Deformation-induced polymorphic transformation of β-SiС

DOI: 10.62564/M4-OR1602

Oleksandr Radchenko, Kazbek Gogaev, Oleg Grigoriev, Mykola Bega, Artur Stepanenko, Anatoliy Itsenko

Frantsevich Institute for Problems of Materials Science National Academy of Science of Ukraine


At different temperatures and pressures, some chemical compounds have different types of crystal structures or modifications, the stability of which is determined by the minimum thermodynamic potential [1]. Deformation of the material puts it in a less stable state and can cause polymorphic transformation [2,3]. Silicon carbide has two main modifications - β-SiC (low-temperature - cubic) and α-SiC (high-temperature - hexagonal) [4]. The transition temperature is 2100°C. Transformation under pressure was not investigated. Tapes were rolled from β-SiC powder to the maximum density (rolls with a diameter of 40 mm from the rolling mill had zero exit gap). The maximum normal contact stress did not exceed 0,7 GPa, the temperature did not exceed 40°С. Presses with a diameter of 15 mm were obtained from the original powder and crushed rolling stock. The density of the pressings was 1.05 and 1.23 g/mm3, respectively. The diffraction curves of the samples were taken in discrete scanning mode on a DRON-ZM diffractometer in monochromatized Cu-Kα radiation. The ratio of the atomic radii of carbon and silicon does not allow obtaining simple dense spatial structures [5]. Quantitative analysis of the phase composition of the powders performed using the software package Powdercell 2.4 showed that the phase composition before rolling was ~ 95% β-SiС and ~ 5% α-SiС, while after rolling - ~ 95% α-SiС and ~ 5% β -SiС. The integral width of the α-SiС lines obtained after rolling is significantly greater than the similar characteristic (26 - 46%) in the α-SiС powder supplied by the same company (Qinhuangdao Eno High-Tech Material Development Co. LTD, Китай). Results of X-ray phase analysis of granules from powders | β-SiС and strips rolled at the maximum load showed that polymorphic transformation of β-SiС into α-SiС took place during rolling.

Keywords
Powder, polymorphic transformation, β-SiC (low-temperature - cubic)

Acknowledgments
Not provided

References
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