Aluminum-lithium alloy efficient passivation process and obtained high-stability powder

Abstract

The invention discloses an aluminum-lithium alloy passivation method which is characterized in that a passivated aluminum-lithium alloy sequentially comprises an aluminum-lithium alloy core, a passivation layer growth film and a passivation layer coating film from inside to outside; the total thickness of the passivation layer growth film and the passivation layer coating film is 1-1.5 [mu] m; specifically, potassium dichromate is used, a magnetic stirrer is adopted, and the passivation film is formed on the surface of the aluminum-lithium alloy; the passivated aluminum-lithium alloy can be added into a solid propellant. The compact passivation film is formed on the surface of the aluminum-lithium alloy, so that the influence of external water vapor on the aluminum-lithium alloy is effectively prevented and isolated, and the stability of the aluminum-lithium alloy in the storage and use processes is maintained.

Description

Technical Field

[0001] The present application relates to the technical field of metal powder material preparation, and in particular to a method for preparing a passivated aluminum-lithium alloy powder. Background Art

[0002] Rocket propellants are substances that are ejected from rocket engines in large quantities in the form of fluid jets to generate thrust for propulsion. They are divided into liquid propellants and solid propellants. Aluminum powder is usually used in solid propellants to provide combustion heat, thereby making the thrust of the rocket higher. However, due to the presence of an oxide film on the surface of aluminum powder, it is difficult to ignite it, and when the propellant containing aluminum powder burns, the actual specific impulse of the aluminum powder will be lost to a certain extent due to the melting agglomeration of aluminum powder particles on the combustion end surface and incomplete combustion. In order to improve the propulsion efficiency and address the problem of specific impulse loss of aluminum powder, the industry has begun to explore the use of aluminum-lithium alloy powder as an alternative material. However, aluminum-lithium alloy powder also faces certain challenges during use and storage. Due to its high activity, it is easily affected by the environment and oxidized or corroded, which in turn affects its performance. Therefore, in order to maintain the stability and performance of aluminum-lithium alloy powder during long-term use and storage, appropriate surface passivation treatment is required.

[0003] With the development of technology, for the passivation of aluminum-lithium alloy, Chinese invention patent CN114589302 discloses a method for preparing heat-resistant liquid high-stability modified aluminum-lithium alloy powder, which uses aminosilane and di-claw silane to modify the aluminum-lithium alloy, thereby obtaining aluminum-lithium alloy powder with high stability. Chinese invention patent CN17303989 discloses a modified aluminum-lithium alloy fuel with excellent wet heat stability and compatibility and a preparation method thereof, which uses ammonium reagents to pretreat the aluminum-lithium alloy powder to reduce the high chemical activity on the surface of the aluminum-lithium alloy powder, and then uses carboxylates to passivate it. However, this type of method uses a variety of chemical reagents, and the low surface energy materials are extremely unstable and easily fail in practical applications.

[0004] Therefore, it is particularly important to develop a simple, efficient and safe method to prepare a stable passivation layer on the surface of aluminum-lithium alloy powder. Summary of the invention

[0005] The present application aims to provide an improved passivated aluminum-lithium alloy and a preparation method thereof, aiming to solve the problem that the aluminum-lithium alloy powder is easily affected by the environment during storage, especially the poor stability in a humid environment, and the compatibility with other propellant components during the preparation of solid propellants.

[0006] To solve the above problems, follow the steps below:

[0007] S1. Put the potassium dichromate and deionized water into a beaker to prepare a 2-12 g / 100 ml solution, and stir evenly in a magnetic stirrer.

[0008] S2. Heat the magnetic stirrer to 20-40°C and maintain 20-40°C during stirring.

[0009] S3: Ensure that the gear is 10-12, add 1-10g of aluminum-lithium alloy powder, and react for 20-45 minutes.

[0010] S4. After the reaction, the powder is filtered and dried at 45-55°C for 4-5h.

[0011] S5. Prepare 3-10g / 100ml potassium dichromate solution and stir evenly in a magnetic stirrer.

[0012] S6. Heat the magnetic stirrer to 20-30°C and maintain 20-30°C during stirring.

[0013] S7. Ensure that the aluminum-lithium alloy powder after passivation is added at the 10-12 gear, ultrasonically disperse for 10-20 seconds, and then passivate for 20-30 minutes.

[0014] S8. Perform the second passivation by thermal curing in deionized water at 40-55°C.

[0015] Compared with the prior art, the present invention has the following beneficial effects:

[0016] 1. The oxide film of aluminum-lithium alloy is dense and uniform, which prevents the reaction of oxygen atoms and significantly improves the corrosion resistance.

