Porous aluminum ball and preparation method thereof

Abstract

The invention belongs to the technical field of porous materials, and particularly relates to a porous aluminum ball and a preparation method thereof.The method comprises the steps that hydrogen is charged into molten aluminum to be dissolved to reach a saturated state, the molten aluminum with the hydrogen dissolved to reach the saturated state drips in a preset size, and in the dripping process, air is blown to falling molten aluminum drops to cool the molten drops; and the temperature is reduced in the molten drop cooling process, so that hydrogen is separated out, and closed porous aluminum balls are obtained.

Description

Technical Field

[0001] This invention belongs to the field of porous materials technology, specifically a porous aluminum sphere and its preparation method. Background Technology

[0002] Porous aluminum materials possess many excellent properties, such as excellent sound absorption, reducing noise pollution; good thermal performance, serving as both insulation to reduce heat transfer and heat dissipation to improve equipment cooling efficiency; and lightweight, as aluminum has a low density and its porous structure further reduces its weight, making it easy to process and install, thus reducing the overall structural weight. However, porous aluminum (foamed aluminum) prepared using common methods often exhibits inconsistent pore sizes and the coexistence of closed and open pores, resulting in uneven density and pore distribution. This leads to inconsistent overall performance in practical applications, preventing the perfect realization of its superior sound and heat insulation properties.

[0003] Therefore, there is an urgent need to design a method for preparing porous aluminum spheres to obtain porous aluminum spheres with controllable pore size and closed pores. Summary of the Invention

[0004] To obtain porous aluminum materials with controllable pore size and closed pores, this invention provides a porous aluminum sphere and its preparation method. The method involves filling molten aluminum with hydrogen gas until it reaches saturation, then dripping the saturated aluminum molten aluminum into a predetermined size droplet. During the dripping process, the falling aluminum molten droplet is cooled by blowing gas, and the temperature decreases during the cooling process, causing hydrogen gas to be released, thus obtaining a closed-pore porous aluminum sphere.

[0005] A method for preparing porous aluminum spheres includes the following steps: S1. Melt the aluminum raw material to a molten state to obtain the first aluminum liquid; S2. Expose the first molten aluminum to hydrogen gas, so that the hydrogen gas dissolves in the first molten aluminum to obtain a second molten aluminum; S3. The second aluminum liquid is dripped into a predetermined size, and nitrogen gas with a temperature of -20~20℃ and a flow rate of 20~40m / s is blown onto the droplets formed by the dripping of the second aluminum liquid to cool the droplets. During the cooling process, the temperature of the droplets decreases, causing hydrogen gas to be released, and porous aluminum spheres are obtained.

[0006] In a preferred embodiment of the method for preparing porous aluminum spheres according to the present invention, in step S3, the second aluminum liquid is dripped at a preset size using a perforated mold, wherein the perforation diameter of the perforated mold is 50~150mm.

[0007] In a preferred embodiment of the method for preparing porous aluminum spheres according to the present invention, in step S3, the direction of the nitrogen gas blown toward the molten droplet is the first direction, the direction of the second aluminum liquid droplet is the second direction, the second direction is the vertical direction, and the angle between the first direction and the second direction is 45°~135°.

[0008] In a preferred embodiment of the method for preparing porous aluminum spheres according to the present invention, in step S1, the aluminum raw material is pure aluminum or an aluminum alloy.

[0009] In a preferred embodiment of the method for preparing porous aluminum spheres according to the present invention, in step S1, the aluminum raw material is melted to a molten state in an inert atmosphere or vacuum to obtain a first aluminum liquid.

[0010] In a preferred embodiment of the method for preparing porous aluminum spheres according to the present invention, the melting temperature in step S1 is 680~750℃; step S1 further includes: continuously stirring the first aluminum liquid.

[0011] In a preferred embodiment of the method for preparing porous aluminum spheres according to the present invention, in step S2, the first aluminum liquid is exposed to hydrogen gas, and the hydrogen gas dissolves in the first aluminum liquid and reaches a saturated state to obtain the second aluminum liquid.

[0012] In a preferred embodiment of the method for preparing porous aluminum spheres according to the present invention, in step S3, pressure is applied to the second molten aluminum to accelerate the dripping of the second molten aluminum.

