KR20230026739A - Reaction bonded silicon carbide and method of preparing the same - Google Patents

Abstract

The present invention relates to reaction bonded silicon carbide (RBSC), a reaction bonded silicon carbide composite, and a manufacturing method thereof, and to reaction bonded silicon carbide which has a denser structure, less cracking, and excellent mechanical properties at high temperatures than reaction bonded silicon carbide prepared by a conventional manufacturing method, a composite including the same, and a method for preparing the same.

Description

Reaction bonded silicon carbide and method of preparing the same {Reaction bonded silicon carbide and method of preparing the same}

The present invention relates to reaction sintered silicon carbide (RBSC), a reaction sintered silicon carbide composite, and a method for producing the same, which has a denser structure and less cracking than reaction sintered silicon carbide prepared according to a conventional method, It relates to reaction-sintered silicon carbide having excellent mechanical properties at high temperatures, a composite including the same, and a method for preparing the same.

Reaction-bonded silicon carbides (RBSC) are generally composed of a mixture of silicon carbide and unreacted residual silicon. As a method of forming silicon carbide by reacting carbon and silicon at a high temperature, a large amount of unreacted silicon carbide is generated in this process, and the high-temperature strength of reaction-sintered silicon carbide containing low-melting-point silicon is rapidly reduced. In the case of producing reaction-sintered silicon carbide 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 a 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 prepare reaction-sintered silicon carbide has been generally used. However, the reaction-sintered silicon carbide produced through the above technology still contains a large amount of excess silicon, and its application is limited because it is difficult to impregnate carbon and silicon powder into complex structures such as fiber-reinforced composite materials.

In order to overcome these problems, reaction-sintered silicon carbide was prepared by preparing porous carbon using various polymer raw materials such as phenol and furupril resin, rather than carbon powder, as a starting material. As a way,

1. Reaction sintering after making porous carbon A representative process for producing silicon carbide is a process of melting and impregnating silicon after making porous carbon preforms by thermally decomposing phenolic resin or pitch at high temperature.

2. A process of melting and impregnating silicon after mixing furfuryl resin, a dispersant, and a pore-forming material, which are carbon raw materials, to create porous carbon nanoparticles by high-temperature thermal decomposition

3. Process of producing reactive sintered silicon carbide by making porous carbon through a sol-gel method

etc. have been suggested.

However, the pyrolysis process of the pitch blocks the surface of the pores, making it difficult for the molten silicon to penetrate. In the phenol resin pyrolysis process, carbon and silicon are not completely reacted, so there is a problem in that a large amount of unreacted silicon and coke pieces, which are lumps of carbon, remain. When furupril resin is pyrolyzed to produce porous carbon, the content of excess silicon and carbon can be greatly reduced by properly adjusting the density and particle size of carbon.

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, Causing crack formation in the preform. In these cracks, only silicon exists without carbon. Therefore, in the case of the reaction-sintered silicon carbide prepared by the above method, a large amount of silicon or carbon is included in an excessive amount, and thus strength, high-temperature characteristics, and the like 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 has been made to solve the above problems, and an object to be solved by the present invention is to provide a method for producing reaction-sintered silicon carbide having a small content of unreacted residual silicon or carbon and having a dense structure.

Another object is to provide a reaction-sintered silicon carbide having excellent mechanical properties at high temperatures as produced thereby.

In order to solve the above problems, the present invention 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 for producing reaction sintered silicon carbide (RBSC), characterized in that the volume of closed pores isolated from the outside is 1% or less relative to the total volume.

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

In the reaction-sintered silicon carbide or composite produced according to the manufacturing method of the present invention, molten silicon can penetrate densely into the porous carbon nanoparticle structure, and the size of the carbon nanoparticle is fine, so that unreacted residual carbon and The significantly reduced amount of silicon results in excellent mechanical properties at high temperatures and improved resistance to oxidation.

In addition, since reaction sintered silicon carbide having a dense structure can be manufactured, there is an advantage in that mechanical properties are further improved due to less occurrence of cracks during shrinkage.

