Experiments in the Laboratory for Soft and Complex Matter Studies at NTNU:

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1 1 Experiments in the Laboratory for Soft and Complex Matter Studies at NTNU: Active full-time researchers in our NTNU lab : (exp. = experiments, sim. = simulations) Prof. Jon Otto Fossum Post.doc NN (to be hired soon) Ph.D. student Henrik Hemmen Ph.D. student Elisabeth Lindbo Hansen Ph.D. student Zbigniew Rozynek Research Technician Ole Tore Buset, (helps us in all exp. activities) Masterstudents? Regular visiting scientists in our NTNU lab : Adjunct Prof. Kenneth D. Knudsen, (exp.) is full-time Senior Researcher at IFE Main supervisor for project number 1.d), see below:: Prof. Arne Mikkelsen Principal contact for all projects given below: Prof. Jon Otto Fossum, jon.fossum@ntnu.no, tel , room E3-160 Realfagbygget NTNU. You may also contact the other supervisors listed, of course. In many of the experiments that we describe below, it may be necessary to perform synchrotron X-ray investigations either in France, Brazil, South-Korea, or Sweden, or neutron scattering at IFE, Kjeller. Some of the activities below are new, while some are ongoing, and in the latter cases, the master student projects are continuations of these ongoing activities. The projects we offer have a common denominator and a common basic question: What kind of relations are there between physics and structures on the nano-scale, and macroscopic and global behaviors on the human scale? It is in this context that we for example study self-organization of nano-particles: Think of how to make something smart from nano-particles, something which is so large that you can hold it in your hand. Such an object contains about nanoparticles (Avogadro s number). Even if you use as little as 1 millisecond in order to move a nano-particle into its planned place in a pre-designed structure, one particle by one particle, it will take about 300 million years to organize the particles the way you want. This means that self-organization of nano-particles is the only practical way to do this, and that basic studies of self-organization of particles is a hot topic in science. See also the following popular science presentations and other news from the lab: University of Amsterdam, Netherlands: News and Agenda: Clay soil landslides cause greater damage after minor rainfall, November European Space Agency (ESA) 2009 Meet the teams 2009: Complex Norwegian Space Centre, November 11th 2009: Spinnville studentmuligheter Forskning.no April 13th 2009: Leire i fritt fall European Space Agency (ESA), January 12th 2009: Four student teams selected to fly their theses! Norwegian Space Centre, January 13th 2009: Norwegian students become weightless Forskning.no April 6th 2007: Nanoleire demper støt Research Council of Norway NANOMAT news April 2007: Norske leireforskere i teten Research Council of Norway NANOMAT Newsletter May 2007: Fra komplekse fenomener i leire til nanoteknologi

2 2 We need more master-students, and we offer the following projects Note that we may hire students for a 1 month summer-job (for each student) during summer of 2010, as a jump-start to the project of the fall semester The projects that we offer, are outlined in the following pages. They are all experimental physics projects. List of contents: 1. Nano-science 1: Spontaneous self-organization from nano-particles: Nematic phases: 1. a) Drying of droplets with suspended nanoparticles 1. b) Liquid crystalline phases and self-organization 1. c) Temperature dependent ordering in synthetic clay liquid crystals design of an experiment using in-house equipment and experimental work at world class synchrotron facilities 1. d) Optical studies of field induced order-disorder transitions 2. Nano-science 2: Guided self-organization from nano-particles: 2. a) Complex nanowire pattern assembly via external electric field 2. b) Dual-field induced self-organization from clay particles: X-Ray studies 2. c) Self-organization from clay particles in volatile state supported by membrane vibration: SAXS/WAXS and electron microscope studies 3. Petroleum related physics, environmental physics, nano science: Studies of fluid transport in nano-structures: 3. a) Fluid-transport in nanoporous materials 4. Geophysics, petroleum related physics, environmental physics: Pattern-formation in soft materials: 4. a) Characterization of the roughness of fractures in soft transparent gels 4. b) Avalanches in clays

