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Quantification of amorphous phases in the silt fraction of Mexican pre‐Hispanic adobe earth bricks
Author(s) -
Pérez Nora A.,
Bucio Lauro,
Bokhimi Xim,
Lima Enrique,
Soto Enrique
Publication year - 2016
Publication title -
journal of applied crystallography
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.429
H-Index - 162
ISSN - 1600-5767
DOI - 10.1107/s1600576716002806
Subject(s) - amorphous solid , allophane , adobe , materials science , mineralogy , analytical chemistry (journal) , sample (material) , soil test , lunar soil , sample preparation , chemistry , geology , crystallography , soil water , environmental chemistry , soil science , archaeology , geography , chromatography , clay minerals
This study is focused on quantifying the amorphous phases in soil‐related material samples by quantitative phase analysis (QPA) with a carefully designed methodological strategy in the X‐ray diffraction sample measurement and in the refinement procedure. The configuration applied was Debye–Scherrer geometry with Mo K α radiation which, together with meticulous instrumental profile modelling using an LaB 6 standard, allowed the refinement of a minimum of sample‐related parameters. This method was applied to two micro‐samples of adobe earth bricks from The Great Pyramid of Cholula, Mexico, and one local soil micro‐sample containing several amorphous and semi‐crystalline phases such as allophane, volcanic glass and opal. The results obtained by the QPA method, complemented by elemental particle induced X ray emission (PIXE) spectrometry analysis, were compared with a silicon chemical environment analysis by 29 Si MAS‐NMR. An average amorphous content of 40 wt% was calculated with the QPA/PIXE results, which is in agreement within 10% with the NMR experiments. Consequently, the methodology proposed could be of interest for further studies of cultural heritage geomaterials, which usually contain amorphous phases in their composition and allow only micro‐sampling.