Modified carbon fibers, carbon fiber-reinforced composite coatings, and methods of making and using the same

Abstract

The application discloses a modified carbon fiber, a carbon fiber reinforced composite coating and a preparation method and application thereof. The preparation method of the modified carbon fiber comprises the following steps: in-situ constructing a zinc oxide seed layer and a zinc oxide micro-nano structure on the surface of the carbon fiber by using a hydrothermal method to obtain the carbon fiber with the zinc oxide micro-nano structure; and performing surface functionalization treatment on the carbon fiber with the zinc oxide micro-nano structure by using a silane coupling agent to obtain the modified carbon fiber. The preparation method provided by the application has mild conditions and simple process, the bonding strength of the prepared modified carbon fiber and resin is obviously improved, and the interface performance and the erosion resistance of the modified carbon fiber and resin are obviously enhanced.

Description

Technical Field

[0001] This invention belongs to the technical field of carbon fiber reinforced composite materials for marine environmental service, specifically relating to a modified carbon fiber, a carbon fiber reinforced composite coating, its preparation method and application. Background Technology

[0002] Nearshore docks and pilot stations, offshore wind power equipment, bridge construction and other marine equipment or engineering are in the typical "four high environment" of the ocean: high humidity, high heat, high salt spray and high ultraviolet radiation. Under the influence of factors such as saturated oxygen and marine microorganisms, the corrosion rate of materials is accelerated, their service life is shortened and even huge safety hazards are generated. In different areas of the ocean, the splash zone is a typical area of ​​strong corrosion damage in the marine environment due to the coupled effects of strong ultraviolet radiation, high oxygen content, alternating wet and dry seawater, seawater scouring and silt erosion. The degree of corrosion is 5 to 10 times that of the fully immersed marine zone.

[0003] Among numerous protective methods, organic protective coatings are widely used due to their advantages such as low cost, simple process, and corrosion resistance. However, due to defects such as pores and cracks easily forming during the curing process, as well as their poor mechanical properties, they are difficult to meet the service requirements of high erosion resistance protective materials in the harsh service environment of the splash zone. Carbon fiber and its composites are widely used in aerospace, military, and rail transportation fields due to their excellent mechanical properties, heat resistance, corrosion resistance, and impact resistance. Fiber-reinforced composites prepared by adding carbon fiber as a filler to an epoxy resin matrix have better mechanical properties, designability, and corrosion resistance, making them a promising approach to solving the corrosion problem of metal materials in the splash zone. However, due to the smooth surface and low chemical activity of carbon fiber, the wettability of the carbon fiber resin composite coating interface is poor, and the bonding force between the fiber and the resin matrix interface is also weak, resulting in poor interfacial bond strength. The interfacial failure problem of carbon fiber reinforced composite coatings in harsh marine environments is a key factor affecting their long-term safe service. Therefore, constructing carbon fiber composites with synergistic reinforcement through interfacial interlocking and chemical bonding is an important current development trend. Most current research attempts to improve the interfacial properties of composite materials to some extent by simply modifying the surface or by using sizing agents to construct an interfacial layer on the fiber surface. However, due to the limited modification mechanism and weak modification effect, the improvement in interfacial properties is limited.

[0004] Zinc oxide micro / nanostructures can not only grow zinc oxide nanoparticles, nanowires, and nanoflower-like morphologies on fiber surfaces, but also offer mild preparation conditions and simple processes, making them widely applicable and highly effective for modifying various fiber surfaces. However, most researchers simply grow zinc oxide structures onto fiber surfaces, resulting in sparse and unevenly distributed structures that lead to poor interfacial bonding between fibers and resins, making delamination between the resin and carbon fibers easy. The challenge lies in improving the uneven growth of zinc oxide structures on carbon fiber surfaces and addressing the interfacial bonding strength between carbon fibers and resins. Ultimately, this leads to the design of carbon fiber reinforced composites with strong interfacial bonding to meet the requirements for excellent mechanical properties, wear resistance, and erosion resistance in harsh marine environments. Summary of the Invention

[0005] The main objective of this invention is to provide a modified carbon fiber, a carbon fiber reinforced composite coating, its preparation method and application, in order to overcome the shortcomings of the prior art.

[0006] To achieve the aforementioned objectives, the technical solution adopted by this invention includes:

[0007] This invention provides a method for preparing modified carbon fiber, comprising:

[0008] A zinc oxide seed layer and a zinc oxide micro-nano structure were sequentially constructed in situ on the surface of carbon fibers using a hydrothermal method to obtain carbon fibers with a zinc oxide micro-nano structure.

[0009] Furthermore, the carbon fibers with zinc oxide micro / nano structures are surface-functionalized using a silane coupling agent to obtain modified carbon fibers.

[0010] The present invention also provides modified carbon fibers prepared by the aforementioned preparation method.

[0011] The present invention also provides a carbon fiber reinforced composite coating, which is obtained by mixing the aforementioned modified fiber, epoxy resin and curing agent and applying it to the surface of a substrate for curing.

[0012] The present invention also provides a carbon fiber reinforced composite material, which is obtained by mixing the aforementioned modified fiber, epoxy resin and curing agent and then curing them.

[0013] The embodiments of the present invention also provide the use of the aforementioned modified carbon fibers, carbon fiber reinforced composite coatings, or carbon fiber reinforced composite materials in the preparation of materials for marine environmental service.

[0014] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0015] (1) In this invention, the dense zinc oxide micro-nano structure on the carbon fiber surface is obtained by first treating the carbon fiber surface with zinc oxide seed solution to grow a zinc oxide seed layer, which provides active sites for the subsequent growth of zinc oxide micro-nano structure. Then, the dense zinc oxide micro-nano structure is efficiently grown in situ on the carbon fiber surface by hydrothermal method.

[0016] (2) The interfacial mechanical interlocking effect in the carbon fiber reinforced composite material of the present invention is to increase the surface roughness of the carbon fiber by pre-growing a zinc oxide seed layer on the carbon fiber surface and then growing zinc oxide micro-nano structures in situ, thereby improving the interfacial bonding strength between the carbon fiber and the resin and forming a strong mechanical interlocking effect.

