Carbon Nanoinclusions Research Articles

Assessing the Effect of Fe3O4 Nanoparticles on the Thermomechanical Performance of Different Forms of Carbon Allotropes/Epoxy Hybrid Nanocomposites

The incorporation of ceramic nanoinclusions in carbon nanocomposites can induce additional functionality in the field of magnetic properties, piezoelectricity, etc. In this study, series of nanocomposites, consisting of different carbon nanoinclusions (carbon black, MWCNTs, graphene nanoplatelets, nanodiamonds) and magnetite nanoparticles incorporated into a commercially available epoxy resin were developed varying the filler type and concentration. Experimental data from the static tensile tests and dynamic mechanical analysis (DMA) demonstrated that the elastic tensile modulus and storage modulus of hybrid nanocomposites increase with an increase in filler content up to almost 100% due to the inherent filler properties and the strong interactions at the interface between the epoxy matrix and the nanoinclusions. Strong interactions are implied by the increasing values of the glass transition temperature recorded by differential scanning calorimetry (DSC). On the contrary, tensile strength and fracture strain of the nanocomposites were found to decrease with filler content. The results highlight the potentials and capabilities of developing hybrid multifunctional nanocomposites with enriched properties while holding their structural integrity.

Amorphous carbon nano-inclusions for strategical enhancement of thermoelectric performance in Earth-abundant Cu3SbS4

Cu3SbS4 is an effective, low cost and non-toxic thermoelectric compound for intermediate temperature applications. However, its tetragonal structure needs to be tuned for efficient phonon scattering to reduce thermal conductivity and enhance zT. In this present article, the semiconductive carbon black nano-inclusions effect on Cu3SbS4 thermoelectric performance is studied. The thermoelectric properties of the fabricated samples are investigated in the temperature range of 300–623 K. Addition of amorphous carbon nano-inclusions in Cu3SbS4 causes a reduction in the thermal conductivity by phonon scattering and improvement in the Seebeck coefficient by carrier energy filtering mechanisms. The maximum figure of merit of 0.51 is obtained for 3 mol.% carbon nano-inclusion sample at 623 K. Additionally, enhancement of thermal stability and mechanical stability (hardness) with increased carbon nano-inclusion concentration is observed. It is found that grain boundary hardening and dispersion strengthening are the reasons for the enhancement. Moreover, our detailed studies demonstrate that the addition of carbon nano-inclusions in Cu3SbS4 can produce efficient, non-toxic, and inexpensive state-of-the-art thermoelectric devices.

Electrically Conductive Networks from Hybrids of Carbon Nanotubes and Graphene Created by Laser Radiation.

A technology for the formation of electrically conductive nanostructures from single-walled carbon nanotubes (SWCNT), multi-walled carbon nanotubes (MWCNT), and their hybrids with reduced graphene oxide (rGO) on Si substrate has been developed. Under the action of single pulses of laser irradiation, nanowelding of SWCNT and MWCNT nanotubes with graphene sheets was obtained. Dependences of electromagnetic wave absorption by films of short and long nanotubes with subnanometer and nanometer diameters on wavelength are calculated. It was determined from dependences that absorption maxima of various types of nanotubes are in the wavelength region of about 266 nm. It was found that contact between nanotube and graphene was formed in time up to 400 fs. Formation of networks of SWCNT/MWCNT and their hybrids with rGO at threshold energy densities of 0.3/0.5 J/cm2 is shown. With an increase in energy density above the threshold value, formation of amorphous carbon nanoinclusions on the surface of nanotubes was demonstrated. For all films, except the MWCNT film, an increase in defectiveness after laser irradiation was obtained, which is associated with appearance of C–C bonds with neighboring nanotubes or graphene sheets. CNTs played the role of bridges connecting graphene sheets. Laser-synthesized hybrid nanostructures demonstrated the highest hardness compared to pure nanotubes. Maximum hardness (52.7 GPa) was obtained for MWCNT/rGO topology. Regularity of an increase in electrical conductivity of nanostructures after laser irradiation has been established for films made of all nanomaterials. Hybrid structures of nanotubes and graphene sheets have the highest electrical conductivity compared to networks of pure nanotubes. Maximum electrical conductivity was obtained for MWCNT/rGO hybrid structure (~22.6 kS/m). Networks of nanotubes and CNT/rGO hybrids can be used to form strong electrically conductive interconnections in nanoelectronics, as well as to create components for flexible electronics and bioelectronics, including intelligent wearable devices (IWDs).

