CN113587693A - Ultrathin bionic forest-shaped liquid absorption core structure with high capillary performance and preparation method thereof - Google Patents
Ultrathin bionic forest-shaped liquid absorption core structure with high capillary performance and preparation method thereof Download PDFInfo
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- CN113587693A CN113587693A CN202110909128.XA CN202110909128A CN113587693A CN 113587693 A CN113587693 A CN 113587693A CN 202110909128 A CN202110909128 A CN 202110909128A CN 113587693 A CN113587693 A CN 113587693A
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F28—HEAT EXCHANGE IN GENERAL
- F28D—HEAT-EXCHANGE APPARATUS, NOT PROVIDED FOR IN ANOTHER SUBCLASS, IN WHICH THE HEAT-EXCHANGE MEDIA DO NOT COME INTO DIRECT CONTACT
- F28D15/00—Heat-exchange apparatus with the intermediate heat-transfer medium in closed tubes passing into or through the conduit walls ; Heat-exchange apparatus employing intermediate heat-transfer medium or bodies
- F28D15/02—Heat-exchange apparatus with the intermediate heat-transfer medium in closed tubes passing into or through the conduit walls ; Heat-exchange apparatus employing intermediate heat-transfer medium or bodies in which the medium condenses and evaporates, e.g. heat pipes
- F28D15/04—Heat-exchange apparatus with the intermediate heat-transfer medium in closed tubes passing into or through the conduit walls ; Heat-exchange apparatus employing intermediate heat-transfer medium or bodies in which the medium condenses and evaporates, e.g. heat pipes with tubes having a capillary structure
- F28D15/046—Heat-exchange apparatus with the intermediate heat-transfer medium in closed tubes passing into or through the conduit walls ; Heat-exchange apparatus employing intermediate heat-transfer medium or bodies in which the medium condenses and evaporates, e.g. heat pipes with tubes having a capillary structure characterised by the material or the construction of the capillary structure
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Abstract
The invention discloses an ultrathin bionic forest-shaped liquid absorption core structure with high capillary performance and a preparation method thereof.A copper substrate has a natural forest-shaped structure and comprises main stem crystal branches and branches, the main stem and the surface of the substrate form a vertical angle or an inclination angle, and a gap is formed between the main stems; the branches are micro-nano particles and comprise secondary branches and tertiary branches. The tree-shaped liquid absorption core structure has the advantages that the mutually staggered micron-sized channels are formed among the trunks, so that the flow supplement of the working medium can be promoted, the resistance of liquid backflow is reduced, and the heat transfer efficiency is improved; the nanometer channel is formed between the branches and can provide capillary force. Therefore, the tree-forest-shaped liquid absorption core structure provided by the invention has high capillary performance under an ultrathin condition, and provides conditions for application of an ultrathin two-phase heat exchange device.
Description
Technical Field
The invention relates to the technical field of heat exchangers, in particular to an ultrathin bionic forest-shaped liquid absorption core structure with high capillary performance and a preparation method thereof.
Background
With the advent of the 5G era, portable devices have been developed in the directions of ultra-thinness, light weight, high performance and long endurance, which poses new challenges to the heat dissipation requirements of electronic chips. Ultra-thin two-phase heat transfer devices are produced. Due to the reduction of the thickness, the vapor space and the thickness of the liquid absorption core are also greatly reduced. Especially at thicknesses < 0.3 mm, slight variations in thickness cause the thermal resistance to increase exponentially. This requires the wick to be as thin as possible while ensuring high capillary performance. The traditional wick structure is a single micron scale structure, such as metal sintered particles, machined channels, wire mesh, etc., and can not meet the requirements of ultrathin two-phase heat transfer devices due to the characteristics of low porosity, heavy weight, low capillary performance, etc.
The dendritic micro pin fin copper structure (CN 106435665A) has a natural multi-scale structure, large specific surface area and strong capillary force, and is very suitable for the field of heat and mass transfer; compared with the common copper Surface, the dendritic micro pin fin copper array can improve the heat transfer coefficient by about two times (Y. Wang, S. Lyu, J. Luo, Z. Luo, Y. Fu, Y. Heng, J and Zhang, D. Mo., Applied Surface science, 2017, 422, 388-393). Luo (J. Luo, D. Mo, Y. Wang, S. Lyu., Acs Nano, 2021, 15(4), 6614 and 6621.) applies bionic forest structure to ultrathin uniform temperature plate to obtain the thickness of 1.26 × 104 W⋅m-1 K-1Effective thermal conductivity of. The bionic forest-shaped structure is proved to have a better strengthening effect in two-phase heat exchange, so that a forest-shaped liquid absorption core structure with low thickness and high capillarity needs to be developed, and conditions are provided for application of an ultrathin two-phase heat exchange device.
