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Open AccessArticle

Joule Heating of Carbon-Based Materials Obtained by Carbonization of Para-Aramid Fabrics

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Daniel Karthik

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Jiri Militky

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Yuanfeng Wang

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Mohanapriya Venkataraman

C 2023, 9(1), 23; https://doi.org/10.3390/c9010023 - 15 Feb 2023

Viewed by 601

Abstract

The Joule heating behavior of carbon-based materials obtained by the process of carbonization of industrial para-aramid fabric wastes are investigated in the present work. Carbonization involves a process of thermally decomposing organic material, thereby altering its physical and chemical properties to obtain carbon-rich [...] Read more.

The Joule heating behavior of carbon-based materials obtained by the process of carbonization of industrial para-aramid fabric wastes are investigated in the present work. Carbonization involves a process of thermally decomposing organic material, thereby altering its physical and chemical properties to obtain carbon-rich materials that are electrically conductive and display Joule heating behavior. The principle of Joule heating is based on the intrinsic electrical resistance of the material across an applied voltage. Here, para-aramid woven fabric wastes are converted into activated carbon materials through straightforward, controlled, single-step thermal treatments by three different kinds of atmosphere, i.e., in the CO₂ evolved from charcoal, a mixture of gases from ammonium bicarbonate salt (NH₄HCO₃), and Nitrogen gas (N₂), respectively, inside a high-temperature furnace. The carbonization temperatures were varied from 800 to 1100 °C. The carbonization process variables were optimized to obtain carbon-rich materials with lower electrical resistivity. The results of electrical resistivity measurements show that for all three methods, the electrical resistivity decreases with increasing carbonization temperatures. An experimental setup consisting of an infrared (IR) camera, positioned over the surface of the fabric specimen to record the surface temperature of the material connected to a DC power supply, was employed. The kinetics of Joule heating and subsequent cooling were also analyzed at a fixed voltage of 5 V by recording the changes in surface temperature with respect to time. The heating–cooling cycle is described by a simple kinetic model of first order. Full article

(This article belongs to the Special Issue Nanocarbon-Based Composites and Their Thermal, Electrical, and Mechanical Properties)

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Open AccessArticle

Galling-Free Fine Blanking of Titanium Plates Using Carbon-Supersaturated High-Speed Steel Punch

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Tatsuhiko Aizawa

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Kenji Fuchiwaki

C 2023, 9(1), 15; https://doi.org/10.3390/c9010015 - 25 Jan 2023

Cited by 1 | Viewed by 405

Abstract

A carbon-supersaturated (CS-) high-speed steel punch was prepared using low-temperature plasma carburizing for fine blanking of pure titanium plates. The bare high-speed steel punch was also prepared as a reference to describe the adhesion and abrasive galling in the fine blanking of the [...] Read more.

A carbon-supersaturated (CS-) high-speed steel punch was prepared using low-temperature plasma carburizing for fine blanking of pure titanium plates. The bare high-speed steel punch was also prepared as a reference to describe the adhesion and abrasive galling in the fine blanking of the titanium plates, even in a single shot. The CS-punch was free from severe chemical galling, even after repeatedly fine-blanking the pure titanium plates. A microstructure analysis, element mapping and a chemical composition analysis demonstrated that titanium debris fragments slightly deposited at the CS-punch edges in the presence of agglomerated free-carbon film due to the CS-punch. This galling-free fine-blanking behavior came from the in situ formation of free carbon tribofilms. This in situ lubrication resulted in the completely burnished surfaces of pure titanium blanks. Full article

(This article belongs to the Special Issue Nanocarbon-Based Composites and Their Thermal, Electrical, and Mechanical Properties)

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Open AccessArticle

Comparison of the Electrochemical Response of Carbon-Fiber-Reinforced Plastic (CFRP), Glassy Carbon, and Highly Ordered Pyrolytic Graphite (HOPG) in Near-Neutral Aqueous Chloride Media

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Stanley Udochukwu Ofoegbu

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Mário Guerreiro Silva Ferreira

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Helena I. S. Nogueira

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Mikhail Zheludkevich

C 2023, 9(1), 7; https://doi.org/10.3390/c9010007 - 07 Jan 2023

Viewed by 871

Abstract

Carbon-fiber-reinforced polymers (CFRP), being conductive, are capable of supporting cathodic oxygen reduction reactions (ORR) and thus promote galvanic corrosion when coupled to many metallic materials. Hence, understanding cathodic processes at carbon surfaces is critical to developing new strategies for the corrosion protection of [...] Read more.

Carbon-fiber-reinforced polymers (CFRP), being conductive, are capable of supporting cathodic oxygen reduction reactions (ORR) and thus promote galvanic corrosion when coupled to many metallic materials. Hence, understanding cathodic processes at carbon surfaces is critical to developing new strategies for the corrosion protection of multi-material assemblies. In the present work, the electrochemical responses of CFRP, glassy carbon, and HOPG (Highly Ordered Pyrolytic Graphite) have been evaluated in a quiescent 50 mM NaCl solution, and their respective activities towards ORR have been ranked. Employing the averages of the specific charges (CFRP, 129.52 mC cm⁻²; glassy carbon, 89.95 mC cm⁻²; HOPG, 60.77 mC cm⁻²) passed during 1 h polarization of each of the 3 carbon surfaces at −1000 mV_SCE in the test media as a ranking criterion, the propensities of the 3 carbon surfaces (CFRP, GC, and HOPG) to support cathodic activities that can lead to anodic metal dissolution on galvanic coupling to metallic materials are ranked thusly; CFRP > GC > HOPG. This ranking is consistent with the trend of capacitance values obtained in this work: CFRP (19.5 to 34.5 μF cm⁻²), glassy carbon (13.6 to 85.5 μF cm⁻²), and HOPG (1.4 to 1.8 μF cm⁻²). A comparison of electrochemical data at potentials relevant to galvanic coupling to metals indicated that at these cathodic potential(s) the CFRP surface is the most electrochemically active of the studied carbon surfaces. On the basis of the values and trends of the electrochemical parameters evaluated, it is postulated that the observed differences in the electrochemical responses of these 3 carbon-rich surfaces to ORR are significantly due to differences in the proportions of edge sites present on each carbon surface. These results could provide valuable insights on plausible strategies for designing carbon surfaces and carbon fiber composites with reduced activity toward ORR for corrosion protection applications or enhanced activity towards ORR for energy applications. Full article

(This article belongs to the Special Issue Nanocarbon-Based Composites and Their Thermal, Electrical, and Mechanical Properties)

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Open AccessArticle

Pull-Out of Pristine and Functionalized Carbon Nanotubes from Cement: A Molecular Modelling Study

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Isabel Lado-Touriño

C 2022, 8(4), 80; https://doi.org/10.3390/c8040080 - 16 Dec 2022

Viewed by 796

Abstract

Carbon nanotubes (CNTs) are widely used as reinforcements in cement-based composites. The improvement in the mechanical properties of the resulting materials depends on the characteristics of the interface formed between CNTs and the cement matrix. The experimental characterization of the interfacial properties of [...] Read more.

