A carbon-carbon guide tube and preparation method thereof

Abstract

The present application relates to the technical field of carbon / carbon composite materials, and specifically discloses a carbon-carbon guide tube and a preparation method thereof. The preparation method of the carbon-carbon guide tube comprises: cutting carbon fibers into short fibers, combing the short fibers into a mesh; immersing the mesh into an impregnation liquid in the equipment to obtain a pre-impregnated mesh; laying multiple layers of impregnated mesh on the surface of a mold; curing the multiple layers of impregnated mesh on the mold, demolding to obtain a blank; carbonizing and graphitizing the blank; subjecting the graphitized blank to a chemical vapor deposition densification process and a pyrolytic carbon coating process in sequence to obtain a carbon-carbon guide tube. The method for preparing the carbon-carbon guide tube does not require the preparation of a preform, thereby eliminating the problem of carbon fiber waste generated during the manufacturing process of the preform, and can shorten the manufacturing cycle, improve production efficiency, and reduce production costs. The carbon-carbon guide tube prepared by the method has good mechanical properties and corrosion resistance, and can meet the use requirements of the guide tube for the thermal field of a photovoltaic direct-pull single crystal silicon furnace.

Description

Technical Field

[0001] The present application relates to the technical field of carbon / carbon composite materials, and in particular to a carbon-carbon flow guide tube and a preparation method thereof. Background Art

[0002] Carbon / carbon composite materials refer to high-performance composite materials formed by carbon fiber and its fabric reinforced carbon matrix. This material has excellent properties such as light weight, low thermal expansion coefficient, high temperature resistance, corrosion resistance, stable friction coefficient, good thermal conductivity and electrical conductivity. It is the best candidate material for manufacturing high-temperature thermal field components and friction components, and is considered to be one of the most promising high-temperature structural materials in the 21st century. In recent years, in addition to being widely used in the aerospace field, carbon / carbon composite materials have also been widely used in many civilian high-temperature fields due to their excellent performance and comprehensive cost-effectiveness. For example, in the photovoltaic industry, it is mainly used for crucibles, insulation tubes and guide tubes. The guide tube is one of the key components of the thermal field system of the single crystal silicon pulling furnace, mainly used to control the axial temperature gradient of the thermal field and guide the argon gas flow. The guide tube blocks the thermal radiation of the single crystal furnace body and molten silicon to the crystal, which is conducive to the heat dissipation of the crystal, forming the temperature gradient required for crystal growth, so as to increase the crystal growth rate.

[0003] The Chinese invention patent with the publication number CN1907915A discloses a method for preparing a hot field carbon / carbon guide tube for a single crystal silicon pulling furnace, wherein a carbon cloth and a thin carbon fiber mesh are wound around each other and then needled to form a quasi-three-dimensional structure guide tube preform, and reinforcing fibers are introduced into the guide tube preform in the vertical direction of the guide tube preform to obtain the guide tube preform, and the guide tube preform is subjected to vapor deposition, phenolic resin impregnation carbonization, repeated hot isostatic pressing asphalt impregnation carbonization, 2000~2500℃ high temperature purification, and lathe processing to obtain the guide tube of the required size. Due to the complex shape of the guide tube and the difficulty of needle puncture, it is necessary to prepare a preform, and the preform manufacturing takes a long time. At the same time, the guide tube preform needs to reserve processing allowance, which is difficult to process. Carbon fiber waste is generated during the preform manufacturing process, resulting in low material utilization and high production cost. Summary of the invention

[0004] In view of the fact that the above method for preparing carbon / carbon guide tube adopts a needle punching process to prepare the guide tube preform, the needle punching is difficult, the preform manufacturing takes a long time, and at the same time, the guide tube preform needs to reserve processing allowance, the processing size is difficult to grasp, and carbon fiber waste is generated during the preform manufacturing process, resulting in low material utilization and high production cost. This application develops a low-cost carbon / carbon guide tube preparation technology, which is as follows.

[0005] In a first aspect, the present application proposes a method for preparing a carbon-carbon guide tube, and adopts the following technical solution.

