KR20010060412A - Fabrication Method of Al2O3/Al Foam Filter - Google Patents

Abstract

PURPOSE: A method for preparing an alumina/aluminium foam filter is provided, to improve the abrasion resistance and strength of the foam filter, thereby allowing the filter to be used after the dust is removed mechanically. CONSTITUTION: The method comprises the steps of dipping the ceramic filter comprising silicate-based oxides into the molten aluminium maintained at the temperature of 800-1,100 deg.C, to obtain the alumina/aluminium foam filter by the exchange reaction. Preferably the pore rate of the strut of the foam filter is less than 20% to allow the exchange reaction to be occurred. The ceramic foam is commonly prepared by coating an urethane foam filter with the ceramic slurry which comprises silica, kaolin, clay, mullite or their mixtures; and drying and sintering it.

Description

Fabrication Method of Al2O3 / Al Foam Filter

The present invention relates to a ceramic foam filter, and more particularly, to a method of manufacturing a ceramic foam filter of an alumina / aluminum composite having excellent strength and wear resistance.

In general, ceramic filters are made of a slurry made of ceramic powders such as zirconia (ZrO ₂ ), silicon carbide (SiC), and alumina (Al ₂ O ₃ ), and a urethane foam filter is put therein. The ceramic slurry is coated on the urethane foam, and then, after drying and firing, the urethane is combusted to prepare a ceramic foam filter having pores in the strut and having excellent heat resistance and wear resistance.

However, since the ceramic foam filter uses a ceramic material, it is excellent in heat resistance and abrasion resistance, but weak in fracture toughness, and thus weak in resistance to mechanical impact.

Therefore, when trying to separate the dust collected in the foam filter by mechanical vibration, the foam filter is subjected to a strong mechanical shock, there is a problem that can not be reused.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object thereof is to manufacture a filter for dust removal having strong wear resistance and mechanical impact, thereby providing a ceramic foam filter which can be repeatedly used even after shaking off dust collected on the filter by mechanical impact. To provide.

In order to achieve the above object, the present invention is a ceramic foam filter composed of a silicate-based oxide, the ceramic foam filter is deposited in a molten aluminum molten aluminum kept at 800 ~ 1100 ℃ by substitution reaction by foaming the alumina / aluminum composite It is characterized by producing a filter.

In order to enable the substitution reaction, the porosity of the strut of the foam filter is preferably less than 20%.

Hereinafter, the present invention will be described in more detail.

The present invention is coated with a urethane foam filter of a ceramic slurry composed of silicate-based oxides such as silica (silica), kaoline (clay), clay, mullite (mullite), and then dried and calcined to prepare a ceramic foam filter, Using this ceramic foam filter as a preform, a foam filter of an alumina / aluminum composite was prepared by immersing in a molten aluminum molten metal kept at 800 to 1100 ° C. for substitution reaction.

In the substitution reaction, silica (SiO ₂ ) of a ceramic foam filter composed of a silicate oxide is substituted with aluminum to form alumina. Aluminum is used here because it is easy to make a molten bath with a low melting point, high reactivity with silicic acid, and the resulting alumina has high abrasion resistance and impact resistance.

Therefore, the ceramic foam filter, which is a preform used for the substitution reaction with the molten aluminum, should be made of a silicate-based oxide, and can be used as long as it is manufactured by a conventional method.

In addition, in order to enable the substitution reaction, the interparticle porosity of the strut constituting the foam filter should be less than 20%. This is because the formation of the alumina / aluminum complex becomes difficult when the porosity of the pillar is 20% or more.

When the silicate foam filter, which is a preform, is substituted with molten aluminum, a reaction temperature of 800-1100 ° C. is appropriate, and the reaction time is determined by the size of the ceramic foam filter or the size of the pillars constituting the ceramic foam filter. It cannot be limited.

The reason for limiting the reaction temperature to 800 ° C. or more is to consider 660 ° C., which is the melting temperature of aluminum, and the time required for the substitution reaction. That is, below 800 ° C., the silica included in the silicate-based oxide may be alumina by the following reaction, but it takes a long time and the crystals of the resulting alumina are not produced as stable alpha alumina.

