Microstructure and mechanical properties of three porous Si3N4 ceramics fabricated by different techniques

Three porous Si3N4 ceramics were fabricated using the same starting Si3N4 powder by techniques of (1) oxidation-bonding combined with sol-gel infiltration sintering (OB-IS), (2) cold-pressing combined with pressureless-sintering (CP-PS), and (3) 3D-printing combined with pressureless-sintering (3DP-PS). Due to the obvious difference in microstructure, phase composition, linear shrinkage, pore size distribution and porosity, the three porous Si3N4 ceramics possess characteristic in mechanical properties. Si3N4-(OB-IS) possesses lower flexural strength (23-120 MPa), fracture toughness (0.4-1.4 MPa m(1/2)) and Young's modulus (9.1-26.3 GPa) but the highest Vickers hardness (1.1-4.1 GPa). Si3N4-(CP-PS) possesses the highest flexural strength (143-207 MPa), fracture toughness (2.3-3.4 MPa m(1/2)) and Young's modulus (45.8-58.5 GPa) but lower Vickers hardness (0.8-1.1 GPa). Si3N4-(3DP-PS) possesses the lowest flexural strength (13 MPa), fracture toughness (0.3 MPa m(1/2)), Young's modulus (3.9 GPa) and Vickers hardness (0.4 GPa). (C) 2012 Elsevier B.V. All rights reserved.