A modified aluminum-lithium alloy fuel with excellent wet heat stability and compatibility and a preparation method thereof

Abstract

The present invention relates to a modified aluminum-lithium alloy fuel with excellent wet heat stability and compatibility and a preparation method thereof. The method comprises: 1) adding aluminum-lithium alloy powder to an ammonium reagent, stirring and dispersing, and obtaining a pre-treated powder after suction filtration and drying; 2) adding a carboxylate to an organic solvent for ultrasonic dispersion to obtain a carboxylate organic solution; 3) adding the pre-treated powder obtained in step 1) to the carboxylate organic solution obtained in step 2), stirring and reacting until the solvent is completely volatilized to form a carboxylate modified layer; and then vacuum drying to obtain a modified aluminum-lithium alloy powder. The modified aluminum-lithium alloy powder prepared by the present invention can maintain no obvious hydrogen evolution reaction for 3 hours under the condition of mechanical shear force added in hot water at 50 to 70°C, is well cured when applied to a solid propellant formulation, has a dense cross section and no pores, and significantly improves the stability of the aluminum-lithium alloy fuel in a high wet heat environment and the compatibility in the solid propellant under the premise of ensuring energy density.

Description

Technical Field

[0001] The invention relates to a method for modifying aluminum-lithium alloy powder, in particular to a modified aluminum-lithium alloy fuel with excellent wet-heat stability and compatibility and a preparation method thereof, belonging to the technical field of energetic materials. Background Art

[0002] Compared with Al, Li has low melting and boiling points, high calorific value of combustion (43.5kJ / g vs.31.4kJ / g) and chemical activity. Adding a small amount of Li to Al can not only greatly improve the reaction activity of Al and reduce its ignition temperature, but also change the structure and density of the surface oxide film, promote the further contact between the active metal inside the particles and the external oxidant, so that the Al-Li alloy powder burns faster and reacts more completely. When the propellant containing pure Al powder burns, due to the melting agglomeration of Al particles at the combustion end surface, incomplete combustion and two-phase flow loss, its actual specific impulse will be lost to a certain extent. Relevant scholars have found through theoretical calculations and experimental verification that using Al-Li alloy fuel instead of aluminum powder in solid propellants can not only significantly improve the specific impulse of the propellant, but also significantly reduce the HCl content in the combustion products of the chlorine-containing oxidant system, and reduce the corrosion of tail feather signals and launch site equipment. However, the addition of Li changes the dense structure of the surface oxide layer of the single Al particles. The oxidizing medium can diffuse inward through the surface oxide layer, resulting in continuous oxidation of the active metal inside the Al-Li alloy powder, which makes its wet heat stability and compatibility worse, affecting its application in the field of solid propellants and mixed explosives. Therefore, it is necessary to stabilize the aluminum-lithium alloy powder to improve its performance stability in storage and transportation and its processability in application.

[0003] Related studies have shown that by constructing a core-shell coating structure on the surface of active metal powders, it is possible to block air, moisture, etc. to maintain activity, and to functionally modify the surface. Chinese invention patent CN111500091A discloses a method for preparing a polyphenol compound / nitrogen-containing polymer coated micro-nano aluminum powder. The coating treatment not only improves the stability of aluminum powder in hot liquids, but also increases the active sites and oxidation efficiency of aluminum powder oxidation reactions, improves the burning rate of aluminum powder, and can improve the detonation performance of aluminum-containing explosives. Chinese invention patent CN111423293A discloses a fluorine-containing material for coating the surface of aluminum powder. The fluorine-containing material thermally decomposes during the reaction to release highly oxidizing fluorine-containing gas molecules that react with aluminum oxide to undergo a pre-ignition reaction, thinning or even removing the aluminum oxide shell layer, and improving the reaction efficiency of aluminum powder in explosive explosions.

[0004] However, the materials and technical solutions for surface passivation coating of aluminum powder are not suitable for aluminum-lithium alloy powder. After the surface coating of aluminum-lithium alloy powder is treated by the above method, the powder still undergoes obvious hydrogen evolution reaction in hot water or even room temperature water. In addition, the coating layer of aluminum-lithium alloy powder should have a strong interface bonding force with the powder to ensure that it does not break or fall off during the process. At the same time, the coating material must also have good compatibility with components such as nitrate esters and terminal hydroxyl polybutadiene in the propellant, so as not to affect the curing and mechanical properties of the propellant formula.

