KR20190057958A - Process for Forming High Density SiC Coating on Graphite Foam And Coating Agent For The Same - Google Patents

Abstract

A method for coating silicon carbide on a surface of graphite foam using silica sol and organosilane is disclosed. The present invention provides a method for manufacturing a coating layer of silicon carbide on graphite foam, which comprises the steps of: coating a coating agent comprising silica sol and organosilane on graphite foam; drying the coated graphite foam; and heat-treating the dried graphite foam to form a silicon carbide coating layer. The present invention can provide graphite foam excellent in surface properties and oxidation resistance.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a method for forming a dense silicon carbide coating on a graphite foam,

The present invention relates to a method of forming a coating of silicon carbide on a graphite foam, and more particularly, to a method of coating silicon carbide on the surface of a graphite foam using silica sol and organosilane.

Graphite material is high in noble strength, very strong against thermal shock and corrosion, has high thermal conductivity and electric conductivity, and can be easily processed. It is used for semiconductor, solar cell industry as heat treatment jig (JIG), heating element, .

However, the graphite material is disadvantageous in that the oxidation progresses at a temperature of 400 ° C or higher and the physical properties thereof rapidly decrease. In order to overcome such disadvantages, various methods for preventing oxidation of graphite have been studied.

Coating methods for preventing oxidation of graphite include coatings of silicon carbide (SiC), silicon nitride (Si ₃ N ₄ ), and mullite using a chemical vapor deposition process (CVD), magnesia (MgO) Coatings of alumina (Al ₂ O ₃ ) and chromium oxide (Cr ₂ O ₃ ) are being actively promoted.

The coating method by plasma spraying has a disadvantage in that the coating layer is required to be thick since the coating method of the plasma spraying tends to cause peeling due to poor adhesion with a material.

On the other hand, since the graphite surface coated with silicon carbide (SiC) has a strong covalent bond with silicon and carbide, it has no change in physical properties or chemical composition even at a temperature of 2000 ° C or more. It has strength, hardness, abrasion resistance, And is used as a main coating material because of its excellent oxidizing property.

Generally, a method of coating silicon carbide on a graphite surface includes a chemical vapor deposition method using an organic silicon compound, a method using a silicon silicon or gas infiltration method, and a gas-solid reaction method using a silicon monoxide (SiO 2) gas.

Methyltrichrolosilane (MTS) is mainly used as a precursor in the case of coating silicon carbide by chemical vapor deposition. At this time, due to the process of flowing hydrogen gas together to remove the chlorine component from the methyltrichlorosilane precursor, There is a danger that the use of hydrogen gas may cause fire. Also, due to the corrosiveness of hydrochloric acid (HCl) gas as a by-product, there is a lot of difficulty in handling due to corrosion of the equipment and chlorine pollution in the final product.

Korean Patent Registration No. 10-0951633 discloses a method of coating a graphite surface with a polyphenylcarbosilane solution and then heat-treating the graphite surface to improve oxidation resistance in the graphite.

However, since the yield of polyphenylcarbosilane is less than about 60% in the process of converting to organic ceramic through organic conversion, cracks due to volume reduction can not be avoided when heat treatment is performed at 1200 ° C. or more. There is a problem that the oxidation resistance is difficult to be maintained for a long time when the coating layer is cracked.

Korean Registered Patent Publication No. 10-0951633 (2010.04.09. Announcement.)

In order to solve the above problems, the inventors of the present invention provide a silicon carbide coated graphite foam which is excellent in surface characteristics as well as oxidation resistance by using low concentration silacasol in Patent Application No. 2017-138128 I have suggested a method. The inventors of the present invention have found that when silica sol is used as a SiC precursor, silica powder is oxidized and the strength is lowered when silica powder is used at a high concentration to obtain a dense and thick SiC coating layer.

Accordingly, it is an object of the present invention to provide a method for producing a silicon carbide coated graphite foam which forms a dense silicon carbide coating layer, has excellent surface characteristics, and is excellent in oxidation resistance.

Another object of the present invention is to provide a coating agent suitable for the above-mentioned production method.

According to an aspect of the present invention, there is provided a method of manufacturing a semiconductor device, the method including: coating a graphite foam with a coating agent including a hydrophobic surface treated silica sol and an organosilane; Drying the coated graphite foam; And heat-treating the dried graphite foam to form a silicon carbide coating layer. The present invention also provides a method for producing a coating layer of silicon carbide on a graphite foam.

