High calorific value spherical boron-based composite fuel assembled with polymer binder and preparation method thereof

Abstract

This invention provides a high-calorific-value spherical boron-based composite fuel assembled with a polymer binder and its preparation method. The fuel comprises boron, with a polymer binder or a polymer binder and molybdenum salt assembled on the boron. The boron matrix is ​​boron powder, mono-modified boron powder, or binary modified boron powder. The polymer binder is polyvinyl alcohol, polyacrylic acid, or polyvinylpyrrolidone. The morphology of the boron-based composite fuel is rough-surfaced spherical particles. This method uses spray drying to prepare the high-calorific-value spherical boron-based composite fuel assembled with a polymer binder. This invention simultaneously solves the problems of limited surface activity of boron powder, uniform nanoscale composite of boron powder and metal oxide in modified boron powder, and optimized spherical morphology to improve process performance, representing an integrated solution.

Description

Technical Field

[0001] This invention belongs to the field of high-energy fuel technology, and relates to boron fuel, specifically to a high-calorific-value spherical boron-based composite fuel assembled with a polymer binder and its preparation method. Background Technology

[0002] Boron possesses extremely high calorific value (approximately 58.5 kJ / g) and volumetric calorific value, making it considered one of the most promising metallic fuels in the fields of solid propellants and explosives. Theoretically, applying boron powder to fuel-rich propellants or high-energy explosives could significantly enhance the range and destructive power of weapon systems. However, in practical applications, the energy release of nano- or micron-sized boron powder faces multiple physical and chemical obstacles, mainly in the following three aspects:

[0003] First, boron powder is typically covered with a natural oxide layer (B₂O₃), which has a boiling point as high as 1860℃. In the initial stages of ignition, the liquid B₂O₃ coats the boron particles, hindering oxygen diffusion and making complete combustion difficult, resulting in low energy release efficiency. Therefore, there is an urgent need for a method to improve the energy release efficiency of boron powder.

[0004] Secondly, traditional boron-based fuels often sacrifice energy efficiency when improving process performance. To improve the dispersibility and mechanical properties of boron powder in propellant slurry, polymeric binders are typically introduced for granulation or coating. However, existing granulation technologies mostly employ inert binders (non-energetic binders). While these inert components provide a binding effect, they do not contribute to calorific value. Instead of improving the energy release efficiency of boron powder, they "dilute" its high energy density, leading to a decrease in the overall energy output performance of the final composite fuel and failing to fully realize the advantages of boron as a high-energy fuel.

[0005] Furthermore, boron powder exhibits poor morphology, processability, and flowability. Amorphous or irregularly shaped boron powder has a large specific surface area and high surface energy, making it highly prone to agglomeration. This results in strong hygroscopicity, high viscosity, and poor flowability in propellant slurries. This not only deteriorates processing performance and limits the high-solids-content loading of boron powder in formulations but also leads to uneven distribution of binders on the boron powder surface, making it difficult to form an effective protective and reinforcing layer.

[0006] To address the aforementioned issues, existing technologies mostly employ single-method improvements. For example, while boron powder can be compounded with binders through physical mixing or solvent evaporation, this often results in uneven binder coating, failing to effectively improve the agglomeration problem of boron powder; or although granulation is achieved, the particle morphology remains irregular, and the improvement in flowability is limited. More critically, there is currently a lack of a preparation technology that can organically combine "high energy" and "sphericity." Most existing technologies fail to compensate for the ignition delay caused by the oxide layer by utilizing the combustion-promoting effect of a specified binder, nor do they achieve dense packing with high sphericity through morphology control technology. This results in bottlenecks in the practical application of boron-based fuels, such as incomplete energy release and poor slurry processing performance. Summary of the Invention

[0007] To address the shortcomings of existing technologies, the present invention aims to provide a high-calorific-value spherical boron-based composite fuel assembled with a polymer binder and its preparation method, thereby solving the technical problem that existing boron-based composite fuels cannot simultaneously possess both high calorific value and excellent processing performance.

