2010


Di Girolamo G.ab, Blasi C.a, Pagnotta L.b, Schioppa M.a
(2010) Ceramics International, 36 (8), pp. 2273-2280. Cited 2 times.
a ENEA, UTTMATB, Brindisi Research Centre, S.S. 7 Appia, km 713.7, 72100 Brindisi, Italy
b Department of Mechanical Engineering, University of Calabria, Ponte Pietro Bucci Cubo 44C, 87036 Rende (CS), Italy
Abstract
Yttria partially stabilized zirconia (YSZ) thick thermal barrier coatings were fabricated by Atmospheric Plasma Spraying (APS) and isothermally annealed at 1315 °C for different durations. The phase composition of as-sprayed and heat-treated free-standing coatings was investigated by X-ray Diffraction (XRD) and the Rietveld method was employed for quantitative phase analysis. High-temperature exposure of YSZ coatings produced the partial decomposition of metastable t′ zirconia phase and the corresponding increase in the amount of stable tetragonal t, cubic c and monoclinic m phases with increasing the aging time. The thermophysical properties of as-sprayed and annealed YSZ coatings, such as thermal expansion and heat capacity, were measured. The thermal expansion coefficient kept almost constant in-plane direction after heat treatment. Otherwise, it changed in through-thickness direction due to any structural changes and high-temperature sintering of the porous microstructure. The sintering also influenced the specific heat capacity Cp which increased with increasing the annealing time. © 2010 Elsevier Ltd and Techna Group S.r.l. All rights reserved.
Author Keywords
A. Plasma spraying;  C. Thermal properties;  D. ZrO2;  E. Thermal applications
Document Type: Article
Source: Scopus

 

Resta V., Laera A.M., Piscopiello E., Schioppa M., Tapfer L.
(2010) Journal of Physical Chemistry C, 114 (41), pp. 17311-17317.
ENEA, Unità Tecnica Tecnologie Dei Materiali Brindisi (UTTMATB), Strada Statale 7 Appia-706, I-72100 Brindisi, Italy
Abstract
An innovative unimolecular precursor structure based on cadmium-bis(benzylthiolates), Cd(SBz)2, has been devised for the preparation of polymer/CdS nanocomposite materials through a simple and inexpensive synthetic route. Cd(SBz)2 and [Cd(SBz)2] 2•MI, MI being methyl imidazole, dispersed in a polymer matrix have been later thermolyzed in very mild conditions in the range of temperatures, TA, 175 °C ≤ TA ≤ 240 °C. Optical absorbance, photoluminescence spectroscopy, and X-ray diffraction show that, for both precursors, CdS nanocrystal (NC) nucleation and growth start well below the literature threshold values and that in the analyzed temperature range the NC's size is finely tuned in quantum confinement regime conditions. Methyl imidazole added precursor shows highly efficient reactivity at lower temperatures, while the differences become smaller for higher values. Transmission electron microscopy ensures that in the entire range of temperatures, the synthesis of highly dense and homogeneous distributed CdS NCs over the whole extent of the matrix has been achieved with [Cd(SBz) 2]2•MI precursor. The results show that benzylthiolates are really promising molecules as precursors for optoelectronic and/or photovoltaic nanocomposite based devices. © 2010 American Chemical Society.
Document Type: Article
Source: Scopus

 

Valerini D.ab, Signore M.A.a, Rizzo A.a, Tapfer L.a
(2010) Journal of Applied Physics, 108 (8), art. no. 083536.
a Department of Advanced Physical Technologies and New Materials, ENEA, Brindisi Research Center, S.S. 7 km. 706, 72100 Brindisi, Italy
b CNR-IMM, Institute for Microelectronics and Microsystems, University Campus, Via Monteroni, 73100 Lecce, Italy
Abstract
The optical functions (complex dielectric function, complex index of refraction, and complex conductivity) of sputtered zirconium nitride films are derived starting from optical reflectance measurements. Their evolution with the different bias voltages applied during the films growth is used to deduce information about the variations in the electronic structure influenced by a different oxygen and nitrogen content in the films. Improvement in the electrical conductivity is observed at increasing bias voltage due to a reduction in both oxygen contamination and nitrogen content. The separation of the different contributions (free conduction electrons and different electronic transitions) in the optical functions is achieved through the Drude-Lorentz model, allowing the detection of an unusual low-energy electronic transition in films grown at low bias voltages. Through considerations about the electronic structure and about the results coming from other characterization techniques, this transition can be ascribed to the presence of defects/impurities, nitrogen superstoichiometry, or oxygen contamination. © 2010 American Institute of Physics.
Document Type: Article
Source: Scopus

 

