Alberto Barone | Università degli Studi di Palermo (original) (raw)

Papers by Alberto Barone

Applied Surface Science, 2003

In usual dry laser cleaning of opaque samples, short laser pulses are projected onto the sample s... more In usual dry laser cleaning of opaque samples, short laser pulses are projected onto the sample surface to be cleaned. Energy transferred from light ejects extraneous particles away from the surface. Laser beam fluence is limited by the damage reached by high temperature that the sample surface can produce. We have experimentally shown that for thin samples, the thermo-elastic wave propagates within the whole sample thickness, thus also the rear surface, while temperature effects are limited to the front surface. Therefore, the proposed ''verso'' laser cleaning technique (the pulsed laser beam impinges on rear sample surface) can be applied to any opaque ''mechanically thin'' film and is useful for samples having delicate treatments on the surface to be cleaned (e.g. written paper, painted tiles, magnetic films). We have applied our technique to paper sheets showing that it is possible to efficiently clean the surface without damaging ink marks on it. Using a probe beam deflection (PBD) technique in both direct and reverse configuration we have shown that the ''verso'' cleaning effect is due to the higher penetration depth of the thermo-elastic wave with respect to the temperature profile propagation. #

Applied Surface Science, 2009

Exchange-coupled monocomponent magnetic films constituted of disk-shaped Ni and Fe nanoparticles ... more Exchange-coupled monocomponent magnetic films constituted of disk-shaped Ni and Fe nanoparticles were produced by ultrafast pulsed laser deposition, in vacuum. These films show a peculiar cauliflower-like structure, made of granular agglomerates of nanoparticles sticking to one another with a significant shape and orientation anisotropy. Both as-deposited Ni and Fe films present hysteresis loops with a high in-plane remanence ratio (0.61 and 0.81 at 250 K, respectively), relatively low values of the saturation and coercive fields and a steep slope near coercivity. At temperature of 10 K and 250 K, the magnetization curves confirm the strong influence of the production technique on the topologic structure of these films, and consequently on their magnetic properties. In perspective, the striking and intriguing properties of these nanogranular films appear very promising for potential application as permanent magnets and in data storage technology.

Journal of Materials Processing Technology, 2008

Giant magnetoresistance effect is found in films of magnetic nanoparticles uniformly mixed with n... more Giant magnetoresistance effect is found in films of magnetic nanoparticles uniformly mixed with non-magnetic metallic nanoparticles produced by ultrashort pulsed laser deposition (uPLD). The uPLD, which uses femtosecond laser pulses, has been recently reported as a powerful technique for obtaining nanoparticles and nanogranular films. As-deposited Co–Cu and Fe–Ag films in a moderate volume fraction range of magnetic component (15–25%) present detectable values of this magnetoresistive effect, although the average size of the particles is higher than in typical nanogranular materials for magnetoresistive applications. The determined longitudinal, transverse and perpendicular magnetoresistance behaviours, at the temperatures of 10 and 250 K, confirm the strong influence of the production technique on the complex microstructure of these films and consequently on their peculiar magneto-transport properties. In perspective, by optimizing the production parameters, these nanogranular films appear very promising for potential application in magnetic recording and data storage technology.

Sensors and Actuators A-physical, 2006

A mechanical vibration sensor based on a novel elastomagnetic composite made of magnetic micropar... more A mechanical vibration sensor based on a novel elastomagnetic composite made of magnetic microparticles uniformly dispersed in an elastic non-magnetic matrix is presented. A theoretical model predicting a linear behaviour of the sensor response with the vibration frequency and amplitude is reported. The obtained experimental results are in agreement with the model predictions for magnetic particle volume content lower than 15%. The ability of this kind of sensor to work at low frequencies, where other devices present a lack of reliability, is a very interesting characteristic of this elastomagnetic sensor.

Applied Surface Science, 2004

Laser-assisted particle removal has acquired a growing importance in last few years, finding appl... more Laser-assisted particle removal has acquired a growing importance in last few years, finding applications in several fields ranging from microelectronics to conservation and restoration of materials having cultural or historical interest. Recently new ‘indirect’ laser cleaning techniques such as ‘shock’ and ‘verso’ laser cleaning have been developed. Here we present a simple laser cleaning mechanical model in order to associate cleaning efficiency to surface deformation characteristics during cleaning pulse and apply it to examine the behaviour of ‘verso’ laser cleaning which has experimentally shown promising results on cellulosic (paper and cotton) materials.

