Catalytic Chemical Vapor Deposition Research Articles

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.

Long-term stability of low-temperature deposited Cat-CVD SiN x thin film against damp-heat stress

In this paper, we systematically investigated the damp heat (DH) stability of silicon nitride (SiN x ) films formed by catalytic CVD (Cat-CVD) at low substrate temperatures (T sub) of 100 °C–137 °C, aiming at application as a gas barrier and antireflection layer of perovskite/silicon tandem solar cells. We have found that the optical properties of the SiN x films, such as refractive index and reflection of the films, were changed only slightly for <2% after DH testing for >500 days. The Fourier transform IR spectroscopy studies demonstrated that the SiN x films were hardly oxidized under the DH test for the sample formed at high T sub. A slight oxidization occurs only in the SiN x film formed at a low T sub of 100 °C after DH testing for 274 days. These results indicate the high stability of the Cat-CVD SiN x films and their feasibility for application in the surface coating of solar cells.

Gradient multilayer interface–coupled FeNi@C@SiO2 for enhanced anti–corrosion and preeminent microwave absorption

Developing high–efficient microwave absorbing (MA) materials with anti–corrosion (AC) properties to tackle the harsh hygrothermal marine conditions remains a challenge. Herein, we employed catalytic chemical vapor deposition and the Stöber technique to fabricate gradient multilayer interface–coupled FeNi@C@SiO2 composites, guided by the hetero–interface engineering. The resulting composites exhibited exceptional MA properties and AC behavior. Specifically, they showcased a remarkable effective absorption bandwidth of 6.27 GHz at 1.40 mm, outperforming that of FeNi (3.80 GHz). This improved bandwidth was attributed to the electron conduction pathway provided by the C layer, which facilitated electron migration and hopping. The C@SiO2 layer, containing defects and –OH functional groups, induced abundant dipole polarization and optimizes the impedance matching of FeNi. Furthermore, the RCS reduction value of FeNi@C@SiO2 could reach 16.73 dB·m2. Moreover, the corrosion rate of FeNi@C@SiO2 was 7.48 × 10−11 m/s, significantly lower than that of FeNi (1.29 × 10−10 m/s). This reduction was primarily due to the intrinsic inertness and impermeability of the C@SiO2 layer, effectively isolating the corrosive medium from the substrate. This investigation presents a novel point of reference for the advancement of bifunctional MA materials intended to cope with extreme environments.

Influence of platinum content (X) in the LaNi5PtX catalyst and reaction conditions on the properties of ferromagnetic Ni-filled CNTs

This research highlights the synthesis of carbon nanostructures using the catalytic chemical vapor deposition (CCVD) method, a hybrid process combining chemical vapor deposition (CVD) and Gas-Solid Heterogeneous Catalysis (GSHC). Intermetallic catalysts, LaNi5Ptx (x = 0, 0.05, 0.5, 1.0), were fabricated through an arc melting procedure to serve as templates for the catalytic conversion of carbon precursors into solid materials. These catalysts, featuring the ferromagnetic transition metal Ni, tend to aggregate into larger particles, reducing the rate of hydrocarbon cracking at the catalyst surface. Rare earth metals like Lanthanum were introduced to form an alloy with a higher melting point to prevent thermal aggregation. Additionally, Pt was incorporated to modify the catalytic properties of the alloy. The study primarily explores the impact of catalyst composition on carbon nanotube (CNT) production. The introduction of platinum content to the catalyst influences the rate at which Ni is filled. The research aimed to alter the catalyst's composition by varying platinum doping in the Pauli paramagnetic lanthanum nickel alloy (LaNi5) to understand the growth mechanism and morphological variations of Ni-filled CNTs. Platinum and lanthanum oxides significantly influence nickel filling in CNTs, resulting in an increased filling rate as the catalyst's Pt content varies from 0 to 1.0. However, higher Pt doping content disrupts the CNT structure with spontaneous nickel encapsulation.

