Review articleNeutron scattering, a powerful tool to study clay minerals
Introduction
The usefulness of smectites in many industries stems from their ability to take up and retain large amounts of water due largely to their high interlayer surface area and presence of hydrated cations (Bérend et al., 1995, Cases et al., 1992, Cases et al., 1997, Ormerod and Newman, 1983). Neutron scattering spectroscopy has been used to probe water mobility dynamics in clay minerals for more than 4 decades (Adams et al., 1979, Cebula et al., 1981, Hunter et al., 1971, Olejnik and White, 1972, Olejnik et al., 1970, Poinsignon et al., 1987, Ross and Hall, 1978, Tuck et al., 1984, Tuck et al., 1985), but interest in this methodology has increased markedly since the mid 1990s (Bordallo et al., 2008, Chakrabarty et al., 2006, Gates et al., 2012, Kamitakahara and Wada, 2008, Malikova et al., 2006, Michot et al., 2007, Nair et al., 2005, Powell et al., 1997, Powell et al., 1998, Swenson et al., 2000, Swenson et al., 2001a, Williams et al., 1998) in conjunction with developments in molecular dynamic simulations (Skipper et al., 1991, Skipper et al., 1994, Skipper et al., 1995, De Siqueira et al., 1999, Greathouse et al., 2000, Skipper et al., 2000, De Carvalho and Skipper, 2001, Sutton and Sposito, 2001, Marry et al., 2002, Marry and Turq, 2003, Marry et al., 2008, Wang et al., 2004, Wang et al., 2006, Malikova et al., 2006).
Water mobility in smectites is largely controlled by the type of interlayer cation (Bordallo et al., 2008, Cases et al., 1992, Gates et al., 2012). The interactions of water (solutes) with the different surfaces of smectites often have diffusion or exchange times on the order of 10 ps to 100 ms that correspond in part to the time scale probed by neutron spectroscopy. Other methods, such as nuclear magnetic resonance (e.g., Bowers et al., 2011), are also highly successful at probing these interactions, but will not be discussed here.
Neutron scattering has several features that make it a powerful technique to study the structure and dynamics of heterogeneous systems such as smectite–water dynamics. The wavelength of thermal neutrons is suitable for probing the structure of a clay at the molecular level (neutron powder diffraction, NPD), as well as their long range order in colloidal dispersions and the macroscopic structure of the particles themselves (small-angle neutron scattering, SANS) (Cebula and Thomas, 1978). When compared to X-ray diffraction, neutron diffraction offers the advantage of a smaller attenuation coefficient, thus making surface effects negligible. Moreover in the study of sol or gel states the wavelength of the neutrons can be adjusted, so that Bragg diffraction reflections resulting from the clay mineral structure can be avoided. Additionally, by varying the hydrogen-deuterium ratio of the fluid, or possibly even the clay mineral itself, the contrast between the mineral particles and their surrounding water molecules can be better identified. On the other hand, although water dynamics can be investigated by many experimental techniques, such as infrared and Raman spectroscopies (Brubach et al., 2001) and nuclear magnetic resonance (NMR) (Kyakuno et al., 2011), neutron scattering spectroscopy offers a number of advantages presented in this work (Bordallo et al., 2008, Cebula et al., 1979, Cole et al., 2006, Malikova et al., 2008). Due to the exceptionally large scattering cross-section of the H-atoms, incoherent inelastic neutron scattering (IINS) enables probing of diffusive proton motions over a broad time-scale (from few nano to a few hundred ps) as well as the observation of quite high vibrational frequencies (up to 2000 cm− 1).
To date, neutron flux has been a key challenge in the study of many interesting problems in clay science, where understanding of kinetic effects is of the foremost importance. The unprecedented neutron flux offered by the European Spallation Source (operational in 2020) will, however, open up new opportunities for enquiry. For example, ESS will enable detailed dynamic analysis of real-time hydration and dehydration processes in clays. In order to better take advantage of this experimental technique, the most important theoretical points that must be known by novices, as well as examples of successful experiments, are described in this review.
Section snippets
Neutron scattering: an overview
Neutrons are non-charged subatomic particles, first postulated by Rutherford in 1920 and later observed by J. Chadwick in 1932. They are found in all atomic nuclei with exception of the hydrogen atom (1H) and have a comparable mass to protons, a magnetic moment of − 1.913 μb and a nuclear spin of 1/2.