Applied Surface Science, 2007

Nanoparticles were synthesized by irradiating a nickel target with femtosecond laser pulses in hi... more Nanoparticles were synthesized by irradiating a nickel target with femtosecond laser pulses in high vacuum, and subsequently analyzed. The proof-of-principle experiments aim to modify the size characteristics of the produced nanoparticles. For nickel it is found that: (i) ultraviolet laser pulses lead to a remarkable change in the nanoparticles size distribution with respect to visible laser pulses; (ii) irradiation of the femtosecond pulses induced ablation plume with a second, delayed ultraviolet laser pulse can change the size characteristics of the produced nanoparticles.

Proceedings of The Combustion Institute, 2009

In this work we compare the results of several nanoparticle measurement techniques with the aim o... more In this work we compare the results of several nanoparticle measurement techniques with the aim of investigating the formation of nanoparticles in non-sooting to slightly sooting flames. In slightly sooting conditions there is quite good agreement between Differential Mobility Analyser (DMA), Atomic Force Microscopy (AFM), and optical measurements on particle size and concentration. However, in rich flames below the onset of soot, DMA measures a strong drop-off in the total particle volume fraction at low fuel to air mixtures, which is not observed in optical or AFM measurements that detect a more gradual decrease in particle concentration with decreasing C/O and almost constant spectroscopic properties. The disagreement is significantly larger than experimental error and is only observed when the particle size distribution includes solely particles smaller than about 3 nm.Particle losses in the DMA sampling system does not seem to be the only possible reason for justifying the discrepancy with the other techniques. Further investigations are necessary in order to characterize chemically and physically this class of nanoparticles which constitute the earliest stage in the formation of particulate carbon.

Sensors and Actuators A-physical, 2005

The development of a novel magnetoelastic sensor, based on the stress influence on amplitude of t... more The development of a novel magnetoelastic sensor, based on the stress influence on amplitude of the resonant mechanical waves inside a Fe62.5Co6Ni7.5Zr6Cu1Nb2B15 ribbon, for strain and/or stress real-time monitoring in civil buildings is reported. This novel sensor exhibits better sensitivity than resistive and vibrating wire strain gauges, good reliability and stability.

Nanotechnology, 2006

This paper focuses on the development and optimization of electroplated cobalt-nickel (CoNi) allo... more This paper focuses on the development and optimization of electroplated cobalt-nickel (CoNi) alloys for use in biomedical microdevices. CoNi films were electrodeposited from glycine-containing electrolyte solutions at acidic pH. The influence of pH (2.5-5), temperature (55 and 80 • C), current density (from −5 to −40 mA cm −2 ), glycine concentration (0.5 and 1 mol dm −3 ) and the nature of the metal salts (chlorides or sulphates) on the composition and the magnetic properties of the films were systematically analyzed. The cobalt content varied between 50 and 83 wt% depending on the applied conditions. As a result, deposits showed variable morphologies, different structures (either hexagonal close-packed (hcp) or mixed hcp and face-centered cubic phases) and tunable magnetic properties, ranging from semi-hard (18.51 kA m −1 , i.e. 233 Oe) to very soft (1.43 kA m −1 , i.e. 18 Oe). To understand the role of glycine in this system, a comparison of the electrochemical processes, and the structural and magnetic properties is made for samples produced in glycine-containing and glycine-free baths.

Sensors and Actuators A-physical, 2006

The piezoresistivity in a heterogeneous material formed by conducting nickel particles uniformly ... more The piezoresistivity in a heterogeneous material formed by conducting nickel particles uniformly dispersed into a silicone-insulating matrix has been studied as a function of the filler content. A proper experimental apparatus was realized to investigate the direct dependence of resistivity on an uniaxial strain. In particular, when the volume fraction of the conductive charge approaches the conduction percolation threshold, at a proper value of the volume strain a little increment (2%) of the relative deformation can induce a transition from the insulating to conducting state accompanied by a giant resistivity change (about nine orders of magnitude). Some evidence that elastomer matrix properties contribute to determine both the peculiar development of the elasto-resistive coupling and its reversibility has been also found. The obtained results indicate the opportunity to optimize the investigated composite materials for the application as core of novel sensor devices governed by a threshold strain.

