An efficient passivation process for aluminum-lithium alloys and the resulting high-stability powder

Abstract

The application discloses a kind of aluminum lithium alloy passivation methods, the passivation aluminum lithium alloy is successively included from inside to outside, aluminum lithium alloy core, passivation layer growth film, passivation layer coating film;The sum thickness of the passivation layer growth film and the passivation layer coating film film is 1~1.5 μm;Specifically using potassium dichromate, using magnetic stirrer, forms the passivation film on the surface of aluminum lithium alloy;Aluminum lithium alloy can be added into solid propellant after passivation of the application.The application forms dense passivation film on the surface of aluminum lithium alloy, effectively prevents and insulates the influence of external water vapor on aluminum lithium alloy, maintains the stability of aluminum lithium alloy during storage and use.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of metal powder material preparation, and particularly relates to a passivated aluminum-lithium alloy powder and a preparation method thereof. BACKGROUND

[0002] Rocket propellant is a substance that is ejected in the form of a fluid jet from a rocket engine in large quantities to generate thrust for propulsion, and is divided into liquid propellant and solid propellant. In the solid propellant, aluminum powder is usually used to provide combustion heat, so that the thrust of the rocket is higher. However, due to the presence of the surface oxide film, the aluminum powder is difficult to ignite, and when the propellant containing aluminum powder burns, due to the phenomena such as melting and agglomeration of aluminum powder particles on the combustion end face, incomplete combustion, etc., the actual specific impulse of the aluminum powder will have a certain loss. In order to improve the propelling efficiency and solve the problem of specific impulse loss of aluminum powder, the industry has begun to explore the use of aluminum-lithium alloy powder as a substitute material. However, the 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 is prone to oxidation or corrosion, thereby affecting its performance. Therefore, in order to maintain the stability and performance of the aluminum-lithium alloy powder during long-term use and storage, appropriate surface passivation treatment is required.

[0003] With the development of technology, the Chinese invention patent CN114589302 for passivation of aluminum-lithium alloy discloses a preparation method of heat-resistant liquid high-stability modified aluminum-lithium alloy powder, which uses amino silane and double-claw silane to modify the aluminum-lithium alloy, thereby obtaining aluminum-lithium alloy powder with high stability. The 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 an ammonium reagent to pretreat the aluminum-lithium alloy powder to reduce the high chemical activity of the surface of the aluminum-lithium alloy powder, and then uses a carboxylate to passivate the aluminum-lithium alloy powder. However, this type of method uses a large number of chemical reagents, and the low-surface-energy material is extremely unstable and is prone to failure in actual application.

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

[0005] The application aims to provide an improved passivated aluminum-lithium alloy and a preparation method thereof, and aims to solve the problems 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 preparation of the solid propellant.

[0006] To solve the above problems, the following steps are taken:

[0007] S1, the potassium dichromate, deionized water into a beaker, preparation 2-12g / 100ml solution, in a magnetic stirrer stirring uniform.

[0008] S2, the magnetic stirrer to 20-40℃, stirring process to keep 20-40℃.

[0009] S3, ensure that in the case of 10-12 gear, put in 1-10g aluminum lithium alloy powder, reaction 20-45min.

[0010] S4, after the reaction powder through suction filtration, 45-55℃ drying 4-5h.

[0011] S5, preparation 3-10g / 100ml of potassium dichromate solution, in a magnetic stirrer stirring uniform.

[0012] S6, the magnetic stirrer to 20-30℃, stirring process to keep 20-30℃.

[0013] S7, ensure that in the case of 10-12 gear, put in passivated aluminum lithium alloy powder, ultrasonic dispersion 10-20S, again passivation 20-30min.

[0014] S8, after the second passivation through in 40-55℃ deionized water heat curing.

[0015] Compared with the prior art, the beneficial effects of the present application are:

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

[0017] 2, the unique process combines secondary passivation, ultrasonic dispersion and heat curing to create alloy materials, overcome the caking problem and improve performance.

[0018] 3, the innovative passivation process for preparing aluminum lithium alloy solves the traditional defects, improves storage stability and overall performance.

[0019] The application will be further described in detail below in combination with the drawings and specific embodiments. BRIEF DESCRIPTION OF DRAWINGS

[0020] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed in the embodiment description will be briefly introduced. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.

[0021] Figure 1 The structure of the aluminum lithium alloy particles described in embodiment 1 of the present application is shown in the figure.

[0022] Figure 2 SEM image of unpassivated Al-Li alloy particles;

[0023] Figure 3 SEM image of Al-Li alloy particles described in Example 1 of the present application.

[0024] Figure 4 SEM image of Al-Li alloy particles passivated DETAILED DESCRIPTION

[0025] In order to make the objectives, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are some but not all of the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by a person of ordinary skill in the art without creative work fall within the protection scope of the present application.

