1,720,967 research outputs found
Thermal and microchemical characterisations of CaSO4-SiO2 investment materials for casting jewellery alloys
No full textDifferential thermal analysis (DTA) and thermogravimetry (TG), X-ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM) and energy dispersive spectrometry (EDS) were used to study the thermal decomposition of calcium sulphate in the CaSO4 (25 wt%)-bonded silica investment which is the commonly used material for casting jewellery gold-based alloys. The thermal decomposition of CaSO4 generates sulphur dioxide, leads to gas porosity in the molten gold-based alloys and therefore, defective jewellery products. This latter reaction was studied as a function of the temperature and atmosphere (air, argon and argon-5% hydrogen). in order to simulate, as for as possible, different casting conditions used by the jewellery industry. Furthermore, special attention was given to the effect of the presence of Zn, Cu2O. CuO and Ag2O on the thermal decomposition of CaSO4. DTG-TG results confirmed that the temperature of the thermal decomposition of CaSO4 bonded with silica was lower with respect to the nearly pure CaSO4. Unfortunately, it was very close to the casting temperature of some typical gold alloys. in addition, the temperature of the decomposition was further lowered when inert and reducing atmospheres are used, as well as in the presence of ZnO, Cu2O. CuO and Ag2O. (C) 1998 Elsevier Science B.V
A novel scientific approach to the conservation of archaeological copper alloys artefacts
No full textA novel research approach focused on innovative materials and methods to assure the long-term stability of bronze archaeological artefacts during exhibition and storage is reported. The work deals with the application of advanced analytical techniques and the development, characterisation and testing of materials and procedures for the conservation, protection and restoration of ancient Cu-based alloy artefacts. Our first aim was the selection of Cu-based alloy artefacts from different archaeological sites in Southern Italy with respect of chemical composition, metallurgical features and corrosion products. This step allowed the identification of the ancient alloys, the study of natural patinas and the identification of the involved degrading agents and mechanisms. Then the selection of long-term reliable, safe and environmentally friendly strategies for conservation was carried out. An original analytical approach based on the production of reference Cu-based alloys submitted to accelerated degradation tests was used to produce corroded samples for testing new materials with corrosion inhibiting properties
Il Progetto ATENA: Applicazione di metodologie innovative per la conservazione di manufatti metallici e ceramici da scavo archeologico e per il recupero delle relative tecniche di produzione
No full textQui di seguito viene illustrato il progetto scientifico ATENA, svolto presso l'Istituto per lo Studio dei Materiali Nanostrutturati (ISMN) del Consiglio Nazionale delle Ricerche (CNR) e co-finanziato dal MIUR con Decreto Direttoriale 9-10-2002, n. 1105/2002. Il progetto si propone di applicare avanzate tecniche diagnostiche strumentali al fine di acquisire la dettagliata conoscenza microchimica e microstrutturale di manufatti metallici e ceramici antichi, di definirne il meccanismo di alterazione e/o degrado e di progettare, sintetizzare e validare opportuni prodotti e formulazioni per il restauro conservativo di tali manufatti. Le conoscenze acquisite sono utilizzabili anche per il recupero delle antiche tecniche di produzione e per una loro possibile riproposizione sia nel campo del restauro integrativo che nell'ambito dell'artigianato culturale
Surface Characterization of Organic Films for the Conservation of Bronze Archaeological Artefacts
No full textSynthesis and characterization of methylcyclopentadienyl-(eta(3)-allyl)platinum and its use as a metallo-organic chemical vapour deposition precursor of platinum
No full textThis communication reports on rapid, efficient synthesis of the metal-organic chemical vapor deposition (MOCVD) precursor (methylcyclopentadienyl)allylplatinum. The compound is shown to be an effective precursor for the deposition of platinum thin films giving deposits of high quality and purity, probably due to the nature of ligands which seems to be good leaving groups as confirmed by mass spectrometric pathway
Recovering bronze metallurgy from archaeological artefacts for the production of reference materials in conservation science
No full textThe production of reference Cu-based alloys is the first step of an original experimental protocol to be used in the field of conservation and restoration of metal artefacts. The production of these synthetic alloys has a double value. They can be used both as suitable substitutes of unique archaeological pieces for testing new materials and methods for conservation, and as guidelines for contemporary metal production. We report on a research activity focused on the recovery of the ancient production techniques from the investigation of archaeological copper-based artefacts. The chemical, physical and metallurgical characterization of several Cu-based artefacts, found in different Italian archaological sites, was carried out by bulk and surface techniques in order to investigate the nature and properties of the metallic substrates and the corrosion products. Chemical and metallurgial formulations of the ancient archaeological alloys were obtained by data analyses. On the basis of these results, a set of Cu-based alloys with different chemical compositions and metallurgical features was produced. The chemical and physical characterization showed that these modern Cu-based alloys strictly resemble the ancient ones constituting the archaeological artefacts from a chemical, micro-morphological and metallurgical point of view
Il degrado di manufatti ceramici archeologici: sistemi diagnostici e metodologie di intervento.
No full textGoing Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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