Modified nano-alumina-based composite fiber and preparation method thereof

Abstract

The invention relates to a modified nano-alumina-based composite fiber and a preparation method thereof.The modified nano-alumina-based composite fiber is prepared through a melt blending technology, modified nano-alumina is evenly inlaid in spinnable asphalt under the action of a silane coupling agent, and the modified nano-alumina has a uniform structure; the diameter of the modified nano-alumina-based composite fiber is 10-30 [mu] m, the highest breaking strength can reach 580.4 MPa, and the highest Young modulus can reach 37.32 GPa. According to the prepared composite fiber, the wettability between a reinforcement body and matrix metal is remarkably improved, harmful reactions between the reinforcement body and the matrix metal can be effectively inhibited, and the situation that the overall performance of the aluminum-based composite fiber is affected due to the fact that the fiber strength is reduced due to the fact that a carbon fiber coating is not compact, cracked, stripped and the like is avoided; meanwhile, the preparation process is simple, the steps are few, operation is easy and convenient, compared with a coating process, the equipment investment cost is low, and industrial production is easy to achieve.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of composite fiber preparation, and particularly relates to a modified nano-alumina-based composite fiber and a preparation method thereof. BACKGROUND

[0002] Aluminum matrix composite is an advanced composite material taking aluminum or aluminum alloy as a matrix and taking particles, fibers, whiskers or new nano-materials as a reinforcing body. It combines the high strength and high modulus of the reinforcing body with the light weight and thermal conductivity of aluminum, and is widely used in the fields of aerospace, automobile, electronics and sports equipment. It is mainly prepared by powder metallurgy and molten metal impregnation processes.

[0003] Carbon fibers become an ideal reinforcing body of aluminum matrix composite due to their high strength, light weight and thermal stability. They mainly include polyacrylonitrile-based carbon fibers and pitch-based carbon fibers. The polyacrylonitrile-based carbon fibers have high strength and modulus, but their production cost is high, and their application in cost-sensitive fields is limited. The pitch-based carbon fibers are prepared from pitch and other substances rich in condensed aromatic hydrocarbons through a series of processes, and have the advantages of good high-temperature resistance, good corrosion resistance, high modulus, low thermal expansion coefficient and high thermal conductivity. Their relatively low cost provides a new material selection for metal matrix composites. Their high cost performance and excellent thermal performance help to expand the application scenarios of composite materials in the fields of automobiles, machinery and electronics.

[0004] At present, there are still some key problems that have not been solved in the process of manufacturing carbon fiber reinforced aluminum matrix composite, such as poor wettability between carbon fibers and aluminum matrix, serious interfacial reaction at high temperature, which causes poor adhesion between fibers and matrix, brittle phase generated on the surface of fibers, and further causes interfacial cracks. The existing technology usually solves the above problems by preparing a coating on the surface of the fiber, but the surface coating technology also has the following significant disadvantages: first, the difference between the thermal expansion coefficients of the coating material and the aluminum matrix is large, and the temperature change in the preparation process will produce residual stress, which causes the coating to crack or the interface to peel off; second, the coating process is complex, the cost is high and the stability is poor; thus, the large-scale application of the coating method is restricted. SUMMARY

[0005] The present application provides a modified nano-alumina-based composite fiber and a preparation method thereof. The wettability between the reinforcing body and the matrix metal of the prepared composite fiber is significantly improved, and the occurrence of harmful reactions between the two can be effectively inhibited, avoiding the reduction of fiber strength caused by the non-dense, cracking and peeling of the carbon fiber coating, which affects the overall performance of the aluminum matrix composite fiber. At the same time, the preparation process is simple, the steps are few, the operation is simple, the equipment investment cost is low compared with the coating process, and the industrial production is easy to realize.

[0006] In order to achieve the above purpose, the technical scheme adopted by the present application is as follows:

[0007] A modified nano-alumina-based composite fiber is prepared by a melt blending process, wherein the modified nano-alumina is uniformly embedded in spinnable pitch under the action of a silane coupling agent, and has a uniform structure; the modified nano-alumina-based composite fiber has a diameter of 10-30 μm, a breaking strength of 400-580.4 MPa, and a Young's modulus of 26.39-37.32 GPa.

