KR102606184B1 - Reaction bonded silicon carbide and method of preparing the same - Google Patents

Abstract

The present invention relates to reaction sintered silicon carbide (RBSC), reaction sintered silicon carbide composites, and their manufacturing methods. Compared to reaction sintered silicon carbide manufactured according to a conventional manufacturing method, the structure is dense and cracks are less likely to occur, It relates to reaction-sintered silicon carbide with excellent mechanical properties at high temperatures, composites containing the same, and methods for manufacturing them.

Description

Reaction bonded silicon carbide and method of preparing the same}

The present invention relates to reaction sintered silicon carbide (RBSC), reaction sintered silicon carbide composites, and their manufacturing methods. Compared to reaction sintered silicon carbide manufactured according to a conventional manufacturing method, the structure is dense and cracks are less likely to occur, It relates to reaction-sintered silicon carbide with excellent mechanical properties at high temperatures, composites containing the same, and methods for manufacturing them.

Reaction-Bonded Silicon Carbides (RBSC) generally consists of a mixture of silicon carbide and unreacted residual silicon. This is a method of forming silicon carbide by reacting carbon and silicon at high temperature. During this process, a large amount of unreacted excess silicon is generated, and the high-temperature strength of reaction-sintered silicon carbide containing silicon with a low melting point is rapidly reduced. When reaction sintering silicon carbide is produced by reacting coarse carbon powder and silicon powder at high temperature, unreacted carbon remains inside the coarse carbon powder, reducing strength and oxidation resistance. On the other hand, when fine carbon powder and silicon powder are reacted at high temperature, the density of carbon is too low, and a large amount of unreacted silicon remains, resulting in a significant decrease in high-temperature strength. Therefore, when carbon powder and silicon powder are used as starting materials, a method of reducing the amount of excess silicon by mixing silicon carbide powder together to produce reaction sintered silicon carbide has been generally used. However, reaction-sintered silicon carbide manufactured through the above technology still contains a large amount of excess silicon, and its use has been limited because it is difficult to impregnate complex structures such as fiber-reinforced composite materials with carbon and silicon powder.

To overcome these problems, reaction-sintered silicon carbide was manufactured by producing porous carbon using various polymer raw materials such as phenol and furupryl resin, rather than carbon powder, as the starting material. As a method,

1. Reaction sintering after making porous carbon A typical process for manufacturing silicon carbide is the process of pyrolyzing phenolic resin or pitch at high temperature to create a porous carbon preform and then melting and impregnating silicon.

2. A process of mixing furfuryl resin, a carbon raw material, with a dispersant and a pore-forming material, pyrolyzing them at high temperature to create porous carbon nanoparticles, and then melting and impregnating them with silicon.

3. Process of producing reaction sintered silicon carbide by creating porous carbon through the sol-gel method

etc. have been proposed.

However, the thermal decomposition process of pitch blocks the surface of the pores, making it difficult for molten silicon to penetrate. The phenol resin thermal decomposition process has a problem in that carbon and silicon do not completely react, leaving behind large amounts of unreacted silicon and coke pieces, which are lumps of carbon. When making porous carbon by pyrolyzing furupryl resin, the content of excess silicon and carbon can be greatly reduced by adjusting the appropriate carbon density and particle size.

However, the above pyrolysis process has a very high shrinkage rate during the process of making carbon, so when coated on a fiber-reinforced composite material or base material, the fiber and substrate do not shrink, but the pyrolysis carbon shrinks by about 30 to 50% during the formation process, resulting in carbon It causes crack formation in the preform. In these crack areas, only silicon exists without carbon. Therefore, in the case of reaction-sintered silicon carbide manufactured by the above method, a large amount of silicon or carbon is excessively contained, and strength and high temperature characteristics are deteriorated.

Z. Luo et. al., Influence of Phenolic Resin Impregnation on the Properties of Reaction-Bonded Silicon Carbide, International Journal of Applied Ceramic Technology, 10(3) (2013) 519-526.

