Carbon fiber with multi-scale surface structure, application of carbon fiber and method for synergistically improving mechanical property and heat-conducting property of composite explosive

Abstract

The invention relates to the technical field of composite energetic materials, and discloses a carbon fiber with a multi-scale surface structure, an application of the carbon fiber and a method for synergistically improving the mechanical property and heat-conducting property of a composite explosive, and a morphology-controllable zinc oxide nanowire grows in situ on the surface of the carbon fiber coated with polydopamine through a simple and convenient hydrothermal method. And constructing the multi-scale heterostructure carbon fiber filler. Then the multi-scale carbon fiber filler is uniformly dispersed in the composite explosive, through a firm interface structure and a continuous heat transfer path formed between the filler and a high polymer binder, synergistic improvement of heat conduction and mechanical properties of the composite explosive is achieved, the mechanical property improvement amplitude of the composite explosive is 30%-50%, and the heat conduction property improvement amplitude of the composite explosive is 5%-20%. The method is high in expandability and suitable for large-scale preparation, and has important practical application value in the fields of weapon charging and the like.

Description

Technical Field

[0001] The present invention relates to the technical field of composite energetic materials, and in particular to a carbon fiber with a multi-scale surface structure, an application thereof, and a method for synergistically improving the mechanical and thermal conductivity of mixed explosives. Background Art

[0002] The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.

[0003] In high-performance composite explosives (PBX) for weapons, the low thermal conductivity of both the explosive crystals and the polymer binder makes it easy for temperature gradients to form within the explosive components under the complex thermophysical conditions present during weapon transportation, storage, and use. This leads to uneven thermal expansion and thermal stress. Furthermore, the high density of explosive crystals and the numerous interfaces within the components reduce the strength and toughness of the explosive. Consequently, the thermal stresses induced by temperature differences can easily exceed the inherent destructive strength of the composite explosive, causing cracking or failure of the components, thereby compromising their safety and reliability. Therefore, improving the mechanical and thermal conductivity of composite explosives is an important approach to enhancing the thermophysical environmental adaptability of explosive components.

[0004] To enhance the ability of mixed explosives to adapt to thermal environments, the mechanical properties of mixed explosives have been improved. For example, patents (CN106631639A, 2017) and literature (Appl Surf Sci, 2022, 572, 151448) use a modifier containing catechol groups to coat the surface of explosive particles, improving the interfacial strength between the explosive and the binder, thereby enhancing mechanical properties. Chinese patents (CN109734547B, 2019; CN109369315B, 2020) enhance the mechanical properties of mixed explosives by in-situ grafting hyperbranched polymers onto the surface of the explosive to enhance the interfacial interaction between the binder and the explosive surface. On the other hand, the thermal conductivity of mixed explosives is enhanced. For example, patent (CN107759427A, 2018) invented an alternating microlayered thermally conductive PBX mixed explosive and its preparation method, which is mainly based on the efficient dispersion of thermally conductive fillers such as graphene and carbon nanotubes in PBX. Patent (CN110183291A, 2019) invented a method for improving the thermal conductivity of mixed explosives, using Chinese ink as a thermally conductive filler, which is efficiently dispersed in the mixed explosive to achieve a significant improvement in its thermal conductivity coefficient. However, the current technical means for achieving improved thermal conductivity or mechanical properties of mixed explosives mainly focus on optimizing a single performance. There is a certain constraint relationship between the different properties of mixed explosives, making it difficult to achieve a synergistic improvement in performance. Therefore, how to design and construct high-strength fillers, build a strong interface structure and thermal conductive network inside the mixed explosive, and achieve synergistic optimization of the thermal conductivity and mechanical properties of mixed explosives is a major technical bottleneck in this research field.

[0005] The prior art document "Research Progress on Carbon Fiber Surface Modification and Its Effect on Carbon Fiber / Resin Interface" discloses the following content: "Ulises et al. studied the effect of the morphology of zinc oxide nanowires introduced on the carbon fiber surface on the interfacial strength of fiber composites. Zinc oxide plays a role in stitching the interface between the matrix and the fiber, "and zinc oxide nanoparticles increase the specific surface area of the fiber." The increase in specific surface area can effectively reduce interfacial stress concentration, "smoothly transfer stress from the aggregate to the fiber," and thus improve the shear strength of the composite material.

