A kind of porous aluminum powder and preparation method thereof

Abstract

The present invention discloses a porous aluminum powder and a preparation method thereof, comprising the following steps: (1) removing the oxide film on the surface of the aluminum powder and dispersing it in water, adding a soluble iron salt, reacting in situ to form an Al-Fe bimetallic complex, separating the precipitate after the reaction, washing, and obtaining Al-Fe powder; (2) binding the Al-Fe powder to a conductive substrate through a magnetic field to form a powder anode, performing anodic electrolysis on the powder anode in a dilute acid electrolyte, and then collecting and washing the powder on the conductive substrate to obtain porous aluminum powder. The preparation method of the present invention is simple to operate, low in cost, pollution-free, and suitable for industrial production.

Description

Technical Field

[0001] The invention relates to the technical field of powder materials, and in particular to porous aluminum powder and a preparation method thereof. Background Art

[0002] Pigmented aluminum powder is favored by designers for its unique aesthetic design, corrosion resistance and metallic shiny effect. Due to its metallic luster and parallel characteristics to the coated object, in a coating containing clear paint and aluminum powder, the gloss and color depth of pigmented aluminum powder change with the incident angle and viewing angle of the incident light.

[0003] After years of development, the application scope of aluminum powder has become more and more extensive. Its main uses include industrial paints, automotive coatings, plastic granulation, architectural coatings and water-based inks.

[0004] Porous aluminum powder has a surface porous structure, and there is also a surface aluminum oxide layer in the pores. It has excellent thermal stability. Compared with ordinary aluminum powder, the porous characteristics make it easier to be colored by pigments and have higher color fastness.

[0005] A Chinese patent with publication number CN105647244A provides a method for preparing porous aluminum powder. The method mixes aluminum powder, a foaming agent and a loosening agent, then sintering the mixture, grinding it into powder to form porous aluminum powder for exterior wall coatings. Although the material has good application effects in terms of sound absorption after being mixed with loosening agents, carbonates and other substances, the method does not provide data to prove the porosity of aluminum powder particles.

[0006] The Chinese patent with publication number CN105033242A discloses a method for preparing active porous aluminum powder with specific surface area, which solves the problems of high cost, low yield and unsuitability for industrial production in the existing preparation of nano-aluminum. The steps are: under a hydrogen protection environment, add anhydrous aluminum chloride, iodine and halogenated hydrocarbons to ordinary aluminum powder for reaction, filter after the reaction to obtain low-activity nano-particle aluminum powder, continue to add sodium hydride, carry out semi-solid phase reaction, add tetrahydrofuran and stir to obtain liquid, and then add the liquid dropwise to a 90°C toluene solution. The obtained precipitate is the finished product. This method uses a variety of chemical reagents, has many steps, and uses chemical substances with high risk factors such as hydrogen and anhydrous aluminum chloride.

[0007] Currently, there is a lack of technology for preparing porous aluminum powder, and the existing methods for preparing porous aluminum powder have problems such as high cost, high pollution, and being unfavorable for industrial production. Summary of the invention

[0008] The invention provides a method for preparing porous aluminum powder. The preparation method is simple to operate, low in cost, pollution-free and suitable for industrial production.

[0009] The technical solution of the present invention is as follows:

[0010] A method for preparing porous aluminum powder comprises the following steps:

[0011] (1) removing the oxide film on the surface of aluminum powder and dispersing it in water, adding soluble iron salt, reacting in situ to form an Al-Fe bimetallic complex, separating the precipitate after the reaction, washing, and obtaining Al-Fe powder;

[0012] (2) Al-Fe powder is bound to a conductive substrate by a magnetic field to form a powder anode, and the powder anode is subjected to anodic electrolysis in a dilute acid electrolyte. The powder on the conductive substrate is then collected and cleaned to obtain porous aluminum powder.

[0013] The preparation method of the present invention belongs to the electrochemical anodization method, and its reaction mechanism is: first, the oxide film layer on the surface of the aluminum powder is removed, and then a soluble iron salt is added to in-situ deposit nano zero-valent iron on the surface of the aluminum powder through a replacement reaction to generate ferromagnetic Al-Fe powder; the Al-Fe powder is formed into a powder electrode, and then anodic electrolysis is performed in a dilute acid electrolyte, the Al-Fe powder undergoes anodic corrosion, the zero-valent iron on the surface of the aluminum powder is anodized into iron ions, and a porous structure is formed on the surface of the aluminum powder, thereby obtaining porous aluminum powder.

[0014] Preferably, the aluminum powder has a particle size of 10 μm-1 mm; more preferably, 10-75 μm.

[0015] In step (1), the mass ratio of aluminum powder to soluble iron salt is 2-8:1; more preferably 3-5:1; most preferably 4:1.

