A method for preparing a carbon coating using synthetic camphor

Abstract

The present invention discloses a method for preparing a carbon coating using synthetic camphor. The method comprises: S1, laying a layer of synthetic camphor on the bottom of a crucible, then placing degummed fibers on top of the synthetic camphor, then covering the fiber surface with a layer of synthetic camphor, and tightening the crucible; S2, placing the crucible containing the fibers and synthetic camphor in a cracking furnace for staged high-temperature treatment, followed by cooling in the furnace, to obtain fibers with a carbon coating on the surface. The method for preparing the carbon coating is simple to operate, highly efficient, low-cost, and environmentally friendly and safe.

Description

Technical Field

[0001] The present invention generally relates to the field of composite materials, and in particular to a method for preparing a carbon coating using synthetic camphor. Background Art

[0002] Fiber surface coating technology has always been a hot topic in the field of fiber research. On the one hand, fiber surface coating is a key component in achieving non-brittle fracture in fiber-reinforced ceramic matrix composites; on the other hand, coating is also a necessary means to adjust the fiber surface state and change its function.

[0003] Currently, there are two main methods for preparing C coatings: CVD and immersion pyrolysis. However, existing C coating processes still have the following shortcomings: CVD is a complex coating process with strict requirements for deposition time, mixed gas ratio, and pressure. While the immersion pyrolysis process is relatively simple, it produces coatings with many defects. Summary of the Invention

[0004] The invention provides a method for preparing a carbon coating by using synthetic camphor, which is used to overcome the problems in the prior art of complex carbon coating preparation process and many defects in the prepared carbon coating.

[0005] To achieve the above object, the present invention provides a method for preparing a carbon coating using synthetic camphor, comprising the following steps:

[0006] S1. Laying a layer of synthetic camphor on the bottom of a crucible, then placing degummed fiber on top of the synthetic camphor, then covering the fiber surface with a layer of synthetic camphor, and tightening the crucible; the crucible can withstand high temperatures above 1250°C;

[0007] S2. The crucible containing the fiber and the synthetic camphor is placed in a cracking furnace for segmented high-temperature treatment, and then cooled with the furnace to obtain a fiber with a carbon coating on the surface.

[0008] The beneficial effects of the present invention are as follows:

[0009] 1. The present invention firstly utilizes the characteristic that synthetic camphor can be completely pyrolyzed at low temperature (160°C) and decomposes the synthetic camphor into gaseous carbon elemental substance by heating the cracking furnace; secondly, the sealing property of the sealable crucible is utilized to allow the carbon-containing atmosphere generated by the decomposition of the synthetic camphor to remain in the crucible for a long time and evenly coat the fibers, and finally uniformly and continuously deposit on the fiber surface to form a coating.

[0010] 2. The preparation method of the carbon coating of the present invention is simple to operate, high in efficiency, low in cost, and environmentally friendly and safe. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the structures shown in these drawings without paying any creative work.

[0012] Figure 1 This is an SEM image of the SiC fiber coated with C prepared in Example 1 of the present invention;

[0013] Figure 2 This is an SEM image of the SiC fiber coated with C prepared in Example 2 of the present invention;

[0014] Figure 3 This is an SEM image of the SiC fiber coated with C prepared in Example 3 of the present invention;

[0015] Figure 4 This is an SEM image of the SiC fiber coated with C prepared in Example 4 of the present invention;

[0016] Figure 5 This is an SEM image of the SiC fiber coated with C prepared in Example 5 of the present invention;

[0017] Figure 6 This is an SEM image of the SiC fiber coated with C prepared in Example 6 of the present invention;

[0018] Figure 7 This is an SEM image of the Al2O3 fiber coated with a C coating prepared in Example 7 of the present invention;

[0019] Figure 8 This is an SEM image of the Al2O3 fiber coated with a C coating prepared in Example 8 of the present invention;

[0020] Figure 9 This is an SEM image of the Al2O3 fiber coated with a C coating prepared in Example 9 of the present invention;

[0021] Figure 10 This is an SEM image of the Al2O3 fiber coated with a C coating prepared in Example 10 of the present invention;

[0022] Figure 11 This is an SEM image of the SiC fiber coated with C prepared in Example 11 of the present invention;

[0023] Figure 12 This is an SEM image of the SiC fiber coated with C prepared in Example 12 of the present invention;

[0024] The purpose, features and advantages of the present invention will be further described with reference to the accompanying drawings and in conjunction with the embodiments. DETAILED DESCRIPTION

