0000000000170169
AUTHOR
Federico Micciulla
showing 13 related works from this author
Heat-resistant unfired phosphate ceramics with carbon nanotubes for electromagnetic application
2014
Composite materials, containing low concentrations of carbon nanotubes (CNTs) of three different diameters and heat-resistant phosphate ceramic as a matrix were prepared by cold-pressing method. Their dielectric properties were studied at room temperature in a wide frequency range (20 Hz–1 MHz). It was found experimentally and proved theoretically via modeling of the composites as a random capacitor–resistor–diode network that electrical percolation concentration depends significantly on the diameter of the nanoinclusions. The main conclusion is that the best candidate providing both the lower percolation threshold and high absolute values of ac conductivity is thinner carbon nanotubes (in …
Nanocomposites of epoxy resin with graphene nanoplates and exfoliated graphite: Synthesis and electrical properties
2014
Nanocomposites are nowadays one of the most promising materials. Among different fillers, e.g. carbon nanotubes and silicon carbide nanowires (NWSiC), already used with epoxy resin matrices, graphene exfoliated graphite (EG) and graphene nanoplates have some characteristics that make them unique for electromagnetic shielding materials. However, there is still an unresolved problem of proper dispersion that will ensure the homogeneity of samples. To overcome this drawback, inorganic fibres were proposed. An amount of 0.25 phr (parts per hundred; filler content presented as wt.% of the whole polymeric matrix) NWSiC, added to the EG 1 phr/epoxy resin sample, efficiently prevents filler agglome…
Electrical transport in carbon black-epoxy resin composites at different temperatures
2013
Citation: J. Appl. Phys. 114, 033707 (2013); doi: 10.1063/1.4815870 (Received 3 May 2013; accepted 27 June 2013; published online 17 July 2013) Results of broadband electric/dielectric properties of different surface area—carbon black/epoxy resin composites above the percolation threshold are reported in a wide temperature range (25–500 K). At higher temperatures (above 400 K), the electrical conductivity of composites is governed by electrical transport in polymer matrix and current carriers tunneling from carbon black clusters to polymer matrix. The activation energy of such processes decreases when the carrier concentration increases, i.e., with the increase of carbon black concentration…
DIELECTRIC PROPERTIES OF EPOXY RESIN COMPOSITES FILLED WITH NANOCARBON INCLUSIONS
2013
The epoxy resin composites with various carbon additives were investigated in the frequency range of 20 Hz - 3 GHz at temperatures from room to 500 K. The dielectric properties were found to be strongly impacted by percolation threshold. The lowest percolation threshold (< 0.25 wt.%), was observed in composites with single-walled carbon nanotubes.
Electromagnetic shielding efficiency in Ka-band: carbon foam versus epoxy/carbon nanotube composites
2012
The wide application of microwaves stimulates searching for new materials with high electrical conductivity and electromagnetic (EM) interference shielding effectiveness (SE). We conducted a comparative study of EM SE in K a -band demonstrated by ultra-light micro-structural porous carbon solids (carbon foams) of different bulk densities, 0.042 to 0.150 g/cm 3 , and conventional flexible epoxy resin filled with carbon nanotubes (CNTs) in small concentrations, 1.5 wt.%. Microwave probing of carbon foams showed that the transmission through a 2 mm-thick layer strongly decreases with decreasing the pore size up to the level of 0.6%, due to a rise of reflectance ability. At the same time, 1 mm…
Preliminary studies on nanocomposite based on high quality Silicon Carbide nanofibers
2012
Nanocomposites are nowadays the most promising new materials due to their unique properties (such as high mechanical strength, chemical and thermal resistance). The nanocomposite matrix is blended with a nanostructured filler. In this study, Silicon Carbide nanofibers (NFSiC) and their bundles were tested as a reinforcement of two epoxy resins: EPIKOTE 828 and EL 20. PAP-4 (33 phr) and P-900 (40 phr) were used as hardeners in the two cases, respectively. Several samples were prepared in the range between 0.1 and 5 % wt for both types of resins and fillers (NFSiC and NFSiC bundles). Mechanical and electrical properties were tested. The fillers were obtained using a new simple, fast, low-cost…
Epoxy composites filled with high surface area-carbon fillers
2013
