0000000000170170
AUTHOR
Stefano Bellucci
Heat-resistant unfired phosphate ceramics with carbon nanotubes for electromagnetic application
Composite materials, containing low concentrations of carbon nanotubes (CNTs) of three different diameters and heat-resistant phosphate ceramic as a matrix were prepared by cold-pressing method. Their dielectric properties were studied at room temperature in a wide frequency range (20 Hz–1 MHz). It was found experimentally and proved theoretically via modeling of the composites as a random capacitor–resistor–diode network that electrical percolation concentration depends significantly on the diameter of the nanoinclusions. The main conclusion is that the best candidate providing both the lower percolation threshold and high absolute values of ac conductivity is thinner carbon nanotubes (in …
Nanocomposites of epoxy resin with graphene nanoplates and exfoliated graphite: Synthesis and electrical properties
Nanocomposites are nowadays one of the most promising materials. Among different fillers, e.g. carbon nanotubes and silicon carbide nanowires (NWSiC), already used with epoxy resin matrices, graphene exfoliated graphite (EG) and graphene nanoplates have some characteristics that make them unique for electromagnetic shielding materials. However, there is still an unresolved problem of proper dispersion that will ensure the homogeneity of samples. To overcome this drawback, inorganic fibres were proposed. An amount of 0.25 phr (parts per hundred; filler content presented as wt.% of the whole polymeric matrix) NWSiC, added to the EG 1 phr/epoxy resin sample, efficiently prevents filler agglome…
Dielectric properties of graphite-based epoxy composites
International audience; Composite materials based on epoxy resin filled with various kinds of graphite particles: exfoliated graphite, natural graphite, and coarse, medium and fine artificial graphites have been prepared. Results of broadband dielectric investigations of such materials in wide temperature (25-450 K) and frequency (20 Hz-3 THz) ranges are presented. The dielectric permittivity strongly increases with graphite particle size. The graphite particle size and shape also have a strong impact on freezing temperature, conductivity activation energy and composite electromagnetic absorption properties at room temperature. The lowest percolation threshold is observed for exfoliated gra…
Theoretical Simulations on Electric Properties of CNT-Me and GNR-Me Interconnects Using Effective Media Approach
Abstract To overcome disadvantages of nowadays microtechnology, a further miniaturization of electronic devices, high integration level as well as increase of both operation frequencies and power density is required, including the use of adequate materials and innovative chip interconnects. Due to their unique physical properties, especially due to a ballistic (without losses) mechanism of conductivity, carbon nanotubes (CNTs) and graphene nanoribbons (GNRs) attract a permanently growing technological interest, for example, as promising candidates for nanointerconnects in a high-speed electronics.
Influence of F centres on structural and electronic properties of AlN single-walled nanotubes
We analyse the influence of uncharged N vacancies (neutral F centres), created either under conditions of AlN nanotube growth or by its soft irradiation, on the atomic and electronic structure. Periodic one-dimensional (1D) density functional theory (DFT) calculations on models of defective single-walled nanotubes (SW NTs) allow us to analyse how NT chirality and concentration of F centres change their properties compared to the corresponding defect-free nanotubes. We have simulated reconstruction around periodically repeated F centres on 1 nm AlN SW NTs with armchair- and zigzag-type chiralities. To achieve the limit of an isolated vacancy for both chiralities, we have considered different…
General Approach to the Description of Fundamental Properties of Disordered Nanosized Media
Physics of non-regular nanosystems is a branch of physics dealing with nanoagents – nanoparticles when non-regular nanosized morphological characteristics predetermine the nature and essence of physical phenomenon (nanophenomenon). In particular, multiple technological interfaces of nanoparticles with morphologically regular systems imply a creation of micro- or mesostructures with essential nanodimensional effects (e.g. in various schemes of functionalization of nanocarbon systems, viz. carbon nanotubes (CNTs), graphene nanoribbons (GNRs), graphene nanoflakes (GNFs), carbon-based nanoaerogels and nanofoams, etc.). However, classes of nanomaterials, in addition to nanocarbon systems, can be…
