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C, Volume 8, Issue 3 (September 2022) – 15 articles

Cover Story (view full-size image): The empirical observation of dynamically evolving carbon nanotube (CNT) clusters is exceptionally difficult. A methodology is presented to characterize a large cluster of individual single-walled CNTs with atomic resolution, using hierarchical molecular dynamic simulations to create initial cluster topologies that further enables high-fidelity simulation-based research. The methodology does not rely upon physical nucleation to build individual CNTs, and thus mitigates considerable computational intensity while still preserving the spatial fidelity of the carbon nanotube shapes and behaviors. Qualitative agreement is shown compared to electron microscopy images, including the presence of physical defects in the nanotubes, such as buckling, crimping, and fusing. View this paper
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14 pages, 3975 KiB  
Article
Structural Evolution of Polyimide-Derived Carbon during Phosphoric Acid Activation
by Alexander M. Puziy, Olga I. Poddubnaya, Barbara Gawdzik, Magdalena Sobiesiak and Myroslav Sprynskyy
C 2022, 8(3), 47; https://doi.org/10.3390/c8030047 - 19 Sep 2022
Cited by 6 | Viewed by 2219
Abstract
Carbon adsorbents were obtained by carbonization of polyimide polymer with and without the presence of phosphoric acid at temperatures in the range of 400–1000 °C. Carbons produced in the presence of phosphoric acid have been demonstrated to contain up to 13.2% phosphorus. The [...] Read more.
Carbon adsorbents were obtained by carbonization of polyimide polymer with and without the presence of phosphoric acid at temperatures in the range of 400–1000 °C. Carbons produced in the presence of phosphoric acid have been demonstrated to contain up to 13.2% phosphorus. The structure of phosphorus-containing compounds was investigated by XPS and 31P MAS NMR methods. Deconvolution of the P 2p peak with variable binding energy showed the presence of only phosphates/polyphosphates. However, a low value of the O/P ratio is an indirect indication of the possible presence of phosphonates. A 31P MAS NMR study revealed the existence of several kinds of phosphates as well as a minor quantity (1–9%) of phosphonates. All discovered phosphorus-containing compounds are acidic and therefore give carbon the ability to absorb metal cations. The study of copper ion adsorption demonstrated that phosphorus-containing carbon shows a significant adsorption capability even in extremely acidic conditions. At pH 3–6, phosphorus-containing carbon may completely remove copper from the aqueous solution. Phosphorus-containing carbon has a higher adsorption capacity for copper ions than ion exchange resins with carboxyl or sulfo groups. Full article
(This article belongs to the Special Issue Carbons for Health and Environmental Protection)
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15 pages, 4699 KiB  
Article
Brewer’s Spent Grain Biochar: Grinding Method Matters
by Arvind K. Bhakta, Youssef Snoussi, Mohamed El Garah, Souad Ammar and Mohamed M. Chehimi
C 2022, 8(3), 46; https://doi.org/10.3390/c8030046 - 15 Sep 2022
Cited by 5 | Viewed by 2430
Abstract
The present work is based on the principle of biomass waste valorization. Brewer’s spent grains (BSG) come from breweries as by-products. Their huge amount of production on an industrial scale should focus our attention on their valorization, which creates challenges as well as [...] Read more.