[0006] A method for preparing a carbon-carbon flow guide tube, comprising: A. Cut the carbon fiber into short fibers and comb the short fibers into a web; B. Immerse the mesh into the impregnation liquid in the equipment, first evacuate the mesh to allow the mesh to absorb the impregnation liquid, and then pressurize the equipment to further press the impregnation liquid into the pores of the mesh to obtain a pre-impregnated mesh; C. Laying multiple layers of the impregnated mesh on the surface of the mold; D. solidifying the multi-layer impregnated mesh on the mold and demoulding to obtain a green body; E. carbonizing the green body; F. graphitizing the carbonized body; G. The graphitized green body is subjected to a chemical vapor deposition densification process and a pyrolytic carbon coating process in sequence to obtain a carbon-carbon guide tube.

[0007] By adopting the above technical solution, the mesh is a mesh made of short fibers interwoven with each other, and the mesh has more micropores. The vacuuming in step B can remove the air in the micropores, making it easier for the impregnation liquid to penetrate into the micropores, so that the mesh absorbs the impregnation liquid, and then pressurizes the impregnation liquid to further penetrate into the micropores, thereby improving the density and water resistance of the product, improving the bending strength and corrosion resistance of the product, improving the strength and hardness of the product, and increasing the life of the product. The amount of impregnation liquid that soaks the mesh can be 10~100g / m 2 . The purpose of laying multiple layers of impregnated mesh is to make the final thickness of the product reach the designed value, solidify it to shape it, and demold it to obtain the blank. After carbonization and graphitization, the crystal structure of the material is transformed into graphite phase under high temperature conditions, which makes the material have good high temperature resistance. The subsequent chemical vapor deposition densification process makes the outer surface of the blank more dense. The material undergoes a pyrolytic carbon coating process, and the deposited natural gas components are pyrolyzed and embedded in carbon fibers to enhance the bonding strength between the natural gas components and the blank. The density of the carbon-carbon guide tube prepared by this method is ≥1.3g / cm 3 , bending strength ≥ 150MPa, ash content ≤ 200ppm, with good mechanical properties and corrosion resistance, can meet the use requirements of the guide tube for the thermal field of photovoltaic direct-pull single crystal silicon furnace, low ash content does not pollute the crystal liquid. The method for preparing the carbon-carbon guide tube does not require the preparation of a preform, eliminates the problem of carbon fiber waste generated during the preform manufacturing process, and can shorten the manufacturing cycle, improve production efficiency, and reduce production costs.

[0008] A preferred solution of the preparation method of the carbon-carbon guide tube is that in step A, the specification of the carbon fiber is 12K or 24K carbon fiber; the length of the short fiber is 30-100 mm; the weight of the mesh tire is 40-120 g / m 2 .

[0009] By adopting the above technical solution, 12K or 24K carbon fiber has good flexibility and is suitable for use in high temperature thermal fields after treatment. The short fibers of this length are evenly distributed after combing. The gram weight makes the guide tube have suitable density and strength.

[0010] A preferred solution of the preparation method of the carbon-carbon guide tube is that in step B, the impregnation liquid is one of phenol-formaldehyde resin, epoxy resin and bismaleimide resin. Alcohol is added to the impregnation liquid as a diluent, and the alcohol addition ratio is 10% to 30% of the mass of the impregnation liquid.

[0011] By adopting the above technical solution, these impregnating liquids can better bond the carbon fibers, and using alcohol as a diluent improves the effect of the impregnating liquid on soaking the mesh.

[0012] A preferred embodiment of the preparation method of the carbon-carbon guide tube is that in step B, the equipment is first evacuated to -0.085~-0.095MPa and maintained for 0.5~1.5h, and then pressurized to 1.0~2.5MPa and maintained for 1~4h.

[0013] By adopting the above technical solution, the mesh absorbs the impregnation liquid under the negative pressure, and then the impregnation liquid is further pressed into the mesh under the pressure. If there is no vacuuming step, the impregnation effect is reduced.

