Aluminum-based microwave energetic material with core-shell structure as well as preparation method and application of aluminum-based microwave energetic material

Abstract

The invention belongs to the technical field of energetic materials, and discloses a core-shell structure aluminum-based microwave energetic material and a preparation method and application thereof.The preparation method comprises the steps that in order to construct an interface layer on the surface of aluminum powder, the aluminum powder is added into a silane coupling agent solution, a cyclodextrin solution, a butyl titanate solution and a perfluorododecyl mercaptan / dopamine hydrochloride solution, and four kinds of suspension liquid A are formed; adding the suspension B containing the bimetallic composite oxide into the suspension A, and stirring to obtain four suspensions C; and filtering, washing and drying the suspension C to obtain the aluminum-based microwave energetic material with the core-shell structure. According to the invention, interface chemical bonds or electrostatic interaction is constructed between aluminum and AB2O4 by using the interface layer, so that oxidation of aluminum is effectively prevented, interface polarization is enhanced at the same time, and a core / shell structure further shortens the mass and heat transfer distance of a reaction between fuel and potassium oxide, so that the microwave ignition delay time is remarkably shortened, and the microwave ignition efficiency is improved. Efficient microwave energy coupling and controllable combustion performance are achieved, and excellent microwave response characteristics are shown.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of energetic materials, and particularly relates to a core-shell structure aluminum-based microwave energetic material, a preparation method and application thereof. BACKGROUND

[0002] As a new type of insensitive ignition technology, microwave ignition uses an alternating electromagnetic field to penetrate the internal structure and heat the energetic material by dielectric heating, achieving multi-point synchronous ignition of the entire substrate and significantly improving the efficiency and stability of ignition and combustion in extreme environments [1] . In addition, in theory, the strong electromagnetic field of microwaves can heat unburned condensed phase materials and ionize the combustion products of high-energy materials, thereby increasing the combustion temperature [2-3] . Therefore, by dynamically adjusting the microwave power and impedance matching in real time, the thrust of small solid rocket engines can be increased, and the burning rate and energy release of propellants can be controlled in real time, breaking through the limitations of traditional thrust systems lacking adjustability.

[0003] However, common explosives and existing solid propellants cannot be ignited by microwaves in a low delay time, so it is necessary to develop microwave-sensitive solid propellants. Aluminum has multiple important uses in propellants, explosives and pyrotechnics, but due to its low dielectric properties, it needs to be microwave sensitized. Ferrites with spinel structure (AB2O4, A=Cu, Ni, Mn, Co, B=Fe, Co) are important microwave absorbing materials. This type of material usually has both dielectric loss and magnetic loss capabilities [4-5] , and can effectively convert electromagnetic energy into heat energy as a microwave absorber. However, the contact area between the wave-absorbing oxide particles and the aluminum particles is small, and the electromagnetic impedance matching is poor, resulting in low heating efficiency of aluminum through heat conduction after the oxide absorbs microwave energy.

[0004] [1] S.J. Barkley, K. Zhu, J.E. Lynch, et al. Microwave plasma enhancement of multiphase flames: On-demand control of solid propellant burning rate, Combust . Flame 199 (2019) 14-23. [2] K. Rao, I. Hemawan, C. Wichman, et al. Combustion dynamics for energetically enhanced flames using direct microwave energy coupling, P .Combust . Inst . 33 (2011) 3233-3240. [3] Z. Alibay, D.J. Kline, M.C. Rehwoldt, et al.Mechanism of microwave-initiated ignition of sensitized energetic nanocomposites, Chem . Eng .J. 415 (2021), 128657. [4] J. Liu, Z. Jia, W. Zhou, et al. Self-assembledMoS2 / magnetic ferrite CuFe2O4nanocomposite for high-efficiency microwaveabsorption, Chem. Eng. J. 429 (2022), 132253. [5] L. Zhang, S. Li, L. Duan, et al. Construction of hierarchicalZnO-NiCo2O4-NiCo2O4core-shell microstructure with efficient microwaveabsorption[J]. Appl. Surf. Sci. 649(2024), 159203. SUMMARY In order to overcome the problem of impedance mismatch of microwave absorption performance of aluminum-based ignition powder in the prior art, the purpose of the present application is to provide a core-shell structure aluminum-based microwave energetic material and a preparation method and application. Through the multi-component synergistic effect of the material and the multiple loss mechanism induced by the heterojunction interface, the microwave absorption performance can be significantly enhanced, and the problem of long microwave ignition time of aluminum-based ignition powder is solved.

[0005] To achieve the above purpose, the technical scheme adopted by the present application is as follows: The preparation method of the core-shell structure aluminum-based microwave energetic material comprises the following steps: The aluminum powder is added into a solution of silane coupling agent, or the aluminum powder is added into a solution of cyclodextrin, or the aluminum powder is added into a solution of butyl titanate, or the aluminum powder is added into a solution containing perfluorododecanethiol and dopamine hydrochloride, and then stirred to form a suspension A; The suspension B containing bimetallic oxide is added into the suspension A and stirred to obtain a suspension C; Filter, wash and dry the suspension C to obtain the core-shell structure aluminum-based microwave energetic material.

[0006] Further, the solution of the silane coupling agent is prepared by adding the silane coupling agent into a mixture of one or more of water, ethanol and tris buffer solution, and then ultrasonic treatment; wherein the concentration of the silane coupling agent is 1-1.6 mg / mL.

[0007] Further, the silane coupling agent is KH-550.

[0008] Further, the solution of the cyclodextrin is prepared by adding the cyclodextrin into a mixture of one or more of water, ethanol and tris buffer solution, and then ultrasonic treatment; wherein the concentration of the cyclodextrin is 0.5-1.5 mg / mL.