3 3 Project descriptions (supervisors in parenthesis): 1.a) Drying of droplets with suspended nanoparticles (H. Hemmen, E. Lindbo Hansen, J.O. Fossum) Water droplets containing disc-shaped clay nanoparticles: The effectst o fparicle concentration, ordering and other parameters on the resulting patterns after drying. This project focuses on patterns formed by drying of droplets containing disk-shaped clay nanoparticles. Preliminary experiments performed by us have shown that the resulting patterns depend strongly on the type of ordering present in the droplet before drying: If the initial concentration of particles is high, and in particluar if the particles have orientational order, an extended fractal network is produced (Fig 1a); If the initial concentration is low, and there is no orientational order, the coffee stain effect [1] can be seen (Fig 1b). A more thourough study of this phenomenon, with b) Figure 1. Our own preliminary observations of patterns formed after drying. Right image is a close up.a) High particle concentration and orientational order before drying. b) Low particle concentration and isotropic order before drying. a) varying concentration, droplet size, drying rate etc. is needed. We have plans to study these samples using a range of experimental techniques, e.g. optical microscope, small and wide angle x-ray diffraction, SEM/TEM and AFM. It is also interesting to study the ordering and transport of particles during the drying process, and also using other types and shapes of particles. This project has relevance for degined nanostructerd thin film paterning. [1] Capillary flow as the cause of ring stains from dried liquid drops, R. D. Deegan et al., Nature 386 (1997). Fig 2: From [3].

4 4 1.b) Liquid crystalline phases and self-organization (E. Lindbo Hansen, K.D. Knudsen-IFE, J.O. Fossum) Liquid crystalline phases of disc-shaped nanoparticles in water: the ordering effects of walls, boundaries and bubbles. This project focuses on the liquid crystalline order that our group has shown develops in initially isotropic aqueous suspensions of disc-shaped sodium-fluorohectorite clay nanoparticles in the gravitational field [1,2]. The master student who chooses this project will get to travel to synchrotron sources in either France, Brazil or South-Korea and experience how x-ray scattering techniques apply to studies on soft and complex matter. Neutron experiments at IFE, KJeller can also bee foreseen.the main aim of the proposed project is to further investigate the effects of container walls, Fig 3: From [4]. suspension-air interfaces and heating induced bubbles on the nematic order of nanosized clay platelets suspended in water. As illustrated in Fig 3 to the left, X-rays scattered off anisotropic samples will show anisotropic scattering patterns. It is also possible to extract quantitative measures of the degree of order from such diffractograms, by calculating values for the so-called nematic order parameter S 2 [3]. Another way to investigate nematically ordered samples, is to observe the samples between crossed linear polarizers. Isotropic samples will allow no light to emerge from between a crossed polarizers setup, and the field of view of a camera observing the setup will thus be dark. Nematically ordered, anisotropic samples on the other hand will change the polarization state of the incoming light so that some light will be transmitted from a crossed polarizers setup. A camera can record the amount of light transmitted, and this can be related to the degree of ordering in the sample. As a master student on this project, you will become familiar with investigations of ordering through both such birefringence observations, and through in-house and synchrotron based x-ray scattering experiments. [1] Orientational order in gravity dispersed clay colloids: A synchrotron x-ray scattering study of Na fluorohectorite suspensions, E. DiMasi, J. O. Fossum, T. Gog, and C. Venkataraman, Phys. Rev. E 64, (2001). [2] Phase diagram of polydisperse Na-fluorohectorite-water suspensions: A synchrotron small angle x-ray scattering study, D. M. Fonseca, Y. Méheust, J. O. Fossum, K. D. Knudsen and K. P. S. Parmar, Phys. Rev. E 79, (2009). [3] Inferring orientation distributions in anisotropic powders of nano-layered crystallites from a single twodimensional WAXS image, Y. Méheust, K. D. Knudsen and J. O. Fossum, J. Appl. Cryst. 39, 661 (2006). [4] Colloidal Dispersion of Clay Nanoplatelets: Optical birefringence and x-ray scattering studies of nematic phases, E. L. Hansen, Master s thesis, NTNU (2008).