Boosting effect of single-atom Sn on catalytic activity of Ni towards synthesis of carbon nanofibers from ethylene

Nickel and its alloys are widely used for the synthesis of carbon nanofibers via catalytic chemical vapor deposition of various hydrocarbons. In the present research, a series of Ni-Sn alloys with tin loading varied in a range from 0.1 to 25.0 at% were prepared and characterized. Alloying of nickel with a small amount of tin was found to accelerate significantly the catalytic process of ethylene decomposition accompanied by carbon deposition. For the NiSn(0.25) sample, the carbon yield reaches 195 g/gcat after 30 min at 550 °C. At the highest Sn loading (25.0 at%), the process is completely suppressed. A new mechanism explaining the observed interaction of ethylene with Ni-Sn alloys was proposed. Single-atom Sn species are responsible for the increased catalytic activity. A single-atom Ni-Sn alloy is considered an efficient catalyst with enhanced stability for the production of carbon nanofibers.

In‐Vitro Investigation of the α‐Amylase Inhibition Activity of Bare Bis‐Benzylidene‐Cyclohexanone Synthesized by a Highly Selective Solvent‐Free Route

AbstractCurrent work reports the highly selective, solvent‐free synthesis of an endorsed bioactive compound, Bis benzylidine cyclohexanone (BBC) through solid acid catalysed cross aldol condensation route and checks its in‐vitro bio activity. The catalytic support (Multiwalled carbon nanotube) employed was synthesized through the highly sophisticated catalytic chemical vapor deposition (CVD) method and simple mechanical grinding strategy was adopted to decorate sulfonic acid on the support. The C1s X‐ray photoelectron peak of at 290.3 eV confirms the effective interaction of sulfonic acid with MWCNT. The sharp and intense desorption peaks observed at approximately 528.7 °C and 655.15 °C in the TPD analysis unmistakably substantiate the strong acidity of the synthesized system. The alpha amylase inhibition activity of the synthesized compound was calculated to be around 88.5 %, which is in par with the commercial drug as it could inhibit only 96 %. Further, the in‐silico (Docking and Molecular Dynamic Simulation) investigations unveiled a new target site for the compound and this can further be studied in detail to advance the applications in drug design. Detailed scrutiny of various parameters was conducted to validate the bioactivity and pharmaceutical potential of the synthesized compound.

Properties of Erbium-Doped Silicon Oxycarbide Thin Films

This research paper presents findings on the properties of erbium ions incorporated within an amorphous silicon oxycarbide host matrix. A special analysis is made on photoluminescence emission. The experimental samples were prepared using tetraethoxysilane and erbium oxide as reagents via Catalytic chemical vapor deposition. Notably, a unique preparation method was employed for thin films obtention, avoiding plasma damage, which had not been utilized for this purpose previously. One of the most important accomplishments of this study consists in achieving a broad band PL emission centered at 580 nm, which is attributed to the incorporation of erbium ions into a silicon oxycarbide matrix. The obtained results indicate a direct correlation between the photoluminescence emission evolution and the presence of erbium oxide used during the deposition process. The observed photoluminescence emission is attributed to the formation of erbium-silica-based complexes that facilitate energy transfer to the erbium ions. This research opens new possibilities in areas such as optoelectronics, sensing, and telecommunications. The findings obtained have numerous potential applications, particularly in advancing the design of LEDs, lasers, and waveguides.

