Carbon / carbon boat and method of making the same

Abstract

The application discloses a carbon / carbon boat and a preparation method thereof. The carbon / carbon boat comprises a boat body and two boat end covers located at the end of the boat body. The boat body is divided into a support layer A and a functional layer C from outside to inside in the thickness direction. The boat end cover is divided into a support layer B and a functional layer D from outside to inside in the thickness direction. The reinforcing bodies of the support layer A and the support layer B are stacked by carbon fiber no-woven cloth and carbon fiber net tire and are obtained by Z-direction continuous needling. The reinforcing bodies of the functional layer C and the functional layer D are stacked by carbon fiber net tire and are obtained by Z-direction continuous needling. The content of the carbon matrix in the support layer A is less than the content of the carbon matrix in the functional layer C. The content of the carbon matrix in the support layer B is less than the content of the carbon matrix in the functional layer D. The application can effectively reduce the adhesion between the boat and the carried material product, consume the boat, and cause the quality problem of the product due to the consumption of the boat into the product.

Description

Technical Field

[0001] This invention belongs to the field of powder metallurgy technology, specifically relating to a carbon / carbon boat and its preparation method. Background Technology

[0002] In the preparation process of tungsten carbide powder, carbon powder and tungsten powder are loaded into a boat in a certain ratio and sintered in a high-temperature reduction furnace. Because graphite has excellent properties such as high temperature resistance, thermal conductivity and chemical stability, the containers for holding mixed powder raw materials are usually made of graphite.

[0003] Currently, graphite boats are used as containers for preparing tungsten carbide powder. However, they suffer from short service life due to damage. The main mechanisms of damage during use are as follows: First, graphite is brittle. When external force is used to strike the graphite boat to remove tungsten carbide powder, the boat is easily broken and cannot be reused, especially when the wall thickness decreases after use. Second, during the sintering process of tungsten carbide powder preparation, tungsten powder can react with carbon in the graphite boat, consuming the boat and even causing it to stick together. This leads to the continuous consumption of the boat and the thinning of its wall thickness, rendering it unusable. Furthermore, sticking to the boat will adversely affect the performance of the finished product.

[0004] Patent CN 101169310A discloses a boat made of carbon / carbon composite material and its production process. Although it can improve the lifespan of the boat compared to graphite boats, the improvement is limited. In addition, the material is easy to adhere to the fiber bundles on the surface of the boat, which not only contaminates the material, but also causes the fiber bundles to fall off, which accelerates the consumption of the boat and is not conducive to extending the lifespan of the boat.

[0005] Therefore, there is an urgent need to provide a low-cost, high-performance vessel to reduce product production costs while ensuring that product quality is not affected. Summary of the Invention

[0006] To address the problems of short lifespan and high cost caused by cracking and breakage of graphite boats as sintering containers for powder metallurgy products, as well as the issues of adhesion and reaction consumption between the graphite boat and the product during sintering, which shorten the lifespan of the boat itself, and material adhesion leading to product quality problems, the first objective of this invention is to provide a carbon / carbon boat. The carbon / carbon boat provided by this invention has excellent mechanical properties (able to withstand external impacts); and the adhesion between the boat and the product is greatly improved, thereby significantly extending the service life of the boat.

[0007] The second objective of this invention is to provide a method for preparing a carbon / carbon boat dish, which is simple and controllable.

[0008] To achieve the above objectives, the present invention adopts the following technical solution:

[0009] This invention provides a carbon / carbon boat dish, which includes a boat dish body and two boat dish end caps located at the ends of the boat dish body. The boat dish body is divided into a support layer A and a functional layer C from the outside to the inside in the thickness direction, and the boat dish end caps are divided into a support layer B and a functional layer D from the outside to the inside in the thickness direction.

[0010] The reinforcements of both support layer A and support layer B are made by laminating carbon fiber nonwoven fabric and carbon fiber mesh, and continuously needle-punching in the Z direction. The reinforcements of both functional layer C and functional layer D are made by laminating carbon fiber mesh, and continuously needle-punching in the Z direction. The carbon matrix content in support layer A is less than the carbon matrix content in functional layer C, and the carbon matrix content in support layer B is less than the carbon matrix content in functional layer D.

[0011] In this invention, the carbon / carbon boat has an internal surface and an external surface. The surface that directly contacts the product during use is the internal surface, and the surface that does not directly contact it is the external surface. Therefore, the inner surface of the boat body reinforcement is the internal surface of the boat, and the outer surface is its external surface; the upper and lower surfaces of the end cap reinforcement can be the internal and external surfaces of the boat, respectively. The internal surface of the boat is the functional layer, and the external surface of the boat is the support layer.

[0012] The carbon / carbon boat provided by this invention consists of a support layer (including support layer A and support layer B) and a functional layer (including functional layer C and functional layer D). The fiber content and fiber weaving structure of the support layer and the functional layer are different: the carbon fiber content of the support layer is higher than that of the functional layer, and the fiber arrangement is more ordered than that of the functional layer; the densification pyrolytic carbon content of the functional layer is higher than that of the support layer, and the fiber arrangement is more disordered than that of the support layer. The support layer is located on the outer layer of the carbon / carbon boat, while the functional layer is located on the inner layer. The functional layer comes into contact with the material during application. In this invention, the support layer of the boat has a relatively high carbon fiber content and contains a non-woven fabric layer, which is beneficial to improving mechanical properties and can effectively prevent damage to the boat caused by external impact. The functional layer has a relatively low carbon fiber content (i.e., relatively high porosity) and a relatively high carbon matrix content. The low carbon fiber content helps to reduce the interfacial area between the carbon fiber and the carbon matrix, and improves the bonding force between the components of the boat. Therefore, it can effectively reduce the adhesion between the boat and the product it carries, thus reducing the consumption of the boat and the quality problems caused by the boat entering the product. In addition, the functional layer does not contain a non-woven fabric layer, which avoids the problem of accelerated consumption of the fabric caused by the overall shedding of fiber bundles in the non-woven fabric.

[0013] In a preferred embodiment, the main body of the vessel and the end cap are connected by mortise and tenon joints. In this invention, the main body and end cap are designed as separate units connected by mortise and tenon joints. If the lifespans of the main body and end cap are inconsistent, the damaged parts can be disassembled and replaced, reducing costs.