5 5 1.c) Temperature dependent ordering in synthetic clay liquid crystals design of an experiment using in-house equipment and experimental work at world class synchrotron facilities. (H. Hemmen, E. Lindbo Hansen, J.O. Fossum, K.D. Knudsen-IFE) This project should be interesting both for the engineering-minded and the scientificminded master student. If you choose this project you will have to design, from scratch, (or redesign an existing) sample cell that can quickly change temperatures in the range from ~0 to ~95 C while at the same time being small enough to fit in our X-ray sample chamber and furthermore be transparent to X-rays. Our group has an in-house X-ray scattering apparatus that will be to your disposal during the testing of your sample cell. After completing the sample holder, you will be able to use it for real-life research. We have previously done experiments at a synchrotron in Campinas, Brazil, that indicate that nematic order is induced around air-bubbles formed by temperature-increase in samples containing clay nano-particles in water-salt solution [1]. Temperature-induced nematic order of nanoparticles can be a cheap and successful way of creating future nanotechnology materials. Your project, after completion of the sample cell, will do experiments that increase the fundamental understanding of the physics of this subject. At NTNU, we have a highly competent mechanical workshop that will help in creation of the sample cell. After testing of the sample cell at our low-flux inhouse X-ray scattering machine, a trip to a synchrotron will enable you to do high quality scientific experiments at a world class scientific facility. In synchrotrons, electrons are accelerated in circular paths at near-light-speed velocities [2]. This results in extremely high flux X-ray emission (remember that all charged om [4]. particles emit EM-radiation when accelerated). Our group regularly does experiments at synchrotron facilities in France, Brazil, South Korea and Sweden. The ESRF synchrotron ring in Grenoble, France (where you might go) is arguably the best experimental research facility in the world for studies in research fields as diverse as crystallography, protein structure determination, material science, soft condensed matter studies, X-ray imaging, X-ray spectroscopy etc. The ESRF storage ring is shown on the picture above [3]. Doing experiments of course also means doing data analysis. In addition to the data you will get from the experiments with your sample cell, we have a collection of data from previous synchrotron experiments. During the project you will be taught how to study and analyze X-ray diffraction data, and extract meaningful information from complex twodimensional diffractograms. The master student who chooses this project will have the opportunity to do synchrotron experiments at an international research facility. [1] SAXS study of the positional order in a colloidal solution of fluorohectorite clay at different temperatures,d.d.m. Fonseca, Y. Méheust, J.O. Fossum, K.D. Knudsen,The International Conference on Small Angle Scattering, Kyoto, (July 2006). [2] Neutron and synchrotron radiation for condensed matter studies. J. Baruchel, J.L. Hodeau, M.S. Lehmann, J.R. Regnard and C. Schlenker. Springer Verlag, (1993). [3] The European Synchrotron Radiation Facility webpage.

6 6 1.d) Optical studies of field induced order-disorder transitions (A. Mikkelsen, E. Lindbo Hansen, J.O. Fossum) Optical studies on field induced order-disorder transitions: the effects of electric, magnetic and mechanical fields on anisotropic colloidal particles. This project is focused on the reponse of anisotropic, colloidal particles to external fields. The applied fields can be electric, magnetic or mechanical in nature and the response will be studied optically by birefringence observations with laser and white light, by light scattering studies, and possibly also with x-rays. Due to their anisotropy, nanoscaled platelets of synthetic clays suspended in water or oil will orient in response to applied fields, and such oriented systems will display a special kind of optical property known as birefringence. If such samples are placed between crossed polarizers, the light that reaches a camera observing the samples will be a direct result of the degree of anisotropy. Samples that are ordered will cause light to be transmitted towards the observer whereas isotropic samples will not affect the polarization of light, and the field of view for an observer will thus be dark. As a master student on this project, you will be given the opportunity to study both isotropic suspensions and nematically ordered samples [1] of plateshaped clay nanoparticles by several experimental methods. Optical birefrigence in laser and white light will be studied on both nematic samples, and on initially isotropic samples where short electric pulses [2] or flows will cause a temporary ordering that decays once the fields are switched off (Fig. 5). The decay is caused by the rotational Brownian diffusion, which promotes a random ordering of the nanoplatelets. You will also be able to study order-disorder transitions induced by flows via a static light scattering cell on an instrument known as a rheometer, and you may also be given the opportunity of performing dynamic light scattering experiments. The latter will primarily be used to study diffusion and particle or aggregate sizes, whereas the static scattering gives information on structure and order. Fig 5: From [2]. Electric induced order studied by laser birefrigence. [1] Orientational order in gravity dispersed clay colloids: A synchrotron x-ray scattering study of Na fluorohectorite suspensions, E. DiMasi, J. O. Fossum, T. Gog, and C. Venkataraman, Phys. Rev. E 64, (2001). [2] Viscosity and transient electric birefringence study of clay colloidal aggregation, A. Bakk, J. O. Fossum, G. J. da Silva, H. M. Adland, A. Mikkelsen, and A. Elgsaeter, Phys. Rev. E 65, (2002).

