Porous aluminum-based wick and manufacturing method and application thereof

Abstract

The invention provides a porous aluminum-based wick and a manufacturing method and application thereof. The porous aluminum-based wick comprises a heat conduction substrate and a wick structure, wherein the wick structure is arranged on the heat conduction substrate; the wick structure comprises a microporous matrix, a macroscopic channel and a nano surface layer, the microporous matrix is made of aluminum alloy, and adjacent pores are communicated with each other to form a continuous capillary network; the macroscopic channel is of a periodic three-dimensional network structure and is arranged in the microporous matrix in a penetrating manner; and the nano surface layer is arranged on the surface of the microporous substrate and the wall surface of the macroscopic channel. Due to the integrated design of the multi-scale pores, the capillary force and the permeability of the wick are effectively improved, the heat transfer resistance is reduced, and the heat dissipation efficiency is enhanced. The manufacturing method is simple, rapid and low in cost, and the obtained wick can be widely applied to phase-change heat dissipation devices such as flat heat pipes and vapor chambers and meets the heat dissipation requirements of high-heat-flux electronic devices.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of heat management and heat transfer enhancement, and particularly relates to a porous aluminum-based wick, a manufacturing method thereof and an application thereof. BACKGROUND

[0002] With the rapid development of the electronic information industry, the heat dissipation problem of high-power-density chips and power devices is becoming increasingly serious. The heat spreading plate, as a typical phase change heat dissipation element, is widely used to solve local hot spots due to its high thermal conductivity and high temperature characteristics. However, the performance of such phase change heat transfer elements is highly dependent on the capillary structure design of the internal wick. Traditional wicks mainly use two types of groove structures or sintered porous structures: groove (micro-channel) wicks have small flow resistance, but the capillary force is limited and it is difficult to process fine grooves; sintered metal porous wicks have strong capillary force and large liquid storage capacity, but the reduction of pore size will increase the permeation resistance, restricting the liquid return. In order to balance the capillary pumping capacity and the return fluency, composite structure wicks have appeared in recent years.

[0003] Some existing patents report the preparation of composite porous wicks. Patent No. CN102345994A discloses a sintered double-pore structure wick. However, in this method, the pore structure mainly depends on the random accumulation of powders with different particle sizes, and the connectivity and uniformity of the pores are difficult to guarantee, and the pore structure cannot be accurately controlled. Patent No. CN106871675A discloses a multi-layer composite wick flat plate heat pipe and its preparation method, combining sintered layers and textured micro-groove layers. The manufacturing of this design requires separate sintering and machining and then assembly, which is a complex process and has thermal resistance between layers.

[0004] Other existing patents use additive manufacturing to regulate the structure and performance of porous materials. Patent No. CN114472919B discloses a method of using SLM to form a 3D printed porous metal thin net structure. This method realizes the high-quality preparation of porous thin net structures; however, this patent focuses on the batch printing process of thin net-like porous structures, does not involve the application of this structure in the field of wicks, and does not involve the TPMS structure and surface hydrophilic modification process. Patent No. CN110385436A discloses a method of using 3D printing to prepare metal wicks with different pore sizes, but the pores are randomly combined structures, and does not propose the design and control of the pore size through the TPMS structure and ordered pore layout. Patent No. US11633789B2 proposes forming an inner wall capillary structure through local sintering during additive manufacturing. Patent No. US20170064868A1 proposes first building a 3D porous area with low power sintering, and then melting a dense area with high power to manufacture a precise three-dimensional porous core layer and a dense support structure. SUMMARY

[0005] In order to overcome the shortcomings of existing liquid suction cores, which have low wettability and heat transfer performance, the core problem to be solved by this invention is: how to construct a multi-scale interconnected pore structure on aluminum alloy material to take into account both capillary suction and reflux channels, and to significantly improve wettability through simplification, thereby improving heat transfer performance.

[0006] To address this issue, the present invention provides a porous aluminum-based wicking core, its manufacturing method, and its applications. The present invention utilizes a selective laser melting additive manufacturing method to produce a multi-scale porous aluminum-based wicking core. This wicking core can be used in phase change heat transfer devices such as vapor chambers, which facilitates vapor-liquid exchange and improves condensation and evaporation efficiency. Furthermore, this wicking core significantly reduces the wetting contact angle of the working fluid, enhancing capillary driving force and boiling heat transfer performance.

