Abstract

In the current work we present a series of nanocomposite materials printed via stereolithography using an acrylic organic matrix together with graphite nanoplatelets (GNP) as inorganic filler. It was generally observed that presence of GNP decreases the mechanical properties with respect to the unmodified resin, probably because the presence of pores around GNP. However, composites containing 2.5 wt% GNP showed electrical resistivity values in the range of 10⁶ Ohm·cm, nine orders of magnitude below unmodified resin. In these conditions we state we have a material with characteristic semiconductive properties.

Abstract

Currently, due to the great advances achieved in medicine, together with those related to materials science and engineering, in recent years there has been a growing interest in the use of flexible sensors for monitoring the human body. The present work shows the development of flexible piezoresistive sensors based on polyvinylidene fluoride (PVDF) reinforced with carbon nanotubes (CNTs). First, the analysis of the electrical properties shows an increase in the electrical conductivity with CNT content. This increase is less pronounced at higher CNT contents due to an electrical network saturation, where the main electrical transport mechanisms are dominated by the CNT aggregates. In this context, the electromechanical analysis shows a higher sensitivity, by means of Gauge Factor, at lower CNT contents due to a higher prevalence of tunneling transport mechanisms between neighboring nanoparticles, which is reflected in a more exponential electromechanical behavior. Finally, the analysis of the electromechanical properties at cycling loading shows an elevated repeatability of the electrical response between consecutive cycles, which is indicative of the high robustness of the manufactured sensors.

Abstract

Heat dissipation is an issue that is acquiring great importance to increase the efficiency in the utilization of the energy and extending the lifespan of the equipment. Traditionally, heat dissipation has been carried out using metals, but the increase in the requirements of equipment and devices, composites have gained importance. Graphite based composites have relevance in heat dissipation, particularly when the disperse material is a metal or metal carbide. The reason is the great value of thermal conductivity combined with good mechanical properties and lightness. Research has focused until nowadays on the composite graphite-MoC, although there are other composites with great potential, as that proposed in this manuscript: graphite- Cr3C2. The preparation of the composite graphite-Cr3C2 consisted in mechanical mixing of the staring powders, subsequent obtaining of the green compact of 40 mm in diameter and, finally, sintering at 2000 °C for 20 minutes under an applied pressure of 30 MPa in the Spark Plasma Sintering apparatus. The sintered material exhibited electrical and thermal conductivities in the in-plane direction of 1.08 MS/m and 215 W/m · °C, respectively, and a flexural strength of 113 MPa, which makes this material a suitable candidate for its application in heat dissipation.