[0025] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0026] In addition, the technical solutions between the various embodiments of the present invention can be combined with each other, but it must be based on the fact that ordinary technicians in this field can implement it. When the combination of technical solutions is mutually contradictory or cannot be implemented, it should be deemed that such a combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

[0027] To achieve the above object, the present invention provides a method for preparing a carbon coating using synthetic camphor, comprising the following steps:

[0028] S1. Laying a layer of synthetic camphor on the bottom of a crucible, then placing degummed fiber on top of the synthetic camphor, then covering the fiber surface with another layer of synthetic camphor, and tightening the crucible; wherein the crucible can withstand high temperatures above 1250°C;

[0029] S2. The crucible containing the fiber and the synthetic camphor is placed in a cracking furnace for segmented high-temperature treatment, and then cooled with the furnace to obtain a fiber with a carbon coating on the surface.

[0030] Preferably, the amount of synthetic camphor added is not less than one half of the volume of the crucible and not more than four fifths of the volume of the crucible.

[0031] Preferably, in step S1, the fiber is SiC fiber or Al2O3 fiber.

[0032] Preferably, the degumming process of the SiC fiber is as follows: heating at a rate of 5°C / min under an Ar atmosphere, and then keeping the temperature at 800°C for 2h to complete the degumming;

[0033] The degumming process of Al2O3 fiber is as follows: in air atmosphere, heating at a rate of 5-10℃ / min, and then keeping at 700℃ for 2h to complete the degumming.

[0034] Preferably, the crucible is one of a graphite crucible, an alumina crucible, a quartz crucible, a porcelain crucible and a corundum crucible.

[0035] Preferably, the amount of synthetic camphor added is not less than 1 / 2 and not more than 4 / 5 of the crucible volume. This is to ensure that the amount of camphor used is as large as possible without causing damage to the crucible due to excessive pressure inside the crucible caused by the camphor turning into gas during the high-temperature treatment.

[0036] Preferably, the mass ratio of the added synthetic camphor to the fiber is (250-500):1.

[0037] Preferably, the staged high temperature treatment specifically includes:

[0038] In an Ar atmosphere or vacuum condition, the crucible containing the fiber and synthetic camphor is heated to 160°C to 250°C at a heating rate of 1°C / min, and kept at this temperature for 2 to 3 hours to fully pyrolyze the camphor. The crucible is then heated to 500°C to 1200°C at a heating rate of 5 to 10°C / min, and kept at this temperature for 2 to 3 hours to increase the rate of carbon deposition, and then cooled with the furnace;

[0039] The above steps are carried out 1 to 4 times to obtain a fiber with a carbon coating on its surface. The coating thickness increases to a certain extent as the number of times increases, and the continuity and uniformity of the coating also improve with the increase in the number of repetitions.

[0040] During the decomposition stage, camphor decomposes poorly below 160°C, but decomposes completely above 160°C. However, for environmental and safety reasons, the decomposition temperature does not need to be set too high; a temperature not exceeding 250°C is sufficient. Generally speaking, the deposition temperature determines the thermodynamics and kinetics of carbon formation from the pyrolysis of hydrocarbons and oxyhydroxides. From a reaction thermodynamic perspective, the deposition temperature determines the form of the intermediate products during the decomposition of hydrocarbons and oxyhydroxides: smaller groups exist at higher temperatures, while larger groups exist at lower temperatures. From a reaction kinetic perspective, the relationship between the reaction rate constant and temperature conforms to the Arrhenius relationship, with increasing deposition temperature accelerating the reaction rate. When pyrolytic carbon was deposited using synthetic camphor as a source material, carbonaceous flocs and carbon black particles were observed on the furnace walls and crucible surfaces at deposition temperatures below 500°C. This indicates that while the gas phase generated by the camphor source nucleated and grains grew, the deposit was neither smooth nor uniform. At higher temperatures, the deposition process is often controlled by diffusion and mass transfer, resulting in poor structural uniformity. Consequently, when the deposition temperature reached 1200°C, the deposit on the fiber surface became relatively rough.

[0041] Example 1

[0042] In this embodiment, a C coating is prepared on the surface of SiC fiber according to the following steps:

[0043] 1. Place a layer of synthetic camphor on the bottom of the graphite crucible, add a bundle of degummed KD-ⅡSiC fibers about 10 cm in length, and cover the surface of the KD-ⅡSiC fibers with another layer of synthetic camphor. The amount of synthetic camphor added should be no less than half of the crucible volume and no more than four-fifths of the crucible volume. Tighten the graphite crucible.

