Catalytic Chemical Vapor Deposition Research Articles

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.

Understanding the Reaction Chemistry of 1,1,3,3-Tetramethyldisilazane as a Precursor Gas in a Catalytic Chemical Vapor Deposition Process.

The reaction chemistry of 1,1,3,3-tetramethyldisilazane (TMDSZ) in catalytic chemical vapor deposition (Cat-CVD), including its primary decomposition on a heated W filament and secondary gas-phase reactions in a Cat-CVD reactor, was studied using 10.5 eV vacuum ultraviolet single-photon ionization and/or laser-induced electron ionization in tandem with time-of-flight mass spectrometry. It has been demonstrated that TMDSZ initially breaks down to form various species, including methyl radical (•CH3), ammonia (NH3), and 1,1-dimethylsilanimine (DMSA). The activation energies (Ea) for the formation of •CH3 and NH3 were determined to be 61.2 ± 1.0 and 42.1 ± 0.9 kJ mol-1, respectively, in the temperature range of 1400-2000 and 900-2400 °C. It was found that the formation of DMSA may have two different contributing routes, i.e., a concerted one (Ea = 33.6 ± 2.3 kJ mol-1) at lower temperatures of 900-1500 °C and a stepwise one (Ea = 155.0 ± 7.8 kJ mol-1) at higher temperatures of 2100-2400 °C. The secondary gas-phase reactions occurring in the Cat-CVD reactor environment were found to stem from two competing processes. The first one, free-radical short-chain reactions initiated by •CH3 formation and propagated by H abstraction reactions, is the dominating chemical process, producing many high-mass stable alkyl-substituted or silyl-substituted disilazane or trisilazane products via radical recombination reactions. Head-to-tail cycloaddition of unstable DMSA is the second contributing chemical process, which forms cyclodisilazane species. In addition, evidence was found for the conversion of NH3 into H2 and N2 in the Cat-CVD reactor.

ZIF-67 derived Co@carbon nanotubes anchored on carbon fiber for efficient microwave absorption and mechanical enhancement

Rational design of multifunctional and high-performance electromagnetic wave (EMW) absorbers is highly desirable but still remains a challenge. Herein, the 3D heterostructural Co@carbon nanotubes/carbon fiber (Co@CNTs/CF) hybrids derived from ZIF-67/CF were successfully fabricated via the in-situ synthesis of ZIF-67 on CF and subsequent catalytic chemical vapour deposition. Intriguingly, the as-obtained composites acquire adjustable EMW absorption and favorable mechanical properties simultaneously. Specifically, taking advantage of adequate conductive paths, plentiful heterogeneous interfaces, suitable defect vacancies, appropriate magnetic loss, as well as optimized impedance matching, Co@CNTs/CF delivers a brilliant EMW absorption intensity of −45.11 dB at only 1.15 mm together with a broad effective absorption bandwidth (EAB) of 4.0 GHz (1.23 mm), and an unexpected minimal reflection loss up to −65.63 dB (3.84 GHz) coupled with an EAB of 3.6 GHz at merely 1.09 mm, respectively. In addition, the tunable EAB can be achieved in 2.6–18 GHz, covering 96 % of the test frequency by changing the absorber thickness from 0.93 to 5.0 mm (29 wt%). Moreover, the maximum radar cross section reduction can reach 48.8 dBm2. The uniform layer of CNTs with moderate crystallinity also enables Co@CNTs/CF to improve the tensile strength and Weibull modulus compared to unsized CF. This study paves a novel avenue for developing multifunctional materials based on CF through an efficient, controllable and low-cost approach.

Facile constructing Ti3C2Tx/TiO2@C heterostructures for excellent microwave absorption properties

Optimizing and enhancing the performance of electromagnetic wave (EMW) absorption materials relies on the modification of their composition and structure through heterogeneous interface engineering. Ti3C2Tx’s high conductivity results in an impedance mismatch, which hinders efficient EMW absorption. Herein, a one–step catalytic chemical vapor deposition (CCVD) method is used to construct the Ti3C2Tx/TiO2@C heterogeneous structure. Upon annealing at 500 °C, amorphous carbon is uniformly deposited on the Ti3C2Tx surface, thereby incorporating the scale–like TiO2 generated during the process. The inclusion of the amorphous carbon layer and TiO2 reduces the substrate’s conductivity, achieving optimized impedance matching. Additionally, building heterogeneous interfaces between Ti3C2Tx, TiO2, and C enriches multiple loss mechanisms involving dipole and interfacial polarization, ultimately enabling optimal EMW absorption performance. The minimum reflection loss (RLmin) value of Ti3C2Tx/TiO2@C–500 is –53.12 dB when its thickness and frequency are 1.15 mm and 13.80 GHz, respectively. Moreover, thermal infrared imaging confirms that coatings fabricated using Ti3C2Tx/TiO2@C–500 demonstrate a favorable heat dissipation rate, validating its effectiveness in addressing the challenge of efficient heat dissipation in electronic devices. This study significantly contributes to the progress of two–dimensional (2D) materials, enabling high–performance EMW absorption and expanding their applications in complex scenarios.