Electrical transport in carbon black-epoxy resin composites at different temperatures
Citation: J. Appl. Phys. 114, 033707 (2013); doi: 10.1063/1.4815870 (Received 3 May 2013; accepted 27 June 2013; published online 17 July 2013) Results of broadband electric/dielectric properties of different surface area—carbon black/epoxy resin composites above the percolation threshold are reported in a wide temperature range (25–500 K). At higher temperatures (above 400 K), the electrical conductivity of composites is governed by electrical transport in polymer matrix and current carriers tunneling from carbon black clusters to polymer matrix. The activation energy of such processes decreases when the carrier concentration increases, i.e., with the increase of carbon black concentration…
Formation of linear Ni nanochains inside carbon nanotubes: Prediction from density functional theory
Abstract First principles calculations have been performed to investigate the ground state properties of monoperiodic single-walled carbon nanotubes (CNTs) containing nanochain of aligned Ni atoms inside. Using the PBE exchange-correlation functional ( E xc ) within the framework of density functional theory (DFT) we predict the clusterization of Ni filaments in ( n ,0) CNTs for n ⩾ 9 and for ( n , n ) CNTs for n ⩾ 6. The variations in formation energies obtained for equilibrium defective nanostructures allow us to predict the most stable Ni@CNT compositions. Finally, the electronic charge redistribution has been calculated in order to explore intermolecular properties leading to stronger…
Electromagnetic shielding efficiency in Ka-band: carbon foam versus epoxy/carbon nanotube composites
The wide application of microwaves stimulates searching for new materials with high electrical conductivity and electromagnetic (EM) interference shielding effectiveness (SE). We conducted a comparative study of EM SE in K a -band demonstrated by ultra-light micro-structural porous carbon solids (carbon foams) of different bulk densities, 0.042 to 0.150 g/cm 3 , and conventional flexible epoxy resin filled with carbon nanotubes (CNTs) in small concentrations, 1.5 wt.%. Microwave probing of carbon foams showed that the transmission through a 2 mm-thick layer strongly decreases with decreasing the pore size up to the level of 0.6%, due to a rise of reflectance ability. At the same time, 1 mm…
Nanosensor Devices for CBRN-Agents Detection: Theory and Design
Pressing challenges of recent decades, associated with agents that are aggressive towards humans – substances and radiation of chemical, biological, radiological, and nuclear (CBRN) agents – require scientific and technological responses. These responses lie in the areas of agent detection and protection from them. The mentioned bio destructive agents can be divided into 2 groups: (1) chemical and biochemical, and (2) radiative (leading to chemical destruction of biomass). In this study, we consider models of universal track nanosensors that are capable of producing a correlated electrical response to the flow of active agents.
Preliminary studies on nanocomposite based on high quality Silicon Carbide nanofibers
Nanocomposites are nowadays the most promising new materials due to their unique properties (such as high mechanical strength, chemical and thermal resistance). The nanocomposite matrix is blended with a nanostructured filler. In this study, Silicon Carbide nanofibers (NFSiC) and their bundles were tested as a reinforcement of two epoxy resins: EPIKOTE 828 and EL 20. PAP-4 (33 phr) and P-900 (40 phr) were used as hardeners in the two cases, respectively. Several samples were prepared in the range between 0.1 and 5 % wt for both types of resins and fillers (NFSiC and NFSiC bundles). Mechanical and electrical properties were tested. The fillers were obtained using a new simple, fast, low-cost…
Epoxy composites filled with high surface area-carbon fillers
Citation: J. Appl. Phys. 114, 164304 (2013); doi: 10.1063/1.4826529 (Received 24 July 2013; accepted 6 October 2013; published online 22 October 2013) A comprehensive analysis of electrical, electromagnetic (EM), mechanical, and thermal properties of epoxy resin composites filled with 0.25–2.0 wt. % of carbon additives characterized by high surface area, both nano-sized, like carbon nanotubes (CNTs) and carbon black (CBH), and micro-sized exfoliated graphite (EG), was performed. We found that the physical properties of both CNTs- and CBH-based epoxy resin composites increased all together with filler content and even more clearly for CBH than for CNTs. In the case of EG-based composites, go…
