Method for preparing ultra-long and ultra-thick plate-shaped carbon / carbon composite material in large scale at low cost

Abstract

The invention discloses a method for preparing an ultra-long and ultra-thick plate-shaped carbon / carbon composite material on a large scale at low cost, which comprises the following steps: carrying out primary graphitization treatment on a carbon fiber preform to obtain a carbon fiber blank, loading the carbon fiber blank into a chemical vapor deposition furnace to carry out chemical vapor deposition treatment, and then carrying out secondary graphitization treatment to obtain the ultra-long and ultra-thick plate-shaped carbon / carbon composite material. A carbon / carbon green body is obtained, and the carbon / carbon green body is subjected to resin carbon densification treatment; according to the chemical vapor deposition, in the CVI deposition process, the flowing direction of gas in the deposition process is effectively controlled through the arrangement of an original chemical vapor deposition device, the freshness of carbon source gas in a deposition chamber is made to be consistent, an independent gas channel area is formed around each product, gas makes full contact with all parts of a blank, densification is uniform, the microstructure of the product is controllable, and the product quality is improved. After the product is subjected to high-temperature heat treatment at 2000-2500 DEG C, the graphitization degree range is 40-70%.

Description

Technical Field

[0001] The invention relates to the technical field of carbon / carbon composite material preparation, and in particular to a method for preparing ultra-long and ultra-thick plate-shaped carbon / carbon composite materials in large quantities at low cost. Background Art

[0002] Carbon / carbon composite materials have the advantages of low density, high strength, high specific modulus, high thermal conductivity, low expansion coefficient, good friction performance, good thermal shock resistance and high dimensional stability. They are often used in high-temperature ablation-resistant materials and high-temperature structural materials. They have good application prospects in aviation, aerospace, nuclear energy, medicine and other fields. They can be used to make rocket and missile engine nozzles, aircraft antennas, aircraft and rail transit brake devices, photovoltaic fields and other components.

[0003] At present, the domestic batch preparation method of plate-shaped carbon / carbon composite materials has the problems of being unable to produce products with super-long (1200mm) and super-thick (100mm) dimensions, complicated production process, unable to produce in large quantities, high production cost, unable to control product microstructure, unstable product quality, etc. For example, the domestic patent number is 200910093946.6, a high-performance carbon-based composite material rapid directional infiltration gas flow control method, its graphite tooling design can only adapt to ring-shaped preforms, and cannot be directional infiltration for plate-shaped or special-shaped preforms, and if the air pressure, temperature and gas flow are not controlled in stages, the effect of rapid densification cannot be achieved. For example, the domestic patent number is 200410026035.9, the thermal gradient chemical vapor deposition method for preparing carbon / carbon composite thick-walled plates, the method described in this patent can indeed quickly prepare high-density carbon / carbon composite materials, but there are certain differences in the general product structure, special fixtures are required, and it is only suitable for single-piece production, which is difficult to industrialize. Patent No. 202110296058.5 is a vapor deposition device and a method for preparing carbon / carbon composite materials. This patent can produce larger-sized special-shaped carbon / carbon composite materials, but the batch production efficiency still cannot meet the demand. Patent No. 201310438377.0 is a method for rapidly preparing high-density carbon / carbon composite materials in batches. This patent is a method for rapidly preparing high-density carbon / carbon composite materials in batches, but the airflow in this method cannot flow evenly at the bottom of the blank, and there is a significant difference in the freshness of the carbon source gas in the upper and lower areas of the deposition chamber. There is a significant difference in the performance of the upper and lower layers of the product, and the product quality varies greatly. The carbon microstructure of the product (characterized by the degree of graphitization) cannot be evenly and effectively controlled.

[0004] Therefore, how to provide a method for preparing ultra-long and ultra-thick plate-shaped carbon / carbon composite materials in large quantities at low cost, with controllable product microstructure and good ablation resistance, has become a difficult problem that needs to be solved urgently by technical personnel in this field. Summary of the invention

[0005] In view of the deficiencies in the prior art, the purpose of the present invention is to provide a method for preparing ultra-long (length ≥ 1200mm) and ultra-thick (thickness ≥ 100mm) plate-like carbon / carbon composite materials in large quantities at low cost. During the CVI deposition process, an original chemical vapor deposition device is set up to effectively control the flow direction of the gas during the deposition process, so that the freshness of the carbon source gas in the deposition chamber is consistent, and an independent gas channel area is formed around each product. The gas is in full contact with all parts of the blank, the densification is uniform, and the product microstructure is controllable. After the product is subjected to high-temperature heat treatment at 2000-2500°C, the graphitization degree ranges from 40 to 70%. The products in this graphitization degree range have good ablation resistance and are suitable for use as high-temperature structural materials and ablation-resistant materials for aerospace, and have good material properties and development and application prospects.

