EDX/XRD-based identification of micrometer-sized domains in scanning electron micrographs of fired clay
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ORIGINAL ARTICLE
EDX/XRD-based identification of micrometer-sized domains in scanning electron micrographs of fired clay Hawraa Kariem . Thomas Kiefer . Christian Hellmich . Wolfgang Gaggl . Andreas Steiger-Thirsfeld . Josef Fu¨ssl
Received: 17 December 2019 / Accepted: 7 July 2020 Ó The Author(s) 2020
Abstract The thermal and mechanical properties of bricks are strongly dependent on both the chemical composition and the microstructural features of the used fired clay material. Focussing on the latter, we here identify, in terms of volume fraction, shape, and orientation characteristics, one-to-several micrometer-sized subdomains (‘‘material phases’’) within the SEM-imaged microstructure of two raw clays fired at
Electronic supplementary material The online version of this article (https://doi.org/10.1617/s11527-020-01531-7) contains supplementary material, which is available to authorized users. H. Kariem T. Kiefer (&) C. Hellmich J. Fu¨ssl Institute for Mechanics of Materials and Structures, TU Wien, Karlsplatz 13/202, 1040 Vienna, Austria e-mail: [email protected] H. Kariem e-mail: [email protected]
880 and 1100 centigrades: (1) quartz grains, (2) muscovite, (3) Fe–Mg mica, (4) feldspar grains, (5) decarbonated dolomite, (6) pores, or (7) binding matrix. This identification rests on the simultaneous use of Scanning Electron Microscopy (SEM) and Energy-dispersive X-ray spectroscopy (EDX), with correspondingly obtained data entering statistical analyses based on the Otsu algorithm, and complemented by minimum grain size and grain shape requirements, as well as by logical exclusion criteria. Crystalline and amorphous phase shares were additionally confirmed by X-ray powder diffraction measurements (PXRD). As for the investigated clays, an increased firing temperature results in dehydroxylation of muscovite, and in a reduced appearance of feldspar grains. Keywords Fired clay Microstructure Quantitative mineralogical analysis PXRD SEM-EDX
C. Hellmich e-mail: [email protected] J. Fu¨ssl e-mail: [email protected] W. Gaggl Wienerberger AG, Clay Building Materials Europe, Hauptstrasse 4, 2332 Hennersdorf bei Wien, Austria e-mail: [email protected] A. Steiger-Thirsfeld University Service Center for TEM (USTEM), TU Wien, Wiedner Hauptstrasse 8-10, 1040 Vienna, Austria e-mail: [email protected]
1 Introduction Clays and clay minerals may provide a wide range of chemical and physical properties [1–3], which renders them suitable for many different applications. Of particular interest in civil engineering and architecture are the thermal conductivity and the mechanical properties of bricks and clay blocks, as they define their sustainability and competitiveness, in
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comparison to other construction materials [4]. During production, the composition of the raw clay and the firing temperature govern the resulting mineralogy and microstructure, which in turn, dictate the
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