[0013] To solve the above-mentioned technical problems, according to another aspect of the present invention, the present invention provides the following technical solution: A porous aluminum sphere is obtained by the above-mentioned method for preparing a porous aluminum sphere.

[0014] As a preferred embodiment of the porous aluminum ball of the present invention, the porous aluminum ball is a closed-cell porous aluminum ball, the diameter of the porous aluminum ball is 3~170mm, and the pore size of the porous aluminum ball is 1.5~50mm.

[0015] The beneficial effects of this invention are as follows: This invention proposes a porous aluminum sphere and its preparation method. Hydrogen gas is introduced into molten aluminum and dissolved until saturation. The saturated aluminum is then dripped into a predetermined size. During the dripping process, nitrogen is blown onto the falling droplets to cool them. The temperature decreases during cooling, causing hydrogen to precipitate, resulting in closed-cell porous aluminum spheres. The hydrogen precipitation rate can be controlled by adjusting the nitrogen blowing temperature and rate, thus obtaining closed-cell porous aluminum spheres with different diameters and / or pore sizes. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0017] Figure 1 The porous aluminum sphere prepared by the present invention and its preparation method; Figure 2 This is a cross-sectional view of a porous aluminum sphere prepared by the porous aluminum sphere and its preparation method according to the present invention.

[0018] The realization of the objective, functional features and advantages of the present invention will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0019] The technical solutions described below in conjunction with the embodiments will be clearly and completely described. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0020] The present invention involves filling molten aluminum with hydrogen gas until it is saturated, then dropping the saturated aluminum into droplets of a predetermined size. During the dropping process, the falling aluminum droplets are cooled by blowing air, and the temperature decreases during the cooling process, causing hydrogen gas to be released, thus obtaining closed-cell porous aluminum spheres.

[0021] According to one aspect of the present invention, the present invention provides the following technical solution: A method for preparing porous aluminum spheres includes the following steps: S1. Melt the aluminum raw material to a molten state to obtain the first aluminum liquid; In an embodiment of the present invention, aluminum raw material is added to a melting chamber and melted under a nitrogen atmosphere to obtain a first aluminum liquid. The melting temperature is 680~750℃. The first aluminum liquid is stirred during melting to ensure its fluidity.

[0022] S2. Expose the first molten aluminum to hydrogen gas, so that the hydrogen gas dissolves in the first molten aluminum to obtain a second molten aluminum; In an embodiment of the present invention, hydrogen gas is uniformly injected into the melting chamber through a multi-hole nozzle, so that the hydrogen gas dissolves in the first aluminum liquid until saturation is reached, thereby obtaining the second aluminum liquid.

[0023] S3. The second molten aluminum is dripped into a predetermined size, and nitrogen gas at a temperature of -20~20℃ and a flow rate of 20~40m / s is blown onto the droplets formed by the dripping of the second molten aluminum. The droplets are cooled, and during the cooling process, the temperature of the droplets decreases, causing hydrogen gas to be released, resulting in porous aluminum spheres, such as... Figure 1 As shown; a cross-sectional view of the porous aluminum sphere is shown below. Figure 2 As shown.

[0024] In an embodiment of the invention, the discharge hole (50-150mm in diameter) at the bottom of the melting chamber is opened, and hydrogen is continuously introduced to increase the pressure in the melting chamber. The pressure generated by the excess hydrogen gas injected into the melting chamber is used to discharge the molten aluminum into the cooling chamber. The cooling chamber maintains a nitrogen atmosphere, and nitrogen gas at -20 to 20°C is blown out through the blowing pipe at a speed of 20-40m / s, causing the molten aluminum to disperse and fall. At the same time, due to the decrease in temperature, the solubility of hydrogen in the molten aluminum decreases, and hydrogen is precipitated and forms porous aluminum spheres.

[0025] Preferably, in step S3, the blowing temperature is -20~20℃. Specifically, the blowing temperature can be, for example, but not limited to, any one of -20℃, -10℃, 0℃, 10℃, 20℃, or a range between two of them.

[0026] Furthermore, the blowing temperature is within the range of -20~20℃, and the lower the temperature, the larger the diameter of the porous aluminum spheres obtained after cooling.

