C | Topical Collection : Nanocarbon-Based Composites and Their Thermal, Electrical, and Mechanical Properties

2024

Jump to: 2023, 2022, 2021, 2020

12 pages, 6521 KiB

Open AccessArticle

Novel Superhard Tetragonal Hybrid sp³/sp² Carbon Allotropes C_x (x = 5, 6, 7): Crystal Chemistry and Ab Initio Studies

by Samir F. Matar and Vladimir L. Solozhenko

C 2024, 10(3), 64; https://doi.org/10.3390/c10030064 - 16 Jul 2024

Viewed by 980

Abstract

Novel superhard tetragonal carbon allotropes C₅, C₆, and C₇, characterized by the presence of sp³- and sp²-like carbon sites, have been predicted from crystal chemistry and extensively studied by quantum density functional theory [...] Read more.

Novel superhard tetragonal carbon allotropes C₅, C₆, and C₇, characterized by the presence of sp³- and sp²-like carbon sites, have been predicted from crystal chemistry and extensively studied by quantum density functional theory (DFT) calculations. All new allotropes were found to be cohesive, with crystal densities and cohesive energies decreasing along the C₅-C₆-C₇ series due to the greater openness of the structures resulting from the presence of C=C ethene and C=C=C propadiene subunits, and they were mechanically stable, with positive sets of elastic constants. The Vickers hardness evaluated by different models qualifies all allotropes as superhard, with H_v values ranging from 90 GPa for C₅ to 79 GPa for C₇. Phonon band structures confirm that the new allotropes are also dynamically stable. The electronic band structures reveal their metallic-like behavior due to the presence of sp²-hybridized carbon. Full article

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18 pages, 3429 KiB

Open AccessArticle

Low-Temperature Deposition of Diamond Films by MPCVD with Graphite Paste Additive

by Stephen Yang-En Guu, Fu-Cheng Lin, Yu-Sen Chien, Alen Jhang and Yon-Hua Tzeng

C 2024, 10(2), 39; https://doi.org/10.3390/c10020039 - 16 Apr 2024

Viewed by 2391

Abstract

Modern integrated circuits (ICs) take advantage of three-dimensional (3D) nanostructures in devices and interconnects to achieve high-speed and ultra-low-power performance. The choice of electrical insulation materials with excellent dielectric strength, electrical resistivity, strong mechanical strength, and high thermal conductivity becomes critical. Diamond possesses [...] Read more.

Modern integrated circuits (ICs) take advantage of three-dimensional (3D) nanostructures in devices and interconnects to achieve high-speed and ultra-low-power performance. The choice of electrical insulation materials with excellent dielectric strength, electrical resistivity, strong mechanical strength, and high thermal conductivity becomes critical. Diamond possesses these properties and is recently recognized as a promising dielectric material for the fabrication of advanced ICs, which are sensitive to detrimental high-temperature processes. Therefore, a high-rate low-temperature deposition technique for large-grain, high-quality diamond films of the thickness of a few tens to a few hundred nanometers is desirable. The diamond growth rate by microwave plasma chemical vapor deposition (MPCVD) decreases rapidly with lowering substrate temperature. In addition, the thermal conductivity of non-diamond carbon is much lower than that of diamond. Furthermore, a small-grain diamond film suffers from poor thermal conductivity due to frequent phonon scattering at grain boundaries. This paper reports a novel MPCVD process aiming at high growth rate, large grain size, and high sp³/sp² ratio for diamond films deposited on silicon. Graphite paste containing nanoscale graphite and oxy-hydrocarbon binder and solvent vaporizes and mixes with gas feeds of hydrogen, methane, and carbon dioxide to form plasma. Rapid diamond growth of diamond seeds at 450 °C by the plasma results in large-grained diamond films on silicon at a high deposition rate of 200 nm/h. Full article

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16 pages, 5473 KiB

Open AccessArticle

Comprehensive Study on Carbon-Coated Silver for Improved Tribo-Electrical and Wetting Performance

by Bruno Alderete, Frank Mücklich and Sebastian Suarez

C 2024, 10(1), 16; https://doi.org/10.3390/c10010016 - 4 Feb 2024

Viewed by 1877

Abstract

The rise in electrification has considerably increased the demand for high-efficiency and durable electrical contact materials. Carbon nanoparticles (CNP) are a promising coating material due to their intrinsic transport properties (thus minimizing the impact on conductivity), their proven solid lubricity (potentially improving tribological [...] Read more.

