Solid Freeform Fabrication of Silicon Nitride Shapes by Selective Laser Reaction Sintering (SLRS)

SelectiveLaser ReactionSinteringis a variation ofselective laser sintering (SLS) that incorporates anjn~situreaction underthe·scannedbeamtofabricate shapes from materials not directly accessible by traditional SLS. Thispaperclescribesaninvestigation into the production of silicon nitride (Si3N4) shapes by lasersinteringsiliconpowderinanammonia (NH3) atmosphere. The effect of gas pressure and the importance of gas/laserinteractionsarediscussed. Single and multiple layer shapes are fabricated. The material is analyzed by x~ray diffraction spectroscopy (XRDS) for phase content and scanning electron microscopy (SEM) for macrostructure. Data is presented that demonstrates conversion rates from silicon to silicon nitride on the order of 85%.