[0006] In order to achieve the above object, the present invention adopts the following technical solution:

[0007] The present invention discloses a method for preparing ultra-long and ultra-thick plate-shaped carbon / carbon composite materials in large quantities at low cost, wherein a carbon fiber preform is subjected to a primary graphitization treatment to obtain a carbon fiber blank, the carbon fiber blank is loaded into a chemical vapor deposition furnace for chemical vapor deposition treatment, and then a secondary graphitization treatment is performed to obtain a carbon / carbon blank, and then the carbon / carbon blank is subjected to a resin carbon densification treatment to obtain the obtained carbon / carbon blank;

[0008] The chemical vapor deposition is carried out in a vapor deposition device, which includes a base and a deposition chamber arranged above the base; an air inlet and a gas mixing chamber are arranged below the base, a bottom plate is arranged above the base, and a vent is arranged on the side of the bottom plate; the deposition chamber is mounted on the bottom plate and is connected to the gas mixing chamber through the vent; a gas separation outer wall and a gas separation inner wall are arranged on one side of the deposition chamber, the vent is located between the gas separation outer wall and the gas separation inner wall in the vertical direction, a plurality of gas separation ports are arranged at intervals on the gas separation inner wall, side walls are arranged on both sides adjacent to the gas separation outer wall and the gas separation inner wall in the deposition chamber, a plurality of support points are distributed at intervals along the height direction on the side walls, N material plates are arranged at intervals along the height direction of the deposition chamber, the material plates are supported by the support points, and a top wall is also arranged in the deposition chamber; the top wall covers the material plates on the vertical projection plane;

[0009] During the loading, several carbon fiber blanks are placed in parallel on the bottom plate and the material plate, and the bottom is suspended by arranging gaskets between the bottom plate, the material plate and the carbon fiber blanks. The length direction of the carbon fiber blanks is perpendicular to the inner wall of the gas separator. During the chemical vapor deposition, the carbon source gas enters the mixing chamber from the air inlet, and then enters the deposition chamber from the air vent in the mixing chamber. After being separated by the gas separation port on the inner wall of the gas separator, it flows along the four sides of the blank from one side of the deposition chamber to the other side, and finally converges upward, passes through the outer side of the top wall, and is discharged from the air outlet on the upper part of the deposition chamber.

[0010] In the preparation method provided by the present invention, chemical vapor deposition is carried out in a vapor deposition device, and the deposition chamber of the vapor deposition device includes a ventilation outer wall, a ventilation inner wall, a side wall and a top wall; the side wall is provided with a support point, and the support point has the function of supporting a material plate, and a gasket is provided on the material plate and the bottom plate, and the product blank can be loaded on the gasket, and a blank placement space is reserved between the bottom plate and the material plate on the side wall; the entire deposition chamber is divided into a number of small deposition spaces by arranging the material plate, and no baffle is arranged at the blank outlet end in the deposition chamber to ensure smooth flow of air. The outgoing gas flows converge upward and are discharged from the deposition chamber from the gas outlet at the upper part of the deposition chamber. During the chemical vapor deposition process, the gas flow is guided by the ventilation outer wall, ventilation inner wall, side wall, top wall, bottom plate, material plate and gasket of the deposition chamber, and flows evenly along the surface of the blank. An enveloping gas flow channel is formed around the blank (including the bottom of the blank), which enhances the gas penetration into the blank, is beneficial to control the deposited carbon structure, and greatly improves the utilization rate of the carbon source gas. The deposition chamber has high space utilization rate, and can produce ultra-long and ultra-thick plate-shaped carbon / carbon composite materials in large quantities at low cost.

[0011] In a preferred embodiment, the density of the carbon fiber preform is 0.3-0.6 g / cm 3 .

[0012] In a preferred solution, the size of the carbon fiber preform is 5-20 mm larger than the size of the finished product.

[0013] In a preferred embodiment, the carbon fiber preform is a 2.5D needle-punched structure, which is formed by alternating layers of a PANCF non-woven fabric and a PANCF non-woven fabric web and continuously needle-punching the preform.

[0014] Further preferably, in the carbon fiber preform, the non-wefted fabric is alternately laid at 0° / 90°.

[0015] In a preferred embodiment, the primary graphitization treatment is carried out under argon protection, the temperature of the primary graphitization treatment is 2000-2500° C., and the time of the primary graphitization treatment is 2-5 hours.

[0016] In a preferred embodiment, during the process of loading the carbon fiber blanks into the chemical vapor deposition furnace, gaps are left between adjacent carbon fiber blanks in each layer.

[0017] Preferably, the diameter of the air inlet is 20-50 mm.

[0018] In a preferred embodiment, the diameter of the vent is 30-80 mm.

[0019] In a preferred solution, the width of the gas distribution port is 20-100 mm.

[0020] Further preferably, the width of the gas separation port increases gradually from bottom to top.

[0021] More preferably, the width of the air distribution openings in the first layer is 25-40 mm, and the width of the air distribution openings in the Nth layer is increased by 2-20 mm, preferably 4-8 mm, compared with the width of the air distribution openings in the N-1th layer.

[0022] In a preferred embodiment, the distance from the upper surface of the carbon fiber blank in each layer to the material plate is 20-80 mm.

[0023] Further preferably, the distance from the upper surface of the carbon fiber blank to the material plate in each layer increases gradually from bottom to top.

[0024] Further preferably, the distance from the upper surface of the carbon fiber blank in the first layer to the material plate is 20-40 mm, preferably 20-30 mm, and the distance from the upper surface of the carbon fiber blank in the Nth layer to the material plate is increased by 2-20 mm, preferably 2-5 mm, compared to the distance from the upper surface of the carbon fiber blank in the N-1th layer to the material plate.

[0025] In a preferred solution, the height of the gasket is 20-80 mm.

[0026] Further preferably, the height of the gasket increases gradually from bottom to top;

[0027] Further preferably, the height of the gasket in the first layer is 20-40 mm, preferably 20-30 mm, and the height of the gasket in the Nth layer is 2-20 mm, preferably 2-4 mm, higher than the height of the gasket in the N-1th layer.