The rise in electrification has considerably increased the demand for high-efficiency and durable electrical contact materials. Carbon nanoparticles (CNP) are a promising coating material due to their intrinsic transport properties (thus minimizing the impact on conductivity), their proven solid lubricity (potentially improving tribological performance), and their hydrophobic wetting behavior (potentially providing atmospheric protection). In this study, carbon nanotube and nanohorn coatings are produced via electrophoretic deposition on silver-plated surfaces, followed by tribo-electrical and wetting characterization. The proposed coatings do not negatively affect the conductivity of the substrate, showing resistance values on par with the uncoated reference. Tribo-electrical characterization revealed that the coatings reduce adhesive wear during fretting tests while maintaining stable and constant electrical contact resistance. Furthermore, CNP-coated surfaces show a hydrophobic wetting behavior toward water, with graphite and carbon nanotube (CNT) coatings approaching super-hydrophobicity. Prolonged exposure to water droplets during sessile drop tests caused a reduction in contact angle (CA) measurement; however, CNT coatings’ CA reduction after five minutes was only approximately 5°. Accordingly, CNP (specifically CNT) coatings show auspicious results for their application as wear and atmospheric protective barriers in electrical contacts. Full article

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2023

Jump to: 2024, 2022, 2021, 2020

17 pages, 7719 KiB

Open AccessArticle

Graphene and Nanoclay as Processing Aid Agents: A Study on Rheological Behavior in Polystyrene

by Julie Genoyer, Emna Helal, Giovanna Gutierrez, Nima Moghimian, Eric David and Nicole R. Demarquette

C 2023, 9(4), 96; https://doi.org/10.3390/c9040096 - 7 Oct 2023

Viewed by 1773

Abstract

The effectiveness of layered particles as processing aid agents in molten polystyrene was studied. Three graphene grades and two clays of different lateral size were selected for this purpose. The morphologies of the composites were observed using scanning electron microscopy. Steady shear measurements [...] Read more.

The effectiveness of layered particles as processing aid agents in molten polystyrene was studied. Three graphene grades and two clays of different lateral size were selected for this purpose. The morphologies of the composites were observed using scanning electron microscopy. Steady shear measurements were carried out and the Carreau–Yasuda model with yield stress was applied to the experimental results. A decrease in viscosity was observed at 2 wt.% of particle content for almost all composites. The most efficient particle for reducing viscosity was found to be graphene in a loose agglomerated configuration. Graphene and clay particles with similar dispersion states had a similar effect on the viscosity, inducing a decrease by 29% and 22%, respectively, suggesting comparable efficiency as processing aid agents. The observed decrease in viscosity is attributed to the phenomenon of superlubricity, which is a lubricating mechanism that is closely linked to the atomic structure of the particles. Full article

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14 pages, 2825 KiB

Open AccessArticle

Electrical Resistance Evolution of Graphite and Talc Geological Heterostructures under Progressive Metamorphism

by Augusto Gonçalves Nobre, Fabio Ramos Dias de Andrade, Andres Fabian Salazar-Naranjo, Josue Neroti Rigue, Ricardo Barreto da Silva, Silvio Roberto Farias Vlach and Romulo Augusto Ando

C 2023, 9(3), 75; https://doi.org/10.3390/c9030075 - 30 Jul 2023

Cited by 2 | Viewed by 1919

Abstract

The electrical properties of isolated graphene established precedents for studies of electrical superconducting materials at room temperature. After the discovery of stabilized graphene and graphite nanoplatelets in a geological context, the interest in characterizing the properties of these minerals arose. This work evaluates [...] Read more.

The electrical properties of isolated graphene established precedents for studies of electrical superconducting materials at room temperature. After the discovery of stabilized graphene and graphite nanoplatelets in a geological context, the interest in characterizing the properties of these minerals arose. This work evaluates the electrical resistance evolution of mineral graphite and talc heterostructures under progressive metamorphism simulated in the laboratory. The experiments were conducted on an end-loaded piston-cylinder apparatus. This equipment allows for the application of equal pressure in all sample directions (lithostatic pressure) and heating, simulating geological phenomena. The behavior of two sets of mineral samples were compared: graphite and talc in billets and powder. Samples in billets were submitted to treatments at 400 °C and 4 kbar; 400 °C and 6 kbar; and 700 °C and 9 kbar. The powder samples were subjected to 700 °C and 9 kbar, with two ways of disposing the mineral powders (mixed and in adjacent contact) beyond 900 °C and 9 kbar (in adjacent contact). The results show that the samples in billets had lower electrical resistance when compared to the powder samples. The lowest electrical resistance was observed in the sample treated at 400 °C and 6 kbar, conditions that are consistent with metamorphic mineral assemblage observed in the field. Powdered samples showed better cleavage efficiency during the experiment, resulting in thinner flakes and even graphene, as pointed out by Raman spectroscopy. However, these flakes were not communicating, which resulted in high electrical resistance, due to the need for an electrical current to pass through the talc, resulting in a Joule effect. The maximum electrical resistance obtained in the experiment was obtained in the sample submitted to 900 °C, in which talc decomposed into other mineral phases that were even more electrically insulating. This work demonstrates that electrical resistance prospecting can be an efficient tool to identify potential target rocks with preserved mineral nanometric heterostructures that can form an important raw material for the nanotechnology industry. Full article