[0044] 2. Place the graphite crucible containing synthetic camphor and SiC fiber into the cracking furnace. Under vacuum conditions, heat the graphite crucible containing SiC fiber and synthetic camphor to 200°C at a heating rate of 1°C / min and keep it warm for 2 hours. This stage allows the camphor to fully decompose at its decomposition temperature. Then heat it to 500°C at a rate of 10°C / min, keep it warm for 1 hour, and then cool it with the furnace. This stage can accelerate the deposition of carbon and make it fully deposited.

[0045] Figure 1 This is a SEM image of a SiC fiber coated with a C coating prepared by performing the above steps once in Example 1 of the present invention. The thickness of the C coating on its surface is about 50 nm.

[0046] Example 2

[0047] In this embodiment, a C coating is prepared on the surface of SiC fiber according to the following steps:

[0048] 1. Place a layer of synthetic camphor on the bottom of the graphite crucible, add a bundle of degummed KD-ⅡSiC fibers about 10 cm in length, and cover the surface of the KD-ⅡSiC fibers with another layer of synthetic camphor. The amount of synthetic camphor added should be no less than half of the crucible volume and no more than four-fifths of the crucible volume. Tighten the graphite crucible.

[0049] 2. Place the graphite crucible containing synthetic camphor and SiC fiber into the cracking furnace. Under vacuum conditions, heat the graphite crucible containing SiC fiber and synthetic camphor to 200°C at a heating rate of 1°C / min and keep it warm for 2 hours. This stage allows the camphor to fully decompose at its decomposition temperature. Then heat it to 800°C at a rate of 10°C / min, keep it warm for 1 hour, and then cool it with the furnace. This stage can accelerate the deposition of carbon and make it fully deposited.

[0050] The purpose of keeping warm in the first stage is to allow the camphor to fully decompose at its decomposition temperature, and the purpose of heating and keeping warm in the second stage is to accelerate the deposition of carbon and make it fully deposited.

[0051] Figure 2 This is a SEM image of a SiC fiber coated with a C coating prepared by performing the above steps once in Example 2 of the present invention. The thickness of the C coating on its surface is about 50 nm.

[0052] Example 3

[0053] The method for preparing a C coating on the surface of a SiC fiber in this embodiment is carried out according to the following steps:

[0054] 1. Place a layer of synthetic camphor on the bottom of the graphite crucible, add a bundle of degummed KD-ⅡSiC fibers about 10 cm in length, and cover the surface of the KD-ⅡSiC fibers with another layer of synthetic camphor. The amount of synthetic camphor added should be no less than half of the crucible volume and no more than four-fifths of the crucible volume. Tighten the graphite crucible.

[0055] 2. Place the graphite crucible containing synthetic camphor and SiC fiber into the cracking furnace. Under vacuum conditions, heat the graphite crucible containing SiC fiber and synthetic camphor to 200°C at a heating rate of 1°C / min and keep it warm for 2 hours. This stage allows the camphor to fully decompose at its decomposition temperature. Then heat it to 1200°C at a rate of 10°C / min, keep it warm for 1 hour, and then cool it with the furnace. This stage can accelerate the deposition of carbon and make it fully deposited.

[0056] Figure 3 This is a SEM image of a SiC fiber coated with a C coating, prepared by performing the above steps once in Example 3 of the present invention. The thickness of the C coating on its surface is about 50 nm.

[0057] Example 4

[0058] In this embodiment, a C coating is prepared on the surface of SiC fiber according to the following steps:

[0059] 1. Place a layer of synthetic camphor on the bottom of the graphite crucible, add a bundle of degummed KD-ⅡSiC fibers about 10 cm long, and cover the fiber surface with another layer of synthetic camphor. The amount of synthetic camphor added should be no less than half of the crucible volume and no more than four-fifths of the crucible volume. Tighten the graphite crucible.

[0060] 2. Place the graphite crucible containing synthetic camphor and SiC fiber into the cracking furnace. Under vacuum conditions, heat the graphite crucible containing SiC fiber and synthetic camphor to 200°C at a heating rate of 1°C / min and keep it warm for 2 hours. This stage allows the camphor to fully decompose at its decomposition temperature. Then heat it to 500°C at a rate of 10°C / min, keep it warm for 2 hours, and then cool it with the furnace. This stage can accelerate the deposition of carbon and make it fully deposited.

