EA019657B1 - Method of making amorphous silicon dioxide nanopowder - Google Patents

Abstract

The invention relates to methods for producing metal oxide nanopowders, in particular, silicon dioxide nanopowder. The method for producing amorphous silicon dioxide nanopowder comprises evaporation, condensation of material vapor and deposition of nanopowder, characterized in that minced silicon dioxide is loaded into reaction crucible, and the silicon dioxide is reduced by blowing with water vapors, while carbonic reducing agent is passed through the water vapors, wherein the temperature of initial minced silicon dioxide and carbonaceous additives is maintained within 1150-1250°C. The reaction products are discharged via reaction crucible top section.

Description

The invention relates to methods for producing nanopowders of metal oxides, in particular nanopowders of silicon dioxide.

There are methods for producing nanopowders. A method for producing metal nanopowders by decomposing a metal carbonyl using an induction plasma torch of the Russian Federation No. 2008152775 involves providing a metal carbonyl, introducing a metal carbonyl into an induction plasma torch, decomposing a metal carbonyl inside an induction plasma torch to form nanosized metal particles, rapidly cooling nanosized metal particles and collecting nanoscale particles. The disadvantage of this method is the conversion of metals to their carbonyls, and the metal carbonyl is exposed to a temperature of about 3000-11000 K in an induction plasma torch, which requires the use of plasma equipment.

Closest to the claimed invention is a method for producing nanopowders and a device for its implementation (RF patent No. 2353573, publ. 06/27/2008), including evaporation, condensation of material vapor and precipitation of the nanopowder. The disadvantages of this method are the evaporation of the target by a pulsed electron beam with an energy of not more than 100 keV, a pulse duration of 20 to 300 μs, an energy density of at least 1 MJ / cm and a gas pressure drop system in the range of 1-20 Pa.

The objective of this method is to simplify the process of obtaining a nanopowder of amorphous silicon dioxide.

The solution of this problem is achieved by the fact that in the method for producing nanopowder of amorphous silicon dioxide, including evaporation and deposition of nanopowder, water vapor is blown through a reaction volume containing crushed silicon dioxide, previously passed through a carbon reducing agent, the process is carried out at a temperature of 1150-1250 ° C, and the reaction products are removed through the upper part of the reaction volume.

When obtaining amorphous silicon dioxide nanopowder according to the proposed method, crushed silicon dioxide is used, for example, silica sand, carbon reducing agent (coal coke) and water vapor, which, in turn, interact with carbon reducing agent to form hydrogen gas and carbon monoxide at temperatures above 740 ° C according to the reaction:

H ₂ O _(|) + C ₍₁₎ = 2H _(|) + CO _(|) . (one)

The products of reaction (1) reduce silicon dioxide at a temperature above 1150 ° C to gaseous silicon monoxide:

The presence of hydrogen in reaction (2) lowers the temperature of the onset of reaction (2) compared with the use of carbon monoxide as a reducing agent.

The resulting gaseous silicon monoxide, interacting with oxygen from water vapor, forms silicon dioxide, which precipitates when leaving the reactor:

However, increasing the temperature, almost simultaneously, of reactions 2 and 3 above 1250 ° C, the likelihood of the appearance of 8Su reactions in the products increases.

The resulting silicon dioxide is formed at the temperatures (not more than 1250 ° C) significantly lower than the melting temperature 8ίΟ ₂ which prevents coagulation of the particles to 8ίΟ ₂ and contributes to obtaining fine particles, a virtually complete absence interval transition 81O _(z) 81O ₂ (t) does it is possible to obtain amorphous particles.

To obtain amorphous silicon dioxide nanopowder according to the claimed method, an apparatus (see figure) was used, consisting of a ceramic crucible 1, tilted upside down (reaction volume), in the upper part of which crushed silicon dioxide was loaded 2, and carbonaceous reducing agent was loaded into coal coke 3. Silicon dioxide and coal coke were separated by a cardboard partition to prevent mixing during installation of the crucible in a temperature controlled furnace 4 operating in the temperature range of 20-1300 ° C. Two holes were drilled in the bottom of the crucible, in one of which an alundum tube 5 was inserted to supply water vapor, and in the second, a alundum tube of larger diameter 6 was removed to remove reaction products. The junction of the alundum tubes and the crucible is sealed with a gas-tight coating to prevent the escape of gases. Water vapor was blown through an alundum tube 5 connected to a volumetric flask 7 using a silicone line 8. The alundum tube 5 for supplying water vapor was installed so that its lower end was placed in a carbon reducing agent 3. Water vapor was formed as a result of heating the water in the flask 7 of resistance furnace 9. The temperature in the furnace was stabilized by an automatic temperature controller. Hydrogen was formed as a result of the interaction of water vapor with carbon coke by reaction 1 with 740 ° C.

- 1 019657

The starting products used were quartz sand and carbonaceous reducing agent, coal coke with a carbon content of ~ 92%.

Particle size measurements of the obtained silica powder show that they are less than 100 nm. This allows us to call the obtained powders nanopowders. X-ray phase analysis led to the conclusion about the amorphous state of the obtained powders.

The method is illustrated by the following examples.

Example 1

Silica sand was poured into an alundum crucible and carbonaceous reducing agent - coal coke in the manner described above, was installed in a silica furnace, heated to a temperature of 1100 ° C, and water vapor was passed. Analysis of the waste products showed the presence of H ₂ , H ₂ O vapor, CO and the absence of both 8ίΟ and δίθ ₂ .

Example 2

Quartz sand was poured into the alundum crucible and carbonaceous reducing agent - coal coke in the manner described above, was installed in a silica furnace, heated to a temperature of 1175 ° C, and water vapor was passed. The reaction of the formation of powder 8ίΟ ₂ was intense. In addition, H ₂ , pairs of H ₂ O, CO, CO _{2 were} detected in the reaction products. 8ίΟ in the reaction products was practically absent.

Example 3

Quartz sand and carbon reducing agent were poured into the alundum crucible - coal coke in the order described above, installed in a silica furnace, heated to a temperature of 1300 ° C, and water vapor was passed. H ₂ , pairs of H ₂ O, CO, CO ₂ , 81O ₂ , 81O were found in the reaction products. The reaction of the formation of 81O ₂ powder proceeded with a reduced yield due to the incomplete oxidation of 81O.

Thus, the possibility of obtaining silicon dioxide nanopowders without using a high-temperature plasma, an intense pulsed electron beam, and vacuum has been shown. In addition, the distillation of silicon dioxide through the gas phase 81O ₂ ( _T ) ^ 81O ( _g ) ^ 81O ₂ ( _T ) purifies the obtained silicon dioxide powder from non-combustible impurities (in the indicated temperature range) contained in the initial silicon dioxide.

Claims (1)

CLAIM The method of producing amorphous silica nanopowder, including evaporation and precipitation of nanopowder, characterized in that through the reaction volume containing crushed silicon dioxide, water vapor is blown, previously passed through a carbonaceous reducing agent, the process is carried out at a temperature of 1150-1250 ° C, and the reaction products are removed through the top of the reaction volume.