Neutron scattering techniques are based on the analysis of momentum and energy transfer, which may occur following interactions between neutrons and matter. Note that during such interaction the
Smectite swelling at ambient conditions
As already mentioned (Table 1), neutron scattering lengths are isotope-dependent. For instance, neutron scattering lengths for H, D, Si, and Al are − 3.74, 6.67, 4.15, and 3.45 fm, respectively. As a consequence, structural studies of water in clay minerals are possible and largely benefit from the isotopic dependence on scattering length. Using H2O/D2O exchange yields additional information that is helpful on getting the precise location of hydrated species. The use of neutron diffraction to
Quasi-elastic neutron scattering (QENS) of clay minerals
The first studies of smectites by means of QENS date back to 1970 (Hunter et al., 1971, Olejnik and White, 1972, Olejnik et al., 1970) and since then, it has been possible to achieve remarkable results regarding the water dynamics and the variety of diffusion processes in these materials (Bordallo et al., 2008, Swenson et al., 2000, Nair et al., 2005 Gates et al., 2012, Chakrabarty et al., 2006, Malikova et al., 2006, Michot et al., 2007, Poinsignon et al., 1987, Swenson et al., 2001b).
The QENS
Molecular dynamics and Monte-Carlo simulations: getting the most of experimental data
Molecular simulations (molecular dynamics and Monte Carlo approaches) offer a description of matter at the atomic level, Fig. 9. Therefore they are useful tools to interpret many experiments covering spatial and time scales matched by neutron scattering in clay minerals.
In molecular dynamics simulations (MD), the atoms are considered as classical objects submitted to the Newton's equation of motion, which is propagated step by step thanks to an algorithm (usually Verlet or Velocity Verlet
Final remarks and perspectives
Neutron scattering methods have been applied to problems in the Earth and mineral sciences for many decades and more recently a rebirth of its use has been observed. This current growing interest is partly due to the development of improved neutron sources as well as the development of new methods and instrumentation. With this in mind, and considering that there is a wide range of interesting phenomena of interest to clay scientists that can be studied using neutron scattering, this review
Acknowledgments
MLM research is supported through the Brazilian Science without Borders (Process number 246604/2012-3) program. Some travel support was provided to WPG from the Australian Research Council's Discovery Project Scheme DP130102203. HNB thanks the invaluable discussions with Nikolaos Tspatsaris about many issues regarding how to better present the complex theory of neutron scattering to non-experts. We acknowledge the support of the ISIS Facility, ILL and FRM2 for providing the neutron facilities
References (94)
- et al.
Dynamics of absorbed water in saponite clay: neutron scattering study
Chem. Phys. Lett.
(2006) - et al.
In situ neutron diffraction analysis of the influence of geometric confinement on crystalline swelling of montmorillonite
Appl. Clay Sci.
(2006) - et al.
QINS studies of water diffusion in Na-montmorillonite
Physica B
(2000) - et al.
Do more strongly hydrogen-bonded water molecules reorient more slowly?
Chem. Phys. Lett.
(2006) Optimization of the chopper system for the cold-neutron time-of-flight spectrometer NEAT at the HMI, Berlin
Phys. B: Condens. Matter Phys.
(1992)- et al.
Diffusion of water in clays— microscopic simulation and neutron scattering
Chem. Phys.
(2005) - et al.
Structure and dynamics of intercalated water in clay minerals
Physica B
(1989) - et al.
The structure and dynamics of 2-dimensional fluids in swelling clays
Chem. Geol.
(2006) - et al.
Molecular simulation of interlayer structure and dynamics in 12.4 Å Cs-smectite hydrates
J. Colloid Interface Sci.
(2001) - et al.
Molecular modeling of the 10-Å phase at subduction zone conditions
Earth Planet. Sci. Lett.
(2004)
Effects of substrate structure and composition on the structure, dynamics and energetics of water at mineral surfaces: a molecular dynamics modeling study
Geochim. Cosmochim. Acta
The diffusion of interlamellar water in the 23.3 Å Na-montmorillonite-pyridine/H2O intercalate by quasielastic neutron scattering
Clay Clay Miner.
Properties of water in calcium and hexadecyltrimethylammonium-exchanged bentonite
Clay Clay Miner.
Neutron Diffraction
Quasielastic Neutron Scattering, Principles and Applications in Solid State Chemistry, Biology and Materials Science
Mechanism of adsorption and desorption of water vapour by homoionic montmorillonites: 2. The Li+, Na+, K+, Rb+ and the Cs+ exchanged form
Clay Clay Miner.
Quasi-elastic neutron scattering studies on clay interlayer-space highlighting the effect of the cation in confined water dynamics
J. Phys. Chem. C
Alkali metal and H2O dynamics at the smectite/water interface
J. Phys. Chem. C
Dependence of water dynamics upon confinement size
J. Phys. Chem. B
Mechanism of adsorption and desorption of water vapour by homoionic montmorillonites: 1. The sodium exchanged form
Langmuir
Mechanism of adsorption and desorption of water vapour by homoionic montmorillonite: 3. The Mg2 +, Ca2 +, Sr2 + and Ba2 + exchanged forms
Clay Clay Miner.