[0006] The difference between this application and the reference document is that the advantages of this application over the reference document are: ① Dual interface reinforcement: Polydopamine is anchored to the carbon fiber surface through π-π conjugation, and simultaneously forms a coordination bond with zinc oxide nanowires, achieving synergistic interface reinforcement of chemical bonding and physical anchoring. ② Multi-level stress transfer optimization: A gradient modulus interface is constructed through the polydopamine layer, combined with uniformly distributed zinc oxide nanowires, to better reduce stress concentration and effectively extend the crack propagation path. Summary of the Invention

[0007] The present invention addresses the shortcomings of existing technologies by providing a carbon fiber with a multiscale surface structure, its application, and a method for synergistically improving the mechanical and thermal conductivity of mixed explosives. The method utilizes a simple hydrothermal method to in-situ grow morphologically controllable zinc oxide nanowires on the surface of polydopamine-coated carbon fibers, using polydopamine as an interface reinforcement layer to construct a multiscale heterogeneous structured filler. This multiscale carbon fiber filler is then uniformly dispersed in the mixed explosive. The strong interface structure and continuous heat transfer path formed between the filler and the polymer binder achieve synergistic improvements in the thermal and mechanical properties of the mixed explosive.

[0008] The technical solutions of the present invention are as follows:

[0009] The present invention provides a carbon fiber material with a multi-scale surface structure, wherein the carbon fiber surface is coated with polydopamine; zinc oxide nanowires are uniformly grown on the polydopamine surface. The polydopamine in the carbon fiber material has a thickness of 10-15 nm, and the zinc oxide nanowires have a length of 400-850 nm and a diameter of 40-130 nm.

[0010] Preferably, the thickness of the polydopamine in the carbon fiber material is 10-15 nm, the length of the zinc oxide nanowire is 400-800 nm, and the diameter is 40-100 nm.

[0011] According to a preferred embodiment, the carbon fibers are chopped carbon fibers, preferably with a diameter of 2-10 μm and a length of 1-3 mm.

[0012] Another aspect of the present invention provides a method for preparing the carbon fiber material as described above, comprising the following steps:

[0013] Step (1): adding carbon fiber and dopamine to a Tris buffer solution in a certain mass ratio, stirring and reacting, thereby obtaining polydopamine-coated carbon fiber; the longer the reaction time, the greater the loading amount and thickness of polydopamine on the carbon fiber; the mass ratio of carbon fiber to dopamine and the stirring speed have little effect on the structure;

[0014] Step (2): preparing a zinc oxide seed solution and a growth solution of a certain concentration, immersing the polydopamine-coated carbon fiber in the zinc oxide seed solution and performing a heat treatment (the concentration of the seed solution affects the loading amount of zinc oxide nanowires on the carbon fiber, but has little effect on the length and diameter of the zinc oxide nanowires; the heat treatment conditions mainly allow the zinc oxide nanowires to be coated on the surface of the carbon fiber, and have little effect on the length and diameter of the zinc oxide nanowires), and then immersing it in a zinc oxide growth solution for a hydrothermal reaction (the higher the concentration of the growth solution, the longer the reaction time, and the larger the diameter and length of the zinc oxide nanowires; the conditions of the hydrothermal reaction mainly provide a certain temperature and pressure for the system to ensure that the zinc oxide seed layer on the surface of the carbon fiber can epitaxially grow into zinc oxide nanowires, and have little effect on the length and diameter of the zinc oxide nanowires), so as to uniformly grow zinc oxide nanowires on the surface of the carbon fiber to obtain a carbon fiber filler with a multi-scale surface structure.

[0015] According to a preferred embodiment, the pH value of the Tris buffer solution in step (1) is 8.5, the stirring speed is 200-600 rpm, and the stirring reaction time is 4-6 h.

[0016] According to a preferred embodiment, the zinc oxide seed solution in step (2) is a mixed solution of zinc acetate dihydrate, sodium hydroxide, and ethanol, wherein the concentrations of zinc acetate dihydrate and sodium hydroxide are the same, both being 2 to 6 mmol / L. The heat treatment environment is an oven atmosphere, the heat treatment temperature is 150° C., and the heat treatment time is 15 to 45 minutes.

[0017] According to a preferred embodiment, the zinc oxide growth solution in step (2) is a mixed solution of zinc nitrate hexahydrate, hexamethylenetetramine, and deionized water, wherein the concentrations of zinc nitrate hexahydrate and hexamethylenetetramine are the same, both ranging from 6.25 to 100 mmol / L. The hydrothermal reaction is carried out in a water bath or hydrothermal reactor at a temperature of 90°C and a reaction time of 0.5 to 4 hours.