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8 pages, 5356 KiB

Open AccessArticle

Graphene Oxide Membranes: Controlled Laser Reduction for Sensing Applications

by Aiden Rowley, Yijing Stehle, Luke Kilby and Caleb Bashant

C 2023, 9(3), 74; https://doi.org/10.3390/c9030074 - 30 Jul 2023

Cited by 1 | Viewed by 1748

Abstract

Reduced graphene oxide (rGO) has attracted attention as an active electrode material for flexible electrochemical devices due to its high electric conductivity and large surface area. Compared to other reduction processes, laser reduction is a precise, low-cost, and chemical-free process that is directly [...] Read more.

Reduced graphene oxide (rGO) has attracted attention as an active electrode material for flexible electrochemical devices due to its high electric conductivity and large surface area. Compared to other reduction processes, laser reduction is a precise, low-cost, and chemical-free process that is directly applied to graphene oxide (GO) membranes. This study aims to develop rGO through laser irradiation for application as electrodes in thin flexible electrochemical sensors. Laser irradiation parameters will be optimized to achieve reduction of a low oxygen to carbon (O/C) ratio and surface impedance. The influence of humidity on the impedance of rGO electrodes will be studied. The observed instability of the rGO electrode is related to incomplete reduction and oxygenated defects involved in reduction. Partially removed oxygenated functional groups not only influence the impedance of the electrode but make it sensitive to the humidity of the working environment. The result provides references for GO’s laser reduction optimization, demonstrates the potential of applying rGO as an electrode in sensing applications, but also reveals the limitation of applying the laser reduced rGO electrode in a non-constant humidity environment. Full article

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13 pages, 5319 KiB

Open AccessArticle

Effective Elastic Modulus of Wavy Single-Wall Carbon Nanotubes

by Chensong Dong

C 2023, 9(2), 54; https://doi.org/10.3390/c9020054 - 26 May 2023

Viewed by 1446

Abstract

A simple method for determining the effective elastic modulus of wavy single-wall carbon nanotubes (SWCNTs) is presented in this paper. The effective modulus of curved SWCNTs is derived using Castigliano’s theorem. The effect of curvature on the effective modulus is studied. This method [...] Read more.

A simple method for determining the effective elastic modulus of wavy single-wall carbon nanotubes (SWCNTs) is presented in this paper. The effective modulus of curved SWCNTs is derived using Castigliano’s theorem. The effect of curvature on the effective modulus is studied. This method is verified by finite element analysis (FEA). The distributions of effective moduli are studied by Monte Carlo simulation. The effective modulus of a general wavy SWCNT is derived by considering the SWCNT as a number of curved SWCNT sections. Full article

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20 pages, 8155 KiB

Open AccessArticle

Study of the Influence of Silicon-Containing Diamond-like Carbon Coatings on the Wear Resistance of SiAlON Tool Ceramics

by Marina A. Volosova and Anna A. Okunkova

C 2023, 9(2), 50; https://doi.org/10.3390/c9020050 - 16 May 2023

Viewed by 1598

Abstract

DLC coatings have low adhesive bond strength with the substrate and a high level of residual stresses. This paper is devoted to researching a complex of characteristics of a DLC-Si coating deposited on samples of SiAlON ceramics with intermediate coatings (CrAlSi)N pre-formed to [...] Read more.