3D simulation of dry friction of metal-based composites

A numerical 3D model of friction at mesoscale of the contact patch between steel samples and composite steel samples with carbon nanoinclusions has been developed based on the movable cellular automaton method. The response function of automata simulating steel corresponds to an elastic-plastic body with linear hardening, and the function for simulating carbon corresponds to an elastic-plastic body with bilinear hardening. Von Mises criterion is used for breaking bonds between the automata, and the criterion based on plastic heat is used for coupling the automata. The values of basic parameters of the model, as well as the loading conditions, that allow the formation of the characteristic quasi-liquid layer in the friction zone are determined. It was shown that the presence of carbon nanoinclusions in the contact region leads to decreasing of the coefficient of friction, lower values of stress, and higher shear strain in the friction zone.

Structure and Properties of Self-Organized 2D and 3D Antimony/Carbon Composites

The conditions of synthesis of antimony/carbon composites by interlayer self-assembly from colloidal solutions and melts are discussed. The morphology and the structure of these composites are examined. The potential to produce composites of 2D and 3D morphologies is demonstrated. The 2D composite has a multilayer graphene structure with submicron antimony inclusions, while the 3D composite has a spheroidal shell structure with a deformed film-shell with carbon nanoinclusions. The difference in properties of these composites is demonstrated: the 2D composite is conductive, while the 3D composite has a nonlinear current–voltage characteristic that indicates the emergence of novel functional properties of the spheroidal antimony/carbon composite. A model of exfoliation of the layered precursor with covalent interlayer coupling is proposed. This model provides an explanation for the experimentally observed nonlinear hydrodynamic processes in the colloidal antimony solution.

Innovative Composites with Carbon Nanofillers for Self-Sensing Structural RC Beams

The progress of nanotechnology resulted in the development of new instruments in the civil engineering and its applications. In particular, the use of carbon nanofillers into the matrix of construction materials can provide enhanced properties to the material in both of mechanical and electrical performance. In constructions, concrete is among the most used material. Due to the peculiarities of its components and its structure, it is suitable to modifications, at the nanometer level too. Moreover, to guarantee structural safety it is desirable to achieve a diffuse monitoring of structures in order to identify incipient situations of damages and possible risk for people. The ideal solution would be to realize structures able to identify easily and quickly their behavior modifications. This paper presents a research work about the characterization of the self-sensing abilities of novel cementitious composites with conductive carbon nanoinclusions and their application into a structural reinforced concrete beam. The self-sensing evidence is achieved through the correlation between the variation of strains and the variation of electrical resistance or resistivity. Nanomodified cement pastes with different carbon nanofillers has been tested. The experimental campaign shows the potentialities of this new types of sensors made of nanomodified concrete for diffuse Structural Health Monitoring.

Enhanced melting behavior of carbon based phase change nanocomposites in horizontally oriented latent heat thermal energy storage system

Present study describes the numerical analysis of the melting process of phase change nanocomposites in a horizontally oriented shell-tube latent heat thermal energy storage system. Organic alkane n-eicosane is considered as the pristine phase change material. The influence of different carbon based allotropes in enhancing the thermal conductivity of n-eicosane is considered in this work. To enhance the thermal conductivity of organic alkane, highly conductive carbon nano inclusions of various dimensionalities such as spherical (nanodiamond), one dimensional (single-walled carbon nanotube) and two-dimensional (graphene nanoplatelets) structures were considered. Effective thermal conductivity of such nanocomposites are theoretically modeled based on effective medium formulation considering the influence of interfacial thermal boundary resistance between the nanostructure and the surrounding host matrix into account. Numerical results show that the interfacial thermal boundary resistance and dimensionality of the nano inclusion significantly affects the thermal conductivity enhancement of such nanocomposites. For a fixed nanomaterial loading of 1vol%, spherical nanoparticle inclusions enhance the melting rate only by ∼2%. The inclusion of 1vol% loading of single-walled carbon nanotube and graphene nanoplatelets increases the melting rate by 27% and 40% respectively due to significant thermal conductivity enhancement of the nanocomposite compared to that of pure organic alkane.

