A metastable Al / NH4CuF3 intermolecular complex and its preparation method

Abstract

The application discloses a preparation method of Al / NH4CuF3 metastable intermolecular complex. The method is characterized in that: firstly, NH4CuF3 with a nano-network structure is prepared through a solvothermal reaction; then, n-Al is filled into the nanopore channels of the NH4CuF3 in a manner of ultrasonic-assisted dispersion, so as to form n-Al / NH4CuF3 MICs with good dispersity. The n-Al / NH4CuF3 MICs prepared by the method can etch a passivation layer and reduce the reaction energy barrier of the aluminum powder and an oxidizing agent, depending on the low-temperature decomposition of the NH4CuF3 to release F and the thermal decomposition of the NH4CuF3 to generate HF. In addition, a large amount of gaseous products are generated by the decomposition of the NH4CuF3, so that the generation of a reaction sintering phenomenon is relieved, and the combustion efficiency of the n-Al is improved.

Description

Technical Field

[0001] This invention belongs to the field of energetic materials, specifically relating to an Al / NH4CuF3 metastable intermolecular complex and its preparation method. Background Technology

[0002] Metastable intermolecular complexes (MICs) typically consist of solid fuels and oxidants. These composite energetic materials, formed through various composite technologies, possess high energy density, high energy release rates, and high exothermic properties, and are widely used in mining, ordnance, aerospace, micro-driven micro-ignition, bio-sterilization, and underwater blasting. The solid fuel components in MICs typically include Al, Mg, B, and Si. Due to its high abundance, ease of processing, and low cost, Al has consistently been a hot research and application topic. However, the inherent passivation layer hinders the redox reaction between Al and the oxidant.

[0003] To address the barrier effect of the passivation layer, etching has proven effective. This process relies on the reaction of F with Al₂O₃, forming AlF₃, which has a lower decomposition temperature. The high temperature provided by the aluminothermic reaction can vaporize AlF₃, weakening or even eliminating the barrier effect. Furthermore, F, with its strong electronegativity, can effectively oxidize fuels. This potential advantage clearly makes it a current research hotspot. Currently, the most studied fluorinated F oxidants fall into two categories: metal fluorides and fluoropolymers. The former includes FeF₃, CoF₂, NiF₂, and CuF₂, while the latter includes PTFE and PVDF. Metal fluorides decompose at lower temperatures, releasing free F ions that react with the passivation layer on the Al powder surface. The main reaction often occurs at higher temperatures. First, fluoropolymers decompose, releasing small fluorinated gaseous molecules such as CF₂ and HF. Then, these gaseous molecules diffuse to the Al particle surface and react with the passivation layer. These pre-reaction phenomena between the fluorinated oxidants and Al lower the reaction energy barrier between the Al core and the oxidant.

[0004] Although metal fluorides and fluoropolymers are widely used in MIC systems, their inherent limitations remain, such as the high hygroscopicity of metal fluorides and the poor processability of fluoropolymers, which restrict the practical application of these oxidants. In addition, high-yield MICs are also attracting considerable attention. Summary of the Invention

[0005] The purpose of this invention is to provide a method for preparing Al / NH4CuF3MICs. This method first uses a solvothermal method to prepare a fluorinated NH4CuF3 oxidant with a nano-network structure, and then uses ultrasonic-assisted dispersion to prepare Al / NH4CuF3MICs with high gas production, low ignition delay, and low reaction initiation temperature, effectively improving the combustion efficiency of n-Al.

[0006] The technical solution for achieving the objective of this invention is as follows:

[0007] Introducing ammonium perchlorate (AP), energetic metal-organic frameworks (EMOFs), and nitrocellulose (NCs) into Al-based micromolecular compounds (MICs) can generate a large amount of gas at the reaction interface, avoiding sintering and improving fuel combustion efficiency. Simultaneously, the high-gas-producing energetic complex possesses stronger external energy-generating capabilities, meeting the requirements of many application scenarios. Therefore, to improve the combustion efficiency of aluminum powder, fluorination reactions can replace traditional oxidation reactions and increase the amount of bulk products generated in the system.

