High-performance carbon-graphite sealing material for aero-engine and preparation method of high-performance carbon-graphite sealing material

Abstract

The invention discloses a high-performance carbon graphite sealing material for an aero-engine and a preparation method thereof, and the method comprises the following steps: uniformly mixing superfine high-structure pitch coke powder, superfine graphite anode scrap powder, superfine green coke powder and nano carbon black to obtain composite aggregate, and putting the composite aggregate into a kneading pot; adding a mixed solution of higher fatty acid and absolute ethyl alcohol, mixing, removing absolute ethyl alcohol and water, adding the activated asphalt into the mixing and kneading pot, mixing and kneading, hot rolling, cooling, crushing and sieving to obtain the activated asphalt coated composite aggregate; putting the mixture into a high-pressure reaction kettle, vacuumizing, introducing argon into a replacement kettle, heating to 350-550 DEG C, pressurizing, preserving heat, cooling, and milling by a Raymond mill and airflow to prepare modified composite aggregate powder; and putting the modified composite aggregate powder into a kneading pot, removing moisture, adding the modified asphalt into the kneading pot, kneading, carrying out hot rolling, cooling, crushing and sieving to obtain pressed powder, carrying out compression molding and warm isostatic pressing to obtain a green body, and carrying out primary roasting and graphitization to obtain the carbon-graphite sealing material.

Description

Technical Field

[0001] The invention belongs to the technical field of materials and relates to a carbon graphite sealing material, in particular to a high-performance carbon graphite sealing material for an aero-engine and a preparation method thereof. Background Art

[0002] Carbon graphite materials are widely used in key strategic sectors such as aviation, aerospace, high-speed rail, chemical industry, nuclear power, shipbuilding, photovoltaic power generation, and electrical discharge machining. Due to their outstanding properties, such as excellent chemical stability, self-lubricity, and low thermal expansion coefficient, carbon graphite materials can maintain reliable sealing performance under high speed, high temperature, and high pressure differential conditions, occupying an irreplaceable position in aircraft engine sealing systems.

[0003] The traditional preparation process for carbon-graphite sealing materials for aircraft engines relies primarily on a solid-phase process. This process primarily uses calcined coke and artificial graphite, which have good interlayer slip properties and low activity, as carbon aggregates, and molten pitch as a binder. The carbon-graphite sealing material is produced through a process of kneading, flaking, crushing, screening, pressing, repeated impregnation, multiple calcinations, and high-temperature graphitization. This process suffers from the following fundamental issues: 1) The solid-phase process makes it difficult to uniformly mix the agglomerated aggregate and molten pitch. Because the molten pitch only coats the surface of the agglomerated carbon aggregate particles, the aggregate surface not coated by the binder is easily exposed again during the crushing process. This leads to the formation of cavities through bridging during the molding process, and the formation of sharp microcracks or interconnected pores on the binder-free surface during heat treatment. 2) Multiple impregnation and repeated calcination damage the homogeneity of the material: Although the carbonaceous aggregate used in this process has good plasticity, its surface energy is low and the sintering driving force is poor, making it difficult to achieve a single calcination and graphitization (one-calcination) to produce a carbon-graphite sealing material that meets the requirements. When repeated impregnation and multiple calcinations are used to compensate for this, the carbon-graphite sealing material easily forms a physical property gradient with a dense outer layer and a sparse inner layer, which in turn damages the homogeneous structure of the material, often manifesting as failure behaviors such as edge collapse, brittle fracture, and abnormal wear. Therefore, the traditional process has a long production process and a low yield rate. Moreover, the prepared carbon-graphite sealing material has poor homogeneity, obvious random tip cracks, poor stability, low bulk density, poor mechanical properties, high porosity, and obvious interphase defects, making it difficult to meet the material selection requirements of the new generation of high-performance aircraft engines. In addition, multiple impregnation and calcination will not only increase the company's equipment investment costs, labor costs, and raw material costs, but also increase environmental governance costs.

[0004] Therefore, how to shorten the production process, reduce production costs, reduce environmental pollution, and produce aviation carbon graphite sealing materials with good structure, large size, dense structure, low porosity, high mechanical strength, good homogeneity and stability has always been the research focus of technical personnel in this field. Summary of the Invention

[0005] In view of the above-mentioned deficiencies in the prior art, the present invention aims to provide a high-performance carbon graphite sealing material for aircraft engines and a preparation method thereof. The production process of the present invention is short, the production cost is low, the yield is high, and it is environmentally friendly. The high-performance carbon graphite material prepared has a good primary structure, large size, dense structure, low porosity, high mechanical strength, good homogeneity and stability, and the bulk density of the graphitized material after primary calcination is ≥1.90 g / cm 3 .