[0017] 2. The original process combines secondary passivation, ultrasonic dispersion and thermal curing to create alloy materials, overcome the agglomeration problem and improve performance.

[0018] 3. Use innovative passivation technology to prepare aluminum-lithium alloys, solve traditional defects, and improve storage stability and overall performance.

[0019] The present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0021] Figure 1 This is a schematic diagram of the aluminum-lithium alloy particle structure described in Example 1 of the present application;

[0022] Figure 2 is the SEM image of unpassivated aluminum-lithium alloy particles;

[0023] Figure 3 This is a SEM image of the aluminum-lithium alloy particles described in Example 1 of the present application.

[0024] Figure 4 The thickness of the passivation film of aluminum-lithium alloy particles is shown in the figure DETAILED DESCRIPTION

[0025] In order to make the purpose, technical solution and advantages of the embodiments of the present application clearer, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0026] The term "comprising" and other equivalent descriptions involved in the specification and claims of this application are intended to cover non-exclusive inclusions, including both the contents clearly described in the specification and claims, and the steps or units that are not described in the specification and claims but are inherent in the product, method or structure.

[0027] The present application provides a passivated aluminum-lithium alloy powder, first, the original powder area inside, in which the pore structure formed by the gas phase preparation and the gas action can be seen; second, it is a darker dense layer, the layer structure is extremely tight, and there are almost no holes; third, it is the growth layer of the oxide film, which is thicker than the dense layer, and has obvious textures and holes on the surface. Overall, the thickness of the oxide film is about 1.3μm. The formed oxide deposits, on the one hand, can effectively prevent and isolate the influence of the external environment water vapor on the aluminum-lithium alloy, improve the antioxidant performance, ensure that the aluminum-lithium alloy is not corroded during storage, and have good compatibility with other components of the propellant; in addition, the oxide layer can form a good interface bonding force with the aluminum-lithium alloy matrix, which helps to maintain the overall integrity of the material at high temperatures. The enhancement of the interface bonding force can reduce the internal stress concentration and crack propagation of the material caused by temperature changes, thereby improving the thermal stability of the material.

[0028] The passivated aluminum-lithium alloy powder in this application has good compatibility with solid propellants. The material itself has a low density and good mechanical properties, which allows it to be used as a lightweight filling material in solid propellants and provide a certain strength support. In addition, the passivated aluminum-lithium alloy powder can better interact with other components in the propellant due to the change in surface properties without causing adverse chemical reactions. In addition to chemical stability, the passivated aluminum-lithium alloy powder can also maintain good physical property stability. For example, during the mixing, pressing and other processing processes, the powder is not prone to agglomeration, stratification and other phenomena.

[0029] The passivated aluminum-lithium alloy powder in this application participates in the combustion reaction more effectively, releases more energy, and thus significantly improves the combustion efficiency. This improvement is not only reflected in the sufficiency and uniformity of the combustion process, but also directly leads to the enhancement of thrust output and the improvement of fuel utilization. At the same time, due to more complete combustion, the generation of harmful emissions is also greatly reduced, which is of great significance for environmental protection and pollution reduction; in addition, the compatibility of the passivated aluminum-lithium alloy powder with solid propellant also brings about an improvement in the overall operating stability of the system. During the combustion process, the alloy powder can maintain stable physical and chemical properties, and is not prone to agglomeration, stratification, etc., thereby ensuring uniform combustion and stable output of the propellant. This improvement in stability is undoubtedly an important technological breakthrough for the development of high-tech fields such as rocket engines and missiles.

[0030] The aluminum-lithium alloy material described in the embodiment of the present application adopts a potassium dichromate passivation process to form two layers of dense protective films on the surface of the particles, and the specific steps are as follows:

[0031] Pretreatment of aluminum-lithium alloy particles: Screen out impurities from vacuum-stored aluminum-lithium alloy particles in a protective atmosphere, and select aluminum-lithium alloy particles with a particle size of 20 to 30 μm;

[0032] Preparation of passivation solution: Prepare 2-12g / 100ml potassium dichromate solution in a beaker and adjust the pH value to 4-6 with hydrochloric acid;

[0033] Passivation film formation: Stir in a magnetic stirrer at a speed of 8 to 10 for 30 to 45 minutes;

[0034] Curing and drying: The passivated powder is washed and filtered for thermal curing, and then dried in a drying oven for 4 hours;

[0035] Preparation of passivation solution: Prepare 3-10g / 100ml potassium dichromate solution in a beaker and adjust the pH value to 4-6 with hydrochloric acid;

[0036] Secondary passivation: Stir in a magnetic stirrer at a speed of 10 to 12 for 20 to 45 minutes;

[0037] The passivated powder was washed, filtered, thermally cured, and dried in a drying oven for 4 h.

