Composite fluorosilane-coated aluminum-based alloy powder, preparation method and application thereof

Abstract

The present application relates to a kind of composite fluorosilane coated aluminum base alloy powder, preparation method and its application, belong to energetic material technical field.The first fluorosilane with less than or equal to nine fluorine atoms and the second fluorosilane with more than nine fluorine atoms are compounded to coat aluminum base alloy powder, the total amount of the first fluorosilane and the second fluorosilane is 20%~50% of the mass of the aluminum base alloy powder, and the mass ratio of the first fluorosilane and the second fluorosilane is 1:1.25~3.5.Compared with single fluorosilane coating, when the composite fluorosilane of specific composition and content is coated on aluminum base alloy powder, the polymerization product between fluorosilane will also be coated on the alloy powder, so that the coating layer is more dense, which greatly improves its storage performance, and the coating layer does not obviously fall off within a certain storage time, with good long-term stability.In addition, it also has good hydrophobic performance, which improves the stability of alloy powder in liquid phase.

Description

TECHNICAL FIELD

[0001] The present application relates to a kind of composite fluorosilane coated aluminum base alloy powder, preparation method and its application, belong to energetic material technical field. BACKGROUND

[0002] In order to improve the performance of propellant, the introduction of active metal powder into explosive and solid propellant field has become the direction of many scholars. Compared with pure aluminum powder, aluminum lithium alloy, aluminum tin alloy and other aluminum base alloy have greater combustion heat and more energy. Take aluminum lithium alloy, AP propellant containing aluminum lithium alloy powder can effectively reduce the emission of HCl gas to the outside, so that missile weapon is difficult to be detected. Aluminum lithium, aluminum tin, aluminum magnesium and other aluminum base alloy powder as high-energy additive of solid propellant, can not only improve the specific impulse of propellant, but also improve the use performance of weapon. It is the ideal fuel in solid propellant, but the research and application of aluminum base alloy powder are still in the research stage.

[0003] Compared with ordinary aluminum powder, the addition of lithium, tin, magnesium and other metal elements changes the structure of aluminum powder surface oxide layer, which will promote the rupture of oxide layer and have adverse effect on storage. Moreover, the activity of lithium and other metal elements is good, which makes them have poor compatibility with other components in propellant. Therefore, aluminum base alloy powder needs to be modified to improve its storage performance and application performance. Although single fluorosilane coating can solve the above problems to some extent, its performance still needs to be further improved. SUMMARY

[0004] Therefore, the purpose of the present application is to provide a kind of composite fluorosilane coated aluminum base alloy powder, preparation method and its application.

[0005] To achieve the above-mentioned purpose, the technical solutions of the present application are as follows.

[0006] A kind of composite fluorosilane coated aluminum base alloy powder, the first fluorosilane with the number of fluorine atoms less than or equal to nine and the second fluorosilane with the number of fluorine atoms greater than nine are used to coat the aluminum base alloy powder, the total amount of the first fluorosilane and the second fluorosilane is 20% to 50% of the mass of the aluminum base alloy powder, and the mass ratio of the first fluorosilane to the second fluorosilane is 1:1.25 to 3.5.

[0007] Preferably, the first fluorosilane is one or more of trifluoropropyltrimethoxysilane, hexafluorobutyltriethoxysilane, nonafluorohexyltriethoxysilane, nonafluorohexyltrimethoxysilane and trimethylpentaf luorophenylsilane.

[0008] Preferably, the second fluorosilane is one or more of perfluorooctyltrichlorosilane, perfluorodecyltrimethoxysilane, perfluorododecyltrichlorosilane, perfluorodecyltriethoxysilane, perfluorodecyltriisopropoxysilane and perfluorooctanesulfonylaminopropyl.

[0009] Preferably, the content of aluminum in the aluminum-based alloy powder is 90% to 98%.

[0010] Preferably, the particle size of the aluminum-based alloy powder is 5 μm to 50 μm.

[0011] Preferably, the aluminum-based alloy powder is an aluminum-lithium alloy powder, an aluminum-tin alloy powder, or an aluminum-magnesium alloy powder.

