High‐Strength Sub‐Micrometer Spherical Particles Fabricated by Pulsed Laser Melting in Liquid

Sub‐micrometer spherical particles that are obtained by pulsed laser melting in liquid (PLML) are usually observed to be single crystalline, and it is suggested that they are mechanically very strong. In this study, fracture tests of various sub‐micrometer spherical particles are performed by compressive force application. The results indicate that B₄C and TiO₂ sub‐micrometer spherical particles exhibit brittle fracture behavior under tensile fracture mode at the center of the particles. The fracture strength of the sub‐micrometer spherical particles is larger than that of the bulk material reported in the literature by about one order of magnitude. TiO₂ sub‐micrometer spherical particles obtained by PLML are stronger than the commercially available TiO_x sub‐micrometer spherical particles with a porous structure. In addition, due to the single crystallinity of particles, smaller particles have larger fracture strength, becoming up to 10–40% of ideal tensile fracture strength calculated based on density functional theory. Thus, these results demonstrate that sub‐micrometer spherical particles obtained using PLML exhibit fairly strong and unique mechanical properties, and therefore they are very promising for various mechanical applications at the sub‐micrometer size scale.