[0014] In a preferred embodiment, the overall density of the carbon / carbon boat dish is ≥1.45 g / cm³. 3 The density of the main body of the boat-shaped vessel is ≥1.48 g / cm³. 3 The density of the boat-shaped end cap is ≥1.40 g / cm³. 3 .

[0015] Further optimization involves ensuring that the density of the end cap is lower than that of the main body of the vessel. When the density of the end cap is lower than that of the main body, it is easier to maintain a consistent lifespan between the main body and the end cap.

[0016] In a preferred embodiment, the density of the reinforcement in the carbon / carbon boat dish is 0.30~0.40 g / cm³. 3 The density of both support layer A and support layer B is 0.41~0.55 g / cm³. 3 The densities of functional layers C and D are both 0.12~0.24 g / cm³. 3 .

[0017] In a preferred embodiment, the thickness of the functional layer C is 50-70% of the total thickness of the boat body, and the thickness of the functional layer D is 50-70% of the thickness of the boat end cap.

[0018] In a preferred embodiment, the density of the reinforcement in support layer A and support layer B gradually decreases from the outside to the inside. This creates a density gradient, with higher density on the outside and relatively lower density on the inside, effectively forming a gradual transition layer. This facilitates the bonding between the support layer and the functional layer, resulting in a product with superior thermal shock resistance under extreme high-temperature conditions. Furthermore, the porosity of the reinforcement in this design also exhibits a density gradient—lower porosity on the outside and higher porosity on the inside—which promotes gas permeation from the inside to the outside (in the thickness direction). This effectively avoids surface sealing caused by chemical vapor deposition, thereby improving the densification rate and reducing manufacturing costs.

[0019] In a further preferred embodiment, the weight ratio of the carbon fiber non-woven fabric layer to the carbon fiber mesh in the reinforcement of support layer A and support layer B is 50~70:30~50, and the proportion of carbon fiber non-woven fabric decreases from the outside to the inside, while the proportion of carbon fiber mesh layers increases. By reducing the frequency of non-woven fabric layups, the proportion of non-woven fabric in the reinforcement of support layer A and support layer B decreases from the outside to the inside, thus reducing the density gradient.

[0020] The inventors discovered that by using a gradient increase in the number of carbon fiber mesh layers, not only can the mechanical properties of key parts of the boat be ensured to be comparable to those of a boat without a density gradient, but the cost of the boat is also reduced due to the increased proportion of carbon fiber mesh. At the same time, the efficiency of chemical vapor deposition is improved, enabling low-cost and rapid preparation of carbon / carbon boats.

[0021] In a further preferred embodiment, the reinforcement of the support layer A and the support layer B can be divided into M gradient layers from the outside to the inside, where M≥2, preferably 2~5. Each gradient layer is formed by alternating layers of single-layer carbon fiber nonwoven fabric and mesh layer units, continuously needle-punched in the Z direction. Each mesh layer unit consists of n layers of carbon fiber mesh, where n≥1, preferably 1~5. The number of carbon fiber mesh layers in the mesh layer unit of the Mth gradient layer is 1 or more greater than the number of carbon fiber mesh layers in the mesh layer unit of the (M-1)th gradient layer. At the same time, the number of carbon fiber nonwoven fabric and mesh layer units in any gradient layer is ≥5.

[0022] The inventors discovered that the boat with the above-mentioned preferred layer design has better mechanical properties: it can withstand external impacts without damage.

[0023] In a preferred embodiment, both functional layers C and D have a carbon coating on their surfaces. In this invention, functional layers C and D have low fiber content and high carbon content. Furthermore, this preferred embodiment features a dense carbon coating, which further reduces adhesion between the vessel and the supported material, thus extending the product's lifespan.

[0024] This invention also provides a method for preparing a carbon / carbon boat dish.

[0025] Carbon fiber mesh is stacked at the outer diameter of the mold, and the functional layer C is obtained by continuous needle punching in the Z direction. Then, carbon fiber non-woven fabric and carbon fiber mesh are alternately wrapped and stacked on the surface of the functional layer C in different combinations, and the boat body is obtained by continuous needle punching in the Z direction.

[0026] Carbon fiber nonwoven fabric and carbon fiber mesh are alternately stacked in different combinations, and the reinforcement of support layer B is obtained by continuous needle punching in the Z direction. Then, carbon fiber mesh is stacked on the surface of the reinforcement of support layer B and continuously needle punched in the Z direction to obtain the reinforcement of the boat end cap.

[0027] or,

[0028] Carbon fiber mesh is stacked and continuously needled in the Z direction to obtain the reinforcement of functional layer D. Then, carbon fiber non-woven fabric and carbon fiber mesh are stacked alternately in different combinations on the surface of functional layer D and continuously needled in the Z direction to obtain the reinforcement of the boat end cap.

[0029] Then, the reinforcement of the boat body and the reinforcement of the boat end cap are subjected to chemical vapor deposition on a carbon matrix. After machining, the boat body and the boat end cap are obtained respectively. The boat body and the two boat end caps are assembled to obtain a carbon / carbon boat.

[0030] In this invention, since the main body of the boat is cylindrical or cuboid, and the end cap of the boat is plate-shaped, a mold is required in the preparation process of the main body of the boat, preferably a wooden mold, while the end cap of the boat does not require a mold.

[0031] In a preferred embodiment, carbon fiber nonwoven fabric and carbon fiber mesh are alternately wound and layered on the surface of functional layer C in M ​​different combinations, and the reinforcement of the boat body is obtained by continuous needle punching in the Z direction layer by layer; M≥2, preferably 2~5, and in any combination, it is made by alternating layers of single-layer carbon fiber nonwoven fabric and mesh layer units, and continuous needle punching in the Z direction layer by layer; the mesh layer unit is composed of n layers of carbon fiber mesh, n≥1, preferably 1~5, and it is controlled that in the Mth combination process, the number of carbon fiber mesh layers in the mesh layer unit is 1 or more less than the number of carbon fiber mesh layers in the mesh layer unit in the M-1th combination process, and at the same time, in any combination, the number of carbon fiber nonwoven fabric and mesh layer units is ≥5.