1 is a view showing the microstructure of silicon carbide manufactured according to a conventional manufacturing method through a resin pyrolysis process.
2 is a photograph of the microstructure of a porous carbon nanoparticle structure prepared through chemical vapor deposition.
3 is a photograph of the microstructure of a porous carbon nanoparticle structure under different temperature conditions during chemical vapor deposition.
4 is a photograph of the microstructure of a porous carbon preform manufactured by a conventional process.
5 is a photograph of the microstructure of a porous carbon preform manufactured by a conventional process.
6 is a graph showing the distribution of pore sizes of the carbon nanoparticle structures produced when the temperature conditions are changed during chemical vapor deposition in the manufacturing method according to the present invention.
7 is a dot graph showing the grain size of the carbon nanoparticle structure produced when the temperature conditions are changed during chemical vapor deposition in the manufacturing method according to the present invention.
8 is a dot graph showing the porosity of carbon nanoparticle structures produced when temperature conditions are varied during chemical vapor deposition in the manufacturing method according to the present invention.
9 is a photograph of a microstructure of reaction-sintered silicon carbide prepared 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.
10 is an EDS elemental analysis result of the microstructure of reaction-sintered silicon carbide prepared 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 is a picture.
11 is a diagram showing residual silicon according to chemical vapor deposition temperature conditions evaluated by image analysis of the microstructure of reaction-sintered silicon carbide manufactured by the manufacturing method according to the present invention.
12 is an X-ray diffraction pattern of reaction-sintered silicon carbide prepared according to a manufacturing method according to a preferred embodiment of the present invention, and displays diffraction peaks represented by a phase of residual silicon and a phase of silicon carbide.
13 is an X-ray diffraction pattern of reaction-sintered silicon carbide prepared according to a manufacturing method according to another embodiment of the present invention, and displays diffraction peaks represented by a phase of residual silicon and a phase of silicon carbide.
14 is a view showing the content of residual silicon in reaction-sintered silicon carbide prepared according to the manufacturing method of the present invention according to temperature conditions during chemical vapor deposition.
15 is a view showing the Vicker's hardness of reaction-sintered silicon carbide prepared according to the production method of the present invention according to chemical vapor deposition temperature conditions.
16 is a photograph of the microstructure of a porous carbon support prepared according to the prior art.

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

In the present specification, "closed pores" are pores existing in a solid-phase object and refer to pores in which the gas phase is not connected to the outside.

In the present specification, a "porous carbon nanoparticle structure" is a structure formed of an aggregate of carbon nanoparticles, and means that the structure is porous because it has a plurality of pores.

In the present specification, "acetylene decomposition inhibitory gas" means a gas introduced to suppress the decomposition reaction of acetylene, which is a precursor of chemical vapor deposition.

In this specification, "excess by mole" means that one substance exceeds the equivalent weight between two reacting substances. That is, when molten silicon is infiltrated into the carbon nanoparticle structure, an excess 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, in the case of manufacturing reaction-sintered silicon carbide according to the prior art, the particles of the carbon preform are too large, so the molten silicon cannot react to the inside of the carbon, leaving a large amount of unreacted carbon, or the pores are small, so that the molten silicon There were difficulties in manufacturing a homogeneous silicon carbide material, such as not sufficiently penetrating into the carbon preform, leaving a large amount of residual silicon that did not react with carbon, or cracking the silicon carbide structure during shrinkage after sintering.

In order to solve these problems, the present invention 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 producing reaction sintered silicon carbide (RBSC), characterized in that the volume of closed pores isolated from the outside is 1% or less relative to the total volume.

By using the chemical vapor deposition process, it is possible to improve production efficiency by reducing the conventional two-step process consisting of resin impregnation and pyrolysis process into a single process, and since chemical vapor deposition is a gas process, more diverse and complex structures It also has the advantage of being easy to apply to the shape.

When chemical vapor deposition is performed using acetylene gas as a precursor of carbon nanoparticles, the particle size of the prepared carbon preform can be finely controlled in nano units to form a structure of carbon nanoparticles, and the carbon nanoparticle structure has a porous structure with many fine pores inside, so that when reacting with molten silicon, molten silicon can penetrate deep into the inside, 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, the porous carbon nanoparticle structure has a very small volume of 0.1% or less of the volume of the entire structure, so that cracks hardly occur after the reaction, and the prepared reaction-sintered silicon carbide could have a very dense structure.

The reaction-sintered silicon carbide prepared by this method is silicon carbide having a homogeneous and dense structure with almost no residual silicon, and has the advantage of significantly improving 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.

As such, the crystal grain size of the carbon nanoparticles can be controlled by adjusting the chemical vapor deposition conditions, 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 molten silicon does not penetrate into the inside of the carbon nanoparticle structure because the internal pores are greatly reduced because the particles are too fine. As a result, the content of internal closed pores increases and the content of unreacted residual silicon increases. Therefore, there may be problems such as weakening of the mechanical properties of the prepared reaction-sintered silicon carbide at high temperatures and generation of cracks. Conversely, when the crystal grain size exceeds 5 μm, the size of the carbon particles becomes excessively large, so residual carbon that does not react is generated inside each particle, and when the content of the 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, the closed pores are preferably 0.1% or less of the volume of the entire porous carbon nanoparticle structure, and as the size of the closed pores increases, the strength of the prepared reaction-sintered silicon carbide weakens and cracks may occur, increasing the amount of residual silicon. can be made

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.