[0017] (3) This invention forms a chemical bond at the interface between carbon fiber and resin through surface functionalization treatment. Based on the growth of zinc oxide micro-nano structures on the surface of carbon fiber, further surface chemical grafting modification is carried out to introduce amino groups, so that a strong chemical bond can be formed between carbon fiber and resin. Under the dual action of mechanical interlocking and chemical bonding, the interface bonding strength and interface stress transmission can be effectively improved.

[0018] (4) The mechanical interlocking effect and chemical bonding strengthening synergistic effect of carbon fiber reinforced composite material significantly improve the interfacial properties of carbon fiber reinforced composite material, reducing its erosion mass by 25%, erosion volume by 20%, and wear rate by 45%.

[0019] (5) The method provided by the present invention is applicable to improving the interfacial properties of carbon fiber composite materials, thereby improving the anti-friction and wear properties and anti-erosion properties of fiber reinforced composite materials. Attached Figure Description

[0020] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0021] Figure 1 This is a SEM image of the carbon fiber with the growth interface reinforcement phase in Embodiment 1 of the present invention;

[0022] Figure 2 This is a morphology diagram of the carbon fiber-resin interface after an erosion test of the carbon fiber reinforced composite material in Example 1 of the present invention.

[0023] Figure 3 This is a SEM image of the carbon fiber with the growth interface reinforcement phase in Embodiment 2 of the present invention;

[0024] Figure 4 This is a morphology diagram of the carbon fiber-resin interface of the carbon fiber reinforced composite material in Example 2 of the present invention after an erosion test.

[0025] Figure 5 This is a SEM image of the carbon fiber with the growth interface reinforcement phase in Comparative Example 1 of the present invention.

[0026] Figure 6 This is a morphology diagram of the carbon fiber-resin interface of the carbon fiber reinforced composite material in Comparative Example 1 of the present invention after an erosion test.

[0027] Figure 7 This is a SEM image of the carbon fiber with the growth interface reinforcement phase in Comparative Example 2 of the present invention.

[0028] Figure 8 This is a diagram of the carbon fiber-resin interface morphology of the carbon fiber reinforced composite material in Comparative Example 2 of the present invention after an erosion test.

[0029] Figure 9 This is a SEM image of the carbon fiber with the growth interface reinforcement phase in Comparative Example 3 of the present invention.

[0030] Figure 10 This is a morphology diagram of the carbon fiber-resin interface in the carbon fiber reinforced composite material of Comparative Example 3 of the present invention after erosion test.

[0031] Figure 11 This is a SEM image of the carbon fiber with the growth interface reinforcement phase in Comparative Example 4 of the present invention.

[0032] Figure 12 This is a morphology diagram of the carbon fiber-resin interface in the carbon fiber reinforced composite material of Comparative Example 3 of the present invention after erosion test.

[0033] Figure 13 These are friction wear rate data graphs of the composite materials in Examples 1-2 and Comparative Examples 1-4 of this invention;

[0034] Figure 14 These are erosion test mass loss data graphs of the composite materials in Examples 1-2 and Comparative Examples 1-4 of the present invention;

[0035] Figure 15 These are erosion test volume loss data graphs of the composite materials in Examples 1-2 and Comparative Examples 1-4 of the present invention. Detailed Implementation

[0036] In view of the deficiencies of the prior art, the inventors of this case, through long-term research and extensive practice, have proposed the technical solution of this invention. The technical solution of this invention will be clearly and completely described below. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0037] Specifically, as one aspect of the technical solution of this invention, a method for preparing modified carbon fiber includes:

[0038] A zinc oxide seed layer and a zinc oxide micro-nano structure were sequentially constructed in situ on the surface of carbon fibers using a hydrothermal method to obtain carbon fibers with a zinc oxide micro-nano structure.

[0039] Furthermore, the carbon fibers with zinc oxide micro / nano structures are surface-functionalized using a silane coupling agent to obtain modified carbon fibers.

[0040] In some preferred embodiments, the preparation method specifically includes:

[0041] (1) A first mixed reaction system containing at least carbon fiber, alkaline substance and zinc salt is subjected to hydrothermal reaction, then cooled to room temperature, and then heated up and repeated the hydrothermal reaction and cooling operation to obtain carbon fiber with surface-grown seed layer.

[0042] (2) A second mixed reaction system containing at least the carbon fiber, organic ammonium salt, and zinc salt with the surface-grown seed layer is subjected to a hydrothermal reaction to obtain carbon fiber with zinc oxide micro-nano structure.

[0043] (3) The carbon fibers with zinc oxide micro-nano structures are placed in a mixed solution containing silane coupling agent and solvent for functionalization treatment to obtain modified carbon fibers.

[0044] Furthermore, the carbon fiber includes any one or more combinations of carbon fiber powder, chopped carbon fiber, and carbon fiber cloth, and is not limited thereto.

[0045] Furthermore, the alkaline substance includes, but is not limited to, sodium hydroxide and / or ammonia.

[0046] Furthermore, the zinc salt mentioned in step (1) includes any one or more combinations of zinc sulfate, zinc acetate dihydrate, zinc nitrate, and zinc chloride, and is not limited thereto.

[0047] Further, the mass ratio of the alkaline substance to the zinc salt in step (1) is 1:(1.8 to 2.5).

[0048] Furthermore, the process parameters used in the hydrothermal reaction in step (1) include: temperature of 120-150℃, reaction time of 8-14h, and stirring speed of 100-300rpm.

[0049] Furthermore, the number of times the hydrothermal reaction and cooling operations are repeated in step (1) is 2 to 5.

[0050] In some preferred embodiments, step (2) specifically includes:

[0051] The carbon fiber and zinc salt obtained in step (1) are mixed with water and heated to dissolve and disperse under the conditions of stirring speed of 500-1000 rpm and temperature of 40-65℃ to form a carbon fiber / zinc salt dispersion. At the same time, ammonia water is used to adjust the pH value of the carbon fiber / zinc salt solution to 7.5-9.0.

[0052] Organic ammonium salts are mixed with water and heated to dissolve them under conditions of stirring speed of 500-1000 rpm and temperature of 40-65℃ to form an organic ammonium salt solution.