[0026] The term "comprising" and other similar descriptions in the specification and claims of the present application are intended to cover the inclusions that are not exclusive, that is, both the contents explicitly 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 Al-Li alloy powder, which has three parts. The first part is the original powder region inside, in which the pore structure formed by the gas effect in the gas phase preparation can be seen. The second part is a dense layer with darker color, in which the structure is extremely tight and almost no pores exist. The third part is the growth layer of the oxide film, which has a larger thickness compared with the dense layer, and the surface has obvious texture and pores. Overall, the thickness of the oxide film is about 1.3 μm. The formed oxide deposit can effectively prevent and isolate the influence of external environmental water vapor on the Al-Li alloy, improve the oxidation resistance, ensure that the Al-Li alloy is not eroded during storage, and has good compatibility with other components of the propellant. In addition, the oxide layer can form a good interfacial bonding force with the Al-Li alloy substrate, which is helpful to maintain the overall integrity of the material at high temperature. The enhancement of the interfacial bonding force can reduce the stress concentration and crack propagation in the material caused by temperature change, thereby improving the thermal stability of the material.

[0028] The passivated aluminum-lithium alloy powder in this application exhibits good compatibility with solid propellants. The material itself possesses low density and good mechanical properties, enabling it to function as both a lightweight filler and provide structural strength in solid propellants. Furthermore, the altered surface properties of the passivated aluminum-lithium alloy powder allow for better interaction with other components in the propellant without triggering adverse chemical reactions. In addition to chemical stability, the passivated aluminum-lithium alloy powder also maintains good physical property stability. For example, during processing such as mixing and pressing, the powder is less prone to agglomeration or stratification.

[0029] The passivated aluminum-lithium alloy powder in this application participates in the combustion reaction more effectively, releasing more energy and thus significantly improving combustion efficiency. This improvement is not only reflected in the completeness and uniformity of the combustion process but also directly leads to enhanced thrust output and improved fuel utilization. Simultaneously, due to more complete combustion, the generation of harmful emissions is greatly reduced, which is of great significance for environmental protection and pollution reduction. Furthermore, the compatibility of the passivated aluminum-lithium alloy powder with solid propellants also improves the overall operational stability of the system. During combustion, the alloy powder maintains stable physical and chemical properties, and is less prone to agglomeration or stratification, thereby ensuring uniform combustion and stable output of the propellant. This improved stability undoubtedly represents a significant technological breakthrough for the development of high-tech fields such as rocket engines and missiles.

[0030] The aluminum-lithium alloy material described in this application uses a potassium dichromate passivation process to form two dense protective films on the particle surface. The specific steps are as follows:

[0031] Pretreatment of aluminum-lithium alloy particles: Impurities are removed from vacuum-stored aluminum-lithium alloy particles in a protective atmosphere, and aluminum-lithium alloy particles with a size of 20-30 μm are selected.

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

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

[0034] Curing and drying: The passivated powder is washed, filtered, heat-cured, and dried in a drying oven for 4 hours;

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

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

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

[0038] Example 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, and 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. The average grain size of the grains in the aluminum film 10 is 30 μm. The aluminum-lithium alloy particles contain 10.40 wt% lithium and 89.60 wt% aluminum. The aluminum-lithium alloy material is prepared by the following method:

[0040] Pretreatment of aluminum-lithium alloy particles: Impurities are removed from vacuum-stored aluminum-lithium alloy particles in an inert gas atmosphere, and aluminum-lithium alloy particles with a size of 30μm are selected.

[0041] Passivation solution preparation: Prepare a 3g / 100ml potassium dichromate solution in a beaker and adjust the pH to 6 using hydrochloric acid;

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

[0043] Curing and drying: The passivated powder is washed, filtered, heat-cured, and dried in a drying oven for 4 hours;

[0044] Passivation solution preparation: Prepare a 4g / 100ml potassium dichromate solution in a beaker and adjust the pH to 6 using hydrochloric acid;

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

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

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

Claims

1. A passivation process for aluminum-lithium alloy powder, characterized in that, The passivated aluminum-lithium alloy, from the inside out, comprises an aluminum-lithium alloy core, a passivation layer growth film, and a passivation layer coating film; the total thickness of the passivation layer growth film and the passivation layer coating film is 1-1.5 μm; the aluminum-lithium alloy powder passivation process includes the following steps: S1. Put potassium dichromate and deionized water into a beaker to prepare a 2-12 g / 100 ml potassium dichromate solution, and stir evenly in a magnetic stirrer. S2. Heat the magnetic stirrer to 20-40℃ and maintain the temperature at 20-40℃ during stirring. S3. With the magnetic stirrer set to 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℃ for 4-5 hours. S5. Prepare a potassium dichromate solution of 3-10g / 100ml and stir it evenly in a magnetic stirrer. S6. Heat the magnetic stirrer to 20-30℃ and maintain the temperature at 20-30℃ during stirring. S7. With the magnetic stirrer set to level 10-12, add the passivated aluminum-lithium alloy powder, ultrasonically disperse for 10-20 seconds, and then passivate for 20-30 minutes. S8. The aluminum-lithium alloy powder treated in S7 is thermally cured in deionized water at 40-55℃ to complete the second passivation.

2. The aluminum-lithium alloy powder passivation process as described in 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 aluminum-lithium alloy powder passivation process as described in claim 1, characterized in that, The aluminum-lithium alloy contains 90-95 wt.% aluminum and 5-10 wt.% lithium.

4. A solid propellant, characterized in that, Its components include passivated aluminum-lithium alloys obtained by any one of the processes described in claims 1 to 3.

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