Graphitized carbon fiber cloth

Abstract

The invention relates to graphitized carbon fiber cloth, and belongs to the technical field of silicon carbide preparation. The graphitized carbon fiber cloth comprises a base body and carbon fiber bundles in the base body, the base body is tar pitch, the carbon fiber bundles are graphitized carbon fiber bundles, and the graphitized carbon fiber bundles are arranged in the tar pitch base body in parallel. The included angle phi between the graphitized carbon fiber bundle and the short edge of the graphitized carbon fiber cloth is more than or equal to 0 degree and less than or equal to 90 degrees. The graphitized carbon fiber cloth provided by the invention wraps the outer side of a crucible in a process of preparing silicon carbide by a PVT method, the erosion effect of Si atmosphere on a heat preservation felt can be reduced, so that the uniformity of a temperature field in the growth process of the silicon carbide is improved, and the graphitized carbon fiber cloth has relatively long service life and good reusability.

Description

Technical Field

[0001] The present application relates to a graphitized carbon fiber cloth, and belongs to the technical field of silicon carbide preparation. Background Art

[0002] At present, the induction furnaces on the market are mostly used to grow SiC through the PVT method. The principle is to use alternating current to pass through the multi-turn induction coil on the induction furnace outside the graphite crucible to form an induced magnetic field of the same frequency in the crucible, thereby generating an induced electromotive force. The high-purity graphite crucible material has good conductivity, so it will generate induced current on the crucible wall to form eddy currents, and produce a skin effect under the action of the Lorentz force, so that the induced current converges on the outer wall of the crucible and generates Joule heat, which is heated as a heat source in the furnace cavity through thermal convection, thermal radiation and heat conduction.

[0003] During the growth of SiC, the carbon powder, silicon powder and SiC powder at the bottom of the crucible are continuously heated to generate a gas source, which is then transmitted from the bottom of the crucible to the top of the crucible along with the flow field and the heat field to achieve growth on the seed crystal. Since Si atmosphere easily reacts with graphite to generate SiC, the hard felt carbon fiber and soft felt chopped fibers in the insulation felt are easily reacted with Si atmosphere. During the crystal growth process, Si atmosphere overflows through the gaps in the crucible and reacts with the insulation felt to easily form SiC polycrystals, thereby corroding the insulation felt and affecting the insulation effect, resulting in uneven thermal field or poor insulation effect during the crystal growth process, affecting product quality.

[0004] Carbon fiber is a high modulus fiber with a content of more than 90%. It has a series of excellent qualities such as high strength, good toughness, high temperature resistance, oxidation resistance, and wear resistance. Different carbon fibers have different physical and chemical properties. For example, according to the specifications of carbon fiber, it is divided into 1k, 3k, 6k, 12k, 24k and above large-filament carbon fiber cloth, which has different tensile strengths, and according to the carbonization of carbon fiber, it is divided into graphitized carbon fiber cloth, carbon fiber cloth, and pre-oxidized carbon fiber cloth, which have different degrees of high temperature resistance.

[0005] In the prior art, when growing SiC by the PVT method, there are problems such as poor insulation effect and uneven thermal field after the insulation felt is corroded, which leads to poor quality of SiC products, especially the problem of polymorphism. Therefore, it is necessary to provide a solution to the above technical problems and improve the quality of SiC products. Summary of the invention

[0006] In order to solve the above problems, a graphitized carbon fiber cloth is provided, which has certain properties of high temperature resistance, high tensile strength and electromagnetic shielding effect. When the graphitized carbon fiber cloth is applied to the SiC crystal growth temperature field, on the one hand, the thermal insulation performance can be increased, and on the other hand, the erosion of the thermal insulation felt can be reduced.

[0007] According to one aspect of the present application, a graphitized carbon fiber cloth is provided, which includes a matrix and carbon fiber bundles in the matrix, the matrix is ​​tar pitch, the carbon fiber bundles are graphitized carbon fiber bundles, and the graphitized carbon fiber bundles are arranged in parallel in the tar pitch matrix.

[0008] Tar pitch is the binder, and graphitized carbon fiber bundles are the support. Since Si atmosphere is more easily captured by the tar pitch binder, it can effectively reduce the erosion of Si atmosphere on the insulation felt during the preparation of silicon carbide crystals by the PVT method, thereby ensuring the insulation effect of the insulation felt, ensuring the uniformity and stability of the temperature field during the crystal growth process, and reducing the generation of polymorphism. The support is a graphitized carbon fiber bundle, which can significantly improve the tensile strength and high temperature resistance of the carbon fiber cloth, and can meet the use environment of more than 2000°C during the growth of silicon carbide.