The present invention was created to solve the above-mentioned problems, and the object to be solved by the present invention is to provide a method for producing reaction-sintered silicon carbide with a small content of unreacted residual silicon or carbon and a dense structure.

Another task is to provide reaction-sintered silicon carbide manufactured thereby, which has excellent mechanical properties at high temperatures.

In order to solve the above-described problem, the present invention includes the steps of 1) forming a porous carbon nanoparticle structure by chemical vapor deposition (CVD) of a mixed gas containing acetylene (C ₂ H ₂ ) gas on a substrate; and

2) infiltrating and reacting molten silicon (Si) into the porous carbon nanoparticle structure;

The porous carbon nanoparticle structure provides a method of manufacturing reaction sintered silicon carbide (RBSC), characterized in that the volume of closed pores disconnected from the outside is 1% or less compared to the total volume.

The present invention also provides reaction-sintered silicon carbide, which contains silicon (Si) that has penetrated into the pores of the porous carbon nanoparticle structure, and the residual content of the silicon is 10% by weight or less.

The reaction-sintered silicon carbide or its composite produced according to the manufacturing method of the present invention allows molten silicon to penetrate densely into the porous carbon nanoparticle structure, and the carbon nanoparticles have a fine size, so that unreacted residual carbon and Because the amount of silicon is significantly small, mechanical properties at high temperatures are excellent and resistance to oxidation is improved.

In addition, reaction sintering silicon carbide with a dense structure can be manufactured, which has the advantage of further improving mechanical properties by reducing the occurrence of cracks during shrinkage.

Figure 1 is a diagram showing the microstructure of silicon carbide manufactured according to a conventional manufacturing method through a resin pyrolysis process.
Figure 2 is a photograph of the microstructure of a porous carbon nanoparticle structure manufactured through chemical vapor deposition.
Figure 3 is a photograph of the microstructure of a porous carbon nanoparticle structure under different temperature conditions during chemical vapor deposition.
Figure 4 is a photograph of the microstructure of a porous carbon preform manufactured by a conventional process.
Figure 5 is a photograph of the microstructure of a porous carbon preform manufactured by a conventional process.
Figure 6 is a graph showing the distribution of pore sizes of the carbon nanoparticle structure produced when the temperature conditions during chemical vapor deposition are changed in the manufacturing method according to the present invention.
Figure 7 is a dot graph showing the grain size of the carbon nanoparticle structure produced when temperature conditions were changed during chemical vapor deposition in the manufacturing method according to the present invention.
Figure 8 is a dot graph showing the porosity of the carbon nanoparticle structure produced when temperature conditions were changed during chemical vapor deposition in the manufacturing method according to the present invention.
Figure 9 is a photograph of the microstructure of reaction-sintered silicon carbide manufactured by infiltrating and reacting molten silicon into a carbon nanoparticle structure manufactured under different temperature conditions during chemical vapor deposition in the manufacturing method according to the present invention.
Figure 10 shows the results of EDS elemental analysis of the microstructure of reaction-sintered silicon carbide manufactured by infiltrating and reacting molten silicon into a carbon nanoparticle structure manufactured under different temperature conditions during chemical vapor deposition in the manufacturing method according to the present invention. It's a photo.
Figure 11 is a diagram showing residual silicon according to chemical vapor deposition temperature conditions evaluated through image analysis of the microstructure of reaction-sintered silicon carbide manufactured by the manufacturing method according to the present invention.
Figure 12 is an
Figure 13 is an
Figure 14 is a diagram showing the content of residual silicon in reaction-sintered silicon carbide manufactured according to the manufacturing method of the present invention according to temperature conditions during chemical vapor deposition.
Figure 15 is a diagram showing the Vickers hardness of reaction-sintered silicon carbide manufactured according to the manufacturing method of the present invention according to chemical vapor deposition temperature conditions.
Figure 16 is a photograph of the microstructure of a porous carbon support manufactured according to the prior art.

Prior to a detailed description of the present invention, the meaning of terms used in this specification is defined.

In this specification, “closed pores” refer to pores existing in a solid object and in which the gas phase is not connected to the outside.