[0018] Another aspect of the present invention provides the use of the aforementioned carbon fiber material in improving the thermal conductivity of the material.

[0019] Preferably, the application is, for example, uniformly dispersing the carbon fiber material as a heat conductive material in explosives.

[0020] Another aspect of the present invention provides a method for synergistically improving the mechanical and thermal conductivity of mixed explosives, comprising uniformly dispersing the carbon fiber material as described above as a thermal conductive material in the explosive.

[0021] On the other hand, the present invention provides a mixed explosive with excellent mechanical and thermal conductivity, comprising 0.3wt% to 2wt% of the carbon fiber material with a multi-scale surface structure as described above, 3wt% to 4.7wt% of a polymer binder and 95wt% of explosive powder.

[0022] According to a preferred embodiment, the explosive is one of hexanitrohexaazaisopentazolidine (CL-20), octogenol (HMX), hexanitroquinone (RDX), 1,3,5-triamino-2,4,6-trinitrobenzene (TATB), 1-oxy-diamino-3,5-dinitropyrazine (LLM-105), and 1,1-diamino-2,2-dinitroethylene explosive (FOX-7).

[0023] According to a preferred embodiment, the polymer binder is one of fluororubber, polyurethane, and vinyl acetate cellulose.

[0024] Another aspect of the present invention provides a method for preparing the aforementioned mixed explosive, comprising the following steps:

[0025] Step (1): preparing the carbon fiber material as described above;

[0026] Step (2): uniformly mixing the modified carbon fiber and the polymer binder solution by ultrasonic dispersion;

[0027] Step (3): adding the mixture of step (2) to explosives, obtaining explosive molding powder by water suspension method, filtering, washing, drying, and pressing into explosive columns, thereby obtaining mixed explosive pieces with synergistically improved mechanical and thermal conductivity properties.

[0028] According to a preferred embodiment, the ultrasonic frequency in step (1) is 100 kHz and the ultrasonic time is 10 min.

[0029] Preferably, the water suspension granulation method described in step (2) refers to the process of dispersing explosive powder in water, stirring to form a suspension, heating to 60°C, adding a pre-prepared mixed solution of carbon fiber and binder, and applying vacuum to remove the organic solvent, so that the binder is gradually coated to obtain explosive molding powder.

[0030] Preferably, the drug column pressing described in step (3) refers to using a stainless steel mold to press it into a small drug column of Φ20mm×6mm under 120kN conditions, and using a laser flash method to test the thermal conductivity and an INSTRON electronic universal testing machine to test the mechanical properties.

[0031] Compared with the existing technology, the beneficial effects of the present invention are:

[0032] 1. A carbon fiber with a multi-scale surface structure, its application, and a method for synergistically improving the mechanical and thermal conductivity of mixed explosives. The polydopamine layer on the surface of the carbon fiber with a multi-scale surface structure can serve as an interface reinforcement layer to improve the interface strength between zinc oxide nanowires and carbon fibers. The arrayed zinc oxide nanowires can increase the roughness and complexity of the carbon fiber surface, forming a mechanical interlocking structure with the binder, enhancing interfacial interactions and optimizing thermal conductivity paths.

[0033] 2. A carbon fiber with a multiscale surface structure, its application, and a method for synergistically improving the mechanical and thermal conductivity of mixed explosives. The carbon fiber with a multiscale surface structure is applied to mixed explosives to achieve synergistic improvements in the mechanical and thermal conductivity of the mixed explosives, effectively enhancing their environmental adaptability. The mechanical properties of the mixed explosives are improved by 30% to 50%, and the thermal conductivity is improved by 5% to 20%. This method is highly scalable and suitable for large-scale production, with important practical applications in areas such as weapons charges. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 1 is a process flow chart of the preparation method of the present invention;

[0035] Figure 2 Scanning electron microscope images of a carbon fiber material with a multi-scale surface structure according to Example 1 of the present invention; (a) is a carbon fiber magnified 8000 times, with a scale bar of 1 μm; (b) is a carbon fiber magnified 60,000 times, with a scale bar of 100 nm;

[0036] Figure 3 Brazilian stress-strain curves of the mixed explosives added with different carbon fiber materials in Example 1 provided by the present invention;

[0037] Figure 4 This is a Brazilian stress-strain curve diagram of the mixed explosive with zinc oxide nanowires of different diameters added in Example 1 of the present invention. DETAILED DESCRIPTION

[0038] The specific embodiments listed in the present invention are only examples of the present invention, and the present invention is not limited to the specific embodiments described below. For those skilled in the art, any equivalent modifications and substitutions to the embodiments described below are also within the scope of the present invention. Therefore, equivalent transformations and modifications made without departing from the spirit and scope of the present invention should be included within the scope of the present invention. If specific conditions are not specified in the embodiments, they are carried out according to conventional conditions or conditions recommended by the manufacturer. All reagents or instruments without the manufacturer specified are conventional products that can be purchased commercially. In order to better illustrate the present invention, numerous specific details are given in the specific embodiments below. Those skilled in the art should understand that the present invention can also be implemented without certain specific details. In other embodiments, methods, means, equipment and steps well known to those skilled in the art are not described in detail in order to highlight the main purpose of the present invention.