[0061] Figure 4 This is an SEM image of a SiC fiber coated with a C coating after performing the above steps once, prepared in Example 4 of the present invention. The thickness of the C coating on its surface is about 50 nm.

[0062] Example 5

[0063] In this embodiment, a C coating is prepared on the surface of SiC fiber according to the following steps:

[0064] 1. Place a layer of synthetic camphor on the bottom of the graphite crucible, add a bundle of degummed KD-ⅡSiC fibers about 10 cm long, and cover the fiber surface with another layer of synthetic camphor. The amount of synthetic camphor added should be no less than half of the crucible volume and no more than four-fifths of the crucible volume. Tighten the graphite crucible.

[0065] 2. Place the graphite crucible containing synthetic camphor and SiC fiber into the cracking furnace. Under vacuum conditions, heat the graphite crucible containing SiC fiber and synthetic camphor to 200°C at a heating rate of 1°C / min and keep it warm for 2 hours. This stage allows the camphor to fully decompose at its decomposition temperature. Then heat it to 800°C at a rate of 10°C / min, keep it warm for 2 hours, and then cool it with the furnace. This stage can accelerate the deposition of carbon and make it fully deposited.

[0066] Figure 5 This is a SEM image of a SiC fiber coated with a C coating, prepared by performing the above steps once in Example 5 of the present invention. The thickness of the C coating on its surface is about 50 nm.

[0067] Example 6

[0068] The method for preparing a C coating on the surface of a SiC fiber in this embodiment is carried out according to the following steps:

[0069] 1. Place a layer of synthetic camphor on the bottom of the graphite crucible, add a bundle of degummed KD-ⅡSiC fibers about 10 cm long, and cover the fiber surface with another layer of synthetic camphor. The amount of synthetic camphor added should be no less than half of the crucible volume and no more than four-fifths of the crucible volume. Tighten the graphite crucible.

[0070] 2. Place the graphite crucible containing synthetic camphor and SiC fiber into the cracking furnace. Under vacuum conditions, heat the graphite crucible containing SiC fiber and synthetic camphor to 200°C at a heating rate of 1°C / min and keep it warm for 2 hours. This stage allows the camphor to fully decompose at its decomposition temperature. Then heat it to 1200°C at a rate of 10°C / min, keep it warm for 2 hours, and then cool it with the furnace. This stage can accelerate the deposition of carbon and make it fully deposited.

[0071] Figure 6 This is a SEM image of a SiC fiber coated with a C coating prepared by performing the above steps once in Example 6 of the present invention. The thickness of the C coating on its surface is about 50 nm.

[0072] Example 7

[0073] The method for preparing a C coating on the surface of an Al2O3 fiber in this embodiment is carried out according to the following steps:

[0074] 1. Place a layer of synthetic camphor on the bottom of the graphite crucible, add a bundle of about 10 cm of degummed Al2O3 fibers, and cover the fiber surface with another layer of synthetic camphor. The amount of synthetic camphor added should be no less than half of the crucible volume and no more than four-fifths of the crucible volume. Tighten the graphite crucible.

[0075] 2. Place the graphite crucible containing synthetic camphor and Al2O3 fiber into the cracking furnace. Under Ar atmosphere, heat the graphite crucible containing Al2O3 fiber and synthetic camphor to 200℃ at a heating rate of 1℃ / min and keep it warm for 2h. This stage can make the camphor fully decompose at its decomposition temperature. Then heat it to 800℃ at a rate of 10℃ / min and keep it warm for 2h. Then cool it with the furnace. This stage can accelerate the deposition of carbon and make it fully deposited.

[0076] Figure 7 This is an SEM image of an Al2O3 fiber coated with a C coating prepared by performing the above steps once in Example 7 of the present invention. The thickness of the C coating on its surface is about 50 nm.

[0077] Example 8

[0078] The method for preparing a C coating on the surface of an Al2O3 fiber in this embodiment is carried out according to the following steps:

[0079] 1. Place a layer of synthetic camphor on the bottom of the graphite crucible, add a bundle of about 10 cm of degummed Al2O3 fibers, and cover the fiber surface with another layer of synthetic camphor. The amount of synthetic camphor added should be no less than half of the crucible volume and no more than four-fifths of the crucible volume. Tighten the graphite crucible.

