KR101138440B1 - Porous body with silicon carbide enhancement layer and fabrication method thereof - Google Patents

Abstract

The present invention provides a silicon carbide-reinforced porous substrate comprising a silicon carbide impregnated layer formed by penetrating into a substrate from a porous substrate surface, and a silicon carbide vapor deposition layer formed on the substrate surface. The silicon carbide precursor solution is pressurized to penetrate into the surface of the porous base material to form an impregnation layer, and subsequently to form a silicon carbide reinforcement layer by vapor deposition to prevent cracking or peeling, and to enhance the durability of the reinforcement layer. Can be promoted.

Description

Silicon Carbide Reinforced Porous Substrate and Formation Method {POROUS BODY WITH SILICON CARBIDE ENHANCEMENT LAYER AND FABRICATION METHOD THEREOF}

The present invention relates to a silicon carbide reinforcement layer and a method of forming the same, and in particular, proposes a new silicon carbide reinforcement layer having improved durability by forming a silicon carbide vapor deposition layer on a porous substrate through a silicon carbide impregnation layer.

Silicon carbide (SiC) is a ceramic material excellent in chemical resistance, oxidation resistance, heat resistance, and wear resistance. By coating the material such as metal or ceramic using the excellent physical properties of silicon carbide can improve the chemical resistance, oxidation resistance, heat resistance and wear resistance.

Silicon carbide is also present as a natural stone, but can also be produced by synthesizing silica and carbon by chemical reaction, it is possible to form a silicon carbide reinforcement layer on the surface of the material by coating or chemical vapor deposition (CVD) method.

In general, the silicon carbide reinforcement layer is formed by a chemical reaction such as vapor deposition. The gaseous state compound containing Si and the gaseous state compound containing C are reacted to coat a solid silicon carbide layer on the base material. The advantages of vapor deposition are that the composition can be easily controlled and the detailed structure of the deposited material is also easy.

However, the silicon carbide reinforcement layer produced by vapor deposition shows a rapid change in chemical composition at the interface with the base material, so residual stress tends not to be sufficiently relaxed, and peeling or cracking occurs due to the difference in thermal expansion coefficient between materials. easy. In order to solve this drawback, there is a problem in that the residual stress must be relieved through the formation of a buffer layer in advance between the reinforcing layer and the base material or through the interfacial coating of the gradient composition.

In addition, since the vapor deposition layer forms a silicon carbide reinforcement layer at a high temperature through a chemical reaction, the base material capable of forming the reinforcement layer is limited. That is, a metal having a low melting point in the process of depositing silicon carbide on the surface of the metal by chemical vapor deposition using a process temperature of 1000 ° C. or more may cause problems such as melting of the metal.

On the other hand, silicon carbide coating using a polymer precursor has been proposed. For example, the Si-C-containing polymer is coated on the surface of the base material in a solution state to form a silicon carbide coating layer. However, in this case, the thickness of the coating layer is very small, so that the repeated coating process must be performed and the high temperature must be maintained in the heat treatment process after coating. Depending on the conditions such as the concentration of the impurity is contained in the stoichiometric silicon carbide layer can not be obtained or the physical properties of the formed coating layer has a disadvantage in that it does not function as a reinforcing layer.

The present invention has been made under the above technical background, and an object of the present invention is to provide a silicon carbide reinforcement layer having excellent adhesion to a base material and improved durability.

Another object of the present invention is to provide a silicon carbide vapor deposition layer to which no buffer layer or gradient composition layer is added.

Still another object of the present invention is to provide a method of forming a new silicon carbide reinforcement layer having improved durability on a porous base material surface.

Other objects and technical features of the present invention will be presented in more detail in the following detailed description.

In order to achieve the above object, the present invention provides a porous base material having open pores in a mesh structure on the surface and inside thereof, and a silicon carbide impregnating layer formed by penetrating into the base material from the base material surface through the open pores; And a silicon carbide vapor deposition layer formed on the surface of the base material and contacting the silicon carbide impregnation layer on the base material surface, wherein the silicon carbide impregnation layer is thicker than the silicon carbide vapor deposition layer. Provide a carbide reinforced porous base material.

