A steam chamber capillary wick structure and its preparation method

Abstract

This invention relates to the field of phase change heat transfer technology, and provides a capillary wick structure for a vapor chamber and its preparation method. First, a micron-scale array structure is prepared on the surface of a metal substrate at the bottom of the vapor chamber. Then, the surface of the metal substrate with the micron-scale array structure is oxidized. Subsequently, a carbon nanotube growth catalyst is loaded onto the surface of the metal substrate, and then vertically oriented carbon nanotubes are grown on the surface of the metal substrate via chemical vapor deposition. The capillary wick structure prepared by this invention can simultaneously increase the density of bubble nucleation sites and enhance capillary action, endowing the metal substrate with excellent phase change heat transfer performance.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of phase change heat transfer, in particular to a vapor chamber capillary structure and a preparation method thereof. BACKGROUND

[0002] A chip is a semiconductor material on which electronic components such as resistors, capacitors and circuits composed of the same are integrated and encapsulated in a plastic or ceramic package. With the advent of the 5G era, the size of transistors in the chip is exponentially reduced, and chip manufacturers are also increasing the number of transistors to achieve higher component density and clock frequency. In addition, in order to further improve the performance of the chip, more processing units are often laid out in high-performance computers, which leads to further increase in the heat power of electronic devices in the chip. Heat dissipation is crucial to the performance and reliability of the chip. If heat cannot be effectively dissipated, the temperature of the chip will continue to rise, causing the leakage current of the device to increase, the threshold voltage to decrease, and the performance of the chip to decrease. Moreover, as the temperature rises, the failure rate of electronic components and equipment increases exponentially, which will cause immeasurable loss to actual production and life.

[0003] A vapor chamber is a container or device for heat transfer through liquid-gas phase change. The liquid absorbs heat at the bottom of the capillary core of the vapor chamber and undergoes phase change to become gas. Then the gas is liquefied at the condensation end at the top of the vapor chamber to release heat. Finally, through continuous gas-liquid circulation, high-efficiency heat dissipation is achieved.

[0004] In the vapor chamber, the capillary core is a key component. The main functions of the capillary core are heat transfer and liquid transport. Common metal and metal oxide capillary cores are inert, lack bubble nucleation sites, have low thermal conductivity, are easily oxidized at high temperatures, and have unadjustable shape and performance, poor structural stability, and ultimately low critical heat flux (CHF) and boiling heat transfer coefficient (HTC), which affects the heat dissipation efficiency. SUMMARY

[0005] The problem to be solved by the present application is how to improve the critical heat flux and boiling heat transfer coefficient of the capillary core structure to improve the heat dissipation efficiency of the vapor chamber.

[0006] To solve the above problems, the present application provides a preparation method of a vapor chamber capillary core structure, comprising:

[0007] S1, preparing a micron-level array structure on a metal substrate at the bottom of the vapor chamber;

[0008] S2, oxidizing the metal substrate after S1, and then preparing a carbon nanotube growth catalyst on the oxidized metal substrate;

[0009] S3, preparing vertically oriented carbon nanotubes on the metal substrate after S2 by chemical vapor deposition, to finally obtain a vapor chamber capillary core structure.

[0010] Optionally, the micron-scale array structure includes one of the following: micropits, microchannels, micropillars, and microcones arrayed on the metal substrate.

[0011] Optionally, the micron-scale array structure is fabricated on the metal substrate using at least one of laser processing, milling, embossing, and casting.

[0012] Optionally, the parameters of the laser processing include: a nanosecond laser power of 30-100W, a repetition frequency of 100kHz, a spot diameter of 50μm, a scanning speed of 5000-10000mm / s, and a pulse duration of 200ns.

[0013] Optionally, the oxidation treatment of the metal substrate after S1 includes immersing the metal substrate after S1 in a 1 mol / L NaOH solution at 60-80°C for 12-18 hours.

[0014] Optionally, the carbon nanotube growth catalyst includes Zif-67, and the preparation of the carbon nanotube growth catalyst on the oxidized metal substrate includes immersing the oxidized metal substrate in a Zif-67 precursor solution for 20-24 hours.

[0015] Optionally, the Zif-67 precursor solution is obtained by dissolving 500-1000 mg of 2-methylimidazole and 100-500 mg of cobalt nitrate in 20 mL of methanol solution and then mixing them.