[0032] In the preparation of the reinforcement of the boat body, since a mold is required to control the shape of the boat body, the functional layer C needs to be prepared first. Then, according to the design of the support layer A, carbon fiber non-woven fabric and carbon fiber mesh are laid from the inside to the outside in M ​​combinations. Therefore, in the first combination, the Mth gradient layer of the support layer A is laid, that is, the carbon fiber mesh content is the highest.

[0033] In a preferred embodiment, carbon fiber nonwoven fabric and carbon fiber mesh are alternately layered in M ​​different combinations, and the reinforcing body of the support layer B is obtained by continuous needle punching in the Z direction layer by layer. M ≥ 2, preferably 2 to 5. In any combination, it is made by alternating layers of single-layer carbon fiber nonwoven fabric and mesh layer units, and continuous needle punching in the Z direction layer by layer. The mesh layer unit consists of n layers of carbon fiber mesh, n ≥ 1, preferably 1 to 5. In the Mth combination process, the number of carbon fiber mesh layers in the mesh layer unit is controlled to be 1 or more greater than the number of carbon fiber mesh layers in the (M-1)th combination process. At the same time, in any combination, the number of carbon fiber nonwoven fabric and mesh layer units is ≥ 5.

[0034] Since the end cap of the boat is plate-shaped, either the support layer B or the functional layer D can be prepared first. When the support layer B is prepared first, the first gradient layer is laid according to the design of the reinforcement of the support layer B, that is, the carbon fiber mesh content is the lowest. When the functional layer D is prepared first, the reinforcement of the support layer B is obtained from the inside out. The carbon fiber non-woven fabric and carbon fiber mesh are laid according to M combinations. Therefore, in the first combination, the Mth gradient layer of the support layer A is laid according to the design, that is, the carbon fiber mesh content is the highest.

[0035] In a preferred embodiment, carbon fiber nonwoven fabric and carbon fiber mesh are alternately layered on the surface of functional layer D in different combinations, and the reinforcement of the boat end cap is obtained by continuous needle punching in the Z direction. M≥2, preferably 2~5. In any combination, it is made by alternating layers of single-layer carbon fiber nonwoven fabric and mesh layer units, and continuous needle punching in the Z direction. The mesh layer unit is composed of n layers of carbon fiber mesh, n≥1, preferably 1~5. In the Mth combination process, the number of carbon fiber mesh layers in the mesh layer unit is controlled to be 1 or more less than the number of carbon fiber mesh layers in the (M-1)th combination process. At the same time, in any combination, the number of carbon fiber nonwoven fabric and mesh layer units is ≥5.

[0036] In a preferred embodiment, the angle between the non-woven fabric layers in the reinforcement of support layer A and support layer B is 0° / 90°.

[0037] In a preferred embodiment, the interlayer density of the reinforcements in support layer A and support layer B is 10-20 layers / cm, and the Z-axis continuous needle-punching density is 20-30 needles / cm. 2 .

[0038] In a preferred embodiment, the interlayer density of the reinforcing bodies of functional layer C and functional layer D is 10-20 layers / cm, and the Z-axis continuous needle-punching density is 30-40 needles / cm. 2 .

[0039] In a preferred embodiment, the chemical vapor deposition uses natural gas and / or propylene as the carbon source gas, nitrogen as the carrier gas, a carbon source gas flow rate of 0.20~0.60 SL / Min, a carrier gas flow rate of 0.10~0.30 SL / Min, a deposition temperature of 950~1250℃, a deposition pressure of 0.8~10.0 kPa, and a deposition time of 210~280 h.

[0040] In the chemical vapor deposition process of this invention, the flow rate of the gas introduced is based on the natural volume of the billet to be densified, and the flow rate is the amount of gas introduced per cubic decimeter of the billet to be densified.

[0041] In a further preferred embodiment, the chemical vapor deposition is divided into three stages. In the first stage, the carbon source gas is natural gas, the carrier gas is nitrogen, the flow rate of natural gas is 0.40~0.60 SL / Min, the flow rate of nitrogen is 0.20~0.30 SL / Min, the deposition temperature is 1150~1250℃, the deposition pressure is 3.0~10.0 Kpa, and the deposition time is 100~130 h.

[0042] In the second stage, the carbon source gas is natural gas, the carrier gas is nitrogen, the flow rate of natural gas is 0.30~0.50SL / Min, the flow rate of nitrogen is 0.15~0.25SL / Min, the deposition temperature is 1050~1149℃, the deposition pressure is 3.0~10Kpa, and the deposition time is 80~100h.

[0043] In the third stage, the carbon source gas is propylene, the carrier gas is nitrogen, the flow rate of propylene is 0.3~0.5 SL / Min, the flow rate of nitrogen is 0.10~0.18 SL / Min, the deposition temperature is 950~1149℃, the deposition pressure is 0.8~1.6Kpa, and the deposition time is 30~50h.

[0044] According to its purpose, the chemical vapor deposition of this invention can be divided into densification deposition and coating deposition. The first and second stages of chemical vapor deposition are densification deposition, and the third stage of chemical vapor deposition is coating deposition.

[0045] The first stage of chemical vapor deposition uses a high flow rate and temperature, which is conducive to the rapid densification of carbon fiber preforms: because the preforms have a low density, high porosity, and a relatively high proportion of macropores.

[0046] The inventors discovered that, compared to the first-stage chemical vapor deposition, the second-stage chemical vapor deposition reduces the carbon source gas flow rate and lowers the deposition temperature. The synergistic effect of these two factors facilitates the penetration and deposition of carbon source gas into the core, effectively improving the utilization rate of carbon source gas while ensuring a high deposition densification rate.

[0047] In the first and second chemical vapor deposition stages (densification deposition), natural gas is used as the carbon source gas. Natural gas molecules are small and, combined with the deposition temperature, easily diffuse into the core of the preform. At the same time, combined with the preform design, the reinforcing functional layer is a mesh layer. The mesh layer has high porosity, which itself is conducive to gas permeation. The combined effect of the two is conducive to improving the deposition densification efficiency and avoids the problem of low densification efficiency and subsequent inability to densify due to premature surface sealing.