[0009] It should be noted that the tar pitch and graphitized carbon fiber bundles used in this application are commonly used materials, and those skilled in the art can choose them according to their needs. In addition, this application does not limit the preparation process of graphitized carbon fiber cloth, and the commonly used preparation process in this field can be adopted, and the prepreg method can also be adjusted according to needs.

[0010] Optionally, the angle between the graphitized carbon fiber bundle and the short side of the graphitized carbon fiber cloth is

[0011] Optional, Optional,

[0012] in The size of will affect the angle at which the carbon fiber bundle cuts the magnetic flux lines, thus affecting the amount of Joule heat generated on the carbon fiber surface. When the size is within an appropriate range, the heat generated by the graphitized carbon fiber cloth can be reduced, thereby reducing the degree of reaction between the graphitized carbon fiber cloth and the Si atmosphere, thereby increasing the service life of the graphitized carbon fiber cloth.

[0013] Optionally, the spacing between the graphitized carbon fiber bundles is d, 0.5 mm ≤ d ≤ 5.0 mm;

[0014] Optional, 1.5mm≤d≤2.0mm.

[0015] The size of d will affect the shielding effect of graphitized carbon fiber on electromagnetic signals. If d is too large, the electromagnetic signal shielding effect is poor, and the density of the graphitized carbon fiber bundle is low. The Si atmosphere is more likely to react with tar pitch, and the shielding effect of the graphitized carbon fiber bundle is poor, resulting in more serious erosion of the Si atmosphere on the tar pitch, reducing the service life of the graphitized carbon fiber cloth; if d is too small, the graphitized carbon fiber bundle is prone to adhesion in the preparation process, resulting in changes in the angle at which the graphitized carbon fiber bundle cuts the magnetic flux lines. The increase in magnetic flux increases the calorific value of the graphitized carbon fiber cloth, and if d is too small, there is also the problem of a large amount of graphitized carbon fiber bundles used and a high cost; and when the size of d is within an appropriate range, it has a good electromagnetic signal shielding effect, at which time the calorific value of the graphitized carbon fiber cloth can be reduced, thereby reducing the degree of reaction between the graphitized carbon fiber cloth and the Si atmosphere, thereby increasing the service life of the graphitized carbon fiber cloth.

[0016] Optionally, the graphitized carbon fiber bundles are arranged in parallel to form a braided layer, and the graphitized carbon fiber cloth includes L braided layers arranged in parallel, 1≤L≤5;

[0017] Optional, 2≤L≤3.

[0018] If the size of L is too small, the shielding effect of the graphitized carbon fiber cloth on the Si atmosphere is poor, which makes it easy for the Si atmosphere to penetrate the tar pitch and corrode the thermal insulation felt. If L is too large, on the one hand, the cost will increase, and on the other hand, the large number of carbon fiber bundle weaving layers will easily cause a stronger skin effect on the carbon fiber surface, generating eddy currents on the surface and increasing the heat generation, resulting in a reduced life of the graphitized carbon fiber cloth.

[0019] Optionally, the spacing of the braided layers is D, 1.5mm≤D≤2.0mm.

[0020] The size of D will affect the heat generation of the graphitized carbon fiber cloth. If D is too large, the thickness of the graphitized fiber cloth will increase. After the thickness increases, the transmittance of the magnetic flux lines decreases, resulting in more absorption, and it is easier to reflect inside the graphitized carbon fiber cloth, resulting in increased heat generation. If D is too small, the carbon fiber bundles are more likely to adhere during processing and the shielding effect of the carbon fiber cloth will deteriorate.

[0021] It should be noted that the present application does not limit the preparation method of the graphitized carbon fiber cloth. For example, when the graphitized carbon fiber cloth includes multiple parallel woven layers, all the woven layers can be pre-impregnated with tar pitch at the same time, or they can be pre-impregnated layer by layer and then bonded together, and the thickness of the layer after pre-impregnation can be controlled to be close to the spacing D between the woven layers.

[0022] According to another aspect of the present application, there is provided a use of any of the above-mentioned graphitized carbon fiber cloths in preparing silicon carbide by a PVT method.

[0023] Optionally, the graphitized carbon fiber cloth is wrapped around the outside of the crucible.

[0024] The beneficial effects of this application include but are not limited to:

[0025] 1. According to the graphitized carbon fiber cloth of the present application, which is applied between the crucible and the thermal insulation felt, it is possible to capture the Si atmosphere overflowing from the crucible, and preferentially form SiC polycrystals on the surface of the graphitized carbon fiber cloth, thereby improving the erosion of the Si atmosphere on the thermal insulation felt when preparing SiC crystals by the PVT method, thereby ensuring the thermal insulation effect of the thermal insulation felt and the uniformity and stability of the temperature field, thereby reducing the generation of polymorphism and improving the crystal quality.

