Carbon / carbon heating device and method for manufacturing the same

Abstract

The application relates to the technical field of carbon materials, in particular to a carbon / carbon heating device and a preparation method thereof.The preparation method comprises the following steps: mixing dispersed short carbon fibers, a dispersing agent, carbon material powder, water-based phenolic resin and water, stirring and uniformly dispersing, pouring into a preset shape filter tank for suction filtration to obtain a short fiber mesh reinforced sheet layer with a preset shape; performing impregnation treatment on the short fiber mesh reinforced sheet layer, and obtaining a prepreg reinforced sheet layer after drying; laying carbon fiber filaments and performing glue coating treatment, and forming a carbon fiber filament layer with a preset shape after drying; cutting a carbon fiber cloth into a preset shape and performing impregnation treatment to form a carbon fiber cloth layer; and stacking and arranging the prepreg reinforced sheet layer, the carbon fiber filament layer and the carbon fiber cloth layer in a staggered mode, wrapping the surface of a cylindrical heater mold in an oxygen-free environment, heating and curing to form a cylindrical preform, and performing carbonization, cycle densification, high-temperature purification and machining treatment to form the carbon / carbon heating device. The application can improve the uniformity of the device conductivity.

Description

Technical Field

[0001] This application relates to the field of carbon materials technology, and in particular to a carbon / carbon heating device and its preparation method. Background Technology

[0002] With the development of materials science, carbon / carbon heating devices have become an excellent alternative to graphite heaters, possessing characteristics such as low density, high mechanical properties, high ablation resistance, chemical inertness, thermal shock resistance, and near-net-shape forming, thus better meeting the performance requirements of heaters. However, traditional carbon / carbon heaters typically involve needle-punching carbon fiber cloth and carbon fiber mesh into cylindrical preforms, followed by densification treatment, and then processing them into connected narrow cylindrical strips. In this fabrication process, due to the needle-punching process, the preform contains many pores of varying sizes. During densification, these surface pores are easily filled and blocked, resulting in poor density and electrical conductivity uniformity. Furthermore, due to the numerous needle-punched holes in the preform along the Z-axis, some small, difficult-to-fill areas inevitably exist during densification, leading to high apparent porosity and poor resistance to silicon vapor corrosion. Moreover, the entire process is complex, time-consuming, and costly. Summary of the Invention

[0003] To address the aforementioned problems in the prior art, this application provides a carbon / carbon heating device and its preparation method, which can effectively improve the mechanical properties of the material. The specific technical solution is as follows:

[0004] On one hand, this application provides a method for preparing a carbon / carbon heating device, the method comprising:

[0005] Dispersed short carbon fibers, dispersant, carbon material powder, water-based phenolic resin and water are mixed and stirred to disperse evenly to obtain fiber composite dispersion.

[0006] The fiber composite dispersion is poured into a filter tank of a preset shape for filtration to obtain a short fiber web reinforced sheet of the preset shape. The preset shape is set to mimic the shape of the serpentine resistance wire of the carbon / carbon heating device.

[0007] The short fiber web reinforced sheet is impregnated with resin and dried to obtain a prepreg reinforced sheet;

[0008] Carbon fiber filaments are laid out and coated with adhesive. After drying, a carbon fiber filament layer of a predetermined shape is formed. The carbon fiber filaments in the carbon fiber filament layer are bent and twisted to match the twisted shape of the serpentine resistance wire.

[0009] The carbon fiber cloth is cut into the preset shape and coated with adhesive. After drying, a carbon fiber cloth layer is formed. The dimensions of the prepreg reinforcement layer, the carbon fiber filament layer and the carbon fiber cloth layer are matched.

[0010] The prepreg reinforcement sheets, the carbon fiber filament layers, and the carbon fiber cloth layers are arranged in an alternating manner and wrapped around the surface of the cylindrical heater mold. They are then heated and cured in an oxygen-free environment to form a cylindrical preform.

[0011] The cylindrical preform is subjected to carbonization, cyclic densification, high-temperature purification, and machining to form a carbon / carbon heating device.

[0012] Preferably, the dispersed short carbon fibers are obtained by desizing and air-dispersing short carbon fiber bundles.

[0013] Preferably, the dispersed short carbon fibers are arranged in a disordered manner and are in the form of filaments.

[0014] Preferably, the length of the short carbon fiber is 20-70 mm.

[0015] Optionally, the dispersant includes one or more of hydroxypropyl methylcellulose, hydroxyethyl methylcellulose, or polyethylene glycol.

[0016] Preferably, the particle size of the carbon material powder is less than or equal to 20 μm.

[0017] Preferably, the weight ratio of the short carbon fibers to water is 1:10-100.

[0018] Preferably, the weight ratio of the dispersant to water is 1:50-250.

[0019] Preferably, the weight ratio of the aqueous phenolic resin to water is 1:4-50.

[0020] Preferably, the thickness of the carbon fiber filament layer is 0.10-0.25 mm.

[0021] Preferably, the thickness of the carbon fiber cloth layer is 0.15-0.35 mm.

[0022] Preferably, the thickness of the short fiber mesh reinforcing sheet is 0.5-8 mm.

