Experimental and molecular dynamics multiscale study on sintering and interfacial reaction of Fe2O3/CaO particle system

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High-temperature sintering and solid-state reaction within the intricate Fe2O3/CaO system are pivotal factors influencing material characteristics. The current work focused on the sintering and reaction behavior of Fe2O3/CaO particles at high temperatures with a multiscale study of in-situ high-temperature stage microscopy (HTSM) and molecular dynamics (MD). The laws governing atomic migration and the evolution of crystal structure during the sintering process were simulated at the nanoscale. The results elucidated that a heightened heating rate fosters particle shrinkage and concomitant reduction in surface area. The sintering activation energy (Esin) exhibited an increment proportional to the linear shrinkage of the particles. Furthermore, an augmented potential barrier in advanced stages impeded subsequent sintering behavior. Augmented temperature promoted the particle shrinkage and sintering neck formation, culminating in pore closure and a diminution in the free surface. However, this promotional effect attenuated with escalating temperatures. Particle shrinkage and sintering neck formation are contingent upon atomic migration and diffusion, with the growth of sintering necks primarily reliant on atom diffusion along the surface of the sintering necks. The atomic diffusion activation energy was determined to be 49.5 kJ/mol within the temperature range of 1073–1473 K. Within the Fe2O3/CaO system, the preferential generation of Ca2Fe2O5 (C2F) over CaFe2O4 (CF) was found, leading to a decrease in the atomic diffusion barrier and an enhancement of the diffusivity, with the latter dominating in later stages. The highest mobility of O2–, Fe3+, and Ca2+ was discerned in CF, and the sintering shrinkage of the particles predominantly hinges on the generation of CF.