Fluorosilane-catechol co-coated aluminum-lithium alloy powder, preparation method and application thereof
By co-coating aluminum-lithium alloy powder with fluorosilane and catechol, the problems of fragile coating and poor compatibility were solved, resulting in better storage and combustion performance and improving the overall performance of the propellant.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- BEIJING INST OF TECH
- Filing Date
- 2024-04-03
- Publication Date
- 2026-06-09
Smart Images
Figure CN118271142B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to a fluorosilane-catechol co-coated aluminum-lithium alloy powder, its preparation method, and its application, belonging to the field of energetic materials technology. Background Technology
[0002] To improve propellant performance, incorporating reactive metal powders into explosives and solid propellants has become a research focus for many scholars. Compared to pure aluminum powder, aluminum-lithium alloys, aluminum-tin alloys, and other aluminum-lithium alloys possess greater heat of combustion and higher energy. Specifically, AP propellants containing aluminum-lithium alloy powder can effectively reduce HCl gas emissions, making missiles harder to detect. Using aluminum-lithium, aluminum-tin, aluminum-magnesium, and other aluminum-lithium alloy powders as high-energy additives in solid propellants can improve both the specific impulse of the propellant and the performance of the weapon. It is an ideal fuel for solid propellants, but research and application of aluminum-lithium alloy powders are currently still in the research stage.
[0003] Compared to ordinary aluminum powder, the addition of metallic elements such as lithium alters the structure of the oxide layer on the surface of the aluminum powder, which promotes oxide layer cracking and adversely affects storage. Furthermore, the high reactivity of metallic elements such as lithium makes them less compatible with other components in the propellant. Therefore, it is necessary to modify aluminum-lithium alloy powder to improve its storage and application performance. Currently, there has been some progress in modifying aluminum-lithium alloys with low lithium content. The inventors previously disclosed a composite fluorosilane-coated aluminum-based alloy powder, its preparation method, and its application (Chinese Patent Application 202310911322.0). However, for aluminum-lithium alloys with high lithium content, the inventors found that when using composite fluorosilane to coat high-lithium-content aluminum-lithium alloys, the lithium phase coating layer is fragile and prone to cracking. Summary of the Invention
[0004] In view of this, the purpose of this invention is to provide an aluminum-lithium alloy powder co-coated with fluorosilane and catechol, its preparation method and its application.
[0005] To achieve the above objectives, the technical solution of the present invention is as follows.
[0006] A fluorosilane-catechol co-coated aluminum-lithium alloy powder is disclosed. First, an aluminum-lithium alloy powder is coated with a composite of a first fluorosilane with nine or fewer fluorine atoms and a second fluorosilane with more than nine fluorine atoms. Then, a second coating is performed using catechol, allowing the catechol to fully penetrate the cracks in the composite fluorosilane coating layer, resulting in the fluorosilane-catechol co-coated aluminum-lithium alloy powder. The aluminum-lithium alloy powder contains at least 6% lithium by mass, the total amount of the first and second fluorosilanes is 20%–50% of the mass of the aluminum-lithium alloy powder, the mass ratio of the first and second fluorosilanes is 1:1.25–3.5, and the mass of catechol is 1%–5% of the mass of the aluminum-lithium alloy powder.
[0007] Preferably, the first fluorosilane is one or more of trifluoropropyltrimethoxysilane, hexafluorobutyltriethoxysilane, nonafluorohexyltriethoxysilane, nonafluorohexyltrimethoxysilane, and trimethylpentafluorophenylsilane.
[0008] Preferably, the second fluorosilane is one or more of perfluorooctyltrichlorosilane, perfluorodecyltrimethoxysilane, perfluorododecyltrichlorosilane, perfluorodecyltriethoxysilane, perfluorodecyltriisopropoxysilane, and perfluorooctylsulfonylpropyl.
[0009] Preferably, the aluminum-lithium alloy powder contains 89% to 94% aluminum and 6% to 11% lithium by mass.
[0010] Preferably, the particle size of the aluminum-lithium alloy powder is 5μm to 50μm.
[0011] A method for preparing aluminum-lithium alloy powder co-coated with fluorosilane and catechol according to the present invention includes the following steps:
[0012] (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;
[0013] (2) Add aluminum-lithium 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 coating layer on the surface of the aluminum-lithium alloy powder. After centrifugation, washing and drying, aluminum-lithium alloy powder coated with composite fluorosilane is obtained.