[0023] Preferably, the fiber areal density of the short fiber web reinforcing sheet is 30-250 g / m². 2 .

[0024] Preferably, the weight ratio of carbon material powder to short carbon fibers in the short fiber mesh reinforced sheet is 4-30:100.

[0025] Preferably, in the cylindrical preform, the prepreg reinforcement layer is stacked adjacent to the carbon fiber filament layer or adjacent to the carbon fiber cloth layer.

[0026] Preferably, the annular interfaces of different prepreg reinforcing layers in the cylindrical preform are staggered.

[0027] Preferably, during the heating and curing process of the cylindrical preform, it is wrapped and compressed using a vacuum bag film.

[0028] Preferably, the process of impregnating the short fiber web reinforcing sheet with resin and drying it to obtain the prepreg reinforcing sheet includes:

[0029] The phenolic resin solution is poured onto the short fiber web reinforcing sheet, filtered, and dried to obtain the prepreg reinforcing sheet.

[0030] Preferably, the phenolic resin solution comprises phenolic resin, a coupling agent, and an ethanol solvent.

[0031] Preferably, the coupling agent includes one or more of KH-550, KH-560 or KH570.

[0032] Preferably, the coupling agent accounts for 0.2-0.8% by mass in the phenolic resin solution.

[0033] Preferably, the viscosity of the coupling agent is 200-2200 mPa·s.

[0034] Preferably, the diameter parameter of the carbon fiber filament is 3K to 12K.

[0035] Preferably, the drying temperature of the carbon fiber filament layer is 50–90°C, and the drying time is 1–3 hours.

[0036] Preferably, during the carbonization, cyclic densification, or high-temperature purification process of the cylindrical preform, the inner ring of the cylindrical preform is supported by a supporting mold, and / or the outer ring of the cylindrical preform is fixed by a fastening ring.

[0037] Preferably, after the cylindrical preform undergoes carbonization, cyclic densification, high-temperature purification, and machining to form a carbon / carbon heating device, the method further includes:

[0038] The surface of the carbon / carbon heating device is treated with a silicon carbide coating, the thickness of which is 5-150 μm.

[0039] Preferably, the density of the carbon / carbon heating device is greater than or equal to 1.5 g / cm³. 3 .

[0040] Preferably, the bending strength of the carbon / carbon heating device is greater than or equal to 165 MPa.

[0041] Preferably, the open area ratio of the carbon / carbon heating device is less than or equal to 1.4%.

[0042] Preferably, the carbon / carbon heating device includes a serpentine resistance wire and at least two electrode connection portions, the electrode connection portions being connected to the serpentine resistance wire.

[0043] On the other hand, this application provides a carbon / carbon heating device, which is prepared by the above-described method for preparing a carbon / carbon heating device.

[0044] On the other hand, this application provides an application of the above-mentioned carbon / carbon heating device in the field of heaters.

[0045] Based on the above technical solution, this application has at least the following beneficial effects:

[0046] The technical solution of this application employs a pre-shaped filter tank to shape and filter the fiber composite dispersion, first forming a planar prepreg reinforcement layer with a serpentine resistance wire shape, and simultaneously forming a shaped carbon fiber filament layer and a carbon fiber cloth layer. These layers are then interleaved and stacked to wrap the surface of a cylindrical heater mold, forming a cylindrical preform structure. This allows for near-net-size carbon / carbon heating devices, improving material utilization and reducing the risk of machining damage. Furthermore, the prepreg reinforcement layer includes short carbon fibers and carbon material powder dispersed in a mesh-like overlap. The carbon fiber filaments are bent to match the serpentine resistance wire's meandering shape, and the interleaved carbon fiber cloth simultaneously enhances the preform's strength, initial density, density uniformity, and conductivity, reducing device porosity. This improves the heater's resistance uniformity, heating uniformity, corrosion resistance, and production efficiency, while reducing the densification cycle and production costs. Attached Figure Description

[0047] To more clearly illustrate the technical solutions of this application, the accompanying drawings used in the description of the embodiments or prior art will be briefly introduced below. Obviously, the drawings described below are merely some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without any creative effort.

[0048] Figure 1 This is a schematic flowchart of a method for preparing a carbon / carbon heating device according to an embodiment of this application;

[0049] Figure 2 This is a schematic diagram of the structure of a carbon / carbon heating device provided in an embodiment of this application. Detailed Implementation

[0050] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.

[0051] For the terms defined below, unless a different definition is given elsewhere in the claims or this specification, these definitions shall apply. All numerical values, whether explicitly indicated or not, are defined herein as being modified by the term "about." The term "about" generally refers to a range of numerical values ​​that a person skilled in the art would consider equivalent to the stated values ​​to produce substantially the same properties, functions, results, etc. A range of numerical values ​​indicated by a low value and a high value is defined as including all numerical values ​​included within that range and all subranges included within that range.

[0052] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of this application described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion.

[0053] The following combination Figure 1 This application provides a method for preparing a carbon / carbon heating device, comprising the following steps S1-S6:

[0054] S1: Mix the dispersed short carbon fibers, dispersant, carbon material powder, water-based phenolic resin and water, stir and disperse evenly to obtain a fiber composite dispersion.