[0027] Preferably, in step S3, the blowing rate is 20~40m / s. Specifically, the blowing rate can be, for example, but not limited to, any one of 20m / s, 25m / s, 30m / s, 35m / s, 40m / s, or a range between two of them.

[0028] Preferably, in step S3, the second molten aluminum is dripped at a preset size using a perforated mold, wherein the diameter of the perforated mold is 50-150 mm. Specifically, the diameter can be, for example, but not limited to, any one or a range between 50 mm, 75 mm, 100 mm, 125 mm, and 150 mm.

[0029] Furthermore, the perforated mold can be a perforated base plate, disposed between the melting chamber and the cooling chamber. The melting chamber is the place where aluminum raw materials are melted to a molten state and hydrogen is dissolved. The cooling chamber is the place where molten droplets dripping from the melting chamber from the perforated base plate are cooled and recovered. The perforated base plate is provided with a switchable drip hole, through which the second molten aluminum can drip from the melting chamber into the cooling chamber.

[0030] Preferably, in step S3, the direction of the nitrogen gas blown towards the molten droplet is the first direction, the direction of the second aluminum liquid droplet falling is the second direction, the second direction is a vertical direction, and the angle between the first direction and the second direction is 45°~135°. Specifically, the angle between the first direction and the second direction can be, for example, but not limited to, any one of 45°, 60°, 90°, 120°, and 135° or a range between two of them.

[0031] Preferably, in step S1, the aluminum raw material is pure aluminum or an aluminum alloy.

[0032] Preferably, in step S1, the aluminum raw material is melted to a molten state in an inert atmosphere or vacuum to obtain the first aluminum liquid.

[0033] Preferably, in step S1, the melting temperature is 680~750℃, and step S1 further includes: maintaining stirring of the first molten aluminum. Specifically, the melting temperature can be, for example, but not limited to, any one or a range between 680℃, 700℃, 720℃, 740℃, and 750℃.

[0034] Furthermore, the stirring is to maintain the fluidity of the first molten aluminum.

[0035] Preferably, in step S2, the first molten aluminum is exposed to hydrogen gas, and the hydrogen gas dissolves in the first molten aluminum to reach saturation, thereby obtaining the second molten aluminum.

[0036] Preferably, in step S3, pressure is applied to the second molten aluminum to accelerate its dripping.

[0037] According to another aspect of the present invention, the present invention provides the following technical solution: A porous aluminum sphere is obtained by the above-mentioned method for preparing a porous aluminum sphere.

[0038] Preferably, the porous aluminum sphere is a closed-cell porous aluminum sphere, and the diameter of the porous aluminum sphere is 3~170mm. Specifically, the diameter of the porous aluminum sphere can be, for example, but not limited to, any one or a range between two of 3mm, 10mm, 50mm, 90mm, 110mm, 130mm, 160mm, and 170mm.

[0039] Preferably, the pore size of the porous aluminum sphere is 1.5~50mm. Specifically, the pore size of the porous aluminum sphere can be, for example, but not limited to, any one or a range between 1.5mm, 10mm, 20mm, 30mm, 40mm, and 50mm.

[0040] The technical solution of the present invention will be further described below with reference to specific embodiments.

[0041] Example 1 1000 kg of pure aluminum was added to the melting chamber and melted under a nitrogen atmosphere to obtain molten aluminum liquid at a melting temperature of 680℃. While melting, the molten aluminum is stirred to maintain its fluidity. Hydrogen is injected evenly into the melting chamber through a multi-hole nozzle, allowing the hydrogen to dissolve in the molten aluminum until saturation is achieved. Open the discharge hole (50mm diameter) at the bottom of the melting chamber and continue to introduce hydrogen gas to increase the pressure in the melting chamber. Use the pressure generated by the excess hydrogen gas injected into the melting chamber to discharge the molten aluminum into the cooling chamber. The cooling chamber maintains a nitrogen atmosphere, and nitrogen gas at -20°C is blown out at a speed of 20 m / s through the blowing pipe, causing the molten aluminum to disperse and fall. At the same time, due to the decrease in temperature, the solubility of hydrogen in the molten aluminum decreases, and hydrogen gas is released and forms porous aluminum spheres. 81% of these spheres have a diameter of 40~45 mm and an average pore size of 16.2 mm.