[0008] A preparation method of a modified nano-alumina-based composite fiber, comprising the following steps:

[0009] 1) adding nano-alumina into a solvent I containing a silane coupling agent to perform surface organic treatment, improving the interface bonding of the nano-alumina and the organic matrix material through a chemical bonding mechanism, then separating the solvent I, vacuum drying the product, and obtaining silane-modified nano-alumina;

[0010] 2) fully reacting the silane-modified nano-alumina and phenolic resin in a solvent II, so that the active groups of the silane directly react with the hydroxymethyl groups of the phenolic resin to form a firm interface connection; after the reaction, removing the solvent II by a rotary evaporator, vacuum drying the product, and obtaining modified nano-alumina;

[0011] 3) melting spinnable pitch at a set temperature, adding the modified nano-alumina into the spinnable pitch, fully mixing and uniformly the two at a set pressure, breaking into fine powder after standing and cooling, and obtaining a composite fiber precursor;

[0012] 4) sending the composite fiber precursor into a spinning device to perform melt spinning, and obtaining an aluminum composite fiber green yarn;

[0013] 5) heating the aluminum composite fiber green yarn to perform stabilization treatment, so that the oxygen-containing functional groups in the fiber undergo a cyclization reaction to form a stable oxygen-containing functional group structure, and obtaining an aluminum composite fiber oxidized yarn;

[0014] 6) performing carbonization treatment on the stabilized aluminum composite fiber oxidized yarn under nitrogen protection, and obtaining the modified nano-alumina-based composite fiber.

[0015] In the step 1), the solvent I is an ethanol solution with a mass concentration of 60%-80%.

[0016] In the step 1), the silane coupling agent is one of KH550, KH560, KH570, TESPT and VTES; the addition amount of the silane coupling agent is 2%-5% of the nano-alumina by mass fraction, the surface organic treatment temperature is 40-60 ℃, and the time is 0.5-2.5 h.

[0017] The addition amount of the phenolic resin in the step 2) is 2%-5% of the nano-alumina by mass fraction; the solvent II is DMF, the reaction temperature is 80-130 DEG C, and the reaction time is 0.5-2.5h.

[0018] The spinnable pitch in the step 3) is oil-based pitch or coal-based pitch, the softening point is 250-280 DEG C, the coking value is greater than or equal to 70%, and the quinoline insoluble content is less than or equal to 0.5%; the mass ratio of the spinnable pitch to the modified nano-alumina is 4:1-3:2; the melt-mixing temperature is 300-350 DEG C, the pressure is 0.1-0.6 MPa, and the mixing time is 2-5h.

[0019] The spinning device in the step 4) has a spinneret aperture of 0.2-0.6mm, the spinning temperature is 280-370 DEG C, the spinning pressure is 0.1-2.5 MPa, and the spinning speed is 350-1000m / min.

[0020] The temperature increasing rate of the stabilization treatment in the step 5) is 0.2-1 DEG C / min, the final temperature is 280-340 DEG C, and the constant temperature time is 0-2.5h.

[0021] The temperature increasing rate of the carbonization treatment in the step 6) is 2-10 DEG C / min, the final temperature is 800-1300 DEG C, and the constant temperature time is 0-2.5h.

[0022] Compared with the prior art, the present application has the following beneficial effects:

[0023] 1) The active groups generated by the hydrolysis of the silane coupling agent can form stable covalent bonds with the hydroxyl groups on the surface of the nano-alumina, realizing the organic modification of the inorganic surface of the nano-alumina, reducing the surface energy and reducing the agglomeration;

[0024] 2) The active groups remaining on the surface of the nano-alumina after the silane modification can directly react with the hydroxymethyl groups of the phenolic resin, forming a firm interface connection, which can strengthen the structure of the composite fiber and improve the mechanical properties;

[0025] 3) The modified nano-alumina has better wettability and compatibility with the carbon-hydrogen matrix of the pitch, which is beneficial to reducing the interfacial tension and forming a stable dispersion system;

