A kind of perfluorohexanone coated aluminum-based metal powder and preparation method thereof

Abstract

The present invention provides a perfluorohexanone-coated aluminum-based metal powder and a preparation method thereof, specifically relating to the technical field of metal powder surface coating. The perfluorohexanone-coated aluminum-based metal powder prepared by the present invention comprises aluminum-based metal powder and perfluorohexanone coated on the surface of the aluminum-based metal powder; the perfluorohexanone content in the perfluorohexanone-coated aluminum-based metal powder is 1 to 10 wt%. The present invention utilizes perfluorohexanone to coat the aluminum-based metal powder, and under the interaction of physical adsorption and chemical bonds, the perfluorohexanone is tightly adsorbed to form a coating layer; the small molecular weight and high fluorine content of perfluorohexanone not only retain a high active metal content, but also generate a large amount of gaseous fluorine free radicals after thermal decomposition, thereby reducing the ignition temperature and ignition delay time of the aluminum-based metal powder. As shown in the table, the perfluorohexanone-coated aluminum alloy powder prepared by the present invention can be ignited at 40W with an ignition delay of 12 to 21ms, and at 100W, the ignition delay is 6ms.

Description

Technical Field

[0001] The invention belongs to the technical field of metal powder surface coating, and particularly relates to perfluorohexanone-coated aluminum-based metal powder and a preparation method thereof. Background Art

[0002] Micro-nano metal powders, with their high reactivity and energy density, are used in metal fuels. Micro-nano aluminum powders and aluminum alloy powders are often added to solid propellants to increase their combustion rate and specific impulse due to their high calorific value, low price, and readily available supply. However, due to their high surface energy, micro-nano aluminum powders and aluminum alloy powders easily react with oxygen in the air during preparation and storage, forming a dense oxide shell. This results in a long ignition delay for these powders.

[0003] In existing technology, fluorinated polymers such as polytetrafluoroethylene and perfluoropolyether, as well as fluorinated macromolecular organic acids such as perfluorotetradecanoic acid, are often used to coat micro-nano aluminum-based metal powders to improve their ignition performance. However, due to the large molecular weight of fluorinated polymers, the active metal content in the coated micro-nano aluminum-based metal particles is low, which reduces the combustion performance of the propellant. Fluorinated macromolecular organic acids, with a smaller molecular weight than polymers, increase the active metal content in the coated micro-nano aluminum-based metal particles. However, due to their stable structure and resistance to thermal decomposition, the coated micro-nano aluminum-based metal particles require a longer ignition delay time. Summary of the Invention

[0004] In view of this, the object of the present invention is to provide a perfluorohexanone-coated aluminum-based metal powder. The perfluorohexanone-coated aluminum-based metal powder provided by the present invention has a low ignition temperature and a short ignition delay time.

[0005] In order to solve the above technical problems, the present invention provides the following technical solutions:

[0006] The present invention provides a perfluorohexanone-coated aluminum-based metal powder, comprising aluminum-based metal powder and perfluorohexanone coated on the surface of the aluminum-based metal powder;

[0007] The content of perfluorohexanone in the perfluorohexanone-coated aluminum-based metal powder is 1 to 10 wt %.

[0008] Preferably, the aluminum-based metal powder includes aluminum powder or aluminum alloy powder.

[0009] Preferably, the particle size of the aluminum-based metal powder is 10 nm to 500 μm.

[0010] Preferably, the aluminum alloy powder includes one or more of aluminum-magnesium alloy powder, aluminum-lithium alloy powder, aluminum-zirconium alloy powder and aluminum-titanium alloy powder.

[0011] Preferably, when the aluminum alloy powder is an aluminum-magnesium alloy powder, the molar ratio of magnesium to aluminum in the aluminum-magnesium alloy powder is 1 to 3:1.

