Catalytic Chemical Vapor Deposition Research Articles

Preparation and performance study of carbon nanotube/polyphenylene sulfidecomposite materials based on floating catalytic chemical vapor deposition and continuous dusting powder

AbstractCarbon nanotubes (CNTs) are commonly used to enhance composite performance due to their exceptional properties. However, existing preparation methods suffer from complexity, poor interfacial bonding, and inadequate CNT dispersion. To address these issues, a new method for CNT composite preparation using floating catalytic chemical vapor deposition (FCCVD) is proposed in this study. Here, polyphenylene sulfide (PPS) powder is uniformly spread onto the continuously formed CNT network using a vibrator to prepare a CNT/PPS composite film. Subsequently, multilayer composite films are hot‐pressed into molds to produce CNT/PPS composites. The study investigates the mechanical, electrical, and thermal properties of these composites. Due to the preserved 3D CNT conductive network and strong interfacial bonding between PPS and CNTs bundles, the CNT/PPS composite demonstrates excellent electrical conductivity, mechanical strength, and electrothermal performance. This method offers a simple, effective, environmentally friendly, and promising approach for producing high‐performance CNT composite materials.Highlights A novel method for the fabrication of CNT/PPS composites. 3D conductive network enables composites to obtain high conductivity at low CNT content. The prepared CNT/PPS composites have excellent electrical, mechanical, and electrothermal properties.

Formation of n-type polycrystalline silicon with controlled doping concentration by flash lamp annealing of catalytic CVD amorphous silicon films

Formation of n-type polycrystalline silicon with controlled doping concentration by flash lamp annealing of catalytic CVD amorphous silicon films

Integration of carbon microsheets and helical carbon nanocoils for efficient microwave absorption

The integration of multi-dimensional materials is a powerful approach for the construction of high-performance microwave absorbers. In this work, 2D-like carbon microsheets (CMSs) have been directly synthesized on the surfaces of 3D helical carbon nanocoils (CNCs) through a Cu catalyzed chemical vapor deposition process. The junctions formed between CMSs and CNCs create numerous polarization sites, which enhances interfacial polarization. The planar morphology of CMSs is beneficial to enhance the multiple scattering of microwave, while the 3D helical CNCs prevent the aggregation of 2D-like CMSs and simultaneously enhance the conductive loss and cross-polarization loss. By controlling the growth time, the morphologies of CMS are precisely tailored and their impedance matching is adjusted. Consequently, CMS/CNC demonstrates exceptional microwave absorption (MA) performance with a broad effective bandwidth of 6.5 GHz and a minimum reflection loss of −39.3 dB at a remarkably low filling ratio of 4 wt%. This study provides a novel multi-dimensional integrated structure for efficient MA.

Low-Temperature Synthesis of Linear Carbon Chain inside Single-Walled Carbon Nanotubes

Linear carbon chain (LCC) has attracted much interest concerning its structure and applications. It has been reported that LCC possesses higher strength, elastic modulus, and stiffness than any known material, which provides a possibility for LCC as a new composite material, yet its chemical stability remains an issue [1]. Therefore, finding a method to efficiently synthesize LCC has become a meaningful research topic in recent years. A landmark study on LCC synthesis was given by using double-walled carbon nanotubes (DWCNTs) as the template combined with a high-temperature annealing treatment at 1460°C to acquire long chains composed of more than 6,000 carbon atoms [2]. Except for DWCNTs, LCC synthesis starting from single-walled carbon nanotubes (SWCNT) as templates was also reported. However, given the instability of SWCNTs at higher temperature [2] the synthesis efficiency is not as good as for DWCNTs. As far as we know, there is still no report on an efficient LCC synthesis inside SWCNTs. Herein, we report the low-temperature (400°C) efficient LCC synthesis starting from a SWCNT template.To this end, a SWCNT dispersion [3] underwent a surfactant exchange process and was fabricated into a SWCNT film by the filtration method. The SWCNT film was annealed under 400°C in an argon atmosphere to synthesize LCC. Raman spectroscopy (laser wavelength 532 nm) was used to characterize the efficiency of the LCC synthesis. A strong peak at 1863 cm-1 appeared after annealing, originating from the well-known C-mode of the linear carbon chain [4] thereby confirming its existence inside SWCNTs. SWCNTs synthesized by a low-pressure alcohol catalytic chemical vapor deposition (ACCVD) method [5] were also adopted for the LCC synthesis template, resulting in a similar LCC Raman peak at 1863 cm-1. We attribute this successful low-temperature LCC synthesis to the appropriate surfactant which could be encapsulated inside CNTs and converted to LCC during the annealing process.Keywords: Linear Carbon Chain, Single-walled Carbon Nanotubes, Surfactants

