Composite boron powder and preparation method thereof

Abstract

The present invention relates to a composite boron powder and a preparation method thereof. The composite boron powder is prepared by a secondary condensation method using a vinylidene fluoride / propylene alcohol copolymer as a compounding agent, a polyethylene glycol monobutyl ether acrylate / acrylonitrile / allylamine / hydroxyethyl acrylate copolymer as an auxiliary compounding agent, an epoxy resin as a high-strength composite adhesive, and diethylenetriamine as a curing agent. The amounts of the components are based on the mass of the boron powder: the mass of the vinylidene fluoride / propylene alcohol copolymer is 1-2% of the mass of the boron powder, the mass of the polyethylene glycol monobutyl ether acrylate / acrylonitrile / allylamine / hydroxyethyl acrylate copolymer is 0.3-1% of the mass of the boron powder, the mass of the epoxy resin is 2-3% of the mass of the boron powder, and the mass of the diethylenetriamine is 0.15-0.4% of the mass of the boron powder.

Description

Technical Field

[0001] The invention belongs to the field of fuel-rich propellants for solid ramjet engines and relates to composite boron powder and a preparation method thereof. Background Art

[0002] Air-breathing cruise vehicles are capable of full-range powered cruising, offering unique advantages such as rapid response, strong penetration capability, ballistic maneuvers without significant speed loss, and high terminal velocity. They represent a disruptive development direction for future aircraft. Scramjet engines are a bottleneck technology limiting the development of air-breathing cruise vehicles, and are considered a key strategic development direction by the world's leading aerospace powers. Solid scramjet engines not only offer the advantages of high specific impulse and high propulsion efficiency at hypersonic speeds, but also possess the inherent advantages of traditional solid rocket engines, such as simple structure, compact size, low cost, high safety and reliability, and excellent storability and maintainability. These engines meet the engineering application requirements of low-cost, high-reliability, strong environmental adaptability, and long-term, all-weather operation.

[0003] Solid scramjet engines use solid fuel-rich propellant as a power source, with a fuel content of 30-50%. Therefore, fuel performance is one of the key factors that determine whether the potential excellent performance of solid rocket ramjet engines can be fully utilized. Boron-containing fuel-rich propellant has a very high calorific value and is the preferred propellant for solid scramjet engines.

[0004] However, boron powder has high melting and boiling points, making it difficult to melt and vaporize. The ignition temperature is relatively high (1900K), and during the combustion process, highly sticky boron oxide (B2O3) is produced, which covers the surface of the boron powder, making it difficult to ignite the boron powder and difficult to burn fully.

[0005] Impurities such as B2O3 and H3BO3 on the surface of boron powder can trigger condensation reactions between hydroxyl-terminated polybutadiene (HTPB) molecules during the charging process, potentially leading to further polymerization of the HTPB. This reaction can seriously interfere with the charging process of propellants using HTPB as a binder. For example, during the charging process of boron-rich solid propellants, the mixing of boron powder and HTPB in the presence of H3BO3 can cause certain compounds to undergo condensation reactions to form polymers. The more thorough the mixing, the more polymers are produced, and in severe cases, viscosity issues can render the charge useless. Furthermore, because impurities such as B2O3 and H3BO3 severely impact process performance, the boron content in propellants cannot be increased. Generally, the boron content in propellants does not exceed 30%. Since boron powder is the primary source of energy in boron-containing propellants, a low boron content can compromise the propellant's energy performance.

[0006] In addition, due to the active chemical properties of boron powder, it is very easy to oxidize to form B2O3 during storage, and then generate highly viscous and loose H3BO3 to cover the surface of the boron powder, causing the boron powder to aggregate and seriously affect the dispersion of the boron powder. Since H3BO3 is a loose porous structure, it will absorb oxygen and water in the air, causing further oxidation of the boron powder, seriously affecting the storage performance of the propellant. Summary of the Invention

