A device and method for preparing a BN interfacial phase on the surface of a continuous carbon fiber bundle

Abstract

The present application relates to the technical field of composite material interface regulation, and particularly relates to a device and method for preparing BN interface phase on the surface of continuous carbon fiber bundle, which comprises a fiber conveying assembly and, along the wire running direction, a high-temperature degumming device, a mechanical yarn spreading device, a low-temperature plasma activation device, a BN precursor impregnation device, a liquid removal device, a temperature rising complexing device, a high-temperature pyrolysis conversion device and a cooling protection device. The carbon fiber bundle completes the degumming, yarn spreading, surface activation, BN precursor impregnation, liquid removal and film control, temperature rising complexing, pyrolysis conversion and protection cooling treatment in turn in continuous operation. The present application improves the exposure degree of single filaments in the bundle and the precursor impregnation and adhesion capacity through yarn spreading and double-sided surface activation, and reduces the migration, aggregation and cracking risk of the precursor in the subsequent heat treatment process through liquid removal and film control and temperature rising complexing, so that the continuous and controllable preparation of the BN interface phase on the surface of the continuous carbon fiber bundle can be realized.

Description

Technical Field

[0001] This invention relates to the field of composite material interface control technology, specifically to an apparatus and method for preparing a BN interface phase on the surface of a continuous carbon fiber bundle. Background Technology

[0002] In carbon fiber reinforced ceramic matrix composites, the interfacial structure between the fiber and the matrix has a significant impact on crack deflection, load transfer, damage tolerance, and service reliability. A suitable interfacial phase can regulate the bonding strength between the fiber and the matrix, causing cracks to deflect near the interface, thereby improving the toughness and reliability of the composite material.

[0003] Carbon nanotubes (BN) possess characteristics such as high temperature resistance, oxidation resistance, layered structure, and low shear strength, making them suitable as interfacial phase materials in carbon fiber reinforced ceramic matrix composites to regulate the interfacial bonding state between the fibers and the ceramic matrix. Existing methods for preparing BN interfacial phases include chemical vapor deposition (CVD), impregnation pyrolysis, powder coating, and batch liquid phase processing for preforms. Among these, CVD can obtain high-quality interfacial layers, but it typically suffers from problems such as complex equipment, long processing cycles, and high costs.

[0004] For continuous carbon fiber bundles, the bundle contains a large number of closely bonded monofilaments. During impregnation, the liquid precursor tends to preferentially adhere to the outer fiber surface, while the inner monofilaments are insufficiently exposed, resulting in uneven distribution of the BN precursor inside and outside the bundle. If the precursor is impregnated directly without unwinding and surface activation, problems such as insufficient wetting, local enrichment, and uneven film thickness can easily occur. If excess liquid is not removed and stabilization treatment is not performed promptly after impregnation, the precursor liquid film may migrate, accumulate, and crack locally during subsequent heating, affecting the continuity and uniformity of the final BN interfacial phase.

[0005] Continuous carbon fiber bundles typically have a sizing agent on their surface. This sizing agent needs to be removed before preparing the BN interfacial phase to improve subsequent surface activation and precursor impregnation. After high-temperature pyrolysis, the carbon fiber bundles and their surface interfacial layer must also avoid direct contact with oxygen in the air during cooling to reduce the risk of high-temperature oxidation. Therefore, it is necessary to provide an apparatus and method for preparing the BN interfacial phase of continuous carbon fiber bundles, which integrates steps such as degumming, yarn spreading, surface activation, BN precursor impregnation, liquid removal and film control, temperature-increasing complexation stabilization, high-temperature pyrolysis conversion, and protective cooling to achieve continuous and controllable preparation of the BN interfacial phase on the surface of continuous carbon fiber bundles. Summary of the Invention

[0006] To address the shortcomings in the aforementioned background technology, this invention provides a device and method for preparing a BN interface phase on the surface of a continuous carbon fiber bundle, which addresses issues such as insufficient exposure of monofilaments within the bundle, uneven wetting and distribution of the BN liquid precursor, easy migration and aggregation of the precursor after impregnation, difficulty in continuously connecting the pyrolysis conversion process, and easy oxidation during the cooling process after high-temperature treatment. The device includes a fiber conveying assembly and, sequentially arranged along the continuous running direction of the carbon fiber bundle, a high-temperature degumming device, a mechanical yarn spreading device, a low-temperature plasma activation device, a BN precursor impregnation device, a liquid removal device, a heating complexing device, a high-temperature pyrolysis conversion device, and a cooling protection device.

[0007] The first objective of this invention is to provide a continuous carbon fiber bundle surface BN interface phase preparation device, including a fiber conveying assembly and a high-temperature degumming device, a mechanical yarn spreading device, a low-temperature plasma activation device, a BN precursor impregnation device, a dehydration device, a heating complexing device, a high-temperature pyrolysis conversion device, and a cooling protection device arranged sequentially along the continuous running direction of the carbon fiber bundle. The fiber conveying assembly is used to sequentially pass the carbon fiber bundle through a high-temperature degumming device, a mechanical yarn spreading device, a low-temperature plasma activation device, a BN precursor impregnation device, a dehydration device, a heating complexing device, a high-temperature pyrolysis conversion device, and a cooling protection device. The high-temperature degumming device is used to remove the sizing agent from the surface of the carbon fiber bundles; The mechanical yarn spreading device is used to spread the carbon fiber bundle to increase the exposure of the monofilaments within the bundle. The low-temperature plasma activation device is used to activate the surface of the carbon fiber bundles; The BN precursor impregnation device is used to immerse the carbon fiber bundle in the BN liquid precursor and to attach the BN liquid precursor to the surface of the carbon fiber bundle. The dehydration device is used to remove excess BN liquid precursor and control the amount of BN liquid precursor adhering to the surface of the carbon fiber bundle. The heating complexing device is used to evaporate the solvent, complex the solute and solidify the BN precursor solution attached to the surface of the carbon fiber bundle to form a BN precursor layer. The high-temperature pyrolysis conversion device is used to convert the BN precursor layer into the BN interface phase; The cooling protection device is used to protect and cool the carbon fiber bundles after the BN interface phase is formed.

[0008] In one embodiment, the fiber conveying assembly includes an unwinding mechanism and a traction winding mechanism located behind the cooling protection device. The unwinding mechanism is used to set up the carbon fiber bundle and, under the traction of the traction winding mechanism, to rotate the carbon fiber bundle and continuously feed the carbon fiber bundle along the wire feeding direction. The fiber conveying assembly also includes a tension control mechanism; the tension control mechanism is used to maintain the continuous and stable operation of the carbon fiber bundle during the processes of yarn spreading, BN precursor impregnation, heating complexation and high-temperature pyrolysis conversion.