[0026] 4) The prepared composite fiber has significantly improved wettability between the reinforcing body and the matrix metal, and can effectively inhibit the occurrence of harmful reactions between the two, avoiding the reduction of fiber strength caused by the non-dense, cracking and peeling of the carbon fiber coating, and affecting the overall performance of the aluminum-based composite fiber;

[0027] 5) The preparation process is simple, has few steps and is easy to operate, and compared with the coating process, the equipment investment cost is low and the industrial production is easy to realize. BRIEF DESCRIPTION OF DRAWINGS

[0028] Figure 1 The scanning electron microscope image of the modified nanometer alumina-based composite fiber prepared in Example 1 of the present application.

[0029] Figure 2 The scanning electron microscope image of the modified nanometer alumina-based composite fiber prepared in Example 2 of the present application.

[0030] Figure 3 The scanning electron microscope image of the modified nanometer alumina-based composite fiber prepared in Example 3 of the present application. DETAILED DESCRIPTION

[0031] The modified nanometer alumina-based composite fiber is prepared by using a melt blending process. The modified nanometer alumina is uniformly embedded in spinnable pitch under the action of a silane coupling agent, and has a uniform structure. The diameter of the modified nanometer alumina-based composite fiber is 10-30 μm, the breaking strength is 400-580.4 MPa, and the Young's modulus is 26.39-37.32 GPa.

[0032] A preparation method of a modified nanometer alumina-based composite fiber, comprising the following steps:

[0033] 1) The nanometer alumina is added into a solvent I containing a silane coupling agent for surface organic treatment, so as to improve the interface bonding of the nanometer alumina and the organic matrix material through a chemical bonding mechanism. After the solvent I is separated, the product is vacuum dried to obtain the nanometer alumina modified by silane;

[0034] 2) The nanometer alumina modified by silane is fully reacted with phenolic resin in a solvent II, so that the active groups of the silane are directly reacted with the hydroxymethyl groups of the phenolic resin to form a firm interface connection. After the reaction, the solvent II is removed by a rotary evaporator, and the product is vacuum dried to obtain the modified nanometer alumina;

[0035] 3) The spinnable pitch is melted at a set temperature, the modified nanometer alumina is added into the pitch, and the two are fully mixed and uniformly mixed at a set pressure. After standing and cooling, the mixture is broken into fine powder to obtain a composite fiber precursor;

[0036] 4) The composite fiber precursor is sent into a spinning device for melt spinning to prepare an aluminum composite fiber green yarn;

[0037] 5) The aluminum composite fiber green yarn is heated for stabilization treatment, so that the oxygen-containing functional groups in the fiber undergo cyclization reaction to form a stable oxygen-containing functional group structure (to prevent deformation or melting in subsequent high-temperature treatment), and an aluminum composite fiber oxidized yarn is obtained;

[0038] 6) The aluminum composite fiber oxidized silk after the stabilization treatment is carbonized under nitrogen protection, the non-carbon atoms in the fiber molecules are removed, the fiber molecular structure becomes more regular, the crystal structure and orientation of the fiber are optimized, the mechanical properties are improved, and the modified nano-alumina-based composite fiber is prepared.

[0039] In the step 1), the solvent one is an ethanol solution with a mass concentration of 60% to 80%.

[0040] In the step 1), the silane coupling agent is one of KH550 (3-aminopropyl triethoxysilane), KH560 (3-glycidyl ether propyl trimethoxysilane), KH570 (3-methacryloyloxy propyl trimethoxysilane), TESPT (bis (3-triethoxysilyl propyl) tetrasulfide) and VTES (vinyl triethoxysilane); the addition amount of the silane coupling agent is 2% to 5% of the nano-alumina in mass fraction, the surface organic treatment temperature is 40 to 60℃, and the time is 0.5 to 2.5h.

[0041] In the step 2), the addition amount of the phenolic resin is 2% to 5% of the nano-alumina in mass fraction; the solvent two is DMF ((N, N-dimethylformamide), the reaction temperature is 80 to 130℃, and the reaction time is 0.5 to 2.5h.