[0007] To achieve the above objectives, the present invention adopts the following technical solution:

[0008] This invention provides a porous aluminum-based liquid absorbent core, comprising a thermally conductive substrate and a liquid absorbent core structure disposed on the thermally conductive substrate; the liquid absorbent core structure includes a microporous substrate, macroscopic channels, and a nanoscale surface layer; wherein, the microporous substrate is made of aluminum alloy and has pores with a size of 41-83 μm distributed inside, the porosity of the microporous substrate is 20%-60%, and adjacent pores are interconnected to form a continuous capillary network; the macroscopic channels have a periodic three-dimensional network structure and are disposed throughout the microporous substrate; the nanoscale surface layer is disposed on the surface of the microporous substrate and the wall of the macroscopic channels.

[0009] In this invention, the porous aluminum-based wicking core comprises three parts: a microporous matrix, macroscopic channels, and a nanoscale surface layer. The microporous matrix provides capillary suction, the macroscopic channels reduce liquid flow resistance, and the nanoscale surface layer enhances wetting and boiling heat transfer. The microporous matrix is ​​formed through controlled SLM (Self-Laminated Melting) process, with pore sizes on the order of tens of micrometers. The macroscopic channels are formed by introducing periodic structures such as TPMS into the design model, with dimensions ranging from sub-millimeter to millimeter, extending throughout the entire thickness of the wicking core. The nanoscale surface layer is created by alkaline etching to grow nanoporous oxides in situ on the aluminum surface. These three pore sizes work together to form a three-dimensional pore network.

[0010] In this invention, the porous aluminum-based liquid wick can be manufactured by selective laser melting (SLM) additive manufacturing.

[0011] In some embodiments, the pores of the microporous matrix are formed by controlling the laser scanning spacing and energy density.

[0012] In some embodiments, the aluminum alloy comprises Al–Si aluminum alloy powder; the Si content in the Al–Si aluminum alloy powder is 5% to 12%.

[0013] In some implementations, the cross-section of the macroscopic channel is a regular curved surface shape.

[0014] In some implementations, the macroscopic channel comprises a Gyroid structure or a Diamond structure in a three-period minimal surface (TPMS).

[0015] In some implementations, the characteristic scale of the macroscopic channel is 0.5 to 1.0 mm; the characteristic scale refers to the period length of the TPMS structural unit, that is, the distance between two adjacent repeating units.

[0016] In some implementations, the relative density of the macroscopic channels is adjusted using implicit function parameters.

[0017] In this invention, the microporous substrate and the macroscopic channel are interconnected; "the macroscopic channel is disposed throughout the microporous substrate" can be understood as the macroscopic channel being embedded inside the microporous substrate.

[0018] In some embodiments, the macroscopic channel is arranged along the thickness direction of the liquid-absorbing core structure.

[0019] In some embodiments, the macroscopic channels are arranged in an array on the longitudinal section of the liquid-absorbing core structure, that is, the TPMS structural units are periodically and repeatedly arranged in a regular row and column pattern in the plane to ensure uniform distribution of fluid in all directions, while also optimizing the strength of the structure.

[0020] In some embodiments, the nanoscale surface layer is formed by surface treatment of the microporous substrate with an alkaline solution. Surface treatment of the microporous substrate with an alkaline solution creates a nanoscale rough porous layer on the surface of the microporous substrate; this structure gives the wick superhydrophilic properties, improving capillary absorption capacity and heat transfer performance.

[0021] In some embodiments, the diameter of the nanopores in the nanosurface layer is 50–500 nm.

[0022] In some embodiments, the nanosurface layer is composed of fibrous or sheet-like alumina; it has a superwetting structure.

[0023] In some embodiments, the static contact angle of the nanoscale surface layer is less than 5°. The static contact angle refers to the angle between the tangent of the liquid surface and the solid surface at the gas-liquid-solid three-phase contact line when the droplet reaches equilibrium on the solid surface. The method for detecting the static contact angle includes: using a contact angle measuring instrument, dropping a deionized water droplet (approximately 2 μL) onto the sample surface, capturing the droplet profile with a high-speed camera, and automatically calculating the contact angle using software.

[0024] In some embodiments, the total thickness of the absorbent core structure is 4 to 6 mm.

[0025] In some embodiments, the thickness of the microporous substrate accounts for 80% of the total thickness of the absorbent core structure.

[0026] In some embodiments, the material of the thermally conductive substrate is the same as the material of the liquid-absorbing core.

