Aluminum-bismuth-based high-energy metal fuel and preparation method thereof

Abstract

The invention discloses an aluminum-bismuth-based high-energy metal fuel and a preparation method thereof, and core-shell Al-coated Bi fuel with excellent reaction kinetics and thermodynamic properties is successfully prepared by coating metal bismuth (Bi) on the surfaces of aluminum powder (Al) particles. The metal fuel comprises aluminum powder and 5-30% of bismuth coated on the surface of the aluminum powder. Compared with Al powder not coated with Bi, the Al (at) Bi metal fuel prepared through the method has the advantages that the combustion efficiency is improved, and the flame temperature and the peak pressure are improved. Meanwhile, the ignition threshold value of Al (at) Bi is obviously reduced compared with that of Al. The invention provides a metal fuel with excellent combustion performance. The metal fuel can be widely applied to the fields of spaceflight, national defense, micro electro mechanical systems and the like.

Description

Technical Field

[0001] The present invention relates to the field of energetic materials, and in particular to an aluminum-bismuth-based high-energy metal fuel and a preparation method thereof. Background Art

[0002] Aluminum powder, a common high-energy fuel, is widely used to enhance the performance and explosive heat of propellants and explosives due to its high calorific value, low toxicity, and low cost. However, in practice, aluminum powder suffers from issues such as a high ignition threshold, incomplete combustion, and low combustion efficiency, resulting in actual performance far below theoretically calculated levels.

[0003] Currently, a common strategy for improving the combustion performance of aluminum powder is to reduce its particle size. However, this results in an increase in specific surface area, a higher proportion of surface alumina, a lower active aluminum content, and poorer stability, making it difficult to store and use. Additionally, coating aluminum powder with fluoropolymers can improve its combustion performance, but fluoropolymers generally have a low density, which results in a lower density for the coated aluminum powder. Low-density metal fuels are not conducive to increasing the charge density of metal-mixed explosives.

[0004] The current research and development focus on aluminum powder fuel is on how to improve its combustion performance while ensuring its safety and usability. Therefore, new formulation systems and preparation methods that enhance the combustion reaction performance of aluminum powder are urgently needed. Summary of the Invention

[0005] The purpose of the present invention is to provide an aluminum-bismuth-based high-energy metal fuel and a preparation method thereof in order to solve the above problems.

[0006] The present invention achieves the above-mentioned purpose through the following technical solutions:

[0007] The present invention provides a method for preparing a bismuth-aluminum-based high-energy metal fuel, comprising the following steps:

[0008] Step S1, dissolving Bi(NO3)3·5H2O, OP-10 and PVP in an organic solvent to prepare a chemical plating solution;

[0009] Step S2, dissolving NH4F in deionized water to prepare a surface etching solution, introducing the surface etching solution into the chemical plating solution, and stirring to obtain a mixed solution;

[0010] Step S3, adding aluminum powder to the mixed solution obtained in step S2, and stirring thoroughly in a water bath;

[0011] Step S4, stopping heating and stirring, filtering and drying to obtain gray-black Al@Bi powder.

[0012] Preferably in the present invention, the organic solvent in step S1 is one or more of ethylene glycol, propylene glycol, butylene glycol, and diethylene glycol; 100 ml of organic solvent is used per 1 g of aluminum powder.

[0013] Preferably in the present invention, the addition amounts of OP-10 and PVP in step S1 are 1 ml and 0.3 g per 1 g of aluminum powder, respectively.

[0014] Preferably in the present invention, after the surface etching solution is introduced into the electroless plating solution in step S2, the pH of the mixed solution is maintained at 5 - 7.

[0015] Preferably in the present invention, the water bath temperature in step S3 is 10 - 50 °C.

[0016] Preferably in the present invention, the mass ratio of Bi in Bi(NO3)3·5H2O to aluminum powder is 0.05 - 0.30:1.

[0017] The present invention also provides an aluminum-bismuth-based high-energy metal fuel, in which metallic bismuth is coated on the surface of aluminum powder to form a core-shell structure. Among them, bismuth accounts for 5% - 30% of the mass fraction of aluminum powder. [[ID=1,7]]

[0018] Preferably in the present invention, the aluminum powder is one or both of nano-aluminum powder and micro-aluminum powder.

[0019] The bismuth composite aluminum powder metal fuel prepared by the method of the present invention can be used in formulations such as propellants and explosives.

[0020] The beneficial effects of the present invention are as follows: The composite of low-melting-point metal bismuth in aluminum powder can effectively reduce the activation energy of aluminum powder oxidation and significantly increase the thermal weight gain of aluminum powder, thereby improving the reactivity and reaction efficiency of aluminum powder; Combustion tests show that the flame area of aluminum powder increases after composite bismuth, the highest flame temperature increases, and the composite of bismuth increases the pressure output of aluminum powder; Compared with aluminum powder, bismuth can also pre-oxidize and release energy at a lower temperature, thereby reducing the ignition threshold of aluminum powder. Description of the Drawings

[0021] Figure 1 It is the scanning electron microscope micrograph and energy spectrum diagram before and after Bi composite.

