Preparation process of dense and thickened oxide shell aluminum powder

Abstract

The present invention provides a process for preparing aluminum powder with a dense and thickened oxide shell, comprising the following steps: 1) de-molding and activating the aluminum powder; 2) adding a mixed solution containing an oxidant, an etchant, and a dispersant to the activated micron aluminum powder, with the volume ratio of aluminum powder to the mixed solution being 1:3 to 1:5, ultrasonically stirring the mixture, reacting for 1 to 3 hours, and filtering and washing; 3) vacuum drying and repeating step 2); 4) adding experimental water, bubbling CO2, ultrasonically stirring the mixture for 10 to 20 minutes, drying, and pyrolysis. This process achieves de-molding and activation of the oxide layer of high-purity micron aluminum powder. This process achieves dense and thickened oxide shells on high-purity micron aluminum powder (1-50 μm). The treated micron aluminum powder with an oxide shell is non-reactive in hot water, enabling non-hazardous use of the micron aluminum powder in certain production scenarios. The original sphericity and particle morphology of the micron aluminum powder are maintained.

Description

Technical Field

[0001] The invention relates to the technical field of metal surface treatment, and in particular to a preparation process of aluminum powder with dense and thickened oxide shell. Background Art

[0002] Micron-sized, high-purity aluminum powder is a highly reactive and flammable powder with active chemical properties. It reacts with water and oxygen at room temperature, generating hydrogen that combusts and explodes upon exposure to open flames. This property poses significant safety risks in certain industrial applications, particularly wet-process production, and also poses challenges in ensuring effective use. Existing methods for producing aluminum powder with an oxide shell primarily utilize oxidation of high-purity aluminum powder in air, oxidation by heating at a certain temperature (aluminum powder ignition point is 550°C), and reaction with oxygen and water. The first two processes form a thin oxide film on the surface of the aluminum powder particles, with a thickness ranging from a few to twenty nanometers for high-purity spherical aluminum powder ("Research on the Activity and Oxide Film Thickness of Micron-sized Aluminum Powder," published by Beijing Institute of Technology). The thinner the particle size, the thinner the oxide shell. This thin oxide film prevents further oxidation of the underlying aluminum. However, the thin and uneven oxide film prevents a dense, passivated surface layer, allowing chemical reactions to occur upon contact with water. The third process of reacting with oxygen and water has the problem of uneven thickness of the oxide shell, rough particle surface, leakage points, etc. due to the release of hydrogen and the influence of the original oxide film of the aluminum powder. Figure 2 In wet mixing processes, interference reactions can occur locally or across the entire system, leading to system instability and failure to achieve ideal passivation and performance. The present invention provides a process for preparing a dense, thickened oxide-shell aluminum powder. Due to the presence of a dense alumina ceramic layer, the aluminum powder is fully passivated to a large extent, resisting reaction with hot water. The powder's sphericity and activity performance indicators are largely maintained, addressing the non-hazardous use of aluminum powder in multiple industries. Summary of the Invention

[0003] The present invention aims to provide a process for preparing aluminum powder with a dense, thickened oxide shell. The processed micronized aluminum powder maintains its original sphericity while maintaining a uniform, dense, and leak-free oxide shell. It also resists hot water reaction, achieving breakthroughs in maintaining the dense, thickened oxide shell morphology and achieving passivation effects. This wet process can address the non-hazardous use of aluminum powder in multiple industries.

[0004] To achieve the above objectives, the present invention adopts the following technical solutions:

[0005] A process for preparing aluminum powder with a dense and thickened oxide shell layer comprises the following steps:

[0006] 1) Aluminum powder stripping and activation: The aluminum powder is a fine high-purity spherical aluminum powder with a size of 1 to 50 μm. The aluminum powder is added to a solution containing an etchant or a mixed solution of an etchant and a dispersant, and ultrasonically stirred for 10 to 30 minutes. The volume ratio of aluminum powder to solution is 1:3 to 1:5. The powder is fully filtered and washed to obtain activated fine spherical aluminum powder.