[0039] Unless otherwise defined, all technical and scientific terms used herein have the same meanings as commonly understood by those skilled in the art. Unless otherwise specified, the units used in this specification are International Standard Units, and the numerical values and numerical ranges appearing in this invention should be understood to include the inevitable systematic errors in industrial production.

[0040] The features and performance of the present invention are further described in detail below with reference to the embodiments.

[0041] Example 1

[0042] Refer to Figure 1 The process flow chart shown is for preparing mixed explosives:

[0043] Step (1): Weigh 0.12 g of tris (hydroxymethyl)aminomethane (Tris) and dissolve it in 200 mL of deionized water. Then, add dilute hydrochloric acid dropwise to prepare a Tris buffer solution with a pH of 8.5. Then, add 0.5 g of 1 mm long chopped carbon fiber and 0.25 g of dopamine to the Tris buffer solution. Stir evenly at a speed of 200 rpm. After reacting for 4 hours, wash with deionized water and dry to obtain polydopamine-coated carbon fiber.

[0044] Step (2): Weigh 0.11g zinc acetate dihydrate and 0.02g sodium hydroxide and dissolve them in 250mL ethanol to prepare a 2mmol / L zinc oxide seed solution. Immerse 0.5g of polydopamine-coated carbon fiber in the zinc oxide seed solution and filter it. Heat treat it in an oven at 150℃ for 15min to obtain carbon fiber coated with zinc oxide seeds. Weigh 0.185g zinc nitrate hexahydrate and 0.0875g hexamethylenetetramine and dissolve them in 200mL deionized water to prepare a 6.25mmol / L zinc oxide growth solution. Add the above 0.5g of zinc oxide seed-coated carbon fiber to a hydrothermal reactor containing the zinc oxide growth solution, and react in a water bath at 90℃ for 0.5h. Then, use ultrasonic washing and drying to obtain a carbon fiber material with a multi-scale surface structure in the present invention; polydopamine thickness: 10nm, zinc oxide nanowire length: 420nm, diameter: 40nm; scanning electron microscope image as shown Figure 2 shown.

[0045] Step (3): Weigh 0.15g of the filler prepared in step (2) and add it to a polymer solution containing 2.35g of polyurethane. Disperse it ultrasonically at a frequency of 100kHz for 10 minutes to obtain a filler-containing binder solution for use. Weigh 47.5g of TATB explosive, add 50g of water, and stir and disperse to form an explosive suspension. Heat to 60°C, start adding the filler-containing binder solution dropwise, and apply vacuum to remove the organic solvent. After the solvent evaporates, the explosive molding powder is obtained. After filtering, washing with water, drying, and pressing into a powder column, a mixed explosive with synergistically improved mechanical and thermal conductivity properties can be obtained. The results of mechanical and thermal conductivity tests show that compared with the pure mixed explosive, the Brazilian tensile strength and strain of the mixed explosive obtained in this embodiment are increased by 35% and 80%, respectively, and the thermal conductivity coefficient is increased by 7.5%. At the same content, compared with the mixed explosive in which only carbon fibers coated with zinc oxide nanowires of the same diameter and length are added, the Brazilian tensile strength and strain are increased by 15% and 20%, respectively.

[0046] Example 2

[0047] Step (1): Weigh 0.12 g of tris(hydroxymethyl)aminomethane (Tris) and dissolve it in 200 mL of deionized water. Then, add dilute hydrochloric acid dropwise to prepare a Tris buffer solution with a pH of 8.5. Then, add 0.5 g of 2 mm long chopped carbon fiber and 0.25 g of dopamine to the Tris buffer solution. Stir evenly at a speed of 300 rpm. After reacting for 5 hours, wash with deionized water and dry to obtain polydopamine-coated carbon fiber.