DLC coatings have low adhesive bond strength with the substrate and a high level of residual stresses. This paper is devoted to researching a complex of characteristics of a DLC-Si coating deposited on samples of SiAlON ceramics with intermediate coatings (CrAlSi)N pre-formed to improve the adhesive bond strength employing vacuum-plasma spraying. DLC-Si coatings were formed by chemical vapor deposition in a gas mixture of acetylene, argon, and tetramethylsilane supplied through a multichannel gas purge system controlling the tetramethylsilane volume by 1, 4, 7, and 10%. The SiAlON samples with deposited (CrAlSi)N/DLC-Si coatings with different silicon content in the DLC layer were subjected to XPS and EDX analyses. Tribological tests were carried out under conditions of high-temperature heating at 800C. The nanohardness and elasticity modulus of the rational (CrAlSi)N/DLC-Si coating with Si-content of 4.1% wt. were 26 ± 1.5 GPa and 238 ± 6 GPa, correspondingly. The rational composition of (CrAlSi)N/DLC-Si coating was deposited on cutters made of SiAlON ceramics and tested in high-speed machining of aircraft nickel-chromium alloy compared to uncoated and DLC-coated samples. The average operating time (wear resistance) of (CrAlSi)N/DLC-Si(4.1% wt.)-coated end mills before reaching the accepted failure criterion was 15.5 min when it was 10.5 min for the original cutters. Full article

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21 pages, 5381 KiB

Open AccessReview

Graphene Nanocomposites in Space Sector—Fundamentals and Advancements

by Ayesha Kausar, Ishaq Ahmad, M. H. Eisa and Malik Maaza

C 2023, 9(1), 29; https://doi.org/10.3390/c9010029 - 3 Mar 2023

Cited by 16 | Viewed by 6061

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

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11 pages, 1450 KiB

Open AccessArticle

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

by Daniel Karthik, Jiri Militky, Yuanfeng Wang and Mohanapriya Venkataraman

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

Cited by 3 | Viewed by 3077

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

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12 pages, 5369 KiB

Open AccessArticle

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

by Tatsuhiko Aizawa and Kenji Fuchiwaki

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

Cited by 4 | Viewed by 2047

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

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20 pages, 5171 KiB

Open AccessReview

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

Cited by 7 | Viewed by 2760

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

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26 pages, 5004 KiB

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

by Stanley Udochukwu Ofoegbu, Mário Guerreiro Silva Ferreira, Helena I. S. Nogueira and Mikhail Zheludkevich

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

Cited by 4 | Viewed by 3599

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

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2022

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13 pages, 3239 KiB

Open AccessArticle

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

by Isabel Lado-Touriño

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

Cited by 1 | Viewed by 1966

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

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25 pages, 4041 KiB

Open AccessReview

Technology Features of Diamond Coating Deposition on a Carbide Tool

by Evgeny Ashkinazi, Sergey Fedorov, Alexander Khomich, Vladimir Rogalin, Andrey Bolshakov, Dmitry Sovyk, Sergey Grigoriev and Vitaly Konov

C 2022, 8(4), 77; https://doi.org/10.3390/c8040077 - 9 Dec 2022

Cited by 7 | Viewed by 4316

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

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14 pages, 8451 KiB

Open AccessArticle

Detonation Synthesis Nanodiamond Soot as a Promising Filler for Polymer Composites

by Oleg V. Lebedev, Tikhon S. Kurkin, Evgeny K. Golubev, Alexander L. Vasiliev, Andrey K. Gatin, Galina P. Goncharuk and Alexander N. Ozerin

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

Cited by 2 | Viewed by 2185

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

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11 pages, 2107 KiB

Open AccessArticle

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

by Abiodun Odusanya, Imteaz Rahaman, Pallab Kumar Sarkar, Abdelrahman Zkria, Kartik Ghosh and Ariful Haque

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

Cited by 2 | Viewed by 3718

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

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13 pages, 2014 KiB

Open AccessArticle

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

by Wei Liu and Giorgio Speranza

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

Cited by 4 | Viewed by 3460

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

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11 pages, 5358 KiB

Open AccessArticle

Carbon Composites—Graphene-Oxide-Catalyzed Sugar Graphitization

by Madhu Singh and Randy L. Vander Wal

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

Cited by 3 | Viewed by 3852

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

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11 pages, 2932 KiB

Open AccessArticle

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

by Margarita Kozlova, Sergey Butrim, Maksim Solovyev, Artem Pushkarev, Irina Pushkareva, Valery Kalinichenko, Svetlana Akelkina and Sergey Grigoriev

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

Cited by 6 | Viewed by 3872

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

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12 pages, 2363 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

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

by Olena Okhay, Alexandre Cunha Bastos, Kateryna Andreeva, Sampo Tuukkanen and Alexander Tkach

C 2022, 8(1), 12; https://doi.org/10.3390/c8010012 - 2 Feb 2022

Cited by 2 | Viewed by 3462

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

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19 pages, 3725 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

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

by Petros Kasaira Mubari, Théotime Beguerie, Marc Monthioux, Elsa Weiss-Hortala, Ange Nzihou and Pascal Puech