Simulation of electromagnetic properties in carbon nanotubes and graphene-based nanostructures
As carbon nanotubes (CNT) and graphene nanostructures (GNR) constitute the basis of high-speed nanoelectronics and nanosensors, we examine the fundamental properties of var- ious CNT-metal (Me), GNR-Me, and CNT-graphene interconnects. The cluster approach based on the multiple scattering theory as well as effective medium approximation were used to model the dispersion law, electronic density of states (DOS), and conductivity, etc. Multiple scattering problems were solved for nanostructures with radial (quantum dots) and axial (nanowires, nano- tubes) symmetry. Interconnect capacitances and impedances have been evaluated in the GHz and THz regimes. Parametrical numerical simulations of cond…
Resistance simulations for junctions of SW and MW carbon nanotubes with various metal substrates
Abstract This theoretical study focuses on junctions between the carbon nanotubes (CNTs) and contacting metallic elements of a nanocircuit. Numerical simulations on the conductance and resistance of these contacts have been performed using the multiple scattering theory and the effective media cluster approach. Two models for CNT-metal contacts have been considered in this paper: a) first principles “liquid metal” model and b) semi-empirical model of “effective bonds” based on Landauer notions on ballistic conductivity. Within the latter, which is a more adequate description of chirality effects, we have simulated both single-wall (SW) and multi-wall (MW) CNTs with different morphology. Res…
Optical, infrared and electron-microscopy studies of metallic clusters in layered crystals
Abstract An influence of ( Cd i ) n metallic clusters on the optical absorption and phonon spectra of CdI 2 crystals was studied. Metallic clusters of spherical shape were formed during the growth of non-stoichiometric crystals. Radii of clusters are in range from 10 to 500 nm according to scanning electron microscopy (SEM) data. The density of clusters was estimated from fractal dimension calculations. The fractal dimension of ( Cd i ) n clusters has been found to be varied from 1.488 to 1.793. In the framework of Mie theory the spectral and size dependencies of extinction coefficients were calculated. From the experimentally obtained spectra it is evident that the metallic clusters are re…
Surfactant-assisted synthesis of Cd1−xCoxS nanocluster alloys and their structural, optical and magnetic properties
We report the synthesis of Co-doped CdS nanoclusters (Cd1−xCoxS) for different doping concentrations (x = 0.10, 0.20 and 0.30) and characterization of their structural, optical, and magnetic properties. The structural properties studied by X-ray diffraction revealed hexagonal-greenockite structure and a decrease of the lattice parameters (a and c) with doping, showing incorporation of Co in the lattice. The morphology of the nanoclusters was studied by scanning electron microscopy. The optical absorption studies, using diffused reflectance spectroscopy, revealed that Co doping modifies the absorption band edge. Ferromagnetic phase was observed in the magnetization measurements at room-tempe…
First-principles calculations on Fe-Pt nanoclusters of various morphologies
Financial support provided by Scientific Research Project for Students and Young Researchers Nr. SJZ/2016/17 implemented at the Institute of Solid State Physics, University of Latvia, is greatly acknowledged. A.P. and R.E. express their gratitude to High-performance computer centers of ISSP (University of Latvia) and St. Petersburg University. This research was partially supported by Graphene Flagship GrapheneCore1-AMD-696656-4.
Microwave response properties of epoxy resin composites filled with graphitic fillers
Composite materials based on epoxy resin filled with various kinds of graphite particles: exfoliated graphite (EG), natural graphite, and coarse, medium and fine artificial graphites have been prepared. The dielectric permittivity strongly increases with graphite particle size. This effect is related to the distance of the investigated filler concentrations to the composites' percolation threshold. Microwave experiments show that exfoliated graphite is, out of investigated graphite particles, the only one being a really effective additive for producing electromagnetic (EM) interference (EMI) shielding: 2 wt.% epoxy/EG is absolutely opaque to electromagnetic radiation at 30 GHz.
