Aluminum powder sintered micron-sized porous membrane layer as well as preparation method and application thereof

Abstract

The invention discloses an aluminum powder sintered micron-sized porous membrane layer as well as a preparation method and application thereof. According to the method, spherical aluminum powder with the particle size of 1-15 microns is used as a raw material, absolute ethyl alcohol is used as a dispersion medium, the aluminum powder and the absolute ethyl alcohol are mixed in proportion and subjected to ultrasonic dispersion treatment, evenly-suspended aluminum powder slurry is prepared, the surface of a base body is coated with the slurry through a blade coating technology, and after the absolute ethyl alcohol is removed through low-temperature drying, the aluminum powder is obtained. And carrying out high-temperature sintering in a vacuum or protective atmosphere to prepare the aluminum powder sintered micron-sized porous membrane layer with the pore diameter of 0.5-30 microns and the thickness of 50-1000 microns. The preparation method is simple in process, not only solves the problems that the fine aluminum powder is easy to agglomerate and difficult to disperse, but also is free of carbon residue, good in bonding strength and communicated in pore structure after being sintered due to the fact that no organic binder is added, and is especially suitable for high-performance heat pipe capillary cores, filtering materials and electrolytic capacitor anode porous materials.

Description

Technical Field

[0001] This invention belongs to the field of metal porous material preparation technology, specifically relating to a method for preparing a binder-free sintered micron-sized porous film based on fine aluminum powder, and its application in phase change heat transfer, filtration separation, porous electrodes and other fields. Background Technology

[0002] Currently, the process for sintering porous films from aluminum powder mostly adopts a wet slurry preparation + sintering route: aluminum powder is mixed with water or a water / alcohol mixture as a dispersion medium, along with a certain amount of organic binders (such as PVA, PVB, cellulose), pH adjusters, dispersants, rust inhibitors, and other auxiliary additives to prepare a slurry with a certain viscosity and thixotropic properties. This slurry is then coated, dried, and sintered to obtain a porous film. While this process can improve the dispersion and forming properties of aluminum powder to some extent, the widespread introduction of water and various chemical additives into the system brings a series of problems: On the one hand, highly active aluminum powder in aqueous systems easily reacts with water and dissolved oxygen, producing hydrogen gas and causing pitting and crevice corrosion, posing safety hazards and damaging the integrity of the particle surface; on the other hand, alkaline or acidic pH adjusters and rust inhibitors accelerate the hydrolysis and oxidation of the aluminum surface, further thickening the existing alumina film, which is difficult to effectively destroy during sintering, resulting in difficulty in growing sintering necks, uncontrollable pore structure, and a decline in the mechanical and capillary properties of the porous film.

[0003] To lower the sintering temperature or improve the forming process, existing technologies often employ surface modification of aluminum powder or the addition of sintering aids. For example, copper and tin are coated onto the surface of the aluminum powder, or pretreatment is performed using acids, alkalis, or complexing agents. While these methods improve the metallurgical bonding during sintering to some extent, they also introduce various heterogeneous metal phases and chemical residues, resulting in a complex phase composition and diverse interface states in the sintered product. This makes it difficult to guarantee the chemical cleanliness of the porous film, especially the surface of the micropore walls. Furthermore, some modifying elements may reduce the material's corrosion resistance and thermal conductivity, which is detrimental to applications in fields requiring high reliability and cleanliness, such as heat pipes and electrodes. Therefore, existing aluminum powder sintering porous film preparation processes still have significant shortcomings in avoiding hydrogen evolution corrosion, inhibiting oxide film thickening, and obtaining high-purity porous structures, requiring further improvement. Summary of the Invention

[0004] To address the shortcomings of the existing technologies, this invention aims to provide a micron-sized porous film sintered from aluminum powder, its preparation method, and its applications. This invention achieves control over the selection of raw materials, forming, and sintering, thereby enabling the production of micron-sized porous films of varying thicknesses. It offers advantages such as simple operation, low cost, and high reliability.