[0005] CN114539009A discloses a method for preparing a modified aluminum-lithium alloy powder with high stability and high compatibility, which comprises ultrasonically dispersing the aluminum-lithium alloy powder in an organic solvent to obtain an aluminum-lithium alloy powder dispersion; then adding alkyl methoxysilane and small molecule methoxysilane to the aluminum-lithium alloy powder dispersion, stirring and reacting at room temperature for 30 to 180 minutes, so that the two react by coupling on the surface of the aluminum-lithium alloy powder to form a dense copolymer coating layer; then filtering, washing, and vacuum drying to obtain the modified aluminum-lithium alloy powder. Although the modified aluminum-lithium alloy powder obtained by this method can stably exist in a high temperature and high humidity environment, the modified aluminum-lithium alloy powder needs to be kneaded into a drug in the later propellant, and mechanical stirring is inevitable. Mechanical stirring will have a strong shear force, which will destroy the integrity of the coating layer, so that the modified aluminum-lithium alloy powder obtained by this method cannot stably exist in the later propellant drug-making process.

[0006] In view of this, the present invention is proposed. Summary of the invention

[0007] In view of the application bottleneck problems of existing aluminum-lithium alloy powder, such as poor stability in wet and hot environment, easy oxidation and hydrogen evolution resulting in a significant decrease in activity, poor compatibility with common components of solid rocket propellant, and influence on propellant solidification and molding, the present invention provides a modified aluminum-lithium alloy fuel with excellent wet and hot stability and compatibility and a preparation method thereof, so as to obtain a modified aluminum-lithium alloy fuel with excellent wet and hot stability and compatibility at a low coating amount, and improve the application efficiency of aluminum-lithium alloy powder as a high-energy metal fuel in the field of solid rocket propellant and mixed explosive.

[0008] To achieve the above object, the present invention adopts the following technical solution:

[0009] A method for preparing a modified aluminum-lithium alloy powder having excellent wet heat stability and compatibility, the method comprising the following steps:

[0010] 1) adding aluminum-lithium alloy powder to an ammonium reagent, stirring and dispersing the powder, and filtering and drying the powder to obtain a pretreated powder;

[0011] 2) adding the carboxylate into an organic solvent and performing ultrasonic dispersion to obtain a carboxylate organic solution;

[0012] 3) adding the pretreated powder obtained in step 1) into the carboxylate organic solution obtained in step 2), stirring and reacting until the solvent is completely evaporated to form a carboxylate modified layer; then vacuum drying is performed to obtain a modified aluminum-lithium alloy powder.

[0013] The present invention adopts ammonium reagent to pretreat aluminum-lithium alloy powder to reduce the high chemical activity of the surface of the aluminum-lithium alloy powder, and then uses carboxylate to passivate the aluminum-lithium alloy powder. The prepared modified aluminum-lithium alloy powder can be kept in 50-70°C hot water with shear force for 3 hours without obvious hydrogen evolution reaction, is well cured when applied to solid propellant formulations, has a dense cross-section and is free of pores, and significantly improves the stability of aluminum-lithium alloy fuel in a high humidity and heat environment and the compatibility in solid propellants while ensuring energy density (mass combustion calorific value>31kJ / g).

[0014] Furthermore, in step 1), the stirring and dispersing time is 30 to 60 minutes.

[0015] Furthermore, in step 3), the stirring reaction is carried out at 55-65°C, preferably at 60°C.

[0016] Furthermore, the aluminum-lithium alloy powder is a spherical aluminum-lithium alloy powder. Preferably, the lithium content of the spherical aluminum-lithium alloy powder is 3%-8%, and the median diameter is 2-50 μm.

[0017] Furthermore, the mass ratio of the aluminum-lithium alloy powder described in step 1) to the carboxylate described in step 2) is 1:(0.005-0.03).