3SiO ₂ + 4Al → 2Al ₂ O ₃ + 3Si

In addition, the reason for limiting the temperature of the substitution reaction to 1100 ° C or less is to minimize the surface oxidation of the molten aluminum used in the reaction. This is because the surface of the molten aluminum molten metal is exposed to the atmosphere so that the aluminum in the surface layer contacts with oxygen to alumina to form a solid oxide layer. The alumina sintered layer thus formed is not only an obstacle to the operation of taking out the alumina / aluminum foam filter formed after the substitution reaction of the foam filter, but also the consumption of aluminum used as a reactant is not preferable.

Thus, in consideration of reactivity and workability, the temperature of a suitable substitution reaction is about 1000 degreeC.

On the other hand, the shape and constituents of aluminum used in the reaction are not particularly limited, but it is preferable to use agglomerated aluminum in consideration of oxidizing property in the atmosphere during melting, and the higher the purity, the better.

Hereinafter, a preferred embodiment of the present invention will be described with reference to experimental data.

Example

As shown in Table 1, a ceramic foam was coated by depositing urethane foam on a slurry obtained by ball milling a fused silica powder or a mullite powder in an alumina pot for 24 hours. The ceramic coated urethane foam was degreased and fired in an electric furnace to prepare a ceramic preform.

The preform thus prepared was reacted with molten aluminum at a temperature range of 750 to 1200 ° C. for 3 hours to prepare a foam filter of an alumina / aluminum composite.

Experiment No. Preform Characteristics Reaction temperature with metal Al (℃) Manufacturing Characteristics of Alumina / Aluminum Composites Characteristics of the complex Composition of Ceramic Foam Filter Foam filter column porosity (%) Thickness (mm / hr) Manufacture of Complex Characteristics of the complex Fracture Toughness (Mpa · m ^1/2 ) Example 1 Mullite 3 800 2.0 Good High strength and high wear resistance 7 Example 2 Mullite 3 1000 2.5 Good High strength and high wear resistance 7 Example 3 Silica 2 1000 3.0 Good High strength and high wear resistance 7 Comparative Example 1 Mullite 3 750 0.1 Poor reactivity Lack of wear resistance - Comparative Example 2 Mullite 3 1200 2.5 Bad Blown out Al surface oxidation 7 Comparative Example 3 Mullite 25 1000 0.1 Unreacted Manufacturing difficulty - Comparative Example 4 Mullite 1 ~ 2 - - - Destruction when removing dust 3

As shown in Table 1, the specimens 1 to 3 prepared according to the present invention had good reactivity, and also excellent strength and wear resistance of the composite.

In contrast to the results of Examples 1 to 3, the results of Comparative Examples 1 to 4 are as follows.

In Comparative Examples 1 and 2, the reaction temperature of the reaction between the ceramic preform and the molten aluminum is beyond the scope of the present invention. The strength was insufficient because the alumina produced was not a stable phase.

In Comparative Example 2, although the temperature was high at 1200 ° C., the substitution reaction was sufficiently performed, resulting in a thickness of 2.5 mm / hr. Have difficulty.

On the other hand, in Comparative Example 3, the porosity of the mullite foam filter post, which is a preform, was high at 25%, so the reactivity with molten aluminum was insufficient, making it difficult to manufacture a composite.

And, Comparative Example 4 shows the fracture toughness of the conventional mullite foam filter, it was found that the fracture toughness is weak compared to the alumina / aluminum composite foam filter of the present invention range.

As described above, the present invention can prepare alumina / aluminum composite foam filter having excellent abrasion resistance and strong resistance to mechanical impact, so that dust collected on the foam filter can be separated and reused.

Claims (2)

In a ceramic foam filter composed of a silicate oxide, The ceramic foam filter is immersed in a molten aluminum molten metal maintained at 800 ~ 1100 ℃ to form an alumina / aluminum composite by a substitution reaction. The method of claim 1, wherein the porosity of the strut of the foam filter is less than 20%.