[0048] Step (2): Weigh 0.165g of zinc acetate dihydrate and 0.03g of sodium hydroxide and dissolve them in 250mL of ethanol to prepare a 3mmol / L zinc oxide seed solution. Immerse 0.5g of polydopamine-coated carbon fiber in the zinc oxide seed solution and filter it. Heat treat it in an oven at 150°C for 25min to obtain zinc oxide seed-coated carbon fiber. Weigh 0.37g of zinc nitrate hexahydrate and 0.175g of hexamethylenetetramine and dissolve them in 200mL of deionized water to prepare a 12.5mmol / L zinc oxide growth solution. Add the above 0.5g of zinc oxide seed-coated carbon fiber to a hydrothermal reactor containing the zinc oxide growth solution, react in a water bath at 90°C for 1h, and then ultrasonically wash and dry to obtain a filler with a multi-scale surface structure according to the present invention; polydopamine thickness: 12nm, zinc oxide nanowire length: 480nm, diameter: 52nm.

[0049] Step (3): Weigh 0.25g of the filler prepared in step (2) and add it to a polymer solution containing 2.25g of fluororubber. Ultrasonic dispersion is performed at a frequency of 100kHz for 10 minutes to obtain a filler-containing binder solution for use. Weigh 47.5g of HMX explosive, add 50g of water, and stir and disperse to form an explosive suspension. Heat to 60°C, start adding the filler-containing binder solution dropwise, and apply vacuum to remove the organic solvent. After the solvent evaporates, the explosive molding powder is obtained. After filtering, washing with water, drying, and pressing into a powder column, a mixed explosive with synergistically improved mechanical and thermal conductivity properties can be obtained. Through mechanical and thermal conductivity tests, the results show that compared with the pure mixed explosive, the Brazilian tensile strength and strain of the mixed explosive obtained in this embodiment are increased by 41% and 102% respectively, and the thermal conductivity coefficient is increased by 11.4%. At the same content, compared with the mixed explosive added with carbon fiber coated with zinc oxide nanowires of the same diameter and length, the Brazilian tensile strength and strain are increased by 20% and 18% respectively.

[0050] Example 3

[0051] Step (1): Weigh 0.12 g of tris (hydroxymethyl)aminomethane (Tris) and dissolve it in 200 mL of deionized water. Then, add dilute hydrochloric acid dropwise to prepare a Tris buffer solution with a pH of 8.5. Then, add 0.5 g of 3 mm long chopped carbon fiber and 0.25 g of dopamine to the Tris buffer solution. Stir evenly at a speed of 400 rpm. After reacting for 6 hours, wash with deionized water and dry to obtain polydopamine-coated carbon fiber.

[0052] Step (2): Weigh 0.22g zinc acetate dihydrate and 0.04g sodium hydroxide and dissolve them in 250mL ethanol to prepare a 4mmol / L zinc oxide seed solution. Immerse 0.5g of polydopamine-coated carbon fiber in the zinc oxide seed solution and filter it. Heat treat it in an oven at 150°C for 35min to obtain zinc oxide seed-coated carbon fiber. Weigh 0.74g zinc nitrate hexahydrate and 0.35g hexamethylenetetramine and dissolve them in 200mL deionized water to prepare a 25mmol / L zinc oxide growth solution. Add the above 0.5g zinc oxide seed-coated carbon fiber to a hydrothermal reactor containing the zinc oxide growth solution and react in a water bath at 90°C for 2h. After ultrasonic washing and drying, obtain a filler with a multi-scale surface structure according to the present invention, wherein the polydopamine thickness is 15nm, the zinc oxide nanowire length is 590nm, and the diameter is 73nm.

[0053] Step (3): Weigh 0.5g of the filler prepared in step (2) and add it to a polymer solution containing 2g of vinyl acetate cellulose. Disperse it ultrasonically at a frequency of 100kHz for 10 minutes to obtain a filler-containing binder solution for use. Weigh 47.5g of CL-20 explosive, add 50g of water, and stir and disperse to form an explosive suspension. Heat to 60°C, start adding the filler-containing binder solution dropwise, and apply vacuum to remove the organic solvent. After the solvent evaporates, the explosive molding powder is obtained. After filtering, washing with water, drying, and pressing into a powder column, a mixed explosive with synergistically improved mechanical and thermal conductivity properties can be obtained. The results of mechanical and thermal conductivity tests show that compared with the pure mixed explosive, the Brazilian tensile strength and strain of the mixed explosive obtained in this embodiment are increased by 37% and 110%, respectively, and the thermal conductivity coefficient is increased by 13.2%. At the same content, compared with the mixed explosive added with carbon fiber coated with zinc oxide nanowires of the same diameter and length, the Brazilian tensile strength and strain are increased by 22% and 18%, respectively.