[0007] In order to solve the problems in the prior art of propellant process deterioration, energy improvement difficulties and storage difficulties caused by the presence of high-viscosity substances on the surface of boron powder that affect the process performance, the present invention provides a composite boron powder and a preparation method thereof. The present invention uses a vinylidene fluoride / propylene alcohol copolymer that can destroy the boron oxide layer and improve the combustion efficiency of the boron powder to compound with the boron powder. The copolymer with a multi-hydroxy structure can fully combine with the oxide layer on the surface of the boron powder and firmly cover the surface of the boron powder. At the same time, an epoxy resin with high mechanical strength is used for secondary compounding, which completely isolates the boron powder from contact with air, solves the storage problem of the boron powder and the problem of reduced combustion efficiency caused by oxidation of the boron powder when directly exposed to air. At the same time, it solves the problem of boron powder agglomeration caused by the generation of sticky products due to oxidation of the boron powder, which leads to deterioration of the process performance. The effective amount of boron powder in the propellant can be effectively increased, and the energy performance of the propellant can be improved. The boron powder prepared by compounding with the epoxy resin with high mechanical strength has a regular morphology, which is more conducive to improving the process performance of the propellant.

[0008] The technical solution of the present invention is to first provide a composite boron powder, the raw material components of which include boron powder, vinylidene fluoride / propylene alcohol copolymer, acrylate polyethylene glycol monobutyl ether ester / acrylonitrile / allylamine / hydroxyethyl acrylate copolymer, epoxy resin and diethylenetriamine. The composite boron powder uses the vinylidene fluoride / propylene alcohol copolymer as a compounding agent, the acrylate polyethylene glycol monobutyl ether ester / acrylonitrile / allylamine / hydroxyethyl acrylate copolymer as an auxiliary compounding agent, the epoxy resin as a high-strength composite adhesive, and the diethylenetriamine as a curing agent, and is prepared by a secondary condensation method.

[0009] Furthermore, the amounts of the above components are based on the mass of the boron powder: the mass of the vinylidene fluoride / propylene alcohol copolymer is 1 to 2% of the mass of the boron powder, the mass of the polyethylene glycol monobutyl ether acrylate / acrylonitrile / allylamine / hydroxyethyl acrylate copolymer is 0.3 to 1% of the mass of the boron powder, the mass of the epoxy resin is 2 to 3% of the mass of the boron powder, and the mass of the diethylenetriamine is 0.15 to 0.4% of the mass of the boron powder.

[0010] The present invention also provides a method for preparing the composite boron powder, comprising the following steps:

[0011] Step 1, fluoride compounding: vinylidene fluoride / propylene alcohol copolymer is prepared into a dilute solution with a mass concentration of 0.5-1% by using ethyl acetate as a solvent; in a reactor equipped with a condenser, an exhaust gas discharge device and a stirring device, the dilute ethyl acetate solution of vinylidene fluoride / propylene alcohol copolymer is added under stirring, and then a copolymer of polyethylene glycol monobutyl ether ester, acrylonitrile, allylamine and hydroxyethyl acrylate is added; after the copolymer of polyethylene glycol monobutyl ether ester, acrylonitrile, allylamine and hydroxyethyl acrylate is completely dissolved, the temperature of the reaction system is increased to 70°C to 80°C, boron powder is added thereto, and the mixture is stirred under reflux for 2-5 hours, and then 45-60% of the ethyl acetate solvent is removed by distillation and concentration under stirring to obtain a suspension of fluoride compounded boron powder;

[0012] Step 2, surface modification of composite boron powder: adding epoxy resin to the suspension of fluoride composite boron powder in step 1 under high-speed stirring, stirring rapidly to fully mix, then adding diethylenetriamine, stirring rapidly to fully mix, then adding petroleum ether to the system, stirring and dispersing under high-speed stirring conditions to fully disperse the boron powder;

[0013] Step 3, solidification of the composite boron powder: the composite boron powder dispersed in step 2 is filtered to remove the solvent, and the composite boron powder is dried in a cyclone dryer, and then the product is placed in a dry environment for solidification. After solidification, particle size classification is performed to obtain the composite boron powder.

[0014] In the step 2, the material mixing temperature is 30° C. to 40° C., the mixing time after adding the epoxy resin is 1 to 2 hours, the mixing time after adding the diethylenetriamine is 0.5 to 1 hour, the amount of petroleum ether used is 4 to 6 times the mass of the boron powder, and the stirring and dispersion time after adding the petroleum ether is 1 to 2 hours.

