Device and method for continuously depositing BN interface layer on SiC fiber surface

Abstract

The invention discloses a device and a method for continuously depositing a BN interface layer on a SiC fiber surface, a concentric sleeve type gas inlet pipe is arranged in a vapor deposition furnace of the device, the concentric sleeve type gas inlet pipe is composed of an inner circle gas inlet pipe and an outer ring gas inlet pipe, the inner circle gas inlet pipe is used for introducing an N source and protective gas, the outer ring gas inlet pipe is used for introducing a B source and H2, and the outer ring gas inlet pipe is used for introducing the protective gas. According to the concentric sleeve type gas inlet pipe, on one hand, through isolation of gas inlets of the two gas inlet pipes, a B source and an N source are in a separated state before the B source and the N source need to react, and the situation that a white ammonium chloride by-product generated by instant contact reaction of the two gases blocks a pipeline, pollutes a fiber surface interface layer and becomes poor in uniformity is avoided; and on the other hand, the air inlets are annularly formed along the SiC fiber wire passing channel, air can enter the air source in the direction parallel to the fiber wire passing direction, the flow field can be parallel to the SiC fiber wire passing direction, and the BN interface layer can be evenly and stably deposited on the surface of the SiC fiber.

Description

Technical Field

[0001] The invention belongs to the field of composite materials, and in particular relates to a device and a method for continuously depositing a BN interface layer on the surface of a SiC fiber. Background Art

[0002] Ceramic-based thermostructural composites have attracted great interest in order to reduce fuel consumption and pollutant emissions from aircraft engines. In fact, these materials are paving the way for new, lighter engines that provide more complete combustion due to their high operating temperatures. The lightweighting of components achieved through the use of ceramic matrix composites (CMCs) and the reduction of emissions of combustion byproducts such as nitrogen oxides are consistent with these goals.

[0003] The materials with layered structures used in the interface of ceramic matrix composites (CMCs) consist of a series of atomic planes, similar to graphene, and are characterized by anisotropic structures. The presence of weak interlayer bonds (van der Waals forces) is conducive to crack deflection. The interface of CMCs is mainly represented by pyrolytic carbon or PyC and pyrolytic boron nitride or BN.

[0004] The intended applications of CMCs include high temperature environments in oxidizing and corrosive atmospheres. Under the conditions of use, microcracks formed inside SiC / SiC provide access to the external atmosphere, including oxygen and water vapor. In an oxygen-containing atmosphere, starting at 450°C, PyC oxidizes to form gaseous CO 2 and CO. During the oxidation process, BN forms liquid B 2 O 3 , which slows down the oxidation process. The BN interface layer can resist active oxidation up to a temperature of about 900 °C, depending on the degree of crystallization and the orientation of the basal plane.

[0005] The interface layer is the weak link of ceramic matrix composites (CMCs) compared to the matrix and SiC fibers, both from a mechanical (beneficial) and chemical (detrimental) perspective. During the melt infusion (MI) step, the interface layer may come into contact with liquid Si. At this point, pyrolytic carbon (PyC) is rapidly consumed to form SiC. In contrast, boron carbide (BN) has poor wettability to Si (wetting angle of about 145 degrees) and is more resistant to chemical attack by Si. Therefore, BN has become the material of choice for the interface layer of SiC / SiC composites in next-generation aero engines. BN interfaces offer a very good compromise between crack deflection and oxidation / corrosion resistance in CMC composites.

[0006] At present, there are many methods for preparing BN coating on the surface of SiC fiber. The method with the most industrial prospects is to use vapor deposition to prepare BN coating on the surface of SiC fiber. BN obtained at low temperature is usually observed to have an amorphous and isotropic structure, usually called a-BN, similar to PyC. 2 The turbulent layer structure formed by -BN, called t-BN, is less ordered than hexagonal BN (h-BN) or rhombohedral BN (r-BN) and is characterized by local stacking defects such as rotation, translation and curvature of the atomic layers, which include interlayer covalent bonds. These defects increase the strength of the interlayer bonds compared to perfectly ordered layered structures such as h-BN. t-BN interfaces can achieve fairly strong fiber-matrix interfacial bonding, which is beneficial for the mechanical behavior of CMCs, provided that the BN coating achieves cohesive failure. t-BN is usually synthesized by chemical vapor deposition (CVD) at lower temperatures and / or higher pressures than h-BN and r-BN. In industrial composites manufactured by chemical vapor infiltration (CVI), variations in the thickness of the interfacial layer are usually observed due to differences in the gas penetration gradient through the depth of the fiber preform. In addition, in woven preforms, the contacting fibers may locally prevent the growth of the interfacial layer during their deposition due to lack of space. To minimize these percolation gradients, a BN interface layer can be obtained by using lower fabrication temperatures for CVI (usually limited to temperatures below 1000°C and performed at low pressures (100-1333Pa)), which leads to the formation of t-BN or even a-BN. In order to achieve a uniform and highly crystalline deposited BN interface layer, a solution is to deposit the BN interface on a SiC fiber bundle using a continuous deposition furnace.

[0007] However, in the prior art, there is an integrated device for continuously preparing BN coating on the surface of SiC fiber by CVD method, but it has the following shortcomings:

[0008] (1) The gas source is introduced from one side of the SiC fiber bundle in the direction of wire feeding and is perpendicular to the wire feeding direction. On the one hand, the vertical flow field will increase the contact points between the fiber and the gas source, resulting in an increase in the probability of gas phase nucleation and an increase in the unevenness of the BN interface deposited on the surface of the SiC fiber. On the other hand, the gas source gas is ventilated in the same pipeline, which will cause the gas source gas to react prematurely, resulting in the consumption of the reaction gas source and the generation of a large number of by-products, increasing the risk of blockage of the air intake pipeline.

[0009] (2) The various devices in the existing integrated equipment for continuously preparing the BN interface layer on the surface of SiC fibers are connected through each other. The overall vacuum system will cause the source gas and by-products to diffuse into the wire collecting tank and the wire releasing tank, contaminating the original wire and the SiC fiber bundle with the BN interface layer deposited on it.

