Modified aluminum-lithium alloy, preparation method thereof and propellant

Abstract

The invention provides a modified aluminum-lithium alloy, a preparation method thereof and a propellant, the modified aluminum-lithium alloy comprises an inner core, a middle layer and a shell, and the material of the inner core comprises an aluminum-lithium alloy; the inner core is coated with the middle layer, the material of the middle layer comprises at least one of silane coupling agents with active end groups, and the active end groups comprise at least one of hydroxyl and amino; the middle layer is coated with the shell, and the shell is made of materials including hydroxyl-terminated poly (dimethyl siloxane) and silicon dioxide. By means of the double-layer coating structure, the chemical stability of the material can be improved, and the performance stability of the modified aluminum-lithium alloy in the storage and use process is improved; meanwhile, the interface bonding force between the shell and the inner core is effectively enhanced, the structural stability of the material is greatly improved, and the risk that the coating structure falls off or cracks is reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of metal powder processing, and in particular to a modified aluminum-lithium alloy, a preparation method thereof, and a propellant. Background Art

[0002] Highly reactive metal powders play a central role in high-energy material systems such as solid propellants and explosives. Aluminum-lithium alloy powder (Al-Li alloy powder) is considered an ideal high-energy fuel additive due to its high calorific value, low density, low ignition temperature, and excellent specific impulse enhancement. The addition of Al-Li alloy effectively reduces corrosion of system components by combustion products, reduces two-phase flow losses, and improves the specific impulse performance of the propellant. However, in practical applications, the inherent high activity of Al-Li alloy powders leads to numerous instabilities, significantly restricting their engineering applications.

[0003] The metallic lithium contained in aluminum-lithium alloys is extremely chemically active and easily reacts with moisture, oxygen, and carbon dioxide in the air to produce byproducts such as LiOH, Li2O, or lithium carbonate. This damages the surface integrity of the alloy powder, leading to a decrease in its activity and specific heat value. These reactions are exothermic and may be accompanied by the release of hydrogen, posing a safety hazard during storage and transportation. The deactivation of aluminum-lithium alloys is more pronounced in humid and hydrothermal environments, posing significant challenges in the propellant preparation, storage, and loading processes. Furthermore, aluminum-lithium alloy powders react with propellant components (such as ammonium perchlorate and hydroxy-terminated butadiene), creating defects such as pores during the curing process, significantly impacting the structural stability and safety of the grain.

[0004] Therefore, there is an urgent need to improve the stability of aluminum-lithium alloy powder. Summary of the Invention

[0005] In view of the technical problems existing in the background technology, the present application provides a modified aluminum-lithium alloy, a preparation method thereof, and a propellant, aiming to improve the chemical stability and structural stability of the aluminum-lithium alloy.

[0006] In a first aspect, an embodiment of the present application provides a modified aluminum-lithium alloy, comprising: A core, wherein the material of the core comprises an aluminum-lithium alloy; an intermediate layer, coated outside the core, wherein the material of the intermediate layer includes at least one silane coupling agent having an active end group, wherein the active end group includes at least one of a hydroxyl group and an amino group; and The shell is coated outside the middle layer, and the material of the shell includes hydroxyl-terminated poly (dimethylsiloxane) and silicon dioxide.

[0007] Optionally, in some embodiments of the present application, the silane coupling agent comprises at least one of KH550, 3-aminopropyltriethoxysilane, and triisopropylsilanol.

[0008] Optionally, in some embodiments of the present application, the hydroxyl-terminated poly(dimethylsiloxane) is a dihydroxyl-terminated poly(dimethylsiloxane).

[0009] Optionally, in some embodiments of the present application, the silicon dioxide comprises at least one of silicon dioxide nanoparticles and modified silicon dioxide, the modified silicon dioxide being silicon dioxide nanoparticles having fluorosilane connected to the surface, the fluorosilane having a structural formula of R-(CF2) n -(CH2) m -Si(OR’)3, wherein R and R’ are each independently selected from substituted or unsubstituted alkyl, n is greater than or equal to 3, and m is greater than or equal to 2.

[0010] Optionally, in some embodiments of the present application, the fluorosilane comprises at least one of perfluorooctyltriethoxysilane, tridecafluoroheptyltriethoxysilane, trifluoromethyltrimethoxysilane, and perfluoropolyetherpropyltrimethoxysilane.

[0011] Optionally, in some embodiments of the present application, the silicon dioxide nanoparticles have an average particle size of 5-50 nm.

[0012] Optionally, in some embodiments of the present application, the hydroxyl-terminated poly(dimethylsiloxane) has a molecular weight of 50,000-110,000.

[0013] Optionally, in some embodiments of the present application, in the shell, the silicon dioxide has a mass percentage content of 1%-5%.

[0014] Optionally, in some embodiments of the present application, the core has an average particle size of 30-55 μm.

[0015] Optionally, in some embodiments of the present application, in the core, lithium has a mass percentage content of 2%-5%.

[0016] Optionally, in some embodiments of the present application, the intermediate layer has a thickness of 5-50 nm.

[0017] Optionally, in some embodiments of the present application, the shell has a thickness of 30-60 nm.

[0018] In a second aspect, embodiments of the present application provide a preparation method of a modified aluminum-lithium alloy, comprising the following steps: mixing silicon dioxide, hydroxyl-terminated poly(dimethylsiloxane), and a first solvent, and then removing the solvent to obtain a shell material; dispersing the aluminum-lithium alloy in a second solvent to form an alloy dispersion, and mixing the alloy dispersion with an aqueous solution of a silane coupling agent to obtain a primary product; mixing the primary product, the shell material, and a third solvent, and performing a drying treatment to obtain a modified aluminum-lithium alloy.

[0019] Optionally, in some embodiments of the present application, the mass ratio of the silicon dioxide and the hydroxyl-terminated poly(dimethylsiloxane) is 1-3:100.

[0020] Optionally, in some embodiments of the present application, the mass ratio of the aluminum-lithium alloy and the silane coupling agent is 1:0.05-0.1.

[0021] Optionally, in some embodiments of the present application, the mass ratio of the primary product and the shell material is 100:2-10.

[0022] Optionally, in some embodiments of the present application, the first solvent comprises one or more of n-hexane, cyclohexane, n-heptane, and ethanol.

[0023] Optionally, in some embodiments of the present application, the second solvent comprises one or more of n-heptane and ethanol.

[0024] Optionally, in some embodiments of the present application, the third solvent comprises one or more of n-heptane and ethanol.

[0025] Optionally, in some embodiments of the present application, the temperature of the drying treatment is 60-70°C.

[0026] Optionally, in some embodiments of the present application, the time of the drying treatment is 10-20 h.

[0027] Optionally, in some embodiments of the present application, in the step of mixing the silicon dioxide, the hydroxyl-terminated poly(dimethylsiloxane), and the first solvent, and then removing the solvent to obtain the shell material, the silicon dioxide comprises at least one of silicon dioxide nanoparticles and modified silicon dioxide, and the preparation method of the modified silicon dioxide comprises: mixing silicon dioxide nanoparticles, fluorosilane, and a dispersion solvent, and then performing vacuum drying to obtain modified silicon dioxide.

