MgAl2O4-based glass ceramics synthesized by thermal plasma melting

Abstract

The relevance of research and application of glass-ceramic materials based on spinel (MgAl2O4) is due to its unique properties such as strength, heat resistance, and high thermal conductivity. These properties make spinel a popular material for creating hi-tech products and coatings.The paper presents the experimental results of the production spinel-based glass ceramics with the silicon dioxide content 10 to 50 wt.%. Thermal plasma melting is used obtain glassceramic samples, at 10 kW power and 90 s melting time. The obtained samples are studied by XRF, EDX, IRFS, SEM methods.It is shown that the introduction of SiO2 in the amount of not over 20 wt.% into the mixture with stoichiometric spinel, phase transformations with the formation of binary 2MgO·SiO2, MgO·SiO2, 3Al2O3·2SiO2 compounds do not occur. With increasing SiO2 content from 30 to 50 wt.%, the effect from SiO2 is significant, a quasi-amorphous phase appears in the material matrix. At the same time, the SiO2 content of 30 wt.% provides weak intensity of the stoichiometric crystalline phase MgAl2O4 at 2θ = 36.6, 44.7, 59.3, 65.4 degrees. Samples with the SiO2 content 40 to 50 wt.% are X-ray amorphous. In this case, the diffusion halo narrows due to the dominance of Si4+ during the lattice formation. This phenomenon is also confirmed by IRFS results.Based on SEM observations, a complete dissolution of the MgAl2O4 crystalline phase occurs. When the content of SiO2 is 30 to 40 wt.%, dissolution of the spinel crystalline phase is accompanied by the formation of local regions rich in Mg and Al, i.e., differentiation proceeds in the condensed phase.The research results will be of interest for the development of heat-shielding materials, and can be used for the catalyst development, in electronics and other industries producing hi-tech ceramics.