IFEG   20353
INSTITUTO DE FISICA ENRIQUE GAVIOLA
Unidad Ejecutora - UE
congresos y reuniones científicas
Título:
Characterization of pigments in ceramics pots of Aguada culture (11th century AD, Catamarca, Argentina) through BEI image processing.
Autor/es:
GALVAN JOSA, V.; BERTOLINO, S.; CASTELLANO, G.; LAGUENS, A; RIVEROS, J.
Lugar:
Cabo Frío, Brasil
Reunión:
Congreso; XI Latin American Seminar of Analysis by X-Ray Techniques SARX 2008; 2008
Institución organizadora:
Laboratório de Instrumentacao Nuclear PEN-COPPE/UFRJ, Brasil
Resumen:
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Scanning electron microscopy is a
powerful technique in several fields of science and technology. In particular
it is an important complement in the characterization of materials for which
x-ray analysis is not conclusive. Such is the case of thin paint layers on
ceramic pots, where the interaction
volume can be greater than the paint thickness, or the X-ray spectrum corresponding to the paint may not
differ from the one corresponding to the ceramic body. This also occurs when the pigment
matrix chemical composition is similar to that of the pot body. In this work, a new methodology for the
treatment of SEM images with these characteristics was
developed,
in order to determine the chemical and mineralogical composition of black and
white pigments of ceramic pieces belonging to the Ambato
style of Aguada culture (Catamarca province, Argentina, 11th century AD).
Backscattered electron images (BEI) normally provide
information of mean atomic number in each region, but when the signal-to-noise
ratio is low or the difference in the mean atomic number is less than 0.02%,
chemical contrast may be imperceptible to human eye, since it can discriminate
only about 30 from the 256 grey levels of an 8-bit image. The BEI
images acquired for the samples studied showed no apparent contrast between
black and white pigments. Through image processing algorithms using space and
frequency filters, chemical contrast between pigments has been brought to
evidence.
The
mineralogical differences between each pigment and ceramic body have been
corroborated by quantification diagrams using the x-ray diffraction software
TOPAS.