KR101623914B1 - Method for fabrication of high density SiCf/SiC composites with homogeneous microstructure - Google Patents

Abstract

The present invention relates to a method for preparing a silicon carbide fiber-reinforced silicon carbide composite having a uniform microstructure, and more particularly, to a method for manufacturing a silicon carbide fiber-reinforced silicon carbide composite having a uniform microstructure, comprising the steps of: (1) preparing a tubular silicon carbide (SiC) And a step (2) of forming a silicon carbide matrix phase in the preform by supplying the raw material gas to the outer circumferential surface and the inner circumferential surface of the preform while rotating the tubular silicon carbide fiber preform, A process for producing a silicon carbide composite (SiC _f / SiC) is provided. The method for producing a silicon carbide fiber-reinforced silicon carbide composite according to the present invention can produce a high-density composite having improved microstructure uniformity in a short period of time. As compared with the conventional manufacturing method, There is an effect that can be saved. In addition, the composites produced in accordance with the present invention can be used as high strength / high toughness structural materials in gas turbines, aerospace and next generation reactors.

Description

FIELD OF THE INVENTION [0001] The present invention relates to a silicon carbide fiber reinforced silicon carbide (SiCf / SiC) composite having a uniform microstructure,

The present invention relates to a method for producing a silicon carbide fiber-reinforced silicon carbide composite (SiCf / SiC) having a uniform microstructure, more specifically, to a method for producing a silicon carbide fiber- (SiCf / SiC) by depositing a silicon matrix onto a silicon carbide fiber-reinforced silicon carbide composite (SiCf / SiC).

With the demand for higher industrial structure and improved energy efficiency, there is a growing demand for materials that function in extreme environments such as ultra-high temperatures. Ceramics fiber reinforced composites are recognized as key materials in industries such as diesel particulate filters for automobiles, space, aviation, and nuclear power, which maintain high strength, high toughness, corrosion resistance and high reliability characteristics even in extreme environments such as ultra-high temperatures. For fiber-reinforced composites to exhibit superior performance in extreme environments, high-strength heat-resistant ceramics fibers become a basic element, and a method of weaving and densifying such ceramics fibers into desired shapes is needed.

On the other hand, silicon carbide (SiC) is a ceramic material possessing excellent thermal and mechanical properties. Since its discovery by E. G. Acheson in 1891, it has been made into powder using an electrochemical method and a vapor phase chemical vapor deposition (CVD) method.

Silicon carbide fibers were developed by NASA, Textron and Dow Corning in the United States in the mid 1970s to develop Sylamic ™ fibers. In Japan, Nippon Carbon developed ultra low oxygen content NiCalon ™ fibers. Ube modified the precursor polymers A fully crystallized fiber Tyranno ™ was prepared. In particular, Tyranno ™ fiber has a stoichiometric ratio of C / Si of 1.08, which is close to 1, and shows stability in anoxic atmosphere to 1900 ° C and in oxygen atmosphere to 1000 ° C. It is known as a suitable fiber.

However, high density and high mechanical strength are required for application to industrial fields such as space, aviation, and nuclear power, and even if high-density ceramics are produced by using silicon carbide powder, there is a disadvantage that brittle fracture occurs in terms of mechanical strength.

At this time, the silicon carbide fiber reinforced silicon carbide composite (SiC _f / SiC) has an advantage that it can be used in a high temperature and extreme environment due to its excellent thermal and mechanical characteristics. Therefore, it can be used not only as a high temperature material for space use and structural materials for gas turbines, but also as an excellent radiation resistant material as a fourth generation reactor and a structural material of a future fusion reactor.

As a method for producing silicon carbide fiber reinforced silicon carbide composite (SiC _f / SiC), there are chemical vapor infiltration (CVI), polymer impregnation and pyrolysis (PIP), reaction sintering RS: reaction sintering), NITE (nano-infiltrated transient eutectoid), and combinations thereof.

For example, Korean Patent Laid-Open No. 10-2001-0087910 discloses a method for producing a silicon carbide fiber-reinforced silicon carbide composite (SiC _f / SiC) through a method of producing a fiber reinforced chemical vapor deposition silicon carbide base matrix composite, that is, Have been disclosed.