[0027] In some embodiments, the thermally conductive substrate and the liquid-absorbing core structure are integrally formed; the liquid-absorbing core structure and the thermally conductive substrate can be metallurgically bonded to achieve the effect of zero interfacial thermal resistance.

[0028] The present invention also provides a method for manufacturing a porous aluminum-based liquid-absorbing core, which includes the following steps:

[0029] S1. Place the thermally conductive substrate above the wick structure, and embed the macroscopic channels in a periodic three-dimensional network structure into the wick structure to construct a three-dimensional model of the wick:

[0030] S2. Using aluminum alloy powder as raw material, selective laser melting is used to 3D print the three-dimensional model to obtain a liquid-absorbing core sample;

[0031] S3. The liquid absorption core sample is heat-treated in an inert atmosphere at a temperature of 300–500°C.

[0032] S4. The heat-treated liquid-absorbing core sample is surface-treated with alkaline solution to obtain a porous aluminum-based liquid-absorbing core.

[0033] In this invention, a porous aluminum-based liquid-absorbing core is directly printed using the SLM additive manufacturing method. On the one hand, by adjusting the laser parameters (power, scanning speed, scanning spacing, etc.), an incompletely melted area appears during the printing process, thereby generating micropores in the solid matrix. On the other hand, in the model design before printing, a through-hole TPMS three-dimensional channel space is reserved. During printing, the powder in this area is melted by the laser to form the channel wall, and the unscanned powder is removed to become a large through-hole.

[0034] In step S1 of the present invention, the three-dimensional model of the liquid aspiration core can be constructed in CAD.

[0035] In some embodiments, the macroscopic channel comprises a Gyroid structure or a Diamond structure in a three-period minimal surface; preferably, the macroscopic channel is a Gyroid structure in a three-period minimal surface.

[0036] In some implementations, the relative density of the macroscopic channel is adjusted by an implicit function parameter; when the macroscopic channel is a Gyroid structure, the implicit function expression is: sin(ax) + cos(ay) + sin(az) = C, where parameter a is a periodic parameter and C is a threshold constant, and the relative density of the channel can be changed by adjusting C.

[0037] In some embodiments, the particle size of the aluminum alloy powder is 15–53 μm.

[0038] In some embodiments, the 3D printing process includes: laying a powder layer in an inert atmosphere, filling the porous matrix area of ​​the wicking structure in a unidirectional parallel scanning manner according to a preset scanning path; laying the next powder layer after one layer is scanned, repeating the above process until the entire wicking and substrate structure is constructed, resulting in a porous wicking sample integrated with the thermally conductive substrate; during the printing process, the laser scanning automatically avoids the position of macroscopic channels in the model to form through-holes.

[0039] Preferably, the selective laser melting process employs an interlayer rotational scanning strategy. Specifically, after each layer of powder is scanned and melted, the scanning path (i.e., the laser scanning vector direction) of the next layer is rotated 90° relative to the previous layer.

[0040] In step S2 of the present invention, by precisely controlling the process conditions of selective laser melting (SLM), a TPMS structure embedded in a microporous substrate is formed, thereby achieving the synergistic manufacturing of micropores and macroscopic channels.

[0041] In step S2 of this invention, the microporous substrate region of the wicking structure employs a low energy density to form an incompletely melted microporous structure. By using differentiated process parameters for different regions in a single printing job, a composite component with a porous wicking structure and a dense thermally conductive substrate is integrally manufactured. The microporous substrate is formed using a specially designed low volumetric energy density process to produce functional incompletely melted pores. In contrast, the thermally conductive substrate region is printed using a conventional high volumetric energy density process to ensure its structure is completely dense (relative density > 99.5%), thereby achieving excellent thermal conductivity.

[0042] In step S2 of the present invention, the scanning parameters of selective laser melting are obtained through orthogonal experiments.

[0043] In some embodiments, in step S2, the laser power range in the selective laser melting is 300–500 W.

[0044] In some embodiments, in step S2, the scanning speed in the selective laser melting is 1000–1400 mm / s.

[0045] In some embodiments, in step S2, the thickness of the powder layer in the selective laser melting is 20–50 μm.

[0046] In some embodiments, in step S2, the electric scanning interval in the selective laser melting is 0.1 to 0.3 mm.

[0047] In a specific implementation, the energy density of the selective laser melting is controlled at 30–50 J / mm². 3 To ensure the structural integrity while preserving micropores in the microporous matrix region.