Pasquini L.a, Callini E.a, Piscopiello E.b, Montone A.c, Jensen T.R.d, Antisari M.V.c, Bonetti E.a
(2010) Materials Research Society Symposium Proceedings, 1216, pp. 88-93.
a Department of Physics, CNISM, University of Bologna, Bologna, 140127, Italy
b ENEA, C.R. Brindisi, Brindisi, 172100, Italy
c ENEA, C.R. Casaccia, Rome, 100123, Italy
d Department of Chemistry, iNANO, University of Aarhus, Aarhus, DK-8000, Denmark
Abstract
Mg nanoparticles with metal-oxide core-shell morphology were synthesized by inert-gas condensation and decorated by in-situ deposition of transition metals: Pd, Ni, Ti. The effects of nanoparticle size on the hydrogen sorption kinetics and the specific action of the different catalysts are presented and discussed in connection with structural and functional analysis. © 2010 Materials Research Society.
Document Type: Conference Paper
Source: Scopus

 

Tagliente M.A.a , Bello V.b, Pellegrini G.b, Mattei G.b, Mazzoldi P.b, Massaro M.a, Carbone D.a
(2010) Nuclear Instruments and Methods in Physics Research, Section B: Beam Interactions with Materials and Atoms, 268 (19), pp. 3063-3065. Cited 2 times.
a ENEA, Advanced Physical Technologies and New Materials, Centro Ricerche Brindisi, SS.7 Appia km 706, I-72100 Brindisi, Italy
b Dipartimento di Fisica, CNISM, Universit di Padova, via Marzolo 8, I-35131 Padova, Italy
Abstract
Tin dioxide nanoparticles embedded in silica matrix were fabricated by ion implantation combined with thermal oxidation. Silica substrate was implanted with a 150 keV Sn+ ions beam with a fluence of 1.0 × 10 17 ions/cm2. The sample was annealed for 1 h in a conventional furnace at a temperature of 800 °C under flowing O2 gas. According to the structural characterization performed by X-ray diffraction and transmission electron microscopy techniques, metallic tetragonal tin nanoparticles with a volume average size of 12.8 nm were formed in the as-implanted sample. The annealing in oxidizing atmosphere promotes the total oxidation of the tin nanoparticles into tin dioxide nanoparticles with a preferential migration toward the surface of the matrix, where large and coalesced nanoparticles were observed, and a small diffusion toward the bulk, where smaller nanoparticles were found. © 2010 Elsevier B.V. All rights reserved.
Author Keywords
Ion implantation;  SnO2 nanoparticles;  Structural properties
Document Type: Conference Paper
Source: Scopus

 

Di Girolamo, G., Massaro, M., Piscopiello, E., Tapfer, L.
(2010) Nuclear Instruments and Methods in Physics Research, Section B: Beam Interactions with Materials and Atoms, 268 (19), pp. 2878-2882.
ENEA, Brindisi Research Centre, Strada Statale 7 Appia km 713, 72100 Brindisi, Italy
Abstract
Metal ion implantation in inert polymers may produce ultra-thin conducting films below the polymer surface. These subsurface films are promising structures for strain gauge applications. To this purpose, polycarbonate substrates were irradiated at room temperature with low-energy metal ions (Cu+ and Ni+) and with fluences in the range between 1 × 1016 and 1 × 1017 ions/cm2, in order to promote the precipitation of dispersed metal nanoparticles or the formation of a continuous thin film. The nanoparticle morphology and the microstructural properties of polymer nanocomposites were investigated by glancing-incidence X-ray diffraction and transmission electron microscopy (TEM) measurements. At lower fluences (<5 × 1016 ions/cm2) a spontaneous precipitation of spherical-shaped metal nanoparticles occurred below the polymer top-surface (∼50 nm), whereas at higher fluences the aggregation of metal nanoparticles produced the formation of a continuous polycrystalline nanofilm. Furthermore, a characteristic surface plasmon resonance peak was observed for nanocomposites produced at lower ion fluences, due to the presence of Cu nanoparticles. A reduced electrical resistance of the near-surface metal-polymer nanocomposite was measured. The variation of electrical conductivity as a function of the applied surface load was measured: we found a linear relationship and a very small hysteresis. © 2010 Elsevier B.V. All rights reserved.
Author Keywords
Metal ion implantation;  Polymer;  Strain gauge
Document Type: Conference Paper
Source: Scopus

 