Carbon nanotubes (CNTs) are widely used as reinforcements in cement-based composites. The improvement in the mechanical properties of the resulting materials depends on the characteristics of the interface formed between CNTs and the cement matrix. The experimental characterization of the interfacial properties of these composites is still limited and hard to achieve with currently available technologies. In this work, molecular dynamics and molecular mechanics pull-out simulations of pristine and functionalized CNTs, taken from a tobermorite crystal, were carried out to study interfacial shear strength (ISS) from an atomic perspective. ISS was calculated from the potential energy of the systems. The effects of the CNT diameter and the degree of functionalization on the pull-out process were analyzed according to the ISS and non-bonded energy results. The influence of H-bonding and electrostatic interactions between the CNT and the matrix were also studied. The results show that ISS decreases with increasing CNT radius for pristine CNTs and depends upon the number of H-bonds for functionalized CNTs. ISS values are positively correlated to E_{non-bonded energy}, which is related to the number of carboxyl groups on the CNT surface. A high degree of functionalization increases both the number of H-bonds and the number of Ca²⁺-O interactions between the CNT and the tobermorite surface. This results in a stronger interfacial interaction and, therefore, an elevated ISS value. Full article

(This article belongs to the Special Issue Nanocarbon-Based Composites and Their Thermal, Electrical, and Mechanical Properties)

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Open AccessArticle

Detonation Synthesis Nanodiamond Soot as a Promising Filler for Polymer Composites

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Oleg V. Lebedev

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Tikhon S. Kurkin

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Evgeny K. Golubev

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Alexander L. Vasiliev

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Andrey K. Gatin

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Galina P. Goncharuk

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Alexander N. Ozerin

C 2022, 8(4), 69; https://doi.org/10.3390/c8040069 - 27 Nov 2022

Cited by 2 | Viewed by 831

Abstract

In this work, the results of a complex investigation of structure and properties of nanodiamond soot (NDS) of detonation synthesis are presented. Size distribution of NDS particles, dispersed in different liquid media, was investigated using dynamic light scattering and laser diffraction analysis methods. [...] Read more.

In this work, the results of a complex investigation of structure and properties of nanodiamond soot (NDS) of detonation synthesis are presented. Size distribution of NDS particles, dispersed in different liquid media, was investigated using dynamic light scattering and laser diffraction analysis methods. The results of the investigation, as well as the results of zeta-potential measurements, allowed us to characterize the agglomeration process of the NDS particles as independent of the medium, making NDS a good model filler for research of composite-modified nanosized particles. Additional data obtained using scanning electron microscopy, scanning tunneling microscopy, atomic force microscopy, X-ray diffraction, and Raman spectroscopy, demonstrated that in NDS the spherical nanodiamond (ND) particles with diameter ~5 nm are densely packed into strong-coupled aggregates with diameter ~300 nm, surrounded by graphite nanoribbons. X-ray diffraction analysis estimated the volume fraction of NDs in NDS as ~45 vol.%, simultaneously showing that the graphite is not defective, which was confirmed with the electron diffraction method. It was demonstrated that this structure of NDS allows to efficiently use NDS as a filler for polymer composites to increase polymer characteristics such as electrical conductivity or tribological characteristics, similarly to conventionally applied fillers such as carbon black. Full article

(This article belongs to the Special Issue Nanocarbon-Based Composites and Their Thermal, Electrical, and Mechanical Properties)

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Open AccessArticle

Laser-Assisted Growth of Carbon-Based Materials by Chemical Vapor Deposition

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C 2022, 8(2), 24; https://doi.org/10.3390/c8020024 - 26 Apr 2022

Cited by 1 | Viewed by 1723

Abstract

Carbon-based materials (CBMs) such as graphene, carbon nanotubes (CNT), highly ordered pyrolytic graphite (HOPG), and pyrolytic carbon (PyC) have received a great deal of attention in recent years due to their unique electronic, optical, thermal, and mechanical properties. CBMs have been grown using [...] Read more.

Carbon-based materials (CBMs) such as graphene, carbon nanotubes (CNT), highly ordered pyrolytic graphite (HOPG), and pyrolytic carbon (PyC) have received a great deal of attention in recent years due to their unique electronic, optical, thermal, and mechanical properties. CBMs have been grown using a variety of processes, including mechanical exfoliation, pulsed laser deposition (PLD), and chemical vapor deposition (CVD). Mechanical exfoliation creates materials that are irregularly formed and tiny in size. On the other hand, the practicality of the PLD approach for large-area high-quality CMB deposition is quite difficult. Thus, CVD is considered as the most effective method for growing CBMs. In this paper, a novel pulsed laser-assisted chemical vapor deposition (LCVD) technique was explored to determine ways to reduce the energy requirements to produce high quality CBMs. Different growth parameters, such as gas flow rate, temperature, laser energy, and deposition time were considered and studied thoroughly to analyze the growth pattern. CBMs are grown on Si and Cu substrates, where we find better quality CBM films on Cu as it aids the surface solubility of carbon. Raman spectroscopy confirms the presence of high-quality PyC which is grown at a temperature of 750 °C, CH₄ gas flow rate of 20 sccm, a laser frequency of 10 Hz, and an energy density of 0.116 J/cm² per pulse. It is found that the local pulsed-laser bombardment helps in breaking the carbon-hydrogen bonds of CH₄ at a much lower substrate temperature than its thermal decomposition temperature. There is no significant change in the 2D peak intensity in the Raman spectrum with the further increase in temperature which is the indicator of the number of the graphene layer. The intertwined graphene flakes of the PyC are observed due to the surface roughness, which is responsible for the quenching in the Raman 2D signal. These results will provide the platform to fabricate a large area single layer of graphene, including the other 2D materials, on different substrates using the LCVD technique. Full article

(This article belongs to the Special Issue Nanocarbon-Based Composites and Their Thermal, Electrical, and Mechanical Properties)

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Open AccessArticle

Chemical Reduction of GO: Comparing Hydroiodic Acid and Sodium Borohydride Chemical Approaches by X-ray Photoelectron Spectroscopy

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Wei Liu

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Giorgio Speranza

C 2022, 8(2), 20; https://doi.org/10.3390/c8020020 - 22 Mar 2022

Viewed by 1765

Abstract

The efficiency of two wet chemical processes based on hydroiodic acid (HI) and sodium borohydride (NaBH₄) used to reduce graphene oxide (GO) have been studied. At this aim, the oxygen abundance of reduced graphene oxide (rGO) was studied as a function [...] Read more.

The efficiency of two wet chemical processes based on hydroiodic acid (HI) and sodium borohydride (NaBH₄) used to reduce graphene oxide (GO) have been studied. At this aim, the oxygen abundance of reduced graphene oxide (rGO) was studied as a function of the reductant concentration. A number of rGO samples were produced and their chemical compositions were studied using X-ray photoelectron spectroscopy. The analyses show that the reduction of the oxygen concentration proceeds non-linearly. At the beginning, when pristine GO is utilized a higher extent of reduction is obtained. The oxygen concentration decreases from ~32% to 10.5% by increasing the HI concentration to 0.24 M. A steeper reduction was observed for NaBH₄, where the oxygen concentration lowers to ~13.6% using just 50 mg of NaBH₄. Next, reduction reactions performed with increasing amounts of reductants in aqueous suspensions show a progressive saturation effect, indicating a limit in the final oxygen concentration. We obtained a residual oxygen concentration of 5.3% using 7.58 M of HI and 8.6% with 1200 mg of NaBH_4. The chemical analysis highlights that the reduction of the oxygen concentration in rGO samples is mainly derived from the cleavage of C-OH bonds and the next reconstruction of C-C bonds. Full article

(This article belongs to the Special Issue Nanocarbon-Based Composites and Their Thermal, Electrical, and Mechanical Properties)

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Open AccessArticle

Carbon Composites—Graphene-Oxide-Catalyzed Sugar Graphitization

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Madhu Singh

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Randy L. Vander Wal

C 2022, 8(1), 15; https://doi.org/10.3390/c8010015 - 14 Feb 2022

Viewed by 2307

Abstract

Utilization of biopolymers to form graphitic carbons is challenged by their high oxygen content and resulting curved and defective carbon lamellae upon high-temperature heat-treatment. Two composites, one with graphene-oxide (GO) and the other with reduced graphene-oxide (rGO) as fillers, respectively, in a matrix [...] Read more.