Multipurpose experimental characterization of smart nanocomposite cement-based materials for thermal-energy efficiency and strain-sensing capability

Novel nanocomposite smart multifunctional materials are emerging as promising technological advances in construction industry, where thermal-energy efficiency needs should meet environmental sustainability and mechanical performance requirements. In this view, new cement-based materials showed encouraging results in terms of added functional properties combining all the above mentioned capabilities with electrical conductivity and self-sensing potential for a variety of field scopes, e.g. vibration measurements, damage detection, structural health monitoring, electromagnetic shielding, self-heating pavements for deicing and more. The present paper deals with the development and multipurpose experimental characterization of cement-based materials doped with different carbon nanoinclusions consisting of: multi-walled carbon nanotubes, carbon nanofibers, carbon black, and graphene nanoplatelets. The study investigates morphology, optical features, thermal characteristics, electrical properties and strain-sensing capability of the different composites, through a campaign of in-lab experimental measurements. The results highlight the peculiar behavior of each composite material, which is strictly related to the adopted nanoinclusions, that reveal to be suitable for specific purposes. In particular, all carbon nanoinclusions are seen to reduce solar reflectance capability, while they produce negligible variations in thermal emittance. Graphene nanoplatelets represent the most effective nanoinclusion to increase thermal conductivity and diffusivity, which is related to their structural and geometrical characteristics and better capability to distribute the thermal wave. Consistently, the same graphene samples produce the largest electrical conductivity and capacitance. However, multi-walled carbon nanotubes, even though providing comparatively smaller contributions to electrical conductivity, are seen to be the best nanoinclusions for providing strain-sensing capabilities to the cement-based composites.

Enhanced thermal conductivity of phase change nanocomposite in solid and liquid state with various carbon nano inclusions

We report contrasting enhancement in the solid state and liquid state thermal conductivity of phase change nanocomposite seeded with various carbon nano inclusions. Phase change nanocomposites were prepared using n-Dodecanoic acid as the host matrix. Single-walled carbon nanohorns, multi-walled carbon nanotubes and few-layer graphene nanosheets were considered as the nano inclusions. Thermal conductivity measurements were carried out using a custom built transient hotwire technique. The thermal conductivity enhancement significantly depends on the shape and aspect ratio of the nano inclusions. Maximum thermal conductivity enhancement was obtained in the presence of graphene nanosheets as the nanofiller candidate followed by carbon nanotubes and carbon nanohorns. The thermal conductivity enhancement was significantly higher in the solid state than the liquid state of the material for all the nano composites. Thermal conductivity enhancement results were compared with the effective medium theory calculations and Yamada-Ota model calculations considering the role of interfacial thermal resistance between the nanomaterial and the surrounding host matrix. The model calculations show that that the interfacial thermal resistance significantly limits the thermal conductivity enhancement in the liquid state compared to the solid state. The model calculations also show that interfacial thermal resistance is an order of magnitude higher at the solid-liquid interface compared to that of solid-solid interface which leads to a contrasting thermal conductivity enhancement in liquid and solid state of the nanocomposites.

Simulation of the adhesion properties of the polyethylene/carbon nanotube interface

The properties of a polyethylene matrix in contact with carbon nanoinclusions, such as carbon nanotubes and graphene plates, are studied via the molecular-dynamics method. Ultimate shear stresses for the polyethylene/graphene interface are calculated, and the effect of the filler aspect ratio on the nanocomposite elastic modulus is considered.

Nanoglasses and amorphous nanocrystalline materials: Some new approaches

This work is devoted to nanoglasses obtained by the consolidation of amorphous nanoparticles and other methods. The structure and properties of these materials areanalyzed. The manifestation of ductility in metallic glasses is emphasized. The properties and fields of application of film composites based on carbon nanoinclusions and refractory compounds in amorphous matrices are described. The problems requiring further studies are stressed.

Investigation of surface film nanostructure and assessment of its impact on friction force stabilization during automotive braking

Abstract The unique nanostructure formed during severe as well as moderate braking on the surface of brake discs was investigated by conventional and analytical Transmission Electron Microscopy. In both cases nanocrystalline magnetite mixed with carbon nanoinclusions and minor amounts of other pad constituents were identified. On the basis of these observations the friction performance of a single micro-contact was simulated with the method of Movable Cellular Automata. Inspite of a simplified nanostructure which was examined in two dimensions only, the calculated mean coefficient of friction fitted well to the value usually demanded for automotive braking. Furthermore, the model predicts that oxide films without soft nanoinclusions are not capable of providing smooth velocity accommodation at the pad–disc interface and thus lead to unstable friction behaviour.