[0048] In a specific implementation, during the selective laser melting in step S2, the laser power is 360W, the scanning speed is 1400mm / s, and the scanning interval is 0.24mm. Under these parameters, the porosity of the obtained microporous matrix is ​​approximately 47%, and the average pore diameter is 68μm.

[0049] In this invention, the heat treatment can eliminate residual stress in the liquid-absorbing core sample, enhance the metallurgical bonding strength, and maintain the integrity of the microporous structure.

[0050] In some embodiments, the heat treatment holding time in step S3 is 2 hours.

[0051] In some embodiments, in step S3, after the heat treatment, a cooling treatment and a surface cleaning treatment are performed sequentially to remove unfused loose powder.

[0052] In this invention, the printed liquid-absorbing core sample is immersed in a NaOH solution for etching (i.e., surface treatment). Utilizing the reaction of aluminum with NaOH to generate sodium aluminate and hydrogen gas, numerous nanoscale etching pits and oxidation products are formed on the pore wall surface. By controlling the etching concentration and time, nanopores can be obtained while ensuring the main pore structure does not collapse. The nanopores significantly improve the hydrophilicity and capillary suction capacity of the material surface. After etching treatment, the porous aluminum-based liquid-absorbing core exhibits significantly faster spreading and re-absorption rates of the working fluid, and an increased capillary suction height.

[0053] In step S4 of the present invention, under the action of alkaline solution, the pores of the microporous matrix and the TPMS structure inside it will generate a nanolayer. This "all-round" nanolayer coverage significantly improves the overall capillary liquid absorption capacity of the liquid absorption core structure.

[0054] In step S4 of the present invention, the surface treatment method includes immersing the heat-treated absorbent core sample in an alkaline solution; those skilled in the art should understand that, in this process, the pore wall surface of the microporous substrate and the wall surface of the macroscopic channel will be corroded by the alkaline solution to form a nano-surface layer, thereby significantly improving the wetting performance.

[0055] In some embodiments, in step S4, the alkaline solution comprises a sodium hydroxide solution with a concentration of 0.25–0.75 mol / L; preferably, the concentration of the sodium hydroxide solution is 0.3–0.7 mol / L; more preferably, the concentration of the sodium hydroxide solution is 0.3–0.6 mol / L.

[0056] In some embodiments, the surface treatment temperature in step S4 is 20–30°C.

[0057] In some embodiments, the surface treatment time in step S4 is 3 to 9 minutes.

[0058] In a specific embodiment, in step S4, the alkaline solution is sodium hydroxide with a concentration of 0.5 mol / L, and the surface treatment time is 6 minutes. Under these conditions, uniform sheet-like / needle-like nanostructures can be formed on the micropore walls of the porous aluminum-based absorbent core, further reducing the wetting contact angle of the material and increasing the capillary absorption height.

[0059] In this invention, the surface treatment involves an alkaline solution reacting on the aluminum alloy surface to generate a nanoporous oxide layer.

[0060] In this invention, preferably, the porous aluminum-based absorbent core after surface treatment is cleaned with deionized water and dried to obtain a finished porous aluminum-based absorbent core with a nano-rough structure on its surface.

[0061] The present invention also provides a porous aluminum-based liquid absorbent core, which is obtained by the manufacturing method described above.

[0062] The present invention also provides an application of the porous aluminum-based liquid wick as described above in a phase change heat dissipation element.

[0063] In this invention, preferably, the phase change heat dissipation element includes a heat spreader.

[0064] The porous aluminum-based wicking core can be directly used as the internal capillary structure of a heat spreader. Specifically, it is installed in a vacuum-sealed heat spreader, which can be filled with working fluids such as ammonia or acetone. Due to its multi-scale porous structure, the wicking core has a large capillary suction force and an improved working fluid reflux permeability, enabling the device to achieve efficient phase change heat transfer under high heat flux density conditions and operate stably.

[0065] The solution of the present invention can achieve at least the following technical effects:

[0066] Compared with the prior art, the positive effects of the present invention are:

[0067] 1. The porous aluminum-based liquid-absorbing core of the present invention integrates nano / micro / millimeter pores at different levels to achieve a coordinated and unified function of capillary liquid absorption, liquid reflux and vapor-liquid separation; traditional technology makes it difficult to obtain such a cross-scale ordered pore structure in a single material at the same time.

[0068] 2. The introduction of TPMS biomimetic three-dimensional channels into the porous aluminum-based wicking core of this invention makes the internal flow channels of the wicking core more uniform and interconnected, reducing flow losses caused by right-angle turns in traditional grooves and random sintering holes. The large specific surface area of ​​the TPMS channels also facilitates vapor-liquid exchange, improving condensation and evaporation efficiency.

