A method for anti-corrosion treatment of the surface of a microchannel heat sink

Abstract

The present invention discloses a method for anti-corrosion treatment of the surface of a microchannel radiator. The method includes the following steps: placing a copper substrate in a vacuum chamber, evacuating the chamber; introducing a mixed gas of argon and hydrogen into the vacuum chamber and heating the chamber; maintaining a first set temperature in the vacuum chamber, stopping the introduction of the mixed gas of argon and hydrogen, and introducing methane gas into the chamber to grow graphene on the copper substrate; after the growth of graphene on the copper substrate is completed, stopping the introduction of methane gas into the vacuum chamber and allowing natural cooling; when the vacuum chamber cools down to a second set temperature, performing a vacuum pumping operation on the chamber; when the vacuum chamber cools down to a third set temperature, stopping the vacuum pumping of the chamber and taking out the grown sample. The beneficial effect of the present invention is that a graphene protection layer is grown inside or on the surface of the microchannel, which can significantly improve the anti-corrosion ability of the microchannel heat exchanger, extend its service life, and maintain its heat exchange efficiency.

Description

Technical Field

[0001] The present invention belongs to the technical field of microchannel heat dissipation, and particularly relates to a method for anti-corrosion treatment of the surface of a microchannel heat sink. Background Art

[0002] The engineering background of microchannel heat sinks stems from the cooling of high-density electronic devices in the 1980s and the heat transfer problems of microelectromechanical systems that emerged in the 1990s. With the development of microfabrication technology, people have been able to manufacture microscale heat exchangers composed of channels with a hydraulic diameter of 10 - 1000 μm. If a micro-compression condensation system is used to replace the micro-condenser, active cooling can be achieved, supporting the high-speed operation of high-density heat electronic devices.

[0003] Microchannel heat dissipation technology is widely used in the automotive air-conditioning industry. For application scenarios with high-efficiency heat exchange requirements, microchannel heat exchangers also play an important role. The working process of microchannels is mainly as follows: The microchannel heat exchanger is in close contact with the heat source, and heat is transferred to the heat sink through heat conduction. The coolant enters the microchannel through the heat exchanger, exchanges and takes away the heat in the form of convective heat transfer, and flows out from the outlet of the heat exchanger, thus forming a cycle to achieve the purpose of cooling. As a heat exchange device, in order to improve the heat exchange performance of the microchannel heat exchanger, the heat exchanger material is mainly metal with a relatively high thermal conductivity, especially high-thermal-conductivity oxygen-free copper or steel and stainless steel. However, metals are easily corroded by acidic, alkaline, or salt solutions, resulting in a decrease in the efficiency of the microchannel heat exchanger and failing to achieve a good heat exchange effect. By technical means, treating the surface of the microchannel heat sink to enhance its corrosion resistance to acids, alkalis, and salts is of great significance for maintaining the heat exchange efficiency in the long term.

[0004] The heat exchanger material is mainly metal with a relatively high thermal conductivity, especially high-thermal-conductivity oxygen-free copper or steel and stainless steel. However, the untreated metal surface is prone to corrosion and has low heat exchange efficiency, resulting in a decrease in the efficiency of the microchannel heat exchanger and failing to achieve a good heat exchange effect. By technical means, treating the surface of the microchannel heat sink to enhance its heat exchange capacity is of great significance for maintaining the heat exchange efficiency in the long term.

[0005] In existing materials, graphene and boron nitride have a very high in-plane thermal conductivity, which can significantly improve the in-plane thermal uniformity of the heat exchanger, thereby improving the heat exchange efficiency.

[0006] Graphene also has obvious advantages in enhancing the solid-liquid heat transfer coefficient. It has an ultra-high thermal conductivity, which can quickly transfer heat to the liquid. This helps to improve the heat storage capacity of the liquid, thereby enhancing the efficiency of solid-liquid phase change heat transfer. The advantages of graphene lie not only in its ability to quickly transfer heat to the liquid, but also in its ability to prevent heat leakage. It can form a heat insulation layer to prevent heat from transferring from the solid to the lower temperature direction of the liquid, enabling the temperature of the liquid to rise faster, thus increasing the efficiency of solid-liquid heat transfer.