C 2022, 8(1), 4; https://doi.org/10.3390/c8010004 - 3 Jan 2022

Cited by 23 | Viewed by 4871

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

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2021

Jump to: 2024, 2023, 2022, 2020

13 pages, 3174 KiB

Open AccessArticle

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

by Varun Shenoy Gangoli, Chris J. Barnett, James D. McGettrick, Alvin Orbaek White and Andrew R. Barron

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

Cited by 5 | Viewed by 4249

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

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10 pages, 3777 KiB

Open AccessArticle

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

by Natalia Kamanina, Andrey Toikka, Bulat Valeev and Dmitry Kvashnin

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

Cited by 4 | Viewed by 2920

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

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13 pages, 5661 KiB

Open AccessArticle

Premade Nanoparticle Films for the Synthesis of Vertically Aligned Carbon Nanotubes

by Abdul Hoque, Ahamed Ullah, Beth S. Guiton and Noe T. Alvarez

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

Cited by 2 | Viewed by 3858

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

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13 pages, 29458 KiB

Open AccessArticle

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

by Rajyashree Sundaram, Atsuko Sekiguchi, Guohai Chen, Don Futaba, Takeo Yamada, Ken Kokubo and Kenji Hata

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

Cited by 3 | Viewed by 3516

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

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18 pages, 2014 KiB

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 21 | Viewed by 12600

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

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13 pages, 1265 KiB

Open AccessArticle

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

by Oluwakemi Ajala, Caroline Werther, Rauf Mahmudzade, Peyman Nikaeen and Dilip Depan

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

Cited by 2 | Viewed by 2703

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

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15 pages, 3081 KiB

Open AccessArticle

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

by Sri Hari Bharath Vinoth Kumar, Josefa Ibaceta-Jaña, Natalia Maticuic, Krystian Kowiorski, Matthias Zelt, Ulrich Gernert, Ludwika Lipińska, Bernd Szyszka, Rutger Schlatmann, Uwe Hartmann and Ruslan Muydinov

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

Cited by 2 | Viewed by 4771

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

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38 pages, 11507 KiB

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 10 | Viewed by 4932

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

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18 pages, 3531 KiB

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 3 | Viewed by 3122

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

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12 pages, 5960 KiB

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

Cited by 2 | Viewed by 4397

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

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13 pages, 1495 KiB

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

Cited by 3 | Viewed by 2944

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

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34 pages, 7568 KiB

Open AccessArticle

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

by Matteo Strozzi, Oleg V. Gendelman, Isaac E. Elishakoff and Francesco Pellicano

C 2021, 7(3), 61; https://doi.org/10.3390/c7030061 - 9 Aug 2021

Cited by 4 | Viewed by 2791

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

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14 pages, 3330 KiB

Open AccessArticle

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

by Torben Schlebrowski, Melanie Fritz, Lucas Beucher, Yongxin Wang, Stefan Wehner and Christian B. Fischer

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

Cited by 2 | Viewed by 2665

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

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14 pages, 12683 KiB

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 7 | Viewed by 3248

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

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23 pages, 8516 KiB

Open AccessArticle

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

by Nectarios Vidakis, Markos Petousis, Emmanuel Velidakis, Nikolaos Mountakis, 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 23 | Viewed by 4393

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

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8 pages, 2435 KiB

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 - 6 Jul 2021

Cited by 139 | Viewed by 15898

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

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16 pages, 1818 KiB

Open AccessReview

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

by Emmi Välimäki, Lasse Yli-Varo, Henrik Romar and Ulla Lassi

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

Cited by 8 | Viewed by 6408

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

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8 pages, 2597 KiB

Open AccessArticle

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

by Massimo Cazzanelli, Luca Basso, Claudio Cestari, Nicola Bazzanella, Enrico Moser, Michele Orlandi, Alessandro Piccoli and Antonio Miotello

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

Cited by 5 | Viewed by 3446

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

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13 pages, 3833 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

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 - 1 Feb 2021

Cited by 7 | Viewed by 3633

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

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2020

Jump to: 2024, 2023, 2022, 2021

12 pages, 1171 KiB

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 6 | Viewed by 3294

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

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13 pages, 6034 KiB

Open AccessArticle

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

by Felipe M. de Souza, Jonghyun Choi, Sanket Bhoyate, Pawan K. Kahol and Ram K. Gupta

C 2020, 6(2), 27; https://doi.org/10.3390/c6020027 - 1 May 2020

Cited by 10 | Viewed by 4281

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

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15 pages, 1544 KiB

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 19 | Viewed by 4281

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

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Nanocarbon-Based Composites and Their Thermal, Electrical, and Mechanical Properties

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