RU2822148C1 - Method of producing strontium aluminosilicate glass - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention relates to chemical industry and can be used in medicine, particularly in dentistry. Method of producing strontium aluminosilicate glass includes preparing a mixture by averaging components, placing the mixture in corundum crucibles, melting in an electric furnace, producing glass and controlling quality, wherein the mixture includes quartz glass, alumina and strontium carbonate, the preparation of which further includes separate grinding of components to a particle size of 5–7 mcm and their mechanical activation, thereafter, the averaged composition of the charge is granulated.

EFFECT: acceleration of technological process due to reduction of melting time.

1 cl, 6 tbl

Description

The invention relates to the chemical industry and can be used in medicine, in particular in dentistry.

There is a known method for producing glass ceramics, the disadvantage of which is the duration of the technological process.

The closest in technical essence and achieved result is the method of synthesis of fluorine-containing strontium aluminosilicate glass in corundum crucibles with exposure for 1-2 hours at temperatures of 1500-1600ºC [Karimova K.Kh., Savinkov V.I., Sigaev V.N. Features of the synthesis of glasses used as fillers in glass cements for dentistry // Advances in chemistry and chemical technology. T. 33. 2019. No. 4.].

The disadvantage of this method is the duration of the technological process.

The technical result of the proposed method is to speed up the technological process.

The technical result is achieved by the fact that The method for producing strontium aluminosilicate glass includes preparing a charge by averaging the components, placing the charge in corundum crucibles, melting in an electric furnace, glass production and quality control, and that the charge includes quartz glass, alumina and strontium carbonate, the preparation of which additionally includes separate grinding of the components until particle size 5-7 microns and their mechanical activation, after which granulation of the average composition of the charge is carried out.

The proposed method differs from the prototype in that the charge includes quartz glass, alumina and strontium carbonate, the preparation of which additionally includes separate grinding of the components to a particle size of 5-7 microns and their mechanical activation, after which the average composition of the charge is granulated.

A comparative analysis of the known and proposed methods is presented in Table 1.

Table 1

Comparative analysis of the known and proposed methods

Known method
[Karimova K.Kh., Savinkov V.I., Sigaev V.N. Features of the synthesis of glasses used as fillers in glass cements for dentistry // Advances in chemistry and chemical technology. T. 33. 2019. No. 4.] Suggested method Preparing the charge by averaging oxide powders
↓
Placing the charge in powder form in a corundum crucible
↓
Melting in an electric furnace
60-120 min.
↓
Glass production at temperatures of 1500-1600ºС
↓
Quality control Preparing the charge by
separate grinding, mechanical activation and averaging of components
↓
Granulation of the charge
↓
Placing granular charge into a corundum crucible
↓
Melting in an electric furnace
30 min.
↓
Glass production at a temperature of 1450ºС
↓
Quality control

Example

Quartz glass, GK-1 alumina and strontium carbonate were used as starting materials.

The chemical composition of the starting materials is presented in Table 2.

Mechanical activation and separate grinding of quartz glass, alumina and strontium carbonate were carried out in a Sand planetary mill for 15 minutes. When the grinding time is reduced to 10 minutes, the granulometric composition lies in the range of 15-30 microns, which increases the cooking time and increases the cooking temperature by 25-30 C. When the grinding time is reduced. Mechanical activation of fine powders allows us to activate the components of the charge, reduce the activation energy, shift the limiting stage of silicate formation from the diffusion stage to the kinetic stage, accelerate the process of formation and accumulation of silicate melt and reduce the cooking temperature. Fine powders of the starting components were averaged in a laboratory mixer. The mixture was granulated in a laboratory granulator to obtain granules with a size of 2-5 mm.

table 2

Chemical composition of starting materials

Material Oxide content, mass. % _SiO2 SrO _{Al2O3 ​ Fe2O3 ​} CaO MgO _{Na2O K2O} ppp Quartz glass 99.60 - 0.35 0.02 0.10 0.60 0.01 0.01 - Alumina GK-1 0.05 - 98.29 0.04 - - 0.40 - 1.20 Strontium carbonate 0.03 68.52 - 0.01 - 0.02 0.11 - 31.20

Compositions of raw material mixtures 1, 2, 3 were prepared (Table 3).

