ISSN:
1573-9139
Source:
Springer Online Journal Archives 1860-2000
Topics:
Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
Notes:
Conclusions The reported results form a part of the complex investigations carried out at the Ukrainian Scientific-Research Institute of Refractories on the structure evolution processes in the polycrystalline fibers based on zirconium dioxide. Using the methods of x-ray phase analysis, petrographic analysis, and electron microscopy, we studied the phase formation in the polycrystalline ZrO2 fibers of three systems (additiveless ZrO2, CaO-containing ZrO2, and Y2O3-containg ZrO2) in the 1000–1500°C range. It was established that the additiveless zirconium dioxide fibers are represented by the monoclinic ZrO2 and that at 1400°C, their strength decreases due to a significant change in the volume of the unit cells (as a result of the tetragonal-monoclinic transformation). A study of the phase composition of the ZrO2-Y2O3 and the ZrO2-CaO fibers established that the structure of the fibers of the former system contains a large quantity of the tetragonal phase and finer crystals. After the second firing at 1500°C, the monoclinic phase of ZrO2 appears during the cooling process; its quantity depends on the resistance offered by the solid solutions to the eutectoid decomposition and increases with increasing temperature of the initial technological firing. The presence of significant quantities of the monoclinic phase of ZrO2 leads to destructive changes in the fibers and to an increased additional shrinkage of the material at 1500°C. The minimum content of the monoclinic ZrO2 and the finer structure (smaller grain size) are observed in the Y2O3-stabilized zirconium dioxide fibers that were fired in advance at 1200°C.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF01280847
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