[0006] The technical solution of the present invention is achieved as follows: A method for preparing a high-performance carbon graphite sealing material for an aircraft engine comprises the following steps: S1: D 50 Ultra-fine high-structure asphalt coke powder ≤5μm, D 50 Ultrafine graphite anode powder ≤7μm, D 50 Ultrafine green coke powder ≤ 2 μm and nano carbon black are uniformly mixed to obtain a composite aggregate for later use; wherein the mass ratio of ultrafine high-structure pitch coke powder, ultrafine graphite anode waste powder, ultrafine green coke powder and nano carbon black is 60-80:5-15:5-15:3-10; S2: adding the composite aggregate from step S1 to a kneading pot, and simultaneously mixing higher fatty acids and anhydrous ethanol in a mass ratio of 1-3:97-99, and then adding and kneading for 1-3 hours. After heating to remove anhydrous ethanol and water, the temperature is further raised to 130-160°C, and then activated asphalt at 160-180°C is added to the kneading pot, and the mixture is kneaded and hot-rolled, cooled, crushed, and sieved to obtain activated asphalt-coated composite aggregate; S3: Place the activated asphalt-coated composite aggregate of S2 into a high-pressure reactor, evacuate, and replace the air in the reactor with nitrogen or argon. Then, heat it to 350-550℃ at a rate of 40-60℃ / h, keep it at that temperature for 4-10h, and control the pressure at 1-5MPa. Then, cool it to room temperature at a rate of 40-50℃ / h, and then grind it into a particle size of D by Raymond mill and air flow mill. 50 Modified composite aggregate powder of 12~15μm; S4: The modified composite aggregate powder of S3 is put into a kneading pot, heated to remove moisture, and then continued to heat to 130-160°C. Then, modified asphalt at 180-200°C is added to the kneading pot, and kneaded again, hot rolled, cooled, crushed, and sieved to obtain pressed powder; S5: The pressed powder of S4 is subjected to compression molding and isostatic pressing to obtain a green body, which is then calcined and graphitized to obtain the high-performance carbon-graphite sealing material.

[0007] Furthermore, the ultrafine green coke powder is obtained by pretreating green coke powder, and the pretreatment steps are: placing the green coke powder in a reactor, then heating it to 350-400°C at 5-10°C / min under a nitrogen atmosphere, keeping it warm for 5-10 hours, cooling it to room temperature and then crushing it to obtain the ultrafine green coke powder, and the green coke powder is one or more of green petroleum coke, green pitch coke, green needle coke, mesophase carbon microbeads and onion charcoal.

[0008] The ultrafine high-structure coke powder has a mosaic structure and a flow basin structure.

[0009] The nano carbon black is one or more of N339, N330, N234, N660, semi-reinforced carbon black and spray carbon black.

[0010] Furthermore, the distribution ratio of mosaic structure and watershed structure in ultrafine high-structure asphalt coke powder is 6~8:2~4.

[0011] Furthermore, in step S1, during mixing, the ultrafine high-structure pitch coke powder, ultrafine graphite butt powder, ultrafine green coke powder and nano carbon black are put into a double-motion mixer and mixed for 20 to 60 minutes.

[0012] Furthermore, the higher fatty acid is one or more of oleic acid, stearic acid and lauric acid; and the mass ratio of the higher fatty acid to the composite aggregate is 1-3:97-99.

[0013] Furthermore, the activated asphalt has a quinoline insoluble matter content of ≤0.5%, a softening point of ≤85%, a coking value of ≥45%, an ash content of ≤0.03%, and a toluene insoluble matter of ≥10%; and the mass ratio of the activated asphalt to the composite aggregate is 30~40:60~70.

[0014] Furthermore, the preparation method of the activated asphalt is: the low quinoline insoluble medium-temperature asphalt is modified with a modifier, wherein the modifier is one or more of octadecyltrimethylammonium chloride, urea, propyl mercaptan and thioglycolic acid, and the mass ratio of the modifier to the low quinoline insoluble medium-temperature asphalt is 2~5:95~98.

[0015] Furthermore, the modified asphalt is prepared by mixing one or more of heavy oil, ethylene tar, coal tar and anthracene oil with high-temperature asphalt or modified asphalt in a mass ratio of 10~20:80~90; the mass ratio of modified asphalt to modified composite aggregate powder is 5~20:80~95.

[0016] Furthermore, in step S5, the powder is pressed at 1-3 MPa and then left for 10-20 hours, then vacuum-packaged with a plastic film and warm isostatically pressed at 150-200 MPa to prepare a green body, which is then calcined at 900-1100 °C for 4-10 hours to obtain a calcined product, which is then graphitized at 2500-2800 °C for 4-10 hours to obtain the high-performance carbon graphite material.

[0017] The present invention also provides a high-performance carbon-graphite sealing material for an aero-engine. The high-performance carbon-graphite sealing material is prepared according to the above-mentioned method for preparing a high-performance carbon-graphite sealing material for an aero-engine.

[0018] Compared with the prior art, the present invention has the following beneficial effects: 1. The present invention adopts D 50 Ultrafine high-structured pitch coke powder ≤5 μm, D 50 Ultrafine graphite anode powder ≤7 μm, D 50 Four types of ultrafine aggregates, including ultrafine green coke powder and nano-carbon black ≤2 μm, can effectively reduce the number of pores connecting the aggregates, reduce the porosity, and increase the bulk density; ultrafine aggregates have fewer defects, which is beneficial to improving the mechanical properties of carbon-graphite materials.

[0019] Ultrafine green coke powder is waste powder from the negative electrode industry. It is low-cost and has a volatile matter content of ≥13%. After low-temperature heat treatment to remove harmful sintering components (ionone, 1,7-dimethyldibenzothiophene, naphtho[2,3-b]thiophene, hexadecylamide, etc.), the green coke powder can be used as a solid-phase densifier. It can not only form in-situ welds between adjacent aggregate particles, promote volume shrinkage, and increase self-sintering performance, but also fill pores and reduce open porosity according to the grading principle.