[0007] Aluminum powder with a size of more than 20 μm is mixed with an etchant solution, and the etchant mass concentration after mixing is 1% to 5%.

[0008] Aluminum powder with a size of no more than 20 μm is added to a mixed solution of an etchant and a dispersant, wherein the mass concentration of the etchant after mixing is 1% to 10%, and the mass concentration of the dispersant is 5-10‰.

[0009] 2) Preparation of Oxide Shell Aluminum Powder: Add a mixed solution containing an oxidant, an etchant, and a dispersant to the activated micronized aluminum powder, with the volume ratio of aluminum powder to the mixed solution being 1:3 to 1:5, and perform ultrasonic stirring, react for 1 to 3 hours, and then filter and wash thoroughly;

[0010] Ultrasonic stirring is as follows: aluminum powder not larger than 20μm is subjected to intermittent ultrasonic stirring, with the interval time being 5 to 10 minutes every 5 to 15 minutes; aluminum powder larger than 20μm is subjected to continuous ultrasonic stirring;

[0011] 3) drying the aluminum powder treated in step 2) under vacuum at a temperature of 70 to 200° C., cooling, and then adding the aluminum powder to a mixed solution containing an oxidant, an etchant, and a dispersant, and repeating the operation in step 2);

[0012] In the mixed solution, the mass concentration of the oxidant is 5-15%, the mass concentration of the etchant is 1-10%, and the mass concentration of the dispersant is 5-10‰.

[0013] The etchant is one or more of ammonium chloride solution, ammonium bifluoride solution, and ammonium fluorosilicate solution.

[0014] The dispersant is one or more of sodium pyrophosphate, trisodium phosphate, and tetrasodium phosphate.

[0015] The oxidant is one or more of sodium peroxide, potassium peroxide and benzoyl peroxide.

[0016] The vacuum drying conditions are 50-80°C, 1-2 hours; 80-100°C, 1-2 hours; 100-150°C, 1-2 hours; 150-200°C, 0.5-2 hours; vacuum pressure -0.03 to -0.08 MPa.

[0017] 4) The aluminum powder treated in step 3) is added to 3-4 times the volume of experimental water, CO2 is introduced, ultrasonic stirring is performed for 10-20 minutes, and then dried at 70-200°C and pyrolyzed at 450-500°C to obtain a dense oxide shell aluminum powder.

[0018] The drying conditions are 50-80°C, -0.02-0.08MPa, 3-6 hours; 80-100°C, 1-2 hours; 150-200°C, 1-2 hours; and the pyrolysis time is 2 hours.

[0019] The liquid used for filtration and washing in the present invention is pure water, and a special filtration device for powder is used, and the filtration and washing is performed for more than 5 times.

[0020] The chemicals used in the present invention are all analytically pure reagents.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] 1) Before preparing the oxide shell, the present invention performs de-molding and activation on the oxide layer on the surface of the high-purity micron aluminum powder to enhance the surface activity of the aluminum powder.

[0023] 2) The dense thickening of the oxide shell of high-purity aluminum powder with a grade of 1 to 50 μm was achieved, and the thickness of the oxide shell was 30 to 100 nm.

[0024] 3) A breakthrough has been achieved in the passivation effect. The treated micron-sized aluminum powder with oxide shell does not react in hot water, enabling the non-hazardous use of micron-sized aluminum powder in certain production scenarios.

[0025] 4) The original sphericity and particle morphology of micron aluminum powder are maintained.