[0014] (3) Add the aluminum-lithium alloy powder coated with composite fluorosilane to an alcohol solution of catechol, the amount of alcohol being 5% to 8% of the mass of aluminum-lithium alloy powder, stir for 30 min to 40 min to allow catechol to fully enter the cracks of the composite fluorosilane coating layer, filter, wash and dry to obtain an aluminum-lithium alloy powder co-coated with fluorosilane and catechol.
[0015] Preferably, in step (1), the fluorosilanes are added sequentially from shortest to longest chain length during mixing.
[0016] Preferably, in step (2), the organic solvent is one or more of n-heptane, ethyl acetate, isopropanol, acetone, anhydrous ethanol, and n-hexane.
[0017] Preferably, in step (3), the alcohol is one or more of methanol, ethanol, isopropanol, pentaerythritol, allyl alcohol, propylene glycol, and ethylene glycol. More preferably, the alcohol is isopropanol.
[0018] An application of the fluorosilane-catechol co-coated aluminum-lithium alloy powder of the present invention, wherein the fluorosilane-catechol co-coated aluminum-lithium alloy powder is used as a high-energy additive for solid propellants.
[0019] Beneficial effects
[0020] This invention provides an aluminum-lithium alloy powder co-coated with fluorosilane and catechol. Based on the composite fluorosilane coating, catechol is used for a secondary coating. The catechol can penetrate into the gaps or openings of the composite fluorosilane coating layer, repairing it to some extent and making the coating layer denser. This significantly improves its storage performance; the coating layer does not significantly peel off after a certain storage period, exhibiting good long-term stability. Furthermore, the finished powder is finer, effectively reducing the agglomeration of the alloy powder. In addition, it also possesses certain hydrophobic properties, improving the stability of the alloy powder in the liquid phase.
[0021] This invention provides a method for preparing aluminum-lithium alloy powder co-coated with fluorosilane and catechol. First, specific fluorosilanes are mixed, and then the aluminum-lithium alloy powder is modified to obtain a certain degree of liquid phase stability. To address the problem of weak and brittle coating layer in the lithium phase region of high-lithium-content aluminum-lithium alloys, catechol is introduced to bond and repair the broken coating layer. The stability of the repaired aluminum-lithium alloy powder is greatly improved, and it can remain stable in hot water for more than two hours without reacting, thus improving the problem of poor compatibility of high-lithium-content aluminum-lithium alloy powder in propellants.
[0022] This invention provides a method for preparing aluminum-lithium alloy powder co-coated with fluorosilane and catechol. In this method, the amount of alcohol used must be strictly controlled. Excessive amount will cause the aluminum-lithium alloy to react with the alcohol, destroying the particle structure of the alloy powder and rendering the alloy powder unusable.
[0023] This invention provides an application of aluminum-lithium alloy powder co-coated with fluorosilane and catechol. The combustion heat of the aluminum-lithium alloy powder treated with fluorosilane and catechol is significantly increased compared to the original powder, and the treated alloy powder is passivated to a certain extent, thereby improving the compatibility of the alloy powder with other components in the propellant. In addition, the increased combustion heat also improves the combustion performance of the propellant. Attached Figure Description
[0024] Figure 1 The image shows the infrared characterization of the aluminum-lithium alloy powder coated with fluorosilane-catechol in Example 1.
[0025] Figure 2 Comparison of scanning electron microscope (SEM) images of aluminum-lithium alloy powder coated with fluorosilane in Comparative Example 1 (left), aluminum-lithium alloy powder coated with fluorosilane-catechol in Example 1 (middle), and aluminum-lithium alloy powder coated with fluorosilane-catechol in Comparative Example 2 with excessive alcohol coating (right), after one week of storage.
[0026] Figure 3 This is a comparison of the stability of the fluorosilane-catechol coated aluminum-lithium alloy powder (left) and the initial aluminum-lithium alloy powder (right) in the liquid phase in Example 1.
[0027] Figure 4 The contact angle between the fluorosilane-catechol coated aluminum-lithium alloy powder in Example 1 and water. Detailed Implementation
[0028] The present invention will be further described in detail below with reference to specific embodiments.
[0029] Comparative Example 1
[0030] At room temperature and pressure, 10g of aluminum-lithium alloy powder (lithium content 10%, particle size 50μm) was added to 200mL of ethyl acetate. After sonication for 10min, 4g of hexafluorobutyltriethoxysilane was added and stirred for 20min to allow the fluorosilane to form a dense coating on the surface of the aluminum-lithium alloy. After the reaction was completed, the powder was centrifuged, washed, centrifuged again, and dried to obtain a fluorosilane-coated aluminum-lithium alloy powder.
