Embedded electrode ceramic carbon fiber composite tube

Abstract

The invention discloses an embedded electrode ceramic carbon fiber composite tube, and relates to the technical field of electromagnetic flowmeters, the embedded electrode ceramic carbon fiber composite tube comprises a hollow cylindrical ceramic guide tube, the outer wall of the ceramic guide tube is provided with a groove and a protrusion, the groove and the protrusion are arranged in an interpenetrating mode in the axis direction of the ceramic guide tube, and the outer wall of the ceramic guide tube is provided with a composite material layer. The center of the ceramic conduit is provided with connecting electrode holes in bilateral symmetry, a grounding electrode hole is arranged below the ceramic conduit, the interiors of the connecting electrode holes and the grounding electrode hole are processed to be in an internal thread shape, the arrangement of the middle composite material layer effectively absorbs external impact force and vibration energy, and the stress of the ceramic lining layer is dispersed. The impact resistance and the vibration resistance of the measuring tube are remarkably improved, and the probability of breakage of the ceramic lining layer is reduced in the mounting, transporting and using processes; meanwhile, due to the matched thermal expansion coefficient of the composite material layer and the ceramic material, the situation of ceramic cracking caused by temperature shock is reduced, and the threshold value of bearable temperature change is increased.

Description

Technical Field

[0001] This invention relates to the field of electromagnetic flowmeter technology, specifically to an embedded electrode ceramic carbon fiber composite tube. Background Technology

[0002] Electromagnetic flow meters are velocity-type flow meters that measure conductive media based on Faraday's law of electromagnetic induction. They mainly consist of a sensor and a converter. Widely used in various industrial applications, they offer advantages such as high measurement accuracy, wide range, and unobstructed flow. The sensor is a crucial component of the electromagnetic flow meter, converting the flow signal into a voltage signal and determining the flow meter's accuracy and stability. The sensor primarily consists of a metal conduit lined with insulating material, an excitation system, and a signal output system.

[0003] In China, the lining of electromagnetic flowmeter conduits is mostly made of synthetic materials such as fluoroplastics and rubber. The disadvantages of these materials are low temperature resistance, poor wear resistance, poor resistance to negative pressure, easy electrode leakage, poor lining roundness, and unstable flow field.

[0004] With the development of technology in related fields, more and more electromagnetic flow meters using ceramic as the liner have emerged. Although ceramic liner can solve the above problems to some extent, it also has problems such as high brittleness, heavy weight, difficult installation, and high cost.

[0005] Chinese patent application number CN202410919118.8 discloses a method for the overall sintering and preparation of ceramic linings and electrodes for electromagnetic flowmeter components. Step 1: Raw material preparation: High-purity nano-grade alumina powder is selected as the main raw material, with additives added as auxiliary materials; zirconium oxide, cerium oxide, yttrium oxide, and lanthanum oxide are then mixed and sieved, followed by mixing at 120 degrees Celsius. After mixing, granulated powder is prepared for later use. Step 2: Equipment molding: The granulated powder obtained in Step 1 is loaded into a mold, placed in an isostatic pressing chamber, and molded under 150 MPa pressure. The blank is then rough-machined and sintered at high temperature. The ceramic lining of the electromagnetic flowmeter conduit containing conductive electrodes obtained after high-temperature sintering has the characteristics of high temperature resistance, resistance to positive and negative pressure, resistance to acid and alkali corrosion, wear resistance, leak-proof, and high hygiene level. It is superior to traditional rubber and fluoroplastic electromagnetic flowmeter conduit linings and conductive electrodes, offering higher cost-effectiveness and making it the best alternative to conventional linings.

[0006] Chinese patent application number CN202322883814.1 discloses a ceramic-lined electromagnetic flowmeter, comprising a flowmeter housing and a high-temperature resistant lined conduit assembly. The flowmeter housing includes a connecting rod and a retaining plate, the retaining plate connecting to the high-temperature resistant lined conduit assembly. The high-temperature resistant lined conduit assembly is equipped with an electrode mounting structure and a connecting side plate, relating to the field of flow meters. This utility model is a ceramic-lined electromagnetic flowmeter that can be clamped and installed on-site in pipelines and is applied to high-temperature media conditions. The flowmeter has a simple structure, is easy to install, and significantly reduces production and usage costs.

