M.O. Figueiredo

Universidade NOVA de Lisboa | NOVA · Department of Materials Science (DCM)

Poster

Poster

The contribution of laterites to geodiversity in Guinea-Bissau is represented by different forms of relief with focus on: boual/bowal, laterite plateaus, slope deposits, collapsed duricrusts, wendous/vendus (seasonal lakes). Geodiversity also deals how local people adapt and use rocks and soils, such as the interaction of ethnic/traditional uses (a...

Resumo: Apesar de ser um elemento disperso e escasso na natureza, as propriedades químicas e físicas do rénio tornaram este metal muito procurado para aplicações tecnológicas avançadas, aumentando assim o seu valor económico. Com o objectivo de compreender o comportamento mineroquímico do rénio no principal mineral carreador (molibdenite) tendo em...

Selenium is an essential nutrient for humans, animals and microorganisms, but it becomes toxic at concentrations slightly above the nutritional levels. This naturally occurring trace element can be released to the environment from various anthropogenic sources such as mining, agricultural, petrochemical and industrial processes and its toxicity is...

Rhenium is a very scarce element, occurring in the Earth's crust mainly carried by molybdenite (MoS2). Due to a very low availability comparative to actual industrial demand, rhenium is nowadays one of the most expensive mineral commodities and an increased interest is focused on exploring residues resulting from a long-term mining, particularly of...

Decorative panels of ceramic glazed tiles comprise a valuable cultural heritage in Mediterranean countries. Their preservation requires the development of a systematic scientific approach. Exposure to an open-air environment allows for a large span of deterioration effects. Successfully overcoming these effects demands a careful identification of i...

Despite being a very scarce element, the remarkable physical and chemical properties of rhenium render it a highly demanded commodity for advanced applications in important industrial fields, therefore increasing its economic value. The research project MinReMol was conceived to highlight the minerochemical behavior of rhenium in molybdenite (main...

Conserving the cultural heritage is a general concern and the use of non-destructive techniques to characterize ancient materials is important. Serious deterioration effects in environmentally exposed ancient glazed ceramic tiles arise from the development of micro-organisms (algae/fungi) within the pore system. Subsequent biodegradation processes...

Decorated glazed ceramic tiles are used as an ornamental art, constituting an important cultural heritage whose preservation is mandatory. Environmental conditions are responsible for the degradation of exposed ancient tile panels originating various pathologies, related to the development of microorganisms. This is the case of a valuable 18th cent...

Ferrihydrite is natural ferric oxyhydroxide occurring exclusively nanocrystalline. With ideal formula 5 Fe2 O3 . 9 H2 O, ferrihydrite is quite abundant in sediments, weathering crusts and mine wastes, being characteristic of red pre-soils formed by loose weathered rock plus mineral debris (regoliths) and commonly designated as “2-line” or “6-line”...

The chemical and physical properties of rhenium render it a highly demanded metal for advanced applications in im- portant industrial fields. This very scarce element occurs mainly in ores of porphyry copper-molybdenum deposits as- sociated with the mineral molybdenite, MoS2, but it has also been found in granite pegmatites and quartz veins as well...

Indium is a typical chalcophile element of the Earth's crust, with a very low average content that seldom forms specific minerals, occurring mainly as dispersed in polymetallic sulphides. Indium recovery is based primarily on zinc extraction from sphalerite, the prototype of so-called tetrahedral sulphides, wherein metal ions fill half of the avail...

The composition of cobalt blue pigments used in ancient blue-and-white Chinese glazes is known to have changed between the 14th and the 17th century and ratios of some main chemical components plus trace elements are relevant guide-lines to establish the porcelain manufacture period. Once archaeological findings of Chinese porcelains can contribute...

In Portugal there are three uranium provinces-Beiras, Trás-os-Montes and Alto Alentejo-from which uranium mining only took place in the first one. Extraction in the Beiras province was undertaken in about 60 mines. The first license dates from 1907 to mine radium, and the interest in uranium only started after the Second World War when the market d...

The modern X-ray sources available at large-scale installation facilities allow for the study of materials through powerful chemical and structural characterization techniques, particularly X-ray absorption spectroscopy. Along the last decade, the non-destructive characterization of a diversity of cultural materials - glazed ceramics (decorated til...

The Iberian Pyrite Belt is one of the most outstanding European ore provinces and hosts one of the largest concentrations of massive sulfide deposits today, totaling 1,850 million metric tons (Mt) in more than 90 deposits. Lagoa Salgada is a small orebody (estimated to have at least 4 Mt) and, as yet, an unexploited orebody found within this ore pr...