Utilization of biopolymers to form graphitic carbons is challenged by their high oxygen content and resulting curved and defective carbon lamellae upon high-temperature heat-treatment. Two composites, one with graphene-oxide (GO) and the other with reduced graphene-oxide (rGO) as fillers, respectively, in a matrix of sugar, each for the same added 2.5 wt.%, exhibited different degrees of graphitization compared to pure sugar on its own. Reactive oxygen groups on GO contribute to reactive templating and crystallite formation. Under high-temperature heat-treatment, sugar, a well-known non-graphitizing precursor, is converted to graphitic carbon in the presence of GO. Possessing fewer oxygen groups, rGO forms two phases in the sugar matrix—a non-graphitic phase and a graphitic phase. The latter is attributed to the remaining oxygen on the rGO. Full article

(This article belongs to the Special Issue Nanocarbon-Based Composites and Their Thermal, Electrical, and Mechanical Properties)

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Open AccessArticle

Structural and Electrochemical Characteristics of Platinum Nanoparticles Supported on Various Carbon Carriers

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C 2022, 8(1), 14; https://doi.org/10.3390/c8010014 - 14 Feb 2022

Cited by 3 | Viewed by 2210

Abstract

Graphene-like materials have attracted significant attention as alternative catalyst carriers due to the broad possibilities of changing their shape, composition, and properties. In this study we investigated the structural and electrochemical characteristics of platinum electrocatalysts supported on reduced graphene oxide (rGO), including those [...] Read more.

Graphene-like materials have attracted significant attention as alternative catalyst carriers due to the broad possibilities of changing their shape, composition, and properties. In this study we investigated the structural and electrochemical characteristics of platinum electrocatalysts supported on reduced graphene oxide (rGO), including those modified with amine functionalities, nitrogen heteroatoms (rGO-Am), and oxygen enriched (rGO-O). Synthesis of Pt nanoparticles (20 wt.%) on the graphene-like nanomaterials surface was carried out using a modified polyol procedure. The Pt²⁰/rGO-Am showed a lower Pt nanoparticles size together with high Pt utilization and EASA values compared to rGO-supported catalysts and the Pt/C reference sample due to the uniform distribution of nucleation centers on the surface of graphene nanoparticles, and the greater ability of these centers to electrically bond with platinum. Full article

(This article belongs to the Special Issue Nanocarbon-Based Composites and Their Thermal, Electrical, and Mechanical Properties)

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Open AccessFeature PaperArticle

Reduced Graphene Oxide—Polycarbonate Electrodes on Different Supports for Symmetric Supercapacitors

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Olena Okhay

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Alexandre Cunha Bastos

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Kateryna Andreeva

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Sampo Tuukkanen

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Alexander Tkach

C 2022, 8(1), 12; https://doi.org/10.3390/c8010012 - 02 Feb 2022

Cited by 1 | Viewed by 2092

Abstract

Electrode materials for electrochemical capacitors or supercapacitors (SCs) are widely studied, as they are needed for the development of energy storage devices in electrical vehicles and flexible electronics. In the current work, a self-supported paper of reduced graphene oxide (rGO) with polycarbonate (PC) [...] Read more.

Electrode materials for electrochemical capacitors or supercapacitors (SCs) are widely studied, as they are needed for the development of energy storage devices in electrical vehicles and flexible electronics. In the current work, a self-supported paper of reduced graphene oxide (rGO) with polycarbonate (PC) (as rGO-PC composite) was prepared by simple vacuum filtration and low-temperature annealing. rGO-PC as a freestanding single electrode was studied in a three-electrode system and presented a capacitive energy storage mechanism. To fabricate SCs based on rGO-PC, flexible polyethylene terephthalate (PET) with layers of both Cu tape (Cu tape) and carbon tape (C tape) (PET/Cu/C), as well as PET covered by graphene ink (PET/GrI), were used as supports. Fabricated flexible symmetric SCs have shown similar behavior with a higher areal capacitance value than that on PET/Cu/C substrate. Full article

(This article belongs to the Special Issue Nanocarbon-Based Composites and Their Thermal, Electrical, and Mechanical Properties)

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Open AccessFeature PaperArticle

The X-ray, Raman and TEM Signatures of Cellulose-Derived Carbons Explained

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Petros Kasaira Mubari

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C 2022, 8(1), 4; https://doi.org/10.3390/c8010004 - 03 Jan 2022

Cited by 1 | Viewed by 2056

Abstract

Structural properties of carbonized cellulose were explored to conjugate the outcomes from various characterization techniques, namely X-ray diffraction (XRD), Raman spectroscopy, and high-resolution transmission electron microscopy. All these techniques have evidenced the formation of graphene stacks with a size distribution. Cellulose carbonized at [...] Read more.

Structural properties of carbonized cellulose were explored to conjugate the outcomes from various characterization techniques, namely X-ray diffraction (XRD), Raman spectroscopy, and high-resolution transmission electron microscopy. All these techniques have evidenced the formation of graphene stacks with a size distribution. Cellulose carbonized at 1000 and 1800 °C at a heating rate of 2 °C/min showed meaningful differences in Raman spectroscopy, whereas in XRD, the differences were not well pronounced, which implies that the crystallite sizes calculated by each technique have different significations. In the XRD patterns, the origin of a specific feature at a low scattering angle commonly reported in the literature but poorly explained so far, was identified. The different approaches used in this study were congruous in explaining the observations that were made on the cellulose-derived carbon samples. The remnants of the basic structural unit (BSU) are developed during primary carbonization. Small graphene-based crystallites inherited from the BSUs, which formerly developed during primary carbonization, were found to coexist with larger ones. Even if the three techniques give information on the average size of graphenic domains, they do not see the same characteristics of the domains; hence, they are not identical, nor contradictory but complementary. The arguments developed in the work to explain which characteristics are deduced from the signal obtained by each of the three characterization techniques relate to physics phenomena; hence, they are quite general and, therefore, are valid for all kind of graphenic materials. Full article

(This article belongs to the Special Issue Nanocarbon-Based Composites and Their Thermal, Electrical, and Mechanical Properties)

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Open AccessArticle

Increased Electrical Conductivity of Carbon Nanotube Fibers by Thermal and Voltage Annealing

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C 2022, 8(1), 1; https://doi.org/10.3390/c8010001 - 23 Dec 2021

Cited by 2 | Viewed by 2676

Abstract

We report the effect of annealing, both electrical and by applied voltage, on the electrical conductivity of fibers spun from carbon nanotubes (CNTs). Commercial CNT fibers were used as part of a larger goal to better understand the factors that go into making [...] Read more.

We report the effect of annealing, both electrical and by applied voltage, on the electrical conductivity of fibers spun from carbon nanotubes (CNTs). Commercial CNT fibers were used as part of a larger goal to better understand the factors that go into making a better electrical conductor from CNT fibers. A study of thermal annealing in a vacuum up to 800 °C was performed on smaller fiber sections along with a separate analysis of voltage annealing up to 7 VDC; both exhibited a sweet spot in the process as determined by a combination of a two-point probe measurement with a nanoprobe, resonant Raman spectroscopy, and X-ray photoelectron spectroscopy (XPS). Scaled-up tests were then performed in order to translate these results into bulk samples inside a tube furnace, with similar results that indicate the potential for an optimized method of achieving a better conductor sample made from CNT fibers. The results also help to determine the surface effects that need to be overcome in order to achieve this. Full article

(This article belongs to the Special Issue Nanocarbon-Based Composites and Their Thermal, Electrical, and Mechanical Properties)

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Open AccessArticle

Carbon Nanotubes Use for the Semiconductors ZnSe and ZnS Material Surface Modification via the Laser-Oriented Deposition Technique

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C 2021, 7(4), 84; https://doi.org/10.3390/c7040084 - 07 Dec 2021

Cited by 2 | Viewed by 1897

Abstract

It is known that a material’s volume and the surface structuring by the nanoparticles causes a significant change in the material’s basic properties. In this aspect, the structuration of the surface of semiconductors is of interest, because their wide potential application in optoelectronics [...] Read more.

