RU2737438C1 - Method of producing high-temperature resistant silica fiber - Google Patents

Abstract

FIELD: manufacturing technology.

SUBSTANCE: present invention relates to a method of producing high-temperature resistant silica fiber, which can be used for building heat insulation, high-temperature insulation of electrical equipment, for fire protection and protective clothing, firefighters and rescuers. Charge for glass melting consists of quartz sand, alumina, soda, sodium sulphate, carbon nanopowder at the following ratio of components, wt%: sand 65.9-68.6; alumina 2.5-2.8; soda 27.4-30.1; sodium sulphate 1.2-1.5; carbon nanopowder (over 100%) 1.5-2.5. Charge is treated with ultrasound for 30-40 minutes at frequency 18 kHz and melting at temperature 1440-1460°C. After glass cooking, glass beads of the following composition are produced, wt. %: SiO₂ 75.30-78.40; Al₂O₃ 2.80-3.15; Na₂O and/or K₂O 18.50-21.43; carbon nanoparticles 0.05-0.07, impurities CaO; MgO; TiO₂; Fe₂O₃ 0.10-0.26. From glass beads on multifilter feeders having 1200 or 2400 spinnerets, glass fiber is formed, which is subjected to leaching and silica fiber of following composition is obtained, wt.%: SiO₂ 95.75-96.80; Al₂O₃ 3.10-3.35; Na₂O and/or K₂O 0.05-0.75; CaO; MgO; TiO₂; Fe₂O₃ 0.05-0.15.

EFFECT: low glass melting temperature and glass fiber formation, improved chemical homogeneity of the glass, reduced drop-over drop, reduced fiber leaching time.

1 cl, 7 tbl, 3 ex

Description

Technology area

The invention relates to the glass industry, in particular to a method for the production of high-temperature-resistant silica (at least 1000 ° C) fiber, which can be used for thermal insulation of buildings, high-temperature insulation, for example, for thermal insulation of electrical equipment, and for fire protection, for example, for fire curtains, protective clothing for firefighters and rescuers, etc.

State of the art

In the modern world, there are many types of inorganic fibers that make up the segment of high temperature resistant fibers. These fibers primarily include silica fibers, ceramic fibers, quartz fibers, etc.

The production of high-temperature-resistant materials from silica fiber is based on the leaching of low-melting oxides from silicate glasses of the simplest and complex compositions under the action of solutions of acids or their salts (MS Aslanova. Glass fibers, Moscow, Chemistry, 1979, p. 203) [1] , as a result of which the fiber is enriched with silicon oxide, the content of which is determined by the composition of the original glass and can be 94-99 wt. %.

To date, all known glass compositions used for the production of high-temperature-resistant silica fiber can be divided into two groups according to the content of the main components:

1 low-component - sodium silicate and sodium aluminosilicate;

2 multicomponent - alkali-free aluminoborosilicate with a high content of oxides of iron, titanium, phosphorus, etc.

The first group of glasses has an increased content of silicon oxide, which causes high glass melting and clarification temperatures and leads, accordingly, to high energy consumption for glass making processes. In addition, high melting temperatures cause the destruction of refractories and undesirable saturation of the molten glass with transition metal oxides, which reduce the crystallization stability of the glass and increase the breakage during the production of glass fiber.

Glasses of the second group are melted at lower temperatures than glasses of the first group. However, glass fibers obtained from glasses of the second group lose more than 50% of the mass during leaching (such oxides as В ₂ О ₃ , CaO, MgO, Al ₂ O ₃ pass into solution), which leads to the development of high porosity and, as a consequence , to a significant decrease in the strength characteristics of silica fibers in comparison with the strength of the original glass fiber, as well as compared with the strength of fibers obtained from glasses of the first group (MS Aslanova. Glass fibers, Moscow, Chemistry, 1979, p. 203-204) [one]. In addition, as noted above, the presence of transition metal oxides in glass increases drop breakage during fiber production.

However, not all types of glasses can be used for fiber production. The suitability of glasses for making fibers from them is determined by their physicochemical properties, such as viscosity, surface tension, crystallization stability, gas saturation, chemical and thermal homogeneity.

The ability of the molten glass to be drawn into the fiber is determined by the ratio of its viscosity to surface tension, and the stability of the fiber formation process and its technological parameters depend on the crystallization stability, viscosity, chemical homogeneity of the molten glass and the content of gases in it.