[0026] 2. According to the graphitized carbon fiber cloth of the present application, by improving the structure of the graphitized carbon fiber bundle in the graphitized carbon fiber cloth, it is possible to ensure the protective effect of the graphitized carbon fiber cloth on the thermal insulation felt while improving the service life of the graphitized carbon fiber cloth itself, and it has good reusability. The graphitized carbon fiber cloth also has good high temperature resistance and tensile strength, and can meet the use environment of more than 2000°C during the growth of silicon carbide. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] The drawings described herein are used to provide a further understanding of the present application and constitute a part of the present application. The illustrative embodiments of the present application and their descriptions are used to explain the present application and do not constitute an improper limitation on the present application. In the drawings:

[0028] Figure 1 This is a schematic diagram of the structure of the braided layer in the graphitized carbon fiber cloth involved in the embodiment of the present application;

[0029] Figure 2 It is a schematic diagram of the arrangement of graphitized carbon fiber bundles in a woven layer of the graphitized carbon fiber cloth involved in an embodiment of the present application. DETAILED DESCRIPTION

[0030] The present application is described in detail below in conjunction with examples, but the present application is not limited to these examples. Unless otherwise specified, the raw materials in the examples of the present application are purchased through commercial channels.

[0031] The present application scheme is described below through specific embodiments.

[0032] Example 1

[0033] like Figure 1 and Figure 2As shown, the present application provides a graphitized carbon fiber cloth, which includes a matrix and carbon fiber bundles in the matrix, wherein the matrix is ​​tar pitch, the carbon fiber bundles are graphitized carbon fiber bundles, and the graphitized carbon fiber bundles are arranged in parallel in the tar pitch matrix.

[0034] The angle between the graphitized carbon fiber bundle and the short side of the graphitized carbon fiber cloth is In an alternative embodiment, In another alternative embodiment In another alternative embodiment The spacing of the graphitized carbon fiber bundles is d, and in one optional embodiment, 0.5 mm ≤ d ≤ 5.0 mm, and in another optional embodiment, 1.5 mm ≤ d ≤ 2.0 mm. The graphitized carbon fiber bundles are arranged in parallel to form a braided layer, and the graphitized carbon fiber cloth includes L braided layers arranged in parallel, and in one optional embodiment, 1 ≤ L ≤ 5, and in another optional embodiment, 2 ≤ L ≤ 3. The spacing of the braided layers is D, and in one optional embodiment, 1.5 mm ≤ D ≤ 2.0 mm.

[0035] The product after the preparation of the graphitized carbon fiber cloth is in the form of a roll similar to conventional cloth, wherein the width of the roll is the short side of the graphitized carbon fiber cloth, and the extension direction of the roll is the long side of the graphitized carbon fiber cloth, based on which technicians in this field can accurately determine the long side and short side of the graphitized carbon fiber cloth.

[0036] Example 2

[0037] The specific structural parameters of graphitized carbon fiber cloth samples 1 to 16 are shown in Table 1 below. Except for the different structural parameters in Table 1, other conditions of graphitized carbon fiber cloth samples 1 to 16 are the same.

[0038] Table 1 Structural parameters of graphitized carbon fiber cloth of samples 1 to 16

[0039]

[0040]

[0041] The performance tests were conducted on the graphitized carbon fiber cloth samples 1 to 16 in Table 1, including service life performance, thermal insulation felt protection effect performance, tensile strength performance, and the influence on the qualified rate of crystal growth during the preparation process of the PVT method. The unit of tensile strength is MPa. The test complies with the test regulations for the mechanical performance indicators of carbon fiber cloth in the Chinese standard GB50367-2013. The tensile test is conducted along the short side direction of the graphitized carbon fiber cloth. The test conditions for service life performance, thermal insulation felt protection effect performance, and qualified rate of crystal growth are carried out under the same conditions of growing SiC crystals by the PVT method. The test is conducted after the crystal growth is completed. The service life performance, the protection effect performance of the thermal insulation felt, and the qualified rate of crystal growth are measured and calculated, wherein the service life performance is characterized by the weight loss rate of the graphitized carbon fiber cloth, and the unit is %, the weight loss rate of the graphitized carbon fiber cloth = (the weight of the graphitized carbon fiber cloth before crystal growth - the weight of the graphitized carbon fiber cloth after the end) / the weight of the graphitized carbon fiber cloth before crystal growth * 100%; wherein the protection effect performance of the thermal insulation felt is characterized by the weight loss rate of the thermal insulation felt, and the unit is %, the weight loss rate of the thermal insulation felt = (the weight of the thermal insulation felt before crystal growth - the weight of the thermal insulation felt after the end) / the weight of the thermal insulation felt before crystal growth * 100%; wherein the qualified rate of crystal growth = (the number of crystals excluding polymorphs) / the total number of crystals * 100%.