[0055] In some embodiments, the dispersed short carbon fibers are obtained by desizing and air-dispersing short carbon fiber bundles. Specifically, the short carbon fiber bundles can be placed in an oxygen-free atmosphere heat treatment furnace and kept at 600-1500℃ for 1-5 hours to remove the sizing agent on the surface of the carbon fibers. Then, the desizing short carbon fiber bundles are dispersed into disordered, fine, short fiber filaments using an air-dispersing method to obtain dispersed short carbon fibers.

[0056] Specifically, the dispersed short carbon fibers are arranged randomly and have a filamentous shape, facilitating the formation of a mesh-like, overlapping short-fiber reinforced sheet. Thus, millimeter-sized short carbon fibers are dispersed into filaments by airflow, then uniformly dispersed into a dispersion liquid, and finally filtered into a thin, planar prepreg sheet. This avoids the fiber packing density gradient problem encountered during thick-layer filtration, and the introduced longer fiber length results in superior mechanical reinforcement. Furthermore, it promotes the anisotropic uniformity of the device and the dispersion and loading of carbon material particles, reducing porosity and improving the product's strength and density uniformity.

[0057] In some embodiments, the length of the short carbon fiber is 20-70 mm. The length of the short carbon fiber can be any value within the above range, such as 20 mm, 30 mm, 40 mm, 50 mm, 60 mm, 70 mm, etc., which will not be listed here.

[0058] In an optional embodiment, the dispersant includes one or more of hydroxypropyl methylcellulose, hydroxyethyl methylcellulose, or polyethylene glycol to achieve uniform dispersion of short carbon fibers, carbon material powder, and waterborne phenolic resin.

[0059] In some embodiments, the particle size of the carbon material powder is less than or equal to 20 μm, preferably less than or equal to 15 μm, thereby ensuring low porosity and strength of the preform. Optionally, the carbon material powder may be one or more of the following, including but not limited to graphite powder, carbon nanotubes, carbon nanofibers, carbon powder, and silicon carbide powder.

[0060] By adding an appropriate amount of carbon material powder as a carbon matrix to the short fiber mesh reinforcement layer, the electrical properties of the preform can be improved, its heating efficiency can be increased, and the initial density of the material can be increased, reducing the densification cycle and production cost.

[0061] In some implementations, the weight ratio of short carbon fibers to water is 1:10-100. The upper limit of this weight ratio can be 1:10, 1:15, 1:20, 1:25, 1:30, etc., and the lower limit of this weight ratio can be 1:100, 1:95, 1:90, 1:85, 1:80, etc. It is understood that the weight ratio can be any value within the above range, and is not limited to examples.

[0062] In some embodiments, the weight ratio of dispersant to water is 1:50-250. The upper limit of this weight ratio can be 1:50, 1:60, 1:70, 1:80, 1:90, etc., and the lower limit of this weight ratio can be 1:250, 1:230, 1:210, 1:190, 1:170, etc. It is understood that the weight ratio can be any value within the above range, and is not limited to examples.

[0063] The weight ratio of waterborne phenolic resin to water is 1:4-50. The upper limit of this weight ratio can be 1:4, 1:6, 1:8, 1:10, 1:12, etc., and the lower limit of this weight ratio can be 1:50, 1:45, 1:40, 1:35, 1:30, etc. Understandably, the weight ratio can be any value within the above range, without being limited to examples.

[0064] In some embodiments, the weight ratio of carbon material powder to short carbon fibers in the short fiber mesh reinforced sheet is 4-30:100. The upper limit of this weight ratio can be 4:30, 4:35, 4:40, 4:45, 4:50, etc., and the lower limit of this weight ratio can be 1:100, 1:95, 1:90, 1:85, 1:80, etc. It is understood that the weight ratio can be any value within the above range, and is not limited to examples.

[0065] By setting the above material ratio, it is possible to ensure an appropriate weight and volume ratio between short carbon fibers and carbon material powder, guaranteeing the strength and density of the product, while ensuring good dispersion of short carbon fibers, water-based phenolic resin, and fiber impregnation.

[0066] S2: Pour the fiber composite dispersion into a filter tank of a preset shape for filtration to obtain a short fiber web reinforced sheet of a preset shape. The preset shape is set to mimic the shape of the serpentine resistance wire of the carbon / carbon heating device.

[0067] Specifically, the preset shape matches the shape of the cylindrical carbon / carbon heater after it is unfolded into a plane, and at least part of the filter tank is a serpentine strip, that is, an S-shaped meandering shape.

[0068] Specifically, the bottom of the filter tank is provided with a suction hole, and the bottom of the tank is provided with a rigid substrate with mesh, such as a steel substrate, and a mesh is arranged on the substrate.

[0069] Specifically, the fiber composite dispersion is poured into a filter tank of a pre-designed shape and filtered from the bottom to form a narrow strip layer of corresponding mesh fibers, which is a short fiber mesh reinforced sheet in the form of a flat, thin mesh.