Combustion and Flame, 2003

Atomic Force Microscopy (AFM) has been used for the characterization of nanometric particles prod... more Atomic Force Microscopy (AFM) has been used for the characterization of nanometric particles produced in rich flames. Very small particles (about 2 nm) have been found in pre-inception region of soot forming premixed flames, whereas both small nanoparticles as well as large soot particles have been found in the soot region of the flames. The smaller particles are very flat in shape if compared with the bigger ones, and this probably depends upon the different nature of the collected particles.Particle size distribution functions are reported for different sampling conditions. The results of AFM measurements are in good agreement with previous measurements performed with ultraviolet (UV) light scattering/extinction technique on the same flames.

Proceedings of The Combustion Institute, 2005

The size distribution of the nanoparticles formed in premixed ethylene–air flames and collected t... more The size distribution of the nanoparticles formed in premixed ethylene–air flames and collected thermophoretically on mica cleaved substrates is obtained by atomic force microscopy (AFM). The distribution function extends from 1 to about 5 nm in non-sooting flames and in the soot pre-inception region of the richer flames, while it becomes bimodal and larger particles are formed in the soot inception region of the slightly sooting flames. The distribution is compared with the size distribution of nano-sized organic carbon (NOC) and soot particles, obtained by “in situ” multi-wavelength extinction and light scattering methods. The deposition efficiency is estimated from the differences between these two size distribution functions as a function of the equivalent diameter of the nanoparticles. Furthermore, the coagulation coefficient of particles in flame is obtained from the temporal evolution of the number concentration of the nanoparticles inside the flames. NOC particles, which are rapidly produced in locally rich combustion regions, have peculiar properties since their sticking coefficient both for coagulation and adhesion result to be orders of magnitudes lower than that expected by larger aerosols, like soot particles. The experimental results are interpreted by modelling the van der Waals interactions of the nanoparticles in terms of Lennard-Jones potentials and in the framework of the gas kinetic theory. The estimated adhesion and coagulation efficiencies are in good agreement with those calculated from AFM and optical data. The very low efficiency values observed for the smaller particles could be ascribed to the high energy of these particles due to their Brownian motion, which causes thermal rebound effects prevailing over adhesion mechanisms due to van der Waals forces.

Chemosphere, 2003

UV–visible extinction and scattering and two extra situ sampling techniques: atomic force microsc... more UV–visible extinction and scattering and two extra situ sampling techniques: atomic force microscopy (AFM) and differential mobility analysis (DMA) are used to follow the evolution of the particles formed in flames. These particle sizing techniques were chosen because of their sensitivity to detect inception particles, which have diameters, d<5 nm, too small to be observed with typical particle measurement instrumentation. The size of the particles determined by AFM and DMA compares well with the size determined by in situ optical measurements, indicating that the interpretation of the UV–visible optical signal is quite good, and strongly showing the presence of d=2–4 nm particles. UV–visible extinction measurements are also used to determine the concentration of d=2–4 nm particles at the exhausts of practical combustion systems. A numerical model, able to reproduce the experimentally observed low coagulation rate of nanoparticles with respect to soot particles, is used to investigate the operating conditions in the combustion chamber and exhaust system for which 2–4 nm particles survive the exhaust or grow to larger sizes. Combustion generated nanoparticles are suspected to affect human and environmental health because of their affinity for water, small size, low rate of coagulation, and large surface area/weight ratio. The ability to isolate nanoparticles from soot particles in hydrosols collected from combustion may be useful for future analysis by a variety of techniques and toxicological assays.

Environmental Engineering Science, 2008

ENVIRONMENTAL ENGINEERING SCIENCE Volume 25, Number 10, 2008 © Mary Ann Liebert, Inc. DOI: 10.108... more ENVIRONMENTAL ENGINEERING SCIENCE Volume 25, Number 10, 2008 © Mary Ann Liebert, Inc. DOI: 10.1089/ees.2007.0189 ... Coagulation of Organic Carbon Nanoparticles in Exhaust Conditions ... Gianluca Lanzuolo,1,* Lee Anne Sgro,1 Andrea De Filippo,1 ...