[0008] To solve the above-mentioned technical problems, the present invention adopts the following technical solution.

[0009] A high-calorific-value spherical boron-based composite fuel assembled with a polymer binder includes a boron matrix on which a polymer binder is assembled.

[0010] The boron matrix is ​​boron powder, mono-modified boron powder, or binary modified boron powder.

[0011] The mono-modified boron powder is prepared by depositing metal oxides on the surface of boron powder using atomic layer deposition (ALD); the binary modified boron powder is prepared by depositing metal oxides and molybdenum metal on the surface of boron powder using ALD.

[0012] The polymeric adhesive is polyvinyl alcohol (PVA), polyacrylic acid (PAA), or polyvinylpyrrolidone (PVP).

[0013] The boron-based composite fuel has the morphology of rough-surfaced spherical particles.

[0014] The present invention also has the following technical features.

[0015] Preferably, the polymeric binder accounts for 5 wt% to 15 wt% of the boron-based composite fuel by mass.

[0016] More preferably, the polymeric adhesive accounts for 5 wt% of the boron-based composite fuel.

[0017] Preferably, the diameter of the spherical particles is 5 to 20 μm.

[0018] Preferably, the metal oxide is Nb2O5.

[0019] Preferably, the boron matrix is ​​boron powder B, mono-modified boron powder B@Nb2O5, or binary modified boron powder B@Mo@Nb2O5.

[0020] The present invention also protects a method for preparing a high-calorific-value spherical boron-based composite fuel assembled with a polymer binder as described above, wherein the method employs a spray drying method to prepare the high-calorific-value spherical boron-based composite fuel assembled with a polymer binder.

[0021] Specifically, the method includes the following steps.

[0022] Step 1: Add water to the polymer adhesive and heat to boiling while stirring until the polymer adhesive is completely dissolved.

[0023] Step 2: Add the boron matrix to the solution prepared in Step 1 and stir continuously for 30 minutes to obtain a liquid. Then, continuously sonicate the liquid and insert the spray drying feed pipe into the liquid.

[0024] Step 3: The atmosphere of the spray dryer is high-purity nitrogen. Set the reaction temperature, feed rate and spray pressure of the spray dryer. After the reaction temperature of the spray dryer reaches the preset value, start the peristaltic pump.

[0025] Step 4: After the liquid material has completely entered the spray dryer, turn off the peristaltic pump and the spray dryer. After the temperature drops to room temperature, open the material collector and collect the sample to obtain the high-calorific-value spherical boron-based composite fuel assembled with polymer binder.

[0026] Preferably, in step 2, the material concentration of the liquid is 6 wt% to 48 wt%.

[0027] Preferably, in step 3, the reaction temperature is 120°C to 180°C, the feed rate is 5 r / min to 15 r / min, and the spray pressure is 0.05 MPa to 0.2 MPa.

[0028] Compared with the prior art, the present invention has the following technical effects.

[0029] (I) This invention provides an integrated solution that simultaneously addresses the limitations of boron powder surface activity, the uniform nanoscale composite of boron powder and metal oxides in modified boron powder, and the optimization of spherical morphology to improve process performance. The boron-based composite fuel of this invention is a metastable boron-based composite fuel, with an oxidation peak temperature that can be lowered to as low as 540℃; this is more than 100℃ lower than that of boron powder, mono-modified boron powder, or binary modified boron powder. The calorific value of the boron-based composite fuel of this invention is 32.4 kJ / mol to 33.3 kJ / mol, and the combustion efficiency is increased to 90% to 92%.

