Carbon-carbon plate-based nickel transition layer-carbon fiber tube composite sealing element and preparation method thereof

Abstract

The invention provides a carbon-carbon plate-based nickel transition layer-carbon fiber tube composite sealing element and a preparation method thereof. The carbon-carbon plate-based nickel transition layer-carbon fiber tube composite sealing element comprises a carbon-carbon plate base body, a nickel transition layer with a micro-nano concave-convex structure on the surface and a carbon fiber tube coating which are sequentially arranged, the preparation raw materials of the carbon fiber tube coating comprise 60-80 wt% of a carbon fiber tube, 10-20 wt% of ceramic particles and 10-20 wt% of a phenolic resin binder. The carbon-carbon plate pores are filled with the nickel layer, the sealing surface is densified through the carbon fiber tube coating, the leakage rate is controlled, the sealing stability under dynamic friction is improved through the toughness of the carbon fiber tube, and the core performance requirement of a sealing scene is met; the hardness of the carbon fiber tube coating is guaranteed through the ceramic particles, the toughness is improved through the carbon fiber tube, and the advantage of light weight of a carbon-carbon base material is reserved through the low-density characteristic of the carbon fiber tube coating.

Description

Technical Field

[0001] This invention belongs to the field of sealing technology, and particularly relates to a carbon-carbon plate-based nickel transition layer-carbon fiber tube composite seal and its preparation method. It aims to solve the performance shortcomings of existing sealing materials under harsh working conditions and meet the requirements for the stability, life and multifunctionality of seals in scenarios such as high temperature, corrosion and dynamic friction. Background Technology

[0002] Seals are core components of industrial equipment and are widely used in aerospace, chemical, energy, and precision machinery fields. Their performance directly determines the reliability and lifespan of the equipment.

[0003] As industrial technology upgrades towards high temperature, high pressure, strong corrosion, and lightweight, traditional sealing materials such as metals, ordinary ceramics, and resin-based composite materials can no longer meet the requirements of harsh working conditions. Summary of the Invention

[0004] In view of this, the purpose of the present invention is to provide a carbon-carbon plate-based nickel transition layer-carbon fiber tube composite seal and its preparation method, which achieves multiple functions such as sealing, lightweight, electromagnetic shielding, wear resistance and crack resistance in a synergistic manner.

[0005] This invention provides a carbon-carbon plate-based nickel transition layer-carbon fiber tube composite seal, comprising a carbon-carbon plate substrate, a nickel transition layer with a micro-nano uneven structure on the surface, and a carbon fiber tube coating arranged sequentially.

[0006] The raw materials for preparing the carbon fiber tube coating include 60-80 wt% carbon fiber tube, 10-20 wt% ceramic particles, and 10-20 wt% phenolic resin binder.

[0007] Preferably, the carbon-carbon plate substrate has a thickness of 3~10mm, a porosity of 15~20%, and a roughness Ra=0.8~1.2μm.

[0008] Preferably, the thickness of the nickel transition layer with micro-nano uneven structure on the surface is 100~200μm;

[0009] The nickel transition layer contains 98.5% to 99.5% nickel and 0.5% to 1.5% phosphorus.

[0010] Preferably, the roughness Ra of the nickel transition layer with micro-nano uneven structure on the surface is 1.5~2μm;

[0011] The thickness of the carbon fiber tube coating is 80~150μm; the hardness is ≥2500.

[0012] Preferably, the coefficient of thermal expansion of the carbon-carbon plate substrate is 1×10⁻⁶. -6 ~3×10 -6 / ℃;

[0013] The coefficient of thermal expansion of the nickel transition layer with a micro-nano uneven structure on its surface is 13 × 10⁻⁶. -6 / ℃;

[0014] The coefficient of thermal expansion of the carbon fiber tube coating is 8×10⁻⁶. -6 ~10×10 -6 / ℃.

[0015] Preferably, the carbon fiber tube has a diameter of 5~10μm and a length of 50~100μm;

[0016] The ceramic particles are selected from silicon carbide or alumina, and the particle size is 1~5μm;

[0017] The phenolic resin adhesive has a glass transition temperature ≥250℃ after curing.

[0018] This invention provides a method for preparing the carbon-carbon plate-based nickel transition layer-carbon fiber tube composite seal as described above, comprising the following steps:

[0019] After grinding the surface of the carbon carbon plate, ultrasonic degreasing is performed, followed by chemical roughening to obtain a pretreated carbon carbon plate.

[0020] The pretreated carbon plate is activated with colloidal palladium, de-gelled with hydrochloric acid, then chemically plated with nickel, micro-etched with dilute sulfuric acid, and then electroplated with thickened nickel. Finally, it is roughened by plasma to form a nickel transition layer with a micro-nano uneven structure on the surface.

[0021] 60-80 wt% carbon fiber tube, 10-20 wt% ceramic particles, and 10-20 wt% phenolic resin binder are ball-milled and mixed with ethanol to form a slurry with a viscosity of 200-300 mPa·s. The slurry is then sprayed using plasma spraying and directly cured to obtain a carbon-carbon plate-based nickel transition layer-carbon fiber tube composite seal.

[0022] Preferably, the electroless nickel plating solution includes 26-28 g / L nickel sulfate, 19-21 g / L reducing agent, 28-32 g / L complexing agent, 14-16 g / L sodium acetate, and 1.8-2.2 mg / L stabilizer; the electroless nickel plating temperature is 84-86℃, and the pH value is 6.5.

