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Optimization of Phase Purity of β′‐Sialon Ceramics Produced from Silazanes and Nano‐Sized Alumina
Author(s) -
Parcianello Giulio,
Bernardo Enrico,
Colombo Paolo
Publication year - 2012
Publication title -
journal of the american ceramic society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.9
H-Index - 196
eISSN - 1551-2916
pISSN - 0002-7820
DOI - 10.1111/j.1551-2916.2012.05179.x
Subject(s) - sialon , ceramic , materials science , polymer , pyrolysis , amorphous solid , nanocrystalline material , chemical engineering , phase (matter) , composite material , nanotechnology , organic chemistry , chemistry , engineering
The use of preceramic polymers in the synthesis of Sialon ceramics has been scarcely discussed in the literature. In this article we report the production of virtually phase‐pure β′‐Sialon ceramics from a mixture of commercially available polysilazanes and γ ‐ Al 2 O 3 nanopowder, pyrolized in N 2 atmosphere in the 1300°C–1600°C range. This approach combines the advantage of embedding nano‐sized fillers in preceramic polymers, in terms of their reactivity towards the Si – N based ceramic pyrolysis residue, with the complex interactions with residual carbon, also present as a secondary phase in the same ceramic residue. Starting from a polymer ( PSZ 20) yielding a SiCN amorphous ceramic after pyrolysis, the Sialon phase purity is greatly affected by the residual C content: for an optimized polymer/filler ratio ( PSZ 20/ Al 2 O 3 = 2), β′‐Sialon can be produced possesing only small quantities of quasi‐amorphous SiC as a secondary phase. Additional improvements based on the partial replacement of PSZ 20 with a polymer ( PHPS ) not containing C in the backbone, lead to the production of pure nanocrystalline β′‐Sialon powders (average grain size of 100–200 nm).