[0012] A preparation method of the composite fluorosilane-coated aluminum-based alloy powder according to the present application, the method steps comprising:

[0013] (1) mixing the first fluorosilane and the second fluorosilane sufficiently and self-polymerizing to a solution color no longer changing to obtain a fluorosilane mixed solution;

[0014] (2) adding the aluminum-based alloy powder into an organic solvent to disperse uniformly, then adding the fluorosilane mixed solution, stirring for 10 min to 30 min to form a dense coating layer on the surface of the aluminum-based alloy powder, and obtaining a composite fluorosilane-coated aluminum-based alloy powder after centrifugation, washing, and drying.

[0015] Preferably, in step (1), the fluorosilanes are added in the order of chain length from short to long during mixing.

[0016] Preferably, in step (2), the organic solvent is one or more of n-heptane, ethyl acetate, isopropyl alcohol, acetone, anhydrous ethanol, and n-hexane.

[0017] An application of the composite fluorosilane-coated aluminum-based alloy powder according to the present application, the composite fluorosilane-coated aluminum-based alloy powder being used as a high-energy additive of a solid propellant.

[0018] Advantages

[0019] The present application provides a composite fluorosilane-coated aluminum-based alloy powder. Compared with single fluorosilane coating, when the composite fluorosilane of specific composition and content is used to coat the aluminum-based alloy powder, the polymerization products between the fluorosilanes will also coat the alloy powder, making the coating layer more dense, greatly improving the storage performance, and the coating layer does not fall off obviously within a certain storage time, having good long-term stability, and the finished powder is fine, which can well improve the agglomeration phenomenon of the alloy powder. In addition, it also has good hydrophobicity, improving the stability of the alloy powder in the liquid phase.

[0020] The present application provides a preparation method of a composite fluorosilane-coated aluminum-based alloy powder. First, specific fluorosilanes are mixed and self-polymerized to obtain a fluorosilane solution, then the aluminum-based alloy powder is modified to obtain a certain liquid stability, and then can stably exist in hot water and AP aqueous solution for more than two hours without reaction, improving the poor compatibility of the alloy powder in the propellant.

[0021] The present application provides a kind of application of composite fluorosilane coated aluminum base alloy powder, the combustion heat of aluminum base alloy powder treated by composite fluorosilane is obviously increased compared with original powder, and the alloy powder after being treated by composite fluorosilane is passivated to a certain extent, which can further provide the compatibility of alloy powder and other components in propellant.In addition, the increased combustion heat also improves the combustion performance of propellant. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 It is the scanning electron microscope photograph contrast chart of composite fluorosilane coated aluminum lithium alloy powder (left) in example 1 and single fluorosilane coated aluminum lithium alloy powder (right) in comparative example 1 after being stored for one week.

[0023] Figure 2 It is the stability contrast chart of composite fluorosilane coated aluminum lithium alloy powder (left) in example 1 and initial aluminum lithium alloy powder (right) in liquid phase.

[0024] Figure 3 It is the contact angle of composite fluorosilane coated aluminum lithium alloy powder in example 1 and water. DETAILED DESCRIPTION

[0025] The present application will be further described in detail below in combination with specific examples.

[0026] Comparative example 1

[0027] At normal temperature and pressure, 10 g of aluminum lithium alloy powder with lithium content of 5% and particle size of 50 μm is added into 200 mL of ethyl acetate.Ultrasonic treatment is carried out for 10 min, and then 4 g of perfluorodecyltrimethoxysilane is added into the solution, and stirring is carried out for 20 min to allow the fluorosilane to densely coat the surface of the aluminum lithium alloy.After the stirring is completed, centrifugation, washing, centrifugation and drying are carried out to obtain a single fluorosilane coated aluminum lithium alloy powder.

[0028] Example 1

[0029] Trifluoropropyltrimethoxysilane, perfluorododecyltrichlorosilane and perfluorodecyltriethoxysilane are fully mixed in a mass ratio of 1:1.25:0.75 to obtain a fluorosilane mixed solution, and the solution is black.

[0030] At normal temperature and pressure, 10 g of aluminum lithium alloy powder with lithium content of 5% and particle size of 50 μm is added into 200 mL of ethyl acetate.Ultrasonic treatment is carried out for 10 min, and then 4 g of perfluorodecyltrimethoxysilane is added into the solution, and stirring is carried out for 20 min to allow the fluorosilane to densely coat the surface of the aluminum lithium alloy.After the stirring is completed, centrifugation, washing, centrifugation and drying are carried out to obtain a single fluorosilane coated aluminum lithium alloy powder.

