Fabrication of Low‐Shrinkage, Porous Silicon Nitride Ceramics by Addition of a Small Amount of Carbon

Abstract

Successful net‐shape sintering offers a significant advantage for producing large or complicated products. Porous Si3N4 ceramics with very low shrinkage were developed, in the present investigation, by the addition of a small amount of carbon. Carbon powders (1–5 vol%) of two types, with different mean particle sizes (13 nm and 5 μm), were added to α‐Si3N4−5 wt% Y2O3 powders. SiC nanoparticles formed through reaction of the added carbon with SiO2 on the Si3N4 surface or with the Si3N4 particles themselves. Such reaction‐formed SiC nanoparticles apparently had an effective reinforcing effect, as in nanocomposites. Sintered Si3N4 porous ceramics with a high porosity of 50%–60%, a very small linear shrinkage of ∼2%–3%, and a strength of ∼100 MPa were obtained.