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1. Quasi steady-state modelling and characterization of diffusion-controlled dissolution from polydisperse spheroidal particles, I: modelling

   https://doi.org/10.1098/rspa.2023.0721  

   Wang, Yanxing; Wan, Hui; Refuaiti, Rusitan; Wei, Tie; Shu, Fangjun (March 2024, Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences)

   A quasi steady-state model (QSM) for accurately predicting the detailed diffusion-dominated dissolution process of polydisperse spheroidal (prolate, oblate, and spherical) particle systems with a broad range of distributions of particle size and aspect ratio has been developed. A rigorous, mathematics-based QSM of the dissolution of single spheroidal particles has been incorporated into the well-established framework of polydisperse dissolution models based on the assumption of uniform bulk concentration. Validation against experimental results shows that this model can accurately predict the increase in bulk concentration of polydisperse systems with various particle sizes and shape parameters. A series of representative instances involving the dissolution of polydisperse felodipine particles at various concentration ratios is used to demonstrate the model’s effectiveness, rendering it a valuable tool for understanding and managing complex systems with diverse particle characteristics. 

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2. Quasi-steady-state modelling and characterization of diffusion-controlled dissolution from monodisperse prolate and oblate spheroidal particles

   https://doi.org/10.1098/rspa.2022.0283  

   Wang, Yanxing; Wan, Hui; Wei, Tie; Nevares, Dominick; Shu, Fangjun (November 2022, Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences)

   A quasi-steady-state model of the dissolution of a single prolate or oblate spheroidal particle has been developed based on the exact solution of the steady-state diffusion equation for mass transfer in an unconfined media. With appropriate treatment of bulk concentration, the model can predict the detailed dissolution process of a single particle in a container of finite size. The dimensionless governing equations suggest that the dissolution process is determined by three dimensionless control parameters, initial solid particle concentration, particle aspect ratio and the product of specific volume of solid particles and saturation concentration of the dissolved substance. Using this model, the dissolution processes of felodipine particles are analysed in a broad range of space of the three control parameters and some characteristics are identified. The effects of material properties indicated by the product of specific volume and saturation concentration are also analysed. The model and the analysis are applicable to the system of monodisperse spheroidal particles of the same shape. 

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3. Effects of polydispersity on the plastic behaviors of dense two-dimensional granular systems under shear

   https://doi.org/10.1103/PhysRevE.108.054605  

   Jiang, Yonglun; Sussman, Daniel M; Weeks, Eric R (November 2023, Physical Review E)

   We study particle-scale motion in sheared highly polydisperse amorphous materials, in which the largest particles are as much as ten times the size of the smallest. We find strikingly different behavior from the more commonly studied amorphous systems with low polydispersity. In particular, an analysis of the nonaffine motion of particles reveals qualitative differences between large and small particles: The smaller particles have dramatically more nonaffine motion, which is induced by the presence of the large particles. We characterize how the nonaffine motion changes from the low- to high-polydispersity regimes. We further demonstrate a quantitative way to distinguish between “large” and “small” particles in systems with broad distributions of particle sizes. A macroscopic consequence of the nonaffine motion is a decrease in the energy dissipation rate for highly polydisperse samples, which is due both to a geometric consequence of the changing jamming conditions for higher polydispersity and to the changing character of nonaffine motion. 

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4. Imaging Cycle-Induced Damage of MnO ₂ Microparticles

   https://doi.org/10.1149/1945-7111/abb7ed  

   Bush, Stevie N.; Experton, Juliette; de La Serve, Anais Teyssendier; Johnson, Emily P.; Martin, Charles R. (January 2020, Journal of The Electrochemical Society)

   MnO 2 has been proposed as an electrode material in electrochemical energy storage devices. However, poor cycle life, especially in aqueous electrolytes, remains a detriment to commercialization. Prior studies have suggested a number of explanations for this capacity loss; however, experiments aimed at elucidating the details of the degradation process (es) are sparse. We describe here a microtube-membrane construct that allows for electrodeposition of monodisperse MnO 2 microparticles distributed across the membrane surface, and for subsequent electrochemical cycling of these MnO 2 particles. This allowed for a detailed analysis of the effect of cycling on the MnO 2 , by simply imaging the membrane surface before and after cycling. When an aqueous electrolyte was used, gross changes in particle shape, size and morphology were observed over the course of 500 cycles. Partial dissolution occurred as well. No such changes were observed when the MnO 2 particles were cycled (up to 500 times) in a propylene carbonate electrolyte solution. 

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5. Effect of particle shape on stratification in drying films of binary colloidal mixtures

   https://doi.org/10.1063/5.0270685  

   Liu, Binghan; Grest, Gary S; Cheng, Shengfeng (July 2025, The Journal of Chemical Physics)

   The role of particle shape in evaporation-induced auto-stratification in polydisperse colloidal suspensions is explored with molecular dynamics simulations of mixtures of spheres and aspherical particles. A unified framework based on the competition between diffusion and diffusiophoresis is proposed to understand the effects of shape and size dispersity. In general, particles diffusing more slowly (e.g., larger particles) tend to accumulate more strongly at the evaporation front. However, larger particles have larger surface areas and therefore greater diffusiophoretic mobility. Hence, they are more likely to be driven away from the evaporation front via diffusiophoresis. For a rapidly dried bidisperse suspension containing small and large spheres, the competition leads to “small-on-top” stratification. Here, we employ a computational model in which the diffusion coefficient is inversely proportional to particle mass. For a mixture of spheres and aspherical particles with similar mass, the diffusion contrast is reduced, and the spheres are always enriched at the evaporation front as they have the smallest surface area for a given mass and, therefore, the lowest diffusiophoretic mobility. For a mixture of solid and hollow spheres that have the same outer radius and thus the same surface area, the diffusiophoretic contrast is suppressed, and the system is dominated by diffusion. Consequently, the solid spheres, which have a larger mass and diffuse more slowly, accumulate on top of the hollow spheres. Finally, for a mixture of thin disks and long rods that differ significantly in shape but have similar mass and surface area, both diffusion and diffusiophoresis contrasts are suppressed, and the mixture does not stratify. 

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