Carbon Nanotubes: A Review of Synthesis Methods and Applications

Carbon nanotubes (CNTs) are cylindrical-shaped materials composed of hexagonally arranged hybridized carbon atoms with versatility in synthesis methods and diverse applications. This review is focused on the fabrication, physicochemical and spectroscopic characterization, and industrial applications of CNTs. This review discusses some promising synthesis methods for the preparation of CNTs such as catalytic chemical vapor deposition, arc discharge, and laser ablation. A comparative discussion is made between these synthesis methods in terms of strengths, opportunities and challenges. Furthermore, functionalization and purification of CNTs’ surface leading to improved functionality has also been highlighted in this article. Finally, the analytical techniques employed to shed light on the physicochemical and morphological properties of CNTs are described.

The influence of structure of carbon nanofibers on their interaction with polyethylene matrix

The development of methods for purposeful modification of the polyethylene matrix with carbon nanostructures to create stronger and more durable pipe composites is an important direction in polymer science. Carbon nanofibers (CNFs) of three types, obtained via catalytic chemical vapor deposition of ethylene (Type I), trichloroethylene (Type II), and a mixture of ethylene and acetonitrile (Type III), were applied as modifying additives to improve the physical and mechanical characteristics of polyethylene. The polyethylene/CNF composites were prepared using a laboratory plasticizer. The introduction of CNFs (Type I) with a densely packed structure into the polymer matrix was found to provide the formation of a uniform fine-spherulitic structure that results in increased tensile strength, yield strength, elastic modulus, and abrasive wear. Such a positive effect is observed when the CNF content in the composite does not exceed 1.0 wt%. An increase in the abrasion resistance by a factor of 1.6 was observed.

Enhanced synthesis of sponge-type multiwalled carbon nanotubes using SiO2-Fe2O3 catalysts via aerosol-assisted chemical vapor deposition: Electrochemical and absorption capacity studies

Carbon nanotube sponges synthesized at the laboratory scale typically use a Fe-based organometallic catalyst, but low-cost alternatives with a higher yield ratio are needed for large-scale production. This work introduces a catalyst made from a mixture of silicon dioxide (SiO2) and hematite (Fe2O3) as an innovative alternative for the high-yield production of spongy-type multi-walled carbon nanotubes (ST-MWCNTs). We used a ball-milled mixture of SiO2 and Fe2O3 powders as the catalyst and toluene and N, N-dimethylformamide as carbon and nitrogen sources in an aerosol-assisted catalytic chemical vapor deposition system. Incorporating SiO2 into the Fe-based catalyst increased production yield to 184 % of the catalyst weight. The synthesized ST-MWCNTs exhibited a high crystallinity ratio (ID/IG = 0.34) with a unique entangled bundle-type nanotube configuration. At the same time, the presence of Si atoms and oxygen-type functionalities, demonstrated by X-ray photoelectron spectroscopy, modified their electrochemical behavior, making them suitable for supercapacitor or sensor applications. Additionally, the spongy structure demonstrated a reversible absorption capacity of over 15 times its weight with organic solvents like gasoline or ethylene glycol. This new catalyst configuration opens alternatives for generating higher amounts of 3D carbon nanomaterials with potential energy storage, water filtration, and environmental remediation applications.