[0016] Step (1) comprises: dispersing aluminum powder in water, adding acid solution for stirring, adding water to cool the reaction system after bubbles are generated, and then adding soluble iron salt to generate Al-Fe bimetallic complex through replacement reaction, separating the precipitate after the reaction is completed, washing, and obtaining Al-Fe powder.

[0017] Preferably, in step (1), the acid solution is hydrochloric acid.

[0018] Preferably, in step (2), the conductive substrate is titanium or graphite.

[0019] Preferably, in step (2), the condition of the anode electrode is constant current 1A electrolysis for 2min-4h.

[0020] Preferably, in step (2), the dilute acid electrolyte is dilute sulfuric acid and / or oxalic acid solution.

[0021] Furthermore, the mass concentration of the dilute sulfuric acid is 5-20%; the concentration of oxalic acid is 2-5 mol / L.

[0022] Further preferably, when the electrolyte is dilute sulfuric acid with a mass concentration of 5-20%, electrolysis is performed at a constant current of 1A for 2-7 minutes; when the electrolyte is oxalic acid with a concentration of 2-5 mol / L, electrolysis is performed at a constant current of 1A for 1-4 hours.

[0023] Further preferably, when the aluminum powder particle size is 30-75 μm, the electrolyte is dilute sulfuric acid with a mass concentration of 5-20%, and the constant current is 1A for electrolysis for 2-7 min; when the aluminum powder particle size is 10-30 μm, the electrolyte is 2-5 mol / L oxalic acid, and the constant current is 1A for electrolysis for 1-4 h.

[0024] The invention also provides porous aluminum powder prepared by the above preparation method.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] The existing preparation conditions of porous aluminum powder are harsh. The present invention is an easy-to-operate pore-making process for anodized aluminum powder with strong applicability. The aluminum powder that cannot be used as an electrode is loaded with zero-valent iron powder in situ and then fixed on the current collecting carrier electrode by magnetic force to form an anode. A suitable electrolyte is selected to perform anodic electrolysis to form pores in the aluminum powder, thereby providing an economically feasible new method for the preparation of porous aluminum powder. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 This is a photo of the ferromagnetic Al-Fe powder synthesized in Example 1.

[0028] Figure 2 It is a powder anode loaded with zero-valent iron Al-Fe powder fixed by magnetic force.

[0029] Figure 3 This is a scanning electron microscope image of the synthesized ferromagnetic Al-Fe powder.

[0030] Figure 4 This is a low-magnification scanning electron microscope photograph of Al-Fe powder after anodic electrolysis (electrolysis in 10% dilute sulfuric acid electrolyte for 5 minutes).

[0031] Figure 5 This is a high-magnification scanning electron microscope photograph of Al-Fe powder after anodic electrolysis (electrolysis in 4 mol / L oxalic acid electrolyte for 120 min).

[0032] Figure 6 This is a scanning electron microscope photograph of Al-Fe powder after anodic electrolysis (electrolysis in 4 mol / L oxalic acid electrolyte for 120 min).

[0033] Figure 7 This is the XPS graph of the porous aluminum powder prepared in Example 2. DETAILED DESCRIPTION

[0034] Example 1

[0035] Take 5g aluminum powder (800 mesh) and place it in a 500mL beaker. First add 15mL water, then add 15mL concentrated hydrochloric acid (12mol / L) to remove the aluminum oxide film on the surface of the aluminum powder, stir, and when obvious bubbles are generated, add 15mL water again to cool the reaction system. Finally, add 5g FeCl3·6H2O to the reaction system for in-situ reaction to form Al-Fe bimetallic complex. After reacting for 15 minutes, use deionized water to wash the powder to obtain Al-Fe powder (product). The obtained Al-Fe powder is shown in the picture below. Figure 1 Scanning electron micrographs are shown in Figure 3 shown.

[0036] Furthermore, the Al-Fe powder is bound to the titanium sheet by a magnetic field to form a powder anode (such as Figure 2 As shown), and then anodic electrolysis (3min, constant current 1A) was performed in dilute sulfuric acid (10%) to obtain porous aluminum powder, as shown Figure 3 , Figure 4 As shown in Figure 2, after anodic electrolysis treatment, the surface of powdered aluminum presents regular nanoporous structure.

[0037] Example 2

[0038] Take 10g aluminum powder (200 mesh) and place it in a 1000mL beaker. First add 30mL of water, then add 30mL of concentrated hydrochloric acid (12mol / L) to remove the aluminum oxide film on the surface of the aluminum powder, stir, and when obvious bubbles are generated, add 30mL of water again to cool the reaction system. Finally, add 10g of FeCl3·6H2O to the reaction system for in-situ reaction to form an Al-Fe bimetallic complex. After reacting for 15min, the powder is washed with deionized water to obtain Al-Fe powder (product).

[0039] Furthermore, the Al-Fe powder was bound to the titanium sheet by a magnetic field to form a powder anode, and then anodic electrolysis was performed in oxalic acid (4 mol / L) (120 minutes, voltage 5 V) to obtain porous aluminum powder, such as Figure 5 shown.

