2014

Di Girolamo G.a, Marra F.b, Schioppa M.c, Blasi C.c, Pulci G.b, Valente T.b
(2014) Surface and Coatings Technology, Article in Press.
aENEA, Materials Technology Unit, Casaccia Research Centre, Rome, Italy;
bDept. of Chemical Engineering, Materials, Environment, Sapienza University of Rome, INSTM Reference Laboratory for Engineering of Surface Treatments, Rome, Italy;
cENEA, Materials Technology Unit, Brindisi Research Centre, Brindisi, Italy
Abstract
Ceramic thermal barrier coatings (TBCs) are advanced systems for more efficient turbine engines. In this work, thick lanthanum zirconate TBCs were fabricated by Air Plasma Spraying (APS). The coatings showed a lamellar microstructure containing splat boundaries, pores and microcracks. After thermal exposure at 1200 and 1350. °C the partial sintering of the porous microstructure occurred.High-temperature evolution of the mechanical properties was investigated by arranging specific bending tests up to 1500. °C using SiC testing assembly which allowed to calculate the strain by means of curvature measurement. The mechanical properties improved with increasing the testing temperature, due to the inelastic deformation and stress relaxation which counteracted the sintering effects.The elastic modulus increased after thermal aging, but decreased for the aged coatings tested at higher temperature.The thermal expansion coefficient of as-sprayed coatings slightly increased after thermal aging, while a reduction of specific heat capacity was noticed. © 2014 Elsevier B.V.
Author Keywords
Coatings; Heat capacity; Lanthanum zirconate; Plasma spraying; Young's modulus
Document Type: Article in Press
Source: Scopus

 

Pfister V.a, Tundo A.b, Luprano V.A.M.a
(2014) Construction and Building Materials, 61, pp. 278-284.
aENEA, Brindisi Research Center, SS. 7 'Appia' km 706, 72100 Brindisi, Italy;
bENEA, Ufficio Territoriale di Bari, Viale Japigia 188, 70126 Bari, Italy
Abstract
The evaluation of the concrete properties in a structure has a fundamental importance for safety and structural integrity assessments. An adequate knowledge of the structural concrete performances can be obtained from a large number of cores where performing destructive tests. Non-destructive ultrasonic waves test can be performed before other kind of tests, allowing to improve the assessment of the structural concrete performances and to extend the results to the same kind of elements of the structure, not directly investigated by destructive tests. The aim of this work is to test a new method to identify a good practice to select the position of testing points on which extract the cores starting from an analysis of a preliminary campaign of non-destructive measurements. In this way it is possible to reduce risk of errors of the compressive strength evaluation by a different approach from those used nowadays. The data obtained from an experimental campaign with both non-destructive and destructive tests on 75 concrete columns were considered to validate the new method. The implications of a completely random choice and the guided choice, using the method proposed, were analysed with an iterative and exhaustive approach. European Standard (EN 13791) was followed for in situ measurements and preliminary data analysis. © 2014 Published by Elsevier Ltd.
Author Keywords
Concrete strength; Coring point selection; Non-Destructive Testing (NDT); Ultrasonic pulse velocity
Document Type: Article
Source: Scopus

 

Lionetto F.a, Calò E.a, Di Benedetto F.ac, Pisignano D.bd, Maffezzoli A.a
(2014) Composites Science and Technology, 96, pp. 47-55.
aDepartment of Engineering for Innovation, University of Salento, Via per Monteroni, 73100 Lecce, Italy;
bDepartment of Mathematics and Physics Ennio De Giorgi, University of Salento, Via per Arnesano, 73100 Lecce, Italy;
cENEA, Technical Unit of Material Technologies Brindisi, StradaStatale 7 Appia km. 706, 72100 Brindisi, Italy;
dNational Nanotechnology Laboratory of Istituto Nanoscienze-CNR, Via per Arnesano, 73100 Lecce, Italy
Abstract
A new procedure for the alignment of carbon nanotubes in a thermosetting matrix is proposed in this study. The two-step approach is based on (i) the alignment of carbon nanotubes (CNTs) in thermoplastic fibres by electrospinning and (ii) the transfer of these nanocompositefibres into a reactive thermosetting resin, in which they are easily soluble. After fibre dissolution, the CNTs remain aligned in the cured thermosetting matrix.The proof of concept is demonstrated by producing electrospunpolymethyl methacrylate (PMMA) fibres filled with single wall carbon nanotubes (SWCNTs) in the form of unidirectional tape, which are then solubilised into a vinylester (VE) matrix. The PMMA is easily dissolved by the styrene present in the VE resin, leaving SWCNTs aligned in the cured VE network, as confirmed by Raman spectroscopy studies. A 50% increase in elastic modulus (SWCNT 1.3. wt.%) has been obtained by dynamic mechanical analysis carried out in tensile mode at 1. Hz. Thanks to its ability to orient carbon nanotubes in a thermosetting matrix, the proposed method can be exploited also to transfer oriented nanofillers into continuous fibre composites, thus obtaining multiscale or hierarchical composites. © 2014 Elsevier Ltd.
Author Keywords
A. Carbon nanotubes; A. Nanocomposite; B. Curing; D. Raman spectroscopy; E. Electrospinning
Document Type: Article
Source: Scopus