[0010] (3) In an integrated device with a through-hole structure, when one part is damaged, the entire device needs to be disassembled for repair, which will result in poor airtightness and difficulty in assembly. Summary of the invention

[0011] In view of the deficiencies of the prior art, one of the objectives of the present invention is to provide a device for continuously depositing a BN interface layer on the surface of a SiC fiber.

[0012] The second object of the present invention is to provide a method for continuously depositing a BN interface layer on the surface of a SiC fiber. The method of the present invention can not only continuously and uniformly deposit a BN interface layer on the surface of a SiC fiber, avoiding surface encrustation, gas phase nucleation and uneven coating during deposition in a SiC fiber preform, but also obtain a BN interface layer of desired thickness through continuous wire walking in a single direction.

[0013] To achieve the above object, the present invention adopts the following technical solution:

[0014] The present invention discloses a device for continuously depositing a BN interface layer on the surface of a SiC fiber. The device sequentially comprises an unwinding tank, a degumming furnace, a vapor deposition furnace, a heat treatment furnace, and a winding tank.

[0015] The vapor deposition furnace is provided with a concentric sleeve-type air inlet pipe, which consists of an inner circle air inlet pipe and an outer ring air inlet pipe, wherein the inner circle air inlet pipe is used to introduce N source and protective gas, and the outer ring air inlet pipe is used to introduce B source and H 2 ;

[0016] The center line of the inner circular air inlet pipe is located on the SiC fiber wire running channel;

[0017] The length of the inner circular air intake pipe extending into the vapor deposition furnace is greater than the length of the outer circular air intake pipe extending into the vapor deposition furnace, so that the air intake port of the inner circular air intake pipe is placed in front of the air intake port of the outer circular air intake pipe.

[0018] The equipment provided by the present invention is provided with a concentric sleeve-type air inlet pipe, which is composed of an inner circle air inlet pipe and an outer ring air inlet pipe, wherein the inner circle air inlet pipe is used to introduce N source and protective gas, and the outer ring air inlet pipe is used to introduce B source and H 2On the one hand, the isolation of the two air inlet ports makes the B source and the N source separated before they are needed to react, avoiding the byproducts such as white ammonium chloride produced by the instantaneous contact reaction of the two gases to block the pipeline and cause the interface layer on the fiber surface to be polluted and the uniformity to deteriorate; on the other hand, the air inlet arranged along the SiC fiber wire-feeding channel can realize the air source to be parallel to the fiber wire-feeding direction, which can overcome the problem that the vertical flow field will increase the contact points between the fiber and the air source when the air is fed perpendicular to the wire-feeding direction, resulting in an increased probability of gas phase nucleation, and can realize the flow field parallel to the SiC fiber wire-feeding direction, so as to realize the uniform and stable deposition of the BN interface layer on the SiC fiber surface. In addition, in the deposition furnace of the prior art, the two source gases start to react as soon as they come into contact, while the present invention adopts a separate air intake method for the two source gases, avoiding the ineffective reaction of the source gases before entering the deposition area.

[0019] In addition, in the present invention, the air inlet port of the inner circle air inlet pipe is placed in front of the air inlet port of the outer ring air inlet pipe. The front air inlet of the inner circle air inlet pipe can guide the outer ring gas to form a specific flow path and flow pattern, so that the gas is more evenly distributed in the reaction chamber of the chemical vapor deposition furnace, avoiding the occurrence of air flow dead corners or local flow rates that are too high or too low, providing a more stable and uniform gas environment for the chemical vapor deposition process, and is beneficial to improving the quality and consistency of the deposition interface layer. In addition, during the flow process, the gas in the outer ring forms a barrier on the side close to the reaction chamber so that the gas at the outlet end of the inner circle air inlet pipe maintains a slightly positive pressure compared to the inside of the reaction chamber, reducing the diffusion of the deposited atoms of the outer ring gas to the outlet end of the inner circle air inlet pipe for reaction and deposition, which can significantly reduce the deposition rate of BN and improve uniformity.

[0020] In the present invention, a concentric sleeve-type air inlet pipe is arranged in the reaction chamber. In addition, a protective atmosphere air inlet pipe is also arranged in the outer layer of the reaction chamber, which is mainly used to introduce protective atmosphere into the outer layer to maintain a slight positive pressure and prevent leakage of reaction gas.

[0021] According to a preferred embodiment, the unwinding tank comprises a wire unwinding machine, a movable roller group A, and a sealable chamber. The wire unwinding machine and the roller group A are located in the sealable chamber, and the sealable chamber is connected to the degumming furnace.

[0022] According to a preferred embodiment, the winding tank includes a wire collecting machine, a movable roller group B, and a sealable chamber. The wire collecting machine and the roller group B are located in the sealable chamber, and the sealable chamber is connected to the zone vapor deposition furnace.

[0023] In a preferred embodiment, the winding tank and the unwinding tank are independently provided with an air inlet and an air outlet.

[0024] In a preferred solution, the degumming furnace has a length of 800-120 mm and a diameter of 80-100 mm.

[0025] In actual operation, when degumming SiC fibers, the degumming furnace maintains negative pressure or slightly positive pressure.

[0026] Preferably, the vapor deposition furnace has a length of 800-1200 mm, a diameter of 80-100 mm, and a maximum temperature of 1200-1400°C.

[0027] In a preferred embodiment, the vapor deposition furnace is divided into a non-constant temperature area and a constant temperature area, and the constant temperature area has three sections with independently controlled temperatures: a front section, a middle section, and a rear section.

[0028] Since BN with different structures can be deposited at different temperatures, the present invention controls the temperature of the vapor deposition furnace in three sections. If the front section is controlled at a low temperature and the back section is controlled at a high temperature, then the inner layer of the SiC fiber deposited during continuous wire feeding is isotropic (BN 1 ), the outer layer is anisotropic gradient structure, on the contrary, if it is reversed, the front section is the high temperature zone, then the inner layer of the deposited SiC fiber is anisotropic (BN 2 ), the outer layer is isotropic, while for the middle section, according to the required structure of the BN layer, it is set to the same temperature as the front section, or the same temperature as the rear section. By controlling the different temperatures of the three sections, BN interface layers with different gradient structures can be formed, and the gradient structure interface layer can play a dual role of protecting the fiber and crack deflection.