[0007] In addition, graphene can effectively control its own heat diffusion during solid-liquid phase change heat transfer, resist heat diffusion under high-temperature conditions, thereby better inhibiting heat loss, improving thermal efficiency, and reducing energy waste. Moreover, the surface of graphene has a special optical structure. According to the different characteristics of the incident ambient light, it will induce a three-dimensional effect to improve the surface structure of the heat exchanger, provide more reflective surfaces, increase heat storage, and effectively increase the heat transfer efficiency.

[0008] The Chinese patent with the publication number CN113446883A and the publication date of September 28, 2021, discloses a two-fluid loop rubbing wave-shaped microchannel heat sink based on elastic turbulence, and the Chinese patent with the publication number CN217818315U and the publication date of November 15, 2022, discloses a porous folded microchannel flat tube for heat dissipation. However, existing patents describe the fabrication and structural forms of microchannels, and pay less attention to the anti-corrosion treatment inside the microchannel heat exchanger. Summary of the Invention

[0009] In view of this, the present invention discloses a method for anti-corrosion treatment of the surface of a microchannel heat sink, aiming to improve the anti-corrosion ability of the microchannel heat exchanger, extend its service life, and maintain its heat transfer efficiency.

[0010] The embodiments of this specification provide the following technical solutions: A method for anti-corrosion treatment of the surface of a microchannel heat sink, including the following steps:

[0011] Step 1: Place the copper substrate in a vacuum chamber and evacuate the vacuum chamber.

[0012] Step 2: Introduce a mixed gas of argon and hydrogen into the vacuum chamber and heat the vacuum chamber.

[0013] Step 3: Keep the first set temperature in the vacuum chamber, stop introducing the mixed gas of argon and hydrogen, and introduce methane gas into the vacuum chamber to grow graphene on the copper substrate.

[0014] Step 4: After the graphene growth on the copper substrate is completed, stop introducing methane gas into the vacuum chamber and allow it to cool naturally.

[0015] Step 5: When the vacuum chamber cools down to the second set temperature, perform a vacuum pumping operation on the vacuum chamber;

[0016] Step 6: When the vacuum chamber cools down to the third set temperature, stop vacuum pumping the vacuum chamber and take out the grown sample.

[0017] Further, in Step 1, vacuum pumping is performed on the vacuum chamber, and the air pressure in the vacuum chamber is made less than 10 Pa.

[0018] Further, in Step 2, the volume flow rate of the mixed gas of argon and hydrogen is 90 - 110 sccm, and the heating time for the vacuum chamber is 4 - 6 min.

[0019] Further, in Step 3, the first set temperature is 950 °C, the volume flow rate of methane gas is 4 - 6 sccm, and the growth time for growing graphene on the copper substrate is 9 - 11 min.

[0020] Further, Step 3 also includes: When introducing methane gas, the pressure inside the vacuum chamber can be increased by adjusting the vacuum valve of the vacuum chamber, and the pressure inside the vacuum chamber is made less than the atmospheric pressure.

[0021] Further, in Step 5, the cooling time for the first set temperature to cool down to the second set temperature is greater than 2 hours.

[0022] Further, in Step 5, the second set temperature is 700 °C.

[0023] Further, in Step 6, the third set temperature is 200 °C.

[0024] Compared with the prior art, the beneficial effects that can be achieved by at least one of the above technical solutions adopted in the embodiments of this specification at least include:

[0025] After growing the graphene protective layer, the microchannel can significantly reduce the temperature difference of the outlet water temperature, effectively prevent the increase of the interfacial thermal resistance, and improve the use efficiency of the microchannel heat exchanger.

[0026] Growing a graphene protective layer inside or on the surface of the microchannel can significantly improve the corrosion resistance of the microchannel heat exchanger, extend its service life, and maintain its heat exchange efficiency. Brief Description of the Drawings

[0027] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present application. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0028] Figure 1It is the flowchart of the method according to the embodiments of the present invention.