[0023] The plating solution used for thickened nickel electroplating includes nickel sulfamate 380~420 g / L, nickel chloride 5.5~6.5 g / L, boric acid 28~32 g / L and sodium dodecyl sulfate 0.35~0.45 g / L; the electroplating temperature for thickened nickel is 48~52℃, and the pH value is 4.0.

[0024] Preferably, the plasma spraying uses a power of 35~45kW, a spraying distance of 120~150mm, and a spraying rate of 6~8g / min;

[0025] The curing temperature is 100~160℃ and the time is 110~130min.

[0026] Preferably, the fracture toughness of the carbon-carbon plate-based nickel transition layer-carbon fiber tube composite seal is ≥3.5 MPa·m. 1 / 2 Friction coefficient ≤ 0.08, leakage rate ≤ 1×10 -7 Pa·m 3 / s, density is 1.2~1.5g / cm³ 3 .

[0027] This invention provides a carbon-carbon plate-based nickel transition layer-carbon fiber tube composite seal, comprising a carbon-carbon plate substrate, a nickel transition layer with a micro-nano uneven structure on the surface, and a carbon fiber tube coating arranged sequentially. The raw materials for preparing the carbon fiber tube coating include 60-80 wt% carbon fiber tube, 10-20 wt% ceramic particles, and 10-20 wt% phenolic resin binder. This invention controls the leakage rate by filling the pores of the carbon-carbon plate with a nickel layer and densifying the sealing surface with a carbon fiber tube coating. It also utilizes the toughness of the carbon fiber tube to improve the sealing stability under dynamic friction, meeting the core performance requirements of sealing applications. The carbon fiber tube coating ensures hardness through ceramic particles and enhances toughness through the carbon fiber tube, while its low-density characteristics retain the lightweight advantages of the carbon-carbon substrate. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of the process for preparing a carbon-carbon plate-based nickel transition layer-carbon fiber tube composite seal according to an embodiment of the present invention. Detailed Implementation

[0029] This invention provides a carbon-carbon plate-based nickel transition layer-carbon fiber tube composite seal, comprising a carbon-carbon plate substrate, a nickel transition layer with a micro-nano uneven structure on the surface, and a carbon fiber tube coating arranged sequentially.

[0030] The raw materials for preparing the carbon fiber tube coating include 60-80 wt% carbon fiber tube, 10-20 wt% ceramic particles, and 10-20 wt% phenolic resin binder.

[0031] The sealing component provided by this invention is a composite sealing structure of "carbon-carbon plate-nickel transition layer-carbon fiber tube coating". The nickel layer fills the pores of the carbon-carbon plate, the carbon fiber tube coating densifies the sealing surface, controls the leakage rate, and utilizes the toughness of the carbon fiber tube to improve the sealing stability under dynamic friction, thus meeting the core performance requirements of sealing scenarios.

[0032] The composite seal provided by this invention includes a carbon-carbon plate matrix, which provides high-temperature support and a lightweight foundation. The carbon-carbon plate matrix has a thickness of 3-10 mm, a porosity of 15-20%, and a roughness Ra of 0.8-1.2 μm. Preferably, this invention uses a carbon-carbon plate formed by combining polyacrylonitrile (PAN)-based carbon fiber and resin-based carbon, with a thickness of 3-10 mm. The thickness varies depending on the sealing application; for example, 5-8 mm is used for pump and valve seals, and 3-5 mm for aerospace precision seals. The porosity is 15-20%; too high a porosity makes subsequent nickel layer filling difficult, while too low a porosity results in insufficient substrate toughness. The tensile strength at room temperature is ≥300 MPa, and the long-term operating temperature is ≥1000℃.

[0033] The carbon-carbon plate substrate surface must undergo ultrasonic degreasing and chemical roughening to ensure that the surface is free of oil stains, i.e., oil residue ≤0.1mg / cm³. 2 With a roughness Ra=0.8~1.2μm, it provides a uniform substrate for the nickel transition layer.

[0034] The carbon-carbon plate-based nickel transition layer-carbon fiber tube composite seal provided by this invention includes a nickel transition layer with a micro-nano uneven structure on the surface of the carbon-carbon plate substrate. The nickel transition layer is a two-layer structure consisting of a chemically plated base nickel layer and an electroplated thickened nickel layer. The thickness of the nickel transition layer is 100-200 μm, wherein the base nickel layer is 20-30 μm thick to ensure bonding with the substrate; the thickened nickel layer is 80-170 μm thick to ensure density. The nickel transition layer contains 98.5-99.5% Ni and 0.5-1.5% P by mass. Phosphorus reduces internal stress in the nickel layer, preventing cracking.

[0035] This invention achieves a "micro-nano uneven structure" on the surface through plasma roughening, which on the one hand mechanically anchors the upper carbon fiber tube coating, and on the other hand increases the contact area with the coating; the coefficient of thermal expansion of the nickel transition layer with the micro-nano uneven structure on the surface is 13×10. -6 / ℃, with a thermal expansion coefficient of 1×10⁻⁶ compared to the carbon-carbon plate substrate. -6 ~3×10 -6 / ℃ and the coefficient of thermal expansion of the carbon fiber tube coating is 8×10. -6 ~10×10 -6 / ℃, forming a gradient match and reducing temperature stress.

[0036] The carbon-carbon plate-based nickel transition layer-carbon fiber tube composite seal provided by the present invention includes a carbon fiber tube coating disposed on the nickel transition layer; the thickness of the carbon fiber tube coating is 80~150μm, specifically 80μm, 90μm, 100μm, 110μm, 120μm, 130μm, 140μm or 150μm; and the hardness is ≥2500.

