KR100355349B1 - Manufacturing method of reaction-bonded silicon carbide - Google Patents

Abstract

The present invention relates to a method for producing reaction-bonded silicon carbide, wherein the first mixture comprising silicon carbide powder, thermosetting resin and thermoplastic resin is cured in real time by heat reaction centrifugal molding in a centrifugal molding machine to form a first layer. , The second mixture comprising silicon powder, thermosetting resin and thermoplastic resin is cured in real time by heat reaction centrifugal molding in a centrifugal molding machine to form a second layer to form a double structure of the first layer and the second layer It provides a method for producing a reaction-bonded silicon carbide comprising the step of removing the thermoplastic resin of the molded body, thermally decomposing the thermosetting resin of the molded body to carbonize the molded body, and heating the carbonized molded body to a high temperature. According to the present invention, when manufacturing a reaction-bonded silicon carbide product, there is no need for a hydrostatic forming apparatus for forming a large tube, a high temperature vacuum furnace for pretreatment, and a high temperature vacuum melting furnace for molten silicon infiltration, and a furnace made of molten silicon. Since there is no risk of damage to the jig, it is possible to manufacture large-scale, economically dense reaction-bonded silicon carbide products with low maintenance costs.

Description

MANUFACTURING METHOD OF REACTION-BONDED SILICON CARBIDE}

The present invention relates to a method for producing reaction-bonded silicon carbide.

Reaction-bonded silicon carbide penetrates molten silicon into a molded body composed of silicon carbide and carbon, and new silicon carbide formed by the reaction of molten silicon and carbon bonds the silicon carbide particles that originally constituted the molded body, and the pores therebetween. It is filling material. Reaction-bonded silicon carbide is widely used as a heat dissipation tube because of its excellent wear resistance, erosion resistance, heat resistance and high thermal conductivity. The manufacturing method is a method of mixing a raw material powder consisting of silicon carbide and carbon with an organic binder to prepare a tubular shaped body by using a molding method such as hydrostatic molding, degreasing it, pre-sintering and then impregnating in molten silicon. It is a general process.

The sintering pretreatment process is carried out at a high temperature of 1800 ~ 2000 ℃, in order to charge the preform pre-treated in the molten silicon, a large vacuum furnace having a large crucible and a vacuum atmosphere as a silicon melting furnace is essential. Therefore, in order to manufacture a large part, such as a large tube, expensive investment equipment such as a hydrostatic pressure forming apparatus, a high temperature pretreatment furnace, and a high temperature vacuum furnace is required, and the initial investment cost is enormous. In addition, since it is used at high temperatures and handles eroded molten metal, the life of parts and smelters is shortened, and the consumption cost of expensive parts is large, and maintenance costs occupy a large proportion of production cost.

Inex Silicon Carbide Tube is a method of injecting molten silicon into a molded body to reduce enormous investment costs and production costs (Taghi Daroudi et al, 'Low-Cost Melt-Formed Siliconized Silicon Carbide Radiant Tube Materials', J. Am. Ceram Soc., 76 (1), 173-179, 1993), but the amount of silicon remaining in the reaction-bonded silicon carbide is very high, which acts as a cause of lowering the heat resistance including high temperature strength.

An object of the present invention is to produce a reaction-bonded silicon carbide product economically by eliminating the need for a silicon smelter, easy to form large parts, and one-step heat treatment.

1 is a front sectional view showing a double-layer molded body of silicon carbide and silicon as an embodiment of the present invention.

FIG. 2 is a perspective view of the double layer molded product of FIG. 1. FIG.

*** Explanation of symbols for main parts of drawing ***

10: silicon carbide layer 20: silicon layer

The present invention is to cure the first mixture comprising silicon carbide powder, thermosetting resin and thermoplastic resin in real time by heat reaction centrifugal molding in a centrifugal molding machine to form the first layer, and includes silicon powder, thermosetting resin and thermoplastic resin The second mixture was cured in real time by heat reaction centrifugal molding in a centrifugal molding machine to form a second layer to prepare a molded body having a double structure of the first layer and the second layer, and remove the thermoplastic resin of the molded body. In addition, there is provided a reaction-bonded silicon carbide production method comprising thermally decomposing the thermosetting resin of the molded body to carbonize the molded body, and heating the carbonized molded body to a high temperature.