[0005] Moreover, the preparation method described herein achieves uniform dispersion and coating of micro-spherical aluminum powder through the synergistic effect of anhydrous ethanol and ultrasonic dispersion, completely eliminating organic binders and preparing a porous membrane layer with controllable pore size, high cleanliness, and strong bonding force.

[0006] This invention provides a method for preparing a micron-sized porous film layer by sintering aluminum powder, comprising the following steps: S1. Raw material preparation: Select spherical aluminum powder with an average particle size of 1~15μm as the skeleton material; S2. Slurry preparation: The spherical aluminum powder is mixed with anhydrous ethanol in a predetermined ratio and ultrasonically dispersed until a uniformly suspended aluminum powder slurry is formed. S3. Scraping and forming: The aluminum powder slurry obtained in S2 is coated onto the substrate surface through a scraping process to form a pre-made wet film; S4. Drying: The substrate coated with the pre-made wet film is dried, and the anhydrous ethanol in the pre-made wet film is completely evaporated to form an aluminum powder film stacked layer, thus obtaining a substrate including the aluminum powder film stacked layer. S5. Sintering: The substrate including the aluminum powder film stacked layer is placed in a sintering furnace and sintered at high temperature in a protective atmosphere or vacuum environment. After cooling, a substrate covered with the aluminum powder sintered micron-sized porous film layer is obtained.

[0007] Preferably, the spherical aluminum powder has good flowability and packing characteristics, which is conducive to forming regular and interconnected pore channels.

[0008] Preferably, the average particle size of the spherical aluminum powder can be any one of 1~3μm, 4~6μm, 7~9μm, 10~12μm, and 13~15μm; by screening spherical aluminum powder with different particle size distributions, the pore size of the sintered porous film layer of aluminum powder can be controlled.

[0009] Furthermore, in the preparation method of the present invention, in step S2, the mass ratio of the spherical aluminum powder to anhydrous ethanol is any one of the following: 1.8:1, 1.7:1, 1.6:1, 1.5:1, 1.4:1, 1.3:1, 1.2:1, 1.1:1, 1:1, 1:1.1, 1:1.2, 1:1.3, 1:1.4, 1:1.5, 1:1.6, 1:1.7, or 1:1.8.

[0010] Preferably, the ultrasonic dispersion time is any one of 5 min, 10 min, 15 min, 20 min, 25 min, 30 min, 35 min, 40 min, 45 min, 50 min, 55 min, and 60 min.

[0011] Preferably, the drying temperature in step S4 is 80~120℃ and the drying time is 60~180min.

[0012] Furthermore, in the preparation method of the present invention, in step S3, the matrix is ​​selected from any one of aluminum and aluminum alloys, copper and copper alloys, steel, titanium and titanium alloys, nickel and nickel alloys, or layered metal composite materials.

[0013] Furthermore, in the preparation method of the present invention, in step S5, the sintering temperature of the high-temperature sintering is 580℃~650℃, the heating rate is 2~10℃ / min, and the holding time is 30min~240min.

[0014] Furthermore, in the preparation method of the present invention, in step S5, the vacuum degree of the vacuum environment is better than 1×10⁻ 2 Pa, or the protective atmosphere is nitrogen, hydrogen, or argon with a dew point below -40°C.

[0015] Preferably, the sintering temperature of the high-temperature sintering process can be any temperature of 580℃, 590℃, 600℃, 610℃, 620℃, 630℃, 640℃ or 650℃.

[0016] Preferably, the heating rate can be 2℃ / min, 3℃ / min, 4℃ / min, 5℃ / min, 5℃ / min, 6℃ / min, 7℃ / min, 8℃ / min, 9℃ / min or 10℃ / min.

[0017] Preferably, the sintering time is 30 min to 240 min, more preferably 60 min to 180 min. The pore size of the porous membrane can be controlled by adjusting the sintering temperature, heating rate, and sintering time.

[0018] Furthermore, in the preparation method of the present invention, in step S5, when the substrate is an aluminum alloy, the sintering temperature is 580℃~620℃ to prevent the aluminum alloy from overheating.