[0031] Comparative Example 2
[0032] Trifluoropropyltrimethoxysilane and hexafluorobutyltriethoxysilane were thoroughly mixed at a mass ratio of 1:1.25 until the solution was free of bubbles and the color no longer changed, thus obtaining a fluorosilane mixed solution.
[0033] At room temperature and pressure, 10g of aluminum-lithium alloy powder (lithium content 10%, particle size 50μm) was added to 200mL of ethyl acetate. After sonication for 10min, 4g of a fluorosilane mixed solution was added, and the mixture was stirred for 20min to allow the fluorosilane to densely coat the aluminum-lithium alloy surface. After the reaction was complete, the mixture was centrifuged and washed, and a catechol alcohol solution prepared with 0.1g of catechol and 1.5g of ethanol was added. The mixture was stirred, sonicated for 30min, centrifuged, washed, centrifuged again, and dried to obtain a fluorosilane-catechol coated aluminum-lithium alloy powder.
[0034] Example 1
[0035] Trifluoropropyltrimethoxysilane and hexafluorobutyltriethoxysilane were thoroughly mixed at a mass ratio of 1:1.25 until the solution was free of bubbles, thus obtaining a fluorosilane mixed solution.
[0036] At room temperature and pressure, 10g of aluminum-lithium alloy powder (lithium content 10%, particle size 50μm) was added to 200mL of ethyl acetate. After sonication for 10min, 4g of a fluorosilane mixed solution was added, and the mixture was stirred for 20min to allow the fluorosilane to densely coat the aluminum-lithium alloy surface. After the reaction was completed, the mixture was centrifuged and washed, and a catechol alcohol solution prepared with 0.1g of catechol and 0.5g of allyl alcohol was added. The mixture was stirred, sonicated for 30min, centrifuged, washed, centrifuged again, and dried to obtain a fluorosilane-catechol coated aluminum-lithium alloy powder.
[0037] To investigate the bonding mechanism between fluorosilane catechol and the surface of aluminum-lithium alloy powder, the alloy powder prepared in this embodiment was subjected to infrared analysis. Figure 1 The infrared characteristic peak at 615°C is caused by the stretching vibration of the Si-O bond, which is due to the combination of catechol and fluorosilane. The characteristic peak at 1050°C is caused by the asymmetric stretching vibration of the Al-O-Si bond, which is due to the grafting of fluorosilane and alloy powder surface.
[0038] Electron micrograph of the composite fluorosilane-coated aluminum-lithium alloy powder described in this embodiment after one week of storage ( Figure 1 Electron micrographs of aluminum-lithium alloy powder coated with a single fluorosilane in Comparative Example 1 after one week of storage (in the middle section) and (in the comparative example 1). Figure 1 Compare (left) with, for example Figure 2 As shown, comparison revealed that the composite fluorosilane-coated aluminum-lithium alloy powder described in this embodiment exhibited a crystalline structure on the outer coating after one week of storage. This crystalline structure is formed by the outward growth of catechol after filling the cracks in the coating layer, and no cracks were visible on the surface. In contrast, the aluminum-lithium alloy powder with a single fluorosilane coating in Comparative Example 1 showed coating layer fracture after one week of storage. This indicates that the modified alloy powder prepared in this embodiment has better storage performance than the modified alloy powder with a single fluorosilane coating. Comparative Example 2 Figure 2 (Right) is an electron micrograph of excess alcohol in catechol solution. It can be seen that the surface structure of the alloy powder is greatly destroyed due to the reaction between lithium and alcohol, and the crystal structure collapses. This shows that excess alcohol will cause the aluminum-lithium alloy to react with alcohol, destroy the particle structure of the alloy powder, and make the alloy powder unusable.
[0039] The fluorosilane-catechol coated aluminum-lithium alloy powder described in this embodiment and the initial aluminum-lithium alloy powder were compared by placing them in hot water at 70°C. Figure 3As shown in the image (right) of the fluorosilane-catechol coated aluminum-lithium alloy powder in this embodiment after 3 hours in hot water at 70°C, no surface reaction is observed. The image (left) of the initial aluminum-lithium alloy powder after 1 minute in water at 25°C shows a vigorous reaction. This indicates that the alloy powder coated with various fluorosilanes has a certain degree of stability in the liquid environment. To verify that the fluorosilane-catechol coated aluminum-lithium alloy powder in this embodiment has a certain degree of hydrophobicity to increase its storage performance in the environment, the water contact angle test results are as follows: Figure 4 As shown.