7 Laboratory for Soft and Complex Matter Studies-NTNU Jon Otto Fossum ( 7 2.a) Complex nanowire pattern assembly via external electric field (Z. Rozynek, J.O. Fossum) Nanospheres, nanodiscs, nanowires, nanotubes and nanorods have recently been extensively explored due to their unique properties and the capabilities to bind chemical, physical and biological entities of interest. Nanowires are one type of small entities with a large aspect ratio. The geometrical shape and the multifunctionalities realized in multicomponent nanowires allow tuning of their physical, chemical, and electrical properties. Nanowires often need to be transported and assembled in suspension in order to exploit and capture their unique properties. To date, the properties of simple nanowire-based devices have been determined using nanowires deposited on the surface of a substrate either at random or else by directed assembly controlled by flowing fluids or electric fields. These latter approaches represent a significant advance over random assembly, yet remain limited in that the end-to-end registry and three-dimensional (3D) orientation of nanowires are not controlled, thus precluding the rational assembly of more complex architectures with interesting and potentially useful functional properties. Nonuniform electric fields have been used to manipulate dielectric particles that are suspended in liquid media. Complex nanowires pattern can be got via the application of external electric field, which is shown in figure1. a b Fig.1 (a) E-field structuring in a quadrupole with connected pairs of electrodes (b) Electric field and its gradient are both along the radical direction. Nanowires aligned chained and attached to the inner electrode. a b Fig.2 E-field induced structuring in a 3-pair electrode system. E-field applied vertically (a) and horizontally (b) References 1. Parmar, K. P. S.; Méheust, Y.; Schjelderupsen, B. and Fossum, J. O. Langmuir 2008, 24, Fan, D.L.; Zhu, F.Q.; Cammarata, R.C., et al. Appl. Phys. Lett. 2004, 85 (18),

8 8 2.b) Dual-field induced self-organization from clay particles: X-Ray studies. (Z. Rozynek, K.D. Knudsen-IFE, J.O. Fossum) This project gives the opportunity to become familiar with X-ray scattering techniques such as: small/wide angle x-ray scattering (SAXS/WAXS). You will be taught both how to perform the in-house SAXS/WAXS experiments (figure 1) and analyze x-ray diffractograms. You will be also involved in a sample cell design. The master student who chooses this project will have the opportunity to do synchrotron experiments at an international research facility. Fig.1. SAXS/WAXS in-house equipment Electrorheological (ER) fluids and magnetorheological (MR) suspensions show dramatic and reversible rheological changes in applied electric or magnetic fields, which may induce change from viscous liquids to visco-plastic solids in the order of milliseconds/seconds in such suspensions - follow this link to see a movie:!!! The dramatic rheological changes are closely related to changes in microstructure. In zero external field (first 3 seconds of the movie), the microstructure is isotropic, whereas upon application of external field (for example 500V/mm), the particles aggregate into columnar structures [1,2]. So far our group has been focusing on one-field and one-directional induced selfassembly (either electric or magnetic field) as it is show in figures 2 and 3 below. Fig.2. Two copper electrodes and the liquid sample filling in 1mm gap (left). Fig.3. Particles are forming chains along the electric field (right). This time we would like to focus on so called two-field induced assembly using either: - two (or even more) electric fields perpendicular (or in other configuration) to each other, - or/and combining electric and magnetic fields together Ad.1. By alternating these electric fields, the orientation order can possibly be improved, hence electrorheological effect improves. New phenomena are expected to emerge!!! Ad.2. The sample will exhibit dual responsive properties under external magnetic and electric fields, so that the rheological effect can be enhanced!!! [1] [2] Wang B, Z. M., Rozynek Z and Fossum J O "Electrorheological properties of organically modified nanolayered laponite: Influence of intercalation, adsorption and wettability." J. Mat. Chem (2009)