Jarosite, KFe(3)(SO(4))(2)(OH)(6), is a secondary iron sulphate often found in acid mine drainage (AMD) environments, particularly in mining wastes from polymetallic sulphide ore deposits. Despite the negative environmental connotation usually ascribed to secondary sulphate minerals due to the release of hazardous elements to aquifers and soils, ja...

Iron is a powerful chromophore element whose pigmenting properties were the first to be recognized among transition metals. The interest in blue iron minerals as pigments for painting was enhanced with the use of vivianite—a natural hydrated ferrous phosphate, Fe3(PO4)2⋅8H2O—which in medieval Europe became an alternative to the expensive lapis lazu...

Currently, iron sulphates formed in abandoned sulphide-ore mines have a very negative connotation within acid mine drainage (AMD) because in general these secondary hydroxilated and/or hydrated minerals concentrate a large span of toxic elements. However, this apparently penalizing feature may occasionally turn out to be a positive contribution, on...

Discovered in 1863, indium is nowadays a strategic scarce metal used both in classical technologic fields (like low melting-temperature alloys and solders) and in innovative nano-technologies to produce "high-tech devices" by means of new materials, namely liquid crystal displays (LCDs), organic light emitting diodes (OLEDs) and the recently introd...

Variations in the interactions between marine ecosystems, thermohaline circulation, external forcing and atmospheric greenhouse gases concentrations are not yet fully represented in detailed models of the glacial-interglacial transitions. Most of the research on past productivity changes has been focused so far on high-productivity areas such as up...

The trade of Chinese blue-and-white porcelains to Europe became intense along the XVII century following the maritime contact first established by the Portuguese navigators by the end of XVI century and nowadays European museums and traders face an increased need for ascertaining the authenticity of such art objects through non-destructive tests. W...

An environmental concern for uranium-producing countries is the possible dissemination of this radionuclide in soils nearby mineral deposits, even non-exploited ones. This is the case of the Nisa uranium deposit in Alto-Alentejo, East-central Portugal, considered economically impracticable after prospecting efforts that left behind masses of accumu...

Sulphur occurs under a diversity of formal oxidation states being simultaneously an essential plant nutrient and an environmental pollutant. Intermediate formal valences between 6+ (sulphate) and 4+ (sulphite) were assigned by previous authors in soil colloids by X-ray absorption spectroscopy; a search for similar electronic states was undertaken b...

: Since the involvement in a national research project 1 in 1995-1997 with the partnership of the National Tile Museum in Lisbon, until a recent European project 2 with partners from Mediterranean countries which cultural patrimony entails glazed ceramic tiles, the authors have been active in the non-destructive characterization of ceramic and vitr...

A review is presented on constructive techniques plus materials and the processes involved in degradation phenomena observed in two historical monuments: the Zambujeiro dolmen (Portugal) and the Roman Aqueduct of Carthage (Tunisia). Dolmens are particularly impressive megalithic constructions for the dimensions of granite blocks. At Zambujeiro, th...

Lead-rich blue-and-white tile glazes (16th to 17th century, Portuguese manufacture) were studied by x-ray absorption near-edge spectroscopy (XANES) to assess the speciation and coordination environment of zinc, a fuser metal commonly used along with lead in ancient glazes. Zincite (ZnO) and smithsonite (ZnCO3) were used as model compounds for Zn2+...

The colours of natural and synthetic beryl (ideally Be3Al2Si6O18) have been attributed either to the presence of chromophore ions partially replacing Al and/or Be (Cr³⁺, Fe2+/3+, Mn²⁺) or to the occurrence of colour centres related to the presence of multi-atomic groups. However, no full explanation has been proposed for the blue colour in natural...

Ceramic tiles used to manufacture artistic panels during the XVI to the XVIII centuries were decorated with high-lead soda-lime glazes, incorporating a diversity of chromophore cations, as ascertained by SRXRF (synchrotron radiation X-ray fluorescence). Previous X-ray absorption spectroscopy (XAS) studies have shown that sodium and lead are hosted...

The convergence between extended structure provided by X‐ray diffraction and local structure of antimony extracted from spectroscopic data is reached through an alternative crystallographic description for a Sb‐pyrochlore arrangement within the same space group symmetry of pyrochlore structure‐type. A full account on this description is presented,...

The blue colour in ancient soda-lime glasses has been attributed to the presence of copper and/or cobalt but the origin of different shades is not yet fully interpreted. As a contribution to this question, a non-destructive X-ray absorption study at [ Cu]K-edge was undertaken on the blue (turquoise) layer from a “Nueva Cadiz” type tubular glass bea...