[0020] Ultrafine graphite butt powder is obtained by crushing the butts in the field of high-power graphite electrodes. It has low cost, high graphitization degree, excellent electrical and thermal conductivity, and low bonding force between carbon atoms in the same layer. 2 Hybridization forms covalent bonds, the distance between layers is large, each layer can slide, and has good self-lubricating properties. Therefore, the use of ultrafine graphite residual powder is not only beneficial to improving the preparation process and reducing the porosity, but also beneficial to increasing the thermal uniformity of heat-treated products, thereby improving the yield of carbon graphite sealing materials.

[0021] Nano-carbon black is more easily adsorbed on the surface of ultrafine high-structure asphalt coke powder, ultrafine green coke powder and ultrafine residual graphite residual powder. After being coated with low-quinoline insoluble medium-temperature asphalt and then using a low-temperature pressurized carbonization process similar to the preparation of green coke, nano-carbon black can not only act as a nucleating agent to induce the epitaxial growth of the intermediate phase and promote self-sintering, but also increase the wear resistance and service life of carbon-graphite materials.

[0022] Ultrafine high-structure asphalt coke powder is synthesized by blending high-temperature coal tar asphalt and medium- and low-temperature coal tar. The proportion of condensed aromatic hydrocarbons is 0.5 to 1.5 times higher than that of aliphatic hydrocarbons. It has a large specific surface area, a turbulent surface, and a strong interface bonding force with the adhesive. It also takes into account the contradictory issues such as the Hastelloy grindability coefficient, powder resistivity, powder strength and thermal properties. During the sintering process, the high proportion of condensed aromatic hydrocarbons makes it easier to undergo polycondensation to form continuous large-sized graphite crystallites. The orientation and stacking degree of the crystallites are higher, which further enhances the degree of graphitization of the material, thereby improving the thermal conductivity and self-lubricating properties of the carbon-graphite sealing material. In addition, the ultrafine carbonaceous particles are less likely to increase the strength of the carbon-graphite sealing material due to the small number of interconnected pores and interface defects between the aggregates. The ultrafine high-structure asphalt coke powder in the present invention is composed of a mosaic structure and a basin-type structure, which can effectively balance the structure-activity relationship between the self-lubricating properties, graphitization degree, thermal conductivity and mechanical strength of the carbon-graphite material.

[0023] Therefore, ultrafine high-structure asphalt coke powder, ultrafine green coke powder, ultrafine residual graphite residual powder and nano carbon black can play their respective functions and roles to a great extent and achieve a composite effect.

[0024] 2. The van der Waals force and Coulomb force between ultrafine high-structure asphalt coke powder, ultrafine raw coke powder, ultrafine residual graphite residual powder and nano carbon black cause them to form soft agglomerates. The higher fatty acids of the present invention are dispersed in low-cost, non-toxic anhydrous ethanol, which can effectively disperse the soft agglomerated particles. At the same time, the higher fatty acids have good mutual solubility with binders such as asphalt. After heating, the higher fatty acids can easily penetrate into the micropores of carbon aggregates, while keeping the oleophilic hydrocarbon end facing outward, activating the carbon aggregate, and combining the oleophilic hydrocarbon group with the activated asphalt, thereby enhancing the wetting and adsorption capacity of the activated asphalt on the carbon aggregate.

[0025] 3. The low-quinoline and low-softening-point medium-temperature asphalt used in the present invention has good fluidity, low impurity content, and is easy to spread, infiltrate and penetrate on the surface of carbon aggregate particles, thereby constructing a "green coke-like" interface transition layer on the surface and in the pores of the carbon aggregate particles. To a certain extent, it can effectively reduce the difference in thermal expansion coefficients of ultrafine high-structure asphalt coke powder, ultrafine green coke powder, ultrafine residual graphite residual powder and nano-carbon black, increase the heteroatom content, free radical content, active functional group and wettability of carbon atoms at the edge of carbon aggregate, which is beneficial to increase the interfacial bonding force between aggregate particles, promote the formation of sintering necks, and increase self-sintering performance, self-adhesion performance, mechanical strength and yield; at the same time, the medium-temperature asphalt has a low softening point, which is beneficial to remove harmful components of the medium-temperature asphalt during the kneading process.

[0026] The present invention uses nitrogen- or sulfur-containing octadecyltrimethylammonium chloride, urea, propyl mercaptan, thioglycolic acid and other substances to modify the low quinoline insoluble medium-temperature asphalt, which can not only increase the heteroatom content in the low quinoline insoluble medium-temperature asphalt, but also cause free radical substitution reaction and intramolecular free radical coupling reaction with the side chain carbon atoms of the low quinoline insoluble medium-temperature asphalt, thereby increasing the coking value and molecular weight of the low quinoline insoluble medium-temperature asphalt.

[0027] 4. In the process of preparing the modified composite aggregate powder of the present invention, the pressure is controlled to be 1~5 MPa, which is beneficial to promoting the migration of low quinoline insoluble matter in medium-temperature asphalt and the generation of intermediate phase to increase homogeneity and self-sintering performance, and also helps to reduce the porosity of the composite aggregate powder itself and increase the coking value and true density; low-temperature carbonization is beneficial to the coking layer on the surface of the composite aggregate powder to have more heteroatoms and free radicals remaining, increasing the activity of the composite aggregate powder and its wettability to asphalt, thereby improving the self-sintering ability and self-adhesion ability.

[0028] 5. The modified asphalt of the present invention is prepared by mixing heavy oil, ethylene tar, coal tar and anthracene oil with high-temperature asphalt or modified asphalt. It can effectively adjust the thermal expansion coefficient of the carbon-containing resin in the high-temperature asphalt and modified asphalt, and increase the fluidity and softening point of the high-temperature asphalt and modified asphalt.