The present work is based on the principle of biomass waste valorization. Brewer’s spent grains (BSG) come from breweries as by-products. Their huge amount of production on an industrial scale should focus our attention on their valorization, which creates challenges as well as opportunities. One way to valorize BSG by-products is to convert them into biochar, a functional material with multiple potential applications. With an emphasis on sustainable development and the circular economy, in this work, we focused on a comparative study of the different mechanical processes of BSG grinding and their effect on the resulting biochar formed after pyrolysis. Home appliances such as blenders, coffee mills, and mortar and pestles were used for this purpose. FESEM images confirmed the successful creation of five different morphologies from the same BSG under the same pyrolysis conditions. Interestingly, a novel Chinese tea leaf egg-like biochar was also formed. It was found that a series of physical pretreatments of the biomass resulted in the reduced roughness of the biochar surface, i.e., they became smoother, thus negatively affecting the quality of the biochar. XRD revealed that the biomass physical treatments were also reflected in the crystallinity of some biochar. Via a Raman study, we witnessed the effect of mechanical pressure on the biomass for affecting the biochar features through pressure-induced modifications of the biomass’s internal structure. This induced enhanced biochar graphitization. This is a good example of the role of mechanochemistry. DSC revealed the thermochemical transformation of the five samples to be exothermic reactions. This study opens up an interesting possibility for the synthesis of biochar with controlled morphology, crystallinity, degree of graphitization, and heat capacity. Full article
(This article belongs to the Special Issue Advanced Carbon Based Nanomaterials)
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17 pages, 26314 KiB  
Article
Investigation of Electron Transfer Mechanistic Pathways of Ferrocene Derivatives in Droplet at Carbon Electrode
by Sidra Ayaz, Afzal Shah and Shamsa Munir
C 2022, 8(3), 45; https://doi.org/10.3390/c8030045 - 9 Sep 2022
Cited by 2 | Viewed by 2302
Abstract
The results of cyclic, differential pulse and square wave voltammetric studies of four ferrocene derivatives, i.e., 4-ferrocenyl-3-methyl aniline (FMA), 3-Chloro-4-ferrocenyl aniline (CFA), 4-ferrocenyl aniline (FA) and ferrocenyl benzoic acid (FBA) on carbon electrode, revealed that the redox behavior of these compounds is [...] Read more.
The results of cyclic, differential pulse and square wave voltammetric studies of four ferrocene derivatives, i.e., 4-ferrocenyl-3-methyl aniline (FMA), 3-Chloro-4-ferrocenyl aniline (CFA), 4-ferrocenyl aniline (FA) and ferrocenyl benzoic acid (FBA) on carbon electrode, revealed that the redox behavior of these compounds is sensitive to pH, concentration, scan number and scan rate. One electron, diffusion controlled, with a quasi-reversible redox signal displaying ferrocene/ferrocenium couple was observed for each of the studied ferrocenyl derivatives. Quasi-reversibility of this signal is evidenced by ∆Ep, Ia/Ic current ratio and ksh values. Another one electron and one proton irreversible oxidation signal was noticed in the voltammograms of these compounds except FBA. This signal corresponds to the electro-oxidation of the amine group and its irreversibility, as supported by ∆Ep, Ia/Ic current ratio and ksh values, is due to the influence of the electron donating nature of the amine group. A number of electrochemical parameters such as D, ksh, LOD and LOQ were evaluated for the targeted ferrocene derivatives. The obtained parameters are expected to provide insights into the redox mechanism for understanding their biochemical actions. The electrochemistry presented in this work is done using a unique environmentally benign and cost-effective droplet electrochemical approach. Full article
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14 pages, 4311 KiB  
Article
Power Generation Characteristics of Polymer Electrolyte Fuel Cells Using Carbon Nanowalls as Catalyst Support Material
by Takayuki Ohta, Hiroaki Iwata, Mineo Hiramatsu, Hiroki Kondo and Masaru Hori
C 2022, 8(3), 44; https://doi.org/10.3390/c8030044 - 27 Aug 2022
Cited by 2 | Viewed by 2520
Abstract
We evaluated the power generation characteristics of a polymer electrolyte fuel cell (PEFC) composed of Pt-supported carbon nanowalls (CNWs) and a microporous layer (MPL) of carbon black on carbon paper (CP) as catalyst support materials. CNWs, standing vertically on highly crystallizing graphene sheets, [...] Read more.