In this specification, “porous carbon nanoparticle structure” means a structure formed from a collection of carbon nanoparticles, and the structure has a plurality of pores and is therefore porous.

As used herein, “acetylene decomposition inhibitor gas” refers to a gas introduced to suppress the decomposition reaction of acetylene, a precursor for chemical vapor deposition.

As used herein, “excess by mole” means that there is an excess of equivalent weight of one substance between the two reacting substances. That is, when molten silicon is infiltrated into the carbon nanoparticle structure, an excess amount of silicon means that the number of moles of silicon is greater than the number of moles of carbon.

Hereinafter, the configuration and effects of the present invention will be described in more detail.

As described above, when reaction-sintered silicon carbide is manufactured according to the prior art, the particles of the carbon preform are too large and the molten silicon cannot react to the inside of the carbon, resulting in a lot of unreacted carbon remaining, or the pores are small and the molten silicon is There were difficulties in manufacturing a homogeneous silicon carbide material, such as not sufficiently penetrating into the carbon preform, leaving a lot of residual silicon that did not react with carbon, or cracks occurring in the silicon carbide structure during the shrinkage process after sintering.

In order to solve this problem, the present invention includes the following steps: 1) forming a porous carbon nanoparticle structure by chemical vapor deposition (CVD) of a mixed gas containing acetylene (C ₂ H ₂ ) gas on a substrate; and

2) infiltrating and reacting molten silicon (Si) into the porous carbon nanoparticle structure;

The porous carbon nanoparticle structure solves this problem by providing a method for manufacturing reaction sintered silicon carbide (RBSC), which is characterized in that the volume of closed pores disconnected from the outside is less than 1% compared to the total volume.

By using the chemical vapor deposition process, production efficiency can be improved by reducing the conventional two-step process consisting of resin impregnation and thermal decomposition process into a single process. Since chemical vapor deposition is a gas process, it has a more diverse and complex structure. It has the advantage of being easy to apply to shapes.

When chemical vapor deposition is performed using acetylene gas as a precursor for carbon nanoparticles, the particle size of the manufactured carbon preform can be finely controlled in nanoscale, so that it can be formed into a structure of carbon nanoparticles, and the carbon nanoparticle structure can be formed. It has a porous structure with many fine pores on the inside, so when reacted with molten silicon, the molten silicon can penetrate deep into the interior, and the content of residual carbon and silicon can be significantly reduced due to the fine particle size of carbon nanoparticles. there was.

In addition, in the porous carbon nanoparticle structure, the volume of closed pores cut off from the outside is very small, less than 0.1% of the volume of the entire structure, so cracks rarely occur after reaction, and the produced reaction-sintered silicon carbide It was able to have a very dense structure.

The reaction-sintered silicon carbide produced by this method is a silicon carbide with a homogeneous and dense structure with almost no residual silicon, and has the advantage of markedly improved physical properties at high temperatures.

In a preferred embodiment of the present invention, the carbon nanoparticles may have a grain size of 100 nm to 5 μm.

In this way, the crystal grain size of carbon nanoparticles can be controlled by adjusting the conditions of chemical vapor deposition, which is an advantage of the chemical vapor deposition process. When the crystal grain size is less than 100 nm, there is a problem in that the particles become too fine and the internal pores are greatly reduced, preventing molten silicon from penetrating into the interior of the carbon nanoparticle structure. As a result, the content of internal waste pores increases and the content of unreacted residual silicon increases. Therefore, there may be problems such as weakened mechanical properties of the produced reaction-sintered silicon carbide at high temperatures and the occurrence of cracks. Conversely, when the crystal grain size exceeds 5㎛, the size of the carbon particles becomes too large, so residual carbon that cannot react is generated inside each particle, and when the content of residual carbon increases, the strength is weakened. there is. Preferably, the crystal grain size of the carbon nanoparticles may be 100 nm to 500 nm.

In addition, it is desirable that the amount of closed pores is 0.1% or less compared to the volume of the entire porous carbon nanoparticle structure. As the size of closed pores increases, the strength of the reaction sintered silicon carbide produced weakens and cracks may occur, increasing the amount of residual silicon. It can be done.