[0016] Optionally, immersing the oxidized metal substrate in the Zif-67 precursor solution includes immersing one side of the oxidized metal substrate with the micron-scale array structure into the Zif-67 precursor solution in a manner perpendicular to the surface of the Zif-67 precursor solution.

[0017] Optionally, in S3, the metal substrate after S2 is placed in a tube furnace and calcined at 800-850°C for 3-5 hours under the conditions of melamine and N2 to H2 flow ratio of 93:7-99:1.

[0018] The present invention also provides a steam chamber capillary wick structure, which is prepared by the steam chamber capillary wick structure preparation method described above.

[0019] This invention first prepares a micron-scale array structure on the surface of a metal substrate at the bottom of the steam chamber to increase the surface roughness of the substrate, thereby increasing the number of micron-scale bubble nucleation sites, promoting bubble separation, increasing the carrier for phase change, and improving heat transfer capacity, thus contributing to an improved boiling heat transfer coefficient. Then, the surface of the metal substrate with the prepared micron-scale array structure is oxidized to increase the bonding force between the carbon nanotube catalyst and the metal substrate, resulting in a more uniform distribution of the carbon nanotube catalyst on the metal substrate surface. The carbon nanotube catalyst is used to promote carbon nanotube growth; therefore, by loading a carbon nanotube growth catalyst onto the metal substrate surface, it is possible to uniformly grow carbon nanotubes on the metal substrate surface via chemical vapor deposition. The vertically oriented carbon nanotube array has a strong capillary wicking effect, which helps to increase capillary force, enhance liquid transport capacity, and allow for timely liquid replenishment, thereby increasing the critical heat flux density. In summary, the capillary wick structure prepared by this invention can simultaneously increase the density of bubble nucleation sites and enhance capillary action, endowing the metal substrate with excellent phase change heat transfer performance. Attached Figure Description

[0020] Figure 1 This is a flowchart illustrating the preparation method of the steam chamber capillary wick structure in an embodiment of the present invention;

[0021] Figure 2 This is a schematic diagram illustrating the working principle of the steam chamber in an embodiment of the present invention;

[0022] Figure 3 This is a schematic diagram of the preparation process of the capillary wick structure of the steam chamber in an embodiment of the present invention;

[0023] Figure 4 This is a scanning electron microscope image of the layered CNTs structure prepared in Example 1 of the present invention;

[0024] Figure 5 The results are from the capillary climb test of pure copper and layered CNTs in Example 1 of this invention.

[0025] Explanation of reference numerals in the attached figures:

[0026] 1-Steam chamber; 2-Capillary wick structure. Detailed Implementation

[0027] Carbon nanotube (CNT) coatings possess excellent thermal conductivity, high specific surface area, strong capillary action, and easily controllable morphology. These advantages allow CNTs to increase the density of bubble nucleation sites and enhance the wettability of heated surfaces, thereby synergistically enhancing critical heat flux (CHF) and boiling heat transfer coefficient (HTC). However, since the effective nucleation size of bubbles is 3-10 μm, meaning that effective nucleation requires bubbles within this size range, and the pore size of carbon nanotube arrays is typically on the order of tens to hundreds of nanometers, far smaller than the effective nucleation size of bubbles, a simple carbon nanotube coating has limited effect on enhancing the density of bubble nucleation sites. It cannot provide a sufficiently large surface area or pores to accommodate the size required for bubble formation, thus limiting bubble nucleation and growth, and consequently restricting further enhancement of HTC. Furthermore, in the field of boiling heat transfer, most carbon nanotubes are prepared by electrodeposition or self-assembly. Carbon nanotubes prepared by these methods are usually randomly distributed on the substrate surface and exhibit a horizontal orientation. This arrangement weakens the capillary effect between carbon nanotubes, leading to a decrease in CHF. In addition, the random distribution of CNTs also hinders the detachment of bubbles, resulting in a decrease in HTC.

[0028] It is evident that carbon nanotube capillary cores have limited effect on enhancing the density of bubble nucleation sites, and the random distribution of carbon nanotubes weakens the capillary effect, thereby limiting the improvement of critical heat flux density and boiling heat transfer coefficient.

[0029] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0030] Please see Figure 1 As shown, a method for preparing a steam chamber capillary wick structure according to an embodiment of the present invention includes:

[0031] S1, a micron-scale array structure is fabricated on a metal substrate at the bottom of the vapor chamber;

[0032] S2, the metal substrate after S1 is oxidized, and then a carbon nanotube growth catalyst is prepared on the oxidized metal substrate.