[0054] Example 4

[0055] Step (1): Weigh 0.12 g of tris(hydroxymethyl)aminomethane (Tris) and dissolve it in 200 mL of deionized water. Then, add dilute hydrochloric acid dropwise to prepare a Tris buffer solution with a pH of 8.5. Then, add 2 g of 3 mm long chopped carbon fiber and 0.25 g of dopamine to the Tris buffer solution. Stir evenly at a speed of 500 rpm. After reacting for 6 hours, wash with deionized water and dry to obtain polydopamine-coated carbon fiber.

[0056] Step (2): Weigh 0.33g zinc acetate dihydrate and 0.06g sodium hydroxide and dissolve them in 250mL ethanol to prepare a 6mmol / L zinc oxide seed solution. Immerse 2g of polydopamine-coated carbon fiber in the zinc oxide seed solution and filter it. Heat treat it in an oven at 150°C for 45min to obtain zinc oxide seed-coated carbon fiber. Weigh 1.48g zinc nitrate hexahydrate and 0.7g hexamethylenetetramine and dissolve them in 200mL deionized water to prepare a 50mmol / L zinc oxide growth solution. Add the above 2g of zinc oxide seed-coated carbon fiber to a hydrothermal reactor containing the zinc oxide growth solution and react in a water bath at 90°C for 3h. After ultrasonic washing and drying, a filler with a multi-scale surface structure according to the present invention is obtained. The polydopamine thickness is 15nm, the zinc oxide nanowire length is 670nm, and the diameter is 85nm.

[0057] Step (3): Weigh 1.5g of the filler prepared in step (2) and add it to a polymer solution containing 3.5g of fluororubber. Disperse it for 10 minutes under ultrasound at a frequency of 100kHz to obtain a filler-containing binder solution for use. Weigh 95g of LLM-105 explosive, add 100g of water, and stir and disperse to form an explosive suspension. Heat to 60°C, start adding the filler-containing binder solution dropwise, and apply vacuum to remove the organic solvent. After the solvent evaporates, the explosive molding powder is obtained. After filtering, washing with water, drying, and pressing into a powder column, a mixed explosive with synergistically improved mechanical and thermal conductivity properties can be obtained. Through mechanical and thermal conductivity tests, the results show that compared with the pure mixed explosive, the Brazilian tensile strength and strain of the mixed explosive obtained in this embodiment are increased by 43% and 96% respectively, and the thermal conductivity coefficient is increased by 17.4%. At the same content, compared with the mixed explosive added with carbon fiber coated with zinc oxide nanowires of the same diameter and length, the Brazilian tensile strength and strain are increased by 12% and 25% respectively.

[0058] Example 5

[0059] Step (1): Weigh 0.12 g of tris(hydroxymethyl)aminomethane (Tris) and dissolve it in 200 mL of deionized water. Then, add dilute hydrochloric acid dropwise to prepare a Tris buffer solution with a pH of 8.5. Then, add 3 g of chopped carbon fibers with a length of 3 mm and 0.25 g of dopamine to the Tris buffer solution. Stir evenly at a speed of 600 rpm. After reacting for 6 hours, wash with deionized water and dry to obtain polydopamine-coated carbon fibers.

[0060] Step (2): Weigh 0.33g zinc acetate dihydrate and 0.06g sodium hydroxide and dissolve them in 250mL ethanol to prepare a 6mmol / L zinc oxide seed solution. Immerse 2.5g of polydopamine-coated carbon fiber in the zinc oxide seed solution and filter it. Heat treat it in an oven at 150°C for 30min to obtain zinc oxide seed-coated carbon fiber. Weigh 2.22g zinc nitrate hexahydrate and 1.05g hexamethylenetetramine and dissolve them in 200mL deionized water to prepare a 75mmol / L zinc oxide growth solution. Add the above 2.5g zinc oxide seed-coated carbon fiber to a hydrothermal reactor containing the zinc oxide growth solution and react in a water bath at 90°C for 3h. After ultrasonic washing and drying, a filler with a multi-scale surface structure according to the present invention is obtained. The polydopamine thickness is 15nm, the zinc oxide nanowire length is 730nm, and the diameter is 105nm.