[0009] Further, the solution of the butyl titanate is prepared by adding the butyl titanate into a mixture of one or more of water, ethanol and tris buffer solution, and then ultrasonic treatment; wherein the concentration of the butyl titanate is 1-3 mg / mL.

[0010] Further, the solution containing perfluorododecanethiol and dopamine hydrochloride is prepared by adding perfluorododecanethiol and dopamine hydrochloride into a mixture of one or more of water, ethanol and tris buffer solution, and then ultrasonic treatment; wherein the concentration of the perfluorododecanethiol is 0.5-1.6 mg / mL, and the concentration of the dopamine hydrochloride is 0.5-1.6 mg / mL.

[0011] Further, the particle size of the aluminum powder is 0.6-3 µm; and the double metal oxide is CuFe2O4, NiFe2O4, MnFe2O4, CoFe2O4, CuCo2O4, NiCo2O4 or MnCo2O4.

[0012] Further, the equivalent ratio of the aluminum powder to the double metal oxide is 0.5-3, and the equivalent ratio Φ is calculated by the following formula: Φ = n Al / n AB2O4. , wherein, n Al is the amount of substance of the aluminum powder, n AB2O4 is the double metal oxide, n Al / n AB2O4 is the actual amount-of-substance ratio of the aluminum powder to the AB2O4, n Al / n AB2O4 is the actual amount-of-substance ratio of the aluminum powder to the AB2O4.

[0013] The core-shell structure aluminum-based microwave energetic material prepared by the above method.

[0014] The core-shell structure aluminum-based microwave energetic material is applied to microwave ignition propellants, pyrotechnics and propellants.

[0015] Compared with the prior art, the present application has the following advantages: The present application introduces an interface layer component by interface structure regulation method, and guides the high dielectric coating of double metal oxide AB2O4 to anchor on the aluminum surface through chemical bond or electrostatic adsorption, so as to obtain Al@AB2O4 high-energy particles with core-shell structure. In the present application, the interface layer component is used to establish the interface interaction between aluminum and AB2O4, which effectively prevents the oxidation of aluminum. The microwave absorption performance and combustion performance of the particles are regulated by regulating the type and thickness of the interface layer and the double metal oxide. At the same time, the interface layer component not only strengthens the interaction between Al and AB2O4 to form an Al@AB2O4 core-shell structure, but also significantly shortens the transmission distance of mass and heat, and enhances the microwave energy absorption capacity through the interface polarization effect, thereby solving the problem of poor microwave ignition performance of aluminum. In the present application, the gradient interface design not only enhances the interface polarization and relaxation polarization effect, optimizes the impedance matching, but also significantly improves the microwave absorption performance of the material through multi-stage reflection / scattering path, which provides a new way for solving high-efficiency microwave absorption. The experimental results show that the ignition delay time of Al@AB2O4 is as low as 23.41 ms under 64 W microwave, the maximum pressure of 25 mg of Al@AB2O4 powder burning in a 13 mL closed detonation vessel is 463.31 kPa, and the burning rate in air is 7.48 m / s. The aluminum-based high-energy ignition powder has low microwave ignition delay time, high energy release and good combustion performance. The core-shell structure aluminum-based microwave energetic material prepared by the present application realizes high-efficiency microwave energy coupling and controllable combustion performance through multi-stage structure design, and exhibits excellent combustion and microwave response characteristics.

[0016] Further, the double metal oxide is a ferrite (AB2O4, A=Cu, Ni, Mn, Co, B=Fe, Co) with a spinel structure, which is an important microwave absorption material. This kind of material usually has dielectric loss and magnetic loss ability, and can effectively convert electromagnetic energy into heat energy through violent aluminothermic reaction with aluminum powder, solving the problem of poor microwave ignition performance of aluminum, and reducing the ignition delay time of aluminum in the microwave field. BRIEF DESCRIPTION OF DRAWINGS

[0017] Figure 1 SEM image of Al@KH-550 in Example 1; Figure 2 SEM image of Al@β-CD in Example 2; Figure 3 SEM image of Al@PF in Example 3; Figure 4 SEM image of Al@TiO2 in Example 4 Figure 5TEM graph of Al@KH-550@CuFe2O4 in Example 1; Figure 6 Microwave ignition process graph of Al@KH-550@CuFe2O4 in Example 1 at 64 W; Figure 7 Microwave ignition delay time graph of Al@KH-550@CuFe2O4 in Example 1, Example 3, Example 4, Example 5, Example 6, and Example 7; Figure 8 Maximum pressure graph of combustion in a closed bomb of Al@KH-550@CuFe2O4 in Example 1; Figure 9 TG curve of KH-550 and PF in Example 1 and Example 2; Figure 10 Microwave ignition process graph of Al@PF@CuFe2O4 in Example 2 at 64 W; Figure 11 Burning rate graph of Al@PF@CuFe2O4 in Example 2 under air atmosphere; Figure 12 SEM graph of Al / β-CD@CuFe2O4 in Example 8; Figure 13 Microwave ignition delay time graph of Al@TiO2@CuFe2O4 in Example 9; Figure 14 Microwave ignition delay time graph of Al@KH-550@CuFe2O4 in Comparative Example 1; Figure 15 Microwave ignition delay time graph of Al@PF@CuFe2O4 in Comparative Example 2; Figure 16 Microwave ignition graph of Al@KH-550@CoFe2O4 in Comparative Example 3 at microwave power of 64 W; Figure 17 Microwave ignition graph of Al@KH-550@MnFe2O4 in Comparative Example 4 at microwave power of 64 W; Figure 18 Microwave ignition graph of Al@KH-550@NiFe2O4 in Comparative Example 5 at microwave power of 64 W. DETAILED DESCRIPTION

[0018] For the purpose of facilitating the understanding of the present application, a more comprehensive description of the present application will be given below with reference to the relevant drawings. The preferred embodiments of the present application are shown in the drawings. However, the present application can be realized in various different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the disclosure of the present application more thorough and comprehensive.

