Abstract

ABSTRACTsurvey is presented of developments in silicon nitride and sialon ceramic microstructures designed for application in differing temperature regimes.For low temperature (< 1000°C) application, pressureless-sinterable sialons with moderate (10-15%) intergranular glass, anisotropic β′ grains and high values of MOR and Kc (1 GPa and 6-10MPa| m respectively) are preferred.Improved hardness and high temperature capability may be achieved by tailoring intergranularp hases for crystallisation and further enhanced by the introduction of mixed α′/β′ Sialon microstructures. Examples are given of microstructural evolution in β′- Y3Al5O12(garnet), β′-Nd3Si3Al3O12N2 and α′/β′/garnet ceramics and a comparison of their mechanical behaviour.Novel Sialon ceramics containing dispersed transition metal compounds (TiN, TiB2) may be formed by in-situ redox reaction, utilising the α′ Sialon phase as an oxygen receptor. The dispersed phase may enhance hardness and toughness and confer electro-discharge machinability.Oxidation instability of Sialon compositions dictates the use of diphasic Si3N4/M2Si2O7 microstructures for application above 1300°C. The thermal cycle during pressurised sintering of these non-sialon compositions is critical in avoiding crystallisation of mixed polymorphs of the intergranular disilicate, with consequent microcracking.

Talk to us

Join us for a 30 min session where you can share your feedback and ask us any queries you have

Schedule a call

Disclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.