SU712249A1 - Composition for chemical polishing of articles made of single-crystals of high-melting oxides - Google Patents

Description

The invention relates to the field of crystal processing, in particular, to substances for the chemical polishing of articles made of single crystals of refractory oxides.

A known composition for the chemical polishing of products from single crystals of refractory oxides, including vanadium pentoxide {.

The disadvantage of this composition lies in the low corrosion resistance of structural materials, by means of which polishing of single crystals is carried out.

The closest technical solution known is the composition for chemical polishing of single crystal products, including sodium 2J tetraborate.

The disadvantage of this composition is low quality and polishing performance.

The aim of the invention is to improve the quality and productivity of polishing.

This is achieved by the fact that the composition for the chemical polishing of products from single crystals of refractory oxides, including sodium tetraborate, additionally contains lithium fluoride in the following ratio of components, wt. %:

Tetraborate sodium 90-98

Lithium fluoride 2-10

Such a composition reduces the melt viscosity, lowers the polishing temperature to 850-EOO C, which allows you to improve the quality of the IBO polished surface, productivity and durability of the equipment.

The high polishing qualities of the proposed composition are due to the fact that, when melted, sodium tetraborate interacts with lithium fluoride, resulting in the formation of LiaBuO and NaF, the latter being a mineralizer that accelerates the chemical polishing reaction. The mechanism of action of F ions in the melt is that fluorine destroys the anionic framework of the salt as a result of breaking the bond between sodium and oxygen. The destruction of the anionic skeleton reduces the melt viscosity, promotes an increase in the mobility of the ions, and, consequently, accelerates the polishing process.

Fluorine ion is able to replace oxygen in the crystal lattice of the crystal. The proximity of the size of fluoride and oxygen ions

Claims (2)

allows for a lack of oxygen to take its place. The increased activity of the mixture relative to the crystal lattice is also due to the destructive action of fluoride ions on the structural lattice and the formation of intermediates within the surface layers, for example, A1Pl for. The application of the proposed composition provides a reduction in the time required for washing the polished product in a 50% solution of boiling hydrochloric acid. Example 1. Take borax powder and mix it with 2% lithium fluoride. The single crystals of alumina polished with this composition as follows. A mixture of borax with lithium fluoride is poured into a platinum crucible, placed in a furnace heated to 900-950 ° C. If it is necessary to increase the level of the melt, powder of the same concentration is filled into the crucible. After melting the borax with the addition of lithium fluoride, the samples of single crystals of alumina on the platinum holders are immersed in the crucible with the melt, held for 5-10 minutes. The polishing rate is 3-4 µm / min. Exposure time determines the thickness of the removed layer. Then the samples are removed from the rasilav and washed in boiling 50% hydrochloric acid and then in boiling Example 2. Take borax powder and mix it with 10% lithium fluoride. The single crystals of alumina are polished in this melt as follows. Borax powder with lithium fluoride is poured into a platinum crucible, placed in a furnace heated to 850 ° C. After melting the borax with 10% lithium fluoride additive, the samples of single crystals of alumina are placed on the platinum holder in the melt. The holding time in the melt is not more than 5 minutes, since the polishing rate in this case is 5-6 µm / min. Then the samples are removed from the melt and washed in a 50% solution of 45 boiling hydrochloric acid and in boiling water. 40 Example 3. Take borax powder and mix it with 7% lithium fluoride. The single crystals of the alumo-magnesium spinel AbOsMgO are polished in this melt as follows. The borax powder with lithium fluoride is poured into the crucible, the crucible is placed in a furnace heated to 850–900 ° C, and after the powder is melted, the samples on the platinum holder are placed in the melt. The holding time in the melt is 5–10 min, the polishing rate is 3–6 μm / min. Then the samples are removed from the oven and washed in a 50% solution of boiling hydrochloric acid, and then in boiling water. The use of a lithium fluoride concentration of less than 2% does not give the desired effect and is slightly different in effect from a pure borax melt. The use of a composition with a concentration of LiF more than 10% leads to a sharp increase in the rate of polishing. On the surface there are many holes. In addition, at such concentrations of lithium fluoride, separation of the melt is observed, and it is not possible to obtain a high-quality surface of the single crystal. The preferred composition containing sodium tetraborate 93%, lithium fluoride-7%. The invention Composition for the chemical polishing of products from single crystals of refractory oxides, including sodium tetraborate, excluding with the fact that, in order to improve the quality and performance of polishing, it additionally contains lithium fluoride in the following ratio of components, weight. %: Sodium tetraborate 90-98 Lithium fluoride 2-10 Sources of information taken into account during the examination 1. Ionic melts. Sat Issue 3. Kiev, “Naukova Dumka, 1975, p. 191-194. 2. USSR author's certificate number 477000, cl. In 28D 5/06, 1973.