[0029] Figure 2 It is a schematic diagram of the thermal measurement system according to the embodiments of the present invention.

[0030] Figure 3 It is a comparison diagram of the graphene-protected sample (right) and the ordinary sample (left) according to the embodiments of the present invention.

[0031] Reference numerals in the figure: 1. Liquid flow monitoring and control device; 2. Microchannel heat exchanger; 3. Constant temperature heater; 4. Power supply and control circuit. Detailed implementation manners

[0032] The embodiments of the present application will be described in detail below with reference to the accompanying drawings.

[0033] It should be noted that, without conflict, the embodiments in the present application and the features in the embodiments may be combined with each other. The present invention will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0034] The present invention grows graphene inside or on the surface of the microchannel to improve the heat exchange capacity of the microchannel. The CVD chemical vapor deposition technology is adopted, wherein methane (CH4) is used as the carbon source to grow graphene. As Figure 1 shown, the process of growing graphene is as follows:

[0035] Connect the vacuum chamber, place the copper substrate (microchannel), turn on the vacuum pump and the vacuum baffle valve to evacuate the vacuum chamber until the pressure in the vacuum chamber is less than 10 Pa;

[0036] Open the gas valve and the heater, introduce the mixed gas of argon and hydrogen at 100 sccm, and heat for 5 minutes to rise to the first set temperature (950 °C);

[0037] After the temperature rises to 950 °C, keep this temperature, close the mixed gas of argon and hydrogen, open the methane gas valve, and set the methane gas flow rate to 5 sccm. During this process, the vacuum valve can be appropriately closed to increase the pressure in the chamber, but control it within the atmospheric pressure, and the growth time is 10 minutes;

[0038] After the growth is completed, close the methane gas valve, start natural cooling, and when the temperature drops to the second set temperature (700 °C), open the vacuum valve to evacuate the vacuum. The cooling process should not be too fast, and the duration is generally more than 2 hours;

[0039] When the temperature drops below the third set temperature (200 °C), turn off the vacuum pump, open the vacuum chamber, and take out the grown sample.

[0040] There are three important process parameters during the graphene growth process:

[0041] 1. Temperature

[0042] In this system, methane is selected as the growth carbon source, carburization is carried out at a temperature of 1000 °C, and carbon precipitation is carried out at a temperature of 900 - 600 °C.

[0043] 2. Carbon source concentration - gas type and flow rate

[0044] Before growth, argon is used as a protector to clean the quartz tube cavity, and hydrogen is used to reduce the substrate surface. 80 sccm of methane is used as the growth gas.

[0045] 3. Vacuum control

[0046] Vacuum degree control is used to control the precursor concentration and surface distribution on the growth substrate surface, and is used to cooperate with different growth processes to control the growth thickness of graphene.

[0047] Among them, controlling the growth thickness of the graphene layer has a certain impact on the improvement of heat transfer capacity. When the graphene layer is relatively thin, the heat transfer efficiency increases with the increase of the radian and reaches the maximum value at a thickness of about 30 nm.

[0048] In the embodiment of the present invention, the microchannel is made of ordinary oxygen-free copper, and graphene is grown on its channel surface to form a protective layer. The femtosecond laser pump-probe thermal reflectance method is used to measure the thermal conductivity and heat transfer energy of the microchannel protective layer. The physical process in the femtosecond laser pump-probe thermal reflectance method test is divided into two steps: the first step is to use a pulsed laser beam to irradiate the surface of the measured sample, and heat the sample by converting light energy into heat energy. This step is called the pump process. The heat energy gradually transfers into the sample, and due to the influence of the thermal properties of the material, the heat transfer processes of different samples are different, resulting in different temperature distributions inside the sample. Temperature affects the optical properties (reflectivity) of the sample; the second step is to use another pulsed laser beam to irradiate the sample to observe the change of the optical properties of the sample. This step is called the probe process.