[0014] A preferred solution of the preparation method of the carbon-carbon guide tube is that between step B and step C, it also includes: preparing a mold, the outer dimensions of the mold are 2-5 mm smaller than the inner dimensions of the pre-prepared carbon-carbon guide tube, and the mold surface is evenly coated with a mold release agent with a temperature resistance of 200°C and above. In step C, the joint positions of adjacent layers of the impregnated mesh are staggered, and the thickness of the multiple layers of the impregnated mesh laid on the mold surface is 5-7 times the designed wall thickness of the carbon-carbon guide tube.

[0015] By adopting the above technical solution, the outer dimensions of the mold are 2-5 mm smaller than the inner dimensions of the pre-prepared carbon-carbon guide tube, which reserves the diameter expansion for the subsequent high-temperature graphitization of the carbon-carbon guide tube. The thickness of the multi-layer impregnated mesh is 5-7 times the designed wall thickness of the carbon-carbon guide tube, which reserves the wall thickness shrinkage for the subsequent high-temperature graphitization of the carbon-carbon guide tube. The mold material can be stainless steel or aluminum.

[0016] A preferred embodiment of the preparation method of the carbon-carbon guide tube is that step D adopts a vacuum bag-autoclave molding process: a combination of multiple layers of impregnated mesh laid on the mold surface is placed in a vacuum bag, and then the vacuum bag is placed in an autoclave, the vacuum bag is evacuated, and the internal air pressure of the autoclave is set to 1.5-3.0 MPa and the temperature is set to 150-200°C, and maintained for 2-10 hours to solidify the multiple layers of impregnated mesh, and the green body is obtained by cooling, demolding, and trimming.

[0017] By adopting the above technical solution, vacuum is drawn to prevent oxygen from oxidizing the mesh during the curing process. External pressure is applied to keep the impregnation liquid from penetrating and wetting the mesh, and heating can accelerate the curing process of the impregnation liquid on the mesh.

[0018] A preferred embodiment of the preparation method of the carbon-carbon guide tube is that the carbonization in step E is maintained at 800-1100° C. for 16-20 hours; and the graphitization in step F is maintained at 1800-2200° C. for 8-15 hours.

[0019] By adopting the above technical solution, the organic matter in the green body evaporates or is decomposed after the green body is carbonized to obtain a carbon structure. After the green body is graphitized, the thermodynamically unstable carbon atoms are orderly transformed from a chaotic layer structure to a graphite crystal structure, making its surface denser, improving its structural strength, high temperature resistance and oxidation resistance, and its structure is stable at high temperatures after graphitization.

[0020] A preferred embodiment of the preparation method of the carbon-carbon guide tube is that the chemical vapor deposition densification process is: natural gas is introduced into the chemical vapor deposition furnace at 800-1100°C, and the flow rate of the natural gas is 1.5-3.0 m 3 / h, the vacuum degree in the furnace is 2500~3500Pa, and the time is 100~350h.

[0021] By adopting the above technical solution, ionized natural gas components are deposited on the surface of the green body and formed into a film, thereby improving the surface density of the green body.

[0022] A preferred embodiment of the preparation method of the carbon-carbon guide tube is that the pyrolytic carbon coating process is: after the chemical vapor deposition densification process is completed, continue to use the same temperature as the chemical vapor deposition densification process in the chemical vapor deposition furnace, and adjust the flow rate of natural gas to 0.5~1.0m 3 / h, the vacuum degree in the furnace is 500~1000Pa, and the holding time is 10~50h.

[0023] By adopting the above technical solution, the pyrolytic carbon coating improves the bonding strength between the natural gas component and the green body, and the chemical vapor deposition densification and pyrolytic carbon coating processes are completed at one time, which reduces the equipment heating and cooling cycle, improves production efficiency, and reduces production costs.

[0024] On the second aspect, the present application also proposes a carbon-carbon guide tube and adopts the following technical solution.

[0025] A carbon-carbon guide tube is prepared according to the above-mentioned preparation method.

[0026] By adopting the above technical solution, the density of the carbon-carbon guide tube is ≥1.3g / cm 3, flexural strength ≥150MPa, ash content ≤200ppm, has good mechanical properties and corrosion resistance, and can meet the use requirements of guide tubes for thermal fields of photovoltaic CZ-type single crystal silicon furnaces.

