Application of an Internal Standard Technique by Transmission X-Ray Diffraction to Assess Layer Charge of a Montmorillonite by Using the Alkylammonium Method

Janek, M.; Smrčok, Ľubomír

doi:10.1346/ccmn.1999.0470201

Cited by 8 publications

(5 citation statements)

References 22 publications

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“…z n for atoms in the various smectites used for PLSNs is summarized in Table 1. 12, 14–21 The complete structure factor for a silicate layer and a centrosymmetric interlayer may be expressed simply as a sum of the structure factor for the layer, F (θ) layer , and interlayer, F (θ) interlayer , both having the same functional form as eq 2 and referenced ( z = 0) with respect to the center of symmetry of each subunit 15…”

Section: Ideal Scattering Profilementioning

confidence: 99%

“… a Examples include SWy1 and SWy2 (Source Clay Mineral Repository, University of Missouri), M

_{+}^{0.68}

[Al 3.32 Mg 0.4 Fe

_{3+}^{0.26}

_{2+}^{0.12}

][Si 7.84 Al 0.16 ]O 20 (OH) 4 ,16, 17, SAz‐1 (Source Clay Mineral Repository), M

_{+}^{0.56}

[Al 2.68 Mg 0.1.2 Fe

_{3+}^{0.14}

]Si 8 O 20 (OH) 4 ,18 and Mnt (Nanocore, Inc.), M

_{+}^{1.08}

[Al 3.38 Mg 0.54 ][Si 7.64 Al 0.36 ]O 20 (OH) 4 19…”

Section: Ideal Scattering Profilementioning

confidence: 99%

See 1 more Smart Citation

X‐ray powder diffraction of polymer/layered silicate nanocomposites: Model and practice

Vaia

Liu²

2002

J Polym Sci B Polym Phys

140

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X-ray powder diffraction in reflection (Bragg-Brentano parafocusing geometry) is extensively used to characterize the structure of polymer/layered silicate nanocomposites (PLSNs). The large basal spacings (d 001 Ͼ 2.0 nm) necessitates the collection of data at scattering angles (2) of less than 10°. The calculation of an ideal scattering profile for PLSNs provides an avenue to ascertain the influence of experimental parameters and the arrangement, organization, concentration, and composition of constituents on the experimentally observed pattern. This enables better experimental technique, more complete utilization of the scattering data, insight into inconsistencies between scattering and microscopy, and minimization of incorrect interpretation or overinterpretation of data. Because of the strong dependence of theoretical and experimental factors at low values of 2, careful sample preparation and data evaluation are necessary and should be complemented by microscopic observations, especially for PLSNs with low volume fractions of organically-modified layered silicates (OLS) that are suspected of having exfoliated morphologies. X-ray powder diffraction in reflection alone is insufficient to completely characterize and ascribe PLSN morphology.

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Section: Ideal Scattering Profilementioning

confidence: 99%

“… a Examples include SWy1 and SWy2 (Source Clay Mineral Repository, University of Missouri), M

_{+}^{0.68}

[Al 3.32 Mg 0.4 Fe

_{3+}^{0.26}

_{2+}^{0.12}

][Si 7.84 Al 0.16 ]O 20 (OH) 4 ,16, 17, SAz‐1 (Source Clay Mineral Repository), M

_{+}^{0.56}

[Al 2.68 Mg 0.1.2 Fe

_{3+}^{0.14}

]Si 8 O 20 (OH) 4 ,18 and Mnt (Nanocore, Inc.), M

_{+}^{1.08}

[Al 3.38 Mg 0.54 ][Si 7.64 Al 0.36 ]O 20 (OH) 4 19…”

Section: Ideal Scattering Profilementioning

confidence: 99%

X‐ray powder diffraction of polymer/layered silicate nanocomposites: Model and practice

Vaia

Liu²

2002

J Polym Sci B Polym Phys

140

View full text Add to dashboard Cite

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“…X-ray diffraction (XRD) measurements indicate that the interlayer microscopic structure is determined by both the density of the clay layer charge and the alkyl chain length of alkylammonium ions (Weiss 1963;Lagaly 1981;Laird et al 1989;Laird 1994;Janek and Smrcok 1999). Several ideal structure modes of intercalated alkylammonium ions have been proposed.…”

Section: Introductionmentioning

confidence: 99%

Molecular dynamics insight into the cointercalation of hexadecyltrimethyl-ammonium and acetate ions into smectites