[0042] Among them, the PVT method crystal growth process includes the following steps: 1) preparing graphite material and silicon carbide powder raw materials and placing them in a crucible; 2) wrapping graphitized carbon fiber cloth on the outside of the crucible, and the short side direction of the graphitized carbon fiber cloth is parallel to the axial direction of the crucible during wrapping, and then placing the wrapped crucible into an induction furnace, and there is also insulation felt on the outside of the wrapped crucible; 3) placing a seed crystal to start crystal growth, specifically including: S1, maintaining the pressure at 50mbar, heating rate at 5℃ / min, temperature increased to 2100℃, and maintaining time for 10h; S2, reducing the pressure to 5mbar, reducing the pressure at a rate of 0.2mbar / min, maintaining the temperature at 2200℃, stabilizing for 5h after reducing the pressure, and the temperature during stabilization is 2250℃; S3, the growth process temperature is 2300℃, and the growth time is 50h.

[0043] During the PVT crystal growth process, except for the different graphitized carbon fiber cloths used, other conditions were controlled to be the same. After the end, the service life performance, thermal insulation felt protection effect performance, and tensile strength performance of the graphitized carbon fiber cloth samples 1 to 16 were measured and calculated. The results are shown in Table 2 below.

[0044] Table 2 Performance test results of graphitized carbon fiber cloth samples 1 to 16

[0045]

[0046] Using the same PVT method crystal growth conditions as above, when graphitized carbon fiber cloth is not set, the weight loss rate of the insulation felt is 23%, and the qualified rate of crystal growth is 74%. Further combined with the results in Table 2, it can be seen that by setting the graphitized carbon fiber cloth, the erosion of the Si atmosphere on the insulation felt during the crystal growth process can be significantly improved, thereby ensuring the insulation effect of the insulation felt during the crystal growth process, making the temperature field more uniform and stable during the crystal growth process, thereby effectively reducing the occurrence of polymorphism and improving the crystal quality. Further according to the results in Table 2, it can be seen that samples 1 to 4 not only have a good insulation felt protection effect, but also the graphitized carbon fiber cloth has a better service life and good reusability.

[0047] The above is only the embodiment of the present application, and the protection scope of the present application is not limited by these specific embodiments, but is determined by the claims of the present application. For those skilled in the art, the present application can have various changes and variations. Any modification, equivalent replacement, improvement, etc. made within the technical ideas and principles of the present application should be included in the protection scope of the present application.

Claims

1. A graphitized carbon fiber cloth, characterized in that: The graphitized carbon fiber cloth comprises a matrix and carbon fiber bundles in the matrix, the matrix is ​​tar pitch, the carbon fiber bundles are graphitized carbon fiber bundles, the graphitized carbon fiber bundles are arranged in parallel in the tar pitch matrix, and the angle between the graphitized carbon fiber bundles and the short side of the graphitized carbon fiber cloth is φ, 0°≤φ≤90°.

2. The graphitized carbon fiber cloth according to claim 1, characterized in that: 0°≤φ≤30°.

3. The graphitized carbon fiber cloth according to claim 2, characterized in that: 5°≤φ≤20°.

4. The graphitized carbon fiber cloth according to claim 1, characterized in that: The spacing between the graphitized carbon fiber bundles is d, 0.5 mm≤d≤5.0 mm.

5. The graphitized carbon fiber cloth according to claim 4, characterized in that: 1.5mm≤d≤2.0mm.

6. The graphitized carbon fiber cloth according to claim 1, characterized in that: The graphitized carbon fiber bundles are arranged in parallel to form a braided layer, and the graphitized carbon fiber cloth includes L braided layers arranged in parallel, 1≤L≤5.

7. The graphitized carbon fiber cloth according to claim 6, characterized in that: 2≤L≤3。 8. The graphitized carbon fiber cloth according to claim 6, characterized in that: The spacing of the braided layers is D, 1.5 mm ≤ D ≤ 2.0 mm.

9. Use of the graphitized carbon fiber cloth according to any one of claims 1 to 8 in the preparation of silicon carbide by PVT method.

10. The use according to claim 9, characterized in that: The graphitized carbon fiber cloth is wrapped around the outside of the crucible.

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