Recursos Minerais - RM
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Browsing Recursos Minerais - RM by Subject "Absorção de raios X"
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- An approach to the binding state of indium in natural chalcogenides through the analysis of In L3 edge XANES spectraPublication . Silva, Teresa; de Oliveira, Daniel Pipa Soares; Veiga, JP; Rosa, Diogo; Figueiredo, M. OndinaA study using synchrotron radiation X-ray absorption spectroscopy at In L3-edge is presented, as a contribution to interpret the binding state of indium in natural chalcogenides considering the increase of applications of this scarce metal.
- An insight into the firing conditions of Chinese blue-and-white porcelain through XANESPublication . Coutinho, ML; Veiga, JP; Ruivo, Andreia; Silva, Teresa; Salas-Colera, Eduardo; Bottura Scardina, Silvia; Lima, Augusta; Figueiredo, Elin; Cotte, Marine; Lima, M.M.R.A.ABSTRACT: Chinese blue-and-white porcelain is found in archaeological excavations worldwide, being significant evidence of global trade routes and cultural exchange. Synchrotron radiation-based techniques have been applied for studying cobalt speciation to establish a correlation between the cobalt and iron oxidation state and local coordination environment in the rich blue shades of Chinese blue-and-white porcelain. However, the relationship between the firing atmosphere conditions and the speciation of cobalt has not been established yet. In this study, underglaze blue models were produced and fired in air or under reducing atmospheres to ascertain the effect of the firing atmosphere in cobalt and iron speciation. The experimental results were compared with data obtained on historical samples of ancient porcelain shards. The microstructure and colour of the produced underglaze blue models were investigated by variable pressure scanning electron microscopy (VP-SEM-EDS), using a hyperspectral imaging camera (Vis-SWIR reflectance spectroscopy) and colorimetry. The formal valence and coordination of cobalt and iron ions of the glaze were determined by X-ray absorption spectroscopy (XAS), particularly X-ray absorption near edge structure (XANES), using synchrotron radiation. Spectral features demonstrated that both cobalt and iron speciation were affected by the firing atmosphere and therefore could be used to ascertain the firing atmosphere.
- An X-ray spectrometry and absorption spectroscopy study of blue-and-white glazes from ancient Chinese porcelains [Abstract]Publication . Figueiredo, M. Ondina; Silva, Teresa; Veiga, JP
- Ancient Chinese blue-and-white porcelain glazes : can we measure the oxidation state of cobalt through X-ray absorption spectroscopy?Publication . Figueiredo, M. Ondina; Silva, Teresa; Veiga, JP
- Chromophore behaviour of iron, copper, cobalt and antimony in ancient tile, faience and porcelain glazes plus archaeological glass beads : an overview on X-ray absorption near-edge spectroscopy studiesPublication . Figueiredo, M. Ondina; Veiga, JP; Silva, Teresa
- Co and Cu K-edge XANES study of the glazed tiles from the Fronteira Palace (Lisbon, Portugal) [Poster]Publication . Coutinho, ML; Silva, Teresa; Figueiredo, Elin; Rolim, M.; Salas-Colera, Eduardo; Veiga, JPABSTRACT: The Fronteira Palace located in Lisbon was built during the second half of the seventeenth century. The Palace is known for its unique azulejos (Portuguese glazed tiles) dated from the 17th and 18th century which were profusely used both in the interior of the palace and on its magnificent formal gardens. The gardens have a unique cladding of high relief lustre tiles combined with blue-and-white tiles adorning the Gallery of the Kings (Figure 1). Samples of azulejos from Gallery of the Kings, were characterized in a previous work by PIXE. They display a silica alkali-lead glass or silica alkali glass and chromophores based on Co for the blue colouring and Cu for the red-lustre effect . In fact, the analyses showed that the colourless glaze has a lead-alkali silicate composition and a copper-rich lustre overlay, in agreement with the Manise lustreware production (Spain) after the XVII century. To achieve a comparison between manufacturing techniques and pigments used samples were characterized using X-Ray Absorption Spectroscopy. XANES techniques can provide information on the structural behaviour of transition metals in the vitreous matrix - namely, their bonding state and coordination environment, providing relevant information regarding the Co and Cu as chromophores.
- From ceramics and glasses to mortars and stones: using synchrotron radiation to study cultural heritage [Poster]Publication . Veiga, JP; Silva, Teresa; Coutinho, MLABSTRACT: The use of Synchrotron Radiation to study cultural heritage, either through objects with museum interest or materials from historical monuments is no longer a novelty. Advanced nondestructive characterization techniques to understand degradation phenomena, ageing mechanisms and ancient manufacturing techniques is now a well-established trend. Profiting from the properties of synchrotron radiation and using large scale facilities such as ESRF (European Synchrotron Radiation Facility, Grenoble, France), BESSY (Berliner Elektronenspeicherring-Gesellschaft für Synchrotronstrahlung, Berlin, Germany) and former LURE (Laboratoire pour l’Utilization du Rayonement Synchrotron, Orsay, France), it was possible to study a great diversity of materials and objects of cultural value from different ages and provenances through X-rays. Synchrotron radiation sources available at these large-scale facilities provide powerful chemical and structural characterization tools such as micro X-ray fluorescence and X-ray absorption spectroscopies (XANES and EXAFS). Different case studies will be presented regarding the variety of materials studied by a group of Portuguese researchers from the past two decades (ceramics, glasses, inorganic pigments and lithologic materials).
- Indium before entering thin filmsPublication . Figueiredo, M. Ondina
- Indium-carrier minerals in polymetallic sulphide ore deposits : a crystal chemical insight into an indium binding state supported by X-ray absorption spectroscopy dataPublication . Figueiredo, M. Ondina; Silva, Teresa; de Oliveira, Daniel Pipa Soares; Rosa, Diogo
- Lead in jarosite : an X-ray absorption spectroscopy approachPublication . Figueiredo, M. Ondina; Veiga, JP; Silva, Teresa; Mirao, Jose
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