Fabrication of β-sialon powder from kaolin

Advanced ceramics from a preceramic polymer and nano-fillers

“…If we consider the mullite formation from the oxidation of AlN, N 2 gas should be released and this may cause the foaming, effectively observed. Mullite is reported to be actually a source for the corundum contamination, also revealed in the XRD, due to its reduction/nitridation to SiAlON, as follows 17 4 The presence of SiC, at 1450 • C, lowered both the amount of carbon for nitridation and the amount of Si in the final ceramic product, and this is consistent with the formation of Si 2 Al 4 O 4 N 4 instead of Si 3 Al 3 O 3 N 5 .…”

“…Different processes are related to the particular sources for the two oxides (including the use of metallic Al) and include sol-gel processing, 6-8 co-precipitation, 9 hydrothermal synthesis, 10 chemical vapour deposition, 11 sintering of silica-coated alumina micropowders, 3,12 and, above all, reaction sintering of natural alumino-silicates (derived from clay) and reactive alumina mixtures. 2,13,14 The usual preparation of SiAlON ceramics 15 is based on sintering mixtures of Si 3 N 4 , Al 2 O 3 , AlN and SiO 2 , but a cheaper processing may come from the usage, like in the case of mullite synthesis, of alumina/silica mixtures or natural alumino-silicates, 16,17 subjected to carbothermal reduction and nitridation.…”

Multifunctional advanced ceramics from preceramic polymers and nano-sized active fillers

“…3a (lower pattern), are not attributable to unreacted Al 2 O 3 (they are visible also for a formulation comprising only MK polymer and AlN), but are a consequence of mullite reduction and nitridation (3Al 2 O 3 2SiO 2 + 6C + 2 N 2 → Si 2 Al 4 O 4 N 4 + 6CO + Al 2 O 3 ). 63 Secondly, phase separation of the preceramic ceramic residue, upon high temperature pyrolysis in N 2 , greatly complicates the formation of the desired Sialon phase, above all because of the formation of SiC. The presence of SiC is critical, since it reduces the availability of Si (to form ␤ -phase with the expected z value) and C (for carbothermal reaction).…”

Carbon Fiber Reinforced β‐SiAlON for Ultra High Temperature Ablative Heat Shields

“…Such solid solutions have been named “SiAlON,” the acronym of these four elements. The above solid solutions are called β‐SiAlON as they are derived from the structure of β‐silicon nitride: …”