[0080] 2. Place the graphite crucible containing synthetic camphor and Al2O3 fiber into the cracking furnace. Under a vacuum environment, heat the graphite crucible containing Al2O3 fiber and synthetic camphor to 200°C at a heating rate of 1°C / min and keep it warm for 2 hours. This stage can allow the camphor to fully decompose at its decomposition temperature. Then heat it to 800°C at a rate of 10°C / min, keep it warm for 2 hours, and then cool it with the furnace. This stage can accelerate the deposition of carbon and make it fully deposited.

[0081] Figure 8 This is an SEM image of an Al2O3 fiber coated with a C coating prepared by performing the above steps once in Example 8 of the present invention. The thickness of the C coating on its surface is about 50 nm.

[0082] Example 9

[0083] The method for preparing a C coating on the surface of an Al2O3 fiber in this embodiment is carried out according to the following steps:

[0084] 1. Place a layer of synthetic camphor on the bottom of the graphite crucible, add a bundle of about 10 cm of degummed Al2O3 fibers, and cover the fiber surface with another layer of synthetic camphor. The amount of synthetic camphor added should be no less than half of the crucible volume and no more than four-fifths of the crucible volume. Tighten the graphite crucible.

[0085] 2. Place the graphite crucible containing synthetic camphor and Al2O3 fiber into the cracking furnace. Under a vacuum environment, heat the graphite crucible containing Al2O3 fiber and synthetic camphor to 200°C at a heating rate of 1°C / min and keep it warm for 2 hours. This stage can allow the camphor to fully decompose at its decomposition temperature. Then heat it to 800°C at a rate of 5°C / min, keep it warm for 2 hours, and then cool it with the furnace. This stage can accelerate the deposition of carbon and make it fully deposited.

[0086] Cycling the pyrolysis of camphor and deposition of carbon coating 2 to 6 times can improve the continuity and uniformity of the coating and gradually thicken the fiber surface coating to a thickness of more than 100 nm.

[0087] Figure 9 This is an SEM image of a carbon-coated Al2O3 fiber prepared after four cycles of Example 9. As can be seen, four cycles of carbon deposition under vacuum have a significant effect, with the thickness of the carbon coating increasing significantly, reaching approximately 110 nm on the Al2O3 fiber surface.

[0088] Example 10

[0089] The method for preparing a C coating on the surface of an Al2O3 fiber in this embodiment is carried out according to the following steps:

[0090] 1. Place a layer of synthetic camphor on the bottom of the graphite crucible, add a bundle of about 10 cm of degummed Al2O3 fibers, and cover the fiber surface with another layer of synthetic camphor. The amount of synthetic camphor added should be no less than half of the crucible volume and no more than four-fifths of the crucible volume. Tighten the graphite crucible.

[0091] 2. Place the graphite crucible containing synthetic camphor and Al2O3 fiber into the cracking furnace. Under Ar slightly positive pressure environment, heat the graphite crucible containing Al2O3 fiber and synthetic camphor to 200℃ at a heating rate of 1℃ / min and keep it warm for 2h. This stage can make the camphor fully decompose at its decomposition temperature; then heat it to 800℃ at a rate of 5℃ / min, keep it warm for 2h, and then cool it with the furnace. This stage can accelerate the deposition of carbon and make it fully deposited.

[0092] Cycling the pyrolysis of camphor and deposition of carbon coating 2 to 6 times can improve the continuity and uniformity of the coating and gradually thicken the fiber surface coating to a thickness of more than 100 nm.

[0093] Figure 10 This is an SEM image of the C-coated Al2O3 fiber prepared in Example 10 of the present invention. As can be seen, compared to Example 9, the deposition effect is more pronounced with the same number of cycles (four) under a slightly positive pressure environment, achieving a coating thickness of approximately 180 nm on the Al2O3 fiber surface. This is because the slightly positive pressure environment allows the decomposed camphor gases to remain more stably within the crucible.

[0094] Example 11

[0095] The method for preparing a C coating on the surface of a SiC fiber in this embodiment is carried out according to the following steps:

[0096] 1. Place a layer of synthetic camphor on the bottom of the graphite crucible, add a bundle of about 10 cm of degummed SiC fibers, and cover the fiber surface with another layer of synthetic camphor. The amount of synthetic camphor added should be no less than half of the crucible volume and no more than four-fifths of the crucible volume. Tighten the graphite crucible.

[0097] 2. Place the graphite crucible containing synthetic camphor and SiC fibers into a cracking furnace. Under vacuum, heat the crucible to 200°C at a rate of 1°C / min and hold for 2 hours. This allows the camphor to fully decompose at its decomposition temperature. Then, heat the crucible to 800°C at a rate of 5°C / min, hold for 2 hours, and then cool the furnace. This stage accelerates and fully deposits carbon.

