Search results for "Microanalysis"
showing 10 items of 59 documents
Microchemical surface analysis of historic copper-based coins by the combined use of FIB-FESEM-EDX, OM, FTIR spectroscopy and solid-state electrochem…
2019
[EN] A multi-technique strategy, including microscopy, spectroscopic and electrochemical techniques, is proposed to study thin corrosion layers that form on the surface of historic copper-based coins. An accurate characterisation of this external corrosion layer is important for selecting a suitable conservation and/or restoration treatment. For this purpose, a series of copper-based coins from different historical periods and provenances, which mainly exhibited atmospheric corrosion, was analysed. The morphology of the corrosion layer and the upper core of coins was studied in trenches done on coin surfaces with a focused ion beam gun, coupled to a field emission scanning electron microsco…
High spatial resolution analysis of the iron oxidation state in silicate glasses using the electron probe
2018
The iron oxidation state in silicate melts is important for understanding their physical properties, although it is most often used to estimate the oxygen fugacity of magmatic systems. Often high spatial resolution analyses are required, yet the available techniques, such as μrXANES and μMössbauer, require synchrotron access. The flank method is an electron probe technique with the potential to measure Fe oxidation state at high spatial resolution but requires careful method development to reduce errors related to sample damage, especially for hydrous glasses. The intensity ratios derived from measurements on the flanks of FeLα and FeLβ X-rays (FeLβf/FeLαf) over a time interval (time-depend…
Evidence for a biogenic, microorganismal origin of rock varnish from the Gangdese Belt of Tibet
2010
In the present study we examined material from the Ashikule Basin of Tibet. Chemical analyses were performed by use of energy dispersive X-ray spectroscopy and electron probe microanalysis to clarify whether the varnish layers that had developed on the surface of the rhyolite are indeed composed of varnish bodies and silica glaze. Electron microscopic analyses revealed that the surface of the varnish is covered both by filamentous hyphae bacterial and cocci-shaped forms. Within the varnish mineral layer in those samples two forms of bacteria-like microorganisms exist; cocci as tightly packed bacterial aggregates [within varnish bodies], and bacillus-like microorganisms [within the varnish m…
Study and dating of medieval ceramic tiles by analysis of enamels with atomic absorption spectroscopy, X-ray fluorescence and electron probe microana…
2002
Abstract This paper reports an analytical study of enamel on fragments of medieval tiles using atomic spectroscopy techniques — AAS, XRF and SEM/EDX. The samples came from a hermitage in the region of Valencia (Spain) and have different motifs, mainly floral ones in a wide variety of colors. A study of the soluble salts in the biscuits and mortar was carried out using AAS to determine their present capacity to produce efflorescence and the type of efflorescence. XRF was used to identify the oxides responsible for the different colors and the pigments used over large areas of the tiles (white and green). SEM/EDX was used to characterize the white and green and smaller areas of other colors. …
XRD microstructural analysis of mullites obtained from kaolinite–alumina mixtures
2000
Abstract A microstructural study of mullite obtained by the reaction sintering of kaolinite–α–alumina mixtures in the range 1150–1700°C has been performed by using X-ray line profile analyses together with scanning and transmission electron microscopy equipped with microanalysis by energy dispersion (SEM-EDS, TEM-AEM). Two kinds of morphology corresponding to primary (elongated grains) and secondary (equiaxed grains) mullite have been observed. A bimodal crystallite size distribution has been detected through XRD microstructural analysis from 1300°C. The results obtained by this method are compared with SEM/TEM data.
Concept of Biogenic Ferromanganese Crust Formation: Coccoliths as Bio-seeds in Crusts from Central Atlantic Ocean (Senghor Seamount/Cape Verde)
2011
At depths of 2,000 to 3,000 m, seamounts from the Cape Verde archipelago (Central Atlantic Ocean) are largely covered with ferromanganese crusts. Here we studied 60 to 150 mm thick crusts from the Senghor Seamount (depth: 2257.4 m). The crusts have a non lamellated texture and are covered with spherical nodules. The chemical composition shows a dominance of MnO2 (26.1%) and Fe2O3 (38.8%) with considerable amounts of Co (0.74%) and TiO2 (2.1%). Analysis by scanning electron probe microanalyzer (EPMA) revealed a well defined compositional zonation of micro-layers; the distribution pattern of Mn does not match that of Fe. Analysis by high resolution scanning electron microscopy (SEM) revealed…
The determination of certain major and minor elements in geological samples by inductively coupled plasma atomic emission spectrometry. Some interfer…
2000
Direct ICP-AES measurements of the digested geological standard reference material samples yielded the wrong information about their composition. The differences between certified and measured concentrations of the samples were due to the complicated sample matrix. The measured concentrations can be successfully corrected by using a multiple linear regression technique. The correction is based on the multiple regression line calculated from the analytical results at synthetic mixtures of matrix elements, where concentrations varied on five levels. There were no significant (P = 0.05) differences between certified and measured concentrations in standard reference materials after the correcti…
Identification of Earth Pigments by Applying Hierarchical Cluster Analysis to Solid State Voltammetry. Application to Severely Damaged Frescoes
2007
Multivariate chemometric methods are applied for identifying earth pigments from square-wave voltammetric measurements performed at pigment-modified paraffin-impregnated graphite electrodes allowing for a separation between hematite-based earths, French ochres, Spanish ochres, siennas, umbers and green earths. This methodology is applied to the identification of the pigments in samples from the ceiling frescoes of Antonio Palomino (dated 1707) in the vaulted nave of the Sant Joan del Mercat church in Valencia (Spain). These frescoes suffered considerable damage by fire during the Spanish Civil War in 1936, resulting in severe chemical and chromatic alterations. Electrochemical data, support…
Archaeometrical study of paleometallurgical materials from the archaeological site “Cerro de las Balsas — Chinchorro” (La Albufereta, Alacant, Spain)
2008
An Iberian archaeological site located in the east of Spain is one of the most important cupellation centers found in the 4th century b.c. Different metallurgical materials were found in the archaeological site as minerals, cast slags, forged slags, metallic lead, cupella fragments and bronzes. Also was found reverbs remains used for cupper-based materials and cupellation procedure, and hearth forge remains for obtained iron material. The recuperated samples were studied by comparing samples of the same type of material by macroanalysis and microanalysis. The microanalysis and quantitation of the different archaeological materials was carried out by SEM/EDX. The information provides about t…
Localization of Ca(2+)-stores and tissue compartments with a Ca(2+)-binding capacity in the organ of Corti of the guinea-pig by electron energy-loss …
1992
SUMMARY The addition of 10 mM CaCl2 to glutaraldehyde fixative leads to the formation of small electron-dense deposits in the organ of Corti of the guinea-pig. These precipitates are mainly attached to cell membranes in contact with different extracellular lymphatic fluids. A higher number of precipitates is localized in the acellular parts of tectorial and basilar membrane. Electron energy-loss spectroscopy (EELS) was used to determine the elemental composition of the deposits formed. The spectra showed a prominent signal at the Ca2+ L2,3 ionization edge. Oxygen could also be detected in all the precipitates analysed. EELS analysis of mitochondria of the inner and outer hair cells after co…