In the chemical vapor deposition process in step 1), a mixed gas containing acetylene gas is used as a carbon precursor for the porous carbon nanoparticle structure.

The mixed gas may further include propylene, methane, hydrogen gas, etc. in addition to acetylene gas.

In addition, the mixed gas includes, in addition to acetylene gas, an acetylene decomposition-inhibiting gas to control the decomposition reaction rate by suppressing the decomposition reaction of acetylene gas and to control the particle size and porosity of the porous carbon nanoparticle structure formed accordingly. It may contain more.

The acetylene decomposition-inhibiting gas may include hydrogen gas (H ₂ ), and may further include one or more gases selected from hydrocarbon gases represented by the molecular formula 1 below.

[Molecular Formula 1]

C _x H _y

In the molecular formula 1, x≤y and x≤5.

For example, hydrocarbon gases represented by the molecular formula 1 include CH ₄ , C ₃ H ₆ , etc., but are not necessarily limited thereto.

Preferably, the chemical vapor deposition process may be performed under pressure conditions of 10 to 760 torr and temperature conditions of 900 to 1,600°C. When the pressure is less than 10 torr, chemical vapor deposition is performed too slowly, which causes a problem in that deposition efficiency decreases and carbon deposition unevenness due to the flow of gas occurs significantly. Also, on the contrary, if the pressure is too high, exceeding 760 torr, a phenomenon occurs in which the density of carbon becomes excessively low.

In addition, if the temperature condition is less than 900℃, there may be a problem of the carbon structure being formed too densely, and if the temperature condition exceeds 1,600℃, the pore size and porosity of the carbon nanoparticle structure increase and the particles of the carbon nanoparticle When the size is reduced and molten silicon penetrates, penetration may not occur sufficiently and the amount of remaining silicon may increase as it fails to react.

Preferably, chemical vapor deposition in step 1) may be performed at a temperature range of 900 to 1,150 °C.

Step 2) is a step of infiltrating and reacting molten silicon into the prepared porous carbon nanoparticle structure. In this process, the molten silicon reacts with carbon, and the molten silicon penetrates into the pores between the particles of the porous carbon nanoparticle structure. The size of the nanoparticles is sufficiently small that almost no unreacted carbon remains inside. Since silicon can also penetrate sufficiently, unreacted silicon is rarely found at less than 5% of the total weight ratio, forming a dense structure, and producing uniform reaction-sintered silicon carbide as a whole.

In a preferred embodiment of the present invention, the molten silicon infiltrated in step 2) may be in excess on a molar basis with respect to the porous carbon nanoparticle structure. Preferably, molten silicon can be added in an excess amount of 2 times or more compared to the number of moles of the formed carbon nanoparticle structure.

Additionally, the molten silicon penetration and reaction steps may be performed in an inert gas atmosphere. Preferably, it can be performed under an argon gas atmosphere. When carried out in an inert gas atmosphere, oxidation of molten silicon can be prevented and dense reaction sintered silicon carbide can be manufactured.

Additionally, preferably, the penetration and reaction steps of molten silicon may be performed at a temperature range of 1,450 to 1,800°C. If carried out at a temperature of less than 1,450°C, the viscosity of the molten silicon increases so that it does not penetrate well into the pores of the carbon nanoparticle structure, and the structure of the produced reaction sintered silicon carbide is not dense, and if carried out above 1,800°C, there is a problem. There is a problem in that manufacturing costs increase due to unnecessary energy consumption.

The present invention also includes the steps of: 1) forming a porous carbon nanoparticle structure by chemical vapor deposition (CVD) of a mixed gas containing acetylene (C ₂ H ₂ ) gas on a substrate; and

2) Penetrating molten silicon (Si) containing one or more metals selected from the group consisting of zirconium (Zr), titanium (Ti), molybdenum (Mo), and aluminum (Al) into the porous carbon nanoparticle structure. And reacting; including,

The porous carbon nanoparticle structure provides a method of manufacturing a reaction sintered silicon carbide (RBSC) composite, characterized in that the volume of closed pores disconnected from the outside is 1% or less compared to the total volume.