Parameters such as viscosity, surface tension and crystallization stability are determined by the composition of the glass and the batch, respectively. The gas saturation and chemical homogeneity of the molten glass are mainly determined by technological factors and the quality of raw materials.

Good homogenization and degassing of the glass melt, which is ensured by the introduction of special clarifiers (fluorine compounds, sodium sulfate, saltpeter) into the glass, and an increase in the cooking temperature, are of great importance for a stable glass fiber forming process.

Thus, the ability of glasses for a stable fiberizing process is determined primarily by the properties of the glass, as well as the type and quality of the raw materials.

A known method of producing heat-insulating fiberglass from a charge of the following composition, wt. % (SU 1728149 A1, class C03C 13/00, publ. 04.23.1992) [2], of the following composition, wt. %:

quartz sand 32.0-38.0 nepheline 9.0-22.0 dolomite 15.8-32.0 a piece of chalk 4.1-18.0 sodium sulfate 1.5-5.2 coal 0.07-0.31

followed by melting and fiberglass production.

The disadvantage of this method is the fact that the specified composition of the charge is used only for the production of staple fiber, since the ratio of quartz sand and the sum of the components (dolomite, chalk, nepheline) determines the high surface tension of the resulting melt, which prevents the pulling of fibers and the production of continuous fiberglass. In addition, it should be noted that in the process of silicate and glass formation, carbon completely burns out, as a result of which carbon is no longer included in the final glass.

A known method of obtaining fiberglass (US 6468932 B1, class C03C 13/00, publ. 22.10.2002) [3], resistant at high temperatures, by leaching fiberglass of the following composition, wt. %:

SiO ₂ 70-75 Na ₂ O and / or K ₂ O 15-25 Al ₂ O ₃ 1-5 additional components up to 5

The disadvantage of this composition is its use for the production of only staple fiber, while the high content of silicon oxide causes a high cooking temperature.

A known method of obtaining continuous temperature-resistant silica fiber, including obtaining glass fibers from glass melt with a sufficiently low melting temperature of 1430-1440 ° C (BY 7886 C1, CL CO3C 13/02, publ. 28.02.2006) [4]. The glass is multicomponent and has the following composition, wt. %: SiO ₂ 76-80, Na ₂ O and / or K ₂ O 20-24, impurities: Al ₂ O ₃ , Fe ₂ O ₃ , TiO ₂ , CaO, MgO, CoO, As ₂ O ₃ , ZrO ₂ not more than 1.5. Glass fiber is produced from the specified glass composition, from which, after acid extraction, a silica fiber is obtained, including SiO ₂ and impurities of Na ₂ O, Al ₂ O ₃ , Fe ₂ O ₃ , TiO ₂ , CaO, MgO, CoO, As ₂ O ₃ and Zr ₂ O ₃ in an amount of 0.2-2.0 wt. %.

The disadvantage of the method according to [4] is the use of arsenic oxide As ₂ O ₃ , which is introduced into the mixture to improve the clarification process of the molten glass. However, this oxide belongs to a group of extremely toxic substances that pose a high danger to both the environment and humans. In this regard, in the production of glass and glass products, they try to exclude As ₂ O ₃ from the composition and replace it with safer components that provide the same function.

The closest in technical essence to the claimed technical solution is the production of fiberglass and high-temperature silica fiber based on it (RU 2165393 C1, class C03C 13/00, publ. 20.04.2001) [5], including the composition of the charge, glass melting at a temperature of 1470 -1490 ° C, forming continuous glass fiber at a temperature of 1210-1310 ° C from glass having the following composition, wt. %: Al ₂ O ₃ 2.5-3.5; Na ₂ O 20-25; CoO 0.01-1.0; SO ₃ 0.01-1.0; SiO ₂ - the rest, and the fiber in a small amount may also contain at least one oxide selected from the group CaO, MgO, TiO ₂ , Fe ₂ O ₃ , ZrO ₂ . Then the glass fiber is subjected to leaching to obtain a silica fiber of the following composition, wt. %: SiO ₂ 94-96; Al ₂ O ₃ - 3-4; Na ₂ O 0.01-0.1; CoO 0.01-1.0; SO ₃ 0.01-1.0 and at least one of the group of CaO oxides 0.01-0.5; MgO 0.01-0.5; TiO ₂ 0.01-0.1; Fe ₂ O ₃ 0.01-0.5; ZrO ₂ 0.01-0.5.