[0028] Optionally, in some embodiments of the present application, the mass-volume ratio of the silicon dioxide nanoparticles and the fluorosilane is 1.5 g:0.8-1.2 mL.

[0029] Optionally, in some embodiments of the present application, the dispersion solvent comprises one or more of ethanol, isopropanol, acetone, and tetrahydrofuran.

[0030] Optionally, in some embodiments of the present application, the temperature of the vacuum drying is 50-80℃.

[0031] Optionally, in some embodiments of the present application, the time of the vacuum drying is 5-8 h.

[0032] In a third aspect, the embodiments of the present application provide a propellant comprising the modified aluminum-lithium alloy described above, or the modified aluminum-lithium alloy prepared by the preparation method described above.

[0033] The technical solution proposed in the present application has the following beneficial effects: By constructing an -O-Si-NH2 / OH intermediate layer between the shell and the aluminum-lithium alloy core through the silane coupling agent, one side of the intermediate layer is connected with the metal atoms (Li or Al) on the surface of the core through siloxyl groups (-Si-O-), and the other side is combined with the hydroxyl groups on the hydroxyl-terminated poly(dimethylsiloxane) (PDMS) through intermolecular hydrogen bonds between active groups and hydroxyl groups, the interface bonding force between the shell and the core is effectively enhanced through the double interface forces, the resistance of the shell to external forces is improved, which helps to improve the structural stability of the modified aluminum-lithium alloy, reduce the probability of cracking or falling off of the shell during preparation, transportation and use, protect the core from being exposed, and improve the safety and quality stability of the modified aluminum-lithium alloy.

[0034] The shell is a composite structure of soft and hard combination. Among them, the network constructed by PDMS is a flexible structure, which has much higher flexibility than polystyrene and PVDF film layers, can be well coated to form a dense coating layer and achieve excellent water and oxygen isolation effect, and can also serve as a flexible buffer to enhance the resistance to external forces. At the same time, the introduction of silicon dioxide can not only form a micro-rigid support skeleton to provide mechanical strength and further improve the impact resistance and hot water resistance, but also can improve the surface roughness of the shell, reduce the surface free energy, improve the air / water interface stability, further enhance the protection effect of the core, and at the same time, enhance the compatibility between the modified aluminum-lithium alloy and the components such as HTPB and nitrate plasticizer in the propellant system, and improve the dispersibility and stability of the modified aluminum-lithium alloy in the propellant system.

[0035] The above description is only a summary of the technical solutions of the present application, in order to more clearly understand the technical means of the present application, the specific embodiments of the present application can be implemented in accordance with the content of the description, and in order to make the above and other purposes, features and advantages of the present application more obvious and easy to understand, the following specific embodiments of the present application are described. BRIEF DESCRIPTION OF DRAWINGS

[0036] In order to more clearly illustrate the technical solutions of the present application, the drawings used in the present application will be briefly introduced as follows. Obviously, the drawings described below are only some embodiments of the present application, and other drawings can also be obtained by those skilled in the art without any creative effort on the basis of these drawings.

[0037] Figure 1 SEM images of the materials of Example 1, Comparative Example 1 and Comparative Example 2 in Experimental Example (I); Figure 2 TEM image of the modified aluminum-lithium alloy of Example 1 in Experimental Example (I); Figure 3 Infrared spectrograms of the materials of Example 1, Comparative Example 1 and Comparative Example 2 in Experimental Example (I); Figure 4 Actual photos of the water dispersions of the materials of Example 1, Comparative Example 1 and Comparative Example 2 in Experimental Example (II); Figure 5 Contact angle comparison chart of the materials of Example 1, Example 10, Comparative Examples 1 to 6 in Experimental Example (II); Figure 6 Surface topography chart of the materials of Example 1, Example 10, Comparative Example 3 and Comparative Example 5 in Experimental Example (III); Figure 7 Mass change curve chart of the materials of Example 1, Comparative Example 1 and Comparative Example 2 during storage in Experimental Example (IV); Figure 8 Calorific value change comparison chart of the materials of Example 1 and Comparative Example 1 before and after boiling in Experimental Example (IV); Figure 9 SEM images of the materials of Example 1 and Comparative Example 1 after stirring in Experimental Example (IV); Figure 10 SEM images of the propellants based on the modified aluminum-lithium alloy of Example 1 and the aluminum-lithium alloy of Comparative Example 1. DETAILED DESCRIPTION

[0038] The embodiments of the technical solutions of the present application will be described in detail below with reference to the drawings. The following embodiments are only used to more clearly illustrate the technical solutions of the present application, and therefore only serve as examples, but cannot limit the protection scope of the present application.

[0039] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the present application belongs; the terms used herein are only for the purpose of describing specific embodiments of the present application, and are not intended to limit the present application; the terms "include" and "have" and any variations thereof in the specification and claims of the present application and the above description of drawings are intended to cover non-exclusive inclusion.

[0040] Various embodiments of the present application can exist in a range of forms; it should be understood that the description in a range form is merely for the convenience and brevity, and should not be understood as a hard limitation on the scope of the present application; therefore, it should be considered that the range description has disclosed all possible sub-ranges and single values within the range. For example, it should be considered that the range description from 1 to 6 has disclosed sub-ranges, such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., as well as single values within the range, such as 1, 2, 3, 4, 5, and 6, regardless of the range. In addition, whenever a numerical range is indicated in this document, it refers to any cited number (fraction or integer) within the indicated range.

[0041] In the description of the embodiments of the present application, the technical terms "first", "second", and the like are only used to distinguish different objects, and cannot be understood as indicating or implying relative importance or implicitly indicating the number, specific order, or primary and secondary relationship of the indicated technical features. In the description of the embodiments of the present application, the meaning of "a plurality of" is two or more, unless otherwise explicitly and specifically limited.

[0042] Reference herein to "an embodiment" means that a particular feature, structure, or characteristic described in connection with the embodiment can be included in at least one embodiment of the present application. The occurrence of the phrase in various places in the specification does not necessarily all refer to the same embodiment, nor is it necessarily independent or alternative embodiments to each other. It is explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0043] In the description of the embodiments of the present application, the term "and / or" is only a description of the association relationship of the associated objects, which means that there can be three relationships, for example, A and / or B, which can mean that A exists alone, A and B exist together, and B exists alone. In addition, the character " / " in this document generally represents an "or" relationship between the front and rear associated objects.

[0044] In the description of the embodiments of the present application, the term "at least one" means one or more, "a plurality of" means two or more (including two), and similarly, "a plurality of groups" means two or more groups (including two groups), and "a plurality of pieces" means two or more pieces (including two pieces). "At least one", "at least one of the following" or the like means any combination of these items, including any combination of single item (s) or multiple items (s). For example, "at least one of a, b, or c", or "at least one of a, b, and c", can mean a, b, c, a-b (i.e. a and b), a-c, b-c, or a-b-c, where a, b, and c can be single or multiple.

