In situ X-ray crystallographic study of the structural evolution of colloidal crystals upon heating (original) (raw)
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Langmuir, 2015
In situ X-ray diffraction studies of structural evolution of colloidal crystal films formed by polystyrene spherical particles upon incremental heating are reported. The Bragg peak parameters, such as peak position, integrated intensity, and radial and azimuthal widths were analyzed as a function of temperature. A quantitative study of colloidal crystal lattice distortions and mosaic spread as a function of temperature was carried out using Williamson−Hall plots based on mosaic block model. The temperature dependence of the diameter of polystyrene particles was obtained from the analysis of Bragg peaks, and the form factor contribution extracted from the diffraction patterns. Four stages of structural evolution in a colloidal crystal upon heating were identified. Based on this analysis, a model of the heating and melting process in the colloidal crystal film is suggested. (A.V.Z.). Figure 9. Schematic diagram of the structural evolution in a colloidal crystal film under incremental heating at nanoscopic (top row) and mesoscopic (bottom row) length scales.
Thin colloidal crystals : a series of structural transitions
Journal de Physique, 1983
2014 Nous étudions des couches minces de cristaux colloïdaux formés de billes de polystyrène de diamètre 1,1 03BCm en suspension aqueuse. Ces couches minces sont produites par le confinement des cristaux colloidaux entre deux plaques de verre rapprochées, lesquelles, aux échelles colloïdales, se comportent comme des parois répulsives et parfaitement lisses. Dans le cas où les deux plaques de verre forment un dièdre, nous réalisons le passage continu entre deux et trois dimensions. L'observation directe au microscope optique révèle que ce passage est caractérisé par une série de transitions structurelles consistant en un changement du nombre de couches cristallines mais aussi en un changement de structures dans les couches. Abstract. 2014 We study thin layers of colloidal crystals made of polystyrene balls (1.1 03BCm diameter) in aqueous suspension. These thin layers are produced by confining colloidal crystals between two glass planes, which act as repulsive and perfectly smooth boundaries at colloidal scales. When the two planes form a wedge, a continuous passage from 2 to 3 dimensions is realized. Direct observation with an optical microscope reveals that this passage is characterized by a series of structural transitions consisting of changes in the number of layers and also in the structure of each layer.
Melting of Colloidal Crystal Films
Physical Review Letters, 2010
We study melting mechanisms in single and polycrystalline colloidal films composed of diametertunable microgel spheres with short-ranged repulsive interactions and confined between two glass walls. Thick films (>4 layers), thin-films ( 4 layers), and monolayers exhibit different melting behaviors. Thick films melt from grain boundaries in polycrystalline solid films and from film-wall interfaces in singlecrystal films; a liquid-solid coexistence regime is observed in thick films but vanishes at a critical thickness of 4 layers. Thin solid films (2 to 4 layers) melt into the liquid phase in one step from both grain boundaries and from within crystalline domains. Monolayers melt in two steps with a middle hexatic phase.
Imaging the Sublimation Dynamics of Colloidal Crystallites
Science, 2006
We studied the kinetics of sublimating crystals with single-particle resolution by experiments with colloidal spheres and by computer simulations. A short-range attraction between spheres led to crystallites one to three layers thick. The spheres were tracked with optical microscopy while the attraction was reduced and the crystals sublimated. Large crystallites sublimated by escape of particles from the perimeter. The rate of shrinkage was greatly enhanced, however, when the size decreased to less than 20 to 50 particles, depending on the location in the phase diagram. At this size, the crystallites transformed into a dense amorphous structure, which rapidly vaporized. The enhancement of kinetics by metastable or unstable phases may play a major role in the melting, freezing, and annealing of crystals.
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.