[0009] In one embodiment, the high-temperature degumming device is a continuous wire-feed tubular heating device, which is provided with a tubular heating channel, a protective gas inlet, a degumming exhaust gas outlet, a carbon fiber bundle inlet, and a carbon fiber bundle outlet; wherein, both the carbon fiber bundle inlet and the carbon fiber bundle outlet are provided with two air-sealing cavities connected sequentially from the outside to the inside, and a high-temperature resistant flexible slit seal is provided between the inner air-sealing cavity and the end of the tubular heating device; The mechanical yarn spreading device includes multiple yarn spreading rollers arranged along the running direction of the carbon fiber bundle, and the carbon fiber bundle passes around the multiple yarn spreading rollers in sequence. By adjusting the running path and wrap angle of the carbon fiber bundle through multiple staggered spreading rollers, the carbon fiber bundle is transformed from a bundled state to a spread state.

[0010] In one embodiment, the low-temperature plasma activation device includes a plasma processing chamber, and a first plasma processing unit and a second plasma processing unit disposed within the plasma processing chamber; the plasma processing chamber is provided with a working gas inlet and an exhaust port; the first plasma processing unit and the second plasma processing unit are respectively disposed on both sides of the carbon fiber bundle, so that the unfolded carbon fiber bundle can undergo bilateral activation treatment. The BN precursor impregnation device includes a constant temperature impregnation tank for holding BN liquid precursor, and multiple immersion guide rollers disposed in the constant temperature impregnation tank. The immersion guide rollers are used to change the running path of the carbon fiber bundle in the constant temperature impregnation tank so that the carbon fiber bundle is immersed in the BN liquid precursor. The BN precursor impregnation device also includes a heating device and an ultrasonic auxiliary device; The heating device is installed in a constant temperature impregnation tank to heat the BN liquid precursor contained therein; The ultrasonic-assisted device is installed in a constant-temperature impregnation tank to improve the dispersion state of the BN liquid precursor in the impregnation tank and promote the entry of the BN liquid precursor into the interior of the unfolded carbon fiber bundle.

[0011] In one embodiment, the dehydration device includes at least one set of opposing pressure rollers, and when the carbon fiber bundle passes through the gap between the opposing pressure rollers, excess BN liquid precursor on its surface and inside the bundle is squeezed out; The heating and complexing device is a continuous wire-feeding heating device, which gradually transforms the liquid BN precursor into a semi-solid BN precursor layer attached to the surface of the carbon fiber bundle. The high-temperature pyrolysis conversion device is a continuous wire-feed high-temperature furnace, which is equipped with an independently temperature-controlled heating zone, a protective gas inlet, a tail gas outlet, and a temperature detection element. In the high-temperature protective atmosphere, the BN precursor layer undergoes pyrolysis conversion to form a BN interface phase located on the surface of the carbon fiber bundle. The cooling protection device adopts an inert gas convection cooling device, which continuously introduces nitrogen or argon gas to protect and cool the carbon fiber bundles after the BN interface phase is formed. The high-temperature pyrolysis conversion device and the cooling protection device are sealed and connected. Both the carbon fiber bundle inlet of the high-temperature pyrolysis conversion device and the carbon fiber bundle outlet of the cooling protection device are provided with a double-stage gas seal cavity and a flexible slit seal.

[0012] A second objective of this invention is to provide a method for preparing a BN interface phase on the surface of a continuous carbon fiber bundle, using the aforementioned apparatus, the method comprising: S1, the carbon fiber bundles are continuously passed through a high-temperature degumming device to remove the sizing agent from the surface of the carbon fiber bundles under a protective atmosphere. S2, the degummed carbon fiber bundles are spread out by a mechanical yarn spreading device; S3, the unfolded carbon fiber bundle is passed through a low-temperature plasma activation device to activate the surface of the carbon fiber bundle; S4, the activated carbon fiber bundle is passed through the BN precursor impregnation device, the carbon fiber bundle is immersed in the BN liquid precursor and the BN liquid precursor is attached to the surface of the carbon fiber bundle. S5, the impregnated carbon fiber bundles are passed through a dehydration device to remove excess BN liquid precursor and control the amount of precursor attached. S6, the dehydrated carbon fiber bundles are passed through a heating complexing device to form a BN precursor layer from the BN liquid precursor attached to the surface of the carbon fiber bundles. S7, the carbon fiber bundles forming the BN precursor layer are passed through a high-temperature pyrolysis conversion device to convert the BN precursor layer into the BN interface phase; S8 allows the carbon fiber bundles forming the BN interface phase to be protected and cooled by a cooling protection device.

[0013] In one embodiment, the high-temperature adhesive removal device has an adhesive removal temperature of 450–550°C and an adhesive removal atmosphere of nitrogen, argon, or a mixture thereof. In the aforementioned low-temperature plasma activation device, air is used as the working gas to perform double-sided low-temperature plasma activation treatment on the unfolded carbon fiber bundle; the plasma power is 400-600W, and the equivalent treatment time is 10s.

[0014] In one embodiment, the BN liquid precursor comprises a boron-containing compound, a nitrogen-containing compound, and a solvent; the boron-containing compound comprises one or more of boric acid, borate, borate ester, and boron oxide; the nitrogen-containing compound comprises one or more of urea, melamine, ammonium salt, and amine compounds; and the solvent comprises water, ethanol, or a mixture thereof. The BN precursor impregnation temperature is 40-50℃, the impregnation time is 30-40s, and the impregnation effect of BN liquid precursor is improved by ultrasonic assistance.

[0015] In one embodiment, the heating complexation device has a heating complexation temperature of 80–200°C to allow the solvent to evaporate and the BN liquid precursor to form a semi-solid BN precursor layer. In the high-temperature pyrolysis conversion device, the high-temperature pyrolysis conversion temperature is 1000-1200℃, and the processing atmosphere is nitrogen or a mixture of nitrogen and ammonia; when a mixture of ammonia and nitrogen is used, the ammonia gas fraction is 10%-20%.

[0016] In one embodiment, the fiber bundle feed rate is 0.2–2 m / min; Repeat steps S4 to S6 once or more to adjust the amount of BN precursor layer attached and the final thickness of the BN interface phase.

[0017] This invention provides an apparatus and method for preparing a BN interface phase on the surface of continuous carbon fiber bundles. Compared with the prior art, this invention has at least the following advantages: First, the present invention sets high-temperature degumming, mechanical yarn spreading, and low-temperature plasma activation before BN precursor impregnation, which can remove the sizing agent on the surface of the carbon fiber bundle, increase the exposure of the monofilaments in the bundle, and improve the wetting and adhesion ability of the carbon fiber surface to the BN liquid precursor.

[0018] Secondly, the present invention uses a BN precursor impregnation device to immerse the expanded and activated carbon fiber bundles into a BN liquid precursor, and removes excess liquid using a dehydration device. This allows control over the amount of precursor adhering to the surface of the carbon fiber bundles, reducing the risk of local enrichment and uneven film thickness.

[0019] Third, the present invention sets up a heating complexation stabilization device between the liquid removal device and the high-temperature pyrolysis conversion device, so that the BN liquid precursor forms a relatively stable BN precursor layer before pyrolysis, which is beneficial to reduce the migration, aggregation and cracking of the precursor during the subsequent heating process.