[0042] Example 2 1000 kg of pure aluminum was added to the melting chamber and melted under a nitrogen atmosphere to obtain molten aluminum liquid at a melting temperature of 720℃. While melting, the molten aluminum is stirred to maintain its fluidity. Hydrogen is injected evenly into the melting chamber through a multi-hole nozzle, allowing the hydrogen to dissolve in the molten aluminum until saturation is achieved. Open the discharge hole (50mm diameter) at the bottom of the melting chamber and continue to introduce hydrogen gas to increase the pressure in the melting chamber. Use the pressure generated by the excess hydrogen gas injected into the melting chamber to discharge the molten aluminum into the cooling chamber. The cooling chamber maintains a nitrogen atmosphere, and nitrogen gas at 0°C is blown out at a speed of 20 m / s through the blowing pipe, causing the molten aluminum to disperse and fall. At the same time, due to the decrease in temperature, the solubility of hydrogen in the molten aluminum decreases, and hydrogen gas is released and forms porous aluminum spheres. 81% of these spheres have a diameter of 40~45 mm and an average pore size of 8.37 mm.

[0043] Example 3 1000 kg of pure aluminum was added to the melting chamber and melted under a nitrogen atmosphere to obtain molten aluminum liquid at a melting temperature of 750℃. While melting, the molten aluminum is stirred to maintain its fluidity. Hydrogen is injected evenly into the melting chamber through a multi-hole nozzle, allowing the hydrogen to dissolve in the molten aluminum until saturation is reached. Hydrogen is then continued to be introduced to increase the pressure in the melting chamber. Open the discharge hole (50mm diameter) at the bottom of the melting chamber and continue to introduce hydrogen gas to increase the pressure in the melting chamber. Use the pressure generated by the excess hydrogen gas injected into the melting chamber to discharge the molten aluminum into the cooling chamber. The cooling chamber maintains a nitrogen atmosphere, and nitrogen gas at 20°C is blown out at a speed of 20 m / s through the blowing pipe, causing the molten aluminum to disperse and fall. At the same time, due to the decrease in temperature, the solubility of hydrogen in the molten aluminum decreases, and hydrogen gas is released and forms porous aluminum spheres. The proportion of these spheres with a diameter of 39~44 mm is 81%, and the average pore size is 2.43 mm.

[0044] Example 4 1000 kg of pure aluminum was added to the melting chamber and melted under a nitrogen atmosphere to obtain molten aluminum liquid at a melting temperature of 680℃. While melting, the molten aluminum is stirred to maintain its fluidity. Hydrogen is injected evenly into the melting chamber through a multi-hole nozzle, allowing the hydrogen to dissolve in the molten aluminum until saturation is achieved. Open the discharge hole (50mm diameter) at the bottom of the melting chamber and continue to introduce hydrogen gas to increase the pressure in the melting chamber. Use the pressure generated by the excess hydrogen gas injected into the melting chamber to discharge the molten aluminum into the cooling chamber. The cooling chamber maintains a nitrogen atmosphere, and nitrogen gas at -20°C is blown out at a speed of 30 m / s through the blowing pipe, causing the molten aluminum to disperse and fall. At the same time, due to the decrease in temperature, the solubility of hydrogen in the molten aluminum decreases, and hydrogen gas is released and forms porous aluminum spheres, of which 85% have a diameter of 30~38 mm and an average pore size of 14.4 mm.

[0045] Example 5 1000 kg of pure aluminum was added to the melting chamber and melted under a nitrogen atmosphere to obtain molten aluminum liquid at a melting temperature of 680℃. While melting, the molten aluminum is stirred to maintain its fluidity. Hydrogen is injected evenly into the melting chamber through a multi-hole nozzle, allowing the hydrogen to dissolve in the molten aluminum until saturation is achieved. Open the discharge hole (50mm diameter) at the bottom of the melting chamber and continue to introduce hydrogen gas to increase the pressure in the melting chamber. Use the pressure generated by the excess hydrogen gas injected into the melting chamber to discharge the molten aluminum into the cooling chamber. The cooling chamber maintains a nitrogen atmosphere, and nitrogen gas at -20°C is blown out at a speed of 40 m / s through the blowing pipe, causing the molten aluminum to disperse and fall. At the same time, due to the decrease in temperature, the solubility of hydrogen in the molten aluminum decreases, and hydrogen gas is released and forms porous aluminum spheres. The proportion of these spheres with a diameter of 15~21 mm is 89%, and the average pore size is 12.0 mm.