[0007] However, the sealing effect of the above solutions is not as good as that of one-piece sintering. The difference in thermal expansion coefficients between metal and ceramic makes them prone to thermal cracking during the firing process. Ceramic conduits have low strength, are brittle, and are difficult to install. By wrapping carbon fiber material, the strength of ceramics can be increased by more than three times. Summary of the Invention

[0008] To address the above problems, this invention provides an embedded electrode ceramic carbon fiber composite tube, which solves the aforementioned issues.

[0009] To achieve the above objectives, the present invention provides the following technical solution: an embedded electrode ceramic carbon fiber composite tube, comprising a hollow cylindrical ceramic conduit, wherein the outer wall of the ceramic conduit is provided with grooves and protrusions, the grooves and protrusions being interpenetrating each other along the axial direction of the ceramic conduit, the outer wall of the ceramic conduit being provided with a composite material layer, the center of the ceramic conduit being provided with symmetrical connecting electrode holes, and the bottom of the ceramic conduit being provided with a grounding electrode hole, the connecting electrode hole and the grounding electrode hole being internally threaded, and electrodes being respectively provided inside the connecting electrode hole and the grounding electrode hole, and connecting copper posts being respectively connected inside the connecting electrode hole and the grounding electrode hole, the outer wall of the connecting copper post being fixed with a PTFE sleeve, and the other end of the connecting copper post being respectively connected with a screw; The copper terminal block has a countersunk hole and a stepped groove. The copper terminal block is generally stepped shaft-shaped with an external thread at the head, the thread size being the same as that of the electrode hole, and an internal thread at the tail. The external thread of the copper terminal block is screwed into the ceramic conduit to contact the electrode. The copper terminal block is inserted into a PTFE sleeve for electrode insulation.

[0010] Preferably, the outer layer of the composite material layer is an oxidation-resistant ceramic coating, the middle layer of the composite material layer is a carbon fiber layer + ceramic composite matrix, the surface of the carbon fiber layer is in situ grown with nano-sized ceramic whiskers and combined with the ceramic composite matrix, and the inner layer of the composite material layer is a corrosion-resistant resin coating.

[0011] Preferably, microcapsules are incorporated into the oxidation-resistant ceramic coating, and the microcapsules contain a low-melting-point metal repair agent.

[0012] Preferably, the carbon fiber layer of the composite material layer is made of recycled carbon fiber with a length of 5-10 mm, mixed with basalt fiber in a ratio of 3:7, placed in a high-speed mixer, stirred for 20 minutes, and the mixed fiber is printed into a tubular preform using a selective laser melting 3D printer. The preform is placed in a tube furnace, and a mixture of silicon tetrachloride and hydrogen gas with a volume ratio of 1:5 is introduced and kept at 1000°C for 3 hours to grow silicon carbide whiskers in situ on the surface of the carbon fiber.

[0013] Preferably, the corrosion-resistant resin coating of the composite material layer is applied using a CNC fiber laying machine, where carbon fibers of 10-15mm in length are arranged in a staggered orientation at 0° / 90° to avoid stress concentration during processing caused by disordered fibers. Low-viscosity epoxy resin (viscosity ≤ 500 mPa·s) is injected into the arranged fibers and pre-cured at 60°C for 30 minutes to form a "semi-rigid" preform.

[0014] Preferably, the ceramic conduit uses a high-purity alumina ceramic tube formed by isostatic pressing as the main body of the measuring conduit, the electrode adopts a threaded structure pre-embedded design, and the ceramic conduit and the electrode are sintered together with metal materials such as platinum / iridium or Hastelloy metal powder directly in one step through a gradient sintering process.

[0015] Preferably, the low-melting-point metal repair agent is a tin and bismuth alloy microcapsule with a diameter of 50-100μm and a core material content of 70%, which is mixed with alumina ceramic powder in a 1:9 ratio to form a coating slurry. The slurry is then coated onto the surface of the pipe using a high-pressure airless spraying device, with the thickness controlled at 100-120μm, and subsequently sintered at 800℃ for 1 hour.

[0016] Preferably, the ceramic conduit and the pipe interface are provided with a metal corrugated pipe and a composite sealing gasket.

