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Publication . Article . 2019

Synchrotron-Based Phase Mapping in Corroded Metals: Insights from Early Copper-Base Artifacts

Jiayi Li; Pierre Gueriau; Marta Bellato; Andrew King; Luc Robbiola; Mathieu Thoury; Martin Baillon; +6 Authors
Closed Access
Published: 05 Feb 2019 Journal: Analytical Chemistry, volume 91, pages 1,815-1,825 (issn: 0003-2700, eissn: 1520-6882, Copyright policy )
Publisher: American Chemical Society (ACS)
Country: France
Abstract
International audience; The detailed description of corrosion processes in ancient and historical metal artifacts currently relies on the in-depth study of prepared cross sections. The in-plane elemental and phase distributions can be established from a combination of light and electron microscopy characterization. Here, we show that high-resolution virtual sectioning through synchrotron X-ray microcomputed tomography allows a precise noninvasive 3D description of the distribution of both internal and external mineral phases in whole objects. In fragments of early copper artifacts (third–second millennium BC) from Southern Mesopotamia and the Indus valley, this approach provided essential clues on long-term corrosion processes. Major and minor phases were identified through semiquantitative evaluation of attenuation coefficients using polychromatic X-ray illumination. We found evidence for initially unidentified phases through statistical processing of images. We discuss interpretation of the distribution of these phases. A good correlation between the corrosion phases identified by CT and by invasive BSE-SEM is demonstrated. In addition to the stratigraphy of the copper corrosion compounds, we examine and discuss the variations observed in the attenuation coefficients of Cu(I) phases. Semiquantitative synchrotron X-ray microtomography phase mapping requires no specific sample preparation, in particular polishing or surface finishing, and any material tearing or displacement is avoided. We also provide evidence for the noninvasive observation of phases rapidly altered upon preparation of real cross sections. The method can be applied when cross-sectioning even of minute fragments is impossible.
Subjects by Vocabulary

Microsoft Academic Graph classification: Phase mapping Statistical processing Copper chemistry.chemical_element chemistry Synchrotron law.invention law Tomography Characterization (materials science) Mineralogy Attenuation Phase (matter)

Subjects

Analytical Chemistry, [SHS.MUSEO]Humanities and Social Sciences/Cultural heritage and museology, Chemical speciation, Synchrotron, 3D, Archaeology, Textile, Copper, Mesopotamia, Tomography, Indus, [SHS.ARCHEO]Humanities and Social Sciences/Archaeology and Prehistory, [CHIM.MATE]Chemical Sciences/Material chemistry, [PHYS]Physics [physics], [SHS.ART]Humanities and Social Sciences/Art and art history, [CHIM]Chemical Sciences, [CHIM.ANAL]Chemical Sciences/Analytical chemistry

Funded by
EC| IPERION CH
Project
IPERION CH
Integrated Platform for the European Research Infrastructure ON Cultural Heritage
  • Funder: European Commission (EC)
  • Project Code: 654028
  • Funding stream: H2020 | RIA
,
EC| E-RIHS PP
Project
E-RIHS PP
The European Research Infrastructure for Heritage Science Preparatory Phase
  • Funder: European Commission (EC)
  • Project Code: 739503
  • Funding stream: H2020 | CSA
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