[0018] Furthermore, in step 1), the ammonium reagent is one of ammonium chloride, ammonium fluoride, ammonium iodide, ammonium sulfite, ammonium bicarbonate, ammonium acetate, ammonium sulfide, ammonium bisulfide or ammonium nitrate.

[0019] Furthermore, in step 2), the carboxylate is at least one of sodium tartrate, sodium oxalate, sodium malate, sodium citrate dihydrate, sodium benzoate or sodium salicylate.

[0020] Furthermore, in step 3), the organic solvent is one of petroleum ether, ethyl ether, ethyl acetate, acetone or N,N-dimethylformamide.

[0021] The present invention also provides a modified aluminum-lithium alloy powder having excellent wet heat stability and compatibility, wherein the modified aluminum-lithium alloy powder is prepared by the preparation method of the present invention.

[0022] Furthermore, the content of the carboxylate modified layer is ≤ 3.0% of the mass of the aluminum-lithium alloy powder.

[0023] Compared with the prior art, the present invention has the following advantages:

[0024] (1) The present invention uses an ammonium reagent 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 a carboxylate to passivate it. The prepared modified aluminum-lithium alloy powder can be kept in 50-70°C hot water with shear force for 3 hours without obvious hydrogen evolution reaction, and is well cured when applied to solid propellant formulations. The cross-section is dense and free of pores, and the stability of aluminum-lithium alloy fuel in a high humidity and heat environment and the compatibility in solid propellants are significantly improved while ensuring the energy density (mass combustion calorific value>31kJ / g);

[0025] (2) The modified aluminum-lithium alloy fuel preparation method provided by the present invention is simple, the process is stable and reliable, and the equipment investment is low. At the same time, the reagents and agents involved in the modification process are cheap and easy to obtain, and low-cost mass production can be easily achieved, which can provide strong support for the large-scale practical application of aluminum-lithium alloy fuel in solid propellants. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 Comparison of the stability of Al-5Li alloy powder in pure water before and after modification;

[0027] Figure 2 The quantitative hydrogen evolution test results of modified Al-5Li alloy powder;

[0028] Figure 3 This paper compares the curing effects of Al-5Li alloy powder before and after modification when used in a certain formula propellant. DETAILED DESCRIPTION

[0029] The following are specific embodiments of the present invention, and the embodiments are intended to further describe the present invention rather than to limit the present invention.

[0030] Example 1

[0031] 1) At room temperature, 20 g of Al-5Li alloy powder with a median diameter of 16 μm was added to 100 ml of a solution containing ammonium fluoride, and the mixture was mechanically stirred at 300 rpm for 30 min, and then filtered, and dried in a vacuum drying oven at 80° C. for 1 h to obtain a pretreated aluminum-lithium alloy powder;

[0032] 2) adding 0.16 g of sodium citrate dihydrate into 100 ml of ethyl acetate and performing ultrasonic dispersion for 5 min to obtain a carboxylate organic solution;

[0033] 3) The pretreated aluminum-lithium alloy powder obtained in step 1) is added to the carboxylate organic solution obtained in step 2), and mechanically stirred at 300 rpm in a 60°C water bath until the solvent is completely evaporated to form a carboxylate modified layer; then vacuum dried in a 70°C vacuum drying oven for 1.0 h to obtain a modified Al-5Li alloy powder, which is labeled AL-1.

[0034] It is calculated that the content of the carboxylate modified layer is 0.5 wt.% of the mass of the aluminum-lithium alloy powder.

[0035] Example 2

[0036] 1) At room temperature, 40 g of Al-5Li alloy powder with a median diameter of 28 μm was added to 200 ml of a solution containing ammonium fluoride, mechanically stirred at 300 rpm for 30 min, and then filtered, and dried in a vacuum drying oven at 80° C. for 1 h to obtain a pretreated aluminum-lithium alloy powder;

[0037] 2) adding 1.2 g of sodium oxalate into 200 ml of N,N-dimethylformamide and performing ultrasonic dispersion for 10 min to obtain a carboxylate organic solution;

[0038] 3) The pretreated aluminum-lithium alloy powder obtained in step 1) is added to the carboxylate organic solution obtained in step 2), and mechanically stirred at 300 rpm in a 70°C water bath until the solvent is completely evaporated to form a carboxylate modified layer; then vacuum dried in a 70°C vacuum drying oven for 1.0 h to obtain a modified Al-5Li alloy powder, which is labeled AL-2.