[0008] A method for preparing Al / NH4CuF3 MICs includes the following steps:

[0009] Step 1: Anhydrous CuCl2 and NH4F in different mass ratios are added to a solvent. The two solid components are completely dissolved by water bath heating and magnetic stirring. The solution is then transferred to a reaction vessel for a solvothermal reaction. By controlling the mass ratio of CuCl2 and NH4F and the solvothermal reaction temperature, pure-phase NH4CuF3 is synthesized. After cooling, the suspension is removed, centrifuged, washed, and dried to obtain NH4CuF3 powder.

[0010] Step 2: The prepared NH4CuF3 powder and nano-aluminum powder n-Al are added to the dispersant, and an Al / NH4CuF3 suspension is obtained by ultrasonic-assisted dispersion. The dispersant is removed by evaporation and drying to obtain Al / NH4CuF3 MICs.

[0011] Furthermore, in step 1, anhydrous CuCl2 can be replaced with anhydrous CoCl2, FeCl3, or NiCl2.

[0012] Furthermore, in step 1, the solvent is a mixed solution of glycerol and ethanol.

[0013] Furthermore, in step 1, the solvothermal reaction process in the reactor also requires stirring.

[0014] Furthermore, the equipment for solvothermal reactions combines heating and magnetic stirring functions, with a solvothermal reaction temperature of 90–180°C and a stirring rate of 150–500 rpm.

[0015] Furthermore, in step 1, the detergent is selected from one or two of anhydrous ethanol, n-hexane, and deionized water.

[0016] Furthermore, in step 2, the particle size distribution of n-Al is 30–500 nm, and Al can be replaced by Mg, Si, B, or Ti; the proportion of n-Al in Al / NH4CuF3 MICs is 5 wt%–50 wt%.

[0017] Furthermore, in step 2, the dispersant is selected from one or more of anhydrous ethanol, n-hexane, and cyclohexane.

[0018] Furthermore, in step 2, the ultrasonic-assisted dispersion time is 10–60 min; the evaporation drying temperature is 50–80 °C; and the drying time is 1–24 h.

[0019] The Al / NH4CuF3 metastable intermolecular complex was prepared by the above method.

[0020] Compared with the prior art, the present invention has the following advantages:

[0021] (1) NH4CuF3 with a nano-network structure was prepared by solvothermal method. n-Al was filled into the nanopores of NH4CuF3 by simple ultrasonic-assisted dispersion to form well-dispersed n-Al / NH4CuF3MICs. (2) NH4CuF3 decomposes to release HF and NH3 gaseous products. These functional gases have an etching effect on the passivation layer of Al powder, and the large amount of gaseous products alleviates the reaction sintering and improves the combustion efficiency of Al powder. (3) Performance analysis and comparison with n-Al / CuF2 and n-Al / CuO showed that n-Al / NH4CuF3 has a lower reaction start temperature, a lower ignition delay time and a stronger external working ability. (4) The synthesis and composite process of this invention are carried out in the liquid phase, which has low equipment requirements, simple reaction, low cost and easy operation. Attached Figure Description

[0022] Figure 1 The following is a schematic diagram of the preparation process of the n-Al / NH4CuF3 MICs obtained in the examples below.

[0023] Figure 2 The following examples illustrate the characterization results of the structure and morphology of the nanostructured NH4CuF3 and n-Al / NH4CuF3 MICs prepared in the examples. (a) and (b) are SEM images of NH4CuF3; (c) is a macroscopic photograph of NH4CuF3; (d) and (e) are SEM images of n-Al / NH4CuF3 MICs; and (f) is the XRD pattern of NH4CuF3.

[0024] Figure 3 The image shows the TG-DSC-FTIR curve of NH4CuF3.

[0025] Figure 4 The DSC curves are for n-Al / NH4CuF3-1, n-Al / CuF2-1, and n-Al / CuO-1.

[0026] Figure 5 SEM images of the combustion products of n-Al / NH4CuF3-2, n-Al / CuF2-2, and n-Al / CuO-2.