[0048] The third chemical vapor deposition stage (coating deposition) uses propylene as the carbon source gas. Propylene gas has the characteristics of high carbon content and easy decomposition into pyrolytic carbon at high temperature. Combined with the temperature and pressure requirements of this stage, a dense sealing layer of pyrolytic carbon is formed on the surface of the carbon / carbon boat. The sealing layer of pyrolytic carbon effectively fills the pores on the surface of the boat, preventing the product contained in the boat from entering the boat through the pores during use, which would lead to increased material loss.

[0049] In this invention, machining is performed after the first stage of chemical vapor deposition is completed.

[0050] The machining between the chemical vapor deposition stages is called machining 1 between the first and second stages, and machining 2 between the second and third stages.

[0051] The machining 1 mentioned above is the machining of the surface of the porous body of the reinforcement.

[0052] The aforementioned machining 2 is to process the densified reinforcement into the final product size.

[0053] After machining 2, the reinforcing body undergoes a third-stage chemical vapor deposition process. The boat body and end caps are then assembled using mortise and tenon joints to obtain the carbon / carbon boat of the present invention.

[0054] Beneficial effects

[0055] The carbon / carbon boat provided by this invention consists of a support layer (including support layer A and support layer B) and a functional layer (including functional layer C and functional layer D). The fiber content and fiber weaving structure of the support layer and the functional layer are different: the carbon fiber content of the support layer is higher than that of the functional layer, and the fiber arrangement is more ordered than that of the functional layer; the densification pyrolytic carbon content of the functional layer is higher than that of the support layer, and the fiber arrangement is more disordered than that of the support layer. The support layer is located on the outer layer of the carbon / carbon boat, while the functional layer is located on the inner layer of the carbon / carbon boat and comes into contact with the material during application. In this invention, the support layer has a relatively high carbon fiber content and contains a non-woven fabric layer, which is beneficial to improving mechanical properties and can effectively prevent damage to the boat caused by external impact. The functional layer has a relatively low carbon fiber content (i.e., relatively high porosity) and a relatively high carbon matrix content. The low carbon fiber content helps to reduce the interfacial area between the carbon fiber and the carbon matrix, and improves the bonding force between the components of the boat. Therefore, it can effectively reduce the adhesion between the boat and the product it carries, thus reducing the consumption of the boat and the quality problems caused by the boat entering the product. In addition, the functional layer does not contain a non-woven fabric layer, which avoids the problem of accelerated consumption of the fabric caused by the overall shedding of fiber bundles in the non-woven fabric. Attached Figure Description

[0056] Figure 1 This is a schematic diagram of the carbon / carbon boat before assembly;

[0057] Figure 2 This is a schematic diagram of the carbon / carbon boat after assembly. Detailed Implementation

[0058] The present invention will be further illustrated below with reference to examples.

[0059] Example 1

[0060] Step 1: Preparation of the main body of the boat and the end cap reinforcement

[0061] The carbon / carbon boat reinforcement includes a boat body and two boat end caps located at the ends of the boat body.

[0062] Preparation of the boat-shaped vessel body reinforcement: On a wooden cylindrical tool with an outer diameter equal to the inner diameter of the boat-shaped vessel body, first, wrap the mesh layer layer by layer until it meets the thickness requirements of the drawing, and then needle-punch in the Z direction (needling density is 35 needles / cm). 2 That is, a density of 0.18 g / cm³ is obtained. 3 Functional layer C is formed, and then a layer of carbon fiber nonwoven fabric and a mesh layer unit are alternately stacked. Continuous needle punching is performed in the Z-direction. The Z-direction needle punching is based on the winding of each layer of nonwoven fabric or each layer of carbon fiber mesh layer, and one needle punch is performed after each layer is wound. The needle punching density is 25 needles / cm. 2 The interlayer density was controlled at 15 layers / cm. First, the mesh layer unit between adjacent non-woven fabric units consisted of 3 mesh layers, and this cycle was repeated 7 times (this step involves winding 28 layers: 7 layers of non-woven fabric + 21 layers of mesh). Then, the mesh layer unit between adjacent non-woven fabric units consisted of 2 mesh layers, and this cycle was repeated 6 times (this step involves winding 18 layers: 6 layers of non-woven fabric + 12 layers of mesh). Finally, the mesh layer unit between adjacent non-woven fabric units consisted of 1 mesh layer, i.e., one layer of non-woven fabric was wound, followed by one layer of carbon fiber mesh. This cycle was repeated a total of 8 times (this step involves winding 16 layers: 8 layers of non-woven fabric + 8 layers of mesh). The resulting carbon fiber non-woven fabric to carbon fiber mesh weight ratio was (60:40), and the density was 0.47 g / cm³. 3 Support layer A; after demolding, a density of 0.35 g / cm³ is obtained. 3 The main body of the boat-shaped vessel is reinforced.

[0063] Preparation of end cap reinforcement: Unlike the preparation of boat-shaped reinforcement, the preparation of end cap reinforcement does not require a mold. It can be directly laid on a flat plate, and the other preparation processes are the same.

[0064] Step 2: Densification and Preparation of Carbon / Carbon Boat

[0065] The prepared boat-shaped reinforcement and end cap reinforcement were placed in a chemical vapor deposition (CVD) furnace for CVD densification. Tooling was used to ensure that the surfaces of both reinforcements were in contact with the carbon source gas phase. The specific CVD process is as follows:

[0066] In the first stage, natural gas was used as the carbon source gas and nitrogen as the carrier gas. Based on the natural volume of the reinforced body billet, the natural gas flow rate was 0.50 SL / Min and the nitrogen flow rate was 0.25 SL / Min per cubic decimeter of billet. The deposition temperature was 1200℃, the deposition process pressure was controlled at about 5.5 kPa, and the deposition time was 110 h.

[0067] In the second stage, natural gas was used as the carbon source gas and nitrogen as the carrier gas. Based on the natural volume of the reinforced billet, the natural gas flow rate was 0.40 SL / Min and the nitrogen flow rate was 0.20 SL / Min per cubic decimeter of billet. The deposition temperature was 1100℃, the deposition process pressure was controlled at about 4.0 kPa, and the deposition time was 90 h.