The biggest feature of the present invention is to integrally form the silicon carbide molded body and the silicon source. That is, a first layer is formed by mixing a thermosetting resin precursor and a silicon carbide raw material powder, and a silicon powder and a thermosetting resin mixture penetrated into silicon carbide are formed thereon to prepare a double layer molded body. The bilayer molded body can be made into a tube form using a centrifugal molding machine. When the tube-shaped molded body is thick, the thermosetting resin is cured by heating the mold of the centrifugal molding machine to maintain the shape of the molded body.

The cured double layered molded product is thermally decomposed in a vacuum or inert gas atmosphere to carbonize the thermosetting resin. The carbonized molded body consists of two layers: silicon carbide / carbon layer and silicon / carbon layer. When the carbonized molded body is heated above the melting temperature of silicon in a vacuum or inert atmosphere, and the molten silicon penetrates into the silicon carbide / carbon layer along the capillary inside the molded body, silicon and carbon react to form silicon carbide. The space formed between the silicon carbide added as the raw material powder and the newly formed silicon carbide is filled with molten silicon and, after cooling, becomes a silicon carbide / silicon composite material, that is, reaction-bonded silicon carbide.

Referring to the method of manufacturing the reaction-bonded silicon carbide according to the present invention in more detail.

First, the silicon carbide powder and the resin composition are uniformly mixed. At this time, the silicon carbide raw material powder of appropriate size is basis weight in an appropriate fraction and mixed with the resin composition at low temperature. The particle size of the silicon carbide powder may vary depending on the use temperature or the end use, but in general, an average particle diameter of 3 μm or more is sufficient, and in a product requiring heat resistance, a range of 3 to 500 μm is preferable. In the present invention, the average particle diameter of silicon carbide is in the range of 3 to 2000 µm. In addition, the weight ratio of silicon carbide powder to the mixture is suitably in the range of 60 to 90%.

A resin composition adds surfactant and a hardening | curing agent to a thermosetting resin and a thermoplastic resin solution as needed. The thermosetting resin determines the strength of the shaped body and provides the raw material of carbon used for the reaction bonding, and the thermoplastic resin moves to the surface through the capillary and evaporates at a temperature lower than the pyrolysis temperature of the thermosetting resin, resulting in the It serves to secure the discharge passage. Since the pore structure at the time of reaching the pyrolysis process may vary according to the fraction of the thermosetting resin and the thermoplastic resin, the thermosetting resin or the thermoplastic resin is preferably not more than 40% and not more than 70% of the total resin amount. The weight ratio of the thermosetting resin and the thermoplastic resin is suitably in the range of 70:30 to 40:60. When the fraction of the thermosetting resin is more than 70%, the curing proceeds rapidly and it is difficult to control the curing rate, and when the fraction of the thermoplastic resin is 60% or more, the curing rate becomes too slow. Since the curing agent determines the curing rate, it is appropriately adjusted according to the heat transfer or curing temperature of the mold.

In order to prevent the polymerization reaction of the thermosetting resin, the mixing of the silicon carbide powder and the resin composition is preferably performed while maintaining a low temperature of 5 ° C. or lower, and if necessary, removes bubbles from the mixture under vacuum.

The mixture is then placed in a mold and centrifuged while heating. When the mixture is filled with the metal mold in an appropriate amount and centrifuged, the mixture moves to the mold wall surface, and curing of the thermosetting resin can be induced by heating the outer wall of the mold during centrifugal molding. Although it depends on the thickness of a tube, it is preferable to perform heat centrifugal molding over 1 to 5 hours.

After the centrifugal molding is completed, additional heat treatment for curing may be necessary depending on the thickness of the molded body. In this case, the mold outer wall is continuously heated to completely cure the molded body.

The silicon powder and the resin composition are uniformly mixed in the same manner as the mixture of the silicon carbide powder and the resin composition. The average particle diameter of the silicon powder is 1 ~ 2000㎛, the weight ratio of the mixture is suitable in the range of 60 ~ 90%. After the mixed silicon powder and the resin composition are filled into the mold having the above-mentioned molded body containing silicon carbide, heat centrifugal molding is performed in the same manner. In this case, additional heat treatment for curing may be performed according to the thickness of the molded body.

