Fluoride-modified liquid metal medium aluminized agent and preparation method thereof

Abstract

This invention discloses a fluoride-modified liquid metal thermite and its preparation method, belonging to the field of thermite preparation technology. It utilizes Galinstan eutectic to prepare liquid metal; aluminum powder and liquid metal are synthesized using physical mixing and ultrasonic treatment to obtain liquid metal-modified aluminum; FeCl3·6H2O is added to a perfluorooctanoic acid aqueous solution and stirred, followed by a hydrothermal reaction; the resulting product is washed to obtain Fe(PFO)3; the liquid metal-modified aluminum is mixed with iron perfluorooctanoate and ultrasonically treated to obtain Fe(PFO)3@LM-Al; Fe(PFO)3@LM-Al and iron oxide are added to anhydrous ethanol and ultrasonically stirred to obtain Fe(PFO)3@LM-Al@Fe2O3. This invention, using the above method, raises the high-temperature thermal oxidation reaction temperature of aluminum powder to before the melting point of 660℃, achieving a breakthrough in the thermal mass transfer process of aluminum powder.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of aluminum thermal agent preparation, in particular to a fluoride-modified liquid metal medium aluminum thermal agent and a preparation method thereof. BACKGROUND

[0002] Aluminum powder is easy to oxidize at room temperature, and the generated Al2O3 on the surface will hinder the heat and mass transfer of the aluminum powder, and affect the contact between the internal aluminum core and the external oxygen environment, so the aluminum powder needs to be modified. In the existing research, nano metal oxides are generally added to the micro-nano aluminum powder system to prepare composite aluminum thermal agents by physical mixing method, so as to improve the thermal performance and ignition and combustion performance of the aluminum powder. Although this method can improve the thermal performance of the aluminum powder, the aluminum thermal agent obtained by the method has limited promotion effect on the heat release of the aluminum powder, and the nano metal oxides and the aluminum cannot be in close contact under the microscope, and the energy density of the system has a large space for improvement.

[0003] It has been proved that fluorine-containing polymers can effectively promote the energy release of aluminum powder, but the fluorine-containing polymers have a long chain random coil structure under the microscope, which easily causes the adhesion of aluminum powder particles, and thus the aluminum particles cannot be fully combusted and energy-released.

[0004] The selection of fluorine-containing small molecules for coating modification of aluminum powder can avoid the problems caused by the coating of fluorine-containing polymers on the aluminum powder, but the existing research shows that the thermal stability of the small molecules is poor, and the fluorine content is not high, which affects the stability of the aluminum powder and has limited catalytic effect. SUMMARY

[0005] The application aims to provide a fluoride-modified liquid metal medium aluminum thermal agent and a preparation method thereof to solve the above problems.

[0006] To achieve the above-mentioned purpose, the application provides a fluoride-modified liquid metal medium aluminum thermal agent and a preparation method thereof. The high-activity aluminum thermal agent is composed of fluorides, iron oxides and aluminum powder. The preparation method specifically comprises the following steps:

[0007] Step one, preparation of liquid metal: Galinstan eutectic with Ga: In: Sn = 68: 22: 10 is used to prepare liquid metal, and the melting point is-19 DEG C. The prepared liquid metal is convenient for participating in mechanical stirring at room temperature;

[0008] Step two, preparation of aluminum powder / liquid metal composite energetic particles: physical mixing and ultrasonic treatment are used to synthesize aluminum powder and liquid metal to obtain liquid metal modified aluminum;

[0009] Step three, preparation of iron perfluorooctanoate: FeCl3·6H2O is added to the aqueous solution of perfluorooctanoic acid, stirred and mixed, and then subjected to hydrothermal reaction. The obtained product is washed to obtain Fe(PFO)3.

[0010] Step 4, Preparation of Fe(PFO)3@LM-Al perfluorooctanoate-liquid metal modified aluminum composite particles: Liquid metal modified aluminum and perfluorooctanoate are mixed and the aluminothermic agent is prepared by ultrasonic treatment;

[0011] Step 5, Preparation of Fe(PFO)3@LM-Al@Fe2O3 energetic compound: Fe(PFO)3@LM-Al and iron oxide were added to anhydrous ethanol at a mass ratio of 4:3 and ultrasonically stirred to obtain Fe(PFO)3@LM-Al@Fe2O3.