Disclosure of Invention
The invention aims to overcome the defects of the prior art and provides an ultrathin bionic forest-shaped liquid absorption core structure with high capillary performance, which is used for solving the application problem of an ultrathin two-phase heat exchange device.
The invention also aims to provide a preparation method of the ultrathin bionic forest-shaped liquid absorbing core structure with high capillary performance.
In order to achieve the purpose, the invention adopts the following technical scheme:
a copper substrate has a natural forest-shaped structure and comprises main stem crystal branches and branches, wherein the main stem and the surface of the substrate form a vertical angle or an inclined angle, and a gap is formed between the main stems; the branches are small micro-nano particles and comprise secondary branches or tertiary branches; the forest-shaped liquid absorbing core structure further comprises a channel between main trunks and a channel between branches.
Preferably, in the above ultrathin biomimetic forest-like wick structure: the trunk and the surface of the substrate form a vertical angle or an inclined angle, and the angle is 10-90 degrees.
Preferably, in the above ultrathin biomimetic forest-like wick structure: the length of the trunk is 1-2000 μm.
Preferably, in the above ultrathin biomimetic forest-like wick structure: the trunks are uniformly distributed, and the width of gaps between the trunks is 1-500 mu m.
Preferably, in the above ultrathin biomimetic forest-like wick structure: the particle size of the branches is 0.5-100 μm.
The preparation method of the ultrathin bionic forest-shaped liquid absorption core structure comprises the following steps: taking the pretreated copper sheet as a cathode, taking sulfuric acid and copper sulfate as electrolyte, carrying out electrodeposition reaction by adopting a method of gradually increasing current density, and finally sintering under a reduction protective atmosphere to obtain the bionic forest-shaped liquid absorption core structure.
Preferably, in the above-mentioned production method: the molar concentration of copper sulfate in the electrolyte is 0.4-1.0M, and the molar concentration of sulfuric acid is 0.2-2.0M.
Preferably, in the above-mentioned production method: the current density acceleration rate is 0.1-2000 mA/cm2/s。
Preferably, in the above-mentioned production method: the temperature of the sintering treatment is 200-1000 ℃.
Compared with the prior art, the invention has the following beneficial effects:
the bionic forest-shaped liquid absorption core structure has a natural multi-scale structure, the main bodies form a channel structure which is mutually staggered, the flowing resistance of a working medium is reduced, and rich branches form nano-scale holes which can provide capillary force, so that the bionic forest-shaped liquid absorption core structure can present high capillary performance under an ultrathin condition.
The inventionCan be less than 100 μm, which is much less than the thickness of most current ultra-thin wicks (about 1000 μm), and which not only has advantages in thickness, but also has excellent wicking properties. In contrast to other wick structures, the capillary performance parameter of a forest-like structure is only 1/10 times its thicknessΔP c *KCan reach 3.7 times of the original value. Its porosity is as high as 80-92%, much higher (about 50%) than other conventional wick structures, and is one of the reasons for its high capillary properties.
The bionic forest-shaped liquid absorption core structure disclosed by the invention has high capillary performance under an ultrathin condition, so that conditions are provided for application of an ultrathin two-phase heat transfer device. Meanwhile, the catalyst can also be used in other fields such as catalysis and separation.
Drawings
FIG. 1 is a top and side electron microscope image of examples 1 and 2.
FIG. 2 is a graph showing the liquid-absorbing performance of examples 1 and 2.
FIG. 3 is a graph of capillary performance parameters for examples 1 and 2 and other wick structuresΔPc*KCompare the figures.
Detailed Description
The present invention is described in further detail below with reference to specific figures and examples. The described embodiments are only some, but not all embodiments of the present application. The description is illustrative and is not intended to limit the scope of the invention.
Example 1: preparation of ultrathin bionic tree-shaped liquid absorption core structure
(1) Sample pretreatment: the cathode adopts red copper foil, acetone, ethanol and deionized water are sequentially used for cleaning to remove surface oil stains and oxide layers, and then the red copper foil is dried for later use.
(2) Copper crystal branch deposition: at the mixture ratio of 0.7M CuSO4And 0.75M H2SO4In the electrolyte solution, the current acceleration is kept to be 0.67-1.33 mA/cm2And/s, depositing for 160 s, and drying the obtained sample after cleaning.
(3) And (3) performing high-temperature sintering treatment under the condition of a reduction protective atmosphere, further enhancing the mechanical strength of the sample, and preparing to obtain the ultrathin bionic forest-shaped liquid absorption core structure.