[0022] Figure 2 It is the (a) XRD and (b) XPS spectra before and after Bi composite.

[0023] Figure 3 It is the (a) thermogravimetry (TG) and (b) differential scanning calorimetry (DSC) curves in the air environment before and after Bi composite.

[0024] Figure 4 It is the SEM image and XRD pattern after heat treatment of Bi composite in air atmosphere above 1000 °C.

[0025] Figure 5 The highest flame temperature and (b) photos of the flame propagation process at different Bi contents before and after Bi compounding.

[0026] Figure 6 The (a) ignition delay time and (b) ignition energy before and after Bi compounding. Specific implementation manners

[0027] In order to make the objectives, technical solutions and advantages of the present invention clearer, the following will describe in detail the implementation method of the present invention in combination with the drawings and embodiments, so as to fully understand how the present invention applies technical means to solve technical problems and the implementation process of achieving technical effects and implement accordingly.

[0028] Many specific details are set forth in the following description in order to provide a thorough understanding of the present invention. However, the present invention may be implemented in other ways different from those described herein. Therefore, the protection scope of the present invention is not limited by the specific embodiments disclosed below.

[0029] Example 1

[0030] Dissolve a solution containing 0.1 g of bismuth in Bi(NO3)3·5H2O, 1 mL of OP-10 and 0.3 g of PVP in 100 mL of ethylene glycol, and mechanically stir to obtain an electroless plating solution; dissolve NH4F in deionized water to prepare a surface etching solution. Introduce the surface etching solution into the electroless plating solution, stir evenly to obtain a mixed solution, and maintain a slightly acidic environment for removing Al2O3 on the surface of aluminum powder, so that active Al is exposed to a solution containing a high concentration of Bi 3+ ; add 1 g of aluminum powder to the mixed liquid, and mechanically stir in a water bath at 25 °C for 10 min; finally, stop heating and stirring, filter and dry to obtain a composite powder. The powder morphology is as shown in Figure 1 (b), and a large number of nanoparticles are in-situ grown on the surface of Al powder. According to Figure 2 XRD and XPS spectra analysis, the powder is a composite material of metallic Bi and Al powder.

[0031] Example 2

[0032] Dissolve a solution containing 0.2 g of bismuth in Bi(NO3)3·5H2O, 1 mL of OP-10 and 0.3 g of PVP in 100 mL of ethylene glycol, and mechanically stir to obtain an electroless plating solution; dissolve NH4F in deionized water to prepare a surface etching solution. Introduce the surface etching solution into the electroless plating solution, stir evenly to obtain a mixed solution, and maintain a slightly acidic environment; add 1 g of aluminum powder to the mixed liquid, and mechanically stir in a water bath at 25 °C for 10 min; finally, stop heating and stirring, filter and dry to obtain a composite powder. The powder morphology is as shown in Figure 1As shown in (c), a dense shell layer coats the surface of the Al powder. According to the energy spectrum diagram, the surface composition mainly consists of Bi, Al, and a small amount of O. According to Figure 2 XRD and XPS spectrum analysis shows that the powder is a composite material of metallic Bi and Al powder.

[0033] Example 3

[0034] A solution containing 0.3 g of Bi(NO3)3·5H2O with 0.3 g of bismuth, 1 mL of OP-10, and 0.3 g of PVP was dissolved in 100 mL of ethylene glycol, and mechanically stirred to obtain an electroless plating solution; NH4F was dissolved in deionized water to prepare a surface etching solution. The surface etching solution was introduced into the electroless plating solution, and stirred evenly to obtain a mixed solution, maintaining a slightly acidic environment; 1 g of aluminum powder was added to the mixed liquid, and mechanically stirred in a water bath at 25 °C for 10 min; finally, heating and stirring were stopped, and the composite powder was obtained by filtration and drying. The powder morphology is as shown in Figure 1 (c), and a dense shell layer forms on the surface of the Al powder. According to Figure 2 XRD and XPS spectrum analysis shows that the powder is a composite material of metallic Bi and Al powder.

[0035] Comparative Example 1

[0036] Comparative Example 1 is pure aluminum powder identical to the aluminum powder in the raw materials of Examples 1-3, without bismuth compounding. According to Figure 1 (a), the surface of the Al powder is smooth under microscopic morphology, containing a small amount of tubular Al2O3.

[0037] Performance Test

[0038] I. Thermogravimetric analysis (TG) and differential scanning calorimetry (DSC)

[0039] Figure 3 (a) and Figure 3 (b) show the TG curve and DSC curve of Al@Bi in an air atmosphere. When the temperature exceeds 1000 °C, aluminum undergoes oxidation. Compared with pure Al powder, the exotherm and weight increase of Al@Bi are significantly improved, and Al@Bi reacts more completely at high temperatures. Figure 4 The XRD pattern shows that after heat treatment of pure aluminum powder and aluminum powder compounded with 20% Bi in air at 1000 °C for 10 min, the aluminum powder compounded with 20% Bi almost completely reacts to form aluminum oxide, while the uncompounded pure aluminum powder still contains a large amount of unreacted metallic aluminum after heat treatment. This also indicates that the compounding of Bi is beneficial to the reaction of aluminum powder at high temperatures and improves the combustion efficiency of aluminum powder.

