Surface treatment method for aging resistance of aluminum powder

Abstract

The invention discloses a surface treatment method for aging resistance of aluminum powder. The method comprises the following steps: uniformly mixing a PVDF precursor solution and aluminum powder by ultrasonic waves, carrying out gas-phase induced phase separation in a water vapor environment to form gel, carrying out liquid-phase induced phase separation on the gel in ethanol to uniformly embed the aluminum powder into the PVDF gel, and finally carrying out vacuum freeze drying to obtain the aluminum powder coated with PVDF on the surface. By adopting an ice template method and a gelation technology, effective coating of PVDF on the aluminum powder is realized, the anti-aging performance of the aluminum powder is enhanced, the ignition capability of the aluminum powder is improved, and generation of a reaction product aluminum fluoride with a low boiling point is promoted, so that the aluminum powder has the advantages of aging resistance, low ignition threshold and high energy output capability.

Description

Technical Field

[0001] The invention belongs to the field of metal material preparation and relates to a surface treatment method for anti-aging of aluminum powder. Background Art

[0002] Aluminum powder is widely used in rocket propellants, energy materials, spray coatings, additives and other fields. However, there is a common problem with aluminum powder in some specific applications - insufficient anti-aging performance. As time goes by and the external environment affects it, aluminum powder may oxidize, corrode and its particle structure may be damaged, causing its performance to gradually decrease, thus affecting its application effect.

[0003] In order to improve the anti-aging properties of aluminum powder, meet higher usage requirements, and extend its service life, researchers have proposed a variety of surface treatment methods. These methods aim to effectively improve the anti-aging properties of aluminum powder to cope with the adverse effects of external factors such as oxidation and corrosion. Some traditional surface coating technologies have been tried to improve the antioxidant capacity of aluminum powder. U.S. Patent (USPatent 10,563,087) uses a thermal curing / UV curing method to coat the composite cured layer of a cured resin layer and a fluororesin layer on the surface of aluminum powder. Although this method can improve the anti-aging properties of aluminum powder to a certain extent, it has some defects that cannot be ignored: (1) These traditional technologies usually increase manufacturing costs. Since additional materials and equipment are required, the production cost of aluminum powder may increase, which is not conducive to its promotion and application in cost-sensitive industries; (2) Due to the complexity and instability of the coating process, these methods are not suitable for large-scale production, resulting in production efficiency limitations.

[0004] In recent years, polyvinylidene fluoride (PVDF) material has become a material of great concern due to its excellent anti-aging and corrosion resistance. In the literature (Advanced Engineering Materials, 2015, 17 (1): 95-101.), Michael R. Zachariah proved that PVDF material has good compatibility with aluminum powder, and PVDF will undergo a pre-ignition reaction with the alumina shell on the surface of aluminum powder during the decomposition process, promoting the release of aluminum powder energy. The Chinese patent (CN110508802A) uses a heterogeneous precipitation method to coat PVDF on the surface of aluminum powder. Although this method can achieve surface treatment of aluminum powder by PVDF to a certain extent, its preparation process involves highly corrosive chemical reagents such as hydrofluoric acid and tetrahydrofuran, which is not conducive to its development in industrial production. In addition, it is a challenging task to effectively apply PVDF to the surface of aluminum powder. In traditional methods, the combination between PVDF and aluminum powder is not strong, and delamination problems are prone to occur, thereby limiting its application in the anti-aging of aluminum powder.

[0005] Therefore, a novel and effective surface treatment method is needed to closely combine PVDF and aluminum powder to form a uniform and dense coating layer, thereby improving the anti-aging performance of aluminum powder, enhancing its ignition ability, and promoting the formation of low-boiling point reaction product aluminum fluoride. Such a surface treatment method will bring huge potential advantages and market value to the application of aluminum powder in rocket propellants, energetic materials and other fields. Summary of the invention

[0006] The purpose of the present invention is to provide a surface treatment method for aluminum powder anti-aging. The method effectively applies PVDF material to the surface of aluminum powder to achieve significant improvement of the anti-aging performance of aluminum powder.

[0007] The technical solution to achieve the purpose of the present invention is:

[0008] A surface treatment method for aluminum powder anti-aging, using ice template method and gelation technology to compound PVDF and aluminum powder, comprising the following steps:

[0009] PVDF is dissolved in N,N-dimethylformamide to form a PVDF precursor solution. The PVDF precursor solution and aluminum powder are ultrasonically mixed and then placed in a water vapor environment at 15 to 25°C for gas-induced phase separation to form a gel. The gel is then placed in ethanol at 10 to 25°C for liquid-induced phase separation to uniformly embed the aluminum powder in the PVDF gel. Finally, the solution is vacuum freeze-dried to obtain aluminum powder coated with PVDF on the surface.