[0040] Example 2
[0041] Nonafluorohexyltriethoxysilane, perfluorododecanetrichlorosilane and perfluorodecyltriethoxysilane were thoroughly mixed in a mass ratio of 1:0.25:0.75 until the solution was free of bubbles to obtain a fluorosilane mixed solution;
[0042] At room temperature and pressure, 20g of aluminum-lithium alloy powder (lithium content 6%, particle size 50μm) was added to 300mL of ethyl acetate. After sonication for 10min, 6g of a fluorosilane mixed solution was added, and the mixture was stirred for 30min to allow the fluorosilane to densely coat the aluminum-lithium alloy surface. After the reaction was completed, the mixture was centrifuged and washed. A catechol alcohol solution prepared by adding 0.1g of catechol, 0.2g of allyl alcohol, and 0.3g of isopropanol was added, stirred, sonicated for 30min, centrifuged, washed, centrifuged again, and dried to obtain a fluorosilane-catechol coated aluminum-lithium alloy powder.
[0043] The infrared results of the fluorosilane-catechol coated aluminum-lithium alloy powder described in this embodiment are similar to those in Example 1.
[0044] The fluorosilane-catechol coated aluminum-lithium alloy powder described in this embodiment remained dense and stable after being stored for one week.
[0045] The microstructure of the fluorosilane-catechol coated aluminum-lithium alloy powder described in this embodiment did not change when placed in hot water at 70°C, indicating that the alloy powder coated with fluorosilane-catechol has a certain degree of stability in the liquid phase environment.
[0046] The fluorosilane-catechol coated aluminum-lithium alloy powder described in this embodiment has a contact angle with water exceeding 40 degrees, exhibiting excellent hydrophobic properties.
[0047] Example 3
[0048] Hexafluorobutyltriethoxysilane, perfluorododecanetrichlorosilane and perfluorodecyltriethoxysilane were thoroughly mixed in a mass ratio of 1:1:1 until the solution was free of bubbles to obtain a fluorosilane mixed solution.
[0049] At room temperature and pressure, 10g of aluminum-lithium alloy powder (lithium content 9%, particle size 30μm) was added to 200mL of anhydrous ethanol. After sonication for 10min, 5g of a fluorosilane mixed solution was added, and the mixture was stirred for 30min to allow the fluorosilane to densely coat the aluminum-lithium alloy surface. After the reaction was completed, the mixture was centrifuged and washed. A catechol alcohol solution prepared by adding 0.1g of catechol, 0.2g of ethanol, and 0.3g of isopropanol was added, stirred, sonicated for 30min, centrifuged, washed, centrifuged again, and dried to obtain a fluorosilane-catechol coated aluminum-lithium alloy powder.
[0050] The infrared results of the fluorosilane-catechol coated aluminum-lithium alloy powder described in this embodiment are similar to those in Example 1.
[0051] The fluorosilane-catechol coated aluminum-lithium alloy powder described in this embodiment remained dense and stable after being stored for one week.
[0052] The microstructure of the fluorosilane-catechol coated aluminum-lithium alloy powder described in this embodiment did not change when placed in hot water at 70°C, indicating that the alloy powder coated with fluorosilane-catechol has a certain degree of stability in the liquid environment.
[0053] The fluorosilane-catechol coated aluminum-lithium alloy powder described in this embodiment has a contact angle with water exceeding 40 degrees, exhibiting excellent hydrophobic properties.
[0054] Example 4
[0055] Nonafluorohexyltriethoxysilane, perfluorodecyltrimethoxysilane and perfluorododecanetrichlorosilane were thoroughly mixed in a mass ratio of 1:1:0.75 until the solution was free of bubbles, thus obtaining a fluorosilane mixed solution.
[0056] At room temperature and pressure, 20g of aluminum-lithium alloy powder (lithium content 11%, particle size 65μm) was added to 200mL of anhydrous ethanol. After sonication for 10min, 5g of a fluorosilane mixed solution was added, and the mixture was stirred for 30min to allow the fluorosilane to densely coat the aluminum-lithium alloy surface. After the reaction was completed, the mixture was centrifuged and washed, and a catechol alcohol solution prepared with 0.1g of catechol, 0.2g of ethylene glycol, and 0.3g of isopropanol was added. The mixture was stirred, sonicated for 30min, centrifuged, washed, centrifuged again, and dried to obtain a fluorosilane-catechol coated aluminum-lithium alloy powder.