Investigation of Ferromagnetic Nanoparticles’ Behavior in a Radio Frequency Electromagnetic Field for Medical Applications

This work raises the hypothesis that it is possible to use ferromagnetic carbon nanotubes filled with iron to hyperthermally destroy cancer cells in a radiofrequency electromagnetic field. This paper describes the synthesis process of iron-filled multi-walled carbon nanotubes (Fe-MWCNTs) and presents a study of their magnetic properties. Fe-MWCNTs were synthesized by catalytic chemical vapor deposition (CCVD). Appropriate functionalization properties of the nanoparticles for biomedical applications were used, and their magnetic properties were studied to determine the heat generation efficiency induced by exposure of the particles to an external electromagnetic field. The response of the samples was measured for 45 min of exposure. The results showed an increase in sample temperature that was proportional to concentration. The results of laboratory work were compared to the simulation using COMSOL software.

Kinetics insights into size effects of carbon nanotubes’ growth and their supported platinum catalysts for 4,6-dinitroresorcinol hydrogenation

Size effects are a well-documented phenomenon in heterogeneous catalysis, typically attributed to alterations in geometric and electronic properties. In this study, we investigate the influence of catalyst size in the preparation of carbon nanotube (CNT) and the hydrogenation of 4,6-dinitroresorcinol (DNR) using Fe2O3 and Pt catalysts, respectively. Various Fe2O3/Al2O3 catalysts were synthesized for CNT growth through catalytic chemical vapor deposition. Our findings reveal a significant influence of Fe2O3 nanoparticle size on the structure and yield of CNT. Specifically, CNT produced with Fe2O3/Al2O3 containing 28% (mass) Fe loading exhibits abundant surface defects, an increased area for metal-particle immobilization, and a high carbon yield. This makes it a promising candidate for DNR hydrogenation. Utilizing this catalyst support, we further investigate the size effects of Pt nanoparticles on DNR hydrogenation. Larger Pt catalysts demonstrate a preference for 4,6-diaminoresorcinol generation at (1 0 0) sites, whereas smaller Pt catalysts are more susceptible to electronic properties. The kinetics insights obtained from this study have the potential to pave the way for the development of more efficient catalysts for both CNT synthesis and DNR hydrogenation.

Synthesis of carbon nanotubes via CCVD of ethylbenzene over SrFe12O19/SiO2 oxide and their application for photodegradation of the remazol red dye

Carbon-based materials have stood out due to their variety of applications such as photocatalysis. Thus, strontium hexaferrite dispersed in silica was prepared by the Pechini method and used as a catalyst in the ethylbenzene reaction to produce carbon filaments and subsequent application in the photodegradation of the remazol red dye. The presence of SrFe12O19, α-Fe2O3 and amorphous silica phases was confirmed in the XRD (X-ray diffraction), Raman and XPS (X-ray photoelectron spectroscopy) analysis. The SEM (scanning electron microscopy) and TEM (transmission electron microscopy) results of the fresh oxides indicate cluster and sponge-like morphology. The formation of carbon filaments was observed by SEM analysis as a result of catalytic chemical vapor deposition (CCVD) of ethylbenzene. TEM images confirm the generation of multi-walled carbon nanotubes with an average diameter of 27.9 nm. Besides the presence of the SrFe12O19 and SiO2 phases, the diffractograms of the samples after the reaction shows the formation of graphite carbon and Fe0, confirming the reduction of α-Fe2O3 which was also verified in the TPR-H2 profile. The growth of nanotubes occurs from metallic iron, considering that the tip of the tube contains only iron, according to EDS (energy-dispersive X-ray spectroscopy) results. The Raman spectrum exhibited the characteristic D and G bands of carbon, where the ID/IG ratio decreased with increasing temperature. The reaction with the best catalytic performance achieved an average ethylbenzene conversion of 99 % and was more selective to ethene (∼93 %) at 650 °C. Furthermore, it was possible to carry out a simple theoretical-computational study regarding the distribution of the sites in a 2D plane by constructing maps and proposing a mechanism for the formation of carbon nanotubes from the ethylbenzene conversion. Finally, the obtained materials were applied in the remazol red dye degradation, achieving complete degradation in 15 min for the material synthesized at 650 °C.