In addition to acetylene gas, the mixed gas may further include propylene, methane, hydrogen gas, and the like.

In addition to acetylene gas, in the mixed gas, in order 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, an acetylene decomposition inhibitory gas is added to the mixed gas. may contain more.

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

[Molecular formula 1]

C _x H _y

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

For example, the hydrocarbon gas represented by the molecular formula 1 includes CH ₄ , C ₃ H ₆ , and the like, but is 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, there is a problem in that chemical vapor deposition is performed too slowly, resulting in low deposition efficiency and large non-uniformity of carbon deposition according to gas flow. In addition, conversely, when the pressure is too high, exceeding 760 torr, a phenomenon in which the density of carbon is excessively lowered occurs.

In addition, when the temperature condition is less than 900 ° C, there may be a problem in that the carbon structure is formed too densely, and when the temperature condition exceeds 1,600 ° C, the pore size and porosity of the carbon nanoparticle structure increase and the particle of the carbon nanoparticle When the size is reduced and molten silicon penetrates, the amount of residual silicon remaining without reaction may increase due to insufficient penetration.

Preferably, the 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. Since silicon is also sufficiently permeable, unreacted silicon is hardly found at 5% or less of the total weight ratio, forms a dense structure, and can produce uniform reaction-sintered silicon carbide as a whole.

In a preferred embodiment of the present invention, the amount of molten silicon permeated in step 2) may be in excess based on the number of moles relative to the porous carbon nanoparticle structure. Preferably, the molten silicon may be added in an excess of 2 times or more relative to the number of moles of the formed carbon nanoparticle structure.

In addition, the step of infiltrating and reacting molten silicon may proceed in an inert gas atmosphere. Preferably, it can be carried out under an argon gas atmosphere. When proceeding in an inert gas atmosphere, oxidation of molten silicon can be prevented to produce dense reaction-sintered silicon carbide.

Also, preferably, the step of infiltrating and reacting molten silicon may be performed in a temperature range of 1,450 to 1,800 °C. When performed 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 prepared reaction-sintered silicon carbide is not dense. There is a problem in that manufacturing costs increase due to unnecessary energy consumption.

The present invention also includes: 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 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 for producing a reaction sintered silicon carbide (RBSC) composite, characterized in that the volume of closed pores isolated from the outside is 1% or less relative to the total volume.

In this case, a metal such as zirconium, titanium or molybdenum added into the molten silicon reacts with silicon to form a compound or a compound with carbon to form carbide, thereby reducing the amount of residual silicon or reducing the amount of reaction-sintered silicon carbide. properties can be controlled.

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

In addition, zirconium or titanium may form a carbide of ZrC or TiC to increase the melting point and improve high-temperature stability.

In a preferred embodiment of the present invention, the molten silicon (Si) may satisfy Conditional Expression 2 below.

[conditional expression 2]

은 상기 용융 규소 내 포함된 지르코늄(Zr), 티타늄(Ti) 및 몰리브데넘(Mo) 및 알루미늄(Al)으로 이루어진 군에서 선택된 하나 이상의 금속의 중량백분율(wt%)의 합이다.In the above conditional expression 2,

is the sum of weight percentages (wt%) of at least one metal selected from the group consisting of zirconium (Zr), titanium (Ti), molybdenum (Mo), and aluminum (Al) included in the molten silicon.

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

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

Here, the residual content of silicon means 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 such a structure, silicon is uniformly distributed in the reaction-sintered silicon carbide, and its content is less than 10% by weight, so that the reaction-sintered silicon carbide has 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, peak intensities at diffraction angles of 28 to 30 degrees and 47 to 48 degrees are independently peak intensities at 35 to 36 degrees. It may be less than 1/10 of

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

Referring to FIG. 12, peaks represented by the residual silicon phase appear at diffraction angles of about 28 to 30 degrees and 47 to 49 degrees, and the size of the peak is a peak near 35 degrees having the strongest intensity among peaks represented by the β-SiC phase. It can be seen that the strength is significantly smaller than 1/10 compared to

13 is a graph showing an X-ray diffraction pattern for reaction-sintered silicon carbide having a higher content of residual silicon. Referring to FIG. 13, more peaks represented by unreacted residual silicon are observed, and the number of peaks It can be seen that the strength is also remarkably high. In particular, it can be seen that the difference in intensity between the peak of residual silicon at a diffraction angle of 28 to 30 degrees and the peak of β-SiC found at a diffraction angle of 35 to 36 degrees is significantly less than 20%.