[0053] Furthermore, the organic ammonium salt solution is mixed with the carbon fiber / zinc salt dispersion and reacted at 120-150°C for 10-14 hours, followed by drying to obtain carbon fibers with zinc oxide micro-nano structures.

[0054] Furthermore, the mass-to-volume ratio of the carbon fiber, zinc salt, and water in the seed layer grown on the surface is (0.2–0.5) g : (0.29–0.33) g : 20 mL.

[0055] Furthermore, the concentration of the ammonia solution is 2–10 wt%.

[0056] Furthermore, the mass ratio of the organic ammonium salt to water is (0.0001~0.0003):1.

[0057] Furthermore, the volume ratio of the organic ammonium salt solution to the carbon fiber / zinc salt dispersion is (0.5-1.5):1.

[0058] Furthermore, the drying process is carried out at a temperature of 60–90°C for 8–12 hours.

[0059] Furthermore, the zinc salt mentioned in step (2) includes any one or more combinations of zinc nitrate, zinc chloride, and zinc acetate, and is not limited thereto.

[0060] Furthermore, the organic ammonium salt includes any one or more combinations of hexadecyltrimethylammonium bromide, tetraethylammonium sulfate, hexadecyltrimethylammonium fluoride, and alanine dimethylamine salt, and is not limited thereto.

[0061] In some preferred embodiments, step (3) specifically includes: mixing silane coupling agent, solvent and water, then adding carbon fiber with zinc oxide micro-nano structure and reacting for 8 to 15 hours under the conditions of stirring speed of 500 to 800 rpm and temperature of 60 to 80°C, and then washing and drying to obtain modified carbon fiber.

[0062] Furthermore, the volume ratio of the silane coupling agent, anhydrous ethanol, and water is 23:(200-400):(1-5).

[0063] Furthermore, the solvent includes, but is not limited to, anhydrous ethanol.

[0064] Furthermore, the silane coupling agent includes any one or more combinations of N-β-aminoethyl-γ-aminopropyltrimethoxysilane, N-(2-aminoethyl)-3-propanaminomethoxymethylsilane, and 3-aminopropyltriethoxysilane, and is not limited thereto.

[0065] Furthermore, the washing process includes washing with anhydrous ethanol 3 to 5 times.

[0066] Furthermore, the drying process is carried out at a temperature of 60–90°C for 8–12 hours.

[0067] In some preferred embodiments, the preparation method further includes: pre-treating the carbon fibers; the pre-treatment includes at least degreasing, desizing, and oxidation treatment.

[0068] In some more specific embodiments, the method for preparing the modified carbon fiber includes the following steps:

[0069] (1) Pre-growth of seed layer on carbon fiber surface: The pretreated carbon fiber is added to a mixture of sodium hydroxide and zinc salt for hydrothermal reaction and cooled to room temperature; the temperature is raised again for hydrothermal reaction and cooled to room temperature to obtain carbon fiber with zinc oxide seed layer grown on the surface.

[0070] (2) Growth of zinc oxide micro-nano structure on carbon fiber surface: The carbon fiber with zinc oxide seed layer obtained in step (1) is put into a mixed solution of organic ammonium salt and zinc salt for hydrothermal reaction, taken out and dried to obtain carbon fiber with zinc oxide micro-nano structure, that is: carbon fiber with zinc oxide micro-nano structure.

[0071] (3) Functional treatment of carbon fiber surface: The carbon fiber with zinc oxide micro-nano structure obtained in step (2) is immersed in a mixed solution of silane coupling agent and ethanol for reaction. After being taken out, washed and dried, modified carbon fiber with silanol grafted on the surface is obtained.

[0072] (4) The modified carbon fiber obtained in step (3) is mixed evenly with resin and cured to obtain an interface-reinforced carbon fiber composite material.

[0073] Preferably, the carbon fiber mentioned in step (1) includes, but is not limited to, carbon fiber products in the form of carbon fiber powder, chopped carbon fiber, carbon fiber cloth, etc.

[0074] Preferably, in step (1), the zinc salt is one or more of zinc sulfate, zinc acetate dihydrate, zinc nitrate, and zinc chloride; the mass ratio of sodium hydroxide to zinc salt in the mixture of sodium hydroxide and zinc salt is 1:(1.8-2.5); the reaction temperature of the pretreated carbon fiber added to the sodium hydroxide and zinc salt solution is 120-150°C, the reaction time is 8-14h, and the stirring speed is 100-300rpm; step (1) also includes: repeating the step of "heating up again to carry out hydrothermal reaction and cooling to room temperature" for a total of 2-5 times.

[0075] Preferably, the reaction steps for growing zinc oxide micro / nano structures on the carbon fiber surface in step (2) include: mixing the carbon fiber and zinc salt obtained in step (1) in 20 mL of deionized water at a mass ratio of (0.2-0.5):(0.29-0.33), heating and dispersing at a stirring speed of 500-1000 rpm and a temperature of 40-65°C to obtain a carbon fiber / zinc salt solution; adjusting the pH of the carbon fiber / zinc salt solution to (7.5-9.0) with ammonia water, wherein the ammonia water concentration is (2-10 wt%); mixing organic ammonium salt and deionized water at a mass ratio of 0.00025:1, heating and dissolving at a stirring speed of 500-1000 rpm and a temperature of 40-65°C to obtain an organic ammonium salt solution; adding an equal volume of the obtained organic ammonium salt solution to the carbon fiber / zinc salt solution, reacting at 120-150°C for 10-14 h, and drying in an oven at 60-90°C for 8-12 h to obtain carbon fibers with grown zinc oxide micro / nano structures.

[0076] Preferably, in step (2), the ammonium salt is one or more of hexadecyltrimethylammonium bromide, tetraethylammonium sulfate, hexadecyltrimethylammonium fluoride, and alanine dimethylamine salt, and the zinc salt is one or more of zinc nitrate, zinc chloride, or zinc acetate.

[0077] Preferably, the silane coupling agent in step (3) is one or more of N-β-aminoethyl-γ-aminopropyltrimethoxysilane, N-(2-aminoethyl)-3-propanaminomethoxymethylsilane, and 3-aminopropyltriethoxysilane; the steps of functionalizing the carbon fiber surface include: mixing the silane coupling agent and anhydrous ethanol at a volume ratio of 23:(200-400), then adding 1-5 mL of deionized water for reaction, taking it out, washing it, and drying it to obtain modified carbon fibers with silanol grafted on the surface.