It is known that a material’s volume and the surface structuring by the nanoparticles causes a significant change in the material’s basic properties. In this aspect, the structuration of the surface of semiconductors is of interest, because their wide potential application in optoelectronics can extend the products’ transparency, hardness, wettability, and other important parameters. This paper presents possible methods for the surface modification of zinc selenide and zinc sulfide when carbon nanotubes are deposited on the surface by the application of the laser-oriented technique. It also shows changes of the spectral, mechanical, and wetting characteristics of the considered materials. Using the molecular dynamic simulations, the possible process of the carbon nanotubes penetration into the considered surfaces is presented. The simulation results are partially supported by the obtained experimental data. Full article

(This article belongs to the Special Issue Nanocarbon-Based Composites and Their Thermal, Electrical, and Mechanical Properties)

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Open AccessArticle

Premade Nanoparticle Films for the Synthesis of Vertically Aligned Carbon Nanotubes

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C 2021, 7(4), 79; https://doi.org/10.3390/c7040079 - 19 Nov 2021

Viewed by 2233

Abstract

Carbon nanotubes (CNTs) offer unique properties that have the potential to address multiple issues in industry and material sciences. Although many synthesis methods have been developed, it remains difficult to control CNT characteristics. Here, with the goal of achieving such control, we report [...] Read more.

Carbon nanotubes (CNTs) offer unique properties that have the potential to address multiple issues in industry and material sciences. Although many synthesis methods have been developed, it remains difficult to control CNT characteristics. Here, with the goal of achieving such control, we report a bottom-up process for CNT synthesis in which monolayers of premade aluminum oxide (Al₂O₃) and iron oxide (Fe₃O₄) nanoparticles were anchored on a flat silicon oxide (SiO₂) substrate. The nanoparticle dispersion and monolayer assembly of the oleic-acid-stabilized Al₂O₃ nanoparticles were achieved using 11-phosphonoundecanoic acid as a bifunctional linker, with the phosphonate group binding to the SiO₂ substrate and the terminal carboxylate group binding to the nanoparticles. Subsequently, an Fe₃O₄ monolayer was formed over the Al₂O₃ layer using the same approach. The assembled Al₂O₃ and Fe₃O₄ nanoparticle monolayers acted as a catalyst support and catalyst, respectively, for the growth of vertically aligned CNTs. The CNTs were successfully synthesized using a conventional atmospheric pressure-chemical vapor deposition method with acetylene as the carbon precursor. Thus, these nanoparticle films provide a facile and inexpensive approach for producing homogenous CNTs. Full article

(This article belongs to the Special Issue Nanocarbon-Based Composites and Their Thermal, Electrical, and Mechanical Properties)

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Open AccessArticle

Influence of Carbon Nanotube Attributes on Carbon Nanotube/Cu Composite Electrical Performances

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C 2021, 7(4), 78; https://doi.org/10.3390/c7040078 - 15 Nov 2021

Cited by 1 | Viewed by 1963

Abstract

Carbon nanotube (CNT)/copper composites offer promise as lightweight temperature-stable electrical conductors for future electrical and electronic devices substituting copper. However, clarifying how constituent nanotube structures influence CNT/Cu electrical performances has remained a major research challenge. Here, we investigate the correlation between the CNT/Cu [...] Read more.

Carbon nanotube (CNT)/copper composites offer promise as lightweight temperature-stable electrical conductors for future electrical and electronic devices substituting copper. However, clarifying how constituent nanotube structures influence CNT/Cu electrical performances has remained a major research challenge. Here, we investigate the correlation between the CNT/Cu electrical performances and nanotube structure by preparing and characterizing composites containing nanotubes of different structural attributes. We prepared three types of composites—single-wall (SW)-CNT/Cu wires, SW-CNT/Cu pillars, and multi-wall (MW)-CNT/Cu wires. The composites were fabricated from the corresponding CNT templates by two-step Cu electrodeposition, which retains template nanotube attributes through the fabrication process. The nanotube characteristics (diameter, G/D, alignment, etc.) in each template as well as the internal structure and electrical performances of the corresponding composites were characterized. SW-CNT/Cu wires and pillars outperformed MW-CNT/Cu wires, showing ≈ 3× higher room-temperature four-probe conductivities (as high as 30–40% Cu-conductivity). SW-CNT/Cu also showed up to 4× lower temperature coefficients of resistances i.e., more temperature-stable conductivities than MW-CNT/Cu. Our results suggest that few-walled small-diameter nanotubes can contribute to superior temperature-stable CNT/Cu conductivities. Better CNT crystallinity (high G/D), fewer nanotube ends/junctions, and nanotube alignment may be additionally beneficial. We believe that these results contribute to strategies for improving CNT/Cu performances to enable the real-world application of these materials as Cu substitutes. Full article

(This article belongs to the Special Issue Nanocarbon-Based Composites and Their Thermal, Electrical, and Mechanical Properties)

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Open AccessArticle

Crystallization Kinetics of Poly(lactic acid)–Graphene Nanoscroll Nanocomposites: Role of Tubular, Planar, and Scrolled Carbon Nanoparticles

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C 2021, 7(4), 75; https://doi.org/10.3390/c7040075 - 31 Oct 2021

Cited by 1 | Viewed by 1588

Abstract

Graphene nanoscrolls (GNS) are 1D carbon-based nanoparticles. In this study, they were investigated as a heterogeneous nucleating agent in the poly(lactic acid) (PLA) matrix. The isothermal and non-isothermal melting behavior and crystallization kinetics of PLA-GNS nanocomposites were investigated using a differential scanning calorimeter [...] Read more.

Graphene nanoscrolls (GNS) are 1D carbon-based nanoparticles. In this study, they were investigated as a heterogeneous nucleating agent in the poly(lactic acid) (PLA) matrix. The isothermal and non-isothermal melting behavior and crystallization kinetics of PLA-GNS nanocomposites were investigated using a differential scanning calorimeter (DSC). Low GNS content not only accelerated the crystallization rate, but also the degree of crystallinity of PLA. The Avrami model was used to fit raw experimental data, and to evaluate the crystallization kinetics for both isothermal and non-isothermal runs through the nucleation and growth rate. Additionally, the effect of the dimensionality and structure of the nanoparticle on the crystallization behavior and kinetics of PLA is discussed. GNS, having a similar fundamental unit as CNT and GNP, were observed to possess superior mechanical properties when analyzed by the nanoindentation technique. The scrolled architecture of GNS facilitated a better interface and increased energy absorption with PLA compared to CNTs and GNPs, resulting in superior mechanical properties. Full article

(This article belongs to the Special Issue Nanocarbon-Based Composites and Their Thermal, Electrical, and Mechanical Properties)

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Open AccessArticle

Applicability of Atmospheric Pressure Plasma Jet (APPJ) Discharge for the Reduction in Graphene Oxide Films and Synthesis of Carbon Nanomaterials

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Sri Hari Bharath Vinoth Kumar

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C 2021, 7(4), 71; https://doi.org/10.3390/c7040071 - 14 Oct 2021

Cited by 1 | Viewed by 2190

Abstract

Atmospheric pressure plasma jets (APPJ) are widely used in industry for surface cleaning and chemical modification. In the recent past, they have gained more scientific attention especially in the processing of carbon nanomaterials. In this work, a novel power generation technique was applied [...] Read more.