[0010] Preferably, the concentration of the PVDF precursor solution is 0.06 to 0.16 g / mL.

[0011] Preferably, the mass ratio of aluminum powder to PVDF is 5 to 9:3.

[0012] Preferably, the ultrasound frequency is 30 Hz and the ultrasound time is 5 h.

[0013] Preferably, the gas phase induced phase separation time is 20 to 24 hours, and the liquid phase induced phase separation time is 0.5 hours.

[0014] Preferably, the conditions for vacuum freeze drying are: temperature of -80°C, air pressure of 0.1 kPa, and drying time of 15 h.

[0015] Compared with the prior art, the present invention has the following significant advantages:

[0016] (1) Enhanced anti-aging performance: The present invention uses an ice template method combined with gelation technology to effectively wrap PVDF on the surface of aluminum powder to form a tight coating layer. Compared with traditional surface coating technology, the PVDF coating layer and aluminum powder are more firmly bonded, effectively preventing coating delamination and instability problems. This significantly enhances the anti-aging performance of aluminum powder, and can stably resist erosion by external factors such as oxidation and corrosion for a long time, extending the service life of aluminum powder.

[0017] (2) Low agglomeration characteristics of aluminum powder: In traditional surface treatment methods, aluminum powder particles are often prone to agglomeration, that is, multiple aluminum powder particles combine with each other to form agglomerates. This agglomeration phenomenon leads to uneven distribution of the coating on the surface of the aluminum powder, reducing the stability and performance of the coating. The present invention adopts an ultrasonic dispersion and gelation preparation process to effectively disperse the aluminum powder particles evenly and avoid the occurrence of agglomeration. Ultrasonic dispersion technology can disperse aluminum powder particles from an aggregated state through the action of sound waves, so that each aluminum powder particle can exist independently and be evenly distributed in the PVDF matrix, so that the PVDF coating layer can be more evenly covered on the surface of each aluminum powder particle, ensuring the stability and consistency of the coating. At the same time, the gelation preparation process adopted in the present invention also has a positive effect on the low agglomeration characteristics of aluminum powder. During the gelation process, the interaction between PVDF and aluminum powder is enhanced, so that the coating can be more firmly attached to the surface of each aluminum powder particle and form a tight interface bond, further enhancing the dispersibility between aluminum powder particles.

[0018] (3) Simple, efficient and low cost: The ice template method and gelation technology used in the present invention are simpler and more efficient than traditional coating methods. The present invention reduces the complexity and process steps of coating preparation, and does not require the use of expensive materials and equipment, which helps to reduce production costs, improve production efficiency, is more economical, and can be widely used in large-scale production. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 Schematic diagram of treating aluminum powder using the ice template method in Example 1.

[0020] Figure 2 This is the SEM image of the PVDF surface-treated aluminum powder prepared in Example 1.

[0021] Figure 3 XRD spectra of the aluminum powder before and after surface treatment under aging conditions in Example 1.

[0022] Figure 4 This is a high-speed ignition photograph of the PVDF surface-treated aluminum powder prepared in Example 1. DETAILED DESCRIPTION

[0023] The present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0024] Example 1

[0025] Step 1: Prepare PVDF precursor solution: dissolve 0.5 g PVDF in 5 mL N,N-dimethylformamide and stir until uniform.

[0026] Step 2: Preparation of PVDF sol precursor containing aluminum powder: 300 mg of aluminum powder was gradually added to the PVDF precursor solution, and the aluminum powder was fully embedded in the PVDF gel through sufficient ultrasonic stirring. The ultrasonic frequency was 30 Hz and the ultrasonic time was 5 h, so that each aluminum powder particle could fully contact with the PVDF gel.

[0027] Step 3: Preparation of PVDF gel with uniformly dispersed aluminum powder: The PVDF sol precursor containing aluminum powder is first placed in a water vapor environment for gas-induced phase separation for 24 hours, and then placed in ethanol for liquid-induced phase separation for 0.5 hours to obtain a PVDF gel with uniformly dispersed aluminum powder.

[0028] Step 4: Preparation of PVDF-coated aluminum powder: The PVDF gel with evenly dispersed aluminum powder is frozen to solidify PVDF on the surface of the aluminum powder. Next, the sample is placed under vacuum conditions for drying. The vacuum freeze-drying conditions are: temperature of -80°C, air pressure of 0.1 kPa, and drying time of 15 hours. The excess solvent is removed to finally obtain PVDF-coated aluminum powder.

[0029] Example 2

[0030] Step 1: Prepare PVDF precursor solution: dissolve 0.8 g PVDF in 5 mL N,N-dimethylformamide and stir until uniform.

