High-output-efficiency energetic film and preparation method thereof
Energetic films made of Al/ammonium fluoride/fluoropolymer were prepared by electrospinning, which solved the problem of hindered reaction process of Al/fluoropolymer films and achieved improved high energy output and environmental tolerance.
Patent Information
- Application Number
- CN202511139141.6
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-08-14
- Publication Date
- 2025-10-31
AI Technical Summary
Existing Al/fluoropolymer energetic films experience hindered reaction processes during low-speed thermal oxidation and high-speed combustion, and the combustion products are difficult to evaporate effectively, affecting reaction efficiency.
An energetic thin film was prepared by electrospinning using a dual-fluorine strategy of Al/ammonium fluoride/fluoropolymer. By utilizing the low-temperature fluorination capability of ammonium fluoride and the high hydrophobicity of the polymeric fluorinating agent, an energetic thin film with both high energy output efficiency and high environmental tolerance was prepared.
It improves the ignition sensitivity and component dispersion of energetic thin films, enhances mass and heat transfer efficiency, and ensures that the reaction proceeds efficiently at lower temperatures.
Smart Images
Figure CN120867010A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the construction of micro / nano composite energetic materials, specifically a type of Al / ammonium fluoride / fluoropolymer high-output-efficiency energetic thin film and its preparation method. Background Technology
[0002] Fluorine (F) is extremely electronegative and possesses strong oxidizing properties. Therefore, when used as an oxidant in metallic (metalloid) fuels such as aluminum (Al), magnesium (Mg), silicon (Si), and boron (B), it can undergo rapid redox reactions and release a large amount of energy. Among these, Al, as the most commonly used metallic fuel, has had its reaction process and mechanism extensively discussed, regardless of whether it involves low-speed thermal oxidation or high-speed combustion. Regardless of the reaction mechanism, the Al₂O₃ passivation layer demonstrates its blocking effect on the internal Al core, hindering or affecting subsequent reaction processes.
[0003] A key characteristic of the Al-F combustion system lies in the "stripping" effect of fluorine (F) on the passivation layer. Firstly, F "etches and strips" the primary passivation layer, directly influencing the ignition process of Al fuel. Specifically, fluorides, through a pre-ignition reaction (PIR), etch and destroy the primary passivation layer of Al, making it easier for the internal aluminum core to be exposed and directly contact the external oxides / fluorides, thus lowering the ignition energy of Al fuel and maintaining a lower reaction energy barrier. This process often occurs at lower temperatures (compared to the Al-O combustion system). Furthermore, the etching of the passivation layer by F is exothermic, providing exothermic compensation for the entire reaction system. Secondly, F "evaporates and strips" combustion products, affecting the combustion process of Al fuel. Specifically, the product of the fluorination reaction, AlF3 (boiling point: 1291℃), is more easily evaporated than the product of the Al-O combustion system, Al2O3 (greater than 3000℃), which promotes the mass transfer between the active component Al nucleus and oxides / fluorides during the reaction process, enhances the interdiffusion ability between fuel and oxidant / fluorinator, and ensures that the reaction process remains highly efficient. Summary of the Invention
[0004] The purpose of this invention is to provide a type of Al / ammonium fluoride / fluoropolymer high-output-efficiency energetic thin film and its preparation method.
[0005] This invention utilizes the low-temperature fluorine release capability of ammonium fluoride and the high hydrophobicity of polymeric fluorinating agents to obtain an energetic thin film with both high energy output efficiency and high environmental tolerance through a dual-fluorine strategy.
[0006] First, an Al / ammonium fluoride / fluoropolymer precursor solution was prepared via a stepwise mechanical-physical mixing process. Then, an Al / ammonium fluoride / fluoropolymer energetic thin film was prepared by electrospinning.
[0007] When the prepared energetic thin film is stimulated by external factors, the ammonium fluoride metal oxide releases HF gaseous products, which etch and activate metallic Al, releasing energy from Al at relatively low temperatures. The generated energy triggers the premature decomposition of the fluoropolymer, further accelerating the energy release of the energetic thin film. Furthermore, the fluoropolymer acts as a protective layer, effectively preventing excessive oxidation of Al during long-term storage and providing moisture resistance to the ammonium fluoride metal oxide. The energetic thin film prepared by this method exhibits both high energy output efficiency and high environmental tolerance.
[0008] The technical solution for achieving the objective of this invention is as follows:
[0009] A method for preparing a class of high-output-efficiency energetic thin films made of Al / ammonium fluoride / fluoropolymer includes the following steps:
[0010] Step 1: P(VDF-HFP) is added to a mixed solution of N,N-dimethylformamide (DMF) and acetone, and completely dissolved by magnetic stirring. Next, Al powder is added to the polymer solution, and stirring continues to disperse it. Finally, ammonium fluoride is added to the suspension, and stirring continues for 12 hours to form a well-dispersed Al / ammonium fluoride / fluoropolymer precursor solution.
