(2c) Ceramic Powders in the Laser Sintering Processes

In selective laser sintering (SLS) a laser beam is used to partially melt particles in a layer of powders [1]. With subsequent increments of powder layers it is possible to create three dimensional structures. This technique can be used in prototyping applications able to produce customized objects of predetermined shape. With SLS it is possible to process powders polymer, ceramics and metal, therefore it appears to be particularly suited to build three dimensional scaffolds made of biocompatible materials. In SLS techniques increasing the energy transferred by laser increases the strength of the structure obtained, but it also produces a volume contraction of the sintered material which reduces the precision of the final object [2]. Since the energy required for sintering depends on the particle size. The use of smaller particles allows the use of smaller sintering energies and therefore the production of complex and more precise structures due to reduced melting [3]

In this paper powders with different particle size distributions of ceramics were obtained by mixing a coarser grained powder, with particles in the range between 10 and 100 microns, and a finer grained powder, with particles in the submicron range. The powder composition and the powder laying procedure were studied and optimized in order to obtain specimens with of the desired mechanical properties. The equipment used is a three dimensional laser sintering equipment using a 40W CO₂ laser beam purposely built. The density and the mechanical resistance of the specimens are studied as a function of the fines content and of the amount of energy released by the laser beam on the unit surface of the lighted area. A simple model approach is used to estimate the strength of the single sintered contact.

References

[1] Tang, Y., Fuh, J.Y.H., Loh, H.T., Wong, Y.S., Lu, L. 2003 Direct laser sintering of a silica sand. Materials and Design 24, 623–629

[2] Tia, X., Günster, J, Melcher, J., Li, D., Heinrich, J.G. 2009 Process parameters analysis of direct laser sintering and post treatment of porcelain components using Taguchi’s method. J. Europ. Ceram. Soc. 29, 1903–1915.

[3] Salmoria, G.V., Klauss, P., Modolon Zepon, K., Kanis, L.A. 2013 The effects of laser energy density and particle size in the selective laser sintering of polycaprolactone/progesterone specimens: morphology and drug release. Int. J. Adv. Manuf. Technol. 66, 1113–1118.