Classification and Operating Principles of Nanodevices
The chapter presents and explains the classification of sensors in accordance with their physicochemical principles of functioning, as well as the types of recognition. Several prototypes of physical, chemical and biosensors based on polar molecular compounds such as indandione, fluorene and carbazole derivatives are described from the point of view of their structure and energy. One of the most important applications of nanosensitive materials is realized in the class of memory nanodevices. The realization of bistability in molecular or layered derivatives is usually carried out through processes based on tautomers and conformers, as well as phase transition processes. Typical examples of …
Atomic and electronic structure of both perfect and nanostructured Ni(111) surfaces: First-principles calculations
article i nfo In this study, we perform first principles simulations on both atomically smooth and nanostructured Ni(111) slabs. The latter contains periodically distributed nickel nanoclusters atop a thin metal film gradually growing from adatoms and serving as a promising catalyst. Applying the generalized gradient approximation within the formalism of the density functional theory we compare the atomic and electronic structures of Ni bulk, as well as both perfect and nanostructured (111) surfaces obtained using two different ab initio approaches: (i) the linear combination of atomic orbitals and (ii) the projector augmented plane waves. The most essential inter-atomic forces between the …
Nanosensor Systems Simulations
The chapter presents functionalized CNT and GNR nanostructures as the basis for the creation of physical, chemical and biochemical nanosensors. We have shown in our simulations the sensitivity of electron conductivity of FET-type nanodevices (based on CNTs and GNRs) to local doping by nitrogen and boron. This phenomenon provides the prospective of creating nanosensors.
Epoxy Resin/Carbon Black Composites Below the Percolation Threshold
International audience; A set of epoxy resin composites filled with 0.25-2.0 wt.% of commercially available ENSACO carbon black (CB) of high and low surface area (CBH and CBL respectively) has been produced. The results of broadband dielectric spectroscopy of manufactured CB/epoxy below the percolation threshold in broad temperature (200 K to 450 K) and frequency (20 Hz to 1 MHz) ranges are reported. The dielectric properties of composites below the percolation threshold are mostly determined by alpha relaxation in pure polymer matrix. The glass transition temperature for CB/epoxy decreases in comparison with neat epoxy resin due to the extra free volume at the polymer-filler interface. At …
CNT Arrays Grown upon Catalytic Nickel Particles as Applied in the Nanoelectronic Devices: Ab Initio Simulation of Growth Mechanism
Carbon nanotubes, due to their exceptional and unique properties, have aroused a lot of research interest making them promising candidates as interconnects for future high-speed nanoelectronics. To predict a growth mechanism for carbon nanotubes (CNTs) upon a metal particle as synthesized in the porous membrane block then incorporated in the nanoelectronic device, we have performed a series of large-scale DFT-LCAO calculations using the CRYSTAL-06 code. Carbon adatoms can appear upon the densely-packed Ni(111) catalyst surface due to dissociation of hydrocarbon molecules (e.g., CH4) when applying the CVD method for the nanotube growth. We have started with adsorption properties of carbon at…
Real time polymer nanocomposites-based physical nanosensors: theory and modeling.
Functionalized carbon nanotubes and graphene nanoribbons nanostructures, serving as the basis for the creation of physical pressure and temperature nanosensors, are considered as tools for ecological monitoring and medical applications. Fragments of nanocarbon inclusions with different morphologies, presenting a disordered system, are regarded as models for nanocomposite materials based on carbon nanoсluster suspension in dielectric polymer environments (e.g., epoxy resins). We have formulated the approach of conductivity calculations for carbon-based polymer nanocomposites using the effective media cluster approach, disordered systems theory and conductivity mechanisms analysis, and obtain…
Simulations on the mechanism of CNT bundle growth upon smooth and nanostructured Ni as well as θ-Al2O3 catalysts
Abstract In the current study, we have performed ab initio DFT calculations on the gradually growing 2D periodic models of capped single-wall carbon nanotubes (SW CNTs) upon their perpendicular junctions with the Ni(111) substrate, in order to understand the peculiarities of the initial stage of their growth on either smooth or nanostructured catalytic particles. Appearance of the adsorbed carbon atoms upon the substrate follows from the dissociation of CVD hydrocarbon molecules, e.g., CH4: (CH4)ads → (CH)ads+3Hads and (CH)ads → Cads+Hads. (Since the effective growth of CNTs upon Ni nanoparticles occur inside the nanopores of amorphous alumina, we have also simulated analogous surface react…
Graphene, Fullerenes, Carbon Nanotubes: Electronic Subsystem
This chapter introduces the reader to the analysis of the structural and electronic system properties of various carbon allotropes (CNT, graphene) and several molecular derivatives. The genesis of the electronic system formation is investigated in detail. Non-regular defected nanocarbon systems are considered for possible applications in different fields, including energy storage; chemical, biochemical and electrochemical sensing; water purification; and catalysis.