[0017] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. The intermediate composite material layer effectively absorbs external impact and vibration energy, disperses the stress of the ceramic lining layer, and significantly improves the impact and vibration resistance of the measuring tube. During installation, transportation and use, the probability of the ceramic lining layer cracking is reduced. At the same time, the thermal expansion coefficient of the composite material layer matches that of the ceramic material, reducing the possibility of ceramic cracking due to sudden temperature changes and increasing the threshold of temperature change that can be withstood.

[0018] 2. The ceramic tube features raised grooves on its outer surface, and the composite material reinforcement layer significantly enhances its bending and tensile strength. The composite material layer effectively buffers external impacts and vibrations, reducing the risk of breakage due to ceramic brittleness. The transition layer alleviates interfacial stress caused by temperature changes, raising the temperature change threshold of the ceramic tube. The lightweight and high-strength properties of the composite material substantially reduce the product's weight.

[0019] 3. A high-purity alumina ceramic tube, formed by isostatic pressing, is used as the main body of the measuring conduit. The electrodes adopt a pre-embedded threaded structure design, and metal materials such as platinum / iridium and Hastelloy alloy powder are directly sintered with the ceramic tube in one step through a gradient sintering process. The electrode signal leads use copper post threaded connections, making installation more convenient. Attached Figure Description

[0020] Figure 1 This is a schematic cross-sectional view of the entire invention; Figure 2 This is a perspective view of the ceramic conduit of the present invention; Figure 3 This is a partially enlarged schematic diagram of the present invention; Figure 4 This is a cross-sectional view of the wiring copper post of the present invention.

[0021] The diagram shows the following labels: 1. Ceramic conduit; 2. Composite material layer; 3. Electrode; 4. Screw; 5. Terminal copper post; 6. PTFE sleeve; 7. Electrode connection hole; 8. Grounding electrode hole; 11. Groove; 12. Protrusion; 51. Countersunk hole; 52. Step groove. Detailed Implementation

[0022] The embodiments of the present invention will be described in further detail below with reference to the accompanying drawings and examples. The following examples are for illustrative purposes only and should not be construed as limiting the scope of the invention.

[0023] Please see Figure 1 , Figure 2 , Figure 3 and Figure 4An embedded electrode ceramic carbon fiber composite tube includes a hollow cylindrical ceramic conduit 1. The outer wall of the ceramic conduit 1 is provided with grooves 11 and protrusions 12, which are interlaced along the axial direction of the ceramic conduit 1. The outer surface of the ceramic tube is designed with grooves of varying heights. The outer surface of the ceramic conduit 1 is wrapped with a composite material reinforcement layer, which significantly improves the bending strength and tensile strength of the ceramic conduit 1. The outer wall of the ceramic conduit 1 is provided with a composite material layer 2, which effectively buffers external impacts and vibrations, reducing the risk of ceramic fracture due to brittleness. The transition layer can alleviate the interfacial stress caused by temperature changes and improve the temperature change threshold of the ceramic conduit 1. The lightweight and high-strength properties of composite materials significantly reduce the product's weight. The intermediate composite layer 2 effectively absorbs external impact and vibration energy, dispersing the stress of the ceramic lining layer and significantly improving the measuring tube's impact and vibration resistance. This reduces the probability of the ceramic lining layer cracking during installation, transportation, and use. Simultaneously, the matching thermal expansion coefficient of composite layer 2 with the ceramic material reduces the likelihood of ceramic cracking due to sudden temperature changes, increasing the temperature tolerance threshold. The lower density of composite layer 2 effectively reduces the overall weight of the measuring tube, lessening the requirements for the support structure and lowering installation costs. The use of composite material layer 2 eliminates the need to excessively increase the thickness of the ceramic lining layer, saving ceramic materials, reducing manufacturing and processing costs, and lowering overall costs. The ceramic conduit 1 has symmetrical connecting electrode holes 7 in its center, and a grounding electrode hole 8 is located below it. Both connecting electrode holes 7 and grounding electrode holes 8 are internally threaded. Electrodes 3 are respectively installed inside the connecting electrode holes 7 and grounding electrode holes 8. Connecting copper posts 5 are respectively connected to the connecting electrode holes 7 and grounding electrode holes 8. A PTFE sleeve 6 is fixed to the outer wall of the connecting copper post 5, and screws 4 are connected to the other end of each connecting copper post 5. This three-layer composite structure—an inner ceramic lining, a middle composite material layer 2, and an outer metal protective layer—combines the wear and corrosion resistance of ceramics, the impact resistance and toughening properties of composite materials, and the high strength and easy connection properties of metals.