[0069] 3. The nano-surface layer in the porous aluminum-based wick of this invention significantly reduces the wetting contact angle of the working fluid, enhancing capillary driving force and boiling heat transfer performance. This modification compensates for the slightly smooth surface of additive manufacturing, further improving the performance of the wick.

[0070] 4. This invention directly prepares porous aluminum-based liquid-absorbing cores by optimizing the process parameters in the manufacturing method. Compared with 3D printing of materials such as copper or stainless steel, it has the advantages of being lighter and more corrosion-resistant. Moreover, the process is simple and does not require auxiliary templates, and it is fast and efficient. It can be extended to mass production of complex capillary structures.

[0071] 5. This invention utilizes the inherent characteristics of the SLM process, eliminating the need for additional material filling or post-sintering steps, and can directly generate uniformly distributed micropores by controlling the laser power density; furthermore, the desired pores can be formed in the overall structure simply by optimizing process parameters in a single step (such as adjusting the scanning spacing), simplifying the manufacturing process. Attached Figure Description

[0072] Figure 1 This is a three-dimensional structural diagram of the liquid absorption core structure in the porous aluminum-based liquid absorption core of the present invention.

[0073] Figure 2 yes Figure 1 A partially enlarged cross-sectional schematic diagram of the liquid absorption core structure shown.

[0074] Figure 3 This is a schematic diagram of the manufacturing process of the porous aluminum-based liquid-absorbing core of the present invention.

[0075] Figure 4 These are metallographic photographs of porous aluminum-based liquid-absorbing cores printed under different process parameters.

[0076] Figure 5These are SEM comparison images of the nanostructure morphology on the surface of the liquid absorbent core with different surface treatment processes.

[0077] Figure 6 It is the contact angle of the porous aluminum-based liquid-absorbing core before and after surface treatment.

[0078] Figure 7 This is the experimental performance test curve of the porous aluminum-based liquid-absorbing core of the present invention applied to a heat spreader.

[0079] Explanation of reference numerals in the attached figures:

[0080] 1. Unmelted pores; 2. TPMS channels. Detailed Implementation

[0081] The technical solution of the present invention will be further described below through embodiments.

[0082] Example 1

[0083] This embodiment discloses a method for manufacturing a porous aluminum-based liquid wick with a Gyroid structure. Figure 3 A schematic diagram of the manufacturing process for a porous aluminum-based liquid-absorbing core.

[0084] The manufacturing method includes the following steps:

[0085] S1: A 3D structural model of the absorbent core was designed using 3D modeling software (CAD). The model's dimensions are 50mm × 50mm × 6mm (length × width × thickness). Gyroid-type TPMS channels 2 are filled in the center of the model as macroscopic channels. The relative density of the macroscopic channels is adjusted using implicit function parameters. The implicit function expression is: sin(ax) + cos(ay) + sin(az) = C, where parameter a is the periodic parameter and C is a threshold constant. Adjusting C changes the relative density of the channels. The channel period is 2mm, and the threshold C is set to 0.4, resulting in a curved channel network penetrating the thickness of the microporous matrix. The channel period refers to the distance between two adjacent complete repeating units in the TPMS structure; the threshold C is a constant term in the TPMS implicit function equation, used to control the relative density and porosity of the structure.

[0086] S2: AlSi10Mg with a particle size of 15–53 μm was selected as the raw material, with a Si content of 5%–12%. The above model was imported into the printer slicing software, and the powder layer thickness was set to 0.03 mm (30 μm). A "rotational scanning" strategy was used for printing: the laser scanned parallel to the X direction, and adjacent alternating scans were performed in the Y direction to reduce stress. The laser power was set to 360 W, the scanning speed to 1400 mm / s, and the fill scan spacing to 0.24 mm (medium scan spacing). Since the matrix region contains a micropore model, the positions corresponding to these micropores were not exposed by the laser during slicing, forming unmelted pores 1. When scanning the channel region of the Gyroid structure, since there were no pre-placed pores in this region, the laser melted and spread the powder according to the morphology. After printing, a liquid-absorbing core sample was obtained.