[0028] In a preferred embodiment, the gap size between adjacent carbon fiber blanks in each layer is 20 to 100 mm.

[0029] Further preferably, the gap sizes between the carbon fiber blanks increase gradually from bottom to top.

[0030] More preferably, the gap between the carbon fiber blanks in the first layer is 20-40 mm, preferably 25-35, and the gap between the carbon fiber blanks in the Nth layer is 2-20 mm, preferably 2-5 mm, larger than the gap between the carbon fiber blanks in the N-1th layer.

[0031] In the present invention, the gasket under the preform, the distance from the upper surface of the preform to the material plate and the gap between the preforms form an independent confined reaction area around each preform, the width of the gas distribution port increases gradually from bottom to top, and the gap size between adjacent carbon fiber blanks in each layer increases gradually from bottom to top. This makes up for the difference in carbon source gas pressure and freshness, and achieves the effect of uniform densification of each blank in each layer.

[0032] In the preferred embodiment, the width of the gas distribution port, the height of the gasket, the distance from the upper surface of the preform to the material plate, and the size of the preform gap change gradually from layer to layer, increasing by 2-20 mm from bottom to top to compensate for the influence of the decrease in the freshness of the carbon source gas on the densification effect, so that the thick plate blank of the present invention can be uniformly vapor deposited and densified in the entire vapor deposition furnace.

[0033] In a preferred embodiment, during the chemical vapor deposition, the furnace temperature is controlled to be 950-1120° C. and the furnace pressure is controlled to be 2-10 kPa.

[0034] In a preferred embodiment, the chemical vapor deposition is performed in 3-5 times, each chemical vapor deposition time is 60-160 hours, and the total chemical vapor deposition time is 300-500 hours.

[0035] In a preferred embodiment, during the chemical vapor deposition, the flow rate of the carbon source gas is controlled to be 2-5 L / (kg.min). kg is the total weight of the carbon fiber blank.

[0036] Further preferably, during the first chemical vapor deposition, the flow rate of the carbon source gas is 3-5 L / (kg.min), and the flow rate of the carbon source gas during the subsequent chemical vapor deposition is reduced by 10-20% compared with the flow rate of the carbon source gas during the previous chemical vapor deposition.

[0037] The inventors have discovered that by gradually reducing the flow rate of the carbon source gas by 10-20% as the density of the green body increases during chemical vapor deposition, it is possible to avoid excessive deposition reactions occurring in the outer layer of the green body due to excessive carbon source gas flow, which would lead to difficulty in densifying the inner layer of the green body and affect the densification efficiency and uniformity of the green body.

[0038] In a preferred embodiment, the second graphitization treatment is carried out under argon protection, the temperature of the second graphitization treatment is 2000-2500° C., and the time of the second graphitization treatment is 2-5 hours.

[0039] In a preferred embodiment, the density of the carbon / carbon blank is 1.20 to 1.50 g / cm 3 .

[0040] In a preferred embodiment, the resin carbon densification process is as follows: placing the carbon / carbon blank in a resin impregnating agent for sequential impregnation treatment, followed by sequential carbonization treatment and high-temperature heat treatment.

[0041] Further preferably, the high temperature heat treatment is carried out under argon protection, the temperature of the high temperature heat treatment is 2000-2500° C., and the treatment time is 2-5 hours.

[0042] In actual operation, the carbon fiber preform is placed in a heat treatment furnace, evacuated and replaced with gas, and then graphitized or subjected to high-temperature heat treatment under argon protection, and finally mechanically processed to remove the surface dense layer of a preset thickness.

[0043] In a preferred embodiment, the density of the ultra-long and ultra-thick plate-shaped carbon / carbon composite material is 1.83 to 1.95 g / cm 3 .

[0044] Principles and advantages

[0045] The preparation method provided by the present invention is that chemical vapor deposition is carried out in a vapor deposition device, the vapor deposition device includes a base, a bottom plate and a deposition chamber, the deposition chamber includes a ventilation outer wall, a ventilation inner wall, a side wall and a top wall; the side wall is provided with a support point, the support point has the function of supporting a material plate, the material plate and the bottom plate are provided with a gasket, the product blank can be loaded on the gasket, and a blank placement space is reserved between the bottom plate and the material plate on the side wall; the entire deposition chamber is divided into a number of small deposition spaces by arranging the material plate, and no baffle is arranged at the blank outlet end in the deposition chamber to ensure smooth outflow of the airflow, and the outlet airflow The gases converge upward and are discharged from the gas outlet at the upper part of the deposition chamber. During the chemical vapor deposition process, the gas flow is guided by the ventilation outer wall, ventilation inner wall, side wall, top wall, bottom plate, material plate and gasket of the deposition chamber, so that the freshness of the carbon source gas is kept in a relatively consistent state. At the same time, the gas flows evenly along the surface of each layer of the blank. An enveloping gas flow channel is formed around each blank (including the bottom of the blank), which enhances the gas penetration into the blank, is beneficial to control the deposited carbon structure, and greatly improves the utilization rate of the carbon source gas. The deposition chamber has high space utilization rate, and can produce ultra-long and ultra-thick plate-shaped carbon / carbon composite materials in large quantities at low cost.