Applied Surface Science, 2005

We present femtosecond optical time-resolved pump-probe investigations of superconducting hybrids... more We present femtosecond optical time-resolved pump-probe investigations of superconducting hybrids structures consisting of Nb/NiCu bilayers with various thickness. Measurements performed on pure Nb and NiCu films are also given. The photoresponse experiments provide the quasiparticle relaxation times in bilayers of different thickness ratios. The study of the photoresponse as a function of the temperature reveals the spatial evolution of the superconductor order parameter across the bilayers. #

Sensors and Actuators A: Physical, 2005

The development of a versatile magnetoelastic sensor prototype for on-line elastic deformation mo... more The development of a versatile magnetoelastic sensor prototype for on-line elastic deformation monitoring and fracture alarm in civil engineering is reported. The sensor is based on the variation of resonant longitudinal magnetoelastic waves amplitude due to elastic status change in the amorphous Fe 62.5 Co 6 Ni 7.5 Zr 6 Cu 1 Nb 2 B 15 active core. Tests on a tufa wall under mass loading were conducted. The obtained results show a good reliability and sensitivity (1 mV/10 m) of the sensor response in the m-cm deformation range. The sensor is able to predict the approaching to the fracture regime, monitoring a preceding characteristic behavior.

Applied Surface Science, 2006

Ultrashort pulsed laser ablation in vacuum of different targets was performed in order to investi... more Ultrashort pulsed laser ablation in vacuum of different targets was performed in order to investigate the possibility of producing nanoparticles with controlled size and shape. A systematic morphology characterization of deposited products was performed for nickel and silicon as a function of laser pulse intensity and wavelength, at a fixed pulse repetition rate. The nanoparticles were investigated by atomic force microscopy, and clear trends for their size and shape anisotropy were evidenced. The best conditions to obtain nanosized particles of oblate ellipsoidal shape, with the minor axis below 10 nm, were determined in the case of nickel targets. Our results show that ultrashort pulse laser deposition can be considered as an interesting technique for the tailoring of nanogranular films with the desired particles dimension and shape, according to the peculiar properties required in specific applications. Moreover, the preliminary features are very promising from the point of view of the production of magnetoresistive films with specific anisotropy.

Applied Surface Science, 2005

Gold nanoparticles have been prepared by alcoholic reduction of Au(III) ions in presence of a pol... more Gold nanoparticles have been prepared by alcoholic reduction of Au(III) ions in presence of a polymeric stabilizer (poly(N-vinyl pyrrolidone), PVP). On-line UV–vis spectroscopic characterization and transmission electron microscopy (TEM) analysis are presented. Optical spectroscopy data show that the temporal evolution of absorption spectra and the absorbance peak properties are correlated to the off-line size measurements obtained at chemical reaction end by TEM micrographs. The Au cluster size behaves linearly with time above a threshold temperature (70 °C), according to a deposition-controlled growth mechanism.

Experimental Thermal and Fluid Science, 2012

ABSTRACT The formation mechanisms of combustion generated metal oxide nanoparticles were explored... more ABSTRACT The formation mechanisms of combustion generated metal oxide nanoparticles were explored in a stoichiometric laminar premixed flame doped with droplets of cadmium, nickel(II) and lead(II) nitrate aqueous solutions. Generated particles were thermophoretically collected and analyzed by Atomic Force Microscopy (AFM). The results showed that most of the particles have sizes lower than 10 nm. The size distribution function shapes and time evolutions depend on the metal salt solubility and thermal decomposition characteristics. By comparing the thermophoretically collected matter and the amount of injected metal precursors, a size dependent adhesion efficiency of the particles on probe mica plates has been found. The results showed that nanoparticles have a low capability to adhere on a surface, regardless of the used metal. The adhesion efficiency quickly decreases for particles smaller than 10 nm. As a consequence, the smallest particles are present in the flame with a relative high number concentration. This feature is of great interest when developing filtering systems able to remove nanoparticles with size lower than 10 nm at the exhaust of combustion systems.

Environmental Science & Technology, 2008

We measured the size distribution and UV extinction spectra of carbonaceous nanoparticles present... more We measured the size distribution and UV extinction spectra of carbonaceous nanoparticles present in the size range of 1-100 nm in the exhausts of 2004 model gasoline and diesel powered vehicles and compared the results with those obtained in premixed flames. In addition to soot particles, nanoparticles of organic carbon (NOC) were measured in the emissions of these test vehicles in significant number and mass concentrations. The number and mass concentration of NOC was higher than soot in gasoline vehicle emissions. In diesel emissions, NOC had a higher number concentration than soot in terms of number concentration, but in terms of mass concentration, soot was higher than NOC. The size (1-3 nm) and extinction spectra in the UV-visible (strong in the UV and transparent in the visible) of macromolecules/nanoparticles collected in water samples from the vehicles are similar to those measured in laboratory hydrocarbon-air flames, suggesting that these nanoparticles are formed in hydrocarbon combustion reactions. We advance the hypothesis that NOC in vehicle emissions are produced by high-temperature combustion processes and not by low-temperature condensation processes.