[0037] In this invention, the raw materials for preparing the carbon fiber tube coating include 60-80 wt% carbon fiber tube, 10-20 wt% ceramic particles, and 10-20 wt% phenolic resin binder.

[0038] The carbon fiber tube has a content of 60-80 wt%, specifically 60 wt%, 65 wt%, 70 wt%, 75 wt%, or 80 wt%. The carbon fiber tube has a diameter of 5-10 μm and a length of 50-100 μm, and the carbon fiber tube with the above parameters provides toughness and lightweight.

[0039] The content of the ceramic particles is 10~20 wt%, specifically 10 wt%, 12 wt%, 14 wt%, 16 wt%, 18 wt%, or 20 wt%. The ceramic particles are selected from silicon carbide or silicon oxide and have a particle size of 1~5 μm; the ceramic particles provide wear resistance.

[0040] The phenolic resin binder has a content of 10~20 wt%, specifically 10 wt%, 12 wt%, 14 wt%, 16 wt%, 18 wt%, or 20 wt%. The phenolic resin binder is selected as a high-temperature resistant type, with a curing thickness glass transition temperature ≥250℃, to achieve intercomponent bonding.

[0041] This invention provides a method for preparing the carbon-carbon plate-based nickel transition layer-carbon fiber tube composite seal as described above, comprising the following steps:

[0042] The carbon carbon plate is ground and then ultrasonically degreased, followed by chemical roughening to obtain a pretreated carbon carbon plate.

[0043] The pretreated carbon plate is activated with colloidal palladium, de-gelled with hydrochloric acid, then chemically plated with nickel, micro-etched with dilute sulfuric acid, and then electroplated with thickened nickel. Finally, it is roughened by plasma to form a nickel transition layer with a micro-nano uneven structure on the surface.

[0044] 60-80 wt% carbon fiber tube, 10-20 wt% ceramic particles, and 10-20 wt% phenolic resin binder are ball-milled and mixed with ethanol to form a slurry with a viscosity of 200-300 mPa·s. The slurry is then sprayed using plasma spraying and directly cured to obtain a carbon-carbon plate-based nickel transition layer-carbon fiber tube composite seal.

[0045] The method provided by this invention includes a process of substrate pretreatment, transition layer densification, functional coating customization, and finished product post-treatment, achieving multi-functional integration of "high temperature sealing stability + wear resistance and crack resistance + lightweight + electromagnetic shielding".

[0046] This invention involves grinding the surface of a carbon carbon fiber plate, followed by ultrasonic degreasing and chemical roughening to obtain a pretreated carbon carbon fiber plate. Preferably, 500-grit silicon carbide sandpaper with a hardness of HV1800 is used to grind the carbon carbon fiber plate surface. The purpose of grinding is to make the surface resin layer 3-20 μm higher than the carbon fiber, preventing the carbon fiber from being directly exposed and oxidized. This invention also controls the surface roughness Ra of the carbon carbon fiber plate to ≤0.5 μm to ensure thorough subsequent degreasing; after grinding, compressed air is used to blow away surface dust.

[0047] This invention involves placing the ground carbon steel plate into an ultrasonic cleaner at a power of 20-40 kHz; adding acetone solvent and ultrasonically cleaning at 25-30°C for 10-15 minutes; this invention utilizes the ultrasonic cavitation effect to remove surface oil contaminants, such as residual cutting fluid and fingerprints, achieving an oil removal rate of ≥99%. After ultrasonic cleaning, the plate is rinsed three times with deionized water and dehydrated with ethanol to prevent water residue from affecting subsequent roughening.

[0048] This invention involves immersing the degreased carbon-carbon steel plate in a 35% (w / w) nitric acid solution. The concentration of the nitric acid solution needs precise control; too low a concentration will result in insufficient roughening, while too high a concentration will corrode the substrate. The plate is then kept at a temperature of 38-42°C for 15-20 minutes. The strong oxidizing properties of nitric acid create honeycomb-like micropores on the surface of the carbon-carbon steel plate, with a pore size of 1-3 μm. These micropores increase the contact area with the nickel layer. After roughening, the plate is ultrasonically cleaned in ethanol to remove residual acid, and then dried. The drying temperature is 75-85°C, specifically 75°C, 80°C, or 85°C, for 110-130 minutes, specifically 110 minutes, 115 minutes, 120 minutes, 125 minutes, or 130 minutes.

[0049] The present invention involves activating the pretreated carbon-carbon plate with colloidal palladium, debinding it with hydrochloric acid, then chemically plating a base nickel layer, micro-etching it with dilute sulfuric acid, followed by electroplating a thicker nickel layer, and then plasma roughening it to form a nickel transition layer with a micro-nano uneven structure on the surface.

[0050] In this invention, the colloidal palladium activation uses a colloidal palladium solution comprising 0.28~0.32 g / L PdCl2, 10 mL / L hydrochloric acid, and the remainder water. The colloidal palladium solution is kept at a temperature of 45~55℃, specifically 45℃, 50℃, or 55℃, for 9~11 min, specifically 9 min, 10 min, or 11 min. After this temperature holding period, the colloidal palladium particles adsorb onto the surface of the carbon-carbon plate, with a particle size of 5~10 nm, forming "catalytically active sites" for subsequent electroless plating, ensuring uniform deposition of nickel ions.