[0033] In S3, vertically oriented carbon nanotubes were prepared on the metal substrate following S2 using chemical vapor deposition, ultimately obtaining a vapor chamber capillary core structure.

[0034] In this embodiment, a micron-scale array structure is first fabricated on the surface of a metal substrate at the bottom of the steam chamber to increase the surface roughness of the substrate. Since the nucleation size of bubbles is on the micron scale, fabricating a micron-scale array structure on the substrate surface greatly increases the number of micron-scale bubble nucleation sites, increases the carrier for phase change heat transfer, improves heat transfer capacity, and is beneficial to improving the boiling heat transfer coefficient (HTC). Then, an oxidation treatment is performed on the surface of the metal substrate with the fabricated micron-scale array structure to increase the bonding force between the carbon nanotube growth catalyst and the metal substrate, resulting in a more uniform loading of the carbon nanotube growth catalyst on the metal substrate surface. The carbon nanotube growth catalyst is used to promote carbon nanotube growth; therefore, by loading the carbon nanotube growth catalyst onto the surface of the metal substrate, it is possible to subsequently grow carbon nanotubes on the surface of the metal substrate via chemical vapor deposition. The vertically oriented carbon nanotube array has a strong capillary wicking effect, which helps to increase capillary force, enhance liquid transport capacity, and allow the liquid to be replenished in a timely manner, thereby increasing the critical heat flux (CHF).

[0035] Therefore, the capillary wick structure prepared in this embodiment can simultaneously increase the density of bubble nucleation sites and enhance capillary action, endowing the metal substrate with excellent phase change heat transfer performance, such as... Figure 2 As shown, in the steam chamber, the liquid absorbs heat at the capillary wick at the bottom of the steam chamber and undergoes a phase change, transforming into a gas. The gas liquefies at the condenser end at the top of the steam chamber, releasing heat and achieving efficient heat dissipation, significantly enhancing the heat dissipation performance of the steam chamber.

[0036] It is understandable that capillary wicking is a surface phenomenon, that is, the microstructure of a solid surface has pores, and when a liquid comes into contact with the solid surface, these pores exert an inward attraction (also called capillary force) on the liquid, causing the liquid to spread rapidly on the solid surface.

[0037] Vertically oriented carbon nanotubes (CNTs) possess a highly ordered structure, with their ends facing the same direction, forming a forest-like structure. This vertical alignment provides numerous micropores, enhancing capillary wicking on the CNT surface. Furthermore, the vertically ordered arrangement of CNTs reduces the diffusion path of liquid molecules on the CNT surface, further enhancing the liquid diffusion rate. This embodiment, by fabricating vertically oriented carbon nanotubes on a metal substrate, helps improve the capillary effect on the heated surface, enhances the rewetting of the liquid on the heated surface, hinders the expansion of the gas film, helps avoid localized overheating of the heated surface, and enhances CHF (hydrocarbon flux).

[0038] In some embodiments, the micron-scale array structure includes one of micropits, microchannels, micropillars, and microcones arrayed on the metal substrate.

[0039] By fabricating micron-scale array structures on the surface of a metal substrate, the micron-scale roughness of the substrate is increased, thereby increasing the density of bubble nucleation sites. A micron-scale array structure refers to structures such as pits, channels, and pillars, with dimensions at the micron level, distributed in an array on the metal substrate. For ease of explanation, micron-scale pits are called micropits, micron-scale channels are called microchannels, micron-scale pillars are called micropillars, and micron-scale conical structures are called microcones. Of course, in addition to these shapes or structures, other forms of structures can also be fabricated; for example, micropits can be spherical, trapezoidal, or similar shapes. Figure 3 The structure shown resembles a cup.

[0040] This embodiment transforms a planar metal substrate into a micron-scale structure by using pits, pillars, and other micron-sized structures, thereby increasing the heat transfer area. As a result, the number of bubble nucleation sites also increases, leading to an increase in the heat transfer coefficient.

[0041] In some embodiments, the micron-scale array structure is fabricated on the metal substrate using at least one of laser processing, milling, embossing, and casting.

[0042] Laser processing is a non-contact processing method that enables high-precision and high-speed processing. Furthermore, laser processing can fabricate complex micron-sized structures, offering advantages such as high precision, fast processing speed, and wide applicability. Therefore, this embodiment prioritizes the use of laser processing to fabricate micron-sized array structures.