[0046] The present invention can realize the mass production of super-long (≥1200mm) and super-thick (≥100mm) plate-shaped carbon / carbon composite materials. The vapor deposition device designed by the present invention has a simple structure, the carbon source gas freshness in the upper and lower areas of the deposition chamber is relatively consistent, the gas flows evenly around the blank, the blank densification efficiency is high, the deposited carbon is evenly distributed, the product microstructure is controllable, and the product has a graphitization degree of 40-70% after high-temperature heat treatment at 2000-2500°C. The products in this graphitization degree range have good ablation resistance, are suitable for use as high-temperature structural materials and ablation-resistant materials for aerospace, and have good material properties and development and application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] Figure 1 is a cross-sectional view of the vapor deposition device of the present invention;

[0048] Figure 2 A top view of the vapor deposition device of the present invention;

[0049] Figure 3 is a schematic diagram of the structure of the sleeve of the present invention,

[0050] Among them, 1-air inlet, 2-gas mixing chamber, 3-air vent, 4-base, 5-bottom plate, 6-gas separation inner wall, 7-gas separation port, 8-gas separation outer wall, 9-blank, 10-material plate, 11-furnace, 12-top wall, 13-exhaust port, 14-side wall, 15-support point, 16-gasket;

[0051] Figure 4 A schematic diagram of the gas separation inner wall and the gas separation ports with gradient distribution thereon;

[0052] Figure 5 A three-dimensional diagram of the vapor deposition apparatus of the present invention. DETAILED DESCRIPTION

[0053] In order to enable those skilled in the art to better understand the technical solutions in this application, this application will be described clearly and completely in conjunction with specific embodiments below. Obviously, the embodiments described are only part of the embodiments of this application, not all of them. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of this application.

[0054] like Figures 1 to 3 As shown, the present invention provides a method for preparing a carbon / carbon composite material, which adopts the vapor deposition device designed by the present invention, including a base 4 and a deposition chamber arranged above the base 4; an air inlet 1 and a gas mixing chamber 2 are provided below the base 4, a bottom plate 5 is provided above the base 4, the deposition chamber is installed on the bottom plate 5, and a vent 3 is provided on the bottom plate 5; the deposition chamber includes a gas separation inner wall 6, a gas separation port 7 is provided on the gas separation inner wall 6, a gas separation outer wall 8, a side wall 14, a material plate 10 and a top wall 12, an exhaust port 13 is provided above the furnace 11, a material plate support point 15 is provided on the side wall 14, and gaskets 16 are provided on the bottom plate 5 and the material plate 10.

[0055] The vapor deposition device provided by the present invention, when in use, places the blank on the gasket 16 on the bottom plate 5 and the material plate 10, and after the gas passes through the gas distribution port 6, it flows along the slits around the blank (including the bottom of the blank), forming independent gas channel spaces around the blank, and the carbon source gas can fully contact the surface of the blank, penetrate deeply into the blank, and undergo a vapor deposition reaction. By adjusting the width of each layer of gas distribution ports, adjusting the gap around each layer and each blank, including the gasket height, the gap between the blanks, the gap between the blanks and the material plate, etc., the effects of adjusting the freshness, pressure and flow rate of the gas around the blank are achieved, so that each layer and each blank is uniformly densified, and the product microstructure is controllable. The device has a high space utilization rate for the furnace, which is convenient for mass and low-cost production of blanks. In the actual working process, the gap size between the material plates can be adjusted according to the thickness of the blank, so as to make full use of the space in the deposition chamber and the utilization rate of the carbon source gas, and increase the number of blanks loaded into the furnace. At the same time, the ineffective space inside the deposition chamber is reduced, ensuring uniform and rapid flow of gas, and reducing the loss of freshness during gas flow. Therefore, the vapor deposition device provided by the present invention has a simple structure, is easy to use, has high deposition efficiency and good uniformity, can effectively control the flow direction of the gas during the deposition process so that it can fully contact the blank to be processed, and can prepare ultra-long and ultra-thick carbon / carbon composite materials in large quantities at low cost.

[0056] In the preferred implementation case, a gas separation port 7 is provided on the gas separation inner wall 6, and the air flow enters the partition area of ​​each layer of the billet through the gas separation port, and flows evenly on the bottom plate, material plate, side wall, top wall, around the billet (including the bottom of the billet), and along the slits on the surface of the billet, thereby greatly improving the utilization rate of the carbon source gas.

[0057] In a preferred embodiment, the diameter of the air inlet is 20-50 mm.

[0058] In a preferred embodiment, the diameter of the vent is 30-80 mm.

[0059] In a preferred embodiment, the width of the gas separation opening is 20-100 mm.

[0060] In a further embodiment, the width of the gas separation port increases gradually from bottom to top.

[0061] In a further preferred embodiment, the width of the gas separation openings in the first layer is 25-40 mm, and the width of the gas separation openings in the Nth layer is increased by 2-20 mm, preferably 4-8 mm, compared with the width of the gas separation openings in the N-1th layer.

[0062] In a preferred embodiment, the distance from the upper surface of the carbon fiber blank in each layer to the material plate is 20-80 mm.

[0063] In a further preferred embodiment, the distance from the upper surface of the carbon fiber blank to the material plate in each layer increases gradually from bottom to top.

[0064] In a further preferred embodiment, the distance from the upper surface of the carbon fiber blank in the first layer to the material plate is 20-40 mm, preferably 20-30 mm, and the distance from the upper surface of the carbon fiber blank in the Nth layer to the material plate is increased by 2-20 mm, preferably 2-5 mm, compared to the distance from the upper surface of the carbon fiber blank in the N-1th layer to the material plate.

