Dolomite stabilized zirconia for refractory application : Part-I phase analysis, densification behavior and microstructure of partial stabilized zirconia
In the continuous casting of steel, Zircon and Zirconia based products are used due to its high thermal stability, excellent erosion resistance, self-opening, consistent casting speed and resistance to oxygen lancing during casting for removal of inclusion clogging and to streamline the flow. Higher casting sequences of molten steel CaO or MgO stabilized zirconia nozzles were being used and for industrial application point of view, dolomite stabilized zirconia (DSZ) could be a better substitute for the stabilization of zirconia. DSZ samples were prepared having 3,4,5,6 and 7 mole % of dolomite by solid state route using high purity monoclinic zirconia and dolomite. The decomposition behaviour, phase stability and densification behavior of co-grounded zirconia-dolomite mixer were studied. It was observed that finer dolomite particle size (-63?m) resulted in higher amount of t/c ZrO2 phase stabilization as a function of temperature. The effect of pre-calcination temperature on phase formation and densification was optimized. Higher t-phases were achieved with 3, 4 and 5 mol% dolomite whereas 6 and 7 mol% dolomite had more of cubic phases. The non-isothermal densification of the pre calcination compact showed two stage sintering behavior. Effect of sintering schedule on densification and phase formation of DSZ was co-related. Substructure grain was observed in cubic grain for 5mole% dolomite addition in SEM micrograph. Tetragonal zirconia precipitates in cubic zirconia with increasing dolomite content in the partial stabilized zirconia.
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