[0078] Preferably, the reaction temperature in step (3) is 60-80℃, the reaction time is 8-15h, and the stirring speed is 500-800rpm.

[0079] Preferably, the washing in step (3) involves washing with anhydrous ethanol 3 to 5 times, and the drying involves drying in an oven at 60 to 90°C for 8 to 12 hours.

[0080] Preferably, the specific steps of the pretreatment include: immersing the carbon fiber in a 5-10 wt% sodium hydroxide solution and treating it at a temperature of 60-80°C and a stirring speed of 300-800 rpm for 6-10 hours, followed by rinsing with deionized water 3-5 times; then immersing the treated carbon fiber in acetone and treating it at a temperature of 40-70°C and a stirring speed of 300-800 rpm for 4-8 hours, followed by rinsing with deionized water 3-5 times, and then drying it in an oven at 40-90°C for 6-12 hours to obtain desizing carbon fiber; finally, immersing the desizing carbon fiber in a 30-60 wt% nitric acid solution and treating it at a temperature of 60-90°C and a stirring speed of 300-800 rpm for 6-10 hours, followed by rinsing with deionized water 3-5 times to obtain oxidized carbon fiber, i.e., the pretreated carbon fiber; wherein the pretreatment at least ensures that the surface of the obtained carbon fiber contains hydroxyl and / or carboxyl functional groups.

[0081] Preferably, in step (4), the stirring speed of the modified carbon fiber and the resin is 600-3500 rpm; the stirring time is 5-8 min.

[0082] Preferably, the curing temperature of the interface-reinforced carbon fiber composite material in step (4) is 25-80℃ in a three-stage heating curing process, and the total curing time is 12-24h.

[0083] Another aspect of the present invention provides modified carbon fibers prepared by the aforementioned preparation method.

[0084] Another aspect of the present invention provides a carbon fiber reinforced composite coating, which is obtained by mixing the aforementioned modified fiber, epoxy resin and curing agent and applying the mixture to the surface of a substrate for curing.

[0085] Furthermore, the epoxy resin includes any one or more combinations of epoxy E51, epoxy E44, and epoxy E38, and is not limited thereto.

[0086] Furthermore, the curing agent includes, but is not limited to, 1618 epoxy curing agent.

[0087] Furthermore, the curing temperature is 25–80℃, with three-stage heating and curing, and the total curing time is 12–24 hours.

[0088] Another aspect of the present invention provides a carbon fiber reinforced composite material, which is obtained by mixing the aforementioned modified fibers, epoxy resin and curing agent and then curing them.

[0089] Furthermore, the curing temperature is 25–80℃, with three-stage heating and curing, and the total curing time is 12–24 hours.

[0090] Furthermore, the epoxy resin includes any one or more combinations of epoxy E51, epoxy E44, and epoxy E38, and is not limited thereto.

[0091] Furthermore, the curing agent includes, but is not limited to, 1618 epoxy curing agent.

[0092] Another aspect of the present invention provides the use of the aforementioned modified carbon fibers, carbon fiber reinforced composite coatings, or carbon fiber reinforced composite materials in the preparation of materials for use in harsh marine environments.

[0093] The present invention has the following advantages: mild conditions and simple process; significantly improved bonding strength between the interface-reinforced carbon fiber and resin; significantly enhanced interfacial properties and erosion resistance of the modified fiber and resin; compared with unmodified carbon fiber, the modified carbon fiber has a 10% to 50% reduction in wear rate after friction and wear test, and the prepared carbon fiber reinforced composite coating has a 18% to 25% reduction in mass loss and a 10% to 20% reduction in volume loss after erosion test.

[0094] The technical solution of the present invention will be further described in detail below with reference to several preferred embodiments and accompanying drawings. This embodiment is implemented on the premise of the technical solution of the invention, and provides detailed implementation methods and specific operation processes. However, the protection scope of the present invention is not limited to the following embodiments.

[0095] Unless otherwise specified, the experimental materials used in the examples below can be purchased from conventional biochemical reagent companies.

[0096] The following examples and comparative examples illustrate the carbon fiber pretreatment process, which includes the following steps:

[0097] Carbon fibers were immersed in a 19 wt% sodium hydroxide solution and treated at 80°C and 800 rpm for 6 hours, followed by rinsing with deionized water 5 times. The treated carbon fibers were then immersed in acetone and treated at 70°C and 800 rpm for 8 hours, followed by rinsing with deionized water 5 times. Subsequently, the carbon fibers were dried in an oven at 80°C for 12 hours to obtain desizing carbon fibers. Finally, the desizing carbon fibers were immersed in a 37 wt% nitric acid solution and treated at 85°C and 800 rpm for 6 hours, followed by rinsing with deionized water 5 times to obtain oxidized carbon fibers, i.e., the pretreated carbon fibers. The pretreatment ensured that the surface of the obtained carbon fibers contained hydroxyl and / or carboxyl functional groups.

[0098] Example 1

[0099] (1): Pre-growth of seed layer on carbon fiber surface: The pretreated carbon fiber powder was added to a mixture of sodium hydroxide and zinc acetate dihydrate (the mass ratio of sodium hydroxide to zinc acetate dihydrate was 1:1.8), and a hydrothermal reaction was carried out for 14 hours under the conditions of stirring speed of 300 rpm and temperature of 150℃. The mixture was then cooled to room temperature. The steps of “heating up again for hydrothermal reaction and cooling to room temperature” were repeated 3 times to obtain carbon fiber with zinc oxide seed layer grown on the surface.