[0030] (II) Compared to the raw boron powder, the three boron-based nanocomposite fuels B@PVA, B@Nb2O5@PVA, and B@Nb2O5@Mo@PVA prepared in this invention exhibit significantly lower DSC peak temperatures. The exothermic peak temperature of B@PVA is advanced to 630℃, indicating that the composite of B and PVA, as well as the spheroidization process, is beneficial to improving the ignition and combustion process of boron. The exothermic peak temperature of B@Nb2O5@PVA is 566℃, indicating that the Nb2O5 modified layer on the surface of the boron powder and PVA have a synergistic effect, which has a good optimization effect on the ignition and combustion performance of the boron powder. The exothermic peak temperature of B@Nb2O5@Mo@PVA is the lowest, at 549℃, which is 124℃ lower than that of boron powder. This indicates that the synergistic effect of the binary composite modified layer, PVA binder, and spheroidization process on the boron powder greatly optimizes the ignition and combustion performance of the boron powder. The reason why the boron-based composite fuel prepared by this invention has a significantly lower DSC peak temperature and optimized ignition and combustion performance may be that the spherical shape promotes the uniform diffusion of heat and oxygen in the gaps between the spherical fuels during ignition and combustion. During ignition and combustion, the mono- or binary modified layers on the surface of PVA and boron powder promote the diffusion of oxygen from the fuel surface to the central B component through multiple composite mechanisms. This plays a synergistic role in promoting the rupture of the boron oxide shell on the surface of boron powder, thereby causing the ignition process to occur earlier, reducing the exothermic peak temperature, and significantly improving the ignition and combustion performance.

[0031] (III) The three boron-based nanocomposite fuels prepared in this invention—B@PVA, B@Nb2O5@PVA, and B@Nb2O5@Mo@PVA—possess high calorific value and high combustion efficiency. Replacing PVA with HTPB does not improve the calorific value or combustion efficiency compared to boron powder raw materials. This demonstrates that polymers PVA, PAA, and PVB can significantly improve the calorific value and combustion efficiency of boron-containing fuels. The composite fuel B / PVA (solvent evaporation) sample prepared by solvent evaporation of PVA and boron powder, and the B / PVA (ball milling) sample prepared by ball milling of PVA and boron powder, show a slight increase in calorific value compared to the raw boron powder, but the improvement is not as significant as that of B@PVA, B@PAA, and B@PVB. Therefore, the spherical structure prepared by spray drying facilitates sufficient contact between PVA and boron powder, enhancing the ignition and combustion characteristics of boron powder.

[0032] (IV) The preparation method of the present invention is simple, efficient, reproducible and low cost; it has high control precision and is easy to industrialize, showing good application prospects in the field of high-energy solid fuel modification. Attached Figure Description

[0033] Figure 1 SEM image of B@PVA composite fuel.

[0034] Figure 2 SEM and mapping images of B@Nb2O5@PVA composite fuel.

[0035] Figure 3 SEM and mapping images of B@Nb2O5@Mo@PVA composite fuel.

[0036] Figure 4 The images show DSC data for samples B, B@PVA, B@Nb2O5@PVA, and B@Nb2O5@Mo@PVA, where a represents B, b represents B@PVA, c represents B@Nb2O5@PVA, and d represents B@Nb2O5@Mo@PVA.

[0037] The specific content of the present invention will be further explained in detail below with reference to the embodiments. Detailed Implementation

[0038] It should be noted that, unless otherwise specified, all materials and devices used in this invention are those known in the art.

[0039] In this invention, boron powder can also be referred to as boron particles or boron fuel; all three are the same concept. The boron powder is amorphous boron fuel and / or crystalline boron fuel, with a particle size distribution ranging from micrometers to nanometers. Preferably, the particle size of the boron powder is 100 nm to 5 μm.

[0040] In this invention, the polymeric adhesive is polyvinyl alcohol (PVA), polyacrylic acid (PAA), or polyvinylpyrrolidone (PVP). The number-average molecular weight of polyvinyl alcohol (PVA) is 10,000. The number-average molecular weight of polyacrylic acid (PAA) is 24,000. The number-average molecular weight of polyvinylpyrrolidone (PVP) is 10,000.

[0041] In this invention, the boron powder is boron raw material that has not been modified by atomic layer deposition. The unary modified boron powder is boron powder with a modification layer such as B@Nb2O5 deposited on its surface by atomic layer deposition technology. The binary modified boron powder is boron powder with two modification layers such as B@Mo@Nb2O5 deposited on its surface by atomic layer deposition technology.