[0020] Fourth, the present invention continuously connects the high-temperature pyrolysis conversion device with the cooling protection device, so that the carbon fiber bundle after the formation of the BN interface phase is cooled in a protective atmosphere, which can reduce the oxidation risk during the cooling process after high-temperature treatment.

[0021] Fifth, this invention continuously connects the processes of degumming, yarn spreading, activation, BN precursor impregnation, dehydration, temperature-raising complexation stabilization, high-temperature pyrolysis conversion, and protective cooling through continuous yarn feeding. This reduces process fluctuations caused by offline transfer and repeated clamping, and improves the continuity and controllability of the preparation process of the BN interface phase on the surface of continuous carbon fiber bundles. Attached Figure Description

[0022] Figure 1 is a schematic diagram of the front production line structure of the continuous carbon fiber bundle surface BN interface phase preparation device of the present invention. Figure 2 is a schematic diagram of the back-end production line structure of the continuous carbon fiber bundle surface BN interface phase preparation device of the present invention. Figure 3 is a schematic diagram of the continuous wire-feeding high-temperature degumming tube furnace end double-stage gas seal structure of the present invention; Figure 4 is a schematic diagram of the internal structure of the mechanical yarn spreading device of the present invention; Figure 5 These are scanning electron microscope (SEM) comparison images of the BN interface phase on the surface of the carbon fiber bundles obtained in Example 1 and the comparative example. Figure 5 (a) and Figure 5 (c) The cross-sectional and surface morphologies of the BN interface phase obtained in Example 1 are shown respectively. Figure 5 (b) and Figure 5 (d) shows the cross-sectional morphology and surface morphology of the BN interface phase obtained in the comparative example, respectively; Figure 6 The X-ray photoelectron spectroscopy (XPS) spectra of the BN interface phases obtained in Example 1 and the comparative example are shown below. Figure 6 (a) is the total X-ray photoelectron spectrum of the BN interface phase obtained in Example 1. Figure 6 (b) is the total X-ray photoelectron spectrum of the BN interface phase obtained in the comparative example; Explanation of reference numerals in the attached drawings: 1. Unwinding mechanism; 2. Carbon fiber bundle; 3. High-temperature degumming tube furnace; 4. Mechanical yarn spreading device; 5. Yarn spreading roller; 6. Low-temperature plasma activation device; 7. BN precursor impregnation device; 8. Roller pressing dehydration device; 9. Heating complexing tube furnace; 10. High-temperature pyrolysis tube furnace; 11. Protective gas supply and exhaust gas discharge assembly; 12. Cooling device; 13. Traction and winding mechanism; 14. Gas seal cavity; 15. High-temperature resistant flexible slit seal; 16. Protective gas inlet; 17. Exhaust gas outlet; 18. Gradient guide. Detailed Implementation

[0023] In order to illustrate the technical means and effects adopted by the present invention to achieve the intended purpose, the following detailed description is provided in conjunction with the embodiments.

[0024] This invention primarily targets continuous carbon fiber bundles, which contain numerous interconnected monofilaments. During impregnation, liquid precursors tend to preferentially adhere to the outer fiber surface, resulting in insufficient exposure of the inner monofilaments and uneven distribution of the BN precursor within and outside the bundle. If the precursor is impregnated directly without unwinding and surface activation, problems such as insufficient wetting, localized enrichment, and uneven film thickness can easily occur. Furthermore, if excess liquid is not removed and stabilization treatment is not performed promptly after impregnation, the precursor liquid film may migrate, accumulate, and crack locally during subsequent heating, affecting the continuity and uniformity of the final BN interfacial phase.

[0025] The purpose of this invention is to provide a device and method for preparing a BN interface phase on the surface of a continuous carbon fiber bundle. By unwinding the yarn and activating the surface on both sides, the exposure of the monofilaments within the bundle and the wetting and adhesion of the carbon fiber surface to the precursor are improved. By dehydration and film control and heating and complexation, the risk of migration, aggregation and cracking of the precursor during subsequent heat treatment is reduced. By continuously connecting each processing step, the invention solves the problems of repeated clamping and manual transfer of carbon fiber bundles, unstable connection between processes, uneven distribution of precursors inside and outside the bundle, and difficulty in continuously controlling the thickness of the interface layer in existing discontinuous preparation processes. Thus, the invention achieves continuous, uniform and controllable preparation of a BN interface phase on the surface of a continuous carbon fiber bundle.

[0026] To achieve the above objectives, see Figures 1-4 As shown, a continuous carbon fiber bundle surface BN interface phase preparation device includes a fiber conveying assembly and a high-temperature degumming device, a mechanical yarn spreading device 4, a low-temperature plasma activation device 6, a BN precursor impregnation device 7, a dehydration device 8, a heating complexing device 9, a high-temperature pyrolysis conversion device 10, and a cooling protection device 12 arranged sequentially along the continuous running direction of the carbon fiber bundle. The fiber conveying assembly is used to sequentially pass the carbon fiber bundle through a high-temperature degumming device, a mechanical yarn spreading device, a low-temperature plasma activation device, a BN precursor impregnation device, a dehydration device, a heating complexing device, a high-temperature pyrolysis conversion device, and a cooling protection device. The high-temperature degumming device is used to remove the sizing agent from the surface of the carbon fiber bundles; The mechanical yarn spreading device 4 is used to spread the carbon fiber bundle to increase the exposure of the monofilaments inside the bundle. The low-temperature plasma activation device 6 is used to activate the surface of the carbon fiber bundle; The BN precursor impregnation device 7 is used to impregnate the carbon fiber bundle with the BN liquid precursor and to attach the BN liquid precursor to the surface of the carbon fiber bundle. The dehydration device 8 is used to remove excess BN liquid precursor and control the amount of BN liquid precursor adhering to the surface of the carbon fiber bundle. The heating complexing device 9 is used to evaporate the solvent, complex the solute and solidify the BN precursor solution attached to the surface of the carbon fiber bundle to form a BN precursor layer. The high-temperature pyrolysis conversion device 10 is used to convert the BN precursor layer into the BN interface phase; The cooling protection device 12 is used to protect and cool the carbon fiber bundles after the BN interface phase is formed.

[0027] To achieve continuous feeding of carbon fiber bundles, a fiber feeding assembly is provided, including an unwinding mechanism 1 and a traction and winding mechanism 13 located behind a cooling protection device. The unwinding mechanism 1 is used to support the carbon fiber bundle and, under the traction of the traction and winding mechanism 13, rotates the carbon fiber bundle and continuously feeds the carbon fiber bundle along the yarn feeding direction. The fiber feeding assembly also includes a tension control mechanism; the tension control mechanism is used to maintain the continuous and stable operation of the carbon fiber bundle during the yarn spreading, BN precursor impregnation, heating complexation, and high-temperature pyrolysis conversion processes.