In the present invention, the coating agent comprises 20 to 40% by weight of silica sol; 20 to 40% by weight of an organosilane; And 20 to 40% by weight of an organic solvent.

In the present invention, the silica content and the organic silane content in the silica sol in the coating agent are preferably 1: 0.5 to 1: 1.5 by weight.

In the present invention, the drying step is followed by a step of removing silica in the graphite foam by a centrifugal separation method. The present invention provides a method for producing a coating layer of silicon carbide on a graphite foam.

In the present invention, any coating method selected from the impregnation method, the spray coating method, and the spin coating method may be used.

In the present invention, it is preferable that the drying is performed at 100 ° C or lower for 12-24 hours.

In the present invention, the heat treatment is preferably performed at 1400-1800 ° C in an inert gas or a vacuum atmosphere.

In the present invention, it is preferable that the heat treatment is performed at 1,400 ° C for 2 hours and then at 1,600 ° C for 1 hour. .

In the present invention, the organosilane includes at least one selected from the group consisting of DMDMS, MTMS, TEOS and GPTMS, or at least two compounds selected from the group consisting of DMDMS, MTMS, TEOS and GPTMS.

According to another aspect of the present invention, there is provided a silica sol comprising 20 to 40% by weight of silica sol; 20 to 40% by weight of an organosilane; And 20 to 40% by weight of an organic solvent.

In the present invention, the silica content and the organic silane content in the silica sol in the coating agent are preferably 1: 0.5 to 1: 1.5 by weight.

According to the present invention, a method of forming a coating of silicon carbide on a graphite foam can provide a graphite foam excellent in surface characteristics and oxidation resistance by forming a silicon carbide coating on the graphite foam using silica sol and organosilane .

Figure 1 is a flow chart of a method of forming a coating of silicon carbide on a graphite foam in accordance with an embodiment of the present invention.
FIG. 2 is an external view (FIG. 2A) of a grap pipe foam of the present invention and FIG. 2B is an image of a surface of a grap pipe foam taken by a field emission scanning electron microscope (FE-SEM).

While the invention is susceptible to various modifications and alternative forms, specific embodiments thereof are shown by way of example in the drawings and will herein be described in detail. It should be understood, however, that the invention is not intended to be limited to the particular embodiments, but includes all modifications, equivalents, and alternatives falling within the spirit and scope of the invention.

Throughout this specification, when an element is referred to as " including " an element, it is understood that it may include other elements as well, without departing from the other elements unless specifically stated otherwise.

Hereinafter, a method of forming a coating of silicon carbide on a graphite foam according to one aspect of the present invention will be described in detail with reference to the accompanying drawings.

1 is a flow chart of a method of forming a coating of silicon carbide on a graphite foam in accordance with an aspect of the present invention. The present invention is characterized by forming a silicon carbide coating having excellent crystallinity by using a silica sol and an organosilane in coating a surface of a graphite foam with silicon carbide by inducing a direct reaction between silicon and carbon. As a result, graphite foams are coated without cracks to improve oxidation resistance and can be used as a material exposed to an oxidizing atmosphere such as air at a temperature higher than 1,200 ° C.

A method of forming a coating of silicon carbide on a graphite foam comprising silicon according to an aspect of the present invention includes the steps of coating a coating comprising silica sol and organosilane on a graphite foam (S10) drying the coated graphite foam (S20) and heat-treating the dried graphite foam (S30).

The manufacturing method of the present invention will be described separately for each step.

First, step (S10) of coating a coating agent containing silica sol and organosilane on the graphite foam is performed. In the present invention, the coating agent may include 20 to 40% by weight of the hydrophobic surface-treated silica sol, 20 to 40% by weight of the organosilane, and 20 to 40% by weight of the organic solvent.

The silica sol of the present invention is preferably an organic silica sol. As a result, the wettability of the surface of the silica and the carbon fiber can be enhanced. The silica sol of the present invention may contain 20 to 100 parts by weight of silica based on 100 parts by weight of the total amount of the silica sol.

In addition, the viscosity of the silica sol is not limited thereto, but may be 50 cps or less, for example, 5 to 10 cps. If the viscosity exceeds 50 cps, an excessive amount of silica particles adsorb to the surface, and the oxygen contained therein may have an adverse effect.

In addition, the average particle diameter of the silica sol may be several hundred nanometers to several nanometers smaller than the diameter of the carbon fiber, since adsorption may not be good when the diameter of the silica sol is about the same as or larger than the diameter of the carbon fiber (several micrometers). Preferably, the average particle diameter is 10-20 nm.