[0061] Step (3): Weigh 2g of the filler prepared in step (2) and add it to a polymer solution containing 3g of polyurethane. Disperse it ultrasonically at a frequency of 100kHz for 10 minutes to obtain a filler-containing binder solution for use. Weigh 95g of RDX explosive, add 100g of water, and stir and disperse to form an explosive suspension. Heat to 60°C, start adding the filler-containing binder solution dropwise, and apply vacuum to remove the organic solvent. After the solvent evaporates, the explosive molding powder is obtained. After filtering, washing with water, drying, and pressing into a powder column, a mixed explosive with synergistically improved mechanical and thermal conductivity properties can be obtained. The results of mechanical and thermal conductivity tests show that compared with the pure mixed explosive, the Brazilian tensile strength and strain of the mixed explosive obtained in this embodiment are increased by 42% and 97% respectively, and the thermal conductivity coefficient is increased by 16.3%. At the same content, compared with the mixed explosive added with carbon fiber coated with zinc oxide nanowires of the same diameter and length, the Brazilian tensile strength and strain are increased by 10% and 15% respectively.

[0062] Example 6

[0063] Step (1): Weigh 0.12 g of tris(hydroxymethyl)aminomethane (Tris) and dissolve it in 200 mL of deionized water. Then, add dilute hydrochloric acid dropwise to prepare a Tris buffer solution with a pH of 8.5. Then, add 2.5 g of 3 mm long chopped carbon fiber and 0.25 g of dopamine to the Tris buffer solution. Stir evenly at a speed of 600 rpm. After reacting for 6 hours, wash with deionized water and dry to obtain polydopamine-coated carbon fiber.

[0064] Step (2): Weigh 0.33g zinc acetate dihydrate and 0.06g sodium hydroxide and dissolve them in 250mL ethanol to prepare a 6mmol / L zinc oxide seed solution. Immerse 2.5g of polydopamine-coated carbon fiber in the zinc oxide seed solution and filter it. Heat treat it in an oven at 150°C for 30min to obtain zinc oxide seed-coated carbon fiber. Weigh 2.96g zinc nitrate hexahydrate and 1.4g hexamethylenetetramine and dissolve them in 200mL deionized water to prepare a 100mmol / L zinc oxide growth solution. Add the above 2.5g zinc oxide seed-coated carbon fiber to a hydrothermal reactor containing the zinc oxide growth solution and react in a water bath at 90°C for 4h. After ultrasonic washing and drying, a filler with a multi-scale surface structure according to the present invention is obtained. The polydopamine thickness is 15nm, the zinc oxide nanowire length is 800nm, and the diameter is 130nm.

[0065] Step (3): Weigh 2g of the filler prepared in step (2) and add it to a polymer solution containing 3g of polyurethane. Disperse it ultrasonically at a frequency of 100kHz for 10 minutes to obtain a filler-containing binder solution for use. Weigh 95g of FOX-7 explosive, add 100g of water, and stir and disperse to form an explosive suspension. Heat to 60°C, start adding the filler-containing binder solution dropwise, and apply vacuum to remove the organic solvent. After the solvent evaporates, the explosive molding powder is obtained. After filtering, washing with water, drying, and pressing into a powder column, a mixed explosive with synergistically improved mechanical and thermal conductivity properties can be obtained. The results of mechanical and thermal conductivity tests show that compared with the pure mixed explosive, the Brazilian tensile strength and strain of the mixed explosive obtained in this embodiment are increased by 42% and 97% respectively, and the thermal conductivity coefficient is increased by 14.3%. At the same content, compared with the mixed explosive added with carbon fiber coated with zinc oxide nanowires of the same diameter and length, the Brazilian tensile strength and strain are increased by 15% and 20% respectively.

[0066] Example 7 Effect of Variation in the Thickness of Zinc Oxide Nanowires on the Performance of Mixed Explosives

[0067] like Figure 4 As shown in the graph, the 40 nm ZnO nanowires have higher Brazilian tensile strength and higher strain rate than the 73 nm and 105 nm ZnO nanowires.

[0068] Example 8: Differences in the effects of different carbon fiber materials on the performance of mixed explosives

[0069] like Figure 3Shown are the effects of no filler, the addition of the same amount of unmodified carbon fiber, the addition of polydopamine-coated carbon fiber (polydopamine thickness: 15 nm), the addition of carbon fiber coated with zinc oxide nanowires (diameter 52 nm, length 480 nm), and the addition of carbon fiber coated with polydopamine and zinc oxide nanowires (polydopamine thickness: 15 nm, zinc oxide nanowire diameter 52 nm, length 480 nm) on the mechanical properties of the mixed explosives (the added mass of all fillers is the same).