Alfano M.a, Di Girolamo G.b, Pagnotta L.a, Sun D.c
(2010) Strain, 46 (5), pp. 409-418. Cited 2 times.
a Department of Mechanical Engineering, University of Calabria, Ponte P. Bucci, Cubo 44C, 87036 Rende (CS), Italy
b ENEA Department Adv. Phys. Technol. and New Materials (FIM), Brindisi Research Center, Strada Statale 7 Appia, km 713.7, 72100 Brindisi, Italy
c National Centre for Advanced Tribology (NCATS), School of Engineering Sciences, University of Southampton, United Kingdom
Abstract
Thermal barrier coatings (TBCs) are widely adopted to protect mechanical components in gas turbine engines operating at high temperature. Basically, the surface temperature of these components must be low enough to retain material properties within acceptable bounds and to extend component life. From this standpoint, air plasma-sprayed (APS) ceria and yttria co-stabilized zirconia (CYSZ) is particularly promising because it provides enhanced thermal insulation capabilities and resistance to hot corrosion. However, essential mechanical properties, such as hardness and Young's modulus, have been less thoroughly investigated. Knowledge of Young's modulus is of concern because it has a significant effect on strain tolerance and stress level and, hence, on durability. The focus of the present study was to determine the mechanical properties of APS CYSZ coatings. In particular, X-ray diffraction (XRD) is adopted for phase analysis of powders and as-sprayed coatings. In addition, scanning electron microscopy (SEM) and image analysis (IA) are employed to explore coating microstructure and porosity. Finally, the Young's modulus of the coating is determined using nanoindentation and a resonant method. The results obtained are then discussed and a cross-check on their consistency is carried out by resorting to a micromechanical model. © 2010 Blackwell Publishing Ltd.
Author Keywords
ceria-yttria stabilized zirconia;  hardness and Young's modulus;  plasma spray
Document Type: Conference Paper
Source: Scopus

 

Gattia D.M.a, Antisari M.V.a, Marazzi R.a, Montone A.a, Piscopiello E.b, Mingazzini C.c
(2010) Materials Research Society Symposium Proceedings, 1204, pp. 73-78.
a ENEA, MAT-COMP, Research Centre of Casaccia, Via Anguillarese 301, 00123 Rome, Italy
b ENEA, MAT-COMP, Research Centre of Brindisi, SS.7, Appia, km 706, 72100 Brindisi, Italy
c ENEA, MAT-ING, Research Centre of Faenza, Via Ravegnana 186, 48018 Faenza, Italy
Abstract
The AC powered electric arc has been used to synthesize single wall carbon nanohorns aggregates with Ca dispersed inside. To this purpose the electric arc has been ignited between two electrodes, one of which was constituted by a mixture of graphite and CaCO3. The experimental evidence on the microstructure and on the chemical composition has been obtained by observation with a transmission electron microscope equipped with X-ray microanalysis. X-ray diffraction revealed the presence of residual CaCO3 indicating that the process has still to be optimized. The experiment represents a first attempt to decorate carbon nanostructures with alkaline earth metals, in particular Ca, by this relatively simple method. These composites are theorized to adsorb relevant amounts of hydrogen. Further work will be focused to optimize the dispersion of Ca atoms in the carbon nanostructure. © 2010 Materials Research Society.
Document Type: Conference Paper
Source: Scopus

 

Tondo E.a, Boniardi M.b, Cannoletta D.a, De Riccardis M.F.c, Bozzini B.a
(2010) Journal of Power Sources, 195 (15), pp. 4772-4778. Cited 2 times.
a Dipartimento di Ingegneria dell'Innovazione, Università del Salento, via Monteroni, I-73100 Lecce, Italy
b Dipartimento di Meccanica, Politecnico di Milano, via La Masa 34, 20156 Milano, Italy
c ENEA Brindisi Research Centre, SS.7 Appia Km 712, 72100 Brindisi, Italy
Abstract
Durability seems to be the single most critical issue for the widespread application of SOFCs. Among critical issues, the stability of interconnects - operating at high temperatures in aggressive gas environments - calls for the selection of cheap materials exhibiting high corrosion performance, accompanied by low surface contact resistance. Use of coated AISI 430 stainless steel is currently the state-of-the-art choice. In this paper we propose Y2O3, Y2O3/Co3O4 and Y2O3/Au composite films as innovative coatings for AISI 430 plates. These coatings were electrodeposited from chloride salts dissolved in hydroalcoholic solutions containing chitosan as binder. The evolution of the crystalline structure of the electrodeposits with heat-treatment conditions has been studied by XRD, their chemical composition has been evaluated by EDX analysis, their morphology has been observed by SEM and the adhesion has been measured by scratch testing. Coated samples were oxidised in air at 800 °C for times up to 500 h and the area-specific resistance (ASR) as a function of exposure time has been measured. All the coated samples developed ASR values below 100 mΩ cm2, the target value for SOFC applications. The ASR was found to increase in the order: Y2O3/Au, Y2O3, and Y2O3/Co3O4. © 2010 Elsevier B.V. All rights reserved.
Author Keywords
ASR;  Chitosan;  Electrodeposition;  Interconnect;  SOFC;  Yttria
Document Type: Article
Source: Scopus