Applied Surface Science, 2003

In usual dry laser cleaning of opaque samples, short laser pulses are projected onto the sample s... more In usual dry laser cleaning of opaque samples, short laser pulses are projected onto the sample surface to be cleaned. Energy transferred from light ejects extraneous particles away from the surface. Laser beam fluence is limited by the damage reached by high temperature that the sample surface can produce. We have experimentally shown that for thin samples, the thermo-elastic wave propagates within the whole sample thickness, thus also the rear surface, while temperature effects are limited to the front surface. Therefore, the proposed ''verso'' laser cleaning technique (the pulsed laser beam impinges on rear sample surface) can be applied to any opaque ''mechanically thin'' film and is useful for samples having delicate treatments on the surface to be cleaned (e.g. written paper, painted tiles, magnetic films). We have applied our technique to paper sheets showing that it is possible to efficiently clean the surface without damaging ink marks on it. Using a probe beam deflection (PBD) technique in both direct and reverse configuration we have shown that the ''verso'' cleaning effect is due to the higher penetration depth of the thermo-elastic wave with respect to the temperature profile propagation. #

Applied Surface Science, 2009

Exchange-coupled monocomponent magnetic films constituted of disk-shaped Ni and Fe nanoparticles ... more Exchange-coupled monocomponent magnetic films constituted of disk-shaped Ni and Fe nanoparticles were produced by ultrafast pulsed laser deposition, in vacuum. These films show a peculiar cauliflower-like structure, made of granular agglomerates of nanoparticles sticking to one another with a significant shape and orientation anisotropy. Both as-deposited Ni and Fe films present hysteresis loops with a high in-plane remanence ratio (0.61 and 0.81 at 250 K, respectively), relatively low values of the saturation and coercive fields and a steep slope near coercivity. At temperature of 10 K and 250 K, the magnetization curves confirm the strong influence of the production technique on the topologic structure of these films, and consequently on their magnetic properties. In perspective, the striking and intriguing properties of these nanogranular films appear very promising for potential application as permanent magnets and in data storage technology.

Journal of Materials Processing Technology, 2008

Giant magnetoresistance effect is found in films of magnetic nanoparticles uniformly mixed with n... more Giant magnetoresistance effect is found in films of magnetic nanoparticles uniformly mixed with non-magnetic metallic nanoparticles produced by ultrashort pulsed laser deposition (uPLD). The uPLD, which uses femtosecond laser pulses, has been recently reported as a powerful technique for obtaining nanoparticles and nanogranular films. As-deposited Co–Cu and Fe–Ag films in a moderate volume fraction range of magnetic component (15–25%) present detectable values of this magnetoresistive effect, although the average size of the particles is higher than in typical nanogranular materials for magnetoresistive applications. The determined longitudinal, transverse and perpendicular magnetoresistance behaviours, at the temperatures of 10 and 250 K, confirm the strong influence of the production technique on the complex microstructure of these films and consequently on their peculiar magneto-transport properties. In perspective, by optimizing the production parameters, these nanogranular films appear very promising for potential application in magnetic recording and data storage technology.

Sensors and Actuators A-physical, 2006

A mechanical vibration sensor based on a novel elastomagnetic composite made of magnetic micropar... more A mechanical vibration sensor based on a novel elastomagnetic composite made of magnetic microparticles uniformly dispersed in an elastic non-magnetic matrix is presented. A theoretical model predicting a linear behaviour of the sensor response with the vibration frequency and amplitude is reported. The obtained experimental results are in agreement with the model predictions for magnetic particle volume content lower than 15%. The ability of this kind of sensor to work at low frequencies, where other devices present a lack of reliability, is a very interesting characteristic of this elastomagnetic sensor.

Applied Surface Science, 2004

Laser-assisted particle removal has acquired a growing importance in last few years, finding appl... more Laser-assisted particle removal has acquired a growing importance in last few years, finding applications in several fields ranging from microelectronics to conservation and restoration of materials having cultural or historical interest. Recently new ‘indirect’ laser cleaning techniques such as ‘shock’ and ‘verso’ laser cleaning have been developed. Here we present a simple laser cleaning mechanical model in order to associate cleaning efficiency to surface deformation characteristics during cleaning pulse and apply it to examine the behaviour of ‘verso’ laser cleaning which has experimentally shown promising results on cellulosic (paper and cotton) materials.