[0045] In order to improve the stability of the aluminum lithium alloy powder, the commonly used method is to use hydrophobic components such as polystyrene and polyvinylidene fluoride (PVDF) to construct a coating layer on the outer surface of the aluminum lithium alloy powder, so as to isolate the contact between the powder and the active components in the air. However, the coating performance of polystyrene is poor, and it is found in actual application that a large amount of polystyrene needs to be invested to form a coating layer, and the compactness of the coating layer is limited; PVDF is relatively high in price, and may react with aluminum lithium alloy, and has poor stability; in addition, the coating layers prepared by the two materials both have the problem of being difficult to resist external force, which leads to cracking or peeling of the coating layer during preparation, transportation and use, and exposure of the internal active metal.

[0046] It is found through research that the reasons for the easy cracking or peeling of the coating layer include: poor adhesion of the coating material, resulting in poor coating effect; or, although it can be coated on the surface of the alloy powder, the interface bonding property of the obtained coating layer is poor, so when subjected to external force (for example, shear stress in the mixing process, friction, collision and the like during transportation or use), the coating layer is easily peeled off from the surface of the aluminum lithium alloy. Therefore, it is necessary to improve the coating performance, interface bonding capacity and impact resistance of the coating layer itself, and based on this, the application provides a modified aluminum lithium alloy, which comprises a core, an intermediate layer and an outer shell. The material of the core comprises aluminum lithium alloy; the intermediate layer is coated outside the core, and the material of the intermediate layer comprises at least one of silane coupling agents with active end groups, wherein the active end groups comprise at least one of hydroxyl and amino groups; the outer shell is coated outside the intermediate layer, and the material of the outer shell comprises hydroxyl-terminated poly(dimethylsiloxane) (PDMS) and silicon dioxide.

[0047] The modified aluminum lithium alloy provided in the application constructs a double-layer coating structure outside the core, effectively blocks water and oxygen in the outside world or organic components in the propellant system, thereby helping to improve the chemical stability of the material and improve the performance stability of the modified aluminum lithium alloy during storage and use; at the same time, through the double interface force, the interface bonding force between the outer shell and the core is effectively enhanced, the structural stability of the material is greatly improved, the risk of peeling or cracking of the coating structure is reduced, the probability of performance degradation or safety accidents of the material during preparation, transportation or use is reduced, which helps to improve the safety and quality reliability of the material.

[0048] Specifically, the shell is PDMS doped with silicon dioxide. The PDMS has good hydrophobicity and film-forming property, can be well coated to form a dense shell, thereby effectively blocking the erosion of external water and oxygen, preventing the reaction between the aluminum lithium alloy and the propellant components (such as hydroxyl-terminated polybutadiene (HTPB), nitrate plasticizer, ammonium perchlorate, etc.), enhancing the compatibility between the modified aluminum lithium alloy and the components such as HTPB and nitrate plasticizer in the propellant system, and improving the dispersibility and stability of the components in the propellant system. At the same time, the network constructed by PDMS is a flexible structure, which has much higher flexibility than polystyrene and PVDF film layers, can be used as a flexible buffer, and can enhance the resistance to external forces. In addition, the introduction of silicon dioxide can form a micro-rigid support skeleton, provide mechanical strength, further improve the impact resistance and hot water resistance, and on the other hand, can also improve the surface roughness of the shell, reduce the surface free energy, improve the air / water interface stability, and further enhance the protection effect on the core.

[0049] In addition, in terms of structural stability, the application uses hydroxyl-terminated PDMS as the shell material, and an intermediate layer is arranged between the shell and the core. The intermediate layer is made of silane coupling agent, and the silane coupling agent forms -O-Si- active groups (-NH2 or -OH) after silanol hydrolysis. In this way, one side of the -O-Si-NH2 / OH intermediate layer is connected to the metal atoms (Li or Al) on the surface of the core through siloxyl groups (-Si-O-), and the other side is combined with the hydroxyl groups on the hydroxyl-terminated poly(dimethylsiloxane) (PDMS) through intermolecular hydrogen bonds between active groups and hydroxyl groups. Through the double interface force, the interface bonding force between the shell and the core is effectively enhanced, the resistance of the shell to external forces is improved, which helps to improve the structural stability of the modified aluminum lithium alloy, reduces the probability of cracking or falling off of the shell during preparation, transportation and use, protects the core from being exposed, and improves the safety and quality stability of the modified aluminum lithium alloy.

[0050] In some embodiments of the application, the average particle size of the core is 30-55 μm; for example, it can be 30 μm, 35 μm, 40 μm, 45 μm, 50 μm, 55 μm, and a value between any two of the above values.

[0051] In some embodiments of the application, the mass percentage of lithium in the core is 2%-5%; for example, it can be 2%, 3%, 4%, 5%, and a value between any two of the above values.

[0052] In some embodiments of the application, the silane coupling agent can include but is not limited to at least one of KH550, 3-aminopropyl triethoxysilane (APTS), and triisopropylsilanol.

[0053] In some embodiments of the present application, the thickness of the intermediate layer is 5-20 nm; for example, it can be 5 nm, 6 nm, 7 nm, 8 nm, 9 nm, 10 nm, 11 nm, 12 nm, 13 nm, 14 nm, 15 nm, 16 nm, 17 nm, 18 nm, 19 nm, 20 nm, and a value between any two of the above values.

[0054] The hydroxyl-terminated poly(dimethylsiloxane) can be a monohydroxyl-terminated PDMS or a dihydroxyl-terminated PDMS. Preferably, the hydroxyl-terminated poly(dimethylsiloxane) is a dihydroxyl-terminated poly(dimethylsiloxane). In this way, the interaction between the hydroxyl-terminated PDMS and the silica is enhanced, the silica is better fixed, the stability of the shell structure is maintained, and the silica can effectively play its role.

[0055] The silica can include at least one of silica nanoparticles and modified silica, the modified silica being silica nanoparticles having fluorosilane connected to the surface, the fluorosilane having a structural formula of R-(CF2) n -(CH2) m -Si(OR’)3, where R and R’ are each independently selected from substituted or unsubstituted alkyl, n is greater than or equal to 3, and m is greater than or equal to 2. Specifically, the silica incorporated into the shell can be silica nanoparticles without surface modification or silica nanoparticles with surface modification by fluorosilane. The surface modification can improve the hydrophobicity of the silica, thereby improving the hydrophobicity of the shell and further improving the protection effect on the aluminum-lithium alloy powder.

[0056] Specifically, the fluorosilane can include, but is not limited to, at least one of perfluorooctyltriethoxysilane, tridecafluorohexyltriethoxysilane, trifluoromethyltrimethoxysilane, and perfluoropolyetherpropyltrimethoxysilane.

[0057] In some embodiments of the present application, the average particle size of the silica nanoparticles is 5-50 nm; for example, it can be 5 nm, 8 nm, 10 nm, 12 nm, 15 nm, 17 nm, 20 nm, 25 nm, 30 nm, 35 nm, 40 nm, 45 nm, 50 nm, and a value between any two of the above values. Controlling the particle size of the silica nanoparticles in this range can balance the improvement in the surface roughness, impact strength, and hot water resistance of the modified aluminum-lithium alloy, while ensuring the stability of the shell system, avoiding the shedding of silica, and preventing the reduction of surface roughness and impact resistance due to excessively low particle size, and the easy shedding of silica due to excessively high particle size. As a preferred embodiment, the average particle size of the silica nanoparticles can be 5-20 nm.