[0051] After activation, the colloidal palladium is immediately immersed in a 5-10% hydrochloric acid solution for decolloidalization. The decolloidalization temperature is 38-42℃, specifically 38℃, 40℃, or 42℃; the decolloidalization time is 30s-60s, specifically 30s, 35s, 40s, 45s, 50s, 55s, or 60s. This invention removes the chloride ion protective film on the surface of the colloidal palladium through decolloidalization, exposing the active palladium atoms and avoiding "pinhole" defects in the subsequent electroless nickel plating layer.

[0052] In this invention, a carbon-carbon plate after degumming is placed in a chemical plating bath. The plating solution includes 26-28 g / L nickel sulfate, 19-21 g / L reducing agent, 28-32 g / L complexing agent, 14-16 g / L sodium acetate, and 1.8-2.2 mg / L stabilizer. The reducing agent is sodium hypophosphite. The complexing agent includes lactic acid and citric acid in a mass ratio of 2:1. The stabilizer is thiourea.

[0053] The electroless nickel plating temperature is 84~86℃, specifically 84℃, 85℃, or 86℃; the pH value for the electroless nickel plating is 6.5, and this invention uses dilute sulfuric acid or sodium hydroxide to adjust the required pH value; the loading amount is 1 dm³. 2 / L; electroless nickel plating is performed by holding the substrate at a temperature of 55-60 minutes in the plating bath. This invention utilizes a reducing agent to... 2+ Ni atoms are reduced to deposited on the substrate surface to form a 20-30 μm base nickel layer. A composite complexing agent prevents Ni(OH)2 precipitation, and a stabilizer inhibits the unevenness caused by "plating autocatalysis". After plating, the surface is cleaned with acetone to remove residual plating solution and then dried. The drying temperature is 75-85℃, specifically 80℃.

[0054] This invention involves immersing a carbon-carbon plate with a base nickel layer in 20wt% dilute sulfuric acid for etching. The etching temperature is 38~42℃, specifically 38℃, 40℃, or 42℃; the etching time is 30s~120s, specifically 30s, 40s, 50s, 60s, 70s, 80s, 90s, 100s, 110s, or 120s. This invention removes the oxide film (NiO) on the surface of the base nickel layer through dilute sulfuric acid etching, exposing a fresh nickel surface, providing a "clean complexing surface" for electroplating thicker nickel, and preventing interlayer peeling.

[0055] This invention involves electroplating thickened nickel after micro-etching with dilute sulfuric acid. Specifically, a micro-etched carbon plate is placed in an electroplating bath as the cathode; a pure nickel plate with a purity ≥99.9% is used as the anode. The plating solution for thickened nickel electroplating includes 380~420 g / L nickel sulfamate, 5.5~6.5 g / L nickel chloride, 28~32 g / L boric acid, and 0.35~0.45 g / L sodium dodecyl sulfate; in a specific embodiment, the plating solution includes 400 g / L nickel sulfamate, 6 g / L nickel chloride, 30 g / L boric acid, and 0.4 g / L sodium dodecyl sulfate. The electroplating temperature for thickened nickel in this invention is 48~52℃, specifically 48℃, 50℃, or 52℃; the pH value is 4.0, preferably adjusted using boric acid buffer.

[0056] This invention involves placing a nickel-plated, thickened carbon-carbon plate into a plasma treatment machine for plasma roughening under an argon atmosphere. The power is 20-30 kW, and the plasma roughening time is 5-8 minutes. Argon ions bombard the nickel layer surface, forming a micro-nano uneven structure (similar to a "serrated" shape) with Ra=1.5-2.0 μm. This provides mechanical anchoring points for the subsequent carbon fiber tube coating, improving the bonding strength by more than 30%. This invention performs plasma roughening on the nickel layer surface to form a micro-nano anchoring structure; selects a carbon fiber tube coating with a coefficient of thermal expansion close to that of the nickel layer, and forms a chemical bond through an adhesive, improving interlayer bonding strength and preventing interlayer delamination under temperature cycling.

[0057] This invention involves ball milling 60-80 wt% carbon fiber tube, 10-20 wt% ceramic particles, and 10-20 wt% phenolic resin binder with ethanol to form a slurry with a viscosity of 200-300 mPa·s. The slurry is then sprayed using plasma spraying and directly cured to obtain a carbon-carbon plate-based nickel transition layer-carbon fiber tube composite seal.

[0058] In this invention, the amount of ethanol added accounts for 28-32% of the total mass of the carbon fiber tube, ceramic particles, and phenolic resin binder. The invention involves ball milling in a planetary ball mill at a speed of 200 rpm for 55-65 minutes. Through the dispersing effect of ethanol and the shear force of the ball mill, SiC particles uniformly fill the gaps in the carbon fiber tube, and the resin coats the surface to form a "core-shell" structure. Ultimately, the slurry annual pressure is controlled at 200-300 mPa·s to ensure smooth spraying.

[0059] This invention employs atmospheric plasma spraying equipment for plasma spraying; the plasma spraying power is 35~45kW to ensure that the resin partially melts but does not decompose; the spraying distance is 120~150mm to avoid overheating and oxidation of the nickel layer; the powder feeding rate is 6~8g / min; the slurry is heated by the plasma flame, with a center temperature of 10000℃ and an edge temperature of 800~1000℃, and the ethanol evaporates instantly. The carbon fiber and SiC particles are deposited on the surface of the nickel layer under the bonding of the resin, forming a coating of 80~150μm with a thickness error of ≤±5μm.