[0019] In order to solve the problem of long ignition delay time of aluminum-based microwave ignition powder, the preparation method of the core-shell structure aluminum-based microwave energetic material provided by the present application first adds aluminum powder into a solution in which an interfacial layer component is fully dissolved or hydrolyzed to obtain aluminum powder coated with the interfacial layer component, then adds AB2O4 suspension into the above solution, and induces AB2O4 to anchor on the surface of aluminum by introducing chemical bonds or electrostatic adsorption effect through the interfacial layer component to construct microwave-sensitive Al@AB2O4 core-shell high-energy particles, which specifically includes the following steps: 1) Preparation of the interfacial layer: add silane coupling agent (KH-550) into a solvent, ultrasonic for 5-30 min to obtain solution A; wherein the concentration of KH-550 is 1-1.6 mg / mL; Add cyclodextrin (β-CD) into a solvent, ultrasonic for 5-30 min to obtain solution B; wherein the concentration of β-CD is 0.5-1.5 mg / mL; Add butyl titanate (TBT) into a solvent, ultrasonic for 5-30 min to obtain solution C; wherein the concentration of TBT is 1-3 mg / mL; Add perfluorododecanethiol (PFDT) and dopamine hydrochloride (DA) into a solvent, ultrasonic for 5-30 min to obtain solution D, i.e. PF interfacial layer, to obtain solution D; wherein the concentration of DA is 0.5-1.6 mg / mL, the concentration of PFDT is 0.5-1.6 mg / mL, and the concentrations of DA and PFDT are the same.

[0020] The solvent in the present application includes but is not limited to water, ethanol, tris buffer solution and the mixed solvent of any one or several thereof.

[0021] 2) Preparation of the suspension A: add aluminum powder (Al) into solution A, or add aluminum powder into solution B, or add aluminum powder into solution C, or add aluminum powder into solution D, and magnetically stir for 1 h at a stirring speed of 500-900 r / min to coat the aluminum powder with the interfacial layer component and form the suspension A; 3) Preparation of the suspension B: add bimetallic oxide AB2O4 into ethanol, and adopt ultrasonic to form uniform suspension B; Suspension B is added to suspension A and mechanically stirred at a speed of 200-500 r / min for 6-8 h. AB2O4 is induced to anchor on the aluminum surface through chemical bonds introduced by the interfacial layer components or electrostatic adsorption, thus obtaining suspension C. In this invention, the equivalent ratio of Al to AB2O4 is 0.5~3, and the particle size of Al is 0.6-3 µm.

[0022] First, the mass of each component in the energetic material needs to be determined. The mass of each component is calculated based on the equivalent ratio (Φ), which is defined as: Φ = In the formula, Let be the amount of substance of Al. It is AB2O4. This represents the actual amounts of Al and AB₂O₄. This represents the theoretical amount of substance of Al and AB2O4.

[0023] The theoretical amount of substance of Al and AB2O4 is calculated based on the reaction equation of the aluminothermic reaction between Al and AB2O4.

[0024] In the bimetallic oxide AB₂O₄ used in this invention, A = Cu, Ni, Mn, or Co; B = Fe or Co. Specifically, AB₂O₄ is CuFe₂O₄, NiFe₂O₄, MnFe₂O₄, CoFe₂O₄, CuCo₂O₄, NiCo₂O₄, or MnCo₂O₄.

[0025] 4) Post-treatment: The suspension C was filtered, washed, and dried in a vacuum drying oven with a vacuum degree of 0.4 × 10⁻⁶. 5 ~0.2×10 5 The drying process was carried out at a temperature of 40℃~60℃ and a drying time of 8 h~12 h to obtain microwave-sensitive Al@AB2O4 core-shell high-energy particles, namely core-shell structured aluminum-based microwave energetic materials.

[0026] The core-shell structured aluminum-based microwave energetic material prepared by this invention includes one of KH-550, β-CD, TB and TPF interface layers, and AB2O4 (microwave absorber); wherein, the KH-550, β-CD, TBT or PF interface layer is coated on the surface of aluminum particles, and AB2O4 acts as a microwave absorber anchored on the Al surface, forming Al@AB2O4 core-shell high-energy particles, which can rapidly absorb electromagnetic energy and convert it into heat to achieve rapid ignition.

[0027] The core-shell structured aluminum-based microwave energetic material prepared by this invention can be used in microwave ignition agents, pyrotechnic agents, and propellants.

[0028] The following are specific examples.

[0029] Example 1 (1) Al@KH-550 The crosslinking agent KH-550 was added to a 40 ml mixed solution of water and ethanol in a volume ratio of 1:7, and ultrasonic treatment was performed for 5 min to obtain a solution with a KH-550 concentration of 1 mg / mL; then 0.18 g of aluminum powder was added, and magnetic stirring was performed at room temperature for 1 h to form a relatively uniform aluminum suspension. At this time, the silanol produced by the hydrolysis of KH-550 was adsorbed on the surface of the aluminum powder and crosslinking reaction occurred, thereby forming a "molecular bridge" with a spatial network structure, and an Al@KH-550 suspension 1 was obtained, wherein Al@KH-550 is aluminum particles coated with KH-550 on the surface.

[0030] As Figure 1 The morphology of Al@KH-550 can be seen from the figure, and it can be seen that the product is a core-shell structure formed by an aluminum core and an external KH-550, and the KH-550 is uniformly coated on the surface of the aluminum particles. The surface of the particles is relatively smooth, and there are small particle-shaped protrusions in some parts.