[0029] The front section of the multi-temperature zone vapor deposition furnace refers to a section close to the degumming furnace, and the rear section of the vapor deposition furnace refers to a section close to the heat treatment device.

[0030] In addition to the three independently temperature-controlled front, middle and rear sections, there is a very short non-constant temperature zone at the front end of the vapor deposition furnace. The same is true for the heat treatment furnace. The temperature of the constant temperature reaction zone of the vapor deposition device is greater than the temperature of the non-constant temperature reaction zone of the vapor deposition device, and the temperature of the constant temperature zone of the heat treatment furnace is greater than the temperature of the non-constant temperature zone of the heat treatment furnace. Therefore, during the movement of the SiC fiber bundle, it first passes through the non-constant temperature zone of the vapor deposition furnace for preheating, and then enters the constant temperature reaction zone for deposition. Subsequently, the SiC fiber bundle moves through the constant temperature zone of the heat treatment device via a roller group to complete the heat treatment, and then is collected in the wire collecting machine. The wire collecting machine is located in the winding tank, and its temperature is lower than the crystal conversion temperature of the constant temperature zone. This can prevent the formed crystalline interface from continuing to grow at high temperature.

[0031] In a preferred embodiment, the reaction chamber of the vapor deposition furnace is formed of a graphite tube, and the inner diameter of the graphite tube is 30 to 60 mm, preferably 30 to 40 mm. The above dimensions can prevent the reaction chamber from being blocked by byproducts and the generation of gas vortexes, and can also improve deposition efficiency.

[0032] In a preferred embodiment, the length of the inner circular air inlet pipe extending into the vapor deposition furnace is 2 to 6 cm longer than the length of the outer circular air inlet pipe extending into the vapor deposition furnace.

[0033] Preferably, the air inlet port of the inner circular air inlet pipe is located in a constant temperature area of ​​the vapor deposition furnace.

[0034] By controlling the air inlet port of the inner circular air inlet pipe to be located in the constant temperature area of ​​the vapor deposition furnace, the deposition point is controlled in the constant temperature area. The gas is first heated for a distance in the graphite pipe in the non-constant temperature area at the front end of the vapor deposition furnace for preheating, and then enters the constant temperature reaction area for deposition.

[0035] In a preferred solution, four sub-inlets are evenly distributed in the circumferential direction of the air inlet port of the outer ring air inlet pipe, and the four sub-inlets are arranged at 90 degrees and surround the SiC fiber wire-feeding channel.

[0036] Further preferably, the four gas inlets are all fed with B source and H at the same time. 2 Or four sub-inlets are connected to the B source and H through two sub-inlets symmetrical at 180°. 2 .

[0037] Further preferably, the distance between the center lines of the four sub-air inlets and the center line of the inner circular air inlet pipe is adjustable within the range of 2 to 20 mm.

[0038] More preferably, the four sub-inlets are all provided with threads, and the inlets can be connected to one or more gas paths. The four inlets are all provided with threads, so that the inlets can be connected to one or more gas paths.

[0039] The inventors found that by further setting four sub-inlets in the inlet port of the outer ring inlet pipe, it is possible to introduce gas at different distances from the fiber and at a suitable gas mixing point, thereby controlling the point where the fiber and the reactant first contact each other, that is, by changing the concentration, flow rate and other parameters when the B source gas contacts the fiber, the reaction rate can be adjusted. Controlling the vertical distance of the annular area inlet from the center can adjust the diffusion path of the gas along the vertical direction of the fiber, thereby adjusting the diffusion time. This means that the B source gas (such as boron chloride) and the N source gas (ammonia molecules) need a shorter or longer time to fully contact, thereby slowing down and accelerating the starting speed of the reaction, so as to ensure that the B source gas can be fully and evenly mixed with other gas components, and then react with the fiber as expected, thereby improving the uniformity of the BN interface layer. Of course, the distance also needs to be controlled. If the distance is too far or too close, the concentration of the reaction gas source will be different, which will cause local over-reaction or under-reaction, resulting in uneven BN interface layer.

[0040] In a preferred embodiment, a heating belt is wound around the outer wall of the outer ring air inlet pipe. The present invention is achieved by winding a heating belt around the outer wall. First, the gas source is preheated to avoid being too cold when entering the chemical vapor deposition furnace, resulting in insufficient isothermal zone length. By maintaining the temperature of the boron source gas by tracing the heat, it can have appropriate activity and reaction performance when participating in the reaction, ensuring that the reaction can proceed efficiently and evenly. If the temperature of the boron source gas is too low, the reaction rate may slow down, or even lead to incomplete reaction, affecting the quality of the interface layer and the deposition rate. Second, to prevent gas condensation, B source gas, such as boron chloride (BCl 3 ), is a colorless gas with a strong pungent odor at room temperature and pressure, but its boiling point is relatively low, only 12.5°C. If the ambient temperature is low, boron chloride gas is prone to condensation, changing from gas to liquid or even solid, which will affect its transmission and use in pipelines or equipment. Heat tracing can keep the boron chloride gas within a certain temperature range to prevent it from condensing and ensure its stable existence and transportation in gaseous form. Third, when the B source (boron chloride) gas condenses into a liquid or solid state, it may accumulate on the inner wall of the pipeline. Over time, these accumulations may gradually increase, causing the inner diameter of the pipeline to become smaller, or even completely block the pipeline, affecting the normal operation of the entire process. Heat tracing can keep the boron chloride gas in a gaseous state, reduce the accumulation and solidification in the pipeline, reduce the risk of pipeline blockage, and ensure smooth gas transportation. Fourth, boron chloride will undergo strong hydrolysis when it comes into contact with water to produce boric acid and hydrogen chloride. If there is moisture in the pipeline and the temperature is low, the boron chloride gas will condense and come into contact with water, causing a hydrolysis reaction. This will not only consume the boron chloride, but may also generate corrosive hydrogen chloride gas, causing corrosion to the pipeline and equipment. Heat tracing can increase the temperature in the pipeline and reduce moisture condensation, thereby reducing the possibility of hydrolysis reaction, protecting the pipeline and equipment and extending their service life.