[0019] Furthermore, in the preparation method of the present invention, by screening spherical aluminum powder with different particle size distributions, and simultaneously adjusting the sintering temperature, heating rate and sintering time, the pore size of the sintered porous film of aluminum powder can be controlled; aluminum powder with small particle size can be used to obtain an aluminum powder sintered porous film with small pore size; and aluminum powder with large particle size can be used to obtain an aluminum powder sintered porous film with large pore size.

[0020] Furthermore, in the preparation method of the present invention, in step S2, the mass ratio of the spherical aluminum powder to anhydrous ethanol is 1.8:1 to 1:1.8. The selection of this ratio range is based on the following technical considerations: 1) When the mass ratio of aluminum powder to anhydrous ethanol is less than 1:1.8, the slurry viscosity will be too low, the rheological properties will be poor, and it will be difficult to maintain the predetermined wet film thickness during the coating process. The slurry will easily flow to the surroundings. Moreover, due to the low solid content, the particle packing density after drying is insufficient, which will lead to excessive shrinkage of the sintered film layer, which will easily generate macroscopic cracks and fail to form a continuous and dense porous skeleton. 2) When the mass ratio of aluminum powder to anhydrous ethanol is higher than 1.8:1, the slurry viscosity will be too high, and it will be difficult to break up the agglomerates by ultrasonic dispersion, resulting in uneven distribution of aluminum powder particles in the slurry. The resistance during coating is high, which can easily generate drag marks or uneven coating. Moreover, during the drying process, due to the rapid evaporation of solvent and the obstruction of the path, cracks may easily appear on the surface of the film layer or voids may be generated inside, which will seriously affect the bonding force between the film layer and the substrate.

[0021] Furthermore, in the preparation method of the present invention, in step S1, the average particle size of the spherical aluminum powder is 1~15μm. The selection of this particle size range is based on the following technical considerations: 1) When the particle size is too small (below 1μm), the specific surface area is large, the particles are easy to agglomerate, and dispersion is difficult. The membrane pore size is too small, the permeation resistance is large, and the fluid transport capacity is poor. The sintering activity is too high, and it is easy to over-sinter, resulting in pore closure. 2) When the particle size is too large (above 15μm), the membrane pore size is too large, the capillary suction is insufficient, it cannot meet the application requirements of capillary cores, the particles settle quickly, the distribution is uneven, the number of sintering necks is small, and the membrane strength is low.

[0022] Furthermore, in the preparation method of the present invention, in step S5, the sintering temperature of the high-temperature sintering is 580℃~650℃. The selection of this temperature range is based on the following technical considerations: 1) When the temperature is too low (below 580℃), the diffusion rate of aluminum atoms is slow, and effective metallurgical bonding cannot be formed between particles (the sintering neck cannot be formed or is too thin and weak), resulting in extremely poor bonding between the porous film and the substrate, as well as between particles, and the film is loose, making it very easy to peel off or shatter during use. 2) Due to the proximity to the melting point of aluminum (approximately 660℃), aluminum powder particles will soften or even partially melt and collapse, causing the pores between particles to be filled or sealed by molten metal, the pore size to shrink sharply or even become completely dense, losing the air permeability and liquid permeability characteristics of porous materials; at the same time, excessively high temperatures will cause excessive grain growth, reducing the mechanical properties of the material.

[0023] Furthermore, in the preparation method of the present invention, in step S5, the holding time for high-temperature sintering is 30 min to 240 min. The selection of this time range is based on the following technical considerations: 1) When the time is too short (below 30 min), the system is in the initial stage of sintering, the atomic migration at the particle contact interface is insufficient, the sintering neck has not fully grown, the pore shape of the porous layer is irregular and the structure is unstable, resulting in low mechanical strength. 2) When the time is too long (above 240 min), although the strength is improved, it will lead to excessive coarsening of particles, small pores merging into large pores or pores undergoing spheroidization and shrinkage, resulting in a decrease in total porosity; at the same time, the long-term high-temperature holding time greatly increases energy consumption and time costs, reducing production efficiency.