Structural and electronic properties of single-walled AlN nanotubes of different chiralities and sizes
Four models of single-walled AlN nanotubes (NTs), which possess (i) two different chiralities (armchair or zigzag type) and (ii) two different uniform diameters for both types of NTs (1 or 6 nm) have been constructed, in order to analyse the dependence of their properties on both morphology and thickness. Periodic one-dimensional (1D) DFT calculations performed on these models have allowed us to analyse how the chirality and curvature of the NT change its properties as compared to both AlN bulk with either wurtzite or zinc-blende structures and their densely packed surfaces. We have found that the larger the diameter of the AlN NT, the smaller the width of its bandgap, the strengths of its …
Scattering Processes in Nanocarbon-Based Nanointerconnects
Cluster approach based on the multiple scattering theory (MST) formalism, realistic analytical and coherent potentials as well as effective medium approximation (EMA–CPA) can be effectively used for nanosized systems modelling. Major attention is paid now to applications of carbon nanotubes (CNTs) and graphene nanoribbons (GNRs) with various morphology which possess unique physical properties in nanoelectronics, e.g. contacts of CNTs or GNRs with other conducting elements of a nanocircuit, which can be promising candidates for interconnects in high-speed electronics. The main problems connected with the resistance of C–Me junctions with metal particles appear due to the influence of chirali…
Defect-induced blue luminescence of hexagonal boron nitride
Abstract Native defect-induced photoluminescence around 400 nm (blue luminescence - BL) was studied in hBN materials with different size and various origins. The following spectral characterizations were used: spectra of luminescence and its excitation, luminescence dependence on temperature, luminescence kinetics, optically stimulated luminescence and infrared absorption. It was found, that the BL is characteristic for all these materials, which were studied. The BL forms a wide, asymmetric and phonon-assisted emission band at 380 nm. This luminescence can be excited either through the exciton processes, or with light from two defect-induced excitation bands at 340 nm and 265 nm. It was fo…
Luminescence, vibrational and XANES studies of AlN nanomaterials
Abstract The paper reports comparative studies on synthesized aluminium nitride nanotubes, nanoparticles and commercially available micron-sized AlN powder using different spectroscopic techniques: cathodoluminescence measurements (CL), X-ray absorption near edge spectroscopy (XANES) and Fourier-transform infrared spectroscopy (FTIR). Crucial distinctions in CL spectra are observed for nano- and microsized aluminium nitride powders; systematic shift of the IR absorption maximum has been detected for nanostructured aluminium nitride as compared to commercial samples. Through XANES experiments on Al K-edge structural differences between nano- and bulk AlN are revealed, intensity of features i…
Cadmium clusters in CdI2layered crystals: the influence on the optical properties
The influence of overstoichiometric Cd i atoms on the optical properties of cadmium iodide layered crystals has been investigated. The results of optical absorption, luminescence, and luminescence excitation studies of CdI 2 crystals with controlled deviation from stoichiometric composition allow observing correlations between the Cd i concentration and features in absorption and emission spectra up to concentrations of 10 18 cm -3 . At higher concentrations the overstoichiometric cadmium atoms form clusters, which were observed using scanning electron microscopy. The extinction spectra of (CdI i ) n clusters are calculated in the frame of Mie theory and are found to correlate with the opti…
Multiwall carbon-nanotube interconnects: radial effects on physical models and resistance calculations for various metal substrates
Based on a model with singular attractive potential of equidistant conductive cylinders, we illustrate an approach to calculate the electron spectrum of metallic multiwall carbon nanotubes (MW CNT) with an arbitrary number of coaxial layers. We compute the number of electrically active channels, N ch , in the ideal case when all MW CNT shells are contacted to the electrodes, starting from the one-electron spectrum. The dependence of N ch on the temperature and on both the innermost and outermost shells radii allows us to discuss the potential performances of MW CNT interconnects, affecting the power dissipation of integrated circuits. Our description improves over the isolated shells model,…
Theoretical simulations of regular and defective aluminium nitride nanotubes
For theoretical simulation on AlN nanotubes (NTs) of different chiralities (armchair-and zigzag-type) and uniform diameters, we have considered their single-walled (SW) 1D periodic models. For this aim, we have performed ab initio DFT calculations on AlN SW NTs using formalism of the localized Gaussian-type atomic functions as implemented in CRYSTAL-03 computer code. We have shown that the smaller the diameter of AlN single-walled nanotube is, the closer its electronic and structural properties to AlN bulk. We have analysed an influence of N vacancies (neutral F centres) created by either soft irradiation of nanotubes or under experimental conditions of their growth, on the atomic and elect…
