engleski

In situ high temperature study of ZrO2 ball-milled to nanometre sizes

Nanostructured ZrO2 was prepared by high-energy ball-milling at different conditions and sintered at high temperatures. Structural and microstructural changes during the ball-milling were monitored using Raman spectroscopy (RS), X-ray powder diffraction (XRD), transmission electron microscopy (TEM) and selected area electron diffraction (SAED). The sintering process was monitored in situ at high temperature (300 to 1400  C) by RS and XRD. The results of RS showed that the ball-milling had very small or no influence on the transition from starting monoclinic ZrO2 to high-temperature tetragonal ZrO2. It was concluded that partial transition from monoclinic to tetragonal polymorph, observed in some previous ball-milling experiments, can be attributed to the stabilizing influence of impurities introduced due to the wearing of the milling media. In the present experiment ZrO2 ball-milling assembly was used, which reduced the influence of an additional material. The results of line broadening analysis, performed using Rietveld refinements of the ball-milling products with powder-to-ball weight ratio (R) 1:10, indicated a decrease of the crystallite size and increase of the microstrains with an increase of the ball-milling time up to 3 h. Further increase of the ball-milling time up to 10 h had very small influence on the size and strain of the obtained m- ZrO2 products. A difference between the results of in situ RS and XRD analysis of the samples subjected to prolonged ball- milling was attributed to the chemical and microstractural differences between the surface and bulk of the ZrO2 particles during the sintering at high temperatures.

ZrO2 ; high-energy ball-milling ; nanostructured ; high temperature sintering

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