[0024] Furthermore, in the preparation method of the present invention, in step S5, the heating rate of the high-temperature sintering is 2~10℃ / min. The selection of this heating rate range is based on the following technical considerations: 1) When the rate is too fast (above 10℃ / min): a large temperature gradient is easily generated between the substrate and the film layer, and between the surface and interior of the film layer, leading to thermal stress concentration, which may cause the film layer to crack or warp and peel off from the substrate; in addition, excessively fast heating may cause the gas or trace residual solvent adsorbed on the particle surface to expand in volume before it can escape through the pores, damaging the microstructure of the film layer. 2) When the rate is too slow (below 2℃ / min): the process cycle is long, the production efficiency is low, and the energy consumption is high.

[0025] Preferably, the thickness of the pre-made wet film in step S3 can be controlled by machining a concave plane on the substrate or by controlling the height of the scraper, and the thickness of the pre-made wet film is 50~1000μm.

[0026] Furthermore, in the preparation method of the present invention, if the substrate is graphite material in step S3, then after the high-temperature sintering in step S5 is completed, a micron-sized porous film layer of aluminum powder sintered from the substrate is obtained.

[0027] The present invention also provides a sintered aluminum powder micron-sized porous membrane, which can be obtained by any of the above preparation methods. The sintered aluminum powder micron-sized porous membrane is formed by connecting spherical aluminum powder particles through a sintering neck. The porosity of the sintered aluminum powder micron-sized porous membrane is 25%~50%, the pore size distribution is 0.5~30μm, and the thickness of the sintered aluminum powder micron-sized porous membrane is 50~1000μm.

[0028] Preferably, the pore size of the aluminum powder sintered micron-sized porous film is 0.5~10μm.

[0029] An application of a sintered aluminum powder micron-sized porous film, wherein the sintered aluminum powder micron-sized porous film is applied to the liquid-absorbing capillary core or filter material of a phase change heat transfer device or the anode porous material of an electrolytic capacitor.

[0030] Compared with the prior art, the advantages of the present invention are as follows: This invention uses only aluminum powder and anhydrous ethanol as raw materials. The anhydrous ethanol can be evaporated and collected for reuse. No other substances are introduced. The application of porous aluminum film reduces the consideration of harmful components, and the material has good reliability and consistency.

[0031] This invention can control the pore size of the sintered porous film layer of aluminum powder by screening spherical aluminum powder with different particle size distributions and simultaneously adjusting the sintering temperature, heating rate and sintering time.

[0032] This invention can be formed in one step on a base material such as aluminum and aluminum alloys, copper and copper alloys, steel, titanium and titanium alloys, or nickel and nickel alloys, or layered metal composite materials, forming a metallurgical bond with the base material. This avoids brazing contamination and ensures contact thermal resistance and cleanliness in capillary wick applications.

[0033] This invention can be formed on a graphite matrix material, and after sintering, it can be naturally peeled off to form a pure aluminum porous membrane layer, which can be extended to applications such as filter materials.

[0034] The present invention has a simple process, is easy to operate, has strong controllability, and is low in cost. Attached Figure Description

[0035] Figure 1 This is a microscopic morphology diagram of the aluminum powder sintered micron-sized porous film prepared in Example 1 of the present invention.

[0036] Figure 2 This is a microscopic morphology diagram of the aluminum powder sintered micron-sized porous film prepared in Example 2 of the present invention.

[0037] Figure 3 This is a microscopic morphology diagram of the aluminum powder sintered micron-sized porous film prepared in Example 3 of the present invention.

[0038] Figure 4 This is a microscopic morphology diagram of the aluminum powder sintered micron-sized porous film prepared in Example 4 of the present invention.

[0039] Figure 5 This is a microscopic morphology diagram of the aluminum powder sintered micron-sized porous film prepared in Example 5 of the present invention.