[0060] This invention involves placing the sprayed coating into a curing oven for curing. First, the coating is dried at 80°C in air for 30 minutes to remove residual ethanol; then, curing is performed under argon protection at a temperature of 100-160°C for 110-130 minutes.

[0061] In a specific embodiment of the present invention, the preferred curing method is to use a stepped temperature increase of "100℃×1h + 150℃×2h"; the resin forms a three-dimensional network structure through the condensation reaction of phenolic hydroxyl groups and methylene groups, which firmly bonds the carbon fiber tube to the SiC particles, while retaining more than 5% elongation at break, and the final coating hardness HV≥2500, and the flatness of the sealing surface ≤0.02mm / m.

[0062] The fracture toughness of the carbon-carbon plate-based nickel transition layer-carbon fiber tube composite seal prepared by this invention is ≥3.5 MPa·m. 1 / 2 Friction coefficient ≤ 0.08, leakage rate ≤ 1×10 -7 Pa·m 3 / s, density is 1.2~1.5g / cm³ 3 .

[0063] The composite seal provided by this invention has a three-layer structure: a carbon-carbon plate, a plasma-coated roughened nickel transition layer, and a carbon fiber tube coating. The micro-nano anchoring structure of the nickel transition layer and the direct resin curing process of the carbon fiber tube coating form a dual combination, which not only solves the problems of insufficient interlayer bonding and mismatch of thermal expansion coefficients in existing technologies, but also compensates for the brittleness of a single coating through the synergy of the toughness of the carbon fiber tube and the wear resistance of the ceramic particles, allowing the seal to maintain its density under dynamic friction and temperature cycling conditions. At the same time, the dual-layer process of "chemical plating + electroplating" of the nickel transition layer achieves multi-functional integration of pore filling, oxidation resistance, and electromagnetic shielding. The low-density characteristics of the carbon fiber tube coating retain the lightweight advantage of the carbon-carbon substrate. Combined with the synergistic process of spraying and curing, it ultimately achieves a multi-functional synergy of sealing, lightweight, wear resistance, crack resistance, and electromagnetic shielding, perfectly adapting to harsh sealing scenarios such as medium and high temperature and strong corrosion, filling the application gap of carbon-carbon plates in the sealing field.

[0064] Before testing, the carbon-carbon plate-based nickel transition layer-carbon fiber tube composite sealant of the present invention undergoes the following treatment: precision grinding: the sealing surface is ground on a precision grinding machine with 800-grit diamond sandpaper (hardness HV2500) to control the flatness of the sealing surface ≤0.02mm / m (detected with a laser flatness meter) to ensure that the sealing surface fits tightly with the part to be sealed and reduce leakage channels.

[0065] This invention conducts performance tests on carbon-carbon plate-based nickel transition layer-carbon fiber tube composite seals: ① Leakage rate test: a helium mass spectrometer leak detector (minimum detectable leak rate 1×10⁻⁶) is used. -12 Pa·m 3 / s), tested at room temperature and pressure of 1MPa; ② Bonding strength test: using a tensile shear tester (range 0-50kN) to test the tensile shear bonding strength between the nickel layer and the carbon fiber tube coating; ③ Electromagnetic shielding test: using a shielding effectiveness meter (test frequency 30MHz~1GHz); 4. Elongation at break: electronic tensile tester, loading rate 2mm / min, specimen gauge length 20mm); 5. Coating hardness: Vickers hardness tester, load 1kg, holding time 15s.

[0066] To further illustrate the present invention, the following detailed description, in conjunction with embodiments, of a carbon-carbon plate-based nickel transition layer-carbon fiber tube composite seal and its preparation method, is provided by the present invention, but should not be construed as limiting the scope of protection of the present invention.

[0067] use Figure 1 The process flow diagram shown illustrates the preparation of a carbon-carbon plate-based nickel transition layer-carbon fiber tube composite seal.

[0068] Example 1

[0069] Step 1: Carbon board pretreatment:

[0070] Grinding process: The surface of the carbon fiber plate is ground on a grinding machine using 500-grit silicon carbide sandpaper (hardness HV1800) to make the surface resin layer 12μm higher than the carbon fiber and to control the surface roughness Ra≤0.5μm (=0.3μm); after grinding, the surface dust is blown away with compressed air.

[0071] Ultrasonic degreasing: The ground carbon plate is placed in an ultrasonic cleaner (power 30kHz, acetone solvent (analytical grade, purity ≥99.5%)) and ultrasonicated at 28℃ for 12 minutes. The oil removal rate is ≥99%. Then it is rinsed 3 times with deionized water and dehydrated with ethanol.

[0072] Chemical roughening: Immerse the degreased carbon plate in a 35% nitric acid solution and keep it at 40°C for 18 minutes; after roughening, ultrasonically clean it with ethanol for 5 minutes to remove residual acid from the surface, and then dry it at 80°C for 2 hours.

[0073] Step 2: Preparation of Nickel Transition Layer

[0074] Activation of colloidal palladium: Immerse a carbon plate in a 0.3 g / L colloidal palladium solution (composition: PdCl2 0.3 g / L + hydrochloric acid 10 mL / L, water balance) and keep it at 50 °C for 10 min.

[0075] Hydrochloric acid degelatination: Immediately after activation, immerse in 8% hydrochloric acid solution (40℃) for 45 seconds to degelatinate.