[0027] Figure 6 The ignition delay time and combustion time are for n-Al / NH4CuF3-2, n-Al / CuF2-2 and n-Al / CuO-2.

[0028] Figure 7 SEM images of n-Al / NH4CuF3-2, n-Al / CuF2-2, and n-Al / CuO-2. Detailed Implementation

[0029] The present invention will be further described below with reference to embodiments and accompanying drawings.

[0030] The preparation process of Al / NH4CuF3MICs includes the following steps:

[0031] Step 1: Anhydrous CuCl2 was added to a mixed solution of 30 mL glycerol and 30 mL ethanol. The solution was heated in a water bath with magnetic stirring until completely dissolved. Then, solid NH4F was added to the container, and the mixture was heated in a water bath for a period of time while maintaining the same stirring rate. The solution was then transferred to a reaction vessel and reacted for 12 hours. Finally, the cooled suspension was centrifuged to obtain the solid product, which was washed several times with anhydrous ethanol. The resulting product was then dried in a vacuum oven at 60°C for 6 hours to obtain the nano-network structure of NH4CuF3.

[0032] Step 2: The prepared NH4CuF3 and a certain amount of n-Al are added to the dispersant, and an Al / NH4CuF3 suspension is obtained by ultrasonic-assisted dispersion. The dispersant is removed by evaporation drying in a vacuum oven at 60°C to obtain Al / NH4CuF3 MICs.

[0033] Specifically, the volume ratio of glycerol to ethanol in the mixed solution includes 1:5, 1:3, 1:2, 5:7 and 1:1.

[0034] Specifically, the water bath heating before adding NH4F solid was 2 hours, and the heating after adding NH4F solid was 1.5 hours.

[0035] Specifically, the magnetic stirring speed in the water bath and the reaction vessel is 150-500 rpm, and more preferably, the magnetic stirring speed is 300 rpm.

[0036] Specifically, the solid surface is washed with anhydrous ethanol at least five times to remove impurities such as glycerol.

[0037] Specifically, the size of n-Al is 30–500 nm, and more preferably, the particle size distribution of n-Al is 50–200 nm.

[0038] Specifically, the dispersant is one or more of anhydrous ethanol, n-hexane, and cyclohexane, with anhydrous ethanol being the most preferred single dispersant.

[0039] Specifically, the ultrasonic-assisted dispersion time is 40 minutes, and ice needs to be added for cooling.

[0040] Example 1

[0041] 810 mg of anhydrous CuCl2 was added to a mixed solution of 30 mL glycerol and 30 mL ethanol. The solution was heated in a water bath at 50 °C and magnetically stirred at 300 rpm for 2 h to ensure complete dissolution. Then, 444 mg of ammonium fluoride solid was added to the container, and the mixture was heated in a water bath for another 1.5 h with the same stirring rate. The solution was then transferred to a reaction vessel and reacted at 90 °C for 12 h. Magnetic stirring at 300 rpm was also required during the reaction in the reaction vessel. Finally, the cooled suspension was centrifuged at 11000 rpm for solid-liquid separation, and the solid product was washed five times with anhydrous ethanol. The final product was dried in a vacuum oven at 60 °C for 6 h to obtain NH4CuF3 with a nano-network structure. In the following examples, 37.5 mg of n-Al and 208.5 mg of NH4CuF3 were dispersed in 50 mL of anhydrous ethanol and sonicated for 40 min. After centrifugation, washing, and drying, n-Al / NH4CuF3-1 MICs were obtained.

[0042] Based on the scheme of Example 1, the following schemes are obtained by adjusting some process parameters:

[0043] Example 2

[0044] 810 mg of anhydrous CuCl2 was added to a mixed solution of 30 mL glycerol and 30 mL ethanol. The solution was heated in a water bath at 50 °C and magnetically stirred at 300 rpm for 2 hours until completely dissolved. Then, 666 mg of ammonium fluoride solid was added to the container, and the water bath was heated for another 1.5 hours with the same stirring rate. The solution was then transferred to a reaction vessel and reacted at 90 °C for 12 hours. Magnetic stirring at 300 rpm was also required during the reaction in the reaction vessel. Finally, the cooled suspension was centrifuged at 11,000 rpm for solid-liquid separation, and the solid product was washed five times with anhydrous ethanol. The final product was dried in a vacuum oven at 60 °C for 6 hours to obtain the solid product.