The presence of ZrO ₂ oxide in the glass composition reduces the crystallization stability of the glass and increases the breakage during the production of glass fiber. The increased breakage of the production process can also be associated with the existing chemical heterogeneity and insufficient degassing of the glass melt, especially in the near-wall zones of the glass furnace.

Disclosure of invention

The essence of the technical problem is as follows.

The method for the production of silica fiber is based on the method of leaching fibers from low-component glasses of the Na ₂ O-SiO ₂ , Na ₂ O-Al ₂ O ₃ -SiO ₂ systems or multicomponent alkali-free glasses of the Al ₂ O ₃ -B ₂ O ₃ -SiO system in acid solutions ₂ containing oxides Fe ₂ O ₃ , TiO ₂ , etc.

As shown by the analysis of the prior art, the use of multicomponent glasses for the production of silica fiber is irrational due to the significant loss of strength of the glass fiber during leaching.

The use of low-component glasses is associated with high energy costs to maintain a high melting and clarification temperature due to the high content of refractory silicon oxide in the glass composition. In turn, a high glass melting temperature in the range of 1450-1550 ° C initiates the dissolution of refractories in the melt, saturating it with transition metal oxides, which reduces the chemical homogeneity of the glass melt and further negatively affects the fiberization process.

In addition, the high silica content results in a high melt surface tension, which makes fiber drawing difficult.

An important role in the fiberization process is also played by the process of homogenization of the molten glass, which is accelerated by introducing such components as clarifiers into the charge. However, as experience has shown, often toxic substances are used for the clarification process, which is naturally undesirable from the point of view of ecology and danger to human health.

Thus, there is a need to create a method for producing silica fiber from low-component sodium aluminosilicate glasses, which would reduce the glass melting temperature and clarify the glass melt, minimize drip breakage during fiber production, reduce the fiber leaching time, slightly reduce the loss of fiber strength characteristics during leaching. ... In this case, it is necessary to replace toxic clarifiers with components that are safe for human health.

The claimed technical solution solves this problem.

The objective of the proposed technical solution is to create a method for producing high-temperature resistant (not less than 1000 ° C) silica fiber from low-component sodium aluminosilicate glasses.

The technical result of this invention is to lower the glass melting temperature, increase the chemical homogeneity of the glass, lower the glass fiber forming temperature and drop breakage, increase the useful time of the spinneret during fiber production, and also reduce the fiber leaching time. Reducing the glass melting temperature and the temperature of fiber production in the spinneret can significantly reduce energy consumption. An increase in the chemical homogeneity of the glass and a decrease in drop breakage make it possible to stabilize the glass fiber forming process and, accordingly, increase the productivity of the spinneret. It should also be noted that the proposed technical solution makes it possible to achieve an increase in the chemical homogeneity of the glass melt using non-toxic substances as clarifiers.

The technical result is achieved by the fact that a method for producing high-temperature-resistant silica fiber, including the following operations:

charge preparation, glass melting, glass fiber production, glass fiber leaching, and the glass melting charge is made up of quartz sand, alumina, soda, sodium sulfate, carbon nanopowder in the following ratio, wt. %:

sand 65.9-68.6 alumina 2.5-2.8 soda 27.4-30.1 sodium sulfate 1.2-1.5 carbon nanopowder (over 100%) 1.5-2.5

and treated with ultrasound for 30-40 minutes at a frequency of 18 kHz, after melting the glass, glass beads of the following composition are formed, wt. %:

SiO ₂ 75.30-78.40 Al ₂ O ₃ 2.80-3.15 Na ₂ O and / or K ₂ O 18.50-21.43 carbon nanoparticles 0.05-0.07 CaO, MgO, TiO ₂ , Fe ₂ O ₃ 0.10-0.26,

from glass balls on multi-filter feeders with 1200 or 2400 dies, continuous glass fiber of the following composition is produced, wt. %:

SiO ₂ 5.30-78.40 Al ₂ O ₃ 2.80-3.15 Na ₂ O and / or K ₂ O 18.50-21.43 CaO, MgO, TiO ₂ , Fe ₂ O ₃ 0.12-0.30,

leaching of glass fiber is carried out and silica fiber of the following composition is obtained, wt. %:

SiO ₂ 95.75-96.80 Al ₂ O ₃ 3.10-3.35 Na ₂ O and / or K ₂ O 0.05-0.75 CaO, MgO, TiO ₂ , Fe ₂ O ₃ 0.05-0.15.