 

Borriello C.a, Masala S.a, Bizzarro V.b, Nenna G.a, Re M.c, Pesce E.c, Minarini C.a, Di Luccio T.a
(2010) AIP Conference Proceedings, 1255, pp. 117-119.
a ENEA, UTTP NANO C. R. Portici, piazzale E. Fermi, 80055 Portici (NA), Italy
b IMAST, piazzale E.Fermi, 80055 Portici (NA), Italy
c ENEA MATCOMP, C. R. Brindisi, SS7 Appia Km 713, 72100 Brindisi, Italy
Abstract
Luminescent PVK:CdS and P3HT:CdS nanocomposites with enhanced electrooptical properties have been synthesized. The nucleation and growth of CdS nanoparticles have been obtained by the thermolysis of a single Cd and S precursor dispersed in the polymers. The size distribution and morphology of the nanoparticles have been studied by TEM analyses. Monodispersive and very small nanoparticles of diameter below 3 nm in PVK and 2 nm in P3HT, have been obtained. The application of such nanocomposites as emitting layers in OLED devices is discussed. © 2010 American Institute of Physics.
Author Keywords
CdS nanoparticles;  Conducting polymers;  Electroluminescence;  Nanocomposites
Document Type: Conference Paper
Source: Scopus

 

Resta V., Laera A.M., Piscopiello E., Capodieci L., Ferrara M.C., Tapfer L.
(2010) Physica Status Solidi (A) Applications and Materials, 207 (7), pp. 1631-1635. Cited 1 time.
ENEA, Unitá Tecnica Tecnologie dei Materiali Brindisi (UTTMATB), Centro Ricerche Brindisi, Strada Statale 7 Appia, 72100 Brindisi, Italy
Abstract
Highly porous nanocrystalline films of TiO2 sensitized with semiconductor nanocrystals (NCs) are very promising for photovoltaic applications, NCs being more versatile and efficient than organic dyes as sensitizer. In this framework, the visible light absorption of TiO2 can be improved by the superposition of CdS NC absorption band, that is tunable between 2.5 and 5.2 eV. Here, we report on a novel in situ approach for the synthesis of CdS NCs in mesoporous sol-gel TiO2 anatase films by using as starting reagent for CdS, [Cd(SBz)2]MI, where MI represents 1-methylimidazole. The precursor has been adsorbed into the TiO2 pores and then decomposed at 480 °C, the procedure being studied for TiO2 films with different porosity. The matrices have been investigated by atomic force microscopy. X-ray diffraction measurements on TiO2 matrix and on the corresponding CdS/TiO2 nanocomposite material revealed a variation of the NCs size of both TiO 2 and CdS as a function of the matrix porosity. The optical properties of the TiO2 and CdS/TiO2 have been studied by UV-Vis transmission spectroscopy. CdS/TiO2 nanocomposites, having higher absorption efficiency with respect to TiO2, are suitable as building blocks for 3rd generation solar cell design.
Author Keywords
CdS/TiO2;  Nanocomposites;  Optical properties;  Precursors;  Sol-gel synthesis;  Structure
Document Type: Article
Source: Scopus

 

Signore M.A., Valerini D., Rizzo A., Tapfer L., Capodieci L., Cappello A.
(2010) Journal of Physics D: Applied Physics, 43 (22), art. no. 225401, . Cited 1 time.
ENEA, Department of Physical Technologies and New Materials, Appia, km 706, 72100 Brindisi, Italy
Abstract
Ion bombardment during thin film growth is known to cause structural and morphological changes in the deposited films, thus affecting their physical properties. In this work zirconium nitride films have been deposited by the ion assisted magnetron sputtering technique. The ion energy is controlled by varying the voltage applied to the substrate in the range 0-25 V. The deposited ZrN films are characterized for their structure, surface roughness, oxygen contamination, optical reflectance and electrical resistivity. With increasing substrate voltage crystallinity of the films is enhanced with a preferential orientation of the ZrN grains having the (1 1 1) axis perpendicular to the substrate surface. At the same time, a decrease in electrical resistivity and oxygen contamination content is observed up to 20 V. A higher substrate voltage (25 V) causes an inversion in the observed experimental trends. The role of oxygen contamination decrease and generation of nitrogen vacancies due to ionic assistance have been considered as a possible explanation for the experimental results. © 2010 IOP Publishing Ltd.
Document Type: Article
Source: Scopus

 

