A Universal Formation Mechanism of Hollow Multi-Shelled Structures Dominated by Concentration Waves

Hollow multi-shelled structures (HoMS), a new family of hierarchical nano/micro-structured materials, have evoked intensive studies to discover their unique temporal-spatial ordering features. The theoretical understanding of the general synthetic methods of HoMS, i.e. the sequential templating approach (STA), makes it possible to understand, predict, and control the shell formation process. Herein, a mathematical model is established based on the experiment results, which reveal the appearance of concentration waves in the STA. The numerical simulation results not only correspond well to the experimental observations but also explain the regulation methods. Whereby, the underlying physical essence of STA is elucidated, suggesting that HoMS is the concrete representation of the concentration waves. Thereafter the formation of HoMS is not limited to the solid-gas reactions through high-temperature calcination, but could be extended to solution systems under low-temperature conditions.