A core-shell structure manganese-based nano-thermite and a preparation method thereof

Abstract

The application discloses a kind of core-shell structure manganese-based nano thermite and its preparation method, belong to energetic material technical field.The thermite is with micron aluminum powder as core, polyvinylidene fluoride and nanometer manganese oxide composite as shell layer, form dense spherical microstructure.Its preparation method includes: polyvinylidene fluoride is dissolved in solvent, micron aluminum powder and manganese oxide are added and are dispersed into precursor liquid by ultrasonic, by adjusting voltage, receiving distance and other parameters, using electrostatic spraying technology, core-shell structure microspheres are prepared by one-step method.The application effectively solves the agglomeration problem of nanometer manganese oxide using electrostatic spraying process, realizes the uniform coating of components in micron scale;Polyvinylidene fluoride shell layer serves as buffer and isolation layer, significantly reduces the mechanical sensitivity of material, greatly improves safety;At the same time, the structure effectively inhibits the micro-explosion and splashing phenomenon in the combustion process, realizes the stability, continuity and completeness of reaction.

Description

Technical Field

[0001] This invention belongs to the field of energetic materials preparation and application technology, specifically relating to a core-shell structured manganese oxide / aluminum / polyvinylidene fluoride nanocomposite thermite prepared by electrostatic spraying technology and its preparation method. It can significantly reduce the mechanical sensitivity and enhance the safety performance of thermite while improving the reaction completeness and combustion stability of the thermite. Background Technology

[0002] Thermite is a metastable intermolecular composite energetic material composed of aluminum powder and metal oxides. Due to its high energy density, high heat of reaction, and high adiabatic combustion temperature, it is widely used in military and civilian fields such as micro-thrusters, localized heating, welding, and energetic ignition propellants. Traditional micron-sized thermite is limited by the mass transfer and diffusion distance between reactants, resulting in problems such as high ignition energy, slow reaction rate, and incomplete combustion. With the development of nanotechnology, nano-thermite, due to its huge specific surface area and extremely short mass transfer distance, exhibits a reaction rate several orders of magnitude higher than that of traditional thermite. To further improve the energy release efficiency, enhance combustion performance, and expand its applications, scholars at home and abroad have conducted extensive research in areas such as novel formulation development, microstructure design, and interface modification.

[0003] In the development of novel formulations and oxides, the patent "A Preparation Method of Aluminothermic Agent" (CN120483840A) discloses a method for preparing aluminothermic agent using CuN(CN)2 as an oxidant, providing a new oxide selection approach for aluminothermic energetic materials. This system can provide 1528.9 J / g of heat and 50 kPa of gas production pressure, and the product contains high-temperature resistant aluminum nitride. The patent "A High-Entropy Oxide Powder Based on Self-Propagating Reaction and Its Preparation Method and Application" (CN119977001A) demonstrates the application of aluminothermic agents in the preparation of high-entropy oxide powders. It shows the preparation of materials with excellent electrical conductivity and thermal stability through a high-temperature self-propagating reaction, reflecting the broad prospects of aluminothermic reactions in the field of materials synthesis. In terms of microstructure regulation and confined assembly, to increase reaction sites and suppress particle aggregation, the patent "A High-Exothermic Three-Dimensional Porous Nano-Thermite and Its Confined Assembly Preparation Method" (CN120483838A) utilizes a biological template to construct a hierarchical structure of mesoporous CuO, which is then confined and assembled with nano-aluminum powder to form an aluminite with a unique ridge-like, plate-like, and porous tetrahedral structure, effectively enhancing exothermic and combustion performance. Furthermore, the patent "A Nanocomposite Thermite Composed of Gallium-Aluminum Alloy and Three-Dimensional Porous Oxides and Its Preparation Method and Application" (CN119100902A) introduces liquid gallium to suppress the formation of an oxide layer on the aluminum surface and combines this with the confining effect of three-dimensional porous oxides to develop a high-performance aluminum-gallium-based nanocomposite aluminite, shortening the mass transfer diffusion length. Regarding interface modification and coating technologies, core-shell structures and surface coatings have proven to be effective means of regulating reaction characteristics. The patent "An aluminothermic system for ultra-low condensed-phase combustion products and its preparation method" (CN120554189A) designs a system combining BiF3@TACN core-shell structured particles and acid-activated nano-aluminum powder. Utilizing the high-reactivity interface of nanoscale bismuth-based fluorides and the activation strategy of high-energy gas-producing compounds, it achieves the output of ultra-low condensed-phase combustion products. The patent "A composite aluminothermic agent for demolition and its preparation method" (CN120247633A) proposes a composite aluminothermic agent for demolition, in which the surface of the fuel metal particles is modified by a fluoropolymer coating, supplemented with flux and a strong oxidant, effectively improving the agent's environmental adaptability and demolition performance. Bio-templating methods and liquid metal modification processes are relatively cumbersome and costly, making large-scale industrial production difficult. For magnetic metal oxides, simple physical mixing or conventional assembly methods are insufficient to completely break their magnetic agglomeration, leading to uneven contact between the oxidant and reducing agent and incomplete reaction. Although fluoropolymer coating can improve environmental adaptability, how to construct uniform, dense fluoropolymer-based aluminothermic microspheres with core-shell structure at the micrometer scale through a simple and efficient one-step process, while significantly reducing mechanical sensitivity and achieving high and stable energy release through the fluorination-oxidation synergistic mechanism, remains an urgent problem to be solved.

