Synthesis and characterization of semi-transparent gehlenite ceramic spheres obtained by selective laser sintering

Abstract

Selective laser sintering (SLS) is a novel additive manufacturing technique that has been recently applied to the sintering of powdered materials. In this work, radiation with laser was applied to a ceramic oxide powder blend to develop semi-transparent ceramic spheres. The powders bed consisted of different ceramics oxides which were irradiated with a continuous CO₂ laser (λ = 10.6 μm) with a power density of 155 W/cm², at both; static (punctually radiated) and non-static (dynamic) conditions. X-ray diffraction confirmed the presence of silicate phases, “gehlenite type”. Punctually radiated samples show semi-spheres with a completely sintered surface without visible cracks, however there were aggregates that did not fuse in the matrix. On the contrary, the use of dynamic radiation decreased the number of aggregates in the ceramic spheres, and a homogeneous sintered surface was obtained. Raman spectra show the introduction of the ceramic oxides into the silica matrix when the powder blend is punctually radiated with laser, while the dynamic parameters aid the crystallization of the silica matrix. Therefore, laser sintering using a continuous laser source with non-static radiation is a better alternative to produce semi-transparent ceramic spheres from a ceramic oxide powder bed with greater densification and better optical properties in transmittance–reflectance.