[0027] In summary, the carbon-carbon guide tube and its preparation method of the present application have the following beneficial effects: (1) The preparation of the carbon-carbon guide tube does not require the preparation of a preform, thus avoiding the problem of carbon fiber waste generated during the manufacturing process of the preform, and at the same time can shorten the manufacturing cycle, improve production efficiency, and reduce production costs; (2) The present method can be used to prepare guide tubes with complex shapes and structures; (3) The present method uses a mold as a solid tool and uses a mold with a reduced size to wrap the mesh, which can realize the formation of the carbon-carbon guide tube in a standard size and improve material utilization; (4) The present method can realize the chemical vapor deposition densification and pyrolytic carbon coating processes at one time, reducing the equipment heating and cooling cycle, improving production efficiency, and reducing production costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 This is a schematic diagram of the installation of the carbon-carbon guide tube prepared in the embodiment for use in the high-temperature thermal field of a single crystal furnace and for being arranged above the crucible liquid level. DETAILED DESCRIPTION

[0029] The embodiments of the present application are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the following embodiments, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection claimed in this application.

[0030] Example 1 (1) Cut 12K carbon fiber into short fibers of 70 mm in length, and use a web machine to comb the short fibers into a web with a gram weight of 80 g / m 2 , where K represents the number of thousands of carbon fibers.

[0031] (2) Place the carbon fiber mesh into a vacuum-pressure resin impregnation tank so that the mesh is completely immersed in the impregnation liquid in the tank. The impregnation liquid is a mixed solution of phenolic resin and alcohol, and the alcohol addition ratio is 10% of the mass of phenolic resin. In order to fully impregnate the mesh, the vacuum-pressure resin impregnation tank is first evacuated to -0.09MPa and maintained for 1 hour, so that the air in the micropores of the mesh is extracted to form near-vacuum pores, eliminating the obstruction of air and making it easy for the impregnation liquid to penetrate into the micropores. Then, the vacuum-pressure resin impregnation tank is pressurized to 1.5MPa and maintained for 2 hours. After the end, the phenolic resin in the tank is drained out under pressure to obtain a pre-impregnated mesh.

[0032] (3) Prepare a stainless steel mold. The outer dimensions of the mold are 2 mm smaller than the inner dimensions of the finished carbon-carbon guide tube to reserve expansion for the subsequent high-temperature graphitization of the carbon-carbon guide tube. Evenly apply a mold release agent that is resistant to 200°C on the surface of the mold.

[0033] (4) Lay the prepreg mesh uniformly on the surface of the stainless steel mold, with each layer laid at the same height on the mold surface, cut and align the front and rear ends, and then lay the next layer. The joints of each layer are staggered, and the laying thickness is 6 times the final carbon-carbon guide tube wall thickness.

[0034] (5) The vacuum bag-autoclave molding process is adopted. The mold wrapped with the multi-layer prepreg mesh is placed in a vacuum bag, and then the vacuum bag is placed in an autoclave. The vacuum pipeline is connected, the autoclave is closed, the vacuum bag is evacuated, and the air pressure in the autoclave is set to 2.0 MPa and the temperature is set to 180°C. The vacuum bag is maintained for 5 hours. The multi-layer prepreg mesh is solidified. After cooling to room temperature, the vacuum bag is removed from the autoclave, and the guide tube blank is obtained after demoulding and trimming.

[0035] (6) The solidified guide tube blank is transferred to a carbonization furnace for carbonization treatment at a carbonization temperature of 900°C and a carbonization time of 17 hours.

[0036] (7) The carbonized guide tube blank is transferred to a high-temperature furnace for graphitization treatment. The graphitization temperature is 2000°C and the graphitization time is 10 hours.

[0037] (8) The graphitized guide tube blank is transferred to a deposition furnace for chemical vapor deposition densification and pyrolytic carbon coating processes. The chemical vapor deposition densification process is to introduce natural gas into the chemical vapor deposition furnace at 1050°C with a flow rate of 2.5 m 3 / h, the vacuum degree in the furnace is 3000Pa, and the holding time is 200h. After the chemical vapor deposition densification process is completed, the pyrolytic carbon coating process is continued in the furnace, including maintaining the temperature condition of 1050℃, but adjusting the flow rate of natural gas to 0.5m 3 / h, the vacuum degree in the furnace is 800Pa, and the holding time is 50h to obtain a carbon-carbon guide tube.

