Fabrication Of Carbon Nanotubes Research Articles

Microstructural and mechanical properties of CNT-reinforced ZrO2-Y2O3 coated boiler tube steel T-91

The main purpose of this study was to fabricate carbon nanotubes (CNTs) reinforced zircon­nium yttrium coatings on boiler tube steel and to investigate the microstructural and mechanical properties of these coatings. Plasma sprayed conventional ZrO2-Y2O3, ZrO2-Y2O3 and 1 wt.% CNT and ZrO2-Y2O3 and 4 wt.% CNT were prepared and deposited successfully on boiler tube steel material T-91 (ASTM SA-213) by plasma thermal spray technology. Microhardness, porosity, XRD (X-ray diffraction), SEM/EDAX (scanning elec­tron microscopy/energy dispersive X-ray spectroscopy), X-ray mapping and cross-sectional analyses were used to analyse the specimens. The hardness of CNT reinforced ZrO2-Y2O3 increased with the increase in the percentage of CNT, whereas the porosity of the composite coatings decreased with the increase in the CNT percentage. The observed increase in hardness may be attributed to the content of CNT in the composite coating. The present research gives important information related to the fabrication and physical characteristics of CNT-reinforced ZrO2-Y2O3 coatings deposited on T-91 boiler tube steel.

Plasma-modified flaky FeSiAl alloy for efficient growth of carbon nanotube arrays with high carbon conversion rate

The large-scale fabrication of high-quality carbon nanotube (CNT) arrays with highly uniform orientation is challenging due to the relatively low carbon conversion rate. Herein, a plasma-modified flaky FeSiAl (FSA) catalyst was developed for the high- efficiency conversion from acetylene to CNT arrays by catalytic chemical vapor deposition (CCVD). The surface nanoparticles of plasma-modified FSA were refined and oxidized, resulting in an increase in the catalytic active oxides as well as a high carbon conversion rate up to ~97.2%. The growth mechanism analysis confirmed the base-symmetric growth mode of CNT arrays and the maximum theoretical CNT array yield was predicted to be ~8.20 g when using 0.5 g plasma-modified FSA catalysts. The apparent activation energy of CNT arrays was calculated to be ~53.17 kJ/mol, indicating the coexistence of surface diffusion on the catalysts and step-edge diffusion at the graphene-catalyst interface. This work provides a highly efficient methodology for the low-cost and large-scale production of CNT arrays with potential application in the field of high-performance energy storage.

Multiwalled Carbon Nanotube-Based Freestanding Filters for Efficient Removal of Fine Particulate Matters (PM0.3), Microplastics (MP0.3), and Bioaerosols

Air pollution caused by various hazards such as particulate matters (PM), microplastics (MP), bioaerosols (BA), etc. has become a global concern for public health across the globe. In recent decades, nanofiltration-based air purification techniques have rapidly evolved as a viable solution to address worldwide air pollution challenges. Herein, we report a simple, cost-effective, and scalable technique for the fabrication of lightweight, freestanding, and flexible multiwalled carbon nanotube (MWCNT) membranes for air filter applications. The developed membrane filter possesses excellent capturing efficiency of more than 99% for PM0.3, MP0.3, and BA. Additionally, the developed membrane has also been well investigated in terms of hydrophobic behavior (contact angle ∼148 ± 7°), narrow pore size (∼16 nm), packing density (∼0.65 g/cc), porosity (∼56%), pressure drop (∼139.7 Pascal), flexibility, and reusability, reflecting its self-cleaning feature, physical sieve characteristics, adaptability, and commercialization. Thus, the filter developed in this work shows its potential utility toward the removal of indoor pollution and in air filter industries as well.