[0040] Figure 6 This is a microscopic morphology diagram of the aluminum powder sintered micron-sized porous film prepared in Example 6 of the present invention.

[0041] Figure 7 This is a microscopic morphology diagram of the aluminum powder sintered micron-sized porous film prepared in Example 7 of the present invention. Detailed Implementation

[0042] To provide a clearer understanding of the technical features, objectives, and effects of the present invention, specific embodiments are now described in detail with reference to the accompanying drawings. The described embodiments are merely some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention. Where specific conditions are not specified in the detailed embodiments, conventional conditions or conditions provided by the manufacturer shall apply.

[0043] In the following description, when referring to the accompanying drawings, the same numbers in different drawings denote the same or similar elements unless otherwise indicated. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with this disclosure. Rather, they are merely examples of apparatuses and methods consistent with some aspects of this disclosure as detailed in the appended claims. The terminology used in this disclosure is for the purpose of describing particular embodiments only and is not intended to be limiting of this disclosure. Example 1

[0044] Spherical aluminum powder with a particle size range of 1~3μm was used. The aluminum powder and anhydrous ethanol were mixed at a mass ratio of 1:1 and dispersed into a uniform slurry using an ultrasonic device for 10 minutes. The slurry was then filled into a machined recessed plane of a 6063 substrate, with a depth of 100μm. The slurry was leveled using a scraper, and the substrate coated with the pre-prepared wet film was placed in a vacuum drying oven at 100℃ for 60 minutes. The anhydrous ethanol in the pre-prepared wet film completely evaporated, forming an aluminum powder film deposited layer, resulting in a substrate including the aluminum powder film deposited layer. This substrate was then placed in a sintering furnace and sintered under a vacuum atmosphere with a vacuum degree less than 1×10⁻⁻⁻⁻⁶. 2 Pa, heating rate of 10℃ / min, sintering temperature of 600℃, sintering time of 60min, after high-temperature sintering, a matrix coated with a micron-sized porous film layer of aluminum powder is obtained, product #1.

[0045] In this embodiment 1, the matrix is ​​6063 aluminum alloy, and the chemical composition of the spherical aluminum powder is shown in Table 1.

[0046] Table 1 Chemical composition of spherical aluminum powder element Al (wt.%) Cu (wt.%) Si (wt.%) Fe (wt.%) <![CDATA[H2O(wt.%)]]> content margin ≤0.015 ≤0.12 ≤0.12 ≤0.10 Scanning electron microscope (SEM) images of the aluminum powder sintered micron-sized porous film prepared in Example 1 are shown below. Figure 1 As shown, the sintered aluminum powder micron-sized porous membrane is formed by connecting spherical aluminum powder particles through a sintering neck. The porosity of the sintered aluminum powder micron-sized porous membrane is approximately 35%, the pore size distribution is 0.5~10μm, and the thickness is approximately 80μm.

[0047] The No. 1 product obtained in Example 1 was used in the heat pipe capillary wick component, which reduced the thermal resistance of the brazing interface between the substrate and the capillary wick. Example 2

[0048] The only difference between Example 2 and Example 1 is that the spherical aluminum powder and anhydrous ethanol are mixed at a mass ratio of 1.8:1, and the ultrasonic dispersion time is 15 min. The depth of the concave plane on the substrate is 500 μm, and the drying time is 120 min. The heating rate for high-temperature sintering is 5 °C / min, ultimately yielding a substrate coated with a micron-sized porous film layer of sintered aluminum powder, product #2. The scanning electron microscope image of the micron-sized porous film layer of sintered aluminum powder is shown below. Figure 2 As shown.

[0049] The porosity of the aluminum powder sintered micron-sized porous membrane obtained in Example 2 is about 37%, the pore size distribution is 0.5~10μm, and the thickness is about 400μm.

