KR20070066732A - Method for preparing graphite coated with silica - Google Patents

Abstract

A method for preparing graphite coated with silica, which saves energy, prolongs the service life of refractories, and stabilizes ironmaking and steelmaking processes accordingly by coating the surface of graphite powder with silica, thereby reducing thermal conductivity of graphite and enhancing oxidation resistance of graphite, is provided. A method for preparing coated graphite comprises the steps of: mixing 5 to 75 weight parts of graphite powder with 100 weight parts of a solution obtained by dissolving 0.04 to 0.85 mol/L of TEOS(tetra ethoxy silane) into ethanol to prepare a slurry; filtering the slurry to coat the surface of the graphite powder with the TEOS; mixing 7 to 85 weight parts of the TEOS coated graphite powder with 100 weight parts of a solution obtained by dissolving 0.1 to 0.9 mol/L of water and 0.1 to 0.5 mol/L of ammonia into ethanol to pyrolyze the TEOS on the surface of the graphite powder; and filtering the solution, and drying the filtered solution to coat the surface of the graphite powder with silica.

Description

Manufacturing method of silica coated graphite {METHOD FOR PREPARING GRAPHITE COATED WITH SILICA}

1 is a scanning electron microscope photograph taken by enlarging the surface of a silica-coated graphite powder prepared by the silica-coated graphite production method of the present invention 200 times.

The present invention relates to a method for producing a coating of graphite, and more particularly to a method for producing a coating of graphite to improve the low thermal conductivity and oxidation resistance by coating silica on the graphite.

Recently, the development of low thermal conductivity refractory material is required to realize energy saving due to the characteristics of the steel-making industry, which is an energy-saving industry, and research on this is being conducted worldwide. In particular, in order to reduce the thermal conductivity of graphite-based refractory materials, it is necessary to lower the high thermal conductivity of graphite above all.

The chemical composition of graphite is carbon, which is composed of almost pure carbon and has high thermal conductivity, low modulus of elasticity, low coefficient of thermal expansion and relatively satisfactory strength which increases with temperature up to 2700 ° C. Also, low density and ease of processing It has many advantages as a material for high temperature structure, etc., and is excellent in corrosion resistance to molten steel and is one of the most important materials used as a fireproof material in the steel and steel industry.

However, the graphite as described above reacts with oxygen at a high temperature of about 500 ° C. or more, wears a surface and has a significant evaporation rate at a high temperature, and causes a severe wear phenomenon in the flow of high temperature gas, thereby limiting the graphite-containing refractory life. In addition, it has been pointed out that the uniform problem of plate-like graphite and oxide powder is difficult and the hydrophobic surface cannot be used, so that an aqueous system cannot be used in the manufacturing process.

The present invention has been made in view of the above problems, by coating the surface of the graphite powder with silica to reduce the thermal conductivity of the graphite to save energy, it is possible to extend the refractory life by increasing the oxidation resistance, accordingly steel and steel It is to provide a method for producing silica coated graphite capable of stabilizing the operation process.

In accordance with another aspect of the present invention, there is provided a method for preparing a coating of graphite, the method comprising the steps of preparing a slurry by mixing 5 to 75 parts by weight of graphite powder to 100 parts by weight of a solution dissolved in ethanol, and filtering the slurry. Coating the teos on the surface of the graphite powder, and mixing 7 to 85 parts by weight of the teos-coated graphite powder to 100 parts by weight of a solution in which water and ammonia are dissolved in ethanol. Hydrolysis, and filtering and drying the solution to coat silica on the surface of the graphite powder.

In the preparing of the slurry, the theos mixed in the ethanol is preferably used at a concentration of 0.04 mol / L to 0.85 mol / L.

In the hydrolysis step, the water mixed with the ethanol is preferably used at a concentration of 0.1 mol / L to 0.9 mol / L.

In the hydrolysis step, ammonia mixed in the ethanol is preferably used at a concentration of 0.1 mol / L to 0.5 mol / L.

Hereinafter, the present invention will be described in detail.

First, a slurry is prepared by mixing 5 to 75 parts by weight of graphite powder to 100 parts by weight of a solution in which theos is dissolved in ethanol.

The concentration at which theos is diluted in the ethanol solvent is preferably used at a concentration of 0.04 mol / L to 0.85 mol / L, and more preferably 0.10 mol / L to 0.7 mol / L. When the theos is less than 0.04 mol / L concentration, the amount of silica coated on the surface of the graphite powder is so small that there is almost no coating effect. When the concentration is greater than 0.85 mol / L, the silica is inhomogeneous on the surface of the graphite powder. The coating process is difficult to control the coating process, there is a problem that the economic efficiency is also bad.

On the other hand, the graphite powder mixed in the theos solution can be used as a natural natural graphite, artificial graphite, or commercially available products, of course, can be used by grinding to a suitable size, without being limited to a specific shape or size. .

And the graphite powder is contained in 5 to 75 parts by weight based on 100 parts by weight of the theos solution, if the content is less than 5 parts by weight there is a problem that the manufacturing and production efficiency is lowered, if it exceeds 75 parts by weight of the slurry mixture There is a problem that the property is lowered and the coating amount of silica on the surface of the graphite powder is reduced.