[0004] Based on this, the present invention utilizes electrostatic spraying technology to prepare core-shell structured microspheres, which are a thermite sample that can effectively solve the agglomeration of nanoparticles, significantly reduce mechanical sensitivity, and achieve stable combustion. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention provides a core-shell structured manganese-based nano-aluminothermic agent and its preparation method.

[0006] This invention utilizes electrostatic spraying technology to construct a microsphere structure with micron-sized aluminum powder as the core and a composite of polyvinylidene fluoride (PVDF) and nano-manganese oxide as the shell. This structure effectively isolates the oxidant and reductant from direct contact, significantly reducing mechanical sensitivity. Simultaneously, the fluorine-containing species released during the decomposition of PVDF during the reaction promote the removal of the oxide layer on the aluminum powder surface and undergo a synergistic reaction with manganese oxides, thereby achieving efficient and stable combustion of the thermite.

[0007] To achieve the above objectives, the present invention provides the following technical solution: On one hand, the present invention provides a method for preparing a core-shell structured manganese-based nano-aluminothermic agent, providing the following technical solution: Step 1: Dissolve polyvinylidene fluoride in the organic solvent N,N-dimethylformamide and stir magnetically until completely dissolved to form a homogeneous binder solution; Step 2: Add micron-sized aluminum powder and nano-sized manganese oxide powder to the above binder solution, and perform magnetic stirring and ultrasonic dispersion treatment to prepare a uniformly dispersed electrostatic spray precursor suspension. Step 3: Place the precursor suspension in the syringe of the electrostatic spraying device, adjust the spinning voltage, receiving distance and propulsion speed, and deposit core-shell structured nano-aluminothermic microspheres on the receiving device. Step 4: Place the collected microspheres in a vacuum drying oven to dry them and remove residual solvents to obtain the final core-shell structured manganese-based nano-aluminothermic agent.

[0008] As a preferred embodiment, the organic solvent is N,N-dimethylformamide.

[0009] As a preferred embodiment, the nano-manganese oxide is manganese dioxide, manganese trioxide, or manganese tetroxide.

[0010] As a preferred embodiment, the average particle size of the micron-sized aluminum powder is 20 μm, and the average particle size of the nano-manganese oxide is 50 nm.

[0011] As a preferred embodiment, the mass ratio of each component in the precursor suspension satisfies a stoichiometric ratio φ = 1.0~1.4, preferably φ = 1.2.

[0012] As a preferred option, the dispersion process in step 2 varies depending on the valence state of the manganese oxide: when the manganese oxide is manganese dioxide, magnetic stirring for 1 hour is combined with ultrasonic treatment for 1 hour; when the manganese oxide is manganese trioxide, due to its ferrimagnetism and tendency to agglomerate, magnetic stirring for 1 hour is combined with intermittent ultrasonic treatment for 1.5 hours; when the manganese oxide is manganese tetroxide, it is pre-dispersed in a solvent containing surfactant before being mixed with aluminum powder and ultrasonicated.