[0050] The product No. 2 obtained in Example 2 was used in a porous electrode to provide a large specific surface area for electrochemical reactions. Example 3

[0051] The only difference between Example 3 and Example 1 is that the ultrasonic dispersion time is 20 min, the depth of the concave plane on the substrate is 60 μm, and the drying time is 150 min. The high-temperature sintering heating rate is 2℃ / min, the sintering temperature is 580℃, and the sintering time is 30 min. After high-temperature sintering, a substrate coated with a micron-sized porous film layer of sintered aluminum powder is obtained, ultimately yielding product #3. The scanning electron microscope image of the micron-sized porous film layer of sintered aluminum powder is shown below. Figure 3 As shown.

[0052] The porosity of the aluminum powder sintered micron-sized porous membrane obtained in Example 3 is about 50%, the pore size distribution is 0.5~15μm, and the thickness is about 50μm. Example 4

[0053] The only difference between Example 4 and Example 1 is that the spherical aluminum powder and anhydrous ethanol are dispersed in a mass ratio of 1:1.8 using ultrasound for 20 minutes. The depth of the concave plane on the substrate is 300 μm, and the drying time is 150 minutes. The high-temperature sintering heating rate is 2℃ / min, the sintering temperature is 580℃, and the sintering time is 30 minutes. After high-temperature sintering, a substrate coated with a micron-sized porous film layer of sintered aluminum powder is obtained, product #4. The scanning electron microscope image of the micron-sized porous film layer of sintered aluminum powder is shown below. Figure 4 As shown.

[0054] The porosity of the aluminum powder sintered micron-sized porous membrane obtained in Example 4 is about 46%, the pore size distribution is 0.5~15μm, and the thickness is about 270μm. Example 5

[0055] The only difference between Example 5 and Example 1 is that the substrate is made of stainless steel, and the ultrasonic dispersion time is 30 min. The depth of the concave plane on the substrate is 400 μm, and the drying time is 120 min. The high-temperature sintering heating rate is 5℃ / min, the sintering temperature is 580℃, and the sintering time is 240 min. After high-temperature sintering, a substrate coated with a micron-sized porous film layer of sintered aluminum powder is obtained, product #5. A scanning electron microscope image of the micron-sized porous film layer of sintered aluminum powder is shown below. Figure 5 As shown.

[0056] The porosity of the aluminum powder sintered micron-sized porous membrane obtained in Example 5 is about 40%, the pore size distribution is 0.5~20μm, and the thickness is about 360μm. Example 6

[0057] The only difference between Example 6 and Example 1 is that the substrate is made of stainless steel, the particle size of the spherical aluminum powder ranges from 13 to 15 μm, the mass ratio of spherical aluminum powder to anhydrous ethanol is 1.8:1, the ultrasonic dispersion time is 5 min, the depth of the concave plane on the substrate is 500 μm, and the drying time is 120 min. The sintering temperature is 650℃, and the sintering time is 60 min, finally obtaining product #6. The scanning electron microscope image of the sintered micron-sized porous film of aluminum powder is shown below. Figure 6 As shown.

[0058] The porosity of the aluminum powder sintered micron-sized porous membrane obtained in Example 6 is about 32%, the pore size distribution is 10~30μm, and the thickness is about 400μm. Example 7

[0059] The only difference between Example 7 and Example 1 is that the substrate is graphite material, and the ultrasonic dispersion time is 30 min. The depth of the concave plane on the substrate is 1200 μm, and the drying time is 120 min. The sintering temperature is 650℃, and the sintering time is 60 min. After high-temperature sintering, a naturally exfoliated aluminum powder sintered micron-sized porous film layer, product #7, is obtained. The scanning electron microscope image of the aluminum powder sintered micron-sized porous film layer is shown below. Figure 7 As shown.

[0060] The porosity of the aluminum powder sintered micron-sized porous membrane obtained in Example 7 is about 25%, the pore size distribution is 0.5~3μm, and the thickness is about 1000μm.

[0061] Comparative Example 1 The only difference between Comparative Example 1 and Example 1 is that the spherical aluminum powder and anhydrous ethanol are mixed in a mass ratio of 2:1, and the ultrasonic dispersion time is 60 min, resulting in product #8.