Through the above process, a double-layered molded article in which a molded article containing silicon is formed on the molded article containing silicon carbide in duplicate is obtained. 1 and 2 illustrate an example of a double layer molded article.

After the final molded product is produced, the heating is performed slowly to remove the thermoplastic resin. When the thermoplastic resin is removed from the molded body, the space filled by the thermoplastic resin is emptied, thereby obtaining a three-dimensional pore structure connected throughout the molded body.

Next, the molded body is heated to a high temperature in a vacuum or inert atmosphere to pyrolyze the thermosetting resin to carbonize the molded body. At this time, carbon is formed at 400 ° C. or higher, and when heated to a temperature higher than that, sintering of carbon occurs and the strength of the molded article gradually increases. The carbonized molded body consists of two layers: silicon carbide / carbon layer and silicon / carbon layer.

After the thermoplastic resin and the thermosetting resin are removed, the molded body is heated to 1400 ° C. or more, which is a melting temperature of silicon. In this process, the silicon in the silicon / carbon layer moves to the silicon carbide / carbon layer by capillary flow, reacts with carbon to form silicon carbide, and the other space is filled with molten silicon. As heating conditions, the temperature range of 1400-1650 degreeC for 5 to 180 minutes in a vacuum or reducing atmosphere is suitable.

After all of this process is completed, a porous silicon carbide layer, such as formwork, is left in the double-layered molding, which can be removed by sandblasting or lapping to obtain a dense reactive bonded silicon carbide product in its final form.

Hereinafter, the present invention will be described in more detail with reference to Examples. However, the present invention is not limited in scope by these examples.

Reaction-bonded silicon carbide was prepared in the form of a tube. The particle size of the silicon carbide powder used in this example was 5 ~ 210㎛, a single size of the powder was used or a mixture of powders of different sizes. The average particle diameter of the silicon powder was 1, 5, 70, 2000㎛, and like silicon carbide, a single size of the powder was used or a mixture of powders of different sizes. The thermosetting resin was used furfuryl alcohol (furfuryl alcohol), furfuryl alcohol resin (furfuryl alcohol resin), the weight ratio of the two components was 50:50. Glycol was used as the thermoplastic resin. Xylene sulfonic acid and p-toluene sulfonic acid were used as a curing agent, and Triton X-100 (Union Carbide, USA) was used as a dispersant for liquid resins, that is, a surface active agent. , Butanol was used. Tables 1 to 3 show the compositions of silicon carbide, silicon, thermosetting resin and thermoplastic resin.

Composition (wt%) of silicon carbide powder Silicon Carbide Composition Powder Average Particle Size (㎛) 210 150 100 65 45 35 25 16 10 5 One 10 50 30 10 2 25 50 25 3 80 20 4 37.6 62.4 5 15.6 10.4 8.3 7.3 7.3 7.3 6.3 37.5 6 100 7

Composition table of silicon powder (wt%) Silicon composition Powder Average Particle Size (㎛) 2000 70 5 One One 81.25 18.75 2 72 28 3 61 25 14 4 100

Composition of resin Furtherance Weight percent of each component Thermoplastic Thermosetting resin Surfactant Hardener Thermoplastic / Thermosetting Resin Ratio X-100 Butanol One 50.6 32.8 10.1 6.5 60.7 / 39.3 2 37.9 45.4 7.6 9.1 45.7 / 54.3 3 33.7 33.7 9.6 14.5 8.5 50/50 4 25.9 44.4 7.4 11.1 11.1 36.8 / 63.2 5 21.9 61.4 4.4 12.3 26.3 / 73.7