[0041] In a preferred embodiment, both the air inlet port of the inner circle air inlet pipe and the air inlet port of the outer ring air inlet pipe are provided with a porous graphite plate.

[0042] In actual operation, the size of the holes in the orifice plate can be changed to adapt to the type of fiber to be coated. The diameter of the holes in the orifice plate can be changed according to the gas flow rate to ensure that the gas flow is plug flow.

[0043] Further preferably, the diameter of the holes in the graphite orifice plate is 0.5 mm to 2 mm.

[0044] The porous graphite plate further diverts the airflow to achieve plug flow and reduce the reverse diffusion of the airflow. The gas flows in a parallel manner, avoiding the local gas concentration difference caused by airflow turbulence, ensuring that the gas composition and flow rate at each point in the reaction area are basically consistent, providing a good gas environment for the uniform growth of the interface layer. The parallel flow design helps to reduce the dead zone in the flow field, that is, the area where the gas flow is not smooth or stagnant. In the dead zone, the reaction gas cannot be effectively updated, which will lead to a decrease in the concentration of the reactants and affect the deposition effect.

[0045] In a preferred embodiment, the vapor deposition furnace further comprises an air outlet pipe, the end of the air outlet pipe is an air outlet, a concentric sleeve-type air inlet pipe is placed in front of the air outlet pipe, and the center line of the air outlet pipe is located on the SiC fiber wire running channel.

[0046] In the present invention, the direction close to the unwinding tank is the rear, and the direction close to the reeling and unwinding tank is the front.

[0047] Preferably, the inner diameter of the inner circular inlet pipe in the vapor deposition furnace is smaller than the inner diameter of the outlet pipe. By controlling the inner diameter of the inner circular inlet pipe to be smaller than the inner diameter of the outlet pipe, it helps to prevent byproducts from entering the degumming furnace and also effectively prevents the reverse diffusion of reactants.

[0048] According to a preferred solution, the gas outlet of the heat treatment furnace is connected in series with a cold trap, two filter tanks, a tail gas treatment tower, and a vacuum pump group through a pipeline, and then connected to the tail gas treatment device through a vacuum unit. A pipeline is also provided to directly connect to the tail gas treatment device.

[0049] During the vapor deposition and heat treatment process, the required deposition pressure is controlled by drawing negative pressure through a vacuum unit, and the exhaust gas generated during deposition is drawn to the exhaust gas treatment device through a cold trap and a filter tank vacuum unit.

[0050] In the present invention, the heat treatment furnace and the vapor deposition furnace are through-connected, and the protective gas will enter from the air inlet of the heat treatment furnace, and then enter the exhaust gas treatment device from the air outlet of the heat treatment furnace through the vacuum unit, all of which are in a vacuum environment, that is, the heat treatment furnace is heat treated with protective gas alone, and the chemical vapor deposition furnace is the same. After the reaction gas is introduced, it is extracted by the vacuum system of the deposition furnace when leaving the chemical vapor deposition furnace to prevent the reaction gas from entering the heat treatment furnace.

[0051] The preferred solution is that the unwinding tank, degumming furnace, vapor deposition furnace, heat treatment furnace and winding tank can be moved separately by the bottom slide rail, which is convenient for alignment, disassembly and maintenance.

[0052] Preferably, the equipment further comprises a vacuum system and an exhaust gas treatment device.

[0053] The present invention also provides a method for continuously depositing a BN interface layer on the surface of a SiC fiber. In the device, the SiC fiber is unwound by an unwinding tank, debonded by a debonding furnace, BN deposited by a vapor deposition furnace, and then crystalline stabilized by a heat treatment furnace, and finally wound up by a winding tank to obtain a SiC fiber containing a crystalline BN interface layer.

[0054] During BN deposition, N source and protective gas are introduced through the inner circular inlet pipe, and B source and H are introduced through the outer circular inlet pipe. 2 .

[0055] In the actual operation process, before vapor deposition, the vacuum system connected to the vapor deposition furnace is first evacuated, and then inert gas is introduced from the front end of the vapor deposition furnace for gas replacement, and gas replacement is performed 3 to 6 times in total.

[0056] In a preferred embodiment, during BN deposition, the B source and H are introduced through the four sub-inlet ports provided at the inlet port of the outer ring inlet pipe. 2 , where the four gas inlets are simultaneously fed with B source and H 2 Or four sub-inlets are connected to the B source and H through two sub-inlets symmetrical at 180°. 2 .

[0057] In a preferred embodiment, when depositing BN, the deposition temperature is controlled to be 600-1200° C. and the pressure is controlled to be 0.5 KPa-6 KPa, preferably 0.5 KPa-4 KPa.

[0058] In a preferred embodiment, during BN deposition, the flow rate of the N source is 0.3 to 7.5 L / min, preferably 0.3 to 6 L / min, the flow rate of the protective gas is 0.5 to 3.0 L / min, preferably 0.5 to 2.0 L / min; the flow rate of the B source is 0.1 to 2.5 L / min, preferably 0.1 to 2 L / min; the flow rate of the H 2 The flow rate is 0.1 to 1.5 L / min, preferably 0.1 to 1.2 L / min.

[0059] In a preferred embodiment, the N source is NH 3 .

[0060] Preferably, the protective gas is Ar gas.

[0061] In a preferred embodiment, the B source is selected from BCl 3 , BF 3 , BBr 3 , BI 3 As further preferred, the B source is selected from BCl 3 , BF 3 Any one of .

[0062] Further preferably, during the BN deposition, BN is firstly performed 1 Deposition, followed by BN 2 Deposition, or BN first 2 Deposition, followed by BN 1 Deposition, where BN 1 The deposition temperature is 600-800°C, preferably 650-750°C, BN 2 The deposition temperature is 850-1050°C.