[0065] In a preferred embodiment, the height of the spacer is 20-80 mm.

[0066] In a further preferred embodiment, the height of the gasket increases gradually from bottom to top;

[0067] In a further preferred embodiment, the height of the gasket in the first layer is 20-40 mm, preferably 20-30 mm, and the height of the gasket in the Nth layer is 2-20 mm, preferably 2-4 mm, higher than the height of the gasket in the N-1th layer.

[0068] In a preferred embodiment, the gap size between adjacent carbon fiber blanks in each layer is 20-100 mm.

[0069] In a further preferred embodiment, the gap sizes between the carbon fiber blanks increase gradually from bottom to top.

[0070] In a further preferred embodiment, the gap between the carbon fiber blanks in the first layer is 20-40 mm, preferably 25-35, and the gap between the carbon fiber blanks in the Nth layer is 2-20 mm larger than the gap between the carbon fiber blanks in the N-1th layer, preferably 2-5 mm.

[0071] Of course, in addition to the above-mentioned preferred settings, the distribution, size, quantity, etc. of the vents, gas distribution ports, gaskets and material plates can be adjusted according to actual conditions, which is mainly determined by the shape of the blank and the loading position of the blank.

[0072] The present invention provides a method for preparing an ultra-long and ultra-thick plate-shaped carbon / carbon composite material, comprising the following steps:

[0073] a. Prepare a carbon fiber preform;

[0074] b. performing a primary graphitization treatment on the carbon fiber preform to obtain a carbon fiber blank;

[0075] c. Performing CVD densification treatment on the carbon fiber blank to obtain a CVD blank,

[0076] The CVD densification process is carried out in the vapor deposition apparatus described above.

[0077] When loading, place the carbon fiber blank in the blank placement position reserved between the bottom plate and the material plate, and place it on the gasket on the bottom plate and the material plate;

[0078] d. performing secondary graphitization treatment on the CVD body to obtain a semi-finished product;

[0079] e. The semi-finished product is sequentially subjected to an impregnation curing treatment, a carbonization treatment, a high-temperature heat treatment, and a mechanical processing treatment; the mechanical processing process is to remove a surface dense layer of a preset thickness;

[0080] f. Repeat step e until the density of the graphitized body reaches the target value to obtain a preliminary finished product;

[0081] g. Perform fine processing on the primary finished product to obtain the finished product.

[0082] Preferably, the carbon source gas for CVD densification treatment is natural gas or propylene.

[0083] Preferably, during the CVD densification process, the flow rate of the carbon source gas is 2-5 L / (kg.min), where kg is the total weight of the carbon fiber blank.

[0084] Preferably, in step c, the carbon fiber blank is subjected to at least two CVD densification treatments, and the flow rate of the carbon source gas during each CVD densification treatment is less than the flow rate of the carbon source gas during the previous CVD densification treatment. After each CVD, the blank is mechanically processed to remove the dense layer on the surface of the blank.

[0085] Preferably, in step c, the flow rate of the carbon source gas in the first CVD densification treatment process is 3-5L / (kg.min). As the density of the green body increases, the flow rate of the carbon source gas decreases by 10-20% each time (that is, the flow rate of the carbon source gas in the subsequent CVD densification treatment is 10-20% less than the flow rate of the carbon source gas in the previous CVD densification treatment) to avoid excessive deposition reaction in the outer layer of the green body due to excessive carbon source gas flow, resulting in difficulty in densifying the inner layer of the green body, affecting the densification efficiency and uniformity of the green body. After each CVD, 1 to 2 mm of the dense layer on the surface of the green body is removed by mechanical processing.

[0086] Preferably, the process parameters of the CVD densification treatment are: furnace temperature of 950-1120° C., and furnace pressure of 3-15 kPa.

[0087] Preferably, the total time of chemical vapor deposition is 300-500 hours, which is carried out in 3-5 times, each time for 60-160 hours.

[0088] Preferably, step b specifically comprises: placing the carbon fiber preform into a heat treatment furnace, first evacuating the furnace, heating the furnace to 2000-2500° C. and then keeping the temperature for 2-5 hours, during which time argon gas is used for protection.

[0089] Preferably, step d is specifically as follows: placing the CVD blank into a heat treatment furnace, first evacuating the furnace, heating the furnace to 2000-2500° C. and then maintaining the temperature for 2-5 hours, during which time argon gas is used for protection.

[0090] Preferably, the density of the carbon fiber preform is 0.3-0.6 g / cm 3 .

[0091] Preferably, the size of the carbon fiber preform is 5-20 mm larger than the size of the finished product.

[0092] Preferably, the carbon fiber preform is a 2.5D needle-punched structure, using a layer of PANCF non-woven fabric and a layer of PANCF non-woven fabric web alternately laid.

[0093] Preferably, the non-woven fabric is formed by 0° / 90° alternating plying and continuous needle punching.

[0094] Preferably, the target density of the CVD green body in step c is 1.20-1.50 g / cm 3 .

[0095] Preferably, the target density of the green body in step f is 1.85 g / cm 3 .

[0096] The preparation method of the carbon / carbon composite material provided by the present invention has the advantages of simple vapor deposition device structure, high densification efficiency, small density difference between inside and outside of the blank and between blanks, and can obtain a density of ≥1.850 / cm 3 The ultra-long and ultra-thick carbon / carbon composite materials are suitable for the preparation of large-scale high-temperature structural materials and large-scale ablation-resistant material precursors for aerospace use. The resulting products have good material properties and development and application prospects.

