789 research outputs found
Characterization of nanograined powder samples using the Rietveld method applied to electron diffraction ring patterns
No full textA full-pattern fitting procedure based on the Rietveld method was applied to electron diffraction ring patterns of a two-phase system, exhibiting the co-presence of zinc sulfide (sphalerite) and zinc oxide (Wurtzite). Bright and dark field (DF) images reveal the presence of micrometric aggregates, composed of quasi-spherical nanosized crystallites. These conventional transmission electron microscopy imaging methods provide a general morphological characterization of the specimens although, in the present case, they are not suitable for a detailed characterization of the microstructural features of the analyzed samples. Owing to the overlap and broadening of the diffraction rings of the two phases, DF images cannot provide a satisfactory picture of the individual crystallites of each single phase. To overcome this limit, the mentioned Rietveld approach was applied to model the electron diffraction data. The crystalline domain size and relevant shapes for both phases were successfully evaluated using the proposed methodological approach. The excellent results obtained in the microstructural characterization of the nanostructured multiphase samples demonstrate the capability of this technique, that may represents a fully quantitative method for the routine characterization of crystalline nanomaterials
Experimental status of 7Be production and destruction at astrophysical relevant energies
No full textThe production and destruction of 7Be plays a significant role in the Big Bang Nucleosynthesis as well as in the framework of the solar neutrino. The 3He(α, γ)7Be reaction cross sections has been measured several times in the last decades, but the precision achieved on reaction rate determinations at the relevant astrophysical energies is not yet satisfactory. The experimental status of this reaction will be critically reviewed, and the theoretical descriptions available will be discussed
Puteoli. L’”Acropoli”. L’instrumentum domesticum di età medievale e rinascimentale
No full textNel contributo sono illustratii due nuclei di reperti ceramici e vitrei di notevole interesse. Il primo nucleo è circoscrivibile in un arco cronologico compreso tra la fine del XII secolo e la prima metà del XIII, proveniente da un contesto chiuso – l’Unità Stratigrafica 670 - relativo ad un livello di rifiuti di manufatti d'uso, molto probabilmente proveniente da una residenza di un certo prestigio, data la presenza in strato, di vasellame di lusso d'importazione; lo scarico obliterava un ambiente antico al di sotto di Palazzo Migliaresi. Il secondo nucleo proviene da un saggio di scavo in via S. Procolo, nelle vicinanze della Curia vescovile ed è stato rinvenuto in uno stesso deposito di terreno, relativo a materiale di scarico, che sigillava un tratto di strada basolata di età romana. Il rinvenimento presenta delle caratteristiche di particolare interesse, in quanto i pezzi sembrano appartenere ad un periodo cronologico omogeneo, che copre la prima metà del XVI secolo
L. Manti, F. Di Martino, V. Magaddino, C. Moriello, A. D’Arco, G. Bisogni, C. Carpentieri, G. Gialanella, M. Giannelli, G. Grossi, P. Scampoli
No full textCharacterization of the mistura alloy used for Venetian sesino coins: 16th century
No full textThe information provided by material investigations on ancient coins is interesting in many respects, as concerns the archaeological and historical research. In this study a set of Venetian sesino coins, minted over a period ranging from 1554 until 1605, have been investigated in order to shed light on some aspects of the so‐called mistura (mixture) alloy. The widespread diffusion of these relatively low‐value coins of the Venetian Republic, commonly used in commercial transactions in the second half of 16th century, also outside the territories of the Republic, makes them an important proxy to be used in the reconstruction of the political and historical events of the period. The specific issue of the actual composition of the mistura alloy is herewith addressed for the first time, using a combined approach based on X‐ray fluorescence and X‐ray diffraction nondestructively applied to the analysis of the samples. It turns out that the mistura alloy, traditionally regarded as a Cu‐Ag two phase alloy, over the latest period of circulation of the sesino coins, was actually made of copper only, still containing minor concentrations of lead, to be regarded as an impurity of the alloy and not as an intentional addition
Le sabbie per la produzione di vetro in epoca romana: una nuova prospettiva sulle fonti di approvvigionamento
No full textRiassunto presentato al Congresso FIST GEOITALIA 2003, Forum Italiano di Scienze della Terra, Bellaria (Rimini, Italia), 16-18 settembre 2003
Materials and technological aspects of gilded buckles from a North Eastern Medieval Italian context
No full textThis study concerns the archaeometric characterization
of two artefacts from the medieval site of San Rocco
(Castelfranco Veneto, Italy). Both of them belong to a larger
set of metallic objects, some being part of tomb ornaments
belonging to two very well distinct periods of frequentation
of the site. Both items are buckles and they have been selected
as representative of two very well-known and established
typologies. The older one, at the end of the sixth—
beginning of the seventh century AD, is made of silver, although
relicts of gold have been found. A number of relevant
counterparts of this item have been found in different
sites of the Longobard Italy. The main body of the second
artefact (second half of the fourteenth century AD) consists
of a bent strip of a copper rich alloy, coated on one side
with a nearly continuous, decorated, gold layer. This is a socalled
lyre-buckle, with a widespread diffusion not only in
Italian, but also North European contexts. From the results
of the analyses carried out using low-vacuum scanning electron
microscopy, energy dispersive X-ray spectroscopy, and X-ray diffractometry, information on manufacturing, gilding
technology and materials have been obtained that will be an
useful benchmark for the archaeometric characterization of
similar items from selected collections. In this way, the already
established typological affinity of these two classes
of items will be extended to technological and materials aspects,
also
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