Field-directed micro-casting of non-spherical nanostructures: overcoming high-temperature spheroidization for bio-inspired design

Abstract

Research on the evolution mechanisms of materials under extreme conditions holds significant scientific value. For example, the high-temperature and high-pressure environments triggered by meteorite impacts can cause materials to melt, eject, and undergo rapid cooling, leading to the formation of various micro-nano-scale tektite structures such as dumbbell and toroidal shapes. These microtektites, characterized by their high melting points and small sizes, must undergo the entire process of melting, deformation, and cooling within an extremely short time frame. This poses considerable challenges for experimental simulation and the controllable preparation of materials under extreme conditions. Simultaneously, accurately reproducing and analyzing the mechanisms behind their morphological formation is of great significance for understanding natural impact processes. This paper proposes a novel method based on the synergistic regulation of pulsed laser irradiation and an electromagnetic rotating field. This approach enables the rapid melting, rotation-driven deformation, and ultrafast cooling solidification of Fe₂O₃ nanoparticles in a liquid-phase medium. Subsequently, through the application of “field-assisted mold-free forming” technology, special structures such as dumbbell-shaped, toroidal, and ellipsoidal particles, with sizes ranging from 5 μm to 800 nm, have been successfully fabricated.