[0012] The present invention also provides a method for preparing the perfluorohexanone-coated aluminum-based metal powder described in the above technical solution, characterized in that it comprises the following steps:

[0013] mixing aluminum-based metal powder and perfluorohexanone to obtain perfluorohexanone-coated aluminum-based metal powder;

[0014] The mass ratio of the aluminum-based metal powder to the volume of perfluorohexanone is 1g:5-30mL.

[0015] Preferably, the water content of the perfluorohexanone is ≤50 ppm.

[0016] Preferably, the mixing is carried out under stirring conditions, and the stirring speed is 200r / min to 500r / min.

[0017] Preferably, the mixing temperature is 15 to 30° C., and the mixing time is 0.5 to 2 hours.

[0018] Preferably, the mixing further comprises filtering and drying the obtained mixture.

[0019] The invention provides a perfluorohexanone-coated aluminum-based metal powder, comprising aluminum-based metal powder and perfluorohexanone coated on the surface of the aluminum-based metal powder; the content of perfluorohexanone in the perfluorohexanone-coated aluminum-based metal powder is 1-10 wt%. The present application uses perfluorohexanone to coat aluminum-based metal powder, and physical adsorption occurs between perfluorohexanone and the aluminum-based metal powder. At the same time, the F atoms in perfluorohexanone also form Al-F chemical bonds with Al atoms through high electron affinity. The Al-F chemical bonds and the Coulomb electrostatic attraction between perfluorohexanone and the metal particles work synergistically to make the perfluorohexanone tightly adsorbed on the surface of the aluminum-based metal particles to form a perfluorohexanone coating layer; the perfluorohexanone has a small molecular weight, so that the coated aluminum-based metal powder has a high content of active metal. At the same time, the fluorine content in perfluorohexanone is as high as 72.2%, and the initial pyrolysis temperature of perfluorohexanone is only 640°C. During the combustion process, the perfluorohexanone on the surface of the metal powder particles is thermally decomposed to produce a large amount of gaseous fluorine free radicals. The gaseous fluorine free radicals react with the oxide shell of the aluminum-based metal powder to generate additional reaction heat, thereby promoting the metal core inside the aluminum-based metal particles to participate in the combustion reaction, thereby reducing the ignition temperature and ignition delay time of the aluminum-based metal powder. The test results in Tables 1 and 2 show that the perfluorohexanone-coated aluminum-based metal powder prepared in the present invention can be successfully ignited under a laser ignition power of 40 W, and the ignition delay is 12 to 21 ms. Under a laser ignition power of 100 W, the ignition delay is 6 ms, indicating that the use of perfluorohexanone to coat the aluminum-based metal powder in the present invention can significantly reduce the ignition temperature of the aluminum-based metal powder and shorten the ignition delay time.

[0020] The present invention also provides a method for preparing perfluorohexanone-coated aluminum-based metal powder, which has mild reaction conditions and a simple process flow, provides a new strategy for the surface treatment of energetic materials, and also provides a technical approach for further improving the burning rate and specific impulse of solid propellants using metal fuels. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0022] Figure 1 A flow chart of a method for coating aluminum-based metal powder;

[0023] Figure 2 This is the SEM image of the perfluorohexanone-coated aluminum-magnesium alloy powder obtained in Example 1;

[0024] Figure 3 This is the distribution diagram of fluorine element in the perfluorohexanone-coated aluminum-magnesium alloy powder obtained in Example 1;

[0025] Figure 4 This is an infrared image of a micro-explosion after ignition of the perfluorohexanone-coated aluminum-magnesium alloy powder obtained in Example 1;

[0026] Figure 5 The combustion flame of the micron-sized aluminum-magnesium alloy (a) and the combustion flame of the perfluorohexanone-coated aluminum-magnesium alloy powder obtained in Example 1 (b);

[0027] Figure 6 (a) SEM image of the combustion product of micron-sized aluminum-magnesium alloy and (b) SEM image of the combustion product of perfluorohexanone-coated aluminum-magnesium alloy powder obtained in Example 1;

[0028] Figure 7 The ignition delay time curves of micron-sized aluminum-magnesium alloy and the perfluorohexanone-coated aluminum-magnesium alloy powder obtained in Example 1 at different ignition powers. DETAILED DESCRIPTION

[0029] The present invention provides a perfluorohexanone-coated aluminum-based metal powder, comprising aluminum-based metal powder and perfluorohexanone coated on the surface of the aluminum-based metal powder;

[0030] The content of perfluorohexanone in the perfluorohexanone-coated aluminum-based metal powder is 1 to 10 wt %.

