Synthesis of aluminum-magnesian ceramics MgAl₂O₃ in thermal plasma environment

Abstract

A search for new methods for the synthesis of magnesium-aluminum ceramics is currently an urgent task for the refractory, metallurgical, and optical industries. The paper presents the experimental results of the magnesium-aluminum spinel MgAl2O3  synthesis in the thermal plasma. The samples are synthesized from natural materials such as magnesite MgCO3 and boehmite γ-AlO(OH) in the stoichiometric ratio Al2O3/MgO = 2.53. It is shown that the optimum conditions for the ceramic sample synthesis include 100 A current strength, 90 V voltage, 1 g/s gas rate, 30 s melting time. In these conditions, the formation of a hemispherical melt drop is observed, which confirms a complete melting of the initial components. The density of the crystallized sample is 3.5 g/cm3. The synthesized ceramic matrix is characterized by a high concentration of the stoichiometric phase MgAl2O4. At the same time, for 2θ = 29.4° and 30.8°, the reflection splits, thereby indicating to the nonstoichiometric spinel (Mg, Al)Al2O4  of variable composition. The ceramic matrix morphology represents prismatic grains 30–60 µm in size connected by fibers with a diameter of 1–3 µm.