TEM STUDY OF THE SURFACE-MORPHOLOGY OF EXTRACTED ZRO2-AL2O3 FIBERS

The surface morphology and microstructure of a series of melt extracte d ZrO2-Al2O3 based fibres (ZA, ZAT and ZAS) have been imaged at the na nometre scale by transmission electron microscopy (TEM) using an advan ced Pt/C replica technique. Growth characteristics of ZrO2, Al2O3 and other crystalline phases formed upon heating up to 1550 degrees C are illustrated and described. Several grain morphologies including spheri cal and polygonal grains, as well as grains with rounded plate-like gr owth were observed indicating different active growth mechanisms. ZrO2 particles on the surface of the fibres were almost spherical with som e facetting and rounding of corners. These grains were very fine (< 50 nm) in the ZA and ZAS fibres while they were several microns in size in the ZAT fibres. Al2O3 grains were generally much larger (up to seve ral microns) and exhibited two distinct growth morphologies of layered and rhombohedral type. Different grain morphologies of the ZA and ZAS fibres have been correlated to the phases identified by X-ray diffrac tion.