[0043] In addition, milling is a common machining method that can achieve high-precision micron-level structure machining, with advantages such as fast processing speed and low cost. Imprinting involves applying pressure to a metal substrate to transfer micron-level structures from a mold onto the substrate, offering advantages such as high processing speed, high production efficiency, and suitability for large-area machining. Casting is a common manufacturing method that involves pouring molten metal into a mold, allowing the metal to solidify and form micron-level structures. The machining method can be selected based on specific processing requirements and material properties.

[0044] In some embodiments, the parameters of the laser processing include: a nanosecond laser power of 30-100W, a repetition frequency of 100kHz, a spot diameter of 50μm, a scanning speed of 5000-10000mm / s, and a pulse duration of 200ns.

[0045] When using nanosecond lasers, a laser power of 30-100W provides sufficient energy to process micron-scale structures on metal substrates, ensuring both processing efficiency and quality. A repetition rate of 100kHz means the laser pulses can be emitted continuously at a very high frequency, resulting in fast processing speeds suitable for high-efficiency production. A spot diameter of 50μm allows the laser to be focused onto a very small area, achieving high-precision processing to fabricate fine micron-scale structures. A scanning speed of 5000-10000mm / s enables the laser to move rapidly across the metal substrate surface, improving production efficiency. A pulse duration of 200ns means the laser pulse's duration is very short, reducing the heat-affected zone and preventing overheating and damage to the metal substrate. Through high power, high repetition rate, small spot diameter, high scanning speed, and short pulse duration, laser processing enables the efficient and high-precision fabrication of micron-scale structures.

[0046] In some embodiments, the metal substrate includes one of a copper substrate, an aluminum substrate, a titanium substrate, etc.

[0047] In some embodiments, the oxidation treatment of the metal substrate after S1 includes immersing the metal substrate after S1 in a 1 mol / L NaOH solution at 60-80°C for 12-18 hours.

[0048] In this embodiment, to enhance the bonding force between the carbon nanotube growth catalyst and the metal substrate, the metal substrate is immersed in a 1 mol / L NaOH solution for 12-18 hours at a temperature of 60-80°C, preferably 70°C. The main function of sodium hydroxide is to generate oxides on the substrate surface. Taking a copper substrate as an example, when it is immersed in NaOH solution at an ambient temperature of 60-80°C, copper first reacts with sodium hydroxide to form copper hydroxide, which is then heated to become copper oxide. The morphology of the copper oxide is controlled by adjusting the time the copper substrate is placed in the oven.

[0049] The oxygen atoms on the surface of oxides such as copper oxide can provide more active sites, enhancing surface activity and facilitating the formation of more chemical bonds with the carbon nanotube growth catalyst, thus strengthening the binding force between the two. Furthermore, the presence of oxides such as copper oxide can increase surface energy, making it easier for the carbon nanotube growth catalyst to adsorb onto the surface of these oxides, increasing the contact area and thereby improving the binding force. In addition, by controlling the morphology of oxides such as copper oxide, their surface roughness can be tuned, increasing the surface area and providing more binding sites, which is beneficial for enhancing the binding force with the carbon nanotube growth catalyst and allowing the carbon nanotube growth catalyst to be more uniformly loaded on the surface of metal substrates such as copper substrates.

[0050] In some embodiments, the carbon nanotube growth catalyst includes Zif-67, and the preparation of the carbon nanotube growth catalyst on the oxidized metal substrate includes immersing the oxidized metal substrate in a Zif-67 precursor solution for 20-24 hours.

[0051] In this embodiment, Zif-67 was selected as the catalyst for CNT growth. During preparation, the metal substrate was immersed in the Zif-67 precursor solution. During the immersion process, the Zif-67 precursor solution reacted chemically with the oxides on the surface of the metal substrate to form chemical bonds between Zif-67 and the metal substrate. These chemical bonds may be formed through coordination bonds or covalent bonds, which allows Zif-67 to adhere firmly to the surface of the metal substrate, increasing the bonding force between the two and facilitating the subsequent growth of carbon nanotube arrays.

[0052] Furthermore, carbon nanotube growth catalysts are not limited to Zif-67; other catalysts such as iron salts, cobalt salts, and nickel salts can also be used.

[0053] In some embodiments, the Zif-67 precursor solution is obtained by dissolving 500-1000 mg of 2-methylimidazole and 100-500 mg of cobalt nitrate in 20 mL of methanol solution and then mixing them.