[0097] Example 1

[0098] a. Prepare 54 carbon fiber preforms. The carbon fiber preforms are 2.5D needle-punched structures. They are made of a layer of PANCF non-woven fabric and a layer of PANCF non-woven fabric mesh alternately laid. The non-woven fabric is alternately laid at 0° / 90° and needle-punched continuously. The length × width × height of the carbon fiber preform is 1200mm × 294mm × 125mm, and the density is 0.56g / cm 3 ;

[0099] b. Performing a primary graphitization treatment on the carbon fiber preform to obtain a carbon fiber blank; placing the carbon fiber preform into a heat treatment furnace, first evacuating the vacuum, heating to 2000°C and then keeping the temperature for 2 hours, during which argon gas is filled, the furnace pressure is 0.2-3KPa, the carbon fiber preform is graphitized, and then naturally cooled with the furnace;

[0100] c. Performing CVD densification treatment on the carbon fiber blank to obtain a CVD blank.

[0101] The CVD densification treatment is carried out in a vapor deposition device, which includes a base and a deposition chamber arranged above the base; an air inlet is provided below the base, a bottom plate is provided above the base, and the deposition chamber is installed on the bottom plate; the deposition chamber includes a gas separation outer wall, a gas separation inner wall, and a side wall, a material plate arranged on the side wall, and a gas separation port arranged on the gas separation inner wall, and a gasket arranged on the material plate and the bottom plate; the gas separation ports on the gas separation inner wall are arranged in an array.

[0102] Among them, the length, width and height of the deposition chamber are 2116mm×1491mm×1788mm, the length, width and height of the base are 2117mm×1491mm×400mm, the length, width and height of the bottom plate are 2117mm×1491mm×50mm, the length, width and height of the material plate are 2076mm×1401mm×20mm, the diameter of the air inlet is 30mm, the width of the air vent is 50mm, the gap between the preforms is 40mm, and other tooling dimensions of the deposition chamber (tooling dimensions with gradient changes) are shown in Table 1.

[0103] Table 1. Tooling size data table of layer-by-layer gradient change in Example 1

[0104]

[0105] The carbon source gas is propylene, the furnace temperature is 970 ° C, the deposition time is 450 h, and it is carried out in 5 times, each deposition time is 90 h. The carbon source gas flow rate is 7.5 L / (kg.min), 5.1 L / (kg.min), 4.7 L / (kg.min), 3.4 L / (kg.min), 2.8 L / (kg.min), the furnace pressure is 3-8 kPa, and the green body density obtained by the last CVD is 1.25 g / cm 3 After each CVD, the dense layer of 1.5 mm on the surface of the blank is removed by mechanical processing;

[0106] d. Perform secondary graphitization on the CVD body to obtain a semi-finished product; place the CVD body into a heat treatment furnace, evacuate it first, heat it to 2200°C and keep it warm for 3 hours, during which time argon is filled in, the furnace pressure is 0.2-3KPa, and then it is naturally cooled with the furnace.

[0107] e. The semi-finished product is sequentially subjected to resin impregnation and curing treatment, carbonization treatment, high-temperature heat treatment, and mechanical processing treatment; the mechanical processing process is to remove the surface dense layer of a preset thickness; the high-temperature heat treatment temperature is 2400°C;

[0108] f. Repeat step e until the density of the graphitized body reaches the target value to obtain a primary finished product with a density of 1.87 g / cm 3 ;

[0109] g. The primary finished product is finely processed to obtain the finished product. The product performance index data is shown in Table 4.

[0110] Example 2

[0111] a. Prepare 108 carbon fiber preforms. The carbon fiber preforms are 2.5D needle-punched structures. They are made of a layer of PANCF non-woven fabric and a layer of PANCF non-woven fabric mesh alternately laid, and the non-woven fabric is alternately laid at 0° / 90° and continuously needle-punched. The length × width × height of the carbon fiber preform is 1250mm × 140mm × 125mm, and the density is 0.57g / cm 3 ;

[0112] b. Performing a primary graphitization treatment on the carbon fiber preform to obtain a carbon fiber blank; placing the carbon fiber preform into a heat treatment furnace, first evacuating the vacuum, heating to 2200°C and then keeping the temperature for 2 hours, during which argon gas is filled, and the furnace pressure is 0.2-3KPa to graphitize the carbon fiber preform, and then naturally cooling it with the furnace;

[0113] c. Performing CVD densification treatment on the carbon fiber blank to obtain a CVD blank,

[0114] The CVD densification treatment is carried out in a vapor deposition apparatus. The structure and size of the vapor deposition apparatus are the same as those in Example 1, except that the diameter of the air inlet is 50 mm and the width of the air vent is 80 mm. Other tooling dimensions of the deposition chamber (tooling dimensions with gradient changes) are shown in Table 2.

[0115] Table 2. Tooling size data table of layer-by-layer gradient change in Example 2

[0116]

[0117] The carbon source gas is natural gas, the furnace temperature is 1100 ° C, the deposition time is 400 h, and it is carried out in 4 times, each deposition time is 100 h. The carbon source gas flow rate is 8.2 L / (kg.min), 5.6 L / (kg.min), 5.1 L / (kg.min), 4.6 L / (kg.min), the furnace pressure is 5-10 kPa, and the green body density obtained by the last CVD is 1.36 g / cm 3After each CVD, the dense layer of 1.3 mm on the surface of the blank is removed by mechanical processing;

[0118] d. Perform secondary graphitization on the CVD blank to obtain a primary finished product; load the carbon fiber preform into a heat treatment furnace, evacuate it first, heat it to 2400°C and keep it warm for 3 hours, during which time argon is filled in, and then it is naturally cooled with the furnace.

