Six types of carbon nanoparticle masterbatches were employed during this study, each type containing either single-wall carbon nanotubes (SWCNT), multi-wall carbon nanotubes (02 types, MWCNT), graphene (G), reduced graphene oxide (RGO) or nitrogen doped graphene (NDG). These particles were added to an epoxy matrix at three weight percentages of interest, 0.5 %, 1.0 % and 2 %. The electrical and piezoresistive properties of the formulated nanocomposites were studied, with higher weight fractions yielding higher electrical conductivities whereas the same yielded lower piezoresistive response. Carbon nanotube (CNT) based nanocomposites outperformed graphene/derivative nanocomposites in terms of electrical conductance, showing resistivities between 2 106 Ohmcm as compared to G/RGO/NDG samples, with values between 1011-1012 Ohmcm. CNT based nanocomposites showed strain based gauge factors between ~27, while graphene/derivative nanocomposites showed extremely high resistivities infeasible for piezoresistive monitoring at the studied weight percentages. A clear relationship between the attained electrical conductance of CNT nanocomposites and their strain sensing ability (gauge factor) has also been established, with the dependency following a semi-logarithmic system; GF=A*log(R0)+B.
References
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Anisotropic electrical conductivity in graphene films with vertically aligned single-walled carbon nanotubes: new advances in mechanisms and applications
Glukhova O.E.1,2, Slepchenkov M.M. 1
1 Saratov State University, Saratov, Russia
2 I.M. Sechenov First Moscow State Medical University, Moscow, Russia
glukhovaoe@info.sgu.ru
In this paper, we suggest an idea of a new approach to control the electrical conductivity and its anisotropy in graphene-nanotube films with vertically oriented single-walled carbon nanotubes (SWCNTs) seamlessly connected to graphene. The basis of this approach is the phenomenon of aromaticity occurred in the hexagons of armchair-type SWCNTs at a certain nanotube length, which induces the oscillations of electronic characteristics with increasing the SWCNT length [1]. The proposed idea was tested on the example of two graphene nanomesh (GNM) atomistic models with nanoholes for SWCNTs with the chirality (6,6) and (9,9) in the case of sequentially increasing the SWCNT length. These types of SWCNTs were revealed using original approach called virtual growing, which shown that among the armchair SWCNTs with a diameter of 0.61.2 nm, the energetically favorable SWCNT- graphene junction will be formed with the SWCNTs (6,6) and (9,9). The calculations of geometric parameters of graphene-nanotube atomistic models were obtained using the self-consistent charge density functional tight-binding (SCC-DFTB) method [2]. The calculations of the electron transmission function T(E) and electrical conductivity G were carried out at 300 K using the Landauer-Buttiker formalism [3]. It was found that the nanoholes in monolayer graphene form conducting pathways in one direction, inducing anisotropy of the conducting properties. The anisotropy of the G value reaches 5 times. The formation of SWCNTs in the nanoholes does not remove anisotropy, amplifying it up to 7 times. The value of electrical conductivity G is strongly influenced by the length of the formed nanotube. It was found that a sharp increase in the value of G occurs at a certain length of 0.615 nm, 0.984 nm, 1.353 nm, and so on with in steps of 0.369 nm. These values of the SWCNT length were determined by the number of atomic layers in the SWCNT framework that is a multiple of three. Especially noticeable jumps in electrical conductivity occur for the armchair direction of electron transport. Thus, by adjusting the SWCNT length, it is possible to enhance or weaken the anisotropy of the conductive properties of graphene-nanotube films.
Acknowledgement. This work was supported by the Ministry of Science and Higher Education of the Russian Federation, grant FSRR-2020-0004.
References:
[1] F. Buonocore, F. Trani, D. Ninno, A. Di Matteo, G. Cantele, G. Iadonisi, Nanotechnology, 19, 025711 (2008).
[2] M. Elstner, D. Porezag, G. Jungnickel, J. Elsner, M. Haugk, Th. Frauenheim, S. Suhai, G. Seifert, Phys. Rev. B 58, 7260 (1998).
[3] S. Datta, Quantum Transport: Atom to Transistor. 2nd ed. Cambridge: Cambridge University Press; 2005
O.E. Glukhova received Ph.D. in Vacuum and Plasma Electronics (1997) and Dr. Sc. in Solid State Electronics and Nanoelectronics (2009) from the Saratov State University, Russia. She is a head of Department of Radiotechnique and electrodynamics at Saratov State University and leads the Division of Mathematical modeling in Educational and scientific institution of nanostructures and biosystems at Saratov State University. Her main fields of investigation are: nanoelectronics, molecular modeling of biomaterials and nanostructures, molecular electronics, mechanics of nanostructures, quantum chemistry and molecular dynamics, carbon nanostructures (fullerenes, nanotubes, graphene, graphane). She has published more 200 peer-reviewed journal papers and five monographs.
Oxygen evolution reaction on pristine and defective nitrogen-doped carbon nanotubes and graphene
Murdachaew G.1, and Laasonen K.1
1) Aalto University, Department of Chemistry and Materials Science, Finland
kari.laasonen@aalto.fi
Hydrogen obtained by electrochemical water splitting on a suitable catalyst has raised a lot of interest. The ideal catalyst should be efficient, stable under operating conditions, and composed of earth-abundant elements. Density functional theory simulations within a simple thermodynamic model of the more difficult half-reaction, the anodic oxygen evolution reaction (OER), with a single-walled carbon nanotube as a catalyst, showed that the presence of < 1 % nitrogen reduces the required OER overpotential significantly. We performed an extensive exploration of systems and active sites with various nitrogen functionalities [1] (graphitic, pyridinic, or pyrrolic) obtained by introducing nitrogen and simple lattice defects (atomic substitutions, vacancies, or Stone-Wales rotations). The lowest predicted overpotentials were about 0.4 V, close to what has been measured experimentally for the best-performing nitrogen-doped nanocarbon catalysts. The lowest predicted overpotential of 0.39 V was obtained for a model system with a Stone-Wales defect in combination with pyrrolic nitrogen doping. The most OER-active sites/systems were carbon atoms in the vicinity of Stone-Wales pyrrolic nitrogen, followed by graphitic nitrogen. For the majority of the nanotube-based systems, the third step of the four-step OER mechanism, the formation of attached OOH, is the potential-determining step of the reaction. The nanotube radius and chirality effects were examined by considering OER in the limit of large radius by studying graphene as a model system. They exhibited trends similar to those of the nanotube-based systems but often with reduced reactivity due to weaker attachment of the OER intermediate molecules.