[0013] As a preferred embodiment, in step 3, the spinning voltage of the electrostatic spraying device is 15~19kV, preferably 17kV; the receiving distance is 13~17cm, preferably 17cm; and the propulsion rate is 0.6~1.0mL / h, preferably 0.8mL / h.

[0014] As a preferred embodiment, in step 3, the receiving device is a rotating drum with aluminum foil covering its surface, and the preparation environment temperature is controlled at 20~25℃ and the relative humidity is less than 50%.

[0015] On the other hand, the core-shell structured manganese-based nano-aluminothermic agent prepared by the above method is characterized in that: the aluminothermic agent microspheres have a distinct core-shell structure, with micron-sized aluminum powder at the center, and a composite layer formed by polyvinylidene fluoride and nano-manganese oxide uniformly coating the surface of the aluminum powder, with a uniform and dense coating layer thickness.

[0016] Compared with the prior art, the technical method and product provided by the present invention have the following beneficial effects: (1) Significantly improved safety: The core-shell structure constructed by electrostatic spraying utilizes polyvinylidene fluoride as an inert physical barrier to isolate the highly active nano-manganese oxide from the aluminum powder, effectively preventing direct contact between the two at room temperature. Tests show that, compared with physically mixed samples, the 50% probability critical impact energy of the manganese tetroxide system is increased to 13708.81 mJ, and the critical friction load is increased to 104.18 N, greatly reducing mechanical sensitivity and solving the safety problem of accidental ignition of nano-aluminothermic agents.

[0017] (2) Improved combustion stability: Physically mixed thermite often results in violent micro-explosions and splashing during combustion due to uneven component distribution. The core-shell structure of this invention ensures the uniform distribution of oxidant and reductant at the micrometer scale, making the reaction more synchronous and controlled. Experiments show that the prepared thermite microspheres have a clear and continuous flame outline with no splashing. In particular, the manganese tetroxide system achieves a mild and continuous combustion of up to 700 ms, which is suitable for applications requiring stable energy release processes.

[0018] (3) Improved reaction completeness: Polyvinylidene fluoride not only acts as a binder, but the HF gas generated by its decomposition can also etch the alumina passivation layer on the surface of aluminum powder in situ, promoting the release of internal active aluminum. Combustion product analysis shows that the reaction products of the sample prepared in this invention are mainly manganese fluoride and manganese trioxide, with no obvious unreacted aluminum residue, proving that the fluorination-oxidation synergistic reaction mechanism effectively improves energy utilization efficiency.

[0019] (4) The process parameters are controllable and have strong universality: The preparation process provided by the present invention is simple. The morphology of microspheres can be controlled by adjusting parameters such as voltage and distance. It is applicable to different manganese oxide systems and can be customized with different energy release characteristics according to needs. Attached Figure Description

[0020] To more clearly illustrate the technical solutions in this invention or the prior art, the accompanying drawings used in the description of the embodiments will be briefly introduced below.

[0021] Figure 1 This is a process flow diagram of the preparation of core-shell structured manganese-based nano-aluminothermic agent precursor liquid by electrostatic spraying in an embodiment of the present invention; Figure 2 The following are DSC curves of Embodiment 1 and Comparative Example 1 of the present invention; Figure 3 These are the DSC curves of Embodiment 2 and Comparative Example 2 of the present invention; Figure 4 These are the DSC curves of Embodiment 3 and Comparative Example 3 of the present invention; Figure 5 This is a comparison diagram of the combustion flame morphology of Embodiment 1 and Comparative Example 1 over time. Figure 6 This is a comparison diagram of the combustion flame morphology of Embodiment 2 and Comparative Example 2 of the present invention over time; Figure 7 This is a comparison diagram of the combustion flame morphology of Embodiment 3 and Comparative Example 3 over time. Detailed Implementation

[0022] The embodiments of the present invention are described in detail below. The embodiments described below are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0023] In this document, 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 application pertains.