[0031] (2) Al@KH-550@CuFe2O4 20 ml of a 0.32 g CuFe2O4 ethanol suspension was added to the Al@KH-550 suspension 1, and mechanical stirring was performed for 8 h to anchor the CuFe2O4 on the surface of the Al@KH-550 through covalent bonds, and a suspension 2 was obtained; then filtration, washing, and vacuum drying at 50°C were performed to obtain microwave-sensitive Al@KH-550@CuFe2O4 core-shell high-energy particles, i.e., core-shell structure aluminum-based microwave energetic materials.

[0032] Figure 5 The morphology of Al@KH-550@CuFe2O4 can be seen from the figure, and it can be seen that in the presence of the APTES interfacial layer, the nano CuFe2O4 is uniformly adsorbed, coated, and embedded on the surface of the Al particles.

[0033] Figure 6 The ignition schematic diagram of the microwave-sensitive Al@KH-550@CuFe2O4 in a microwave field in an air atmosphere can be seen from the figure, and it can be seen that the entire combustion process lasted for 61.0 ms, and the maximum flame appeared at 15.8 ms.

[0034] Figure 7 The ignition delay time diagram of the Al@KH-550@CuFe2O4 microwave ignition measured by the photoelectric sensor can be seen from the figure, and it can be seen that the ignition delay time is as low as 23.41 ms at 64 W.

[0035] Figure 8The graph shows the maximum pressure of 25 mg Al@KH-550@CuFe2O4 powder burning in a 13 mL sealed igniter. It can be seen that the maximum combustion pressure is 463.31 kPa.

[0036] Figure 9 The TG curves of KH-550 and PF show that KH-550 can decompose rapidly at low temperatures, which is beneficial for ignition and start-up.

[0037] The above experimental results confirm that Al@KH-550@CuFe2O4 has excellent microwave absorption performance, can respond quickly in a microwave field, and achieve ignition in a short time; at the same time, it also has high energy release and good combustion performance.

[0038] Example 2 (1) Al@PF Dopamine hydrochloride was added to 20 ml of Tris-HCl (pH=8.5) and stirred for 10 min until the dopamine hydrochloride solution turned from colorless to brown. Perfluorododecyl mercaptan was then added, and the mixture was sonicated for 30 min to obtain a solution with a dopamine hydrochloride concentration of 1 mg / ml and a perfluorododecyl mercaptan concentration of 1 mg / ml. 20 ml of ethanol solution was then added. Subsequently, 0.18 g of aluminum powder was added to the dopamine hydrochloride solution, and the mixture was magnetically stirred at room temperature for 1 h to form a relatively homogeneous aluminum suspension. Polydopamine, through strong chelation of phenolic hydroxyl and amino groups, formed a PDA layer on the surface of the aluminum powder via molecular assembly. Subsequently, the thiol of PFDT coupled with the catechol portion on the PDA via a Michael addition reaction to form PF, yielding Al / PF suspension 1, where Al / PF consists of aluminum particles coated with PF.

[0039] Figure 3 The image shows the morphology of Al@PF. It can be seen that the product is a core-shell structure formed by an aluminum core and an outer PF. Moreover, the PF is uniformly coated on the surface of the aluminum particles. Most of the particle surface is relatively smooth, with small granular protrusions in some areas.

[0040] (2) Al@PF@CuFe2O4 20 ml of 0.32 g CuFe2O4 ethanol suspension was added to Al@PF suspension 1, and CuFe2O4 was anchored on the surface of Al@PF by mechanical stirring for 8 h to obtain suspension 2; then filtered, washed, and vacuum dried at 50 °C to obtain microwave-sensitive Al@PF@CuFe2O4 core-shell high-energy particles, i.e. core-shell structured aluminum-based microwave energetic material.

[0041] Figure 10This is a schematic diagram of the ignition of microwave-sensitive Al@PF@CuFe2O4 in a microwave field in air. It can be seen that the Al@PF@CuFe2O4 reaction is violent and rapid, emitting bright light. The center of the combustion flame near the probe tip is white at a relatively high temperature. The entire combustion process lasts for 18.2 ms, and the maximum flame appears at 1.0 ms.

[0042] Figure 11 The combustion rate of Al@PF@CuFe2O4 in air atmosphere is shown. It can be seen that the combustion rate of Al@PF@CuFe2O4 reaches 7.48 m / s. This is mainly due to the thermal decomposition of the PFDT interface layer, which releases a large amount of fluorinated gas products. These products react with aluminum and alumina at a temperature lower than the melting phase transition temperature of aluminum, thus accelerating the combustion of aluminum.

[0043] The results from Al@KH-550@CuFe2O4 and Al@PF@CuFe2O4 show that this invention solves the problem of poor microwave ignition performance of aluminum by controlling the microwave absorption and combustion performance of the particles through regulating the type and thickness of the interface layer and high dielectric material. Due to the rapid decomposition of KH-550 at low temperatures, Al@KH-550@CuFe2O4 can achieve rapid ignition under a microwave field, exhibiting a lower ignition delay time.

[0044] Example 3 The difference from Example 1 is that when the ratio is 0.5, 0.079 g Al and 0.421 g CuFe2O4 are weighed, and the rest are the same as in Example 1.

[0045] Figure 7 The ignition delay time diagram for Al@KH-550@CuFe2O4 microwave ignition, measured by a photoelectric sensor, shows that the ignition delay time at 64W is 35.11 ms.

[0046] Example 4 The difference from Example 1 is that when the ratio is 1, 0.136 g of Al and 0.364 g of CuFe2O4 are weighed, and the rest are the same as in Example 1.

[0047] Figure 7 The ignition delay time diagram of Al@KH-550@CuFe2O4 microwave ignition, measured by a photoelectric sensor, shows that the ignition delay time at 64W is 28.24 ms.