[0028] The high-temperature degumming device 3 is a continuous wire-feeding tubular heating device, which includes a tubular heating channel, a protective gas inlet, a degumming exhaust gas outlet, a carbon fiber bundle inlet, and a carbon fiber bundle outlet.

[0029] See Figure 3 As shown, the tubular heating device has a carbon fiber bundle inlet and an outlet at both ends, respectively; two air-sealing cavities 14 connected sequentially from the outside to the inside are provided at both the carbon fiber bundle inlet and outlet to form a double-stage air-sealing cavity; a high-temperature resistant flexible slit seal 15 is provided between the inner air-sealing cavity 14 and the end of the tubular heating device; the slit width of the flexible slit seal 15 is 0.2 to 0.5 mm larger than the thickness of the expanded fiber bundle.

[0030] It should be noted that the air-sealed cavity is a closed cavity with symmetrically placed inlets and outlets for transmitting carbon fiber bundles.

[0031] Each air-sealed chamber 14 is provided with a protective gas inlet 16, and the tubular heating device is provided with an air inlet 16 near the carbon fiber bundle inlet, and the tubular heating device is provided with an exhaust gas outlet 17 near the carbon fiber bundle outlet. The protective gas enters the furnace body and the double-stage gas seal chamber through the air inlet 16. The slight positive pressure inside the furnace is maintained at 200-300 Pa. The tail gas is discharged through the tail gas outlet 17, so that the protective gas at the inlet and outlet always flows from inside the furnace to the outside, thereby suppressing air backflow.

[0032] To increase the exposure of single filaments in carbon fiber bundles, see [link / reference]. Figure 4 As shown, the mechanical yarn spreading device 4 includes five yarn spreading rollers 5 arranged in a staggered pattern along the direction of the carbon fiber bundle. The axial height difference between adjacent yarn spreading rollers 5 is 30 mm, and the center distance between the rollers is 80 mm. The carbon fiber bundle passes over each yarn spreading roller 5 with a tension of 8 N, with a wrap angle of 15° to 35°, and the bundle width gradually widens from about 6 mm to 30 mm. After high-temperature pyrolysis and cooling, the bundle is slowly gathered to 8-12 mm by a tapering guide 18 for winding. This gathering only changes the transverse arrangement width of the monofilaments, without causing the monofilaments that have formed the precursor layer to re-bond back to their original tight bundle state.

[0033] By adjusting the running path and wrap angle of the carbon fiber bundle through multiple staggered spreading rollers 5, the carbon fiber bundle is transformed from a bundled state to a spread state.

[0034] The low-temperature plasma activation device 6 includes a plasma processing chamber, and a first plasma processing unit and a second plasma processing unit disposed within the plasma processing chamber; the plasma processing chamber is provided with a working gas inlet and an exhaust port; the first plasma processing unit and the second plasma processing unit are respectively disposed on both sides of the carbon fiber bundle 2, so that the unfolded carbon fiber bundle 2 can undergo bilateral activation treatment; wherein, the two ends of the plasma processing chamber are provided with a carbon fiber bundle inlet and an outlet.

[0035] The BN precursor impregnation device 7 includes a constant temperature impregnation tank for holding BN liquid precursor, and a plurality of immersion guide rollers disposed in the constant temperature impregnation tank. The immersion guide rollers are used to change the running path of the carbon fiber bundle 2 in the constant temperature impregnation tank so that the carbon fiber bundle 2 is immersed in the BN liquid precursor. The BN precursor impregnation device 7 also includes a heating device and an ultrasonic auxiliary device; The heating device is installed in a constant temperature impregnation tank to heat the BN liquid precursor contained therein; The ultrasonic-assisted device is installed in a constant-temperature impregnation tank to improve the dispersion state of the BN liquid precursor in the impregnation tank and to promote the entry of the BN liquid precursor into the interior of the unfolded carbon fiber bundle 2.

[0036] The dehydration device 8 includes at least one set of pressure rollers arranged opposite each other. When the carbon fiber bundle 2 passes through the gap between the pressure rollers arranged opposite each other, excess BN liquid precursor on its surface and inside the bundle is squeezed out. The heating and complexing device 9 is a continuous wire-feeding heating device that gradually transforms the liquid BN precursor into a semi-solid BN precursor layer attached to the surface of the carbon fiber bundle 2. The high-temperature pyrolysis conversion device 10 is a continuous wire-feed high-temperature tube furnace. This furnace is equipped with an independently temperature-controlled heating zone, a protective gas inlet, a tail gas outlet, and temperature detection elements. In the high-temperature protective atmosphere, the BN precursor layer undergoes pyrolysis conversion, forming a BN interface phase on the surface of the carbon fiber bundle 2. The carbon fiber bundle enters the tube furnace through an inlet equipped with the same dual-stage air-sealing cavity and high-temperature resistant flexible slit seal 15 as the high-temperature degumming device, thereby suppressing air backflow. The cooling protection device 12 employs an inert gas convection cooling system, continuously introducing nitrogen or argon gas to protect and cool the carbon fiber bundle 2 after the formation of the BN interface phase. The cooling protection device 12 is located at the carbon fiber bundle outlet and features the same dual-stage gas seal cavity and high-temperature resistant flexible slit seal 15 as the high-temperature degumming device, thereby preventing air backflow.

[0037] It should be noted that the high-temperature pyrolysis conversion device 10 has carbon fiber bundle inlets and outlets at both ends, and the cooling protection device 12 has carbon fiber bundle inlets and outlets at both ends. The carbon fiber bundle outlet of the high-temperature pyrolysis conversion device 10 and the carbon fiber bundle inlet of the cooling protection device 12 are sealed together. Therefore, the high-temperature pyrolysis conversion device 10 has a double-stage air seal cavity and a flexible slit seal 15, similar to those used in the high-temperature adhesive removal device, at the carbon fiber bundle inlet to suppress backflow of air. Similarly, the cooling protection device 12 has a double-stage air seal cavity and a high-temperature resistant flexible slit seal 15, similar to those used in the high-temperature adhesive removal device, at the carbon fiber bundle outlet to suppress backflow of air. Likewise, the high-temperature pyrolysis conversion device 10 has an air inlet 16 near the carbon fiber bundle inlet and an exhaust gas outlet 17 near the carbon fiber bundle outlet; similarly, the cooling protection device 12 has an exhaust gas outlet 17 near the carbon fiber bundle inlet and an air inlet 16 near the carbon fiber bundle outlet. A protective gas supply and exhaust gas discharge assembly 11 is provided on the outer side between the high-temperature pyrolysis conversion device 10 and the cooling protection device 12. The protective gas supply and exhaust gas discharge assembly 11 is connected to the air inlets 16 of the high-temperature pyrolysis conversion device 10 and the cooling protection device 12 via gas supply pipelines, and to the corresponding exhaust gas outlets 17 via exhaust gas pipelines. During operation, the protective gas enters the high-temperature pyrolysis conversion device 10 and the cooling protection device 12 through the air inlets 16, flows along the inside of the devices towards the exhaust gas outlet 17, and is then discharged through the exhaust gas outlet 17 and the exhaust gas pipeline. By adjusting the protective gas supply and exhaust gas discharge, a protective atmosphere and a slight positive pressure are maintained inside the high-temperature pyrolysis conversion device 10 and the cooling protection device 12, thereby suppressing backflow of external air and reducing the oxidation risk of the carbon fiber bundle 2 and its surface BN interface phase during high-temperature pyrolysis and cooling.