[0100] (2): Growth of zinc oxide micro-nano structures on carbon fiber surface: The carbon fiber with zinc oxide seed layer obtained in step (1) and zinc nitrate hexahydrate were mixed in 20 mL of deionized water at a mass ratio of 0.2:0.29. The mixture was stirred at 1000 rpm and heated at 55 °C to dissolve and disperse, thus obtaining a carbon fiber / zinc salt solution. The pH of the carbon fiber / zinc salt solution was adjusted to 8.0 by ammonia water (wherein the ammonia water concentration was 2 wt%). Hexadecyltrimethylammonium bromide and deionized water were mixed at a mass ratio of 0.00025:1. The mixture was stirred at 1000 rpm and heated at 55 °C to dissolve, thus obtaining an organic ammonium salt solution. An equal volume of the obtained organic ammonium salt solution was added to the carbon fiber / zinc salt solution. The mixture was reacted at 150 °C for 14 h and dried in an oven at 80 °C for 12 h to obtain carbon fiber with grown zinc oxide micro-nano structures.

[0101] (3): Functional treatment of carbon fiber surface: 3-aminopropyltriethoxysilane and anhydrous ethanol were mixed at a volume ratio of 23:200, and 1 mL of deionized water was added. Then the carbon fiber with zinc oxide micro-nano structure obtained in step (2) was immersed and reacted for 12 h at a stirring speed of 800 rpm and a temperature of 80 °C. After taking it out, it was washed 5 times with anhydrous ethanol and dried in an oven at 80 °C for 12 h to obtain modified carbon fiber with surface grafted silanol groups.

[0102] (4): The modified carbon fiber obtained in step (4) is mixed with epoxy E51 and 1618 epoxy curing agent at a mass ratio of 1.456:24.09:14.454 at a stirring speed of 1000 rpm for 8 min. Then, it is cured at 25℃ for 12 h, 40℃ for 8 h, 60℃ for 4 h, and 80℃ for 4 h to obtain an interface-reinforced carbon fiber composite material.

[0103] The morphology of the modified carbon fiber prepared in this embodiment is shown in the figure below. Figure 1 As shown, the zinc oxide structure on the carbon fiber surface grows uniformly and densely, and the in-situ grown zinc oxide is firmly bonded to the carbon fiber, which can produce a strong mechanical interlocking effect between the carbon fiber and the resin. Subsequently, the functionalized modified molecules on the carbon fiber surface introduce amino groups, which have the same groups as the resin curing agent, enabling them to react with epoxy resin to form chemical bonds, which can further improve the interfacial bonding strength between carbon fiber and resin.

[0104] Zinc oxide micro / nano structures grown on the carbon fiber surface form an interfacial mechanical interlock with the resin. After surface functionalization, chemical bonds are formed between the carbon fiber and resin, strengthening the composite material. The synergistic effect of mechanical interlocking and chemical bonding comprehensively improves the macroscopic properties of the carbon fiber composite. Friction and wear tests showed a 45% reduction in wear rate, multiphase flow erosion tests showed a 25% reduction in erosion mass and a 20% reduction in erosion volume loss. Further analysis under a scanning electron microscope (SEM) revealed further improvements. Figure 2 As shown, after the erosion test was completed, the interface between the carbon fiber and the epoxy resin was observed. It was found that the carbon fiber and epoxy resin were tightly bonded at the interface, and the stress was uniformly transferred to the surface of the carbon fiber. This indicates that the composite material with the synergistic effect of mechanical interlocking and chemical bonding at the interface has excellent erosion resistance and wear resistance.

[0105] Example 2

[0106] (1) Pre-growth of seed layer on carbon fiber surface: The pretreated carbon fiber powder is added to a mixture of sodium hydroxide and zinc acetate dihydrate (the mass ratio of sodium hydroxide to zinc acetate dihydrate is 1:2.5). The mixture is subjected to hydrothermal reaction for 14 hours at a stirring speed of 300 rpm and a temperature of 150°C. After cooling to room temperature, the process of “heating up again to carry out hydrothermal reaction and cooling to room temperature” is repeated 3 times to obtain carbon fiber with a zinc oxide seed layer grown on the surface.

[0107] (2) Growth of zinc oxide micro-nano structures on carbon fiber surface: The carbon fiber with zinc oxide seed layer obtained in step (1) and zinc nitrate hexahydrate were mixed in 20 mL of deionized water at a mass ratio of 0.5:0.33. The mixture was stirred at 1000 rpm and heated at 55 °C to dissolve and disperse the mixture, thus obtaining a carbon fiber / zinc salt solution. The pH of the carbon fiber / zinc salt solution was adjusted to 8.35 with ammonia water (ammonia water concentration was 10 wt%). Hexadecyltrimethylammonium bromide and deionized water were mixed at a mass ratio of 0.00025:1. The mixture was stirred at 1000 rpm and heated at 55 °C to dissolve the mixture, thus obtaining an organic ammonium salt solution. An equal volume of the organic ammonium salt solution was added to the carbon fiber / zinc salt solution. The mixture was reacted at 150 °C for 14 h and dried in an oven at 80 °C for 12 h to obtain dried carbon fiber with zinc oxide micro-nano structures.

[0108] (3) Functional treatment of carbon fiber surface: 3-aminopropyltriethoxysilane and anhydrous ethanol were mixed at a volume ratio of 23:400, and 5 mL of deionized water was added. Then the carbon fiber with zinc oxide micro-nano structure obtained in step (2) was immersed and reacted for 12 h at a stirring speed of 800 rpm and a temperature of 80 °C. After taking it out, it was washed 5 times with anhydrous ethanol and dried in an oven at 80 °C for 12 h to obtain modified carbon fiber with surface grafted silanol groups.

[0109] (4) The modified carbon fiber obtained in step (4) is mixed with epoxy E51 and 1618 epoxy curing agent at a mass ratio of 1.456:24.09:14.454 at a stirring speed of 1000 rpm for 8 min. Then it is cured at 25℃ for 12 h, 40℃ for 8 h, 60℃ for 4 h, and 80℃ for 4 h to obtain an interface-reinforced carbon fiber composite material.

[0110] The morphology of the modified carbon fiber prepared in this embodiment is shown in the figure below. Figure 3 As shown, the zinc oxide structure on the carbon fiber surface is still relatively uniform and dense, but the zinc oxide size is smaller than that in Example 1. However, the in-situ grown zinc oxide is still firmly bonded to the carbon fiber, resulting in a strong mechanical interlocking effect between the carbon fiber and the resin. Subsequently, the functionalized modified molecules on the carbon fiber surface introduce amino groups, which have the same groups as the resin curing agent, allowing them to react with the epoxy resin to form chemical bonds, which can further improve the interfacial bonding strength between the carbon fiber and the resin.