Athanassiou A.ab, Blasi L.a, De Giorgi M.a, Caputo G.a, Fragouli D.a, Tsiranidou E.c, Laera A.M.d, Tapfer L.d, Cingolani R.ab
(2010) Polymer Composites, 31 (6), pp. 1075-1083.
a NNL-National Nanotechnology Laboratory, INFM, CNR, Via Arnesano, 73100 Lecce, Italy
b IIT-Italian Institute of Technology, Via Morego 30, Genova, Italy
c Institute of Electronic Structure and Laser (IESL), FORTH, 711 10 Heraklion, Crete, Greece
d ENEA, Centro Ricerche Brindisi, SS7 Appia Km 706, I-72100 Brindisi, Italy
Abstract
The nucleation of two kinds of crystalline nanoparticles, zinc sulfide (ZnS), and cadmium sulfide (CdS), is achieved directly into specific sites of polymer matrices after their irradiation with UV laser pulses. The starting samples consist of polymers doped with precursors of Zn or Cd thiolate that are proved to decompose after the absorption of UV light, resulting into the nanoparticles formation. The growth of the crystalline nanostructures is followed throughout the irradiation of the samples with successive incident pulses, by different methods, such as transmission electron microscopy, atomic force microscopy, confocal microscopy, and X-ray diffraction. Special attention is paid to the difference of the formation pathways of the two kinds of nanoparticles studied, because the Cd thiolate precursor exhibits much higher absorption efficiency than the Zn thiolate one, at the applied UV wavelength. Indeed, CdS nanoparticles become evident after the very first incident UV pulses, whereas the formation of ZnS nanocrystals requires rather prolonged irradiation, always through a macroscopically nondestructive procedure for the polymer matrix. © 2009 Society of Plastics Engineers.
Document Type: Article
Source: Scopus

 

Protopapa M.L.
(2010) Applied Optics, 49 (16), pp. 3014-3024.
Italian National Agency for New Technologies, Energy and Sustainable Economic Development (ENEA), Unità Tecnica Tecnologie dei Materiali Brindisi, Laboratorio Tecnologia dei Materiali (UTTMATB-TEC), CR Brindisi, SS. 7 Appia, 72100 Brindisi, Italy
Abstract
Optical characterization of composite films consisting of a ceramic matrix with embedded layered metal nanoparticles have recently received increasing interest. In particular, two methods have been mainly proposed in order to obtain optical performances of dielectric matrices containing layered nanoclusters (NCs): the first method is based on the simulation of the layered system as composed of alternated films of dielectric material and effective-medium material. Therefore, the optical response of the multilayer stack is calculated, assigning to the effective-medium layers the dielectric constant εYamaf, obtained by the Yamaguchi theory, and calculating the interference between the beams reflected and refracted at each interface inside the stack. The second method considers the multilayer stack as a single-layer effectivemedium film whose dielectric constant is calculated by the Maxwell Garnett (MG) theory. In particular, this second method is recognized to be valid in the case of nanoparticles uniformly distributed inside a dielectric matrix. The present study shows that the interference method, as it has been applied up to now, does not allow reproducing reflectance and transmittance spectra calculated by the MG theory in the case of a uniform distribution of NCs. © 2010 Optical Society of America.
Document Type: Article
Source: Scopus

 

Penza M.a, Rossi R.a, Alvisi M.a, Signore M.A.a, Cassano G.a, Pentassuglia R.a, Suriano D.a, Pfister V.a, Serra E.b
(2010) Lecture Notes in Electrical Engineering, 54 LNEE, pp. 185-191.
a ENEA, CR Brindisi, Department of Physical Technologies and New Materials, P.O. Box 51, 72100 Brindisi, Italy
b ENEA, CR Casaccia, Department of Physical Technologies and New Materials, Via Anguillarese 301, 00060 Rome, Italy
Abstract
Vertically-aligned carbon nanotubes (CNTs) films have been grown by radiofrequency plasma-enhanced chemical vapor deposition system onto alumina substrates, coated with 2.5 nm thick Fe catalyst, for NO2, H 2 and C2H5OH gas sensing applications, at sensor temperatures from room-temperature to 150°C. The CNTs appear in the form of forest-like structure. Nanoclusters of noble metals with nominal thickness of 5 nm of Pt, Ru and Ag have been sputtered on the top-surface of the vertically-aligned CNTs layers to enhance the gas sensitivity. It was demonstrated that the gas sensitivity of the metal modified CNTs-sensors significantly improved by a factor up to an order of magnitude through a spillover effect, and a broader selectivity was provided. The gas sensing properties of the CNTs-sensors, including the metal-modified CNTs, are characterized by a change of the electrical conductivity in a model of the charge transfer with a semiconducting p-type character. The metal-functionalized CNTs-sensors exhibit high sensitivity, fast response, reversibility, good repeatability, sub-ppm range detection limit. A practical application of the CNTs-sensors for monitoring landfill gas is presented. © 2010 Springer Science+Business Media B.V.
Document Type: Conference Paper
Source: Scopus

 

