Density functional theory studies on the reaction mechanism of alumina synthesis with a new sol-gel routine

Alumina is a widely used advanced ceramic material whose properties depend on the particle size, porosity and purity of the ceramic. Powder with high quality is the key to get high performance alumina. Among those powder synthesis methods, the sol-gel method is considered to be a good route to get high quality powders. However, the existing sol-gel methods for preparing alumina still have some disadvantages, such as complicated process and high production cost of the raw material (aluminum alkoxide). With the assistance of density functional theory, we aim to explain the reaction mechanism of alumina powder synthesis by an improved sol-gel routine. This is expected to solve the above-mentioned disadvantages. In this study, the hydrolysis-polymerization mechanism of tris(dimethylamino)aluminum (Al(NMe₂)₃) monomer and dimer were investigated at the level of B3LYP-D3BJ/6-311G(d,p) using Gaussian16 software. It provides a theoretical guidance for experimental studies on the synthesis of alumina powders. The results show that the hydrolysis reaction of Al(NMe₂)₃ monomer is completed in three steps, all of which are spontaneous and can occur rapidly. The calculated polymerization reaction is also spontaneous, but the depolymerization reaction can hardly occur due to the high energy barrier. The hydrolysis of the dimer is finished in six steps, all of which are spontaneous, including the calculated polymerization reaction. Our studies show that the hydrolysis-polymerization reaction of Al(NMe₂)₃ dimer is theoretically feasible and can be used to prepare alumina. In addition, alumina powder was synthesized using above method, verified the feasibility of it.

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