[0042] The high-calorific-value spherical boron-based composite fuel assembled with the polymer binder of the present invention is used as a boron-based fuel in the field of explosives.

[0043] The following are specific embodiments of the present invention. It should be noted that the present invention is not limited to the following specific embodiments. All equivalent modifications made based on the technical solutions of this application fall within the protection scope of the present invention.

[0044] Example 1: This embodiment provides a method for preparing high-calorific-value spherical boron-based composite fuel assembled with a polymer binder, the method comprising the following steps.

[0045] Step 1: Weigh 320 mg of PVA polymer adhesive and pour it into an Erlenmeyer flask. Measure 25 ml of water with a graduated cylinder and pour it into the Erlenmeyer flask. Add a magnetic stir bar to the Erlenmeyer flask and place it in a heating mantle to heat to boiling until the polymer adhesive is completely dissolved.

[0046] Step 2: Weigh 6g of boron powder, pour it into the solution prepared in Step 1, and stir continuously for 30 minutes to obtain a liquid. Turn off the heating jacket, place the conical flask containing the liquid in an ultrasonic machine, and continuously sonicate it. Insert the spray drying feed tube into the liquid.

[0047] Step 3: The atmosphere of the spray dryer is high-purity nitrogen. Set the spray dryer parameters to 160℃ reaction temperature, 10r / min feed rate, and 0.05Mpa spray pressure. After the reaction temperature reaches the preset value, start the peristaltic pump.

[0048] Step 4: After the liquid material has completely entered the spray dryer, turn off the peristaltic pump and the spray dryer. After the temperature drops to room temperature, open the material collector and collect the sample to obtain boron-based composite fuel B@PVA.

[0049] In the B@PVA material obtained in this embodiment, the PVA content is 5wt%.

[0050] Figure 1 The image shows a SEM image of B@PVA. Under low magnification, the sample morphology consists of rough, spherical particles with good sphericity. The size of the spherical particles ranges from 5 μm to 30 μm. Further magnification reveals numerous grooves and pores on the surface of these spherical particles.

[0051] Example 2: This embodiment provides a method for preparing high-calorific-value spherical boron-based composite fuel assembled with a polymer binder, the method comprising the following steps.

[0052] Step 1: Prepare B@Nb2O5 mono-modified boron powder using atomic layer deposition technology.

[0053] Step 1.1: Spread boron powder evenly on the sample stage, then place the sample stage in the reaction chamber of the atomic layer deposition equipment. Use a mechanical pump to evacuate the reaction chamber to below 20 Pa. Set the temperature of the ALD reaction chamber to 230℃, set the temperature of the niobium ethanol storage tank to 120℃, and set the carrier gas flow rate to 105 ml / min.

[0054] Step 1.2: Niobium ethanol vapor is introduced into the reaction chamber by a carrier gas through bubbling, so that the niobium ethanol vapor molecules are adsorbed on the surface of boron powder. The introduction time is 60s. Then, the niobium ethanol physically adsorbed on the sample surface is blown off the sample surface for 60s.

[0055] Step 1.3: Inject water vapor into the reaction chamber to allow water molecules to fully react with niobium ethanol molecules chemically adsorbed on the surface of boron powder. The injection time is 60s. Then, blow away excess water molecules and byproducts from the sample surface for 60s.

[0056] Step 1.4, and steps 1.2 to 1.3 constitute one cycle of Nb2O5 deposition. Repeating steps 1.2 to 1.3 can control the number of Nb2O5 deposition cycles to 10 cycles, thus obtaining B@Nb2O5 mono-modified boron powder.

[0057] Step 2: Weigh 320 mg of PVA and pour it into an Erlenmeyer flask. Measure 25 ml of water with a graduated cylinder and pour it into the Erlenmeyer flask. Add a magnetic stir bar to the Erlenmeyer flask and place it in a heating mantle to heat to boiling until the polymer adhesive is completely dissolved.

