SU1723054A2 - Method of producing quartz glass - Google Patents

Abstract

Use: obtaining high-purity quartz glass for photomask blanks, substrates, optical elements and fiber optics products; in electronic and optical industry. The essence of the invention: obtaining silica glass by the sol-gel method. The hydrolysis of the alkyl silicate with an aqueous solution of hydrochloric acid with the addition of finely divided silica powder is carried out to form sol. An aqueous solution of ammonia is added and the mixture is poured into a mold to convert the sol to gel. The resulting gel is kept in deionized water for an estimated time. Move the gel in 0.01-0.2 N. a solution of hydrofluoric acid in deionized water for 1-1.5 hours. Drying is carried out in the open air. The gel is heat treated in an oven at 1200 ° C. 1 tab.

Description

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The invention relates to the glass industry, in particular to methods for producing quartz glass of high purity and defectlessness by the sol-gel process, and can be used in the production of electronic and optical industry, in particular, in the manufacture of photomask blanks, substrates, optical elements and fiber products optics.

The closest in technical essence to the present invention is a method of producing quartz glass, including the formation of sol by the hydrolysis of an alkyl silicate with an aqueous solution of hydrochloric acid with the addition of fine silica powder, the formation of a gel by adding an aqueous solution of ammonia to pH 5-6, pouring the gel with deionized water over time, it will determine

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It is derived from the expression t km, where t is the dwell time in deionized water (hours); m is the gel block mass (grams); k - coefficient varying in the range of 4.5-4.7 (h), drying and heat treatment.

The disadvantages of the known method are cracking of suitable blocks of dry gel, prepared according to a known technology, with further heat treatment and foaming of the glass, which also appears during the heat treatment process.

The aim of the invention is to increase the yield of products.

The goal is achieved by the fact that in the method of producing silica glass by the sol-gel process, including the formation of sol by the hydrolysis of an alkyl silicate with an aqueous solution of hydrochloric acid with the addition of fine silica powder, the formation of a gel

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ammonia solution to pH 5-6 - pouring the gel with deionized water, holding it for a period of time, defined by the expression t km1 3, drying and heat treatment, after keeping the billet in deionized water, hold the gel in 0.01-0.02 n. hydrofluoric acid in deionized water for 1-1.5 hours

When a wet gel block is immersed in a weak solution of hydrofluoric acid, the gel block surface is modified due to the expansion of pores in the surface layers of the gel, which favors the removal of water vapor and alcohol from the gels and reduces the likelihood of cracking, and the introduction of fluoride ions into the gel volume helps remove bound water at the stage of sintering the gel, which reduces the foaming and the formation of bubbles, and therefore increases the yield of products. 1.1-1.5 hours of exposure of the gel block in the acid solution is enough for diffusion of fluorine ions in the gl kill the wet gel and pickle the surface with the above purpose,

Acid concentration less than 0.01 n. does not lead to surface etching for a specified time, and at a concentration greater than 0.02, deep uneven etching of the samples occurs, resulting in cracking during drying and sintering.

Depending on the hermetic forms used, it is possible to obtain dry gel blanks and, therefore, quartz glass of various configurations.

Example 1. T150 ml of tetraethoxysilane was added 50 ml of 0.1 N HCl solution. The mixture was vigorously stirred. As a result of the hydrolysis reaction, the temperature of the mixture increased. Upon reaching 50 ° C, 50 ml of deionized water was added. After 15 minutes of stirring, 50 g of ultra-fine silica powder was added and stirring continued for another 15 minutes. Next, ammonia water was added to the resulting sol with stirring to pH 5-6, and the mixture was poured into ten hermetically sealed square polymer forms, where gel plates weighing 40 g were formed. After the formation of the gel, the forms were opened, poured with deionized water and kept for an estimated time of 15, 7 hours. Thus, 6 batches of gels of 10 pcs. Each were prepared. each After that, 1 batch, after soaking in deionized water, was dried in air in the open state at 20–25 ° C to a constant mass (f 5 days). The remaining 5 batches were kept in a weak solution of hydrofluoric acid in deionized water with a concentration of from 0.005 n. up to 0.025 n ..

moreover, depending on the concentration, the exposure time was also changed: for example, 2 batches - 105 minutes (0.005 n. solution); 3 batches -90 min (0.01 n. Solution); 4 batches - 75 minutes (0.015

n. solution); 5 batch - 60 min (0.02 n. Solution); 6 batch - 45 min (0.025 n. Solution). Further, these 5 batches were dried under the same conditions as batch 1. All the obtained gel preparations were monitored for defects (cracking).

The results of the control are placed in the table.

Then, all 6 batches were heat treated at 1200 ° С until the gel permeates into quartz glass. After that, each batch was checked again for defects (bubbles, cracks, deformation of the workpiece). The results of the control were placed in the table.

Example 2. To 1.5 l of tetraethoxysilane was added 1 l of 0.05 n. a solution of HCI and 500 g of ultrafine silica powder. The mixture was vigorously stirred for 1 hour. To the resulting sol, with stirring, ammonia water was poured to pH 5-6 and the mixture was poured into 10 hermetically sealed square polymer forms, where gel plates weighing 300 g were formed. Plates were poured with deionized water and kept for 31 h, after then the water was drained, and the plates were dried in air at 20–25 ° C to constant mass. Thus, we received a batch of 10 gel blocks.

Similarly, they prepared 5 more batches of 10 pcs. each After incubation in deionized water for 31 h, they were additionally kept in a weak solution of hydrofluoric acid according to the program of Example 1, i.e. 2 batches - 105 min (0.005 n. Solution); 3 batch - 90 min (0.01 n. Solution); 4 batch - 75 min (0.015 N, solution); 5 batch - 60 min (0.02 n. Solution); 6 batch 45 min (0.025 n. Solution).

These batches were then removed from the acid and dried under the same conditions as batch 1. All the resulting dry gels were monitored for defects.

(cracking). The results of the control are placed in the table. Further, all 6 batches were subjected to heat treatment at 1200 ° С before transferring the gel to quartz glass. After that, each control was again checked.

Claims (1)

batch for defects already in the glass. The results of the control are placed in the table. Invention Formula The method for producing quartz glass is a per second Ms 1549931. characterized in that, in order to increase the yield of useful products, after soaking in deionized water, the billet gel is kept in 0.01-0.02 n. a solution of hydrofluoric acid in deionized water for 1-1.5 hours