[0070] In some embodiments, the thickness of the short fiber mesh reinforcement layer is 0.5-8 mm, preferably 1-6 mm. By setting the thickness of the short fiber mesh reinforcement layer to the above range, it is beneficial for layer bonding and mold wrapping, and to ensure that the stacking thickness of the short fiber mesh reinforcement layer, the short fiber mesh reinforcement layer and the carbon fiber cloth layer is appropriate, thereby improving the interlayer bonding force and Z-direction uniformity, and further improving the mechanical and electrical properties of the product.

[0071] In some embodiments, the fiber areal density of the short fiber web reinforcing sheets is 30-250 g / m². 2 Preferably 90-200g / m 2This improves the fiber web overlap density and the stability of carbon material particle loading, while avoiding excessive density that could affect the impregnation effect.

[0072] S3: The short fiber web reinforcement sheet is impregnated with resin and dried to obtain a prepreg reinforcement sheet.

[0073] In some embodiments, phenolic resin solution is poured onto a short fiber web reinforcement layer, filtered, and dried to obtain a prepreg reinforcement sheet. This wet molding process forms a uniformly distributed prepreg layer with more even short fiber distribution. Winding onto a cylindrical mold is simpler and more reliable. Furthermore, the impregnation treatment achieves Z-axis penetration of the phenolic resin solution, ensuring sufficient fiber wetting in the short fiber web reinforcement layer and improving the preform density and bond strength.

[0074] In some implementations, the drying temperature of the prepreg-reinforced sheets is 50–90°C, and the drying time is 1–3 hours. In this way, the drying effect is ensured while the probability of sheet deformation is reduced by drying at a lower temperature.

[0075] S4: Lay out carbon fiber filaments and apply adhesive. After drying, a carbon fiber filament layer of the preset shape is formed. The carbon fiber filaments in the carbon fiber filament layer are bent and twisted to match the meandering shape of the serpentine resistance wire.

[0076] Specifically, multiple bundles of carbon fiber filaments can be laid out in parallel single layers according to a predetermined shape and the dimensions of the prepreg reinforcement sheet to form a continuous carbon fiber filament layer along its length. In some cases, the carbon fiber filaments can be laid directly on the prepreg reinforcement sheet for easier alignment of shape and size. This method of pre-forming continuous carbon fiber filaments into a serpentine narrow strip layer avoids the cutting and damage of continuous carbon fibers during the processing of the serpentine structure after the preform is formed into a cylindrical shape, thus better ensuring the mechanical reinforcement effect of the product. Simultaneously, since the axial conductivity of carbon fiber filaments is higher than that in the radial direction, introducing continuous carbon fiber filaments can reduce the resistance of the heater and improve its heating efficiency.

[0077] Specifically, after applying an adhesive to a lay-up layer of carbon fiber filaments, the layer is placed in an oven for drying to obtain a prepreg carbon fiber filament layer. In one embodiment, T700 carbon fiber filaments are used to form the carbon fiber filament layer.

[0078] In some implementations, the diameter parameters of the carbon fiber filaments are 3K to 12K to ensure product strength and uniform conductivity along its length.

[0079] In some embodiments, the drying temperature of the carbon fiber filament layer is 50–90°C, and the drying time is 1–3 hours.

[0080] In some embodiments, the thickness of the carbon fiber filament layer is 0.10-0.25 mm, preferably 0.15-0.2 mm. Setting the thickness of the carbon fiber filament layer to the above range facilitates sheet bonding and mold encapsulation, as well as ensuring the enhancement of electrical properties.

[0081] S5: Cut the carbon fiber cloth into a preset shape and apply adhesive. After drying, a carbon fiber cloth layer is formed. The dimensions of the prepreg reinforcement layer, the carbon fiber filament layer and the carbon fiber cloth layer are matched.

[0082] Specifically, the carbon fiber cloth layer may include at least one layer of carbon fiber cloth, preferably multiple layers of carbon fiber cloth, in order to protect the structural integrity of the prepreg reinforcement sheet and the carbon fiber filament layer, and enhance the interlayer bonding and isotropy of the preform.

[0083] In some embodiments, the thickness of the carbon fiber cloth layer is 0.15-0.35 mm, preferably 0.2-0.3 mm. By setting the thickness of the carbon fiber cloth layer to the above range, it is beneficial to ensure both the sheet lamination and mold wrapping, while also ensuring the strength enhancement effect and density uniformity.

[0084] Specifically, carbon fiber cloth is cut into a predetermined shape, coated with phenolic resin, and dried to form a carbon fiber cloth layer with the same shape and size as the prepreg reinforcement layer and carbon fiber filament layer. The drying temperature is 50–90℃, and the drying time is 1–3 hours.

[0085] In some embodiments, both the impregnation and coating processes described above are achieved using a phenolic resin solution, which includes phenolic resin, a coupling agent, and an ethanol solvent.

[0086] In an optional embodiment, the coupling agent includes one or more of KH-550, KH-560, or KH570.

[0087] In some embodiments, the coupling agent accounts for 0.2-0.8% of the mass of the phenolic resin solution.

[0088] In some implementations, the viscosity of the coupling agent is 200-2200 mPa·s.

[0089] By configuring the coupling agent as described above, the bonding strength of the laminated structure can be enhanced, and the probability of delamination and tearing of the product can be reduced.

