Randomness in the structures of kaolinitic clay minerals

Brindley, G. W.; Robinson, Keith

doi:10.1039/tf946420b198

Cited by 113 publications

(41 citation statements)

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“…The Brindley and Robinson (1946) model, based on +_b/3 random layer shifts, assumed that the hydroxyl sheet in an idealized layer would coincide with itself after such displacements. To allow for layer structure distortions, Brindley (1980) later proposed that the shifts only approximate _+ b/3 to ensure the proper matching of basal oxygens and hydroxyls.…”

Section: The +_b/3 Modelmentioning

confidence: 99%

“…It can be easily shown that "7 = (0, b/3), if b/a = V~ and t~ = -a/3. The present model is a version of that proposed by Brindley and Robinson (1946), but it has been extended to account for the real crystal structure. The model proposed here not only differs from the model having +_b/3 shifts by a more realistic value for ~-, but also it excludes the unfavorable stacking resulting from tl--r translations.…”

Section: Defects In Crystals Characterized By One Layer Typementioning

confidence: 99%

“…These differences are the direct result of the presence of layer stacking faults. Several attempts have been made to understand the nature of the stacking faults in kaolinite (Brindley and Robinson, 1946;Mitra and Bhattacherjee, 1970;Murray, 1954;Planqon andTchoubar, 1977a, 1977b;Tchoubar et al, 1982). These workers based their concepts on an idealization of the kaolinite structure.…”

Section: Introductionmentioning

confidence: 99%

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Stacking Faults in Kaolin-Group Minerals in the Light of Real Structural Features

Bookin

Drits

Plançon

et al. 1989

Clays and clay miner.

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Ahstraet--A comparison of the structural characteristics of the kaolin-group minerals, mainly kaolinite and dickite, shows that they differ in both the two-dimensional periodicity in the l:l layers and the rotation angles of the polyhedra. Distortions in a real 1:1 layer, compared with an idealized layer, do not allow such stacking faults as +_ 120 ~ laye:-rotations and vacancy displacements, because the second layer is incommensurable with the first. The 1:1 layer structure and the fact that the unit cell is symmetrical with respect to the plane passing through the long diagonal of the unit cell suggest the possibility of defects resulting from the two stacking sequences for the same layers. For a regular alternation of translations, a halloysite-like structure should be the end-member of such a series of defect kaolinite types.The formation of layers having vacant octahedral C-sites is another possible type of fault. Because of the minor difference between ~ and 90 ~ dickite-like layers should exist. A regular alternation of B and C layers yields dickite as the end-member structure. In materials containing few defects, stacking faults of both types lead to similar X-ray powder diffraction patterns. Thus, the nature of the stacking faults is difficult to determine experimentally. In materials containing many defects, however, the two models lead to different calculated diffraction patterns. Therefore, only a study of defect-rich types of kaolinite can determine which types of defects exist in natural kaolinite samples.

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Section: The +_b/3 Modelmentioning

confidence: 99%

Section: Defects In Crystals Characterized By One Layer Typementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Stacking Faults in Kaolin-Group Minerals in the Light of Real Structural Features

Bookin

Drits

Plançon

et al. 1989

Clays and clay miner.

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“…The hydrated form is irreversibly converted to the dehydrated form upon drying below 100°C. Water loss sharpens the basal reflections and reduces the basal d-spacings to approximately 7.2 Å, although this value is never so small as that of typical kaolinite (7.14 Å) [7]. In the hydrated halloysite, the TO sheets, which are double layers consisting of Sicentered tetrahedral and Al-centered octahedral layers, are separated from each other by a water monolayer.…”

mentioning

confidence: 95%

The effect of halloysite modification combined with in situ matrix modifications on the structure and properties of polypropylene/halloysite nanocomposites

Khünová¹,

Kristóf²,

Kelnar³

et al. 2013

Express Polym. Lett.

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The effect of various modifications/intercalations of halloysite and the combination of these modifications with in situ PP matrix modification was investigated with respect to the structure and properties of the polypropylene/halloysite nanocomposites. Hexadecyl-tri-methyl-ammonium-bromide (HEDA), 3-aminopropyltrimethoxysilane and urea were used as the intercalators/modifiers. The best intercalation was found for urea, although an unexpected insignificant impact on the mechanical properties also resulted as a consequence of the urea polarity and the significant decrease in PP crystallinity. However, the simultaneous application of 4,4!-diphenylmethylene dimaleinimide (DBMI) brought about an increase in the mechanical behavior by increasing the halloysite/PP affinity as a result of in situ matrix modification. This effect was further supported by coupling between the PP and halloysite (HNT) in the system containing urea-intercalated HNT. This can be explained by the occurrence of a urea-supported reaction between the imide ring of DBMI and the OH groups of the HNT, which resulted in the best mechanical behaviors achieved in this study

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“…It is of interest to deal with the effects of certain types of defects on the diffraction. This sort of approach was first used to study disordered kaolinite (Brindley & Robinson, 1946) and later on a series of natural kaolinites (Planqon & Tchoubar, 1977b). It is well worth noting that the hkl reflections with k = 3n seemed to be largely unaffected by translational stacking faults, while those with k :/: 3n were influenced by them deforming into (hk) asymmetrical bands.…”

Section: Introductionmentioning

confidence: 99%

Use of R Factors in the Study of the Structural Defects in Phyllosilicates by X-ray Powder Diffraction

Taşer¹,

Küçükçelebi²,

Armagˇan³

et al. 1997

J Appl Cryst

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The R factors employed in crystal structure analysis can also be used in connection with clay minerals to determine the amount of defects whose types are already known. For this purpose, using the unit-cell parameters of kaolinite with identical layers, (02,11) and (20,13) diffraction bands were calculated on the basis of a variable parameter model containing only +b/3 translational stacking faults. The parameters of the model were varied to obtain the best fit between the calculated and observed patterns with respect to both intensity and profile. Three different R factors were used as a criterion for the best fit and the parameters yielding the smallest R value were accepted as describing the actual structure. In addition, a linear regression analysis is performed between observed and calculated intensities to determine the quality of the fit. Correlation coefficients, obtained from this analysis, are used as an indication of the effectiveness of corresponding R factors.

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Randomness in the structures of kaolinitic clay minerals

Cited by 113 publications

References 0 publications

Stacking Faults in Kaolin-Group Minerals in the Light of Real Structural Features

Stacking Faults in Kaolin-Group Minerals in the Light of Real Structural Features

The effect of halloysite modification combined with in situ matrix modifications on the structure and properties of polypropylene/halloysite nanocomposites

Use of R Factors in the Study of the Structural Defects in Phyllosilicates by X-ray Powder Diffraction

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