[0058] In some embodiments of the present application, the molecular weight of the hydroxyl-terminated poly (dimethylsiloxane) is 50000-110000; for example, it can be 50000, 60000, 70000, 80000, 90000, 100000, 110000, and a value between any two of the above values. By using the hydroxyl-terminated PDMS in the above molecular weight range, the cross-linking degree of the shell network can be controlled, and the flexibility and compactness thereof can be improved.

[0059] In some embodiments of the present application, the mass percentage content of the silicon dioxide in the shell is 1%-5%; for example, it can be 1%, 2%, 3%, 4%, 5%, and a value between any two of the above values. By controlling the proportion of silicon dioxide in the shell, the soft and hard composite degree of the shell can be controlled, so that the flexibility and impact resistance of the shell are balanced and improved. It can be understood that the mass percentage content mentioned here refers to the content of silicon dioxide. When the silicon dioxide is unmodified silicon dioxide nanoparticles, the mass percentage content of the silicon dioxide nanoparticles in the shell is 1%-5%; when the silicon dioxide is modified silicon dioxide, the mass percentage content of the modified silicon dioxide in the shell is 1%-5%.

[0060] In some embodiments of the present application, the thickness of the shell is 30-60 nm; for example, it can be 30 nm, 40 nm, 50 nm, 60 nm, and a value between any two of the above values.

[0061] In a second aspect, the embodiments of the present application propose a preparation method of the modified aluminum-lithium alloy, which can prepare the modified aluminum-lithium alloy described above. The preparation method comprises the following steps: S10, mixing silicon dioxide, hydroxyl-terminated poly (dimethylsiloxane) and a first solvent, and then removing the solvent to obtain a shell material; S20, dispersing an aluminum-lithium alloy in a second solvent to prepare an alloy dispersion liquid, and then mixing the alloy dispersion liquid with an aqueous solution of a silane coupling agent to obtain a primary product; S30, mixing the primary product, the shell material and a third solvent, and performing drying treatment to obtain a modified aluminum-lithium alloy.

[0062] In the preparation method proposed in the embodiments of the present application, the aluminum-lithium alloy is first mixed with a silane coupling agent, and then -O-Si-NH2 / OH bonds are formed through silanol hydrolysis to connect with metal atoms (Li or Al) on the surface of the aluminum-lithium alloy, thereby constructing a chemically combined coupling intermediate layer Li / Al-O-Si-NH2 / OH to provide a stable bonding basis for the subsequent shell. Then, a shell material containing silicon dioxide and hydroxyl-terminated PDMS is added for reaction. The hydroxyl-terminated PDMS is attached to the intermediate layer by intermolecular hydrogen bonds, and at the same time, the silicon dioxide is doped in the PDMS network, thereby jointly forming the shell to obtain a modified aluminum-lithium alloy. The modified aluminum-lithium alloy includes a core, an intermediate layer, and a shell. The material of the core includes the aluminum-lithium alloy. The intermediate layer is coated outside the core, and the material of the intermediate layer includes at least one of the silane coupling agents with active end groups, wherein the active end groups include at least one of hydroxyl and amino groups. The shell is coated outside the intermediate layer, and the material of the shell includes hydroxyl-terminated poly(dimethylsiloxane) and silicon dioxide.

[0063] In step S10, the silicon dioxide can refer to silicon dioxide nanoparticles without surface modification, or silicon dioxide nanoparticles after fluorosilane surface modification. Through surface modification, the hydrophobicity of the silicon dioxide can be improved, thereby improving the hydrophobicity of the shell and further improving the protection effect on the aluminum-lithium alloy powder. When the silicon dioxide nanoparticles after fluorosilane surface modification (named modified silicon dioxide) are used, a preparation step of the modified silicon dioxide is further included before step S10. The preparation method of the modified silicon dioxide can include: mixing silicon dioxide nanoparticles, fluorosilane, and a dispersion solvent, and then performing vacuum drying to obtain the modified silicon dioxide.

[0064] The fluorosilane can include, but is not limited to, at least one of perfluorooctyltriethoxysilane, tridecafluorohexyltriethoxysilane, trifluoromethyltrimethoxysilane, and perfluoropolyether propyl trimethoxysilane.

[0065] The dispersion solvent includes one or more of ethanol, isopropyl alcohol, acetone, and tetrahydrofuran.

[0066] In some embodiments of the present application, the mass-volume ratio of the silicon dioxide nanoparticles to the fluorosilane is 1.5 g: 0.8-1.2 mL. That is, the volume of the fluorosilane added corresponding to 1.5 g of silicon dioxide nanoparticles can be 0.8-1.2 mL, for example, 0.8 mL, 0.9 mL, 1.0 mL, 1.1 mL, 1.2 mL, and a value between any two of the above values.

[0067] To ensure sufficient mixing, the silica is effectively and sufficiently modified. When mixing the silica nanoparticles, fluorosilane, and dispersion solvent, magnetic stirring can be performed at 30-50°C under inert gas protection for 12-24 h. The inert gas can include, but is not limited to, nitrogen, helium, argon, etc.

[0068] In some embodiments of the present application, the temperature of the vacuum drying is 50-80°C; for example, it can be 50°C, 55°C, 60°C, 65°C, 70°C, 75°C, 80°C, and a value between any two of the above values.

[0069] In some embodiments of the present application, the time of vacuum drying is 5-8 h; for example, it can be 5 h, 6 h, 7 h, 8 h, and a value between any two of the above values.

[0070] Returning to step S10, in some embodiments of the present application, the mass ratio of the silica to the hydroxyl-terminated poly(dimethylsiloxane) is 1-3:100; for example, it can be 1:100, 1.5:100, 2:100, 2.5:100, 3:100, and a value between any two of the above values. In this way, it is helpful to regulate the proportion of silica in the shell and balance the flexibility and impact resistance of the shell.

[0071] In some embodiments of the present application, the first solvent is used to provide a liquid phase environment to assist in the dispersion and mixing of raw materials, which can specifically include, but is not limited to, one or more of n-hexane, cyclohexane, n-heptane, and ethanol.

[0072] To ensure mixing effect, when mixing the silica, hydroxyl-terminated poly(dimethylsiloxane), and first solvent, magnetic stirring can be performed at 30-50°C for 0.5-2 h, and then subsequent steps are performed.

[0073] In actual operation, the solvent component in the mixing system can be removed by any method. In some embodiments of the present application, the step of removing the solvent can include vacuum degassing at 40-50°C for 1-2 h. The temperature can be 40°C, 41°C, 42°C, 43°C, 44°C, 45°C, 46°C, 47°C, 48°C, 49°C, 50°C, and a value between any two of the above values; the time of vacuum degassing can be 1 h, 1.1 h, 1.2 h, 1.3 h, 1.4 h, 1.5 h, 1.6 h, 1.7 h, 1.8 h, 1.9 h, 2 h, and a value between any two of the above values. In this way, not only can the solvent be effectively and sufficiently removed, but also other components in the mixing system can be avoided from being damaged.

[0074] In addition, in order to remove the solvent more fully, the solvent can be recovered by stirring before vacuum degassing, for example, stirring at 40-50°C for 1-2 h. In this way, not only the solvent can be removed, but also the silica and PDMS can be mixed and dispersed better.