We evaluated the power generation characteristics of a polymer electrolyte fuel cell (PEFC) composed of Pt-supported carbon nanowalls (CNWs) and a microporous layer (MPL) of carbon black on carbon paper (CP) as catalyst support materials. CNWs, standing vertically on highly crystallizing graphene sheets, were synthesized on an MPL/CP by plasma-enhanced chemical vapor deposition (PECVD) using inductively coupled plasma (ICP). Pt nanoparticles were supported on the CNW surface using the liquid-phase reduction method. The three types of voltage loss, namely those due to activated polarization, resistance polarization, and diffusion polarization, are discussed for the power generation characteristics of the PEFC using the Pt/CNWs/MPL/CP. The relationship between the height or gap area of the CNWs and the voltage loss of the PEFC is demonstrated, whereby the CNW height increased with the extension of growth time. The three-phase interface area increased with the increase in the CNW height, resulting in mitigation of the loss due to activated polarization. The gap area of the CNWs varied when changing the CH4/H2 gas ratio. The loss due to diffusion polarization was reduced by enlarging the gap area, due to the increased diffusion of fuel gas and discharge of water. The secondary growth of the CNWs caused the three-phase interface area to decrease as a result of platinum aggregation, impedance of the supply of ionomer dispersion solution to the bottom of the CNWs, and inhibition of fuel gas and water diffusion, which led to the loss of activated and diffuse polarizations. The voltage losses can be mitigated by increasing the height of CNWs while avoiding secondary growth. Full article
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11 pages, 1834 KiB  
Article
Laser-Induced Refractive Index Indicates the Concurrent Role of the Bio-Structuration Process in the Comparison with the Nano-Structuration One
by Natalia Kamanina, Svetlana Likhomanova and Yulia Zubtsova
C 2022, 8(3), 43; https://doi.org/10.3390/c8030043 - 26 Aug 2022
Cited by 2 | Viewed by 1741
Abstract
It should be remarked that the basic knowledge collected from complicated area of the structuration process of the organic materials, including the liquid crystal (LC) ones, useful for the optoelectronics and biomedicine, requires extending the types of the novel matrix model materials and [...] Read more.
It should be remarked that the basic knowledge collected from complicated area of the structuration process of the organic materials, including the liquid crystal (LC) ones, useful for the optoelectronics and biomedicine, requires extending the types of the novel matrix model materials and the class of the dopants, which can change the spectral and photorefractive features of the matrixes with good advantage. In the current paper the effect of the introduction of the bio-objects (based on DNA) and of the nano-objects (based on fullerenes, quantum dots, carbon nanotubes, shungites, graphenes) in the organic conjugated materials has been comparatively discussed. The influence of this process on the photorefractive features, namely on the laser-induced change of the refractive index, has been studied. The clear innovative tendency of the alternative using of the bio-objects together or instead of the nano-objects ones has been analyzed via considering of the modification of the spectral and non-linear optical characteristics. Full article
(This article belongs to the Special Issue Carbon Nanohybrids for Biomedical Applications)
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17 pages, 4061 KiB  
Article
Structural Descriptors of Benzenoid Hydrocarbons: A Mismatch between the Estimates and Parity Effects in Helicenes
by Denis Sh. Sabirov, Ottorino Ori, Alina A. Tukhbatullina and Igor S. Shepelevich
C 2022, 8(3), 42; https://doi.org/10.3390/c8030042 - 25 Aug 2022
Cited by 3 | Viewed by 2019
Abstract
Benzenoid hydrocarbons have regular structures, attracting the opportunity to test the structural descriptors of their series. In the present study, we compared information entropy, Wiener indices, topological efficiencies, topological roundness, and symmetries of oligoacenes, phenacenes, and helicenes. We found and discussed the mismatches [...] Read more.
Benzenoid hydrocarbons have regular structures, attracting the opportunity to test the structural descriptors of their series. In the present study, we compared information entropy, Wiener indices, topological efficiencies, topological roundness, and symmetries of oligoacenes, phenacenes, and helicenes. We found and discussed the mismatches between the descriptors and the symmetry of benzenoids. Among the studied series, helicenes demonstrate the parity effect when the information entropy and topological roundness form saw-like functions depending on the number of the member, odd or even. According to our quantum chemical calculations, this parity effect has no consequences for such molecular properties as molecular polarizability and frontier molecular orbital energies. Further, we demonstrated that the changes in the structural descriptors upon the chemical reactions of benzenoids could be used for the numerical description of chemical processes. Interestingly, the view of the information entropy reaction profile is similar to the energy profiles of chemical reactions. Herewith, the intermediate chemical compounds have higher information entropy values compared with the initial and final compounds, which reminisce the activation barrier. Full article
(This article belongs to the Section Carbon Skeleton)
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18 pages, 2459 KiB  
Article
Effect of Porosity and Surface Chemistry on CO2 and CH4 Adsorption in S-Doped and S-/O-co-Doped Porous Carbons
by Snezana Reljic, Manuel Martinez-Escandell and Joaquin Silvestre-Albero
C 2022, 8(3), 41; https://doi.org/10.3390/c8030041 - 15 Aug 2022
Cited by 10 | Viewed by 3044
Abstract
The aim of this study was to determine the adsorption performance of a petroleum pitch-based activated carbon (PPAC1:3) before and after a post-treatment with H2S. In the first step, a microporous activated carbon (PPAC1:3) with a highly developed porous structure was [...] Read more.