Atmospheric pressure plasma jets (APPJ) are widely used in industry for surface cleaning and chemical modification. In the recent past, they have gained more scientific attention especially in the processing of carbon nanomaterials. In this work, a novel power generation technique was applied to realize the stable discharge in N₂ (10 vol.% H₂) forming gas in ambient conditions. This APPJ was used to reduce solution-processed graphene oxide (GO) thin films and the result was compared with an established and optimized reduction process in a low–pressure capacitively coupled (CCP) radiofrequency (RF) hydrogen (H₂) plasma. The reduced GO (rGO) films were investigated by Raman spectroscopy and X-ray photoelectron spectroscopy (XPS). Effective deoxygenation of GO was observed after a quick 2 s treatment by AAPJ. Further deoxygenation at longer exposure times was found to proceed with the expense of GO–structure integrity. By adding acetylene gas into the same APPJ, carbon nanomaterials on various substrates were synthesized. The carbon materials were characterized by Raman spectroscopy, scanning electron microscopy (SEM), and energy-dispersive X-ray (EDX) analyses. Fullerene-like particles and graphitic carbon with short carbon nanotubes were detected on Si and Ag surfaces, respectively. We demonstrate that the APPJ tool has obvious potential for the versatile processing of carbon nanomaterials. Full article

(This article belongs to the Special Issue Nanocarbon-Based Composites and Their Thermal, Electrical, and Mechanical Properties)

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Open AccessArticle

Nanoporous Carbon Magnetic Hybrid Derived from Waterlock Polymers and Its Application for Hexavalent Chromium Removal from Aqueous Solution

by

Georgios Asimakopoulos

,

Angeliki Karakassides

,

Maria Baikousi

,

Christina Gioti

,

Dimitrios Moschovas

,

Apostolos Avgeropoulos

,

Athanasios B. Bourlinos

,

Alexios P. Douvalis

,

Constantinos E. Salmas

and

Michael A. Karakassides

C 2021, 7(4), 69; https://doi.org/10.3390/c7040069 - 30 Sep 2021

Cited by 2 | Viewed by 1892

Abstract

Sodium polyacrylate is the superabsorbent waterlock polymer used in disposable diapers, which are the third largest single consumer item in landfills. As diapers are difficult to recycle, their use produces an incredible amount of environmental waste. In the present article, we present a [...] Read more.

Sodium polyacrylate is the superabsorbent waterlock polymer used in disposable diapers, which are the third largest single consumer item in landfills. As diapers are difficult to recycle, their use produces an incredible amount of environmental waste. In the present article, we present a reliable and facile approach to transform sodium polyacrylate, the main constitute in the used diapers, in a carbon-based magnetic sorbent material, capable for use in environmental applications. A nanoporous carbon magnetic hybrid material was prepared by reacting NaPA with iron acetate species under chemical activation conditions. Analysis of the characterization results revealed, the creation of a nanoporous structure, with high specific surface area value (S_gBET = 611 m²/g), along with the formation of nanosized zero valent iron nanoparticles and iron carbide (Fe₃C), inside the carbon pore system. ⁵⁷Fe Mössbauer spectroscopy verified also the existence of these two main iron-bearing phases, as well as additional minor magnetic phases, such as Fe₃O₄ and γ-Fe₂O₃. Vibrating sample magnetometry (VSM) measurements of the obtained hybrid confirmed its ferromagnetic/ferrimagnetic behavior. The hybrid material demonstrated a rapid sorption of Cr(VI) ions (adsorption capacity: 90 mg/g, 24 h, pH = 3). The results showed highly pH-dependent sorption efficiency of the hybrids, whereas a pseudo-second-order kinetic model described their kinetics. Full article

(This article belongs to the Special Issue Nanocarbon-Based Composites and Their Thermal, Electrical, and Mechanical Properties)

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Open AccessArticle

Atomic Layer Deposition of Nanolayered Carbon Films

by

Zhigang Xiao

,

Kim Kisslinger

and

Rebhadevi Monikandan

C 2021, 7(4), 67; https://doi.org/10.3390/c7040067 - 27 Sep 2021

Viewed by 2035

Abstract

In this paper, carbon thin films were grown using the plasma-enhanced atomic layer deposition (PE-ALD). Methane (CH₄) was used as the carbon precursor to grow the carbon thin film. The grown film was analyzed by the high-resolution transmission electron micrograph (TEM), [...] Read more.

In this paper, carbon thin films were grown using the plasma-enhanced atomic layer deposition (PE-ALD). Methane (CH₄) was used as the carbon precursor to grow the carbon thin film. The grown film was analyzed by the high-resolution transmission electron micrograph (TEM), X-ray photoelectron spectroscopy (XPS) analysis, and Raman spectrum analysis. The analyses show that the PE-ALD-grown carbon film has an amorphous structure. It was found that the existence of defective sites (nanoscale holes or cracks) on the substrate of copper foil could facilitate the formation of nanolayered carbon films. The mechanism for the formation of nanolayered carbon film in the nanoscale holes was discussed. This finding could be used for the controlled growth of nanolayered carbon films or other two-dimensional nanomaterials while combining with modern nanopatterning techniques. Full article

(This article belongs to the Special Issue Nanocarbon-Based Composites and Their Thermal, Electrical, and Mechanical Properties)

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Open AccessArticle

Conformational Analysis of [60]PCBM from DFT Simulations of Electronic Energies, Bond Strain and the ¹³C NMR Spectrum: Input Geometry Determination and Ester Bond Rotation Dynamics

by

Tong Liu

and

T. John S. Dennis

C 2021, 7(3), 66; https://doi.org/10.3390/c7030066 - 21 Sep 2021

Viewed by 1801

Abstract

With the aim of determining the best input geometry for DFT calculations of [60]PCBM, the geometry of 24 chemically possible [60]PCBM conformers were optimised and their electronic energies and average bond strains were determined. A DFT analysis of the relevant dihedral angles provided [...] Read more.

With the aim of determining the best input geometry for DFT calculations of [60]PCBM, the geometry of 24 chemically possible [60]PCBM conformers were optimised and their electronic energies and average bond strains were determined. A DFT analysis of the relevant dihedral angles provided insights into the dynamical behaviour of the ester group through sterically restricted bond rotations. In addition, the ¹³C NMR spectra of the six better performing conformers were simulated and compared with an experiment. There is a close correlation between average bond strain, total electronic energy and mean absolute error of the simulated ¹³C NMR spectra of the ester carbons. The best overall candidate conformer for the input geometry had the C61-C4, C4-C3 and C3-C2 single bonds of the alkyl chain in syn, anti and anti arrangements, respectively, and had the C2-C1 and C1-O single bonds of the ester in syn and anti arrangements, respectively. This contrasts strikingly with most representations of PCBM in the literature, which depict all relevant bonds in anti arrangements. Full article

(This article belongs to the Special Issue Nanocarbon-Based Composites and Their Thermal, Electrical, and Mechanical Properties)

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Open AccessArticle

Applicability and Limitations of Simplified Elastic Shell Theories for Vibration Modelling of Double-Walled Carbon Nanotubes

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C 2021, 7(3), 61; https://doi.org/10.3390/c7030061 - 09 Aug 2021

Cited by 3 | Viewed by 1453

Abstract

The applicability and limitations of simplified models of thin elastic circular cylindrical shells for linear vibrations of double-walled carbon nanotubes (DWCNTs) are considered. The simplified models, which are based on the assumptions of membrane and moment approximate thin-shell theories, are compared with the [...] Read more.

The applicability and limitations of simplified models of thin elastic circular cylindrical shells for linear vibrations of double-walled carbon nanotubes (DWCNTs) are considered. The simplified models, which are based on the assumptions of membrane and moment approximate thin-shell theories, are compared with the extended Sanders–Koiter shell theory. Actual discrete DWCNTs are modelled by means of couples of concentric equivalent continuous thin, circular cylindrical shells. Van der Waals interaction forces between the layers are taken into account by adopting He’s model. Simply supported and free–free boundary conditions are applied. The Rayleigh–Ritz method is considered to obtain approximate natural frequencies and mode shapes. Different aspect and thickness ratios, and numbers of waves along longitudinal and circumferential directions, are analysed. In the cases of axisymmetric and beam-like modes, it is proven that membrane shell theory, differently from moment shell theory, provides results with excellent agreement with the extended Sanders–Koiter shell theory. On the other hand, in the case of shell-like modes, it is found that both membrane and moment shell theories provide results reporting acceptable agreement with the extended Sanders–Koiter shell theory only for very limited ranges of geometries and wavenumbers. Conversely, for shell-like modes it is found that a newly developed, simplified shell model, based on the combination of membrane and semi-moment theories, provides results in satisfactory agreement with the extended Sanders–Koiter shell theory in all ranges. Full article

(This article belongs to the Special Issue Nanocarbon-Based Composites and Their Thermal, Electrical, and Mechanical Properties)

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Open AccessArticle

The Growth Behavior of Amorphous Hydrogenated Carbon a-C:H Layers on Industrial Polycarbonates—A Weak Interlayer and a Distinct Dehydrogenation Zone

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and

C 2021, 7(3), 59; https://doi.org/10.3390/c7030059 - 29 Jul 2021

Cited by 1 | Viewed by 1468

Abstract

Polycarbonate (PC) is a material that is used in many areas: automotive, aerospace engineering and data storage industries. Its hardness is of particular importance, but some applications are affected by its low wettability or scratch susceptibility. This can be changed either by blending [...] Read more.