[0075] In step S20: The silane coupling agent can include, but is not limited to, at least one of KH550, 3-aminopropyl triethoxysilane (APTS), and triisopropylsilanol.

[0076] The second solvent can include, but is not limited to, one or more of n-heptane and ethanol. Among them, the ethanol can be anhydrous ethanol or an aqueous solution of ethanol.

[0077] In some embodiments of the present application, the mass ratio of the aluminum-lithium alloy to the silane coupling agent is 1:0.05-0.1; for example, it can be 1:0.05, 1:0.06, 1:0.07, 1:0.08, 1:0.09, 1:0.1, and a value between any two of the above values.

[0078] The formation of the intermediate layer has a lower requirement for the reaction temperature and can be carried out at room temperature (20-40°C). The mixing time can be 1-3 h, and stirring can be continued during the mixing to ensure that the reaction proceeds uniformly and fully.

[0079] In step S30: In some embodiments of the present application, the mass ratio of the primary product to the shell material is 100:2-10; for example, it can be 100:2, 100:3, 100:4, 100:5, 100:6, 100:7, 100:8, 100:9, 100:10, and a value between any two of the above values.

[0080] In some embodiments of the present application, the third solvent can include, but is not limited to, one or more of n-heptane and ethanol. Among them, the ethanol can be anhydrous ethanol or an aqueous solution of ethanol.

[0081] The formation of the shell has a lower requirement for the reaction temperature and can be carried out at room temperature (20-40°C). The mixing time can be 0.5-2 h, and stirring can be continued during the mixing to ensure that the reaction proceeds uniformly and fully.

[0082] In some embodiments of the present application, the drying treatment temperature is 60-70°C; for example, it can be 60°C, 61°C, 62°C, 63°C, 64°C, 65°C, 66°C, 67°C, 68°C, 69°C, 70°C, and a value between any two of the above values.

[0083] In some embodiments of the present application, the drying treatment is performed for 10-20 hours. For example, the drying treatment can be performed for 10 hours, 11 hours, 12 hours, 13 hours, 14 hours, 15 hours, 16 hours, 17 hours, 18 hours, 19 hours, 20 hours, or any value within the range of any two of the above values.

[0084] In a third aspect, the embodiments of the present application provide a propellant, which comprises the modified aluminum-lithium alloy described above or the modified aluminum-lithium alloy prepared by the preparation method described above.

[0085] Some specific examples are listed below. It should be noted that the examples described below are exemplary and are used to explain the present application, and cannot be understood as a limitation of the present application. If a specific technology or condition is not specified in the examples, the technology or condition described in the literature in the art or according to the product manual is used. If the manufacturer of the reagent or instrument is not specified, it is a conventional product that can be obtained on the market.

[0086] Example 1 1) Preparation of modified SiO2: SiO2 was pre-dried at 120°C for 12 hours to obtain pre-dried SiO2 with an average particle size of about 20 nm. 1.5 g of the pre-dried SiO2 was dispersed in 200 mL of anhydrous ethanol, 800 μL of FAS was added, and the mixture was magnetically stirred at 40°C under argon protection for 24 hours, followed by centrifugation. The solid phase was washed with ethanol for 3 times, and vacuum dried at 60°C for 6 hours to obtain the modified SiO2.

[0087] 2) Preparation of shell material: 10 g of dihydroxyl-terminated PDMS (molecular weight of 50000) was added with 0.3 g of modified SiO2 and 8 mL of anhydrous ethanol, and the mixture was magnetically stirred at 40°C for 1 hour, followed by vacuum degassing at 50°C for 2 hours to obtain the shell material (named as SC).

[0088] 3) Preparation of intermediate layer: 3 g of aluminum-lithium alloy powder (Al-5Li, average particle size of about 50 μm, mass percentage of Li of 5%) was added into 50 mL of anhydrous ethanol and treated with ultrasonic wave for 0.5 min to achieve sufficient dispersion to obtain an alloy dispersion liquid. Silane coupling agent KH550 was dispersed in water to obtain a silane solution with a concentration of about 3 g / mL. According to the mass ratio of aluminum-lithium alloy to silane coupling agent of 1:0.05, the silane solution was added to the alloy dispersion liquid, and the mixture was stirred at room temperature (about 25°C) for 1 hour to form an intermediate layer mainly composed of Si–O–Al or Si–O–Li bonds on the surface of the powder to obtain a reaction mixture containing the primary product Al-5Li@KH550. The reaction mixture was subjected to suction filtration, and then vacuum dried at 40°C for 12 hours to obtain the primary product Al-5Li@KH550 for use in the subsequent experiments.

[0089] 4) Preparation of modified aluminum-lithium alloy: The shell material synthesized above was dissolved in anhydrous ethanol to obtain a shell material solution. The shell material solution was slowly added to the reaction mixture prepared in step 3) at a mass ratio of primary product to shell material of 100:5, 50 μl of ultrapure water was added, and stirring was performed at room temperature for 30 min. Then, vacuum filtration was performed, the solid was separated, and the solid was transferred to a vacuum drying oven and dried at 60 °C for 12 h to obtain the modified aluminum-lithium alloy (Al-5Li@KH550@SC).

[0090] Example 2 1) Preparation of modified SiO2: SiO2was pre-dried at 120 °C for 12 h to obtain pre-dried SiO2with an average particle size of about 20 nm. 1.5 g of the pre-dried SiO2was dispersed in 200 mL of anhydrous ethanol, 1 mL of FAS was added, and magnetic stirring was performed at 40 °C under argon protection for 24 h, followed by centrifugation. The solid phase was washed with ethanol for 3 times, and vacuum drying was performed at 60 °C for 6 h to obtain the modified SiO2.

[0091] 2) Preparation of shell material: 10 g of dihydroxyl-terminated PDMS (molecular weight of 50000) was taken, 0.1 g of modified SiO2and 8 mL of anhydrous ethanol were added, magnetic stirring was performed at 40 °C for 1 h, and vacuum degassing was performed at 50 °C for 2 h to obtain the shell material (named as SC).

[0092] 3) Preparation of intermediate layer: 3 g of aluminum-lithium alloy powder (Al-5Li, average particle size of about 50 μm, mass percentage of Li of 5%) was added to 50 mL of anhydrous ethanol and treated with ultrasonic wave for 0.5 min to achieve sufficient dispersion to obtain an alloy dispersion liquid. Silane coupling agent KH550 was dispersed in water to obtain a silane solution with a concentration of about 3 g / mL. According to a mass ratio of aluminum-lithium alloy to silane coupling agent of 1:0.1, the silane solution was added to the alloy dispersion liquid, and stirring was performed at room temperature (about 25 °C) for 1 h to form an intermediate layer mainly with Si–O–Al or Si–O–Li bonds on the surface of the powder to obtain a reaction mixture containing the primary product Al-5Li@KH550.

[0093] 4) Preparation of modified aluminum-lithium alloy: The shell material synthesized above was dissolved in anhydrous ethanol to obtain a shell material solution. The shell material solution was slowly added to the reaction mixture prepared in step 3) at a mass ratio of primary product to shell material of 100:2, 50 μl of ultrapure water was added, and stirring was performed at room temperature for 30 min. Then, vacuum filtration was performed, the solid was separated, and the solid was transferred to a vacuum drying oven and dried at 70 °C for 10 h to obtain the modified aluminum-lithium alloy (Al-5Li@KH550@SC).