[0039] It is calculated that the content of the carboxylate modified layer is 2.5 wt.% of the mass of the aluminum-lithium alloy powder.

[0040] Example 3

[0041] 1) At room temperature, 100 g of Al-5Li alloy powder with a median diameter of 10 μm was added to 500 ml of a solution containing ammonium fluoride, and the mixture was mechanically stirred at 300 rpm for 60 min, and then filtered, and dried in a vacuum drying oven at 80° C. for 1 h to obtain a pretreated aluminum-lithium alloy powder;

[0042] 2) adding 1.0 g of sodium benzoate into 500 ml of ether and performing ultrasonic dispersion for 5 min to obtain a carboxylate organic solution;

[0043] 3) The pretreated aluminum-lithium alloy powder obtained in step 1) is added to the carboxylate organic solution obtained in step 2), and mechanically stirred at 250 rpm in a 60°C water bath until the solvent is completely evaporated to form a carboxylate modified layer; then vacuum dried in a 70°C vacuum drying oven for 1.5 hours to obtain a modified Al-5Li alloy powder, which is labeled AL-3.

[0044] It is calculated that the content of the carboxylate modified layer is 0.9 wt.% of the mass of the aluminum-lithium alloy powder.

[0045] Example 4

[0046] 1) At room temperature, 100 g of Al-5Li alloy powder with a lithium content of 3% and a median diameter of 2 μm was added to 500 ml of a solution containing ammonium chloride, and the mixture was mechanically stirred at 300 rpm for 60 min, and then filtered, and dried in a vacuum drying oven at 80° C. for 1 h to obtain a pretreated aluminum-lithium alloy powder;

[0047] 2) adding 1.0 g of sodium benzoate into 500 ml of ether and performing ultrasonic dispersion for 5 min to obtain a carboxylate organic solution;

[0048] 3) adding the pretreated aluminum-lithium alloy powder obtained in step 1) to the carboxylate organic solution obtained in step 2), and mechanically stirring at 250 rpm in a 55°C water bath until the solvent is completely evaporated to form a carboxylate modified layer; and then vacuum drying in a 70°C vacuum drying oven for 1.5 h to obtain a modified Al-5Li alloy powder.

[0049] It is calculated that the content of the carboxylate modified layer is 0.8 wt.% of the mass of the aluminum-lithium alloy powder.

[0050] Example 5

[0051] 1) At room temperature, 100 g of Al-5Li alloy powder with a lithium content of 8% and a median diameter of 50 μm was added to 500 ml of a solution containing ammonium iodide, mechanically stirred at a speed of 300 rpm for 60 min, then filtered, and dried in a vacuum drying oven at 80° C. for 1 h to obtain a pretreated aluminum-lithium alloy powder;

[0052] 2) adding 1.0 g of sodium benzoate into 500 ml of ether and performing ultrasonic dispersion for 5 min to obtain a carboxylate organic solution;

[0053] 3) adding the pretreated aluminum-lithium alloy powder obtained in step 1) to the carboxylate organic solution obtained in step 2), and mechanically stirring at 250 rpm in a 65°C water bath until the solvent is completely evaporated to form a carboxylate modified layer; and then vacuum drying in a 70°C vacuum drying oven for 1.5 h to obtain a modified Al-5Li alloy powder.

[0054] It is calculated that the content of the carboxylate modified layer is 0.85 wt.% of the mass of the aluminum-lithium alloy powder.

