(581a) Titania Powders in the Selective Laser Sintering Processes

In selective laser sintering (SLS) a laser beam is used to partially melt particles in a layer of powders. 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 with different shapes and materials, e.g. polymer, ceramics and metals. In SLS technique the strength of the final structures increases with the energy transferred by laser. However, it also produces a volume contraction of the sintered material reducing the precision of the final object. Since the energy required for sintering depends on the particle size, sintering energies can be reduced using smaller particles, which also allow the production of more complex and precise structures due to reduced melting.

In this work, mixtures of titania powders with different particle size distributions were employed. They were obtained by mixing a coarser grained powder (particles in the range 10 - 100 microns) with a finer grained powder (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 theoretical modelling approach is also used to estimate the strength of the single sintered contact.