[0024] Please see Figure 3 and Figure 4The copper terminal block 5 has a countersunk hole 51 and a stepped groove 52. The copper terminal block 5 is generally stepped shaft-shaped with an external thread at the head (the thread size is the same as the electrode hole) and an internal thread at the tail. The external thread of the copper terminal block 5 is screwed into the ceramic conduit 1 to contact the electrode 3. The copper terminal block 5 is inserted into a PTFE sleeve 6 for insulation of the electrode 3. The corrosion-resistant resin coating of the composite material layer 2 is applied using a CNC fiber laying machine, arranging carbon fibers 10-15mm in length at a staggered orientation of 0° / 90° to avoid stress concentration caused by disordered fibers. Low-viscosity epoxy resin (viscosity ≤ 500 mPa·s) is injected into the arranged fibers and pre-cured at 60°C for 30 minutes to form a "semi-rigid" preform. The ceramic conduit 1 uses a high-purity alumina ceramic tube formed by isostatic pressing as the main body of the measuring conduit. The electrode 3 adopts a threaded pre-embedded design. The ceramic conduit 1 and the electrode 3 are sintered together with metal materials such as platinum / iridium or Hastelloy alloy powder directly in one step through a gradient sintering process. The signal lead-out of the electrode 3 uses a copper column threaded connection, which makes the installation more convenient. A metal bellows and a composite sealing gasket are provided at the interface between the ceramic conduit 1 and the pipeline.

[0025] Please see Figure 1 , Figure 2 , Figure 3 and Figure 4 The outer layer of the composite material layer 2 is an oxidation-resistant ceramic coating. The middle layer of the composite material layer 2 is a carbon fiber layer + ceramic composite matrix. Nanoscale ceramic whiskers are grown in situ on the surface of the carbon fiber layer and combined with the ceramic composite matrix. The inner layer of the composite material layer 2 is a corrosion-resistant resin coating. The reinforcing effect of the outer metal protective layer and the middle composite material layer 2 improves the pressure resistance of the measuring tube, making it suitable for larger pipe diameters and higher pressure environments, thus expanding the application field of the electromagnetic flowmeter. The middle composite material layer 2 uses a high-strength fiber-reinforced resin matrix composite material. Through fiber interlacing and resin matrix filling, as well as winding molding process, it tightly wraps the ceramic lining to achieve stress dispersion and matching of thermal expansion coefficients. The carbon fiber layer of the composite material layer 2 uses recycled carbon fibers with a length of 5-10mm, and is mixed with basalt fibers in a 3:7 ratio. The mixture is placed in a high-speed mixer and stirred for 20 minutes. The mixed fibers are then printed into a tubular preform using a selective laser melting 3D printer. The preform is placed in a tube furnace, and a mixture of silicon tetrachloride and hydrogen (volume ratio 1:5) is introduced and held at 1000℃ for 3 hours. Silicon carbide whiskers are grown in situ on the carbon fiber surface. By combining "low-cost alternative materials + interface modification technology," the problems of high raw material costs and weak interfacial bonding are simultaneously solved. Instead of relying on pure high-performance carbon fibers, recycled carbon fibers and basalt fibers are mixed in a 3:7 ratio to prepare the preform. This reduces raw material costs and improves overall toughness through complementary fiber types. Nanoscale ceramic whiskers, such as silicon carbide whiskers, are grown in situ on the surface of carbon fibers and then composited with a ceramic matrix. The whiskers act as a "bridge" to connect the ceramic conduit 1 and the composite material layer 2, solving the problem of mismatch in their thermal expansion coefficients, while avoiding the defects of conventional coatings that are prone to wear, and improving thermal shock resistance and interfacial bonding strength. Metallurgical waste slag is used to replace part of the special ceramic powder, which is then refined through ball milling and compounded with resin. This reduces the cost of the matrix, realizes the resource utilization of industrial solid waste, and allows for flexible control of the matrix's strength and corrosion resistance by adjusting the proportion of waste slag.