[0087] Figure 4 These are metallographic photographs of porous aluminum-based liquid-absorbing cores printed under different process parameters. For example... Figure 4 As shown, from left to right, the porous aluminum-based liquid-absorbing cores were printed under conditions of small scanning spacing (0.1 mm), medium scanning spacing (0.24 mm), and large scanning spacing (0.3 mm), respectively. This demonstrates the direct impact of scanning spacing on porosity, proving that the porosity characteristics of the microporous matrix can be precisely controlled by adjusting the laser scanning spacing.

[0088] S3: The absorbent core sample was placed in a vacuum furnace, filled with argon gas for protection, heated to 380℃ and held for 2 hours, then cooled with the furnace to remove residual internal stress and promote the sintering and adhesion of unmelted powder to the walls. After removal, the sample was blown from both sides of the channel opening with an air gun to remove any loose powder remaining in the channel. The sample was then ultrasonically cleaned in anhydrous ethanol for 5 minutes to remove surface-adhered powder particles. At this point, the absorbent core sample was uniformly grayish-white, and the porous structure was basically formed. The overall porosity of the sample was measured to be approximately 47%, and the channel diameter of the Gyroid structure was approximately 0.8 mm.

[0089] S4: Prepare a 0.5 mol / L NaOH aqueous solution in a beaker (room temperature approximately 25°C). Immerse the dried absorbent core sample in the solution for surface treatment and begin timing the etching process. Tiny bubbles (hydrogen gas) will appear on the sample surface after about 1 minute of reaction. After 6 minutes of continuous etching, remove the sample with tweezers, immediately immerse it in pure water for 1 minute to neutralize the residual alkali, then transfer it to fresh pure water for ultrasonic cleaning for 2 minutes, and finally remove it and dry it with nitrogen gas.

[0090] S5: Observe the microstructure of the sample before and after corrosion using a scanning electron microscope.

[0091] A porous aluminum-based liquid-absorbing core is obtained by the above manufacturing method. Figure 1 This is a three-dimensional structural diagram of the liquid absorption core structure in a porous aluminum-based liquid absorption core; Figure 2 yes Figure 1The diagram shows a partially enlarged cross-sectional view of the liquid-absorbing core structure. This porous aluminum-based liquid-absorbing core includes a thermally conductive substrate and a liquid-absorbing core structure disposed on the thermally conductive substrate. The liquid-absorbing core structure includes a microporous substrate, macroscopic channels, and a nanoscale surface layer. The microporous substrate is made of aluminum alloy and contains pores with sizes ranging from 41 to 83 μm, an average pore diameter of 68 μm, and a porosity of 47%. Adjacent pores are interconnected to form a continuous capillary network. The macroscopic channels have a periodic three-dimensional network structure and extend throughout the microporous substrate. The nanoscale surface layer is disposed on the surface of the microporous substrate and the walls of the macroscopic channels. The macroscopic channels are Gyroid structures in a three-period minimal surface, with a characteristic dimension of approximately 0.8 mm. The macroscopic channels are arranged along the thickness direction of the liquid-absorbing core structure. In the longitudinal section of the liquid-absorbing core structure, the macroscopic channels are arranged in an array. The diameter of the nanopores in the nanosurface layer is 50–500 nm; the nanosurface layer is composed of fibrous or sheet-like alumina; the static contact angle of the nanosurface layer is less than 5°. The total thickness of the wicking structure is 4–6 mm; the thickness of the microporous substrate accounts for 80% of the total thickness of the wicking structure; the material of the thermally conductive substrate is the same as that of the wicking core; the thermally conductive substrate and the wicking structure are integrally formed.

[0092] Figure 6 It refers to the contact angle of the porous aluminum-based liquid-absorbing core before and after surface treatment; such as Figure 6 As shown: the surface of the uncorroded micropore wall is relatively smooth, with only overlapping textures from the printed molten pool; after 6 minutes of corrosion, the surface is covered with a large number of sheet-like and needle-like nanostructures, the pore walls become uneven, and the pore edges become blunt and slightly enlarged. Contact angle tests show that the static contact angle of the uncorroded sample is about 68.7°, which drops to nearly 0° after corrosion (spreading immediately upon contact with a water droplet).

[0093] This embodiment demonstrates that by using SLM printing combined with alkaline etching modification, a multi-scale porous aluminum-based liquid-absorbing core with a superhydrophilic surface can be successfully prepared.

[0094] Example 2

[0095] This embodiment discloses a method for manufacturing a porous aluminum-based liquid-absorbing core with a diamond structure. The three-dimensional structural model of this embodiment is filled with diamond-type TPMS channels in the center, while maintaining other parameters (channel period 2 mm, thickness 6 mm). The printing process is the same as in Example 1, and both are subjected to etching with 0.5 mol / L NaOH for 6 minutes.