Applied Surface Science, 2007

Nanoparticles were synthesized by irradiating a nickel target with femtosecond laser pulses in hi... more Nanoparticles were synthesized by irradiating a nickel target with femtosecond laser pulses in high vacuum, and subsequently analyzed. The proof-of-principle experiments aim to modify the size characteristics of the produced nanoparticles. For nickel it is found that: (i) ultraviolet laser pulses lead to a remarkable change in the nanoparticles size distribution with respect to visible laser pulses; (ii) irradiation of the femtosecond pulses induced ablation plume with a second, delayed ultraviolet laser pulse can change the size characteristics of the produced nanoparticles.

Proceedings of The Combustion Institute, 2009

In this work we compare the results of several nanoparticle measurement techniques with the aim o... more In this work we compare the results of several nanoparticle measurement techniques with the aim of investigating the formation of nanoparticles in non-sooting to slightly sooting flames. In slightly sooting conditions there is quite good agreement between Differential Mobility Analyser (DMA), Atomic Force Microscopy (AFM), and optical measurements on particle size and concentration. However, in rich flames below the onset of soot, DMA measures a strong drop-off in the total particle volume fraction at low fuel to air mixtures, which is not observed in optical or AFM measurements that detect a more gradual decrease in particle concentration with decreasing C/O and almost constant spectroscopic properties. The disagreement is significantly larger than experimental error and is only observed when the particle size distribution includes solely particles smaller than about 3 nm.Particle losses in the DMA sampling system does not seem to be the only possible reason for justifying the discrepancy with the other techniques. Further investigations are necessary in order to characterize chemically and physically this class of nanoparticles which constitute the earliest stage in the formation of particulate carbon.

Sensors and Actuators A-physical, 2005

The development of a novel magnetoelastic sensor, based on the stress influence on amplitude of t... more The development of a novel magnetoelastic sensor, based on the stress influence on amplitude of the resonant mechanical waves inside a Fe62.5Co6Ni7.5Zr6Cu1Nb2B15 ribbon, for strain and/or stress real-time monitoring in civil buildings is reported. This novel sensor exhibits better sensitivity than resistive and vibrating wire strain gauges, good reliability and stability.

Nanotechnology, 2006

This paper focuses on the development and optimization of electroplated cobalt-nickel (CoNi) allo... more This paper focuses on the development and optimization of electroplated cobalt-nickel (CoNi) alloys for use in biomedical microdevices. CoNi films were electrodeposited from glycine-containing electrolyte solutions at acidic pH. The influence of pH (2.5-5), temperature (55 and 80 • C), current density (from −5 to −40 mA cm −2 ), glycine concentration (0.5 and 1 mol dm −3 ) and the nature of the metal salts (chlorides or sulphates) on the composition and the magnetic properties of the films were systematically analyzed. The cobalt content varied between 50 and 83 wt% depending on the applied conditions. As a result, deposits showed variable morphologies, different structures (either hexagonal close-packed (hcp) or mixed hcp and face-centered cubic phases) and tunable magnetic properties, ranging from semi-hard (18.51 kA m −1 , i.e. 233 Oe) to very soft (1.43 kA m −1 , i.e. 18 Oe). To understand the role of glycine in this system, a comparison of the electrochemical processes, and the structural and magnetic properties is made for samples produced in glycine-containing and glycine-free baths.

Sensors and Actuators A-physical, 2006

The piezoresistivity in a heterogeneous material formed by conducting nickel particles uniformly ... more The piezoresistivity in a heterogeneous material formed by conducting nickel particles uniformly dispersed into a silicone-insulating matrix has been studied as a function of the filler content. A proper experimental apparatus was realized to investigate the direct dependence of resistivity on an uniaxial strain. In particular, when the volume fraction of the conductive charge approaches the conduction percolation threshold, at a proper value of the volume strain a little increment (2%) of the relative deformation can induce a transition from the insulating to conducting state accompanied by a giant resistivity change (about nine orders of magnitude). Some evidence that elastomer matrix properties contribute to determine both the peculiar development of the elasto-resistive coupling and its reversibility has been also found. The obtained results indicate the opportunity to optimize the investigated composite materials for the application as core of novel sensor devices governed by a threshold strain.