[0090] S6: The prepreg reinforcement layers, carbon fiber filament layers and carbon fiber cloth layers are stacked alternately and wrapped around the surface of the cylindrical heater mold, and then heated and cured in an oxygen-free environment to form a cylindrical preform.

[0091] Specifically, prepreg reinforcement layers, carbon fiber filament layers, and carbon fiber cloth layers are alternately layered and bonded onto a cylindrical heated mold. For example, the prepreg reinforcement layers, carbon fiber filament layers, and carbon fiber cloth layers are wrapped sequentially and cyclically. Alternatively, in the cylindrical preform, the prepreg reinforcement layers are stacked adjacent to the carbon fiber filament layers or adjacent to the carbon fiber cloth layers. For example, a carbon fiber filament layer or carbon fiber cloth layer is sandwiched between two adjacent prepreg reinforcement layers. This ensures the bonding strength while also ensuring the mechanical and electrical properties of the product.

[0092] In some embodiments, the ratio of carbon fiber filament layer, carbon fiber cloth layer, and prepreg reinforcement sheet layer is (4-8):(2-6):10.

[0093] In some embodiments, the carbon fiber content of the cylindrical preform is 0.35-0.55 g / cm³. 3 The combination of carbon fiber filament layers enhances the overall mechanical properties of the product and reduces its resistivity. Furthermore, the addition of a certain amount of carbon material powder during the prepreg formation process results in a higher density for the cylindrical preform, reducing the number of subsequent densification cycles and significantly lowering production costs.

[0094] In some embodiments, the annular interfaces of different prepreg reinforcement layers in the cylindrical preform are staggered. An annular interface refers to the interface formed when the two ends of the prepreg reinforcement layers are joined together along their length. After two adjacent prepreg reinforcement layers are annularly wrapped around the mold, their two ends along their length are joined but staggered, thereby reducing the impact of thickness differences and strength performance caused by the interface. Understandably, the number and thickness of the layers are set based on the thickness required by the heating device.

[0095] In some embodiments, the cylindrical preform is wrapped and compressed using a vacuum bag film during the heating and curing process. Specifically, after each layer is aligned and stacked and wrapped in a ring around a heating mold, a high-temperature resistant vacuum bag film is used to seal the stacked material on the cylindrical heating mold to compact and fix the stacked material. The material is then placed in a vacuum-treated oven for heating and curing. After demolding, a cylindrical preform based on vacuum bag film molding is obtained. In this way, carbon material is first prepared into a pre-formed planar prepreg of a predetermined shape, then stacked and wrapped onto a cylindrical mold, and vacuum bag heat-molded into a cylindrical preform with a serpentine resistance wire structure. This significantly simplifies the preform molding process, better conforms to the shape and size of the finished carbon-carbon heating device, improves material utilization, and reduces production costs.

[0096] In some implementations, the curing temperature is 180-200℃ and the holding time is 3-4 hours.

[0097] In this embodiment, the cylindrical preform uses a continuous carbon fiber filament layer and a wet-process uniformly dispersed prepreg reinforcement layer, which not only ensures the high-temperature mechanical strength of the composite material, but also greatly improves the fiber uniformity of the material, thereby improving the resistance uniformity and heating uniformity of the heating device.

[0098] S7: Carbonize, circulate, purify at high temperature, and machine the cylindrical preform to form a carbon / carbon heating device.

[0099] In some embodiments, during the carbonization, cyclic densification, or high-temperature purification processes of the cylindrical preform, the inner ring of the cylindrical preform is supported by a supporting mold, and / or the outer ring of the cylindrical preform is fixed by a fastening ring. Specifically, the supporting mold can be annular and placed on the inner ring of the cylindrical preform, while the fastening ring is fixed to the outer ring of the cylindrical preform to provide heating support and fixation, thus avoiding preform deformation during the high-temperature process.

[0100] In some embodiments, the density of the carbon / carbon heating device is greater than or equal to 1.5 g / cm³. 3 .

[0101] In some implementations, the flexural strength of the carbon / carbon heating device is greater than or equal to 165 MPa.

[0102] In some embodiments, the carbon / carbon heating device has an open area of ​​less than or equal to 1.4%, exhibiting extremely low porosity, which significantly improves the mechanical properties and corrosion resistance of the heating device.

[0103] In some implementations, reference is made to Figure 2 The carbon / carbon heating device includes a serpentine resistance wire 2 and at least two electrode connection portions 1, which are connected to the serpentine resistance wire 2. Accordingly, the preset shape includes a portion that matches the serpentine resistance wire 2 and a portion that matches the electrode connection portions 1. The electrode connection portion 1 is a sheet-like structure connected to the serpentine resistance wire 2, enabling external electrode connection and improving the overall structural strength.

[0104] In some implementations, the annular interface is located at the electrode connection portion, which is beneficial for connection strength and staggered interface settings between different layers.

[0105] In one embodiment, at least four electrode connection portions are provided to provide at least two spare electrode connection portions in addition to the two main electrode connection portions, so as to facilitate the replacement of electrode connections and improve product life.

[0106] In some implementations, the carbonization temperature is 650-950°C.