[0119] e. The semi-finished product is sequentially subjected to resin impregnation and curing treatment, carbonization treatment, high-temperature heat treatment, and mechanical processing treatment; the mechanical processing process is to remove the surface dense layer of a preset thickness; the high-temperature heat treatment temperature is 2280°C;

[0120] f. Repeat step e until the density of the graphitized body reaches the target value to obtain a primary finished product with a density of 1.91 g / cm 3 ;

[0121] g. The primary finished product is finely processed to obtain the finished product. The product performance index data is shown in Table 4.

[0122] Example 3

[0123] a. Prepare 196 carbon fiber preforms. The carbon fiber preforms are 2.5D needle-punched structures. They are made of a layer of PANCF non-woven fabric and a layer of PANCF non-woven fabric mesh alternately laid, and the non-woven fabric is alternately laid at 0° / 90° and continuously needle-punched. The size of the carbon fiber preform is 1300mm×120mm×50mm, and the density is 0.45g / cm 3 ;

[0124] b. Performing a primary graphitization treatment on the carbon fiber preform to obtain a carbon fiber blank; placing the carbon fiber preform into a heat treatment furnace, first evacuating the vacuum, heating to 2100°C and then keeping the temperature for 2 hours, during which argon gas is filled, and the furnace pressure is 0.2-3KPa to graphitize the carbon fiber preform, and then naturally cooling it with the furnace;

[0125] c. Performing CVD densification treatment on the carbon fiber blank to obtain a CVD blank,

[0126] The CVD densification treatment is carried out in a vapor deposition apparatus. The structure and size of the vapor deposition apparatus are the same as those in Example 1, except that the width of the air inlet is 20 mm and the diameter of the air vent is 30 mm. Other tooling dimensions of the deposition chamber (tooling dimensions with gradient changes) are shown in Table 3.

[0127] Table 3. Tooling size data table of layer-by-layer gradient change in Example 3

[0128]

[0129]

[0130] The carbon source gas is natural gas, the furnace temperature is 1080 ° C, the deposition time is 390 h, and it is carried out in 3 times, each deposition time is 130 h. The carbon source gas flow rate is 7.7 L / (kg.min), 6.1 L / (kg.min), and 4.8 L / (kg.min), respectively. The furnace pressure is 5-10 kPa. The density of the green body obtained by the last CVD is 1.45 g / cm 3 After each CVD, the dense layer of 1.2 mm on the surface of the blank is removed by mechanical processing;

[0131] d. Perform secondary graphitization on the CVD blank to obtain a primary finished product; load the carbon fiber preform into a heat treatment furnace, evacuate it first, heat it to 2500°C and keep it warm for 3 hours, during which time argon is filled in, and then it is naturally cooled with the furnace.

[0132] e. The semi-finished product is sequentially subjected to resin impregnation and curing treatment, carbonization treatment, high-temperature heat treatment, and mechanical processing treatment; the mechanical processing process is to remove the surface dense layer of a preset thickness; the high-temperature heat treatment temperature is 2350°C;

[0133] f. Repeat step e until the density of the graphitized body reaches the target value to obtain a primary finished product with a density of 1.95 g / cm 3 ;

[0134] g. The primary finished product is finely processed to obtain the finished product. The product performance index data is shown in Table 4.

[0135] Comparative Example 1

[0136] Other conditions are the same as those in Example 1, except that the tooling size does not have a gradient change and the size of the first layer is used. The product performance data is shown in Table 4.

[0137] Table 4. Product performance index data table of examples and comparative examples

[0138]

[0139]

[0140] The above description of the disclosed embodiments enables one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for preparing ultra-long and ultra-thick plate-shaped carbon / carbon composite materials in large quantities and at low cost, characterized in that: The carbon fiber preform is subjected to a primary graphitization treatment to obtain a carbon fiber blank, the carbon fiber blank is loaded into a chemical vapor deposition furnace for chemical vapor deposition, and then subjected to a secondary graphitization treatment to obtain a carbon / carbon blank, and then the carbon / carbon blank is subjected to a resin carbon densification treatment to obtain the carbon / carbon blank; The chemical vapor deposition is carried out in a vapor deposition device, which includes a base and a deposition chamber arranged above the base; an air inlet and a gas mixing chamber are arranged below the base, a bottom plate is arranged above the base, and a vent is arranged on the side of the bottom plate; the deposition chamber is mounted on the bottom plate and is connected to the gas mixing chamber through the vent; a gas separation outer wall and a gas separation inner wall are arranged on one side of the deposition chamber, the vent is located between the gas separation outer wall and the gas separation inner wall in the vertical direction, a plurality of gas separation ports are arranged at intervals on the gas separation inner wall, side walls are arranged on both sides adjacent to the gas separation outer wall and the gas separation inner wall in the deposition chamber, a plurality of support points are distributed at intervals along the height direction on the side walls, N material plates are arranged at intervals along the height direction of the deposition chamber, the material plates are supported by the support points, and a top wall is also arranged in the deposition chamber; the top wall covers the material plates on the vertical projection plane; During the loading, several carbon fiber blanks are placed in parallel on the bottom plate and the material plate, and the bottom is suspended by arranging gaskets between the bottom plate, the material plate and the carbon fiber blanks. The length direction of the carbon fiber blanks is perpendicular to the inner wall of the gas separator. During the chemical vapor deposition, the carbon source gas enters the mixing chamber from the air inlet, and then enters the deposition chamber from the air vent in the mixing chamber. After being separated by the gas separation port on the inner wall of the gas separator, it flows along the four sides of the blank from one side of the deposition chamber to the other side, and finally converges upward, passes through the outer side of the top wall, and is discharged from the air outlet on the upper part of the deposition chamber.

