Mechanical Properties and Microstructure of Si₃N₄ Matrix Composite with Nano-Meter Scale SiC Particles

Microstructure and Mechanical Properties of Sinter–Post‐HIPed Si3N4–SiC Composites

“…Unlike strength, fracture toughness was higher for the specimens processed with longer presintering times. However, the toughness enhancement found with SiC addition in previous studies 4,7 was not observed, although toughness did increase slightly at higher SiC contents. The absence of SiC particle toughening also was reported, 19 a phenomenon ascribed to the fact that no microstructural change was generated by SiC dispersion.…”

Carbothermal Reaction of Silica–Phenol Resin Hybrid Gels to Produce Silicon Nitride/Silicon Carbide Nanocomposite Powders

“…38 Si 3 N 4 may nucleate through reaction (7), but grows mainly via reaction (8) because the solid carbon is not available everywhere. Therefore, above the boundary temperatures, e.g., at 15251C, where SiC was the equilibrium product and reaction (7) was thus thermodynamically unfavorable compared with reaction (5), Si 3 N 4 was also produced via reaction (8) because of the deficiency of carbon for reaction (5) and the sufficiency of CO for reaction (8). This was also evidenced by our observation that, even at 15501C, Si 3 N 4 whiskers were produced above the sample surface and on the upper part of the wall of the sample boat.…”

“…To obtain high‐quality final products, the SiC nanoparticles must be uniformly dispersed in the composite powder. The methods reported for the fabrication of the nanocomposite powders have included chemical vapor deposition 6 from or pyrolysis 4,7 of organic precursors (to make amorphous Si–N–C powders, which crystallize into Si 3 N 4 /SiC nanocomposites during sintering), mechanical mixing of a Si 3 N 4 micro/nanopowder with a SiC nanopowder 8 or an Si–N–C amorphous powder, 9 adding carbon to a Si 3 N 4 powder (SiC nanoparticles are produced in situ during sintering through the reaction between the carbon and the silica located on the surface of the Si 3 N 4 particles), 10,11 partial reaction of a Si 3 N 4 powder with pyrolyzed carbon, 12–14 nitridation of SiC, 15 and carbothermal reaction of a mixture of silica and carbon powders in a nitrogen atmosphere 16,17 . Among these approaches, the use of amorphous Si–N–C powders has achieved the most uniform distribution of SiC, and consequently excellent mechanical properties.…”

Structural development and properties of SiC-Si3N4 nano/microcomposites

“…One of the ways suggested some years ago is by preparation of Si3N4-based composites with SiC as a reinforcing phase. The other possible preparation method reported [7,8] is mechanical mixture of submicron Si3N4 and SiC crystalline starting powders. More recently, SiC-Si3N4 nanocomp0sites have been developed [5][6][7][8].…”