[0040] Example 3

[0041] 5 g of aluminum powder was placed in a 1000 mL beaker, 30 mL of water was added first, and then 15 mL of concentrated hydrochloric acid (12 mol / L) was added to remove the aluminum oxide film on the surface of the aluminum powder. The mixture was stirred. When obvious bubbles were generated, 15 mL of water was added again to cool the reaction system. Finally, 5 g of FeCl3·6H2O was added to the reaction system for in-situ reaction to form an Al-Fe bimetallic complex. After reacting for 15 min, the powder was washed with deionized water to obtain Al-Fe powder (product).

[0042] Furthermore, the Al-Fe powder was bound to several titanium sheets by a magnetic field to form several powder anodes, and then anodic electrolysis was carried out in a dilute sulfuric acid electrolyte (5%-20%) (3-5 min, constant current 1 A) and oxalic acid (concentration 4 mol / L) (1-4 h, constant current 1 A) to obtain porous aluminum powder. The results are shown in Table 1.

[0043] Table 1 Specific surface area and average pore size of different aluminum powders after anodic electrolysis in different electrolytes

[0044]

[0045]

[0046] The present invention investigates the process of two representative aluminum powders being formed into porous by anodic electrolysis in different electrolytes. As can be seen from Table 1, aluminum powder can generate porous aluminum in both dilute sulfuric acid and concentrated acetic acid electrolytes. Large-scale aluminum powder (such as 200 mesh) has a slightly longer electrolysis time to generate porous aluminum, while small-scale aluminum powder (such as 800 mesh) has a relatively short electrolysis time. In oxalic acid electrolyte, the specific surface area of ​​800-mesh aluminum powder increases with the increase of electrolysis time, and it has a relatively small average pore size and good porosity. In sulfuric acid electrolyte, as the concentration of dilute sulfuric acid increases from 5% to 10%, the specific surface area of ​​200-mesh aluminum powder increases slightly after constant current 1A electrolysis for 5 minutes. When the sulfuric acid concentration is 15-20%, the specific surface area of ​​the aluminum powder after electrolysis decreases. Due to surface dissolution, the surface electrolysis micropores collapse, and the specific surface area becomes smaller. In sulfuric acid electrolysis, 800 mesh aluminum powder requires a shorter electrolytic pore-forming time (3 minutes). Similarly, when the sulfuric acid concentration is 15-20%, the specific surface area of ​​the aluminum powder after electrolysis decreases significantly. Due to the small particles, surface dissolution is more likely to occur, and the surface electrolytic micropores collapse.

[0047] The embodiments described above provide a detailed description of the technical solutions and beneficial effects of the present invention. It should be understood that the above are only specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, supplements and equivalent substitutions made within the scope of the principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for preparing porous aluminum powder, characterized in that: The following steps are involved: (1) removing the oxide film on the surface of aluminum powder and dispersing it in water, adding soluble iron salt, reacting in situ to form Al-Fe bimetallic complex, separating the precipitate after the reaction, washing, and obtaining Al-Fe powder; (2) Al-Fe powder is bound to a conductive substrate by a magnetic field to form a powder anode, the powder anode is subjected to anodic electrolysis in a dilute acid electrolyte, and then the powder on the conductive substrate is collected and cleaned to obtain porous aluminum powder; The dilute acid electrolyte is dilute sulfuric acid and / or oxalic acid solution; the mass concentration of the dilute sulfuric acid is 5-20%; the concentration of oxalic acid is 2-5 mol / L.

2. The method for preparing porous aluminum powder according to claim 1, characterized in that: The particle size of the aluminum powder is 10 μm-1 mm.

3. The method for preparing porous aluminum powder according to claim 1, characterized in that: In step (1), the mass ratio of aluminum powder to soluble iron salt is 2-8:

1.

4. The method for preparing porous aluminum powder according to claim 1, characterized in that: Step (1) comprises: dispersing aluminum powder in water, adding acid solution and stirring, adding water to cool the reaction system after bubbles are generated, and then adding soluble iron salt to generate Al-Fe bimetallic complex through replacement reaction, and separating the precipitate after the reaction is completed, washing, and obtaining Al-Fe powder.

5. The method for preparing porous aluminum powder according to claim 4, characterized in that: The acid solution is hydrochloric acid.

6. The method for preparing porous aluminum powder according to claim 1, characterized in that: In step (2), the conditions for anodic electrolysis are constant current 1A electrolysis for 2 min-4 h.

7. The method for preparing porous aluminum powder according to claim 1, characterized in that: When the aluminum powder particle size is 30-75μm, the electrolyte is dilute sulfuric acid with a mass concentration of 5-20%, and the constant current is 1A for electrolysis for 2-7min; when the aluminum powder particle size is 10-30μm, the electrolyte is 2-5mol / L oxalic acid, and the constant current is 1A for electrolysis for 1-4h.

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