[0058] Step 3: Weigh 6g of B@Nb2O5 mono-modified boron powder and pour it into the solution prepared in Step 2. Stir continuously for 30 minutes to obtain a liquid. Turn off the heating jacket and place the conical flask containing the liquid in an ultrasonic machine for continuous ultrasonication. Insert the spray drying feed tube into the liquid.

[0059] Step 4: The atmosphere of the spray dryer is high-purity nitrogen. Set the spray dryer parameters to 180℃ reaction temperature, 15r / min feed rate, and 0.1MPa spray pressure. After the reaction temperature reaches the preset value, start the peristaltic pump.

[0060] Step 5: After the liquid material has completely entered the spray dryer, turn off the peristaltic pump and the spray dryer. After the temperature drops to room temperature, open the material collector and collect the sample to obtain boron-based composite fuel B@Nb2O5@PVA.

[0061] In the B@Nb2O5@PVA material obtained in this embodiment, the PVA content is 5wt% and the Nb2O5 deposition cycle number is 10 cycles.

[0062] Figure 2 The images show SEM and mapping of the B@Nb2O5@PVA composite fuel. The sample has a regular morphology, consisting of rough-surfaced spherical particles with a size ranging from 5 to 20 μm. The elemental distribution diagrams show that the distribution areas and trends of B, O, and C elements are almost identical, indicating that the components of the B@Nb2O5@PVA material prepared using spray drying technology are uniformly distributed.

[0063] Example 3: This embodiment provides a method for preparing high-calorific-value spherical boron-based composite fuel assembled with a polymer binder, the method comprising the following steps.

[0064] Step 1: Prepare B@Mo@Nb2O5 binary modified boron powder using atomic layer deposition technology.

[0065] Step 1.1: Spread boron powder evenly on the sample stage, then place the sample stage in the reaction chamber of the atomic layer deposition equipment, use a mechanical pump to evacuate the reaction chamber to below 150 Pa, and set the temperature of the reaction chamber to 200℃.

[0066] Step 1.2: Si₂H₆ is injected into the adjustable precursor storage container. The carrier gas and the pneumatic valve of the mechanical pump are closed to bring the system to a near-static state. Then, the precursor from the storage container is injected into the reaction chamber over 30 seconds to allow for saturation adsorption of the precursor on the boron particles. After sufficient adsorption, the pneumatic valve of the mechanical pump is opened to remove excess precursor or physically adsorbed precursor from the reaction chamber over 25 seconds. Then, the carrier gas is used for purging over 25 seconds.

[0067] Step 1.3: MoF6 is injected into an adjustable precursor storage container, which allows for precise control of the amount of precursor entering the system. The pneumatic valves of the carrier gas and mechanical pump are closed, bringing the system to a near-static state. The precursor from the storage container is then injected into the reaction chamber over 30 seconds, allowing MoF6 to fully react with Si2H6 adsorbed on the boron particles. After the reaction is complete, the pneumatic valve of the mechanical pump is opened to remove excess precursor or byproducts from the reaction chamber over 25 seconds. Then, the carrier gas is used for purging for 25 seconds. The carrier gas is either high-purity argon or high-purity nitrogen.

[0068] Step 1.4, steps 1.2 to 1.3 constitute one cycle of elemental Mo deposition. Steps 1.2 to 1.3 are repeated to control the number of deposition cycles of elemental Mo on boron particles to be 5 cycles.

[0069] Step 1.5: Keep the sample in situ, set the temperature of the ALD reaction chamber to 230℃, the temperature of the niobium ethanol storage tank to 120℃, and the carrier gas flow rate to 105ml / min.

[0070] Step 1.6: The vapor of niobium ethanol is introduced into the reaction chamber by a carrier gas through bubbling, so that the niobium ethanol vapor molecules are adsorbed on the surface of boron powder. The introduction time is 60s. Then, the niobium ethanol physically adsorbed on the sample surface is blown off the sample surface for 60s.