[0107] In some embodiments, the density of the carbonized device ligand obtained after cyclic densification is greater than or equal to 1.5 g / cm³. 3 ;

[0108] In some implementations, the densification process is repeated 2-3 times, while related technologies require 4-5 densification processes of the same duration. Compared with the prior art, this embodiment can significantly reduce the number of densification processes, thereby reducing preparation time and production costs.

[0109] In some embodiments, the high-temperature purification temperature is 2000-2400°C, thereby reducing the ash impurities in the material and increasing the graphitization degree of the carbon matrix.

[0110] Understandably, based on the preparation method of this embodiment, the purified carbonized preform structure has formed the required shape and structure of the carbon / carbon heating device. Only simple machining processes such as edge processing and surface polishing are required, which can process the carbon / carbon heating device close to the net size, reducing processing damage and material waste.

[0111] In some embodiments, after step S7, the method further includes S8: applying a silicon carbide coating to the surface of the carbon / carbon heating device, wherein the thickness of the silicon carbide coating is 5-150 μm, preferably 40-150 μm. This silicon carbide coating densifies the surface of the heating device, thereby improving its resistance to corrosion such as silicon vapor and its wear resistance, significantly extending product lifespan, and reducing high-temperature volatile pollution from the heating device.

[0112] In one embodiment, a silicon carbide coating is formed using a CVD process. Exemplarily, methyltrichlorosilane (MTS / CH3SiCl3) or silane (SiH4) can be used as the precursor gaseous silicon source, with argon or hydrogen as the carrier, and the reaction deposition is carried out at 1000-1400°C, 1-10 kPa pressure, and a hydrogen / MTS molar ratio of 5:1-20:1 for 1-10 hours to generate the silicon carbide coating.

[0113] In summary, the technical solution of this application employs a pre-shaped filter tank to shape and filter the fiber composite dispersion, first forming a planar prepreg reinforcement layer with a serpentine resistance wire shape, and simultaneously forming a shaped carbon fiber filament layer and a carbon fiber cloth layer. These layers are then overlapped and wrapped around the surface of a cylindrical heater mold to form a cylindrical preform structure, thereby molding a carbon / carbon heating device to near-net-shape, improving material utilization and reducing the risk of machining damage. Furthermore, the prepreg reinforcement layer includes short carbon fibers and carbon material powder dispersed in a mesh-like overlap. The carbon fiber filaments are bent to match the meandering shape of the serpentine resistance wire, and the carbon fiber cloth is overlapped and interleaved. Compared to the traditional needle-punched preform preparation method, this method can simultaneously enhance the strength, initial density, density uniformity, and conductivity of the preform, reduce device porosity, thereby improving the heater's resistance uniformity, heating uniformity, corrosion resistance, and production efficiency, while reducing the densification cycle and production costs.

[0114] The embodiments of this application are described below in conjunction with the above technical solutions.

[0115] The carbon / carbon heating devices of Examples 1-8 were prepared by the following method:

[0116] 1. Place the short carbon fiber bundles in an oxygen-free atmosphere heat treatment furnace and keep them at 600-1500℃ for 1-5 hours to remove the sizing agent from the fiber surface. Then, use airflow dispersion to break the short carbon fiber bundles into disordered fine short fiber filaments.

[0117] 2. After the short carbon fibers are dispersed by airflow, add dispersant, graphite powder, water-based phenolic resin and water in a set ratio, stir and disperse evenly to obtain a fiber composite dispersion.

[0118] 3. Prepare a filter tank with a serpentine, meandering narrow strip shape, with a filtration hole at the bottom and a mesh steel plate base on top. Lay a mesh on the base, and then pour the fiber composite dispersion from step 2 into the filter tank for filtration to form a short fiber mesh reinforced sheet of the corresponding preset shape.

[0119] 4. Pour the phenolic resin solution onto the short fiber web reinforcement layer, and filter it again to allow the phenolic resin solution to fully wet the fiber surface. The phenolic resin solution contains phenolic resin, coupling agent and ethanol solvent.

[0120] 5. Place the impregnated short fiber web reinforcement sheet in an oven for drying to remove the solvent and obtain the prepreg reinforcement sheet. The drying temperature is 50-90℃ and the time is 1-3 hours.

[0121] 6. Multiple bundles of continuous carbon fiber filaments are laid parallel to each other on the surface of the prepreg reinforcement sheet according to its shape and size, so that the surface is covered with a layer of continuous carbon fiber filaments. Then, phenolic resin is applied to the surface and placed in an oven for drying to obtain the carbon fiber filament layer. The drying temperature is 50-90℃ and the time is 1-3h.

[0122] 7. Cut the carbon fiber cloth into the designed preset shape and size, then coat its surface with phenolic resin adhesive and place it in an oven for drying to obtain the carbon fiber cloth layer. The drying temperature is 50-90℃ and the time is 1-3h.

[0123] 8. According to the set number of layers and proportions, the prepreg reinforcement sheet, carbon fiber filament layer and carbon fiber cloth layer are stacked and wrapped alternately on the outer surface of the cylindrical heater mold with the long sides aligned. The connection positions of each layer are staggered. The prepreg reinforcement sheet and carbon fiber filament layer are arranged alternately, and some carbon fiber filament layers are replaced by carbon fiber cloth layers.

