Description of X-ray powder pattern of turbostratically disordered layer structures with a Rietveld compatible approach

Ufer, Kristian; Roth, Georg; Kleeberg, R.; Stanjek, Helge; Dohrmann, R.; Bergmann, Jörg

doi:10.1524/zkri.219.9.519.44039

Cited by 134 publications

(110 citation statements)

References 32 publications

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“…Morocco natural bentonite (IBECO) was obtained from the Federal Institute for Geosciences and Natural Resources (BGR) in Hannover (Germany). Powder X-ray diffraction (XRD) analyses were used to characterize the mineralogical composition of the phyllosilicate clay minerals according to (Chipera and Bish 2001;Ufer et al 2004). The results show that KGa-1b and KGa-2 contain predominantly titanium as a trace of anatase (Pruett and Webb 1993).…”

Section: Materials and Methodologymentioning

confidence: 99%

Sorption of uranium(VI) at the clay mineral–water interface

2010

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Batch experiments were conducted to study the sorption of uranium on selected clay minerals (KGa-1b and KGa-2 reference kaolinite, SWy-2 and STx-1b reference montmorillonite, and IBECO natural bentonite) as a function of pH (4-9) and 0.001, 0.01, and 0.025 M NaCl in equilibrium with the CO 2 partial pressure of the atmosphere. Uranium concentrations were kept below 100 lg L -1 to avoid precipitation of amorphous Uraniumhydroxides. Solely PTFE containers and materials were used, because experiments showed significant sorption at higher pH on glass ware. All batch experiments were performed over a period of 24 h, since kinetic experiments proved that the common 10 or 15 min are in many cases by far not sufficient to reach equilibrium. Kaolinite showed much greater uranium sorption than the other clay minerals due to the more aluminol sites available. Sorption on the poorly crystallized KGa-2 was higher than on the wellcrystallized KGa-1b. Uranium sorption on STx-1b and IBECO exhibited parabolic behavior with a sorption maximum around pH 6.5. Sorption of uranium on montmorillonites showed a distinct dependency on sodium concentrations because of the effective competition between uranyl and sodium ions, whereas less significant differences in sorption were found for kaolinite. The presence of anatase as impurity in kaolinite enhanced the binding of uranyl-carbonate complexes with surface sites. The kinetic of uranium sorption behavior was primarily dependent on the clay minerals and pH. A multisite surface complexation model without assuming exchange is based on the binding of the most dominant uranium species to aluminol and silanol edge sites of montmorillonite, respectively to aluminol and titanol surface sites of kaolinite. For eight surface species, the log_k was determined from the experimental data using the parameter estimation code PEST together with PHREEQC.

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Section: Materials and Methodologymentioning

confidence: 99%

Sorption of uranium(VI) at the clay mineral–water interface

2010

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“…This kind of disorder can be described with the Ufer single-layer model (Ufer et al, 2004). The model is very effective in reproducing the asymmetric broadening caused by the turbostratic disorder and can be coupled with the texture analysis (Lutterotti et al, 2010).…”

Section: B Preliminary Analysis For Axial Symmetry Using One Imagementioning

confidence: 99%

Rietveld texture analysis from synchrotron diffraction images. II. Complex multiphase materials and diamond anvil cell experiments

et al. 2014

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Synchrotron X-ray diffraction images are increasingly used to characterize crystallographic preferred orientation distributions (texture) of fine-grained polyphase materials. Diffraction images can be analyzed quantitatively with the Rietveld method as implemented in the software package Materials Analysis Using Diffraction. Here we describe the analysis procedure for diffraction images collected with high energy X-rays for a complex, multiphase shale, and for those collected in situ in diamond anvil cells at high pressure and anisotropic stress.

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“…Other minor phases, e.g., orthoclase and pyrite with contributions less than 1 vol.%, were neglected from the analysis. The stacking-disordered structure of illite-smectite was modeled with the approach described by Ufer et al (2004) included in MAUD (Lutterotti et al, 2010). Note that for the texture analysis methods, the first setting for monoclinic crystals such as illite-mica and illite-smectite needs to be applied; i.e., (100) is the cleavage plane instead of a more familiar second setting with (001) as the cleavage plane (Matthies and Wenk, 2009).…”

Section: Synchrotron X-ray Diffractionmentioning

confidence: 99%

Linking preferred orientations to elastic anisotropy in Muderong Shale, Australia

et al. 2015

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The significance of shales for unconventional hydrocarbon reservoirs, nuclear waste repositories, and geologic carbon storage has opened new research frontiers in geophysics. Among many of its unique physical properties, elastic anisotropy had long been investigated by experimental and computational approaches. Here, we calculated elastic properties of Cretaceous Muderong Shale from Australia with a self-consistent averaging method based on microstructural information. The volume fraction and crystallographic preferred orientation distributions of constituent minerals were based on synchrotron x-ray diffraction experiments. Aspect ratios of minerals and pores, determined from scanning electron microscopy, were introduced in the self-consistent averaging. Our analysis suggested that phyllosilicates (i.e., illite-mica, illite-smectite, kaolinite, and chlorite) were dominant with [Formula: see text]. The shape of clay platelets displayed an average aspect ratio of 0.05. These platelets were aligned parallel to the bedding plane with a high degree of preferred orientation. The estimated porosity at ambient pressure was [Formula: see text] and was divided into equiaxial pores and flat pores with an average aspect ratio of 0.01. Our model gave results that compared satisfactorily with values derived from ultrasonic velocity measurements, confirming the validity and reliability of our approximations and averaging approach.

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Description of X-ray powder pattern of turbostratically disordered layer structures with a Rietveld compatible approach

Cited by 134 publications

References 32 publications

Sorption of uranium(VI) at the clay mineral–water interface

Sorption of uranium(VI) at the clay mineral–water interface

Rietveld texture analysis from synchrotron diffraction images. II. Complex multiphase materials and diamond anvil cell experiments

Linking preferred orientations to elastic anisotropy in Muderong Shale, Australia

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