[0026] Pre-treatment of raw materials: Recycled carbon fiber and basalt fiber are mixed. Recycled carbon fiber with a length of 5-10mm is mixed with basalt fiber at a ratio of 3:7 and placed in a high-speed mixer at 1500r / min for 20 minutes to ensure uniform fiber dispersion and a fiber mixing uniformity of ≥95%, avoiding fiber agglomeration that would affect subsequent molding. Steel slag with a particle size ≤10μm is mixed with alumina ceramic powder at a ratio of 4:6, and 0.5% silane coupling agent KH-550 is added. The mixture is ball-milled for 4 hours at a ball-to-material ratio of 3:1, and the particle size of the mixed powder is controlled at 5-8μm to ensure matrix fluidity and avoid uneven impregnation in subsequent processes. By combining "short process technology + intelligent monitoring" to replace traditional multi-step sintering, the problems of complex processing and batch differences are solved.

[0027] Microwave heating is used to replace conventional high-temperature furnace sintering, combined with molding processes. Microwaves enable uniform heating of the material's interior, reducing sintering time from the traditional 10-20 hours to 1-2 hours, lowering energy consumption by more than 40%, and avoiding uneven shrinkage that occurs in conventional sintering, thus improving dimensional accuracy. First, carbon fiber and resin composite preforms are directly formed using 3D printing selective laser melting technology, eliminating the need for traditional preform weaving steps. Then, ceramic slurry is injected using a vacuum pressure impregnation process. Printing allows for precise control of the fiber distribution in the preform, while impregnation ensures uniform matrix filling, solving the performance differences caused by uneven impregnation in conventional processes. It also enables the integrated fabrication of complex structures such as irregularly shaped pipes, reducing the need for subsequent processing. Temperature, pressure, and density sensors are embedded during the manufacturing process, and AI algorithms are used to adjust process parameters such as sintering temperature and infiltration pressure in real time. For example, when the sensor detects a localized low density, the infiltration pressure in the corresponding area is automatically increased to ensure that the performance deviation of each batch of products is controlled within ±5%, solving the problem of poor batch consistency in conventional technologies. A selective laser melting 3D printer is used to print the mixed fibers into a tubular preform with an inner diameter of 50mm, an outer diameter of 60mm, and a length of 300mm. The preform is placed in a tube furnace, and a mixture of silicon tetrachloride and hydrogen gas at a volume ratio of 1:5 is introduced. The furnace is held at 1000℃ for 3 hours, during which silicon carbide whiskers with a length of 5-10μm and a diameter of 0.5-1μm are grown in situ on the carbon fiber surface, with a whisker coverage of ≥90%, ensuring a 40% increase in the interfacial bonding strength between the fiber and the matrix.

[0028] By combining "multi-layer structure + composite protection", a single structural design is replaced, improving environmental adaptability and service life; The composite pipe is designed with a three-layer structure. The outer layer uses an oxidation-resistant ceramic coating, such as an alumina-zirconia composite coating. The middle layer is a carbon fiber and ceramic composite matrix that provides strength. The inner layer is a corrosion-resistant resin coating, such as polytetrafluoroethylene modified resin. The outer layer solves the problem of high-temperature oxidation resistance, the inner layer solves the problem of corrosion from corrosive media, and the middle layer ensures structural strength, avoiding the shortcomings of conventional single structures that "pay attention to one aspect but lose another." A "metal corrugated pipe + composite gasket" structure is used at the pipe joint to replace the traditional rigid connection. The corrugated pipe can absorb the thermal stress generated by the pipe due to the alternation of hot and cold, avoiding the problem of cracking that is common in conventional rigid connections. At the same time, the gasket is made of carbon fiber-rubber composite material, which combines sealing and high temperature resistance, and improves thermal shock resistance. Simultaneously, microcapsules containing low-melting-point metal repair agents, such as tin-bismuth alloys, are incorporated into the outer ceramic coating. When micro-cracks appear in the coating, the high temperature causes the microcapsules to rupture, releasing the repair agent to fill the cracks and self-repair the antioxidant barrier. This solves the problem of conventional coatings being unable to recover after wear, extending the service life of pipelines in high-temperature and oxygen-rich environments.