[0038] The carbon-carbon flow guide tube prepared in this embodiment has a density of 1.37 g / cm 3 , flexural strength 160MPa, ash content 180ppm, with good mechanical properties, corrosion resistance and high temperature resistance, the high temperature thermal field temperature of the single crystal furnace is 1000℃~1600℃, the carbon-carbon guide tube has a temperature resistance of more than 2500℃, which can meet the use requirements of the guide tube for the thermal field of the photovoltaic direct-pull single crystal silicon furnace.

[0039] Example 2 (1) Cut 24K carbon fiber into short fibers of 30 mm in length, and use a web machine to comb the short fibers into a web with a gram weight of 40 g / m2 , where K represents the number of thousands of carbon fibers.

[0040] (2) Place the carbon fiber mesh into a vacuum-pressure resin impregnation tank so that the mesh is completely immersed in the impregnation liquid in the tank. The impregnation liquid is a mixed solution of phenolic resin and alcohol, and the alcohol addition ratio is 20% of the mass of phenolic resin. In order to fully impregnate the mesh, the vacuum-pressure resin impregnation tank is first evacuated to -0.085MPa and maintained for 0.5h, so that the air in the micropores of the mesh is extracted to form near-vacuum pores, eliminating the obstruction of air and making it easy for the impregnation liquid to penetrate into the micropores. Then, the vacuum-pressure resin impregnation tank is pressurized to 1.0MPa and maintained for 1h. After the end, the phenolic resin in the tank is drained under pressure to obtain a pre-impregnated mesh.

[0041] (3) Prepare a stainless steel mold. The outer dimensions of the mold are 3.5 mm smaller than the inner dimensions of the finished carbon-carbon guide tube to reserve expansion for the subsequent high-temperature graphitization of the carbon-carbon guide tube. Evenly apply a mold release agent that is resistant to 200°C on the surface of the mold.

[0042] (4) Lay the prepreg mesh evenly on the surface of the stainless steel mold, with each layer laid at the same height on the mold surface, cut and align the front and rear ends, and then lay the next layer. The joints of each layer are staggered, and the laying thickness is 5 times the final carbon-carbon guide tube wall thickness.

[0043] (5) The vacuum bag-autoclave molding process is adopted. The mold wrapped with the multi-layer prepreg mesh is placed in a vacuum bag, and then the vacuum bag is placed in an autoclave. The vacuum pipeline is connected, the autoclave is closed, the vacuum bag is evacuated, and the air pressure in the autoclave is set to 1.5 MPa and the temperature is set to 150°C. The vacuum bag is maintained for 2 hours. The multi-layer prepreg mesh is solidified. After cooling to room temperature, the vacuum bag is removed from the autoclave, and the guide tube blank is obtained after demoulding and trimming.

[0044] (6) The solidified guide tube blank is transferred to a carbonization furnace for carbonization treatment at a carbonization temperature of 800°C and a carbonization time of 16 hours.

[0045] (7) The carbonized guide tube blank is transferred to a high-temperature furnace for graphitization treatment. The graphitization temperature is 1800°C and the graphitization time is 8 hours.

[0046] (8) The graphitized guide tube blank is transferred to a deposition furnace for chemical vapor deposition densification and pyrolytic carbon coating processes. The chemical vapor deposition densification process is to introduce natural gas into the chemical vapor deposition furnace at 800°C with a flow rate of 1.5 m 3 / h, the vacuum degree in the furnace is 2500Pa, and the holding time is 100h. After the chemical vapor deposition densification process is completed, the pyrolytic carbon coating process is continued in the furnace, including maintaining the temperature condition of 800℃, but adjusting the flow rate of natural gas to 0.75m 3 / h, the vacuum degree in the furnace is 500Pa, and the holding time is 10h to obtain a carbon-carbon guide tube.

