Еffect of graphene filler oxidation on the thermal destruction of epoxy-graphene composites

The participation of the electronic subsystem of graphene nanoparticles in heat transfer on the interfaphase surface with epoxy polymer, its participation in the thermodestruction processes of epoxy matrix and the concentration interval of the subsystem's influence on the thermal destruction of the polymer matrix are investigated. For such purpose, epoxy resin composites with oxidized and non-oxidized graphene nanoparticles have been used.The particles were obtained by electrochemical method and those are characterized by the same dispersion and analogical of defect spectra. The particles have the same crystal structure, however in composites with oxidized graphene, the participation of the electronic subsystem in thermophysical processes on the interfacial surface is blocked by the atomic layer of adsorbed oxygen. Сomposites of epoxy resin filled with the same particles of nonoxidized and oxidized nanoparticles in the filler content 0.0, 1.0, 2.0, and 5.0 wt%. The multilayered graphene particles were studied by X-ray diffraction analysis (XRD) and Raman spectroscopy (RS) methods. It was shown that the graphene particles are the 2D dimensional structures with about of 100 layers. Desorption curves of epoxy and its composites have been obtained using a programmable thermal desorption mass-spectroscopic (TDMS) technique for fragments with 15≤ m/z ≤108 and temperature interval 35 - 800 оС. The activation energy of desorption was determined from the Wigner-Polanyi equation as 35 - 150 kJ/mol, temperature and mass dependences of the quantity of desorbed atomic fragments have been calculated. It were established the graphene electron subsystem takes part in polymer structure thermodestruction for epoxy composites with nonoxidized graphene enhancing their heat resistance at graphene content С ≤ 1 wt%. With increasing filler content, the thermodestruction behavior in pristine epoxy and its composites with nonoxidized and oxidized graphene is analogical. The thermodestruction characterizes by the stepwise variations in the desorption intensity of atomic fragments. The electron subsystem of graphene particles does not participate in the heat resistance variations.

Ultrafast carrier dynamics in graphene and graphene nanostructures

In this paper we provide a comprehensive view on the ultrafast conduction dynamics in graphene and graphene nanostructures. We show that ultrafast conduction in graphene can be well understood within a simple thermodynamic picture, by taking into account the dynamical interplay between electron heating and cooling, with the driving electric field acting as a supplier of thermal energy to graphene electron population. At the same time, the conductive properties of graphene nanostructures, such as graphene nanoribbons (GNRs) and carbon nanotubes (CNTs), can be well explained within the concept typical for disordered materials, such as e.g. organic semiconductors - the conduction by the free charge experiencing long-range localization.

Active tuning of hybrid plasmonics in graphene-covered metallic nanotrench-=SUP=-*-=/SUP=-

Graphene has recently emerged as a possible platform for integrated optoelectronics and hybrid photonic devices because of its promising electronic and optical characteristics. Here, we propose the active tuning of hybrid plasmonics in intrinsic graphene-based gold rectangle nanotrench by modifying the graphene electron system. We found that the plasmonics response in graphene thicknesses can be unprecedentedly tuned by altering the thickness of thick graphene covering nanotrench geometry. It is explained as the active plasmonics hybridization leading to the tunability of the enhanced e -field localized within the graphene-covered metallic nanotrench. This study can be useful for optoelectronic devices based on hybrid graphene structures at IR wavelengths.

THE INTENSITY OF SCATTERING OF CHARGE CARRIERS IN GRAPHENE, LOCATED ON A SUBSTRATE OF HEXAGONAL BORON NITRIDE

The results of modeling the scattering intensities of charge carriers in graphene located on a substrate of hexagonal boron nitride are presented. Graphene is considered a promising material for the formation of new semiconductor devices with good characteristics for the microwave and HF bands. Formulas are presented that allow modeling of the main electron scattering intensities in a single layer of graphene placed on a substrate of boron nitride. The dependences of the scattering intensity on optical phonons associated with the interface between graphene and a layer of hexagonal boron nitride are obtained when the thickness of the gap between these layers changes. Simulation of fixed rate dispersion was carried out as for normal temperature equal to 300 K and at elevated – equal to 370, which is connected with the necessity of considering the temperature rise of the graphene layer with increasing electron energy. The analysis of the obtained dependences showed that at electron energy values that exceed a value equal to approximately 0.165 eV, there is a predominance of electron scattering on optical phonons inherent in the inner layer of graphene, electron-electron scattering, as well as scattering on optical phonons associated with the interface between graphene and a layer of hexagonal boron nitride, over other types of scattering. At low energy values, which are less than about 0.03 eV, the dispersion on impurities prevails over other types of dispersion. Based on the obtained dependences of electron scattering intensities in graphene, it becomes possible to implement the Monte – Carlo statistical method to determine the characteristics of electron transfer in semiconductor devices containing layers of graphene and hexagonal boron.