[0011] Step 2: Inject the obtained precursor solution into a 5mL syringe, replace the syringe with a dedicated all-metal needle for electrospinning (needle inner diameter 0.51mm), slowly push the injection piston to expel excess gas, and then fix the syringe on the electrospinning equipment. After adjusting the distance between the needle tip and the collecting plate to 12cm, charge the metal needle positively and the collecting plate negatively. After setting the flow rate of the precursor, click start. Under the combined action of electrostatic force and surface tension, the precursor solution propelled by the needle is rapidly atomized into charged droplets and flies towards the collecting plate. During this process, most of the solvent in the precursor solution will evaporate rapidly, and the solid product on the collecting plate needs to be further dried in a vacuum oven to obtain a high-output-efficiency energetic film of Al / ammonium fluoride / fluoropolymer.
[0012] Furthermore, in step 1, P(VDF-HFP) can be replaced with PVDF. The mixed solution of N,N-dimethylformamide (DMF) and acetone can be replaced with a mixed solution of N,N-dimethylacetamide (DMAc) and acetone.
[0013] Furthermore, in step 1, after P(VDF-HFP) is added to the solution, it is initially a turbid liquid. As the stirring time increases, the P(VDF-HFP) particles gradually dissolve, and the liquid gradually becomes transparent and viscous.
[0014] Furthermore, in step 1, after adding Al powder, the mixture needs to be stirred for more than 3 hours to ensure that the Al powder particles are evenly dispersed in the solution.
[0015] Furthermore, in step 1, when ammonium fluoride is added to the above suspension, stirring should continue for 12 hours to ensure that Al and ammonium fluoride are uniformly dispersed in the liquid phase.
[0016] Furthermore, in step 1, the container is kept sealed during the stirring process to prevent the solvent from evaporating prematurely.
[0017] Furthermore, in step 2, a 5mL disposable syringe is used, and the needle is a special all-metal needle to ensure that the particles flowing through the needle are successfully charged.
[0018] Furthermore, in step 2, after the precursor solution is transferred to the syringe, there may be some air bubbles inside the solution. During the venting process, the syringe can be gently tapped to allow the air bubbles to escape.
[0019] Furthermore, in step 2, the charge values of the needle and the collecting plate are adjustable to ensure that the sprayed droplets are cone-shaped.
[0020] Furthermore, in step 2, the product collected on the collection plate may contain solvent that has not been completely evaporated, and the product needs to be placed in a vacuum oven for further drying after collection.
[0021] Compared with the prior art, the present invention has the following advantages:
[0022] (1) Since ammonium fluoride and Al can undergo an ignition reaction at a lower temperature, Al / ammonium fluoride / fluorinated polymer has a higher ignition sensitivity compared with the traditional Al / fluorinated polymer binary energetic film; (2) The Al / ammonium fluoride / fluorinated polymer energetic film prepared by electrospinning has a greater dispersion of each component than the Al / ammonium fluoride / fluorinated polymer energetic film prepared by the traditional hot drying process, which increases the mass and heat transfer efficiency between components.
[0023] The present invention will be further described below with reference to embodiments and accompanying drawings. Attached Figure Description
[0024] Figure 1 This is a schematic diagram of the preparation process of an Al / ammonium fluoride / fluoropolymer energetic thin film.
[0025] Figure 2 This is a macroscopic image of an Al / ammonium fluoride / fluoropolymer energetic thin film.
[0026] Figure 3 The microstructure of the Al / ammonium fluoride / fluoropolymer energetic film is shown.
[0027] Figure 4 The DSC curves are for Al / (NH4)3BiF6 / P(VDF-HFP) and Al / P(VDF-HFP).
[0028] Figure 5 The results show the water contact angle test results for Al / (NH4)3BiF6 / P(VDF-HFP) and Al / P(VDF-HFP). Detailed Implementation
[0029] The present application will be further described below with reference to the accompanying drawings.
[0030] The preparation of high-output-efficiency energetic films of Al-fluorinated metal ammonium oxide@fluoropolymer includes the following steps:
[0031] like Figure 1 As shown: Step 1, 60 mg of P(VDF-HFP) powder was poured into a solution of DMF and acetone and stirred for 30 min to completely dissolve it, forming a transparent viscous solution. Next, 40 mg of aluminum powder was added to the solution, and stirring was continued for 180 min to form a well-dispersed suspension. Then, 60 mg of (NH4)3BiF6 was added, and stirring was continued for 12 h to obtain the precursor solution for the electrospinning process.