In a preferred embodiment of the present invention, the reaction-sintered silicon carbide is contained inside the closed pores and is isolated from the outside, the volume ratio to the total reaction-sintered silicon carbide volume may be 1% or less. The closed pores are the sum of the volumes of all closed pores generated during the manufacturing process, such as the volume of closed pores existing in the original porous carbon nanoparticle structure during the manufacturing process and the volume of closed pores generated due to bubbles generated due to insufficient penetration of molten silicon. , the smaller the volume, the better the strength of silicon carbide. More preferably, the volume ratio of the closed pores disconnected from the outside may be 0.5% or less, more preferably 0.1% or less, relative to the total volume of the reaction-sintered silicon carbide.

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

In a preferred embodiment of the present invention, the reaction-sintered silicon carbide may have a Vicker's Hardness of 20 to 30 GPa. The present invention has a structure in which the content of residual silicon in silicon carbide is minimized, so that it can have stronger hardness than a silicon carbide structure in which a large amount of silicon remains. It is suitable for use in jet engines, gas turbines, and the like.

Hereinafter, the present invention will be described in more detail through examples. Since the embodiments described below do not limit the scope of the present invention and merely illustrate specific embodiments of the present invention, it is easy for those skilled in the art to implement by adding/changing and omitting other components in addition to the core components. And, which is included in the technical spirit of the present invention.

<Example>

Example 1

A woven fabric of silicon carbide fibers was loaded 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. A porous carbon nanoparticle structure was prepared. .

The microstructure of the porous carbon nanoparticle structure thus prepared is shown in FIG. 3 .

Molten silicon was uniformly penetrated into the porous carbon nanoparticle structure by capillary force. The infiltration process was carried out in an Ar gas atmosphere in a vacuum furnace, an excess of silicon of about twice the weight was charged, and impregnation was performed for about 30 minutes while maintaining 1600 ° C. Thereafter, the reaction-sintered silicon carbide formed by infiltrating and reacting with the molten silicon was cooled.

Example 2

It was carried out in the same manner as in Example 1, but the temperature condition during chemical vapor deposition was changed to 1,200 ° C.

Example 3

It was carried out in the same manner as in Example 1, but the temperature condition was changed to 1,300 ° C. during chemical vapor deposition.

Example 4

It was carried out in the same manner as in Example 1, but the temperature condition was changed to 1,400 ° C. during chemical vapor deposition.

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

In an autoclave in a nitrogen atmosphere, a pretreatment step of heat-treating the pitch at a temperature of 200 to 400 ° C was performed, and a step of forming pores by heating to 500 ° C in a high-pressure nitrogen atmosphere of 3.5 MPa was performed. Then, the pore-formed pitch was calcined at 1000° C. to prepare a porous carbon support.

The thus-prepared carbon support was impregnated with molten silicon to prepare reaction-sintered silicon carbide. The microstructure of the porous carbon support prepared according to Comparative Example 1 is shown in FIG. 16, and is not composed of spherical carbon nanoparticles, but has spherical coarse pores formed in carbon and a network structure including a large number of closed pores. It was confirmed that it has

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

Specifically, after carbon black powder was dispersed in a solvent to prepare porous carbon, silicon carbide powder was mixed together to reduce the content of residual silicon. Thereafter, tape casting was performed after adding a binder and a plasticizer, and the binder was removed. Thereafter, porous carbon was prepared through a carbonization process after impregnation with a phenolic resin. Reaction-sintered silicon carbide was prepared 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 FIG. 4, and as a result of the measurement, the open cell porosity was about 40% by volume, and the amount of residual silicon after making reaction-sintered silicon carbide was about 20~ As 30% by volume, it was confirmed that a remarkably high residual silicon was included compared to the examples.

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

After incorporating triethylene glycol, which forms pores in furfuryl alcohol resin, which is a carbon source, and diethylene, which is a dispersant, p-toluene sulfonic acid was added to cure it. After performing a crosslinking process at 60-95°C, a pyrolysis process was performed at a temperature of 1100°C or lower to prepare a porous carbon preform. Thereafter, molten silicon was impregnated to prepare reaction-sintered silicon carbide.

The microstructure of the porous carbon support prepared according to Comparative Example 3 is shown in FIG. 17, and in the porous carbon support prepared in Comparative Example 3, a lot of volumetric shrinkage occurred and a number of cracks were confirmed during the manufacturing process. Since silicon carbide is difficult to form in cracks, it was confirmed that it is difficult to obtain reaction-sintered silicon carbide of a quality suitable for applications where reaction-sintered silicon carbide is generally used.

