CNT and its application in solar cells are discussed.

Green synthesis and characterization of multiwall carbon nanotubes from sugarcane bagasse as a biogenic catalyst via chemical vapour deposition method using LPG as hydrocarbon source

In this study, sugarcane bagasse was used as an environment-friendly green catalyst for the synthesis of MWCNTs using the chemical vapour deposition method. The process was carried out at a relatively low temperature of 700 °C using liquified petroleum gas (LPG) as a hydrocarbon source. The formation of carbon nanotubes was confirmed using scanning electron microscopy (SEM). Transmission Electron microscopy (TEM) revealed that the obtained MWCNTs has a diameter in the range of 13 nm and a d-spacing of 0.33 nm. The EDAX and ICP-AES analysis confirmed the presence of various minerals like calcium, magnesium, iron and silica which have contributed to the formation of MWCNTs. The structural integrity of MWCNTs was evaluated by Raman spectroscopy and functional characterisation was done by FTIR.

The effect of multi-walled carbon nanotubes on mechanical properties and water adsorption of lightweight foamed concrete

The paper investigates the impact of carbon nanotube-based modifiers on the performance characteristics of lightweight foamed concrete (LFC). The method involves saturating quartz sand with a solution containing a catalyst for carbon nanotube (CNT) growth, followed by the subsequent chemical vapor deposition (CVD) synthesis of CNTs. Evaluation of nanomodified sand samples was conducted using SEM and TEM, thermogravimetry, Raman spectroscopy, and XRD. Compression and flexural strength tests of (LFC) specimens indicated that the optimal proportion of nanomodified sand introduced is 1% by weight with a particle size of 0.16 mm. This resulted in a notable 35% increase in compressive strength and an approximately 32% improved in flexural strength. Furthermore, the modified sample with CNT-based sand exhibited a 27% reduction in water absorption. The paper also presents a potential mechanism to explain the impact of carbon nanotube-based modified sand on the evolving structure of (LFC).

Synthesis and enhanced room-temperature thermoelectric properties of CuO-MWCNT hybrid nanostructured composites.

This work presents the synthesis of novel copper oxide-multiwalled carbon nanotube (CuO-MWCNT) hybrid nanostructured composites and a systematic study of their thermoelectric performance at near-room temperatures as a function of MWCNT wt% in the composite. The CuO-MWCNT hybrid nanostructured composites were synthesized by thermal oxidation of a thin metallic Cu layer pre-deposited on the MWCNT network. This resulted in the complete incorporation of MWCNTs in the nanostructured CuO matrix. The thermoelectric properties of the fabricated CuO-MWCNT composites were compared with the properties of CuO-MWCNT networks prepared by mechanical mixing and with the properties of previously reported thermoelectric [CuO]99.9[SWCNT]0.1 composites. CuO-MWCNT hybrid composites containing MWCNTs below 5 wt% showed an increase in the room-temperature thermoelectric power factor (PF) by ∼2 times compared with a bare CuO nanostructured reference thin film, by 5-50 times compared to mixed CuO-MWCNT networks, and by ∼10 times the PF of [CuO]99.9[SWCNT]0.1. The improvement of the PF was attributed to the changes in charge carrier concentration and mobility due to the processes occurring at the large-area CuO-MWCNT interfaces. The Seebeck coefficient and PF reached by the CuO-MWCNT hybrid nanostructured composites were 688 μV K-1 and ∼4 μW m-1 K-2, which exceeded the recently reported values for similar composites based on MWCNTs and the best near-room temperature inorganic thermoelectric materials such as bismuth and antimony chalcogenides and highlighted the potential of CuO-MWCNT hybrid nanostructured composites for applications related to low-grade waste heat harvesting and conversion to useable electricity.

Synthesis of nanocomposites of montmorillonite with carbon nanotubes as a potential material for water purification

The main goal of this research is to create nanocomposites based on unmodified and iron-modified (FeNP) montmorillonite (Mt) and carbon nanotubes (CNT) synthesized using the chemical vapor deposition method. The target area for the application of these materials is the creation of water treatment systems. This paper compares the efficiency of the CNT synthesis process on Mt before and after modification with FeNP of different concentrations and provides the characterization of the CNT microstructure and structure using different methods, such as scanning electron microscopy, high-resolution transmission electron imaging, and Raman spectroscopy. For initial verification of properties important for water purification, Mt+CNT and Mt+FeNP+CNT nanocomposites on a carbon nonwoven fabric (CF) are tested in this work. Incubation of the above-mentioned samples in a water–oil mixture reveals complex adsorption dynamics. The CF+Mt+FeNP+CNT sample shows a very good oil adsorption capacity due to its superhydrophobic and oleophilic properties.

Synthesis of novel hollow carbon nanotubes @ Co-Fe alloy/iron phthalocyanine electrocatalyst by self-assembly method for OER and ORR study

The exploration of an inexpensive catalyst with effective oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) activities to replace precious metal electrocatalysts has been of great interest in recent years. In this paper, CNT@Co-Fe/FePc composites were synthesized with high efficiency using a self-assembly strategy. In the synthesis process, carbon nanotubes (CNTs) were synthesized as the base material using crab shells as templates and honey as the carbon and nitrogen source. CoFe alloy nanoparticles derived from CoFe-based prussian blue analogs were self-assembled and anchored on CNTs, and then iron phthalocyanine with Fe-N4 portion was coupled with CNTs by π-π stacking. Finally formed a homogeneous and stable composite material. The self-assembly method is simple and efficient to achieve good metal loading. The prepared CNT@Co2-Fe1/FePc exhibits excellent catalytic performance and stability for OER and ORR in alkaline electrolyte. The overpotential at 10 mA cm−2 of CNT@Co2-Fe1/FePc for OER is 343 mV with a very small Tafel slope of 43.59 mV dec−1. CNT@Co2-Fe1/FePc has high methanol tolerance and persistence for ORR. This work provides a strategy for the construction of transition metal-carbon composite electrocatalytic materials with excellent catalytic performance and stability for OER and ORR reactions.