Implementation of the invention

Sand, alumina and soda are the main components of the charge, since by means of these materials, silicon oxide, aluminum oxide and sodium oxide, respectively, are introduced, which are the main components of glass and determine its physicochemical properties.

Carbon nanopowder added to the charge as an additive enhances the processes of silicate and glass formation, while the specific surface area of carbon nanoparticles ranges from 400 m ² / g to 600 m ² / g.

The introduction of nanosized carbon powder into the charge activates the glass-making processes due to additional local overheating of the charge and the molten glass at the locations of carbon nanoparticles. Thus, intensification of glass melting occurs due to an increase in the amount of heat transferred to the charge and the glass melt in the melting zone. In addition, carbon nanopowder activates reactions in the charge, during which the release of gaseous substances takes place, which contributes to their faster removal and reduction in the molten glass.

Sodium sulphate is a source of sodium oxide and is also used as a clarifying additive to help free gas inclusions from the molten glass melt.

These raw materials are mixed in the following ratio, wt. %: sand 65.90-68.60; alumina 2.50-2.80; soda 27.4-30.1; sodium sulfate 1.2-1.5 and over 100%, carbon nanopowder 1.5-2.5 is introduced.

To increase the homogeneity and exclude stratification of the charge during its preparation, during stirring and before loading into the furnace, it is additionally processed with ultrasound. Ultrasonic homogenization is a purely mechanical process. Under the action of ultrasonic waves, the charge is subjected to an intense effect of alternating pressure, as a result of which the agglomerates of the charge particles formed during its storage are destroyed, and the uniform distribution of the charge particles relative to each other.

The charge is processed using an UZG-34 ultrasonic generator. The ultrasound frequency is 18 kHz, the processing time is 30-40 minutes. These parameters are optimal for obtaining a charge with increased homogeneity, increased chemical activity and cooking ability. At a frequency of less than 18 kHz and a processing time of less than 30 minutes, the charge does not achieve homogeneity, as a result of which defects (filaments, charge stones, etc.) appear in the melt during the melting process, which impede the homogenization of the molten glass, which can lead to fiber breakage in the process pulling it out.

The obtained homogeneous charge is loaded into a glass-melting furnace and melted at a temperature of 1440-1460 ° C, the resulting glass melt is clarified, which is then fed from the feeder of the melting furnace to the machine for the production of glass beads. The machine for the production of glass beads divides the stream of molten glass from the hole in the bottom of the feeder into blanks, rolls the blanks to a spherical shape, and calibrates the glass balls in shape and size.

As a result, the obtained glass beads have the following chemical composition, wt. %:

SiO ₂ 75.30-78.40 Al ₂ O ₃ 2.80-3.15 Na ₂ O and / or K ₂ O 18.50-21.43 carbon nanoparticles 0.05-0.07 CaO, MgO, TiO ₂ , Fe ₂ O ₃ 0.10-0.26.

It should be noted that the mass fraction of carbon nanoparticles in the charge is selected in such a way that part of them remains in the glass after melting and production of glass beads.

Glass beads with a diameter of 6 µm to 9 µm are produced from glass beads on multi-filter feeders with 800, 1200 or 2400 nozzles at a temperature of 1190-1290 ° C.

Thermal inhomogeneity of the molten glass in the spinneret has a negative effect on glass fiber production, especially along the length of the spinneret field, which, like chemical heterogeneity, can lead to a violation of the stable fiberization process. However, carbon nanoparticles remaining in the glass, during re-melting in the feeder, continue to locally heat the molten glass, providing the latter to all dies with the same viscosity, which reduces fiber breakage and thereby increases productivity during its production.

The resulting glass fiber has the following composition, wt. %:

SiO ₂ 75.30-78.40 Al ₂ O ₃ 2.80-3.15 Na ₂ O and / or K ₂ O 18.50-21.43 CaO, MgO, TiO ₂ , Fe ₂ O ₃ 0.12-0.30.