[0012] Preferably, in the above-mentioned fluoride-modified liquid metal medium aluminothermic agent and its preparation method, the specific process of step two is as follows: aluminum powder and liquid metal are mixed for 8 hours using ultrasonic stirring with a power of 200W and a frequency of 40kHz, and then vacuum filtered to obtain liquid metal-modified aluminum.

[0013] Preferably, in the above-mentioned fluoride-modified liquid metal medium aluminothermic agent and its preparation method, the proportion of liquid metal is adjusted to 10% when the aluminum powder and liquid metal are mixed.

[0014] Preferably, in the above-mentioned fluoride-modified liquid metal medium aluminothermic agent and its preparation method, the obtained liquid metal-modified aluminum is dried in an oven at 50°C for 12 hours.

[0015] Preferably, in the above-mentioned fluoride-modified liquid metal medium aluminothermic agent and its preparation method, the specific preparation process in step three is as follows: add 10 mL of 0.1 mmol·mL⁻¹ to a beaker. -1 Weigh 4 mmol of FeCl3·6H2O and add it to the aqueous solution of perfluorooctanoic acid; stir the mixture thoroughly at 50°C for 1 h and then transfer it to a hydrothermal reactor and react it in an oven at 100°C for 12 h to obtain the product.

[0016] Preferably, in the above-mentioned fluoride-modified liquid metal medium aluminothermic agent and its preparation method, the obtained product is finally washed and dried in an oven at 60°C for 24 hours to obtain perfluorooctanoic acid ferric.

[0017] Preferably, in the above-mentioned fluoride-modified liquid metal medium aluminothermic agent and its preparation method, the specific preparation process in step four is as follows: using ultrasonic stirring with a power of 200W and a frequency of 40kHz, liquid metal modified aluminum and Fe(PFO)3 are ultrasonically stirred in 20ml of anhydrous ethanol until the solvent is completely evaporated; the resulting mixture is vacuum filtered and dried in an oven at 50℃ for 12 hours to obtain Fe(PFO)3@LM-Al.

[0018] Preferably, in the above-mentioned fluoride-modified liquid metal medium aluminothermic agent and its preparation method, the ultrasonic stirring conditions in step five are as follows: the mixture is stirred under ultrasonic stirring with a power of 200W and a frequency of 40kHz, and the obtained mixture is dried in an oven at 50°C for 12 hours to obtain Fe(PFO)3@LM-Al@Fe2O3.

[0019] Therefore, this invention provides a fluoride-modified liquid metal thermite with the above-mentioned structure and its preparation method. The liquid metal initially embrittles the aluminum shell, weakening its hard outer shell. The gaseous small molecules produced by the decomposition of the fluoride react with the aluminum powder in a pre-ignition reaction, breaking the embrittled aluminum shell. Simultaneously, this process releases heat, further promoting the cracking of the embrittled aluminum shell. After the above steps, cracks appear in the aluminum shell, allowing the internal aluminum cores to initially contact the external oxidizing environment through these cracks, resulting in an thermite reaction. The heat released by the thermite reaction back-absorbs the aluminum particles, creating a positive cycle that further promotes the cracking of the aluminum shell. More aluminum cores melt and come into contact with the external oxygen environment, thereby improving its thermal performance and ignition / combustion performance. This invention innovatively introduces liquid metal to etch the surface of aluminum powder and prepares high-purity fluoride Fe(PFO)3, which forms composite particles with LM-Al core-shell. Further, iron oxide particles are coated on its surface to form a composite energetic compound. By utilizing the exothermic reaction of fluoride with aluminum powder pre-ignition, the high-temperature thermal oxidation reaction temperature of aluminum powder is increased to the melting point of 660°C, achieving a breakthrough in the heat transfer process of aluminum powder.

[0020] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0021] Figure 1 The FTIR spectrum (a), XRD pattern (b), SEM image (c), and TG-DTG curve (d) of Fe(PFO)3 and PFOA perfluorooctanoic acid prepared according to an embodiment of the present invention of a fluoride-modified liquid metal medium aluminothermic agent and its preparation method are shown.

[0022] Figure 2 (a) SEM and (b) EDS images of Fe(PFO)3@LM-Al composite particles from an embodiment of the fluoride-modified liquid metal medium aluminothermic agent and its preparation method of the present invention.

[0023] Figure 3 (a) FTIR spectrum and (b) XRD pattern of Fe(PFO)3@LM-Al composite particles in an embodiment of the fluoride-modified liquid metal medium aluminothermic agent and its preparation method of the present invention.