[0063] In a preferred solution, during BN deposition, air is introduced along the direction of SiC fiber wire feeding or against the direction of SiC fiber bundle wire feeding. By adding two directions, namely, air introduction along the wire feeding direction and against the wire feeding direction, a BN interface phase with a more complex structure can be obtained by repeatedly feeding back and forth.

[0064] In a preferred solution, the wire feeding speed of the SiC fiber is 0.1 to 2 m / min, preferably 0.1 to 1.5 m / min.

[0065] In a preferred embodiment, the heat treatment temperature is 1200-1600°C, preferably 1200-1300°C.

[0066] Preferably, during the BN deposition, protective gas is continuously introduced into the air inlet of the winding tank and the air inlet of the unwinding tank, and the flow rate of the protective gas is 1 to 5.0 L / min. As a further preferred embodiment, the protective gas is nitrogen or argon.

[0067] Continuous air intake maintains an inert environment while preventing the gas in the reaction chamber from overflowing into the winder and unwinder, thus avoiding damage to the winder, unwinder and roller caused by the source gas and by-products generated during the deposition process.

[0068] In a preferred embodiment, the thickness of the crystalline BN interface layer in the SiC fiber containing the crystalline BN interface layer is 50 to 5000 nm. In the present invention, the coordination of the concentration of the gas source, the speed of the wire running, and the vertical distance of the four gas inlets from the center wire running is sufficient to obtain the BN interface layer of the required thickness through a single continuous wire running.

[0069] Advantages of the present invention:

[0070] 1) The concentric sleeve-type air intake method designed by the present invention is that the N source and the protective gas are introduced from the inner circular air intake pipe, and the B source and the H 2The air is introduced into the air inlet pipe from the outer ring. On the one hand, the isolation of the two air inlet ports makes the B source and the N source in a separate state before the reaction is required, avoiding the by-products such as white ammonium chloride produced by the instantaneous contact reaction of the two gases to block the pipeline and cause the interface layer on the fiber surface to be contaminated and the uniformity to deteriorate; on the other hand, the air inlet arranged along the SiC fiber wire-feeding channel can realize the air source to be parallel to the fiber wire-feeding direction, which can overcome the problem that the vertical flow field will increase the contact points between the fiber and the air source and increase the probability of gas phase nucleation when the air is fed perpendicular to the wire-feeding direction, and can realize the flow field parallel to the wire-feeding direction of the SiC fiber, so as to realize the uniform and stable deposition of the BN interface layer on the surface of the SiC fiber; and it can avoid the ineffective reaction of the gas source gas before entering the deposition area.

[0071] 2) The present invention arranges the air inlet port of the inner circle air inlet pipe in front of the air inlet port of the outer ring air inlet pipe, which can guide the outer ring gas to form a specific flow path and flow pattern, so that the gas source gas is more evenly distributed, avoiding air flow dead corners or local flow velocities that are too high or too low, providing a more stable and uniform gas environment for the chemical vapor deposition process, and is beneficial to improving the quality and consistency of the deposition interface layer.

[0072] 3) Since BN with different structures can be deposited at different temperatures, the present invention controls the temperature of the vapor deposition furnace in three sections. If the front section is controlled to be low temperature and the back section is controlled to be high temperature, then the inner layer of the SiC fiber deposited during continuous wire walking is isotropic (BN 1 ), the outer layer is anisotropic gradient structure, on the contrary, if it is reversed, the front section is the high temperature zone, then the inner layer of the deposited SiC fiber is anisotropic (BN 2 ), the outer layer is isotropic, and for the middle section, according to the required BN layer structure, it is set to the same temperature as the front section, or the same temperature as the rear section. By controlling the different temperatures of the three sections, BN interface layers with different gradient structures can be formed. The gradient structure interface layer can play a dual role in protecting the fiber and crack deflection.

[0073] 4) The spacing between the center lines of the four air inlets uniformly distributed in the circumferential direction of the air inlet port of the outer ring air inlet pipe of the vapor deposition furnace involved in the present invention and the center line of the inner circle air inlet pipe is adjustable, so that the gas source can be introduced at different distances from the fiber and at a suitable gas mixing point, thereby controlling the point where the fiber and the gas source reactant first contact each other. In this way, the reaction rate can be adjusted by changing the concentration, flow rate and other parameters when the B source gas contacts the fiber. Controlling the vertical distance of the air inlet in the annular area from the center can adjust the diffusion path of the gas along the vertical direction of the fiber, thereby adjusting the diffusion time, thereby ensuring that the B source gas can be fully and evenly mixed with other gas components, and then react with the fiber as expected, thereby improving the uniformity of the BN interface layer.

[0074] 5) The outer wall of the outer ring air inlet pipe designed in the present invention is wrapped with a heating belt to preheat the gas source to avoid condensation of the gas source and ensure that the reaction can be carried out efficiently and evenly.

[0075] 6) The inlet pipe port in the present invention is designed with a porous graphite plate, which can further divert the airflow to achieve plug flow and reduce the reverse diffusion of the airflow. The parallel flow design helps to reduce the dead zone in the flow field and avoid areas where the gas flow is poor or stagnant, providing a good gas environment for the uniform growth of the interface layer. BRIEF DESCRIPTION OF THE DRAWINGS

[0076] Figure 1 The present invention is a schematic diagram of the structure of an apparatus for continuously depositing a BN interface layer on the surface of a SiC fiber. In the figure, 1. a wire unwinding machine in a wire unwinding tank, 2. a wire collecting machine in a wire collecting tank, 3. a degumming furnace, 4. a vapor deposition furnace, 5. a heat treatment furnace, 6. a liquid volume control plate, 7. a bellows, 8. a furnace plug, 9. a wire-passing graphite tube, 10. a concentric sleeve-type air inlet pipe, 11. a SiC fiber, 12. an inner circle air inlet pipe, 13. a branch air inlet in an outer ring air inlet pipe, 14. a protective gas purge pipe of a heat treatment furnace, 15. a protective gas air inlet pipe of a degumming furnace, 16. a protective gas air outlet pipe of a degumming furnace, 17. a vacuum pipe, 18. an inflatable sealing ring + an electric hydraulic revolving door, 19. a protective gas interface of a wire collecting tank, and 20. a guide wire wheel.