9 9 2.c) Self-organization from clay particles in volatile state: SAXS/WAXS and electron microscope studies. (Z. Rozynek, K.D. Knudsen-IFE, J.O. Fossum) This project gives the opportunity to become familiar with X-ray scattering techniques such as: small/wide angle x-ray scattering (SAXS/WAXS) and scanning electron microscopy (SEM). You will be taught both how to perform the in-house SAXS/WAXS experiments, analyze x-ray diffractograms and operate the SEM. You will be also involved in a sample cell design. Electrorheological fluids (ERFs) are complex liquids that become very viscous, in an applied electric field. The transition from liquid into a solid-like state indicates that there is an internal ordering of the ER-constituents, which leads to dramatic changes in the rheological properties. Application of an electric field induces polarization of the suspended dielectric particles and a chain-like structure can be formed along the electric field direction [1]. The most common ERFs are suspensions of 1- to 100-µm polarizable particles at volume fractions of dispersed in an inert insulting liquid. For an electric field E of ~ V/mm the particles form chains that span the gap between the field-generating electrodes [2]. By following this link you can see the chain formation of clay particles suspended in silicon oil as an example of an ERF: In zero external field (first 3 seconds of the movie), the microstructure is isotropic, whereas upon application of external field (for example 500V/mm), the particles aggregate into columnar structures [3,4]. So far many researchers have been focused on that type of self-assembly described above. The recipe for making ERF is very simple and what one needs to do is to choose particles with high dielectric constant (such that an external electric field can induce the electric dipole in the particle) and immerse is in the non-polar and non-conducting matrix, for example a silicone oil / vegetable oil. What if we this time do something completely different and not use any liquid medium, but we let the particles to self-assembly in the air/gas?! Yes, it is possible, see figures below. a) Fig.1. Two copper electrodes with the gap of 1mm gap. Particles suspended in the silicone oil a) and the selfassembly that took place in air only b). This is a very new direction in our research activities. Why not to join our group and make fascinating research? [1] Tao R and Sun J M 1991Phys. Rev. Lett [2] Fossum J O, Meheust Y, Parmar K P S, Knudsen K D, Måløy K J and Fonseca D M 2006 Europhys. Lett [3] Wang B, Z. M., Rozynek Z and Fossum J O (2009). "Electrorheological properties of organically modified nanolayered laponite: influance of intercalation, adsorption and wettability." J. Mat. Chem [4]

10 10 3.a) Fluid-transport in nanoporous materials (H. Hemmen, J.O. Fossum) This project is part of and a continuation of an international collaboration involving the researchers in Brazil, in France and in South-Korea. The project deals with experimental studies of nanoporous media, and fluid transport/diffusion in such systems. This physics may have relevance for membrane technology, and for control of polluting agents in for example clay based soils. The latter application is relevant for sub-sea oil reservoirs, as well as for containment and storage of radioactive waste. Most porous materials that surround us, absorb water, either due to direct contact with liquid water, or from water vapor in the surrounding air that condenses in small pores. The water may often be modeled as capillary flow: The water wets the porous material and is pulled in (blotting paper effect). This gives a water front that progresses as the square root of the time. But if the material has pores with nanometer size (1 water molecule is about 0.2 nm), the observed dynamics is often different from this, and there is today no good understanding of this so-called anomalous water transport. Small-Angle-X-ray-Scattering (SAXS) studies of water transport in a nanoporous clay material has been studied by us recently, and the project will continue such studies. The following pictures show examples of 2-dimensional SAXS diffractograms form our studies in our home-lab. at NTNU. Such diffractograms give direct information about the water content in different pore sizes in nanoporous materials. We also want to extend our studies beyond clay based nanoporous systems, and include other nanoporous materials, such as zeolites or paper (the blotting paper effect studied by X-rays). The project may include work at the Federal University of Pernambuco in Recife, Brazil, for NMR studies [1]. Reference: [1] Fluid imbibition in paper fibers: Precursor front, Eduardo N. de Azevedo, Lars R. Alme, M. Engelsberg, Jon Otto Fossum, and Paul Dommersnes, Phys.Rev.E 78, (2008)

