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

Electromagnetic and electromechanical applications of graphene-based materials

This volume contains the extended abstracts of the contributions presented at the workshop Nanoscale Excitations in Emergent Materials (NEEM 2015) held in Rome from 12 to 14 October 2015, an event organized and supported in the framework of the Bilateral Cooperation Agreement between Italy and India within the project of major relevance "Investigating local structure and magnetism of cobalt nano-structures", funded by the Italian Ministry of Foreign Affairs and the Department of Science and Technology in India

Vernice polimerica conduttiva piezoresistiva a base acquosa contenente grafene per applicazioni elettromagnetiche e di sensoristica

La presente invenzione si colloca nell’ambito delle nanotecnologie e più specificatamente si riferisce alla realizzazione di nuovi materiali nano strutturati e a base grafene, dotati di proprietà elettriche, elettromagnetiche, elettromeccaniche controllate. In particolare la presente invenzione riguarda la formulazione e l’ottenimento di una vernice polimerica a base acquosa, che presenta proprietà elettriche ovvero piezoresistive ovvero elettromagnetiche controllate, partendo da una vernice polimerica a base acquosa commerciale ovvero da una soluzione liquida polimerica a base acquosa caricata con nanoplacchette di grafene (GNP), ottenute mediante esfoliazione di grafite espansa. Tale vernice è utilizzabile in applicazioni di schermatura elettromagnetica (ad esempio per la realizzazione di materiali con proprietà radar assorbenti (RAM)) ovvero per la realizzazione di dispositivi antistatici o di rivestimenti piezoresistivi per il monitoraggio distribuito dello stato di deformazione di una struttura. Oltre alle suddette caratteristiche elettriche, piezoresistive ed elettromagnetiche, i rivestimenti così ottenuti risultano leggeri, facilmente lavorabili, e adatti per essere deposti su qualsiasi substrato

RF shielding performance of thin flexible graphene nanoplatelets‐based papers

Thin and flexible freestanding graphene nanoplatelets (GNPs)-based paper-like materials are fabricated and experimentally characterized to assess their employment as radiofrequency electromagnetic interference shields. Samples are obtained by vacuum filtration of ultrasonicated suspensions. Different suspensions are prepared by mixing either acetone/DMF or acetone/NMP and worm-like exfoliated graphite expanded at the temperature of 1150 °C or 1250 °C for 5s. We investigated the effect of thermal annealing and mechanical compression on the sheet resistance, thickness, dc electrical conductivity and electromagnetic shielding of the produced GNP papers. Their shielding effectiveness (SE) is measured in the frequency range 10 MHz-18 GHz and validated by simulations. Electrical conductivity of 144 kS/m and SE as high as 55 dB are reached for a few microns thick GNP paper subjected to a compression of 5 MPa

Water-based Piezoresistive Conductive Polymeric Paint Containing Graphene for Electromagnetic and Sensor Applications

The present invention belongs in the field of nanotechnologies and more specifically regards production of new nanostructured and graphene-based materials, presenting controlled electrical, electromagnetic, and electromechanical properties. In particular, the present invention regards formulation and production of a water-based polymeric paint, which has controlled electrical or else piezoresitive or else electromagnetic properties, starting from a commercial water-based polymeric paint or else from a water-based polymeric liquid solution filled with graphene nanoplatelets (GNPs), obtained by means of exfoliation of expanded graphite. Said paint can be used in electromagnetic-shielding applications (for example, for producing radar-absorbent materials – RAMs) or else for producing antistatic devices or piezoresistive coatings for distributed monitoring of the state of strain of a structure. In addition to the aforesaid electrical, piezoresistive, and electromagnetic characteristics, the coats thus obtained are light, easy to process, and suitable for being laid on any substrate. All the purposes of the invention have been achieved through the process according to Claims 1 to 13. The process developed for producing said paint is simple, inexpensive, fast, and suitable for low-cost mass production. Moreover, it makes use of alcohol-water mixtures as solvent. It envisages the following steps: a) subjecting commercial graphite intercalation compound (GIC) to thermal expansion to obtain known structures such as TEGO, WEG, or expanded graphite (EG), or else using EG of a commercial type; b) dispersing and shredding said TEGO, WEG, or EG structures in water-based paint/ polymer possibly diluted with alcohol-water mixture, in variable concentrations according to the desired final properties; and c) subjecting the suspension to ultrasonication, wherein the parameters of the sonication cycle such as the temperature of the suspension, the energy released and the duration are defined on the basis of the properties of the material that is to be obtained. The paint can be laid with multiple techniques, such as, by way of non-limiting example, spraying, dip-coating, and ink-jet. Advantageously, according to the invention, it is possible to control the electrical, piezoresistive, and electromagnetic properties of the coating obtained with said paint through: 1. the amount of GNPs dispersed within the matrix; 2. appropriate definition and concentration of the alcohol-water mixture used as solvent; and 3. control of the dispersion of the GNPs within the paint, wherein said control is obtained through the sequential action of a mechanical rod stirrer, which has the function of shredding the expanded graphite in suspension, and of a sonicator with ultrasound tip, which has the function of exfoliating and dispersing the expanded graphite previously shredded