[0094] Example 3 1) Preparation of modified SiO2: SiO2 was pre-dried at 120℃ for 12 h to obtain pre-dried SiO2 with an average particle size of about 20 nm. 1.5 g of the pre-dried SiO2 was dispersed in 200 mL of anhydrous ethanol, 1200 μL of FAS was added, and the mixture was stirred at 40℃ under argon protection for 24 h, followed by centrifugation. The solid was washed with ethanol for 3 times, and dried at 60℃ under vacuum for 6 h to obtain the modified SiO2.

[0095] 2) Preparation of shell material: 10 g of dihydroxyl-terminated PDMS (molecular weight of 50000) was added with 0.2 g of the modified SiO2 and 8 mL of anhydrous ethanol, and the mixture was stirred at 40℃ for 1 h, followed by vacuum degassing at 50℃ for 2 h to obtain the shell material (named as SC).

[0096] 3) Preparation of intermediate layer: 3 g of aluminum-lithium alloy powder (Al-5Li, average particle size of about 50 μm, mass percentage of Li of 5%) was added into 50 mL of anhydrous ethanol and treated with ultrasonic wave for 0.5 min to achieve sufficient dispersion to obtain an alloy dispersion liquid. Silane coupling agent KH550 was dispersed in water to obtain a silane solution with a concentration of about 3 g / mL. According to the mass ratio of aluminum-lithium alloy to silane coupling agent of 1:0.08, the silane solution was added into the alloy dispersion liquid, and the mixture was stirred at room temperature (about 25℃) for 1 h to form an intermediate layer mainly composed of Si–O–Al or Si–O–Li bonds on the surface of the powder, thereby obtaining a reaction mixture containing the primary product Al-5Li@KH550.

[0097] 4) Preparation of modified aluminum-lithium alloy: the shell material synthesized above was dissolved in anhydrous ethanol to obtain a shell material solution. According to the mass ratio of the primary product to the shell material of 100:2, the shell material solution was slowly added into the reaction mixture prepared in step 3), 50 μL of ultrapure water was added, and the mixture was stirred at room temperature for 30 min, followed by vacuum filtration to separate the solid, which was then transferred into a vacuum drying oven and dried at 65℃ for 20 h to obtain the modified aluminum-lithium alloy (Al-5Li@KH550@SC).

[0098] Example 4 The scheme of this example is basically the same as that of Example 1, except that the silane coupling agent in this example is changed to triisopropylsilanol. Except for this, other parameters and conditions remain unchanged.

[0099] Example 5 The scheme of this embodiment is basically the same as that of Example 1, except that in this embodiment, the mass ratio of the primary product to the shell material is changed to 100:2. Other parameters and conditions remain unchanged.

[0100] Example 6 The scheme of this embodiment is basically the same as that of Example 1, except that in this embodiment, the mass ratio of the primary product to the shell material is changed to 100:10. Other parameters and conditions remain unchanged.

[0101] Example 7 The scheme of this embodiment is basically the same as that of Example 1, except that in this embodiment, the mass ratio of the primary product to the shell material is changed to 100:12. Other parameters and conditions remain unchanged.

[0102] Example 8 The scheme of this embodiment is basically the same as that of Example 1, except that in this embodiment, the molecular weight of the dihydroxyl-terminated PDMS is 110000. Apart from this, other parameters and conditions remain unchanged.

[0103] Example 9 The scheme of this embodiment is basically the same as that of Example 1, except that in this embodiment, the molecular weight of the dihydroxyl-terminated PDMS is 10000. Apart from this, other parameters and conditions remain unchanged.

[0104] Example 10 The scheme of this embodiment is essentially the same as that of Example 1, differing only in that the modified aluminum-lithium alloy in this embodiment is Al-5Li@KH550@SiO2-PDMS. Accordingly, in the preparation method, the following steps (step 1) of "dispersing 1.5 g of pre-dried SiO2 in 200 mL of anhydrous ethanol, adding 800 μL of FAS, magnetically stirring at 40°C under argon for 24 h, and then centrifuging, removing the solid phase, washing it three times with ethanol, and vacuum drying it at 60°C for 6 h to obtain the modified SiO2" are omitted. In step 2), the pre-dried SiO2 is directly used to prepare the shell material. Other parameters and conditions remain unchanged.

[0105] Comparative Example 1 This comparative example is the aluminum-lithium alloy powder used in Example 1 (Al-5Li, with an average particle size of about 50 μm and a mass percentage of Li of 5%).

[0106] Comparative Example 2 This comparative example is basically the same as Example 1, except that the modified aluminum-lithium alloy in this comparative example is Al-5Li@KH550, and accordingly, step 4 is removed from the preparation method. Apart from this, all other parameters and conditions remain unchanged.

[0107] Comparative Example 3 The scheme of the present comparative example is basically the same as that of Example 1, except that the modified aluminum-lithium alloy in the present comparative example is Al-5Li@KH550@PDMS, and accordingly, in the preparation method, step 2) is removed, and at the same time, in step 4), the shell material is replaced by a dihydroxyl-terminated PDMS (molecular weight of 50000). Except for this, other parameters and conditions are unchanged.

[0108] Comparative Example 4 The scheme of the present comparative example is basically the same as that of Example 1, except that the modified aluminum-lithium alloy in the present comparative example is Al-5Li@KH550@KH550-SiO2-PDMS, and accordingly, in the preparation method, FAS is replaced by KH550. Except for this, other parameters and conditions are unchanged.

[0109] Comparative Example 5 The scheme of the present comparative example is basically the same as that of Example 1, except that the modified aluminum-lithium alloy in the present comparative example is Al-5Li@KH550@FAS-Al2O3-PDMS, and accordingly, in the preparation method, silica is replaced by alumina. Except for this, other parameters and conditions are unchanged.

[0110] Comparative Example 6 The scheme of the present comparative example is basically the same as that of Example 1, except that the modified aluminum-lithium alloy in the present comparative example is Al-5Li@SC, and accordingly, in the preparation method, step 3) is removed, and at the same time, step 4) is modified as follows: 3 g of aluminum-lithium alloy powder (Al-5Li, average particle size of about 50 μm, mass percentage content of Li of 5%) was added to 50 mL of anhydrous ethanol and treated with ultrasonic waves for 0.5 min to achieve sufficient dispersion, to obtain an alloy dispersion liquid.

[0111] The shell material synthesized above was dissolved in anhydrous ethanol to obtain a shell material solution. According to a mass ratio of aluminum-lithium alloy powder to shell material of 100:5, the shell material solution was slowly added dropwise to the reaction mixture prepared in step 3), and 50 μl of ultrapure water was added, and stirred at room temperature for 30 min, and then vacuum filtration was performed, and the solid was separated and transferred to a vacuum drying oven and dried at 60°C for 12 h, to obtain a modified aluminum-lithium alloy (Al-5Li@SC).

[0112] Except for this, other parameters and conditions are unchanged.