[0038] This invention provides a method for preparing a BN interface phase on the surface of a continuous carbon fiber bundle, using the aforementioned apparatus for preparing a BN interface phase on the surface of a continuous carbon fiber bundle. The method includes: S1, the carbon fiber bundles are continuously passed through a high-temperature degumming device to remove the sizing agent from the surface of the carbon fiber bundles under a protective atmosphere. S2, the degummed carbon fiber bundles are spread out by a mechanical yarn spreading device; S3, the unfolded carbon fiber bundle is passed through a low-temperature plasma activation device to activate the surface of the carbon fiber bundle; S4, the activated carbon fiber bundle is passed through the BN precursor impregnation device, the carbon fiber bundle is immersed in the BN liquid precursor and the BN liquid precursor is attached to the surface of the carbon fiber bundle. S5, the impregnated carbon fiber bundles are passed through a dehydration device to remove excess BN liquid precursor and control the amount of precursor attached. S6, the dehydrated carbon fiber bundles are passed through a heating complexing device to form a BN precursor layer from the BN liquid precursor attached to the surface of the carbon fiber bundles. S7, the carbon fiber bundles forming the BN precursor layer are passed through a high-temperature pyrolysis conversion device to convert the BN precursor layer into the BN interface phase; S8 allows the carbon fiber bundles forming the BN interface phase to be protected and cooled by a cooling protection device.

[0039] The high-temperature adhesive removal device has an adhesive removal temperature of 450–550°C and uses nitrogen, argon, or a mixture thereof as the adhesive removal atmosphere; the effective heating length is 1.5 m. In the aforementioned low-temperature plasma activation device, air is used as the working gas to perform double-sided low-temperature plasma activation treatment on the unfolded carbon fiber bundle; the plasma power is 400-600W, and the equivalent treatment time is 10s.

[0040] The BN liquid precursor comprises a boron-containing compound, a nitrogen-containing compound, and a solvent; the boron-containing compound comprises one or more of boric acid, borates, borate esters, and boron oxides; the nitrogen-containing compound comprises one or more of urea, melamine, ammonium salts, and amine compounds; the solvent comprises water, ethanol, or a mixture thereof; preferably, the BN liquid precursor is composed of boric acid, urea, deionized water, and anhydrous ethanol, wherein the concentration of boric acid is 0.4–0.5 mol / L, the concentration of urea is 3.0–3.6 mol / L, and the volume ratio of deionized water to anhydrous ethanol is 5:5–9:1; The BN precursor impregnation temperature is 40-50℃, the impregnation time is 30-40s, and the impregnation effect of BN liquid precursor is improved by ultrasonic assistance.

[0041] In the heating complexation device, the heating complexation temperature is 80-200℃, the effective heating length is 0.8-1.2m, and the processing atmosphere is air, so as to evaporate the solvent and form a semi-solid BN precursor layer from the BN liquid precursor; In the high-temperature pyrolysis conversion device, the high-temperature pyrolysis conversion temperature is 1000-1200℃, and the processing atmosphere is nitrogen or a mixture of nitrogen and ammonia; when a mixture of ammonia and nitrogen is used, the ammonia gas fraction is 10%-20%.

[0042] The apparatus provided by this invention sets the fiber bundle feeding speed to 0.2–2 m / min; and repeats S4–S6 once or more to adjust the amount of BN precursor layer adhesion and the final BN interfacial phase thickness. The resulting BN interfacial phase thickness is 20–200 nm.

[0043] It should be noted that steps S1 to S8 are completed sequentially in continuous wire feeding mode.

[0044] To illustrate the apparatus for preparing the BN interface phase on the surface of continuous carbon fiber bundles provided by the present invention, specific examples will be used for explanation.

[0045] Example 1 See Figures 1-4 As shown, this embodiment provides a continuous carbon fiber bundle surface BN interface phase preparation apparatus, including an unwinding mechanism 1, a high-temperature degumming tubular furnace 3, a mechanical yarn spreading device 4, a low-temperature plasma activation device 6, a BN precursor impregnation device 7, a roller pressing dehydration device 8, a heating complexing tubular furnace 9, a high-temperature pyrolysis tubular furnace 10, a cooling device 12, and a traction winding mechanism 13 arranged sequentially along the continuous running direction of the carbon fiber bundle 2. The unwinding mechanism 1, the traction winding mechanism 13, and the corresponding tension control components together constitute a fiber conveying assembly, used to allow the carbon fiber bundle 2 to pass sequentially through each processing unit in a continuous spinning state.

[0046] This embodiment uses T700-12K carbon fiber bundles for continuous fabrication. After being drawn out from the unwinding mechanism 1, the carbon fiber bundle 2 runs continuously along the yarn feeding direction under the traction of the traction and winding mechanism 13. During operation, the running tension of the carbon fiber bundle 2 can be adjusted by the tension control component to maintain stable feeding during degumming, yarn spreading, BN precursor impregnation, heating complexation, and high-temperature pyrolysis conversion, reducing loosening, entanglement, yarn breakage, or fuzzing. The yarn feeding speed is 0.2 m / min, and the running tension is 8 N.

[0047] The carbon fiber bundle 2 first enters a high-temperature degumming tubular furnace 3. The high-temperature degumming tubular furnace 3 can employ a continuous wire-feed tubular heating structure and is equipped with a protective gas inlet and a degumming exhaust gas outlet. During the degumming process, nitrogen, argon, or a mixture thereof are introduced into the high-temperature degumming tubular furnace 3 as a protective atmosphere, allowing the carbon fiber bundle 2 to be heated under this protective atmosphere to remove the sizing agent from its surface. The processing temperature of the high-temperature degumming tubular furnace 3 is 500℃, the nitrogen flow rate is 2.0 L / min, the furnace internal micro-positive pressure is 200 Pa, and the effective heating length can be 1.5 m. This step reduces the impact of the sizing agent on subsequent surface activation and BN precursor impregnation processes.

[0048] After high-temperature degumming, the carbon fiber bundle 2 enters the mechanical yarn spreading device 4. The mechanical yarn spreading device 4 includes multiple spreading rollers 5 arranged along the running direction of the carbon fiber bundle 2. The carbon fiber bundle 2 sequentially passes around the multiple spreading rollers 5. By adjusting the position, spacing, and wrap angle of the spreading rollers 5 (20°), the originally bundled carbon fiber bundle 2 is gradually spread out, thereby increasing the exposure of the monofilaments within the bundle. The spreading width is 30mm. This treatment facilitates subsequent low-temperature plasma activation and the entry of BN liquid precursor into the bundle.