[0031] In the present invention, unless otherwise specified, the raw materials and equipment used are commercially available products well known in the art.

[0032] In the present invention, the particle size of the aluminum-based metal powder is preferably 10 nm to 500 μm, more preferably 50 nm to 100 μm. In a specific embodiment of the present invention, the particle size of the aluminum alloy powder obtained is 45 μm.

[0033] In the present invention, the aluminum-based metal powder preferably includes aluminum powder or aluminum alloy powder; the aluminum alloy powder preferably includes one or more of aluminum-magnesium alloy powder, aluminum-lithium alloy powder, aluminum-zirconium alloy powder and aluminum-titanium alloy powder; when the aluminum alloy powder is preferably aluminum-magnesium alloy powder, the molar ratio of magnesium to aluminum in the aluminum-magnesium alloy powder is preferably 1 to 3:1, more preferably 1.3 to 2.5:1, and more preferably 1.5 to 2:1.

[0034] In the present invention, the content of perfluorohexanone in the perfluorohexanone-coated aluminum-based metal powder is 1 to 10 wt %, preferably 2 to 8 wt %, and more preferably 3 to 6 wt %.

[0035] The present invention utilizes perfluorohexanone to coat aluminum-based metal powder, generating physical adsorption between the perfluorohexanone and the aluminum-based metal powder. Simultaneously, F atoms in the perfluorohexanone form Al-F chemical bonds with Al atoms through high electron affinity. The Al-F chemical bonds and the Coulomb electrostatic attraction between the perfluorohexanone and the aluminum-based metal particles synergistically act to tightly adsorb the perfluorohexanone on the surface of the aluminum-based metal powder particles to form a perfluorohexanone coating layer. The perfluorohexanone has a small molecular weight and a fluorine content as high as 72.2%. By utilizing the perfluorohexanone to coat the aluminum-based metal powder, it is ensured that the coated metal powder contains highly active metal and that the propellant has high combustion performance. The high fluorine content causes the perfluorohexanone to generate a large amount of gaseous fluorine free radicals after thermal decomposition. The gaseous fluorine free radicals react with the aluminum-based metal oxide shell to generate additional reaction heat, thereby promoting the metal core inside the aluminum-based metal particles to participate in the combustion reaction, thereby reducing the ignition temperature and ignition delay time of the aluminum-based metal powder.

[0036] The present invention also provides a method for preparing the perfluorohexanone-coated aluminum-based metal powder described in the above technical solution, comprising the following steps:

[0037] mixing aluminum-based metal powder and perfluorohexanone to obtain aluminum-based perfluorohexanone-coated metal powder;

[0038] The ratio of the mass of the metal powder to the volume of perfluorohexanone is 1 g:5 to 30 mL.

[0039] In the present invention, the method for preparing the aluminum-based metal powder preferably comprises the following steps:

[0040] The molten aluminum or aluminum alloy is broken into fine droplets using an atomizing turntable to obtain aluminum-based metal powder.

[0041] In the present invention, the diameter of the atomizing turntable is preferably 0.01 to 0.1 m, more preferably 0.03 to 0.08 m; the rotation speed of the atomizing turntable is preferably 2300 to 3000 rad / s, more preferably 2600 to 2800 rad / s. The present invention controls the diameter and rotation speed of the atomizing turntable to obtain aluminum-based metal powders of different particle sizes. In a specific embodiment of the present invention, the diameter of the atomizing turntable is 0.05 m, and the rotation speed of the atomizing turntable is 2664 rad / s. In a specific embodiment of the present invention, the molten magnesium-aluminum alloy is broken into fine droplets by using the atomizing turntable, which are condensed in a collector.