Liu

Wang

et al. 2009

American Mineralogist

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Classical molecular dynamic simulations are performed to investigate the microscopic properties of hexadecyltrimethylammonium (HDTMA) intercalated smectites with and without the cointercalation of acetate groups. Three model smectites with distinct layer-charge characteristics are selected as the frameworks and their HDTMA intercalates correspond to the representative monolayer, bilayer, and paraffin configurations of the aliphatic chains. In the organoclays without cointercalation, all trimethylammonium headgroups of HDTMA are fixed firmly above the center of the surface six-member rings through electrostatic attractions with surface oxygen, whereas the alkyl chains are a little more mobile. It is found that the cointercalations can significantly increase the basal spacings of the pure HDTMA intercalated smectites. The distributions and mobility of the HDTMA headgroups are not affected by the acetate ions because of the overwhelming attractions coming from the clay sheets. The acetate groups are fixed by the HDTMA headgroups through ion pairing. This simulation study provides a molecular level basis to understand the effects of cointercalation on properties of organoclays.

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“…Recent experimental results support our simulated smooth curves. 24 As a reference, Fig. 2 also shows estimates of the basal spacing for the hypothetical case that alkylammonium would behave as a bulk fluid between the clay platelets, using computed bulk fluid densities of alkanes.…”

mentioning

confidence: 99%

Molecular order and disorder of surfactants in clay nanocomposites

Tambach

Boek

Smit

2006

Phys. Chem. Chem. Phys.

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Disorder of intercalated surfactant molecules in clay minerals causes gradual swelling, rather than commonly assumed swelling in discrete steps.Nanocomposites of clay minerals and surfactants are of practical importance in many fields.1 Beside the use of these systems for pollution removal from waste water, 2 they can also be used as catalysts, 3 to stabilize clay formations while drilling for hydrocarbons, 4 or for improving the strength of polymers. 5,6The nanocomposites are obtained through exchange of natural counter ions by ionic surfactants, such as alkylammonium. 7Despite the importance of such nanocomposites, their behaviour is not understood. It is commonly assumed that the distance between the clay platelets (basal spacing) increases stepwise or linearly with increasing alkylammonium chain length. 8 The traditional explanation for this observation is that the surfactants form all-trans conformations between the clay platelets, 8 either in layers or tilted in a liquid crystalline ordered phase. However, this explanation has recently been debated. 9 X-Ray diffraction measurements show a complex intercalation behaviour.7 For example, when basal spacings are measured, corresponding to values in-between monolayer and bilayer structures, then these values are usually attributed to layer charge heterogeneity.10 In this case, the explanation is that different layer charges within a clay sample cause a varying surfactant loading in the interlayers between two clay platelets and therefore an ensemble of monoand bilayer structures, but this has never been directly confirmed experimentally. As X-ray diffraction peaks for such states overlap, the resulting peak is broad and difficult to interpret.Molecular simulations are ideally suited for obtaining more insight in the intercalation behaviour of surfactants in clay minerals. Several simulation studies have been carried out to compute the basal spacing for some clay minerals and some alkylammonium surfactants. 6,[11][12][13] These simulation studies show increasing disorder (phase transitions) of the surfactants in mica clay minerals with increasing temperature.6,12 Our simulations are complementary to the previous studies, in the sense that they cover an extensive range of surfactant chain lengths. Also, in contrast with mica, we consider clay minerals that are able of swelling. We find, for the first time, full quantitative agreement between the experimental and simulated swelling behaviour of alkylammonium in montmorillonite and vermiculite clay minerals. Based on our simulations, we give a new explanation for the gradual increase of the clay platelets distance. We show evidence that this is a true physical phenomenon, caused by disorder of the surfactant molecules.Out of several available molecular clay models, 6,14,15 we choose a clay model 15 that has proven to be successful in predicting the basal spacing of natural clay minerals with water, 15,16 the swelling capabilities of clay minerals, 17,18 and hysteresis in clay swelling. 17,19 In our simulations, we ...

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Application of an Internal Standard Technique by Transmission X-Ray Diffraction to Assess Layer Charge of a Montmorillonite by Using the Alkylammonium Method

Cited by 8 publications

References 22 publications

X‐ray powder diffraction of polymer/layered silicate nanocomposites: Model and practice

X‐ray powder diffraction of polymer/layered silicate nanocomposites: Model and practice

Molecular dynamics insight into the cointercalation of hexadecyltrimethyl-ammonium and acetate ions into smectites

Molecular order and disorder of surfactants in clay nanocomposites

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