[0071] Step 1.7: Inject water vapor into the reaction chamber to allow water molecules to fully react with niobium ethanol molecules chemically adsorbed on the sample surface. The infusion time is 60s. Then, blow away excess water molecules and byproducts from the sample surface for 60s.

[0072] Steps 1.8 and 1.6 to 1.7 constitute one cycle of Nb2O5 deposition. By repeating steps 1.6 to 1.7 to control the number of Nb2O5 deposition cycles to 10 cycles, B@Mo@Nb2O5 binary modified boron powder can be obtained.

[0073] Step 2: Weigh 320 mg of PVA and pour it into an Erlenmeyer flask. Measure 25 ml of water with a graduated cylinder and pour it into the Erlenmeyer flask. Add a magnetic stir bar to the Erlenmeyer flask and place it in a heating mantle to heat to boiling until the polymer adhesive is completely dissolved.

[0074] Step 3: Weigh 6g of B@Mo@Nb2O5 binary modified boron powder and pour it into the solution prepared in Step 2. Stir continuously for 30 minutes to obtain a liquid. Turn off the heating jacket and place the conical flask containing the liquid in an ultrasonic machine for continuous ultrasonication. Insert the spray drying feed tube into the liquid.

[0075] Step 4: The atmosphere of the spray dryer is high-purity nitrogen. Set the spray dryer parameters to 180℃ reaction temperature, 15r / min feed rate, and 0.1MPa spray pressure. After the reaction temperature reaches the preset value, start the peristaltic pump.

[0076] Step 5: After the liquid material has completely entered the spray dryer, turn off the peristaltic pump and the spray dryer. After the temperature drops to room temperature, open the material collector and collect the sample to obtain the boron-based composite fuel B@Mo@Nb2O5@PVA.

[0077] In the B@Mo@Nb2O5@PVA material obtained in this embodiment, the PVA content is 5wt%, the number of Mo deposition cycles is 5 cycles, and the number of Nb2O5 deposition cycles is 10 cycles.

[0078] Figure 3 SEM and mapping images of B@Nb2O5@Mo@PVA composite fuel. The morphology is regular, consisting of rough-surfaced spherical particles with numerous grooves and pores on the surface. The particle size ranges from 5 to 20 μm.

[0079] Example 4: This embodiment provides a method for preparing high-calorific-value spherical boron-based composite fuel assembled with a polymer binder. The method is basically the same as that in Example 1, except that the polymer binder PVA is replaced with an equal amount of polymer binder PAA. PAA is easily soluble in water and can be dissolved without heating with a heating mantle.

[0080] Example 5: This embodiment provides a method for preparing high-calorific-value spherical boron-based composite fuel assembled with a polymer binder. The method is basically the same as that in Example 1, except that the polymer binder PVA is replaced with an equal amount of polymer binder PVP. PVP is easily soluble in water and can be dissolved without heating with a heating mantle.

[0081] Example 6: This embodiment provides a method for preparing high-calorific-value spherical boron-based composite fuel assembled with a polymer binder. This method is basically the same as that in Example 2, except that the polymer binder PVA is replaced with an equal amount of polymer binder PAA. PAA is easily soluble in water and can be dissolved without heating with a heating mantle.

[0082] Example 7: This embodiment provides a method for preparing high-calorific-value spherical boron-based composite fuel assembled with a polymer binder. This method is basically the same as that in Embodiment 2, except that the polymer binder PVA is replaced with an equal amount of polymer binder PVP. PVP is easily soluble in water and can be dissolved without heating with a heating mantle.

[0083] Example 8: This embodiment provides a method for preparing high-calorific-value spherical boron-based composite fuel assembled with a polymer binder. This method is basically the same as that in Example 3, except that the polymer binder PVA is replaced with an equal amount of polymer binder PAA. PAA is easily soluble in water and can be dissolved without heating with a heating mantle.

[0084] Example 9: This embodiment provides a method for preparing high-calorific-value spherical boron-based composite fuel assembled with a polymer binder. This method is basically the same as that in Example 3, except that the polymer binder PVA is replaced with an equal amount of polymer binder PVP. PVP is easily soluble in water and can be dissolved without heating with a heating mantle.

