Quantification Curves for XRD Analysis of Mixed-Layer 14Å/10Å Clay Minerals

Pons, C. H.; Calle, C. de la; Vidales, J. L. Martı́n de

doi:10.1346/ccmn.1995.0430212

Cited by 9 publications

(5 citation statements)

References 29 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The distribution of the number of layers per particle was determined by comparing the experimental SAXS patterns with the theoretical intensities calculated from structural models (Pons et al, 1995;Ben Rhaiem et al, 1987, 2001. SAXS computation models assumed particles to be stacks of almost parallel silicate layers, independent of the degree of order within these stacks (Ben Rhaiem et al, 1987, 2001).…”

Section: Methodsmentioning

confidence: 99%

See 1 more Smart Citation

Study of the structural evolution of the 10 Å unstable hydrate of kaolinite during dehydration by XRD and SAXS

et al. 2003

View full text Add to dashboard Cite

This work deals with understanding the structural evolution of the dehydration of the 10 A Ê unstable hydrate of kaolinite. The method used to characterize this hydrate is based on a comparison between the experimental and the calculated X-ray diffraction pro®les. The study was achieved in two steps: (i) the quantitative interpretation of 00l re¯ections enabled the determination of the number of intercalated water molecules, their positions and the stacking mode of the clay layers along the normal to the (a,b) plane; and (ii) the study of the hkl re¯ections with h and/or k T 0 enabled the characterization of the structural evolution in the (a,b) plane of the hydrated kaolinite during dehydration. The hydrate is made up of two demixed phases. The ®rst phase is homogenous and corresponds to a 10 A Ê hydrated kaolinite, characterized by two H 2 O molecules per Si 2 Al 2 O 5 (OH) 4 situated at Z = 7.1 A Ê from the surface oxygen. Two adjacent layers are translated with respect to each other, with T 1 = À0.155a + 0.13b + 10n. The abundance of this phase decreases during dehydration. The second phase is made up of 10 A Ê hydrated layers, 8.4 A Ê hydrated layers and 7.2 A Ê dehydrated kaolinite layers, randomly interstrati®ed. The abundance of this second phase increases during dehydration. The corresponding interlayer shifts are respectively T 21 = À0.155a + 0.13b + 10n for the 10 A Ê hydrated layer, T 22 = À0.355a + 0.35b + 8.4n for the 8.4 A Ê hydrate and T 23 = À0.36a À 0.024b + 7.2n for the natural kaolinite. In addition to these interlayer shifts, some translation defects are introduced, such as Àb/3, which exists in the initial kaolinite. The interpretation of the small-angle X-ray scattering (SAXS) patterns showed that the particle thickness remained the same before and after the hydration treatments, whereas X-ray diffraction (XRD) results indicated that the hydration of kaolinite caused a decrease of the mean number of layers " m per crystallite from 40 to 20 layers. This decrease is related to the presence of H 2 O molecules situated within the micropores in the kaolinite particles that leave their interlayer space after heating at 573 K. The resulting dehydrated compound is characterized by the same basal distance and mean number of layers " m per crystallite as for the natural kaolinite, while the proportion of the defects, such as the Àb/3 translation, increases in the completely dehydrated compound (45%) compared with the natural kaolinite (10%).

show abstract

Section: Methodsmentioning

confidence: 99%

“…The diffracted intensity for a unit cell along the 00 rod of the reciprocal space is given by the relation (Pons et al, 1995;:…”

Section: Methodsmentioning

confidence: 99%

Study of the structural evolution of the 10 Å unstable hydrate of kaolinite during dehydration by XRD and SAXS

et al. 2003

View full text Add to dashboard Cite

show abstract

“…Data were recorded in the range 5˚ -50˚2θ with a step of 0.02˚2θ and 0.05 s per step. The mineralogical and structural characteristics were determined by comparing the experimental X-ray patterns with the theoretical patterns calculated from structural models [10,11] and permits determination of the number and the position of the intercalated water molecules. The XRD patterns were calculated using the z-coordinates, where the origin of the atomic coordinates was taken at the basal oxygen atoms [2].…”

Section: X-ray Measurement and Simulation Principlementioning

confidence: 99%

Structural Properties of Synthetic Na-Hectorite Exchanged with Heavy Metals

Salah¹

2011

MSA

View full text Add to dashboard Cite

show abstract

“…The textural and structural evolution during drying was determined by comparing the experimental SAXS patterns with the theoretical intensities calculated from structural models (Mering, 1949;Kakinoki & Komura, 1952;MacEwan, 1956MacEwan, , 1958Reynolds, 1980;Plangon, 1981;Drits & Tchoubar, 1990;Pons et al, 1995). The theoretical profiles were calculated from the matrix expression developed by Plangon (1981):…”

Section: Calculation Of the Theoretical Intensitiesmentioning

confidence: 99%

“…where di and ds are the d-spacings of the illite and smectite la.yers, respectively, and Psi is the probability of passing from a smectitic to an illitic layer. The relationships between the different kinds of layer proportions and probabilities are given by (Reynolds, 1980;Drits & Tchoubar, 1990;Pons et al, 1995):…”

Section: Calculation Of the Theoretical Intensitiesmentioning

confidence: 99%

Evolution of the Microstructure of Interstratified Ca-Saturated Clays During Dehydration: SAXS and HRTEM Analysis

Rhaïem¹

1998

Clay Minerals

View full text Add to dashboard Cite

This paper aims at characterizing the structural and textural evolution of three mixed-layered clays in Ca-form from Southern and Central Tunisia, These samples contain various amounts of mixed-layer smectite-illite associated with crystallites of kaolinite. The clay fractions were prepared in the Ca-form and submitted to suction pressures increasing from 3.2 up to 1000 kPa. The structural and textural changes of the pastes obtained were studied by TEM and SAXS. The TEM observations and SAXS quantitative analysis on samples at low stress (3.2 kPa) showed that the thickness of the particles (number of layers per particle) and their lateral extension (in the plane of layers) decrease with increasing illite content. The textural evolution during drying, as described by SAXS, is controlled by the geometry of particles which is determined by the mineralogy of the structural units. With increasing illite content, the particles became shorter, rigid and had flat surfaces. This geometry increases their ability to associate face-to-face during dehydration. When the 2:1 fraction contains a high proportion of smectite, the architecture of the clay-water system at high water content (low stress) seems to be analogous to that of smectites. However, contrary to the behaviour of pure smectites reported in the literature, desiccation led first to a rupture of particles and a reorganization of the geometry of the pore system. This behaviour is due to the rigidity of particles caused by the presence of non-exchangeable K. The structural evolution showed that for an illite-rich sample a transition from the three-water layer to the one-water layer state occurred at 1000 kPa, whereas for smectite-rich materials, the hydration state of layers, i.e. three water layers, was not affected.

show abstract

Quantification Curves for XRD Analysis of Mixed-Layer 14Å/10Å Clay Minerals

Cited by 9 publications

References 29 publications

Study of the structural evolution of the 10 Å unstable hydrate of kaolinite during dehydration by XRD and SAXS

Study of the structural evolution of the 10 Å unstable hydrate of kaolinite during dehydration by XRD and SAXS

Structural Properties of Synthetic Na-Hectorite Exchanged with Heavy Metals

Evolution of the Microstructure of Interstratified Ca-Saturated Clays During Dehydration: SAXS and HRTEM Analysis

Contact Info

Product

Resources

About