[0057] The infrared results of the fluorosilane-catechol coated aluminum-lithium alloy powder described in this embodiment are similar to those in Example 1.
[0058] The coating layer of the fluorosilane-catechol aluminum-lithium alloy powder described in this embodiment remained dense and stable after being stored for one week.
[0059] The microstructure of the fluorosilane-catechol coated aluminum-lithium alloy powder described in this embodiment did not change when placed in hot water at 70°C, indicating that the alloy powder coated with fluorosilane-catechol has a certain degree of stability in the liquid phase environment.
[0060] The fluorosilane-catechol coated aluminum-lithium alloy powder described in this embodiment has a contact angle with water exceeding 40 degrees, exhibiting excellent hydrophobic properties.
[0061] In summary, the invention includes, but is not limited to, the above embodiments. Any equivalent substitutions or partial improvements made under the spirit and principles of this invention shall be considered to be within the protection scope of this invention.
Claims
1. A fluorosilane-catechol co-coated aluminum-lithium alloy powder, characterized in that: First, aluminum-lithium 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. Then, a second coating is performed using catechol, allowing the catechol to fully penetrate the cracks in the composite fluorosilane coating layer, resulting in aluminum-lithium alloy powder co-coated with fluorosilane and catechol. The lithium mass fraction in the aluminum-lithium alloy powder is 6% or more, the total amount of the first and second fluorosilanes is 20% to 50% of the mass of the aluminum-lithium alloy powder, the mass ratio of the first and second fluorosilanes is 1:1.25 to 3.5, and the mass of catechol is 1% to 5% of the mass of the aluminum-lithium alloy powder. The first fluorosilane is one or more of trifluoropropyltrimethoxysilane, hexafluorobutyltriethoxysilane and nonafluorohexyltriethoxysilane; The second fluorosilane is one or more of perfluorododecyltrichlorosilane, perfluorodecyltriethoxysilane, and perfluorodecyltrimethoxysilane; When using catechol for secondary coating, an alcoholic solution of catechol is used, and the amount of alcohol is 5% to 8% of the mass of the aluminum-lithium alloy powder. The alcohol is one or more of methanol, ethanol, isopropanol, pentaerythritol, propylene alcohol, propylene glycol, and ethylene glycol.
2. The aluminum-lithium alloy powder co-coated with fluorosilane and catechol as described in claim 1, characterized in that: The aluminum-lithium alloy powder contains 89% to 94% aluminum and 6% to 11% lithium by mass.
3. The aluminum-lithium alloy powder co-coated with fluorosilane and catechol as described in claim 1 or 2, characterized in that: The particle size of the aluminum-lithium alloy powder is 5μm~50μm.
4. A method for preparing aluminum-lithium alloy powder co-coated with fluorosilane-catechol 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-lithium 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 coating layer on the surface of the aluminum-lithium alloy powder. After centrifugation, washing and drying, aluminum-lithium alloy powder coated with composite fluorosilane is obtained. (3) Add the composite fluorosilane-coated aluminum-lithium alloy powder to an alcohol solution of catechol, the amount of alcohol being 5% to 8% of the mass of the aluminum-lithium alloy powder, stir for 30 min to 40 min to allow the catechol to fully enter the cracks of the composite fluorosilane coating layer, filter, wash and dry to obtain an aluminum-lithium alloy powder co-coated with fluorosilane and catechol. In step (3), the alcohol is one or more of methanol, ethanol, isopropanol, pentaerythritol, propenol, propylene glycol and ethylene glycol.
5. The method for preparing a fluorosilane-catechol co-coated aluminum-lithium 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 a fluorosilane-catechol co-coated aluminum-lithium 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. A method for preparing a fluorosilane-catechol co-coated aluminum-lithium alloy powder as described in any one of claims 4 to 6, characterized in that: In step (3), the alcohol is isopropanol.
8. The application of an aluminum-lithium alloy powder co-coated with fluorosilane and catechol as described in any one of claims 1 to 3, characterized in that: The fluorosilane-catechol co-coated aluminum-lithium alloy powder is used as a high-energy additive for solid propellants.