Silicon oxide SiO ₂ is the main component, as it forms a silicon-oxygen glass frame. In the composition of glass and glass fiber, according to the present invention, the amount of SiO _{2 is} limited to the range from 75.30 wt. % up to 78.40 wt. %. The SiO ₂ content is less than 75.30 wt. % negatively affects the mechanical properties of the fiberglass. The SiO ₂ content is more than 78.40 wt. % increases the viscosity of the glass, which complicates the process of clarifying the molten glass, leads to an increase in the content of gas bubbles in the glass and the development of inhomogeneities in the glass. Inhomogeneities, in turn, are an undesirable factor in the further development of fiberglass, since they can lead to drop breakage during the formation of fiberglass.

Aluminum oxide Al ₂ O _{3 is} also a structure-forming component. In the composition of glass and glass fiber according to the present invention, the amount of Al ₂ O _{3 is} limited to a range of 2.80 wt. % up to 3.15 wt. %. Alumina combined with silicon oxide provides excellent mechanical and chemical properties of glass fibers. Accordingly, when the content of Al ₂ O _{3 is} less than 2.80 wt. % the mechanical performance of the fiberglass will decrease. The Al ₂ O ₃ content is more than 3.15 wt. % increases the viscosity of the glass, which also complicates the process of clarifying the glass melt and leads to the same problems as when the SiO ₂ content is more than 78.40 wt. %.

Alkali metal oxides Na ₂ O, K ₂ O play the role of smoother, i.e. reduce the melting temperature of glass, reduce the surface tension of the molten glass. In the composition of glass and glass fiber, according to the present invention, the amount of alkali oxides is limited to the range from 18.50 wt. % up to 21.43 wt. %. The content of alkali oxides is less than 18.50 wt. % in combination with refractory oxides of aluminum and silicon does not allow to reduce the glass melting temperature. The content of alkali oxides is more than 21.43 wt. % negatively affects the mechanical properties of the fiberglass. In the range from 18.50 wt. % up to 21.43 wt. % the surface tension is reduced, which contributes to better homogenization. In addition, the introduction of alkali oxides reduces the tendency of glass to crystallize, which can also lead to droplet breakage during molding.

Additional components in small amounts, such as CaO, MgO, TiO ₂ , Fe ₂ O ₃ , do not have a significant effect on the fiberization process, at the same time, they can additionally slightly increase the fiber strength and facilitate the melting process. However, these components can increase the risk of developing unwanted glass crystallization. In this connection, it is necessary to minimize the content of these additional components CaO, MgO, TiO ₂ , Fe ₂ O ₃ . This can be achieved by introducing alumina into the charge as a source of Al ₂ O ₃ , the content of impurity components in which is much lower than in kaolin, which is usually used in glass making as a source of alumina.

After pulling the fiberglass goes to leaching - treatment in a sulfuric acid solution, followed by washing in water and drying, as a result, silica fiber of the following composition is obtained, wt. %:

SiO ₂ 95.75-96.80 Al ₂ O ₃ 3.10-3.35 Na ₂ O and / or K ₂ O 0.05-0.75 CaO, MgO, TiO ₂ , Fe ₂ O ₃ 0.05-0.15.

During acid treatment, only alkaline oxides are removed from the glass fiber, as a result of which the mass fractions of SiO ₂ and Al ₂ O ₃ in the silica fiber increase, which leads to its high temperature resistance. The leaching time depends on the fiber diameter: for a fiber with a diameter of 9 microns, the acid treatment time is 83-87 minutes, for 7.5 microns - 60-65 minutes.

This technical solution makes it possible to obtain a high-temperature-resistant silica fiber and has the following advantages:

- improving the chemical homogeneity of the glass and the quality of glass beads;

- lowering the temperature of glass melting and, accordingly, lowering the consumption of energy resources for heating the melting basin and the feeder of the glass-making furnace;

- increase in the specific removal of molten glass;

- lowering the temperature in the spinneret during the production of fiberglass;

- increase in the performance of the spinneret feeder while reducing the consumption of glass beads;

- reduction of drop breakage during fiber production;

- an increase in the coefficient of the useful time of the spinneret (coefficient showing the use of the device over time and representing the ratio of the operating time of the device to the duration of the work shift);

- reducing the time of leaching of fiberglass.

The following examples serve to further illustrate the present invention and prove the advantage of the claimed technical solution.