The aim of this study was to determine the adsorption performance of a petroleum pitch-based activated carbon (PPAC1:3) before and after a post-treatment with H2S. In the first step, a microporous activated carbon (PPAC1:3) with a highly developed porous structure was produced through a chemical activation route with KOH. Afterward, the synthesized activated carbon was thermally treated yielding two different series of functionalized activated carbons: (i) a series of carbons were treated directly with H2S at elevated temperatures (600 °C and 800 °C), and (ii) a series of carbons were generated by combining an oxidation treatment with plasma followed by H2S treatment at elevated temperatures (600 °C and 800 °C). The chemical and structural characteristics of the S-doped and S-/O-co-doped porous carbons were investigated by means of different experimental techniques, such as XRD, RAMAN, FESEM, XPS, TPD, N2, and CO2 adsorption, and finally tested in CO2 and CH4 adsorption at atmospheric and high pressure. The functionalized porous carbons possessed specific surface areas of 2420–2690 m2/g, total pore volume of 1.05–1.18 cm3/g, and sulfur content up to 2.55 atom % (the sulfur content of the original carbon was 0.19%). After a careful analysis of the carbon dioxide and methane uptake at atmospheric (0.1 MPa) and high pressure (4 MPa), adsorption results confirm that the microporous structure is the main structural parameter defining the adsorption performance and, to a lower extent, the surface chemistry. Overall, a significant improvement in the total uptake can be appreciated after the H2S treatment. Full article
(This article belongs to the Special Issue Carbons for Health and Environmental Protection)
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13 pages, 2763 KiB  
Article
Amperometric Biosensor Based on Laccase Enzyme, Gold Nanoparticles, and Glutaraldehyde for the Determination of Dopamine in Biological and Environmental Samples
by Anderson M. Santos, Ademar Wong, Orlando Fatibello-Filho and Fernando C. Moraes
C 2022, 8(3), 40; https://doi.org/10.3390/c8030040 - 1 Aug 2022
Cited by 8 | Viewed by 2529
Abstract
The present work reports the development and application of an amperometric biosensor based on carbon paste electrode modified with laccase enzyme, glutaraldehyde, and gold nanoparticles (Lac-Glu-AuNPs/CPE) for the determination of the neurotransmitter dopamine (DA). The materials were characterized morphologically and chemically using scanning [...] Read more.
The present work reports the development and application of an amperometric biosensor based on carbon paste electrode modified with laccase enzyme, glutaraldehyde, and gold nanoparticles (Lac-Glu-AuNPs/CPE) for the determination of the neurotransmitter dopamine (DA). The materials were characterized morphologically and chemically using scanning electron microscopy (SEM), transmission electron microscopy (TEM), and cyclic voltammetry. Optimization studies were performed in order to determine the optimal amount of enzyme and pH level that can yield the best conditions of analysis. The application of the biosensor in optimal conditions using the amperometric technique yielded a linear concentration range of 8.0 × 10−7–6.2 × 10−5 mol L−1 with a limit of detection of 6.0 × 10−8 mol L−1. The proposed biosensor was successfully applied for the determination of DA in biological and environmental samples. In addition, the application of the biosensor for the conduct of electrochemical measurements showed that the sensing device has good repeatability and stability, and it does not suffer from matrix interference effects. The proposed biosensor exhibited an analytical signal of 85% after 10 days of consecutive use. Full article
(This article belongs to the Special Issue Carbon Nanohybrids for Biomedical Applications)
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11 pages, 5260 KiB  
Article
Stability of Carboxyl-Functionalized Carbon Nanotubes in Simulated Cement Pore Solution and Its Effect on the Compressive Strength and Porosity of Cement-Based Nanocomposites
by Laura Silvestro, Geannina Terezinha Dos Santos Lima, Artur Spat Ruviaro and Philippe Jean Paul Gleize
C 2022, 8(3), 39; https://doi.org/10.3390/c8030039 - 19 Jul 2022
Cited by 4 | Viewed by 2285
Abstract
The application of carbon nanotubes to produce cementitious composites has been extensively researched. However, the dispersion of this nanomaterial remains a technical limitation for its use. Thus, initially, this study assessed the stability of carboxyl-functionalized CNT on aqueous suspensions and simulated cement pore [...] Read more.