Di Girolamo G.a, Blasi C.a, Pilloni L.b, Schioppa M.a
(2010) Ceramics International, 36 (4), pp. 1389-1395. Cited 8 times.
a ENEA, Brindisi Research Centre, 72100 Brindisi, Italy
b ENEA, Casaccia Research Centre, 00123 Rome, Italy
Abstract
Thick mullite (3Al2O3-2SiO2) coatings were fabricated by atmospheric plasma spraying (APS) in a mixture of crystalline and amorphous phases, as confirmed by X-ray diffraction (XRD) analysis. The coatings were isothermally heat treated in order to study recrystallization mechanism of the glassy phase. The morphology and the microstructure of both mullite feedstock and coatings were investigated by using scansion electron microscopy (SEM). The porosity of as-sprayed coating was in the range between 2 and 3% and substantially remained unchanged after thermal treatment. The thermal expansion of as-sprayed and annealed coatings was measured during heating up to the temperature of crystallization and the corresponding high-temperature extent of shrinkage was calculated. The differential scanning calorimetry (DSC) curves at different heating rates showed a sharp exothermic peak between 1243 and 1253 K, suggesting a rapid recrystallization of the amorphous phase. Finally, the heat capacity of recrystallized mullite coating was measured by DSC experiments. It was approximately 1.02 × 103 J/kg K at 373 K and increased with increasing test temperature. © 2010 Elsevier Ltd and Techna Group S.r.l.
Author Keywords
C. Thermal properties;  D. Mullite;  E. Thermal applications;  Plasma spraying
Document Type: Article
Source: Scopus

 

Alfano M.a, Di Girolamo G.b, Pagnotta L.a, Sun D.cd, Zekonyte J.c, Wood R.J.K.c
(2010) Journal of Materials Science, 45 (10), pp. 2662-2669. Cited 2 times.
a Department of Mechanical Engineering, University of Calabria, Ponte Pietro Bucci Cubo 44C, Rende 87036, Italy
b ENEA, Brindisi Research Center, S.S. 7 Appia, km 706, Brindisi 72100, Italy
c National Centre for Advanced Tribology (NCATS), School of Engineering Sciences, University of Southampton, Southampton, United Kingdom
d NIBEC, University of Ulster, Newtonabbey BT37 0QB, United Kingdom
Abstract
In this study, ceria-yttria co-stabilized zirconia (CYSZ) free-standing coatings, deposited by air plasma spraying (APS), were isothermally annealed at 1315 °C in order to explore the effect of sintering on the microstructure and the mechanical properties (i.e., hardness and Young's modulus). To this aim, coating microstructure, before and after heat treatment, was analyzed using scanning electron microscopy, and image analysis was carried out in order to estimate porosity fraction. Moreover, Vickers microindentation and depth-sensing nanoindentation tests were performed in order to study the evolution of hardness and Young's modulus as a function of annealing time. The results showed that thermal aging of CYSZ coatings leads to noticeable microstructural modifications. Indeed, the healing of finer pores, interlamellar, and intralamellar microcracks was observed. In particular, the porosity fraction decreased from ~10 to ~5% after 50 h at 1315 °C. However, the X-ray diffraction analyses revealed that high phase stability was achieved, as no phase decomposition occurred after thermal aging. In turn, both the hardness and Young's modulus increased, in particular, the increase in stiffness (with respect to "as produced" samples) was equal to ~25%, whereas the hardness increased to up to ~60%. © 2010 Springer Science+Business Media, LLC.
Document Type: Article
Source: Scopus

 

Di Girolamo G., Blasi C., Schioppa M., Tapfer L.
(2010) Ceramics International, 36 (3), pp. 961-968. Cited 3 times.
ENEA, Department of Advanced Physics, Technologies and New Materials, Brindisi Research Centre, S.S. 7 Appia, km 713.7, 72100 Brindisi, Italy
Abstract
Thick plasma sprayed thermal barrier coatings are suitable for thermal and hot corrosion protection of metal components in land-based turbine and diesel engines. In this work, ceria-yttria co-stabilized zirconia coatings were deposited by atmospheric plasma spraying in a mixture of non-transformable tetragonal t′ and cubic c zirconia phases. Free-standing coatings were isothermally annealed at 1315 °C for different times and their crystal structure was studied by XRD. No phase decomposition occurred. Columnar grains grew in the molten splats with increasing annealing time according to a preferential direction and, after 50 h of heat treatment, they were partially replaced by equiaxed grains. Both in-plane and out-of-plane thermal expansion coefficients (CTEs) were measured from coating expansion during heating. The CTE was slightly sensitive to thermal exposure in out-of-plane direction, whereas it kept almost constant in plane direction. The specific heat capacity Cp of annealed coatings, measured by differential scanning calorimetry (DSC), decreased in comparison with as-sprayed coating, due to high-temperature sintering. © 2009 Elsevier Ltd and Techna Group S.r.l.
Author Keywords
C. Thermal properties;  D. ZrO2;  E. Thermal applications;  Plasma spraying
Document Type: Article
Source: Scopus