Repeated fast selective growth of prepatternable monolayer graphene of electronic quality

Pattern formation is becoming indispensable in many applications of high-quality synthetic graphene. Nevertheless, the use of multiple lithography and etching steps can often degrade the properties of graphene due to residual disorder. Here, we report a facile, selective, and recyclable method for graphene synthesis from acetylene (C2H2) via catalytic chemical vapor deposition on a bimetal catalyst (Cu–Ni alloy). The synergistic pairing of the Cu–Ni alloy and C2H2 facilitates a rapid (ca. 1 min) synthesis of high-quality graphene under an intermediate temperature condition, e.g., 800 °C, that is quite relaxed from the far-flung method based on a Cu–CH4 pair. Prepatterned Cu–Ni alloy not only produces monolayer graphene patterns without any postprocessing but is also detachable from the resultant graphene patterns electrochemically, hinting at catalyst recyclability. Our test device of an organic field-effect transistor based on the prepatterned monolayer graphene outperforms its top-down counterpart that has undergone lithography and etching. Our facile selective growth of prepatternable monolayer graphene at intermediate temperatures, along with catalyst recyclability, may altogether lend adaptability, productivity, and sustainability to graphene-incorporated applications.

Self-Organized Growth of the Mo2C/Graphene Core-Shell Nanostructured Anode Material for Lithium-Ion Batteries via a Catalytic CVD Process

Self-Organized Growth of the Mo₂C/Graphene Core-Shell Nanostructured Anode Material for Lithium-Ion Batteries via a Catalytic CVD Process

In situ Preparation of SiOx/Carbon Nanotube Composite Films with Excellent Mechanical and Electrochemical Properties as an Anode Material for Lithium‐Ion Batteries

Silicon monoxide (SiOx) has become one of the most promising anode materials for next‐generation lithium‐ion batteries (LIBs) due to its high theoretical capacity. However, the inherent low electrical conductivity and large volume change during lithiation/delithiation processes hinder its practical applications. Here, a novel and facile strategy is designed to prepare SiOx/carbon nanotube (CNT) composite films in one step by using a method involving floating catalytic chemical vapor deposition (FCCVD). That is, SiOx particles and CNTs form at high temperature and winded directly on a drum to give rise to a film in an open air environment. The composite film is made up of a 3D CNT network with SiOx particles uniformly embedded. The as‐prepared composite film not only has a tensile strength of 78 MPa and elongation at break of 52%, but also exhibits a high specific capacity of 966.4 mA h g−1 after 120 cycles at the current density of 0.1 A g−1 and a good rate capacity of 448.7 mA h g−1 at the current density of 2 A g−1 when used as an anode material for LIBs. The results from the in‐situ preparation and resultant composite suggest a new route for developing high‐performance anode materials for LIBs.