Nanotechnology Application Challenges: Nanomanagement, Nanorisks and Consumer Behaviour
New emerging technologies are entering the society, which makes civil society the location for moral authority. Society is about the quality of human relationships; it is where people have to accept responsibility for the consequences of their actions; it is where the nano meets the micro and the micro meets the macro issues. Society belongs to all of us and everyone has his role to play. A new way of system thinking – nanothinking demonstrates technology trends from perfectness to non-regularity. The removal of current contradictions between regular and non-regular systems and the corresponding nanophenomena is the way to novel processes in the development of nanosciences and nanotechnolog…
CNT and Graphene Growth: Growing, Quality Control, Thermal Expansion and Chiral Dispersion
The chapter presents and discusses the production of graphene sheets of carbon nanotubes (CNT) of various types. The Iijima arc discharge method, following the purification methods, is described identifying advantages and disadvantages. Several types of non-regularities such as the Stone–Wales defect and corner effect, which locally increases reactivity, are described from the structural point of view. The laser ablation method is presented as one of the most prominent methods in the production of CNTs. The catalytic chemical vapour deposition (CVD) method is a very effective tool for the controlled production of different carbon shells. The sporadic and simulated growth of CNTs depends on …
Introduction to Non-regular Nanosystems
The chapter presents a short description of the main topics in non-regular nanosystems. In general, the scientific content of the discussed problems is based on the research interests of the authors of this book. Non-regularity is considered as a basic stimulus for the operational abilities of novel nanomaterials.
Spectral characterization of bulk and nanostructured aluminum nitride
Spectral characteristics including photoluminescence (PL) spectra and its excitation spectra for different AlN materials (AlN ceramics, macro size powder and nanostructured forms such as nanopowder, nanorods and nanotips) were investigated at room temperature. Besides the well known UV-blue (around 400 nm) and red (600 nm) luminescence, the 480 nm band was also observed as an asymmetric long-wavelength shoulder of the UV-blue PL band. This band can be related to the luminescence of some kind of surface defects, probably also including the oxygen-related defects. The mechanisms of recombination luminescence and excitation of the UV-blue luminescence caused by the oxygen-related defects were …
Spintronics and Nanomemory Systems
The chapter presents and explains the possibilities of CNT forest growth on Fe–Pt nanoparticles for the magnetic nanomemory. The magnetoresistance phenomena – giant magnetoresistance and tunnelling magnetoresistance (GMR and TMR) – for nanomemory devices are based on CNTs of various morphologies (i.e. various chiralities, diameters). It includes metal- and semiconductor-like CNTs which can be considered as alternative variants for electromagnetic nanosensoring and magnetic nanomemory. The chapter also presents simulations of Fe–Pt magnetically disordered nanodrops, as well as spin transport models.
Microstructure of Ag2BI4(B = Ag, Cd) superionics studied by SEM, impedance spectroscopy and fractal dimension analysis
Two silver ion conducting solid electrolytes, Ag2HgI4 and Ag2CdI4, representing a wide class of AgI-based halogenide superionics have been the subjects of study by means of electrical impedance spectroscopy, SEM, porosity measurements and fractal dimension analysis. Even though both materials have been obtained by the same method under strictly identical conditions they were found to exhibit certain differences at the microstructural level. Thus, by the direct measurements of porosity and density it was found that the grain boundaries are better developed in silver mercuric iodide. On the assumption that pore geometry in the materials under study displays fractal character it was shown that…
Graphene as a tunable resistor
We present the design of a graphene-based electronically tuneable microstrip attenuator operating at a frequency of 5 GHz. The use of graphene as a variable resistor is discussed and the modelling of its electromagnetic properties at microwave frequencies is fully addressed. The design of the graphene-based attenuator is described. The structure integrates a patch of graphene, whose characteristics can range from being a fairly good conductor to a highly lossy material, depending on the applied voltage. By applying the proper voltage through two high-impedance bias lines, the surface resistivity of graphene can be modified, thereby changing the insertion loss of the microstrip attenuator.