[0049] The unfolded carbon fiber bundle 2 enters the low-temperature plasma activation device 6. The low-temperature plasma activation device 6 includes a plasma processing chamber, a first plasma processing unit, a second plasma processing unit, a working gas inlet, and an exhaust port. The first and second plasma processing units are respectively located on both sides of the carbon fiber bundle 2, allowing the unfolded carbon fiber bundle 2 to undergo bilateral activation treatment. The low-temperature plasma activation treatment uses air as the working gas, with a plasma power of 500W and an equivalent treatment time of 10s. This step improves the wettability and adhesion of the BN liquid precursor to the surface of the carbon fiber bundle 2.

[0050] The carbon fiber bundle 2, activated by low-temperature plasma, enters the BN precursor impregnation device 7. The BN precursor impregnation device 7 includes a constant-temperature impregnation tank, a heating device, an ultrasonic auxiliary device, and immersion guide rollers. The constant-temperature impregnation tank contains BN liquid precursor, and the immersion guide rollers are used to change the running path of the carbon fiber bundle 2 within the tank, ensuring that the carbon fiber bundle 2 is immersed in the BN liquid precursor. The ultrasonic auxiliary device is used to improve the dispersion state of the BN liquid precursor within the impregnation tank and promote its penetration into the unfolded carbon fiber bundle 2.

[0051] In this embodiment, the BN liquid precursor can be composed of boric acid, urea, deionized water, and anhydrous ethanol. The concentration of boric acid is 0.45 mol / L, the concentration of urea is 3.30 mol / L, and the volume ratio of deionized water to anhydrous ethanol is 7:3. The impregnation temperature of the BN precursor is 45°C, and the impregnation residence time is 35 s. By controlling the concentration of the BN liquid precursor, the impregnation temperature, the impregnation residence time, and the feeding speed of the carbon fiber bundle 2, the amount of BN liquid precursor adhering to the surface of the carbon fiber bundle 2 can be adjusted.

[0052] The impregnated carbon fiber bundles 2 enter the roller pressing dehydration device 8. The roller pressing dehydration device 8 includes a set of opposing pressure rollers with a gap of 0.18 mm. As the carbon fiber bundles 2 pass through the gap, excess BN liquid precursors on their surface and within the bundle are squeezed out, thereby controlling the amount of precursors adhering to the surface of the carbon fiber bundles 2 and the uniformity of the wet film. The clamping force of the pressure rollers is adjustable to accommodate different specifications of carbon fiber bundles 2 and different target adhesion amounts. Through roller pressing dehydration, the risk of excess liquid migration, aggregation, and localized accumulation during subsequent heating processes can be reduced.

[0053] After dehydration, the carbon fiber bundles 2 enter a heated complexing tube furnace 9. The heated complexing tube furnace 9 is a continuous wire-feed heating device with a processing temperature of 150℃ and a processing time of 5 minutes; the processing atmosphere can be air. During the heated complexing process, the solvent in the BN liquid precursor adhering to the surface of the carbon fiber bundles 2 gradually evaporates, and the boron-containing and nitrogen-containing components undergo complexation and solidification, causing the BN liquid precursor to gradually transform into a semi-solid BN precursor layer adhering to the surface of the carbon fiber bundles 2. This step improves the morphological stability of the precursor layer before entering the high-temperature pyrolysis transformation.

[0054] The carbon fiber bundle 2, after forming the BN precursor layer, enters the high-temperature pyrolysis tube furnace 10. The high-temperature pyrolysis tube furnace 10 can adopt a continuous wire-feed high-temperature furnace structure and is equipped with independently temperature-controlled heating zones, protective gas inlets, exhaust gas outlets, and temperature detection elements. The processing temperature of the high-temperature pyrolysis tube furnace 10 is 1100℃, and the processing uses a mixture of 15% ammonia and 85% nitrogen by volume, with a gas flow rate of 2.5 L / min. In the high-temperature protective atmosphere, the BN precursor layer undergoes pyrolysis transformation, forming a BN interface phase on the surface of the carbon fiber bundle 2.

[0055] Both the high-temperature pyrolysis tubular furnace 10 and the cooling device 12 are connected to the protective gas supply and exhaust gas discharge assembly 11. The protective gas supply and exhaust gas discharge assembly 11 supplies a mixture of 15% ammonia and 85% nitrogen by volume to the high-temperature pyrolysis tubular furnace 10 via independent gas supply lines, and supplies nitrogen or argon to the cooling device 12. The exhaust gas generated during the high-temperature pyrolysis process and the protective gas discharged from the cooling device 12 are discharged through their respective exhaust gas outlets 17. By adjusting the gas flow rate of each gas supply line, a slight positive pressure is maintained inside the high-temperature pyrolysis tubular furnace 10 and the cooling device 12 to reduce air backflow and high-temperature oxidation.

[0056] The carbon fiber bundles 2, after high-temperature pyrolysis conversion, enter the cooling device 12. The cooling device 12 is located after the high-temperature pyrolysis tube furnace 10 and can employ an inert gas convection cooling structure. During the cooling process, nitrogen or argon gas can be introduced into the cooling device 12 to provide protective cooling for the carbon fiber bundles 2 after the formation of the BN interfacial phase, ensuring that the temperature of the cooled carbon fiber bundles 2 does not exceed 60°C. Protective cooling reduces the time that the high-temperature treated carbon fiber bundles 2 and their surface BN interfacial phase are in direct contact with air, thus reducing the risk of oxidation during the cooling process.

[0057] After cooling, the carbon fiber bundle 2 is wound up by the traction winding mechanism 13. Through the above continuous spinning process, the carbon fiber bundle 2 sequentially completes degumming, yarn spreading, double-sided plasma activation, BN precursor impregnation, roll pressing dehydration, heating complexation, high-temperature pyrolysis conversion and protective cooling treatment, thereby realizing the continuous preparation of the BN interface phase on the surface of the continuous carbon fiber bundle.

[0058] Scanning electron microscopy was used to observe the cross-sectional and surface morphology of randomly selected monofilaments from the outer, middle, and inner layers of the fiber bundle, and the thickness of the BN interfacial phase was measured. Figure 5 (a) and Figure 5 As shown in (c), after preparation using the continuous process described in this embodiment, a relatively continuous BN interface phase was formed on the surface of the carbon fiber. The interface phase covered the fiber surface relatively completely, and no obvious large-area shedding or local agglomeration was observed. Statistically, the average thickness of the BN interface phase obtained by the continuous process was 55.3 nm, with a standard deviation of 4.8 nm. The average thicknesses of the BN interface phase on the surfaces of the outer, middle, and inner monofilaments of the fiber bundle were 58.1 nm, 55.7 nm, and 52.2 nm, respectively, with an inner-outer layer thickness ratio of 0.90 and an interface phase surface coverage of 92.6%.

