In situ X-ray crystallographic study of the structural evolution of colloidal crystals upon heating (original) (raw)
Premelting at Defects Within Bulk Colloidal Crystals
Science, 2005
Premelting is the localized loss of crystalline order at surfaces and defects at temperatures below the bulk melting transition. It can be thought of as the nucleation of the melting process. Premelting has been observed at the surfaces of crystals but not within. We report observations of premelting at grain boundaries and dislocations within bulk colloidal crystals using realtime video microscopy. The crystals are equilibrium close-packed, threedimensional colloidal structures made from thermally responsive microgel spheres. Particle tracking reveals increased disorder in crystalline regions bordering defects, the amount of which depends on the type of defect, distance from the defect, and particle volume fraction. Our observations suggest that interfacial free energy is the crucial parameter for premelting in colloidal and atomic-scale crystals.
Melting of a colloidal crystal
Physica A: Statistical Mechanics and its Applications
A melting transition for a system of hard spheres interacting by a repulsive Yukawa potential of DLVO form is studied. To find the location of the phase boundary, we propose a simple theory to calculate the free energies for the coexisting liquid and solid. The free energy for the liquid phase is approximated by a virial expansion. The free energy of the crystalline phase is calculated in the spirit of the Lenard-Jonnes and Devonshire (LJD) theory. The phase boundary is found by equating the pressures and chemical potentials of the coexisting phases. When the approximation leading to the equation of state for the liquid breakes down, the first order transition line is also obtained by applying the Lindemann criterion to the solid phase. Our results are then compared with the Monte Carlo simulations.
Colloidal Crystallization As Compared with Polymer Crystallization
Polymer Journal, 2008
Recent work made in the author's laboratory on the morphology (especially, giant colloidal crystals), crystal structure, fundamental properties such as phase transition, light-scattering, viscosity and elasticity, crystallization kinetics and electrooptics of colloidal crystals have been reviewed. Colloidal crystals are really crystal as typical other crystals, metals, polymers and ice, for example. However, the inter-particle force of colloidal crystal is ''repulsion'' exclusively and being different from the other typical crystals, where the inter-particle ''attraction'' plays an important role for crystallization. It is pointed out that the apparent ''attraction'' is induced inevitably for the colloidal crystallization in a closed vessel.
Soft matter, 2018
The structural rearrangement of polystyrene colloidal crystals under dry sintering conditions has been revealed by in situ grazing incidence X-ray scattering. The measured diffraction patterns were analysed using distorted wave Born approximation (DWBA) theory and the structural parameters of the as-grown colloidal crystals of three different particle sizes were determined for the in-plane and out-of-plane directions in a film. By analysing the temperature evolution of the diffraction peak positions, integrated intensities, and widths, the detailed scenario of the structural rearrangement of crystalline domains at the nanoscale has been revealed, including thermal expansion, particle shape transformation and crystal amorphisation. Based on DWBA analysis, we demonstrate that in the process of dry sintering, the shape of colloidal particles in a crystal transforms from a sphere to a polyhedron. Our results deepen the understanding of the thermal annealing of polymer colloidal crystals...
Structure of crystals of hard colloidal spheres
Physical Review Letters, 1989
We report light-scattering measurements of powder diffraction patterns of crystals of essentially hard colloidal spheres. These are consistent with structures formed by stacking close-packed planes of particles in a sequence of permitted lateral positions, A, B,C, which shows a high degree of randomness. Crystals grown slowly, while still containing many stacking faults, show a tendency towards facecentered-cubic packing; possible explanations for this observation are discussed.
Melting of two-dimensional tunable-diameter colloidal crystals
Physical Review E, 2008
Melting of two-dimensional colloidal crystals is studied by video microscopy. The samples were composed of microgel spheres whose diameters could be temperature tuned, and whose pair potentials were measured to be short ranged and repulsive. We observed two-step melting from the crystal to a hexatic phase and from the hexatic to the liquid phase as a function of the temperature-tunable volume fraction. The translational and orientational susceptibilities enabled us to definitively determine the phase transition points, avoiding ambiguities inherent in other analyses and resolving a "dislocation precursor stage" in the solid phase that some of the traditional analyses may incorrectly associate with the hexatic phase. A prefreezing stage of the liquid with ordered patches was also found.
Unravelling structural rearrangement of polymer colloidal crystals under dry sintering conditions
2018
Structural rearrangement of polystyrene colloidal crystals under dry sintering conditions has been revealed by in situ grazing incidence X-ray scattering. Measured diffraction patterns were analysed using distorted wave Born approximation (DWBA) theory and the structural parameters of as-grown colloidal crystals of three different particle sizes were determined for in-plane and out-of-plane directions in a film. By analysing the temperature evolution of diffraction peak positions, integrated intensities, and widths the detailed scenario of structural rearrangement of crystalline domains at a nanoscale has been revealed, including thermal expansion, particle shape transformation and crystal amorphisation. Based on DWBA analysis we demonstrate that in the process of dry sintering the shape of colloidal particles in a crystal transforms from a sphere to a polyhedron. Our results deepen the understanding of thermal annealing of polymer colloidal crystals as an efficient route to the des...
Crystallization of Soft Crystals
Langmuir, 2009
The crystallization of micelles formed by surfactant F127 solvated by 20% in water was investigated in the vicinity of a hydrophilic interface. Upon entering the crystalline phase from low temperature, a large correlation length develops without preferential texture. Upon heating, the correlation length decreases and Oswald ripening is observed with crystallites orienting with respect to each other while retaining long-range and textured correlation.
Physical Review E, 2004
High-resolution synchrotron small-angle x-ray diffraction is applied to characterize the structure and longrange order in a sedimentary hard-sphere colloidal crystal before and during its drying. The principles of the technique and the influence of the coherence properties of the x-ray beam are discussed in detail. The capillary forces generated during the drying process are shown to destroy the long-range order and to break the crystal into smaller crystallites with slightly different orientations. The diffraction is shown to switch from the dynamic regime in the long-range-ordered crystal to nearly kinematic diffraction in the mosaic ͑short-range-ordered͒ crystal.
Observation of solid–solid transitions in 3D crystals of colloidal superballs
Nature Communications, 2017
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