The application of carbon nanotubes to produce cementitious composites has been extensively researched. However, the dispersion of this nanomaterial remains a technical limitation for its use. Thus, initially, this study assessed the stability of carboxyl-functionalized CNT on aqueous suspensions and simulated cement pore solution for 6 h through UV–visible spectroscopy. Subsequently, a CNT content of 0.1% by cement weight was incorporated into the cement pastes, and the compressive strength after 7, 14, 28, and 91 days was evaluated. In addition, the porosity of the CNT cementitious composites at 28 days of hydration was investigated by mercury intrusion porosimetry (MIP), and the microstructure was evaluated via scanning electron microscopy (SEM). The simulated cement pore solution’s alkaline environment affects the CNT stability, progressively reducing the dispersed CNT concentration over time. CNT reduced the cementitious matrix pores < 50 nm by 8.5%; however, it resulted in an increase of 4.5% in pores > 50 nm. Thus, CNT incorporation did not significantly affect the compressive strength of cement pastes. SEM results also suggested a high porosity of CNT cementitious composites. The CNT agglomeration trend in an alkaline environment affected the CNT performance in cement-based nanocomposites. Full article
(This article belongs to the Collection Novel Applications of Carbon Nanotube-Based Materials)
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11 pages, 3455 KiB  
Article
Study of the Adsorption of Bacillus subtilis and Bacillus cereus Bacteria on Enterosorbent Obtained from Apricot Kernels
by Lucian Lupascu, Oleg Petuhov, Nina Timbaliuc and Tudor Lupascu
C 2022, 8(3), 38; https://doi.org/10.3390/c8030038 - 8 Jul 2022
Cited by 5 | Viewed by 2214
Abstract
This paper presents the results of scientific research on the structural parameters and the adsorption capacity of activated carbon obtained from apricot kernels (AC-A) in a fluidized layer. The obtained results highlight the fact that the described procedure allows obtaining a mesoporous carbon [...] Read more.
This paper presents the results of scientific research on the structural parameters and the adsorption capacity of activated carbon obtained from apricot kernels (AC-A) in a fluidized layer. The obtained results highlight the fact that the described procedure allows obtaining a mesoporous carbon adsorbent with increased adsorption capacities (SBET = 1424 m2/g) and with quality indices corresponding to the requirements of the carbon enterosorbents imposed by the European Pharmacopoeia Monograph. Adsorption kinetics studies of the bacteria Bacillus subtilis and Bacillus cereus have shown that the time to establish the adsorption equilibrium is 75–90 min. The adsorption of the mentioned bacteria on the carbon enterosorbent AC-A was studied depending on the temperature (26 and 36 °C) and pH of the solution (1.97–4.05). Scanning Electron Microscopy (SEM) showed that the immobilization of bacteria takes place on the outer surface of the carbon adsorbent due to the fact that the geometric dimensions of the bacteria are often larger than the macro diameter of the activated carbon pores. FTIR investigations also indicated the presence of bacteria on the surface of the activated carbon. Full article
(This article belongs to the Section Carbon Materials and Carbon Allotropes)
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14 pages, 12277 KiB  
Article
Bottom-Up Synthesis Strategies Enabling the Investigation of Metal Catalyst-Carbon Support Interactions
by Hamed Bateni, Prathamesh T. Prabhu, Hannah E. Gebur and Jean-Philippe Tessonnier
C 2022, 8(3), 37; https://doi.org/10.3390/c8030037 - 28 Jun 2022
Viewed by 2340
Abstract
The structural versatility and vibrant surface chemistry of carbon materials offer tremendous opportunities for tailoring the catalytic performance of supported metal nanoparticles through the modulation of interfacial metal-support interactions (MSI). MSI’s geometric and structural effects are well documented for these materials. However, other [...] Read more.