[0076] Electroless nickel plating: The descaled carbon-carbon plate is placed in an electroless plating bath. The plating solution formula includes 27 g / L nickel sulfate, 20 g / L sodium hypophosphite, 30 g / L complexing agent (lactic acid:citric acid = 2:1), 15 g / L sodium acetate, and 2 mg / L thiourea stabilizer. The temperature is controlled at 85℃, pH at 6.5, and the loading rate is 1 dm³. 2 / L, heat for 1 hour to form a 25μm base nickel layer. The composite complexing agent prevents Ni(OH)2 precipitation, and the stabilizer inhibits the unevenness caused by "plating autocatalysis". After plating, the surface is cleaned with acetone to remove residual plating solution, and then dried at 80℃.

[0077] Dilute sulfuric acid micro-etching: Immerse the bottom nickel layer carbon plate in 20% dilute sulfuric acid (40℃) for 1 minute to remove the oxide film (NiO) on the surface of the bottom nickel layer, exposing the fresh nickel surface, providing a "clean bonding surface" for electroplating thicker nickel, and avoiding interlayer peeling.

[0078] Thickened nickel electroplating: A micro-etched carbon plate is used as the cathode (the anode is a pure nickel plate with a purity ≥99.9%) and placed in the electroplating tank. The plating solution formula is: nickel sulfamate 400g / L, nickel chloride 6g / L, boric acid 30g / L and sodium dodecyl sulfate 0.4g / L. The temperature is controlled at 50℃, pH 4.0, and current density at 4A / dm². Electroplating is carried out for 8~10 hours to ensure a uniform plating thickness of 130μm. Nickel chloride improves the toughness of the plating layer, and sodium dodecyl sulfate prevents the formation of "pitting" in the plating layer. The plating solution is stirred every 2 hours during the electroplating process to avoid uneven concentration.

[0079] Plasma roughening: The electroplated nickel-coated carbon plate is placed in a plasma treatment machine (argon atmosphere, purity ≥99.99%), with a power of 25kW and a treatment time of 6 minutes. Argon ions bombard the surface of the nickel layer to form a micro-nano uneven structure with Ra=1.8μm (similar to "serration"), which provides mechanical anchoring points for the subsequent carbon fiber tube coating, improving the bonding force by more than 30%.

[0080] Step 3: Preparation of carbon fiber tube coating

[0081] Coating slurry preparation: Weigh the raw materials according to the ratio of "70wt% multi-walled carbon fiber tubes + 15wt% SiC particles + 15wt% p-tert-butylphenol formaldehyde resin", add 30% anhydrous ethanol of the total mass, and put it into a planetary ball mill (speed 200 r / min) for 1 hour; through the dispersion effect of ethanol and the shear force of ball milling, the SiC particles uniformly fill the gaps of carbon fiber tubes, and the resin coats the fiber surface to form a "core-shell" structure. Finally, control the slurry viscosity to 250 mPa·s (to ensure smooth spraying).

[0082] Plasma spraying: Atmospheric plasma spraying equipment (model: APS-3000) is used, with the following parameters set: power 40kW, spraying distance 135mm, and spraying rate 7g / min; the slurry is heated by the plasma flame: center temperature 10000℃, edge temperature 800-1000℃, ethanol evaporates instantly, and carbon fiber tubes and SiC particles are deposited on the nickel layer surface under resin bonding to form a 120μm coating (thickness error ≤±5μm).

[0083] Direct resin curing: The sprayed coating is placed in a curing oven and dried at 80℃ in air for 30 minutes to remove residual ethanol; then, it is switched to argon protection (flow rate 2L / min) and cured in a stepped temperature increase of "100℃×1h + 150℃×2h" to firmly bond the carbon fiber tube to the SiC particles, while retaining more than 5% elongation at break. The final coating hardness HV≥2500 and the flatness of the sealing surface ≤0.02mm / m.

[0084] Step 4: Pre-test processing

[0085] Precision grinding: The sealing surface is ground on a precision grinding machine using 800-grit diamond sandpaper (hardness HV2500) to control the flatness of the sealing surface to ≤0.02mm / m (detected with a laser flatness meter) to ensure that the sealing surface fits tightly with the part to be sealed and reduce leakage channels.

[0086] The present invention uses the above-mentioned performance testing method to conduct performance tests on composite seals, and the results are as follows: leakage rate is 6.8 × 10⁻⁶. -9 Pa·m 3 / s; the tensile-shear bond strength between the nickel layer and the carbon fiber tube coating is 35MPa; the shielding performance test data is 75dB; the density is 3.2g / cm³. 3 The coefficient of friction is 0.07; the coating hardness is HV2800; and the elongation at break is 8.5%.

[0087] Example 2: Adjusting the concentration of colloidal palladium and the ratio of complexing agent

[0088] Process differentiation adjustments (compared with Example 1)

[0089] 1. Colloidal palladium activation: increase the concentration to 0.4 g / L (PdCl2 0.4 g / L + hydrochloric acid 12 mL / L), temperature 52℃, hold for 12 min (excess palladium ions lead to coarse crystals in the coating).

[0090] 2. Electroless nickel plating: The ratio of the composite complexing agent was changed to lactic acid:citric acid = 3:1 (excessive complexing ability inhibits uniform nickel layer deposition).

[0091] The remaining processes are completely consistent with those in Example 1.