[0015] In the step 3, the boron powder is dried in a cyclone dryer at a temperature of 70° C. to 80° C. for 2 to 4 hours; and the curing temperature is 60° C. to 70° C. for 1 to 2 days.

[0016] The presence of highly viscous substances on the surface of boron powder causes it to aggregate, severely affecting its dispersibility and leading to a significant deterioration in the propellant's process performance. To prevent the highly viscous substances on the boron powder's surface from affecting propellant performance, washing is generally used to remove the surface oxide layer. However, due to its active chemical properties, boron powder easily oxidizes to form B2O3, which in turn forms a highly viscous and loose H3BO3 coating on the boron powder's surface. H3BO3 has a loose, porous structure that absorbs oxygen and water from the air, leading to further oxidation of the boron powder. Therefore, washing to remove the highly viscous oxide layer on the boron powder's surface does not completely resolve the problem of boron powder oxidation affecting storage performance and causing deterioration in propellant process performance. Furthermore, because the oxide layer on the boron powder's surface is tightly bonded to the boron powder, washing cannot completely and thoroughly remove the oxide layer.

[0017] Therefore, compared with the prior art, the present invention has the following beneficial effects:

[0018] 1. The present invention adopts a vinylidene fluoride / propylene alcohol copolymer containing a polyhydroxy structure, which can react with H3BO3 on the surface of the boron powder to form a borate ester and tightly cover the surface of the boron powder to form a dense coating layer, thereby destroying and preventing the formation of the boron oxide layer and improving the combustion efficiency of the boron powder. The polyhydroxy structure of the copolymer can fully combine with the oxide layer on the surface of the boron powder, and fluorine can destroy the oxide layer generated by the combustion of the boron powder, producing gaseous products, reducing the formation of the condensed phase, and improving the combustion performance of the boron powder.

[0019] 2. The present invention uses PANE (polyethylene glycol monobutyl ether acrylate / acrylonitrile / allylamine / hydroxyethyl acrylate copolymer), which contains highly active side chains that can effectively fill the defects of boron powder and form a chelate with the boron powder matrix. The PANE molecular main chain is entangled with PVFA (vinylidene fluoride / propylene alcohol copolymer) molecules, which can further improve the reaction efficiency of PVFA and boric acid and improve the structural regularity of boron powder. The introduction of fluorine into the polypropylene alcohol structure helps to inhibit the formation of a cohesive phase and improve the combustion efficiency of boron powder. The polyhydroxy structure of PVFA reacts rapidly with H3BO3 at a higher temperature to form a coating layer. The sedimentation of the composite boron powder in the solvent is greatly enhanced. After stopping stirring, it was found that the boron powder can completely settle to the bottom of the reactor, and the solution is transparent and clear.

[0020] 3. The present invention adopts an epoxy resin with high mechanical strength, which completely isolates the contact between boron powder and air during the compounding process, solves the storage problem of boron powder and the problem of reduced combustion efficiency caused by oxidation of boron powder due to direct exposure to air. At the same time, it solves the problem of boron powder agglomeration caused by the generation of sticky products due to oxidation, which leads to deterioration of process performance. It can effectively increase the effective amount of boron powder in the propellant. At the same time, the boron powder prepared by compounding with the epoxy resin with high mechanical strength has a regular morphology, which is more conducive to improving the process performance of the propellant.

[0021] 4. In the preparation method of the present invention, in order to improve the reaction efficiency, PVFA is dissolved in ethyl acetate, which is deposited on the surface of the boron powder under the action of PANE and reacts with boric acid to form a dense coating layer, which isolates air and water while also improving the combustion efficiency and structural regularity of the propellant.

[0022] 5. In the preparation method of the present invention, the mechanism of condensation of boric acid and alcohol to form a polymer is adopted, and the secondary condensation method is used to compound the boron powder, so that the boron powder is prepared into a micro-unit powder with high mechanical strength, isolating the boron powder from contact with air, and solving the problem of propellant process deterioration caused by the generation of oxides due to environmental influences during the storage of boron powder. It also solves the problem of propellant process deterioration caused by high boron powder content, increases the boron powder content, and improves the energy performance of the propellant.