 

Ferlito E.P.a, Ricciari R.a, Padalino M.a, Grasso S.b, Battaglia A.c, Sciuto M.c, Mello D.a, Tapfer L.d, Gerardi C.a
(2014) Surface and Interface Analysis, Article in Press.
aST Microelectronics Stradale Primosole 50 95121 Catania Italy;
bSTMicroelectronics Via C. Olivetti 2 Agrate Brianza, Milano Italy;
c3Sun Contrada Blocco Torrazze 95121 Catania Italy;
dUTTMATB S. S ENEA 7Appia km 706 72100 Brindisi Italy
Abstract
Among the transparent conductor, one of the most interesting is the Al doped MgxZn1-xO films for their electrical properties that make it very attracting for solar cell application. In this work, the Mg distribution in Al doped MgxZn1-xO films was investigated in order to find a reliable methods to determine Mg distribution. In particular, X-ray diffraction, Auger electron spectroscopy and time of flight secondary ion mass spectrometry were used to characterize the film. Time of flight secondary ion mass spectrometry MCs+ results appear to be the most promising analytical technique. © 2014 John Wiley & Sons, Ltd.
Author Keywords
Auger; MgxZn1-xO; ToF-SIMS; XRD
Document Type: Article in Press
Source: Scopus

 

Jafrancesco D.a, Sansoni P.a, Francini F.a, Contento G.b, Cancro C.c, Privato C.c, Graditi G.c, Ferruzzi D.d, Mercatelli L.a, Sani E.a, Fontani D.a
(2014) Renewable Energy, 63, pp. 263-271
aCNR-INO National Institute of Optics, Largo E. Fermi 6, Firenze 50125, Italy;
bENEA Brindisi Research Centre, SS 7 Appia Km 712, Italy;
cENEA Portici Research Centre, Via Vecchio Macello, 80055 Portici, NA, Italy;
dINAF Astrophysical Observatory of Arcetri, Largo E. Fermi 5, Firenze 50125, Italy
Abstract
The optical design of a concentration system for a solar furnace is studied, proposing several possible solutions. The foreseen use of this solar furnace is to test components and methodologies for solar applications. The analysis assesses and compares the optical performances of several possible configurations. The possibility of employing in a solar furnace an array of off-axis mirrors as primary optics is examined comparing simulations with various diameters and different configurations. In particular the paper compares spherical mirrors, parabolic mirrors with axis inclined with respect to the heliostat rays and a paraboloid with axis parallel to the rays arriving from the heliostat. It proposes an optimal solution, with spherical mirrors on a spherical envelope, which is compared to the heliostat-axis paraboloid. Considering realisation tolerances, mirrors positioning, mirrors pointing and solar divergence effects they equivalently concentrate the sunlight on the receiver. © 2013 Elsevier Ltd.
Author Keywords
Concentrating solar power; Lighting simulation; Optical design; Solar energy; Solar furnace
Document Type: Article
Source: Scopus

 