[0026] 5) Improved the use of high-purity micron aluminum powder in the production of some industries. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 This is the original morphology of 10μm high-purity fine aluminum powder;

[0028] Figure 2 This is the morphology of the thickened oxide layer aluminum powder (10μm) produced by the reaction of aluminum powder with water and oxygen in the prior art;

[0029] Figure 3 This is a morphology image of the thickened oxide shell aluminum powder (2 μm) prepared in Example 1 of the present invention;

[0030] Figure 4 This is a morphology diagram of the thickened oxide shell aluminum powder (5 μm) prepared in Example 2 of the present invention. DETAILED DESCRIPTION

[0031] The invention will be described in detail below with reference to the accompanying drawings, but it should be noted that the implementation of the present invention is not limited to the following embodiments.

[0032] Example 1:

[0033] The aluminum powder is a 2 μm fine high-purity spherical aluminum powder. The preparation process of the dense and thickened oxide shell aluminum powder in the embodiment includes the following steps:

[0034] 1) Aluminum powder stripping and activation: Aluminum powder was added to a mixed solution containing an etchant and a dispersant, and ultrasonically stirred for 30 minutes. The volume ratio of aluminum powder to the mixed solution was 1:4. The mixture was fully filtered and washed to obtain activated fine spherical aluminum powder.

[0035] The mass concentration of the etchant is 4%, and the mass concentration of the dispersant is 10‰.

[0036] 2) Preparation of Oxide Shell Aluminum Powder: A mixed solution containing an oxidant, an etchant, and a dispersant was added to the activated micron aluminum powder, with the volume ratio of aluminum powder to the mixed solution being 1:4. Intermittent ultrasonic stirring was performed, with an interval of 5 minutes of ultrasonication every 15 minutes. The reaction was carried out for 3 hours, and the powder was thoroughly filtered and washed.

[0037] 3) Vacuum-dry the aluminum powder treated in step 2) at 70°C for 2 hours, 90°C for 2 hours, 120°C for 1 hour, and 160°C for 0.5 hours, using a vacuum pressure of -0.08 MPa. Cool the powder and add it to a mixed solution containing an oxidant, an etchant, and a dispersant, repeating step 2).

[0038] In the mixed solution, the mass concentration of the oxidant is 9%, the mass concentration of the etchant is 2%, and the mass concentration of the dispersant is 6‰;

[0039] The etchant used in this embodiment is ammonium chloride solution; the dispersant is sodium pyrophosphate; and the oxidant is sodium peroxide.

[0040] 4) The aluminum powder treated in step 3) was added to 3-4 times the volume of experimental water, CO2 was introduced, ultrasonic stirring was performed for 20 minutes, and then dried under the following conditions: 70°C, -0.02MPa, 4 hours; 95°C, 2 hours; 170°C, 1.5 hours; and pyrolysis was performed at a temperature of 450-500°C for 2 hours to obtain a dense oxide shell micron aluminum powder.

[0041] like Figure 3 As shown, the dense oxide shell micron aluminum powder prepared in this embodiment has an oxide shell thickness of 30-50 nm, an oxygen content of 2.0-3.6%, and an active aluminum content of 93-95%. The treated micron aluminum powder maintains the original powder sphericity, has a uniform and dense oxide shell, has no leaks, and does not react with hot water.

[0042] Example 2:

[0043] The aluminum powder is a 5 μm fine high-purity spherical aluminum powder. The preparation process of the dense and thickened oxide shell aluminum powder in the embodiment includes the following steps:

[0044] 1) Aluminum powder stripping and activation: Aluminum powder was added to a mixed solution containing an etchant and a dispersant, and ultrasonically stirred for 10 minutes. The volume ratio of aluminum powder to the mixed solution was 1:3.5. The mixture was fully filtered and washed to obtain activated fine spherical aluminum powder.

[0045] The mass concentration of the etchant is 3%, and the mass concentration of the dispersant is 6‰.

[0046] 2) Preparation of Oxide Shell Aluminum Powder: A mixed solution containing an oxidant, an etchant, and a dispersant was added to the activated micronized aluminum powder at a volume ratio of 1:3.5. Ultrasonic stirring was performed at intervals of 5 minutes for 10 minutes, and the reaction was continued for 1 hour. The mixture was then filtered and washed thoroughly.