Polycarbonate (PC) is a material that is used in many areas: automotive, aerospace engineering and data storage industries. Its hardness is of particular importance, but some applications are affected by its low wettability or scratch susceptibility. This can be changed either by blending with other polymers, or by surface modifications, such as the application of an amorphous hydrogenated carbon layer (a-C:H). In this study, individual a-C:H layers of different thicknesses (10–2000 nm) were deposited on PC by RF PECVD. Both the layer morphology with AFM and SEM and the bonding states of the carbon on the surface with synchrotron-assisted XPS and NEXAFS were studied. The aim was to investigate the coatability of PC and the stability of the a-C:H. Special attention was paid to the interlayer region from 0 to 100 nm, since this is responsible for the layer to base material bonding, and to the zone of dehydrogenation (from about 1000 nm), since this changes the surface composition considerably. For PC, the interlayer was relatively small with a thickness of only 20 nm. Additionally, a correlation was found between the evolving grain structure and the development of the C‒H peak according to NEXAFS C K-edge measurements. Full article

(This article belongs to the Special Issue Nanocarbon-Based Composites and Their Thermal, Electrical, and Mechanical Properties)

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Open AccessArticle

Reduction of Device Operating Temperatures with Graphene-Filled Thermal Interface Materials

by

Jacob S. Lewis

C 2021, 7(3), 53; https://doi.org/10.3390/c7030053 - 21 Jul 2021

Cited by 4 | Viewed by 1831

Abstract

The majority of research into few layer graphene (FLG) thermal interface materials (TIM) concerns the direct quantification of innate composite properties with much less direct analysis of these materials in realistic applications. In this study, equilibrium temperatures of engineered device substitutes fixed to [...] Read more.

The majority of research into few layer graphene (FLG) thermal interface materials (TIM) concerns the direct quantification of innate composite properties with much less direct analysis of these materials in realistic applications. In this study, equilibrium temperatures of engineered device substitutes fixed to passive heat sink solutions with varying FLG concentration TIMs are experimentally measured at varying heat dissipation rates. A custom, precisely-controlled heat source’s temperature is continually measured to determine equilibrium temperature at a particular heat dissipation. It is found that altering the used FLG TIM concentrations from 0 vol.% to as little as 7.3 vol.% resulted in a decrease of combined TIM and passively-cooled heat sink thermal resistance from 4.23

^{\circ}

C/W to 2.93

^{\circ}

C/W, amounting to a reduction in operating temperature of ≈

108^{\circ}

C down to ≈

85^{\circ}

C at a heat dissipation rate of 20 W. The results confirm FLG TIMs’ promising use in the application of device heat dissipation in a novel, controllable experimental technique. Full article

(This article belongs to the Special Issue Nanocarbon-Based Composites and Their Thermal, Electrical, and Mechanical Properties)

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Fused Filament Fabrication Three-Dimensional Printing Multi-Functional of Polylactic Acid/Carbon Black Nanocomposites

by

,

,

,

,

Peder Erik Fischer-Griffiths

,

Sotirios Grammatikos

and

Lazaros Tzounis

C 2021, 7(3), 52; https://doi.org/10.3390/c7030052 - 17 Jul 2021

Cited by 15 | Viewed by 2383

Abstract

Conductive Polymer Composites (CPCs) have recently gained an extensive scientific interest as feedstock materials in Fused Filament Fabrication (FFF) Three-dimensional (3D) printing. Polylactic Acid (PLA), widely used in FFF 3D printing, as well as its Carbon Black (CB) nanocomposites at different weight percentage [...] Read more.

Conductive Polymer Composites (CPCs) have recently gained an extensive scientific interest as feedstock materials in Fused Filament Fabrication (FFF) Three-dimensional (3D) printing. Polylactic Acid (PLA), widely used in FFF 3D printing, as well as its Carbon Black (CB) nanocomposites at different weight percentage (wt.%) filler loadings (0.5, 1.0, 2.5 and 5.0 wt.%), were prepared via a melt mixing filament extrusion process in this study and utilized to manufacture FFF 3D printed specimens. The nanocomposites were examined for their electrical conductivity. The highest loaded 3D printed CPC (5.0 wt.%) was tested as an electrothermal Joule heating device. Static tensile, flexural, Charpy’s impact and Vickers microhardness mechanical properties were investigated for the neat and PLA/CB 3D printed nanocomposites. Dynamic Mechanical Analysis (DMA) revealed a stiffening mechanism for the PLA/CB nanocomposites. Scanning Electron Microscopy (SEM) elucidated the samples’ internal and external microstructural characteristics. The PLA/CB 5.0 wt.% nanocomposite demonstrated also antibacterial properties, when examined with a screening process, against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus). It can be envisaged that the 3D printed PLA/CB CPCs exhibited a multi-functional performance, and could open new avenues towards low-cost personalized biomedical objects with complex geometry, amongst others, i.e., surgery tools, splints, wearables, etc. Full article

(This article belongs to the Special Issue Nanocarbon-Based Composites and Their Thermal, Electrical, and Mechanical Properties)

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Open AccessArticle

Comments on the XPS Analysis of Carbon Materials

by

David J. Morgan

C 2021, 7(3), 51; https://doi.org/10.3390/c7030051 - 06 Jul 2021

Cited by 59 | Viewed by 5494

Abstract

The surface chemistry of carbon materials is predominantly explored using x-ray photoelectron spectroscopy (XPS). However, many published papers have critical failures in the published analysis, stemming from an ill-informed approach to analyzing the spectroscopic data. Herein, a discussion on lineshapes and changes in [...] Read more.

The surface chemistry of carbon materials is predominantly explored using x-ray photoelectron spectroscopy (XPS). However, many published papers have critical failures in the published analysis, stemming from an ill-informed approach to analyzing the spectroscopic data. Herein, a discussion on lineshapes and changes in the spectral envelope of predominantly graphitic materials are explored, together with the use of the D-parameter, to ascertain graphitic content, using this information to highlight a simple and logical approach to strengthen confidence in the functionalization derived from the carbon core-level spectra. Full article

(This article belongs to the Special Issue Nanocarbon-Based Composites and Their Thermal, Electrical, and Mechanical Properties)

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Open AccessArticle

Fluorescent Nanodiamonds Synthesized in One-Step by Pulsed Laser Ablation of Graphite in Liquid-Nitrogen

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,

and

C 2021, 7(2), 49; https://doi.org/10.3390/c7020049 - 21 Jun 2021

Cited by 2 | Viewed by 1908

Abstract

In this work, we present a relevant upgrade to the technique of pulsed laser ablation of fluorescent nanodiamonds (NDs), relying on an automatized graphite-target movement maintaining a constant level of liquid nitrogen over its surface during hours of deposition. Around 60 mg of [...] Read more.

In this work, we present a relevant upgrade to the technique of pulsed laser ablation of fluorescent nanodiamonds (NDs), relying on an automatized graphite-target movement maintaining a constant level of liquid nitrogen over its surface during hours of deposition. Around 60 mg of NDs nanopowder was synthesized and optomagnetically characterized to assess its optical quality. Chemical purification of the ablated nanopowders, which removes the graphitic byproducts, permits to obtain pure fluorescent NDs with an efficiency of 7 ± 1% with respect to the total nanopowder mass. This value compares positively with the efficiency of other commercial NDs synthesis techniques such as detonation, cavitation, and high pressure–high temperature. Full article

(This article belongs to the Special Issue Nanocarbon-Based Composites and Their Thermal, Electrical, and Mechanical Properties)

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Open AccessFeature PaperArticle

Energy Absorption in Carbon Fiber Composites with Holes under Quasi-Static Loading

by

Omar Alhyari

and

Golam Newaz

C 2021, 7(1), 16; https://doi.org/10.3390/c7010016 - 01 Feb 2021

Cited by 6 | Viewed by 1967

Abstract

Composite tubular structures have shown promise as energy absorbers in the automobile industry. This paper investigates the energy absorption characteristics of carbon fiber reinforced plastic (CFRP) tubes with pre-existing holes. Holes may represent an extreme case of impact damage that perforates the tube, [...] Read more.