Electrical and electromechanical properties of stretchable multilayer-graphene/PDMS composite foils.

Multilayer graphene (MLG)/polydimethylsiloxane (PDMS) composite foils are developed for possible application in wearable electronics as stretchable conductors or in strain sensing. The MLG/PDMS foils are prepared through infiltration of PDMS into porous freestanding MLG papers. The freestanding MLG papers are first produced through vacuum filtration of MLG-flake suspensions and are characterized by sheet resistance in the range from ~0.7 to ~1.1 Ω/□ and average thickness in the range from ~75 to ~110 μm. The electromechanical characteristic of the produced MLG/PDMS foils is assessed experimentally by measuring the dc electrical resistance of the produced specimen during tensile strength tests. It results that the breaking load of the new composite foils, occurring after an elongation of ~11 mm, which corresponds to a deformation of ~80%, is nearly doubled with respect to the one of neat PDMS. Moreover, for an elongation up to 2 mm the total dc resistance of the foil exhibits an increase lower than the 20% of its original value

Electromechanical characterization of flexible and highly conducting multilayer graphene/polydimethylsiloxane composite paper

Multilayer graphene (MLG)/polydimethylsiloxane (PDMS) composite has been prepared by infiltrating free-standing MLG paper, obtained through the vacuum filtration of MLG-suspension using a nanoporous filter, with PDMS prepolymer. Electrical properties of both free-standing MLG paper and MLG/PDMS composite paper were investigated by four-point probe measurements. The obtained results show that the annealed MLG paper is characterized by a sheet resistance of ~ 0,69 Ω/□ which does not increase significantly with polymer infiltration. Moreover the electromechanical behaviour of the composite paper has been investigated experimentally by measuring the DC electrical resistance of the produced specimen during a tensile strength test. It results that the breaking of composite paper occurs at ~ 80% strain, like for the neat polymer, but with a more than doubled applied load. Furthermore, it is noted that for strain smaller than ~ 10%, the electrical resistance of MLG/PDMS composite paper is nearly constant

Synthesis and DC Electrical Conductivity Studies of Multilayer Graphene/Zinc Oxide Nanowires Composite Foils

Flexible composite foils made up of multilayer graphene (MLG) and ZnO nanowires (ZnO-NW) are produced via vacuum filtration of acetone-based suspension. The sheet resistance and effective dc electrical conductivity of the foils, with increasing content of ZnO-NW over a fixed amount of MLG, is measured in order to investigate the effect of ZnO inclusion in MLG papers. An enhancement in the dc conductivity of the composite foils with respect to a plain MLG-foil is noticed only for very low amounts of ZnO loading. The peak conductivity of 16.8 kS/m, representing an increase of 31% with respect to the conductivity of a plain MLG-foil, is observed at the optimum concentration of 10%wt ZnO over the MLG content. This confirms the physical and electronic interaction at the interface between MLG and ZnO-NW. At higher concentration of ZnO-NW, a linear decay in the effective conductivity of the foils is observed

Highly conductive multilayer-graphene paper as a flexible lightweight electromagnetic shield

A graphene-based porous paper made of multilayer graphene (MLG) microsheets is developed for application as a flexible electrically conducting shielding material at radio frequency. The production process is based on the thermal expansion of a graphite intercalated compound, the successive liquid-phase exfoliation of the resulting expanded graphite in a proper solvent, and finally the vacuum filtration of the MLG-suspension using a nanoporous alumina membrane. Enhancement of the electrical conductivity and electromagnetic shielding properties of the MLG paper is achieved by gentle annealing at 250 °C overnight, and by mechanical compression at 5 MPa. The obtained results show that the developed MLG papers are characterized by an electrical conductivity up to 1443.2 S/cm, porosity around 43%, high flexibility, shielding effectiveness up to 55 dB at 18 GHz with a thickness of 18 μm. Numerical simulations are performed in order to understand the main factors contributing to the shielding performance of the new materia