Table 3

Compositions of raw material mixtures for melting strontium aluminosilicate glass

Composition number Quartz glass, % Alumina, % Strontium carbonate, % 1 66 17 17 2 70 15 15 3 68 15 17

A granulated mixture was placed in a corundum crucible with a volume of 100 cm2. The crucible with the charge was placed in a furnace with lanthanum chromium heaters. Glass melting was carried out at 1450ºС with exposure at a maximum temperature of 0.5 hours.

The chemical composition of the glasses is presented in Table 4.

Table 4

Chemical composition of experimental compositions and imported glass

Compound Oxide content, mass. % _SiO2 SrO _{Al2O3 ​ Fe2O3 ​} CaO MgO _{Na2O K2O} - 1 65.91 10.46 23.40 0.01 0.03 0.11 0.10 0.01 - 2 69.95 8.62 21.17 0.03 0.04 0.09 0.13 0.01 - 3 72.04 6.46 21.25 0.03 0.03 0.09 0.14 - -

The properties of the synthesized glasses are presented in Table 5.

Table 5

Characteristics of strontium aluminosilicate glasses

Composition number Density, kg/m ³ Refractive index TCLE, ·10 ^-7 °С ^-1 Modulus of normal elasticity, N/m ² Shear modulus, N/m ² The dielectric constant 1 2515 1.536 35.4 7820 3342 5.71 2 2480 1.533 35.2 7701 3283 5.42 3 2445 1.531 33.5 7656 3258 5.21

Separate grinding with subsequent averaging of the charge and its granulation makes it possible to increase the yield of the finished product in comparison with glass melting from a powder charge by more than three times, and also speed up the glass melting process by 2-3 times due to the use of mechanically activated finely dispersed mixture. The proposed method does not use aluminum fluoride or phosphorus oxides as raw materials, which significantly reduces the volatilization of the charge during the cooking process and ensures a stable chemical composition and properties of the final product. The use of a mechanically activated charge with a particle size of 5-7 microns in a crucible after separate grinding makes it possible to accelerate the processes of silicate formation and melting of strontium aluminosilicate glass. The use of quartz glass will speed up the process of formation and accumulation of silicate melt. The elimination of volatile components in the initial charge in the proposed method, in comparison with the prototype, allows us to obtain a final product with the necessary performance indicators. Thus, the refractive index of the synthesized strontium aluminosilicate glass is n=1.531-1.536. As is known, one of the main requirements for glasses used as fillers in dentistry is a refractive index of 1.53-1.54.

The quality indicators of the final product in the proposed and known methods are presented in Table 6.

Table 6

Quality indicators of the final product in the proposed and known methods

Quality indicators Known method Suggested method 1 2 3 Glass composition, % SiO ₂ – 27-29
Al ₂ O ₃ – 23-25
S ₂ O – 23-25
P ₂ O ₅ – 11-13
AlF ₃ – 12-15 Compositions 1, 2, 3 from the example Charge (aggregate state) Charge powder Granular charge Separate grinding and mechanical activation of charge components, microns – 5-7 Crucible material Corundum crucible Corundum crucible Cooking temperature, ºС 1500-1600 1450 Cooking time, h 1-2 0.5 Refractive index 1.525 1.531-1.536 Density, g/cm ³ 2.90 2.445-2.515 TCLE, 10 ^-7 deg ^-1 53 33.5-35.4 Tg, ºС 620 625 Microhardness, kg/mm ² 560-610 680

Claims (1)

A method for producing strontium aluminosilicate glass, including preparing a charge by averaging the components, placing the charge in corundum crucibles, melting in an electric furnace, glass production and quality control, characterized in that the charge includes quartz glass, alumina and strontium carbonate, the preparation of which additionally includes separate grinding of components to a particle size of 5-7 microns and their mechanical activation, after which granulation of the average composition of the charge is carried out.