The structural versatility and vibrant surface chemistry of carbon materials offer tremendous opportunities for tailoring the catalytic performance of supported metal nanoparticles through the modulation of interfacial metal-support interactions (MSI). MSI’s geometric and structural effects are well documented for these materials. However, other potential support effects such as electronic metal-carbon interactions remain poorly understood. Such limitations are tied to constraints intrinsic to commonly available carbon materials such as activated carbon (e.g., microporosity) and the top-down approach that is often used for their synthesis. Nonetheless, it is crucial to understand the interplay between the structure, properties, and performance of carbon-supported metal catalysts to take steps toward rationalizing their design. The present study investigates promising and scalable bottom-up synthesis approaches, namely hydrothermal carbonization (HTC) and evaporation-induced self-assembly (EISA), that offer great flexibility for controlling the carbon structure. The opportunities and limitations of the methods are discussed with a particular focus on harnessing the power of oxygen functionalities. A remarkable production yield of 32.8% was achieved for mesoporous carbons synthesized via EISA. Moreover, these carbon materials present similar external surface areas of 316 ± 19 m2/g and average pore sizes of 10.0 ± 0.1 nm while offering flexibility to control the oxygen concentration in the range of 5–26 wt%. This study provides the cornerstone for future investigations of metal-carbon support interactions and the rational design of these catalysts. Full article
(This article belongs to the Collection Young Carbon Scientists)
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21 pages, 3855 KiB  
Review
Hydrogen Storages Based on Graphene Nano-Flakes: Density Functional Theory Approach
by Hiroto Tachikawa
C 2022, 8(3), 36; https://doi.org/10.3390/c8030036 - 27 Jun 2022
Cited by 5 | Viewed by 2102
Abstract
Carbon materials such as graphene, carbon nanotubes, fullerene, and graphene nanoflakes (GNFs) are used for hydrogen storage. The doping of alkali metals to these materials generally increases the accumulation density of molecular hydrogen (H2). However, the reason why the doping enhances [...] Read more.
Carbon materials such as graphene, carbon nanotubes, fullerene, and graphene nanoflakes (GNFs) are used for hydrogen storage. The doping of alkali metals to these materials generally increases the accumulation density of molecular hydrogen (H2). However, the reason why the doping enhances the ability of the H2 storage of GNF is not clearly known, although there are some explanations. In addition, the information on the storage capacity of GNF is ambiguous. In the present review article, we introduce our recent theoretical studies on the interaction of GNF with H2 molecules carried out to elucidate the mechanism of hydrogen storage in alkali-doped GNFs. As alkali metals, lithium (Li), sodium (Na), and potassium (K) were examined, and the abilities of hydrogen storage were discussed. Next, the mechanism of Li-diffusion on GNF, which plays a crucial role in Li-battery, was presented. There are several unanswered questions. In particular, does lithium diffuse randomly on GNF? Or is there a specific diffusion path? We present our study, which elucidates the factors governing lithium diffusion on GNF. If the dominant factor is known, it is possible to arbitrarily control the diffusion path of lithium. This will lead to the development of highly functional battery materials. Finally, the molecular design of H adsorption–desorption reversible storage devices based on GNF will be introduced. Elucidating the mechanism of hydrogen storage, Li-diffusion on GNF, and molecular design of storage device is important in understanding the current molecular devices and provide a deeper insight into materials chemistry. Full article
(This article belongs to the Special Issue Carbon Materials for Physical and Chemical Hydrogen Storage)
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11 pages, 2918 KiB  
Article
Spark Desensitization of Nanothermites via the Addition of Highly Electro-Conductive Carbon Particles
by Pierre Gibot
C 2022, 8(3), 35; https://doi.org/10.3390/c8030035 - 23 Jun 2022
Cited by 1 | Viewed by 1880
Abstract
In the past decade, the formulation of spark-desensitized nanothermites has considerably advanced, making them safe to handle. When ignited, these materials reveal impressive properties such as high temperatures (>1000 °C), intense heat releases (>kJ/cm3), and sometimes gas generation. Unfortunately, these energetic [...] Read more.
