Quantitative X-ray diffraction phase analysis of poorly ordered nontronite clay

仪器资料 · 发表于 2018-4-19 08:23:47

Quantitative X-ray diffraction phase analysis of poorly ordered nontronite clay in nickel laterites

Studies of the extraction of nickel from low-grade laterite ores require a much
better quantitative understanding of the poorly ordered mineral phases present,
including turbostratically disordered nontronite. Whole pattern refinements
with nontronite X-ray diffraction data from a Western Australian nickel deposit
(Bulong) using a nontronite lattice model (Pawley phase) with two space groups
(P3 and C2/m) and a peaks phase group model were performed to improve the
accuracy of quantitative X-ray diffraction of nickel laterite ore samples.
Modifications were applied when building the new models to accommodate
asymmetric peak shape and anisotropic peak broadening due to the turbostratic
disorder. Spherical harmonics were used as convolution factors to represent
anisotropic crystal size and strain and asymmetric peak shape when using the
lattice model. A peaks phase group model was also developed to fit the
anisotropic peak broadening in the nontronite pattern. The quantitative results
of the new Pawley phase and peaks phase group models were compared and
verified with synthetic mixtures of nontronite, quartz and goethite simulating
various West Australian laterite ore compositions. The models developed in this
paper demonstrate adequate accuracy for quantification of nontronite in the
synthesized reference materials and should be generally applicable to
quantitative phase analysis of nontronite in nickel laterite ore samples.