As an example, the SNS-40 product of Dio Paint Co., Ltd. can be used as the silica sol of the present invention, and the amount of silica to be coated by diluting with methanol, isopropanol, propylene glycol or the like can be adjusted within the above range.

In the present invention, various silanes may be used as the silane. At least one silane selected from the group consisting of dimethyldimethoxysilane (DMDMS), methyltrimethoxysilane (MTMS), tetraethoxysilane (TEOS) and 3-glycidoloxypropyl-trimethoxysilane (GPTMS) Or a compound thereof.

In the present invention, methyltrimethoxysilane (MTMS), tetraethoxysilane (TEOS) and 3-glycidoloxypropyl-trimethoxysilane (GPTMS), which are hydrolyzable by water and have three or more alkyl groups, ) Or at least two of them are preferably used in combination. For example, the MTMS and the TEOS can be used in combination.

Also, in the present invention, the organosilane may be an organosilane compound prepared by hydrolysis and condensation polymerization of silane such as MTMS and TEOS by water.

The silane as a raw material for the production of the organosilane or the organosilane compound is preferably contained in the coating agent in an amount of 20 to 40% by weight. In addition, it is preferable that the distilled water for hydrolysis of the silane is contained in an amount of 15 to 20% by weight. Preferably, the weight ratio of silane to distilled water is preferably maintained in the range of 1: 0.8 to 1: 1.5.

In the present invention, it is preferable that the organic solvent is included in the range of 20 to 40% by weight. When the content of the organic solvent is less than 20% by weight, the viscosity of the coating increases and the coating film is difficult to form. When the content of the organic solvent is more than 40% by weight, shrinkage of the coating film occurs largely in the course of forming a coating film and drying.

Further, in the present invention, the coating agent may further include an additive. For example, a surfactant may be used as the additive in the present invention. Surfactants connect hydrophobic surface-treated nanocolloidal sol and silane hydrolyzate to each other. In addition, they improve the leveling property of the coating surface and defects such as pinholes, crater phenomena Generation can be prevented. In the coating agent of the present invention, the surfactant is preferably contained in an amount of 0.01 to 1.0% by weight.

In the present invention, the content of the silica sol and the organosilane is set at an appropriate ratio such that the organosilane supplies a carbon source for the formation of SiC. For example, in the present invention, the silica solids content and the organosilane content in the silica sol may be 1: 0.5 to 1: 2 by weight. More preferably, the silica solids content and the organosilane content in the silica sol may be from 1: 0.5 to 1: 1.5 by weight.

As shown in FIG. 2, the graphite foam is composed of fine carbon short fibers of 0.5 to several micrometers.

In the present invention, the coating material may be coated on the graphite foam by any one coating method selected from the group consisting of a coating method, an impregnation method, a spray coating method and a spin coating method. Wherein the silica sol in the coating can be impregnated on the graphite foam in the range of from several tens nanometers to several hundred nanometers.

Next, step (S20) of drying the coated graphite foam is performed.

The drying is performed for removing the dispersion medium or the organic solvent of the coating material impregnated in the graphite foam, and at a temperature of 100 ° C or lower for 12-24 hours. Preferably at 30 to 80 ° C.

The method of the present invention may optionally further comprise the step of removing the coating material remaining inside the graphite foam by the centrifugal separation method after step S20. This removes the precipitated silica into the interior of the graphite foam surface coating. Such centrifugation is preferably performed immediately after impregnation or before drying.

Finally, a step (S30) of heat-treating the dried graphite foam is performed. At this stage, the silica sol and organosilane act as a Si source for the reaction with SiC. Also, the carbon of the organosilane acts as the carbon source of the SiC reaction. This inhibits the formation of silicon oxide on the graphite foam and is converted into crystalline silicon carbide and coated. Further, in the present invention, the coating layer can be formed at a high density by providing the organosilane as a source of the SiC reaction as compared with the case of using silacazole alone.

The heat treatment may be performed at 1400-1800 占 폚 in an inert gas or a vacuum atmosphere, preferably at 1400-1600 占 폚. The heat treatment process should be performed at a minimum temperature of 1400 ° C or higher, at which the silica powder can be converted into SiC in an inert gas atmosphere or in a vacuum atmosphere in which oxygen is removed. In addition, when the temperature exceeds 1800 DEG C, the oxidation characteristic for the purpose of the invention may not be good.