[0085] Comparative Example 1: This embodiment provides a method for preparing high-calorific-value spherical boron-based composite fuel assembled with a polymer binder. This method is essentially the same as in Example 1, except that the polymer binder PVA is replaced with an equal amount of polymer binder HTPB. In the B@HTPB material obtained in this comparative example, the HTPB content is 5 wt%. The solvent water is replaced with ethyl acetate, and the heating step is omitted. In this comparative example, the number-average molecular weight of the polymer binder hydroxyl-terminated polybutadiene (HTPB) is 2800.

[0086] Comparative Example 2: This comparative example provides a method for preparing a B / PVA (solvent evaporation method) composite fuel, wherein the PVA content in the B / PVA composite fuel is 5 wt%. The preparation steps of this comparative example are as follows: weigh PVA and boron powder according to the ratio, dissolve PVA in hot water and then add boron powder, stir with a magnetic stirrer for 15 min, stir evenly, evaporate the solvent in an oven to dry the material, and mechanically crush the resulting block to obtain the B / PVA composite fuel.

[0087] Comparative Example 3: This comparative example provides a method for preparing a B / PVA (ball milling) composite fuel, wherein the PVA content in the B / PVA composite fuel is 5 wt%. The preparation steps of this comparative example are as follows: weigh PVA and boron powder according to the ratio, stir and mix PVA and boron powder, and then composite them through a ball mill to obtain the B / PVA (ball milling) composite fuel.

[0088] Performance testing: First, DSC testing of boron-based fuels.

[0089] Weigh boron-based fuel into an alumina crucible and place it in a DSC testing device. Set the instrument's heating rate to 10℃ / min, the test temperature range to room temperature - 900℃, and the atmosphere to air to obtain the DSC curve of the boron-based nanocomposite fuel.

[0090] Figure 4 The following are DSC data plots for samples B, B@PVA, B@Nb2O5@PVA, and B@Nb2O5@Mo@PVA. Figure 4 As shown in Table 1, the peak exothermic temperature of raw material B is 677℃. The spherical B@PVA composite fuel prepared in this invention has an earlier peak exothermic temperature of 663℃, indicating that the composite with PVA and the spheroidization process are beneficial to improving the ignition and combustion process of boron. The composite fuel B@Nb2O5@PVA prepared by mono-modified boron powder has an exothermic peak temperature of 566℃, indicating that the Nb2O5 modified layer on the surface of the boron powder and PVA have a synergistic effect, which has a good optimization effect on the ignition and combustion performance of the boron powder. The composite fuel B@Nb2O5@Mo@PVA prepared by binary-modified boron powder has the lowest peak exothermic temperature of 549℃, indicating that the synergistic effect of the composite modified layer, PVA binder and spheroidization process on the boron powder greatly optimizes the ignition and combustion performance of the boron powder.

[0091] The reason why the boron-based composite fuel prepared by this invention has a significantly reduced DSC peak temperature and optimized ignition and combustion performance may be that the spherical shape promotes the uniform diffusion of heat and oxygen in the gaps between the spherical fuels during ignition and combustion. During ignition and combustion, the mono- or binary modified layers on the surface of PVA and boron powder promote the diffusion of oxygen from the fuel surface to the central B component through multiple composite mechanisms. This plays a synergistic role in promoting the rupture of the boron oxide shell on the surface of the boron powder, thereby causing the ignition process to occur earlier, reducing the exothermic peak temperature, and significantly improving the ignition and combustion performance.

[0092] Table 1. DSC peak temperature of boron-based fuels

[0093] Second, the heat of combustion of boron-based fuels was tested.

