z-logo
Premium
Semi‐quantitative analysis of the formation of a calcium oxalate protective layer for monumental limestone using combined micro‐XRF and micro‐XRPD
Author(s) -
Vanmeert F.,
Mudronja D.,
Fazinic S.,
Janssens K.,
Tibljas D.
Publication year - 2013
Publication title -
x‐ray spectrometry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.447
H-Index - 45
eISSN - 1097-4539
pISSN - 0049-8246
DOI - 10.1002/xrs.2486
Subject(s) - powder diffraction , ammonium oxalate , calcium oxalate , chemistry , diffraction , oxalate , materials science , calcite , analytical chemistry (journal) , layer (electronics) , mineralogy , crystallography , chromatography , inorganic chemistry , nanotechnology , physics , optics
A current method for the protection of cretaceous limestone present in various monuments consists of performing a passivating treatment with ammonium oxalate (AmOx). A calcium oxalate protective layer is formed on the surface and enhances the acid resistance of the stone. The in‐depth formation of the calcium oxalate layer was investigated on cross sections by using combined micro X‐ray fluorescence and micro X‐ray powder diffraction (µXRF/µXRPD). XRPD showed the presence of both whewellite and weddellite in the calcite stone matrix. A correction was made for sample misalignment, which was visible in both the fluorescence and the diffraction line measurements. A semi‐quantitative analysis was performed on the basis of Klug's equation for a two‐phase mixture (the presence of weddellite was neglected) without the need for a known reference sample. By assuming two extreme compositions for a reference weight fraction (1 and 99 wt%), it was possible to obtain whewellite concentration profiles, which can be used for comparing the effectiveness of different methods for the application of AmOx to the stone surface and the effect of treatment time and AmOx concentration used. It is shown that for the relative amounts of whewellite formed, the differences due to the assumed weight fractions are smaller than the errors due to sample heterogeneity and preferred orientation. Copyright © 2013 John Wiley & Sons, Ltd.

This content is not available in your region!

Continue researching here.

Having issues? You can contact us here