[0092] The present invention uses the above-mentioned performance testing method to conduct performance tests on composite seals, and the results are as follows: leakage rate is 8.3 × 10⁻⁶. -9 Pa·m 3 / s (increased by 22.1%, coarse coating crystals with micropores); the tensile-shear bonding force between the nickel layer and the carbon fiber tube coating was 32MPa (decreased by 8.6%, uneven bonding between the nickel layer and the substrate interface); shielding performance test data was 70dB (decreased by 6.7%, decreased coating density, weakened conductivity continuity); density: 3.1g / cm³ 3 (Reduced by 3.1%, coating porosity slightly increased); friction coefficient: 0.09 (increased by 28.6%, coating surface roughness increased, frictional resistance increased); coating hardness: HV2650 (reduced by 5.4%, SiC particle dispersion uniformity decreased); elongation at break: 7.2% (reduced by 15.3%, nickel layer internal stress increased, coating toughness weakened).

[0093] Example 3: Adjusting the electroplating current density and coating resin type

[0094] Process differentiation adjustments (only 2 variables, the rest are the same as in Example 1)

[0095] 1. Thickened nickel plating: Current density increased to 5A / dm 2 The electroplating time is shortened to 7.5 hours (the total thickness of the nickel layer is maintained at 130 μm).

[0096] 2. Coating slurry preparation: The resin is replaced with phenolic epoxy resin, the dosage is kept at 15wt%, and the ball milling time is extended to 1.5h.

[0097] The present invention uses the above-mentioned performance testing method to conduct performance tests on composite seals, and the results are as follows: leakage rate is 9.1×10⁻ 9 Pa·m 3 / s (increased by 33.8%, high current density leads to increased coating stress and microcracks); the tensile-shear bonding strength between the nickel layer and the carbon fiber tube coating is 31MPa (decreased by 11.4%, the interfacial compatibility between epoxy resin and nickel layer is weaker than that of the original phenolic resin); shielding performance test data is 72dB (decreased by 4.0%, coating stress cracks lead to discontinuity in conductive path); density: 3.08g / cm³ 3 (Reduced by 3.8%, insufficient resin crosslinking, increased coating porosity); Coefficient of friction: 0.085 (increased by 21.4%, increased frictional resistance due to microcracks in the coating); Coating hardness: HV2700 (reduced by 3.6%, insufficient resin bonding strength, particles easily fall off); Elongation at break: 6.2% (reduced by 27.1%, epoxy resin is more brittle than the original resin).

[0098] Example 4: Adjusting the plasma atmosphere + chemically coarsening acid solution

[0099] Process differentiation adjustments (only 2 variables, the rest are the same as in Example 1)

[0100] 1. Chemical roughening: Replace the acid solution with a mixture of 25% sulfuric acid and 10% nitric acid, and keep warm at 40℃ for 18 minutes;

[0101] 2. Plasma roughening: The argon atmosphere was changed to nitrogen (purity ≥99.99%), power 25kW, treatment for 6min (surface roughness Ra=1.2μm).

[0102] The present invention uses the above-mentioned performance testing method to conduct performance tests on composite seals, and the results are as follows: the leakage rate is 10.5 × 10⁻ 9 Pa·m 3 / s (increased by 54.4%, excessive coarsening with mixed acid led to pitting on the substrate surface, resulting in poor sealing and adhesion); the tensile-shear bonding strength between the nickel layer and the carbon fiber tube coating was 29 MPa (decreased by 17.1%, due to weak nitrogen plasma bombardment intensity and shallow anchoring structure on the nickel layer surface); shielding performance test data was 68 dB (decreased by 9.3%, due to increased contact resistance between the nickel layer and the substrate caused by pitting in the substrate); density: 3.05 g / cm³ 3 (4.7% decrease, increased gap between coating and nickel layer interface); coefficient of friction: 0.1 (42.9% increase, increased microscopic defects on sealing surface, increased frictional resistance); coating hardness: HV2580 (7.9% decrease, insufficient anchoring structure, coating is easily crushed); elongation at break: 5.8% (31.8% decrease, coating and nickel layer interface is easily peeled off, toughness decreases).

[0103] Example 5: Adjusting the coating slurry ratio + plasma spraying powder feeding rate

[0104] 1. Process differentiation adjustment (only 2 variables, the rest are the same as in Example 1)

[0105] Coating slurry preparation: The raw material ratio is changed to: 65wt% multi-walled carbon fiber tubes + 20wt% SiC particles + 15wt% resin, while the amount of anhydrous ethanol added and the ball milling parameters remain unchanged;

[0106] Plasma spraying: Spraying rate increased to 9g / min, power 40kW, and spraying distance 135mm unchanged (coating thickness 135μm, error ≤±4μm).

[0107] The present invention uses the above-mentioned performance testing method to conduct performance tests on composite seals, and the results are as follows: leakage rate is 9.7×10⁻ 9 Pa·m 3 / s (increased by 42.6%, excessively rapid powder feeding led to insufficient slurry melting and poor coating density); the tensile-shear bonding force between the nickel layer and the carbon fiber tube coating was 30MPa (decreased by 14.3%, due to a decrease in carbon fiber content and fewer anchoring points); the shielding performance test data was 66dB (decreased by 12.0%, due to a decrease in the proportion of conductive phase in carbon fiber and fewer shielding pathways); density: 3.02g / cm³ 3 (Reduced by 5.6%, due to insufficient coating melting and high internal porosity); Friction coefficient: 0.095 (increased by 42.9%, due to excessive SiC particle agglomeration and rough friction surface); Coating hardness: HV2550 (reduced by 8.9%, due to stress concentration caused by particle agglomeration and decreased hardness); Elongation at break: 5.5% (reduced by 35.3%, due to weakened carbon fiber reinforcement and significantly increased coating brittleness).