[0024] In this document, when values ​​are described as ranges, it should be understood that such disclosure includes disclosure of all possible subranges within that range, as well as the specific numerical values ​​falling within that range, regardless of whether the specific numerical value or specific subrange is explicitly specified.

[0025] In this article, the terms "multiple" or "more than" are used unless otherwise specified, referring to a quantity greater than or equal to 2. For example, "one or more" means one or more types.

[0026] In this document, the terms "preferred" and "more preferred" are used only to describe implementation methods or embodiments with better effects, and should be understood as not constituting a limitation on the scope of protection of this invention.

[0027] In this document, terms such as "further" are used for descriptive purposes to indicate differences in content, but should not be construed as limiting the scope of protection of this invention.

[0028] In this article, the term "and / or" describes an association between objects, indicating that three relationships can exist. For example, A and / or B means: A or B, or A and B.

[0029] In this document, the term "about" means + / - 10% of a specified value, preferably + / - 5%, and more preferably + / - 1%.

[0030] In this article, the terms “include,” “including,” “have,” “contain,” etc., are all open-ended terms, meaning that they include but are not limited to.

[0031] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar to or equivalent to those described herein may be used in the implementation or testing of this invention.

[0032] The present invention will be described in detail below with reference to the embodiments.

[0033] like Figure 1 As shown, the present invention provides a process flow for electrostatic spraying of thermite precursor liquid and physical mixing of manganese-based thermite.

[0034] Example 1: This embodiment provides a core-shell structured thermite (denoted as ES-12) using manganese dioxide as an oxidant. The specific preparation steps are as follows: (1) Ingredients: According to the chemical equivalence ratio φ=1.2, weigh out 332mg of micron aluminum powder, 668mg of nano manganese dioxide, and 200mg of polyvinylidene fluoride.

[0035] (2) Solution preparation: Add polyvinylidene fluoride to 10 mL of N,N-dimethylformamide and stir on a magnetic stirrer for 2 hours until completely dissolved.

[0036] (3) Precursor dispersion: Aluminum powder and manganese dioxide powder are added to polyvinylidene fluoride solution, magnetically stirred for 1 hour, and then ultrasonically treated in an ultrasonic disperser for 1 hour to obtain a uniformly dispersed black precursor suspension.

[0037] (4) Electrostatic spraying: The precursor solution is drawn into a 20mL syringe and installed in the electrostatic spraying device. The metal needle is connected to the positive terminal of the high-voltage power supply, and the aluminum foil receiving plate is grounded. The process parameters are adjusted as follows: spinning voltage 17kV, distance between needle and receiving plate 17cm, and micro-pump propulsion speed 0.8mL / h. Under the action of the electric field, the droplets are atomized and solidified during flight, depositing on the receiving plate.

[0038] (5) Post-processing: Collect the sediment and dry it in a vacuum drying oven at 50°C for 24 hours to obtain ES-12 nano aluminothermic microspheres.

[0039] Example 2: This embodiment provides a core-shell thermite (denoted as ES-23) using manganese trioxide as an oxidant. The difference from Example 1 is that the raw material ratio is adjusted to: 291 mg of micron-sized aluminum powder, 709 mg of nano-manganese trioxide, and 200 mg of polyvinylidene fluoride, maintaining φ=1.2. To address the weak magnetic agglomeration problem of manganese trioxide, the dispersion process in step (3) is adjusted as follows: after magnetic stirring for 1 hour, intermittent ultrasonic treatment with a 2-second working time followed by a 1-second pause is used for 1.5 hours to ensure sufficient dispersion of the magnetic particles. The remaining electrostatic spraying parameters are the same as in Example 1.

[0040] Example 3: This embodiment provides a core-shell thermite (denoted as ES-34) using manganese tetroxide as the oxidant. The difference from Example 1 is that the raw material ratio is adjusted to: 239 mg of micron-sized aluminum powder, 761 mg of nano-manganese tetroxide, and 200 mg of polyvinylidene fluoride. To address the strong magnetism and agglomeration tendency of manganese tetroxide, in step (3), the manganese tetroxide powder is first dispersed in a small amount of N,N-dimethylformamide containing 1 wt% surfactant and pre-ultrasonicated for 30 minutes before being mixed with the polyvinylidene fluoride solution and aluminum powder. The remaining parameters are the same as in Example 1.