[0029] The oxidation-resistant ceramic coating incorporates microcapsules containing a low-melting-point metal repair agent. The low-melting-point metal repair agent is a tin-bismuth alloy microcapsule with a diameter of 50-100 μm and a core material content of 70%, mixed with alumina ceramic powder at a 1:9 ratio to form a coating slurry. This slurry is then applied to the pipe surface using a high-pressure airless spraying device, with a thickness controlled at 100-120 μm. Subsequently, it is sintered at 800℃ for 1 hour to prepare the tin-bismuth alloy microcapsule with a diameter of 50-100 μm and a core material content of 70%, mixed with alumina ceramic powder at a 1:9 ratio to form the coating slurry. The slurry was applied to the surface of the pipe using a high-pressure airless spraying device with a spraying pressure of 10MPa and a spraying distance of 150mm. The thickness was controlled at 100-120μm. The coating was then sintered at 800℃ for 1 hour. The coating adhesion was tested by cross-cut test with a strength of ≥5MPa to ensure that it would not easily fall off at high temperatures. Modified steel slag-alumina powder and resin were mixed in an 8:2 ratio to form a slurry. Under vacuum conditions of -0.095 MPa and pressure of 0.5 MPa, the slurry was impregnated into the preform for 30 minutes. The impregnated pipe was then placed in a microwave sintering furnace and heated to 1200℃ at a rate of 10℃ / min. After holding at this temperature for 1 hour, it was allowed to cool naturally, replacing the traditional 10-20 hour high-temperature sintering method. The sintered pipe had a density ≥2.2 g / cm³ and a porosity ≤5%, ensuring structural compactness. Plasma spraying was then used to further enhance the sintering process. The coating technology involves spraying an alumina-zirconia composite coating with a thickness of 50-80μm on the outer layer of the pipe and coating an inner layer with a polytetrafluoroethylene modified resin with a thickness of 20-30μm. A 316L metal corrugated pipe with a shrinkage range of ±5mm is installed at the pipe joint. A carbon fiber-rubber sealing gasket with a hardness of Shore A70 is used to complete the flexible connection. A CNC fiber laying machine is used to arrange carbon fibers with a length of 10-15mm in a 0° / 90° staggered orientation to avoid stress concentration caused by disordered fibers. Low-viscosity epoxy resin with a viscosity ≤500 mPascals per second is injected into the arranged fibers and pre-cured at 60°C for 30 minutes to form a "semi-rigid" preform, which improves the resistance to deformation during processing. The fiber orientation is ≥90%, and the hardness of the preform after pre-curing is Shore D40-50, ensuring that it is not easy to break during processing. Fiber orientation reduces processing stress concentration, resin pre-impregnation improves material rigidity, and ultrasonic-assisted cutting reduces the risk of brittle fracture. The combination of these three factors significantly improves processing efficiency and reduces crack rate.

[0030] The interface sealing blocks the oxygen infiltration channel, and the self-healing coating automatically repairs leaks when cracks appear. This dual protection ensures long-term stability in high-temperature and oxygen-rich environments. Recycled fibers and industrial waste replace some of the expensive raw materials, 3D printing reduces waste from prefabrication, and microwave sintering shortens the time and reduces energy consumption. All three work together to achieve the cost target.

[0031] In-situ growth of silicon carbide whiskers alleviates the difference in thermal expansion between the fiber and the matrix, gradient coating reduces thermal stress on the outer layer, flexible interface absorbs overall thermal deformation of the pipeline, and three layers of protection ensure stability during hot and cold cycles.

[0032] The resin pre-impregnation in the pretreatment stage not only provides rigidity to solve processing difficulties, but also provides a uniform substrate for subsequent impregnation to ensure sintering quality; the interface sealing not only blocks oxidation channels to prevent oxidation, but also reduces stress concentration caused by processing pores to assist processing, achieving "one-step measures, multiple benefits".

[0033] When cutting the completed composite pipe, use an ultrasonic-assisted cutting device with an ultrasonic frequency of 20kHz and a cutting speed of 100mm / min to cut the pipe. Ultrasonic vibration can reduce brittle fracture of the material and reduce the risk of cracking. Drilling was performed using a CNC drilling machine at a speed of 3000 r / min and a feed rate of 0.1 mm / r with a diamond-coated drill bit. By precisely controlling the parameters, delamination was avoided, and the surface roughness Ra was ≤1.6 μm. After drilling, there were no burrs or delamination on the hole wall. After processing, the pipe was placed in a vacuum tank and injected with low-melting-point glass powder slurry with a melting point of 600℃. The tank was kept at a vacuum of -0.09 MPa for 20 minutes to fill the tiny pores generated during processing. After sealing, the porosity of the pipe was ≤2%, preventing oxygen from seeping into the pores during subsequent oxidation.