[0029] 6. The present invention adopts a double-motion mixer to mix four aggregates with different physical properties in one pot, which can effectively improve the mixing uniformity and mixing efficiency. The present invention does not use toxic solvents, does not require impregnation and multiple roasting, effectively shortens the production process, saves labor input costs and equipment input costs, and avoids the problem of poor homogeneity of carbon graphite materials due to impregnation. The high-performance carbon graphite material obtained has a good structure, large size, dense structure, low porosity, high mechanical strength, good homogeneity, and a volume density of ≥1.90 g / cm 3 . BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 -ESR curves of composite aggregate and modified composite aggregate in Example 1.

[0031] Figure 2 -Example 1 Changes in contact angles of composite aggregate and modified composite aggregate and modified asphalt at 190°C.

[0032] Figure 3 -Microscopic morphology of the composite aggregate and the modified composite aggregate in Example 1 at different magnifications.

[0033] Figure 4 -Industrial CT scanning results of the high-performance carbon graphite materials prepared in Comparative Example 1 and Example 2.

[0034] Figure 5-Microscopic morphology of the polished surface of the high-performance carbon graphite material prepared in Comparative Example 1 and Examples 1, 2 and 3.

[0035] Figure 6 -Microscopic morphology of the interface of high-performance carbon graphite materials prepared in Comparative Example 1 and Example 2.

[0036] Figure 7 -Macroscopic photograph of the high performance carbon graphite material prepared in Example 2. DETAILED DESCRIPTION

[0037] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0038] The ultrafine green coke powder used in the following examples and comparative examples is ultrafine green petroleum coke, and all of them are obtained by placing the green petroleum coke into a reactor, then heating to 380°C at 5°C / min under a nitrogen atmosphere, keeping warm for 5 hours, cooling to room temperature and then crushing; the ultrafine high-structure coke powder used has a mosaic structure and a watershed structure, and the distribution ratio of the mosaic structure and the watershed structure of the ultrafine high-structure coke powder in Example 1 and the comparative example is 6:4, and the distribution ratio of the mosaic structure and the watershed structure of the ultrafine high-structure coke powder in Examples 2 and 3 is 8:2.

[0039] Example 1 1) Ultrafine high-structure pitch coke powder (D 50 ≤5 μm), ultrafine graphite anode powder (D 50 ≤7 μm), ultrafine green petroleum coke (D 50 ≤2 μm) and nano carbon black N330 were put into a double-motion mixer at a mass ratio of 60:15:15:10 and mixed for 30 min to obtain composite aggregate for standby use.

[0040] 2) Oleic acid and anhydrous ethanol were added to a stainless steel container in a mass ratio of 1:99. After mechanical stirring and uniform dispersion, the mixture was added to a kneading pot. The composite aggregate prepared in step 1) was added to the kneading pot in small amounts and multiple times. After mixing for 1 hour, the mixture was heated to 80°C to remove the anhydrous ethanol, thereby obtaining a composite aggregate rich in active polar groups. The mass ratio of oleic acid to composite aggregate was 2:98.

[0041] 3) Based on step 2), the temperature is raised to 110°C, dry-mixed for 1 hour, moisture is removed, and the temperature is continued to be raised to 155°C. After the temperature is reached, 170°C activated asphalt (wherein the mass ratio of activated asphalt to composite aggregate is 35:65) is added to the kneading pot, kneaded at 175°C for 1 hour, opened the lid for 10 minutes, and hot-rolled at 175°C for 3 times. After cooling to room temperature, the sheet is crushed and passed through a 100-mesh sieve to obtain activated asphalt-coated composite aggregate; wherein the activated asphalt is obtained by modifying low quinoline insoluble medium-temperature asphalt with thioglycolic acid, and the mass ratio of thioglycolic acid to low quinoline insoluble medium-temperature asphalt is 5:95.

[0042] 4) The activated asphalt-coated composite aggregate prepared in step 3) was placed in a high-pressure reactor, and vacuum was evacuated using a vacuum pump, and the air in the high-pressure reactor was replaced by argon gas. The temperature was then raised to 450°C at a rate of 50°C / h, kept at that temperature for 10 h, and the pressure was controlled at 2 MPa. Finally, the temperature was programmed to cool to room temperature at a rate of 50°C / h, and then the particles were pulverized by Raymond milling and air flow grinding to obtain a particle size of D 50 The modified composite aggregate is 14 μm.

[0043] 5) The modified asphalt prepared in step 4) was combined with modified composite aggregate in a mass ratio of 10:90 to prepare a pressed powder according to step 3) (mixing temperature: 190°C, volatile matter of the pressed powder: 11%); the modified asphalt was prepared by mixing ethylene tar and high-temperature asphalt in a mass ratio of 15:85.

[0044] 6) The pressed powder prepared in step 5) was molded at 1 MPa, left for 10 h, and then vacuum-sealed with a plastic film. The green body was then warm isostatically pressed at 200 MPa to obtain a carbon graphite green body with a green body density of 1.53 g / cm 3 .

[0045] 7) The carbon graphite material green body prepared in step 6) was placed in a ring-type calcining furnace for landfilling, treated at 1050 °C for 4 h, and then cooled to room temperature to obtain a bulk density of 1.71 g / cm 3 of baked goods.

[0046] 8) The calcined product prepared in step 7) was placed in a vacuum graphitization furnace, treated at 2500 °C for 4 h, and then cooled to room temperature to obtain a bulk density of 1.91 g / cm 3 High performance carbon graphite material.