Combustion and Flame, 2003

Atomic Force Microscopy (AFM) has been used for the characterization of nanometric particles prod... more Atomic Force Microscopy (AFM) has been used for the characterization of nanometric particles produced in rich flames. Very small particles (about 2 nm) have been found in pre-inception region of soot forming premixed flames, whereas both small nanoparticles as well as large soot particles have been found in the soot region of the flames. The smaller particles are very flat in shape if compared with the bigger ones, and this probably depends upon the different nature of the collected particles.Particle size distribution functions are reported for different sampling conditions. The results of AFM measurements are in good agreement with previous measurements performed with ultraviolet (UV) light scattering/extinction technique on the same flames.

Proceedings of The Combustion Institute, 2005

The size distribution of the nanoparticles formed in premixed ethylene–air flames and collected t... more The size distribution of the nanoparticles formed in premixed ethylene–air flames and collected thermophoretically on mica cleaved substrates is obtained by atomic force microscopy (AFM). The distribution function extends from 1 to about 5 nm in non-sooting flames and in the soot pre-inception region of the richer flames, while it becomes bimodal and larger particles are formed in the soot inception region of the slightly sooting flames. The distribution is compared with the size distribution of nano-sized organic carbon (NOC) and soot particles, obtained by “in situ” multi-wavelength extinction and light scattering methods. The deposition efficiency is estimated from the differences between these two size distribution functions as a function of the equivalent diameter of the nanoparticles. Furthermore, the coagulation coefficient of particles in flame is obtained from the temporal evolution of the number concentration of the nanoparticles inside the flames. NOC particles, which are rapidly produced in locally rich combustion regions, have peculiar properties since their sticking coefficient both for coagulation and adhesion result to be orders of magnitudes lower than that expected by larger aerosols, like soot particles. The experimental results are interpreted by modelling the van der Waals interactions of the nanoparticles in terms of Lennard-Jones potentials and in the framework of the gas kinetic theory. The estimated adhesion and coagulation efficiencies are in good agreement with those calculated from AFM and optical data. The very low efficiency values observed for the smaller particles could be ascribed to the high energy of these particles due to their Brownian motion, which causes thermal rebound effects prevailing over adhesion mechanisms due to van der Waals forces.

Chemosphere, 2003

UV–visible extinction and scattering and two extra situ sampling techniques: atomic force microsc... more UV–visible extinction and scattering and two extra situ sampling techniques: atomic force microscopy (AFM) and differential mobility analysis (DMA) are used to follow the evolution of the particles formed in flames. These particle sizing techniques were chosen because of their sensitivity to detect inception particles, which have diameters, d<5 nm, too small to be observed with typical particle measurement instrumentation. The size of the particles determined by AFM and DMA compares well with the size determined by in situ optical measurements, indicating that the interpretation of the UV–visible optical signal is quite good, and strongly showing the presence of d=2–4 nm particles. UV–visible extinction measurements are also used to determine the concentration of d=2–4 nm particles at the exhausts of practical combustion systems. A numerical model, able to reproduce the experimentally observed low coagulation rate of nanoparticles with respect to soot particles, is used to investigate the operating conditions in the combustion chamber and exhaust system for which 2–4 nm particles survive the exhaust or grow to larger sizes. Combustion generated nanoparticles are suspected to affect human and environmental health because of their affinity for water, small size, low rate of coagulation, and large surface area/weight ratio. The ability to isolate nanoparticles from soot particles in hydrosols collected from combustion may be useful for future analysis by a variety of techniques and toxicological assays.

Environmental Engineering Science, 2008

ENVIRONMENTAL ENGINEERING SCIENCE Volume 25, Number 10, 2008 © Mary Ann Liebert, Inc. DOI: 10.108... more ENVIRONMENTAL ENGINEERING SCIENCE Volume 25, Number 10, 2008 © Mary Ann Liebert, Inc. DOI: 10.1089/ees.2007.0189 ... Coagulation of Organic Carbon Nanoparticles in Exhaust Conditions ... Gianluca Lanzuolo,1,* Lee Anne Sgro,1 Andrea De Filippo,1 ...

Applied Surface Science, 2005

We present femtosecond optical time-resolved pump-probe investigations of superconducting hybrids... more We present femtosecond optical time-resolved pump-probe investigations of superconducting hybrids structures consisting of Nb/NiCu bilayers with various thickness. Measurements performed on pure Nb and NiCu films are also given. The photoresponse experiments provide the quasiparticle relaxation times in bilayers of different thickness ratios. The study of the photoresponse as a function of the temperature reveals the spatial evolution of the superconductor order parameter across the bilayers. #

Sensors and Actuators A: Physical, 2005

The development of a versatile magnetoelastic sensor prototype for on-line elastic deformation mo... more The development of a versatile magnetoelastic sensor prototype for on-line elastic deformation monitoring and fracture alarm in civil engineering is reported. The sensor is based on the variation of resonant longitudinal magnetoelastic waves amplitude due to elastic status change in the amorphous Fe 62.5 Co 6 Ni 7.5 Zr 6 Cu 1 Nb 2 B 15 active core. Tests on a tufa wall under mass loading were conducted. The obtained results show a good reliability and sensitivity (1 mV/10 m) of the sensor response in the m-cm deformation range. The sensor is able to predict the approaching to the fracture regime, monitoring a preceding characteristic behavior.