Fabrication and application of CNT fiber-ultra-fine diamond composites via electrophoretic deposition and instantaneous Joule-heating method

One-dimensional carbon nanotube (CNT) fibers combined with three-dimensional ultra-fine diamond have a synergistic effect that can be used in a variety of applications. The current challenge is how to combine the two materials quickly and efficiently. To actualize the combination of the two materials, a two-step method is adopted in this study. The electrophoretic deposition method, which allows ultra-fine diamond particles to adhere uniformly and controllably to the surface of carbon nanotube fibers. The instantaneous Joule-heating method can realize the instantaneous high-temperature recombination of diamond and CNT fibers. CNT fibers' flexibility and thermal conductivity are combined with ultra-fine diamond's high hardness in this composite. A polishing tool was made by knitting ultra-fine diamond/CNT fiber threads on non-woven fabric and used to dry polish potassium dihydrogen phosphate (KDP) crystals. CNT fibers were examined for wear, surface morphology, and KDP surface roughness before and after processing. The results reveal that the composite material-prepared tool has greater wear resistance and machining efficiency.

Fabrication of Carboxylated Carbon Nanotube Buckypaper Composite Films for Bovine Serum Albumin Detection

The salient point of this study is to fabricate carbon nanotube (CNT) buckypaper composite films prepared through the methods of pumping filtration and spin coating. Firstly, carboxylated CNTs were used to make the original buckypaper specimen and further modify the buckypaper surface by incorporating different surface modifiers. Then, all of original (unmodified) and modified buckypaper composite films had different concentrations of bovine serum albumin (BSA) added, and differential pulse voltammetry (DPV) electrochemical measurement was used to measure the characteristics of the various buckypaper composite films, after adding different concentrations of BSA. The experimental results show that the contact angles for four modified specimens are smaller than that of the original unmodified S–BP specimen (62°). These results indicate that the four modifiers used in this study can improve the hydrophilic properties of the original, unmodified S–BP specimen, and benefit the subsequent bonding of a modified specimen with aqueous BSA. In addition to the improvement of the hydrophilic properties of the modified specimen, which affects the bonding with BSA, the bonding type produced by the modifier also plays an essential role in the bonding between specimen and BSA. Therefore, the S–BP–EDC/NHS and S–BP–TA specimens have better linear dependence between log (BSA concentration) and oxidation current data.

Fabrication of multiwall carbon nanotubes decorated with MoS2 nanoflowers for adsorption of Ag(I) from aqueous solution

In this work, a facile solvothermal method was employed to fabricate multiwall carbon nanotubes (MWCNTs) decorated with MoS2 nanoflowers (MoS2/MWCNTs) nanohybrid using carboxylation multiwall carbon nanotubes (MWCNTs-COOH) as skeleton for MoS2 in-situ growth, and the MoS2/MWCNTs nanohybrid was used as a novel sorbent to adsorb Ag(I) from aqueous solution. The structures and components of the obtained samples before and after adsorption were analyzed by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), zeta potential analyzer and N2 adsorption-desorption isotherms. Meanwhile, the effect of solution pH, initial concentrations of Ag(I), contact time and temperature on the adsorption performance of the MoS2/MWCNTs nanohybrid for Ag(I) in aqueous solution were explored by batch experiments. The results show that MoS2 was decorated on MWCNTs in nanoflower-like structure, which could avoid agglomeration of MWCNTs and MoS2, expose as much of the sulfur-rich surface as possible, and provide abundant adsorption sites and transport channels for Ag(I) ions. The specific surface area of the MoS2/MWCNTs nanohybrid was 4.5 times that of pure MoS2. At the optimal adsorption conditions, the maximum adsorption capacity of the MoS2/MWCNTs nanohybrid for Ag(I) was 601.97 mg/g. The formation of Ag2S was main contribution for the adsorption, besides that, there was electrostatic adsorption. Based on the advantages of the simple synthesis method and high adsorption capacity, the MoS2/MWCNTs nanohybrid could be a promising candidate material for Ag(I) removal from wastewater.

