Structural development and properties of SiC-Si3N4 nano/microcomposites

Dense Amorphous Zirconia–Alumina by Low‐Temperature Consolidation of Spray‐Pyrolyzed Powders

“…A bulk processing route for metastable and nanocrystalline materials emerges from the results of hot-pressing experiments on amorphous ZrO 2 -Al 2 O 3 powders described above, which establish the good sinterability of the amorphous phases at temperatures lower than 0.4T m with moderate pressures. The present results are distinct from other reports on 10 sintering with amorphous starting materials such as glass-ceramics, [33][34][35][36][37][38][39] amorphous mullite based powders, [10][11][12] amorphous Si-C-N [13][14][15]40 and Si-Zr-N-O powders. 41 The amorphous phases in the conventional glass and glass-ceramic systems are readily obtained from the molten states at ordinary cooling rates, and are sufficiently stable even above the glass transition temperatures so that sintering can take place through viscous flow of the supercooled liquid without crystallization.…”

“…Consolidation of particulate nanocrystalline and other metastable ceramics into dense forms requires activation in the form of high temperature, static or dynamic loading, or a combination of these. Such activation also triggers transformation to a more stable phase and grain growth, [7][8][9][10][11][12][13][14][15][16][17][18][19][20] leading to the loss of the initial desired structure by the time full density is attained. On the other hand, conditions that allow the desired metastable phase or nanometric grain size to be retained may not be adequate for complete densification.…”

Recent developments in ceramic nanocomposites

“…A small amount of amorphous Si-C-N powder was mixed with commercial Si 3 N 4 to enhance the densification rate, which resulted in a substantial refinement of the microstructure. Sajgalik et al 51 produced SiC/Si 3 N 4 nano-/microcomposites by hot pressing at 1,750°C for 30 minutes. The presence of SiC inclusions at the grain boundaries hindered Si 3 N 4 grain growth and also created subgrain stress boundaries.…”