[0040] II. Flame propagation process and flame temperature test

[0041] As shown in Figure 5As shown, during the flame propagation process, the flame of pure Al powder combustion is weak, indicating its low reactivity. Compared with pure Al powder, the flame brightness and size of Al@Bi are significantly increased. With the increase of bismuth concentration, the flame size and brightness first increase and then decrease, and the combustion duration first shortens and then increases. When the Bi content is in the range of 10% - 20%, the combustion intensity is the largest. In addition, micro-explosions are observed when the bismuth concentrations are 5%, 10%, 15% and 20%. With the increase of bismuth content, the flame temperature shows a trend of first rising and then falling. When the Bi content is 15%, the flame temperature is the highest, reaching 1730 °C. This temperature is about 44% higher than the flame temperature of pure aluminum powder at 1200 °C, indicating a significant increase in the energy release rate of Al@Bi. From the above analysis, it can be seen that Al@Bi can promote the release of a large amount of active aluminum and increase the flame temperature of aluminum combustion. Therefore, the combustion performance of Al@Bi is improved.

[0042] III. Ignition Performance Test

[0043] The ignition performance of the sample is evaluated by synchronously capturing the laser trigger time and the sample ignition process with a camera. Figure 6 (a) shows the ignition delay time of the sample. With the increase of laser power, the ignition delay time of Al@Bi decreases. At a certain laser power, the ignition delay time of Al@Bi first decreases and then increases with the increase of Bi content. When the bismuth content reaches 20%, the ignition delay time is the smallest. The ignition energy determined by calculation is as Figure 6 (b) shown. Compared with pure Al, the ignition energy of Al@Bi is significantly reduced. When the Bi concentration is 20%, the ignition energy drops to 1.345 J, which is 54% lower than the ignition energy of 2.995 J of Al. After analysis, the reason for the significant reduction of the ignition energy after Bi compounding is that Bi can be oxidized at a lower temperature, releasing heat and increasing the temperature around Al. In addition, compared with silver-white Al, gray-black Al@Bi has higher sensitivity to laser, so the absorption of laser by Al@Bi is more obvious.

[0044] Although the present invention has been described herein with reference to its explanatory embodiments, the above embodiments are only the preferred embodiments of the present invention, and the embodiments of the present invention are not limited by the above embodiments. It should be understood that those skilled in the art can design many other modifications and embodiments, and these modifications and embodiments will fall within the scope and spirit of the principles disclosed in this application.

Claims

1. A preparation method of a bismuth-aluminum-based high-energy metal fuel, characterized in that: It includes the following steps: Step S1: Dissolve Bi(NO3)3·5H2O, OP-10 and PVP in an organic solvent to prepare an electroless plating solution. Step S2: Dissolve NH4F in deionized water to prepare a surface etching solution, introduce the surface etching solution into the electroless plating solution, and stir evenly to obtain a mixed solution. Step S3: Add aluminum powder to the mixed solution obtained in Step S2 and stir well in a water bath. Step S4: Stop heating and stirring, filter and dry to obtain gray-black Al@Bi powder.

2. The preparation method of a bismuth-aluminum-based high-energy metal fuel according to claim 1, characterized in that: The organic solvent in Step S1 is one or more of ethylene glycol, propylene glycol, butylene glycol, and diethylene glycol; 100 ml of organic solvent is used per 1 g of aluminum powder.

3. The preparation method of a bismuth-aluminum-based high-energy metal fuel according to claim 2, characterized in that: The addition amounts of OP-10 and PVP in Step S1 are 1 ml and 0.3 g per 1 g of aluminum powder respectively.

4. The preparation method of a bismuth-aluminum-based high-energy metal fuel according to claim 3, characterized in that: After the surface etching solution is introduced into the electroless plating solution in Step S2, the pH of the mixed solution is maintained at 5 - 7.

5. The preparation method of a bismuth-aluminum-based high-energy metal fuel according to claim 4, characterized in that: The water bath temperature in Step S3 is 10 - 50 °C.

6. The preparation method of a bismuth-aluminum-based high-energy metal fuel according to claim 5, characterized in that: The mass ratio of Bi to aluminum powder in Bi(NO3)3·5H2O is 0.05 - 0.30:

1.

7. A high-energy aluminum-bismuth-based metal fuel prepared by the preparation method according to claims 1-6, characterized in that: Coat metallic bismuth on the surface of aluminum powder to form a core-shell structure, and bismuth accounts for 5% - 30% of the mass fraction of aluminum powder.

8. The aluminum-bismuth-based high-energy metal fuel according to claim 7, wherein: The aluminum powder is one or both of nano-aluminum powder and micro-aluminum powder.

9. The aluminum-bismuth-based high-energy metal fuel according to claim 8, characterized in that: It is used in fields such as propellants and explosives.

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