[0068] In the third stage, propylene was used as the carbon source gas and nitrogen as the carrier gas. Based on the natural volume of the reinforced body billet, the propylene flow rate was 0.40 SL / Min and the nitrogen flow rate was 0.15 SL / Min per cubic decimeter of billet. The deposition temperature was 990℃, the deposition process pressure was controlled at about 1.2 kPa, and the deposition time was 40 h.

[0069] Machining is performed between chemical vapor deposition stages. The machining between the first and second stages of chemical vapor deposition is called machining 1, and the machining between the second and third stages of chemical vapor deposition is called machining 2. Machining 1 is the surface machining of the reinforced porous body to make the next deposition more efficient, and machining 2 is the final dimensional machining.

[0070] The carbon / carbon boat of this invention is obtained by assembling the boat body and end caps obtained after the third stage of chemical vapor deposition through mortise and tenon joints. The performance and lifespan data of the boat are shown in Table 1.

[0071] Example 2

[0072] Step 1: Preparation of the main body of the boat and the end cap reinforcement

[0073] The carbon / carbon boat reinforcement includes a boat body and two boat end caps located at the ends of the boat body.

[0074] Preparation of the boat-shaped vessel body reinforcement: On a wooden cylindrical tool with an outer diameter equal to the inner diameter of the boat-shaped vessel body, wrap the mesh layer by layer until it meets the thickness requirements of the drawing, and then needle-punch in the Z direction (needling density is 30 needles / cm). 2 This yields a density of 0.14 g / cm³. 3Functional layer C is formed, and then a layer of carbon fiber nonwoven fabric and a mesh layer unit are alternately stacked. Continuous needle punching is performed in the Z-direction. The Z-direction needle punching is based on the winding of each layer of nonwoven fabric or each layer of carbon fiber mesh layer, and one needle punch is performed after each layer is wound. The needle punching density is 20 needles / cm. 2 The interlayer density is controlled at 10 layers / cm. First, the mesh layer unit of adjacent non-woven fabric unit layers is controlled to consist of 5 mesh layers, and this cycle is repeated twice (this step involves winding 12 layers: 2 layers of non-woven fabric + 10 layers of mesh). Then, the mesh layer unit of adjacent non-woven fabric unit layers is controlled to consist of 4 mesh layers, and this cycle is repeated twice (this step involves winding 10 layers: 2 layers of non-woven fabric + 8 layers of mesh). Finally, the mesh layer unit of adjacent non-woven fabric unit layers is controlled to consist of 3 mesh layers, and this cycle is repeated twice (this step involves winding 8 layers: 2 layers of non-woven fabric). The process involves winding 6 layers of non-woven fabric and 6 layers of mesh, then controlling the mesh layer unit between adjacent non-woven fabric units to consist of 2 layers of mesh, repeating this cycle twice (this step involves winding 6 layers, 2 layers of non-woven fabric + 4 layers of mesh). Finally, the mesh layer unit between adjacent non-woven fabric units is controlled to consist of 1 layer of mesh, i.e., winding one layer of non-woven fabric and then winding one layer of carbon fiber mesh; this cycle is repeated a total of 5 times (this step involves winding a total of 10 layers, 5 layers of non-woven fabric + 5 layers of mesh), resulting in a carbon fiber non-woven fabric to carbon fiber mesh weight ratio of (55:45) and a density of 0.41 g / cm³. 3 The support layer A, after demolding, yields a density of 0.30 g / cm³. 3 The main body of the boat-shaped vessel is reinforced.

[0075] Preparation of end cap reinforcement: Unlike the preparation of boat-shaped reinforcement, the preparation of end cap reinforcement does not require a mold. It can be directly laid on a flat plate, and the other preparation processes are the same.

[0076] Step 2: Densification and Preparation of Carbon / Carbon Boat

[0077] The prepared boat-shaped reinforcement and end cap reinforcement were placed in a chemical vapor deposition (CVD) furnace for CVD densification. Tooling was used to ensure that the surfaces of both reinforcements were in contact with the carbon source gas phase. The specific CVD process is as follows:

[0078] In the first stage, natural gas was used as the carbon source gas and nitrogen as the carrier gas. Based on the natural volume of the reinforced body billet, the natural gas flow rate was 0.40 SL / Min and the nitrogen flow rate was 0.20 SL / Min per cubic decimeter of billet. The deposition temperature was 1100℃, the deposition process pressure was controlled at about 5.0 kPa, and the deposition time was 120 h.

[0079] In the second stage, natural gas was used as the carbon source gas and nitrogen as the carrier gas. Based on the natural volume of the reinforced body billet, the natural gas flow rate was 0.40 SL / Min and the nitrogen flow rate was 0.20 SL / Min per cubic decimeter of billet. The deposition temperature was 1100℃, the deposition process pressure was controlled at about 5.0 kPa, and the deposition time was 90 h.

[0080] In the third stage, natural gas was used as the carbon source gas and nitrogen as the carrier gas. Based on the natural volume of the reinforced body billet, the natural gas flow rate was 0.40 SL / Min and the nitrogen flow rate was 0.20 SL / Min per cubic decimeter of billet. The deposition temperature was 1100℃, the deposition process pressure was controlled at about 5.0 kPa, and the deposition time was 40 h.

[0081] Machining is performed between chemical vapor deposition stages. The machining between the first and second stages of chemical vapor deposition is called machining 1, and the machining between the second and third stages of chemical vapor deposition is called machining 2. Machining 1 is the surface machining of the reinforced porous body to make the next deposition more efficient, and machining 2 is the final dimensional machining.

[0082] The carbon / carbon boat of this invention is obtained by assembling the boat body and end caps obtained after the third stage of chemical vapor deposition through mortise and tenon joints. The performance and lifespan data of the boat are shown in Table 1.

[0083] Example 3

[0084] Step 1: Preparation of the main body of the boat and the end cap reinforcement

[0085] The carbon / carbon boat reinforcement includes a boat body and two boat end caps located at the ends of the boat body.