Example 1

Initial raw materials such as quartz sand, alumina, soda are crushed, sieved, mixed with sodium sulfate and carbon nanopowder to obtain a charge. The starting components are mixed in the following amount, wt. %: quartz sand 65.9; alumina 2.8; soda 30.1; sodium sulfate 1.2; nanoparticles (over 100%) 1.5 (table 1).

The resulting mixture is subjected to the action of the ultrasonic generator UZG-34 to exclude the stratification process. The ultrasound frequency is 18 kHz, the processing time is 30 minutes.

The resulting mixture is loaded into a glass furnace, melted at a temperature of 1460 ° C, clarified, and glass beads are produced. The chemical composition of glass beads is shown in Table 2.

Glass beads are loaded into a multifilter melting feeder and re-melted in order to produce glass fiber: for a fiber with a diameter of 9 µm, the feeder should contain 2400 dies, for a fiber with a diameter of 7.5 µm - 1200 dies. The temperature in the feeder in the case of fiber production with a diameter of 9 μm is 1200 ° C, with a diameter of 7.5 μm - 1205 ° C.

The chemical composition of fiberglass is shown in Table 3.

To obtain silica fiber, the method of leaching with hot solutions of sulfuric acid is used, followed by washing in water and drying. The chemical composition of the silica fiber is shown in Table 4.

Technical and economic indicators at all stages of the method are presented in tables 5-7.

The method of obtaining silica fiber according to the prototype [5] was also developed by the applicant and tested in JSC "Scientific and Production Association Stekloplastic", which allows comparing the technical and economic indicators of obtaining silica fiber according to the proposed method and according to the method according to the prototype.

Example 2

The sequence of operations for the implementation of the proposed method is the same as in example 1, with the exception of a different ratio of the initial components of the raw mixture, the processing time of the charge by ultrasound, which is 35 minutes at a frequency of 18 kHz and other technological parameters for the implementation of the method are given in tables 1-7.

Example 3

The sequence of operations for the implementation of the proposed method is the same as in example 1, with the exception of a different ratio of the initial components of the raw mixture, the processing time of the charge by ultrasound, which is 40 minutes at a frequency of 18 kHz, and other technological parameters for the implementation of the method are given in tables 1-7.

Thus, the proposed method allows you to obtain a silica fiber with high temperature resistance (above 1000 ° C), which is due to the increased content of refractory oxides SiO ₂ and Al ₂ O ₃ in its composition, while significantly reducing energy costs at all stages of the technological process, which as a result, it allows to reduce the cost of finished products.

The resulting silica fiber effectively works as heat and electrical insulation, heat protection, etc., at high temperatures, in conditions of high humidity, corrosive environments and increased radiation, and is also an excellent environmentally friendly replacement for asbestos.

Claims (9)

1. A method of obtaining high-temperature-resistant silica fiber, including the following stages: preparation of a charge, glass melting, production of glass fiber, leaching of glass fiber, characterized in that the charge for glass melting is composed of quartz sand, alumina, soda, sodium sulfate, carbon nanopowder in the following ratio of components, wt%: sand 65.9-68.6 alumina 2.5-2.8 soda 27.4-30.1 sodium sulfate 1.2-1.5 carbon nanopowder (over 100%) 1.5-2.5 and treated with ultrasound for 30-40 minutes at a frequency of 18 kHz, after melting the glass, glass beads are formed with the following composition, wt%: SiO ₂ 75.30-78.40 Al ₂ O ₃ 2.80-3.15 Na ₂ O and / or K ₂ O 18.50-21.43 carbon nanoparticles 0.05-0.07 CaO, MgO, TiO ₂ , Fe ₂ O ₃ 0.10-0.26, and then from glass beads on multi-spinning feeders with 1200 or 2400 spinnerets, glass fiber is produced with the following composition, wt%: SiO ₂ 75.30-78.40 Al ₂ O ₃ 2.80-3.15 Na ₂ O and / or K ₂ O 18.50-21.43 CaO, MgO, TiO ₂ , Fe ₂ O ₃ 0.12-0.30, leaching of which obtains silica fiber of the following composition, wt%: SiO ₂ 95.75-96.80 Al ₂ O ₃ 3.10-3.35 Na ₂ O and / or K ₂ O 0.05-0.75 CaO, MgO, TiO ₂ , Fe ₂ O ₃ 0.05-0.15 2. A method of producing silica fiber according to claim 1, characterized in that the specific surface area of carbon nanopowder is from 400 to 600 m ² / g.