Composite tubular structures have shown promise as energy absorbers in the automobile industry. This paper investigates the energy absorption characteristics of carbon fiber reinforced plastic (CFRP) tubes with pre-existing holes. Holes may represent an extreme case of impact damage that perforates the tube, e.g., stones from road surface impacting the tubes. Tubes with holes represent more conservative performance characteristics, since impact damage of the same size will have residual material, which may carry some load. Tubes with holes can provide the lower limit of CFRP tube performance under axial crushing relative to impact damaged tubes with perforation diameter close to the hole diameter. In this study, tubes with lay-up of [05/902/04] with one and two holes in defined locations and different diameters are experimentally studied under quasi-static loading. It was found that specific energy absorption (SEA) reduces by 50% with one or two holes of 15 mm size, 100 mm from top of the tube. The SEA reduction is about 60% lower than the regular tube when the diameter of the hole is 20 mm located at 100 mm from top. The most severe reduction occurs if the location of single or double holes are 75 mm from the top. In this case, a SEA reduction of 75% can be expected. Results indicate that holes can significantly alter the energy absorption capability of the tubes. It is also clear that in axial crushing of composite tubes, the location of the hole (100 to 75 mm) appears to create more pronounced effect than the size of the hole itself (15 vs. 20 mm) for the cases investigated. The failure modes for tubes with holes seem to preserve similar damage modes with delamination, frond creation, and brittle fracture, which is typically observed in regular composite tubes under axial crushing load. This is due to primarily front end crushing, which dominates the failure modes, while hole induced damage occurs later. Full article

(This article belongs to the Special Issue Nanocarbon-Based Composites and Their Thermal, Electrical, and Mechanical Properties)

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Open AccessArticle

Effects of the Stacking Faults on the Electrical Resistance of Highly Ordered Graphite Bulk Samples

by

Andreas Hentrich

and

Pablo D. Esquinazi

C 2020, 6(3), 49; https://doi.org/10.3390/c6030049 - 25 Jul 2020

Cited by 3 | Viewed by 2072

Abstract

High anisotropy and the existence of two-dimensional highly conducting interfaces at stacking faults parallel to the graphene planes of the graphite structure influence, in a non-simple way, the transport properties of highly oriented graphite. We report two related effects on the electrical resistance [...] Read more.

High anisotropy and the existence of two-dimensional highly conducting interfaces at stacking faults parallel to the graphene planes of the graphite structure influence, in a non-simple way, the transport properties of highly oriented graphite. We report two related effects on the electrical resistance of highly oriented pyrolytic as well as of natural graphite bulk samples, measured with the four points method in the temperature range 300 K

\leq T \leq

410 K. A qualitative and quantitative change in the temperature dependence of the resistance was obtained by simply enlarging the electrodes and contacting the edges of the internal interfaces on the same sample. Additionally, at temperatures

T ≳ 350

K the resistance can change with time. We show that this temperature-dependent annealing effect is related to the stacking faults and can irreversibly change the absolute value of the resistance and its temperature dependence. A partial recovery is obtained after leaving the sample at normal conditions for several days. The overall results stress the importance of the electrodes location on a bulk graphite sample, the contribution of the stacking faults in the interpretation of the measured transport properties and the need of systematic studies on the influence of high temperature annealing on the interfaces properties. Full article

(This article belongs to the Special Issue Nanocarbon-Based Composites and Their Thermal, Electrical, and Mechanical Properties)

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Open AccessArticle

Expendable Graphite as an Efficient Flame-Retardant for Novel Partial Bio-Based Rigid Polyurethane Foams

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C 2020, 6(2), 27; https://doi.org/10.3390/c6020027 - 01 May 2020

Cited by 8 | Viewed by 2653

Abstract

The rigid polyurethane foam (PU) is a versatile material, used especially for construction and household applications. The current situation demands a facile, cost-efficient, and greener approach for developing the polyurethanes from bio-derived materials. In this study, we present a novel bio-polyol synthesized using [...] Read more.

The rigid polyurethane foam (PU) is a versatile material, used especially for construction and household applications. The current situation demands a facile, cost-efficient, and greener approach for developing the polyurethanes from bio-derived materials. In this study, we present a novel bio-polyol synthesized using carvone, an extract from caraway, spearmint, or dill seeds via facile thiol-ene reaction. Our one-step reaction uses a UV irradiation to allow the room temperature conversion of the carvone to a high purity bio-polyol, as confirmed from the standard analytical characterizations. The hydroxyl number of 365 mg KOH/g close to its theoretical limit confirms the high conversion yield of the polyol for rigid PU synthesis. To overcome the flammability issues in PU, expandable graphite (EG) powder was used as an additive flame-retardant during the synthesis step. The resulting foams with EG maintained the uniform closed cell structure (>95%) with a high compression strength of 175 kPa. The addition of EG in PU results in the formation of a protective char layer during the flammability test and reduces the weight loss from 40.70% to 3.55% and burning time from 87 to 11 s. Our results confirm that the carvone-based polyol can be a novel alternative to the petroleum polyols for an industrial-scale application. Full article

(This article belongs to the Special Issue Nanocarbon-Based Composites and Their Thermal, Electrical, and Mechanical Properties)

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Open AccessArticle

Power Cycling and Reliability Testing of Epoxy-Based Graphene Thermal Interface Materials

by

Jacob S. Lewis

,

Timothy Perrier

,

Amirmahdi Mohammadzadeh

,

Fariborz Kargar

and

Alexander A. Balandin

C 2020, 6(2), 26; https://doi.org/10.3390/c6020026 - 25 Apr 2020

Cited by 15 | Viewed by 2865

Abstract

We report on the lifespan evolution of thermal diffusivity and thermal conductivity in curing epoxy-based thermal interface materials with graphene fillers. The performance and reliability of graphene composites have been investigated in up to 500 power cycling measurements. The tested composites were prepared [...] Read more.

We report on the lifespan evolution of thermal diffusivity and thermal conductivity in curing epoxy-based thermal interface materials with graphene fillers. The performance and reliability of graphene composites have been investigated in up to 500 power cycling measurements. The tested composites were prepared with an epoxy resin base and randomly oriented fillers consisting of a mixture of few-layer and single-layer graphene. The power cycling treatment procedure was conducted with a custom-built setup, while the thermal characteristics were determined using the “laser flash” method. The thermal conductivity and thermal diffusivity of these composites do not degrade but instead improve with power cycling. Among all tested filled samples with different graphene loading fractions, an enhancement in the thermal conductivity values of 15% to 25% has been observed. The obtained results suggest that epoxy-based thermal interface materials with graphene fillers undergo an interesting and little-studied intrinsic performance enhancement, which can have important implications for the development of next-generation thermal interface materials. Full article

(This article belongs to the Special Issue Nanocarbon-Based Composites and Their Thermal, Electrical, and Mechanical Properties)

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Open AccessReview

Graphene Nanocomposites in Space Sector—Fundamentals and Advancements

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C 2023, 9(1), 29; https://doi.org/10.3390/c9010029 - 03 Mar 2023

Viewed by 674

Abstract

Graphene is one of the most significant carbon nanomaterials, with a one-atom-thick two-dimensional nanostructure. Like other nanocarbons, graphene has been used as a polymer reinforcement. This review explores the impact of graphene and graphene-based nanocomposites on aerospace applications. The fabrication and indispensable features [...] Read more.