[0047] The carbon-carbon flow guide tube prepared in this embodiment has a density of 1.40 g / cm 3 , flexural strength 166MPa, ash content 190ppm, with good mechanical properties, corrosion resistance and high temperature resistance, the high temperature thermal field temperature of the single crystal furnace is 1000℃~1600℃, the carbon-carbon guide tube has a temperature resistance of more than 2500℃, which can meet the use requirements of the guide tube for the thermal field of the photovoltaic direct-pull single crystal silicon furnace.

[0048] Example 3 (1) Cut 12K carbon fiber into short fibers of 100 mm in length, and use a web machine to comb the short fibers into a web with a gram weight of 120 g / m 2 , where K represents the number of thousands of carbon fibers.

[0049] (2) Place the carbon fiber mesh into a vacuum-pressure resin impregnation tank so that the mesh is completely immersed in the impregnation liquid in the tank. The impregnation liquid is a mixed solution of phenolic resin and alcohol, and the alcohol addition ratio is 30% of the mass of phenolic resin. In order to fully impregnate the mesh, the vacuum-pressure resin impregnation tank is first evacuated to -0.095MPa and maintained for 1.5h, so that the air in the micropores of the mesh is extracted to form near-vacuum pores, eliminating the obstruction of air and making it easy for the impregnation liquid to penetrate into the micropores. Then, the vacuum-pressure resin impregnation tank is pressurized to 2.5MPa and maintained for 4h. After the end, the phenolic resin in the tank is drained out under pressure to obtain a pre-impregnated mesh.

[0050] (3) Prepare a stainless steel mold. The outer dimensions of the mold are 5 mm smaller than the inner dimensions of the finished carbon-carbon guide tube to reserve expansion for the subsequent high-temperature graphitization of the carbon-carbon guide tube. Evenly apply a mold release agent that is resistant to 200°C on the surface of the mold.

[0051] (4) Lay the prepreg mesh uniformly on the surface of the stainless steel mold, with each layer laid on the mold surface at the same height, cut and align the front and rear ends, and then lay the next layer. The joints of each layer are staggered, and the laying thickness is 7 times the final carbon-carbon guide tube wall thickness.

[0052] (5) The vacuum bag-autoclave molding process is adopted. The mold wrapped with the multi-layer prepreg mesh is placed in a vacuum bag, and then the vacuum bag is placed in an autoclave. The vacuum pipeline is connected, the autoclave is closed, the vacuum bag is evacuated, and the air pressure in the autoclave is set to 3.0 MPa and the temperature is set to 200 °C. The vacuum bag is maintained for 10 hours. The multi-layer prepreg mesh is solidified. After cooling to room temperature, the vacuum bag is removed from the autoclave, and the guide tube blank is obtained after demoulding and trimming.

[0053] (6) The solidified guide tube blank is transferred to a carbonization furnace for carbonization treatment at a carbonization temperature of 1100°C and a carbonization time of 20 hours.

[0054] (7) The carbonized guide tube blank is transferred to a high-temperature furnace for graphitization treatment. The graphitization temperature is 2200°C and the graphitization time is 15 hours.

[0055] (8) The graphitized guide tube blank is transferred to a deposition furnace for chemical vapor deposition densification and pyrolytic carbon coating processes. The chemical vapor deposition densification process is to introduce natural gas into the chemical vapor deposition furnace at 1100°C with a flow rate of 3.0 m 3 / h, the vacuum degree in the furnace is 3500Pa, and the holding time is 350h. After the chemical vapor deposition densification process is completed, the pyrolytic carbon coating process is continued in the furnace, including maintaining the temperature condition of 1100℃, but adjusting the flow rate of natural gas to 1.0m 3 / h, the vacuum degree in the furnace is 1000Pa, and the holding time is 30h to obtain a carbon-carbon guide tube.

[0056] The carbon-carbon flow guide tube prepared in this embodiment has a density of 1.39 g / cm 3 , flexural strength 162MPa, ash content 195ppm, with good mechanical properties, corrosion resistance and high temperature resistance, the high temperature thermal field temperature of the single crystal furnace is 1000℃~1600℃, the carbon-carbon guide tube has a temperature resistance of more than 2500℃, which can meet the use requirements of the guide tube for the thermal field of the photovoltaic direct-pull single crystal silicon furnace.