The heat treatment is performed in an inert gas or a vacuum atmosphere, and the inert gas may be any one selected from the group consisting of argon, helium, and nitrogen.

Accordingly, the thickness of the coated silicon carbide can be in the range of tens to hundreds of nanometers, and the thickness can be adjusted to a desired range according to the process conditions.

≪ Example 1 >

SNS-40 product (SiO2 35-45%, viscosity 10 cps or less, average particle size 10-20 nm) was used as silica sol. A coating sample was prepared for each coating by diluting to a concentration of 25 wt% and 50 wt% to control the amount of silica to be coated. On the other hand, a non-diluted coating (100 wt%) sample was prepared for comparison.

The impregnated 30 mm x 30 mm x 10 mm sized graphite foam was washed with ethanol and dried at 80 for 30 minutes. Followed by impregnation with the above silica sol for 5 minutes using a dip coater. The coated graphite foam was then dried at 70 DEG C for 6 hours. The dried graphite foam was maintained at 1,400 ° C for 2 hours and then heat-treated at 1600 ° C for 1 hour to obtain a graphite foam coated with silicon carbide excellent in crystallinity.

As a result of visual observation of the coated foam, the use of 25 wt% silacasol resulted in good coating of silicon carbide on the graphite and no collapse of the foam after heat treatment. However, when the 50 wt% silica sol was used, the foam did not collapse but the foam was broken due to the weak strength of the foam due to the reaction of the graphite with oxygen generated by the decomposition of the silica sol. Also, it was confirmed that the coating layer did not completely cover the surface of 100 wt% silica sol.

≪ Example 2 >

The SNS-40 product of Dio Paint Co., Ltd. was diluted to a concentration of 25 wt% as in Example 1. Subsequently, an organic silane (TEOS) having the same weight as the solid content (silica) content of the silica sol was added to prepare a mixed solution. The diluted silica sol and organosilane were mixed to prepare a coating agent.

The prepared coating agent was impregnated in the same manner as in Example 1, followed by drying and heat treatment to prepare a silicon carbide coated graphite coated foam.

As a result of visual observation, silicon carbide was coated well on the graphite, the oxidation of the foam was hardly observed, and the collapse of the foam did not occur after the heat treatment.

The preferred embodiments of the present invention have been described above. It will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims. Therefore, the disclosed embodiments should be considered in an illustrative rather than a restrictive sense. The scope of the present invention is defined by the appended claims rather than by the foregoing description, and all differences within the scope of equivalents thereof should be construed as being included in the present invention.

Claims (11)

Coating a coating comprising silica sol and organosilane on a graphite foam;
Drying the coated graphite foam; And
And heat treating the dried graphite foam to form a silicon carbide coating layer on the graphite foam. The method according to claim 1,
Wherein the coating agent comprises 20 to 40% by weight of silica sol; 20 to 40% by weight of an organosilane; And 20 to 40% by weight of an organic solvent. The method according to claim 1,
Wherein the silica content and the organic silane content in the silica sol in the coating agent are 1: 0.5 to 1: 1.5 by weight. The method according to claim 1,
Further comprising, after said drying step, removing silica in the graphite foam by centrifugation. ≪ RTI ID = 0.0 > 8. < / RTI > The method according to claim 1,
Wherein the coating is formed by any one coating method selected from the group consisting of impregnation, spray coating and spin coating. The method according to claim 1,
Wherein the drying is carried out at 100 DEG C or less for 12 to 24 hours. The method according to claim 1,
Wherein the heat treatment is performed at 1400-1800 DEG C in an inert gas or a vacuum atmosphere. The method according to claim 1,
Wherein the heat treatment is carried out at 1,400 ° C for 2 hours and then at 1,600 ° C for 1 hour. The method for manufacturing a coating layer of silicon carbide on a graphite foam according to claim 1, The method according to claim 1,
Wherein the organosilane comprises at least one compound selected from the group consisting of DMDMS, MTMS, TEOS and GPTMS, or at least two compounds selected from the group consisting of DMDMS, MTMS, TEOS and GPTMS. 20 to 40% by weight of silica sol; 20 to 40% by weight of an organosilane; And 20 to 40% by weight of an organic solvent. 11. The method of claim 10,
Wherein the content of silica in the silica sol and the content of the organic silane in the coating agent is 1: 0.5 to 1: 1.5 by weight.

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