[0038] Embodiment 1

[0039] like Figure 1 As shown, this embodiment provides an aluminum-lithium alloy material, including aluminum-lithium alloy particles 10 and an oxide film growth region 20 formed on the surface of the aluminum-lithium alloy particles 10, an oxide film 30 is formed on the surface of the aluminum film 20, a bonding interface is formed between the film 20 and the aluminum-lithium alloy particles 10, an atomic diffusion layer is formed at the bonding interface, and the average grain size of the grains in the aluminum film 10 is 30μm. Among the aluminum-lithium alloy particles, lithium accounts for 10.40wt% and aluminum accounts for 89.60wt%; the aluminum-lithium alloy material is prepared by the following method:

[0040] Pretreatment of aluminum-lithium alloy particles: screen out impurities from vacuum-stored aluminum-lithium alloy particles in an inert gas atmosphere, and select aluminum-lithium alloy particles with a particle size of 30 μm;

[0041] Preparation of passivation solution: Prepare 3g / 100ml potassium dichromate solution in a beaker and adjust the pH to 6 with hydrochloric acid;

[0042] Passivation film formation: Stir in a magnetic stirrer at a speed of 10 for 30 min;

[0043] Curing and drying: The passivated powder is washed and filtered for thermal curing, and then dried in a drying oven for 4 hours;

[0044] Preparation of passivation solution: Prepare 4g / 100ml potassium dichromate solution in a beaker and adjust the pH to 6 with hydrochloric acid;

[0045] Secondary passivation: Stir in a magnetic stirrer at gear 10 for 40 min;

[0046] The passivated powder was washed, filtered, thermally cured, and dried in a drying oven for 4 h.

[0047] The effect of aluminum-lithium alloy particles before and after passivation can be seen in Figure 2 and Figure 3 . Figure 2 This is the SEM image of the aluminum-lithium alloy particles in the original powder, which shows metallographic structures such as "grooves" and "channels". Figure 3 This is the SEM image of the aluminum-lithium alloy particles after passivation. It can be seen that they are completely coated and there is no metallographic structure of the original powder. Figure 4 This is a graph showing the thickness of the passivation film of aluminum-lithium alloy. It can be seen from the figure that the thickness of the passivation film is 1 to 1.5 μm.

Claims

1. A passivated aluminum-lithium alloy, characterized in that: From the inside to the outside, it includes an aluminum-lithium alloy core, a passivation layer growth film, and a passivation layer coating film in sequence; the total thickness of the passivation layer growth film and the passivation layer coating film is 1 to 1.5 μm.

2. The passivated aluminum-lithium alloy according to claim 1, characterized in that: The total mass of the passivation layer growth film and the passivation layer coating film is 3-5% of the mass of the aluminum-lithium alloy.

3. The passivated aluminum-lithium alloy according to claim 1, characterized in that: The aluminum content of the aluminum-lithium alloy is 90-95 wt.%, and the lithium content is 5-10 wt.%.

4. The method for preparing the passivated aluminum-lithium alloy according to claims 1 to 3, characterized in that: Potassium dichromate is used with a magnetic stirring machine to form an oxide coating on the surface of the aluminum-lithium alloy.

5. The preparation method according to claim 4, characterized in that: The method comprises the following steps: S1. Put the potassium dichromate and deionized water into a beaker to prepare a 2-12 g / 100 ml solution, and stir evenly in a magnetic stirrer. S2. Heat the magnetic stirrer to 20-40°C and maintain 20-40°C during stirring. S3: Ensure that the gear is 10-12, add 1-10g of aluminum-lithium alloy powder, and react for 20-45 minutes. S4. After the reaction, the powder is filtered and dried at 45-55°C for 4-5h. S5. Prepare 3-10g / 100ml potassium dichromate solution and stir evenly in a magnetic stirrer. S6. Heat the magnetic stirrer to 20-30°C and maintain 20-30°C during stirring. S7. Ensure that the aluminum-lithium alloy powder after passivation is added at the 10-12 gear, ultrasonically disperse for 10-20 seconds, and then passivate for 20-30 minutes. S8. Perform the second passivation by thermal curing in deionized water at 40-55°C.

6. The preparation method according to claim 5, characterized in that: In S1, potassium dichromate solution is used for reaction at a concentration of 2-12 g / 100 ml.

7. The preparation method according to claim 5, characterized in that: In S3, potassium dichromate solution is used, and the reaction is kept warm for 20 to 45 minutes at a level of 10 to 12.

8. A solid propellant, characterized in that: Its components include the passivated aluminum-lithium alloy as described in claims 1 to 3 or the passivated aluminum-lithium alloy prepared by the method as described in claims 4 to 8.

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