CETMIC   05378
CENTRO DE TECNOLOGIA DE RECURSOS MINERALES Y CERAMICA
Unidad Ejecutora - UE
congresos y reuniones científicas
Título:
Compositional design of porous â-si3n4 prepared by pressureless-sintering compositions in the si-y-mg-(ca)-o-n system.
Autor/es:
M. QUINLAN; K. P. PLUCKNETT; L.B GARRIDO; L. GENOVA
Lugar:
Daytona Beach-USA
Reunión:
Congreso; Cocoa Beach ACerS composites meeting; 2007
Resumen:
Porous â-Si3N4 can be microstructurally engineered to provide similar mechanical properties to dense â-Si3N4, with the additional benefits of reduced mass. However, while flexural strengths exceeding 1 GPa can be achieved by tailoring the microstructure of the material, through alignment of anisotropic â-Si3N4 grains, the porosity levels of such materials are still relatively low (< 15 vol. %). This also requires moderately complex processing techniques to be employed, such as tape-casting and sinter-forging. In the present study, an alternate approach is taken where compositional design is advocated, with the aim of producing a more porous â-Si3N4 structure (ideally 20-40 vol. % porosity) with high grain aspect ratios (i.e. >10:1). This approach makes use of a low volume fraction of multiple sintering aids, where each additive plays one or more roles in the sintering behavior of Si3N4 (i.e. densification aid, transformation aid and/or whisker growth aid). Compositions are based on various ratios of Y2O3:MgO, both with and without CaO additions. Sintering has been conducted in a nitrogen atmosphere (0.1 MPa) between 1400 and 1700°C. The effects of processing parameters (e.g. composition, sintering temperature and time) will be discussed, paying particular attention to microstructure development, including both the densification behavior and á- to â-Si3N4 transformation kinetics.