[0124] 9. A composite sheet layer sealed with a high-temperature resistant vacuum bag film on a cylindrical heating mold is placed in an oven by connecting a high-temperature resistant vacuum pipeline system. The vacuum pipeline extending out of the oven is connected to a vacuum pump to continuously evacuate the vacuum. The oven is then heated and cured at 180°C for 4 hours to obtain a vacuum-packed cylindrical preform.

[0125] 10. After demolding the formed cylindrical preform, add carbon / carbon supports and fastening rings to the inside and outside respectively, and place it in a carbonization furnace for carbonization treatment to obtain carbon / carbon molding material at a carbonization temperature of 650-950℃.

[0126] 11. Perform cyclic densification treatment on carbon / carbon molding material to obtain carbonized preforms with a preset density;

[0127] 12. The carbonized preform is subjected to high-temperature purification treatment to reduce the ash impurities of the material while increasing the graphitization degree of the carbon matrix. The high-temperature purification temperature is 2000-2400℃.

[0128] 13. The carbonized preform after high-temperature purification is machined to obtain a carbon / carbon heating device;

[0129] 14. Apply silicon carbide coating to the surface of the carbon / carbon heating device.

[0130] refer to Figure 2 , Figure 2 This is a schematic diagram of the structure of a carbon / carbon heater provided in an embodiment.

[0131] The relevant parameters for Examples 1-8 are shown in Table 1.

[0132] The specific methods used for testing the material parameters are as follows:

[0133] 1) The bending strength test was conducted using a universal testing machine, and the test standard selected was GB / T 1449-2005;

[0134] 2) Test method for bulk density: The volume of the product is calculated by measuring the length, width and thickness, the machining accuracy of the finished product is controlled to be +0.1mm, and the bulk density is calculated by weighing the product.

[0135] 3) The porosity was tested using the boiling method, and the test standard was GB / T 24529-2009;

[0136] 4) Resistivity test method: Measure the resistance value at both ends of a sample of a specific size (500*25*4) using a DC low resistance tester, and calculate the resistivity value of the material.

[0137] Table 1

[0138]

[0139] In summary, this application has at least the following beneficial effects: The technical solution of this application uses a filter tank of a pre-shaped form to shape and filter the fiber composite dispersion, first forming a planar prepreg reinforcement layer with a serpentine resistance wire shape, and simultaneously forming a shaped carbon fiber filament layer and a carbon fiber cloth layer. The above layers are then wrapped around the surface of a cylindrical heater mold in an alternating layer to form a cylindrical preform structure, thereby forming a carbon / carbon heating device with near-net-size molding, improving material utilization and reducing the risk of machining damage. In addition, the prepreg reinforcement layer includes short carbon fibers and carbon material powder dispersed in a mesh-like overlapping pattern. The carbon fiber filaments are bent to match the meandering shape of the serpentine resistance wire, and the carbon fiber cloth is interlaced, which can simultaneously enhance the strength, initial density, density uniformity, and conductivity of the preform, reduce the porosity of the device, thereby improving the resistance uniformity, heating uniformity, corrosion resistance, and production efficiency of the heater, and reducing the densification cycle and production cost.

[0140] The carbon / carbon heating device prepared in this application has a preset density of up to 1.5 g / cm³. 3 The above specifications include a flexural strength ≥ 165 MPa, an open area ratio ≤ 1.4%, and a resistivity ≤ 15.5 x 10⁻⁶. -6 Ω·m. In a preferred embodiment, the density can reach 1.55 g / cm³. 3 The above specifications include a bending strength ≥ 175 MPa, an open area ratio ≤ 0.95%, and a resistivity ≤ 14 x 10⁻⁶. -6 Ω·m. The resistivity of carbon / carbon heating devices prepared using conventional needle-punched preforms is generally greater than 20 x 10⁻⁶ Ω·m. -6 In high-temperature furnaces using low-voltage, high-current heating methods, the resistivity of heating elements is often too high (Ω·m), resulting in slow heating. To meet application requirements, the heating element needs to be thickened, increasing material costs, weight, and assembly space. Alternatively, the resistance wire needs to be widened, increasing current density unevenness at bends and thus complicating shape and size design. The heating element of this application, however, has a resistivity close to that of graphite, eliminating the need to modify the shape and size of traditional graphite heaters or their electrical application requirements. Furthermore, it offers a high heating rate and superior heating performance.

[0141] The foregoing description has fully disclosed the specific embodiments of this application. It should be noted that any modifications made by those skilled in the art to the specific embodiments of this application do not depart from the scope of the claims. Accordingly, the scope of the claims of this application is not limited to the foregoing specific embodiments.

