Alternative Metallocenes in Floating Catalyst-CVD: Synthesis of Novel Carbon Nanostructures

The Floating Catalyst Chemical Vapor Deposition (FCCVD) method has attracted extensive research interests from both academia and industry due to its high potential for carbon nanotube (CNT) mass production. As aerospace aims become increasingly demanding, there is an ever growing need for mass producing lightweight structural composites. By infiltrating bismaleimide (BMI) resin and curing under pressure, CNT/BMI nanocomposites with high CNT loading are exhibiting excellent mechanical properties. By further integrating CNT into carbon fiber (CF), the mechanical and electrical improvements in axial, transverse and through-thickness direction demonstrate potential for multifunctional applications. In this work, a FCCVD reactor designed and assembled at the High-Performance Materials Institute was used for CNT synthesis. The CNT aerogel formed was continuously spun onto a rotating mandrel while continuously spraying a BMI/acetone solution, forming an ultra-thin prepreg material ranging from 1-5 μm in thickness. The quality of the CNTs collected was characterized using Raman Spectroscopy, Scanning Electron Microscopy (SEM), Thermogravimetric Analysis (TGA), and Transmission Electron Microscopy (TEM). To evaluate the ultra-thin FCCVD-CNT prepregs, six layers were stacked in the same alignment direction, and cured using a vacuum-assisted bagging system and hot press. Electrical conductivity tests were conducted in both the aligned and the transverse directions. Furthermore, the ultra-thin CNT prepregs were integrated into the aerospace-grade unidirectional IM7/CYCOM® 5250-4 prepregs following an alternating order. The assembly was finally vacuum-bagged to expel air and cured with a hot press. The microstructure and interface of CF/CNT hybrid composites and CNT/BMI composites were observed under SEM. This paper reports on a fabrication process of CNT prepregs, which could be potentially used to scale-up the CNT/BMI composites and CF/CNT interply hybrid composites manufacturing.

Dry spinning yarns from vertically aligned carbon nanotube arrays produced by an improved floating catalyst chemical vapor deposition method

In this paper, we report an efficient process to grow well-aligned carbon nanotube (CNT) arrays with a good area distribution density (about 5.6 ×107 CNT/mm2). Vertically aligned carbon nanotubes (VA-CNTs) have been produced by controlling flow rate, temperature and catalyst nanoparticles using a floating catalyst chemical vapor deposition (FC-CVD) technique. They were synthesized on quartz substrates at 800 °C from toluene as a carbon source. VA-CNT samples were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), Raman spectroscopy and their surface area and pore size were determined by nitrogen adsorption analysis. The synthesized CNTs have a length of 500 µm and diameters ranging from 120±40 nm. The CNT filaments form a strength structure and exhibit a good vertical alignment. The remarkable properties of CNTs make them attractive for separation applications, especially for water and wastewater treatment.

Electrochemical activation to enhance the volumetric performance of carbon nanotube electrodes

Effect of alignment and packing density on the stress relaxation process of carbon nanotube fibers spun from floating catalyst chemical vapor deposition method

An effective and cost-effective approach to synthesize new materials can be determined via research on a carbon nanotube (CNT) aerogel. This review paper gives an overview of the current synthetic methodologies and routes to enhance understanding. It also investigates the appropriate issues on the development of CNT-based three-dimensional (3-D) porous materials in an attempt to fill the knowledge gap regarding viability. First, an elaborate description on CNTs is provided, followed by a focus on CNT macrostructure fabrication, showcasing their key features, disadvantages, advantages and other aspects that were considered as related. Then, the methods for synthesis pertaining to the CNT aerogel are discussed with a focus on a floating catalyst chemical vapour deposition method as well as the growth mechanism pertaining to CNTs employing the method. Key parameters, including catalyst, reaction time, carbon source, carrier gas and reaction temperature, which could cast an impact on the efficiency of the process are discussed subsequently.

Low Temperature Growth of Vertically Aligned Carbon Nanotubes via Floating Catalyst Chemical Vapor Deposition Method

The floating catalyst chemical vapor deposition (FCCVD) method for producing single‐walled carbon nanotubes (SWNTs) has demonstrated great potential in transparent conductive film (TCF) application. In FCCVD, reducing the concentration of carbon nanotubes (CNTs) is a well‐agreed method of improving the conductivity of SWNT TCF, achieved by producing thinner and longer CNT bundles. However, this method decreases the yield dramatically, which has persisted throughout the TCF development. Here, the production of large‐diameter double‐walled CNT (DWNT) TCFs via FCCVD is reported, which overcomes the tradeoff between performance and yield. These TCFs of DWNTs with an average diameter of ≈4 nm have a low sheet resistance of 35 Ω sq−1 at 90% transmittance. The conductivity here aligns with the best‐performing SWNT TCFs reported to date, showing a production yield greater than two orders of magnitude. The main factor contributing to the high performance and yield is considered to be the large tube diameter, which greatly improves the yield threshold of CNT bundling and leads to long tube length and unique junctions broadening. Moreover, the application of DWNT TCFs in perovskite solar cells exhibits a power conversion efficiency of 17.4%, which has not been reported yet in indium‐free CNT‐based solar cells.