[0047] 3) Vacuum-dry the aluminum powder treated in step 2) at 60°C for 2 hours, 80°C for 2 hours, 130°C for 1 hour, and 170°C for 1 hour, using a vacuum pressure of -0.06 MPa. Cool the powder and add it to a mixed solution containing an oxidant, an etchant, and a dispersant, repeating step 2).

[0048] In the mixed solution, the mass concentration of the oxidant is 5%, the mass concentration of the etchant is 3%, and the mass concentration of the dispersant is 8‰;

[0049] The etchant used in this embodiment is ammonium bifluoride; the dispersant is sodium pyrophosphate; and the oxidant is potassium peroxide.

[0050] 4) The aluminum powder treated in step 3) was added to 3-4 times the volume of experimental water, and CO2 was introduced. Ultrasonic stirring was performed for 10 minutes, followed by drying at 60°C, -0.06 MPa for 4 hours, 80°C for 2 hours, and 170°C for 1 hour. The powder was then pyrolyzed at 450-500°C for 2 hours to obtain a dense oxide-shelled micron aluminum powder.

[0051] like Figure 4 As shown, the dense oxide shell micron aluminum powder prepared in this embodiment has an oxide shell thickness of 30-70 nm, an oxygen content of 2.5-5%, and an active aluminum content of 93-96%. The treated micron aluminum powder maintains the original powder sphericity, has a uniform and dense oxide shell, has no leaks, and does not react with hot water.

[0052] Example 3:

[0053] The aluminum powder is a 25 μm fine high-purity spherical aluminum powder. The preparation process of the dense and thickened oxide shell aluminum powder in the embodiment includes the following steps:

[0054] 1) Aluminum powder stripping and activation: Add aluminum powder to a solution containing an etchant and stir ultrasonically for 15 minutes. The volume ratio of aluminum powder to solution is 1:4.5. Filter and wash thoroughly to obtain activated fine spherical aluminum powder.

[0055] The mass concentration of the etchant is 4.5%.

[0056] 2) Preparation of Oxide Shell Aluminum Powder: A mixed solution containing an oxidant, an etchant, and a dispersant was added to the activated micron aluminum powder, with the volume ratio of aluminum powder to the mixed solution being 1:4.5. The mixture was continuously ultrasonically stirred for 2 hours and filtered thoroughly.

[0057] 3) Vacuum-dry the aluminum powder treated in step 2) at 70°C for 1.5 hours, 90°C for 2 hours, 150°C for 1 hour, and 190°C for 2 hours, using a vacuum pressure of -0.04 MPa. Cool the powder and add it to a mixed solution containing an oxidant, an etchant, and a dispersant, repeating step 2).

[0058] In the mixed solution, the mass concentration of the oxidant is 10%, the mass concentration of the etchant is 4% and 1%, and the concentration of the dispersant is 5‰;

[0059] The etchants used in this embodiment are ammonium chloride and ammonium bifluoride; the dispersant is trisodium phosphate; and the oxidant is benzoyl peroxide.

[0060] 4) The aluminum powder treated in step 3) was added to 3-4 times the volume of experimental water, and CO2 was introduced. Ultrasonic stirring was performed for 15 minutes, followed by drying at 70°C, -0.04 MPa for 3 hours, 100°C for 1 hour, and 200°C for 1 hour. The powder was then pyrolyzed at 450-500°C for 2 hours to obtain a dense oxide-shelled micron aluminum powder.

[0061] The dense oxide shell micron aluminum powder prepared in this example has an oxide shell thickness of 50-100 nm, an oxygen content of 3-8%, and an active aluminum content of 91-96.5%. The treated micron aluminum powder maintains the original powder sphericity, has a uniform and dense oxide shell, has no leaks, and does not react with hot water.

[0062] The above description is only the basic principle of the patent of this invention and does not impose any limitation on the patent of this invention. Any equivalent changes and modifications based on the present invention are within the scope of the technical protection scheme of this patent.