<Experimental example>

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

3 to 5 show photographs of microstructures of the carbon nanoparticle structures prepared in Examples 1 to 4 and Comparative Examples 1 and 2.

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

Referring to FIGS. 4 and 5 , it can be seen that spherical pores are formed in the carbon nanoparticle structure of Comparative Example prepared according to the conventional manufacturing method. In contrast, the porous carbon nanoparticle structure prepared according to the embodiment of the present invention shown in FIG. 3 was confirmed to have spherical carbon nanoparticles and a more open microstructure.

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

division deposition temperature
(℃) 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 - Carbon black powder size dependent 40 to 44 Comparative Example 3 - several μm 42.5

As can be seen from Table 1, it can be seen that when the chemical vapor deposition temperature is 1100° C., the crystal grain size of the carbon nanoparticles is the largest and the porosity is low. It was confirmed that as the vapor deposition temperature increased, the size and crystal grain size of the carbon nanoparticles decreased and the porosity increased. As the crystal grain size increases, the particles become coarser and the content of residual carbon may increase. In addition, as the porosity increases, the content of residual silicon may increase.

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 the distribution of large-sized pores increases as the vapor deposition temperature increases.

Experimental Example 2: Microstructure of reaction-sintered silicon carbide

9, 10 and 11 show photographs of microstructures of reaction-sintered silicon carbide prepared according to Examples 1 to 4.

In Fig. 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 the residual silicon was uniformly distributed throughout the structure and dispersed in the form of small particles.

10 and 11 are views showing the results of EDS elemental analysis of reaction-sintered silicon carbide prepared according to each example, and it can be seen that the content of residual silicon increases as the chemical vapor deposition temperature 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 in the silicon phase, so it can be predicted that the 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 FIGS. 12 and 13, respectively.

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

Therefore, it can be seen that performing the 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 content of residual carbon and silicon

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

It can be confirmed that the content of residual silicon increases significantly at 1200 ° C compared to when the chemical vapor deposition temperature is 1100 ° C. It can be seen that it would be preferable to prepare a carbon nanoparticle structure by carrying out.

Experimental Example 4: Vickers Hardness Measurement

15 is a graph comparing the measured Vickers hardness of reaction-sintered silicon carbide prepared 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 a significant difference in Vickers hardness value between Example 1 deposited at 1100 ° C and Example 2 deposited at 1200 ° C appears. could

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;
The porous carbon nanoparticle structure is a method for producing reaction sintered silicon carbide (RBSC), characterized in that the volume of closed pores isolated from the outside is 1% or less relative to the total volume.
According to claim 1,
The method for producing reaction-sintered silicon carbide, characterized in that the carbon nanoparticles have a grain size of 100 nm to 5 μm.
According to claim 1,
The method for producing reaction-sintered silicon carbide, characterized in that the mixed gas further comprises an acetylene decomposition inhibitory gas to control the particle size and porosity of the carbon nanoparticle structure by suppressing the decomposition reaction of acetylene gas.
According to claim 3,
The acetylene decomposition inhibiting gas is a method for producing reaction-sintered silicon carbide, characterized in that it comprises at least one gas selected from hydrogen (H ₂ ) gas and hydrocarbon gas represented by the following molecular formula 1:
[Molecular Formula 1]
C _x H _y
In the above molecular formula 1, x≤y and x≤5.
According to claim 1,
Chemical vapor deposition in step 1) is a method for producing reactive sintered silicon carbide, characterized in that carried out in a pressure range of 10 ~ 760 torr and a temperature range of 900 ~ 1,600 ℃.
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 one or more metals selected from the group consisting of zirconium (Zr), titanium (Ti) and molybdenum (Mo) into the porous carbon nanoparticle structure; Including,
The method for producing a reaction sintered silicon carbide (RBSC) composite, characterized in that the porous carbon nanoparticle structure has a volume of closed pores disconnected from the outside of 1% or less relative to the total volume.
A reaction-sintered silicon carbide comprising silicon (Si) penetrated into pores of a porous carbon nanoparticle structure, wherein the residual content of silicon is 10% by weight or less.
According to claim 7,
In the X-ray diffraction pattern of the reaction-sintered silicon carbide, the intensity of the peaks at diffraction angles of 28 to 30 degrees and 47 to 48 degrees is each independently less than 1/10 of the peak intensity at 35 to 36 degrees. sintered silicon carbide.
According to claim 7,
Reaction-sintered silicon carbide, characterized in that the average size of the residual silicon particles included in the reaction-sintered silicon carbide is 1 μm or less.

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