[0086] Preparation of the boat-shaped vessel body reinforcement: On a wooden cylindrical tool with an outer diameter equal to the inner diameter of the boat-shaped vessel body, first, wrap the mesh layer layer by layer until it meets the thickness requirements of the drawing, and then needle-punch in the Z direction (needling density is 40 needles / cm). 2 This yields a density of 0.22 g / cm³. 3 Functional layer C is formed, and then a layer of carbon fiber nonwoven fabric and a mesh layer unit are alternately stacked. Continuous needle punching is performed in the Z-direction. The Z-direction needle punching is based on the winding of each layer of nonwoven fabric or each layer of carbon fiber mesh layer, and needle punching is performed once after each layer is wound. The needle punching density is controlled to be 30 needles / cm. 2The interlayer density was controlled at 20 layers / cm. First, the mesh layer between adjacent non-woven units was controlled to consist of 2 mesh layers, and this cycle was repeated 20 times (this step involves winding 60 layers: 20 layers of non-woven fabric + 40 layers of mesh). Then, the mesh layer between adjacent non-woven units was controlled to consist of 1 mesh layer, i.e., one layer of non-woven fabric was wound, followed by one layer of carbon fiber mesh; this cycle was repeated 20 times (this step involves winding a total of 40 layers: 20 layers of non-woven fabric + 20 layers of mesh), resulting in a carbon fiber non-woven fabric to carbon fiber mesh weight ratio of (65:35) and a density of 0.50 g / cm³. 3 The support layer A, after demolding, yields a density of 0.38 g / cm³. 3 The main body of the boat-shaped vessel is reinforced.

[0087] Preparation of end cap reinforcement: Unlike the preparation of boat-shaped reinforcement, the preparation of end cap reinforcement does not require a mold. It can be directly laid on a flat plate, and the other preparation processes are the same.

[0088] Step 2: Densification and Preparation of Carbon / Carbon Boat

[0089] The prepared boat-shaped reinforcement and end cap reinforcement were placed in a chemical vapor deposition (CVD) furnace for CVD densification. Tooling was used to ensure that the surfaces of both reinforcements were in contact with the carbon source gas phase. The specific CVD process is as follows:

[0090] In the first stage, natural gas was used as the carbon source gas and nitrogen as the carrier gas. Based on the natural volume of the reinforced body billet, the natural gas flow rate was 0.40 SL / Min and the nitrogen flow rate was 0.20 SL / Min per cubic decimeter of billet. The deposition temperature was 1250℃, the deposition process pressure was controlled at about 3.2 kPa, and the deposition time was 130 h.

[0091] In the second stage, natural gas was used as the carbon source gas and nitrogen as the carrier gas. Based on the natural volume of the reinforced body billet, the natural gas flow rate was 0.30 SL / Min and the nitrogen flow rate was 0.15 SL / Min per cubic decimeter of billet. The deposition temperature was 1149℃, the deposition process pressure was controlled at about 3.5 kPa, and the deposition time was 100 h.

[0092] In the third stage, propylene was used as the carbon source gas and nitrogen as the carrier gas. Based on the natural volume of the reinforced billet, the propylene flow rate was 0.30 SL / Min and the nitrogen flow rate was 0.10 SL / Min per cubic decimeter of billet. The deposition temperature was 1049℃, the deposition process pressure was controlled at about 0.9 kPa, and the deposition time was 50 h.

[0093] Machining is performed between chemical vapor deposition stages. The machining between the first and second stages of chemical vapor deposition is called machining 1, and the machining between the second and third stages of chemical vapor deposition is called machining 2. Machining 1 is the surface machining of the reinforced porous body to make the next deposition more efficient, and machining 2 is the final dimensional machining.

[0094] The carbon / carbon boat of this invention is obtained by assembling the boat body and end caps obtained after the third stage of chemical vapor deposition through mortise and tenon joints. The performance and lifespan data of the boat are shown in Table 1.

[0095] Example 4

[0096] Step 1: Preparation of the main body of the boat and the end cap reinforcement

[0097] The carbon / carbon boat reinforcement includes a boat body and two boat end caps located at the ends of the boat body.

[0098] Preparation of the boat-shaped vessel body reinforcement: On a wooden cylindrical tool with an outer diameter equal to the inner diameter of the boat-shaped vessel body, first, wrap the mesh layer layer by layer until it meets the thickness requirements of the drawing, and then needle-punch in the Z direction (needling density is 35 needles / cm). 2 That is, a density of 0.18 g / cm³ is obtained. 3 Functional layer C is formed, and then a layer of carbon fiber nonwoven fabric and a mesh layer unit are alternately stacked. Continuous needle punching is performed in the Z-direction. The Z-direction needle punching is based on the winding of each layer of nonwoven fabric or each layer of carbon fiber mesh layer, and one needle punch is performed after each layer is wound. The needle punching density is 25 needles / cm. 2 The interlayer density was controlled at 15 layers / cm; this cycle was repeated 60 times (this step involves winding 120 layers in total, 60 layers without fiber cloth and 60 layers of mesh) to obtain a reinforcement that meets the requirements of the drawings, with a density of 0.55 g / cm³. 3 Support layer A. After demolding, a density of 0.40 g / cm³ is obtained. 3 The main body of the boat-shaped vessel is reinforced.

[0099] Step 2: Densification and Preparation of Carbon / Carbon Boat

[0100] The prepared boat-shaped reinforcement and end cap reinforcement were placed in a chemical vapor deposition furnace for chemical vapor deposition densification. Tooling was used to ensure that the surfaces of both reinforcements were in contact with the carbon source gas phase. The chemical vapor deposition process and machining requirements were the same as in Example 1.

[0101] The carbon / carbon boat of this invention is obtained by assembling the boat body and end caps obtained after the third stage of chemical vapor deposition through mortise and tenon joints. The performance and lifespan data of the boat are shown in Table 1.

[0102] Example 5

[0103] Step 1: Preparation of the main body of the boat and the end cap reinforcement

[0104] Step one (preparation of the reinforcing agent) in this embodiment is the same as in Example 1.

[0105] Step 2: Densification and Preparation of Carbon / Carbon Boat

[0106] The prepared boat-shaped reinforcement and end cap reinforcement were placed in a chemical vapor deposition (CVD) furnace for CVD densification. Tooling was used to ensure that the surfaces of both reinforcements were in contact with the carbon source gas phase. The specific CVD process is as follows:

[0107] In the first stage, natural gas was used as the carbon source gas and nitrogen as the carrier gas. Based on the natural volume of the reinforced body billet, the natural gas flow rate was 0.50 SL / Min and the nitrogen flow rate was 0.25 SL / Min per cubic decimeter of billet. The deposition temperature was 1200℃, the deposition process pressure was controlled at about 5.5 kPa, and the deposition time was 110 h.

