RESUMEN
The exfoliation of graphite to graphene nanoplatelets (GnP) in a molten salt medium is investigated in this study. It is shown that this mechanical force-free process yielded a large-sized GnP product (>15 microns) with a low defect density. The effect of the surface tension of the molten salt on graphite exfoliation efficiency was investigated for a series of alkali chloride salts (CsCl, KCl, NaCl and eutectic NaCl-KCl) at 850 °C. It was demonstrated that the produced GnP could be completely and easily separated from the salt. Molten salt with the lowest value of surface tension (CsCl) displayed the highest wettability of the graphitic layers and hence facilitated total exfoliation of the graphite to GnP. The exfoliation of graphite in molten salts is applicable in the thermal energy storage field, as well as in exfoliation of other layered materials. Herein, it is demonstrated that the thermal conductivity of the GnP-CsCl composite is enhanced by â¼300% compared to the neat salt.
RESUMEN
Oil was employed as an 'entrance door' for loading rubber with carbon-based fillers of different size and dimensionalities: 1D carbon nanotubes (CNTs), 2D graphene nanoplatelets (GNPs), and 3D graphite. This approach was explored, as a proof of concept, in the preparation of tire tread, where oil is commonly used to reduce the viscosity of the composite mixture. Rubber was loaded with carbon black (CB, always used) and one or more of the above fillers to enhance the thermal and mechanical properties of the composite. The CNT-loaded system showed the best enhancement in mechanical properties, followed by the CNT-GNP one. Rubber loaded with both graphite and GNP showed the best enhancement in thermal conductivity (58%). The overall enhancements in both mechanical and thermal properties of the various systems were analyzed through an overall relative efficiency index in which the total filler concentration in the system is also included. According to this index, the CNT-loaded system is the most efficient one. The oil as an 'entrance door' is an easy and effective novel approach for loading fillers that are in the nanoscale and provide high enhancement of properties at low filler concentrations.
RESUMEN
An oil-based composite is employed to monitor the exposure to oxygen inside food packaging, aiming at evaluating the package integrity and the freshness of food. The composite is an oxygen-sensitive printable ink consisting of electrically conductive silver microflakes, embedded in a vegetable oil matrix. The sensitivity of the oil to oxygen is driven by its high content of unsaturated fatty acids that polymerize and shrink upon exposure to atmospheric oxygen. Shrinkage increases the silver concentration and induces percolation, manifested by a steep increase in the electrical conductivity of the composite. We found that the electrical conductivity of the composite is related to its exposure time to air. Employing linseed oil as a matrix demonstrates an increase in electrical conductivity from 10-11 to 10-3 S/cm after only 6 days of exposure to air. We also show that this time span could be modified by changing the oil type to fit various expiration periods of food products.