Synthesis of MWCNTs by chemical vapor deposition of methane using FeMo/MgO catalyst: role of hydrogen and kinetic study

This study aims to investigate the role of hydrogen on CNTs synthesis and kinetics of CNTs formation. The CNTs were synthesized by catalytic chemical vapor deposition of methane over FeMo/MgO catalyst. The experimental results revealed that hydrogen plays an important role in the structural changes of catalyst during the pre-reduction process. The catalyst structure fully transformed into metallic FeMo phases, resulting in an increased yield of 5 folds higher than those of the non-reduced catalyst. However, the slightly larger diameter and lower crystallinity ratio of CNTs was obtained. The hydrogen co-feeding during the synthesis can slightly increase the CNTs yield. After achieving the optimum amount of hydrogen addition, further increase in hydrogen would inhibit the methane decomposition, resulting in lower product yield. The hydrogenation of carbon to methane was proceeded in hydrogen co-feed process. However, the hydrogenation was non-selective to allotropes of carbon. Therefore, the addition of hydrogen would not benefit neither maintaining the catalyst stability nor improving the crystallinity of the CNT products. The kinetic model of CNTs formation, derived from the two types of active site of dissociative adsorption of methane, corresponded well to the experimental results. The rate of CNTs formation greatly increases with the partial pressure of methane but decreases when saturation is exceeded. The activation energy was found to be 13.22 kJ mol−1, showing the rate controlling step to be in the process of mass transfer.

Mass production of carbon nanotube fibers and hybrid yarns for high-performance helical auxetic yarn strain sensors

With the spectacular physical properties of electrical conductivity, mechanical strength and thermal conductivity, carbon nanotube (CNT) fibers are favored in many fields such as energy storage devices, sensing, electromagnetic shielding and structural reinforcement, especially in flexible sensing devices. However, the lower tensile properties of CNT fibers limit their further application in stretchable strain sensors, especially when monitoring large deformation variables. Here, large-scale continuous production of CNT fibers has achieved through floating catalytic chemical vapor deposition (FCCVD) technology. In the meantime, the CNT fibers were hybrid with Kevlar fibers to obtain hybrid CNT yarns with the strength of 168.4 MPa and the electrical conductivity of 7.78 × 104 S m−1. The strength of the hybrid CNT yarns produced by this method is higher than that of 40 count cotton yarns, which is perfectly suited for the fabrication of textile devices. Through knitting with three-dimensional elastic fabrics, the textile-based sensors exhibit promising sensing ability, washability, weather tolerance and sweat resistance, owing to the excellent physical and chemical properties of the hybrid CNT yarns. Moreover, stretchable strain sensors exhibit fast response and cycle stability, which provides unique opportunities in designing smart textiles with fast response and environmental durability.

Solution Combustion Synthesis of Ni-Based Nanocatalyst Using Ethylenediaminetetraacetic Acid and Nickel-Carbon Nanotube Growth Behavior.

We studied the influence of the ethylenediaminetetraacetic acid (EDTA) content used as combustion fuel when fabricating nickel oxide (NiO) nanocatalysts via solution combustion synthesis, as well as the growth behavior of carbon nanotubes (CNTs) using this catalyst. Nickel nitrate hexahydrate (Ni(NO3)2∙6H2O) was used as the metal precursor (an oxidizer), and the catalysts were synthesized by adjusting the molar ratio of fuel (EDTA) to oxidizer in the range of 1:0.25 to 2.0. The results of the crystal structure analysis showed that as the EDTA content increased beyond the chemical stoichiometric balance with Ni(NO3)2∙6H2O (F/O = 0.25), the proportion of Ni metal within the catalyst particles decreased, and only single-phase NiO was observed. Among the synthesized catalysts, the smallest crystallite size was observed with a 1:1 ratio of Ni ions to EDTA. However, an increase in the amount of EDTA resulted in excessive fuel supply, leading to an increase in crystallite size. Microstructure analysis revealed porous NiO agglomerates due to the use of EDTA, and differences in particle growth based on the fuel ratio were observed. We analyzed the growth behavior of CNTs grown using NiO nanocatalysts through catalytic chemical vapor deposition (CCVD). As the F/O ratio increased, it was observed that the catalyst particles grew excessively beyond hundreds of nanometers, preventing further CNT growth and leading to a rapid termination of CNT growth. Raman spectroscopy was used to analyze the structural characteristics of CNTs, and it was found that the ID/IG ratio indicated the highest CNT crystallinity near an F/O ratio of 1:1.