[0054] Zif-67 is a metal-organic framework material whose synthesis is based on the coordination interaction between metal ions and organic ligands. In the synthesis of Zif-67, 2-methylimidazole acts as the organic ligand, and cobalt ions in cobalt nitrate act as the metal ion. First, 2-methylimidazole and cobalt nitrate are dissolved separately in methanol to form two solutions. 2-Methylimidazole is an organic molecule containing a nitrogen atom with a lone pair of electrons, exhibiting strong electrophilicity. The cobalt ion in cobalt nitrate is a metal ion with a positive charge. In methanol, the molecules of 2-methylimidazole and cobalt nitrate undergo a coordination reaction, with the lone pair of electrons on the nitrogen atom forming a coordinate bond with the cobalt ion, thus forming the precursor of Zif-67. As the reaction proceeds, multiple 2-methylimidazole molecules coordinate with the cobalt nitrate ion, forming a structure composed of alternating metal ions and organic ligands—the Zif-67 metal-organic framework material.

[0055] In some embodiments, immersing the oxidized metal substrate in the Zif-67 precursor solution includes immersing one side of the oxidized metal substrate with the micron-scale array structure into the Zif-67 precursor solution in a manner perpendicular to the surface of the Zif-67 precursor solution.

[0056] Through extensive experimental research, the inventors discovered that when immersing a metal substrate in a precursor solution, vertical immersion results in a more uniform growth of the loaded carbon nanotube catalyst compared to other methods. "Vertical" here refers to the orientation of the surface of the metal substrate with its micron-scale array structure relative to the solution surface. It should be noted that this vertical orientation refers to the overall vertical or near-vertical orientation, not a strictly vertical orientation.

[0057] Vertical immersion of the metal substrate in the Zif-67 precursor solution results in a more uniform growth of the supported carbon nanotube catalyst. This is likely because vertical immersion creates a uniform liquid film on the substrate surface, facilitating the uniform deposition of the precursor. Therefore, vertical immersion ensures a more uniform liquid film compared to other methods. Furthermore, vertical immersion allows the precursor to diffuse more easily to all parts of the substrate surface, achieving uniform deposition and growth. Other methods, such as horizontal immersion, may result in uneven solution distribution on the substrate surface, affecting the uniformity of catalyst growth.

[0058] In some embodiments, in step S3, the metal substrate after step S2 is placed in a tube furnace and calcined at 800-850°C for 3-5 hours under the conditions of melamine and a N2 to H2 flow ratio of 93:7-99:1.

[0059] In this embodiment, a metal substrate treated with S2 is placed in a tube furnace, and a carbon nanotube array is prepared using chemical vapor deposition (CVD). Specifically, the substrate is calcined at 800°C for 3 hours in the presence of melamine, with a N2 to H2 flow rate ratio of 93:7-99:1. Melamine itself contains carbon, so it undergoes a cracking reaction during CVD, releasing carbon atoms as the carbon source for carbon nanotube growth. During the CVD preparation of the carbon nanotube array, N2 and H2 gases provide an inert atmosphere and a reducing atmosphere, respectively, which helps maintain the stability of the sample. By adjusting the N2 to H2 flow rate ratio, the concentration of the reducing atmosphere can be controlled, promoting the reduction reaction of metal oxides. Specifically, H2 can react with the metal surface at high temperatures, removing oxides and impurities from the surface, thereby providing a clean metal surface for carbon nanotube growth. In addition, hydrogen can reduce the possibility of excessive oxidation of carbon nanotubes under high-temperature conditions, helping to maintain the structure and quality of the carbon nanotubes. Maintaining an inert atmosphere such as N2 can reduce interference from oxygen and other impurities in the experiment, ensuring the purity of the reaction. Furthermore, nitrogen can be used to dilute carbon sources such as melamine to adjust the concentration of the carbon source and control the growth rate and quality of carbon nanotubes.

[0060] This invention also provides a steam chamber capillary wick structure, which is prepared using the steam chamber capillary wick structure preparation method described above.

[0061] The present invention will now be described in detail.

[0062] Example 1

[0063] First, examine the copper substrate at the bottom of the steam chamber ( Figure 3 (a) is shown in the figure. Laser processing is performed to prepare a micro-pit array, resulting in a micro-pit@Cu substrate. Figure 3 (b) shows that the nanosecond laser has a power of 30-100W, a repetition frequency of 100kHz, a spot diameter of 50μm, a scanning speed of 5000-10000mm / s, and a pulse duration of 200ns.