[0034] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. An embedded electrode ceramic carbon fiber composite tube, characterized in that: The device includes a hollow cylindrical ceramic conduit (1). The outer wall of the ceramic conduit (1) is provided with grooves (11) and protrusions (12). The grooves (11) and protrusions (12) are interwoven with each other along the axial direction of the ceramic conduit (1). The outer wall of the ceramic conduit (1) is provided with a composite material layer (2). The center of the ceramic conduit (1) is provided with symmetrical connecting electrode holes (7). The bottom of the ceramic conduit (1) is provided with a grounding electrode hole (8). The connecting electrode hole (7) and the grounding electrode hole (8) are internally threaded. Electrodes (3) are respectively provided inside the connecting electrode hole (7) and the grounding electrode hole (8). A connecting copper post (5) is respectively connected inside the connecting electrode hole (7) and the grounding electrode hole (8). A PTFE sleeve (6) is fixed to the outer wall of the connecting copper post (5). A screw (4) is respectively connected to the other end of the connecting copper post (5). The copper terminal block (5) has a countersunk hole (51) and a stepped groove (52). The copper terminal block (5) is a stepped shaft with an external thread at the head, the thread size being the same as that of the electrode hole, and an internal thread at the tail. The external thread of the copper terminal block (5) is screwed into the ceramic conduit (1) to contact the electrode (3). The copper terminal block (5) is inserted into a PTFE sleeve (6) for insulation of the electrode (3).

2. The embedded electrode ceramic carbon fiber composite tube according to claim 1, characterized in that: The outer layer of the composite material layer (2) is an oxidation-resistant ceramic coating, the middle layer of the composite material layer (2) is a carbon fiber layer + ceramic composite matrix, the surface of the carbon fiber layer is in situ grown with nano-sized ceramic whiskers and combined with the ceramic composite matrix, and the inner layer of the composite material layer (2) is a corrosion-resistant resin coating.

3. The embedded electrode ceramic carbon fiber composite tube according to claim 2, characterized in that: Microcapsules are incorporated into the oxidation-resistant ceramic coating, and the microcapsules contain a low-melting-point metal repair agent.

4. The embedded electrode ceramic carbon fiber composite tube according to claim 2, characterized in that: The carbon fiber layer of the composite material layer (2) is made of recycled carbon fiber with a length of 5-10 mm. It is mixed with basalt fiber in a ratio of 3:7, placed in a high-speed mixer, and stirred for 20 minutes. The mixed fiber is printed into a tubular preform using a selective laser melting 3D printer. The preform is placed in a tube furnace, and a mixture of silicon tetrachloride and hydrogen gas with a volume ratio of 1:5 is introduced. The furnace is kept at 1000°C for 3 hours to grow silicon carbide whiskers in situ on the surface of the carbon fiber.

5. The embedded electrode ceramic carbon fiber composite tube according to claim 2, characterized in that: The corrosion-resistant resin coating of the composite material layer (2) is applied using a CNC fiber laying machine, where carbon fibers of 10-15mm in length are arranged in a staggered orientation at 0° / 90° to avoid stress concentration caused by disordered fibers. Low-viscosity epoxy resin with a viscosity ≤500 mPascals is injected into the arranged fibers and pre-cured at 60°C for 30 minutes to form a "semi-rigid" preform.

6. The embedded electrode ceramic carbon fiber composite tube according to claim 1, characterized in that: The ceramic conduit (1) uses a high-purity alumina ceramic tube formed by isostatic pressing as the main body of the measuring conduit. The electrode (3) adopts a threaded structure pre-embedded design. The ceramic conduit (1) and the electrode (3) are sintered together with metal materials such as platinum / iridium and Hassell alloy metal powder directly and once through a gradient sintering process.

7. The embedded electrode ceramic carbon fiber composite tube according to claim 3, characterized in that: The low-melting-point metal repair agent is a tin and bismuth alloy microcapsule with a diameter of 50-100μm and a core material content of 70%. It is mixed with alumina ceramic powder in a 1:9 ratio to form a coating slurry. The slurry is coated on the surface of the pipe using a high-pressure airless spraying device with a thickness controlled at 100-120μm, and then sintered at 800℃ for 1 hour.

8. The embedded electrode ceramic carbon fiber composite tube according to claim 1, characterized in that: The ceramic conduit (1) is provided with a metal bellows and a composite sealing gasket at the interface with the pipe.

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