Simulation of Fundamental Properties of CNT- and GNR-Metal Interconnects for Development of New Nanosensor Systems
Cluster approach based on the multiple scattering theory formalism, realistic analytical and coherent potentials, as well as effective medium approximation (EMA-CPA), can be effectively used for nano-sized systems modeling. Major attention is paid now to applications of carbon nanotubes (CNTs) and graphene nanoribbons (GNRs) with various morphology which possess unique physical properties in nanoelectronics, e.g., contacts of CNTs or (GNRs) with other conducting elements of a nanocircuit, which can be promising candidates for interconnects in high-speed electronics. The main problems solving for resistance C-Me junctions with metal particles appear due to the influence of chirality effects …
Ab initio simulations on the atomic and electronic structure of single-walled BN nanotubes and nanoarches
To simulate the perfect single-walled boron nitride nanotubes and nanoarches with armchair- and zigzag-type chiralities and uniform diameter of � 5 nm, we have constructed their one-dimensional (1D) periodic models. In this study, we have compared the calculated properties of nanotubes with those for both hexagonal and cubic phases of bulk: bond lengths, binding energies per B–N bond, effective atomic charges as well as parameters of total and projected one-electron densities of states. For both phases of BN bulk, we have additionally verified their lattice constants. In the density functional theory (DFT), calculations performed using formalism of the localized Gaussian-type atomic functio…
Novel non-destructive evaluation technique for the detection of poor dispersion of carbon nanotubes in nanocomposites
Abstract A wide use of advanced carbon nanotube polymer composites can be boosted by new non-destructive evaluation (NDE) techniques that can test the quality of the products to ensure that their specifications are met. It is well known in literature that the parameter that far more than others can affect the enhancing capabilities of the carbon nanotubes is their dispersion. Here we have presented a novel NDE technique based on infrared thermography able to evaluate the dispersion of the added nanoparticles in polymer nanocomposites. The NDE technique was used to compare pairs of samples whose difference is represented only by the level of dispersion. It was found a significant difference …
Potentials and Electronic Structure Calculations of Non-regular Nanosystems
Methods of numerical investigations of potentials and pseudopotentials for fundamental properties calculations (electronic, vibrational, electron-phonon phenomena, etc.) of condensed matter constitute a basic principle of modelling. It is very essential to find specific analytical approaches to the calculation of atomic and ‘crystalline’ potentials to make the calculations most effective. In particular, we pay attention to the modelling of pure Coulomb contributions and their exchange-correlation corrections in the framework of Xα- и Xαβ-approximations.
Bottom-up realization and electrical characterization of a graphene-based device.
We propose a bottom-up procedure to fabricate an easy-to-engineer graphene-based device, consisting of a microstrip-like circuit where few-layer graphene nanoplatelets are used to contact two copper electrodes. The graphene nanoplatelets are obtained by the microwave irradiation of intercalated graphite, i.e., an environmentally friendly, fast and low-cost procedure. The contact is created by a bottom-up process, driven by the application of a DC electrical field in the gap between the electrodes, yielding the formation of a graphene carpet. The electrical resistance of the device has been measured as a function of the gap length and device temperature. The possible use of this device as a …
Surface Nanophysics: Macro-, Meso-, Micro- and Nano-approaches
The surface factor is very important for manipulating objects at a nanoscale. Thermodynamic behaviour is observed from the classical point of view, and conditional division into macro-, meso-, micro- and nano-approaches is presented. Processes of physical and chemical adsorption on the surface are presented from the energy and structure aspects. The occurrence of electronic states of the surface is presented from the classical point of view in comparison with molecular electronic states. One of the most important non-invasive optical methods to investigate nanoparticles is the surface plasmon resonance (SPR), which is quite useful for practical detection of nanoparticles in the surrounding …