Graphene is one of the most significant carbon nanomaterials, with a one-atom-thick two-dimensional nanostructure. Like other nanocarbons, graphene has been used as a polymer reinforcement. This review explores the impact of graphene and graphene-based nanocomposites on aerospace applications. The fabrication and indispensable features of graphene-derived nanocomposites have been considered. Numerous polymers and nanocomposites have been employed for aerospace systems such as reinforced thermosetting/thermoplastic polymers and epoxy/graphene nanocomposites. Moreover, graphene-modified carbon-fiber-based composites have been discussed for the space sector. Aerospace nanocomposites with graphene have been investigated for superior processability, structural features, morphology, heat stability, mechanical properties, flame resistance, electrical/thermal conductivity, radiation protection, and adhesion applications. Subsequently, epoxy and graphene-derived nanocomposites have been explored for heat/mechanically stable aerospace engineering structures, radiation-shielding materials, adhesives, coatings, etc. Full article

(This article belongs to the Special Issue Nanocarbon-Based Composites and Their Thermal, Electrical, and Mechanical Properties)

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Avant-Garde Polymer and Nano-Graphite-Derived Nanocomposites—Versatility and Implications

by

Ayesha Kausar

C 2023, 9(1), 13; https://doi.org/10.3390/c9010013 - 19 Jan 2023

Viewed by 548

Abstract

Graphite (stacked graphene layers) has been modified in several ways to enhance its potential properties/utilities. One approach is to convert graphite into a unique ‘nano-graphite’ form. Nano-graphite consists of few-layered graphene, multi-layered graphene, graphite nanoplatelets, and other graphene aggregates. Graphite can be converted [...] Read more.

Graphite (stacked graphene layers) has been modified in several ways to enhance its potential properties/utilities. One approach is to convert graphite into a unique ‘nano-graphite’ form. Nano-graphite consists of few-layered graphene, multi-layered graphene, graphite nanoplatelets, and other graphene aggregates. Graphite can be converted to nano-graphite using physical and chemical methods. Nano-graphite, similar to graphite, has been reinforced in conducting polymers/thermoplastics/rubbery matrices to develop high-performance nanocomposites. Nano-graphite and polymer/nano-graphite nanomaterials have characteristics that are advantageous over those of pristine graphitic materials. This review basically highlights the essential features, design versatilities, and applications of polymer/nano-graphite nanocomposites in solar cells, electromagnetic shielding, and electronic devices. Full article

(This article belongs to the Special Issue Nanocarbon-Based Composites and Their Thermal, Electrical, and Mechanical Properties)

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Open AccessReview

Technology Features of Diamond Coating Deposition on a Carbide Tool

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C 2022, 8(4), 77; https://doi.org/10.3390/c8040077 - 09 Dec 2022

Cited by 1 | Viewed by 1130

Abstract

The production of carbide tools with polycrystalline diamond coatings, which are used for processing modern carbon composite materials, includes a number of technological techniques that ensure reliable adhesion of the coating to the substrate. This review examines these features of substrate-surface pretreatment to [...] Read more.

The production of carbide tools with polycrystalline diamond coatings, which are used for processing modern carbon composite materials, includes a number of technological techniques that ensure reliable adhesion of the coating to the substrate. This review examines these features of substrate-surface pretreatment to improve adhesion, which includes chemical etching, mechanical hardening, modification by ion beams, plasma treatment and application of buffer layers between the substrate and the coating. This review also discusses the advantages and disadvantages of the most common methods for obtaining polycrystalline diamond coatings using hot filament and deposition of coatings from microwave plasma. Full article

(This article belongs to the Special Issue Nanocarbon-Based Composites and Their Thermal, Electrical, and Mechanical Properties)

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Open AccessReview

Graphene Synthesis and Its Recent Advances in Applications—A Review

by

Anuluxan Santhiran

,

Poobalasuntharam Iyngaran

,

Poobalasingam Abiman

and

Navaratnarajah Kuganathan

C 2021, 7(4), 76; https://doi.org/10.3390/c7040076 - 10 Nov 2021

Cited by 8 | Viewed by 3855

Abstract

Owing to the remarkable chemical and physical properties, graphene has been widely investigated by researchers over the last 15 years. This review summarizes major synthetic methods such as mechanical exfoliation, liquid phase exfoliation, unzipping of carbon nanotube, oxidation-reduction, arc discharge, chemical vapor deposition, [...] Read more.

Owing to the remarkable chemical and physical properties, graphene has been widely investigated by researchers over the last 15 years. This review summarizes major synthetic methods such as mechanical exfoliation, liquid phase exfoliation, unzipping of carbon nanotube, oxidation-reduction, arc discharge, chemical vapor deposition, and epitaxial growth of graphene in silicon carbide. Recent advances in the application of graphene in graphene-based lithium ion batteries, supercapacitors, electrochemical sensors, transparent electrodes and environmental based remedies are discussed. Full article

(This article belongs to the Special Issue Nanocarbon-Based Composites and Their Thermal, Electrical, and Mechanical Properties)

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Open AccessReview

Fabrication and Supercapacitor Applications of Multiwall Carbon Nanotube Thin Films

by

Kyle Jiang

and

Rosario A. Gerhardt

C 2021, 7(4), 70; https://doi.org/10.3390/c7040070 - 30 Sep 2021

Cited by 4 | Viewed by 2295

Abstract

Multiwalled carbon nanotubes (MWCNTs) are a one-dimensional nanomaterial with several desirable material properties, including high mechanical tensile modulus and strength, high electrical conductivity, and good thermal conductivity. A wide variety of techniques have been optimized to synthesize MWCNTs and to fabricate thin films [...] Read more.

Multiwalled carbon nanotubes (MWCNTs) are a one-dimensional nanomaterial with several desirable material properties, including high mechanical tensile modulus and strength, high electrical conductivity, and good thermal conductivity. A wide variety of techniques have been optimized to synthesize MWCNTs and to fabricate thin films of MWCNTs. These synthesis and fabrication methods vary based on precursor materials, process parameters, and physical and chemical principals, and have a strong influence on the properties of the nanotubes and films. Thus, the fabrication methods determine the performance of devices that can exploit the advantageous material properties of MWCNTs. Techniques for the fabrication of carbon nanotubes and carbon nanotube thin films are reviewed, followed by a discussion of the use of MWCNTs as an electrode material for electrochemical double-layer supercapacitors (EDLCs). EDLCs feature high power density, excellent reversibility and lifetime, and improved energy density over electrolytic capacitors. Beyond surveying fabrication techniques previously explored for MWCNT electrodes, an alternative approach based on inkjet printing capable of depositing a small amount of active material is discussed. Such an approach allows for a high degree of control over electrode properties and can potentially reduce cost and active material waste, which are essential components to the gradual conversion to green energy. Full article

(This article belongs to the Special Issue Nanocarbon-Based Composites and Their Thermal, Electrical, and Mechanical Properties)

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Open AccessReview

Carbons Formed in Methane Thermal and Thermocatalytic Decomposition Processes: Properties and Applications

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C 2021, 7(3), 50; https://doi.org/10.3390/c7030050 - 25 Jun 2021

Cited by 1 | Viewed by 3150

Abstract

The hydrogen economy will play a key role in future energy systems. Several thermal and catalytic methods for hydrogen production have been presented. In this review, methane thermocatalytic and thermal decomposition into hydrogen gas and solid carbon are considered. These processes, known as [...] Read more.

The hydrogen economy will play a key role in future energy systems. Several thermal and catalytic methods for hydrogen production have been presented. In this review, methane thermocatalytic and thermal decomposition into hydrogen gas and solid carbon are considered. These processes, known as the thermal decomposition of methane (TDM) and thermocatalytic decomposition (TCD) of methane, respectively, appear to have the greatest potential for hydrogen production. In particular, the focus is on the different types and properties of carbons formed during the decomposition processes. The applications for carbons are also investigated. Full article

(This article belongs to the Special Issue Nanocarbon-Based Composites and Their Thermal, Electrical, and Mechanical Properties)

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