[0045] Example 3

[0046] 810 mg of anhydrous CuCl2 was added to a mixed solution of 30 mL glycerol and 30 mL ethanol. The solution was heated in a water bath at 50 °C and magnetically stirred at 300 rpm for 2 hours until completely dissolved. Then, 888 mg of ammonium fluoride solid was added to the container, and the water bath was heated for another 1.5 hours with the same stirring rate. The solution was then transferred to a reaction vessel and reacted at 90 °C for 12 hours. Magnetic stirring at 300 rpm was also required during the reaction in the reaction vessel. Finally, the cooled suspension was centrifuged at 11,000 rpm for solid-liquid separation, and the solid product was washed five times with anhydrous ethanol. The final product was dried in a vacuum oven at 60 °C for 6 hours to obtain the solid product.

[0047] Example 4

[0048] 810 mg of anhydrous CuCl2 was added to a mixed solution of 30 mL glycerol and 30 mL ethanol. The solution was heated in a water bath at 50 °C and magnetically stirred at 300 rpm for 2 hours until completely dissolved. Then, 444 mg of ammonium fluoride solid was added to the container, and the water bath was heated for another 1.5 hours with the same stirring rate. The solution was then transferred to a reaction vessel and reacted at 120 °C for 12 hours. Magnetic stirring at 300 rpm was also required during the reaction in the reaction vessel. Finally, the cooled suspension was centrifuged at 11,000 rpm for solid-liquid separation, and the solid product was washed five times with anhydrous ethanol. The final product was dried in a vacuum oven at 60 °C for 6 hours to obtain the solid product.

[0049] Example 5

[0050] 810 mg of anhydrous CuCl2 was added to a mixed solution of 30 mL glycerol and 30 mL ethanol. The solution was heated in a water bath at 50 °C and magnetically stirred at 300 rpm for 2 hours until completely dissolved. Then, 666 mg of ammonium fluoride solid was added to the container, and the water bath was heated for another 1.5 hours with the same stirring rate. The solution was then transferred to a reaction vessel and reacted at 150 °C for 12 hours. Magnetic stirring at 300 rpm was also required during the reaction in the reaction vessel. Finally, the cooled suspension was centrifuged at 11,000 rpm for solid-liquid separation, and the solid product was washed five times with anhydrous ethanol. The final product was dried in a vacuum oven at 60 °C for 6 hours to obtain the solid product.

[0051] Example 6

[0052] 37.5 mg of n-Al and 417.0 mg of NH4CuF3 were dispersed in 50 mL of anhydrous ethanol and sonicated for 40 min. After centrifugation, washing and drying, n-Al / NH4CuF3-0.5MICs were obtained.

[0053] Example 7

[0054] 37.5 mg of n-Al and 278.0 mg of NH4CuF3 were dispersed in 50 mL of anhydrous ethanol and sonicated for 40 min. After centrifugation, washing and drying, n-Al / NH4CuF3-1.5MICs were obtained.

[0055] Example 8

[0056] 75 mg of n-Al and 208.6 mg of NH4CuF3 were dispersed in 50 mL of anhydrous ethanol and sonicated for 40 min. After centrifugation, washing and drying, n-Al / NH4CuF3-2 MICs were obtained.

[0057] Example 9

[0058] 112.5 mg of n-Al and 208.5 mg of NH4CuF3 were dispersed in 50 mL of anhydrous ethanol and sonicated for 40 min. After centrifugation, washing and drying, n-Al / NH4CuF3-3 MICs were obtained.

[0059] In the above embodiments, Al can be replaced with Mg, Si, B, or Ti. Anhydrous CuCl2 can be replaced with anhydrous CoCl2, FeCl3, or NiCl2.

