Yulia S. Kudryashova

One of the promising methods for process intensification for micromixing, co-precipitation, and crystallization in continuous reactors is the use of vigorous vortices. A combination of the high intensity of the kinetic energy input with the small volume of the micromixing volume allows to concentrate the energy dissipation rate up to 10⁴ W/kg and more. As the embodiment of such an idea, four new types of microreactors with intensively swirled flows were created and studied as a tool for continuous co-precipitation and crystallization. A correlation between residence time and segregation index was found: the smaller residence time, the higher energy dissipation rate and better quality of micromixing. A method for the synthesis of oxides of a number of transition metals in microreactors with intensively swirled flows with subsequent thermal treatment of co-precipitation products has been developed. This method was used to obtain ensembles of nanosized particles of zirconium oxides, as well as calcium and strontium fluorides. In comparison with the currently widely used hydro- and solvothermal methods, the proposed method has high productivity (around 10 m³/day for lab scale device), can significantly reduce the duration of the process, provides low energy consumption, does not require a large number of labor-intensive operations, is technologically advanced and easily scalable.

Yttrium-aluminum garnet (YAG) nanoparticles are synthesized by the coprecipitation of yttrium and aluminum hydroxides in a microreactor with freely impinging jets, followed by the thermal treatment of the coprecipitation products. According to the results of X-ray phase analysis, the coprecipitated hydroxides are X-ray amorphous. Analysis of the product of the thermal treatment of hydroxides at 1000°C for 10 min indicates the formation of Y₃Al₅O₁₂ crystals. The method developed by us makes it possible to carry out the synthesis quickly, ensures low energy consumption, does not require laborious operations, and is technologically advanced and easily scalable.

In a microreactor with colliding jets using solutions of titanium tetraisopropylate and water in isopropyl alcohol, a number of titanium dioxide powders are obtained. It is shown that an additional heat treatment of samples up to 350°C for 30 min is sufficient for the formation of the anatase phase. The developed method allows synthesis in a short time, provides low energy consumption, does not require labor-intensive operations, and is technological and easily scalable.

A new solvothermal method has been developed for preparing nanocrystalline titania powders by reacting titanium isopropoxide with acetic acid. The photocatalytic activity of a sample prepared at 250°C

The possibility of synthesizing the nanosized CoFe₂O₄ particles in organic solvents, such as glycerol and diphenyl oxide, at 250°C and atmospheric pressure under conditions of distillation of the formed water was studied. In the case of glycerol, we obtained the adduct of the latter with cobalt ferrite. The reaction in diphenyl oxide resulted in the formation of ferrite particles sized 8–10 nm.