Contento G.a, Oliviero M.b, Bianco N.b, Naso V.b
(2014) International Journal of Thermal Sciences, 76, pp. 147-154. Cited 2 times.
aENEA-Italian National Agency for New Technologies, Energy and Sustainable Economical Development Brindisi Research Centre, SS 7 Appia km 730, Italy;
bDipartimento di Ingegneria Industriale, Università Degli Studi di Napoli Federico II, P.le Tecchio 80, 80125 Napoli, Italy
Abstract
A simplified analytical-numerical method to model radiation heat transfer in metallic foams is proposed. It modifies a model taken from the literature and allows to predict the radiative conductivity for high and low porosity foams. A simplified cubic representative elementary volume of the foam is assumed and radiative heat flux is evaluated by computing radiosities and view factors. The analytical approach proposed in this paper slightly modifies some coefficients of the original model. Test ray-tracing and numerical simulations based onto Monte Carlo method are carried out in order to consistently calculate some view factors. The comparison with experimental results shows that predictions of the proposed model are more accurate than those of the original one. © 2013 Elsevier Masson SAS. All rights reserved.
Author Keywords
Metallic foams; Modelling; Radiative conductivity Porosity; Radiative heat transfer
Document Type: Article
Source: Scopus

 

Greco A.a, Maffezzoli A.a, Casciaro G.b, Caretto F.b
(2014) Composites Part B: Engineering, 67, pp. 233-238.
aDepartment of Engineering for Innovation, University of Salento, Via per Monteroni, 73100 Lecce, Italy;
bENEA, Italian National Agency for New Technologies, Energy and Sustainable Economic Development, Brindisi Research Centre, S.S. 7, Km. 706c, 72100 Brindisi, Italy
Abstract
This work is aimed to study the mechanical properties of basalt fibers, and their adhesion to polypropylene (PP) matrices. Single filament tensile tests were used to calculate the strength of different types of fibers, characterized by different providers and surface treatment. Single fiber fragmentation tests (SFFT) were used to calculate the critical length of the fibers, in a homopolymer PP matrix and in a maleic anhydride modified PP matrix. It was shown that the tensile strength of the fibers is not significantly influenced by the origin or the surface treatment. Only fibers without any sizing show very reduced mechanical properties. On the other hand, the tensile strength was shown to be severely dependent on the filament length. Weibull theory was used in order to calculate the fitting parameters σ0 and β, which were necessary in order to extrapolate the tensile strength to the critical length determined by SFFT. This allowed calculating the adhesion properties of the basalt fibers. It was shown that fiber-matrix adhesion is dependent on both the presence of sizing on the fiber surface, as well as on the modification of the matrix. © 2014 Elsevier Ltd. All rights reserved.
Author Keywords
A. Thermoplastic resin; B. Fiber/matrix bond; B. Mechanical properties; Basalt fibers
Document Type: Article
Source: Scopus

 

Di Girolamo G.a, Marra F.b, Blasi C.c, Schioppa M.c, Pulci G.b, Serra E.a, Valente T.b
(2014) Ceramics International, 40 (7 PART B), pp. 11433-11436.
aENEA, Materials Technology Unit, Casaccia Research Centre, Rome, Italy;
bDepartment of Chemical Engineering Materials Environment, Sapienza University of Rome, INSTM Reference Laboratory for Engineering of Surface Treatments, Rome, Italy;
cENEA, Materials Technology Unit, Brindisi Research Centre, Brindisi, Italy
Abstract
Rare-earth zirconates are potential materials for thermal barrier coatings. Their properties are not still well known, due to any lacks in processing and characterization techniques. To this purpose lanthanum zirconate coatings were herein manufactured by plasma spraying. The coatings exhibited high porosity, due to the presence of pores, splat boundaries and microcracks. The high-temperature evolution of mechanical properties was investigated by arranging specific bending tests up to 1500 °C using SiC testing assembly which allows to reconstruct and measure the sample curvature and the deformation. At higher temperatures the coatings showed an inelastic behavior, related to their unique microstructure, as well as a toughening effect. © 2014 Elsevier Ltd and Techna Group S.r.l. All rights reserved.
Author Keywords
C. Mechanical properties; E. Thermal applications; Plasma spraying
Document Type: Article
Source: Scopus

 