[0060] Figure 1The above is a flowchart of the preparation process of n-Al / NH4CuF3 MICs. By following the above steps, NH4CuF3 with a nano-network structure can be obtained, and n-Al can be filled into the nanopores to form well-dispersed n-Al / NH4CuF3 MICs. Figure 2 XRD patterns of solid products prepared at different raw material mass ratios and different solvothermal reaction temperatures. Figure 3 The image includes SEM images, macroscopic images, and XRD patterns of NH4CuF3. As shown in the figure, the above steps successfully prepared NH4CuF3 with a nano-network structure. Furthermore, the image also includes SEM images of n-Al / NH4CuF3MICs. These images show that n-Al was filled into the nanopores of NH4CuF3 using an ultrasonic-assisted dispersion method, forming a well-dispersed composite. Figure 4 The data curves for TG-DSC-FTIR of NH4CuF3 show that NH4CuF3 can release gaseous products of HF and NH3 at relatively low temperatures. The presence of these gaseous products can effectively etch the passivation layer and increase the reaction initiation temperature of the aluminum powder (e.g., ...). Figure 5 This reduces ignition delay. Furthermore, the high gas production performance alleviates the reaction sintering phenomenon of n-Al / NH4CuF3MICs, improving the combustion efficiency of aluminum powder. For example... Figure 6 Compared to n-Al / CuF2 and n-Al / CuO, n-Al / NH4CuF3 was found to have a lower ignition delay time. Figure 7 The high gas production performance of n-Al / NH4CuF3 reduces the reaction sintering phenomenon, resulting in smaller particle size of the combustion products.

[0061] 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 Al / NH4CuF3 MICs, characterized in that, Includes the following steps: Step 1: Anhydrous CuCl2 and NH4F in different mass ratios are added to a solvent. The two solid components are completely dissolved by water bath heating and magnetic stirring. The solution is then transferred to a reaction vessel for solvothermal reaction. Pure phase NH4CuF3 is synthesized by controlling the mass ratio of CuCl2 and NH4F and the solvothermal reaction temperature. After cooling, the suspension is taken out, centrifuged, washed and dried to obtain NH4CuF3 powder. Step 2: The prepared NH4CuF3 powder and nano-aluminum powder n-Al are added to the dispersant, and an Al / NH4CuF3 suspension is obtained by ultrasonic-assisted dispersion. The dispersant is removed by evaporation and drying to obtain Al / NH4CuF3 MICs.

2. The production method according to claim 1, characterized by, In step 1, anhydrous CuCl2 can be replaced with anhydrous CoCl2, FeCl3, or NiCl2.

3. The preparation method according to claim 1, characterized in that, In step 1, the solvent is a mixed solution of glycerol and ethanol.

4. The preparation method according to claim 1, characterized in that, In step 1, the solvothermal reaction process in the reactor also requires stirring.

5. The preparation method according to claim 4, characterized in that, The equipment for solvothermal reactions combines heating and magnetic stirring functions. The solvothermal reaction temperature is 90–180℃, and the stirring speed is 150–500 rpm.

6. The preparation method according to claim 1, characterized in that, In step 1, the detergent can be one or two of anhydrous ethanol, n-hexane, and deionized water.

7. The preparation method according to claim 1, characterized in that, In step 2, the particle size distribution of n-Al is 30–500 nm, and Al can be replaced by Mg, Si, B, or Ti; the proportion of n-Al in Al / NH4CuF3 MICs is 5 wt%–50 wt%.

8. The preparation method according to claim 1, characterized in that, In step 2, the dispersant is selected from one or more of anhydrous ethanol, n-hexane, and cyclohexane.

9. The preparation method according to claim 1, characterized in that, In step 2, the ultrasonic-assisted dispersion time is 10–60 min; the evaporation drying temperature is 50–80 °C; and the drying time is 1–24 h.

10. An Al / NH4CuF3 metastable intermolecular complex prepared by the preparation method according to claims 1-9.

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