The present invention also provides a porous base material, preparing a silicon carbide precursor solution, immersing the porous base material in a container containing the silicon carbide precursor solution, and applying pressure in the container containing the silicon carbide precursor solution to the inside of the porous base material surface The method of forming a silicon carbide reinforcing layer comprising the step of infiltrating a silicon carbide precursor solution into a furnace, heat treating a porous base material into which the silicon carbide precursor solution has penetrated, and forming a silicon carbide reinforcement layer by vapor deposition on the surface of the porous base material. do.

The present invention may further include silicon carbide powder as an additive to the silicon carbide precursor, depending on the type of base material with open pores of the network structure.

According to the present invention, it is possible to form a silicon carbide reinforcement layer having improved durability on the surface of the various base materials. In addition, the thickness of the silicon carbide layer can be easily adjusted, and there is no need for a buffer layer or a gradient composition layer between the base material and the reinforcement layer, thereby simplifying the process and reducing the manufacturing cost.

1 is a schematic cross-sectional view showing a silicon carbide reinforced layer according to an embodiment of the present invention.
Figure 2 is a schematic cross-sectional view showing a silicon carbide reinforced layer according to another embodiment of the present invention.
3 is a process chart showing a method for forming a silicon carbide reinforcement layer according to the present invention.
Figure 4 is a schematic diagram showing a silicon carbide penetration process when forming a silicon carbide reinforcement layer according to the present invention.
5 is a cross-sectional photograph of the base material is complete impregnation.
Figure 6 is a photograph showing a reinforcing layer of the graphite surface formed silicon carbide reinforcing layer according to the invention.
DESCRIPTION OF THE REFERENCE SYMBOLS
10: porous base material 12: silicon carbide impregnated layer
14: silicon carbide coating layer 20: silicon carbide vapor deposition layer

The present invention forms a silicon carbide reinforcing layer on the porous base material, thereby improving chemical resistance, oxidation resistance, heat resistance, and abrasion resistance of the base material, as well as preventing unnecessary particles generated from the base material.

1 is a cross-sectional view of a porous silicon substrate on which a silicon carbide reinforcement layer is formed in accordance with an embodiment of the present invention. A silicon carbide impregnated layer 12 having a predetermined depth is formed from a surface of the porous matrix 10 and a porous matrix (10) It is shown that the silicon carbide vapor deposition layer 20 is formed on the surface while bordering the upper surface of the impregnation layer.

The porous base material may include metals, ceramics, graphite, and other composite materials having open pores distributed in a mesh structure on the surface and the inside thereof. The pores distributed in the porous base material may vary depending on the type of material, and may have various pore sizes ranging from several micrometers to several millimeters, and the pore size is not limited. In addition, not only the pores are naturally distributed in the nature of the base material, but also a composite material intentionally formed in a porous structure in the manufacturing process may be included in the porous base material of the present invention. The shape of the porous base material may have a variety of structures, for example, disk-shaped, hexahedral, prismatic, etc., the present invention is not limited to the shape of the porous base material.

The silicon carbide impregnated layer 12 formed by penetrating into the base material from the base material surface through the open pores of the porous base material is a buffer of the silicon carbide vapor deposition layer 20 formed on the base material surface and in contact with the silicon carbide impregnated layer on the base material surface. Play a role. The silicon carbide vapor deposition layer and the base material have poor adhesion due to heterogeneous material properties due to differences in coefficient of thermal expansion or difference in chemical composition. Peeling and cracking are likely to occur at the interface. The silicon carbide impregnated layer improves the interfacial adhesion characteristics of silicon carbide vapor deposition by changing the chemical composition of the base material similarly to the silicon carbide while being distributed within the pores of the base material as the support material near the surface of the porous base material. As a result, there is no need to form a buffer portion or a gradient composition layer between the separate silicon carbide vapor deposition layer and the base material, providing manufacturing advantages and greatly improving the durability of the finished silicon carbide reinforcement layer.

The thickness of the silicon carbide vapor deposition layer may vary depending on the type, use, shape, etc. of the porous base material, and preferably in the range of 10 to 500 μm.

The silicon carbide impregnated layer may vary depending on the thickness, size, and shape of the base material, but it is preferable to form a thicker than the silicon carbide vapor deposition layer in terms of improving durability of the reinforcing layer. To this end, in the present invention, as described below, the silicon carbide is impregnated to the surface of the base material by applying a pressure at a temperature higher than room temperature.

The depth of the silicon carbide impregnated layer may vary depending on the thickness of the vapor deposition layer, preferably 0.3 mm or more.