[0024] Figure 4This is a TG-DSC curve of Fe(PFO)3@LM-Al composite particles under N2 atmosphere in an embodiment of the present invention, which describes a fluoride-modified liquid metal medium aluminothermic agent and its preparation method.

[0025] Figure 5 The images show SEM and EDS images of Fe(PFO)3@LM-Al@Fe2O3 composite particles from an embodiment of the fluoride-modified liquid metal medium aluminothermic agent and its preparation method of the present invention.

[0026] Figure 6 The images show (a) XRD and (b) XPS images of Fe(PFO)3@LM-Al@Fe2O3 composite particles from an embodiment of the present invention of a fluoride-modified liquid metal medium aluminothermic agent and its preparation method.

[0027] Figure 7 The TG-DSC curve of Fe(PFO)3@LM-Al@Fe2O3 is shown in the embodiment of the fluoride-modified liquid metal medium aluminothermic agent and its preparation method of the present invention. Detailed Implementation

[0028] To better understand the above technical solutions, a detailed description of the solutions will be provided below in conjunction with the accompanying drawings and specific embodiments. Obviously, the described embodiments are merely some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0029] The terminology used in the embodiments of this invention is for the purpose of describing particular embodiments only and is not intended to limit the invention. The singular forms “a,” “the,” and “the” as used in the embodiments of this invention and the appended claims are also intended to include the plural forms, and “multiple” generally includes at least two unless the context clearly indicates otherwise.

[0030] It should also be noted that the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that an article or device that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such an article or device. Without further limitation, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the article or device that includes said element.

[0031] This application provides a fluoride-modified liquid metal medium thermite and its preparation method. The highly active thermite is synthesized by combining fluoride, iron oxide, and aluminum powder. The preparation method specifically includes the following steps:

[0032] Step 1, Preparation of liquid metal: Using a Galinstan eutectic of Ga:In:Sn = 68:22:10 with a melting point of -19℃, liquid metal is prepared. The prepared liquid metal is easy to participate in mechanical stirring at room temperature.

[0033] Step 2, Preparation of aluminum powder / liquid metal composite energetic particles: Aluminum powder and liquid metal are synthesized by physical mixing and ultrasonic treatment to obtain liquid metal modified aluminum; aluminum powder and liquid metal are mixed for 8 hours using ultrasonic stirring with a power of 200W and a frequency of 40kHz, and then vacuum filtered to obtain liquid metal modified aluminum; the proportion of liquid metal is adjusted to 10% when mixing aluminum powder and liquid metal; the obtained liquid metal modified aluminum is dried in an oven at 50℃ for 12 hours.

[0034] Step 3, Preparation of Ferric Perfluorooctanoate: FeCl3·6H2O was added to an aqueous solution of perfluorooctanoic acid and stirred. A hydrothermal reaction was then carried out. The resulting product was washed to obtain Fe(PFO)3. 10 mL of 0.1 mmol·mL⁻¹ of ferric perfluorooctanoate was added to a beaker. -1 4 mmol of FeCl3·6H2O was weighed and added to the aqueous solution of perfluorooctanoic acid. The mixture was stirred thoroughly at 50°C for 1 h and then transferred to a hydrothermal reactor. The mixture was reacted in an oven at 100°C for 12 h to obtain the product. Finally, the product was washed and dried in an oven at 60°C for 24 h to obtain iron perfluorooctanoate.

[0035] Step 4, Preparation of Fe(PFO)3@LM-Al perfluorooctanoate-liquid metal modified aluminum composite particles: Liquid metal modified aluminum and perfluorooctanoate were mixed and the aluminothermic agent was prepared by ultrasonic treatment; the liquid metal modified aluminum and Fe(PFO)3 were ultrasonically stirred in 20 ml of anhydrous ethanol using an ultrasonic stirrer with a power of 200 W and a frequency of 40 kHz until the solvent was completely evaporated; the resulting mixture was vacuum filtered and dried in an oven at 50 °C for 12 hours to obtain Fe(PFO)3@LM-Al.

[0036] Step 5, Preparation of the energetic compound Fe(PFO)3@LM-Al@Fe2O3: Fe(PFO)3@LM-Al and iron oxide were added to anhydrous ethanol at a mass ratio of 4:3. The mixture was stirred under ultrasonic stirring at a power of 200W and a frequency of 40kHz. The resulting mixture was dried in an oven at 50℃ for 12 hours to obtain Fe(PFO)3@LM-Al@Fe2O3.