[0077] Figure 2 This is a schematic diagram of the structure of a closed vapor deposition furnace of the device of the present invention.

[0078] Figure 3 This is a cross-sectional view of a vapor deposition furnace of Example 1 in which an annular ventilation pipe is arranged on the outer periphery of the SiC fiber wire-feeding channel. In the figure, 11, SiC fiber, 12, inner circle air inlet pipe, 13, branch air inlet ports in the outer ring air inlet pipe, 21, reaction chamber, 22, protective atmosphere air inlet pipe, 23, heating furnace tube.

[0079] Figure 4 Microscopic morphology of the BN interface layer of SiC fiber deposited by the method of Example 1.

[0080] Figure 5 Microscopic morphology of the BN interface layer of SiC fiber deposited by the method of Example 2.

[0081] Figure 6 Microscopic morphology of the BN interface layer of SiC fiber deposited by the method of Example 3.

[0082] Figure 7 Photograph of the vapor deposition furnace after deposition in Comparative Example 1.

[0083] Figure 8Microscopic morphology of the BN interface layer of SiC fiber after deposition using the method of Comparative Example 1.

[0084] Fig. 9 Microscopic morphology of the BN interface layer of SiC fiber deposited by the method of Comparative Example 2.

[0085] Fig.10 Microscopic morphology of the BN interface layer of SiC fiber deposited by the method of Comparative Example 3. DETAILED DESCRIPTION

[0086] The present invention is further described below in conjunction with the accompanying drawings and embodiments.

[0087] like Figure 1 As shown, the present invention is a device for continuously depositing a BN interface layer on the surface of SiC fiber, the device sequentially comprises an unwinding tank, a debonding furnace 3, a vapor deposition furnace 4, a heat treatment furnace 5, and a winding tank; in addition, it also comprises a vacuum system and an exhaust gas treatment device.

[0088] The vapor deposition furnace 4 is provided with a concentric sleeve-type air inlet pipe 10, which is composed of an inner circle air inlet pipe 12 and an outer ring air inlet pipe, wherein the inner circle air inlet pipe 12 is used to introduce N source and protective gas, and the outer ring air inlet pipe is used to introduce B source and H 2 ,

[0089] The center line of the inner circular air inlet pipe 12 is located on the wire-running channel of the SiC fiber 11;

[0090] The length of the inner circular air inlet pipe 12 extending into the vapor deposition furnace is greater than the length of the outer circular air inlet pipe extending into the vapor deposition furnace, so that the air inlet port of the inner circular air inlet pipe 12 is placed in front of the air inlet port of the outer circular air inlet pipe.

[0091] The unwinding tank comprises a wire unwinding machine 1, a movable roller group A, and a sealable chamber. The wire unwinding machine 1 and the roller group A are located in the sealable chamber, and the sealable chamber is connected to the degumming furnace.

[0092] The winding tank includes a wire collecting machine 2, a movable roller group B, and a sealable chamber. The wire collecting machine 2 and the roller group B are located in the sealable chamber, and the sealable chamber is connected to the vapor deposition furnace 4.

[0093] The winding tank and the unwinding tank are both independently provided with an air inlet and an air outlet. During chemical vapor deposition, protective gas nitrogen or argon is continuously introduced into the air inlet of the winding tank and the air inlet of the unwinding tank, and the gas flow rate is 1 to 5.0 L / min.

[0094] The degumming furnace 3 has a length of 800-120 mm and a diameter of 80-100 mm.

[0095] The vapor deposition furnace 4 has a length of 800 to 1200 mm, a diameter of 80 to 100 mm, and a maximum temperature of 1200 to 1400°C.

[0096] The vapor deposition furnace 4 is divided into a non-constant temperature area and a constant temperature area. The constant temperature area has three sections: a front section, a middle section, and a rear section with independent temperature control.

[0097] The reaction chamber 21 of the vapor deposition furnace 4 is composed of a graphite tube, and the inner diameter of the graphite tube is 30-60 mm.

[0098] The length of the inner circular air inlet pipe 12 extending into the vapor deposition furnace is 2 to 6 cm longer than the length of the outer circular air inlet pipe extending into the vapor deposition furnace.

[0099] The air inlet port of the inner circular air inlet pipe 12 is located in the constant temperature area of ​​the vapor deposition furnace.

[0100] In a preferred technical solution, four sub-inlets 13 are evenly distributed in the circumferential direction inside the air inlet port of the outer ring air inlet pipe, and the sub-inlets are arranged at 90 degrees and surround the SiC fiber wire-running channel.

[0101] The four gas inlets 13 are all fed with B source and H 2 , or four sub-inlets are connected to the B source and H through two sub-inlets symmetrical at 180°. 2 .

[0102] The distance between the center line of the four sub-inlet ports 13 and the center line of the inner circular air inlet pipe is adjustable within the range of 2 to 20 mm.

[0103] The four sub-inlet ports 13 are all provided with threads, and the inlet ports can be connected to one or more gas paths. The four sub-inlet ports are all provided with threads, so that the sub-inlet ports can be connected to one or more gas paths.

[0104] The outer wall of the outer ring air inlet pipe is wrapped with a heating belt.

[0105] The air intake port of the inner circle air intake pipe 12 and the air intake port of the outer ring air intake pipe are both provided with a porous graphite plate.

[0106] The diameter of the holes in the graphite orifice plate is 0.5 mm to 2 mm.

[0107] The vapor deposition furnace 4 also includes an air outlet pipe, the end of which is an air outlet, a concentric sleeve-type air inlet pipe is arranged in front of the air outlet pipe, and the center line of the air outlet pipe is located on the SiC fiber wire running channel.

[0108] The inner diameter of the inner circular inlet pipe 12 in the vapor deposition furnace 4 is smaller than the inner diameter of the outlet pipe. By controlling the inner diameter of the inner circular inlet pipe to be smaller than the inner diameter of the outlet pipe, it is helpful to prevent byproducts from entering the degumming furnace, and it can also effectively prevent the reverse diffusion of reactants.