[0048] Example 5 The difference from Example 1 is that when the ratio is 2, 0.214 g of Al and 0.286 g of CuFe2O4 are weighed, and the rest are the same as in Example 1.

[0049] Figure 7 The ignition delay time diagram of Al@KH-550@CuFe2O4 microwave ignition, measured by a photoelectric sensor, shows that the ignition delay time at 64W is 25.41 ms.

[0050] Example 6 The difference from Example 1 is that when the ratio is 2.5, 0.242g of Al and 0.258g of CuFe2O4 are weighed, and the rest are the same as in Example 1.

[0051] Figure 7 The ignition delay time diagram for Al@KH-550@CuFe2O4 microwave ignition, measured by a photoelectric sensor, shows that the ignition delay time at 64W is 25.12 ms.

[0052] Example 7 The difference from Example 1 is that when the ratio is 3, 0.264g of Al and 0.236g of CuFe2O4 are weighed, and the rest are the same as in Example 1.

[0053] Figure 7 The ignition delay time of Al@KH-550@CuFe2O4 was measured using a photoelectric sensor. It can be seen that the ignition delay time at 64W is 29.28 ms.

[0054] Example 8 β-CD was added to 20 ml of water and sonicated for 30 min until a transparent solution was formed. The concentration of β-CD was 1.2 mg / mL. Then 20 ml of ethanol was added to form a water-ethanol mixed solution. 0.18 g of Al was added and mechanically stirred for 1 h to form an Al suspension, resulting in Al / β-CD suspension 1. Al / β-CD is aluminum powder with β-CD coated on its surface.

[0055] Figure 2 The image shows the morphology of Al / β-CD, which reveals that it consists of an aluminum powder core and an outer layer of β-CD. However, the β-CD is not uniformly coated on the surface of the aluminum powder particles; most of the particle surface remains uncoated. The β-CD coating on the aluminum powder surface is mainly achieved through physical forces such as van der Waals forces and hydrogen bonds. These adsorption forces are relatively weak, resulting in poor coating performance.

[0056] 20 ml of 0.32 g CuFe2O4 suspension was added to Al / β-CD suspension 1, and CuFe2O4 was anchored on the surface of Al / β-CD by mechanical stirring for 8 h to obtain suspension 2. Suspension 2 was then filtered, washed, and vacuum dried at 50 °C to obtain microwave-sensitive Al / β-CD@CuFe2O4 core-shell high-energy particles, i.e., core-shell structured aluminum-based microwave energetic material.

[0057] Figure 12 The image shows the morphology of Al / β-CD@CuFe2O4. It can be seen that in the presence of the β-CD interface layer, CuFe2O4 cannot be uniformly coated on the surface of Al particles, and the shell layer is relatively thick, resulting in a long ignition delay time under microwave field.

[0058] Example 9 TBT was dissolved in 5 ml of water, and the pH of 35 ml of ethanol solution was adjusted to 5-6 with acetic acid. The solution was sonicated for 5 min to obtain a TBT concentration of 1.5 mg / ml. Then, 0.18 g of aluminum powder was added to the ethanol solution, and the TBT aqueous solution was added dropwise. The mixture was mechanically stirred for 1 h to form an aluminum suspension. TBT formed a continuous and dense TiO2 gel network coating layer on the surface of the aluminum powder through hydrolysis and condensation reaction, resulting in Al@TiO2 suspension 1. Al@TiO2 consists of aluminum particles coated with TiO2.

[0059] Figure 4 The image shows the morphology of Al@TiO2. It can be seen that the product is a core-shell structure formed by an aluminum core and an outer TiO2 core. Moreover, TiO2 is uniformly coated on the surface of the aluminum particles.

[0060] from Figure 1 , Figure 2 , Figure 3 , Figure 4 The morphology shows that the prepared KH-550, β-CD, PF or TBT interface layer components coat the aluminum particles. KH-550, PF and TBT can form a uniform coating shell on the aluminum surface, which is beneficial to the anchoring of AB2O4 on the aluminum particle surface.

[0061] 20 ml of 0.32 g CuFe2O4 suspension was added to Al / TiO2 suspension 1, and CuFe2O4 was anchored on the surface of Al / TiO2 by mechanical stirring for 8 h to obtain suspension 2. Suspension 2 was then filtered, washed, and vacuum dried at 50 °C to obtain microwave-sensitive Al@TiO2@CuFe2O4 core-shell high-energy particles, i.e., core-shell structured aluminum-based microwave energetic material.

[0062] Figure 13For microwave ignition of Al@TiO2@CuFe2O4, the ignition delay time measured by the photoelectric sensor shows that the ignition delay time at 64W is 61.50 ms. TBT coats TiO2 onto the surface of aluminum powder through hydrolysis-condensation. Since aluminum powder is relatively dangerous at high temperatures, the crystallinity of TiO2 cannot be improved by heat treatment, resulting in a microwave ignition delay time of more than 60 milliseconds.

[0063] Example 10 (1) Al@KH-550 The crosslinking agent KH-550 was added to a 40 ml mixed solution of water and ethanol in a volume ratio of 1:1 and sonicated for 30 min to obtain a solution with a KH-550 concentration of 1.6 mg / mL. Then, 0.182 g of aluminum powder was added and the solution was magnetically stirred at room temperature for 1 h at a stirring speed of 500 r / min to form a relatively uniform aluminum suspension. At this time, the silanol produced by the hydrolysis of KH-550 was adsorbed on the surface of the aluminum powder and underwent a crosslinking reaction, thereby forming a "molecular bridge" with a spatial network structure, resulting in Al@KH-550 suspension 1, wherein Al@KH-550 is aluminum particles coated with KH-550.