Next, the prepared slurry is filtered to remove the solution, and the theos is coated on the graphite powder surface.

The method of removing the solution contained in the slurry may include various methods such as a centrifugal separation method using a centrifugal separator in addition to the filtering method using a filter, and if the desired purpose can be achieved. There is no need to specifically limit the method.

When the slurry is filtered to remove the solution, graphite powder coated on the surface of the theos is obtained.

Next, 7 to 85 parts by weight of the above-coated graphite powder is mixed with 100 parts by weight of a solution of water and ammonia dissolved in ethanol to hydrolyze the theos on the surface of the graphite powder.

Water used to hydrolyze the theos coated on the graphite powder is diluted in ethanol solvent and used at a concentration of 0.1 mol / L to 0.9 mol / L. When the content is less than 0.1 mol / L, the hydrolysis is used. There is a problem that the reaction does not occur or the reaction rate is too slow to reduce the production and production efficiency. When it exceeds 0.9 mol / L, the hydrolysis reaction proceeds too fast, resulting in poor coating properties. A problem arises in that it cannot be uniformly coated.

The theos hydrolysis rate is too slow to use a catalyst. As a catalyst, ammonia is suitable, and dilution with ethanol solvent with water is preferably used at a concentration of 0.1 mol / L to 0.5 mol / L. If the ammonia is less than 0.1mol / L concentration, the hydrolysis of the theos is too slow, so it is not efficient. If it exceeds 0.5mol / L concentration, silica is unevenly coated on the graphite surface, so that the control of the coating process is difficult. There is a difficult problem.

On the other hand, the graphite powder coated on the surface is contained in 7 to 85 parts by weight based on 100 parts by weight of a solution diluted with water and ammonia dissolved in ethanol, when the content is less than 7 parts by weight is less efficient manufacturing and production If there is a problem, if it exceeds 85 parts by weight, there is a problem that the mixing of the slurry is lowered and the coating amount of silica is too small on the graphite surface.

Finally, the solvent mixed with water, ammonia, ethanol and graphite powder is filtered to remove the solvent and dried to coat silica on the surface of the graphite powder.

In order to remove the solvent after hydrolysis of the surface of the graphite powder, the solvent is removed by various methods such as filtering and centrifugation as described above, and then the graphite powder is dried to coat silica on the surface. will be.

Hereinafter, the present invention will be described with reference to the following examples. However, these examples are only for illustrating the present invention, the present invention is not limited thereto.

<Example>

70 g of graphite powder was added to a solution of TEOS (0.5 mol / L) dissolved in 1000 ml of ethanol and mixed for 60 minutes while stirring. The slurry was filtered to remove the solution, thereby preparing graphite powder coated with theos. The theos on the surface of the graphite was hydrolyzed by adding the above-coated graphite powder and stirring for 60 minutes while stirring 1000 ml of a solution of water (0.15 mol / L) and ammonia (0.3 mol / L) in ethanol. Thereafter, the residue was filtered to remove the remaining solution and dried for 2 hours with hot air at 80 ° C.

1 is a scanning electron microscope (SEM) photograph taken by enlarging the surface of silica coated graphite powder 200 times according to the present embodiment. As shown in Figure 1, it can be seen that the surface of the obtained graphite powder is coated with silica.

According to the carbonaceous coating method of the present invention as described above, by coating the surface of the graphite powder with silica, it is possible to improve the low thermal conductivity and oxidation resistance.

In addition, by reducing the thermal conductivity of the graphite it is possible to extend the refractory life by improving the oxidation resistance and energy saving effect, thereby stabilizing the steel and steel manufacturing process.

In addition, the surface of the graphite powder is modified to be hydrophilic to improve the refractory production process and quality, the mixing and molding process using an aqueous system can be applied to the refractory manufacturing process, it is possible to apply to the amorphous refractory.

Claims (4)

As a coating production method of graphite, Preparing a slurry by mixing 5 to 75 parts by weight of graphite powder to 100 parts by weight of a solution of theo-osolated in ethanol; Filtering the slurry to coat the theos on the graphite powder surface; Hydrolyzing the theos on the surface of the graphite powder by mixing 7 to 85 parts by weight of the teos-coated graphite powder to 100 parts by weight of a solution of water and ammonia dissolved in ethanol; Filtering the solution and drying to coat silica on the surface of the graphite powder. The method of claim 1, The step of preparing the slurry, the coating method of the graphite, characterized in that the theos mixed in the ethanol is used at a concentration of 0.04 mol / L to 0.85 mol / L. The method of claim 1, The hydrolysis step, the coating method of the graphite, characterized in that the water mixed in the ethanol is used at a concentration of 0.1 mol / L to 0.9 mol / L. The method of claim 1, The hydrolysis step, the coating method of the graphite, characterized in that the ammonia mixed in the ethanol is used at a concentration of 0.1 mol / L to 0.5 mol / L.

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