Clay alignment in electric fields (original) (raw)
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Electric Alignment of Plate Shaped Clay Aggregates in Oils
Frontiers in Physics, 2016
We experimentally investigate the rotation of plate shaped aggregates of clay mineral particles immersed in silicone oil. The rotation is induced by an external electric field. The rotation time is measured as a function of the following parameters: electric field strength, the plate geometry (length and width) and the dielectric properties of the plates. We find that the plates always align with their longest axis parallel to the direction of the electric field (E), independently of the arrangement of individual clay mineral particles within the plate. The rotation time is found to scale as E −2 and is proportional to the viscosity (η), which coincides well with a model that describes orientation of dipoles in electric fields. As the length of the plate is increased we quantify a difference between the longitudinal and transverse polarizability. Finally, we show that moist plates align faster. We attribute this to the change of the dielectric properties of the plate due to the presence of water.
Packing and voids in electro-rheological structures of polarized clay particles
2006
Oil suspensions of fluorohectorite clay particles exhibit a dramatic meso-structural ordering when submitted to a strong electric field. This is due to dipolar interaction between polarized fluorohectorite particles, which orientate and aggregate to form chains and/or bundle-like structures along the direction of the applied electric field. We have used synchrotron small angle X-ray scattering to get insight into the nature of the porous medium in the bundles. Three types of fluorohectorite clay samples corresponding to three different intercalated cations Na+, Ni2+ and Fe3+ were studied. The two-dimensional SAXS images from bundles of fluorohectorites exhibit a marked anisotropy which is analyzed by fitting ellipses to iso-intensity lines of SAXS patterns. This also provides principal directions along which one-dimensional spectra are computed. They display a power law behavior typical of porous media, separated by crossovers. The crossovers are interpreted in terms of typical length scales for the clay particle bundles, providing for the first time a quantitative image of the 3D geometry inside such bundles of polarized clay particles. The exponents of the power laws indicate either predominant surface- (for 2 types of samples) or bulk- (for the last type) scattering, at all length scales investigated.
Dipolar structuring of organically modified fluorohectorite clay particles
The European Physical Journal E, 2012
This report focuses on both the characterization of organically modified fluorohectorite (Fh) clay particles and their electric-field-induced alignment when suspended in a non-polar liquid (silicone oil). Thermal decomposition temperatures of the surfactant molecules adsorbed on the clay surfaces and those being intercalated between clay crystalline layers were measured by thermal gravimetric analysis (TGA). Zeta potential measurements confirmed the successful modification of the clay surfaces. Optical microscopy observations showed that the sedimentation of modified particles was much slower compared to that of the non-modified system. It was shown that organic modification has a significant effect on colloidal stability of the system, preventing particles from forming large aggregates when suspended in a non-polar liquid. There are also signs of a slight increase in overall alignment of the clay particles when exposed to in an electric field, with the nematic order parameter (S 2) being higher for the organically modified particles, compared to that of the non-modified counterparts. This behaviour is mainly a result of the formation of smaller and more uniform aggregates, in contrast to the large aggregate structures formed by non-modified clay particles.
Electric field nematic alignment of fluorohectorite clay particles in oligomeric matrices
Journal of Materials Research, 2013
During my time at the University of Oslo I had the great pleasure of having Prof. Knut Jørgen Måløy as my supervisor. Whenever a problem arose or when I felt something needed discussion he was ready to help and always had good suggestions on how to move forward. My co-supervisors Jon Otto Fossum and Eirik Grude Flekkøy have always been available for discussions, and have been ready with suggestions and advice. For this I am extremely grateful. A very special thanks goes to my co-authors, especially Zbigniew Rozynek who was always ready to help and provide suggestions and I thoroughly enjoyed working with him on the projects presented here. It was also a great pleasure to work with Paul Dommersnes who always had good ideas and ways to progress the projects. I would like to thank all my colleagues for their input and tips on all matters from experimental work, calculations and L A T E X to the fantastic social environment in the group. In particular I would like to thank Joakim Bergli, Olav Aursjø, Micheal Niebling and Benjy Marks for their input to any physics related questions I would have. Mihailo Jankov has been a great friend, colleague and technician and I am appreciative for his help, advice on the experimental aspects and indeed for having an open ear for matters concerning the world outside. A special thanks also goes to all my friends, but in particular Torquil, Pål, Christian and Narita, who have all encouraged me and believed in me and have had to listen to me when things were not working. To all my friends, family and colleagues who have taken the time to read through my manuscripts both during my PhD and Master Degree studies in Oslo and Edinburgh:
Dipolar ordering of clay particles in various carrier fluids
The objective of the paper is to show that clay particles can be aligned in different hosting media, such as: silicone oil, paraffin-wax, polystyrene and ambient air. The use of an electric field is an easily controllable, non-intrusive manner of inducing such an alignment. Depending on the medium used, a large span in time constants for the orientation and reorganization has been observed. Furthermore, the reorientation may be frozen into the material, thus permanently changing its properties. Se investigan ejemplos de complejidad en materiales compuestos. El objetivo de este artículo es demostrar que se pueden alinear partículas de arcilla en diferentes medios como aceite de silicona, parafina-cera, poliestireno, y aire. El uso de un campo eléctrico resulta una vía fácilmente controlable y no-intrusiva de inducir el alineamiento. Se observa un amplio rango de constantes de tiempo para la orientación y la reorganización en dependencia del medio utilizado. Aún más, la reorientación ...
