Selective laser sintering of ceramic materials

Conventional manufacturing techniques require part-specific tooling to fabricate objects. A new approach called Selective Laser Sintering has been developed at the University of Texas which does not require tooling to manufacture objects. This process utilizes a computer controlled laser beam to selectively sinter a thin layer of powder. The desired part is generated by laying down a number of such layers and successively sintering them.; The aim of the research work reported in this dissertation is to apply this process to directly manufacture ceramic objects and to understand the influence of material and laser parameters on the final properties of the object.; Two approaches to produce ceramic objects are discussed in this dissertation. Most of the work was carried out using the first approach in which a blend of high temperature ceramic powder and low temperature inorganic material was processed. When irradiated with a focused laser beam, the less refractory component of the blend melts and binds the high temperature powder together. A subsequent secondary heat treatment may be necessary to develop the microstructure and strength of the part. Alumina mixed with ammonium phosphate or boron oxide were selected as model systems. It was observed that the density and strength of the part depends on material properties like composition and particle size of the initial powder blends, secondary heat treatment parameters and laser parameters such as laser wavelength, intensity and scan speed.; Preliminary studies were also carried out to demonstrate the feasibility of the second approach to powder processing by SLS in which laser irradiated powder reacts with the gas in the environment. As proof of principle, single layers of silicon powder were processed with a CO{dollar}sb2{dollar} laser at different scan speeds at various nitrogen pressures. {dollar}alpha{dollar}-silicon nitride was observed to form. Further research needs to be done to extend this technique to process multiple layers.