[0096] The results showed that the porous aluminum-based liquid-absorbing cores of Examples 1 and 2 were printed with good quality. Performance tests indicated that, under the same working conditions, the capillary suction performance of both was similar, with a rise height of approximately 46 mm. However, the isotropic nature of the Gyroid structure resulted in more uniform liquid supply in multiple directions, giving it slightly better performance than the Diamond structure.

[0097] Examples 3-10

[0098] This set of examples investigated the effects of different surface treatment process parameters on the performance of porous aluminum-based absorbent cores. Specifically, in step S4 of Examples 3-5, the NaOH concentration for surface treatment of the absorbent core samples was 0.25 mol / L, and the treatment times were 3 min, 6 min, and 9 min, respectively. In step S4 of Examples 6-7, the NaOH concentration for surface treatment of the absorbent core samples was 0.5 mol / L, the same as in Example 1, but the treatment times were 3 min and 9 min, respectively. In step S4 of Examples 8-10, the NaOH concentration for surface treatment of the absorbent core samples was 0.75 mol / L, and the treatment times were 3 min, 6 min, and 9 min, respectively.

[0099] Figure 5 These are SEM comparison images of the nanostructure morphology on the surface of absorbent cores with different surface treatment processes. SEM (JSM-7800F) observation revealed that: after 3 minutes of etching in a 0.25 mol / L sodium hydroxide solution, only a few scattered nano-etched pits were formed on the absorbent core samples; as the time increased to 6 and 9 minutes, the nanosheet structure gradually became denser. When the sodium hydroxide concentration was increased to 0.5 mol / L, a relatively complete nano-rough layer was formed after 3 minutes; the nanostructure size and density reached their optimal levels at 6 minutes; and some signs of pore wall thinning appeared at 9 minutes. When the sodium hydroxide concentration was increased to 0.75 mol / L, some micropores collapsed after 3 minutes of etching, and large areas of the pore walls detached after 6 minutes, indicating structural damage.

[0100] Therefore, the preferred conditions for surface treatment of the liquid absorption core sample in this invention are a 0.25 mol / L NaOH solution and a surface treatment time of 3-9 min; or a 0.5 mol / L NaOH solution and a surface treatment time of 3-9 min.

[0101] The preferred conditions for surface treatment of the absorbent core sample are a NaOH solution with a concentration of approximately 0.5 mol / L and a surface treatment time of 6 minutes (the conditions in Example 1). Under these conditions, the nanostructure on the absorbent core surface is well-preserved, and the main pore structure remains intact, resulting in the most significant improvement in capillary performance.

[0102] Example 1

[0103] This effective embodiment verifies the heat transfer performance of the porous aluminum-based wicking core from Example 1, comparing it to a control wicking core without surface treatment. Both wicking cores were assembled onto an aluminum-based heat spreader (10mm thick) of the same size for heat dissipation testing. The heat source was a 30×30mm electric heating element, with water cooling in the condensation section. The input power was gradually increased until drying failure occurred.

[0104] Figure 7 These are the experimental performance test curves of the porous aluminum-based liquid-absorbing core of the present invention applied to a heat spreader. The results show that the untreated sample dries out at around 200W; while the sample of Example 1 can operate stably at around 240W before the same failure phenomenon occurs, improving the maximum heat transfer capacity by about 20%.

[0105] As can be seen from the above description of the embodiments, the multi-scale porous aluminum-based liquid wick provided by the present invention is innovative in both structural design and manufacturing method, and can significantly improve the performance of phase change heat transfer devices.

[0106] It should be noted that, without departing from the principle of this invention, improvements or modifications can be made to the specific structure and process parameters, and these improvements or equivalent modifications are also within the protection scope of this invention.

Claims

1. A porous aluminum-based wick, characterized by, It comprises a heat-conducting substrate and a liquid-absorbing core structure, wherein the liquid-absorbing core structure is arranged on the heat-conducting substrate; The liquid-absorbing core structure comprises a microporous matrix, macroscopic channels and a nanometer surface layer; wherein The material of the microporous matrix is aluminum alloy, and the microporous matrix is internally distributed with pores with a size of 41-83 μm, and the porosity of the microporous matrix is 20%-60%, and adjacent pores are connected to form a continuous capillary network; The macroscopic channels are arranged in the microporous matrix in a periodic three-dimensional network structure; The nanometer surface layer is arranged on the pore wall surface of the microporous matrix and the wall surface of the macroscopic channels.

