Peculiarities of the formation of the structure of CMCs based on Al2O3 micropowder and SiC nanopowder in the process of electrosintering

Abstract

The influence of silicon carbide nanoadditives on the microstructure of the composite based on aluminum oxide microparticles during hot pressing due to electrosintering is investigated. The introduction of silicon carbide nanoparticles into the material leads to the formation of a specific structure of the material. A dispersion-strengthened nanocomposite of the "micro/nano" type is formed. On the other hand, all ceramic material containing granular silicon carbide powder is composite. In the process of sintering, a liquid phase is formed at a lower temperature, compared to the sintering of "micro-micro" particles. Such a complex structure of the composite leads to a significant improvement in the physical and mechanical properties of the material. In addition to the size of the SiC particles, the defects of the crystal lattice of the starting materials have a significant impact on the sintering and properties of the studied compositions. Nanodispersed silicon carbide powder has a more defective crystal lattice compared to the lattice of silicon carbide micropowder. The silicon carbide nanopowders used are more defective and, therefore, more active for sintering, since the process takes place under maximally non-equilibrium conditions. The microstructure obtained with different compositions of nanoadditives and sintering modes is studied. The peculiarities of the effect of various nanoadditives from Al2O3 and SiC on the microstructure and properties of the obtained materials were revealed. It was established that the use of this method makes it possible to improve such mechanical properties of the material as microhardness (HV = 25.0 GPa) and crack resistance (KIC = 6.5 MPa·m1/2).