[0111] Zinc oxide micro / nano structures grown on the carbon fiber surface form an interfacial mechanical interlock with the resin. After surface functionalization, chemical bonds are formed between the carbon fiber and resin, strengthening the composite material. The synergistic effect of mechanical interlocking and chemical bonding comprehensively improves the macroscopic properties of the carbon fiber composite. Friction and wear tests showed a 40% reduction in wear rate, and multiphase flow erosion tests showed a 23% reduction in erosion mass and an 18% reduction in erosion volume loss. Further analysis under a scanning electron microscope (SEM) revealed further improvements. Figure 4 As shown, after the erosion test was completed, the interface between the carbon fiber and the epoxy resin was observed. It was found that the carbon fiber and epoxy resin were still tightly bonded at the interface, and the stress was uniformly transferred to the surface of the carbon fiber. This indicates that the composite material with the synergistic effect of mechanical interlocking and chemical bonding at the interface has excellent erosion resistance and wear resistance.

[0112] Example 3

[0113] (1) Pre-growth of seed layer on carbon fiber surface: The pre-treated short carbon fiber is added to a mixture of sodium hydroxide and zinc sulfate (the mass ratio of sodium hydroxide to zinc sulfate is 1:2.0). The mixture is subjected to hydrothermal reaction for 12 hours at a stirring speed of 100 rpm and a temperature of 120°C. After cooling to room temperature, the above steps of "heating up again to carry out hydrothermal reaction and cooling to room temperature" are repeated for a total of 5 times to obtain carbon fiber with zinc oxide seed layer grown on the surface.

[0114] (2) Growth of zinc oxide micro-nano structures on carbon fiber surface: The carbon fiber and zinc chloride with zinc oxide seed layer obtained in step (1) were mixed in 20 mL of deionized water at a mass ratio of 0.2:0.29 and dissolved and dispersed by stirring at 500 rpm and heating at 40 °C to obtain carbon fiber / zinc salt solution; the pH of carbon fiber / zinc salt solution was adjusted to 7.5 by ammonia water (ammonia water concentration was 10 wt%); tetraethylammonium sulfate and deionized water were mixed at a mass ratio of 0.00025:1 and dissolved by stirring at 500 rpm and heating at 40 °C to obtain organic ammonium salt solution; an equal volume of the obtained organic ammonium salt solution was added to the carbon fiber / zinc salt solution, reacted at 120 °C for 12 h, and dried in an oven at 60 °C for 12 h to obtain dried carbon fiber with zinc oxide micro-nano structure.

[0115] (3) Functional treatment of carbon fiber surface: N-β-aminoethyl-γ-aminopropyltrimethoxysilane and anhydrous ethanol were mixed at a volume ratio of 23:200, and 1 mL of deionized water was added. Then, the carbon fiber with zinc oxide micro-nano structure obtained in step (2) was immersed in the mixture and reacted at a stirring speed of 500 rpm and a temperature of 60 °C for 15 h. After removal, the carbon fiber was washed three times with anhydrous ethanol and dried in an oven at 60 °C for 12 h to obtain modified carbon fiber with surface grafted silanol groups.

[0116] (4) The modified carbon fiber obtained in step (4) is mixed with epoxy E44 and 1618 epoxy curing agent at a mass ratio of 1.456:24.09:14.454 at a stirring speed of 1000 rpm for 8 min. Then it is cured at 25℃ for 12 h, 40℃ for 8 h, 60℃ for 4 h, and 80℃ for 4 h to obtain an interface-reinforced carbon fiber composite material.

[0117] The interface-reinforced carbon fiber composite material prepared in this embodiment also exhibits excellent performance.

[0118] Example 4

[0119] (1) Pre-growth of seed layer on carbon fiber surface: The pretreated carbon fiber powder is added to a mixture of sodium hydroxide and zinc nitrate (the mass ratio of sodium hydroxide to zinc nitrate is 1:2.3). The mixture is subjected to hydrothermal reaction for 12 hours at a stirring speed of 200 rpm and a temperature of 130°C. After cooling to room temperature, the process of “heating up again to carry out hydrothermal reaction and cooling to room temperature” is repeated twice to obtain carbon fiber with a zinc oxide seed layer grown on the surface.

[0120] (2) Growth of zinc oxide micro-nano structures on carbon fiber surface: The carbon fiber and zinc chloride with zinc oxide seed layer obtained in step (1) were mixed in 20 mL of deionized water at a mass ratio of 0.3:0.30 and dissolved and dispersed by stirring at 8000 rpm and heating at 65 °C to obtain carbon fiber / zinc salt solution; the pH of carbon fiber / zinc salt solution was adjusted to 9.0 by ammonia water (ammonia water concentration was 10 wt%); alanine dimethylamine salt and deionized water were mixed at a mass ratio of 0.00025:1 and dissolved by stirring at 8000 rpm and heating at 65 °C to obtain organic ammonium salt solution; an equal volume of the obtained organic ammonium salt solution was added to the carbon fiber / zinc salt solution, reacted at 130 °C for 10 h, and dried in an oven at 90 °C for 8 h to obtain dried carbon fiber with zinc oxide micro-nano structures.

[0121] (3) Functional treatment of carbon fiber surface: N-(2-aminoethyl)-3-propanaminomethoxymethylsilane and anhydrous ethanol were mixed at a volume ratio of 23:300, and 3 mL of deionized water was added. Then the carbon fiber with zinc oxide micro-nano structure obtained in step (2) was immersed in the mixture and reacted for 8 h at a stirring speed of 700 rpm and a temperature of 75 °C. After being taken out, it was washed 4 times with anhydrous ethanol and dried in an oven at 90 °C for 8 h to obtain modified carbon fiber with silanol grafted on the surface.

[0122] (4) The modified carbon fiber obtained in step (4) is mixed with epoxy E44 and 1618 epoxy curing agent at a mass ratio of 1.456:24.09:14.454 at a stirring speed of 1000 rpm for 8 min. Then it is cured at 25℃ for 12 h, 40℃ for 8 h, 60℃ for 4 h, and 80℃ for 4 h to obtain an interface-reinforced carbon fiber composite material.

