Multi-step mechanism of carbonization in templated polyacrylonitrile derived fibers: ReaxFF model uncovers origins of graphite alignment

Saha, Biswajit; Furmanchuk, Al’ona; Dzenis, Yuris A.; Schatz, George C.

doi:10.1016/j.carbon.2015.07.048

Cited by 57 publications

(50 citation statements)

References 43 publications

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“…As mentioned earlier, only the reactive simulations for idealized ladder PAN have been previously reported 29,34,35 . Equipped with the CHON-2019 ReaxFF parameters set we can determine if the structural differences of the proposed oxidized PAN and idealized ladder PAN see we did plot a percentage of the produced N2 molecules with respect to maximum possible number of these molecules produced for each of the systems.…”

Section: Resultsmentioning

confidence: 99%

Atomistic Scale Analysis of the Carbonization Process for C/H/O/N-Based Polymers with the ReaxFF Reactive Force Field

Kowalik¹,

et al. 2019

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During the carbonization process of raw polymer precursors, graphitic structures can evolve. The presence of these graphitic structures affects mechanical properties of the carbonized carbon fibers. To gain a better understanding of the chemistry behind the evolution of these structures, we performed atomistic scale simulations using the ReaxFF reactive force field. Three different polymers were considered as a precursor: idealized ladder PAN (polyacrylonitrile), a proposed oxidized PAN and PBO (poly(p-phenylene-2,6-benzobisoxazole)). We determined the underlying molecular details of polymers conversion into a carbon fiber structure. Since these are C/H/O/N-based polymers, we first developed an improved force field for C/H/O/N chemistry based on the Density Functional Theory (DFT) data with a particular focus on N2 formation kinetics and its interactions with polymer-associated radicals formed during the carbonization process. Then, using this improved force field, we performed atomistic scale simulations of the initial stage of the carbonization process for the considered polymers. Based on our simulation data we determined the molecular pathways for the formation of low-molecular weight gas-species, all-carbon rings crucial for further graphitic structures evolution and possible alignment of the evolved all-carbon 6-membered rings clusters.

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Section: Resultsmentioning

confidence: 99%

Atomistic Scale Analysis of the Carbonization Process for C/H/O/N-Based Polymers with the ReaxFF Reactive Force Field

Kowalik¹,

et al. 2019

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“…The mechanical properties of CNFs with and without the graphitic skin layer are investigated in this study using large-scale molecular dynamics (MD) simulations. This computational technique has been successfully applied to analysis of chemical reactions leading to the formation of carbon fiber microstructure from molecular precursors [25][26][27][28][29][30][31][32], oxidation of carbon fibers [33], as well as the elementary processes involved in mechanical deformation of carbon fibers [27,28,[34][35][36][37]. The high computational cost of MD simulations, however, prevents application of this technique for direct evaluation of the mechanical properties of fibers with heterogeneous microstructure, such as the ones of core-skin carbon fibers.…”

Section: Generation Of the Model Carbon Nanofibersmentioning

confidence: 99%

Computational study of the effect of core–skin structure on the mechanical properties of carbon nanofibers

Joshi

Zhigilei

2021

J Mater Sci

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The effect of the core-skin structure on the mechanical properties of carbon nanofibers is investigated in large-scale molecular dynamics simulations of tensile deformation of carbon nanofibers with the core-skin and homogeneous structures. Contrary to an established notion of the deleterious effect of the skin layer on the strength of carbon fibers, the presence of a high-quality skin layer is found to increase both the Young's modulus and tensile strength of the nanofiber. A detailed analysis of the fracture process indicates that the nanofiber strengthening is related to the ability of skin layer to suppress crack nucleation at the core-skin interface. The computational predictions suggest that the design of new approaches to carbon fiber manufacturing and processing leading to the generation of a high-quality skin layer while avoiding the introduction of structural defects at the core-skin interface may yield a significant enhancement of the mechanical properties of carbon fibers.

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“…Reactive Force Field (ReaxFF) molecular dynamics simulations because the method uses bond order in calculating the potential, resulting in a smooth transition over bond dissociation and formation. PAN, [37,39] polyimide, [40,41] polycarbonate, [42] phenolic resin, [43] and high-density polyethylene (HDPE) [44] have all been studied by such means at different stages in their pyrolytic process. These studies provide valuable insights into chemical features that affect the carbonization process.…”

Section: Computationally This Has Been Studied By Assessing Mechanisms Of Carbonization In Polymers Bymentioning

confidence: 99%

“…[15] Another potential benefit of using such composites as precursors could be in the pyrolysis itself, whereby interactions between the already formed graphitic carbon aids in forming a carbon. [39] Even simply using carbon nanotubes as a filler component in PAN carbonization seems to aid in the process, forming more ordered graphitic structures than PAN carbonized without them. This has been investigated by Saha, et.…”

Section: Carbon Polymer Composites As Precursorsmentioning

confidence: 99%

“…using ReaxFF, showing that the nanofiller's π-conjugated system and the π -electrons from C N groups interact by van der Waals forces, and covalent bonding between the filler and polymer provides more stabilization for intermediates during carbonization. [39] By starting with a carbon, functionalization may be achieved by incorporation and subsequent pyrolysis of a polymer under more moderate conditions. [92,93] This approach can be attractive to maximize the number of functional moieties that either may not survive higher pyrolysis conditions or are lost progressively during pyrolysis.…”

Section: Carbon Polymer Composites As Precursorsmentioning

confidence: 99%

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Polymer‐Based Synthetic Routes to Carbon‐Based Metal‐Free Catalysts

2018

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Carbons are increasingly important as possible alternatives to expensive metal catalysts owing to the wide range of chemical properties they can exhibit and the growing set of synthetic routes available to produce them. This Progress Report discusses the process of making catalytic carbons from polymeric precursors, focusing on mechanisms of carbonization and how the polymer structures and synthetic procedures affect the resulting carbons. In considering what is necessary to move laboratory catalytic carbons to industrial and commercial applications, the cost and complexity to produce them are a considerable challenge to overcome. Industrially produced carbons are typically made from biopolymers such as lignin while many of the catalytic carbons studied in literature are from synthetic polymers. Thus, studying polymer-derived carbons can provide insights into the carbonization process and the properties of catalytic carbons, which can subsequently be translated to improve biopolymerderived carbons in an economical way. Aspects of polymer carbonization discussed include carbonization mechanisms, effects of crosslinkers, polymer microstructure, heteroatom control, and effects nanostructuring.

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Multi-step mechanism of carbonization in templated polyacrylonitrile derived fibers: ReaxFF model uncovers origins of graphite alignment

Cited by 57 publications

References 43 publications

Atomistic Scale Analysis of the Carbonization Process for C/H/O/N-Based Polymers with the ReaxFF Reactive Force Field

Atomistic Scale Analysis of the Carbonization Process for C/H/O/N-Based Polymers with the ReaxFF Reactive Force Field

Computational study of the effect of core–skin structure on the mechanical properties of carbon nanofibers

Polymer‐Based Synthetic Routes to Carbon‐Based Metal‐Free Catalysts

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