[0108] In the second stage, natural gas was used as the carbon source gas and nitrogen as the carrier gas. Based on the natural volume of the reinforced billet, the natural gas flow rate was 0.40 SL / Min and the nitrogen flow rate was 0.20 SL / Min per cubic decimeter of billet. The deposition temperature was 1100℃, the deposition process pressure was controlled at about 4.0 kPa, and the deposition time was 90 h.

[0109] In the third stage, propylene was used as the carbon source gas and nitrogen as the carrier gas. Based on the natural volume of the reinforced body billet, the propylene flow rate was 0.40 SL / Min and the nitrogen flow rate was 0.15 SL / Min per cubic decimeter of billet. The deposition temperature was 990℃, the deposition process pressure was controlled at about 1.2 kPa, and the deposition time was 40 h.

[0110] Machining is performed between chemical vapor deposition stages. The machining between the first and second stages of chemical vapor deposition is called machining 1, and the machining between the second and third stages of chemical vapor deposition is called machining 2. Machining 1 is the surface machining of the reinforced porous body to make the next deposition more efficient, and machining 2 is the final dimensional machining.

[0111] The carbon / carbon boat of this invention is obtained by assembling the boat body and end caps obtained after the third stage of chemical vapor deposition through mortise and tenon joints. The performance and lifespan data of the boat are shown in Table 1.

[0112] Comparative Example 1

[0113] All other conditions were the same as in Example 1, except that the main body and end cap reinforcement of the boat did not have functional layers, but only support layers. The performance and lifespan data of the carbon / carbon boat are shown in Table 1.

[0114] Comparative Example 2

[0115] All other conditions are the same as in Example 1, except that the weight ratio of carbon fiber nonwoven fabric to carbon fiber mesh in the support layer of the boat body reinforcement is 45:65, and the density of support layers A and B is 0.38 g / cm³. 3 This is not within the scope of the present invention. The obtained performance and lifespan data for the carbon / carbon boat are shown in Table 1.

[0116] Comparative Example 3

[0117] Other conditions are the same as in Example 1, except that the number of alternating layers of non-woven fabric units and mesh layer units (1 layer each) should be 8. The obtained carbon / carbon boat performance and lifetime data are shown in Table 1.

[0118] Comparative Example 4

[0119] Other conditions were the same as in Example 1, except that propylene was used as the carbon source gas, and all three stages were carried out according to the chemical vapor deposition third stage process parameters (temperature, pressure, flow rate) in Example 1. The deposition time for each stage was the same as in Example 1. The performance and lifetime data of the obtained carbon / carbon boat are shown in Table 1.

[0120] Comparative Example 5

[0121] Other conditions were the same as in Example 1, except that the third stage of chemical vapor deposition used the deposition process parameters (temperature, pressure, flow rate) of the second stage in Example 1, but the deposition time remained at 40 hours. The obtained carbon / carbon boat performance and lifetime data are shown in Table 1.

[0122] The density, flexural strength, and service life of the carbon / carbon boat obtained from the above embodiments and comparative examples are shown in Table 1 below:

[0123] Note: The lifespan evaluation method for carbon / carbon boats is the total amount of sintered material in the boat before damage. Performance data for graphite boats are also presented in Table 1.

[0124] Table 1. Performance and lifespan data of carbon / carbon boats

[0125]

[0126] The above description is merely a preferred embodiment of the present invention and does not constitute any limitation on the invention. Any modifications, alterations, or equivalent structural transformations made to the above embodiments based on the technical essence of the present invention shall still fall within the protection scope of the present invention.

Claims

1. A carbon / carbon boat dish, characterized in that: The carbon / carbon boat / vessel includes a boat / vessel body and two boat / vessel end caps located at the ends of the boat / vessel body. The boat / vessel body is divided into a support layer A and a functional layer C in the thickness direction from the outside to the inside. The boat / vessel end caps are divided into a support layer B and a functional layer D in the thickness direction from the outside to the inside. The reinforcement of the support layer A and the support layer B are both made of carbon fiber nonwoven fabric and carbon fiber mesh laminated and continuously needle-punched in the Z direction. The reinforcement of the functional layer C and the functional layer D are both made of carbon fiber mesh laminated and continuously needle-punched in the Z direction. The carbon matrix content in the support layer A is less than the carbon matrix content in the functional layer C, and the carbon matrix content in the support layer B is less than the carbon matrix content in the functional layer D.

2. The carbon / carbon boat according to claim 1, characterized in that: The main body of the vessel and the end cap of the vessel are connected by mortise and tenon joints; The density of the carbon / carbon boat dish as a whole is ≥1.45 g / cm³. 3 The density of the main body of the boat-shaped vessel is ≥1.48 g / cm³. 3 The density of the boat-shaped end cap is ≥1.40 g / cm³. 3 ; The density of the reinforcement in the carbon / carbon boat dish is 0.30~0.40 g / cm³. 3 The density of both support layer A and support layer B is 0.41~0.55 g / cm³. 3 The densities of functional layers C and D are both 0.12~0.24 g / cm³. 3 ; The thickness of functional layer C is 50-70% of the total thickness of the boat body, and the thickness of functional layer D is 50-70% of the thickness of the boat end cap. The density of the reinforcement in support layer A and support layer B gradually decreases from the outside to the inside.

3. A carbon / carbon boat according to claim 1 or 2, characterized in that: In the reinforcements of support layer A and support layer B, the weight ratio of carbon fiber non-woven fabric to carbon fiber mesh is 50~70:30~50, and from the outside to the inside, the proportion of carbon fiber non-woven fabric layers decreases and the proportion of carbon fiber mesh layers increases.