At this time, the chemical vapor deposition method disclosed in the above-mentioned prior patents is advantageous in that SiC having a stoichiometric ratio can be easily obtained because the SiC matrix is deposited between SiC fibers using gas as a starting material at a temperature of about 1000 캜 , It is possible to minimize the damage of the fiber at a high temperature by filling the matrix phase between the SiC fibers and to produce a composite having a high temperature characteristic with a minimum of impurities. However, in order to deposit a SiC matrix in a high density, it is necessary to operate for several tens of hours, residual pores may be present, and manufacturing cost is high. In particular, there is a problem in that it is difficult to deposit into the SiC fiber by deposition of the matrix on the surface of the composite in the deposition on the SiC substrate, and it is difficult to produce a high-density composite when the thickness of the SiC matrix is large .

Therefore, when the SiC matrix is deposited at a high density within a short period of time, improvement of the characteristics of the product and reduction of the manufacturing cost can be expected, and a manufacturing process capable of achieving this is required.

The inventors of the present invention have been studying a method for solving the problems caused by the conventional chemical vapor deposition as described above. The inventors of the present invention have found that, when a tubular silicon carbide fiber preform is rotated and a raw material gas is supplied to the inner circumferential surface and the outer circumferential surface of the preform, A silicon carbide fiber reinforced silicon carbide composite having a uniform microstructure can be produced in a short period of time by depositing a silicon carbide base phase in the interior of the silicon carbide base.

Korean Patent Publication No. 10-2001-0087910

It is an object of the present invention to provide a method for producing a silicon carbide fiber reinforced silicon carbide composite having a uniform microstructure and a silicon carbide fiber reinforced silicon carbide composite produced thereby.

In order to achieve the above object,

Preparing a silicon carbide (SiC) fiber preform in the form of a tube (step 1); And

(Step 2) of forming a silicon carbide matrix phase in the preform by supplying the raw material gas to the outer circumferential surface and the inner circumferential surface of the preform while rotating the tubular silicon carbide fiber preform while rotating the silicon carbide fiber preform; Silicon composite (SiC _f / SiC).

In addition,

A holder for fixing a silicon carbide (SiC) fiber preform in a tubular form;

A raw material gas supply unit which is spaced apart from an inner circumferential surface and an outer circumferential surface of the silicon carbide fiber preform fixed to the holder at a predetermined interval and supplies the gaseous organosilicon compound to the inner circumferential surface and the outer circumferential surface of the silicon carbide fiber preform; And

And a holder rotating part connected to one end of the holder to rotate the holder. The present invention also provides an apparatus for manufacturing a silicon carbide fiber-reinforced silicon carbide composite.

Further,

The present invention provides a silicon carbide fiber reinforced silicon carbide composite produced by a manufacturing method,

Structural materials comprising the silicon carbide fiber-reinforced silicon carbide composites, especially high temperature structural materials for the nuclear reactor, aerospace, defense, and energy industries.

The method for producing a silicon carbide fiber-reinforced silicon carbide composite according to the present invention can produce a high-density composite having improved microstructure uniformity in a short period of time. As compared with the conventional manufacturing method, There is an effect that can be saved. In addition, the composites produced in accordance with the present invention can be used as high strength / high toughness structural materials in gas turbines, aerospace and next generation reactors.

1 is a conceptual view showing a manufacturing apparatus capable of carrying out the manufacturing method according to the present invention;
2 is a photograph showing a cross section of the composite prepared in Example 1 and Comparative Example 1 according to the present invention,
3 is a graph showing the compression compression strength of the composite prepared in Example 1 and Comparative Example 1 according to the present invention.

According to the present invention,

Preparing a silicon carbide (SiC) fiber preform in the form of a tube (step 1); And

(Step 2) of forming a silicon carbide matrix phase in the preform by supplying the raw material gas to the outer circumferential surface and the inner circumferential surface of the preform while rotating the tubular silicon carbide fiber preform while rotating the silicon carbide fiber preform; Silicon composite (SiC _f / SiC).

Hereinafter, the method for producing the silicon carbide fiber-reinforced silicon carbide composite according to the present invention will be described in detail for each step.

In the method for producing a silicon carbide fiber-reinforced silicon carbide composite according to the present invention, step 1 is a step of preparing a silicon carbide (SiC) fiber preform in the form of a tube.

The silicon carbide fiber preform of step 1 is a support of the composite to be produced in the present invention. The silicon carbide fiber preform exhibits porosity and can easily deposit the silicon carbide base.

At this time, the silicon carbide fiber preform of step 1 may be manufactured by directly weaving a fiber made of silicon carbide, preferably by filament winding or braiding silicon carbide fiber. However, the silicon carbide fiber preform is not limited thereto, and the preform can be produced by a conventional method of producing a tube-shaped preform exhibiting porous properties.

The silicon carbide fiber preform in step 1 may be prepared in the form of a tube. The inner diameter of the tubular silicon carbide fiber preform may be 10 to 300 mm, and the inner diameter of the preform may be suitably changed have.

