Phase development and properties of high-temperature ceramic in the system mullite-ZrO2

Gaida Sedmale ,  Ingunda Sperberga ,  Janis Grabis ,  Alexey Hmelov 

Riga Technical University, Miera 34, Riga, Latvia

Abstract

Mullite-zirconia ceramics were explored by different prepared powders. Conventional and hydrothemal treatment methods of starting components, characteristics of synthesised powders and their influence on sintering rates, phase composition and properties of mullite-zirconia ceramics were studied and compared. Compositions of Al2O3 (gamma),SiO2.nH2O, ZrO2 mon. and Y2O3 for conventional and of Al(NO3).9H2O, SiO2-aeroc, ZrOO(NO3).2H2O and Y(NO3).6H2O for hydrothermal preparing of starting powders were used to fulfil the mullite stoichiometric composition. The pressed samples were sintered at temperatures from 1000 to 15000C. The effect of hydrothermal preparing process on grain size (average 50-150nm) of sintered samples is emphasized.

It is shown that densification is largely affected by milling time by conventional, as well hydrothermal preparing. XRD and SEM examinations showed the differences in mullite and ZrO2 (tetr.) crystalline phases formed starting from 13000C from conventional powders. In comparision with previously mentioned samples from hydrothermally prepared powders had a higher tendency to form a mullite phase, starting already from 10000C.

Bending strenght and pressure resistance measurements for samples from conventionally prepared powders showed that these values are remarkably influenced by milling time - for the maximum time (24h) the pressure resistance for at 14000C sintered samples reached 280-300 MPa, bending strenght - 70-75 MPa.

 

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Presentation: Poster at E-MRS Fall Meeting 2008, Symposium I, by Gaida Sedmale
See On-line Journal of E-MRS Fall Meeting 2008

Submitted: 2008-05-08 12:27
Revised:   2009-06-07 00:48