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Abstract

In the present paper the structure and thermal properties of europium cerium oxides were investigated. The material for the research was obtained via solid state synthesis. The initial powders: ceria CeO2 and europia Eu2O3 were mixed in 1:1 mass ratio (non-stoichiometric proportion with the excess of CeO2) and milled. The sintering process was performed using high temperature vacuum press at 1350°C. Calorimetric analysis was conducted both for initial powders and milled mixture. The structure, phase composition and thermal diffusivity of obtained material were investigated in as-sintered condition. It was revealed that the obtained material was multi-phase. Non-stoichiometric phases including Ce0.5Eu0.5O1.75 with fluorite type structure and different lattice parameters were present. Thermal diffusivity decreased in the range from 25 to 900°C from 1.49 to 0.57 mm2/s and then increased to 0.70 mm2/s at 1400°C.
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Abstract

The primary microstructure of new Co-based superalloy of Co-20Ni-7Al-7W (at.%) type was showed in this article. The alloy was manufactured by induction melting in vacuum furnaces. This alloy is a part of new group of high-temperature materials based on Co solid solution and strengthened by coherent L12 phase similar to Ni-based superalloys with γʹ phase. The final form of Coss/L12 microstructure is obtained after fully heat treatment included homogenization, solutionizing and aging processes. But first step of heat treatment thermal parameters determination is characterization of primary microstructure of alloys after casting process with special attentions on segregations of alloying elements in solid solution and presences of structural elements such as eutectic areas, and other phases precipitations. In analysed case the relatively high homogeneity of chemical composition was expected especially in the case of W distribution, what was confirmed be SEM/EDS analysis in dendritic and interdendritic areas.
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