[0023] The preparation method of the composite boron powder of the present invention adopts a secondary condensation method to compound the boron powder, and adopts a fluoride that can destroy the boron oxide layer and improve the combustion efficiency of the boron powder to compound the boron powder. The fluoride with a polyhydroxy structure can fully combine with the oxide layer on the surface of the boron powder and firmly cover the surface of the boron powder. The secondary compounding is carried out using an epoxy resin with high mechanical strength to completely isolate the contact between the boron powder and the air. The technical solution of the present invention effectively improves the storage performance and combustion performance of the boron powder, solves the problem of propellant process deterioration due to sticky impurities in the boron powder, can effectively increase the amount of boron powder in the propellant, improves the energy performance of the propellant, and improves the comprehensive performance of the boron-rich fuel propellant. It provides important technical support for the application of solid ramjet engines and has broad application prospects.

[0024] The technical solution of the present invention effectively improves the storage performance and combustion performance of boron powder, solves the problem of propellant process deterioration due to sticky impurities in boron powder, improves the energy performance of the propellant, and effectively improves the comprehensive performance of the propellant using composite boron powder.

[0025] The composite boron powder obtained by the present invention was mixed with a hydroxybutyl adhesive in a 1:1 mass ratio. The viscosity and yield value of the mixture were tested at different time points at 40°C. The yield value of the mixture was less than 1.5 Pa after 5 hours, and the viscosity was less than 10 Pa.s, indicating excellent process performance. After one year of storage, the viscosity and yield value increased by less than 1%, indicating that the composite boron powder was minimally affected by air during storage and exhibited excellent storage properties. DETAILED DESCRIPTION

[0026] The present invention is further described below through specific examples, but those skilled in the art should be aware that the examples do not limit the scope of patent protection of the present invention in any way, and modifications or simple replacements made by those skilled in the art on the basis of the technical solution of the present invention should be included in the scope of patent protection of the present invention.

[0027] Example 1

[0028] A method for preparing composite boron powder comprises the following steps:

[0029] 180g of ethyl acetate was added to a reactor equipped with a condensing device, an exhaust gas discharge device, and a stirring device. 1g of PVFA (vinylidene fluoride / propylene alcohol copolymer, the same below) was added under stirring. After dissolving, 0.5g of PANE (polyethylene glycol monobutyl ether acrylate / acrylonitrile / allylamine / hydroxyethyl acrylate copolymer, the same below) was added and stirred to fully dissolve. The system temperature was then raised to 80°C and 100g of boron powder was added thereto. The mixture was stirred at reflux for 2.5 hours. Stirring was stopped until the solution became clear. Stirring was continued, 100g of ethyl acetate was removed by distillation, and the system temperature was lowered to 35°C. 2.4g of epoxy resin was added to the system under high-speed stirring, and the mixture was rapidly stirred for 1 hour to fully mix. 0.18g of diethylenetriamine was then added and rapidly stirred for 30 minutes to fully mix. 450g of petroleum ether was then added to the system and rapidly stirred for 1 hour to fully disperse the boron powder. The solvent was removed by filtration, and the boron powder was placed in a cyclone dryer and dried at 80° C. for 2 hours. The product was then placed in a dry environment at 60° C. for curing for 1 day to obtain a composite boron powder product.

[0030] The basic physical and chemical properties of the obtained product are shown in Table 1, the energy properties are shown in Table 2, and the process properties are shown in Table 3.

[0031] Table 1 Basic physical and chemical properties

[0032]

[0033] Table 2 Energy performance

[0034]

[0035] Table 3 Process performance

[0036]

[0037] Example 2

[0038] A method for preparing composite boron powder comprises the following steps:

[0039] 400g of ethyl acetate was added to a reactor with a condensing device, an exhaust gas discharge device, and a stirring device. 2.5g of PVFA was added under stirring. After dissolving, 1.2g of PANE was added and stirred to fully dissolve it. The system temperature was then raised to 80°C and 200g of boron powder was added thereto. The mixture was stirred at reflux for 3 hours. The stirring was stopped until the solution became clear. Stirring was continued, 210g of ethyl acetate was removed by distillation, and the system temperature was lowered to 35°C. 5g of epoxy resin was added to the system under high-speed stirring, stirred rapidly for 1 hour to fully mix it, and then 0.5g of diethylenetriamine was added and stirred rapidly for 30 minutes to fully mix it. 1000g of petroleum ether was then added to the system and stirred rapidly for 1 hour to fully disperse the boron powder. The solvent was filtered off and the boron powder was placed in a cyclone dryer and dried at 80°C for 2 hours. The product was then placed in a 60°C dry environment and cured for 2 days to obtain a composite boron powder product.