Carbon fiber/epoxy composite property enhancement through incorporation of carbon nanotubes at the fiber-matrix interphase – Part II: Mechanical and electrical properties of carbon nanotube coated carbon fiber composites

A new method to achieve a uniform coating of carbon nanotubes (CNTs) onto carbon fibers (CFs) has been developed which enables the scalable fabrication of CNT modified CF/epoxy composites. In this method, CNTs are coated onto CFs by immersion into a CNT/water suspension resulting in a uniform coating of CNTs. Unidirectional CF/epoxy composites with the CNT layer of 100–200 nm were fabricated by a prepregging method and mechanical/electrical properties were evaluated. The results show that the compressive, short beam shear strengths and Mode I interlaminar fracture toughness were improved by 22 %, 11 % and 48 % respectively after the incorporation of only 0.39 wt% CNTs. Electrical conductivities in 90˚ and through thickness direction were improved by two or three orders of magnitude (Log Resistivity: 1.24 and 2.31) respectively. These results indicate the importance of designing the fiber–matrix interphase to improve fiber reinforced polymer composite mechanical and electrical properties.

Construction of carbon nanotubes bridged MoS2/ZnO Z-scheme nanohybrid towards enhanced visible light driven photocatalytic water disinfection and antibacterial activity

We fabricated carbon nanotubes (CNTs) bridged MoS2/ZnO nanohybrids from the hydrothermal process for the heterostructure photocatalysts. The nanohybrids were effectively operated as visible light action for the photocatalytic of organic compounds and heavy metal reduction. The results exhibit that the great photocatalytic efficiency from nanohybrids for the 94.5% of tetracycline (TC) degradation after 60 min of irradiation. Enhanced environmental pollutants removal was due to inhibition in recombination of photogenerated electron-hole pairs. The nanohybrids also displayed better photocatalytic performance and reduction capacity (Cr (VI) ions removal), about 10–15 folds as greater than that of bulk MoS2, and ZnO photocatalysts. The nanohybrid showing a wonderful photocatalytic antibacterial capability of 99.9% towards E. coli after 5 min and supplying a favourable environmentally friendly for water disinfection. Based on this studies, we believe that a promising candidate nanohybrids for the photocatalytic of various water contaminants under visible light activity.

In-situ fabrication of dense structure nitrogen-doped carbon nanotube embedded Co/Co2P accelerating the electrochemical kinetics of lithium-sulfur battery

Accelerating the sluggish electrochemical kinetics of polysulfide conversion using electrocatalysis is an effective strategy to enhance the electrochemical performance of lithium-sulfur (Li-S) battery. A rational catalyst needs to maximize its ability to capture and catalyze the polysulfide. Herein, we report a novel catalyst that exhibits a network structure of dense nitrogen-doped carbon nanotube (CNT) embedded with Co/Co2P. The dense nitrogen-doped CNT plays the role of “tentacles” to capture and confine the polysulfide via physical and chemical interactions, and the embedded Co/Co2P that wrapped by the dense CNT acts as an electrocatalyst to catalyze the sulfur redox. As a result, the Li-S battery using Co/Co2P@N-CNT modified separator can deliver a capacity of 1405 mAh g−1 at 0.1C. It can also maintain a capacity of 647 mAh g−1 after 500 cycles, with a very low decay rate of 0.07% per cycle at 1C. Importantly, a high reversible areal capacity of 3.2 mAh cm−2 can be obtained over 60 cycles, even under a raised sulfur content of 4.8 mg cm−2. This work provides a deep understanding of the architecture design of a highly efficient electrocatalyst for high-performance Li-S battery.

Boosting the Fischer-Tropsch synthesis performances of cobalt-based catalysts via geometric and electronic engineering: Construction of hollow structures

It is highly desirable but challenging to accelerate the dissociative adsorption of CO and lower the energy barriers of C–C coupling in the Fischer-Tropsch synthesis (FTS), both of which are prerequisite for high productivities of long-chain hydrocarbons. Herein, we report the fabrication of N-doped carbon nanotubes assembled hollow polyhedrons with embedded hollow Co (H-Co) nanoparticles (NPs) (H-Co@NCNHP) for highly efficient FTS. H-Co@NCNHP affords an extremely high C5+ space time yield of 1.67 × 10−5 mol gcat−1 s−1, outperforming most of Co-based catalysts reported to date. Theoretical calculations demonstrate that, as compared with solid Co NPs with symmetric arrangement of d-orbital electrons, H-Co NPs induce the electron rearrangement of d orbitals (especially dz2) toward the Fermi level, promoting the d-2π* /p coupling between Co active sites and adsorbed CO/intermediates.

