Browsing by Author "Vavrukh, Valentyna"
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Item Applicability assessment of the vickers indentation for determining the fracture toughness of yttria-stabilized zirconia(Видавництво Львівської політехніки, 2023-02-28) Vavrukh, Valentyna; Klimczyk, Piotr; Priakhin, Volodymyr; Petryk, Vitalii; Momot, Kinga; Lviv Polytechnic National University; Krakow Institute of TechnologyCrack growth resistance of ZrO2-(3-8) mol% Y2O3 ceramics was investigated. Young's modulus by the ultrasonic flaw detection method were determined. Vickers hardness and parameters of cracks after Vickers indentation were obtained. Based on the Young's modulus values, Vickers hardness, and parameters of cracks, the fracture toughness of the investigated ceramics was calculated using 9 different equations of the Vickers indentation method. A comparative analysis of the calculated fracture toughness values with those obtained by the single-edge notch beam method was carried out. It was found that choosing the optimal equation for calculating fracture toughness by the Vickers indentation method is quite difficult and requires comparison with the results of standardized tests. It was shown that to determine crack resistance characteristics of the yttria-stabilized zirconia ceramics, the use of only the Vickers indentation method without comparison with other methods of fracture mechanics is incorrect.Item Effects of the yttria content and sintering temperature on the phase evolution in yttria-stabilized zirconia(Видавництво Львівської політехніки, 2022-02-22) Vavrukh, Valentyna; Lviv Polytechnic National UniversityThe microstructure of YSZ ceramics stabilized by the various amount of yttria, namely 3 mol % Y2O3 (3YSZ), 4 mol% Y2O3 (4YSZ) and 5 mol % Y2O3 (5YSZ) has been studied. Three sintering temperatures, namely 1450 °C, 1500 °C and 1550 °C were used for each series of samples (3YSZ, 4YSZ, 5YSZ). The total area of the monoclinic and cubic zirconia phases in the microstructure of ceramics and the regularities of distribution of these phases were determined by ImageJ. Peculiarities of changes in volume percentage of the monoclinic and cubic phases with an increase in sintering temperature of ceramics were found. Quantitative analysis of these phases was carried out. The total distribution of the monoclinic and cubic phases by ranges of their areas was presented. Correlations between the yttria content, the sintering temperature and changes in the microstructure and phase balance of the studied ceramics were found.