[0098] Cycling the pyrolysis of camphor and deposition of carbon coating 2 to 6 times can improve the continuity and uniformity of the coating and gradually thicken the fiber surface coating to a thickness of more than 100 nm.

[0099] Figure 11 This is an SEM image of a SiC fiber coated with a carbon coating prepared in Example 11 of the present invention. As can be seen from the figure, four cycles of carbon coating deposition under a vacuum environment have a significant effect, with the thickness significantly increased. The carbon coating on the SiC fiber surface can reach approximately 115 nm.

[0100] Example 12

[0101] The method for preparing a C coating on the surface of a SiC fiber in this embodiment is carried out according to the following steps:

[0102] 1. Place a layer of synthetic camphor on the bottom of the graphite crucible, add a bundle of about 10 cm of degummed SiC fibers, and cover the fiber surface with another layer of synthetic camphor. The amount of synthetic camphor added should be no less than half of the crucible volume and no more than four-fifths of the crucible volume. Tighten the graphite crucible.

[0103] 2. Place the graphite crucible containing synthetic camphor and SiC fibers in a cracking furnace. Under a slightly positive Ar pressure, heat the crucible to 200°C at a rate of 1°C / min and hold for 2 hours. This allows the camphor to fully decompose at its decomposition temperature. Then, heat the crucible to 800°C at a rate of 5°C / min, hold for 2 hours, and then cool the furnace. This stage accelerates and fully deposits carbon.

[0104] Cycling the pyrolysis of camphor and deposition of carbon coating 2 to 6 times can improve the continuity and uniformity of the coating and gradually thicken the fiber surface coating to a thickness of more than 100 nm.

[0105] Figure 12 This is an SEM image of a SiC fiber coated with a C coating prepared in Example 12 of the present invention. As can be seen, compared to Example 11, the deposition effect is more pronounced with the same number of cycles (four) under a slightly positive pressure environment, achieving a coating thickness of approximately 138 nm on the SiC fiber surface. This is because the slightly positive pressure environment allows the decomposed camphor gases to remain more stably within the crucible.

[0106] While various embodiments of the present invention have been described above, the foregoing description is intended to be illustrative, non-exhaustive, and not limiting of the disclosed embodiments. Numerous modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments. Therefore, the scope of the present invention shall be determined by the scope of the claims.

Claims

1. A method for preparing a carbon coating using synthetic camphor, characterized in that: The following steps are involved: S1. Lay a layer of synthetic camphor on the bottom of the crucible, add a layer of synthetic camphor that is not less than 1 / 2 and not more than 4 / 5 of the volume of the crucible, and the mass ratio of the added synthetic camphor to the fiber is (250-500):1, then place the degummed fiber on top of the synthetic camphor, cover the fiber surface with a layer of synthetic camphor, and tighten the crucible; the crucible can withstand high temperatures above 1250°C; The fiber is SiC fiber or Al2O3 fiber; S2, the crucible containing the fiber and the synthetic camphor is placed in a cracking furnace for staged high-temperature treatment, specifically comprising: in an Ar atmosphere or vacuum condition, heating the crucible containing the fiber and the synthetic camphor to 160°C to 250°C at a heating rate of 1°C / min, keeping the temperature for 2 to 3h, then heating the crucible to 500°C to 1200°C at a heating rate of 5 to 10°C / min, keeping the temperature for 2 to 3h, and then cooling with the furnace; The process of pyrolyzing camphor and depositing a carbon coating is cycled 2 to 6 times in sequence to improve the continuity and uniformity of the coating, and gradually thicken the coating on the fiber surface, thereby obtaining a fiber with a carbon coating on the surface, and the thickness of the carbon coating is increased to more than 100 nm.

2. The method for preparing a carbon coating using synthetic camphor according to claim 1, wherein: The crucible is one of a graphite crucible, an alumina crucible and a quartz crucible.

3. The method for preparing a carbon coating using synthetic camphor according to claim 1, wherein: The degumming process of SiC fiber was as follows: in Ar atmosphere, the temperature was increased at a rate of 5°C / min, and then kept at 800°C for 2h to complete the degumming; The degumming process of Al2O3 fiber is as follows: in air atmosphere, heating at a rate of 5~10℃ / min, and then keeping at 700℃ for 2h to complete the degumming.

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