[0042] In the present invention, the metal powder is preferably prepared in an inert environment. In a specific embodiment of the present invention, the metal powder is prepared under argon protection.

[0043] In the present invention, the water content of the perfluorohexanone is preferably ≤50 ppm, more preferably ≤40 ppm. Perfluorohexanone readily absorbs moisture from the air at room temperature and must undergo rigorous water-free treatment before use. By strictly controlling the water content of the perfluorohexanone, the present invention prevents deactivation and agglomeration of the aluminum-based metal powder caused by the presence of moisture during the coating process, ensuring that the coated aluminum-based metal powder has a high active metal content.

[0044] In the present invention, the volume ratio of the aluminum-based metal powder to perfluorohexanone is preferably 1 g:5-30 mL, more preferably 1 g:10-25 mL, and even more preferably 1 g:15-20 mL. In the present invention, perfluorohexanone serves as both an organic solvent and a reactant.

[0045] In the present invention, the mixing is carried out under stirring conditions, and the stirring speed is preferably 200 r / min to 500 r / min, more preferably 300 r / min to 400 r / min. The mixing time is preferably 0.5 to 2 hours, more preferably 1 to 1.5 hours. The mixing temperature is preferably 15 to 30°C, more preferably 20 to 25°C. The present invention has no special requirements for the mixing method, and operations well known in the art can be used.

[0046] In the present invention, after the mixing, the obtained mixture is preferably filtered and dried to obtain a perfluorohexanone-coated aluminum-based metal powder. In the present invention, the drying is preferably performed in a vacuum environment, the vacuum degree of the vacuum environment is preferably -0.07 to -0.085 MPa, the drying time is preferably 3 to 6 hours, more preferably 4 to 5 hours, and the drying temperature is preferably 30 to 40°C, more preferably 35 to 40°C.

[0047] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions of the present invention will be clearly and completely described below in conjunction with specific embodiments. The embodiments described are only part of the embodiments of the present invention, not all of them. Any modifications, equivalent replacements, improvements, etc. made to the embodiments of the present invention based on the technical essence and general principles of the present invention without creative work shall be within the scope of protection of the present invention.

[0048] Figure 1 It is a flow chart of the aluminum-based metal powder coating method, such as Figure 1 As shown, aluminum-based metal powder is first prepared, and then the prepared aluminum-based metal powder is mixed with perfluorohexanone, fully stirred, filtered, and dried to obtain perfluorohexanone-coated aluminum-based metal powder.

[0049] Preparation of spherical aluminum-magnesium alloy powder in the following examples:

[0050] Under argon protection, the centrifugal atomization method is adopted, and an atomizing turntable with a diameter of 0.05m is used to break the molten alloy liquid with a magnesium-aluminum molar ratio of 6:4 into fine droplets at a speed of 2664rad / s. The droplets are then condensed in the collector to obtain micron-sized aluminum-magnesium alloy powder with an average particle size of 45μm.

[0051] Example 1

[0052] At room temperature and pressure, 50 g of micron-grade aluminum-magnesium alloy powder was added to 500 mL of perfluorohexanone, stirred at room temperature for 1.5 hours, filtered, and dried under vacuum at 35°C for 4 hours. After drying to constant weight, 51.5 g of perfluorohexanone-coated aluminum alloy powder was weighed, wherein the perfluorohexanone content was 3 wt%.

[0053] Example 2

[0054] At room temperature and pressure, 50 g of micron-grade aluminum-magnesium alloy powder was added to 1000 mL of perfluorohexanone, stirred at room temperature for 1.5 hours, filtered, and dried under vacuum at 35°C for 4 hours. After drying to constant weight, 52.7 g of perfluorohexanone-coated aluminum alloy powder was weighed, with a perfluorohexanone content of 5 wt%.