Constructing the charge channel with CFx using a well-dispersed carbon nanotube arrays to boost high-rate primary battery

Pursuing ultra-high specific energy density for lithium fluorinated carbon (Li/CFx) battery requires a high fluorine to carbon ratio, resulting in low-conductivity and surface-polarization issues, which restricts battery of high-rate performance. Herein, the rich charge transport channels among CFx were constructed using a well-dispersed and highly-oriented carbon nanotube arrays (CNTA) to enhance high-rate performance in Li/CFx battery. The advantage of high-orientation lies in maintaining the appropriate van der Waals forces of this CNTA prepared by catalytic chemical vapor deposition (CCVD), which helps to avoid carbon nanotubes (CNT) entanglement and achieves good dispersion. Compared with conductive additives of commercial carbon nanotubes (CCNT) and super-P (CSP), CNTA effectively releases CFx surface-polarization favouring to Li+ diffusion. Therefore, battery performance was enhanced with reduced voltage delay and low impedance. At a discharge rate of 5 C, the Li/CFx battery using CNTA had a specific capacity of 697.32 mAh/g, while these batteries using CCNT and CSP lost discharge-performance. This highly-oriented CNTA enriches the conductive additives system of lithium primary batteries and provides a novel pathway for suppressing CFx polarization.

Effect of purification methods on the quality and morphology of plastic waste-derived carbon nanotubes

Recent innovative research efforts on the usage of plastic wastes as a cheap carbon source for carbon nanotubes (CNTs) production have emerged as a low-cost and sustainable means of producing CNTs. However, plastic waste-derived CNTs are rarely used in some purity-sensitive and high-alignment needed applications due to the poor quality of CNTs resulting from the abundance of impurities such as non-crystalline amorphous carbon, metallic nanoparticles, and other impurities. Therefore, purification is a crucial issue to be addressed to fully harness all potential applications of CNTs derived from waste plastic materials. Here, the effect of employing different purification methods on the morphology and purity of waste plastic-derived CNTs was investigated. CNTs were synthesized using waste polypropylene plastic as carbon feedstock via a single-stage catalytic chemical vapour deposition (CVD) technique. As-produced CNTs were purified using liquid-phase oxidation (chemical oxidation in nitric acid), gas-phase oxidation in air, and a combination of both liquid- and gas-phase oxidation methods. The synthesized and purified CNTs were characterized for morphology, purity, surface functional groups, thermal stability, and crystallinity using Transmission electron microscopy (TEM), Raman spectroscopy, Fourier Transform Infrared spectroscopy (FTIR), Thermogravimetric analysis (TGA), and X-ray diffraction (XRD), respectively. Results obtained showed that a combination of both liquid and gas phase oxidation purification techniques resulted in purer, better quality, and less defective CNTs with an IG’/IG value of 0.89 and ID/IG value of 0.86, while chemically treated CNTs (CNT-PC) presented more structurally defective CNTs and shortened nanotubes compared to other investigated treatment methods with an ID/IG value of 0.96. CNTs purified by a multi-step protocol (CNT-PAC) showed the highest weight loss of 72.3% indicating the highest quality and the presence of filamentous carbon. This study confirms that the choice of purification techniques influences the morphology and quality of plastic-derived CNTs.

Co-production of biochar and carbon nanotube from sewage sludge in a two-stage process coupling pyrolysis and catalytic chemical vapor deposition

Co-production of biochar and carbon nanotube from sewage sludge in a two-stage process coupling pyrolysis and catalytic chemical vapor deposition

Effects of CCVD parameters on the growth of VACNT over AZO substrate

Both, aluminum doped zinc oxide (AZO) and vertically aligned carbon nanotubes (VACNT) have outstanding properties and promising applications in the future, however, there is little information in the scientific literature on whether this is feasible. In this study, we investigated the effects of catalyst layer deposition parameters and the synthesis parameters by using a simple and cost-effective dip coating method to form alumina support layer and iron and cobalt bimetal catalyst layer on the AZO surface thereafter performing synthesis via catalytic chemical vapor deposition technique at 650 °C.In order to gain useful information about the structure of the VACNTs, several parameters were varied during both catalyst layer preparation (e.g. catalyst ink concentration) and CCVD synthesis (e.g. water vapor gas feed, the presence of hydrogen gas). The resulting samples were investigated by scanning electron microscopy, transmission electron microscopy and Raman spectroscopy. The results indicated that the length and structure of CNTs were strongly affected by the catalyst ink concentration and water vapor.

