Porous á-Si3N4 ceramics prepared with fugitive graphite filler

CHANDA , P; K P. PLUCKNETT; GARRIDO, L. B.; GENOVA,L

Daytona beach

Congreso; 34 International Conference and Exposition on Advanced Ceramics and Composites (ICACC2010),; 2010

Porous silicon nitride (Si3N4) ceramics have been prepared by pressureless-sintering of a-Si3N4 pellets with single Y2O3 additions (5 wt. %). In order to vary the porosity, fugitive graphite particle filler has been used, with the nominal graphite content varied up to 10 weight percent (on top of the baseline composition). After the preparation of isostatically pressed pellets, removal of the graphite filler is achieved using a low temperature oxidation treatment. Optimization of the oxidation treatment was performed using thermogravimetric analysis. After oxidation, samples were pressureless-sintered in a nitrogen atmosphere at temperatures between 1500 and 1750°C, for two hours. Post sinter evaluation of the materials was then conducted using scanning electron microscopy and x-ray diffraction, while pore size was determined for selected samples using mercury intrusion porosimetry. Strengths of up to 178 MPa were determined using ball-on-ring biaxial testing, which were subsequently related to the maximum estimated flaw size in the sintered material