In the method of manufacturing the silicon carbide fiber-reinforced silicon carbide composite according to the present invention, the raw material gas is supplied to the outer circumferential surface and the inner circumferential surface of the preform while rotating the tubular silicon carbide fiber preform, matrix phase.

By forming the silicon carbide base matrix through the step 2, a high density silicon carbide base matrix with a minimized density gradient can be produced and the strength can be improved. Further, when a stress is applied to a silicon carbide matrix and a crack propagates, the interface and the fiber absorb energy and the fracture toughness of the ceramic can be improved. As a result, the brittle fracture defect of the monolith ceramic Can be solved.

On the other hand, in the case of forming a silicon carbide base matrix by a conventional manufacturing method such as chemical vapor deposition, the supply path of the raw material is blocked as the density of the base material is increased due to deposition of the base material into the preform, There has been a problem that necessarily arises. In order to prevent such a problem, a method of performing chemical vapor deposition by supplying a low-concentration raw material at a low temperature as possible has been sought. However, in this case, the process must be performed over several hours, There is a problem that occurs.

At this time, in step 2, the silicon carbide preform is rotated to form a silicon carbide base matrix in the interior of the preform, thereby depositing the silicon carbide base matrix onto the surface of the preform in a time faster than in the prior art, thereby preventing such cost loss, Improvement and a high-density composite can be produced.

Meanwhile, the silicon carbide matrix phase formed in step 2 may be formed in the interior of the preform through chemical vapor deposition.

On the other hand, the chemical vapor deposition, for example,

Supplying an organosilicon compound containing silicon and carbon to the outer circumferential surface and the inner circumferential surface of the preform (step a); And

And forming a silicon carbide matrix phase from the supplied organosilicon compound (step b).

At this time, the organosilicon compound used as the raw material in the step a may be a compound containing silicon and carbon such as methyltrichlorosilane, dimethyltrichlorosilane, ethyltrichlorosilane, However, the raw materials are not limited thereto, and suitable materials capable of forming silicon carbide through chemical vapor deposition can be used.

The chemical vapor deposition may be performed at a temperature of 900 to 1600 占 폚 and a pressure of 1 to 760 torr. If the chemical vapor deposition is carried out at a temperature outside the above-described range, silicon carbide having a non-stoichiometric ratio may be formed, which may cause a decrease in strength and a decrease in high temperature characteristics.

Further, even when the chemical vapor deposition is performed under a condition outside the pressure range, there is a problem that it is difficult to form a phase having a chemical quantitation ratio of 1.

On the other hand, in the case of carrying out the chemical vapor deposition while rotating the preform through the manufacturing method of the present invention, the process time can be shortened, and ultimately, the process cost can be remarkably reduced.

In the step 2 according to the present invention, the silicon carbide fiber preform preferably rotates at a speed of 0.001 to 60 rpm. If the rotational speed of the silicon carbide fiber preform does not satisfy the above range, the density of the composite to be produced may be lowered.

The pyrolytic carbon (PyC), the boron nitride (BN) or the pyrolytic carbon and the silicon carbide are added to the surface of the silicon carbide fiber preform before the silicon carbide matrix phase of the step 2 is formed. Coating,

The pyrolytic carbon and the silicon carbide may be sequentially and repeatedly coated to coat the multi-layered structure layer in which the pyrolytic carbon and the silicon carbide are alternately layered.

The coating layer of pyrolytic carbon (PyC), boron nitride (BN), pyrolytic carbon and silicon carbide can improve the mechanical strength and toughness of the composite to be finally produced.

At this time, the coating layer may be coated on the surface of the preform fiber coated with a thickness of 20 to 1000 nm. If the thickness of the coating layer is less than the above range, brittle fracture may occur. If the thickness exceeds the above range, the strength of the composite decreases.

In addition,

A holder for fixing a silicon carbide (SiC) fiber preform in a tubular form;

A raw material gas supply unit which is spaced apart from an inner circumferential surface and an outer circumferential surface of the silicon carbide fiber preform fixed to the holder at a predetermined interval and supplies the gaseous organosilicon compound to the inner circumferential surface and the outer circumferential surface of the silicon carbide fiber preform; And

And a holder rotating part connected to one end of the holder to rotate the holder. The present invention also provides an apparatus for manufacturing a silicon carbide fiber-reinforced silicon carbide composite.

1 is a schematic view of the manufacturing apparatus, and the manufacturing apparatus will be described in detail with reference to the accompanying drawings.