 

Serra A.a, Re M.b, Palmisano M.b, Vittori Antisari M.c, Filippo E.a, Buccolieri A.a, Manno D.a
(2010) Sensors and Actuators, B: Chemical, 145 (2), pp. 794-799. Cited 2 times.
a Dipartimento di Scienza dei Materiali, Laboratorio di Fisica delle Nanostrutture, Università del Salento I, 73100 Lecce, Italy
b ENEA-Centro Ricerche Brindisi, SS Appia, km 706, 72100 Brindisi, Italy
c ENEA-Centro Ricerche Casaccia, via Anguillarese 301, 00123 Santa Maria di Galeria, Roma, Italy
Abstract
In this work, we report about the synthesis of silver-titanium dioxide nanostructures and their usage for building up thin films. We shows that nanoparticles of titania enveloped by very thin silver layer were obtained. In addition, these particles were suitable to obtain an active layer for solid-state gas sensor. In particular, we investigate the electrical modifications following the exposure to reactive gases of obtained films. In this way, the sensing performances of active layers were evaluated. The whole sensing characterization was carried out on thin films deposited on alumina and completely processed by microelectronic standard procedures. © 2010 Elsevier B.V. All rights reserved.
Author Keywords
Gas sensors;  Nanoparticles synthesis;  TEM;  Thin films
Document Type: Article
Source: Scopus

 

Penza M.a, Rossi R.a, Alvisi M.a, Serra E.b
(2010) Nanotechnology, 21 (10), art. no. 105501. Cited 13 times.
a ENEA, Department of Physical Technologies and New Materials, PO Box 51 Br-4, I-72100 Brindisi, Italy
b ENEA, Department of Physical Technologies and New Materials, Via Anguillarese 301, I-00060 Rome, Italy
Abstract
Vertically aligned carbon nanotube (CNT) layers were synthesized on Fe-coated low-cost alumina substrates using radio-frequency plasma enhanced chemical vapour deposition (RF-PECVD) technology. A miniaturized CNT-based gas sensor array was developed for monitoring landfill gas (LFG) at a temperature of 150 °C. The sensor array was composed of 4 sensing elements with unmodified CNT, and CNT loaded with 5nm nominally thick sputtered nanoclusters of platinum (Pt), ruthenium (Ru) and silver (Ag). Chemical analysis of multicomponent gas mixtures constituted of CO2, CH4, H2, NH 3, CO and NO2 has been performed by the array sensor responses and pattern recognition based on principal component analysis (PCA). The PCA results demonstrate that the metal-decorated and vertically aligned CNT sensor array is able to discriminate the NO2 presence in the multicomponent mixture LFG. The NO2 gas detection in the mixture LFG was proved to be very sensitive, e.g.: the CNT:Ru sensor shows a relative change in the resistance of 1.50% and 0.55% for NO2 concentrations of 3.3ppm and 330ppb dispersed in the LFG, respectively, with a wide NO2 gas concentration range measured from 0.33 to 3.3ppm, at the sensor temperature of 150 °C. The morphology and structure of the CNT networks have been characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and Raman spectroscopy. A forest-like nanostructure of vertically aligned CNT bundles in the multi-walled form appeared with a height of about 10 νm and a single-tube diameter varying in the range of 5-35nm. The intensity ratio of the Raman spectroscopy D-peak and G-peak indicates the presence of disorder and defects in the CNT networks. The size of the metal (Pt, Ru, Ag) nanoclusters decorating the CNT top surface varies in the range of 5-50nm. Functional characterization based on electrical charge transfer sensing mechanisms in the metal-modified CNT-chemoresistor array demonstrates high sensitivity by providing minimal sub-ppm level detection, e.g., download up to 100ppb NO2, at the sensor temperature of 150 °C. The gas sensitivity of the CNT sensor array depends on operating temperature, showing a lower optimal temperature of maximum sensitivity for the metal-decorated CNT sensors compared to unmodified CNT sensors. Results indicate that the recovery mechanisms in the CNT chemiresistors can be altered by a rapid heating pulse from room temperature to about 110 °C. A comparison of the NO2 gas sensitivity for the chemiresistors based on disorderly networked CNTs and vertically aligned CNTs is also reported. Cross-sensitivity towards relative humidity of the CNT sensors array is investigated. Finally, the sensing properties of the metal-decorated and vertically aligned CNT sensor arrays are promising to monitor gas events in the LFG for practical applications with low power consumption and moderate sensor temperature. © 2010 IOP Publishing Ltd.
Document Type: Article
Source: Scopus