[0031] Step 2: Preparation of PVDF sol precursor containing aluminum powder: 300 mg of aluminum powder was gradually added to the PVDF precursor solution, and the aluminum powder was fully embedded in the PVDF gel through sufficient ultrasonic stirring. The ultrasonic frequency was 30 Hz and the ultrasonic time was 5 h, so that each aluminum powder particle could fully contact with the PVDF gel.

[0032] Step 3: Preparation of PVDF gel with uniformly dispersed aluminum powder: The PVDF sol precursor containing aluminum powder is first placed in a water vapor environment for gas-induced phase separation for 24 hours, and then placed in ethanol for liquid-induced phase separation for 0.5 hours to obtain a PVDF gel with uniformly dispersed aluminum powder.

[0033] Step 4: Preparation of PVDF-coated aluminum powder: The PVDF gel with evenly dispersed aluminum powder is frozen to solidify PVDF on the surface of the aluminum powder. Next, the sample is placed under vacuum conditions for drying. The vacuum freeze-drying conditions are: temperature of -80°C, air pressure of 0.1 kPa, and drying time of 15 hours. The excess solvent is removed to finally obtain aluminum powder coated with PVDF.

[0034] Example 3

[0035] Step 1: Prepare PVDF precursor solution: dissolve 0.3 g PVDF in 5 mL N,N-dimethylformamide and stir until uniform.

[0036] Step 2: Preparation of PVDF sol precursor containing aluminum powder: 100 mg of aluminum powder was gradually added to the PVDF precursor solution, and the aluminum powder was fully embedded in the PVDF gel through sufficient ultrasonic stirring. The ultrasonic frequency was 30 Hz and the ultrasonic time was 5 h, so that each aluminum powder particle could fully contact with the PVDF gel.

[0037] Step 3: Preparation of PVDF gel with uniformly dispersed aluminum powder: The PVDF sol precursor containing aluminum powder is first placed in a water vapor environment for gas-induced phase separation for 24 hours, and then placed in ethanol for liquid-induced phase separation for 0.5 hours to obtain a PVDF gel with uniformly dispersed aluminum powder.

[0038] Step 4: Preparation of PVDF-coated aluminum powder: The PVDF gel with evenly dispersed aluminum powder is frozen to solidify PVDF on the surface of the aluminum powder. Next, the sample is placed under vacuum conditions for drying. The vacuum freeze-drying conditions are: temperature of -80°C, air pressure of 0.1 kPa, and drying time of 15 hours. The excess solvent is removed to finally obtain aluminum powder coated with PVDF.

[0039] Figure 1 This is a schematic diagram of the ice template method for treating aluminum powder in Example 1. The surface processing process of the aluminum powder can be clearly seen from the figure.

[0040] Figure 2 The SEM images of the PVDF surface treated aluminum powder prepared in Example 1, (a) and (b) are magnified 2000 times, (c) and (d) are magnified 5000 times. Figure 2 It can be clearly seen that the aluminum powder after surface treatment presents a three-dimensional porous structure at the microscopic level.

[0041] Figure 3 The XRD spectra of the aluminum powder before and after surface treatment under aging conditions in Example 1 are shown. It can be clearly seen from the figure that the aluminum powder after surface treatment has strong anti-aging performance.

[0042] Figure 4 This is a high-speed photograph of the ignition of the PVDF surface-treated aluminum powder obtained in Example 1. It can be seen from the figure that the aluminum powder treated with PVDF surface has good ignition performance.

Claims

1. A surface treatment method for aluminum powder anti-aging, characterized in that: The steps include: PVDF is dissolved in N,N-dimethylformamide to form a PVDF precursor solution. The PVDF precursor solution and aluminum powder are ultrasonically mixed and then placed in a water vapor environment at 15-25°C for gas-induced phase separation to form a gel. The gel is then placed in ethanol at 10-25°C for liquid-induced phase separation to uniformly embed the aluminum powder in the PVDF gel. Finally, the solution is vacuum freeze-dried to obtain aluminum powder coated with PVDF.

2. The surface treatment method according to claim 1, characterized in that: The concentration of the PVDF precursor solution is 0.06~0.16g / mL.

3. The surface treatment method according to claim 1, characterized in that: The mass ratio of aluminum powder to PVDF is 5~9:

3.

4. The surface treatment method according to claim 1, characterized in that: The ultrasonic frequency was 30 Hz and the ultrasonic time was 5 h.

5. The surface treatment method according to claim 1, characterized in that: The gas phase induced phase separation time is 20~24h, and the liquid phase induced phase separation time is 0.5h.

6. The surface treatment method according to claim 1, characterized in that: The conditions for vacuum freeze drying are: temperature of -80°C, air pressure of 0.1 kPa, and drying time of 15 h.

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