In this case, metals such as zirconium, titanium, or molybdenum added to the molten silicon react with silicon to form a compound or combine with carbon to form carbide to reduce the amount of remaining silicon or to form a reaction sintered silicon carbide. Physical properties can be controlled.

For example, molybdenum can react with silicon to form SiMO ₂ , which can further reduce the content of residual silicon and improve the high-temperature strength of silicon carbide.

Additionally, zirconium or titanium can form carbides of ZrC or TiC, which increases the melting point and improves high-temperature stability.

In a preferred embodiment of the present invention, the molten silicon (Si) may satisfy the following conditional equation 2.

[Conditional expression 2]

In condition equation 2 above, is the sum of weight percentages (wt%) of one or more metals selected from the group consisting of zirconium (Zr), titanium (Ti), molybdenum (Mo), and aluminum (Al) contained in the molten silicon.

If the content of the metal exceeds 50wt%, the content of compounds other than silicon carbide increases in the composite, which may reduce the mechanical properties of high-strength silicon carbide. If the metal content is less than 0.5wt%, the effect of adding it may be reduced. it's tough.

The present invention also provides reaction-sintered silicon carbide, which contains silicon (Si) that has penetrated into the pores of the porous carbon nanoparticle structure, and the residual content of the silicon is 10% by weight or less.

Here, the residual content of silicon refers to the percentage ratio of the weight of the silicon phase present in the reaction-sintered silicon carbide to the total weight of the reaction-sintered silicon carbide.

By having this structure, the reaction-sintered silicon carbide has silicon uniformly distributed within it, and its content is less than 10% by weight, providing excellent mechanical properties such as strength at high temperatures. Preferably, the residual content of silicon may be 5% by weight or less.

In a preferred embodiment of the present invention, in the X-ray diffraction pattern of the reaction-sintered silicon carbide, the peak intensities at diffraction angles of 28 to 30 degrees and 47 to 48 degrees are each independently the peak intensity at 35 to 36 degrees. It may be less than 1/10 of .

Figure 12 is a graph showing the X-ray diffraction pattern of reaction sintered silicon carbide manufactured according to a preferred embodiment of the present invention. ■ is the diffraction peak shown by the β-SiC phase, and ● is the diffraction peak shown by the unreacted residual silicon phase.

Referring to Figure 12, the peaks shown by the residual silicon phase appear at diffraction angles of about 28 to 30° and 47 to 49°, and the peak size is around 35°, which has the strongest intensity among the peaks shown by the β-SiC phase. It can be seen that the intensity is significantly less than 1/10 compared to .

Figure 13 is a graph showing an It can be seen that the strength is also significantly high. In particular, it can be seen that the difference in intensity between the peak of residual silicon that appears at a diffraction angle of 28 to 30 degrees and the peak of β-SiC found at 35 to 36 degrees is significantly less than 20%.

In a preferred embodiment of the present invention, the reaction-sintered silicon carbide may have a volume ratio of closed pores contained within the reaction-sintered silicon carbide and cut off from the outside in a volume ratio of 1% or less compared to the total reaction-sintered silicon carbide volume. Waste pores are the sum of the volumes of all waste pores generated during the manufacturing process, including the volume of waste pores that existed in the original porous carbon nanoparticle structure and the volume of waste pores created by air bubbles caused by insufficient penetration of molten silicon. , the smaller the volume, the better the strength of silicon carbide. More preferably, the volume of the closed pores disconnected from the outside may be 0.5% or less, more preferably 0.1% or less, compared to the total volume of reaction-sintered silicon carbide.

In a preferred embodiment of the present invention, the average size of the residual silicon particles contained in the reaction-sintered silicon carbide may be 1 μm or less. When the residual silicon has an average particle size exceeding 1㎛, when silicon carbide is exposed to high temperature, silicon has a lower melting point than silicon carbide, which causes the physical properties at high temperatures to be weakened.