[0055] Example 6

[0056] 1) At room temperature, 100 g of Al-5Li alloy powder with a lithium content of 5% and a median diameter of 30 μm was added to 500 ml of a solution containing ammonium sulfite, and the mixture was mechanically stirred at 300 rpm for 60 min, and then filtered, and dried in a vacuum drying oven at 80° C. for 1 h to obtain a pretreated aluminum-lithium alloy powder;

[0057] 2) adding 1.0 g of sodium benzoate into 500 ml of ether and performing ultrasonic dispersion for 5 min to obtain a carboxylate organic solution;

[0058] 3) adding the pretreated aluminum-lithium alloy powder obtained in step 1) to the carboxylate organic solution obtained in step 2), and mechanically stirring at 250 rpm in a 58°C water bath until the solvent is completely evaporated to form a carboxylate modified layer; and then vacuum drying in a 70°C vacuum drying oven for 1.5 h to obtain a modified Al-5Li alloy powder.

[0059] It is calculated that the content of the carboxylate modified layer is 0.82 wt.% of the mass of the aluminum-lithium alloy powder.

[0060] Example 7

[0061] 1) At room temperature, 100 g of Al-5Li alloy powder with a lithium content of 6% and a median diameter of 15 μm was added to 500 ml of a solution containing ammonium bicarbonate, mechanically stirred at a speed of 300 rpm for 60 min, then filtered, and dried in a vacuum drying oven at 80° C. for 1 h to obtain a pretreated aluminum-lithium alloy powder;

[0062] 2) adding 1.0 g of sodium benzoate into 500 ml of ether and performing ultrasonic dispersion for 5 min to obtain a carboxylate organic solution;

[0063] 3) adding the pretreated aluminum-lithium alloy powder obtained in step 1) to the carboxylate organic solution obtained in step 2), and mechanically stirring at 250 rpm in a 62°C water bath until the solvent is completely evaporated to form a carboxylate modified layer; and then vacuum drying in a 70°C vacuum drying oven for 1.5 h to obtain a modified Al-5Li alloy powder.

[0064] It is calculated that the content of the carboxylate modified layer is 0.88 wt.% of the mass of the aluminum-lithium alloy powder.

[0065] Example 8

[0066] 1) At room temperature, 100 g of Al-5Li alloy powder with a lithium content of 6% and a median diameter of 35 μm was added to 500 ml of a solution containing ammonium acetate, mechanically stirred at a speed of 300 rpm for 60 min, and then filtered, and dried in a vacuum drying oven at 80° C. for 1 h to obtain a pretreated aluminum-lithium alloy powder;

[0067] 2) adding 1.0 g of sodium benzoate into 500 ml of ether and performing ultrasonic dispersion for 5 min to obtain a carboxylate organic solution;

[0068] 3) adding the pretreated aluminum-lithium alloy powder obtained in step 1) to the carboxylate organic solution obtained in step 2), and mechanically stirring at 250 rpm in a 60°C water bath until the solvent is completely evaporated to form a carboxylate modified layer; and then vacuum drying in a 70°C vacuum drying oven for 1.5 h to obtain a modified Al-5Li alloy powder.

[0069] It is calculated that the content of the carboxylate modified layer is 0.91 wt.% of the mass of the aluminum-lithium alloy powder.

[0070] Example 9

[0071] 1) At room temperature, 100 g of Al-5Li alloy powder with a lithium content of 4% and a median diameter of 8 μm was added to a 500 ml solution of ammonium sulfide, mechanically stirred at a speed of 300 rpm for 60 min, then filtered, and dried in a vacuum drying oven at 80° C. for 1 h to obtain a pretreated aluminum-lithium alloy powder;

[0072] 2) adding 1.0 g of sodium salicylate into 500 ml of ether and performing ultrasonic dispersion for 5 min to obtain a carboxylate organic solution;

[0073] 3) adding the pretreated aluminum-lithium alloy powder obtained in step 1) to the carboxylate organic solution obtained in step 2), and mechanically stirring at 250 rpm in a 60°C water bath until the solvent is completely evaporated to form a carboxylate modified layer; and then vacuum drying in a 70°C vacuum drying oven for 1.5 h to obtain a modified Al-5Li alloy powder.

[0074] It is calculated that the content of the carboxylate modified layer is 0.93 wt.% of the mass of the aluminum-lithium alloy powder.