In the past decade, the formulation of spark-desensitized nanothermites has considerably advanced, making them safe to handle. When ignited, these materials reveal impressive properties such as high temperatures (>1000 °C), intense heat releases (>kJ/cm3), and sometimes gas generation. Unfortunately, these energetic systems are systematically characterized by an extreme sensitivity to electrostatic discharges, which can cause accidental ignitions during preparation, handling, and transport. The present study examines the electrostatic discharge sensitivity response of an Al/WO3 energetic formulation doped with highly conductive carbon nanoparticles (Ketjenblack EC600JD). The results showed an increased threshold from <0.14 mJ to almost 40 mJ with 18.80 vol. % of KB EC600JD in the energetic mixture. The energetic material was also desensitized to friction stress with a threshold greater than 360 N, in contrast to a value of <4.9 N for an un-doped Al/WO3 energetic composite material. The reactive performance of the system (w/o Ketjenblack additive) was verified in open medium by means of an optical igniter. The heat release was determined by a calorimetric bomb and a decrease of 50% was recorded for the carbon-doped energetic system compared to the pristine Al/WO3 composition. Full article
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17 pages, 5184 KiB  
Article
Digital Synthesis of Realistically Clustered Carbon Nanotubes
by Bryan T. Susi and Jay F. Tu
C 2022, 8(3), 34; https://doi.org/10.3390/c8030034 - 22 Jun 2022
Cited by 4 | Viewed by 2524
Abstract
A computational approach for creating realistically structured carbon nanotubes is presented to enable more accurate and impactful multi-scale modeling and simulation techniques for nanotube research. Much of the published literature to date involving computational modeling of carbon nanotubes simplifies their structure as being [...] Read more.
A computational approach for creating realistically structured carbon nanotubes is presented to enable more accurate and impactful multi-scale modeling and simulation techniques for nanotube research. Much of the published literature to date involving computational modeling of carbon nanotubes simplifies their structure as being long and straight, and often existing as isolated individual nanotubes. However, imagery of nanotubes has shown over several decades that nanotubes agglomerate together and exhibit looping and curvature due both to inter- and intra-nanotube attraction. The research presented in this paper leverages multi-scale simulations consisting of a simple bead-spring model for initial nanotube relaxation followed by a differential geometry approach to create an atomic representation of carbon nanotubes, and then finalized with molecular dynamics simulations using the Tersoff potential model for carbon that allows dynamic bonding and cleavage. The result is atomically accurate representations of carbon nanotubes that exist as single nanotubes, or as clusters of multiple nanotubes. The presented approach is demonstrated using (5,5) single-walled carbon nanotubes. The synthesized nanotubes are shown to relax into the curving and looping structures observed in transmission or scanning electron microscopy, but also exhibit nano-scale defects due to buckling, crimping, and twisting that are resolved during the molecular dynamics simulations. These features locally compromise the desired strength characteristics of nanotubes and therefore the presented procedure will enable more accurate modeling and simulation of nanotubes in subsequent research by representing them less as the theoretically straight and independent entities, but as realistically imperfect. Full article
(This article belongs to the Collection Novel Applications of Carbon Nanotube-Based Materials)
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8 pages, 1623 KiB  
Article
Atmospheric Pressure Plasma-Jet Treatment of PAN-Nonwovens—Carbonization of Nanofiber Electrodes
by Andreas Hoffmann, Matthias Uhl, Maximilian Ceblin, Felix Rohrbach, Joachim Bansmann, Marcel Mallah, Holger Heuermann, Timo Jacob and Alexander J. C. Kuehne
C 2022, 8(3), 33; https://doi.org/10.3390/c8030033 - 22 Jun 2022
Cited by 3 | Viewed by 2499
Abstract
Carbon nanofibers are produced from dielectric polymer precursors such as polyacrylonitrile (PAN). Carbonized nanofiber nonwovens show high surface area and good electrical conductivity, rendering these fiber materials interesting for application as electrodes in batteries, fuel cells, and supercapacitors. However, thermal processing is slow [...] Read more.
Carbon nanofibers are produced from dielectric polymer precursors such as polyacrylonitrile (PAN). Carbonized nanofiber nonwovens show high surface area and good electrical conductivity, rendering these fiber materials interesting for application as electrodes in batteries, fuel cells, and supercapacitors. However, thermal processing is slow and costly, which is why new processing techniques have been explored for carbon fiber tows. Alternatives for the conversion of PAN-precursors into carbon fiber nonwovens are scarce. Here, we utilize an atmospheric pressure plasma jet to conduct carbonization of stabilized PAN nanofiber nonwovens. We explore the influence of various processing parameters on the conductivity and degree of carbonization of the converted nanofiber material. The precursor fibers are converted by plasma-jet treatment to carbon fiber nonwovens within seconds, by which they develop a rough surface making subsequent surface activation processes obsolete. The resulting carbon nanofiber nonwovens are applied as supercapacitor electrodes and examined by cyclic voltammetry and impedance spectroscopy. Nonwovens that are carbonized within 60 s show capacitances of up to 5 F g−1. Full article
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