[0064] (2) Al@KH-550@ NiFe2O4 20 ml of 0.318 g NiFe2O4 ethanol suspension was added to Al@KH-550 suspension 1, and mechanical stirring was carried out for 8 h to anchor NiFe2O4 to the surface of Al@KH-550 through covalent bonds, resulting in suspension 2; subsequently, it was filtered, washed, and vacuum dried at 50℃ (vacuum degree 0.4 × 10⁻⁶). 5 ~0.2×10 5 Pa), to obtain a core-shell structured aluminum-based microwave energetic material.

[0065] Example 11 (1) Al@KH-550 The crosslinking agent KH-550 was added to a 40 ml mixed solution of water and ethanol in a volume ratio of 1:1 and sonicated for 15 min to obtain a solution with a KH-550 concentration of 1 mg / mL. Then, 0.185 g of aluminum powder was added and the solution was magnetically stirred at room temperature for 1 h at a stirring speed of 900 r / min to form a relatively uniform aluminum suspension. At this time, the silanol produced by the hydrolysis of KH-550 was adsorbed on the surface of the aluminum powder and underwent a crosslinking reaction, thereby forming a "molecular bridge" with a spatial network structure, resulting in Al@KH-550 suspension 1, wherein Al@KH-550 is aluminum particles coated with KH-550.

[0066] (2) Al@KH-550@MnFe2O4 20 ml of 0.315 g MnFe2O4 ethanol suspension was added to Al@KH-550 suspension 1, and mechanical stirring was carried out for 8 h to anchor MnFe2O4 to the surface of Al@KH-550 through covalent bonds, resulting in suspension 2; subsequently, it was filtered, washed, and vacuum dried at 45℃ (vacuum degree 0.4 × 10⁻⁶). 5 ~0.2×10 5 After 10 h of (Pa) the core-shell structure aluminum-based microwave energetic material was obtained.

[0067] Example 12 (1) Al@KH-550 The crosslinking agent KH-550 was added to a 40 ml mixed solution of water and ethanol in a volume ratio of 1:1 and sonicated for 20 min to obtain a solution with a KH-550 concentration of 1.3 mg / mL. Then, 0.183 g of aluminum powder was added and the solution was magnetically stirred at room temperature for 1 h at a stirring speed of 700 r / min to form a relatively uniform aluminum suspension. At this time, the silanol produced by the hydrolysis of KH-550 was adsorbed on the surface of the aluminum powder and underwent a crosslinking reaction, thereby forming a "molecular bridge" with a spatial network structure, resulting in Al@KH-550 suspension 1, wherein Al@KH-550 is aluminum particles coated with KH-550.

[0068] (2) Al@KH-550@ CoFe2O4 20 ml of 0.317 g CoFe2O4 ethanol suspension was added to Al@KH-550 suspension 1, and mechanical stirring was carried out for 8 h to allow CoFe2O4 to be covalently anchored on the surface of Al@KH-550, resulting in suspension 2; subsequently, it was filtered, washed, and vacuum dried at 50 °C (vacuum degree 0.4 × 10⁻⁶). 5 ~0.2×10 5 After 10 h of (Pa) the core-shell structure aluminum-based microwave energetic material was obtained.

[0069] Example 13 (1) Al@PF Dopamine hydrochloride was added to 20 ml of Tris-HCl (pH=8.5) and stirred for 10 min until the solution changed from colorless to brown. Perfluorododecyl mercaptan (PFD) was then added, and the mixture was sonicated for 30 min. Finally, 20 ml of ethanol was added to obtain a solution with a dopamine hydrochloride concentration of 0.5 mg / ml and a PFD concentration of 0.5 mg / ml. Subsequently, 0.177 g of aluminum powder was added to the dopamine hydrochloride solution, and the mixture was magnetically stirred at 800 r / min for 1 h at room temperature to form a relatively homogeneous aluminum suspension. Polydopamine (PDA) formed a PDA layer on the aluminum powder surface through strong chelation between phenolic hydroxyl and amino groups. Subsequently, the thiol of PFDT coupled with the catechol portion of the PDA via a Michael addition reaction to form PF, resulting in Al / PF suspension 1, where Al / PF consists of aluminum particles coated with PF.

[0070] (2) Al@PF@CuCo2O4 20 ml of 0.323 g CuCo2O4 ethanol suspension was added to Al@PF suspension 1, and CuCo2O4 was anchored on the surface of Al@PF by mechanical stirring for 8 h to obtain suspension 2; then filtered, washed, and vacuum dried at 60℃ (vacuum degree 0.4×10). 5 ~0.2×10 5 After 8 hours of processing, a core-shell structured aluminum-based microwave energetic material was obtained.

[0071] Example 14 (1) Al@PF Dopamine hydrochloride was added to 20 ml of Tris-HCl (pH=8.5) and stirred for 10 min until the solution changed from colorless to brown. Perfluorododecyl mercaptan (PFD) was then added, and the mixture was sonicated for 30 min. Finally, 20 ml of ethanol was added to obtain a solution with a dopamine hydrochloride concentration of 1.6 mg / ml and a PFD concentration of 1.6 mg / ml. Subsequently, 0.18 g of aluminum powder was added to the dopamine hydrochloride solution, and the mixture was magnetically stirred at 600 r / min for 1 h at room temperature to form a relatively homogeneous aluminum suspension. Polydopamine (PDA) formed a PDA layer on the aluminum powder surface through strong chelation between phenolic hydroxyl and amino groups via molecular assembly. Subsequently, the thiol of PFDT coupled with the catechol portion of the PDA via a Michael addition reaction to form PF, resulting in Al / PF suspension 1, where Al / PF consists of aluminum particles coated with PF.