[0046] Example 6 1000 kg of pure aluminum was added to the melting chamber and melted under a nitrogen atmosphere to obtain molten aluminum liquid at a melting temperature of 680℃. While melting, the molten aluminum is stirred to maintain its fluidity. Hydrogen is injected evenly into the melting chamber through a multi-hole nozzle, allowing the hydrogen to dissolve in the molten aluminum until saturation is achieved. Open the discharge hole (80mm diameter) at the bottom of the melting chamber and continue to introduce hydrogen gas to increase the pressure in the melting chamber. Use the pressure generated by the excess hydrogen gas injected into the melting chamber to discharge the molten aluminum into the cooling chamber. The cooling chamber maintains a nitrogen atmosphere, and nitrogen gas at -20°C is blown out at a speed of 20 m / s through the blowing pipe, causing the molten aluminum to disperse and fall. At the same time, due to the decrease in temperature, the solubility of hydrogen in the molten aluminum decreases, and hydrogen gas is released and forms porous aluminum spheres. 74% of these spheres have a diameter of 60~72 mm and an average pore size of 25.1 mm.

[0047] Example 7 1000 kg of pure aluminum was added to the melting chamber and melted under a nitrogen atmosphere to obtain molten aluminum liquid at a melting temperature of 680℃. While melting, the molten aluminum is stirred to maintain its fluidity. Hydrogen is injected evenly into the melting chamber through a multi-hole nozzle, allowing the hydrogen to dissolve in the molten aluminum until saturation is achieved. Open the discharge hole (150mm diameter) at the bottom of the melting chamber and continue to introduce hydrogen gas to increase the pressure in the melting chamber. Use the pressure generated by the excess hydrogen gas injected into the melting chamber to discharge the molten aluminum into the cooling chamber. The cooling chamber maintains a nitrogen atmosphere, and nitrogen gas at -20°C is blown out at a speed of 20 m / s through the blowing pipe, causing the molten aluminum to disperse and fall. At the same time, due to the decrease in temperature, the solubility of hydrogen in the molten aluminum decreases, and hydrogen gas is released and forms porous aluminum spheres. The proportion of these spheres with a diameter of 118~126 mm is 68%, and the average pore size is 47.0 mm.

[0048] Comparative Example 1 1000 kg of pure aluminum was added to the melting chamber and melted under a nitrogen atmosphere to obtain molten aluminum liquid at a melting temperature of 680℃. While melting, the molten aluminum is stirred to maintain its fluidity. Hydrogen is injected evenly into the melting chamber through a multi-hole nozzle, allowing the hydrogen to dissolve in the molten aluminum until saturation is achieved. Open the discharge hole (50mm diameter) at the bottom of the melting chamber and continue to introduce hydrogen gas to increase the pressure in the melting chamber. Use the pressure generated by the excess hydrogen gas injected into the melting chamber to discharge the molten aluminum into the cooling chamber. The cooling chamber maintains a nitrogen atmosphere, and -25°C nitrogen gas is blown out at a speed of 20 m / s through the blowing pipe, causing the molten aluminum to disperse and fall. At the same time, due to the decrease in temperature, the solubility of hydrogen in the molten aluminum decreases, and hydrogen gas is released and forms porous aluminum spheres. 88% of these spheres have a diameter of 40~45 mm, with an average pore size of 20 mm. However, due to the excessively low blowing temperature and the excessively fast cooling rate, the hydrogen gas dissipates rapidly, and the surface of the aluminum spheres is basically covered by holes with incomplete pore shapes. Most of the products obtained are incomplete spheres.