[0059] The elemental composition of the interface phase was analyzed using X-ray photoelectron spectroscopy, and the results are as follows: Figure 6As shown in (a), characteristic B 1s and N 1s peaks appear at binding energies of approximately 191.5 eV and 398.0 eV, respectively, indicating that the obtained interfacial phase contains B and N elements. After peak area integration and relative sensitivity factor correction, the B / N atomic ratio of the obtained interfacial phase is 1.02, which is close to the stoichiometry of B and N.

[0060] Example 2 The difference between this embodiment and embodiment 1 is that the BN precursor impregnation, roll pressing dehydration and heating complexation process can be repeated once or multiple times to adjust the amount of BN precursor layer and the final BN interface phase thickness.

[0061] Specifically, two or more sets of sequentially arranged BN precursor impregnation devices 7, roller pressing dehydration devices 8, and heating complexing tube furnaces 9 can be set up along the continuous fiber feeding path, so that the carbon fiber bundle 2 can sequentially complete multiple BN precursor impregnation, dehydration and film control, and heating complexing treatments during continuous operation. The BN liquid precursor concentration, impregnation temperature, and impregnation residence time in each stage of the BN precursor impregnation device 7 can be the same, or they can be set separately according to the target precursor adhesion amount; the clamping force of each stage of the roller pressing dehydration device 8 can also be adjusted according to the wet film state of the corresponding stage.

[0062] By repeatedly impregnating the BN precursor, rolling to remove liquid, and heating to complex, the amount of BN precursor layer can be gradually increased while avoiding local enrichment caused by excessive impregnation in a single step, and the thickness of the final BN interface phase can be further adjusted. The thickness of the resulting BN interface phase can be 20–200 nm.

[0063] Comparative Example The same T700-12K carbon fiber bundles and BN liquid precursors as in Example 1 were used for non-continuous batch preparation. First, a 1m long carbon fiber bundle was placed in a nitrogen atmosphere at 500℃ for 7.5 min to remove the glue. After cooling, it was not continuously mechanically spread but manually laid flat. Then, it was treated on both sides for 10 s under 500W air plasma. The entire fiber bundle was then immersed in a precursor solution at 45℃ for 35 s, removed, and allowed to drip naturally for 2 min. It was then complexed in a 150℃ oven for 5 min, and finally transferred to a tube furnace at 1100℃ for pyrolysis in a mixture of 15% ammonia and 85% nitrogen for 5 min. Except for continuous conveying, mechanical spreading, roller pressing for dehydration, and continuous atmosphere connection, the raw materials and main temperature parameters were the same as in Example 1.

[0064] The samples obtained from the non-continuous batch process were characterized by scanning electron microscopy and X-ray photoelectron spectroscopy using the same method as in Example 1. Figure 5 (b) and Figure 5As shown in (d), the uniformity of the BN interfacial phase distribution on the surface of the monofilaments at different locations in the comparative example is relatively poor, with localized differences in interfacial phase thickness and incomplete coverage. Statistical analysis revealed that the average thickness of the BN interfacial phase obtained from the non-continuous batch process was 51.3 nm, with a standard deviation of 14.7 nm. The average thicknesses of the BN interfacial phase on the surfaces of the outer, middle, and inner monofilaments were 62.3 nm, 51.0 nm, and 40.6 nm, respectively, with an inner-outer layer thickness ratio of 0.65 and an interfacial phase surface coverage of 81.4%.

[0065] The total X-ray photoelectron spectrum of the interfacial phase obtained in the comparative example is as follows: Figure 6 As shown in (b), characteristic peaks were detected at the binding energy positions corresponding to B 1s and N 1s. After peak area integration and relative sensitivity factor correction, the B / N atomic ratio was 1.05. Compared with the comparative example, the thickness standard deviation of the BN interface phase obtained in Example 1 was significantly reduced, the inner-outer layer thickness ratio increased by 0.25, and the surface coverage increased by 11.2 percentage points. This indicates that continuous mechanical yarn spreading, roller pressing for dehydration and film control, and the continuous connection of each processing step are beneficial to improving the uniformity of distribution and coverage integrity of the BN interface phase on the surface of the inner and outer monofilaments of the yarn bundle.

[0066] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the principles of the present invention should be included within the protection scope of the present invention.

Claims

1. An apparatus for preparing a BN interface phase on the surface of a continuous carbon fiber bundle, characterized in that, It includes a fiber conveying assembly and a high-temperature degumming device (3), a mechanical yarn spreading device (4), a low-temperature plasma activation device (6), a BN precursor impregnation device (7), a dehydration device (8), a heating complexing device (9), a high-temperature pyrolysis conversion device (10), and a cooling protection device (12) arranged sequentially along the continuous running direction of the carbon fiber bundle. The fiber conveying assembly is used to sequentially pass the carbon fiber bundle through a high-temperature degumming device, a mechanical yarn spreading device, a low-temperature plasma activation device, a BN precursor impregnation device, a dehydration device, a heating complexing device, a high-temperature pyrolysis conversion device, and a cooling protection device. The high-temperature degumming device (3) is used to remove the sizing agent from the surface of the carbon fiber bundles; The mechanical yarn spreading device (4) is used to spread the carbon fiber bundle to increase the exposure of the monofilaments in the bundle. The low-temperature plasma activation device (6) is used to activate the surface of the carbon fiber bundle; The BN precursor impregnation device (7) is used to impregnate the carbon fiber bundle with the BN liquid precursor and to attach the BN liquid precursor to the surface of the carbon fiber bundle. The dehydration device (8) is used to remove excess BN liquid precursor and control the amount of BN liquid precursor adhering to the surface of the carbon fiber bundle. The heating complexing device (9) is used to evaporate the solvent, complex the solute and solidify the BN precursor solution attached to the surface of the carbon fiber bundle to form a BN precursor layer. The high-temperature pyrolysis conversion device (10) is used to convert the BN precursor layer into the BN interface phase; The cooling protection device (12) is used to protect and cool the carbon fiber bundles after the BN interface phase is formed.

2. The apparatus for preparing the BN interface phase on the surface of a continuous carbon fiber bundle according to claim 1, characterized in that, The fiber conveying assembly includes an unwinding mechanism (1) and a traction winding mechanism (13) located behind the cooling protection device. The unwinding mechanism (1) is used to set up the carbon fiber bundle and, under the traction of the traction winding mechanism (13), make the carbon fiber bundle rotate and continuously transport the carbon fiber bundle along the wire feeding direction. The fiber conveying assembly also includes a tension control mechanism; the tension control mechanism is used to maintain the continuous and stable operation of the carbon fiber bundle during the processes of yarn spreading, BN precursor impregnation, heating complexation and high-temperature pyrolysis conversion.

