Morphology Of Carbon Nanomaterials Research Articles

Holistic utilization of waste plastics through a tandem process

In this study, a tandem process that combines catalytic pyrolysis with catalytic chemical vapor deposition (CVD) was performed to investigate the conversion of waste plastics to carbon nanomaterials, oil, and for hydrogen production. This study primarily explored the effects of plastic types and the plastic feeding rate on the pyrolysis products and the quality and morphology of carbon nanomaterials. High-density polyethylene (HDPE), low-density polyethylene (LDPE), polypropylene (PP), polystyrene (PS), and polyethylene terephthalate (PET) were used as carbon precursors for the growth of carbon nanomaterials on nickel foams. Results showed that PS produced the highest liquid oil with just 2 % of predominantly amorphous structured carbon nanomaterials. PET had the lowest hydrogen yield and approximately 42 % amorphous carbon due to the formation of more CO2 and CO. Most importantly, since HDPE, LDPE, and PP produced more graphitic carbon nanomaterial with fewer structural defects compared to PET and PS, they are more favorable for the production of hydrogen and carbon nanomaterials. Additionally, HDPE loading significantly affected the quality of the produced carbon nanomaterial, particularly higher or lower feedstock loading resulting in more defects. This proposed tandem process shows great potential for upcycling waste plastics for secondary use.

Simultaneous Construct Surface Microstructural and Internal Network‐Like Conductive Pathways of Poly(l‐lactic acid)/Carbon Nanomaterials Composite Foams

AbstractThe poly(l‐lactic acid) (PLLA)/carbon nanomaterials composite foams with hierarchical surface microstructural and internal conductive pathways are successfully prepared by a simple crystallization‐assisted rapid phase separation (CARPS). The dimension and morphology of carbon nanomaterials can induce different crystallization forms to construct the hierarchical surface microstructure, and they are distributed on the phase interface of solvent and non‐solvent to form conductive pathways. It is found that the heterogeneous nucleation of nanomaterials promotes a significant increase in crystallinity, and a stacked granular structure formed on the surface promotes the increase of the water contact angle to 148.7°. Foams with interconnecting pore structures contribute to the formation of 85.3% porosity and 12.33 g g−1 oil absorption. Carbon nanomaterials are distributed on the pore walls of the porous foam, which converts the foam from an insulating material to a conducting polymer. Furthermore, the uniform distribution of nanomaterials significantly affects the thermal stability of the PLLA. In belief, the multifunctional biodegradable foam, prepared by a CARPS method, makes it promising for industrial production and has potential applications in electrical conductivity, oil‐water separation, and many other fields.

Structural Characteristics of Commercially Available and Self Synthesized Carbon Nanomaterials

The element carbon has been used as a source of energy for the past few hundred years, and now in this era of technology, carbon has played a significant and very prominent role in almost all fields of science and technology. The interesting characteristic of carbon is its ability to form many allotropes due to its valency. In recent decades, various allotropes and forms of carbon have been invented, including fullerenes, carbon nanotubes (CNTs), and graphene. So as an honor to this marvelous element, we humans should know about its various forms of existence. In this present work, we shed light on structural studies of commercially available and self-synthesized carbon nanoparticles. A brief introduction is given to the types, structures, and shapes of the allotropes of carbon for a better understanding. The crystallographic structure of the carbon nanomaterials (CNMs) is investigated by X-ray diffraction (XRD) peak profile analysis. The microstructure is characterized based on crystallite size, interplanar spacing, density, strain, and dislocation density. Raman spectroscopy is particularly well studied to characterize the molecular morphology of CNMs.

Comparative study of mechanical strengths of cement pastes incorporating carbon nanomaterials with distinct surface chemistry and morphology

This work investigated the use of two-dimensional graphene oxide (GO), one-dimensional oxidized carbon nanotube (OCNT) and graphene oxide nanoribbon (GONR), with a C/O ratio of 0.77, 2.79, 33.5, respectively, to reveal how the surface chemistry and dimensionality of carbon nanomaterials (CNMs) affect the mechanical strengths of cement pastes. The prepared GONR features the high oxidation degree similar to GO and high aspect ratio similar to OCNT, thus exhibiting both the characteristics of GO and OCNT in enhancing the mechanical strengths of cement pastes. With 0.01 wt% GONR admixed, the flexural and compressive strengths of cement pastes at 28 days were improved by 35.9% and 16.7%, respectively. Among the three CNMs, those with a higher oxidation degree promoted the formation of hydration products. Findings from this exploratory study shed light on the influence of surface chemistry and morphology of CNMs on cementitious composites.