[0070] from Figure 3 As can be seen in the figure, the addition of polydopamine enhances the Brazilian tensile strength of the mixed explosive, but the strain is not as good as that of the carbon fiber coated with zinc oxide nanowires. Carbon fibers coated with both polydopamine and zinc oxide nanowires show significant improvements in both Brazilian tensile strength and strain compared to either element alone, demonstrating a synergistic effect. The formula of the mixed explosive is as follows: explosive (content 95wt%): 1,3,5-triamino-2,4,6-trinitrobenzene (TATB), polymer binder (content 4.6wt%): fluororubber, carbon fiber filler (content 0.4wt%).

[0071] The above-described embodiments merely represent specific implementation methods of the present application. While the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of protection of the present application. It should be noted that a person skilled in the art could make various modifications and improvements without departing from the technical concept of the present application, all of which fall within the scope of protection of the present application.

Claims

1. A carbon fiber material with a multi-scale surface structure, characterized in that: The surface of the carbon fiber is coated with polydopamine; zinc oxide nanowires are uniformly grown on the surface of the polydopamine.

2. The carbon fiber material with a multi-scale surface structure according to claim 1, characterized in that: The carbon fiber is chopped carbon fiber.

3. The method for preparing a carbon fiber material with a multi-scale surface structure according to claim 1 or 2, characterized in that: The steps include: Step (1): adding carbon fiber and dopamine to a Tris buffer solution, stirring and reacting to obtain polydopamine-coated carbon fiber; Step (2): preparing a zinc oxide seed solution and a growth solution, immersing the polydopamine-coated carbon fiber in the zinc oxide seed solution and performing a heat treatment, and then immersing it in a zinc oxide growth solution for a hydrothermal reaction to uniformly grow zinc oxide nanowires on the surface of the carbon fiber, thereby obtaining a carbon fiber material with a multi-scale surface structure.

4. The method for preparing a carbon fiber material with a multi-scale surface structure according to claim 3, characterized in that: The zinc oxide seed solution described in step (2) is a mixed solution of zinc acetate dihydrate, sodium hydroxide and ethanol, and the concentrations of zinc acetate dihydrate and sodium hydroxide are the same, and are both 2-6 mmol / L.

5. The method for preparing a carbon fiber material with a multi-scale surface structure according to claim 3, characterized in that: The heat treatment environment in step (2) is an oven atmosphere, the heat treatment temperature is 150° C., and the heat treatment time is 15 min to 45 min.

6. The method for preparing a carbon fiber material with a multi-scale surface structure according to claim 3, characterized in that: The zinc oxide growth solution described in step (2) is a mixed solution of zinc nitrate hexahydrate, hexamethylenetetramine and deionized water, and the concentrations of zinc nitrate hexahydrate and hexamethylenetetramine are the same, both of which are 6.25-100 mmol / L.

7. The method for preparing a carbon fiber material with a multi-scale surface structure according to claim 3, characterized in that: The hydrothermal reaction in step (2) is carried out in a water bath and a hydrothermal reactor environment, the reaction temperature is 90° C., and the reaction time is 0.5 h to 4 h.

8. A method for synergistically improving the mechanical and thermal conductivity of mixed explosives, characterized in that: The steps include: Step (1): preparing the carbon fiber material as claimed in claim 1 or 2; Step (2): uniformly mixing the modified carbon fiber material and the polymer binder solution by ultrasonic dispersion; Step (3): adding the mixture of step (2) to explosives, obtaining explosive molding powder by water suspension method, filtering, washing, drying, and pressing into explosive columns, thereby obtaining mixed explosive pieces with synergistically improved mechanical and thermal conductivity properties.

9. A method for synergistically improving the mechanical and thermal conductivity of mixed explosives according to claim 8, characterized in that: The mass percentage of the carbon fiber material in step (2) is 0.3wt% to 2wt%; the mass percentage of the polymer binder is 3wt% to 4.7wt%; and the mass percentage of the explosive powder in step (3) is 95wt%.

10. A method for synergistically improving the mechanical and thermal conductivity of mixed explosives according to claim 8, characterized in that: The explosive is one of hexanitrohexaazaisopentazolane (CL-20), octogenol (HMX), hexogenol (RDX), 1,3,5-triamino-2,4,6-trinitrobenzene (TATB), 1-oxy-diamino-3,5-dinitropyrazine (LLM-105), and 1,1-diamino-2,2-dinitroethylene explosive (FOX-7); and the polymer binder is one of fluororubber, polyurethane, and vinyl acetate cellulose.

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