As shown in Fig. 1, one end of the tubular silicon carbide fiber preform 1 used as a support of the composite is fixed to the holder 2. Fig. The raw material gas supplying units 3 and 4 may be provided at predetermined intervals from the inner circumferential surface and the outer circumferential surface of the preform so as to form a silicon carbide base matrix in the interior of the preform fixed to the holder, Of the organosilicon compound can be deposited inside the preform through the inner and outer circumferential surfaces of the preform. In order to rotate the preform fixed to the holder, a holder rotation part 5 for rotating the holder may be connected to one end of the holder. By rotating the holder through the holder rotation part, the silicon carbide preform fixed to the holder is rotated, and the silicon carbide base matrix phase can be formed on the surface of the preform fiber while rotating the silicon carbide preform.

At this time, the holder rotation part preferably rotates at a speed of 0.001 to 60 rpm. If the holder rotation part rotates at a speed out of the range, there may occur a problem that the density of the composite to be manufactured is lowered due to the reason that the rotation speed of the silicon carbide fiber preform is too slow or too fast.

Further, the present invention provides a silicon carbide fiber-reinforced silicon carbide composite produced by a manufacturing method,

And a structural material comprising the above silicon carbide fiber-reinforced silicon carbide composite.

The silicon carbide fiber-reinforced silicon carbide composite prepared according to the present invention is manufactured by depositing a silicon carbide base matrix on the surface while rotating the preform as described above. As a result, the production time is shortened as compared with the conventional composite, The process cost is low, and for this reason, there is an advantage that it can be supplied at low cost in the market. In addition, there is an advantage in that the composite is manufactured at a higher density than the conventional composite, and the mechanical strength is further improved.

On the other hand, stability in high temperature, excellent radiation resistance and excellent mechanical strength are required in the field of nuclear reactors, particularly in the field of structural materials constituting reactors. At this time, the structural material including the silicon carbide fiber-reinforced silicon carbide composite can satisfy all of the high temperature stability, excellent radiation resistance and excellent mechanical strength required in the core structural material field of a nuclear reactor.

Furthermore, the structural material can be used as a high temperature structural material in aerospace, defense, energy industries, etc., as well as core structural materials of nuclear reactors.

Hereinafter, the present invention will be described in more detail with reference to the following examples. It should be noted, however, that the following examples are illustrative of the invention and are not intended to limit the scope of the invention.

Example 1 Production of silicon carbide fiber-reinforced silicon carbide composite (SiC _f / SiC) 1

Step 1: Silicon carbide (SiC) fibers were wound by filament winding in two layers at an interfiber angle of 55 degrees to produce a tubular silicon carbide fiber preform having an inner diameter of 10 mm.

Step 2: One end of the silicon carbide fiber preform produced in the step 1 was fixed to a holder of the apparatus shown in Fig. 1, and the silicon carbide fiber preform was rotated at a speed of 0.5 rpm, and the raw material gas was introduced into the inner circumferential surface and the outer circumferential surface of the preform, And the silicon carbide phase was deposited inside the preform.

At this time, the silicon carbide matrix phase was supplied to the inner and outer surfaces of the preform for 2.5 hours at a temperature of 1000 ° C and a pressure of 10 torr using methyltrichlorosilane (MTS, CH ₃ SiCl ₃ ) as a raw material, (SiCf / SiC) composites were prepared by the deposition method.

Example 2 Production of silicon carbide fiber-reinforced silicon carbide composite (SiC _f / SiC) 2

In Example 1, except that pyrolytic carbon (PyC) was formed to a thickness of 200 nm on the inner circumferential surface and the outer circumferential surface of the preform at a temperature of 1100 캜 before the silicon carbide matrix phase of the step 2 was deposited, 1 to prepare a silicon carbide fiber-reinforced silicon carbide composite (SiC _f / SiC).

≪ Comparative Example 1 &

Except that the silicon carbide fiber preform in Step 2 was not rotated and the raw material was supplied to the inner and outer circumferential surfaces for 2.5 hours to perform the chemical vapor deposition to deposit the silicon carbide base phase in the preform , A silicon carbide fiber reinforced silicon carbide composite (SiC _f / SiC) was produced in the same manner as in Example 2.

<Experimental Example 1> Measurement of density of composite

The density of the silicon carbide fiber-reinforced silicon carbide composites prepared in the above Examples and Comparative Examples was measured by the Archimedes method.

The composite of Comparative Example 1 prepared by performing the chemical vapor deposition without rotating the silicon carbide fiber preform was measured to have a density of about 1.78 g / cm ³ .