[0042] In the step 3), the spinnable pitch is oil-based pitch or coal-based pitch, the softening point is 250 to 280℃, the coking value is ≥70%, and the quinoline insoluble content is ≤0.5%; the mass ratio of the spinnable pitch to the modified nano-alumina is 4:1 to 3:2; the melt mixing temperature is 300 to 350℃, the pressure is 0.1 to 0.6MPa, and the mixing time is 2 to 5h.

[0043] In the step 4), the spinning device has a spinneret aperture of 0.2 to 0.6mm, the spinning temperature is 280 to 370℃, the spinning pressure is 0.1 to 2.5MPa, and the spinning rate is 350 to 1000m / min.

[0044] In the step 5), the heating rate of the stabilization treatment is 0.2 to 1℃ / min, the final temperature is 280 to 340℃, and the constant temperature time is 0 to 2.5h.

[0045] In the step 6), the heating rate of the carbonization treatment is 2 to 10℃ / min, the final temperature is 800 to 1300℃, and the constant temperature time is 0 to 2.5h.

[0046] In order to more directly reflect the present application, the embodiments of the present application are further described in combination with examples. The following examples are merely the preferred specific embodiments of the present application, but the protection scope of the present application is not limited thereto, and any skilled person in the art can obtain the technical solutions within the technical range disclosed by the present application, including simple changes or equivalent replacements, which are all within the protection scope of the present application.

[0047] Example 1

[0048] In this example, the preparation process of the modified nano-alumina-based composite fiber is as follows:

[0049] 80 g of nano-alumina and 2.4 g of KH550 were put into 450 ml of ethanol solution (solvent one) with a mass concentration of 75%, and after heating and stirring at 60℃ for 1 h, the solvent one was removed by reduced pressure distillation, and then the product was vacuum dried to obtain nano-alumina.

[0050] The dried nano-alumina was stirred with 2.4 g of phenolic resin in DMF (solvent two) for 1.5 h, the mixing temperature was 100℃, and after uniform mixing, the solvent two was removed by rotary evaporation, and then the product was vacuum dried to obtain modified nano-alumina.

[0051] 320 g of oil-based spinnable pitch was put into a heating tank and heated to 330℃ to become a flow state. The softening point of the oil-based spinnable pitch was 270℃, the coking value was 73%, and the quinoline insoluble content was 0.35%. The modified nano-alumina was added to the molten spinnable pitch, stirred at 330℃ and 0.1 MPa for 3 h, and then poured out onto a tray to cool. After crushing and passing through a 100 mesh screen, the fine powder obtained was the composite fiber precursor.

[0052] The composite fiber precursor was sent into a spinning device for melt spinning, the spinneret aperture was 0.3 mm, the spinning temperature was 345℃, the spinning pressure was 1.5 MPa, and the spinning rate was 400 m / min, to obtain aluminum composite fiber filaments.

[0053] The aluminum composite fiber filaments were heated to 320℃ at a heating rate of 0.3℃ / min in an air atmosphere, and kept at this temperature for 1 h, to obtain aluminum composite fiber oxidized filaments.

[0054] The aluminum composite fiber oxidized filaments were heated to 1000℃ at a heating rate of 8℃ / min in a nitrogen atmosphere, and kept at this temperature for 1 h, to obtain modified nano-alumina-based composite fibers.

[0055] The scanning electron microscope image of the modified nano-alumina-based composite fiber prepared in this example is shown in Figure 1 Table 1.

[0056] Example 2

[0057] In this example, the preparation process of the modified nano-alumina-based composite fiber is as follows:

[0058] 80 g of nano-alumina and 1.6 g of KH560 were placed in 450 ml of ethanol solution (solvent 1) with a mass concentration of 75%, heated and stirred at 45°C for 1.5 h, the solvent 1 was removed by reduced pressure distillation, and then the product was vacuum dried to obtain nano-alumina.

[0059] The dried nano-alumina was stirred with 1.6 g of phenolic resin in DMF (solvent 2) for 1 h at a mixing temperature of 110°C, and then the solvent 2 was removed by rotary evaporation after uniform mixing, and the product was vacuum dried to obtain modified nano-alumina.

