Growth fusion of submicron spherical boron carbide particles by repetitive pulsed laser irradiation in liquid media

We studied the fabrication of B4C submicron particles by laser irradiation of boron nanoparticles dispersed in an organic solvent. The spherical shape of the formed particles suggests that instantaneous melt formation and solidification by quenching are involved in the particle-forming process. B4C particles gradually became larger with irradiation time at relatively low laser fluence (1.5 J cm-2 pulse-1) by repetitive melting and fusion of the particles, and the B4C yield increased with irradiation time to 90% for 600 min of irradiation. At higher laser fluences, the B4C yield decreased due to the explosive ablation of boron or B4C to form H3BO3, and thus only the larger B4C particles were observed. The dielectric constant of the organic solvent also affected the generated B4C particle size, probably due to the degree of particle aggregation. Thus, this technique can provide a new approach for fabricating spherical submicron particles of ceramic materials, such as carbides, with simple and safe processes. (orig.)