Jamming of Nano-Ellipsoids in a Microsphere: A Quantitative Analysis of Packing Fraction by Small-Angle Scattering

Abstract

The packing of particles is ubiquitous, and it is of fundamental importance, particularly in materials science in the nanometric length scale. It becomes more intriguing when constituent particles deviate from spherical symmetry owing to the inherent complexity in quantifying their positional and rotational correlation. For quantitative estimation of packing fraction, it requires a thorough analysis of the positional correlation of jammed particles. This article adopts a novel approach for determination of the packing fraction of strongly correlated nano-ellipsoids in a microsphere using small-angle scattering. The method has been elucidated through a quantitative analysis of structural correlation of nano-hematite ellipsoids in 3D micrometric granules, which are realized using rapid evaporative assembly. Owing to the deviation from spherical symmetry, the conventional analysis of scattering data fails to interpret the actual packing fraction of the anisotropic particles. The structural correlation gets smeared out because of orientation distribution among the packed anisotropic particles, which leads to an anomaly in the estimation of packing fraction using the conventional analysis approach. It is illustrated that consideration of an interparticle distance distribution function of the correlated nano-ellipsoids becomes indispensable in determining their packing fraction.

Time-Resolved SAXS Investigation of Correlation-Collapse in Self-Assembled Silica Microgranules during Pozzolanic Gelling

“…At this juncture, we would like to mention that our earlier works on such self-assembled porous microgranules primarily focused on understanding the structural correlation − and the formation mechanisms ,,, of such correlated nanostructured granules synthesized using spray-drying through evaporation-induced assembly. These works elaborated the use of small-angle scattering techniques for characterization of the granules and provide an essential prerequisite for their quantitative characterization by SAXS/SANS. ,, The characteristic feature in the SAXS profile for the correlated nanostructures is the internanoparticle correlation peak at q ∼ 0.43 nm –1 and an associated power-law behavior at low q owing to larger granular structure.…”

Evidence of Size Stratification in Colloidal Glass Microgranules Realized by Rapid Evaporative Assembly

“…They have drawn special attraction in the last decade owing to their potential applications in several fields, including bioremediation, filtration, water treatment, etc. 19 Furthermore, such assembled granules play an important role as model systems to study fundamental physics aspects, e.g., the nature of packing of isotropic and/or anisotropic nano-objects, 20 anomalous freezing in nanopores, etc. 21 Over the last two decades, it has been established that such colloidal-glass microgranules can be obtained using a widely utilized and energy-efficient industrial process, popularly known as spray drying.…”

“…They have drawn special attraction in the last decade owing to their potential applications in several fields, including bioremediation, filtration, water treatment, etc . Furthermore, such assembled granules play an important role as model systems to study fundamental physics aspects, e.g., the nature of packing of isotropic and/or anisotropic nano-objects, anomalous freezing in nanopores, etc …”