[0047] Example 2 1) Ultrafine high-structure pitch coke powder (D 50 ≤5 μm), ultrafine graphite anode powder (D 50 ≤7 μm), ultrafine raw petroleum coke powder (D50 ≤2 μm) and nano carbon black N330 were put into a double-motion mixer in a mass ratio of 75:12:8:5 and mixed for 30 min to obtain composite aggregate for standby use.

[0048] 2) Stearic acid and anhydrous ethanol were added to a stainless steel container in a mass ratio of 1:99. After mechanical stirring and uniform dispersion, the mixture was added to a kneading pot. The composite aggregate prepared in step 1) was added to the kneading pot in small portions. After mixing for 1 hour, the mixture was heated to 80°C to remove the anhydrous ethanol, thereby obtaining a composite aggregate rich in active polar groups. The mass ratio of stearic acid to composite aggregate was 3:97.

[0049] 3) Based on step 2), the temperature is raised to 110°C, dry-mixed for 1 hour, moisture is removed, and the temperature is continued to be raised to 155°C. After reaching the temperature, 170°C activated asphalt (wherein the mass ratio of activated asphalt to composite aggregate is 30:70) is added to the kneading pot, kneaded at 175°C for 1 hour, uncovered for 10 minutes, and hot-rolled at 175°C for 3 times. After cooling to room temperature, the sheet is crushed and passed through a 100-mesh sieve to obtain activated asphalt-coated composite aggregate; wherein the activated asphalt is obtained by modifying low-quinoline-insoluble medium-temperature asphalt with octadecyltrimethylammonium chloride, and the mass ratio of octadecyltrimethylammonium chloride to low-quinoline-insoluble medium-temperature asphalt is 5:95.

[0050] 4) The activated asphalt-coated composite aggregate prepared in step 3) was placed in a high-pressure reactor, and vacuum was drawn using a vacuum pump, and the air in the high-pressure reactor was replaced by argon gas. The temperature was then raised to 500°C at a rate of 50°C / h, kept at that temperature for 10 h, and the pressure was controlled at 3 MPa. Finally, the temperature was programmed to cool to room temperature at a rate of 50°C / h, and then the aggregate was subjected to Raymond milling and air flow grinding to obtain a particle size of D 50 The modified composite aggregate powder is 14 μm.

[0051] 5) The modified asphalt prepared in step 4) was combined with modified composite aggregate powder in a mass ratio of 18:82 to prepare pressed powder according to step 3) (mixing temperature: 185°C, pressed powder volatile matter: 12%); the modified asphalt was prepared by mixing anthracene oil and modified asphalt in a mass ratio of 15:85.

[0052] 6) The pressed powder prepared in step 5) was molded at 1 MPa, left for 10 h, and then vacuum-sealed with a plastic film. The green body was then warm isostatically pressed at 200 MPa to obtain a carbon graphite green body with a green body density of 1.55 g / cm 3 .

[0053] 7) The carbon graphite material green body prepared in step 6) was placed in a ring-type calcining furnace for landfilling, treated at 1050 °C for 4 h, and then cooled to room temperature to obtain a bulk density of 1.72 g / cm 3 of baked goods.

[0054] 8) The calcined product prepared in step 7) was placed in a vacuum graphitization furnace, treated at 2500 °C for 4 h, and then cooled to room temperature to obtain a bulk density of 1.93 g / cm 3 High performance carbon graphite material.

[0055] Example 3 This embodiment is the same as embodiment 2 except that the ultra-fine high-structure pitch coke powder (D 50 ≤5 μm), ultrafine graphite anode powder (D 50 ≤7 μm), ultrafine raw petroleum coke powder (D 50 The mass ratio of carbon black (≤2 μm) and nano carbon black N330 is 80:5:12:3, and the volume density of the high-performance carbon graphite material is 1.90 g / cm 3 .

[0056] Comparative Example 1 1) Ultrafine high-structure pitch coke powder (D 50 ≤5 μm), ultrafine graphite anode powder (D 50 ≤7 μm), ultrafine raw petroleum coke powder (D 50 ≤2 μm) and nano carbon black N330 were put into a double-motion mixer at a mass ratio of 75:12:8:5 and mixed for 30 min to obtain composite aggregate for later use; 2) The composite aggregate prepared in step 1) was placed in a kneading pot and dry-mixed at 120°C for 1 hour. The mixture was then dehydrated and heated to 155°C. Once the temperature reached 155°C, modified asphalt at 170°C (with a mass ratio of modified asphalt to composite aggregate of 36:64) was added to the kneading pot and kneaded at 185°C for 1 hour. After kneading with the lid uncovered for 10 minutes, the mixture was hot-rolled three times at 185°C. After cooling to room temperature, the mixture was crushed and passed through a 200-mesh sieve to obtain a pressed powder (volatile matter of 14.5%). The modified asphalt was prepared by blending anthracene oil and modified asphalt in a mass ratio of 15:85.

[0057] 3) The pressed powder prepared in step 2) was molded at 1 MPa, left for 10 h, and then the green body was vacuum-sealed with a plastic film and warm isostatically pressed at 200 MPa to obtain a carbon graphite green body with a green body density of 1.56 g / cm 3 .

[0058] 4) The carbon graphite green body prepared in step 3) was placed in a ring-type calcining furnace for landfilling, treated at 1050 °C for 4 h, and then cooled to room temperature to obtain a bulk density of 1.68 g / cm 3 of baked goods.