[0049] Comparative Example 2 1000 kg of pure aluminum was added to the melting chamber and melted under a nitrogen atmosphere to obtain molten aluminum liquid at a melting temperature of 680℃. While melting, the molten aluminum is stirred to maintain its fluidity. Hydrogen is injected evenly into the melting chamber through a multi-hole nozzle, allowing the hydrogen to dissolve in the molten aluminum until saturation is achieved. Open the discharge hole (50mm diameter) at the bottom of the melting chamber and continue to introduce hydrogen gas to increase the pressure in the melting chamber. Use the pressure generated by the excess hydrogen gas injected into the melting chamber to discharge the molten aluminum into the cooling chamber. The cooling chamber maintains a nitrogen atmosphere. Nitrogen gas at 25°C is blown out at a speed of 20 m / s through the blowing pipe, causing the molten aluminum to disperse and fall. At the same time, due to the decrease in temperature, the solubility of hydrogen in the molten aluminum decreases, and hydrogen gas is released and forms porous aluminum spheres. 91% of these spheres have a diameter of 40-45 mm, with an average pore size of 1.9 mm. Due to the excessively high blowing temperature and slow cooling rate, some aluminum spheres cannot be completely solidified. Furthermore, the hydrogen gas escape rate is too slow, resulting in large internal pores and small surface pores. Within each sphere, the pore shape is uneven, and after falling, the spheres take on non-spherical shapes such as ellipsoids or hills.

[0050] Comparative Example 3 1000 kg of pure aluminum was added to the melting chamber and melted under a nitrogen atmosphere to obtain molten aluminum liquid at a melting temperature of 680℃. While melting, the molten aluminum is stirred to maintain its fluidity. Hydrogen is injected evenly into the melting chamber through a multi-hole nozzle, allowing the hydrogen to dissolve in the molten aluminum until saturation is achieved. Open the discharge hole (50mm diameter) at the bottom of the melting chamber and continue to introduce hydrogen gas to increase the pressure in the melting chamber. Use the pressure generated by the excess hydrogen gas injected into the melting chamber to discharge the molten aluminum into the cooling chamber. The cooling chamber maintains a nitrogen atmosphere. Nitrogen gas at -20°C is blown out at a speed of 10 m / s through the blowing pipe, causing the molten aluminum to disperse and fall. At the same time, due to the decrease in temperature, the solubility of hydrogen in the molten aluminum decreases, and hydrogen precipitates and forms porous aluminum spheres. 90% of these spheres have a diameter of 53~55 mm, with an average pore size of 22.0 mm. Due to the low blowing rate, it is basically impossible to disperse the falling droplets, resulting in irregular shapes of the aluminum spheres. Hydrogen cannot completely escape from some of the aluminum spheres, and the resulting closed pores are uneven.

[0051] Comparative Example 4 1000 kg of pure aluminum was added to the melting chamber and melted under a nitrogen atmosphere to obtain molten aluminum liquid at a melting temperature of 680℃. While melting, the molten aluminum is stirred to maintain its fluidity. Hydrogen is injected evenly into the melting chamber through a multi-hole nozzle, allowing the hydrogen to dissolve in the molten aluminum until saturation is achieved. Open the discharge hole (50mm diameter) at the bottom of the melting chamber and continue to introduce hydrogen gas to increase the pressure in the melting chamber. Use the pressure generated by the excess hydrogen gas injected into the melting chamber to discharge the molten aluminum into the cooling chamber. The cooling chamber maintains a nitrogen atmosphere. Nitrogen gas at -20°C is blown out at a speed of 50 m / s through the blowing pipe, causing the molten aluminum to disperse and fall. At the same time, due to the decrease in temperature, the solubility of hydrogen in the molten aluminum decreases, and hydrogen gas is released and forms porous aluminum spheres. 92% of these spheres have a diameter of 10~15 mm and an average pore size of 8 mm. Due to the excessively fast blowing rate, some aluminum spheres do not have a porous structure, resulting in solid aluminum spheres or granules.

[0052] Examples 1, 2, and 3 illustrate the effect of blowing temperature on the hydrogen evolution rate during the cooling and solidification of the dripping second aluminum liquid, which further affects the pore size of the resulting porous aluminum spheres. At blowing temperatures of -20 to 20°C, the lower the blowing temperature, the faster the hydrogen evolution rate, and the larger the pore size of the formed porous aluminum spheres; conversely, the higher the blowing temperature, the slower the hydrogen evolution rate, and the smaller the pore size of the formed porous aluminum spheres.