Citation: J. Appl. Phys. 114, 164304 (2013); doi: 10.1063/1.4826529 (Received 24 July 2013; accepted 6 October 2013; published online 22 October 2013) A comprehensive analysis of electrical, electromagnetic (EM), mechanical, and thermal properties of epoxy resin composites filled with 0.25–2.0 wt. % of carbon additives characterized by high surface area, both nano-sized, like carbon nanotubes (CNTs) and carbon black (CBH), and micro-sized exfoliated graphite (EG), was performed. We found that the physical properties of both CNTs- and CBH-based epoxy resin composites increased all together with filler content and even more clearly for CBH than for CNTs. In the case of EG-based composites, go…
Microwave response properties of epoxy resin composites filled with graphitic fillers
2014
Composite materials based on epoxy resin filled with various kinds of graphite particles: exfoliated graphite (EG), natural graphite, and coarse, medium and fine artificial graphites have been prepared. The dielectric permittivity strongly increases with graphite particle size. This effect is related to the distance of the investigated filler concentrations to the composites' percolation threshold. Microwave experiments show that exfoliated graphite is, out of investigated graphite particles, the only one being a really effective additive for producing electromagnetic (EM) interference (EMI) shielding: 2 wt.% epoxy/EG is absolutely opaque to electromagnetic radiation at 30 GHz.
Epoxy Resin/Carbon Black Composites Below the Percolation Threshold
2013
International audience; A set of epoxy resin composites filled with 0.25-2.0 wt.% of commercially available ENSACO carbon black (CB) of high and low surface area (CBH and CBL respectively) has been produced. The results of broadband dielectric spectroscopy of manufactured CB/epoxy below the percolation threshold in broad temperature (200 K to 450 K) and frequency (20 Hz to 1 MHz) ranges are reported. The dielectric properties of composites below the percolation threshold are mostly determined by alpha relaxation in pure polymer matrix. The glass transition temperature for CB/epoxy decreases in comparison with neat epoxy resin due to the extra free volume at the polymer-filler interface. At …
Cadmium clusters in CdI2layered crystals: the influence on the optical properties
2007
The influence of overstoichiometric Cd i atoms on the optical properties of cadmium iodide layered crystals has been investigated. The results of optical absorption, luminescence, and luminescence excitation studies of CdI 2 crystals with controlled deviation from stoichiometric composition allow observing correlations between the Cd i concentration and features in absorption and emission spectra up to concentrations of 10 18 cm -3 . At higher concentrations the overstoichiometric cadmium atoms form clusters, which were observed using scanning electron microscopy. The extinction spectra of (CdI i ) n clusters are calculated in the frame of Mie theory and are found to correlate with the opti…
Novel non-destructive evaluation technique for the detection of poor dispersion of carbon nanotubes in nanocomposites
2019
Abstract A wide use of advanced carbon nanotube polymer composites can be boosted by new non-destructive evaluation (NDE) techniques that can test the quality of the products to ensure that their specifications are met. It is well known in literature that the parameter that far more than others can affect the enhancing capabilities of the carbon nanotubes is their dispersion. Here we have presented a novel NDE technique based on infrared thermography able to evaluate the dispersion of the added nanoparticles in polymer nanocomposites. The NDE technique was used to compare pairs of samples whose difference is represented only by the level of dispersion. It was found a significant difference …
Bottom-up realization and electrical characterization of a graphene-based device.
2016
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 …
Dielectric properties of graphite-based epoxy composites
2014
International audience; Composite materials based on epoxy resin filled with various kinds of graphite particles: exfoliated graphite, natural graphite, and coarse, medium and fine artificial graphites have been prepared. Results of broadband dielectric investigations of such materials in wide temperature (25-450 K) and frequency (20 Hz-3 THz) ranges are presented. The dielectric permittivity strongly increases with graphite particle size. The graphite particle size and shape also have a strong impact on freezing temperature, conductivity activation energy and composite electromagnetic absorption properties at room temperature. The lowest percolation threshold is observed for exfoliated gra…