[0049] Figure 2 It is a schematic diagram of the heat transfer measurement system. Among them, the liquid flow monitoring and control device 1 is connected to the microchannel heat exchanger 2 through a water flow pipeline. A constant temperature heater 3 is arranged below the microchannel heat exchanger 2, and a power supply and a control circuit 4 are arranged on the constant temperature heater 3. And an inlet water temperature measurement module is arranged on the inlet side of the microchannel heat exchanger 2, and an outlet water temperature measurement module is arranged on the outlet side of the microchannel heat exchanger 2. The measured inlet and outlet liquid temperatures and related heat transfer performance data are shown in the following table:

[0050] Outlet water temperature (°C) Sample temperature (°C) Temperature difference (°C) Growth of protective layer 27.2 35.1 7.9 No growth of protective layer 29.4 51.5 22.1

[0051] It can be seen from the above data that after growing the graphene protective layer, the microchannel can significantly reduce the temperature difference of the outlet water temperature, effectively prevent the increase of the interfacial thermal resistance, and improve the use efficiency of the microchannel heat exchanger. A sodium chloride solution with a concentration of 3.5% was configured to test the corrosion resistance of the microchannel with the protective layer grown.

[0052] After the two microchannel samples with and without the protective layer were subjected to brine corrosion for 96 hours, the corrosion conditions on the surfaces of the samples were compared as Figure 3 shown. It can be seen that there are obvious differences between the surfaces of the microchannel samples protected by graphene and the unprotected samples. Rust marks can be seen on the surface of the ordinary samples, while no obvious corrosion is seen on the protected samples.

[0053] In summary, growing a graphene protective layer inside or on the surface of the microchannel can significantly improve the corrosion resistance of the microchannel heat exchanger, extend its service life, and maintain its heat exchange efficiency.

[0054] As mentioned above, only the specific embodiments of the present invention are described, and the scope of the invention implementation cannot be limited by them. Therefore, the replacement of equivalent components or the equivalent changes and modifications made according to the protection scope of the present invention patent should still fall within the scope covered by this patent. In addition, the technical features in the present invention, between technical features, between technical features and technical solutions, and between technical solutions can be freely combined and used.

Claims

1. A method for anti-corrosion treatment of the surface of a microchannel heat sink, characterized in that, It includes the following steps: Step 1: Place the copper substrate in a vacuum chamber and evacuate the vacuum chamber. Step 2: Introduce a mixed gas of argon and hydrogen into the vacuum chamber and heat the vacuum chamber. Step 3: Keep the first set temperature in the vacuum chamber, stop introducing the mixed gas of argon and hydrogen, and introduce methane gas into the vacuum chamber to grow graphene on the copper substrate; the first set temperature is 950 °C. When introducing methane gas, adjust the vacuum valve of the vacuum chamber to increase the pressure in the vacuum chamber and make the pressure in the vacuum chamber less than the atmospheric pressure. Step 4: After the graphene growth on the copper substrate is completed, stop introducing methane gas into the vacuum chamber and let it cool naturally. Step 5: When the vacuum chamber cools down to the second set temperature, perform a vacuum pumping operation on the vacuum chamber. The cooling time from the first set temperature to the second set temperature is more than 2 hours, and the second set temperature is 700 °C. Step 6: When the vacuum chamber cools down to the third set temperature, stop vacuum pumping the vacuum chamber and take out the grown sample. The third set temperature is 200 °C.

2. The method for anti-corrosion treatment of the surface of the microchannel heat sink according to claim 1, characterized in that, In step 1, evacuate the vacuum chamber and make the air pressure in the vacuum chamber less than 10 Pa.

3. The method for surface anti-corrosion treatment of the microchannel radiator according to claim 1, characterized in that In step 2, the volume flow rate of the mixed gas of argon and hydrogen is 90 - 110 sccm, and the heating time of the vacuum chamber is 4 - 6 min.

4. The method for surface anti-corrosion treatment of the microchannel heat sink according to claim 1, characterized in that, In step 3, the volume flow rate of the methane gas is 4 - 6 sccm, and the growth time of graphene on the copper substrate is 9 - 11 min.

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