Demonstration of Excellent Crystalline Silicon Surface Passivation (S < 1.27 cm s−1) by High‐Rate DC‐Sputtered Hydrogenated Amorphous Silicon

The surface passivation quality of intrinsic hydrogenated amorphous silicon (i‐a‐Si:H) layers deposited by constant DC power‐facing target sputtering (FTS) technology is investigated. An n‐type crystalline silicon wafer passivated with a 42 nm‐thick i‐a‐Si:H shows an effective carrier lifetime of 11 ms, which corresponds to a low upper limit effective surface recombination velocity Seff of 1.27 cm s−1. An ultrathin 5 nm‐thick i‐a‐Si:H film achieves an implied open‐circuit voltage (iVoc) of 730 mV at a high deposition rate of 31 nm min−1. It is found that constant DC‐FTS does not cause sputtering damage under high deposition rate conditions. This work demonstrates that i‐a‐Si:H deposited by constant DC‐FTS can achieve the same passivation quality as i‐a‐Si:H deposited by plasma‐enhanced chemical vapor deposition or catalytic chemical vapor deposition, paving the way for the fabrication of silicon heterojunction solar cells without the use of explosive and toxic gases.

Upcycling of composite packaging waste to carbon nanotubes via chemical vapor deposition of pyrolysis gas

Based on the necessity of evaluating composite packaging wastes from both environmental and economic perspectives, it aimed to obtain carbon nanotube (CNT) from the pyrolysis gas product of this material by the catalytic chemical vapor deposition method (CCVD) via an upcycling approach. In the first stage, composite packaging wastes were pyrolyzed. Secondly, the composition of the gas via gas chromatography was determined. In the third stage, CNT production studies were carried out by the CCVD method in a tubular reactor at four different temperatures between 600 and 900 °C with nickel catalyst. The effects of temperature and carbon source feeding ratio on the properties of the obtained CNTs were investigated. CNTs produced in this study were compared with a commercial product. As a result, high-quality multi-walled carbon nanotube of 20–30 nm diameter and in micrometer scale length comparable to commercial products were produced from the gaseous product at 800 °C under Ni-catalysis.

Lightweight HfC nanowire-carbon fiber/graphene aerogel composites for high-efficiency electromagnetic interference shielding

Electromagnetic interference (EMI) and pollution triggered by electromagnetic waves are becoming a severe issue with the rapid development of various e-devices. Developing low-density and high-efficiency electromagnetic shielding materials is of great importance. Carbon aerogel materials have received worldwide attention due to their significant electromagnetic interference shielding properties and physicochemical stability. Herein, lightweight hafnium carbide nanowire (HfCnw)-carbon fiber (CF)/graphene aerogel (GA) composites with excellent electromagnetic shielding performance were fabricated by successively introducing CF via hydrothermal process, pyrolytic carbon (PyC) coating via chemical vapor infiltration (CVI), and HfCnw via catalytic chemical vapor deposition (CCVD) into GA. It was found that the electrical conductivity of the HfCnw-CF/GA composites with the HfCnw growth time of 4 h reached 94.0 S/cm, which was far higher than 1.1 S/cm of pristine GA and 2.7 S/cm of the CF/GA composites. The EMI shielding effectiveness (SE) of the HfCnw-CF/GA composites was as high as 66.4 dB in the X-band, which was 3 times that (25.4 dB) for GA and 1.5 times that (45.8 dB) for the CF/GA composites. The EMI shielding performance of the HfCnw-CF/GA composites was improved mainly due to the enhanced multiple reflection loss, conductance loss, and interfacial polarization loss. Moreover, the HfCnw-CF/GA composites had a specific SE (SSE) value of 364.1 dB cm3/g, which exhibits good application prospects in the EMI field to meet the needs for light weight and high SE.