[0037] The morphological characterization and analysis of the product obtained from the above steps were performed using the following methods:

[0038] The microstructures of Fe(PFO)3, Fe(PFO)3@LM-Al, and Fe(PFO)3@LM-Al@Fe2O3 were studied using scanning electron microscopy (SEM, ZEISS GeminiSEM 300, Germany). The test conditions were: accelerating voltage 10V and probe beam current 3pA-20nA.

[0039] The phase compositions of Fe(PFO)3, Fe(PFO)3@LM-Al, and Fe(PFO)3@LM-Al@Fe2O3 were obtained using X-ray diffraction (XRD, Rigaku Ultima IV, Japan). The test conditions were as follows: wavelength Voltage 40kV, current 40mA.

[0040] The chemical composition of Fe(PFO)3 and Fe(PFO)3@LM-Al was determined using a Fourier transform infrared spectrometer (Thermo Fisher Scientific Nicolet iS20, USA) under the following conditions: resolution 4 cm⁻¹. -1 The number of scans was 32, and the test wavenumber range was 400 / 600-4000 cm⁻¹. -1 .

[0041] The elemental composition and relative content of Fe(PFO)3@LM-Al@Fe2O3 were studied using an X-ray photoelectron spectroscopy analyzer (XPS, Thermo Scientific K-Alpha, USA). The test conditions were: excitation source: Al Kα rays (1486.6 eV), beam spot: 400 μm.

[0042] The characterization and analysis process of Fe(PFO)3 is as follows: Figure 1 As shown, Figure 1 (a) FTIR spectrum, (b) XRD pattern, (c) SEM image and (d) TG-DTG curve of Fe(PFO)3 and PFOA perfluorooctanoic acid prepared for this purpose.

[0043] Figure 1 (a) The FTIR spectrum of Fe(PFO)3 shows that PFOA at 1750.08 cm⁻¹ -1 The free COOH band at that point no longer exhibits tensile vibration. At 1686.96 cm⁻¹ -1 and 1651.28cm -1 A new absorption peak appeared at this point, corresponding to the O=CO- ionization of Fe. 3+ The stretching vibrations of ions proved that Fe 3+ The H group that successfully replaced the carboxyl group of PFOA + This further confirms that no residual PFOA was present in the product, achieving a high purity, consistent with...Figure 1 (d) The results of TG-DTG are consistent. Also, 1148.88cm -1 and 1208.18cm -1 The peak value at 984 cm⁻¹ is attributed to the symmetric stretching vibration (νs-Cf²) and antisymmetric stretching vibration (νas-CF²) of the FCF. Furthermore, 984 cm⁻¹ -1 and 1452cm -1 The infrared absorption peaks at these locations belong to the symmetric stretching vibrations (vas-(F-CF2-)) of the F-CF2 functional group and the antisymmetric stretching vibrations (vCF3-CF2) of the CF3-CF2 functional group, respectively. PFOA and Fe(PFO)3 show absorption peaks in the 1600–500 cm⁻¹ range. -1 The similar absorption bands and characteristic peak intensities within the range indicate that the reaction products retain fluorinated alkyl groups, which hardly participate in the chemical reaction.

[0044] Figure 1 (b) shows the XRD patterns of PFOA and Fe(PFO)3. The characteristic diffraction peaks of PFOA disappear, and new characteristic diffraction peaks of Fe(PFO)3 are formed, indicating that Fe(PFO)3 is a crystalline organic salt. The intensity of the characteristic diffraction peaks of Fe(PFO)3 is slightly lower, which is attributed to its low crystallinity.

[0045] Figure 1 (c) The SEM image of Fe(PFO)3 shows that the prepared perfluorooctanoic acid iron exhibits a micron-sized sheet-like structure with a certain thickness. This structure is beneficial for forming a coating film on the surface of spherical aluminum powder particles, thus obtaining core-shell structured composite particles.

[0046] The TG-DTG curve of the prepared Fe(PFO)3 is as follows: Figure 1 As shown in (d), PFOA sublimates before 150℃, resulting in almost 100% weight loss, with the maximum mass loss peak appearing at 139.02℃ on its DTG curve. However, the prepared Fe(PFO)3 showed no significant mass loss at low temperatures, indicating a high purity with almost no residual PFOA. The main thermogravimetric stage peak temperature of Fe(PFO)3 was 340.47℃, at which point the decomposition of ferric perfluorooctanoate was almost complete. Compared to PFOA, the prepared Fe(PFO)3 exhibited high thermal stability, which is beneficial for its application in energetic materials.