[0031] The electron microscope image of the composite fluorosilane coated aluminum-based alloy powder of the present example after storage for one week Figure 1 is compared with the electron microscope image of the single fluorosilane coated aluminum-lithium alloy powder of Comparative Example 1 after storage for one week (left) Figure 1 As shown in Figure 2 , it is found by comparison that the coating layer of the composite fluorosilane coated aluminum-based alloy powder of the present example is still dense and stable after storage for one week. However, the surface of the single fluorosilane coated aluminum-lithium alloy powder of Comparative Example 1 has coating layer shedding (small holes on the coating layer) after storage for one week. It is indicated that the modified alloy powder prepared in the present example has better storage performance than the single fluorosilane coated modified alloy powder.

[0032] The composite fluorosilane coated aluminum-based alloy powder of the present example and the initial aluminum-lithium alloy powder are put into hot water at 70℃ for comparison, as shown in Figure 3 , it can be seen from the picture (left) of the composite fluorosilane coated aluminum-based alloy powder of the present example after existing in hot water at 70℃ for 3h that the surface does not react. The picture (right) of the initial aluminum-lithium alloy powder after existing in water at 25℃ for 1min shows that it reacts violently. It is indicated that the alloy powder coated by multiple fluorosilanes has certain stability in liquid phase environment. In addition, the composite fluorosilane coated aluminum-based alloy powder of the present example and the initial aluminum-lithium alloy powder are put into AP aqueous solution for 2h, no gas is released, and the micro-morphology does not change.

[0033] In order to confirm that the composite fluorosilane coated aluminum-based alloy powder of the present example has certain hydrophobicity to increase its storage performance in the environment, the water contact angle test result is shown in ​ , the contact angle with water can be more than 90 degrees, which has good hydrophobicity.

[0034] Example 2

[0035] Nonafluorohexyltriethoxysilane, perfluorodecyltrimethoxysilane, perfluorododecyltrichlorosilane and perfluorodecyltriethoxysilane are fully mixed in a mass ratio of 1:0.25:0.75:0.5 to a black solution to obtain a fluorosilane mixed solution;

[0036] At normal temperature and pressure, 20g of aluminum-lithium alloy powder (lithium content of 5%, particle size of 50μm) is added into 300mL of ethyl acetate, 6g of fluorosilane mixed solution is added after ultrasonic treatment for 10min, and stirring is carried out for 30min to allow the fluorosilane to be densely coated on the surface of the aluminum-lithium alloy; after centrifugation, washing, centrifugation and drying, a composite fluorosilane coated aluminum-based alloy powder is obtained.

[0037] The composite fluorosilane coated aluminum-based alloy powder of the present example is still dense and stable after storage for one week.

[0038] The composite fluorosilane coated aluminum-based alloy powder of the present example was placed in hot water at 70°C and AP aqueous solution, respectively, and the micro-morphology did not change, indicating that the alloy powder coated with multiple fluorosilanes has certain stability in liquid phase environment.

[0039] The contact angle of the composite fluorosilane coated aluminum-based alloy powder of the present example with water can exceed 90 degrees, having good hydrophobic performance.

[0040] Example 3

[0041] Hexafluorobutyl triethoxysilane, perfluorododecane trichlorosilane and perfluorodecyl triethoxysilane were mixed in a mass ratio of 1:1:1 until the solution was black to obtain a fluorosilane mixed solution;

[0042] At normal temperature and pressure, 10 g of aluminum-tin alloy powder (tin content of 5%, particle size of 30 μm) was added to 200 mL of anhydrous ethanol, and after ultrasonic treatment for 10 min, 5 g of the fluorosilane mixed solution was added, and stirred for 30 min to allow the fluorosilane to be densely coated on the surface of the aluminum-lithium alloy; after centrifugation, washing, centrifugation and drying, a composite fluorosilane coated aluminum-based alloy powder was obtained.

[0043] The composite fluorosilane coated aluminum-based alloy powder of the present example was stored for one week, and the coating layer was still dense and stable.

[0044] The composite fluorosilane coated aluminum-based alloy powder of the present example was placed in hot water at 70°C and AP aqueous solution, respectively, and the micro-morphology did not change, indicating that the alloy powder coated with multiple fluorosilanes has certain stability in liquid phase environment.

[0045] The contact angle of the composite fluorosilane coated aluminum-based alloy powder of the present example with water can exceed 90 degrees, having good hydrophobic performance.

