The microstructure and phase composition of the high-content Al2O3-Y2O3-doped spark plasma-sintered silicon nitride were investigated. Fully dense silicon nitride ceramics with a typical α-Si3N4 equiaxed structure with average grain size from 200 to 530 nm, high elastic modulus of 288 GPa, and high hardness of 2038 HV were spark plasma sintered (SPSed) at 1550 °C. Silicon nitride with elongated β-Si3N4 grains, higher hardness of 1800 HV, density of 3.25 g/cm3, and Young’s modulus 300 GPa SPSed at 1650 °C was also reviewed.
The review considers various manifestations of fractality The review considers various manifestations of fractality in the description of the synthesis of macromolecules and the in the description of the synthesis of macromolecules and the formation of the quasi-equilibrium state in polymers, fluctuation formation of the quasi-equilibrium state in polymers, fluctuation free volume, macromolecular frameworks, order parameters, and free volume, macromolecular frameworks, order parameters, and dissipative structures, acting as centres of shear stress in clusters. dissipative structures, acting as centres of shear stress in clusters. The possibility of numerical modelling of the properties of net-The possibility of numerical modelling of the properties of network polymers within the framework of fractal formalism is work polymers within the framework of fractal formalism is demonstrated. The methods for determination of the fractal demonstrated. The methods for determination of the fractal dimension are described. The bibliography includes 248 referen-dimension are described. The bibliography includes 248 references ces. .
The interest in nitride coatings based on high-entropy alloys (HEAs) has increased rapidly in the last decade. According to a number of papers, such high-entropy nitride (HEN) coatings have a single-phase structure and properties that significantly exceed those of simpler nitride systems. These properties include high hardness, wear resistance, oxidation resistance and thermal stability. It is believed that these distinctive properties are due to the high entropy of mixing, which increases with an increase in the number of elements in the composition. However, comparison with various binary and ternary systems shows that better properties are not typical of each HEA-based coating, and the effect of the number of elements competes with other factors that can make even more pronounced contributions to the structure and properties of the coating. Because of fragmentation of data on the structure and properties of high-entropy coatings, a unified concept of alloying is needed. This review compares the methods for obtaining HEN coatings, describes their structural features and analyzes the main properties, such as hardness, wear resistance and oxidation resistance, in order to establish an understanding of the influence of the number of elements and their role in the composition of coatings.
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