[0075] Example 10

[0076] 1) At room temperature, 100 g of Al-5Li alloy powder with a lithium content of 7% and a median diameter of 20 μm was added to 500 ml of a solution containing ammonium hydrogen sulfide, mechanically stirred at a speed of 300 rpm for 60 min, then filtered, and dried in a vacuum drying oven at 80° C. for 1 h to obtain a pretreated aluminum-lithium alloy powder;

[0077] 2) adding 2 g of sodium malate into 500 ml of ether and performing ultrasonic dispersion for 5 min to obtain a carboxylate organic solution;

[0078] 3) adding the pretreated aluminum-lithium alloy powder obtained in step 1) to the carboxylate organic solution obtained in step 2), and mechanically stirring at 250 rpm in a 60°C water bath until the solvent is completely evaporated to form a carboxylate modified layer; and then vacuum drying in a 70°C vacuum drying oven for 1.5 h to obtain a modified Al-5Li alloy powder.

[0079] It is calculated that the content of the carboxylate modified layer is 0.93 wt.% of the mass of the aluminum-lithium alloy powder.

[0080] Embodiment 11

[0081] 1) At room temperature, 100 g of Al-5Li alloy powder with a lithium content of 5% and a median diameter of 18 μm was added to 500 ml of a solution containing ammonium nitrate, mechanically stirred at a speed of 300 rpm for 60 min, then filtered, and dried in a vacuum drying oven at 80° C. for 1 h to obtain a pretreated aluminum-lithium alloy powder;

[0082] 2) adding 0.5 g of sodium tartrate into 500 ml of petroleum ether and performing ultrasonic dispersion for 5 min to obtain a carboxylate organic solution;

[0083] 3) adding the pretreated aluminum-lithium alloy powder obtained in step 1) to the carboxylate organic solution obtained in step 2), and mechanically stirring at 250 rpm in a 60°C water bath until the solvent is completely evaporated to form a carboxylate modified layer; and then vacuum drying in a 70°C vacuum drying oven for 1.5 h to obtain a modified Al-5Li alloy powder.

[0084] It is calculated that the content of the carboxylate modified layer is 0.91 wt.% of the mass of the aluminum-lithium alloy powder.

[0085] Comparative Example 1

[0086] 1) At room temperature, 20 g of Al-5Li alloy powder with a median diameter of 16 μm was added to 100 ml of a solution containing ammonium fluoride, and the mixture was mechanically stirred at 300 rpm for 30 min at room temperature, and then filtered, and dried in a vacuum drying oven at 80° C. for 1 h to obtain a pretreated aluminum-lithium alloy powder;

[0087] 2) 0.6 g of phosphate was dissolved in 100 ml of petroleum ether, and the pretreated aluminum-lithium alloy powder was added to ethyl acetate and mechanically stirred at 300 rpm in a 60°C water bath until the solvent was completely evaporated, and then dried in a 100°C vacuum drying oven for 2.0 h to obtain a modified Al-5Li alloy fuel, which was marked as AT-1.

[0088] It is calculated that the content of the modified layer is 2.3wt.% of the mass of the aluminum-lithium alloy powder.

[0089] Test Example 1: Mass Combustion Heat Value Test

[0090] This test example examines the mass combustion calorific value of the modified Al-5Li alloy fuel prepared in the examples of the present invention and the comparative examples.

[0091] Test method: Accurately weigh 0.9-1.1g (accurate to 0.0002g) of the analytical sample in a crucible, gently place the crucible on the oxygen bomb stand, and connect the two ends to the electrode columns with ignition wires. The ignition wire needs to maintain good contact with the sample and cannot be in direct contact with the crucible; add 10ml of distilled water to the oxygen bomb, tighten the oxygen bomb cover, and use an oxygenator to slowly fill 3.0MPa of oxygen into the oxygen bomb. The oxygen filling time must not be less than 15s; then place the oxygen bomb in the inner cylinder, enter the sample mass, sulfur, hydrogen, moisture and other data, cover the upper cover, and click the test button to start the test; after the test, read the value and record it to complete the test.

