In the present work, the influence of polymorphic transformations on the porosity of plasma sprayed products produced from pure aluminum oxide was investigated. Scanning electron microscopy, quantitative X-ray diffraction analysis, and X-ray computer tomography are used to quantify the porosity. It was established that the plasma sprayed products is a mixture of α, γ and δ aluminum oxides with different densities. When heating, these phase modifications undergo the polymorphic transformations which are accompanied by change in the volume. Opposite variations in the volume of the modifications can lead to both decrease and increase in porosity of material as the temperature of heat treatment increases. It was shown that the non-monotonic behavior of temperature dependence of the porosity is shown to be steadily repeated; this is related to the occurrence of polymorphic transformations. This allows us to change purposefully the porosity of plasma sprayed pure aluminum-oxide products by heat treatments.Keywords: Plasma sprayed products, aluminum oxide, heat treatment, polymorphic transformations, porosity
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