[0059] 5) The calcined product prepared in step 4) was placed in a vacuum graphitization furnace, treated at 2500 °C for 4 h, and then cooled to room temperature to obtain a bulk density of 1.81 g / cm 3 carbon graphite materials.

[0060] Comparative Example 2 This comparative example is the same as Example 1, except that the ultra-fine high-structure pitch coke powder (D 50 ≤5 μm), ultrafine graphite anode powder (D 50 ≤7 μm), ultrafine raw petroleum coke powder (D 50 The mass ratio of carbon black (≤2 μm) and nano carbon black N330 is 55:4:20:21, and the volume density of the high-performance carbon graphite material is 1.75 g / cm 3 .

[0061] Comparative Example 3 This comparative example is the same as Example 1, except that the ultra-fine high-structure pitch coke powder (D 50 ≤5 μm), ultrafine graphite anode powder (D 50 ≤7 μm), ultrafine raw petroleum coke powder (D 50 The mass ratio of the carbon black (≤2 μm) and nano carbon black N330 is 90:5:3:2, and the volume density of the high-performance carbon graphite material is 1.72 g / cm 3 .

[0062] Comparative Example 4 This comparative example is the same as Example 1, except that the ultrafine high-structure pitch coke powder used in this example has only a flow basin structure, and the volume density of the high-performance carbon graphite material obtained is 1.81 g / cm 3 .

[0063] Comparative Example 5 This comparative example is the same as Example 1, except that the high-performance carbon graphite material prepared in this example uses ultrafine flake graphite instead of ultrafine raw petroleum coke powder to obtain a bulk density of 1.73 g / cm 3 .

[0064] Comparative Example 6 This comparative example is the same as Example 1, except that the D 50 The volume density of the high-performance carbon graphite material is 1.76g / cm 3 .

[0065] Comparative Example 7 This comparative example is the same as Example 1, except that the D 50 The volume density of the high-performance carbon graphite material is 1.74g / cm 3 .

[0066] Comparative Example 8 This comparative example is the same as Example 1, except that linoleic acid is used instead of oleic acid in this example, and the volume density of the high-performance carbon graphite material obtained is 1.85 g / cm 3 .

[0067] Comparative Example 9 This comparative example is the same as Example 1, except that activated asphalt is not used in this example, and low quinoline insoluble medium temperature asphalt is used directly. The volume density of the high performance carbon graphite sealing material obtained is 1.84g / cm 3 .

[0068] Comparative Example 10 This comparative example is the same as Example 1, except that the mass ratio of the modifier to the low quinoline insoluble medium-temperature asphalt in this example is 1:99. The volume density of the obtained high-performance carbon graphite sealing material is 1.81 g / cm 3 .

[0069] Comparative Example 11 This comparative example is the same as Example 1, except that in step 5) of this example, high-temperature asphalt is used directly instead of modified asphalt. The volume density of the high-performance carbon graphite sealing material obtained is 1.83 g / cm 3 .

[0070] 1. The free radical content in the composite aggregate (obtained in step 1) and the modified composite aggregate in Example 1 was detected by ESR method. The obtained ESR curve is as follows: Figure 1 As shown in the figure, it can be seen that the derivative ESR spectrum intensity of the modified composite aggregate is significantly greater than that of the composite aggregate. Through Origin fitting of the characteristic peaks, it can be seen that the integral areas of the modified composite aggregate powder and the composite aggregate are 982.20 and 216.26, respectively, that is, the integral area of ​​the modified composite aggregate powder is 4.54 times that of the composite aggregate, indicating that the free radical content and chemical activity in the modified composite aggregate prepared by the present invention are higher than those of the composite aggregate.

[0071] 2. The contact angle variation curves of the composite aggregate and modified composite aggregate of Example 1 and modified asphalt at 190°C are shown in FIG. Figure 2 As shown by Figure 2It can be seen that at 190 °C, the contact angles of the modified composite aggregate and modified asphalt at 200, 400, 600, 800 and 1000 s are 101.7°, 69.4°, 47.3°, 36.5° and 31.4°, respectively, which are 27.82%, 43.58%, 53.90%, 59.76% and 61.75% smaller than the contact angles of the composite aggregate and modified asphalt, respectively. This indicates that the "coke-like" interfacial transition layer constructed on the surface or in the pores of the composite aggregate can not only increase the chemical activity, but also increase its wettability with the modified asphalt.

[0072] 3. The microscopic morphology of the composite aggregate and the modified composite aggregate in Example 1 is shown in FIG. Figure 3 As shown, Figure 3 (a~d) are the microscopic morphologies of composite aggregates. Figure 3 (e~h) are microscopic morphologies of the modified composite aggregates of Example 1. Figure 3 (a) and Figure 3 (e) It can be seen that the composite aggregate is irregular in shape and has high particle packing density; the modified composite aggregate is spherical, which helps to increase the contact area between particles and reduce the specific surface area; Figure 3 (b-d) It can be seen that nano-carbon black is adsorbed on the surface of larger carbon aggregates, and the nano-carbon black agglomerates more seriously in some areas. The carbon black adsorbed on the surface of larger carbon aggregates can not only act as a nucleating agent to induce the epitaxial growth of the mesophase, but also increase the wear resistance of carbon-graphite sealing materials used in aircraft engines (reduce the wear rate); however, the agglomerated carbon black in some areas will affect the processability, homogeneity, stability and dynamic performance of the carbon-graphite material. Figure 3 As shown in Figures (f-h), compared to the composite aggregate, the modified composite aggregate has no visible carbon black on its surface, and the particles are spherical with smoother edges and flake-like material attached to the surface. This not only facilitates dense packing and random orientation of the carbon-graphite material during molding (favoring increased isotropy), but also increases the contact area between particles, increasing the number of "sintering necks" formed and promoting improved sintering performance.