[0072] (2) Al@PF@NiCo2O4 20 ml of 0.32 g NiCo2O4 ethanol suspension was added to Al@PF suspension 1, and NiCo2O4 was anchored on the surface of Al@PF by mechanical stirring for 8 h to obtain suspension 2; then filtered, washed, and vacuum dried at 40℃ (vacuum degree 0.4 × 10⁻⁶). 5 ~0.2×10 5 After 12 hours of treatment, a core-shell structured aluminum-based microwave energetic material was obtained.

[0073] Comparative Example 1 The crosslinking agent KH-550 was added to a 40 ml mixed solution of water and ethanol in a volume ratio of 1:7 and sonicated for 5 min. Then, 0.18 g of aluminum powder was added and the mixture was magnetically stirred at room temperature for 1 h to form a relatively uniform aluminum suspension. At this time, the concentration of KH-550 in the system was 1.6 mg / mL, and Al@KH-550 suspension 1 was obtained.

[0074] 20 ml of 0.32 g CuFe2O4 suspension was added to Al@KH-550 suspension 1. The CuFe2O4 was covalently anchored on the surface of Al@KH-550 by mechanical stirring for 8 h to obtain suspension 2. Suspension 2 was then filtered, washed, and vacuum dried at 50 °C to obtain microwave-sensitive Al@KH-550@CuFe2O4 core-shell high-energy particles, i.e., core-shell structured aluminum-based microwave energetic materials.

[0075] Figure 14 The ignition delay time diagram measured by the photoelectric sensor for microwave ignition of Al@KH-550@CuFe2O4 shows that the ignition delay time is 47.67 ms at 64W. Due to the high concentration of KH-550 interface layer components and the thick coating layer on the surface of aluminum powder, the heat converted from microwave absorption by CuFe2O4 in the microwave field is transferred to the aluminum particles more slowly, resulting in a longer ignition delay time.

[0076] Comparative Example 2 0.18 g of aluminum powder was added to a dopamine hydrochloride solution and magnetically stirred at room temperature for 1 h to form a relatively uniform aluminum suspension. At this time, the concentrations of dopamine hydrochloride and perfluorodecyl mercaptan in the mixed system were 1.6 mg / ml, and Al / PF suspension 1 was obtained.

[0077] 20 ml of 0.32 g CuFe2O4 suspension was added to Al@PF suspension 1, and CuFe2O4 was covalently anchored to the surface of Al@PF by mechanical stirring for 8 h to obtain suspension 2. Suspension 2 was then filtered, washed, and vacuum dried at 50 °C to obtain microwave-sensitive Al@PF@CuFe2O4 core-shell high-energy particles.

[0078] Figure 15The ignition delay time diagram measured by the photoelectric sensor for microwave ignition of Al@PF@CuFe2O4 shows that the ignition delay time is 46.78 ms at 64W. Due to the high concentration of PF interface layer components, the thick coating layer on the aluminum powder surface, and the slow decomposition of PF, the microwave ignition threshold is high, requiring high-power microwave input. Ignition is difficult at a microwave power of 38W.

[0079] Comparative Example 3 The crosslinking agent KH-550 was added to a 40 ml mixed solution of water and ethanol in a volume ratio of 1:7 and sonicated for 5 min. Then, 0.183 g of aluminum powder was added and the mixture was magnetically stirred at room temperature for 1 h to form a relatively uniform aluminum suspension. At this time, the concentration of KH-550 in the system was 1 mg / mL, and Al@KH-550 suspension 1 was obtained.

[0080] 20 ml of 0.317 g CoFe2O4 suspension was added to Al@KH-550 suspension 1, and mechanical stirring was carried out for 8 h to anchor CoFe2O4 on the surface of Al@KH550 to obtain suspension 2; then suspension 2 was filtered, washed, and vacuum dried at 50 °C to obtain microwave-sensitive Al@KH-550@CoFe2O4 core-shell high-energy particles.

[0081] Figure 16 The image shows the microwave ignition diagram of Al@KH-550@CoFe2O4 at a microwave power of 64W. With CoFe2O4 as the shell, the ignition delay time under microwave is relatively long, and the combustion exhibits particle jetting and poor incomplete combustion performance.

[0082] Comparative Example 4 The crosslinking agent KH-550 was added to a 40 ml mixed solution of water and ethanol in a volume ratio of 1:7 and sonicated for 5 min. Then, 0.185 g of aluminum powder was added and the mixture was magnetically stirred at room temperature for 1 h to form a relatively uniform aluminum suspension. At this time, the concentration of KH-550 in the system was 1 mg / mL, and Al@KH-550 suspension 1 was obtained.

[0083] 20 ml of 0.315 g MnFe2O4 suspension was added to Al@KH-550 suspension 1, and the MnFe2O4 was anchored on the surface of Al@KH-550 by mechanical stirring for 8 h to obtain suspension 2; then suspension 2 was filtered, washed, and vacuum dried at 50 °C to obtain microwave-sensitive Al@KH-550@MnFe2O4 core-shell high-energy particles.

[0084] Figure 17The image shows the microwave ignition diagram of Al@KH-550@MnFe2O4 at a microwave power of 64W. With MnFe2O4 as the shell, it absorbs less microwave and has poor combustion performance under microwave field.

[0085] Comparative Example 5 The crosslinking agent KH-550 was added to a 40 ml mixed solution of water and ethanol in a volume ratio of 1:7 and sonicated for 5 min. Then, 0.182 g of aluminum powder was added and the mixture was magnetically stirred at room temperature for 1 h to form a relatively uniform aluminum suspension. At this time, the concentration of KH-550 in the system was 1 mg / mL, and Al@KH-550 suspension 1 was obtained.