[0040] The basic physical and chemical properties of the obtained product are shown in Table 4, the energy properties are shown in Table 5, and the process properties are shown in Table 6.

[0041] Table 4 Basic physical and chemical properties

[0042]

[0043] Table 5 Energy performance

[0044]

[0045] Table 6 Process performance

[0046]

[0047] Example 3

[0048] A method for preparing composite boron powder comprises the following steps:

[0049] 420g of ethyl acetate was added to a reactor with a condensing device, an exhaust gas discharge device, and a stirring device. 2.5g of PVFA was added under stirring. After dissolving, 0.9g of PANE was added and stirred to fully dissolve the mixture. The temperature of the system was then raised to 80°C and 180g of boron powder was added thereto. The mixture was stirred for 3 hours under reflux. The solution was clarified by stopping stirring. Stirring was continued, 250g of ethyl acetate was removed by distillation, and the temperature of the system was reduced to 35°C. 4.4g of epoxy resin was added to the system under high-speed stirring, stirred rapidly for 1 hour to fully mix the mixture, and then 0.6g of diethylenetriamine was added and stirred rapidly for 30 minutes to fully mix the mixture. 900g of petroleum ether was then added to the system and stirred rapidly for 1 hour to fully disperse the boron powder. The solvent was removed by filtration, and the boron powder was placed in a cyclone dryer and dried at 80°C for 2 hours. The product was then placed in a 60°C dry environment and cured for 1 day to obtain a composite boron powder product.

[0050] The basic physical and chemical properties of the obtained product are shown in Table 7, the energy properties are shown in Table 8, and the process properties are shown in Table 9.

[0051] Table 7 Basic physical and chemical properties

[0052]

[0053] Table 8 Energy performance

[0054]

[0055] Table 9 Process performance

[0056]

[0057] Example 4

[0058] A method for preparing composite boron powder comprises the following steps:

[0059] 750g of ethyl acetate was added to a reactor with a condensing device, an exhaust gas discharge device, and a stirring device. 4.5g of PVFA was added under stirring. After dissolving, 1.8g of PANE was added and stirred to fully dissolve the mixture. The temperature of the system was then raised to 80°C and 300g of boron powder was added thereto. The mixture was stirred for 3 hours under reflux. The stirring was stopped until the solution became clear. Stirring was continued, 400g of ethyl acetate was removed by distillation, and the temperature of the system was lowered to 35°C. 7.5g of epoxy resin was added to the system under high-speed stirring, stirred rapidly for 1 hour to fully mix the mixture, and then 0.75g of diethylenetriamine was added and stirred rapidly for 30 minutes to fully mix the mixture. 1500g of petroleum ether was then added to the system and stirred rapidly for 1 hour to fully disperse the boron powder. The solvent was removed by filtration, and the boron powder was placed in a cyclone dryer and dried at 80°C for 2 hours. The product was then placed in a 60°C dry environment and cured for 1 day to obtain a composite boron powder product.

[0060] The basic physical and chemical properties of the obtained product are shown in Table 10, the energy properties are shown in Table 11, and the process properties are shown in Table 12.

[0061] Table 10 Basic physical and chemical properties

[0062]

[0063] Table 11 Energy performance

[0064]

[0065] Table 12 Process performance

[0066]

[0067] Example 5

[0068] A method for preparing composite boron powder comprises the following steps:

[0069] 2000g of ethyl acetate was added to a reactor with a condensing device, an exhaust gas discharge device, and a stirring device. 12g of PVFA was added under stirring. After dissolving, 5g of PANE was added and stirred to fully dissolve it. The system temperature was then raised to 80°C and 1000g of boron powder was added thereto. The mixture was stirred under reflux for 4 hours. The stirring was stopped until the solution was clear. Stirring was continued, 900g of ethyl acetate was distilled off, and the system temperature was lowered to 35°C. 25g of epoxy resin was added to the system under high-speed stirring, stirred rapidly for 1 hour to fully mix it, and then 3g of diethylenetriamine was added and stirred rapidly for 30 minutes to fully mix it. 5000g of petroleum ether was then added to the system and stirred rapidly for 1.5 hours to fully disperse the boron powder. The solvent was removed by filtration, and the boron powder was placed in a cyclone dryer and dried at 80°C for 2 hours. The product was then placed in a 60°C dry environment and cured for 1 day to obtain a composite boron powder product.