11 11 4.a) Characterization of the roughness of fractures in soft transparent gels (H. Hemmen, J. O. Fossum) This project focuses on experimental determination of the roughness of fractures in gels, in particular gels prepared by dispersing synthetic clay nanoparticles (Laponite) in deionized water. This topic has been the subject for several previous projects in our group[1-3], and as a result of that records of previous experimental preparations, experimental data and reference literature are easily available to any student who chooses this project (you will have a head start). The characterization of fracture-roughness by using fractals has been a hot topic for a long time now. Experiments have shown that that when one considers the statistical variations of the fracture surfaces, fractures in systems as different as plaster, steel or wood all have the same roughness [4]. The fractal study of nature is in itself a very useful tool, as master students working this project quickly will find out. In fact when one tries to extract universality from complex systems, one of the main obstacles is finding the right level of description. This is illustrated by the figure on the left [2]: The fracture surface on top of a clay-water gel is indeed complex, but by removing redundant information, we can describe the surface s roughness by a single fractal variable ζ. om [4]. This project will be challenging (and therefore also rewarding) in several ways. It will involve reading up on previous work, i.e. both experiments done in our group and experiments available in international journals. It will further involve setting up and improving our setup for controlled creation of fracture surfaces in gels, as well as performing experiments and doing data analysis. Because this is a project that is already quite mature, it is not unlikely that the work may lead to submission of a manuscript to an international peer-review journal before completion of the thesis work. The master student who chooses this project will have the opportunity to travel to Brazil to do MRI experiments in a collaborating group at the federal university of Pernambuco. [1] Experimental Research on Fractures in Gels. Knut Magnus. Master degree thesis, NTNU Department of Physics, June 2008 [2] Experimental Studies of Nanostructured Clay Gels. Henrik Hemmen. Master degree thesis, NTNU Department of Physics, June 2008 [3] An Experimental Study of Fractures in Gels. Christian A. Nielsen. Master degree thesis, NTNU Department of Physics, July 2007 [4] Scaling properties of cracks. E. Bouchaud. J. Phys.: Condens. Matter, 9. (1997).

12 12 4.b) Avalanches in clays (J.O. Fossum, H. Hemmen) Different mechanisms for the onset and development of landslides have been reported. However, the extreme instability ( quickness ) of clayey soils in particular remains poorly understood. Quickclay has caused many deadly landslides in Canada, Russia, Alaska, Norway and Sweden. The occurrence of quickclay landslides is usually attributed to variations in water content and/or external perturbation of the soil. As merely one example of the latter, the infamous Rissa slide (movies are available from the Norwegian geotechnical service) was caused by small excavation works at a nearby farm. So far [1], our group has investigated this extreme sensitivity by studying the flow behaviour of quickclay with different water contents in a rheometer. The sample used was a quickclay collected from 10m depth at Tiller, Trondheim which is similar in composition to quickclays that may be collected from other regions in the world. Our Fig. 1: Laboratory landslides: Picture of the final stage of the slides: in the four lines from left to right the concentration of quickclay in water increases [1]. laboratory experiments (performed in Amsterdam) on the Tiller natural quicklay samples reveal a spectacular liquefaction of the material under flow that explains the instability. Laboratory landslide experiments in addition show that, contrary to what is expected, higher water content does not lead to more unstable soils. For high clay content, the liquefaction occurs in a very thin layer of the material, the rest of the clay moving as a solid block; this explains the large distances over which quickclay landslides travel. We have reproduced the flow behaviour of the natural samples mixing different clays, water and salt, which has allowed us to assess the impact on the quickness of the different constituents of the clay. In order to investigate such avalanches further, we want one master student to setup and use the following type of tilted plane experiment in our lab [2]: Fig. 2: Left: Tilted plsne experiment for studies of avalanches [2]. Right: Avalanches in systems of sand and glass beads repesectiveøy sturdied using the experimental tilted plane setup to the left [2]. [1]Quick Clay and Landslides of Clayey Soils, A. Khaldoun, P.Moller, A. Fall, G. Wegdam, B. de Leuw, Y. Meheust, J.O. Fossum, D. Bonn, Phys. Rev. Lett. 103, (2009) [2] Avalanche dynamics on a rough inclined plane, T. Börzsönyi, T.C. Halsey, R. E. Ecke, Phys. Rev. E 78, (2008)