[0032] Step 2: Inject the obtained precursor solution into a 5mL syringe, replace the syringe with a dedicated all-metal needle for electrospinning (needle inner diameter 0.51mm), tap the syringe barrel several times to ensure that air bubbles inside the liquid are expelled, then slowly push the injection piston to expel excess gas, and then fix the syringe on the electrospinning equipment. After adjusting the distance between the needle tip and the collecting plate to 12cm, charge the metal needle positively and the collecting plate negatively. After setting the flow rate of the precursor, click start. Under the combined action of electrostatic force and surface tension, the precursor solution pushed out by the needle is rapidly atomized into charged droplets and flies towards the collecting plate. During this period, most of the solvent in the precursor solution will evaporate rapidly, and the solid product on the collecting plate needs to be further dried in a vacuum oven to obtain an Al / (NH4)3BiF6 / P(VDF-HFP) energetic thin film.
[0033] Specifically, in step 1, the stirring process uses magnetic stirring at a speed of 600 rpm.
[0034] Specifically, in step 1, the volume ratio of DMF to acetone used is 1:2.
[0035] Specifically, in step 2, the metal needle is charged with +13kV, and the collecting plate is charged with -4kV.
[0036] Specifically, in step 2, after the solid product is collected, it needs to be placed in a vacuum oven and dried at 80°C for 6 hours to completely remove the residual solvent.
[0037] Example 1
[0038] Step 1: 60 mg of P(VDF-HFP) powder was poured into a solution of DMF and acetone and stirred for 30 min until completely dissolved to form a transparent, viscous solution. Next, 40 mg of aluminum powder was added to the solution, and stirring continued for 180 min to form a well-dispersed suspension. Then, 60 mg of (NH4)3BiF6 was added, and stirring continued for 12 h to obtain the precursor solution for the electrospinning process.
[0039] Step 2: Inject the obtained precursor solution into a 5 mL syringe, replace the syringe with a dedicated all-metal needle for electrospinning (needle inner diameter 0.51 mm), slowly push the injection piston to expel excess gas, and then fix the syringe on the electrospinning equipment. After adjusting the distance between the needle tip and the collecting plate to 12 cm, charge the metal needle to +13 kV and the collecting plate to -4 kV. Set the flow rate of the precursor to 2 mL / h. Under the combined action of electrostatic force and surface tension, the precursor solution propelled by the needle is rapidly atomized into charged droplets and flies towards the collecting plate. During this period, most of the solvent in the precursor solution will evaporate rapidly. The solid product on the collecting plate needs to be further dried in a vacuum oven at 80 °C for 6 h to obtain an Al / (NH4)3BiF6 / P(VDF-HFP) energetic thin film.
[0040] Example 2
[0041] Step 1: 60 mg of PVDF powder was poured into a solution of DMF and acetone and stirred for 30 min until completely dissolved to form a transparent, viscous solution. Next, 40 mg of aluminum powder was added to the solution, and stirring continued for 180 min to form a well-dispersed suspension. Then, 60 mg of (NH4)2NiF6 was added, and stirring continued for 12 h to obtain the precursor solution for the electrospinning process.
[0042] Step 2: Inject the obtained precursor solution into a 5 mL syringe, replace the syringe with a dedicated all-metal needle for electrospinning (needle inner diameter 0.51 mm), slowly push the injection piston to expel excess gas, and then fix the syringe on the electrospinning equipment. After adjusting the distance between the needle tip and the collecting plate to 12 cm, charge the metal needle to +13 kV and the collecting plate to -4 kV. Set the flow rate of the precursor to 2 mL / h. Under the combined action of electrostatic force and surface tension, the precursor solution propelled by the needle is rapidly atomized into charged droplets and flies towards the collecting plate. During this period, most of the solvent in the precursor solution will evaporate rapidly. The solid product on the collecting plate needs to be further dried in a vacuum oven at 80 °C for 6 h to obtain an Al / (NH4)2NiF6 / PVDF energetic film.
[0043] Example 3
[0044] Step 1: 60 mg of P(VDF-HFP) powder was poured into a solution of DMF and acetone and stirred for 30 min until completely dissolved, forming a transparent viscous solution. Next, 40 mg of aluminum powder was added to the solution, and stirring continued for 180 min to form a well-dispersed suspension. Then, 60 mg of (NH4)2NiF6 was added, and stirring continued for 12 h to obtain the precursor solution for the electrospinning process.
[0045] Step 2: Inject the obtained precursor solution into a 5 mL syringe, replace the syringe with a dedicated all-metal needle for electrospinning (needle inner diameter 0.51 mm), slowly push the injection piston to expel excess gas, and then fix the syringe on the electrospinning equipment. After adjusting the distance between the needle tip and the collecting plate to 15 cm, charge the metal needle to +13 kV and the collecting plate to -5 kV. Set the flow rate of the precursor to 2 mL / h. Under the combined action of electrostatic force and surface tension, the precursor solution propelled by the needle is rapidly atomized into charged droplets and flies towards the collecting plate. During this period, most of the solvent in the precursor solution will evaporate rapidly. The solid product on the collecting plate needs to be further dried in a vacuum oven at 80 °C for 6 h to obtain the Al / (NH4)2NiF6 / PVDF-HFP energetic film.