[0092] The test results are shown in Table 1:

[0093] Table 1. Test results of mass combustion calorific value of Al-5Li alloy powder before and after modification

[0094] sample Mass combustion heat value (kJ / g) Al-5Li alloy powder raw material 31.09±0.23 Modified Al-5Li alloy powder (AL-1) 31.50±0.27 Modified Al-5Li alloy powder (AL-2) 31.16±0.19 Modified Al-5Li alloy powder (AL-3) 31.37±0.31 Modified Al-5Li alloy powder (AT-1) 29.28±0.26

[0095] The above results show that the mass calorific value of the Al-5Li alloy powder (AL-1, AL-2 and AL-3) modified by Examples 1-3 is at a comparable level with the original powder, and has not been significantly reduced, indicating that the modification process has well maintained the energy density of the Al-5Li alloy powder. However, the mass calorific value of the modified Al-5Li alloy powder (AT-1) obtained by the method of Comparative Example 1 is significantly lower than that of the original stone powder, indicating that the modification process of Comparative Example 1 cannot well maintain the energy density of the Al-5Li alloy powder.

[0096] Test Example 2: Stability Test

[0097] This test example investigates the stability of the modified Al-5Li alloy powders prepared in the examples of the present invention and the comparative examples.

[0098] 1. Stability test in pure water

[0099] Test method: Pour 1700ml pure water into a water bath and set the temperature to 70℃. When the temperature reaches 70℃, weigh 20g powder and 60g pure water and add them into a 250ml beaker. Place it in a 70℃ water bath and stir it mechanically at 200rpm for 180min. Observe the state of the powder, whether there is any reaction (a lot of bubbles), and whether the solution is clear.

[0100] The test results are shown in Figure 1 ,in, Figure 1 (a) and Figure 1(b) are the stability results of Al-5Li alloy powder without surface modification in pure water at room temperature (25°C) and hot water at 70°C, respectively. Figure 1 (c) is the stability result of the modified Al-5Li alloy powder (AL-1) of Example 1 in 70°C hot water.

[0101] like Figure 1 (a) and (b) show that the Al-5Li alloy powder without surface modification undergoes obvious hydrogen evolution reaction in pure water at room temperature (25°C), continuously produces bubbles, and the pure water quickly becomes turbid due to the reaction products; in hot water at 70°C, a violent oxidation hydrogen evolution reaction occurs, producing a large number of bubbles; Figure 1 (c) shows that after ammonium fluoride pretreatment and carboxylate passivation treatment, the Al-5Li alloy powder (AL-1) remained stable in 70°C hot water within 3.0 h, no visible bubbles were generated, and the aqueous solution remained clear and transparent, indicating that the modification treatment significantly improved the stability of the Al-5Li alloy powder in hot water.

[0102] 2. Quantitative hydrogen evolution test

[0103] Test method: Weigh 60g of distilled water and add it to a 250ml conical flask with a rotor, place it in a 2000ml beaker with 500ml pure water, and place it on a magnetic stirrer to heat it, and set the temperature to 70℃; take a 250ml measuring cylinder filled with water and invert it in a 1000ml beaker with 400ml pure water, and adjust its liquid level to the 0 scale line; when the temperature rises to 70℃, weigh 20g of powder and pour it into the conical flask and connect it to the lower end of the condenser, the outlet of the upper end of the condenser is sealed with a rubber plug with a glass tube, one end of the hose is connected to the glass tube, and the other end is passed into the inverted 250ml measuring cylinder and must not be higher than the liquid level; connect the condenser to the chiller, start the chiller, turn on the magnetic stirrer to start the test; after stabilization for 10 minutes, record the time and the reading of the measuring cylinder, and then record it every 30 minutes. After the required time or after an obvious reaction occurs (a lot of bubbles, the liquid level of the measuring cylinder drops rapidly), the test is ended. (For detailed diagram and details of the test device, please refer to the Chinese invention patent application "A test device and evaluation method for the anti-hydration performance of passivated aluminum powder" CN115791586A).

[0104] The test results are shown in Figure 2 ,in, Figure 2 (a) is the quantitative hydrogen evolution test result of the modified Al-5Li alloy powder (AL-1) of Example 1, Figure 2 (b) is the quantitative hydrogen evolution test result of the modified Al-5Li alloy powder (AT-1) of Comparative Example 1.