[0123] The interface-reinforced carbon fiber composite material prepared in this embodiment also exhibits excellent performance.

[0124] Comparative Example 1

[0125] Compared to Example 1, this comparative example only involves the pretreatment operation in step 1 on the carbon fiber, while the relevant parameters and conditions are the same as in Example 1.

[0126] The morphology of the modified carbon fibers prepared in this comparative example is shown in the figure below. Figure 5 As shown, the carbon fiber surface is smooth, but slight etching occurs due to nitric acid treatment. Although hydroxyl / carboxyl groups are introduced onto the surface, the surface activity remains low, resulting in poor bonding strength with the resin.

[0127] Friction and wear experiments showed that the wear of the pretreated carbon fiber composite material was far more severe than in Example 1. Multiphase flow erosion experiments revealed increased erosion volume loss in the in-situ zinc oxide seed layer reinforced carbon fiber composite material. Further analysis under a scanning electron microscope (e.g., ...) Figure 6 As shown, after observing the interface between carbon fiber and epoxy resin after the two tests, it was found that the bonding between carbon fiber and epoxy resin at the interface was poor, the stress could not be uniformly transmitted, and the carbon fiber itself broke. This indicates that the technology of this application improves the erosion resistance and wear resistance of carbon fiber reinforced composite materials through the synergistic effect of interface mechanical interlocking and chemical bonding.

[0128] Comparative Example 2

[0129] Compared to Example 1, this comparative example only removes the seed layer growth step in step (1) (the pretreatment is still retained), and all other method steps are the same.

[0130] The morphology of the modified carbon fibers prepared in this comparative example is shown in the figure below. Figure 7 As shown, zinc oxide structures can be observed to grow on the surface of carbon fibers, but the growth is sparse and uneven. Most of the zinc oxide cannot grow to the surface of carbon fibers. Although hydroxyl / carboxyl groups are introduced into the surface due to the pretreatment, the surface activity is low, and there is only a mechanical interlocking effect with the resin, resulting in poor bonding strength with the resin.

[0131] Friction and wear tests showed that the wear rate of the carbon fiber composite material obtained in Comparative Example 2 decreased by 10%. Multiphase flow erosion tests showed that the erosion mass of the in-situ zinc oxide seed layer reinforced carbon fiber composite material decreased by 12.8%, and the volume loss decreased by 13.5%. Further analysis under a scanning electron microscope (e.g., ...) Figure 8 As shown, after the erosion test, the interface between carbon fiber and epoxy resin was observed. It was found that the bonding between carbon fiber and epoxy resin at the interface was improved compared with Comparative Example 1, but the bonding was still worse than that of Example 1. Although the crack propagation was blocked, the interfacial bonding strength was still poor. This indicates that the dense and uniform zinc oxide micro-nano structure obtained by the pre-grown seed layer can better enhance the bonding strength between the fiber and the resin. However, the interfacial mechanical interlocking alone is not as effective as the synergistic effect of interfacial mechanical interlocking and chemical bonding in improving the erosion and wear resistance of carbon fiber reinforced composite materials.

[0132] Comparative Example 3

[0133] Compared with Example 1, this comparative example only removes the carbon fiber surface functionalization step in step (3), while all other method steps are the same.

[0134] The morphology of the modified carbon fibers prepared in this comparative example is shown in the figure below. Figure 9 As shown, zinc oxide structures are grown on the surface of carbon fibers, and they are neatly arranged, uniformly grown and dense. Compared with the example, no surface functionalization treatment was performed, so it only has a single mechanical interlocking effect with the resin. However, the surface roughness of the carbon fibers is increased, and the mechanical interlocking effect is stronger than the previous two comparative cases.

[0135] Friction and wear tests showed that the wear rate of the carbon fiber composite material obtained in Comparative Example 3 decreased by 33%. Multiphase flow erosion tests showed that the erosion mass of the in-situ zinc oxide seed layer reinforced carbon fiber composite material decreased by 18.2%, and the volume loss decreased by 16.5%. Further analysis under a scanning electron microscope (e.g., ...) Figure 10 As shown, after the erosion test, the interface between the carbon fiber and epoxy resin was observed. It was found that the bonding between the carbon fiber and epoxy resin at the interface was better than that in Comparative Example 1 and Comparative Example 2, but the overall performance was slightly worse than that in Example 1. This further illustrates that the dense and uniform zinc oxide micro-nano structure obtained by the pre-grown seed layer better enhances the bonding strength between the fiber and the resin and enhances the interfacial mechanical interlocking effect between the carbon fiber and the resin. However, the interfacial mechanical interlocking alone is not as effective as the synergistic effect of interfacial mechanical interlocking and chemical bonding in improving the erosion resistance and wear resistance of carbon fiber reinforced composite materials.

[0136] Comparative Example 4

[0137] Compared to Example 1, this comparative example lacks the step of growing the surface zinc oxide micro / nano structure in step (2), but is otherwise the same as Example 1.

[0138] The morphology of the modified carbon fibers prepared in this comparative example is shown in the figure below. Figure 11 As shown, although zinc oxide structures are grown on the surface of carbon fibers, the growth is sparse and the morphology is similar to that of Comparative Example 1. Compared with the example, although surface functionalization treatment was also performed, the roughness is lower and the mechanical interlocking effect with the resin is weaker than that of Example 1. However, due to the surface functionalization treatment, the binding effect with the resin is stronger than that of Comparative Example 1.

[0139] Friction and wear tests showed that the wear rate of the carbon fiber composite material obtained in Comparative Example 4 decreased by 3.4%. Multiphase flow erosion tests showed that the erosion mass of this composite material decreased by 6.3%, and the volume loss decreased by 7.1%. Further analysis under a scanning electron microscope (e.g., ...) Figure 12 As shown, after the erosion test, the interface between carbon fiber and epoxy resin was observed. It was found that the bonding between carbon fiber and epoxy resin at the interface was better than that in Comparative Example 1, but the overall performance was worse than that in Example 1. This indicates that growing a certain size and a dense and uniform zinc oxide micro-nano structure can better enhance the bonding strength between the fiber and the resin. Enhancing the interfacial mechanical interlocking effect between carbon fiber and resin plays a significant role in enhancing the bonding force between the fiber and the resin. However, neither interfacial mechanical interlocking alone nor surface functionalization treatment alone can improve the erosion resistance and wear resistance of carbon fiber reinforced composite materials as much as the technology of this application through the synergistic effect of interfacial mechanical interlocking and chemical bonding.