3. The apparatus for preparing the BN interface phase on the surface of a continuous carbon fiber bundle according to claim 1, characterized in that, The high-temperature degumming device (3) is a continuous wire-feeding tubular heating device. The continuous wire-feeding tubular heating device is provided with a tubular heating channel, a protective gas inlet, a degumming tail gas outlet, a carbon fiber bundle inlet, and a carbon fiber bundle outlet. Among them, the carbon fiber bundle inlet and the carbon fiber bundle outlet are provided with two air-sealing cavities (14) connected sequentially from the outside to the inside, and a high-temperature resistant flexible slit seal (15) is provided between the air-sealing cavity (14) located on the inside and the end of the tubular heating device. The mechanical yarn spreading device (4) includes multiple yarn spreading rollers (5) arranged along the running direction of the carbon fiber bundle (2), and the carbon fiber bundle (2) passes around the multiple yarn spreading rollers (5) in sequence. The running path and wrap angle of the carbon fiber bundle are adjusted by multiple staggered spreading rollers (5), so that the carbon fiber bundle changes from a bundled state to a spread state.

4. The apparatus for preparing the BN interface phase on the surface of a continuous carbon fiber bundle according to claim 1, characterized in that, The low-temperature plasma activation device (6) includes a plasma processing chamber, and a first plasma processing unit and a second plasma processing unit disposed in the plasma processing chamber; the plasma processing chamber is provided with a working gas inlet and an exhaust port; the first plasma processing unit and the second plasma processing unit are respectively disposed on both sides of the carbon fiber bundle (2), so that the unfolded carbon fiber bundle (2) can be activated on both sides. The BN precursor impregnation device (7) includes a constant temperature impregnation tank for holding BN liquid precursor, and multiple immersion guide rollers disposed in the constant temperature impregnation tank. The immersion guide rollers are used to change the running path of the carbon fiber bundle (2) in the constant temperature impregnation tank so that the carbon fiber bundle (2) is immersed in the BN liquid precursor. The BN precursor impregnation device (7) also includes a heating device and an ultrasonic auxiliary device; The heating device is installed in a constant temperature impregnation tank to heat the BN liquid precursor contained therein; The ultrasonic-assisted device is set in a constant temperature impregnation tank to improve the dispersion state of the BN liquid precursor in the impregnation tank and to promote the BN liquid precursor to enter the interior of the unfolded carbon fiber bundle (2).

5. The apparatus for preparing the BN interface phase on the surface of a continuous carbon fiber bundle according to claim 1, characterized in that, The dehydration device (8) includes at least one set of pressure rollers arranged opposite each other. When the carbon fiber bundle (2) passes through the gap between the pressure rollers arranged opposite each other, excess BN liquid precursor on its surface and inside the bundle is squeezed out. The heating complexing device (9) is a continuous wire-feeding heating device, which gradually transforms the BN liquid precursor into a semi-solid BN precursor layer attached to the surface of the carbon fiber bundle (2). The high-temperature pyrolysis conversion device (10) is a continuous wire-feeding high-temperature furnace. The continuous wire-feeding high-temperature furnace is equipped with an independently temperature-controlled heating zone, a protective gas inlet, a tail gas outlet, and a temperature detection element. In the high-temperature protective atmosphere, the BN precursor layer undergoes pyrolysis conversion to form a BN interface phase located on the surface of the carbon fiber bundle (2). The cooling protection device (12) adopts an inert gas convection cooling device, which continuously introduces nitrogen or argon to protect and cool the carbon fiber bundle (2) after the BN interface phase is formed. The high-temperature pyrolysis conversion device (10) and the cooling protection device (12) are sealed and connected. Both the carbon fiber bundle inlet of the high-temperature pyrolysis conversion device and the carbon fiber bundle outlet of the cooling protection device are provided with a double-stage gas seal cavity and a flexible slit seal.

6. A method for preparing a BN interface phase on the surface of a continuous carbon fiber bundle, characterized in that, Using the apparatus according to any one of claims 1 to 5, the method comprises: S1, the carbon fiber bundles are continuously passed through a high-temperature degumming device to remove the sizing agent from the surface of the carbon fiber bundles under a protective atmosphere. S2, the degummed carbon fiber bundles are spread out by a mechanical yarn spreading device; S3, the unfolded carbon fiber bundle is passed through a low-temperature plasma activation device to activate the surface of the carbon fiber bundle; S4, the activated carbon fiber bundle is passed through the BN precursor impregnation device, the carbon fiber bundle is immersed in the BN liquid precursor and the BN liquid precursor is attached to the surface of the carbon fiber bundle. S5, the impregnated carbon fiber bundles are passed through a dehydration device to remove excess BN liquid precursor and control the amount of precursor attached. S6, the dehydrated carbon fiber bundles are passed through a heating complexing device to form a BN precursor layer from the BN liquid precursor attached to the surface of the carbon fiber bundles. S7, the carbon fiber bundles forming the BN precursor layer are passed through a high-temperature pyrolysis conversion device to convert the BN precursor layer into the BN interface phase; S8 allows the carbon fiber bundles forming the BN interface phase to be protected and cooled by a cooling protection device.

7. The method for preparing the BN interface phase on the surface of continuous carbon fiber bundles according to claim 6, characterized in that, In the high-temperature adhesive removal device, the adhesive removal temperature is 450-550℃, and the adhesive removal atmosphere is nitrogen, argon, or a mixture thereof. In the aforementioned low-temperature plasma activation device, air is used as the working gas to perform double-sided low-temperature plasma activation treatment on the unfolded carbon fiber bundle; the plasma power is 400-600W, and the equivalent treatment time is 10s.

8. The method for preparing the BN interface phase on the surface of continuous carbon fiber bundles according to claim 6, characterized in that, The BN liquid precursor comprises a boron-containing compound, a nitrogen-containing compound, and a solvent; the boron-containing compound comprises one or more of boric acid, borate, borate ester, and boron oxide; the nitrogen-containing compound comprises one or more of urea, melamine, ammonium salt, and amine compounds; the solvent comprises water, ethanol, or a mixture thereof. The BN precursor impregnation temperature is 40-50℃, the impregnation time is 30-40s, and the impregnation effect of BN liquid precursor is improved by ultrasonic assistance.

9. The method for preparing the BN interface phase on the surface of continuous carbon fiber bundles according to claim 6, characterized in that, In the heating complexation device, the heating complexation temperature is 80-200°C, so as to evaporate the solvent and form a semi-solid BN precursor layer from the BN liquid precursor. In the high-temperature pyrolysis conversion device, the high-temperature pyrolysis conversion temperature is 1000-1200℃, and the processing atmosphere is nitrogen or a mixture of nitrogen and ammonia; when a mixture of ammonia and nitrogen is used, the ammonia gas fraction is 10%-20%.

10. The method for preparing the BN interface phase on the surface of continuous carbon fiber bundles according to claim 6, characterized in that, The fiber bundle feed rate is 0.2–2 m / min; Repeat steps S4 to S6 once or more to adjust the amount of BN precursor layer attached and the final thickness of the BN interface phase.

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