[0105] Figure 2The quantitative hydrogen evolution test results of (a) show that the Al-5Li alloy powder (AL-1) modified in Example 1 has no hydrogen evolution reaction within 3.0 h in 70°C hot water, showing excellent hot water oxidation resistance; Figure 2 The quantitative hydrogen evolution test results of (b) show that the Al-5Li alloy powder (AT-1) modified by Comparative Example 1 produces a large amount of hydrogen within 3.0 hours in 70°C hot water.

[0106] Test Example 3: Compatibility Test

[0107] This test example investigated the compatibility of Al-5Li alloy powder before and after modification.

[0108] Test method: Use a stirring paddle to mix the metal powder with liquid adhesive, plasticizer, oxidant and other components in a certain proportion, and then place the medicine column in an oven at 50-65℃ for molding and curing to form a medicine column.

[0109] The test results are shown in Figure 3 ,in, Figure 3 (a) shows the curing effect of Al-5Li alloy powder before modification in a certain formula propellant. Figure 3 (b) shows the curing effect of modified Al-5Li alloy powder (AL-1) in a certain formula propellant.

[0110] from Figure 3 (a) It can be seen that the propellant containing the original Al-5Li alloy powder contains obvious pores after solidification; Figure 3 (b) It can be seen that the modified Al-5Li alloy powder is used in the same formula propellant and the solidified cross-section is dense and defect-free, indicating that ammonium fluoride pretreatment and carboxylate passivation treatment significantly improve the compatibility of aluminum-lithium alloy fuel in solid propellants.

Claims

1. A method for preparing a modified aluminum-lithium alloy powder having excellent wet heat stability and compatibility, It is characterized in that The preparation method comprises the following steps: 1) adding aluminum-lithium alloy powder to an ammonium reagent, stirring and dispersing the powder, and filtering and drying the powder to obtain a pretreated powder; 2) adding the carboxylate into an organic solvent and performing ultrasonic dispersion to obtain a carboxylate organic solution; 3) adding the pretreated powder obtained in step 1) into the carboxylate organic solution obtained in step 2), stirring and reacting until the solvent is completely evaporated to form a carboxylate modified layer; then vacuum drying is performed to obtain a modified aluminum-lithium alloy powder.

2. The preparation method according to claim 1, It is characterized in that In step 1), the stirring and dispersing time is 30 to 60 minutes.

3. The preparation method according to claim 1, It is characterized in that In step 3), the stirring reaction temperature is 50-70°C.

4. The preparation method according to any one of claims 1 to 3, It is characterized in that The aluminum-lithium alloy powder is a spherical aluminum-lithium alloy powder, the lithium content of the spherical aluminum-lithium alloy powder is 3% to 8%, and the median diameter is 2 to 50 μm.

5. The preparation method according to any one of claims 1 to 3, It is characterized in that The mass ratio of the aluminum-lithium alloy powder described in step 1) to the carboxylate described in step 2) is 1:(0.005-0.03).

6. The preparation method according to any one of claims 1 to 3, It is characterized in that In step 1), the ammonium reagent is one of ammonium chloride, ammonium fluoride, ammonium iodide, ammonium sulfite, ammonium bicarbonate, ammonium acetate, ammonium sulfide, ammonium bisulfide or ammonium nitrate.

7. The preparation method according to any one of claims 1 to 3, It is characterized in that In step 2), the carboxylate is at least one of sodium tartrate, sodium oxalate, sodium malate, sodium citrate dihydrate, sodium benzoate or sodium salicylate.

8. The preparation method according to any one of claims 1 to 3, It is characterized in that In step 3), the organic solvent is one of petroleum ether, diethyl ether, ethyl acetate or N,N-dimethylformamide.

9. A modified aluminum-lithium alloy powder with excellent wet heat stability and compatibility, It is characterized in that The modified aluminum-lithium alloy powder is prepared by the preparation method described in any one of claims 1-8.

10. The modified aluminum-lithium alloy powder according to claim 9, It is characterized in that The content of the carboxylate modified layer is ≤ 3.0% of the mass of the aluminum-lithium alloy powder.

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