2. The porous aluminum-based wick of claim 1, wherein, The pores of the microporous matrix are formed by controlling the laser scanning interval and energy density; The aluminum alloy comprises Al-Si series aluminum alloy powder, and the Si content in the Al-Si series aluminum alloy powder is 5%-12%.

3. The porous aluminum-based wick of claim 1, wherein, The macroscopic channels satisfy at least one of the following conditions: i. The cross section of the macroscopic channels is a regular curved surface shape; ii. The macroscopic channels comprise Gyroid structure or Diamond structure in the triperiodic minimal surface; iii. The characteristic scale of the macroscopic channels is 0.5-1.0 mm; iv. The relative density of the macroscopic channels is adjusted by an implicit function parameter; v. The macroscopic channels are arranged along the thickness direction of the liquid-absorbing core structure; vi. On the longitudinal section of the liquid-absorbing core structure, the macroscopic channels are arranged in an array form.

4. The porous aluminum-based wick of claim 1, wherein, The nanometer surface layer satisfies at least one of the following conditions: i. The nanometer surface layer is formed by surface treatment of the microporous matrix with an alkaline solution; ii. The diameter of the nanopores of the nanometer surface layer is 50-500 nm; iii. The nanometer surface layer is composed of fibrous or flaky aluminum oxide; iv. The static contact angle of the nanometer surface layer is less than 5°.

5. The porous aluminum-based wick of claim 1, wherein, The porous aluminum-based liquid-absorbing core satisfies at least one of the following conditions: i. The total thickness of the liquid-absorbing core structure is 4-6 mm; ii. The thickness of the microporous matrix accounts for 80% of the total thickness of the liquid-absorbing core structure; iii. The material of the heat-conducting substrate is the same as that of the liquid-absorbing core; iv. The heat-conducting substrate is integrally formed with the liquid-absorbing core structure.

6. A method of manufacturing a porous aluminum-based wick, characterized by, It comprises the following steps: S1. Arranging the heat-conducting substrate above the liquid-absorbing core structure, and embedding the macroscopic channels in a periodic three-dimensional network structure in the liquid-absorbing core structure to construct a three-dimensional model of the liquid-absorbing core; S2. Using aluminum alloy powder as raw material, and adopting selective laser melting to 3D print the three-dimensional model to obtain a liquid-absorbing core sample; S3. In an inert atmosphere, heat treating the liquid-absorbing core sample, and the heat treatment temperature is 300-500 ℃; S4. Surface treating the heat-treated liquid-absorbing core sample with an alkaline solution to obtain a porous aluminum-based liquid-absorbing core.

7. The production method according to claim 6, wherein The manufacturing method satisfies at least one of the following conditions: i. The macroscopic channels comprise Gyroid structure or Diamond structure in the triperiodic minimal surface; ii. The particle size of the aluminum alloy powder is 15-53 μm; iii. The process of the 3D printing comprises: laying a powder layer under an inert atmosphere, filling the porous matrix area of the liquid-absorbing core structure in a unidirectional parallel scanning manner according to a preset scanning path.

8. The production method according to claim 7, wherein Steps S2-S4 meet at least one of the following process conditions: i. In step S2, the laser power in the selective laser melting ranges from 300 to 500 W; ii. In step S2, the scanning speed in the selective laser melting is 1000-1400 mm / s; iii. In step S2, the powder layer thickness in the selective laser melting is 20-50 μm; iv. In step S2, the electric scanning interval in the selective laser melting is 0.1-0.3 mm; v. In step S3, the holding time of the heat treatment is 2 h; vi. In step S3, after the heat treatment, a cooling treatment and a surface cleaning treatment are sequentially performed; vii. In step S4, the alkali solution comprises a sodium hydroxide solution, and the concentration of the sodium hydroxide solution is 0.25-0.75 mol / L; viii. In step S4, the temperature of the surface treatment is 20-30 °C; ix. In step S4, the time of the surface treatment is 3-9 min.

9. A porous aluminum-based wick, characterized by, The porous aluminum-based liquid-absorbing core is obtained by using the manufacturing method according to any one of claims 6-8.

10. Use of the porous aluminum-based liquid-absorbing core according to any one of claims 1-5 or the porous aluminum-based liquid-absorbing core according to claim 9 in a phase change heat dissipation element.

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