[0057] Comparative Example 1 This comparative example prepares a carbon-carbon guide tube, which differs from Example 1 in that the vacuuming step is omitted in step (2). Step (2) of this comparative example is specifically as follows: placing a carbon fiber mesh tire into a vacuum-pressure resin impregnation tank, so that the mesh tire is completely immersed in the impregnation liquid in the tank, the impregnation liquid is a mixed solution of phenolic resin and alcohol, and the alcohol addition ratio is 10% of the mass of phenolic resin, the vacuum-pressure resin impregnation tank is pressurized to 1.5MPa and maintained for 2h, and after the end, the phenolic resin in the tank is drained under pressure to obtain a pre-impregnated mesh tire.

[0058] The other steps of this comparative example are the same as those of Example 1. The density of the carbon-carbon guide tube prepared in this comparative example is 1.14 g / cm 3 , flexural strength 133MPa, ash content 185ppm, and mechanical properties are lower than those in Example 1. This is because the micropores of the mesh are filled with air after the vacuum is lacking, and the impregnation liquid is not easy to penetrate into the micropores, resulting in a decrease in the flexural strength after molding.

[0059] Comparative Example 2 This comparative example prepares a carbon-carbon guide tube, which differs from Example 1 in that the vacuuming parameters in step (2) are different. In step (2) of this comparative example, the vacuum-pressure resin impregnation tank is first evacuated to -0.05MPa and maintained for 1 hour. The other steps of this comparative example are the same as those in Example 1. The carbon-carbon guide tube prepared in this comparative example has a density of 1.21g / cm 3 , flexural strength 140MPa, ash content 191ppm, the mechanical properties are slightly lower than those in Example 1. This is because the vacuum degree is not high enough, there is still some air in the micropores of the mesh, the amount of impregnation liquid penetrating into the micropores is small, and the flexural strength after molding is slightly reduced.

[0060] Comparative Example 3 This comparative example prepares a carbon-carbon guide tube. The difference from Example 1 is that the pyrolytic carbon coating process is omitted in step (8). The other steps of this comparative example are the same as those of Example 1. The density of the carbon-carbon guide tube prepared in this comparative example is 1.28 g / cm 3 , flexural strength 143MPa, ash content 182ppm, and the mechanical properties are slightly lower than those in Example 1. This is because after chemical vapor deposition, no pyrolytic carbon coating process is performed, and the bonding strength between the deposited film and the blank is reduced, resulting in a decrease in the surface density of the guide tube, which reduces the flexural strength of the guide tube.

[0061] like Figure 1 In the high-temperature thermal field of the single crystal furnace, the crucible is used to load molten silicon liquid. The carbon-carbon guide tube prepared in the above embodiment is used to be arranged on the crucible to control the temperature gradient of the thermal field and guide the argon gas flow, provide the necessary protective gas environment, prevent the silicon liquid from being contaminated, and ensure the temperature stability during the single crystal growth process.

[0062] The above embodiments do not require the preparation of a preform in the preparation of the carbon-carbon guide tube, eliminating the problem of carbon fiber waste generated during the manufacturing process of the preform, and can also shorten the manufacturing cycle, improve production efficiency, and reduce production costs. In the embodiment of the method for preparing a carbon-carbon guide tube, a mold is used as a base, and a prepreg mesh is laid on the mold for thermoforming. A mold with a complex structure can be designed, thereby preparing a guide tube with a complex shape and structure. The mold is set to be 2 to 5 mm smaller than the inner shape of the finished carbon-carbon guide tube, so that the finished carbon-carbon guide tube meets the size requirements without the need for excessive trimming of the finished product to meet the size requirements, thereby improving material utilization and maintaining the high mechanical strength of the product. In the embodiment of the method for preparing a carbon-carbon guide tube, the chemical vapor deposition densification and pyrolytic carbon coating processes are completed continuously and isothermally in the same equipment, eliminating the equipment heating and cooling cycle, improving production efficiency, and reducing production costs.