[0041] Comparative Examples 1-3: To illustrate the effects of the present invention, Comparative Examples 1 (PM-12), 2 (PM-23), and 3 (PM-34) were set up. Comparative Examples 1-3 used the same mass ratio of raw materials as Examples 1-3 above, but the preparation method employed a traditional physical mixing method: the raw materials were added to cyclohexane, magnetically stirred for 30 minutes, and sonicated for 30 minutes. After drying the mixture, it was ground and sieved to obtain a powder sample. The physical mixing method cannot form a core-shell structure; microscopically, the components exhibit a disordered stacking state.

[0042] Test Case: Performance Testing and Analysis The thermal properties, combustion properties, and mechanical sensitivity of the samples prepared in the above embodiments and comparative examples were tested.

[0043] (1) Thermal performance test like Figure 2 The figures shown are DSC curves for Example 1 and Comparative Example 1. Figure 3 The following are the DSC curves for Example 2 and Comparative Example 2. Figure 4 The following are DSC curves for Example 3 and Comparative Example 3.

[0044] Example 1: The DSC curve of sample ES-12 initially shows a distinct endothermic peak near 168.66℃, corresponding to the melting of the outer polyvinylidene fluoride (PVDF) binder, confirming the existence of the core-shell structure. Its main exothermic peak temperature is delayed to 518.33℃, and the peak shape is sharper and taller. The calculated activation energy Ea is increased to 244.44 kJ / mol. This indicates that the dense PVDF-manganese dioxide composite shell acts as a physical barrier at low temperatures, hindering premature diffusion between components and increasing the reaction initiation temperature; once the shell constraint is broken, the reaction rapidly and concentratedly erupts inside the microspheres, releasing even stronger energy.

[0045] Comparative Example 1: The DSC curve of sample PM-12 shows that the main exothermic peak appears at 492.92℃, with a relatively broad peak shape. This is because the contact between aluminum powder and manganese dioxide particles in the physically mixed sample is uneven, and the reaction is mainly limited by random contact points between particles. The calculated activation energy Ea is 211.35 kJ / mol.

[0046] Example 2: Sample ES-23 also exhibited the obvious endothermic melting characteristics of polyvinylidene fluoride. Its main exothermic peak temperature slightly increased to 514.26℃, but the activation energy Ea increased to 258.78 kJ / mol, which is relatively high among the three electrostatic spray samples. This high activation energy, combined with the extremely short ignition delay time shown in its combustion test, indicates that although this structure requires high energy to initiate, once initiated, the reaction kinetics are extremely fast, demonstrating the characteristics of an ideal metastable energetic material.

[0047] Comparative Example 2: Since manganese trioxide has a moderate oxidizing capacity, the peak temperature of the exothermic reaction of PM-23 is about 509.41℃, and the calculated activation energy Ea is 239.26kJ / mol.

[0048] Example 3: Sample ES-34 exhibited the highest thermal stability. Its main exothermic peak shifted further to 529.55℃, and the exothermic peak showed multiple shoulder peaks, indicating a more complex reaction process. The calculated activation energy Ea was as high as 288.76 kJ / mol, the highest among all tested samples. This extremely high activation energy is attributed to the synergistic effect of the polyvinylidene fluoride coating and the low-activity manganese tetroxide, which significantly increased the energy barrier for the aluminothermic reaction. While this characteristic limited its instantaneous burst power, it endowed the material with excellent thermal safety and resistance to accidental ignition.

[0049] Comparative Example 3: Because manganese tetroxide has a spinel structure and Mn 2+ / Mn 3+ Due to the mixed valence state, oxygen ion migration is subject to greater resistance, resulting in low reactivity of the PM-34 sample itself. Its main exothermic peak temperature is 502.42℃, and its activation energy Ea is 245.02 kJ / mol.