The origin of a red colour in ancient soda-lime glasses has been attributed either to the presence of both copper clusters and cuprous oxide or to copper alone. As a contribution to this question, a non-destructive X-ray absorption study at the [ Cu]K-edge was undertaken on the red layer from a singular “rosette”-type archaeological glass bead date...

Aged lead-rich, tin-opacified glazes from polychrome tiles manufactured in the 16th–18th century were studied to ascertain the structural role of lead. Glaze fragments with white, blue, yellow, brown and green colouring were analysed using non-destructive X-ray techniques, both laboratorial – X-ray diffraction to identify crystalline components – a...

The pattern of minor elements incorporation in columbites from granitic pegmatites of Alto Ligonha, Mozambique, was disclosed on the basis of synchrotron radiation X-ray fluorescence (SRXRF) data. Major elements (Fe, Mn, Nb, Ta) were analyzed with an electron microprobe (EPMA).Minor and trace element contents display a common general trend pointing...

Using synchrotron radiation-based analytical (SRXRF) and spectroscopic (XAS) non-destructive techniques, a study was carried out on lead-rich, tin-opacified yellow glazes (silica-lime-alkali type glasses) decorating ancient tiles (17–19th century).These glasses have a rather complex chemistry, being currently assumed that the yellow pigment used fo...

An X-ray absorption study on O 1s edge was carried out on natural oxides with rutile-type crystal structure – the minerals rutile (TiO2), pyrolusite (MnO2), cassiterite (SnO2) and plattnerite (β-PbO2). Despite the chemical bonding being essentially ionic, the differences in the outer electron shell of cations clearly influence post-edge features of...

During an emergency archaeological intervention conducted in downtown Lisbon (the Old City), ceramic foundry crucibles were collected in a layer of embankment debris used after the earthquake that destroyed the city in 1755. A chemical and phase-constitution study was undertaken to complement the dating and to ascertain the kind of foundries (metal...

Volcanic glasses with phonolitic composition from Boavista Island (Cape Verde Archipelago) display lower silica and higher water contents, plus a calculated composition indicating an excess of normative albite, when compared to vitreous rocks with similar composition reported for other Atlantic islands. A complete chemical study of vitrophyric rock...

The geochemical processes involved in phosphorous enrichment of volcanic rocks under shallow seawater are not yet fully understood. As a contribution to this problematic, a detailed chemical characterization of phosphatized basaltic hyaloclastites assigned at Sal Island, Cape Verde archipelago, was undertaken using synchrotron radiation X-ray fluor...

The results of a photon microprobe (synchrotron radiation XRF) study of tubular blue glass beads of the Nueva Cadiz type uncovered by recent excavations in the center of Lisbon are reported as a contribution to the non-destructive chemical characterization of these cultural artifacts, aiming ultimately at ascertaining their provenance and manufactu...

The semiconductive behaviour of amorphous and crystalline Cr-oxide films deposited on stainless steels was studied by capacitance and photoelectrochemical measurements. The amorphous films presented metallic behaviour. For the crystalline films, bandgaps were determined for direct and indirect transitions. Doping densities evaluated from Mott–Schot...

Structural features and materials plus construction and reconstruction techniques used at the Aqueduct of Carthage are reviewed. A minerochemical study of mortars from the water conduits, pillars and arches was undertaken. Differentiating features between mortar types - early Roman, Byzantine, medieval (Hafsid) and modern - are outlined on the basi...

This chapter discusses the geochemical and mineralogical research that were undertaken to determine the origin of degradation observed in stone monuments of the Misericórdia church. This facade was constructed using volcanic rocks of trachyte composition. The degradation process in these stones is correlated to the precipitation of secondary phases...

Among the volcanic rocks from Azores Islands, trachyte stones have been preferentially used through centuries in many monument facades because of their color and softness. After a few centuries, these stones show remarkable decaying. This chapter describes the study conducted to compare the trachyte stones from quarries and monument to point out th...

The results of a photon microprobe study on the influence of size and orientation of single mineral grains on geochemical data when analysing geological samples are presented. A large crystal of primary pegmatitic muscovite and an aggregate of small lamellar secondary lepidolite grains were analysed at various points. The primary synchrotron radiat...

The results of a photon microprobe study carried out on incrustations and sublimates collected at active fumaroles of the Fogo Island volcano (Cape Verde Archipelago) following the eruption of April 1995 are reported. The mineral phases studied were previously identified by X-ray powder diffraction: sulfur, sodium and potassium chlorides, calcium s...

Surface treatment of zinc galvanised steel, using chromate based baths, was extensively used in order to both improve the corrosion resistance and enhance the chemical adhesion of organic coatings. Although the detailed formation mechanism of chromium conversion coatings has remained a subject of wide interest for 30 years, it still remains to be c...