[0064] After laser processing, Zif-67 was used as a catalyst for CNT growth and Zif-67 assembly was carried out. In order to enhance the bonding force between Zif-67 and copper substrate, the copper substrate was first soaked in 1 mol / L NaOH solution for 12 h at an ambient temperature of 70℃ to obtain CuO / micro-pit@Cu substrate.

[0065] Then, 500-1000 mg of 2-methylimidazole and 100-500 mg of cobalt nitrate were dissolved in 20 mL of methanol solution and stirred until homogeneous. The 2-methylimidazole solution and the cobalt nitrate solution were mixed; the solution immediately turned purple. After stirring for 5 min, the prepared CuO / micro-pit@Cu substrate was vertically immersed into the mixed solution and soaked at room temperature for 24 h to synthesize Zif-67 / CuO / micro-pit@Cu. Figure 3 (c) The sample was washed three times with methanol and dried with N2.

[0066] Finally, the Zif-67 / CuO / micro-pit@Cu sample was placed in a tube furnace, and carbon nanotube arrays were prepared using chemical vapor deposition (CVD). Figure 3 (d) The specific conditions are calcination at 800℃ for 3 hours in the presence of 0.5-1.5g of melamine, with a N2 to H2 flow ratio of 93:7-99:1.

[0067] It should be noted that, Figure 3 (b) Figure 3 (c) Figure 3 (d) shows a magnified view of the micro-pit within the dashed box. It can be seen that... Figure 3 In (c), a dodecahedral Zif-67 compound is uniformly deposited on the inner surface of the micropit and the surface of the metal substrate. Zif-67 is a cobalt compound used to catalyze carbon source growth. After CVD treatment, Figure 3(d) shows spherical cobalt particles at the top of carbon nanotubes (CNTs).

[0068] like Figure 4 The image shown is a scanning electron microscope (SEM) image of the CNT structure. The SEM results indicate that a layered carbon nanotube array was successfully fabricated on the copper surface. Layered carbon nanotubes refer to carbon nanotube arrays that grow at both the top and bottom of the micropits, and can be divided into a top layer of carbon nanotubes and a bottom layer of carbon nanotubes. Figure 4 (b) is Figure 4 (a) Enlarged view of the circled area, from Figure 4 (a) and Figure 4 (b) It can be seen that the ends of the carbon nanotubes are connected to spherical cobalt particles, indicating that the cobalt-catalyzed carbon nanotube array structure has been successfully prepared. Figure 4 (c) is a side view of the carbon nanotube array. Figure 4 (c) It can be seen that the carbon nanotubes prepared by this invention are vertically oriented, with a length of 12-20 μm. The vertically oriented carbon nanotube array is beneficial for enhancing the capillary effect and strengthening CHF. In addition, the laser-processed micro-pit array greatly increases the number of micron-scale bubble nucleation sites and promotes bubble detachment, which is beneficial for enhancing HTC.

[0069] like Figure 5 The image shows the capillary climb test results for pure copper (Bare Cu) and layered CNTs. The capillary force test results indicate that water exhibits virtually no climb on the pure copper surface within the 0-1 minute timeframe. Figure 5 (a) shows that CNTs@Cu indicates that carbon nanotubes are grown on the surface of a copper substrate, and CNTs@micropits@Cu indicates that micropits are first prepared on the surface of the copper substrate and then carbon nanotubes are grown. For easy distinction, this is called layered carbon nanotubes. Figure 5 It can be seen that the water climbs a distance of 57 mm on the surface of the layered carbon nanotubes. This indicates that the layered carbon nanotube array has a significant capillary effect, which can promote liquid transport and enhance the rewetting of liquid at dry sites.

[0070] Table 1 shows the test results of boiling heat transfer performance for pure copper and layered carbon nanotube arrays. Here, Bare Cu represents a pure copper substrate, micro-pits@Cu indicates micro-pits were fabricated only on the copper substrate surface, CNTs@Cu indicates carbon nanotubes were grown directly on the copper substrate surface, and CNTs@micro-pits@Cu indicates micro-nanotubes were grown after micro-pits were fabricated on the copper substrate surface; these are referred to as layered carbon nanotubes. CHF represents the critical heat flux density, and HTC represents the boiling heat transfer coefficient.