[0140] The friction test wear rate data in Examples 1-2 and Comparative Examples 1-4 are as follows: Figure 13 As shown; the erosion test mass loss data in Examples 1-2 and Comparative Examples 1-4 are as follows: Figure 14 As shown; the erosion test volume loss data in Examples 1-2 and Comparative Examples 1-4 are as follows: Figure 15 As shown.

[0141] In addition, the inventors of this case also conducted experiments with other raw materials, process operations, and process conditions described in this specification, referring to the aforementioned embodiments, and obtained relatively ideal results in all cases.

[0142] It should be understood that the technical solutions of the present invention are not limited to the specific embodiments described above. Any technical modifications made to the technical solutions of the present invention without departing from the spirit and scope of the claims are within the scope of protection of the present invention.

Claims

1. A method for preparing modified carbon fiber, characterized in that, include: (1) A first mixed reaction system containing at least carbon fiber, alkaline substance and zinc salt is subjected to a hydrothermal reaction, then cooled to room temperature, and then heated and repeated the hydrothermal reaction and cooling operation to obtain carbon fiber with a seed layer grown on the surface; wherein the carbon fiber includes any one or more combinations of carbon fiber powder and chopped carbon fiber. (2) A second mixed reaction system containing at least the carbon fiber, organic ammonium salt, and zinc salt, comprising the surface-grown seed layer, is subjected to a hydrothermal reaction to obtain carbon fiber with zinc oxide micro / nano structure; wherein the organic ammonium salt comprises any one or more combinations of hexadecyltrimethylammonium bromide, tetraethylammonium sulfate, hexadecyltrimethylammonium fluoride, and alanine dimethylamine salt. (3) The carbon fibers with zinc oxide micro-nano structures are placed in a mixed solution containing silane coupling agent and solvent for functionalization treatment to obtain modified carbon fibers.

2. The preparation method according to claim 1, characterized in that: The alkaline substance includes sodium hydroxide and / or ammonia. And / or, the zinc salt in step (1) includes any one or more combinations of zinc sulfate, zinc acetate dihydrate, zinc nitrate, and zinc chloride.

3. The preparation method according to claim 1, characterized in that: The mass ratio of the alkaline substance to the zinc salt in step (1) is 1: (1.8 to 2.5).

4. The preparation method according to claim 1, characterized in that: The process parameters used in the hydrothermal reaction in step (1) include: temperature of 120-150℃, reaction time of 8-14h, and stirring speed of 100-300rpm.

5. The preparation method according to claim 1, characterized in that: The number of times the hydrothermal reaction and cooling operations are repeated in step (1) is 2 to 5.

6. The preparation method according to claim 1, characterized in that, Step (2) specifically includes: The carbon fiber and zinc salt obtained in step (1) are mixed with water and heated to dissolve and disperse under the conditions of stirring speed of 500-1000 rpm and temperature of 40-65℃ to form a carbon fiber / zinc salt dispersion. At the same time, the pH value of the carbon fiber / zinc salt solution is adjusted to 7.5-9.0 using ammonia water. Organic ammonium salts are mixed with water and heated to dissolve them under conditions of stirring speed of 500-1000 rpm and temperature of 40-65°C to form an organic ammonium salt solution. Furthermore, the organic ammonium salt solution is mixed with the carbon fiber / zinc salt dispersion and reacted at 120–150 °C for 10–14 h, followed by drying to obtain carbon fibers with zinc oxide micro / nano structures.

7. The preparation method according to claim 6, characterized in that: The mass-to-volume ratio of carbon fiber, zinc salt, and water in the surface-grown seed layer is (0.2–0.5) g : (0.29–0.33) g : 20 mL; And / or, the concentration of the ammonia solution is 2-10 wt%; And / or, the mass ratio of the organic ammonium salt to water is (0.0001 to 0.0003):1; And / or, the volume ratio of the organic ammonium salt solution to the carbon fiber / zinc salt dispersion is (0.5~1.5):

1.

8. The preparation method according to claim 6, characterized in that: The drying process is carried out at a temperature of 60–90°C for 8–12 hours.

9. The preparation method according to claim 6, characterized in that: The zinc salt mentioned in step (2) includes any one or a combination of zinc nitrate, zinc chloride, and zinc acetate.

10. The preparation method according to claim 1, characterized in that, Step (3) specifically includes: mixing silane coupling agent, solvent and water, then adding carbon fiber with zinc oxide micro-nano structure and reacting it for 8 to 15 hours under the conditions of stirring speed of 500 to 800 rpm and temperature of 60 to 80℃, and then washing and drying to obtain modified carbon fiber. The volume ratio of the silane coupling agent, anhydrous ethanol, and water is 23:(200-400):(1-5); the silane coupling agent includes any one or more combinations of N-β-aminoethyl-γ-aminopropyltrimethoxysilane, N-(2-aminoethyl)-3-propylaminomethoxymethylsilane, and 3-aminopropyltriethoxysilane; the drying treatment temperature is 60-90℃, and the time is 8-12h.

11. Modified carbon fiber prepared by any one of claims 1-10.

12. A carbon fiber reinforced composite coating, characterized in that: The carbon fiber reinforced composite coating is obtained by mixing the modified carbon fiber, epoxy resin and curing agent as described in claim 11 and applying them to the surface of the substrate for curing.

13. A carbon fiber reinforced composite material, characterized in that: The carbon fiber reinforced composite material is obtained by mixing the modified carbon fiber, epoxy resin and curing agent as described in claim 11 and then curing them.

14. Use of the modified carbon fiber of claim 11, the carbon fiber reinforced composite coating of claim 12, or the carbon fiber reinforced composite material of claim 13 in the preparation of materials for marine environments.

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