In a preferred embodiment of the present invention, the reaction-sintered silicon carbide may have a Vickers hardness of 20 to 30 GPa. The present invention has a structure that minimizes the content of residual silicon in silicon carbide, so it can have stronger hardness compared to a silicon carbide structure with a lot of silicon remaining. It is suitable for use in jet engines, gas turbines, etc.

Below, the present invention will be described in more detail through examples. The examples described below do not limit the scope of the present invention, but merely illustrate specific embodiments of the present invention, so it is easy for those skilled in the art to implement it by adding/changing or omitting other components other than the core configuration. And this is included in the technical idea of the present invention.

<Example>

Example 1

A woven fabric of silicon carbide fibers was charged into a vacuum furnace, and then a single gas of C ₂ H ₂ was flowed at a flow rate of 200 sccm for 1 hour at a pressure of 50 torr and a temperature of 1,100°C to prepare a porous carbon nanoparticle structure. .

The microstructure of the porous carbon nanoparticle structure prepared in this way is shown in Figure 3.

Molten silicon was uniformly infiltrated into the porous carbon nanoparticle structure using capillary force. The infiltration process was performed in an Ar gas atmosphere in a vacuum furnace, an excess amount of silicon of about twice the weight was charged, and the material was impregnated at 1600°C for about 30 minutes. Afterwards, the reaction-sintered silicon carbide formed by penetration and reaction of molten silicon was cooled.

Example 2

The same procedure as in Example 1 was carried out, but the temperature conditions during chemical vapor deposition were changed to 1,200°C.

Example 3

The same procedure as in Example 1 was carried out, but the temperature conditions during chemical vapor deposition were changed to 1,300°C.

Example 4

The same procedure as in Example 1 was carried out, but the temperature conditions during chemical vapor deposition were changed to 1,400°C.

Comparative Example 1 - Reaction-sintered silicon carbide using porous carbon support manufactured from coal tar pitch, coal-based synpitch, and petroleum pitch

In an autoclave in a nitrogen atmosphere, a pretreatment step was performed in which the pitch was heat treated at a temperature of 200 to 400°C, and then heated to 500°C in a high-pressure nitrogen atmosphere of 3.5 MPa to form pores. Next, the pore-formed pitch was calcined at 1000°C to prepare a porous carbon support.

Reaction-sintered silicon carbide was produced by impregnating the carbon support prepared in this way with molten silicon. The microstructure of the porous carbon support prepared according to Comparative Example 1 is shown in Figure 16. It is not composed of spherical carbon nanoparticles, but rather has spherical coarse pores formed in the carbon and a network structure containing a large number of closed pores. It was confirmed that it had .

Comparative Example 2 - Reaction-sintered silicon carbide using a porous carbon support prepared from phenolic resin

Specifically, carbon black powder was dispersed in a solvent to produce porous carbon, and then silicon carbide powder was mixed to reduce the content of residual silicon. Afterwards, a binder and plasticizer were added, tape casting was performed, and the binder was removed. Afterwards, porous carbon was manufactured by impregnating it with phenol resin and then going through a carbonization process. Reaction-sintered silicon carbide was manufactured by infiltrating molten silicon into the prepared porous carbon.

The microstructure of the porous carbon support prepared according to Comparative Example 2 is shown in Figure 4. As a result of measurement, the open cell porosity was about 40% by volume, and the amount of residual silicon after manufacturing with reaction sintered silicon carbide was about 20~ It was confirmed that it contained significantly higher residual silicon than the example at 30% by volume.

Comparative Example 3 - Reaction-sintered silicon carbide using a porous carbon support prepared from furfuryl alcohol resin, diethylene, triethylene glycol, and p-toluene sulfonic acid.

Triethylene glycol, which forms pores, and diethylene, a dispersant, were mixed into furfuryl alcohol resin, a carbon raw material, and then cured by adding p-toluene sulfonic acid. A crosslinking process was performed at 60-95°C and then a pyrolysis process was performed at a temperature of 1100°C or lower to prepare a porous carbon preform. Afterwards, reaction-sintered silicon carbide was manufactured by impregnating the molten silicon.