 

Penza M.a, Rossi R.a, Alvisi M.a, Signore M.A.a, Serra E.a, Paolesse R.b, D'Amico A.c, Di Natale C.c
(2010) Sensors and Actuators, B: Chemical, 144 (2), pp. 387-394. Cited 5 times.
a ENEA, Department of Physical Technologies and New Materials, PO Box 51-Br4, I-72100 Brindisi, Italy
b Department of Chemical Sciences and Technologies, University of Rome Tor Vergata, Via della Ricerca Scientifica, I-00133 Rome, Italy
c Department of Electronic Engineering, University of Rome Tor Vergata, Via di Tor Vergata 110, I-00133 Rome, Italy
Abstract
In this paper the effect of the surface functionalization of the carbon nanotubes (CNT) networked films with a metalloporphyrins layer is investigated for gas sensing. Modified film exhibits an increased sensitivity of the electrical resistance towards the concentrations of common volatile compounds (alcohols, amines, aromatic and ketones), at room temperature. Furthermore, a part of the adsorption properties of the functional units is transferred to the sensor signal and, as a consequence, the selectivity of the sensor is also modified. Principal Component Analysis (PCA) demonstrates that the functionalization provides enough selectivity change to turn a triplicate of the same CNT film into an effective sensor array capable of the compounds recognition. These findings are then promising for the development of arrays of CNT-based gas nanosensors with broad selectivities for fingerprinting analysis of complex samples. © 2009 Elsevier B.V. All rights reserved.
Author Keywords
Carbon nanotubes networks gas sensors;  CNTs functionalizations;  Metalloporphyrins;  VOC detection
Document Type: Article
Source: Scopus

 

Signore M.A., Rizzo A., Tapfer L., Piscopiello E., Capodieci L., Cappello A.
(2010) Thin Solid Films, 518 (8), pp. 1943-1946. Cited 2 times.
ENEA, UTS FIM, CR Brindisi, SS 7 Appia Km 714, 72100 Brindisi, Italy
Abstract
ZrNx films were deposited by radiofrequency reactive magnetron sputtering technique in nitrogen and water vapour atmosphere varying the working temperature from room temperature to 600 °C. The films' physical properties were investigated using X-ray diffraction, Secondary Ion Mass Spectroscopy, Atomic Force Microscopy and Transmission Electron Microscopy. It was found that the increase of temperature caused a decrease in the oxygen incorporation and a transition from cubic phase of Zr2ON2 to ZrN one. The formation of nanosized crystalline particles dispersed in the amorphous matrix was observed. © 2009 Elsevier B.V. All rights reserved.
Author Keywords
Atomic Force Microscopy;  Magnetron sputtering;  Secondary Ion Mass Spectrometry;  Transmission Electron Microscopy;  X-ray diffraction;  Zirconium oxynitride
Document Type: Article
Source: Scopus

 

Fragouli D.a, Laera A.M.b, Caputo G.a, Resta V.b, Pompa P.P.a, Tapfer L.b, Cingolani R.ac, Athanassiou A.ac
(2010) Journal of Nanoscience and Nanotechnology, 10 (2), pp. 1267-1272. Cited 1 time.
a National Nanotechnology Laboratory of INFM-CNR, Via Arnesano Km 5, 73100 Lecce, Italy
b ENEA, Centro Ricerche Brindisi, SS7Appia Km 706, 1-72100 Brindisi, Italy
c IIT- Italian Institute of Technology, Via Morego 30, Genova, Italy
Abstract
Polymer films embedding cadmium thiolate precursors have been irradiated with ultraviolet laser pulses resulting in the formation of cadmium sulfide crystalline nanoparticles through a macroscopically non-destructive procedure for the host matrix. Controlling the number of the incident laser pulses, the gradual increase of the size of the nanoparticles is accomplished, and consequently the progressive change of the emission characteristics of the formed nanocomposites. The X-ray diffraction and transmission electron microscopy measurements were used for the full characterization of the nanoparticles. This study compares two polymer matrices, poly(methyl methacrylate) and a cyclic olefin copolymer, and reveals the importance of each one for the emission characteristics of the formed cadmium sulfide nanocrystals. It is found that the poly(methyl methacrylate) matrix contributes to the increase of the trap states on the surface of the formed nanocrystals, causing the broadening of their emission. On the other hand the cadmium sulfide nanoparticles, grown into the cyclic olefin copolymer matrix, exhibit narrower emission spectra. Copyright © 2010 American Scientific Publishers. All rights reserved.
Author Keywords
Cds nanoparticles;  Metal Precursors;  Nanocomposites;  Polymer Matrix;  UV Laser
Document Type: Conference Paper
Source: Scopus