Example 1

150 µm silicon carbide powder, 80.6 wt% of thermosetting resin, 5.7 wt% of perfuryl alcohol, 5.7 wt% of perfuryl alcohol resin, 4.9 wt% of diethylene glycol, 2.3 wt% of curing agent, and 1.0 wt% of Triton X-100. Mix uniformly. This mixture was placed in vacuo for 30-60 minutes to remove bubbles in the mixture. Thereafter, the mixture was placed in a circular metal mold and centrifuged at a rotational speed of 100 to 500 for 10 to 60 minutes to have a mold, and then the outer wall of the mold was heated to cure the thermosetting resin. The silicon and resin mixture was mixed in the same manner as above to fill the mold, and then double-molded on the silicon carbide where molding and curing were completed. The composition of the silicon and resin mixture was 51.1 wt% of silicon of 2000 μm, 11.7 wt% of silicon of 70 μm, 8.3 wt% of perfuryl alcohol, 8.3 wt% of perfuryl alcohol resin, 9.6 wt% of ethylene glycol, 4.1 wt% of butanol, X -100 2.8 wt%, and a curing agent 4.1 wt%. After molding and curing, the double molded body was heated to a temperature of 150 ° C. or higher to remove the thermoplastic resin, and carbonized by thermal decomposition of the thermosetting resin at a temperature of 400 ° C. or higher. The double-molded carbonized product was heat-treated in a vacuum or reducing atmosphere at a temperature of 1400 to 1650 ° C. for 5 to 180 minutes to prepare a reaction bonded silicon carbide tube.

Example 2

150 μm silicon carbide powder 15.5 wt%, 35 μm silicon carbide powder 46.7 wt%, 5 μm silicon carbide powder 15.5 wt%, perfuryl alcohol 5.1 wt%, perfuryl alcohol resin 5.1 wt%, diethylene glycol 8.4 wt%, X 1.7 wt% of -100 and 2.0 wt% of curing agent were mixed uniformly. Also, 42.3 wt% of 70 μm silicon, 16.7 wt% of 5 μm silicon, 9.9 wt% of 1 μm silicon, 8.3 wt% of fufuryl alcohol resin, 8.3 wt% of fufurtyl alcohol resin, 9.3 wt% of ethylene glycol, 1.9 wt% of X-100 and a curing agent. 3.3 wt% were mixed uniformly. Reaction-bonded silicon carbide tubes were prepared in the same manner as in Example 1 using the silicon carbide and resin mixtures and the silicon and resin mixtures.

According to the present invention, when manufacturing a reaction-bonded silicon carbide product, there is no need for a hydrostatic forming apparatus for forming a large tube, a high temperature vacuum furnace for pretreatment, and a high temperature vacuum melting furnace for molten silicon infiltration, and a furnace made of molten silicon. Since there is no risk of damage to the jig, it is possible to manufacture large-scale, economically dense reaction-bonded silicon carbide products with low maintenance costs.

Claims (16)

Filling the mold with a first mixture comprising 60 to 90 wt% of silicon carbide powder having a mean particle size of 3 to 2000 μm, a thermosetting resin and a thermoplastic resin, and curing the mold in real time by centrifugal molding while heating the outer wall of the mold to form a first layer. Let's A second mixture containing 60 to 90 wt% of silicon powder having a mean particle size of 1 to 2000 μm, a thermosetting resin and a thermoplastic resin is filled into the mold and cured in real time by centrifugal molding while heating the outer wall of the mold to form a second layer. To form a molded body having a double structure of the first layer and the second layer, The molded body is heated to 150 ° C. or higher to remove the thermoplastic resin, The molded body is heated to a temperature of 400 ° C. or higher in a vacuum or inert atmosphere to pyrolyze the thermosetting resin to carbonize the molded body, It consists of heating the carbonized molded body in a vacuum or reducing atmosphere for 5 to 180 minutes in the range of 1400 ~ 1650 ℃, The thermosetting resin is fufuryl alcohol and fufuryl alcohol resin, the thermoplastic resin is glycol, the fraction of the thermosetting resin is characterized in that 40 to 70% range Reaction-bonded silicon carbide production method. delete delete delete delete The method of claim 1, further comprising mixing a curing agent with the first mixture and the second mixture. The method of claim 6, wherein the curing agent comprises xylene sulfonic acid, p-toluene sulfonic acid. The method of claim 1, further comprising adding a surface active agent to the first mixture and the second mixture. The method of claim 8, wherein the surfactant is Triton X-100 or butanol. delete The method of claim 1, wherein the weight ratio of the thermosetting resin and the thermoplastic resin in the first mixture and the second mixture is in the range of 70:30 to 40:60. The method of claim 1, wherein the first mixture and the second mixture are mixed with each component while maintaining a low temperature of 5 ° C. or less. The method of claim 1, wherein the heating reaction centrifugal molding is performed for 1 to 5 hours. The method of claim 1, further comprising heating a mold outer wall after forming the first layer or after forming the second layer. delete delete