Multipurpose utilization of silicon tetrafluoride and zirconium dioxide

In Tomsk Polytechnic University there was developed and patented a technique of multipurpose utilization of zirconium dioxide and silicon tetrafluoride, which allows simultaneous obtaining of artificial zircon. At the heart of this technique lies a chemical reaction:

SiF4 + 2ZrO2 = ZrSiO4 + ZrF4

Silicon tetrafluoride SiF4 is a large-tonnage derivative in production of superphosphates, aluminium, and hydrofluoride. In normal conditions it is a highly toxic, gaseous material, which emissions in the atmosphere can do great harm to ecology and human health. Utilization of silicon tetrafluoride is a far complicated process, including stages of absorption and hydrolysis with further utilization of great amounts of fluorine containing liquids.

Zirconium dioxide is applied in ceramic industry; it is used for production of high-temperature crucibles and linings. Processing of used or subquality materials is impeded because of its chemical inertness. Silicon tetrafluoride reacts well with zirconium dioxide according to the reaction given above. Zirconium tetrafluoride obtained as a second product in the result of interaction between silicon tetrafluoride with zirconium dioxide is an expensive semiproduct of zirconium. It is used for obtaining of metallic zirconium.

Zircon is a natural mineral that is a zirconium silicate ZrSiO4. In industry zircon is used in two directions ‛ to obtain zirconium compounds and as an abrasive material. As an abrasive material zircon is valued for its high solidity and for existence of so-called gravel deposits that allow using already grinded material. There are two disadvantages of using natural zircon as an abrasive material, namely circularity of its natural elements, and the presence of radioactive thorium additives in it.

Obtaining of artificial zircon allows getting rid of the both disadvantages. Artificial zircon has a perfect crystal structure and appears as rhombohedral crystals. Artificial zircon contains no additives, and this strengthens crystal structure and makes solidity of crystal as high as possible. The size of artificial zircon crystals can be regulated within very extent limits ‛ from microns up to millimeters.

It is significant to mention about the simplicity of technological solution of interaction between silicon tetrafluoride and zirconium dioxide. The interaction is going in the device of columnar type which is loaded with grinded zirconium dioxide wastes. In the lower part of the column there is a supply of silicon tetrafluoride. The column is heated up to 900°C. Then goes an interaction between silicon tetrafluoride and zirconium dioxide, the front of zircon formation reaction is moving from the bottom to the top. Generated zirconium tetrafluoride is sublimated at such temperatures and precipitates in the upper refrigerated part of the device.

The advantage of the offered construction is its simplicity and possibility to automize technological process. The price for development of technical report for manufacturing complex design amounts 70 000