4. The carbon / carbon boat according to claim 3, characterized in that: The reinforcement of support layer A and support layer B is divided into M gradient layers from the outside to the inside, where M≥2. Each gradient layer is made by alternating layers of single-layer carbon fiber nonwoven fabric and mesh layer units, continuously needle-punched in the Z direction. Each mesh layer unit consists of n layers of carbon fiber mesh, where n≥1. The number of carbon fiber mesh layers in the mesh layer unit of the Mth gradient layer is at least one more than the number of carbon fiber mesh layers in the mesh layer unit of the (M-1)th gradient layer. At the same time, the number of carbon fiber nonwoven fabric and mesh layer units in each gradient layer is ≥5.

5. A carbon / carbon boat according to claim 1 or 2, characterized in that: Both functional layer C and functional layer D have a carbon coating on their surfaces.

6. A method for preparing a carbon / carbon boat according to any one of claims 1-5, characterized in that: Carbon fiber mesh is stacked at the outer diameter of the mold, and the functional layer C is obtained by continuous needle punching in the Z direction. Then, carbon fiber non-woven fabric and carbon fiber mesh are alternately wrapped and stacked on the surface of the functional layer C in different combinations, and the boat body is obtained by continuous needle punching in the Z direction. Carbon fiber nonwoven fabric and carbon fiber mesh are alternately stacked in different combinations, and the reinforcement of support layer B is obtained by continuous needle punching in the Z direction. Then, carbon fiber mesh is stacked on the surface of the reinforcement of support layer B and continuously needle punched in the Z direction to obtain the reinforcement of the boat end cap. or Carbon fiber mesh is stacked and continuously needled in the Z direction to obtain the reinforcement of functional layer D. Then, carbon fiber non-woven fabric and carbon fiber mesh are stacked alternately in different combinations on the surface of functional layer D and continuously needled in the Z direction to obtain the reinforcement of the boat end cap. Then, the reinforcement of the boat body and the reinforcement of the boat end cap are subjected to chemical vapor deposition on a carbon matrix. After machining, the boat body and the end cap are obtained respectively. The boat body and the two boat end caps are assembled to obtain a carbon / carbon boat.

7. The method for preparing a carbon / carbon boat according to claim 6, characterized in that: On the surface of functional layer C, carbon fiber nonwoven fabric and carbon fiber mesh are alternately wound and stacked in M ​​different combinations, and the reinforcement of the boat body is obtained by continuous needle punching in the Z direction layer by layer; wherein M≥2, in any combination, it is made by alternating stacking of single-layer carbon fiber nonwoven fabric and mesh layer units, and continuous needle punching in the Z direction layer by layer; the mesh layer unit is composed of n layers of carbon fiber mesh, n≥1, and it is controlled that in the Mth combination process, the number of carbon fiber mesh layers in the mesh layer unit is at least 1 less than the number of carbon fiber mesh layers in the (M-1)th combination process, and at the same time, in any combination, the number of carbon fiber nonwoven fabric and mesh layer units is ≥5. Carbon fiber nonwoven fabric and carbon fiber mesh are alternately layered in M ​​different combinations, and the reinforcement of the support layer B is obtained by continuous needle punching in the Z direction, where M≥2. In any combination, it is made by alternating layers of single-layer carbon fiber nonwoven fabric and mesh layer units, and continuous needle punching in the Z direction. The mesh layer unit consists of n layers of carbon fiber mesh, n≥1, and it is controlled that in the Mth combination process, the number of carbon fiber mesh layers in the mesh layer unit is at least 1 greater than the number of carbon fiber mesh layers in the (M-1)th combination process. At the same time, in any combination, the number of carbon fiber nonwoven fabric and mesh layer units is ≥5. Carbon fiber nonwoven fabric and carbon fiber mesh are alternately stacked on the surface of functional layer D in different combinations, and the reinforcement of the boat end cap is obtained by continuous needle punching in the Z direction. M≥2. In any combination, it is made by alternating stacking of single-layer carbon fiber nonwoven fabric and mesh layer units, and continuous needle punching in the Z direction. The mesh layer unit is composed of n layers of carbon fiber mesh, n≥1, and it is controlled that in the Mth combination process, the number of carbon fiber mesh layers in the mesh layer unit is at least 1 less than the number of carbon fiber mesh layers in the (M-1)th combination process. At the same time, in any combination, the number of carbon fiber nonwoven fabric and mesh layer units is ≥5.

8. A method for preparing a carbon / carbon boat according to claim 6 or 7, characterized in that: In the reinforcement of support layer A and support layer B, the angle between the non-woven fabric layers is 0° / 90°. In the reinforcement of support layer A and support layer B, the interlayer density is 10-20 layers / cm, and the Z-axis continuous needle-punching density is 20-30 needles / cm. 2 ; The reinforcements of functional layer C and functional layer D have an interlayer density of 10-20 layers / cm and a Z-axis continuous needle-punching density of 30-40 needles / cm. 2 .

9. A method for preparing a carbon / carbon boat according to claim 6 or 7, characterized in that: The chemical vapor deposition uses natural gas and / or propylene as the carbon source gas, nitrogen as the carrier gas, and the flow rate of the carbon source gas is 0.20~0.60 SL / Min, the flow rate of the carrier gas is 0.10~0.30 SL / Min, the deposition temperature is 950~1250℃, the deposition pressure is 0.8~10.0 kPa, and the deposition time is 210~280 h.

10. A method for preparing a carbon / carbon boat according to claim 6 or 7, characterized in that: The chemical vapor deposition is divided into three stages. In the first stage, the carbon source gas is natural gas, the carrier gas is nitrogen, the flow rate of natural gas is 0.40~0.60 SL / Min, the flow rate of nitrogen is 0.20~0.30 SL / Min, the deposition temperature is 1150~1250℃, the deposition pressure is 3.0~10.0 kPa, and the deposition time is 100~130 h. In the second stage, the carbon source gas is natural gas, the carrier gas is nitrogen, the flow rate of natural gas is 0.30~0.50SL / Min, the flow rate of nitrogen is 0.15~0.25SL / Min, the deposition temperature is 1050~1149℃, the deposition pressure is 3.0~10Kpa, and the deposition time is 80~100h. In the third stage, the carbon source gas is propylene, the carrier gas is nitrogen, the flow rate of propylene is 0.3~0.5 SL / Min, the flow rate of nitrogen is 0.10~0.18 SL / Min, the deposition temperature is 950~1149℃, the deposition pressure is 0.8~1.6Kpa, and the deposition time is 30~50h.

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