Facile fabrication of carbon nanotube embedded pore filling ion exchange membrane with high ion exchange capacity and permselectivity for high-performance reverse electrodialysis

The harvesting salinity gradient power of reverse electrodialysis is mainly derived from ion-exchange membranes (IEMs). Among IEMs for the assembly of reverse electrodialysis stacks, pore-filling ion exchange membranes (PIEMs) and nanocomposite IEMs have been considered for high performance. In our study, we fabricated multiwall carbon nanotube (MWCNT) nanocomposite PIEMs, in which nanocomposite IEM and PIEM were hybridized by a simple impregnation process using an aqueous MWCNT solution. The MWCNT composition in the PIEM could be precisely controlled by the impregnation times and MWCNT concentration in the solution. Additionally, the MWCNTs in the PIEMs were homogenously dispersed without any aggregation. The ion exchange capacities and permselectivities of the MWCNT nanocomposite PIEMs increased with increasing MWCNT content in the PIEMs due to the formation of an optimized ion pathway by reconstruction of the ion-conducting moiety in the electrolyte polymer by hydrophobic MWCNTs. The open-circuit voltages, currents, and power densities of the reverse electrodialysis stacks made with MWCNT nanocomposite IEMs were better than those of PIEMs without MWCNTs, indicating improved performance. This improvement originated from the high ion exchange capacities and permselectivities of the MWCNT nanocomposite PIEMs.

Development and Fabrication of Carbon Nanotube (CNT)/CuO Nanocomposite for Volatile Organic Compounds (VOCs) Gas Sensor Application

Development and Fabrication of Carbon Nanotube (CNT)/CuO Nanocomposite for Volatile Organic Compounds (VOCs) Gas Sensor Application

Cost-effective method for fabricating carbon nanotube network transistors by reusing a 99% semiconducting carbon nanotube solution

Carbon nanotubes (CNTs) are one-dimensional materials that have been proposed to replace silicon semiconductors and have been actively studied due to their high carrier mobility, high current density, and high mechanical flexibility. Specifically, highly purified, pre-separated, and solution-processed semiconducting CNTs are suitable for mass production. These CNTs have advantages, such as room-temperature processing compatibility, while enabling a fast and straightforward manufacturing process. In this paper, CNT network transistors were fabricated on a total of five 8 inch wafers by reusing a highly purified and pre-separated 99% semiconductor-enriched CNT solution. The results confirmed that the density of semiconducting CNTs deposited on the five selected wafers was notably uniform, even though the CNT solution was reused up to four times after the initial CNT deposition. Moreover, there was no significant degradation in the key CNT network transistor metrics. Therefore, we believe that our findings regarding this CNT reuse method may provide additional guidance in the field of wafer-scale CNT electronics and may contribute strongly to the development of practical device applications at an ultralow cost.

Cryogenic-environment resistant, highly elastic hybrid carbon foams for pressure sensing and electromagnetic interference shielding

Elastic carbon foams are promising material candidates for various applications, including strain/pressure sensing and electromagnetic interference (EMI) shielding, but typically suffer from brittleness, low sensitivity, narrow pressure detection range, and poor performance stability. Herein, a facile and scalable method was demonstrated to fabricate carbon nanotube (CNT) embedded carbonized melamine foams (CNT/CMFs) by a direct pyrolysis process. The hybrid CNT/CMFs show tunable electrical conductivity while providing ultrahigh elasticity even under deep cryogenic conditions (−196 °C). An ultrahigh sensitivity (up to 103.24 kPa−1) and a broad pressure detection range (0–175 kPa) were achieved by the hybrid foam sensors, attributing to the hierarchical structures composed of a nanofibrous CNT layer and macropores. The foam-based sensors exhibit ultrahigh cryogenic-temperature resistance, which retains stable performance after immersing in liquid nitrogen for 36 h and experiencing 5000 cycles of repeated compression-release. Moreover, the CNT/CMFs show an exceptional EMI shielding effectiveness and a high specific shielding effectiveness of 6147.3 dB cm2 g−1 with an absorption-dominant shielding mechanism due to the highly porous structure. The cryogenic-temperature resistant CNT/CMFs with these superior strain/pressure sensing and EMI shielding performance are promising for their practical applications as wearable electronics operating in both mild and harsh environments.