[0086] 20 ml of 0.318 g NiFe2O4 suspension was added to Al@KH-550 suspension 1, and NiFe2O4 was anchored on the surface of Al@KH-550 by mechanical stirring for 8 h to obtain suspension 2; then suspension 2 was filtered, washed, and vacuum dried at 50 °C to obtain microwave-sensitive Al@KH-550@NiFe2O4 core-shell high-energy particles.

[0087] Figure 18 The image shows the microwave ignition diagram of Al@KH-550@NiFe2O4 at a microwave power of 64W. With NiFe2O4 as the shell, it absorbs less microwave and has poor combustion performance under microwave field.

[0088] In Examples 1-9 and Comparative Examples 1-5, the microwave absorption and combustion performance of the particles were controlled by adjusting the interface layer (type and concentration) and AB2O4 (type and dosage). The selected interface layer and the spinel-structured ferrite (AB2O4) both effectively addressed the problem of poor microwave ignition performance of aluminum. Furthermore, in Example 1, KH-550 was selected as the interface layer at a concentration of 1 mg / mL, with 0.18 g of Al and 0.32 g of CuFe2O4, resulting in the shortest ignition delay time under a microwave field. Due to the rapid decomposition of KH-550 at low temperatures, Al@KH-550@CuFe2O4 could achieve rapid ignition under a microwave field, exhibiting an even lower ignition delay time.

[0089] This invention employs an interface structure control strategy, introducing specific interface layer components onto the aluminum surface and utilizing chemical bonds or electrostatic adsorption to guide the anchoring of a high-dielectric AB2O4 coating onto the aluminum surface, successfully constructing microwave-sensitive Al@AB2O4 high-energy particles. By controlling the type and thickness of the interface layer and the high dielectric content, the microwave absorption and combustion performance of the material are effectively optimized, thus solving the key problem of low microwave energy coupling efficiency of aluminum particles. Based on a core-shell structure and the synergistic effect of multiple components, this design constructs a core-shell structured aluminum-based microwave energetic material with abundant heterogeneous interfaces and a multi-layered structure. It not only optimizes impedance matching but also significantly improves microwave absorption performance through enhanced interfacial polarization and multiple loss mechanisms. This invention provides a new approach to solving the problem of microwave ignition of common explosives and existing solid propellants within a low delay time.

[0090] The above description is only of the preferred embodiment of the present invention and should not be construed as limiting the scope of the claims. The present invention is not limited to the above embodiments, and variations in its specific structure are permitted. All variations made within the scope of the independent claims of the present invention are also within the scope of protection of the present invention.

[0091] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to limit the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

Claims

1. A method for preparing core-shell structured aluminum-based microwave energetic materials, characterized in that, Includes the following steps: Aluminum powder is added to a solution of silane coupling agent, or to a solution of cyclodextrin, or to a solution of tetrabutyl titanate, or to a solution containing perfluorododecyl mercaptan and dopamine hydrochloride, and then stirred to form suspension A. Suspension B containing bimetallic oxides is added to suspension A and stirred to obtain suspension C; The suspension C was filtered, washed, and dried to obtain a core-shell structured aluminum-based microwave energetic material.

2. The method for preparing the core-shell structured aluminum-based microwave energetic material according to claim 1, characterized in that, The silane coupling agent solution is prepared by adding the silane coupling agent to a mixture of one or more of water, ethanol and Tris buffer solution, followed by sonication; wherein the concentration of the silane coupling agent is 1~1.6 mg / mL.

3. The method for preparing core-shell structured aluminum-based microwave energetic materials according to claim 1 or 2, characterized in that, The silane coupling agent is KH-550.

4. The method for preparing the core-shell structured aluminum-based microwave energetic material according to claim 1, characterized in that, The cyclodextrin solution is prepared by adding cyclodextrin to one or more of the following: water, ethanol and Tris buffer solution, followed by sonication; wherein the concentration of cyclodextrin is 0.5~1.5 mg / mL.

5. The method for preparing the core-shell structured aluminum-based microwave energetic material according to claim 1, characterized in that, The solution of tetrabutyl titanate is prepared by adding tetrabutyl titanate to a mixture of one or more of water, ethanol and Tris buffer solution, followed by sonication; wherein the concentration of tetrabutyl titanate is 1~3 mg / mL.

6. The method for preparing the core-shell structured aluminum-based microwave energetic material according to claim 1, characterized in that, The solution containing perfluorododecanethiol and dopamine hydrochloride is prepared by adding perfluorododecanethiol and dopamine hydrochloride to one or a mixture of water, ethanol and Tris buffer solution, followed by sonication. The concentration of perfluorododecanethiol is 0.5~1.6 mg / mL and the concentration of dopamine hydrochloride is 0.5~1.6 mg / mL.

7. The method for preparing the core-shell structured aluminum-based microwave energetic material according to claim 1, characterized in that, The aluminum powder has a particle size of 0.6-3 µm; the bimetallic oxide is CuFe2O4, NiFe2O4, MnFe2O4, CoFe2O4, CuCo2O4, NiCo2O4 or MnCo2O4.

8. The method for preparing the core-shell structured aluminum-based microwave energetic material according to claim 1, characterized in that, The equivalence ratio of aluminum powder to bimetallic oxide is 0.5~3, and the equivalence ratio Φ is calculated by the following formula: Φ= In the formula, This refers to the amount of aluminum powder. It is a bimetallic oxide. This represents the actual molar ratio of aluminum powder to AB₂O₄. This represents the theoretical molar ratio of aluminum powder to bimetallic oxide.

9. Core-shell structured aluminum-based microwave energetic materials prepared by the method according to any one of claims 1-8.

10. The application of the core-shell structured aluminum-based microwave energetic material prepared by the method according to any one of claims 1-8 in microwave ignition agents, pyrotechnic agents and propellants.

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