[0094] The additive (half a sheet of lens paper) and the test sample were weighed separately using an electronic balance. The weighed sample was then wrapped in the same lens paper and placed in a corundum crucible. An ignition wire and cotton thread were installed on the oxygen bomb holder. The cotton thread was pressed to the bottom of the lens paper wrapping the sample. 10 ml of deionized water was added to the oxygen bomb cartridge. The oxygen bomb holder was installed and the oxygen bomb cap was tightened. The oxygen bomb was then installed on the calorimeter. After inputting the mass of the test sample, the mass of the additive, and the calorific value of the additive into the computer control software, the test was started. The instrument displayed the calorific value test results after the test was completed.

[0095] The calorific value and combustion efficiency of the samples in Examples 1 to 9 and Comparative Examples 1 to 3 are shown in Table 2. The calorific value was obtained using the above-described test method, the theoretical calorific value was calculated based on the content of each component in the sample, and the combustion efficiency was obtained by dividing the calorific value by the theoretical calorific value. The three boron-based nanocomposite fuels, B@PVA, B@Nb2O5@PVA, and B@Nb2O5@Mo@PVA, exhibit high calorific values ​​and high combustion efficiencies. Replacing PVA with HTPB did not improve the calorific value or combustion efficiency compared to boron powder raw materials, demonstrating that polymers PVA, PAA, and PVB can significantly improve the calorific value and combustion efficiency of boron-containing fuels. Furthermore, replacing PVA in the three boron-based nanocomposite fuels B@PVA, B@Nb2O5@PVA, and B@Nb2O5@Mo@PVA with PAA and PVP to prepare the corresponding boron-based nanocomposite fuels in Examples 4-9 also exhibited considerably high calorific values ​​and combustion efficiencies.

[0096] The composite fuel B / PVA (solvent evaporation) sample prepared by solvent evaporation of PVA and boron powder, and the B / PVA (ball milling) sample prepared by ball milling of PVA and boron powder, showed a slight increase in calorific value compared to the raw boron powder, but the improvement was not as significant as that of B@PVA, B@PAA, and B@PVB. Therefore, it is evident that the spherical structure prepared by spray drying facilitates sufficient contact between PVA and boron powder, thereby enhancing the ignition and combustion characteristics of the boron powder.

[0097] Table 2 Calorific value and combustion efficiency of boron-based fuels

Claims

1. A high-calorific-value spherical boron-based composite fuel assembled with a polymer binder, characterized in that, Includes a boron matrix, on which a polymeric adhesive is assembled; The boron matrix is ​​boron powder, mono-modified boron powder, or binary modified boron powder; The mono-modified boron powder is prepared by depositing metal oxides on the surface of boron powder using atomic layer deposition (ALD); the binary modified boron powder is prepared by depositing metal oxides and molybdenum metal on the surface of boron powder using ALD. The polymeric adhesive is polyvinyl alcohol, polyacrylic acid, or polyvinylpyrrolidone; The boron-based composite fuel has the morphology of rough-surfaced spherical particles.

2. The high-calorific-value spherical boron-based composite fuel assembled with the polymer binder as described in claim 1, characterized in that, The polymeric binder accounts for 5 wt% to 15 wt% of the boron-based composite fuel.

3. The high-calorific-value spherical boron-based composite fuel assembled with the polymer binder as described in claim 2, characterized in that, The polymeric binder accounts for 5 wt% of the boron-based composite fuel.

4. The high-calorific-value spherical boron-based composite fuel assembled with the polymer binder as described in claim 1, characterized in that, The diameter of the spherical particles is 5 to 20 μm.

5. The high-calorific-value spherical boron-based composite fuel assembled with the polymer binder as described in claim 1, characterized in that, The metal oxide is Nb2O5.

6. The high-calorific-value spherical boron-based composite fuel assembled with the polymer binder as described in claim 5, characterized in that, The boron matrix is ​​boron powder B, mono-modified boron powder B@Nb2O5, or binary modified boron powder B@Mo@Nb2O5.

7. A method for preparing a high-calorific-value spherical boron-based composite fuel assembled with a polymer binder as described in any one of claims 1 to 6, characterized in that, This method uses spray drying to prepare high-calorific-value spherical boron-based composite fuels assembled with polymer binders.

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