Optimisation of synthesis parameters for Co-Mo/MgO catalyst yield in MWCNTs production

This study examined the impact of synthesis parameter on Cobalt-Molybdenum supported with magnesium oxide (Co-Mo/MgO) catalyst yield in production of multiwall carbon nanotube (MWCNT). Wet impregnation was used to synthesis the Co-Mo/MgO bimetallic catalyst, while a catalytic chemical vapour deposition reactor (CCVD) was used for the synthesis of carbon nanotubes (CNTs). Factorial and central composite design techniques were used to optimise the catalyst and multi-wall carbon nanotubes (MWCNTs). Thermogravimetric analysis/ Differential thermal analysis (TGA/DTA), selected area (electron) diffraction (SAED), X-Ray diffraction analysis (XRD), and Brunauer–Emmett–Teller (BET) were used to characterise the catalyst and MWCNTs that were produced. The Co-Mo/MgO catalyst had an optimal yield of 93.22%, 247.30 m2/g of specific surface area at 120 °C drying temperature, 16 g of mass support, and a 10-hour drying time. The maximum catalyst yield of 40.62% was obtained at calcination temperature of 500 °C and a holding period of 2 hours. The catalyst with the highest degradation temperature of 398.21 °C was observed at 600 °C, when calcined for 4 hours. It was discovered that the surface area of Co-Mo/MgO catalyst from the BET analysis under ideal conditions varied depending on the holding time. The XRD and SAED revealed the growth of CNTs of concentric graphene pattern with the Co-Mo/MgO catalyst.

Pushing the limits of PLA by exploring the power of MWCNTs in enhancing thermal, mechanical properties, and weathering resistance

The present study focuses on enhancing the mechanical, thermal, and degradation behavior of polylactic acid (PLA) by adding carbon nanotubes (CNTs) with different concentrations of 0.5, 1, 3, and 5%. The CNTs were prepared using catalytic chemical vapor deposition, and the prepared PLA/CNTs nanocomposite films were characterized using techniques such as FT-IR, Raman spectroscopy, TGA, SEM, and XRD. The distinct diffraction patterns of multi-walled carbon nanotubes (MWCNTs) at 2θ angles of 25.7° and 42.7° were no longer observed in the prepared nanocomposites, indicating uniform dispersion of MWCNTs within the PLA matrix. The presence of MWCNTs enhanced the crystallinity of PLA as the CNT loading increased. Mechanical tests demonstrated that incorporating CNTs positively influenced the elongation at the break while decreasing the ultimate tensile strength of PLA. The PLA-3%CNTs composition exhibited the highest elongation at break (51.8%) but the lowest tensile strength (64 MPa). Moreover, thermal gravimetric analysis confirmed that the prepared nanocomposites exhibited greater thermal stability than pure PLA. Among the nanocomposites, PLA-5% CNTs exhibited the highest thermal stability. Furthermore, the nanocomposites demonstrated reduced surface degradation in accelerated weathering tests, with a more pronounced resilience to UV radiation and moisture-induced deterioration observed in PLA-3% CNTs.