The microstructure of the porous carbon support manufactured according to Comparative Example 3 is shown in Figure 17. The porous carbon support of Comparative Example 3 suffered significant volumetric shrinkage during the manufacturing process, and many cracks were confirmed. Because it is difficult for silicon carbide to form in areas where cracks occur, it was confirmed that it was difficult to obtain reaction-sintered silicon carbide of a quality suitable for the applications for which reaction-sintered silicon carbide is generally used.

<Experimental example>

Experimental Example 1: Microstructure, porosity, and particle size of carbon nanoparticle structure

Photographs of the microstructure of the carbon nanoparticle structures prepared in Examples 1 to 4 and Comparative Examples 1 and 2 are shown in Figures 3 to 5.

Figure 3 is a photograph of the carbon nanoparticle structure of Examples 1 to 4, Figure 4 is a photograph of the microstructure of the carbon nanoparticle structure of Comparative Example 1, and Figure 5 is a photograph of the microstructure of the carbon nanoparticle structure of Comparative Example 2. am.

Referring to Figures 4 and 5, it can be seen that spherical pores are formed in the carbon nanoparticle structure of the comparative example manufactured according to the conventional manufacturing method. In contrast, it was confirmed that the porous carbon nanoparticle structure manufactured according to the example of the present invention shown in Figure 3 had spherical carbon nanoparticles formed and had a more open microstructure.

Additionally, the crystal grain size and porosity of each carbon nanoparticle structure are shown in Table 1 below.

division deposition temperature
(℃) Crystal grain size
(nm) porosity
(%) Example 1 1100 396 51.1 Example 2 1200 220 71.1 Example 3 1300 157 80.5 Example 4 1400 95 84.3 Comparative Example 1 - Network structure 64.8~87 Comparative Example 2 - Depending on carbon black powder size 40~44 Comparative Example 3 - several ㎛ 42.5

As can be seen in Table 1 above, when the chemical vapor deposition temperature is 1100°C, the largest carbon nanoparticle crystal grain size is observed and the porosity is low. It was confirmed that as the temperature of vapor deposition increases, the size and crystal grain size of carbon nanoparticles decreases and the porosity increases. As the crystal grain size increases, the particles become coarser and the content of residual carbon may increase. Additionally, as the porosity increases, the content of residual silicon may increase.

Additionally, Figure 6 is a graph showing the pore size distribution of the porous carbon nanoparticle structures according to Examples 1 to 4. It can be seen that as the temperature of vapor deposition increases, the distribution of large pores increases.

Experimental Example 2: Microstructure of reaction sintered silicon carbide

Photographs of the microstructure of reaction-sintered silicon carbide prepared according to Examples 1 to 4 are shown in FIGS. 9, 10, and 11.

In Figure 9, the black portion of the microstructure represents residual silicon and the bright portion represents silicon carbide. At a deposition temperature of 1100°C, it was confirmed that residual silicon was uniformly distributed throughout the structure and dispersed in the form of small particles.

Figures 10 and 11 are diagrams showing the results of EDS elemental analysis of reaction-sintered silicon carbide manufactured according to each example. It can be seen that the content of residual silicon increases as the temperature of chemical vapor deposition increases.

As the temperature of chemical vapor deposition increases, the distribution of residual silicon increases, and at 1400°C, it has a structure in which silicon carbide crystals are distributed within the silicon phase, so it can be predicted that physical properties at high temperatures will deteriorate.

Experimental Example 2: X-ray diffraction pattern

The content of residual silicon can be predicted from the X-ray diffraction pattern. X-ray diffraction patterns of the reaction-sintered silicon carbide prepared according to Examples 1 and 2 are shown in Figures 12 and 13, respectively.

Comparing Figures 12 and 13, it can be seen that the intensity of the diffraction peak appearing from the silicon phase of the reaction-sintered silicon carbide of Example 1 in which chemical vapor deposition was performed at 1100° C. was very weak. On the contrary, it can be seen that the intensity of the diffraction peak appearing from the silicon phase of the reaction-sintered silicon carbide of Example 2, in which chemical vapor deposition was performed at 1200°C, was significantly stronger than that of Example 1.