[0113] Experimental Example (I) Characterization 1.1 Take the aluminum lithium alloy powder Al-5Li of Comparative Example 1, Al-5Li@KH550 of Comparative Example 2 and modified aluminum lithium alloy Al-5Li@KH550@SC of Example 1, and observe the surface morphology of the materials by scanning electron microscope (SEM). The results are shown in Figure 1 , in which the SEM images of Al-5Li, Al-5Li@KH550 and Al-5Li@KH550@SC are shown from left to right, and in each image, the upper right corner is a magnified image of a single particle.

[0114] Result analysis: From the figure, it can be seen that the modified aluminum lithium alloy is a spherical structure, and the aluminum lithium alloy core in the material is completely covered by the shell, and the shell structure is dense. By comparing the three images, it can be seen that with the addition of KH550 and the shell material, at least two levels of coating layers are formed outside the aluminum lithium alloy core, and the outer coating layer is more dense than the inner coating layer.

[0115] 1.2 Take the modified aluminum lithium alloy Al-5Li@KH550@SC of Example 1, and detect it by transmission electron microscope (TEM), and the results are shown in Figure 2 .

[0116] Result analysis: From the figure, it can be seen that the Si element and the N element have different enrichment areas, and it can be concluded that the green N element near the core is enriched, which proves that the intermediate layer-O-Si-NH2 is formed, and its thickness is about 10 nm. The yellow Si element enrichment represents the position of the two-layer coating layer, and it can be inferred that the outer coating layer is about 35 nm.

[0117] 1.3 Take the aluminum lithium alloy powder Al-5Li of Comparative Example 1, Al-5Li@KH550 of Comparative Example 2 and modified aluminum lithium alloy Al-5Li@KH550@SC of Example 1, and scan them by infrared spectrum detector, and the detection results are shown in Figure 3 .

[0118] Result analysis: After treating Al-5Li with KH550, the peak area at about 3275 cm -1 is enhanced, which proves that it is the stretching vibration peak of-NH2, and at the same time, the CH-Si stretching vibration peak at 1187 cm -1 appears, which proves that KH550 is successfully connected with Al-5Li. Further, when mixed with the shell material, Si-O-Si covalent bond appears, which indicates that PDMS is successfully coated.

[0119] Experimental example (two) comparison of hydrophobicity The modified aluminum-lithium alloy Al-5Li@KH550@SC of Example 1, the modified aluminum-lithium alloy Al-5Li@KH550@SiO2-PDMS of Example 10, the aluminum-lithium alloy powder Al-5Li of Comparative Example 1, Al-5Li@KH550 of Comparative Example 2, the modified aluminum-lithium alloy Al-5Li@KH550@PDMS of Comparative Example 3, Al-5Li@KH550@KH550-SiO2-PDMS of Comparative Example 4, Al-5Li@KH550@FAS-Al2O3-PDMS of Comparative Example 5, and Al-5Li@SC of Comparative Example 6 were subjected to hydrophobicity detection.

[0120] 4.1 The modified aluminum-lithium alloy was dispersed in water, shaken to make the dispersion uniform, and then left to stand to observe the results, as shown in Table 2. Figure 4

[0121] 4.2 The modified aluminum-lithium alloy was pressed into a sheet, and then the contact angle thereof was detected by a contact angle detector, and the results are shown in Table 1. Figure 5

[0122] Table 1

[0123] Obviously, the contact angles of Examples 1 and 11 are much higher than those of Comparative Examples 1, 2 and 6, and Figure 4 The dispersion state of the modified aluminum-lithium alloy in water in Example 11 also well verifies this, which shows that the modified aluminum-lithium alloy proposed in the present application can improve the hydrophobicity by being subjected to double-layer coating, effectively block water and oxygen, and improve the chemical stability of the modified aluminum-lithium alloy; Examples 1 and 10 have higher contact angles than Comparative Examples 3 to 5, and the compatibility with water is obviously poorer than Comparative Examples 3 to 5, which shows that the incorporation of FAS-modified silicon dioxide in the shell is more conducive to improving the hydrophobicity of the material; Further, compared with Example 10, the hydrophobicity of Example 1 is better, which shows that the incorporation of modified silicon dioxide in the shell is more conducive to improving the chemical stability of the modified aluminum-lithium alloy.

[0124] Experimental Example (Three) Surface Roughness Comparison The modified aluminum-lithium alloy Al-5Li@KH550@SC of Example 1, the modified aluminum-lithium alloy Al-5Li@KH550@SiO2-PDMS of Example 10, the modified aluminum-lithium alloy Al-5Li@KH550@PDMS of Comparative Example 3, and Al-5Li@KH550@FAS-Al2O3-PDMS of Comparative Example 5 were observed for surface morphology of the modified aluminum-lithium alloy by SEM, and the detection results are shown in Table 3. Figure 6

[0125] ​​​Result analysis: As can be seen from the figure, Al-5Li@KH550@SC has greater surface roughness, which shows that the incorporation of fluorosilane modified silicon dioxide in the shell helps to improve the surface roughness.

[0126] Experimental example (four) stability comparison 4.1 Take the modified aluminum lithium alloy Al-5Li@KH550@SC of example 1, the aluminum lithium alloy powder Al-5Li of comparative example 1, and Al-5Li@KH550 of comparative example 2, and place them in a 60℃ temperature, 70% humidity environment for 60 days. During this period, the mass of the material is detected every 10 days, and the mass change curve is drawn. The results are shown in Figure 7 , in which the abscissa Time represents the storage days, and the ordinate Mass Variation Rate represents the mass change rate.

[0127] As can be seen from the figure, the mass change of the materials of comparative example 2 and example 1 is small, showing good storage performance.

[0128] 4.2 Take the materials of each example and comparative example, store them in a 60℃ temperature, 70% humidity environment for 60 days, and examine the mass (W 0天 ) at 0 days and the mass (W 60天 ) at 60 days of storage, and calculate the mass growth rate. The results are recorded in Table 2. Mass growth rate (%) = (W 60天 -W 0天 ) x 100 / W 0天 .

[0129] 4.3 Take the materials of each example and comparative example, disperse them in equal amounts of water, and heat them at 60℃ for 1 h. By weighing 0.2000g of the corresponding powder each time, using an oxygen-nitrogen calorimeter, the heat value before and after heating is detected under 3MPa oxygen, and the heat value loss rate is calculated. The results are shown in Figure 8 and Table 2. Heat value loss rate (%) = (Q0-Q 1h ) x 100 / Q0.

[0130] 4.4 Take the materials of each example and comparative example, stir them with a stirring paddle at a speed of 600 rpm for 1 hour, observe the morphology damage after stirring, calculate the percentage of the number of particles with intact morphology to the number of particles with damaged morphology under the same magnification and the same frame selection range, and record it as the morphology integrity, the results are shown in Figure 9 and Table 2.