[0047] Characterization analysis of Fe(PFO)3@LM-Al was performed, such as... Figures 2-4 As shown, Figure 2 (a) SEM and (b) EDS images of Fe(PFO)3@LM-Al composite particles; Figure 3 (a) FTIR spectrum and (b) XRD pattern of Fe(PFO)3@LM-Al composite particles;Figure 4 The TG-DSC curves of Fe(PFO)3@LM-Al composite particles under N2 atmosphere are shown.

[0048] Depend on Figure 2 SEM and EDS images of the Fe(PFO)3@LM-Al composite particles show that the iron perfluorooctanoate content in the sample is 20%, and obvious flakes are observed on the LM-Al surface. Figure 2 As shown in (a), the fluorine element spectrum of Fe(PFO)3@LM-Al shows that fluorine is uniformly distributed on the surface of aluminum powder, indicating that Fe(PFO)3 has a good coating effect. Furthermore, compared with LM-Al, the surface layer of Fe(PFO)3@LM-Al also contains O and Fe elements, confirming the formation of a Fe(PFO)3 coating layer on the LM-Al surface. Core-shell Fe(PFO)3@LM-Al composite particles were successfully prepared.

[0049] To further determine the formation of the perfluorooctanoic acid (PFOA) coating on the surface of the aluminum particles, FTIR and XRD tests were performed on the composite particles. The FTIR spectrum of the Fe(PFO)3@LM-Al composite particles is shown below. Figure 3 As shown in (a), Fe(PFO)3@LM-Al composite particles at 1147.92 cm⁻¹ -1 and 1204.81cm -1 The infrared absorption peak at [location] can be attributed to the symmetric stretching vibration (vs-CF2) and antisymmetric stretching vibration (vas-CF2) of FCF. Furthermore, O=CO groups were also detected at 1640.64 cm⁻¹ in the FT-IR spectrum of the Fe(PFO)₃@LM-Al composite particles. -1 and 1679.21cm -1 The absorption peak at this point indicates that the aluminum particles were successfully coated by the Fe(PFO)3 film.

[0050] observe Figure 3 The XRD pattern of the Fe(PFO)3@LM-Al composite particles shown in (b) reveals significant characteristic diffraction peaks of aluminum. Further magnification of the XRD pattern details reveals a characteristic diffraction peak of Fe(PFO)3 near 17.9°, indicating that Fe(PFO)3 successfully adhered to the surface of the aluminum particles. However, due to the relatively low crystallinity of ferric perfluorooctanoate, the diffraction peak intensity appears weak.

[0051] Figure 4(a) This shows the mass change of the Fe(PFO)3@LM-Al composite particles during the heating process. It can be seen that the modified aluminum powder exhibits three stages of weight change: thermal weight loss occurs around 340℃, attributed to the thermal decomposition of Fe(PFO)3; thermal weight gain occurs around 600℃, attributed to the thermal oxidation of solid aluminum to form Al2O3; and thermal weight gain occurs between 800℃ and 1100℃, attributed to the thermal oxidation process of molten aluminum. Figure 4 (b) It can be seen that the modified composite particles exhibit an exothermic peak around 375℃, which is attributed to a pre-ignition reaction between the Fe(PFO)3 coating layer and the aluminum particles; the endothermic peak at 646℃ is due to the melting of the solid modified aluminum; and the exothermic peak appearing after 800℃ is attributed to the thermal oxidation of the molten aluminum. These phenomena are consistent with... Figure 4 (a) corresponds to the TG test results.

[0052] Characterization analysis of Fe(PFO)3@LM-Al@Fe2O3 was performed, such as... Figures 5-6 As shown, Figure 5 SEM and EDS images of Fe(PFO)3@LM-Al@Fe2O3 composite particles; Figure 6 (a) XRD and (b) XPS images of Fe(PFO)3@LM-Al@Fe2O3 composite particles.

[0053] Figure 5 As can be seen, under the modification process adopted in this invention, iron oxide is uniformly coated on the Fe(PFO)3@LM-Al surface. Figure 6 As shown in (a), the XRD pattern mainly consists of aluminum peaks (2θ = 38.4°, 44.7°, 65.1°, 78.2°, and 82.4°) and Fe2O3 peaks (2θ = 24.1°, 33.1°, 35.6°, 49.4°, and 62.4°). The results indicate that the structure of the Fe(PFO)3@LM-Al@Fe2O3 phase remains unchanged compared to that of aluminum powder.