[0050] (2) Combustion performance test The combustion process is recorded using a laser ignition device and a high-speed camera, such as... Figure 5 The figure shown is a comparison diagram of the combustion flame morphology of Embodiment 1 and Comparative Example 1 over time; as shown Figure 6 The figure shown is a comparison of the combustion flame morphology of Embodiment 2 and Comparative Example 2 over time; as shown Figure 7 The figure shown is a comparison of the combustion flame morphology of Embodiment 3 and Comparative Example 3 over time.

[0051] Table 1 shows the peak temperature and activation energy Ea of Example 1 and Comparative Example 1 at four heating rates under argon conditions; Table 2 shows the peak temperature and activation energy Ea of Example 2 and Comparative Example 2 at four heating rates under argon conditions; Table 3 shows the peak temperature and activation energy Ea of Example 3 and Comparative Example 3 at four heating rates under argon conditions.

[0052] Table 1. Peak temperature and activation energy Ea of Example 1 and Comparative Example 1 at four heating rates under argon conditions. Table 2. Peak temperatures and activation energies Ea of Example 2 and Comparative Example 2 at four heating rates under argon conditions. Table 3. Peak temperatures and activation energies Ea of Examples 3 and Comparative Example 3 at four heating rates under argon conditions. Example 1: Sample ES-12 exhibited stable and controllable combustion characteristics. The ignition delay time was shortened to 56 ms. After ignition, the flame outline was clear, and the combustion process was smooth and continuous, with no obvious splashing observed. Its maximum flame height was 9.85 cm, which, although lower than the comparative sample, maintained continuous combustion for a relatively long time. This indicates that the polyvinylidene fluoride shell effectively suppressed the instantaneous violent reaction, transforming the explosive energy release into stable and continuous combustion.

[0053] Comparative Example 1: Sample PM-12 exhibited extremely violent unsteady-state combustion characteristics. The ignition delay time was 66 ms. After ignition, the sample immediately initiated explosive jet combustion, reaching a maximum flame height of 16.94 cm in just 140 ms. The combustion process was accompanied by intense flashes, dense micro-explosions, and a large number of molten droplets and combustion products splashing, indicating that uneven contact of components in the physically mixed sample led to excessively rapid local reactions and uncontrollable energy release.

[0054] Example 2: Sample ES-23 exhibited optimal ignition characteristics. Its ignition delay time was only 49 ms, significantly reduced by 49.0% compared to Comparative Example 2. During combustion, the flame propagation was stable, with the maximum flame height maintained at a moderate level of 6.07 cm. This demonstrates that the uniform coating structure formed by the electrostatic spraying process of this invention effectively overcomes the agglomeration problem of manganese trioxide, creating microscopic conditions that facilitate reaction initiation and achieving a balance between rapid ignition and stable combustion.

[0055] Comparative Example 2: Due to the magnetic agglomeration of manganese trioxide, the mixing uniformity was the worst, resulting in the longest ignition delay time for sample PM-23, reaching 73 ms. After combustion started, micro-explosions and unstable flame patterns were also observed, with a maximum flame height of 11.15 cm, indicating problems of localized energy concentration and dissipation.

[0056] Example 3: Sample ES-34 exhibited extremely high combustion stability. Its ignition delay time was 51 ms, similar to the comparative sample. After ignition, the flame was extremely stable without any violent fluctuations, and the maximum flame height decreased to 5.58 cm. Notably, this sample achieved sustained combustion for up to 700 ms, demonstrating a mild and persistent energy release pattern. This indicates that the synergistic effect of the polyvinylidene fluoride coating and the low-activity manganese tetroxide significantly suppressed unstable combustion, making it suitable for applications requiring high energy release stability.

[0057] Comparative Example 3: Due to the low oxygen content and low reactivity of manganese tetroxide, the combustion intensity of sample PM-34 was weaker than that of the other two comparative samples. Its ignition delay time was 53 ms, and its maximum flame height was 9.59 cm.