Neutron scattering from colloids
Faraday Discuss. Chem. Soc.
Neutron diffraction from clay–water systems
Clay Clay Miner.
Diffusion of water in Li–Montmorillonite studied by quasi-elastic neutron scattering
Clay Clay Miner.
Computer simulation of interlayer molecular structure in sodium montmorillonite hydrates
Langmuir
Molecular models of hydroxide, oxyhydroxide, and clay phases and the development of a general force field
J. Phys. Chem. B
Atomistic computer simulation of the clay–fluid interface in colloidal laponite
J. Chem. Phys.
Mode d'Empilement des feuillets dans les vermiculites hydratees a'deux couches
Clay Miner.
The structure of pore fluids in swelling clays at elevated pressures and temperatures
J. Phys. Condens. Matter
New insights on the distribution of interlayer water in bi-hydrated smectite from X-ray diffraction profile modeling of 00l reflections
Chem. Mater.
Hydration properties and interlayer organization of water and ions in synthetic Na-smectite with tetrahedral layer charge. Part 1. Results from X-ray diffraction profile modeling
J. Phys. Chem. C
Hydration properties and interlayer organization of water and ions in synthetic Na-smectite with tetrahedral layer charge. Part 2. Toward a precise coupling between molecular simulations and diffraction data
J. Phys. Chem. C
Understanding Molecular Simulations, From Algorithms to Applications
Thermodynamic properties of adsorbed water molecules and electrical conduction in montmorillonites and silicas
J. Phys. Chem.
Neutron time-of-flight quantification of water desorption isotherms of montmorillonite
J. Phys. Chem. C
Translational diffusion of water and its dependence on temperature in charged and uncharged clays: a neutron scattering study
J. Chem. Phys.
Molecular dynamics simulation of water mobility in magnesium-smectite hydrates
J. Am. Chem. Soc.
Incoherent neutron scattering function for molecular diffusion in lamellar systems
Mol. Phys.
Interfacial water structure in montmorillonite from neutron diffraction experiments
Clay Clay Miner.
Molecular dynamics simulations of water and sodium diffusion in smectite interlayer nanopores as a function of pore size and temperature
J. Phys. Chem. C
Investigating the anisotropic features of particle orientation in synthetic swelling clay porous media
Clay Clay Miner.
Cited by (34)
Layer charge effects on anisotropy of interlayer water and structural OH dynamics in clay minerals probed by high-resolution neutron spectroscopy
2021, Applied Clay ScienceCitation Excerpt :The non-linear loss of S(Q, |ω| < Δω) intensity with increased T indicated the onset of motions faster than the instrumental resolution (~4.1 × 10−9 s). In other words, thermally local structural fluctuations and D2O motions were out of the instrument resolution in the ns time scales (Qvist et al., 2011; Martins et al., 2014), but contributed to a Q- and T-dependent change in S(Q, |ω| < Δω). Thus, the EFW scans (Figs. 2 and 3) indicate, not unexpectedly, that non-localised D2O motions initialised at higher temperature than corresponding localised OH motions.
Prediction of the radionuclide inventory in the European Spallation Source target using FLUKA
2020, Nuclear Instruments and Methods in Physics Research, Section B: Beam Interactions with Materials and AtomsCitation Excerpt :The European Spallation Source (ESS) is a large-scale facility that will be used for studies of the structure and dynamics of materials using neutrons [1,2]. Neutron scattering is a well-developed method and is used extensively to investigate the fundamental properties of materials in fields such as physics, chemistry, biology, medicine and geology [3–5]. The ESS facility consists of a linear accelerator that will deliver 2.86 ms proton pulses at a rate of 14 Hz onto a tungsten target, where fast neutrons will be produced via spallation reactions.
The pH influence on the intercalation of the bioactive agent ciprofloxacin in fluorohectorite
2018, Applied Clay ScienceCitation Excerpt :Therefore, the results from the EFW experiments (Fig. 7a, Fig. 7b and Fig. 7c) demonstrate that all samples have a dynamical process that falls within the observation time window of MARS, with LiFHt showing the largest MSD at 300 K. Up to 250 K (23 °C) the MSD of LiFHt, at both ambient conditions and after drying, presents the same behavior while above this temperature the former exhibit a second change in the slope. In the case of clay minerals, such slope change is commonly attributed to the presence of bulk-like water that is easily removed on heating at 100 °C (Gates et al., 2012; Martins et al., 2014; Gates et al., 2017). Moreover, after drying LiFHt loses 36% of its MSD at 300 K (Fig. 7a), i.e. 64% of its MSD is conserved.
Clay mineral–water interactions
2018, Developments in Clay Science