[0055] Structure and performance test:

[0056] Ignition delay tests were conducted on micron-sized aluminum-magnesium alloy powder and the perfluorohexanone-coated aluminum alloy powder obtained in Example 1 in an air atmosphere. The samples were ignited using different laser ignition powers, and 1 to 3 parallel experiments were set at the same power to ensure the accuracy of the data acquisition system and reduce the error in the ignition delay time. The specific test conditions are as follows: before each test, magnesium-aluminum alloy samples of equal mass were weighed and filled into a crucible and placed inside the combustion chamber. By adjusting the power of the CO2 laser igniter, lasers of different powers could be triggered to ignite the samples. All sample ignition tests were conducted under normal pressure, an ambient temperature of 22°C, and a relative humidity of 30%. During the sample experiment, the samples were uniformly weighed and stirred, and the samples were placed in a cylindrical Al2O3 crucible with a diameter of 5 mm. The results of the laser ignition power and ignition delay measurements of the micron-sized aluminum-magnesium alloy powder and the perfluorohexanone-coated aluminum alloy powder prepared in Example 1 are shown in Tables 1 and 2.

[0057] Table 1 Ignition delay test results of micron-grade aluminum-magnesium alloy powder

[0058]

[0059] Table 2 Ignition delay test results of perfluorohexanone-coated aluminum-magnesium alloy powder prepared in Example 1

[0060]

[0061] As can be seen from Tables 1 and 2, the micron-sized aluminum-magnesium alloy powder cannot be ignited under a laser ignition power of 40W, while the perfluorohexanone-coated aluminum alloy powder prepared by the present invention can be successfully ignited under a laser ignition power of 40W. This shows that the perfluorohexanone-coated aluminum alloy powder has a low ignition temperature. The ignition delay of the micron-sized aluminum-magnesium alloy powder is 102-144ms at a laser ignition power of 100W; the ignition delay is 111-213ms at a laser ignition power of 80W; and the ignition delay is 333-336ms at a laser ignition power of 60W. The ignition delay of the perfluorohexanone-coated aluminum alloy powder prepared by the present invention is 6ms at a laser ignition power of 100W; the ignition delay is 6-9-213ms at a laser ignition power of 80W; the ignition delay is 6ms at a laser ignition power of 60W; and the ignition delay is 12-21ms at a laser ignition power of 40W. It can be seen that the perfluorohexanone-coated aluminum alloy powder has low ignition delay.

[0062] Figure 2 This is the SEM image of the perfluorohexanone-coated aluminum-magnesium alloy powder obtained in Example 1. Figure 2 It can be seen from the figure that the present invention obtains spherical micron-sized aluminum-magnesium alloy powder with an average particle size of 45 μm.

[0063] Figure 3 The distribution diagram of fluorine element in the perfluorohexanone-coated aluminum-magnesium alloy powder obtained in Example 1. Figure 3 It can be seen that perfluorohexanone is successfully coated on the outside of the aluminum-magnesium alloy powder, and the obtained perfluorohexanone-coated aluminum-magnesium alloy powder has high dispersion, which makes the combustion efficiency high.

[0064] Figure 4 This is an infrared image of the micro-explosion of the perfluorohexanone-coated aluminum-magnesium alloy powder obtained in Example 1 after ignition. Figure 4 It can be seen that the perfluorohexanone on the surface of the particles accelerates the heat release process after thermal decomposition, promoting the rapid increase of temperature and pressure inside the aluminum-magnesium alloy particles and the occurrence of micro-explosion.

[0065] Figure 5 The combustion flame of micron-sized aluminum-magnesium alloy (a) and the combustion flame of perfluorohexanone-coated aluminum-magnesium alloy powder obtained in Example 1 (b). Figure 5 As can be seen in Figure a, when the laser ignition power is 60W, the combustion of the uncoated aluminum-magnesium alloy particles is unstable and the visible light produced is weak. Figure 5 As can be seen in Figure b, when the laser ignition power is 60W, the combustion reaction of the aluminum alloy powder coated with perfluorohexanone is violent, and the alloy particles are obviously molten.