Applied Surface Science, 2006

Ultrashort pulsed laser ablation in vacuum of different targets was performed in order to investi... more Ultrashort pulsed laser ablation in vacuum of different targets was performed in order to investigate the possibility of producing nanoparticles with controlled size and shape. A systematic morphology characterization of deposited products was performed for nickel and silicon as a function of laser pulse intensity and wavelength, at a fixed pulse repetition rate. The nanoparticles were investigated by atomic force microscopy, and clear trends for their size and shape anisotropy were evidenced. The best conditions to obtain nanosized particles of oblate ellipsoidal shape, with the minor axis below 10 nm, were determined in the case of nickel targets. Our results show that ultrashort pulse laser deposition can be considered as an interesting technique for the tailoring of nanogranular films with the desired particles dimension and shape, according to the peculiar properties required in specific applications. Moreover, the preliminary features are very promising from the point of view of the production of magnetoresistive films with specific anisotropy.

Applied Surface Science, 2005

Gold nanoparticles have been prepared by alcoholic reduction of Au(III) ions in presence of a pol... more Gold nanoparticles have been prepared by alcoholic reduction of Au(III) ions in presence of a polymeric stabilizer (poly(N-vinyl pyrrolidone), PVP). On-line UV–vis spectroscopic characterization and transmission electron microscopy (TEM) analysis are presented. Optical spectroscopy data show that the temporal evolution of absorption spectra and the absorbance peak properties are correlated to the off-line size measurements obtained at chemical reaction end by TEM micrographs. The Au cluster size behaves linearly with time above a threshold temperature (70 °C), according to a deposition-controlled growth mechanism.

Experimental Thermal and Fluid Science, 2012

ABSTRACT The formation mechanisms of combustion generated metal oxide nanoparticles were explored... more ABSTRACT The formation mechanisms of combustion generated metal oxide nanoparticles were explored in a stoichiometric laminar premixed flame doped with droplets of cadmium, nickel(II) and lead(II) nitrate aqueous solutions. Generated particles were thermophoretically collected and analyzed by Atomic Force Microscopy (AFM). The results showed that most of the particles have sizes lower than 10 nm. The size distribution function shapes and time evolutions depend on the metal salt solubility and thermal decomposition characteristics. By comparing the thermophoretically collected matter and the amount of injected metal precursors, a size dependent adhesion efficiency of the particles on probe mica plates has been found. The results showed that nanoparticles have a low capability to adhere on a surface, regardless of the used metal. The adhesion efficiency quickly decreases for particles smaller than 10 nm. As a consequence, the smallest particles are present in the flame with a relative high number concentration. This feature is of great interest when developing filtering systems able to remove nanoparticles with size lower than 10 nm at the exhaust of combustion systems.

Environmental Science & Technology, 2008

We measured the size distribution and UV extinction spectra of carbonaceous nanoparticles present... more We measured the size distribution and UV extinction spectra of carbonaceous nanoparticles present in the size range of 1-100 nm in the exhausts of 2004 model gasoline and diesel powered vehicles and compared the results with those obtained in premixed flames. In addition to soot particles, nanoparticles of organic carbon (NOC) were measured in the emissions of these test vehicles in significant number and mass concentrations. The number and mass concentration of NOC was higher than soot in gasoline vehicle emissions. In diesel emissions, NOC had a higher number concentration than soot in terms of number concentration, but in terms of mass concentration, soot was higher than NOC. The size (1-3 nm) and extinction spectra in the UV-visible (strong in the UV and transparent in the visible) of macromolecules/nanoparticles collected in water samples from the vehicles are similar to those measured in laboratory hydrocarbon-air flames, suggesting that these nanoparticles are formed in hydrocarbon combustion reactions. We advance the hypothesis that NOC in vehicle emissions are produced by high-temperature combustion processes and not by low-temperature condensation processes.