Contento G.a, Oliviero M.b, Bianco N.c, Naso V.c
(2014) International Journal of Heat and Mass Transfer, 76, pp. 409-588.
aENEA - Italian National Agency for New Technologies, Energy and Sustainable Economical Development, Brindisi Research Centre, SS 7 Appia km 730, Brindisi, Italy;
bIstituto Per I Polimeri, Compositi e Biomateriali, Cons. Naz. Delle Ric., P.le Fermi, 1, 80055 Portici, Italy;
cDipartimento di Ingegneria Industriale, Università degli Studi di Napoli Federico II, P.le Tecchio, 80, 80125 Napoli, Italy
Abstract
A theoretical approach proposed in the literature has been used to develop a new radiative heat transfer model based on the tetrakaidecahedric representation of open cell metal foams proposed by Lord Kelvin. The analytical approach has been combined with numerical simulations based onto ray-tracing Monte Carlo method. An iterative matrix algebra implemented procedure has been used to consistently calculate the coefficients involved in view factors. The radiative conductivity of foams has been evaluated by means of the proposed model. Predictions are compared both with experimental results from the literature, obtained on several metallic foams, and with predictions given by an existing simpler model based on a cubic representation of the foam unit cell. The agreement of experimental results with predictions derived by means of the proposed model is good and far better than that with predictions by the simpler model. © 2014 Elsevier Ltd. All rights reserved.
Author Keywords
Metal foams; Modeling; Porosity; Radiative conductivity; Radiative heat transfer
Document Type: Article
Source: Scopus

 

Di Girolamo G.a, Brentari A.b, Blasi C.c, Serra E.a
(2014) Ceramics International, 40 (8 PART B), pp. 12861-12867.
aENEA, Materials Technology Unit, Casaccia Research Center, Rome, Italy;
bENEA, Materials Technology Unit, Faenza Research Center, Faenza, Italy;
cENEA, Materials Technology Unit, Brindisi Research Center, Brindisi, Italy
Abstract
Alumina-based coatings are employed in many industrial applications, in order to protect the surface of metal components against high temperature, wear, corrosion and erosion. In this work two different alumina-based coatings were fabricated by atmospheric plasma spraying (APS), starting from powder particles composed of pure Al2O3 and Al2O3-3 wt% TiO2, respectively. Their phase composition was investigated by X-Ray Diffraction (XRD) and revealed that both the as-sprayed coatings were mainly composed of metastable γ- and α-Al2O3 phases. The γ phase recrystallized to α phase after heat treatment. The porous microstructure was analyzed by Scanning Electron Microscopy (SEM) and Energy Dispersive Spectroscopy (EDS). Thin TiO2-rich splats were observed within the microstructure of alumina-titania coatings. The pure alumina coatings exhibited similar porosity and higher microhardness than the alumina-titania ones (12.8 against 9.9 GPa). Both the coatings herein analyzed are particularly promising for high-temperature anti-wear applications, because of their enhanced mechanical properties. © 2014 Elsevier Ltd and Techna Group S.r.l.
Author Keywords
Coatings; D. Alumina; Microstructure; Plasma spraying
Document Type: Article
Source: Scopus

 

Di Girolamo G.a, Brentari A.b, Blasi C.c, Pilloni L.a, Serra E.a
(2014) Metallurgical and Materials Transactions A, Article in Press.
aTechnical Unit of Materials, Casaccia Research Centre, ENEA, Rome, Italy;
bTechnical Unit of Materials, Faenza Research Centre, ENEA, Rome, Italy;
cTechnical Unit of Materials, Brindisi Research Centre, ENEA, Brindisi, Italy
Abstract
MCrAlY coatings are usually adopted to improve the environmental resistance of Ni-based superalloy components of turbine engines against high-temperature oxidation and hot corrosion. In this work, CoNiCrAlYRe coatings were produced by atmospheric plasma spraying. The coatings exhibited relatively low oxygen content and porosity. X-ray diffraction, scanning electron microscopy, and energy dispersive spectroscopy analyses revealed that the high-temperature exposure at 1383 K (1110 °C) promoted the growth of an oxide scale on the top surface being composed of a continuous and dense Al2O3 inner layer followed by an outer mixed layer (Cr2O3 and spinels). The oxide scale was mainly composed of Al2O3, while the formation of mixed oxides occurred at lesser extent. After high-temperature exposure, the formation of internal oxides in some areas reduced the inter-lamellar cohesion, so that a decrease in microhardness was found. © 2014 The Minerals, Metals & Materials Society and ASM International.
Document Type: Article in Press
Source: Scopus