[0109] The gas outlet of the heat treatment furnace 5 is connected in series with a cold trap, two filter tanks, a tail gas treatment tower, and a vacuum pump group through pipelines, and then connected to the tail gas treatment device through a vacuum unit. A pipeline is also provided to directly connect to the tail gas treatment device.

[0110] The unwinding tank, the degumming furnace 3, the vapor deposition furnace 4, the heat treatment furnace 5 and the winding tank can be moved separately by the bottom slide rail, which is convenient for alignment, disassembly and maintenance.

[0111] in addition, Figure 2 It is a side view of the vapor deposition furnace. It can be seen that the SiC fiber 11 is located in the center. The inner circle air inlet pipe 12 and the sub-air inlet port 13 in the outer ring air inlet pipe surround it and are all arranged in the reaction chamber. In addition, in the outer layer of the reaction chamber, inside the heating furnace tube 23, a protective atmosphere air inlet pipe is also arranged, which is mainly used to introduce protective atmosphere into the outer layer, maintain a slight positive pressure, and prevent leakage of reaction gas.

[0112] The following is a specific implementation example of a method for continuously depositing a BN interface layer on the surface of a SiC fiber:

[0113] Embodiment 1:

[0114] This embodiment 1 provides a method for continuously depositing a BN interface layer on the surface of a SiC fiber. The above-mentioned equipment is used to control the length of the inner circular air inlet pipe extending into the vapor deposition furnace to be 2 cm longer than the length of the outer circular air inlet pipe extending into the vapor deposition furnace. The vapor deposition furnace has an independently controlled temperature of a front section of 200 mm, a middle section of 400 mm, and a rear section of 200 mm, with a diameter of 80 mm. During BN deposition, the temperature of the front and middle sections is controlled at 750°C, and the temperature of the rear section is controlled at 1000°C.

[0115] The SiC fiber is connected to the above Figure 1 In the device for continuously depositing a BN interface layer on the surface of SiC fiber shown in FIG, the SiC fiber (at a wire speed of 0.5 m / min) first moves to a degumming furnace for degumming after passing through an unwinding tank. During degumming, the temperature of the degumming furnace is controlled at 650°C. Then, the SiC fiber moves from the degumming furnace to the front section and middle section of the vapor deposition furnace, and isotropic BN is carried out at a temperature of 750°C. 1 The deposition of various anisotropic BN was carried out at 1000℃ in the back-end area. 2 The vapor deposition furnace performs BN deposition. 1 With BN 2 During deposition, NH 3 and Ar, and the outer ring inlet pipe is fed with BCl 3 Source and H 2 . Control BCl 3 The flow rate is 0.1L / min, H 2The flow rate is 0.1L / min, NH 3 The flow rate of is 0.3L / min, and the flow rate of Ar is 0.5L / min; then it moves to the heat treatment furnace for heat treatment at a temperature of 1200℃, and finally it is coiled in the coiling tank.

[0116] In this embodiment 1, the BN deposition is continuously performed on the surface of the SiC fiber by the device to obtain an interface layer such as Figure 4 As shown, it can be seen that the interface is clear and the thickness is uniform, and the thickness of the BN interface layer is 276.4nm.

[0117] Embodiment 2:

[0118] The other conditions are the same as those in Example 1, except that the four sub-intake ports evenly distributed in the circumferential direction of the inlet port of the outer ring inlet pipe are used to independently introduce BCl 3 Source and H 2 The spacing between the center lines of the four air inlets and the center line of the inner air inlet pipe is controlled to be 10 mm. In addition, the wire feeding speed of the SiC fiber is controlled to be 1 m / min.

[0119] In this embodiment 2, BN is continuously deposited on the surface of SiC fiber by the device to obtain an interface layer such as Figure 5 As shown, it can be seen that the interface is clear and the thickness is uniform, and the thickness of the BN interface layer is 200.86nm.

[0120] By adjusting the vertical distance between the four air inlets and the center wire, the concentration of the B source is controlled, so that the thickness of BN decreases and the deposition rate is reduced without affecting the uniformity.

[0121] Example 3

[0122] The other conditions were the same as those in Example 2, except that the wire speed of the SiC fiber was 1.5 m / min.

[0123] In this embodiment 2, the BN deposition is continuously performed on the surface of the SiC fiber by the device to obtain an interface layer such as Figure 6 As shown, it can be seen that the interface is clear and the thickness is uniform, with a thickness of 163.45 nm.

[0124] Comparative Example 1

[0125] Other conditions are the same as those in Example 1, except that when the gas source is not separated and the gas flow is perpendicular to the SiC fiber running direction, the pipeline is easily blocked by gas phase nucleation and byproduct formation. Figure 7 As shown, Figure 8 This is the microscopic morphology of the BN interface layer of the SiC fiber after deposition in this comparative example. It can be seen that its surface is rough and the BN morphology is incomplete.

[0126] Comparative Example 2

[0127] The other conditions are the same as those in Example 1, except that the debonding treatment is not performed. It can be seen that the deposited BN interface is unclear and has many flocculent byproducts. The microscopic morphology of the BN interface layer of the SiC fiber after deposition in this comparative example is shown in FIG. Fig. 9 shown.

[0128] Comparative Example 3

[0129] The other conditions are the same as those in Example 1 except that no heat treatment is performed. The micromorphology of the BN interface layer of the SiC fiber after deposition in this comparative example is shown in FIG. Fig.10 As shown, the interface of the deposited BN is not clear.

Claims

1. A device for continuously depositing a BN interface layer on the surface of SiC fiber, characterized in that: The equipment includes an unwinding tank, a degumming furnace, a vapor deposition furnace, a heat treatment furnace, and a winding tank in sequence. The vapor deposition furnace is provided with a concentric sleeve-type air inlet pipe, which is composed of an inner circle air inlet pipe and an outer ring air inlet pipe, wherein the inner circle air inlet pipe is used to introduce N source and protective gas, and the outer ring air inlet pipe is used to introduce B source and H2; The center line of the inner circular air inlet pipe is located on the SiC fiber wire running channel; The length of the inner circular air intake pipe extending into the vapor deposition furnace is greater than the length of the outer circular air intake pipe extending into the vapor deposition furnace, so that the air intake port of the inner circular air intake pipe is placed in front of the air intake port of the outer circular air intake pipe.