Claims

1. A process for preparing a dense and thickened oxide shell aluminum powder, characterized in that: The following steps are involved: 1) Aluminum powder stripping and activation: Add aluminum powder to a solution containing an etchant or a mixed solution of an etchant and a dispersant, and stir ultrasonically for 10 to 30 minutes. The volume ratio of aluminum powder to solution is 1:4.5; or the volume ratio of aluminum powder to the mixed solution is 1:3.5 or 1:

4. Filter and wash thoroughly to obtain activated aluminum powder. 2) Preparation of aluminum powder with an oxide shell: Add a mixed solution containing an oxidant, an etchant, and a dispersant to activated aluminum powder in a volume ratio of 1:3 to 1:5, perform ultrasonic stirring, react for 1 to 3 hours, and filter and wash. 3) The aluminum powder treated in step 2) is vacuum dried at a temperature of 70-200°C, cooled, and then added to a mixed solution containing an oxidant, an etchant, and a dispersant, and the operation in step 2) is repeated; 4) Add 3-4 times the volume of experimental water to the aluminum powder treated in step 3), introduce CO2, and ultrasonically stir for 10-20 minutes. Then, dry at 70-200°C and pyrolyze at 450-500°C to obtain a dense and thickened oxide shell aluminum powder.

2. The process for preparing a dense and thickened oxide shell aluminum powder according to claim 1, characterized in that: The aluminum powder is fine high-purity spherical aluminum powder with a size of 1 to 50 μm.

3. The process for preparing a dense and thickened oxide shell aluminum powder according to claim 1, characterized in that: In the above step 1), aluminum powder larger than 20 μm is mixed with an etchant solution, and the etchant mass concentration after mixing is 1% to 5%; aluminum powder smaller than 20 μm is added to a mixed solution of an etchant and a dispersant, wherein the etchant mass concentration after mixing is 1% to 10%, and the dispersant mass concentration is 5-10‰.

4. The process for preparing a dense and thickened oxide shell aluminum powder according to claim 1, characterized in that: In the mixed solution in the above steps 2) and 3), the mass concentration of the oxidant is 5-15%, the mass concentration of the etchant is 1-10%, and the mass concentration of the dispersant is 5-10‰.

5. The process for preparing a dense and thickened oxide shell aluminum powder according to claim 1, characterized in that: The etchant is one or more of ammonium chloride, ammonium bifluoride, and ammonium fluorosilicate solution.

6. The process for preparing a dense and thickened oxide shell aluminum powder according to claim 1, characterized in that: The dispersant is one or more of sodium pyrophosphate, trisodium phosphate, and tetrasodium phosphate.

7. The process for preparing a dense and thickened oxide shell aluminum powder according to claim 1, characterized in that: The oxidant is one or more of sodium peroxide, potassium peroxide and benzoyl peroxide.

8. The process for preparing a dense and thickened oxide shell aluminum powder according to claim 1, characterized in that: The ultrasonic stirring in the above step 2) is as follows: aluminum powder smaller than 20 μm is subjected to intermittent ultrasonic stirring, with an interval of 5 to 10 minutes every 5 to 15 minutes; aluminum powder larger than 20 μm is subjected to continuous ultrasonic stirring.

9. The process for preparing a dense and thickened oxide shell aluminum powder according to claim 1, characterized in that: The drying conditions in step 3) are 50-80°C for 1-2 hours; 80-100°C for 1-2 hours; 100-150°C for 1-2 hours; 150-200°C for 0.5-2 hours; and a vacuum pressure of -0.03 to -0.08 MPa.

10. The process for preparing a dense and thickened oxide shell aluminum powder according to claim 1, characterized in that: The drying conditions in the above step 4) are 50-80°C, -0.02-0.08 MPa, 3-6 hours; 80-100°C, 1-2 hours; 150-200°C, 1-2 hours; and the pyrolysis time is 2 hours.

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