[0062] During slurry preparation, due to excessive aluminum powder addition, even with extended ultrasonic dispersion time of 60 minutes, the slurry still exhibited significant agglomeration, a marked increase in viscosity, and poor flowability. In the coating process, the slurry was difficult to spread evenly, resulting in noticeable scratches, streaks, and localized build-up on the surface, making it impossible to obtain a uniformly thick pre-fabricated wet film. This exceeded the applicable scope of the coating process, making smooth forming impossible. After drying and sintering, product #8 showed uneven film thickness, uneven pore distribution, and obvious surface defects, failing to meet the quality and performance requirements for micron-sized porous films.

[0063] Comparative Example 2 The only difference between Comparative Example 2 and Example 1 is that the spherical aluminum powder and anhydrous ethanol are mixed in a mass ratio of 1:2, and the ultrasonic dispersion time is 15 minutes, resulting in product #9.

[0064] During slurry preparation, the high proportion of anhydrous ethanol resulted in a relatively low solid content in the aluminum powder, leading to a thin slurry. After ultrasonic dispersion, the aluminum powder particles settled rapidly in the slurry, and after a short period of standing, significant solid-liquid separation occurred, with a clear anhydrous ethanol layer on top and deposited aluminum powder particles at the bottom. During the coating process, the low slurry concentration and poor dispersion stability prevented the aluminum powder particles from uniformly filling the substrate surface, resulting in areas with insufficient material or incomplete filling. Due to insufficient slurry filling, the coating thickness was uneven, and the aluminum powder deposited layer was discontinuous or locally sparse after drying. After sintering, the No. 9 product exhibited poor film integrity, uneven pore distribution, and defects such as cracks and warping in some areas due to insufficient aluminum powder filling, affecting the mechanical strength and performance of the micron-sized porous film.

[0065] Comparative Example 3 The only difference between Comparative Example 3 and Example 1 is that the spherical aluminum powder has a particle size greater than 15 μm and less than or equal to 45 μm, the spherical aluminum powder and anhydrous ethanol are mixed at a mass ratio of 1.8:1, the ultrasonic dispersion time is 5 min, the depth of the concave plane on the substrate is 500 μm, and the drying time is 150 min. The sintering temperature is 650℃, and the sintering time is 60 min. After high-temperature sintering, a naturally exfoliated aluminum powder sintered micron-sized porous film layer is obtained, ultimately yielding product #10.

[0066] Because coarse-grained aluminum powder is used, its specific surface area is small. Under the same vacuum sintering conditions, the surface activity of the particles is low, resulting in insufficient sintering driving force and incomplete development of the sintering neck. The particles mainly make point contact. This inadequate sintering structure results in poor mechanical strength of the porous membrane layer, and the pore size is too large, making it difficult to meet the performance requirements of precision filtration or separation applications.

[0067] The porous membrane obtained in Comparative Example 3 has a porosity of about 40%, a pore size distribution of 35~50μm, and a thickness of about 400μm.

[0068] Comparative Example 4 The only difference between Comparative Example 4 and Example 1 is that the spherical aluminum powder has a particle size of less than 1 μm and greater than or equal to 0.1 μm, and is ultrasonically dispersed for 60 min to finally obtain product #11.

[0069] Due to the use of nanoscale aluminum powder, which has an extremely high specific surface area and surface energy, particle agglomeration is highly likely. Furthermore, the excessively rapid material migration rate during sintering leads to over-fusion of particles and abnormal grain growth. The interconnected pore network originally formed by particle accumulation collapses rapidly, transforming the porous structure from open interconnected pores to isolated closed pores, resulting in a sharp decrease in porosity. This over-densification structure blocks fluid transport channels, failing to meet the flux and permeability requirements of applications such as filtration and separation.

[0070] The porous membrane obtained in Comparative Example 4 has a porosity of about 15%, a pore size distribution of 0.1~0.4μm, and a thickness of about 50μm.