[0070] The basic physical and chemical properties of the obtained product are shown in Table 13, the energy properties are shown in Table 14, and the process properties are shown in Table 15.

[0071] Table 13 Basic physical and chemical properties

[0072]

[0073] Table 14 Energy performance

[0074]

[0075] Table 15 Process performance

[0076]

[0077] Example 6

[0078] A method for preparing composite boron powder on an enlarged scale comprises the following steps:

[0079] 150 kg of ethyl acetate was added to a reactor equipped with a condensing device, an exhaust gas discharge device, and a stirring device. 900 g of PVFA was added under stirring. After dissolving, 300 g of PANE was added and stirred to fully dissolve the mixture. The system temperature was then raised to 80 ° C and 50 kg of boron powder was added thereto. The mixture was stirred under reflux for 5 hours. Stirring was stopped until the solution became clear. Stirring was continued, and 80 kg of ethyl acetate was removed by distillation. The system temperature was then lowered to 35 ° C. 1.25 kg of epoxy resin was added to the system under high-speed stirring, rapidly stirred for 2 hours to fully mix the mixture, and then 150 g of diethylenetriamine was added and rapidly stirred for 1 hour to fully mix the mixture. 240 kg of petroleum ether was then added to the system and rapidly stirred for 2 hours to fully disperse the boron powder. The solvent was removed by filtration, and the boron powder was placed in a cyclone dryer and dried at 80 ° C for 4 hours. The product was then placed in a 60 ° C drying environment and cured for 2 days to obtain a composite boron powder product.

[0080] The basic physical and chemical properties of the obtained product are shown in Table 16, the energy properties are shown in Table 17, and the process properties are shown in Table 18.

[0081] Table 16 Basic physical and chemical properties

[0082]

[0083] Table 17 Energy performance

[0084]

[0085] Table 18 Process performance

[0086]

[0087] Comparative Example 1

[0088] This Example 1 lists the properties of the same batch of boron powder as Example 6, except that the boron powder is the raw material for the preparation method described in Example 1 of the present invention, and does not include the vinylidene fluoride / propylene alcohol copolymer composite, acrylate polyethylene glycol monobutyl ether ester / acrylonitrile / allylamine / hydroxyethyl acrylate copolymer auxiliary composite, epoxy resin as a high-strength composite adhesive, and diethylenetriamine curing agent of the present invention, and is not processed by the method of the present invention for comparison.

[0089] The basic physical and chemical properties of the product are shown in Table 19, the energy properties are shown in Table 20, and the process properties are shown in Table 21.

[0090] Table 19 Basic physical and chemical properties

[0091]

[0092] Table 20 Energy performance

[0093]

[0094] Table 21 Process performance

[0095]

[0096] The raw boron powder in Example 6 and the boron powder in Comparative Example 1 are from the same batch. The difference is that Example 6 uses a secondary condensation method to prepare the boron powder into a composite boron powder, while the boron powder used in Comparative Example is not modified.

[0097] It can be seen from Example 6 and Comparative Example 1 that, relative to conventional boron powder, the composite boron powder of the present invention does not have boron elements on its surface, and the composite boron powder achieves complete isolation of the boron powder from the air. Since the composite boron powder contains fluorine compounds, the measured calorific value is greatly improved, and the combustion efficiency is greatly improved. Since the composite boron powder is compounded by the secondary condensation method, there is an organic composite layer with a low density on its surface, which leads to a decrease in the density of the boron powder and an increase in the particle size. Since the composite boron powder completely isolates the boron powder from the air, its process performance is improved relative to ordinary boron powder. In particular, after one year of storage, the viscosity and yield value of the composite boron powder have not changed, while the viscosity and yield value of ordinary boron powder have increased significantly.

[0098] While various embodiments of the present invention have been described above, the foregoing description is intended to be illustrative, non-exhaustive, and not limiting of the disclosed embodiments. Numerous modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments. Therefore, the scope of the present invention shall be determined by the scope of the claims.