[0073] 4. The industrial CT scanning results of the carbon graphite materials obtained in Example 2 and Comparative Example 1 are as follows: Figure 4 As shown, Figure 4 (a-a3) are the industrial CT scanning results of comparative example 1, Figure 4 (b~b3) are the industrial CT scanning results of Example 2. Figure 4 It can be seen that compared with composite aggregates, the high-performance carbon-graphite material prepared using modified composite aggregates has a dense structure, fewer defects, and no obvious microcracks and ductile cracks, which further illustrates that this method can improve the homogeneity of high-performance carbon-graphite materials. It is difficult to compensate for defects such as the difference in thermal expansion coefficients between different phases and the extension of tip cracks by simply matching composite aggregates.

[0074] 5. The microscopic morphology of the polished surface of the carbon graphite material obtained in Examples 1 to 3 and Comparative Example 1 is as follows: Figure 5 As shown, compared with Comparative Example 1, the high-performance carbon graphite materials prepared in Examples 1 to 3 have significantly fewer pores, significantly smaller pore sizes, and more uniform pore distribution, indicating that the construction of an interface transition layer can promote volume shrinkage, increase self-sintering performance, and ultimately give the carbon graphite material a denser microstructure.

[0075] 6. The microscopic morphology of the interface of the carbon graphite material obtained in Example 2 and Comparative Example 1 is as follows: Figure 6 As shown in the figure, it can be seen that the interfacial bonding force between adjacent carbon phases in Example 2 is strong, which shows that the present invention constructs a highly chemically active "coke-like" interface transition layer on the surface and pores of the composite aggregate, promotes the formation of a "sintering neck", and is beneficial to improving the self-sintering performance of the carbon-graphite material.

[0076] 7. Referring to JB / T8133 standard, the bulk density, open porosity, resistivity, flexural strength, compressive strength and Shore hardness of the carbon graphite materials prepared in Examples 1 to 3 and Comparative Examples 1 to 11 were tested. The specific performance parameters are shown in the following table: As can be seen from the table above, the carbon graphite material prepared from the composite aggregate has high bulk density, flexural strength, compressive strength and Shore hardness. The bulk density after one-time calcination and graphitization reaches 1.81 g / cm 3 , which shows that the formula design of composite aggregate can play a composite effect, but due to the agglomeration of carbonaceous aggregate and the difference in thermal expansion coefficient between different carbon phases, its yield is low, homogeneity is poor, and batch stability is uncontrollable. The modified composite aggregate prepared by the method of the present invention is used as aggregate, modified asphalt is added, and the high-performance carbon graphite material prepared by one-time roasting and graphitization not only has a high yield, but also has better physical properties such as bulk density and mechanical strength. At present, there is no research on the use of ultrafine aggregates to play the synergistic effect between different aggregates, and combined with their sintering activity and thermal expansion coefficient regulation, and only one roasting and graphitization is required to prepare a carbon graphite material with a volume density greater than 1.90g / cm 3 , and a flexural strength greater than 80 MPa has been reported. Furthermore, good comprehensive physical properties are closely related to the material's microstructure and porosity. Compared to the comparative example, Examples 1-3 exhibit greater volume shrinkage and lower open porosity, indicating that the high-performance carbon-graphite material prepared using the modified composite aggregate has a denser structure and exhibits sintering behavior similar to that of green coke.

[0077] 8. After vacuum impregnation of the high-performance carbon-graphite sealing material prepared in Examples 1-3 with an antioxidant impregnation solution of a certain concentration (the impregnation solution and solution can be found in CN202210294660.X, "An Antioxidant for Aeroengine Graphite Material, Preparation Method, and Application Method thereof"), the material was cured at 750°C in an N2 atmosphere to obtain an antioxidant, high-performance carbon-graphite sealing material. The friction coefficient, wear value, and limiting PV value of the antioxidant, high-performance carbon-graphite materials prepared in Examples 1-3 and a Shanghai (UK) Morgan carbon-graphite material (M234AO) currently used in a certain engine were tested using a friction and wear tester and a PV value test bench under the same test conditions. The test results are shown in the table below: As can be seen from the above table, the carbon graphite matrix materials prepared in Examples 1 to 3 have increased bulk density and reduced porosity after impregnation with antioxidants; compared with M234AO, their comprehensive performance such as anti-oxidation weight loss, friction factor, wear rate and ultimate PV value is better. This is mainly attributed to the fact that the microstructure of the carbon graphite matrix material prepared by the present invention is better, and its comprehensive performance such as homogeneity, mechanical properties and yield rate are all improved simultaneously.

[0078] Finally, it should be noted that the above embodiments of the present invention are merely examples for illustrating the present invention and are not intended to limit the embodiments of the present invention. Those skilled in the art will appreciate that other variations and modifications can be made based on the above description. It is not possible to enumerate all embodiments here. Any obvious variations or modifications arising from the technical solution of the present invention remain within the scope of protection of the present invention.