2. The device for continuously depositing a BN interface layer on the surface of SiC fiber according to claim 1, characterized in that: The unwinding tank comprises a wire unwinding machine, a movable roller group A, and a sealable chamber, wherein the wire unwinding machine and the roller group A are located in the sealable chamber, and the sealable chamber is connected to the degumming furnace; The winding tank includes a wire collecting machine, a movable roller group B, and a sealable chamber. The wire collecting machine and the roller group B are located in the sealable chamber, and the sealable chamber is connected to the zone vapor deposition furnace; The movable roller group A and the movable roller group B are each correspondingly arranged with N rollers, wherein N ≥ 1; The winding tank and the unwinding tank are both independently provided with an air inlet and an air outlet.

3. The device for continuously depositing a BN interface layer on a SiC fiber surface according to claim 1, characterized in that: The degumming furnace has a length of 800-120 mm and a diameter of 80-100 mm; The vapor deposition furnace has a length of 800-1200 mm, a diameter of 80-100 mm, and a maximum temperature of 1200-1400° C.; The vapor deposition furnace is divided into a non-constant temperature area and a constant temperature area, and the constant temperature area has three sections: a front section, a middle section, and a rear section with independent temperature control; The reaction chamber of the vapor deposition furnace is composed of a graphite tube, and the inner diameter of the graphite tube is 30-60 mm.

4. The device for continuously depositing a BN interface layer on the surface of SiC fiber according to claim 3, characterized in that: The length of the inner circular air inlet pipe extending into the vapor deposition furnace is 2 to 6 cm longer than the length of the outer circular air inlet pipe extending into the vapor deposition furnace; The air inlet port of the inner circular air inlet pipe is located in the constant temperature area of ​​the vapor deposition furnace; The air inlet port of the outer ring air inlet pipe is evenly distributed with four sub-air inlets in the circumferential direction, and the four sub-air inlets are arranged at 90 degrees and surround the SiC fiber wire-running channel; The four sub-air inlets are all simultaneously fed with the B source and H2, or the four sub-air inlets are respectively fed with the B source and H2 through two sub-air inlets symmetrical at 180°; The distance between the center line of the four sub-inlet ports and the center line of the inner circular inlet pipe is adjustable within the range of 2 to 20 mm; The four sub-gas inlets are all provided with threads, and the gas inlets are connected to one or more gas paths; The outer wall of the outer ring air inlet pipe is wrapped with a heating belt; The air inlet port of the inner circle air inlet pipe and the air inlet port of the outer ring air inlet pipe are both provided with a porous graphite plate; The diameter of the holes in the graphite orifice plate is 0.5 mm to 2 mm; The vapor deposition furnace also includes an air outlet pipe, and the inner diameter of the inner circular air inlet pipe in the vapor deposition furnace is smaller than the inner diameter of the air outlet pipe.

5. The device for continuously depositing a BN interface layer on the surface of SiC fiber according to claim 1 or 3, characterized in that: The gas outlet of the heat treatment furnace is connected in series with a cold trap, two filter tanks, a tail gas treatment tower, and a vacuum pump group through a pipeline, and then connected to the tail gas treatment device through a vacuum unit, and is also provided with a pipeline directly connected to the tail gas treatment device; The unwinding tank, degumming furnace, vapor deposition furnace, heat treatment furnace and winding tank can be moved independently by the bottom slide rail; The equipment also includes a vacuum system and an exhaust gas treatment device.

6. A method for continuously depositing a BN interface layer on a SiC fiber surface, characterized in that: In the device described in any one of claims 1 to 5, the SiC fiber is unwound by an unwinding tank, debonded by a debonding furnace, BN deposited by a vapor deposition furnace, and then crystallized by a heat treatment furnace, and finally wound by a winding tank to obtain the SiC fiber containing a crystalline BN interface layer. During BN deposition, N source and protective gas are introduced through the inner circular air inlet pipe, and B source and H2 are introduced through the outer circular air inlet pipe.

7. The method for continuously depositing a BN interface layer on the surface of SiC fiber according to claim 6, characterized in that: During BN deposition, the B source and H2 are introduced through four sub-inlets provided at the inlet port of the inner circular inlet pipe, wherein the four sub-inlets are simultaneously introduced with the B source and H2 or the four sub-inlets are respectively introduced with the B source and H2 through two sub-inlets symmetrical at 180°; When BN is deposited, the deposition temperature is controlled to be 600~1200℃ and the pressure is 0.5KPa~6KPa. During BN deposition, the flow rate of the N source is 0.3-7.5 L / min, the flow rate of the protective gas is 0.5-3.0 L / min, the flow rate of the B source is 0.1-2.5 L / min, and the flow rate of the H2 is 0.1-1.5 L / min. The N source is NH3; The protective gas is Ar gas; The B source is selected from any one of BCl3, BF3, BBr3, and BI3.

8. The method for continuously depositing a BN interface layer on the surface of SiC fiber according to claim 7, characterized in that: During the BN deposition, BN1 deposition is performed first, and then BN2 deposition is performed, or BN2 deposition is performed first, and then BN1 deposition is performed, wherein the temperature of BN1 deposition is 600-800°C, and the temperature of BN2 deposition is 850-1050°C.

9. The method for continuously depositing a BN interface layer on the surface of SiC fiber according to claim 7, characterized in that: During the BN deposition, air is introduced along the direction of the SiC fiber or in the direction opposite to the direction of the SiC fiber bundle. The SiC fiber wire speed is 0.1-2 m / min. During the BN deposition, protective gas is continuously introduced into the air inlet of the winding tank and the air inlet of the unwinding tank, and the flow rate of the protective gas is 1 to 5.0 L / min.

10. A method for continuously depositing a BN interface layer on the surface of SiC fiber according to any one of claims 6 to 9, characterized in that: The temperature of the heat treatment is 1200-1600°C; In the SiC fiber containing the crystalline BN interface layer, the thickness of the crystalline BN interface layer is 50 to 5000 nm.

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