Example 2: preparation of ultrathin bionic tree-shaped liquid absorption core structure
(1) Sample pretreatment: the cathode adopts red copper foil, acetone, ethanol and deionized water are sequentially used for cleaning to remove surface oil stains and oxide layers, and then the red copper foil is dried for later use.
(2) Copper crystal branch deposition: at the mixture ratio of 0.7M CuSO4And 0.75M H2SO4In the electrolyte solution, the current acceleration is kept to be 0.67-1.33 mA/cm2And/s, depositing for 220 s, and drying the obtained sample after cleaning.
(3) And (3) performing high-temperature sintering treatment under the condition of a reduction protective atmosphere, further enhancing the mechanical strength of the sample, and preparing to obtain the ultrathin bionic forest-shaped liquid absorption core structure.
As shown in Table 1, the porosity of the forest-like structure samples prepared according to the invention is as high as 84% and 87% and much higher than 50% of the traditional wick when the thickness is only 53 μm and 101 μm, and the capillary performance is improved to a certain extent due to the high porosity. Referring to fig. 2, when the working fluid is ethanol, the liquid absorption height of examples 1 and 2 is over 60 mm in 100s and is much higher than that of a sintered stainless steel powder wick with a thickness of 1500 μm (s. Zhang, c. Chen, g. Chen, yang. Sun, y. Tang, z. wang., International Communications in Heat and Mass Transfer, 2020, 116.), and the liquid absorption height in 100s is only 40 mm.
As shown in fig. 3, comparing examples 1 and 2 with other wick structures, most ultra-thin wicks currently have a thickness of about 1000 μm, while the thickness of the biomimetic forest-like structure can be less than 100 μm. Compared with other wick structures, the wick with the bionic forest-shaped structure has advantages in thickness and excellent capillary performance. Of samples of 101 μm thicknessΔP c *K3.7 times that of a 2 mm sintered metal powder wick structure. In conjunction with fig. 1, the forest-like high capillary performance is attributed to its natural multi-scale structure, and the abundant branches on the upper part of the forest-like structure form nano-scale holes, which can provide capillary force; lower part ofThe structure of the channels which are staggered with each other is formed, the flowing and the supplement of working media are promoted, and the increase of the permeability is facilitated, so that the forest-shaped structure can present high capillary performance under the ultrathin condition.
TABLE 1 sample information for examples 1-3
| Sample (I) | Thickness/mum | Porosity/% | ΔP c *K/N(working medium is ethanol) |
| Example 1 | 53 | 84 | 8.62×10-8 |
| Example 2 | 101 | 87 | 9.35×10-8 |
Claims (9)
1. An ultrathin bionic forest-shaped liquid absorption core structure is characterized in that a copper substrate has a natural forest-shaped structure and comprises main stem crystal branches and branches, the main stem and the surface of the substrate form a vertical angle or an inclination angle, and a gap is formed between the main stems; the branches are small micro-nano particles and comprise secondary branches or tertiary branches; the forest-shaped liquid absorbing core structure further comprises a channel between main trunks and a channel between branches.
2. The ultra-thin biomimetic forest-like wick structure of claim 1, wherein: the trunk and the surface of the substrate form a vertical angle or an inclined angle, and the angle is 10-90 degrees.
3. The ultra-thin biomimetic forest-like wick structure of claim 1, wherein: the length of the trunk is 1-2000 μm.
4. The ultra-thin biomimetic forest-like wick structure of claim 1, wherein: the trunks are uniformly distributed, and the width of gaps between the trunks is 1-500 mu m.
5. The ultra-thin biomimetic forest-like wick structure of claim 1, wherein: the particle size of the branches is 0.5-100 μm.
6. A method of making the ultrathin biomimetic forest-like wick structure of claim 1, comprising the steps of: taking the pretreated copper sheet as a cathode, taking sulfuric acid and copper sulfate as electrolyte, carrying out electrodeposition reaction by adopting a method of gradually increasing current density, and finally sintering under a reduction protective atmosphere to obtain the bionic forest-shaped liquid absorption core structure.
7. The method of claim 6, wherein: the molar concentration of copper sulfate in the electrolyte is 0.4-1.0M, and the molar concentration of sulfuric acid is 0.2-2.0M.
8. The method of claim 6, wherein: the current density acceleration rate is 0.1-2000 mA/cm2/s。
9. The method of claim 6, wherein: the temperature of the sintering treatment is 200-1000 ℃.
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN116576703A (en) * | 2023-05-11 | 2023-08-11 | 广东思泉热管理技术有限公司 | Preparation process of vapor chamber with fishbone-shaped capillary structure and product thereof |
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