[0071] This invention has been described through the specific embodiments described above. Those skilled in the art should understand that various modifications and equivalent substitutions can be made to this invention without departing from its scope. Parts not described in detail in this specification are well-known to those skilled in the art. Furthermore, various modifications can be made to this invention for specific situations or circumstances without departing from its scope. Therefore, this invention is not limited to the specific embodiments disclosed, but should include all embodiments falling within the scope of the claims.

Claims

1. A method for preparing a micron-sized porous film layer sintered from aluminum powder, characterized in that, Includes the following steps: S1. Raw material preparation: Select spherical aluminum powder with an average particle size of 1~15μm as the skeleton material; S2. Slurry preparation: The spherical aluminum powder is mixed with anhydrous ethanol in a predetermined ratio and ultrasonically dispersed until a uniformly suspended aluminum powder slurry is formed. S3. Scraping and forming: The aluminum powder slurry obtained in S2 is coated onto the substrate surface through a scraping process to form a pre-made wet film; S4. Drying: The substrate coated with the pre-made wet film is dried, and the anhydrous ethanol in the pre-made wet film is completely evaporated to form an aluminum powder film stacked layer, thus obtaining a substrate including the aluminum powder film stacked layer. S5. Sintering: The substrate including the aluminum powder film stacked layer is placed in a sintering furnace and sintered at high temperature in a protective atmosphere or vacuum environment. After cooling, a substrate covered with the aluminum powder sintered micron-sized porous film layer is obtained.

2. The preparation method according to claim 1, characterized in that, In step S2, the ultrasonic dispersion time is 5 min to 60 min; the mass ratio of the spherical aluminum powder to anhydrous ethanol is 1.8:1 to 1:1.

8.

3. The preparation method according to claim 1, characterized in that, In step S3, the matrix is ​​selected from any one of aluminum and aluminum alloys, copper and copper alloys, steel, titanium and titanium alloys, nickel and nickel alloys, or layered metal composite materials.

4. The preparation method according to claim 1, characterized in that, In step S5, the sintering temperature of the high-temperature sintering is 580℃~650℃, the heating rate is 2~10℃ / min, and the holding time is 30min~240min.

5. The preparation method according to claim 1, characterized in that, In step S5, the vacuum level of the vacuum environment is better than 1×10⁻ 2 Pa, or the protective atmosphere is nitrogen, hydrogen, or argon with a dew point below -40°C.

6. The preparation method according to claim 1, characterized in that, By screening spherical aluminum powder with different particle size distributions and simultaneously adjusting the sintering temperature, heating rate, and sintering time, the pore size of the sintered porous film of aluminum powder can be controlled; aluminum powder with small particle size can be used to obtain a sintered porous film of aluminum powder with small pore size; and aluminum powder with large particle size can be used to obtain a sintered porous film of aluminum powder with large pore size.

7. The preparation method according to claim 1, characterized in that, In step S3, if the substrate is graphite material, then after the high-temperature sintering in step S5 is completed, a micron-sized porous aluminum powder sintered layer is obtained that is naturally peeled off from the substrate.

8. A micron-sized porous aluminum powder sintered film prepared by the preparation method according to any one of claims 1 to 7, characterized in that, The aluminum powder sintered micron-sized porous membrane is formed by connecting spherical aluminum powder particles through a sintering neck; the porosity of the aluminum powder sintered micron-sized porous membrane is 25%~50%, the pore size distribution is 0.5~30μm, and the thickness of the aluminum powder sintered micron-sized porous membrane is 50~1000μm.

9. An application of a micron-sized porous film layer sintered from aluminum powder, characterized in that, The aluminum powder sintered micron-sized porous film is the aluminum powder sintered micron-sized porous film as described in claim 8, and the aluminum powder sintered micron-sized porous film prepared by any of the preparation methods described in claims 1 to 7. The aluminum powder sintered micron-sized porous film is applied to the liquid-absorbing capillary core or filter material of phase change heat transfer device or the anode porous material of electrolytic capacitor.

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