[0058] (3) Mechanical sensitivity test Impact sensitivity and friction sensitivity were tested according to national standard methods. The test results are shown in Table 4 below: Table 4. Mechanical sensitivity test results for each group of samples at 50% response probability. As shown in Table 1, all the samples prepared using the electrostatic spraying method of this invention exhibit significantly higher critical impact energies and frictional loads than their corresponding physical mixing counterparts. Among them, Example 3 (ES-34) demonstrates the highest safety, with a critical impact energy of 13708.81 mJ, more than 2.3 times that of the PM-12 sample. This is because the polyvinylidene fluoride shell effectively buffers the mechanical impact force and isolates the oxidant from the hard contact between the oxidant and the reducing agent, thereby significantly improving the inherent safety of the material. In summary, the manganese-based core-shell structured nano-aluminothermic agent prepared by electrostatic spraying technology in this invention not only solves the problems of agglomeration and incomplete reaction existing in traditional physical mixing methods, but more importantly, it achieves stable combustion process and significantly improved safety performance while ensuring energy release, thus possessing significant application value.

[0059] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A core-shell structured manganese-based nano-aluminothermic agent, characterized in that: It includes a composite of micron-sized aluminum powder as the core layer and manganese oxide and polyvinylidene fluoride as the shell layer; the thermite exhibits a spherical microstructure with micron-sized aluminum powder as the core and manganese oxide nanoparticles coated with polyvinylidene fluoride binder to form a dense outer shell.

2. The core-shell structured manganese-based nano-aluminothermic agent according to claim 1, characterized in that: The manganese oxide is selected from one or a mixture of several of manganese dioxide, manganese trioxide, or manganese tetroxide.

3. The core-shell structured manganese-based nano-aluminothermic agent according to claim 2, characterized in that: The mass ratio of the micron-sized aluminum powder, manganese oxide, and polyvinylidene fluoride is designed based on a stoichiometric ratio φ=1.2, wherein the mass of polyvinylidene fluoride in the composite is fixed, and the specific ratio range includes: (1) When the manganese oxide is manganese dioxide, the mass ratio of aluminum powder, manganese dioxide and polyvinylidene fluoride is 1:2.0:0.6; (2) When the manganese oxide is manganese trioxide, the mass ratio of aluminum powder: manganese trioxide: polyvinylidene fluoride is 1:2.4:0.7; (3) When the manganese oxide is manganese tetroxide, the mass ratio of aluminum powder: manganese tetroxide: polyvinylidene fluoride is 1:3.2:0.

8.

4. The core-shell structured manganese-based nano-aluminothermic agent according to claim 1, characterized in that: The average particle size of the micron-sized aluminum powder is 20 μm, and the average particle size of the manganese oxide is 50 nm.

5. The method for preparing the core-shell structured manganese-based nano-aluminothermic agent according to any one of claims 1-4, characterized in that, Includes the following steps: (1) Dissolve polyvinylidene fluoride in a solvent and stir until completely dissolved to form a homogeneous solution; (2) Micron-sized aluminum powder and manganese oxide were added to the above homogeneous solution and then prepared into a uniformly dispersed electrostatic spray precursor suspension by magnetic stirring and ultrasonic dispersion treatment. (3) The electrostatic spray precursor suspension is placed in an electrostatic spray device. Under the action of a high voltage electric field, it is sprayed out through the nozzle to form a jet. After the solvent evaporates, it is deposited on the receiving device to obtain core-shell structured nano-aluminothermic microspheres.

6. The preparation method according to claim 5, characterized in that: The solvent mentioned in step (1) is N,N-dimethylformamide.

7. The preparation method according to claim 5, characterized in that: In step (2), the manganese oxide is manganese trioxide or manganese tetroxide, which is pre-dispersed by intermittent ultrasound or by adding a surfactant.

8. The preparation method according to claim 5, characterized in that: The process parameters for electrostatic spraying in step (3) are: spinning voltage of 15~19kV, receiving distance of 13~17cm, and feeding speed of 0.6~1.0mL / h.

9. The preparation method according to claim 5, characterized in that: The optimal process parameters for the electrostatic spraying are: spinning voltage 17kV, receiving distance 17cm, and feed rate 0.8mL / h.

10. The preparation method according to claim 5, characterized in that: The operating environment temperature for steps (1)-(3) is 25℃, and the relative humidity is controlled below 50%RH.

Images