[0060] 320 g of coal-tar pitch was placed in a heating tank and heated to 320°C to become a flow state. The softening point of the coal-tar pitch was 265°C, the coking value was 82%, and the quinoline insoluble content was 0.42%. The modified nano-alumina was added to the molten coal-tar pitch, stirred at 325°C and 0.1 MPa for 4 h, and then poured onto a tray for cooling. After crushing and passing through a 100 mesh screen, the fine powder obtained was the composite fiber precursor.

[0061] The composite fiber precursor was sent to a spinning device for melt spinning, with a spinneret aperture of 0.3 mm, a spinning temperature of 325°C, a spinning pressure of 0.5 MPa, and a spinning rate of 500 m / min, to obtain aluminum composite fiber filaments.

[0062] The aluminum composite fiber filaments were heated to 300°C at a heating rate of 0.2°C / min in an air atmosphere and held at this temperature for 1 h to obtain aluminum composite fiber oxidized filaments.

[0063] The aluminum composite fiber oxidized filaments were heated to 1200°C at a heating rate of 5°C / min in a nitrogen atmosphere and held at this temperature for 1 h to obtain modified nano-alumina-based composite fibers.

[0064] The scanning electron microscope image of the modified nano-alumina-based composite fiber prepared in this example is shown in Figure 2 The diameter and mechanical property test results of the modified nano-alumina-based composite fiber are shown in Table 1.

[0065] Example 3

[0066] In this example, the preparation process of the modified nano-alumina-based composite fiber is as follows:

[0067] Put 120 g of nano-alumina and 3 g of KH560 into 600 ml of ethanol solution (solvent one) with a mass concentration of 75%, heat and stir at 45℃ for 2 h, remove the solvent one by reduced pressure distillation, and then vacuum dry the product to obtain nano-alumina.

[0068] Stir the dried nano-alumina with 3 g of phenolic resin in DMF (solvent two) for 2 h, the mixing temperature is 110℃, after uniform mixing, remove the solvent two by rotary evaporation, and then vacuum dry the product to obtain modified nano-alumina.

[0069] Take 280 g of coal-based spinnable pitch and put it into a heating tank, heat to 330℃ to make it flow. The softening point of the coal-based spinnable pitch is 272℃, the coking value is 85%, and the quinoline insoluble content is 0.48%. Add the modified nano-alumina into the molten coal-based spinnable pitch, stir at 335℃ and 0.2 MPa for 3.5 h, after uniform mixing, pour out to a tray to cool, crush and pass through a 100 mesh screen to obtain fine powder, which is a composite fiber precursor.

[0070] Put the composite fiber precursor into a spinning device for melt spinning, the spinneret aperture is 0.4 mm, the spinning temperature is 330℃, the spinning pressure is 0.5 MPa, and the spinning rate is 800 m / min to obtain aluminum composite fiber green yarn.

[0071] Heat the aluminum composite fiber green yarn in an air atmosphere to 320℃ at a heating rate of 0.2℃ / min, and keep the temperature constant for 0.5 h to obtain aluminum composite fiber oxidized yarn.

[0072] Heat the aluminum composite fiber oxidized yarn in a nitrogen atmosphere to 1000℃ at a heating rate of 8℃ / min, and keep the temperature constant for 2 h to obtain modified nano-alumina-based composite fiber.

[0073] The scanning electron microscope image of the modified nano-alumina-based composite fiber prepared in this example is shown in Figure 3 The diameter and mechanical property test results of the modified nano-alumina-based composite fiber are shown in Table 1.

[0074] Table 1 Diameter and mechanical property test results of the modified nano-alumina-based composite fiber

[0075] Example Average diameter (pm) Breaking strength (MPa) Young's modulus (GPa) 1 20.2 530.5 37.32 2 18.5 580.4 35.14 3 24.6 489.1 36.55

[0076] The above only describes the preferred specific embodiments of the present application, but the protection scope of the present application is not limited thereto, any person skilled in the art can make equivalent substitutions or changes to the technical solutions and inventive concepts of the present application within the technical scope disclosed by the present application, which should be covered within the protection scope of the present application.