Claims

1. A method for preparing a high-performance carbon graphite sealing material for an aircraft engine, characterized in that: The following steps are involved: S1: D 50 Ultra-fine high-structure asphalt coke powder ≤5μm, D 50 Ultrafine graphite anode powder ≤7μm, D 50 Ultrafine green coke powder ≤ 2 μm and nano carbon black are uniformly mixed to obtain a composite aggregate for later use; wherein the mass ratio of ultrafine high-structure pitch coke powder, ultrafine graphite anode waste powder, ultrafine green coke powder and nano carbon black is 60-80:5-15:5-15:3-10; S2: higher fatty acids and anhydrous ethanol are mixed uniformly in a mass ratio of 1-3:97-99 and added to a kneading pot. At the same time, the composite aggregate from step S1 is added to the kneading pot and kneaded for 1-3 hours. After heating to remove anhydrous ethanol and water, the temperature is further raised to 130-160°C. Activated asphalt at 160-180°C is then added to the kneading pot. The mixture is kneaded and hot-rolled, cooled, crushed, and sieved to obtain activated asphalt-coated composite aggregate. S3: Place the activated asphalt-coated composite aggregate of S2 into a high-pressure reactor, evacuate, and replace the air in the reactor with nitrogen or argon. Then, heat it to 350-550℃ at a rate of 40-60℃ / h, keep it at that temperature for 4-10h, and control the pressure at 1-5MPa. Then, cool it to room temperature at a rate of 40-50℃ / h, and then grind it into a particle size of D by Raymond mill and air flow mill. 50 Modified composite aggregate powder of 12~15μm; S4: The modified composite aggregate powder of S3 is added to a kneading pot, heated to remove moisture, and then further heated to 130-160°C. Modified asphalt at 180-200°C is then added to the kneading pot, kneaded, hot-rolled, cooled, crushed, and sieved to obtain pressed powder. S5: The pressed powder of S4 is subjected to compression molding and isostatic pressing to obtain a green body, which is then calcined and graphitized to obtain the high-performance carbon-graphite sealing material.

2. The method for preparing a high-performance carbon graphite sealing material for an aero-engine according to claim 1, wherein: The ultrafine green coke powder is obtained by pre-treating green coke powder, wherein the pre-treatment steps are as follows: placing the green coke powder in a reactor, then heating it to 350-400°C at 5-10°C / min under a nitrogen atmosphere, keeping the temperature for 5-10 hours, cooling it to room temperature, and then crushing it to obtain the ultrafine green coke powder, wherein the green coke powder is one or more of green petroleum coke, green pitch coke, green needle coke, mesophase carbon microbeads, and onion charcoal; The ultrafine high-structure coke powder has a mosaic structure and a watershed structure; The nano carbon black is one or more of N339, N330, N234, N660, semi-reinforced carbon black and spray carbon black.

3. The method for preparing a high-performance carbon graphite sealing material for an aero-engine according to claim 1 or 2, characterized in that: The distribution ratio of mosaic structure and watershed structure in ultrafine high-structure asphalt coke powder is 6~8:2~4.

4. The method for preparing a high-performance carbon graphite sealing material for an aero-engine according to claim 1, wherein: In step S1, during mixing, ultrafine high-structure pitch coke powder, ultrafine graphite butt powder, ultrafine green coke powder and nano carbon black are put into a double-motion mixer and mixed for 20 to 60 minutes.

5. The method for preparing a high-performance carbon graphite sealing material for an aero-engine according to claim 1 or 2, characterized in that: The higher fatty acid is one or more of oleic acid, stearic acid and lauric acid; the mass ratio of the higher fatty acid to the composite aggregate is 1-3:97-99.

6. The method for preparing a high-performance carbon graphite sealing material for an aero-engine according to claim 1 or 2, characterized in that: The activated asphalt has a quinoline insoluble matter content of ≤0.5%, a softening point of ≤85%, a coking value of ≥45%, an ash content of ≤0.03%, and a toluene insoluble matter of ≥10%; the mass ratio of the activated asphalt to the composite aggregate is 30~40:60~70.

7. The method for preparing a high-performance carbon graphite sealing material for an aircraft engine according to claim 6, characterized in that: The preparation method of the activated asphalt is as follows: the activated asphalt is obtained by modifying the low-quinoline-insoluble medium-temperature asphalt with a modifier, wherein the modifier is one or more of octadecyltrimethylammonium chloride, urea, propyl mercaptan and thioglycolic acid, and the mass ratio of the modifier to the low-quinoline-insoluble medium-temperature asphalt is 2~5:95~98.

8. The method for preparing a high-performance carbon graphite sealing material for an aero-engine according to claim 1, characterized in that: Modified asphalt is prepared by mixing one or more of heavy oil, ethylene tar, coal tar and anthracene oil with high-temperature asphalt or modified asphalt in a mass ratio of 10~20:80~90; the mass ratio of modified asphalt to modified composite aggregate powder is 5~20:80~95.

9. The method for preparing a high-performance carbon graphite sealing material for an aircraft engine according to claim 1, characterized in that: In step S5, the powder is pressed at 1-3 MPa and molded, and then left for 10-20 hours. It is then vacuum-packaged with a plastic film and warm isostatically pressed at 150-200 MPa to prepare a green body. The green body is then calcined at 900-1100°C for 4-10 hours to obtain a calcined product. The high-performance carbon graphite material is then obtained after graphitization treatment at 2500-2800°C for 4-10 hours.

10. A high-performance carbon graphite sealing material for aircraft engines, characterized in that: The high-performance carbon graphite sealing material for an aero-engine is prepared according to the method for preparing the material according to any one of claims 1 to 9.

Images