Subscriber access provided by La Trobe University Library
Article
New Details to Relaxation Dynamics of Dielectric Composite Materials Comprising Longitudinally Opened Carbon Nanotubes Ivan V. Lounev, Delyus R. Musin, and Ayrat M Dimiev J. Phys. Chem. C, Just Accepted Manuscript • DOI: 10.1021/acs.jpcc.7b08406 • Publication Date (Web): 29 Sep 2017 Downloaded from http://pubs.acs.org on September 30, 2017
Just Accepted “Just Accepted” manuscripts have been peer-reviewed and accepted for publication. They are posted online prior to technical editing, formatting for publication and author proofing. The American Chemical Society provides “Just Accepted” as a free service to the research community to expedite the dissemination of scientific material as soon as possible after acceptance. “Just Accepted” manuscripts appear in full in PDF format accompanied by an HTML abstract. “Just Accepted” manuscripts have been fully peer reviewed, but should not be considered the official version of record. They are accessible to all readers and citable by the Digital Object Identifier (DOI®). “Just Accepted” is an optional service offered to authors. Therefore, the “Just Accepted” Web site may not include all articles that will be published in the journal. After a manuscript is technically edited and formatted, it will be removed from the “Just Accepted” Web site and published as an ASAP article. Note that technical editing may introduce minor changes to the manuscript text and/or graphics which could affect content, and all legal disclaimers and ethical guidelines that apply to the journal pertain. ACS cannot be held responsible for errors or consequences arising from the use of information contained in these “Just Accepted” manuscripts.
The Journal of Physical Chemistry C is published by the American Chemical Society. 1155 Sixteenth Street N.W., Washington, DC 20036 Published by American Chemical Society. Copyright © American Chemical Society. However, no copyright claim is made to original U.S. Government works, or works produced by employees of any Commonwealth realm Crown government in the course of their duties.
Page 1 of 16
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
The Journal of Physical Chemistry
New Details to Relaxation Dynamics of Dielectric Composite Materials Comprising Longitudinally Opened Carbon Nanotubes Ivan V. Louneva, Delyus R. Musinb and Ayrat M. Dimievb* a
Institute of Physics, Kazan Federal University; Laboratory for Advanced Carbon Nanomaterials, Chemical Institute, Kazan Federal University, Kremlyovskaya Street 18, Kazan 420008, Russian Federation b
Corresponding author: e-mail
[email protected], (Ayrat M. Dimiev) Abstract The difference between intact and longitudinally opened multi-walled carbon nanotubes (referred to as CNT and OCNT) has been studied in their application as conductive filler in polymer composite materials. The dielectric properties have been studied in a broad frequency range at the temperatures varying from 293K through 373K. Introduction of as little as 0.5% and 1.0% of the conductive filler dramatically increased both parts of the complex permittivity. The percolation threshold is registered at ~1.5% filling fraction. The main frequency dispersion of the dielectric permittivity lies in the low frequency end of the tested spectrum: from 102 Hz through 104 Hz. At equal filling fractions, the permittivity of the OCNT-based samples exceeds that of the intact CNT-based samples. The relaxation dynamics is largely affected by the nanoscale geometry of the filler: the temperature dependence of such parameters as dielectric strength, activation energy and relaxation time demonstrated significant difference between the charge transfer mechanism in the CNT-based and OCNT-based samples. The obtained activation energy is 150 kJ/mol and 85kJ/mol for materials comprising CNTs and OCNTs, respectively. The relaxation mechanism is complex, and the exact factors behind the macroscopic dielectric properties of the tested materials cannot be singled out with certainty. Several experimental data suggest that the individual nanotubes, not their aggregates, play the major role in the observed electrical properties of the composites. At the low loading fractions, we attained the highest dielectric strength values among all the data reported by present day for the CNT/polymer host systems.
Introduction Introducing conductive filler into a dielectric polymer host is the broadly used strategy to controllably alter electro-magnetic properties of as-fabricated composite materials.1-4 These materials have a broad range of potential applications. Controlling permittivity of polymer 1 ACS Paragon Plus Environment
The Journal of Physical Chemistry
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
composites opens the avenues for fabricating materials that can shield and/or absorb electromagnetic radiation.5,6 Among all the types of conductive filler, carbon nanotubes have several advantages due to their high aspect ratio and excellent electrical conductivity;7 thus, only small loading fractions are needed to significantly alter electrical properties of the polymer host. The interest toward this field was awakened by the work of Coleman et al.,8 where the percolative character of the charge transfer was demonstrated for the first time. In the following years, the field was developed by several groups.9-21 The experimental details related to the exact percolation threshold, and the maximally achieved permittivity values varied in a broad range depending on the type of the used carbon nanotubes, and, most importantly, on the degree of their aggregation in resulted composites. The pertinent physics behind the electromagnetic behavior of these materials remains elusive. The major approach in describing their properties is the percolation theory,22-24 that predicts a power-law behavior of composites. In particular, a sharp increase in a tested property is predicted in close vicinity of the percolation threshold. The percolation theory is considered universal, i.e. independent on the nature of the host and the filler. Although this approach has garnered significant interest among physicists, experiments poorly support the universality of the power laws. In addition to the percolation theory, a microcapacitor model was proposed recently to explain electronic properties of dielectric composites.6,19,20 According to this model, the composite material is considered a network of microcapacitors randomly distributed in a dielectric host. Regardless of the complementary approaches of the percolation theory and the microcapacitor model, the precise physical behavior of composite materials remains poorly understood. Silicon-based elastomers possess a range of unique properties, advancing them over other polymers: extremely high flexibility, low weight, and chemical resistivity. Composite materials of silicon elastomers with carbon nanotubes were investigated in several reports.14,25-27 In particular, composites comprising multi-walled carbon nanotubes (MWCNT) and longitudinallyopened MWCNTs were studied in the frequency range 1-1000 MHz.25,26 The notable increase in the permittivity values was registered mainly in the low frequency end of the tested range, at the frequencies