[0108] As can be seen from the above embodiments, the present invention provides a carbon-carbon plate-based nickel transition layer-carbon fiber tube composite seal, comprising a carbon-carbon plate substrate, a nickel transition layer with a micro-nano uneven structure on the surface, and a carbon fiber tube coating arranged sequentially; the raw materials for preparing the carbon fiber tube coating include 60-80 wt% carbon fiber tube, 10-20 wt% ceramic particles, and 10-20 wt% phenolic resin binder. The present invention controls the leakage rate by filling the pores of the carbon-carbon plate with a nickel layer and densifying the sealing surface with a carbon fiber tube coating, and improves the sealing stability under dynamic friction by utilizing the toughness of the carbon fiber tube, thus meeting the core performance requirements of sealing scenarios; the carbon fiber tube coating ensures hardness through ceramic particles and enhances toughness through the carbon fiber tube, and its low-density characteristics retain the lightweight advantages of the carbon-carbon substrate.

[0109] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A carbon-carbon plate-based nickel transition layer-carbon fiber tube composite seal, comprising a carbon-carbon plate substrate, a nickel transition layer with a micro-nano uneven structure on the surface, and a carbon fiber tube coating arranged sequentially. The raw materials for preparing the carbon fiber tube coating include 60-80 wt% carbon fiber tube, 10-20 wt% ceramic particles, and 10-20 wt% phenolic resin binder.

2. The carbon-carbon plate-based nickel transition layer-carbon fiber tube composite sealant according to claim 1, characterized in that, The carbon-carbon plate substrate has a thickness of 3~10mm, a porosity of 15~20%, and a roughness Ra=0.8~1.2μm.

3. The carbon-carbon plate-based nickel transition layer-carbon fiber tube composite sealant according to claim 1, characterized in that, The thickness of the nickel transition layer with micro-nano uneven structure on the surface is 100~200μm; The nickel transition layer contains 98.5% to 99.5% nickel and 0.5% to 1.5% phosphorus.

4. The carbon-carbon plate-based nickel transition layer-carbon fiber tube composite sealant according to claim 1, characterized in that, The surface roughness Ra of the nickel transition layer with micro-nano uneven structure is 1.5~2μm; The thickness of the carbon fiber tube coating is 80~150μm; Hardness ≥2500.

5. The carbon-carbon plate-based nickel transition layer-carbon fiber tube composite sealant according to claim 1, characterized in that, The coefficient of thermal expansion of the carbon-carbon plate substrate is 1×10⁻⁶. -6 ~3×10 -6 / ℃; The coefficient of thermal expansion of the nickel transition layer with a micro-nano uneven structure on its surface is 13 × 10⁻⁶. -6 / ℃; The coefficient of thermal expansion of the carbon fiber tube coating is 8×10⁻⁶. -6 ~10×10 -6 / ℃.

6. The carbon-carbon plate-based nickel transition layer-carbon fiber tube composite sealant according to claim 1, characterized in that, The carbon fiber tube has a diameter of 5~10μm and a length of 50~100μm; The ceramic particles are selected from silicon carbide or alumina, and the particle size is 1~5μm; The phenolic resin adhesive has a glass transition temperature ≥250℃ after curing.

7. A method for preparing a carbon-carbon plate-based nickel transition layer-carbon fiber tube composite seal according to any one of claims 1 to 6, comprising the following steps: After grinding the surface of the carbon carbon plate, ultrasonic degreasing is performed, followed by chemical roughening to obtain a pretreated carbon carbon plate. The pretreated carbon plate is activated with colloidal palladium, de-gelled with hydrochloric acid, then chemically plated with nickel, micro-etched with dilute sulfuric acid, and then electroplated with thickened nickel. Finally, it is roughened by plasma to form a nickel transition layer with a micro-nano uneven structure on the surface. 60-80 wt% carbon fiber tube, 10-20 wt% ceramic particles, and 10-20 wt% phenolic resin binder are ball-milled and mixed with ethanol to form a slurry with a viscosity of 200-300 mPa·s. The slurry is then sprayed using plasma spraying and directly cured to obtain a carbon-carbon plate-based nickel transition layer-carbon fiber tube composite seal.

8. The preparation method according to claim 7, characterized in that, The electroless nickel plating solution used includes nickel sulfate 26~28 g / L, reducing agent 19~21 g / L, composite complexing agent 28~32 g / L, sodium acetate 14~16 g / L, and stabilizer 1.8~2.2 mg / L; the electroless nickel plating temperature is 84~86℃, and the pH value is 6.5; The plating solution used for thickened nickel electroplating includes nickel sulfamate 380~420 g / L, nickel chloride 5.5~6.5 g / L, boric acid 28~32 g / L and sodium dodecyl sulfate 0.35~0.45 g / L; the electroplating temperature for thickened nickel is 48~52℃, and the pH value is 4.

0.

9. The preparation method according to claim 7, characterized in that, The plasma spraying uses a power of 35~45kW, a spraying distance of 120~150mm, and a spraying rate of 6~8g / min. The curing temperature is 100~160℃ and the time is 110~130min.

10. The preparation method according to claim 7, characterized in that, The fracture toughness of the carbon-carbon plate-based nickel transition layer-carbon fiber tube composite seal is ≥3.5 MPa·m. 1 / 2 Friction coefficient ≤ 0.08, leakage rate ≤ 1×10 -7 Pa·m 3 / s, density is 1.2~1.5g / cm³ 3 .

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