Effects of nitrogen-doped carbon nanotubes on the discharge performance of Li-air batteries

Catalysts can determine the structure and properties of carbon nanotube (CNT) fibers fabricated using the floating catalyst chemical vapor deposition (FCCVD) method. The tail gas left over when CNT fibers are fabricated by the FCCVD method has been proven to contain deactivated iron nanoparticles, as well as carbide gas and hydrogen. This study demonstrates that the deactivated iron nanoparticles in tail gas can be successfully activated in a double furnace system under certain conditions. CNT fibers can be successfully prepared using the activated iron nanoparticles by adding the precursor without the catalyst. These CNT fibers are composed of double-walled carbon nanotubes (DWNTs) and have low density, high strength, and electrical conductivity. DOI: http://dx.doi.org/10.5755/j01.ms.23.3.17050

Transparent conducting films (TCFs) are critical components of many optoelectronic devices that pervade modern technology. Due to their excellent optoelectronic properties and flexibility, single-walled carbon nanotube (SWNT) films are regarded as an important alternative to doped metal oxides or brittle and expensive ceramic materials. Compared with liquid-phase processing, the dry floating catalyst chemical vapor deposition (FCCVD) method without dispersion of carbon nanotubes (CNTs) in solution is more direct and simpler. By overcoming the tradeoff between CNT length and solubility during film fabrication, the dry FCCVD method enables production of films that contain longer CNTs and offer excellent optoelectronic properties. This review focuses on fabrication of SWNT films using the dry FCCVD method, covering SWNT synthesis, thin-film fabrication and performance regulation, the morphology of SWNTs and bundles, transparency and conductivity characteristics, random bundle films, patterned films, individual CNT networks, and various applications, especially as TCFs in touch displays. Films based on SWNTs produced by the dry FCCVD method are already commercially available for application in touch display devices. Further research on the dry FCCVD method could advance development of not only industrial applications of CNTs but also the fundamental science of related nanostructured materials and nanodevices.

Various techniques for the synthesis of carbon nanotubes (CNTs) are being developed to meet an increasing demand as a result of their versatile applications. Swirled floating catalyst chemical vapour deposition (SFCCVD) is one of these techniques. This method was used to synthesise CNTs on a continuous basis using acetylene gas as a carbon source, ferrocene dissolved in xylene as a catalyst precursor, and both hydrogen and argon as carrier gases. Transmission electron microscopy analyses revealed that a mixture of single and multi-wall carbon nanotubes and other carbon nanomaterials were produced within the pyrolytic temperature range of 900–1 100°C and acetylene flow rate range of 118–370 ml min –1 . Image comparison of raw and purified products showed that low contents of iron particles and amorphous carbon were contained in the synthesised carbon nanotubes. Diamond films were produced at high ferrocene concentration, hydrogen flow rate and pyrolysis temperatures, while carbon nanoballs were formed and attached to the surface of the CNTs at low ferrocene content and low pyrolysis temperature. : SFCCVD, CNTs, continuous production, pyrolysis, diamond films

The raw carbon nanotubes (CNTs) were prepared by the floating catalyst chemical vapor deposition method. The raw carbon nanotubes were functionalized, impregnated with iron nanoparticles, and characterized using high resolution transmission electron microscopy (HRTEM), scanning electron microscopy with energy dispersive spectroscopy (SEM‐EDS), Fourier transform infrared spectroscopy (FTIR), Differential Scanning Calorimetry (DSC), and thermogravimetric analysis (TGA). The three types of these multiwalled carbon nanotubes were applied as adsorbents for the removal of bromate from drinking water. The effects of the pH, the concentration of anion, the adsorbent dose, the contact time, and the coanions on the adsorption process have been investigated. The results concluded that the highest adsorption capacities were 0.3460 and 0.3220 mg/g through using CNTs‐Fe and raw CNTs, respectively, at the same conditions. The results showed that the CNTs‐Fe gives higher adsorption capacity compared with the raw CNTs and the functionalized CNTs. The presence of nitrate () in the solution decreases the adsorption capacity of all CNTs compared with chloride (Cl−) associated with pH adjustment caused by nitric acid or hydrochloric acid, respectively. However, the adsorption of all MWNCTs types increases as the pH of solution decreases.

Reduced graphene oxide-carbon nanotube grown on carbon fiber as binder-free electrode for flexible high-performance fiber supercapacitors

Single-walled carbon nanotubes (SWCNTs), multi-walled carbon nanotubes (MWCNTs), and carbon nanofibers (CNFs) in hybrid structures were synthesized on austenitic stainless steel substrates (Type:304). The formation of nanoparticles on substrates occurred under hydrogen gas (H2) with temperature of 720 °C. The effects of reductive heat treatment on the growth of carbon nanostructures at 15, 45, 60, 75 and 80 minutes were examined with scanning electron microscope (SEM), transmission electron microscope (TEM), X-ray diffractrometer (XRD) and thermogravimetric analysis (TGA). The samples were synthesized using thermal chemical vapor deposition (Thermal CVD) under atmospheric pressure of acetylene gas (C2H2). The combination of carbon nanotubes and carbon nanofibers in hybrid structure was synthesized on a substrate using a long time to adjust the surface by heating treatment. The hybrid structure of carbon could not be observed when used in surface treatment time was 80 minutes. Shorter ( 75 min) substrate heat treatments did not produce hybrid carbon nanostructures at this temperature.