Multilayer Graphene Nanoplatelets Research Articles

Electro-Mechanical Properties of Multilayer Graphene-Based Polymeric Composite Obtained through a Capillary Rise Method.

A new sensor made of a vinyl-ester polymer composite filled with multilayer graphene nanoplatelets (MLG) is produced through an innovative capillary rise method for application in strain sensing and structural health monitoring. The new sensor is characterized by high stability of the piezoresistive response under quasi-static consecutive loading/unloading cycles and monotonic tests. This is due to the peculiarity of the fabrication process that ensures a smooth and clean surface of the sensor, without the presence of filler agglomerates acting as micro- or macro-sized defects in the composite.

Free and forced vibrations of functionally graded polymer composite plates reinforced with graphene nanoplatelets

This paper investigates the free and forced vibration characteristics of functionally graded multilayer graphene nanoplatelet (GPL)/polymer composite plates within the framework of the first-order shear deformation plate theory. The weight fraction of GPL nanofillers shows a layer-wise variation along the thickness direction with GPLs uniformly dispersed in the polymer matrix in each individual layer. The effective Young’s modulus is predicted by the modified Halpin-Tsai model while the effective Poisson’s ratio and mass density are determined by the rule of mixture. Governing differential equations of motion are derived and Navier solution based technique is employed to obtain the natural frequencies and dynamic response of simply supported functionally graded GPL/polymer plates under a dynamic loading. A parametric study is conducted, with a particular focus on the effects of GPL distribution pattern, weight fraction, geometry and size as well as the total number of layers on the dynamic characteristics of the plates.

Measuring the Thermal Diffusivity of Multi-Layered Graphene Nanoplatelets (GNPs) by a Periodic Heating Method

The present paper describes ways of increasing the accuracy of measurements of thermophysical properties (namely, thermal diffusivity) of materials. The knowledge of these characteristics is very important for modeling industrial processes, since their high-accuracy determination can reduce wasteful consumption of energy resources while developing novel thermal insulation materials, technologies, as well as methods for building construction. The method proposed herein is based on periodic heating and can be used to improve the measurement accuracy and find the optimal parameters for producing thermal insulation materials. Periodic temperature oscillations were generated by means of the Peltier element. Mathematical and physical models were developed, and the measurement setup was automated using the LabView graphical programming environment. The analysis of possible error sources was performed, and the ways of decreasing error values were suggested. The equipment was experimentally calibrated using a standard material (Plexiglas), and the obtained data proved the appropriateness of the developed mathematical model. Moreover, a number of tests were performed with a nanomaterial, namely, graphene nanoplatelets (GNPs). The proposed method and the experimental measurement setup made it possible to reveal a strong dependence between the thermal diffusivity of the GNPs and the moisture content. This finding will be considered in further studies concerning the above-mentioned nanomaterial.

Optical Properties and Aggregation of Graphene Nanoplatelets

In the present paper, the optical density of dispersions of randomly oriented multilayer graphene nanoplatelets (GNPs) was estimated. Calculated and experimental data were compared for aqueous GNP dispersions stabilized with various surfactants. It was shown that the sonication of an expanded graphite compound (EGC) in aqueous surfactant solutions leads to the transformation of EGC worm-like particles into weak GNP aggregates which are able to pass into solution upon dilution and agitation of the system. They may be filtered and washed out of surfactants. The concentrated GNP dispersions containing these weak aggregates can be used to synthesize different graphene-based nanostructures and obtain novel composite materials.

Simultaneous ultrasonication‐assisted internal mixing to prepare MWCNTs‐filled epoxy composites with increased strength and thermal conductivity

The uniform dispersion of carbon nanotubes in epoxy resin is one of the key factors to achieve the composites with desirable mechanical and physical property enforcement. However, the widely used dispersion methods have their own respective limitations in pursuing satisfactory nanotube dispersion. Herein, a new dispersion approach, based on the synergetic effect of combining high speed internal mixing with running simultaneously continuous ultrasonication treatment, has been proposed. The dispersion of nanotubes was carried out in a high speed internal mixer, consisting of twin kneading block structured rotors and an integrated ultrasonic horn, which was intercalated into the central position between the twin rotors. At first, the FEM simulation was conducted to optimize the kneading element assembly and illuminate the geometry influence of the ultrasonic horn intercalation on the mixing flow. Afterwards, to confirm the feasibility of the approach, pristine MWCNTs (P‐CNTs), oxidation modified MWCNTs (M‐CNTs) and M‐CNTs/multilayer graphene nanoplatelets (MGPs) hybrid are dispersed into epoxy resin. The dispersion of each sample in its liquid epoxy state is investigated under transparent optical microscopy. More characterizations, including SEM, TG/DTA, tensile test, and thermal conductivity measurements, were conducted on the cured composites. Competitive reinforcements on mechanical tensile property and thermal conductivity were observed. Especially, at a 1.5 wt% M‐CNTs/MGPs hybrid content, the composite mechanical tensile strength and thermal conductivity were 47% and 30% higher than those of neat epoxy. This preliminary study demonstrates the feasibility and practicability of the proposed approach to achieving good MWCNTs dispersion and distribution in epoxy resin. POLYM. COMPOS., 37:870–880, 2016. © 2014 Society of Plastics Engineers