[0054] The elemental composition of the Fe(PFO)3@LM-Al@Fe2O3 composite particles was further characterized using X-ray photoelectron spectroscopy, and the results are as follows: Figure 6As shown in (b), analysis reveals that the Fe(PFO)3@LM-Al@Fe2O3 sample not only contains typical signals related to Al 2p, Al 2s, O 1s, and C 1s, but also significant signals related to Ga (23.21 eV, 160.18 eV, 1117.25 eV, and 1144.18 eV), In (443.8 eV), and Sn (485.77 eV and 494.65 eV). This indicates that the surface of the aluminum powder particles is covered by liquid metals (Ga, In, Sn). Furthermore, the presence of binding energies belonging to Fe (55.20 eV, 710.15 eV, 723.66 eV) suggests that during this process, LM-Al and the oxides are modified to form a tightly encapsulated core-shell structure.

[0055] The product obtained in this application was subjected to thermal performance characterization and testing. The testing methods are as follows:

[0056] The thermal properties of the samples were studied using thermogravimetric-differential scanning calorimetry (TG-DSC, Netzsch STA 449F3, Germany), with a temperature range of 50 to 1200 °C and a heating rate of 20 °C / min. -1 The nitrogen flow rate is 50 mL / min. -1 .

[0057] The thermal properties of Fe(PFO)3@LM-Al@Fe2O3 were analyzed, such as... Figure 7 As shown, Figure 7 TG-DSC curve of Fe(PFO)3@LM-Al@Fe2O3.

[0058] like Figure 7 The effect of Fe2O3 as a coating medium on the thermal oxidation performance of Fe(PFO)3@LM-Al was observed using simultaneous thermal analysis (TG-DSC). The test atmosphere was nitrogen. As shown in the figure, the mass of the Fe(PFO)3@LM-Al@Fe2O3 composite particles begins to decrease around 300℃.

[0059] Observations revealed an exothermic peak around 440℃ in the composite particles. According to the research of Pantoya et al., this exothermic peak is attributed to the pre-ignition reaction of aluminum powder: after the thermal decomposition of Fe(PFO)3, the molecular chain breaks, and the decomposition products move thermally in the system in the form of gaseous fluorocarbon fragments, which leads to some fluorine elements being locked on the surface of aluminum particles. That is, the aluminum powder and the coating layer undergo a chemical exothermic reaction to generate AlF3.

[0060] Although the TG curve of the Fe(PFO)3@LM-Al@Fe2O3 composite particles shows significant thermal weight loss, the endothermic peak formed by the thermal decomposition of Fe(PFO)3 near 340℃ is not shown on the DSC curve of the Fe(PFO)3@LM-Al@Fe2O3 composite particles. This may be because the exothermic effect formed by the pre-reaction of aluminum powder with Fe(PFO)3 is greater than the endothermic effect caused by the thermal decomposition of Fe(PFO)3, so an exothermic peak is shown at this temperature.

[0061] The DSC curve of pure micron-sized aluminum powder shows an endothermic peak of aluminum core melting near 660℃. However, the DSC curve of Fe(PFO)3@LM-Al@Fe2O3 composite particles shows a large exothermic peak near 605℃ before the melting point. This is attributed to the following factors: the surface treatment of pure aluminum powder with liquid metal leads to the initial embrittlement of the aluminum shell; then, the gaseous small molecules generated by the decomposition of fluoride react with the aluminum powder in a pre-ignition reaction, destroying the embrittled aluminum shell. At the same time, this reaction releases heat, further promoting the cracking of the embrittled aluminum shell; after the above steps, cracks are formed in the aluminum shell, and the internal aluminum cores come into initial contact with the external oxidation environment through the cracks, resulting in an aluminothermic reaction. The heat released by the aluminothermic reaction back-eats the aluminum particles, playing a positive cycle role, further promoting the cracking of the aluminum shell. More aluminum cores melt and come into contact with the external oxygen environment, which is reflected in the fact that the thermal oxidation exothermic peak occurs before the melting point of the aluminum powder.