[0071] Table 1:

[0072] Sample Superheat (K) CHF(W-cm -2 )]]> HTC (kW m -2 K -1 )]]> Bare Cu 31.7 114.5 38.2 Micro-pits @ Cu 11.4 124.0 109.3 CNTs @ Cu 29.9 253.8 86.3 CNTs @ Micro-pits @ Cu 21.7 257.9 119.0

[0073] As shown in Table 1, the control group of pure copper had the lowest CHF and HTC, at 114.5 W·cm⁻¹. -2 and 38.2 kW·m -2 K -1 The wall surface exhibited the highest superheat at 31.7℃, indicating the worst phase change heat transfer capacity. Conversely, the CHF on the surface of the layered carbon nanotubes was 257.9 W·cm⁻¹. -2 HTC has a power output of 119 kW·m. -2 K -1 The content of these components is 125.2% and 211.5% higher than that of pure Cu, respectively.

[0074] The enhancement of CHF is mainly due to the strong capillary wicking effect provided by the vertically grown CNT array (e.g., Figure 5 As shown, enhanced liquid rewetting hinders the expansion of the gas film. The reason for HTC enhancement is mainly that the micro-pit array of laser processing increases the micron-level roughness, which matches the bubble nucleation size and greatly increases the density of bubble nucleation sites. The above results confirm that the layered CNT capillary cores prepared in the embodiments of the present invention can impart excellent phase change heat transfer performance to the copper substrate and significantly enhance the heat dissipation performance of the vapor cavity.

[0075] While the present invention has been disclosed above, its scope of protection is not limited thereto. Those skilled in the art can make various changes and modifications without departing from the spirit and scope of the present invention, and all such changes and modifications will fall within the scope of protection of the present invention.

Claims

1. A method for producing a vapor chamber capillary structure, characterized by, The preparation method comprises the following steps: S1, preparing a microarray structure on a metal substrate at the bottom of a vapor cavity; S2, performing an oxidation treatment on the metal substrate after S1, and then preparing a carbon nanotube growth catalyst on the oxidized metal substrate; The oxidation treatment on the metal substrate after S1 comprises: immersing the metal substrate after S1 in a 1 mol / L NaOH solution at 60-80℃ for 12-18 h; the carbon nanotube growth catalyst comprises Zif-67, and the preparation of the carbon nanotube growth catalyst on the oxidized metal substrate comprises: immersing the oxidized metal substrate in a Zif-67 precursor solution and soaking for 20-24 h; the immersing of the oxidized metal substrate in the Zif-67 precursor solution comprises: immersing the side of the oxidized metal substrate with the microarray structure in the Zif-67 precursor solution in a manner perpendicular to the liquid surface of the Zif-67 precursor solution; S3, preparing vertically oriented carbon nanotubes on the metal substrate after S2 by a chemical vapor deposition method, and finally obtaining a vapor cavity capillary structure.

2. The method of claim 1, wherein the vapor chamber capillary wick structure is formed by the steps of: The microarray structure comprises one of micropits, microchannels, microcolumns and microcones arranged in an array on the metal substrate.

3. The method of claim 2, wherein the vapor chamber capillary wick structure is formed by a process comprising: The microarray structure is prepared on the metal substrate by at least one of laser processing, milling, stamping and casting.

4. The method of claim 3, wherein the vapor chamber capillary wick structure is formed by a process comprising: The parameters of the laser processing comprise: a nanosecond laser power of 30-100 W, a repetition frequency of 100 kHz, a spot diameter of 50 µm, a scanning speed of 5000-10000 mm / s, and a pulse duration of 200 ns.

5. The method of claim 1, wherein the vapor chamber capillary wick structure is formed by a process comprising: The Zif-67 precursor solution is obtained by dissolving 500-1000 mg of 2-methylimidazole and 100-500 mg of cobalt nitrate in 20 mL of methanol solution and mixing. ​ 6. The method of claim 1, wherein the vapor chamber capillary wick structure is formed by a process comprising: In S3, the metal substrate after S2 is placed in a tube furnace, calcined at 800-850℃ for 3-5 h under the conditions of melamine and a flow ratio of N2 to H2 of 93:7-99:

1.

7. A vapor chamber wick structure, characterized by, The vapor cavity capillary structure is prepared by the preparation method of any one of claims 1-6. The preparation method of any one of claims 1-6.

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