Claims

1. A composite boron powder, characterized in that: The raw material components include boron powder, vinylidene fluoride / propylene alcohol copolymer, acrylate polyethylene glycol monobutyl ether ester / acrylonitrile / allylamine / hydroxyethyl acrylate copolymer, epoxy resin and diethylenetriamine. The composite boron powder is prepared by a secondary condensation method using vinylidene fluoride / propylene alcohol copolymer as a compounding agent, acrylate polyethylene glycol monobutyl ether ester / acrylonitrile / allylamine / hydroxyethyl acrylate copolymer as an auxiliary compounding agent, epoxy resin as a high-strength composite adhesive, and diethylenetriamine as a curing agent. The amount of each component is based on the mass of the boron powder. The mass of the vinylidene fluoride / propylene alcohol copolymer is 1-2% of the mass of the boron powder, the mass of the polyethylene glycol monobutyl ether acrylate / acrylonitrile / allylamine / hydroxyethyl acrylate copolymer is 0.3-1% of the mass of the boron powder, the mass of the epoxy resin is 2-3% of the mass of the boron powder, and the mass of the diethylenetriamine is 0.15-0.4% of the mass of the boron powder.

2. A method for preparing composite boron powder according to claim 1, characterized in that: The following steps are involved: Step 1, fluoride compounding: preparing a vinylidene fluoride / propylene alcohol copolymer solution; In a reactor equipped with a condensing device, an exhaust gas discharge device and a stirring device, a vinylidene fluoride / propylene alcohol copolymer solution is added under stirring, and then a polyethylene glycol monobutyl ether acrylate / acrylonitrile / allylamine / hydroxyethyl acrylate copolymer is added. After the polyethylene glycol monobutyl ether acrylate / acrylonitrile / allylamine / hydroxyethyl acrylate copolymer is completely dissolved, the temperature of the reaction system is increased, boron powder is added, and the mixture is stirred under reflux. 45-60% of the ethyl acetate solvent is removed by distillation and concentration under stirring to obtain a suspension of fluoride-complexed boron powder. Step 2, surface modification of composite boron powder: adding epoxy resin to the suspension of fluoride composite boron powder in step 1 under high-speed stirring, stirring rapidly to fully mix, then adding diethylenetriamine, stirring rapidly to fully mix, then adding petroleum ether to the system, stirring and dispersing under high-speed stirring conditions, so that the boron powder is fully dispersed to obtain a dispersed composite boron powder; Step 3, solidification of the composite boron powder: the composite boron powder dispersed in step 2 is filtered to remove the solvent, and the dispersed composite boron powder is dried in a cyclone dryer, and then the product is placed in a dry environment for solidification. After solidification, particle size classification is performed to obtain the composite boron powder.

3. The method for preparing the composite boron powder according to claim 2, wherein: In the step 1, the mass concentration of the vinylidene fluoride / propylene alcohol copolymer solution is 0.5-1%.

4. The method for preparing the composite boron powder according to claim 2, wherein: In the step 1, the preparation of the vinylidene fluoride / propylene alcohol copolymer solution includes: The vinylidene fluoride / propylene alcohol copolymer is prepared into a solution with a mass concentration of 0.5-1% by using ethyl acetate.

5. The method for preparing the composite boron powder according to claim 2, wherein: In the step 1, the temperature of the reaction system is raised to 70° C. to 80° C., and the reaction system is stirred under reflux for 2 to 5 hours.

6. The method for preparing the composite boron powder according to claim 2, wherein: In the step 2, the material mixing temperature is 30° C. to 40° C., the mixing time after adding the epoxy resin is 1 to 2 hours, the mixing time after adding the diethylenetriamine is 0.5 to 1 hour, the amount of petroleum ether used is 4 to 6 times the mass of the boron powder, and the stirring and dispersion time after adding the petroleum ether is 1 to 2 hours.

7. The method for preparing composite boron powder according to claim 2, wherein: In the step 3, the boron powder is dried in a cyclone dryer at a temperature of 70° C. to 80° C. for 2 to 4 hours; and the curing temperature is 60° C. to 70° C. for 1 to 2 days.

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