2. The method for preparing ultra-long and ultra-thick plate-shaped carbon / carbon composite materials in large quantities and at low cost according to claim 1, characterized in that: The density of the carbon fiber preform is 0.3-0.6 g / cm 3 ; The carbon fiber preform is a 2.5D needle-punched structure, which is formed by alternately laying a layer of PANCF non-woven fabric and a layer of PANCF non-woven fabric web, and continuously needle-punching; In the carbon fiber preform, the non-wefted fabric is alternately laid at 0° / 90°; The primary graphitization treatment is carried out under argon protection, the temperature of the primary graphitization treatment is 2000-2500° C., and the time of the primary graphitization treatment is 2-5 hours.

3. A method for preparing ultra-long and ultra-thick plate-shaped carbon / carbon composite materials in large quantities and at low cost according to claim 1 or 2, characterized in that: In the process of loading the carbon fiber blanks into the chemical vapor deposition furnace, gaps are left between adjacent carbon fiber blanks in each layer; the size of the gaps between adjacent carbon fiber blanks in each layer is 20 to 100 mm; The diameter of the air inlet is 20-50mm; The diameter of the vent is 30-80mm; The width of the air distribution port is 20-100mm; The distance between the upper surface of the carbon fiber blank and the material plate in each layer is 20-80 mm; The height of the spacer is 20-80 mm.

4. The method for preparing ultra-long and ultra-thick plate-shaped carbon / carbon composite materials in large quantities and at low cost according to claim 3, characterized in that: The width of the gas separation port increases gradually from bottom to top; The height of the gasket increases gradually from bottom to top; The distance from the upper surface of the carbon fiber blank to the material plate in each layer increases gradually from bottom to top; The gap sizes between the carbon fiber blanks increase gradually from bottom to top.

5. The method for preparing ultra-long and ultra-thick plate-shaped carbon / carbon composite materials in large quantities and at low cost according to claim 4, characterized in that: The width of the air distribution opening in the first layer is 25-40 mm, and the width of the air distribution opening in the Nth layer is 2-20 mm greater than the width of the air distribution opening in the N-1th layer; The distance from the upper surface of the carbon fiber blank in the first layer to the material plate is 20-40 mm, and the distance from the upper surface of the carbon fiber blank in the Nth layer to the material plate is 2-20 mm longer than the distance from the upper surface of the carbon fiber blank in the N-1th layer to the material plate. The height of the gasket in the first layer is 20-40 mm, and the height of the gasket in the Nth layer is 2-20 mm higher than that of the gasket in the N-1th layer. The gaps between the carbon fiber blanks in the first layer are 20-40 mm, and the gaps between the carbon fiber blanks in the Nth layer are 2-20 mm larger than the gaps between the carbon fiber blanks in the N-1th layer.

6. The method for preparing ultra-long and ultra-thick plate-shaped carbon / carbon composite materials in large quantities and at low cost according to claim 1 or 2, characterized in that: During the chemical vapor deposition, the furnace temperature is controlled to be 950-1120° C. and the furnace pressure is controlled to be 2-10 kPa; The chemical vapor deposition is performed in 3-5 times, each chemical vapor deposition time is 60-160 hours, and the total chemical vapor deposition time is 300-500 hours; During the chemical vapor deposition, the flow rate of the carbon source gas is controlled to be 2-5 L / (kg.min).

7. The method for preparing ultra-long and ultra-thick plate-shaped carbon / carbon composite materials in large quantities and at low cost according to claim 6, characterized in that: During the first chemical vapor deposition, the flow rate of the carbon source gas is 3-5 L / (kg.min), and the flow rate of the carbon source gas during the next chemical vapor deposition is reduced by 10-20% compared with the flow rate of the carbon source gas during the previous chemical vapor deposition.

8. The method for preparing ultra-long and ultra-thick plate-shaped carbon / carbon composite materials in large quantities and at low cost according to claim 1 or 2, characterized in that: The second graphitization treatment is carried out under argon protection, the temperature of the second graphitization treatment is 2000-2500° C., and the time of the second graphitization treatment is 2-5 hours; The density of the carbon / carbon blank is 1.20-1.50 g / cm 3 .

9. The method for preparing ultra-long and ultra-thick plate-shaped carbon / carbon composite materials in large quantities and at low cost according to claim 1 or 2, characterized in that: The resin carbon densification process is: placing the carbon / carbon blank in a resin impregnating agent for sequential impregnation treatment, then sequentially performing carbonization treatment, and then performing high-temperature heat treatment to obtain the product; the temperature of the high-temperature heat treatment is 2000-2500°C, and the treatment time is 2-5h.

10. The method for preparing ultra-long and ultra-thick plate-shaped carbon / carbon composite materials in large quantities and at low cost according to claim 1 or 2, characterized in that: The density of the ultra-long and ultra-thick plate-shaped carbon / carbon composite material is 1.83-1.95 g / cm 3 .

Images