[0066] Figure 6 The SEM image (a) of the combustion product of micron-sized aluminum-magnesium alloy and the SEM image (b) of the combustion product of the perfluorohexanone-coated aluminum-magnesium alloy powder obtained in Example 1. Figure 6 As can be seen in Figure a, the surface of the uncoated aluminum-magnesium alloy particles presents a nano-scale porous structure with obvious oxidation characteristics. However, the oxide layer on the particle surface is only partially broken and shrinks, which still has protective properties and prevents the aluminum core inside the particle from further participating in the combustion reaction. Figure 6 As can be seen in Figure b, a large amount of gaseous fluorine radicals generated by the thermal decomposition of perfluorohexanone on the surface of the aluminum alloy powder coated with perfluorohexanone react with the oxide layer on the surface of the aluminum-magnesium alloy particles, prompting the aluminum core inside the aluminum-magnesium alloy particles to flow out and fully burn.

[0067] Figure 7 The ignition delay time curves of micron-sized aluminum-magnesium alloy and perfluorohexanone-coated aluminum-magnesium alloy powder obtained in Example 1 at different ignition powers. Figure 7 It can be seen that the ignition delay time of the perfluorohexanone-coated aluminum alloy powder obtained in Example 1 is much lower than that of the micron-sized aluminum-magnesium alloy, indicating that the perfluorohexanone-coated aluminum-magnesium alloy powder obtained in this application has a low ignition delay time.

[0068] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A perfluorohexanone-coated aluminum-based metal powder, comprising aluminum-based metal powder and perfluorohexanone coated on the surface of the aluminum-based metal powder; The content of perfluorohexanone in the perfluorohexanone-coated aluminum-based metal powder is 3 wt%; The preparation method of the perfluorohexanone-coated aluminum-based metal powder comprises the following steps: mixing aluminum-based metal powder and perfluorohexanone to obtain perfluorohexanone-coated aluminum-based metal powder; The mass ratio of the aluminum-based metal powder to the volume of perfluorohexanone is 1 g:10 mL.

2. The perfluorohexanone-coated aluminum-based metal powder according to claim 1, characterized in that: The aluminum-based metal powder includes aluminum powder or aluminum alloy powder.

3. The perfluorohexanone-coated aluminum-based metal powder according to claim 1 or 2, characterized in that: The particle size of the aluminum-based metal powder is 10 nm to 500 μm.

4. The perfluorohexanone-coated aluminum-based metal powder according to claim 2, characterized in that: The aluminum alloy powder includes one or more of aluminum-magnesium alloy powder, aluminum-lithium alloy powder, aluminum-zirconium alloy powder and aluminum-titanium alloy powder.

5. The perfluorohexanone-coated aluminum-based metal powder according to claim 4, characterized in that: When the aluminum alloy powder is an aluminum-magnesium alloy powder, the molar ratio of magnesium to aluminum in the aluminum-magnesium alloy powder is 1 to 3:

1.

6. The method for preparing the perfluorohexanone-coated aluminum-based metal powder according to any one of claims 1 to 5, characterized in that: The steps are: mixing aluminum-based metal powder and perfluorohexanone to obtain perfluorohexanone-coated aluminum-based metal powder; The mass ratio of the aluminum-based metal powder to the volume of perfluorohexanone is 1 g:10 mL.

7. The preparation method according to claim 6, characterized in that The water content of the perfluorohexanone is ≤50ppm.

8. The preparation method according to claim 6, characterized in that The mixing is carried out under stirring conditions, and the stirring speed is 200r / min to 500r / min.

9. The preparation method according to claim 6 or 8, characterized in that: The mixing temperature is 15-30° C. and the mixing time is 0.5-2 h.

10. The preparation method according to claim 6 or 8, characterized in that: The mixing step further comprises filtering and drying the obtained mixture.

Images