Carbon Nanosheets Synthesis in a Gliding Arc Reactor: On the Reaction Routes and Process Parameters

Non-thermal plasma is a promising technology for high purity nanomaterial synthesis in a fast, flexible and controllable process. Gliding arc discharge, as one of the most efficient non-thermal plasmas, has been widely used in gas treatment but rarely studied for the nanomaterial synthesis. In this study, a comparison study for carbon nanosheets synthesis including toluene dissociation and graphite exfoliation was investigated in a 2D gliding arc reactor at atmospheric pressure. The effects of gas flow rate, precursor concentration and power input on the structures of carbon nanosheets produced through the two synthesis routes were explored and compared. Amorphous carbon nanosheets were produced in both approaches with a few crystalline structures formation in the case of toluene dissociation. The thickness of carbon nanosheets synthesized from graphite exfoliation was less than 3 nm, which was thinner and more uniform than that from toluene dissociation. The flow rate of carrier gas has direct influence on the morphology of carbon nanomaterials in the case of toluene dissociation. Carbon spheres were also produced along with nanosheets when the flow rate decreased from 2 to 0.5 L/min. However, in the case of graphite exfoliation, only carbon nanosheets were observed regardless of the change in flow rate of the carrier gas. The generated chemical species and plasma gas temperatures were measured and estimated for the mechanism study, respectively.

Synthesis of Carbon Nano Materials from Carbohydrate Rich Biogenic Precursors using Chemical Vapor Deposition Method and Optimization of Parameters by Taguchi Optimization Method

Carbon Nano Materials (CNM) from biogenic carbohydrate rich non-edible precursors such as Syzygium cumini (Jamun), Tamarindus indica (Imli) and Litchi chinensis (Imli) seeds were synthesized by chemical vapour deposition method (CVD). Parameters were optimized by Taguchi optimization method, four parameters such as precursor, temperature, carrier gas and duration and three levels S. cumini, T. indica and L. chinensis as a precursor, Argon (Ar), Nitrogen (N2) and Hydrogen (H2) as a carrier gas, 1 hour (hr), 2 hours and 3 hours (hrs) for duration of pyrolysis, 800oC, 900oC and 1000oC for temperature were selected. In the present work, impact of precursor is 35.84% which is the most effective factor than temperature (29.59%) and other parameters such as duration (19.50%) and the least effective factor is carrier gas (15.07%). Impact of parameter on the yield which described by the deviation of signal to noise (S/N) ratio. The result of deviation of S/N ratio shows T. indica seed (precursor), 9000C (temperature), 2 hr (duration) and Ar (carrier gas) are the best parameters. The morphology of CNM is studied by SEM characterization and the nature of synthesized CNM by RAMAN spectroscopy.

Effects of hydrogen/carbon molar ratio on graphene nano-flakes synthesis by a non-thermal plasma process

Few-layer graphene nano-flakes (GNFs) are successfully prepared via hydrocarbon pyrolysis using a non-thermal plasma process based on a magnetically stabilized gliding arc discharge (MSGAD) at atmospheric pressure. The effects of feedstock gas type and hydrogen flow rate on the morphology of carbon nanomaterials are investigated. When the hydrogen/carbon (H/C) molar ratio is 4, the synthesized GNFs consist of 10 layers per stack with dimensions between 100 and 300 nm in a 4.57.2% yield. The energy cost is 0.1–0.2 kWh/g, which makes this process feasible for large-scale GNFs production. The results show that appropriately increasing the H/C molar ratio promotes the morphological transformation of carbon nanomaterials from spherical carbon nanoparticles (SCNs) to GNFs, improve the quality of GNFs and reduce the stacking of graphite layers. However, increasing the H/C ratio reduces the yields of carbon nanomaterials, so as to increase the energy cost. Analysis suggests that increasing the H/C ratio reduces the concentration of polycyclic aromatic hydrocarbon (PAH) and generates more H atoms, which helps form a two-dimensional nucleation and promotes planar growth. However, an excessive H/C ratio may introduce some defects due to an etching effect.