2 is a partial cross-sectional view showing another embodiment of the present invention, the silicon carbide coating layer 14 is further formed on the surface of the porous base material while forming a boundary with the silicon carbide impregnated layer 12 of the porous base material 10. The silicon carbide coating layer 14 makes interfacial contact with the silicon carbide vapor deposition layer 20 and constitutes a silicon carbide reinforcement layer. Due to the presence of the silicon carbide coating layer, the interfacial adhesion characteristics between the porous base material and the silicon carbide vapor deposition layer are further improved. The silicon carbide coating layer may be formed at the same time as the silicon carbide impregnated layer is formed as described below, or may be formed through a repeated coating process sequentially after the impregnated layer is formed.

The silicon carbide-reinforced porous base material according to the present invention facilitates the formation of a silicon carbide coating layer on the surface of the base material by impregnating silicon carbide into the base material, and impregnating layer and vapor deposition layer, coating layer and vapor deposition layer, or vapor deposition layer and A roughness layer may be formed on the surface of the porous base material to improve the adhesion property of the base material surface. For example, the roughness layer may be formed such that surface roughness exists on the surface of the base material when the base material is formed, and may be imparted to the surface by treating the surface of the base material with a rough abrasive.

3 is a process chart showing a method for forming a silicon carbide reinforcement layer according to the present invention. First, prepare a porous base material (step S10). As described above, the porous base material may have pores due to the characteristics of the material itself, but a composite material in which pores are intentionally distributed is also possible. The porous base material may first form a roughness layer on the surface before forming the reinforcing layer. An intentional roughness layer may be formed on the surface of the porous base material to facilitate silicon carbide impregnation, or to facilitate formation of a silicon carbide coating layer or vapor deposition layer. In addition, the roughness layer may advantageously form the impregnation layer in the case where the pores are small in the base metal or the connection state of the pores is poor.

Next, to prepare a silicon carbide precursor solution (step S20). The material used as the silicon carbide precursor is not particularly limited, and as the polymer material containing silicon and carbon, for example, polycarbosilane (POLYCARBOSILANE), polyphenylcarbosilane (POLYPHENYLCARBOSILANE), arylphenylcarbosilane (ALLYLPHENYCARBOSILANE) and the like are used. Can be. The solvent used in the silicon carbide precursor solution may be an organic solvent, an inorganic solvent, or the like without particular limitation, and it is preferable to adjust the viscosity of the precursor solution to facilitate the impregnation with respect to the pore size inside the base material.

In the precursor solution preparation step, the silicon carbide powder may be further included as an additive in the silicon carbide precursor according to the type or pore size of the base material. Silicon carbide powder not only enhances the impregnation effect but is also effective in controlling the viscosity of the precursor solution.

Next, the prepared silicon carbide precursor solution is impregnated into the porous base material (step S30). This process will be described with reference to FIG. 4. The silicon carbide precursor solution 112 is contained in the sealed container 100, and the porous base material 110 is immersed in the precursor solution. In the present invention, since the precursor solution cannot be impregnated into the base material only by the conventional deeping, nitrogen gas 120 is supplied to the sealed container so as to apply pressure to the sealed container. Apply pressure to the porous substrate. Through this, the precursor solution may be uniformly impregnated into the base material. Impregnation pressure is controlled in the range of 5 atm ~ 100 atm through the flow regulator 140.

In order to facilitate the impregnation process and to prevent infiltration of impurities, a vacuum pump 170 for maintaining the inside of the container in a vacuum may be connected to the container, and a heater 130 is installed around the container to adjust the temperature of the precursor solution. Maintain higher than room temperature. Through the temperature controller 150, the precursor solution in the vessel is controlled to a temperature of 50 ~ 100 ℃.

Maintaining the precursor solution above room temperature not only facilitates the penetration of the silicon carbide precursor solution into the porous matrix surface, but also facilitates the formation of the silicon carbide coating layer by allowing the silicon carbide precursor to dissolve easily in the solvent and have good dispersibility. . Therefore, the coating layer may be formed on the surface of the base material simultaneously with the formation of the impregnation layer. Alternatively, the impregnation layer may be formed first, and then the coating layer may be subsequently formed while the pressure is removed.