Under application of an electric field greater than a triggering electric field Ecsim0.4E_c \sim 0.4Ecsim0.4 kV/mm, suspensions obtained by dispersing particles of the synthetic clay fluoro-hectorite in a silicon oil, aggregate into chain- and/or column-like structures parallel to the applied electric field. This micro-structuring results in a transition in the suspensions' rheological behavior, from a Newtonian-like behavior to a shear-thinning rheology with a significant yield stress. This behavior is studied as a function of particle volume fraction and strength of the applied electric field, EEE. The steady shear flow curves are observed to scale onto a master curve with respect to EEE, in a manner similar to what was recently found for suspensions of laponite clay [42]. In the case of Na-fluorohectorite, the corresponding dynamic yield stress is demonstrated to scale with respect to EEE as a power law with an exponent alphasim1.93\alpha \sim 1.93alphasim1.93, while the static yield stress inferred from consta...
Clays and Clay Minerals, 2000
Homoionic Ca-saturated clay pastes were prepared and drying curves were obtained by applying suction pressures from 1 kPa to 100 MPa. A transmission device was used to study particle orientation by placing the clay in a cell specially designed to obtain diagrams corresponding to different sample orientations. The 00l and hk0 reflections were compared to determine the best reflections for studying clay-particle orientation. Depending on the clay, 00l reflections or the 020 reflection and/or hkl bands can be used to analyze orientation. In many cases the 020 reflection is preferred because the intensity of the peak is high and appears to be independent of the H20 content and the degree of stacking order of layers along the [001] direction. For interstratified clays, the conditions required to obtain 00l reflections depended on several factors, the most important of which is the water content. Also, the intensity relating to particie orientation depends on (1) particle extension (size) in the (001) plane and (2) the crystal structure. Illite crystals of <1000 A gave a poorly oriented clay matrix. In contrast, large aggregates of illite, smectite, and kaolinite particles (>10,000 A) showed a strongly oriented system. The particles of smectites may be curved and the dry material was poorly oriented owing to weak cohesion forces between the layers in comparison to illite. The study of the orientation of particles by X-ray diffraction on hydrated samples may be affected by sample mounting techniques. Any change in the content or the way the sample is mounted may modify the microstructure of a material. Clay containing a high water content affects the disorientation of particles, whereas, for the dry samples, pore size, pore volume, and solid continuity are associated with the geometry and crystal structure of the clay matrix.
Electric-field-induced structuring and rheological properties of kaolinite and halloysite
Applied Clay Science, 2013
Electric-field-induced structuring of kaolinite and halloysite particles was studied in respect to their electrorheological (ER) response in silicone oil and in paraffin dispersions. The structural and morphological properties of both clay minerals were studied by XRD, FTIR, SEM, TEM and TGA techniques. The dipolar arrangement induced under application of an electric field was investigated by 2D-WAXS and optical microscopy techniques. The ER response of the samples was measured by both the shear rate controlled method and bifurcation tests. Kaolinite particle dispersions were found to have an improved ER response relative to dispersions of halloysite particles. Finally, the electric currents of these ER fluids were measured and the results revealed differences in the current-magnitude between halloysite-and kaolinite-based silicone oil dispersions.
Journal of Physics: Condensed Matter, 2010
The electric field induced structuring in clay-oil suspensions has been studied by means of wide angle x-ray scattering (WAXS), rheometry, scanning electron microscopy (SEM), as well as leak current density and dielectric constant measurements. The clay particles' orientation distribution was inferred from the azimuthal changes of the clay diffraction peak intensity. The angular width of that distribution was quantified through an orientational order parameter. Chain and column formation processes were distinguished by comparison of the time evolution of the diffraction peak amplitude with that of the current density. Leak current density was measured for different electric field strengths E and clay particle concentrations . The following scaling relation was found: J ∝ 0.74 E 2.12 . In addition, the dependence of the yield stress on the electric field and on the particle concentration was measured and shown to scale as: τ y ∝ 0.87 E 1.66 .
Viscosity and transient electric birefringence study of clay colloidal aggregation
Physical Review E, 2002
We study a synthetic clay suspension of laponite at different particle and NaCl concentrations by measuring stationary shear viscosity and transient electrically induced birefringence ͑TEB͒. On one hand the viscosity data are consistent with the particles being spheres and the particles being associated with large amount bound water. On the other hand the viscosity data are also consistent with the particles being asymmetric, consistent with single laponite platelets associated with a very few monolayers of water. We analyze the TEB data by employing two different models of aggregate size ͑effective hydrodynamic radius͒ distribution: ͑1͒ bidisperse model and ͑2͒ log-normal distributed model. Both models fit, in the same manner, fairly well to the experimental TEB data and they indicate that the suspension consists of polydisperse particles. The models also appear to confirm that the aggregates increase in size vs increasing ionic strength. The smallest particles at low salt concentrations seem to be monomers and oligomers.