Claims

1. A modified nano-alumina-based composite fiber, characterized in that, The modified nano-alumina was prepared by melt blending and spinning process. Under the action of silane coupling agent, the modified nano-alumina was uniformly embedded in the spinnable pitch, resulting in a uniform structure. The diameter of the modified nano-alumina-based composite fiber was 10-30 μm, the tensile strength was 400-580.4 MPa, and the Young's modulus was 26.39-37.32 GPa.

2. A method for preparing the modified nano-alumina-based composite fiber as described in claim 1, characterized in that, Includes the following steps: 1) Nano-alumina was added to solvent one containing silane coupling agent for surface organic treatment. The interfacial bonding between nano-alumina and organic matrix material was improved through chemical bonding mechanism. Then solvent one was separated and the product was vacuum dried to obtain silane-modified nano-alumina. 2) The silane-modified nano-alumina was fully reacted with phenolic resin in solvent 2, so that the active groups of silane and the hydroxymethyl groups of phenolic resin could react directly to form a strong interfacial bond; after the reaction, solvent 2 was removed by rotary evaporator, and the product was vacuum dried to obtain modified nano-alumina. 3) Melt the spinnable pitch at a set temperature, add modified nano-alumina to it, mix the two thoroughly and evenly under a set pressure, let it stand and cool, and then crush it into fine powder to obtain the composite fiber precursor. 4) The composite fiber precursor is fed into a spinning device for melt spinning to prepare aluminum composite fiber raw silk. 5) The aluminum composite fiber raw silk is heated to stabilize it, so that the oxygen-containing functional groups in the fiber undergo a cyclization reaction to form a stable oxygen-containing functional group structure, thus obtaining aluminum composite fiber oxide silk. 6) The stabilized aluminum composite fiber oxide filaments were carbonized under nitrogen protection to obtain modified nano-alumina-based composite fibers.

3. The method for preparing modified nano-alumina-based composite fibers according to claim 2, characterized in that, In step 1), solvent one is an ethanol solution with a mass concentration of 60% to 80%.

4. The method for preparing modified nano-alumina-based composite fibers according to claim 2, characterized in that, In step 1), the silane coupling agent is one of KH550, KH560, KH570, TESPT and VTES; the amount of silane coupling agent added is 2% to 5% of the nano alumina by mass fraction, the surface organic treatment temperature is 40 to 60°C, and the time is 0.5 to 2.5 h.

5. The method for preparing modified nano-alumina-based composite fibers according to claim 2, characterized in that, In step 2), the amount of phenolic resin added is 2% to 5% of the nano-alumina by mass fraction; the second solvent is DMF, the reaction temperature is 80 to 130°C, and the reaction time is 0.5 to 2.5 h.

6. The method for preparing modified nano-alumina-based composite fibers according to claim 2, characterized in that, In step 3), the spinnable pitch is oil-based pitch or coal-based pitch, with a softening point of 250-280℃, a coking value ≥70%, and a quinoline insoluble content ≤0.5%; the mass ratio of spinnable pitch to modified nano-alumina is 4:1-3:2; the melting and mixing temperature is 300-350℃, the pressure is 0.1-0.6MPa, and the mixing time is 2-5h.

7. The method for preparing modified nano-alumina-based composite fibers according to claim 2, characterized in that, In step 4), the spinneret aperture of the spinning device is 0.2-0.6 mm, the spinning temperature is 280-370℃, the spinning pressure is 0.1-2.5 MPa, and the spinning speed is 350-1000 m / min.

8. The method for preparing modified nano-alumina-based composite fibers according to claim 2, characterized in that, In step 5), the stabilization treatment has a heating rate of 0.2–1 °C / min, a final temperature of 280–340 °C, and a holding time of 0–2.5 h.

9. The method for preparing modified nano-alumina-based composite fibers according to claim 2, characterized in that, In step 6), the heating rate of the carbonization treatment is 2-10℃ / min, the final temperature is 800-1300℃, and the holding time is 0-2.5h.

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