To this day, CO2 laser-based systems remain the primary choice for PBF-LB/P due to the high absorption of polymer powders in the MIR spectral range. The addition of absorption-enhancing nano-additives allows polymer powders to be processed using energy-efficient, shorter laser wavelengths. To take advantage of the opportunities and in order to overcome the process challenges presented by nano-additives, it is necessary to understand the effects of nano-additives on various material states in PBF-LB/P, especially under NIR laser radiation. To this end, polyamide powders (PA12, PA11) were additivated with CB nanoparticles in quantities of 0.005 vol% and 0.05 vol%, analyzed and processed at 808 nm. For the nano-additivation part, the focus was on surface coating, specifically mechanical and wet mixing, with a brief look at CB nanoparticles incorporated into the polymer matrix. In this way, various dispersions of CB nanoparticles were obtained and their effects formed the subject of powder rheological, thermal, optical, and mechanical analyses in this work. Quantitatively, it was shown that the CB nanoparticles acted as flow aids for polyamide powders, as heterogeneous nuclei within the polyamide melt and as enhancers for laser attenuation. Especially their quantity and dispersion had a major impact on the magnitude of these effects. All of them together changed the way the material responded to the energy input of MIR and NIR laser radiation, affecting not only the processability, but also the mechanical properties and dimensional accuracy of the printed parts. The accumulated findings show how the dispersion of minute amounts of nano-additives can have a great influence on the material behavior in PBF-LB/P and help steer the material properties in the desired direction.
Alexander Sommereyns (Thu,) studied this question.