[0063] Although the present application has been described in detail with reference to the aforementioned embodiments, it is still possible for those skilled in the art to modify the technical solutions described in the aforementioned embodiments, or to make equivalent substitutions for some of the technical features therein. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present application should be included in the protection scope of the present application.

Claims

1. A method for preparing a carbon-carbon flow guide tube, characterized in that: include: A. Cut the carbon fiber into short fibers and comb the short fibers into a web; B. Immerse the mesh into the impregnation liquid in the equipment, first evacuate the mesh to allow the mesh to absorb the impregnation liquid, and then pressurize the equipment to further press the impregnation liquid into the pores of the mesh to obtain a pre-impregnated mesh; C. Laying multiple layers of the impregnated mesh on the mold surface; D. solidifying the multi-layer impregnated mesh on the mold and demoulding to obtain a green body; E. carbonizing the green body; F. graphitizing the carbonized body; G. The graphitized green body is subjected to a chemical vapor deposition densification process and a pyrolytic carbon coating process in sequence to obtain a carbon-carbon guide tube.

2. The method for preparing the carbon-carbon flow guide tube according to claim 1, characterized in that: In step A, the specification of the carbon fiber is 12K or 24K carbon fiber; the length of the short fiber is 30-100 mm; the weight of the mesh tire is 40-120 g / m 2 .

3. The method for preparing the carbon-carbon flow guide tube according to claim 1, characterized in that: In step B, the impregnation liquid is one of phenol-formaldehyde resin, epoxy resin and bismaleimide resin; alcohol is added to the impregnation liquid as a diluent, and the alcohol addition ratio is 10% to 30% of the mass of the impregnation liquid.

4. The method for preparing the carbon-carbon flow guide tube according to claim 1, characterized in that: In step B, the equipment is first evacuated to -0.085~-0.095MPa and maintained for 0.5~1.5h, and then pressurized to 1.0~2.5MPa and maintained for 1~4h.

5. The method for preparing the carbon-carbon flow guide tube according to claim 1, characterized in that: Between step B and step C, it also includes: preparing a mold, the outer dimensions of the mold are 2-5 mm smaller than the inner dimensions of the pre-prepared carbon-carbon guide tube, and the mold surface is evenly coated with a release agent that is resistant to temperatures of 200°C and above; in step C, the joint positions of adjacent layers of the impregnated mesh are staggered, and the thickness of the multiple layers of the impregnated mesh laid on the mold surface is 5-7 times the designed wall thickness of the carbon-carbon guide tube.

6. The method for preparing the carbon-carbon flow guide tube according to claim 1 or 5, characterized in that: Step D adopts a vacuum bag-autoclave molding process: the assembly of multiple layers of impregnated mesh laid on the mold surface is placed in a vacuum bag, and then the vacuum bag is placed in an autoclave, the vacuum bag is evacuated, and the internal air pressure of the autoclave is set to 1.5-3.0 MPa and the temperature is set to 150-200°C, maintained for 2-10 hours, so that the multiple layers of impregnated mesh are solidified, cooled, and demolded to obtain the green body.

7. The method for preparing the carbon-carbon flow guide tube according to claim 1, characterized in that: The carbonization in step E is maintained at 800-1100° C. for 16-20 hours; the graphitization in step F is maintained at 1800-2200° C. for 8-15 hours.

8. The method for preparing the carbon-carbon flow guide tube according to claim 1, characterized in that: The chemical vapor deposition densification process is as follows: natural gas is introduced into the chemical vapor deposition furnace at a temperature of 800-1100°C, with a flow rate of 1.5-3.0 m 3 / h, the vacuum degree in the furnace is 2500~3500Pa, and the holding time is 100~350h.

9. The method for preparing the carbon-carbon flow guide tube according to claim 8, characterized in that: The pyrolytic carbon coating process is as follows: after the chemical vapor deposition densification process is completed, continue to use the same temperature as the chemical vapor deposition densification process in the chemical vapor deposition furnace, and adjust the flow rate of natural gas to 0.5-1.0m 3 / h, the vacuum degree in the furnace is 500~1000Pa, and the holding time is 10~50h.

10. A carbon-carbon flow guide tube, characterized in that: Prepared according to the preparation method according to any one of claims 1 to 9.

Images