A Review of High-Energy Density Lithium-Air Battery Technology: Investigating the Effect of Oxides and Nanocatalysts

In vehicles that require a lot of electricity, such as electric vehicles, it is necessary to use high-energy batteries. Among the developed batteries, the lithium-ion battery has shown better performance. This battery has an energy density of 10 equal to that of a lithium-ion battery and uses air oxygen as the active material of the cathode and anode like a lithium-ion battery made of lithium metal. The cathode used in these batteries must have special properties such as strong catalytic activity and high conductivity, and nanotechnology has greatly helped to improve the materials used in the cathode of lithium-air batteries. The importance of proper catalyst distribution and the relationship between the oxide product and the catalyst and the indirect effect of the ORR catalyst on the OER reaction is not present in the fuel cell. The maximum capacity of lithium-air battery theory using graphene under optimal electron conduction conditions and the experimental maximum obtained for graphene by optimizing the structure geometry, examples of structural engineering using carbon fiber and carbon nanotubes in cathode fabrication with the ability to perform the reaction properly while providing space for lithium oxide placement, are examined. This article describes the mechanism of this battery, and its components are examined. The challenges of using this battery and the application of nanotechnology to solve these challenges are also discussed.

Fabrication and implementation of carbon nanotubes for piezoresistive-sensing applications: A review

This paper presents a substantial review of the preparation and implementation of carbon nanotubes (CNTs) for piezoresistive strain-sensing applications. CNT has been a breakthrough material among flexible electronics, and over the last two decades, it has been thoroughly studied and evolved in terms of its fabrication and utilization techniques. The enhanced electromechanical characteristics of CNT allow researchers to produce high-quality sensors for various applications. One of its critical applications is piezoresistive sensors. Indeed, the responses of thin film CNT-based sensors towards applied micro- and macroscale pressures have provided crucial information to the involved application. The significance of piezoresistive sensing is constantly rising in this era of flexible microelectronics. For example, vital physiological signals can be detected through small-scaled structural changes of the sensing prototypes. Sensors like these have been fabricated with a range of process materials and can be deployed for biomedical applications. A review of the exploitation of CNT-based sensors for piezoresistive activities is showcased here. Some common techniques to fabricate CNTs are also mentioned, in addition to the classification of piezoresistive sensing prototypes based on single-walled and multi-walled CNTs.

Highly enhanced microwave absorption for carbon nanotube/barium ferrite composite with ultra-low carbon nanotube loading

• A facile approach for fabricated carbon nanotube (CNT)/barium ferrite (BaFe 12 O 19 ) composite with good dispersion of carbon nanotube was developed. • In view of the thermal stability of CNT in different atmosphere and the formation mechanism of BaFe 12 O 19 , uniform dispersion of CNT was achieved in the CNT-BaFe 12 O 19 composite. • The as-prepared CNT/BaFe 12 O 19 composite exhibits excellent microwave absorption ability. Barium ferrite (BaFe 12 O 19 ) is considered as potential microwave absorption (MA) material thanks to the large saturation magnetization, high Curie temperature, and excellent chemical stability. The integration of carbon nanotube (CNT) can improve the dielectric loss of BaFe 12 O 19 for further enhanced MA performance, nevertheless, the MA performance is still not desirable because of the poor CNT dispersion in the CNT/BaFe 12 O 19 composites, which usually prepared via the ball-milling method, unless high CNT loading was used. Herein, according to the thermal stability of CNT in different atmosphere and the formation mechanism of BaFe 12 O 19 from precursor, CNT was introduced in the precursor of BaFe 12 O 19 uniformly during auto-ignition process and calcined under different atmosphere. When CNT loading is only 2.0 wt%, the CNT/BaFe 12 O 19 composites obtained exhibits a minimum reflection loss ( R L min ) of -43.9 dB and effective bandwidth (with RL < -10 dB) of 3.9 GHz with the thickness of 1.5 mm, which are much superior to -10.2 dB and 2.2 GHz for pure BaFe 12 O 19 , and -13.6 dB and 2.5 GHz for CNT/BaFe 12 O 19 composite prepared by ball-milling method. These results may pave the way to design high-performance BaFe 12 O 19 based microwave absorbers.