The porous base material impregnated with the silicon carbide precursor solution is taken out of a closed container, dried, and then the solvent of the precursor solution impregnated through heat treatment is removed, and the silicon carbide is sintered to be mixed with the base material inside the base material surface (step S40). Heat treatment of the porous base material is preferably carried out at a temperature of 250 ~ 1500 ℃. In order to remove the solvent from the silicon carbide precursor solution and thermally harden the silicon carbide, the heat treatment temperature must be maintained at 200 ° C. or higher, and the porous base material having a large coefficient of thermal expansion or low melting point is heat-treated at low temperature in an amorphous state to prevent deformation. In addition, the base material having a low coefficient of thermal expansion or high melting point allows the impregnated layer to be uniformly formed in the pore distribution of the base material in a crystalline state at a high temperature. The formed impregnation layer constitutes a layer in which the silicon carbide in the amorphous state (and / or the crystalline state) and the base material component are combined into a mesh structure.

In the case where the silicon carbide coating layer is additionally formed, the heat treatment may be performed simultaneously with the impregnation layer and the coating layer, and after performing the heat treatment on the impregnation layer, the silicon carbide coating layer may be formed and subsequently the heat treatment on the coating layer may be performed.

Finally, the silicon carbide reinforcement layer is formed by vapor deposition on the surface of the porous base material (step S50). The silicon carbide vapor deposition layer is formed on the impregnation layer or the coating layer on the surface of the porous base material by applying high temperature heat together with the raw material source in the vacuum chamber, in which an impregnation layer (and / or coating layer) is formed between the base material and the vapor deposition layer. It acts as a buffer layer to mitigate the change in the coefficient of thermal expansion, and prevents direct contact between the components of the base material and the vapor phase deposition layer is chemically stable.

Example  One

Graphite samples were prepared as the porous base material. The graphite sample had a density of 1.85 g / cm 3, a thermal expansion coefficient of 5.5 × 10 ⁻⁶ / ° C., and a specific resistance of 11.0 μm. A silicon carbide precursor solution was prepared by mixing 20 wt% of polyphenylcarbosilane as a silicon carbide precursor and 10 wt% of silicon carbide powder (size: 20 nm) as an additive, and preparing silicon carbide precursor solution in the apparatus shown in FIG. 4. The precursor solution was impregnated.

In the present embodiment, the precursor solution was impregnated with the base material by heating to the container with a heater for 30 minutes at 10 atm while maintaining the temperature of the precursor solution at 70 ℃. After impregnation, the temperature was raised to 200 ° C. at 3 ° C. per minute and maintained for 2 hours as a drying process, and then gradually cooled. Then, as a heat treatment step, the temperature was raised to 1400 ° C. at 3 ° C. per minute in an Ar atmosphere and maintained for 2 hours, and then gradually cooled.

In order to investigate the relationship between temperature and pressure during the impregnation of the porous base material, the precursor solution at room temperature was dipped for 30 minutes without applying pressure to the surface of the same base material as a comparative example.

A cross-sectional photograph of the base material having been impregnated is shown in FIG. 5. From the base material surface shown in Figure 5 from the base material surface to the inside to check the degree of silicon carbide impregnation according to the impregnation temperature and pressure based on the upper layer (3), the middle portion (2), the deep layer (1). Table 1 shows the contents of the constituent elements.

Comparison of Silicon Carbide Penetration in Graphite (weight%) Element Heating, Pressure Impregnation (Examples) Room temperature, atmospheric impregnation (comparative example) Upper part Mezzanine Deep Upper part Mezzanine Deep C 93.97 95.28 96.27 96.8 96.98 97.58 O 2.65 4.20 3.33 2.91 2.79 2.16 Si 3.38 0.52 0.40 0.29 0.23 0.26 Total 100.00 100.00 100.00 100.00 100.00 100.00

Comparing the impregnation levels of Examples and Comparative Examples from Table 1, when the pressure of 10 atm was applied in the precursor solution at 70 ° C., the silicon content was 10 times higher in the upper layer and 2 times higher in the middle layer than in the comparative example. It can be confirmed that it is twice or more, and from this, it can be seen that the degree of impregnation is much better than when no pressure is applied in a room temperature solution.

Example  2

Graphite samples were prepared as the porous base material. The graphite sample had a density of 1.84 g / cm 3 and a porosity of about 18%. A precursor solution was prepared by mixing 20 wt% of polycarbosilane as a silicon carbide precursor in a solvent, and the silicon carbide precursor solution was impregnated into the base material in the apparatus shown in FIG. 4.