[0046] Figure 1 This is a schematic diagram of the preparation process of an Al-fluorinated ammonium metal oxide@fluoropolymer energetic thin film. Figure 2 Macroscopic image of an Al-fluorinated ammonium metal oxide@fluoropolymer energetic film prepared by electrospinning. Figure 3 The image shows the microstructure of an Al-fluorinated ammonium metal oxide@fluoropolymer energetic film. As can be seen from the figure, the overall framework is a multi-layered, dense network structure composed of intertwined fluoropolymer fibers. Most particles exist embedded within the polymer fibers, and the fiber surface is uneven, possibly due to varying particle sizes or partial embedding of aluminum particles. Figure 4 The figures show the DSC curves of Al / (NH4)3BiF6 / P(VDF-HFP) and Al / P(VDF-HFP). As can be seen from the figure, under the promoting effect of (NH4)3BiF6, the reaction peak temperature of Al / (NH4)3BiF6 / P(VDF-HFP) is significantly lower than that of Al / P(VDF-HFP) by 73℃, indicating that Al / (NH4)3BiF6 / P(VDF-HFP) can trigger the redox reaction at a lower temperature. Figure 5 The figures show the water contact angle test results for Al / (NH4)3BiF6 / P(VDF-HFP) and Al / P(VDF-HFP). As can be seen from the figures, the film prepared by electrospinning has a larger water contact angle and stronger anti-aging properties.
[0047] The above embodiments are merely descriptions of preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.
Claims
1. A method for preparing a high-output-efficiency energetic thin film, characterized in that, Includes the following steps: Step 1: Prepare Al / ammonium fluoride / fluoropolymer precursor solution by stepwise mechanical and physical mixing. First, dissolve the fluoropolymer in a solvent and stir continuously until the fluoropolymer is completely dissolved. Next, add Al to the polymer solution and continue stirring to disperse. Finally, add ammonium fluoride to the above suspension and continue stirring to form a well-dispersed precursor solution. Step 2: Prepare Al-ammonium fluoride metal@fluoropolymer energetic films using electrospinning. Inject the obtained precursor solution into a syringe, replace the all-metal electrospinning needle, slowly push the injection piston to expel excess gas, and then fix the syringe on the electrospinning equipment. After adjusting the distance between the needle tip and the collecting plate, charge the metal needle positively and the collecting plate negatively. After setting the flow rate of the precursor, click the start button. Under the combined action of electrostatic force and surface tension, the precursor solution pushed out by the needle is rapidly atomized into charged droplets and flies towards the collecting plate. During this period, most of the solvent in the precursor solution will evaporate rapidly, and the solid product on the collecting plate needs to be further dried in an oven to finally obtain the Al-ammonium fluoride metal@fluoropolymer energetic film.
2. The preparation method according to claim 1, characterized in that, In step 1, all mechanical and physical mixing methods employ magnetic stirring.
3. The preparation method according to claim 1, characterized in that, In step 1, the fluoropolymer selected is polyvinylidene fluoride (PVDF) or poly(vinylidene fluoride-hexafluoropropylene)P (VDF-HFP); during the polymer dissolution process, the solution gradually changes from a turbid liquid to a transparent one, and after complete dissolution, the solution becomes clear.
4. The preparation method according to claim 1, characterized in that, In step 1, the ammonium fluoride is (NH4)3BiF6, (NH4)2NiF6, or (NH4)3FeF6.
5. The preparation method according to claim 1, characterized in that, In step 1, the continuous stirring process after adding ammonium fluoride takes a long time. Usually, the container is sealed to prevent the solution from evaporating prematurely due to excessive stirring time.
6. The preparation method according to claim 1, characterized in that, In step 2, the inner diameter of the needle is 0.51 mm, and the distance between the tip of the needle and the collection plate is adjusted to be between 12-18 cm.
7. The preparation method according to claim 1, characterized in that, In step 2, the metal needle is positively charged and the collecting plate is negatively charged. The difference between the two static voltages is between 12-19kV, ensuring good atomization of the precursor liquid.
8. The preparation method according to claim 1, characterized in that, In step 2, after the solid product on the collection plate is collected, it needs to be dried in a vacuum oven to remove any solution that has not completely evaporated during the electrospinning process.
9. A high-output-efficiency energetic thin film prepared by the method according to any one of claims 1-8, characterized in that, High-output-efficiency energetic films are Al / ammonium fluoride / fluoropolymer energetic films.