[0053] Examples 1, 4, and 5 illustrate the effect of the blowing rate on the formation of spherical porous structures during the cooling and solidification of the dripping second aluminum liquid, further affecting the diameter and pore size of the obtained porous aluminum spheres. At blowing rates of 20-40 m / s, the slower the blowing rate, the larger the diameter and pore size of the obtained porous aluminum spheres; the faster the blowing rate, the smaller the diameter and pore size of the obtained porous aluminum spheres.

[0054] Examples 1, 6, and 7 illustrate the effect of the aperture size of the perforated mold on the diameter of the resulting porous aluminum ball. The larger the aperture size of the perforated mold, the larger the diameter of the resulting porous aluminum ball.

[0055] This invention proposes a porous aluminum sphere and its preparation method. Hydrogen gas is introduced into molten aluminum and dissolved until saturation. The saturated aluminum is then dripped into a predetermined size. During the dripping process, nitrogen is blown onto the falling droplets to cool them. The temperature decreases during cooling, causing hydrogen to precipitate, resulting in closed-cell porous aluminum spheres. The hydrogen precipitation rate can be controlled by adjusting the nitrogen blowing temperature and rate, thus obtaining closed-cell porous aluminum spheres with different diameters and / or pore sizes.

[0056] The above description is merely a preferred embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural transformations made using the contents of the present invention under the inventive concept of the present invention, or direct / indirect applications in other related technical fields, are included within the patent protection scope of the present invention.

Claims

1. A method for preparing porous aluminum spheres, characterized in that, Includes the following steps: S1. Melt the aluminum raw material to a molten state to obtain the first aluminum liquid; S2. Expose the first molten aluminum to hydrogen gas, so that the hydrogen gas dissolves in the first molten aluminum to obtain a second molten aluminum; S3. The second aluminum liquid is dripped into a predetermined size, and nitrogen gas with a temperature of -20~20℃ and a flow rate of 20~40m / s is blown onto the droplets formed by the dripping of the second aluminum liquid to cool the droplets. During the cooling process, the temperature of the droplets decreases, causing hydrogen gas to be released, and porous aluminum spheres are obtained.

2. The method for preparing a porous aluminum sphere according to claim 1, characterized in that, In step S3, the second aluminum liquid is dripped at a preset size using a perforated mold, wherein the diameter of the perforated mold is 50~150mm.

3. The method for preparing a porous aluminum sphere according to claim 1, characterized in that, In step S3, the direction of the nitrogen gas blown toward the molten droplet is the first direction, the direction of the second aluminum liquid droplet is the second direction, the second direction is the vertical direction, and the angle between the first direction and the second direction is 45°~135°.

4. The method for preparing a porous aluminum sphere according to claim 1, characterized in that, In step S1, the aluminum raw material is pure aluminum or an aluminum alloy.

5. The method for preparing a porous aluminum sphere according to claim 1, characterized in that, In step S1, the aluminum raw material is melted to a molten state in an inert atmosphere or vacuum to obtain the first aluminum liquid.

6. The method for preparing a porous aluminum sphere according to claim 5, characterized in that, In step S1, the melting temperature is 680~750℃; step S1 also includes: continuously stirring the first aluminum liquid.

7. The method for preparing a porous aluminum sphere according to claim 1, characterized in that, In step S2, the first aluminum liquid is exposed to hydrogen gas, and the hydrogen gas dissolves in the first aluminum liquid and reaches a saturated state to obtain the second aluminum liquid.

8. The method for preparing a porous aluminum sphere according to claim 1, characterized in that, In step S3, pressure is applied to the second molten aluminum to accelerate its dripping.

9. A porous aluminum sphere, characterized in that, The porous aluminum sphere is obtained by a method for preparing porous aluminum spheres as described in any one of claims 1 to 8.

10. A porous aluminum sphere according to claim 9, characterized in that, The porous aluminum ball is a closed-cell porous aluminum ball with a diameter of 3~170mm and a pore size of 1.5~50mm.

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