Corrosion resistance and artistic appearance of passive chromium oxide coatings developed over stainless steel by chemical conversion methods are revisited. Preparation technique and thermal processing of the films were optimized to improve protection efficiency and the control of colour development - from yellow to green through violet - is at pre...

The results from an experimental study on rust conversion by phosphoric acid are presented. Steel surfaces were pre-rusted for variable periods in a natural atmosphere, subsequently brushed and pretreated with phosphoric acid solutions at different concentrations. It was found that the conversion of rust depends strongly on the time of exposure and...

The application of ion chromatography, conductometry and total carbon analysis to the study of desalination of 18th century tiles and mortars is described. Ion chromatography is shown to be a simple and adequate technique for the identification and quantitative analysis of ions which are extracted during desalination. Chloride, nitrate, sulphate, c...

The Influence of the Interfacial Conditions on Rust Conversion by Phosphoric Acid

A Influência das Condições Interfaciais na Conversão de Ferrugem pelo Ácido Fosfórico

The application of ion chromatography, conductometry and total carbon analysis to the study of desalination of seventeenth-century tiles is described. Mechanical stirring of the immersion water leads to erosion of the ceramic body and does not seem to have much effect on the total amount of salts removed except during the initial period. Water abso...

The detection of sub-trace concentrations (ng g−1) of heavy elements in geological samples by X-ray fluorescence may be achieved by the use of synchrotron radiation (SXRF). Minimum detection limits range from a few μg g−1 to tenths of ng g−1 depending on the atomic number of the analyte vs. the matrix mean atomic number. Recently, the assessment of...

Corrosion-resistant chromium oxide films over stainless steel (Fe-27 Cr alloy) were obtained by chemical conversion and thermal treatment. It was found that as-converted films are amorphous and thermal treatment promotes crystallization. Films treated at 573 K and 973 K present a trigonal corundum-type structure. At 1073 K, a second crystalline pha...

Improved Performance of Phosphoric Acid Anti-Corrosive Pretreatments when Aluminium Hydroxide is Added

Members of the solid solution series Zn1-x Fe x Al2O4 (x = 0.2, 0.4, 0.6 and 1.0) with spinel structure were synthesized by direct solid-state reaction of the simple metal oxides and metallic iron in evacuated silica ampoules at 1175C. Two aliquots of the single-phase spinels obtained for each composition were annealed under vacuum at 1075 C and 72...

Members of the spinel solid solution series ZnFeyAl2-yO4 (y = 0, 0.2, 0.4, 0.6, 1.0, 1.5, and 2) were synthesized by direct solid state reaction of the simple metal oxides in air at 1400 K. Two aliquots of the single-phase spinels obtained for each composition were annealed at 1350 and 1000 K for 48 hr and then quenched in water.The structural stud...

Chromium oxide coatings deposited on stainless-steel surfaces were studied by X-ray absorption spectroscopy (XAS) using synchrotron radiation. Migration of manganese from the steel substrate into the film was found to be significant when gamma-Cr2O3 was developed by thermal treatment of an originally amorphous coating. The passivating efficiency of...

A description is presented of fluorescence spectrometric experiments using synchrotron radiation and an energydispersive detection system performed at the LURE (DCI storage ring) where a study of geological materials is under development. Early results obtained for natural lithium aluminosilicates (lepidolites) from pegmatite formations in northern...

Although many papers have been published about the use of phosphoric acid as a pretreatment for rusted steel surfaces, the main mechanisms involved in its action are not yet well understood. In the present paper the authors advance a further contribution towards a knowledge of those mechanisms through the results of experimental work in which they...

A Utilização de Pré-Tratamentos com Base em Ácido Fosfórico Aditivado ou Não com Hidróxido de Alumínio sobre Aço Deficientemente Decapado

Intense phosphatization of basaltic hyaloclastites from Sal, Cape Verde islands, is described. Petrogenetic considerations are presented on the basis of field relations and petrographic, mineralogic and geochemical data. It is suggested that phosphatization may be connected with P liberation from phospho-organic compounds either present in a supraj...

Ti 2p X-ray absorption spectra for a series of minerals have been measured. Crystal field multiplet calculations can explain the spectral shape. The asymmetry of the e g , peak is shown to be related to distortions of the Ti IV octahedron. It is found, theoretically as well as experimentally, that the absorption spectra are more sensitive to tetr...

Natural iron-containing gahnite spinels (ZnAl2O4) are investigated using Mossbauer spectroscopy. Ferrous and ferric iron are completely ordered into tetrahedral and octahedral sites, respectively. Spectra recorded at 295, 77 and 11 K show a dramatic change in the absorption envelope; this effect is ascribed to an inhomogeneous electric field gradie...