[0062] Therefore, this invention provides a fluoride-modified liquid metal medium thermite with the above-mentioned structure and its preparation method. It innovatively introduces liquid metal to etch the surface of aluminum powder and prepares high-purity fluoride Fe(PFO)3, which forms composite particles with LM-Al core-shell. Further, iron oxide particles are coated on its surface to form a composite energetic compound. By utilizing the exothermic reaction of fluoride with aluminum powder pre-ignition, the high-temperature thermal oxidation reaction temperature of aluminum powder is increased to the melting point of 660°C, achieving a breakthrough in the heat transfer process of aluminum powder.

[0063] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the technical solutions of the present invention, and these modifications or equivalent substitutions cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A method for preparing a fluoride-modified liquid metal medium aluminothermic agent, characterized in that: A highly active thermite is prepared by combining fluoride, iron oxide, and aluminum powder. The specific preparation method includes the following steps: Step 1, Preparation of liquid metal: Using a Galinstan eutectic of Ga:In:Sn = 68:22:10 with a melting point of -19℃, liquid metal is prepared. The prepared liquid metal is easy to participate in mechanical stirring at room temperature. Step 2, Preparation of aluminum powder / liquid metal composite energetic particles: Aluminum powder and liquid metal are synthesized by physical mixing and ultrasonic treatment to obtain liquid metal modified aluminum; Step 3, Preparation of iron perfluorooctanoate: FeCl3·6H2O was added to an aqueous solution of perfluorooctanoic acid and stirred and mixed, and then subjected to a hydrothermal reaction. The resulting product was washed to obtain Fe(PFO)3. Step 4, Preparation of Fe(PFO)3@LM-Al perfluorooctanoate-liquid metal modified aluminum composite particles: Liquid metal modified aluminum and perfluorooctanoate are mixed and treated with ultrasound; Step 5, Preparation of Fe(PFO)3@LM-Al@Fe2O3 energetic compound: Fe(PFO)3@LM-Al and iron oxide were added to anhydrous ethanol at a mass ratio of 4:3 and ultrasonically stirred to obtain Fe(PFO)3@LM-Al@Fe2O3.

2. The method for preparing a fluoride-modified liquid metal medium aluminothermic agent according to claim 1, characterized in that: The specific process of step two is as follows: aluminum powder and liquid metal are mixed for 8 hours using ultrasonic stirring with a power of 200W and a frequency of 40kHz, and then vacuum filtered to obtain liquid metal modified aluminum.

3. The method for preparing a fluoride-modified liquid metal medium aluminothermic agent according to claim 2, characterized in that: When the aluminum powder and liquid metal are mixed, the proportion of liquid metal is adjusted to 10%.

4. The method for preparing a fluoride-modified liquid metal medium aluminothermic agent according to claim 3, characterized in that: The obtained liquid metal modified aluminum was dried in an oven at 50°C for 12 hours.

5. The method for preparing a fluoride-modified liquid metal medium aluminothermic agent according to claim 1, characterized in that: The specific preparation process in step three is as follows: Add 10 mL of 0.1 mmol·mL⁻¹ to the beaker. -1 Weigh 4 mmol of FeCl3·6H2O and add it to the aqueous solution of perfluorooctanoic acid; stir the mixture thoroughly at 50°C for 1 h and then transfer it to a hydrothermal reactor and react it in an oven at 100°C for 12 h to obtain the product.

6. The method for preparing a fluoride-modified liquid metal medium aluminothermic agent according to claim 5, characterized in that: Finally, the obtained product was washed and dried in an oven at 60°C for 24 hours to obtain perfluorooctanoic acid iron.

7. The method for preparing a fluoride-modified liquid metal medium aluminothermic agent according to claim 1, characterized in that: The specific preparation process in step four is as follows: using ultrasonic stirring with a power of 200W and a frequency of 40kHz, liquid metal modified aluminum and Fe(PFO)3 are ultrasonically stirred in 20ml of anhydrous ethanol until the solvent is completely evaporated; the resulting mixture is vacuum filtered and dried in an oven at 50℃ for 12 hours to obtain Fe(PFO)3@LM-Al.

8. The method for preparing a fluoride-modified liquid metal medium aluminothermic agent according to claim 1, characterized in that: In step five, the ultrasonic stirring conditions are as follows: the mixture is stirred under ultrasonic stirring with a power of 200W and a frequency of 40kHz, and the resulting mixture is dried in an oven at 50°C for 12 hours to obtain Fe(PFO)3@LM-Al@Fe2O3.

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