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Microstructure determination of IQ‐WB clays: a direct procedure by small‐angle X‐ray scattering
Author(s) -
Segad M.
Publication year - 2013
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/s0021889813020931
Subject(s) - small angle x ray scattering , lamellar structure , microstructure , scattering , materials science , analytical chemistry (journal) , chemistry , crystallography , chromatography , composite material , optics , physics
An accurate characterization of the microstructure of raw and pure homoionic clays from Wadi Bashira in Iraq (IQ‐WB) has been carried out experimentally, using small‐angle X‐ray scattering (SAXS) and dynamic light scattering. The structures of lamellar IQ‐WB dispersions were identified by these techniques and by complementary free swelling and dialysis experiments. SAXS measurements were used to resolve the characteristic distance, h s , between individual platelets in Na IQ‐WB and between platelets inside tactoids formed in Ca clays. The tactoids in raw and Ca IQ‐WB have well formed lamellar structures where h s = 1.9 nm. The average lateral size, 〈 D 〉, of a platelet is determined to be a few hundred nanometres. Analysis of the SAXS peaks, based on the Scherrer relation, revealed a small difference in the average number of platelets per tactoid, 〈 N 〉 = 6–9, depending on platelet size and the concentrations of divalent counter‐ions. It was also found that the average tactoid size can be estimated from an empirical relation as follows: 〈 N 〉≃δ + α〈 D 〉, where δ is a constant and α the slope.