Designing a strategy for fabrication of single-walled carbon nanotube via CH4/N2 gas by the chemical vapor deposition method

Fe/Mo catalysts supported on alumina are suggested for the growth of single-walled carbon nanotubes (SWCNTs) by chemical vapor deposition (CVD) in methane (CH4). One obvious synergistic advantage identified by molybdenum (Mo) is that by controlling the reaction temperature, it eliminates the need to activate the catalyst in hydrogen gas (H2). So as activation of the growth catalyst in H2 is a costly and extra step in the CVD method, this is a significant result of the present study. Herein, the sample quality and the dependence of carbon mass yield on CVD growth conditions are disserted. The activity of the catalyst is perused in the form of oxide under CH4 flow (160 sccm) and in the temperature range of 680 to 1000 °C. We came to the conclusion that the Fe/Mo/Al2O3 oxide catalyst is activated at temperatures as low as 800 °C. Under these conditions (800 °C, 160 sccm of CH4), the temperature is not enough for the tube to grow, but by increasing it, the desired conditions can be achieved (900 –1000 °C).

Controllable fabrication of metal-confined carbon nanotubes from the self-templated conversion of supramolecular gel nanofibers

Nanostructured supramolecular gels with self-assembled fibrillar networks are promising candidates for fabricating advanced functional materials for energy-related applications. Several fundamental challenges, including poor structural stability and monotonous fibrous morphology, greatly hinder their practical applications. To the best of our knowledge, supramolecular gel-derived carbon nanotubes (CNTs) have not been reported in the literature. Herein, we present a unique strategy for controllable fabrication of metal-confined carbon nanotubes (M/CNT) from the self-templated conversion of guanosine-based supramolecular gel (GSMG) nanofibers. Benefitting from the high tunability of GSMGs, it was demonstrated that the introduction of metal source (Ni and Fe) to improve the stability of the material and simply changing the KOH concentrations in the precursor materials, the structure of GSMG nanofibers derived active materials was controllably tuned from metal-constrained solid carbon nanofiber to hollow M/CNT. The optimized NiFe/B, N-CNT showed a superior oxygen evolution reaction catalytic activity with a low overpotential of 355 mV at a current density of 10 mA cm−2. By taking advantage of the unique structural features of supramolecular gels, this strategy provides a simple and effective synthetic route for functional CNT.

Fabrication and mechanical properties of multi-walled carbon nanotubes doped AlN ceramics prepared by spark plasma sintering

In this study, multi-walled carbon nanotubes (MWCNTs) are uniformly dispersed in aluminium nitride (AlN) powders, and the MWCNTs-doped AlN ceramics are sintered at 1500 °C with a holding time of 5 min by spark plasma sintering using Y 2 O 3 as the sintering additive. The effects of the MWCNTs content on the microstructure and mechanical properties of the as-obtained ceramic composites are investigated. The results reveal that many submicron pores are generated when protecting the structure of the CNTs, thereby reducing the density of the AlN ceramic. However, the gradual filling of the grain gap may compensate for the strengthening after CNT doping. The relative density and hardness reach the maximum values of 89.6% of the theoretical density and 7.0 ± 0.3 GPa, respectively, at the doping amount of 2.5 wt%.