Polyethyleneglycol-polyhydroxylbutyrate functionalized carbon nanotubes for industrial electroplating wastewater treatment

This study focuses on the production and purification of multi-walled carbon nanotubes (P-CNTs) via a catalytic chemical vapor deposition method and subsequent functionalization with amino polyethylene glycol (NH2-PEG) and its mixture with polyhydroxybutyrate (PHB) through a multi-step purification process to produce NH2-PEG-CNTs and NH2-PEG-PHB-CNTs, respectively. The developed nanoadsorbents were used to treat electroplating wastewater via batch adsorption to sorb potentially toxic metals and emerging pollutants. The nanoadsorbents were characterized before and after treatment with wastewater after thermal regeneration analyzed using HRSEM/EDS/SAED, DLS Nanozetasizer, BET, TGA/DTG, and FTIR. The nanoadsorbents showed a homogeneous distribution of clean and smooth crystalline interwoven tubular/cylindrical shapes and sizes, with broad polydispersed/high aspect ratio, large surface area, mesopores, and functional groups. The batch adsorption study showed simultaneous multi-capturing of toxic metals from industrial electroplating wastewater with a directly proportional relationship between contact time, adsorbent dosage andtemperature, and electrostatic activities via the positive surface charge of the nanoadsorbents (pH > pHzpc). The highest removal of Fe (15.86 %), Ni (79.82 %), Pb (79.82 %), and Cu (84.97 %) were obtained using NH2-PEG-PHB-CNTs. In addition, the ANOVA results show that the adsorption process depends on other parameters such as the concentration of toxic metals in the wastewater, its hydration energy, electronegativity, ionic mobility in the electrostatic activities, pH of the nanoadsorbents, water holding capacity of the polymer-functionalized nanoadsorbents, and synergistic effects of the bi-polymer. Moreover, the nanoadsorbents have a stable morphology after thermal regeneration for reusability purposes, and treated wastewater can be safely reused in the electroplating industry or for other purposes, such as agriculture.

Fabrication of a Co-Mo-Based Metal-Organic Framework for Growth of Double-Walled Carbon Nanotubes.

Double-walled carbon nanotubes (DWCNTs) make up a unique class of carbon nanotubes (CNTs) that are particularly intriguing for scientific research and are promising candidates for technological applications. A more precise level of control and greater yields can be achieved via catalytic chemical vapor deposition (CCVD), which involves the breakdown of a carbonaceous gas over nanoparticles. The addition of molybdenum to the system can increase the selectivity with regard to the number of walls that exist in the obtained CNTs. As reported herein, we have designed and synthesized a novel Co-Mo-MOF, [Co(3-bpta)1.5(MoO4)]·H2O (where 3-bpta = N,N'-bis(3-pyridyl)terephthalamide), and employed the Co-Mo-MOF as a bimetallic catalyst precursor for the CCVD approach to prepare high-quality DWCNTs. The Co-Mo-MOF was employed after being calcined in N2 and H2 at 1100 °C and decomposing into CoO, CoMoO4, and MoO3. Existing CoMoO4 is unaltered after reduction in H2 at 1100 °C, while CoO and MoO3 are converted into Co0 and MoO2, and more CoMoO4 is created at the expense of Co0 and MoO2 without clearly defining agglomeration. Finally, the interaction between metallic Co particles and C2H4 is what initiates the formation of DWCNTs. In-depth discussion is provided in this paper regarding the mechanism underlying the high selectivity and activity of Co-Mo catalysts in regulating the development and structure of DWCNTs. The DWCNTs also offer excellence performance when they are used as water purification agents and as selective sorbents. This work opens a feasible way to use MOFs as a way to produce MWCNTs, thus blazing a new trail in the field of MOF-derived carbon-based materials.