ZIF-67@carbon fiber derived magnetic-dielectric synergistic heterostructure for excellent microwave absorption under ultrathin thickness

Aiming to solve the aggravating electromagnetic radiation issues, high-performance electromagnetic wave (EMW) absorbers are urgently required. Recently, integrating carbonaceous and magnetic materials to obtain dielectric-magnetic double EMW loss has been intensively explored. Here, Co3O4/Co@carbon nanofibers/carbon nanotubes anchored on carbon fiber (Co3O4/Co@CNFs/CNTs/CF) hybrids (CFFs) with distinctive heterostructure were synthesized by annealing ZIF-67@CF and catalytic chemical vapor deposition, and deliver great superiorities in microwave dissipation. Specifically, when at a low filling ratio of 25 wt% in paraffin wax, CFF650 acquires a superb minimum reflection loss up to −60.85 dB at only 1.22 mm together with a broad effective absorption bandwidth of 4.24 GHz at merely 1.38 mm. Remarkably, the specific reflection loss of CFF650 achieves an unexpected value, comparable to many distinguished carbon-based composites previously reported. Besides, the simulation of radar cross section values ascertains the fulfilling stealth ability of CFFs under radar detection. These excellent characteristics benefit from the diverse components and unique heterostructures, which form rich conductive networks, plentiful heterogeneous interfaces, appropriate defect polarization and dipole polarization, sufficient magnetic loss as well as optimal impedance matching. Combined with the feasible and efficient fabrication method, this work offers a significant promise of CF-based composites for practical applications in EMW absorption.

Raman study of directly synthetized graphene oxide films on Si, SiO2/Si and GaAs by remote-catalyzed CVD

Graphene oxide (GO) is an organic material with interesting properties for nanotechnology. Therefore, it is important to understand the processes that lead to its mass production for deposition onto large-size wafers and with high quality; as well as the control of the number of monolayers and the degree of oxidation. In this work, we propose an alternative method for measuring the oxidation degree of GO. We use simulated Raman spectra from different molecular models that, under computational calculations based on density functional theory (DFT), allow us to explain the measured Raman spectra and the approximate molecular structure of the material. In addition, we report on a methodology based on a process of remotely catalyzed chemical vapor deposition (CVD) to synthesize GO in millimeter areas directly onto three different substrates: SiO2/Si, Si, and GaAs. The results can be used to optimize the synthesis processes of GO and improving the performance of this organic material.

A Green Approach to Obtaining Glycerol Carbonate by Urea Glycerolysis Using Carbon-Supported Metal Oxide Catalysts.

The results of sustainable and selective synthesis of glycerol carbonate (GC) from urea and glycerol under ambient pressure using carbon-fiber-supported metal oxide catalysts are reported. Carbon fibers (CF) were prepared via a catalytic chemical vapor deposition method (CCVD) using Ni as a catalyst and liquefied petroleum gas (LPG) as a cheap carbon source. Supported metal oxide catalysts were obtained by an incipient wetness impregnation technique using Zn, Ba, Cr, and Mg nitrates. Finally, the samples were pyrolyzed and oxidized in an air flow. The obtained catalysts (10%MexOy/CFox) were tested in the reaction of urea glycerolysis at 140 °C for 6 h under atmospheric pressure, using an equimolar ratio of reagents and an inert gas flow for NH3 removal. Under the applied conditions, all of the prepared catalysts increased the glycerol conversion and glycerol carbonate yield compared to the blank test, and the best catalytic performance was shown by the CFox-supported ZnO and MgO systems. Screening of the reaction conditions was carried out by applying ZnO/CFox as a catalyst and considering the effect of reaction temperature, molar ratio of reagents, and the mode of the inert gas flow through the reactor on the catalytic process. Finally, a maximum yield of GC of about 40%, together with a selectivity to glycerol carbonate of ~100%, was obtained within 6 h of reaction at 140 °C using a glycerol-to-urea molar ratio of 1:1 while flowing Ar through the reaction mixture. Furthermore, a positive heterogeneous catalytic effect of the CFox support on the process was noticed.

Catalytic Chemical Vapor Deposition Methodology for Carbon Nanotubes Synthesis

AbstractCarbon nanomaterial is a smart material of the 21st century. This review encompasses various studies involved in carbon nanotube synthesis (CNTs) (Single and multi‐walled) using the catalytic chemical vapor deposition method (CVD). Due to their structural features, the promising branch of nanotechnology is that CNTs possess electrical, magnetic, thermal, chemical, mechanical, and optical properties. 90 to 99 % CNTs were synthesized by the CVD method (Tip growth model and Base growth model) while 80 to 80 % were by laser ablation and only 70 % by arc discharge methods. In CVD method has used a gaseous phase hydrocarbon to pass through a tube‐shaped reactor in the presence of various catalysts at 500–1000 °C to form CNTs. This is one of the significant advantages as compared to other growth methodologies. Further, various parameters responsible for CNTs production are also explored. By comparing hydrocarbons such as methane, graphite, and coal, coal is an abundant and economically viable carbon source.