This book presents a comprehensive overview of the freezing of colloidal suspensions and explores cutting-edge research in the field. It is the first book to deal with this phenomenon from a multidisciplinary perspective, and examines the various occurrences, their technological uses, the fundamental phenomena, and the different modeling approaches. Its chapters integrate input from fields as diverse as materials science, physics, biology, mathematics, geophysics, and food science, and therefore provide an excellent point of departure for anyone interested in the topic. The main content is supplemented by a wealth of figures and illustrations to elucidate the concepts presented, and includes a final chapter providing advice for those starting out in the field. As such, the book provides an invaluable resource for materials scientists, physicists, biologists, and mathematicians, and will also benefit food engineers, civil engineers, and materials processing professionals.

This book addresses the properties of particles in colloidal suspensions. It has a focus on particle aggregates and the dependency of their physical behaviour on morphological parameters. For this purpose, relevant theories and methodological tools are reviewed and applied to selected examples. The book is divided into four main chapters. The first of them introduces important measurement techniques for the determination of particle size and interfacial properties in colloidal suspensions. A further chapter is devoted to the physico-chemical properties of colloidal particles—highlighting the interfacial phenomena and the corresponding interactions between particles. The book’s central chapter examines the structure-property relations of colloidal aggregates. This comprises concepts to quantify size and structure of aggregates, models and numerical tools for calculating the (light) scattering and hydrodynamic properties of aggregates, and a discussion on van-der-Waals and double layer interactions between aggregates. It is illustrated how such knowledge may significantly enhance the characterisation of colloidal suspensions. The final part of the book refers to the information, ideas and concepts already presented in order to address technical aspects of the preparation of colloidal suspensions—in particular the performance of relevant dispersion techniques and the stability of colloidal suspensions.

In this dissertation I present my research on the effective interactions of colloidal particles induced by a smaller species, as well as the structure of colloidal particles undergoing freeze casting. In this research I have used a wide variety of computational techniques in order to understand these systems. Specifically, in Chapter 2 I study nanoparticle haloing in a system of silica microspheres and highly charged polystyrene nanoparticles. Computer simulations are employed to determine the effective microsphere0́3 microsphere potential induced by the nanoparticles. From these simulations I am also able to determine the degree of nanoparticle adsorption on the microsphere surface. In Chapter 3 I investigate the depletion interaction in a system of charged microspheres and rigid rods. The effect of both rod concentration and screening length is explored. In Chapter 4 I study the effective interactions between charged colloids in the presence of multivalent counterions. The role of colloid charge is investigated and the onset of like-charged attraction is determined and compared with theoretical predictions. In order to study this system, I extended the geometric cluster algorithm to efficiently simulate systems interacting through the Coulomb potential. In Chapter 5 computer simulations are employed to elucidate the experimentally observed crystal phases of the Q and MS-2 virus particles in solution with multivalent salt and non-adsorbing polymer. Freeze casting is studied in Chapter 6. In this process colloidal particles are pushed by an advancing ice front. I use molecular dynamics simulations to study the dynamics of the colloidal particles and the resulting structures formed. iii

This research was focused on developing the underlying framework for the mechanisms that control the nature of the solidification of a broad range of porous media. To encompass the scope of porous media under consideration we considered material ranging from a dilute colloidal suspension to a highly packed saturated host matrix with a known geometry. The basic physical processes that occur when the interstitial liquid phase solidifies revealed a host of surprises with a broad range of implications from geophysics to materials science and engineering. We now understand that ostensibly microscopic films of unfrozen liquid control both the equilibrium and transport properties of a highly packed saturated host matrix as well as a rather dilute colloidal suspension. However, our description of the effective medium behavior in these settings is rather different and this sets the stage for the future research based on our past results. Once the liquid phase of a saturated relatively densely packed material is frozen, there is a rich dynamical behavior of particles for example due to the directed motion driven by thermomolecular pressure gradients or the confined Brownian motion of the particles. In quite striking contrast, when one freezes a dilute suspension the behavior can be rather more like that of a binary alloy with the particles playing the role of a ``solute''. We probed such systems quantitatively by (i) using X ray photon correlation spectroscopy (XPCS) and Small Angle X-ray Scattering (SAXS) at the Advanced Photon Source at Argonne (ii) studying the Argonne cell in the laboratory using optical microscopy and imagery (because it is not directly visible while in the vacuum can). (3) analyzed the general transport phenomena within the framework of both irreversible thermodynamics and alloy solidification and (4) applied the results to the study of the redistribution of solid particles in a frozen interstitial material. This research has gone a long way towards establishing a quantitative foundation for a wide class of problems in environmental and technological settings.

This thesis presents an in-depth study on the effect of colloidal particle shape and formation mechanism on self-organization and the final crystal symmetries that can be achieved. It demonstrates how state-of-the-art X-ray diffraction techniques can be used to produce detailed characterizations of colloidal crystal structures prepared using different self-assembly techniques, and how smart systems can be used to investigate defect formation and diffusion in-situ. One of the most remarkable phenomena exhibited by concentrated suspensions of colloidal particles is the spontaneous self-organization into structures with long-range spatial and/or orientational orders. The study also reveals the subtle structural variations that arise by changing the particle shape from spherical to that of a rounded cube. In particular, the roundness of the cube corners, when combined with the self-organization pathway, convective assembly or sedimentation, was shown to influence the final crystal symmetries.