[0046] Example 4

[0047] Hexafluorobutyl triethoxysilane, perfluorododecane trichlorosilane and perfluorodecyl triethoxysilane were mixed in a mass ratio of 1:1:1 until the solution was black to obtain a fluorosilane mixed solution;

[0048] At normal temperature and pressure, 10 g of aluminum-tin alloy powder (tin content of 5%, particle size of 30 μm) was added to 200 mL of anhydrous ethanol, and after ultrasonic treatment for 10 min, 5 g of the fluorosilane mixed solution was added, and stirred for 30 min to allow the fluorosilane to be densely coated on the surface of the aluminum-lithium alloy; after centrifugation, washing, centrifugation and drying, a composite fluorosilane coated aluminum-based alloy powder was obtained.

[0049] The composite fluorosilane coated aluminum-based alloy powder of the present example was stored for one week, and the coating layer was still dense and stable.

[0050] The composite fluorosilane coated aluminum-based alloy powder described in this example was placed in hot water at 70 DEG C and AP aqueous solution, and the micro-morphology did not change, indicating that the alloy powder coated with various fluorosilanes has certain stability in liquid phase environment.

[0051] The contact angle of the composite fluorosilane coated aluminum-based alloy powder described in this example with water can exceed 90 degrees, and has good hydrophobic properties.

[0052] In summary, the application includes but is not limited to the above examples, any equivalent replacement or partial improvement made under the spirit and principles of the application will be considered within the protection scope of the application.

Claims

1. A composite fluorosilane-coated aluminum-based alloy powder, characterized in that: Aluminum-based alloy powder is coated with a composite of a first fluorosilane with fluorine atoms less than or equal to nine and a second fluorosilane with fluorine atoms greater than nine. The total amount of the first fluorosilane and the second fluorosilane is 20% to 50% of the mass of the aluminum-based alloy powder, and the mass ratio of the first fluorosilane to the second fluorosilane is 1:1.25 to 3.

5. The first fluorosilane is one or more of trifluoropropyltrimethoxysilane, hexafluorobutyltriethoxysilane, nonafluorohexyltriethoxysilane, and trimethylpentafluorophenylsilane; The second fluorosilane is one or more of perfluorooctyltrichlorosilane, perfluorodecyltrimethoxysilane, perfluorododecyltrichlorosilane, perfluorodecyltriethoxysilane, perfluorodecyltriisopropoxysilane, and perfluorooctylsulfonylpropyl. When a first fluorosilane and a second fluorosilane are combined, the first fluorosilane and the second fluorosilane are thoroughly mixed and allowed to self-polymerize until the solution color no longer changes, thus obtaining a fluorosilane mixed solution.

2. The composite fluorosilane-coated aluminum-based alloy powder as described in claim 1, characterized in that: The particle size of the aluminum-based alloy powder is 5μm~50μm.

3. The composite fluorosilane-coated aluminum-based alloy powder as described in claim 1, characterized in that: The aluminum-based alloy powder is an aluminum-lithium alloy powder, an aluminum-tin alloy powder, or an aluminum-magnesium alloy powder.

4. A method for preparing composite fluorosilane-coated aluminum-based alloy powder as described in any one of claims 1 to 3, characterized in that: The method steps include: (1) Mix the first fluorosilane and the second fluorosilane thoroughly and allow them to self-polymerize until the solution color no longer changes, to obtain a fluorosilane mixed solution; (2) Add aluminum-based alloy powder to an organic solvent and disperse it evenly. Then add the fluorosilane mixed solution and stir for 10 min to 30 min to form a dense coating layer on the surface of the aluminum-based alloy powder. After centrifugation, washing and drying, a composite fluorosilane-coated aluminum-based alloy powder is obtained.

5. The method for preparing composite fluorosilane-coated aluminum-based alloy powder as described in claim 4, characterized in that: In step (1), the fluorosilanes are added sequentially from shortest to longest chain length during mixing.

6. The method for preparing composite fluorosilane-coated aluminum-based alloy powder as described in claim 4, characterized in that: In step (2), the organic solvent is one or more of n-heptane, ethyl acetate, isopropanol, acetone, anhydrous ethanol and n-hexane.

7. The application of the composite fluorosilane-coated aluminum-based alloy powder as described in any one of claims 1 to 3, characterized in that: The composite fluorosilane-coated aluminum-based alloy powder is used as a high-energy additive for solid propellants.

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