Preparation of spherical particles by laser melting in liquid using TiN as a raw material

Submicron spherical particles comprising TiN, TiO2, and TiOxNy were prepared by nanosecond pulsed laser irradiation of TiN colloidal nanoparticles. A second harmonic generation Nd:YAG laser (wavelength: 532 nm) was used. We investigated how laser fluence, irradiation time, and raw material concentration affected spherical particle diameters and compositions. Laser irradiation of about 80 mJ/cm(2) was required to obtain spherical particles. When laser fluence was increased to more than 350 mJ/cm(2), spherical particles disappeared and nanoparticles formed. In the fluence range in which spheronization occurred, particle sizes increased with the laser fluence. XRD spectra showed that the oxidation of particles occurred during melting. From EDS mapping and XPS spectra, oxidization was clearly visible on particle surfaces, and the presence of TiOxNy and TiO2 was confirmed. Irradiation time and raw material concentration had little effect on product grain size.