Claims

1. A method for preparing a carbon / carbon heating device, characterized in that, The preparation method includes: Dispersed short carbon fibers, dispersant, carbon material powder, water-based phenolic resin and water are mixed and stirred to disperse evenly to obtain fiber composite dispersion. The fiber composite dispersion is poured into a filter tank of a preset shape for filtration to obtain a short fiber web reinforced sheet of the preset shape. The preset shape is set to mimic the shape of the serpentine resistance wire of the carbon / carbon heating device. The short fiber web reinforcing sheet is impregnated with resin and dried to obtain a prepreg reinforcing sheet; Carbon fiber filaments are laid out and coated with adhesive. After drying, a carbon fiber filament layer of a predetermined shape is formed. The carbon fiber filaments in the carbon fiber filament layer are bent and twisted to match the twisted shape of the serpentine resistance wire. The carbon fiber cloth is cut into the preset shape and coated with adhesive. After drying, a carbon fiber cloth layer is formed. The dimensions of the prepreg reinforcement layer, the carbon fiber filament layer and the carbon fiber cloth layer are matched. The prepreg reinforcement sheets, the carbon fiber filament layers, and the carbon fiber cloth layers are arranged in an alternating manner and wrapped around the surface of the cylindrical heater mold. They are then heated and cured in an oxygen-free environment to form a cylindrical preform. The cylindrical preform is subjected to carbonization, cyclic densification, high-temperature purification, and machining to form a carbon / carbon heating device.

2. The preparation method according to claim 1, characterized in that, The preparation method satisfies at least one of the following characteristics: The dispersed short carbon fibers are obtained by desizing and air-dispersing short carbon fiber bundles. The dispersed short carbon fibers are arranged in a disordered manner, and the short carbon fibers are in the form of filaments. The short carbon fibers have a length of 20-70 mm; The dispersant includes one or more of hydroxypropyl methylcellulose, hydroxyethyl methylcellulose, or polyethylene glycol; The particle size of the carbon material powder is less than or equal to 20 μm; The weight ratio of the short carbon fibers to water is 1:10-100; The weight ratio of the dispersant to water is 1:50-250; The weight ratio of the aqueous phenolic resin to water is 1:4-50; The thickness of the carbon fiber filament layer is 0.10-0.25 mm; The thickness of the carbon fiber cloth layer is 0.15-0.35 mm.

3. The preparation method according to claim 1, characterized in that, The short fiber web reinforced sheet satisfies at least one of the following characteristics: The thickness of the short fiber mesh reinforcing layer is 0.5-8 mm; The fiber areal density of the short fiber web reinforcing sheet is 30-250 g / m². 2 ; The weight ratio of carbon material powder to short carbon fibers in the short fiber mesh reinforced sheet is 4-30:

100.

4. The preparation method according to claim 1, characterized in that, The cylindrical prefabricated body satisfies at least one of the following characteristics: In the cylindrical preform, the prepreg reinforcing sheet is stacked adjacent to the carbon fiber filament layer or adjacent to the carbon fiber cloth layer; The annular interfaces of different prepreg reinforcing layers in the cylindrical preform are arranged alternately. During the heating and curing process of the cylindrical preform, it is wrapped and compressed using a vacuum bag film.

5. The preparation method according to claim 1, characterized in that, The process of impregnating the short fiber web reinforcing sheet with resin and drying it to obtain a prepreg reinforcing sheet includes: The phenolic resin solution is poured onto the short fiber web reinforcing sheet, filtered, and dried to obtain the prepreg reinforcing sheet.

6. The preparation method according to any one of claims 1-5, characterized in that, The impregnation and coating processes are performed using a phenolic resin solution, wherein the phenolic resin solution meets at least one of the following characteristics: The phenolic resin solution comprises phenolic resin, a coupling agent, and an ethanol solvent; The coupling agent includes one or more of KH-550, KH-560 or KH570; The coupling agent comprises 0.2-0.8% by mass in the phenolic resin solution; The viscosity of the coupling agent is 200-2200 mPa·s.

7. The preparation method according to any one of claims 1-5, characterized in that, The preparation method satisfies at least one of the following characteristics: The diameter parameters of the carbon fiber filaments are 3K to 12K; The drying temperature of the carbon fiber filament layer is 50–90°C, and the drying time is 1–3 hours.

8. The preparation method according to any one of claims 1-5, characterized in that, During the carbonization, cyclic densification, or high-temperature purification process of the cylindrical preform, the inner ring of the cylindrical preform is supported by a supporting mold, and / or the outer ring of the cylindrical preform is fixed by a fastening ring.

9. The preparation method according to any one of claims 1-5, characterized in that, After the cylindrical preform undergoes carbonization, cyclic densification, high-temperature purification, and machining to form a carbon / carbon heating device, the method further includes: The surface of the carbon / carbon heating device is treated with a silicon carbide coating, the thickness of which is 5-150 μm.

10. The preparation method according to any one of claims 1-5, characterized in that, The carbon / carbon heating device satisfies at least one of the following characteristics: The density of the carbon / carbon heating device is greater than or equal to 1.5 g / cm³. 3 ; The bending strength of the carbon / carbon heating device is greater than or equal to 165 MPa; The open area ratio of the carbon / carbon heating device is less than or equal to 1.4%; The carbon / carbon heating device includes a serpentine resistance wire and at least two electrode connection portions, which are connected to the serpentine resistance wire.

11. A carbon / carbon heating device, characterized in that, The carbon / carbon heating device is prepared by the method described in any one of claims 1-10.

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