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.

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Ceramic solid solutions of the (1-x)SrTiO3–xBiScO3 system with xј0, 0.05, 0.1, 0.2, 0.3, 0.4, and 0.5 were synthesized for the first time via solid-state processing techniques. Both of the end members in this system are not ferroelectric materials. X-ray diffraction analysis revealed that at room temperature the samples with xј0.2, 0.3, and 0.4 consist of mixtures of cubic center-symmetric Pm3m phase and tetragonal polar P4mm phaseyesBelgorod State Universit

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In this article, the coatings of ZrB2-xMoSi2-Y2O3-yAl (x = 24, 35, 45 wt %; y = 10, 15, 20 wt %) were applied to the surface of a carbon/carbon composite to protect against high-temperature oxidation using a multi-chamber detonation accelerator. The kinetic analysis of the formation processes of a glass-forming layer during the oxidation of the initial components of the system ZrB2-MoSi2-Y2O3-Al in an air atmosphere at a temperature of 1400 °C was carried out and the kinetically significant stages of the heterogeneous reaction were determined. It is shown that the speed and density of the formation of a glassy matrix can be adjusted by fine-tuning the ratio of components in the initial powder.

Abstract:In this work, dense zircon-based ceramic coatings were obtained from inexpensive zircon powder on a steel substrate by using a new multi-chamber gas-dynamic accelerator. The microstructure and phase composition of the coating were characterized by scanning electron microscopy, optical microscopy, and X-ray diffraction. The mechanical properties of the coatings were evaluated using microindentation, wear tests and bonding strength tests. The results showed that the obtained zircon-based ceramic coatings were continuous without cracks and bonded well with substrate without a sublayer. The zircon-based ceramic coatings consisted of c-ZrO 2 (major phase), m-ZrO 2 and SiO 2 . The zircon-based ceramic coatings had a porosity of 0.1%, hardness of 526 ± 65 HV 0.2 , and a fracture toughness of 2.5 ± 0.6 (MPa·m 1/2 ). The coatings showed the low specific wear rate and average erosion rate. The failure mode occurring in the tested coatings was cohesive.

The microstructure and physical properties of new Y2O3 and Al2O3 oxide-doped silicon nitride ceramics fabricated by cold isostatic pressing and free sintering were investigated. The phase composition of produced material was also studied by X-ray diffraction at room and elevated temperature. The fabricated ceramics featured a microstructure of Si5AlON7 grains with a fine-grained α-Si3N4 with a small amount of Y2SiAlON5. Described ceramics is attractive for many high-temperature structural applications due to beneficial combination of fine-grained structure with improved mechanical properties and small weight loss.