Characterization of the thermal conductivity and diffusivity of graphene nanoplatelets strips: a low-cost technique.

This paper proposes a new technique to characterize the thermal conductivity and diffusivity of thin strips made by graphene nanoplatelets (GNP). The evaluation of these parameters is essential for a reliable design of thermal and electrothermal applications of graphene and is usually performed by means of assessed but expensive techniques such as those based on Raman effects and laser flash. The technique proposed here is simpler and less demanding in terms of equipment, and combines the results of an experimental characterization of the strip heated by the Joule effect obtained with infrared camera, with those provided by an electro-thermal model. Specifically, the evaluation of the thermal conductivity and diffusivity is the result of the analysis of the transient behavior of the measured and simulated solutions. The methodology is here successfully validated by applying it to commercial graphene strips and benchmarking against the thermal parameters provided by the manufacturers. Then, a complete characterization is provided for commercial strips based on different formulations of GNP and binders such as polyurethane, epoxy resin, and boron nitride. For these materials, the values of thermal conductivity and diffusivity are found in the ranges (50-450) W m-1K-1and (0.5-3.5) × 10-4m2s-1, respectively.

Temperature-dependent electrical resistivity of macroscopic graphene nanoplatelet strips.

This paper studies the temperature dependence of the electrical resistivity of low-cost commercial graphene-based strips, made from a mixture of epoxy and graphene nanoplatelets. An equivalent homogenous resistivity model is derived from the joint use of experimental data and simulation results obtained by means of a full three-dimensional (3D) numerical electrothermal model. Three different types of macroscopic strips (with surface dimensions of cm2) are analyzed, differing in their percentage of graphene nanoplatelets. The experimental results show a linear trend of resistivity in a wide temperature range (-60°C to +60°C), and a negative temperature coefficient . The derived analytical model of temperature-dependent resistivity follows the simple law commonly adopted for conventional conducting materials, such us copper. The model is then validated by using the graphene strips as heating elements by exploiting the Joule effect. These results suggest that such materials can be used as thermistors in sensing or heating applications.

A monitorable and renewable pollution filter based on graphene nanoplatelets.

This paper deals with the fabrication, modeling and experimental characterization of a monitorable and renewable graphene-based pollution filter. The main goal is to demonstrate a method to monitor the status of such a filter in real time during its operating phases: pollutant adsorption, saturation, and regeneration. The filter is realized by a disk of pressed graphene nanoplatelets. This is a low-cost type of graphene which has recently drawn great interest due to its potential use in large scale industrial production. Here the nanomaterial is obtained through the exfoliation method assisted by microwave irradiation, by exploiting the thermal expansion of commercial intercalated graphite, according to a low-cost and ecologically friendly procedure. The filter is used here to adsorb acetonitrile, a toxic water-soluble organic compound that is present in some industrial solvents and paints. The monitoring method is based on the interpretation of the time variation of the electrical impedance measured during filter operation. There are two main results of the paper: Firstly, the graphene filter is shown to be effective in adsorbing the above pollutant, with the additional feature of being fully renewable: all the pollutant can be removed from the filter without the need of costly physical or chemical processes. Secondly, monitoring of the time-evolution of the electrical impedance allows efficient detection of the different phases of the filter life cycle: clean, polluted, saturated and regenerated. This feature is of potential interest since it enables the predictive maintenance of such filters.

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 gas sensor is demonstrated by measuring the sensitivity of its electrical resistance to the presence of gas. The measured results demonstrate a good degree of reproducibility in the fabrication process, and the competitive performance of devices, thus making the proposed technique potentially attractive for industrial applications.

[Prophylaxis of superficial tumors of the bladder with interferon alfa-2B]. / Profilassi dei tumori superficiali della vescica con interferone alpha 2b.

The AA. report the results obtained on patients suffering from surface bladder cancer [Ta-T1 (G1-G2)] treated with alpha 2b interferon with the aim to elongate the relapse period. The results turned out to be very satisfactory as concerns the tolerability of the drug as well as the actual improvement in relapse onset. Moreover, the AA. could notice the grading steadiness or decrease, as to neglistic relapses.

[Percutaneous punctures guided by echography]. / La puntura percutanea guidata dall'ecografia.

It is possible to carry out percutaneous injections of lesions in any organ under the direction of echography. This is particularly so in the liver, pancreas and kidney. The procedure has been used in 79 patients for diagnostic and/or therapeutic purposes and has provided very good and promising results. The technique is harmless, causes only minimum discomfort to the patient and, in many cases, enables the routine diagnostic approach to be short-circuited because more laborious, expensive techniques can be avoided.