Therefore, it can be seen that performing chemical vapor deposition at a temperature of less than 1200°C is advantageous in reducing the content of residual silicon.

Experimental Example 3: Measurement of residual carbon and silicon content

Figure 14 is a graph comparing the content of silicon remaining in reaction-sintered silicon carbide prepared according to Examples 1 to 4.

It can be seen that the content of residual silicon significantly increases when the chemical vapor deposition temperature is 1200℃ compared to 1100℃. Therefore, in order to improve the mechanical properties of reaction sintered silicon carbide, chemical vapor deposition is performed at a temperature below 1200℃. It can be seen that it would be desirable to produce a carbon nanoparticle structure by performing.

Experimental Example 4: Vickers hardness measurement

In addition, Figure 15 is a graph comparing the measured Vickers hardness of reaction sintered silicon carbide manufactured according to Examples 1 to 4.

Each residual silicon content corresponds to Examples 1 to 4 in descending order, and it can be seen that there is a significant difference in Vickers hardness value between Example 1, which was deposited at 1100 ° C., and Example 2, which was deposited at 1200 ° C. I was able to.

Claims (9)

1) Forming a porous carbon nanoparticle structure by chemical vapor deposition (CVD) of a mixed gas containing acetylene (C ₂ H ₂ ) gas on a substrate; and
2) infiltrating and reacting molten silicon (Si) into the porous carbon nanoparticle structure;
A method of producing reaction sintered silicon carbide (RBSC), wherein the porous carbon nanoparticle structure has a volume of closed pores disconnected from the outside compared to the total volume of 1% or less.
According to paragraph 1,
A method of producing reaction sintered silicon carbide, characterized in that the carbon nanoparticles have a grain size of 100 nm to 5 μm.
According to paragraph 1,
The mixed gas further includes an acetylene decomposition inhibitor gas to control the particle size and porosity of the carbon nanoparticle structure by suppressing the decomposition reaction of the acetylene gas.
According to paragraph 3,
The acetylene decomposition-inhibiting gas is a method for producing reaction-sintered silicon carbide, characterized in that it includes at least one gas selected from hydrogen (H ₂ ) gas and a hydrocarbon gas represented by the following molecular formula 1:
[Molecular Formula 1]
C _x H _y
In the molecular formula 1, x≤y and x≤5.
According to paragraph 1,
A method for producing reaction sintered silicon carbide, characterized in that the chemical vapor deposition in step 1) is performed at a pressure range of 10 to 760 torr and a temperature range of 900 to 1,600°C.
1) Forming a porous carbon nanoparticle structure by chemical vapor deposition (CVD) of a mixed gas containing acetylene (C ₂ H ₂ ) gas on a substrate; and
2) infiltrating and reacting molten silicon (Si) containing at least one metal selected from the group consisting of zirconium (Zr), titanium (Ti), and molybdenum (Mo) into the porous carbon nanoparticle structure; Including,
A method for producing a reaction-sintered silicon carbide (RBSC) composite, wherein the porous carbon nanoparticle structure has a volume of closed pores disconnected from the outside of 1% or less compared to the total volume.
Contains silicon (Si) that has penetrated into the pores of the porous carbon nanoparticle structure,
The porous carbon nanoparticle structure is a reaction-sintered silicon carbide, characterized in that the volume of closed pores disconnected from the outside is 1% or less compared to the total volume, and the residual content of silicon is 10% by weight or less.
In clause 7,
In the X-ray diffraction pattern of the reaction-sintered silicon carbide, the intensities of the peaks at diffraction angles of 28 to 30 degrees and 47 to 48 degrees are each independently less than 1/10 of the peak intensity at 35 to 36 degrees. Sintered silicon carbide.
In clause 7,
Reaction-sintered silicon carbide, characterized in that the average size of residual silicon particles contained in the reaction-sintered silicon carbide is 1㎛ or less.