In this example, the precursor solution was impregnated with the base material by heating the container with a heater for 60 minutes at 10 atm while maintaining the temperature of the precursor solution at 70 ° C. In order to investigate the relationship between temperature and pressure during impregnation, the precursor solution at room temperature was dipped for 60 minutes without applying pressure to the surface of the same base material as a comparative example. Each sample was heated to 3 ° C. per minute to 200 ° C. in a drying step, and then cooled slowly, and then gradually cooled to 4 ° C. per minute in an N ₂ atmosphere at 800 ° C. in a heat treatment step, and then slowly cooled.

In order to confirm the silicon carbide impregnation degree according to the impregnation temperature and pressure, the content of each element of the base material at the point 5mm from the surface of the base material was investigated and shown in Table 2.

Comparison of Silicon Carbide Penetration in Graphite (weight%) element Heating, pressure impregnation (example) Room temperature, atmospheric impregnation (comparative example) C 94.27 94.37 O 5.55 5.57 Si 0.18 0.06 Total 100 100

Comparing the impregnation levels of the Examples and Comparative Examples from Table 2, when the pressure of 10 atm in a precursor solution of 70 ℃ is confirmed that the content of silicon is more than three times compared to the Comparative Example, from this pressure in a room temperature solution It can be seen that the degree of impregnation is very excellent than when not added.

6 is a photograph showing a silicon carbide impregnated layer formed on the surface of the porous base material according to Example 2 confirmed that a large amount of silicon is distributed

Next, a silicon carbide vapor deposition layer was formed on the surface of the porous base material by CVD to a thickness of 100 μm. The vapor deposition layer formed was excellent in durability as the reinforcement layer on the surface of the base material together with the impregnation layer, and particles were not generated from graphite as the base material.

It was confirmed from this example that the formation of a uniform and stable impregnation layer greatly influences the interfacial adhesion and durability of the vapor deposition layer that is subsequently formed.

The present invention has been exemplarily described through the preferred embodiments, but the present invention is not limited to such specific embodiments, and various forms within the scope of the technical idea presented in the present invention, specifically, the claims. May be modified, changed, or improved.

Claims (11)

Porous base material with open pores in the mesh structure on the surface and inside,
A silicon carbide impregnating layer formed by penetrating into the base material from the base material surface through the open pores;
A silicon carbide vapor deposition layer formed over the base material surface and in contact with the silicon carbide impregnation layer on the base material surface;
The silicon carbide impregnation layer is formed thicker than the silicon carbide vapor deposition layer, characterized in that
Silicon carbide reinforced porous base material. The silicon carbide-reinforced porous substrate of claim 1, wherein the silicon carbide vapor deposition layer has a thickness in the range of 10 μm to 500 μm. The silicon carbide reinforced porous base material according to claim 1, wherein the silicon carbide impregnated layer has a depth of 0.3 mm or more. The silicon carbide coating layer of claim 1, further comprising a silicon carbide coating layer formed on the surface of the porous base material while forming a boundary with the silicon carbide impregnated layer of the porous base material, wherein the silicon carbide vapor deposition layer is formed on the silicon carbide coating layer. Reinforced porous base material. The silicon carbide reinforced porous base material according to claim 1, wherein the surface of the porous base material has a roughness layer formed thereon. Prepare a porous base material,
Preparing a silicon carbide precursor solution,
The porous base material is immersed in a container containing a silicon carbide precursor solution,
Applying pressure to a container containing the silicon carbide precursor solution to infiltrate the silicon carbide precursor solution into the porous base material surface;
Heat-treating the porous base material impregnated with the silicon carbide precursor solution,
Forming a silicon carbide reinforcement layer by vapor deposition on the surface of the porous base material;
Silicon carbide reinforcement layer forming method. The method of claim 6, wherein the silicon carbide precursor solution is infiltrated into the surface of the porous base material while maintaining the silicon carbide precursor solution at a temperature of 50 to 100 ° C. 7. The method of claim 6, wherein the silicon carbide precursor solution is penetrated into the surface of the porous base material by applying a pressure of 5 atm to 100 in the container containing the silicon carbide precursor solution. The method of claim 6, wherein the heat treatment of the porous base material is silicon carbide reinforcement layer forming method, characterized in that performed at a temperature of 250 ~ 1500 ℃. The method of claim 6, further comprising forming a silicon carbide coating layer on the surface of the porous base material. The method of claim 6, wherein the silicon carbide precursor solution comprises silicon carbide powder as an additive.

Images