[0131] Table 2

[0132] Comparing Comparative Examples 1 to 3 and each of the examples, the material prepared in each of the examples exhibits a low mass increase after being stored in a humid heat environment for a period of time and exhibits a small heat value loss after being boiled in water, indicating that the modified aluminum-lithium alloy proposed in the present application has good chemical stability. Meanwhile, the material in each of the examples maintains a relatively complete morphology after being mechanically stirred, indicating that the modified aluminum-lithium alloy proposed in the present application has good structural stability. The coating layer in the modified aluminum-lithium alloy has high resistance to external forces, which can reduce the risk of cracking or falling off of the coating layer during preparation, transportation and use. Further, comparing Example 1, Example 10 and Comparative Examples 3, 5 and 6, it can be seen that Example 1 and 10 have lower heat value loss rate and mass increase rate, and higher morphology integrity, indicating that the incorporation of silicon dioxide in the shell is conducive to improving the impact resistance and hot water resistance, and enhancing the protection effect on the core. Further, comparing Example 1, Example 10 and Comparative Example 4, the heat value loss rate and mass increase rate of Example 1 are the lowest, Example 10 is the second, and Comparative Example 4 is the highest, indicating that the modification of silicon dioxide by FAS helps to improve the hydrophobicity of the shell and further improve the chemical stability of the material.

[0133] Experimental Example (Five) Comparison of Application Effects Take the materials of Example 1 and Comparative Example 1 to prepare propellants, and then compare the micro-morphologies, as shown in Figure 10 The left side of the figure is the SEM image of the propellant, and the right side is the SEM image of the corresponding modified aluminum-lithium alloy. The components of the propellant are composed of modified aluminum-lithium alloy (17wt%), adhesive hydroxyl-terminated polybutadiene (HTPB, 12wt%), plasticizer diisooctyl sebacate (DOS, 2wt%), curing agent isophorone diisocyanate (IPDI, 1wt%), oxidizer ammonium perchlorate (AP, 68wt%). The propellant is prepared by slurry casting method: the adhesive HTPB (12%), plasticizer DOS (2%) and curing agent IPDI (1%) are sequentially added to a vacuum degassing mixer for uniform mixing to obtain a liquid matrix. Then the modified aluminum-lithium alloy (17%), oxidizer AP (68%) are sequentially added to the liquid matrix and mixed thoroughly to form a high-viscosity slurry. The slurry is then poured into a polytetrafluoroethylene mold and cured in a 60°C oven for 7 days.

[0134] As can be seen from the figure, the surface of the propellant corresponding to Example 1 does not have obvious pores, while the surface of the propellant corresponding to Comparative Example 1 has many pores, indicating that the modified aluminum-lithium alloy proposed in the present application has good compatibility with the components of the propellant and has good dispersibility and stability in the propellant system.

[0135] Note that the present application is not limited to the above-described embodiments. The above-described embodiments are merely examples, and embodiments having substantially the same configuration, function, and effect as the technical idea of the present application are included in the technical scope of the present application. Furthermore, other modes constructed by applying various modifications to the embodiments, or by combining part of the configurations of the embodiments, which can be conceived by those skilled in the art, without departing from the spirit of the present application, are also included in the scope of the present application.

Claims

1. A modified aluminum-lithium alloy, characterized in that: include: A core, wherein the material of the core comprises an aluminum-lithium alloy; an intermediate layer, coated outside the core, wherein the material of the intermediate layer includes at least one silane coupling agent having an active end group, wherein the active end group includes at least one of a hydroxyl group and an amino group; and The shell is coated outside the middle layer, and the material of the shell includes hydroxyl-terminated poly (dimethylsiloxane) and silicon dioxide.

2. The modified aluminum-lithium alloy according to claim 1, characterized in that The silane coupling agent includes at least one of KH550, 3-aminopropyltriethoxysilane, and triisopropylsilanol; and / or, The hydroxyl-terminated poly(dimethylsiloxane) is a bis-hydroxyl-terminated poly(dimethylsiloxane); and / or, The molecular weight of the hydroxyl-terminated poly(dimethylsiloxane) is 50,000 to 110,000; and / or, The silicon dioxide comprises at least one of silicon dioxide nanoparticles and modified silicon dioxide, wherein the modified silicon dioxide is silicon dioxide nanoparticles with fluorosilane connected to the surface, and the structural formula of the fluorosilane is R-(CF2) n -(CH2) m -Si(OR')3, wherein R and R' are each independently selected from substituted or unsubstituted alkyl groups, n is greater than or equal to 3, and m is greater than or equal to 2.

3. The modified aluminum-lithium alloy according to claim 2, characterized in that The fluorosilane includes at least one of perfluorooctyltriethoxysilane, tridecafluorohexyltriethoxysilane, trifluoromethyltrimethoxysilane, and perfluoropolyetherpropyltrimethoxysilane; and / or The average particle size of the silicon dioxide nanoparticles is 5 to 50 nm.

4. The modified aluminum-lithium alloy according to claim 1, characterized in that In the shell, the mass percentage of the silicon dioxide is 1% to 5%; and / or, The average particle size of the core is 30-55 μm; and / or, The thickness of the intermediate layer is 5 to 50 nm; and / or, The thickness of the shell is 30-60 nm.

5. A method for preparing the modified aluminum-lithium alloy according to any one of claims 1 to 4, characterized in that: The following steps are involved: mixing silica, hydroxyl-terminated poly(dimethylsiloxane), and a first solvent, and then removing the solvent to obtain a shell material; dispersing the aluminum-lithium alloy in a second solvent to prepare an alloy dispersion, and then mixing the alloy dispersion with an aqueous solution of a silane coupling agent to obtain a primary product; The primary product, the shell material and the third solvent are mixed and dried to obtain a modified aluminum-lithium alloy.

6. The preparation method according to claim 5, characterized in that The mass ratio of the silicon dioxide to the hydroxyl-terminated poly(dimethylsiloxane) is 1 to 3:100; and / or, The mass ratio of the aluminum-lithium alloy to the silane coupling agent is 1:0.05-0.1; and / or, The mass ratio of the primary product to the shell material is 100:2~10.

7. The preparation method according to claim 5, characterized in that The first solvent includes one or more of n-hexane, cyclohexane, n-heptane, and ethanol; and / or, The second solvent includes one or more of n-heptane and ethanol; and / or, The third solvent includes one or more of n-heptane and ethanol; and / or, The drying temperature is 60-70°C; and / or, The drying time is 10 to 20 hours.

8. The preparation method according to claim 5, characterized in that In the step of mixing silica, hydroxyl-terminated poly(dimethylsiloxane), and a first solvent and then removing the solvent to obtain a shell material, the silica comprises at least one of silica nanoparticles and modified silica, and the preparation method of the modified silica comprises: The silicon dioxide nanoparticles, fluorosilane and a dispersing solvent are mixed and then vacuum dried to obtain modified silicon dioxide.

9. The preparation method according to claim 8, characterized in that The mass volume ratio of the silica nanoparticles to the fluorosilane is 1.5 g: 0.8-1.2 mL; and / or, The dispersing solvent includes one or more of ethanol, isopropanol, acetone, and tetrahydrofuran; and / or, The vacuum drying temperature is 50°C to 80°C; and / or, The vacuum drying time is 5 to 8 hours.

10. A propellant, characterized in that: The modified aluminum-lithium alloy comprises the modified aluminum-lithium alloy according to any one of claims 1 to 4, or the modified aluminum-lithium alloy prepared by the preparation method according to any one of claims 5 to 9.

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