On the other hand, when the preform is rotated and the silicon carbide phase is deposited in the second embodiment according to the present invention, the density of the composite is about 5 to 10% as compared with Comparative Example 1 in which the matrix is deposited without rotation, Or more.

&Lt; Experimental Example 2 >

In order to analyze the cross-section of the composite of Example 2 and Comparative Example 1, cross sections cut in the longitudinal direction of the composite were observed using micro-CT (Computed Tomography), which is a non-destructive method, and the results are shown in FIG.

As shown in Fig. 2, the composite of Example 2 in which the silicon carbide fiber preform is rotated and the matrix phase is deposited shows that the cut surfaces (a and b sides) at positions opposite to each other have high homogeneity,

The composite cross section of Comparative Example 1 shows that the homogeneity of the cross section is relatively low despite the fact that the preform is not rotated and the chemical vapor deposition is performed for a long time.

From the above analysis results, it can be seen that a high-density composite having excellent homogeneity can be produced through the production method of the present invention.

Experimental Example 3: Compressive Strength Analysis of Composite

In order to analyze the mechanical properties of the composite of Example 2 and Comparative Example 1, the compression strength of the composite was analyzed through a universal testing machine, and the results are shown in FIG.

As shown in Fig. 3, the composite of Example 2 and Comparative Example 1 showed a load-displacement curve showing the fracture behavior of the fiber-reinforced composite. At this time, the composite prepared in Example 2 of the present invention showed a compression compression strength value of 374 MPa, while the composite of Comparative Example 1 showed a compression compression strength value of 258 MPa, from which the composite prepared according to the present invention Can exhibit a higher strength characteristic than the composite in the prior art.

1: Silicon carbide preform
2: holder
3, 4: Feed gas supply unit
5:

Claims (13)

Preparing a silicon carbide (SiC) fiber preform in the form of a tube (step 1); And
(Step 2) of forming a silicon carbide matrix phase in the preform by supplying the raw material gas to the outer circumferential surface and the inner circumferential surface of the preform while rotating the tubular silicon carbide fiber preform while rotating the silicon carbide fiber preform; Silicon composite (SiC _f / SiC).
2. The method of claim 1, wherein the silicon carbide fiber preform of step 1 is fabricated by filament winding or braiding silicon carbide fibers.
2. The method of claim 1, wherein the silicon carbide matrix phase of step 2 is formed through chemical vapor deposition.
4. The method of claim 3, wherein the chemical vapor deposition comprises:
Supplying an organosilicon compound containing silicon and carbon to the outer circumferential surface and the inner circumferential surface of the preform (step a); And
And forming a silicon carbide matrix phase from the supplied organosilicon compound (step b). &Lt; RTI ID = 0.0 &gt; 11. &lt; / RTI &gt;
The method of claim 4, wherein the organosilicon compound is at least one selected from the group consisting of methyltrichlorosilane, dimethyltrichlorosilane, and ethyltrichlorosilane. Method of manufacturing fiber reinforced silicon carbide composites.
4. The method of claim 3, wherein the chemical vapor deposition is performed at a temperature of 900 to 1600 DEG C and a pressure of 1 to 760 torr.
The method of claim 1, wherein the silicon carbide fiber preform rotates at a speed of 0.001 to 60 rpm.
The method of claim 1, wherein the pyrolytic carbon (PyC) is added to the surface of the silicon carbide fiber preform before forming the silicon carbide matrix phase of step 2; Boron nitride (BN); Or a combination of pyrolytic carbon and silicon carbide on the surface of the silicon carbide fiber-reinforced silicon carbide composite.
The method according to claim 8, wherein the coating of the pyrolytic carbon and the silicon carbide is performed by sequentially coating the pyrolytic carbon and the silicon carbide repeatedly to coat the multilayered structure layer in which the pyrolytic carbon and the silicon carbide are alternately layered. Method of manufacturing fiber reinforced silicon carbide composites.
9. The method of claim 8, wherein the coating is performed at a thickness of 50 to 1000 nm.
A holder for fixing a silicon carbide (SiC) fiber preform in a tubular form;
A raw material gas supply unit which is spaced apart from an inner circumferential surface and an outer circumferential surface of the silicon carbide fiber preform fixed to the holder at a predetermined interval and supplies the gaseous organosilicon compound to the inner circumferential surface and the outer circumferential surface of the silicon carbide fiber preform; And
And a holder rotating part connected to one end of the holder to rotate the holder.
A silicon carbide fiber reinforced silicon carbide composite produced by the manufacturing method of claim 1.
A structural material comprising the silicon carbide fiber-reinforced silicon carbide composite of claim 12.

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