Controllable synthesis of carbon nanomaterials by direct current arc discharge from the inner wall of the chamber

A direct current (DC) has been applied to prepare many carbon nanomaterials, including fullerene, graphene, and carbon nanohorns (CNHs) from inner wall of chamber. However, the growth mechanism of these carbon nanomaterials is not clear. Amorphous spherical carbon nanoparticles (SCNs), the typical ‘dahlia-like’ CNHs, and graphene with the layer numbers of 2–5 were synthesized controllably from the inner wall of the chamber by DC arc discharge method using argon, nitrogen, and hydrogen as buffer gas. Simultaneously, the effect of buffer gas pressure on the morphology of carbon nanomaterials was investigated systematically. Furthermore, the formation mechanism of these carbon nanomaterials by DC arc discharge was also investigated. Given that argon atom was difficult to bond with the carbon cluster, the random bond between carbon clusters contributed to combine into amorphous SCNs; the CN bond was the key factor in the formation of CNHs, and hydrogen contributes to form graphene sheets by terminating carbon dangling bonds. With increasing the pressure of buffer gas, intense quenching resulted in formation of carbon nanomaterials with high purity. The study on the growth mechanism of carbon nanomaterials in the inner wall of chamber promotes the preparation of carbon nanomaterials controllable by arc discharge method.

The effects of hydrogen proportion on the synthesis of carbon nanomaterials with gaseous detonation (deflagration) method

Using ferrocene, H2 and O2, Carbon nanomaterials were prepared with gaseous detonation (deflagration) method. The effects of H2 on the phase and morphology of carbon nanomaterials were studied by various proportions of H2 in the reaction. The prepared samples were characterized by x-ray diffractometer, transmission electron microscope and Raman spectrometer. The results show that hydrogen proportion has a great influence on the phase and morphology of carbon nanomaterials. The high hydrogen proportion leads to much unreacted hydrogen, which could protect the iron atom from oxidation of carbon and dilute the reactants contributing to uniform particle size. In addition, the graphitization degree of multi-walled carbon nanotubes, observed in samples with high H2 proportion, is high enough to see the lattice fringes, but the degree of graphitization of whole sample is lower than which fabricated with low H2 proportion, and it may result from the low energy generation.

Preliminary Study: Direct Growth Carbon Nanomaterials on Metal Substrate to Improve Corrosion Resistance

Metals are increasingly used in engineering due to their high specific strength. However, some of pure metals do not posses good corrosion resistance. Therefore carbon nanomaterials (CNMs) has been studied to overwhelm the corrosion existed on the metal’s surface. CNMs are synthesized directly on various metal substrates by Chemical Vapor Deposition (CVD) technique without addition of any external catalyst, in reactor at temperature of 800°C. Argon with a flow rate of 200ml/min was used as a carrier gas and acetone as a carbon source. In this study, two different metals were used as metal substrate: mild steel and stainless steel 316. The morphology, existence of CNTs and elemental analysis of the CNMs on metal substrate are evaluated using Scanning Electron Microscopy (SEM), X-ray Diffraction (XRD) and Energy Dispersive X-ray (EDX), respectively. It was proven that the different element composition of metal substrate influenced the size and morphology of CNMs. The most suitable metal to grow CNTs was found to be stainless steel.

Controlled synthesis of carbon nanocables and branched-nanobelts

Two kinds of new morphology of carbon nanomaterials, carbon nanocables and branched-nanobelts can been produced by pyrolyzing ethylene glycol monvethyl ether (CH 3CH 2OCH 2CH 2OH) with Fe as catalyst at 650–700 °C. The carbon nanocables are made of two parts, the interior carbon nanowires encapsulated in the outer carbon nanotubes. For the nanocables, HRTEM images reveal that the crystallinity of the outer carbon nanotubes is better than that of the interior carbon nanowires. HRTEM image shows that the junctions of the branched-nanobelts are composed of graphitic layers that are almost perpendicular to the respective axis of the branched-nanobelts. The catalysts, temperature and reaction time were investigated. The possible growth mechanism for the as-synthesized carbon structures is discussed.